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  1. Audiological results with Baha in conductive and mixed hearing loss.

    Science.gov (United States)

    Pfiffner, Flurin; Caversaccio, Marco-Domenico; Kompis, Martin

    2011-01-01

    The level of improvement in the audiological results of Baha(®) users mainly depends on the patient's preoperative hearing thresholds and the type of Baha sound processor used. This investigation shows correlations between the preoperative hearing threshold and postoperative aided thresholds and audiological results in speech understanding in quiet of 84 Baha users with unilateral conductive hearing loss, bilateral conductive hearing loss and bilateral mixed hearing loss. Secondly, speech understanding in noise of 26 Baha users with different Baha sound processors (Compact, Divino, and BP100) is investigated. Linear regression between aided sound field thresholds and bone conduction (BC) thresholds of the better ear shows highest correlation coefficients and the steepest slope. Differences between better BC thresholds and aided sound field thresholds are smallest for mid-frequencies (1 and 2 kHz) and become larger at 0.5 and 4 kHz. For Baha users, the gain in speech recognition in quiet can be expected to lie in the order of magnitude of the gain in their hearing threshold. Compared to its predecessor sound processors Baha(®) Compact and Baha(®) Divino, Baha(®) BP100 improves speech understanding in noise significantly by +0.9 to +4.6 dB signal-to-noise ratio, depending on the setting and the use of directional microphone. For Baha users with unilateral and bilateral conductive hearing loss and bilateral mixed hearing loss, audiological results in aided sound field thresholds can be estimated with the better BC hearing threshold. The benefit in speech understanding in quiet can be expected to be similar to the gain in their sound field hearing threshold. The most recent technology of Baha sound processor improves speech understanding in noise by an order of magnitude that is well perceived by users and which can be very useful in everyday life. Copyright © 2011 S. Karger AG, Basel.

  2. Thermal conductivity of silicic tuffs: predictive formalism and comparison with preliminary experimental results

    International Nuclear Information System (INIS)

    Lappin, A. R.

    1980-07-01

    Performance of both near- and far-field thermomechanical calculations to assess the feasibility of waste disposal in silicic tuffs requires a formalism for predicting thermal conductivity of a broad range of tuffs. This report summarizes the available thermal conductivity data for silicate phases that occur in tuffs and describes several grain-density and conductivity trends which may be expected to result from post-emplacement alteration. A bounding curve is drawn that predicts the minimum theoretical matrix (zero-porosity) conductivity for most tuffs as a function of grain density. Comparison of experimental results with this curve shows that experimental conductivities are consistently lower at any given grain density. Use of the lowered bounding curve and an effective gas conductivity of 0.12 W/m 0 C allows conservative prediction of conductivity for a broad range of tuff types. For the samples measured here, use of the predictive curve allows estimation of conductivity to within 15% or better, with one exception. Application and possible improvement of the formalism are also discussed

  3. Colloidal graphite/graphene nanostructures using collagen showing enhanced thermal conductivity

    Science.gov (United States)

    Bhattacharya, Soumya; Dhar, Purbarun; Das, Sarit K; Ganguly, Ranjan; Webster, Thomas J; Nayar, Suprabha

    2014-01-01

    In the present study, the exfoliation of natural graphite (GR) directly to colloidal GR/graphene (G) nanostructures using collagen (CL) was studied as a safe and scalable process, akin to numerous natural processes and hence can be termed “biomimetic”. Although the exfoliation and functionalization takes place in just 1 day, it takes about 7 days for the nano GR/G flakes to stabilize. The predominantly aromatic residues of the triple helical CL forms its own special micro and nanoarchitecture in acetic acid dispersions. This, with the help of hydrophobic and electrostatic forces, interacts with GR and breaks it down to nanostructures, forming a stable colloidal dispersion. Surface enhanced Raman spectroscopy, X-ray diffraction, photoluminescence, fluorescence, and X-ray photoelectron spectroscopy of the colloid show the interaction between GR and CL on day 1 and 7. Differential interference contrast images in the liquid state clearly reveal how the GR flakes are entrapped in the CL fibrils, with a corresponding fluorescence image showing the intercalation of CL within GR. Atomic force microscopy of graphene-collagen coated on glass substrates shows an average flake size of 350 nm, and the hexagonal diffraction pattern and thickness contours of the G flakes from transmission electron microscopy confirm ≤ five layers of G. Thermal conductivity of the colloid shows an approximate 17% enhancement for a volume fraction of less than approximately 0.00005 of G. Thus, through the use of CL, this new material and process may improve the use of G in terms of biocompatibility for numerous medical applications that currently employ G, such as internally controlled drug-delivery assisted thermal ablation of carcinoma cells. PMID:24648728

  4. Colloidal graphite/graphene nanostructures using collagen showing enhanced thermal conductivity.

    Science.gov (United States)

    Bhattacharya, Soumya; Dhar, Purbarun; Das, Sarit K; Ganguly, Ranjan; Webster, Thomas J; Nayar, Suprabha

    2014-01-01

    In the present study, the exfoliation of natural graphite (GR) directly to colloidal GR/graphene (G) nanostructures using collagen (CL) was studied as a safe and scalable process, akin to numerous natural processes and hence can be termed "biomimetic". Although the exfoliation and functionalization takes place in just 1 day, it takes about 7 days for the nano GR/G flakes to stabilize. The predominantly aromatic residues of the triple helical CL forms its own special micro and nanoarchitecture in acetic acid dispersions. This, with the help of hydrophobic and electrostatic forces, interacts with GR and breaks it down to nanostructures, forming a stable colloidal dispersion. Surface enhanced Raman spectroscopy, X-ray diffraction, photoluminescence, fluorescence, and X-ray photoelectron spectroscopy of the colloid show the interaction between GR and CL on day 1 and 7. Differential interference contrast images in the liquid state clearly reveal how the GR flakes are entrapped in the CL fibrils, with a corresponding fluorescence image showing the intercalation of CL within GR. Atomic force microscopy of graphene-collagen coated on glass substrates shows an average flake size of 350 nm, and the hexagonal diffraction pattern and thickness contours of the G flakes from transmission electron microscopy confirm ≤ five layers of G. Thermal conductivity of the colloid shows an approximate 17% enhancement for a volume fraction of less than approximately 0.00005 of G. Thus, through the use of CL, this new material and process may improve the use of G in terms of biocompatibility for numerous medical applications that currently employ G, such as internally controlled drug-delivery assisted thermal ablation of carcinoma cells.

  5. Boys with Oppositional Defiant Disorder/Conduct Disorder Show Impaired Adaptation During Stress: An Executive Functioning Study.

    Science.gov (United States)

    Schoorl, Jantiene; van Rijn, Sophie; de Wied, Minet; van Goozen, Stephanie; Swaab, Hanna

    2018-04-01

    Evidence for problems in executive functioning (EF) in children with oppositional defiant disorder/conduct disorder (ODD/CD) is mixed and the impact stress may have on EF is understudied. Working memory, sustained attention, inhibition and cognitive flexibility of boys with ODD/CD (n = 65) and non-clinical controls (n = 32) were examined under typical and stressful test conditions. Boys with ODD/CD showed impaired working memory under typical testing conditions, and impairments in working memory and sustained attention under stressful conditions. In contrast to controls, performance on sustained attention, cognitive flexibility and inhibition was less influenced by stress in boys with ODD/CD. These results suggest that boys with ODD/CD show impairments in adaptation to the environment whereas typically developing boys show adaptive changes in EF.

  6. Report on the results of the safety culture survey conducted in PNRI

    International Nuclear Information System (INIS)

    Garcia, Corazon M.; Nohay, Carl M.; Badinas, Nelson P.; Melendez, Johnylen V.; Parami, Vangeline K.

    2001-01-01

    An initial safety culture survey was conducted in the Philippine Nuclear Research Institute (PNRI). Sixty six (66) questionnaires as given in A. Adams and A. Williamson's Measurement of Safety Culture in the Nuclear Industry, UNSW, July 1999 were distributed to the different units of PNRI. The number of sets of survey sheets distributed to the different units corresponded to the number of personnel in the unit based on the information obtained from them. Results were obtained from only 33 respondents. ANSTO has been requested to analyze the results of this survey. While waiting for the results from ANSTO, we attempted to proceed with this analysis in order to learn and practice applying the procedure based on the reference cited above.The respondents from the PNRI showed on the overall neutral views towards safety and their work. Although a minority showed positive responses to safety while a small minority showed negative responses. A remarkable result is that all respondents show strong concern over the welfare of the institute, indicating that there is still a good chance for safety culture to be developed positively among the employees given the proper strategies for motivation. (author)

  7. Transparent conducting materials: Overview and recent results

    NARCIS (Netherlands)

    Deelen, J. van; Illiberi, A.; Hovestad, A.; Barbu, I.; Klerk, L.; Buskens, P.

    2012-01-01

    An overview of different transparent conductors is given. In addition, atmospheric pressure CVD of ZnO resulted in conductivities below 1 mΩ cm for a temperature of 480°C, whereas at a process temperature of 200°C a value of 2 mΩ cm was obtained. Also atmospheric pressure spatial ALD was used to

  8. Comparison of Audiological Results Between a Transcutaneous and a Percutaneous Bone Conduction Instrument in Conductive Hearing Loss.

    Science.gov (United States)

    Gerdes, Timo; Salcher, Rolf Benedikt; Schwab, Burkard; Lenarz, Thomas; Maier, Hannes

    2016-07-01

    In conductive, mixed hearing losses and single-sided-deafness bone-anchored hearing aids are a well-established treatment. The transcutaneous transmission across the intact skin avoids the percutaneous abutment of a bone-anchored device with the usual risk of infections and requires less care.In this study, the audiological results of the Bonebridge transcutaneous bone conduction implant (MED-EL) are compared to the generally used percutaneous device BP100 (Cochlear Ltd., Sydney, Australia). Ten patients implanted with the transcutaneous hearing implant were compared to 10 matched patients implanted with a percutaneous device. Tests included pure-tone AC and BC thresholds and unaided and aided sound field thresholds. Speech intelligibility was determined in quiet using the Freiburg monosyllable test and in noise with the Oldenburg sentence test (OLSA) in sound field with speech from the front (S0). The subjective benefit was assessed with the Abbreviated Profile of Hearing Aid Benefit. In comparison with the unaided condition there was a significant improvement in aided thresholds, word recognition scores (WRS), and speech reception thresholds (SRT) in noise, measured in sound field, for both devices. The comparison of the two devices revealed a minor but not significant difference in functional gain (Bonebridge: PTA = 27.5 dB [mean]; BAHA: PTA = 26.3 dB [mean]). No significant difference between the two devices was found when comparing the improvement in WRSs and SRTs (Bonebridge: improvement WRS = 80% [median], improvement SRT = 6.5 dB SNR [median]; BAHA: improvement WRS = 77.5% [median], BAHA: improvement SRT = 6.9 dB SNR [median]). Our data show that the transcutaneous bone conduction hearing implant is an audiologically equivalent alternative to percutaneous bone-anchored devices in conductive hearing loss with a minor sensorineural hearing loss component.

  9. Authoritarian parenting attitudes as a risk for conduct problems Results from a British national cohort study.

    Science.gov (United States)

    Thompson, Anne; Hollis, Chris; Dagger, David Richards

    2003-04-01

    This study examines the associations, and possible causal relationship, between mothers' authoritarian attitudes to discipline and child behaviour using cross-sectional and prospective data from a large population sample surveyed in the 1970 British Cohort Study. Results show a clear linear relationship between the degree of maternal approval of authoritarian child-rearing attitudes and the rates of conduct problems at age 5 and age 10. This association is independent of the confounding effects of socio-economic status and maternal psychological distress. Maternal authoritarian attitudes independently predicted the development of conduct problems 5 years later at age 10. The results of this longitudinal study suggest that authoritarian parenting attitudes expressed by mothers may be of significance in the development of conduct problems.

  10. Results of gap conductance tests in the power burst facility

    International Nuclear Information System (INIS)

    Garner, R.W.; Sparks, D.T.

    1977-01-01

    Light water reactor (LWR) fuel rod behavior studies are being conducted by the Thermal Fuels Behavior Program of EG and G Idaho, Inc. These studies are being performed under contract to the Energy Research and Development Adminstration at the Idaho National Engineering Laboratory (INEL), as part of the Nuclear Regulatory Commission's Water Reactor Safety Research Fuel Behavior Program. Experimental data for verification of analytical models developed to predict light water nuclear fuel rod behavior under normal and postulated accident conditions are being obtained from a variety of in-reactor and out-of-reactor experiments. This paper summarizes the results of tests performed in the Power Burst Facility (PBF) to obtain data from which the thermal response, gap conductance, and stored energy of LWR fuel rods can be determined. Primary objectives of the PBF gap conductance test program are (a) to obtain data on a variety of pressurized water reactor (PWR) and boiling water reactor (BWR) fuel rod designs, under a wide range of operating conditions, from which gap conductance values can be determined and (b) to evaluate experimentally the power oscillation method for measuring the gap conductance and thermal response of a fresh or burned LWR fuel rod. Tests have been performed with both irradiated and unirradiated PWR-type fuel and with fresh BWR-type fuel rods. Some PWR rod test results are described, and the thermal response data from BWR rod tests are discussed in greater detail. Comparisons are made of gap conductance values determined by the tests with analytically calculated values using the Fuel Rod Analysis Program-Transient (FRAP-T) computer code. These comparisons provide insight into both the experimental measurements methods and the validity of the gap conductance models

  11. Iatrogenic hypernatremia in hemodialysis patients: A result of erroneous online conductivity monitor and conductivity meter reading.

    Science.gov (United States)

    Obialo, Chamberlain I; John, Smitha; Bashir, Khalid

    2017-10-01

    Hyponatremia is common in chronic kidney disease and in end stage kidney disease (ESKD) but hypernatremia is infrequent in ESKD. The incidence of hypernatremia is higher in ambulatory peritoneal dialysis (PD) than in hemodialysis (HD) patients. In PD patients it is often a result of excessive ultrafiltration but in HD it is often a result of dialysate composition errors. Dialysate composition errors can inadvertently cause either hyponatremia or hypernatremia. We present two cases of symptomatic hypernatremia which manifested as increased thirst, excessive weight gain and worsening hypertension in HD patients. The hypernatremia was caused by a combination of errors in online conductivity reading and a faulty hand held conductivity meter. Symptoms were relieved in both patients after replacement of the dialysis machine. © 2017 International Society for Hemodialysis.

  12. An improved method for interpreting API filter press hydraulic conductivity test results

    International Nuclear Information System (INIS)

    Heslin, G.M.; Baxter, D.Y.; Filz, G.M.; Davidson, R.R.

    1997-01-01

    The American Petroleum Institute (API) filter press is frequently used to measure the hydraulic conductivity of soil-bentonite backfill during the mix design process and as part of construction quality controls. However, interpretation of the test results is complicated by the fact that the seepage-induced consolidation pressure varies from zero at the top of the specimen to a maximum value at the bottom of the specimen. An analytical solution is available which relates the stress, compressibility, and hydraulic conductivity in soil consolidated by seepage forces. This paper presents the results of a laboratory investigation undertaken to support application of this theory to API hydraulic conductivity tests. When the API test results are interpreted using seepage consolidation theory, they are in good agreement with the results of consolidometer permeameter tests. Limitations of the API test are also discussed

  13. Discrete Element Modeling Results of Proppant Rearrangement in the Cooke Conductivity Cell

    Energy Technology Data Exchange (ETDEWEB)

    Earl Mattson; Hai Huang; Michael Conway; Lisa O' Connell

    2014-02-01

    The study of propped fracture conductivity began in earnest with the development of the Cooke cell which later became part of the initial API standard. Subsequent developments included a patented multicell design to conduct 4 tests in a press at the same time. Other modifications have been used by various investigators. Recent studies by the Stim-Lab proppant consortium have indicated that the flow field across a Cooke proppant conductivity testing cell may not be uniform as initially believed which resulted is significantly different conductivity results. Post test analysis of low temperature metal alloy injections at the termination of proppant testing prior to the release of the applied stress suggest that higher flow is to be expected along the sides and top of the proppant pack than compared to the middle of the pack. To evaluate these experimental findings, a physics-based two-dimensional (2-D) discrete element model (DEM) was developed and applied to simulate proppant rearrangement during stress loading in the Cooke conductivity cell and the resulting porosity field. Analysis of these simulations are critical to understanding the impact of modification to the testing cell as well as understanding key proppant conductivity issues such as how these effects are manifested in proppant concentration testing results. The 2-D DEM model was constructed to represent a realistic cross section of the Cooke cell with a distribution of four material properties, three that represented the Cooke cell (steel, sandstone,square rings), and one representing the proppant. In principle, Cooke cell materials can be approximated as assemblies of independent discrete elements (particles) of various sizes and material properties that interact via cohesive interactions, repulsive forces, and frictional forces. The macroscopic behavior can then be modeled as the collective behavior of many interacting discrete elements. This DEM model is particularly suitable for modeling proppant

  14. Analysis of nonlocal phonon thermal conductivity simulations showing the ballistic to diffusive crossover

    Science.gov (United States)

    Allen, Philip B.

    2018-04-01

    Simulations [e.g., X. W. Zhou et al., Phys. Rev. B 79, 115201 (2009), 10.1103/PhysRevB.79.115201] show nonlocal effects of the ballistic/diffusive crossover. The local temperature has nonlinear spatial variation not contained in the local Fourier law j ⃗(r ⃗) =-κ ∇ ⃗T (r ⃗) . The heat current j ⃗(r ⃗) depends not just on the local temperature gradient ∇ ⃗T (r ⃗) but also on temperatures at points r⃗' within phonon mean free paths, which can be micrometers long. This paper uses the Peierls-Boltzmann transport theory in nonlocal form to analyze the spatial variation Δ T (r ⃗) . The relaxation-time approximation (RTA) is used because the full solution is very challenging. Improved methods of extrapolation to obtain the bulk thermal conductivity κ are proposed. Callaway invented an approximate method of correcting RTA for the q ⃗ (phonon wave vector or crystal momentum) conservation of N (Normal as opposed to Umklapp) anharmonic collisions. This method is generalized to the nonlocal case where κ (k ⃗) depends on the wave vector of the current j ⃗(k ⃗) and temperature gradient i k ⃗Δ T (k ⃗) .

  15. Conductivity-limiting bipolar thermal conductivity in semiconductors

    Science.gov (United States)

    Wang, Shanyu; Yang, Jiong; Toll, Trevor; Yang, Jihui; Zhang, Wenqing; Tang, Xinfeng

    2015-01-01

    Intriguing experimental results raised the question about the fundamental mechanisms governing the electron-hole coupling induced bipolar thermal conduction in semiconductors. Our combined theoretical analysis and experimental measurements show that in semiconductors bipolar thermal transport is in general a “conductivity-limiting” phenomenon, and it is thus controlled by the carrier mobility ratio and by the minority carrier partial electrical conductivity for the intrinsic and extrinsic cases, respectively. Our numerical method quantifies the role of electronic band structure and carrier scattering mechanisms. We have successfully demonstrated bipolar thermal conductivity reduction in doped semiconductors via electronic band structure modulation and/or preferential minority carrier scatterings. We expect this study to be beneficial to the current interests in optimizing thermoelectric properties of narrow gap semiconductors. PMID:25970560

  16. Conduct disorders as a result of specific learning disorders

    OpenAIRE

    VOKROJOVÁ, Nela

    2012-01-01

    This thesis focuses on relationship between specific learning disorders and conduct disorders in puberty. The theoretical part explains the basic terms apearing in the thesis such as specific learning disorders, conduct disorders, puberty and prevention of conduct disorder formation. It presents Czech and foreign research which have already been done in this and related areas. The empirical part uses a quantitative method to measure anxiety and occurrence of conduct disorders in second grade ...

  17. Gun Shows and Gun Violence: Fatally Flawed Study Yields Misleading Results

    Science.gov (United States)

    Hemenway, David; Webster, Daniel; Pierce, Glenn; Braga, Anthony A.

    2010-01-01

    A widely publicized but unpublished study of the relationship between gun shows and gun violence is being cited in debates about the regulation of gun shows and gun commerce. We believe the study is fatally flawed. A working paper entitled “The Effect of Gun Shows on Gun-Related Deaths: Evidence from California and Texas” outlined this study, which found no association between gun shows and gun-related deaths. We believe the study reflects a limited understanding of gun shows and gun markets and is not statistically powered to detect even an implausibly large effect of gun shows on gun violence. In addition, the research contains serious ascertainment and classification errors, produces results that are sensitive to minor specification changes in key variables and in some cases have no face validity, and is contradicted by 1 of its own authors’ prior research. The study should not be used as evidence in formulating gun policy. PMID:20724672

  18. Nonlinear heat conduction equations with memory: Physical meaning and analytical results

    Science.gov (United States)

    Artale Harris, Pietro; Garra, Roberto

    2017-06-01

    We study nonlinear heat conduction equations with memory effects within the framework of the fractional calculus approach to the generalized Maxwell-Cattaneo law. Our main aim is to derive the governing equations of heat propagation, considering both the empirical temperature-dependence of the thermal conductivity coefficient (which introduces nonlinearity) and memory effects, according to the general theory of Gurtin and Pipkin of finite velocity thermal propagation with memory. In this framework, we consider in detail two different approaches to the generalized Maxwell-Cattaneo law, based on the application of long-tail Mittag-Leffler memory function and power law relaxation functions, leading to nonlinear time-fractional telegraph and wave-type equations. We also discuss some explicit analytical results to the model equations based on the generalized separating variable method and discuss their meaning in relation to some well-known results of the ordinary case.

  19. Preliminary functional results and quality of life after implantation of a new bone conduction hearing device in patients with conductive and mixed hearing loss.

    Science.gov (United States)

    Ihler, Friedrich; Volbers, Laura; Blum, Jenny; Matthias, Christoph; Canis, Martin

    2014-02-01

    To review functional results and quality of life of the first patients implanted with a newly introduced bone conduction implant system. Retrospective chart analysis of 6 patients (6 ears) implanted for conductive hearing loss (CHL) and mixed hearing loss (MHL) in 1 tertiary referral center between July 2012 and February 2013. Implantation of a new bone conduction hearing device. Pure tone audiometry (air conduction and bone conduction thresholds, pure tone average, air-bone gap, and functional gain), speech audiometry (Freiburg Monosyllabic Test), intraoperative and postoperative complication rate, and patient satisfaction (Glasgow benefit inventory [GBI]) were assessed. Air-conduction pure tone average (PTA) was 58.8 ± 8.2 dB HL. Unaided average air-bone gap (ABG) was 33.3 ± 6.2 dB. Aided air-conduction PTA in sound field was 25.2 ± 5.1 dB HL. Aided average ABG was -0.3 ± 7.3 dB. Average functional gain was 33.6 ± 7.2 dB. Mean improvement of GBI was +36.1. No intraoperative complications occurred. During a follow-up period of 8.5 ± 2.2 months, no device failure and no need for revision surgery occurred. Audiometric results of the new bone conduction hearing system are satisfying and comparable to the results of devices that have been applied previously for CHL and MHL. Intraoperatively and postoperatively, no complications were noted.

  20. Results of experimental investigations on the heat conductivity of nanofluids based on diathermic oil for high temperature applications

    International Nuclear Information System (INIS)

    Colangelo, Gianpiero; Favale, Ernani; Risi, Arturo de; Laforgia, Domenico

    2012-01-01

    Highlights: ► This work reports experimental results for nanofluids using diathermic oil as base fluid. ► Nanofluids with CuO, Al 2 O 3 , ZnO and Cu, with different shapes and concentrations have been tested. ► Thermal conductivity enhancement of nanofluids with diathermic oil is higher than those with demineralized water. ► Better results were obtained with ZnO, for nanofluids with metal oxide nanoparticles. -- Abstract: The work reported in this paper shows the experimental results from a study on diathermic oil based nanofluids. Diathermic oil finds application in renewable energy, cogeneration and cooling systems. For example, it is used in solar thermodynamic or biomass plants, where high efficiency, compact volumes and high energy fluxes are required. Besides diathermic oil is very important in those applications where high temperatures are reached or where the use of water or vapor is not suitable. Therefore an improvement of diathermic oil thermo-physical properties, by using of nanoparticles, can increase the performance of the systems. In literature there are not many experimental data on diathermic oil based nanofluids because many experimental campaigns are focused on water nanofluids. Samples of nanofluids, with nanoparticles of CuO, Al 2 O 3 , ZnO and Cu, having different shapes and concentrations varying from 0.0% up to 3.0%, have been produced and their thermal conductivity has been measured by means of hot-wire technique, according to the standard ASTM D 2717-95. Measurements were carried out to investigate the effects of volume fraction, particle size of nanoparticles on the thermal conductivity of the nanofluid. The effect of temperature has been also investigated in the range 20–60 °C. A dependence was observed on the measured parameters and the results showed that the heat transfer performance of diathermic oil enhances more than water with the same nanoparticles.

  1. Effect of spatial variation of thermal conductivity on non-fourier heat conduction in a finite slab

    International Nuclear Information System (INIS)

    Goharkhah, Mohammad; Amiri, Shahin; Shokouhmand, Hossein

    2009-01-01

    The non-Fourier heat conduction problem in a finite slab is studied analytically. Dependence of thermal conductivity on space has been considered. The Laplace transform method is used to remove the time-dependent terms in the governing equation and the boundary conditions. The hyperbolic heat conduction (HHC) equation has been solved by employing trial solution method and collocation optimization criterion. Results show that the space-dependent thermal conductivity strongly affects the temperature distribution. A temperature peak on the insulated wall of the slab has been observed due to linear variation of thermal conductivity. It has been shown that the magnitude of the temperature peak increases with increasing the dimensionless relaxation time. To validate the approach, the results have been compared with the analytical solution obtained for a special case which shows a good agreement

  2. Heat conductivity of buffer materials

    International Nuclear Information System (INIS)

    Boergesson, L.; Fredrikson, Anders; Johannesson, L.E.

    1994-11-01

    The report deals with the thermal conductivity of bentonite based buffer materials. An improved technique for measuring the thermal conductivity of buffer materials is described. Measurements of FLAC calculations applying this technique have led to a proposal of how standardized tests should be conducted and evaluated. The thermal conductivity of bentonite with different void ratio and degree of water saturation has been determined in the following different ways: * Theoretically according to three different investigations by other researchers. * Laboratory measurements with the proposed method. * Results from back-calculated field tests. Comparison and evaluation showed that these results agreed very well, when the buffer material was almost water saturated. However, the influence of the degree of saturation was not very well predicted with the theoretical methods. Furthermore, the field tests showed that the average thermal conductivity in situ of buffer material (compacted to blocks) with low degree of water saturation was lower than expected from laboratory tests. 12 refs, 29 figs, 11 tabs

  3. Functional results of Vibrant Soundbridge middle ear implants in conductive and mixed hearing losses.

    Science.gov (United States)

    Bernardeschi, Daniele; Hoffman, Caroline; Benchaa, Tarek; Labassi, Samia; Beliaeff, Michel; Sterkers, Olivier; Grayeli, Alexis Bozorg

    2011-01-01

    Our purpose was to evaluate the results of Vibrant Soundbridge (VSB) in conductive or mixed hearing loss. Twenty-five adult patients (29 ears) with a mixed or conductive hearing loss and various etiologies were included in this retrospective study. The preoperative ipsilateral pure tone average was 71 ± 3.0 dB, and the average bone conduction threshold was 42 ± 2.8 dB (n = 29). The transducer was placed on the long apophysis of the incus (n = 16), in the round window (n = 10) or on the stapes (n = 3). No complications were noted. The bone conduction threshold remained unchanged. VSB was activated in all cases. The postoperative pure tone average without VSB was 63 ± 3.9 dB (n = 24) and with VSB in free-field condition 24 ± 2.1 dB (n = 22). VSB is safe and efficacious for auditory rehabilitation in conductive and mixed hearing losses. Copyright © 2011 S. Karger AG, Basel.

  4. Are Corporate Universities (CU possible in emerging countries? A survey conducted in Argentina showed impacting results

    Directory of Open Access Journals (Sweden)

    Leandro A. Viltard

    2014-09-01

    Full Text Available At the time of our investigation, the CU was not a widespread concept in Argentina, being viewed as a “foreign - far long project” (coming from developed countries and standing for the long term. It is suggested that the rate of CU evolution, in emerging countries like Argentina, is more related to mentality issues than to CU strategic or operative limitations. Although the executives who replied to a survey were not the only power factor in their organization, their comments allow us to think that, in those countries, the CU may have a better future perspective. The research used a quali-quantitative methodology, which was based on a survey to top executives of different kinds of companies located in Argentina. The research design was not experimental and transversal, as it was limited to a specific moment in time.

  5. Conducting Polymer 3D Microelectrodes

    Directory of Open Access Journals (Sweden)

    Jenny Emnéus

    2010-12-01

    Full Text Available Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained showed uniformity and good adhesion to both horizontal and vertical surfaces. Electrodes in combination with metal/conducting polymer materials have been characterized by cyclic voltammetry and the presence of the conducting polymer film has shown to increase the electrochemical activity when compared with electrodes coated with only metal. An electrochemical characterization of gold/polypyrrole electrodes showed exceptional electrochemical behavior and activity. PC12 cells were finally cultured on the investigated materials as a preliminary biocompatibility assessment. These results show that the described electrodes are possibly suitable for future in-vitro neurological measurements.

  6. Example-based illustrations of design, conduct, analysis and result interpretation of multi-regional clinical trials.

    Science.gov (United States)

    Quan, Hui; Mao, Xuezhou; Tanaka, Yoko; Binkowitz, Bruce; Li, Gang; Chen, Josh; Zhang, Ji; Zhao, Peng-Liang; Ouyang, Soo Peter; Chang, Mark

    2017-07-01

    Extensive research has been conducted in the Multi-Regional Clinical Trial (MRCT) area. To effectively apply an appropriate approach to a MRCT, we need to synthesize and understand the features of different approaches. In this paper, examples are used to illustrate considerations regarding design, conduct, analysis and interpretation of result of MRCTs. We start with a brief discussion of region definitions and the scenarios where different regions have differing requirements for a MRCT. We then compare different designs and models as well as the corresponding interpretation of the results. We highlight the importance of paying special attention to trial monitoring and conduct to prevent potential issues associated with the final trial results. Besides evaluating the overall treatment effect for the entire MRCT, we also consider other key analyses including quantification of regional treatment effects within a MRCT, and assessment of consistency of these regional treatment effects. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. [Conduct disorders in seven-year-old children--results of ELSPAC study 1. Co-morbidity].

    Science.gov (United States)

    Kukla, L; Hrubá, D; Tyrlík, M; Matejová, H

    2008-01-01

    The interest of experts in conduct disorders (CD) research is growing during the last two decades. The research areas include the diagnostics, ethiopathogenesis and treatment and also the comorbidity, especially with the hyperkinetic syndrome incidence (Attention Deficit Hyperactivity Disorder--ADHD). This paper intends to describe the conduct disorder occurrence and its other manifestations of divergence found during the investigation of children followed in the prospective longitudinal study ELSPAC in seven, respectively eight years of their age. Data of 6100 seven-year-old children characterizing their behaviour was collected from mothers and attending physicians. In the school year during which this investigation phase took place 2518 of the children reached eight years of age and their behaviour, temperament and school results were also evaluated by their teachers. The children were divided into three groups according to the presence or absence of the symptoms, which characterize conduct disorders (found by physicians): "stubborn negativistic behaviour", "inability to pay attention", "aggressiveness" and "inadequacy of reactions". The presence of two of these symptoms was found in 3%, presence of all four symptoms in additional 1.4% of children. Parents and teachers more often indicated various symptoms of hyperactivity in children with conduct disorders. In almost 5% of the ELSPAC cohort children in seven years of their age those symptoms were diagnosed, which match the Conduct Disorder criteria and Attention Deficit Hyperactivity Disorder (ADHD) criteria. In agreement with similar studies these frequent comorbidities were found: sleep disorders, psychomotor development disorders and laterality changes. The cognitive abilities evaluated by mothers and also teachers based on schoolwork results were more often worsened in children with conduct disorders. Various data indicating their worse social adaptability (which significantly disturbed the class) occurred

  8. A New Method for a Virtue-Based Responsible Conduct of Research Curriculum: Pilot Test Results.

    Science.gov (United States)

    Berling, Eric; McLeskey, Chet; O'Rourke, Michael; Pennock, Robert T

    2018-02-03

    Drawing on Pennock's theory of scientific virtues, we are developing an alternative curriculum for training scientists in the responsible conduct of research (RCR) that emphasizes internal values rather than externally imposed rules. This approach focuses on the virtuous characteristics of scientists that lead to responsible and exemplary behavior. We have been pilot-testing one element of such a virtue-based approach to RCR training by conducting dialogue sessions, modeled upon the approach developed by Toolbox Dialogue Initiative, that focus on a specific virtue, e.g., curiosity and objectivity. During these structured discussions, small groups of scientists explore the roles they think the focus virtue plays and should play in the practice of science. Preliminary results have shown that participants strongly prefer this virtue-based model over traditional methods of RCR training. While we cannot yet definitively say that participation in these RCR sessions contributes to responsible conduct, these pilot results are encouraging and warrant continued development of this virtue-based approach to RCR training.

  9. Influence of conductive electroactive polymer polyaniline on ...

    Indian Academy of Sciences (India)

    Conductive electroactive polymer polyaniline is utilized to substitute conductive additive acetylene black in the LiMn1.95Al0.05O4 cathode for lithium ion batteries. Results show that LiMn1.95Al0.05O4 possesses stable structure and good performance. Percolation theory is used to optimize the content of conductive additive ...

  10. Testing Delays Resulting in Increased Identification Accuracy in Line-Ups and Show-Ups.

    Science.gov (United States)

    Dekle, Dawn J.

    1997-01-01

    Investigated time delays (immediate, two-three days, one week) between viewing a staged theft and attempting an eyewitness identification. Compared lineups to one-person showups in a laboratory analogue involving 412 subjects. Results show that across all time delays, participants maintained a higher identification accuracy with the showup…

  11. Thermal conductivity of water: Molecular dynamics and generalized hydrodynamics results

    Science.gov (United States)

    Bertolini, Davide; Tani, Alessandro

    1997-10-01

    Equilibrium molecular dynamics simulations have been carried out in the microcanonical ensemble at 300 and 255 K on the extended simple point charge (SPC/E) model of water [Berendsen et al., J. Phys. Chem. 91, 6269 (1987)]. In addition to a number of static and dynamic properties, thermal conductivity λ has been calculated via Green-Kubo integration of the heat current time correlation functions (CF's) in the atomic and molecular formalism, at wave number k=0. The calculated values (0.67+/-0.04 W/mK at 300 K and 0.52+/-0.03 W/mK at 255 K) are in good agreement with the experimental data (0.61 W/mK at 300 K and 0.49 W/mK at 255 K). A negative long-time tail of the heat current CF, more apparent at 255 K, is responsible for the anomalous decrease of λ with temperature. An analysis of the dynamical modes contributing to λ has shown that its value is due to two low-frequency exponential-like modes, a faster collisional mode, with positive contribution, and a slower one, which determines the negative long-time tail. A comparison of the molecular and atomic spectra of the heat current CF has suggested that higher-frequency modes should not contribute to λ in this temperature range. Generalized thermal diffusivity DT(k) decreases as a function of k, after an initial minor increase at k=kmin. The k dependence of the generalized thermodynamic properties has been calculated in the atomic and molecular formalisms. The observed differences have been traced back to intramolecular or intermolecular rotational effects and related to the partial structure functions. Finally, from the results we calculated it appears that the SPC/E model gives results in better agreement with experimental data than the transferable intermolecular potential with four points TIP4P water model [Jorgensen et al., J. Chem. Phys. 79, 926 (1983)], with a larger improvement for, e.g., diffusion, viscosities, and dielectric properties and a smaller one for thermal conductivity. The SPC/E model shares

  12. Development of the conductive glove for glove box operation. Production of prototypes and their experimental results

    International Nuclear Information System (INIS)

    Kodato, Kazuo; Enuma, Masahito; Kawasaki, Takeshi; Nogami, Yoshitaka; Kaneko, Kazunori; Kimura, Masanori; Yasumori, Tomokazu

    2014-02-01

    The glove used at glove boxes in the nuclear fuel plants is usually made with Chlorosulfonated polyethylene rubber. The rubber is excellent in terms of resistance to radiation because it has no double bond in its main chain of the component, however, it deteriorates rapidly in high dose environment such as direct contact of alpha ray. Plutonium oxide powder is treated in glove boxes at plutonium fuel facilities where the alpha ray from plutonium oxide powder adhered on surface of a glove causes the deterioration of the rubber. Therefore the effective method for prevent of the rapid deterioration is to decrease the amount of adhered powder, and the glove with conductive property which can prevent static electric charge on its surface has been developed and tested. The results showed that the rubber has less adherent property to powder compared with conventional one. (author)

  13. Effect of particle size ratio on the conducting percolation threshold of granular conductive-insulating composites

    International Nuclear Information System (INIS)

    He Da; Ekere, N N

    2004-01-01

    In this paper, we apply Monte Carlo simulation to investigate the conductive percolation threshold of granular composite of conductive and insulating powders with amorphous structure. We focus on the effect of insulating to conductive particle size ratio λ = d i /d c on the conducting percolation threshold p c (the volume fraction of the conductive powder). Simulation results show that, for λ = 1, the percolation threshold p c lies between simple cubic and body centred cubic site percolation thresholds, and that as λ increases the percolation threshold decreases. We also use the structural information obtained by the simulation to study the nonlinear current-voltage characteristics of composite with solid volume fraction of conductive powder below p c in terms of electron tunnelling for nanoscale powders, dielectric breakdown for microscale or larger powders, and pressing induced conduction for non-rigid insulating powders

  14. Computational analysis of electrical conduction in hybrid nanomaterials with embedded non-penetrating conductive particles

    Science.gov (United States)

    Cai, Jizhe; Naraghi, Mohammad

    2016-08-01

    In this work, a comprehensive multi-resolution two-dimensional (2D) resistor network model is proposed to analyze the electrical conductivity of hybrid nanomaterials made of insulating matrix with conductive particles such as CNT reinforced nanocomposites and thick film resistors. Unlike existing approaches, our model takes into account the impenetrability of the particles and their random placement within the matrix. Moreover, our model presents a detailed description of intra-particle conductivity via finite element analysis, which to the authors’ best knowledge has not been addressed before. The inter-particle conductivity is assumed to be primarily due to electron tunneling. The model is then used to predict the electrical conductivity of electrospun carbon nanofibers as a function of microstructural parameters such as turbostratic domain alignment and aspect ratio. To simulate the microstructure of single CNF, randomly positioned nucleation sites were seeded and grown as turbostratic particles with anisotropic growth rates. Particle growth was in steps and growth of each particle in each direction was stopped upon contact with other particles. The study points to the significant contribution of both intra-particle and inter-particle conductivity to the overall conductivity of hybrid composites. Influence of particle alignment and anisotropic growth rate ratio on electrical conductivity is also discussed. The results show that partial alignment in contrast to complete alignment can result in maximum electrical conductivity of whole CNF. High degrees of alignment can adversely affect conductivity by lowering the probability of the formation of a conductive path. The results demonstrate approaches to enhance electrical conductivity of hybrid materials through controlling their microstructure which is applicable not only to carbon nanofibers, but also many other types of hybrid composites such as thick film resistors.

  15. Heat conduction in superconducting lead thallium alloys

    International Nuclear Information System (INIS)

    Ho, J.L.N.

    1975-01-01

    The heat conduction of six strong coupling superconducting Pb--Tl alloy specimens (1 to 20 percent wt Tl) was investigated with the emphasis on the effects of impurities upon the phonon thermal conductivity. All the specimens were annealed at 275 0 C for one week. Results show that the superconducting state phonon thermal conductivity of Pb--Tl is in reasonably good agreement with BRT theory. The strong coupling superconductivity of lead alloys can be handled by scaling the gap parameter using a constant factor. The results presented also show that the phonon thermal conductivity at low temperatures of well annealed lead-thallium alloys can be analyzed in terms of phonon scattering by the grain boundaries, point defects, conduction electrons, and other phonons. The phonon-dislocation scattering was found to be unimportant. The phonon relaxation rate due to point defects is in reasonably good agreement with the Klemens theory for the long range strain field scattering introduced by the thallium impurities. At low temperatures, the normal state phonon thermal conductivity showed an increase in the phonon-electron relaxation rate as the thallium concentration increases. The increase of the phonon-electron relaxation rate is attributed to the change of the Fermi surface caused by the presence of thallium impurity. The effect of the strong electron-phonon coupling character upon the phonon-electron relaxation rate has also been considered in terms of the electron-phonon enhancement factor found in the specific heat measurements

  16. Low thermal conductivity skutterudites

    Energy Technology Data Exchange (ETDEWEB)

    Fleurial, J P; Caillat, T; Borshchevsky, A

    1997-07-01

    Recent experimental results on semiconductors with the skutterudite crystal structure show that these materials possess attractive transport properties and have a good potential for achieving ZT values substantially larger than for state-of-the-art thermoelectric materials. Both n-type and p-type conductivity samples have been obtained, using several preparation techniques. Associated with a low hole effective mass, very high carrier mobilities, low electrical resistivities and moderate Seebeck coefficients are obtained in p-type skutterudites. For a comparable doping level, the carrier mobilities of n-type samples are about an order of magnitude lower than the values achieved on p-type samples. However, the much larger electron effective masses and Seebeck coefficients on p-type samples. However, the much larger electron effective masses and Seebeck coefficients make n-type skutterudite promising candidates as well. Unfortunately, the thermal conductivities of the binary skutterudites compounds are too large, particularly at low temperatures, to be useful for thermoelectric applications. Several approaches to the reduction of the lattice thermal conductivity in skutterudites are being pursued: heavy doping, formation of solid solutions and alloys, study of novel ternary and filled skutterudite compounds. All those approaches have already resulted in skutterudite compositions with substantially lower thermal conductivity values in these materials. Recently, superior thermoelectric properties in the moderate to high temperature range were achieved for compositions combining alloying and filling of the skutterudite structure. Experimental results and mechanisms responsible for low thermal conductivity in skutterudites are discussed.

  17. Thermal Conductivity of Polymer Composite poypropilene-Sand

    International Nuclear Information System (INIS)

    Betha; Mashuri; Sudirman; Karo Karo, Aloma

    2001-01-01

    Thermal conductivity composite materials polypropylene (PP)-sand have been investigated. PP composite with sand to increase thermal conductivity from the polymer. The composite in this observation is done by mixing matrix (PP melt flow 2/10)and filler sand)by means tool labo plastomil. The result of thermal conductivity is composite of PP-sand which is obtained increase and followed by the raising of filler particle volume fraction. The analysis of thermal conductivity based on the model Cheng and Vachon, model Lewis and Nielsen where this model has the function to support experiment finding. It is proved that Lewis' and Nielsen's model almost approach experiment result. And then thermal conductivity raising will be analyzed by the model of pararel-series conductive with the two (2)phases system. It is showed that sand in PP MF 2 composite have the big role to increase the thermal conductivity than sand in PP MF 10 composition, but it is not easy to shape conductive medium

  18. Studies on conducting polymer and conducting polymerinorganic composite electrodes prepared via a new cathodic polymerization method

    Science.gov (United States)

    Singh, Nikhilendra

    show significantly improved performance over bulk Pt or Ni electrodes in electrochemical hydrogen evolution applications. A variety of conducting polymer-inorganic composite materials are considered, showing that the obtained results are not limited to the mentioned inorganic materials and polymers. Various conducting polymer-inorganic composite electrodes with silver (Ag), gold (Au) and PEDOT are also reported and discussed in detail. The results presented herein open new pathways into the exploration, fabrication and applications of conducting polymer and conducting polymer-based inorganic composites in the field of energy storage and electrocatalysis.

  19. Enhancement in electrical conductivity of Li 2 O

    Indian Academy of Sciences (India)

    The study of electrical conductivity of 30Li2O : (70 – ) B2O3 : V2O5 glass samples has been carried out. The results have been explained by dividing the temperature range into two regions. In region I, conductivity shows Arrhenius behaviour for all the samples. The conductivity increases with addition of V2O5.

  20. Studies on electrical conductivity of poly phenylene vinylene

    International Nuclear Information System (INIS)

    Khattab, Asaad F.; Ahmad, Saddam M.

    2009-01-01

    Four Pp polymers have been synthesized through Wit ting reaction, 1 poly(p-phenylene vinylene), 2 = poly(p phenylene vinylene-co-m-phenylene vinylene), 3 = poly(p-phenylene vinylene-co-o-phenylene vinylene) and 4 poly(p-phenylene-1,5-hexadiene). Electrical conductivity measurements show that the conductivity of polymer 3 is higher than that of polymers 1 and 2. The dihedral angle measurements indicates that the irregularity of polymer chains is the main reason for this fact. The interruption of chain conjugation by aliphatic segments (polymer 4) will increase the conductivity by increasing the chain mobility.The electrical conductivity of the polymers is increased by doping with iodine and by raising the temperature. The effect of annealing with different temperatures on conductivity was studied; the results show that structural conformation of polymeric chain is the main factor affecting electrical conductivity. (author)

  1. AC conductivity of a quantum Hall line junction

    International Nuclear Information System (INIS)

    Agarwal, Amit; Sen, Diptiman

    2009-01-01

    We present a microscopic model for calculating the AC conductivity of a finite length line junction made up of two counter- or co-propagating single mode quantum Hall edges with possibly different filling fractions. The effect of density-density interactions and a local tunneling conductance (σ) between the two edges is considered. Assuming that σ is independent of the frequency ω, we derive expressions for the AC conductivity as a function of ω, the length of the line junction and other parameters of the system. We reproduce the results of Sen and Agarwal (2008 Phys. Rev. B 78 085430) in the DC limit (ω→0), and generalize those results for an interacting system. As a function of ω, the AC conductivity shows significant oscillations if σ is small; the oscillations become less prominent as σ increases. A renormalization group analysis shows that the system may be in a metallic or an insulating phase depending on the strength of the interactions. We discuss the experimental implications of this for the behavior of the AC conductivity at low temperatures.

  2. Studies on conductance of uranyl soaps

    International Nuclear Information System (INIS)

    Mehrotra, K.N.; Sharma, M.; Gahlaut, A.S.

    1987-01-01

    Specific conductance of uranyl soaps in dimethylformamide indicates two critical micelle concentrations CMC(I) and CMC(II). The value of CMC(II) decreases with the increase in chain length of the soap, whereas CMC(I) does not vary at all. The results show that the soaps behave as simple electrolyte. The major conductance at infinite dilution (μsub(o)) and dissociation constant (K) of these soaps have been evaluated. (author). 12 refs

  3. Thermal conductivity of electrospun polyethylene nanofibers.

    Science.gov (United States)

    Ma, Jian; Zhang, Qian; Mayo, Anthony; Ni, Zhonghua; Yi, Hong; Chen, Yunfei; Mu, Richard; Bellan, Leon M; Li, Deyu

    2015-10-28

    We report on the structure-thermal transport property relation of individual polyethylene nanofibers fabricated by electrospinning with different deposition parameters. Measurement results show that the nanofiber thermal conductivity depends on the electric field used in the electrospinning process, with a general trend of higher thermal conductivity for fibers prepared with stronger electric field. Nanofibers produced at a 45 kV electrospinning voltage and a 150 mm needle-collector distance could have a thermal conductivity of up to 9.3 W m(-1) K(-1), over 20 times higher than the typical bulk value. Micro-Raman characterization suggests that the enhanced thermal conductivity is due to the highly oriented polymer chains and enhanced crystallinity in the electrospun nanofibers.

  4. Relaxation behavior of ion conducting glasses

    International Nuclear Information System (INIS)

    Bunde, A.; Dieterich, W.; Maass, P.; Meyer, M.

    1997-01-01

    We investigate by Monte Carlo simulations the diffusion of ions in an energetically disordered lattice, where the Coulomb interaction between the mobile ions is explicitly taken into account. We show that the combined effect of Coulomb interaction and disorder can account for the ionic ac-conductivity in glasses and the recently discovered non-Arrhenius behavior of the dc-conductivity in glassy fast ionic conductors. Our results suggest that glassy ionic conductors can be optimized by lowering the strength of the energetic disorder but that the ionic interaction effects set an upper bound for the conductivity at high temperatures. (author)

  5. Inhibition of large conductance calcium-dependent potassium ...

    African Journals Online (AJOL)

    conductance, calcium and voltage- dependent potassium (BKCa) channels thereby promoting vasoconstriction. Our results show that the Rho-kinase inhibitor, Y-27632, induced concentration-dependent relaxation in rat mesenteric artery.

  6. Nanoionics phenomenon in proton-conducting oxide: Effect of dispersion of nanosize platinum particles on electrical conduction properties

    Directory of Open Access Journals (Sweden)

    Hiroshige Matsumoto et al

    2007-01-01

    Full Text Available High-temperature proton conductors are oxides in which low-valence cations are doped as electron acceptors; the incorporation of water molecules into the oxides results in the formation of protonic defects that act as charge carriers. Since the protons thus formed are in equilibrium with other electronic defects, electrons and holes, the oxides possibly have different proton-conduction properties at and near boundaries when they are in contact with another phase. In this paper, we present our recent experimental observation of a marked change in the electrical properties of a proton conductor upon the dispersal of fine platinum particles in the oxide. First, the material shows extremely low electrical conductivity in comparison with the original proton-conducting perovskite. Second, there was a threshold amount of platinum at which such a drop in conductivity occurred. A percolation model is employed to explain these experimental results; the fine platinum particles dispersed in the proton-conducting oxide wears highly resistive skin that is formed due to shifts in defect equilibriums, which prevents ionic/electronic conduction. The experiments suggest that the ion-conducting properties of oxides can be varied by introducing interfaces at a certain density; nanoionics is a key to yielding enhanced and/or controlled ionic conduction in solids.

  7. Online Italian fandoms of American TV shows

    Directory of Open Access Journals (Sweden)

    Eleonora Benecchi

    2015-06-01

    Full Text Available The Internet has changed media fandom in two main ways: it helps fans connect with each other despite physical distance, leading to the formation of international fan communities; and it helps fans connect with the creators of the TV show, deepening the relationship between TV producers and international fandoms. To assess whether Italian fan communities active online are indeed part of transnational online communities and whether the Internet has actually altered their relationship with the creators of the original text they are devoted to, qualitative analysis and narrative interviews of 26 Italian fans of American TV shows were conducted to explore the fan-producer relationship. Results indicated that the online Italian fans surveyed preferred to stay local, rather than using geography-leveling online tools. Further, the sampled Italian fans' relationships with the show runners were mediated or even absent.

  8. Multicenter Clinical Trial of Vibroplasty Couplers to Treat Mixed/Conductive Hearing Loss: First Results.

    Science.gov (United States)

    Zahnert, Thomas; Löwenheim, Hubert; Beutner, Dirk; Hagen, Rudolf; Ernst, Arneborg; Pau, Hans-Wilhelm; Zehlicke, Thorsten; Kühne, Hilke; Friese, Natascha; Tropitzsch, Anke; Lüers, Jan-Christoffer; Mlynski, Robert; Todt, Ingo; Hüttenbrink, Karl-Bernd

    2016-01-01

    To evaluate the safety and effectiveness of round window (RW), oval window (OW), CliP and Bell couplers for use with an active middle ear implant. This is a multicenter, long-term, prospective trial with consecutive enrollment, involving 6 university hospitals in Germany. Bone conduction, air conduction, implant-aided warble-tone thresholds and Freiburger monosyllable word recognition scores were compared with unaided preimplantation results in 28 moderate-to-profound hearing-impaired patients after 12 months of follow-up. All patients had previously undergone failed reconstruction surgeries (up to 5 or more). In a subset of patients, additional speech tests at 12 months postoperatively were used to compare the aided with the unaided condition after implantation with the processor switched off. An established quality-of-life questionnaire for hearing aids was used to determine patient satisfaction. Postoperative bone conduction remained stable. Mean functional gain for all couplers was 37 dB HL (RW = 42 dB, OW = 35 dB, Bell = 38 dB, CliP = 27 dB). The mean postoperative Freiburger monosyllable score was 71% at 65 dB SPL. The postimplantation mean SRT50 (speech reception in quiet for 50% understanding of words in sentences) improved on average by 23 dB over unaided testing and signal-to-noise ratios also improved in all patients. The International Outcome Inventory for Hearing Aids (IOI-HA)quality-of-life questionnaire was scored very positively by all patients. A significant improvement was seen with all couplers, and patients were satisfied with the device at 12 months postoperatively. These results demonstrate that an active implant is an advantage in achieving good hearing benefit in patients with prior failed reconstruction surgery. © 2016 S. Karger AG, Basel.

  9. Conductive heat flow at the TAG Active Hydrothermal Mound: Results from 1993-1995 submersible surveys

    Science.gov (United States)

    Becker, K.; Von Herzen, R.; Kirklin, J.; Evans, R.; Kadko, D.; Kinoshita, M.; Matsubayashi, O.; Mills, R.; Schultz, A.; Rona, P.

    We report 70 measurements of conductive heat flow at the 50-m-high, 200-m-diameter TAG active hydrothermal mound, made during submersible surveys with Alvin in 1993 and 1995 and Shinkai 6500 in 1994. The stations were all measured with 5-thermistor, 0.6- or 1-m-long Alvin heat flow probes, which are capable of determining both gradient and thermal conductivity, and were transponder-navigated to an estimated accuracy of ±5-10 m relative to the 10-m-diameter central complex of black smokers. Within 20 m of this complex, conductive heat flow values are extremely variable (0.1- > 100 W/m²), which can only be due to local spatial and possible temporal variability in the immediate vicinity of the vigorous discharge sites. A similar local variability is suggested in the “Kremlin” area of white smokers to the southeast of the black smoker complex. On the south and southeast side of the mound, there is very high heat flow (3.7- > 25 W/m²) on the sedimented terraces that slope down from the Kremlin area. Heat flow is also high (0.3-3 W/m²) in the pelagic carbonate sediments on the surrounding seafloor within a few tens of meters of the southwest, northwest, and northeast sides of the mound. On the west side of the sulfide rubble plateau that surrounds the central black smoker peak, there is a coherent belt of very low heat flow (smokers, suggestive of local, shallow recharge of bottom water. The three submersible surveys spanned nearly two years, but showed no indication of any temporal variability in conductive heat flow over this time scale, whether natural or induced by ODP drilling in 1994.

  10. Dielectric relaxation of glass particles with conductive nano-coatings

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Shahid [Applied Technologies Department, QinetiQ Limited, Cody Technology Park, Farnborough, Hampshire, GU14 0LX (United Kingdom)

    2009-03-21

    This research focuses on the dielectric properties of particles consisting of glass cores with nanometre conductive coatings. The effects of the core glass particle shape (sphere, flake and fibre) and size are investigated for different coating characteristics over the frequency range 0.5-18 GHz. Experimental results for the coated glass particle combinations show the existence of a dielectric loss peak. This feature is associated with interfacial relaxation between the insulating core glass particle and the nanoscale conductive coating. The relaxation mechanism provides enhanced loss that is not observed in conventional solid metal particle composites. The results are fitted to a model, which shows that the relaxation frequency increases with increasing coating conductivity and thickness, with additional parameters identified for further particle optimizations.

  11. Direct current hopping conductance along DNA chain

    Institute of Scientific and Technical Information of China (English)

    Ma Song-Shan; Xu Hui; Liu Xiao-Liang; Li Ming-Jun

    2007-01-01

    This paper proposes a model of direct current(DC) electron hopping transport in DNA,in which DNA is considered as a binary one-dimensional disordered system.To quantitatively study the DC conductivity in DNA,it numerically calculates the DC conductivity of DNA chains with difierent parameter values.The result shows that the DC conductivity of DNA chain increases with the increase of temperature.And the conductivity of DNA chain is depended on the probability P.which represents the degree of compositional disorder in a DNA sequence to some extent.For P<0.5,the conductivity of DNA chain decreases with the increase of P,while for P≥0.5,the conductivity increases with the increase of p.The DC conductivity in DNA chain also varies with the change of the electric field,it presents non-Ohm's law conductivity characteristics.

  12. Heat Conduction of Air in Nano Spacing

    Directory of Open Access Journals (Sweden)

    Zhang Yao-Zhong

    2009-01-01

    Full Text Available Abstract The scale effect of heat conduction of air in nano spacing (NS is very important for nanodevices to improve their life and efficiency. By constructing a special technique, the changes of heat conduction of air were studied by means of measuring the heat conduction with heat conduction instrument in NS between the hot plate and the cooling plate. Carbon nanotubes were used to produce the nano spacing. The results show that when the spacing is small down to nanometer scale, heat conduction plays a prominent role in NS. It was found that the thickness of air is a non-linear parameter for demarcating the heat conduction of air in NS and the rate of heat conduction in unit area could be regard as a typical parameter for the heat conduction characterization at nanometer scale.

  13. Mixed conductivity in Co-doped lanthanum gallate

    International Nuclear Information System (INIS)

    Keppeler, F.M.; Nafe, H.; Aldinger, F.; Sammes, N.M.

    1998-01-01

    Materials of the composition La 0.8 Sr 0.2 Ga 0.85 Co x Mg 0.15 O 3-δ (x = 0 to 0.25) were synthesised using standard solid state technique resulting in phase purity and high density. Conductivity measurements at different temperatures and oxygen partial pressures revealed an ionic to metallic-like transition in conduction behaviour with rising Co amount. Samples with low Co contents (x=0.05) showed ionic behaviour with an average value of 0.15 S/cm at 900 deg C while heavy doping (x=0.25) resulted in metallic type conduction with a value of 5.43 S/cm at 900 deg C in air. Copyright (1998) Australasian Ceramic Society

  14. Enhancement of electrical conductivity in the Gum Arabica complex

    International Nuclear Information System (INIS)

    Pradhan, Sourav S.; Sarkar, A.

    2009-01-01

    Gum Arabica is a natural biopolymer obtained from plant Acacia Arabica. In this present study the electro-active nature of its complex has been investigated. The complexes were developed using pure Gum Arabica and pure Citric acid by the sol-gel process. The scope of complex formation has been investigated and their natures were examined experimentally. The experiments which were carried out in this work are namely d.c V-I characteristics, d.c Arrhenius, ion transference number measurement, UV-VIS and IR photo-absorption. Solid specimen of the complex at various concentration of Citric acid has been developed for d.c experiments and adequate specimens were also developed for UV-VIS experiment. The result of d.c V-I characteristics on specimens at different Citric acid concentrations shows that d.c conductivity increases with concentration of the acid. The said enhancement is observed to be about 100 times that of pure hosts. The ion transference number measurement shows that the total conductivity increases with external acid concentration of which d.c conductivity enhance many times compared to that of ionic part. The result from d.c Arrhenius study shows that electro-thermal activation energy decreases with increasing acid concentration leading to enhancement of electronic conductivity of the complex. The result of UV-VIS study confirms the formation of the acid complex of Gum Arabica. The nature of photo-absorption indicates very clearly that main absorption region shows gradual shifts towards longer wavelength with increase of acid concentration. The result of FTIR absorption shows the structural concepts of electro-activity and complex formation indication of pure Gum Arabica. The overall analysis shows that the electro-activity of the mentioned biopolymer may be tailored.

  15. Photo control of transport properties in a disordered wire: Average conductance, conductance statistics, and time-reversal symmetry

    International Nuclear Information System (INIS)

    Kitagawa, Takuya; Oka, Takashi; Demler, Eugene

    2012-01-01

    In this paper, we study the full conductance statistics of a disordered 1D wire under the application of light. We develop the transfer matrix method for periodically driven systems to analyze the conductance of a large system with small frequency of light, where coherent photon absorptions play an important role to determine not only the average but also the shape of conductance distributions. The average conductance under the application of light results from the competition between dynamic localization and effective dimension increase, and shows non-monotonic behavior as a function of driving amplitude. On the other hand, the shape of conductance distribution displays a crossover phenomena in the intermediate disorder strength; the application of light dramatically changes the distribution from log-normal to normal distributions. Furthermore, we propose that conductance of disordered systems can be controlled by engineering the shape, frequency and amplitude of light. Change of the shape of driving field controls the time-reversals symmetry and the disordered system shows analogous behavior as negative magneto-resistance known in static weak localization. A small change of frequency and amplitude of light leads to a large change of conductance, displaying giant opto-response. Our work advances the perspective to control the mean as well as the full conductance statistics by coherently driving disordered systems. - Highlights: ► We study conductance of disordered systems under the application of light. ► Full conductance distributions are obtained. ► A transfer matrix method is developed for driven systems. ► Conductances are dramatically modified upon the application of light. ► Time-reversal symmetry can also be controlled by light application.

  16. Electron conductivity model for dense plasmas

    International Nuclear Information System (INIS)

    Lee, Y.T.; More, R.M.

    1984-01-01

    An electron conductivity model for dense plasmas is described which gives a consistent and complete set of transport coefficients including not only electrical conductivity and thermal conductivity, but also thermoelectric power, and Hall, Nernst, Ettinghausen, and Leduc--Righi coefficients. The model is useful for simulating plasma experiments with strong magnetic fields. The coefficients apply over a wide range of plasma temperature and density and are expressed in a computationally simple form. Different formulas are used for the electron relaxation time in plasma, liquid, and solid phases. Comparisons with recent calculations and available experimental measurement show the model gives results which are sufficiently accurate for many practical applications

  17. Synthesis, ionic conductivity, and thermal properties of proton conducting polymer electrolyte for high temperature fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Takahito; Hamaguchi, Yohei; Uno, Takahiro; Kubo, Masataka [Department of Chemistry for Materials, Faculty of Engineering, Mie University, 1577 Kurima Machiya-cho, Tsu, Mie 514-8507 (Japan); Aihara, Yuichi; Sonai, Atsuo [Samsung Yokohama Research Institute, 2-7 Sugasawa-cho, Tsurumi-ku, Yokohama 230-0027 (Japan)

    2006-01-16

    Hyperbranched polymer (poly-1a) with sulfonic acid groups at the end of chains was successfully synthesized. Interpenetration reaction of poly-1a with a hyperbranched polymer with acryloyl groups at the end of chains (poly-1b) as a cross-linker afforded a tough electrolyte membrane. The poly-1a and the resulting electrolyte membrane showed the ionic conductivities of 7x10{sup -4} and 8x10{sup -5} S/cm, respectively, at 150C under dry condition. The ionic conductivities of the poly-1a and the electrolyte membrane exhibited the VTF type temperature dependence. And also, both poly-1a and the resulting electrolyte membrane were thermally stable up to 200C. (author)

  18. Complex conductivity results to silver nanoparticles in partically saturated laboratory columns

    Data.gov (United States)

    U.S. Environmental Protection Agency — Laboratory complex conductivity data from partially saturated sand columns with silver nanoparticles. This dataset is not publicly accessible because: It involves...

  19. Perceptions of acceptable conducts by university students

    Directory of Open Access Journals (Sweden)

    Dora Nazaré Marques

    2016-07-01

    Conclusion: Academic misconducts were mainly considered more acceptable than professional misconducts. Our results show that perceptions of acceptable conducts amongst optometry students are not very different from other students, and, against our initial prediction, do not show a general change in misconduct perception when students become more mature. Universities should pay more attention to this problem and take action.

  20. Thermal conductivity of supercooled water.

    Science.gov (United States)

    Biddle, John W; Holten, Vincent; Sengers, Jan V; Anisimov, Mikhail A

    2013-04-01

    The heat capacity of supercooled water, measured down to -37°C, shows an anomalous increase as temperature decreases. The thermal diffusivity, i.e., the ratio of the thermal conductivity and the heat capacity per unit volume, shows a decrease. These anomalies may be associated with a hypothesized liquid-liquid critical point in supercooled water below the line of homogeneous nucleation. However, while the thermal conductivity is known to diverge at the vapor-liquid critical point due to critical density fluctuations, the thermal conductivity of supercooled water, calculated as the product of thermal diffusivity and heat capacity, does not show any sign of such an anomaly. We have used mode-coupling theory to investigate the possible effect of critical fluctuations on the thermal conductivity of supercooled water and found that indeed any critical thermal-conductivity enhancement would be too small to be measurable at experimentally accessible temperatures. Moreover, the behavior of thermal conductivity can be explained by the observed anomalies of the thermodynamic properties. In particular, we show that thermal conductivity should go through a minimum when temperature is decreased, as Kumar and Stanley observed in the TIP5P model of water. We discuss physical reasons for the striking difference between the behavior of thermal conductivity in water near the vapor-liquid and liquid-liquid critical points.

  1. Lattice dynamics and lattice thermal conductivity of thorium dicarbide

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Zongmeng [Institute of Theoretical Physics and Department of Physics, East China Normal University, Shanghai 200241 (China); Huai, Ping, E-mail: huaiping@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Qiu, Wujie [Institute of Theoretical Physics and Department of Physics, East China Normal University, Shanghai 200241 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Ke, Xuezhi, E-mail: xzke@phy.ecnu.edu.cn [Institute of Theoretical Physics and Department of Physics, East China Normal University, Shanghai 200241 (China); Zhang, Wenqing [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhu, Zhiyuan [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2014-11-15

    The elastic and thermodynamic properties of ThC{sub 2} with a monoclinic symmetry have been studied by means of density functional theory and direct force-constant method. The calculated properties including the thermal expansion, the heat capacity and the elastic constants are in a good agreement with experiment. Our results show that the vibrational property of the C{sub 2} dimer in ThC{sub 2} is similar to that of a free standing C{sub 2} dimer. This indicates that the C{sub 2} dimer in ThC{sub 2} is not strongly bonded to Th atoms. The lattice thermal conductivity for ThC{sub 2} was calculated by means of the Debye–Callaway model. As a comparison, the conductivity of ThC was also calculated. Our results show that the ThC and ThC{sub 2} contributions of the lattice thermal conductivity to the total conductivity are 29% and 17%, respectively.

  2. Mixed conductivity in Co-doped lanthanum gallate

    Energy Technology Data Exchange (ETDEWEB)

    Keppeler, F.M.; Nafe, H.; Aldinger, F. [Pulvermetallurgisches Laboratorium, Stuttgart (Germany). Max-Planck-Institut fur Metallforschung; Sammes, N.M. [The University of Waikato, Hamilton (New Zealand). Department of Technology

    1998-12-31

    Materials of the composition La{sub 0.8}Sr{sub 0.2}Ga{sub 0.85}Co{sub x}Mg{sub 0.15}O{sub 3-{delta}} (x = 0 to 0.25) were synthesised using standard solid state technique resulting in phase purity and high density. Conductivity measurements at different temperatures and oxygen partial pressures revealed an ionic to metallic-like transition in conduction behaviour with rising Co amount. Samples with low Co contents (x=0.05) showed ionic behaviour with an average value of 0.15 S/cm at 900 deg C while heavy doping (x=0.25) resulted in metallic type conduction with a value of 5.43 S/cm at 900 deg C in air. Copyright (1998) Australasian Ceramic Society 12 refs., 5 figs.

  3. Augmenting a Ballet Dance Show Using the Dancer's Emotion: Conducting Joint Research in Dance and Computer Science

    Science.gov (United States)

    Clay, Alexis; Delord, Elric; Couture, Nadine; Domenger, Gaël

    We describe the joint research that we conduct in gesture-based emotion recognition and virtual augmentation of a stage, bridging together the fields of computer science and dance. After establishing a common ground for dialogue, we could conduct a research process that equally benefits both fields. As computer scientists, dance is a perfect application case. Dancer's artistic creativity orient our research choices. As dancers, computer science provides new tools for creativity, and more importantly a new point of view that forces us to reconsider dance from its fundamentals. In this paper we hence describe our scientific work and its implications on dance. We provide an overview of our system to augment a ballet stage, taking a dancer's emotion into account. To illustrate our work in both fields, we describe three events that mixed dance, emotion recognition and augmented reality.

