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Sample records for rigid gas-permeable contact

  1. 21 CFR 886.5916 - Rigid gas permeable contact lens.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Rigid gas permeable contact lens. 886.5916 Section 886.5916 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... against the cornea of the eye to correct vision conditions. The device is made of various materials, such...

  2. Clinical observation on Hiline rigid gas permeable contact lens for keratoconus

    Directory of Open Access Journals (Sweden)

    Hui Ding

    2016-03-01

    Full Text Available AIM:To investigate the effect of the Hiline rigid gas permeable contact lens(Hiline RGPCLfor keratoconus in clinical practice and the predictors for RGPCL fitting.METHODS:Fifty-seven eyes in 36 patients with keratoconus fitted with Hiline RGPCL were divided into three groups, mild(n=10, moderate(n=24and advanced(n=23group. After fitting evaluation, visual acuity measurements were taken to compare the best corrected visual acuity wearing spectacle lenses and Hiline RGPCL. The predictors for RGPCL fitting by the corneal curvature were analyzed.RESULTS:In all groups, the application of Hiline RGPCL obtained acceptable vision. There was statistically significant improvement in vision with the Hiline RGPCL than that of with spectacle lenses in mild group(t=-2.968,P=0.016, moderate group(t=-6.293,Pt=-12.792,Pr=0.715,P=0.02. In moderate group, the base curve of RGPCL correlated with average K as well as 0.2mm steeper average K(r=0.495,P=0.014. In advanced group, the base curve of RGPCL correlated with every indicator, especially the corneal curvature in central area(r=0.802,PCONCLUSION:Guiding by corneal topography, improvement of visual acuity is successfully achieved by fitting with Hiline RGPCL. Selecting different predictors in different grades can reduce the complexity and improve the usefulness of the Hiline RGPCL in clinical practice.

  3. Clinical evaluation of a computerized topography software method for fitting rigid gas permeable contact lenses.

    Science.gov (United States)

    Szczotka, L B; Capretta, D M; Lass, J H

    1994-10-01

    Computerized videokeratoscope software programs now have the ability to assist in the design of rigid gas permeable (RGP) contact lenses and simulate fluorescein patterns. We evaluated the performance of Computed Anatomy's Topographic Modeling System (TMS-1) and its Contact Lens Fitting Program (version 1.41) in fitting RGP lenses in 31 subjects. Computerized topographic analysis, balanced manifest refraction, slit lamp examination, and keratometry were performed. Initial lens parameters were ordered according to manufacturer's programmed recommendations for base curve, power, lens diameter, optic zone diameter, and edge lift. Final lens parameters were based on clinical performance. Lenses were recorded for base curve changes of 0.1 mm or more, power alterations of +/- 0.50 D or more, or for any alteration in diameter/optic zone. Twenty-seven patients were analyzed for all five recommended parameters. Thirteen of 27 patients (48%) required no parameter changes. Nine of 27 patients (33%) required one parameter change, four of 27 patients (15%) required two parameter changes, and one patient (4%) needed three parameters altered. The most prevalent change was a power alteration, required in nine of 27 patients (33%); however, comparisons of all initial to final parameters showed no statistically significant differences. Comparison of initial base curves to that which would have been chosen via standard keratometry also showed no significant difference. This study found the TMS-1 default lens recommendations to be clinically unacceptable. This system, however, could be an alternative method of initial lens selection if used to titrate a fit or if software enhancements are incorporated to account for lens movement and flexure.

  4. The effects of high-Dk rigid contact lens center thickness, material permeability, and blinking on the oxygen uptake of the human cornea.

    Science.gov (United States)

    Gardner, Hope Patterson; Fink, Barbara A; Mitchell, Lynn G; Hill, Richard M

    2005-06-01

    The human corneal oxygen uptake responses associated with the static (nonblinking) and dynamic (blinking) wear of five rigid gas-permeable materials with high oxygen permeabilities were determined for three different center thicknesses and compared with the responses for the normal open eye and severe hypoxic stress (static wear of polymethylmethacrylate). Corneal oxygen uptake rates were measured with a Clark-type polarographic electrode during two sessions with each of 10 human subjects. Measurements were made on the right eye for the normal open eye (air) and after 5 minutes of static and dynamic wear of polymethylmethacrylate and five rigid gas-permeable contact lens materials: Fluoroperm 92 (paflufocon A, Dk = 92), Fluoroperm 151 (paflufocon D, Dk = 151), 1992 Menicon SF-P (melafocon A, Dk = 102), 1995 Menicon SF-P (melafocon A, Dk = 159), and Menicon Z (tisilfocon A, Dk = 163-250). Lenses were manufactured in three different center thicknesses (0.12, 0.16, and 0.20 mm), with all other parameters remaining constant. Repeated-measures analysis of variance was used and included lens material (five levels), blinking condition (two levels), and lens thickness (three levels) as within-subject effects. Significant differences were found in corneal oxygen responses to lens material (p Dk rigid lens materials studied here, moderate changes in lens thickness or material permeability may result in modest differences in corneal hypoxic relief, whereas blinking results in no significant improvement to corneal oxygenation.

  5. Aberration changes of the corneal anterior surface following discontinued use of rigid gas permeable contact lenses.

    Science.gov (United States)

    Yu, Qing; Wu, Jiang-Xiu; Zhang, He-Ning; Ye, Sheng; Dong, Shi-Qi; Zhang, Chen-Hao

    2013-01-01

    To record aberrations with a corneal topographic device on the anterior surface of the cornea at different time-points prior to wearing and following discontinued use of rigid gas permeable (RGP) contact lenses. The effect of wearing RGP on the anterior surface of the cornea was discussed to provide guidance for clinical refractive error correction. The study objects were 24 eyes from 24 patients. All patients underwent identical examination procedures prior to lens use, as well as afterwards, including slit-lamp examination, non-contact tonometer measurement, computer optometry and corneal curvature measurement, subjective refraction test, and corneal topography analysis. The patients wore contact lenses everyday for 1 month and then discontinued. Corneal topographies were recorded at certain time points of 30 minutes, 1 day, 3, 7 and 14 days following use. Total corneal aberration at each time point following discontinued use of RGP contact lenses was less than the time point prior to use. Detailed results were as follows: root mean square (RMS) (pre)=(1.438±0.328)µm, RMS (30 minutes)=(1.076±0.355)µm, RMS (1 day)=(1.362±0.402)µm, RMS (3 days)=(1.373±0.398)µm, RMS (7 days)=(1.387±0.415)µm, and RMS (14 days)=(1.430±0.423)µm. Results showed that at 30 minutes after discontinued use of RGP contact lenses, almost all 2(nd)- and 3(rd)-order aberrations change. Quadrafoil Z10 and spherical Z12 of the 4(th)-order were also changed. Alterations to Z5, Z6, and Z12 at 1 day after discontinued use were significant differences compared with the time period prior to RGP use: Z5 and Z6 decreased, and Z12 increased slightly. Z5 and Z6 remained decreased at 3 days after discontinued use, but Z9 and Z10 continued to increase and Z12 returned to levels prior to RGP use. At 14 days after discontinued use, all aberrations were not significantly different from the values prior to use. The use RGP contact lenses greatly reduced total aberration of the anterior surface of

  6. Aberration changes of the corneal anterior surface following discontinued use of rigid gas permeable contact lenses

    Directory of Open Access Journals (Sweden)

    Shi-Qi Dong

    2013-04-01

    Full Text Available AIM: To record aberrations with a corneal topographic device on the anterior surface of the cornea at different time-points prior to wearing and following discontinued use of rigid gas permeable (RGP contact lenses. The effect of wearing RGP on the anterior surface of the cornea was discussed to provide guidance for clinical refractive error correction. METHODS: The study objects were 24 eyes from 24 patients. All patients underwent identical examination procedures prior to lens use, as well as afterwards, including slit-lamp examination, non-contact tonometer measurement, computer optometry and corneal curvature measurement, subjective refraction test, and corneal topography analysis. The patients wore contact lenses everyday for 1 month and then discontinued. Corneal topographies were recorded at certain time points of 30 minutes, 1 day, 3, 7 and 14 days following use. RESULTS: Total corneal aberration at each time point following discontinued use of RGP contact lenses was less than the time point prior to use. Detailed results were as follows:root mean square (RMS (pre=(1.438±0.328μm, RMS (30 minutes=(1.076±0.355μm, RMS (1 day=(1.362±0.402μm, RMS (3 days=(1.373±0.398μm, RMS (7 days=(1.387±0.415μm, and RMS (14 days=(1.430±0.423μm. Results showed that at 30 minutes after discontinued use of RGP contact lenses, almost all 2nd- and 3rd-order aberrations change. Quadrafoil Z10 and spherical Z12 of the 4th-order were also changed. Alterations to Z5, Z6, and Z12 at 1 day after discontinued use were significant differences compared with the time period prior to RGP use:Z5 and Z6 decreased, and Z12 increased slightly. Z5 and Z6 remained decreased at 3 days after discontinued use, but Z9 and Z10 continued to increase and Z12 returned to levels prior to RGP use. At 14 days after discontinued use, all aberrations were not significantly different from the values prior to use. CONCLUSION: The use RGP contact lenses greatly reduced total

  7. Novel model for multispecies biofilms that uses rigid gas-permeable lenses.

    Science.gov (United States)

    Peyyala, Rebecca; Kirakodu, Sreenatha S; Ebersole, Jeffrey L; Novak, Karen F

    2011-05-01

    Oral biofilms comprise complex multispecies consortia aided by specific inter- and intraspecies interactions occurring among commensals and pathogenic bacterial species. Oral biofilms are primary initiating factors of periodontal disease, although complex multifactorial biological influences, including host cell responses, contribute to the individual outcome of the disease. To provide a system to study initial stages of interaction between oral biofilms and the host cells that contribute to the disease process, we developed a novel in vitro model system to grow biofilms on rigid gas-permeable contact lenses (RGPLs), which enable oxygen to permeate through the lens material. Bacterial species belonging to early- and late-colonizing groups were successfully established as single- or three-species biofilms, with each group comprising Streptococcus gordonii, Streptococcus oralis, and Streptococcus sanguinis; S. gordonii, Actinomyces naeslundii, and Fusobacterium nucleatum; or S. gordonii, F. nucleatum, and Porphyromonas gingivalis. Quantification of biofilm numbers by quantitative PCR (qPCR) revealed substantial differences in the magnitude of bacterial numbers in single-species and multispecies biofilms. We evaluated cell-permeable conventional nucleic acid stains acridine orange, hexidium iodide, and Hoechst 33258 and novel SYTO red, blue, and green fluorochromes for their effect on bacterial viability and fluorescence yield to allow visualization of the aggregates of individual bacterial species by confocal laser scanning microscopy (CLSM). Substantial differences in the quantity and distribution of the species in the multispecies biofilms were identified. The specific features of these biofilms may help us better understand the role of various bacteria in local challenge of oral tissues.

  8. [Analysis of aberration changes of the corneal anterior surface following discontinued use of rigid gas permeable contact lenses].

    Science.gov (United States)

    Yu, Qing; Wu, Jiang-xiu; Zhang, He-ning; Ye, Sheng; Dong, Shi-qi; Zhang, Chen-hao

    2011-04-01

    The present study used a corneal topographic device to record aberrations on the anterior surface of the cornea at different time-points prior to wearing and following discontinued use of rigid gas permeable (RGP) contact lenses. The effect of wearing RGPCL on the anterior surface of the cornea was discussed to provide guidance for clinical refractive error correction. The study objects were 60 eyes from 30 patients. All patients underwent identical examination procedures prior to lens use, as well as afterwards, including slit-lamp examination, non-contact tonometer measurement, computer optometry & corneal curvature measurement, subjective refraction test, and corneal topography analysis. The patients wore contact lenses every day for 1 month and then discontinued. Corneal topographies were recorded at certain time points of 30 min, 1 day, 3 days, 1 week, and 2 weeks following use. Total corneal aberration at each time point following discontinued use of RGP contact lenses was less than the time point prior to use. Detailed results are as follows; root mean square (RMS) (pre) = (1.438 ± 0.328), RMS (30 min) = (1.076 ± 0.355), RMS (1 day) = (1.362 ± 0.402), RMS (3 day) = (1.373 ± 0.398), RMS (7 day) = (1.387 ± 0.415), and RMS (14 day) = (1.448 ± 0.423). Results showed that at 30 minutes after discontinued use of RGP contact lenses, almost all 2(nd)- and 3(rd)-order aberrations were altered. Quadrafoil Z10 and spherical Z12 of the 4(th)-order were also changed. Alterations to Z5, Z6, and Z12 at 1 day after discontinued use were significant compared with the time period prior to RGP use: Z5 and Z6 decreased, and Z12 increased slightly (F = 2.869 ∼ 5.549, P = 0.001 ∼ 0.042). Z5 and Z6 remained decreased at 3 days after discontinued use, but Z9 and Z10 continued to increase and Z12 returned to levels prior to RGP use (P > 0.05). At 2 weeks after discontinued use, all aberrations were not significantly different from the values prior to use (P > 0.05). The

  9. Novel Model for Multispecies Biofilms That Uses Rigid Gas-Permeable Lenses ▿

    Science.gov (United States)

    Peyyala, Rebecca; Kirakodu, Sreenatha S.; Ebersole, Jeffrey L.; Novak, Karen F.

    2011-01-01

    Oral biofilms comprise complex multispecies consortia aided by specific inter- and intraspecies interactions occurring among commensals and pathogenic bacterial species. Oral biofilms are primary initiating factors of periodontal disease, although complex multifactorial biological influences, including host cell responses, contribute to the individual outcome of the disease. To provide a system to study initial stages of interaction between oral biofilms and the host cells that contribute to the disease process, we developed a novel in vitro model system to grow biofilms on rigid gas-permeable contact lenses (RGPLs), which enable oxygen to permeate through the lens material. Bacterial species belonging to early- and late-colonizing groups were successfully established as single- or three-species biofilms, with each group comprising Streptococcus gordonii, Streptococcus oralis, and Streptococcus sanguinis; S. gordonii, Actinomyces naeslundii, and Fusobacterium nucleatum; or S. gordonii, F. nucleatum, and Porphyromonas gingivalis. Quantification of biofilm numbers by quantitative PCR (qPCR) revealed substantial differences in the magnitude of bacterial numbers in single-species and multispecies biofilms. We evaluated cell-permeable conventional nucleic acid stains acridine orange, hexidium iodide, and Hoechst 33258 and novel SYTO red, blue, and green fluorochromes for their effect on bacterial viability and fluorescence yield to allow visualization of the aggregates of individual bacterial species by confocal laser scanning microscopy (CLSM). Substantial differences in the quantity and distribution of the species in the multispecies biofilms were identified. The specific features of these biofilms may help us better understand the role of various bacteria in local challenge of oral tissues. PMID:21421785

  10. Contact lens rehabilitation following repaired corneal perforations

    Science.gov (United States)

    Titiyal, Jeewan S; Sinha, Rajesh; Sharma, Namrata; Sreenivas, V; Vajpayee, Rasik B

    2006-01-01

    Background Visual outcome following repair of post-traumatic corneal perforation may not be optimal due to presence of irregular keratometric astigmatism. We performed a study to evaluate and compare rigid gas permeable contact lens and spectacles in visual rehabilitation following perforating corneal injuries. Method Eyes that had undergone repair for corneal perforating injuries with or without lens aspiration were fitted rigid gas permeable contact lenses. The fitting pattern and the improvement in visual acuity by contact lens over spectacle correction were noted. Results Forty eyes of 40 patients that had undergone surgical repair of posttraumatic corneal perforations were fitted rigid gas permeable contact lenses for visual rehabilitation. Twenty-four eyes (60%) required aphakic contact lenses. The best corrected visual acuity (BCVA) of ≥ 6/18 in the snellen's acuity chart was seen in 10 (25%) eyes with spectacle correction and 37 (92.5%) eyes with the use of contact lens (p < 0.001). The best-corrected visual acuity with spectacles was 0.20 ± 0.13 while the same with contact lens was 0.58 ± 0.26. All the patients showed an improvement of ≥ 2 lines over spectacles in the snellen's acuity chart with contact lens. Conclusion Rigid gas permeable contact lenses are better means of rehabilitation in eyes that have an irregular cornea due to scars caused by perforating corneal injuries. PMID:16536877

  11. Comparative Study of Antibacterial and Antifungal Effects of Rigid Gas Permeable Contact Lens Disinfecting Solutions

    OpenAIRE

    Kuzman, Tomislav; Barišić Kutija, Marija; Kordić, Rajko; Popović Suić, Smiljka; Jandroković, Sonja; Škegro, Ivan; Pokupec, Rajko

    2013-01-01

    The aim of this study was to compare antimicrobial efficacy of rigid contact lens disinfecting solutions. We tested five commercially available solutions: Unique pH (Alcon Laboratories), Boston Advance (Polymer Technology Corp.), Nitilens Conditioner GP (Avizor), Total Care (AMO), Boston Simplus (Bausch&Lomb). Their efficacy to disinfect saline solution experimentally contaminated with American Type Culture Collection (ATCC): Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922...

  12. Short-term corneal changes with gas-permeable contact lens wear in keratoconus subjects: a comparison of two fitting approaches.

    Science.gov (United States)

    Romero-Jiménez, Miguel; Santodomingo-Rubido, Jacinto; Flores-Rodríguez, Patricia; González-Méijome, Jose-Manuel

    2015-01-01

    To evaluate changes in anterior corneal topography and higher-order aberrations (HOA) after 14-days of rigid gas-permeable (RGP) contact lens (CL) wear in keratoconus subjects comparing two different fitting approaches. Thirty-one keratoconus subjects (50 eyes) without previous history of CL wear were recruited for the study. Subjects were randomly fitted to either an apical-touch or three-point-touch fitting approach. The lens' back optic zone radius (BOZR) was 0.4mm and 0.1mm flatter than the first definite apical clearance lens, respectively. Differences between the baseline and post-CL wear for steepest, flattest and average corneal power (ACP) readings, central corneal astigmatism (CCA), maximum tangential curvature (KTag), anterior corneal surface asphericity, anterior corneal surface HOA and thinnest corneal thickness measured with Pentacam were compared. A statistically significant flattening was found over time on the flattest and steepest simulated keratometry and ACP in apical-touch group (all p<0.01). A statistically significant reduction in KTag was found in both groups after contact lens wear (all p<0.05). Significant reduction was found over time in CCA (p=0.001) and anterior corneal asphericity in both groups (p<0.001). Thickness at the thinnest corneal point increased significantly after CL wear (p<0.0001). Coma-like and total HOA root mean square (RMS) error were significantly reduced following CL wearing in both fitting approaches (all p<0.05). Short-term rigid gas-permeable CL wear flattens the anterior cornea, increases the thinnest corneal thickness and reduces anterior surface HOA in keratoconus subjects. Apical-touch was associated with greater corneal flattening in comparison to three-point-touch lens wear. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  13. Oxygen permeability (Dk) of thirty-seven rigid contact lens materials.

    Science.gov (United States)

    Benjamin, William J; Cappelli, Quido A

    2002-02-01

    Oxygen permeability (Dk) was determined for 37 available rigid contact lens materials in a masked fashion. The results were compared with those of an earlier study that included different lots of 14 test materials assessed in the current study. Six lenses of different thicknesses in each test and reference material were obtained. Test materials were arranged in sets of six to eight materials per set. Each set of materials, with inclusion of at least two reference materials for the purpose of simultaneous calibration, was measured to obtain preliminary amperages. Four preliminary measures were performed per thickness, resulting in 24 per material, in a schedule designed to spread the potential effects of machine drift and other factors. The mean preliminary amperages were used to derive corrected Dk values according to American National Standards Institute (ANSI) Z80.20-1998, and the values were linearly calibrated using the measured and established Dk values of the reference materials. The resistance (t/Dk) vs. thickness (t) plots for the 37 test and seven reference materials were approximated linearly. In 54 of 57 linear regressions, the coefficients of determination (R2) were >0.96, and in 48 instances were >0.98. Fourteen Dk values from the current study and an earlier study were linearly correlated (R2 = 0.9846), with a slope close to unity (+1.056) and intercept close to zero (-0.292). Ten of the current values fell within 10% of their corresponding earlier values. Only three current Dk values fell outside of the ANSI Z80.20-1998 tolerance for Dk (+/-20%). Two of these Dk values met the product tolerance when an obvious outlying point was graphically identified and omitted from the linear resistance (t/Dk) vs. thickness (t) regression. Omission of a single outlying point from a linear resistance vs. thickness regression can help provide a more valid Dk value. The ANSI Z80.20-1998 tolerance of +/-20% on Dk and the measurement reproducibility of +/-10% were

  14. Therapeutic efficiency of sodium hyaluronate eye drops on dry eye in juvenile with myopia wearing rigid gas permeable contact lens

    Directory of Open Access Journals (Sweden)

    Bin Zhang

    2016-03-01

    Full Text Available AIM:To investigate the therapeutic efficiency of preservative-free sodium hyaluronate eye drops on dry eye in juvenile myopia wearing rigid gas permeable contact lens(RGP.METHODS:Ninety cases with dry eye related to wearing RGP in juvenile with myopia from January to May 2015 were selected. The patients aged 12.75±4.15 years old,with diopter of -3.50±1.50D as spherical equivalent and received normalized RGP. They were divided into 3 groups randomly,each group of 30 cases(60 eyes:group A used rewetting drops,1 drop each time,4 times per day; group B used preservative-free sodium hyaluronate eye drops(1g/L,1 drop each time,4 times per day; group C used rewetting drops at first, then sodium hyaluronate eye drops was used 15 minutes later.All cases had been detected and evaluated by subjective symptoms of dry eye,Schirmer I test(SⅠt,break-up time(BUTand corneal fluorescent staining,at pre-therapy and 1, 2, 4wk of post-therapy.RESULTS:The subjective symptoms of dry eye,corneal fluorescent staining and BUT of three groups had been obviously improved at 1wk after therapies than those before therapies(PP>0.05.Every index of the three groups measured at 2 and 4wk after treatments had no significant differences compared to those measured at 1wk(P>0.05.There was no significant difference on subjective symptoms,SⅠt and BUT between group A and B(P>0.05,except on corneal fluorescent staining, on which group B was superior to group A and on which the difference was significant(PPPCONCLUSION:Preservative-free sodium hyaluronate eye drops(1g/Lcan stabilize the tear film and promote the repair of corneal epithelial defects and significantly improve dry eye symptoms and signs in juvenile myopia wearing RGP,so it has certain clinical application value.

  15. Instrumentation for Measurement of Gas Permeability of Polymeric Membranes

    Science.gov (United States)

    Upchurch, Billy T.; Wood, George M.; Brown, Kenneth G.; Burns, Karen S.

    1993-01-01

    A mass spectrometric 'Dynamic Delta' method for the measurement of gas permeability of polymeric membranes has been developed. The method is universally applicable for measurement of the permeability of any gas through polymeric membrane materials. The usual large sample size of more than 100 square centimeters required for other methods is not necessary for this new method which requires a size less than one square centimeter. The new method should fulfill requirements and find applicability for industrial materials such as food packaging, contact lenses and other commercial materials where gas permeability or permselectivity properties are important.

  16. High Dk piggyback contact lens system for contact lens-intolerant keratoconus patients.

    Science.gov (United States)

    Sengor, Tomris; Kurna, Sevda Aydin; Aki, Suat; Ozkurt, Yelda

    2011-01-01

    The aim of the study was to examine the clinical success of high Dk (oxygen permeability) piggyback contact lens (PBCL) systems for the correction of contact lens intolerant keratoconus patients. Sixteen patients (29 eyes) who were not able to wear gas-permeable rigid lenses were included in this study. Hyper Dk silicone hydrogel (oxygen transmissibility or Dk/t = 150 units) and fluorosilicone methacrylate copolymer (Dk/t = 100 units) lenses were chosen as the PBCL systems. The clinical examinations included visual acuity and corneal observation by biomicroscopy, keratometer reading, and fluorescein staining before and after fitting the PBCL system. INDICATIONS FOR USING PBCL SYSTEM WERE: lens stabilization and comfort, improving comfort, and adding protection to the cone. Visual acuities increased significantly in all of the patients compared with spectacles (P = 0). Improvement in visual acuity compared with rigid lenses alone was recorded in 89.7% of eyes and no alteration of the visual acuity was observed in 10.3% of the eyes. Wearing time of PBCL systems for most of the patients was limited time (mean 6 months, range 3-12 months); thereafter they tolerated rigid lenses alone except for 2 patients. The PBCL system is a safe and effective method to provide centering and corneal protection against mechanical trauma by the rigid lenses for keratoconus patients and may increase contact lens tolerance.

  17. Rigid body formulation in a finite element context with contact interaction

    Science.gov (United States)

    Refachinho de Campos, Paulo R.; Gay Neto, Alfredo

    2018-03-01

    The present work proposes a formulation to employ rigid bodies together with flexible bodies in the context of a nonlinear finite element solver, with contact interactions. Inertial contributions due to distribution of mass of a rigid body are fully developed, considering a general pole position associated with a single node, representing a rigid body element. Additionally, a mechanical constraint is proposed to connect a rigid region composed by several nodes, which is useful for linking rigid/flexible bodies in a finite element environment. Rodrigues rotation parameters are used to describe finite rotations, by an updated Lagrangian description. In addition, the contact formulation entitled master-surface to master-surface is employed in conjunction with the rigid body element and flexible bodies, aiming to consider their interaction in a rigid-flexible multibody environment. New surface parameterizations are presented to establish contact pairs, permitting pointwise interaction in a frictional scenario. Numerical examples are provided to show robustness and applicability of the methods.

  18. Dynamic Multi-Rigid-Body Systems with Concurrent Distributed Contacts: Theory and Examples

    International Nuclear Information System (INIS)

    TRINKLE, JEFFREY C.; TZITZOURIS, J.A.; PANG, J.S.

    2001-01-01

    Consider a system of rigid bodies with multiple concurrent contacts. The multi-rigid-body contact problem is to predict the accelerations of the bodies and the normal friction loads acting at the contacts. This paper presents theoretical results for the multi-rigid-body contact problem under the assumptions that one or more contacts occur over locally planar, finite regions and that friction forces are consistent with the maximum work inequality. Existence and uniqueness results are presented for this problem under mild assumptions on the system inputs. In addition, the performance of two different time-stepping methods for integrating the dynamics are compared on two simple multi-body systems

  19. Gas and Water Permeability of Concrete

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.; Martin, P. L.; Romero, F. J.; Gutierrez-Rodirgo, V.; Barcala, J. M.

    2012-11-01

    The gas pressure of concrete samples was measured in an unsteady-state equipment working under low injection pressures and in a newly fine tuned steady-state setup working under different pressures. These measurements allowed the estimation of the intrinsic and relative gas permeability of the concrete and of the effect of boundary conditions on them. Permeability decreased with water content, but it was also greatly affected by the hydraulic history of concrete, i.e. if it had been previously dried or wetted. In particular, and for a given degree of saturation, the gas permeability of concrete previously saturated was lower than if the concrete had been just air dried or saturated after air drying. In any case, the gas permeability was about two orders of magnitude higher than the liquid water permeability (10-16 vs. 10-18 m2), probably due to the chemical reactions taking place during saturation (carbonation). The relative gas permeability of concrete increased sharply for water degrees of saturation smaller than 50%. The boundary conditions also affected the gas permeability, which seemed to be mostly conditioned by the back pressure and the confining pressure, increasing as the former increased and decreasing as the latter increased, i.e. decreasing as the effective pressure increased. Overall the increase of pressure head or injection pressure implied a decrease in gas permeability. External,microcracking during air-drying could not be ruled out as responsible for the decrease of permeability with confining pressure. The apparent permeability obtained applying the Klinkenberg method for a given effective pressure was only slightly smaller than the average of all the values measured for the same confining pressure range. For this reason it is considered that the Klinkenberg effect was not relevant in the range of pressures applied. (Author) 37 refs.

  20. Contact Lens Visual Rehabilitation in Keratoconus and Corneal Keratoplasty

    Directory of Open Access Journals (Sweden)

    Yelda Ozkurt

    2012-01-01

    Full Text Available Keratoconus is the most common corneal distrophy. It’s a noninflammatory progressive thinning process that leads to conical ectasia of the cornea, causing high myopia and astigmatism. Many treatment choices include spectacle correction and contact lens wear, collagen cross linking, intracorneal ring segments implantation and finally keratoplasty. Contact lenses are commonly used to reduce astigmatism and increase vision. There are various types of lenses are available. We reviewed soft contact lenses, rigid gas permeable contact lenses, piggyback contact lenses, hybrid contact lenses and scleral-semiscleral contact lenses in keratoconus management. The surgical option is keratoplasty, but even after sutur removal, high astigmatism may stil exists. Therefore, contact lens is an adequate treatment option to correct astigmatism after keratoplasty.

  1. Frictionless contact of a rigid punch indenting a transversely isotropic elastic layer

    Directory of Open Access Journals (Sweden)

    Rajesh Patra

    2016-03-01

    Full Text Available This article is concerned with the study of frictionless contact between a rigid punch and a transversely isotropic elastic layer. The rigid punch is assumed to be axially symmetric and is being pressed towards the layer by an applied concentrated load. The layer is resting on a rigid base and is assumed to be ufficiently thick in comparison with the amount of indentation by the rigid punch. The relationship between the applied load $P$ and the contact area is obtained by solving the mathematically formulated problem through use of Hankel transform of different order. Effect of indentation on the distribution of normal stress at the surface as well as the relationship between the applied load and the area of contact have been shown graphically.

  2. Towards a Biohybrid Lung: Endothelial Cells Promote Oxygen Transfer through Gas Permeable Membranes.

    Science.gov (United States)

    Menzel, Sarah; Finocchiaro, Nicole; Donay, Christine; Thiebes, Anja Lena; Hesselmann, Felix; Arens, Jutta; Djeljadini, Suzana; Wessling, Matthias; Schmitz-Rode, Thomas; Jockenhoevel, Stefan; Cornelissen, Christian Gabriel

    2017-01-01

    In patients with respiratory failure, extracorporeal lung support can ensure the vital gas exchange via gas permeable membranes but its application is restricted by limited long-term stability and hemocompatibility of the gas permeable membranes, which are in contact with the blood. Endothelial cells lining these membranes promise physiological hemocompatibility and should enable prolonged application. However, the endothelial cells increase the diffusion barrier of the blood-gas interface and thus affect gas transfer. In this study, we evaluated how the endothelial cells affect the gas exchange to optimize performance while maintaining an integral cell layer. Human umbilical vein endothelial cells were seeded on gas permeable cell culture membranes and cultivated in a custom-made bioreactor. Oxygen transfer rates of blank and endothelialized membranes in endothelial culture medium were determined. Cell morphology was assessed by microscopy and immunohistochemistry. Both setups provided oxygenation of the test fluid featuring small standard deviations of the measurements. Throughout the measuring range, the endothelial cells seem to promote gas transfer to a certain extent exceeding the blank membranes gas transfer performance by up to 120%. Although the underlying principles hereof still need to be clarified, the results represent a significant step towards the development of a biohybrid lung.

  3. Compact rock material gas permeability properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huanling, E-mail: whl_hm@163.com [Key Laboratory of Coastal Disaster and Defence, Ministry of Education, Hohai University, Nanjing 210098 (China); LML, University of Lille, Cite Scientifique, 59655 Villeneuve d’Ascq (France); Xu, Weiya; Zuo, Jing [Institutes of Geotechnical Engineering, Hohai University, Nanjing 210098 (China)

    2014-09-15

    Natural compact rocks, such as sandstone, granite, and rock salt, are the main materials and geological environment for storing underground oil, gas, CO{sub 2,} shale gas, and radioactive waste because they have extremely low permeabilities and high mechanical strengths. Using the inert gas argon as the fluid medium, the stress-dependent permeability and porosity of monzonitic granite and granite gneiss from an underground oil storage depot were measured using a permeability and porosity measurement system. Based on the test results, models for describing the relationships among the permeability, porosity, and confining pressure of rock specimens were analyzed and are discussed. A power law is suggested to describe the relationship between the stress-dependent porosity and permeability; for the monzonitic granite and granite gneiss (for monzonitic granite (A-2), the initial porosity is approximately 4.05%, and the permeability is approximately 10{sup −19} m{sup 2}; for the granite gneiss (B-2), the initial porosity is approximately 7.09%, the permeability is approximately 10{sup −17} m{sup 2}; and the porosity-sensitivity exponents that link porosity and permeability are 0.98 and 3.11, respectively). Compared with moderate-porosity and high-porosity rocks, for which φ > 15%, low-porosity rock permeability has a relatively lower sensitivity to stress, but the porosity is more sensitive to stress, and different types of rocks show similar trends. From the test results, it can be inferred that the test rock specimens’ permeability evolution is related to the relative particle movements and microcrack closure.

  4. High-Dk piggyback contact lenses over Intacs for keratoconus: a case report.

    Science.gov (United States)

    Smith, Kyle A; Carrell, James D

    2008-07-01

    The authors describe a case of a keratoconic patient with Intacs fitted with a high-Dk piggyback contact lens system. A 41-year-old man presented to the clinic 1 week after Intacs surgery for keratoconus with complaints of poor visual acuity (VA) and monocular polyopia OU. The patient was corrected to 20/30 in both eyes with rigid gas permeable contact lenses but could not tolerate the lenses for more than 8 hours OD and 2 hours OS. The patient was then successfully fit with a high-Dk piggyback contact lens system. The patient was able to wear the piggyback contact lenses comfortably 12 to 18 hours per day and was corrected to 20/25 OD, 20/30 OS, and 20/20 OU. Patients with Intacs for keratoconus may require a combination of soft and rigid contact lenses for the best possible VA. Contact lens fitting with a high-Dk piggyback contact lens system can provide optimal comfort, corneal health, and VA for patients with Intacs for keratoconus.

  5. Surface modification of fluorosilicone acrylate RGP contact lens via low-temperature argon plasma

    International Nuclear Information System (INIS)

    Yin Shiheng; Wang Yingjun; Ren Li; Zhao Lianna; Kuang Tongchun; Chen Hao; Qu Jia

    2008-01-01

    A fluorosilicone acrylate rigid gas permeable (RGP) contact lens was modified via argon plasma to improve surface hydrophilicity and resistance to protein deposition. The influence of plasma treatment on surface chemical structure, hydrophilicity and morphology of RGP lens was investigated by X-ray photoelectron spectrometer (XPS), contact angle measurements and scanning electron microscope (SEM), respectively. The contact angle results showed that the hydrophilicity of the contact lens was improved after plasma treatment. XPS results indicated that the incorporation of oxygen-containing groups on surface and the transformation of silicone into hydrophilic silicate after plasma treatment are the main reasons for the surface hydrophilicity improvement. SEM results showed that argon plasma with higher power could lead to surface etching

  6. Contact point generation for convex polytopes in interactive rigid body dynamics

    DEFF Research Database (Denmark)

    Silcowitz-Hansen, Morten; Abel, Sarah Maria Niebe; Erleben, Kenny

    When computing contact forces in rigid body dynamics systems, most state-of-the-art solutions use iterative methods such as the projected Gauss–Seidel (PGS) method. Methods such as the PGS method are preferred for their robustness. However, the time-critical nature of interactive applications...... combined with the linear convergence rates of such methods, will often result in visual artifacts in the final simulation. With this paper, we address an issue which is of major impact on the animation quality, when using methods such as the PGS method. The issue is robust generation of contact points...... for convex polytopes. A novel contact point generation method is presented, which is based on growth distances and Gauss maps. We demonstrate improvements when using our method in the context of interactive rigid body simulation...

  7. Clinical research on high oxygen permeable contact lens used after photorefractive keratectomy surgery

    Directory of Open Access Journals (Sweden)

    Hao-Jiang Yang

    2013-07-01

    Full Text Available AIM: To evaluate the outcome of high oxygen permeable contact lens used after photorefractive keratectomy(PRKsurgery.METHODS: Totally 95 patients(190 eyesafter PRK were included. Patients were randomly assigned to wear high oxygen permeable contact lens in one eye and normal lens in the fellow eye after surgery. The subjective symptoms and corneal epithelial status after PRK were evaluated. Uncorrected visual acuity(UCVAand haze were assessed at 6 months after PRK.RESULTS: Complaints of blurred vision, pain and photophobia were statistically more among the normal lens group than high oxygen permeable contact lens group(PPP=0.35. There was no difference in UCVA and haze 6 months after surgery(P=0.55. CONCLUSION: High oxygen permeable contact lens can significantly produce less the corneal irritated symptoms, reduce the discomfort feeling and promote healing of corneal epithelium after PRK.

  8. Fitting an MSD (mini scleral design) rigid contact lens in advanced keratoconus with INTACS.

    Science.gov (United States)

    Dalton, Kristine; Sorbara, Luigina

    2011-12-01

    Keratoconus is a bilateral degenerative disease characterized by a non-inflammatory, progressive central corneal ectasia (typically asymmetric) and decreased vision. In its early stages it may be managed with spectacles and soft contact lenses but more commonly it is managed with rigid contact lenses. In advanced stages, when contact lenses can no longer be fit, have become intolerable, or corneal damage is severe, a penetrating keratoplasty is commonly performed. Alternative surgical techniques, such as the use of intra-stromal corneal ring segments (INTACS) have been developed to try and improve the fit of rigid contact lenses in keratoconic patients and avoid penetrating keratoplasties. This case report follows through the fitting of rigid contact lenses in an advanced keratoconic cornea after an INTACS procedure and discusses clinical findings, treatment options, and the use of mini-scleral and scleral lens designs as they relate to the challenges encountered in managing such a patient. Mini-scleral and scleral lenses are relatively easy to fit, and can be of benefit to many patients, including advanced keratoconic patients, post-INTAC patients and post-penetrating keratoplasty patients. 2011 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  9. GAS-FOVEAL CONTACT

    DEFF Research Database (Denmark)

    Alberti, Mark; la Cour, Morten

    2018-01-01

    PURPOSE: To compare gas-foveal contact in face-down positioning (FDP) and nonsupine positioning (NSP), to analyze causes of gas-foveal separation and to determine how gas-foveal contact affects clinical outcome after idiopathic macular hole repair. METHODS: Single center, randomized controlled...... study. Participants with an idiopathic macular hole were allocated to either FDP or NSP. Primary outcome was gas-foveal contact, calculated by analyzing positioning in relation to intraocular gas fill. Positioning was measured with an electronic device recording positioning for 72 hours postoperatively....... RESULTS: Positioning data were available for 33/35 in the FDP group and 35/37 in the NSP group, thus results are based on 68 analyzed participants. Median gas-foveal contact was 99.82% (range 73.6-100.0) in the FDP group and 99.57% (range 85.3-100.0) in the NSP group (P = 0.22). In a statistical model...

  10. A Systematic Procedure to Describe Shale Gas Permeability Evolution during the Production Process

    Science.gov (United States)

    Jia, B.; Tsau, J. S.; Barati, R.

    2017-12-01

    Gas flow behavior in shales is complex due to the multi-physics nature of the process. Pore size reduces as the in-situ stress increases during the production process, which will reduce intrinsic permeability of the porous media. Slip flow/pore diffusion enhances gas apparent permeability, especially under low reservoir pressures. Adsorption not only increases original gas in place but also influences gas flow behavior because of the adsorption layer. Surface diffusion between free gas and adsorption phase enhances gas permeability. Pore size reduction and the adsorption layer both have complex impacts on gas apparent permeability and non-Darcy flow might be a major component in nanopores. Previously published literature is generally incomplete in terms of coupling of all these four physics with fluid flow during gas production. This work proposes a methodology to simultaneously take them into account to describe a permeability evolution process. Our results show that to fully describe shale gas permeability evolution during gas production, three sets of experimental data are needed initially: 1) intrinsic permeability under different in-situ stress, 2) adsorption isotherm under reservoir conditions and 3) surface diffusivity measurement by the pulse-decay method. Geomechanical effects, slip flow/pore diffusion, adsorption layer and surface diffusion all play roles affecting gas permeability. Neglecting any of them might lead to misleading results. The increasing in-situ stress during shale gas production is unfavorable to shale gas flow process. Slip flow/pore diffusion is important for gas permeability under low pressures in the tight porous media. They might overwhelm the geomechanical effect and enhance gas permeability at low pressures. Adsorption layer reduces the gas permeability by reducing the effective pore size, but the effect is limited. Surface diffusion increases gas permeability more under lower pressures. The total gas apparent permeability might

  11. Measurements of gas permeability and non-Darcy flow in gas-water-hydrate systems

    Energy Technology Data Exchange (ETDEWEB)

    Ersland, G.; Husebo, J.; Graue, A.; Kvamme, B. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology; Baldwin, B. [Green Country Petrophysics LLC, Dewey, OK (United States); Stevens, J.; Howard, J. [ConocoPhillips, OK (United States)

    2008-07-01

    Storage of carbon dioxide (CO{sub 2}) in natural gas hydrate reservoirs may offer stable long-term storage of a greenhouse gas while benefiting from methane production, without requiring heat. By exposing hydrate to a thermodynamically preferred hydrate former, CO{sub 2}, the hydrate may be maintained macroscopically in the solid state and retain the stability of the formation. However, there is concern over the flow capacity in such reservoirs. This depends on several factors, notably thermodynamic destabilization of hydrate in small pores due to capillary effects; the presence of liquid channels separating the hydrate from the mineral surfaces; and, the connectivity of gas or liquid filled pores and channels. This paper described a technique for measuring gas permeability in gas-water-hydrate systems. It reported on several experiments that measured gas permeability during stages of hydrate growth in sandstone core plugs. Interactions between minerals and surrounding molecules were also discussed. The formation of methane hydrate in porous media was monitored and quantified with magnetic resonance imaging (MRI). MRI images of hydrate growth within the porous rock were provided along with measurements of gas permeability and non-Darcy flow effects at various hydrate saturations. Gas permeability was measured at steady state flow of methane through the hydrate-bearing core sample. Significant gas permeability was recorded for porous sandstone even when hydrates occupied up to 60 per cent of the pore space. It was concluded that MRI imaging can be used effectively to map and quantify hydrate saturation in sandstone core plugs. 27 refs., 2 tabs., 10 figs.

  12. Detection of gas-permeable fuel particles for highl 7490 temperature gas-cooled reactors

    International Nuclear Information System (INIS)

    Thiele, B.A.; Stinton, D.P.; Costanzo, D.A.

    1980-01-01

    Fuel for High-Temperature Gas-Cooled Reactors (HTGR) consists of uranium oxide-carbide and thoria microspheres coated with layers of pyrolytic carbon and silicon carbide. The pyrolytic carbon coatings must be gas-tight to perform properly during irradiation. Therefore, particles must be carefully characterized to determine the number of defective particles (ie bare kernels, and cracked or permeable coatings). Although techniques are available to determine the number of bare kernels or cracked coatings, no reliable technique has been available to measure coating permeability. This work describes a technique recently developed to determine whether coatings for a batch of particles are gas-tight or permeable. Although most of this study was performed on Biso-coated particles, the technique applies equally well to Triso-coated particles. About 150 randomly selected Biso-particle batches were studied in this work. These batches were first subjected to an 18-hr chlorination at 15000C, and the volatile thorium tetrachloride released through cracked or very permeable coatings was measured versus chlorination time. Chlorinated batches were also radiographed to detect any thorium that had migrated from the kernel into the coatings. From this work a technique was developed to determine coating permeability. This consists of an 18-hr chlorination of multiple samples without measurement of the heavy metal released. Each batch is then radiographed and the heavy metal diffusion within each particle is examined so it can be determined if a particle batch is permeable, slightly permeable, or gas-tight. (author)

  13. Compositional simulations of producing oil-gas ratio behaviour in low permeable gas condensate reservoir

    OpenAIRE

    Gundersen, Pål Lee

    2013-01-01

    Master's thesis in Petroleum engineering Gas condensate flow behaviour below the dew point in low permeable formations can make accurate fluid sampling a difficult challenge. The objective of this study was to investigate the producing oil-gas ratio behaviour in the infinite-acting period for a low permeable gas condensate reservoir. Compositional isothermal flow simulations were performed using a single-layer, radial and two-dimensional, gas condensate reservoir model with low permeabili...

  14. Gas Permeability Evolution Mechanism and Comprehensive Gas Drainage Technology for Thin Coal Seam Mining

    Directory of Open Access Journals (Sweden)

    Fangtian Wang

    2017-09-01

    Full Text Available A thin coal seam mined as a protective coal seam above a gas outburst coal seam plays a central role in decreasing the degree of stress placed on a protected seam, thus increasing gas permeability levels and desorption capacities to dramatically eliminate gas outburst risk for the protected seam. However, when multiple layers of coal seams are present, stress-relieved gas from adjacent coal seams can cause a gas explosion. Thus, the post-drainage of gas from fractured and de-stressed strata should be applied. Comprehensive studies of gas permeability evolution mechanisms and gas seepage rules of protected seams close to protective seams that occur during protective seam mining must be carried out. Based on the case of the LongWall (LW 23209 working face in the Hancheng coal mine, Shaanxi Province, this paper presents a seepage model developed through the FLAC3D software program (version 5.0, Itasca Consulting Group, Inc., Minneapolis, MI, USA from which gas flow characteristics can be reflected by changes in rock mass permeability. A method involving theoretical analysis and numerical simulation was used to analyze stress relief and gas permeability evolution mechanisms present during broken rock mass compaction in a goaf. This process occurs over a reasonable amount of extraction time and in appropriate locations for comprehensive gas extraction technologies. In using this comprehensive gas drainage technological tool, the safe and efficient co-extraction of thin coal seams and gas resources can be realized, thus creating a favorable environment for the safe mining of coal and gas outburst seams.

  15. Degassing, gas retention and release in Fe(0) permeable reactive barriers.

    Science.gov (United States)

    Ruhl, Aki S; Jekel, Martin

    2014-04-01

    Corrosion of Fe(0) has been successfully utilized for the reductive treatment of multiple contaminants. Under anaerobic conditions, concurrent corrosion leads to the generation of hydrogen and its liberation as a gas. Gas bubbles are mobile or trapped within the irregular pore structure leading to a reduction of the water filled pore volume and thus decreased residence time and permeability (gas clogging). With regard to the contaminant transport to the reactive site, the estimation of surface properties of the reactive material indicated that individual gas bubbles only occupied minor contact areas of the reactive surface. Quantification of gas entrapment by both gravimetrical and tracer investigations revealed that development of preferential flow paths was not significant. A novel continuous gravimetrical method was implemented to record variations in gas entrapment and gas bubble releases from the reactive filling. Variation of grain size fractions revealed that the pore geometry had a significant impact on gas release. Large pores led to the release of comparably large gas amounts while smaller volumes were released from finer pores with a higher frequency. Relevant processes are explained with a simplified pictorial sequence that incorporates relevant mechanisms. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Assessment of porous material anisotropy and its effect on gas permeability

    Science.gov (United States)

    Wałowski, Grzegorz

    2017-10-01

    The results of experimental research upon the assessment of porous material anisotropy and its effect on gas permeability of porous materials with respect to the gas flow. The conducted research applied to natural materials with an anisotropic gap-porous structure and - for comparative purposes - to model materials such as coke, pumice and polyamide agglomerates. The research was conducted with the use of a special test stand that enables measuring the gas permeability with respect to three flow orientations compared with symmetric cubic-shaped samples. The research results show an explicit impact of the flow direction on the permeability of materials porous, which results from their anisotropic internal structures. The anisotropy coefficient and permeability effective coefficient of such materials was determined and an experimental evaluation of the value of this coefficient was conducted with respect to the gas stream and the total pressure drop across the porous deposit. The process of gas permeability was considered in the category of hydrodynamics of gas flow through porous deposits. It is important to broaden the knowledge of gas hydrodynamics assessment in porous media so far unrecognised for the development of a new generation of clean energy sources, especially in the context of biogas or raw gas production.

  17. Gas permeability of ice-templated, unidirectional porous ceramics

    Science.gov (United States)

    Seuba, Jordi; Deville, Sylvain; Guizard, Christian; Stevenson, Adam J.

    2016-01-01

    We investigate the gas flow behavior of unidirectional porous ceramics processed by ice-templating. The pore volume ranged between 54% and 72% and pore size between 2.9 ?m and 19.1 ?m. The maximum permeability (?? m?) was measured in samples with the highest total pore volume (72%) and pore size (19.1 ?m). However, we demonstrate that it is possible to achieve a similar permeability (?? m?) at 54% pore volume by modification of the pore shape. These results were compared with those reported and measured for isotropic porous materials processed by conventional techniques. In unidirectional porous materials tortuosity (?) is mainly controlled by pore size, unlike in isotropic porous structures where ? is linked to pore volume. Furthermore, we assessed the applicability of Ergun and capillary model in the prediction of permeability and we found that the capillary model accurately describes the gas flow behavior of unidirectional porous materials. Finally, we combined the permeability data obtained here with strength data for these materials to establish links between strength and permeability of ice-templated materials.

  18. The Researches on Reasonable Well Spacing of Gas Wells in Deep and low Permeability Gas Reservoirs

    Science.gov (United States)

    Bei, Yu Bei; Hui, Li; Lin, Li Dong

    2018-06-01

    This Gs64 gas reservoir is a condensate gas reservoir which is relatively integrated with low porosity and low permeability found in Dagang Oilfield in recent years. The condensate content is as high as 610g/m3. At present, there are few reports about the well spacing of similar gas reservoirs at home and abroad. Therefore, determining the reasonable well spacing of the gas reservoir is important for ensuring the optimal development effect and economic benefit of the gas field development. This paper discusses the reasonable well spacing of the deep and low permeability gas reservoir from the aspects of percolation mechanics, gas reservoir engineering and numerical simulation. considering there exist the start-up pressure gradient in percolation process of low permeability gas reservoir, this paper combined with productivity equation under starting pressure gradient, established the formula of gas well spacing with the formation pressure and start-up pressure gradient. The calculation formula of starting pressure gradient and well spacing of gas wells. Adopting various methods to calculate values of gas reservoir spacing are close to well testing' radius, so the calculation method is reliable, which is very important for the determination of reasonable well spacing in low permeability gas reservoirs.

  19. Permeability of volcanic rocks to gas and water

    Science.gov (United States)

    Heap, M. J.; Reuschlé, T.; Farquharson, J. I.; Baud, P.

    2018-04-01

    The phase (gas or liquid) of the fluids within a porous volcanic system varies in both time and space. Laboratory experiments have shown that gas and water permeabilities can differ for the same rock sample, but experiments are biased towards rocks that contain minerals that are expected react with the pore fluid (such as the reaction between liquid water and clay). We present here the first study that systematically compares the gas and water permeability of volcanic rocks. Our data show that permeabilities to argon gas and deionised water can differ by a factor between two and five in two volcanic rocks (basalt and andesite) over a confining pressure range from 2 to 50 MPa. We suggest here that the microstructural elements that offer the shortest route through the sample-estimated to have an average radius 0.1-0.5 μm using the Klinkenberg slip factor-are accessible to gas, but restricted or inaccessible to water. We speculate that water adsorption on the surface of these thin microstructural elements, assumed here to be tortuous/rough microcracks, reduces their effective radius and/or prevents access. These data have important implications for fluid flow and therefore the distribution and build-up of pore pressure within volcanic systems.

  20. Contact lenses fitting after intracorneal ring segments implantation in keratoconus

    Directory of Open Access Journals (Sweden)

    Luciane Bugmann Moreira

    2013-08-01

    Full Text Available PURPOSE: Evaluate contact lenses fitting after intracorneal ring implantation for keratoconus, its visual acuity and comfort. METHODS: Retrospective study of patients undergoing contact lenses fitting, after intracorneal ring for keratoconus. The criterion for contact lens fitting was unsatisfactory visual acuity with spectacle correction as referred by the patients. All patients were intolerants to contact lenses prior to intracorneal implantation. Visual acuity analysis was done by conversion of Snellen to logMAR scales. The comfort was evaluated according subjective questioning of good, medium or poor comfort. RESULTS: Nineteen patients were included in the study. Two patients (10.5% did not achieved good comfort with contact lenses and underwent penetrating keratoplasties. All the others 17 patients showed good or medium comfort. Four rigid gas-permeable contact lenses were fitted, one piggyback approach, 3 toric soft contact lenses, 2 soft lenses specially design for keratoconus and 7 disposable soft lenses. The average visual acuity improved from 0.77 ± 0.37 to 0.19 ± 0.13 logMAR units after contact lenses fitting. CONCLUSION: Contact lens fitting after intracorneal ring is possible, provides good comfort, improves visual acuity, and therefore, may postpone the need for penetrating keratoplasty.

  1. Plasma surface modification of rigid contact lenses decreases bacterial adhesion.

    Science.gov (United States)

    Wang, Yingming; Qian, Xuefeng; Zhang, Xiaofeng; Xia, Wei; Zhong, Lei; Sun, Zhengtai; Xia, Jing

    2013-11-01

    Contact lens safety is an important topic in clinical studies. Corneal infections usually occur because of the use of bacteria-carrying contact lenses. The current study investigated the impact of plasma surface modification on bacterial adherence to rigid contact lenses made of fluorosilicone acrylate materials. Boston XO and XO2 contact lenses were modified using plasma technology (XO-P and XO2-P groups). Untreated lenses were used as controls. Plasma-treated and control lenses were incubated in solutions containing Staphylococcus aureus or Pseudomonas aeruginosa. MTT colorimetry, colony-forming unit counting method, and scanning electron microscopy were used to measure bacterial adhesion. MTT colorimetry measurements showed that the optical density (OD) values of XO-P and XO2-P were significantly lower than those of XO and XO2, respectively, after incubation with S. aureus (P lenses and to the XO2-P versus XO2 lenses incubated with S. aureus (P lenses incubated with P. aeruginosa (P lenses. Plasma surface modification can significantly decrease bacterial adhesion to fluorosilicone acrylate contact lenses. This study provides important evidence of a unique benefit of plasma technology in contact lens surface modification.

  2. Soil gas measurements at high permeabilities and below foundation depth

    International Nuclear Information System (INIS)

    Johner, H.U; Surbeck, H.

    2000-01-01

    We started a project of soil gas measurements beneath houses. Since the foundations of houses often lie deeper than 0.5 to 1 m - the depth where soil gas measurements are often made - the first approach was to apply the method developed previously to deeper soil layers. The radon availability index (RAI), which was defined empirically, proved to be a reliable indicator for radon problems in nearby houses. The extreme values of permeability, non-Darcy flow and scale dependence of permeability stimulated the development of a multi-probe method. A hydrological model was applied to model the soil gas transport. The soil gas measurements below foundation depth provided a wealth of new information. A good classification of soil properties could be achieved. If soil gas measurements are to be made, the low permeability layer has to be traversed. A minimum depth of 1 .5 m is suggested, profiles to below the foundation depth are preferable. There are also implications for mitigation works. A sub-slab suction system should reach the permeable layer to function well. This also holds for radon wells. If a house is located on a slope, it is most convenient to install the sub-slab suction system on the hillside, as the foundation reaches the deepest levels there

  3. How soft is that pillow? The perceptual localization of the hand and the haptic assessment of contact rigidity.

    Science.gov (United States)

    Pressman, Assaf; Karniel, Amir; Mussa-Ivaldi, Ferdinando A

    2011-04-27

    A new haptic illusion is described, in which the location of the mobile object affects the perception of its rigidity. There is theoretical and experimental support for the notion that limb position sense results from the brain combining ongoing sensory information with expectations arising from prior experience. How does this probabilistic state information affect one's tactile perception of the environment mechanics? In a simple estimation process, human subjects were asked to report the relative rigidity of two simulated virtual objects. One of the objects remained fixed in space and had various coefficients of stiffness. The other virtual object had constant stiffness but moved with respect to the subjects. Earlier work suggested that the perception of an object's rigidity is consistent with a process of regression between the contact force and the perceived amount of penetration inside the object's boundary. The amount of penetration perceived by the subject was affected by varying the position of the object. This, in turn, had a predictable effect on the perceived rigidity of the contact. Subjects' reports on the relative rigidity of the object are best accounted for by a probabilistic model in which the perceived boundary of the object is estimated based on its current location and on past observations. Therefore, the perception of contact rigidity is accounted for by a stochastic process of state estimation underlying proprioceptive localization of the hand.

  4. GAS PERMEABILITY OF GEOSYNTHETIC CLAY LINERS

    Directory of Open Access Journals (Sweden)

    Helena Vučenović

    2017-01-01

    Full Text Available Geosynthetic clay liners (GCL are manufactured hydraulic barriers consisting of mineral and geosynthetic components. They belong to a group of geosynthetic products whose primary purpose is to seal and they have been used in many geotechnical and hydrotechnical applications, landfi lls and liquid waste lagoons for quite a while. They are used in landfill final cover systems to prevent the infi ltration of precipitation into the landfi ll body and the penetration of gases and liquids from the landfill into the atmosphere and environment. Laboratory and fi eld research and observations on regulated landfi lls have proven the eff ectiveness of GCL as a barrier for the infi ltration of precipitation into the landfi ll body as well as the drainage of fl uid beneath the landfill. Due to the presence of high concentrations of gases in the landfill body, there is a growing interest in determining the efficiency of GCL as a gas barrier. It was not until the last twenty years that the importance of this topic was recognized. In this article, current GCL gas permeability studies, the testing methods and test results of gas permeability in laboratory conditions are described.

  5. A soft-rigid contact model of MPM for granular flow impact on retaining structures

    Science.gov (United States)

    Li, Xinpo; Xie, Yanfang; Gutierrez, Marte

    2018-02-01

    Protective measures against hazards associated with rapid debris avalanches include a variety of retaining structures such as rock/boulder fences, gabions, earthfill barriers and retaining walls. However, the development of analytical and numerical methods for the rational assessment of impact force generated by granular flows is still a challenge. In this work, a soft-rigid contact model is built under the coding framework of MPM which is a hybrid method with Eulerian-Lagrangian description. The soft bodies are discretized into particles (material points), and the rigid bodies are presented by rigid node-based surfaces. Coulomb friction model is used to implement the modeled contact mechanics, and a velocity-dependent friction coefficient is coupled into the model. Simulations of a physical experiment show that the peak and residual value of impact forces are well captured by the MPM model. An idealized scenario of debris avalanche flow down a hillslope and impacting on a retaining wall are analyzed using the MPM model. The calculated forces can provide a quantitative estimate from which mound design could proceed for practical implementation in the field.

  6. Effect of temperature on the permeability of gas adsorbed coal under triaxial stress conditions

    Science.gov (United States)

    Li, Xiangchen; Yan, Xiaopeng; Kang, Yili

    2018-04-01

    The combined effects of gas sorption, stress and temperature play a significant role in the changing behavior of gas permeability in coal seams. The effect of temperature on nitrogen and methane permeability of naturally fractured coal is investigated. Coal permeability, P-wave velocity and axial strain were simultaneously measured under two effective stresses and six different temperatures. The results showed that the behavior of nitrogen and methane permeability presented nonmonotonic changes with increasing temperature. The variation in the P-wave velocity and axial strain showed a good correspondence with coal permeability. A higher effective stress limited the bigger deformation and caused the small change in permeability. Methane adsorption and desorption significantly influence the mechanical properties of coal and play an important role in the variations in coal permeability. The result of coal permeability during a complete stress-strain process showed that the variation in permeability is determined by the evolution of the internal structure. The increase in the temperature of the gas saturated coal causes the complex interaction between matrix swelling, matrix shrinkage and micro-fracture generation, which leads to the complex changes in coal structure and permeability. These results are helpful to understand the gas transport mechanism for exploiting coal methane by heat injection.

  7. Reduction in ionic permeability of a silicone hydrogel contact lenses after one month of daily wear

    International Nuclear Information System (INIS)

    Ferreira da Silva, Ana Rita; González-Méijome, José M; Compañ, Vicente

    2015-01-01

    Purpose. To compare the ionic permeability using the ionoflux method of new and worn samples of a silicone hydrogel contact lens material. Methods. An ionoflux experimental setup was established to measure the ionic permeability (NaCl) of soft contact lenses. Samples of a silicone hydrogel lens (Comfilcon A, Coopervision, Pleasanton, CA) with optical powers of −1.00, −1.50 and −4.75 diopters (D) were used in this study. Three samples of each power were measured after being worn for one month on a daily wear basis. Lenses were cleaned and disinfected every night using multipurpose disinfecting solutions. Three samples of new lenses from the same batch and the same optical power were also measured to evaluate the effect of lens wear on the ionic permeability of the lens material. Before measurement, the lenses were equilibrated with a 1 M NaCl solution during one week before of each measurement. Results. Lens power had minimal effect on the ionic permeability of a modern silicone hydrogel contact lens with the −1.00 lens having a 15% lower permeability compared to the other two lenses. After one month of lens wear the apparent ionic permeability for lenses with −1.50 D decreased by 15%. In the case of −1.00 and −4.75 D lenses there was a decrease of 26%. Conclusions. The ionic permeability of silicone hydrogel lenses of different optical powers was not significantly different. Worn lenses present a significant reduction of the ionic permeability after a month of wear. The potential effect this reduction on lens movement and discomfort associated to lens wear should be further evaluated. (paper)

  8. Study on the surface of fluorosilicone acrylate RGP contact lens treated by low-temperature nitrogen plasma

    International Nuclear Information System (INIS)

    Ren Li; Yin Shiheng; Zhao Lianna; Wang Yingjun; Chen Hao; Qu Jia

    2008-01-01

    In order to improve the surface hydrophilicity of fluorosilicone acrylate rigid gas permeable (RGP) contact lens, low temperature nitrogen plasma was used to modify the lens surface. Effects of plasma conditions on the surface structures and properties were investigated. Results indicated that the surface hydrophilicity of RGP contact lens was significantly improved after treatment. X-ray photoelectron spectroscopy (XPS) results showed that the nitrogen element was successfully incorporated into the surface. Furthermore, some new bonds such as N-C=O, F - and silicate were formed on the lens surface after nitrogen plasma treatment, which could result in the improvement of the surface hydrophilicity. Scanning electronic microscope (SEM) results indicated that nitrogen plasma with moderate power could make the surface smoother in some degree, while plasma with higher power could etch the surface

  9. Oxygen permeability of the pigmented material used in cosmetic daily disposable contact lenses

    Directory of Open Access Journals (Sweden)

    Galas S

    2016-12-01

    Full Text Available Stephen Galas, Lenora L Copper Johnson & Johnson Vision Care Inc., Jacksonville, FL, USA Purpose: To evaluate the individual contributions of pigment colorant and packing solution containing polyvinyl pyrrolidone (PVP on the oxygen permeability (Dk of a cosmetic printed etafilcon A daily disposable contact lens packaged with PVP. Method: The oxygen transport of a contact lens is evaluated through the central optical zone of the lens. Cosmetic printed contact lenses contain pigment colorant in the periphery or mid-periphery of the lens. Therefore, to assess the impact of cosmetic print on oxygen permeability, special lenses need to be produced that contain the colorant within the central optical zone. This technique was used to obtain multiple measurements of nonedge-corrected Dk/t of both the center pigmented lens and its nonpigmented equivalent, using a polarographic measurement described in International Organization for Standardization (ISO 18369-4:2006(E, and the Dk derived for each measurement is corrected for edge effect. In addition, the edge-corrected Dk values of lenses made from the same monomer batch were measured. The lenses were packaged and autoclaved with and without proprietary technology which embeds PVP in the contact lens during autoclaving. The resulting Dk value of the printed lens material was then used with thickness data to generate true Dk/t profiles for a given lens power. Results: The edge-corrected Dk of the printed etafilcon A lens with offset pigment colorant was measured to be 19.7×10-11 (cm2/s (mL O2/mL·mmHg at 35°C. This was within ±20% tolerance range as specified in ISO 18369-2:2012(E for the edge-corrected Dk of the nonpigmented etafilcon A control lens evaluated during the same session, 19.5×10-11 (cm2/s (mL O2/mL·mmHg. The edge-corrected Dk values of the lenses packaged with PVP (mean 20.1, standard deviation [SD] 0.3 were also within the ±20% tolerance range compared to those packaged without PVP

  10. Gas and water permeability of concrete for reactor buildings small specimens

    International Nuclear Information System (INIS)

    Mills, R.H.

    1986-03-01

    The effect on permeability of artifical aging by drying shrinkage and by freeze-thaw was determined by observing mass transfer of gas and water under a pressure gradient. It was found that damage due to freeze-thaw was negligible but that cracking around aggregate caused by drying shrinkage resulted in significantly increased permeability to both gas and water. The absence of freeze-thaw damage was attributed to self-dessication. Since the concrete was not exposed to an external source of water, the chemical reaction was sustained by consumption of mixing water. The resulting air voids were, apparently, sufficient to absorb expansive pressures due to ice formation. The response to lateral prestress was different for cracked and uncracked concrete. Although, in all cases, increased prestress resulted in reduced leakage, the effect was stronger in cracked concrete. Mean pore diameter as determined by gas diffusion was not, however, substantially affected because the leakage in cracked concrete remained very low. Reinforcing steel did not have a great influence on permeability of small specimens. Gas transmission through concrete was strongly influenced by moisture content. Free moisture constituted a barrier to gas flow, acting as a virtual solid. This is important since aging of concrete results in reduced free moisture. Ultrasonic pulse velocity appeared to vary with moisture content and porosity of concrete in the same way as gas permeability and gave promise of being effective for in-situ monitoring of concrete in reactor buildings

  11. Recovery of ammonia and phosphate minerals from swine wastewater using gas-permeable membranes

    Science.gov (United States)

    Gas-permeable membrane technology is useful to recover ammonia from liquid manures. In this study, phosphorus (P) recovery via magnesium chloride precipitation was enhanced by combining it with ammonia recovery through gas-permeable membranes. Anaerobically digested swine effluent containing approx...

  12. Effect of retrograde gas condensate in low permeability natural gas reservoir; Efeito da condensacao retrograda em reservatorios de gas natural com baixa permeabilidade

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Paulo Lee K.C. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Faculdade de Engenharia Mecanica; Ligero, Eliana L.; Schiozer, Denis J. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Engenharia de Petroleo

    2008-07-01

    Most of Brazilian gas fields are low-permeability or tight sandstone reservoirs and some of them should be gas condensate reservoir. In this type of natural gas reservoir, part of the gaseous hydrocarbon mixture is condensate and the liquid hydrocarbon accumulates near the well bore that causes the loss of productivity. The liquid hydrocarbon formation inside the reservoir should be well understood such as the knowledge of the variables that causes the condensate formation and its importance in the natural gas production. This work had as goal to better understanding the effect of condensate accumulation near a producer well. The influence of the porosity and the absolute permeability in the gas production was studied in three distinct gas reservoirs: a dry gas reservoir and two gas condensate reservoirs. The refinement of the simulation grid near the producer well was also investigated. The choice of simulation model was shown to be very important in the simulation of gas condensate reservoirs. The porosity was the little relevance in the gas production and in the liquid hydrocarbon formation; otherwise the permeability was very relevant. (author)

  13. Mapping the Fluid Pathways and Permeability Barriers of a Large Gas Hydrate Reservoir

    Science.gov (United States)

    Campbell, A.; Zhang, Y. L.; Sun, L. F.; Saleh, R.; Pun, W.; Bellefleur, G.; Milkereit, B.

    2012-12-01

    An understanding of the relationship between the physical properties of gas hydrate saturated sedimentary basins aids in the detection, exploration and monitoring one of the world's upcoming energy resources. A large gas hydrate reservoir is located in the MacKenzie Delta of the Canadian Arctic and geophysical logs from the Mallik test site are available for the gas hydrate stability zone (GHSZ) between depths of approximately 850 m to 1100 m. The geophysical data sets from two neighboring boreholes at the Mallik test site are analyzed. Commonly used porosity logs, as well as nuclear magnetic resonance, compressional and Stoneley wave velocity dispersion logs are used to map zones of elevated and severely reduced porosity and permeability respectively. The lateral continuity of horizontal permeability barriers can be further understood with the aid of surface seismic modeling studies. In this integrated study, the behavior of compressional and Stoneley wave velocity dispersion and surface seismic modeling studies are used to identify the fluid pathways and permeability barriers of the gas hydrate reservoir. The results are compared with known nuclear magnetic resonance-derived permeability values. The aim of investigating this heterogeneous medium is to map the fluid pathways and the associated permeability barriers throughout the gas hydrate stability zone. This provides a framework for an understanding of the long-term dissociation of gas hydrates along vertical and horizontal pathways, and will improve the knowledge pertaining to the production of such a promising energy source.

  14. Capacity expansion analysis of UGSs rebuilt from low-permeability fractured gas reservoirs with CO2 as cushion gas

    Directory of Open Access Journals (Sweden)

    Yufei Tan

    2016-11-01

    Full Text Available The techniques of pressurized mining and hydraulic fracturing are often used to improve gas well productivity at the later development stage of low-permeability carbonate gas reservoirs, but reservoirs are watered out and a great number of micro fractures are produced. Therefore, one of the key factors for underground gas storages (UGS rebuilt from low-permeability fractured gas reservoirs with CO2 as the cushion gas is how to expand storage capacity effectively by injecting CO2 to displace water and to develop control strategies for the stable migration of gas–water interface. In this paper, a mathematical model was established to simulate the gas–water flow when CO2 was injected into dual porosity reservoirs to displace water. Then, the gas–water interface migration rules while CO2 was injected in the peripheral gas wells for water displacement were analyzed with one domestic UGS rebuilt from fractured gas reservoirs as the research object. And finally, discussion was made on how CO2 dissolution, bottom hole flowing pressure (BHFP, CO2 injection rate and micro fracture parameters affect the stability of gas–water interface in the process of storage capacity expansion. It is shown that the speed of capacity expansion reaches the maximum value at the fifth cycle and then decreases gradually when UGS capacity is expanded in the pattern of more injection and less withdrawal. Gas–water interface during UGS capacity expansion is made stable due to that the solubility of CO2 in water varies with the reservoir pressure. When the UGS capacity is expanded at constant BHFP and the flow rate, the expansion speed can be increased effectively by increasing the BHFP and the injection flow rate of gas wells in the central areas appropriately. In the reservoir areas with high permeability and fracture-matrix permeability ratio, the injection flow rate should be reduced properly to prevent gas–water interface fingering caused by a high-speed flow

  15. A theoretical model for gas permeability in a composite membrane

    International Nuclear Information System (INIS)

    Serrano, D. A

    2009-01-01

    We present in this work an analytical expression for permeability in a two-layer composite membrane, which was derived assuming the same hypothesis as those of Adzumi model for permeability in a homogeneous membrane. Whereas in Adzumi model permeability shows a linear dependence on the mean pressure, our model for a composite membrane related permeability to pressure through a rather complex expression, which covers the whole range of flow, from molecular-Knudsen to viscous-Poiseuille regimes. The expression obtained for permeability contained information of membrane structural properties as pore size, porosity and thickness of each layer, as well as gas nature and operational conditions. Our two-layer-model expression turns into Adzumi formula when the structure of the layers approach to each other. [es

  16. The Dependence of Water Permeability in Quartz Sand on Gas Hydrate Saturation in the Pore Space

    Science.gov (United States)

    Kossel, E.; Deusner, C.; Bigalke, N.; Haeckel, M.

    2018-02-01

    Transport of fluids in gas hydrate bearing sediments is largely defined by the reduction of the permeability due to gas hydrate crystals in the pore space. Although the exact knowledge of the permeability behavior as a function of gas hydrate saturation is of crucial importance, state-of-the-art simulation codes for gas production scenarios use theoretically derived permeability equations that are hardly backed by experimental data. The reason for the insufficient validation of the model equations is the difficulty to create gas hydrate bearing sediments that have undergone formation mechanisms equivalent to the natural process and that have well-defined gas hydrate saturations. We formed methane hydrates in quartz sand from a methane-saturated aqueous solution and used magnetic resonance imaging to obtain time-resolved, three-dimensional maps of the gas hydrate saturation distribution. These maps were fed into 3-D finite element method simulations of the water flow. In our simulations, we tested the five most well-known permeability equations. All of the suitable permeability equations include the term (1-SH)n, where SH is the gas hydrate saturation and n is a parameter that needs to be constrained. The most basic equation describing the permeability behavior of water flow through gas hydrate bearing sand is k = k0 (1-SH)n. In our experiments, n was determined to be 11.4 (±0.3). Results from this study can be directly applied to bulk flow analysis under the assumption of homogeneous gas hydrate saturation and can be further used to derive effective permeability models for heterogeneous gas hydrate distributions at different scales.

  17. Gas permeability and thermal behavior of polypropylene films used for packaging minimally processed fresh-cut potatoes: a case study.

