Brazilian urban porosity : Treat or threat?

NARCIS (Netherlands)

Moreno Pessoa, I.; Tasan-Kok, M.T.; Korthals Altes, W.K.

2016-01-01

Urban areas have spatial discontinuities, such as disconnected neighbourhoods, brownfield areas and leftover places. They can be captured by the metaphor of urban porosity. This paper aims to highlight the potential social consequences of urban porosity by creating a ‘porosity index’. The authors

Zeolites with Continuously Tuneable Porosity**

Science.gov (United States)

Wheatley, Paul S; Chlubná-Eliášová, Pavla; Greer, Heather; Zhou, Wuzong; Seymour, Valerie R; Dawson, Daniel M; Ashbrook, Sharon E; Pinar, Ana B; McCusker, Lynne B; Opanasenko, Maksym; Čejka, Jiří; Morris, Russell E

2014-01-01

Zeolites are important materials whose utility in industry depends on the nature of their porous structure. Control over microporosity is therefore a vitally important target. Unfortunately, traditional methods for controlling porosity, in particular the use of organic structure-directing agents, are relatively coarse and provide almost no opportunity to tune the porosity as required. Here we show how zeolites with a continuously tuneable surface area and micropore volume over a wide range can be prepared. This means that a particular surface area or micropore volume can be precisely tuned. The range of porosity we can target covers the whole range of useful zeolite porosity: from small pores consisting of 8-rings all the way to extra-large pores consisting of 14-rings. PMID:25284344

Cylindrical dust acoustic waves with transverse perturbation

International Nuclear Information System (INIS)

Xue Jukui

2003-01-01

The nonlinear dust acoustic waves in dusty plasmas with the combined effects of bounded cylindrical geometry and the transverse perturbation are studied. Using the perturbation method, a cylindrical Kadomtsev-Petviashvili (CKP) equation that describes the dust acoustic waves is deduced for the first time. A particular solution of this CKP equation is also obtained. It is shown that the dust acoustic solitary waves can exist in the CKP equation

3D-printing porosity: A new approach to creating elevated porosity materials and structures.

Science.gov (United States)

Jakus, A E; Geisendorfer, N R; Lewis, P L; Shah, R N

2018-05-01

We introduce a new process that enables the ability to 3D-print high porosity materials and structures by combining the newly introduced 3D-Painting process with traditional salt-leaching. The synthesis and resulting properties of three 3D-printable inks comprised of varying volume ratios (25:75, 50:50, 70:30) of CuSO 4 salt and polylactide-co-glycolide (PLGA), as well as their as-printed and salt-leached counterparts, are discussed. The resulting materials are comprised entirely of PLGA (F-PLGA), but exhibit porosities proportional to the original CuSO 4 content. The three distinct F-PLGA materials exhibit average porosities of 66.6-94.4%, elastic moduli of 112.6-2.7 MPa, and absorbency of 195.7-742.2%. Studies with adult human mesenchymal stem cells (hMSCs) demonstrated that elevated porosity substantially promotes cell adhesion, viability, and proliferation. F-PLGA can also act as carriers for weak, naturally or synthetically-derived hydrogels. Finally, we show that this process can be extended to other materials including graphene, metals, and ceramics. Porosity plays an essential role in the performance and function of biomaterials, tissue engineering, and clinical medicine. For the same material chemistry, the level of porosity can dictate if it is cell, tissue, or organ friendly; with low porosity materials being far less favorable than high porosity materials. Despite its importance, it has been difficult to create three-dimensionally printed structures that are comprised of materials that have extremely high levels of internal porosity yet are surgically friendly (able to handle and utilize during surgical operations). In this work, we extend a new materials-centric approach to 3D-printing, 3D-Painting, to 3D-printing structures made almost entirely out of water-soluble salt. The structures are then washed in a specific way that not only extracts the salt but causes the structures to increase in size. With the salt removed, the resulting medical polymer

Controlling porosity of porous carbon cathode for lithium oxygen batteries: Influence of micro and meso porosity

Science.gov (United States)

Kim, Minjae; Yoo, Eunjoo; Ahn, Wha-Seung; Shim, Sang Eun

2018-06-01

In rechargeable lithium-oxygen (Li-O2) batteries, the porosity of porous carbon materials plays a crucial role in the electrochemical performance serving as oxygen diffusion path and Li ion transfer passage. However, the influence of optimization of porous carbon as an air electrode on cell electrochemical performance remains unclear. To understand the role of carbon porosity in Li-O2 batteries, carbon materials featuring controlled pore sizes and porosity, including C-800 (nearly 96% microporous) and AC-950 (55:45 micro/meso porosity), are designed and synthesized by carbonization using a triazine-based covalent organic polymer (TCOP). We find that the microporous C-800 cathode allows 120 cycles with a limited capacity of 1000 mAh g-1, about 2 and 10 times higher than that of mixed-porosity AC-950 and mesoporous CMK-3, respectively. Meanwhile, the specific discharge capacity of the C-800 electrode at 200 mA g-1 is 6003 mAh g-1, which is lower than that of the 8433 and 9960 mAh g-1 when using AC-950 and CMK-3, respectively. This difference in the electrochemical performance of the porous carbon cathode with different porosity causes to the generation and decomposition of Li2O2 during the charge and discharge cycle, which affects oxygen diffusion and Li ion transfer.

Impact of kinetic mass transfer on free convection in a porous medium

Science.gov (United States)

Lu, Chunhui; Shi, Liangsheng; Chen, Yiming; Xie, Yueqing; Simmons, Craig T.

2016-05-01

We investigate kinetic mass transfer effects on unstable density-driven flow and transport processes by numerical simulations of a modified Elder problem. The first-order dual-domain mass transfer model coupled with a variable-density-flow model is employed to describe transport behavior in porous media. Results show that in comparison to the no-mass-transfer case, a higher degree of instability and more unstable system is developed in the mass transfer case due to the reduced effective porosity and correspondingly a larger Rayleigh number (assuming permeability is independent on the mobile porosity). Given a constant total porosity, the magnitude of capacity ratio (i.e., immobile porosity/mobile porosity) controls the macroscopic plume profile in the mobile domain, while the magnitude of mass transfer timescale (i.e., the reciprocal of the mass transfer rate coefficient) dominates its evolution rate. The magnitude of capacity ratio plays an important role on the mechanism driving the mass flux into the aquifer system. Specifically, for a small capacity ratio, solute loading is dominated by the density-driven transport, while with increasing capacity ratio local mass transfer dominated solute loading may occur at later times. At significantly large times, however, both mechanisms contribute comparably to solute loading. Sherwood Number could be a nonmonotonic function of mass transfer timescale due to complicated interactions of solute between source zone, mobile zone and immobile zone in the top boundary layer, resulting in accordingly a similar behavior of the total mass. The initial assessment provides important insights into unstable density-driven flow and transport in the presence of kinetic mass transfer.

Data Qualification Report: Calculated Porosity and Porosity-Derived Values for Lithostratigraphic Units for use on the Yucca Mountain Project

Energy Technology Data Exchange (ETDEWEB)

P. Sanchez

2001-05-30

The qualification is being completed in accordance with the Data Qualification Plan DQP-NBS-GS-000006, Rev. 00 (CRWMS M&O 2001). The purpose of this data qualification activity is to evaluate for qualification the unqualified developed input and porosity output included in Data Tracking Number (DTN) M09910POROCALC.000. The main output of the analyses documented in DTN M09910POROCALC.000 is the calculated total porosity and effective porosity for 40 Yucca Mountain Project boreholes. The porosity data are used as input to Analysis Model Report (AMR) 10040, ''Rock Properties Model'' (MDL-NBS-GS-000004, Rev. 00), Interim Change Notice [ICN] 02 (CRWMS M&O 2000b). The output from the rock properties model is used as input to numerical physical-process modeling within the context of a relationship developed in the AMR between hydraulic conductivity, bound water and zeolitic zones for use in the unsaturated zone model. In accordance with procedure AP-3.15Q, the porosity output is not used in the direct calculation of Principal Factors for post-closure safety or disruptive events. The original source for DTN M09910POROCALC.000 is a Civilian Radioactive Waste Management System (CRWMS) Management and Operating Contractor (M&O) report, ''Combined Porosity from Geophysical Logs'' (CRWMS M&O 1999a and hereafter referred to as Rael 1999). That report recalculated porosity results for both the historical boreholes covered in Nelson (1996), and the modern boreholes reported in CRWMS M&O (1996a,b). The porosity computations in Rael (1999) are based on density-porosity mathematical relationships requiring various input parameters, including bulk density, matrix density and air and/or fluid density and volumetric water content. The main output is computed total porosity and effective porosity reported on a foot-by-foot basis for each borehole, although volumetric water content is derived from neutron data as an interim output. This qualification

Data Qualification Report: Calculated Porosity and Porosity-Derived Values for Lithostratigraphic Units for use on the Yucca Mountain Project

International Nuclear Information System (INIS)

P. Sanchez

2001-01-01

The qualification is being completed in accordance with the Data Qualification Plan DQP-NBS-GS-000006, Rev. 00 (CRWMS M and O 2001). The purpose of this data qualification activity is to evaluate for qualification the unqualified developed input and porosity output included in Data Tracking Number (DTN) M09910POROCALC.000. The main output of the analyses documented in DTN M09910POROCALC.000 is the calculated total porosity and effective porosity for 40 Yucca Mountain Project boreholes. The porosity data are used as input to Analysis Model Report (AMR) 10040, ''Rock Properties Model'' (MDL-NBS-GS-000004, Rev. 00), Interim Change Notice [ICN] 02 (CRWMS M and O 2000b). The output from the rock properties model is used as input to numerical physical-process modeling within the context of a relationship developed in the AMR between hydraulic conductivity, bound water and zeolitic zones for use in the unsaturated zone model. In accordance with procedure AP-3.15Q, the porosity output is not used in the direct calculation of Principal Factors for post-closure safety or disruptive events. The original source for DTN M09910POROCALC.000 is a Civilian Radioactive Waste Management System (CRWMS) Management and Operating Contractor (M and O) report, ''Combined Porosity from Geophysical Logs'' (CRWMS M and O 1999a and hereafter referred to as Rael 1999). That report recalculated porosity results for both the historical boreholes covered in Nelson (1996), and the modern boreholes reported in CRWMS M and O (1996a,b). The porosity computations in Rael (1999) are based on density-porosity mathematical relationships requiring various input parameters, including bulk density, matrix density and air and/or fluid density and volumetric water content. The main output is computed total porosity and effective porosity reported on a foot-by-foot basis for each borehole, although volumetric water content is derived from neutron data as an interim output. This qualification report uses

Controlled porosity solubility modulated osmotic pump tablets of gliclazide.

Science.gov (United States)

Banerjee, Arti; Verma, P R P; Gore, Subhash

2015-06-01

A system that can deliver drug at a controlled rate is very important for the treatment of various chronic diseases such as diabetes, asthma, and heart disease. Poorly water-soluble drug with pH-dependent solubility such as gliclazide (GLZ) offers challenges in the controlled-release formulation because of low dissolution rate and poor bioavailability. Solid dispersion (SD) of GLZ consisted of hydroxypropyl cellulose (HPC-SSL) as a polymeric solubilizer was manufactured by hot melt extrusion (HME) technology. Then, controlled porosity osmotic pump (CPOP) tablet of gliclazide was designed to deliver drug in a controlled manner up to 16 h. The developed formulation was optimized for type and level of pore former and coating weight gain. The optimized formulation was found to exhibit zero order kinetics independent of pH and agitation speed but depends on osmotic pressure of dissolution media indicated that mechanism of drug release was osmotic pressure. The in vivo performance prediction of developed formulation using convolution approach revealed that the developed formulation was superior to the existing marketed extended-release formulation in terms of attaining steady state plasma levels and indicated adequate exposure in translating hypoglycemic response. The prototype solubilization method combined with controlled porosity osmotic pump based technique could provide a unique way to increase dissolution rate and bioavailability of many poorly water-soluble, narrow therapeutic index drugs used in diabetes, cardiovascular diseases, etc.

SALTSTONE VARIABILITY STUDY - MEASUREMENT OF POROSITY

International Nuclear Information System (INIS)

Harbour, J; Vickie Williams, V; Tommy Edwards, T; Russell Eibling, R; Ray Schumacher, R

2007-01-01

One of the goals of the Saltstone Variability Study is to identify the operational and compositional variables that control or influence the important processing and performance properties of Saltstone mixes. One of the key performance properties is porosity which is a measure of the volume percent of a cured grout that is occupied by salt solution (for the saturated case). This report presents (1) the results of efforts to develop a method for the measurement of porosity of grout samples and (2) initial results of porosity values for samples that have been previously produced as part of the Saltstone Variability Study. A cost effective measurement method for porosity was developed that provides reproducible results, is relatively fast (30 to 60 minutes per sample) and uses a Mettler Toledo HR83 Moisture Analyzer that is already operational and routinely calibrated at Aiken County Technology Laboratory. The method involves the heating of the sample at 105 C until no further mass loss is observed. This mass loss value, which is due to water evaporation, is then used to calculate the volume percent porosity of the mix. The results of mass loss for mixes at 105 C were equivalent to the results obtained using thermal gravimetric analysis. The method was validated by comparing measurements of mass loss at 105 C for cured portland cement in water mixes to values presented in the literature for this system. A stereopycnometer from Quantachrome Instruments was selected to measure the cured grout bulk densities. Density is a property that is required to calculate the porosities. A stereopycnometer was already operational at Aiken County Technology Laboratory, has been calibrated using a solid stainless steel sphere of known volume, is cost effective and fast (∼15 minutes per sample). Cured grout densities are important in their own right because they can be used to project the volume of waste form produced from a given amount of salt feed of known composition. For mixes

Porosity Prediction of Plain Weft Knitted Fabrics

Directory of Open Access Journals (Sweden)

Muhammad Owais Raza Siddiqui

2014-12-01

Full Text Available Wearing comfort of clothing is dependent on air permeability, moisture absorbency and wicking properties of fabric, which are related to the porosity of fabric. In this work, a plug-in is developed using Python script and incorporated in Abaqus/CAE for the prediction of porosity of plain weft knitted fabrics. The Plug-in is able to automatically generate 3D solid and multifilament weft knitted fabric models and accurately determine the porosity of fabrics in two steps. In this work, plain weft knitted fabrics made of monofilament, multifilament and spun yarn made of staple fibers were used to evaluate the effectiveness of the developed plug-in. In the case of staple fiber yarn, intra yarn porosity was considered in the calculation of porosity. The first step is to develop a 3D geometrical model of plain weft knitted fabric and the second step is to calculate the porosity of the fabric by using the geometrical parameter of 3D weft knitted fabric model generated in step one. The predicted porosity of plain weft knitted fabric is extracted in the second step and is displayed in the message area. The predicted results obtained from the plug-in have been compared with the experimental results obtained from previously developed models; they agreed well.