  4. Morphometric Brain Abnormalities in Boys with Conduct Disorder

    Science.gov (United States)

    Huebner, Thomas; Vloet, Timo D.; Marx, Ivo; Konrad, Kerstin; Fink, Gereon R.; Herpertz, Sabine C.; Herpertz-Dahlmann, Beate

    2008-01-01

    Conduct disorder (CD) is associated with antisocial personality behavior that violates the basic rights of others. Results, on examining the structural brain aberrations in boys' CD, show that boys with CD and cormobid attention-deficit/hyperactivity disorder showed abnormalities in frontolimbic areas that could contribute to antisocial…

  5. Vocal intensity in lecturers: Results of measurements conducted during lecture sessions

    Directory of Open Access Journals (Sweden)

    Witold Mikulski

    2013-12-01

    Full Text Available Background: Occupational voice users (inter alia: lecturers speak with different levels of vocal intensity. Speakers adjust this intensity knowingly (e.g. to underline the importance of fragments of the speech or unknowingly. The unknown adjustment of voice intensity occurs e.g. in the presence of high acoustic background noise (so-called Lombard effect, but it also results from many other factors: hearing loss, construction of the vocal tract, habits and others. The aim of the article is to confirm the thesis that in similar conditions of acoustic properties of the room different lecturers speak with different levels of vocal intensity. Materials and Methods: The study was conducted in a group of 10 lecturers in the same conference room. A-weighted sound pressure level determined at 1 m from the lecturer's mouth was adopted as a parameter defining the intensity of the lecturer's voice. The levels of all lecturers' voice intensity were compared and evaluated according to the criteria defined in EN ISO 9921. Results: Nine in ten lecturers were speaking with normal voice intensity (60-65 dB and only one full-time university lecturer was speaking with raised voice (66-71 dB. Conclusions: It was found that in the room of the same acoustic conditions the lecturers spoke with different intensities of voice. Some lecturers occasionally, and one all the time spoke with the voice intensity specified by PN-EN ISO 9921 as a raised voice. The results of the preliminary study warrant further studies in a larger group of teachers. Med Pr 2013;64(6:797–804

  6. Quantum chaos and conductivity in disordered systems

    International Nuclear Information System (INIS)

    Suzuki, A.; Matsutani, S.

    2001-01-01

    The hopping conductivity in a disordered system which is composed of small (semi-) metallic granules is presented. Due to the irregular shape of each granule, the level statistics of a free electron in granule is expressed by a random matrix, and a formula for the temperature-dependent conductivity (TDC) is obtained for such a disordered system. This TDC shows an apparent metal-insulator transition and is in good agreement with experimental results for disordered carbons

  7. Conductivity of oriented bis-azo polymer films

    DEFF Research Database (Denmark)

    Apitz, D.; Bertram, R.P.; Benter, N.

    2006-01-01

    The conductivity properties of electro-optic photoaddressable, dense bis-ozo chromophore polymer films are investigated by using samples corona poled at various temperatures. A dielectric spectrometer is applied to measure the frequency dependence of the conductivity at different temperatures...... before and after heating the material to above the glass transition temperature. The results show that the orientation of the chromophores changes the charge-carrier mobility. Ionic conductivity dominates in a more disordered configuration of the material, while the competing process of hole hopping...... takes over as a transition to a liquid-crystalline phase occurs when the material is heated to much higher than the gloss transition temperature. Such micro-crystallization strongly enhances the conductivity....

  8. Ballistic and Diffusive Thermal Conductivity of Graphene

    Science.gov (United States)

    Saito, Riichiro; Masashi, Mizuno; Dresselhaus, Mildred S.

    2018-02-01

    This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. Phonon-related thermal conductivity of graphene is calculated as a function of the temperature and sample size of graphene in which the crossover of ballistic and diffusive thermal conductivity occurs at around 100 K. The diffusive thermal conductivity of graphene is evaluated by calculating the phonon mean free path for each phonon mode in which the anharmonicity of a phonon and the phonon scattering by a 13C isotope are taken into account. We show that phonon-phonon scattering of out-of-plane acoustic phonon by the anharmonic potential is essential for the largest thermal conductivity. Using the calculated results, we can design the optimum sample size, which gives the largest thermal conductivity at a given temperature for applying thermal conducting devices.

  9. Effective thermal conductivity of nanofluids: the effects of microstructure

    International Nuclear Information System (INIS)

    Fan Jing; Wang Liqiu

    2010-01-01

    We examine numerically the effects of particle-fluid thermal conductivity ratio, particle volume fraction, particle size distribution and particle aggregation on macroscale thermal properties for seven kinds of two-dimensional nanofluids. The results show that the radius of gyration and the non-dimensional particle-fluid interfacial area are two important parameters in characterizing the geometrical structure of nanoparticles. A non-uniform particle size is found to be unfavourable for the conductivity enhancement, while particle-aggregation benefits the enhancement especially when the radius of gyration of aggregates is large. Without considering the interfacial thermal resistance, a larger non-dimensional particle-fluid interfacial area between the base fluid and the nanoparticles is also desirable for enhancing thermal conductivity. The nanofluids with nanoparticles of connected cross-shape show a much higher (lower) effective thermal conductivity when the particle-fluid conductivity ratio is larger (smaller) than 1.

  10. Method for Measuring Thermal Conductivity of Small Samples Having Very Low Thermal Conductivity

    Science.gov (United States)

    Miller, Robert A.; Kuczmarski, Maria a.

    2009-01-01

    This paper describes the development of a hot plate method capable of using air as a standard reference material for the steady-state measurement of the thermal conductivity of very small test samples having thermal conductivity on the order of air. As with other approaches, care is taken to ensure that the heat flow through the test sample is essentially one-dimensional. However, unlike other approaches, no attempt is made to use heated guards to block the flow of heat from the hot plate to the surroundings. It is argued that since large correction factors must be applied to account for guard imperfections when sample dimensions are small, it may be preferable to simply measure and correct for the heat that flows from the heater disc to directions other than into the sample. Experimental measurements taken in a prototype apparatus, combined with extensive computational modeling of the heat transfer in the apparatus, show that sufficiently accurate measurements can be obtained to allow determination of the thermal conductivity of low thermal conductivity materials. Suggestions are made for further improvements in the method based on results from regression analyses of the generated data.

  11. Consequences of Early Conductive Hearing Loss on Long-Term Binaural Processing.

    Science.gov (United States)

    Graydon, Kelley; Rance, Gary; Dowell, Richard; Van Dun, Bram

    The aim of the study was to investigate the long-term effects of early conductive hearing loss on binaural processing in school-age children. One hundred and eighteen children participated in the study, 82 children with a documented history of conductive hearing loss associated with otitis media and 36 controls who had documented histories showing no evidence of otitis media or conductive hearing loss. All children were demonstrated to have normal-hearing acuity and middle ear function at the time of assessment. The Listening in Spatialized Noise Sentence (LiSN-S) task and the masking level difference (MLD) task were used as the two different measures of binaural interaction ability. Children with a history of conductive hearing loss performed significantly poorer than controls on all LiSN-S conditions relying on binaural cues (DV90, p = binaural cues. Fifteen children with a conductive hearing loss history (18%) showed results consistent with a spatial processing disorder. No significant difference was observed between the conductive hearing loss group and the controls on the MLD task. Furthermore, no correlations were found between LiSN-S and MLD. Results show a relationship between early conductive hearing loss and listening deficits that persist once hearing has returned to normal. Results also suggest that the two binaural interaction tasks (LiSN-S and MLD) may be measuring binaural processing at different levels. Findings highlight the need for a screening measure of functional listening ability in children with a history of early otitis media.

  12. Active Bone Conduction Prosthesis: BonebridgeTM

    Directory of Open Access Journals (Sweden)

    Zernotti, Mario E.

    2015-10-01

    Full Text Available Introduction Bone conduction implants are indicated for patients with conductive and mixed hearing loss, as well as for patients with single-sided deafness (SSD. The transcutaneous technology avoids several complications of the percutaneous bone conduction implants including skin reaction, skin growth over the abutment, and wound infection. The Bonebridge (MED-EL, Austria prosthesis is a semi-implantable hearing system: the BCI (Bone Conduction Implant is the implantable part that contains the Bone Conduction-Floating Mass Transducer (BC-FMT, which applies the vibrations directly to the bone; the external component is the audio processor Amadé BB (MED-EL, Austria, which digitally processes the sound and sends the information through the coil to the internal part. Bonebridge may be implanted through three different approaches: the transmastoid, the retrosigmoid, or the middle fossa approach. Objective This systematic review aims to describe the world́s first active bone conduction implant system, Bonebridge, as well as describe the surgical techniques in the three possible approaches, showing results from implant centers in the world in terms of functional gain, speech reception thresholds and word recognition scores. Data Synthesis The authors searched the MEDLINE database using the key term Bonebridge. They selected only five publications to include in this systematic review. The review analyzes 20 patients that received Bonebridge implants with different approaches and pathologies. Conclusion Bonebridge is a solution for patients with conductive/mixed hearing loss and SSD with different surgical approaches, depending on their anatomy. The system imparts fewer complications than percutaneous bone conduction implants and shows proven benefits in speech discrimination and functional gain.

  13. Conductivity in insulators due to implantation of conducting species

    International Nuclear Information System (INIS)

    Prawer, S.; Kalish, R.

    1993-01-01

    Control of the surface conductivity of insulators can be accomplished by high dose ion implantation of conductive species. The use of C + as the implant species is particularly interesting because C can either form electrically insulating sp 3 bonds or electrically conducting sp 2 bonds. In the present work, fused quartz plates have been irradiated with 100 keV C + ions to doses up to 1 x 10 17 ions/cm 2 at room temperature and at 200 deg C. The ion beam induced conductivity was monitored in-situ and was found to increase by up to 8 orders to magnitude for the ion dose range studied. Xe implantations over a similar range did not induce any changes in the conductivity showing that the increase in conductivity is caused by the presence of the C in the fused quartz matrix and not by damage. The dependence of the conductivity on implantation temperature and on post implantation annealing sheds light on the clustering of the C implants. The temperature dependence of the conductivity for the highest doses employed (1 x 10 17 C + /cm 2 ) can be described very well by lnσ α T. This is considered to be a peculiar dependence which does not comply with any of the standard models for conduction. 9 refs., 1 tab., 6 figs

  14. Study on thermal conductivity of HTR spherical fuel element matrix graphite

    International Nuclear Information System (INIS)

    Zhang Kaihong; Liu Xiaoxue; Zhao Hongsheng; Li Ziqiang; Tang Chunhe

    2014-01-01

    Taking the spherical fuel element matrix graphite ball samples as an example, this paper introduced the principle and method of laser thermal conductivity meter, as well as the specific heat capacity, and analyzed the effects of different test methods and sampling methods on the thermal conductivities at 1000 ℃ of graphite material. The experimental results show that the thermal conductivities of graphite materials tested by synchronous thermal analyzer combining with laser thermal conductivity meter were different from that directly by laser thermal conductivity meter, the former was more reliable and accurate than the later; When sampling from different positions, central samples had higher thermal conductivities than edging samples, which was related to the material density and porosity at the different locations; the thermal conductivities had obvious distinction between samples from different directions, which was because the layer structure of polycrystalline graphite preferred orientation under pressure, generally speaking, the thermal conductivities perpendicular to the molding direction were higher than that parallel to the molding direction. Besides this, the test results show that the thermal conductivities of all the graphite material samples were greater than 30 W/(m (K), achieving the thermal performance index of high temperature gas cooled reactor. (authors)

  15. Smoking Status and the Five-Factor Model of Personality: Results of a Cross-Sectional Study Conducted in Poland.

    Science.gov (United States)

    Buczkowski, Krzysztof; Basinska, Małgorzata A; Ratajska, Anna; Lewandowska, Katarzyna; Luszkiewicz, Dorota; Sieminska, Alicja

    2017-01-27

    Tobacco smoking is the single most important modifiable factor in increased morbidity and premature mortality. Numerous factors-including genetics, personality, and environment-affect the development and persistence of tobacco addiction, and knowledge regarding these factors could improve smoking cessation rates. This study compared personality traits between never, former, and current smokers, using the Five-Factor Model of Personality in a country with a turbulent smoking reduction process. : In this cross-sectional study, 909 Polish adults completed the Revised Neuroticism-Extraversion-Openness Personality Inventory. Our results showed that current smokers' scores for extraversion, one of the five global dimensions of personality, were higher relative to never smokers. Neuroticism, openness to experience, agreeableness, and conscientiousness did not differ significantly according to smoking status. Facet analysis, which described each dimension in detail, showed that current smokers' activity and excitement seeking (facets of extraversion) scores were higher relative to those of never and former smokers. In turn, current smokers' dutifulness and deliberation (facets of conscientiousness) scores were lower than those found in former and never smokers. Never smokers scored the highest in self-consciousness (a facet of neuroticism) and compliance (a component of agreeableness). The study conducted among Polish individuals showed variation in personality traits according to their smoking status; however, this variation differed from that reported in countries in which efforts to reduce smoking had begun earlier relative to Poland. Knowledge regarding personality traits could be useful in designing smoking prevention and cessation programs tailored to individuals' needs.

  16. Thermal conductivity of nanoscale thin nickel films

    Institute of Scientific and Technical Information of China (English)

    YUAN Shiping; JIANG Peixue

    2005-01-01

    The inhomogeneous non-equilibrium molecular dynamics (NEMD) scheme is applied to model phonon heat conduction in thin nickel films. The electronic contribution to the thermal conductivity of the film is deduced from the electrical conductivity through the use of the Wiedemann-Franz law. At the average temperature of T = 300 K, which is lower than the Debye temperature ()D = 450 K,the results show that in a film thickness range of about 1-11 nm, the calculated cross-plane thermal conductivity decreases almost linearly with the decreasing film thickness, exhibiting a remarkable reduction compared with the bulk value. The electrical and thermal conductivities are anisotropic in thin nickel films for the thickness under about 10 nm. The phonon mean free path is estimated and the size effect on the thermal conductivity is attributed to the reduction of the phonon mean free path according to the kinetic theory.

  17. The contribution of thermal radiation to the thermal conductivity of porous UO2

    International Nuclear Information System (INIS)

    Bakker, K.; Kwast, H.; Cordfunke, E.H.P.

    1994-09-01

    The influence of cylindrical, spherical and ellipsoidal inclusions on the overall thermal conductivity was computed with the finite element technique. The results of these calculations were compared with equations that describe the effect of inclusions on the overall thermal conductivity. The analytical equation of Schulz that describes the effect of inclusions on the overall thermal conductivity is in good agreement with the results of the finite element computations. This good agreement shows that among a variety of porosity correction formulas, the equation of Schulz gives the best description of the effect of inclusions on the overall thermal conductivity. This equation and the results of finite element calculations allow us to compute the contribution of radiation to the overall thermal conductivity of UO 2 with oblate ellipsoidal porosity. The present radiation calculations show that Hayes and Peddicord overestimated the contribution of thermal radiation to the thermal conductivity. (orig.)

  18. The Electrical Conductivity of Stretched Polyaniline and Polypyrrole Coated Yarns

    Directory of Open Access Journals (Sweden)

    M. Nouri

    2009-12-01

    Full Text Available The nylon and nylon/lycra yarns were coated with electrically conductive polymers such as polyaniline and polypyrrole, via chemical polymerization process. Electrical conductivity of the coated yarns was measured at variousstrain levels using two-point probe technique and their strain sensitivities were studied. The results showed that, electrical conductivity of the coated yarns decreased with an increase in strain level. A sharp decrease in the electrical conductivity of the nylon/lycra coated yarn with the strain level was recorded whereas, a small drop in the electrical conductivity of the nylon coated yarn was observed. Linear relationships were found between the electrical conductivity and length for the nylon and nylon/lycra coated yarns. The polyaniline coated yarns showed higher strain sensitivity compared to polypyrrole coated yarns. Repeatability of the strain sensitivity of the coated yarns was examined and the coated nylon/lycra yarn showed better repeatability compared to that of coated nylon yarn. The coated yarns were proposed as a flexible strain sensor in the field of intelligent materials.

  19. Auroral zone E-region conductivities during solar minimum derived from EISCAT data

    International Nuclear Information System (INIS)

    Schlegel, K.

    1988-01-01

    From two years of EISCAT data (1985-1986, a period of low solar activity) 8337 E-region conductivity profiles have been calculated as 5-min averages. From these profiles the height of the conductivity maxima for the Hall and Pedersen conductivities (H max ), the height-integrated Hall and Pedersen conductivities and the ratio of both have been computed. Histograms as well as average values of these quantities are displayed as a function of K p and of magnetic local time. The former results showed quantitatively the increase of the conductivities and the decrease of H max with increasing magnetic activity. The latter results revealed that on the average the conductivities are maximal in the early morning hours due to hard particle precipitation, H max being affected both by the solar zenith angle and by particle precipitation. The solar zenith angle dependence of the conductivities is only significant for low K p -values. Latitudinal profiles of the height-integrated conductivities show quantitatively the southward shift of the average conductivity maximum with increasing magnetic activity

  20. Quantum conductance of zigzag graphene oxide nanoribbons

    International Nuclear Information System (INIS)

    Kan, Zhe; Nelson, Christopher; Khatun, Mahfuza

    2014-01-01

    The electronic properties of zigzag graphene oxide nanoribbons (ZGOR) are presented. The results show interesting behaviors which are considerably different from the properties of the perfect graphene nanoribbons (GNRs). The theoretical methods include a Huckel-tight binding approach, a Green's function methodology, and the Landauer formalism. The presence of oxygen on the edge results in band bending, a noticeable change in density of states and thus the conductance. Consequently, the occupation in the valence bands increase for the next neighboring carbon atom in the unit cell. Conductance drops in both the conduction and valence band regions are due to the reduction of allowed k modes resulting from band bending. The asymmetry of the energy band structure of the ZGOR is due to the energy differences of the atoms. The inclusion of a foreign atom's orbital energies changes the dispersion relation of the eigenvalues in energy space. These novel characteristics are important and valuable in the study of quantum transport of GNRs

  1. Stretchable Conductive Composites from Cu-Ag Nanowire Felt.

    Science.gov (United States)

    Catenacci, Matthew J; Reyes, Christopher; Cruz, Mutya A; Wiley, Benjamin J

    2018-04-24

    Materials that retain a high conductivity under strain are essential for wearable electronics. This article describes a conductive, stretchable composite consisting of a Cu-Ag core-shell nanowire felt infiltrated with a silicone elastomer. This composite exhibits a retention of conductivity under strain that is superior to any composite with a conductivity greater than 1000 S cm -1 . This work also shows how the mechanical properties, conductivity, and deformation mechanism of the composite changes as a function of the stiffness of the silicone matrix. The retention of conductivity under strain was found to decrease as the Young's modulus of the matrix increased. This was attributed to void formation as a result of debonding between the nanowire felt and the elastomer. The nanowire composite was also patterned to create serpentine circuits with a stretchability of 300%.

  2. The contribution of thermal radiation to the thermal conductivity of porous UO2

    International Nuclear Information System (INIS)

    Bakker, K.; Kwast, H.; Cordfunke, E.H.P.

    1995-01-01

    The influence of cylindrical, spherical and ellipsoidal inclusions on the overall thermal conductivity was computed with the finite element technique. The results of these calculations were compared with equations that describe the effect of inclusions on the overall thermal conductivity. The analytical equation of Schulz [B. Schulz, KfK-1988 (1974)] that describes the effect of inclusions on the overall thermal conductivity is in good agreement with the results of the finite element computations. This good agreement shows that among a variety of porosity correction formulas, the equation of Schulz gives the best description of the effect of inclusions on the overall thermal conductivity. This equation and the results of finite element calculations allow us to compute the contribution of radiation to the overall thermal conductivity of UO 2 with oblate ellipsoidal porosity. The present radiation calculations show that Hayes and Peddicord [S.L. Hayes and K.L. Peddicord, J. Nucl. Mater. 202 (1993) 87] overestimated the contribution of thermal radiation to the thermal conductivity. ((orig.))

  3. Characterization and Conduction Mechanism of Highly Conductive Vanadate Glass

    Directory of Open Access Journals (Sweden)

    Tetsuaki Nishida

    2015-12-01

    Full Text Available This paper reviews recent studies of highly conductive barium iron vanadate glass with a composition of 20 BaO ∙ 10 Fe2O3 ∙ 70 V2O5 (in mol %. Isothermal annealing of the vanadate glass for several ten minutes at a given temperature, higher than glass transition temperature or crystallization temperature, caused an increase in σ. Substitution of CuI (3d10, ZnII (3d10 and CuII (3d9 for FeIII (3d5 was investigated to elucidate the effect of electron configuration on the conductivity (σ. A marked decrease in the activation energy of conduction (Ea was also observed after the annealing. Values of Ea were correlated to the energy gap between the donor level and the conduction band (CB in the n-type semiconductor model. Isothermal annealing of ZnII-substituted vanadate glass (20 BaO ∙ 5 ZnO ∙ 5 Fe2O3 ∙ 70 V2O5 at 450 °C for 30 min showed an increase in σ from 2.5 × 10–6 to 2.1 × 10–1 S cm–1, which was one order of magnitude larger than that of non-substituted vanadate glass (3.4 × 10–2 S cm–1. Under the same annealing condition, σ’s of 2.0 × 10–1 and 3.2 × 10–1 S cm–1 were observed for 20 BaO ∙ 5 Cu2O ∙ 5 Fe2O3 ∙ 70 V2O5 and 20 BaO ∙ 5 CuO ∙ 5 Fe2O3 ∙ 70 V2O5 glasses, respectively. These results demonstrate an increase in the carrier (electron density in the CB, primarily composed of anti-bonding 4s-orbitals.

  4. Proton-conductive nanochannel membrane for fuel-cell applications.

    Science.gov (United States)

    Oleksandrov, Sergiy; Lee, Jeong-Woo; Jang, Joo-Hee; Haam, Seungjoo; Chung, Chan-Hwa

    2009-02-01

    Novel design of proton conductive membrane for direct methanol fuel cells is based on proton conductivity of nanochannels, which is acquired due to the electric double layer overlap. Proton conductivity and methanol permeability of an array of nanochannels were studied. Anodic aluminum oxide with pore diameter of 20 nm was used as nanochannel matrix. Channel surfaces of an AAO template were functionalized with sulfonic groups to increase proton conductivity of nanochannels. This was done in two steps; at first -SH groups were attached to walls of nanochannels using (3-Mercaptopropyl)-trimethyloxysilane and then they were converted to -SO3H groups using hydrogen peroxide. Treatment steps were analyzed by Fourier Transform Infrared spectroscopy and X-ray Photoelectron Spectroscopy. Proton conductivity and methanol permeability were measured. The data show methanol permeability of membrane to be an order of magnitude lower, than that measured of Nafion. Ion conductivity of functionalized AAO membrane was measured by an impedance analyzer at frequencies ranging from 1 Hz to 100 kHz and voltage 50 mV to be 0.15 Scm(-1). Measured ion conductivity of Nafion membrane was 0.05 Scm(-1). Obtained data show better results in comparison with commonly used commercial available proton conductive membrane Nafion, thus making nanochannel membrane very promising for use in fuel cell applications.

  5. Thermodynamic parameters of elasticity and electrical conductivity ...

    African Journals Online (AJOL)

    The thermodynamic parameters (change in free energy of elasticity, DGe; change in enthalpy of elasticity, DHe; and change in entropy of elasticity, DSe) and the electrical conductivity of natural rubber composites reinforced separately with some agricultural wastes have been determined. Results show that the reinforced ...

  6. The Association between Parent-Child Conflict and Adolescent Conduct Problems over Time: Results from a Longitudinal Adoption Study

    Science.gov (United States)

    Klahr, Ashlea M.; McGue, Matt; Iacono, William G.; Burt, S. Alexandra

    2010-01-01

    A handful of prior adoption studies have confirmed that the cross-sectional relationship between child conduct problems and parent/child conflict is at least partially shared environmental in origin. However, as the direction of causation between parenting and delinquency remains unclear, this relationship could be better explained by the adolescent's propensity to elicit conflictive parenting, a phenomenon referred to as an evocative gene-environment correlation. The current study thus examined the prospective relationship between conduct problems and parent-child conflict in a sample of adoptive families. Participants included 672 adolescents in 405 adoptive families assessed at two time points roughly 4 years apart. Results indicated that parent-child conflict predicts the development of conduct problems, whereas conduct problems do not predict increases in parent-child conflict. Such findings suggest that evocative gene-environment correlations are highly unlikely as an explanation of prior shared environmental effects during adolescence. Moreover, because the adolescents in this study do not share genes with their adoptive parents, the association between conduct problems and parent-child conflict is indicative of shared environmental mediation in particular. Implications of our findings are discussed. PMID:21038930

  7. Study of the thermal conductivity of ZnO nanowires/PMMA composites

    International Nuclear Information System (INIS)

    Igamberdiev, Kh. T.; Yuldashev, Sh. U.; Cho, H. D.; Kang, T. W.; Rakhimova, Sh. M.; Akhmedov, T. Kh.

    2012-01-01

    From thermal conductivity measurements on ZnO nanowires (NWs)/poly(methyl methacrylate) PMMA composites, the thermal conductivities of the ZnO nanowires were determined. The thermal conductivity of a ZnO NW decreases considerably with decreasing nanowire diameter, and for a ZnO nanowire with a diameter of 250 nm, the thermal conductivity at room temperature is approximately two times lower than that of bulk ZnO at the same temperature. The results of this study show that the thermal conductivity of a ZnO NW is mainly determined by increased phonon-surface boundary scattering. These results could be useful for the design of ZnO-nanowire-based devices.

  8. Entertaining politics, seriously?! : How talk show formats blur conceptual boundaries

    NARCIS (Netherlands)

    Schohaus, Birte

    2017-01-01

    What happens behind the scenes of a talk show? Why do some politicians seem to appear on every show while others are hardly ever seen? Birte Schohaus conducted a multi-layered research in which she conducted interviews with journalists, producers, PR advisors and (former) politicians and combined

  9. Dimensional quantization effects in the thermodynamics of conductive filaments

    Science.gov (United States)

    Niraula, D.; Grice, C. R.; Karpov, V. G.

    2018-06-01

    We consider the physical effects of dimensional quantization in conductive filaments that underlie operations of some modern electronic devices. We show that, as a result of quantization, a sufficiently thin filament acquires a positive charge. Several applications of this finding include the host material polarization, the stability of filament constrictions, the equilibrium filament radius, polarity in device switching, and quantization of conductance.

  10. Evaluation of Cow Milk Electrical Conductivity Measurements

    Directory of Open Access Journals (Sweden)

    Constantin Gavan

    2017-11-01

    Full Text Available The efficiency of subclinical mastitis diagnosis using an electrical conductivity (EC meter was evaluated in the dairy farm of Agricultural Research and Development Station ( ARDS Simnic Craiova. The results were compared with those obtained by using the California Mastitis Test (CMT and the Somatic Cell Count (SCC.The milk quarter samples ( 1176 from Holstein Friesian cows were analyzed between September and December 2015. The EC evaluation with  the EC meter  ,showed a high proportion of results differing from SCC and CMT results. The CMT still shows to be the most accessible and efficient test in comparison to the EC meter tested.

  11. Composites of aluminum alloy and magnesium alloy with graphite showing low thermal expansion and high specific thermal conductivity

    Science.gov (United States)

    Oddone, Valerio; Boerner, Benji; Reich, Stephanie

    2017-12-01

    High thermal conductivity, low thermal expansion and low density are three important features in novel materials for high performance electronics, mobile applications and aerospace. Spark plasma sintering was used to produce light metal-graphite composites with an excellent combination of these three properties. By adding up to 50 vol.% of macroscopic graphite flakes, the thermal expansion coefficient of magnesium and aluminum alloys was tuned down to zero or negative values, while the specific thermal conductivity was over four times higher than in copper. No degradation of the samples was observed after thermal stress tests and thermal cycling. Tensile strength and hardness measurements proved sufficient mechanical stability for most thermal management applications. For the production of the alloys, both prealloyed powders and elemental mixtures were used; the addition of trace elements to cope with the oxidation of the powders was studied.

  12. Structure, ionic Conductivity and mobile Carrier Density in Fast Ionic Conducting Chalcogenide Glasses

    International Nuclear Information System (INIS)

    Wenlong Yao

    2006-01-01

    This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M 2 S + (0.1 Ga 2 S 3 + 0.9 GeS 2 ) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga 2 S 3 + 0.9 GeS 2 was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M 2 S + (0.1Ga 2 S 3 + 0.9 GeS 2 ) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na 2 S + B 2 S 3 (x (le) 0.2) glasses by neutron and synchrotron x-ray diffraction. Similar results were obtained both in neutron and synchrotron x-ray diffraction experiments. The results provide direct

  13. Quantized Hall conductance as a topological invariant

    International Nuclear Information System (INIS)

    Niu, Q.; Thouless, Ds.J.; Wu, Y.S.

    1984-10-01

    Whenever the Fermi level lies in a gap (or mobility gap) the bulk Hall conductance can be expressed in a topologically invariant form showing the quantization explicitly. The new formulation generalizes the earlier result by TKNN to the situation where many body interaction and substrate disorder are also present. When applying to the fractional quantized Hall effect we draw the conclusion that there must be a symmetry breaking in the many body ground state. The possibility of writing the fractionally quantized Hall conductance as a topological invariant is also carefully discussed. 19 references

  14. Methodological approaches to conducting pilot and proof tests on reverse-osmosis systems: Results of comparative studies

    Science.gov (United States)

    Panteleev, A. A.; Bobinkin, V. V.; Larionov, S. Yu.; Ryabchikov, B. E.; Smirnov, V. B.; Shapovalov, D. A.

    2017-10-01

    When designing large-scale water-treatment plants based on reverse-osmosis systems, it is proposed to conduct experimental-industrial or pilot tests for validated simulation of the operation of the equipment. It is shown that such tests allow establishing efficient operating conditions and characteristics of the plant under design. It is proposed to conduct pilot tests of the reverse-osmosis systems on pilot membrane plants (PMPs) and test membrane plants (TMPs). The results of a comparative experimental study of pilot and test membrane plants are exemplified by simulating the operating parameters of the membrane elements of an industrial plant. It is concluded that the reliability of the data obtained on the TMP may not be sufficient to design industrial water-treatment plants, while the PMPs are capable of providing reliable data that can be used for full-scale simulation of the operation of industrial reverse-osmosis systems. The test membrane plants allow simulation of the operating conditions of individual industrial plant systems; therefore, potential areas of their application are shown. A method for numerical calculation and experimental determination of the true selectivity and the salt passage are proposed. An expression has been derived that describes the functional dependence between the observed and true salt passage. The results of the experiments conducted on a test membrane plant to determine the true value of the salt passage of a reverse-osmosis membrane are exemplified by magnesium sulfate solution at different initial operating parameters. It is shown that the initial content of a particular solution component has a significant effect on the change in the true salt passage of the membrane.

  15. Thermal conductivity and magnon-phonon resonant interaction in antiferromagnetic ferrous chloride

    International Nuclear Information System (INIS)

    Laurence, Guy

    1973-01-01

    An apparatus has been studied and built to measure thermal conductivity between 0,3 K and 80 K. The thermal conductivity in the c plane and along the c axis have been measured in FeCl 2 . These results show an anomalous behaviour of the thermal conductivity below the Neel temperature. A calculation of the thermal conductivity of magneto-elastic modes arising from a magnon-phonon resonant interaction renders an account of this behaviour. From the present results, the magneto-elastic coupling constant G 44 is found to be 3,5 meV. Finally, an experimental study of the thermal conductivity magnetic field dependence of FeCl 2 was performed.(author) [fr

  16. Results of Toxicity Studies Conducted on Outfall X-08 and Its Contributing Waste Streams, November 1999 - June 2000

    International Nuclear Information System (INIS)

    Specht, W.L.

    2000-01-01

    This interim report summarizes the results of toxicity tests, Toxicity Identification Evaluations, and chemical analyses that have been conducted on SRS's NPDES Outfall X-08 and its contributing waste streams between November 1999 and June 2000

  17. Effects of Aggregation on Blood Sedimentation and Conductivity

    Science.gov (United States)

    Zhbanov, Alexander; Yang, Sung

    2015-01-01

    The erythrocyte sedimentation rate (ESR) test has been used for over a century. The Westergren method is routinely used in a variety of clinics. However, the mechanism of erythrocyte sedimentation remains unclear, and the 60 min required for the test seems excessive. We investigated the effects of cell aggregation during blood sedimentation and electrical conductivity at different hematocrits. A sample of blood was drop cast into a small chamber with two planar electrodes placed on the bottom. The measured blood conductivity increased slightly during the first minute and decreased thereafter. We explored various methods of enhancing or retarding the erythrocyte aggregation. Using experimental measurements and theoretical calculations, we show that the initial increase in blood conductivity was indeed caused by aggregation, while the subsequent decrease in conductivity resulted from the deposition of erythrocytes. We present a method for calculating blood conductivity based on effective medium theory. Erythrocytes are modeled as conducting spheroids surrounded by a thin insulating membrane. A digital camera was used to investigate the erythrocyte sedimentation behavior and the distribution of the cell volume fraction in a capillary tube. Experimental observations and theoretical estimations of the settling velocity are provided. We experimentally demonstrate that the disaggregated cells settle much slower than the aggregated cells. We show that our method of measuring the electrical conductivity credibly reflected the ESR. The method was very sensitive to the initial stage of aggregation and sedimentation, while the sedimentation curve for the Westergren ESR test has a very mild slope in the initial time. We tested our method for rapid estimation of the Westergren ESR. We show a correlation between our method of measuring changes in blood conductivity and standard Westergren ESR method. In the future, our method could be examined as a potential means of accelerating

  18. Properties of polyacrylic acid-coated silver nanoparticle ink for inkjet printing conductive tracks on paper with high conductivity

    International Nuclear Information System (INIS)

    Huang, Qijin; Shen, Wenfeng; Xu, Qingsong; Tan, Ruiqin; Song, Weijie

    2014-01-01

    Silver nanoparticles with a mean diameter of approximately 30 nm were synthesized by reduction of silver nitrate with triethanolamine in the presence of polyacrylic acid. Silver nanoparticle-based ink was prepared by dispersing silver nanoparticles into a mixture of water and ethylene glycol. The mechanism for the dispersion and aggregation of silver nanoparticles in ink is discussed. The strong electrostatic repulsions of the carboxylate anions of the adsorbed polyacrylic acid molecules disturbed the aggregation of metal particles in solutions with a high pH value (pH > 5). An inkjet printer was used to deposit this silver nanoparticle-based ink to form silver patterns on photo paper. The actual printing qualities of the silver tracks were then analyzed by variation of printing passes, sintering temperature and time. The results showed that sintering temperature and time are associated strongly with the conductivity of the inkjet-printed conductive patterns. The conductivity of printed patterns sintered at 150 °C increased to 2.1 × 10 7  S m −1 , which was approximately one third that of bulk silver. In addition, silver tracks on paper substrate also showed better electrical performance after folding. This study demonstrated that the resulting ink-jet printed patterns can be used as conductive tracks in flexible electronic devices. - Highlights: • An ink from silver nanoparticles coated with polyacrylic acid was prepared. • The ink was used for inkjet-printed tracks at varying printing parameters. • The conductivity of printed tracks sintered at 150 °C increased to 2.1 × 10 7  S/m. • Mechanism for dispersion and aggregation of the nanoparticles in ink is discussed

  19. Properties of polyacrylic acid-coated silver nanoparticle ink for inkjet printing conductive tracks on paper with high conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qijin [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Shen, Wenfeng, E-mail: wfshen@nimte.ac.cn [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Xu, Qingsong [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Tan, Ruiqin [Faculty of Information Science and Engineering, Ningbo University, Ningbo, Zhejiang 315211 (China); Song, Weijie, E-mail: weijiesong@nimte.ac.cn [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China)

    2014-10-15

    Silver nanoparticles with a mean diameter of approximately 30 nm were synthesized by reduction of silver nitrate with triethanolamine in the presence of polyacrylic acid. Silver nanoparticle-based ink was prepared by dispersing silver nanoparticles into a mixture of water and ethylene glycol. The mechanism for the dispersion and aggregation of silver nanoparticles in ink is discussed. The strong electrostatic repulsions of the carboxylate anions of the adsorbed polyacrylic acid molecules disturbed the aggregation of metal particles in solutions with a high pH value (pH > 5). An inkjet printer was used to deposit this silver nanoparticle-based ink to form silver patterns on photo paper. The actual printing qualities of the silver tracks were then analyzed by variation of printing passes, sintering temperature and time. The results showed that sintering temperature and time are associated strongly with the conductivity of the inkjet-printed conductive patterns. The conductivity of printed patterns sintered at 150 °C increased to 2.1 × 10{sup 7} S m{sup −1}, which was approximately one third that of bulk silver. In addition, silver tracks on paper substrate also showed better electrical performance after folding. This study demonstrated that the resulting ink-jet printed patterns can be used as conductive tracks in flexible electronic devices. - Highlights: • An ink from silver nanoparticles coated with polyacrylic acid was prepared. • The ink was used for inkjet-printed tracks at varying printing parameters. • The conductivity of printed tracks sintered at 150 °C increased to 2.1 × 10{sup 7} S/m. • Mechanism for dispersion and aggregation of the nanoparticles in ink is discussed.

  20. Spin and spinless conductivity in polypyrrole. Evidence for mixed-valence conduction

    Energy Technology Data Exchange (ETDEWEB)

    Zotti, G.; Schiavon, G. (Ist. di Polarografia ed Elettrochimica Preparativa, Padova (Italy))

    In situ conductivity of polypyrrole (as tosylate) as a function of oxidative doping level attains a maximum at three-quarters the total oxidation charge and the relevant in situ ESR signal corresponds to an equal concentration of spin-carrying (polaron) and spinless (bipolaron) species. Results are explained on the basis of mixed-valence conduction. Bipolaron conduction, taking the place of polaron-bipolaron conductivity at higher oxidation levels, accounts for persisting conductivity in the high-oxidation state.

  1. Atomistic simulations of highly conductive molecular transport junctions under realistic conditions

    KAUST Repository

    French, William R.; Iacovella, Christopher R.; Rungger, Ivan; Souza, Amaury Melo; Sanvito, Stefano; Cummings, Peter T.

    2013-01-01

    We report state-of-the-art atomistic simulations combined with high-fidelity conductance calculations to probe structure-conductance relationships in Au-benzenedithiolate (BDT)-Au junctions under elongation. Our results demonstrate that large increases in conductance are associated with the formation of monatomic chains (MACs) of Au atoms directly connected to BDT. An analysis of the electronic structure of the simulated junctions reveals that enhancement in the s-like states in Au MACs causes the increases in conductance. Other structures also result in increased conductance but are too short-lived to be detected in experiment, while MACs remain stable for long simulation times. Examinations of thermally evolved junctions with and without MACs show negligible overlap between conductance histograms, indicating that the increase in conductance is related to this unique structural change and not thermal fluctuation. These results, which provide an excellent explanation for a recently observed anomalous experimental result [Bruot et al., Nat. Nanotechnol., 2012, 7, 35-40], should aid in the development of mechanically responsive molecular electronic devices. © 2013 The Royal Society of Chemistry.

  2. Ac-electrical conductivity of poly(propylene) before and after X-ray irradiation

    International Nuclear Information System (INIS)

    Gaafar, M.

    2001-01-01

    Study on the ac-electrical conductivity of poly(propylene), before and after X-ray irradiation within the temperature range 300-360 K are reported. The measurements have been performed in a wide range of frequencies (from 0 to 10 5 Hz) and under the effect of different X-ray irradiation doses (from 0 to 15 Gy). Cole-Cole diagrams have been used to show the frequency dependence of the complex impedance at different temperatures. The results exhibit semicircles which are consistent with existing equivalent circuit model. Analysis of the results reveal semiconducting features based mainly on a hopping mechanism. The study shows a pronounced effect of X-ray irradiation on the electrical conductivity at zero frequency σ DC . At the early stage of irradiation, σ DC increased as a result of free radical formation. As the irradiation progressed, it decreased as a result of crosslinking, then it increased again due to irradiation induced degradation, which motivates the generation of mobile free radicals. The study shows that this polymer is one among other polymers which its electrical conductivity is modified by irradiation

  3. Ac-electrical conductivity of poly(propylene) before and after X-ray irradiation

    Science.gov (United States)

    Gaafar, M.

    2001-05-01

    Study on the ac-electrical conductivity of poly(propylene), before and after X-ray irradiation within the temperature range 300-360 K are reported. The measurements have been performed in a wide range of frequencies (from 0 to 10 5 Hz) and under the effect of different X-ray irradiation doses (from 0 to 15 Gy). Cole-Cole diagrams have been used to show the frequency dependence of the complex impedance at different temperatures. The results exhibit semicircles which are consistent with existing equivalent circuit model. Analysis of the results reveal semiconducting features based mainly on a hopping mechanism. The study shows a pronounced effect of X-ray irradiation on the electrical conductivity at zero frequency σDC. At the early stage of irradiation, σDC increased as a result of free radical formation. As the irradiation progressed, it decreased as a result of crosslinking, then it increased again due to irradiation induced degradation, which motivates the generation of mobile free radicals. The study shows that this polymer is one among other polymers which its electrical conductivity is modified by irradiation.

  4. Universal conductance and conductivity at critical points in integer quantum Hall systems.

    Science.gov (United States)

    Schweitzer, L; Markos, P

    2005-12-16

    The sample averaged longitudinal two-terminal conductance and the respective Kubo conductivity are calculated at quantum critical points in the integer quantum Hall regime. In the limit of large system size, both transport quantities are found to be the same within numerical uncertainty in the lowest Landau band, and , respectively. In the second-lowest Landau band, a critical conductance is obtained which indeed supports the notion of universality. However, these numbers are significantly at variance with the hitherto commonly believed value . We argue that this difference is due to the multifractal structure of critical wave functions, a property that should generically show up in the conductance at quantum critical points.

  5. Thermal conductivity of polymer composites with oriented boron nitride

    International Nuclear Information System (INIS)

    Ahn, Hong Jun; Eoh, Young Jun; Park, Sung Dae; Kim, Eung Soo

    2014-01-01

    Highlights: • Thermal conductivity depended on the orientation of BN in the polymer matrices. • Hexagonal boron nitride (BN) particles were treated by C 27 H 27 N 3 O 2 and C 14 H 6 O 8 . • Amphiphilic-agent-treated BN particles are more easily oriented in the composite. • BN/PVA composites with C 14 H 6 O 8 -treated BN showed the highest thermal conductivity. • Thermal conductivity of the composites was compared with several theoretical models. - Abstract: Thermal conductivity of boron nitride (BN) with polyvinyl alcohol (PVA) and/or polyvinyl butyral (PVB) was investigated as a function of the degree of BN orientation, the numbers of hydroxyl groups in the polymer matrices and the amphiphilic agents used. The composites with in-plane orientation of BN showed a higher thermal conductivity than the composites with out-of-plane orientation of BN due to the increase of thermal pathway. For a given BN content, the composites with in-plane orientation of BN/PVA showed higher thermal conductivity than the composites with in-plane orientation of BN/PVB. This result could be attributed to the improved degree of orientation of BN, caused by a larger number of hydroxyl groups being present. Those treated with C 14 H 6 O 8 amphiphilic agent demonstrated a higher thermal conductivity than those treated by C 27 H 27 N 3 O 2 . The measured thermal conductivity of the composites was compared with that predicted by the several theoretical models

  6. Classification of conductance traces with recurrent neural networks

    Science.gov (United States)

    Lauritzen, Kasper P.; Magyarkuti, András; Balogh, Zoltán; Halbritter, András; Solomon, Gemma C.

    2018-02-01

    We present a new automated method for structural classification of the traces obtained in break junction experiments. Using recurrent neural networks trained on the traces of minimal cross-sectional area in molecular dynamics simulations, we successfully separate the traces into two classes: point contact or nanowire. This is done without any assumptions about the expected features of each class. The trained neural network is applied to experimental break junction conductance traces, and it separates the classes as well as the previously used experimental methods. The effect of using partial conductance traces is explored, and we show that the method performs equally well using full or partial traces (as long as the trace just prior to breaking is included). When only the initial part of the trace is included, the results are still better than random chance. Finally, we show that the neural network classification method can be used to classify experimental conductance traces without using simulated results for training, but instead training the network on a few representative experimental traces. This offers a tool to recognize some characteristic motifs of the traces, which can be hard to find by simple data selection algorithms.

  7. Resonance-induced sensitivity enhancement method for conductivity sensors

    Science.gov (United States)

    Tai, Yu-Chong (Inventor); Shih, Chi-yuan (Inventor); Li, Wei (Inventor); Zheng, Siyang (Inventor)

    2009-01-01

    Methods and systems for improving the sensitivity of a variety of conductivity sensing devices, in particular capacitively-coupled contactless conductivity detectors. A parallel inductor is added to the conductivity sensor. The sensor with the parallel inductor is operated at a resonant frequency of the equivalent circuit model. At the resonant frequency, parasitic capacitances that are either in series or in parallel with the conductance (and possibly a series resistance) is substantially removed from the equivalent circuit, leaving a purely resistive impedance. An appreciably higher sensor sensitivity results. Experimental verification shows that sensitivity improvements of the order of 10,000-fold are possible. Examples of detecting particulates with high precision by application of the apparatus and methods of operation are described.

  8. Anisotropic conductivity imaging with MREIT using equipotential projection algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Degirmenci, Evren [Department of Electrical and Electronics Engineering, Mersin University, Mersin (Turkey); Eyueboglu, B Murat [Department of Electrical and Electronics Engineering, Middle East Technical University, 06531, Ankara (Turkey)

    2007-12-21

    Magnetic resonance electrical impedance tomography (MREIT) combines magnetic flux or current density measurements obtained by magnetic resonance imaging (MRI) and surface potential measurements to reconstruct images of true conductivity with high spatial resolution. Most of the biological tissues have anisotropic conductivity; therefore, anisotropy should be taken into account in conductivity image reconstruction. Almost all of the MREIT reconstruction algorithms proposed to date assume isotropic conductivity distribution. In this study, a novel MREIT image reconstruction algorithm is proposed to image anisotropic conductivity. Relative anisotropic conductivity values are reconstructed iteratively, using only current density measurements without any potential measurement. In order to obtain true conductivity values, only either one potential or conductivity measurement is sufficient to determine a scaling factor. The proposed technique is evaluated on simulated data for isotropic and anisotropic conductivity distributions, with and without measurement noise. Simulation results show that the images of both anisotropic and isotropic conductivity distributions can be reconstructed successfully.

  9. Thermal conductivity of technetium

    International Nuclear Information System (INIS)

    Minato, K.; Serizawa, H.; Fukuda, K.

    1998-01-01

    The thermal diffusivity of technetium was measured on a disk sample of 5 mm in diameter and 1 mm in thickness by the laser flash method from room temperature to 1173 K, and the thermal conductivity was determined by the measured thermal diffusivity and density, and the reported specific heat capacity. The thermal diffusivity of technetium decreases with increasing temperature though it is almost constant above 600 K. The thermal conductivity of technetium shows a minimum around 400 K, above which the thermal conductivity increases with temperature. The electronic and phonon components of the thermal conductivity were evaluated approximately. The increase in the thermal conductivity of technetium with temperature is due to the increase in the electronic component. (orig.)

  10. Highly Confined Electronic and Ionic Conduction in Oxide Heterostructures

    DEFF Research Database (Denmark)

    Pryds, Nini

    2015-01-01

    The conductance confined at the interface of complex oxide heterostructures provides new opportunities to explore nanoelectronic as well as nanoionic devices. In this talk I will present our recent results both on ionic and electronic conductivity at different heterostructures systems. In the first...... unattainable for Bi2O3-based materials, is achieved[1]. These confined heterostructures provide a playground not only for new high ionic conductivity phenomena that are sufficiently stable but also uncover a large variety of possible technological perspectives. At the second part, I will discuss and show our...

  11. Fabrication and analysis of small-scale thermal energy storage with conductivity enhancement

    International Nuclear Information System (INIS)

    Thapa, Suvhashis; Chukwu, Sam; Khaliq, Abdul; Weiss, Leland

    2014-01-01

    Highlights: • Useful thermal conductivity envelope established for small scale TES. • Paraffin conductivity enhanced from .5 to 3.8 W/m K via low-cost copper insert. • Conductivity increase beyond 5 W/m K shows diminished returns. • Storage with increased conductivity lengthened thermoelectric output up to 247 s. - Abstract: The operation and useful operating parameters of a small-scale Thermal Energy Storage (TES) device that collects and stores heat in a Phase Change Material (PCM) is explored. The PCM utilized is an icosane wax. A physical device is constructed on the millimeter scale to examine specific effects of low-cost thermal conductivity enhancements that include copper foams and other metallic inserts. Numerical methods are utilized to establish useful operating range of small-scale TES devices in general, and the limits of thermal conductivity enhancement on thermoelectric operation specifically. Specific attention is paid to the manufacturability of the various constructs as well as the resulting thermal conductivity enhancement. A maximum thermal conductivity of 3.8 W/m K is achieved in experimental testing via copper foam enhancement. A simplified copper matrix achieves conductivity of 3.7 W/m K and allows significantly reduced fabrication effort. These results compare favorably to baseline wax conductivity of .5 W/m K. Power absorption is recorded of about 900 W/m 2 . Modeling reveals diminishing returns beyond 4–6 W/m K for devices on this scale. Results show the system capable of extending thermoelectric operation several minutes through the use of thermal energy storage techniques within the effective conductivity ranges

  12. Conductivity in redox modified conducting polymers. In-situ conductivity of poly(cyclopentadithiophenes) bearing p-nitrophenyl and 4-N-methylpyridinium groups

    Energy Technology Data Exchange (ETDEWEB)

    Zotti, G. [Consiglio Nazionale delle Ricerche, (Italy). Istituto di Polarografia ed Elettrochimica Preparativa; Berlin, A. [Milan Univ. (Italy). Dipartimento di Chimica Organica e Industriale; Pagani, G. [Milan Univ. (Italy). Dipartimento di Chimica Organica e Industriale; Schiavon, G. [Consiglio Nazionale delle Ricerche, (Italy). Istituto di Polarografia ed Elettrochimica Preparativa; Zecchin, S. [Consiglio Nazionale delle Ricerche, (Italy). Istituto di Polarografia ed Elettrochimica Preparativa

    1995-01-01

    Redox-modified polythiophenes exhibiting the highest mixed-valence conductivities of any polymer containing a pendant redox group are reported. The ordering of the polymer, in which the backbone has been oxidized to a bipolaron conducting state and the redox sites have been reduced to a mixed-valence conducting state, encourages inter-site hopping and results in the high conductivities. Electron interactions are shown not have an influence on the conduction. (orig.)

  13. Thin films of conductive ZnO patterned by micromolding resulting in nearly isolated features

    NARCIS (Netherlands)

    Göbel, Ole; Blank, David H.A.; ten Elshof, Johan E.

    2010-01-01

    Patterned and continuous thin films of conductive Al-doped zinc oxide (ZnO:Al) were prepared on different substrates from a polymeric precursor solution. Their electric conductivity and light transmittance (for visible and UV light) was measured at room temperature. By means of a simple device,

  14. High H⁻ ionic conductivity in barium hydride.

    Science.gov (United States)

    Verbraeken, Maarten C; Cheung, Chaksum; Suard, Emmanuelle; Irvine, John T S

    2015-01-01

    With hydrogen being seen as a key renewable energy vector, the search for materials exhibiting fast hydrogen transport becomes ever more important. Not only do hydrogen storage materials require high mobility of hydrogen in the solid state, but the efficiency of electrochemical devices is also largely determined by fast ionic transport. Although the heavy alkaline-earth hydrides are of limited interest for their hydrogen storage potential, owing to low gravimetric densities, their ionic nature may prove useful in new electrochemical applications, especially as an ionically conducting electrolyte material. Here we show that barium hydride shows fast pure ionic transport of hydride ions (H(-)) in the high-temperature, high-symmetry phase. Although some conductivity studies have been reported on related materials previously, the nature of the charge carriers has not been determined. BaH2 gives rise to hydride ion conductivity of 0.2 S cm(-1) at 630 °C. This is an order of magnitude larger than that of state-of-the-art proton-conducting perovskites or oxide ion conductors at this temperature. These results suggest that the alkaline-earth hydrides form an important new family of materials, with potential use in a number of applications, such as separation membranes, electrochemical reactors and so on.

  15. Electromagnetic properties of conducting polymers encapsulated in an insulating matrix

    International Nuclear Information System (INIS)

    Esnouf, Stephane

    1995-01-01

    The aim of this work is to study the electronic properties of conducting polymers encapsulated in zeolite. We studied two kinds of polymers: intrinsic conducting polymers (poly-pyrrole) and pyrolyzed polymers (polyacrylonitrile and poly-furfuryl alcohol). These systems were characterized by electron paramagnetic resonance and microwave conductivity measurements. In the first part, we present the preparation and the characterization of encapsulated poly-pyrrole. Conductivity measurements show that the encapsulated material is insulating, certainly because a strong interaction with the zeolite traps the charge carriers. In the second part, we focus on pyrolyzed encapsulated polyacrylonitrile. This system has a metal-like susceptibility at room temperature and a relatively high microwave conductivity. These results demonstrate the formation during the pyrolysis of extended aromatic clusters. Finally, we study pyrolyzed encapsulated poly-furfuryl alcohol. We show that the only effect of the pyrolysis is to fragment the polymers. We also discuss the spin relaxation and the EPR line broadening. (author) [fr

  16. High-temperature thermal conductivity of uranium chromite and uranium niobate

    International Nuclear Information System (INIS)

    Fedoseev, D.V.; Varshavskaya, I.G.; Lavrent'ev, A.V.; Oziraner, S.N.; Kuznetsova, D.G.

    1979-01-01

    The technique of determining thermal conductivity coefficient of uranium niobate and uranium chromite on heating with laser radiation is described. Determined is the coefficient of free-convective heat transfer (with provision for a conduction component) by means of a standard specimen. The thermal conductivity coefficients of uranium chromite and niobate were measured in the 1300-1700 K temperature range. The results are presented in a diagram form. It has been calculated, that the thermal conductivity coefficient for uranium niobate specimens is greater in comparison with uranium chromite specimens. The thermal conductivity coefficients of the materials mentioned depend on temperature very slightly. Thermal conductivity of the materials considerably depends on their porosity. The specimens under investigation were fabricated by the pressing method and had the following porosity: uranium chromite - 30 %, uranium niobate - 10 %. Calculation results show, that thermal conductivity of dense uranium chromite is higher than thermal conductivity of dense uranium niobate. The experimental error equals approximately 20 %, that is mainly due to the error of measuring the temperature equal to +-25 deg, with a micropyrometer

  17. Structure, ionic conductivity and mobile carrier density in fast ionic conducting chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Wenlong [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M2S + (0.1 Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga2S3 + 0.9 GeS2 was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M2S + (0.1Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na2S + B2S3 (x ≤ 0.2) glasses by neutron and synchrotron x-ray diffraction

  18. Electronic Conductivity of Doped-Lanthanum Gallate Electrolytes

    Science.gov (United States)

    Yamaji, Katsuhiko; Xiong, Yue Ping; Kishimoto, Haruo; Horita, Teruhisa; Sakai, Natsuko; Brito, Manuel E.; Yokokawa, Harumi

    Electronic conductivity of doped lanthanum gallate electrolytes were determined by using a Hebb-Wagner type polarization cell. Electronic conductivity of cobalt-doped, La0.8Sr0.2Ga0.8Mg0.15Co0.5O3-δ (LSGMC), and non cobalt-doped, La0.8Sr0.2Ga0.8Mg0.2O2.8 (LSGM8282), were measured as a function of oxygen partial pressures. The electronic conductivity of LSGM8282 showed a linear dependence on p(O2)1/4 in the higher p(O2) region, which is attributed to the electronic hole conductivity. The electronic conductivity of LSGMC showed a linear dependence on p(O2)1/6 in the higher p(O2) region. LSGMC has higher electronic conductivity than LSGM, and the conductivity was not clearly changed with temperatures between 600 and 800 °C. In lower p(O2) region, the electronic conductivity data have poor reproducibility and did not show any dependence on p(O2) because of the degradation of the electrolytes in severe reducing atmospheres.

  19. Composition and conductance distributions of single GeSi quantum rings studied by conductive atomic force microscopy combined with selective chemical etching.

    Science.gov (United States)

    Lv, Y; Cui, J; Jiang, Z M; Yang, X J

    2013-02-15

    Atomic force microscopy imaging combined with selective chemical etching is employed to quantitatively investigate three-dimensional (3D) composition distributions of single GeSi quantum rings (QRs). In addition, the 3D quantitative composition distributions and the corresponding conductance distributions are simultaneously obtained on the same single GeSi QRs by conductive atomic force microscopy combined with selective chemical etching, allowing us to investigate the correlations between the conductance and composition distributions of single QRs. The results show that the QRs' central holes have higher Ge content, but exhibit lower conductance, indicating that the QRs' conductance distribution is not consistent with their composition distribution. By comparing the topography, composition and conductance profiles of the same single QRs before and after different etching processes, it is found that the conductance distributions of GeSi QRs do not vary with the change of composition distribution. Instead, the QRs' conductance distributions are found to be consistent with their topographic shapes, which can be supposed to be due to the shape determined electronic structures.

  20. Tile Effect of P reconsolidation on the Thermal Conductivity of Particulate Beds

    International Nuclear Information System (INIS)

    Weidenfeld, G.

    2001-09-01

    The thermal conductivity of particulate beds is an important property for many industrial handling processes as well as storage of particulate materials. This property can be affected by a few conditions, such as, temperature and external axial pressure. In the first part of this work, a background for the thermal conductivity of particulate bed is given. This includes a review of experimental and theoretical studies on the thermal conductivity of particulate beds. It is also a reviewed parameters that influence the thermal conductivity of particulate beds, such as, temperature. This study presents a new experimental apparatus that enables to measure the thermal conductivity in steady-state while the particulate bed is under axial consolidation stresses. The experimental apparatus was analyzed and characterized experimentally and by numerical simulations. An analytical model, that predicts the thermal conductivity of particulate beds under axial consolidation stress was developed. The model results were compared to the experimental results for 0.5 and 1 mm steel spheres and showed a good agreement. The experimental results showed a significant effect of the compression state on the bed and its pre-consolidation for 0.5 and 1 mm steel spheres. The effect of the compression state on the bed and its pre-consolidation was even more significant for limestone powder

  1. Integration of conducting polymer network in non-conductive polymer substrates

    DEFF Research Database (Denmark)

    Hansen, Thomas Steen; West, Keld; Hassager, Ole

    2006-01-01

    Anew method for integration ofconjugated, inherently conducting polymers into non-conductive polymer substrates has been developed. Alayer of the conducting polymer is polymerised by chemical oxidation, e.g. using Fe(ID) p-toluene sulfonate (ferri tosylate) followed by washing with a solvent which...... simultaneously removes residual and spent oxidant and at the same time dissolves the top layer of the polymer substrate. This results in an integration of the conducting polymer into the surface layers of the polymer substrate. Several combinations of conducting polymers and substrates have been tested...... absorption during sequential reactive ion etching has allowed for analysis of the PEDOT distribution within the surface layer of thePMMA substrate. The surface resistance ofthe conducting polymer layer remains low while the surface layer at the same time adapts some of the mechanical properties...

  2. Single Molecule Conductance of Oligothiophene Derivatives

    Science.gov (United States)

    Dell, Emma J.

    This thesis studies the electronic properties of small organic molecules based on the thiophene motif. If we are to build next-generation devices, advanced materials must be designed which possess requisite electronic functionality. Molecules present attractive candidates for these ad- vanced materials since nanoscale devices are particularly sought after. However, selecting a molecule that is suited to a certain electronic function remains a challenge, and characterization of electronic behavior is therefore critical. Single molecule conductance measurements are a powerful tool to determine properties on the nanoscale and, as such, can be used to investigate novel building blocks that may fulfill the design requirements of next-generation devices. Combining these conductance results with strategic chemical synthesis allows for the development of new families of molecules that show attractive properties for future electronic devices. Since thiophene rings are the fruitflies of organic semiconductors on the bulk scale, they present an intriguing starting point for building functional materials on the nanoscale, and therefore form the structural basis of all molecules studied herein. First, the single-molecule conductance of a family of bithiophene derivatives was measured. A broad distribution in the single-molecule conductance of bithiophene was found compared with that of a biphenyl. This increased breadth in the conductance distribution was shown to be explained by the difference in 5-fold symmetry of thiophene rings as compared to the 6-fold symmetry of benzene rings. The reduced symmetry of thiophene rings results in a restriction on the torsion angle space available to these molecules when bound between two metal electrodes in a junction, causing each molecular junction to sample a different set of conformers in the conductance measurements. By contrast, the rotations of biphenyl are essentially unimpeded by junction binding, allowing each molecular junction

  3. The Preparation and Property of Graphene /Tin Oxide Transparent Conductive Film

    Directory of Open Access Journals (Sweden)

    SUN Tao

    2017-02-01

    Full Text Available Graphene doped tin oxide composites were prepared with SnCIZ·2HZ 0 and graphene oxide as raw materials with sol-gel method and then spincoated on the quartz glass to manufacture a new transparent conductive film. The composite film was characterized with X-ray diffraction(XRDand scanning electron microscopy(SEM analysis. XRD results show that the graphene oxide was successfully prepared with Hummers method. The graphene layers and particulate SnOZ can be clearly observed in SEM photos. The transmittance and conductivity of the thin films were tested with ultraviolet visible spectrophotometer and Hall effect measurement. The results show that the transmittivity of composite film in visible region is more than 90% and surface square resistance is 41 S2/口.The graphene/ SnOZ film exhibits a higher performance in transparence and conductivity than commercial FTO glass.

  4. Dielectric and conductivity properties of composite polyaniline/polyurethane network

    Science.gov (United States)

    Liang, C.; Gest, J.; Leroy, G.; Carru, J.-C.

    2013-09-01

    In this work, we present the dielectric characterization of polyaniline/polyurethane composite. The samples consisting of 0.5%, 1%, and 5% of polyaniline were deposited on glass fiber, and the measurements were performed in a frequency range of 20 Hz to 20 GHz. The results showed a dielectric relaxation strongly dependent on the concentration of polyaniline. This phenomenon is explained by a theoretical model. In this model, we assume that the alternative conductivity of the polymer network systems is due to conducting clusters whose lengths followed a Gaussian distribution. Depending on their size and the frequency of the excitation signal, the clusters showed a resistive or capacitive effect.

  5. Nonlinear dynamics in cardiac conduction

    Science.gov (United States)

    Kaplan, D. T.; Smith, J. M.; Saxberg, B. E.; Cohen, R. J.

    1988-01-01

    Electrical conduction in the heart shows many phenomena familiar from nonlinear dynamics. Among these phenomena are multiple basins of attraction, phase locking, and perhaps period-doubling bifurcations and chaos. We describe a simple cellular-automation model of electrical conduction which simulates normal conduction patterns in the heart as well as a wide range of disturbances of heart rhythm. In addition, we review the application of percolation theory to the analysis of the development of complex, self-sustaining conduction patterns.

  6. Pressure and graphite effects on electrical conductivity in pyroxene

    Science.gov (United States)

    Wang, D.; Liu, T.; Shen, K.; Li, B.

    2017-12-01

    The geophysical observations including magnetotelluric (MT) and geomagnetic deep sounding show the distribution of electrical conductivity in the Earth's interior. The laboratory-based conductivity measurements of minerals and rocks are usually used to interpret the geophysical observations. Pyroxene is the second most abundant components in the upper mantle, and the electrical conductivity of pyroxene is important to understanding the bulk electrical conductivity. The electrical conductivity of a mineral is affected by many factors, such as its chemical composition, temperature, pressure. Here we report the effects of pressure and graphite on the electrical conductivity of pyroxene and applied to interpretation of MT observation. The starting materials are natural of orthopyroxene and clinopyroxe crystals. A powder sample with grain size 10 um was packed in a Mo capsule and hot-pressed at high pressures and temperatures using a 1000-ton Walker-type uniaxial split-cylinder apparatus. A mixture of pyroxene and a few percent of diamond was annealed at high pressure and temperature. All the hot-pressed samples before and after electrical conductivity measurements, were characterized by scanning electron microscopy, Fourier-Transform Infrared and Raman spectroscopy. High pressure conductivity experiments were carried out in a Walker-type multi-anvil apparatus using a 14/8 assembly. We use a Solartron 1260 Impedance/Gain -phase analyzer with 1V applied voltage within a frequency range of 1M-0.1 Hz to collect data. Complex impedance data on were collected in several heating and cooling cycles The electrical conductivity of pyroxene was made at 4,7,10 GPa, and electrical conductivity of the graphite-bearing pyroxene was measured at 4GPa. The results show the electrical conductivity decrease with the increasing of pressure, which may correspond to the transform from orthopyroxene to clinopyroxene. The results can be used to explain a drop of the electrical conductivity in

  7. Nonlocal conductivity in type-II superconductors

    International Nuclear Information System (INIS)

    Mou, C.; Wortis, R.; Dorsey, A.T.; Huse, D.A.

    1995-01-01

    Multiterminal transport measurements on YBa 2 Cu 2 O 7 crystals in the vortex liquid regime have shown nonlocal conductivity on length scales up to 50 microns. Motivated by these results we explore the wave vector (k) dependence of the dc conductivity tensor, σ μν (k), in the Meissner, vortex lattice, and disordered phases of a type-II superconductor. Our results are based on time-dependent Ginzburg-Landau (TDGL) theory and on phenomenological arguments. We find four qualitatively different types of behavior. First, in the Meissner phase, the conductivity is infinite at k=0 and is a continuous function of k, monotonically decreasing with increasing k. Second, in the vortex-lattice phase, in the absence of pinning, the conductivity is finite (due to flux flow) at k=0; it is discontinuous there and remains qualitatively like the Meissner phase for k>0. Third, in the vortex liquid regime in a magnetic field and at low temperature, the conductivity is finite, smooth and nonmonotonic, first increasing with k at small k and then decreasing at larger k. This third behavior is expected to apply at temperatures just above the melting transition of the vortex lattice, where the vortex liquid shows strong short-range order and a large viscosity. Finally, at higher temperatures in the disordered phase, the conductivity is finite, smooth and again monotonically decreasing with k. This last, monotonic behavior applies in zero magnetic field for the entire disordered phase, i.e., at all temperatures above T c , while in a field the nonmonotonic behavior may occur in a low-temperature portion of the disordered phase

  8. The longitudinal optical conductivity in bilayer graphene and other two-dimensional systems

    Energy Technology Data Exchange (ETDEWEB)

    Yang, C.H., E-mail: chyang@nuist.edu.cn [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Ao, Z.M., E-mail: zhimin.ao@uts.edu.au [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology, Sydney ,PO Box 123, Broadway, Sydney, NSW 2007 (Australia); Wei, X.F. [West Anhui University, Luan 237012 (China); Jiang, J.J. [Department of Physics, Sanjing College, Nanjing 210012 (China)

    2015-01-15

    The longitudinal optical conductivity in bilayer graphene is calculated using the dielectric function by defining the density operator theoretically, while the effect of the broadening width determined by the scattering sources on the optical conductivity is also investigated. Some features, such as chirality, energy dispersion and density of state (DOS) in bilayer graphene, are similar to those in monolayer graphene and a traditional two-dimensional electron gas (2DEG). Therefore, in this paper, the bilayer graphene optical conductivity is compared with the results in these two systems. The analytical and numerical results show that the optical conductivity per graphene layer is almost a constant and close to e{sup 2}/(4ℏ), which agrees with the experimental results.

  9. 16 CFR 5.57 - Order to show cause.

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Order to show cause. 5.57 Section 5.57 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE STANDARDS OF CONDUCT Disciplinary Actions Concerning Postemployment Conflict of Interest § 5.57 Order to show cause. (a...

  10. Tuning thermal conductivity in molybdenum disulfide by electrochemical intercalation

    Science.gov (United States)

    Zhu, Gaohua; Liu, Jun; Zheng, Qiye; Zhang, Ruigang; Li, Dongyao; Banerjee, Debasish; Cahill, David G.

    2016-01-01

    Thermal conductivity of two-dimensional (2D) materials is of interest for energy storage, nanoelectronics and optoelectronics. Here, we report that the thermal conductivity of molybdenum disulfide can be modified by electrochemical intercalation. We observe distinct behaviour for thin films with vertically aligned basal planes and natural bulk crystals with basal planes aligned parallel to the surface. The thermal conductivity is measured as a function of the degree of lithiation, using time-domain thermoreflectance. The change of thermal conductivity correlates with the lithiation-induced structural and compositional disorder. We further show that the ratio of the in-plane to through-plane thermal conductivity of bulk crystal is enhanced by the disorder. These results suggest that stacking disorder and mixture of phases is an effective mechanism to modify the anisotropic thermal conductivity of 2D materials. PMID:27767030

  11. Reinforced Conductive Polyaniline-Paper Composites

    Directory of Open Access Journals (Sweden)

    Jinhua Yan

    2015-05-01

    Full Text Available A method for direct aniline interfacial polymerization on polyamideamine-epichlorohydrin (PAE-reinforced paper substrate is introduced in this paper. Cellulose-based papers with and without reinforcement were considered. The polyaniline (PANI-paper composites had surface resistivity lower than 100 Ω/sq after more than 3 polymerizations. Their mechanical strength and thermal stability were analyzed by tensile tests and thermogravimetric analysis (TGA. Fourier transform infrared (FTIR results revealed that there was strong interaction between NH groups in aniline monomers and OH groups in fibers, which did not disappear until after 3 polymerizations. Scanning electron microscopy (SEM and field emission (FE SEM images showed morphological differences between composites using reinforced and untreated base papers. Conductive composites made with PAE-reinforced base paper had both good thermal stability and good mechanical strength, with high conductivity and a smaller PANI amount.