    Science.gov (United States)

    Siracusa, Valentina; Blanco, Ignazio; Romani, Santina; Tylewicz, Urszula; Dalla Rosa, Marco

    2012-10-01

    This work reports an experimental study on the permeability and thermal behavior of commercial polypropylene (PP) film used for fresh-cut potatoes packaging. The permeability was tested using oxygen, carbon dioxide, nitrogen, mix of these 3 gases, normally used for modified atmosphere packaging (MAP) and Air, to understand if it would be possible to extend the shelf life of this food product designed for the catering field in respect to the packaging behavior. The temperature influence on permeability data, from 5 to 40 °C, was analyzed, before and after 4, 8, 12, 15, and 20 d of food contact, pointing out the dependence between temperature and gas transmission rate (GTR), solubility (S), diffusion coefficient (D), and time lag (t(L)) parameters. The activation energies (E) of the permeation process were determined with the different gases used in the experiments. The thermal behavior of PP film was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) to well understand its thermal stability. Fourier transformed-infrared with attenuated total reflectance (FT-IR/ATR) spectroscopy was also performed in order to study the influence of the food contact on the chemical characteristics of the polymer film. The results obtained were discussed and compared each other. Studied samples showed, for all investigated gases, an increase of gas permeability and S values at higher temperature. Heat resistance classification among the sample as it is and stored in modified atmospheres was made. Finally all performed experiments have showed good polymer stability for the shelf-life storage potatoes under study. Study of packaging material was performed in a range of temperature, which can simulate the service condition to assess the suitability of a commercial polymer film for modified atmosphere packaging of fresh-cut potatoes minimally processed designed for catering purpose. © 2012 Institute of Food Technologists®

  18. Heat Transfer Measurement and Modeling in Rigid High-Temperature Reusable Surface Insulation Tiles

    Science.gov (United States)

    Daryabeigi, Kamran; Knutson, Jeffrey R.; Cunnington, George R.

    2011-01-01

    Heat transfer in rigid reusable surface insulations was investigated. Steady-state thermal conductivity measurements in a vacuum were used to determine the combined contribution of radiation and solid conduction components of heat transfer. Thermal conductivity measurements at higher pressures were then used to estimate the effective insulation characteristic length for gas conduction modeling. The thermal conductivity of the insulation can then be estimated at any temperature and pressure in any gaseous media. The methodology was validated by comparing estimated thermal conductivities with published data on a rigid high-temperature silica reusable surface insulation tile. The methodology was also applied to the alumina enhanced thermal barrier tiles. Thermal contact resistance for thermal conductivity measurements on rigid tiles was also investigated. A technique was developed to effectively eliminate thermal contact resistance on the rigid tile s cold-side surface for the thermal conductivity measurements.

  19. Synthesis of Plate-Like Nanoalumina and Its Effect on Gas Permeability of Carbon Fiber Epoxy Composite

    Directory of Open Access Journals (Sweden)

    Ghadamali Karimi Khozani

    2017-03-01

    Full Text Available In recent years considerable efforts have been made to develop gas impermeable polymer systems. Compared with metal system counterparts they have advantages such as low density and production costs. The most important challenge in development of impermeable polymer systems is to reduce their gas permeability by proper selection of system composition and process conditions. In this work, nanoparticles were initially synthesized using Al (NO33•9H2O and sodium dodecyl sulfate as a structure-directing agent via hydrothermal method and a plate-like structure was characterized by FESEM and EDAX analyses. In the second step, epoxy/plate-like nanoalumina nanocomposites and epoxy-carbon fiber composites containing 1, 2.5, and 5 wt% nanoalumina were prepared. The effect of nanoparticle loading level on permeability of nitrogen, argon, and carbon dioxide in epoxy/plate-like nanoalumina nanocomposites was investigated. It was observed that the permeability of epoxy/plate-like nanoalumina nanocomposites toward nitrogen, argon, and carbon dioxide gases reduced 83%, 74%, and 50%, respectively. It was deduced that the permeability reduction was clearly associated with the diameter of gas molecules. Generally speaking, the results showed that the incorporation of plate-like nanoalumina particles significantly reduced the gas permeability. Also, carbon dioxide gas permeability of carbon fiber epoxy composites containing plate-like nanoalumina was investigated to show the effect of ingredients on the gas permeability of the system. The results indicated that carbon dioxide gas permeability of epoxy carbon fiber composite containing 5 wt% of plate-like nanoalumina was totally reduced 84%.

  20. Gas-liquid contacting in mixing vessels

    International Nuclear Information System (INIS)

    Mann, R.

    1983-01-01

    This report by Dr. R. Mann of UMIST presents a critical survey of literature on the contacting of gases with liquids in stirred vessels. Research undertaken in the last fifteen years in analysed, and promising areas for future research are identified. The report deals with physical contacting, mass transfer between the gas and liquid phases and the utilisation of the stirred vessel as a gas-liquid reactor. Three sections are given on gas-liquid contacting: physical aspects; interphase mass transfer; and chemical reactions. It also discusses recent new approaches and includes a summary of conclusions, nomenclature and references

  1. High frequency permeameter with semi-rigid pick-up coil

    International Nuclear Information System (INIS)

    Shin, Sung-Yong; Shin, Kwang-Ho . E-mail : khshin@star.ks.ac.kr; Kim, Jong-sung; Kim, Young-Hak; Lim, Sang-Ho; Sa-gong, Geon

    2006-01-01

    In this study, we propose the application of semi-rigid cable loop as a single turn shielded loop pick-up coil for the high frequency permeameter. Since the semi-rigid cable pick-up coil has simple structure, it is very easy to make the pick-up coil with bending and conventional soldering. The permeability of cobalt base amorphous ribbon was investigated using the developed permeameter for demonstrating its performance. The permeability of the amorphous ribbon was driven from the S-parameters measured using a network analyzer and permameter having the semi-rigid pick-up coil

  2. Effects of silica composition on gas permeability of ENR/PVC ...

    African Journals Online (AJOL)

    At higher SiO2 loadings, the mechanical strength of the membrane decreased due to the agglomeration of SiO2 particles. Gas permeation test was done on ENR/PVC/SiO2 membranes using NO2 gas and CO2 gas. The permeability of both gasses increased with the amount of SiO2 added to the membrane, which attributed ...

  3. Intrinsically Microporous Polymer Membranes for High Performance Gas Separation

    KAUST Repository

    Swaidan, Raja

    2014-11-01

    This dissertation addresses the rational design of intrinsically microporous solutionprocessable polyimides and ladder polymers for highly permeable and highly selective gas transport in cornerstone applications of membrane-based gas separation – that is, air enrichment, hydrogen recovery and natural gas sweetening. By virtue of rigid and contorted chains that pack inefficiently in the solid state, polymers of intrinsic microporosity (PIMs) have the potential to unite the solution-processability, mechanical flexibility and organic tunability of commercially relevant polymers with the microporosity characteristics of porous crystalline materials. The performance enhancements of PIMs over conventional low-free-volume polymers have been primarily permeability-driven, compromising the selectivity essential to commercial viability. An approach to unite high permeability with high selectivity for performance transcending the state-of-the-art in air and hydrogen separations was demonstrated via a fused-ring integration of a three-dimensional, shape persistent triptycene moiety optimally substituted with short, branched isopropyl chains at the 9,10-bridgeheads into a highly inflexible backbone. The resulting polymers exhibited selectivities (i.e., O2/N2, H2/N2, H2/CH4) similar to or higher than commercial materials matched with permeabilities up to three hundred times higher. However, the intra-chain rigidity central to such conventional PIM-design principles was not a singular solution to suppression of CO2-induced plasticization in CO2/CH4 mixedgas separations. Plasticization diminishes the sieving capacity of the membrane, resulting in costly hydrocarbon losses that have significantly limited the commercialization of new polymers. Unexpectedly, the most permeable and selective PIMs designed for air and hydrogen separations strongly plasticized in 50:50 CO2/CH4 mixtures, enduring up to three-fold increases in mixed-gas CH4 permeability by 30 bar and strong drops in

  4. A fractal analytical model for the permeabilities of fibrous gas diffusion layer in proton exchange membrane fuel cells

    International Nuclear Information System (INIS)

    Xiao, Boqi; Fan, Jintu; Ding, Feng

    2014-01-01

    The study of water and gas transport through fibrous gas diffusion layer (GDL) is important to the optimization of proton exchange membrane fuel cells (PEMFCs). In this work, analytical models of dimensionless permeability, and water and gas relative permeabilities of fibrous GDL in PEMFCs are derived using fractal theory. In our models, the structure of fibrous GDL is characterized in terms of porosity, tortuosity fractal dimension (D T ), pore area fractal dimensions (d f ), water phase (d f,w ) and gas phase (d f,g ) fractal dimensions. The predicted dimensionless permeability, water and gas relative permeabilities based on the proposed models are in good agreement with experimental data and predictions of numerical simulations reported in the literature. The model reveals that, although water phase and gas phase fractal dimensions strongly depend on porosity, the water and gas relative permeabilities are independent of porosity and are a function of water saturation only. It is also shown that the dimensionless permeability decreases significantly with the increase of tortuosity fractal dimension. On the other hand, there is only a small decrease in the water and gas relative permeabilities when tortuosity fractal dimension increases. One advantage of the proposed analytical model is that it contains no empirical constant, which is normally required in past models

  5. Gas-induced friction and diffusion of rigid rotors

    Science.gov (United States)

    Martinetz, Lukas; Hornberger, Klaus; Stickler, Benjamin A.

    2018-05-01

    We derive the Boltzmann equation for the rotranslational dynamics of an arbitrary convex rigid body in a rarefied gas. It yields as a limiting case the Fokker-Planck equation accounting for friction, diffusion, and nonconservative drift forces and torques. We provide the rotranslational friction and diffusion tensors for specular and diffuse reflection off particles with spherical, cylindrical, and cuboidal shape, and show that the theory describes thermalization, photophoresis, and the inverse Magnus effect in the free molecular regime.

  6. Infiltrados corneales asociados al uso de lentes de contacto Corneal infiltrates associated with contact lens wear

    Directory of Open Access Journals (Sweden)

    Vivian Padrón Álvarez

    2001-12-01

    Full Text Available Se estudiaron 15 pacientes que usan lentes de contacto rígidas, permeables al gas (LCRPG y lentes de contacto blandas (LCB que presentaron infiltrados corneales. Se realizó estudio microbiológico de las lesiones y seguimiento clínico de estos casos. En 3 de los casos estudiados el cultivo fue positivo a estafilococo aureus, el resto de los estudios microbiológicos fueron negativos. Todos los pacientes respondieron rápidamente al retirar la lente de contacto y al tratamiento con antibióticos tópicos y ninguno tuvo afectación permanente de la agudeza visual. El diagnóstico exacto y el manejo apropiado de los infiltrados corneales en pacientes que usan lentes de contacto es de gran importancia por la posibilidad de infección o de secuela visual permanente.15 patients wearing gas permeable rigid contact lenses (GPRCL and soft contanct lenses (SCL that presented corneal infiltrates were studied. A microbiological study of the injuries and a clinical follow-up of these cases were conducted. In 3 of the studied cases the culture was positive to Staphyloccocus aureus. The rest of the mircobiological studies were negative. All the patients responded rapidly to the contact lens removal and to the treatment with topical antibiotics. None of them had permanent affection of visual acuity. The accurate diagnosis and the appropiate management of the corneal infiltrates in patients wearing contact lenses is very important due to the possibility of infection or of permanent visual sequela.

  7. Ammonia gas permeability of meat packaging materials.

    Science.gov (United States)

    Karim, Faris; Hijaz, Faraj; Kastner, Curtis L; Smith, J Scott

    2011-03-01

    Meat products are packaged in polymer films designed to protect the product from exterior contaminants such as light, humidity, and harmful chemicals. Unfortunately, there is almost no data on ammonia permeability of packaging films. We investigated ammonia permeability of common meat packaging films: low-density polyethylene (LDPE; 2.2 mil), multilayer polyolefin (MLP; 3 mil), and vacuum (V-PA/PE; 3 mil, 0.6 mil polyamide/2.4 mil polyethylene). The films were fabricated into 10 × 5 cm pouches and filled with 50 mL deionized water. Pouches were placed in a plexiglass enclosure in a freezer and exposed to 50, 100, 250, or 500 ppm ammonia gas for 6, 12, 24, and 48 h at -17 ± 3 °C and 21 ± 3 °C. At freezing temperatures, no ammonia residues were detected and no differences in pH were found in the water. At room temperature, ammonia levels and pH of the water increased significantly (P packaging materials have low ammonia permeability and protect meat products exposed to ammonia leaks during frozen storage.

  8. Mixed Finite Element Simulation with Stability Analysis for Gas Transport in Low-Permeability Reservoirs

    Directory of Open Access Journals (Sweden)

    Mohamed F. El-Amin

    2018-01-01

    Full Text Available Natural gas exists in considerable quantities in tight reservoirs. Tight formations are rocks with very tiny or poorly connected pors that make flow through them very difficult, i.e., the permeability is very low. The mixed finite element method (MFEM, which is locally conservative, is suitable to simulate the flow in porous media. This paper is devoted to developing a mixed finite element (MFE technique to simulate the gas transport in low permeability reservoirs. The mathematical model, which describes gas transport in low permeability formations, contains slippage effect, as well as adsorption and diffusion mechanisms. The apparent permeability is employed to represent the slippage effect in low-permeability formations. The gas adsorption on the pore surface has been described by Langmuir isotherm model, while the Peng-Robinson equation of state is used in the thermodynamic calculations. Important compatibility conditions must hold to guarantee the stability of the mixed method by adding additional constraints to the numerical discretization. The stability conditions of the MFE scheme has been provided. A theorem and three lemmas on the stability analysis of the mixed finite element method (MFEM have been established and proven. A semi-implicit scheme is developed to solve the governing equations. Numerical experiments are carried out under various values of the physical parameters.

  9. LEAK AND GAS PERMEABILITY TESTING DURING SOIL-GAS SAMPLING AT HAL'S CHEVRON LUST SITE IN GREEN RIVER, UTAH

    Science.gov (United States)

    The results of gas permeability and leak testing during active soil-gas sampling at Hal’s Chevron LUST Site in Green River, Utah are presented. This study was conducted to support development of a passive soil-gas sampling method. Gas mixtures containing helium and methane were...

  10. Substituted polynorbornenes as promising materials for gas separation membranes

    International Nuclear Information System (INIS)

    Finkelshtein, Evgenii Sh; Bermeshev, Maksim V; Gringolts, Mariya L; Starannikova, L E; Yampolskii, Yu P

    2011-01-01

    Published results concerning the synthesis and study of the transport characteristics of polynorbornenes are considered and analyzed. Conclusions are drawn regarding the effect of the backbone rigidity and the nature of side groups on the gas permeability level. The prospects of using addition organosilicon polynorbornenes as gas separating membrane materials are discussed.

  11. Estimating the gas permeability of commercial volatile corrosion inhibitors at elevated temperatures with thermo-gravimetry

    CSIR Research Space (South Africa)

    Pieterse, N

    2006-08-01

    Full Text Available ) in the surrounding atmosphere. However, the rate at which the VCI can be delivered across the air gap to a metal surface is determined by the gas permeability. This is the product of the vapour pressure and the diffusion coefficient: S-A = PADAB. The gas permeability...

  12. Oxygen permeability of the pigmented material used in cosmetic daily disposable contact lenses.

    Science.gov (United States)

    Galas, Stephen; Copper, Lenora L

    2016-01-01

    To evaluate the individual contributions of pigment colorant and packing solution containing polyvinyl pyrrolidone (PVP) on the oxygen permeability (Dk) of a cosmetic printed etafilcon A daily disposable contact lens packaged with PVP. The oxygen transport of a contact lens is evaluated through the central optical zone of the lens. Cosmetic printed contact lenses contain pigment colorant in the periphery or mid-periphery of the lens. Therefore, to assess the impact of cosmetic print on oxygen permeability, special lenses need to be produced that contain the colorant within the central optical zone. This technique was used to obtain multiple measurements of nonedge-corrected Dk/t of both the center pigmented lens and its nonpigmented equivalent, using a polarographic measurement described in International Organization for Standardization (ISO) 18369-4:2006(E), and the Dk derived for each measurement is corrected for edge effect. In addition, the edge-corrected Dk values of lenses made from the same monomer batch were measured. The lenses were packaged and autoclaved with and without proprietary technology which embeds PVP in the contact lens during autoclaving. The resulting Dk value of the printed lens material was then used with thickness data to generate true Dk/t profiles for a given lens power. The edge-corrected Dk of the printed etafilcon A lens with offset pigment colorant was measured to be 19.7×10 -11 (cm 2 /s) (mL O 2 /mL·mmHg) at 35°C. This was within ±20% tolerance range as specified in ISO 18369-2:2012(E) for the edge-corrected Dk of the nonpigmented etafilcon A control lens evaluated during the same session, 19.5×10 -11 (cm 2 /s) (mL O 2 /mL·mmHg). The edge-corrected Dk values of the lenses packaged with PVP (mean 20.1, standard deviation [SD] 0.3) were also within the ±20% tolerance range compared to those packaged without PVP (mean 20.0, SD 0.3). The pigment colorant and PVP embedded in the contact lens during autoclaving were not found to

  13. Effect of gas type on foam film permeability and its implications for foam flow in porous media.

    Science.gov (United States)

    Farajzadeh, R; Muruganathan, R M; Rossen, W R; Krastev, R

    2011-10-14

    The aim of this paper is to provide a perspective on the effect of gas type on the permeability of foam films stabilized by different types of surfactant and to present a critical overview of the tracer gas experiments, which is the common approach to determine the trapped fraction of foam in porous media. In these experiments some part of the gas is replaced by a "tracer gas" during the steady-state stage of the experiments and trapped fraction of foam is determined by fitting the effluent data to a capacitance mass-transfer model. We present the experimental results on the measurement of the gas permeability of foam films stabilized with five surfactants (non-ionic, anionic and cationic) and different salt concentrations. The salt concentrations assure formation of either common black (CBF) or Newton black films (NBF). The experiments are performed with different single gasses. The permeability of the CBF is in general higher than that of the NBF. This behavior is explained by the higher density of the surfactant molecules in the NBF compared to that of CBF. It is also observed that the permeability coefficient, K(cm/s), of CBF and NBF for non-ionic and cationic surfactants are similar and K is insensitive to film thickness. Compared to anionic surfactants, the films made by the non-ionic surfactant have much lower permeability while the films made by the cationic surfactant have larger permeability. This conclusion is valid for all gasses. For all types of surfactant the gas permeability of foam film is largely dependent on the dissolution of gas in the surfactant solution and increases with increasing gas solubility in the bulk liquid. The measured values of K are consistent with rapid diffusion of tracer gasses through trapped gas adjacent to flowing gas in porous media, and difficulties in interpreting the results of tracer-foam experiments with conventional capacitance models. The implications of the results for foam flow in porous media and factors leading

  14. Map of gas and vapor permeability in polymer blends

    Czech Academy of Sciences Publication Activity Database

    Pientka, Zbyněk; Brožová, Libuše; Bleha, Miroslav

    2004-01-01

    Roč. 163, 1-3 (2004), s. 137-142 ISSN 0011-9164 R&D Projects: GA AV ČR IAA4050104 Institutional research plan: CEZ:AV0Z4050913 Keywords : gas * vapor * permeability Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.057, year: 2004

  15. Enhanced recovery of ammonia from swine manure anaerobic digester effluent using gas-permeable membranes and aeration

    Science.gov (United States)

    Atmospheric ammonia pollution from livestock wastes can be reduced using gas-permeable membrane technology by converting ammonia contained in the manure into ammonium salt for use in fertilizers. In this study, gas-permeable membrane technology was enhanced using aeration combined with nitrificatio...

  16. Rational design of intrinsically ultramicroporous polyimides containing bridgehead-substituted triptycene for highly selective and permeable gas separation membranes

    KAUST Repository

    Swaidan, Raja

    2014-08-12

    Highly ultramicroporous, solution-processable polyimides bearing 9,10-bridgehead-substituted triptycene demonstrated the highest BET surface area reported for polyimides (840 m2 g-1) and several new highs in gas selectivity and permeability for hydrogen (1630-3980 barrers, H2/CH4 ∼ 38) and air (230-630 barrers, O 2/N2 = 5.5-5.9) separations. Two new dianhydrides bearing 9,10-diethyl- and 9,10-dipropyltriptycenes indicate that the ultramicroporosity is optimized for fast polymeric sieving with the use of short, bulky isopropyl bridgeheads and methyl-substituted diamines (TrMPD, TMPD, and TMBZ) that increase intrachain rigidity. Mechanically, the triptycene-based analogue of a spirobisindane-based polyimide exhibited 50% increases in both tensile strength at break (94 MPa) and elastic modulus (2460 MPa) with corresponding 90% lower elongations at break (6%) likely due to the ability of highly entangled spiro-based chains to unwind. To guide future polyimide design, structure/property relationships are suggested between the geometry of the contortion center, the diamine and bridgehead substituent, and the mechanical, microstructural, and gas transport properties. © 2014 American Chemical Society.

  17. Rational design of intrinsically ultramicroporous polyimides containing bridgehead-substituted triptycene for highly selective and permeable gas separation membranes

    KAUST Repository

    Swaidan, Raja; Al-Saeedi, Majed; Ghanem, Bader; Litwiller, Eric; Pinnau, Ingo

    2014-01-01

    Highly ultramicroporous, solution-processable polyimides bearing 9,10-bridgehead-substituted triptycene demonstrated the highest BET surface area reported for polyimides (840 m2 g-1) and several new highs in gas selectivity and permeability for hydrogen (1630-3980 barrers, H2/CH4 ∼ 38) and air (230-630 barrers, O 2/N2 = 5.5-5.9) separations. Two new dianhydrides bearing 9,10-diethyl- and 9,10-dipropyltriptycenes indicate that the ultramicroporosity is optimized for fast polymeric sieving with the use of short, bulky isopropyl bridgeheads and methyl-substituted diamines (TrMPD, TMPD, and TMBZ) that increase intrachain rigidity. Mechanically, the triptycene-based analogue of a spirobisindane-based polyimide exhibited 50% increases in both tensile strength at break (94 MPa) and elastic modulus (2460 MPa) with corresponding 90% lower elongations at break (6%) likely due to the ability of highly entangled spiro-based chains to unwind. To guide future polyimide design, structure/property relationships are suggested between the geometry of the contortion center, the diamine and bridgehead substituent, and the mechanical, microstructural, and gas transport properties. © 2014 American Chemical Society.

  18. Computerized videokeratoscopy contact lens software for RGP fitting in a bilateral postkeratoplasty patient: a clinical case report.

    Science.gov (United States)

    Szczotka, L B; Reinhart, W

    1995-01-01

    Computerized videokeratoscopy systems now allow interactive rigid gas permeable (RGP) fitting evaluation using fluorescein pattern simulations through updated software programs. We used Computed Anatomy's Topographic Modeling System-1 (TMS-1) Custom Design Contact Lens Program successfully to refit a symptomatic bilateral post-penetrating keratoplasty patient. No trial lenses were used. For each eye the base curve, optic zone size, and edge lift were chosen from the optimal fluorescein pattern designed and titrated on the TMS-1 unit. Lens powers were based on the patient's previous lenses and overrefraction. Dispensed lenses provided a clinically acceptable fit, good comfort, and maximal visual acuity, and no adjustments were necessary. Corneal videokeratoscopy can be successfully employed to titrate an RGP fit, even on irregular corneas.

  19. iCub Whole-body Control through Force Regulation on Rigid Noncoplanar Contacts

    Directory of Open Access Journals (Sweden)

    Francesco eNori

    2015-03-01

    Full Text Available This paper details the implementation on the humanoid robot iCub of state-of-the-art algorithms for whole-body control. We regulate the forces between the robot and its surrounding environment to stabilize a desired robot posture. We assume that the forces and torques are exerted on rigid contacts. The validity of this assumption is guaranteed by constraining the contact forces and torques, e.g. the contact forces must belong to the associated friction cones. The implementation of this control strategy requires to estimate the external forces acting on the robot, and the internal joint torques. We then detail algorithms to obtain these estimations when using a robot with an iCub-like sensor set, i.e. distributed six-axis force-torque sensors and whole-body tactile sensors. A general theory for identifying the robot inertial parameters is also presented. From an actuation standpoint, we show how to implement a joint torque control in the case of DC brushless motors. In addition, the coupling mechanism of the iCub torso is investigated. The soundness of the entire control architecture is validated in a real scenario involving the robot iCub balancing and making contacts at both arms.

  20. A relative permeability model to derive fractional-flow functions of water-alternating-gas and surfactant-alternating-gas foam core-floods

    International Nuclear Information System (INIS)

    Al-Mossawy, Mohammed Idrees; Demiral, Birol; Raja, D M Anwar

    2013-01-01

    Foam is used in enhanced oil recovery to improve the sweep efficiency by controlling the gas mobility. The surfactant-alternating-gas (SAG) foam process is used as an alternative to the water-alternating-gas (WAG) injection. In the WAG technique, the high mobility and the low density of the gas lead the gas to flow in channels through the high permeability zones of the reservoir and to rise to the top of the reservoir by gravity segregation. As a result, the sweep efficiency decreases and there will be more residual oil in the reservoir. The foam can trap the gas in liquid films and reduces the gas mobility. The fractional-flow method describes the physics of immiscible displacements in porous media. Finding the water fractional flow theoretically or experimentally as a function of the water saturation represents the heart of this method. The relative permeability function is the conventional way to derive the fractional-flow function. This study presents an improved relative permeability model to derive the fractional-flow functions for WAG and SAG foam core-floods. The SAG flow regimes are characterized into weak foam, strong foam without a shock front and strong foam with a shock front. (paper)

  1. Damageable contact between an elastic body and a rigid foundation

    Science.gov (United States)

    Campo, M.; Fernández, J. R.; Silva, A.

    2009-02-01

    In this work, the contact problem between an elastic body and a rigid obstacle is studied, including the development of material damage which results from internal compression or tension. The variational problem is formulated as a first-kind variational inequality for the displacements coupled with a parabolic partial differential equation for the damage field. The existence of a unique local weak solution is stated. Then, a fully discrete scheme is introduced using the finite element method to approximate the spatial variable and an Euler scheme to discretize the time derivatives. Error estimates are derived on the approximate solutions, from which the linear convergence of the algorithm is deduced under suitable regularity conditions. Finally, three two-dimensional numerical simulations are performed to demonstrate the accuracy and the behaviour of the scheme.

  2. Adherence of Pseudomonas aeruginosa to contact lenses

    International Nuclear Information System (INIS)

    Miller, M.J.

    1988-01-01

    The purpose of this research was to examined the interactions of P. aeruginosa with hydrogel contact lenses and other substrata, and characterize adherence to lenses under various physiological and physicochemical conditions. Isolates adhered to polystyrene, glass, and hydrogel lenses. With certain lens types, radiolabeled cells showed decreased adherence with increasing water content of the lenses, however, this correlation with not found for all lenses. Adherence to rigid gas permeable lenses was markedly greater than adherence to hydrogels. Best adherence occurred near pH 7 and at a sodium chloride concentration of 50 mM. Passive adhesion of heat-killed cells to hydrogels was lower than the adherence obtained of viable cells. Adherence to hydrogels was enhanced by mucin, lactoferrin, lysozyme, IgA, bovine serum albumin, and a mixture of these macromolecules. Adherence to coated and uncoated lenses was greater with a daily-wear hydrogel when compared with an extended-wear hydrogel of similar polymer composition. Greater adherence was attributed to a higher concentration of adsorbed macromolecules on the 45% water-content lens in comparison to the 55% water-content lens

  3. Gas fireplace contact burns in young children.

    Science.gov (United States)

    Zettel, Julie C; Khambalia, Amina; Barden, Wendy; Murthy, Trisha; Macarthur, Colin

    2004-01-01

    Contact burns from domestic appliances are common in young children. Recently, gas fireplaces have been recognized as a potential cause of contact burns in young children. We sought to quantify the frequency of gas fireplace contact burns in young children, to identify the etiology of contact, to describe the clinical presentation, and to describe clinical outcomes. Children with gas fireplace contact burn injuries presenting to The Hospital for Sick Children in Toronto (1999-2002) were identified using three data sources: the Canadian Hospitals Injury Reporting and Prevention Program Database, the Burn Unit Registry, and the Rehabilitation Services Database. Demographic, clinical, and outcomes data were collected on all children. During the 4-year study period, 27 children presented to the hospital because of a gas fireplace contact burn (approximately 9% of all contact burns). The median age of the children was 14 months (range, 8-36 months), with 16 boys (59%). Most children were burned in their own home. With regard to etiology, 10 children (37%) lost their balance near the fireplace, 2 (7%) walked too close to the glass front, and 8 (30%) touched the glass front out of curiosity. Almost half (44%) of the children burned the palms and digits of both hands. The median total burn surface area was 1% (range, 0.2-2.5%). In total, 30% of children were admitted to hospital, and 11% required skin grafts. All children had full wound closure after 4 to 43 days. Given the etiology of these burns (loss of balance or curiosity), passive prevention, such as barriers or changes in the composition of glass panels, may be the most effective approach to combat them.

  4. Permeability in Rotliegend gas sandstones to gas and brine as predicted from NMR, mercury injection and image analysis

    DEFF Research Database (Denmark)

    Rosenbrand, Esther; Fabricius, Ida Lykke; Fisher, Quentin

    2015-01-01

    Permeability characterisation of low permeability, clay-rich gas sandstones is part of production forecasting and reservoir management. The physically based Kozeny (1927) equation linking permeability with porosity and pore size is derived for a porous medium with a homogeneous pore size, whereas...... the pore sizes in tight sandstones can range from nm to μm. Nuclear magnetic resonance (NMR) transverse relaxation was used to estimate a pore size distribution for 63 samples of Rotliegend sandstone. The surface relaxation parameter required to relate NMR to pore size is estimated by combination of NMR...

  5. Gas-liquid Relative Permeability Estimation in 2D Porous Media by Lattice Boltzmann Method: Low Viscosity Ratio 2D LBM Relative Permeability

    Directory of Open Access Journals (Sweden)

    Sadegh Mahmoudi

    2013-04-01

    Full Text Available This work is a primary achievement in studying the CO2 and N2–oil systems. To predict gas-liquid relative permeability curves, a Shan-Chen type multicomponent multiphase lattice Boltzmann model for two-phase flow through 2D porous media is developed. Periodic and bounce back boundary conditions are applied to the model with the Guo scheme for the external body force (i.e., the pressure gradient. The influence of relationship between cohesion and adsorption parameters and the interfacial tension values in Young's equation, pore structure (micro scan image derived porous media response is compared with corresponding porosity and permeability ideal sphere pack structure, and saturation distribution on relative permeability curves are studied with the aim to achieve the realistic stable condition for the simulation of gas-liquid systems with a low viscosity ratio.

  6. Stress and Damage Induced Gas Flow Pattern and Permeability Variation of Coal from Songzao Coalfield in Southwest China

    Directory of Open Access Journals (Sweden)

    Minghui Li

    2016-05-01

    Full Text Available The permeability of coal is a critical parameter in estimating the performance of coal reservoirs. Darcy’s law describes the flow pattern that the permeability has a linear relationship with the flow velocity. However, the stress induced deformation and damage can significantly influence the gas flow pattern and permeability of coal. Coals from Songzao coalfield in Chongqing, southwest China were collected for the study. The gas flow velocities under different injection gas pressures and effective stresses in the intact coal and damaged coal were tested using helium, incorporating the role of gas flow pattern on the permeability of coal. The relationships between the flow velocity and square of gas pressure gradient were discussed, which can help us to investigate the transformation conditions of gas linear flow and gas nonlinear flow in the coal. The results showed that the gas flow in the intact coal existed pseudo-initial flow rate under low effective stress. The low-velocity non-Darcy gas flow gradually occurred and the start-up pressure gradient increased in the coal as the effective stress increased. The gas flow rate in the damaged coal increased nonlinearly as the square of pressure gradient increased under low effective stress. The instability of gas flow caused by high ratio of injection gas pressure over effective stress in the damaged coal contributed to the increase of the gas flow rate. As the effective stress increased, the increase of gas flow rate in coal turned to be linear. The mechanisms of the phenomena were explored according to the experimental results. The permeability of coal was corrected based on the relationships between the flow velocity and square of gas pressure gradient, which showed advantages in accurately estimating the performance of coal reservoirs.

  7. Ultraviolet radiation for the sterilization of contact lenses

    International Nuclear Information System (INIS)

    Gritz, D.C.; Lee, T.Y.; McDonnell, P.J.; Shih, K.; Baron, N.

    1990-01-01

    Two sources of ultraviolet (UV) radiation with peak wavelengths in the UV-C or UV-B ranges were compared for their ability to sterilize contact lenses infected with Pseudomonas aeruginosa, Streptococcus pneumoniae, Acanthamoeba castellani, Candida albicans, and Aspergillus niger. Also examined was the effect of prolonged UV light exposure on soft and rigid gas permeable (RGP) contact lenses. The UV-C lamp (253.7 nm, 250 mW/cm2 at 1 cm) was germicidal for all organisms within 20 minutes but caused destruction of the soft lens polymers within 6 hours of cumulative exposure. UV-C caused damage to RGP lenses in less than 100 hours. The UV-B lamp (290-310 nm, 500 mW/cm2 at 1 cm) was germicidal for all organisms tested (except Aspergillus) with a 180-minute exposure and caused less severe changes in the soft lens polymers than did the UV-C lamp, although cumulative exposure of 300 hours did substantially weaken the soft lens material. RGP materials were minimally affected by exposure to 300 hours of UV-B. Ultraviolet light is an effective germicidal agent but is injurious to soft lens polymers; its possible utility in the sterilization of RGP lenses and lens cases deserves further study

  8. Modelling of fast hydrogen permeability of alloys for membrane gas separation

    Science.gov (United States)

    Zaika, Yu. V.; Rodchenkova, N. I.

    2017-05-01

    The method of measuring the specific hydrogen permeability is used to study various alloys that are promising for gas separation installations. The nonlinear boundary value problem of hydrogen permeability complying with the specific features of the experiment and its modifications taking into account the high transfer rate is presented. Substantial difference from the quasi-equilibrium model (Richardson approximation in the assumption of the equilibrium Sieverts' law near the surface) has been discussed. The model is tested on published experimental data on Ta77Nb23 alloy.

  9. Effect of a low-permeability layer on calculated gas flow at Yucca Mountain

    International Nuclear Information System (INIS)

    Lu, Ning; Amter, S.; Ross, B.

    1990-01-01

    Yucca Mountain is being studied to determine its suitability as a location for a high-level nuclear waste repository. Amter and Ross developed a model called TGIF (Topographic Induced Flow) to simulate gas flow under Yucca Mountain. The TGIF model differs significantly from previous gas flow models. It uses a governing equation that is based on the concept of freshwater head, thus avoiding the numerical problems associated with the near-cancellation of the forces due to gravity and the pressure gradient. Unlike most other models, dipping, layered media can be simulated. This paper describes a systematic sensitivity study that was designed to test several aspects of the TGIF model when used to simulate gas flow under Yucca Mountain. Values of three important inputs to the model were systematically varied to form a matrix of 80 runs. The matrix consisted of five values of permeability contrast between a bedded tuff layer and surrounding welded units (in all cases, bulk permeabilities were used to represent the combined effect of both fractures and matrix permeability), four temperature profiles representing different stages of repository cooldown, and four finite-difference grids

  10. Effect of a low-permeability layer on calculated gas flow at Yucca Mountain

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Ning; Amter, S.; Ross, B. [Disposal Safety, Inc., Washington, DC (USA)

    1990-12-31

    Yucca Mountain is being studied to determine its suitability as a location for a high-level nuclear waste repository. Amter and Ross developed a model called TGIF (Topographic Induced Flow) to simulate gas flow under Yucca Mountain. The TGIF model differs significantly from previous gas flow models. It uses a governing equation that is based on the concept of freshwater head, thus avoiding the numerical problems associated with the near-cancellation of the forces due to gravity and the pressure gradient. Unlike most other models, dipping, layered media can be simulated. This paper describes a systematic sensitivity study that was designed to test several aspects of the TGIF model when used to simulate gas flow under Yucca Mountain. Values of three important inputs to the model were systematically varied to form a matrix of 80 runs. The matrix consisted of five values of permeability contrast between a bedded tuff layer and surrounding welded units (in all cases, bulk permeabilities were used to represent the combined effect of both fractures and matrix permeability), four temperature profiles representing different stages of repository cooldown, and four finite-difference grids.

  11. Detection and control of as-produced pyrocarbon permeability in biso-coated high-temperature gas-cooled reactor fuel particles

    International Nuclear Information System (INIS)

    Stinton, D.P.; Thiele, B.A.; Lackey, W.J.; Morgan, C.S.

    1980-05-01

    About 60 Biso-coated particle batches with coatings deposited in either 0.13- or 0.24-m dia coaters were studied in this work. These batches were carefully characterized for permeability by neon-helium intrusion, long-term chlorination followed by radiography, and fission gas release. These methods of permeability measurement were compared and correlated with deposition conditions as well as pyrocarbon properties. The results from several irradiation tests were also used to evaluate the validity of the permeability measurements. The neon-helium and long-term chlorination techniques correlated very clearly. Coatings with neon-to-helium ratios below 0.3 were gastight by the chlorination procedure, whereas those with ratios above 0.4 were permeable. The fission gas release technique was unable to distinguish between slightly permeable coatings and gastight ones. Therefore, neon-helium and long-term chlorination procedures are preferred over the fission gas release technique. Results from several irradiation tests verified that coatings with neon-to-helium ratios below 0.3 were gastight, whereas those with ratios above about 0.4 were permeable. 10 figures, 2 tables

  12. Recovery of ammonia and production of high-grade phosphates from side-stream digester effluents using gas-permeable membranes

    Science.gov (United States)

    Phosphorus recovery was combined with ammonia recovery using gas-permeable membranes. In a first step, the ammonia and alkalinity were removed from municipal side-stream wastewater using low-rate aeration and a gas-permeable membrane manifold. In a second step, the phosphorus was removed using magne...

  13. Permeability changes in coal resulting from gas desorption

    Energy Technology Data Exchange (ETDEWEB)

    Levine, J.R.; Johnson, P.W.

    1992-11-30

    This report documents studies on the effects of gas sorption on coal, with the intent of eventually evaluating how sorption and strain affect permeability. These studies were, carried out at the University of Alabama during the period from 1989 through 1992. Two major experimental methods were developed and used. In the strain experiments, electronic strain gauges were attached to polished blocks of coal in order to measure linear and volumetric swelling due to gas sorption. The effects of bedding plane orientation, of gas type, and of coal type were investigated. In the gravimetric experiment the weight of small samples of coal was measured during exposure to high pressure gases. Sample measurements were corrected for buoyancy effects and for sample swelling, and the results were plotted in the form of Langmuir isotherms. Experiments were conducted to determine the effect of grain size, coal type, moisture, and of sorbant gas. The advantage of this method is that it can be applied to very small samples, and it enabled comparison liptinite versus vitrinite concentrates, and kerogen rich versus kerogen depleted oil shales. Also included is a detailed discussion of the makeup of coal and its effect on gas sorption behavior.

  14. Fine-Tuned Intrinsically Ultramicroporous Polymers Redefine the Permeability/Selectivity Upper Bounds of Membrane-Based Air and Hydrogen Separations

    KAUST Repository

    Swaidan, Raja

    2015-08-20

    Intrinsically ultramicroporous (<7 Å) polymers represent a new paradigm in materials development for membrane-based gas separation. In particular, they demonstrate that uniting intrachain “rigidity”, the traditional design metric of highly permeable polymers of intrinsic microporosity (PIMs), with gas-sieving ultramicroporosity yields high-performance gas separation membranes. Highly ultramicroporous PIMs have redefined the state-of-the-art in large-scale air (e.g., O2/N2) and hydrogen recovery (e.g., H2/N2, H2/CH4) applications with unprecedented molecular sieving gas transport properties. Accordingly, presented herein are new 2015 permeability/selectivity “upper bounds” for large-scale commercial membrane-based air and hydrogen applications that accommodate the substantial performance enhancements of recent PIMs over preceding polymers. A subtle balance between intrachain rigidity and interchain spacing has been achieved in the amorphous microstructures of PIMs, fine-tuned using unique bridged-bicyclic building blocks (i.e., triptycene, ethanoanthracene and Tröger’s base) in both ladder and semiladder (e.g., polyimide) structures.

  15. Abatement of ammonia emissions from digested manure using gas-permeable membranes

    Science.gov (United States)

    A new strategy to avoid ammonia emissions from anaerobically digested swine manure was tested using the gas-permeable membrane process. Evaluation of the efficiency of ammonia recovery from digestate as well as mitigation of ammonia emissions to the atmosphere were carried out. Digestate was colle...

  16. Inflammation-free, gas-permeable, lightweight, stretchable on-skin electronics with nanomeshes

    Science.gov (United States)

    Miyamoto, Akihito; Lee, Sungwon; Cooray, Nawalage Florence; Lee, Sunghoon; Mori, Mami; Matsuhisa, Naoji; Jin, Hanbit; Yoda, Leona; Yokota, Tomoyuki; Itoh, Akira; Sekino, Masaki; Kawasaki, Hiroshi; Ebihara, Tamotsu; Amagai, Masayuki; Someya, Takao

    2017-09-01

    Thin-film electronic devices can be integrated with skin for health monitoring and/or for interfacing with machines. Minimal invasiveness is highly desirable when applying wearable electronics directly onto human skin. However, manufacturing such on-skin electronics on planar substrates results in limited gas permeability. Therefore, it is necessary to systematically investigate their long-term physiological and psychological effects. As a demonstration of substrate-free electronics, here we show the successful fabrication of inflammation-free, highly gas-permeable, ultrathin, lightweight and stretchable sensors that can be directly laminated onto human skin for long periods of time, realized with a conductive nanomesh structure. A one-week skin patch test revealed that the risk of inflammation caused by on-skin sensors can be significantly suppressed by using the nanomesh sensors. Furthermore, a wireless system that can detect touch, temperature and pressure is successfully demonstrated using a nanomesh with excellent mechanical durability. In addition, electromyogram recordings were successfully taken with minimal discomfort to the user.

  17. On the the Contact Lens Problem: Modeling Rigid and Elastic Beams on Thin Films

    Science.gov (United States)

    Trinh, Philippe; Wilson, Stephen; Stone, Howard

    2011-11-01

    Generally, contact lenses are prescribed by the practitioner to fit each individual patient's eye, but these fitting-philosophies are based on empirical studies and a certain degree of trial-and-error. A badly fitted lens can cause a range of afflictions, which varies from mild dry-eye-discomfort, to more serious corneal diseases. Thus, at this heart of this problem, is the question of how a rigid or elastic plate interacts with the free-surface of a thin viscous film. In this talk, we present several mathematical models for the study of these plate-and-fluid problems. Asymptotic and numerical results are described, and we explain the role of elasticity, surface tension, viscosity, and pressure in determining the equilibrium solutions. Finally, we discuss the implications of our work on the contact lens problem, as well as on other coating processes which involve elastic substrates.

  18. Experimental Study of Matrix Permeability of Gas Shale: An Application to CO2-Based Shale Fracturing

    Directory of Open Access Journals (Sweden)

    Chengpeng Zhang

    2018-03-01

    Full Text Available Because the limitations of water-based fracturing fluids restrict their fracturing efficiency and scope of application, liquid CO2 is regarded as a promising substitute, owing to its unique characteristics, including its greater environmental friendliness, shorter clean-up time, greater adsorption capacity than CH4 and less formation damage. Conversely, the disadvantage of high leak-off rate of CO2 fracturing due to its very low viscosity determines its applicability in gas shales with ultra-low permeability, accurate measurement of shale permeability to CO2 is therefore crucial to evaluate the appropriate injection rate and total consumption of CO2. The main purpose of this study is to accurately measure shale permeability to CO2 flow during hydraulic fracturing, and to compare the leak-off of CO2 and water fracturing. A series of permeability tests was conducted on cylindrical shale samples 38 mm in diameter and 19 mm long using water, CO2 in different phases and N2 considering multiple influencing factors. According to the experimental results, the apparent permeability of shale matrix to gaseous CO2 or N2 is greatly over-estimated compared with intrinsic permeability or that of liquid CO2 due to the Klinkenberg effect. This phenomenon explains that the permeability values measured under steady-state conditions are much higher than those under transient conditions. Supercritical CO2 with higher molecular kinetic energy has slightly higher permeability than liquid CO2. The leak-off rate of CO2 is an order of magnitude higher than that of water under the same injection conditions due to its lower viscosity. The significant decrease of shale permeability to gas after water flooding is due to the water block effect, and much longer clean-up time and deep water imbibition depth greatly impede the gas transport from the shale matrix to the created fractures. Therefore, it is necessary to substitute water-based fracturing fluids with liquid or super

  19. Use of Contact Lenses in Eyes with Severe Keratoconus: Long-term Results

    Directory of Open Access Journals (Sweden)

    Zerrin Tuncer

    2012-05-01

    Full Text Available Pur po se: To evaluate the long-term results of rigid gas permeable (RGP contact lenses in severe keratoconic eyes. Ma te ri al and Met hod: Severe keratoconic eyes with RGP contact lenses were evaluated retrospectively. Re sults: Long-term follow-up results of RGP contact lenses applied to 59 eyes of 42 patients (25 women, 17 men with a diagnosis of severe keratoconus were analyzed. Follow-up period was 3 to 12 years (mean: 6.57±3.60. The mean age at first exam was 25.88±9.10 years, the mean corneal curve K1 was 6.49±0.40 mm and K2 was 5.91±0.40 mm. Mean visual acuities with spectacles and contact lenses were 0.26±0.10 lines (0.63±0.20 logMAR and 0.66±0.20 lines (0.20±0.10 logMAR, respectively. The difference between both visual acuities was statistically significant (p=0.0001. At the last visit, the mean visual acuity with RGP contact lenses was 0.68±0.20 lines (0.19±0.10 logMAR. There was no statistically significant difference in visual acuity between first and last examinations with contact lenses (p=0.32. During the long-term follow-up period, apical scarring developed in 17 eyes. Only the 2 eyes of one patient needed penetrating keratoplasty after 6 years of RGP contact lens use. Dis cus si on: Use of RGP contact lenses should be considered before penetrating keratoplasty in cases of severe keratoconus. (Turk J Ophthalmol 2012; 42: 202-6

  20. Characterization of the mechanical and hydraulic damage in the excavation damaged zone of MHM with gas permeability measurement

    International Nuclear Information System (INIS)

    Yang, D.

    2008-09-01

    On the feasibility evaluation of nuclear waste storage in deep formations, the essential issues are as follows: the stability of underground structures over the reversible period, the influence of cavity excavation on geomechanical properties of the wall rock and the variation of those properties during the different phases while storage realization. The work presented here covers the investigations on the variation of geomechanical properties of the approximately 500 m deep MHM in France (mudstone in the departments of Meuse/Haute-Marne), chosen as a potential medium for nuclear waste disposal by ANDRA. In order to measure the very low permeability of mudstone and to observe the dependency on saturation, a special test scheme on measurement of gas permeability has been developed. In the scheme, in situ referenced stresses have been chosen as the stresses acting on the solid matrix. The gas permeability has been determined with both analytical and numerical methods. To estimate the mechanical damage of storage induced by the excavation, laboratory tests on gas permeability have been conducted on samples recovered from different locations situated at different distances from the wall of the main access shaft of the MHM (from 0,1 m to 12,5 m). Results of gas permeability obtained under an isotropic stress of 11 MPa vary between 10 -21 and 10 -22 m 2 and do not show significant variations between damaged zones (near the wall) and intact zones (sample located 12 m from the wall). The observations in laboratory tests coincide with in situ damage characterizations. The variation of gas permeability under the cycle of loading and unloading is an order less than the initial value under the isotropic stress. Taking into account the precision of the testing system, this variation is not significant. The oviparous intact samples have been imposed different saturations by salt solutions (with a relative humidity from 25 % to 98 %) to form a cycle of de- and re-saturation. The

  1. Suitability of Torrent Permeability Tester to measure air-permeability of covercrete

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, C.; Gonzales-Gasca, C. [Institute of Construction Sciences ' Eduardo Torroja' , Madrid (Spain); Torrent, R. [Portland Cement Institute, (Argentina)

    2000-07-01

    Suitability of the Torrent Permeability Tester (TPT) to measure the permeability of covercrete to air, both in the laboratory and the field, is investigated, and test results obtained in laboratory studies are discussed. The tests performed included the determination of air permeability (TPT method), oxygen permeability (Cembureau method) and capillary suction, rapid chloride permeability test (ASTM C 1202), as well as a one-year carbonation depth test. Concrete specimens of various compositions and curing regimes were used in the tests; the gas-permeability tests were repeated on the same specimens after 28 days, than again at 6 months and 12 months. Test results confirmed the suitability of the TPT as a useful tool in the characterization of the quality the of concrete cover. It was found to be sensitive to changes in concrete quality; repeatable for sensitive properties such as gas permeability ; also, it was found to correlate well with other durability-related properties. 10 refs., 8 tabs., 8 figs.

  2. Gas-permeable hydrophobic tubular membranes for ammonia recovery in bio-electrochemical systems

    NARCIS (Netherlands)

    Kuntke, P.; Zamora, P.; Saakes, M.; Buisman, C.J.N.; Hamelers, H.V.M.

    2016-01-01

    The application of a gas-permeable hydrophobic tubular membrane in bio-electrochemical systems enables efficient recovery of ammonia (NH3) from their cathode compartments. Due to a hydrogen evolution reaction at the cathode, no chemical addition was required to increase the pH for

  3. Rigid Bodies in Contact

    DEFF Research Database (Denmark)

    Niebe, Sarah Maria

    . A contact point determination method, based on boolean surface maps, is developed to handle collisions between tetrahedral meshes. The novel nonsmooth nonlinear conjugate gradient (NNCG) method is presented. The NNCG method is comparable in terms of accuracy to the state-of-the-art method, projected Gauss...

  4. Captura de amonio procedente de estiercol mediante membranas permeables de gases (capture of ammonnia from turkey manure using gas-permeable membranes)

    Science.gov (United States)

    This paper, written in Spanish, describes the capture and recovery of gaseous ammonia from turkey manure using gas-permeable membranes technology with formation of stabilized ammonium salts. Bench experiments were carried out in Maryland using a pilot prototype system with turkey litter inside contr...

  5. Permeability measuremens of brazilian Eucalyptus

    Directory of Open Access Journals (Sweden)

    Marcio Rogério da Silva

    2010-09-01

    Full Text Available The permeability of Brazilian Eucalyptus grandis and Eucalyptus citriodora wood was measured in a custom build gas analysis chamber in order to determine which species could be successfully treated with preservatives. Liquid permeability was tested using an emulsion of Neen oil and a control of distillated water. Air was used to test the gas phase permeability. For both Eucalyptus grandis and Eucalyptus citriodora, the longitudinal permeability of gas was shown to be about twice as great as the liquid phase permeability. No radial permeability was observed for either wood. The permeability of air and water through the sapwood of Eucalyptus grandis was greater than that through the sapwood of Eucalyptus citriodora. The permeability of neen oil preservative through the sapwood of Eucalyptus grandis was also greater than through the sapwood of E. Citradora, but the difference was not statistically significant. Scanning Electron Microscopy images showed that the distribution and obstruction in the vessels could be correlated with observed permeability properties. Irrespective of the causes of differences in permeability between the species, the fluid phase flux through the sapwood of both species was significant, indicating that both Eucalyptus grandis and Eucalyptus citriodora could be successfully treated with wood preservative.

  6. Effect of direct contact with iron on gas evolution behavior of aluminum

    International Nuclear Information System (INIS)

    Hashizume, Shuji; Matsumoto, Junko; Banba, Tsunetaka

    1998-01-01

    Dry Low-Level Radioactive Waste (LLW), incombustible solid LLW, generated from nuclear power stations is planed to be solidified with cement backfill in drums. The solidified dry LLW will be buried to shallow underground at Rokkasyo LLW Disposal Center. It is well known that corrosion of aluminum and hydrogen gas evolution occur in high pH environments such as mortar. Gas evolution from aluminum is likely to effect the leachability of solidified dry LLW with mortar. Though aluminum removal from dry LLW is planed, a small amount of aluminum will be actually included in dry LLW. Large effects of pH and temperature on corrosion rate of aluminum and gas evolution were recognized in our previous study. It was also found that 1.5 mole hydrogen gas evolves while 1 mole aluminum corrodes under 60degC. Actually aluminum in drums is likely to contact with carbon steel of which main element is iron. The gas evolution behavior of aluminum is expected to be affected by its direct contact with iron. Therefore, effect of direct contact with iron on gas evolution behavior of aluminum was studied. The corrosion rate of aluminum increased by contacting it with iron in simulating mortar environments. The amount of gas evolution from aluminum was reduced by contacting with iron. The reduction in gas evolution was considered to result from the change of cathode reaction from hydrogen evolution to oxygen reduction. When aluminum contacts with iron, the corrosion and gas evolution behavior of aluminum is significantly affected oxygen in environment. (author)

  7. ETUDE VARIATIONNELLE DU CONTACT SANS FROTTEMENT ENTRE UN CORPS ELASTIQUE ET UNE FONDATION RIGIDE

    Directory of Open Access Journals (Sweden)

    B TENIOU

    2002-06-01

    Full Text Available Le but de ce travail est l'étude variationnelle du contact sans frottement entre un corps élastique et une fondation rigide. La loi de comportement de ce corps est non-linéaire et le contact est modélisé par les conditions de Signorini. Ce travail est divisé en trois parties. La première est destinée à définir quelques outils de l'analyse fonctionnelle. La seconde est consacrée aux résultats d'existence et d'unicité de la solution. La troisième est réservée à l'étude de quelques propriétés de la solution. Ce travail diffère de celui de Drabla, Sofonea et Teniou [1] par l'étude de nouvelles propriétés de la solution qui sont dues à l'introduction d'un paramètre dans la loi de comportement et le changement d'une condition aux limites.

  8. Device for measuring the tritium concentration in a measuring gas

    International Nuclear Information System (INIS)

    Koran, P.

    1987-01-01

    The measuring gas is brought into contact via a measuring gas path with a diaphragm permeable to water, which separates the measuring gas path from a counter gas path leading to a proportional detector. The measuring gas path and the counter gas path are in counterflow in the area of diaphragm. The preferably hose diaphragm consists of a well-known ion exchange material, which can be used for gas drying purposes, which is permeable to water and tritium compounds similar to water, but is impermeable to other gases and liquids contained in air, particularly rare gases. In this way, the tritium concentration can be measured with great rare gas suppression. (orig./HP) [de

  9. Contact heating of water products of combustion of natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Aronov, I Z

    1978-01-01

    The USSR's NIIST examined the processes and equipment for heating water by submerged combustion using natural gas. Written for engineers involved with the design and application of thermal engineering equipment operating with natural gas, the book emphasizes equipment, test results, and methods of calculating heat transfer for contact gas economizers developed by Scientific Research Institute of Sanitary Engineering and other Soviet organizations. The economic effectiveness of submerged-combustion heating depends on several factors, including equipment design. Recommendations cover cost-effective designs and applications of contact economizers and boilers.

  10. Permeability changes in coal resulting from gas desorption. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Levine, J.R.; Johnson, P.W.

    1992-11-30

    This report documents studies on the effects of gas sorption on coal, with the intent of eventually evaluating how sorption and strain affect permeability. These studies were, carried out at the University of Alabama during the period from 1989 through 1992. Two major experimental methods were developed and used. In the strain experiments, electronic strain gauges were attached to polished blocks of coal in order to measure linear and volumetric swelling due to gas sorption. The effects of bedding plane orientation, of gas type, and of coal type were investigated. In the gravimetric experiment the weight of small samples of coal was measured during exposure to high pressure gases. Sample measurements were corrected for buoyancy effects and for sample swelling, and the results were plotted in the form of Langmuir isotherms. Experiments were conducted to determine the effect of grain size, coal type, moisture, and of sorbant gas. The advantage of this method is that it can be applied to very small samples, and it enabled comparison liptinite versus vitrinite concentrates, and kerogen rich versus kerogen depleted oil shales. Also included is a detailed discussion of the makeup of coal and its effect on gas sorption behavior.

  11. Recovery of ammonia from swine manure using gas-permeable membranes: Effect of aeration

    Science.gov (United States)

    Gas-permeable membranes can recover ammonia from manure, reducing pollution whilst converting ammonia into ammonium salt fertilizer. The process involves manure pH control to increase ammonium (NH4) recovery rate that is normally carried out using an alkali. In this study a new strategy to avoid the...

  12. Effect of temperature on sandstone permeability

    DEFF Research Database (Denmark)

    Rosenbrand, Esther; Kjøller, Claus

    Hot water injection in geothermal sandstone aquifers is considered for seasonal energy storage in Denmark. However, an increase in the aquifer temperature might reduce permeability, and thereby increase production costs. An understanding of the factors that control permeability is required in order...... and the Klinkenberg procedure showed the expected correlation between the two measures, however, differences could be around one order of magnitude. In tight gas sandstones, permeability is often sensitive to net stress, which might change due to the pore pressure change in the Klinkenberg procedure. Besides...... affecting the Klinkenberg procedure, the combined effect of slip and changes in permeability would affect production during pressure depletion in tight gas sandstone reservoirs; therefore effects of gas slip and net stress on permeability were combined in a model based on the Klinkenberg equation. A lower...

  13. Verification of capillary pressure functions and relative permeability equations for gas production

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Jaewon [Arizona State Univ., Tempe, AZ (United States)

    2016-10-25

    The understanding of multiphase fluid flow in porous media is of great importance in many fields such as enhanced oil recovery, hydrology, CO2 sequestration, contaminants cleanup and natural gas production from hydrate bearing sediments. However, there are many unanswered questions about the key parameters that characterize gas and water flows in porous media. The characteristics of multiphase fluid flow in porous media such as water retention curve, relative permeability, preferential fluid flow patterns and fluid-particle interaction should be taken into consideration for a fundamental understanding of the behavior of pore scale systems.

  14. Causes of poor sealant performance in soil-gas-resistant foundations

    International Nuclear Information System (INIS)

    Scott, A.

    1994-01-01

    Sealants for radon-resistant foundation construction must seal the gap between concrete sections. Modern sealants have such low permeability that seal performance depends only on the permeability of the material that contacts the sealant. The surface permeability of concrete walls and floors was measured by a specially designed permeameter, which measures the airflow induced by a pressure difference across a temporary test seal applied to the surface. The permeability of bulk concrete is about 10 -15 m 2 . Areas free of surface defects had surface permeability ranging from 10 -14 to 10 -16 m 2 . However, surface defects are common on concrete wall surfaces, which increase the permeability to >10 -12 m 2 , too high for standard seal designs to be adequate as the only method of soil gas and radon exclusion. Radon-resistant seals require either extended contact widths or mechanical removal of the surface layer and defects. (au) (4 refs.)

  15. Gas diffusion, non-Darcy air permeability, and computed tomography images of a clay subsoil affected by compaction

    DEFF Research Database (Denmark)

    Schjønning, Per; Lamandé, Mathieu; Berisso, Feto Esimo

    2013-01-01

    Soil productivity and other soil functions are dependent on processes in the untilled subsoil. Undisturbed soil cores were collected at the 0.3- to 0.4-m depth from a heavy clay soil in Finland subjected to a single heavy traffic event by agricultural machinery three decades before sampling....... Untrafficked control plots were used as a reference. Computed tomography (CT) scanning was performed on soil cores at a field-sampled field capacity water content. Gas diffusion and air permeability were measured when the soil cores were drained to −1000 hPa matric potential (air permeability also at −100...... and −300 hPa). The air-filled pore space was measured with an air pycnometer and also calculated from mass balance and CT data. Gas diffusion and air permeability were also measured on a straight model tube and on autoclaved aerated concrete. The compaction treatment had not influenced soil total porosity...

  16. Molecular dynamics study of contact mechanics: contact area and interfacial separation from small to full contact

    OpenAIRE

    Yang, C.; Persson, B. N. J.

    2007-01-01

    We report a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. We study the contact area and the interfacial separation from small contact (low load) to full contact (high load). For small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load. For high load the contact area approaches to the nominal contact area (i.e., complete contact), and the i...

  17. Contact mechanics: contact area and interfacial separation from small contact to full contact

    International Nuclear Information System (INIS)

    Yang, C; Persson, B N J

    2008-01-01

    We present a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. The numerical calculations mainly focus on the contact area and the interfacial separation from small contact (low load) to full contact (high load). For a small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load. For a high load the contact area approaches the nominal contact area (i.e. complete contact), and the interfacial separation approaches zero. The numerical results have been compared with analytical theory and experimental results. They are in good agreement with each other. The present findings may be very important for soft solids, e.g. rubber, or for very smooth surfaces, where complete contact can be reached at moderately high loads without plastic deformation of the solids

  18. Permeability and Selectivity of PPO/Graphene Composites as Mixed Matrix Membranes for CO2 Capture and Gas Separation

    Directory of Open Access Journals (Sweden)

    Riccardo Rea

    2018-01-01

    Full Text Available We fabricated novel composite (mixed matrix membranes based on a permeable glassy polymer, Poly(2,6-dimethyl-1,4-phenylene oxide (PPO, and variable loadings of few-layer graphene, to test their potential in gas separation and CO2 capture applications. The permeability, selectivity and diffusivity of different gases as a function of graphene loading, from 0.3 to 15 wt %, was measured at 35 and 65 °C. Samples with small loadings of graphene show a higher permeability and He/CO2 selectivity than pure PPO, due to a favorable effect of the nanofillers on the polymer morphology. Higher amounts of graphene lower the permeability of the polymer, due to the prevailing effect of increased tortuosity of the gas molecules in the membrane. Graphene also allows dramatically reducing the increase of permeability with temperature, acting as a “stabilizer” for the polymer matrix. Such effect reduces the temperature-induced loss of size-selectivity for He/N2 and CO2/N2, and enhances the temperature-induced increase of selectivity for He/CO2. The study confirms that, as observed in the case of other graphene-based mixed matrix glassy membranes, the optimal concentration of graphene in the polymer is below 1 wt %. Below such threshold, the morphology of the nanoscopic filler added in solution affects positively the glassy chains packing, enhancing permeability and selectivity, and improving the selectivity of the membrane at increasing temperatures. These results suggest that small additions of graphene to polymers can enhance their permselectivity and stabilize their properties.

  19. Measurement of gas permeability through geo-synthetic clay liners; Mesure de la permeabilite au gaz a travers des geosynthetiques bentonitiques

    Energy Technology Data Exchange (ETDEWEB)

    Bouazza, A.; Vangpaisal, T. [Monash University, Melbourne, Victoria (Australia)

    2000-07-01

    While much research has been performed to investigate the ability of GCLs to limit flow through minimization of the saturated hydraulic conductivity, very little is known about their capabilities to control gas flux and therefore reducing gas migration into the atmosphere or the areas surrounding landfills. The aim of this study was to assess gas flow through GCLs with a simple and reliable testing procedure. A gas permeameter was developed to study gas flow through partially saturated geo-synthetic clay liners (GCLs). Measurements of the differential pressure across the GCL sample at varying flow rates were used to calculate gas permeability at different moisture contents. For the range of water content studied (65% < {omega} < 128%) a decrease of around 4 orders of magnitude in the GCL permeability has been observed. This suggests that the GCL degree of hydration during the design life of a waste containment facility is an important issue to address in the design process of a lining or cover system using a GCL. (authors)

  20. Polymer/Silicate Nanocomposites Used to Manufacture Gas Storage Tanks With Reduced Permeability

    Science.gov (United States)

    Campbell, Sandi G.; Johnston, Chris

    2004-01-01

    Over the past decade, there has been considerable research in the area of polymer-layered silicate nanocomposites. This research has shown that the dispersion of small amounts of an organically modified layered silicate improves the polymer strength, modulus, thermal stability, and barrier properties. There have been several reports on the dispersion of layered silicates in an epoxy matrix. Potential enhancements to the barrier properties of epoxy/silicate nanocomposites make this material attractive for low permeability tankage. Polymer matrix composites (PMCs) have several advantages for cryogenic storage tanks. They are lightweight, strong, and stiff; therefore, a smaller fraction of a vehicle's potential payload capacity is used for propellant storage. Unfortunately, the resins typically used to make PMC tanks have higher gas permeability than metals. This can lead to hydrogen loss through the body of the tank instead of just at welds and fittings. One approach to eliminate this problem is to build composite tanks with thin metal liners. However, although these tanks provide good permeability performance, they suffer from a substantial mismatch in the coefficient of thermal expansion, which can lead to failure of the bond between the liner and the body of the tank. Both problems could be addressed with polymersilicate nanocomposites, which exhibit reduced hydrogen permeability, making them potential candidates for linerless PMC tanks. Through collaboration with Northrop Grumman and Michigan State University, nanocomposite test tanks were manufactured for the NASA Glenn Research Center, and the helium permeability was measured. An organically modified silicate was prepared at Michigan State University and dispersed in an epoxy matrix (EPON 826/JeffamineD230). The epoxy/silicate nanocomposites contained either 0 or 5 wt% of the organically modified silicate. The tanks were made by filament winding carbon fibers with the nanocomposite resin. Helium permeability

  1. Effect of corneal cross-linking on contact lens tolerance in keratoconus.

    Science.gov (United States)

    Ünlü, Metin; Yüksel, Erdem; Bilgihan, Kamil

    2017-07-01

    The aim was to investigate changes in corneal sensation and rigid gas-permeable (RGP) contact lens tolerance after corneal cross-linking (CXL) on patients with keratoconus. Thirty eyes of 30 patients, who were RGP lens intolerant, were treated with CXL. The main outcome measures were corneal sensation evaluation by Cochet-Bonnet esthesiometry, sub-basal nerve fibre assessment by corneal in vivo confocal microscopy and RGP contact lens tolerance evaluation with the Likert scale and wearing time. All eyes were evaluated preoperatively and post-operatively at one, three and six months after CXL procedure. The mean age was 25.3 ± 6.2 years. Preoperatively, the maximum keratometry (Kmax) in study eyes was 56.89 ± 4.60 D. Six months after CXL, it reduced to 56.03 ± 4.85 D (p = 0.01). Preoperative mean corneal sensation was 0.44 ± 0.05 g/mm 2 , (range: 0.40 to 0.55); it was significantly decreased at the first month and increased to preoperative values after six months. The sub-basal nerve plexus could not be visualised in 90 per cent of the patients by confocal microscopy at one month post-operatively. Gradual restoration of corneal innervation with almost similar preoperative levels at post-operative month six was noted. There were significant differences in Likert scores between preoperative and third and sixth months after CXL. Likert scale scores correlated significantly with corneal sensitivity. It can be concluded that increased RGP contact lens tolerance after CXL may be associated with the potential role of decreased corneal sensitivity and corneal flattening after CXL. © 2016 Optometry Australia.

  2. Field data provide estimates of effective permeability, fracture spacing, well drainage area and incremental production in gas shales

    KAUST Repository

    Eftekhari, Behzad

    2018-05-23

    About half of US natural gas comes from gas shales. It is valuable to study field production well by well. We present a field data-driven solution for long-term shale gas production from a horizontal, hydrofractured well far from other wells and reservoir boundaries. Our approach is a hybrid between an unstructured big-data approach and physics-based models. We extend a previous two-parameter scaling theory of shale gas production by adding a third parameter that incorporates gas inflow from the external unstimulated reservoir. This allows us to estimate for the first time the effective permeability of the unstimulated shale and the spacing of fractures in the stimulated region. From an analysis of wells in the Barnett shale, we find that on average stimulation fractures are spaced every 20 m, and the effective permeability of the unstimulated region is 100 nanodarcy. We estimate that over 30 years on production the Barnett wells will produce on average about 20% more gas because of inflow from the outside of the stimulated volume. There is a clear tradeoff between production rate and ultimate recovery in shale gas development. In particular, our work has strong implications for well spacing in infill drilling programs.

  3. Long-term bioventing performance in low-permeability soils

    International Nuclear Information System (INIS)

    Phelps, M.B.; Stanin, F.T.; Downey, D.C.

    1995-01-01

    Short-term and long-term bioventing treatability testing has shown that in situ air injection and extraction is a practical method for sustaining increased oxygen levels and enhancing aerobic biodegradation of petroleum hydrocarbons in low-permeability soils. At several test sites, initial physical parameter analysis of soils and air permeability tests indicated that impacted soils (fine sandy silts and clays) had low air permeabilities. Measurements of depleted soil-gas oxygen levels and increased soil-gas carbon dioxide levels indicated that the natural process of aerobic biodegradation of petroleum hydrocarbons was oxygen-limited. Initial treatability testing consisted of air permeability tests to measure the permeability of the soils to air and in situ respiration tests to measure the rates at which native microorganisms could biodegrade the contaminants when provided with sufficient oxygen. During the long-term treatment period, active air injection or extraction systems were operated for 1 year or longer. Soil gas was periodically monitored within the treatment zone to evaluate the success of the bioventing systems in increasing soil-gas oxygen levels in the low-permeability soils. Follow-up respiration tests and soil and soil-gas sampling were conducted to evaluate changes in respiration rates and contaminant concentrations with time

  4. Axisymmetric wave propagation in gas shear flow confined by a rigid-walled pipeline

    International Nuclear Information System (INIS)

    Chen Yong; Huang Yi-Yong; Chen Xiao-Qian; Bai Yu-Zhu; Tan Xiao-Dong

    2015-01-01

    The axisymmetric acoustic wave propagating in a perfect gas with a shear pipeline flow confined by a circular rigid wall is investigated. The governing equations of non-isentropic and isentropic acoustic assumptions are mathematically deduced while the constraint of Zwikker and Kosten is relaxed. An iterative method based on the Fourier–Bessel theory is proposed to semi-analytically solve the proposed models. A comparison of numerical results with literature contributions validates the present contribution. Meanwhile, the features of some high-order transverse modes, which cannot be analyzed based on the Zwikker and Kosten theory, are analyzed (paper)

  5. Rigid telescopy and contact endoscopy in the diagnosis and surgery of Reinke’s oedema: Clinical and histological assessment

    Directory of Open Access Journals (Sweden)

    Jovanović Milan B.

    2005-01-01

    Full Text Available We focussed our attention on the use of both rigid telescopy and contact endoscopy in order to assess their effectiveness in the diagnosis and surgery of Reinke’s oedema. Changes were observed in a sample of 40 patients, suffering from different stages of Reinke’s oedema, who had undergone microlaryngoscopies. For the first time during our laryngological praxis, we discussed a number of parameters that appeared to be significant in the monitoring and detailed evaluation of this vocal fold disease. With contact endoscopy, during the early stages of the disease, the cells and nuclei of normal squamous layered epithelium continued to display uniform morphological features. The appearance of epithelial changes helps to distinguish between different stages of Reinke’s oedema, which can be associated with severe inflammation or keratinisation. With latter-stage oedemas, the following was observed: various changes in the blood vessels of the glottis, which when viewed through the endoscope have an unusual “loop-like” or “branching” appearance, as well as elongated and varicose blood vessels, and the build-up of erythrocytes inside atypical capillaries. Both endoscope techniques are non-invasive and very appropriate for precisely diagnosing Reinke’s oedema within a relatively short period of time. Rigid telescopy has the advantage of enabling the systematic observation of many details in the large area of both vocal fold mucosae, particularly when access to the larynx is difficult. This enables dynamic monitoring and immediate pathology consultations inside the operating theatre. The special contribution of contact endoscopy is that, both in vivo and in situ, it allows a detailed scanning and mapping to be performed of all cell changes and of vascularisation throughout the entire mucosa surface. Video-assisted telescopy does not permit a completely first-rate surgical resection of Reinke’s oedema, because of unsatisfactory control or

  6. Gas permeability of thin polyimide foils prepared by in-situ polymerisation

    International Nuclear Information System (INIS)

    Stolarz, Anna; Varlam, Mihai; Wellum, Roger

    2008-01-01

    The entrance windows to the gas detector chambers as well as to the target containers used in high-energy and high-intensity accelerators must be as thin as possible to minimise energy losses of the particles used in astrophysics and nuclear physics studies. Because of their good physical properties, polyimide foils are often considered as suitable material for such windows, but commercially available foils, having a thickness greater than 7-8 μm (>1 mg/cm 2 ), would cause energy losses of particles significant for some nuclear reactions studied. Foils prepared by in-situ polymerisation can, however, be as thin as 0.07 μm (∼10 μg/cm 2 ). The permeability of 4 μm foils produced by in-situ polymerisation has been measured at room temperature for He and Ar. For He measurements were performed in the pressure range of 4-70 mbar and for Ar in the range of 20-140 mbar and the permeability was found to be in good agreement with the values published for the thicker commercial foils

  7. Hydrogen extraction from liquid lithium-lead alloy by gas-liquid contact method

    International Nuclear Information System (INIS)

    Xie Bo; Weng Kuiping; Hou Jianping; Yang Guangling; Zeng Jun

    2013-01-01

    Hydrogen extraction experiment from liquid lithium-lead alloy by gas-liquid contact method has been carried out in own liquid lithium-lead bubbler (LLLB). Experimental results show that, He is more suitable than Ar as carrier gas in the filler tower. The higher temperature the tower is, the greater hydrogen content the tower exports. Influence of carrier gas flow rate on the hydrogen content in the export is jagged, no obvious rule. Although the difference between experimental results and literature data, but it is feasible that hydrogen isotopes extraction experiment from liquid lithium-lead by gas-liquid contact method, and the higher extraction efficiency increases with the growth of the residence time of the alloy in tower. (authors)

  8. Foam film permeability: theory and experiment.

    Science.gov (United States)

    Farajzadeh, R; Krastev, R; Zitha, Pacelli L J

    2008-02-28

    The mass transfer of gas through foam films is a prototype of various industrial and biological processes. The aim of this paper is to give a perspective and critical overview of studies carried out to date on the mass transfer of gas through foam films. Contemporary experimental data are summarized, and a comprehensive overview of the theoretical models used to explain the observed effects is given. A detailed description of the processes that occur when a gas molecule passes through each layer that forms a foam film is shown. The permeability of the film-building surfactant monolayers plays an important role for the whole permeability process. It can be successfully described by the models used to explain the permeability of surfactant monolayers on aqueous sub-phase. For this reason, the present paper briefly discusses the surfactant-induced resistance to mass transfer of gases through gas-liquid interface. One part of the paper discusses the experimental and theoretical aspects of the foam film permeability in a train of foam films in a matrix or a cylinder. This special case is important to explain the gas transfer in porous media or in foams. Finally, this paper will highlight the gaps and challenges and sketch possible directions for future research.