Porosity and Health: Perspective of Traditional Persian Medicine

Science.gov (United States)

Tafazoli, Vahid; Nimrouzi, Majid; Daneshfard, Babak

2016-01-01

Background: The authors of this manuscript aimed to show the importance of porosity and condensation in health according to traditional Persian medicine (TPM) with consideration of new evidence in conventional medicine. Methods: Cardinal traditional medical and pharmacological texts were searched for the traditional terms of takhalkhol (porosity) and takassof (condensity) focused on preventive methods. The findings were classified and compared with new medical findings. Results: According to traditional Persian medicine, porosity and condensity are the two crucial items that contribute to human health. Somatotype is a taxonomy based on embryonic development, which may be considered in parallel with porosity and condensation. However, these terms are not completely the same. There are many causes for acquired porosity comprising hot weather, too much intercourse, rage, starvation, and heavy exercises. In general, porosity increases the risk of diseases as it makes the body organs vulnerable to external hot and cold weather. On the other hand, the porose organs are more susceptible to accumulation of morbid matters because the cellular wastes cannot be evacuated in the normal way. There are some common points between traditional and conventional medicine in the context of porosity and condensity. The relation between diet and somatotype is an example. Conclusion: Condensity and porosity are the two basic items cited in the TPM resources and contribute to health maintenance and disease prevention of body organs. Creating a balance between these two states in different body organs, strongly contributes to disease prevention, treatment and diminishing chronic diseases period. Choosing proper modality including diet, drug therapy, and manual therapy depends on the amount porosity and stiffness of the considered organ and the preferred porosity of the affected organ keeping in a normal healthy state. PMID:27840513

The attitudes, beliefs and behaviours of GPs regarding exercise for chronic knee pain: a systematic review

Directory of Open Access Journals (Sweden)

Foster Nadine E

2010-01-01

Full Text Available Abstract Background Joint pain, specifically chronic knee pain (CKP, is a frequent cause of chronic pain and limitation of function and mobility among older adults. Multiple evidence-based guidelines recommend exercise as a first-line treatment for all patients with CKP or knee osteoarthritis (KOA, yet healthcare practitioners' attitudes and beliefs may limit their implementation. This systematic review aims to identify the attitudes, beliefs and behaviours of General Practitioners (GPs regarding the use of exercise for CKP/KOA. Methods We searched four electronic databases between inception and January 2008, using subject headings to identify studies examining the attitudes, beliefs or behaviours of GPs regarding the use of exercise for the treatment of CKP/KOA in adults aged over 45 years in primary care. Studies referring to patellofemoral pain syndrome or CKP secondary to other causes or that occurring in a prosthetic joint were excluded. Once inclusion and exclusion criteria were applied, study data were extracted and summarised. Study quality was independently reviewed using two assessment tools. Results From 2135 potentially relevant articles, 20 were suitable for inclusion. A variety of study methodologies and approaches to measuring attitudes beliefs and behaviours were used among the studies. Quality assessment revealed good reporting of study objective, type, outcome factors and, generally, the sampling frame. However, criticisms included use of small sample sizes, low response rates and under-reporting of non-responder factors. Although 99% of GPs agreed that exercise should be used for CKP/KOA and reported ever providing advice or referring to a physiotherapist, up to 29% believed that rest was the optimum management approach. The frequency of actual provision of exercise advice or physiotherapy referral was lower. Estimates of provision of exercise advice and physiotherapy referral were generally higher for vignette-based studies

Earth formation porosity log

International Nuclear Information System (INIS)

Smith, H.D.; Smith, M.P.; Schultz, W.E.

1977-01-01

A method for determining the porosity of earth formations in the vicinity of a cased well borehole is described, comprising the steps of: irradiating the earth formations in the vicinity of the cased well borehole with fast neutrons from a source of fast neutrons passed into the borehole; and generating a signal representative of the fast neutron population present in the well borehole at a location in the borehole, the signal is functionally related to the porosity of the earth formations in the vicinity of the borehole

Mechanistic Effects of Porosity on Structural Composite Materials

Science.gov (United States)

Siver, Andrew

As fiber reinforced composites continue to gain popularity as primary structures in aerospace, automotive, and powersports industries, quality control becomes an extremely important aspect of materials and mechanical engineering. The ability to recognize and control manufacturing induced defects can greatly reduce the likelihood of unexpected catastrophic failure. Porosity is the result of trapped volatiles or air bubbles during the layup process and can significantly compromise the strength of fiber reinforced composites. A comprehensive study was performed on an AS4C-UF3352 TCR carbon fiber-epoxy prepreg system to determine the effect of porosity on flexural, shear, low-velocity impact, and damage residual strength properties. Autoclave cure pressure was controlled to induce varying levels of porosity to construct six laminates with porosity concentrations between 0-40%. Porosity concentrations were measured using several destructive and nondestructive techniques including resin burnoff, sectioning and optical analysis, and X-ray computed tomography (CT) scanning. Ultrasonic transmission, thermography, and CT scanning provided nondestructive imaging to evaluate impact damage. A bilinear relationship accurately characterizes the change in mechanical properties with increasing porosity. Strength properties are relatively unaffected when porosity concentrations are below approximately 2.25% and decrease linearly by up to 40% in high porosity specimens.

Kinetics of dodecanoic acid adsorption from caustic solution by activated carbon.

Science.gov (United States)

Pendleton, Phillip; Wu, Sophie Hua

2003-10-15

This study examines the influences of adsorbent porosity and surface chemistry and of carbon dosage on dodecanoic acid adsorption kinetics from aqueous and 2 M NaOH solutions as batch adsorption processes. Both adsorbents are steam-activated carbons prepared from either coconut or coal precursors. Prior to use the adsorbents were washed in deionized water or 2 M NaOH. Mass transfer coefficients and effective overall diffusion coefficients indicate a minor contribution from adsorbent porosity. In contrast, high surface oxygen content impedes transport to and into the adsorbent structure. Carbon dosage shows a proportional increase in transport coefficients with increasing mass; these coefficients are constant when normalized per unit mass. Neither water nor NaOH treatment of the adsorbents has a significant influence on dodecanoic acid adsorption kinetics. Molecular and Knudsen diffusion coefficients are defined to demonstrate that the overall effective diffusion coefficient values and the diffusion process are controlled by surface diffusion.

Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former

Science.gov (United States)

Medřický, Jan; Curry, Nicholas; Pala, Zdenek; Vilemova, Monika; Chraska, Tomas; Johansson, Jimmy; Markocsan, Nicolaie

2015-04-01

Yttria-stabilized zirconia thermal barrier coatings are extensively used in turbine industry; however, increasing performance requirements have begun to make conventional air plasma sprayed coatings insufficient for future needs. Since the thermal conductivity of bulk material cannot be lowered easily; the design of highly porous coatings may be the most efficient way to achieve coatings with low thermal conductivity. Thus the approach of fabrication of coatings with a high porosity level based on plasma spraying of ceramic particles of dysprosia-stabilized zirconia mixed with polymer particles, has been tested. Both polymer and ceramic particles melt in plasma and after impact onto a substrate they form a coating. When the coating is subjected to heat treatment, polymer burns out and a complex structure of pores and cracks is formed. In order to obtain desired porosity level and microstructural features in coatings; a design of experiments, based on changes in spray distance, powder feeding rate, and plasma-forming atmosphere, was performed. Acquired coatings were evaluated for thermal conductivity and thermo-cyclic fatigue, and their morphology was assessed using scanning electron microscopy. It was shown that porosity level can be controlled by appropriate changes in spraying parameters.

On the field determination of effective porosity

International Nuclear Information System (INIS)

Javandel, I.

1989-03-01

Effective porosity of geologic materials is a very important parameter for estimating groundwater travel time and modeling contaminant transport in hydrologic systems. Determination of a representative effective porosity for nonideal systems is a problem still challenging hydrogeologists. In this paper, some of the conventional field geophysical and hydrological methods for estimating effective porosity of geologic materials are reviewed. The limitations and uncertainties associated with each method are discussed. 30 refs., 8 figs

Zeolites with continuously tuneable porosity

OpenAIRE

Wheatley, Paul S; Chlubná-Eliášová, Pavla; Greer, Heather; Zhou, Wuzong; Seymour, Valerie R; Dawson, Daniel M; Ashbrook, Sharon E; Pinar, Ana B; McCusker, Lynne B; Opanasenko, Maksym; Cejka, Jiří; Morris, Russell E

2014-01-01

Czech Science Foundation. Grant Number: P106/12/G015 Zeolites are important materials whose utility in industry depends on the nature of their porous structure. Control over microporosity is therefore a vitally important target. Unfortunately, traditional methods for controlling porosity, in particular the use of organic structure-directing agents, are relatively coarse and provide almost no opportunity to tune the porosity as required. Here we show how zeolites with a continuously tuneabl...

Transient porosity pulses and microfracturing during a stress-generating retrograde metamorphic reaction

Science.gov (United States)

Renard, F.; Zheng, X.; Cordonnier, B.; Zhu, W.; Jamtveit, B.

2017-12-01

Several geological processes involve mineral transformations where nominally dry rocks transform into hydrated ones when left in contact with water (i.e. eclogitization, serpentinization). In these systems, the transformation induces stress if the rock is confined, and the new minerals create a so-called force of crystallization. Here, we study a model retrograde metamorphic reaction, the hydration of periclase, MgO, into brucite, Mg(OH)2, to quantify the coupling between reaction, stress generation, porosity evolution and fracturing. This hydration reaction generates a volume increase of 110%, and a density decrease of 33.8% of the solid. Samples of a microporous MgO ceramics were reacted at 170-211°C, 5-80 MPa confining pressure, 6-95 MPa differential stress and 5 MPa pore fluid pressure. They were installed into an X-ray transparent triaxial deformation rig, called Hades, and mounted on a synchrotron microtomography stage. Each experiment lasted between 2 and 5 hours, during which between 35 and 130 three-dimensional images were acquired, allowing to follow the chemical transformation and the deformation of the sample. Below 30 MPa mean pressure, the hydration reaction was coupled to fracturing of the MgO ceramics, and the transformation rate followed a sigmoidal kinetics curve with a slow initiation, a fast reaction coupled to fracturing and the generation of a transient porosity pulse, and a slow-down until an almost complete transformation of periclase into brucite.. Conversely, above 30 MPa, the reaction kinetics was very slow, without fracturing over the time scale of the experiment. When considering the driving force of the hydration reaction, stress generation should be several hundreds MPa, whereas the present experiments show that fracturing occurred only below 30 MPa. This indicates that the potential energy due to phase transformation generates much lower stress than what is estimated from non-equilibrium thermodynamics. A possible interpretation of

Porosity study on free mineral addition cement paste

International Nuclear Information System (INIS)

Salgueiro, W.; Somoza, A.; Cabrera, O.; Consolati, G.

2004-01-01

A study of the hydration process and the porosity evolution in a cement paste is presented. The analysis of porosity was made in samples with water to cement ratios (w/c) of 0.24, 0.40 and 0.60 at age of 3, 7, 28 and 365 days, respectively. Information on the evolution of total porosity and on the strength of the paste were obtained using positron annihilation lifetime spectroscopy (PALS), scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical tests (compression and flexion) and water absorption techniques. Specifically, positron lifetime technique allowed us to analyze the evolution of gel and capillary porosity during the hydration process. Using a simple function proposed, reasonable fits to the experimental data of the porosity evolution as a function of the compression strength were obtained

Porosity-induced relaxation of strains in GaN layers studied by means of micro-indentation and optical spectroscopy

KAUST Repository

Najar, Adel

2012-05-04

We report the fabrication of porous GaNnanostructures using UV-assisted electroless etching of bulk GaN layer grown on c-plane sapphire substrate in a solution consisting of HF:CH3OH:H2O2. The morphology of the porous GaNnanostructures was characterized for different etching intervals using high resolution scanning electron microscopy. The geometry and size of resultant pores do not appear to be affected by the etching time; however, the pore density was augmented for longer etching time. Micro-indentation tests were carried out to quantify the indentation modulus for different porous GaNnanostructures. Our results reveal a relationship between the elastic properties and the porosity kinetics, i.e., a decrease of the elastic modulus was observed with increasing porosity. The photoluminescence(PL) and Raman measurements carried out at room temperature for the etched samples having a high degree of porosity revealed a strong enhancement in intensity. Also, the peak of the PL wavelength was shifted towards a lower energy. The high intensity of PL was correlated to an increase of scattered photons within the porous media and to the reduction of the dislocation density.

Theory of wave propagation in partially saturated double-porosity rocks: a triple-layer patchy model

Science.gov (United States)

Sun, Weitao; Ba, Jing; Carcione, José M.

2016-04-01

Wave-induced local fluid flow is known as a key mechanism to explain the intrinsic wave dissipation in fluid-saturated rocks. Understanding the relationship between the acoustic properties of rocks and fluid patch distributions is important to interpret the observed seismic wave phenomena. A triple-layer patchy (TLP) model is proposed to describe the P-wave dissipation process in a double-porosity media saturated with two immiscible fluids. The double-porosity rock consists of a solid matrix with unique host porosity and inclusions which contain the second type of pores. Two immiscible fluids are considered in concentric spherical patches, where the inner pocket and the outer sphere are saturated with different fluids. The kinetic and dissipation energy functions of local fluid flow (LFF) in the inner pocket are formulated through oscillations in spherical coordinates. The wave propagation equations of the TLP model are based on Biot's theory and the corresponding Lagrangian equations. The P-wave dispersion and attenuation caused by the Biot friction mechanism and the local fluid flow (related to the pore structure and the fluid distribution) are obtained by a plane-wave analysis from the Christoffel equations. Numerical examples and laboratory measurements indicate that P-wave dispersion and attenuation are significantly influenced by the spatial distributions of both, the solid heterogeneity and the fluid saturation distribution. The TLP model is in reasonably good agreement with White's and Johnson's models. However, differences in phase velocity suggest that the heterogeneities associated with double-porosity and dual-fluid distribution should be taken into account when describing the P-wave dispersion and attenuation in partially saturated rocks.

Particle track membranes with higher porosity

International Nuclear Information System (INIS)

Heinrich, B.; Gemende, B.; Lueck, H.B.

1992-01-01

Possibilities of improvement of flux and dirt loading capacity of particle track membranes have been examined. Three different ways were investigated: using a divergent ion beam for the irradiation; enlarging the surface porosity through a conical pore shape; creating an asymmetrical membrane structure with two different porosities. Mathematical models and experimental results have been discussed. 9 figs, 3 tabs

Porosity Assessment for Different Diameters of Coir Lignocellulosic Fibers

Science.gov (United States)

da Luz, Fernanda Santos; Paciornik, Sidnei; Monteiro, Sergio Neves; da Silva, Luiz Carlos; Tommasini, Flávio James; Candido, Verônica Scarpini

2017-10-01

The application of natural lignocellulosic fibers (LCFs) in engineering composites has increased interest in their properties and structural characteristics. In particular, the inherent porosity of an LCF markedly affects its density and the adhesion to polymer matrices. For the first time, both open and closed porosities of a natural LCF, for different diameter ranges, were assessed. Fibers extracted from the mesocarp of the coconut fruit were investigated by nondestructive methods of density measurements and x-ray microtomography (microCT). It was found that, for all diameter ranges, the closed porosity is significantly higher than the open porosity. The total porosity increases with diameter to around 60% for coir fibers with more than 503 μm in diameter. The amount and characteristics of these open and closed porosities were revealed by t test and Weibull statistics as well as by microCT.

Plant fibre composites - porosity and volumetric interaction

DEFF Research Database (Denmark)

Madsen, Bo; Thygesen, Anders; Lilholt, Hans

2007-01-01

the combination of a high fibre volume fraction, a low porosity and a high composite density is optimal. Experimental data from the literature on volumetric composition and density of four types of plant fibre composites are used to validate the model. It is demonstrated that the model provides a concept......Plant fibre composites contain typically a relative large amount of porosity, which considerably influences properties and performance of the composites. The large porosity must be integrated in the conversion of weight fractions into volume fractions of the fibre and matrix parts. A model...... is presented to predict the porosity as a function of the fibre weight fractions, and to calculate the related fibre and matrix volume fractions, as well as the density of the composite. The model predicts two cases of composite volumetric interaction separated by a transition fibre weight fraction, at which...

Porosity model for simultaneous radionuclide transfer in compact clay

International Nuclear Information System (INIS)

Grambow, B.; Ribet, S.; Landesman, C.; Altman, S.