  12. Magnetic field induced augmented thermal conduction phenomenon in magneto-nanocolloids

    International Nuclear Information System (INIS)

    Katiyar, Ajay; Dhar, Purbarun; Nandi, Tandra; Das, Sarit K.

    2016-01-01

    Magnetic field induced augmented thermal conductivity of magneto-nanocolloids involving nanoparticles, viz. Fe_2O_3, Fe_3O_4, NiO and Co_3O_4 dispersed in different base fluids have been reported. Experiments reveal the augmented thermal transport under external applied magnetic field. A maximum thermal conductivity enhancement ∼114% is attained at 7.0 vol% concentration and 0.1 T magnetic flux density for Fe_3O_4/EG magneto-nanocolloid. However, a maximum ∼82% thermal conductivity enhancement is observed for Fe_3O_4/kerosene magneto-nanocolloid for the same concentration but relatively at low magnetic flux density (∼0.06 T). Thereby, a strong effect of fluid as well as particle physical properties on the chain formation propensity, leading to enhanced conduction, in such systems is observed. Co_3O_4 nanoparticles show insignificant effect on the thermal conductivity enhancement of MNCs due to their minimal magnetic moment. A semi-empirical approach has been proposed to understand the mechanism and physics behind the thermal conductivity enhancement under external applied magnetic field, in tune with near field magnetostatic interactions as well as Neel relaxivity of the magnetic nanoparticles. Furthermore, the model is able to predict the phenomenon of enhanced thermal conductivity as a function of physical parameters and shows good agreement with the experimental observations. - Highlights: • Heat conduction in magneto-nanocolloids augments tremendously under magnetic field. • Oxide nanoparticles of Fe, Ni and Co dispersed in variant base fluids are used. • Enhancement in heat conduction is due to the formation of thermally conductive chains. • Proposed semi-empirical model shows good agreement with the experimental results.

  13. Change in the electrical conductivity of SnO2 crystal from n-type to p-type conductivity

    International Nuclear Information System (INIS)

    Villamagua, Luis; Stashans, Arvids; Lee, Po-Ming; Liu, Yen-Shuo; Liu, Cheng-Yi; Carini, Manuela

    2015-01-01

    Highlights: • Switch from n-type to p-type conductivity in SnO 2 has been studied. • Computational DFT + U method where used. • X-ray diffraction and X-ray photoelectron spectroscopy where used. • Al- and N-codoped SnO 2 compound shows stable p-type conductivity. • Low resistivity (3.657 × 10 −1 Ω cm) has been obtained. • High carrier concentration (4.858 × 10 19 cm −3 ) has been obtained. - Abstract: The long-sought fully transparent technology will not come true if the n region of the p–n junction does not get as well developed as its p counterpart. Both experimental and theoretical efforts have to be used to study and discover phenomena occurring at the microscopic level in SnO 2 systems. In the present paper, using the DFT + U approach as a main tool and the Vienna ab initio Simulation Package (VASP) we reproduce both intrinsic n-type as well as p-type conductivity in concordance to results observed in real samples of SnO 2 material. Initially, an oxygen vacancy (1.56 mol% concentration) combined with a tin-interstitial (1.56 mol% concentration) scheme was used to achieve the n-type electrical conductivity. Later, to attain the p-type conductivity, crystal already possessing n-type conductivity, was codoped with nitrogen (1.56 mol% concentration) and aluminium (12.48 mol% concentration) impurities. Detailed explanation of structural changes endured by the geometry of the crystal as well as the changes in its electrical properties has been obtained. Our experimental data to a very good extent matches with the results found in the DFT + U modelling

  14. Significantly enhanced thermal conductivity of indium arsenide nanowires via sulfur passivation.

    Science.gov (United States)

    Xiong, Yucheng; Tang, Hao; Wang, Xiaomeng; Zhao, Yang; Fu, Qiang; Yang, Juekuan; Xu, Dongyan

    2017-10-16

    In this work, we experimentally investigated the effect of sulfur passivation on thermal transport in indium arsenide (InAs) nanowires. Our measurement results show that thermal conductivity can be enhanced by a ratio up to 159% by sulfur passivation. Current-voltage (I-V) measurements were performed on both unpassivated and S-passivated InAs nanowires to understand the mechanism of thermal conductivity enhancement. We observed a remarkable improvement in electrical conductivity upon sulfur passivation and a significant contribution of electrons to thermal conductivity, which account for the enhanced thermal conductivity of the S-passivated InAs nanowires.

  15. Electrical conductivity imaging in the western Pacific subduction zone

    Science.gov (United States)

    Utada, Hisashi; Baba, Kiyoshi; Shimizu, Hisayoshi

    2010-05-01

    Oceanic plate subduction is an important process for the dynamics and evolution of the Earth's interior, as it is regarded as a typical downward flow of the mantle convection that transports materials from the near surface to the deep mantle. Recent seismological study showed evidence suggesting the transportation of a certain amount of water by subduction of old oceanic plate such as the Pacific plate down to 150-200 km depth into the back arc mantle. However it is not well clarified how deep into the mantle the water can be transported. The electromagnetic induction method to image electrical conductivity distribution is a possible tool to answer this question as it is known to be sensitive to the presence of water. Here we show recent result of observational study from the western Pacific subduction zone to examine the electrical conductivity distribution in the upper mantle and in the mantle transition zone (MTZ), which will provide implications how water distributes in the mantle. We take two kinds of approach for imaging the mantle conductivity, (a) semi-global and (b) regional induction approaches. Result may be summarized as follows: (a) Long (5-30 years) time series records from 8 submarine cables and 13 geomagnetic observatories in the north Pacific region were analyzed and long period magnetotelluric (MT) and geomagnetic deep sounding (GDS) responses were estimated in the period range from 1.7 to 35 days. These frequency dependent response functions were inverted to 3-dimensional conductivity distribution in the depth range between 350 and 850 km. Three major features are suggested in the MTZ depth such as, (1) a high conductivity anomaly beneath the Philippine Sea, (2) a high conductivity anomaly beneath the Hawaiian Islands, and (3) a low conductivity anomaly beneath and in the vicinity of northern Japan. (b) A three-year long deployment of ocean bottom electro-magnetometers (OBEM's) was conducted in the Philippine Sea and west Pacific Ocean from 2005

  16. A methodology to investigate the contribution of conduction and radiation heat transfer to the effective thermal conductivity of packed graphite pebble beds, including the wall effect

    Energy Technology Data Exchange (ETDEWEB)

    De Beer, M., E-mail: maritz.db@gmail.com [School of Mechanical and Nuclear Engineering, North-West University, Private Bag X6001, Potchefstroom 2520 (South Africa); Du Toit, C.G., E-mail: Jat.DuToit@nwu.ac.za [School of Mechanical and Nuclear Engineering, North-West University, Private Bag X6001, Potchefstroom 2520 (South Africa); Rousseau, P.G., E-mail: pieter.rousseau@uct.ac.za [Department of Mechanical Engineering, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa)

    2017-04-01

    Highlights: • The radiation and conduction components of the effective thermal conductivity are separated. • Near-wall effects have a notable influence on the effective thermal conductivity. • Effective thermal conductivity is a function of the macro temperature gradient. • The effective thermal conductivity profile shows a characteristic trend. • The trend is a result of the interplay between conduction and radiation. - Abstract: The effective thermal conductivity represents the overall heat transfer characteristics of a packed bed of spheres and must be considered in the analysis and design of pebble bed gas-cooled reactors. During depressurized loss of forced cooling conditions the dominant heat transfer mechanisms for the passive removal of decay heat are radiation and conduction. Predicting the value of the effective thermal conductivity is complex since it inter alia depends on the temperature level and temperature gradient through the bed, as well as the pebble packing structure. The effect of the altered packing structure in the wall region must therefore also be considered. Being able to separate the contributions of radiation and conduction allows a better understanding of the underlying phenomena and the characteristics of the resultant effective thermal conductivity. This paper introduces a purpose-designed test facility and accompanying methodology that combines physical measurements with Computational Fluid Dynamics (CFD) simulations to separate the contributions of radiation and conduction heat transfer, including the wall effects. Preliminary results obtained with the methodology offer important insights into the trends observed in the experimental results and provide a better understanding of the interplay between the underlying heat transfer phenomena.

  17. Hydraulic conductivity and soil-sewage sludge interactions

    Directory of Open Access Journals (Sweden)

    Silvio Romero de Melo Ferreira

    2011-10-01

    Full Text Available One of the main problems faced by humanity is pollution caused by residues resulting from the production and use of goods, e.g, sewage sludge. Among the various alternatives for its disposal, the agricultural use seems promising. The purpose of this study was to evaluate the hydraulic conductivity and interaction of soil with sandy-silty texture, classified as Spodosols, from the Experimental Station Itapirema - IPA, in Goiana, state of Pernambuco, in mixtures with sewage sludge from the Mangueira Sewage Treatment Station, in the city of Recife, Pernambuco at rates of 25, 50 and 75 Mg ha-1. Tests were conducted to let water percolate the natural saturated soil and soil-sludge mixtures to characterize their physical, chemical, and microstructural properties as well as hydraulic conductivity. Statistical data analysis showed that the presence of sewage sludge in soils leads to an increase of the < 0.005 mm fraction, reduction in real specific weight and variation in optimum moisture content from 11.60 to 12.90 % and apparent specific dry weight from 17.10 and 17.50 kN m-3. In the sludge-soil mixture, the quartz grains were covered by sludge and filling of the empty soil macropores between grains. There were changes in the chemical characteristics of soil and effluent due to sewage sludge addition and a small decrease in hydraulic conductivity. The results indicate the possibility that soil acidity influenced the concentrations of the elements found in the leachate, showing higher levels at higher sludge doses. It can be concluded that the leaching degree of potentially toxic elements from the sewage sludge treatments does not harm the environment.

  18. Conductivity and Space Charges in PE with Additives

    DEFF Research Database (Denmark)

    Holbøll, Joachim; Henriksen, Mogens; Hjerrild, J.

    2003-01-01

    temperatures. Space charge formation under an applied electrical field of 20 kV/mm was investigated by means of the pulse-electro-acoustic method (PEA) at room temperature. The results were compared to space charge formation and conductivity in common LDPE. The measurements showed considerable differences...... between materials and only minor influence of crosslinking process and the addition of antioxidant with respect to the electrical properties of the material. Possible correlations between conductivity and space charge formation are discussed in the paper. The relevance of the findings for application...

  19. Investigated conductive fracture in the granitic rocks by flow-meter logging

    International Nuclear Information System (INIS)

    Ogata, Nobuhisa; Koide, Kaoru; Takeichi, Atsushi

    1997-01-01

    Test of the use of a measurement technique for the hydraulic conductivity of geological structures which act as flow paths or are impermeable to groundwater flow. In order to prove the value of flow-meter logging as an in-situ technique for detecting conductive fractures in granitic rocks, the method has been applied to a borehole near the Tono uranium mine, Gifu, Japan. This study in involved with detecting a conductive fracture and calculating the hydraulic conductivities. The results were as follows: (1) In a zone of groundwater inflow into the borehole, the hydraulic conductivity was calculated to be of the order of the 10 -3 - 10 -4 (cm/sec) from flow-meter logging. This value agreed with the results of a in-situ borehole permeability test carried out with a similar depth interval. (2) The study showed that flow-meter logging is effective for detecting the distribution of high conductivity fractures and calculating the hydraulic conductivity. (author)

  20. Synthesis and characterization of electrical conducting nanoporous carbon structures

    International Nuclear Information System (INIS)

    El Mir, L.; Kraiem, S.; Bengagi, M.; Elaloui, E.; Ouederni, A.; Alaya, S.

    2007-01-01

    Nanoporous organic xerogel compounds were prepared by sol-gel method from pyrogallol-formaldehyde (PF) mixtures in water using perchloric acid as catalyst. The preparation conditions of electrical conducting carbon (ECC) structures were explored by changing the pyrolysis temperature. The effect of this preparation parameters on the structural and electrical properties of the obtained ECCs were studied, respectively, by thermogravimetric analysis (TGA), nitrogen adsorption isotherms, IR spectroscopy and electrical conductivity measurements. The analysis of the obtained results revealed that, the polymeric insulating phase was transformed progressively with pyrolysis temperature into carbon conducting phase; this means the formation of long continuous conducting path for charge carriers when the carbon microparticles inside the structure agglomerated with thermal treatment and the samples exhibited tangible percolation behaviour where the percolation threshold can be determined by pyrolysis temperature. The temperature-dependent conductivity and the I(V) characteristics of the obtained ECC structures show a non-ohmic behaviour. The results obtained from TGA and differential thermal analyser (DTA) thermograms, scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographs, IR spectroscopy and X-ray diffraction revealed that, the obtained ECC structures consist of amorphous and nanoporous electrical conducting carbon materials

  1. Heat conduction in graphene: experimental study and theoretical interpretation

    International Nuclear Information System (INIS)

    Ghosh, S; Nika, D L; Pokatilov, E P; Balandin, A A

    2009-01-01

    We review the results of our experimental investigation of heat conduction in suspended graphene and offer a theoretical interpretation of its extremely high thermal conductivity. The direct measurements of the thermal conductivity of graphene were performed using a non-contact optical technique and special calibration procedure with bulk graphite. The measured values were in the range of ∼3000-5300 W mK -1 near room temperature and depended on the lateral dimensions of graphene flakes. We explain the enhanced thermal conductivity of graphene as compared to that of bulk graphite basal planes by the two-dimensional nature of heat conduction in graphene over the whole range of phonon frequencies. Our calculations show that the intrinsic Umklapp-limited thermal conductivity of graphene grows with the increasing dimensions of graphene flakes and can exceed that of bulk graphite when the flake size is on the order of a few micrometers. The detailed theory, which includes the phonon-mode-dependent Gruneisen parameter and takes into account phonon scattering on graphene edges and point defects, gives numerical results that are in excellent agreement with the measurements for suspended graphene. Superior thermal properties of graphene are beneficial for all proposed graphene device applications.

  2. Conductivity determination of electrolytes at high pressure and temperature

    International Nuclear Information System (INIS)

    Crovetto, Rosa; Gutierrez, Norberto; Petragalli, I.P

    1981-01-01

    An experimental layout is designed that would allow operation up to 350 deg C and 10 8 Pascal, thus facilitating measurements of conductivity in electrolytes with an accuracy of 0.1%. The unit was tested with ClK solutions at 25 deg C and pressures up to 6 x 10 7 Pascal, showing that under these conditions it yields results in good agreement with the electric conductivity data found in the bibliography. (M.E.L.) [es

  3. Transparent conducting oxide nanotubes

    Science.gov (United States)

    Alivov, Yahya; Singh, Vivek; Ding, Yuchen; Nagpal, Prashant

    2014-09-01

    Thin film or porous membranes made of hollow, transparent, conducting oxide (TCO) nanotubes, with high chemical stability, functionalized surfaces and large surface areas, can provide an excellent platform for a wide variety of nanostructured photovoltaic, photodetector, photoelectrochemical and photocatalytic devices. While large-bandgap oxide semiconductors offer transparency for incident light (below their nominal bandgap), their low carrier concentration and poor conductivity makes them unsuitable for charge conduction. Moreover, materials with high conductivity have nominally low bandgaps and hence poor light transmittance. Here, we demonstrate thin films and membranes made from TiO2 nanotubes heavily-doped with shallow Niobium (Nb) donors (up to 10%, without phase segregation), using a modified electrochemical anodization process, to fabricate transparent conducting hollow nanotubes. Temperature dependent current-voltage characteristics revealed that TiO2 TCO nanotubes, doped with 10% Nb, show metal-like behavior with resistivity decreasing from 6.5 × 10-4 Ωcm at T = 300 K (compared to 6.5 × 10-1 Ωcm for nominally undoped nanotubes) to 2.2 × 10-4 Ωcm at T = 20 K. Optical properties, studied by reflectance measurements, showed light transmittance up to 90%, within wavelength range 400 nm-1000 nm. Nb doping also improves the field emission properties of TCO nanotubes demonstrating an order of magnitude increase in field-emitter current, compared to undoped samples.

  4. Electrohydromechanical analysis based on conductivity gradient in microchannel

    International Nuclear Information System (INIS)

    Jiang Hongyuan; Ren Yukun; Ao Hongrui; Ramos, Antonio

    2008-01-01

    Fluid manipulation is very important in any lab-on-a-chip system. This paper analyses phenomena which use the alternating current (AC) electric field to deflect and manipulate coflowing streams of two different electrolytes (with conductivity gradient) within a microfluidic channel. The basic theory of the electrohydrodynamics and simulation of the analytical model are used to explain the phenomena. The velocity induced for different voltages and conductivity gradient are computed. The results show that when the AC electrical signal is applied on the electrodes, the fluid with higher conductivity occupies a larger region of the channel and the interface of the two fluids is deflected. It will provide some basic reference for people who want to do more study in the control of different fluids with conductivity gradient in a microfluidic channel. (classical areas of phenomenology)

  5. Sensing the water content of honey from temperature-dependent electrical conductivity

    International Nuclear Information System (INIS)

    Guo, Wenchuan; Liu, Yi; Zhu, Xinhua; Zhuang, Hong

    2011-01-01

    In order to predict the water content in honey, electrical conductivity was measured on blossom honey types milk-vetch, jujube and yellow-locust with the water content of 18–37% between 5 and 40 °C. The regression models of electrical conductivity were developed as functions of water content and temperature. The results showed that increases in either water content or temperature resulted in an increase in the electrical conductivity of honey with greater changes at higher water content and/or higher temperature. The linear terms of water content and temperature, a quadratic term of water content, and the interaction effect of water content and temperature had significant influence on the electrical conductivity of honey (p < 0.0001). Regardless of blossom honey type, the linear coefficient of the determination of measured and calculated electrical conductivities was 0.998 and the range error ratio was larger than 100. These results suggest that the electrical conductivity of honey might be used to develop a detector for rapidly predicting the water content in blossom honey

  6. The equivalent thermal conductivity of lattice core sandwich structure: A predictive model

    International Nuclear Information System (INIS)

    Cheng, Xiangmeng; Wei, Kai; He, Rujie; Pei, Yongmao; Fang, Daining

    2016-01-01

    Highlights: • A predictive model of the equivalent thermal conductivity was established. • Both the heat conduction and radiation were considered. • The predictive results were in good agreement with experiment and FEM. • Some methods for improving the thermal protection performance were proposed. - Abstract: The equivalent thermal conductivity of lattice core sandwich structure was predicted using a novel model. The predictive results were in good agreement with experimental and Finite Element Method results. The thermal conductivity of the lattice core sandwich structure was attributed to both core conduction and radiation. The core conduction caused thermal conductivity only relied on the relative density of the structure. And the radiation caused thermal conductivity increased linearly with the thickness of the core. It was found that the equivalent thermal conductivity of the lattice core sandwich structure showed a highly dependent relationship on temperature. At low temperatures, the structure exhibited a nearly thermal insulated behavior. With the temperature increasing, the thermal conductivity of the structure increased owing to radiation. Therefore, some attempts, such as reducing the emissivity of the core or designing multilayered structure, are believe to be of benefit for improving the thermal protection performance of the structure at high temperatures.

  7. Conductance of single-atom platinum contacts: Voltage dependence of the conductance histogram

    DEFF Research Database (Denmark)

    Nielsen, S.K.; Noat, Y.; Brandbyge, Mads

    2003-01-01

    The conductance of a single-atom contact is sensitive to the coupling of this contact atom to the atoms in the leads. Notably for the transition metals this gives rise to a considerable spread in the observed conductance values. The mean conductance value and spread can be obtained from the first...... peak in conductance histograms recorded from a large set of contact-breaking cycles. In contrast to the monovalent metals, this mean value for Pt depends strongly on the applied voltage bias and other experimental conditions and values ranging from about 1 G(0) to 2.5 G(0) (G(0)=2e(2)/h) have been...... reported. We find that at low bias the first peak in the conductance histogram is centered around 1.5 G(0). However, as the bias increases past 300 mV the peak shifts to 1.8 G(0). Here we show that this bias dependence is due to a geometric effect where monatomic chains are replaced by single-atom contacts...

  8. Experimental and numerical study on thermal conductivity of partially saturated unconsolidated sands

    Science.gov (United States)

    Lee, Youngmin; Keehm, Youngseuk; Kim, Seong-Kyun; Shin, Sang Ho

    2016-04-01

    A class of problems in heat flow applications requires an understanding of how water saturation affects thermal conductivity in the shallow subsurface. We conducted a series of experiments using a sand box to evaluate thermal conductivity (TC) of partially saturated unconsolidated sands under varying water saturation (Sw). We first saturated sands fully with water and varied water saturation by drainage through the bottom of the sand box. Five water-content sensors were integrated vertically into the sand box to monitor water saturation changes and a needle probe was embedded to measure thermal conductivity of partially saturated sands. The experimental result showed that thermal conductivity decreases from 2.5 W/mK for fully saturated sands to 0.7 W/mK when water saturation is 5%. We found that the decreasing trend is quite non-linear: highly sensitive at very high and low water saturations. However, the boundary effects on the top and the bottom of the sand box seemed to be responsible for this high nonlinearity. We also found that the determination of water saturation is quite important: the saturation by averaging values from all five sensors and that from the sensor at the center position, showed quite different trends in the TC-Sw domain. In parallel, we conducted a pore-scale numerical modeling, which consists of the steady-state two-phase Lattice-Boltzmann simulator and FEM thermal conduction simulator on digital pore geometry of sand aggregation. The simulation results showed a monotonous decreasing trend, and are reasonably well matched with experimental data when using average water saturations. We concluded that thermal conductivity would decrease smoothly as water saturation decreases if we can exclude boundary effects. However, in dynamic conditions, i.e. imbibition or drainage, the thermal conductivity might show hysteresis, which can be investigated with pore-scale numerical modeling with unsteady-state two-phase flow simulators in our future work.

  9. Magnetic field induced augmented thermal conduction phenomenon in magneto-nanocolloids

    Energy Technology Data Exchange (ETDEWEB)

    Katiyar, Ajay, E-mail: ajay_cim@rediffmail.com [Research and Innovation Centre (DRDO), Indian Institute of Technology Madras Research Park, Chennai 600 113 (India); Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Dhar, Purbarun, E-mail: purbarun@iitrpr.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Nandi, Tandra, E-mail: tandra_n@rediffmail.com [Defence Materials and Stores Research and Development Establishment (DRDO), G.T. Road, Kanpur 208 013 (India); Das, Sarit K., E-mail: skdas@iitrpr.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India)

    2016-12-01

    Magnetic field induced augmented thermal conductivity of magneto-nanocolloids involving nanoparticles, viz. Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4}, NiO and Co{sub 3}O{sub 4} dispersed in different base fluids have been reported. Experiments reveal the augmented thermal transport under external applied magnetic field. A maximum thermal conductivity enhancement ∼114% is attained at 7.0 vol% concentration and 0.1 T magnetic flux density for Fe{sub 3}O{sub 4}/EG magneto-nanocolloid. However, a maximum ∼82% thermal conductivity enhancement is observed for Fe{sub 3}O{sub 4}/kerosene magneto-nanocolloid for the same concentration but relatively at low magnetic flux density (∼0.06 T). Thereby, a strong effect of fluid as well as particle physical properties on the chain formation propensity, leading to enhanced conduction, in such systems is observed. Co{sub 3}O{sub 4} nanoparticles show insignificant effect on the thermal conductivity enhancement of MNCs due to their minimal magnetic moment. A semi-empirical approach has been proposed to understand the mechanism and physics behind the thermal conductivity enhancement under external applied magnetic field, in tune with near field magnetostatic interactions as well as Neel relaxivity of the magnetic nanoparticles. Furthermore, the model is able to predict the phenomenon of enhanced thermal conductivity as a function of physical parameters and shows good agreement with the experimental observations. - Highlights: • Heat conduction in magneto-nanocolloids augments tremendously under magnetic field. • Oxide nanoparticles of Fe, Ni and Co dispersed in variant base fluids are used. • Enhancement in heat conduction is due to the formation of thermally conductive chains. • Proposed semi-empirical model shows good agreement with the experimental results.

  10. Conducting polymer coated neural recording electrodes

    Science.gov (United States)

    Harris, Alexander R.; Morgan, Simeon J.; Chen, Jun; Kapsa, Robert M. I.; Wallace, Gordon G.; Paolini, Antonio G.

    2013-02-01

    Objective. Neural recording electrodes suffer from poor signal to noise ratio, charge density, biostability and biocompatibility. This paper investigates the ability of conducting polymer coated electrodes to record acute neural response in a systematic manner, allowing in depth comparison of electrochemical and electrophysiological response. Approach. Polypyrrole (Ppy) and poly-3,4-ethylenedioxythiophene (PEDOT) doped with sulphate (SO4) or para-toluene sulfonate (pTS) were used to coat iridium neural recording electrodes. Detailed electrochemical and electrophysiological investigations were undertaken to compare the effect of these materials on acute in vivo recording. Main results. A range of charge density and impedance responses were seen with each respectively doped conducting polymer. All coatings produced greater charge density than uncoated electrodes, while PEDOT-pTS, PEDOT-SO4 and Ppy-SO4 possessed lower impedance values at 1 kHz than uncoated electrodes. Charge density increased with PEDOT-pTS thickness and impedance at 1 kHz was reduced with deposition times up to 45 s. Stable electrochemical response after acute implantation inferred biostability of PEDOT-pTS coated electrodes while other electrode materials had variable impedance and/or charge density after implantation indicative of a protein fouling layer forming on the electrode surface. Recording of neural response to white noise bursts after implantation of conducting polymer-coated electrodes into a rat model inferior colliculus showed a general decrease in background noise and increase in signal to noise ratio and spike count with reduced impedance at 1 kHz, regardless of the specific electrode coating, compared to uncoated electrodes. A 45 s PEDOT-pTS deposition time yielded the highest signal to noise ratio and spike count. Significance. A method for comparing recording electrode materials has been demonstrated with doped conducting polymers. PEDOT-pTS showed remarkable low fouling during

  11. Ballistic heat conduction and mass disorder in one dimension

    International Nuclear Information System (INIS)

    Ong, Zhun-Yong; Zhang, Gang

    2014-01-01

    It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (κ) scales asymptotically as lim L→∞ κ∝L 0.5 where L is the chain length. However, using the nonequilibrium Green's function (NEGF) method and analytical modelling, we show that there exists a critical crossover length scale (L C ) below which ballistic heat conduction (κ∝L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function Ξ i.e. Ξ(ω, L) = exp[−L/λ(ω)], where λ is the frequency-dependent attenuation length. The crossover length can be determined from the minimum attenuation length, which depends on the maximum transmitted frequency. We numerically determine the dependence of the transmittance on frequency and mass composition as well as derive a closed form estimate, which agrees closely with the numerical results. For the length-dependent thermal conductance, we also derive a closed form expression which agrees closely with numerical results and reproduces the ballistic to subballistic thermal conduction crossover. This allows us to characterize the crossover in terms of changes in the length, mass composition and temperature dependence, and also to determine the conditions under which heat conduction enters the ballistic regime. We describe how the mass composition can be modified to increase ballistic heat conduction. (paper)

  12. Ballistic heat conduction and mass disorder in one dimension.

    Science.gov (United States)

    Ong, Zhun-Yong; Zhang, Gang

    2014-08-20

    It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (κ) scales asymptotically as lim(L--> ∞) κ ∝ L(0.5) where L is the chain length. However, using the nonequilibrium Green's function (NEGF) method and analytical modelling, we show that there exists a critical crossover length scale (LC) below which ballistic heat conduction (κ ∝ L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function Ξ i.e. Ξ(ω, L) = exp[-L/λ(ω)], where λ is the frequency-dependent attenuation length. The crossover length can be determined from the minimum attenuation length, which depends on the maximum transmitted frequency. We numerically determine the dependence of the transmittance on frequency and mass composition as well as derive a closed form estimate, which agrees closely with the numerical results. For the length-dependent thermal conductance, we also derive a closed form expression which agrees closely with numerical results and reproduces the ballistic to subballistic thermal conduction crossover. This allows us to characterize the crossover in terms of changes in the length, mass composition and temperature dependence, and also to determine the conditions under which heat conduction enters the ballistic regime. We describe how the mass composition can be modified to increase ballistic heat conduction.

  13. Ionic conducting poly-benzimidazoles

    International Nuclear Information System (INIS)

    Jouanneau, J.

    2006-11-01

    Over the last years, many research works have been focused on new clean energy systems. Hydrogen fuel cell seems to be the most promising one. However, the large scale development of this technology is still limited by some key elements. One of them is the polymer electrolyte membrane 'Nafion' currently used, for which the ratio performance/cost is too low. The investigations we carried out during this thesis work are related to a new class of ionic conducting polymer, the sulfonated poly-benzimidazoles (sPBI). Poly-benzimidazoles (PBI) are aromatic heterocyclic polymers well-known for their excellent thermal and chemical stability. Ionic conduction properties are obtained by having strong acid groups (sulfonic acid SO 3 H) on the macromolecular structure. For that purpose, we first synthesized sulfonated monomers. Their poly-condensation with an appropriate non-sulfonated co-monomer yields to sPBI with sulfonation range from 0 to 100 per cent. Three different sPBI structures were obtained, and verified by appropriate analytical techniques. We also showed that the protocol used for the synthesis resulted in high molecular weights polymers. We prepared ionic conducting membrane by casting sPBI solutions on glass plates. Their properties of stability, water swelling and ionic conductivity were investigated. Surprisingly, the behaviour of sPBI was quite different from the other sulfonated aromatic polymers with same amount of SO 3 H, their stability was much higher, but their water swelling and ionic conductivity were quite low. We attributed these differences to strong ionic interactions between the sulfonic acid groups and the basic benzimidazole groups of our polymers. However, we managed to solve this problem synthesizing very highly sulfonated PBI, obtaining membranes with a good balance between all the properties necessary. (author)

  14. Conductance oscillation in graphene-nanoribbon-based electronic Fabry-Perot resonators

    International Nuclear Information System (INIS)

    Zhang Yong; Han Mei; Shen Linjiang

    2010-01-01

    By using the tight-binding approximation and the Green's function method, the quantum conductance of the Fabry-Perot-like electronic resonators composed of zigzag and metallic armchair edge graphene nanoribbons (GNRs) was studied numerically. Obtained results show that due to Fabry-Perot-like electronic interference, the conductance of the GNR resonators oscillates periodically with the Fermi energy. The effects of disorders and coupling between the electrodes and the GNR on conductance oscillations were explored. It is found that the conductance oscillations appear at the strong coupling and become resonant peaks as the coupling is very weak. It is also found that the strong disorders in the GNR can smear the conductance oscillation periods. In other words, the weak coupling and the strong disorders all can blur the conductance oscillations, making them unclearly distinguished.

  15. Neighborhood Risk, Parental Socialization Styles, and Adolescent Conduct Problems

    Directory of Open Access Journals (Sweden)

    Enrique Gracia

    2010-12-01

    Full Text Available This article aims to analyze the influence of parental socialization styles (authoritarian, authoritative, indulgent and neglectful, and perceived neighborhood risk on three indicators of conduct problems in adolescence (school misconduct, delinquency, and drug use. The sample consists of 1,017 adolescents, aged between 12 and 17. Results from four multivariate factorial designs yielded only main effects of parenting styles and neighborhood risk. Adolescents from authoritative and indulgent families showed lower conduct problems than those with authoritarian and neglectful parents. Also, higher levels of perceived neighborhood risk were significantly associated with more conduct problems. There were no significant interaction effects between parenting styles and perceived neighborhood risk, but results yielded a significant interaction effect between neighborhood risk and sex. Overall, results do not support the idea that parenting styles are more effective under certain neighborhood risk conditions, and suggest that neighbourhood risk influences adolescents’ psychosocial adjustment beyond the influence of parental socialization styles.

  16. Electrical conductivity of chromate conversion coating on electrodeposited zinc

    International Nuclear Information System (INIS)

    Tencer, Michal

    2006-01-01

    For certain applications of galvanized steel protected with conversion coatings it is important that the surface is electrically conductive. This is especially important with mating surfaces for electromagnetic compatibility. This paper addresses electrical conductivity of chromate conversion coatings. A cross-matrix study using different zinc plating techniques by different labs showed that the main deciding factor is the type of zinc-plating bath used rather than the subsequent chromating process. Thus, chromated zinc plate electrodeposited from cyanide baths is non-conductive while that from alkaline (non-cyanide) and acid baths is conductive, even though the plate from all the bath types is conductive before conversion coating. The results correlate well with the microscopic structure of the surfaces as observed with scanning electron microscopy (SEM) and could be further corroborated and rationalized using EDX and Auger spectroscopies

  17. Experimental investigation of the thermal conductivity of the green refractory concrete

    International Nuclear Information System (INIS)

    Santos, W.N. dos; Sylos Cintra Filho, J. de; Baldo, J.B.

    1989-01-01

    In this work the thermal conductivity of an aluminous refractory concrete, cured at 22 0 C and dried at 110 0 C is experimentally measured and the resulting behaviour is analysed as a function of temperature, from room temperature up to 1000 0 C. The experimental technique employed was the hot wire parallel technique, and the calculations which lead the the material thermal conductivity are carried out by using a non linear least squares fitting method. Experimental results show, among others, the strong influence of the adsorbed water in the behaviour of the thermal conductivity of the green refractory concrete, at temperatures below 200 0 C [pt

  18. Voltage-Induced Nonlinear Conduction Properties of Epoxy Resin/Micron-Silver Particles Composites

    Science.gov (United States)

    Qu, Zhaoming; Lu, Pin; Yuan, Yang; Wang, Qingguo

    2018-01-01

    The nonlinear conduction properties of epoxy resin (ER)/micron-silver particles (MP) composites were investigated. Under sufficient high intensity applied constant voltage, the obvious nonlinear conduction properties of the samples with volume fraction 25% were found. With increments in the voltage, the conductive switching effect was observed. The nonlinear conduction mechanism of the ER/MP composites under high applied voltages could be attributed to the electrical current conducted via discrete paths of conductive particles induced by the electric field. The test results show that the ER/MP composites with nonlinear conduction properties are of great potential application in electromagnetic protection of electron devices and systems.

  19. Effect of Interface Structure on Thermal Boundary Conductance by using First-principles Density Functional Perturbation Theory

    Institute of Scientific and Technical Information of China (English)

    GAO Xue; ZHANG Yue; SHANG Jia-Xiang

    2011-01-01

    We choose a Si/Ge interface as a research object to investigate the infiuence of interface disorder on thermal boundary conductance. In the calculations, the diffuse mismatch model is used to study thermal boundary conductance between two non-metallic materials, while the phonon dispersion relationship is calculated by the first-principles density functional perturbation theory. The results show that interface disorder limits thermal transport. The increase of atomic spacing at the interface results in weakly coupled interfaces and a decrease in the thermal boundary conductance. This approach shows a simplistic method to investigate the relationship between microstructure and thermal conductivity.%We choose a Si/Ge interface as a research object to investigate the influence of interface disorder on thermal boundary conductance.In the calculations,the diffuse mismatch model is used to study thermal boundary conductance between two non-metallic materials,while the phonon dispersion relationship is calculated by the first-principles density functional perturbation theory.The results show that interface disorder limits thermal transport.The increase of atomic spacing at the interface results in weakly coupled interfaces and a decrease in the thermal boundary conductance.This approach shows a simplistic method to investigate the relationship between microstructure and thermal conductivity.It is well known that interfaces can play a dominant role in the overall thermal transport characteristics of structures whose length scale is less than the phonon mean free path.When heat flows across an interface between two different materials,there exists a temperature jump at the interface.Thermal boundary conductance (TBC),which describes the efficiency of heat flow at material interfaces,plays an importance role in the transport of thermal energy in nanometerscale devices,semiconductor superlattices,thin film multilayers and nanocrystalline materials.[1

  20. Subspeciality training in hematology and oncology, 2003: results of a survey of training program directors conducted by the American Society of Hematology.

    Science.gov (United States)

    Todd, Robert F; Gitlin, Scott D; Burns, Linda J

    2004-06-15

    A survey of directors of adult and pediatric hematology/oncology subspecialty training programs in the United States and Canada was conducted to assess the environment in which recruitment and training is conducted in these medical disciplines. A total of 107 program directors responded to the survey, representing 66% of internal medicine and 47% of pediatric subspecialty programs in hematology or hematology/oncology. Specific areas covered in the web-based questionnaire included the type and demographics of the training program, profile of the training program director, characteristics of the applicant pool and existing trainee recruits, characteristics of the training program environment and curricula, research productivity of trainees, and the career pathways taken by recent training program graduates (including dominant areas of clinical interest). The results of this survey show considerable heterogeneity in the recruiting practices and the environment in which subspecialty training occurs, leading the authors to recommend improvements in or a heightened attention to issues, including recruitment of minority trainees, flexibility to recruit international medical school graduates, timing of trainee acceptance, maintaining the financial support of Medicare graduation medical education (GME), training of physician scientists, organization of the continuity clinic experience, visibility of nonmalignant hematology as a career path, and level of training program director support.

  1. Lactotripeptides Show No Effect on Human Blood Pressure: Results from a double-blind randomized controlled trial

    NARCIS (Netherlands)

    Engberink, M.F.; Schouten, E.G.; Kok, F.J.; Mierlo, van L.A.J.; Brouwer, I.A.; Geleijnse, J.M.

    2008-01-01

    Milk-derived peptides with ACE-inhibiting properties may have antihypertensive effects in humans. We conducted a randomized double-blind placebo-controlled trial to examine the blood pressure lowering potential of 2 ACE-inhibiting lactotripeptides, ie, Isoleucine-Proline-Proline and

  2. Tritium conductivity and isotope effect in proton-conducting perovskites

    International Nuclear Information System (INIS)

    Mukundan, R.; Brosha, E.L.; Birdsell, S.A.; Costello, A.L.; Garzon, F.H.; Willms, R.S.

    1999-01-01

    The tritium ion conductivities of SrZr 0.9 Yb 0.1 O 2.95 and BaCe 0.9 Yb 0.1 O 2.95 have been measured by ac impedance analysis. The high tritium conductivity of these perovskites could potentially lead to their application as an electrochemical membrane for the recovery of tritium from tritiated gas streams. The conductivities of these perovskites, along with SrCe 0.95 Yb 0.05 O 2.975 , were also measured in hydrogen- and deuterium-containing atmospheres to illustrate the isotope effect. For the strontium zirconate and barium cerate samples, the impedance plot consists of two clearly resolved arcs, a bulk and a grain boundary arc, in the temperature range 50--350 C. However, for the strontium cerate sample, the clear resolution of the bulk conductivity was not possible and only the total conductivity was measurable. Thus, the isotope effect was clearly established only for the strontium zirconate and barium cerate samples. The decrease in bulk conductivity with increasing isotope mass was found to be a result of an increase in the activation energy for conduction accompanied by a decrease in the pre-exponential factor. Since the concentration of the mobile species (H+, D+, or T+) should remain relatively constant at T < 350 C, this increase in activation energy is directly attributable to the increased activation energy for the isotope mobility

  3. High-conductance states in a mean-field cortical network model

    CERN Document Server

    Lerchner, A; Hertz, J

    2004-01-01

    Measured responses from visual cortical neurons show that spike times tend to be correlated rather than exactly Poisson distributed. Fano factors vary and are usually greater than 1 due to the tendency of spikes being clustered into bursts. We show that this behavior emerges naturally in a balanced cortical network model with random connectivity and conductance-based synapses. We employ mean field theory with correctly colored noise to describe temporal correlations in the neuronal activity. Our results illuminate the connection between two independent experimental findings: high conductance states of cortical neurons in their natural environment, and variable non-Poissonian spike statistics with Fano factors greater than 1.

  4. Note: Local thermal conductivities from boundary driven non-equilibrium molecular dynamics simulations

    International Nuclear Information System (INIS)

    Bresme, F.; Armstrong, J.

    2014-01-01

    We report non-equilibrium molecular dynamics simulations of heat transport in models of molecular fluids. We show that the “local” thermal conductivities obtained from non-equilibrium molecular dynamics simulations agree within numerical accuracy with equilibrium Green-Kubo computations. Our results support the local equilibrium hypothesis for transport properties. We show how to use the local dependence of the thermal gradients to quantify the thermal conductivity of molecular fluids for a wide range of thermodynamic states using a single simulation

  5. Stretchable, Porous, and Conductive Energy Textiles

    KAUST Repository

    Hu, Liangbing; Pasta, Mauro; Mantia, Fabio La; Cui, LiFeng; Jeong, Sangmoo; Deshazer, Heather Dawn; Choi, Jang Wook; Han, Seung Min; Cui, Yi

    2010-01-01

    Recently there is strong interest in lightweight, flexible, and wearable electronics to meet the technological demands of modern society. Integrated energy storage devices of this type are a key area that is still significantly underdeveloped. Here, we describe wearable power devices using everyday textiles as the platform. With an extremely simple "dipping and drying" process using single-walled carbon nanotube (SWNT) ink, we produced highly conductive textiles with conductivity of 125 S cm-1 and sheet resistance less than 1 Ω/sq. Such conductive textiles show outstanding flexibility and stretchability and demonstrate strong adhesion between the SWNTs and the textiles of interest. Supercapacitors made from these conductive textiles show high areal capacitance, up to 0.48F/cm2, and high specific energy. We demonstrate the loading of pseudocapacitor materials into these conductive textiles that leads to a 24-fold increase of the areal capacitance of the device. These highly conductive textiles can provide new design opportunities for wearable electronics and energy storage applications. © 2010 American Chemical Society.

  6. Stretchable, Porous, and Conductive Energy Textiles

    KAUST Repository

    Hu, Liangbing

    2010-02-10

    Recently there is strong interest in lightweight, flexible, and wearable electronics to meet the technological demands of modern society. Integrated energy storage devices of this type are a key area that is still significantly underdeveloped. Here, we describe wearable power devices using everyday textiles as the platform. With an extremely simple "dipping and drying" process using single-walled carbon nanotube (SWNT) ink, we produced highly conductive textiles with conductivity of 125 S cm-1 and sheet resistance less than 1 Ω/sq. Such conductive textiles show outstanding flexibility and stretchability and demonstrate strong adhesion between the SWNTs and the textiles of interest. Supercapacitors made from these conductive textiles show high areal capacitance, up to 0.48F/cm2, and high specific energy. We demonstrate the loading of pseudocapacitor materials into these conductive textiles that leads to a 24-fold increase of the areal capacitance of the device. These highly conductive textiles can provide new design opportunities for wearable electronics and energy storage applications. © 2010 American Chemical Society.

  7. Experimental Preparation and Numerical Simulation of High Thermal Conductive Cu/CNTs Nanocomposites

    Directory of Open Access Journals (Sweden)

    Muhsan Ali Samer

    2014-07-01

    Full Text Available Due to the rapid growth of high performance electronics devices accompanied by overheating problem, heat dissipater nanocomposites material having ultra-high thermal conductivity and low coefficient of thermal expansion was proposed. In this work, a nanocomposite material made of copper (Cu reinforced by multi-walled carbon nanotubes (CNTs up to 10 vol. % was prepared and their thermal behaviour was measured experimentally and evaluated using numerical simulation. In order to numerically predict the thermal behaviour of Cu/CNTs composites, three different prediction methods were performed. The results showed that rules of mixture method records the highest thermal conductivity for all predicted composites. In contrast, the prediction model which takes into account the influence of the interface thermal resistance between CNTs and copper particles, has shown the lowest thermal conductivity which considered as the closest results to the experimental measurement. The experimentally measured thermal conductivities showed remarkable increase after adding 5 vol.% CNTs and higher than the thermal conductivities predicted via Nan models, indicating that the improved fabrication technique of powder injection molding that has been used to produced Cu/CNTs nanocomposites has overcome the challenges assumed in the mathematical models.

  8. Near-field radiative heat transfer under temperature gradients and conductive transfer

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Weiliang; Rodriguez, Alejandro W. [Princeton Univ., NJ (United States). Dept. of Electrical Engineering; Messina, Riccardo [CNRS-Univ. de Montpellier (France). Lab. Charles Coulomb

    2017-05-01

    We describe a recently developed formulation of coupled conductive and radiative heat transfer (RHT) between objects separated by nanometric, vacuum gaps. Our results rely on analytical formulas of RHT between planar slabs (based on the scattering-matrix method) as well as a general formulation of RHT between arbitrarily shaped bodies (based on the fluctuating-volume current method), which fully captures the existence of temperature inhomogeneities. In particular, the impact of RHT on conduction, and vice versa, is obtained via self-consistent solutions of the Fourier heat equation and Maxwell's equations. We show that in materials with low thermal conductivities (e.g. zinc oxides and glasses), the interplay of conduction and RHT can strongly modify heat exchange, exemplified for instance by the presence of large temperature gradients and saturating flux rates at short (nanometric) distances. More generally, we show that the ability to tailor the temperature distribution of an object can modify the behaviour of RHT with respect to gap separations, e.g. qualitatively changing the asymptotic scaling at short separations from quadratic to linear or logarithmic. Our results could be relevant to the interpretation of both past and future experimental measurements of RHT at nanometric distances.

  9. Functionalization of silicon nanowires by conductive and non-conductive polymers

    Science.gov (United States)

    Belhousse, S.; Tighilt, F.-Z.; Sam, S.; Lasmi, K.; Hamdani, K.; Tahanout, L.; Megherbi, F.; Gabouze, N.

    2017-11-01

    The work reports on the development of hybrid devices based on silicon nanowires (SiNW) with polymers and the difference obtained when using conductive and non-conductive polymers. SiNW have attracted much attention due to their importance in understanding the fundamental properties at low dimensionality as well as their potential application in nanoscale devices as in field effect transistors, chemical or biological sensors, battery electrodes and photovoltaics. SiNW arrays were formed using metal assisted chemical etching method. This process is simple, fast and allows obtaining a wide range of silicon nanostructures. Hydrogen-passivated SiNW surfaces show relatively poor stability. Surface modification with organic species confers the desired stability and enhances the surface properties. For this reason, this work proposes a covalent grafting of organic material onto SiNW surface. We have chosen a non-conductive polymer polyvinylpyrrolidone (PVP) and conductive polymers polythiophene (PTh) and polypyrrole (PPy), in order to evaluate the electric effect of the polymers on the obtained materials. The hybrid structures were elaborated by the polymerization of the corresponding conjugated monomers by electrochemical route; this electropolymerization offers several advantages such as simplicity and rapidity. SiNW functionalization by conductive polymers has shown to have a huge effect on the electrical mobility. Hybrid surface morphologies were characterized by scanning electron microscopy (SEM), infrared spectroscopy (FTIR-ATR) and contact angle measurements.

  10. Potential of thermally conductive polymers for the cooling of mechatronic parts

    Science.gov (United States)

    Heinle, C.; Drummer, D.

    Adding thermally conductive fillers to polymers the thermal conductivity can be raised significantly. Thermal conductive polymers (TC-plastics) open up a vast range of options to set up novel concepts of polymer technological system solutions in the area of mechatronics. Heating experiment of cooling ribs show the potential in thermal management of mechatronic parts with TC-polymers in comparison with widely used reference materials copper and aluminum. The results demonstrate that especially for certain thermal boundary conditions comparable performance between these two material grades can be measured.

  11. Tensile fracture and thermal conductivity characterization of toughened epoxy/CNT nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Balakrishnan, Anandh [School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019 (United States); Saha, Mrinal C., E-mail: msaha@ou.edu [School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019 (United States)

    2011-01-25

    Rubber toughened epoxy/CNT nanocomposites were manufactured at different weight percents between 0 and 1% of multiwall carbon nanotube (MWNT) using a high intensity ultrasonic liquid processor with a titanium probe. Mechanical properties of manufactured dog bone samples were measured in tension and the results indicated a maximum of 23% increase in the elastic modulus at 0.6% by weight of MWNT. However, the fracture strength showed a maximum decrease of about 11% as a function of increasing MWNT loading. Scanning Electron Microscopy (SEM) images from the neat samples revealed a distinct circular pit at the top left edge of the specimen with an overall tearing deformation causing the fracture paths. Comparatively, all nanocomposite samples on an average seemed to show a prominent brittle fracture with little or no evidence of circular pit formation. The amount of tearing deformation seemed to be enhanced in the nanocomposite specimens as compare to the neat ones. Finally, Transmission Electron Microscopy images indicated that different states of dispersion exist in all of the nanocomposite samples. The data showed that agglomeration of nanotubes increases as a function of weight percent. In addition to mechanical property characterization, thermal conductivity of all the samples was determined as a function of temperature between 30 deg. C and 100 deg. C using the 3{omega} method. The tested samples showed an almost 16% increase in thermal conductivity. The minimal enhancement in thermal conductivity has been analyzed from the standpoint of the Effective Medium Theory. Interfacial thermal resistances exhibit no order of magnitude changes explaining the conductivity results.

  12. Tensile fracture and thermal conductivity characterization of toughened epoxy/CNT nanocomposites

    International Nuclear Information System (INIS)

    Balakrishnan, Anandh; Saha, Mrinal C.

    2011-01-01

    Rubber toughened epoxy/CNT nanocomposites were manufactured at different weight percents between 0 and 1% of multiwall carbon nanotube (MWNT) using a high intensity ultrasonic liquid processor with a titanium probe. Mechanical properties of manufactured dog bone samples were measured in tension and the results indicated a maximum of 23% increase in the elastic modulus at 0.6% by weight of MWNT. However, the fracture strength showed a maximum decrease of about 11% as a function of increasing MWNT loading. Scanning Electron Microscopy (SEM) images from the neat samples revealed a distinct circular pit at the top left edge of the specimen with an overall tearing deformation causing the fracture paths. Comparatively, all nanocomposite samples on an average seemed to show a prominent brittle fracture with little or no evidence of circular pit formation. The amount of tearing deformation seemed to be enhanced in the nanocomposite specimens as compare to the neat ones. Finally, Transmission Electron Microscopy images indicated that different states of dispersion exist in all of the nanocomposite samples. The data showed that agglomeration of nanotubes increases as a function of weight percent. In addition to mechanical property characterization, thermal conductivity of all the samples was determined as a function of temperature between 30 deg. C and 100 deg. C using the 3ω method. The tested samples showed an almost 16% increase in thermal conductivity. The minimal enhancement in thermal conductivity has been analyzed from the standpoint of the Effective Medium Theory. Interfacial thermal resistances exhibit no order of magnitude changes explaining the conductivity results.

  13. Conducting polymer 3D microelectrodes

    DEFF Research Database (Denmark)

    Sasso, Luigi; Vazquez, Patricia; Vedarethinam, Indumathi

    2010-01-01

    Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained...... showed uniformity and good adhesion to both horizontal and vertical surfaces. Electrodes in combination with metal/conducting polymer materials have been characterized by cyclic voltammetry and the presence of the conducting polymer film has shown to increase the electrochemical activity when compared...

  14. Synthesis, characterization and DC conductivity studies of conducting polyaniline/PVA/Fly ash polymer composites

    Science.gov (United States)

    Revanasiddappa, M.; Swamy, D. Siddalinga; Vinay, K.; Ravikiran, Y. T.; Raghavendra, S. C.

    2018-05-01

    The present work is an investigation of dc conduction behaviour of conducting polyaniline/fly ash nano particles blended in polyvinyl Alcohol (PANI/PVA/FA) synthesized via in-situ polymerization technique using (NH4)2S2O8 as an oxidising agent with varying fly ash cenosphere by 10, 20, 30, 40 and 50 wt%. The structural characterization of the synthesised polymer composites was examined using FT-IR, XRD and SEM techniques. Dc conductivity as a function of temperature has been measured in the temperature range from 302K - 443K. The increase of conductivity with increasing temperature reveals semiconducting behaviour of the composites and shows an evidence for the transport properties of the composites.

  15. Thermal conductivity of silicon nanocrystals and polystyrene nanocomposite thin films

    International Nuclear Information System (INIS)

    Juangsa, Firman Bagja; Muroya, Yoshiki; Nozaki, Tomohiro; Ryu, Meguya; Morikawa, Junko

    2016-01-01

    Silicon nanocrystals (SiNCs) are well known for their size-dependent optical and electronic properties; they also have the potential for low yet controllable thermal properties. As a silicon-based low-thermal conductivity material is required in microdevice applications, SiNCs can be utilized for thermal insulation. In this paper, SiNCs and polymer nanocomposites were produced, and their thermal conductivity, including the density and specific heat, was measured. Measurement results were compared with thermal conductivity models for composite materials, and the comparison shows a decreasing value of the thermal conductivity, indicating the effect of the size and presence of the nanostructure on the thermal conductivity. Moreover, employing silicon inks at room temperature during the fabrication process enables a low cost of fabrication and preserves the unique properties of SiNCs. (paper)

  16. Molecular dynamics simulation of thermal conductivities of superlattice nanowires

    Institute of Scientific and Technical Information of China (English)

    YANG; Juekuan(杨决宽); CHEN; Yunfei(陈云飞); YAN; Jingping(颜景平)

    2003-01-01

    Nonequilibrium molecular dynamics simulations were carried out to investigate heat transfer in superlattice nanowires. Results show that for fixed period length superlattice nanowires, the ratio of the total interfacial thermal resistance to the total thermal resistance and the effective thermal conductivities are invariant with the changes in interface numbers. Increasing the period length leads to an increase in the average interfacial thermal resistance, which indicates that the interfacial thermal resistance depends not only on the materials that constitute the alternating segments of superlattice nanowires, but also on the lattice strain throughout the segments. The modification of the lattice structure due to the lattice mismatch should be taken into account in the acoustic mismatch model. Simulation results also demonstrated the size confinement effect on the thermal conductivities for low dimensional structures, i.e. the thermal conductivities and the interfacial thermal resistance increase as the nanowire cross-sectional area increases.

  17. Highly Conductive and Reliable Copper-Filled Isotropically Conductive Adhesives Using Organic Acids for Oxidation Prevention

    Science.gov (United States)

    Chen, Wenjun; Deng, Dunying; Cheng, Yuanrong; Xiao, Fei

    2015-07-01

    The easy oxidation of copper is one critical obstacle to high-performance copper-filled isotropically conductive adhesives (ICAs). In this paper, a facile method to prepare highly reliable, highly conductive, and low-cost ICAs is reported. The copper fillers were treated by organic acids for oxidation prevention. Compared with ICA filled with untreated copper flakes, the ICA filled with copper flakes treated by different organic acids exhibited much lower bulk resistivity. The lowest bulk resistivity achieved was 4.5 × 10-5 Ω cm, which is comparable to that of commercially available Ag-filled ICA. After 500 h of 85°C/85% relative humidity (RH) aging, the treated ICAs showed quite stable bulk resistivity and relatively stable contact resistance. Through analyzing the results of x-ray diffraction, x-ray photoelectron spectroscopy, and thermogravimetric analysis, we found that, with the assistance of organic acids, the treated copper flakes exhibited resistance to oxidation, thus guaranteeing good performance.

  18. Change in the electrical conductivity of SnO{sub 2} crystal from n-type to p-type conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Villamagua, Luis, E-mail: luis.villamagua@tyndall.ie [Grupo de Fisicoquímica de Materiales, Universidad Técnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador); Dipartimento di Ingegneria per l’Ambiente e il Territorio e Ingegneria Chimica, Università della Calabria, 87036 Rende (CS) (Italy); Stashans, Arvids [Grupo de Fisicoquímica de Materiales, Universidad Técnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador); Lee, Po-Ming; Liu, Yen-Shuo; Liu, Cheng-Yi [Department of Chemical and Materials Engineering, National Central University, Jhong-Li, Taiwan (China); Carini, Manuela [Dipartimento di Ingegneria per l’Ambiente e il Territorio e Ingegneria Chimica, Università della Calabria, 87036 Rende (CS) (Italy)

    2015-05-01

    Highlights: • Switch from n-type to p-type conductivity in SnO{sub 2} has been studied. • Computational DFT + U method where used. • X-ray diffraction and X-ray photoelectron spectroscopy where used. • Al- and N-codoped SnO{sub 2} compound shows stable p-type conductivity. • Low resistivity (3.657 × 10{sup −1} Ω cm) has been obtained. • High carrier concentration (4.858 × 10{sup 19} cm{sup −3}) has been obtained. - Abstract: The long-sought fully transparent technology will not come true if the n region of the p–n junction does not get as well developed as its p counterpart. Both experimental and theoretical efforts have to be used to study and discover phenomena occurring at the microscopic level in SnO{sub 2} systems. In the present paper, using the DFT + U approach as a main tool and the Vienna ab initio Simulation Package (VASP) we reproduce both intrinsic n-type as well as p-type conductivity in concordance to results observed in real samples of SnO{sub 2} material. Initially, an oxygen vacancy (1.56 mol% concentration) combined with a tin-interstitial (1.56 mol% concentration) scheme was used to achieve the n-type electrical conductivity. Later, to attain the p-type conductivity, crystal already possessing n-type conductivity, was codoped with nitrogen (1.56 mol% concentration) and aluminium (12.48 mol% concentration) impurities. Detailed explanation of structural changes endured by the geometry of the crystal as well as the changes in its electrical properties has been obtained. Our experimental data to a very good extent matches with the results found in the DFT + U modelling.

  19. Conductivities from attractors

    Energy Technology Data Exchange (ETDEWEB)

    Erdmenger, Johanna [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, D-80805 Munich (Germany); Institut für Theoretische Physik und Astrophysik, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany); Fernández, Daniel [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, D-80805 Munich (Germany); Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavík (Iceland); Goulart, Prieslei [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, D-80805 Munich (Germany); Instituto de Física Teórica, UNESP-Universidade Estadual Paulista,R. Dr. Bento T. Ferraz 271, Bl. II, São Paulo 01140-070, SP (Brazil); Witkowski, Piotr [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, D-80805 Munich (Germany)

    2017-03-28

    In the context of applications of the AdS/CFT correspondence to condensed matter physics, we compute conductivities for field theory duals of dyonic planar black holes in 3+1-dimensional Einstein-Maxwell-dilaton theories at zero temperature. We combine the near-horizon data obtained via Sen’s entropy function formalism with known expressions for conductivities. In this way we express the conductivities in terms of the extremal black hole charges. We apply our approach to three different examples for dilaton theories for which the background geometry is not known explicitly. For a constant scalar potential, the thermoelectric conductivity explicitly scales as α{sub xy}∼N{sup 3/2}, as expected. For the same model, our approach yields a finite result for the heat conductivity κ/T∝N{sup 3/2} even for T→0.

  20. Multiscale Modeling of UHTC: Thermal Conductivity

    Science.gov (United States)

    Lawson, John W.; Murry, Daw; Squire, Thomas; Bauschlicher, Charles W.

    2012-01-01

    We are developing a multiscale framework in computational modeling for the ultra high temperature ceramics (UHTC) ZrB2 and HfB2. These materials are characterized by high melting point, good strength, and reasonable oxidation resistance. They are candidate materials for a number of applications in extreme environments including sharp leading edges of hypersonic aircraft. In particular, we used a combination of ab initio methods, atomistic simulations and continuum computations to obtain insights into fundamental properties of these materials. Ab initio methods were used to compute basic structural, mechanical and thermal properties. From these results, a database was constructed to fit a Tersoff style interatomic potential suitable for atomistic simulations. These potentials were used to evaluate the lattice thermal conductivity of single crystals and the thermal resistance of simple grain boundaries. Finite element method (FEM) computations using atomistic results as inputs were performed with meshes constructed on SEM images thereby modeling the realistic microstructure. These continuum computations showed the reduction in thermal conductivity due to the grain boundary network.

  1. Fluctuation-enhanced electric conductivity in electrolyte solutions.

    Science.gov (United States)

    Péraud, Jean-Philippe; Nonaka, Andrew J; Bell, John B; Donev, Aleksandar; Garcia, Alejandro L

    2017-10-10

    We analyze the effects of an externally applied electric field on thermal fluctuations for a binary electrolyte fluid. We show that the fluctuating Poisson-Nernst-Planck (PNP) equations for charged multispecies diffusion coupled with the fluctuating fluid momentum equation result in enhanced charge transport via a mechanism distinct from the well-known enhancement of mass transport that accompanies giant fluctuations. Although the mass and charge transport occurs by advection by thermal velocity fluctuations, it can macroscopically be represented as electrodiffusion with renormalized electric conductivity and a nonzero cation-anion diffusion coefficient. Specifically, we predict a nonzero cation-anion Maxwell-Stefan coefficient proportional to the square root of the salt concentration, a prediction that agrees quantitatively with experimental measurements. The renormalized or effective macroscopic equations are different from the starting PNP equations, which contain no cross-diffusion terms, even for rather dilute binary electrolytes. At the same time, for infinitely dilute solutions the renormalized electric conductivity and renormalized diffusion coefficients are consistent and the classical PNP equations with renormalized coefficients are recovered, demonstrating the self-consistency of the fluctuating hydrodynamics equations. Our calculations show that the fluctuating hydrodynamics approach recovers the electrophoretic and relaxation corrections obtained by Debye-Huckel-Onsager theory, while elucidating the physical origins of these corrections and generalizing straightforwardly to more complex multispecies electrolytes. Finally, we show that strong applied electric fields result in anisotropically enhanced "giant" velocity fluctuations and reduced fluctuations of salt concentration.

  2. The critical particle size for enhancing thermal conductivity in metal nanoparticle-polymer composites

    Science.gov (United States)

    Lu, Zexi; Wang, Yan; Ruan, Xiulin

    2018-02-01

    Polymers used as thermal interface materials are often filled with high-thermal conductivity particles to enhance the thermal performance. Here, we have combined molecular dynamics and the two-temperature model in 1D to investigate the impact of the metal filler size on the overall thermal conductivity. A critical particle size has been identified above which thermal conductivity enhancement can be achieved, caused by the interplay between high particle thermal conductivity and the added electron-phonon and phonon-phonon thermal boundary resistance brought by the particle fillers. Calculations on the SAM/Au/SAM (self-assembly-monolayer) system show a critical thickness Lc of around 10.8 nm. Based on the results, we define an effective thermal conductivity and propose a new thermal circuit analysis approach for the sandwiched metal layer that can intuitively explain simulation and experimental data. The results show that when the metal layer thickness decreases to be much smaller than the electron-phonon cooling length (or as the "thin limit"), the effective thermal conductivity is just the phonon portion, and electrons do not participate in thermal transport. As the thickness increases to the "thick limit," the effective thermal conductivity recovers the metal bulk value. Several factors that could affect Lc are discussed, and it is discovered that the thermal conductivity, thermal boundary resistance, and the electron-phonon coupling factor are all important in controlling Lc.

  3. Conduction properties of thin films from a water soluble carbon nanotube/hemicellulose complex

    Science.gov (United States)

    Shao, Dongkai; Yotprayoonsak, Peerapong; Saunajoki, Ville; Ahlskog, Markus; Virtanen, Jorma; Kangas, Veijo; Volodin, Alexander; Van Haesendonck, Chris; Burdanova, Maria; Mosley, Connor D. W.; Lloyd-Hughes, James

    2018-04-01

    We have examined the conductive properties of carbon nanotube based thin films, which were prepared via dispersion in water by non-covalent functionalization of the nanotubes with xylan, a type of hemicellulose. Measurements of low temperature conductivity, Kelvin probe force microscopy, and high frequency (THz) conductivity elucidated the intra-tube and inter-tube charge transport processes in this material. The measurements show excellent conductive properties of the as prepared thin films, with bulk conductivity up to 2000 S cm-1. The transport results demonstrate that the hemicellulose does not seriously interfere with the inter-tube conductance.

  4. Screening for Hypothyroidism-Results of a Study Conducted at District Headquarter Hospital, Abbottabad

    International Nuclear Information System (INIS)

    Gul, N.; Farid, J.; Idris, M.; Sarwar, J.

    2016-01-01

    Background: Sub-clinically hypo-functioning thyroid is a condition in which there is biochemical evidence of hypothyroidism but patient is clinically asymptomatic. This concept is not new. The typical picture of this condition is increased thyroid stimulating hormone and normal thyroxine levels. Subclinical hypothyroidism has been found to have variable prevalence ranging from 4-10 percent to 10-26 percent. Methods: This cross sectional study was conducted on 378 adult patients coming to outpatient department of District Headquarter Hospital Abbottabad over a period of two years from February 2013 to February 2015. Results: Out of the 378 individuals studied, 37 (9.78 percent) had subclinical hypothyroidism. Mean age of the patients was 43.5±10.5 years. Females outnumbered males, i.e., 24 out of 37 (65 percent). It was noted that there was no correlation between mean TSH level and gender or age of the patients. Conclusion: Subclinical hypothyroidism is not an uncommon condition and its diagnosis is established easily by doing thyroid hormone levels in fasting condition. Early diagnosis and therapeutic intervention may not only prevent the progression to clinical hypothyroidism but also help in preventing the wastage of resources on doing unnecessary investigations. (author)

  5. Electrical Conductivity of CUXS Thin Film Deposited by Chemical ...

    African Journals Online (AJOL)

    Thin films of CuxS have successfully been deposited on glass substrates using the Chemical Bath Deposition (CBD) technique. The films were then investigated for their electrical properties. The results showed that the electrical conductivities of the CuxS films with different molarities (n) of thiourea (Tu), determined using ...

  6. Ceramic/Metal Composites with Positive Temperature Dependence of Thermal Conductivity

    International Nuclear Information System (INIS)

    Li Jianhui; Yu Qi; Sun Wei; Zhang Rui; Wang Ke; Li Jingfeng; Ichigozaki, Daisuke

    2013-01-01

    Most materials show decreasing thermal conductivity with increasing temperature, but an opposite temperature dependence of thermal conductivity is required for some industrial applications. The present work was conducted with a motivation to develop composite materials with a positive temperature dependence of thermal conductivity. ZrO 2 / stainless steel powders (304L) composite, with 3% stearic acid, was prepared by normal sintering under the protecting of Ar after mixing by mechanical ball milling technique. With the 304L content increasing from 10% to 20%, the thermal conductivity values increased. For all samples, the thermal conductivity in the temperature range of room temperature to 700 °C decreased with temperature below 300 °C, and then began to increase. The increasing thermal conductivity of the composites (within the high temperature range was attributed to the difference of the thermal conductivity and thermal expansion coefficient between ZrO 2 ceramic and 304L stainless steel powders. Two simple models were also used to estimate the thermal conductivity of the composites, which were in good agreement with the experiment results.

  7. Effect of γ-irradiation on the electrical conductivity of some soda lime silicate glass containing blast furnace slag

    International Nuclear Information System (INIS)

    Elalaily, N.A.; Khalil, Magda M.I.; Ahmed, L.S.

    2007-01-01

    The effect of electric field strength on conduction in soda lime silicate glass doped with blast furnace slag with different concentration was studied and the value of jump distance was calculated. The structure and the mixed anion effect in the conductivity have been examined by measuring the electrical conductivity of glass samples at temperature ranging between 20 and 250 deg. C. The results showed that the electrical conductivity of the examined glasses are divided into three ranges depending on the temperature range. The first is from room temperature to about 49.5 deg. C, the second is at a temperature range of 60.3-104 deg. C where the glass shows a decrease in its conductivity with the increase in temperature. This was followed by another increase in the electrical conductivity with the increase in temperature. The results also showed that the glass becomes more insulating as the slag content increased. The effect of irradiation was also studied by exposing glass samples to two different irradiation doses. It can be noticed that irradiation causes an increase in the electrical conductivity, especially at high temperature. The results were discussed and correlated according to the molecular structure of the prepared glass

  8. High conductivity carbon nanotube wires from radial densification and ionic doping

    Science.gov (United States)

    Alvarenga, Jack; Jarosz, Paul R.; Schauerman, Chris M.; Moses, Brian T.; Landi, Brian J.; Cress, Cory D.; Raffaelle, Ryne P.

    2010-11-01

    Application of drawing dies to radially densify sheets of carbon nanotubes (CNTs) into bulk wires has shown the ability to control electrical conductivity and wire density. Simultaneous use of KAuBr4 doping solution, during wire drawing, has led to an electrical conductivity in the CNT wire of 1.3×106 S/m. Temperature-dependent electrical measurements show that conduction is dominated by fluctuation-assisted tunneling, and introduction of KAuBr4 significantly reduces the tunneling barrier between individual nanotubes. Ultimately, the concomitant doping and densification process leads to closer packed CNTs and a reduced charge transfer barrier, resulting in enhanced bulk electrical conductivity.

  9. Measurement of thermal conductance

    International Nuclear Information System (INIS)

    Kuchnir, M.