  9. Mathematical Modeling of Contact Problems of Elasticity Theory with Continuous Unilateral Contact

    Directory of Open Access Journals (Sweden)

    I. V. Stankevich

    2015-01-01

    Full Text Available The work [1] presents the formulation and numerical solution of the problem concerning the unilateral discrete contact interaction of an elastic body and a rigid half-space. However, many parts and components of engineering structures have a pronounced continuous contact within a given surface [2, 3]. In this paper we consider a special case of this option of contact interaction when, the elastic body of finite size, subjected to external forces, is based on a rigid half-space. Contact occurs through a dedicated contact surface, which in general can change their sizes.Developed to solve this problem, a numerical algorithm is a further adaptation and development of the approaches described in [1]. The paper shows results of solving the model problem of the elasticity theory with and without taking friction into account. In the latter case, were additionally obtained numerical data characterizing the convergence of the solution.

  10. Gas permeability of bentonite barriers: development, construction and testing of a measurement system

    Directory of Open Access Journals (Sweden)

    Heraldo Nunes Pitanga

    Full Text Available Abstract This article proposes a testing device to quickly and reliably estimate the gas permeability of bentonite-based clay barriers used in landfill cover systems. The testing methodology is based on a transient gas flow regime that passes through the barrier, therefore not requiring the use of sophisticated equipment that aim to maintain constant differential pressure and measure the gas flow, common requirements for testing methods under a permanent flow regime. To confirm the feasibility of the proposed technique, tests were performed on a pure hydrated bentonite layer, which subsequently encompassed samples of geosynthetic clay liner (GCL at different moisture contents. Geosynthetic clay liners are often selected as a part of the barrier layer for cover systems in solid waste landfills to prevent infiltration of rainfall and migration of biogas into the atmosphere. The results confirmed the equipment reliability and differentiate the different responses of the gas flow barriers studied, considering their different compositions and different moistures.

  11. Contact Problem for an Elastic Layer on an Elastic Half Plane Loaded by Means of Three Rigid Flat Punches

    Directory of Open Access Journals (Sweden)

    T. S. Ozsahin

    2013-01-01

    Full Text Available The frictionless contact problem for an elastic layer resting on an elastic half plane is considered. The problem is solved by using the theory of elasticity and integral transformation technique. The compressive loads P and Q (per unit thickness in direction are applied to the layer through three rigid flat punches. The elastic layer is also subjected to uniform vertical body force due to effect of gravity. The contact along the interface between elastic layer and half plane is continuous, if the value of the load factor, λ, is less than a critical value, . In this case, initial separation loads, and initial separation points, are determined. Also the required distance between the punches to avoid any separation between the punches and the elastic layer is studied and the limit distance between punches that ends interaction of punches is investigated for various dimensionless quantities. However, if tensile tractions are not allowed on the interface, for the layer separates from the interface along a certain finite region. Numerical results for distance determining the separation area, vertical displacement in the separation zone, contact stress distribution along the interface between elastic layer and half plane are given for this discontinuous contact case.

  12. Lattice gas methods for predicting intrinsic permeability of porous media

    Energy Technology Data Exchange (ETDEWEB)

    Santos, L.O.E.; Philippi, P.C. [Santa Catarina Univ., Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica. Lab. de Propriedades Termofisicas e Meios Porosos)]. E-mail: emerich@lmpt.ufsc.br; philippi@lmpt.ufsc.br; Damiani, M.C. [Engineering Simulation and Scientific Software (ESSS), Florianopolis, SC (Brazil). Parque Tecnologico]. E-mail: damiani@lmpt.ufsc.br

    2000-07-01

    This paper presents a method for predicting intrinsic permeability of porous media based on Lattice Gas Cellular Automata methods. Two methods are presented. The first is based on a Boolean model (LGA). The second is Boltzmann method (LB) based on Boltzmann relaxation equation. LGA is a relatively recent method developed to perform hydrodynamic calculations. The method, in its simplest form, consists of a regular lattice populated with particles that hop from site to site in discrete time steps in a process, called propagation. After propagation, the particles in each site interact with each other in a process called collision, in which the number of particles and momentum are conserved. An exclusion principle is imposed in order to achieve better computational efficiency. In despite of its simplicity, this model evolves in agreement with Navier-Stokes equation for low Mach numbers. LB methods were recently developed for the numerical integration of the Navier-Stokes equation based on discrete Boltzmann transport equation. Derived from LGA, LB is a powerful alternative to the standard methods in computational fluid dynamics. In recent years, it has received much attention and has been used in several applications like simulations of flows through porous media, turbulent flows and multiphase flows. It is important to emphasize some aspects that make Lattice Gas Cellular Automata methods very attractive for simulating flows through porous media. In fact, boundary conditions in flows through complex geometry structures are very easy to describe in simulations using these methods. In LGA methods simulations are performed with integers needing less resident memory capability and boolean arithmetic reduces running time. The two methods are used to simulate flows through several Brazilian reservoir petroleum rocks leading to intrinsic permeability prediction. Simulation is compared with experimental results. (author)

  13. Spatial resolution of gas hydrate and permeability changes from ERT data in LARS simulating the Mallik gas hydrate production test

    Science.gov (United States)

    Priegnitz, Mike; Thaler, Jan; Spangenberg, Erik; Schicks, Judith M.; Abendroth, Sven

    2014-05-01

    The German gas hydrate project SUGAR studies innovative methods and approaches to be applied in the production of methane from hydrate-bearing reservoirs. To enable laboratory studies in pilot scale, a large reservoir simulator (LARS) was realized allowing for the formation and dissociation of gas hydrates under simulated in-situ conditions. LARS is equipped with a series of sensors. This includes a cylindrical electrical resistance tomography (ERT) array composed of 25 electrode rings featuring 15 electrodes each. The high-resolution ERT array is used to monitor the spatial distribution of the electrical resistivity during hydrate formation and dissociation experiments over time. As the present phases of poorly conducting sediment, well conducting pore fluid, non-conducting hydrates, and isolating free gas cover a wide range of electrical properties, ERT measurements enable us to monitor the spatial distribution of these phases during the experiments. In order to investigate the hydrate dissociation and the resulting fluid flow, we simulated a hydrate production test in LARS that was based on the Mallik gas hydrate production test (see abstract Heeschen et al., this volume). At first, a hydrate phase was produced from methane saturated saline water. During the two months of gas hydrate production we measured the electrical properties within the sediment sample every four hours. These data were used to establish a routine estimating both the local degrees of hydrate saturation and the resulting local permeabilities in the sediment's pore space from the measured resistivity data. The final gas hydrate saturation filled 89.5% of the total pore space. During hydrate dissociation, ERT data do not allow for a quantitative determination of free gas and remaining gas hydrates since both phases are electrically isolating. However, changes are resolved in the spatial distribution of the conducting liquid and the isolating phase with gas being the only mobile isolating phase

  14. Selectively gas-permeable composite membrane and process for production thereof

    International Nuclear Information System (INIS)

    Okita, K.; Asako, S.

    1984-01-01

    A selectively gas-permeable composite membrane and a process for producing said composite membrane are described. The composite membrane comprises a polymeric material support and a thin membrane deposited on the support, said thin membrane being obtained by glow discharge plasma polymerization of an organosilane compound containing at least one double bond or triple bond. Alternatively, the composite membrane comprises a polymeric material support having an average pore diameter of at least 0.1 micron, a hardened or cross-linked polyorganosiloxane layer on the support, and a thin membrane on the polyorganosiloxane layer, said thin membrane being obtained by plasma polymerization due to glow discharge of an organosilane compound containing at least one double bond or triple bond

  15. Pregnancy-induced progression of keratoconus.

    Science.gov (United States)

    Bilgihan, Kamil; Hondur, Ahmet; Sul, Sabahattin; Ozturk, Sertac

    2011-09-01

    To report eyes with keratoconus that progressed during pregnancy. Seven eyes of 4 patients with progression of keratoconus during pregnancy were included in this study. The mean age of patients and the mean follow-up duration were 29.3 years and 39 months, respectively. Progressive keratoconus was documented with changes in refraction, corneal topography, and rigid gas-permeable lens fitting pattern. Patients with accompanying systemic and ocular diseases associated with keratoconus, uncontrolled atopic disease, and eye rubbing were excluded. Mean increase in spherical equivalent refraction and simulated keratometry values were 1.4 ± 1.1 and 1.1 ± 0.8 diopters, respectively. In eyes wearing rigid gas-permeable lenses, increase in corneal apical touch and decrease in the base curve radius of the best-fitting contact lens were observed. Hormonal changes during pregnancy may affect corneal biomechanics negatively, and pregnancy may be a previously unrecognized risk factor for progression of keratoconus. To our knowledge, this is the first study showing pregnancy-induced keratoconus progression in patients with no accompanying disease.

  16. Which soft lens power is better for piggyback in keratoconus? Part II.

    Science.gov (United States)

    Romero-Jiménez, Miguel; Santodomingo-Rubido, Jacinto; González-Meijóme, Jose-Manuel; Flores-Rodriguez, Patricia; Villa-Collar, Cesar

    2015-02-01

    To evaluate how soft lens power affects rigid gas-permeable (RGP) lens power and visual acuity (VA) in piggyback fittings for keratoconus. Sixteen keratoconus subjects (30 eyes) were included in the study. Piggyback contact lens fittings combining Senofilcon-A soft lenses of -6.00, -3.00, +3.00 and +6.00 D with Rose K2 RGP contact lenses were performed. Corneal topography was taken on the naked eye and over each soft contact lens before fitting RGP lenses. Mean central keratometry, over-refraction, RGP back optic zone radius (BOZR) and estimated final power as well as VA were recorded and analyzed. In comparison to the naked eye, the mean central keratometry flattened with both negative lens powers (psoft lens power (p=1.0); and steepened with the +6.00 soft lens power (p=0.02). Rigid gas-permeable over-refraction did not change significantly between different soft lens powers (all p>0.05). RGP's BOZR decreased significantly with both positive in comparison with both negative soft lens powers (all ppowers separately (both p>0.05). Estimated RGP's final power increased significantly with positive in comparison with negative lens powers (all ppowers separately (both p>0.05). Visual acuity did not change significantly between the different soft lens powers assessed (all p>0.05). The use of negative-powered soft lenses in piggyback fitting reduces RGP lens power without impacting VA in keratoconus subjects. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  17. A drainage data-based calculation method for coalbed permeability

    International Nuclear Information System (INIS)

    Lai, Feng-peng; Li, Zhi-ping; Fu, Ying-kun; Yang, Zhi-hao

    2013-01-01

    This paper establishes a drainage data-based calculation method for coalbed permeability. The method combines material balance and production equations. We use a material balance equation to derive the average pressure of the coalbed in the production process. The dimensionless water production index is introduced into the production equation for the water production stage. In the subsequent stage, which uses both gas and water, the gas and water production ratio is introduced to eliminate the effect of flush-flow radius, skin factor, and other uncertain factors in the calculation of coalbed methane permeability. The relationship between permeability and surface cumulative liquid production can be described as a single-variable cubic equation by derivation. The trend shows that the permeability initially declines and then increases after ten wells in the southern Qinshui coalbed methane field. The results show an exponential relationship between permeability and cumulative water production. The relationship between permeability and cumulative gas production is represented by a linear curve and that between permeability and surface cumulative liquid production is represented by a cubic polynomial curve. The regression result of the permeability and surface cumulative liquid production agrees with the theoretical mathematical relationship. (paper)

  18. Analysis of Gas Permeability Characteristics of Poly(Lactic Acid/Poly(Butylene Succinate Nanocomposites

    Directory of Open Access Journals (Sweden)

    Amita Bhatia

    2012-01-01

    Full Text Available Gas permeability and morphological properties of nanocomposites prepared by the mixing of poly(lactic acid (PLA, poly(butylene succinate (PBS, and clay was investigated. While the composition of PLA and PBS polymers was fixed as 80% and 20% by weight, respectively, for all the nanocomposites, clay contents varied from 1 to 10 wt%. From the morphological studies using both wide angle X-ray diffraction and transmission electron microscopy, the nanocomposite having 1 wt% of clay was considered to have a mixed morphology of intercalated and delaminated structure, while some clusters or agglomerated particles were detected for nanocomposites having 3 and more than 3 wt% of clay content. However, the average particle size of the dispersed PBS phase was reduced significantly from 7 μm to 30–40 nm with the addition of clay in the blend. The oxygen barrier property was improved significantly as compared to the water vapor. A model based on gas barrier property was used for the validation of the oxygen relative permeabilities of PLA/PBS/clay nanocomposites. PLA/PBS/clay nanocomposites validated the Bharadwaj model up to 3 wt% of clay contents only, while for nanocomposites of higher clay contents the Bharadwaj model was invalid due to the clusters and agglomerates formed.

  19. Ocular surface and tear film status among contact lens wearers and non-wearers who use VDT at work: comparing three different lens types.

    Science.gov (United States)

    Tauste, Ana; Ronda, Elena; Baste, Valborg; Bråtveit, Magne; Moen, Bente E; Seguí Crespo, María-Del-Mar

    2018-04-01

    To analyze differences in the ocular surface appearance and tear film status of contact lens wearers and non-wearers in a group of visual display terminals (VDT) workers and additionally to assess differences between lens materials. Cross-sectional study of 236 office workers, of whom 92 were contact lens wearers. Workers provided information on their contact lenses (conventional hydrogel, silicone hydrogel or rigid gas permeable lenses) and exposure to VDT at work. Ocular surface and tear film status were determined by the presence of bulbar, limbal and lid redness, lid roughness and corneal staining type, and by Schirmer's and tear break-up time tests (TBUT). A generalized linear model was used to calculate the crude (cRR) and age- and sex-adjusted (aRR) relative risk to measure the association between ocular surface and tear film abnormalities and contact lens use and type. The aRR of ocular surface abnormalities was higher in contact lens wearers compared to non-wearers: bulbar redness (aRR 1.69; 95% CI 1.25-2.30), limbal redness (aRR 2.87; 1.88-4.37), lid redness (aRR 2.53; 1.35-4.73) and lid roughness (aRR 7.03; 1.31-37.82). VDT exposure > 4 h/day increased wearers' risk of limbal and lid redness. Conventional hydrogel wearers had the highest risk of ocular surface abnormalities, followed by silicone hydrogel wearers. Both contact and non-contact lens wearers had a high prevalence of altered TBUT (77.3 and 75.7% respectively) and Schirmer (51.8 and 41.3%). Regular contact lens use during VDT exposure at work increases risk of bulbar, limbal and lid redness, and lid roughness, especially in soft contact lens wearers. The high prevalence of altered TBUT and Schirmer's results in all participants suggests that VDT use greatly affects tear film characteristics.

  20. Effect of CH4 on the CO2 breakthrough pressure and permeability of partially saturated low-permeability sandstone in the Ordos Basin, China

    Science.gov (United States)

    Zhao, Yan; Yu, Qingchun

    2018-01-01

    The behavior of CO2 that coexists with CH4 and the effect of CH4 on the CO2 stream need to be deeply analyzed and studied, especially in the presence of water. Our previous studies investigated the breakthrough pressure and permeability of pure CO2 in five partially saturated low-permeability sandstone core samples from the Ordos Basin, and we concluded that rocks with a small pore size and low permeability show considerable sealing capacity even under unsaturated conditions. In this paper, we selected three of these samples for CO2-CH4 gas-mixture breakthrough experiments under various degrees of water saturation. The breakthrough experiments were performed by increasing the gas pressure step by step until breakthrough occurred. Then, the effluent gas mixture was collected for chromatographic partitioning analysis. The results indicate that CH4 significantly affects the breakthrough pressure and permeability of CO2. The presence of CH4 in the gas mixture increases the interfacial tension and, thus, the breakthrough pressure. Therefore, the injected gas mixture that contains the highest (lowest) mole fraction of CH4 results in the largest (smallest) breakthrough pressure. The permeability of the gas mixture is greater than that for pure CO2 because of CH4, and the effective permeability decreases with increased breakthrough pressure. Chromatographic partitioning of the effluent mixture gases indicates that CH4 breaks through ahead of CO2 as a result of its weaker solubility in water. Correlations are established between (1) the breakthrough pressure and water saturation, (2) the effective permeability and water saturation, (3) the breakthrough pressure and effective permeability, and (4) the mole fraction of CO2/CH4 in the effluent mixture gases and water saturation. These results deepen our understanding of the multi-phase flow behavior in the porous media under unsaturated conditions, which have implications for formulating emergency response plans for gas

  1. Determination of Intrinsic Permeability for Packed Waste of Indonesian Solid Waste

    Directory of Open Access Journals (Sweden)

    Benno Rahardyan

    2010-11-01

    Full Text Available Gas permeability and intrinsic permeability are the major parameters to promote aeration for packed waste. The objectives of this research are to identify physical parameters of gas transfer from a various type of packed wastes and examine ventilation design theory for landfill to enhance waste stabilization. Method to determine value of gas permeability and intrinsic permeability for packed waste is by flushing the packed column containing various type and physical characteristics of wastes with an air pump. Permeability was calculated by measuring pressure gradient on sampling points of the column using inclined manometer at distance 10 cm, 23 cm, 46 cm, 69 cm, 92 cm and 115 cm from origin. Gas permeability is specifically relied on physical parameters of wastes as follows, density, moisture content, particle size and gas velocity on the surface of compacted waste layer. Compost has finer pore structure and smaller pore size than leaves as well as mixed organic (65% and inorganic wastes (35%. The experiment found the intrinsic permeability of leaves waste are in the order of 10-11 to 10-8 m2, 10-11 to 10-9 m2 for compost and 10-9 m2 for mixed organic (65% and inorganic wastes (35%.

  2. Straylight Measurements in Contact Lens Wear

    NARCIS (Netherlands)

    van der Meulen, Ivanka J. E.; Engelbrecht, Leonore A.; van Vliet, Johannes M. J.; Lapid-Gortzak, Ruth; Nieuwendaal, Carla P.; Mourits, Maarten P.; Schlingemann, Reinier O.; van den Berg, Thomas J. T. P.

    2010-01-01

    Purpose: (1) To quantify the effect of contact lens wear on straylight in rigid and soft contact lens wearers and (2) to relate findings to morphological changes and subjective complaints. Methods: Straylight was measured using the Oculus C-Quant during contact lens wear and after contact lens

  3. Lente de contato em crianças: aspectos epidemiológicos Contact lens in children: epidemiological aspects

    Directory of Open Access Journals (Sweden)

    André Luiz Alves Salame

    2008-06-01

    standard deviation of 2.42. The most common diagnosis was aphakia, in 16 (21.9% cases. Keratoconus was present in 14 (19.1%, leucoma in 11 (15%, anisometropia in 10 (13.7%, refractive errors in 9 (12.3%, irregular astigmatism in 7 (9.5%, ectopia lentis in 4 (5.4%, high myopia in one case (1.3% and one child (1.3% had no ocular pathology, just wishing to change eye color. 52 (71.2% had medical indication, 9 (12.3% had optical indication and 12 (16.4% had cosmetic indication. Contact lenses were fitted in 103 eyes, the most tested lens was rigid gas permeable in 43 (41.7%, soft lens in 41 (39.8% and cosmetic soft lens in 11 (10.6%. CONCLUSION: Aphakia was the most common diagnosis among children in use of contact lens. The incidence of medical indication was higher than the others and the most tested lens was the rigid gas permeable one.

  4. Effect of porosity heterogeneity on the permeability and tortuosity of gas diffusion layers in polymer electrolyte membrane fuel cells

    Science.gov (United States)

    Nabovati, Aydin; Hinebaugh, James; Bazylak, Aimy; Amon, Cristina H.

    2014-02-01

    In this paper, we study the effect of porosity heterogeneity on the bulk hydrodynamic properties (permeability and tortuosity) of simulated gas diffusion layers (GDLs). The porosity distributions of the heterogeneous reconstructed samples are similar to those previously reported in the literature for Toray TGP-H 120™ GDLs. We use the lattice Boltzmann method to perform pore-level flow simulations in the reconstructed GDL samples. Using the results of pore-level simulations, the effect of porosity distribution is characterized on the predicted in- and cross-plane permeability and tortuosity. It was found that porosity heterogeneity causes a higher in-plane permeability and lower in-plane tortuosity, while the effect is opposite in the cross-plane direction, that is a lower cross-plane permeability and a higher cross-plane tortuosity. We further investigate the effect of adding poly-tetra-fluoro-ethylene (PTFE) & binder material to the reconstructed GDL samples. Three fiber volume percentages of 50, 75, and 100% are considered. Overall, increasing the fiber volume percentage reduces the predicted in- and cross-plane permeability and tortuosity values. A previously reported relationship for permeability of fibrous materials is fitted to the predicted permeability values, and the magnitude of the fitting parameter is reported as a function of fiber volume percentage.

  5. Physical Aging, Plasticization and Their Effects on Gas Permeation in “Rigid” Polymers of Intrinsic Microporosity

    KAUST Repository

    Swaidan, Raja

    2015-08-29

    Long-term physical aging and plasticization, two mobility-based phenomena that are counterintuitive in the context of “rigid” polymers of intrinsic microporosity (PIMs), were evaluated using pure- and mixed-gas permeation data for representative ladder and semiladder PIMs. PIMs between 1 and 4 years old retained from 10- to 1000-fold higher H2 and O2 permeabilities than commercial membrane materials with similar or higher selectivities. A triptycene-based ladder polymer (TPIM-1) exhibited very large selectivity gains outweighing permeability losses after 780 days, resulting in unprecedented performance for O2/N2 (P(O2) = 61 Barrer, α(O2/N2) = 8.6) and H2/N2 (P(H2) = 1105 Barrer, α(H2/N2) = 156) separations. Interestingly, TPIM-1 aged more and faster than its more flexible counterpart, PIM-1, which exhibited P(O2) = 317 Barrer and α(O2/N2) = 5.0 at 1380 days. Additionally, the more “rigid” TPIM-1 plasticized more significantly than PIM-1 (i.e., TPIM-1 endured ∼93% increases in mixed-gas CH4 permeability over pure-gas values compared to ∼60% for PIM-1). A flexible 9,10-bridgehead (i.e., TPIM-2) mitigated the enhancements induced by physical aging but reduced plasticization. Importantly, intra-chain rigidity alone, without consideration of chain architecture and ultra-microporosity, is insufficient for designing aging- and plasticization-resistant gas separation membranes with high permeability and high selectivity

  6. Synthetic Rock Analogue for Permeability Studies of Rock Salt with Mudstone

    Directory of Open Access Journals (Sweden)

    Hongwu Yin

    2017-09-01

    Full Text Available Knowledge about the permeability of surrounding rock (salt rock and mudstone interlayer is an important topic, which acts as a key parameter to characterize the tightness of gas storage. The goal of experiments that test the permeability of gas storage facilities in rock salt is to develop a synthetic analogue to use as a permeability model. To address the permeability of a mudstone/salt layered and mixed rock mass in Jintan, Jiangsu Province, synthetic mixed and layered specimens using the mudstone and the salt were fabricated for permeability testing. Because of the gas “slippage effect”, test results are corrected by the Klinkenberg method, and the permeability of specimens is obtained by regression fitting. The results show that the permeability of synthetic pure rock salt is 6.9 × 10−20 m2, and its porosity is 3.8%. The permeability of synthetic mudstone rock is 2.97 × 10−18 m2, with a porosity 17.8%. These results are close to those obtained from intact natural specimens. We also find that with the same mudstone content, the permeability of mixed specimens is about 40% higher than for the layered specimens, and with an increase in the mudstone content, the Klinkenberg permeability increases for both types of specimens. The permeability and mudstone content have a strong exponential relationship. When the mudstone content is below 40%, the permeability increases only slightly with mudstone content, whereas above this threshold, the permeability increases rapidly with mudstone content. The results of the study are of use in the assessment of the tightness of natural gas storage facilities in mudstone-rich rock salt formations in China.

  7. Compliant contact versus rigid contact: A comparison in the context of granular dynamics

    Science.gov (United States)

    Pazouki, Arman; Kwarta, Michał; Williams, Kyle; Likos, William; Serban, Radu; Jayakumar, Paramsothy; Negrut, Dan

    2017-10-01

    We summarize and numerically compare two approaches for modeling and simulating the dynamics of dry granular matter. The first one, the discrete-element method via penalty (DEM-P), is commonly used in the soft matter physics and geomechanics communities; it can be traced back to the work of Cundall and Strack [P. Cundall, Proc. Symp. ISRM, Nancy, France 1, 129 (1971); P. Cundall and O. Strack, Geotechnique 29, 47 (1979), 10.1680/geot.1979.29.1.47]. The second approach, the discrete-element method via complementarity (DEM-C), considers the grains perfectly rigid and enforces nonpenetration via complementarity conditions; it is commonly used in robotics and computer graphics applications and had two strong promoters in Moreau and Jean [J. J. Moreau, in Nonsmooth Mechanics and Applications, edited by J. J. Moreau and P. D. Panagiotopoulos (Springer, Berlin, 1988), pp. 1-82; J. J. Moreau and M. Jean, Proceedings of the Third Biennial Joint Conference on Engineering Systems and Analysis, Montpellier, France, 1996, pp. 201-208]. The DEM-P and DEM-C are manifestly unlike each other: They use different (i) approaches to model the frictional contact problem, (ii) sets of model parameters to capture the physics of interest, and (iii) classes of numerical methods to solve the differential equations that govern the dynamics of the granular material. Herein, we report numerical results for five experiments: shock wave propagation, cone penetration, direct shear, triaxial loading, and hopper flow, which we use to compare the DEM-P and DEM-C solutions. This exercise helps us reach two conclusions. First, both the DEM-P and DEM-C are predictive, i.e., they predict well the macroscale emergent behavior by capturing the dynamics at the microscale. Second, there are classes of problems for which one of the methods has an advantage. Unlike the DEM-P, the DEM-C cannot capture shock-wave propagation through granular media. However, the DEM-C is proficient at handling arbitrary grain

  8. Gas Permeation Properties of Soluble Aromatic Polyimides Based on 4-Fluoro-4,4'-Diaminotriphenylmethane

    Directory of Open Access Journals (Sweden)

    Diego Guzmán-Lucero

    2015-04-01

    Full Text Available A series of new organic polyimides were synthesized from 4-fluoro-4'4"-diaminotriphenylmethane and four different aromatic dianhydrides through a one-step, high-temperature, direct polycondensation in m-cresol at 180–200 °C, resulting in the formation of high-molecular-weight polyimides (inherent viscosities ~ 1.0–1.3 dL/g. All the resulting polyimides exhibited good thermal stability with initial decomposition temperatures above 434 °C, glass-transition temperatures between 285 and 316 °C, and good solubility in polar aprotic solvents. Wide-angle X-ray scattering data indicated that the polyimides were amorphous. Dense membranes were prepared by solution casting and solvent evaporation to evaluate their gas transport properties (permeability, diffusivity, and solubility coefficients toward pure hydrogen, helium, oxygen, nitrogen, methane, and carbon dioxide gases. In general, the gas permeability was increased as both the fractional free volume and d-spacing were also increased. A good combination of permeability and selectivity was promoted efficiently by the bulky hexafluoroisopropylidene and 4-fluoro-phenyl groups introduced into the polyimides. The results indicate that the gas transport properties of these films depend on both the structure of the anhydride moiety, which controls the intrinsic intramolecular rigidity, and the 4-fluoro-phenyl pendant group, which disrupts the intermolecular packing.

  9. Causes of poor sealant performance in soil gas resistant foundations

    International Nuclear Information System (INIS)

    Scott, A.

    1993-01-01

    The surface permeability of concrete walls and floors in houses was measured with a specially designed permeameter, based on measuring the air-flow induced by a pressure difference across a temporary test seal applied to a surface. The permeability of bulk concrete is 10 -16 m 2 . Areas free of surface defects had permeability ranging from 10 -14 to 10- 16 m 2 . However, surface defects are common on concrete wall surfaces, which increase the permeability to >10 -12 m 2 . This is too high for standard seal designs to be adequate as the only method of soil gas and radon exclusion. Satisfactory seals require either extended contact width or mechanical removal of the surface layer. (orig.). (2 figs., 1 tab.)

  10. Rapid estimate of solid volume in large tuff cores using a gas pycnometer

    International Nuclear Information System (INIS)

    Thies, C.; Geddis, A.M.; Guzman, A.G.

    1996-09-01

    A thermally insulated, rigid-volume gas pycnometer system has been developed. The pycnometer chambers have been machined from solid PVC cylinders. Two chambers confine dry high-purity helium at different pressures. A thick-walled design ensures minimal heat exchange with the surrounding environment and a constant volume system, while expansion takes place between the chambers. The internal energy of the gas is assumed constant over the expansion. The ideal gas law is used to estimate the volume of solid material sealed in one of the chambers. Temperature is monitored continuously and incorporated into the calculation of solid volume. Temperature variation between measurements is less than 0.1 degrees C. The data are used to compute grain density for oven-dried Apache Leap tuff core samples. The measured volume of solid and the sample bulk volume are used to estimate porosity and bulk density. Intrinsic permeability was estimated from the porosity and measured pore surface area and is compared to in-situ measurements by the air permeability method. The gas pycnometer accommodates large core samples (0.25 m length x 0.11 m diameter) and can measure solid volume greater than 2.20 cm 3 with less than 1% error

  11. Direct numerical simulation of supercritical gas flow in complex nanoporous media: Elucidating the relationship between permeability and pore space geometry

    Science.gov (United States)

    Landry, C. J.; Prodanovic, M.; Eichhubl, P.

    2015-12-01

    Mudrocks and shales are currently a significant source of natural gas and understanding the basic transport properties of these formations is critical to predicting long-term production, however, the nanoporous nature of mudrocks presents a unique challenge. Mudrock pores are predominantly in the range of 1-100 nm, and within this size range the flow of gas at reservoir conditions will fall within the slip-flow and early transition-flow regime (0.001 clays). Here we present a local effective viscosity lattice Boltzmann model (LEV-LBM) constructed for flow simulation in the slip- and early-transition flow regimes, adapted here for complex geometries. At the macroscopic scale the LEV-LBM is parameterized with local effective viscosities at each node to capture the variance of the mean free path of gas molecules in a bounded system. The LEV-LBM is first validated in simple tube geometries, where excellent agreement with linearized Boltzmann solutions is found for Knudsen numbers up to 1.0. The LEV-LBM is then employed to quantify the length effect on the apparent permeability of tubes, which suggests pore network modeling of flow in the slip and early-transition regime will result in overestimation unless the length effect is considered. Furthermore, the LEV-LBM is used to evaluate the predictive value of commonly measured pore geometry characteristics such as porosity, pore size distribution, and specific solid surface area for the calculation of permeability. We show that bundle of tubes models grossly overestimate apparent permeability, as well as underestimate the increase in apparent permeability with decreasing pressure as a result of excluding topology and pore shape from calculations.

  12. Molten salt hazardous waste disposal process utilizing gas/liquid contact for salt recovery

    International Nuclear Information System (INIS)

    Grantham, L.F.; McKenzie, D.E.

    1984-01-01

    The products of a molten salt combustion of hazardous wastes are converted into a cooled gas, which can be filtered to remove hazardous particulate material, and a dry flowable mixture of salts, which can be recycled for use in the molten salt combustion, by means of gas/liquid contact between the gaseous products of combustion of the hazardous waste and a solution produced by quenching the spent melt from such molten salt combustion. The process results in maximizing the proportion of useful materials recovered from the molten salt combustion and minimizing the volume of material which must be discarded. In a preferred embodiment a spray dryer treatment is used to achieve the desired gas/liquid contact

  13. Gas and water permeability tests of 25 year old concrete from the NPD Nuclear Generating Station

    International Nuclear Information System (INIS)

    Mills, R.H.

    1990-05-01

    Permeability tests on cores recovered from concrete which had been in service for 25 years in the Nuclear Power Demonstration (NPD) reactor showed rates of mass transfer of gas and water which were greater than young fresh concrete of the same proportions and that reported in previous AECB reports. This transparency of the concrete was also 2 orders of magnitude greater than that of comparable concrete which had been stored in the laboratory atmosphere for 19 years. Analysis of the effluent in water permeability tests revealed the presence of unusual amounts of soluble materials, mainly Na and K but little Ca, in the reactor concrete. This suggested service-related deterioration of the concrete rather than the release of soluble Ca by continuing hydration of cement

  14. Synthesis and Characterization of a Novel Microporous Dihydroxyl-Functionalized Triptycene-Diamine-Based Polyimide for Natural Gas Membrane Separation

    KAUST Repository

    Alaslai, Nasser Y.

    2017-07-10

    An intrinsically microporous polyimide is synthesized in m-cresol by a one-pot high-temperature condensation reaction of 4,4\\'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and newly designed 2,6 (7)-dihydroxy-3,7(6)-diaminotriptycene (DAT1-OH). The 6FDA-DAT1-OH polyimide is thermally stable up to 440 °C, shows excellent solubility in polar solvents, and has moderately high Brunauer-Teller-Emmett (BET) surface area of 160 m2 g-1 , as determined by nitrogen adsorption at -196 °C. Hydroxyl functionalization applied to the rigid 3D triptycene-based diamine building block results in a polyimide that exhibits moderate pure-gas CO2 permeability of 70 Barrer combined with high CO2 /CH4 selectivity of 50. Mixed-gas permeation studies demonstrate excellent plasticization resistance of 6FDA-DAT1-OH with impressive performance as potential membrane material for natural gas sweetening with a CO2 permeability of 50 Barrer and CO2 /CH4 selectivity of 40 at a typical natural gas well partial pressure of 10 atm.

  15. Correlation of Gas Permeability in a Metal-Organic Framework MIL-101(Cr)-Polysulfone Mixed-Matrix Membrane with Free Volume Measurements by Positron Annihilation Lifetime Spectroscopy (PALS).

    Science.gov (United States)

    Jeazet, Harold B Tanh; Koschine, Tönjes; Staudt, Claudia; Raetzke, Klaus; Janiak, Christoph

    2013-10-25

    Hydrothermally stable particles of the metal-organic framework MIL-101(Cr) were incorporated into a polysulfone (PSF) matrix to produce mixed-matrix or composite membranes with excellent dispersion of MIL-101 particles and good adhesion within the polymer matrix. Pure gas (O2, N2, CO2 and CH4) permeation tests showed a significant increase of gas permeabilities of the mixed-matrix membranes without any loss in selectivity. Positron annihilation lifetime spectroscopy (PALS) indicated that the increased gas permeability is due to the free volume in the PSF polymer and the added large free volume inside the MIL-101 particles. The trend of the gas transport properties of the composite membranes could be reproduced by a Maxwell model.

  16. Spin-polarized transport in a two-dimensional electron gas with interdigital-ferromagnetic contacts

    DEFF Research Database (Denmark)

    Hu, C.-M.; Nitta, Junsaku; Jensen, Ane

    2001-01-01

    Ferromagnetic contacts on a high-mobility, two-dimensional electron gas (2DEG) in a narrow gap semiconductor with strong spin-orbit interaction are used to investigate spin-polarized electron transport. We demonstrate the use of magnetized contacts to preferentially inject and detect specific spi...

  17. Contact line motion in confined liquid–gas systems: Slip versus phase transition

    KAUST Repository

    Xu, Xinpeng

    2010-11-30

    In two-phase flows, the interface intervening between the two fluid phases intersects the solid wall at the contact line. A classical problem in continuum fluid mechanics is the incompatibility between the moving contact line and the no-slip boundary condition, as the latter leads to a nonintegrable stress singularity. Recently, various diffuse-interface models have been proposed to explain the contact line motion using mechanisms missing from the sharp-interface treatments in fluid mechanics. In one-component two-phase (liquid–gas) systems, the contact line can move through the mass transport across the interface while in two-component (binary) fluids, the contact line can move through diffusive transport across the interface. While these mechanisms alone suffice to remove the stress singularity, the role of fluid slip at solid surface needs to be taken into account as well. In this paper, we apply the diffuse-interface modeling to the study of contact line motion in one-component liquid–gas systems, with the fluid slip fully taken into account. The dynamic van der Waals theory has been presented for one-component fluids, capable of describing the two-phase hydrodynamics involving the liquid–gas transition [A. Onuki, Phys. Rev. E 75, 036304 (2007)]. This theory assumes the local equilibrium condition at the solid surface for density and also the no-slip boundary condition for velocity. We use its hydrodynamicequations to describe the continuum hydrodynamics in the bulk region and derive the more general boundary conditions by introducing additional dissipative processes at the fluid–solid interface. The positive definiteness of entropy production rate is the guiding principle of our derivation. Numerical simulations based on a finite-difference algorithm have been carried out to investigate the dynamic effects of the newly derived boundary conditions, showing that the contact line can move through both phase transition and slip, with their relative

  18. Static friction between rigid fractal surfaces.

    Science.gov (United States)

    Alonso-Marroquin, Fernando; Huang, Pengyu; Hanaor, Dorian A H; Flores-Johnson, E A; Proust, Gwénaëlle; Gan, Yixiang; Shen, Luming

    2015-09-01

    Using spheropolygon-based simulations and contact slope analysis, we investigate the effects of surface topography and atomic scale friction on the macroscopically observed friction between rigid blocks with fractal surface structures. From our mathematical derivation, the angle of macroscopic friction is the result of the sum of the angle of atomic friction and the slope angle between the contact surfaces. The latter is obtained from the determination of all possible contact slopes between the two surface profiles through an alternative signature function. Our theory is validated through numerical simulations of spheropolygons with fractal Koch surfaces and is applied to the description of frictional properties of Weierstrass-Mandelbrot surfaces. The agreement between simulations and theory suggests that for interpreting macroscopic frictional behavior, the descriptors of surface morphology should be defined from the signature function rather than from the slopes of the contacting surfaces.

  19. Polymeric membrane materials: new aspects of empirical approaches to prediction of gas permeability parameters in relation to permanent gases, linear lower hydrocarbons and some toxic gases.

    Science.gov (United States)

    Malykh, O V; Golub, A Yu; Teplyakov, V V

    2011-05-11

    Membrane gas separation technologies (air separation, hydrogen recovery from dehydrogenation processes, etc.) use traditionally the glassy polymer membranes with dominating permeability of "small" gas molecules. For this purposes the membranes based on the low free volume glassy polymers (e.g., polysulfone, tetrabromopolycarbonate and polyimides) are used. On the other hand, an application of membrane methods for VOCs and some toxic gas recovery from air, separation of the lower hydrocarbons containing mixtures (in petrochemistry and oil refining) needs the membranes with preferable penetration of components with relatively larger molecular sizes. In general, this kind of permeability is characterized for rubbers and for the high free volume glassy polymers. Data files accumulated (more than 1500 polymeric materials) represent the region of parameters "inside" of these "boundaries." Two main approaches to the prediction of gas permeability of polymers are considered in this paper: (1) the statistical treatment of published transport parameters of polymers and (2) the prediction using model of ≪diffusion jump≫ with consideration of the key properties of the diffusing molecule and polymeric matrix. In the frames of (1) the paper presents N-dimensional methods of the gas permeability estimation of polymers using the correlations "selectivity/permeability." It is found that the optimal accuracy of prediction is provided at n=4. In the frames of the solution-diffusion mechanism (2) the key properties include the effective molecular cross-section of penetrating species to be responsible for molecular transportation in polymeric matrix and the well known force constant (ε/k)(eff i) of {6-12} potential for gas-gas interaction. Set of corrected effective molecular cross-section of penetrant including noble gases (He, Ne, Ar, Kr, Xe), permanent gases (H(2), O(2), N(2), CO), ballast and toxic gases (CO(2), NO(,) NO(2), SO(2), H(2)S) and linear lower hydrocarbons (CH(4

  20. Novel top-contact monolayer pentacene-based thin-film transistor for ammonia gas detection.

    Science.gov (United States)

    Mirza, Misbah; Wang, Jiawei; Li, Dexing; Arabi, S Atika; Jiang, Chao

    2014-04-23

    We report on the fabrication of an organic field-effect transistor (OFET) of a monolayer pentacene thin film with top-contact electrodes for the aim of ammonia (NH3) gas detection by monitoring changes in its drain current. A top-contact configuration, in which source and drain electrodes on a flexible stamp [poly(dimethylsiloxane)] were directly contacted with the monolayer pentacene film, was applied to maintain pentacene arrangement ordering and enhance the monolayer OFET detection performance. After exposure to NH3 gas, the carrier mobility at the monolayer OFET channel decreased down to one-third of its original value, leading to a several orders of magnitude decrease in the drain current, which tremendously enhanced the gas detection sensitivity. This sensitivity enhancement to a limit of the 10 ppm level was attributed to an increase of charge trapping in the carrier channel, and the amount of trapped states was experimentally evaluated by the threshold voltage shift induced by the absorbed NH3 molecular analyte. In contrast, a conventional device with a 50-nm-thick pentacene layer displayed much higher mobility but lower response to NH3 gas, arising from the impediment of analyte penetrating into the conductive channel, owing to the thick pentacene film.

  1. Chapter 2. Assessment of undiscovered conventional oil and gas resources--Upper Jurassic-Lower Cretaceous Cotton Valley group, Jurassic Smackover interior salt basins total petroleum system, in the East Texas basin and Louisiana-Mississippi salt basins provinces.

    Science.gov (United States)

    Dyman, T.S.; Condon, S.M.

    2006-01-01

    The Jurassic Smackover Interior Salt Basins Total Petroleum System is defined for this assessment to include (1) Upper Jurassic Smackover Formation carbonates and calcareous shales and (2) Upper Jurassic and Lower Cretaceous Cotton Valley Group organic-rich shales. The Jurassic Smackover Interior Salt Basins Total Petroleum System includes four conventional Cotton Valley assessment units: Cotton Valley Blanket Sandstone Gas (AU 50490201), Cotton Valley Massive Sandstone Gas (AU 50490202), Cotton Valley Updip Oil and Gas (AU 50490203), and Cotton Valley Hypothetical Updip Oil (AU 50490204). Together, these four assessment units are estimated to contain a mean undiscovered conventional resource of 29.81 million barrels of oil, 605.03 billion cubic feet of gas, and 19.00 million barrels of natural gas liquids. The Cotton Valley Group represents the first major influx of clastic sediment into the ancestral Gulf of Mexico. Major depocenters were located in south-central Mississippi, along the Louisiana-Mississippi border, and in northeast Texas. Reservoir properties and production characteristics were used to identify two Cotton Valley Group sandstone trends across northern Louisiana and east Texas: a high-permeability blanket-sandstone trend and a downdip, low-permeability massive-sandstone trend. Pressure gradients throughout most of both trends are normal, which is characteristic of conventional rather than continuous basin-center gas accumulations. Indications that accumulations in this trend are conventional rather than continuous include (1) gas-water contacts in at least seven fields across the blanket-sandstone trend, (2) relatively high reservoir permeabilities, and (3) high gas-production rates without fracture stimulation. Permeability is sufficiently low in the massive-sandstone trend that gas-water transition zones are vertically extensive and gas-water contacts are poorly defined. The interpreted presence of gas-water contacts within the Cotton Valley

  2. Rebound coefficient of collisionless gas in a rigid vessel. A model of reflection of field-reversed configuration

    International Nuclear Information System (INIS)

    Takaku, Yuichi; Hamada, Shigeo

    1996-01-01

    A system of collisionless neutral gas contained in a rigid vessel is considered as a simple model of reflection of field-reversed configuration (FRC) plasma by a magnetic mirror. The rebound coefficient of the system is calculated as a function of the incident speed of the vessel normalized by the thermal velocity of the gas before reflection. The coefficient is compared with experimental data of FIX (Osaka U.) and FRX-C/T(Los Alamos N.L.). Agreement is good for this simple model. Interesting is that the rebound coefficient takes the smallest value (∼0.365) as the incident speed tends to zero and approaches unity as it tends to infinity. This behavior is reverse to that expected for a system with collision dominated fluid instead of collisionless gas. By examining the rebound coefficient, therefore, it could be successfully inferred whether the ion mean free path in each experiment was longer or shorter than the plasma length. (author)

  3. Effect Of Hot Water Injection On Sandstone Permeability

    DEFF Research Database (Denmark)

    Rosenbrand, Esther; Fabricius, Ida Lykke

    2012-01-01

    of published results regarding the effect of temperature on sandstone permeability. These tests are performed with mineral oil, nitrogen gas, distilled water and solutions of NaCl, KCl, CaCl2 as well as brines that contain a mixture of salts. Thirteen sandstone formations, ranging from quartz arenites...... to formations with a significant fraction of fine particles including clay minerals are investigated. The porosities range from 0.10 to 0.30 and permeabilities span the range from 1 to 1000 md. To compare different rock types, specific surface is determined from permeability and porosity using Kozeny’s equation...... not account for all the permeability reductions observed. Permeablity reduction occurs both when distilled water is the saturating fluid as well as in tests with NaCl, KCl or CaCl2 solutions, however, this is not the case in tests with mineral oil or nitrogen gas. The formation of a filter cake or influx...

  4. Transport of Gas Phase Radionuclides in a Fractured, Low-Permeability Reservoir

    Science.gov (United States)

    Cooper, C. A.; Chapman, J.

    2001-12-01

    The U.S. Atomic Energy Commission (predecessor to the Department of Energy, DOE) oversaw a joint program between industry and government in the 1960s and 1970s to develop technology to enhance production from low-permeability gas reservoirs using nuclear stimulation rather than conventional means (e.g., hydraulic and/or acid fracturing). Project Rio Blanco, located in the Piceance Basin, Colorado, was the third experiment under the program. Three 30-kiloton nuclear explosives were placed in a 2134 m deep well at 1780, 1899, and 2039 m below the land surface and detonated in May 1973. Although the reservoir was extensively fractured, complications such as radionuclide contamination of the gas prevented production and subsequent development of the technology. Two-dimensional numerical simulations were conducted to identify the main transport processes that have occurred and are currently occurring in relation to the detonations, and to estimate the extent of contamination in the reservoir. Minor modifications were made to TOUGH2, the multiphase, multicomponent reservoir simulator developed at Lawrence Berkeley National Laboratories. The simulator allows the explicit incorporation of fractures, as well as heat transport, phase change, and first order radionuclide decay. For a fractured two-phase (liquid and gas) reservoir, the largest velocities are of gases through the fractures. In the gas phase, tritium and one isotope of krypton are the principle radionuclides of concern. However, in addition to existing as a fast pathway, fractures also permit matrix diffusion as a retardation mechanism. Another retardation mechanism is radionuclide decay. Simulations show that incorporation of fractures can significantly alter transport rates, and that radionuclides in the gas phase can preferentially migrate upward due to the downward gravity drainage of liquid water in the pores. This project was funded by the National Nuclear Security Administration, Nevada Operations Office

  5. Initial Development of an Electronic Testis Rigidity Tester

    Directory of Open Access Journals (Sweden)

    Petros Mirilas

    2011-01-01

    Full Text Available We aimed to develop our previously presented mechanical device, the Testis Rigidity Tester (TRT, into an electronic system (Electronic Testis Rigidity Tester, ETRT by applying tactile imaging, which has been used successfully with other solid organs. A measuring device, located at the front end of the ETRT incorporates a tactile sensor comprising an array of microsensors. By application of a predetermined deformation of 2 mm, increased pressure alters linearly the resistance of each microsensor, producing changes of voltage. These signals were amplified, filtered, and digitized, and then processed by an electronic collector system, which presented them as a color-filled contour plot of the area of the testis coming into contact with the sensor. Testis models of different rigidity served for initial evaluation of ETRT; their evacuated central spaces contained different, increasing glue masses. An independent method of rigidity measurement, using an electric weight scale and a micrometer, showed that the more the glue injected, the greater the force needed for a 2-mm deformation. In a preliminary test, a single sensor connected to a multimeter showed similar force measurement for the same deformation in these phantoms. For each of the testis models compressed in the same manner, the ETRT system offered a map of pressures, represented by a color scale within the contour plot of the contact area with the sensor. ETRT found certain differences in rigidity between models that had escaped detection by a blind observer. ETRT is easy to use and provides a color-coded “insight“ of the testis internal structure. After experimental testing, it could be valuable in intraoperative evaluation of testes, so that the surgeon can decide about orchectomy or orcheopexy.

  6. Dosimetry of skin-contact exposure to tritium gas contaminated surfaces

    International Nuclear Information System (INIS)

    Legare, M.

    1990-12-01

    The radiological hazards from tritium are usually associated with exposure to tritium oxide either by inhalation, ingestion or permeation through skin. However, exposure from skin contact with tritium gas contaminated surfaces represents a different radiological hazard in tritium removal facilities and future fusion power plants. Previous experiments on humans and more recent experiments on hairless rats at Chalk River Laboratories have shown that when a tritium gas-contaminated surface is brought into contact with intact skin, high concentrations of organically-bound tritium in urine and skin are observed which were not seen from single tritiated water (liquid or vapour form) contamination. The results of the rat experiments, which involved measurements of tritium activity in urine and skin, after contact with contaminated stainless steel, are described. These results are also compared to previous data from human experiments. The effect of various exposure conditions and different contaminated surfaces such as brass, aluminum and glass are analysed and related to the results from contaminated stainless steel exposure. Dosimetric models are being developed in order to improve the basis for dose assessment for this mode of tritium uptake. The presently studied model is explained along with the assumptions and methods involved in its derivation. The features of 'STELLA', the software program used to implement the model, are discussed. The methods used to estimate skin and whole body dose from a model are demonstrated. Finally, some experiments for improving the accuracy of the model are proposed. Briefly, this study compares the results from animal and human experiments as well as different exposure conditions, and determines the range of whole body and skin dose that may be involved from skin-contact intake. This information is essential for regulatory purposes particularly in the derivation of doses for skin-contact contamination. (15 figs., 7 tabs., 29 refs.)

  7. Collisions of Constrained Rigid Body Systems with Friction

    Directory of Open Access Journals (Sweden)

    Haijun Shen

    1998-01-01

    Full Text Available A new approach is developed for the general collision problem of two rigid body systems with constraints (e.g., articulated systems, such as massy linkages in which the relative tangential velocity at the point of contact and the associated friction force can change direction during the collision. This is beyond the framework of conventional methods, which can give significant and very obvious errors for this problem, and both extends and consolidates recent work. A new parameterization and theory characterize if, when and how the relative tangential velocity changes direction during contact. Elastic and dissipative phenomena and different values for static and kinetic friction coefficients are included. The method is based on the explicitly physical analysis of events at the point of contact. Using this method, Example 1 resolves (and corrects a paradox (in the literature of the collision of a double pendulum with the ground. The method fundamentally subsumes other recent models and the collision of rigid bodies; it yields the same results as conventional methods when they would apply (Example 2. The new method reformulates and extends recent approaches in a completely physical context.

  8. Gas Transport in Bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.; Gutierre-Rodrigo, V.; Martin, P. I.; Romero, F. J.; Barcala, J. M.

    2013-07-01

    The gas permeability of the Spanish FEBEX bentonite compacted at dry densities of between 1.4 and 1.8 g/cm{sup 3} with high water contents was measured for different confining, injection and back pressures. The results were compared with results obtained in previous investigations for lower degrees of saturation. It was checked that gas permeability was greatly affected by dry density, decreasing about three orders of magnitude when it increased from 1.5 to 1.8 g/cm{sup 3} for similar water content. The increase of water content caused also a decrease in gas permeability. It was found that both gas permeability and the relative gas permeability were mainly related to the accessible porosity. These relationships could be fitted to potential expressions with exponents between 3 and 4, as well as the relationship between intrinsic permeability and void ratio. For gas pressures below 1.2 MPa no effect of the injection or confining pressures on the value of permeability was detected. For a given confining pressure the permeability value decreased as the effective pressure increased, especially if the increase in effective pressure was due to a decrease in gas back pressure. It was checked that the Klinkenberg effect was not significant for this material in the range of pressures applied in the tests. The gas breakthrough pressure values in FEBEX saturated bentonite were determined for different dry densities. They increased clearly with dry density and were always higher than the swelling pressure of the bentonite. In high density samples gas flow tended to stop abruptly after breakthrough, whereas in lower density samples gas flow decreased gradually until a given pressure gradient was reached. The permeabilities computed after breakthrough (which usually did not stabilise) were inversely related to dry density. This would indicate that, even if the flow took place predominantly through preferential pathways that sometimes closed quickly after breakthrough and others

  9. Gas Transport in Bentonite

    International Nuclear Information System (INIS)

    Villar, M. V.; Gutierrez-Rodrigo, V.; Martin, P. L.; Romero, F. J.; Barcala, J. M.

    2013-01-01

    The gas permeability of the Spanish FEBEX bentonite compacted at dry densities of between 1.4 and 1.8 g/cm 3 with high water contents was measured for different confining, injection and back pressures. The results were compared with results obtained in previous investigations for lower degrees of saturation. It was checked that gas permeability was greatly affected by dry density, decreasing about three orders of magnitude when it increased from 1.5 to 1.8 g/cm 3 for similar water content. The increase of water content caused also a decrease in gas permeability. It was found that both gas permeability and the relative gas permeability were mainly related to the accessible porosity. These relationships could be fitted to potential expressions with exponents between 3 and 4, as well as the relationship between intrinsic permeability and void ratio. For gas pressures below 1.2 MPa no effect of the injection or confining pressures on the value of permeability was detected. For a given confining pressure the permeability value decreased as the effective pressure increased, especially if the increase in effective pressure was due to a decrease in gas back pressure. It was checked that the Klinkenberg effect was not significant for this material in the range of pressures applied in the tests. The gas breakthrough pressure values in FEBEX saturated bentonite were determined for different dry densities. They increased clearly with dry density and were always higher than the swelling pressure of the bentonite. In high density samples gas flow tended to stop abruptly after breakthrough, whereas in lower density samples gas flow decreased gradually until a given pressure gradient was reached. The permeabilities computed after breakthrough (which usually did not stabilise) were inversely related to dry density. This would indicate that, even if the flow took place predominantly through preferential pathways that sometimes closed quickly after breakthrough and others remained

  10. Rapid estimate of solid volume in large tuff cores using a gas pycnometer

    Energy Technology Data Exchange (ETDEWEB)

    Thies, C. [ed.; Geddis, A.M.; Guzman, A.G. [and others

    1996-09-01

    A thermally insulated, rigid-volume gas pycnometer system has been developed. The pycnometer chambers have been machined from solid PVC cylinders. Two chambers confine dry high-purity helium at different pressures. A thick-walled design ensures minimal heat exchange with the surrounding environment and a constant volume system, while expansion takes place between the chambers. The internal energy of the gas is assumed constant over the expansion. The ideal gas law is used to estimate the volume of solid material sealed in one of the chambers. Temperature is monitored continuously and incorporated into the calculation of solid volume. Temperature variation between measurements is less than 0.1{degrees}C. The data are used to compute grain density for oven-dried Apache Leap tuff core samples. The measured volume of solid and the sample bulk volume are used to estimate porosity and bulk density. Intrinsic permeability was estimated from the porosity and measured pore surface area and is compared to in-situ measurements by the air permeability method. The gas pycnometer accommodates large core samples (0.25 m length x 0.11 m diameter) and can measure solid volume greater than 2.20 cm{sup 3} with less than 1% error.

  11. Mechanism for calcite dissolution and its contribution to development of reservoir porosity and permeability in the Kela 2 gas field,Tarim Basin,China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This study is undertaken to understand how calcite precipitation and dissolution contributes to depth-related changes in porosity and permeability of gas-bearing sandstone reservoirs in the Kela 2 gas field of the Tarim Basin, Northwestern China. Sandstone samples and pore water samples are col-lected from well KL201 in the Tarim Basin. Vertical profiles of porosity, permeability, pore water chem-istry, and the relative volume abundance of calcite/dolomite are constructed from 3600 to 4000 m below the ground surface within major oil and gas reservoir rocks. Porosity and permeability values are in-versely correlated with the calcite abundance, indicating that calcite dissolution and precipitation may be controlling porosity and permeability of the reservoir rocks. Pore water chemistry exhibits a sys-tematic variation from the Na2SO4 type at the shallow depth (3600-3630 m), to the NaHCO3 type at the intermediate depth (3630―3695 m),and to the CaCl2 type at the greater depth (3728―3938 m). The geochemical factors that control the calcite solubility include pH, temperature, pressure, Ca2+ concen-tration, the total inorganic carbon concentration (ΣCO2), and the type of pore water. Thermodynamic phase equilibrium and mass conservation laws are applied to calculate the calcite saturation state as a function of a few key parameters. The model calculation illustrates that the calcite solubility is strongly dependent on the chemical composition of pore water, mainly the concentration difference between the total dissolved inorganic carbon and dissolved calcium concentration (i.e., [ΣCO2] -[Ca2+]). In the Na2SO4 water at the shallow depth, this index is close to 0, pore water is near the calcite solubility. Calcite does not dissolve or precipitate in significant quantities. In the NaHCO3 water at the intermedi-ate depth, this index is greater than 0, and pore water is supersaturated with respect to calcite. Massive calcite precipitation was observed at this depth

  12. Prediction and control of rock burst of coal seam contacting gas in deep mining

    Energy Technology Data Exchange (ETDEWEB)

    En-yuan Wang; Xiao-fei Liu; En-lai Zhao; Zhen-tang Liu [China University of Mining and Technology, Xuzhou (China). School of Safety Engineering

    2009-06-15

    By analyzing the characteristics and the production mechanism of rock burst that goes with abnormal gas emission in deep coal seams, the essential method of eliminating abnormal gas emission by eliminating the occurrence of rock burst or depressing the magnitude of rock burst was considered. The No.237 working face in Nanshan coal mine was selected as the typical working face contacting gas in deep mining; aimed at this working face, a system of rock burst prediction and control for coal seam contacting gas in deep mining was established using the three-dimensional distinct element code software 3DEC. This system includes three parts: (1) regional prediction of rock burst hazard before mining; (2) local prediction of rock burst hazard during mining; and (3) rock burts control by an electromagnetic radiation method and specific drilling method. 8 refs., 4 figs., 1 tab.

  13. Multi-contact Variable-Compliance Manipulation in Extreme Clutter

    Science.gov (United States)

    2014-06-16

    house to find eggs and young. (b) When noodling , people find catfish holes from which to pull fish out. (c)-(d) A person makes contact along his...Figure 7: Haptic Map of detected rigid contacts. by mapping all the rigid taxels at every time- instant . For visualizing the haptic map, we use point...the environment while reaching into clutter. (a) A raccoon reaches into a bird house to find eggs and young. (b) When noodling , people find catfish

  14. Long wavelength infrared radiation thermometry for non-contact temperature measurements in gas turbines

    Science.gov (United States)

    Manara, J.; Zipf, M.; Stark, T.; Arduini, M.; Ebert, H.-P.; Tutschke, A.; Hallam, A.; Hanspal, J.; Langley, M.; Hodge, D.; Hartmann, J.

    2017-01-01

    The objective of the EU project "Sensors Towards Advanced Monitoring and Control of Gas Turbine Engines (acronym STARGATE)" is the development of a suite of advanced sensors, instrumentation and related systems in order to contribute to the developing of the next generation of green and efficient gas turbine engines. One work package of the project deals with the design and development of a long wavelength infrared (LWIR) radiation thermometer for the non-contact measurement of the surface temperature of thermal barrier coatings (TBCs) during the operation of gas turbine engines. For opaque surfaces (e.g. metals or superalloys) radiation thermometers which are sensitive in the near or short wavelength infrared are used as state-of-the-art method for non-contact temperature measurements. But this is not suitable for oxide ceramic based TBCs (e.g. partially yttria stabilized zirconia) as oxide ceramics are semi-transparent in the near and short wavelength infrared spectral region. Fortunately the applied ceramic materials are non-transparent in the long wavelength infrared and additionally exhibit a high emittance in this wavelength region. Therefore, a LWIR pyrometer can be used for non-contact temperature measurements of the surfaces of TBCs as such pyrometers overcome the described limitation of existing techniques. For performing non-contact temperature measurements in gas turbines one has to know the infrared-optical properties of the applied TBCs as well as of the hot combustion gas in order to properly analyse the measurement data. For reaching a low uncertainty on the one hand the emittance of the TBC should be high (>0.9) in order to reduce reflections from the hot surrounding and on the other hand the absorbance of the hot combustion gas should be low (<0.1) in order to decrease the influence of the gas on the measured signal. This paper presents the results of the work performed by the authors with focus on the implementation of the LWIR pyrometer and the

  15. Rocking Rotation of a Rigid Disk Embedded in a Transversely Isotropic Half-Space

    Directory of Open Access Journals (Sweden)

    Seyed Ahmadi

    2014-06-01

    Full Text Available The asymmetric problem of rocking rotation of a circular rigid disk embedded in a finite depth of a transversely isotropic half-space is analytically addressed. The rigid disk is assumed to be in frictionless contact with the elastic half-space. By virtue of appropriate Green's functions, the mixed boundary value problem is written as a dual integral equation. Employing further mathematical techniques, the integral equation is reduced to a well-known Fredholm integral equation of the second kind. The results related to the contact stress distribution across the disk region and the equivalent rocking stiffness of the system are expressed in terms of the solution of the obtained Fredholm  integral  equation. When the rigid disk is located on the surface or at the remote boundary, the exact closed-form solutions are presented. For verification purposes, the limiting case of an isotropic half-space is considered and the results are verified with those available in the literature. The jump behavior in the results at the edge of the rigid disk for the case of an infinitesimal embedment is highlighted analytically for the first time. Selected numerical results are depicted for the contact stress distribution across the disk region, rocking stiffness of the system, normal stress, and displacement components along the radial axis. Moreover, effects of anisotropy on the rocking stiffness factor are discussed in detail.

  16. Correlation of Gas Permeability in a Metal-Organic Framework MIL-101(Cr)–Polysulfone Mixed-Matrix Membrane with Free Volume Measurements by Positron Annihilation Lifetime Spectroscopy (PALS)

    Science.gov (United States)

    Jeazet, Harold B. Tanh; Koschine, Tönjes; Staudt, Claudia; Raetzke, Klaus; Janiak, Christoph

    2013-01-01

    Hydrothermally stable particles of the metal-organic framework MIL-101(Cr) were incorporated into a polysulfone (PSF) matrix to produce mixed-matrix or composite membranes with excellent dispersion of MIL-101 particles and good adhesion within the polymer matrix. Pure gas (O2, N2, CO2 and CH4) permeation tests showed a significant increase of gas permeabilities of the mixed-matrix membranes without any loss in selectivity. Positron annihilation lifetime spectroscopy (PALS) indicated that the increased gas permeability is due to the free volume in the PSF polymer and the added large free volume inside the MIL-101 particles. The trend of the gas transport properties of the composite membranes could be reproduced by a Maxwell model. PMID:24957061

  17. Verification of aspheric contact lens back surfaces.

    Science.gov (United States)

    Dietze, Holger H; Cox, Michael J; Douthwaite, William A

    2003-08-01

    To suggest a tolerance level for the degree of asphericity of aspheric rigid gas-permeable contact lenses and to find a simple method for its verification. Using existing tolerances for the vertex radius, tolerance limits for eccentricity and p values and were calculated. A keratometer-based method and a method based on sag measurements were used to measure the vertex radius and eccentricity of eight concave progressively aspheric surfaces and six concave ellipsoidal surfaces. The results were compared with a gold standard measurement made using a high-precision mechanical instrument (Form Talysurf). The suggested tolerance for eccentricity and p value and is +/-0.05. The keratometer method was very accurate and precise at measuring the vertex radius (mean deviation +/- SD from Talysurf results, -0.002 +/- 0.008 mm). The keratometer was more precise than and similar in accuracy to the sag method for measurement of asphericity (mean deviation of keratometer method results from Talysurf results, 0.017 +/- 0.018; mean deviation of sag method results from Talysurf results using five semichords, -0.016 +/- 0.032). Neither method was precise enough to verify the asphericity within the suggested tolerance. The keratometer can be efficiently used to verify the back vertex radius within its International Organization for Standardization tolerance and the back surface asphericity within an eccentricity/p value tolerance of +/-0.1. The method is poor for progressive aspheres with large edge blending zones. Deriving the eccentricity from sag measurements is a potential alternative if the mathematical description of the surface is known. The limiting factor of this method is the accuracy and precision of individual sag measurements.

  18. Flow visualization and relative permeability measurements in rough-walled fractures

    International Nuclear Information System (INIS)

    Persoff, P.; Pruess, K.

    1993-01-01

    Two-phase (gas-liquid) flow experiments were done in a natural rock fracture and transparent replicas of natural fractures. Liquid was injected at constant volume flow rate, and gas was injected at either constant mass flow rate or constant pressure. When gas was injected at constant mass flow rate, the gas inlet pressure, and inlet and outlet capillary pressures, generally did not reach steady state but cycled irregularly. Flow visualization showed that this cycling was due to repeated blocking and unblocking of gas flow paths by liquid. Relative permeabilities calculated from flow rate and pressure data show that the sum of the relative permeabilities of the two phases is much less than 1, indicating that each phase interferes strongly with the flow of the other. Comparison of the relative permeability curves with typical curves for porous media (Corey curves) show that the phase interference is stronger in fractures than in typical porous media

  19. A Simple Approach to Characterize Gas-Aqueous Liquid Two-phase Flow Configuration Based on Discrete Solid-Liquid Contact Electrification.

    Science.gov (United States)

    Choi, Dongwhi; Lee, Donghyeon; Kim, Dong Sung

    2015-10-14

    In this study, we first suggest a simple approach to characterize configuration of gas-aqueous liquid two-phase flow based on discrete solid-liquid contact electrification, which is a newly defined concept as a sequential process of solid-liquid contact and successive detachment of the contact liquid from the solid surface. This approach exhibits several advantages such as simple operation, precise measurement, and cost-effectiveness. By using electric potential that is spontaneously generated by discrete solid-liquid contact electrification, the configurations of the gas-aqueous liquid two-phase flow such as size of a gas slug and flow rate are precisely characterized. According to the experimental and numerical analyses on parameters that affect electric potential, gas slugs have been verified to behave similarly to point electric charges when the measuring point of the electric potential is far enough from the gas slug. In addition, the configuration of the gas-aqueous liquid two-phase microfluidic system with multiple gas slugs is also characterized by using the presented approach. For a proof-of-concept demonstration of using the proposed approach in a self-triggered sensor, a gas slug detector with a counter system is developed to show its practicality and applicability.

  20. Research on comprehensive gas permeability improvement technology by hydraulic fracturing and slotting in coal seam with complex geological conditions and low permeability%复杂地质低渗煤层水力压裂-割缝综合瓦斯增透技术研究

    Institute of Scientific and Technical Information of China (English)

    贾同千; 饶孜; 何庆兵; 宋润权; 白鑫

    2017-01-01

    Aiming at the problem of gas drainage in the coal seam with complex geological conditions and low permeability in Baijiao Coal Mine,the hydraulic fracturing technology was applied to carry out the regional gas permeability improvement,and its application effect was analyzed according to the situation of field gas drainage.Aiming at the blind area of regional gas permeability improvement by hydraulic fracturing,the technical measure of localized gas permeability improvement by hydraulic slotting was put forward,then the comprehensive gas permeability improvement technology by hydraulic fracturing and slotting in coal seam with complex geological conditions and low permeability was formed,and the field verification was conducted.The results showed that the average pure flow rate of gas drainage for three fracturing boreholes in the hydraulic fracturing zone increased by 15.8 times than that of regular single borehole gas drainage in 238 floor laneway,and the gas drainage concentration increased by 4%.The pure flow rate of gas drainage in the fractured area increased by 2.1 times than that of the comparison zone,but there existed the blind area by the regional measures of hydraulic fracturing due to the restriction of geological conditions such as fault and coal seam hardness.The gas concentration of drainage borehole in the hydraulic slotting permeability improvement zone increased by 4.9 times on the average,and the pure flow rate of gas increased by 3.3 times on the average.It has strong adaptability to different geological conditions,but the influence range of slotting is small,and the drainage time is short.The comprehensive gas permeability improvement technology by hydraulic fracturing and slotting in coal seam with complex geological conditions and low permeability integrates the advantages of hydraulic fracturing and slotting,and it has strong adaptability to coal seam with complex geological conditions,which improves the gas control level greatly.The field

  1. Recovery of ammonia from poultry litter using flat gas permeable membranes.

    Science.gov (United States)

    Rothrock, M J; Szögi, A A; Vanotti, M B

    2013-06-01

    The use of flat gas-permeable membranes was investigated as components of a new process to capture and recover ammonia (NH3) in poultry houses. This process includes the passage of gaseous NH3 through a microporous hydrophobic membrane, capture with a circulating dilute acid on the other side of the membrane, and production of a concentrated ammonium (NH4) salt. Bench- and pilot-scale prototype systems using flat expanded polytetrafluoroethylene (ePTFE) membranes and a sulfuric acid solution consistently reduced headspace NH3 concentrations from 70% to 97% and recovered 88% to 100% of the NH3 volatilized from poultry litter. The potential benefits of this technology include cleaner air inside poultry houses, reduced ventilation costs, and a concentrated liquid ammonium salt that can be used as a plant nutrient solution. Published by Elsevier Ltd.

  2. Descriptive analysis of the type and design of contact lenses fitted according to keratoconus severity and morphology

    Directory of Open Access Journals (Sweden)

    Letícia Helena Lunardi

    2016-04-01

    Full Text Available ABSTRACT Purpose: Keratoconus is characterized by bilateral asymmetrical corneal ectasia that leads to inferior stromal thinning and corneal protrusion. There is currently a lack of consensus regarding the most efficacious method for fitting contact lenses in patients with keratoconus, given the various topographical patterns and evolution grades observed in affected populations. The purpose of the present study was to evaluate the association between keratoconus evolution grade and topography pattern and the type and design of fitted contact lens. Methods: We performed a retrospective analysis of contact lenses fitted in a total of 185 patients with keratoconus (325 eyes. Keratoconus was classified as either grade I, II, III, or IV based on keratometry and cone morphology (nipple, oval, globus, or indeterminate results. Results: A total of 325 eyes were evaluated in the present study. Of the 62 eyes classified as grade I, 66.1% were fitted with monocurve contact lenses. Of the 162 eyes classified as grade I and II, 51%, 30%, and 19% were fitted with adapted monocurve rigid gas-permeable contact lenses (RGPCL, bicurve lenses, and others lens types, respectively. Bicurve lenses were fitted in 52.1% and 62.2% of eyes classified as grade III and IV, respectively. Of the eyes classified as grade III and IV, monocurve and bicurve RGPCL were fitted in 26% and 55%, respectively. In eyes with oval keratoconus, 45%, 35%, and 20% were fitted with monocurve lenses, bicurve lenses, and other lens types, respectively. In eyes with round cones (nipple morphology, 55%, 30%, and 15% were fitted with bicurve lenses, monocurve lenses, and other lens types, respectively. Conclusion: Monocurve RGPCL were most frequently fitted in patients with mild to moderate keratoconus and oval cones morphology, while bicurve lenses were more frequently fitted in patients with severe and advanced keratoconus. This was probably because bicurve lenses are more appropriate for

  3. Experimental Study on Gas Slippage of Tight Gas Sands in Kirthar Fold Belt Sindh, Pakistan

    Directory of Open Access Journals (Sweden)

    AFTAB AHMEDMAHESAR

    2017-07-01

    Full Text Available The laboratory experiments on samples from Kirthar fold belt of lower Indus basin Sindh Pakistan were carried out to investigate the effect of gas slippage under varying conditions of pore pressures and overburden stress. The samples were dried in an oven at temperature of 600C and were randomly selected for measurement of permeability and porosity. Permeability was measured using nitrogen gas, while the porosity measurements were made using helium gas expansion porosimeter. The bulk volume was determined by measuring sample diameter and length with caliper. The permeability results suggest that gas slippage increases as if low pore pressures are used, which leads to higher measured permeability than intrinsic permeability of samples. An attempt was also made to estimate the permeability using existing correlations and found that there is large scatter in predicted permeability and measured data. This large amount of scatter in the predicted permeability values concludes that unless absolutely necessary, such correlations should not be used where accurate absolute permeability values are needed. Moreover, the permeability and porosity were plotted together to develop a relation between two properties; the power law fitting of the data well explains the relation between permeability and effective porosity

  4. Synthesis and Characterization of a Novel Microporous Dihydroxyl-Functionalized Triptycene-Diamine-Based Polyimide for Natural Gas Membrane Separation.