2010-01-01

Document available in extended abstract form only. Both, a mono and a dual porosity model have been developed to describe diffusion in bentonite as function of compaction, which give similar results for the diffusion coefficients. There are little advantages but more computation time for the dual porosity model compared to the mono-porosity model. A significant change in paradigm has been proposed to describe diffusion accessible porosity in bentonite: Only a single micro-porosity value is considered for anions, cations and neutral species. Hydration water in the interlayers is considered as part of the solid phase and is not considered as a constitutive part of overall porosity. Since hydration water takes part of the solid phase, it is now possible to explicitly account for retention of HTO by formulating exchange between HTO and water in the interlayers. In the adaptation of the model to experimental data, a single fit constant, the geometric factor G = 7 was used, common to all ions and neutral species and for densities between 0.2 and 1.8 kg.dm -3 . The only input parameters to describe the effect of dry density on diffusion coefficients are the micro porosity (total porosity minus interlayer porosity) and the hydration numbers of exchanging cations in the interlayers, both of which can be measured by independent means (DRX, water sorption isotherms). The modelling of simultaneous mass transfer of HTO, Cs, Br and Ni has been undertaken. From the results apparent diffusion coefficients were obtained. Effective diffusion coefficients can of course only be compared to literature data if the the same porosity hypothesis is used for Da-De conversion as used in literature (total porosity for anions and HTO, micro-porosity for anions). Then, the calculated apparent diffusion coefficients for HTO match closely the measured values in the mentioned density range. Considering large experimental data uncertainty the agreement between anion diffusion data and calculations

Estimation and measurement of porosity change in cement paste

International Nuclear Information System (INIS)

Lee, Eunyong; Jung, Haeryong; Kwon, Ki-jung; Kim, Do-Gyeum

2011-01-01

Laboratory-scale experiments were performed to understand the porosity change of cement pastes. The cement pastes were prepared using commercially available Type-I ordinary Portland cement (OPC). As the cement pastes were exposed in water, the porosity of the cement pastes sharply increased; however, the slow decrease of porosity was observed as the dissolution period was extended more than 50 days. As expected, the dissolution reaction was significantly influenced by w/c ratio and the ionic strength of solution. A thermodynamic model was applied to simulate the porosity change of the cement pastes. It was highly influenced by the depth of the cement pastes. There was porosity increase on the surface of the cement pastes due to dissolution of hydration products, such as portlandite, ettringite, and CSH. However, the decrease of porosity was estimated inside the cement pastes due to the precipitation of cement minerals. (author)

Porosity, permeability, and their relationship in granite, basalt, and tuff

International Nuclear Information System (INIS)

1983-04-01

This report discusses the porosity, storage, and permeability of fractured (mainly crystalline) rock types proposed as host rock for nuclear waste repositories. The emphasis is on the inter-relationships of these properties, but a number of reported measurements are included as well. The porosity of rock is shown to consist of fracture porosity and matrix porosity; techniques are described for determining the total interconnected porosity through both laboratory and field measurement. Permeability coefficient, as obtained by experiments ranging from laboratory to crustal scale, is discussed. Finally, the problem of determining the relationship between porosity and permeability is discussed. There is no simple, all encompassing relationship that describes the dependence of permeability upon porosity. However, two particular cases have been successfully analyzed: flow through a single rough fracture, and flow through isotropic porous rock. These two cases are discussed in this report

Porosity effects in flame length of the porous burners

Directory of Open Access Journals (Sweden)

Fatemeh Bahadori

2014-10-01

Full Text Available Furnaces are the devices for providing heat to the industrial systems like boilers, gas turbines and etc. The main challenge of furnaces is emission of huge air pollutants. However, porous burners produce less contaminant compared to others. The quality of the combustion process in the porous burners depends on the length of flame in the porous medium. In this paper, the computational fluid dynamic (CFD is used to investigate the porosity effects on the flame length of the combustion process in porous burner. The simulation results demonstrate that increasing the porosity increases the flame length and the combustion zone extends forward. So, combustion quality increases and production of carbon monoxide decrease. It is possible to conclude that temperature distribution in low porosity burner is lower and more uniform than high porosity one. Therefore, by increasing the porosity of the burner, the production of nitrogen oxides increases. So, using an intermediate porosity in the burner appears to be reasonable.

Porosity measurements of crystalline rocks by laboratory and geophysical methods

International Nuclear Information System (INIS)

Alexander, J.; Hall, D.H.; Storey, B.C.

1981-12-01

Porosity values of igneous and metamorphic crystalline rocks have been determined from core samples taken at specific depths from Altnabreac, by a combination of laboratory and geophysical techniques. Using resaturation and mercury injection methods in three laboratories within I.G.S., porosity values have been derived and the effect of variations in the measuring techniques and results obtained have been compared. Comparison of inter-laboratory porosity values illustrates that systematic errors are present, resulting in higher porosity values for samples subjected to re-testing. This is considered to be caused by the variable nature of the initial samples combined with the inability to completely dry or resaturate samples during a second testing. Geophysical techniques for determining in situ porosity using the neutron log have been carried out in borehole ALA. The neutron log has been calibrated with laboratory derived porosity values and an empirical formula derived enabling porosity values to be ascribed throughout the logged borehole ALA. Comparison of the porosity results from Altnabreac with crystalline samples elsewhere in America, Europe and the U.K. suggest that porosities at Altnabreac are lower than average. However, very few publications concerned with water movement in crystalline areas actually state the method used. (author)

Pulsed neutron porosity logging system

International Nuclear Information System (INIS)

Smith, H.D. Jr.; Smith, M.P.; Schultz, W.E.

1978-01-01

An improved pulsed neutron porosity logging system is provided in the present invention. A logging tool provided with a 14 MeV pulsed neutron source, an epithermal neutron detector, and a fast neutron detector is moved through a borehole. Repetitive bursts of neutrons irradiate the earth formations and, during the bursts, the fast neutron population is sampled. During the interval between bursts the epithermal neutron population is sampled along with background gamma radiation due to lingering thermal neutrons. The fast and epithermal neutron population measurements are combined to provide a measurement of formation porosity

Plant fibre composites - porosity and stiffness

DEFF Research Database (Denmark)

Madsen, Bo; Thygesen, Anders; Lilholt, Hans

2009-01-01

Plant fibre composites contain typically a relatively large amount of porosity which influences their performance. A model, based on a modified rule of mixtures, is presented to include the influence of porosity on the composite stiffness. The model integrates the volumetric composition...... of the composites with their mechanical properties. The fibre weight fraction is used as an independent parameter to calculate the complete volumetric composition. A maximum obtainable stiffness of the composites is calculated at a certain transition fibre weight fraction, which is characterised by a best possible...... combination of high fibre volume fraction and low porosity. The model is validated with experimental data from the literature on several types of composites. A stiffness diagram is presented to demonstrate that the calculations can be used for tailoring and design of composites with a given profile...

Fabrication of dual porosity electrode structure

Science.gov (United States)

Smith, J.L.; Kucera, E.H.

1991-02-12

A substantially entirely fibrous ceramic is described which may have dual porosity of both micro and macro pores. Total porosity may be 60-75% by volume. A method of spraying a slurry perpendicularly to an ambient stream of air is disclosed along with a method of removing binders without altering the fiber morphology. Adding fine ceramic particulates to the green ceramic fibers enhances the sintering characteristics of the fibers. 3 figures.

Generating porosity spectrum of carbonate reservoirs using ultrasonic imaging log

Science.gov (United States)

Zhang, Jie; Nie, Xin; Xiao, Suyun; Zhang, Chong; Zhang, Chaomo; Zhang, Zhansong

2018-03-01

Imaging logging tools can provide us the borehole wall image. The micro-resistivity imaging logging has been used to obtain borehole porosity spectrum. However, the resistivity imaging logging cannot cover the whole borehole wall. In this paper, we propose a method to calculate the porosity spectrum using ultrasonic imaging logging data. Based on the amplitude attenuation equation, we analyze the factors affecting the propagation of wave in drilling fluid and formation and based on the bulk-volume rock model, Wyllie equation and Raymer equation, we establish various conversion models between the reflection coefficient β and porosity ϕ. Then we use the ultrasonic imaging logging and conventional wireline logging data to calculate the near-borehole formation porosity distribution spectrum. The porosity spectrum result obtained from ultrasonic imaging data is compared with the one from the micro-resistivity imaging data, and they turn out to be similar, but with discrepancy, which is caused by the borehole coverage and data input difference. We separate the porosity types by performing threshold value segmentation and generate porosity-depth distribution curves by counting with equal depth spacing on the porosity image. The practice result is good and reveals the efficiency of our method.

Casting Porosity-Free Grain Refined Magnesium Alloys

Energy Technology Data Exchange (ETDEWEB)

Schwam, David [Case Western Reserve University

2013-08-12

The objective of this project was to identify the root causes for micro-porosity in magnesium alloy castings and recommend remedies that can be implemented in production. The findings confirm the key role played by utilizing optimal gating and risering practices in minimizing porosity in magnesium castings. 

Carbonate porosity: some remarks; Porosidade em reservatorios carbonaticos: algumas consideracoes

Energy Technology Data Exchange (ETDEWEB)

Spadini, Adali Ricardo [PETROBRAS, Rio de Janeiro, RJ (Brazil). Exploracao e Producao]. E-mail: spadini@petrobras.com.br; Marcal, Rosely de Araujo [PETROBRAS, Rio de Janeiro, RJ (Brazil)

2005-05-01

Carbonate rocks are the major reservoirs of the largest super-giants fields in the world, including the Ghawar Field in Saudi Arabia, where the producing oil reservoir is the late Jurassic Arab-D limestone with five million barrels per day. Despite the great susceptibility to early diagenesis, that can dramatically modify the porous media, porosity values of carbonates remain essentially the same as that of deposition before burial. Porosity loss is essentially a subsurface process with a drastic reduction below 2500 m of burial depth. The occurrence of good reservoirs deeply buried, sometimes below 4,000 m, indicate that porosity can be preserved in subsurface in response to a series of mechanisms such as early oil emplacement, framework rigidity, abnormal pore pressure, among others. Percolation of geothermal fluids is a process considered to be responsible for generation of porosity in subsurface resulting in some good reservoir rocks. In Campos Basin, areas with burial around 2000 m, petrophysical data show a cyclic distribution that coincides with the shoaling upward cycles typical of the Albian carbonates. The greatest permeabilities coincide with the grain stones of the top of the cycles while the peloidal/oncolite wackestones/pack stones at the base show low values, reflecting the depositional texture. These relationships indicate that preservation of depositional porosity was very effective. The preservation of high porosity values for all the facies are related to early oil entrance in the reservoirs. In some cases, the presence of porosities of almost 30% in fine-grained peloidal carbonates, 3000 m of burial, without any clear effective preservation mechanism, suggest that corrosive subsurface brines have played an important role in porosity evolution. In Santos Basin, where reservoirs are deeply buried, only the grain stones have preserved porosity. The associated low energy facies has virtually no porosity. In this case, the depositional texture

Effect of shrinkage porosity on mechanical properties of ferritic ductile iron

Directory of Open Access Journals (Sweden)

Wang Zehua

2013-05-01

Full Text Available Casting defects could largely affect the mechanical properties of casting products. A number of test pieces made of ductile iron (EN-GJS-400-18-LT with different levels of shrinkage porosity were prepared and then tensile and fatigue tests were performed to investigate the impact of shrinkage porosity on their mechanical properties. The results showed that the tensile strength decreases linearly with increasing of the shrinkage porosity. The tensile elongation decreases sharply with the increase of the shrinkage porosity mainly due to the non-uniform plastic deformation. The fatigue life also dramatically declines with increasing of the porosity and follows a power law relationship with the area percentage of porosity. The existence of the shrinkage porosity made the fatigue fracture complex. The shrinkage pores, especially those close to the surface usually became the crack initiation sites. For test pieces with less porosity, the fatigue fracture was clearly composed of crack initiation, propagation, and overloading. While for samples with high level of porosity, multiple crack initiation sites were observed.

Contributions to the study of porosity in fly ash-based geopolymers. Relationship between degree of reaction, porosity and compressive strength

Directory of Open Access Journals (Sweden)

Y. Luna-Galiano

2016-09-01

Full Text Available The main contribution of this paper relates to the development of a systematic study involving a set of parameters which could potentially have an impact on geopolymer properties: curing temperature, type of activating solution, alkali metal in solution, incorporation of slag (Ca source and type of slag used. The microstructures, degrees of reaction, porosities and compressive strengths of geopolymers have been evaluated. Geopolymers prepared with soluble silicate presented a more compacted and closed structure, a larger amount of gel, lower porosity and greater compressive strength than those prepared with hydroxides. On the other hand, Na-geopolymers were more porous but more resistant than K-geopolymers. Although there is an inverse relation between degree of reaction and porosity, between compressive strength and porosity it is not always inversely proportional and could, in some cases, be masked by changes produced in other influencing parameters.

Geochemical thermodynamic and kinetic modeling that take into account the mass transfer phenomena in saturated porous medium

International Nuclear Information System (INIS)

Gerard, Frederic

1996-01-01

The mass transport mechanisms (advection. mechanical dispersion and molecular diffusion) have been introduced into the thermodynamic and kinetic geochemical code KINDIS. This innovative approach to couple chemical and transport mass transfers has allowed us to develop a reactive transport or hydrochemical code named KIRMAT, which naturally preserve the comprehensive geochemical functions of KINDIS. Mass transport phenomena through the total connected porosity of a water-saturated porous medium are solved over one spatial dimension (ID). The finite difference method is used. An explicit or forward time scheme is computed. The advective finite difference expression may be either centered or upstream weighted. Thus, ail of the hydrodynamic conditions may be modeled (from the pure advection to pure diffusion). The mass transport and geochemical flux are solved simultaneously (one-step algorithm). Moreover. the code KIRMAT is designed to quantify reactive mass transport through a double or dual porosity medium, in which the flow porosity (filled by free water) and the diffusion porosity (containing stagnant water) are viewed as two distinct sub mediums or Systems. Under some given conditions, the need to solve one or the other mass transport equation is a function of the water-rock System size. The accuracy of the kinetic constraint has been improved in KIRMAT. Two new kinetic rate laws have been introduced for the dissolution of the most abundant silicates (alkali feldspars, silica. etc.). These rate laws integrate the quantitatively important inhibitor and catalytic effects involved with some dissolved chemical elements that are ubiquitous in natural aqueous solutions. The basic step. the numerical verification of the code, has been tackled with two complementary approaches. The numerical results from KIRMAT have been compared to those calculated from an exact solution and a new method has been developed and used. We have compared the numerical results of KIRMAT in

Relationship between micro-porosity and tensile properties of 6063 alloy

Directory of Open Access Journals (Sweden)

Li Xiehua

2013-01-01

Full Text Available The micro-porosity is usually present in the as-cast microstructure, which decreases the tensile strength and ductility and therefore limit the application of cast aluminum parts. Although much work has been done to investigate the effects of various casting parameters on the formation of porosity in various aluminum alloys, up to now, little information has been available for the relationship between micro-porosity and tensile properties of 6063 alloy. In this study, the influences of size and area fraction of micro-porosity on the tensile properties and fracture behavior of 6063 aluminum alloy were investigated by means of tensile testing, optical microscopy (OM, and scanning electron microscopy (SEM. The tensile tests were conducted in air at 100 ℃, 200 ℃ and 300 ℃, respectively. Results show that the large micro-porosity with sizes between 100 μm and 800 μm located at the center and top of the ingot, while the small micro-porosity with size between 2 μm and 60 μm distributed at the edge and bottom of the ingot. The area fraction of micro-porosity at the center of the ingot is much bigger than that at the edge of the ingot. When tested at 100 ℃, with the decrease in the area fraction of micro-porosity from the top of the ingot to the bottom of the ingot, the ultimate tensile strength, yield strength and the elongation are increased from 82 to 99 MPa, 32 to 66 MPa and 7% to 11%, respectively. When the temperature is no more than 200 ℃, the strain hardening exponent decreases with an increase in the area fraction of micro-porosity; while the deviation disappears when the temperature reaches 300 ℃. The fracture mode of the alloy is greatly influenced by the size and area fraction of the micro-porosity.