    1977-01-01

    The 6-m long, 45-kG, warm-iron superconducting magnets envisioned for the Energy Doubler stage of the Fermilab accelerator require stiff supports with minimized thermal conductances in order to keep the refrigeration power reasonable. The large number of supports involved in the system required a careful study of their heat conduction from the room temperature wall to the intercepting refrigeration at 20 0 K and to the liquid helium. For this purpose the thermal conductance of this support was measured by comparing it with the thermal conductance of a copper strap of known geometry. An association of steady-state thermal analysis and experimental thermal conductivity techniques forms the basis of this method. An important advantage is the automatic simulation of the 20 0 K refrigeration intercept by the copper strap, which simplifies the apparatus considerably. This relative resistance technique, which uses electrical analogy as a guideline, is applicable with no restrictions for materials with temperature-independent thermal conductivity. For other materials the results obtained are functions of the specific temperature interval involved in the measurements. A comprehensive review of the literature on thermal conductivity indicates that this approach has not been used before. A demonstration of its self-consistency is stressed here rather than results obtained for different supports

  10. High-conductance states in a mean-field cortical network model

    DEFF Research Database (Denmark)

    Lerchner, Alexander; Ahmadi, Mandana; Hertz, John

    2004-01-01

    cortical network model with random connectivity and conductance-based synapses. We employ mean-field theory with correctly colored noise to describe temporal correlations in the neuronal activity. Our results illuminate the connection between two independent experimental findings: high-conductance states......Measured responses from visual cortical neurons show that spike times tend to be correlated rather than exactly Poisson distributed. Fano factors vary and are usually greater than 1, indicating a tendency toward spikes being clustered. We show that this behavior emerges naturally in a balanced...... of cortical neurons in their natural environment, and variable non-Poissonian spike statistics with Fano factors greater than 1. (C) 2004 Elsevier B.V. All rights reserved....

  11. Thermal conductive epoxy enhanced by nanodiamond-coated carbon nanotubes

    Science.gov (United States)

    Zhao, Bo; Jiang, Guohua

    2017-11-01

    Nanodiamond (ND) particles were coated on the surface of carbon nanotubes (CNTs) by chemical reactions. Reliable bonding was formed by the combination of acyl chloride on NDs and amine group on CNTs. ND coated CNTs (CNT-ND) were dispersed into epoxy to fabricate thermal conductive resins. The results show that the surface energy of CNTs is decreased by the coated NDs, which is contributed to the excellent dispersion of CNT-NDs in the epoxy matrix. The heat-transfer channels were built by the venous CNTs cooperating with the coated NDs, which not only plays an effective role of heat conduction for CNTs and NDs, but also avoids the electrical leakage by the protection of NDs surrounding outside of CNTs. Electrical and thermal conductance measurements demonstrate that the influence of the CNT-ND incorporation on the electrical conductance is minor, however, the thermal conductivity is improved significantly for the epoxy filled with CNT-ND.[Figure not available: see fulltext.

  12. Community Violence Exposure and Conduct Problems in Children and Adolescents with Conduct Disorder and Healthy Controls.

    Science.gov (United States)

    Kersten, Linda; Vriends, Noortje; Steppan, Martin; Raschle, Nora M; Praetzlich, Martin; Oldenhof, Helena; Vermeiren, Robert; Jansen, Lucres; Ackermann, Katharina; Bernhard, Anka; Martinelli, Anne; Gonzalez-Madruga, Karen; Puzzo, Ignazio; Wells, Amy; Rogers, Jack C; Clanton, Roberta; Baker, Rosalind H; Grisley, Liam; Baumann, Sarah; Gundlach, Malou; Kohls, Gregor; Gonzalez-Torres, Miguel A; Sesma-Pardo, Eva; Dochnal, Roberta; Lazaratou, Helen; Kalogerakis, Zacharias; Bigorra Gualba, Aitana; Smaragdi, Areti; Siklósi, Réka; Dikeos, Dimitris; Hervás, Amaia; Fernández-Rivas, Aranzazu; De Brito, Stephane A; Konrad, Kerstin; Herpertz-Dahlmann, Beate; Fairchild, Graeme; Freitag, Christine M; Popma, Arne; Kieser, Meinhard; Stadler, Christina

    2017-01-01

    and conduct problems. However, we found evidence for a ceiling effect, i.e., individuals with very high levels of conduct problems could not show a further increase if exposed to CVE and vice versa. Results indicate that there was no evidence for an ecological fallacy being the primary cause of the association, i.e., CVE must be considered a valid risk factor in the etiology of CD.

  13. Community Violence Exposure and Conduct Problems in Children and Adolescents with Conduct Disorder and Healthy Controls

    Directory of Open Access Journals (Sweden)

    Linda Kersten

    2017-11-01

    violence and conduct problems. However, we found evidence for a ceiling effect, i.e., individuals with very high levels of conduct problems could not show a further increase if exposed to CVE and vice versa. Results indicate that there was no evidence for an ecological fallacy being the primary cause of the association, i.e., CVE must be considered a valid risk factor in the etiology of CD.

  14. Modeling of cross-plane interface thermal conductance between graphene nano-ribbons

    International Nuclear Information System (INIS)

    Varshney, Vikas; Lee, Jonghoon; Farmer, Barry L; Voevodin, Andrey A; Roy, Ajit K

    2014-01-01

    Using non-equilibrium molecular dynamics for thermal energy transfer, we investigate the interfacial thermal conductance between non-covalently interacting graphene nano-ribbons (GNRs) of varying lengths and widths in a cross-contact (x-shaped) geometry. Our results show that the out-of-plane conductance between GNRs can vary significantly (up to a factor of 4) depending upon their geometric parameters. We observe that when plotted against aspect ratio, the predicted interface thermal conductance values fit excellently on a single master-plot with a logarithmic scaling, suggesting the importance of GNR aspect ratio towards thermal conductance. We propose a model based on incorporating different thermal conductance characteristics of edge and inner interacting regions which predicts the observed logarithmic dependence on aspect ratio. We also study the effect of graphene edge roughness, temperature, and strain on out-of-plane thermal conductance and discuss the observed results based on local vibrational characteristics of atoms within interacting region, number of interacting phonons, and the degree to which they interact across the interaction zone. (paper)

  15. Thermal conductivity model for nanoporous thin films

    Science.gov (United States)

    Huang, Congliang; Zhao, Xinpeng; Regner, Keith; Yang, Ronggui

    2018-03-01

    Nanoporous thin films have attracted great interest because of their extremely low thermal conductivity and potential applications in thin thermal insulators and thermoelectrics. Although there are some numerical and experimental studies about the thermal conductivity of nanoporous thin films, a simplified model is still needed to provide a straightforward prediction. In this paper, by including the phonon scattering lifetimes due to film thickness boundary scattering, nanopore scattering and the frequency-dependent intrinsic phonon-phonon scattering, a fitting-parameter-free model based on the kinetic theory of phonon transport is developed to predict both the in-plane and the cross-plane thermal conductivities of nanoporous thin films. With input parameters such as the lattice constants, thermal conductivity, and the group velocity of acoustic phonons of bulk silicon, our model shows a good agreement with available experimental and numerical results of nanoporous silicon thin films. It illustrates that the size effect of film thickness boundary scattering not only depends on the film thickness but also on the size of nanopores, and a larger nanopore leads to a stronger size effect of the film thickness. Our model also reveals that there are different optimal structures for getting the lowest in-plane and cross-plane thermal conductivities.

  16. Polypyrrole-vanadium oxide nanocomposite: polymer dominates crystallanity and oxide dominates conductivity

    Science.gov (United States)

    Roy, Swarup; Mishra, Suryakant; Yogi, Priyanka; Saxena, Shailendra K.; Mishra, Vikash; Sagdeo, Pankaj R.; Kumar, Rajesh

    2018-01-01

    A hybrid nanocomposite of polypyrrole (Ppy)-V2O5 has been fabricated and characterized for better understanding of material enabling one to use this for appropriate application as the nanocomposite shows better thermal stability. The characterization has been done using XRD, FT-IR, FESEM, and UV-Vis for their structure, surface morphology, respectively, along with TGA and two-probe method used for checking thermal stability, and DC electrical conductance and dielectric behavior of the electrical phenomena of sample. The analysis of XRD demonstrates that crystallinity of nanocomposites is the same as that of the polymer, even though interaction between conducting Ppy and V2O5 is present as evident from FT-IR spectroscopy. A variation in bandgap, in comparison with Ppy, is observed when V2O5 is added into it. The microstructural study of nanocomposites shows encapsulation of V2O5 particles in Ppy matrix with changes in morphology with increase in doping. Conductance results show that electrical conductivity of Ppy decayed on adding V2O5. It has also been found that addition of V2O5 in Ppy has noticeable effect on the dielectric properties.

  17. Effective thermal conductivity of advanced ceramic breeder pebble beds

    Energy Technology Data Exchange (ETDEWEB)

    Pupeschi, S., E-mail: simone.pupeschi@kit.edu; Knitter, R.; Kamlah, M.

    2017-03-15

    As the knowledge of the effective thermal conductivity of ceramic breeder pebble beds under fusion relevant conditions is essential for the development of solid breeder blanket concepts, the EU advanced and reference lithium orthosilicate material were investigated with a newly developed experimental setup based on the transient hot wire method. The effective thermal conductivity was investigated in the temperature range RT–700 °C. Experiments were performed in helium and air atmospheres in the pressure range 0.12–0.4 MPa (abs.) under a compressive load up to 6 MPa. Results show a negligible influence of the chemical composition of the solid material on the bed’s effective thermal conductivity. A severe reduction of the effective thermal conductivity was observed in air. In both atmospheres an increase of the effective thermal conductivity with the temperature was detected, while the influence of the compressive load was found to be small. A clear dependence of the effective thermal conductivity on the pressure of the filling gas was observed in helium in contrast to air, where the pressure dependence was drastically reduced.

  18. Influence of electrical conductivity on microorganisms and rate of ...

    African Journals Online (AJOL)

    Salt treatments included NaCI amendments to adjust the soil solution electrical conductivities (EC) to 40, 120 and 200 dSm-1. Treated soils were incubated at 28OC. Oil degradation was estimated from the gravimetric determinations of remaining oil. The results showed that amending the ultisol with crude oil stimulated the ...

  19. Structural study of TiO2-based transparent conducting films

    International Nuclear Information System (INIS)

    Hitosugi, T.; Yamada, N.; Nakao, S.; Hatabayashi, K.; Shimada, T.; Hasegawa, T.

    2008-01-01

    We have investigated microscopic structures of sputter and pulsed laser deposited (PLD) anatase Nb-doped TiO 2 transparent conducting films, and discuss what causes the degradation of resistivity in sputter-deposited films. Cross-sectional transmission electron microscope and polarized optical microscope images show inhomogeneous intragrain structures and small grains of ∼10 μm in sputter-deposited films. From comparison with PLD films, these results suggest that homogeneous film growth is the important factor to obtain highly conducting sputter-deposited film

  20. Modeling of Thermal Conductivity of CVI-Densified Composites at Fiber and Bundle Level

    Science.gov (United States)

    Guan, Kang; Wu, Jianqing; Cheng, Laifei

    2016-01-01

    The evolution of the thermal conductivities of the unidirectional, 2D woven and 3D braided composites during the CVI (chemical vapor infiltration) process have been numerically studied by the finite element method. The results show that the dual-scale pores play an important role in the thermal conduction of the CVI-densified composites. According to our results, two thermal conductivity models applicable for CVI process have been developed. The sensitivity analysis demonstrates the parameter with the most influence on the CVI-densified composites’ thermal conductivity is matrix cracking’s density, followed by volume fraction of the bundle and thermal conductance of the matrix cracks, finally by micro-porosity inside the bundles and macro-porosity between the bundles. The obtained results are well consistent with the reported data, thus our models could be useful for designing the processing and performance of the CVI-densified composites. PMID:28774130

  1. Functional results after Bonebridge implantation in adults and children with conductive and mixed hearing loss.

    Science.gov (United States)

    Rahne, Torsten; Seiwerth, Ingmar; Götze, Gerrit; Heider, Cornelia; Radetzki, Florian; Herzog, Michael; Plontke, Stefan K

    2015-11-01

    In patients with conductive hearing loss caused by middle ear disorders or atresia of the ear canal, a Bonebridge implantation can improve hearing by providing vibratory input to the temporal bone. The expected results are improved puretone thresholds and speech recognition. In the European Union, approval of the Bonebridge implantation was recently extended to children. We evaluated the functional outcome of a Bonebridge implantation for eight adults and three children. We found significant improvement in the puretone thresholds, with improvement in the air-bone gap. Speech recognition after surgery was significantly higher than in the best-aided situation before surgery. The Bonebridge significantly improved speech recognition in noisy environments and sound localization. In situations relevant to daily life, hearing deficits were nearly completely restored with the Bonebridge implantation in both adults and children.

  2. Effect of conduction band nonparabolicity on the optical properties in ...

    Indian Academy of Sciences (India)

    the bulk conduction band edge, the correction due to nonparabolicity can be important. [9,10]. In a narrow QW under a strong magnetic field, the optical absorption coefficients calculated with the nonparabolicity correction shows remarkable deviation from results obtained using parabolic energy approximation [11].

  3. Electrically conductive composite material

    Science.gov (United States)

    Clough, Roger L.; Sylwester, Alan P.

    1989-01-01

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

  4. Model calculation of thermal conductivity in antiferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Mikhail, I.F.I., E-mail: ifi_mikhail@hotmail.com; Ismail, I.M.M.; Ameen, M.

    2015-11-01

    A theoretical study is given of thermal conductivity in antiferromagnetic materials. The study has the advantage that the three-phonon interactions as well as the magnon phonon interactions have been represented by model operators that preserve the important properties of the exact collision operators. A new expression for thermal conductivity has been derived that involves the same terms obtained in our previous work in addition to two new terms. These two terms represent the conservation and quasi-conservation of wavevector that occur in the three-phonon Normal and Umklapp processes respectively. They gave appreciable contributions to the thermal conductivity and have led to an excellent quantitative agreement with the experimental measurements of the antiferromagnet FeCl{sub 2}. - Highlights: • The Boltzmann equations of phonons and magnons in antiferromagnets have been studied. • Model operators have been used to represent the magnon–phonon and three-phonon interactions. • The models possess the same important properties as the exact operators. • A new expression for the thermal conductivity has been derived. • The results showed a good quantitative agreement with the experimental data of FeCl{sub 2}.

  5. Thermal conductivity of heterogeneous LWR MOX fuels

    Science.gov (United States)

    Staicu, D.; Barker, M.

    2013-11-01

    It is generally observed that the thermal conductivity of LWR MOX fuel is lower than that of pure UO2. For MOX, the degradation is usually only interpreted as an effect of the substitution of U atoms by Pu. This hypothesis is however in contradiction with the observations of Duriez and Philiponneau showing that the thermal conductivity of MOX is independent of the Pu content in the ranges 3-15 and 15-30 wt.% PuO2 respectively. Attributing this degradation to Pu only implies that stoichiometric heterogeneous MOX can be obtained, while we show that any heterogeneity in the plutonium distribution in the sample introduces a variation in the local stoichiometry which in turn has a strong impact on the thermal conductivity. A model quantifying this effect is obtained and a new set of experimental results for homogeneous and heterogeneous MOX fuels is presented and used to validate the proposed model. In irradiated fuels, this effect is predicted to disappear early during irradiation. The 3, 6 and 10 wt.% Pu samples have a similar thermal conductivity. Comparison of the results for this homogeneous microstructure with MIMAS (heterogeneous) fuel of the same composition showed no difference for the Pu contents of 3, 5.9, 6, 7.87 and 10 wt.%. A small increase of the thermal conductivity was obtained for 15 wt.% Pu. This increase is of about 6% when compared to the average of the values obtained for 3, 6 and 10 wt.% Pu. For comparison purposes, Duriez also measured the thermal conductivity of FBR MOX with 21.4 wt.% Pu with O/M = 1.982 and a density close to 95% TD and found a value in good agreement with the estimation obtained using the formula of Philipponneau [8] for FBR MOX, and significantly lower than his results corresponding to the range 3-15 wt.% Pu. This difference in thermal conductivity is of about 20%, i.e. higher than the measurement uncertainties.Thus, a significant difference was observed between FBR and PWR MOX fuels, but was not explained. This difference

  6. [Conduct disorders in seven-year-old children--results of ELSPAC study. 2. Risk factors].

    Science.gov (United States)

    Kukla, L; Hrubá, D; Tyrlík, M; Matejová, H

    2008-01-01

    Conduct disorders related to hyperactivity and significant attention deficit are caused by several types of risk factors-genetic, biological, environmental and psychosocial. A cohort of children was followed longitudinally in a prospective study during the pregnancy and childhood (ELSPAC). In the age of 7 years, marked behavioural divergences were described in 4,4% of children by their attending physicians. These children were also more often afflicted by other pathological symptoms (hyperactivity, sleep and psychomotor disorders). From the data collected from parents and physicians in the previous phases of investigation we selected possible risk factors which affect the prenatal and postnatal periods: prenatal exposure of children to smoking, alcohol, chemical substances, prenatal development complications, the level of education of parents, family dysfunction, alcoholism of both parents, conflicts with the police, mother's disturbed mental health. In the sample of 3752 children from the city of Brno, no behavioural divergence was found in 96.5% of cases. The presence of one or two of the four observed divergences occurred in 3.2% and 3 to 4 conduct disorder symptoms occurred in 0.3% children, significantly more often in boys. The children with conduct disorders compared to the children with no symptoms had significantly lower average birthweight, lower head circumference, their mothers had more often lower education, smoked and had psychological problems in childhood and as adults and the fathers had more often conflicts with the law. The ELSPAC study did not have the methodological possibility of studying the genetic-environmental interactions; nevertheless it contributes to the evidence supporting that some factors can negatively effect the foetal development and the unfavourable family environment can participate in the development of conduct disorders which can progress during lifetime.

  7. Laboratory performance of sweat conductivity for the screening of cystic fibrosis.

    Science.gov (United States)

    Greaves, Ronda F; Jolly, Lisa; Massie, John; Scott, Sue; Wiley, Veronica C; Metz, Michael P; Mackay, Richard J

    2018-03-28

    There are several complementary English-language guidelines for the performance of the sweat chloride test. These guidelines also incorporate information for the collection of conductivity samples. However, recommendations for the measurement and reporting of sweat conductivity are less clear than for sweat chloride. The aim of the study was to develop an understanding of the testing and reporting practices of sweat conductivity in Australasian laboratories. A survey specifically directed at conductivity testing was sent to the 12 laboratories registered with the Royal College of Pathologists of Australasia Quality Assurance Programs. Nine (75%) laboratories participated in the survey, seven of whom used Wescor Macroduct® for collecting sweat and the Wescor SWEAT·CHEK™ for conductivity testing, and the remaining two used the Wescor Nanoduct®. There was considerable variation in frequency and staffing for this test. Likewise, criteria about which patients it was inappropriate to test, definitions of adequate collection sweat rate, cutoffs and actions recommended on the basis of the result showed variations between laboratories. Variations in sweat conductivity testing and reporting reflect many of the same issues that were revealed in sweat chloride test audits and have the potential to lead to uncertainty about the result and the proper action in response to the result. We recommend that sweat testing guidelines should include clearer statements about the use of sweat conductivity.

  8. Hydraulic conductivity in response to exchangeable sodium percentage and solution salt concentration

    Directory of Open Access Journals (Sweden)

    Jefferson Luiz de Aguiar Paes

    2014-10-01

    Full Text Available Hydraulic conductivity is determined in laboratory assays to estimate the flow of water in saturated soils. However, the results of this analysis, when using distilled or deionized water, may not correspond to field conditions in soils with high concentrations of soluble salts. This study therefore set out to determine the hydraulic conductivity in laboratory conditions using solutions of different electrical conductivities in six soils representative of the State of Pernambuco, with the exchangeable sodium percentage adjusted in the range of 5-30%. The results showed an increase in hydraulic conductivity with both decreasing exchangeable sodium percentage and increasing electrical conductivity in the solution. The response to the treatments was more pronounced in soils with higher proportion of more active clays. Determination of hydraulic conductivity in laboratory is routinely performed with deionized or distilled water. However, in salt affected soils, these determinations should be carried out using solutions of electrical conductivity different from 0 dS m-1, with values close to those determined in the saturation extracts.

  9. Preparation of conductive membranes using poly pyrrole

    International Nuclear Information System (INIS)

    Madaeni, S.; Khavaran, B.

    2003-01-01

    Conductive membranes show many benefits including fouling reduction for feeds containing ionic species. These membranes may be prepared either by conductive polymers or coating of the surfaces of non-conductive membranes with conductive polymer. In this research, the commercial micro filtration GVHP membrane manufactured from PVDF was coated with poly pyrrole using two different techniques. The conductivity of the prepared membranes was measured. In this paper, effects of various factors including concentration of the solutions, oxidizing agents, time for leaving the support in the solutions, support type and temperature on membrane conductivity were investigated

  10. Electric conductivity and bootstrap current in tokamak

    International Nuclear Information System (INIS)

    Mao Jianshan; Wang Maoquan

    1996-12-01

    A modified Ohm's law for the electric conductivity calculation is presented, where the modified ohmic current can be compensated by the bootstrap current. A comparison of TEXT tokamak experiment with the theories shows that the modified Ohm's law is a more close approximation to the tokamak experiments than the classical and neoclassical theories and can not lead to the absurd result of Z eff <1, and the extended neoclassical theory would be not necessary. (3 figs.)

  11. High electric field conduction in low-alkali boroaluminosilicate glass

    Science.gov (United States)

    Dash, Priyanka; Yuan, Mengxue; Gao, Jun; Furman, Eugene; Lanagan, Michael T.

    2018-02-01

    Electrical conduction in silica-based glasses under a low electric field is dominated by high mobility ions such as sodium, and there is a transition from ionic transport to electronic transport as the electric field exceeds 108 V/m at low temperatures. Electrical conduction under a high electric field was investigated in thin low-alkali boroaluminosilicate glass samples, showing nonlinear conduction with the current density scaling approximately with E1/2, where E is the electric field. In addition, thermally stimulated depolarization current (TSDC) characterization was carried out on room-temperature electrically poled glass samples, and an anomalous discharging current flowing in the same direction as the charging current was observed. High electric field conduction and TSDC results led to the conclusion that Poole-Frenkel based electronic transport occurs in the mobile-cation-depleted region adjacent to the anode, and accounts for the observed anomalous current.

  12. Psychosocial profiles of Irish children with conduct disorders, mixed disorders of conduct and emotion and emotional disorders

    OpenAIRE

    Byrne, Jacqueline; Carr, Alan

    1995-01-01

    This paper reports on a retrospective archival study. Forty-one conduct disorder cases, 20 cases with mixed disorders of conduct and emotions and 23 emotional disorder cases were compared on demographic, behavioural and contextual variables. The pattern of treatment received by each group and their therapeutic outcomes were also compared. The three groups had similar demographic characteristics but distinctive psychosocial profiles. Conduct disordered cases showed a predominance of covert beh...

  13. Ionic Conductivity of Polyelectrolyte Hydrogels.

    Science.gov (United States)

    Lee, Chen-Jung; Wu, Haiyan; Hu, Yang; Young, Megan; Wang, Huifeng; Lynch, Dylan; Xu, Fujian; Cong, Hongbo; Cheng, Gang

    2018-02-14

    Polyelectrolytes have many important functions in both living organisms and man-made applications. One key property of polyelectrolytes is the ionic conductivity due to their porous networks that allow the transport of water and small molecular solutes. Among polyelectrolytes, zwitterionic polymers have attracted huge attention for applications that involve ion transport in a polyelectrolyte matrix; however, it is still unclear how the functional groups of zwitterionic polymer side chains affect their ion transport and swelling properties. In this study, zwitterionic poly(carboxybetaine acrylamide), poly(2-methacryloyloxyethyl phosphorylcholine), and poly(sulfobetaine methacrylate) hydrogels were synthesized and their ionic conductivity was studied and compared to cationic, anionic, and nonionic hydrogels. The change of the ionic conductivity of zwitterionic and nonionic hydrogels in different saline solutions was investigated in detail. Zwitterionic hydrogels showed much higher ionic conductivity than that of the widely used nonionic poly(ethylene glycol) methyl ether methacrylate hydrogel in all tested solutions. For both cationic and anionic hydrogels, the presence of mobile counterions led to high ionic conductivity in low salt solutions; however, the ionic conductivity of zwitterionic hydrogels surpassed that of cationic and ionic hydrogels in high salt solutions. Cationic and anionic hydrogels showed much higher water content than that of zwitterionic hydrogels in deionized water; however, the cationic hydrogels shrank significantly with increasing saline concentration. This work provides insight into the effects of polyelectrolyte side chains on ion transport. This can guide us in choosing better polyelectrolytes for a broad spectrum of applications, including bioelectronics, neural implants, battery, and so on.

  14. Length-scale dependent ensemble-averaged conductance of a 1D disordered conductor: Conductance minimum

    International Nuclear Information System (INIS)

    Tit, N.; Kumar, N.; Pradhan, P.

    1993-07-01

    Exact numerical calculation of ensemble averaged length-scale dependent conductance for the 1D Anderson model is shown to support an earlier conjecture for a conductance minimum. Numerical results can be understood in terms of the Thouless expression for the conductance and the Wigner level-spacing statistics. (author). 8 refs, 2 figs

  15. The pressure, internal energy, and conductivity of tantalum plasma

    Energy Technology Data Exchange (ETDEWEB)

    Apfelbaum, E.M. [Russian Academy of Sciences, Joint Institute for High Temperatures, Department of Computational Physics, Moscow (Russian Federation)

    2017-11-15

    The pressure, internal energy, and conductivity of a tantalum plasma were calculated at the temperatures 10-100 kK and densities less than 3 g/cm{sup 3}. The plasma composition, pressure, and internal energy were obtained by means of the corresponding system of the coupled mass action law equations. We have considered atom ionization up to +3. The conductivity was calculated within the relaxation time approximation. Comparisons of our results with available measurements and calculation data show good agreement in the area of correct applicability of the present model. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. a.c. conductance study of polycrystal C60

    International Nuclear Information System (INIS)

    Yan Feng; Wang Yening; Huang Yineng; Gu Min; Zhang Qingming; Shen Huimin

    1995-01-01

    The a.c. (1 60 polycrystal (grain size 30 nm) has been studied from 100 to 350 K. Below 150 K, the a.c. conductance is nearly proportional to the temperature and frequency. This is proposed to be due to the hopping of localized states around the Fermi level. Above 200 K, the a.c. conductance exhibits a rapid increase with temperature, and shows a thermally activated behaviour with an activation energy of 0.389 eV below a certain temperature and 0.104 eV above it. A frequency dependent conductance at a fixed temperature is also obtained with a power law σ similar ω s (s∼0.8). For a sample of normal grain size, we have measured a peak near 250 K and a much smaller conductance. These results indicate that the defective na ture of our sample (small grain size, disorder or impurities) plays an important role for the transport properties. The existence of nanocrystals in the sample may give rise to localized states and improve its a.c. conductance. The two activation energies can be attributed to the coexistence of the crystalline and amorphous phases of C 60 . ((orig.))

  17. Conductivity of two-component systems

    Energy Technology Data Exchange (ETDEWEB)

    Kuijper, A. de; Hofman, J.P.; Waal, J.A. de [Shell Research BV, Rijswijk (Netherlands). Koninklijke/Shell Exploratie en Productie Lab.; Sandor, R.K.J. [Shell International Petroleum Maatschappij, The Hague (Netherlands)

    1996-01-01

    The authors present measurements and computer simulation results on the electrical conductivity of nonconducting grains embedded in a conductive brine host. The shapes of the grains ranged from prolate-ellipsoidal (with an axis ratio of 5:1) through spherical to oblate-ellipsoidal (with an axis ratio of 1:5). The conductivity was studied as a function of porosity and packing, and Archie`s cementation exponent was found to depend on porosity. They used spatially regular and random configurations with aligned and nonaligned packings. The experimental results agree well with the computer simulation data. This data set will enable extensive tests of models for calculating the anisotropic conductivity of two-component systems.

  18. Microbial interspecies electron transfer via electric currents through conductive minerals

    Science.gov (United States)

    Kato, Souichiro; Hashimoto, Kazuhito; Watanabe, Kazuya

    2012-01-01

    In anaerobic biota, reducing equivalents (electrons) are transferred between different species of microbes [interspecies electron transfer (IET)], establishing the basis of cooperative behaviors and community functions. IET mechanisms described so far are based on diffusion of redox chemical species and/or direct contact in cell aggregates. Here, we show another possibility that IET also occurs via electric currents through natural conductive minerals. Our investigation revealed that electrically conductive magnetite nanoparticles facilitated IET from Geobacter sulfurreducens to Thiobacillus denitrificans, accomplishing acetate oxidation coupled to nitrate reduction. This two-species cooperative catabolism also occurred, albeit one order of magnitude slower, in the presence of Fe ions that worked as diffusive redox species. Semiconductive and insulating iron-oxide nanoparticles did not accelerate the cooperative catabolism. Our results suggest that microbes use conductive mineral particles as conduits of electrons, resulting in efficient IET and cooperative catabolism. Furthermore, such natural mineral conduits are considered to provide ecological advantages for users, because their investments in IET can be reduced. Given that conductive minerals are ubiquitously and abundantly present in nature, electric interactions between microbes and conductive minerals may contribute greatly to the coupling of biogeochemical reactions. PMID:22665802

  19. Study of conduction aphasia by positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Shoji, Mikio; Harigawa, Yasuo; Kawarabayashi, Takeshi; Hirai, Shunsaku; Tamada, Junpei.

    1988-04-01

    We reported two cases of conduction aphasia with distinctive language disorder from early stage of stroke, as well as their cerebral blood flow and oxygen consumption investigated with PET. The case was a 72-year-old right handed man whose speech disturbance began acutely. On admission, neurological examination revealed hand pronation sign on the right and speech disturbance. Other neurological findings including cortical functions were normal. Brain CT scan showed low density area in the white matter of the left supramarginal gyrus. The diagnosis was cerebral infarction. The case 2 was a 64-year-old right handed man. He suffered right hemiparesis 2 months before. Neurological examination revealed mild right hemiparesis and speech disturbance. Other cortical functions were noncontributory. Brain CT scan showed old subcortical infarction of the left frontal lobe and new cerebral infarction. with supramarginal gyrus. The low density area of the supramarginal cortex extended into the subcortical white matter. The language performances in these two cases were similar. Two patients were definitely fluent, but the verbal output was contaminated by paraphasias which were predominantly literal. They performed poorly when attempting to repeat despite good comprehension. Thus, the primary characteristics of conduction aphasia were present. PET studies resulted as follows. 1) rCBF reduced 36 % in the supramarginal cortex, 50 % in the white matter. 2) rCMRO/sub 2/ reduced 37 % in the supramarginal cortex, 45 % in the white matter. 3) The CBF and the CMRO/sub 2/ images indicated that cerebral blood flow and oxygen consumption reduced in wider range of area than that shown by brain CT. These results indicated that not only the cortex but also the white matter were damaged in conduction aphasia and several methods including PET should be used to determine the locus of abnormality in conduction aphasia.

  20. Thermal conductivity of crushed salt

    International Nuclear Information System (INIS)

    Kuehn, K.

    Heat transfer through an annular space filled with crushed salt depends primarily on the thermal conductivity, lambda, of the material. This report gives a formula with which lambda can be computed. The formula includes two quantities that can be influenced through screening of the salt smalls: the porosity, psi, and the fraction, alpha, of the more highly resistive heat-flow paths. The report computes and presents graphically the thermal conductivities for various values of psi and alpha. Heat-transfer properties are computed and compared for an annular space filled with crushed salt and for an air gap. The comparison shows that the properties of the annular space are larger only up to a certain temperature, because the properties of the air gap increase exponentially while those f the annular space increase only in an approximately linear way. Experimental results from Project Salt Vault in the U.S. are in good agreement with the calculations performed. Trials in Temperature Experimental Field 2 at the Asse II salt mine will provide an additional check on the calculations. 3 figures, 3 tables

  1. Development of microstrip gas chambers on substrata with electronic conductivity

    International Nuclear Information System (INIS)

    Bouclier, R.; Garabatos, C.; Manzin, G.; Sauli, F.; Shekhtman, L.; Temmel, T.; Della Mea, G.; Maggioni, G.; Rigato, V.; Logachenko, I.

    1994-01-01

    This paper describes several recent developments on Microstrip Gas Chambers (MSGCs). The authors have studied the operating behavior of the detectors in different gas mixtures; maximum stable gains have been achieved in mixtures of argon and dimethyl-ether (DME) in almost equal proportions. Using detectors manufactured on semi-conducting glass substrates, capable of withstanding very high rates (above 10 6 mm -2 s -1 ), they have demonstrated extended lifetime without gain modifications up to a collected charge of 130 mC cm -1 in clean laboratory operating conditions. They have also verified that relaxing the requirements on cleanness conditions, either in the gas mixing system or in the detector construction, may result in fast aging of the devices under irradiation. As an alternative to the semi-conducting glass, they have developed a novel technique to coat regular glass with a thin lead silicate layer having electron conductivity; a new development consisting in coating already manufactured MSGCs with the thin semi-conducting layer is also described. The preliminary results show an excellent rate capability of this kind of devices, intrinsically simpler to manufacture

  2. Evaluation of Regression and Neuro_Fuzzy Models in Estimating Saturated Hydraulic Conductivity

    Directory of Open Access Journals (Sweden)

    J. Behmanesh

    2015-06-01

    Full Text Available Study of soil hydraulic properties such as saturated and unsaturated hydraulic conductivity is required in the environmental investigations. Despite numerous research, measuring saturated hydraulic conductivity using by direct methods are still costly, time consuming and professional. Therefore estimating saturated hydraulic conductivity using rapid and low cost methods such as pedo-transfer functions with acceptable accuracy was developed. The purpose of this research was to compare and evaluate 11 pedo-transfer functions and Adaptive Neuro-Fuzzy Inference System (ANFIS to estimate saturated hydraulic conductivity of soil. In this direct, saturated hydraulic conductivity and physical properties in 40 points of Urmia were calculated. The soil excavated was used in the lab to determine its easily accessible parameters. The results showed that among existing models, Aimrun et al model had the best estimation for soil saturated hydraulic conductivity. For mentioned model, the Root Mean Square Error and Mean Absolute Error parameters were 0.174 and 0.028 m/day respectively. The results of the present research, emphasises the importance of effective porosity application as an important accessible parameter in accuracy of pedo-transfer functions. sand and silt percent, bulk density and soil particle density were selected to apply in 561 ANFIS models. In training phase of best ANFIS model, the R2 and RMSE were calculated 1 and 1.2×10-7 respectively. These amounts in the test phase were 0.98 and 0.0006 respectively. Comparison of regression and ANFIS models showed that the ANFIS model had better results than regression functions. Also Nuro-Fuzzy Inference System had capability to estimatae with high accuracy in various soil textures.

  3. Structural study and DC conductivity of vanadyl doped zinc lithium borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Seema [Physics Department, Deenbandhu Chhotu Ram University of Science & Technology, Murthal-131039 (India); Physics Department, Baba Mast Nath University, Asthal Bohr, Rohtak-124001 (India); Khasa, S., E-mail: skhasa@rediff.com; Dahiya, M. S.; Yadav, Arti [Physics Department, Deenbandhu Chhotu Ram University of Science & Technology, Murthal-131039 (India); Agarwal, A. [Applied Physics Department, Guru Jambheshwar University of Science & Technology, Hisar-125001 (India); Dahiya, S. [Physics Department, Baba Mast Nath University, Asthal Bohr, Rohtak-124001 (India)

    2015-06-24

    Glasses with composition xZnO⋅(30 − x)⋅Li{sub 2}O⋅70B{sub 2}O{sub 3} containing 2 mol% of V{sub 2}O{sub 5} (x = 0, 2, 5, 7 and 10) were prepared by standard melt-quench technique. The amorphous nature of the glass samples was confirmed by using x-ray diffraction. The structural changes in these glasses have been investigated by employing IR spectroscopy in the mid-IR range. The infrared spectroscopic analysis confirms the presence of both triangular and tetraheldral coordinated boron units and absence of boroxol ring. It also shows that metal-oxide vibrations are present which are due to the bonding of lithium and zinc ions with oxygen. The dc conductivity was measured in the temperature range 353-523 K. The dc conductivity results show that conductivity decreases and activation energy increases when Li{sub 2}O is replaced by ZnO, keeping the concentration of B{sub 2}O{sub 3} constant. Decrease in conductivity and increase in activation energy shows that addition of ZnO to the glass matrix shows a “blocking effect” on the overall mobility of alkali ions, but at higher concentration the hopping effect was also observed.

  4. The Impact of Destination Exposure in Reality Shows on Destination Image, Familiarity, and Travel Intention

    Directory of Open Access Journals (Sweden)

    Stacia Reviany Mege

    2017-12-01

    Full Text Available The increasing popularity of reality shows renders them as potential media for tourism promotion. However, there is limited research regarding the impact of destination exposure in reality shows. This study aimed to investigate the impact of destination exposure in television reality shows on destination image, familiarity, and travel intention. To test the hypotheses, a within subject experiment was conducted. A worldwide popular reality show, The Amazing Race, was used as a stimulus for the participants. The results revealed that, in general, both cognitive and affective destination im- ages were rated higher after watching the reality show. Furthermore, familiarity with the destination and travel intention to the destination increased after watching the destination in the reality show. The result of this study will be useful for destination marketing organization and the government to explore alternative promotional media and aid the promotion of tourism destination.

  5. Conductivity in the gravity dual to massive ABJM and the membrane paradigm

    International Nuclear Information System (INIS)

    Lopez-Arcos, Cristhiam; Nastase, Horatiu; Rojas, Francisco; Murugan, Jeff

    2014-01-01

    In this paper we analyze the effect of the massive deformation of the ABJM model on the calculation of conductivity of the dual theory. We show that some of the difficulties presented by the dual geometry, in particular the construction of black holes therein, can be at least partially circumvented by adopting a membrane paradigm-like computation of the conductivity, which requires us to know just the effect of the deformation on the horizon of a black hole in AdS 4 . The deformation at the horizon itself is found by first deforming the flat space near the horizon, and then using the corresponding solution near the horizon as initial conditions for the Einstein’s equations. We find the same result, showing an increase in conductivity, using two types of membrane paradigm computations

  6. High-conductance surface-anchoring of a mechanically flexible platform-based porphyrin complex

    International Nuclear Information System (INIS)

    Hauptmann, Nadine; Buchmann, Kristof; Scheil, Katharina; Berndt, Richard; Groß, Lynn; Herrmann, Carmen; Schütt, Christian; Otte, Franziska L; Herges, Rainer

    2015-01-01

    The conductances of molecular model junctions comprising a triazatriangulenium platform with or without an ethynyl spacer and an upright Zn-porphyrin are probed with a low-temperature scanning probe microscope. The platform alone is found to be highly conductive. The ethynyl-linked Zn-porphyrin moiety reduces the conductance by three orders of magnitude and leads to an unexpected, non-monotonous variation of the force that was measured simultaneously at the tip of the microscope. Density functional theory calculations show that this variation results from an induced tilting of the porphyrin. (paper)

  7. Thermal conductivity of graphene nanoribbons under shear deformation: A molecular dynamics simulation

    Science.gov (United States)

    Zhang, Chao; Hao, Xiao-Li; Wang, Cui-Xia; Wei, Ning; Rabczuk, Timon

    2017-01-01

    Tensile strain and compress strain can greatly affect the thermal conductivity of graphene nanoribbons (GNRs). However, the effect of GNRs under shear strain, which is also one of the main strain effect, has not been studied systematically yet. In this work, we employ reverse nonequilibrium molecular dynamics (RNEMD) to the systematical study of the thermal conductivity of GNRs (with model size of 4 nm × 15 nm) under the shear strain. Our studies show that the thermal conductivity of GNRs is not sensitive to the shear strain, and the thermal conductivity decreases only 12–16% before the pristine structure is broken. Furthermore, the phonon frequency and the change of the micro-structure of GNRs, such as band angel and bond length, are analyzed to explore the tendency of thermal conductivity. The results show that the main influence of shear strain is on the in-plane phonon density of states (PDOS), whose G band (higher frequency peaks) moved to the low frequency, thus the thermal conductivity is decreased. The unique thermal properties of GNRs under shear strains suggest their great potentials for graphene nanodevices and great potentials in the thermal managements and thermoelectric applications. PMID:28120921

  8. Dynamic conductivity and partial ionization in dense fluid hydrogen

    Science.gov (United States)

    Zaghoo, Mohamed

    2018-04-01

    A theoretical description for optical conduction experiments in dense fluid hydrogen is presented. Different quantum statistical approaches are used to describe the mechanism of electronic transport in hydrogen's high-temperature dense phase. We show that at the onset of the metallic transition, optical conduction could be described by a strong rise in atomic polarizability, due to increased ionization, whereas in the highly degenerate limit, the Ziman weak scattering model better accounts for the observed saturation of reflectance. The inclusion of effects of partial ionization in the highly degenerate region provides great agreement with experimental results. Hydrogen's fluid metallic state is revealed to be a partially ionized free-electron plasma. Our results provide some of the first theoretical transport models that are experimentally benchmarked, as well as an important guide for future studies.

  9. A Numerical Method for Analyzing Electromagnetic Scattering Properties of a Moving Conducting Object

    Directory of Open Access Journals (Sweden)

    Lei Kuang

    2014-01-01

    Full Text Available A novel numerical approach is developed to analyze electromagnetic scattering properties of a moving conducting object based on the finite-difference time-domain (FDTD algorithm. Relativistic boundary conditions are implemented into the FDTD algorithm to calculate the electromagnetic field on the moving boundary. An improved technique is proposed to solve the scattered field in order to improve the computational efficiency and stability of solutions. The time-harmonic scattered field from a one-dimensional moving conducting surface is first simulated by the proposed approach. Numerical results show that the amplitude and frequency of the scattered field suffer a modulation shift. Then the transient scattered field is calculated, and broadband electromagnetic scattering properties of the moving conducting surface are obtained by the fast Fourier transform (FFT. Finally, the scattered field from a two-dimensional moving square cylinder is analyzed. The numerical results demonstrate the Doppler effect of a moving conducting object. The simulated results agree well with analytical results.

  10. Electrical transport across nanometric SrTiO3 and BaTiO3 barriers in conducting/insulator/conducting junctions

    Science.gov (United States)

    Navarro, H.; Sirena, M.; González Sutter, J.; Troiani, H. E.; del Corro, P. G.; Granell, P.; Golmar, F.; Haberkorn, N.

    2018-01-01

    We report the electrical transport properties of conducting/insulator/conducting heterostructures by studying current-voltage IV curves at room temperature. The measurements were obtained on tunnel junctions with different areas (900, 400 and 100 μm2) using a conducting atomic force microscope. Trilayers with GdBa2Cu3O7 (GBCO) as the bottom electrode, SrTiO3 or BaTiO3 (thicknesses between 1.6 and 4 nm) as the insulator barrier, and GBCO or Nb as the top electrode were grown by DC sputtering on (100) SrTiO3 substrates For SrTiO3 and BaTiO3 barriers, asymmetric IV curves at positive and negative polarization can be obtained using electrodes with different work function. In addition, hysteretic IV curves are obtained for BaTiO3 barriers, which can be ascribed to a combined effect of the FE reversal switching polarization and an oxygen vacancy migration. For GBCO/BaTiO3/GBCO heterostructures, the IV curves correspond to that expected for asymmetric interfaces, which indicates that the disorder affects differently the properties at the bottom and top interfaces. Our results show the role of the interface disorder on the electrical transport of conducting/insulator/conduction heterostructures, which is relevant for different applications, going from resistive switching memories (at room temperature) to Josephson junctions (at low temperatures).

  11. Thermal conductivity of unsaturated clay-rocks

    Directory of Open Access Journals (Sweden)

    D. Jougnot

    2010-01-01

    Full Text Available The parameters used to describe the electrical conductivity of a porous material can be used to describe also its thermal conductivity. A new relationship is developed to connect the thermal conductivity of an unsaturated porous material to the thermal conductivity of the different phases of the composite, and two electrical parameters called the first and second Archie's exponents. A good agreement is obtained between the new model and thermal conductivity measurements performed using packs of glass beads and core samples of the Callovo-Oxfordian clay-rocks at different saturations of the water phase. We showed that the three model parameters optimised to fit the new model against experimental data (namely the thermal conductivity of the solid phase and the two Archie's exponents are consistent with independent estimates. We also observed that the anisotropy of the effective thermal conductivity of the Callovo-Oxfordian clay-rock was mainly due to the anisotropy of the thermal conductivity of the solid phase.

  12. 3D conductive nanocomposite scaffold for bone tissue engineering

    Directory of Open Access Journals (Sweden)

    Shahini A

    2013-12-01

    Full Text Available Aref Shahini,1 Mostafa Yazdimamaghani,2 Kenneth J Walker,2 Margaret A Eastman,3 Hamed Hatami-Marbini,4 Brenda J Smith,5 John L Ricci,6 Sundar V Madihally,2 Daryoosh Vashaee,1 Lobat Tayebi2,7 1School of Electrical and Computer Engineering, Helmerich Advanced Technology Research Center, 2School of Chemical Engineering, 3Department of Chemistry, 4School of Mechanical and Aerospace Engineering, 5Department of Nutritional Sciences, Oklahoma State University, Stillwater, OK, USA; 6Department of Biomaterials and Biomimetics, New York University, New York, NY; 7School of Material Science and Engineering, Helmerich Advanced Technology Research Center, Oklahoma State University, Tulsa, OK, USA Abstract: Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene poly(4-styrene sulfonate (PEDOT:PSS, in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent

  13. RESULTS OF THE SURVEY CONDUCTED AMONG OPHTHALMOLOGISTS ON THE ISSUE OF EQUIPMENT OF MEDICAL INSTITUTIONS WITH OPHTHALMOLOGY DEVICES

    Directory of Open Access Journals (Sweden)

    S. V. Seraphimov

    2017-01-01

    Full Text Available Introduction. The problem of limited accessibility and quality of ophthalmic medical care remains one of the leading ones in the national healthcare. This article presents results of the survey conducted among ophthalmologists about the effect of large-scale equipment of all medical institutions in the Leningrad Region with modern ophthalmologic devices over the recent years.Objective is to determine the contribution of the health care modernization program to equipping the medical institutions of the Leningrad Region with modern ophthalmologic medical devices, and to identify the main areas for improving the ophthalmologic care for residents of the Leningrad region with cataracts.Materials and methods. According to a specially developed questionnaire, 105 ophthalmologists from the Leningrad Region were interviewed. The survey was conducted among physicians working both in out-patient medical facilities and in medical facilities with in-patient modalities.Results. The results of the study confirmed positive changes that occurred in recent years as a result of equipping medical institutions with modern medical devices. Almost two-thirds (59.9% of respondents noted that equipping with modern medical devices had a significant impact on the quality of the medical and diagnostic measures carried out in healthcare facilities of the region.Conclusions. The equipment had a significant impact on the diagnosis and treatment of all kinds of diseases of the eye and its appendages, especially such eye disease which is so common among the population of the Leningrad Region as cataracts (75.0 per 100 ophthalmologists surveyed. At the same time, in spite of these efforts, the standard for equipping ophthalmologic departments in individual medical institutions has not been fully provided. Only every fifth (20.9% ophthalmologist noted during the survey that the list of available ophthalmic devices was sufficient, and that they all worked properly.

  14. Thermal expansion anomaly and thermal conductivity of U3O8

    International Nuclear Information System (INIS)

    Schulz, B.

    1975-01-01

    The anomaly in the thermal expansion of U 3 O 8 and results of the thermal conductivity of this compound are described. U 3 O 8 powder heat treated at 1,223 K was consolidated by pressing and sintering in air at 1,223 and 1,373 K to a density of 66% and 80.8% TD. The O/U ratio was 2.67 and 2.63 respectively, the crystal structure being orthorhombic in both cases. For UOsub(2.63) the thermal linear expansion was measured in the temperature range 293 K-1,063 K in pressing direction and normal to it, while for UOsub(2.67) measurements were done parallel to the pressing direction. The curves of the linear thermal expansion from 373 K up to 623 K show negative values and above positive for the three curves. The results are related to known data of phase-transition-temperatures of the orthorhombic U 3 O 8 . Measurements of the thermal conductivity were done on UOsub(2.67). Because of the high porosity of the samples, known relationships for the porosity correction of the thermal conductivity were proved on alumina with 34 % porosity. The values of the thermal conductivity of UOsub(2.67) (corrected to zero porosity) show a very slight temperature dependence, they are about three times lower than those of the stoichiometric uranium dioxide in the same temperature range

  15. Control of Transboundary Movement of Radioactive Material Inadvertently Incorporated into Scrap Metal and Semi-finished Products of the Metal Recycling Industries. Results of the Meetings Conducted to Develop a Draft Code of Conduct

    International Nuclear Information System (INIS)

    2014-02-01

    In 2010, the IAEA initiated the development of a code of conduct on the transboundary movement of radioactive material inadvertently incorporated into scrap metal and semi- finished products of the metal recycling industries (Metal Recycling Code of Conduct). The Metal Recycling Code of Conduct was intended to harmonize the approaches of Member States in relation to the discovery of radioactive material that may inadvertently be present in scrap metals and semi-finished products subject to transboundary movement, and their safe handling and management to facilitate regulatory control. The Metal Recycling Code of Conduct was envisaged as being complementary to the Safety Guide on Control of Orphan Sources and Other Radioactive Material in the Metal Recycling and Production Industries (IAEA Safety Standards Series No. SSG-17), which provides recommendations, principally within a national context, on the protection of workers, members of the public and the environment in relation to the control of radioactive material inadvertently incorporated in scrap metal. In February 2013, the third open-ended meeting of technical and legal experts to develop the Metal Recycling Code of Conduct was organized. The objective of this meeting was to address the comments received from Member States and to finalize the text of the draft Metal Recycling Code of Conduct. Representatives from 55 Member States, one non-Member State and the EU, together with seven observers from the metal recycling industry, reviewed the comments and revised the draft accordingly. In September 2013, in Resolution GC(57)/RES/9, the IAEA General Conference recorded that it 'Appreciates the intensive efforts undertaken by the Secretariat to develop a code of conduct on the transboundary movement of scrap metal, or materials produced from scrap metal, that may inadvertently contain radioactive material, and encourages the Secretariat to make the results of the discussion conducted on this issue available to

  16. Solving hyperbolic heat conduction using electrical simulation

    International Nuclear Information System (INIS)

    Gheitaghy, A. M.; Talaee, M. R.

    2013-01-01

    In the present study, the electrical network simulation method is proposed to solve the hyperbolic and parabolic heat conduction problem considering Cattaneo-Vernoute (C.V) constitutive relation. Using this new proposed numerical model and the electrical circuit simulation program HSPICE, transient temperature and heat flux profiles at slab can be obtained easily and quickly. To verify the proposed method, the obtained numerical results for cases of one dimensional two-layer slab under periodic boundary temperature with perfect and imperfect thermal contact are compared with the published results. Comparisons show the proposed technique might be considered as a useful tool in the analysis of parabolic and hyperbolic thermal problems.

  17. Results of the 2008/2009 Knowledge and Opinions Surveys Conducted for the U.S. Department of Energy Hydrogen Program

    Energy Technology Data Exchange (ETDEWEB)

    Schmoyer, R. L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Truett, Tykey [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cooper, Christy [Dept. of Energy (DOE), Washington DC (United States); Chew, Andrea [Dept. of Energy (DOE), Washington DC (United States)

    2010-04-01

    This report presents results of a 2008/2009 survey of hydrogen and fuel cell awareness conducted for the U.S. Department of Energy (DOE). The 2008/2009 survey follows up on a similar DOE survey conducted in 2004, measuring levels of awareness and understanding of hydrogen and fuel cell technologies in four populations: (1) the general public, (2) students, (3) personnel in state and local governments, and (4) potential end users of hydrogen and fuel cell technologies in business and industry. The 2008/2009 survey includes these four groups and adds a fifth group, safety and code officials. The same survey methods were used for both surveys; the 2008/2009 survey report includes a comparison of 2004 and 2008/2009 findings. Information from these surveys will be used to enhance hydrogen and fuel cell education strategies.

  18. Investigation of ionic conduction in PEO-PVDF based blend polymer electrolytes

    Science.gov (United States)

    Patla, Subir Kumar; Ray, Ruma; Asokan, K.; Karmakar, Sanat

    2018-03-01

    We investigate the effect of blend host polymer on solid polymer electrolyte (SPE) films doped with ammonium iodide (NH4I) salt using a variety of experimental techniques. Structural studies on the composite SPEs show that the blending of Poly(ethylene oxide) (PEO)-Poly(vinylidene fluoride) (PVDF) polymers in a suitable ratio enhances the amorphous fraction of the polymer matrix and facilitates fast ion conduction through it. We observe that the addition of a small amount of PVDF in the PEO host polymer enhances the ion - polymer interaction leading to more ion dissociation. As a result, the effective number of mobile charge carriers within the polymer matrix increases. Systematic investigation in these blend SPEs shows that the maximum conductivity (1.01 × 10-3 S/cm) is obtained for PEO - rich (80 wt. % PEO, 20 wt. % PVDF) composites at 35 wt. % NH4I concentration at room temperature. Interestingly, at higher salt concentrations (above 35 wt. %), the conductivity is found to decrease in this system. The reduction of conductivity at higher salt concentrations is the consequence of decrease in the carrier concentration due to the formation of an ion pair and ion aggregates. PVDF-rich compositions (20 wt. % PEO and 80 wt. % PVDF), on the other hand, show a very complex porous microstructure. We also observe a much lower ionic conductivity (maximum ˜ 10-6 S/cm at 15 wt. % salt) in these composite systems relative to PEO-rich composites.

  19. Mean free path dependent phonon contributions to interfacial thermal conductance

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Yi; Liu, Chenhan; Chen, Weiyu; Cai, Shuang; Chen, Chen; Wei, Zhiyong; Bi, Kedong; Yang, Juekuan; Chen, Yunfei, E-mail: yunfeichen@seu.edu.cn

    2017-06-15

    Interfacial thermal conductance as an accumulation function of the phonon mean free path is rigorously derived from the thermal conductivity accumulation function. Based on our theoretical model, the interfacial thermal conductance accumulation function between Si/Ge is calculated. The results show that the range of mean free paths (MFPs) for phonons contributing to the interfacial thermal conductance is far narrower than that for phonons contributing to the thermal conductivity. The interfacial thermal conductance is mainly contributed by phonons with shorter MFPs, and the size effects can be observed only for an interface constructed by nanostructures with film thicknesses smaller than the MFPs of those phonons mainly contributing to the interfacial thermal conductance. This is why most experimental measurements cannot detect size effects on interfacial thermal conductance. A molecular dynamics simulation is employed to verify our proposed model. - Highlights: • A model to account for the interfacial thermal conductance as an accumulation function of phonon mean free path is proposed; • The model predicts that the range of mean free paths (MFPs) for phonons contributing to the interfacial thermal conductance is far narrower than that contributing to the thermal conductivity; • This model can be conveniently implemented to estimate the size effects on the interfacial thermal conductance for the interfaces formed by a nanostructure contacting a substrate.

  20. The Measurement of Thermal Conductivities of Silica and Carbon Black Powders at Different pressures by Thermal COnductivity Probe

    Institute of Scientific and Technical Information of China (English)

    X.G.Liang; X.S.Ge; 等

    1992-01-01

    This investigation was done to study the gas filled powder insulation and thermal conductivity probe for the measurent of thermal conductivity of powders.The mathematical analysis showed that the heat capacity of the probe itself and the thermal rsistance between the probe and powder must be considered .The authors developed a slender probe and measured the effective thermal conductivity of sillca and carbon black powders under a variety of conditions.

  1. Design of instantaneous liquid film thickness measurement system for conductive or non-conductive fluid with high viscosity

    Directory of Open Access Journals (Sweden)

    Yongxin Yu

    2017-06-01

    Full Text Available In the paper, a new capacitive sensor with a dielectric film coating was designed to measure the thickness of the liquid film on a flat surface. The measured medium can be conductive or non-conductive fluid with high viscosity such as silicone oil, syrup, CMC solution and melt. With the dielectric film coating, the defects caused by the humidity in a capacitor can be avoided completely. With a excitation frequency 0-20kHz, the static permittivity of capacitive sensor is obtained and stable when small thicknesses are monitored within the frequency of 0-3kHz. Based on the measurement principle, an experimental system was designed and verified including calibration and actual measurement for different liquid film thickness. Experimental results showed that the sensitivity, the resolution, repeatability and linear range of the capacitive sensor are satisfied to the liquid film thickness measurement. Finally, the capacitive measuring system was successfully applied to the water, silicone oil and syrup film thickness measurement.

  2. Inadequacy of ethical conduct and reporting of stepped wedge cluster randomized trials: Results from a systematic review.

    Science.gov (United States)

    Taljaard, Monica; Hemming, Karla; Shah, Lena; Giraudeau, Bruno; Grimshaw, Jeremy M; Weijer, Charles

    2017-08-01

    Background/aims The use of the stepped wedge cluster randomized design is rapidly increasing. This design is commonly used to evaluate health policy and service delivery interventions. Stepped wedge cluster randomized trials have unique characteristics that complicate their ethical interpretation. The 2012 Ottawa Statement provides comprehensive guidance on the ethical design and conduct of cluster randomized trials, and the 2010 CONSORT extension for cluster randomized trials provides guidelines for reporting. Our aims were to assess the adequacy of the ethical conduct and reporting of stepped wedge trials to date, focusing on research ethics review and informed consent. Methods We conducted a systematic review of stepped wedge cluster randomized trials in health research published up to 2014 in English language journals. We extracted details of study intervention and data collection procedures, as well as reporting of research ethics review and informed consent. Two reviewers independently extracted data from each trial; discrepancies were resolved through discussion. We identified the presence of any research participants at the cluster level and the individual level. We assessed ethical conduct by tabulating reporting of research ethics review and informed consent against the presence of research participants. Results Of 32 identified stepped wedge trials, only 24 (75%) reported review by a research ethics committee, and only 16 (50%) reported informed consent from any research participants-yet, all trials included research participants at some level. In the subgroup of 20 trials with research participants at cluster level, only 4 (20%) reported informed consent from such participants; in 26 trials with individual-level research participants, only 15 (58%) reported their informed consent. Interventions (regardless of whether targeting cluster- or individual-level participants) were delivered at the group level in more than two-thirds of trials; nine trials (28

  3. Structural deformation and intertube conductance of crossed carbon nanotube

    International Nuclear Information System (INIS)

    Yoon, Young-Gui; Mazzoni, Mario S.C.; Choi, Hyoung J.; Ihm, Jisoon; Louie, Steven G.

    2000-01-01

    We present a first-principles study of the structure and quantum electronic conductance of junctions consisting of two crossed (5,5) single-walled carbon nanotubes. The structures are determined by constrained minimization of total energy at a given force between the two tubes, simulating the effects of substrate-tube attraction or an applied force. We find that the intertube contact distance is very sensitive to the applied force in the range of 0-10 nN. The intertube conductance is sizable for realistic deformation expected from substrate interaction. The results explain the recent transport data on crossed nanotubes and show that these systems may be potentially useful as electromechanical devices

  4. Universal parametric correlations of conductance peaks in quantum dots

    International Nuclear Information System (INIS)

    Alhassid, Y.; Attias, H.

    1996-01-01

    We compute the parametric correlation function of the conductance peaks in chaotic and weakly disordered quantum dots in the Coulomb blockade regime and demonstrate its universality upon an appropriate scaling of the parameter. For a symmetric dot we show that this correlation function is affected by breaking time-reversal symmetry but is independent of the details of the channels in the external leads. We derive a new scaling which depends on the eigenfunctions alone and can be extracted directly from the conductance peak heights. Our results are in excellent agreement with model simulations of a disordered quantum dot. copyright 1996 The American Physical Society

  5. Electrical conductivity of quasi-two-dimensional foams.

    Science.gov (United States)

    Yazhgur, Pavel; Honorez, Clément; Drenckhan, Wiebke; Langevin, Dominique; Salonen, Anniina

    2015-04-01

    Quasi-two-dimensional (quasi-2D) foams consist of monolayers of bubbles squeezed between two narrowly spaced plates. These simplified foams have served successfully in the past to shed light on numerous issues in foam physics. Here we consider the electrical conductivity of such model foams. We compare experiments to a model which we propose, and which successfully relates the structural and the conductive properties of the foam over the full range of the investigated liquid content. We show in particular that in the case of quasi-2D foams the liquid in the nodes needs to be taken into account even at low liquid content. We think that these results may provide different approaches for the characterization of foam properties and for the in situ characterization of the liquid content of foams in confining geometries, such as microfluidics.

  6. Influence of Conductive and Semi-Conductive Nanoparticles on the Dielectric Response of Natural Ester-Based Nanofluid Insulation

    Directory of Open Access Journals (Sweden)

    M. Z. H. Makmud

    2018-02-01

    Full Text Available Nowadays, studies of alternative liquid insulation in high voltage apparatus have become increasingly important due to higher concerns regarding safety, sustainable resources and environmentally friendly issues. To fulfil this demand, natural ester has been extensively studied and it can become a potential product to replace mineral oil in power transformers. In addition, the incorporation of nanoparticles has been remarkable in producing improved characteristics of insulating oil. Although much extensive research has been carried out, there is no general agreement on the influence on the dielectric response of base oil due to the addition of different amounts and conductivity types of nanoparticle concentrations. Therefore, in this work, a natural ester-based nanofluid was prepared by a two-step method using iron oxide (Fe2O3 and titanium dioxide (TiO2 as the conductive and semi-conductive nanoparticles, respectively. The concentration amount of each nanoparticle types was varied at 0.01, 0.1 and 1.0 g/L. The nanofluid samples were characterised by visual inspection, morphology and the dynamic light scattering (DLS method before the dielectric response measurement was carried out for frequency-dependent spectroscopy (FDS, current-voltage (I-V, and dielectric breakdown (BD strength. The results show that the dielectric spectra and I-V curves of nanofluid-based iron oxide increases with the increase of iron oxide nanoparticle loading, while for titanium dioxide, it exhibits a decreasing response. The dielectric BD strength is enhanced for both types of nanoparticles at 0.01 g/L concentration. However, the increasing amount of nanoparticles at 0.1 and 1.0 g/L led to a contrary dielectric BD response. Thus, the results indicate that the augmentation of conductive nanoparticles in the suspension can lead to overlapping mechanisms. Consequently, this reduces the BD strength compared to pristine materials during electron injection in high electric

  7. Effects of conductive fillers on temperature distribution of asphalt pavements

    International Nuclear Information System (INIS)

    Chen Mingyu; Wu Shaopeng; Zhang Yuan; Wang Hong

    2010-01-01

    The sun provides a cheap and abundant source of clean and renewable energy. Solar cells have been used to capture this energy and generate electricity. A more useful form of the solar cell would be asphalt pavements, which get heated up by solar radiation. Graphite powders are utilized as thermal conductive fillers to make an asphalt collector conductive so as to improve the efficiency of the asphalt collector. Accounting for the important application conditions and evaluating the effects of the heat conductive materials and the solar energy absorbability of the conductive asphalt collector, a finite element model has been developed to predict temperature distributions in the conductive asphalt solar collector. In this study, an experimental validation exercise was conducted using the measured data taken from full-depth asphalt slabs. Validation results showed that the model can satisfactorily predict the temperature distributions in asphalt concrete slabs. The optimal depth is 25-50 mm for placing pipes that serve as the heat exchanger. Meanwhile, the effect of the surroundings on the solar energy potential of the asphalt collector was noticeable.

  8. Hydraulic conductivity determination of a dark red latosol by gamma attenuation and tensiometry

    International Nuclear Information System (INIS)

    Oliveira, Julio Cesar Martins de; Reichardt, Klaus; Costa, Antonio Carlos Saraiva da

    1995-01-01

    Results for the hydraulic conductivity of a dark red latosol (Oxisol) under laboratory and field conditions are presented. The laboratory experiments simulated field conditions through the measurement of the soil water content profiles as a function of time in soil columns. The data were obtained by the 241 Am gamma-ray transmission method, using standard gamma ray spectrometry equipment. Tensiometers at the depths of 10 and 25 cm were used to obtain the soil water content profiles as a function of time in the field experiments. The hydraulic conductivity functions were determined through internal soil drainage. The results showed higher values of the hydraulic conductivity measured in the field, compared with the laboratory values. The hydraulic conductivity determination methods presented distinct values for the field experiments as well as for the laboratory ones. (author)

  9. Quantum conductance staircase of holes in silicon nanosandwiches

    Directory of Open Access Journals (Sweden)

    Nikolay T. Bagraev

    2017-03-01

    Full Text Available The results of studying the quantum conductance staircase of holes in one-dimensional channels obtained by the split-gate method inside silicon nanosandwiches that are the ultra-narrow quantum well confined by the delta barriers heavily doped with boron on the n-type Si (100 surface are reported. Since the silicon quantum wells studied are ultra-narrow (~2 nm and confined by the delta barriers that consist of the negative-U dipole boron centers, the quantized conductance of one-dimensional channels is observed at relatively high temperatures (T>77 K. Further, the current-voltage characteristic of the quantum conductance staircase is studied in relation to the kinetic energy of holes and their sheet density in the quantum wells. The results show that the quantum conductance staircase of holes in p-Si quantum wires is caused by independent contributions of the one-dimensional (1D subbands of the heavy and light holes. In addition, the field-related inhibition of the quantum conductance staircase is demonstrated in the situation when the energy of the field-induced heating of the carriers become comparable to the energy gap between the 1D subbands. The use of the split-gate method made it possible to detect the effect of a drastic increase in the height of the quantum conductance steps when the kinetic energy of holes is increased; this effect is most profound for quantum wires of finite length, which are not described under conditions of a quantum point contact. In the concluding section of this paper we present the findings for the quantum conductance staircase of holes that is caused by the edge channels in the silicon nanosandwiches prepared within frameworks of the Hall geometry. This longitudinal quantum conductance staircase, Gxx, is revealed by the voltage applied to the Hall contacts, with the plateaus and steps that bring into correlation respectively with the odd and even fractional values.

  10. Complex conductivity of oil-contaminated clayey soils

    Science.gov (United States)

    Deng, Y.; Revil, A.; Shi, X.

    2017-12-01

    Non-intrusive hydrogeophysical techniques have been wildly applied to detect organic contaminants because of the difference of electrical properties for contaminated soil. Among them, spectral induced polarization (SIP) has emerged as a promising tool for the identification of contamination due to its sensitivity to the chemistry of pore water, solid-fluid interfaces and fluid content. Previous works have investigated the influences of oil on the electrical signatures of porous media, which demonstrated the potentials of SIP in the detection of hydrocarbon contamination. However, few works have done on the SIP response of oil in clayey soils. In this study, we perform a set of SIP measurements on the clayey samples under different water saturations. These clayey soils are characterized by relatively high cation exchange capacity. The objective in this work is to test the empirical relationships between the three exponents, including the cementation exponent (m), the saturation exponent (n) and the quadrature conductivity exponent (p), which is expected to reduce the model parameters needed in geophysical and hydraulic properties predictions. Our results show that the complex conductivity are saturation dependent. The magnitude of both in-phase and quadrature conductivities generally decrease with decreasing water saturation. The shape of quadrature conductivity spectra slightly changes when water saturation decreases in some cases. The saturation exponent slightly increases with cation exchange capacity, specific surface area and clay content, with an average value around 2.05. Compared to saturation exponent, the quadrature conductivity exponent apparently increases with cation exchange capacity and specific surface area while has little to do with the clay content. Further, the results indicate that the quadrature conductivity exponent p does not strictly obey to p=n-1 as proposed by Vinegar and Waxman (1984). Instead, it mostly ranges between p=n-1.5 and p=n-0

  11. Electrical Conductivity Model of the Mantle Lithosphere of the Slave Craton (NW Canada) and its tectonic interpretation in the context of Geochemical Results

    Science.gov (United States)

    Lezaeta, P.; Chave, A.; Evans, R.; Jones, A. G.; Ferguson, I.