    Science.gov (United States)

    Alaslai, Nasser; Ma, Xiaohua; Ghanem, Bader; Wang, Yingge; Alghunaimi, Fahd; Pinnau, Ingo

    2017-09-01

    An intrinsically microporous polyimide is synthesized in m-cresol by a one-pot high-temperature condensation reaction of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and newly designed 2,6 (7)-dihydroxy-3,7(6)-diaminotriptycene (DAT1-OH). The 6FDA-DAT1-OH polyimide is thermally stable up to 440 °C, shows excellent solubility in polar solvents, and has moderately high Brunauer-Teller-Emmett (BET) surface area of 160 m 2 g -1 , as determined by nitrogen adsorption at -196 °C. Hydroxyl functionalization applied to the rigid 3D triptycene-based diamine building block results in a polyimide that exhibits moderate pure-gas CO 2 permeability of 70 Barrer combined with high CO 2 /CH 4 selectivity of 50. Mixed-gas permeation studies demonstrate excellent plasticization resistance of 6FDA-DAT1-OH with impressive performance as potential membrane material for natural gas sweetening with a CO 2 permeability of 50 Barrer and CO 2 /CH 4 selectivity of 40 at a typical natural gas well partial pressure of 10 atm. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. A new method using insert-based systems (IBS) to improve cell behavior study on flexible and rigid biomaterials

    OpenAIRE

    Grenade, Charlotte; Moniotte, Nicolas; Rompen, Eric; Vanheusden, Alain; Mainjot, Amélie; De Pauw-Gillet, Marie-Claire

    2016-01-01

    In vitro studies about biomaterials biological properties are essential screening tests. Yet cell cultures encounter difficulties related to cell retention on material surface or to the observation of both faces of permeable materials. The objective of the present study was to develop a reliable in vitro method to study cell behavior on rigid and flexible/permeable biomaterials elaborating two specific insert-based systems (IBS-R and IBS-F respectively). IBS-R was designed as a specific cylin...

  6. Gas transport in low-permeability formations: a review of experimental evidence and modeling approaches

    International Nuclear Information System (INIS)

    Marschall, Paul; Keller, Lukas; Lanyon, Bill; Senger, Rainer

    2012-01-01

    This paper presents a review of phenomenological studies on immiscible fluid flow in porous media, clarifies terminology as used by different disciplines and discusses the different modeling approaches. It concludes with a discussion on the transferability of classical two-phase flow concepts on gas transport processes in low-permeability clay-stones. From a phenomenological point of view, advection and diffusion of dissolved species represent the simplest transport mechanisms in a water-saturated porous medium. The propagation of the dissolved species is controlled by the water velocity and its extent is controlled by the hydrodynamic dispersion - a well-known aggregate representation of the mixing processes due to diffusion, Taylor dispersion and tortuosity. Usually, the dissolution of a gaseous species in water is described by Henry's law, the diffusion of the dissolved gas is represented by Fick's law and the viscous losses of the pore water flow in the pore network are expressed by Darcy's law. Two-phase flow conditions occur when gas invades as a separate phase a water-saturated porous medium. This process is often called drainage, because the non-wetting fluid (gas) displaces a wetting fluid (pore water, 'defending' fluid). The propagation of the gas front is controlled by the complex interaction of gravity, viscous forces and capillary forces. Lenormand et al. (1988) conducted two-phase flow experiments for a wide range of capillary numbers Ca and viscosity ratios M. They identified 3 major flow regimes in the C a -M-space, which they coined viscous fingering, capillary fingering and stable displacement. The regime of stable displacement applies for the special case where the invading fluid has a higher viscosity than the defending fluid (e.g. water imbibition in a gas-filled porous medium). Viscous and capillary fingering are associated with instable displacement of a wetting fluid by the non-wetting fluid, giving rise to phenomena such as migration

  7. Gas-ion laser with gas pressure maintenance means

    International Nuclear Information System (INIS)

    Thatcher, J.B.

    1975-01-01

    A gas-ion laser is described including means to maintain the ionizable gas in the laser cavity at a rather constant pressure over an extended period of time to significantly increase the useful life of the gas-ion laser. The gas laser includes a gas makeup system having a high pressure source or storage container and a regulating valve. The valve has a permeable solid state orifice member through which the gas flows from the high pressure source to the laser cavity to replenish the gas in the laser cavity and maintain the gas pressure in the cavity rather constant. The permeable orifice member is selected from a solid state material having a permeability that is variable in relation to the magnitude of the energy applied to the orifice member. The gas-ion laser has a valve operating means such as a heater for varying the applied energy such as thermal energy to the member to regulate the gas flow. Additionally, the gas-ion laser has a valve control means that is responsive to the gas pressure in the laser cavity for controlling the valve control means to maintain the pressure at a desired level. (U.S.)

  8. Unevenness of Sliding Surface of Overhead Rigid Conductor Lines and Method for Reducing Unevenness

    Science.gov (United States)

    Aboshi, Mitsuo; Shimizu, Masashi

    Rigid conductor lines are used in many subways, because the use of such conductor lines reduces the risk of accidents and because less space is required for their installation. However, as the unevenness of the sliding surface of the rigid conductor lines significantly influences the fluctuations in the contact force between pantographs and contact lines, it is necessary to decrease the unevenness at the construction as well as the maintenance stages. In order to investigate the installation accuracy of overhead rigid conductor lines, we have developed a device that accurately and continuously measures the unevenness of the sliding surface. By using this measuring device, we have confirmed that the unevenness of the sliding surface depends on various factors such as the sag between the support points, the deformation of the aluminum base or the conductive rail in the case of a long wavelength, the slight sagging unevenness between the bolts of the long ear, the undulating wear etc. This paper describes the actual unevenness conditions and the technical methods for decreasing the unevenness of the sliding surface of overhead rigid conductor lines.

  9. Ceratocone: correlação entre grau evolutivo e padrão topográfico com o tipo de lente de contato adaptada Keratoconus: correlation between degrees of severity and topographical pattern with the kind of fitted contact lens

    Directory of Open Access Journals (Sweden)

    Vinícius Coral Ghanem

    2003-01-01

    percentual semelhante de adaptações em relação aos padrões topográficos encontrados. No olho esquerdo não se observou associação estatisticamente significante, apenas tendências. CONCLUSÕES: A maioria dos ceratocones pode ser adaptada com lentes de contato rígidas monocurvas, mas é importante contar com outros desenhos para adaptar os cones de graus avançados e severos. Isso permite, para a maior parte dos pacientes, postergar a necessidade do transplante de córnea. As lentes de contato gelatinosas tóricas e o sistema "piggyback" foram mais adaptados nos cones centrais; enquanto nos cones periféricos inferiores, foram as lentes de contato monocurvas e as bicurvas.PURPOSE: To determine associations between degrees of severity and topographical patterns of keratoconus with fitted contact lenses (CL. METHODS: Retrospective study of 454 patients (881 eyes with keratoconus, 746 fitted with contact lenses, from July 1996 to June 2000. Keratoconus was classified according to degrees of severity and topographical pattern. The first tested contact lens was the spherical rigid gas permeable. When it did not achieve the desired fitting, the bicurve rigid gas permeable and other designs were tried, in search of an apical clearance or slight apical touch fitting relationship. RESULTS: For 15 (3.3% patients glasses were prescribed; 111 eyes (12.6% remained uncorrected; 746 (84.68% eyes were fitted with contact lenses; for 39 eyes (4.44% of 39 patients (8.6% penetrating keratoplasty was recommended. The most common degree of severity found was advanced (575 eyes - 66.86%, followed by the mild variety (160 eyes -18.6%. The average keratometric value of the flattest meridian (K was 47.80 (±3.73 for the eyes fitted with soft CL; 49.03 (±3.7 for the spherical rigid gas permeable contact lenses; of 51.62 (±3.6 for the bicurve contact lenses and 51.14 (±3.5 for the piggyback system. Concerning the topographical pattern, the most frequent was inferior peripheral cone (436

  10. In situ measurements of rock salt permeability changes due to nearby excavation

    International Nuclear Information System (INIS)

    Stormont, J.C.; Howard, C.L.; Daemen, J.J.K.

    1991-07-01

    The Small-Scale Mine-By was an in situ experiment to measure changes in brine and gas permeability of rock salt as a result of nearby excavation. A series of small-volume pressurized brine- and gas-filled test intervals were established 8 m beneath the floor of Room L1 in the WIPP underground. The test intervals were isolated in the bottom of the 4.8-cm diameter monitoring boreholes with inflatable rubber packers, and are initially pressurized to about 2 MPa. Both brine- and gas-filled test intervals were located 1.25, 1.5, 2, 3, and 4 r from the center of a planned large-diameter hole, where r is the radius of the large-diameter hole. Prior to the drilling of the large-diameter borehole, the responses of both the brine- and gas-filled test intervals were consistent with the formation modeled as a very low permeability, low porosity porous medium with a significant pore (brine) pressure and no measurable gas permeability. The drilling of the mine-by borehole created a zone of dilated, partially saturated rock out to about 1.5 r. The formation pressure increases from near zero at 1.5 r to the pre-excavation value at 4 r. Injection tests reveal a gradient of brine permeabilities from 5 x 10 -18 m 2 at 1.25 r to about the pre-excavation value (10 -21 m 2 ) by 3 r. Gas-injection tests reveal measurable gas permeability is limited to within 1.5 r. 17 refs., 24 figs., 6 tabs

  11. Crustal permeability: Introduction to the special issue

    Science.gov (United States)

    Ingebritsen, Steven E.; Gleeson, Tom

    2015-01-01

    The topic of crustal permeability is of broad interest in light of the controlling effect of permeability on diverse geologic processes and also timely in light of the practical challenges associated with emerging technologies such as hydraulic fracturing for oil and gas production (‘fracking’), enhanced geothermal systems, and geologic carbon sequestration. This special issue of Geofluids is also motivated by the historical dichotomy between the hydrogeologic concept of permeability as a static material property that exerts control on fluid flow and the perspective of economic geologists, geophysicists, and crustal petrologists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. Issues associated with fracking, enhanced geothermal systems, and geologic carbon sequestration have already begun to promote a constructive dialog between the static and dynamic views of permeability, and here we have made a conscious effort to include both viewpoints. This special issue also focuses on the quantification of permeability, encompassing both direct measurement of permeability in the uppermost crust and inferential permeability estimates, mainly for the deeper crust.

  12. Modelling of static friction in rubber-metal contact

    NARCIS (Netherlands)

    Deladi, E.L.; de Rooij, Matthias B.; Schipper, Dirk J.

    2007-01-01

    A static friction model for contact between rough rubber and metal surfaces is developed. This model is based on the contact of a viscoelastic–rigid asperity couple. Single asperity contact is modelled in such a way that the asperities stick together in a central region and slip over an annulus at

  13. Transport zonation limits coupled nitrification-denitrification in permeable sediments

    DEFF Research Database (Denmark)

    Kessler, Adam John; Glud, R.N.; Cardenas, M.B.

    2013-01-01

    - and N-15-N-2 gas. The measured two-dimensional profiles correlate with computational model simulations, showing a deep pool of N-2 gas forming, and being advected to the surface below ripple peaks. Further isotope pairing calculations on these data indicate that coupled nitrification......-denitrification is severely limited in permeable sediments because the flow and transport field limits interaction between oxic and anoxic pore water. The approach allowed for new detailed insight into subsurface denitrification zones in complex permeable sediments....

  14. Comparative Analysis of Tear Film Levels of Inflammatory Mediators in Contact Lens Users.

    Science.gov (United States)

    Yüksel Elgin, Cansu; İskeleli, Güzin; Talaz, Serap; Akyol, Sibel

    2016-04-01

    To compare tear films levels of various inflammatory cytokines in asymptomatic contact lens (CL) users. CL users of rigid gas-permeable CLs (RGPCL) (group 1) or silicone hydrogel CLs (SiHCL) (group 2) were compared with non-CL-using healthy subjects (group 3). Tear samples were collected from subjects in each group after ensuring that there were no complications secondary to CL wear in the CL-wearing participants. Tear-film levels of interleukins (ILs)-1β, -6, and -8; granulocyte-macrophage colony-stimulating factor (GM-CSF) (using the Luminex method); and leukotriene B4 (LTB4) (using the ELISA method) were determined. Cytokine levels were compared among the three groups using analysis-of-variance (ANOVA) and Kruskall-Wallis tests. There were significant differences in concentrations of IL-1β, GM-CSF and LTB4 among the three groups (p = 0.002, p = 0.021 and p = 0.009, respectively), as shown by the Kruskall-Wallis test comparing all three groups for the three cytokines. There were no significant differences for IL-6 and IL-8 (p = 0.079 and 0.094, respectively) when all three groups were compared. There were substantial statistically significant differences between RGPCL users, SiHCL users and control subjects in levels of tear film cytokines. Although CL users were asymptomatic, changes in tear-film levels of several important inflammatory mediators revealed that a chronic inflammatory process occurs during CL wear.

  15. Permeability of WIPP Salt During Damage Evolution and Healing

    International Nuclear Information System (INIS)

    BODNER, SOL R.; CHAN, KWAI S.; MUNSON, DARRELL E.

    1999-01-01

    The presence of damage in the form of microcracks can increase the permeability of salt. In this paper, an analytical formulation of the permeability of damaged rock salt is presented for both initially intact and porous conditions. The analysis shows that permeability is related to the connected (i.e., gas accessible) volumetric strain and porosity according to two different power-laws, which may be summed to give the overall behavior of a porous salt with damage. This relationship was incorporated into a constitutive model, known as the Multimechanism Deformation Coupled Fracture (MDCF) model, which has been formulated to describe the inelastic flow behavior of rock salt due to coupled creep, damage, and healing. The extended model was used to calculate the permeability of rock salt from the Waste Isolation Pilot Plant (WIPP) site under conditions where damage evolved with stress over a time period. Permeability changes resulting from both damage development under deviatoric stresses and damage healing under hydrostatic pressures were considered. The calculated results were compared against experimental data from the literature, which indicated that permeability in damaged intact WIPP salt depends on the magnitude of the gas accessible volumetric strain and not on the total volumetric strain. Consequently, the permeability of WIPP salt is significantly affected by the kinetics of crack closure, but shows little dependence on the kinetics of crack removal by sintering

  16. Optimum permeability for a cement based backfill material

    International Nuclear Information System (INIS)

    Jacobs, F.; Wittmann, F.H.; Iriya, K.

    1989-01-01

    In Switzerland it is planned to dispose low- and intermediate radioactive waste (LLW/ILW) in an underground repository. Between the materials present in a repository different chemical reactions may occur. Due to radiolytic decomposition, microbiological degradation and corrosion gas (mainly hydrogen) may be produced. The release of gas can cause the build-up of pressure in the cavern and finally lead to the formation of cracks and/or serious damage in the concrete structure or host rock. Through cracks a contamination of the groundwater and the biosphere could be possible. This investigation develops a suitable cement based material which can be used as backfill for the repository. Besides other aspects mentioned later a suitable backfill material has to be characterized by a certain minimum gas permeability and a as low as possible hydraulic conductivity. On the one hand gas permeability is necessary to release gas overpressure and on the other hand a low hydraulic conductivity should prevent leaching of backfill materials and contamination of the environment

  17. Myopia correction in children: a meta-analysis.

    Science.gov (United States)

    Cui, Yanhui; Li, Li; Wu, Qian; Zhao, Junyang; Chu, Huihui; Yu, Gang; Wei, Wenbin

    2017-06-26

    The purpose of this study was to conduct a meta-analysis comparing rigid gas permeable lenses (RGP) with soft contact lenses (SCL), spectacles and orthokeratology (OK) lenses for myopia control with respect to axial length elongation, spherical equivalent and measures of corneal curvature. Medline, Cochrane, EMBASE, and Google Scholar databases were searched to September 29, 2015 using the following keywords: rigid gas permeable contact lens; refractive error; and refractive abnormalities. Randomized controlled trials, two-arm prospective studies and retrospective studies of children with myopia treated with RGP lenses compared with spectacles, SCL, and OK lenses were included. Outcome measures were changes of axial length, spherical equivalent, flatter meridian, steeper meridian and corneal apical radius. Five studies were included. Three studies reported axial length change after 2-3 years of treatment with RGP lenses and SCL/spectacles and no difference between the groups was noted (pooled mean difference = -0.077, 95% confidence interval [CI]: -0.120 to 0.097, p = 0.840). Two studies reported a change of spherical equivalent after 2-3 years of treatment with RGP lenses and SCL/spectacles, and no difference between the groups was noted (pooled mean difference = 0.275, 95% CI: -0.390 to 0.941, p = 0.417). Two studies compared corneal curvature measures between RGP and OK lenses after 3-6 months of treatment and no differences in any measures of corneal curvature were seen. The effect of RGP lenses and SCL/spectacles on axial length elongation and spherical equivalent and of RGP and OK lenses on corneal curvature in children with myopia was similar.

  18. Investigation on the Permeability Evolution of Gypsum Interlayer Under High Temperature and Triaxial Pressure

    Science.gov (United States)

    Tao, Meng; Yechao, You; Jie, Chen; Yaoqing, Hu

    2017-08-01

    The permeability of the surrounding rock is a critical parameter for the designing and assessment of radioactive waste disposal repositories in the rock salt. Generally, in the locations that are chosen for radioactive waste storage, the bedded rock salt is a sedimentary rock that contains NaCl and Na2SO4. Most likely, there are also layers of gypsum ( {CaSO}_{ 4} \\cdot 2 {H}_{ 2} {O)} present in the salt deposit. Radioactive wastes emit a large amount of heat and hydrogen during the process of disposal, which may result in thermal damage of the surrounding rocks and cause a great change in their permeability and tightness. Therefore, it is necessary to investigate the permeability evolution of the gypsum interlayer under high temperature and high pressure in order to evaluate the tightness and security of the nuclear waste repositories in bedded rock salt. In this study, a self-designed rock triaxial testing system by which high temperature and pressure can be applied is used; the μCT225kVFCB micro-CT system is also employed to investigate the permeability and microstructure of gypsum specimens under a constant hydrostatic pressure of 25 MPa, an increasing temperature (ranging from 20 to 650 °C), and a variable inlet gas pressure (1, 2, 4, 6 MPa). The experimental results show: (a) the maximum permeability measured during the whole experiment is less than 10-17 m2, which indicates that the gypsum interlayer has low permeability under high temperature and pressure that meet the requirements for radioactive waste repository. (b) Under the same temperature, the permeability of the gypsum specimen decreases at the beginning and then increases as the pore pressure elevates. When the inlet gas pressure is between 0 and 2 MPa, the Klinkenberg effect is very pronounced. Then, as the pore pressure increases, the movement behavior of gas molecules gradually changes from free motion to forced directional motion. So the role of free movement of gas molecules gradually

  19. Lattice Boltzmann Simulation of Permeability and Tortuosity for Flow through Dense Porous Media

    Directory of Open Access Journals (Sweden)

    Ping Wang

    2014-01-01

    Full Text Available Discrete element method (DEM is used to produce dense and fixed porous media with rigid mono spheres. Lattice Boltzmann method (LBM is adopted to simulate the fluid flow in interval of dense spheres. To simulating the same physical problem, the permeability is obtained with different lattice number. We verify that the permeability is irrelevant to the body force and the media length along flow direction. The relationships between permeability, tortuosity and porosity, and sphere radius are researched, and the results are compared with those reported by other authors. The obtained results indicate that LBM is suited to fluid flow simulation of porous media due to its inherent theoretical advantages. The radius of sphere should have ten lattices at least and the media length along flow direction should be more than twenty radii. The force has no effect on the coefficient of permeability with the limitation of slow fluid flow. For mono spheres porous media sample, the relationship of permeability and porosity agrees well with the K-C equation, and the tortuosity decreases linearly with increasing porosity.

  20. Scaling behavior of gas permeability measurements in volcanic tuffs

    International Nuclear Information System (INIS)

    Tidwell, V.C.

    1994-01-01

    One of the critical issues facing the Yucca Mountain site characterization and performance assessment programs is the manner in which property scaling is addressed. Property scaling becomes an issue whenever heterogeneous media properties are measured at one scale but applied at another. A research program has been established to challenge current understanding of property scaling with the aim of developing and testing models that describe scaling behavior in a quantitative manner. Scaling of constitutive rock properties is investigated through physical experimentation involving the collection of suites of gas-permeability data measured over a range of discrete scales. The approach is to systematically isolate those factors believed to influence property scaling and investigate their relative contributions to overall scaling behavior. Two blocks of tuff, each exhibiting differing heterogeneity structure, have recently been examined. Results of the investigation show very different scaling behavior, as exhibited by changes in the distribution functions and variograms, for the two tuff samples. Even for the relatively narrow range of measurement scales employed significant changes in the distribution functions, variograms, and summary statistics occurred. Because such data descriptors will likely play an important role in calculating effective media properties, these results demonstrate both the need to understand and accurately model scaling behavior

  1. Investigation of oil production conditions and production operation by solution gas drive in low permeable heterogeneous limestones

    Energy Technology Data Exchange (ETDEWEB)

    Lillie, W

    1966-04-01

    It was the purpose of this study to investigate the production of oil and gas from a low permeable heterogeneous limestone-reservoir by solution gas drive. The rock-samples were subjected to extensive petrolphysical analyses in order to characterize the pore structure of of the limestone material. Laboratory model flow tests were undertaken to outline in detail the production history during the pressure depletion process under reservoir conditions and by using original reservoir fluids. The experiments were carried out at different rates of pressure decline. It can be stated that the rate of pressure decline is the most important factor affecting the oil recovery and the development of the gas-oil-ratio in a model flow test. The present investigation leads to the following conclusion: It is posible to get reliable results which could be the base for a reservoir performance prediction only when the gas and oil phase are maintained at equilibrium conditions within the rock sample during the pressure decline. An additional calculation of the solution gas drive reservoir production history by the Tarner method shows a good agreement of the experimental and the calculated data. (40 refs.)

  2. Relative Permeability of Fractured Rock

    Energy Technology Data Exchange (ETDEWEB)

    Mark D. Habana

    2002-06-30

    Contemporary understanding of multiphase flow through fractures is limited. Different studies using synthetic fractures and various fluids have yielded different relative permeability-saturation relations. This study aimed to extend the understanding of multiphase flow by conducting nitrogen-water relative permeability experiments on a naturally-fractured rock from The Geysers geothermal field. The steady-state approach was used. However, steady state was achieved only at the endpoint saturations. Several difficulties were encountered that are attributed to phase interference and changes in fracture aperture and surface roughness, along with fracture propagation/initiation. Absolute permeabilities were determined using nitrogen and water. The permeability values obtained change with the number of load cycles. Determining the absolute permeability of a core is especially important in a fractured rock. The rock may change as asperities are destroyed and fractures propagate or st rain harden as the net stresses vary. Pressure spikes occurred in water a solute permeability experiments. Conceptual models of an elastic fracture network can explain the pressure spike behavior. At the endpoint saturations the water relative permeabilities obtained are much less than the nitrogen gas relative permeabilities. Saturations were determined by weighing and by resistivity calculations. The resistivity-saturation relationship developed for the core gave saturation values that differ by 5% from the value determined by weighing. Further work is required to complete the relative permeability curve. The steady-state experimental approach encountered difficulties due to phase interference and fracture change. Steady state may not be reached until an impractical length of time. Thus, unsteady-state methods should be pursued. In unsteady-state experiments the challenge will be in quantifying rock fracture change in addition to fluid flow changes.

  3. Experimental characterization of fire-induced response of rigid polyurethane foam

    Energy Technology Data Exchange (ETDEWEB)

    Chu, T.Y.; Gill, W.; Moore, J.W.; Hobbs, M.L.; Gritzo, L.A.; Moya, J.L.

    1995-12-31

    Reported is the result of an experimental investigation of fire-induced response of a 96 kg/m{sup 3} closed cell rigid polyurethane foam. The specimen is 0.37 m in diameter, and 152 mm thick, placed in a cylindrical test vessel. The fire condition is simulated by heating the bottom of the test vessel to 1283 K using a radiant heat source. Real-time x-ray shows that the degradation process involves the progression of a charring front into the virgin material. The charred region has a regular and graded structure consisting of a packed bubble outer layer and successive layers of thin shells. The layer-to-layer permeability appears to be poor. There are indications that gas vents laterally. The shell-like structure might be the result of lateral venting. Although the foam degradation process is quite complicated, the in-depth temperature responses in the uncharted foam appear to be consistent with steady state ablation. The measured temperature responses are well represented by the exponential distribution for steady state ablation. An estimate of the thermal diffusivity of the foam is obtained from the ablation model. The experiment is part of a more comprehensive program to develop material response models of foams and encapsulants.

  4. Universal scaling of permeability through the granular-to-continuum transition

    Science.gov (United States)

    Wadsworth, F. B.; Scheu, B.; Heap, M. J.; Kendrick, J. E.; Vasseur, J.; Lavallée, Y.; Dingwell, D. B.

    2015-12-01

    Magmas fragment forming a transiently granular material, which can weld back to a fluid-continuum. This process results in dramatic changes in the gas-volume fraction of the material, which impacts the gas permeability. We collate published data for the gas-volume fraction and permeability of volcanic and synthetic materials which have undergone this process to different amounts and note that in all cases there exists a discontinuity in the relationship between these two properties. By discriminating data for which good microstructural information are provided, we use simple scaling arguments to collapse the data in both the still-granular, high gas-volume fraction regime and the fluid-continuum low gas-volume fraction regime such that a universal description can be achieved. We use this to argue for the microstructural meaning of the well-described discontinuity between gas-permeability and gas-volume fraction and to infer the controls on the position of this transition between dominantly granular and dominantly fluid-continuum material descriptions. As a specific application, we consider the transiently granular magma transported through and deposited in fractures in more-coherent magmas, thought to be a primary degassing pathway in high viscosity systems. We propose that our scaling coupled with constitutive laws for densification can provide insights into the longevity of such degassing channels, informing sub-surface pressure modelling at such volcanoes.

  5. Wettability determination by contact angle measurements: hvbB coal-water system with injection of synthetic flue gas and CO2.

    Science.gov (United States)

    Shojai Kaveh, Narjes; Rudolph, E Susanne J; Wolf, Karl-Heinz A A; Ashrafizadeh, Seyed Nezameddin

    2011-12-01

    Geological sequestration of pure carbon dioxide (CO(2)) in coal is one of the methods to sequester CO(2). In addition, injection of CO(2) or flue gas into coal enhances coal bed methane production (ECBM). The success of this combined process depends strongly on the wetting behavior of the coal, which is function of coal rank, ash content, heterogeneity of the coal surface, pressure, temperature and composition of the gas. The wetting behavior can be evaluated from the contact angle of a gas bubble, CO(2) or flue gas, on a coal surface. In this study, contact angles of a synthetic flue gas, i.e. a 80/20 (mol%) N(2)/CO(2) mixture, and pure CO(2) on a Warndt Luisenthal (WL) coal have been determined using a modified pendant drop cell in a pressure range from atmospheric to 16 MPa and a constant temperature of 318 K. It was found that the contact angles of flue gas on WL coal were generally smaller than those of CO(2). The contact angle of CO(2) changes from water-wet to gas-wet by increasing pressure above 8.5 MPa while the one for the flue gas changes from water-wet to intermediate-wet by increasing pressure above 10 MPa. Copyright © 2011 Elsevier Inc. All rights reserved.

  6. Bacterial Adhesion Forces to Ag-Impregnated Contact Lens Cases and Transmission to Contact Lenses

    NARCIS (Netherlands)

    Qu, Wenwen; Busscher, Henk J.; van der Mei, Henny C.; Hooymans, Johanna M. M.

    Purpose: To measure adhesion forces of Pseudomonas aeruginosa, Staphylococcus aureus, and Serratia marcescens to a rigid contact lens (CL), standard polypropylene, and Ag-impregnated lens cases using atomic force microscopy and determine bacterial transmission from lens case to CL. Methods: Adhesion

  7. Role of intrachain rigidity in the plasticization of intrinsically microporous triptycene-based polyimide membranes in mixed-Gas CO2/CH4 separations

    KAUST Repository

    Swaidan, Raja

    2014-11-11

    Based on high-pressure pure- and mixed-gas (50:50) CO2/CH4 separation properties of two intrinsically microporous triptycene-based polyimides (TPDA-TMPD and TPDA-6FpDA), the intrachain rigidity central to "conventional PIM" design principles is not a singular solution to intrinsic plasticization resistance. Despite the significant intrachain rigidity in TPDA-TMPD, a 300% increase in PMIX(CH4), 50% decrease in α(CO2/CH4) from 24 to 12, and continuous increase in PMIX(CO2) occurred from 4 to 30 bar. On the other hand, the more flexible and densely packed TPDA-6FpDA exhibited a slight upturn in PMIX(CO2) at 20 bar similar to a dense cellulose acetate (CA) film, also reported here, despite a 4-fold higher CO2 sorption capacity. Microstructural investigations suggest that the interconnected O2- and H2-sieving ultramicroporosity of TPDA-TMPD is more sensitive to slight CO2-induced dilations and is the physical basis for a more extensive and accelerated plasticization. Interchain rigidity, potentially by interchain interactions, is emphasized and may be facilitated by intrachain mobility.

  8. Existence for viscoplastic contact with Coulomb friction problems

    Directory of Open Access Journals (Sweden)

    Amina Amassad

    2002-01-01

    frictional contact between an elastic-viscoplastic body and a rigid obstacle. We model the frictional contact both by a Tresca's friction law and a regularized Coulomb's law. We assume, in a first part, that the contact is bilateral and that no separation takes place. In a second part, we consider the Signorini unilateral contact conditions. Proofs are based on a time-discretization method, Banach and Schauder fixed point theorems.

  9. Radionuclide Migration at the Rio Blanco Site, A Nuclear-stimulated Low-permeability Natural Gas Reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Clay A. Cooper; Ming Ye; Jenny Chapman; Craig Shirley

    2005-10-01

    The U.S. Department of Energy and its predecessor agencies conducted a program in the 1960s and 1970s that evaluated technology for the nuclear stimulation of low-permeability gas reservoirs. The third and final project in the program, Project Rio Blanco, was conducted in Rio Blanco County, in northwestern Colorado. In this experiment, three 33-kiloton nuclear explosives were simultaneously detonated in a single emplacement well in the Mesaverde Group and Fort Union Formation, at depths of 1,780, 1,899, and 2,039 m below land surface on May 17, 1973. The objective of this work is to estimate lateral distances that tritium released from the detonations may have traveled in the subsurface and evaluate the possible effect of postulated natural-gas development on radionuclide migration. Other radionuclides were considered in the analysis, but the majority occur in relatively immobile forms (such as nuclear melt glass). Of the radionuclides present in the gas phase, tritium dominates in terms of quantity of radioactivity in the long term and contribution to possible whole body exposure. One simulation is performed for {sup 85}Kr, the second most abundant gaseous radionuclide produced after tritium.

  10. Effect of Flow Direction on Relative Permeability Curves in Water/Gas Reservoir System: Implications in Geological CO2 Sequestration

    Directory of Open Access Journals (Sweden)

    Abdulrauf Rasheed Adebayo

    2017-01-01

    Full Text Available The effect of gravity on vertical flow and fluids saturation, especially when flow is against gravity, is not often a subject of interest to researchers. This is because of the notion that flow in subsurface formations is usually in horizontal direction and that vertical flow is impossible or marginal because of the impermeable shales or silts overlying them. The density difference between two fluids (usually oil and water flowing in the porous media is also normally negligible; hence gravity influence is neglected. Capillarity is also often avoided in relative permeability measurements in order to satisfy some flow equations. These notions have guided most laboratory core flooding experiments to be conducted in horizontal flow orientation, and the data obtained are as good as what the experiments tend to mimic. However, gravity effect plays a major role in gas liquid systems such as CO2 sequestration and some types of enhanced oil recovery techniques, particularly those involving gases, where large density difference exists between the fluid pair. In such cases, laboratory experiments conducted to derive relative permeability curves should take into consideration gravity effects and capillarity. Previous studies attribute directional dependence of relative permeability and residual saturations to rock anisotropy. It is shown in this study that rock permeability, residual saturation, and relative permeability depend on the interplay between gravity, capillarity, and viscous forces and also the direction of fluid flow even when the rock is isotropic. Rock samples representing different lithology and wide range of permeabilities were investigated through unsteady-state experiments covering drainage and imbibition in both vertical and horizontal flow directions. The experiments were performed at very low flow rates to capture capillarity. The results obtained showed that, for each homogeneous rock and for the same flow path along the core length

  11. Dynamic response characteristics of steel portal frames having semi-rigid joints under sinusoidal wave excitation

    Science.gov (United States)

    Bhatti, Abdul Qadir

    2017-12-01

    To demonstrate the characteristics of the nonlinear response of steel frames, an elastic dynamic response analysis of the semi-rigid frame is performed under the harmonic wave. The semi-rigid contact is represented by the alternating spring which is given stiffness by a three-parameter energy model which approaches the hysterical curve by hardening model. The properties of spectra and hysteric curves are presented. This study shows that (1) the greater the acceleration input capacitance the smaller the instant connection capability and the smaller is the response. (2) However, by allowing an extreme increase in capacitance input acceleration, response spectra can be increased as the contact stiffness results near zero.

  12. Porosity, petrophysics and permeability of the Whitby Mudstone (UK)

    Science.gov (United States)

    Houben, M.; Barnhoorn, A.; Hardebol, N.; Ifada, M.; Boersma, Q.; Douma, L.; Peach, C. J.; Bertotti, G.; Drury, M. R.

    2016-12-01

    Typically pore diameters in shales range from the µm down to the nm scale and the effective permeability of shale reservoirs is a function of the interconnectivity between the pore space and the natural fracture network present. The length and spacing of mechanical induced and natural fractures is one of the factors controlling gas produtivity from unconventional reservoirs. Permeability of the Whitby Mudstone measured on 1 inch cores was linked to microstructure and combined with natural fracture spacing present in outcrops along the Yorkshire coast (UK) to get insight into possible fluid pathways from reservoir to well. We used a combination of different techniques to characterize the porosity (gas adsorption, Scanning Electron Microscopy), mineralogy (X-Ray Fluorescence, X-Ray Diffraction, Scanning Electron Microscopy) and permeability (pressure step decay) of the Whitby Mudstone. In addition, we mapped the natural fracture network as present in outcrops along the Yorkshire coast (UK) at the 10-2-101m scale. Mineralogically we are dealing with a rock that is high in clay content and has an average organic matter content of about 10%. Results show a low porosity (max. 7%) as well as low permeability for the Whitby Mudstone. The permeability, measured parallel to bedding, depends on the confining pressure and is 86 nanodarcy at 10 MPa effective confining pressure and decreases to 16 nanodarcy at 40 MPa effective confining pressure. At the scale of observation the average distance to nearest natural fracture is in the order of 0.13 meter and 90 percent of all matrix elements are spaced within 0.4 meter to the nearest fracture. By assuming darcy flow, a permeability of 100 nanodarcy and 10% of overpressure we calculated that for the Whitby mudstone most of the gas resides in the matrix for less than 60 days until it reaches the fracture network.

  13. Bronchoalveolar permeability changes in rats inhaling gas/particle combinations during rest or exercise

    International Nuclear Information System (INIS)

    Bhalla, D.K.; Phalen, R.F.; Mannix, R.C.; Lavan, S.M.; Crocker, T.T.

    1986-01-01

    Bronchoalveolar (BA) injury in rats exposed at rest or exercise to air pollutants was studied by changes in epithelial permeability. Rats exposed to air, single gases or pollutant combinations were anesthetized, tracheostomized, and placed on an incline. /sup 99m/Tc-DTPA was delivered directly to a major bronchus. Radioactivity measurements were made on blood samples collected during first 10 min. Exposure of resting rats to 0.6 ppm O 3 increased BA permeability just after exposure, but it was normal 24 hrs later; in exercising rats the increase was greater than in rats exposed at rest, and it persisted up to 24 hrs. NO 2 at 6 ppm did not affect permeability. Exposure of resting rats to 2.5 ppm NO 2 + 0.6 ppm O 3 only increased permeability right after the exposure, but in exercising rats this exposure resulted in a greater permeability which remained elevated up to 24 hrs. Exposure of exercising rats to 0.8 ppm O 3 + 10 ppm HCHO increased permeability. Exposure of resting rats to an atmosphere of 0.6 ppm O 3 + 2.5 ppm NO 2 + 5 ppm SO 2 + 1 mg/m 3 sulfates of ferric, ammonium and manganese also produced an increase in permeability that persisted up to 24 hrs. The results suggest potentiation of the pollutant effects by exercise, but there is no indication of synergistic effect of pollutant combinations on BA permeability

  14. Review of the use of rigid and high-impact PVC pipes in natural gas distribution systems in the Netherlands

    Energy Technology Data Exchange (ETDEWEB)

    Mutter, F; Benjamin, P

    1974-08-01

    Because of a number of instances of stress corrosion cracking or crazing occurring in PVC pipes used in Dutch gas distribution systems, VEG-GASINSTITUUT began an intensive investigation of rigid PVC pipes and high-impact pipes in distribution use under various conditions and with varying service lives. The work led to an investigation of laboratory testing techniques in which the stress-cracking phenomenon found in practice could be duplicated under controllable conditions. Pipes of various materials were examined for their resistance to stress cracking, then this resistance was compared with other long- and short-term physical properties of the material.

  15. Apparent dynamic contact angle of an advancing gas--liquid meniscus

    International Nuclear Information System (INIS)

    Kalliadasis, S.; Chang, H.

    1994-01-01

    The steady motion of an advancing meniscus in a gas-filled capillary tube involves a delicate balance of capillary, viscous, and intermolecular forces. The limit of small capillary numbers Ca (dimensionless speeds) is analyzed here with a matched asymptotic analysis that links the outer capillary region to the precursor film in front of the meniscus through a lubricating film. The meniscus shape in the outer region is constructed and the apparent dynamic contact angle Θ that the meniscus forms with the solid surface is derived as a function of the capillary number, the capillary radius, and the Hamaker's constant for intermolecular forces, under conditions of weak gas--solid interaction, which lead to fast spreading of the precursor film and weak intermolecular forces relative to viscous forces within the lubricating film. The dependence on intermolecular forces is very weak and the contact angle expression has a tight upper bound tan Θ=7.48 Ca 1/3 for thick films, which is independent of the Hamaker constant. This upper bound is in very good agreement with existing experimental data for wetting fluids in any capillary and for partially wetting fluids in a prewetted capillary. Significant correction to the Ca 1/3 dependence occurs only at very low Ca, where the intermolecular forces become more important and tan Θ diverges slightly from the above asymptotic behavior toward lower values

  16. permeability of twenty-two small diameter hardwoods growing on southern pine sites

    Science.gov (United States)

    E.T. Choong; F.O. Tesora

    1974-01-01

    Gas permeability of hardwoods growing on southern pine sites is significantly affected by moisture content in the longitudinal direction. The ratio of permeability in the transverse to longitudinal directions is from 12,000:1 for post oak to over 1,000,000:1 for other oaks, but it is not affected by moisture. Although variation in longitudinal permeability varies...

  17. Permeability measurements and modeling of topology-optimized metallic 3-D woven lattices

    International Nuclear Information System (INIS)

    Zhao, Longyu; Ha, Seunghyun; Sharp, Keith W.; Geltmacher, Andrew B.; Fonda, Richard W.; Kinsey, Alex H.; Zhang, Yong; Ryan, Stephen M.; Erdeniz, Dinc; Dunand, David C.; Hemker, Kevin J.; Guest, James K.; Weihs, Timothy P.

    2014-01-01

    Topology optimization was combined with a 3-D weaving technique to design and fabricate structures with optimized combinations of fluid permeability and mechanical stiffness. Two different microarchitected structures are considered: one is a “standard” weave in which all wires were included, while the other is termed an “optimized” weave as specific wires were removed to maximize the permeability of the resulting porous materials with only a limited reduction in stiffness. Permeability was measured and predicted for both structures that were 3-D woven with either Cu or Ni–20Cr wires. The as-woven wires in the Cu lattices were bonded at contact points using solder or braze while the Ni–20Cr wires were bonded at contact points using pack aluminization. Permeability was measured under laminar flow conditions in all three normal directions for unbonded and bonded samples and in the optimized structure it was found to increase between 200% and 600%, depending on direction, over the standard structures. Permeability was also predicted using finite-element modeling with as-fabricated wires positions that were identified with optical microscopy or X-ray tomography; the measurements and predictions show good agreement. Lastly, the normalized permeability values significantly exceed those found for stochastic, metallic foams and other periodic structures with a material volume fraction of over 30%

  18. Nonequilibrium gas absorption in rotating permeable media

    Science.gov (United States)

    Baev, V. K.; Bazhaikin, A. N.

    2016-08-01

    The absorption of ammonia, sulfur dioxide, and carbon dioxide by water and aqueous solutions in rotating permeable media, a cellular porous disk, and a set of spaced-apart thin disks has been considered. The efficiency of cleaning air to remove these impurities is determined, and their anomalously high solubility (higher than equilibrium value) has been discovered. The results demonstrate the feasibility of designing cheap efficient rotor-type absorbers to clean gases of harmful impurities.

  19. Contact and symplectic topology

    CERN Document Server

    Colin, Vincent; Stipsicz, András

    2014-01-01

    Symplectic and contact geometry naturally emerged from the mathematical description of classical physics. The discovery of new rigidity phenomena and properties satisfied by these geometric structures launched a new research field worldwide. The intense activity of many European research groups in this field is reflected by the ESF Research Networking Programme "Contact And Symplectic Topology" (CAST). The lectures of the Summer School in Nantes (June 2011) and of the CAST Summer School in Budapest (July 2012) provide a nice panorama of many aspects of the present status of contact and symplectic topology. The notes of the minicourses offer a gentle introduction to topics which have developed in an amazing speed in the recent past. These topics include 3-dimensional and higher dimensional contact topology, Fukaya categories, asymptotically holomorphic methods in contact topology, bordered Floer homology, embedded contact homology, and flexibility results for Stein manifolds.

  20. In situ permeability testing of rock salt

    International Nuclear Information System (INIS)

    Peterson, E.W.; Lagus, P.L.; Broce, R.D.; Lie, K.

    1981-04-01

    Storage of transuranic (TRU) wastes in bedded salt formations requires a knowledge of the in situ permeability of SENM rock salt. Since assumptions for safety assessments have been made in which these wastes could generate gas pressures on the order of the lithostatic pressure over geologic time scales, the permeability of the surrounding formation becomes an important parameter for determining the manner in which the gases will be contained or dispersed. This report describes the series of tests conducted in the AEC-7 borehole, located near the WIPP site, to determine the in situ gas flow characteristics of the bedded salt. In these tests, compressed air was injected into the borehole and flow into the surrounding formation measured. These measured flow rates were interpreted in terms of formation permeabilities and porosities which were, in turn, used as modeling parameters for the repository response analysis. Two series of field tests were performed. The first series consisted of a number of whole-hole flow tests conducted to provide preliminary design information required for future operation of a guarded straddle packer system capable of measuring permeabilities > or = 0.1 μdarcy. The second series of tests were conducted using the Systems, Science and Software (S-Cubed) designed guarded straddle packer system. In these interval permeability tests, 100-foot lengths of borehole were isolated and the flow characteristics of the surrounding formation examined. In this report, a complete description of the test procedures, instrumentation, and measurement techniques is first given. The analytical/numerical methods used for data interpretation are then presented, followed by results of the interval and permeability tests. (The whole-hole tests are summarized in Appendix A.) Conclusions are presented in the final section

  1. Adhesion of Pseudomonas aeruginosa to orthokeratology and alignment lenses.

    Science.gov (United States)

    Choo, Jennifer D; Holden, Brien A; Papas, Eric B; Willcox, Mark D P

    2009-02-01

    To determine whether contact lenses designed for orthokeratology (OK) are colonized by greater numbers of bacteria compared with standard (alignment fitted) design rigid gas permeable lenses before and after lens wear. Eighteen 1-year-old cats were randomly fitted with an OK lens in one eye and an alignment fitted (AF) lens in the other eye. Both lenses were made in the same diameter and central thickness and of the same material. Two separate wearing periods of 2 weeks and 6 weeks were used. After each wearing period, lenses were soaked in Pseudomonas aeruginosa (6294 or 6206) for 10 min. The lenses were then reinserted onto their respective corneas for a wearing period of 16 hours after which lenses were collected and remaining adhered bacteria quantified. Unworn control lenses were also soaked and bacteria enumerated for comparison. There were no significant differences in the number of bacteria adherent to unworn AF and OK lenses. Analysis of lenses after wear showed OK lenses retained significantly higher numbers of viable bacteria than AF lenses in all studies. OK lenses retain more bacteria than AF rigid gas permeable lenses after bacteria-loaded overnight lens wear. This may increase the risk for an infection in OK patients should suitable conditions be present. Specific education on the cleaning of OK lenses is essential.

  2. A fractal model for predicting permeability and liquid water relative permeability in the gas diffusion layer (GDL) of PEMFCs

    Science.gov (United States)

    He, Guangli; Zhao, Zongchang; Ming, Pingwen; Abuliti, Abudula; Yin, Caoyong

    In this study, a fractal model is developed to predict the permeability and liquid water relative permeability of the GDL (TGP-H-120 carbon paper) in proton exchange membrane fuel cells (PEMFCs), based on the micrographs (by SEM, i.e. scanning electron microscope) of the TGP-H-120. Pore size distribution (PSD), maximum pore size, porosity, diameter of the carbon fiber, pore tortuosity, area dimension, hydrophilicity or hydrophobicity, the thickness of GDL and saturation are involved in this model. The model was validated by comparison between the predicted results and experimental data. The results indicate that the water relative permeability in the hydrophobicity case is much higher than in the hydrophilicity case. So, a hydrophobic carbon paper is preferred for efficient removal of liquid water from the cathode of PEMFCs.

  3. Highly permeable, cement-bounded backfilling mortars for SMA repositories

    International Nuclear Information System (INIS)

    Jacobs, F.; Mayer, G.; Wittmann, F.H.

    1994-03-01

    In low- and intermediate-level waste repositories, gas is produced due e.g. to corrosion. This gas must be able to escape from the repository in order to prevent damage to the repository structure. A cement-based backfill should take over this function. For this purpose, the composition of cement-based materials was varied to study their influence on porosity and permeability. In parallel to this study the behaviour of fresh concrete, the liberation of the heat of hydration and the hardened concrete properties were investigated. To characterize the permeability of cement-based materials the following parameters are important: 1) composition of the material (pore fabric), 2) storage conditions (degree of saturation), 3) degree of hydration (age), 4) measuring fluid. A change in the composition of cement-based materials can vary the permeability by ten orders of magnitude. It is shown that, by using dense aggregates, the transport of the fluid takes place through the matrix and along the aggregate/matrix interface. By using porous aggregates the permeability can be increased by two orders of magnitude. In the case of a dense matrix, porous aggregates do not alter the permeability. Increasing the matrix content or interface content increases permeability. Hence light weight mortars are an obvious choice. Like-grained mixes showed higher permeabilities in combination with better mechanical properties but, in comparison to normal mixes, they showed worse flow properties. With the composition cement-: water-: aggregate content 1:0.4:5.33 the likegrained mix with aggregates ranging from 2 to 3 mm proved to be a suitable material. With a low compaction after 28 days this mix reaches a permeability of 4.10 -12 m 2 and an uniaxial cylinder compressive strength of 16 N/mm 2 . (author) 58 figs., 23 tabs., refs

  4. Oxygen, water, and sodium chloride transport in soft contact lenses materials.

    Science.gov (United States)

    Gavara, Rafael; Compañ, Vicente

    2017-11-01

    Oxygen permeability, diffusion coefficient of the sodium ions and water flux and permeability in different conventional hydrogel (Hy) and silicone-hydrogel (Si-Hy) contact lenses have been measured experimentally. The results showed that oxygen permeability and transmissibility requirements of the lens have been addressed through the use of siloxane containing hydrogels. In general, oxygen and sodium chloride permeability values increased with the water content of the lens but there was a percolation phenomenon from a given value of water uptake mainly in the Si-Hy lenses which appeared to be related with the differences between free water and bound water contents. The increase of ion permeability with water content did not follow a unique trend indicating a possible dependence of the chemical structure of the polymer and character ionic and non-ionic of the lens. Indeed, the salt permeability values for silicone hydrogel contact lenses were one order of magnitude below those of conventional hydrogel contact lenses, which can be explained by a diffusion of sodium ions occurring only through the hydrophilic channels. The increase of the ionic permeability in Si-Hy materials may be due to the confinement of ions in nanoscale water channels involving possible decreased degrees of freedom for diffusion of both water and ions. In general, ionic lenses presented values of ionic permeability and diffusivity higher than most non-ionic lenses. The tortuosity of the ionic lenses is lower than the non-ionic Si-Hy lenses. Frequency 55 and PureVision exhibited the highest water permeability and flux values and, these parameters were greater for ionic Si-Hy lenses than for ionic conventional hydrogel lenses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2218-2231, 2017. © 2016 Wiley Periodicals, Inc.

  5. Investigating Multiphase Flow Phenomena in Fine-Grained Reservoir Rocks: Insights from Using Ethane Permeability Measurements over a Range of Pore Pressures

    Directory of Open Access Journals (Sweden)

    Eric Aidan Letham

    2018-01-01

    Full Text Available The ability to quantify effective permeability at the various fluid saturations and stress states experienced during production from shale oil and shale gas reservoirs is required for efficient exploitation of the resources, but to date experimental challenges prevent measurement of the effective permeability of these materials over a range of fluid saturations. To work towards overcoming these challenges, we measured effective permeability of a suite of gas shales to gaseous ethane over a range of pore pressures up to the saturated vapour pressure. Liquid/semiliquid ethane saturation increases due to adsorption and capillary condensation with increasing pore pressure resulting in decreasing effective permeability to ethane gas. By how much effective permeability to ethane gas decreases with adsorption and capillary condensation depends on the pore size distribution of each sample and the stress state that effective permeability is measured at. Effective permeability decreases more at higher stress states because the pores are smaller at higher stress states. The largest effective permeability drops occur in samples with dominant pore sizes in the mesopore range. These pores are completely blocked due to capillary condensation at pore pressures near the saturated vapour pressure of ethane. Blockage of these pores cuts off the main fluid flow pathways in the rock, thereby drastically decreasing effective permeability to ethane gas.

  6. Calculation of gas migration in fractured rock

    International Nuclear Information System (INIS)

    Thunvik, R.; Braester, C.

    1987-09-01

    Calculations are presented for rock properties characteristic to the Forsmark area. The rock permeability was determined by flow tests in vertical boreholes. It is assumed that the permeability distribution obtained from these boreholes is representative also for the permeability distribution along the repository cavern. Calculations were worked out for two different types of boundary conditions, one in which a constant gas flow rate equivalent to a gas production of 33000 kg/year was assumed and the other in which a constant gas cushion of 0.5 metres was assumed. For the permeability distribution considered, the breakthrough at the sea bottom occurred within one hour. The gaswater displacement took place mainly through the fractures of high permeability and practically no flow took place in the fractures of low permeability. (orig./DG)

  7. Coherent electron focusing with quantum point contacts in a two-dimensional electron gas

    NARCIS (Netherlands)

    Houten, H. van; Beenakker, C.W.J.; Williamson, J.G.; Broekaart, M.E.I.; Loosdrecht, P.H.M. van; Wees, B.J. van; Mooij, J.E.; Foxon, C.T.; Harris, J.J.

    1989-01-01

    Transverse electron focusing in a two-dimensional electron gas is investigated experimentally and theoretically for the first time. A split Schottky gate on top of a GaAs-AlxGa1–xAs heterostructure defines two point contacts of variable width, which are used as injector and collector of ballistic

  8. Bulk and contact resistances of gas diffusion layers in proton exchange membrane fuel cells

    Science.gov (United States)

    Ye, Donghao; Gauthier, Eric; Benziger, Jay B.; Pan, Mu

    2014-06-01

    A multi-electrode probe is employed to distinguish the bulk and contact resistances of the catalyst layer (CL) and the gas diffusion layer (GDL) with the bipolar plate (BPP). Resistances are compared for Vulcan carbon catalyst layers (CL), carbon paper and carbon cloth GDL materials, and GDLs with microporous layers (MPL). The Vulcan carbon catalyst layer bulk resistance is 100 times greater than the bulk resistance of carbon paper GDL (Toray TG-H-120). Carbon cloth (CCWP) has bulk and contact resistances twice those of carbon paper. Compression of the GDL decreases the GDL contact resistance, but has little effect on the bulk resistance. Treatment of the GDL with polytetrafluoroethylene (PTFE) increases the contact resistance, but has little effect on the bulk resistance. A microporous layer (MPL) added to the GDL decreases the contact resistance, but has little effect on the bulk resistance. An equivalent circuit model shows that for channels less than 1 mm wide the contact resistance is the major source of electronic resistance and is about 10% of the total ohmic resistance associated with the membrane electrode assembly.

  9. Prediction of Hydrocarbon Reservoirs Permeability Using Support Vector Machine

    Directory of Open Access Journals (Sweden)

    R. Gholami

    2012-01-01

    Full Text Available Permeability is a key parameter associated with the characterization of any hydrocarbon reservoir. In fact, it is not possible to have accurate solutions to many petroleum engineering problems without having accurate permeability value. The conventional methods for permeability determination are core analysis and well test techniques. These methods are very expensive and time consuming. Therefore, attempts have usually been carried out to use artificial neural network for identification of the relationship between the well log data and core permeability. In this way, recent works on artificial intelligence techniques have led to introduce a robust machine learning methodology called support vector machine. This paper aims to utilize the SVM for predicting the permeability of three gas wells in the Southern Pars field. Obtained results of SVM showed that the correlation coefficient between core and predicted permeability is 0.97 for testing dataset. Comparing the result of SVM with that of a general regression neural network (GRNN revealed that the SVM approach is faster and more accurate than the GRNN in prediction of hydrocarbon reservoirs permeability.

  10. Quantifying tight-gas sandstone permeability via critical path analysis

    Science.gov (United States)

    Rock permeability has been actively investigated over the past several decades by the geosciences community. However, its accurate estimation still presents significant technical challenges, especially in spatially complex rocks. In this letter, we apply critical path analysis (CPA) to estimate perm...

  11. Measurement of relative permeability of fuel cell diffusion media

    KAUST Repository

    Hussaini, I.S.

    2010-06-01

    Gas diffusion layer (GDL) in PEM fuel cells plays a pivotal role in water management. Modeling of liquid water transport through the GDL relies on knowledge of relative permeability functions in the in-plane and through-plane directions. In the present work, air and water relative permeabilities are experimentally determined as functions of saturation for typical GDL materials such as Toray-060, -090, -120 carbon paper and E-Tek carbon cloth materials in their plain, untreated forms. Saturation is measured using an ex situ gravimetric method. Absolute and relative permeability functions in the two directions of interest are presented and new correlations for in-plane relative permeability of water and air are established. © 2010 Elsevier B.V. All rights reserved.

  12. The effect of meniscus on the permeability of micro-post arrays

    International Nuclear Information System (INIS)

    Byon, Chan; Kim, Sung Jin

    2011-01-01

    This study aims to investigate the effect of meniscus curvature on the permeability of the micro-post arrays, which are widely used for applications of microfluidics. An analytical model that accounts for the meniscus curvature is developed. The model considers two common array types: quadratic and hexagonal arrays. The permeability of micro-post arrays is estimated using the capillary rate of rise experiment and numerical simulation. The results obtained from the analytical model match the experimental and numerical results within the error of 5% over the range of parameters commonly found in microfluidic applications (0.06 0.2), where d * and H * are the post-diameter and the post-height, respectively, which are normalized by the pitch. Based on the analytic results, the effects of the post-diameter, post-height and the contact angle on the permeability of post-arrays are investigated. It is shown that the previous permeability models based on the flat meniscus assumption overestimate the experimental value by 26% for the quadratic array and 24% for the hexagonal array when cos θ = 1, d * = 0.5 and H *=1. The effect of the meniscus curvature is shown to become more pronounced as the contact angle or the post-height decreases.

  13. A multicenter study of preventable contact burns from glass fronted gas fireplaces.

    Science.gov (United States)

    Wibbenmeyer, Lucy; Gittelman, Michael A; Kluesner, Karen; Liao, Junlin; Xing, Yunfan; Faraklas, Iris; Anyan, Walter; Gamero, Chelsea; Moulton, Steven; Nederveld, Cindy; Banks, Ashley; Ryan, Colleen M; Conway, Jennifer A; Reilly, Debra A; Fish, Joel; Kelly, Charis; Peltier, George; Schwantke, Emily; Conrad, Peggie F; Caruso, Daniel M; Richey, Karen J; McCrory, Kristine; Elfar, Mohamed S A; Pittinger, Timothy; Sadie, Christine; Greenhalgh, David; Palmieri, Tina; Grossman, Peter H; Richards, Kurt M; Joyce, Teresa; Pozez, Andrea L; Savetamal, Alisa; Harrington, David T; Duncan, Kimberley; Pomerantz, Wendy J; Dillard, B Daniel

    2015-01-01

    Glass fronted gas fireplaces (GFGFs) have exterior surfaces that can reach extremely high temperatures. Burn injuries from contact with the glass front can be severe with long-term sequelae. The Consumer Product Safety Commission reported that these injuries are uncommon, whereas single-center studies indicate a much higher frequency. The purpose of this multi-institutional study was to determine the magnitude and severity of GFGF injuries in North America. Seventeen burn centers elected to participate in this retrospective chart review. Chart review identified 402 children ≤10 years of age who sustained contact burns from contact with GFGF, who were seen or admitted to the study hospitals from January 2006 to December 2010. Demographic, burn, treatment, and financial data were collected. The mean age of the study group was 16.8 ± 13.3 months. The majority suffered burns to their hands (396, 98.5%), with burns to the face being the second, much less common site (14, 3.5%). Two hundred and sixty-nine required rehabilitation therapy (66.9%). The number of GFGF injuries reported was 20 times greater than the approximately 30 injuries estimated by the Consumer Product Safety Commission's 10-year review. For the affected children, these injuries are painful, often costly and occasionally can lead to long-term sequelae. Given that less than a quarter of burn centers contributed data, the injury numbers reported herein support a need for broader safety guidelines for gas fireplaces in order to have a significant impact on future injuries.

  14. Stick-slip behaviour of a viscoelastic flat sliding along a rigid indenter

    NARCIS (Netherlands)

    Budi Setiyana, Budi; Ismail, Rifky; Jamari, J.; Schipper, Dirk Jan

    2016-01-01

    The sliding contact of soft material surface due to a rigid indenter is different from metal and some other polymers. A stick-slip motion is more frequently obtained than a smooth motion. By modeling the soft material as low damping viscoelastic material, this study proposes an analytical model to

  15. Nitrate bioreduction in redox-variable low permeability sediments

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Sen [China University of Geosciences, Wuhan 430074 (China); Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Liu, Yuanyuan [Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Liu, Chongxuan, E-mail: chongxuan.liu@pnnl.gov [China University of Geosciences, Wuhan 430074 (China); Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Shi, Liang; Shang, Jianying [Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Shan, Huimei [China University of Geosciences, Wuhan 430074 (China); Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Zachara, John; Fredrickson, Jim; Kennedy, David; Resch, Charles T.; Thompson, Christopher; Fansler, Sarah [Pacific Northwest National Laboratory, Richland, WA 99354 (United States)

    2016-01-01

    Low permeability zone (LPZ) can play an important role as a sink or secondary source in contaminant transport in groundwater system. This study investigated the rate and end product of nitrate bioreduction in LPZ sediments. The sediments were from the U.S. Department of Energy's Hanford Site, where nitrate is a groundwater contaminant as a by-product of radionuclide waste discharges. The LPZ at the Hanford site consists of two layers with an oxidized layer on top and reduced layer below. The oxidized layer is directly in contact with the overlying contaminated aquifer, while the reduced layer is in contact with an uncontaminated aquifer below. The experimental results showed that nitrate bioreduction rate and end-product differed significantly in the sediments. The bioreduction rate in the oxidized sediment was significantly faster than that in the reduced one. A significant amount of N{sub 2}O was accumulated in the reduced sediment; while in the oxidized sediment, N{sub 2}O was further reduced to N{sub 2}. RT-PCR analysis revealed that nosZ, the gene that codes for N{sub 2}O reductase, was below detection limit in the reduced sediment. Batch experiments and kinetic modeling were performed to provide insights into the role of organic carbon bioavailability, biomass growth, and competition between nitrate and its reducing products for electrons from electron donors. The results revealed that it is important to consider sediment redox conditions and functional genes in understanding and modeling nitrate bioreduction in subsurface sediments. The results also implied that LPZ sediments can be important sink of nitrate and a potential secondary source of N{sub 2}O as a nitrate bioreduction product in groundwater. - Highlights: • Low permeability zones (LPZ) can microbially remove nitrate in groundwater. • The rate and end product of nitrate bioreduction vary within LPZ. • Greenhouse gas N{sub 2}O can be the end product of nitrate bioreduction in LPZ.

  16. A polygeneration from a dual-gas partial catalytic oxidation coupling with an oxygen-permeable membrane reactor

    International Nuclear Information System (INIS)

    Hao, Yanhong; Huang, Yi; Gong, Minhui; Li, Wenying; Feng, Jie; Yi, Qun

    2015-01-01

    Highlights: • A new polygeneration system (PL-PCO-OPMR) to DME/methanol/power is proposed. • Exergeo-economic analysis is adopted to disclose the performance of systems. • Key technological conditions and parameters for PL-PCO-OPMR are optimized. • PL-PCO-OPMR shows high energy efficiency and low CO_2 emission. • PL-PCO-OPMR is an attractive way for high efficient and clean use of COG and CGG. - Abstract: Polygeneration system, typically involving chemicals/fuels and electricity co-production, is a promising technology for the sustainable development of energy and environment. In this study, a new polygeneration system based on coal and coke oven gas (COG) inputs for co-production of dimethyl ether (DME)/methanol and electricity is proposed. In the new system, an appropriate syngas for the synthesis of DME is from coal gasified gas (CGG) reforming of COG coupled with an oxygen-permeable membrane reactor, in which both COG and CGG reforming process and fuel combustion process are incorporated, which reduces exergy destruction in the whole reforming process. In order to obtain the best performance of CO_2 reduction, energy saving and economic benefit, the key operation parameters of the proposed process are analyzed and optimized. The new system is compared with the process based on CH_4/CO_2 dry reforming, in terms of exergy efficiency, exergy cost and CO_2 emissions. Through the new system, the exergy efficiency can be increased by 7.8%, the exergy cost can be reduced by 0.88 USD/GJ and the CO_2 emission can be reduced by 0.023 kg/MJ. These results suggest that the polygeneration system from CGG and COG partial catalytic oxidation coupling with an oxygen-permeable membrane reactor (PL-PCO-OPMR) would be a more attractive way for highly efficient and clean use of CGG and COG.

  17. Pure- and mixed-gas propylene/propane permeation properties of spiro- and triptycene-based microporous polyimides

    KAUST Repository

    Swaidan, Ramy J.; Ghanem, Bader; Swaidan, Raja; Litwiller, Eric; Pinnau, Ingo

    2015-01-01

    Solution-processable polyimides of intrinsic microporosity (PIM-PIs) comprising relatively inflexible and contorted backbones have demonstrated outstanding molecular-sieving behavior in membrane-based separation of gas/gas pairs. In this work, the effects of systematically increasing intra-chain rigidity on the propylene/propane separation properties were compared for PIM-PIs made from 2,3,5,6-tetramethyl-1,4-phenylene diamine (TMPD) and (i) spiro-centered dianhyride (SPDA-TMPD or PIM-PI-1) and (ii) 9,10-diisopropyltriptycene-based dianhydride (TPDA-TMPD or KAUST PI-1). Pure-gas experiments at 2 bar and 35 oC showed significant increases in C3H6 permeability and C3H6/C3H8 selectivity by transitioning from PIM-PI-1 (P(C3H6)=393 Barrer, α(C3H6/C3H8)=6) to KAUST-PI-1 (P(C3H6)=817 Barrer, α(C3H6/C3H8)=16), positioning KAUST-PI-1 considerably above the experimentally observed pure-gas C3H6/C3H8 polymer upper bound. However, 50:50 C3H6/C3H8 mixed-gas feeds induced significant losses in C3H6 permeability and C3H6/C3H8 selectivity relative to the 2 bar pure-gas data for PIM-PI-1 and KAUST-PI-1 as the C3H6/C3H8 selectivity dropped from 6 to 3 and 16 to 5, respectively, at 2 bar C3H6 partial pressure due to plasticization and competitive sorption.

  18. Pure- and mixed-gas propylene/propane permeation properties of spiro- and triptycene-based microporous polyimides

    KAUST Repository

    Swaidan, Ramy Jawdat

    2015-06-03

    Solution-processable polyimides of intrinsic microporosity (PIM-PIs) comprising relatively inflexible and contorted backbones have demonstrated outstanding molecular-sieving behavior in membrane-based separation of gas/gas pairs. In this work, the effects of systematically increasing intra-chain rigidity on the propylene/propane separation properties were compared for PIM-PIs made from 2,3,5,6-tetramethyl-1,4-phenylene diamine (TMPD) and (i) spiro-centered dianhyride (SPDA-TMPD or PIM-PI-1) and (ii) 9,10-diisopropyltriptycene-based dianhydride (TPDA-TMPD or KAUST PI-1). Pure-gas experiments at 2 bar and 35 oC showed significant increases in C3H6 permeability and C3H6/C3H8 selectivity by transitioning from PIM-PI-1 (P(C3H6)=393 Barrer, α(C3H6/C3H8)=6) to KAUST-PI-1 (P(C3H6)=817 Barrer, α(C3H6/C3H8)=16), positioning KAUST-PI-1 considerably above the experimentally observed pure-gas C3H6/C3H8 polymer upper bound. However, 50:50 C3H6/C3H8 mixed-gas feeds induced significant losses in C3H6 permeability and C3H6/C3H8 selectivity relative to the 2 bar pure-gas data for PIM-PI-1 and KAUST-PI-1 as the C3H6/C3H8 selectivity dropped from 6 to 3 and 16 to 5, respectively, at 2 bar C3H6 partial pressure due to plasticization and competitive sorption.

  19. Permeability and long-term durability of concrete in final repository conditions

    International Nuclear Information System (INIS)

    Pihlajavaara, S.

    1990-02-01

    The interrelation of the permeability properties and longterm durability especially in wet repository conditions has been studied. The study is based on the author's long-term experience, literary survey and experiments on the durability, service life prediction, and on water and gas permeability. Degradation models and experimental results on water and gas permeability are presented. The experiments made indicated that high class concrete is practically water and gas tight, especially in the long run when stored under water. This meant that there will hardly be any mass transfer into concrete or out of it, if concrete is of good quality. Concrete structures can be designed to meet the required service life. It can be said that practically the precision increases and the scatter decreases in the service life estimation significantly when the thickness of the anticipated deteriorated surface layer is smaller due to the higher concrete quality. The service life of well-designed concrete silo walls made of high class concrete can be predicted to be at least 1000 years in the repository conditions. (orig.)

  20. Delayed astrocytic contact with cerebral blood vessels in FGF-2 deficient mice does not compromise permeability properties at the developing blood-brain barrier.

    Science.gov (United States)

    Saunders, Norman R; Dziegielewska, Katarzyna M; Unsicker, Klaus; Ek, C Joakim

    2016-11-01

    The brain functions within a specialized environment tightly controlled by brain barrier mechanisms. Understanding the regulation of barrier formation is important for understanding brain development and may also lead to finding new ways to deliver pharmacotherapies to the brain; access of many potentially promising drugs is severely hindered by these barrier mechanisms. The cellular composition of the neurovascular unit of the blood-brain barrier proper and their effects on regulation of its function are beginning to be understood. One hallmark of the neurovascular unit in the adult is the astroglial foot processes that tightly surround cerebral blood vessels. However their role in barrier formation is still unclear. In this study we examined barrier function in newborn, juvenile and adult mice lacking fibroblast growth factor-2 (FGF-2), which has been shown to result in altered astroglial differentiation during development. We show that during development of FGF-2 deficient mice the astroglial contacts with cerebral blood vessels are delayed compared with wild-type animals. However, this delay did not result in changes to the permeability properties of the blood brain barrier as assessed by exclusion of either small or larger sized molecules at this interface. In addition cerebral vessels were positive for tight-junction proteins and we observed no difference in the ultrastructure of the tight-junctions. The results indicate that the direct contact of astroglia processes to cerebral blood vessels is not necessary for either the formation of the tight-junctions or for basic permeability properties and function of the blood-brain barrier. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1201-1212, 2016. © 2016 Wiley Periodicals, Inc.

  1. Large deformation contact mechanics of a pressurized long rectangular membrane. II. Adhesive contact

    Science.gov (United States)

    Srivastava, Abhishek; Hui, Chung-Yuen

    2013-01-01

    In part I of this work, we presented a theory for adhesionless contact of a pressurized neo-Hookean plane-strain membrane to a rigid substrate. Here, we extend our theory to include adhesion using a fracture mechanics approach. This theory is used to study contact hysteresis commonly observed in experiments. Detailed analysis is carried out to highlight the differences between frictionless and no-slip contact. Membrane detachment is found to be strongly dependent on adhesion: for low adhesion, the membrane ‘pinches-off’, whereas for large adhesions, it detaches unstably at finite contact (‘pull-off’). Expressions are derived for the critical adhesion needed for pinch-off to pull-off transition. Above a threshold adhesion, the membrane exhibits bistability, two stable states at zero applied pressure. The condition for bistability for both frictionless and no-slip boundary conditions is obtained explicitly. PMID:24353472

  2. Evaluation of the effect of macerals on coal permeability in Tazareh and Parvadeh mines

    Directory of Open Access Journals (Sweden)

    Farhang Sereshki

    2016-08-01

    Full Text Available In recent decades, the subject of gas emission in underground coal mines in many countries is an important subject. Many factors affect in gas emissions in coal seams. Geological and physical structures of coal are affecting on gas emissions'. Also, composition and mineralization of coal, affect in coal permeability for different gases. In this study, the relationship between maceral composition and coal permeability in Tazareh and Parvadeh mines has been studied. Accordingly, a laboratory studies to investigate the relationship between coal composition and coal permeability was done. In coal samples, with MFORR equipment the permeability test was done. With microscopic analysis, the maceral contents of coal such as Inertinite and Vitrinite have been measured. Accordingly, many coal samples of Parvadeh and Tazareh coal mines have the pyrite as the dominant mineral matter. Parvadeh coal samples has the average percentage of Vitrinite equal 81.34% and 10.52% Inertinite. Also, in the Tazareh coal samples in Eastern Alborz coal mines, the average percentage of Vitrinite is 69.31% and inertinite is 22.47%. The average percentage of Pyrite content in Parvadeh coal samples in Tabas coal mines is 2.38% and in the Tazareh coal samples in Eastern Alborz coal mines is 2.62%.  The permeability test results have been shown, which, with increase of Inertinite contents, the permeability of coal is increasing. Also, test results have been shown, there was a reduction in the coal permeability with increasing of mineral contents and carbonate contents of the coal. So, the coal permeability in Tabas coal samples is more than Eastern Alborz coal samples.

  3. Student understanding of the application of Newton's second law to rotating rigid bodies

    Science.gov (United States)

    Close, Hunter G.; Gomez, Luanna S.; Heron, Paula R. L.