Association of Overweight and Elevation with Chronic Knee and Low Back Pain: A Cross-Sectional Study

Directory of Open Access Journals (Sweden)

Tsuyoshi Hamano

2014-04-01

Full Text Available It is known that overweight is associated with chronic knee pain (CKP and chronic low back pain (CLBP. Several risk factors for these conditions have been postulated, including age, sex, overweight, occupation, and socioeconomic factors. In addition, physical environment has been studied as a potential risk factor in recent years. However, the associations of overweight and physical environment with CKP and CLBP remains unclear. The aim of this study conducted in a rural mountainous region was to examine whether overweight individuals living at higher elevations have an increased probability of experiencing CKP and CLBP. In 2009, we conducted a mail survey with a random sample aged between 40 to 79 years. Questionnaires were sent to 6,000 individuals and a total of 4,559 individuals responded to this survey. After excluding the respondents with missing data, we conducted a logistic regression analysis of the data for 3,109 individuals. There was statistically significantly higher adjusted odds ratio (aOR of CKP for those who were overweight living at low elevation (aOR = 1.90, 95% CI = 1.21–2.98, moderate elevation (aOR = 1.73, 95% CI = 1.05–2.87, and high elevation (aOR = 2.13, 95% CI = 1.31–3.46 than those who were not overweight living at low elevation. However, similar patterns were not observed for CLBP. Our results show that specific overweight–elevation associations were observed for CKP in a rural mountainous region.

GPs' attitudes, beliefs and behaviours regarding exercise for chronic knee pain: a questionnaire survey

Science.gov (United States)

Foster, Nadine E; Porcheret, Mark; Rathod, Trishna; Roddy, Edward

2017-01-01

Objectives The aim of this study was to investigate general practitioners’ (GPs) attitudes, beliefs and behaviours regarding the use of exercise for patients with chronic knee pain (CKP) attributable to osteoarthritis. Setting Primary care GPs in the UK. Participants 5000 GPs, randomly selected from Binley’s database, were mailed a cross-sectional questionnaire survey. Outcome measures GPs’ attitudes and beliefs were investigated using attitude statements, and reported behaviours were identified using vignette-based questions. GPs were invited to report barriers experienced when initiating exercise with patients with CKP Results 835 (17%) GPs responded. Overall, GPs were positive about general exercise for CKP. 729 (87%) reported using exercise, of which, 538 (74%) reported that they would use both general and local (lower limb) exercises. However, only 92 (11% of all responding) GPs reported initiating exercise in ways aligning with best-evidence recommendations. 815 (98%) GPs reported barriers in using exercise for patients with CKP, most commonly, insufficient time in consultations (n=419; 51%) and insufficient expertise (n=337; 41%). Conclusions While GPs’ attitudes and beliefs regarding exercise for CKP were generally positive, initiation of exercise was often poorly aligned with current recommendations, and barriers and uncertainties were reported. GPs’ use of exercise may be improved by addressing the key barriers of time and expertise, by developing a pragmatic approach that supports GPs to initiate individualised exercise, and/or by other professionals taking on this role. PMID:28624759

Geochemical porosity values obtained in core samples from different clay-rocks

International Nuclear Information System (INIS)

Fernandez, A.M.

2010-01-01

Document available in extended abstract form only. Argillaceous formations of low permeability are considered in many countries as potential host rocks for the disposal of high level radioactive wastes (HLRW). In order to determine their suitability for waste disposal, evaluations of the hydro-geochemistry and transport mechanisms from such geologic formations to the biosphere must be undertaken. One of the key questions about radionuclide diffusion and retention is to know the chemistry and chemical reactions and sorption processes that will occur in the rock and their effects on radionuclide mobility. In this context, the knowledge of the pore water chemistry is essential for performance assessment purposes. This information allows to establish a reliable model for the main water-rock interactions, which control the physico-chemical parameters and the chemistry of the major elements of the system. An important issue in order to model the pore water chemistry in clayey media is to determine the respective volume accessible to cations and anions, i.e, the amount of water actually available for chemical reactions/solute transport. This amount is usually referred as accessible porosity or geochemical porosity. By using the anion inventories, i.e. the anion content obtained from aqueous leaching, and assuming that all Cl - , Br - and SO4 2- leached in the aqueous extracts originates from pore water, the concentration of a conservative ion can be converted into the real pore water concentration if the accessible porosity is known. In this work, the accessible porosity or geochemical porosity has been determined in core samples belonging to four different formations: Boom Clay from Hades URL (Belgium, BE), Opalinus Clay from Mont Terri (Switzerland, CH), and Callovo-Oxfordian argillite from Bure URL (France, FR). The geochemical or chloride porosity was defined as the ratio between the pore water volume containing Cl-bearing pore water and the total volume of a sample

Porosity Measurements and Analysis for Metal Additive Manufacturing Process Control.

Science.gov (United States)

Slotwinski, John A; Garboczi, Edward J; Hebenstreit, Keith M

2014-01-01

Additive manufacturing techniques can produce complex, high-value metal parts, with potential applications as critical metal components such as those found in aerospace engines and as customized biomedical implants. Material porosity in these parts is undesirable for aerospace parts - since porosity could lead to premature failure - and desirable for some biomedical implants - since surface-breaking pores allows for better integration with biological tissue. Changes in a part's porosity during an additive manufacturing build may also be an indication of an undesired change in the build process. Here, we present efforts to develop an ultrasonic sensor for monitoring changes in the porosity in metal parts during fabrication on a metal powder bed fusion system. The development of well-characterized reference samples, measurements of the porosity of these samples with multiple techniques, and correlation of ultrasonic measurements with the degree of porosity are presented. A proposed sensor design, measurement strategy, and future experimental plans on a metal powder bed fusion system are also presented.

Mathematical aspects of multi-porosity continua

CERN Document Server

Straughan, Brian

2017-01-01

This book is devoted to describing theories for porous media where such pores have an inbuilt macro structure and a micro structure. For example, a double porosity material has pores on a macro scale, but additionally there are cracks or fissures in the solid skeleton. The actual body is allowed to deform and thus the underlying theory is one of elasticity. Various different descriptions are reviewed. Chapter 1 introduces the classical linear theory of elastodynamics together with uniqueness and continuous dependence results. Chapters 2 and 3 review developments of theories for double and triple porosity using a pressure-displacement structure and also using voids-displacement. Chapter 4 compares various aspects of the pressure-displacement and voids-displacement theories via uniqueness studies and wave motion analysis. Mathematical analyses of double and triple porosity materials are included concentrating on uniqueness and stability studies in chapters 5 to 7. In chapters 8 and 9 the emphasis is on wa...

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

Directory of Open Access Journals (Sweden)

Daolun Li

2015-01-01

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

Causes and remedies for porosity in composite manufacturing

Science.gov (United States)

Fernlund, G.; Wells, J.; Fahrang, L.; Kay, J.; Poursartip, A.

2016-07-01

Porosity is a challenge in virtually all composite processes but in particular in low pressure processes such as out of autoclave processing of prepregs, where the maximum pressure is one atmosphere. This paper discusses the physics behind important transport phenomena that control porosity and how we can use our understanding of the underlying science to develop strategies to achieve low porosity for these materials and processes in an industrial setting. A three step approach is outlined that addresses and discusses: gas evacuation of trapped air, volatiles and off-gassing, and resin infiltration of evacuated void space.

Physical properties of Martian meteorites: Porosity and density measurements

Science.gov (United States)

Coulson, Ian M.; Beech, Martin; Nie, Wenshuang

Martian meteorites are fragments of the Martian crust. These samples represent igneous rocks, much like basalt. As such, many laboratory techniques designed for the study of Earth materials have been applied to these meteorites. Despite numerous studies of Martian meteorites, little data exists on their basic structural characteristics, such as porosity or density, information that is important in interpreting their origin, shock modification, and cosmic ray exposure history. Analysis of these meteorites provides both insight into the various lithologies present as well as the impact history of the planet's surface. We present new data relating to the physical characteristics of twelve Martian meteorites. Porosity was determined via a combination of scanning electron microscope (SEM) imagery/image analysis and helium pycnometry, coupled with a modified Archimedean method for bulk density measurements. Our results show a range in porosity and density values and that porosity tends to increase toward the edge of the sample. Preliminary interpretation of the data demonstrates good agreement between porosity measured at 100× and 300× magnification for the shergottite group, while others exhibit more variability. In comparison with the limited existing data for Martian meteorites we find fairly good agreement, although our porosity values typically lie at the low end of published values. Surprisingly, despite the increased data set, there is little by way of correlation between either porosity or density with parameters such as shock effect or terrestrial residency. Further data collection on additional meteorite samples is required before more definitive statements can be made concerning the validity of these observations.

Ultrasonic technique for measuring porosity of plasma-sprayed alumina coatings

Science.gov (United States)

Parthasarathi, S.; Tittmann, B. R.; Onesto, E. J.

1997-12-01

Porosity is an important factor in plasma-sprayed coatings, especially ceramic coatings. Excessive poros-ity can adversely affect the performance of the coated component in various ways. An ultrasonic nonde-structive measurement technique has been developed to measure porosity in plasma-sprayed alumina coatings. The technique is generic and can be extended to other ceramic coating systems. To test the tech-nique, freestanding alumina coatings with varying levels of porosity were fabricated via plasma spray. Samples with varying porosity, obtained through innovative fabrication techniques, were used to gener-ate a calibration curve. The ultrasonic velocity in the low-frequency range was found to be dependent on the density of freestanding coatings (measured via Archimedian techniques). This dependence is the basis of the development of a technique to measure the density of coatings.

Chalk porosity and sonic velocity versus burial depth

DEFF Research Database (Denmark)

Fabricius, Ida Lykke; Gommesen, Lars; Krogsbøll, Anette Susanne

2008-01-01

Seventy chalk samples from four formations in the overpressured Danish central North Sea have been analyzed to investigate how correlations of porosity and sonic velocity with burial depth are affected by varying mineralogy, fluid pressure, and early introduction of petroleum. The results show th...... for fluid pressure because the cementing ions originate from stylolites, which are mechanically similar to fractures. We find that cementation occurs over a relatively short depth interval.......Seventy chalk samples from four formations in the overpressured Danish central North Sea have been analyzed to investigate how correlations of porosity and sonic velocity with burial depth are affected by varying mineralogy, fluid pressure, and early introduction of petroleum. The results show...... that porosity and sonic velocity follow the most consistent depth trends when fluid pressure and pore-volume compressibility are considered. Quartz content up to 10% has no marked effect, but more than 5% clay causes lower porosity and velocity. The mineralogical effect differs between P-wave and shear velocity...

Porosity Variation in Cenozoic and Upper Chalk from the Ontong Java Pleateau

DEFF Research Database (Denmark)

Borre, Mai Kirstine

1997-01-01

Porosity was obtained from matrix- and intraparticle porosity assessed from image analysis of backscattered electron micrographs of 3000x and 300x magnification. Comparing porosity assessed from image analysis with porosity measured by index properties, it was seen that image analysis data at 300...

Porosity in Ocean Racing Yacht Composites: a Review

Science.gov (United States)

Baley, Christophe; Lan, Marine; Davies, Peter; Cartié, Denis

2015-02-01

Ocean racing yachts are mainly manufactured from carbon/epoxy composites similar to those used by the aeronautical industry but, with some exceptions such as masts, these structures are not produced in autoclaves. This leads to the presence of higher porosity levels. This paper will first present the different types of porosity found in traditional racing yacht structures. Difficulties in evaluating defect levels will then be discussed and published work characterizing the influence of defects will be reviewed. Current developments to improve racing yacht composite quality such as thin ply technology, out-of-autoclave processing and automated fibre placement will then be described, and their implications for porosity will be discussed.

GPs' attitudes, beliefs and behaviours regarding exercise for chronic knee pain: a questionnaire survey.

Science.gov (United States)

Cottrell, Elizabeth; Foster, Nadine E; Porcheret, Mark; Rathod, Trishna; Roddy, Edward

2017-06-17

The aim of this study was to investigate general practitioners' (GPs) attitudes, beliefs and behaviours regarding the use of exercise for patients with chronic knee pain (CKP) attributable to osteoarthritis. Primary care GPs in the UK. 5000 GPs, randomly selected from Binley's database, were mailed a cross-sectional questionnaire survey. GPs' attitudes and beliefs were investigated using attitude statements, and reported behaviours were identified using vignette-based questions. GPs were invited to report barriers experienced when initiating exercise with patients with CKP RESULTS: 835 (17%) GPs responded. Overall, GPs were positive about general exercise for CKP. 729 (87%) reported using exercise, of which, 538 (74%) reported that they would use both general and local (lower limb) exercises. However, only 92 (11% of all responding) GPs reported initiating exercise in ways aligning with best-evidence recommendations. 815 (98%) GPs reported barriers in using exercise for patients with CKP, most commonly, insufficient time in consultations (n=419; 51%) and insufficient expertise (n=337; 41%). While GPs' attitudes and beliefs regarding exercise for CKP were generally positive, initiation of exercise was often poorly aligned with current recommendations, and barriers and uncertainties were reported. GPs' use of exercise may be improved by addressing the key barriers of time and expertise, by developing a pragmatic approach that supports GPs to initiate individualised exercise, and/or by other professionals taking on this role. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Radiographically detectable intracortical porosity

International Nuclear Information System (INIS)

Meema, H.E.

1986-01-01

Since the measurement of intracortical resorptive spaces by histologic methods is difficult and very few data are available in normal humans, we have measured their lengths and widths and calculated the intracortical porosity in metacarpals and phalanges of 79 normal women and 69 normal men, using fine-detail radiographs of the hands and a computerized semi-automatic image analysis system (Zeiss MOP-3), this being the first study of this kind. Several methodological problems were solved satisfactorily, and the results of this study could serve as a data bank for further investigations concerned with intracortical resorption. Significant differences were found between age and sex versus several intracortical resorptive parameters; also significant correlations were found with age in some cases. Normal intracortical porosity was found to be about three times greater in the proximal phalanges than in the metacarpals. It is concluded that this methodology could be used for further studies of intracortical resorption in osteoporosis and other metabolic bone diseases. (orig.)

Contribution to the study of the influence of porosity on carbon oxidation rate

International Nuclear Information System (INIS)

Serpinet, Joseph

1956-01-01

In its first part, this research thesis presents and described experiments of carbon oxidation which comprised the measurement of combustion rate in function of the BET surface of new types of graphite samples, and measurements of other kinetic quantities (reaction rate, Arrhenius activation energy, concentration of various gaseous oxides in reaction products). The second part reports a theoretical and experimental study of the possibility of limitation of the reaction rate, by using the slowness of oxygen diffusion within graphite pores. Results are related to the Thiele-Wheeler theory on chemical reactions in catalyst pores. The third part presents and discusses suggested solutions to replace this 'porosity hypothesis', and to explain why oxidation rate is almost never proportional to the BET surface all along the combustion process of a same graphite sample [fr

Validating predictions of evolving porosity and permeability in carbonate reservoir rocks exposed to CO2-brine

Science.gov (United States)

Smith, M. M.; Hao, Y.; Carroll, S.

2017-12-01

Improving our ability to better forecast the extent and impact of changes in porosity and permeability due to CO2-brine-carbonate reservoir interactions should lower uncertainty in long-term geologic CO2 storage capacity estimates. We have developed a continuum-scale reactive transport model that simulates spatial and temporal changes to porosity, permeability, mineralogy, and fluid composition within carbonate rocks exposed to CO2 and brine at storage reservoir conditions. The model relies on two primary parameters to simulate brine-CO2-carbonate mineral reaction: kinetic rate constant(s), kmineral, for carbonate dissolution; and an exponential parameter, n, relating porosity change to resulting permeability. Experimental data collected from fifteen core-flooding experiments conducted on samples from the Weyburn (Saskatchewan, Canada) and Arbuckle (Kansas, USA) carbonate reservoirs were used to calibrate the reactive-transport model and constrain the useful range of k and n values. Here we present the results of our current efforts to validate this model and the use of these parameter values, by comparing predictions of extent and location of dissolution and the evolution of fluid permeability against our results from new core-flood experiments conducted on samples from the Duperow Formation (Montana, USA). Agreement between model predictions and experimental data increase our confidence that these parameter ranges need not be considered site-specific but may be applied (within reason) at various locations and reservoirs. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Porosity of porcine bladder acellular matrix: impact of ACM thickness.