    2002-12-01

    The Slave Craton, northwestern Canada, contains the oldest known rocks on Earth, with exposed outcrop over an area of about 600x400 km2. The discovery of economic diamondiferous kimberlite pipes during the early 1990s motivated extensive research in the region. Over the last six years, four types of deep-probing magnetotelluric (MT) surveys were conducted within the framework of diverse geoscientific programs, aimed at determining the regional-scale electrical structures of the craton. Two of the surveys involved novel acquisition; one through frozen lake ice along ice roads during winter, and the second deploying ocean-bottom instrumentation from float planes during summer. The latter surveys required one year of recording between summers, thus allowing long period transfer functions that lead to mantle penetration depths of over 300 km. Two-dimensional modeling of the MT data from along the winter road showed the existence of a high conductivity zone at depths of 80-120 km beneath the central Slave craton. This anomalous region is spatially coincident with an ultradepleted harzburgitic layer in the upper mantle that was interpreted by others to be related to a subducted slab emplaced during the mid-Archean. A 3-D electrical conductivity model of the Slave lithosphere has been obtained, by trial and error, to fit the magnetic transfer and MT response functions from the lake experiments. This 3-D model traces the central Slave conductor as a NE-SW oriented mantle structure. Its NE-SW orientation coincides with that of a late fold belt system, with the first phase of craton-wide plutonism at ca 2630-2590 Ma, three-part subdivision of the craton based on SKS results, and with a G10 (garnet) geochemical mantle boundaries. All of these highlight a NE-SW structural grain to the lithospheric mantle of the craton, in sharp contrast to the N-S grain of the crust. Constraints on the depth range and lateral extension of the electrical conductive structure are obtained

  12. Problematic internet users' skin conductance and anxiety increase after exposure to the internet.

    Science.gov (United States)

    Romano, Michela; Roaro, Alessandra; Re, Federica; Osborne, Lisa A; Truzoli, Roberto; Reed, Phil

    2017-12-01

    To examine the impact of cessation of an internet session on skin conductance responses and anxiety of higher and lower problem internet users, in order to explore possible physiological withdrawal effects. Participants were measured in terms of their skin conductance before (15min), during (15min), and after (15min) an internet session, and completed self-report measures of state anxiety and problematic internet use. Higher, but not lower, problem users showed increased skin conductance after internet use was stopped, relative to before their internet session. Higher problem users' GSR scores increased, as the time from internet cessation became longer. Higher problem users also showed increased levels of anxiety, following their internet session, which correlated with their skin conductance scores. These results suggest that, following termination of an internet session, withdrawal-like effects are seen, both psychologically and physiologically. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Growth and Functionality of Cells Cultured on Conducting and Semi-Conducting Surfaces Modified with Self-Assembled Monolayers (SAMs

    Directory of Open Access Journals (Sweden)

    Rajendra K. Aithal

    2016-02-01

    Full Text Available Bioengineering of dermal and epidermal cells on surface modified substrates is an active area of research. The cytotoxicity, maintenance of cell phenotype and long-term functionality of human dermal fibroblast (HDF cells on conducting indium tin oxide (ITO and semi-conducting, silicon (Si and gallium arsenide (GaAs, surfaces modified with self-assembled monolayers (SAMs containing amino (–NH2 and methyl (–CH3 end groups have been investigated. Contact angle measurements and infrared spectroscopic studies show that the monolayers are conformal and preserve their functional end groups. Morphological analyses indicate that HDFs grow well on all substrates except GaAs, exhibiting their normal spindle-shaped morphology and exhibit no visible signs of stress or cytoplasmic vacuolation. Cell viability analyses indicate little cell death after one week in culture on all substrates except GaAs, where cells died within 6 h. Cells on all surfaces proliferate except on GaAs and GaAs-ODT. Cell growth is observed to be greater on SAM modified ITO and Si-substrates. Preservation of cellular phenotype assessed through type I collagen immunostaining and positive staining of HDF cells were observed on all modified surfaces except that on GaAs. These results suggest that conducting and semi-conducting SAM-modified surfaces support HDF growth and functionality and represent a promising area of bioengineering research.

  14. Domain wall conductivity in semiconducting hexagonal ferroelectric TbMnO3 thin films

    International Nuclear Information System (INIS)

    Kim, D J; Gruverman, A; Connell, J G; Seo, S S A

    2016-01-01

    Although enhanced conductivity of ferroelectric domain boundaries has been found in BiFeO 3 and Pb(Zr,Ti)O 3 films as well as hexagonal rare-earth manganite single crystals, the mechanism of the domain wall conductivity is still under debate. Using conductive atomic force microscopy, we observe enhanced conductance at the electrically-neutral domain walls in semiconducting hexagonal ferroelectric TbMnO 3 thin films where the structure and polarization direction are strongly constrained along the c-axis. This result indicates that domain wall conductivity in ferroelectric rare-earth manganites is not limited to charged domain walls. We show that the observed conductivity in the TbMnO 3 films is governed by a single conduction mechanism, namely, the back-to-back Schottky diodes tuned by the segregation of defects. (paper)

  15. Ultra-low temperature curable nano-silver conductive adhesive for piezoelectric composite material

    Science.gov (United States)

    Yan, Chao; Liao, Qingwei; Zhou, Xingli; Wang, Likun; Zhong, Chao; Zhang, Di

    2018-01-01

    Limited by the low thermal resistance of composite material, ultra-low temperature curable conductive silver adhesive with curing temperature less than 100 °C needed urgently for the surface conduction treatment of piezoelectric composite material. An ultra-low temperature curable nano-silver conductive adhesive with high adhesion strength for the applications of piezoelectric composite material was investigated. The crystal structure of cured adhesive, SEM/EDS analysis, thermal analysis, adhesive properties and conductive properties of different content of nano-silver filler or micron-silver doping samples were studied. The results show that with 60 wt.% nano-silver filler the ultra-low temperature curable conductive silver adhesive had the relatively good conductivity as volume resistivity of 2.37 × 10-4 Ω cm, and good adhesion strength of 5.13 MPa. Minor micron-doping (below 15 wt.%) could improve conductivity, but would decrease other properties. The ultra-low temperature curable nano-silver conductive adhesive could successfully applied to piezoelectric composite material.

  16. Effect of Residence Time of Graphitisation on Thermal Conductivity of Molded Graphite

    Directory of Open Access Journals (Sweden)

    Pedy Artsanti

    2010-06-01

    Full Text Available The effect of residence time of graphitisation on thermal conductivity of molded graphite has been examined. The examination has been conducted by varying residence time of graphitisation of molded carbon with petroleum coke as raw material and coal tar pitch. Graphitisation has been conducted by heating molded graphite at 2500 °C in argon atmosphere with residention time of 10, 30 and 90 minutes. Graphitisation degree, density, shrinking mass and porosity of molded graphite were examined and so was its thermal conductivity. The result showed that the decrease of porosity and the increase of graphitisation degree due to the increasing of residention time of graphitisation will increase the thermal conductivity of graphite. Molded graphite graphitisized with residence time for 90 minutes residention time gave thermal conductivity of 2.134 Watt/mK and graphitization degree 0.718.

  17. Forming mechanism of Te-based conductive-bridge memories

    Science.gov (United States)

    Mendes, M. Kazar; Martinez, E.; Marty, A.; Veillerot, M.; Yamashita, Y.; Gassilloud, R.; Bernard, M.; Renault, O.; Barrett, N.

    2018-02-01

    We investigated origins of the resistivity change during the forming of ZrTe/Al2O3 based conductive-bridge resistive random access memories. Non-destructive hard X-ray photoelectron spectroscopy was used to investigate redox processes with sufficient depth sensitivity. Results highlighted the reduction of alumina correlated to the oxidation of zirconium at the interface between the solid electrolyte and the active electrode. In addition the resistance switching caused a decrease of Zr-Te bonds and an increase of elemental Te showing an enrichment of tellurium at the ZrTe/Al2O3 interface. XPS depth profiling using argon clusters ion beam confirmed the oxygen diffusion towards the top electrode. A four-layer capacitor model showed an increase of both the ZrO2 and AlOx interfacial layers, confirming the redox process located at the ZrTe/Al2O3 interface. Oxygen vacancies created in the alumina help the filament formation by acting as preferential conductive paths. This study provides a first direct evidence of the physico-chemical phenomena involved in resistive switching of such devices.

  18. Unconventional strain-dependent conductance oscillations in pristine phosphorene.

    Science.gov (United States)

    Ray, S J; Kamalakar, M Venkata

    2018-05-16

    Phosphorene is a single elemental, two-dimensional semiconductor that has quickly emerged as a high mobility material for transistors and optoelectronic devices. In addition, being a 2D material it can sustain high levels of strain, enabling sensitive modification of its electronic properties. In this paper, we investigate the strain dependent electronic properties of phosphorene nanocrystals. By performing extensive calculations we determine the electrical conductance as a function of uniaxial, as well as biaxial strain stimuli and uncover a unique zone phase diagram. This enables us to uncover conductance oscillations in pristine phosphorene for the first time, by the simple application of strain. We show that such unconventional current-voltage behaviour is tuneable by the nature of strain, and that an additional gate voltage can modulate the amplitude (peak to valley ratio) of the observed phenomena and its switching efficiency. Furthermore, we show that the switching is highly robust against doping and defects. Our detailed results present new leads for innovation in strain based gauging and high-frequency nanoelectronic switches of phosphorene.

  19. Suffering by comparison: Twitter users' reactions to the Victoria's Secret Fashion Show.

    Science.gov (United States)

    Chrisler, Joan C; Fung, Kaitlin T; Lopez, Alexandra M; Gorman, Jennifer A

    2013-09-01

    Social comparison theory suggests that evaluating the self in comparison with others (e.g., peers, celebrities, models) can influence body image. Experimental studies that have tested effects of viewing idealized images in the media often show that women feel worse about themselves after seeing images that illustrate the beauty ideal. Twitter presents a naturally occurring opportunity to study viewers' reactions. An analysis was conducted of 977 tweets sent immediately before and during the 2011 Victoria's Secret Fashion Show that reference the show. Although the majority were idiosyncratic remarks, many tweets contain evidence of upward social comparisons to the fashion models. There were tweets about body image, eating disorders, weight, desires for food or alcohol, and thoughts about self-harm. The results support social comparison theory, and suggest that vulnerable viewers could experience negative affect, or even engage in harmful behaviors, during or after viewing the show or others like it. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Thermal conductivity and heat transfer in superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Chen, G; Neagu, M; Borca-Tasciuc, T

    1997-07-01

    Understanding the thermal conductivity and heat transfer processes in superlattice structures is critical for the development of thermoelectric materials and devices based on quantum structures. This work reports progress on the modeling of thermal conductivity of superlattice structures. Results from the models established based on the Boltzmann transport equation could explain existing experimental results on the thermal conductivity of semiconductor superlattices in both in plane and cross-plane directions. These results suggest the possibility of engineering the interfaces to further reduce thermal conductivity of superlattice structures.

  1. thermal, electrical and structural characterization of fast ion conducting glasses (Ag Br)x(AgPO)1-x

    International Nuclear Information System (INIS)

    Kartini, E.; Yufus, S.; Priyanto, T; Indayaningsih, N; Collins, M F

    2001-01-01

    Fast ion conducting glasses are of considerable technological interest because of their possible application in batteries, sensors, and displays. One of the main scientific challenges is to explain how the disordered structure of the glass is related to the high ionic conductivity that can be achieved at ambient temperature. Fast ion conducting glasses (AgBr) x (AgPO3) 1- x with x=0.0; 0.2; 0.3; 0.4; 0.5; 0.7; and 0.85 were prepared by rapid quenching. The studies of structure, thermal property and electrical conductivity have been made. The X-ray diffraction patterns of this system show that the sample are glasses for x 0.5. The neutron diffraction data shows that all AgBr doped glasses exhibit a strong and relatively sharp diffraction peak at anomalously low momentum transfer value, Q∼ 0.7 Α - 1. The low Q-peak is not observed in AgPO 3 glass, and in the X-ray data. The results of electrical conductivity show that the conduction is essentially ionic and due to silver ions alone. The logarithm of the ionic conductivity increases with increasing AgBr mole fraction, and reaches maximum for x = 0.5. The thermal property results measured by differential scanning calorimetric show that the temperatures of the glass transition, the crystallization and the melt reach minimum for the glass with composition x 0.5. We conclude that there appears to be a relation between higher conductivity at ambient temperature, and the low Q-peak. Based on this investigation a better fast ion conducting glass proposed is (AgBr) 0 .5(AgPO 3 ) 0 .5 with the conductivity of 8 x 10 - 5 S/cm

  2. Phonon thermal conductivity of scandium nitride for thermoelectrics from first-principles calculations and thin-film growth

    DEFF Research Database (Denmark)

    Kerdsongpanya, Sit; Hellman, Olle; Sun, Bo

    2017-01-01

    The knowledge of lattice thermal conductivity of materials under realistic conditions is vitally important since many modern technologies require either high or low thermal conductivity. Here, we propose a theoretical model for determining lattice thermal conductivity, which takes into account......-domain thermoreflectance. Our experimental results show a trend of reduction in lattice thermal conductivity with decreasing domain size predicted by the theoretical model. These results suggest a possibility to control thermal conductivity by microstructural tailoring and provide a predictive tool for the effect...... of the microstructure on the lattice thermal conductivity of materials based on ab initio calculations....

  3. Thermal conductivity predictions of herringbone graphite nanofibers using molecular dynamics simulations.

    Science.gov (United States)

    Khadem, Masoud H; Wemhoff, Aaron P

    2013-02-28

    Non-equilibrium molecular dynamics (NEMD) simulations are used to investigate the thermal conductivity of herringbone graphite nanofibers (GNFs) at room temperature by breaking down the axial and transverse conductivity values into intralayer and interlayer components. The optimized Tersoff potential is used to account for intralayer carbon-carbon interactions while the Lennard-Jones potential is used to model the interlayer carbon-carbon interactions. The intralayer thermal conductivity of the graphene layers near room temperature is calculated for different crease angles and number of layers using NEMD with a constant applied heat flux. The edge effect on a layer's thermal conductivity is investigated by computing the thermal conductivity values in both zigzag and armchair directions of the heat flow. The interlayer thermal conductivity is also predicted by imposing hot and cold Nosé-Hoover thermostats on two layers. The limiting case of a 90° crease angle is used to compare the results with those of single-layer graphene and few-layer graphene. The axial and transverse thermal conductivities are then calculated using standard trigonometric conversions of the calculated intralayer and interlayer thermal conductivities, along with calculations of few-layer graphene without a crease. The results show a large influence of the crease angle on the intralayer thermal conductivity, and the saturation of thermal conductivity occurs when number of layers is more than three. The axial thermal conductivity, transverse thermal conductivity in the crease direction, and transverse thermal conductivity normal to the crease for the case of a five-layer herringbone GNF with a 45° crease angle are calculated to be 27 W∕m K, 263 W∕m K, and 1500 W∕m K, respectively, where the axial thermal conductivity is in good agreement with experimental measurements.

  4. Lithium conducting ionic liquids based on lithium borate salts

    Energy Technology Data Exchange (ETDEWEB)

    Zygadlo-Monikowska, E.; Florjanczyk, Z.; Sluzewska, K.; Ostrowska, J.; Langwald, N.; Tomaszewska, A. [Warsaw University of Technology, Faculty of Chemistry, ul. Noakowskiego 3, 00-664 Warsaw (Poland)

    2010-09-15

    The simple reaction of trialkoxyborates with butyllithium resulted in the obtaining of new lithium borate salts: Li{l_brace}[CH{sub 3}(OCH{sub 2}CH{sub 2}){sub n}O]{sub 3}BC{sub 4}H{sub 9}{r_brace}, containing oxyethylene substituents (EO) of n=1, 2, 3 and 7. Salts of n {>=} 2 show properties of room temperature ionic liquid (RTIL) of low glass transition temperature, T{sub g} of the order from -70 to -80 C. The ionic conductivity of the salts depends on the number of EO units, the highest conductivity is shown by the salt with n = 3; in bulk its ambient temperature conductivity is 2 x 10{sup -5} S cm{sup -1} and in solution in cyclic propylene sulfite or EC/PC mixture, conductivity increases by an order of magnitude. Solid polymer electrolytes with borate salts over a wide concentration range, from 10 to 90 mol.% were obtained and characterized. Three types of polymeric matrices: poly(ethylene oxide) (PEO), poly(trimethylene carbonate) (PTMC) and two copolymers of acrylonitrile and butyl acrylate p(AN-BuA) were used in them as polymer matrices. It has been found that for systems of low salt concentration (10 mol.%) the best conducting properties were shown by solid polymer electrolytes with PEO, whereas for systems of high salt concentration, of the polymer-in-salt type, good results were achieved for PTMC as polymer matrix. (author)

  5. Electronic structure effects on stability and quantum conductance in 2D gold nanowires

    International Nuclear Information System (INIS)

    Kashid, Vikas; Shah, Vaishali; Salunke, H. G.

    2011-01-01

    In this study, we have investigated the stability and conductivity of unsupported, two-dimensional infinite gold nanowires using ab initio density functional theory (DFT). Two-dimensional ribbon-like nanowires with 1–5 rows of gold atoms in the non-periodic direction and with different possible structures have been considered. The nanowires with >2 rows of atoms exhibit dimerization, similar to finite wires, along the non-periodic direction. Our results show that in these zero thickness nanowires, the parallelogram motif is the most stable. A comparison between parallelogram- and rectangular-shaped nanowires of increasing width indicates that zero thickness (111) oriented wires have a higher stability over (100). A detailed analysis of the electronic structure, reveals that the (111) oriented structures show increased delocalization of s and p electrons in addition to a stronger delocalization of the d electrons and hence are the most stable. The density of states show that the nanowires are metallic and conducting except for the double zigzag structure, which is semiconducting. Conductance calculations show transmission for a wide range of energies in all the stable nanowires with more than two rows of atoms. The conductance channels are not purely s and have strong contributions from the d levels, and weak contributions from the p levels.

  6. Conductive polypropylene composites

    International Nuclear Information System (INIS)

    Koszkul, J.

    1997-01-01

    The results of studies on polypropylene composites with three sorts of Polish-made carbon blacks were presented. It was found that composite of 20% black content had properties of an electrically conducting material

  7. Hydrogenation of Penta-Graphene Leads to Unexpected Large Improvement in Thermal Conductivity.

    Science.gov (United States)

    Wu, Xufei; Varshney, Vikas; Lee, Jonghoon; Zhang, Teng; Wohlwend, Jennifer L; Roy, Ajit K; Luo, Tengfei

    2016-06-08

    Penta-graphene (PG) has been identified as a novel two-dimensional (2D) material with an intrinsic bandgap, which makes it especially promising for electronics applications. In this work, we use first-principles lattice dynamics and iterative solution of the phonon Boltzmann transport equation (BTE) to determine the thermal conductivity of PG and its more stable derivative, hydrogenated penta-graphene (HPG). As a comparison, we also studied the effect of hydrogenation on graphene thermal conductivity. In contrast to hydrogenation of graphene, which leads to a dramatic decrease in thermal conductivity, HPG shows a notable increase in thermal conductivity, which is much higher than that of PG. Considering the necessity of using the same thickness when comparing thermal conductivity values of different 2D materials, hydrogenation leads to a 63% reduction in thermal conductivity for graphene, while it results in a 76% increase for PG. The high thermal conductivity of HPG makes it more thermally conductive than most other semiconducting 2D materials, such as the transition metal chalcogenides. Our detailed analyses show that the primary reason for the counterintuitive hydrogenation-induced thermal conductivity enhancement is the weaker bond anharmonicity in HPG than PG. This leads to weaker phonon scattering after hydrogenation, despite the increase in the phonon scattering phase space. The high thermal conductivity of HPG may inspire intensive research around HPG and other derivatives of PG as potential materials for future nanoelectronic devices. The fundamental physics understood from this study may open up a new strategy to engineer thermal transport properties of other 2D materials by controlling bond anharmonicity via functionalization.

  8. a.c. conductance study of polycrystal C{sub 60}

    Energy Technology Data Exchange (ETDEWEB)

    Yan Feng [Nanjing Univ. (China). Nat. Lab. of Solid State Microstructure; Wang Yening [Nanjing Univ. (China). Nat. Lab. of Solid State Microstructure; Huang Yineng [Nanjing Univ. (China). Nat. Lab. of Solid State Microstructure; Gu Min [Nanjing Univ. (China). Nat. Lab. of Solid State Microstructure; Zhang Qingming [Nanjing Univ. (China). Nat. Lab. of Solid State Microstructure; Shen Huimin [Nanjing Univ. (China). Nat. Lab. of Solid State Microstructure

    1995-06-05

    The a.c. (1conductance of a C{sub 60} polycrystal (grain size 30 nm) has been studied from 100 to 350 K. Below 150 K, the a.c. conductance is nearly proportional to the temperature and frequency. This is proposed to be due to the hopping of localized states around the Fermi level. Above 200 K, the a.c. conductance exhibits a rapid increase with temperature, and shows a thermally activated behaviour with an activation energy of 0.389 eV below a certain temperature and 0.104 eV above it. A frequency dependent conductance at a fixed temperature is also obtained with a power law {sigma} similar {omega}{sup s} (s{approx}0.8). For a sample of normal grain size, we have measured a peak near 250 K and a much smaller conductance. These results indicate that the defective na ture of our sample (small grain size, disorder or impurities) plays an important role for the transport properties. The existence of nanocrystals in the sample may give rise to localized states and improve its a.c. conductance. The two activation energies can be attributed to the coexistence of the crystalline and amorphous phases of C{sub 60}. ((orig.)).

  9. Nonlinear Thermal Instability in Compressible Viscous Flows Without Heat Conductivity

    Science.gov (United States)

    Jiang, Fei

    2018-04-01

    We investigate the thermal instability of a smooth equilibrium state, in which the density function satisfies Schwarzschild's (instability) condition, to a compressible heat-conducting viscous flow without heat conductivity in the presence of a uniform gravitational field in a three-dimensional bounded domain. We show that the equilibrium state is linearly unstable by a modified variational method. Then, based on the constructed linearly unstable solutions and a local well-posedness result of classical solutions to the original nonlinear problem, we further construct the initial data of linearly unstable solutions to be the one of the original nonlinear problem, and establish an appropriate energy estimate of Gronwall-type. With the help of the established energy estimate, we finally show that the equilibrium state is nonlinearly unstable in the sense of Hadamard by a careful bootstrap instability argument.

  10. Early age conductive hearing loss causes audiogenic seizure and hyperacusis behavior.

    Science.gov (United States)

    Sun, Wei; Manohar, Senthilvelan; Jayaram, Aditi; Kumaraguru, Anand; Fu, Qiang; Li, Ji; Allman, Brian

    2011-12-01

    Recent clinical reports found a high incidence of recurrent otitis media in children suffering hyperacusis, a marked intolerance to an otherwise ordinary environmental sound. However, it is unclear whether the conductive hearing loss caused by otitis media in early age will affect sound tolerance later in life. Thus, we have tested the effects of tympanic membrane (TM) damage at an early age on sound perception development in rats. Two weeks after the TM perforation, more than 80% of the rats showed audiogenic seizure (AGS) when exposed to loud sound (120 dB SPL white noise, hearing loss recovered. The TM damaged rats also showed significantly enhanced acoustic startle responses compared to the rats without TM damage. These results suggest that early age conductive hearing loss may cause an impaired sound tolerance during development. In addition, the AGS can be suppressed by the treatment of vigabatrin, acute injections (250 mg/kg) or oral intakes (60 mg/kg/day for 7 days), an antiepileptic drug that inhibits the catabolism of GABA. c-Fos staining showed a strong staining in the inferior colliculus (IC) in the TM damaged rats, not in the control rats, after exposed to loud sound, indicating a hyper-excitability in the IC during AGS. These results indicate that early age conductive hearing loss can impair sound tolerance by reducing GABA inhibition in the IC, which may be related to hyperacusis seen in children with otitis media. Published by Elsevier B.V.

  11. A study of conduction aphasia by positron emission tomography

    International Nuclear Information System (INIS)

    Shoji, Mikio; Harigawa, Yasuo; Kawarabayashi, Takeshi; Hirai, Shunsaku; Tamada, Junpei.

    1988-01-01

    We reported two cases of conduction aphasia with distinctive language disorder from early stage of stroke, as well as their cerebral blood flow and oxygen consumption investigated with PET. The case was a 72-year-old right handed man whose speech disturbance began acutely. On admission, neurological examination revealed hand pronation sign on the right and speech disturbance. Other neurological findings including cortical functions were normal. Brain CT scan showed low density area in the white matter of the left supramarginal gyrus. The diagnosis was cerebral infarction. The case 2 was a 64-year-old right handed man. He suffered right hemiparesis 2 months before. Neurological examination revealed mild right hemiparesis and speech disturbance. Other cortical functions were noncontributory. Brain CT scan showed old subcortical infarction of the left frontal lobe and new cerebral infarction. with supramarginal gyrus. The low density area of the supramarginal cortex extended into the subcortical white matter. The language performances in these two cases were similar. Two patients were definitely fluent, but the verbal output was contaminated by paraphasias which were predominantly literal. They performed poorly when attempting to repeat despite good comprehension. Thus, the primary characteristics of conduction aphasia were present. PET studies resulted as follows. 1) rCBF reduced 36 % in the supramarginal cortex, 50 % in the white matter. 2) rCMRO 2 reduced 37 % in the supramarginal cortex, 45 % in the white matter. 3) The CBF and the CMRO 2 images indicated that cerebral blood flow and oxygen consumption reduced in wider range of area than that shown by brain CT. These results indicated that not only the cortex but also the white matter were damaged in conduction aphasia and several methods including PET should be used to determine the locus of abnormality in conduction aphasia. (author)

  12. Thermo-structural analysis and electrical conductivity behavior of epoxy/metals composites

    Science.gov (United States)

    Boumedienne, N.; Faska, Y.; Maaroufi, A.; Pinto, G.; Vicente, L.; Benavente, R.

    2017-05-01

    This paper reports on the elaboration and characterization of epoxy resin filled with metallic particles powder (aluminum, tin and zinc) composites. The scanning electron microscopy (SEM) pictures, density measurements and x-ray diffraction analysis (DRX) showed a homogeneous phase of obtained composites. The differential scanning calorimetry revealed a good adherence at matrix-filler interfaces, confirming the SEM observations. The measured glass transition temperatures depend on composites fillers' nature. Afterwards, the electrical conductivity of composites versus their fillers' contents has been investigated. The obtained results depict a nonlinear behavior, indicating an insulator to conductor phase transition at a conduction threshold; with high contrast of ten decades. Hence, the elaborated materials give a possibility to obtain dielectric or electrically conducting phases, which can to be interesting in the choice of desired applications. Finally, the obtained results have been successfully simulated on the basis of different percolation models approach combined with structural characterization inferences.

  13. Surface and conductivity properties of imidazoles solutions

    International Nuclear Information System (INIS)

    Rogalski, Marek; Domanska, Urszula; Czyrny, Dagmara; Dyczko, Dagmara

    2002-01-01

    The surface tension, σ, of the solutions of benzimidazole, 2-phenylimidazole and 2,4,5-triphenylimidazole in water, or water + 10 mol% of acetonitrile, or in other solvents as well as the solubilities and conductivity of benzimidazole and 2-phenylimidazole in water in function of concentration at 298.15 K were measured. The enthalpy of fusion, or solid-solid phase transition and the melting temperatures were determined for the substances under study by the scanning calorimetry (DSC). These solutions exhibit, in a wide range of concentrations, the normal linear, or parabolic decreasing dependencies and the maximum of surface tension at very low concentrations and show the S-shaped dependencies, being in function of the initial sample, never reported before. The results were confirmed by the conductivity measurements. The results were interpreted in terms of the changing structure of the interface. It was concluded that the observed phenomena were caused by an induced nucleation of benzimidazole, 2-phenylimidazole and especially by 2,4,5-triphenylimidazole by columnar discotic structures due to the initial concentration. The surface properties of these solutions reflect the interactions of hydrophobic parts of the guest molecules adsorbed at the interface, as a result of the hydrogen bonded structure of the solution

  14. Perceived parental acceptance/rejection, some family characteristics and conduct disorder in adolescents.

    Science.gov (United States)

    Kostić, Jelena; Nešić, Milkica; Stanković, Miodrag; Zikić, Olivera

    2014-10-01

    Conduct disorder is characterized by repetitive and persistent presence of dissocial, aggressive and defiant behavioral patterns, thus represents important public issue with comprehensive and far-reaching consequences both for the individual and society. The aim of this study was to investigate the differences in sociodemographic family characteristics and the prominence of parental acceptance/rejection dimensions in groups of adolescents with and without conduct disorder, as well as to examine the connection between parental acceptance/rejection dimensions and externalizing symptoms in the group of adolescents with conduct disorder. This research was conducted on 134 adolescents, aged 15 to 18, using the Parental Acceptance/Rejection Questionnaire (PARQ child), Youth Self-Report (YSR), and a questionnaire constructed for the purpose of this survey. The results showed that the number of adolescents with conduct disorder coming from divorced families was significandy higher than from complete families (44.8% vs 13.4%, respectively; p disorders compared to the controls (31.3% vs 8.9%; respectively; p = 0.001). The perceived rejection dimension and the total index of maternal acceptance/rejection were significantly higher in adolescents with conduct disorder than in those with no such disorder (132.30 ± 38.05 vs 93.91 ± 26.29 respectively; p conduct disorder and severe perceived maternal and paternal rejection showed a significantly higher average score on the subscale of externalizing symptoms (14.55 ± 4.45 and 13.27 + 5.05) compared to adolescents with conduct disorder and lower total index of parental acceptance/rejection (8.32 ± 5.05 and 8.28 ± 5.08). The results suggest that adolescents with conduct disorder perceive their parents as more rejecting and less warm and supportive compared to adolescents without conduct disorder. The perception of significant and severe parental rejection was associated with a significantly higher averaged score on the subscale

  15. Ionic Conductivity of the Perovskites, NaMgF3MgF3 and KZnF3 at High Temperatures

    DEFF Research Database (Denmark)

    Andersen, N. H.; Kjems, Jørgen; Hayes, W.

    1985-01-01

    We have carried out a study of the ionic conductivity of NaMgF3, KMgF3 and KZnF3 up to temperatures close to the melting point. Our results, in contrast to previous reports in the literature, show no abnormal ionic conductivity at high temperatures. Care in interpretation of results is required...... because of surface electronic conduction....

  16. Ionic conductivity in BC3 type boron carbon nanolayers

    Directory of Open Access Journals (Sweden)

    Irina V. Zaporotskova

    2017-06-01

    Full Text Available Studies of ionic conductivity and structuresf in which it can be achieved are of great importance for the development of modern batteries. The use of new materials will allow avoiding such typical disadvantages of batteries as short service life, low capacity and leaks. In this article we present the results of our study of the ionic conductivity in boron carbon nanolayers. We have simulated three types of boron carbon nanolayers containing different amounts of boron. The studies have been carried out using the MNDO method within the framework of the molecular cluster model and the DFT method with the B3LYP functional and the 6–31G basis. To study the ion conduction process we have simulated vacancy formation for each type of the nanolayers and studied the energy and electronic characteristics of these processes. We show that 25% boron substitution is the most energetically favorable for vacancy formation. We have also simulated vacancy migration and determined the thermal conductivity as a function of temperature.

  17. Heat Conduction Analysis Using Semi Analytical Finite Element Method

    International Nuclear Information System (INIS)

    Wargadipura, A. H. S.

    1997-01-01

    Heat conduction problems are very often found in science and engineering fields. It is of accrual importance to determine quantitative descriptions of this important physical phenomena. This paper discusses the development and application of a numerical formulation and computation that can be used to analyze heat conduction problems. The mathematical equation which governs the physical behaviour of heat conduction is in the form of second order partial differential equations. The numerical resolution used in this paper is performed using the finite element method and Fourier series, which is known as semi-analytical finite element methods. The numerical solution results in simultaneous algebraic equations which is solved using the Gauss elimination methodology. The computer implementation is carried out using FORTRAN language. In the final part of the paper, a heat conduction problem in a rectangular plate domain with isothermal boundary conditions in its edge is solved to show the application of the computer program developed and also a comparison with analytical solution is discussed to assess the accuracy of the numerical solution obtained

  18. Ultraviolet laser crystallized ZnO:Al films on sapphire with high Hall mobility for simultaneous enhancement of conductivity and transparency

    International Nuclear Information System (INIS)

    Nian, Qiong; Zhang, Martin Y.; Schwartz, Bradley D.; Cheng, Gary J.

    2014-01-01

    One of the most challenging issues in transparent conductive oxides (TCOs) is to improve their conductivity without compromising transparency. High conductivity in TCO films often comes from a high carrier concentration, which is detrimental to transparency due to free carrier absorption. Here we show that UV laser crystallization (UVLC) of aluminum-doped ZnO (AZO) films prepared by pulsed laser deposition on sapphire results in much higher Hall mobility, allowing relaxation of the constraints of the conductivity/transparency trade-off. X-ray diffraction patterns and morphological characterizations show grain growth and crystallinity enhancement during UVLC, resulting in less film internal imperfections. Optoelectronic measurements show that UVLC dramatically improves the electron mobility, while the carrier concentration decreases which in turn simultaneously increases conductivity and transparency. AZO films under optimized UVLC achieve the highest electron mobility of 79 cm 2 /V s at a low carrier concentration of 7.9 × 10 +19  cm −3 . This is realized by a laser crystallization induced decrease of both grain boundary density and electron trap density at grain boundaries. The infrared (IR) to mid-IR range transmittance spectrum shows UVLC significantly enhances the AZO film transparency without compromising conductivity.

  19. Solution-processed assembly of ultrathin transparent conductive cellulose nanopaper embedding AgNWs

    Science.gov (United States)

    Song, Yuanyuan; Jiang, Yaoquan; Shi, Liyi; Cao, Shaomei; Feng, Xin; Miao, Miao; Fang, Jianhui

    2015-08-01

    Natural biomass based cellulose nanopaper is becoming a promising transparent substrate to supersede traditional petroleum based polymer films in realizing future flexible paper-electronics. Here, ultrathin, highly transparent, outstanding conductive hybrid nanopaper with excellent mechanical flexibility was synthesized by the assembly of nanofibrillated cellulose (NFC) and silver nanowires (AgNWs) using a pressured extrusion paper-making technique. The hybrid nanopaper with a thickness of 4.5 μm has a good combination of transparent conductive performance and mechanical stability using bamboo/hemp NFC and AgNWs cross-linked by hydroxypropylmethyl cellulose (HPMC). The heterogeneous fibrous structure of BNFC/HNFC/AgNWs endows a uniform distribution and an enhanced forward light scattering, resulting in high electrical conductivity and optical transmittance. The hybrid nanopaper with an optimal weight ratio of BNFC/HNFC to AgNWs shows outstanding synergistic properties with a transmittance of 86.41% at 550 nm and a sheet resistance of 1.90 ohm sq-1, equal to the electronic conductivity, which is about 500 S cm-1. The BNFC/HNFC/AgNW hybrid nanopaper maintains a stable electrical conductivity after the peeling test and bending at 135° for 1000 cycles, indicating remarkably strong adhesion and mechanical flexibility. Of importance here is that the high-performance and low-cost hybrid nanopaper shows promising potential for electronics application in solar cells, flexible displays and other high-technology products.Natural biomass based cellulose nanopaper is becoming a promising transparent substrate to supersede traditional petroleum based polymer films in realizing future flexible paper-electronics. Here, ultrathin, highly transparent, outstanding conductive hybrid nanopaper with excellent mechanical flexibility was synthesized by the assembly of nanofibrillated cellulose (NFC) and silver nanowires (AgNWs) using a pressured extrusion paper-making technique. The

  20. Air conditioning using an air-cooled single effect lithium bromide absorption chiller: Results of a trial conducted in Madrid in August 2005

    International Nuclear Information System (INIS)

    Izquierdo, M.; Lizarte, R.; Marcos, J.D.; Gutierrez, G.

    2008-01-01

    Trials were conducted to determine the performance of a commercial (Rotartica 045v) 4.5-kW air-cooled, single effect LiBr/H 2 O absorption chiller for residential use. The experiments were run at La Poveda, Arganda del Rey, Madrid, in August 2005. Three typical August days, with different outdoor temperatures, were chosen for the study. The hot water inlet temperature in the generator varied throughout the day from 80 to 107 o C. Thermal demand was calculated, along with period energy balance and COP. Variations in machine component temperatures were recorded and chilling power and the daily COP calculated for each of the three days. The results for the period as a whole showed that cooling power tended to decline with rising outdoor dry bulb temperatures. At temperatures from 35 to 41.3 o C the chilled water outlet temperature in the evaporator climbed to over 15 o C. The average COP for the period, when auxiliary equipment was included into the calculations, was 0.37

  1. Electrical and thermal behavior of unsaturated soils: experimental results

    Science.gov (United States)

    Nouveau, Marie; Grandjean, Gilles; Leroy, Philippe; Philippe, Mickael; Hedri, Estelle; Boukcim, Hassan

    2016-05-01

    When soil is affected by a heat source, some of its properties are modified, and in particular, the electrical resistivity due to changes in water content. As a result, these changes affect the thermal properties of soil, i.e., its thermal conductivity and diffusivity. We experimentally examine the changes in electrical resistivity and thermal conductivity for four soils with different grain size distributions and clay content over a wide range of temperatures, from 20 to 100 °C. This temperature range corresponds to the thermal conditions in the vicinity of a buried high voltage cable or a geothermal system. Experiments were conducted at the field scale, at a geothermal test facility, and in the laboratory using geophysical devices and probing systems. The results show that the electrical resistivity decreases and the thermal conductivity increases with temperature up to a critical temperature depending on soil types. At this critical temperature, the air volume in the pore space increases with temperature, and the resulting electrical resistivity also increases. For higher temperatures , the thermal conductivity increases sharply with temperature up to a second temperature limit. Beyond it, the thermal conductivity drops drastically. This limit corresponds to the temperature at which most of the water evaporates from the soil pore space. Once the evaporation is completed, the thermal conductivity stabilizes. To explain these experimental results, we modeled the electrical resistivity variations with temperature and water content in the temperature range 20 - 100°C, showing that two critical temperatures influence the main processes occurring during heating at temperatures below 100 °C.

  2. Wet method for measuring starch gelatinization temperature using electrical conductivity.

    Science.gov (United States)

    Morales-Sanchez, E; Figueroa, J D C; Gaytan-Martínez, M

    2009-09-01

    The objective of the present study was to develop a method for obtaining the gelatinization temperature of starches by using electrical conductivity. Native starches from corn, rice, potato, and wheat were prepared with different proportions of water and heated from room temperature to 90 degrees C, in a device especially designed for monitoring the electrical conductivity as a function of temperature. The results showed a linear trend of the electrical conductivity with the temperature until it reaches the onset gelatinization temperature. After that point, the electrical conductivity presented an increment or decrement depending on the water content in the sample and it was related to starch swelling and gelatinization phenomena. At the end gelatinization temperature, the conductivity becomes stable and linear, indicating that there are no more changes of phase. The starch gelatinization parameter, which was evaluated in the 4 types of starches using the electrical conductivity, was compared with those obtained by using differential scanning calorimeter (DSC). The onset temperature at which the electrical conductivity increased or decreased was found to be similar to that obtained by DSC. Also, the final temperature at which the electrical conductivity returned to linearity matched the end gelatinization temperature of the DSC. Further, a wet method for measuring the onset, peak, and end gelatinization temperatures as a function of temperature using the electrical conductivity curves is presented for a starch-water suspension.

  3. Conducting Polymers Functionalized with Phthalocyanine as Nitrogen Dioxide Sensors

    Directory of Open Access Journals (Sweden)

    S. D. Deshpande

    2002-05-01

    Full Text Available The conducting polymers such as polyaniline, polypyrrole and polythiophene were functionalized with copper phthalocyanine using chemical oxidation method. The obtained polymers viz. PANI-CuPc, PPy-CuPc and PT-CuPc were studied as chemical sensors by their response characteristics after exposure to various chemical vapors such as methanol, ammonia and nitrogen dioxide. The results obtained showed that these polymers have moderate sensitivity towards the methanol as well as ammonia vapors whereas they show tremendous sensitivity towards nitrogen dioxide vapors. The sensitivity factor of as high as 50,000 was obtained for PT-CuPc polymers in nitrogen dioxide. In comparison to this, the sensitivity factors of about 100 and 40 were obtained, when these polymers were exposed to ammonia and methanol vapors. The very high selectivity towards the nitrogen dioxide was explained on the basis of charge transfer complex formed between, the phthalocyanine donor and nitrogen dioxide acceptor molecules. On the other hand, ammonia becomes a competing electron donor in CuPc containing conducting polymers. The very low response towards the methanol may be explained on the basis very little charge transfer / interaction between CuPc containing polymers and methanol. Thus, CuPc incorporated conducting polymers have much higher selectivity than their original homopolymer.

  4. Measurement of the Thermal Conductivity of Nano-fluid for the advanced heat exchanger

    International Nuclear Information System (INIS)

    Yoo, Shin; Lee, Jae Young

    2006-01-01

    The enhancement of heat transfer has been widely investigated to provide an effective way to cool down the modern electronic devices. Among the methods, Choi discovered a large amount of increase of thermal conductivity when nano sized particles were suspended in the fluid. It was first introduced by Masuda as a potential heat transfer enhancement media and since then, many researchers have investigated the nanofluids phenomena. Many researchers reported in substantially increasing the thermal conductivity of fluids by adding small amounts of suspended metallic oxide nanoparticles of Cu, CuO, Al 2 O 3 and carbon nano-tube. Masuda reported that the use Al 2 O 3 particles of 13 nm at 4.3% volume fraction increased the thermal conductivity of water by 30%. For carbon nano-tube nanofluids shows even greater enhancement. Xie et al. measured the thermal conductivity of carbon nanotube suspended in organic liquid and water with the enhancement of 10-20%. Recent studies have shown that inserting just 1% concentration of nano-particles sometimes increases about maximum 40% of thermal conductivity. However, there is still few experiments done for TiO 2 nanoparticles. Murshed found that the enhancement of thermal conductivity shows about 30% with 15nm in diameter with maximum 5% volume fraction and about 40% enhancement is observed using 15nmD x 40nm rod-shape nanoparticles of TiO 2 . The present experimental shows that a 20% maximum of enhancement in thermal conductivity using TiO 2 of 10nm for 3% volume fraction. Theses results are compared with previous research with theoretical models. As the first step of the heat transfer of nano fluid, the theories related to the nanofluids investigations have been discussed to understand not only the mechanism of thermal conductivity measurement, but also to understand the nanofluid behavior. Colloidal stability is the key to the nanofluid considered to prevent the agglomeration. Through the results, we will discuss the importance of

  5. Ultra-low Thermal Conductivity in Si/Ge Hierarchical Superlattice Nanowire.

    Science.gov (United States)

    Mu, Xin; Wang, Lili; Yang, Xueming; Zhang, Pu; To, Albert C; Luo, Tengfei

    2015-11-16

    Due to interfacial phonon scattering and nanoscale size effect, silicon/germanium (Si/Ge) superlattice nanowire (SNW) can have very low thermal conductivity, which is very attractive for thermoelectrics. In this paper, we demonstrate using molecular dynamics simulations that the already low thermal conductivity of Si/Ge SNW can be further reduced by introducing hierarchical structure to form Si/Ge hierarchical superlattice nanowire (H-SNW). The structural hierarchy introduces defects to disrupt the periodicity of regular SNW and scatters coherent phonons, which are the key contributors to thermal transport in regular SNW. Our simulation results show that periodically arranged defects in Si/Ge H-SNW lead to a ~38% reduction of the already low thermal conductivity of regular Si/Ge SNW. By randomizing the arrangement of defects and imposing additional surface complexities to enhance phonon scattering, further reduction in thermal conductivity can be achieved. Compared to pure Si nanowire, the thermal conductivity reduction of Si/Ge H-SNW can be as large as ~95%. It is concluded that the hierarchical structuring is an effective way of reducing thermal conductivity significantly in SNW, which can be a promising path for improving the efficiency of Si/Ge-based SNW thermoelectrics.

  6. Thermal Conductivity of Graphene-hBN Superlattice Ribbons.

    Science.gov (United States)

    Felix, Isaac M; Pereira, Luiz Felipe C

    2018-02-09

    Superlattices are ideal model systems for the realization and understanding of coherent (wave-like) and incoherent (particle-like) phonon thermal transport. Single layer heterostructures of graphene and hexagonal boron nitride have been produced recently with sharp edges and controlled domain sizes. In this study we employ nonequilibrium molecular dynamics simulations to investigate the thermal conductivity of superlattice nanoribbons with equal-sized domains of graphene and hexagonal boron nitride. We analyze the dependence of the conductivity with the domain sizes, and with the total length of the ribbons. We determine that the thermal conductivity reaches a minimum value of 89 W m -1 K -1 for ribbons with a superlattice period of 3.43 nm. The effective phonon mean free path is also determined and shows a minimum value of 32 nm for the same superlattice period. Our results also reveal that a crossover from coherent to incoherent phonon transport is present at room temperature for BNC nanoribbons, as the superlattice period becomes comparable to the phonon coherence length. Analyzing phonon populations relative to the smallest superlattice period, we attribute the minimum thermal conductivity to a reduction in the population of flexural phonons when the superlattice period equals 3.43 nm. The ability to manipulate thermal conductivity using superlattice-based two-dimensional materials, such as graphene-hBN nanoribbons, opens up opportunities for application in future nanostructured thermoelectric devices.

  7. Treatment of Wastewater with High Conductivity by Pulsed Discharge Plasma

    Science.gov (United States)

    Wang, Zhaojun; Jiang, Song; Liu, Kefu

    2014-07-01

    A wastewater treatment system was established by means of pulsed dielectric barrier discharge (DBD). The main advantage of this system is that the wastewater is employed as one of the electrodes for the degradation of rhodamine B, which makes use of the high conductivity and lessenes its negative influence on the discharge process. At the same time, the reactive species like ozone and ultraviolet (UV) light generated by the DBD can be utilized for the treatment of wastewater. The effects of some factors like conductivity, peak pulse voltage, discharge frequency and pH values were investigated. The results show that the combination of these reactive species could enhance the degradation of the dye while the ozone played the most important role in the process. The degradation efficiency was enhanced with the increase of energy supplied. The reduction in the concentration of rhodamine B was much more effective with high solution conductivity; under the highest conductivity condition, the degradation rate could rise to 99%.

  8. Treatment of Wastewater with High Conductivity by Pulsed Discharge Plasma

    International Nuclear Information System (INIS)

    Wang Zhaojun; Jiang Song; Liu Kefu

    2014-01-01

    A wastewater treatment system was established by means of pulsed dielectric barrier discharge (DBD). The main advantage of this system is that the wastewater is employed as one of the electrodes for the degradation of rhodamine B, which makes use of the high conductivity and lessenes its negative influence on the discharge process. At the same time, the reactive species like ozone and ultraviolet (UV) light generated by the DBD can be utilized for the treatment of wastewater. The effects of some factors like conductivity, peak pulse voltage, discharge frequency and pH values were investigated. The results show that the combination of these reactive species could enhance the degradation of the dye while the ozone played the most important role in the process. The degradation efficiency was enhanced with the increase of energy supplied. The reduction in the concentration of rhodamine B was much more effective with high solution conductivity; under the highest conductivity condition, the degradation rate could rise to 99%. (plasma technology)

  9. Studies on AC Electrical Conductivity of CdCl2 Doped PVA Polymer Electrolyte

    Directory of Open Access Journals (Sweden)

    M. B. Nanda Prakash

    2013-01-01

    Full Text Available PVA-based polymer electrolytes were prepared with various concentrations of CdCl2 using solvent casting method. Prepared polymer films were investigated using line profile analysis employing X-ray diffraction (XRD data. XRD results show that the crystallite size decreases and then increases with increase in CdCl2. AC conductivity in these polymer increases films first and then decreases. These observations are in agreement with XRD results. The highest ionic conductivity of 1.68E − 08 Scm−1 was observed in 4% of CdCl2 in PVA polymer blend. Crystallite ellipsoids for different concentrations of CdCl2 are computed here using whole pattern powder fitting (WPPF indicating that crystallite area decreases with increase in the ionic conductivity.

  10. Thermal conductivity engineering of bulk and one-dimensional Si-Ge nanoarchitectures.

    Science.gov (United States)

    Kandemir, Ali; Ozden, Ayberk; Cagin, Tahir; Sevik, Cem

    2017-01-01

    Various theoretical and experimental methods are utilized to investigate the thermal conductivity of nanostructured materials; this is a critical parameter to increase performance of thermoelectric devices. Among these methods, equilibrium molecular dynamics (EMD) is an accurate technique to predict lattice thermal conductivity. In this study, by means of systematic EMD simulations, thermal conductivity of bulk Si-Ge structures (pristine, alloy and superlattice) and their nanostructured one dimensional forms with square and circular cross-section geometries (asymmetric and symmetric) are calculated for different crystallographic directions. A comprehensive temperature analysis is evaluated for selected structures as well. The results show that one-dimensional structures are superior candidates in terms of their low lattice thermal conductivity and thermal conductivity tunability by nanostructuring, such as by diameter modulation, interface roughness, periodicity and number of interfaces. We find that thermal conductivity decreases with smaller diameters or cross section areas. Furthermore, interface roughness decreases thermal conductivity with a profound impact. Moreover, we predicted that there is a specific periodicity that gives minimum thermal conductivity in symmetric superlattice structures. The decreasing thermal conductivity is due to the reducing phonon movement in the system due to the effect of the number of interfaces that determine regimes of ballistic and wave transport phenomena. In some nanostructures, such as nanowire superlattices, thermal conductivity of the Si/Ge system can be reduced to nearly twice that of an amorphous silicon thermal conductivity. Additionally, it is found that one crystal orientation, [Formula: see text]100[Formula: see text], is better than the [Formula: see text]111[Formula: see text] crystal orientation in one-dimensional and bulk SiGe systems. Our results clearly point out the importance of lattice thermal conductivity

  11. A Fractal Study on the Effective Thermal Conductivity of Porous Media

    Science.gov (United States)

    Qin, X.; Cai, J.; Wei, W.

    2017-12-01

    Thermal conduction in porous media has steadily received attention in science and engineering, for instance, exploiting and utilizing the geothermal energy, developing the oil-gas resource, ground water flow in hydrothermal systems and investigating the potential host nuclear wastes, etc. The thermal conductivity is strongly influenced by the microstructure features of porous media. In this work, based on the fractal characteristics of the grains, a theoretical model of effective thermal conductivity is proposed for saturated and unsaturated porous media. It is found that the proposed effective thermal conductivity solution is a function of geometrical parameters of porous media, such as the porosity, fractal dimension of granular matrix and the thermal conductivity of the grains and pore fluid. The model predictions are compared with existing experimental data and the results show that they are in good agreement with existing experimental data. The proposed model may provide a better understanding of the physical mechanisms of thermal transfer in porous media than conventional models.

  12. Conducting Meta-Analysis Using SAS

    CERN Document Server

    Arthur, Winfried; Huffcutt, Allen I; Arthur, Winfred

    2001-01-01

    Conducting Meta-Analysis Using SAS reviews the meta-analysis statistical procedure and shows the reader how to conduct one using SAS. It presents and illustrates the use of the PROC MEANS procedure in SAS to perform the data computations called for by the two most commonly used meta-analytic procedures, the Hunter & Schmidt and Glassian approaches. This book serves as both an operational guide and user's manual by describing and explaining the meta-analysis procedures and then presenting the appropriate SAS program code for computing the pertinent statistics. The practical, step-by-step instru

  13. Ionic conductivity in irradiated KCL

    International Nuclear Information System (INIS)

    Vignolo Rubio, J.

    1979-01-01

    The ionic conductivity of X and gamma irradiated KCl single crystals has been studied between room temperature and 600 deg C. The radiation induced damage resulting in a decrease of the conductivity heals by thermal annealing in two steps which are at about 350 and 550 deg C respectively. It has been found that the radiation induced colour centres are not involved in the observed decrease of the ionic conductivity. Howewer, it has been observed that the effects of quenching and plastic deformation on the conductivity of the samples are very similar to the effect induced by irradiation. It is suggested that small radiation induced dislocation loops might cause the ionic conductivity decrease observed in irradiated samples. (auth)

  14. Ionic conductivity in irradiated KCL

    International Nuclear Information System (INIS)

    Vignolo Rubio, J.

    1979-01-01

    The ionic conductivity of X and gamma irradiated KCL single crystals has been studied between room temperature and 600 degree centigree. the radiation induced damage resulting in a decrease of the conductivity heals by thermal annealing in two steps which are at about 350 and 550 degree centigree respectively. It has been found that the radiation induced colour centres are not involved in the observed decrease of the ionic conductivity. However. It has been observed that the effects of quenching and plastic deformation on the conductivity of the samples are very similar to the effect induced by irradiation. It is suggested that, samples radiation induced dislocation loops might cause the ionic conductivity decrease observed in irradiated samples. (Author)

  15. Effect of ionizing radiation on structural and conductive properties of copper nanotubes

    Science.gov (United States)

    Zdorovets, M. V.; Borgekov, D. B.; Kenzhina, I. E.; Kozlovskiy, A. L.

    2018-01-01

    The use of electron radiation is an effective tool for stimulating a controlled modification of structural and conductive properties of nanomaterials in modern materials science. The paper presents the results of studies of the influence of various types of radiation on structural and conductive properties of copper nanotubes obtained by electrochemical synthesis in pores of templates based on polyethylene terephthalate. Such methods as SEM, X-ray diffraction and EDS show that irradiation with a stream of high-energy electrons with doses of 50-250 kGy makes it possible to modify the crystal structure of nanotubes, increasing their conductivity and decreasing the resistance of nanostructures without destroying the structure.

  16. Contribution to the electromagnetic study of conducting polymers and chiral structures

    International Nuclear Information System (INIS)

    Lafosse, Xavier

    1994-01-01

    In this work, an electromagnetic characterisation of organic absorptive materials partially made of conductive polymer is presented. Poly-pyrrole-Teflon alloys containing from 0 to 20 pc (in volume) poly-pyrrole were prepared and characterised from dc to 6 GHz. The complex permittivity shows that these materials are absorptive; the dielectric properties strongly depend on the composition and are correctly modelled by a percolation law. A dielectric relaxation was observed for the conductive alloys and this phenomenon is interpreted as the result of an electronic conduction process insured by a charged carriers hopping. A model was developed; it is in good agreement with these results. The difference between the low and high frequency behaviour is also underlined. Microwave chiral structures were manufactured. A cholesteric arrangement of uniaxial slabs was measured in transmission between 4 and 6 GHz; the experimental results are correctly modelled by cascading quadrupolar scattering matrices. New chiral materials were prepared by mixing millimetric helices made of poly-pyrrole with an insulating matrix. These materials exhibit a rotatory power and a good absorption of electromagnetic waves which is connected to the poly-pyrrole concentration. The interest in using conductive polymers to design absorptive chiral materials in the microwave domain is put in evidence and the experimental results are in good agreement with a numerical model; nevertheless, the optimisation of these materials remains difficult. (author) [fr

  17. Thermal conduction in polymeric nanofluids under mean field approximation: role of interfacial adsorption layers

    International Nuclear Information System (INIS)

    Nisha, M R; Philip, J

    2013-01-01

    Polymeric nanofluids of TiO 2 /PVA (polyvinyl alcohol) and Cu/PVA have been prepared by dispersing nanoparticles of TiO 2 or metallic copper in PVA. The thermal diffusivities and thermal conductivities of these nanofluids have been measured as a function of particle loading following a thermal wave interference technique in a thermal wave resonant cavity. It is found that in both cases thermal conductivity increases with particle concentration, with Cu/PVA nanofluids showing a much larger increase. The results have been compared with the corresponding values calculated following different theoretical models. Comparison of the results with model-based calculations shows that the thermal conductivity variations in these nanofluids are within the framework of the classical mean field theory including the formation of thin interfacial adsorption layers around nanoparticles. Although the molecular weight of PVA is very high, it is found that the adsorption layer thickness is limited by the hydrodynamic radius of the nanoparticles. It is found that particle clustering followed by interfacial layering accounts for the larger increase in thermal conductivity found for Cu/PVA compared to TiO 2 /PVA. (paper)

  18. The measurement of conductivity of copper indium disulphide thin films against temperature and thickness

    International Nuclear Information System (INIS)

    Yussof Wahab; Roslinda Zainal; Samsudi Sakrani

    1996-01-01

    Ternary semiconductor copper indium disulphide (CuInS sub 2) thin films have been prepared by thermal evaporation. Three stacked layers of film starting with copper, indium and finally sulphur was deposited on glass substrate in the thickness ratio of 1: 1: I0. The films were then annealed in carbon block by method known as encapsulated sulphurization at 350 degree C for 4 hours. The XRD analysis for four samples of thickness of 449.5, 586, 612 and 654 nm showed that stoichiometric CuInS sub 2, were formed at this annealing condition. The electrical conductivity of CuInS sub 2 thin films were measured against temperature from 150K to 300K. The conductivity values were between 76.6 Sm sup -1 to 631.26 Sm sup -1 and the result showed that it increase exponentially with temperature for the above temperature range. The resulting activation energies were found to be in the range 0.05 to 0.08 eV. This suggested that hopping mechanism predominant to the conducting process. It also found that the conductivity decreased with increasing film thickness

  19. Structural Deformation and Intertube Conductance of Crossed Carbon Nanotube Junctions

    International Nuclear Information System (INIS)

    Yoon, Young-Gui; Mazzoni, Mario S. C.; Choi, Hyoung Joon; Ihm, Jisoon; Louie, Steven G.

    2001-01-01

    We present a first-principles study of the structure and quantum electronic conductance of junctions consisting of two crossed (5,5) single-walled carbon nanotubes. The structures are determined by constrained minimization of total energy at a given force between the two tubes, simulating the effects of substrate-tube attraction or an applied force. We find that the intertube contact distance is very sensitive to the applied force in the range of 0--10nN. The intertube conductance is sizable for realistic deformation expected from substrate interaction. The results explain the recent transport data on crossed nanotubes and show that these systems may be potentially useful as electromechanical devices

  20. Results for the hybrid laminar flow control experiment conducted in the NASA Langley 8-foot transonic pressure tunnel on a 7-foot chord model

    Science.gov (United States)

    Bobbitt, Percy J.; Ferris, James C.; Harvey, William D.; Goradia, Suresh H.

    1992-01-01

    A description is given of the development of, and results from, the hybrid laminar flow control (HLFC) experiment conducted in the NASA LaRC 8 ft Transonic Pressure Tunnel on a 7 ft chord, 23 deg swept model. The methods/codes used to obtain the contours of the HLFC model surface and to define the suction requirements are outlined followed by a discussion of the model construction, suction system, instrumentation, and some example results from the wind tunnel tests. Included in the latter are the effects of Mach number, suction level, and the extent of suction. An assessment is also given of the effect of the wind tunnel environment on the suction requirements. The data show that, at or near the design Mach number, large extents of laminar flow can be achieved with suction mass flows over the first 25 percent, or less, of the chord. Top surface drag coefficients with suction extending from the near leading edge to 20 percent of the chord were approximately 40 percent lower than those obtained with no suction. The results indicate that HLFC can be designed for transonic speeds with lift and drag coefficients approaching those of LFC designs but with much smaller extents and levels of suction.

  1. Hearing outcomes of the active bone conduction system Bonebridge® in conductive or mixed hearing loss.

    Science.gov (United States)

    Carnevale, Claudio; Til-Pérez, Guillermo; Arancibia-Tagle, Diego J; Tomás-Barberán, Manuel D; Sarría-Echegaray, Pedro L

    2018-05-18

    The active transcutaneous bone conduction implant Bonebridge ® , is indicated for patients affected by bilateral conductive/mixed hearing loss or unilateral sensorineural hearing loss, showing hearing outcomes similar to other percutaneous bone conduction implants, but with a lower rate of complications. The aim of this study was to analyze the hearing outcomes in a series of 26 patients affected by conductive or mixed hearing loss and treated with Bonebridge ® . 26 of 30 patients implanted with Bonebridge ® between October 2012 and May 2017, were included in the study. We compared the air conduction thresholds at the frequencies 500, 1000, 2000, 3000, 4000Hz, the SRT50% and the percentage of correct answers at an intensity of 50dB with and without the implant. "Pure tone average" with the implant was 34.91dB showing an average gain of 33.46dB. Average SRT 50% with the implant was 34.33dB, whereas before the surgery no patient achieved 50% of correct answers at a sound intensity of 50dB. The percentage of correct answers at 50dB changed from 11% without the implant to 85% with it. We only observed one complication consisting of an extrusion of the implant in a patient with a history of 2 previous rhytidectomies. The hearing outcomes obtained in our study are similar to those published in the literature. Bonebridge ® represents an excellent alternative in the treatment of conductive or mixed hearing loss, and with a lower rate of complications. Copyright © 2018 Sociedad Española de Otorrinolaringología y Cirugía de Cabeza y Cuello. Publicado por Elsevier España, S.L.U. All rights reserved.

  2. Validity of the isotropic thermal conductivity assumption in supercell lattice dynamics

    Science.gov (United States)

    Ma, Ruiyuan; Lukes, Jennifer R.

    2018-02-01

    Superlattices and nano phononic crystals have attracted significant attention due to their low thermal conductivities and their potential application as thermoelectric materials. A widely used expression to calculate thermal conductivity, presented by Klemens and expressed in terms of the relaxation time by Callaway and Holland, originates from the Boltzmann transport equation. In its most general form, this expression involves a direct summation of the heat current contributions from individual phonons of all wavevectors and polarizations in the first Brillouin zone. In common practice, the expression is simplified by making an isotropic assumption that converts the summation over wavevector to an integral over wavevector magnitude. The isotropic expression has been applied to superlattices and phononic crystals, but its validity for different supercell sizes has not been studied. In this work, the isotropic and direct summation methods are used to calculate the thermal conductivities of bulk Si, and Si/Ge quantum dot superlattices. The results show that the differences between the two methods increase substantially with the supercell size. These differences arise because the vibrational modes neglected in the isotropic assumption provide an increasingly important contribution to the thermal conductivity for larger supercells. To avoid the significant errors that can result from the isotropic assumption, direct summation is recommended for thermal conductivity calculations in superstructures.

  3. Differential and directional effects of perfusion on electrical and thermal conductivities in liver.

    Science.gov (United States)

    Podhajsky, Ronald J; Yi, Ming; Mahajan, Roop L

    2009-01-01

    Two different measurement probes--an electrical probe and a thermal conductivity probe--were designed, fabricated, calibrated, and used in experimental studies on a pig liver model that was designed to control perfusion rates. These probes were fabricated by photolithography and mounted in 1.5-mm diameter catheters. We measured the local impedance and thermal conductivity, respectively, of the artificially perfused liver at different flow rates and, by rotating the probes, in different directions. The results show that both the local electrical conductivity and the thermal conductivity varied location to location, that thermal conductivity increased with decreased distance to large blood vessels, and that significant directional differences exist in both electrical and thermal conductivities. Measurements at different perfusion rates demonstrated that both the local electrical and local thermal conductivities increased linearly with the square root of perfusion rate. These correlations may be of great value to many energy-based biomedical applications.

  4. Reduce the Sensitivity of CL-20 by Improving Thermal Conductivity Through Carbon Nanomaterials.

    Science.gov (United States)

    Wang, Shuang; An, Chongwei; Wang, Jingyu; Ye, Baoyun

    2018-03-27

    The graphene (rGO) and carbon nanotube (CNT) were adopted to enhance the thermal conductivity of CL-20-based composites as conductive fillers. The microstructure features were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and tested the properties by differential scanning calorimeter (DSC), static electricity accumulation, special height, thermal conductivity, and detonation velocity. The results showed that the mixture of rGO and CNT had better effect in thermal conductivity than rGO or CNT alone under the same loading (1 wt%) and it formed a three-dimensional heat-conducting network structure to improve the heat property of the system. Besides, the linear fit proved that the thermal conductivity of the CL-20-based composites were negatively correlated with the impact sensitivity, which also explained that the impact sensitivity was significantly reduced after the thermal conductivity increased and the explosive still maintained better energy.

  5. Reduce the Sensitivity of CL-20 by Improving Thermal Conductivity Through Carbon Nanomaterials

    Science.gov (United States)

    Wang, Shuang; An, Chongwei; Wang, Jingyu; Ye, Baoyun

    2018-03-01

    The graphene (rGO) and carbon nanotube (CNT) were adopted to enhance the thermal conductivity of CL-20-based composites as conductive fillers. The microstructure features were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and tested the properties by differential scanning calorimeter (DSC), static electricity accumulation, special height, thermal conductivity, and detonation velocity. The results showed that the mixture of rGO and CNT had better effect in thermal conductivity than rGO or CNT alone under the same loading (1 wt%) and it formed a three-dimensional heat-conducting network structure to improve the heat property of the system. Besides, the linear fit proved that the thermal conductivity of the CL-20-based composites were negatively correlated with the impact sensitivity, which also explained that the impact sensitivity was significantly reduced after the thermal conductivity increased and the explosive still maintained better energy.

  6. Complementary variational principle method applied to thermal conductivities of a plasma in a uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Sehgal, A K; Gupta, S C [Punjabi Univ., Patiala (India). Dept. of Physics

    1982-12-14

    The complementary variational principles method (CVP) is applied to the thermal conductivities of a plasma in a uniform magnetic field. The results of computations show that the CVP derived results are very useful.

  7. Modeling electrical conductivities of nanocomposites with aligned carbon nanotubes

    International Nuclear Information System (INIS)

    Bao, W S; Meguid, S A; Zhu, Z H; Meguid, M J

    2011-01-01

    We have developed an improved three-dimensional (3D) percolation model to investigate the effect of the alignment of carbon nanotubes (CNTs) on the electrical conductivity of nanocomposites. In this model, both intrinsic and contact resistances are considered, and a new method of resistor network recognition that employs periodically connective paths is developed. This method leads to a reduction in the size effect of the representative cuboid in our Monte Carlo simulations. With this new technique, we were able to effectively analyze the effects of the CNT alignment upon the electrical conductivity of nanocomposites. Our model predicted that the peak value of the conductivity occurs for partially aligned rather than perfectly aligned CNTs. It has also identified the value of the peak and the corresponding alignment for different volume fractions of CNTs. Our model works well for both multi-wall CNTs (MWCNTs) and single-wall CNTs (SWCNTs), and the numerical results show a quantitative agreement with existing experimental observations.

  8. Quantum Hall Conductivity and Topological Invariants

    Science.gov (United States)

    Reyes, Andres

    2001-04-01

    A short survey of the theory of the Quantum Hall effect is given emphasizing topological aspects of the quantization of the conductivity and showing how topological invariants can be derived from the hamiltonian. We express these invariants in terms of Chern numbers and show in precise mathematical terms how this relates to the Kubo formula.

  9. Sodium conducting polymer electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Skaarup, S.; West, K. (eds.)

    1989-04-01

    This section deals with the aspects of ionic conduction in general as well as specific experimental results obtained for sodium systems. The conductivity as a function of temperature and oxygen/metal ratio are given for the systems NaI, NaCF/sub 3/SO/sub 3/ and NaClO/sub 4/ plus polyethylene oxide. Attempts have been made to produce mixed phase solid electrolytes analogous to the lithium systems that have worked well. These consist of mixtures of polymer and a solid electrolyte. The addition of both nasicon and sodium beta alumina unexpectedly decreases the ionic conductivity in contrast to the lithium systems. Addition of the nonconducting silica AEROSIL in order to increase the internal surface area has the effect of retarding the phase transition at 60 deg. C, but does not enhance the conductivity. (author) 23 refs.

  10. Thermal conductivity measurement of the He-ion implanted layer of W using transient thermoreflectance technique

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Shilian; Li, Yuanfei [Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Wang, Zhigang [Department of Electronic Engineering, Dalian University of Technology, Dalian 116024 (China); Jia, Yuzhen [Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China, Chengdu 610213 (China); Li, Chun [School of Mechanical and Materials Engineering, North China University of Technology, Beijing 100144 (China); Xu, Ben; Chen, Wanqi [Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Bai, Suyuan [School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029 (China); Huang, Zhengxing; Tang, Zhenan [Department of Electronic Engineering, Dalian University of Technology, Dalian 116024 (China); Liu, Wei, E-mail: liuw@mail.tsinghua.edu.cn [Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2017-02-15

    Transient thermoreflectance method was applied on the thermal conductivity measurement of the surface damaged layer of He-implanted tungsten. Uniform damages tungsten surface layer was produced by multi-energy He-ion implantation with thickness of 450 nm. Result shows that the thermal conductivity is reduced by 90%. This technique was further applied on sample with holes on the surface, which was produced by the He-implanted at 2953 K. The thermal conductivity decreases to 3% from the bulk value.

  11. Characterization of dispersed and aggregated Al2O3 morphologies for predicting nanofluid thermal conductivities

    International Nuclear Information System (INIS)

    Feng Xuemei; Johnson, Drew W.

    2013-01-01

    Nanofluids are reported to have enhanced thermal conductivities resulting from nanoparticle aggregation. The goal of this study was to explore through experimental measurements, dispersed and aggregated morphology effects on enhanced thermal conductivities for Al 2 O 3 nanoparticles with a primary size of 54.2 ± 2.0 nm. Aggregation effects were investigated by measuring thermal conductivity of different particle morphologies that occurred under different aggregation conditions. Fractal dimensions and aspect ratios were used to quantify the aggregation morphologies. Fractal dimensions were measured using static light scattering and imaging techniques. Aspect ratios were measured using dynamic light scattering, scanning electron microscopy, and atomic force microscopy. Results showed that the enhancements in thermal conductivity can be predicted with effective medium theory when aspect ratio was considered.