    2013-06-01

    We report on an investigation of student understanding of rigid body dynamics in which we asked students in introductory calculus-based physics to compare the translational motions of identical rigid bodies subject to forces that differed only in the point of contact at which they were applied. There was a widespread tendency to claim that forces that cause rotational motion have a diminished effect on translational motion. A series of related problems was developed to examine whether similar errors would be made in other contexts, and interviews were conducted to probe student thinking in greater depth. In this paper, we describe the results of our investigation and also describe a series of different interventions that culminated in the development of a tutorial that improves student ability to apply Newton's second law to rotating rigid bodies.

  4. Xenon NMR measurements of permeability and tortuosity in reservoir rocks.

    Science.gov (United States)

    Wang, Ruopeng; Pavlin, Tina; Rosen, Matthew Scott; Mair, Ross William; Cory, David G; Walsworth, Ronald Lee

    2005-02-01

    In this work we present measurements of permeability, effective porosity and tortuosity on a variety of rock samples using NMR/MRI of thermal and laser-polarized gas. Permeability and effective porosity are measured simultaneously using MRI to monitor the inflow of laser-polarized xenon into the rock core. Tortuosity is determined from measurements of the time-dependent diffusion coefficient using thermal xenon in sealed samples. The initial results from a limited number of rocks indicate inverse correlations between tortuosity and both effective porosity and permeability. Further studies to widen the number of types of rocks studied may eventually aid in explaining the poorly understood connection between permeability and tortuosity of rock cores.

  5. Immunoglobulin Concentration in Tears of Contact Lens Wearers

    Science.gov (United States)

    Maurya, Rajendra P.; Bhushan, Prashant; Singh, Virendra P.; Singh, Mahendra K.; Kumar, Prakash; Bhatia, Ravindra P.S.; Singh, Usha

    2014-01-01

    Purpose: To evaluate changes in the concentration of tear immunoglobulins in contact lens wearers. Methods: A total of 45 cases including 23 contact lens wearers (43 eyes) and 22 age and sex matched healthy controls having no ocular pathology were studied for immunoglobulins (IgA, IgG, IgM) in their tears by single radial immunodiffusion method. Results: Most of the cases used soft (56.6%) and semi-soft gas permeable (30.4%) contact lenses. Tear IgM was detected in only 17.4% and tear IgG in 43.6% of contact lens wearers, while in controls IgG was detected in 9.1% but none of the controls had IgM. There was a significant rise in total tear IgA (13.17 ± 4.44 mg/dl) in contact lens wearer as compared to controls (8.93 ± 3.79 mg/dl). Rise of tear IgA was more in symptomatic patients (15.38 ± 5.28 mg/dl) and in those wearing hard (19.73 ± 5.43 mg/dl) and semi-soft contact lenses (13.31 ± 5.43 mg/dl). A significant increase in tear IgA was noticed in subjects wearing lenses for >3 years (15.69 ± 5.39 mg/dl). About 43.4% of lens wearers were symptomatic and 80% of their lenses showed deposits and/or haziness. All cases with IgM in tear were symptomatic. Conclusion: The relation of immunoglobulin concentration with increasing duration of wear and material of contact lens shows that tear immunoglobulin rise accrues due to mechanical stimulation, hence contact lenses should not be used for a long period and lenses of hard nature should be discouraged. The maintenance, cleaning and deproteinization of the lenses are of high importance to avoid immunostimulation. PMID:25667732

  6. Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation

    Science.gov (United States)

    Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.

    2012-01-01

    Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.

  7. Modification of Hertzian behaviour in heavily loaded contact in the DMT regime

    International Nuclear Information System (INIS)

    Wu, J-J

    2008-01-01

    The adhesive contact between spheres for a small Tabor parameter is investigated. It is found that the DMT model cannot describe the adhesive contact for a small Tabor parameter. By assuming a new contact distance, the modified Hertzian contact is proposed. For a small Tabor parameter, the rigid-sphere model can describe the adhesive contact behaviour for a small load and the modified Hertzian model can describe the adhesive contact behaviour for a large load

  8. Understanding geological processes: Visualization of rigid and non-rigid transformations

    Science.gov (United States)

    Shipley, T. F.; Atit, K.; Manduca, C. A.; Ormand, C. J.; Resnick, I.; Tikoff, B.

    2012-12-01

    Visualizations are used in the geological sciences to support reasoning about structures and events. Research in cognitive sciences offers insights into the range of skills of different users, and ultimately how visualizations might support different users. To understand the range of skills needed to reason about earth processes we have developed a program of research that is grounded in the geosciences' careful description of the spatial and spatiotemporal patterns associated with earth processes. In particular, we are pursuing a research program that identifies specific spatial skills and investigates whether and how they are related to each other. For this study, we focus on a specific question: Is there an important distinction in the geosciences between rigid and non-rigid deformation? To study a general spatial thinking skill we employed displays with non-geological objects that had been altered by rigid change (rotation), and two types of non-rigid change ("brittle" (or discontinuous) and "ductile" (or continuous) deformation). Disciplinary scientists (geosciences and chemistry faculty), and novices (non-science faculty and undergraduate psychology students) answered questions that required them to visualize the appearance of the object before the change. In one study, geologists and chemists were found to be superior to non-science faculty in reasoning about rigid rotations (e.g., what an object would look like from a different perspective). Geologists were superior to chemists in reasoning about brittle deformations (e.g., what an object looked like before it was broken - here the object was a word cut into many fragments displaced in different directions). This finding is consistent with two hypotheses: 1) Experts are good at visualizing the types of changes required for their domain; and 2) Visualization of rigid and non-rigid changes are not the same skill. An additional important finding is that there was a broad range of skill in both rigid and non-rigid

  9. Effect of desensitizing agents on dentin permeability.

    Science.gov (United States)

    Ishihata, Hiroshi; Kanehira, Masafumi; Nagai, Tomoko; Finger, Werner J; Shimauchi, Hidetoshi; Komatsu, Masashi

    2009-06-01

    To investigate the in vitro efficacy of two dentin desensitizing products at reducing liquid permeability through human dentin discs. The tested hypothesis was that the products, in spite of different chemical mechanisms were not different at reducing or eliminating flow through dentin discs. Dentin slices (1 mm thick) were prepared from 16 extracted human third molars and their permeability was indirectly recorded in a split chamber model, using a chemiluminescence technique, after EDTA treatment (control), after soaking with albumin, and after desensitizer application. Two products were studied: MS Coat, a self-curing resin-containing oxalate product, and Gluma Desensitizer, a glutaraldehyde/HEMA-based agent without initiator. The dentin slices were mounted between an upper chamber, filled with an aqueous solution of 1% potassium ferricyanide and 0.3% hydrogen peroxide, and a lower chamber filled with 1% sodium hydroxide solution and 0.02% luminol. The upper solution was pressurized, and upon contact with the luminol solution a photochemical signal was generated and recorded as a measure of permeability throughout two consecutive pressurizing cycles at 2.5 and 13 kPa (26 and 133 cm H2O), respectively. The permeability of the control and albumin-soaked samples was similarly high. After application of the desensitizing agents, dentin permeability was reduced to virtually zero at both pressure levels (P < 0.001).

  10. Influence of gas hydrates crystals or ice crystals on the permeability of a porous medium; Influence de cristaux d'hydrates de gaz ou de glace sur la permeabilite d'un milieu poreux

    Energy Technology Data Exchange (ETDEWEB)

    Bonnefoy, O

    2005-03-15

    The first part is a bibliographic study. We study the conditions for thermodynamic equilibrium of the hydrates as a bulk medium and the composition of the liquid and solid phases. We then describe the basics of fluid dynamics in a porous medium. Eventually, we merge the two approaches and study the influence of the porous medium on the hydrate stability. An off-shore hydrate field (Blake Ridge) and an on-shore field (Mallik) are precisely described. The latter will be used as a reference case for subsequent numerical simulations. The second part is devoted to the experiments. Their goal is to measure the permeability of a sediment containing crystals. To get closer to natural geologic conditions, crystals are synthesized in absence of free gas. It turns out that hydrates form in a very heterogeneous way in the porous medium, which makes the measurements non representative. We believe that this result has a general character and that, at the laboratory time-scale, it is difficult, to say the least to achieve a uniform distribution of gas hydrates grown from dissolved gas. To circumvent this difficulty, we show, with a theoretical approach, that ice crystals behave much the same way as the hydrate crystals, concerning the Van der Waals forces that govern the agglomeration. This allows us to calculate the Hamaker constant of the hydrates. The second series of experiments focuses on the permeability of a non consolidated porous medium under mechanical stress, where the pores are filled with ice crystals. Two silica beads populations are used to form a porous medium: 3 mm and 0.2 mm. With the large grains, results show two thresholds: for saturations below the lower threshold, the presence of crystals does not modify the permeability. For saturations above the upper threshold, the permeability vanishes almost completely (percolation phenomenon). Between these two limits, the permeability decreases exponentially with the saturation. With the fine grains, the permeability

  11. Mapping of 222Rn and 4He in soil gas over a karstic limestone-granite boundary: correlation of high indoor 222Rn with zones of enhanced permeability

    International Nuclear Information System (INIS)

    O'Connor, P.J.; Gallagher, V.; Van den Boom, G.

    1992-01-01

    Recent indoor radon reconnaissance surveys in Ireland have identified buildings with high radon concentrations (up to 1700 Bq.m -3 ) overlying Carboniferous karstic limestone sequences in the western part of the country. A detailed investigation of indoor 222 Rn and soil gas 222 Rn and 4 He concentrations has been carried out over a karstic limestone-uraniferous granite boundary in County Galway. High indoor 222 Rn concentrations occur in dwellings over both lithologies. Radon migratory routes in bedrock and overburden appear to be controlled by zones of enhanced permeability, e.g. fractures, faults, etc. which are defined by linear arrays of elevated 4 He soil gas values. While the ultimate source of radon remains conjectural, the greatly enhanced permeability of karstified limestone is thought to be of fundamental importance in providing a means of rapid radon transport into overlying soils and buildings. (author)

  12. Permeability of protective coatings to tritium

    International Nuclear Information System (INIS)

    Braun, J.M.

    1987-10-01

    The permeability of four protective coatings to tritium gas and tritiated water was investigated. The coatings, including two epoxies, one vinyl and one urethane, were selected for their suitability in CANDU plant service in Ontario Hydro. Sorption rates of tritium gas into the coatings were considerably larger than for tritiated water, by as much as three to four orders of magnitude. However, as a result of the very large solubility of tritiated water in the coatings, the overall permeability to tritium gas and tritiated water are comparable, being somewhat larger for HTO. Marked differences were also evident among the four coatings, the vinyl proving to be unique in behaviour and morphology. Because of a highly porous surface structure water condensation takes place at high relative humidities, leading to an abnormally high retention of free water. Desorption rates from the four coatings were otherwise quite similar. Of practical importance was the observation that more effective desorption of tritiated water could be carried out at relatively high humidities, in this case 60%. It was believed that isotopic exchange was responsible for this phenomenon. It appears that epoxy coatings having a high pigment-to-binder ratio are most suited for coating concrete in tritium handling facilities

  13. Learning to push and learning to move: The adaptive control of contact forces

    Directory of Open Access Journals (Sweden)

    Maura eCasadio

    2015-11-01

    Full Text Available To be successful at manipulating objects one needs to apply simultaneously well controlled movements and contact forces. We present a computational theory of how the brain may successfully generate a vast spectrum of interactive behaviors by combining two independent processes. One process is competent to control movements in free space and the other is competent to control contact forces against rigid constraints. Free space and rigid constraints are singularities at the boundaries of a continuum of mechanical impedance. Within this continuum, forces and motions occur in compatible pairs connected by the equations of Newtonian dynamics. The force applied to an object determines its motion. Conversely, inverse dynamics determine a unique force trajectory from a movement trajectory. In this perspective, we describe motor learning as a process leading to the discovery of compatible force/motion pairs. The learned compatible pairs constitute a local representation of the environment's mechanics. Experiments on force field adaptation have already provided us with evidence that the brain is able to predict and compensate the forces encountered when one is attempting to generate a motion. Here, we tested the theory in the dual case, i.e. when one attempts at applying a desired contact force against a simulated rigid surface. If the surface becomes unexpectedly compliant, the contact point moves as a function of the applied force and this causes the applied force to deviate from its desired value. We found that, through repeated attempts at generating the desired contact force, subjects discovered the unique compatible hand motion. When, after learning, the rigid contact was unexpectedly restored, subjects displayed after effects of learning, consistent with the concurrent operation of a motion control system and a force control system. Together, theory and experiment support a new and broader view of modularity in the coordinated control of forces and

  14. Lente de contato de material híbrido em pacientes com ceratocone e astigmatismo miópico composto Hybrid material contact lens in keratoconus and myopic astigmatism patients

    Directory of Open Access Journals (Sweden)

    Fernando Leal

    2007-03-01

    óculos, exceto para a freqüência B (3 cpg, maior nos usuários de óculos. As aberrações de alta ordem analisadas apresentaram diminuição estatisticamente significante, quando comparados os pacientes sem e com uso de lentes de contato, com exceção da aberração esférica e do coma. CONCLUSÃO: A lente de contato de material híbrido, quando utilizada por portadores de ceratocone e astigmatismo miópico composto, propiciaram desempenho visual e conforto satisfatórios, em níveis que não diferiram, das lentes de contato rígidas-gás-permeáveis nos dois grupos de pacientes.PURPOSE: To evaluate comfort and visual performance in relation to two different used contact lens types: hybrid material (HM and rigid-gas-permeable (RGP, in patients with regular myopic astigmatism and with keratoconus. METHODS: A randomized, double masked, prospective study of 22 patients with the diagnosis of myopic astigmatism (8 with myopic astigmatism and 14 with keratoconus was conducted. Fifteen patients were female and 7 were male, and mean age was: 32.13 ± 8.12 years. In one of the eyes a rigid-gas-permeable contact lens was adapted (DK 30, and in the other a hybrid material contact lens was adapted (DK 23. All patients were submitted to the following tests: measurement of comfort level by means of the analogical visual scale, tear break-up time, best corrected visual acuity with the Bailey-Lovie scale adapted for 4 meters, functional acuity contrast test (FACT and wavefront analysis. RESULTS: In relation to comfort, there was no association with the evaluated contact lens type (p=0.350. There was a variation in comfort level during the first 7 days. The visual acuity increased between the 7th and the 15th day of adaptation. Visual acuity stabilized right after this period. The visual acuity did not show differences in relation to the studied lens type. It was verified that there was no difference in the tear break-up time (p=0.989 in relation to the studied lenses type and

  15. Bifunctionalized Intrinsically Microporous Polyimides with Simultaneously Enhanced Gas Permeability and Selectivity

    KAUST Repository

    Ma, Xiaohua; Mukaddam, Mohsin Ahmed; Pinnau, Ingo

    2016-01-01

    Two novel intrinsically microporous copolyimides synthesized by condensation reaction of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3,3′,3′-tetramethyl-1,1′-spirobisindane-5,5′-diamino-6,6′-diol, and 3,5-diaminobenzoic acid with diamine ratios of 80/20 (Co-80/20) and 50/50 (Co-50/50) are reported. Unexpectedly, the Co-80/20 not only demonstrates higher microporosity (300 m2 g−1) than the PIM-6FDA-OH homopolymer (190 m2 g−1) but also exhibits simultaneously enhanced CO2 permeability (from 119 to 171 Barrer) and CO2/CH4 selectivity (from 35 to 41) after thermal annealing at 250 °C. This higher permeability originates from enhanced diffusivity (D CO2) and the higher selectivity results from its increased diffusion selectivity (D CO2/D CH4). After crosslinking at 300 °C, the Co-80/20 exhibits an even higher CO2 permeability (261 Barrer) and almost unchanged CO2/CH4 selectivity.

  16. Bifunctionalized Intrinsically Microporous Polyimides with Simultaneously Enhanced Gas Permeability and Selectivity

    KAUST Repository

    Ma, Xiaohua

    2016-03-29

    Two novel intrinsically microporous copolyimides synthesized by condensation reaction of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3,3′,3′-tetramethyl-1,1′-spirobisindane-5,5′-diamino-6,6′-diol, and 3,5-diaminobenzoic acid with diamine ratios of 80/20 (Co-80/20) and 50/50 (Co-50/50) are reported. Unexpectedly, the Co-80/20 not only demonstrates higher microporosity (300 m2 g−1) than the PIM-6FDA-OH homopolymer (190 m2 g−1) but also exhibits simultaneously enhanced CO2 permeability (from 119 to 171 Barrer) and CO2/CH4 selectivity (from 35 to 41) after thermal annealing at 250 °C. This higher permeability originates from enhanced diffusivity (D CO2) and the higher selectivity results from its increased diffusion selectivity (D CO2/D CH4). After crosslinking at 300 °C, the Co-80/20 exhibits an even higher CO2 permeability (261 Barrer) and almost unchanged CO2/CH4 selectivity.

  17. Rigid multibody system dynamics with uncertain rigid bodies

    Energy Technology Data Exchange (ETDEWEB)

    Batou, A., E-mail: anas.batou@univ-paris-est.fr; Soize, C., E-mail: christian.soize@univ-paris-est.fr [Universite Paris-Est, Laboratoire Modelisation et Simulation Multi Echelle, MSME UMR 8208 CNRS (France)

    2012-03-15

    This paper is devoted to the construction of a probabilistic model of uncertain rigid bodies for multibody system dynamics. We first construct a stochastic model of an uncertain rigid body by replacing the mass, the center of mass, and the tensor of inertia by random variables. The prior probability distributions of the stochastic model are constructed using the maximum entropy principle under the constraints defined by the available information. The generators of independent realizations corresponding to the prior probability distribution of these random quantities are further developed. Then several uncertain rigid bodies can be linked to each other in order to calculate the random response of a multibody dynamical system. An application is proposed to illustrate the theoretical development.

  18. Process for hydrogen isotope exchange and concentration between liquid water and hydrogen gas and catalyst assembly therefor

    International Nuclear Information System (INIS)

    Stevens, W.H.

    1975-01-01

    A bithermal, catalytic, hydrogen isotope exchange process between liquid water and hydrogen gas to effect concentration of the deuterium isotope of hydrogen is described. Liquid water and hydrogen gas are contacted with one another and with at least one catalytically active metal selected from Group VIII of the Periodic Table; the catalyst body has a water repellent, gas and water vapor permeable, organic polymer or resin coating, preferably a fluorinated olefin polymer or silicone resin coating, so that the isotope exchange takes place by two simultaneously occurring, and closely coupled in space, steps and concentration is effected by operating two interconnected sections containing catalyst at different temperatures. (U.S.)

  19. Gas and water permeability of concrete for reactor buildings--prototype scale specimens

    International Nuclear Information System (INIS)

    Mills, R.H.

    1987-02-01

    The permeability testing was performed on four concrete cylinders, 0.25 m in diameter and 2 m long, modelling the wall-thickness of reactor containment structures on the prototype scale. Tests were performed on the cylinders before and after artificial induction of longitudinal cracks, intented to model defects developing after some period of adverse service conditions. Permeability increased greatly with the introduction of longitudinal cracks in the concrete, and was also affected by moisture content and casting direction. The influence of reinforcing steel could not be resolved within the bounds of experimental variability. Ultrasound measurements were taken on each cylinder before and after cracking, and a correlation between increased permeability and lowered Ultrasonic Pulse Velocity was observed. Ultrasonic Pulse Velocity measurements thus show promise as a means of continuous monitoring of the integrity of the concrete barrier in service

  20. Recovery of ammonia from anaerobically digested manure using gas-permeable membranes

    Directory of Open Access Journals (Sweden)

    Maria Cruz García-González

    Full Text Available ABSTRACT Nitrogen (N can be recovered from different types of wastewaters. Among these wastewaters, anaerobically digested swine manure (digestate has the highest N content in ammonia form (NH3. It is desirable to reduce N in digestate effluents to safely incorporate them in arable soil in N vulnerable zones (NVZ and to mitigate NH3 emissions during N land application. Additional benefit is to minimize inhibition of the anaerobic process by removing NH3 during the anaerobic digestion process. This work aimed to apply the gas-permeable membrane technology to evaluate ammonia (NH3 recovery from high-ammonia digested swine manure. Anaerobically digested swine manure with NH4+ content of 4,293 mg N L−1 was reduced by 91 % (to 381 mg N L−1 during the 32-day experiment. Although the results showed a total N recovery efficiency of 71 %, it is possible to increase this recovery efficiency to > 90 % by adjusting the area of the membrane system to match the high free ammonia concentration (FA in digested swine manure. Moreover, final digestate pH and alkalinity were kept around 8.1 and 8,923 mgCaCO3 L−1, which are convenient for the anaerobic process or incorporation in arable soil when the process is finished.

  1. Numerical analysis of the non-contacting gas face seals

    Science.gov (United States)

    Blasiak, S.

    2017-08-01

    The non-contacting gas face seals are used in high-performance devices where the main requirements are safety and reliability. Compliance with these requirements is made possible by careful research and analysis of physical processes related to, inter alia, fluid flow through the radial gap and ring oscillations susceptible to being housed in the enclosure under the influence of rotor kinematic forces. Elaborating and developing mathematical models describing these phenomena allows for more and more accurate analysis results. The paper presents results of studies on stationary ring oscillations made of different types of materials. The presented results of the research allow to determine which of the materials used causes the greatest amplitude of the vibration of the system fluid film-working rings.

  2. Contact kinematics of biomimetic scales

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Ranajay; Ebrahimi, Hamid; Vaziri, Ashkan, E-mail: vaziri@coe.neu.edu [Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115 (United States)

    2014-12-08

    Dermal scales, prevalent across biological groups, considerably boost survival by providing multifunctional advantages. Here, we investigate the nonlinear mechanical effects of biomimetic scale like attachments on the behavior of an elastic substrate brought about by the contact interaction of scales in pure bending using qualitative experiments, analytical models, and detailed finite element (FE) analysis. Our results reveal the existence of three distinct kinematic phases of operation spanning linear, nonlinear, and rigid behavior driven by kinematic interactions of scales. The response of the modified elastic beam strongly depends on the size and spatial overlap of rigid scales. The nonlinearity is perceptible even in relatively small strain regime and without invoking material level complexities of either the scales or the substrate.

  3. Effect of Matrix-Wellbore Flow and Porosity on Pressure Transient Response in Shale Formation Modeling by Dual Porosity and Dual Permeability System

    Directory of Open Access Journals (Sweden)

    Daolun Li

    2015-01-01

    Full Text Available A mathematical dual porosity and dual permeability numerical model based on perpendicular bisection (PEBI grid is developed to describe gas flow behaviors in shale-gas reservoirs by incorporating slippage corrected permeability and adsorbed gas effect. Parametric studies are conducted for a horizontal well with multiple infinite conductivity hydraulic fractures in shale-gas reservoir to investigate effect of matrix-wellbore flow, natural fracture porosity, and matrix porosity. We find that the ratio of fracture permeability to matrix permeability approximately decides the bottom hole pressure (BHP error caused by omitting the flow between matrix and wellbore and that the effect of matrix porosity on BHP is related to adsorption gas content. When adsorbed gas accounts for large proportion of the total gas storage in shale formation, matrix porosity only has a very small effect on BHP. Otherwise, it has obvious influence. This paper can help us understand the complex pressure transient response due to existence of the adsorbed gas and help petroleum engineers to interpret the field data better.

  4. Effect of a mechanical damage on permeability and moisture diffusivity of concrete

    International Nuclear Information System (INIS)

    Picandet, V.

    2001-12-01

    The effect of a mechanical damage on transfer parameters of concrete is an original point of view on the coupling between damage and durability. The studied transfer parameters, permeability and moisture diffusivity, allow to characterize the transport ability of a porous media to convey gases or water (liquid and vapour). The theoretical framework of the measurement of these parameters and its applications to concrete is pointed out. The experimental studies are carried on three types of concrete: ordinary concrete, high performance concrete, and high performance steel fiber reinforced concrete. Two kinds of damage are considered and generated in samples: - A continuous damage of the medium, obtained by cyclic uniaxial loading. It is characterized by a loss of stiffness and results in a diffuse microcracking.- A discrete or localised damage, obtained by a diametrical compression of cylindrical specimens. It is characterized by the presence of identifiable and measurable cracks. Measurements of gas permeability are taken using a constant head, Cembureau type, permeameter. For cracked samples, the procedure and analysis of the results are changed in order to make the evaluation of their gas and water permeability. The simple imbibition and positive head imbibition are the disturbances of the moisture equilibrium, which allow the evaluation of the material diffusivity. The local moisture contents of the specimen are measured using a gamma-ray attenuation method. The analysis of profiles using Boltzmann's transformation leads to the moisture diffusivity and then to the water permeability coefficients. Measurements of gas and water permeability are compared in both cases of considered damage. In the first case, a damage - permeability relationship dependent on the fluid of percolation but valid for all concrete types studied could be worked out. (author)

  5. ANALYSIS OF A RIGID WALL IN AN ELASTIC WEIGHTY HALF-PLANE

    Directory of Open Access Journals (Sweden)

    K. V. Dmitrieva

    2016-01-01

    Full Text Available The analysis of stress-strain state of a rigid wall in an elastic weighty half-plane with a broken outline is carried out. To this end, the auxiliary problem of displacements definition in an elastic weighty quarter-plane was solved. Ritz method derived a formula to determine the displacements of elastic flat wedge boundaries in view of its own weight. On the basis of the received expressions the algorithm of displacements definition of a crack in an elastic weighty half-plane with a broken outline is developed. Analytical calculation of a rigid vertical wall located in an elastic weighty half-plane under the influence of a horizontal load, carried out by two methods: by Zhemochkin's method and finite difference method. In the problem statement an elastic half-plane is considered a model of the soil medium, therefore, only compressive normal stresses can arise on the connection of the wall with the elastic base. This assumption implies occurrence of discontinuities soil medium, and leads for the wall to an emergence of two dividing points of boundary conditions. The determination of the boundaries contact of the wall with the elastic half-plane, are not known in advance, is performed by iteratively way at each step set the position of dividing points of boundary conditions and the system of canonical equations of a corresponding method is written.  If tensile stresses appear in wall-base contact and/or there is overlap of the crack edges occurs, then proceeds to the next iteration. Analysis of the results shows that the bending moment and shear forces in sections of the rigid wall in a broken weighty half-plane differ slightly from the same diagrams constructed for a rigid wall in an elastic weightless half-plane. The verification of the results of analytical calculation with the results received by using the LIRA 9.6 that implements the finite element method is obtained. The calculation results for the rigid wall in an elastic weighty half

  6. Pressure effects on interfacial surface contacts and performance of organic solar cells

    NARCIS (Netherlands)

    Agyei-Tuffour, B.; Doumon, Nutifafa Y.; Rwenyagila, E. R.; Asare, J.; Oyewole, O. K.; Shen, Z.; Petoukhoff, C. E.; Zebaze Kana, M. G.; Ocarroll, D. M.; Soboyejo, W. O.

    2017-01-01

    This paper explores the effects of pressure on the interfacial surface contacts and the performance of organic solar cells. A combination of experimental techniques and analytical/computational models is used to study the evolving surface contacts profiles that occur when compliant, semi-rigid and

  7. Jammed packings of deformable and rigid 2D spherocylinders and spheropolygons

    Science.gov (United States)

    Shattuck, Mark

    We study mechanically stable packings of deformable and rigid 2D spheropolygons using computer simulation. A 2D sphereopolygon is a particle shape formed by the collection of all points within a perpendicular distance r from the edge of a polygon. It is a generalization of the 2D spherocylinder and a circle, which are the collection of all points within a distance r from a line and a point. In our model, the spheropolygon can be deformable. The lengths of the sides are fixed, but the angles are only constrained by the requirement that the shape factor, S = 4 πA /p2 is fixed, where A is the area of the polygon and p is the perimeter. The particles can be made rigid by requiring that the shape factor is the maximum possible for the edge length ratios. For example, the maximum for a square is S = π /4. We present densities and average contact numbers for collections of mono- and bi-disperse packings of spheropolygons for a range of shape factors, edge numbers, and system sizes. We find mechically stable packings with fewer than isostatic contacts.

  8. Temperature and coupling dependence of the universal contact intensity for an ultracold Fermi gas

    International Nuclear Information System (INIS)

    Palestini, F.; Perali, A.; Pieri, P.; Strinati, G. C.

    2010-01-01

    Physical properties of an ultracold Fermi gas in the temperature-coupling phase diagram can be characterized by the contact intensity C, which enters the pair-correlation function at short distances and describes how the two-body problem merges into its surrounding. We show that the local order established by pairing fluctuations about the critical temperature T c of the superfluid transition considerably enhances the contact C in a temperature range where pseudogap phenomena are maximal. Our ab initio results for C in a trap compare well with recently available experimental data over a wide coupling range. An analysis is also provided for the effects of trap averaging on C.

  9. Oxygen transport through soft contact lens and cornea: Lens characterization and metabolic modeling

    Science.gov (United States)

    Chhabra, Mahendra

    The human cornea requires oxygen to sustain metabolic processes critical for its normal functioning. Any restriction to corneal oxygen supply from the external environment (e.g., by wearing a low oxygen-permeability contact lens) can lead to hypoxia, which may cause corneal edema (swelling), limbal hyperemia, neovascularization, and corneal acidosis. The need for adequate oxygen to the cornea is a major driving force for research and development of hypertransmissible soft contact lenses (SCLs). Currently, there is no standard technique for measuring oxygen permeability (Dk) of hypertransmissible silicone-hydrogel SCLs. In this work, an electrochemistry-based polarographic apparatus was designed, built, and operated to measure oxygen permeability in hypertransmissible SCLs. Unlike conventional methods where a range of lens thickness is needed for determining oxygen permeabilities of SCLs, this apparatus requires only a single lens thickness. The single-lens permeameter provides a reliable, efficient, and economic tool for measuring oxygen permeabilities of commercial hypertransmissible SCLs. The single-lens permeameter measures not only the product Dk, but, following modification, it measures separately diffusivity, D, and solubility, k, of oxygen in hypertransmissible SCLs. These properties are critical for designing better lens materials that ensure sufficient oxygen supply to the cornea. Metabolism of oxygen in the cornea is influenced by contact-lens-induced hypoxia, diseases such as diabetes, surgery, and drug treatment, Thus, estimation of the in-vivo corneal oxygen consumption rate is essential for gauging adequate oxygen supply to the cornea. Therefore, we have developed an unsteady-state reactive-diffusion model for the cornea-contact-lens system to determine in-vivo human corneal oxygen-consumption rate. Finally, a metabolic model was developed to determine the relation between contact-lens oxygen transmissibility (Dk/L) and corneal oxygen deficiency. A

  10. Influence of gas hydrates crystals or ice crystals on the permeability of a porous medium; Influence de cristaux d'hydrates de gaz ou de glace sur la permeabilite d'un milieu poreux

    Energy Technology Data Exchange (ETDEWEB)

    Bonnefoy, O.

    2005-03-15

    The first part is a bibliographic study. We study the conditions for thermodynamic equilibrium of the hydrates as a bulk medium and the composition of the liquid and solid phases. We then describe the basics of fluid dynamics in a porous medium. Eventually, we merge the two approaches and study the influence of the porous medium on the hydrate stability. An off-shore hydrate field (Blake Ridge) and an on-shore field (Mallik) are precisely described. The latter will be used as a reference case for subsequent numerical simulations. The second part is devoted to the experiments. Their goal is to measure the permeability of a sediment containing crystals. To get closer to natural geologic conditions, crystals are synthesized in absence of free gas. It turns out that hydrates form in a very heterogeneous way in the porous medium, which makes the measurements non representative. We believe that this result has a general character and that, at the laboratory time-scale, it is difficult, to say the least to achieve a uniform distribution of gas hydrates grown from dissolved gas. To circumvent this difficulty, we show, with a theoretical approach, that ice crystals behave much the same way as the hydrate crystals, concerning the Van der Waals forces that govern the agglomeration. This allows us to calculate the Hamaker constant of the hydrates. The second series of experiments focuses on the permeability of a non consolidated porous medium under mechanical stress, where the pores are filled with ice crystals. Two silica beads populations are used to form a porous medium: 3 mm and 0.2 mm. With the large grains, results show two thresholds: for saturations below the lower threshold, the presence of crystals does not modify the permeability. For saturations above the upper threshold, the permeability vanishes almost completely (percolation phenomenon). Between these two limits, the permeability decreases exponentially with the saturation. With the fine grains, the permeability

  11. Plasticity of skin water permeability and skin thickness in the amphibious mangrove rivulus Kryptolebias marmoratus.

    Science.gov (United States)

    Heffell, Quentin; Turko, Andy J; Wright, Patricia A

    2018-03-01

    The skin of amphibious fishes is a multipurpose organ, important for gas and ion exchange and nitrogen excretion when fish are out of water (emersed). We tested the hypothesis that skin permeability is altered to maintain water balance through changes in water permeability and skin thickness during salinity acclimation and/or when fish emerse, using the euryhaline, amphibious fish Kryptolebias marmoratus as a model. We first recorded the behaviour of fish out of water to determine which part of the cutaneous surface was in contact with the substrate. Fish spent about 70% of their time on their ventral surface when out of water. Osmotic permeability of the skin was assessed in fish acclimated to 0.3 or 45‰ using 3 H 2 O fluxes in an in vitro micro-Ussing chamber setup. In freshwater-acclimated fish, 3 H 2 O influx across the skin was significantly higher compared to hypersaline-acclimated fish, with no significant changes in efflux. Prolonged emersion (7 days) resulted in an increase in skin 3 H 2 O influx, but not efflux in fish acclimated to a moist 45‰ substrate. In a separate experiment, dorsal epidermal skin thickness increased while the ventral dermis thickness decreased in fish emersed for over a week. However, there was no link between regional skin thickness and water flux in our experiments. Taken together, these findings suggest that K. marmoratus alter skin permeability to maximize water uptake while emersed in hypersaline conditions, adjustments that probably help them survive months of emersion during the dry season when drinking to replace water loss is not possible.

  12. Using dissolved gas analysis to investigate the performance of an organic carbon permeable reactive barrier for the treatment of mine drainage

    Science.gov (United States)

    Williams, R.L.; Mayer, K.U.; Amos, R.T.; Blowes, D.W.; Ptacek, C.J.; Bain, J.G.

    2007-01-01

    The strongly reducing nature of permeable reactive barrier (PRB) treatment materials can lead to gas production, potentially resulting in the formation of gas bubbles and ebullition. Degassing in organic C based PRB systems due to the production of gases (primarily CO2 and CH4) is investigated using the depletion of naturally occurring non-reactive gases Ar and N2, to identify, confirm, and quantify chemical and physical processes. Sampling and analysis of dissolved gases were performed at the Nickel Rim Mine Organic Carbon PRB, which was designed for the treatment of groundwater contaminated by low quality mine drainage characterized by slightly acidic pH, and elevated Fe(II) and SO4 concentrations. A simple 4-gas degassing model was used to analyze the dissolved gas data, and the results indicate that SO4 reduction is by far the dominant process of organic C consumption within the barrier. The data provided additional information to delineate rates of microbially mediated SO4 reduction and confirm the presence of slow and fast flow zones within the barrier. Degassing was incorporated into multicomponent reactive transport simulations for the barrier and the simulations were successful in reproducing observed dissolved gas trends.

  13. Development of gas-solid direct contact heat exchanger by use of axial flow cyclone

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Akihiko; Yokomine, Takehiko [Kyushu University (Japan). Interdisciplinary Graduate School of Engineering Sciences; Nagafuchi, Tatsuro [Miura Co. Ltd., Matsuyamashi (Japan)

    2004-10-01

    A heat exchanger between particulate or granular materials and gas is developed. It makes use of a swirling gas flow similar to the usual cyclone separators but the difference from them is that the swirl making gas is issued into the cyclone chamber with downward axial velocity component. After it turns the flow direction near the bottom of the chamber, the low temperature gas receives heat from high temperature particles supplied from above at the chamber's center. Through this configuration, a direct contact and quasi counter-flow heat exchange pattern is realized so that the effective recovery of heat carried by particles is achieved. A model heat exchanger was manufactured via several numerical experiments and its performances of heat exchange as well as particle recovery were examined. Attaching a small particle diffuser below the particle-feeding nozzle brought about a drastic improvement of the heat exchange performance without deteriorating the particle recovery efficiency. The outlet gas temperature much higher than the particle outlet temperature was finally obtained, which is never realized in the parallel flow heat exchanger. (author)

  14. Rigid supersymmetry on 5-dimensional Riemannian manifolds and contact geometry

    International Nuclear Information System (INIS)

    Pan, Yiwen

    2014-01-01

    In this note we generalize the methods of http://dx.doi.org/10.1007/JHEP08(2012)141, http://dx.doi.org/10.1007/JHEP01(2013)072 and http://dx.doi.org/10.1007/JHEP05(2013)017 to 5-dimensional Riemannian manifolds M. We study the relations between the geometry of M and the number of solutions to a generalized Killing spinor equation obtained from a 5-dimensional supergravity. The existence of 1 pair of solutions is related to almost contact metric structures. We also discuss special cases related to M=S 1 ×M 4 , which leads to M being foliated by submanifolds with special properties, such as Quaternion-Kähler. When there are 2 pairs of solutions, the closure of the isometry sub-algebra generated by the solutions requires M to be S 3 or T 3 -fibration over a Riemann surface. 4 pairs of solutions pin down the geometry of M to very few possibilities. Finally, we propose a new supersymmetric theory for N=1 vector multiplet on K-contact manifold admitting solutions to the Killing spinor equation

  15. Theory and test research on permeability of coal and rock body influenced by mining

    Energy Technology Data Exchange (ETDEWEB)

    Qing-xin Qi; Hong-yan Li; You-gang Wang; Zhi-gang Deng; Hang Lan; Yong-wei Peng; Chun-rui Li [China Coal Research Institute, Beijing (China)

    2009-06-15

    Stress distribution rules and deformation and failure properties of coal and rock bodies influenced by mining were analyzed. Experimental research on permeability of coal and rock samples under different loading conditions was finished in the laboratory. In-situ measurement of coal permeability influenced by actual mining was done as well. Theory analysis show that permeability varied with damage development of coal and rock under stress, and the influence of fissure on permeability was greatest. Laboratory results show that under different loading conditions permeability was different and it varied with stress, which indicated that permeability was directly related to the loading process. In-situ tests showed that permeability is related to abutment stress to some degree. The above results may be referenced to gas prevention and drainage. 11 refs., 6 figs., 1 tab.

  16. Barometric pressure transient testing applications at the Nevada Test Site: formation permeability analysis. Final report

    International Nuclear Information System (INIS)

    Hanson, J.M.

    1984-12-01

    The report evaluates previous investigations of the gas permeability of the rock surrounding emplacement holes at the Nevada Test Site. The discussion sets the framework from which the present uncertainty in gas permeability can be overcome. The usefulness of the barometric pressure testing method has been established. Flow models were used to evaluate barometric pressure transients taken at NTS holes U2fe, U19ac and U20ai. 31 refs., 103 figs., 18 tabs

  17. Permeability and stress-jump effects on magnetic drug targeting in a permeable microvessel using Darcy model

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, S., E-mail: sachinshaw@gmail.com [Department of Mathematics and Statistical Sciences, Botswana International University of Science and Technology, Private Bag 16, Palapye (Botswana); Sutradhar, A.; Murthy, PVSN [Department of Mathematics, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal (India)

    2017-05-01

    In the present paper, we investigated the influence of permeability of the carrier particle and stress jump condition on the porous spherical surface in magnetic drug targeting through a permeable microvessel. The nature of blood is defined by non-Newtonian Casson fluid in the core region of the microvessel and Newtonian fluid in the peripheral region which is located near the surface of the wall of the microvessel. The magnetic particles are considered as spherical and in nanosize, embedded in the carrier particle along with drug particles. A magnet is placed near the tumor position to generate a magnetic field. The relative motion of the carrier particle is the resultant of the fluidic force, magnetic force and Saffman drag force which are calculated for the spherical carrier particle. Trajectories of the carrier particle along the radial and axial direction are calculated. Effect of different parameters such as stress-jump constant, permeability of the carrier particle, pressure gradient, yield stress, Saffman force, volume fraction of the embedded magnetic nanoparticles, permeability of the microvessel wall, and the radius of the carrier particle on the trajectory of the carrier particle are discussed and displayed graphically. - Highlights: • In the present manuscript, we considered the porous carrier particle which provide a larger surface area contact with the fluid than the solid spherical carrier particle. It shows that the porous carrier particle are captured easily than the solid carrier particle. • Introduce Suffman force on the carrier particle which commences an additional resistance which acts opposite to the surface wall and helps the particles to go away from the tumor position. • Considered stress jump condition at the surface of the porous carrier particle which enhanced the tendency of the carrier particle to be capture near the tumor. • Used Darcy model to define the permeability of the wall of the microvessel.

  18. On the permeability of thermally damaged PBX 9501

    Energy Technology Data Exchange (ETDEWEB)

    Zerkle, David K. [Decision Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Asay, Blaine W.; Parker, Gary R.; Dickson, Peter M. [Dynamic and Energetic Materials Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Smilowitz, Laura B.; Henson, Bryan F. [Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2007-06-15

    Theoretical analysis, modeling, and simulation are used to provide insight into the development of permeability during thermal damage of the high explosive PBX 9501. In a recently published article, Terrones et al. [1] conclude that samples of PBX 9501 thermally damaged at 186 C are not permeable to gas flow in a manner consistent with Darcy's Law. We disagree with their conclusion. We show that they have misreported data from the literature, and that their argument depends on a fluid flow model that is physically incorrect and is applied with inappropriate physical parameters. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  19. Measurement of relative permeability of fuel cell diffusion media

    KAUST Repository

    Hussaini, I.S.; Wang, C.Y.

    2010-01-01

    Gas diffusion layer (GDL) in PEM fuel cells plays a pivotal role in water management. Modeling of liquid water transport through the GDL relies on knowledge of relative permeability functions in the in-plane and through-plane directions

  20. A Generalized Version of a Low Velocity Impact between a Rigid Sphere and a Transversely Isotropic Strain-Hardening Plate Supported by a Rigid Substrate Using the Concept of Noninteger Derivatives

    Directory of Open Access Journals (Sweden)

    Abdon Atangana

    2013-01-01

    Full Text Available A low velocity impact between a rigid sphere and transversely isotropic strain-hardening plate supported by a rigid substrate is generalized to the concept of noninteger derivatives order. A brief history of fractional derivatives order is presented. The fractional derivatives order adopted is in Caputo sense. The new equation is solved via the analytical technique, the Homotopy decomposition method (HDM. The technique is described and the numerical simulations are presented. Since it is very important to accurately predict the contact force and its time history, the three stages of the indentation process, including (1 the elastic indentation, (2 the plastic indentation, and (3 the elastic unloading stages, are investigated.

  1. The role of python eggshell permeability dynamics in a respiration-hydration trade-off.

    Science.gov (United States)

    Stahlschmidt, Zachary R; Heulin, Benoit; DeNardo, Dale F

    2010-01-01

    Parental care is taxonomically widespread because it improves developmental conditions and thus fitness of offspring. Although relatively simplistic compared with parental behaviors of other taxa, python egg-brooding behavior exemplifies parental care because it mediates a trade-off between embryonic respiration and hydration. However, because egg brooding increases gas-exchange resistance between embryonic and nest environments and because female pythons do not adjust their brooding behavior in response to the increasing metabolic requirements of developing offspring, python egg brooding imposes hypoxic costs on embryos during the late stages of incubation. We conducted a series of experiments to determine whether eggshells coadapted with brooding behavior to minimize the negative effects of developmental hypoxia. We tested the hypotheses that python eggshells (1) increase permeability over time to accommodate increasing embryonic respiration and (2) exhibit permeability plasticity in response to chronic hypoxia. Over incubation, we serially measured the atomic and structural components of Children's python (Antaresia childreni) eggshells as well as in vivo and in vitro gas exchange across eggshells. In support of our first hypothesis, A. childreni eggshells exhibited a reduced fibrous layer, became more permeable, and facilitated greater gas exchange as incubation progressed. Our second hypothesis was not supported, as incubation O(2) concentration did not affect the shells' permeabilities to O(2) and H(2)O vapor. Our results suggest that python eggshell permeability changes during incubation but that the alterations over time are fixed and independent of environmental conditions. These findings are of broad evolutionary interest because they demonstrate that, even in relatively simple parental-care models, successful parent-offspring relationships depend on adjustments made by both the parent (i.e., egg-brooding behavioral shifts) and the offspring (i

  2. Salt-saturated concrete strength and permeability

    International Nuclear Information System (INIS)

    Pfeifle, T.W.; Hansen, F.D.; Knowles, M.K.

    1996-01-01

    Laboratory-scale experiments applicable to the use of salt-saturated concrete as a seal material for a transuranic waste repository have been completed. Nitrogen gas permeability measurements were made using a flexible-wall permeameter, a confining pressure of 1 MPa, and gas pressure gradients ranging from 0.3 MPa to 0.75 MPa. Results show that salt-saturated concrete has very low intrinsic permeability with values ranging from 9.4 x 10 -22 m 2 to 9.7 x 10 -17 m 2 . Strength and deformation characteristics were investigated under conditions of triaxial compression with confining pressures ranging from 0 to 15 MPa using either axial strain-rate or axial stress-rate control and show that the failure strength of concrete increases with confining pressure which can be adequately described through pressure-sensitive failure criteria. Axial, radial, and volumetric strains were also measured during each test and these data were used to determine elastic properties. Experimental results are applicable in the design and analysis of scale-related functions and apply to other concrete structures subjected to compressive loadings such as dams and prestressed structural members

  3. Mathematical Modeling of Contact Problems of Elasticity Theory with Unilateral Discrete Contact

    Directory of Open Access Journals (Sweden)

    I. V. Stankevich

    2015-01-01

    Full Text Available Development and operation of modern machinery and latest technology require reliable estimates of the strength characteristics of the critical elements of structures and technological equipment under the impact of high-intensity thermomechanical loading, accompanied, as a rule, by complex contact interaction. Mathematical modeling of stress-strain state of such parts and components in the contact area, based on adequate mathematical models, modern numerical methods and efficient algorithms that implement the direct determination of displacement fields, strains and stresses, is the main tool that allows fast acquisition of data required for the calculations of strength and durability. The paper considers an algorithm for constructing the numerical solution of the contact problem of elasticity theory in relation to the body, which has an obvious one-sided discrete contact interaction with an elastic half-space. The proposed algorithm is specially designed to have a correction of the tangential forces at discrete contact points, allowing us to achieve sufficiently accurate implementation of the adopted law of friction. The algorithm is embedded in a general finite element technology, with which the application code is generated. Numerical study of discrete unilateral contact interaction of an elastic plate and a rigid half-space showed a high efficiency of the developed algorithm and the application code that implements it.

  4. Force-controlled robotic assembly processes of rigid and flexible objects methodologies and applications

    CERN Document Server

    Ghalyan, Ibrahim Fahad Jasim

    2016-01-01

    This book provides comprehensive and integrated approaches for rigid and flexible object assembly. It presents comparison studies with the available force-guided robotic processes and covers contact-state modeling, scheme control strategies, and position searching algorithms. Further, it includes experimental validations for different assembly situations, including those for the assembly of industrial parts taken from the automotive industry. .

  5. Microfluidic passive permeability assay using nanoliter droplet interface lipid bilayers.

    Science.gov (United States)

    Nisisako, Takasi; Portonovo, Shiva A; Schmidt, Jacob J

    2013-11-21

    Membrane permeability assays play an important role in assessing drug transport activities across biological membranes. However, in conventional parallel artificial membrane permeability assays (PAMPA), the membrane model used is dissimilar to biological membranes physically and chemically. Here, we describe a microfluidic passive permeability assay using droplet interface bilayers (DIBs). In a microfluidic network, nanoliter-sized donor and acceptor aqueous droplets are alternately formed in cross-flowing oil containing phospholipids. Subsequently, selective removal of oil through hydrophobic pseudo-porous sidewalls induces the contact of the lipid monolayers, creating arrayed planar DIBs between the donor and acceptor droplets. Permeation of fluorescein from the donor to the acceptor droplets was fluorometrically measured. From the measured data and a simple diffusion model we calculated the effective permeabilities of 5.1 × 10(-6) cm s(-1), 60.0 × 10(-6) cm s(-1), and 87.6 × 10(-6) cm s(-1) with donor droplets at pH values of 7.5, 6.4 and 5.4, respectively. The intrinsic permeabilities of specific monoanionic and neutral fluorescein species were obtained similarly. We also measured the permeation of caffeine in 10 min using UV microspectroscopy, obtaining a permeability of 20.8 × 10(-6) cm s(-1). With the small solution volumes, short measurement time, and ability to measure a wide range of compounds, this device has considerable potential as a platform for high-throughput drug permeability assays.

  6. Permeability measurement of some barrier materials as a function of temperature and pressure

    International Nuclear Information System (INIS)

    Maqsood, M.; Faisal, S.; Ali, J.; Usman, A.; Alamgir, K.; Farooq, K.

    2011-01-01

    Barrier materials possess the ability to restrict the passage of gases, vapors, and organic liquids through their boundaries. These barrier materials have large number of applications in industry and scientific research. To measure the permeability of barrier materials, a specific gas flow system has been developed, pure helium gas is used to measure the back ground reading through SS-316. The permeability and break-through time has been measured through Inconel X-750, NBR and Viton below and above the atmospheric pressure and at different temperatures 20 deg. C, 40 deg. C and 70 deg. C. (author)

  7. Effect of overpressure on gas hydrate distribution

    Energy Technology Data Exchange (ETDEWEB)

    Bhatnagar, G.; Chapman, W.G.; Hirasaki, G.J. [Rice Univ., Houston, TX (United States). Dept. of Chemical and Biomolecular Engineering; Dickens, G.R.; Dugan, B. [Rice Univ., Houston, TX (United States). Dept. of Earth Sciences

    2008-07-01

    Natural gas hydrate systems can be characterized by high sedimentation rates and/or low permeability sediments, which can lead to pore pressure higher than hydrostatic. This paper discussed a study that examined this effect of overpressure on gas hydrate and free gas distribution in marine sediments. A one-dimensional numerical model that coupled sedimentation, fluid flow, and gas hydrate formation was utilized. In order to quantify the relative importance of sedimentation rates and low permeability sediments, a dimensionless sedimentation-compaction group (scN) was defined, that compared the absolute permeability of the sediments to the sedimentation rate. Higher values of scN mean higher permeability or low sedimentation rate which generally yield hydrostatic pore pressure while lower values of scN normally create pore pressure greater than hydrostatic. The paper discussed non-hydrostatic consolidation in gas hydrate systems, including mass balances; constitutive relationships; normalized variables; and dimensionless groups. A numerical solution to the problem was presented. It was concluded that simulation results demonstrated that decreasing scN not only increased pore pressure above hydrostatic values, but also lowered the lithostatic stress gradient and gas hydrate saturation. This occurred because overpressure resulted in lower effective stress, causing higher porosity and lower bulk density of the sediment. 16 refs., 5 figs., 1 appendix.

  8. Permeability of sediment cores from methane hydrate deposit in the Eastern Nankai Trough, Japan

    Science.gov (United States)

    Konno, Y.; Yoneda, J.; Egawa, K.; Ito, T.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Nagao, J.

    2013-12-01

    Effective and absolute permeability are key parameters for gas production from methane-hydrate-bearing sandy sediments. Effective and/or absolute permeability have been measured using methane-hydrate-bearing sandy cores and clayey and silty cores recovered from Daini Atsumi Knoll in the Eastern Nankai Trough during the 2012 JOGMEC/JAPEX Pressure coring operation. Liquid-nitrogen-immersed cores were prepared by rapid depressurization of pressure cores recovered by a pressure coring system referred to as the Hybrid PCS. Cores were shaped cylindrically on a lathe with spraying of liquid nitrogen to prevent hydrate dissociation. Permeability was measured by a flooding test or a pressure relaxation method under near in-situ pressure and temperature conditions. Measured effective permeability of hydrate-bearing sediments is less than tens of md, which are order of magnitude less than absolute permeability. Absolute permeability of clayey cores is approximately tens of μd, which would perform a sealing function as cap rocks. Permeability reduction due to a swelling effect was observed for a silty core during flooding test of pure water mimicking hydrate-dissociation-water. Swelling effect may cause production formation damage especially at a later stage of gas production from methane hydrate deposits. This study was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) that carries out Japan's Methane Hydrate R&D Program conducted by the Ministry of Economy, Trade and Industry (METI).

  9. Three mechanisms model of shale gas in real state transport through a single nanopore

    Science.gov (United States)

    Li, Dongdong; Zhang, Yanyu; Sun, Xiaofei; Li, Peng; Zhao, Fengkai

    2018-02-01

    At present, the apparent permeability models of shale gas consider only the viscous flow and Knudsen diffusion of free gas, but do not take into account the influence of surface diffusion. Moreover, it is assumed that shale gas is in ideal state. In this paper, shale gas is assumed in real state, a new apparent permeability model for shale gas transport through a single nanopore is developed that captures many important migration mechanisms, such as viscous flow and Knudsen diffusion of free gas, surface diffusion of adsorbed gas. According to experimental data, the accuracy of apparent permeability model was verified. What’s more, the effects of pressure and pore radius on apparent permeability, and the effects on the permeability fraction of viscous flow, Knudsen diffusion and surface diffusion were analysed, separately. Finally, the results indicate that the error of the developed model in this paper was 3.02%, which is less than the existing models. Pressure and pore radius seriously affect the apparent permeability of shale gas. When the pore radius is small or pressure is low, the surface diffusion cannot be ignored. When the pressure and the pore radius is big, the viscous flow occupies the main position.

  10. Phenomenally High Transduction Air/gas Transducers for Practical Non-Contact Ultrasonic Applications

    Science.gov (United States)

    Bhardwaj, Mahesh C.

    2009-03-01

    Based on novel acoustic impedance matching layers and high coupling piezoelectric materials this paper describes exceptionally high air/gas transduction ultrasonic transducers. By providing applications oriented performance of these transducers we also usher in the era of much desired Non-Contact Ultrasound (NCU) testing and analysis of a wide range of materials including early stage formation of materials such as uncured composite prepregs, green ceramics and powder metals, plastics, elastomers, porous, hygroscopic, chemically bonded and other materials. Besides quality control, ultimately NCU offers timely opportunities for cost-effective materials production, energy savings, and environment protection.

  11. A Network Model for the Effective Thermal Conductivity of Rigid Fibrous Refractory Insulations

    Science.gov (United States)

    Marschall, Jochen; Cooper, D. M. (Technical Monitor)

    1995-01-01

    A procedure is described for computing the effective thermal conductivity of a rigid fibrous refractory insulation. The insulation is modeled as a 3-dimensional Cartesian network of thermal conductance. The values and volume distributions of the conductance are assigned to reflect the physical properties of the insulation, its constituent fibers, and any permeating gas. The effective thermal conductivity is computed by considering the simultaneous energy transport by solid conduction, gas conduction and radiation through a cubic volume of model insulation; thus the coupling between heat transfer modes is retained (within the simplifications inherent to the model), rather than suppressed by treating these heat transfer modes as independent. The model takes into account insulation composition, density and fiber anisotropy, as well as the geometric and material properties of the constituent fibers. A relatively good agreement, between calculated and experimentally derived thermal conductivity values, is obtained for a variety of rigid fibrous insulations.

  12. Permeability Prediction in Deep Coal Seam: A Case Study on the No. 3 Coal Seam of the Southern Qinshui Basin in China

    Science.gov (United States)

    2013-01-01

    The coal permeability is an important parameter in mine methane control and coal bed methane (CBM) exploitation, which determines the practicability of methane extraction. Permeability prediction in deep coal seam plays a significant role in evaluating the practicability of CBM exploitation. The coal permeability depends on the coal fractures controlled by strata stress, gas pressure, and strata temperature which change with depth. The effect of the strata stress, gas pressure, and strata temperature on the coal (the coal matrix and fracture) under triaxial stress and strain conditions was studied. Then we got the change of coal porosity with strata stress, gas pressure, and strata temperature and established a coal permeability model under tri-axial stress and strain conditions. The permeability of the No. 3 coal seam of the Southern Qinshui Basin in China was predicted, which is consistent with that tested in the field. The effect of the sorption swelling on porosity (permeability) firstly increases rapidly and then slowly with the increase of depth. However, the effect of thermal expansion and effective stress compression on porosity (permeability) increases linearly with the increase of depth. The most effective way to improve the permeability in exploiting CBM or extracting methane is to reduce the effective stress. PMID:24396293

  13. The role of tetragonal-metal-organic framework-5 loadings with extra ZnO molecule on the gas separation performance of mixed matrix membrane

    International Nuclear Information System (INIS)

    Arjmandi, Mehrzad; Pakizeh, Majid; Pirouzram, Omid

    2015-01-01

    The effect of more ZnO molecule in tetragonal structure of MOF-5 than cubic structure on the gas permeation properties of T-MOF-5/polyetherimide mixed matrix membranes was investigated. T-MOF-5 was first successfully synthesized and carefully characterized by XRD, FTIR, SEM and N 2 adsorption technique at 77 K. Novel T-MOF-5/PEI MMMs were prepared using solution casting method and characterized by FTIR and SEM. The SEM pictures of the MMMs showed that T-MOF-5 nanocrystals changed the morphology of PEI and exhibited acceptable contacts between the filler particles and the polymer chains. Gas permeation properties of these membranes with different T-MOF-5 contents were studied for pure H 2 , CO 2 , CH 4 and N 2 gases. Permeation measurement showed that the all gases' permeability, diffusivity and solubility were increased with T-MOF-5 loading. H 2 permeability and the ideal selectivity of H 2 /CO 2 and H 2 /CH 4 in MMM with 25 wt% loading of T-MOF-5 nanocrystals were increased. This behavior was attributed to more ZnO molecule in T-MOF-5 structure. The experimental gas permeations through T-MOF-5/PEI nanocomposite with different filler loadings were fitted on Higuchi model. Good agreement between the experimental data and the predicted gas permeability was obtained

  14. The role of tetragonal-metal-organic framework-5 loadings with extra ZnO molecule on the gas separation performance of mixed matrix membrane

    Energy Technology Data Exchange (ETDEWEB)

    Arjmandi, Mehrzad; Pakizeh, Majid [Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Pirouzram, Omid [Kurdistan University, Kurdistan (Iran, Islamic Republic of)

    2015-06-15

    The effect of more ZnO molecule in tetragonal structure of MOF-5 than cubic structure on the gas permeation properties of T-MOF-5/polyetherimide mixed matrix membranes was investigated. T-MOF-5 was first successfully synthesized and carefully characterized by XRD, FTIR, SEM and N{sub 2} adsorption technique at 77 K. Novel T-MOF-5/PEI MMMs were prepared using solution casting method and characterized by FTIR and SEM. The SEM pictures of the MMMs showed that T-MOF-5 nanocrystals changed the morphology of PEI and exhibited acceptable contacts between the filler particles and the polymer chains. Gas permeation properties of these membranes with different T-MOF-5 contents were studied for pure H{sub 2}, CO{sub 2}, CH{sub 4} and N{sub 2} gases. Permeation measurement showed that the all gases' permeability, diffusivity and solubility were increased with T-MOF-5 loading. H{sub 2} permeability and the ideal selectivity of H{sub 2}/CO{sub 2} and H{sub 2}/CH{sub 4} in MMM with 25 wt% loading of T-MOF-5 nanocrystals were increased. This behavior was attributed to more ZnO molecule in T-MOF-5 structure. The experimental gas permeations through T-MOF-5/PEI nanocomposite with different filler loadings were fitted on Higuchi model. Good agreement between the experimental data and the predicted gas permeability was obtained.

  15. Developments in permeable and low permeability barriers

    International Nuclear Information System (INIS)

    Jefferis, S.A.; Norris, G.H.; Thomas, A.O.

    1997-01-01

    The concept of the reactive treatment zone whereby pollutants are attenuated as they move along a pathway in the ground has enabled a re-thinking of many of the concepts of containment. In particular it offers the potential for the control of the flux from a contaminated area by controlling the contaminant concentration in the pathway(s) as well as or instead of using a low permeability barrier. The paper outlines the basic concepts of the reactive treatment zone and the use of permeable and low permeability reactive systems. The paper then gives a case history of the installation of a permeable barrier using an in-situ reaction chamber

  16. Permeability Measurements of Rock Samples from Conduit Drilling at Unzen Volcano, Japan

    Science.gov (United States)

    Watanabe, T.; Shimizu, Y.; Noguchi, S.; Nakada, S.

    2006-12-01

    The last eruption of Unzen Volcano (1990-1995) was effusive to form lava domes, though magmas at depths are estimated to have contained volatile materials enough to cause explosive eruptions [e.g., Sato et al., 1995]. Most of volatile materials should have escaped from ascending magmas. The escape of gas is controlled by permeability of magmas and country rocks. Unzen Scientific Drilling Project sampled both the latest conduit and its country rock (USDP-4). In order to understand degassing processes, we have measured the permeability of these rock samples. Four cube samples with edges of 25 mm were cut from USDP-4 cores C1, C12 (country rock), C13 and C14 (conduit). Sample C1 is considered as Old Unzen Lava, and Sample C12 volcanic breccia. The transient pulse method was employed to measure the permeability. It applies a step of the fluid pressure difference across a specimen, and measures the decay rate of the fluid pressure difference. This method can be applied to samples with very low permeability, since it determines the permeability without measuring the fluid flux. Nitrogen gas was used as a pore fluid. Our permeametry system is built in a pressure vessel, and the confining pressure and the pore fluid pressure can be controlled independently. The temperature of the measurement system is kept constant within 0.1 degree. The temperature control and the background leak rate limit the measurable permeability to be higher than 10^{-20} m2. Measurements were first conducted under the atmospheric pressure. The permeability in a rock sample varies with the direction by a factor less than 5. Sample C1 has the lowest permeability (10^{-19} m2), and Sample C12 the highest value (10^{-17 m2). The permeability of C13 and C14 is of the order of 10^{- 18} m2. Though only a trace of vesicles can be seen in conduit samples, the interconnection is still maintained. The pressure dependence of the permeability is now investigated up to 50 MPa. The permeability of C13 and C14

  17. Microstructure and permeability of the Whitby Mudstone (UK) as an analogue for the Posidonia shale (NL)

    Science.gov (United States)

    Houben, Maartje; Barnhoorn, Auke; Drury, Martyn; Peach, Colin; Spiers, Christopher

    2015-04-01

    In order to make gas productivity from a shale economically interesting we should find ways to better connect the in-situ pore network to the natural occurring and mechanical induced fractures in the rock. When trying to improve gas productivity a first aim is to understand gas storage and gas flow potential through the rock by investigating the microstructure and measure the matrix porosity and permeability of the unfractured shales. Using a combination of methods we have characterized the porosity and permeability of the Jet Dogger section of the Whitby Mudstone Formation (UK), which we use as an analogue for the Posidonia Shale (NL). The Posidonia shale is a possible unconventional source for gas in Northern Europe. A combination of Precision Ion Polishing (PIPS) and Scanning Electron Microscopy (SEM) has been used to investigate the microstructure and the pores. Microstructurally the circa 8 meter thick Jet section of the Whitby Mudstone Formation can be subdivided into a fossil rich (>15 %) top half with an organic matter content of 7-10% and a sub-mm laminated (alternating clay-rich, carbonate-rich, not necessarily fossils, layers) lower half were the organic matter content varies from 0.3-16%. In addition, any possible flow in the rock has to go through the fine-grained clay matrix (all grains 100 nm) is in the order of 0.5-2.5% and is not connected in 2D. Furthermore, overall more than 40% of the visible porosity is present within the clay matrix (sometimes even up to 80%). Porosity and pore size distributions for pores with smaller diameters (2 < diameter < 100 nm) were determined using Ar and N2 gas adsorption. The adsorption porosity was in the order of 1-5%, were we found 1-2.5% porosity for the top half of the section and 2-5% porosity for the bottom half. Ar gas permeability of the samples was measured on 1-inch diameter cores using Ar-gas-permeametry with a pressure step of 0.2 MPa. The permeability measured was in the order of 2•10-19 - 1•10

  18. Literature review and recommendation of methods for measuring relative permeability of anhydrite from the Salado Formation at the Waste Isolation Pilot Plant

    Energy Technology Data Exchange (ETDEWEB)

    Christiansen, R.L. [Colorado School of Mines, Golden, CO (United States). Dept. of Petroleum Engineering; Howarth, S.M. [Sandia National Labs., Albuquerque, NM (United States)

    1995-08-01

    This report documents a literature review of methods for measuring relative permeability as applied to low permeability anhydrite rock samples from the Salado Formation. About one hundred papers were reviewed, and four methods were identified as promising techniques for measuring the relative permeability of the Salado anhydrite: (1) the unsteady-state high-rate method, (2) the unsteady-state stationary-liquid method, (3) the unsteady-state centrifuge method, and (4) the unsteady-state low-rate method. Except for the centrifuge method, all have been used for low permeability rocks. The unsteady-state high-rate method is preferred for measuring relative permeability of Salado anhydrite, and the unsteady-state stationary-liquid method could be well suited for measuring gas relative permeability of Salado anhydrite. The unsteady-state low-rate method, which combines capillary pressure effects with relative permeability concepts may also prove effective. Likewise, the unsteady-state centrifuge method may be an efficient means for measuring brine relative permeability for Salado anhydrite, especially at high gas saturations.

  19. Literature review and recommendation of methods for measuring relative permeability of anhydrite from the Salado Formation at the Waste Isolation Pilot Plant

    International Nuclear Information System (INIS)

    Christiansen, R.L.

    1995-08-01

    This report documents a literature review of methods for measuring relative permeability as applied to low permeability anhydrite rock samples from the Salado Formation. About one hundred papers were reviewed, and four methods were identified as promising techniques for measuring the relative permeability of the Salado anhydrite: (1) the unsteady-state high-rate method, (2) the unsteady-state stationary-liquid method, (3) the unsteady-state centrifuge method, and (4) the unsteady-state low-rate method. Except for the centrifuge method, all have been used for low permeability rocks. The unsteady-state high-rate method is preferred for measuring relative permeability of Salado anhydrite, and the unsteady-state stationary-liquid method could be well suited for measuring gas relative permeability of Salado anhydrite. The unsteady-state low-rate method, which combines capillary pressure effects with relative permeability concepts may also prove effective. Likewise, the unsteady-state centrifuge method may be an efficient means for measuring brine relative permeability for Salado anhydrite, especially at high gas saturations

  20. Spin injection into a two-dimensional electron gas using inter-digital-ferromagnetic contacts

    DEFF Research Database (Denmark)

    Hu, C.M.; Nitta, J.; Jensen, Ane

    2002-01-01

    We present a model that describes the spin injection across a single interface with two electrodes. The spin-injection rate across a typical hybrid junction made of ferromagnet (FM) and a two-dimensional electron gas (2DEG) is found at the percentage level. We perforin spin-injection-detection ex......-injection-detection experiment on devices with two ferromagnetic contacts on a 2DEG confined in an InAs quantum well. A spin-injection rate of 4.5% is estimated from the measured magnetoresistance....

  1. Elastic-Brittle-Plastic Behaviour of Shale Reservoirs and Its Implications on Fracture Permeability Variation: An Analytical Approach

    Science.gov (United States)

    Masoudian, Mohsen S.; Hashemi, Mir Amid; Tasalloti, Ali; Marshall, Alec M.

    2018-05-01

    Shale gas has recently gained significant attention as one of the most important unconventional gas resources. Shales are fine-grained rocks formed from the compaction of silt- and clay-sized particles and are characterised by their fissured texture and very low permeability. Gas exists in an adsorbed state on the surface of the organic content of the rock and is freely available within the primary and secondary porosity. Geomechanical studies have indicated that, depending on the clay content of the rock, shales can exhibit a brittle failure mechanism. Brittle failure leads to the reduced strength of the plastic zone around a wellbore, which can potentially result in wellbore instability problems. Desorption of gas during production can cause shrinkage of the organic content of the rock. This becomes more important when considering the use of shales for CO2 sequestration purposes, where CO2 adsorption-induced swelling can play an important role. These phenomena lead to changes in the stress state within the rock mass, which then influence the permeability of the reservoir. Thus, rigorous simulation of material failure within coupled hydro-mechanical analyses is needed to achieve a more systematic and accurate representation of the wellbore. Despite numerous modelling efforts related to permeability, an adequate representation of the geomechanical behaviour of shale and its impact on permeability and gas production has not been achieved. In order to achieve this aim, novel coupled poro-elastoplastic analytical solutions are developed in this paper which take into account the sorption-induced swelling and the brittle failure mechanism. These models employ linear elasticity and a Mohr-Coulomb failure criterion in a plane-strain condition with boundary conditions corresponding to both open-hole and cased-hole completions. The post-failure brittle behaviour of the rock is defined using residual strength parameters and a non-associated flow rule. Swelling and shrinkage

  2. Elementary analysis on the main factors affecting the permeability of sandstones

    International Nuclear Information System (INIS)

    Gong Binli

    2006-01-01

    Researches show that in the early stage of sandstone diagenesis, compaction, pressure solution, cementation and replacement reduce both the porosity and the permeability. The cementation of authigenic kaolinite may preserve the tiny intergranular pore-space, and slightly influence the porosity, and even increase the permeability. During the middle to late stage of diagenesis, the organic matter becomes matured, hydrocarbon and acidic water are produced, which forms secondary porosity by the dissolution and the corrosion, and greatly increases the permeability of sandstones and provides a favorable prerequisite for the formation of sandstone-type uranium deposits. The interlayered oxidation alteration, oil-gas reduction and low-temperature hydrothermal alteration also produce secondary porosity in epigenetic reforming stage, which finally decides the permeability after the formation of sandstone-type uranium deposits. This is an important condition for in-situ leaching of sandstone-type uranium deposit. (authors)

  3. The effect of bottom boundary condition type on the behavior of adhesive contact of spherical probe on an elastic film

    International Nuclear Information System (INIS)

    Zhu, X; Xu, W

    2017-01-01

    This study presents an investigation on the behavior of adhesive contact between a rigid sphere and an elastic film which is either perfectly bonded (case I) or in frictionless contact (case II) with a rigid substrate. By using linear fracture mechanics, we formulate an convenient semi-analytical approach to develop relations between the applied force, penetration depth and contact radius. Finite element analysis (FEA) is used to verify the relationships. Our results reveal that the interfacial boundary conditions between the film and substrate have distinct effects on the adhesive contact behavior between the sphere and the film. The aim of the present study is to provide an instructive inspiration for controlling adhesion strength of the thin film subject to adhesive contact. (paper)

  4. Modeling stress/strain-dependent permeability changes for deep geoenergy applications

    Science.gov (United States)

    Rinaldi, Antonio Pio; Rutqvist, Jonny

    2016-04-01

    Rock permeability is a key parameter in deep geoenergy systems. Stress and strain changes induced at depth by fluid injection or extraction may substantially alter the rock permeability in an irreversible way. With regard to the geoenergies, some applications require the permeability to be enhanced to improve productivity. The rock permeability is generally enhanced by shearing process of faults and fractures (e.g. hydroshearing for Enhanced and Deep Geothermal Systems), or the creation of new fractures (e.g. hydrofracturing for shale gas). However, such processes may, at the same time, produce seismicity that can be felt by the local population. Moreover, the increased permeability due to fault reactivation may pose at risk the sealing capacity of a storage site (e.g. carbon sequestration or nuclear waste disposal), providing then a preferential pathway for the stored fluids to escape at shallow depth. In this work we present a review of some recent applications aimed at understanding the coupling between stress (or strain) and permeability. Examples of geoenergy applications include both EGS and CO2 sequestration. To investigate both "wanted" and "unwanted" effects, THM simulations have been carried out with the TOUGH-FLAC simulator. Our studies include constitutive equations relating the permeability to mean effective stress, effective normal stress, volumetric strain, as well as accounting for permeability variation as related to fault/fracture reactivation. Results show that the geomechanical effects have a large role in changing the permeability, hence affecting fluids leakage, reservoir enhancement, as well as the induced seismicity.

  5. The permeability of concrete for reactor containment vessels

    International Nuclear Information System (INIS)

    Mills, R.H.