Science.gov (United States)

Farhat, Walid; Chen, Jun; Erdeljan, Petar; Shemtov, Oren; Courtman, David; Khoury, Antoine; Yeger, Herman

2003-12-01

The objectives of this study are to examine the porosity of bladder acellular matrix (ACM) using deionized (DI) water as the model fluid and dextran as the indicator macromolecule, and to correlate the porosity to the ACM thickness. Porcine urinary bladders from pigs weighing 20-50 kg were sequentially extracted in detergent containing solutions, and to modify the ACM thickness, stretched bladders were acellularized in the same manner. Luminal and abluminal ACM specimens were subjected to fixed static DI water pressure (10 cm); and water passing through the specimens was collected at specific time interval. While for the macromolecule porosity testing, the diffusion rate and direction of 10,000 MW fluoroescein-labeled dextrans across the ACM specimens mounted in Ussing's chambers were measured. Both experiments were repeated on the thin stretched ACM. In both ACM types, the fluid porosity in both directions did not decrease with increased test duration (3 h); in addition, the abluminal surface was more porous to fluid than the luminal surface. On the other hand, when comparing thin to thick ACM, the porosity in either direction was higher in the thick ACM. Macromolecule porosity, as measured by absorbance, was higher for the abluminal thick ACM than the luminal side, but this characteristic was reversed in the thin ACM. Comparing thin to thick ACM, the luminal side in the thin ACM was more porous to dextran than in the thick ACM, but this characteristic was reversed for the abluminal side. The porcine bladder ACM possesses directional porosity and acellularizing stretched urinary bladders may increase structural density and alter fluid and macromolecule porosity. Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 970-974, 2003

Effect of porosity on the tensile properties of low ductility aluminum alloys

Directory of Open Access Journals (Sweden)

Gustavo Waldemar Mugica

2004-06-01

Full Text Available The literature contains reports of several studies correlating the porosity and mechanical properties of aluminum alloys. Most of these studies determine this correlation based on the parameter of global volumetric porosity. These reports, however, fail to separate the effects of microstructural features and porosity on alloys, though recognizing the influence of the latter on their mechanical properties. Thus, when the decrease in tensile strength due to the porosity effect is taken into account, the findings are highly contradictory. An analysis was made of the correlation between mechanical properties and global volumetric porosity and volumetric porosity in the fracture, as well as of the beta-Al5FeSi phase present in 380 aluminum alloy. Our findings indicate that mechanical properties in tension relating to global volumetric porosity lead to overestimations of the porosity effect in detriment to the mechanical properties. Moreover, the proposed models that take into account the effects of particles, both Si and beta-Al5FeSi, are unapplicable to low ductility alloys.

Homogeneity vs. Heterogeneity of Porosity in Boom Clay

International Nuclear Information System (INIS)

Hemes, Susanne; Desbois, Guillaume; Urai, Janos L.; De Craen, Mieke; Honty, Miroslav

2013-01-01

Microstructural investigations on Boom Clay at nano- to micrometer scale, using BIB-SEM methods, result in porosity characterization for different mineral phases from direct observations on high resolution SE2-images of representative elementary areas (REAs). High quality, polished surfaces of cross-sections of ∼ 1 mm 2 size were produced on three different samples from the Mol-Dessel research site (Belgium). More than 33,000 pores were detected, manually segmented and analyzed with regard to their size, shape and orientation. Two main pore classes were defined: Small pores (< 500 nm (ED)) within the clay matrices of samples and =big' pores (> 500 nm (ED)) at the interfaces between clay and non-clay mineral (NCM) grains. Samples investigated show similar porosities regarding the first pore-class, but differences occur at the interfaces between clay matrix and NCM grains. These differences were interpreted to be due to differences in quantitative mineralogy (amount of non-clay mineral grains) and grain-size distributions between samples investigated. Visible porosities were measured as 15 to 17 % for samples investigated. Pore-size distributions of pores in clay are similar for all samples, showing log-normal distributions with peaks around 60 nm (ED) and more than 95 % of the pores being smaller than 500 nm (ED). Fitting pore-size distributions using power-laws with exponents between 1.56 and 1.7, assuming self-similarity of the pore space, thus pores smaller than the pore detection resolution following the same power-laws and using these power-laws for extrapolation of pore-size distributions below the limit of pore detection resolution, results in total estimated porosities between 20 and 30 %. These results are in good agreement with data known from Mercury Porosimetry investigations (35-40 % porosity) and water content porosity measurements (∼ 36 %) performed on Boom Clay. (authors)

Can porosity affect the hyperspectral signature of sandy landscapes?

Science.gov (United States)

Baranoski, Gladimir V. G.; Kimmel, Bradley W.

2017-10-01

Porosity is a fundamental property of sand deposits found in a wide range of landscapes, from beaches to dune fields. As a primary determinant of the density and permeability of sediments, it represents a central element in geophysical studies involving basin modeling and coastal erosion as well as geoaccoustics and geochemical investigations aiming at the understanding of sediment transport and water diffusion properties of sandy landscapes. These applications highlight the importance of obtaining reliable porosity estimations, which remains an elusive task, notably through remote sensing. In this work, we aim to contribute to the strengthening of the knowledge basis required for the development of new technologies for the remote monitoring of environmentally-triggered changes in sandy landscapes. Accordingly, we employ an in silico investigation approach to assess the effects of porosity variations on the reflectance of sandy landscapes in the visible and near-infrared spectral domains. More specifically, we perform predictive computer simulations using SPLITS, a hyperspectral light transport model for particulate materials that takes into account actual sand characterization data. To the best of our knowledge, this work represents the first comprehensive investigation relating porosity to the reflectance responses of sandy landscapes. Our findings indicate that the putative dependence of these responses on porosity may be considerably less pronounced than its dependence on other properties such as grain size and shape. Hence, future initiatives for the remote quantification of porosity will likely require reflectance sensors with a high degree of sensitivity.

Porosity measurement of amorphous materials by gamma ray transmission

International Nuclear Information System (INIS)

Poettker, Walmir Eno

2000-01-01

In this work it is presented the measurement of the total porosity of TRe soil, Sandstone Berea rocks and porous ceramics samples. For the determination of the total porosity, the Arquimedes method (conventional) and the gamma ray transmission methodology were employed. The porosity measurement using the gamma methodology has a significant advantage respect to the conventional method due to the fast and non-destructive determination, and also for supplying results with a greater characterization in small scales, in relation to the heterogeneity of the porosity. The conventional methodology presents good results only for homogeneous samples. The experimental set up for the gamma ray transmission technique consisted of a 241 Am source (59,53 keV), a NaI (Tl) scintillation detector, collimators, a XYZ, micrometric table and standard gamma spectrometry electronics connected to a multichannel analyser. (author)

Porosity estimation by semi-supervised learning with sparsely available labeled samples

Science.gov (United States)

Lima, Luiz Alberto; Görnitz, Nico; Varella, Luiz Eduardo; Vellasco, Marley; Müller, Klaus-Robert; Nakajima, Shinichi

2017-09-01

This paper addresses the porosity estimation problem from seismic impedance volumes and porosity samples located in a small group of exploratory wells. Regression methods, trained on the impedance as inputs and the porosity as output labels, generally suffer from extremely expensive (and hence sparsely available) porosity samples. To optimally make use of the valuable porosity data, a semi-supervised machine learning method was proposed, Transductive Conditional Random Field Regression (TCRFR), showing good performance (Görnitz et al., 2017). TCRFR, however, still requires more labeled data than those usually available, which creates a gap when applying the method to the porosity estimation problem in realistic situations. In this paper, we aim to fill this gap by introducing two graph-based preprocessing techniques, which adapt the original TCRFR for extremely weakly supervised scenarios. Our new method outperforms the previous automatic estimation methods on synthetic data and provides a comparable result to the manual labored, time-consuming geostatistics approach on real data, proving its potential as a practical industrial tool.

Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former

Czech Academy of Sciences Publication Activity Database

Medřický, J.; Curry, N.; Pala, Zdeněk; Vilémová, Monika; Chráska, Tomáš; Johansson, J.; Markocsan, N.

2015-01-01

Roč. 24, č. 4 (2015), s. 622-628 ISSN 1059-9630 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : gas turbine s * high temperature application * porosity of coatings * stabilized zirconia * thermal barrier coatings (TBCs) Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.568, year: 2015

Ultrasonic maps of porosity in aluminum castings

International Nuclear Information System (INIS)

Ghaffari, Bita; Potter, Timothy J.; Mozurkewich, George

2002-01-01

The use of cast aluminum in the automotive industry has grown dramatically in recent years, leading to increased need for quantitative characterization of microporosity. As previously reported in the literature, the attenuation of ultrasound can be used to measure the porosity volume fraction and the mean pore size. An immersion ultrasound system has been built utilizing this technique to scan castings with high spatial resolution. Maps of attenuation are shown to locate areas of varying porosity readily and reliably

Mueller matrix polarimetry on plasma sprayed thermal barrier coatings for porosity measurement.

Science.gov (United States)

Luo, David A; Barraza, Enrique T; Kudenov, Michael W

2017-12-10

Yttria-stabilized zirconia (YSZ) is the most widely used material for thermal plasma sprayed thermal barrier coatings (TBCs) used to protect gas turbine engine parts in demanding operation environments. The superior material properties of YSZ coatings are related to their internal porosity level. By quantifying the porosity level, tighter control on the spraying process can be achieved to produce reliable coatings. Currently, destructive measurement methods are widely used to measure the porosity level. In this paper, we describe a novel nondestructive approach that is applicable to classify the porosity level of plasma sprayed YSZ TBCs via Mueller matrix polarimetry. A rotating retarder Mueller matrix polarimeter was used to measure the polarization properties of the plasma sprayed YSZ coatings with different porosity levels. From these measurements, it was determined that a sample's measured depolarization ratio is dependent on the sample's surface roughness and porosity level. To this end, we correlate the depolarization ratio with the samples' surface roughness, as measured by a contact profilometer, as well as the total porosity level, in percentage measured using a micrograph and stereological analysis. With the use of this technique, a full-field and rapid measurement of porosity level can be achieved.

Tailoring the porosity of hierarchical zeolites by carbon-templating

DEFF Research Database (Denmark)

Zhu, Kake; Egeblad, Kresten; Christensen, Claus H.

2008-01-01

We report the synthesis and characterization of a series of hierarchical porous zeolite single crystal materials with a range of porosities made available by carbon-templating using differently-sized carbon particles as templates for the additional non-micropore porosity. The materials were...

Integrated design of castings: effect of porosity on mechanical performance

International Nuclear Information System (INIS)

Hardin, R A; Beckermann, C

2012-01-01

Porosity can significantly reduce the strength and durability of castings in service. An integrated design approach has been developed where casting simulation is combined with mechanical performance simulations. Predictions of the porosity distribution from the casting process simulation are transferred to and used in stress and fatigue life simulations. Thus, the effect of casting quality on service performance can be evaluated. Results of a study are presented where the measured porosity distribution in cast steel specimens is transferred to an elasto-plastic finite-element stress analysis model. Methods are developed to locally reduce the mechanical properties according to the porosity present, without having to resolve individual pores. Plastic deformation is modeled using porous metal plasticity theory. The predictions are compared to tensile measurements performed on the specimens. The complex deformations and the reductions in the ductility of the specimens due to porosity are predicted well. The predicted stresses are transferred to a fatigue analysis code that takes the porosity distribution into account as well. The measured and predicted fatigue lives are also in good agreement. Finally, the results of a case study are presented that illustrate the utility of the present integrated approach in optimizing the design of a steel casting.

Porosity-dependent fractal nature of the porous silicon surface

Energy Technology Data Exchange (ETDEWEB)

Rahmani, N.; Dariani, R. S., E-mail: dariani@alzahra.ac.ir [Department of Physics, Alzahra University, Tehran, 1993893973 (Iran, Islamic Republic of)

2015-07-15

Porous silicon films with porosity ranging from 42% to 77% were fabricated by electrochemical anodization under different current density. We used atomic force microscopy and dynamic scaling theory for deriving the surface roughness profile and processing the topography of the porous silicon layers, respectively. We first compared the topography of bare silicon surface with porous silicon and then studied the effect of the porosity of porous silicon films on their scaling behavior by using their self-affinity nature. Our work demonstrated that silicon compared to the porous silicon films has the highest Hurst parameter, indicating that the formation of porous layer due to the anodization etching of silicon surface leads to an increase of its roughness. Fractal analysis revealed that the evolution of the nanocrystallites’ fractal dimension along with porosity. Also, we found that both interface width and Hurst parameter are affected by the increase of porosity.

Ultrasonic Characterization of Water Saturated Double Porosity Media

Science.gov (United States)

Bai, Ruonan; Tinel, Alain; Alem, Abdellah; Franklin, Hervé; Wang, Huaqing

Wave propagation through a multilayered structure consisting of a water saturated double porosity medium in an aluminum rectangular box immersed in water is studied. By assuming a plane incident wave from water onto the structure, the reflection and transmission coefficients are derived by application of the boundary conditions at each interface. Numerical computations are done for two particular double porosity media, ROBU® and Tobermorite 11 Å, that are assumed to obey Berryman's extension of Biot's theory [Berryman 1995, 2000]. The influence of the thickness of double porosity medium is investigated. To compare experiments to computations, two comparison coefficients Cnum and Cexp are introduced. The theoretical one Cnum is defined as the ratio of the transmission coefficient of the structure to the transmission coefficient of the box filled exclusively with water. The experimental comparison coefficient Cexp is defined as the ratio of the Fourier transforms of the transmitted signals by the box filled with the double porous medium to that of the transmitted signals by the box filled with water. A method of minimization based on a gradient descent algorithm is used to optimize some of the parameters of the double porosity media such as the bulk moduli.

The Effect of Volumetric Porosity on Roughness Element Drag

Science.gov (United States)

Gillies, John; Nickling, William; Nikolich, George; Etyemezian, Vicken

2016-04-01

Much attention has been given to understanding how the porosity of two dimensional structures affects the drag force exerted by boundary-layer flow on these flow obstructions. Porous structures such as wind breaks and fences are typically used to control the sedimentation of sand and snow particles or create micro-habitats in their lee. Vegetation in drylands also exerts control on sediment transport by wind due to aerodynamic effects and interaction with particles in transport. Recent research has also demonstrated that large spatial arrays of solid three dimensional roughness elements can be used to reduce sand transport to specified targets for control of wind erosion through the effect of drag partitioning and interaction of the moving sand with the large (>0.3 m high) roughness elements, but porous elements may improve the effectiveness of this approach. A thorough understanding of the role porosity plays in affecting the drag force on three-dimensional forms is lacking. To provide basic understanding of the relationship between the porosity of roughness elements and the force of drag exerted on them by fluid flow, we undertook a wind tunnel study that systematically altered the porosity of roughness elements of defined geometry (cubes, rectangular cylinders, and round cylinders) and measured the associated change in the drag force on the elements under similar Reynolds number conditions. The elements tested were of four basic forms: 1) same sized cubes with tubes of known diameter milled through them creating three volumetric porosity values and increasing connectivity between the tubes, 2) cubes and rectangular cylinders constructed of brass screen that nested within each other, and 3) round cylinders constructed of brass screen that nested within each other. The two-dimensional porosity, defined as the ratio of total surface area of the empty space to the solid surface area of the side of the element presented to the fluid flow was conserved at 0.519 for

Synthesis and Preliminary Evaluation of a 2-Oxoquinoline Carboxylic Acid Derivative for PET Imaging the Cannabinoid Type 2 Receptor

Directory of Open Access Journals (Sweden)

Linjing Mu

2014-03-01

Full Text Available Cannabinoid receptor subtype 2 (CB2 has been shown to be up-regulated in activated microglia and therefore plays an important role in neuroinflammatory and neurodegenerative diseases such as multiple sclerosis, amyotrophic lateral sclerosis and Alzheimer’s disease. The CB2 receptor is therefore considered as a very promising target for therapeutic approaches as well as for imaging. A promising 2-oxoquinoline derivative designated KP23 was synthesized and radiolabeled and its potential as a ligand for PET imaging the CB2 receptor was evaluated. [11C]KP23 was obtained in 10%–25% radiochemical yield (decay corrected and 99% radiochemical purity. It showed high stability in phosphate buffer, rat and mouse plasma. In vitro autoradiography of rat and mouse spleen slices, as spleen expresses a high physiological expression of CB2 receptors, demonstrated that [11C]KP23 exhibits specific binding towards CB2. High spleen uptake of [11C]KP23 was observed in dynamic in vivo PET studies with Wistar rats. In conclusion, [11C]KP23 showed promising in vitro and in vivo characteristics. Further evaluation with diseased animal model which has higher CB2 expression levels in the brain is warranted.