  12. Stereochemistry-Dependent Proton Conduction in Proton Exchange Membrane Fuel Cells.

    Science.gov (United States)

    Thimmappa, Ravikumar; Devendrachari, Mruthyunjayachari Chattanahalli; Kottaichamy, Alagar Raja; Tiwari, Omshanker; Gaikwad, Pramod; Paswan, Bhuneshwar; Thotiyl, Musthafa Ottakam

    2016-01-12

    Graphene oxide (GO) is impermeable to H2 and O2 fuels while permitting H(+) shuttling, making it a potential candidate for proton exchange membrane fuel cells (PEMFC), albeit with a large anisotropy in their proton transport having a dominant in plane (σIP) contribution over the through plane (σTP). If GO-based membranes are ever to succeed in PEMFC, it inevitably should have a dominant through-plane proton shuttling capability (σTP), as it is the direction in which proton gets transported in a real fuel-cell configuration. Here we show that anisotropy in proton conduction in GO-based fuel cell membranes can be brought down by selectively tuning the geometric arrangement of functional groups around the dopant molecules. The results show that cis isomer causes a selective amplification of through-plane proton transport, σTP, pointing to a very strong geometry angle in ionic conduction. Intercalation of cis isomer causes significant expansion of GO (001) planes involved in σTP transport due to their mutual H-bonding interaction and efficient bridging of individual GO planes, bringing down the activation energy required for σTP, suggesting the dominance of a Grotthuss-type mechanism. This isomer-governed amplification of through-plane proton shuttling resulted in the overall boosting of fuel-cell performance, and it underlines that geometrical factors should be given prime consideration while selecting dopant molecules for bringing down the anisotropy in proton conduction and enhancing the fuel-cell performance in GO-based PEMFC.

  13. Electrical and Thermal Conductivity and Conduction Mechanism of Ge2Sb2Te5 Alloy

    Science.gov (United States)

    Lan, Rui; Endo, Rie; Kuwahara, Masashi; Kobayashi, Yoshinao; Susa, Masahiro

    2018-06-01

    Ge2Sb2Te5 alloy has drawn much attention due to its application in phase-change random-access memory and potential as a thermoelectric material. Electrical and thermal conductivity are important material properties in both applications. The aim of this work is to investigate the temperature dependence of the electrical and thermal conductivity of Ge2Sb2Te5 alloy and discuss the thermal conduction mechanism. The electrical resistivity and thermal conductivity of Ge2Sb2Te5 alloy were measured from room temperature to 823 K by four-terminal and hot-strip method, respectively. With increasing temperature, the electrical resistivity increased while the thermal conductivity first decreased up to about 600 K then increased. The electronic component of the thermal conductivity was calculated from the Wiedemann-Franz law using the resistivity results. At room temperature, Ge2Sb2Te5 alloy has large electronic thermal conductivity and low lattice thermal conductivity. Bipolar diffusion contributes more to the thermal conductivity with increasing temperature. The special crystallographic structure of Ge2Sb2Te5 alloy accounts for the thermal conduction mechanism.

  14. Electrical and Thermal Conductivity and Conduction Mechanism of Ge2Sb2Te5 Alloy

    Science.gov (United States)

    Lan, Rui; Endo, Rie; Kuwahara, Masashi; Kobayashi, Yoshinao; Susa, Masahiro

    2017-11-01

    Ge2Sb2Te5 alloy has drawn much attention due to its application in phase-change random-access memory and potential as a thermoelectric material. Electrical and thermal conductivity are important material properties in both applications. The aim of this work is to investigate the temperature dependence of the electrical and thermal conductivity of Ge2Sb2Te5 alloy and discuss the thermal conduction mechanism. The electrical resistivity and thermal conductivity of Ge2Sb2Te5 alloy were measured from room temperature to 823 K by four-terminal and hot-strip method, respectively. With increasing temperature, the electrical resistivity increased while the thermal conductivity first decreased up to about 600 K then increased. The electronic component of the thermal conductivity was calculated from the Wiedemann-Franz law using the resistivity results. At room temperature, Ge2Sb2Te5 alloy has large electronic thermal conductivity and low lattice thermal conductivity. Bipolar diffusion contributes more to the thermal conductivity with increasing temperature. The special crystallographic structure of Ge2Sb2Te5 alloy accounts for the thermal conduction mechanism.

  15. Conduction mechanism studies on electron transfer of disordered system

    Institute of Scientific and Technical Information of China (English)

    徐慧; 宋祎璞; 李新梅

    2002-01-01

    Using the negative eigenvalue theory and the infinite order perturbation theory, a new method was developed to solve the eigenvectors of disordered systems. The result shows that eigenvectors change from the extended state to the localized state with the increase of the site points and the disordered degree of the system. When electric field is exerted, the electrons transfer from one localized state to another one. The conductivity is induced by the electron transfer. The authors derive the formula of electron conductivity and find the electron hops between localized states whose energies are close to each other, whereas localized positions differ from each other greatly. At low temperature the disordered system has the character of the negative differential dependence of resistivity and temperature.

  16. Research on the conductivity of a haptic sensor, especially with the sensor under extended condition

    Science.gov (United States)

    Zheng, Yaoyang; Shimada, Kunio

    2008-11-01

    The present paper describes the application of magnetic compound fluid (MCF) rubber as a haptic sensor for use as a material for robot sensors, artificial skin, and so on. MCF rubber is one of several new composite materials utilizing the MCF magnetic responsive fluid developed by Shimada. By applying MCF to silicon oil rubber, we can make MCF rubber highly sensitive to temperature and electric conduction. By mixing Cu and Ni particles in the silicon oil rubber and then applying a strong magnetic field, we can produce magnetic clusters at high density. The clusters form a network, as confirmed by optical observation. The MCF rubber with small deformations can act as an effective sensor. We report herein several experiments in which changes in the MCF rubber's resistance were observed when the rubber was compressed and a deformation was generated. We then made a trial haptic sensor using the MCF conductive rubber and performed many experiments to observe changes in the electrical resistance of the sensor. The experimental results showed that the proposed sensor made with MCF conductive rubber is useful for sensing small amounts of pressure or small deformations. Sometimes, however, the sensor rubber will be extended when we apply this sensor to the finger of the robot or an elbow. In these cases, it is necessary to understand the changes in sensor's conductivity. We therefore carried out some experiments to demonstrate how, under tensile conditions, the sensor's conductivity changes to a small value easier than the sensor in free condition. The results show that the sensors became more sensitive to the same pressure under extended conditions. In the present paper, we first describe the new type of functional fluid MCF rubber and a new composite material based on this MCF fluid. We then explain the production method for MCF conductive rubber and its conductive algorithm. Finally, we report our results regarding the MCF sensitivity when the MCF rubber was pulled

  17. Investigation of the technology of conductive yarns manufacturing

    Science.gov (United States)

    Ryklin, Dzmitry; Medvetski, Sergey

    2017-10-01

    The paper is devoted to development of technology of electrically conductive yarn production. This technology allows manufacturing conductive yarns of copper wire and polyester filament yarns. Method of the predicting of the conductive yarn breaking force was developed on the base of analysing of load-elongation curves of each strand of the yarn. Also the method of the predicting of the conductive yarn diameter was offered. Investigation shows that conductive yarns can be integrated into the textiles structure using sewing or embroidery equipment. Application of developed conductive yarn is wearable electronics creating with wide range of functions, for example, for specific health issue monitoring, navigation tools or communication gadgets.

  18. Influence factors of sand-bentonite mixtures on hydraulic conductivity

    International Nuclear Information System (INIS)

    Chen Yonggui; Ye Weimin; Chen Bao; Wan Min; Wang Qiong

    2008-01-01

    Buffer material is a very important part of the engineering barrier for geological disposal of high-level radioactive nuclear waste. Compacted bentonite is attracting greater attention as buffer and backfill material because it offer impermeability and swelling properties, but the pure compacted bentonite strength decreases with increasing hydration and these will reduce the buffer capability. To solve this problem, sand is often used to form compacted sand-bentonite mixtures (SBMs) providing high thermal conductivity, excellent compaction capacity, long-time stability, and low engineering cost. As to SBMs, hydraulic conductivity is a important index for evaluation barrier capability. Based on the review of research results, the factors affecting the hydraulic conductivity of SBMs were put forward including bentonite content, grain size distribution, moisture content, dry density, compacting method and energy, and bentonite type. The studies show that the hydraulic conductivity of SBMs is controlled by the hydraulic conductivity of the bentonite, it also decreases as dry density and bentonite content increase, but when the bentonite content reach a critical point, the influence of increasing bentonite to decrease the hydraulic conductivity is limited. A fine and well-graded SBMs is likely to have a lower hydraulic conductivity than a coarse and poorly graded material. The internal erosion or erodibility based on the grain size distribution of the SBMs has a negative effect on the final hydraulic conductivity. The lowest hydraulic conductivity is gained when the mixtures are compacted close to optimum moisture content. Also, the mixtures compacted at moisture contents slightly above optimum values give lower hydraulic conductivity than when compacted at slightly under the optimum moisture content. Finally, discussion was brought to importance of compaction method, compacting energy, and bentonite type to the hydraulic conductivity of SBMs. (authors)

  19. Quantum conductance in silicon quantum wires

    CERN Document Server

    Bagraev, N T; Klyachkin, L E; Malyarenko, A M; Gehlhoff, W; Ivanov, V K; Shelykh, I A

    2002-01-01

    The results of investigations of electron and hole quantum conductance staircase in silicon quantum wires are presented. The characteristics of self-ordering quantum wells of n- and p-types, which from on the silicon (100) surface in the nonequilibrium boron diffusion process, are analyzed. The results of investigations of the quantum conductance as the function of temperature, carrier concentration and modulation degree of silicon quantum wires are given. It is found out, that the quantum conductance of the one-dimensional channels is observed, for the first time, at an elevated temperature (T >= 77 K)

  20. High proton conductivity in the molecular interlayer of a polymer nanosheet multilayer film.

    Science.gov (United States)

    Sato, Takuma; Hayasaka, Yuta; Mitsuishi, Masaya; Miyashita, Tokuji; Nagano, Shusaku; Matsui, Jun

    2015-05-12

    High proton conductivity was achieved in a polymer multilayer film with a well-defined two-dimensional lamella structure. The multilayer film was prepared by deposition of poly(N-dodecylacryamide-co-acrylic acid) (p(DDA/AA)) monolayers onto a solid substrate using the Langmuir-Blodgett technique. Grazing-angle incidence X-ray diffraction measurement of a 30-layer film of p(DDA/AA) showed strong diffraction peaks in the out-of-plane direction at 2θ = 2.26° and 4.50°, revealing that the multilayer film had a highly uniform layered structure with a monolayer thickness of 2.0 nm. The proton conductivity of the p(DDA/AA) multilayer film parallel to the layer plane direction was 0.051 S/cm at 60 °C and 98% relative humidity with a low activation energy of 0.35 eV, which is comparable to perfluorosulfonic acid membranes. The high conductivity and low activation energy resulted from the formation of uniform two-dimensional proton-conductive nanochannels in the hydrophilic regions of the multilayer film. The proton conductivity of the multilayer film perpendicular to the layer plane was determined to be 2.1 × 10(-13) S/cm. Therefore, the multilayer film showed large anisotropic conductivity with an anisotropic ratio of 2.4 × 10(11).

  1. Effect of heat treatment temperature on binder thermal conductivities

    International Nuclear Information System (INIS)

    Wagner, P.

    1975-12-01

    The effect of heat treatment on the thermal conductivities of a pitch and a polyfurfuryl alcohol binder residue was investigated. Graphites specially prepared with these two binders were used for the experiments. Measured thermal conductivities were treated in terms of a two-component system, and the binder thermal conductivities were calculated. Both binder residues showed increased thermal conductivity with increased heat treatment temperature

  2. Nuclear Spin Lattice Relaxation and Conductivity Studies of the Non-Arrhenius Conductivity Behavior in Lithium Fast Ion Conducting Sulfide Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Benjamin Michael [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, τ, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single

  3. Electrical conductivity of high-purity germanium crystals at low temperature

    Science.gov (United States)

    Yang, Gang; Kooi, Kyler; Wang, Guojian; Mei, Hao; Li, Yangyang; Mei, Dongming

    2018-05-01

    The temperature dependence of electrical conductivity of single-crystal and polycrystalline high-purity germanium (HPGe) samples has been investigated in the temperature range from 7 to 100 K. The conductivity versus inverse of temperature curves for three single-crystal samples consist of two distinct temperature ranges: a high-temperature range where the conductivity increases to a maximum with decreasing temperature, and a low-temperature range where the conductivity continues decreasing slowly with decreasing temperature. In contrast, the conductivity versus inverse of temperature curves for three polycrystalline samples, in addition to a high- and a low-temperature range where a similar conductive behavior is shown, have a medium-temperature range where the conductivity decreases dramatically with decreasing temperature. The turning point temperature ({Tm}) which corresponds to the maximum values of the conductivity on the conductivity versus inverse of temperature curves are higher for the polycrystalline samples than for the single-crystal samples. Additionally, the net carrier concentrations of all samples have been calculated based on measured conductivity in the whole measurement temperature range. The calculated results show that the ionized carrier concentration increases with increasing temperature due to thermal excitation, but it reaches saturation around 40 K for the single-crystal samples and 70 K for the polycrystalline samples. All these differences between the single-crystal samples and the polycrystalline samples could be attributed to trapping and scattering effects of the grain boundaries on the charge carriers. The relevant physical models have been proposed to explain these differences in the conductive behaviors between two kinds of samples.

  4. Improved estimation of hydraulic conductivity by combining stochastically simulated hydrofacies with geophysical data.

    Science.gov (United States)

    Zhu, Lin; Gong, Huili; Chen, Yun; Li, Xiaojuan; Chang, Xiang; Cui, Yijiao

    2016-03-01

    Hydraulic conductivity is a major parameter affecting the output accuracy of groundwater flow and transport models. The most commonly used semi-empirical formula for estimating conductivity is Kozeny-Carman equation. However, this method alone does not work well with heterogeneous strata. Two important parameters, grain size and porosity, often show spatial variations at different scales. This study proposes a method for estimating conductivity distributions by combining a stochastic hydrofacies model with geophysical methods. The Markov chain model with transition probability matrix was adopted to re-construct structures of hydrofacies for deriving spatial deposit information. The geophysical and hydro-chemical data were used to estimate the porosity distribution through the Archie's law. Results show that the stochastic simulated hydrofacies model reflects the sedimentary features with an average model accuracy of 78% in comparison with borehole log data in the Chaobai alluvial fan. The estimated conductivity is reasonable and of the same order of magnitude of the outcomes of the pumping tests. The conductivity distribution is consistent with the sedimentary distributions. This study provides more reliable spatial distributions of the hydraulic parameters for further numerical modeling.

  5. Hydrogen ion conducting starch-chitosan blend based electrolyte for application in electrochemical devices

    International Nuclear Information System (INIS)

    Shukur, M.F.; Kadir, M.F.Z.

    2015-01-01

    Highlights: • Cation transference number of the highest conducting starch-chitosan-NH 4 Cl-glycerol electrolyte is 0.56. • LSV has shown that the polymer electrolyte is suitable for fabrication of EDLC and proton batteries. • The fabricated EDLC has been charged and discharged for 500 cycles. • Secondary proton battery has been charged and discharged for 40 cycles. - Abstract: This paper reports the characterization of starch-chitosan blend based solid polymer electrolyte (SPE) system and its application in electrochemical double layer capacitor (EDLC) and proton batteries. All the SPEs are prepared via solution cast technique. Results from X-ray diffraction (XRD) verify the conductivity result from our previous work. Scanning electron microscopy (SEM) analysis shows the difference in the electrolyte's surface with respect to NH 4 Cl and glycerol content. From transference number measurements (TNM), transference number of ion (t ion ) of the electrolytes shows that ion is the dominant conducting species. Transference number of cation (t + ) for the highest conducting electrolyte is found to be 0.56. Linear sweep voltammetry (LSV) result confirms the suitability of the highest conducting electrolyte to be used in the fabrication of EDLC and proton batteries. The EDLC has been characterized using cyclic voltammetry (CV) and galvanostatic charge-discharge measurements. The open circuit potential (OCP) of the primary proton batteries for 48 h is lasted at (1.54 ± 0.02) V, while that of secondary proton batteries is lasted at (1.58 ± 0.01) V. The primary proton batteries have been discharged at different constant currents. The secondary proton battery has been charged and discharged for 40 cycles

  6. Conduction at domain walls in oxide multiferroics

    Science.gov (United States)

    Seidel, J.; Martin, L. W.; He, Q.; Zhan, Q.; Chu, Y.-H.; Rother, A.; Hawkridge, M. E.; Maksymovych, P.; Yu, P.; Gajek, M.; Balke, N.; Kalinin, S. V.; Gemming, S.; Wang, F.; Catalan, G.; Scott, J. F.; Spaldin, N. A.; Orenstein, J.; Ramesh, R.

    2009-03-01

    Domain walls may play an important role in future electronic devices, given their small size as well as the fact that their location can be controlled. Here, we report the observation of room-temperature electronic conductivity at ferroelectric domain walls in the insulating multiferroic BiFeO3. The origin and nature of the observed conductivity are probed using a combination of conductive atomic force microscopy, high-resolution transmission electron microscopy and first-principles density functional computations. Our analyses indicate that the conductivity correlates with structurally driven changes in both the electrostatic potential and the local electronic structure, which shows a decrease in the bandgap at the domain wall. Additionally, we demonstrate the potential for device applications of such conducting nanoscale features.

  7. Versatile and Tunable Transparent Conducting Electrodes Based on Doped Graphene

    KAUST Repository

    Mansour, Ahmed E.

    2016-11-25

    The continued growth of the optoelectronics industry and the emergence of wearable and flexible electronics will continue to place an ever increasing pressure on replacing ITO, the most widely used transparent conducting electrode (TCE). Among the various candidates, graphene shows the highest optical transmittance in addition to promising electrical transport properties. The currently available large-scale synthesis routes of graphene result in polycrystalline samples rife with grain boundaries and other defects which limit its transport properties. Chemical doping of graphene is a viable route towards increasing its conductivity and tuning its work function. However, dopants are typically present at the surface of the graphene sheet, making them highly susceptible to degradation in environmental conditions. Few-layers graphene (FLG) is a more resilient form of graphene exhibiting higher conductivity and performance stability under stretching and bending as contrasted to single-layer graphene. In addition FLG presents the advantage of being amenable bulk doping by intercalation. Herein, we explore non-covalent doping routes of CVD FLG, such as surface doping, intercalation and combination thereof, through in-depth and systematic characterization of the electrical transport properties and energy levels shifts. The intercalation of FLG with Br2 and FeCl3 is demonstrated, showing the highest improvements of the figure of merit of TCEs of any doping scheme, which results from up to a five-fold increase in conductivity while maintaining the transmittance within 3% of that for the pristine value. Importantly the intercalation yields TCEs that are air-stable, due to encapsulation of the intercalant in the bulk of FLG. Surface doping with novel solution-processed metal-organic molecular species (n- and p-type) is demonstrated with an unprecedented range of work function modulation, resulting from electron transfer and the formation of molecular surface dipoles. However

  8. AC conductivity for a holographic Weyl semimetal

    Energy Technology Data Exchange (ETDEWEB)

    Grignani, Gianluca; Marini, Andrea; Peña-Benitez, Francisco; Speziali, Stefano [Dipartimento di Fisica e Geologia, Università di Perugia,I.N.F.N. Sezione di Perugia,Via Pascoli, I-06123 Perugia (Italy)

    2017-03-23

    We study the AC electrical conductivity at zero temperature in a holographic model for a Weyl semimetal. At small frequencies we observe a linear dependence in the frequency. The model shows a quantum phase transition between a topological semimetal (Weyl semimetal phase) with a non vanishing anomalous Hall conductivity and a trivial semimetal. The AC conductivity has an intermediate scaling due to the presence of a quantum critical region in the phase diagram of the system. The phase diagram is reconstructed using the scaling properties of the conductivity. We compare with the experimental data of https://www.doi.org/10.1103/PhysRevB.93.121110 obtaining qualitative agreement.

  9. Corneal iron ring after conductive keratoplasty.

    Science.gov (United States)

    Kymionis, George D; Naoumidi, Tatiana L; Aslanides, Ioannis M; Pallikaris, Ioannis G

    2003-08-01

    To report formation of corneal iron ring deposits after conductive keratoplasty. Observational case report. Case report. A 54-year-old woman underwent conductive keratoplasty for hyperopia. One year after conductive keratoplasty, iron ring pattern pigmentation was detected at the corneal epithelium of both eyes. This is the first report of the appearance of corneal iron ring deposits following conductive keratoplasty treatment in a patient. It is suggested that alterations in tear film stability, resulting from conductive keratoplasty-induced changes in corneal curvature, constitute the contributory factor for these deposits.

  10. Phononic thermal conductivity in silicene: the role of vacancy defects and boundary scattering

    Science.gov (United States)

    Barati, M.; Vazifehshenas, T.; Salavati-fard, T.; Farmanbar, M.

    2018-04-01

    We calculate the thermal conductivity of free-standing silicene using the phonon Boltzmann transport equation within the relaxation time approximation. In this calculation, we investigate the effects of sample size and different scattering mechanisms such as phonon–phonon, phonon-boundary, phonon-isotope and phonon-vacancy defect. We obtain some similar results to earlier works using a different model and provide a more detailed analysis of the phonon conduction behavior and various mode contributions. We show that the dominant contribution to the thermal conductivity of silicene, which originates from the in-plane acoustic branches, is about 70% at room temperature and this contribution becomes larger by considering vacancy defects. Our results indicate that while the thermal conductivity of silicene is significantly suppressed by the vacancy defects, the effect of isotopes on the phononic transport is small. Our calculations demonstrate that by removing only one of every 400 silicon atoms, a substantial reduction of about 58% in thermal conductivity is achieved. Furthermore, we find that the phonon-boundary scattering is important in defectless and small-size silicene samples, especially at low temperatures.

  11. Conductive stability of graphene on PET and glass substrates under blue light irradiation

    Science.gov (United States)

    Cao, Xueying; Liu, Xianming; Li, Xiangdi; Lei, Xiaohua; Chen, Weimin

    2018-01-01

    Electrical properties of graphene transparent conductive film under visible light irradiation are investigated. The CVD-grown graphene on Polyethylene Terephthalate (PET) and glass substrates for flexible and rigid touch screen display application are chosen for research. The resistances of graphene with and without gold trichloride (AuCl3) doping are measured in vacuum and atmosphere environment under blue light irradiation. Results show that the conductivities of all samples change slowly under light irradiation. The change rate and degree are related to the substrate material, doping, environment and lighting power. Graphene on flexible PET substrate is more stable than that on rigid glass substrate. Doping can improve the electrical conductivity but induce instability under light irradiation. Finally, the main reason resulting in the graphene resistance slowly increasing under blue light irradiation is analyzed.

  12. Thermal conductivity of REIn3 compounds

    International Nuclear Information System (INIS)

    Mucha, J

    2006-01-01

    The results of measurements of the thermal conductivity of REIn 3 (RE Pr, Nd, Dy, Ho, Tm) compounds as a function of the temperature in the interval 4-300 K in the absence and in the presence of an external magnetic field of 8 T are presented. Except for PRIn 3 all the compounds are antiferromagnetic. YIn 3 was also measured as a reference compound. The results were analysed in the paramagnetic phase, where an influence of the crystalline electric field on the thermal conductivity was found. Drastic changes in the thermal conductivity were observed and analysed in the vicinity of the Neel temperature and in the antiferromagnetic phases of the compounds. Below the Neel temperature an additional magnon contribution to the thermal conductivity was separated out

  13. Surface conductivity of Mercury provides current closure and may affect magnetospheric symmetry

    Directory of Open Access Journals (Sweden)

    P. Janhunen

    2004-04-01

    Full Text Available We study what effect a possible surface conductivity of Mercury has on the closure of magnetospheric currents by making six runs with a quasi-neutral hybrid simulation. The runs are otherwise identical but use different synthetic conductivity models: run 1 has a fully conducting planet, run 2 has a poorly conducting planet ( m and runs 3-6 have one of the hemispheres either in the dawn-dusk or day-night directions, conducting well, the other one being conducting poorly. Although the surface conductivity is not known from observations, educated guesses easily give such conductivity values that magnetospheric currents may close partly within the planet, and as the conductivity depends heavily on the mineral composition of the surface, the possibility of significant horizontal variations cannot be easily excluded. The simulation results show that strong horizontal variations may produce modest magnetospheric asymmetries. Beyond the hybrid simulation, we also briefly discuss the possibility that in the nightside there may be a lack of surface electrons to carry downward current, which may act as a further source of surface-related magnetospheric asymmetry. Key words. Magnetospheric physics (planetary magnetospheres; current systems; solar wind-magnetosphere interactions.6

  14. Thermal conductivity of granular materials

    Energy Technology Data Exchange (ETDEWEB)

    Buyevich, Yu A

    1974-01-01

    Stationary heat transfer in a granular material consisting of a continuous medium containing spherical granules of other substances is considered under the assumption that the spatial distribution of granules is random. The effective thermal conductivity characterizing macroscopic heat transfer in such a material is expressed as a certain function of the conductivities and volume fractions of the medium and dispersed substances. For reasons of mathematical analogy, all the results obtained for the thermal conductivity are valid while computing the effective diffusivity of some admixture in granular materials as well as for evaluation of the effective electric conductivity or the mean dielectric and magnetic permeabilities of granular conductors and dielectrics. (23 refs.)

  15. Electrically conductive, immobilized bioanodes for microbial fuel cells

    International Nuclear Information System (INIS)

    Ganguli, R; Dunn, B

    2012-01-01

    The power densities of microbial fuel cells with yeast cells as the anode catalyst were significantly increased by immobilizing the yeast in electrically conductive alginate electrodes. The peak power densities measured as a function of the electrical conductivity of the immobilized electrodes show that although power increases with rising electrical conductivity, it tends to saturate beyond a certain point. Changing the pH of the anode compartment at that point seems to further increase the power density, suggesting that proton transport limitations and not electrical conductivity will limit the power density from electrically conductive immobilized anodes. (paper)

  16. Davedan Show Di Amphi Theatre Nusa Dua Bali

    Directory of Open Access Journals (Sweden)

    Ni Made Ruastiti

    2018-05-01

    Bali karena berimplikasi positif pada ekonomi para pihak terkait, pengayaan bagi seni pertunjukan daerah setempat, dan identitas bagi kawasan wisata Nusa Dua, Bali. This article was compiled from the research results that aimed to understand the Davedan Show at Amphi Theater Nusa Dua, Bali. This research was conducted due to the imbalance between the assumption and the reality in real life. Generally, tourists visiting Bali are more excited and enthusiastic to watch the tourism performing arts that are based on local traditional art and culture. However, the reality is different. The questions are: how is the form of the Davedan show?; why do the tourists enjoy watching the show ?; what are the implications for the performer, the society, and the tourism industry in Nusa Dua, Bali?. This research applied qualitative research methods, especially the participative implementation that prioritized cooperation between the researchers and the related informants. The data sources of the research were the Davedan show, management, dancers, audiences, and similar research results produced by previous researchers. All data that had been collected by observation, interview, FGD, and literature study were then analyzed with aesthetic postmodern theory, theory of practice, and theory of power relationship. The results showed that: (1 Davedan Show was presented with the concept of a new presentation in the tourism performing arts in Bali. It could be seen from the material, the form, the way of presentation, and the management of the show. Davedan Show, presenting the theme of Treasure of the Archipelago and opening the new adventure gate, was accompanied by ethnic music recordings of the archipelago in a medley then continued with the performance structures of: Balinese, Sumatran, Sundanese, Solo, Borneo and Papuan art and culture; (2 Davedan Show attracted many foreign tourists because the show was based on the existence of market, aesthetic, and cultural ideologies of the

  17. Effect of adverse childhood experiences on physical health in adulthood: Results of a study conducted in Baghdad city

    Directory of Open Access Journals (Sweden)

    Ameel F Al-Shawi

    2015-01-01

    Full Text Available Background: Studies have revealed a powerful relationship between adverse childhood experiences (ACEs and physical and mental health in adulthood. Literature documents the conversion of traumatic emotional experiences in childhood into organic disease later in life. Objective: The aim was to estimate the effect of childhood experiences on the physical health of adults in Baghdad city. Subjects and Methods: A cross-sectional study was conducted from January 2013 to January 2014. The study sample was drawn from Baghdad city. Multistage sampling techniques were used in choosing 13 primary health care centers and eight colleges of three universities in Baghdad. In addition, teachers of seven primary schools and two secondary schools were chosen by a convenient method. Childhood experiences were measured by applying a modified standardized ACEs-International Questionnaire form and with questions for bonding to family and parental monitoring. Physical health assessment was measured by a modified questionnaire derived from Health Appraisal Questionnaire of Centers for Disease Control and Prevention. The questionnaire includes questions on cerebrovascular diseases, diabetes mellitus, tumor, respiratory and gastrointestinal diseases. Results: Logistic regression model showed that a higher level of bonding to family (fourth quartile is expected to reduce the risk of chronic physical diseases by almost the half (odds ratio = 0.57 and exposure to a high level of household dysfunction and abuse (fourth quartile is expected to increase the risk of chronic physical diseases by 81%. Conclusion: Childhood experiences play a major role in the determination of health outcomes in adulthood, and early prevention of ACEs. Encouraging strong family bonding can promote physical health in later life.

  18. Conducting interactive experiments online.

    Science.gov (United States)

    Arechar, Antonio A; Gächter, Simon; Molleman, Lucas

    2018-01-01

    Online labor markets provide new opportunities for behavioral research, but conducting economic experiments online raises important methodological challenges. This particularly holds for interactive designs. In this paper, we provide a methodological discussion of the similarities and differences between interactive experiments conducted in the laboratory and online. To this end, we conduct a repeated public goods experiment with and without punishment using samples from the laboratory and the online platform Amazon Mechanical Turk. We chose to replicate this experiment because it is long and logistically complex. It therefore provides a good case study for discussing the methodological and practical challenges of online interactive experimentation. We find that basic behavioral patterns of cooperation and punishment in the laboratory are replicable online. The most important challenge of online interactive experiments is participant dropout. We discuss measures for reducing dropout and show that, for our case study, dropouts are exogenous to the experiment. We conclude that data quality for interactive experiments via the Internet is adequate and reliable, making online interactive experimentation a potentially valuable complement to laboratory studies.

  19. A conductivity study of preferential solvation of lithium ion in acetonitrile-dimethyl sulfoxide mixtures

    International Nuclear Information System (INIS)

    Mozhzhukhina, Nataliia; Longinotti, M. Paula; Corti, Horacio R.; Calvo, Ernesto J.

    2015-01-01

    The electrical mobility of LiPF 6 in acetonitrile–dimethyl sulfoxide (ACN–DMSO) mixtures, a potential electrolyte in oxygen cathodes of lithium-air batteries, has been studied using a very precise conductance technique, which allowed the determination of the infinite dilution molar conductivity and association constant of the salt in the whole composition range. In the search for preferential Li + ion solvation, we also measured the electrical conductivity of tetrabutylammonium hexafluorophosphate (TBAPF 6 ), a salt formed by a bulky cation, over the same composition range. The results show a qualitative change in the curvature of the LiPF 6 molar conductivity composition dependence for ACN molar fraction (x ACN ) ∼ 0.95, which was not observed for TBAPF 6 . The dependence of the measured Li/Li + couple potential with solvent composition also showed a pronounced change around the same composition. We suggest that these observations can be explained by Li + ion preferential solvation by DMSO in ACN–DMSO mixtures with very low molar fractions of DMSO

  20. Thermal conductance of nanofluids: is the controversy over?

    International Nuclear Information System (INIS)

    Keblinski, Pawel; Prasher, Ravi; Eapen, Jacob

    2008-01-01

    Over the last decade nanofluids (colloidal suspensions of solid nanoparticles) sparked excitement as well as controversy. In particular, a number of researches reported dramatic increases of thermal conductivity with small nanoparticle loading, while others showed moderate increases consistent with the effective medium theories on well-dispersed conductive spheres. Accordingly, the mechanism of thermal conductivity enhancement is a hotly debated topic. We present a critical analysis of the experimental data in terms of the potential mechanisms and show that, by accounting for linear particle aggregation, the well established effective medium theories for composite materials are capable of explaining the vast majority of the reported data without resorting to novel mechanisms such as Brownian motion induced nanoconvection, liquid layering at the interface, or near-field radiation. However, particle aggregation required to significantly enhance thermal conductivity, also increases fluid viscosity rendering the benefit of nanofluids to flow based cooling applications questionable.

  1. Strain and thermal conductivity in ultrathin suspended silicon nanowires

    Science.gov (United States)

    Fan, Daniel; Sigg, Hans; Spolenak, Ralph; Ekinci, Yasin

    2017-09-01

    We report on the uniaxial strain and thermal conductivity of well-ordered, suspended silicon nanowire arrays between 10 to 20 nm width and 22 nm half-pitch, fabricated by extreme-ultraviolet (UV) interference lithography. Laser-power-dependent Raman spectroscopy showed that nanowires connected monolithically to the bulk had a consistent strain of ˜0.1 % , whereas nanowires clamped by metal exhibited variability and high strain of up to 2.3%, having implications in strain engineering of nanowires. The thermal conductivity at room temperature was measured to be ˜1 W /m K for smooth nanowires and ˜0.1 W /m K for rougher ones, similar to results by other investigators. We found no modification of the bulk properties in terms of intrinsic scattering, and therefore, the decrease in thermal conductivity is mainly due to boundary scattering. Different types of surface roughness, such as constrictions and line-edge roughness, may play roles in the scattering of phonons of different wavelengths. Such low thermal conductivities would allow for very efficient thermal energy harvesting, approaching and passing values achieved by state-of-the-art thermoelectric materials.

  2. The effective thermal conductivity of porous media based on statistical self-similarity

    International Nuclear Information System (INIS)

    Kou Jianlong; Wu Fengmin; Lu Hangjun; Xu Yousheng; Song Fuquan

    2009-01-01

    A fractal model is presented based on the thermal-electrical analogy technique and statistical self-similarity of fractal saturated porous media. A dimensionless effective thermal conductivity of saturated fractal porous media is studied by the relationship between the dimensionless effective thermal conductivity and the geometrical parameters of porous media with no empirical constant. Through this study, it is shown that the dimensionless effective thermal conductivity decreases with the increase of porosity (φ) and pore area fractal dimension (D f ) when k s /k g >1. The opposite trends is observed when k s /k g t ). The model predictions are compared with existing experimental data and the results show that they are in good agreement with existing experimental data.

  3. Stem cells show promising results for lymphoedema treatment

    DEFF Research Database (Denmark)

    Toyserkani, Navid Mohamadpour; Quaade, Marlene Louise; Sheikh, Søren Paludan

    2015-01-01

    Abstract Lymphoedema is a debilitating condition, manifesting in excess lymphatic fluid and swelling of subcutaneous tissues. Lymphoedema is as of yet still an incurable condition and current treatment modalities are not satisfactory. The capacity of mesenchymal stem cells to promote angiogenesis......, secrete growth factors, regulate the inflammatory process, and differentiate into multiple cell types make them a potential ideal therapy for lymphoedema. Adipose tissue is the richest and most accessible source of mesenchymal stem cells and they can be harvested, isolated, and used for therapy...... in a single stage procedure as an autologous treatment. The aim of this paper was to review all studies using mesenchymal stem cells for lymphoedema treatment with a special focus on the potential use of adipose-derived stem cells. A systematic search was performed and five preclinical and two clinical...

  4. Dynamical electrical conductivity of graphene.

    Science.gov (United States)

    Rani, Luxmi; Singh, Navinder

    2017-06-28

    For graphene (a Dirac material) it has been theoretically predicted and experimentally observed that DC resistivity is proportional to T 4 when the temperature is much less than Bloch-Grüneisen temperature ([Formula: see text]) and T-linear in the opposite case ([Formula: see text]). Going beyond this case, we investigate the dynamical electrical conductivity in graphene using the powerful method of the memory function formalism. In the zero frequency regime, we obtain the above mentioned behavior which was previously obtained using the Bloch-Boltzmann kinetic equation. In the finite frequency regime, we obtain several new results: (1) the generalized Drude scattering rate, in the zero temperature limit, shows [Formula: see text] behavior at low frequencies ([Formula: see text]) and saturates at higher frequencies. We also observed the Holstein mechanism, however, with different power laws from that in the case of metals; (2) at higher frequencies, [Formula: see text], and higher temperatures [Formula: see text], we observed that the generalized Drude scattering rate is linear in temperature. In addition, several other results are also obtained. With the experimental advancement of this field, these results should be experimentally tested.

  5. Tuning Nanocrystal Surface Depletion by Controlling Dopant Distribution as a Route Toward Enhanced Film Conductivity

    Science.gov (United States)

    Staller, Corey M.; Robinson, Zachary L.; Agrawal, Ankit; Gibbs, Stephen L.; Greenberg, Benjamin L.; Lounis, Sebastien D.; Kortshagen, Uwe R.; Milliron, Delia J.

    2018-05-01

    Electron conduction through bare metal oxide nanocrystal (NC) films is hindered by surface depletion regions resulting from the presence of surface states. We control the radial dopant distribution in tin-doped indium oxide (ITO) NCs as a means to manipulate the NC depletion width. We find in films of ITO NCs of equal overall dopant concentration that those with dopant-enriched surfaces show decreased depletion width and increased conductivity. Variable temperature conductivity data shows electron localization length increases and associated depletion width decreases monotonically with increased density of dopants near the NC surface. We calculate band profiles for NCs of differing radial dopant distributions and, in agreement with variable temperature conductivity fits, find NCs with dopant-enriched surfaces have narrower depletion widths and longer localization lengths than those with dopant-enriched cores. Following amelioration of NC surface depletion by atomic layer deposition of alumina, all films of equal overall dopant concentration have similar conductivity. Variable temperature conductivity measurements on alumina-capped films indicate all films behave as granular metals. Herein, we conclude that dopant-enriched surfaces decrease the near-surface depletion region, which directly increases the electron localization length and conductivity of NC films.

  6. A Progress Evaluation of Four Bilingual Children's Television Shows.

    Science.gov (United States)

    Klein, Stephen P.; And Others

    An evaluation of a bilingual education TV series was conducted involving 6-year-old English speaking, Spanish speaking, and bilingual children at four sites. Children were assigned to control and experimental groups with the latter group seeing four 30 minute shows. A pretest-posttest design was employed with the pretest serving as the covariate…

  7. Properties of conductive thick-film inks

    Science.gov (United States)

    Holtze, R. F.

    1972-01-01

    Ten different conductive inks used in the fabrication of thick-film circuits were evaluated for their physical and handling properties. Viscosity, solid contents, and spectrographic analysis of the unfired inks were determined. Inks were screened on ceramic substrates and fired for varying times at specified temperatures. Selected substrates were given additional firings to simulate the heat exposure received if thick-film resistors were to be added to the same substrate. Data are presented covering the (1) printing characteristics, (2) solderability using Sn-63 and also a 4 percent silver solder, (3) leach resistance, (4) solder adhesion, and (5) wire bonding properties. Results obtained using different firing schedules were compared. A comparison was made between the various inks showing general results obtained for each ink. The changes in firing time or the application of a simulated resistor firing had little effect on the properties of most inks.

  8. Conductance Effects on Inner Magnetospheric Plasma Morphology: Model Comparisons with IMAGE EUV, MENA, and HENA Data

    Science.gov (United States)

    Liemohn, M.; Ridley, A. J.; Kozyra, J. U.; Gallagher, D. L.; Brandt, P. C.; Henderson, M. G.; Denton, M. H.; Jahn, J. M.; Roelof, E. C.; DeMajistre, R. M.

    2004-01-01

    Modeling results of the inner magnetosphere showing the influence of the ionospheric conductance on the inner magnetospheric electric fields during the April 17, 2002 magnetic storm are presented. Kinetic plasma transport code results are analyzed in combination with observations of the inner magnetospheric plasma populations, in particular those from the IMAGE satellite. Qualitative and quantitative comparisons are made with the observations from EW, MENA, and HENA, covering the entire energy range simulated by the model (0 to 300 keV). The electric field description, and in particular the ionospheric conductance, is the only variable between the simulations. Results from the data-model comparisons are discussed, detailing the strengths and weaknesses of each conductance choice for each energy channel.

  9. Analytical and numerical treatment of the heat conduction equation obtained via time-fractional distributed-order heat conduction law

    Science.gov (United States)

    Želi, Velibor; Zorica, Dušan

    2018-02-01

    Generalization of the heat conduction equation is obtained by considering the system of equations consisting of the energy balance equation and fractional-order constitutive heat conduction law, assumed in the form of the distributed-order Cattaneo type. The Cauchy problem for system of energy balance equation and constitutive heat conduction law is treated analytically through Fourier and Laplace integral transform methods, as well as numerically by the method of finite differences through Adams-Bashforth and Grünwald-Letnikov schemes for approximation derivatives in temporal domain and leap frog scheme for spatial derivatives. Numerical examples, showing time evolution of temperature and heat flux spatial profiles, demonstrate applicability and good agreement of both methods in cases of multi-term and power-type distributed-order heat conduction laws.

  10. Theory and simulation of ion conduction in the pentameric GLIC channel.

    Science.gov (United States)

    Zhu, Fangqiang; Hummer, Gerhard

    2012-10-09

    GLIC is a bacterial member of the large family of pentameric ligand-gated ion channels. To study ion conduction through GLIC and other membrane channels, we combine the one-dimensional potential of mean force for ion passage with a Smoluchowski diffusion model, making it possible to calculate single-channel conductance in the regime of low ion concentrations from all-atom molecular dynamics (MD) simulations. We then perform MD simulations to examine sodium ion conduction through the GLIC transmembrane pore in two systems with different bulk ion concentrations. The ion potentials of mean force, calculated from umbrella sampling simulations with Hamiltonian replica exchange, reveal a major barrier at the hydrophobic constriction of the pore. The relevance of this barrier for ion transport is confirmed by a committor function that rises sharply in the barrier region. From the free evolution of Na(+) ions starting at the barrier top, we estimate the effective diffusion coefficient in the barrier region, and subsequently calculate the conductance of the pore. The resulting diffusivity compares well with the position-dependent ion diffusion coefficient obtained from restrained simulations. The ion conductance obtained from the diffusion model agrees with the value determined via a reactive-flux rate calculation. Our results show that the conformation in the GLIC crystal structure, with an estimated conductance of ~1 picosiemens at 140 mM ion concentration, is consistent with a physiologically open state of the channel.

  11. Enhanced growth of neural networks on conductive cellulose-derived nanofibrous scaffolds

    International Nuclear Information System (INIS)

    Kuzmenko, Volodymyr; Kalogeropoulos, Theodoros; Thunberg, Johannes; Johannesson, Sara; Hägg, Daniel; Enoksson, Peter; Gatenholm, Paul

    2016-01-01

    The problem of recovery from neurodegeneration needs new effective solutions. Tissue engineering is viewed as a prospective approach for solving this problem since it can help to develop healthy neural tissue using supportive scaffolds. This study presents effective and sustainable tissue engineering methods for creating biomaterials from cellulose that can be used either as scaffolds for the growth of neural tissue in vitro or as drug screening models. To reach this goal, nanofibrous electrospun cellulose mats were made conductive via two different procedures: carbonization and addition of multi-walled carbon nanotubes. The resulting scaffolds were much more conductive than untreated cellulose material and were used to support growth and differentiation of SH-SY5Y neuroblastoma cells. The cells were evaluated by scanning electron microscopy and confocal microscopy methods over a period of 15 days at different time points. The results showed that the cellulose-derived conductive scaffolds can provide support for good cell attachment, growth and differentiation. The formation of a neural network occurred within 10 days of differentiation, which is a promising length of time for SH-SY5Y neuroblastoma cells. - Highlights: • The conductive scaffolds for neural tissue engineering are derived from cellulose. • The scaffolds are used to support growth and differentiation of SH-SY5Y cells. • Distinctive cell differentiation occurs within 10 days on conductive scaffolds. • Electrical conductivity and nanotopography improve neural network formation.

  12. Role of anisotropic thermal conductivity in the reversed-field pinch dynamics

    International Nuclear Information System (INIS)

    Onofri, M.; Malara, F.; Veltri, P.

    2011-01-01

    Two compressible magnetohydrodynamics simulations of the reversed-field pinch are performed, with isotropic and anisotropic thermal conductivity. We describe in detail the numerical method we use to reproduce the effect of a large parallel thermal conductivity, which makes magnetic field lines almost isothermal. We compare the results of the two simulations, showing that the anisotropic thermal conductivity causes the formation of a hot island when closed magnetic surfaces exist, while temperature becomes almost uniform when the magnetic field is chaotic. After a transient single-helicity state that is formed in the initial phase, a stationary state is reached where the RFP configuration exists in a multiple helicity state, even though the Hartmann number is below the threshold found in previous simulations for the formation of multiple helicity states.

  13. Preparation and Properties of Silver Nanowire-Based Transparent Conductive Composite Films

    Science.gov (United States)

    Tian, Ji-Li; Zhang, Hua-Yu; Wang, Hai-Jun

    2016-06-01

    Silver nanowire-based transparent conductive composite films with different structures were successfully prepared using various methods, including liquid polyol, magnetron sputtering and spin coating. The experimental results revealed that the optical transmittance of all different structural composite films decreased slightly (1-3%) compared to pure films. However, the electrical conductivity of all composite films had a great improvement. Under the condition that the optical transmittance was greater than 78% over the wavelength range of 400-800 nm, the AgNW/PVA/AgNW film became a conductor, while the AZO/AgNW/AZO film and the ITO/AgNW/ITO film showed 88.9% and 94% reductions, respectively, for the sheet resistance compared with pure films. In addition, applying a suitable mechanical pressure can improve the conductivity of AgNW-based composite films.

  14. Estimation of Synaptic Conductances in Presence of Nonlinear Effects Caused by Subthreshold Ionic Currents

    DEFF Research Database (Denmark)

    Vich, Catalina; Berg, Rune W.; Guillamon, Antoni

    2017-01-01

    Subthreshold fluctuations in neuronal membrane potential traces contain nonlinear components, and employing nonlinear models might improve the statistical inference. We propose a new strategy to estimate synaptic conductances, which has been tested using in silico data and applied to in vivo...... recordings. The model is constructed to capture the nonlinearities caused by subthreshold activated currents, and the estimation procedure can discern between excitatory and inhibitory conductances using only one membrane potential trace. More precisely, we perform second order approximations of biophysical...... models to capture the subthreshold nonlinearities, resulting in quadratic integrate-and-fire models, and apply approximate maximum likelihood estimation where we only suppose that conductances are stationary in a 50–100 ms time window. The results show an improvement compared to existent procedures...

  15. Experimental results showing the internal three-component velocity field and outlet temperature contours for a model gas turbine combustor

    CSIR Research Space (South Africa)

    Meyers, BC

    2011-09-01

    Full Text Available by the American Institute of Aeronautics and Astronautics Inc. All rights reserved ISABE-2011-1129 EXPERIMENTAL RESULTS SHOWING THE INTERNAL THREE-COMPONENT VELOCITY FIELD AND OUTLET TEMPERATURE CONTOURS FOR A MODEL GAS TURBINE COMBUSTOR BC Meyers*, GC... identifier c Position identifier F Fuel i Index L (Combustor) Liner OP Orifice plate Introduction There are often inconsistencies when comparing experimental and Computational Fluid Dynamics (CFD) simulations for gas turbine combustors [1...

  16. An experimental correlation approach for predicting thermal conductivity of water-EG based nanofluids of zinc oxide

    Science.gov (United States)

    Ahmadi Nadooshan, Afshin

    2017-03-01

    In this study, the effects of temperature (20 °Cconductivity of zinc oxide/ethylene glycol-water nanofluid have been presented. Nanofluid samples were prepared by a two-step method and thermal conductivity measurements were performed by a KD2 pro instrument. Results showed that the thermal conductivity increases uniformly with increasing solid volume fraction and temperature. The results also revealed that the thermal conductivity of nanofluids significantly increases with increasing solid volume fraction at higher temperatures. Moreover, it can be seen that for more concentrated samples, the effect of temperature was more tangible. Experimental thermal conductivity enhancement of the nanofluid in comparison with the Maxwell model indicated that Maxwell model was unable to predict the thermal conductivity of the present nanofluid. Therefore, a new correlation was presented for predicting the thermal conductivity of ZnO/EG-water nanofluid.

  17. Magnetic field mediated conductance oscillation in graphene p–n junctions

    Science.gov (United States)

    Cheng, Shu-Guang

    2018-04-01

    The electronic transport of graphene p–n junctions under perpendicular magnetic field is investigated in theory. Under low magnetic field, the transport is determined by the resonant tunneling of Landau levels and conductance versus magnetic field shows a Shubnikov–de Haas oscillation. At higher magnetic field, the p–n junction subjected to the quasi-classical regime and the formation of snake states results in periodical backscattering and transmission as magnetic field varies. The conductance oscillation pattern is mediated both by magnetic field and the carrier concentration on bipolar regions. For medium magnetic field between above two regimes, the combined contributions of resonant tunneling, snake states oscillation and Aharanov–Bohm interference induce irregular oscillation of conductance. At very high magnetic field, the system is subjected to quantum Hall regime. Under disorder, the quantum tunneling at low magnetic field is slightly affected and the oscillation of snake states at higher magnetic field is suppressed. In the quantum Hall regime, the conductance is a constant as predicted by the mixture rule.

  18. Shear-induced changes of electrical conductivity in suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Crawshaw, John; Meeten, Gerald [Schlumberger Cambridge Research, Cambridge (United Kingdom)

    2006-12-15

    The effect of shear on electrical conductivity (rheo-conduction) is studied to give information about particle behaviour in suspensions. Past work is reviewed, and expressions are derived for the rheo-conduction of a suspension of nonconducting spheroids in a conducting matrix for current flow, parallel and normal to the suspension flow direction. A simple apparatus to study rheo-conduction in pipe flow is described, and measurements of steady and time-dependent effects are reported for various suspensions of colloidal particles. Suspensions of anisometric rod- and platelike particles at low concentrations showed rheo-conductive changes of sign, magnitude and relaxation that were consistent with the particle shape, concentration and interactions. The rheo-conductive response decreased with increasing volume fraction for platelike kaolinite particles, attributed to orientational jamming. Spherical latex particles gave unexpected rheo-conductive changes consistent with shear disruption of a conductive network of particles. It is concluded that rheo-conduction measurements are a useful adjunct to conventional rheometry. (orig.)

  19. Conducting research literature reviews from the internet to the paper

    CERN Document Server

    Fink, Arlene

    2014-01-01

    Providing readers with an accessible, in-depth look at how to synthesize research literature, Conducting Research Literature Reviews is perfect for students, researchers, marketers, planners, and policymakers who design and manage public and private agencies, conduct research studies, and prepare strategic plans and grant proposals. Bestselling author Arlene Fink shows readers how to explain the need for and significance of research, as well as how to explain a study’s findings. Offering a step-by-step approach to conducting literature reviews, the Fourth Edition features updated examples and covers: how to select databases and evaluate their quality; selecting and organizing key words and other terms in order to effectively search databases and the Web; setting standards for evaluating the quality of research and other literature; extracting and recording information from articles and studies; synthesizing what the reader finds either descriptively or via a meta-analysis; recording and storing the results ...

  20. III-V/Si wafer bonding using transparent, conductive oxide interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Tamboli, Adele C., E-mail: Adele.Tamboli@nrel.gov; Hest, Maikel F. A. M. van; Steiner, Myles A.; Essig, Stephanie; Norman, Andrew G.; Bosco, Nick; Stradins, Paul [National Center for Photovoltaics, National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401 (United States); Perl, Emmett E. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106-9560 (United States)

    2015-06-29

    We present a method for low temperature plasma-activated direct wafer bonding of III-V materials to Si using a transparent, conductive indium zinc oxide interlayer. The transparent, conductive oxide (TCO) layer provides excellent optical transmission as well as electrical conduction, suggesting suitability for Si/III-V hybrid devices including Si-based tandem solar cells. For bonding temperatures ranging from 100 °C to 350 °C, Ohmic behavior is observed in the sample stacks, with specific contact resistivity below 1 Ω cm{sup 2} for samples bonded at 200 °C. Optical absorption measurements show minimal parasitic light absorption, which is limited by the III-V interlayers necessary for Ohmic contact formation to TCOs. These results are promising for Ga{sub 0.5}In{sub 0.5}P/Si tandem solar cells operating at 1 sun or low concentration conditions.

  1. On-chip DNA preconcentration in different media conductivities by electrodeless dielectrophoresis

    KAUST Repository

    Li, Shunbo

    2015-09-01

    © 2015 AIP Publishing LLC. Electrodeless dielectrophoresis is the best choice to achieve preconcentration of nanoparticles and biomolecules due to its simple, robust, and easy implementation. We designed a simple chip with microchannels and nano-slits in between and then studied the trapping of DNA in high conductive medium and low conductive medium, corresponding to positive and negative dielectrophoresis (DEP), respectively. It is very important to investigate the trapping in media with different conductivities since one always has to deal with the sample solutions with different conductivities. The trapping process was analyzed by the fluorescent intensity changes. The results showed that DNA could be trapped at the nano-slit in both high and low conductive media in a lower electric field strength (10 V/cm) compared to the existing methods. This is a significant improvement to suppress the Joule heating effect in DEP related experiments. Our work may give insight to researchers for DNA trapping by a simple and low cost device in the Lab-on-a-Chip system.

  2. DEVELOPMENTAL TAXONOMY OF CONDUCT DISORDER

    Directory of Open Access Journals (Sweden)

    Jelena Kostić

    2015-12-01

    Full Text Available Conduct disorder is a heterogeneous disorder in terms of etiology, course and prognosis, and currently, there is no singular model that would describe the development of the disorder. The results of empirical research on males confirm this heterogeneity, as they point out to two possible developmental pathways: childhood-onset and adolescentonset type. This paper presents the basic elements of developmental taxonomic theory which argues that there are two different developmental pathways to conduct disorder which have different causes and serve as the basis for the current typology of conduct disorders in the classification systems. Such a typology of conduct disorders in the diagnostic classification allows better understanding, prognosis and choice of treatment.

  3. MREIT conductivity imaging of the postmortem canine abdomen using CoReHA

    International Nuclear Information System (INIS)

    Jeon, Kiwan; Lee, Chang-Ock; Minhas, Atul S; Kim, Young Tae; Jeong, Woo Chul; Kim, Hyung Joong; Woo, Eung Je; Kang, Byeong Teck; Park, Hee Myung; Seo, Jin Keun

    2009-01-01

    Magnetic resonance electrical impedance tomography (MREIT) is a new bio-imaging modality providing cross-sectional conductivity images from measurements of internal magnetic flux densities produced by externally injected currents. Recent experimental results of postmortem and in vivo imaging of the canine brain demonstrated its feasibility by showing conductivity images with meaningful contrast among different brain tissues. MREIT image reconstructions involve a series of data processing steps such as k-space data handling, phase unwrapping, image segmentation, meshing, modelling, finite element computation, denoising and so on. To facilitate experimental studies, we need a software tool that automates these data processing steps. In this paper, we summarize such an MREIT software package called CoReHA (conductivity reconstructor using harmonic algorithms). Performing imaging experiments of the postmortem canine abdomen, we demonstrate how CoReHA can be utilized in MREIT. The abdomen with a relatively large field of view and various organs imposes new technical challenges when it is chosen as an imaging domain. Summarizing a few improvements in the experimental MREIT technique, we report our first conductivity images of the postmortem canine abdomen. Illustrating reconstructed conductivity images, we discuss how they discern different organs including the kidney, spleen, stomach and small intestine. We elaborate, as an example, that conductivity images of the kidney show clear contrast among cortex, internal medulla, renal pelvis and urethra. We end this paper with a brief discussion on future work using different animal models

  4. Electrical regulation of Schwann cells using conductive polypyrrole/chitosan polymers.

    Science.gov (United States)

    Huang, Jinghui; Hu, Xueyu; Lu, Lei; Ye, Zhengxu; Zhang, Quanyu; Luo, Zhuojing

    2010-04-01

    Electrical stimulation (ES) can dramatically enhance neurite outgrowth through conductive polymers and accelerate peripheral nerve regeneration in animal models of nerve injury. Therefore, conductive tissue engineering graft in combination with ES is a potential treatment for neural injuries. Conductive tissue engineering graft can be obtained by seeding Schwann cells on conductive scaffold. However, when ES is applied through the conductive scaffold, the impact of ES on Schwann cells has never been investigated. In this study, a biodegradable conductive composite made of conductive polypyrrole (PPy, 2.5%) and biodegradable chitosan (97.5%) was prepared in order to electrically stimulate Schwann cells. The tolerance of Schwann cells to ES was examined by a cell apoptosis assay. The growth of the cells was characterized using DAPI staining and a MTT assay. mRNA and protein levels of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in Schwann cells were assayed by RT-PCR and Western blotting, and the amount of NGF and BDNF secreted was determined by an ELISA assay. The results showed that the PPy/chitosan membranes supported cell adhesion, spreading, and proliferation with or without ES. Interestingly, ES applied through the PPy/chitosan composite dramatically enhanced the expression and secretion of NGF and BDNF when compared with control cells without ES. These findings highlight for the first time the possibility of enhancing nerve regeneration in conductive scaffolds through ES-increased neurotrophin secretion.

  5. High Thermal Conductivity Materials

    CERN Document Server

    Shinde, Subhash L

    2006-01-01

    Thermal management has become a ‘hot’ field in recent years due to a need to obtain high performance levels in many devices used in such diverse areas as space science, mainframe and desktop computers, optoelectronics and even Formula One racing cars! Thermal solutions require not just taking care of very high thermal flux, but also ‘hot spots’, where the flux densities can exceed 200 W/cm2. High thermal conductivity materials play an important role in addressing thermal management issues. This volume provides readers a basic understanding of the thermal conduction mechanisms in these materials and discusses how the thermal conductivity may be related to their crystal structures as well as microstructures developed as a result of their processing history. The techniques for accurate measurement of these properties on large as well as small scales have been reviewed. Detailed information on the thermal conductivity of diverse materials including aluminum nitride (AlN), silicon carbide (SiC), diamond, a...

  6. Nanostructure design for drastic reduction of thermal conductivity while preserving high electrical conductivity.

    Science.gov (United States)

    Nakamura, Yoshiaki

    2018-01-01

    The design and fabrication of nanostructured materials to control both thermal and electrical properties are demonstrated for high-performance thermoelectric conversion. We have focused on silicon (Si) because it is an environmentally friendly and ubiquitous element. High bulk thermal conductivity of Si limits its potential as a thermoelectric material. The thermal conductivity of Si has been reduced by introducing grains, or wires, yet a further reduction is required while retaining a high electrical conductivity. We have designed two different nanostructures for this purpose. One structure is connected Si nanodots (NDs) with the same crystal orientation. The phonons scattering at the interfaces of these NDs occurred and it depended on the ND size. As a result of phonon scattering, the thermal conductivity of this nanostructured material was below/close to the amorphous limit. The other structure is Si films containing epitaxially grown Ge NDs. The Si layer imparted high electrical conductivity, while the Ge NDs served as phonon scattering bodies reducing thermal conductivity drastically. This work gives a methodology for the independent control of electron and phonon transport using nanostructured materials. This can bring the realization of thermoelectric Si-based materials that are compatible with large scale integrated circuit processing technologies.

  7. Thermal conductivity of different colored compomers.

    Science.gov (United States)

    Guler, Cigdem; Keles, Ali; Guler, Mehmet S; Karagoz, Sendogan; Cora, Ömer N; Keskin, Gul

    2017-11-10

    Compomers are mostly used in primary dentition. The thermal conductivity properties of traditional or colored compomers have not been investigated in detail so far. The aim of this in vitro study was to assess and compare the thermal conductivities of traditional and colored compomers. Two sets of compomers - namely, Twinky Star (available in berry, lemon, green, silver, blue, pink, gold and orange shades) and Dyract Extra (available in B1, A3 and A2 shades) - were included in this study. All of the traditional and colored compomers were applied to standard molds and polymerized according to the manufacturers' instructions. Three samples were prepared from each compomer. Measurements were conducted using a heat conduction test setup, and the coefficient of heat conductivity was calculated for each material. The heat conductivity coefficients were statistically analyzed using Kruskal-Wallis and Duncan tests. Uncertainty analysis was also performed on the calculated coefficients of heat conductivity. Statistically significant differences were found (p<0.05) between the thermal conductivity properties of the traditional and colored compomers examined. Among all of the tested compomers, the silver shade compomer exhibited the highest coefficient of heat conductivity (p<0.05), while the berry shade exhibited the lowest coefficient (p<0.05). Uncertainty analyses revealed that 6 out of 11 samples showed significant differences. The silver shade compomer should be avoided in deep cavities. The material properties could be improved for colored compomers.

  8. Thermal conduction mechanisms in isotope-disordered boron nitride and carbon nanotubes

    Science.gov (United States)

    Savic, Ivana; Mingo, Natalio; Stewart, Derek

    2009-03-01

    We present first principles studies which determine dominant effects limiting the heat conduction in isotope-disordered boron nitride and carbon nanotubes [1]. Using an ab initio atomistic Green's function approach, we demonstrate that localization cannot be observed in the thermal conductivity measurements [1], and that diffusive scattering is the dominant mechanism which reduces the thermal conductivity [2]. We also give concrete predictions of the magnitude of the isotope effect on the thermal conductivities of carbon and boron nitride single-walled nanotubes [2]. We furthermore show that intershell scattering is not the main limiting mechanism for the heat flow through multi-walled boron nitride nanotubes [1], and that heat conduction restricted to a few shells leads to the low thermal conductivities experimentally measured [1]. We consequently successfully compare the results of our calculations [3] with the experimental measurements [1]. [1] C. W. Chang, A. M. Fennimore, A. Afanasiev, D. Okawa, T. Ikuno, H. Garcia, D. Li, A. Majumdar, A. Zettl, Phys. Rev. Lett. 2006, 97, 085901. [2] I. Savic, N. Mingo, D. A. Stewart, Phys. Rev. Lett. 2008, 101, 165502. [3] I. Savic, D. A. Stewart, N. Mingo, to be published.

  9. Thermal conductivity measurements at cryogenic temperatures at LASA

    International Nuclear Information System (INIS)

    Broggi, F.; Pedrini, D.; Rossi, L.

    1995-08-01

    Here the improvement realised to have better control of the reference junction temperature and measurements carried out on Nb 3 Sn cut out from 2 different coils (named LASA3 and LASA5), showing the difference between the longitudinal and the transverse thermal conductivity, is described. Two different methods of data analysis are presented, the DAM (derivative approximated method) and the TCI (thermal conductivity integral. The data analysis for the tungsten and the LASA5 coil has been done according to the two methods showing that the TCI method with polynomial functions is not adequate to describe the thermal conductivity. Only a polynomial fit based on the TCI method but limited at a lower order than the nominal, when the data are well distributed along the range of measurements, can describe reasonably the thermal conductivity dependence with the temperature. Finally the measurements on a rod of BSCCO 2212 high T c superconductor are presented

  10. Ionic conduction in 70-MeV C5+-ion-irradiated poly(vinylidenefluoride- co-hexafluoropropylene)-based gel polymer electrolytes

    International Nuclear Information System (INIS)

    Saikia, D.; Kumar, A.; Singh, F.; Avasthi, D.K.; Mishra, N.C.

    2005-01-01

    In an attempt to increase the Li + -ion diffusivity, poly(vinylidenefluoride-co-hexafluoropropylene)-(propylene carbonate+diethyl carbonate)-lithium perchlorate gel polymer electrolyte system has been irradiated with 70-MeV C 5+ -ion beam of nine different fluences. Swift heavy-ion irradiation shows enhancement in ionic conductivity at lower fluences and decrease in ionic conductivity at higher fluences with respect to unirradiated gel polymer electrolyte films. Maximum room-temperature (303 K) ionic conductivity is found to be 2x10 -2 S/cm after irradiation with a fluence of 10 11 ions/cm 2 . This interesting result could be attributed to the fact that for a particular ion beam with a given energy, a higher fluence provides critical activation energy for cross linking and crystallization to occur, which results in the decrease in ionic conductivity. X-ray-diffraction results show decrease in the degree of crystallinity upon ion irradiation at low fluences (≤10 11 ions/cm 2 ) and increase in crystallinity at higher fluences (>10 11 ions/cm 2 ). Analysis of Fourier-transform infrared spectroscopy results suggests the bond breaking at a fluence of 5x10 9 ions/cm 2 and cross linking at a fluence of 10 12 ions/cm 2 and corroborate conductivity and x-ray-diffraction results. Scanning electron micrographs exhibit increased porosity of the polymer electrolyte after ion irradiation

  11. Origin of low thermal conductivity in nuclear fuels.

    Science.gov (United States)

    Yin, Quan; Savrasov, Sergey Y

    2008-06-06

    Using a novel many-body approach, we report lattice dynamical properties of UO2 and PuO2 and uncover various contributions to their thermal conductivities. Via calculated Grüneisen constants, we show that only longitudinal acoustic modes having large phonon group velocities are efficient heat carriers. Despite the fact that some optical modes also show their velocities which are extremely large, they do not participate in the heat transfer due to their unusual anharmonicity. Ways to improve thermal conductivity in these materials are discussed.

  12. Electrochemical and Thermal Studies of Prepared Conducting Chitosan Biopolymer Film

    International Nuclear Information System (INIS)

    Hlaing Hlaing Oo; Kyaw Naing; Kyaw Myo Naing; Tin Tin Aye; Nyunt Wynn

    2005-09-01

    In this paper, chitosan based conducting bipolymer films were prepared by casting and solvent evaporating technique. All prepared chitosan films were of pale yellow colour, transparent, and smooth. Sulphuric acid was chosen as the cross-linking agent. It enhanced conduction pathway in cross-linked chitosan films. Mechanical properties, solid-state, and thermal behavior of prepared chitosan fimls were studied by means of a material testing machine, powder X-ray diffractometry (XRD), thermogravimetric analysis (TG-DTG), and differential scanning calorimetry (DSC). By the XRD diffraction pattern, high molecular weight of chitosan product indicates the semi-crystalline nature, but the prepared chitosan film and doped chitosan film indicate significantly lower in crystallinity prove which of the amorphous characteristics. In addition, DSC thermogram of pure chitosan film exhibited exothermic peak around at 300 C, indicating polymer decomposition of chitosan molecules in chitosan films. Furthermore, these DSC thermograms clearly showed that while pure chitosan film display exothermal decomposition, the doped chitosan films mainly endothermic characteristics. The ionic conductivity of doped chitosan films were in the order of 10 to 10 S cm , which is in the range of semi-conductor. These results showed that cross-linked chitoson films may be used as polymer electrolyte film to fabricate solid state electrochemical cells

  13. Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets

    Science.gov (United States)

    2014-01-01

    In the present study, stable homogeneous graphene nanoplatelet (GNP) nanofluids were prepared without any surfactant by high-power ultrasonic (probe) dispersion of GNPs in distilled water. The concentrations of nanofluids were maintained at 0.025, 0.05, 0.075, and 0.1 wt.% for three different specific surface areas of 300, 500, and 750 m2/g. Transmission electron microscopy image shows that the suspensions are homogeneous and most of the materials have been well dispersed. The stability of nanofluid was investigated using a UV-visible spectrophotometer in a time span of 600 h, and zeta potential after dispersion had been investigated to elucidate its role on dispersion characteristics. The rheological properties of GNP nanofluids approach Newtonian and non-Newtonian behaviors where viscosity decreases linearly with the rise of temperature. The thermal conductivity results show that the dispersed nanoparticles can always enhance the thermal conductivity of the base fluid, and the highest enhancement was obtained to be 27.64% in the concentration of 0.1 wt.% of GNPs with a specific surface area of 750 m2/g. Electrical conductivity of the GNP nanofluids shows a significant enhancement by dispersion of GNPs in distilled water. This novel type of nanofluids shows outstanding potential for replacements as advanced heat transfer fluids in medium temperature applications including solar collectors and heat exchanger systems. PMID:24410867

  14. Thermal conductivity degradation analyses of LWR MOX fuel by the quasi-two phase material model

    International Nuclear Information System (INIS)

    Kosaka, Yuji; Kurematsu, Shigeru; Kitagawa, Takaaki; Suzuki, Akihiro; Terai, Takayuki

    2012-01-01

    The temperature measurements of mixed oxide (MOX) and UO 2 fuels during irradiation suggested that the thermal conductivity degradation rate of the MOX fuel with burnup should be slower than that of the UO 2 fuel. In order to explain the difference of the degradation rates, the quasi-two phase material model is proposed to assess the thermal conductivity degradation of the MIMAS MOX fuel, which takes into account the Pu agglomerate distributions in the MOX fuel matrix as fabricated. As a result, the quasi-two phase model calculation shows the gradual increase of the difference with burnup and may expect more than 10% higher thermal conductivity values around 75 GWd/t. While these results are not fully suitable for thermal conductivity degradation models implemented by some industrial fuel manufacturers, they are consistent with the results from the irradiation tests and indicate that the inhomogeneity of Pu content in the MOX fuel can be one of the major reasons for the moderation of the thermal conductivity degradation of the MOX fuel. (author)

  15. Electrical conductivity of Ni–YSZ composites: Variants and redox cycling

    DEFF Research Database (Denmark)

    Pihlatie, Mikko; Kaiser, Andreas; Mogensen, Mogens Bjerg

    2012-01-01

    -term conductivity changes due to microstructural changes in both the standard and modified cermets with different Ni doping were compared by re-oxidation at 600°C and subsequent thermal excursions up to 1000°C by normalising the conductivity to a constant temperature. Modified cermets show reduced conductivity loss......Short-term changes in the electrical conductivity of different Ni–YSZ composites (cermets) were measured by an in-situ 4-point DC technique. The isothermal reduction was carried out in dry, humidified or wet hydrogen at temperatures from 600 to 850°C. The cermets reduced at 600°C showed a stable...... conductivity of about 1100S/cm, which increased to an enhanced ~2000S/cm upon re-oxidation and subsequent re-reduction cycling at the same temperature. At 850°C, a rapid initial conductivity loss was observed; upon re-reduction after the re-oxidation both the conductivity and its loss rate were largely...