    1983-07-01

    Review of the literature pertaining to water, water vapour and gas transmission through concrete revealed conflicting views on the mechanisms involved and the influence of mix design parameters such as initial porosities and water/cement ratio. Consideration of the effects of ageing and of construction defects in field concrete were totally neglected in published work. Permeability data from three published papers were compared with permeability calculated according to Powers. The ratio of calculated to observed permeability varied from 40 x 10 -3 to 860 x 10 -3 for one group: from 0.17 x 10 3 to 8.6 x 10 3 in the second; and from 24 x 10 3 to 142 x 10 3 for the third. There were therefore wide discrepancies within each group of data and between groups. A bibliography was prepared and an exploratory experimental programme was mounted to determine the relative importance of key parameters such as cement type, porosity and water/cement ratio. Contrary to frequently cited references it was found that permeability of concrete was not significantly influenced by water/cement ratio when the starting porosity was constant. If water/cement ratio was held constant, however, the permeability was strongly influenced by starting porosity. It was also found that with constant water/cement ratio permeability increased with cement content. The value of fly ash and blast furnace slag in partial substitution for Portland cement is neglected in the literature but it is important since such substitutions alleviate alkali-silicate reactions. Permeability of concrete was significantly decreased by partial substitution of Portland cement with fly ash but there was no benefit in the use of blast furnace slag

  6. Experimental studies of direct contact heat transfer in a slurry bubble column at high gas temperature of a helium–water–alumina system

    International Nuclear Information System (INIS)

    Abdulrahman, M.W.

    2015-01-01

    In this paper, the direct contact heat transfer is investigated experimentally for a helium gas at 90 °C injected through a slurry of water at 22 °C and alumina solid particles in a slurry bubble column reactor. This work examines the effects of superficial gas velocity, static liquid height, solid particles concentration and solid particle size, on the volumetric heat transfer coefficient and slurry temperature of the slurry bubble column reactor. These effects are formulated in forms of empirical equations. From the experimental work, it is found that the volumetric heat transfer coefficient and the slurry temperature increase by increasing the superficial gas velocity with a higher rate of increase at lower superficial gas velocity. In addition, the volumetric heat transfer coefficient and the slurry temperature decrease by increasing the static liquid height and/or the solid concentration at any given superficial gas velocity. Furthermore, it is found that the rate of decrease of the volumetric heat transfer coefficient with the solid concentration is approximately the same for different superficial gas velocities, and the decrease of the slurry temperature with the solid concentration is negligible. - Highlights: • Direct contact heat transfer is investigated experimentally in a slurry bubble column. • Empirical equation of direct contact heat transfer Nusselt number is formulated. • The volumetric heat transfer coefficient increases with superficial gas velocity. • The volumetric heat transfer coefficient decreases with the static liquid height. • The volumetric heat transfer coefficient decreases with the solid concentration.

  7. Permeability measurements on rock samples from Unzen Scientific Drilling Project Drill Hole 4 (USDP-4)

    Science.gov (United States)

    Watanabe, Tohru; Shimizu, Yuhta; Noguchi, Satoshi; Nakada, Setsuya

    2008-07-01

    Permeability measurement was made on five rock samples from USDP-4 cores. Rock samples were collected from the conduit zone and its country rock. One sample (C14-1-1) is considered as a part of the feeder dyke for the 1991-1995 eruption. The transient pulse method was employed under confining pressure up to 50 MPa. Compressional wave velocity was measured along with permeability. The measured permeability ranges from 10 - 19 to 10 - 17 m 2 at the atmospheric pressure, and is as low as that reported for tight rocks such as granite. The permeability decreases with increasing confining pressure, while the compressional wave velocity increases. Assuming that pores are parallel elliptical tubes, the pressure dependence of permeability requires aspect ratio of 10 - 4 -10 - 2 at the atmospheric pressure. The pore aperture is estimated to be less than 1 μm. The estimated aspect ratio and pore aperture suggest that connectivity of pores is maintained by narrow cracks. The existence of cracks is supported by the pressure dependence of compressional wave velocity. Narrow cracks (< 1 μm) are observed in dyke samples, and they must have been created after solidification. Dyke samples do not provide us information of pore structures during degassing, since exsolved gas has mostly escaped and pores governing the gas permeable flow should have been lost. Both dyke and country rock samples provide us information of materials around ascending magma. Although the measured small-scale permeability cannot be directly applied to geological-scale processes, it gives constrains on studies of large-scale permeability.

  8. Tritium activity balance in hairless rats following skin-contact exposure to tritium-gas-contaminated stainless-steel surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Trivedi, A

    1994-06-01

    Studies using animals and human volunteers have demonstrated that the dosimetry for skin-contact exposure to contaminated metal surfaces differs from that for the intake of tritiated water or tritium gas. However, despite the availability of some information on the dosimetry for skin-contact with tritium-gas-contaminated metal surfaces, uncertainties in estimating skin doses remain, because of poor accounting for the applied tritium activity in the body (Eakins et al., 1975; Trivedi, 1993). Experiments on hairless rats were performed to account for the tritium activity applied onto the skin. Hairless rats were contaminated through skin-contact exposure to tritium-gas-contaminated stainless-steel planchets. The activity in the first smear was about 35% of the total removable activity (measured by summing ten consecutive swipes). The amount of tritium applied onto the skin can be approximated by estimating the tritium activity in the first smear removed form the contaminated surfaces. 87 {+-} 9% of the transferred tritium was retained in the exposed skin 30 min post-exposure. 30 min post exposure, the unexposed skin and the carcass retained 8 {+-} 6% and 3 {+-} 2% of the total applied tritium activity, respectively. The percentage of tritium evolved from the body or breathed out was estimated to be 2 {+-} 1% of the total applied activity 30 min post-exposure. It is recommended that to evaluate accurately the amount of tritium transferred to the skin, alternative measurement approaches are required that can directly account for the transferred activity onto the skin. 15 refs., 13 tabs., 7 figs.

  9. The influence of slip velocity and temperature on permeability during and after high-velocity fault slip

    Science.gov (United States)

    Tanikawa, W.; Mukoyoshi, H.; Tadai, O.; Hirose, T.; Lin, W.

    2011-12-01

    Fluid transport properties in fault zones play an important role in dynamic processes during large earthquakes. If the permeability in a fault zone is low, high pore-fluid pressures caused by thermal pressurization (Sibson, 1973) or shear-induced compaction (Blanpied et al., 1992) can lead to an apparent reduction of fault strength. Changes in porosity and permeability of fault rocks within a fault zone during earthquakes and the subsequent progressive recovery of these properties may have a large influence on earthquake recurrence (Sleep and Blanpied, 1992). A rotary shear apparatus was used to investigate changes of fluid transport properties in a fault zone by real-time measurement of gas flow rates during and after shearing of hollow sandstone and granite cylinders at various slip rates. Our apparatus measures permeability parallel to the slip plane in both the slip zone and wall rocks. In all cases, permeability decreased rapidly with an increase of friction, but recovered soon after slip, reaching a steady state within several tens of minutes. The rate of reduction of permeability increased with increasing slip velocity. Permeability did not recover to pre-slip levels after low-velocity tests but recovered to exceed them after high-velocity tests. Frictional heating of gases at the slip surface increased gas viscosity, which increased gas flow rate to produce an apparent permeability increase. The irreversible permeability changes of the low-velocity tests were caused by gouge formation due to wearing and smoothing of the slip surface. The increase of permeability after high-velocity tests was caused by mesoscale fracturing in response to rapid temperature rise. Changes of pore fluid viscosity contributed more to changes of flow rate than did permeability changes caused by shear deformation, although test results from different rocks and pore fluids might be different. References Blanpied, M.L., Lockner, D.A., Byerlee, J.D., 1992. An earthquake mechanism

  10. Crustal permeability

    Science.gov (United States)

    Gleeson, Tom; Ingebritsen, Steven E.

    2016-01-01

    Permeability is the primary control on fluid flow in the Earth’s crust and is key to a surprisingly wide range of geological processes, because it controls the advection of heat and solutes and the generation of anomalous pore pressures.  The practical importance of permeability – and the potential for large, dynamic changes in permeability – is highlighted by ongoing issues associated with hydraulic fracturing for hydrocarbon production (“fracking”), enhanced geothermal systems, and geologic carbon sequestration.  Although there are thousands of research papers on crustal permeability, this is the first book-length treatment.  This book bridges the historical dichotomy between the hydrogeologic perspective of permeability as a static material property and the perspective of other Earth scientists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. 

  11. Injection, flow, and mixing of CO2 in porous media with residual gas.

    Energy Technology Data Exchange (ETDEWEB)

    Oldenburg, C.M.; Doughty, C.A.

    2010-09-01

    Geologic structures associated with depleted natural gas reservoirs are desirable targets for geologic carbon sequestration (GCS) as evidenced by numerous pilot and industrial-scale GCS projects in these environments world-wide. One feature of these GCS targets that may affect injection is the presence of residual CH{sub 4}. It is well known that CH{sub 4} drastically alters supercritical CO{sub 2} density and viscosity. Furthermore, residual gas of any kind affects the relative permeability of the liquid and gas phases, with relative permeability of the gas phase strongly dependent on the time-history of imbibition or drainage, i.e., dependent on hysteretic relative permeability. In this study, the effects of residual CH{sub 4} on supercritical CO{sub 2} injection were investigated by numerical simulation in an idealized one-dimensional system under three scenarios: (1) with no residual gas; (2) with residual supercritical CO{sub 2}; and (3) with residual CH{sub 4}. We further compare results of simulations that use non-hysteretic and hysteretic relative permeability functions. The primary effect of residual gas is to decrease injectivity by decreasing liquid-phase relative permeability. Secondary effects arise from injected gas effectively incorporating residual gas and thereby extending the mobile gas plume relative to cases with no residual gas. Third-order effects arise from gas mixing and associated compositional effects on density that effectively create a larger plume per unit mass. Non-hysteretic models of relative permeability can be used to approximate some parts of the behavior of the system, but fully hysteretic formulations are needed to accurately model the entire system.

  12. Experimental Measurement of Relative Permeability Functions for Fuel Cell GDL Materials

    KAUST Repository

    Hussaini, Irfan; Wang, Chao-Yang

    2009-01-01

    Gas diffusion layer in PEM fuel cells plays a pivotal role in water management. Modeling of liquid water transport through the GDL relies on knowledge of relative permeability functions in the in-plane and through-plane directions. In the present work, air and water relative permeabilities are experimentally determined as functions of saturation for typical GDL materials such as Toray-060, -090, -120 carbon paper and E-Tek carbon cloth materials in their plain, untreated forms. Saturation is measured using an ex-situ gravimetric method. Absolute and relative permeability functions in the two directions of interest are presented. Significant departure from the generally assumed cubic function of saturation is observed. ©The Electrochemical Society.

  13. The two-body problem of a pseudo-rigid body and a rigid sphere

    DEFF Research Database (Denmark)

    Kristiansen, Kristian Uldall; Vereshchagin, M.; Gózdziewski, K.

    2012-01-01

    n this paper we consider the two-body problem of a spherical pseudo-rigid body and a rigid sphere. Due to the rotational and "re-labelling" symmetries, the system is shown to possess conservation of angular momentum and circulation. We follow a reduction procedure similar to that undertaken...... in the study of the two-body problem of a rigid body and a sphere so that the computed reduced non-canonical Hamiltonian takes a similar form. We then consider relative equilibria and show that the notions of locally central and planar equilibria coincide. Finally, we show that Riemann's theorem on pseudo......-rigid bodies has an extension to this system for planar relative equilibria....

  14. Dynamic contact with Signorini's condition and slip rate dependent friction

    Directory of Open Access Journals (Sweden)

    Kenneth Kuttler

    2004-06-01

    Full Text Available Existence of a weak solution for the problem of dynamic frictional contact between a viscoelastic body and a rigid foundation is established. Contact is modelled with the Signorini condition. Friction is described by a slip rate dependent friction coefficient and a nonlocal and regularized contact stress. The existence in the case of a friction coefficient that is a graph, which describes the jump from static to dynamic friction, is established, too. The proofs employ the theory of set-valued pseudomonotone operators applied to approximate problems and a priori estimates.

  15. Permeability of hydrogen isotopes through Pd-Ag membrane

    International Nuclear Information System (INIS)

    Yoshida, Hiroshi

    1981-01-01

    This paper represents the permeabilities, diffusion coefficients and isotope effects for hydrogen and deuterium through Pd-25 wt.% Ag alloy tubes The feed gas H 2 or D 2 flowing into the permeation cell was preheated before it reached to the outer surface of the permeation tube made of palladium-silver alloy. Permeation time lag method could be successfully carried out with the present apparatus to measure both permeability and diffusion coefficient. The square-root pressure dependence for the permeation of hydrogen isotopes was observed. The observed systematic temperature dependence indicates that the approximation of the Arrhenius' relation was effective within this experimental conditions. Some tendency of permeation fluxes in relation to the reciprocal temperature, 1/T, was seen. The permeability ratio was larger than the square root of isotopic mass ratio, and it decreased with temperature rise. On the contrary, the diffusion coefficient ratio was much smaller than the square root of isotopic mass ratio. (Kato, T.)

  16. A micro-scale model for predicting contact resistance between bipolar plate and gas diffusion layer in PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Y.; Lin, G.; Shih, A.J.; Hu, S.J. [Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI 48109-2125 (United States)

    2007-01-01

    Contact resistance between the bipolar plate (BPP) and the gas diffusion layer (GDL) in a proton exchange membrane (PEM) fuel cell constitutes a significant portion of the overall fuel cell electrical resistance under the normal operation conditions. Most current methods for contact resistance estimation are experimental and there is a lack of well developed theoretical methods. A micro-scale numerical model is developed to predict the electrical contact resistance between BPP and GDL by simulating the BPP surface topology and GDL structure and numerically determining the status for each contact spot. The total resistance and pressure are obtained by considering all contact spots as resistances in parallel and summing the results together. This model shows good agreements with experimental results. Influences of BPP surface roughness parameters on contact resistance are also studied. This model is beneficial in understanding the contact behavior between BPP and GDL and can be integrated with other fuel cell simulations to predict the overall performance of PEM fuel cells. (author)

  17. Permeability Study of Austenitic Stainless Steel Surfaces Produced by Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Emmanuel Segura-Cardenas

    2017-11-01

    Full Text Available Selective laser melting (SLM is emerging as a versatile process for fabricating different metal components with acceptable mechanical properties and geometrical accuracy. The process has been used in the manufacturing of several parts (e.g., aerospace or biomedical components, and offers the capability to tailor the performance of several surface and mechanical properties. In this work, permeability properties and surface roughness of stainless steel (SS316L surfaces were evaluated through experimentation with three different laser scanning patterns (chessboard, meander, and stripe, and different sloping angles between the fabricated surface and the laser beam incident on the process. Results showed that for each scanning pattern, the roughness decreased as the sloping angle increased consistently in all experimental trials. Furthermore, in the case of the permeability evaluation, the manufactured surfaces showed changes in properties for each series of experiments performed with different scanning patterns. The chessboard pattern showed a change of 67° to 107° in contact angle, while the meander and stripe patterns showed a variation in contact angle in a range of 65° to 85°. The different scanning strategies in the SLM process resulted in an alternative method for surface enhancement with different hydrophobicity properties, valuable for designing the most appropriate permeability characteristics for specific applications.

  18. Selective Gas Permeation in Graphene Oxide-Polymer Self-Assembled Multilayers.

    Science.gov (United States)

    Pierleoni, Davide; Minelli, Matteo; Ligi, Simone; Christian, Meganne; Funke, Sebastian; Reineking, Niklas; Morandi, Vittorio; Doghieri, Ferruccio; Palermo, Vincenzo

    2018-04-04

    The performance of polymer-based membranes for gas separation is currently limited by the Robeson limit, stating that it is impossible to have high gas permeability and high gas selectivity at the same time. We describe the production of membranes based on the ability of graphene oxide (GO) and poly(ethyleneimine) (PEI) multilayers to overcome such a limit. The PEI chains act as molecular spacers in between the GO sheets, yielding a highly reproducible, periodic multilayered structure with a constant spacing of 3.7 nm, giving a record combination of gas permeability and selectivity. The membranes feature a remarkable gas selectivity (up to 500 for He/CO 2 ), allowing to overcome the Robeson limit. The permeability of these membranes to different gases depends exponentially on the diameter of the gas molecule, with a sieving mechanism never obtained in pure GO membranes, in which a size cutoff and a complex dependence on the chemical nature of the permeant is typically observed. The tunable permeability, the high selectivity, and the possibility to produce coatings on a wide range of polymers represent a new approach to produce gas separation membranes for large-scale applications.

  19. Development of vinylic and acetylenic functionalized structures based on high permeable glassy polymers as membrane materials for gas mixtures separation

    Science.gov (United States)

    Roizard, D.; Kiryukhina, Y.; Masalev, A.; Khotimskiy, V.; Teplyakov, V.; Barth, D.

    2013-03-01

    There are several challenging separation problems in industries which can be solved with the help of membrane technologies. It is the case for instance of the purification of gas energy carriers (i.e. H2, CH4) from CO2 as well as the CO2 recovery from flue gas. Glassy polymers containing trimethylsilyl residues like poly(1-trimethylsilyl-1-propyne) [PTMSP] and polyvinyltrimethylsilane [PVTMS] are known to exhibit good membrane properties for gas separation. This paper reports two ways of improving their performances based on the controlled introduction of selective groups - alkyl imidazomium salts (C4I) and polyethyleneglycol (M-PEG)- able to enhance CO2 selectivity. CO2 Isotherm sorption data and permeability measurements have shown that the membrane performances could be significantly improved when C4I and M-PEG were introduced as residues covalently bounded to the main polymer chain. Moreover the introduced bromine reactive centres could also be used to induce chemical crosslinking giving rise to more resistant and stable membranes to organic vapours. With the C4I groups, the CO2 sorption could be enhanced by a factor 4.4.

  20. 复杂瓦斯地质条件下煤层透气性评价及抽采对策研究%Study on coal seam gas permeability evaluation and drainage countermeasures in complex gas geological conditions

    Institute of Scientific and Technical Information of China (English)

    易汉华

    2017-01-01

    针对煤层瓦斯地质条件复杂的米箩煤矿在生产过程中瓦斯抽采难、预抽时间长、矿区范围内可采煤层透气性不确定的问题,采用煤层透气性系数现场测定的方法,对米箩煤矿1号、3号、9号、10号、16号、26号、27号、29号、31号和40号煤层施工测压钻孔进行了煤层透气性系数相关参数的测定,并依据钻孔径向流量法计算公式,对米箩煤矿各煤层透气性系数进行了评价,得出了米箩煤矿矿区范围内1号、3号、9号、10号、16号、26号、27号、29号、31号和40号煤层均为低透气性煤层.通过优化瓦斯抽采钻孔直径和钻孔间距的方式,改善了煤层透气性,并在1108底板瓦斯抽放巷两侧每隔15 m分别增设一个高位钻场,在钻场内向3号煤层布置19个斜向穿层抽采钻孔,有效缩短了110310回采工作面瓦斯预抽时间.%The geological conditions of Miluo Coal Mine is complex,in the production process,gas is difficult to drain,the time of gas drainage is long,and permeability of minable seam was uncertain,aimed at these problems,the permeability coefficient measuring on site was applied,thus,pressure drilling were constructed in No.1,3,9,10,16,26,27,29,31 and No.40 coal seam,whose purpose was to evaluate the permeability coefficient of coal seams.It was proposed that No.1,3,9,10,16,26,27,29,31 and No.40 are of low permeability coal seam.Through the optimization of diameter and spacing of holes for gas drainage,the permeability of coal seam was improved,high-level drilling field was added on two side of 1108 floor drainage roadway,and the spacing of drilling field was 15 m.19 oblique layer-through boreholes were laid out into No.3 coal seam in the drilling field,and this has effectively reduced the pre-pumping time of the gas on 110310 working face.

  1. Contact mechanics of articular cartilage layers asymptotic models

    CERN Document Server

    Argatov, Ivan

    2015-01-01

    This book presents a comprehensive and unifying approach to articular contact mechanics with an emphasis on frictionless contact interaction of thin cartilage layers. The first part of the book (Chapters 1–4) reviews the results of asymptotic analysis of the deformational behavior of thin elastic and viscoelastic layers. A comprehensive review of the literature is combined with the authors’ original contributions. The compressible and incompressible cases are treated separately with a focus on exact solutions for asymptotic models of frictionless contact for thin transversely isotropic layers bonded to rigid substrates shaped like elliptic paraboloids. The second part (Chapters 5, 6, and 7) deals with the non-axisymmetric contact of thin transversely isotropic biphasic layers and presents the asymptotic modelling methodology for tibio-femoral contact. The third part of the book consists of Chapter 8, which covers contact problems for thin bonded inhomogeneous transversely isotropic elastic layers, and Cha...

  2. Flow-permeability feedbacks and the development of segregation pipes in volcanic materials

    Science.gov (United States)

    Rust, Alison

    2014-05-01

    Flow and transformation in volcanic porous media is important for the segregation of melts and aqueous fluids from magmas as well as elutriation of fine ash from pyroclastic flows and vents. The general topic will be discussed in the framework of understanding sets of vertical pipes found in two very different types of volcanic deposits: 1) vesicular (bubbly) cylinders in basalt lava flows and 2) gas escape pipes in pyroclastic flow deposits. In both cases the cylinders can be explained by a flow-permeability feedback where perturbations in porosity and thus permeability cause locally higher flow speeds that in turn locally increase the permeability. For vesicular cylinders in lava flows, the porous medium is a framework of crystals within the magma. Above a critical crystallinity, which depends on the shape and size distribution of the crystals, the crystals form a touching framework. As the water-saturated magma continues to cool, it crystallizes anhydrous minerals, resulting in the exsolution of water vapour bubbles that can drive flow of bubbly melt through the crystal network. It is common to find sets of vertical cylinders of bubby melt in solidified lava flows, with compositions that match the residual melt from 35-50% crystallization of the host basalt. These cylinders resemble chimneys in experiments of crystallising ammonium chloride solution that are explained by reactive flow with porous medium convection. The Rayleigh number for the magmatic case is too low for convection but the growth of steam bubbles as the magma crystallizes induces pore fluid flow up through the permeable crystal pile even if there is no convective instability. This bubble-growth-driven upward flow is reactive and can lead to channelization because of a feedback between velocity and permeability. For the gas escape pipes in pyroclastic flows, the porous medium is a very poorly sorted granular material composed of fragments of solid magma with a huge range of grain sizes from ash

  3. The secondary permeability of Italian clays. A review

    International Nuclear Information System (INIS)

    Gera, F.

    1998-01-01

    Over the years several studies have been performed in Italy on the permeability of various argillaceous formations for the purpose of assessing their potential utilization for the isolation of long-lived radioactive waste. An extensive survey was made of tunnels intersecting clay formations for the purpose of identifying water inflows and of interpreting them in relation to the nature of the water-bearing features present outside the lining. The main objective of the 'Faults in Clays' project was to improve the sensitivity and resolution of geophysical techniques for identifying and characterizing faults intersecting clay strata. The first obvious conclusion is that generalizations are not possible: argillaceous formations are characterized by extreme variability in respect to intrinsic properties, sedimentological and structural set-up, consolidation history and regional stress conditions. As a result of this complexity widely different permeability, for both gas and water, has been observed even in apparently similar materials. In addition, gas data indicate that flow, at a particular location, can vary also as a function of time. (R.P.)

  4. Rigid Body Sampling and Individual Time Stepping for Rigid-Fluid Coupling of Fluid Simulation

    Directory of Open Access Journals (Sweden)

    Xiaokun Wang

    2017-01-01

    Full Text Available In this paper, we propose an efficient and simple rigid-fluid coupling scheme with scientific programming algorithms for particle-based fluid simulation and three-dimensional visualization. Our approach samples the surface of rigid bodies with boundary particles that interact with fluids. It contains two procedures, that is, surface sampling and sampling relaxation, which insures uniform distribution of particles with less iterations. Furthermore, we present a rigid-fluid coupling scheme integrating individual time stepping to rigid-fluid coupling, which gains an obvious speedup compared to previous method. The experimental results demonstrate the effectiveness of our approach.

  5. Pseudomonas aeruginosa Infectious Keratitis in a High Oxygen Transmissible Rigid Contact Lens Rabbit Model

    Science.gov (United States)

    Wei, Cynthia; Zhu, Meifang; Petroll, W. Matthew; Robertson, Danielle M.

    2014-01-01

    Purpose. To establish a rabbit model of infectious Pseudomonas aeruginosa keratitis using ultrahigh oxygen transmissible rigid lenses and characterize the frequency and severity of infection when compared to a non–oxygen transmissible lens material. Methods. Rabbits were fit with rigid lenses composed of ultrahigh and non–oxygen transmissible materials. Prior to wear, lenses were inoculated with an invasive corneal isolate of P. aeruginosa stably conjugated to green fluorescent protein (GFP). Corneas were examined before and after lens wear using a modified Heidelberg Rostock Tomograph in vivo confocal microscope. Viable bacteria adherent to unworn and worn lenses were assessed by standard plate counts. The presence of P. aeruginosa-GFP and myeloperoxidase-labeled neutrophils in infected corneal tissue was evaluated using laser scanning confocal microscopy. Results. The frequency and severity of infectious keratitis was significantly greater with inoculated ultrahigh oxygen transmissible lenses. Infection severity was associated with increasing neutrophil infiltration and in severe cases, corneal melting. In vivo confocal microscopic analysis of control corneas following lens wear confirmed that hypoxic lens wear was associated with mechanical surface damage, whereas no ocular surface damage was evident in the high-oxygen lens group. Conclusions. These data indicate that in the absence of adequate tear clearance, the presence of P. aeruginosa trapped under the lens overrides the protective effects of oxygen on surface epithelial cells. These findings also suggest that alternative pathophysiological mechanisms exist whereby changes under the lens in the absence of frank hypoxic damage result in P. aeruginosa infection in the otherwise healthy corneal epithelium. PMID:25125601

  6. Patterning of super-hydrophobic structures on permeable sensor membranes

    NARCIS (Netherlands)

    Pelt, van S.; Eggermont, J.; Frijns, A.J.H.; Dietzel, A.H.; Colin, S; Morini, GL; Brandner, JJ

    2012-01-01

    For a disposable smart food monitoring system, a gas sensor membrane is needed that isolates the sensor surface from (dust) particles water droplets. At the same time, this membrane must have a high permeability, a sufficiently fast response times and should be water repellent to avoid blocking of

  7. Rigidly foldable origami gadgets and tessellations

    Science.gov (United States)

    Evans, Thomas A.; Lang, Robert J.; Magleby, Spencer P.; Howell, Larry L.

    2015-01-01

    Rigidly foldable origami allows for motion where all deflection occurs at the crease lines and facilitates the application of origami in materials other than paper. In this paper, we use a recently discovered method for determining rigid foldability to identify existing flat-foldable rigidly foldable tessellations, which are also categorized. We introduce rigidly foldable origami gadgets which may be used to modify existing tessellations or to create new tessellations. Several modified and new rigidly foldable tessellations are presented. PMID:26473037

  8. 单一低透突出煤层底抽巷煤气共采技术及实践%Application and Practice of Coal-gas Co-extraction Technology by Floor Drainage Roadway in Single Low-permeability Outburst Seam

    Institute of Scientific and Technical Information of China (English)

    冀超辉

    2015-01-01

    To counter to the serious gas troubles and low mining efficiency present in a single low-permeability outburst coal seam, based on the analysis of the distribution of stress and permeability in the working face, a coal-gas co-extraction technology by floor drainage roadway in a single low-permeability outburst seam was proposed, that is: gas extraction by hydraulic flushing in hole in the original pressure area before mining, gas extraction in the stress reduced area during mining and the gas extraction from gob after mining. The application in Ligou Mine showed that three gas extraction methods can be coordinated and complemented each other, the outburst hazard in the working face was not only eliminated, but also the gas extraction volume increased, as a result, the safe and efficient mining of the single low-permeability outburst seam was realized.%针对单一低透突出煤层存在瓦斯灾害严重、开采效率低等问题,在分析回采工作面应力分布和渗透率分布的基础上,提出了单一低透突出煤层底抽巷煤气共采模式,即采前未卸压区水力冲孔抽采、采中影响区的应力降低区瓦斯抽采和采后的采空区瓦斯抽采模式。李沟煤矿的工程应用结果表明:3种抽采方法互相协调、互为补充,不但消除了工作面突出危险性,而且大大地增加了瓦斯抽采量,实现了单一低透突出煤层煤与瓦斯的安全高效开采。

  9. Micromechanical contact stiffness devices and application for calibrating contact resonance atomic force microscopy

    Science.gov (United States)

    Rosenberger, Matthew R.; Chen, Sihan; Prater, Craig B.; King, William P.

    2017-01-01

    This paper reports the design, fabrication, and characterization of micromechanical devices that can present an engineered contact stiffness to an atomic force microscope (AFM) cantilever tip. These devices allow the contact stiffness between the AFM tip and a substrate to be easily and accurately measured, and can be used to calibrate the cantilever for subsequent mechanical property measurements. The contact stiffness devices are rigid copper disks of diameters 2-18 μm integrated onto a soft silicone substrate. Analytical modeling and finite element simulations predict the elastic response of the devices. Measurements of tip-sample interactions during quasi-static force measurements compare well with modeling simulation, confirming the expected elastic response of the devices, which are shown to have contact stiffness 32-156 N m-1. To demonstrate one application, we use the disk sample to calibrate three resonant modes of a U-shaped AFM cantilever actuated via Lorentz force, at approximately 220, 450, and 1200 kHz. We then use the calibrated cantilever to determine the contact stiffness and elastic modulus of three polymer samples at these modes. The overall approach allows cantilever calibration without prior knowledge of the cantilever geometry or its resonance modes, and could be broadly applied to both static and dynamic measurements that require AFM calibration against a known contact stiffness.

  10. Fluid flow and permeabilities in basement fault zones

    Science.gov (United States)

    Hollinsworth, Allan; Koehn, Daniel

    2017-04-01

    Fault zones are important sites for crustal fluid flow, specifically where they cross-cut low permeability host rocks such as granites and gneisses. Fluids migrating through fault zones can cause rheology changes, mineral precipitation and pore space closure, and may alter the physical and chemical properties of the host rock and deformation products. It is therefore essential to consider the evolution of permeability in fault zones at a range of pressure-temperature conditions to understand fluid migration throughout a fault's history, and how fluid-rock interaction modifies permeability and rheological characteristics. Field localities in the Rwenzori Mountains, western Uganda and the Outer Hebrides, north-west Scotland, have been selected for field work and sample collection. Here Archaean-age TTG gneisses have been faulted within the upper 15km of the crust and have experienced fluid ingress. The Rwenzori Mountains are an anomalously uplifted horst-block located in a transfer zone in the western rift of the East African Rift System. The north-western ridge is characterised by a tectonically simple western flank, where the partially mineralised Bwamba Fault has detached from the Congo craton. Mineralisation is associated with hydrothermal fluids heated by a thermal body beneath the Semliki rift, and has resulted in substantial iron oxide precipitation within porous cataclasites. Non-mineralised faults further north contain foliated gouges and show evidence of leaking fluids. These faults serve as an analogue for faults associated with the Lake Albert oil and gas prospects. The Outer Hebrides Fault Zone (OHFZ) was largely active during the Caledonian Orogeny (ca. 430-400 Ma) at a deeper crustal level than the Ugandan rift faults. Initial dry conditions were followed by fluid ingress during deformation that controlled its rheological behaviour. The transition also altered the existing permeability. The OHFZ is a natural laboratory in which to study brittle fault

  11. Microstructural Dynamics and Rheology of Suspensions of Rigid Fibers

    Science.gov (United States)

    Butler, Jason E.; Snook, Braden

    2018-01-01

    The dynamics and rheology of suspensions of rigid, non-Brownian fibers in Newtonian fluids are reviewed. Experiments, theories, and computer simulations are considered, with an emphasis on suspensions at semidilute and concentrated conditions. In these suspensions, interactions between the particles strongly influence the microstructure and rheological properties of the suspension. The interactions can arise from hydrodynamic disturbances, giving multibody interactions at long ranges and pairwise lubrication forces over short distances. For concentrated suspensions, additional interactions due to excluded volume (contacts) and adhesive forces are addressed. The relative importance of the various interactions as a function of fiber concentration is assessed.

  12. Transport properties of natural gas through polyethylene nanocomposites at high temperature and pressure

    DEFF Research Database (Denmark)

    Adewole, Jimoh K.; Jensen, Lars; Al-Mubaiyedh, Usamah A.

    2012-01-01

    High density polyethylene (HDPE)/clay nanocomposites containing nanoclay concentrations of 1, 2.5, and 5 wt% were prepared by a melt blending process. The effects of various types of nanoclays and their concentrations on permeability, solubility, and diffusivity of natural gas in the nanocomposites...... at constant temperature had little influence on the permeability, whereas increasing the temperature from 30 to 70 degrees C significantly increased the permeability of the gas. Additionally, the effect of crystallinity on permeability, solubility, and diffusivity was investigated. Thus, the permeability...

  13. A Mathematical Pressure Transient Analysis Model for Multiple Fractured Horizontal Wells in Shale Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Yan Zeng

    2018-01-01

    Full Text Available Multistage fractured horizontal wells (MFHWs have become the main technology for shale gas exploration. However, the existing models have neglected the percolation mechanism in nanopores of organic matter and failed to consider the differences among the reservoir properties in different areas. On that account, in this study, a modified apparent permeability model was proposed describing gas flow in shale gas reservoirs by integrating bulk gas flow in nanopores and gas desorption from nanopores. The apparent permeability was introduced into the macroseepage model to establish a dynamic pressure analysis model for MFHWs dual-porosity formations. The Laplace transformation and the regular perturbation method were used to obtain an analytical solution. The influences of fracture half-length, fracture permeability, Langmuir volume, matrix radius, matrix permeability, and induced fracture permeability on pressure and production were discussed. Results show that fracture half-length, fracture permeability, and induced fracture permeability exert a significant influence on production. A larger Langmuir volume results in a smaller pressure and pressure derivative. An increase in matrix permeability increases the production rate. Besides, this model fits the actual field data relatively well. It has a reliable theoretical foundation and can preferably describe the dynamic changes of pressure in the exploration process.

  14. A methodology for determining the evolution law of gob permeability and its distributions in longwall coal mines

    International Nuclear Information System (INIS)

    Zhang, Cun; Tu, Shihao; Zhang, Lei; Bai, Qingsheng; Yuan, Yong; Wang, Fangtian

    2016-01-01

    In order to understand the permeability evolution law of the gob by mining disturbances and obtain the permeability distribution of the fully compacted gob, comprehensive methods including theoretical analyses of monitoring data and numerical simulation are used to determine the permeability of gobs in the mining process. Based on current research, three zones of the vertical stress and permeability in the gob are introduced in this article, which are the caving rock mass accumulation zone, the gradually compacted zone and the fully compacted zone. A simple algorithm is written by using FISH language to be imported into the reservoir model. FISH language is an internal programming language in FLAC3D. It is possible to calculate the permeability at each zone with this algorithm in the mining process. Besides, we analyze the gas flow rates from seven gob gas ventholes (GGV) located on a longwall face operated in a mine of a Huainan coalfield in Huainan City, China. Combined with Darcy’s law, a calculation model of permeability around GGV in the gob is proposed. Using this model, the evolution law of permeability in the gob is deduced; the phases of permeability evolution are the decline stage and the stable stage. The result of the vertical stress monitoring data and good fitting effect of the permeability to the experimental data show that the permeability decline caused by the compaction of the gob is the principal reason for the decline stage. The stable stage indicates that the gob has been fully compacted, and the average period of full gob compaction is 47.75 d. The permeability in the middle of the compacted gob is much smaller than the permeability on the edge of the gob which presents an O shape trend. Besides, the little difference among the results of the numerical simulation, the permeability calculation model and other commonly used calculation models validate the correctness of the permeability calculation model and numerical simulation results

  15. Utilization of ''CONTACT'' experiments to improve the fission gas release knowledge in PWR fuel rods

    Energy Technology Data Exchange (ETDEWEB)

    Charles, M; Abassin, J J; Bruet, M; Baron, D; Melin, P

    1983-03-01

    The CONTACT experiments, which were carried out by the French CEA, within the framework of a CEA-FRAMATOME collaboration agreement, bear on the behaviour of in-pile irradiated PWR fuel rods. We will focus here upon their results dealing with fission gas release. The experimental device is briefly described, then the following results are given: the kinetics of stable fission gas release for various linear ratings; the instantaneous fractional release rates of radioactive gases versus their decay constant in the range 1.5 10/sup -6/-3.6 10/sup -3/s/sup -1/, for various burnups, as also the influence of fuel temperature. Moreover, the influence of the nature and the pressure of the filling gas upon the release is presented for various linear ratings. The experimental results are discussed and analysed with the purpose to model various physical phenomena involved in the release (low-temperature mechanisms, diffusion).

  16. Utilization of ''CONTACT'' experiments to improve the fission gas release knowledge in PWR fuel rods

    International Nuclear Information System (INIS)

    Charles, M.; Abassin, J.J.; Bruet, M.

    1983-01-01

    The CONTACT experiments, which were carried out by the French CEA, within the framework of a CEA-FRAMATOME collaboration agreement, bear on the behaviour of in-pile irradiated PWR fuel rods. We will focus here upon their results dealing with fission gas release. The experimental device is briefly described, then the following results are given: the kinetics of stable fission gas release for various linear ratings; the instantaneous fractional release rates of radioactive gases versus their decay constant in the range 1.5 10 -6 -3.6 10 -3 s -1 , for various burnups, as also the influence of fuel temperature. Moreover, the influence of the nature and the pressure of the filling gas upon the release is presented for various linear ratings. The experimental results are discussed and analysed with the purpose to model various physical phenomena involved in the release (low-temperature mechanisms, diffusion)

  17. The experimental modeling of gas percolation mechanisms in a coal-measure tight sandstone reservoir: A case study on the coal-measure tight sandstone gas in the Upper Triassic Xujiahe Formation, Sichuan Basin, China

    Directory of Open Access Journals (Sweden)

    Shizhen Tao

    2016-12-01

    Full Text Available Tight sandstone gas from coal-measure source rock is widespread in China, and it is represented by the Xujiahe Formation of the Sichuan Basin and the Upper Paleozoic of the Ordos Basin. It is affected by planar evaporative hydrocarbon expulsion of coal-measure source rock and the gentle structural background; hydrodynamics and buoyancy play a limited role in the gas migration-accumulation in tight sandstone. Under the conditions of low permeability and speed, non-Darcy flow is quite apparent, it gives rise to gas-water mixed gas zone. In the gas displacing water experiment, the shape of percolation flow curve is mainly influenced by core permeability. The lower the permeability, the higher the starting pressure gradient as well as the more evident the non-Darcy phenomenon will be. In the gas displacing water experiment of tight sandstone, the maximum gas saturation of the core is generally less than 50% (ranging from 30% to 40% and averaging at 38%; it is similar to the actual gas saturation of the gas zone in the subsurface core. The gas saturation and permeability of the core have a logarithm correlation with a correlation coefficient of 0.8915. In the single-phase flow of tight sandstone gas, low-velocity non-Darcy percolation is apparent; the initial flow velocity (Vd exists due to the slippage effect of gas flow. The shape of percolation flow curve of a single-phase gas is primarily controlled by core permeability and confining pressure; the lower the permeability or the higher the confining pressure, the higher the starting pressure (0.02–0.08 MPa/cm, whereas, the higher the quasi-initial flow speed, the longer the nonlinear section and the more obvious the non-Darcy flow will be. The tight sandstone gas seepage mechanism study shows that the lower the reservoir permeability, the higher the starting pressure and the slower the flow velocity will be, this results in the low efficiency of natural gas migration and accumulation as well as

  18. Les techniques de séparation de gaz par membranes Gas Separation Techniques by Membranes

    Directory of Open Access Journals (Sweden)

    Avrillon R.

    2006-11-01

    through the membrane by applying a pressure difference on either side of the membrane. This pressure difference causes a difference in dissolved gas concentration between the two faces of the membrane and hence a diffusional gas flow through the membrane. Choice of Polymer - The gas sorption capacity of the polymer depends on its free volume and its physical affinity for the gas. For a gas mixture, differences in affinity are selectivity factors. The mobility of sorbed molecules depends on the free volume of the polymer and on the degree of rigidity of the chains. Vitreous polymers are more selective in this respect than rubbery polymers. This is why they are generally chosen for manufacturing gas permeation membranes. Permeability and selectivity are somewhat antinomic properties, especially when the selectivity is of a diffusional type, i. e. when the polymer acts as a molecular sieve. The definition of new polymers providing a better compromise between permeability and selectivity thus goes via research on the relationships between structure and the permeability to the gas to be separated. In polymers in a vitreous state, the chains are fixed overall, but small local movements, for example such as the rotation of an aromatic nucleus around bonds in the para position, remain possible. It seems that such small movements are beneficial for permeability, while not detracting very much from the selectivity. Structures of chains that are unfavorable for compact piling increase permeability in general to the detriment of selectivity. This is true for chains having non-coplanar aromatic nuclei or ones having bulky groups. Tables 2, 3 and 4 give some structural and permeability data for various polyimides. Figures 4 and 5 show the performances for hydrogen/ methane and carbon-dioxide/methane separations of various polyimides synthesized in our laboratories. Asymmetric MembranesThe membranes used in practice have a particular structure that is called asymmetric, which combines

  19. THE STRUCTURE ANALYTICAL RESEARCH OF POROUS PERMEABLE WIRE MATERIAL (in Russian

    Directory of Open Access Journals (Sweden)

    Andrzej JAKUBOWSKI

    2016-04-01

    Full Text Available The details of making technology of porous permeable material with use of wire are allowed to carry out the analytical research of structure and structural characteristics of wire winding body. Its permit for prognostication the final proper-ties of material, that is produced by the following deformation treatment (diameter reduction. Due to the regular orga-nized arrangement of wire, the coil of winding body is considered as a multispan continuous beam, but a contact of coils – as interaction of two cylinders. Possibility of exactly calculation of the contacts between coils is allowed to go over the single fragment displacements into deformation of whole winding body. During research of deformation processes in regards of winding body geometry and used wire mechanical properties, the structural characteristics of porous permea-ble wire material are expected. The optimal number of winding layers, eliminating the distortion of organized final struc-ture, is established. The material pressure–compactness relation is obtained in order to control the technological condi-tions of winding and drafting for guarantee the product required properties.

  20. The permeability evolution of tuffisites and outgassing from dense rhyolitic magma

    Science.gov (United States)

    Heap, M. J.; Tuffen, H.; Wadsworth, F. B.; Reuschlé, T.; Castro, J. M.; Schipper, C. I.

    2017-12-01

    Recent observations of rhyolitic lava effusion from eruptions in Chile indicate that simultaneous pyroclastic venting facilitates outgassing. Venting from conduit-plugging lava domes is pulsatory and occurs through shallow fracture networks that deliver pyroclastic debris and exsolved gases to the surface. However, these fractures become blocked as the particulate fracture infill sinters viscously, thus drastically reducing permeability. Tuffisites, fossilized debris-filled fractures of this venting process, are abundant in pyroclastic material ejected during hybrid explosive-effusive activity. Dense tuffisite-hosting obsidian bombs ejected from Volcán Chaitén (Chile) in 2008 afford an opportunity to better understand the permeability evolution of tuffisites within low-permeability conduit plugs, wherein gas mobility is reliant upon fracture pathways. We use laboratory measurements of the permeability and porosity of tuffisites that preserve different degrees of sintering, combined with a grainsize-based sintering model and constraints on pressure-time paths from H2O diffusion, to place first-order constraints on tuffisite permeability evolution. Inferred timescales of sintering-driven tuffisite compaction and permeability loss, spanning minutes to hours, coincide with observed vent pulsations during hybrid rhyolitic activity and, more broadly, timescales of pressurization accompanying silicic lava dome extrusion. We therefore conclude that sintering exerts a first-order control on fracture-assisted outgassing from low-permeability, conduit-plugging silicic magma.

  1. Radioactive rare gas separation using a separation cell with two kinds of membrane differing in gas permeability tendency

    International Nuclear Information System (INIS)

    Ohno, Masayoshi; Ozaki, Osamu; Sato, Hajime; Kimura, Shoji; Miyauchi, Terukatsu.

    1977-01-01

    A separation cell embodying two kinds of membrane-porous and nonporous, i.e. differing in gas permeability - has a separation factor higher than possible with a conventional separation cell with a single kind of membrane. The performance of such separation cells and of cascades constituted thereof are analyzed theoretically and measured experimentally for different conditions of operation, to determine the applicability of the concept to the separation of rare gases from gaseous waste out of nuclear plants. Theoretical considerations indicate that, in a cascade composed of symmetric separation cells, the separation performance can be improved by recycling part of the effluent from a cell back through the same cell (recycling cascade). It is shown that its performance is better than with the arrangement of diverting another effluent several stages upstream. With the recycling cascade, the symmetric separation recycling rate is determined by the depletion separation and enrichment separation factors relevant to the respective membranes. The separation performance of a 9-stage recycling cascade composed of separation cells with silicone rubber tubular membranes and cellulose acetate tubular membranes is derived for a case of Kr separation from N 2 -Kr mixture. The experimental data coincide well with the analytical results. From both the experimental and the analytical results, it is found that the attainable separation coefficient per stage of the cascade comes to average approximately 0.97. (auth.)

  2. Effect of permeability enhancers on paracellular permeability of acyclovir.

    Science.gov (United States)

    Ates, Muge; Kaynak, Mustafa Sinan; Sahin, Selma

    2016-06-01

    According to Biopharmaceutics Classification System (BCS), acyclovir is a class III (high solubility, low permeability) compound, and it is transported through paracellular route by passive diffusion. The aim of this study was to investigate the effect of various pharmaceutical excipients on the intestinal permeability of acyclovir. The single-pass in-situ intestinal perfusion (SPIP) method was used to estimate the permeability values of acyclovir and metoprolol across different intestinal segments (jejunum, ileum and colon). Permeability coefficient (Peff ) of acyclovir was determined in the absence and presence of a permeation enhancer such as dimethyl β-cyclodextrin (DM-β-CD), sodium lauryl sulfate (SLS), sodium caprate (Cap-Na) and chitosan chloride. All enhancers increased the permeability of paracellularly transported acyclovir. Although Cap-Na has the highest permeability-enhancing effect in all segments, permeation-enhancing effect of chitosan and SLS was only significant in ileum. On the other hand, DM-β-CD slightly decreased the permeability in all intestinal segments. These findings have potential implication concerning the enhancement of absorption of paracellularly transported compounds with limited oral bioavailability. In the case of acyclovir, Cap-Na either alone or in combination with SLS or chitosan has the potential to improve its absorption and bioavailability and has yet to be explored. © 2016 Royal Pharmaceutical Society.

  3. Study of gas-solid contact in an ultra-rapid reactor for cumene catalytic cracking; Etude du contact gaz-solide dans un reacteur a co-courant descendant par la mise en oeuvre du craquage catalytique du cumene

    Energy Technology Data Exchange (ETDEWEB)

    Bayle, J

    1996-11-05

    Few studies have been carried out on the notion of gas-solid contact in ultra-rapid reactors. Both gas and solid move in the reactor and the contact can be directly estimated when using a chemical reaction such as cumene cracking. It`s a pure and light feedstock whose kinetics can be determined in a fixed bed. The study was carried out on a downflow ultra-rapid reactor (ID = 20 mm, length = 1 m) at the University of Western Ontario. It proved that the quench and the ultra-rapid separation of gas and solid must be carefully designed in the pilot plant. Cumene conversion dropped when reducing gas-solid contact, which led to push the temperature over 550 deg. C and increase the cat/oil ratio at 25 working at solid mass fluxes below 85 kg/m{sup 2}.s. Change of selectivity at very short residence time were also observed due to deactivation effects. Experiments made by Roques (1994) with phosphorescent pigments on the Residence Time Distribution of solids gave Hydrodynamic data on a cold flow copy of the pilot plant. Experiments made on packed bed gave kinetic data on the cracking of cumene. These data were combined to optimize a mono dimensional plug flow model for cumene cracking. (author)

  4. Enhancing recovery of ammonia from swine manure anaerobic digester effluent using gas-permeable membrane technology.

    Science.gov (United States)

    Dube, P J; Vanotti, M B; Szogi, A A; García-González, M C

    2016-03-01

    Gas-permeable membrane technology is useful to recover ammonia from manure. In this study, the technology was enhanced using aeration instead of alkali chemicals to increase pH and the ammonium (NH4(+)) recovery rate. Digested effluents from covered anaerobic swine lagoons containing 1465-2097 mg NH4(+)-N L(-1) were treated using submerged membranes (0.13 cm(2) cm(-3)), low-rate aeration (120 mL air L-manure(-1) min(-1)) and nitrification inhibitor (22 mg L(-1)) to prevent nitrification. The experiment included a control without aeration. The pH of the manure with aeration rose from 8.6 to 9.2 while the manure without aeration decreased from 8.6 to 8.1. With aeration, 97-99% of the NH4(+) was removed in about 5 days of operation with 96-98% recovery efficiency. In contrast, without aeration it took 25 days to treat the NH4(+). Therefore, the recovery of NH4(+) was five times faster with the low-rate aeration treatment. This enhancement could reduce costs by 70%. Published by Elsevier Ltd.

  5. Investigation of a ceramic vane with a metal disk thermal and mechanical contact in a gas turbine impeller

    Directory of Open Access Journals (Sweden)

    Resnick S.V.

    2015-01-01

    Full Text Available Promising directions of a new generation gas turbine engines development include using in gas turbines ceramic materials blades with high strength, thermal and chemical stability. One of the serious problems in developing such motors is insufficient knowledge of contact phenomena occurring in ceramic and metal details connection nodes. This work presents the numerical modeling results of thermal processes on ceramic and metal details rough boundaries. The investigation results are used in conducting experimental researches in conditions reproducing operating.

  6. Tile-based rigidization surface parametric design study

    Science.gov (United States)

    Giner Munoz, Laura; Luntz, Jonathan; Brei, Diann; Kim, Wonhee

    2018-03-01

    Inflatable technologies have proven useful in consumer goods as well as in more recent applications including civil structures, aerospace, medical, and robotics. However, inflatable technologies are typically lacking in their ability to provide rigid structural support. Particle jamming improves upon this by providing structures which are normally flexible and moldable but become rigid when air is removed. Because these are based on an airtight bladder filled with loose particles, they always occupy the full volume of its rigid state, even when not rigidized. More recent developments in layer jamming have created thin, compact rigidizing surfaces replacing the loose volume of particles with thinly layered surface materials. Work in this area has been applied to several specific applications with positive results but have not generally provided the broader understanding of the rigidization performance as a function of design parameters required for directly adapting layer rigidization technology to other applications. This paper presents a parametric design study of a new layer jamming vacuum rigidization architecture: tile-based vacuum rigidization. This form of rigidization is based on layers of tiles contained within a thin vacuum bladder which can be bent, rolled, or otherwise compactly stowed, but when deployed flat, can be vacuumed and form a large, flat, rigid plate capable of supporting large forces both localized and distributed over the surface. The general architecture and operation detailing rigidization and compliance mechanisms is introduced. To quantitatively characterize the rigidization behavior, prototypes rigidization surfaces are fabricated and an experimental technique is developed based on a 3-point bending test. Performance evaluation metrics are developed to describe the stiffness, load-bearing capacity, and internal slippage of tested prototypes. A set of experimental parametric studies are performed to better understand the impact of

  7. Dynamic Behavior of Wind Turbine by a Mixed Flexible-Rigid Multi-Body Model

    Science.gov (United States)

    Wang, Jianhong; Qin, Datong; Ding, Yi

    A mixed flexible-rigid multi-body model is presented to study the dynamic behavior of a horizontal axis wind turbine. The special attention is given to flexible body: flexible rotor is modeled by a newly developed blade finite element, support bearing elasticities, variations in the number of teeth in contact as well as contact tooth's elasticities are mainly flexible components in the power train. The couple conditions between different subsystems are established by constraint equations. The wind turbine model is generated by coupling models of rotor, power train and generator with constraint equations together. Based on this model, an eigenproblem analysis is carried out to show the mode shape of rotor and power train at a few natural frequencies. The dynamic responses and contact forces among gears under constant wind speed and fixed pitch angle are analyzed.

  8. Water desalting schemes when using heat gas-vapor mixture in front of contact condenser

    OpenAIRE

    Kuznetsova, Svitlana A.

    2016-01-01

    Ukraine is a country with low quality of fresh water; there are regions with its deficiency. One of the possible solutions to this problem is the desalination of the brackish water from surface and groundwater sources by using heat of the mixture before the contact condenser in gas-steam turbine plants. The plants produce electricity and heat energy for the needs of the industrial, agricultural complexes and the population of Kherson, Nikolaev and Odessa regions. The studies were carried out ...

  9. Quantitative measurement of interocular suppression in anisometropic amblyopia: a case-control study.

    Science.gov (United States)

    Li, Jinrong; Hess, Robert F; Chan, Lily Y L; Deng, Daming; Yang, Xiao; Chen, Xiang; Yu, Minbin; Thompson, Benjamin

    2013-08-01

    The aims of this study were to assess (1) the relationship between interocular suppression and visual function in patients with anisometropic amblyopia, (2) whether suppression can be simulated in matched controls using monocular defocus or neutral density filters, (3) the effects of spectacle or rigid gas-permeable contact lens correction on suppression in patients with anisometropic amblyopia, and (4) the relationship between interocular suppression and outcomes of occlusion therapy. Case-control study (aims 1-3) and cohort study (aim 4). Forty-five participants with anisometropic amblyopia and 45 matched controls (mean age, 8.8 years for both groups). Interocular suppression was assessed using Bagolini striated lenses, neutral density filters, and an objective psychophysical technique that measures the amount of contrast imbalance between the 2 eyes that is required to overcome suppression (dichoptic motion coherence thresholds). Visual acuity was assessed using a logarithm minimum angle of resolution tumbling E chart and stereopsis using the Randot preschool test. Interocular suppression assessed using dichoptic motion coherence thresholds. Patients exhibited significantly stronger suppression than controls, and stronger suppression was correlated significantly with poorer visual acuity in amblyopic eyes. Reducing monocular acuity in controls to match that of cases using neutral density filters (luminance reduction) resulted in levels of interocular suppression comparable with that in patients. This was not the case for monocular defocus (optical blur). Rigid gas-permeable contact lens correction resulted in less suppression than spectacle correction, and stronger suppression was associated with poorer outcomes after occlusion therapy. Interocular suppression plays a key role in the visual deficits associated with anisometropic amblyopia and can be simulated in controls by inducing a luminance difference between the eyes. Accurate quantification of suppression

  10. Characterizing gas permeability and pore properties of Czech granitic rocks

    Czech Academy of Sciences Publication Activity Database

    Konečný, Pavel; Kožušníková, Alena

    2016-01-01

    Roč. 13, č. 4 (2016), s. 331-338 ISSN 1214-9705 R&D Projects: GA ČR GA105/09/0089; GA MŠk(CZ) LO1406; GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : granitic rocks * permeability * pore properties Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.699, year: 2016 https://www.irsm.cas.cz/materialy/acta_content/2016_doi/Konecny_AGG_2016_0015.pdf

  11. Experimental study of the permeability of concrete under variable thermal and hydric conditions

    International Nuclear Information System (INIS)

    Chen, W.

    2011-01-01

    The main objective of this study is to evaluate the variable thermal and hydric effect, with fissuration effect on the hydraulic behaviour of two concretes. Many experimental tests (saturation and permeability measurements, uniaxial and triaxial compressions tests) were carried out in order to investigate the temperature and saturation influence on the behaviour hydraulic on sound and micro-cracked concrete. Moreover, an experimental device for permeability measurement on macro-cracked concrete was realized, it allows to study the behaviour of macro-cracked of concrete confined and subjected to dry gas flow or very moist air at different temperatures. Multiaxial mechanical tests are coupled to the permeability measurements of sound concrete and micro-cracked by freezing and thawing, which allow to measuring the permeability under deviatoric load-unload with the effect of pre-cracking under stress. We also effectuated a test of relative permeability of concrete as a function of water saturation, subjected to drying and re-saturation, conditioning by the different relative humidity imposed. (author)

  12. Membrane barriers for radon gas flow restrictions

    International Nuclear Information System (INIS)

    Archibald, J.F.

    1984-08-01

    Research was performed to assess the feasibility of barrier membrane substances, for use within mining or associated high risk environments, in restricting the diffusion transport of radon gas quantities. Specific tests were conducted to determine permeability parameters of a variety of membrane materials with reference to radon flow capabilities. Tests were conducted both within laboratory and in-situ emanation environments where concentrations and diffusion flows of radon gas were known to exist. Equilibrium radon gas concentrations were monitored in initially radon-free chambers adjacent to gas sources, but separated by specified membrane substances. Membrane barrier effectiveness was demonstrated to result in reduced emanation concentrations of radon gas within the sampling chamber atmosphere. Minimum gas concentrations were evidenced where the barrier membrane material was shown to exhibit lowest radon permeability characteristics

  13. Changes in coal permeability in the process of deformation

    Czech Academy of Sciences Publication Activity Database

    Kožušníková, Alena

    2001-01-01

    Roč. 45, 2-4 (2001), s. 75-77 ISSN 0001-7132. [ Coal Geology Conference /9./. Praha, 25.06.2001-29.06.2001] R&D Projects: GA ČR GA105/00/0875 Institutional research plan: CEZ:AV0Z3086906 Keywords : gas permeability measurement * triaxial state of stress Subject RIV: DB - Geology ; Mineralogy

  14. Modelling the static contact between a fingertip and a rigid wavy surface

    NARCIS (Netherlands)

    Rodriguez Urribarri, Adriana; van der Heide, Emile; Zeng, Xiangqiong; de Rooij, Matthias B.

    2016-01-01

    Surface topography is one of the major parameters affecting friction during touch and consequently tactility. In order to understand and control friction, fine controlled surfaces with a sinusoidal topography are studied to derive an analytical contact model. The Westergaard model on a

  15. A new coal-permeability model: Internal swelling stress and fracture-matrix interaction

    Energy Technology Data Exchange (ETDEWEB)

    Liu, H.H.; Rutqvist, J.

    2009-10-01

    We have developed a new coal-permeability model for uniaxial strain and constant confining stress conditions. The model is unique in that it explicitly considers fracture-matrix interaction during coal deformation processes and is based on a newly proposed internal-swelling stress concept. This concept is used to account for the impact of matrix swelling (or shrinkage) on fracture-aperture changes resulting from partial separation of matrix blocks by fractures that do not completely cut through the whole matrix. The proposed permeability model is evaluated with data from three Valencia Canyon coalbed wells in the San Juan Basin, where increased permeability has been observed during CH{sub 4} gas production, as well as with published data from laboratory tests. Model results are generally in good agreement with observed permeability changes. The importance of fracture-matrix interaction in determining coal permeability, demonstrated in this work using relatively simple stress conditions, underscores the need for a dual-continuum (fracture and matrix) mechanical approach to rigorously capture coal-deformation processes under complex stress conditions, as well as the coupled flow and transport processes in coal seams.

  16. Sealing efficiency of an argillite-bentonite plug subjected to gas pressure, in the context of deep underground nuclear waste storage

    International Nuclear Information System (INIS)

    Liu, Jiang-Feng

    2013-01-01

    In France, the deep underground nuclear waste repository consists of a natural barrier (in an argillaceous rock named argillite), associated to artificial barriers, including plugs of swelling clay (bentonite)-sand for tunnel sealing purposes. The main objective of this thesis is to assess the sealing efficiency of the bentonite-sand plug in contact with argillite, in presence of both water and gas pressures. To assess the sealing ability of partially water-saturated bentonite/sand plugs, their gas permeability is measured under varying confining pressure (up to 12 MPa). It is observed that tightness to gas is achieved under confinement greater than 9 MPa for saturation levels of at least 86-91%. We than assess the sealing efficiency of the bentonite-sand plug placed in a tube of argillite or of Plexiglas-aluminium (with a smooth or a rough interface). The presence of pressurized gas affects the effective swelling pressure at values P gas from 4 MPa. Continuous gas breakthrough of fully water-saturated bentonite-sand plugs is obtained for gas pressures on the order of full swelling pressure (7-8 MPa), whenever the plug is applied along a smooth interface. Whenever a rough interface is used in contact with the bentonite-sand plug, a gas pressure significantly greater than its swelling pressure is needed for gas to pass continuously. Gas breakthrough tests show that the interface between plug/argillite or the argillite itself are two preferential pathways for gas migration, when the assembly is fully saturated. (author)

  17. The effect of intraocular gas and fluid volumes on intraocular pressure.

    Science.gov (United States)

    Simone, J N; Whitacre, M M

    1990-02-01

    Large increases in the intraocular pressure (IOP) of postoperative gas-containing eyes may require the removal of gas or fluid to reduce the IOP to the normal range. Application of the ideal gas law to Friedenwald's equation provides a mathematical model of the relationship between IOP, intraocular gas and fluid volumes, and the coefficient of scleral rigidity. This mathematic model shows that removal of a given volume of gas or fluid produces an identical decrease in IOP and that the more gas an eye contains, the greater the volume reduction necessary to reduce the pressure. Application of the model shows that the effective coefficient of scleral rigidity is low (mean K, 0.0021) in eyes with elevated IOP that have undergone vitrectomy and retinal cryopexy and very low (mean K, 0.0013) in eyes with elevated IOP that have undergone placement of a scleral buckle and band. By using the appropriate mean coefficient of rigidity, the volume of material to be aspirated to produce a given decrease in IOP can be predicted with clinically useful accuracy.

  18. Characterizing hydraulic fractures in shale gas reservoirs using transient pressure tests

    Directory of Open Access Journals (Sweden)

    Cong Wang

    2015-06-01

    This work presents an unconventional gas reservoir simulator and its application to quantify hydraulic fractures in shale gas reservoirs using transient pressure data. The numerical model incorporates most known physical processes for gas production from unconventional reservoirs, including two-phase flow of liquid and gas, Klinkenberg effect, non-Darcy flow, and nonlinear adsorption. In addition, the model is able to handle various types and scales of fractures or heterogeneity using continuum, discrete or hybrid modeling approaches under different well production conditions of varying rate or pressure. Our modeling studies indicate that the most sensitive parameter of hydraulic fractures to early transient gas flow through extremely low permeability rock is actually the fracture-matrix contacting area, generated by fracturing stimulation. Based on this observation, it is possible to use transient pressure testing data to estimate the area of fractures generated from fracturing operations. We will conduct a series of modeling studies and present a methodology using typical transient pressure responses, simulated by the numerical model, to estimate fracture areas created or to quantity hydraulic fractures with traditional well testing technology. The type curves of pressure transients from this study can be used to quantify hydraulic fractures in field application.

  19. Carbon nanotube- and carbon fiber-reinforcement of ethylene-octene copolymer membranes for gas and vapor separation.

    Science.gov (United States)

    Sedláková, Zuzana; Clarizia, Gabriele; Bernardo, Paola; Jansen, Johannes Carolus; Slobodian, Petr; Svoboda, Petr; Kárászová, Magda; Friess, Karel; Izak, Pavel

    2014-01-03

    Gas and vapor transport properties were studied in mixed matrix membranes containing elastomeric ethylene-octene copolymer (EOC or poly(ethylene-co-octene)) with three types of carbon fillers: virgin or oxidized multi-walled carbon nanotubes (CNTs) and carbon fibers (CFs). Helium, hydrogen, nitrogen, oxygen, methane, and carbon dioxide were used for gas permeation rate measurements. Vapor transport properties were studied for the aliphatic hydrocarbon (hexane), aromatic compound (toluene), alcohol (ethanol), as well as water for the representative samples. The mechanical properties and homogeneity of samples was checked by stress-strain tests. The addition of virgin CNTs and CFs improve mechanical properties. Gas permeability of EOC lies between that of the more permeable PDMS and the less permeable semi-crystalline polyethylene and polypropylene. Organic vapors are more permeable than permanent gases in the composite membranes, with toluene and hexane permeabilities being about two orders of magnitude higher than permanent gas permeability. The results of the carbon-filled membranes offer perspectives for application in gas/vapor separation with improved mechanical resistance.

  20. Carbon Nanotube- and Carbon Fiber-Reinforcement of Ethylene-Octene Copolymer Membranes for Gas and Vapor Separation

    Directory of Open Access Journals (Sweden)

    Zuzana Sedláková

    2014-01-01

    Full Text Available Gas and vapor transport properties were studied in mixed matrix membranes containing elastomeric ethylene-octene copolymer (EOC or poly(ethylene-co-octene with three types of carbon fillers: virgin or oxidized multi-walled carbon nanotubes (CNTs and carbon fibers (CFs. Helium, hydrogen, nitrogen, oxygen, methane, and carbon dioxide were used for gas permeation rate measurements. Vapor transport properties were studied for the aliphatic hydrocarbon (hexane, aromatic compound (toluene, alcohol (ethanol, as well as water for the representative samples. The mechanical properties and homogeneity of samples was checked by stress-strain tests. The addition of virgin CNTs and CFs improve mechanical properties. Gas permeability of EOC lies between that of the more permeable PDMS and the less permeable semi-crystalline polyethylene and polypropylene. Organic vapors are more permeable than permanent gases in the composite membranes, with toluene and hexane permeabilities being about two orders of magnitude higher than permanent gas permeability. The results of the carbon-filled membranes offer perspectives for application in gas/vapor separation with improved mechanical resistance.

  1. Gas separation techniques in nuclear facilities

    International Nuclear Information System (INIS)

    Hioki, Hideaki; Morisue, Tetsuo; Ohno, Masayoshi

    1983-01-01

    The literatures concerning the gas separation techniques which are applied to the waste gases generated from nuclear power plants and nuclear fuel reprocessing plants, uranium enrichment and the instrumentation of nuclear facilities are reviewed. The gas permeability and gas separation performance of membranes are discussed in terms of rare gas separation. The investigation into the change of the gas permeability and mechanical properties of membranes with exposure to radiation is reported. The theoretical investigation of the separating cells used for the separation of rare gas and the development of various separating cells are described, and the theoretical and experimental investigations concerning rare gas separation using cascades are described. The application of membrane method to nuclear facilities is explained showing the examples of uranium enrichment, the treatment of waste gases from nuclear reactor buildings and nuclear fuel reprocessing plants, the monitoring of low level β-emitters in stacks, the detection of failed fuels and the detection of water leak in fast breeder reactors. (Yoshitake, I.)

  2. Keratomycosis due to Tintelnotia destructans refractory to common therapy treated successfully with systemic and local terbinafine in combination with polyhexamethylene biguanide.

    Science.gov (United States)

    Behrens-Baumann, Wolfgang J; Hofmüller, Wolfram; Tammer, Ina; Tintelnot, Kathrin

    2018-04-28

    To report on a wearer of rigid gas-permeable contact lenses with a keratomycosis due to Tintelnotia-a new genus of Phaeosphaeriaceae-treated with terbinafine and polyhexamethylene biguanide. Chart review of a patient with fungal keratitis treated additionally with systemic and topical terbinafine 0.25% after symptoms increased under conventional antimycotic therapy with voriconazole. Antifungal susceptibility had been tested in vitro. After starting an additional treatment with systemic and topical terbinafine, the severe corneal infection was sufficiently resolved. The drug was well tolerated without any neurological, dermatological or gastroenterological problems. Terbinafine revealed a marked in vitro antifungal activity of 0.12 µg/ml. The fungus was identified as Tintelnotia destructans. Terbinafine might be considered as a therapeutic option in severe cases of fungal keratitis refractory to common antifungal therapy.

  3. Pore network modelling of heavy oil depressurization : a parametric study of factors affecting critical gas saturation and three-phase relative permeabilities

    Energy Technology Data Exchange (ETDEWEB)

    Bondino, I.; McDougall, S.D. [Heriot-Watt Univ., Edinburgh, Scotland (United Kingdom); Hamon, G. [TotalFina Elf Exploration and Production (France)

    2002-07-01

    A review of how the bubble nucleation process affects the efficiency of heavy oil recovery was presented along with a discussion regarding a pore-scale simulator technique to depressurize heavy oil systems. A light oil depressurization simulation is also presented in which a straightforward instantaneous nucleation (IN) model and a more intricate progressive nucleation (PN) model have been used. Simulation results are compared to those derived from the heavy oil systems. The nucleation of bubbles, their growth by solute diffusion and expansion, plus the final stages of coalescence migration and production are the main steps in the depressurization process which were accounted for in a 3-phase simulator. The model can also determine the impact of bubble density and gas-oil diffusion coefficient on critical gas saturation and 3-phase relative permeability. The difference in results for light and heavy oils was also highlighted. In the first scenario, the evolution of gas was characterized by embryonic bubbles that are quickly and randomly nucleated once bubble-point pressure is reached. A stochastic algorithm was developed for PN from experimental observations. IN and PN observations were not necessarily contradictory. It was determined that the high interfacial tension of heavy oils leads to a more compact, capillary-dominated pattern of gas evolution compared to light oils, resulting in improved recoveries for heavy oil systems. 23 refs., 6 tabs., 23 figs.

  4. Upper Paleozoic coal measures and unconventional natural gas systems of the Ordos Basin, China

    Directory of Open Access Journals (Sweden)

    Xuan Tang

    2012-11-01

    Full Text Available Upper Paleozoic coal measures in the Ordos Basin consist of dark mudstone and coal beds and are important source rocks for gas generation. Gas accumulations include coal-bed methane (CBM, tight gas and conventional gas in different structural areas. CBM accumulations are mainly distributed in the marginal area of the Ordos Basin, and are estimated at 3.5 × 1012 m3. Tight gas accumulations exist in the middle part of the Yishan Slope area, previously regarded as the basin-centered gas system and now considered as stratigraphic lithologic gas reservoirs. This paper reviews the characteristics of tight gas accumulations: poor physical properties (porosity < 8%, permeability < 0.85 × 10−3 μm2, abnormal pressure and the absence of well-defined gas water contacts. CBM is a self-generation and self-reservoir, while gas derived from coal measures migrates only for a short distance to accumulate in a tight reservoir and is termed near-generation and near-reservoir. Both CBM and tight gas systems require source rocks with a strong gas generation ability that extends together over wide area. However, the producing area of the two systems may be significantly different.

  5. Castor oil and mineral oil nanoemulsion: development and compatibility with a soft contact lens.

    Science.gov (United States)

    Katzer, Tatiele; Chaves, Paula; Bernardi, Andressa; Pohlmann, Adriana R; Guterres, Silvia S; Beck, Ruy C R

    2014-03-01

    The non-invasive ophthalmic therapy has a drawback: low residence time in the eye socket. Nanoparticles and contact lenses have been studied as promising ocular drug delivery systems. To develop a nanoemulsion and evaluate its compatibility with a soft contact lens as a potential strategy for ocular delivery. The formulations were developed by spontaneous emulsification and fully characterized. Two drops of nanoemulsion were instilled on the surface of a commercial contact lens and its transparency was measured using a UV-Vis spectrophotometer. Before and after the instillation of the drops, the morphology (scanning electron microscopy - SEM) and ion permeability of the lenses were analyzed. The formulations had a mean particle size of 234 nm, polydispersity below 0.16, zeta potential of -8.56 ± 3.49 mV, slightly acid pH, viscosity ≈1.2 mPa s(-1) and spherical-shaped particles. Nanoemulsion was non-irritant (hen's egg test-chorioallantoic membrane), which was confirmed by the cytotoxicity studies in the SIRC cell cultures. After instillation, SEM analysis showed nanodroplets inside and on the surface of the lenses, although their transparency remained near 100%. No significant differences were found between lens ion permeability coefficients before and after instillation. Formulations presented appropriate physicochemical characteristics and suitability for ocular application. The contact lens remained transparent and ion-permeable after association with the formulation.

  6. On contact modelling in isogeometric analysis

    Science.gov (United States)

    Cardoso, R. P. R.; Adetoro, O. B.

    2017-11-01

    IsoGeometric Analysis (IGA) has proved to be a reliable numerical tool for the simulation of structural behaviour and fluid mechanics. The main reasons for this popularity are essentially due to: (i) the possibility of using higher order polynomials for the basis functions; (ii) the high convergence rates possible to achieve; (iii) the possibility to operate directly on CAD geometry without the need to resort to a mesh of elements. The major drawback of IGA is the non-interpolatory characteristic of the basis functions, which adds a difficulty in handling essential boundary conditions and makes it particularly challenging for contact analysis. In this work, the IGA is expanded to include frictionless contact procedures for sheet metal forming analyses. Non-Uniform Rational B-Splines (NURBS) are going to be used for the modelling of rigid tools as well as for the modelling of the deformable blank sheet. The contact methods developed are based on a two-step contact search scheme, where during the first step a global search algorithm is used for the allocation of contact knots into potential contact faces and a second (local) contact search scheme where point inversion techniques are used for the calculation of the contact penetration gap. For completeness, elastoplastic procedures are also included for a proper description of the entire IGA of sheet metal forming processes.