Mathematical modeling of porosity formation in die cast A356 wheels

International Nuclear Information System (INIS)

Maijer, D.; Cockcroft, S.L.; Wells, M.A.; Luciuk, T.; Hermesmann, C.

2000-01-01

In an effort to leverage recent advances in modeling and process simulation tools, a mathematical model has been developed to predict porosity formation in die cast A356 wheels as part of a collaborative research agreement between researchers at the University of British Columbia and Canadian Autoparts Toyota Incorporated. The heat transfer model represents a three-dimensional, 30 o , slice of the wheel and die and is based on the commercial finite element code ABAQUS. Extensive temperature measurements in the die and in the wheel taken over several cycles in the casting process were used to fine tune and validate the model. Initial work on predicting porosity formation has focused on using the Niyama parameter as a measure of the probability of porosity. To date Niyama porosity predictions agree well with plant experience and show promise for reducing losses associated with porosity. (author)

Porosity prediction from seismic inversion, Lavrans Field, Halten Terrace

Energy Technology Data Exchange (ETDEWEB)

Dolberg, David M.

1998-12-31

This presentation relates to porosity prediction from seismic inversion. The porosity prediction concerns the Lavrans Field of the Halten Terrace on the Norwegian continental shelf. The main themes discussed here cover seismic inversion, rock physics, statistical analysis - verification of well trends, upscaling/sculpting, and implementation. 2 refs., 6 figs.

Evaluation of porosity in Al alloy die castings

Directory of Open Access Journals (Sweden)

M. Říhová

2012-01-01

Full Text Available Mechanical properties of an Al-alloy die casting depend significantly on its structural properties. Porosity in Al-alloy castings is one of the most frequent causes of waste castings. Gas pores are responsible for impaired mechanical-technological properties of cast materials. On the basis of a complex evaluation of experiments conducted on AlSi9Cu3 alloy samples taken from the upper engine block which was die- cast with and without local squeeze casting it can be said that castings manufactured without squeeze casting exhibit maximum porosity in the longitudinal section. The area without local squeeze casting exhibits a certain reduction in mechanical properties and porosity increased to as much as 5%. However, this still meets the norms set by SKODA AUTO a.s.

Particle porosity at plasma are spraying of metals

International Nuclear Information System (INIS)

Petrunichev, V.A.; Koroleva, E.B.; Pushilin, N.P.

1985-01-01

Quantitative dependences of porosity and character of pore distribution in particles of different materials on particle size and composition of atmosphere in a working chamber are studied experimentally as applied to the process of plasma wire sputtering. Wires 1.2 mm in diameter made of tungsten, molybdenum, Kh20N80 alloy, and zirconium served as sputtering materials. It is shown that pore size and character of their distribution in particles of powders obtained by the method of plasma wire sputtering are dependent on sizes of forming particles and determined by conditions of their cooling. Intensive porosity formation is characteristic of wire sputtering in argon plasma with nitrogen additions, but there are critical values of nitrogen concentration in plasma, above which intensive porosity formation in forming particles stops

Properties of Bulk Sintered Silver As a Function of Porosity

Energy Technology Data Exchange (ETDEWEB)

Wereszczak, Andrew A [ORNL; Vuono, Daniel J [ORNL; Wang, Hsin [ORNL; Ferber, Mattison K [ORNL; Liang, Zhenxian [ORNL

2012-06-01

This report summarizes a study where various properties of bulk-sintered silver were investigated over a range of porosity. This work was conducted within the National Transportation Research Center's Power Device Packaging project that is part of the DOE Vehicle Technologies Advanced Power Electronics and Electric Motors Program. Sintered silver, as an interconnect material in power electronics, inherently has porosity in its produced structure because of the way it is made. Therefore, interest existed in this study to examine if that porosity affected electrical properties, thermal properties, and mechanical properties because any dependencies could affect the intended function (e.g., thermal transfer, mechanical stress relief, etc.) or reliability of that interconnect layer and alter how its performance is modeled. Disks of bulk-sintered silver were fabricated using different starting silver pastes and different sintering conditions to promote different amounts of porosity. Test coupons were harvested out of the disks to measure electrical resistivity and electrical conductivity, thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and yield stress. The authors fully recognize that the microstructure of processed bulk silver coupons may indeed not be identical to the microstructure produced in thin (20-50 microns) layers of sintered silver. However, measuring these same properties with such a thin actual structure is very difficult, requires very specialized specimen preparation and unique testing instrumentation, is expensive, and has experimental shortfalls of its own, so the authors concluded that the herein measured responses using processed bulk sintered silver coupons would be sufficient to determine acceptable values of those properties. Almost all the investigated properties of bulk sintered silver changed with porosity content within a range of 3-38% porosity. Electrical resistivity, electrical conductivity

Characterization of porosity in support of mechanical property analysis

International Nuclear Information System (INIS)

Price, R.H.; Martin, R.J. III; Boyd, P.J.

1992-01-01

Previous laboratory investigations of tuff have shown that porosity has a dominant, general effect on mechanical properties. As a result, it is very important for the interpretation of mechanical property data that porosity is measured on each sample tested. Porosity alone, however, does not address all of the issues important to mechanical behavior. Variability in size and distribution of pore space produces significantly different mechanical properties. A nondestructive technique for characterizing the internal structure of the sample prior to testing is being developed and the results are being analyzed. The information obtained from this technique can help in both qualitative and quantitative interpretation of test results

Cold spray NDE for porosity and other process anomalies

Science.gov (United States)

Glass, S. W.; Larche, M. R.; Prowant, M. S.; Suter, J. D.; Lareau, J. P.; Jiang, X.; Ross, K. A.

2018-04-01

This paper describes a technology review of nondestructive evaluation (NDE) methods that can be applied to cold spray coatings. Cold spray is a process for depositing metal powder at high velocity so that it bonds to the substrate metal without significant heating that would be likely to cause additional residual tensile stresses. Coatings in the range from millimeters to centimeters are possible at relatively high deposition rates. Cold spray coatings that may be used for hydroelectric components that are subject to erosion, corrosion, wear, and cavitation damage are of interest. The topic of cold spray NDE is treated generally, however, but may be considered applicable to virtually any cold spray application except where there are constraints of the hydroelectric component application that bear special consideration. Optical profilometry, eddy current, ultrasound, and hardness tests are shown for one set of good, fair, and poor nickel-chrome (NiCr) on 304 stainless steel (304SS) cold spray samples to demonstrate inspection possibilities. The primary indicator of cold spray quality is the cold spray porosity that is most directly measured with witness-sample destructive examinations (DE)—mostly photo-micrographs. These DE-generated porosity values are correlated with optical profilometry, eddy current, ultrasound, and hardness test NDE methods to infer the porosity and other information of interest. These parameters of interest primarily include: • Porosity primarily caused by improper process conditions (temperature, gas velocity, spray standoff, spray angle, powder size, condition, surface cleanliness, surface oxide, etc.) • Presence/absence of the cold spray coating including possible over-sprayed voids • Coating thicknessOptical profilometry measurements of surface roughness trended with porosity plus, if compared with a reference measurement or reference drawing, would provide information on the coating thickness. Ultrasound could provide similar

Determining the mechanical properties of high porosity nickel

International Nuclear Information System (INIS)

Frappier, J.C.; Poirier, J.

1975-01-01

The following tests were carried out on high porosity (40 to 70%) sintered nickel: tensile tests, compression tests, diametral crushing tests, using strain gauges and extensometers. Results were obtained on the relationship elastic properties - porosity, Poisson coefficient in relation to deformation, variations of yield strength, and breaking stress. these various properties were also studied in relation to the sintering methods and the properties of the powders used [fr

Investigation of the porosity of rocks

International Nuclear Information System (INIS)

Hellmuth, K.H.; Siitari-Kauppi, M.

1990-06-01

Methods for characterizing the nature of rock porosity in conjunction with diffusion experiments, are amongst the primary tools used in repository-site selection investigations. At this time no experimental method, alone, is capable of giving an unambiguous picture of the narrow-aperture pore space in crystalline rock. Methods giving information on overall properties must be complemented by those having high spatial resolution; then the lateral distribution of porosity within the matrix and its association with particular mineral phases or features, such as microfissures, fissure fillings, weathered or altered mineral phases etc, and the identification of diffusion pathways in inhomogeneous rock matrices can be determined. Nonsorbing, nonelectrolytic tracers should be used when one wants to determine rock-typical properties of the internal porosity without interference of interactions with surfaces. Preliminary information on a new method fulfilling these criteria is given. Impregnating rock samples with methylmethacrylate labeled with carbon-14 which, after impregnation, was polymerized by gamma radiation, gave specimens that made preparation of sections suitable for quantification by autoradiographic methods easy. Diffusion experiments can be conducted so that labeled MMA diffuses out of rock specimens into inactive free, MMA. Additional information may be gained by leaching PMMA fractions of lower molecular weight from the matrix

Porosity measurement of solid pharmaceutical dosage forms by gamma-ray transmission

International Nuclear Information System (INIS)

Martins de Oliveira, Jose; Andreo Filho, Newton; Vinicius Chaud, Marco; Angiolucci, Tatiana; Aranha, Norberto; Germano Martins, Antonio Cesar

2010-01-01

The aim of the present work is the determination of porosity in tablets by using the gamma-ray transmission technique. Tablet dissolution depends on some inherent characteristics of the manufacturing process, such as compression force, tablet volume, density and porosity, nature of excipients, preparation methods and its physical-chemical properties. Porosity is a measure of empty spaces in a material and can be determined by various techniques. In this paper, we propose the use of a gamma-ray transmission technique to obtain the porosity of experimental formulation of tablets. The results of porosity were compared with those obtained by using conventional methodology (density and mercury intrusion). The experimental setup for gamma-ray transmission consists of a gamma-ray source of 241 Am (photons of 59.6 keV and an activity of 3.7x10 9 Bq), an NaI(Tl) scintillation detector, collimators and a standard gamma-ray spectrometry electronics. Our results suggest that the gamma-ray transmission technique is a powerful tool for non-destructive porosity quantification of solid pharmaceutical forms and presents smaller errors than those obtained with conventional methodologies.

SEM-analysis of grain boundary porosity in three S-176 specimens

International Nuclear Information System (INIS)

Malen, K.; Birath, S.; Mattsson, O.

1980-10-01

Porosity in UO 2 -fuel has been studied in scanning electron microscope (SEM). The aim was to obtain a basis for evaluation of porosity in high burnup power reactor fuel. Three specimens have been analyzed. In the high temperature zones porosity can be seen both on grain boundaries and at grain edges. In the low temperature regions very little changes seem to have occurred during irradiation. (author)

Evolution of porosity and diffusivity associated with chemical weathering of a basalt clast

Energy Technology Data Exchange (ETDEWEB)

Navarre-Sitchler, A.; Steefel, C.I.; Yang, L.; Tomutsa, L.; Brantley, S.L.

2009-02-15

Weathering of rocks as a result of exposure to water and the atmosphere can cause significant changes in their chemistry and porosity. In low-porosity rocks, such as basalts, changes in porosity, resulting from chemical weathering, are likely to modify the rock's effective diffusivity and permeability, affecting the rate of solute transport and thus potentially the rate of overall weathering to the extent that transport is the rate limiting step. Changes in total porosity as a result of mineral dissolution and precipitation have typically been used to calculate effective diffusion coefficients through Archie's law for reactive transport simulations of chemical weathering, but this approach fails to account for unconnected porosity that does not contribute to transport. In this study, we combine synchrotron X-ray microcomputed tomography ({mu}CT) and laboratory and numerical diffusion experiments to examine changes in both total and effective porosity and effective diffusion coefficients across a weathering interface in a weathered basalt clast from Costa Rica. The {mu}CT data indicate that below a critical value of {approx}9%, the porosity is largely unconnected in the basalt clast. The {mu}CT data were further used to construct a numerical pore network model to determine upscaled, effective diffusivities as a function of total porosity (ranging from 3 to 30%) for comparison with diffusivities determined in laboratory tracer experiments. By using effective porosity as the scaling parameter and accounting for critical porosity, a model is developed that accurately predicts continuum-scale effective diffusivities across the weathering interface of the basalt clast.

Hemodynamic transition driven by stent porosity in sidewall aneurysms.

Science.gov (United States)

Bouillot, Pierre; Brina, Olivier; Ouared, Rafik; Lovblad, Karl-Olof; Farhat, Mohamed; Pereira, Vitor Mendes

2015-05-01

The healing process of intracranial aneurysms (IAs) treated with flow diverter stents (FDSs) depends on the IA flow modifications and on the epithelization process over the neck. In sidewall IA models with straight parent artery, two main hemodynamic regimes with different flow patterns and IA flow magnitude were broadly observed for unstented and high porosity stented IA on one side, and low porosity stented IA on the other side. The hemodynamic transition between these two regimes is potentially involved in thrombosis formation. In the present study, CFD simulations and multi-time lag (MTL) particle imaging velocimetry (PIV) measurements were combined to investigate the physical nature of this transition. Measurable velocity fields and non-measurable shear stress and pressure fields were assessed experimentally and numerically in the aneurysm volume in the presence of stents with various porosities. The two main regimes observed in both PIV and CFD showed typical flow features of shear and pressure driven regimes. In particular, the waveform of the averaged IA velocities was matching both the shear stress waveform at IA neck or the pressure gradient waveform in parent artery. Moreover, the transition between the two regimes was controlled by stent porosity: a decrease of stent porosity leads to an increase (decrease) of pressure differential (shear stress) through IA neck. Finally, a good PIV-CFD agreement was found except in transitional regimes and low motion eddies due to small mismatch of PIV-CFD running conditions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Muscular injury in a child diagnosed by 99mTc-MDP bone scan

International Nuclear Information System (INIS)

Tondeur, M.; Piepsz, A.; Ham, H.R.; Haentjens, M.

1989-01-01

An 11-year-old boy had bone scanning to rule out an osseous lesion of the right arm. He presented progressive pain and hard swelling of the right arm. His past medical history and general physical examination were unremarkable. He trained for karate. The scan demonstrated considerable muscular uptake in both arms. CKP and CKP MB levels were both abnormally high, suggesting muscle injury. After a 10-day rest period the bone scan returned to normal. (orig.)

Muscular injury in a child diagnosed by /sup 99m/Tc-MDP bone scan

Energy Technology Data Exchange (ETDEWEB)

Tondeur, M.; Piepsz, A.; Ham, H.R.; Haentjens, M.

1989-06-01

An 11-year-old boy had bone scanning to rule out an osseous lesion of the right arm. He presented progressive pain and hard swelling of the right arm. His past medical history and general physical examination were unremarkable. He trained for karate. The scan demonstrated considerable muscular uptake in both arms. CKP and CKP MB levels were both abnormally high, suggesting muscle injury. After a 10-day rest period the bone scan returned to normal.