  16. Quantum conductance in electrodeposited nanocontacts and magnetoresistance measurements

    DEFF Research Database (Denmark)

    Elhoussine, F.; Encinas, A.; Mátéfi-Tempfli, Stefan

    2003-01-01

    The conductance and magnetoresistance measurements in magnetic Ni-Ni and Co-Ni nanocontacts prepared by electrodeposition within the pores of a track of track-etched polymer membrane were discussed. At room temperature, Ni-Ni constrictions were found to show broad quantization plateaus of conduct...... of conductance during their dissolution in units of e/h, as expected for ferromagnetic ballistic nanocontacts. The measurement of the positive and negative magnetoresistance in Co-Ni nanocontacts was also elaborated....

  17. Interface conductance between roughened Be and steel under thermal deformation

    International Nuclear Information System (INIS)

    Tillack, M.S.; Abelson, R.D.

    1995-01-01

    Predictability and control over temperatures and stresses are necessary in order to assure acceptable tritium release, component reliability and lifetime in solid breeder blankets. These blankets usually contain beryllium multiplier in either pebble-bed or solid block forms. For the solid block forms, uncertainties remain in the prediction of the thermal resistance between the Be and its cladding. Several parameters are important, including surface roughness and flatness, background gas pressure, and external loads which may result from blanket thermal deformations and/or pressure stresses. Differential thermal deformation between Be and steel can cause separation to occur between the two solid surfaces, which could seriously degrade the heat transfer. Existing models and data for solid-solid conductance show inconsistencies, even for steel surfaces. Little data or none exists for the Be-steel system, in which differential surface deformations are expected. In this work, we describe a new model which incorporates the combined influences of thermal deformation and contact pressure. Data were taken with small Be specimens as a function of the relevant parameters. The results show that the inclusion of non-conforming surfaces provides a richer range of behavior. Thermal deformations degrade the heat transfer by about a factor of two from flat surfaces, but this effect tends to decrease above about 100 kW m -2 . Contact pressure (above about 1 MPa) between the two materials can effectively maintain good conductance. The flatness and roughness of the surfaces are the most critical parameters. The work also demonstrates the large degree of variation in conductance with background gas pressure. (orig.)

  18. Research on Melt Degassing Processes of High Conductivity Hard Drawn Aluminum Wire

    Science.gov (United States)

    Xu, Xuexia; Feng, Yanting; Wang, Qing; Li, Wenbin; Fan, Hui; Wang, Yong; Li, Guowei; Zhang, Daoqian

    2018-03-01

    Degassing effects of ultrasonic and vacuum processes on high conductivity hard drawn aluminum melt were studied. Results showed that the degassing efficiency improved with the increase of ultrasonic power within certain range, stabilizing at 70% with 240W. For vacuum degassing process, hydrogen content of aluminum melt decreased with the loading time and was linear with logarithm of vacuum degree. Comparison of degassing effects of ultrasonic, vacuum, vacuum-ultrasonic degassing process showed that vacuum-ultrasonic process presented optimal effect.

  19. Heat and electrical conductivity of thermotropic liquid crystals

    International Nuclear Information System (INIS)

    Saidov, N.S.; Majidov, H.; Saburov, B.S.; Safarov, M.M.

    1989-01-01

    A results of thermal conduction and electrical conduction of chemo tropic liquid crystals are brought in this article. An installation dependence formula of thermal conduction investigating things from the electrical conduction and temperatures is constructed

  20. Reduction in thermal conductivity of BiSbTe lump

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Kaleem [King Saud University, Sustainable Energy Technologies Center, College of Engineering, PO Box 800, Riyadh (Saudi Arabia); Wan, C. [Tsinghua University, State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Beijing (China); Al-Eshaikh, M.A.; Kadachi, A.N. [King Saud University, Research Center, College of Engineering, PO Box 800, Riyadh (Saudi Arabia)

    2017-03-15

    In this work, systematic investigations on the thermal conductivities of BiSbTe lump, microstructured pristine BiSbTe bulk and single wall carbon nanotubes (SWCNTs)/BiSbTe bulk nanocomposites were performed. BiSbTe lumps were crushed to form a coarse powder (200 μm) and effect of particle size reduction on the effective thermal conductivity of BiSbTe (200 μm) bulk were analyzed. For further reduction in the conductivity, a two pronged strategy has been employed. First, additional refinement of BiSbTe (200 μm) were performed through ball milling in an inert environment. Second, SWCNTs in 0.75, and 1.0 vol% were distributed uniformly in the fine BiSbTe ball milled powder. The results showed that the effective thermal conductivities decrease with the reduction in the particle size from lump to BiSbTe (200 μm) bulk as well as with the addition of SWCNTs accompanied by further refinement of BiSbTe particles. The significant reduction in thermal conductivities of the lump was achieved for pure BiSbTe (200 μm) bulk and 0.75 vol% of SWCNTs/BiSbTe composite. This can be ascribed to the enhanced phonon scattering by the grain boundaries between the nanostructured BiSbTe particles as well as the interfaces between BiSbTe and the low dimensional carbon nanotubes. (orig.)

  1. A practical dimensionless equation for the thermal conductivity of carbon nanotubes and CNT arrays

    Directory of Open Access Journals (Sweden)

    Qiang Chen

    2014-05-01

    Full Text Available Experimental results reported in the last decade on the thermal conductivity of carbon nanotubes (CNTs have shown a fairly divergent behavior. An underlying intrinsic consistency was believed to exist in spite of the divergence in the thermal conductivity data of various CNTs. A dimenisonless equation that describes the temperature dependence of thermal conductivity was derived by introducing reduced forms relative to a chosen reference point. This equation can serve as a practical approximation to characterize the conductivity of individual CNT with different structural parameters as well as bulk CNT arrays with different bundle configurations. Comparison of predictions by the equation and historical measurements showed good agreements within their uncertainties.

  2. Factors that Motivate Business Faculty to Conduct Research: An Expectancy Theory Analysis

    Science.gov (United States)

    Chen, Yining; Gupta, Ashok; Hoshower, Leon

    2006-01-01

    In this study, the authors used expectancy theory to examine key factors that motivate business faculty to conduct research. The survey results, from 320 faculty members at 10 business schools, showed that faculty members who assign higher importance ratings to both the extrinsic and the intrinsic rewards of research exhibit higher research…

  3. Conductive ink print on PA66 gear for manufacturing condition monitoring sensors

    Science.gov (United States)

    Futagawa, Shintaro; Iba, Daisuke; Kamimoto, Takahiro; Nakamura, Morimasa; Miura, Nanako; Iizuka, Takashi; Masuda, Arata; Sone, Akira; Moriwaki, Ichiro

    2018-03-01

    Failures detection of rotating machine elements, such as gears, is an important issue. The purpose of this study was to try to solve this issue by printing conductive ink on gears to manufacture condition-monitoring sensors. In this work, three types of crack detection sensor were designed and the sprayed conductive ink was directly sintered on polyimide (PI) - coated polyamide (PA) 66 gears by laser. The result showed that it was possible to produce narrow circuit lines of the conductive ink including Ag by laser sintering technique and the complex shape sensors on the lateral side of the PA66 gears, module 1.0 mm and tooth number 48. A preliminary operation test was carried out for investigation of the function of the sensors. As a result of the test, the sensors printed in this work should be effective for detecting cracks at tooth root of the gears and will allow for the development of better equipment and detection techniques for health monitoring of gears.

  4. Highly Conductive, Transparent Flexible Films Based on Metal Nanoparticle-Carbon Nanotube Composites

    Directory of Open Access Journals (Sweden)

    Wen-Yin Ko

    2013-01-01

    Full Text Available Metallic nanoparticles decorated on MWCNTs based transparent conducting thin films (TCFs show a cheap and efficient option for the applications in touch screens and the replacement of the ITO film because of their interesting properties of electrical conductivity, mechanical property, chemical inertness, and other unique properties, which may not be accessible by their individual components. However, a great challenge that always remains is to develop effective ways to prepare junctions between metallic nanoparticles and MWCNTs for the improvement of high-energy barriers, high contact resistances, and weak interactions which could lead to the formation of poor conducting pathways and result in the CNT-based devices with low mechanical flexibility. Herein, we not only discuss recent progress in the preparation of MNP-CNT flexible TCFs but also describe our research studies in the relevant areas. Our result demonstrated that the MNP-CNT flexible TCFs we prepared could achieve a highly electrical conductivity with the sheet resistance of ~100 ohm/sq with ~80% transmittance at 550 nm even after being bent 500 times. This electrical conductivity is much superior to the performances of other MWCNT-based transparent flexible films, making it favorable for next-generation flexible touch screens and optoelectronic devices.

  5. Transparent conductive-polymer strain sensors for touch input sheets of flexible displays

    International Nuclear Information System (INIS)

    Takamatsu, Seiichi; Takahata, Tomoyuki; Muraki, Masato; Iwase, Eiji; Matsumoto, Kiyoshi; Shimoyama, Isao

    2010-01-01

    A transparent conductive polymer-based strain-sensor array, designed especially for touch input sheets of flexible displays, was developed. A transparent conductive polymer, namely poly(3, 4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS), was utilized owing to its strength under repeated mechanical bending. PEDOT:PSS strain sensors with a thickness of 130 nm exhibited light transmittance of 92%, which is the same as the transmittance of ITO electrodes widely used in flat panel displays. We demonstrated that the sensor array on a flexible sheet was able to sustain mechanical bending 300 times at a bending radius of 5 mm. The strain sensor shows a gauge factor of 5.2. The touch point on a flexible sheet could be detected from histograms of the outputs of the strain sensors when the sheet was pushed with an input force of 5 N. The touch input could be detected on the flexible sheet with a curved surface (radius of curvature of 20 mm). These results show that the developed transparent conductive polymer-based strain-sensor array is applicable to touch input sheets of mechanically bendable displays.

  6. Effect of doped ceria interlayer on cathode performance of the electrochemical cell using proton conducting oxide

    International Nuclear Information System (INIS)

    Sakai, Takaaki; Matsushita, Shotaro; Hyodo, Junji; Okuyama, Yuji; Matsuka, Maki; Ishihara, Tatsumi; Matsumoto, Hiroshige

    2012-01-01

    Highlights: ► Ce 0.8 Yb 0.2 O 2−δ (YbDC) interlayer conducted a large amount of protons. ► YbDC can work as cathode interlayer for proton conducting electrolyte cells. ► Cathode overpotential of the YbDC interlayer cells showed a plateau at about 400 mV. - Abstract: Introduction of doped ceria interlayer to cathode/electrolyte interface of the electrochemical cell with proton conducting electrolyte was investigated using thin Ce 0.8 Yb 0.2 O 2−δ (YbDC) interlayer of about 500 nm thickness. YbDC interlayer conducted a large amount of protons as much as 170 mA cm −2 . It was also found that cathode overpotential of the YbDC interlayer cells consistently showed a plateau at about 400 mV, at which that of the non-interlayer cells did not show, suggesting a possibility that cathode reaction is changed by introducing the doped ceria interlayer. This result also indicates that the interlayer showed high activity for cathode reaction when enough cathodic bias was applied. Especially, the interlayer showed high activity for the improvement of poor cathode reaction between SrZr 0.9 Y 0.1 O 3−α (SZY-91) electrolyte and platinum cathode.

  7. Conductivity studies on commercially available proton-conducting membranes with different equivalent weight

    Energy Technology Data Exchange (ETDEWEB)

    Huslage, J; Buechi, F N; Scherer, G G [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Two perfluorosulfonic acid membranes, Nafion{sup R} 105 and Nafion{sup R} 115 with the same thickness but different equivalent weights (EW = 1000 g/eq. resp. 1100 g/eq.) were characterised by conductivity measurements at different water vapour activities in the temperature range of 25-70{sup o}C. The results demonstrate that a lower membrane equivalent weight opens the possibility to obtain the needed proton conductivity at lower water vapour activity. This is especially important for those fuel cell applications, in which the cell is operated without external humidification of the fuel gases. (author) 5 figs., 5 refs.

  8. Vernotte-Cattaneo approximation for heat conduction in fuel rod

    International Nuclear Information System (INIS)

    Espinosa P, G.; Espinosa M, E. G.

    2009-10-01

    In this paper we explore the applicability of a fuel rod mathematical model based on the Vernotte-Cattaneo transient heat conduction as constitutive law (Non-Fourier approach) for light water reactors transient analysis. In the classical theory of diffusion, the Fourier law of heat conduction is used to describe the relation between the heat conduction is used to describe the relation between the heat flux vector and the temperature gradient assuming that the heat propagation speeds are infinite. The motivation for this research was to eliminate the paradox of an infinite. The motivation for this research was to eliminate the paradox of an infinite thermal wave speed. The time-dependent heat sources were considered in the fuel rod heat transfer model. The close of the main steam isolated valves transient in a boiling water reactor was analyzed for different relaxation times. The results show that for long-times the heat fluxes on the clad surface under Vernotte-Cattaneo approach can be important, while for short-times and from the engineering point of view the changes are very small. (Author)

  9. Ionic conducting poly-benzimidazoles; Polybenzimidazoles conducteurs ioniques

    Energy Technology Data Exchange (ETDEWEB)

    Jouanneau, J

    2006-11-15

    Over the last years, many research works have been focused on new clean energy systems. Hydrogen fuel cell seems to be the most promising one. However, the large scale development of this technology is still limited by some key elements. One of them is the polymer electrolyte membrane 'Nafion' currently used, for which the ratio performance/cost is too low. The investigations we carried out during this thesis work are related to a new class of ionic conducting polymer, the sulfonated poly-benzimidazoles (sPBI). Poly-benzimidazoles (PBI) are aromatic heterocyclic polymers well-known for their excellent thermal and chemical stability. Ionic conduction properties are obtained by having strong acid groups (sulfonic acid SO{sub 3}H) on the macromolecular structure. For that purpose, we first synthesized sulfonated monomers. Their poly-condensation with an appropriate non-sulfonated co-monomer yields to sPBI with sulfonation range from 0 to 100 per cent. Three different sPBI structures were obtained, and verified by appropriate analytical techniques. We also showed that the protocol used for the synthesis resulted in high molecular weights polymers. We prepared ionic conducting membrane by casting sPBI solutions on glass plates. Their properties of stability, water swelling and ionic conductivity were investigated. Surprisingly, the behaviour of sPBI was quite different from the other sulfonated aromatic polymers with same amount of SO{sub 3}H, their stability was much higher, but their water swelling and ionic conductivity were quite low. We attributed these differences to strong ionic interactions between the sulfonic acid groups and the basic benzimidazole groups of our polymers. However, we managed to solve this problem synthesizing very highly sulfonated PBI, obtaining membranes with a good balance between all the properties necessary. (author)

  10. Electrically conducting nanobiocomposites using carbon nanotubes and collagen waste fibers

    International Nuclear Information System (INIS)

    Meiyazhagan, Ashokkumar; Thangavel, Saravanamoorthy; Hashim, Daniel P.; Ajayan, Pulickel M.; Palanisamy, Thanikaivelan

    2015-01-01

    Electrically conducting hybrid biocomposite films were prepared using a simple and cost-effective method by incorporating different types of carbon nanotubes (XCNTs) viz., few walled carbon nanotube (FWCNT) and boron doped carbon nanotube (BCNT) into biopolymers. Collagen extracted from animal skin wastes was blended with guar gum and XCNTs in varying proportions to form flexible and electrically conducting hybrid films. We found that the electrical conductivity of both types of hybrid films increases radically as the XCNT loading increases. BCNT incorporated hybrid films show better electrical conductivity (3.0 × 10 −1 S/cm) than their FWCNT loaded counter parts (4.8 × 10 −4 S/cm) at a dosage of 2 wt.%. On the other hand, mechanical and other physical properties such as transparency, flexibility and surface smoothness of the developed hybrid films were affected as a function of XCNT concentration. We also demonstrated that the developed hybrid films lit up a LED lamp when inserted between batteries and the brightness of the emitted light depended on the XCNT loading. These results suggest a new way to transform an industrial biowaste into innovative advanced materials for applications in fields related to biomedicine, biosensors and electronics. - Highlights: • Hybrid nanobiocomposite films prepared using collagen, guar gum and CNTs. • Examined the effect of CNT doping on the properties of hybrid biocomposite films. • Higher CNT loading improved the conductivity radically, especially for BCNT. • The ability of developed hybrid films to lit up a LED lamp was demonstrated. • The results suggest a new way to transform biowaste into advanced materials

  11. Non-Gaussian conductivity fluctuations in semiconductors

    International Nuclear Information System (INIS)

    Melkonyan, S.V.

    2010-01-01

    A theoretical study is presented on the statistical properties of conductivity fluctuations caused by concentration and mobility fluctuations of the current carriers. It is established that mobility fluctuations result from random deviations in the thermal equilibrium distribution of the carriers. It is shown that mobility fluctuations have generation-recombination and shot components which do not satisfy the requirements of the central limit theorem, in contrast to the current carrier's concentration fluctuation and intraband component of the mobility fluctuation. It is shown that in general the mobility fluctuation consist of thermal (or intraband) Gaussian and non-thermal (or generation-recombination, shot, etc.) non-Gaussian components. The analyses of theoretical results and experimental data from literature show that the statistical properties of mobility fluctuation and of 1/f-noise fully coincide. The deviation from Gaussian statistics of the mobility or 1/f fluctuations goes hand in hand with the magnitude of non-thermal noise (generation-recombination, shot, burst, pulse noises, etc.).

  12. Molecular dynamics study on interfacial thermal conductance of unirradiated and irradiated SiC/C

    International Nuclear Information System (INIS)

    Wang, Qingyu; Wang, Chenglong; Zhang, Yue; Li, Taosheng

    2014-01-01

    SiC f /SiC composite materials have been considered as candidate structural materials for several types of advanced nuclear reactors. Both experimental and computer simulations studies have revealed the degradation of thermal conductivity for this material after irradiation. The objective of this study is to investigate the effect of SiC/graphite interface structure and irradiation on the interfacial thermal conductance by using molecular dynamics simulation. Five SiC/graphite composite models were created with different interface structures, and irradiation was introduced near the interfaces. Thermal conductance was calculated by means of reverse-NEMD method. Results show that there is a positive correlation between the interfacial energy and interfacial C–Si bond quantity, and irradiated models showed higher interfacial energy compared with their unirradiated counterparts. Except the model with graphite atom plane parallel to the interface, the interfacial thermal conductance of unirradiated and irradiated (1000 eV) models, increases as the increase of interfacial energy, respectively. For all irradiated models, lattice defects are of importance in impacting the interfacial thermal conductance depending on the interface structure. For the model with graphite layer parallel to the interface, the interfacial thermal conductance increased after irradiation, for the other models the interfacial thermal conductance decreased. The vibrational density of states of atoms in the interfacial region was calculated to analyze the phonon mismatch at the interface

  13. Comb-push ultrasound shear elastography of breast masses: initial results show promise.

    Science.gov (United States)

    Denis, Max; Mehrmohammadi, Mohammad; Song, Pengfei; Meixner, Duane D; Fazzio, Robert T; Pruthi, Sandhya; Whaley, Dana H; Chen, Shigao; Fatemi, Mostafa; Alizad, Azra

    2015-01-01

    To evaluate the performance of Comb-push Ultrasound Shear Elastography (CUSE) for classification of breast masses. CUSE is an ultrasound-based quantitative two-dimensional shear wave elasticity imaging technique, which utilizes multiple laterally distributed acoustic radiation force (ARF) beams to simultaneously excite the tissue and induce shear waves. Female patients who were categorized as having suspicious breast masses underwent CUSE evaluations prior to biopsy. An elasticity estimate within the breast mass was obtained from the CUSE shear wave speed map. Elasticity estimates of various types of benign and malignant masses were compared with biopsy results. Fifty-four female patients with suspicious breast masses from our ongoing study are presented. Our cohort included 31 malignant and 23 benign breast masses. Our results indicate that the mean shear wave speed was significantly higher in malignant masses (6 ± 1.58 m/s) in comparison to benign masses (3.65 ± 1.36 m/s). Therefore, the stiffness of the mass quantified by the Young's modulus is significantly higher in malignant masses. According to the receiver operating characteristic curve (ROC), the optimal cut-off value of 83 kPa yields 87.10% sensitivity, 82.61% specificity, and 0.88 for the area under the curve (AUC). CUSE has the potential for clinical utility as a quantitative diagnostic imaging tool adjunct to B-mode ultrasound for differentiation of malignant and benign breast masses.

  14. Estimation of Synaptic Conductances in Presence of Nonlinear Effects Caused by Subthreshold Ionic Currents

    Directory of Open Access Journals (Sweden)

    Catalina Vich

    2017-07-01

    Full Text Available Subthreshold fluctuations in neuronal membrane potential traces contain nonlinear components, and employing nonlinear models might improve the statistical inference. We propose a new strategy to estimate synaptic conductances, which has been tested using in silico data and applied to in vivo recordings. The model is constructed to capture the nonlinearities caused by subthreshold activated currents, and the estimation procedure can discern between excitatory and inhibitory conductances using only one membrane potential trace. More precisely, we perform second order approximations of biophysical models to capture the subthreshold nonlinearities, resulting in quadratic integrate-and-fire models, and apply approximate maximum likelihood estimation where we only suppose that conductances are stationary in a 50–100 ms time window. The results show an improvement compared to existent procedures for the models tested here.

  15. Synthesis and conductivity of heptadecatungstovanadodiphosphoric heteropoly acid with Dawson structure

    Energy Technology Data Exchange (ETDEWEB)

    Tong Xia; Zhu Weiming [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Wu Qingyin, E-mail: qywu@zju.edu.cn [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Qian Xueyu; Liu Zhen [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Yan Wenfu [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130012 (China); Gong Jian [Key Lab of Polyoxometalate Science, the Ministry of Education, Northeast Normal University, Changchun 130024 (China)

    2011-07-21

    A new solid high-proton conductor, heptadecatungstovanadodiphosphoric heteropoly acid H{sub 7}P{sub 2}W{sub 17}VO{sub 62}.28H{sub 2}O with Dawson structure was synthesized by the stepwise acidification and the stepwise addition of element solutions. The optimal proportion of component compounds in the synthesis reaction was given. The product was characterized by chemical analysis, potentiometric titration, IR, UV, XRD, {sup 31}P NMR, TG-DTA and electrochemical impedance spectroscopy (EIS). The results indicate that H{sub 7}P{sub 2}W{sub 17}VO{sub 62}.28H{sub 2}O possesses the Dawson structure. EIS measurements show a high conductivity (3.10 x 10{sup -2} S cm{sup -1} at 26 deg. C and 75% relative humidity), with an activation energy of 32.23 kJ mol{sup -1} for proton conduction. The mechanism of proton conduction for this heteropoly acid is Vehicle mechanism.

  16. Tuning the thermal conductance of molecular junctions with interference effects

    Science.gov (United States)

    Klöckner, J. C.; Cuevas, J. C.; Pauly, F.

    2017-12-01

    We present an ab initio study of the role of interference effects in the thermal conductance of single-molecule junctions. To be precise, using a first-principles transport method based on density functional theory, we analyze the coherent phonon transport in single-molecule junctions made of several benzene and oligo(phenylene ethynylene) derivatives. We show that the thermal conductance of these junctions can be tuned via the inclusion of substituents, which induces destructive interference effects and results in a decrease of the thermal conductance with respect to the unmodified molecules. In particular, we demonstrate that these interference effects manifest as antiresonances in the phonon transmission, whose energy positions can be tuned by varying the mass of the substituents. Our work provides clear strategies for the heat management in molecular junctions and, more generally, in nanostructured metal-organic hybrid systems, which are important to determine how these systems can function as efficient energy-conversion devices such as thermoelectric generators and refrigerators.

  17. Ultrafast Terahertz Conductivity of Photoexcited Nanocrystalline Silicon

    DEFF Research Database (Denmark)

    Cooke, David; MacDonald, A. Nicole; Hryciw, Aaron

    2007-01-01

    The ultrafast transient ac conductivity of nanocrystalline silicon films is investigated using time-resolved terahertz spectroscopy. While epitaxial silicon on sapphire exhibits a free carrier Drude response, silicon nanocrystals embedded in glass show a response that is best described by a class...... in the silicon nanocrystal films is dominated by trapping at the Si/SiO2 interface states, occurring on a 1–100 ps time scale depending on particle size and hydrogen passivation......The ultrafast transient ac conductivity of nanocrystalline silicon films is investigated using time-resolved terahertz spectroscopy. While epitaxial silicon on sapphire exhibits a free carrier Drude response, silicon nanocrystals embedded in glass show a response that is best described...

  18. Studies of protonic self-diffusion and conductivity in 12-tungstophophoric acid hydrates by pulsed field gradient 1H NMR and ac Conductivity

    International Nuclear Information System (INIS)

    Slade, R.C.; Pressman, H.A.; Barker, J.; Strange, J.H.

    1988-01-01

    Temperature dependent protonic conductivities σ and 1/H self-diffusion coefficients, D, are reported for polycrystalline hydrates of 12-tungstophosphoric acid (TPA). Conductivities were measured using ac admittane spectrometry and diffusion coefficients by the pulsed field gradient NMR technique. Conductivities for the hydrates TPA.nH 2 O (n=6, 14, 21) increase with n. Examination of σ and D values and of activation techniques shows self-diffusion and conduction to occur by different mechanisms in the higher hydrates. 25 refs.; 14 figs.; 1 table

  19. Conductivity Profile Determination by Eddy Current for Shot Peened Superalloy Surfaces Toward Residual Stress Assessment

    International Nuclear Information System (INIS)

    Shen, Y.; Lo, C. C. H.; Frishman, A. M.; Lee, C.; Nakagawa, N.

    2007-01-01

    This paper describes an eddy current model-based method for inverting near-surface conductivity deviation profiles of surface treated materials from swept-high frequency eddy current (SHFEC) data. This work forms part of our current research directed towards the development of an electromagnetic nondestructive technique for assessing residual stress of shot-peened superalloy components. The inversion procedure is based on the use of a parameterized function to describe the near-surface conductivity as a function of depth for a shot-peened surface, and the laterally uniform multi-layer theory of Cheng, Dodd and Deeds to calculate the resulting coil impedance deviations. The convergence of the inversion procedure has been tested against synthesized eddy current data. As a demonstration, the conductivity deviation profiles of a series of Inconel 718 specimens, shot peened at various Almen intensities, have been obtained by inversion. Several consistency tests were conducted to examine the reliability of the inverted conductivity profiles. The results show that conductivity deviation profiles can be reliably determined from SHFEC data within the accuracy of the current measurement system

  20. A nonconjugated radical polymer glass with high electrical conductivity

    Science.gov (United States)

    Joo, Yongho; Agarkar, Varad; Sung, Seung Hyun; Savoie, Brett M.; Boudouris, Bryan W.

    2018-03-01

    Solid-state conducting polymers usually have highly conjugated macromolecular backbones and require intentional doping in order to achieve high electrical conductivities. Conversely, single-component, charge-neutral macromolecules could be synthetically simpler and have improved processibility and ambient stability. We show that poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a nonconjugated radical polymer with a subambient glass transition temperature, underwent rapid solid-state charge transfer reactions and had an electrical conductivity of up to 28 siemens per meter over channel lengths up to 0.6 micrometers. The charge transport through the radical polymer film was enabled with thermal annealing at 80°C, which allowed for the formation of a percolating network of open-shell sites in electronic communication with one another. The electrical conductivity was not enhanced by intentional doping, and thin films of this material showed high optical transparency.

  1. Research on a haptic sensor made using MCF conductive rubber

    International Nuclear Information System (INIS)

    Zheng Yaoyang; Shimada, Kunio

    2008-01-01

    To provide a new composite material having a high electrical sensitivity in the fields of robotics and sensing, a magnetic rubber having network-like magnetic clusters was developed by utilizing a magnetic compound fluid (MCF). MCF rubber with small deformations can provide an effective sensor. In this paper, we report many experiments in which changes of the MCF rubber's resistance were observed when the rubber was compressed and a deformation was generated; we then made a trial haptic sensor using the MCF conductive rubber and performed many experiments to observe changes of the electrical resistance of the sensor. The results of experiments showed that the proposed sensor made with MCF conductive rubber is useful for sensing small amounts of pressure or small deformations

  2. Research on a haptic sensor made using MCF conductive rubber

    Energy Technology Data Exchange (ETDEWEB)

    Zheng Yaoyang; Shimada, Kunio [Faculty of Symbiotic Systems Science Fukushima University, 1 Kanayakawa, Fukushima 960-1296 (Japan)], E-mail: tei@sss.fukushima-u.ac.jp, E-mail: shimadakun@sss.fukushima-u.ac.jp

    2008-05-21

    To provide a new composite material having a high electrical sensitivity in the fields of robotics and sensing, a magnetic rubber having network-like magnetic clusters was developed by utilizing a magnetic compound fluid (MCF). MCF rubber with small deformations can provide an effective sensor. In this paper, we report many experiments in which changes of the MCF rubber's resistance were observed when the rubber was compressed and a deformation was generated; we then made a trial haptic sensor using the MCF conductive rubber and performed many experiments to observe changes of the electrical resistance of the sensor. The results of experiments showed that the proposed sensor made with MCF conductive rubber is useful for sensing small amounts of pressure or small deformations.

  3. Research on a haptic sensor made using MCF conductive rubber

    Science.gov (United States)

    Zheng, Yaoyang; Shimada, Kunio

    2008-05-01

    To provide a new composite material having a high electrical sensitivity in the fields of robotics and sensing, a magnetic rubber having network-like magnetic clusters was developed by utilizing a magnetic compound fluid (MCF). MCF rubber with small deformations can provide an effective sensor. In this paper, we report many experiments in which changes of the MCF rubber's resistance were observed when the rubber was compressed and a deformation was generated; we then made a trial haptic sensor using the MCF conductive rubber and performed many experiments to observe changes of the electrical resistance of the sensor. The results of experiments showed that the proposed sensor made with MCF conductive rubber is useful for sensing small amounts of pressure or small deformations.

  4. Conductivity variations in composites of. alpha. -zirconium phosphate and alumina

    Energy Technology Data Exchange (ETDEWEB)

    Slade, R.C.T.; Knowles, J.A. (Dept. of Chemistry, Exeter Univ. (UK))

    Composite proton-conducting solid electrolytes have been formed from {alpha}-zirconium hydrogen phosphate ({alpha}-Zr(HPO{sub 4}){sub 2}.H{sub 2}O, {alpha}-ZrP) and aluminas (Al{sub 2}O{sub 3}) in varying mole ratios. Conductivity variations as a function of temperature have been characterised and compared to that for a delaminated {alpha}-ZrP (no alumina). There are no appreciable conductivity enhancements on composite formation, but conductivity for materials ca. 50 mole% in alumina can be comparable to the delaminated materials. Differential scanning calorimetry shows the composites to have different thermal properties to simple admixtures. High resolution {sup 31}P NMR studies show reaction to form aluminium phosphate at the interface between components. (orig.).

  5. Predicting permeability and electrical conductivity of sedimentary rocks from microgeometry

    International Nuclear Information System (INIS)

    Schlueter, E.M.; Cook, N.G.W.

    1991-02-01

    The determination of hydrologic parameters that characterize fluid flow through rock masses on a large scale (e.g., hydraulic conductivity, capillary pressure, and relative permeability) is crucial to activities such as the planning and control of enhanced oil recovery operations, and the design of nuclear waste repositories. Hydraulic permeability and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. The cross-sectional areas and perimeters of the individual pores are estimated from two-dimensional scanning electron micrographs of rock sections. The hydraulic and electrical conductivities of the individual pores are determined from these geometrical parameters, using Darcy's law and Ohm's law. Account is taken of the fact that the cross-sections are randomly oriented with respect to the channel axes, and for possible variation of cross-sectional area along the length of the pores. The effective medium theory from solid-state physics is then used to determine an effective average conductance of each pore. Finally, the pores are assumed to be arranged on a cubic lattice, which allows the calculation of overall macroscopic values for the permeability and the electrical conductivity. Preliminary results using Berea, Boise, Massilon and Saint-Gilles sandstones show reasonably close agreement between the predicted and measured transport properties. 12 refs., 5 figs., 1 tab

  6. Anti-resonance scattering at defect levels in the quantum conductance of a one-dimensional system

    Science.gov (United States)

    Sun, Z. Z.; Wang, Y. P.; Wang, X. R.

    2002-03-01

    For the ballistic quantum transport, the conductance of one channel is quantized to a value of 2e^2/h described by the Landauer formula. In the presence of defects, electrons will be scattered by these defects. Thus the conductance will deviate from the values of the quantized conductance. We show that an anti-resonance scattering can occur when an extra defect level is introduced into a conduction band. At the anti-resonance scattering, exact one quantum conductance is destroyed. The conductance takes a non-zero value when the Fermi energy is away from the anti-resonance scattering. The result is consistent with recent numerical calculations given by H. J. Choi et al. (Phys. Rev. Lett. 84, 2917(2000)) and P. L. McEuen et al. (Phys. Rev. Lett. 83, 5098(1999)).

  7. Auroral ionospheric quiet summer time conductances

    International Nuclear Information System (INIS)

    Brekke, A.; Hall, C.

    1988-01-01

    The auroral zone E-region conductivities and conductances have been studied for 7 quiet time summer days. The Hall- and Pedersen conductances are found to follow the solar zenith variations in a rather regular fashion, and empirical formulas for these conductances are obtained. The choice of proper collision frequency models is found to be of great importance when deriving the conductances, and it is argued that some of the different results presented by other authors may be due to different models of the collision frequencies. The Hall- to Pedersen conductance ratios can only be used as an indicator of the energy of the precipitating auroral particles when the contribution from the background solar ionization is subtracted. When this is done this ratio takes much higher values than previously reported

  8. Conductivity of rf-heated plasma

    International Nuclear Information System (INIS)

    Fisch, N.J.

    1984-05-01

    The electron velocity distribution of rf-heated plasma may be so far from Maxwellian that Spitzer conductivity no longer holds. A new conductivity for such plasmas is derived and the result can be put in a remarkably general form. The new expression should be of great practical value in examining schemes for current ramp-up in tokamaks by means of lower-hybrid or other waves

  9. Thermal conductivity of highly porous mullite material

    International Nuclear Information System (INIS)

    Barea, Rafael; Osendi, Maria Isabel; Ferreira, Jose M.F.; Miranzo, Pilar

    2005-01-01

    The thermal diffusivity of highly porous mullite materials (35-60 vol.% porosity) has been measured up to 1000 deg C by the laser flash method. These materials were fabricated by a direct consolidation method based on the swelling properties of starch granules in concentrated aqueous suspensions and showed mainly spherical shaped pores of about 30 μm in diameter. From the point of view of heat conduction, they behave as a bi-phase material of voids dispersed in the continuous mullite matrix. The temperature dependence of thermal conductivity for the different porosities was modeled by a simple equation that considers the contribution to heat conduction of the mullite matrix and the gas inside the pores, as well as the radiation. The thermal conductivity of the matrix was taken from the measurements done in a dense mullite while the conductivity in the voids was assumed to be that of the testing atmosphere

  10. Molecular motion in polymer electrolytes. An investigation of methods for improving the conductivity of solid polymer electrolytes

    International Nuclear Information System (INIS)

    Webster, Mark Ian

    2002-01-01

    Three methods were explored with a view to enhancing the ionic conductivity of polymer electrolytes; namely the addition of an inert, inorganic filler, the addition of a plasticizer and the incorporation of the electrolyte in the pores of silica matrices. There have been a number of reports, which suggest the addition of nanocrystalline oxides to polymer electrolytes increases the ionic conductivities by about a factor of two. In this thesis studies of the polymer electrolyte NaSCN.P(EO) 8 with added nanocrystalline alumina powder are reported which show no evidence of enhanced conductivity. The addition of a plasticizer to polymer electrolytes will increase the ionic conductivity. A detailed study was made of the polymer electrolytes LiT.P(EO) 10 and LiClO 4 .P(EO) 10 with added ethylene carbonate plasticizer. The conductivities showed an enhancement, however this disappeared on heating under vacuum. The present work suggests that the plasticised system is not thermodynamically stable and will limit the applications of the material. A series of samples were prepared from the polymer electrolyte LiT.P(EO) 8 and a range of porous silicas. The silicas were selected to give a wide range of pore size and included Zeolite Y, ZSM5, mesoporous silica and a range of porous glasses. This gave pore sizes from less than one nm to 50 nm. A variety of experiments, including X-ray diffraction, DSC and NMR, showed that the polymer electrolyte entered to pores of the silica. As a result the polymer was amorphous and the room temperature conductivity was enhanced. The high temperature conductivity was not increased above that for the pure electrolyte. The results suggest that this could be employed in applications, however would require higher conducting electrolytes to be of practical benefit. (author)

  11. A review of conduction aphasia.

    Science.gov (United States)

    Ardila, Alfredo

    2010-11-01

    In this paper, a historical overview of the interpretation of conduction aphasia is initially presented. It is emphasized that the name conduction aphasia was proposed by Wernicke and was interpreted as a disconnection between the temporal and frontal brain language areas; this interpretation was re-taken by Geschwind, attributing the arcuate fasciculus the main role in speech repetition disturbances and resulting in the so-called Wernicke-Geschwind model of language. With the introduction of contemporary neuroimaging techniques, this interpretation of conduction aphasia as a disconnection syndrome due to an impairment of the arcuate fasciculus has been challenged. It has been disclosed that the arcuate fasciculus does not really connect Wernicke's and Broca's areas, but Wernicke's and motor/premotor frontal areas. Furthermore, conduction aphasia can be found in cases of cortical damage without subcortical extension. It is concluded that conduction aphasia remains a controversial topic not only from the theoretic point of view, but also from the understanding of its neurologic foundations.

  12. Influence of magnetic moment formation on the conductance of coupled quantum wires

    International Nuclear Information System (INIS)

    Puller, V I; Mourokh, L G; Bird, J P; Ochiai, Y

    2005-01-01

    In this paper, we develop a model for the resonant interaction between a pair of coupled quantum wires, under conditions where self-consistent effects lead to the formation of a local magnetic moment in one of the wires. Our analysis is motivated by the experimental results of Morimoto et al (2003 Appl. Phys. Lett. 82 3952), who showed that the conductance of one of the quantum wires exhibits a resonant peak at low temperatures, whenever the other wire is swept into the regime where local-moment formation is expected. In order to account for these observations, we develop a theoretical model for the inter-wire interaction that calculated the transmission properties of one (the fixed) wire when the device potential is modified by the presence of an extra scattering term, arising from the presence of the local moment in the swept wire. To determine the transmission coefficients in this system, we derive equations describing the dynamics of electrons in the swept and fixed wires of the coupled-wire geometry. Our analysis clearly shows that the observation of a resonant peak in the conductance of the fixed wire is correlated to the appearance of additional structure (near 0.75 x 2e 2 /h or 0.25 x 2e 2 /h) in the conductance of the swept wire, in agreement with the experimental results of Morimoto et al

  13. Comb-push ultrasound shear elastography of breast masses: initial results show promise.

    Directory of Open Access Journals (Sweden)

    Max Denis

    Full Text Available To evaluate the performance of Comb-push Ultrasound Shear Elastography (CUSE for classification of breast masses.CUSE is an ultrasound-based quantitative two-dimensional shear wave elasticity imaging technique, which utilizes multiple laterally distributed acoustic radiation force (ARF beams to simultaneously excite the tissue and induce shear waves. Female patients who were categorized as having suspicious breast masses underwent CUSE evaluations prior to biopsy. An elasticity estimate within the breast mass was obtained from the CUSE shear wave speed map. Elasticity estimates of various types of benign and malignant masses were compared with biopsy results.Fifty-four female patients with suspicious breast masses from our ongoing study are presented. Our cohort included 31 malignant and 23 benign breast masses. Our results indicate that the mean shear wave speed was significantly higher in malignant masses (6 ± 1.58 m/s in comparison to benign masses (3.65 ± 1.36 m/s. Therefore, the stiffness of the mass quantified by the Young's modulus is significantly higher in malignant masses. According to the receiver operating characteristic curve (ROC, the optimal cut-off value of 83 kPa yields 87.10% sensitivity, 82.61% specificity, and 0.88 for the area under the curve (AUC.CUSE has the potential for clinical utility as a quantitative diagnostic imaging tool adjunct to B-mode ultrasound for differentiation of malignant and benign breast masses.

  14. Phonon dispersion and thermal conductivity of nanocrystal superlattices using three-dimensional atomistic models

    International Nuclear Information System (INIS)

    Zanjani, Mehdi B.; Lukes, Jennifer R.

    2014-01-01

    A computational study of thermal conductivity and phonon dispersion of gold nanocrystal superlattices is presented. Phonon dispersion curves, reported here for the first time from combined molecular dynamics and lattice dynamics calculations, show multiple phononic band gaps and consist of many more dispersion branches than simple atomic crystals. Fully atomistic three dimensional molecular dynamics calculations of thermal conductivity using the Green Kubo method are also performed for the first time on these materials. Thermal conductivity is observed to increase for increasing nanocrystal core size and decrease for increasing surface ligand density. Our calculations predict values in the range 0.1–1 W/m K that are consistent with reported experimental results

  15. Carbon doped PDMS: conductance stability over time and implications for additive manufacturing of stretchable electronics

    International Nuclear Information System (INIS)

    Tavakoli, Mahmoud; Rocha, Rui; Osorio, Luis; Almeida, Miguel; De Almeida, Anibal; Ramachandran, Vivek; Tabatabai, Arya; Lu, Tong; Majidi, Carmel

    2017-01-01

    Carbon doped PDMS (cPDMS), has been used as a conductive polymer for stretchable electronics. Compared to liquid metals, cPDMS is low cost and is easier to process or to print with an additive manufacturing process. However, changes on the conductance of the carbon based conductive PDMS (cPDMS) were observed over time, in particular after integration of cPDMS and the insulating polymer. In this article we investigate the process parameters that lead to improved stability over conductance of the cPDMS over time. Slight modifications to the fabrication process parameters were conducted and changes on the conductance of the samples for each method were monitored. Results suggested that change of the conductance happens mostly after integration of a pre-polymer over a cured cPDMS, and not after integration of the cPDMS over a cured insulating polymer. We show that such changes can be eliminated by adjusting the integration priority between the conductive and insulating polymers, by selecting the right curing temperature, changing the concentration of the carbon particles and the thickness of the conductive traces, and when possible by changing the insulating polymer material. In this way, we obtained important conclusions regarding the effect of these parameters on the change of the conductance over time, that should be considered for additive manufacturing of soft electronics. Also, we show that these changes can be possibly due to the diffusion from PDMS into cPDMS. (paper)

  16. Conduct Disorder and Neighborhood Effects.

    Science.gov (United States)

    Jennings, Wesley G; Perez, Nicholas M; Reingle Gonzalez, Jennifer M

    2018-05-07

    There has been a considerable amount of scholarly attention to the relationship between neighborhood effects and conduct disorder, particularly in recent years. Having said this, it has been nearly two decades since a comprehensive synthesis of this literature has been conducted. Relying on a detailed and comprehensive search strategy and inclusion criteria, this article offers a systematic and interdisciplinary review of 47 empirical studies that have examined neighborhood effects and conduct disorder. Described results suggest that there are generally robust linkages between adverse neighborhood factors and conduct disorder and externalizing behavior problems, as 67 of the 93 (72.04%) effect sizes derived from these studies yielded statistically significant neighborhood effects. The review also identifies salient mediating and moderating influences. It discusses study limitations and directions for future research as well.

  17. Quantized conductance in atom-sized wires between two metals

    DEFF Research Database (Denmark)

    Brandbyge, Mads; Schiøtz, Jakob; Sørensen, Mads Reinholdt

    1995-01-01

    We present experimental and theoretical results for the conductance and mechanical properties of atom-sized wires between two metals. The experimental part is based on measurements with a scanning tunneling microscope (STM) where a point contact is created by indenting the tip into a gold surface...... is the origin of the scatter in the experimental data, and what is the origin of the scaling of the scattering with the number of conductance quanta? The theoretical discussion is based on a free-electron-like model where scattering from the boundary of the nanowire is included. The configurations...... of the nanowires are deduced from molecular dynamics simulations, which also give information about the mechanical properties of the system. We show that such a model can account semiquantitatively for several of the observed effects. One of the main conclusions of the theoretical analysis is that,; due...

  18. Reducing the cost of MWT module technology based on conductive back-sheet foils

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, I.J.; Goris, M.J.A.A.; Eerenstein, W. [ECN Solar Energy, P.O. Box 1, 1755 ZG Petten (Netherlands)

    2013-10-15

    MWT cell and module technology has shown to result in modules with a higher power output than H-pattern modules and to be suitable for use with thin and fragile cells. In this work, the use of low-cost module materials and their effect on module performance and reliability has been assessed. These materials include a conductive back-sheet patterned by milling with no silver plating at the contacts on the foil and no isolation coating on the copper and a low-silver content conductive adhesive. The sensitivity of module performance for the anti-corrosion coating on the copper of the conductive back-sheet is measured, as is the reliability in climate chamber testing of mini-modules made with these materials. The results show that these low cost materials can be used to manufacture module with good performance and reliability. Options are given for further cost reduction.

  19. Noninvasive electrical conductivity measurement by MRI: a test of its validity and the electrical conductivity characteristics of glioma.

    Science.gov (United States)

    Tha, Khin Khin; Katscher, Ulrich; Yamaguchi, Shigeru; Stehning, Christian; Terasaka, Shunsuke; Fujima, Noriyuki; Kudo, Kohsuke; Kazumata, Ken; Yamamoto, Toru; Van Cauteren, Marc; Shirato, Hiroki

    2018-01-01

    This study noninvasively examined the electrical conductivity (σ) characteristics of diffuse gliomas using MRI and tested its validity. MRI including a 3D steady-state free precession (3D SSFP) sequence was performed on 30 glioma patients. The σ maps were reconstructed from the phase images of the 3D SSFP sequence. The σ histogram metrics were extracted and compared among the contrast-enhanced (CET) and noncontrast-enhanced tumour components (NCET) and normal brain parenchyma (NP). Difference in tumour σ histogram metrics among tumour grades and correlation of σ metrics with tumour grades were tested. Validity of σ measurement using this technique was tested by correlating the mean tumour σ values measured using MRI with those measured ex vivo using a dielectric probe. Several σ histogram metrics of CET and NCET of diffuse gliomas were significantly higher than NP (Bonferroni-corrected p ≤ .045). The maximum σ of NCET showed a moderate positive correlation with tumour grade (r = .571, Bonferroni-corrected p = .018). The mean tumour σ measured using MRI showed a moderate positive correlation with the σ measured ex vivo (r = .518, p = .040). Tissue σ can be evaluated using MRI, incorporation of which may better characterise diffuse gliomas. • This study tested the validity of noninvasive electrical conductivity measurements by MRI. • This study also evaluated the electrical conductivity characteristics of diffuse glioma. • Gliomas have higher electrical conductivity values than the normal brain parenchyma. • Noninvasive electrical conductivity measurement can be helpful for better characterisation of glioma.

  20. Ambient effects on the electrical conductivity of carbon nanotubes

    DEFF Research Database (Denmark)

    Roch, Aljoscha; Greifzu, Moritz; Roch Talens, Esther

    2015-01-01

    We show that the electrical conductivity of single walled carbon nanotubes (SWCNT) networks is affected by oxygen and air humidity under ambient conditions by more than a magnitude. Later, we intentionally modified the electrical conductivity by functionalization with iodine and investigated...

  1. Ground-penetrating radar investigations conducted in the 100 areas, Hanford Site: Fiscal Year 1992

    International Nuclear Information System (INIS)

    Bergstrom, K.A.

    1994-01-01

    During Fiscal Year 1992, the Geophysics Group conducted forty- five Ground-Penetrating Radar (GPR) surveys in the 100 Areas (Figure 1) - Objectives for the investigations varied, from locating cribs, trenches and septic systems to helping site boreholes. The results of each investigation were delivered to clients in the form of a map that summarized the interpretation of a given site. No formal reports were prepared. The purpose of this document is to show where and why each of the surveys was conducted. The data and interpretation of each survey are available by contacting the Westinghouse Hanford Company, Geophysics Group. A map showing the location and basic parameters of each survey can be found in the Appendices of this report

  2. The impact of multiple show-ups on eyewitness decision-making and innocence risk.

    Science.gov (United States)

    Smith, Andrew M; Bertrand, Michelle; Lindsay, R C L; Kalmet, Natalie; Grossman, Deborah; Provenzano, Daniel

    2014-09-01

    If an eyewitness rejects a show-up, police may respond by finding a new suspect and conducting a second show-up with the same eyewitness. Police may continue finding suspects and conducting show-ups until the eyewitness makes an identification (Study 1). Relatively low criterion-setting eyewitnesses filter themselves out of the multiple show-ups procedure by choosing the first suspect with whom they are presented (Studies 2 and 3). Accordingly, response bias was more stringent on the second show-up when compared with the first, but became no more stringent with additional show-ups. Despite this stringent shift in response bias, innocence risk increased with additional show-ups, as false alarms cumulate (Studies 2 and 3). Although unbiased show-up instructions decreased innocent suspect identifications, the numbers were still discouraging (Study 4). Given the high number of innocent suspects who would be mistakenly identified through the use of multiple show-up procedures, using such identifications as evidence of guilt is questionable. Although evidence of guilt is limited to identifications from a single show-up, practical constraints might sometimes require police to use additional show-ups. Accordingly, we propose a stronger partition between evidentiary and investigative procedures. PsycINFO Database Record (c) 2014 APA, all rights reserved.

  3. Conduction in Carbon Nanotubes Through Metastable Resonant States

    Science.gov (United States)

    Zhang, Zhengfan; Chandrasekhar, Venkat; Dikin, Dmitriy A.; Ruoff, Rodney S.

    2004-03-01

    We have made transport measurements on individual multi-walled carbon nanotubes [1]. The measurements show that the presence or movement of impurities or defects in the carbon nanotube can radically change its low temperature transport characteristics. The low temperature conductance can either decrease monotonically with decreasing temperature, or show a sudden increase at very low temperatures, sometimes in the same sample. This unusual behavior of the temperature dependence of the conductance is correlated with large variations in the differential conductance as a function of the dc voltage across the wire. The effect is well described as arising from quantum interference of conduction channels corresponding to direct transmission through the nanotube and resonant transmission through a discrete electron state, the so-called Fano resonance. We thank the group of R. P. H. Chang for providing us the nanotubes used in these experiments. Funding for this work was provided by a NASA/MSFC Phase II SBIR, Contract No. NAS8-02102, through a subcontract from Lytec, LLC. [1] Z. Zhang et al., cond-mat/0311360.

  4. Dynamical electrical conductivity of graphene

    Science.gov (United States)

    Rani, Luxmi; Singh, Navinder

    2017-06-01

    For graphene (a Dirac material) it has been theoretically predicted and experimentally observed that DC resistivity is proportional to T 4 when the temperature is much less than Bloch-Grüneisen temperature ({{ \\Theta }\\text{BG}} ) and T-linear in the opposite case (T\\gg {{ \\Theta }\\text{BG}} ). Going beyond this case, we investigate the dynamical electrical conductivity in graphene using the powerful method of the memory function formalism. In the zero frequency regime, we obtain the above mentioned behavior which was previously obtained using the Bloch-Boltzmann kinetic equation. In the finite frequency regime, we obtain several new results: (1) the generalized Drude scattering rate, in the zero temperature limit, shows {ω4} behavior at low frequencies (ω \\ll {{k}\\text{B}}{{ \\Theta }\\text{BG}}/\\hbar ) and saturates at higher frequencies. We also observed the Holstein mechanism, however, with different power laws from that in the case of metals; (2) at higher frequencies, ω \\gg {{k}\\text{B}}{{ \\Theta }\\text{BG}}/\\hbar , and higher temperatures T\\gg {{ \\Theta }\\text{BG}} , we observed that the generalized Drude scattering rate is linear in temperature. In addition, several other results are also obtained. With the experimental advancement of this field, these results should be experimentally tested.

  5. Quantum corrections to conductivity in graphene with vacancies

    Science.gov (United States)

    Araujo, E. N. D.; Brant, J. C.; Archanjo, B. S.; Medeiros-Ribeiro, G.; Alves, E. S.

    2018-06-01

    In this work, different regions of a graphene device were exposed to a 30 keV helium ion beam creating a series of alternating strips of vacancy-type defects and pristine graphene. From magnetoconductance measurements as function of temperature, density of carriers and density of strips we show that the electron-electron interaction is important to explain the logarithmic quantum corrections to the Drude conductivity in graphene with vacancies. It is known that vacancies in graphene behave as local magnetic moments that interact with the conduction electrons and leads to a logarithmic correction to the conductance through the Kondo effect. However, our work shows that it is necessary to account for the non-homogeneity of the sample to avoid misinterpretations about the Kondo physics due the difficulties in separating the electron-electron interaction from the Kondo effect.

  6. The effects of MWNT on thermal conductivity and thermal mechanical properties of epoxy

    Science.gov (United States)

    Ismadi, A. I.; Othman, R. N.

    2017-12-01

    Multiwall nanotube (MWNT) was used as filler in various studies to improve thermal conductivity and mechanical properties of epoxy. Present study varied different weight loading (0, 0.1 %, 0.5 %, 1 %, 1.5 %, 3 % and 5 %) of MWNT in order to observe the effects on the epoxy. Nanocomposite was analyzed by dynamic-mechanical thermal analyser (DMTA) and KD2 pro analyzer. DMTA measured storage modulus (E') and glass transition temperature (Tg) of the nanocomposite. Result showed that Tg value of neat epoxy is higher than all MWNT epoxy nanocomposite. Tg values drop from 81.55 °C (neat epoxy) to 65.03 °C (at 0.1 wt%). This may happen due to the agglomeration of MWNT in the epoxy. However, Tg values increases with the increase of MWNT wt%. Tg values increased from 65.03 °C to 78.53 °C at 1 wt%. Increment of storage modulus (E') at 3 °C (glassy region) was observed as the MWNT loading increases. Maximum value of E' during glassy region was observed to be at 5 wt% with (7.26±0.7) E+08 Pa compared to neat epoxy. On the contrary, there is slight increased and slight decreased with E' values at 100 °C (rubbery region) for all nanocomposite. Since epoxy exhibits low thermal conductivity properties, addition of MWNT has enhanced the properties. Optimum value of thermal conductivity was observed at 3 wt%. The values increased up to 9.03 % compared to neat epoxy. As expected, the result showed decrease value in thermal conductivity at 5 wt% as a result of agglomeration of MWNT in the epoxy.

  7. Optimality and Conductivity for Water Flow: From Landscapes, to Unsaturated Soils, to Plant Leaves

    Energy Technology Data Exchange (ETDEWEB)

    Liu, H.H.

    2012-02-23

    Optimality principles have been widely used in many areas. Based on an optimality principle that any flow field will tend toward a minimum in the energy dissipation rate, this work shows that there exists a unified form of conductivity relationship for three different flow systems: landscapes, unsaturated soils and plant leaves. The conductivity, the ratio of water flux to energy gradient, is a power function of water flux although the power value is system dependent. This relationship indicates that to minimize energy dissipation rate for a whole system, water flow has a small resistance (or a large conductivity) at a location of large water flux. Empirical evidence supports validity of the relationship for landscape and unsaturated soils (under gravity dominated conditions). Numerical simulation results also show that the relationship can capture the key features of hydraulic structure for a plant leaf, although more studies are needed to further confirm its validity. Especially, it is of interest that according to this relationship, hydraulic conductivity for gravity-dominated unsaturated flow, unlike that defined in the classic theories, depends on not only capillary pressure (or saturation), but also the water flux. Use of the optimality principle allows for determining useful results that are applicable to a broad range of areas involving highly non-linear processes and may not be possible to obtain from classic theories describing water flow processes.

  8. Transparent Conducting Graphene Hybrid Films To Improve Electromagnetic Interference (EMI) Shielding Performance of Graphene.

    Science.gov (United States)

    Ma, Limin; Lu, Zhengang; Tan, Jiubin; Liu, Jian; Ding, Xuemei; Black, Nicola; Li, Tianyi; Gallop, John; Hao, Ling

    2017-10-04

    Conducting graphene-based hybrids have attracted considerable attention in recent years for their scientific and technological significance in many applications. In this work, conductive graphene hybrid films, consisting of a metallic network fully encapsulated between monolayer graphene and quartz-glass substrate, were fabricated and characterized for their electromagnetic interference shielding capabilities. Experimental results show that by integration with a metallic network the sheet resistance of graphene was significantly suppressed from 813.27 to 5.53 Ω/sq with an optical transmittance at 91%. Consequently, the microwave shielding effectiveness (SE) exceeded 23.60 dB at the K u -band and 13.48 dB at the K a -band. The maximum SE value was 28.91 dB at 12 GHz. Compared with the SE of pristine monolayer graphene (3.46 dB), the SE of graphene hybrid film was enhanced by 25.45 dB (99.7% energy attenuation). At 94% optical transmittance, the sheet resistance was 20.67 Ω/sq and the maximum SE value was 20.86 dB at 12 GHz. Our results show that hybrid graphene films incorporate both high conductivity and superior electromagnetic shielding comparable to existing ITO shielding modalities. The combination of high conductivity and shielding along with the materials' earth-abundant nature, and facile large-scale fabrication, make these graphene hybrid films highly attractive for transparent EMI shielding.

  9. Fractal analysis of the effect of particle aggregation distribution on thermal conductivity of nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Wei, E-mail: weiw2015@gmail.com [Hubei Subsurface Multi-scale Imaging Key Laboratory, Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074 (China); Cai, Jianchao, E-mail: caijc@cug.edu.cn [Hubei Subsurface Multi-scale Imaging Key Laboratory, Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074 (China); Hu, Xiangyun, E-mail: xyhu@cug.edu.cn [Hubei Subsurface Multi-scale Imaging Key Laboratory, Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074 (China); Han, Qi, E-mail: hanqi426@gmail.com [Hubei Subsurface Multi-scale Imaging Key Laboratory, Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074 (China); Liu, Shuang, E-mail: lius@cug.edu.cn [Hubei Subsurface Multi-scale Imaging Key Laboratory, Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074 (China); Zhou, Yingfang, E-mail: yingfang.zhou@abdn.ac.uk [School of Engineering, University of Aberdeen, FN 264, King' s College, Aberdeen, AB24 3UE (United Kingdom)

    2016-08-26

    A theoretical effective thermal conductivity model for nanofluids is derived based on fractal distribution characteristics of nanoparticle aggregation. Considering two different mechanisms of heat conduction including particle aggregation and convention, the model is expressed as a function of the fractal dimension and concentration. In the model, the change of fractal dimension is related to the variation of aggregation shape. The theoretical computations of the developed model provide a good agreement with the experimental results, which may serve as an effective approach for quantitatively estimating the effective thermal conductivity of nanofluids. - Highlights: • A thermal conductivity model is derived based on fractal aggregation distribution. • The relationship between aggregation shape and fractal dimension is analyzed. • Predictions of the proposed model show good agreement with experimental data.

  10. Effect of electrodes in the radiation induced conductivity for polymers

    International Nuclear Information System (INIS)

    Gregorio Filho, R.; Gross, B.

    1988-01-01

    Samples of PET with 23 μm thickness were exposed to continuous X-rays and the radiation-induced conductivity (RIC) as a function of time were measured, using electrodes of evaporated aluminum and gold. The results showed that the use of higher atomic number metal electrodes increase the received dose rate by sample, without almost modifying the time evolution of the RIC or its dependence with the applied electric field intensity. It is also showed that this increase is caused by the electrode placed in the face of the sample where the radiation strikes, as well as by the one placed in the oposite face. (author) [pt

  11. A novel thick-film electrical conductivity sensor suitable for liquid and soil conductivity measurements

    OpenAIRE

    Atkinson, John; Sophocleous, Marios

    2015-01-01

    Results are reported from an initial evaluation of a novel conductivity sensor that could be incorporated onto a multi-element thick film (screen printed) sensor array designed for soil and water analysis. The new sensor exhibits a repeatable cell constant over a wide range of conductivities and is currently performing very well in an investigation of soil structural properties where its output is being correlated with soil water content in a study of different soil porosities.

  12. Constructal entransy dissipation minimization for 'volume-point' heat conduction

    International Nuclear Information System (INIS)

    Chen Lingen; Wei Shuhuan; Sun Fengrui

    2008-01-01

    minimization of entransy dissipation are different from those based on the minimization of the maximum temperature difference. For the same parameters, the constructs based on minimization of entransy dissipation and the constructs based on minimization of the maximum temperature difference are compared, and the results show that the constructs based on entransy dissipation can decrease the mean temperature difference better than the constructs based on minimization of the maximum temperature difference and therefore can improve the conductive ability greatly. Because the idea of entransy describes the heat transfer ability more suitably, all of the heat conduction constructal problems may be re-optimized based on it.

  13. Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors

    Science.gov (United States)

    Valvano, J. W.; Cochran, J. R.; Diller, K. R.

    1985-05-01

    This paper presents an experimental method to measure the thermal conductivity and thermal diffusivity of biomaterials. Self-heated thermistor probes, inserted into the tissue of interest, are used to deliver heat as well as to monitor the rate of heat removal. An empirical calibration procedure allows accurate thermal-property measurements over a wide range of tissue temperatures. Operation of the instrument in three media with known thermal properties shows the uncertainty of measurements to be about 2%. The reproducibility is 0.5% for the thermal-conductivity measurements and 2% for the thermal-diffusivity measurements. Thermal properties were measured in dog, pig, rabbit, and human tissues. The tissues included kidney, spleen, liver, brain, heart, lung, pancreas, colon cancer, and breast cancer. Thermal properties were measured for 65 separate tissue samples at 3, 10, 17, 23, 30, 37, and 45°C. The results show that the temperature coefficient of biomaterials approximates that of water.

  14. DC conductivity and Seebeck coefficient of nonstoichiometric MgCuZn ferrites

    Directory of Open Access Journals (Sweden)

    Madhuri W.

    2017-02-01

    Full Text Available Nonstoichiometric series of Mg0.5−xCuxZn0.5Fe1.9O4−δ where x = 0.0, 0.1, 0.15, 0.2 and 0.25 has been synthesized by conventional solid state reaction route. The single phase spinel structure of the double sintered ferrites was confirmed by X-ray diffraction patterns (XRD. The ferrite series was studied in terms of DC electrical conductivity and thermoelectric power in the temperature ranging from room temperature to 300 °C and 400 °C, respectively. It was observed that DC electrical conductivity and Seebeck coefficient α decreased with the increase in x. DC electrical conductivity was found to decrease by about 4 orders. All the compositions showed a negative Seebeck coefficient exhibiting n-type semiconducting nature. From the above experimental results, activation energy and mobility of all the samples were estimated. Small polaron hopping conduction mechanism was suggested for the series of ferrites. Owing to their low conductivity the nonstoichiometric MgCuZn ferrites are the best materials for transformer core and high definition television deflection yokes.

  15. Biocompatibility Assessment of Conducting PANI/Chitosan Nanofibers for Wound Healing Applications

    Directory of Open Access Journals (Sweden)

    Panagiota Moutsatsou

    2017-12-01

    Full Text Available As electroactive polymers have recently presented potential in applications in the tissue engineering and biomedical field, this study is aiming at the fabrication of composite nanofibrous membranes containing conducting polyaniline and at the evaluation of their biocompatibility. For that purpose, conducting polyaniline–chitosan (PANI/CS defect free nanofibres of different ratios (1:3; 3:5 and 1:1 were produced with the electrospinning method. They were characterized as for their morphology, hydrophilicity and electrical conductivity. The membranes were then evaluated for their cellular biocompatibility in terms of cell attachment, morphology and cell proliferation. The effect of the PANI content on the membrane properties is discussed. Increase in PANI content resulted in membranes with higher hydrophobicity and higher electrical conductivity. It was found that none of the membranes showed any toxic effects on osteoblasts and fibroblasts, and that they all supported cell attachment and growth, even to a greater extent than tissue culture plastic. The membrane with the PANI/CS ratio 1:3 supports better cell attachment and proliferation for both cell lines due to a synergistic effect of hydrophilicity retention due to the high chitosan content and the conductivity that PANI introduced to the membrane.

  16. Thermal stability and electrical conductivity in polyethers-molybdenum disulfide nanocomposites

    International Nuclear Information System (INIS)

    Mirabal, N.; Aguirre, P.; Santa Ana, M.A.; Benavente, E.; Gonzalez, Guillermo

    2003-01-01

    The intercalation of poly(ethylene oxide) (PEO), into molybdenum disulfide, like that of other electron pair donors, leads to mixed ionic-electronic conductors. At room temperature, intercalates show electrical and lithium-ion conductivities better than MoS 2 and bulk PEO composites, respectively. However, these products are known to be sensitive to temperature; indeed, in the range 80-100 deg. C an irreversible decrease of the electrical conductivity is observed. In order to investigate these features, the thermal behavior of a series of polyethers of different molecular weights (poly(ethylene glycol) (Mw 3400) and PEO with Mw in the range 10 4 -4x10 6 , pure and intercalated in MoS 2 , (Li x (MoS 2 )(polyether) y with x∼0.1 and y=1.1-1.5), was comparatively analyzed. Furthermore, the effect of thermal treatment of the sample on the electrical conductivity was studied for one of the intercalated products. Results indicate that irreversible changes, detected by both loss of weight and a significant conductivity lowering, are occurring in the range from about 100 deg. C to a temperature near to the decomposition point of the organic phase at about 350 deg. C

  17. Prediction of the Thermal Conductivity of Refrigerants by Computational Methods and Artificial Neural Network.

    Science.gov (United States)

    Ghaderi, Forouzan; Ghaderi, Amir H; Ghaderi, Noushin; Najafi, Bijan

    2017-01-01

    Background: The thermal conductivity of fluids can be calculated by several computational methods. However, these methods are reliable only at the confined levels of density, and there is no specific computational method for calculating thermal conductivity in the wide ranges of density. Methods: In this paper, two methods, an Artificial Neural Network (ANN) approach and a computational method established upon the Rainwater-Friend theory, were used to predict the value of thermal conductivity in all ranges of density. The thermal conductivity of six refrigerants, R12, R14, R32, R115, R143, and R152 was predicted by these methods and the effectiveness of models was specified and compared. Results: The results show that the computational method is a usable method for predicting thermal conductivity at low levels of density. However, the efficiency of this model is considerably reduced in the mid-range of density. It means that this model cannot be used at density levels which are higher than 6. On the other hand, the ANN approach is a reliable method for thermal conductivity prediction in all ranges of density. The best accuracy of ANN is achieved when the number of units is increased in the hidden layer. Conclusion: The results of the computational method indicate that the regular dependence between thermal conductivity and density at higher densities is eliminated. It can develop a nonlinear problem. Therefore, analytical approaches are not able to predict thermal conductivity in wide ranges of density. Instead, a nonlinear approach such as, ANN is a valuable method for this purpose.

  18. Application of Conductive Materials to Asphalt Pavement

    Directory of Open Access Journals (Sweden)

    Hai Viet Vo

    2017-01-01

    Full Text Available Snow-melting pavement technique is an advanced preservation method, which can prevent the forming of snow or ice on the pavement surface by increasing the temperature using an embedded heating system. The main scope of this study is to evaluate the impact of conductive additives on the heating efficiency. The electrical resistivity and thermal conductivity were considered to investigate effects of conductive additives, graphite, and carbon fibers on the snow-melting ability of asphalt mixtures. Also, the distribution of the conductive additives within the asphalt concrete body was investigated by microstructural imaging. An actual test was applied to simulate realistic heating for an asphalt concrete mixture. Thermal testing indicated that graphite and carbon fibers improve the snow-melting ability of asphalt mixes and their combination is more effective than when used alone. As observed in the microstructural image, carbon fibers show a long-range connecting effect among graphite conductive clusters and gather in bundles when added excessively. According to the actual test, adding the conductive additives helps improve snow-melting efficiency by shortening processing time and raising the surface temperature.