  7. Rigidity and symmetry

    CERN Document Server

    Weiss, Asia; Whiteley, Walter

    2014-01-01

    This book contains recent contributions to the fields of rigidity and symmetry with two primary focuses: to present the mathematically rigorous treatment of rigidity of structures, and to explore the interaction of geometry, algebra, and combinatorics. Overall, the book shows how researchers from diverse backgrounds explore connections among the various discrete structures with symmetry as the unifying theme.  Contributions present recent trends and advances in discrete geometry, particularly in the theory of polytopes. The rapid development of abstract polytope theory has resulted in a rich theory featuring an attractive interplay of methods and tools from discrete geometry, group theory, classical geometry, hyperbolic geometry and topology.  The volume will also be a valuable source as an introduction to the ideas of both combinatorial and geometric rigidity theory and its applications, incorporating the surprising impact of symmetry. It will appeal to students at both the advanced undergraduate and gradu...

  8. Pore Structure and Limit Pressure of Gas Slippage Effect in Tight Sandstone

    Science.gov (United States)

    You, Lijun; Xue, Kunlin; Kang, Yili; Liao, Yi

    2013-01-01

    Gas slip effect is an important mechanism that the gas flow is different from liquid flow in porous media. It is generally considered that the lower the permeability in porous media is, the more severe slip effect of gas flow will be. We design and then carry out experiments with the increase of backpressure at the outlet of the core samples based on the definition of gas slip effect and in view of different levels of permeability of tight sandstone reservoir. This study inspects a limit pressure of the gas slip effect in tight sandstones and analyzes the characteristic parameter of capillary pressure curves. The experimental results indicate that gas slip effect can be eliminated when the backpressure reaches a limit pressure. When the backpressure exceeds the limit pressure, the measured gas permeability is a relatively stable value whose range is less than 3% for a given core sample. It is also found that the limit pressure increases with the decreasing in permeability and has close relation with pore structure of the core samples. The results have an important influence on correlation study on gas flow in porous medium, and are beneficial to reduce the workload of laboratory experiment. PMID:24379747

  9. Gas migration in argillaceous rock

    International Nuclear Information System (INIS)

    Alonso, E. E.; Olivella, S.

    2007-01-01

    The intrinsic gas permeability of fractured argillaceous rocks depends on the current structure of micro-cracks and fissures of the rock. They are a consequence of the initial state and the subsequent deformations induced by stress and gas pressure changes. Stresses are also coupled with fluid pressures and, therefore, gas flow and mechanical behaviour are intensely coupled. Laboratory experiments, aimed at determining intrinsic permeability, show the relevant effect of volumetric deformations induced by isotropic, as well as deviatoric stress changes. The relevance, in practice, of the flow-mechanical coupling is illustrated by means of some results obtained during the performance of the drift scale test (DST) in fractured tuff in the Yucca Mountain facility. The technique of embedding discontinuities in continuum thermo-hydro-mechanical elements is capable of reproducing observed features of gas flow migration in clayey rocks. An example is described. It is believed that the developed approach provides a powerful computational procedure to handle complex gas phenomena in clayey rocks. (author)

  10. Apparent contact angle and contact angle hysteresis on liquid infused surfaces.

    Science.gov (United States)

    Semprebon, Ciro; McHale, Glen; Kusumaatmaja, Halim

    2016-12-21

    We theoretically investigate the apparent contact angle and contact angle hysteresis of a droplet placed on a liquid infused surface. We show that the apparent contact angle is not uniquely defined by material parameters, but also has a dependence on the relative size between the droplet and its surrounding wetting ridge formed by the infusing liquid. We derive a closed form expression for the contact angle in the limit of vanishing wetting ridge, and compute the correction for small but finite ridge, which corresponds to an effective line tension term. We also predict contact angle hysteresis on liquid infused surfaces generated by the pinning of the contact lines by the surface corrugations. Our analytical expressions for both the apparent contact angle and contact angle hysteresis can be interpreted as 'weighted sums' between the contact angles of the infusing liquid relative to the droplet and surrounding gas phases, where the weighting coefficients are given by ratios of the fluid surface tensions.

  11. Tear exchange and contact lenses: a review.

    Science.gov (United States)

    Muntz, Alex; Subbaraman, Lakshman N; Sorbara, Luigina; Jones, Lyndon

    2015-01-01

    Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses. This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  12. Experimental study of very low permeability rocks using a high accuracy permeameter

    International Nuclear Information System (INIS)

    Larive, Elodie

    2002-01-01

    The measurement of fluid flow through 'tight' rocks is important to provide a better understanding of physical processes involved in several industrial and natural problems. These include deep nuclear waste repositories, management of aquifers, gas, petroleum or geothermal reservoirs, or earthquakes prevention. The major part of this work consisted of the design, construction and use of an elaborate experimental apparatus allowing laboratory permeability measurements (fluid flow) of very low permeability rocks, on samples at a centimetric scale, to constrain their hydraulic behaviour at realistic in-situ conditions. The accuracy permeameter allows the use of several measurement methods, the steady-state flow method, the transient pulse method, and the sinusoidal pore pressure oscillation method. Measurements were made with the pore pressure oscillation method, using different waveform periods, at several pore and confining pressure conditions, on different materials. The permeability of one natural standard, Westerly granite, and an artificial one, a micro-porous cement, were measured, and results obtained agreed with previous measurements made on these materials showing the reliability of the permeameter. A study of a Yorkshire sandstone shows a relationship between rock microstructure, permeability anisotropy and thermal cracking. Microstructure, porosity and permeability concepts, and laboratory permeability measurements specifications are presented, the permeameter is described, and then permeability results obtained on the investigated materials are reported [fr

  13. Preliminary formation analysis for compressed air energy storage in depleted natural gas reservoirs :

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, William Payton

    2013-06-01

    The purpose of this study is to develop an engineering and operational understanding of CAES performance for a depleted natural gas reservoir by evaluation of relative permeability effects of air, water and natural gas in depleted natural gas reservoirs as a reservoir is initially depleted, an air bubble is created, and as air is initially cycled. The composition of produced gases will be evaluated as the three phase flow of methane, nitrogen and brine are modeled. The effects of a methane gas phase on the relative permeability of air in a formation are investigated and the composition of the produced fluid, which consists primarily of the amount of natural gas in the produced air are determined. Simulations of compressed air energy storage (CAES) in depleted natural gas reservoirs were carried out to assess the effect of formation permeability on the design of a simple CAES system. The injection of N2 (as a proxy to air), and the extraction of the resulting gas mixture in a depleted natural gas reservoir were modeled using the TOUGH2 reservoir simulator with the EOS7c equation of state. The optimal borehole spacing was determined as a function of the formation scale intrinsic permeability. Natural gas reservoir results are similar to those for an aquifer. Borehole spacing is dependent upon the intrinsic permeability of the formation. Higher permeability allows increased injection and extraction rates which is equivalent to more power per borehole for a given screen length. The number of boreholes per 100 MW for a given intrinsic permeability in a depleted natural gas reservoir is essentially identical to that determined for a simple aquifer of identical properties. During bubble formation methane is displaced and a sharp N2methane boundary is formed with an almost pure N2 gas phase in the bubble near the borehole. During cycling mixing of methane and air occurs along the boundary as the air bubble boundary moves. The extracted gas mixture changes as a

  14. A vibrating thermoelastic plate in a contact with an obstacle

    Czech Academy of Sciences Publication Activity Database

    Bock, I.; Jarušek, Jiří

    2015-01-01

    Roč. 63, č. 1 (2015), s. 39-52 ISSN 1210-3195 R&D Projects: GA ČR(CZ) GAP201/12/0671 Institutional support: RVO:67985840 Keywords : thermoelastic plate * unilateral dynamic contact * rigid obstacle Subject RIV: BA - General Mathematics http://tatra.mat.savba.sk/paper.php?id_paper=1244

  15. Birationally rigid varieties

    CERN Document Server

    Pukhlikov, Aleksandr

    2013-01-01

    Birational rigidity is a striking and mysterious phenomenon in higher-dimensional algebraic geometry. It turns out that certain natural families of algebraic varieties (for example, three-dimensional quartics) belong to the same classification type as the projective space but have radically different birational geometric properties. In particular, they admit no non-trivial birational self-maps and cannot be fibred into rational varieties by a rational map. The origins of the theory of birational rigidity are in the work of Max Noether and Fano; however, it was only in 1970 that Iskovskikh and Manin proved birational superrigidity of quartic three-folds. This book gives a systematic exposition of, and a comprehensive introduction to, the theory of birational rigidity, presenting in a uniform way, ideas, techniques, and results that so far could only be found in journal papers. The recent rapid progress in birational geometry and the widening interaction with the neighboring areas generate the growing interest ...

  16. Ground water conditions and the relation to uranium deposits in the Gas Hills area, Fremont and Natrona Counties, Wyoming

    International Nuclear Information System (INIS)

    Marks, L.Y.

    1978-03-01

    As ground water apparently leaches, transports, and deposits uranium in the Gas Hills area, central Wyoming, it is important to understand its distribution, movement, and relation to geology and ore bodies. Water table maps were prepared of the Wind River Basin; the most detailed work was in the Gas Hills area. The water table in the Gas Hills area slopes downward to the northwest, ranges in depth from near the ground surface to more than 200 feet, and has seasonal fluctuation of about five feet. Perched water tables and artesian conditions occur locally. The oxidized-unoxidized rock contact is probably roughly parallel to the water table, and averages about 25 feet above it; although locally the two surfaces are considerably farther apart and the oxidized-unoxidized contact may be below the water table. In many places the gradient of the water table changes near the contact between rocks of different permeability. It is conformable with the structure at some anticlines and its gradient changes abruptly near some faults. Most above-normal concentrations of uranium occur at local water table depressions or at water table terraces where the gradient of the water table flattens. At these places, the uraniferous ground water is slowed and is in contact with the reducing agents in the rocks for a relatively long time. This may allow reduction of soluble transported uranium (U +6 ) to insoluble U +4 ) so that uranium is precipitated

  17. Permeability and Microstructure of Suspension Plasma-Sprayed YSZ Electrolytes for SOFCs on Various Substrates

    Science.gov (United States)

    Marr, Michael; Kesler, Olivera

    2012-12-01

    Yttria-stabilized zirconia electrolyte coatings for solid oxide fuel cells were deposited by suspension plasma spraying using a range of spray conditions and a variety of substrates, including finely structured porous stainless steel disks and cathode layers on stainless steel supports. Electrolyte permeability values and trends were found to be highly dependent on which substrate was used. The most gas-tight electrolyte coatings were those deposited directly on the porous metal disks. With this substrate, permeability was reduced by increasing the torch power and reducing the stand-off distance to produce dense coating microstructures. On the substrates with cathodes, electrolyte permeability was reduced by increasing the stand-off distance, which reduced the formation of segmentation cracks and regions of aligned and concentrated porosity. The formation mechanisms of the various permeability-related coating features are discussed and strategies for reducing permeability are presented. The dependences of electrolyte deposition efficiency and surface roughness on process conditions and substrate properties are also presented.

  18. Effect of chain rigidity on network architecture and deformation behavior of glassy polymer networks

    Science.gov (United States)

    Knowles, Kyler Reser

    Processing carbon fiber composite laminates creates molecular-level strains in the thermoset matrix upon curing and cooling which can lead to failures such as geometry deformations, micro-cracking, and other issues. It is known strain creation is attributed to the significant volume and physical state changes undergone by the polymer matrix throughout the curing process, though storage and relaxation of cure-induced strains remain poorly understood. This dissertation establishes two approaches to address the issue. The first establishes testing methods to simultaneously measure key volumetric properties of a carbon fiber composite laminate and its polymer matrix. The second approach considers the rigidity of the polymer matrix in regards to strain storage and relaxation mechanisms which ultimately control composite performance throughout manufacturing and use. Through the use of a non-contact, full-field strain measurement technique known as digital image correlation (DIC), we describe and implement useful experiments which quantify matrix and composite parameters necessary for simulation efforts and failure models. The methods are compared to more traditional techniques and show excellent correlation. Further, we established relationships which represent matrix-fiber compatibility in regards to critical processing constraints. The second approach involves a systematic study of epoxy-amine networks which are chemically-similar but differ in chain segment rigidity. Prior research has investigated the isomer effect of glassy polymers, showing sizeable differences in thermal, volumetric, physical, and mechanical properties. This work builds on these themes and shows the apparent isomer effect is rather an effect of chain rigidity. Indeed, it was found that structurally-dissimilar polymer networks exhibit very similar properties as a consequence of their shared average network rigidity. Differences in chain packing, as a consequence of chain rigidity, were shown to

  19. Copolymers for soft hydrophilic contact lenses: development and investigations

    International Nuclear Information System (INIS)

    Schwach, G.W.

    1978-05-01

    Low esters of methacrylic acid which may be polymerized by different methods are used predominantly for producing soft hydrophilic contact lenses. Compounds of the vinyl-type often are added to improve the optical and mechanical qualities. Composition as well as possibilities of polymerization by irradiation were tested so long until copolymers were found which finally allowed the production of soft hydrophilic contact lenses. Swelling characteristics and permeability of the different elastomeres are to be investigated in order to guarantee sufficient compatibility of contact lenses. Contamination of the lens materials by microorganisms is also a point of special interest. The effects on the hydrophilic contact lens-copolymers by different substances used for cleaning and storage solutions have been investigated as well. (author)

  20. Tunable Gas Permeability of Polymer-Clay Nano Brick Wall Thin Film Assemblies

    Science.gov (United States)

    Gamboa, Daniel; Priolo, Morgan; Grunlan, Jaime

    2010-03-01

    Thin films of anionic natural montmorrilonite (MMT) clay and cationic polyethylenimine (PEI) have been produced by alternately dipping a plastic substrate into dilute aqueous mixtures containing each ingredient. After 40 polymer-clay layers have been deposited, the resulting transparent film exhibits an oxygen transmission rate (OTR) below 0.35 cm^3/m^2 . day when the pH of PEI solution is 10. This low permeability is due to a brick wall nanostructure comprised of completely exfoliated clay bricks in polymeric mortar. This brick wall creates an extremely tortuous path at thicknesses below 250 nm and clay concentration above 80 wt%. A 70-bilayer PEI-MMT assembly has an undetectable OTR (< 0.005 cm^3/m^2 . day), which equates to a permeability below SiOx when multiplied by its film thickness of 231 nm. With optical transparency greater than 86% and the ability to be microwaved, these thin film composites are good candidates for flexible electronics packaging and foil replacement for food.

  1. Permeability coefficient of proton irradiated polyethylene terephatalate thin films

    International Nuclear Information System (INIS)

    Bassani, L.C.; Santos, W.M.S.; Marechal, B.

    1983-01-01

    The principle of operation of an apparatus developed to study gas permation through thin films is described and the measurement method is discussed. Use is made of diffusion theory to obtain a expression for the permeability coefficient as a function of the rate of increase of the pressure in the receiving volume. The Gibbs function for permeation of Helium through Polyethylene Terephtalate (P.E.T.) is determined. The permeability coefficient of Helium is found to increase significantly with the range of the implanted protons although the incident charge has been kept constant. The hypothesis of structural modifications of the proton implanted P.E.T. seems to be confirmed by small angles X-rays scattering experiments on the irradiated samples. (Author) [pt

  2. Effect of porous material heating on the drag force of a cylinder with gas-permeable porous inserts in a supersonic flow

    Science.gov (United States)

    Mironov, S. G.; Poplavskaya, T. V.; Kirilovskiy, S. V.

    2017-10-01

    The paper presents the results of an experimental investigation of supersonic flow around a solid cylinder with a gas-permeable porous insert on its front end and of supersonic flow around a hollow cylinder with internal porous inserts in the presence of heating of the porous material. The experiments were performed in a supersonic wind tunnel with Mach number 4.85 and 7 with porous inserts of cellular-porous nickel. The results of measurements on the filtration stand of the air filtration rate through the cellular-porous nickel when it is heated are also shown. For a number of experiments, numerical modeling based on the skeletal model of a cellular-porous material was carried out.

  3. Rigid multipodal platforms for metal surfaces

    Directory of Open Access Journals (Sweden)

    Michal Valášek

    2016-03-01

    Full Text Available In this review the recent progress in molecular platforms that form rigid and well-defined contact to a metal surface are discussed. Most of the presented examples have at least three anchoring units in order to control the spatial arrangement of the protruding molecular subunit. Another interesting feature is the lateral orientation of these foot structures which, depending on the particular application, is equally important as the spatial arrangement of the molecules. The numerous approaches towards assembling and organizing functional molecules into specific architectures on metal substrates are reviewed here. Particular attention is paid to variations of both, the core structures and the anchoring groups. Furthermore, the analytical methods enabling the investigation of individual molecules as well as monomolecular layers of ordered platform structures are summarized. The presented multipodal platforms bearing several anchoring groups form considerably more stable molecule–metal contacts than corresponding monopodal analogues and exhibit an enlarged separation of the functional molecules due to the increased footprint, as well as restrict tilting of the functional termini with respect to the metal surface. These platforms are thus ideally suited to tune important properties of the molecule–metal interface. On a single-molecule level, several of these platforms enable the control over the arrangement of the protruding rod-type molecular structures (e.g., molecular wires, switches, rotors, sensors with respect to the surface of the substrate.

  4. Nonsmooth Newton method for Fischer function reformulation of contact force problems for interactive rigid body simulation

    DEFF Research Database (Denmark)

    Silcowitz, Morten; Niebe, Sarah Maria; Erleben, Kenny

    2009-01-01

    contact response. In this paper, we present a new approach to contact force determination. We reformulate the contact force problem as a nonlinear root search problem, using a Fischer function. We solve this problem using a generalized Newton method. Our new Fischer - Newton method shows improved...... qualities for specific configurations where the most widespread alternative, the Projected Gauss-Seidel method, fails. Experiments show superior convergence properties of the exact Fischer - Newton method....

  5. Origin and spatial distribution of gas at seismogenic depths of the San Andreas Fault from drill-mud gas analysis

    International Nuclear Information System (INIS)

    Wiersberg, Thomas; Erzinger, Joerg

    2008-01-01

    Data are presented on the molecular composition of drill-mud gas from the lower sedimentary section (1800-3987 m) of the SAFOD (San Andreas Fault Observatory at Depth) Main Hole measured on-line during drilling, as well as C and H isotope data from off-line mud gas samples. Hydrocarbons, H 2 and CO 2 are the most abundant non-atmospheric gases in drill-mud when drilling seismogenic zones. Gas influx into the well at depth is related to the lithology and permeability of the drilled strata: larger formation gas influx was detected when drilling through organic-rich shales and permeable sandstones. The SAF (San Andreas Fault), encountered between approximately 3100 m and 3450 m borehole depth, is generally low in gas, but is encompassed by two gas-rich zones (2700-2900 m and below 3550 m) at the fault margins with enhanced 222 Rn activities and distinct gas compositions. Within the fault, two interstratified gas-rich lenses (3150-3200 m and 3310-3340 m) consist of CO 2 and hydrocarbons (upper zone), but almost exclusively of hydrocarbons (lower zone). The isotopic composition indicates an organic source of hydrocarbons and CO 2 in the entire sedimentary section of the well. Hydrocarbons in sedimentary strata are partly of microbial origin down to ∼2500 m borehole depth. The contribution of thermogenic gas increases between ∼2500 m and 3200 m. Below ∼3200 m, hydrocarbons fully derive from thermal degradation of organic matter. The lack of H 2 in the center of the fault and the high concentration of H 2 in the fractured zones at the fault margins are consistent with H 2 formation by interaction of water with fresh silica mineral surfaces generated by tectonic activities, however, this needs to be verified by laboratory experiments. Based on these studies, it is concluded that the fault zone margins consist of strata with enhanced permeability, separated by a low-permeability fault center

  6. PVC pipes in gas distribution: still going strong!

    NARCIS (Netherlands)

    Hermkens, Rene; Wolters, Mannes; Weller, Jeroen; Visser, Roy; Davidovski, Z.; Belloir, P.; Fumire, J.

    2008-01-01

    In the Netherlands (impact-modified) PVC is the preferred material for low-pressure (30 and 100 mbar) gas distribution systems. More than 50% of the total length (about 122,000 km) of this system is rigid PVC or impact-modified PVC. The installation of rigid PVC (uPVC) pipelines started about 50

  7. Rigidity of Glasses and Macromolecules

    Science.gov (United States)

    Thorpe, M. F.

    1998-03-01

    The simple yet powerful ideas of percolation theory have found their way into many different areas of research. In this talk we show how RIGIDITY PERCOLATION can be studied at a similar level of sophistication, using a powerful new program THE PEBBLE GAME (D. J. Jacobs and M. F. Thorpe, Phys. Rev. E) 53, 3682 (1996). that uses an integer algorithm. This program can analyse the rigidity of two and three dimensional networks containing more than one million bars and joints. We find the total number of floppy modes, and find the critical behavior as the network goes from floppy to rigid as more bars are added. We discuss the relevance of this work to network glasses, and how it relates to experiments that involve the mechanical properties like hardness and elasticity of covalent glassy networks like Ge_xAs_ySe_1-x-y and dicuss recent experiments that suggest that the rigidity transition may be first order (Xingwei Feng, W. J.Bresser and P. Boolchand, Phys. Rev. Lett 78), 4422 (1997).. This approach is also useful in macromolecules and proteins, where detailed information about the rigid domain structure can be obtained.

  8. ScienceHub data set for "Detection of semi-volatile organic compounds in permeable pavement infiltrate"

    Data.gov (United States)

    U.S. Environmental Protection Agency — Observed permeable pavement infiltrate concentrations by EPA (1996) method 8270C Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS) with...

  9. Rigidity-tuning conductive elastomer

    Science.gov (United States)

    Shan, Wanliang; Diller, Stuart; Tutcuoglu, Abbas; Majidi, Carmel

    2015-06-01

    We introduce a conductive propylene-based elastomer (cPBE) that rapidly and reversibly changes its mechanical rigidity when powered with electrical current. The elastomer is rigid in its natural state, with an elastic (Young’s) modulus of 175.5 MPa, and softens when electrically activated. By embedding the cPBE in an electrically insulating sheet of polydimethylsiloxane (PDMS), we create a cPBE-PDMS composite that can reversibly change its tensile modulus between 37 and 1.5 MPa. The rigidity change takes ˜6 s and is initiated when a 100 V voltage drop is applied across the two ends of the cPBE film. This magnitude of change in elastic rigidity is similar to that observed in natural skeletal muscle and catch connective tissue. We characterize the tunable load-bearing capability of the cPBE-PDMS composite with a motorized tensile test and deadweight experiment. Lastly, we demonstrate the ability to control the routing of internal forces by embedding several cPBE-PDMS ‘active tendons’ into a soft robotic pneumatic bending actuator. Selectively activating the artificial tendons controls the neutral axis and direction of bending during inflation.

  10. Rigidity-tuning conductive elastomer

    International Nuclear Information System (INIS)

    Shan, Wanliang; Diller, Stuart; Tutcuoglu, Abbas; Majidi, Carmel

    2015-01-01

    We introduce a conductive propylene-based elastomer (cPBE) that rapidly and reversibly changes its mechanical rigidity when powered with electrical current. The elastomer is rigid in its natural state, with an elastic (Young’s) modulus of 175.5 MPa, and softens when electrically activated. By embedding the cPBE in an electrically insulating sheet of polydimethylsiloxane (PDMS), we create a cPBE–PDMS composite that can reversibly change its tensile modulus between 37 and 1.5 MPa. The rigidity change takes ∼6 s and is initiated when a 100 V voltage drop is applied across the two ends of the cPBE film. This magnitude of change in elastic rigidity is similar to that observed in natural skeletal muscle and catch connective tissue. We characterize the tunable load-bearing capability of the cPBE–PDMS composite with a motorized tensile test and deadweight experiment. Lastly, we demonstrate the ability to control the routing of internal forces by embedding several cPBE–PDMS ‘active tendons’ into a soft robotic pneumatic bending actuator. Selectively activating the artificial tendons controls the neutral axis and direction of bending during inflation. (paper)

  11. Vertical dimensional stability and rigidity of occlusal registration materials.

    Science.gov (United States)

    Walker, Mary P; Wu, Edis; Heckman, M Elizabeth; Alderman, Nicholas

    2009-01-01

    Dimensionally accurate occlusal registration records are essential for restorative dentistry; moreover, since records are not used immediately or may be used more than once, the registration material should exhibit accuracy over time (a concept known as dimensional stability). It has been speculated that materials with increased hardness or rigidity should produce more accurate registration records due to an increased resistance to distortion. This study compared the rigidity and associated dimensional accuracy of a recently marketed bisacrylic occlusal registration material and a vinyl polysiloxane (VPS). Maxillary and mandibular typodont arches were mounted on a plasterless articulator from which teeth No. 3, 13, and 15 had been removed to simulate edentulous spaces. After preparing teeth No. 2, 4, 12, and 14 as bridge abutments, the remaining teeth were equilibrated selectively to produce even anterior contact. Four digital photographs were taken to make vertical interarch measurements at four locations (teeth No. 3, 7, 10, and 14). Following initial photos (controls), 10 interocclusal records were made using each registration material, with material placed only in the segments in which teeth were prepared. The records were used for mounting the maxillary arch against the mandibular arch after 48, 72, and 120 hours. There were significant effects on vertical dimensional change related to arch location, material, and mounting time. Both materials demonstrated significantly larger posterior vertical openings than anterior vertical openings, while the bisacrylate produced a larger posterior opening than VPS at 48 and 72 hours and a larger anterior opening at all mounting times. There also was a significant difference in hardness/rigidity due to material and measurement time; at all measurement times, bisacrylate exhibited a significantly higher hardness number.

  12. Sliding contact on the interface of elastic body and rigid surface using a single block Burridge-Knopoff model

    Science.gov (United States)

    Amireghbali, A.; Coker, D.

    2018-01-01

    Burridge and Knopoff proposed a mass-spring model to explore interface dynamics along a fault during an earthquake. The Burridge and Knopoff (BK) model is composed of a series of blocks of equal mass connected to each other by springs of same stiffness. The blocks also are attached to a rigid driver via another set of springs that pulls them at a constant velocity against a rigid substrate. They studied dynamics of interface for an especial case with ten blocks and a specific set of fault properties. In our study effects of Coulomb and rate-state dependent friction laws on the dynamics of a single block BK model is investigated. The model dynamics is formulated as a system of coupled nonlinear ordinary differential equations in state-space form which lends itself to numerical integration methods, e.g. Runge-Kutta procedure for solution. The results show that the rate and state dependent friction law has the potential of triggering dynamic patterns that are different from those under Coulomb law.

  13. Improved gas distributor for coating HTGR fuel particles

    International Nuclear Information System (INIS)

    Lackey, W.J.; Stinton, D.P.; Sease, J.D.

    1977-01-01

    The important criteria to be considered in design of the gas distributor are: (1) The distributor should ideally spread or disperse the gas over the full area of the coating chamber to maximize the particle gas contact area and thereby increase both particle circulation and the percentage of the input gas that ends up as coating. (2) The gas should not heat up during its passage through the distributor. Otherwise the gas would partially decompose prematurely, causing excessive coating deposition within or on the distributor. (3) The distributor should be designed to minimize accidental drainage of particles from the furnace and blowover of particles into the effluent system. (4) The distributor should be capable of depositing both carbon and SiC coatings of high quality as regards to density, preferred orientation, permeability, defective fraction, and other product attributes. (5) The distributor should be amenable to use with large particle charges and short turnaround times and be simple, inexpensive, and reliable. We have devised a simple distributor that incorporates the five criteria listed above. The new design is termed a blind-hole frit. All the gas passes through the thinned blind-hole regions, and thus the gas velocity is considerably higher than for a flat frit of uniform thickness. Because of its high velocity, the gas does not have time to reach a high enough temperature to cause deposition within the frit. Also most of the resistance to gas flow is provided by the porous distributor and not by the particle bed; therefore, localized variations of the quantity of particles above any particular gas inlet do not significantly alter the flow rate through that inlet

  14. Sliding contact fracture of dental ceramics: Principles and validation

    Science.gov (United States)

    Ren, Linlin; Zhang, Yu

    2014-01-01

    Ceramic prostheses are subject to sliding contact under normal and tangential loads. Accurate prediction of the onset of fracture at two contacting surfaces holds the key to greater long-term performance of these prostheses. In this study, building on stress analysis of Hertzian contact and considering fracture criteria for linear elastic materials, a constitutive fracture mechanics relation was developed to incorporate the critical fracture load with the contact geometry, coefficient of friction and material fracture toughness. Critical loads necessary to cause fracture under a sliding indenter were calculated from the constitutive equation, and compared with the loads predicted from elastic stress analysis in conjunction with measured critical load for frictionless normal contact—a semi-empirical approach. The major predictions of the models were calibrated with experimentally determined critical loads of current and future dental ceramics after contact with a rigid spherical slider. Experimental results conform with the trends predicted by the models. PMID:24632538

  15. Pressure-dependent pure- and mixed-gas permeation properties of Nafion®

    KAUST Repository

    Mukaddam, Mohsin Ahmed

    2016-04-20

    The permeation properties of Nafion® at 35 °C are presented for pure gases H2, N2, O2, CH4, CO2, C2H6 and C3H8, as a function of pressure between 2 and 20 atm. The effect of pressure on permeability and selectivity is analyzed to understand two observed phenomena: compression and plasticization. In pure-gas experiments, at increasing feed pressure, compression of the polymer matrix reduced the permeability of low-sorbing penetrants H2, N2, O2, and CH4. In contrast, permeabilities of more soluble penetrants CO2 and C2H6 increased by 18% and 46% respectively, as plasticization effects overcame compression effects. Permeability of C3H8 decreased slightly with increasing pressure up to 4.6 atm as a result of compression, then increased by 3-fold at 9 atm as a result of plasticization associated with high C3H8 solubility. Binary CO2/CH4 (50:50) mixed-gas experiments at total feed pressures up to 36 atm quantified the effect of CO2 plasticization on separation performance. At 10 atm CO2 partial pressure, CH4 permeability increased by 23% relative to its pure-gas value of 0.078 Barrer, while CO2 permeability decreased by 28%. Consequently, CO2/CH4 selectivity decreased to 19, i.e., 42% below its pure-gas value of 32.

  16. Study on Fluid-solid Coupling Mathematical Models and Numerical Simulation of Coal Containing Gas

    Science.gov (United States)

    Xu, Gang; Hao, Meng; Jin, Hongwei

    2018-02-01

    Based on coal seam gas migration theory under multi-physics field coupling effect, fluid-solid coupling model of coal seam gas was build using elastic mechanics, fluid mechanics in porous medium and effective stress principle. Gas seepage behavior under different original gas pressure was simulated. Results indicated that residual gas pressure, gas pressure gradient and gas low were bigger when original gas pressure was higher. Coal permeability distribution decreased exponentially when original gas pressure was lower than critical pressure. Coal permeability decreased rapidly first and then increased slowly when original pressure was higher than critical pressure.

  17. Contact dynamics math model

    Science.gov (United States)

    Glaese, John R.; Tobbe, Patrick A.

    1986-01-01

    The Space Station Mechanism Test Bed consists of a hydraulically driven, computer controlled six degree of freedom (DOF) motion system with which docking, berthing, and other mechanisms can be evaluated. Measured contact forces and moments are provided to the simulation host computer to enable representation of orbital contact dynamics. This report describes the development of a generalized math model which represents the relative motion between two rigid orbiting vehicles. The model allows motion in six DOF for each body, with no vehicle size limitation. The rotational and translational equations of motion are derived. The method used to transform the forces and moments from the sensor location to the vehicles' centers of mass is also explained. Two math models of docking mechanisms, a simple translational spring and the Remote Manipulator System end effector, are presented along with simulation results. The translational spring model is used in an attempt to verify the simulation with compensated hardware in the loop results.

  18. Analysis of the Behaviour of Semi Rigid Steel End Plate Connections

    Directory of Open Access Journals (Sweden)

    Bahaz A.

    2018-01-01

    Full Text Available The analysis of steel-framed building structures with full strength beam to column joints is quite standard nowadays. Buildings utilizing such framing systems are widely used in design practice. However, there is a growing recognition of significant benefits in designing joints as partial strength/semi-rigid. The design of joints within this partial strength/semi-rigid approach is becoming more and more popular. This requires the knowledge of the full nonlinear moment-rotation behaviour of the joint, which is also a design parameter. The rotational behaviour of steel semi rigid connections can be studied using the finite element method for the following three reasons: i such models are inexpensive; ii they allow the understanding of local effects, which are difficult to measure accurately physically, and iii they can be used to generate extensive parametric studies. This paper presents a three-dimensional finite element model using ABAQUS software in order to identify the effect of different parameters on the behaviour of semi rigid steel beam to column end plate connections. Contact and sliding between different elements, bolt pretension and geometric and material non-linearity are included in this model. A parametric study is conducted using a model of two end-plate configurations: flush and extended end plates. The studied parameters were as follows: bolts type, end plate thickness and column web stiffener. Then, the model was calibrated and validated with experimental results taken from the literature and with the model proposed by Eurocode3. The procedure for determining the moment–rotation curve using finite element analysis is also given together with a brief explanation of how the design moment resistance and the initial rotational stiffness of the joint are obtained.

  19. Contact of a spherical probe with a stretched rubber substrate

    Science.gov (United States)

    Frétigny, Christian; Chateauminois, Antoine

    2017-07-01

    We report on a theoretical and experimental investigation of the normal contact of stretched neo-Hookean substrates with rigid spherical probes. Starting from a published formulation of surface Green's function for incremental displacements on a prestretched, neo-Hookean, substrate [J. Mech. Phys. Solids 56, 2957 (2008), 10.1016/j.jmps.2008.07.002], a model is derived for both adhesive and nonadhesive contacts. The shape of the elliptical contact area together with the contact load and the contact stiffness are predicted as a function of the in-plane stretch ratios λx and λy of the substrate. The validity of this model is assessed by contact experiments carried out using an uniaxally stretched silicone rubber. For stretch ratio below about 1.25, a good agreement is observed between theory and experiments. Above this threshold, some deviations from the theoretical predictions are induced as a result of the departure of the mechanical response of the silicone rubber from the neo-Hokeean description embedded in the model.

  20. On flexible and rigid nouns

    DEFF Research Database (Denmark)

    Rijkhoff, Jan

    2010-01-01

    classes. Finally this article wants to claim that the distinction between rigid and flexible noun categories (a) adds a new dimension to current classifications of parts of speech systems, (b) correlates with certain grammatical phenomena (e.g. so-called number discord), and (c) helps to explain the parts......This article argues that in addition to the major flexible lexical categories in Hengeveld’s classification of parts of speech systems (Contentive, Non-Verb, Modifier), there are also flexible word classes within the rigid lexical category Noun (Set Noun, Sort Noun, General Noun). Members...... by the flexible item in the external world. I will then argue that flexible word classes constitute a proper category (i.e. they are not the result of a merger of some rigid word classes) in that members of flexible word categories display the same properties regarding category membership as members of rigid word...

  1. Gas-partitioning tracer test to qualify trapped gas during recharge

    Science.gov (United States)

    Heilweil, Victor M.; Kip, Solomon D.; Perkins, Kim S.; Ellett, Kevin M.

    2004-01-01

    Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas.

  2. Gas-partitioning tracer test to quantify trapped gas during recharge

    Science.gov (United States)

    Heilweil, V.M.; Solomon, D.K.; Perkins, K.S.; Ellett, K.M.

    2004-01-01

    Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas.

  3. Calculation of force and time of contact formation at diffusion metal joining

    Energy Technology Data Exchange (ETDEWEB)

    Sukhanov, V E [Tsentral' nyj Nauchno-Issledovatel' skij Inst. Chernoj Metallurgii, Moscow (USSR); Grushevskij, A V [Moskovskij Stankoinstrumental' nyj Inst., Moscow (USSR); Surovtsev, A P

    1989-03-01

    An analytical model of contact for mation at diffusion joining is suggested. It is based on the introduction of a rough surface with roughnesses in the form of absolutely rigid spherical segnunts into a smooth laminar body. Mathematical expressions, permitting to calculate maximum welding force (pressure) providing close contact of the surfaces welded and time for contact formation between rough surfaces joined, are obtained. Divergence of calculational and experimental data does not exceed 20%. It is confirmed that the most intensive formation of joining occurs in the initial period of welding -the stage of formation of a physical contact, when deformation processes proceed in tensively. Finite formation of a strength joint occurs at the stage of diffusion interaction.

  4. Vision-based stress estimation model for steel frame structures with rigid links

    Science.gov (United States)

    Park, Hyo Seon; Park, Jun Su; Oh, Byung Kwan

    2017-07-01

    This paper presents a stress estimation model for the safety evaluation of steel frame structures with rigid links using a vision-based monitoring system. In this model, the deformed shape of a structure under external loads is estimated via displacements measured by a motion capture system (MCS), which is a non-contact displacement measurement device. During the estimation of the deformed shape, the effective lengths of the rigid link ranges in the frame structure are identified. The radius of the curvature of the structural member to be monitored is calculated using the estimated deformed shape and is employed to estimate stress. Using MCS in the presented model, the safety of a structure can be assessed gauge-freely. In addition, because the stress is directly extracted from the radius of the curvature obtained from the measured deformed shape, information on the loadings and boundary conditions of the structure are not required. Furthermore, the model, which includes the identification of the effective lengths of the rigid links, can consider the influences of the stiffness of the connection and support on the deformation in the stress estimation. To verify the applicability of the presented model, static loading tests for a steel frame specimen were conducted. By comparing the stress estimated by the model with the measured stress, the validity of the model was confirmed.

  5. Durability of Selected Membrane Materials when Exposed to Chlorine Gas

    Energy Technology Data Exchange (ETDEWEB)

    Eikeland, Marianne Soerflaten

    2001-03-01

    This thesis is focusing on the durability of selected membrane materials when exposed to chlorine gas in the temperature range 30-100{sup o}C. Studies of the changes of membrane separation properties and the mechanisms promoting these changes have been studied. The selected membrane materials were poly(dimethylsioxane) (PDMS), Fluorel, fluorosilicone, and blends of PDMS and Fluorel. The thesis is organised in seven chapters. The first chapter gives an introduction to the background of the work. The second chapter presents the theory for gas separation using dense rubbery membranes. The properties of the selected membrane materials are presented in chapter three. The fourth chapter describes degradation mechanisms for polymeric materials in general and for the selected membrane materials in particular. Presentation of the experimental work is given in chapter five, while the results with discussions are presented in chapter six. The conclusions and recommendations for further studies are given in chapter seven. Five appendixes are attached: Appendix A describes the calculations of permeability and solubility coefficients and the accuracy of the experimental measurements. Appendix B summarises the measured values in tables and Appendix C describes the analytical methods. Appendix D gives the properties of the gases used in the experiments. Appendix E is the article ''Durability of Poly(dimethylsiloxane) when Exposed to Chlorine Gas'', submitted to the Journal of Applied Polymer Science. Highly crosslinked PDMS was found to have an initial high permeability for chlorine gas and a high Cl{sub 2}/O{sub 2} selectivity. However when exposed to chlorine gas the permeability decreased significantly. Crosslinking of the PDMS polymer chain and chlorination of the polymer gave a denser polymer structure and thus lower permeability. Fluorel showed very low permeabilities and selectivities for the gases in question and was thus not interesting for this

  6. Effects of Formation Damage on Productivity of Underground Gas Storage Reservoirs

    Directory of Open Access Journals (Sweden)

    C.I.C. Anyadiegwu

    2013-12-01

    Full Text Available Analysis of the effects of formation damage on the productivity of gas storage reservoirs was performed with depleted oil reservoir (OB-02, located onshore, Niger Delta, Nigeria. Information on the reservoir and the fluids from OB-02 were collected and used to evaluate the deliverabilities of the gas storage reservoir over a 10-year period of operation. The results obtained were used to plot graphs of deliverability against permeability and skin respectively. The graphs revealed that as the permeability decreased, the skin increased, and hence a decrease in deliverability of gas from the reservoir during gas withdrawal. Over the ten years of operating the reservoir for gas storage, the deliverability and permeability which were initially 2.7 MMscf/d and 50 mD, with a skin of 0.2, changed to new values of 0.88 MMscf/d and 24 mD with the skin as 4.1 at the tenth year.

  7. CFD Simulation of rigid venting of the containment of a BWR-5 Mark-II reactor

    International Nuclear Information System (INIS)

    Galindo G, I. F.; Vazquez B, A. K.; Velazquez E, L.; Tijerina S, F.; Tapia M, R.

    2016-09-01

    In conditions of prolonged loss of external energy or a severe accident, venting to the atmosphere is an alternative to prevent overpressure and release of fission products from the primary containment of a nuclear reactor. Due to the importance of flow determination through rigid vents, a computational fluid dynamics (CFD) model is proposed to verify the capacity of rigid vents in the primary containment of a boiling water reactor (BWR) under different operating conditions (pressure, temperature and compositions of the fluids). The model predicts and provides detailed information on variables such as mass flow and velocity of the venting gases. In the proposed model the primary containment gas is vented to the atmosphere via rigid vents (pipes) from the dry and wet pit. Is assumed that the container is pressurized because is in a defined scenario, and at one point the venting is open and the gas released into the atmosphere. The objective is to characterize the flow and validate the CFD model for the overpressure conditions that occur in an accident such as a LOCA, Sbo, etc. The model is implemented with Ansys-Fluent general-purpose CFD software based on the geometry of the venting ducts of the containment of a BWR. The model is developed three-dimensional and resolves at steady state for compressible flow and includes the effects of the turbulence represented by the Reynolds stress model. The CFD results are compared with the values of a one-dimensional and isentropic model for compressible flow. The relative similarity of results leads to the conclusion that the proposed CFD model can help to predict the rigid venting capacity of the containment of a BWR, however more information is required for full validation of the proposed model. (Author)

  8. The effect of a tribo-modified surface layer on friction in elastomer contacts

    OpenAIRE

    Mokhtari, Milad

    2015-01-01

    Friction between rubber and a counter surface has interested many researchers because of its huge practical importance. Rubber components are applied in various industrial applications such as tires, rubber seals, wiper blades, conveyor belts and syringes. The friction between a rubber surface in contact with a rigid surface is still not fully understood. The complexity lies partially in the viscoelastic nature of elastomers next to various parameters such as roughness, contact pressure and s...

  9. CT-3DRA registration for radiosurgery treatments: a comparison among rigid, affine and non rigid approaches

    International Nuclear Information System (INIS)

    Stancanello, J.; Loeckx, D.; Francescon, P.; Calvedon, C.; Avanzo, M.; Cora, S.; Scalchi, P.; Cerveri, P.; Ferrigno, G.

    2004-01-01

    This work aims at comparing rigid, affine and Local Non Rigid (LNR) CT-3D Rotational Angiography (CT-3DRA) registrations based on mutual information. 10 cranial and 1 spinal cases have been registered by rigid and affine transformations; while LNR has been applied to the cases where residual deformation must be corrected. An example of CT-3DRA registration without regularization term and an example of LNR using the similarity criterion and the regularization term as well as 3D superposition of the 3DRA before and after the registration without the regularization term are presented. All the registrations performed by rigid transformation converged to an acceptable solution. The results about the robustness test in axial direction are reported. Conclusions: For cranial cases, affine transformation endowed with threshold-segmentation pre-processing can be considered the most favourable solution for almost all registrations; for some cases, LNR provides more accurate results. For the spinal case rigid transformation is the most suitable when immobilizing patient during examinations; in this case the increase of accuracy by using LNR registrations seems to be not significant

  10. Recovery of flue gas energy in heat integrated IGCC power plants using the contact economizer system

    CSIR Research Space (South Africa)

    Madzivhandila, V

    2010-10-01

    Full Text Available Asia Pacific Confederation of APCChE 2010 Chemical Engineering Congress October 5-8, 2010, Taipei � �� Recovery of flue gas energy in heat integrated IGCC power plants using the contact economizer system Vhutshilo Madzivhandilaa, Thokozani... temperature and the thermal efficiency of the plant. The 13th Asia Pacific Confederation of APCChE 2010 Chemical Engineering Congress October 5-8, 2010, Taipei � �� 1. Introduction The IGCC (Integrated Gasification Combined Cycle) is one...

  11. Torsional Rigidity of Minimal Submanifolds

    DEFF Research Database (Denmark)

    Markvorsen, Steen; Palmer, Vicente

    2006-01-01

    We prove explicit upper bounds for the torsional rigidity of extrinsic domains of minimal submanifolds $P^m$ in ambient Riemannian manifolds $N^n$ with a pole $p$. The upper bounds are given in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped...

  12. Trajectory Correction and Locomotion Analysis of a Hexapod Walking Robot with Semi-Round Rigid Feet

    Science.gov (United States)

    Zhu, Yaguang; Jin, Bo; Wu, Yongsheng; Guo, Tong; Zhao, Xiangmo

    2016-01-01

    Aimed at solving the misplaced body trajectory problem caused by the rolling of semi-round rigid feet when a robot is walking, a legged kinematic trajectory correction methodology based on the Least Squares Support Vector Machine (LS-SVM) is proposed. The concept of ideal foothold is put forward for the three-dimensional kinematic model modification of a robot leg, and the deviation value between the ideal foothold and real foothold is analyzed. The forward/inverse kinematic solutions between the ideal foothold and joint angular vectors are formulated and the problem of direct/inverse kinematic nonlinear mapping is solved by using the LS-SVM. Compared with the previous approximation method, this correction methodology has better accuracy and faster calculation speed with regards to inverse kinematics solutions. Experiments on a leg platform and a hexapod walking robot are conducted with multi-sensors for the analysis of foot tip trajectory, base joint vibration, contact force impact, direction deviation, and power consumption, respectively. The comparative analysis shows that the trajectory correction methodology can effectively correct the joint trajectory, thus eliminating the contact force influence of semi-round rigid feet, significantly improving the locomotion of the walking robot and reducing the total power consumption of the system. PMID:27589766

  13. Planar rigid-flexible coupling spacecraft modeling and control considering solar array deployment and joint clearance

    Science.gov (United States)

    Li, Yuanyuan; Wang, Zilu; Wang, Cong; Huang, Wenhu

    2018-01-01

    Based on Nodal Coordinate Formulation (NCF) and Absolute Nodal Coordinate Formulation (ANCF), this paper establishes rigid-flexible coupling dynamic model of the spacecraft with large deployable solar arrays and multiple clearance joints to analyze and control the satellite attitude under deployment disturbance. Considering torque spring, close cable loop (CCL) configuration and latch mechanisms, a typical spacecraft composed of a rigid main-body described by NCF and two flexible panels described by ANCF is used as a demonstration case. Nonlinear contact force model and modified Coulomb friction model are selected to establish normal contact force and tangential friction model, respectively. Generalized elastic force are derived and all generalized forces are defined in the NCF-ANCF frame. The Newmark-β method is used to solve system equations of motion. The availability and superiority of the proposed model is verified through comparing with numerical co-simulations of Patran and ADAMS software. The numerical results reveal the effects of panel flexibility, joint clearance and their coupling on satellite attitude. The effects of clearance number, clearance size and clearance stiffness on satellite attitude are investigated. Furthermore, a proportional-differential (PD) attitude controller of spacecraft is designed to discuss the effect of attitude control on the dynamic responses of the whole system.

  14. A review of a method for dynamic load distribution, dynamical modeling, and explicit internal force control when two manipulators mutually lift and transport a rigid body object

    International Nuclear Information System (INIS)

    Unseren, M.A.

    1997-01-01

    The paper reviews a method for modeling and controlling two serial link manipulators which mutually lift and transport a rigid body object in a three dimensional workspace. A new vector variable is introduced which parameterizes the internal contact force controlled degrees of freedom. A technique for dynamically distributing the payload between the manipulators is suggested which yields a family of solutions for the contact forces and torques the manipulators impart to the object. A set of rigid body kinematic constraints which restrict the values of the joint velocities of both manipulators is derived. A rigid body dynamical model for the closed chain system is first developed in the joint space. The model is obtained by generalizing the previous methods for deriving the model. The joint velocity and acceleration variables in the model are expressed in terms of independent pseudovariables. The pseudospace model is transformed to obtain reduced order equations of motion and a separate set of equations governing the internal components of the contact forces and torques. A theoretic control architecture is suggested which explicitly decouples the two sets of equations comprising the model. The controller enables the designer to develop independent, non-interacting control laws for the position control and internal force control of the system

  15. A review of a method for dynamic load distribution, dynamical modeling, and explicit internal force control when two manipulators mutually lift and transport a rigid body object

    Energy Technology Data Exchange (ETDEWEB)

    Unseren, M.A.

    1997-04-20

    The paper reviews a method for modeling and controlling two serial link manipulators which mutually lift and transport a rigid body object in a three dimensional workspace. A new vector variable is introduced which parameterizes the internal contact force controlled degrees of freedom. A technique for dynamically distributing the payload between the manipulators is suggested which yields a family of solutions for the contact forces and torques the manipulators impart to the object. A set of rigid body kinematic constraints which restrict the values of the joint velocities of both manipulators is derived. A rigid body dynamical model for the closed chain system is first developed in the joint space. The model is obtained by generalizing the previous methods for deriving the model. The joint velocity and acceleration variables in the model are expressed in terms of independent pseudovariables. The pseudospace model is transformed to obtain reduced order equations of motion and a separate set of equations governing the internal components of the contact forces and torques. A theoretic control architecture is suggested which explicitly decouples the two sets of equations comprising the model. The controller enables the designer to develop independent, non-interacting control laws for the position control and internal force control of the system.

  16. Summary of 1988 WIPP [Waste Isolation Pilot Plant] Facility horizon gas flow measurements

    International Nuclear Information System (INIS)

    Stormont, J.C.

    1990-11-01

    Numerous gas flow measurements have been made at the Waste Isolation Pilot Plant (WIPP) Facility horizon during 1988. All tests have been pressure decay or constant pressure tests from single boreholes drilled from the underground excavations. The test fluid has been nitrogen. The data have been interpreted as permeabilities and porosities by means of a transient numerical solution method. A closed-form steady-state approximation provides a reasonable order-of-magnitude permeability estimate. The effective resolution of the measurement system is less than 10 -20 m 2 . Results indicate that beyond 1 to 5 m from an excavation, the gas flow is very small and the corresponding permeability is below the system resolution. Within the first meter of an excavation, the interpreted permeabilities can be 5 orders of magnitude greater than the undisturbed or far-field permeability. The interpreted permeabilities in the region between the undisturbed region and the first meter from an excavation are in the range of 10 -16 to 10 -20 m 2 . Measurable gas flow occurs to a greater depth into the roof above WIPP excavations of different sizes and ages than into the ribs and floor. The gas flows into the formation surrounding the smallest excavation tested are consistently lower than those at similar locations surrounding larger excavations of comparable age. Gas flow measured in the interbed layers near the WIPP excavations is highly variable. Generally, immediately above and below excavations, relatively large gas flow is measured in the interbed layers. These results are consistent with previous measurements and indicate a limited disturbed zone surrounding WIPP excavations. 31 refs., 99 figs., 5 tabs

  17. Evaluating use stage exposure to food contact materials in a LCA framework

    DEFF Research Database (Denmark)

    Ernstoff, Alexi; Jolliet, Olivier; Fantke, Peter

    2015-01-01

    We present novel methods to incorporate exposure to chemicals within food contact materials (FCM) (e.g. packaging) into life cycle impact assessment (LCIA). Chemical migration into food is modeled as a function of contact temperature, time, and various chemical, FCM, and food properties. In order...... in a way compatible with intake fraction, iF, a metric traditionally used in LCIA. The model predicts PiF increases with temperature and for compounds with lower octanol-water partition coefficients within more permeable materials which are in contact with foods with high ethanol equivalencies (fatty foods)....

  18. Flexible and rigid cystoscopy in women.

    Science.gov (United States)

    Gee, Jason R; Waterman, Bradley J; Jarrard, David F; Hedican, Sean P; Bruskewitz, Reginald C; Nakada, Stephen Y

    2009-01-01

    Previous studies have evaluated the tolerability of rigid versus flexible cystoscopy in men. Similar studies, however, have not been performed in women. We sought to determine whether office-based flexible cystoscopy was better tolerated than rigid cystoscopy in women. Following full IRB approval, women were prospectively randomized in a single-blind manner. Patients were randomized to flexible or rigid cystoscopy and draped in the lithotomy position to maintain blinding of the study. Questionnaires evaluated discomfort before, during, and after cystoscopy. Thirty-six women were randomized to flexible (18) or rigid (18) cystoscopy. Indications were surveillance (16), hematuria (15), recurrent UTIs (2), voiding dysfunction (1), and other (2). All questionnaires were returned by 31/36 women. Using a 10-point visual analog scale (VAS), median discomfort during the procedure for flexible and rigid cystoscopy were 1.4 and 1.8, respectively, in patients perceiving pain. Median recalled pain 1 week later was similar at 0.8 and 1.15, respectively. None of these differences were statistically significant. Flexible and rigid cystoscopy are well tolerated in women. Discomfort during and after the procedure is minimal in both groups. Urologists should perform either procedure in women based on their preference and skill level.

  19. Ultra-microporous triptycene-based polyimide membranes for high-performance gas separation

    KAUST Repository

    Ghanem, Bader

    2014-03-11

    A highly permeable and highly selective polyimide of intrinsic microporosity is prepared using a 9,10-diisopropyl-triptycene contortion center. The three-dimensionality and shape-persistence of triptycene afford exceptional sieving-based gas separation performance transcending the latest permeability/selectivity trade-offs for industrial gas separations involving oxygen and hydrogen. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Ultra-microporous triptycene-based polyimide membranes for high-performance gas separation

    KAUST Repository

    Ghanem, Bader; Swaidan, Raja; Litwiller, Eric; Pinnau, Ingo

    2014-01-01

    A highly permeable and highly selective polyimide of intrinsic microporosity is prepared using a 9,10-diisopropyl-triptycene contortion center. The three-dimensionality and shape-persistence of triptycene afford exceptional sieving-based gas separation performance transcending the latest permeability/selectivity trade-offs for industrial gas separations involving oxygen and hydrogen. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Field determination of vertical permeability to air in the unsaturated zone

    Science.gov (United States)

    Weeks, Edwin P.

    1978-01-01

    The vertical permeability to air of layered materials in the unsaturated zone may be determined from air pressure data obtained at depth during a period when air pressure is changing at land surface. Such data may be obtained by monitoring barometric pressure with a microbarograph or surveying altimeter and simultaneously measuring down-hole pneumatic head differences in specially constructed piezometers. These data, coupled with air-filled porosity data from other sources, may be compared with the results of electric-analog or numerical solution of the one-dimensional diffusion equation to make a trial-and-error determination of the air permeability for each layer. The permeabilities to air may in turn be converted to equivalent hydraulic conductivity values if the materials are well drained, are permeable enough that the Klinkenberg effect is small, and are structurally unaffected by wetting. The method offers potential advantages over present methods to evaluate sites for artificial recharge by spreading; to evaluate ground-water pollution hazards from feedlots, sanitary landfills , and land irrigated with sewage effluent; and to evaluate sites for temporary storage of gas in the unsaturated zone. (Woodard-USGS)

  2. Faulting of gas-hydrate-bearing marine sediments - contribution to permeability

    Science.gov (United States)

    Dillon, William P.; Holbrook, W.S.; Drury, Rebecca; Gettrust, Joseph; Hutchinson, Deborah; Booth, James; Taylor, Michael

    1997-01-01

    Extensive faulting is observed in sediments containing high concentrations of methane hydrate off the southeastern coast of the United States. Faults that break the sea floor show evidence of both extension and shortening; mud diapirs are also present. The zone of recent faulting apparently extends from the ocean floor down to the base of gas-hydrate stability. We infer that the faulting resulted from excess pore pressure in gas trapped beneath the gas hydrate-beating layer and/or weakening and mobilization of sediments in the region just below the gas-hydrate stability zone. In addition to the zone of surface faults, we identified two buried zones of faulting, that may have similar origins. Subsurface faulted zones appear to act as gas traps.

  3. An improved model for predicting electrical contact resistance between bipolar plate and gas diffusion layer in proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zhiliang; Wang, Shuxin [School of Mechanical Engineering, Tianjin University, Tianjin 300072 (China); Zhou, Yuanyuan; Lin, Guosong; Hu, S. Jack [Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI 48109-2125 (United States)

    2008-07-15

    Electrical contact resistance between bipolar plates (BPPs) and gas diffusion layers (GDLs) in PEM fuel cells has attracted much attention since it is one significant part of the total contact resistance which plays an important role in fuel cell performance. This paper extends a previous model by Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783] on the prediction of electrical contact resistance within PEM fuel cells. The original microscale numerical model was based on the Hertz solution for individual elastic contacts, assuming that contact bodies, GDL carbon fibers and BPP asperities are isotropic elastic half-spaces. The new model features a more practical contact by taking into account the bending behavior of carbon fibers as well as their anisotropic properties. The microscale single contact process is solved numerically using the finite element method (FEM). The relationship between the contact pressure and the electrical resistance at the GDL/BPP interface is derived by multiple regression models. Comparisons of the original model by Zhou et al. and the new model with experimental data show that the original model slightly overestimates the electrical contact resistance, whereas a better agreement with experimental data is observed using the new model. (author)

  4. Analysis of Switched-Rigid Floating Oscillator

    Directory of Open Access Journals (Sweden)

    Prabhakar R. Marur

    2009-01-01

    Full Text Available In explicit finite element simulations, a technique called deformable-to-rigid (D2R switching is used routinely to reduce the computation time. Using the D2R option, the deformable parts in the model can be switched to rigid and reverted back to deformable when needed during the analysis. The time of activation of D2R however influences the overall dynamics of the system being analyzed. In this paper, a theoretical basis for the selection of time of rigid switching based on system energy is established. A floating oscillator problem is investigated for this purpose and closed-form analytical expressions are derived for different phases in rigid switching. The analytical expressions are validated by comparing the theoretical results with numerical computations.

  5. Notional Permeability

    NARCIS (Netherlands)

    Kik, R.; Van den Bos, J.P.; Maertens, J.; Verhagen, H.J.; Van der Meer, J.W.

    2012-01-01

    Different layer design of a rock slope and under layers has a large effect on the strengths on the rock slope itself. In the stability formula developed of VAN DER MEER [1988] this effect is represented by the term Notional Permeability with symbol P. A more open, or permeable, structure underneath

  6. Treatment of Gas

    Science.gov (United States)

    ... Funding IFFGD Symposium reports Industry Council Contact Us Treatment of Gas You are here: Home Symptoms & Causes Intestinal Gas ... Controlling Intestinal Gas Foods That May Cause Gas Treatment of Gas Tips on Controlling Gas Adapted from IFFGD Publication # ...

  7. Gas-path leakage seal for a gas turbine

    Science.gov (United States)

    Wolfe, C.E.; Dinc, O.S.; Bagepalli, B.S.; Correia, V.H.; Aksit, M.F.

    1996-04-23

    A gas-path leakage seal is described for generally sealing a gas-path leakage-gap between spaced-apart first and second members of a gas turbine (such as combustor casing segments). The seal includes a generally imperforate foil-layer assemblage which is generally impervious to gas and is located in the leakage-gap. The seal also includes a cloth-layer assemblage generally enclosingly contacting the foil-layer assemblage. In one seal, the first edge of the foil-layer assemblage is left exposed, and the foil-layer assemblage resiliently contacts the first member near the first edge to reduce leakage in the ``plane`` of the cloth-layer assemblage under conditions which include differential thermal growth of the two members. In another seal, such leakage is reduced by having a first weld-bead which permeates the cloth-layer assemblage, is attached to the metal-foil-layer assemblage near the first edge, and unattachedly contacts the first member. 4 figs.

  8. High-permeability criterion for BCS classification: segmental/pH dependent permeability considerations.

    Science.gov (United States)

    Dahan, Arik; Miller, Jonathan M; Hilfinger, John M; Yamashita, Shinji; Yu, Lawrence X; Lennernäs, Hans; Amidon, Gordon L

    2010-10-04

    The FDA classifies a drug substance as high-permeability when the fraction of dose absorbed (F(abs)) in humans is 90% or higher. This direct correlation between human permeability and F(abs) has been recently controversial, since the β-blocker sotalol showed high F(abs) (90%) and low Caco-2 permeability. The purpose of this study was to investigate the scientific basis for this disparity between permeability and F(abs). The effective permeabilities (P(eff)) of sotalol and metoprolol, a FDA standard for the low/high P(eff) class boundary, were investigated in the rat perfusion model, in three different intestinal segments with pHs corresponding to the physiological pH in each region: (1) proximal jejunum, pH 6.5; (2) mid small intestine, pH 7.0; and (3) distal ileum, pH 7.5. Both metoprolol and sotalol showed pH-dependent permeability, with higher P(eff) at higher pH. At any given pH, sotalol showed lower permeability than metoprolol; however, the permeability of sotalol determined at pH 7.5 exceeded/matched metoprolol's at pH 6.5 and 7.0, respectively. Physicochemical analysis based on ionization, pK(a) and partitioning of these drugs predicted the same trend and clarified the mechanism behind these observed results. Experimental octanol-buffer partitioning experiments confirmed the theoretical curves. An oral dose of metoprolol has been reported to be completely absorbed in the upper small intestine; it follows, hence, that metoprolol's P(eff) value at pH 7.5 is not likely physiologically relevant for an immediate release dosage form, and the permeability at pH 6.5 represents the actual relevant value for the low/high permeability class boundary. Although sotalol's permeability is low at pH 6.5 and 7.0, at pH 7.5 it exceeds/matches the threshold of metoprolol at pH 6.5 and 7.0, most likely responsible for its high F(abs). In conclusion, we have shown that, in fact, there is no discrepancy between P(eff) and F(abs) in sotalol's absorption; the data emphasize that

  9. Torsional rigidity, isospectrality and quantum graphs

    International Nuclear Information System (INIS)

    Colladay, Don; McDonald, Patrick; Kaganovskiy, Leon

    2017-01-01

    We study torsional rigidity for graph and quantum graph analogs of well-known pairs of isospectral non-isometric planar domains. We prove that such isospectral pairs are distinguished by torsional rigidity. (paper)

  10. Formation of submarine gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Soloviev, V.; Ginsburg, G.D. (Reserch Institute of Geology and Mineral Resources of the Ocean ' ' VNII Okeangeologia' ' , St. Petersburg (Russian Federation))

    1994-03-01

    Submarine gas hydrates have been discoverd in the course of deep-sea drilling (DSDP and ODP) and bottom sampling in many offshore regions. This paper reports on expeditions carried out in the Black, Caspian and Okhotsk Seas. Gas hydrate accumulations were discovered and investigated in all these areas. The data and an analysis of the results of the deep-sea drilling programme suggest that the infiltration of gas-bearing fluids is a necessary condition for gas hydrate accumulation. This is confirmed by geological observations at three scale levels. Firstly, hydrates in cores are usually associated with comparatively coarse-grained, permeable sediments as well as voids and fractures. Secondly, hydrate accumulations are controlled by permeable geological structures, i.e. faults, diapirs, mud volcanos as well as layered sequences. Thirdly, in the worldwide scale, hydrate accumulations are characteristic of continental slopes and rises and intra-continental seas where submarine seepages also are widespread. Both biogenic and catagenic gas may occur, and the gas sources may be located at various distances from the accumulation. Gas hydrates presumably originate from water-dissolved gas. The possibility of a transition from dissolved gas into hydrate is confirmed by experimental data. Shallow gas hydrate accumulations associated with gas-bearing fluid plumes are the most convenient features for the study of submarine hydrate formation in general. These accumulations are known from the Black, Caspian and Okhotsk Seas, the Gulf of Mexico and off northern California. (au) (24 refs.)

  11. Gas and Oil Flow through Wellbore Flaws

    Science.gov (United States)

    Hatambeigi, M.; Anwar, I.; Reda Taha, M.; Bettin, G.; Chojnicki, K. N.; Stormont, J.

    2017-12-01

    We have measured gas and oil flow through laboratory samples that represent two important potential flow paths in wellbores associated with the Strategic Petroleum Reserve (SPR): cement-steel interfaces (microannuli) and cement fractures. Cement fractures were created by tensile splitting of cement cores. Samples to represent microannuli were created by placing thin steel sheets within split cement cores so flow is channeled along the cement-steel interface. The test sequence included alternating gas and oil flow measurements. The test fluids were nitrogen and silicone oil with properties similar to a typical crude oil stored in the SPR. After correcting for non-linear (inertial) flow when necessary, flows were interpreted as effective permeability and hydraulic aperture using the cubic law. For both samples with cement fractures and those with cement-steel interfaces, initial gas and oil permeabilities were comparable. Once saturated with oil, a displacement pressure had to be overcome to establish gas flow through a sample, and the subsequent gas permeability were reduced by more than 50% compared to its initial value. Keywords: wellbore integrity, leakage, fracture, microannulus, SPR. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of NTESS/Honeywell, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2017-8168 A

  12. Fault reactivation by fluid injection considering permeability evolution in fault-bordering damage zones

    Science.gov (United States)

    Yang, Z.; Yehya, A.; Rice, J. R.; Yin, J.

    2017-12-01

    Earthquakes can be induced by human activity involving fluid injection, e.g., as wastewater disposal from hydrocarbon production. The occurrence of such events is thought to be, mainly, due to the increase in pore pressure, which reduces the effective normal stress and hence the strength of a nearby fault. Change in subsurface stress around suitably oriented faults at near-critical stress states may also contribute. We focus on improving the modeling and prediction of the hydro-mechanical response due to fluid injection, considering the full poroelastic effects and not solely changes in pore pressure in a rigid host. Thus we address the changes in porosity and permeability of the medium due to the changes in the local volumetric strains. Our results also focus on including effects of the fault architecture (low permeability fault core and higher permeability bordering damage zones) on the pressure diffusion and the fault poroelastic response. Field studies of faults have provided a generally common description for the size of their bordering damage zones and how they evolve along their direction of propagation. Empirical laws, from a large number of such observations, describe their fracture density, width, permeability, etc. We use those laws and related data to construct our study cases. We show that the existence of high permeability damage zones facilitates pore-pressure diffusion and, in some cases, results in a sharp increase in pore-pressure at levels much deeper than the injection wells, because these regions act as conduits for fluid pressure changes. This eventually results in higher seismicity rates. By better understanding the mechanisms of nucleation of injection-induced seismicity, and better predicting the hydro-mechanical response of faults, we can assess methodologies and injection strategies to avoid risks of high magnitude seismic events. Microseismic events occurring after the start of injection are very important indications of when injection

  13. Numerical Simulation of Natural Gas Flow in Anisotropic Shale Reservoirs

    KAUST Repository

    Negara, Ardiansyah

    2015-11-09

    Shale gas resources have received great attention in the last decade due to the decline of the conventional gas resources. Unlike conventional gas reservoirs, the gas flow in shale formations involves complex processes with many mechanisms such as Knudsen diffusion, slip flow (Klinkenberg effect), gas adsorption and desorption, strong rock-fluid interaction, etc. Shale formations are characterized by the tiny porosity and extremely low-permeability such that the Darcy equation may no longer be valid. Therefore, the Darcy equation needs to be revised through the permeability factor by introducing the apparent permeability. With respect to the rock formations, several studies have shown the existence of anisotropy in shale reservoirs, which is an essential feature that has been established as a consequence of the different geological processes over long period of time. Anisotropy of hydraulic properties of subsurface rock formations plays a significant role in dictating the direction of fluid flow. The direction of fluid flow is not only dependent on the direction of pressure gradient, but it also depends on the principal directions of anisotropy. Therefore, it is very important to take into consideration anisotropy when modeling gas flow in shale reservoirs. In this work, the gas flow mechanisms as mentioned earlier together with anisotropy are incorporated into the dual-porosity dual-permeability model through the full-tensor apparent permeability. We employ the multipoint flux approximation (MPFA) method to handle the full-tensor apparent permeability. We combine MPFA method with the experimenting pressure field approach, i.e., a newly developed technique that enables us to solve the global problem by breaking it into a multitude of local problems. This approach generates a set of predefined pressure fields in the solution domain in such a way that the undetermined coefficients are calculated from these pressure fields. In other words, the matrix of coefficients

  14. Numerical Simulation of Natural Gas Flow in Anisotropic Shale Reservoirs

    KAUST Repository

    Negara, Ardiansyah; Salama, Amgad; Sun, Shuyu; Elgassier, Mokhtar; Wu, Yu-Shu

    2015-01-01

    Shale gas resources have received great attention in the last decade due to the decline of the conventional gas resources. Unlike conventional gas reservoirs, the gas flow in shale formations involves complex processes with many mechanisms such as Knudsen diffusion, slip flow (Klinkenberg effect), gas adsorption and desorption, strong rock-fluid interaction, etc. Shale formations are characterized by the tiny porosity and extremely low-permeability such that the Darcy equation may no longer be valid. Therefore, the Darcy equation needs to be revised through the permeability factor by introducing the apparent permeability. With respect to the rock formations, several studies have shown the existence of anisotropy in shale reservoirs, which is an essential feature that has been established as a consequence of the different geological processes over long period of time. Anisotropy of hydraulic properties of subsurface rock formations plays a significant role in dictating the direction of fluid flow. The direction of fluid flow is not only dependent on the direction of pressure gradient, but it also depends on the principal directions of anisotropy. Therefore, it is very important to take into consideration anisotropy when modeling gas flow in shale reservoirs. In this work, the gas flow mechanisms as mentioned earlier together with anisotropy are incorporated into the dual-porosity dual-permeability model through the full-tensor apparent permeability. We employ the multipoint flux approximation (MPFA) method to handle the full-tensor apparent permeability. We combine MPFA method with the experimenting pressure field approach, i.e., a newly developed technique that enables us to solve the global problem by breaking it into a multitude of local problems. This approach generates a set of predefined pressure fields in the solution domain in such a way that the undetermined coefficients are calculated from these pressure fields. In other words, the matrix of coefficients

  15. Analysis of a hysteresis motor on asynchronous speed using complex permeability

    International Nuclear Information System (INIS)

    Horii, T.; Yuge, N.; Wakui, G.

    1994-01-01

    Although hysteresis motors have a comparatively small output for their mechanical dimensions compared with other types of motor, they offer the advantages of extremely low vibration and noise levels, and so are widely used as driving motors in acoustic equipment and uranium gas centrifuges. This paper deals with a method for determining the complex permeability in analysis of hysteresis motors. The method assumes that the magnetic intensity distribution is sinusoidal in the direction of rotation. Analysis of the asynchronous speed of a hysteresis motor is then performed for cylindrical coordinates, using modified Bessel functions. The results of calculations are in good agreement with experimental results, confirming the effectiveness of the proposed model and method for determining the complex permeability

  16. Experimental study of very-low permeability rocks by the implementation of a precision permeameter

    International Nuclear Information System (INIS)

    Larive, E.

    2002-12-01

    The measurement of fluid flow through 'tight' rocks is important to provide a better understanding of physical processes involved in several industrial and natural problems. These include deep nuclear waste repositories, management of aquifers, gas, petroleum or geothermal reservoirs, or earthquakes prevention. The major part of this work consisted of the design, construction and use of an elaborate experimental apparatus allowing laboratory permeability measurements (fluid flow) of very low permeability rocks, on samples at a centimetric scale, to constrain their hydraulic behaviour at realistic in-situ conditions.The accuracy permeameter allows the use of several measurement methods, the steady-state flow method, the transient pulse method and the sinusoidal pore pressure oscillation method. Measurements were made with the pore pressure oscillation method, using different waveform periods, at several pore and confining pressure conditions on different materials. The permeability of one natural standard, Westerly granite, and an artificial one, a micro-porous cement, were measured and results obtained agreed with previous measurements made on these materials showing the reliability of the permeameter. A study of a Yorkshire sandstone shows a relationship between rock microstructure, permeability anisotropy and thermal cracking. Microstructure, porosity and permeability concepts, and laboratory permeability measurements specifications are presented, the permeameter is described, and then permeability results obtained on the investigated materials are reported. (author)

  17. High-performance intrinsically microporous dihydroxyl-functionalized triptycene-based polyimide for natural gas separation

    KAUST Repository

    Alaslai, Nasser Y.; Ghanem, Bader; Alghunaimi, Fahd; Pinnau, Ingo

    2016-01-01

    A novel polyimide of intrinsic microporosity (PIM-PI) was synthesized from a 9,10-diisopropyl-triptycene-based dianhydride (TPDA) and dihydroxyl-functionalized 4,6-diaminoresorcinol (DAR). The unfunctionalized TPDA-m-phenylenediamine (mPDA) polyimide derivative was made as a reference material to evaluate the effect of the OH group in TPDA-DAR on its gas transport properties. Pure-gas permeability coefficients of He, H2, N2, O2, CH4, and CO2 were measured at 35 °C and 2 atm. The BET surface area based on nitrogen adsorption of dihydroxyl-functionalized TPDA-DAR (308 m2g-1) was 45% lower than that of TPDA-mPDA (565 m2g-1). TPDA-mPDA had a pure-gas CO2 permeability of 349 Barrer and CO2/CH4 selectivity of 32. The dihydroxyl-functionalized TPDA-DAR polyimide exhibited enhanced pure-gas CO2/CH4 selectivity of 46 with a moderate decrease in CO2 permeability to 215 Barrer. The CO2 permeability of TPDA-DAR was ∼30-fold higher than that of a commercial cellulose triacetate membrane coupled with 39% higher pure-gas CO2/CH4 selectivity. The TPDA-based dihydroxyl-containing polyimide showed good plasticization resistance and maintained high mixed-gas selectivity of 38 when tested at a typical CO2 natural gas wellhead CO2 partial pressure of 10 atm.