Changes in porosity of graphite caused by radiolytic gasification by carbon dioxide

International Nuclear Information System (INIS)

Murdie, Neil; Edwards, I.A.S.; Marsh, Harry

1986-01-01

Methods have been developed to study porosity in nuclear grade graphite. The changes induced during the radiolytic gasification of graphite in carbon dioxide have been investigated. Porosity in radiolytically gasified graphite (0-22.8% wt. loss) was examined by optical microscopy and scanning electron microscopy (SEM). Each sample was vacuum impregnated with a slow-setting resin containing a fluorescent dye. Optical microscopy was used to study pores >2 μm 2 c.s.a. A semi-automatic image analysis system linked to the optical microscope enabled pore parameter data including cross-sectional areas, perimeters, Feret's diameters and shape factors, to be collected. The results showed that radiolytic gasification produced a large increase in the number of pores 2 c.s.a. New open pores 2 c.s.a. were developed by gasification of existing open porosity into the closed porosity ( 2 c.s.a.) within the binder-coke. Open pores, 2-100 μm 2 c.s.a., which were gasified within the coarse-grained mosaics of the binder-coke. In the gasification process to 22.8% wt. loss, the apparent open pore volume increased from 6.6 to 33.8% and the apparent closed pore volumes decreased from approx. 3% to 0.1%. The increase in apparent open porosity from 6.6% (virgin) to 33.8% resulted from gasification within original open porosity and by the opening and development of closed porosity. There was no evidence for creation of porosity from within the 'bulk' graphite, it being developed from existing fine porosity. The structure of pores > 100 μm 2 c.s.a. showed no change because of the inhibition of oxidation by deposition of carbonaceous species from the CH 4 inhibitor. Such species diffuse to the pore wall and are sacrificially oxidised. (author)

A review of porosity-generating mechanisms in crustal shear zones

Science.gov (United States)

Fusseis, F.; Regenauer-Lieb, K.; Revets, S.

2009-04-01

Knowledge of the spatiotemporal characteristics of permeability is critical for the understanding of fluid migration in rocks. In diagenetic and metamorphic rocks different porosity-generating mechanisms contribute to permeability and so influence fluid migration and fluid/rock interaction. However, little is known about their relative contributions to the porosity architecture of a rock in a tectono-metamorphic environment. This presentation reviews porosity-generating mechanisms that affect fluid migration in shear zones, the most important crustal fluid conduits, in the context of the tectonometamorphic evolution of rocks. Mechanisms that generate porosity can be classified in a) those that involve the direct action of a fluid, b) processes in which a fluid partakes or that are supported by a fluid or c) mechanism that do not involve a fluid. a) Hydraulic fracturing, where it happens through the formation of tensile fractures, occurs where pore fluid pressures equalize the combined lithostatic pressure and strength of the rock (Etheridge et al., 1984, Cox & Etheridge, 1989, Oliver, 1996). Here an internally released (devolatilisation reactions, e.g., Rumble, 1994, Hacker, 1997, Yardley, 1997 and references therein) or externally derived (infiltrating from metamorphic, magmatic or meteoric sources, Baumgartner et al., 1997, Jamtveit et al., 1997, Thompson, 1997, Gleeson et al., 2003) fluid directly causes the mechanical failure of a rock. Where a fluid is in chemical disequilibrium with a rock (undersaturated with regard to a chemical species) minerals will be dissolved, generating dissolution porosity. Rocks ‘leached' by the removal of chemical components by vast amounts of fluid are reported to lose up to 60% of their original volume (e.g., Kerrich et al., 1984, McCaig 1988). Dissolution porosity is probably an underrated porosity-generating mechanism. It can be expected along the entire metamorphic evolution, including diagenesis (Higgs et al., 2007) and

Porosity-depth trends of carbonate deposits along the northwest shelf of Australia (IODP Expedition 356)

Science.gov (United States)

Lee, Eun Young; Kominz, Michelle; Reuning, Lars; Takayanagi, Hideko; Knierzinger, Wolfgang; Wagreich, Michael; Expedition 356 shipboard scientists, IODP

2017-04-01

The northwest shelf (NWS) of Australia extends from northern tropical to southern temperate latitudes situated offshore from the low-moderate-relief and semi-arid Australian continent. The shelf environment is dominated throughout by carbonate sedimentation with warm-water and tropical carbonate deposits, connected to the long-term northward drift of Australia bringing the NWS into tropical latitudes. IODP expedition 356 cored seven sites (U1458-U1464) covering a latitudinal range of 29°S-18°S off the NWS. This study focuses on porosity-depth trends of the Miocene - Pleistocene carbonate sediment on the NWS. The NWS is an ideal area to study regional (and furthermore general) carbonate porosity-depth relationships, because it contains a nearly continuous sequence of carbonate sediment ranging in depth from the surface to about 1,100m and in age from Pleistocene to Miocene. Porosity-depth trends of sedimentary rocks are generally controlled by a variety of factors which govern the rates of porosity loss due to mechanical compaction and of porosity loss (or gain) due to chemical processes during diagenesis. This study derives porosity data from Moisture and Density (MAD) technique conducted during IODP Expedition 356. MAD samples were collected from packstone (44%), wackestone (27%), mudstone (15%) and grainstone (7%), with the rest from floatstone, rudstone, dolostone, sandstone and other subordinate lithologies. To understand porosity-depth trends, the porosity data are arranged both exponentially and linearly, and correlated with age models and lithologic descriptions provided by IODP shipboard scientists. Porosity(%)-depth(m) trends of all the porosity data are Porosity=52e-0.0008/Depth (exponential) and Porosity=-0.03Depth+52 (linear). Porosities near surface and in the deepest parts of each well are least well represented by these trend lines. Porosity values of Pleistocene sediment are generally higher than those of Miocene - Pliocene sediment. The initial

Investigating porosity of anthracites during thermoprocessing

Energy Technology Data Exchange (ETDEWEB)

Fialkov, A.S.; Gilyazov, U.Sh.; Samoilov, V.S.; Mel' nichenko, V.M.; Kovalevskii, N.N.

1983-07-01

Changes in the porous structure of anthracite during thermoprocessing up to 3000 C, and the effect of mineral impurities on the materials were studied. A mercury porometer and an electron scanning microscope were used to study Donbass anthracites. A wider spectrum of pore volume distribution was observed for high rank anthracites than for lower rank anthracites. It was established that the specific pore volume in thermographite with an apparent density of more than one unit is three times less than in thermographite with an apparent density of less than one unit. The porosity of thermoanthracite increases sharply in comparison with the starting anthracite. Anthracites are suitable for graphitization after thermoprocessing at 2800-3000 C. The porosity of thermoanthracites depends on the presence and distribution of mineral impurities in the starting anthracite. 4 references.

Monte Carlo simulation of determining porosity by using dual gamma detectors

International Nuclear Information System (INIS)

Zhang Feng; Liu Juntao; Yu Huawei; Yuan Chao; Jia Yan

2013-01-01

Current formation elements spectroscopy logging technology utilize 241 Am-Be neutron source and single BGO detector to determine elements contents. It plays an important role in mineral analysis and lithology identification of unconventional oil and gas exploration, but information measured is relatively ld. Measured system based on 241 Am-Be neutron and dual detectors can be developed to realize the measurement of elements content as well as determine neutron gamma porosity by using ratio of gamma count between near and far detectors. Calculation model is built by Monte Carlo method to study neutron gamma porosity logging response with different spacing and shields. And it is concluded that measuring neutron gamma have high counts and good statistical property contrasted with measuring thermal neutron, but the sensitivity of porosity decrease. Sensitivity of porosity will increase as the spacing of dual detector increases. Spacing of far and near detectors should be around 62 cm and 35 cm respectively. Gamma counts decrease and neutron gamma porosity sensitivity increase when shield is fixed between neutron and detector. The length of main shield should be greater than 10 cm and associated shielding is about 5 cm. By Monte Carlo Simulation study, the result provides technical support for determining porosity in formation elements spectroscopy logging using 241 Am-Be neutron and gamma detectors. (authors)

Influence of porosity on artificial deterioration of marble and limestone by heating

Science.gov (United States)

Sassoni, Enrico; Franzoni, Elisa

2014-06-01

Testing of stone consolidants to be used on-site, as well as research on new consolidating products, requires suitable stone samples, with deteriorated but still uniform and controllable characteristics. Therefore, a new methodology to artificially deteriorate stone samples by heating, exploiting the anisotropic thermal deformation of calcite crystals, has recently been proposed. In this study, the heating effects on a variety of lithotypes was evaluated and the influence of porosity in determining the actual heating effectiveness was specifically investigated. One marble and four limestones, having comparable calcite amounts but very different porosity, were heated at 400 °C for 1 hour. A systematic comparison between porosity, pore size distribution, water absorption, sorptivity and ultrasonic pulse velocity of unheated and heated samples was performed. The results of the study show that the initial stone porosity plays a very important role, as the modifications in microstructural, physical and mechanical properties are way less pronounced for increasing porosity. Heating was thus confirmed as a very promising artificial deterioration method, whose effectiveness in producing alterations that suitably resemble those actually experienced in the field depends on the initial porosity of the stone to be treated.

Influence of porosity on mechanical properties of tetragonal stabilized zirconia

DEFF Research Database (Denmark)

Boccaccini, Dino; Frandsen, Henrik Lund; Soprani, Stefano

2018-01-01

3YSZ specimens with variable open porosity (1–57%) were fabricated, and the stiffness, strength and fracture properties (fracture toughness and R-curve) were measured to investigate their potential use as support structures for solid oxide fuel or electrolysis cells. The ball-on-ring test was used...... to characterize Young's modulus and Weibull strength. The variation of fracture toughness with porosity was investigated and modelled using the results from fracture mechanical testing. A distinct R-curve behaviour was observed in dense 3YSZ specimens, in samples with a porosity around 15% and in some...... supports for SOFC/SOECs from a mechanical point of view....

Self-Assembling Sup-porosity: The Effect On Fluid Flow And Seismic Wave Propagation

Energy Technology Data Exchange (ETDEWEB)

Pyrak-Nolte, Laura J. [Purdue University

2013-04-27

Fractures and joints in the field often contain debris within the void spaces. Debris originates from many different mechanisms: organic and/or inorganic chemical reactions/mineralization, sediment transport, formation of a fracture, mechanical weathering or combinations of these processes. In many cases, the presence of debris forms a sub-porosity within the fracture void space. This sub-porosity often is composed of material that differs from the fracture walls in mineralogy and morphology. The sub-porosity may partially fill voids that are on the order of hundreds of microns and thereby reduce the local porosity to lengths scales on the order of sub-microns to tens of microns. It is quite clear that a sub-porosity affects fracture porosity, permeability and storativity. What is not known is how the existence/formation of a sub-porosity affects seismic wave propagation and consequently our ability to probe changes in the subsurface caused by the formation or alteration of a sub-porosity. If seismic techniques are to be developed to monitor the injection and containment of phases in sequestration reservoirs or the propping of hydraulically induced fracture to enhance oil & gas production, it is important to understand how a sub-porosity within a fracture affects macroscopic seismic and hydraulic measurements. A sub-porosity will directly affect the interrelationship between the seismic and hydraulic properties of a fracture. This reports contains the results of the three main topics of research that were performed (1) to determine the effect of a sub-porosity composed of spherical grains on seismic wave propagation across fractures, (2) to determine the effect of biofilm growth in pores and between grains on seismic wave propagation in sediment, and (3) to determine the effect of the scale of observation (field-of-view) on monitoring alteration the pore space within a fracture caused by reactive flow. A brief summary of the results for each topic is contained in

Porosity-dependent vibration analysis of piezo-magnetically actuated heterogeneous nanobeams

Science.gov (United States)

Ebrahimi, Farzad; Barati, Mohammad Reza

2017-09-01

In this article, the size-dependent and porosity-dependent vibrational behavior of magneto-electro-elastic functionally graded (MEE-FG) nanoscale beams on two-parameter elastic substrate is presented via a third-order shear deformation beam model. Porosity-dependent material coefficients of the nanobeam are compositionally graded throughout the thickness according to a modified power-law model. Incorporation of small size effect is carried out based on Eringen's nonlocal elasticity theory. Through Hamilton's principle, derivation of nonlocal governing equations is performed. After analytically solving these equations, the influences of porosity, elastic foundation, magnetic potential, applied voltage, scale coefficient, material gradation and slenderness ratio on the frequencies of the porous MEE-FG nanobeams are examined.

Void porosity measurements in coastal structures

NARCIS (Netherlands)

Bosma, C.; Verhagen, H.J.; D'Angremond, K.; Sint Nicolaas, W.

2002-01-01

The paper describes the use of two fundamental design parameters, the void porosity and layer thickness in rock armour constructions. These design parameters are very sensible for factors such as the boundary definition of a rock layer, rock production properties, intrinsic properties and

Nonlinear oxidation kinetics of nickel cermets

International Nuclear Information System (INIS)

Galinski, Henning; Bieberle-Huetter, Anja; Rupp, Jennifer L.M.; Gauckler, Ludwig J.

2011-01-01

The oxidation of a cermet of screen-printed nickel (Ni) and gadolinia-doped ceria (CGO) with an approximate median porosity of 50 vol.% has been studied via in situ X-ray diffraction and focused ion beam nanotomography in the temperature range 773-848 K. The oxidation kinetics of Ni to NiO is found to be highly nonlinear with an apparent activation energy of 2.8(2) eV in this temperature range. The nonlinear oxidation kinetics found is in good agreement with theoretical works on oxide growth driven by nonlinear inbuilt fields. Stress-induced Kirkendall void formation has been identified as the physical process that enhances the oxidation of Ni/CGO cermets. Compressive stresses within the Ni matrix result from the thermal expansion mismatch of Ni and CGO and cause plastic deformation as they exceed the yield stress of the Ni matrix. The pore size distribution of Kirkendall voids formed has been measured by FIB nanotomography and shows a significant temperature dependence. It is shown that even one cycle of reoxidation changes irreversibly the microstructure of the cermet which can be interpreted as the onset and main contribution to the mechanical degradation of the cermet.

Double porosity models for the description of water infiltration in wood

DEFF Research Database (Denmark)

Krabbenhøft, Kristian; Damkilde, Lars

2004-01-01

In this paper some of the possibilities of applying double porosity and permeability models to the problem of water infiltration in wood are explored. It is shown that the double porosity model can capture a number of commonly reported anomalies including two-stage infiltration...

Property-porosity relationships for polymer-impregnated superconducting ceramic composite

International Nuclear Information System (INIS)

Salib, S.; Vipulanandan, C.

1990-01-01

A thermoplastic polymer, poly(methyl methacrylate) (PMMA), was used to improve the flexural properties of the high-temperature superconducting ceramic (YBa 2 Cu 3 O 7-δ ). Ceramic specimens with different porosities were prepared by dry compacting 12.5-mm-diameter disk specimens at various uniaxial pressures. Density-pressure relationships have been developed for before- and after-sintering conditions. The PMMA polymer was impregnated into the porous ceramic at room temperature. The mechanical properties were evaluated by concentrically loading simply supported disk specimens. The load-displacement responses were analyzed using the finite-element method. Impregnation of PMMA polymer at room temperature increased the flexural strength and modulus of the superconducting ceramic without affecting its electrical properties. The flexural properties depended on the porosity of the ceramics, and, hence, linear and nonlinear property-porosity relationships have been used to characterize the behavior of superconducting ceramic with an without the polymer

How changing the particle structure can speed up protein mass transfer kinetics in liquid chromatography.