  19. The information seeking and procurment needs of attendees at an industrial trade show

    Directory of Open Access Journals (Sweden)

    N. C. Bresler

    2009-12-01

    Full Text Available Purpose: The purpose of this article is to describe what attracts visitors to an industrial trade show, and to profile them. This will enable the show organisers to attract the right mix of exhibitors and fulfil their dual role of satisfying the needs of both attendees and exhibitors and improve the role of exhibitions in the latter's marketing mix. Problem investigated: The research seeks to elicit the attendance objectives of participants in order to ascertain their information seeking and procurement needs. This can be used to improve the marketing communication of both the organisers and exhibitors. Research methodology: The research design is a multi method, descriptive study. A non probability, judgemental sample was drawn; 1020 interviews were conducted per Electra Mining Africa expo in 2004 and 2006. Both open ended and fixed response questions were posed and due to the similarity of responses, 300 per show were analysed. The researcher fulfilled a participant observer role to enhance the validity and reliability of the findings. Findings/implications: The prime reason for visitation was to see what is new, discover, and gather information, and attendees were not disappointed in that. The trade shows attracted an informed, niche audience. Exhibitors gained access to key decision makers with buying influence. Attendees represented all roles in the buying process and intended to buy some capital items exhibited within the following year. Business contacts were made. The attraction and contact efficiency of the exhibition's were high and may result in conversion efficiency. In terms of market and geographical coverage it is a vertical international show. Originality: This paper contributes to limited research conducted on trade shows, especially in South Africa. It is unique in that it describes the effectiveness of an industrial trade show from a demand perspective in order to improve the facilitating role of exhibition organisers. It

  20. Hunted woolly monkeys (Lagothrix poeppigii show threat-sensitive responses to human presence.

    Directory of Open Access Journals (Sweden)

    Sarah Papworth

    Full Text Available Responding only to individuals of a predator species which display threatening behaviour allows prey species to minimise energy expenditure and other costs of predator avoidance, such as disruption of feeding. The threat sensitivity hypothesis predicts such behaviour in prey species. If hunted animals are unable to distinguish dangerous humans from non-dangerous humans, human hunting is likely to have a greater effect on prey populations as all human encounters should lead to predator avoidance, increasing stress and creating opportunity costs for exploited populations. We test the threat sensitivity hypothesis in wild Poeppigi's woolly monkeys (Lagothrix poeppigii in Yasuní National Park, Ecuador, by presenting human models engaging in one of three behaviours "hunting", "gathering" or "researching". These experiments were conducted at two sites with differing hunting pressures. Visibility, movement and vocalisations were recorded and results from two sites showed that groups changed their behaviours after being exposed to humans, and did so in different ways depending on the behaviour of the human model. Results at the site with higher hunting pressure were consistent with predictions based on the threat sensitivity hypothesis. Although results at the site with lower hunting pressure were not consistent with the results at the site with higher hunting pressure, groups at this site also showed differential responses to different human behaviours. These results provide evidence of threat-sensitive predator avoidance in hunted primates, which may allow them to conserve both time and energy when encountering humans which pose no threat.

  1. Modifying the conductivity of polypyrrole through low-energy lead ion implantation

    International Nuclear Information System (INIS)

    Booth, Marsilea Adela; Leveneur, Jérôme; Costa, Alexsandro Santos; Kennedy, John; Harbison, SallyAnn; Travas-Sejdic, Jadranka

    2012-01-01

    Interest lies in the creation of novel nanocomposite materials obtained through mixing, impregnation or incorporation techniques. One such technique is ion implantation which possesses the potential for retaining properties from the base material and implanted material as well as any effects observed from combining the two. To this end low-energy (15 keV) implantation of lead ions of various fluences was performed in conducting polypyrrole films. The presence of lead-rich particles was evidenced through transmission electron microscopy. An interesting trend was observed between fluence and conductivity. Of the fluences tested, the optimum fluences of lead ion implantation in polypyrrole films for enhanced conductivity are 5 × 10 14 at. cm −2 and 2 × 10 15 at. cm −2 . The conductivity and stability appear to result from a combination of effects: polymer degradation arising from ion beam damage, an increase in charge-carriers (dications) present after implantation and precipitation of Pb-rich nanoparticles. Monitoring conductivity over time showed increased retention of conductivity levels after lead implantation. Improvements in stability for polypyrrole open avenues for application and bring polypyrrole one step closer to practical use. A mechanism is suggested for this advantageous retained conductivity. -- Highlights: ► Implanted and characterized polypyrrole films with Pb ions at different fluences. ► Samples indicate high conductivity when implanted with particular fluences. ► Increase in charge carriers and precipitation of conductive Pb-rich phase. ► Conductivity stability is higher for some implanted fluences than for pristine polypyrrole.

  2. High frequency conductivity in carbon nanotubes

    Directory of Open Access Journals (Sweden)

    S. S. Abukari

    2012-12-01

    Full Text Available We report on theoretical analysis of high frequency conductivity in carbon nanotubes. Using the kinetic equation with constant relaxation time, an analytical expression for the complex conductivity is obtained. The real part of the complex conductivity is initially negative at zero frequency and become more negative with increasing frequency, until it reaches a resonance minimum at ω ∼ ωB for metallic zigzag CNs and ω < ωB for armchair CNs. This resonance enhancement is indicative for terahertz gain without the formation of current instabilities induced by negative dc conductivity. We noted that due to the high density of states of conduction electrons in metallic zigzag carbon nanotubes and the specific dispersion law inherent in hexagonal crystalline structure result in a uniquely high frequency conductivity than the corresponding values for metallic armchair carbon nanotubes. We suggest that this phenomenon can be used to suppress current instabilities that are normally associated with a negative dc differential conductivity.

  3. Effects of temperature and thermally-induced microstructure change on hydraulic conductivity of Boom Clay

    Directory of Open Access Journals (Sweden)

    W.Z. Chen

    2017-06-01

    Full Text Available Boom Clay is one of the potential host rocks for deep geological disposal of high-level radioactive nuclear waste in Belgium. In order to investigate the mechanism of hydraulic conductivity variation under complex thermo-mechanical coupling conditions and to better understand the thermo-hydro-mechanical (THM coupling behaviour of Boom Clay, a series of permeability tests using temperature-controlled triaxial cell has been carried out on the Boom Clay samples taken from Belgian underground research laboratory (URL HADES. Due to its sedimentary nature, Boom Clay presents across-anisotropy with respect to its sub-horizontal bedding plane. Direct measurements of the vertical (Kv and horizontal (Kh hydraulic conductivities show that the hydraulic conductivity at 80 °C is about 2.4 times larger than that at room temperature (23 °C, and the hydraulic conductivity variation with temperature is basically reversible during heating–cooling cycle. The anisotropic property of Boom Clay is studied by scanning electron microscope (SEM tests, which highlight the transversely isotropic characteristics of intact Boom Clay. It is shown that the sub-horizontal bedding feature accounts for the horizontal permeability higher than the vertical one. The measured increment in hydraulic conductivity with temperature is lower than the calculated one when merely considering the changes in water kinematic viscosity and density with temperature. The nuclear magnetic resonance (NMR tests have also been carried out to investigate the impact of microstructure variation on the THM properties of clay. The results show that heating under unconstrained boundary condition will produce larger size of pores and weaken the microstructure. The discrepancy between the hydraulic conductivity experimentally measured and predicted (considering water viscosity and density changes with temperature can be attributed to the microstructural weakening effect on the thermal volume change

  4. Conductive hearing loss and bone conduction devices: restored binaural hearing?

    Science.gov (United States)

    Agterberg, Martijn J H; Hol, Myrthe K S; Cremers, Cor W R J; Mylanus, Emmanuel A M; van Opstal, John; Snik, Ad F M

    2011-01-01

    An important aspect of binaural hearing is the proper detection of interaural sound level differences and interaural timing differences. Assessments of binaural hearing were made in patients with acquired unilateral conductive hearing loss (UCHL, n = 11) or congenital UCHL (n = 10) after unilateral application of a bone conduction device (BCD), and in patients with bilateral conductive or mixed hearing loss after bilateral BCD application. Benefit (bilateral versus unilateral listening) was assessed by measuring directional hearing, compensation of the acoustic head shadow, binaural summation and binaural squelch. Measurements were performed after an acclimatization time of at least 10 weeks. Unilateral BCD application was beneficial, but there was less benefit in the patients with congenital UCHL as compared to patients with acquired UCHL. In adults with bilateral hearing loss, bilateral BCD application was clearly beneficial as compared to unilateral BCD application. Binaural summation was present, but binaural squelch could not be proven. To explain the poor results in the patients with congenital UCHL, two factors seemed to be important. First, a critical period in the development of binaural hearing might affect the binaural hearing abilities. Second, crossover stimulation, referring to additional stimulation of the cochlea contralateral to the BCD side, might deteriorate binaural hearing in patients with UCHL. Copyright © 2011 S. Karger AG, Basel.

  5. Heat conduction in a plate-type fuel element with time-dependent boundary conditions

    International Nuclear Information System (INIS)

    Faya, A.J.G.; Maiorino, J.R.

    1981-01-01

    A method for the solution of boundary-value problems with variable boundary conditions is applied to solve a heat conduction problem in a plate-type fuel element with time dependent film coefficient. The numerical results show the feasibility of the method in the solution of this class of problems. (Author) [pt

  6. The effect of sediment thermal conductivity on vertical groundwater flux estimates

    Science.gov (United States)

    Sebok, Eva; Müller, Sascha; Engesgaard, Peter; Duque, Carlos

    2015-04-01

    The interaction between groundwater and surface water is of great importance both from ecological and water management perspective. The exchange fluxes are often estimated based on vertical temperature profiles taken from shallow sediments assuming a homogeneous standard value of sediment thermal conductivity. Here we report on a field investigation in a stream and in a fjord, where vertical profiles of sediment thermal conductivity and temperatures were measured in order to, (i) define the vertical variability in sediment thermal conductivity, (ii) quantify the effect of heterogeneity in sediment thermal conductivity on the estimated vertical groundwater fluxes. The study was carried out at field sites located in Ringkøbing fjord and Holtum stream in Western Denmark. Both locations have soft, sandy sediments with an upper organic layer at the fjord site. First 9 and 12 vertical sediment temperature profiles up to 0.5 m depth below the sediment bed were collected in the fjord and in the stream, respectively. Later sediment cores of 0.05 m diameter were removed at the location of the temperature profiles. Sediment thermal conductivity was measured in the sediment cores at 0.1 m intervals with a Decagon KD2 Pro device. A 1D flow and heat transport model (HydroGeoSphere) was set up and vertical groundwater fluxes were estimated based on the measured vertical sediment temperature profiles by coupling the model with PEST. To determine the effect of heterogeneity in sediment thermal conductivity on estimated vertical groundwater fluxes, the model was run by assigning (i) a homogeneous thermal conductivity for all sediment layers, calculated as the average sediment thermal conductivity of the profile, (ii) measured sediment thermal conductivities to the different model layers. The field survey showed that sediment thermal conductivity over a 0.5 m profile below the sediment bed is not uniform, having the largest variability in the fjord where organic sediments were also

  7. Enhanced proton conductivity of niobium phosphates by interfacing crystal grains with an amorphous functional phase

    DEFF Research Database (Denmark)

    Huang, Yunjie; Yu, Lele; Li, Haiyan

    2016-01-01

    Niobium phosphate is an interesting proton conductor operational in the intermediate temperature range. In the present work two forms of phosphates were prepared: an amorphous one with high specific area and a crystalline one with low specific surface area. Both phosphates exhibited very low prot...... the high surface area amorphous phosphate was used as the precursor. At 250 °C thus obtained niobium phosphate showed a high and stable conductivity of 0.03 S cm−1 under dry atmosphere and of 0.06 S cm−1 at a water partial pressure of 0.12 atm....... conductivities. An activation process was developed to convert the phosphates into crystal grains with a phosphorus rich amorphous phase along the grain boundaries. As a result, the obtained niobium phosphates showed considerably enhanced and stable proton conductivities. The activation effect was prominent when...

  8. Outcomes for conservative management of traumatic conductive hearing loss.

    Science.gov (United States)

    Grant, Jonathan R; Arganbright, Jill; Friedland, David R

    2008-04-01

    To evaluate the natural history of traumatic conductive hearing loss. Retrospective chart review. Otologic and audiometric evaluations of patients in the early posttraumatic phase were compared with evaluations at follow-up. Assessment included etiologies of trauma, classification of hearing loss, factors causing conductive loss, and analyses of changes in air-bone gaps, pure-tone averages and hearing loss class. There were 45 patients, representing 47 ears, with sufficient initial and follow-up documentation to analyze the natural history of traumatic conductive hearing loss. Overall, 77% of ears showed an improvement in pure-tone averages without surgical intervention. Air-bone gaps closed from an average of 24.8 +/- 12.1 to 13.2 +/- 11.1 dB. Only 11% of ears demonstrated a decrease in pure-tone averages, and 12% showed no change in thresholds. All forms of injury contributing to the conductive hearing loss had good outcomes. Specifically, tympanic membrane perforations showed final air-bone gaps of 14.9 +/- 11.2 dB; cases of hemotympanum had final air-bone gaps of 10.0 +/- 8.1 dB; and suspected ossicular chain disruptions had final air-bone gaps of 13.9 +/- 12.3 dB. Only 5 of 47 ears ultimately required surgical intervention for persistent pathology. Patients with all forms of traumatic conductive hearing loss can be initially managed conservatively. Even suspected ossicular chain disruptions have a high rate of spontaneous reparation. Surgical intervention for perforation or conductive hearing loss should be undertaken in the rare cases when these conditions persist greater than 6 months.

  9. Synthesis of oxide-free aluminum nanoparticles for application to conductive film

    Science.gov (United States)

    Jong Lee, Yung; Lee, Changsoo; Lee, Hyuck Mo

    2018-02-01

    Aluminum nanoparticles are considered promising as alternatives to conventional ink materials, replacing silver and copper nanoparticles, due to their extremely low cost and low melting temperature. However, a serious obstacle to realizing their use as conductive ink materials is the oxidation of aluminum. In this research, we synthesized the oxide-free aluminum nanoparticles using catalytic decomposition and an oleic acid coating method, and these materials were applied to conductive ink for the first time. The injection time of oleic acid determines the size of the aluminum nanoparticles by forming a self-assembled monolayer on the nanoparticles instead of allowing the formation of an oxide phase. Fabricated nanoparticles were analyzed by transmission electron microscopy and x-ray photoelectron spectroscopy to verify their structural and chemical composition. In addition, conductive inks made of these nanoparticles exhibit electrical properties when they are sintered at over 300 °C in a reducing atmosphere. This result shows that aluminum nanoparticles can be used as an alternative conductive material in printed electronics and can solve the cost issues associated with noble metals.

  10. Analytical solution to convection-radiation of a continuously moving fin with temperature-dependent thermal conductivity

    Directory of Open Access Journals (Sweden)

    Moradi Amir

    2013-01-01

    Full Text Available In this article, the simultaneous convection-radiation heat transfer of a moving fin of variable thermal conductivity is studied. The differential transformation method (DTM is applied for an analytic solution for heat transfer in fin with two different profiles. Fin profiles are rectangular and exponential. The accuracy of analytic solution is validated by comparing it with the numerical solution that is obtained by fourth-order Runge-Kutta method. The analytical and numerical results are shown for different values of the embedding parameters. DTM results show that series converge rapidly with high accuracy. The results indicate that the fin tip temperature increases when ambient temperature increases. Conversely, the fin tip temperature decreases with an increase in the Peclet number, convection-conduction and radiation-conduction parameters. It is shown that the fin tip temperature of the exponential profile is higher than the rectangular one. The results indicate that the numerical data and analytical method are in a good agreement with each other.

  11. Phonon scattering and thermal conductance properties in two coupled graphene nanoribbons modulated with bridge atoms

    International Nuclear Information System (INIS)

    Tan, Shi-Hua; Tang, Li-Ming; Chen, Ke-Qiu

    2014-01-01

    The phonon scattering and thermal conductance properties have been studied in two coupled graphene nanoribbons connected by different bridge atoms by using density functional theory in combination with non-equilibrium Green's function approach. The results show that a wide range of thermal conductance tuning can be realized by changing the chemical bond strength and atom mass of the bridge atoms. It is found that the chemical bond strength (bridge atom mass) plays the main role in phonon scattering at low (high) temperature. A simple equation is presented to describe the relationship among the thermal conductance, bridge atom, and temperature.

  12. Origins of variation in conducted vasomotor responses

    DEFF Research Database (Denmark)

    Hald, Bjørn Olav; Welsh, Donald G.; Holstein-Rathlou, Niels-Henrik

    2015-01-01

    , the efficacy of conducted responses varies significantly between different initiating stimuli within the same vascular bed as well as between different vascular beds following the same stimulus. The differences have stimulated proposals of different mechanisms to account for the experimentally observed...... variation. Using a computational approach that allows for introduction of structural and electrophysiological heterogeneity, we systematically tested variations in both arteriolar electrophysiology and modes of stimuli. Within the same vessel, our simulations show that conduction efficacy is influenced...

  13. Modeling liver electrical conductivity during hypertonic injection.

    Science.gov (United States)

    Castellví, Quim; Sánchez-Velázquez, Patricia; Moll, Xavier; Berjano, Enrique; Andaluz, Anna; Burdío, Fernando; Bijnens, Bart; Ivorra, Antoni

    2018-01-01

    Metastases in the liver frequently grow as scattered tumor nodules that neither can be removed by surgical resection nor focally ablated. Previously, we have proposed a novel technique based on irreversible electroporation that may be able to simultaneously treat all nodules in the liver while sparing healthy tissue. The proposed technique requires increasing the electrical conductivity of healthy liver by injecting a hypersaline solution through the portal vein. Aiming to assess the capability of increasing the global conductivity of the liver by means of hypersaline fluids, here, it is presented a mathematical model that estimates the NaCl distribution within the liver and the resulting conductivity change. The model fuses well-established compartmental pharmacokinetic models of the organ with saline injection models used for resuscitation treatments, and it considers changes in sinusoidal blood viscosity because of the hypertonicity of the solution. Here, it is also described a pilot experimental study in pigs in which different volumes of NaCl 20% (from 100 to 200 mL) were injected through the portal vein at different flow rates (from 53 to 171 mL/minute). The in vivo conductivity results fit those obtained by the model, both quantitatively and qualitatively, being able to predict the maximum conductivity with a 14.6% average relative error. The maximum conductivity value was 0.44 second/m, which corresponds to increasing 4 times the mean basal conductivity (0.11 second/m). The results suggest that the presented model is well suited for predicting on liver conductivity changes during hypertonic saline injection. Copyright © 2017 John Wiley & Sons, Ltd.

  14. Detecting Kondo Entanglement by Electron Conductance

    Science.gov (United States)

    Yoo, Gwangsu; Lee, S.-S. B.; Sim, H.-S.

    2018-04-01

    Quantum entanglement between an impurity spin and electrons nearby is a key property of the single-channel Kondo effects. We show that the entanglement can be detected by measuring electron conductance through a double quantum dot in an orbital Kondo regime. We derive a relation between the entanglement and the conductance, when the SU(2) spin symmetry of the regime is weakly broken. The relation reflects the universal form of many-body states near the Kondo fixed point. Using it, the spatial distribution of the entanglement—hence, the Kondo cloud—can be detected, with breaking of the symmetry spatially nonuniformly by electrical means.

  15. Synchronized conductivity modulation to realize broadband lossless magnetic-free non-reciprocity.

    Science.gov (United States)

    Dinc, Tolga; Tymchenko, Mykhailo; Nagulu, Aravind; Sounas, Dimitrios; Alu, Andrea; Krishnaswamy, Harish

    2017-10-06

    Recent research has explored the spatiotemporal modulation of permittivity to break Lorentz reciprocity in a manner compatible with integrated-circuit fabrication. However, permittivity modulation is inherently weak and accompanied by loss due to carrier injection, particularly at higher frequencies, resulting in large insertion loss, size, and/or narrow operation bandwidths. Here, we show that the presence of absorption in an integrated electronic circuit may be counter-intuitively used to our advantage to realize a new generation of magnet-free non-reciprocal components. We exploit the fact that conductivity in semiconductors provides a modulation index several orders of magnitude larger than permittivity. While directly associated with loss in static systems, we show that properly synchronized conductivity modulation enables loss-free, compact and extremely broadband non-reciprocity. We apply these concepts to obtain a wide range of responses, from isolation to gyration and circulation, and verify our findings by realizing a millimeter-wave (25 GHz) circulator fully integrated in complementary metal-oxide-semiconductor technology.Optical non-reciprocity achieved through refractive index modulation can have its challenges and limitations. Here, Dinc et al. introduce the concept of non-reciprocity based on synchronized spatio-temporal modulation of conductivity to achieve different types of non-reciprocal functionality.

  16. Conductivity and dielectric behaviour of indium substituted zinc ferrites prepared by coprecipitation method

    International Nuclear Information System (INIS)

    Cvejić, Željka; Rakić, Srđan; Jankov, Stevan; Skuban, Sonja; Rapajić, Sanja; Srdić, Vladimir V

    2015-01-01

    This paper presents the results concerning dielectric behavior and conductivity of the nanosized Zn 1−x In x Fe 2 O 4 powders (x = 0, 0.15, 0.2, and 0.3), obtained by coprecipitation method. The frequency dependence of dielectric permittivity and conductivity of the samples is determined in the frequency range of 1–10 5 Hz, at temperatures from 300–350 K, while the temperature dependence of conductivity was recorded at 100 Hz, 10 kHz and 100 kHz. The ac conductivity was found to follow universal dielectric response, which is typical for charge transport by hopping or tunneling processes. Analyzing the variation of the parameter n (as a measure of the degree of correlation between conductivity and frequency), with the temperatures we discuss the possible conduction mechanism in investigated samples. Qualitatively, non-overlapping small polarons (NSPT) are usually associated with increase in n with increasing temperature, while correlated barrier hopping (CBH) shows a decrease in n with increasing T. (paper)

  17. Preparation of conductive paper composites based on natural cellulosic fibers for packaging applications.

    Science.gov (United States)

    Youssef, Ahmed M; El-Samahy, Magda Ali; Abdel Rehim, Mona H

    2012-08-01

    Conducting paper based on natural cellulosic fibers and conductive polymers was prepared using unbleached bagasse and/or rice straw fibers (as cellulosic raw materials) and polyaniline (PANi) as conducting polymer. These composites were synthesized by in situ emulsion polymerization using ammonium persulfate (APS) as oxidant in the presence of dodecylbenzene sulfonic acid (DBSA) as emulsifier. The prepared composites were characterized using Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC), and their morphology was investigated using scanning electron microscope (SEM). Electrical conductivity measurements showed that the conductivity of the paper sheets increases by increasing the ratio of PANi in the composite. Mechanical properties of the paper sheets were also investigated, the results revealed that the values of breaking length, burst factor, and tear factor are decreased with increasing ratio of added PANi, and this effect is more pronounced in bagasse-based composites. The new conductive composites can have potential use as anti-static packaging material or anti-bacterial paper for packaging applications. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Hysteresis in the relation between moisture uptake and electrical conductivity in neat epoxy

    KAUST Repository

    Lubineau, Gilles

    2017-05-11

    Monitoring changes in electrical conductivity is a simple way to assess the water uptake from environmental moisture in polymers. However, the relation between water uptake and changes in conductivity is not fully understood. We monitored changes in the electrical volume conductivity of an anhydride-cured epoxy polymer during moisture sorption-desorption experiments. Gravimetric analysis showed that the polymer exhibits a two-stage sorption behavior resulting from the competition between diffusive and reactive mechanisms. As expected, the macroscopic electrical conductivity increases with the diffusion of water. However, our most surprising observation was severe hysteresis in the relation between water uptake and electrical conductivity during the sorption and desorption experiments. This indicates that change in the electrical conductivity depends on both the water uptake and the competition between the diffusive and reactive mechanisms. We studied samples with various thicknesses to determine the relative effects of the diffusive and reactive mechanisms. This is an important observation as it means that general electrical monitoring techniques should be used cautiously when it comes to measuring the moisture content of polymer or polymer-based composite samples.

  19. Ion conductivity of nasicon ceramics

    International Nuclear Information System (INIS)

    Hoj, J.W.; Engell, J.

    1989-01-01

    The Nasicon ss ,Na 1 + X Zr 2 Si X P 3 - X O 12 o , X , 3, includes some of the best solid state sodium conductors known today. Compositions in the interval 1.6 , X , 2.6 show conductivities comparable to the best β double-prime-alumina ceramics. It is well known that the ion conductivity of β-alumina is strongly dependent on the texture of the ceramic. Here a similar behavior is reported for Nasicon ceramics. Ceramics of the bulk composition Na 2.94 Zr 1.49 Si 2.20 P 0.80 O 10.85 were prepared by a gel method. The final ceramics consist of Nasicon crystals with x = 2.14 and a glass phase. The grain size and texture of the ceramics were controlled by varying the thermal history of the gel based raw materials and the sintering conditions. The room temperature resistivity of the resulting ceramics varies from 3.65*10 3 ohm cm to 1.23*10 3 ohm cm. Using the temperature comparison method and estimates of the area of grain boundaries in the ceramics, the resistivity of the Nasicon phase is estimated to be 225 ohm cm at 25 degrees C. B 2 O 3 - or Al 2 O 3 -doping of the glass bearing Nasicon ceramic lower the room temperature resistivity by a factor 2 to 5. The dopants do not substitute into the Nasicon phase in substantial amounts

  20. Experimental and numerical investigation of the effective electrical conductivity of nitrogen-doped graphene nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Mehrali, Mohammad, E-mail: mohamad.mehrali@siswa.um.edu.my [University of Malaya, Department of Mechanical Engineering and Advanced Material Research Centre (Malaysia); Sadeghinezhad, Emad, E-mail: esn802001@yahoo.com [University of Malaya, Department of Mechanical Engineering (Malaysia); Rashidi, Mohammad Mehdi [Tongji University, Shanghai Automotive Wind Tunnel Center (China); Akhiani, Amir Reza; Tahan Latibari, Sara; Mehrali, Mehdi; Metselaar, Hendrik Simon Cornelis [University of Malaya, Department of Mechanical Engineering and Advanced Material Research Centre (Malaysia)

    2015-06-15

    Electrical conductivity is an important property for technological applications of nanofluids that have not been widely investigated, and few studies have been concerned about the electrical conductivity. In this study, nitrogen-doped graphene (NDG) nanofluids were prepared using the two-step method in an aqueous solution of 0.025 wt% Triton X-100 as a surfactant at several concentrations (0.01, 0.02, 0.04, 0.06 wt%). The electrical conductivity of the aqueous NDG nanofluids showed a linear dependence on the concentration and increased up to 1814.96 % for a loading of 0.06 wt% NDG nanosheet. From the experimental data, empirical models were developed to express the electrical conductivity as functions of temperature and concentration. It was observed that increasing the temperature has much greater effect on electrical conductivity enhancement than increasing the NDG nanosheet loading. Additionally, by considering the electrophoresis of the NDG nanosheets, a straightforward electrical conductivity model is established to modulate and understand the experimental results.

  1. Experimental and numerical investigation of the effective electrical conductivity of nitrogen-doped graphene nanofluids

    Science.gov (United States)

    Mehrali, Mohammad; Sadeghinezhad, Emad; Rashidi, Mohammad Mehdi; Akhiani, Amir Reza; Tahan Latibari, Sara; Mehrali, Mehdi; Metselaar, Hendrik Simon Cornelis

    2015-06-01

    Electrical conductivity is an important property for technological applications of nanofluids that have not been widely investigated, and few studies have been concerned about the electrical conductivity. In this study, nitrogen-doped graphene (NDG) nanofluids were prepared using the two-step method in an aqueous solution of 0.025 wt% Triton X-100 as a surfactant at several concentrations (0.01, 0.02, 0.04, 0.06 wt%). The electrical conductivity of the aqueous NDG nanofluids showed a linear dependence on the concentration and increased up to 1814.96 % for a loading of 0.06 wt% NDG nanosheet. From the experimental data, empirical models were developed to express the electrical conductivity as functions of temperature and concentration. It was observed that increasing the temperature has much greater effect on electrical conductivity enhancement than increasing the NDG nanosheet loading. Additionally, by considering the electrophoresis of the NDG nanosheets, a straightforward electrical conductivity model is established to modulate and understand the experimental results.

  2. Experimental and numerical investigation of the effective electrical conductivity of nitrogen-doped graphene nanofluids

    International Nuclear Information System (INIS)

    Mehrali, Mohammad; Sadeghinezhad, Emad; Rashidi, Mohammad Mehdi; Akhiani, Amir Reza; Tahan Latibari, Sara; Mehrali, Mehdi; Metselaar, Hendrik Simon Cornelis

    2015-01-01

    Electrical conductivity is an important property for technological applications of nanofluids that have not been widely investigated, and few studies have been concerned about the electrical conductivity. In this study, nitrogen-doped graphene (NDG) nanofluids were prepared using the two-step method in an aqueous solution of 0.025 wt% Triton X-100 as a surfactant at several concentrations (0.01, 0.02, 0.04, 0.06 wt%). The electrical conductivity of the aqueous NDG nanofluids showed a linear dependence on the concentration and increased up to 1814.96 % for a loading of 0.06 wt% NDG nanosheet. From the experimental data, empirical models were developed to express the electrical conductivity as functions of temperature and concentration. It was observed that increasing the temperature has much greater effect on electrical conductivity enhancement than increasing the NDG nanosheet loading. Additionally, by considering the electrophoresis of the NDG nanosheets, a straightforward electrical conductivity model is established to modulate and understand the experimental results

  3. Vapor phase polymerization deposition of conducting polymer/graphene nanocomposites as high performance electrode materials.

    Science.gov (United States)

    Yang, Yajie; Li, Shibin; Zhang, Luning; Xu, Jianhua; Yang, Wenyao; Jiang, Yadong

    2013-05-22

    In this paper, we report chemical vapor phase polymerization (VPP) deposition of novel poly(3,4-ethylenedioxythiophene) (PEDOT)/graphene nanocomposites as solid tantalum electrolyte capacitor cathode films. The PEDOT/graphene films were successfully prepared on porous tantalum pentoxide surface as cathode films through the VPP procedure. The results indicated that the high conductivity nature of PEDOT/graphene leads to the decrease of cathode films resistance and contact resistance between PEDOT/graphene and carbon paste. This nanocomposite cathode film based capacitor showed ultralow equivalent series resistance (ESR) ca. 12 mΩ and exhibited better capacitance-frequency performance than the PEDOT based capacitor. The leakage current investigation revealed that the device encapsulation process does not influence capacitor leakage current, indicating the excellent mechanical strength of PEDOT-graphene films. The graphene showed a distinct protection effect on the dielectric layer from possible mechanical damage. This high conductivity and mechanical strength graphene based conducting polymer nanocomposites indicated a promising application future for organic electrode materials.

  4. Conducting Polymers

    Indian Academy of Sciences (India)

    would exhibit electronic conductivity, their conductivities (of compressed pellets) were indeed measured by others, and were found to be .... Polyaniline. Polyphenylene. Polypheny lene- vinylene. Table 1. G!NeRAl I ARTICl! structure. Maximum conductivity Stem Stability. Processability. ~. 1.5 x 105. Reacts with Film not n air.

  5. 78 FR 48315 - Safety Zone; North Hero Air Show; North Hero, VT

    Science.gov (United States)

    2013-08-08

    ... FR Federal Register NPRM Notice of Proposed Rulemaking A. Regulatory History and Information The... During this air show there will be low flying planes conducting aerobatic maneuvers east of North Hero...

  6. SIX2 haploinsufficiency causes conductive hearing loss with ptosis in humans.

    Science.gov (United States)

    Guan, Jing; Wang, Dayong; Cao, Wenjian; Zhao, Yali; Du, Renqian; Yuan, Hu; Liu, Qiong; Lan, Lan; Zong, Liang; Yang, Ju; Yin, Zifang; Han, Bing; Zhang, Feng; Wang, Qiuju

    2016-11-01

    The ossicles represent one of the most fundamental morphological features in evolutionary biology of the mammalians. The mobile ossicular morphology abnormalities result in the severe conductive hearing loss. Development and patterning of the middle ear malformation depend on genetic and environmental causes. However, the genetic basis for the risk of congenital ossicle malformation is poorly understood. We show here nine affected individuals in a Chinese pedigree who had bilateral conductive hearing loss with ptosis. We performed whole-genome sequencing and array comparative genomic hybridization (CGH) analysis on DNA samples from the Chinese pedigree. We confirmed the presence of a novel 60 kb heterozygous deletion in size, encompassing SIX2 in our family. Mutation screening in 169 sporadic cases with external ear and middle ear malformations identified no pathogenic variant or polymorphism. We suggest SIX2 haploinsufficiency as a potential congenital factor could be attributed to developmental malformation of the middle ear ossicles and upper eyelid. To the best of our knowledge, this is the first report to provide a description of copy number variation in the SIX2 gene resulting in syndromic conductive hearing loss.

  7. Evaluation of uranium dioxide thermal conductivity using molecular dynamics simulations

    International Nuclear Information System (INIS)

    Kim, Woongkee; Kaviany, Massoud; Shim, J. H.

    2014-01-01

    It can be extended to larger space, time scale and even real reactor situation with fission product as multi-scale formalism. Uranium dioxide is a fluorite structure with Fm3m space group. Since it is insulator, dominant heat carrier is phonon, rather than electrons. So, using equilibrium molecular dynamics (MD) simulation, we present the appropriate calculation parameters in MD simulation by calculating thermal conductivity and application of it to the thermal conductivity of polycrystal. In this work, we investigate thermal conductivity of uranium dioxide and optimize the parameters related to its process. In this process, called Green Kubo formula, there are two parameters i.e correlation length and sampling interval, which effect on ensemble integration in order to obtain thermal conductivity. Through several comparisons, long correlation length and short sampling interval give better results. Using this strategy, thermal conductivity of poly crystal is obtained and comparison with that of pure crystal is made. Thermal conductivity of poly crystal show lower value that that of pure crystal. In further study, we broaden the study to transport coefficient of radiation damaged structures using molecular dynamics. Although molecular dynamics is tools for treating microscopic scale, most macroscopic issues related to nuclear materials such as voids in fuel materials and weakened mechanical properties by radiation are based on microscopic basis. Thus, research on microscopic scale would be expanded in this field and many hidden mechanism in atomic scales will be revealed via both atomic scale simulations and experiments

  8. Effect of recent popularity on heat-conduction based recommendation models

    Science.gov (United States)

    Li, Wen-Jun; Dong, Qiang; Shi, Yang-Bo; Fu, Yan; He, Jia-Lin

    2017-05-01

    Accuracy and diversity are two important measures in evaluating the performance of recommender systems. It has been demonstrated that the recommendation model inspired by the heat conduction process has high diversity yet low accuracy. Many variants have been introduced to improve the accuracy while keeping high diversity, most of which regard the current node-degree of an item as its popularity. However in this way, a few outdated items of large degree may be recommended to an enormous number of users. In this paper, we take the recent popularity (recently increased item degrees) into account in the heat-conduction based methods, and propose accordingly the improved recommendation models. Experimental results on two benchmark data sets show that the accuracy can be largely improved while keeping the high diversity compared with the original models.

  9. Relating Stomatal Conductance to Leaf Functional Traits.

    Science.gov (United States)

    Kröber, Wenzel; Plath, Isa; Heklau, Heike; Bruelheide, Helge

    2015-10-12

    Leaf functional traits are important because they reflect physiological functions, such as transpiration and carbon assimilation. In particular, morphological leaf traits have the potential to summarize plants strategies in terms of water use efficiency, growth pattern and nutrient use. The leaf economics spectrum (LES) is a recognized framework in functional plant ecology and reflects a gradient of increasing specific leaf area (SLA), leaf nitrogen, phosphorus and cation content, and decreasing leaf dry matter content (LDMC) and carbon nitrogen ratio (CN). The LES describes different strategies ranging from that of short-lived leaves with high photosynthetic capacity per leaf mass to long-lived leaves with low mass-based carbon assimilation rates. However, traits that are not included in the LES might provide additional information on the species' physiology, such as those related to stomatal control. Protocols are presented for a wide range of leaf functional traits, including traits of the LES, but also traits that are independent of the LES. In particular, a new method is introduced that relates the plants' regulatory behavior in stomatal conductance to vapor pressure deficit. The resulting parameters of stomatal regulation can then be compared to the LES and other plant functional traits. The results show that functional leaf traits of the LES were also valid predictors for the parameters of stomatal regulation. For example, leaf carbon concentration was positively related to the vapor pressure deficit (vpd) at the point of inflection and the maximum of the conductance-vpd curve. However, traits that are not included in the LES added information in explaining parameters of stomatal control: the vpd at the point of inflection of the conductance-vpd curve was lower for species with higher stomatal density and higher stomatal index. Overall, stomata and vein traits were more powerful predictors for explaining stomatal regulation than traits used in the LES.

  10. [Characteristics of precipitation pH and conductivity at Mt. Huang].

    Science.gov (United States)

    Shi, Chun-e; Deng, Xue-liang; Wu, Bi-wen; Hong, Jie; Zhang, Su; Yang, Yuan-jian

    2013-05-01

    To understand the general characteristics of pH distribution and pollution in precipitation at Mt. Huang, statistical analyses were conducted for the routine measurements of pH and conductivity (K) at Mt. Huang during 2006-2011. The results showed that: (1) Over the period of study, the annual volume weighted mean (VWM) precipitation pH varied from 4.81 to 5.57, with precipitation acidity strengthening before 2009 and weakening thereafter. The precipitation acidity showed evident seasonal variations, with the VWM pH lowest in winter (4.78), and highest in summer (5.33). The occurrence frequency of acid rain was 46% , accounting for 45% of total rainfalls and with the most frequent pH falling into weak acid to neutral rain. (2) The annual VWM K varied from 16.91 to 27.84 microS x cm(-1), with no evident trend. As for ions pollution, the precipitation was relatively clean at Mt. Huang, with the most frequent K range being below 15 microS x cm(-1), followed by 15-25 microS x cm(-1). From February 2010 to December 2011, precipitation samples were collected on daily basis for ions analysis, as well as pH and K measurement in lab. Detailed comparisons were conducted between the two sets of pH and K, one set from field measurement and the other from lab measurement. The results indicated: (1) The lab measured pH (K) was highly correlated with the field pH (K); however, the lab pH tended to move towards neutral comparing with the corresponding field pH, and the shift range was closely correlated with the field pH and rainfall. The shift range of K from field to lab was highly correlated with the total ion concentration of precipitation. The field K showed evident negative correlation with the field pH with a correlation coefficient of -0.51. (2) When sampling with nylon-polyethylene bags, the statistics showed smaller bias between two sets of pH, with higher correlation coefficient between two sets of K. Furthermore, the lab K also showed evident negative correlation with

  11. Hydrogeological study of single water conducting fracture using a crosshole hydraulic test apparatus

    International Nuclear Information System (INIS)

    Yamamoto, Hajime; Shimo, Michito; Yamamoto, Takuya

    1998-03-01

    The Crosshole Injection Test Apparatus has been constructed to evaluate the hydraulic properties and conditions, such as hydraulic conductivity and its anisotropy, storage coefficient, pore pressure etc. within a rock near a drift. The construction started in FY93 and completed on August FY96 as a set of equipments for the use of crosshole hydraulic test, which is composed of one injection borehole instrument, one observation borehole instrument and a set of on-ground instrument. In FY96, in-situ feasibility test was conducted at a 550 m level drift in Kamaishi In Situ Test Site which has been operated by PNC, and the performance of the equipment and its applicability to various types of injection method were confirmed. In this year, a hydrogeological investigation on the single water conducting fracture was conducted at a 250 m level drift in Kamaishi In Situ Test Site, using two boreholes, KCH-3 and KCH-4, both of which are 30 m depth and inclined by 45 degrees from the surface. Pressure responses at the KCH-3 borehole during the drilling of KCH-4 borehole, the results of Borehole TV logging and core observation indicated that a major conductive single-fracture was successfully isolated by the packers. As a result of a series of the single-hole and the crosshole tests (sinusoidal and constant flowrate test), the hydraulic parameters of the single-fracture (such as hydraulic conductivity and storage coefficient) were determined. This report shows all the test result, analysed data, and also describes the hydro-geological structure near the drift. (author)

  12. Kapitza thermal conductance at the interface between Lennard-Jones crystals using non-equilibrium molecular dynamics simulations

    International Nuclear Information System (INIS)

    Merabia, Samy; Termentzidis, Konstantinos

    2012-01-01

    We characterize the thermal Kapitza conductance between Lennard-Jones solids using non-equilibrium molecular dynamics simulations. We consider a series of perfect interfaces between mass-mismatched solids. We show that both the acoustic mismatch model (AMM) and the diffuse mismatch model (DMM) fail to predict the interfacial conductance even for large acoustic mismatched solids. This poor agreement may be explained by the use of equilibrium distributions of phonons in the expression of the conductance. On the other hand, we show that an extension of AMM taking into account the out-of-equilibrium phonon distribution on both sides of the interface leads to a good agreement with the simulation results, even for interfaces between almost similar materials. This opens the way to understand interfacial heat transport across real semi-conductors and dielectrics.

  13. Sweat conductivity and coulometric quantitative test in neonatal cystic fibrosis screening.

    Science.gov (United States)

    Domingos, Mouseline Torquato; Magdalena, Neiva Isabel Rodrigues; Cat, Mônica Nunes Lima; Watanabe, Alexandra Mitiru; Rosário Filho, Nelson Augusto

    2015-01-01

    To compare the results obtained with the sweat test using the conductivity method and coulometric measurement of sweat chloride in newborns (NBs) with suspected cystic fibrosis (CF) in the neonatal screening program. The sweat test was performed simultaneously by both methods in children with and without CF. The cutoff values to confirm CF were >50 mmol/L in the conductivity and >60 mmol/L in the coulometric test. There were 444 infants without CF (185 males, 234 females, and 24 unreported) submitted to the sweat test through conductivity and coulometric measurement simultaneously, obtaining median results of 32 mmol/L and 12 mmol/L, respectively. For 90 infants with CF, the median values of conductivity and coulometric measurement were 108 mmol/L and 97 mmol/L, respectively. The false positive rate for conductivity was 16.7%, and was higher than 50 mmol/L in all patients with CF, which gives this method a sensitivity of 100% (95% CI: 93.8-97.8), specificity of 96.2% (95% CI: 93.8-97.8), positive predictive value of 83.3% (95% CI: 74.4-91.1), negative predictive value of 100% (95% CI: 90.5-109.4), and 9.8% accuracy. The correlation between the methods was r=0.97 (p>0.001). The best suggested cutoff value was 69.0 mmol/L, with a kappa coefficient=0.89. The conductivity test showed excellent correlation with the quantitative coulometric test, high sensitivity and specificity, and can be used in the diagnosis of CF in children detected through newborn screening. Copyright © 2015 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

  14. Complex electric conductivity of rocks

    International Nuclear Information System (INIS)

    Rocha, B.R.P. da.

    1982-01-01

    Laboratory measurements of complex conductivity were made on 28 drill-core samples from area MM1-Prospect 1 of the Carajas Mining District. The objective of this research was to help interpret field geophysical survey of the area using Induced Polarization and AFMAG methods. A petrographic study of the samples was done, using thin sections, polished sections and X-ray diffraction. Copper content, in the form of sulfides, was determined using atomic absorption. As a result of the petrographic study, the samples were classified in five distinct groups: granite, biotite schist, amphibolite and magnetite quartzite-iron formation. The grade of Cu was variable in the five groups, ranging from 50 ppm to 6000 ppm. In conclusion, these measurements show that the field Induced Polarization and AFMAG anomalies near these three drill holes (F1, F2 and F3) are due primarily to the magnetic iron formation, and secondarily due to associated low-grade chalcopyrite mineralization. (author) [pt

  15. Two and Three-Phases Fractal Models Application in Soil Saturated Hydraulic Conductivity Estimation

    Directory of Open Access Journals (Sweden)

    ELNAZ Rezaei abajelu

    2017-03-01

    (porosity, fractal dimension and the intake air suction head.Some indices like RMSE, AIC and R2 were used to evaluate different fractal models. Results and Discussion: The results of the sensitivity analysis of Rawls - Huang model, showed the least sensitivity to changes in porosity and suction entry air and the most sensitivity to changes in fractal dimension. The saturated hydraulic conductivity is underestimated by increasing the fractal dimension in Rawls - Huang model. The high sensitivity of the combined model to changes in fractal dimension, is considered as one of the model limitations.In other words, fractal dimension underestimation increased the error related to the hydraulic conductivity estimation. Sensitivity analysis of Ks regression model was done among parameters like bulk density, dry density, silt, sand, fractal dimension of particle size and porosity. Results showed less sensitivity to fractal dimension and porosity. The highest RMSE was 0.018 for fractal dimension and porosity (in the range of ±30% changes. The results showed that the amount of clay in the estimation of fractal dimension is of crucial importance. Statistical analyzes indicated the high accuracy of the PSF models based on soil texture data.Error indices showed the high accuracy of Rawls and three-phase fractal (pore- solid- fractal models combination in estimating the Ks value. The results suggest that Huang and Zhang model, with the highest correlation, the least Root Mean Square Error and the least Akaike criteria among the studied fractal models for estimation of the Ks values. Fuentesand Hunt models, overestimated soil saturated hydraulic conductivity. Fuentes et al. (1996 as an experimental fractal model to estimate the saturated hydraulic conductivity indicatedvery poor results. Bird model had higher error values compared with the best model, (RMSE =0.73. This model fit well with the measured values compared to Sepaskhah and Taylor models particularly at low Ksvalues. Taylor's two

  16. Skin conductance response to the pain of others predicts later costly helping.

    Directory of Open Access Journals (Sweden)

    Grit Hein

    Full Text Available People show autonomic responses when they empathize with the suffering of another person. However, little is known about how these autonomic changes are related to prosocial behavior. We measured skin conductance responses (SCRs and affect ratings in participants while either receiving painful stimulation themselves, or observing pain being inflicted on another person. In a later session, they could prevent the infliction of pain in the other by choosing to endure pain themselves. Our results show that the strength of empathy-related vicarious skin conductance responses predicts later costly helping. Moreover, the higher the match between SCR magnitudes during the observation of pain in others and SCR magnitude during self pain, the more likely a person is to engage in costly helping. We conclude that prosocial motivation is fostered by the strength of the vicarious autonomic response as well as its match with first-hand autonomic experience.

  17. An Innovative High Thermal Conductivity Fuel Design

    Energy Technology Data Exchange (ETDEWEB)

    Jamil A. Khan

    2009-11-21

    Thermal conductivity of the fuel in today's Light Water Reactors, Uranium dioxide, can be improved by incorporating a uniformly distributed heat conducting network of a higher conductivity material, Silicon Carbide. The higher thermal conductivity of SiC along with its other prominent reactor-grade properties makes it a potential material to address some of the related issues when used in UO2 [97% TD]. This ongoing research, in collaboration with the University of Florida, aims to investigate the feasibility and develop a formal methodology of producing the resultant composite oxide fuel. Calculations of effective thermal conductivity of the new fuel as a function of %SiC for certain percentages and as a function of temperature are presented as a preliminary approach. The effective thermal conductivities are obtained at different temperatures from 600K to 1600K. The corresponding polynomial equations for the temperature-dependent thermal conductivities are given based on the simulation results. Heat transfer mechanism in this fuel is explained using a finite volume approach and validated against existing empirical models. FLUENT 6.1.22 was used for thermal conductivity calculations and to estimate reduction in centerline temperatures achievable within such a fuel rod. Later, computer codes COMBINE-PC and VENTURE-PC were deployed to estimate the fuel enrichment required, to maintain the same burnup levels, corresponding to a volume percent addition of SiC.

  18. An Innovative High Thermal Conductivity Fuel Design

    International Nuclear Information System (INIS)

    Khan, Jamil A.

    2009-01-01

    Thermal conductivity of the fuel in today's Light Water Reactors, Uranium dioxide, can be improved by incorporating a uniformly distributed heat conducting network of a higher conductivity material, Silicon Carbide. The higher thermal conductivity of SiC along with its other prominent reactor-grade properties makes it a potential material to address some of the related issues when used in UO2 (97% TD). This ongoing research, in collaboration with the University of Florida, aims to investigate the feasibility and develop a formal methodology of producing the resultant composite oxide fuel. Calculations of effective thermal conductivity of the new fuel as a function of %SiC for certain percentages and as a function of temperature are presented as a preliminary approach. The effective thermal conductivities are obtained at different temperatures from 600K to 1600K. The corresponding polynomial equations for the temperature-dependent thermal conductivities are given based on the simulation results. Heat transfer mechanism in this fuel is explained using a finite volume approach and validated against existing empirical models. FLUENT 6.1.22 was used for thermal conductivity calculations and to estimate reduction in centerline temperatures achievable within such a fuel rod. Later, computer codes COMBINE-PC and VENTURE-PC were deployed to estimate the fuel enrichment required, to maintain the same burnup levels, corresponding to a volume percent addition of SiC.

  19. Thermal Conductivity Measurement and Analysis of Fully Ceramic Microencapsulated fuel

    International Nuclear Information System (INIS)

    Lee, H. G.; Kim, D. J.; Park, J. Y.; Kim, W. J.; Lee, S. J.

    2015-01-01

    FCM nuclear fuel is composed of tristructural isotropic(TRISO) fuel particle and SiC ceramic matrix. SiC ceramic matrix play an essential part in protecting fission product. In the FCM fuel concept, fission product is doubly protected by TRISO coating layer and SiC ceramic matrix in comparison with the current commercial UO2 fuel system of LWR. In addition to a safety enhancement of FCM fuel, thermal conductivity of SiC ceramic matrix is better than that of UO2 fuel. Because the centerline temperature of FCM fuel is lower than that of the current UO2 fuel due to the difference of thermal conductivity of fuel, an operational release of fission products from the fuel can be reduced. SiC ceramic has attracted for nuclear fuel application due to its high thermal conductivity properties with good radiation tolerant properties, a low neutron absorption cross-section and a high corrosion resistance. Thermal conductivity of ceramic matrix composite depends on the thermal conductivity of each component and the morphology of reinforcement materials such as fibers and particles. There are many results about thermal conductivity of fiber-reinforced composite like as SiCf/SiC composite. Thermal conductivity of SiC ceramics and FCM pellets with the volume fraction of TRISO particles were measured and analyzed by analytical models. Polycrystalline SiC ceramics and FCM pellets with TRISO particles were fabricated by hot press sintering with sintering additives. Thermal conductivity of the FCM pellets with TRISO particles of 0 vol.%, 10 vol.%, 20 vol.%, 30 vol.% and 40 vol.% show 68.4, 52.3, 46.8, 43.0 and 34.5 W/mK, respectively. As the volume fraction of TRISO particles increased, the measured thermal conductivity values closely followed the prediction of Maxwell's equation

  20. Focused Transhepatic Electroporation Mediated by Hypersaline Infusion through the Portal Vein in Rat Model. Preliminary Results on Differential Conductivity.

    Science.gov (United States)

    Pañella, Clara; Castellví, Quim; Moll, Xavier; Quesada, Rita; Villanueva, Alberto; Iglesias, Mar; Naranjo, Dolores; Sánchez-Velázquez, Patricia; Andaluz, Anna; Grande, Luís; Ivorra, Antoni; Burdío, Fernando

    2017-12-01

    Spread hepatic tumours are not suitable for treatment either by surgery or conventional ablation methods. The aim of this study was to evaluate feasibility and safety of selectively increasing the healthy hepatic conductivity by the hypersaline infusion (HI) through the portal vein. We hypothesize this will allow simultaneous safe treatment of all nodules by irreversible electroporation (IRE) when applied in a transhepatic fashion. Sprague Dawley (Group A, n = 10) and Athymic rats with implanted hepatic tumour (Group B, n = 8) were employed. HI was performed (NaCl 20%, 3.8 mL/Kg) by trans-splenic puncture. Deionized serum (40 mL/Kg) and furosemide (2 mL/Kg) were simultaneously infused through the jugular vein to compensate hypernatremia. Changes in conductivity were monitored in the hepatic and tumour tissue. The period in which hepatic conductivity was higher than tumour conductivity was defined as the therapeutic window (TW). Animals were monitored during 1-month follow-up. The animals were sacrificed and selective samples were used for histological analysis. The overall survival rate was 82.4% after the HI protocol. The mean maximum hepatic conductivity after HI was 2.7 and 3.5 times higher than the baseline value, in group A and B, respectively. The mean maximum hepatic conductivity after HI was 1.4 times higher than tumour tissue in group B creating a TW to implement selective IRE. HI through the portal vein is safe when the hypersaline overload is compensated with deionized serum and it may provide a TW for focused IRE treatment on tumour nodules.

  1. Thermal conductivity of sputtered amorphous Ge films

    International Nuclear Information System (INIS)

    Zhan, Tianzhuo; Xu, Yibin; Goto, Masahiro; Tanaka, Yoshihisa; Kato, Ryozo; Sasaki, Michiko; Kagawa, Yutaka

    2014-01-01

    We measured the thermal conductivity of amorphous Ge films prepared by magnetron sputtering. The thermal conductivity was significantly higher than the value predicted by the minimum thermal conductivity model and increased with deposition temperature. We found that variations in sound velocity and Ge film density were not the main factors in the high thermal conductivity. Fast Fourier transform patterns of transmission electron micrographs revealed that short-range order in the Ge films was responsible for their high thermal conductivity. The results provide experimental evidences to understand the underlying nature of the variation of phonon mean free path in amorphous solids

  2. EDITORIAL: On display with transparent conducting films On display with transparent conducting films

    Science.gov (United States)

    Demming, Anna

    2012-03-01

    Transparent conducting films were already featuring in scientific literature over one hundred years ago. In 1894 Aryton and Mather described a conducting varnish for coating the screens of electric apparatus so they would not charge when accidentally brushed by a coat sleeve or other material [1]. Their method began with a similar approach to that used to make savoury jellies; by dissolving gelatine in vinegar, after which less palatable ingredients were incorporated including sulphuric acid and an antisulphuric enamel. While the search for transparent conducting films continued to attract other researchers, the same problem remained: the transparency would be compromised if the film was too thick, and the conductivity would be compromised if the film was too thin. In the early 1950s Gillham and Preston reported that thin gold films sputtered on bismuth oxide and heated resulted in a material that successfully combined the previously mutually exclusive properties of transparency and conductivity [2]. Other oxide films were also found to favourably combine these properties, including tin oxide, as reported by Ishiguro and colleagues in Japan in 1958 [3]. Today tin oxide doped with indium (ITO) has become the industry standard for transparent conducting films in a range of applications including photovoltaic technology and displays. It is perhaps the mounting ubiquity of electronic displays as a result of the increasingly digitised and computerised environment of the modern day world that has begun to underline the main drawback of ITO: expense. In this issue, a collaboration of researchers in Korea present an overview of graphene as a transparent conducting material with the potential to replace ITO in a range of electronic and optoelectronic applications [4]. One of the first innovations in optical microscopy was the use of dyes. This principle first came into practice with the use of ultraviolet light to reveal previously indistinguishable features. As explained

  3. Preparation of Some Novel Copper(I) Complexes and their Molar Conductances in Organic Solvents

    Science.gov (United States)

    Gill, Dip Singh; Rana, Dilbag

    2009-04-01

    Attempts have been made to prepare some novel copper(I) nitrate, sulfate, and perchlorate complexes. Molar conductances of these complexes have been measured in organic solvents like acetonitrile (AN), acetone (AC), methanol (MeOH), N,N-dimethylformamide (DMF), N,Ndimethylacetamide (DMA), and dimethylsulfoxide (DMSO) at 298 K. The molar conductance data have been analyzed to obtain limiting molar conductances (λ0) and ion association constants (KA) of the electrolytes. The results showed that all these complexes are strong electrolytes in all organic solvents. The limiting ionic molar conductances (λo± ) for various ions have been calculated using Bu4NBPh4 as reference electrolyte. The actual radii for copper(I) complex ions are very large and different in different solvents and indicate some solvation effects in each solvent system

  4. A follow-up of adolescents with conduct disorder:

    DEFF Research Database (Denmark)

    Olsson, Martin; Hansson, Kjell

    2009-01-01

    and adolescent psychiatric unit. Using structured questionnaires as independent variables, this study uses multiple regression analysis to predict health outcomes. Results: The results showed that self-concept and verbal intelligence could significantly predict health outcomes. However, in the multivariate......Abstract Background: This study examines Swedish young adults (age 21) with a history of conduct disorder (CD) in adolescence. Research has established CD as a condition for a range of adverse outcomes. Intelligence, aggression, parent–child conflict, parent–child relation and peer......-rejection are known factors influencing the outcome. Aim: The aim of this longitudinal study is to find how self-confidence and intelligence in an inpatient group diagnosed with CD are related to health in young adulthood. Methods: The subjects were diagnosed with CD in their adolescence at the inpatient child...

  5. Can urinary nitrite results be used to conduct antimicrobial option for urinary tract infection in children?

    Science.gov (United States)

    Mahyar, Abolfazl; Ayazi, Parviz; Froozesh, Mahta; Daneshi-Kohan, Mohammad-Mahdi; Barikani, Ameneh

    2012-06-01

    This study was performed to determine the relationship between urinary nitrite results and bacterial resistance to antimicrobial drugs in urinary tract infection of children. In a cross-section study 119 children younger than 12 years with urinary tract infection were evaluated in Qazvin children's hospital. Patients were divided into negative and positive nitrite groups depending on urinary nitrite test result. Rates of antibiotic resistance in the two groups were compared. Sixty seven patients were in the negative nitrite group and 52 in the positive nitrite group. Resistance rates to ceftriaxone, trimethoprim sulfamethoxazole, ampicillin, gentamicin, amikacin, nalidixic acid, cephalothin and nitrofurantoin in the nitrite negative group were 7.5%, 31.3%, 50.7%, 11.9%, 9%, 3%, 14.9% and 11.9%, respectively. These values in the nitrite positive group were 21.2%, 28.8%, 63.5%, 7.7%, 5.8%, 1.9%, 9.6%, and 3.8%, respectively (P>0.05). This study showed that there is no correlation between urinary nitrite results and bacterial resistance to antimicrobial drugs. Therefore, it seems that physicians should not adjust antibiotic therapy for UTI based on nitrite results.

  6. Temperature dependence of the thermal conductivity in chiral carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mensah, N.G. [Department of Mathematics, University of Cape Coast, Cape Coast (Ghana); Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); Nkrumah, G. [Department of Physics, University of Ghana, Legon, Accra (Ghana) and Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)]. E-mail: geon@ug.edu.gh; Mensah, S.Y. [Department of Physics, Laser and Fibre Optics Centre, University of Cape Coast, Cape Coast (Ghana); Allotey, F.K.A. [Institute of Mathematical Sciences, Accra (Ghana)

    2004-08-30

    The thermal conductivity of a chiral carbon nanotube (CCNT) is calculated using a tractable analytical approach. This is based on solving the Boltzmann kinetic equation with energy dispersion relation obtained in the tight binding approximation. The results obtained are numerically analysed. Unusually high electron thermal conductivity {chi}{sub ez} is observed along the tubular axis. The dependence of {chi}{sub ez} against temperature T was plotted for varying {delta}{sub z} and a given {delta}{sub s} ({delta}{sub z} and {delta}{sub s} are the overlapping integrals (exchange energy) for the jumps along the tubular axis and the base helix, respectively). It is noted that {chi}{sub ez} shows a peaking behaviour before falling off at higher temperature. As {delta}{sub z} varies from 0.010 eV to 0.048 eV for a given {delta}{sub s}=0.0150 eV, the peak values of {chi}{sub ez} shift from 40000 W/m K at 100 K to 55000 W/m K at about 300 K. Interestingly our results at 104 K which is 41000 W/m K and occurred at {delta}{sub z}=0.023 eV compares very well with that reported for a 99.9% isotopically enriched {sup 12}C diamond crystal. Another interesting result obtained is the fact that the circumferential electron thermal conductivity {chi}{sub ec} appears to be very small. The ratio of {chi}{sub ez} to {chi}{sub ec} is of the order of 2.

  7. Identification of conductive hearing loss using air conduction tests alone: reliability and validity of an automatic test battery.

    Science.gov (United States)

    Convery, Elizabeth; Keidser, Gitte; Seeto, Mark; Freeston, Katrina; Zhou, Dan; Dillon, Harvey

    2014-01-01

    The primary objective of this study was to determine whether a combination of automatically administered pure-tone audiometry and a tone-in-noise detection task, both delivered via an air conduction (AC) pathway, could reliably and validly predict the presence of a conductive component to the hearing loss. The authors hypothesized that performance on the battery of tests would vary according to hearing loss type. A secondary objective was to evaluate the reliability and validity of a novel automatic audiometry algorithm to assess its suitability for inclusion in the test battery. Participants underwent a series of hearing assessments that were conducted in a randomized order: manual pure-tone air conduction audiometry and bone conduction audiometry; automatic pure-tone air conduction audiometry; and an automatic tone-in-noise detection task. The automatic tests were each administered twice. The ability of the automatic test battery to: (a) predict the presence of an air-bone gap (ABG); and (b) accurately measure AC hearing thresholds was assessed against the results of manual audiometry. Test-retest conditions were compared to determine the reliability of each component of the automatic test battery. Data were collected on 120 ears from normal-hearing and conductive, sensorineural, and mixed hearing-loss subgroups. Performance differences between different types of hearing loss were observed. Ears with a conductive component (conductive and mixed ears) tended to have normal signal to noise ratios (SNR) despite impaired thresholds in quiet, while ears without a conductive component (normal and sensorineural ears) demonstrated, on average, an increasing relationship between their thresholds in quiet and their achieved SNR. Using the relationship between these two measures among ears with no conductive component as a benchmark, the likelihood that an ear has a conductive component can be estimated based on the deviation from this benchmark. The sensitivity and

  8. Highly conductive paper for energy-storage devices

    KAUST Repository

    Hu, L.; Choi, J. W.; Yang, Y.; Jeong, S.; La Mantia, F.; Cui, L.-F.; Cui, Y.

    2009-01-01

    substrates can dramatically improve film adhesion, greatly simplify the coating process, and significantly lower the cost. Supercapacitors based on CNT-conductive paper show excellent performance. When only CNT mass is considered, a specific capacitance

  9. Sound Localization in Patients With Congenital Unilateral Conductive Hearing Loss With a Transcutaneous Bone Conduction Implant.

    Science.gov (United States)

    Vyskocil, Erich; Liepins, Rudolfs; Kaider, Alexandra; Blineder, Michaela; Hamzavi, Sasan

    2017-03-01

    There is no consensus regarding the benefit of implantable hearing aids in congenital unilateral conductive hearing loss (UCHL). This study aimed to measure sound source localization performance in patients with congenital UCHL and contralateral normal hearing who received a new bone conduction implant. Evaluation of within-subject performance differences for sound source localization in a horizontal plane. Tertiary referral center. Five patients with atresia of the external auditory canal and contralateral normal hearing implanted with transcutaneous bone conduction implant at the Medical University of Vienna were tested. Activated/deactivated implant. Sound source localization test; localization performance quantified using the root mean square (RMS) error. Sound source localization ability was highly variable among individual subjects, with RMS errors ranging from 21 to 40 degrees. Horizontal plane localization performance in aided conditions showed statistically significant improvement compared with the unaided conditions, with RMS errors ranging from 17 to 27 degrees. The mean RMS error decreased by a factor of 0.71 (p conduction implant. Some patients with congenital UCHL might be capable of developing improved horizontal plane localization abilities with the binaural cues provided by this device.

  10. Structure-conductivity studies in polymer electrolytes containing multivalent cations

    International Nuclear Information System (INIS)

    Aziz, M.

    1996-05-01

    Understanding the structure - conductivity relationship is of paramount importance for the development of polymer electrolytes. The present studies present the techniques found useful in the elucidation of structure - conductivity relationship in PEO n :ZnBr 2 (n = 8, 1000, 2000, 3000, 4000 and 5000) and PEO n :FeBr x (n= 8, 20 and 50; x = 2 and 3). Local structural studies have been undertaken using X-ray absorption fine structures (XAFS) which includes extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). EXAFS provides interatomic distance and coordination numbers of the nearest neighbours and results from the EXAFS studies showed that high conductivity is associated with stretched M - O interatomic distance. In the studies on ultra dilute Zn samples it was found that the cation is highly solvated by the heteroatom forming a tightly bound environment which inhibits local segmental motion thus impeding ion migration. XANES studies on the PEO and modified PEO complexes of NiBr 2 revealed the sensitivity of XANES to the structural differences. XANES on Zn and Fe samples also revealed the sensitivity to changes in interatomic distances reflected in shifts of the white line. The complementary nature of EXAFS and XANES was reflected in the studies conducted. Morphological studies were undertaken employing differential scanning calorimetry (DSC), variable temperature polarising microscopy (VTPM) and atomic force microscopy (AFM). DSC evidences helped to explain the texture of the iron samples during the drying process, and showed transitions between low melting, PEO and high melting spherulites, and VTPM is able to visualise the spherulites present in the samples. AFM has successfully imaged the as cast PEO 8 :FeBr 2 sample and the surface effect causing extra resistance in the impedance spectra could be seen. Conductivity studies were carried out using a.c. impedance spectra. Fe(ll) samples exhibit the typical semicircle

  11. A facile approach to spinning multifunctional conductive elastomer fibres with nanocarbon fillers

    International Nuclear Information System (INIS)

    Seyedin, Shayan; Razal, Joselito M; Innis, Peter C; Wallace, Gordon G

    2016-01-01

    Electrically conductive elastomeric fibres prepared using a wet-spinning process are promising materials for intelligent textiles, in particular as a strain sensing component of the fabric. However, these fibres, when reinforced with conducting fillers, typically result in a compromise between mechanical and electrical properties and, ultimately, in the strain sensing functionality. Here we investigate the wet-spinning of polyurethane (PU) fibres with a range of conducting fillers such as carbon black (CB), single-walled carbon nanotubes (SWCNTs), and chemically converted graphene. We show that the electrical and mechanical properties of the composite fibres were strongly dependent on the aspect ratio of the filler and the interaction between the filler and the elastomer. The high aspect ratio SWCNT filler resulted in fibres with the highest electrical properties and reinforcement, while the fibres produced from the low aspect ratio CB had the highest stretchability. Furthermore, PU/SWCNT fibres presented the largest sensing range (up to 60% applied strain) and the most consistent and stable cyclic sensing behaviour. This work provides an understanding of the important factors that influence the production of conductive elastomer fibres by wet-spinning, which can be woven or knitted into textiles for the development of wearable strain sensors. (paper)

  12. Effect of Material Composition and Environmental Condition on Thermal Characteristics of Conductive Asphalt Concrete

    Directory of Open Access Journals (Sweden)

    Pan Pan

    2017-02-01

    Full Text Available Conductive asphalt concrete with high thermal conductivity has been proposed to improve the solar energy collection and snow melting efficiencies of asphalt solar collector (ASC. This paper aims to provide some insight into choosing the basic materials for preparation of conductive asphalt concrete, as well as determining the evolution of thermal characteristics affected by environmental factors. The thermal properties of conductive asphalt concrete were studied by the Thermal Constants Analyzer. Experimental results showed that aggregate and conductive filler have a significant effect on the thermal properties of asphalt concrete, while the effect of asphalt binder was not evident due to its low proportion. Utilization of mineral aggregate and conductive filler with higher thermal conductivity is an efficient method to prepare conductive asphalt concrete. Moreover, change in thermal properties of asphalt concrete under different temperature and moisture conditions should be taken into account to determine the actual thermal properties of asphalt concrete. There was no noticeable difference in thermal properties of asphalt concrete before and after aging. Furthermore, freezing–thawing cycles strongly affect the thermal properties of conductive asphalt concrete, due to volume expansion and bonding degradation.

  13. The scope of obligatory civil liability insurance of entities conducting medical activities and liability for damages resulting from violations of patients’ rights in the Polish law

    Directory of Open Access Journals (Sweden)

    Anna Augustynowicz

    2018-04-01

    Full Text Available Abstract: In the elaboration, the objective scope of obligatory civil liability insurance of entities conducting medical activities in the context of protection from damages resulting from violations of patients’ rights was presented. Based on art. 25 sec. 1 of the Act on Medical Activity, insurance protect