  18. High-performance intrinsically microporous dihydroxyl-functionalized triptycene-based polyimide for natural gas separation

    KAUST Repository

    Alaslai, Nasser Y.

    2016-03-22

    A novel polyimide of intrinsic microporosity (PIM-PI) was synthesized from a 9,10-diisopropyl-triptycene-based dianhydride (TPDA) and dihydroxyl-functionalized 4,6-diaminoresorcinol (DAR). The unfunctionalized TPDA-m-phenylenediamine (mPDA) polyimide derivative was made as a reference material to evaluate the effect of the OH group in TPDA-DAR on its gas transport properties. Pure-gas permeability coefficients of He, H2, N2, O2, CH4, and CO2 were measured at 35 °C and 2 atm. The BET surface area based on nitrogen adsorption of dihydroxyl-functionalized TPDA-DAR (308 m2g-1) was 45% lower than that of TPDA-mPDA (565 m2g-1). TPDA-mPDA had a pure-gas CO2 permeability of 349 Barrer and CO2/CH4 selectivity of 32. The dihydroxyl-functionalized TPDA-DAR polyimide exhibited enhanced pure-gas CO2/CH4 selectivity of 46 with a moderate decrease in CO2 permeability to 215 Barrer. The CO2 permeability of TPDA-DAR was ∼30-fold higher than that of a commercial cellulose triacetate membrane coupled with 39% higher pure-gas CO2/CH4 selectivity. The TPDA-based dihydroxyl-containing polyimide showed good plasticization resistance and maintained high mixed-gas selectivity of 38 when tested at a typical CO2 natural gas wellhead CO2 partial pressure of 10 atm.

  19. Impact of Petrophysical Properties on Hydraulic Fracturing and Development in Tight Volcanic Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Yinghao Shen

    2017-01-01

    Full Text Available The volcanic reservoir is an important kind of unconventional reservoir. The aqueous phase trapping (APT appears because of fracturing fluids filtration. However, APT can be autoremoved for some wells after certain shut-in time. But there is significant distinction for different reservoirs. Experiments were performed to study the petrophysical properties of a volcanic reservoir and the spontaneous imbibition is monitored by nuclear magnetic resonance (NMR and pulse-decay permeability. Results showed that natural cracks appear in the samples as well as high irreducible water saturation. There is a quick decrease of rock permeability once the rock contacts water. The pores filled during spontaneous imbibition are mainly the nanopores from NMR spectra. Full understanding of the mineralogical effect and sample heterogeneity benefits the selection of segments to fracturing. The fast flow-back scheme is applicable in this reservoir to minimize the damage. Because lots of water imbibed into the nanopores, the main flow channels become larger, which are beneficial to the permeability recovery after flow-back of hydraulic fracturing. This is helpful in understanding the APT autoremoval after certain shut-in time. Also, Keeping the appropriate production differential pressure is very important in achieving the long term efficient development of volcanic gas reservoirs.

  20. Numerical solution of fractured horizontal wells in shale gas reservoirs considering multiple transport mechanisms

    Science.gov (United States)

    Zhao, Yu-long; Tang, Xu-chuan; Zhang, Lie-hui; Tang, Hong-ming; Tao, Zheng-Wu

    2018-06-01

    The multiscale pore size and specific gas storage mechanism in organic-rich shale gas reservoirs make gas transport in such reservoirs complicated. Therefore, a model that fully incorporates all transport mechanisms and employs an accurate numerical method is urgently needed to simulate the gas production process. In this paper, a unified model of apparent permeability was first developed, which took into account multiple influential factors including slip flow, Knudsen diffusion (KD), surface diffusion, effects of the adsorbed layer, permeability stress sensitivity, and ad-/desorption phenomena. Subsequently, a comprehensive mathematical model, which included the model of apparent permeability, was derived to describe gas production behaviors. Thereafter, on the basis of unstructured perpendicular bisection grids and finite volume method, a fully implicit numerical simulator was developed using Matlab software. The validation and application of the new model were confirmed using a field case reported in the literature. Finally, the impacts of related influencing factors on gas production were analyzed. The results showed that KD resulted in a negligible impact on gas production in the proposed model. The smaller the pore size was, the more obvious the effects of the adsorbed layer on the well production rate would be. Permeability stress sensitivity had a slight effect on well cumulative production in shale gas reservoirs. Adsorbed gas made a major contribution to the later flow period of the well; the greater the adsorbed gas content, the greater the well production rate would be. This paper can improve the understanding of gas production in shale gas reservoirs for petroleum engineers.

  1. Temperature dependence of dynamical permeability characterization of magnetic thin films using shorted microstrip line probe

    International Nuclear Information System (INIS)

    Li, Xiling; Li, Chengyi; Chai, Guozhi

    2017-01-01

    A temperature dependence microwave permeability characterization system of magnetic thin film up to 10 GHz is designed and fabricated. This system can be used at temperatures ranging from room temperature to 200 °C, and is based on a shorted microstrip probe, which is made by microwave printed circuit board. Without contacting the magnetic thin films to the probe, the microwave permeability of the film can be detected without any limitations of sample size and with almost the same accuracy, as shown by comparison with the results obtained from a shorted microstrip transmission-line fixture. The complex permeability can be deduced by an analytical approach from the measured reflection coefficient of a strip line ( S 11 ) with and without a ferromagnetic film material on it. The procedures are the same with the shorted microstrip transmission-line method. The microwave permeability of an oblique deposited CoZr thin film was investigated with this probe. The results show that the room temperature dynamic permeability of the CoZr film is in good agreement with the results obtained from the established short-circuited microstrip perturbation method. The temperature dependence permeability results fit well with the Landau–Lifshitz–Gilbert equation. Development of the temperature-dependent measurement of the magnetic properties of magnetic thin film may be useful for the high-frequency application of magnetic devices at high temperatures. (paper)

  2. Automatic counting of fission fragments tracks using the gas permeation technique

    CERN Document Server

    Yamazaki, I M

    1999-01-01

    An automatic counting system for fission tracks induced in a polycarbonate plastic Makrofol KG (10 mu m thickness) is described. The method is based on the gas transport mechanism proposed by Knudsen, where the gas permeability for a porous membrane is expected to be directly related to its track density. In this work, nitrogen permeabilities for several Makrofol films, with different fission track densities, have been measured using an adequate gas permeation system. The fission tracks were produced by irradiating Makrofol foils with a 252Cf calibrated source in a 2 pi geometry. A calibration curve fission track number versus nitrogen permeability has been obtained, for track densities higher than 1000/cm sup 2 , where the spark gap technique and the visual methods employing a microscope, are not appropriate for track counting.

  3. Rigidity of monodromies for Appell's hypergeometric functions

    Directory of Open Access Journals (Sweden)

    Yoshishige Haraoka

    2015-01-01

    Full Text Available For monodromy representations of holonomic systems, the rigidity can be defined. We examine the rigidity of the monodromy representations for Appell's hypergeometric functions, and get the representations explicitly. The results show how the topology of the singular locus and the spectral types of the local monodromies work for the study of the rigidity.

  4. Moving droplets : The measurement of contact lines

    NARCIS (Netherlands)

    Poelma, C.; Franken, M.J.Z.; Kim, H.; Westerweel, J.

    2014-01-01

    Contact lines are the locations where a gas, liquid and a solid meet. From everyday experience we know that such contact lines can be mobile, for example in the case of a water droplet sliding over a glass surface. However, the continuum description of the flow towards or away from a contact line

  5. Intrinsically Microporous Polymer Membranes for High Performance Gas Separation

    KAUST Repository

    Swaidan, Raja

    2014-01-01

    This dissertation addresses the rational design of intrinsically microporous solutionprocessable polyimides and ladder polymers for highly permeable and highly selective gas transport in cornerstone applications of membrane-based gas separation

  6. Jeans Instability of the Self-Gravitating Viscoelastic Ferromagnetic ...

    Indian Academy of Sciences (India)

    Joginder Singh Dhiman

    2017-11-27

    Nov 27, 2017 ... ing forces such as internal gas pressure or material rigidity, and .... conduction and investigated the influence of porous, magnetic ... tion and MFD viscosity on ferrofluid flow with rotating disk and ... boundary layer, angle of rotation and an expression for ... (M ·∇)H, where μ0 is the permeability of free space.

  7. Processes linked to contact changes in adoptive kinship networks.

    Science.gov (United States)

    Dunbar, Nora; van Dulmen, Manfred H M; Ayers-Lopez, Susan; Berge, Jerica M; Christian, Cinda; Gossman, Ginger; Henney, M Susan M; Mendenhall, Tai J; Grotevant, Harold D; McRoy, Ruth G

    2006-12-01

    The purpose of this study was to reveal underlying processes in adoptive kinship networks that experienced increases or decreases in levels of openness during the child's adolescent years. Intensive case study analyses were conducted for 8 adoptive kinship networks (each including an adoptive mother, adoptive father, adopted adolescent, and birth mother), half of whom had experienced an increase in openness from indirect (mediated) to direct (fully disclosed) contact and half of whom had ceased indirect contact between Waves 1 and 2 of a longitudinal study. Adoptive mothers tended to be more involved in contact with the birth mother than were adoptive fathers or adopted adolescents. Members of adoptive kinship networks in which a decrease in level of contact took place had incongruent perspectives about who initiated the stop in contact and why the stop took place. Birth mothers were less satisfied with their degree of contact than were adoptive parents. Adults' satisfaction with contact was related to feelings of control over type and amount of interactions and permeability of family boundaries. In all adoptive kinship networks, responsibility for contact had shifted toward the adopted adolescent regardless of whether the adolescent was aware of this change in responsibility.

  8. Trench infiltration for managed aquifer recharge to permeable bedrock

    Science.gov (United States)

    Heilweil, V.M.; Watt, D.E.

    2011-01-01

    Managed aquifer recharge to permeable bedrock is increasingly being utilized to enhance resources and maintain sustainable groundwater development practices. One such target is the Navajo Sandstone, an extensive regional aquifer located throughout the Colorado Plateau of the western United States. Spreading-basin and bank-filtration projects along the sandstone outcrop's western edge in southwestern Utah have recently been implemented to meet growth-related water demands. This paper reports on a new cost-effective surface-infiltration technique utilizing trenches for enhancing managed aquifer recharge to permeable bedrock. A 48-day infiltration trench experiment on outcropping Navajo Sandstone was conducted to evaluate this alternative surface-spreading artificial recharge method. Final infiltration rates through the bottom of the trench were about 0.5 m/day. These infiltration rates were an order of magnitude higher than rates from a previous surface-spreading experiment at the same site. The higher rates were likely caused by a combination of factors including the removal of lower permeability soil and surficial caliche deposits, access to open vertical sandstone fractures, a reduction in physical clogging associated with silt and biofilm layers, minimizing viscosity effects by maintaining isothermal conditions, minimizing chemical clogging caused by carbonate mineral precipitation associated with algal photosynthesis, and diminished gas clogging associated with trapped air and biogenic gases. This pilot study illustrates the viability of trench infiltration for enhancing surface spreading of managed aquifer recharge to permeable bedrock. ?? 2010.

  9. Intestinal Permeability: The Basics

    Directory of Open Access Journals (Sweden)

    Ingvar Bjarnason

    1995-01-01

    Full Text Available The authors review some of the more fundamental principles underlying the noninvasive assessment of intestinal permeability in humans, the choice of test markers and their analyses, and the practical aspects of test dose composition and how these can be changed to allow the specific assessment of regional permeability changes and other intestinal functions. The implications of increased intestinal permeability in the pathogenesis of human disease is discussed in relation to findings in patients with Crohn’s disease. A common feature of increased intestinal permeability is the development of a low grade enteropathy, and while quantitatively similar changes may be found in Crohn’s disease these seem to predict relapse of disease. Moreover, factors associated with relapse of Crohn’s disease have in common an action to increase intestinal permeability. While increased intestinal permeability does not seem to be important in the etiology of Crohn’s disease it may be a central mechanism in the clinical relapse of disease.

  10. A review of a method for dynamic load distribution, dynamic modeling, and explicit internal force control when two serial link manipulators mutually lift and transport a rigid body object

    International Nuclear Information System (INIS)

    Unseren, M.A.

    1997-09-01

    The report reviews a method for modeling and controlling two serial link manipulators which mutually lift and transport a rigid body object in a three dimensional workspace. A new vector variable is introduced which parameterizes the internal contact force controlled degrees of freedom. A technique for dynamically distributing the payload between the manipulators is suggested which yields a family of solutions for the contact forces and torques the manipulators impart to the object. A set of rigid body kinematic constraints which restricts the values of the joint velocities of both manipulators is derived. A rigid body dynamical model for the closed chain system is first developed in the joint space. The model is obtained by generalizing the previous methods for deriving the model. The joint velocity and acceleration variables in the model are expressed in terms of independent pseudovariables. The pseudospace model is transformed to obtain reduced order equations of motion and a separate set of equations governing the internal components of the contact forces and torques. A theoretic control architecture is suggested which explicitly decouples the two sets of equations comprising the model. The controller enables the designer to develop independent, non-interacting control laws for the position control and internal force control of the system

  11. A review of a method for dynamic load distribution, dynamic modeling, and explicit internal force control when two serial link manipulators mutually lift and transport a rigid body object

    Energy Technology Data Exchange (ETDEWEB)

    Unseren, M.A.

    1997-09-01

    The report reviews a method for modeling and controlling two serial link manipulators which mutually lift and transport a rigid body object in a three dimensional workspace. A new vector variable is introduced which parameterizes the internal contact force controlled degrees of freedom. A technique for dynamically distributing the payload between the manipulators is suggested which yields a family of solutions for the contact forces and torques the manipulators impart to the object. A set of rigid body kinematic constraints which restricts the values of the joint velocities of both manipulators is derived. A rigid body dynamical model for the closed chain system is first developed in the joint space. The model is obtained by generalizing the previous methods for deriving the model. The joint velocity and acceleration variables in the model are expressed in terms of independent pseudovariables. The pseudospace model is transformed to obtain reduced order equations of motion and a separate set of equations governing the internal components of the contact forces and torques. A theoretic control architecture is suggested which explicitly decouples the two sets of equations comprising the model. The controller enables the designer to develop independent, non-interacting control laws for the position control and internal force control of the system.

  12. Global mass conservation method for dual-continuum gas reservoir simulation

    KAUST Repository

    Wang, Yi; Sun, Shuyu; Gong, Liang; Yu, Bo

    2018-01-01

    In this paper, we find that the numerical simulation of gas flow in dual-continuum porous media may generate unphysical or non-robust results using regular finite difference method. The reason is the unphysical mass loss caused by the gas compressibility and the non-diagonal dominance of the discretized equations caused by the non-linear well term. The well term contains the product of density and pressure. For oil flow, density is independent of pressure so that the well term is linear. For gas flow, density is related to pressure by the gas law so that the well term is non-linear. To avoid these two problems, numerical methods are proposed using the mass balance relation and the local linearization of the non-linear source term to ensure the global mass conservation and the diagonal dominance of discretized equations in the computation. The proposed numerical methods are successfully applied to dual-continuum gas reservoir simulation. Mass conservation is satisfied while the computation becomes robust. Numerical results show that the location of the production well relative to the large-permeability region is very sensitive to the production efficiency. It decreases apparently when the production well is moved from the large-permeability region to the small-permeability region, even though the well is very close to the interface of the two regions. The production well is suggested to be placed inside the large-permeability region regardless of the specific position.

  13. Global mass conservation method for dual-continuum gas reservoir simulation

    KAUST Repository

    Wang, Yi

    2018-03-17

    In this paper, we find that the numerical simulation of gas flow in dual-continuum porous media may generate unphysical or non-robust results using regular finite difference method. The reason is the unphysical mass loss caused by the gas compressibility and the non-diagonal dominance of the discretized equations caused by the non-linear well term. The well term contains the product of density and pressure. For oil flow, density is independent of pressure so that the well term is linear. For gas flow, density is related to pressure by the gas law so that the well term is non-linear. To avoid these two problems, numerical methods are proposed using the mass balance relation and the local linearization of the non-linear source term to ensure the global mass conservation and the diagonal dominance of discretized equations in the computation. The proposed numerical methods are successfully applied to dual-continuum gas reservoir simulation. Mass conservation is satisfied while the computation becomes robust. Numerical results show that the location of the production well relative to the large-permeability region is very sensitive to the production efficiency. It decreases apparently when the production well is moved from the large-permeability region to the small-permeability region, even though the well is very close to the interface of the two regions. The production well is suggested to be placed inside the large-permeability region regardless of the specific position.

  14. Forecast on Water Locking Damage of Low Permeable Reservoir with Quantum Neural Network

    Science.gov (United States)

    Zhao, Jingyuan; Sun, Yuxue; Feng, Fuping; Zhao, Fulei; Sui, Dianjie; Xu, Jianjun

    2018-01-01

    It is of great importance in oil-gas reservoir protection to timely and correctly forecast the water locking damage, the greatest damage for low permeable reservoir. An analysis is conducted on the production mechanism and various influence factors of water locking damage, based on which a quantum neuron is constructed based on the information processing manner of a biological neuron and the principle of quantum neural algorithm, besides, the quantum neural network model forecasting the water locking of the reservoir is established and related software is also made to forecast the water locking damage of the gas reservoir. This method has overcome the defects of grey correlation analysis that requires evaluation matrix analysis and complicated operation. According to the practice in Longxi Area of Daqing Oilfield, this method is characterized by fast operation, few system parameters and high accuracy rate (the general incidence rate may reach 90%), which can provide reliable support for the protection technique of low permeable reservoir.

  15. Characterization of the permeability of the blast furnace lower part

    International Nuclear Information System (INIS)

    Negro, P.; Petit, C.; Urvoy, A.; Sert, D.; Pierret, H.

    2001-01-01

    In the context of high coal injection and high productivity operation, the coke behaviour inside the blast furnace hearth is the main parameter to control. Different and complementary investigations as radioactive and helium tracer injections, liquids and coke samplings, have been carried out at Sollac Fos BF1 using the tuyere probe to determine the hearth permeability and its evolutions as a function of the main control parameters, and to understand the hearth activity. The results of all these experiments give a very consistent picture of a heterogenous hearth with three concentric areas of various permeabilities to gas and liquids. A two concentric zones model has been built, which is in good agreement with the experimental results. It enables to evaluate the impact of the central zone on the liquids flow at the periphery. (author)

  16. The effect of non-condensable gas on direct contact condensation of steam/air mixture

    International Nuclear Information System (INIS)

    Lee, H. C.; Park, S. K.; Kim, M. H.

    1998-01-01

    To investigate the effects of noncondensable gas on the direct contact film condensation of vapor mixture, a series of experiments has been carried out. The rectangular duct inclined 87.deg. to the horizontal plane was used for this experiment. The average heat transfer coefficient of the steam-air mixture was obtained at the atmospheric pressure with four main parameters, air-mass fraction, vapor velocity, film Reynolds number,and the degree of water film subcooling having an influence on the condensation heat transfer coefficient. With the analysis on 88 cases of experiments, a correlation of the average Nusselt number for direct contact film condensation of steam-air mixture at a vertical wall proposed as functions of film Reynolds number, mixture Reynolds number, air mass fraction, and Jacob number. The average heat transfer coefficient for steam-air mixture condensation decreased significantly while air mass fraction increases with the same inlet mixture velocity and inlet film temperature. The average heat transfer coefficients also decreased with the degree of film subcooling increasing and were scarcely affected by film Reynolds number below the mixture Reynolds number about 30,000

  17. Gas ampoule-syringe

    International Nuclear Information System (INIS)

    Gay, D.D.

    1986-01-01

    This patent describes disposable gas ampoule holding or containing a gas such as a radioactive gas, comprising: (a) a cylindrical glass tube which is adapted to hold the gas; (b) a layer of absorbent material which circumscribes and which contacts cylindrical glass tube (a) which absorbs the gas; (c) a plastic tube, which circumscribes and contacts absorbent material layer (b) and which is externally threaded on each of its end portions; (d) a cap, which is threaded onto a first end of plastic tube (c); (e) a cylindrical block, which is positioned in the first end of cylindrical glass tube (a) adjacent to cap (d), which contacts cylindrical glass tube (a), which is composed of a foamed material and which is impregnated with a gas adsorbent material; (f) a cylindrical plunger tip, which is located in the first end of cylindrical glass tube (a) in a gas-tight manner adjacent to cylindrical block (e); (g) an end stopper, which has a central cylindrical shaft that is positioned in the second end of cylindrical glass tube (a); and (h) a cap, which is threaded onto the second end of plastic tube (e). A combination of the disposable gas ampoule and syringe adapted to operably interface with the gas ampoule is also described

  18. Effect of vehicles and sodium lauryl sulphate on xenobiotic permeability and stratum corneum partitioning in porcine skin

    International Nuclear Information System (INIS)

    Merwe, Deon van der; Riviere, Jim E.

    2005-01-01

    Dermal contact with potentially toxic agricultural and industrial chemicals is a common hazard encountered in occupational, accidental spill and environmental contamination scenarios. Different solvents and chemical mixtures may influence dermal absorption. The effects of sodium lauryl sulphate (SLS) on the stratum corneum partitioning and permeability in porcine skin of 10 agricultural and industrial chemicals in water, ethanol and propylene glycol were investigated. The chemicals were phenol, p-nitrophenol, pentachlorophenol, methyl parathion, ethyl parathion, chlorpyrifos, fenthion, simazine, atrazine and propazine. SLS decreased partitioning into stratum corneum from water for lipophilic compounds, decreased partitioning from propylene glycol and did not alter partitioning from ethanol. SLS effects on permeability were less consistent, but generally decreased permeability from water, increased permeability from ethanol and had an inconsistent effect on permeability from propylene glycol. It was concluded that, for the compounds tested, partitioning into the stratum corneum was determined by the relative solubility of the solute in the donor solvent and the stratum corneum lipids. Permeability, however, reflected the result of successive, complex processes and was not predictable from stratum corneum partitioning alone. Addition of SLS to solvents altered partitioning and absorption characteristics across a range of compounds, which indicates that partition coefficients or skin permeability from neat chemical exposure should be used with caution in risk assessment procedures for chemical mixtures

  19. Flow regimes in vertical gas-solid contact systems

    Energy Technology Data Exchange (ETDEWEB)

    Yerushalmi, J.; Cankurt, N. T.; Geldart, D.; Liss, B.

    1976-01-01

    The flow characteristics in fluidized beds, i.e., gas-solid systems, was studied to determine the flow regimes, the interaction of gas and solid in the various flow regimes and the dependence of this interaction and of transition between flow regimes on the properties of the gas and solid, on the gas and solid flow rates, and on the containing vessel. Fluidized beds with both coarse and fine particles are considered. Test results using high speed photography to view the operation of a 2-dimensional bed are discussed. (LCL)

  20. Durable Suit Bladder with Improved Water Permeability for Pressure and Environment Suits

    Science.gov (United States)

    Bue, Grant C.; Kuznetz, Larry; Orndoff, Evelyne; Tang, Henry; Aitchison, Lindsay; Ross, Amy

    2009-01-01

    Water vapor permeability is shown to be useful in rejecting heat and managing moisture accumulation in launch-and-entry pressure suits. Currently this is accomplished through a porous Gortex layer in the Advanced Crew and Escape Suit (ACES) and in the baseline design of the Constellation Suit System Element (CSSE) Suit 1. Non-porous dense monolithic membranes (DMM) that are available offer potential improvements for water vapor permeability with reduced gas leak. Accordingly, three different pressure bladder materials were investigated for water vapor permeability and oxygen leak: ElasthaneTM 80A (thermoplastic polyether urethane) provided from stock polymer material and two custom thermoplastic polyether urethanes. Water vapor, carbon dioxide and oxygen permeability of the DMM's was measured in a 0.13 mm thick stand-alone layer, a 0.08 mm and 0.05 mm thick layer each bonded to two different nylon and polyester woven reinforcing materials. Additional water vapor permeability and mechanical compression measurements were made with the reinforced 0.05 mm thick layers, further bonded with a polyester wicking and overlaid with moistened polyester fleece thermal underwear .This simulated the pressure from a supine crew person. The 0.05 mm thick nylon reinforced sample with polyester wicking layer was further mechanically tested for wear and abrasion. Concepts for incorporating these materials in launch/entry and Extravehicular Activity pressure suits are presented.

  1. Polybenzimidazole-based mixed membranes with exceptional high water vapor permeability and selectivity

    KAUST Repository

    Akhtar, Faheem Hassan

    2017-09-13

    Polybenzimidazole (PBI), a thermal and chemically stable polymer, is commonly used to fabricate membranes for applications like hydrogen recovery at temperatures of more than 300 °C, fuel cells working in a highly acidic environment, and nanofiltration in aggressive solvents. This report shows for the first time use of PBI dense membranes for water vapor/gas separation applications. They showed an excellent selectivity and high water vapor permeability. Incorporation of inorganic hydrophilic titanium-based nano-fillers into the PBI matrix further increased the water vapor permeability and water vapor/N2 selectivity. The most selective mixed matrix membrane with 0.5 wt% loading of TiO2 nanotubes yielded a water vapor permeability of 6.8×104 Barrer and a H2O/N2 selectivity of 3.9×106. The most permeable membrane with 1 wt% loading of carboxylated TiO2 nanoparticles had a 7.1×104 Barrer water vapor permeability and a H2O/N2 selectivity of 3.1×106. The performance of these membranes in terms of water vapor transport and selectivity is among the highest reported ones. The remarkable ability of PBI to efficiently permeate water versus other gases opens the possibility to fabricate membranes for dehumidification of streams in harsh environments. This includes the removal of water from high temperature reaction mixtures to shift the equilibrium towards products.

  2. Polybenzimidazole-based mixed membranes with exceptional high water vapor permeability and selectivity

    KAUST Repository

    Akhtar, Faheem Hassan; Kumar, Mahendra; Villalobos, Luis Francisco; Shevate, Rahul; Vovusha, Hakkim; Schwingenschlö gl, Udo; Peinemann, Klaus-Viktor

    2017-01-01

    Polybenzimidazole (PBI), a thermal and chemically stable polymer, is commonly used to fabricate membranes for applications like hydrogen recovery at temperatures of more than 300 °C, fuel cells working in a highly acidic environment, and nanofiltration in aggressive solvents. This report shows for the first time use of PBI dense membranes for water vapor/gas separation applications. They showed an excellent selectivity and high water vapor permeability. Incorporation of inorganic hydrophilic titanium-based nano-fillers into the PBI matrix further increased the water vapor permeability and water vapor/N2 selectivity. The most selective mixed matrix membrane with 0.5 wt% loading of TiO2 nanotubes yielded a water vapor permeability of 6.8×104 Barrer and a H2O/N2 selectivity of 3.9×106. The most permeable membrane with 1 wt% loading of carboxylated TiO2 nanoparticles had a 7.1×104 Barrer water vapor permeability and a H2O/N2 selectivity of 3.1×106. The performance of these membranes in terms of water vapor transport and selectivity is among the highest reported ones. The remarkable ability of PBI to efficiently permeate water versus other gases opens the possibility to fabricate membranes for dehumidification of streams in harsh environments. This includes the removal of water from high temperature reaction mixtures to shift the equilibrium towards products.

  3. Simulation Model of Membrane Gas Separator Using Aspen Custom Modeler

    Energy Technology Data Exchange (ETDEWEB)

    Song, Dong-keun [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of); Shin, Gahui; Yun, Jinwon; Yu, Sangseok [Chungnam Nat’l Univ., Daejeon (Korea, Republic of)

    2016-12-15

    Membranes are used to separate pure gas from gas mixtures. In this study, three different types of mass transport through a membrane were developed in order to investigate the gas separation capabilities of a membrane. The three different models typically used are a lumped model, a multi-cell model, and a discretization model. Despite the multi-cell model producing similar results to a discretization model, the discretization model was selected for this investigation, due to the cell number dependence of a multi-cell model. The mass transport model was then used to investigate the effects of pressure difference, flow rate, total exposed area, and permeability. The results showed that the pressure difference increased with the stage cut, but the selectivity was a trade-off for the increasing pressure difference. Additionally, even though permeability is an important parameter, the selectivity and stage cut of the membrane converged as permeability increased.

  4. Natural Gas Sweetening by Ultra-Microporous Polyimides Membranes

    KAUST Repository

    Alghunaimi, Fahd

    2017-05-01

    Most natural gas fields in Saudi Arabia contain around 10 mol.% carbon dioxide. The present technology to remove carbon dioxide is performed by chemical absorption, which has many drawbacks. Alternatively, membrane-based gas separation technology has attracted great interest in recent years due to: (i) simple modular design, (ii) potential cost effectiveness, (iii) ease of scale-up, and (iv) environmental friendliness. The state-of-the-art membrane materials for natural gas sweetening are glassy cellulose acetate and polyimide, which were introduced in the 1980s. In the near future, the kingdom is planning to boost its production of natural gas for power generation and increase the feedstock for new petrochemical plants. Therefore, the kingdom and worldwide market has an urgent need for better membrane materials to remove carbon dioxide from raw natural gas. The focus of this dissertation was to design new polyimide membrane materials for CO2/CH4 separation exhibiting high permeability and high selectivity relative to the standard commercial materials tested under realistic mixed-gas feed conditions. Furthermore, this study provided a fundamental understanding of structure/gas transport property relationships of triptycene-based PIM-polyimides. Optimally designed intrinsically microporous polyimide (PIM-PIs) membranes in this work exhibited drastically increased CO2/CH4 selectivities of up to ~75. In addition, a novel triptycene-based hydroxyl-containing polyimide (TDA1-APAF) showed 5-fold higher permeabilities over benchmark commercial materials such as cellulose acetate. Furthermore, this polyimide had a N2/CH4 selectivity of 2.3, thereby making it possible to simultaneously treat CO2- and N2-contaminated natural gas. Also, TDA1-APAF showed a CO2 permeability of 21 Barrer under binary 1:1 CO2/CH4 mixed-gas feed with a selectivity of 72 at a partial CO2 pressure of 10 bar which are significantly better than cellulose triacetate. These results suggest that TDA1

  5. Hyperfine structure of the MnH X 7Sigma + state: A large gas-to-matrix shift in the Fermi contact interaction

    Science.gov (United States)

    Varberg, Thomas D.; Field, Robert W.; Merer, Anthony J.

    1990-06-01

    Sub-Doppler spectra of the A 7Π-X 7Σ+ (0,0) band of gas phase MnH near 5680 Å were recorded by intermodulated fluorescence spectroscopy. The spectra reveal hyperfine splittings arising from both the 55Mn and 1H nuclear spins. Internal hyperfine perturbations have been observed between the different spin components of the ground state at low N`. From a preliminary analysis of several rotational lines originating from the isolated and unperturbed F1(J`=3) spin component of the X 7Σ+(N`=0) level, the 55Mn Fermi contact interaction in the ground state has been measured as bF=Aiso =276(1) MHz. This value is 11% smaller than the value obtained by Weltner et al. from an electron-nuclear double resonance (ENDOR) study of MnH in an argon matrix at 4 K. This unprecedented gas-to-matrix shift in the Fermi contact parameter is discussed.

  6. Hyperfine structure of the MnH X 7Σ+ state: A large gas-to-matrix shift in the Fermi contact interaction

    International Nuclear Information System (INIS)

    Varberg, T.D.; Field, R.W.; Merer, A.J.

    1990-01-01

    Sub-Doppler spectra of the A 7 Π--X 7 Σ + (0,0) band of gas phase MnH near 5680 A were recorded by intermodulated fluorescence spectroscopy. The spectra reveal hyperfine splittings arising from both the 55 Mn and 1 H nuclear spins. Internal hyperfine perturbations have been observed between the different spin components of the ground state at low N double-prime. From a preliminary analysis of several rotational lines originating from the isolated and unperturbed F 1 (J double-prime=3) spin component of the X 7 Σ + (N double-prime=0) level, the 55 Mn Fermi contact interaction in the ground state has been measured as b F =A iso =276(1) MHz. This value is 11% smaller than the value obtained by Weltner et al. from an electron-nuclear double resonance (ENDOR) study of MnH in an argon matrix at 4 K. This unprecedented gas-to-matrix shift in the Fermi contact parameter is discussed

  7. Gas sensor

    International Nuclear Information System (INIS)

    Dorogan, V.; Korotchenkov, Gh.; Vieru, T.; Prodan, I.

    2003-01-01

    The invention relates to the gas sensors on base of metal-oxide films (SnO, InO), which may be used for enviromental control, in the fireextinguishing systema etc. The gas includes an insulating substrate, an active layer, a resistive layer with ohmic contacts. The resistive layer has two or more regions with dofferent resistances , and on the active layer are two or more pairs of ohmic contacts

  8. From Wage Rigidities to Labour Market Rigidities: A Turning-Point in Explaining Equilibrium Unemployment?

    OpenAIRE

    Marco Guerrazzi; Nicola Meccheri

    2009-01-01

    This paper offers a critical discussion of the concept of labour market rigidity relevant to explaining unemployment. Starting from Keynes’s own view, we discuss how the concept of labour market flexibility has changed over time, involving nominal or real wage flexibility, contract flexibility or labour market institution flexibility. We also provide a critical assessment of the factors that lead the search framework highlighting labour market rigidities (frictions) to challenge the more wide...

  9. Applanation tonometry in silicone hydrogel contact lens wearers.

    Science.gov (United States)

    Allen, R J; Dev Borman, A; Saleh, G M

    2007-12-01

    Previous studies have investigated intraocular pressure (IOP) measurements through conventional soft (hydrogel) therapeutic contact lenses, and have found that an accurate IOP can be recorded in normal eyes, and in eyes with abnormal anterior segments. The IOP measurement through soft contact lenses may be affected by the water content and centre thickness of the lens. Silicone hydrogel contact lenses are now being used as therapeutic contact lenses due to their high oxygen permeability. The purpose of this study is to investigate if IOP can be accurately measured in a subject wearing a silicone hydrogel contact lens. In a cohort study, the IOP was measured with a Goldmann applanation tonometer without a contact lens and then repeated with a hydrogel contact lens in situ. The IOP of 20 eyes of 10 volunteers with no ocular pathology was measured. The mean difference (+/-S.D.) found between IOP measurement with (mean 15.55+/-1.70 mmHg) and without (mean 16.05+/-1.90 mmHg) contact lens was found to be -0.5+/-0.89 mmHg. Statistical analysis was performed which revealed a correlation coefficient of 0.89. No significant statistical difference was found between the two groups with paired t-test (p=0.19). Accurate measurement of IOP by applanation tonometry can be achieved through a silicone hydrogel contact lens.

  10. Gas-particle interactions in dense gas-fluidised beds

    NARCIS (Netherlands)

    Li, J.; Kuipers, J.A.M.

    2003-01-01

    The occurrence of heterogeneous flow structures in gas-particle flows seriously affects gas¿solid contacting and transport processes in dense gas-fluidized beds. A computational study, using a discrete particle method based on Molecular Dynamics techniques, has been carried out to explore the

  11. Permeability changes of coal cores and briquettes under tri-axial stress conditions

    Czech Academy of Sciences Publication Activity Database

    Wierzbicki, M.; Konečný, Pavel; Kožušníková, Alena

    2014-01-01

    Roč. 59, č. 4 (2014), s. 1129-1138 ISSN 0860-7001 R&D Projects: GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : coal * gas permeability * tri-axial stress * coal briquettes Subject RIV: DH - Mining, incl. Coal Mining Impact factor: 0.608, year: 2013 http://mining.archives.pl

  12. Identifying Floppy and Rigid Regions in Proteins

    Science.gov (United States)

    Jacobs, D. J.; Thorpe, M. F.; Kuhn, L. A.

    1998-03-01

    In proteins it is possible to separate hard covalent forces involving bond lengths and bond angles from other weak forces. We model the microstructure of the protein as a generic bar-joint truss framework, where the hard covalent forces and strong hydrogen bonds are regarded as rigid bar constraints. We study the mechanical stability of proteins using FIRST (Floppy Inclusions and Rigid Substructure Topography) based on a recently developed combinatorial constraint counting algorithm (the 3D Pebble Game), which is a generalization of the 2D pebble game (D. J. Jacobs and M. F. Thorpe, ``Generic Rigidity: The Pebble Game'', Phys. Rev. Lett.) 75, 4051-4054 (1995) for the special class of bond-bending networks (D. J. Jacobs, "Generic Rigidity in Three Dimensional Bond-bending Networks", Preprint Aug (1997)). This approach is useful in identifying rigid motifs and flexible linkages in proteins, and thereby determines the essential degrees of freedom. We will show some preliminary results from the FIRST analysis on the myohemerythrin and lyozyme proteins.

  13. Frictionless contact analysis of a functionally graded piezoelectric layered half-plane

    International Nuclear Information System (INIS)

    Ke Liaoliang; Yang Jie; Kitipornchai, Sritawat; Wang Yuesheng

    2008-01-01

    This paper investigates the frictionless contact problem of a layered half-plane made of functionally graded piezoelectric material (FGPM) in the plane strain state under the action of a rigid punch whose shape may be flat, triangular or cylindrical. It is assumed that the punch is a perfect electrical insulator with zero electric charge distribution. The electroelastic properties of the FGPM layer vary exponentially along the thickness direction. By using the Fourier integral transform technique, the problem is reduced to a Cauchy singular integral equation which is then numerically solved to determine the contact pressure, contact region, maximum indentation depth, normal stress, electrical potential and electric displacement fields. The stress intensity factor is also given to quantitatively characterize the singularity behavior of the contact pressure at the ends of a flat and triangular punch. Numerical results show that both the material property gradient of the FGPM layer and the punch geometry have a significant influence on the contact performance of the FGPM layered half-plane

  14. Permeability of porour rhyolite

    Science.gov (United States)

    Cashman, K.; Rust, A.; Wright, H.; Roberge, J.

    2003-04-01

    The development of permeability in bubble-bearing magmas determines the efficiency of volatile escape during their ascent through volcanic conduits, which, in turn, controls their explosive potential. As permeability requires bubble connectivity, relationships between permeability and porosity in silicic magmas must be controlled by the formation, growth, deformation and coalescence of their constituent bubbles. Although permeability data on porous volcanic pyroclasts are limited, the database can be greatly extended by including data for ceramic and metallic foams1. Several studies indicate that a single number does not adequately describe the permeability of a foam because inertial effects, which predominate at high flow rates, cause deviations from Darcy's law. These studies suggest that permeability is best modeled using the Forschheimer equation to determine both the Darcy permeability (k1) and the non-Darcian (k2) permeability. Importantly, at the high porosities of ceramic foams (75-95%), both k1 and k2 are strongly dependent on pore size and geometry, suggesting that measurement of these parameters provides important information on foam structure. We determined both the connected porosity (by He-pycnometry) and the permeability (k1 and k2) of rhyolitic samples having a wide range in porosity (22-85%) and vesicle textures. In general, these data support previous observations of a power law relationship between connected porosity and Darcy permeability2. In detail, variations in k1 increase at higher porosities. Similarly, k2 generally increases in both mean and standard deviation with increasing porosity. Measurements made on three mutually perpendicular cores from individual pumice clasts suggest that some of the variability can be explained by anisotropy in the vesicle structure. By comparison with ceramic foams, we suggest that the remaining variability results from differences either in average vesicle size or, more likely, in the size of apertures

  15. Foam flow in a model porous medium: II. The effect of trapped gas.

    Science.gov (United States)

    Jones, S A; Getrouw, N; Vincent-Bonnieu, S

    2018-05-09

    Gas trapping is an important mechanism in both Water or Surfactant Alternating Gas (WAG/SAG) and foam injection processes in porous media. Foams for enhanced oil recovery (EOR) can increase sweep efficiency as they decrease the gas relative permeability, and this is mainly due to gas trapping. However, gas trapping mechanisms are poorly understood. Some studies have been performed during corefloods, but little work has been carried out to describe the bubble trapping behaviour at the pore scale. We have carried out foam flow tests in a micromodel etched with an irregular hexagonal pattern. Image analysis of the foam flow allowed the bubble centres to be tracked and local velocities to be obtained. It was found that the flow in the micromodel is dominated by intermittency and localized zones of trapped gas. The quantity of trapped gas was measured both by considering the fraction of bubbles that were trapped (via velocity thresholding) and by measuring the area fraction containing immobile gas (via image analysis). A decrease in the quantity of trapped gas was observed for both increasing total velocity and increasing foam quality. Calculations of the gas relative permeability were made with the Brooks Corey equation, using the measured trapped gas saturations. The results showed a decrease in gas relative permeabilities, and gas mobility, for increasing fractions of trapped gas. It is suggested that the shear thinning behaviour of foam could be coupled to the saturation of trapped gas.

  16. Normal and friction stabilization techniques for interactive rigid body constraint-based contact force computations

    DEFF Research Database (Denmark)

    Silcowitz-Hansen, Morten; Abel, Sarah Maria Niebe; Erleben, Kenny

    2010-01-01

    We present a novel, yet simple, method for stabilization of normal forces. A normal stabilization term, carefully designed from hypotheses about interactive usability, is added to the contact force problem. Further, we propose friction stabilization as a completely new stabilization paradigm...

  17. Water-saving liquid-gas conditioning system

    Science.gov (United States)

    Martin, Christopher; Zhuang, Ye

    2014-01-14

    A method for treating a process gas with a liquid comprises contacting a process gas with a hygroscopic working fluid in order to remove a constituent from the process gas. A system for treating a process gas with a liquid comprises a hygroscopic working fluid comprising a component adapted to absorb or react with a constituent of a process gas, and a liquid-gas contactor for contacting the working fluid and the process gas, wherein the constituent is removed from the process gas within the liquid-gas contactor.

  18. Intestinal permeability study of minoxidil: assessment of minoxidil as a high permeability reference drug for biopharmaceutics classification.

    Science.gov (United States)

    Ozawa, Makoto; Tsume, Yasuhiro; Zur, Moran; Dahan, Arik; Amidon, Gordon L

    2015-01-05

    The purpose of this study was to evaluate minoxidil as a high permeability reference drug for Biopharmaceutics Classification System (BCS). The permeability of minoxidil was determined in in situ intestinal perfusion studies in rodents and permeability studies across Caco-2 cell monolayers. The permeability of minoxidil was compared with that of metoprolol, an FDA reference drug for BCS classification. In rat perfusion studies, the permeability of minoxidil was somewhat higher than that of metoprolol in the jejunum, while minoxidil showed lower permeability than metoprolol in the ileum. The permeability of minoxidil was independent of intestinal segment, while the permeability of metoprolol was region-dependent. Similarly, in mouse perfusion study, the jejunal permeability of minoxidil was 2.5-fold higher than that of metoprolol. Minoxidil and metoprolol showed similar permeability in Caco-2 study at apical pH of 6.5 and basolateral pH of 7.4. The permeability of minoxidil was independent of pH, while metoprolol showed pH-dependent transport in Caco-2 study. Minoxidil exhibited similar permeability in the absorptive direction (AP-BL) in comparison with secretory direction (BL-AP), while metoprolol had higher efflux ratio (ER > 2) at apical pH of 6.5 and basolateral pH of 7.4. No concentration-dependent transport was observed for either minoxidil or metoprolol transport in Caco-2 study. Verapamil did not alter the transport of either compounds across Caco-2 cell monolayers. The permeability of minoxidil was independent of both pH and intestinal segment in intestinal perfusion studies and Caco-2 studies. Caco-2 studies also showed no involvement of carrier mediated transport in the absorption process of minoxidil. These results suggest that minoxidil may be an acceptable reference drug for BCS high permeability classification. However, minoxidil exhibited higher jejunal permeability than metoprolol and thus to use minoxidil as a reference drug would raise the

  19. A new method for the experimental determination of three-phase relative permeabilities

    International Nuclear Information System (INIS)

    Perez Carrillo, Edgar Ricardo; Jose Francisco Zapata Arango; Santos Santos, Nicolas

    2008-01-01

    Petroleum reservoirs under primary, secondary or tertiary recovery processes usually experience simultaneous flow of three fluids phases (oil, water and gas). Reports on some mathematical models for calculating three-phase relative permeability are available in the Literature. Nevertheless, many of these models were designed based on certain experimental conditions and reservoir rocks and fluids. Therefore, special care has to be taken when applying them to specific reservoirs. At the laboratory level, three-phase relative permeability can be calculated using experimental unsteady-state or steady state methodologies. This paper proposes an unsteady-state methodology to evaluate three-phase relative permeability using the equipment available at the petrophysical analysis Laboratory of the Instituto Colombiano del Petroleo (ICP) of Ecopetrol S.A. Improvements to the equipment were effected in order to achieve accuracy in the unsteady-state measurement of three-phase relative permeability. The target of improvements was directed toward to the attainment of two objectives:1) the modification of the equipment to obtain more reliable experimental data and 2) the appropriate interpretation of the data obtained. Special attention was given to the differential pressure and uncertainty measurement in the determination of fluid saturation in the rock samples. Three experiments for three-phase relative permeability were conducted using a sample A and reservoir rock from the Colombian Foothills. Fluid tests included the utilization of synthetic brine, mineral oil, reservoir crude oil and nitrogen. Two runs were conducted at the laboratory conditions while one run was conducted at reservoir conditions. Experimental results of these tests were compared using 16 mathematical models of three-phase relative permeability. For the three-phase relative permeability to oil, the best correlations between experimental data and tests using Blunt, Hustad Hasen, and Baker's models were

  20. Pressure-dependent pure- and mixed-gas permeation properties of Nafion®

    KAUST Repository

    Mukaddam, Mohsin Ahmed; Litwiller, Eric; Pinnau, Ingo

    2016-01-01

    observed phenomena: compression and plasticization. In pure-gas experiments, at increasing feed pressure, compression of the polymer matrix reduced the permeability of low-sorbing penetrants H2, N2, O2, and CH4. In contrast, permeabilities of more soluble

  1. Advantageous Reservoir Characterization Technology in Extra Low Permeability Oil Reservoirs

    Directory of Open Access Journals (Sweden)

    Yutian Luo

    2017-01-01

    Full Text Available This paper took extra low permeability reservoirs in Dagang Liujianfang Oilfield as an example and analyzed different types of microscopic pore structures by SEM, casting thin sections fluorescence microscope, and so on. With adoption of rate-controlled mercury penetration, NMR, and some other advanced techniques, based on evaluation parameters, namely, throat radius, volume percentage of mobile fluid, start-up pressure gradient, and clay content, the classification and assessment method of extra low permeability reservoirs was improved and the parameter boundaries of the advantageous reservoirs were established. The physical properties of reservoirs with different depth are different. Clay mineral variation range is 7.0%, and throat radius variation range is 1.81 μm, and start pressure gradient range is 0.23 MPa/m, and movable fluid percentage change range is 17.4%. The class IV reservoirs account for 9.56%, class II reservoirs account for 12.16%, and class III reservoirs account for 78.29%. According to the comparison of different development methods, class II reservoir is most suitable for waterflooding development, and class IV reservoir is most suitable for gas injection development. Taking into account the gas injection in the upper section of the reservoir, the next section of water injection development will achieve the best results.

  2. Soft soils reinforced by rigid vertical inclusions

    Directory of Open Access Journals (Sweden)

    Iulia-Victoria NEAGOE

    2013-12-01

    Full Text Available Reinforcement of soft soils by rigid vertical inclusions is an increasingly used technique over the last few years. The system consists of rigid or semi-rigid vertical inclusions and a granular platform for the loads transfer from the structure to the inclusions. This technique aims to reduce the differential settlements both at ground level as below the structure. Reinforcement by rigid inclusions is mainly used for foundation works for large commercial and industrial platforms, storage tanks, wastewater treatment plants, wind farms, bridges, roads, railway embankments. The subject is one of interest as it proves the recently concerns at international level in research and design; however, most studies deal more with the static behavior and less with the dynamic one.

  3. Effects of phase transformation of steam-water relative permeabilities

    Energy Technology Data Exchange (ETDEWEB)

    Verma, A.K.

    1986-03-01

    A combined theoretical and experimental study of steam-water relative permeabilities (RPs) was carried out. First, an experimental study of two-phase concurrent flow of steam and water was conducted and a set of RP curves was obtained. These curves were compared with semi-empirical and experimental results obtained by other investigators for two-phase, two-component flow (oil/gas; gas/water; gas/oil). It was found that while the wetting phase RPs were in good agreement, RPs for the steam phase were considerably higher than the non-wetting phase RPs in two-component systems. This enhancement of steam RP is attributed to phase transformation effects at the pore level in flow channels. The effects of phase transformation were studied theoretically. This study indicates that there are two separate mechanisms by which phase transformation affects RP curves: (1) Phase transformation is converging-diverging flow channels can cause an enhancement of steam phase RP. In a channel dominated by steam a fraction of the flowing steam condenses upstream from the constriction, depositing its latent heat of condensation. This heat is conducted through the solid grains around the pore throat, and evaporation takes place downstream from it. Therefore, for a given bulk flow quality; a smaller fraction of steam actually flows through the throat segments. This pore-level effect manifests itself as relative permeability enhancement on a macroscopic level; and (2) phase transformation along the interface of a stagnant phase and the phase flowing around it controls the irreducible phase saturation. Therefore, the irreducible phase saturation in steam-water flow will depend, among other factors, on the boundary conditions of the flow.

  4. Effect of temperature and α-irradiation on gas permeability for ...

    Indian Academy of Sciences (India)

    Unknown

    polymer membranes that help separate gas. In addition to the chemical composition, the transport properties are related to the main characteristics of copolymers like the glass transition temperature, crystallinity and crosslink- ing ratio. Gas diffusion through polymers is related to the activation energy (Pesiri et al 2003).

  5. Permeability evolution due to dissolution of natural shale fractures reactivated by fracking

    Science.gov (United States)

    Kwiatkowski, Kamil; Kwiatkowski, Tomasz; Szymczak, Piotr

    2015-04-01

    Investigation of cores drilled from gas-bearing shale formations reveals a relatively large number of calcite-cemented fractures. During fracking, some of these fractures will be reactivated [1-2] and may become important flow paths in the resulting fracture system. In this communication, we investigate numerically the effect of low-pH reactive fluid on such fractures. The low-pH fluids can either be pumped during the initial fracking stage (as suggested e.g. by Grieser et al., [3]) or injected later, as part of enhanced gas recovery (EGR) processes. In particular, it has been suggested that CO2 injection can be considered as a method of EGR [4], which is attractive as it can potentially be combined with simultaneous CO2 sequestration. However, when mixed with brine, CO2 becomes acidic and thus can be a dissolving agent for the carbonate cement in the fractures. The dissolution of the cement leads to the enhancement of permeability and interconnectivity of the fracture network and, as a result, increases the overall capacity of the reservoir. Importantly, we show that the dissolution of such fractures proceeds in a highly non-homogeneous manner - a positive feedback between fluid transport and mineral dissolution leads to the spontaneous formation of pronounced flow channels, frequently referred to as "wormholes". The wormholes carry the chemically active fluid deeper inside the system, which dramatically speeds up the overall permeability increase. If the low-pH fluids are used during fracking, then the non-uniform dissolution becomes important for retaining the fracture permeability, even in the absence of the proppant. Whereas a uniformly etched fracture will close tightly under the overburden once the fluid pressure is removed, the nonuniform etching will tend to maintain the permeability since the less dissolved regions will act as supports to keep more dissolved regions open. [1] Gale, J. F., Reed, R. M., Holder, J. (2007). Natural fractures in the Barnett

  6. Dissociation of VE-PTP from VE-cadherin is required for leukocyte extravasation and for VEGF-induced vascular permeability in vivo

    Science.gov (United States)

    Broermann, Andre; Winderlich, Mark; Block, Helena; Frye, Maike; Rossaint, Jan; Zarbock, Alexander; Cagna, Giuseppe; Linnepe, Ruth; Schulte, Dörte; Nottebaum, Astrid Fee

    2011-01-01

    We have recently shown that vascular endothelial protein tyrosine phosphatase (VE-PTP), an endothelial membrane protein, associates with VE-cadherin and is required for optimal VE-cadherin function and endothelial cell contact integrity. The dissociation of VE-PTP from VE-cadherin is triggered by vascular endothelial growth factor (VEGF) and by the binding of leukocytes to endothelial cells in vitro, suggesting that this dissociation is a prerequisite for the destabilization of endothelial cell contacts. Here, we show that VE-cadherin/VE-PTP dissociation also occurs in vivo in response to LPS stimulation of the lung or systemic VEGF stimulation. To show that this dissociation is indeed necessary in vivo for leukocyte extravasation and VEGF-induced vascular permeability, we generated knock-in mice expressing the fusion proteins VE-cadherin-FK 506 binding protein and VE-PTP-FRB* under the control of the endogenous VE-cadherin promoter, thus replacing endogenous VE-cadherin. The additional domains in both fusion proteins allow the heterodimeric complex to be stabilized by a chemical compound (rapalog). We found that intravenous application of the rapalog strongly inhibited VEGF-induced (skin) and LPS-induced (lung) vascular permeability and inhibited neutrophil extravasation in the IL-1β inflamed cremaster and the LPS-inflamed lung. We conclude that the dissociation of VE-PTP from VE-cadherin is indeed required in vivo for the opening of endothelial cell contacts during induction of vascular permeability and leukocyte extravasation. PMID:22025303

  7. Dynamic Modeling and Vibration Analysis for the Vehicles with Rigid Wheels Based on Wheel-Terrain Interaction Mechanics

    Directory of Open Access Journals (Sweden)

    Jianfeng Wang

    2015-01-01

    Full Text Available The contact mechanics for a rigid wheel and deformable terrain are complicated owing to the rigid flexible coupling characteristics. Bekker’s equations are used as the basis to establish the equations of the sinking rolling wheel, to vertical load pressure relationship. Since vehicle movement on the Moon is a complex and on-going problem, the researcher is poised to simplify this problem of vertical loading of the wheel. In this paper, the quarter kinetic models of a manned lunar rover, which are both based on the rigid road and deformable lunar terrain, are used as the simulation models. With these kinetic models, the vibration simulations were conducted. The simulation results indicate that the quarter kinetic model based on the deformable lunar terrain accurately reflects the deformable terrain’s influence on the vibration characteristics of a manned lunar rover. Additionally, with the quarter kinetic model of the deformable terrain, the vibration simulations of a manned lunar rover were conducted, which include a parametric analysis of the wheel parameters, vehicle speed, and suspension parameters. The results show that a manned lunar rover requires a lower damping value and stiffness to achieve better vibration performance.

  8. Natural gas product and strategic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Layne, A.W.; Duda, J.R.; Zammerilli, A.M.

    1993-12-31

    Product and strategic analysis at the Department of Energy (DOE)/Morgantown Energy Technology Center (METC) crosscuts all sectors of the natural gas industry. This includes the supply, transportation, and end-use sectors of the natural-gas market. Projects in the Natural Gas Resource and Extraction supply program have been integrated into a new product focus. Product development facilitates commercialization and technology transfer through DOE/industry cost-shared research, development, and demonstration (RD&D). Four products under the Resource and Extraction program include Resource and Reserves; Low Permeability Formations; Drilling, Completion, and Stimulation: and Natural Gas Upgrading. Engineering process analyses have been performed for the Slant Hole Completion Test project. These analyses focused on evaluation of horizontal-well recovery potential and applications of slant-hole technology. Figures 2 and 3 depict slant-well in situ stress conditions and hydraulic fracture configurations. Figure 4 presents Paludal Formation coal-gas production curves used to optimize the hydraulic fracture design for the slant well. Economic analyses have utilized data generated from vertical test wells to evaluate the profitability of horizontal technology for low-permeability formations in Yuma County, Colorado, and Maverick County, Texas.

  9. A Conjunctival Mass in the Deep Superior Fornix After a Long Retained Hard Contact Lens in a Patient With Keloids

    NARCIS (Netherlands)

    Zola, Enrica; van der Meulen, Ivanka J. E.; Lapid-Gortzak, Ruth; van Vliet, J. Mj; Nieuwendaal, Carla P.

    2008-01-01

    Purpose: To report a case of an upper eyelid mass induced by a rigid contact lens retained for more than 3 years in the eye of a patient with a general history of keloids and to provide a review of the literature on retained contact lenses. Methods: Case report. Results: A 45-year-old woman with an

  10. Experimental study on the response characteristics of coal permeability to pore pressure under loading and unloading conditions

    Science.gov (United States)

    Ye, Zhiwei; Zhang, Lei; Hao, Dingyi; Zhang, Cun; Wang, Chen

    2017-10-01

    In order to study the response characteristics of coal permeability to pore pressure, seepage experiments under different simulated in situ stresses on loading and unloading paths are carried out using the self-developed Gas Flow and Displacement Testing Apparatus (GFDTA) system. Based on the analysis of the experimental data, the relationship between average pore pressure and permeability is found to basically obey the function distribution of a two degree polynomial. In this paper, two aspects of the relationship between permeability and pore pressure are explained: the Klinbenberg effect and expansion, and the penetration of the initial fracture. Under low pore pressure, the decrease in the Klinbenberg effect is the main reason for the decrease in permeability with increased pore pressure. Under relatively high pore pressure, the increase in pore pressure leads to the initial fracture expansion and penetration of the coal sample, which causes an increase in permeability. In order to evaluate the sensitivity of the permeability response to pore pressure changes, the permeability dispersion and pore pressure sensitivity coefficients are defined. After the sensitivity analysis, it was concluded that the loading history changed the fracture structure of the original coal sample and reduced its permeability sensitivity to pore pressure. Under low pore pressure, the Klinbenberg effect is the reason for the decrease in pore pressure sensitivity. Lastly, the permeability-pore pressure relationship is divided into three stages to describe the different response characteristics individually.

  11. Pure- and Mixed-Gas Transport Study of Nafion® and Its Fe3+-Substituted Derivative for Membrane-Based Natural Gas Applications

    KAUST Repository

    Mukaddam, Mohsin A.

    2016-05-26

    The focus of this research project was to develop a fundamental understanding of the structure-gas transport property relationship in Nafion® to investigate its potential use as a gas separation membrane material for natural gas (NG) applications including carbon dioxide removal from NG, helium recovery, higher-hydrocarbon removal, and nitrogen separation from methane. Separation processes account for ~45% of all energy used in chemical plants and petroleum refineries. As the drive for energy savings and sustainability intensifies, more efficient separation technology becomes increasingly important. Saudi Arabia ranks among the world’s top 5 NG producers. Commercial hydrocarbon-based glassy polymers often lose their gas separation properties in the presence of condensable, highly sorbing NG components such as CO2, ethane, propane, n-butane, and C5+ hydrocarbons. This deterioration in gas separation performance results from penetrant-induced dilation and plasticization of the polymer matrix, leading to significant methane and higher hydrocarbon losses. Polymers that have intrinsically low affinity to high-solubility NG components may be less susceptible to plasticization and therefore offer better performance under actual field conditions. By virtue of their strong carbon-fluorine bonds and chemical inertness, perfluoropolymers exhibit very low affinity for hydrocarbon gases. Nafion®, the prototypical perfluoro-sulfonated ionomer, comprising hydrophilic sulfonate groups phase-separated from a hydrophobic perfluorocarbon matrix, has demonstrated interesting permeability and selectivity relationships for gas pairs relevant to NG applications. Gas transport properties of Nafion® indicated gas solubility behavior similar to rubbery polymers but with sieving properties more commonly observed in low free volume glassy polymers. Nafion® demonstrated very low solubility for CO2 and hydrocarbon gases; the trend-line slope of solubility versus penetrant condensability

  12. The Contact Dynamics method: A nonsmooth story

    Science.gov (United States)

    Dubois, Frédéric; Acary, Vincent; Jean, Michel

    2018-03-01

    When velocity jumps are occurring, the dynamics is said to be nonsmooth. For instance, in collections of contacting rigid bodies, jumps are caused by shocks and dry friction. Without compliance at the interface, contact laws are not only non-differentiable in the usual sense but also multi-valued. Modeling contacting bodies is of interest in order to understand the behavior of numerous mechanical systems such as flexible multi-body systems, granular materials or masonry. These granular materials behave puzzlingly either like a solid or a fluid and a description in the frame of classical continuous mechanics would be welcome though far to be satisfactory nowadays. Jean-Jacques Moreau greatly contributed to convex analysis, functions of bounded variations, differential measure theory, sweeping process theory, definitive mathematical tools to deal with nonsmooth dynamics. He converted all these underlying theoretical ideas into an original nonsmooth implicit numerical method called Contact Dynamics (CD); a robust and efficient method to simulate large collections of bodies with frictional contacts and impacts. The CD method offers a very interesting complementary alternative to the family of smoothed explicit numerical methods, often called Distinct Elements Method (DEM). In this paper developments and improvements of the CD method are presented together with a critical comparative review of advantages and drawbacks of both approaches. xml:lang="fr"

  13. Power operated contact apparatus for superconductive circuit

    Energy Technology Data Exchange (ETDEWEB)

    Woods, D.C.; Efferson, K.R.

    1989-10-10

    This patent describes a power operated contact apparatus for extending and retracting one or more electrical leads into and out of a cryostat for making and breaking, at a cryogenic temperature, electrical contact with a superconductive circuit. It comprises at least one rigid elongated lead for extending into a cold space of the cryostat which is at or near a cryogenic temperature. The lead having an inner end and a outer end; a connector fixed at the inner end of the lead for making electrical contact in the cold space with a connector of the superconductive circuit; guide means journaling the lead for allowing the lead to move axially relative to the guide means and sealing against the lead; a foundation for sealed attachment to the cryostat and to the guide means so that the connector on the inner end of the lead is extendable into making electrical contact with the connector of the superconductive circuit in the cold space; power operated means mounted on the foundation and fixed to the outer end of the lead for extending and retracting the lead to and from making electrical contact with the superconductive circuit in the cold space; and means for de-icing the exterior of the leads and guide means when the leads are connected to the superconducting circuit.

  14. Field-scale permeability and temperature of volcanic crust from borehole data: Campi Flegrei, southern Italy

    Science.gov (United States)

    Carlino, Stefano; Piochi, Monica; Tramelli, Anna; Mormone, Angela; Montanaro, Cristian; Scheu, Bettina; Klaus, Mayer

    2018-05-01

    We report combined measurements of petrophysical and geophysical parameters for a 501-m deep borehole located on the eastern side of the active Campi Flegrei caldera (Southern Italy), namely (i) in situ permeability by pumping tests, (ii) laboratory-determined permeability of the drill core, and (iii) thermal gradients by distributed fiber optic and thermocouple sensors. The borehole was drilled during the Campi Flegrei Deep Drilling Project (in the framework of the International Continental Scientific Drilling Program) and gives information on the least explored caldera sector down to pre-caldera deposits. The results allow comparative assessment of permeability obtained from both borehole (at depth between 422 a 501 m) and laboratory tests (on a core sampled at the same depth) for permeability values of 10-13 m2 (borehole test) and 10-15 m2 (laboratory test) confirm the scale-dependency of permeability at this site. Additional geochemical and petrophysical determinations (porosity, density, chemistry, mineralogy and texture), together with gas flow measurements, corroborate the hypothesis that discrepancies in the permeability values are likely related to in-situ fracturing. The continuous distributed temperature profile points to a thermal gradient of about 200 °C km-1. Our findings (i) indicate that scale-dependency of permeability has to be carefully considered in modelling of the hydrothermal system at Campi Flegrei, and (ii) improve the understanding of caldera dynamics for monitoring and mitigation of this very high volcanic risk area.

  15. 222Rn and CO2 soil-gas geochemical characterization of thermally altered clays at Orciatico (Tuscany, Central Italy)

    International Nuclear Information System (INIS)

    Voltattorni, N.; Lombardi, S.; Rizzo, S.

    2010-01-01

    Research highlights: → Soil-gas technique is applied to study gas permeability of Orciatico clay units. → Clay permeability depends on thermal and mechanical alteration degree. → Soil-gas distributions are due to shallow fracturing of clays. → Rn and CO 2 soil-gas anomalies highlight secondary permeability in clay sequence. → Soil-gas results are supported by detailed geoelectrical surveys. - Abstract: The physical properties of clay allow argillaceous formations to be considered geological barriers to radionuclide migration in high-level radioactive-waste isolation systems. As laboratory simulations are short term and numerical models always involve assumptions and simplifications of the natural system, natural analogues are extremely attractive surrogates for the study of long-term isolation. The clays of the Orciatico area (Tuscany, Central Italy), which were thermally altered via the intrusion of an alkali-trachyte laccolith, represent an interesting natural model of a heat source which acted on argillaceous materials. The study of this natural analogue was performed through detailed geoelectrical and soil-gas surveys to define both the geometry of the intrusive body and the gas permeability of a clay unit characterized by different degrees of thermal alteration. The results of this study show that gas permeability is increased in the clay sequences subjected to greater heat input from the emplacement of the Orciatico intrusion, despite the lack of apparent mineral and geotechnical variations. These results, which take into consideration long time periods in a natural, large-scale geological system, may have important implications for the long-term safety of underground storage of nuclear waste in clay formations.

  16. Sub-core permeability and relative permeability characterization with Positron Emission Tomography

    Science.gov (United States)

    Zahasky, C.; Benson, S. M.

    2017-12-01

    This study utilizes preclinical micro-Positron Emission Tomography (PET) to image and quantify the transport behavior of pulses of a conservative aqueous radiotracer injected during single and multiphase flow experiments in a Berea sandstone core with axial parallel bedding heterogeneity. The core is discretized into streamtubes, and using the micro-PET data, expressions are derived from spatial moment analysis for calculating sub-core scale tracer flux and pore water velocity. Using the flux and velocity data, it is then possible to calculate porosity and saturation from volumetric flux balance, and calculate permeability and water relative permeability from Darcy's law. Full 3D simulations are then constructed based on this core characterization. Simulation results are compared with experimental results in order to test the assumptions of the simple streamtube model. Errors and limitations of this analysis will be discussed. These new methods of imaging and sub-core permeability and relative permeability measurements enable experimental quantification of transport behavior across scales.

  17. Fracture network topology and characterization of structural permeability

    Science.gov (United States)

    Hansberry, Rowan; King, Rosalind; Holford, Simon

    2017-04-01

    There are two fundamental requirements for successful geothermal development: elevated temperatures at accessible depths, and a reservoir from which fluids can be extracted. The Australian geothermal sector has successfully targeted shallow heat, however, due in part to the inherent complexity of targeting permeability, obtaining adequate flow rates for commercial production has been problematic. Deep sedimentary aquifers are unlikely to be viable geothermal resources due to the effects of diagenetic mineral growth on rock permeability. Therefore, it is likely structural permeability targets, exploiting natural or induced fracture networks will provide the primary means for fluid flow in geothermal, as well as unconventional gas, reservoirs. Recent research has focused on the pattern and generation of crustal stresses across Australia, while less is known about the resultant networks of faults, joints, and veins that can constitute interconnected sub-surface permeability pathways. The ability of a fracture to transmit fluid is controlled by the orientation and magnitude of the in-situ stress field that acts on the fracture walls, rock strength, and pore pressure, as well as fracture properties such as aperture, orientation, and roughness. Understanding the distribution, orientation and character of fractures is key to predicting structural permeability. This project focuses on extensive mapping of fractures over various scales in four key Australian basins (Cooper, Otway, Surat and Perth) with the potential to host geothermal resources. Seismic attribute analysis is used in concert with image logs from petroleum wells, and field mapping to identify fracture networks that are usually not resolved in traditional seismic interpretation. We use fracture network topology to provide scale-invariant characterisation of fracture networks from multiple data sources to assess similarity between data sources, and fracture network connectivity. These results are compared with

  18. Accelerated production of antigen-specific T-cells for pre-clinical and clinical applications using Gas-permeable Rapid Expansion cultureware (G-Rex)

    Science.gov (United States)

    Vera, Juan F.; Brenner, Lara J.; Gerdemann, Ulrike; Ngo, Minhtran C.; Sili, Uluhan; Liu, Hao; Wilson, John; Dotti, Gianpietro; Heslop, Helen E.; Leen, Ann M.; Rooney, Cliona M.

    2009-01-01

    The clinical manufacture of antigen-specific cytotoxic T lymphocytes (CTL) for adoptive immunotherapy is limited by the complexity and time required to produce large numbers with the desired function and specificity. The culture conditions required are rigorous, and in some cases only achieved in 2cm2 wells in which cell growth is limited by gas exchange, nutrients and waste accumulation. Bioreactors developed to overcome these issues tend to be complex, expensive and not always conducive to CTL growth. We observed that antigen-specific CTL undergo seven to ten divisions post-stimulation. However the expected CTL numbers were achieved only in the first week of culture. By recreating the culture conditions present during this first week - low frequency of antigen-specific T-cells and high frequency of feeder cells - we were able to increase CTL expansion to expected levels which could be sustained for several weeks without affecting phenotype or function. However, the number of 24-well plates needed was excessive and cultures required frequent media changes, increasing complexity and manufacturing costs. Therefore, we evaluated novel gas-permeable culture devices (G-Rex) with a silicone membrane at the base allowing gas exchange to occur uninhibited by depth of medium above. This system effectively supports the expansion of CTL and actually increases output by up to 20-fold while decreasing required technician time. Importantly, this amplified cell expansion is not due to more cell divisions but to reduced cell death. This bioprocess optimization increased T-cell output while decreasing the complexity and cost of CTL manufacture, making cell therapy more accessible. PMID:20445351

  19. A thermodynamical model for the surface tension of silicate melts in contact with H2O gas

    Science.gov (United States)

    Colucci, Simone; Battaglia, Maurizio; Trigila, Raffaello

    2016-01-01

    Surface tension plays an important role in the nucleation of H2O gas bubbles in magmatic melts and in the time-dependent rheology of bubble-bearing magmas. Despite several experimental studies, a physics based model of the surface tension of magmatic melts in contact with H2O is lacking. This paper employs gradient theory to develop a thermodynamical model of equilibrium surface tension of silicate melts in contact with H2O gas at low to moderate pressures. In the last decades, this approach has been successfully applied in studies of industrial mixtures but never to magmatic systems. We calibrate and verify the model against literature experimental data, obtained by the pendant drop method, and by inverting bubble nucleation experiments using the Classical Nucleation Theory (CNT). Our model reproduces the systematic decrease in surface tension with increased H2O pressure observed in the experiments. On the other hand, the effect of temperature is confirmed by the experiments only at high pressure. At atmospheric pressure, the model shows a decrease of surface tension with temperature. This is in contrast with a number of experimental observations and could be related to microstructural effects that cannot be reproduced by our model. Finally, our analysis indicates that the surface tension measured inverting the CNT may be lower than the value measured by the pendant drop method, most likely because of changes in surface tension controlled by the supersaturation.

  20. A Study of Nonlinear Elasticity Effects on Permeability of Stress Sensitive Shale Rocks Using an Improved Coupled Flow and Geomechanics Model: A Case Study of the Longmaxi Shale in China

    Directory of Open Access Journals (Sweden)

    Chenji Wei

    2018-02-01

    Full Text Available Gas transport in shale gas reservoirs is largely affected by rock properties such as permeability. These properties are often sensitive to the in-situ stress state changes. Accurate modeling of shale gas transport in shale reservoir rocks considering the stress sensitive effects on rock petrophysical properties is important for successful shale gas extraction. Nonlinear elasticity in stress sensitive reservoir rocks depicts the nonlinear stress-strain relationship, yet it is not thoroughly studied in previous reservoir modeling works. In this study, an improved coupled flow and geomechanics model that considers nonlinear elasticity is proposed. The model is based on finite element methods, and the nonlinear elasticity in the model is validated with experimental data on shale samples selected from the Longmaxi Formation in Sichuan Basin China. Numerical results indicate that, in stress sensitive shale rocks, nonlinear elasticity affects shale permeability, shale porosity, and distributions of effective stress and pore pressure. Elastic modulus change is dependent on not only in-situ stress state but also stress history path. Without considering nonlinear elasticity, the modeling of shale rock permeability in Longmaxi Formation can overestimate permeability values by 1.6 to 53 times.