Science.gov (United States)

Gritti, Fabrice; Horvath, Krisztian; Guiochon, Georges

2012-11-09

The mass transfer kinetics of a few compounds (uracil, 112 Da), insulin (5.5 kDa), lysozyme (13.4 kDa), and bovine serum albumin (BSA, 67 kDa) in columns packed with several types of spherical particles was investigated under non-retained conditions, in order to eliminate the poorly known contribution of surface diffusion to overall sample diffusivity across the porous particles in RPLC. Diffusivity across particles is then minimum. Based on the porosity of the particles accessible to analytes, it was accurately estimated from the elution times, the internal obstruction factor (using Pismen correlation), and the hindrance diffusion factor (using Renkin correlation). The columns used were packed with fully porous particles 2.5 μm Luna-C(18) 100 Å, core-shell particles 2.6 μm Kinetex-C(18) 100 Å, 3.6 μm Aeris Widepore-C(18) 200 Å, and prototype 2.7 μm core-shell particles (made of two concentric porous shells with 100 and 300 Å average pore size, respectively), and with 3.3 μm non-porous silica particles. The results demonstrate that the porous particle structure and the solid-liquid mass transfer resistance have practically no effect on the column efficiency for small molecules. For them, the column performance depends principally on eddy dispersion (packing homogeneity), to a lesser degree on longitudinal diffusion (effective sample diffusivity along the packed bed), and only slightly on the solid-liquid mass transfer resistance (sample diffusivity across the particle). In contrast, for proteins, this third HETP contribution, hence the porous particle structure, together with eddy dispersion govern the kinetic performance of columns. Mass transfer kinetics of proteins was observed to be fastest for columns packed with core-shell particles having either a large core-to-particle ratio or having a second, external, shell made of a thin porous layer with large mesopores (200-300 Å) and a high porosity (~/=0.5-0.7). The structure of this external shell seems

Biomaterial porosity determined by fractal dimensions, succolarity and lacunarity on microcomputed tomographic images

International Nuclear Information System (INIS)

N'Diaye, Mambaye; Degeratu, Cristinel; Bouler, Jean-Michel; Chappard, Daniel

2013-01-01

Porous structures are becoming more and more important in biology and material science because they help in reducing the density of the grafted material. For biomaterials, porosity also increases the accessibility of cells and vessels inside the grafted area. However, descriptors of porosity are scanty. We have used a series of biomaterials with different types of porosity (created by various porogens: fibers, beads …). Blocks were studied by microcomputed tomography for the measurement of 3D porosity. 2D sections were re-sliced to analyze the microarchitecture of the pores and were transferred to image analysis programs: star volumes, interconnectivity index, Minkowski–Bouligand and Kolmogorov fractal dimensions were determined. Lacunarity and succolarity, two recently described fractal dimensions, were also computed. These parameters provided a precise description of porosity and pores' characteristics. Non-linear relationships were found between several descriptors e.g. succolarity and star volume of the material. A linear correlation was found between lacunarity and succolarity. These techniques appear suitable in the study of biomaterials usable as bone substitutes. Highlights: ► Interconnected porosity is important in the development of bone substitutes. ► Porosity was evaluated by 2D and 3D morphometry on microCT images. ► Euclidean and fractal descriptors measure interconnectivity on 2D microCT images. ► Lacunarity and succolarity were evaluated on a series of porous biomaterials

Experimental kinetic study and modeling of calcium oxide carbonation

International Nuclear Information System (INIS)

Rouchon, L.

2012-01-01

porosity characteristics at the aggregates scale, which could block the access of the gas to the core of aggregates. Temperature jumps during TGA experiments have put in evidence a complex kinetic behavior since three distinct domains must be distinguished, over all the conversion range, whatever the temperature and CO 2 pressure could be. The discussion of the results emphasizes the role of the porosity on the kinetic anti-Arrhenius behavior observed in the second domain. So carbonation reaction can be described by a two scales model: at a non-porous grain scale for the chemical reaction and at the aggregate scale, for the CO 2 intergranular diffusion. The kinetic modeling, thanks to the software CIN4 (developed in collaboration with Astek), is able to couple both modeling scales in order to explain the kinetic slowing down and the influence of temperature and CO 2 partial pressure on the reaction rate. (author)

One-step aerosol synthesis of nanoparticle agglomerate films: simulation of film porosity and thickness

International Nuclear Information System (INIS)

Maedler, Lutz; Lall, Anshuman A; Friedlander, Sheldon K

2006-01-01

A method is described for designing nanoparticle agglomerate films with desired film porosity and film thickness. Nanoparticle agglomerates generated in aerosol reactors can be directly deposited on substrates to form uniform porous films in one step, a significant advance over existing technologies. The effect of agglomerate morphology and deposition mechanism on film porosity and thickness are discussed. Film porosity was calculated for a given number and size of primary particles that compose the agglomerates, and fractal dimension. Agglomerate transport was described by the Langevin equation of motion. Deposition enhancing forces such as thermophoresis are incorporated in the model. The method was validated for single spherical particles using previous theoretical studies. An S-shape film porosity dependence on the particle Peclet number typical for spherical particles was also observed for agglomerates, but films formed from agglomerates had much higher porosities than films from spherical particles. Predicted film porosities compared well with measurements reported in the literature. Film porosities increased with the number of primary particles that compose an agglomerate and higher fractal dimension agglomerates resulted in denser films. Film thickness as a function of agglomerate deposition time was calculated from the agglomerate deposition flux in the presence of thermophoresis. The calculated film thickness was in good agreement with measured literature values. Thermophoresis can be used to reduce deposition time without affecting the film porosity

Reflectance analysis of porosity gradient in nanostructured silicon layers

Science.gov (United States)

Jurečka, Stanislav; Imamura, Kentaro; Matsumoto, Taketoshi; Kobayashi, Hikaru

2017-12-01

In this work we study optical properties of nanostructured layers formed on silicon surface. Nanostructured layers on Si are formed in order to reach high suppression of the light reflectance. Low spectral reflectance is important for improvement of the conversion efficiency of solar cells and for other optoelectronic applications. Effective method of forming nanostructured layers with ultralow reflectance in a broad interval of wavelengths is in our approach based on metal assisted etching of Si. Si surface immersed in HF and H2O2 solution is etched in contact with the Pt mesh roller and the structure of the mesh is transferred on the etched surface. During this etching procedure the layer density evolves gradually and the spectral reflectance decreases exponentially with the depth in porous layer. We analyzed properties of the layer porosity by incorporating the porosity gradient into construction of the layer spectral reflectance theoretical model. Analyzed layer is splitted into 20 sublayers in our approach. Complex dielectric function in each sublayer is computed by using Bruggeman effective media theory and the theoretical spectral reflectance of modelled multilayer system is computed by using Abeles matrix formalism. Porosity gradient is extracted from the theoretical reflectance model optimized in comparison to the experimental values. Resulting values of the structure porosity development provide important information for optimization of the technological treatment operations.

Determination of reservoir effective porosity using nuclear magnetic logging data

International Nuclear Information System (INIS)

Aksel'rod, S.M.; Danevich, V.I.; Sadykov, D.M.

1979-01-01

In connection with the development of nuclear magnetic logging (NML) the possibility has occurred to determine the effective porosity coefficient for rocks directly under the conditions of their occurrence. The initial amplitude of a signal of free precession of NML is proportional to the quantity of free fluid in the rock volume, which is determined by the index of free fluid (IFF). On the basis of the laboratory studies it is shown that the relation between IFF and free water content is always linear and doesn't depend on lithological characteristics of rocks, porous dimensions and distribution. Using this relation it's possible to estimate bound water content. While filling the reservoir with weakly mineralized water the IFF value coincides numerically with the effective porosity coefficient. Otherwise the content of hydrogen nuclei in a volume unit is much less; while calculating the effective porosity coefficient this fact is recorded by the index of the amplitude decrease which depends on temperature and increases with its growth (for oils). In strata containing intercalations of reservoirs and non-reservoirs the averaged according to stratum IFF value determines the mean-weighted values of effective porosity

2.5-D poroelastic wave modelling in double porosity media

Science.gov (United States)

Liu, Xu; Greenhalgh, Stewart; Wang, Yanghua

2011-09-01

To approximate seismic wave propagation in double porosity media, the 2.5-D governing equations of poroelastic waves are developed and numerically solved. The equations are obtained by taking a Fourier transform in the strike or medium-invariant direction over all of the field quantities in the 3-D governing equations. The new memory variables from the Zener model are suggested as a way to represent the sum of the convolution integrals for both the solid particle velocity and the macroscopic fluid flux in the governing equations. By application of the memory equations, the field quantities at every time step need not be stored. However, this approximation allows just two Zener relaxation times to represent the very complex double porosity and dual permeability attenuation mechanism, and thus reduce the difficulty. The 2.5-D governing equations are numerically solved by a time-splitting method for the non-stiff parts and an explicit fourth-order Runge-Kutta method for the time integration and a Fourier pseudospectral staggered-grid for handling the spatial derivative terms. The 2.5-D solution has the advantage of producing a 3-D wavefield (point source) for a 2-D model but is much more computationally efficient than the full 3-D solution. As an illustrative example, we firstly show the computed 2.5-D wavefields in a homogeneous single porosity model for which we reformulated an analytic solution. Results for a two-layer, water-saturated double porosity model and a laterally heterogeneous double porosity structure are also presented.

Hyporheic less-mobile porosity and solute transport in porous media

Science.gov (United States)

MahmoodPoorDehkordy, F.; Briggs, M. A.; Day-Lewis, F. D.; Scruggs, C.; Singha, K.; Zarnetske, J. P.; Lane, J. W., Jr.; Bagtzoglou, A. C.

2017-12-01

Solute transport and reactive processes are strongly influenced by hydrodynamic exchange with the hyporheic zone. Contaminant transport and redox zonation in the hyporheic zone and near-stream aquifer can be impacted by the exchange between mobile and less-mobile porosity zones in heterogeneous porous media. Less-mobile porosity zones can be created by fine materials with tight pore throats (e.g. clay, organics) and in larger, well-connected pores down gradient of flow obstructions (e.g. sand behind cobbles). Whereas fluid sampling is primarily responsive to the more-mobile domain, tracking solute tracer dynamics by geoelectrical methods provides direct information about both more- and less-mobile zones. During tracer injection through porous media of varied pore connectivity, a lag between fluid and bulk electrical conductivity is observed, creating a hysteresis loop when plotted in conductivity space. Thus, the combination of simultaneous fluid and bulk electrical conductivity measurements enables a much improved quantification of less-mobile solute dynamics compared to traditional fluid-only sampling approaches. We have demonstrated the less-mobile porosity exchange in laboratory-scale column experiments verified by simulation models. The experimental approach has also been applied to streambed sediments in column and reach-scale field experiments and verified using numerical simulation. Properties of the resultant hysteresis loops can be used to estimate exchange parameters of less-mobile porosity. Our integrated approach combining field experiments, laboratory experiments, and numerical modeling provides new insights into the effect of less-mobile porosity on solute transport in the hyporheic zone.

Acoustic properties in travertines and their relation to porosity and pore types

NARCIS (Netherlands)

Soete, J.; Kleipool, L.M.; Claes, H.; Claes, S.; Hamaekers, H.; Kele, S.; Özkul, M.; Foubert, A.; Reijmer, J.J.G.; Swennen, R.

2015-01-01

Sonic velocities of Pleistocene travertines were measured under variable confining pressures. Combined with petrographical characteristics and petrophysical data, i.e. porosity, permeability and density, it was determined that travertine porosity, pore types and cementation control

Characterization of porosity in support of mechanical property analysis

International Nuclear Information System (INIS)

Price, R.H.; Martin, R.J. III; Boyd, P.J.

1993-01-01

The general applicability of laboratory data for engineering purposes is a prime concern for the design and licensing of a potential repository of high level nuclear waste at Yucca Mountain. In order for the results of experiments to be applicable to the repository scale, the data must be scaled to in situ size and conditions. Previous laboratory investigations of tuff have shown that porosity has a dominant, general effect on mechanical properties. As a result, it is very important for the interpretation of mechanical property data that porosity is measured on each sampled test. Porosity alone, however, does not address all of the issues important to mechanical behavior. Variability in size and distribution of pore space produces significantly different mechanical properties. A nondestructive technique for characterizing the internal structure of the sample prior to testing is being developed and the results are being analyzed. The information obtained from this technique can help in both qualitative and quantitative interpretation of test results

Local porosity analysis of pore structure in cement paste

International Nuclear Information System (INIS)

Hu Jing; Stroeven, Piet

2005-01-01

Three-dimensional (3-D) local porosity theory (LPT) was originally proposed by Hilfer and recently used for the analysis of pore space geometry in model sandstone. LPT pursues to define the probability density functions of porosity and porosity connectivity. In doing so, heterogeneity differences in various sandstone samples were assessed. However, fundamental issues as to the stochastic concept of geometric heterogeneity are ignored in Hilfer's LPT theory. This paper focuses on proper sampling procedures that should be based on stochastic approaches to multistage sampling and geometric heterogeneity. Standard LPT analysis provides a 3-D microscopic modeling approach to materials. Traditional experimental techniques yield two-dimensional (2-D) section images, however. Therefore, this paper replaces the method for assessing material data in standard LPT theory to a more practical one, based on stereological, 3-D interpretation of quantitative image analysis data. The developed methodology is used to characterize the pore structure in hardened cement paste with various water/cement ratios (w/c) at different hydration stages

Porosity study of synthetic sandstones by non-destructive nuclear techniques

International Nuclear Information System (INIS)

Marques, Leonardo Carmezini

2008-01-01

In this paper, nuclear techniques have been used to describe structural characteristics of ceramic samples. These samples were produced to serve as simulates of sandstones and their mainly component was silica (SiO 2 ). Three sets of these samples with different characteristics were analyzed with the gamma ray transmission and the X-ray microtomography. They had the function to describe parameters as porosity point to point and total average porosity, for the transmission case, and 2D sections average porosity, total average porosity and size porous distribution for microtomography, as well as to investigate possible irregularities in bulk sample. The experimental set up for the Gamma Ray Transmission technique consisted of: a 2'' x 2'' crystal NaI(Tl) detector, an 241 Am radioactive source (59.54 keV, 100 mCi), an automatic micrometric table for the sample XZ movement and standard gamma spectrometry electronics. Lead collimators with 2 mm diameter were placed on the source way out and on the detector entrance. The microtomographic measurements were done with a Skyscan system, model 1172, with a X -ray tube with 20 - 100 kV of voltage range and a CCD camera. Employing gamma ray transmission method was possible to obtain overall porosity values from 25.8 to 34.0 % and from 24.8 to 29.2 % for samples with parallelepiped and cylinder shape, respectively, for ceramic I set; from 58.5 to 61.0 % and from 57.1 to 61.7 % for the same geometric shape of ceramic II set. The samples analyzed by the microtomography achieved resolutions of 1.73 μm, 0.64 μm and 1.28 μm for samples of ceramic set I, II and III, respectively. This methodology provided average total porosity values from 26.6 to 29.4 %, from 48.4 to 51.0 % and from 28.2 to 30.6 % to I, II and III ceramic sets, respectively. The porous size profiles of each ceramic sample were also measured. (author)

Estimation of water-filled and air-filled porosity in the unsaturated zone, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Nelson, P.H.

1993-01-01

Water content and porosity vary considerably within the unsaturated zone at Yucca Mountain. Measurement of these quantities has been based on core samples. A log-based approach offers the advantage of in-situ measurements, continuous throughout the borehole. This paper describes an algorithm which determines the air-filled and water-filled porosities from density and dielectric logs. The responses of density and dielectric logs are formulated in terms of the matrix properties, air-filled porosity and water-filled porosity. Porosity values obtained from logs from borehole USW G-2 are in reasonable agreement with estimates from core determinations

Transient analysis of carbon monoxide transport phenomena and adsorption kinetics in HT-PEMFC during dynamic current extraction

International Nuclear Information System (INIS)

Raj, Kamal Abdul Rasheedj; Chan, Siew Hwa

2015-01-01

Highlights: • Increasing the fuel cell temperature reduces outlet CO concentration. • Increasing the CO inlet (initial) concentration increases outlet CO concentration. • Increasing current density step and dwell time increases outlet CO concentration. • Increasing in the CL and GDL porosities reduces outlet CO concentration. - Abstract: This paper investigates the transport phenomena of carbon monoxide (CO) and adsorption kinetics, in a high-temperature proton exchange membrane fuel cell (HT-PEMFC) during step-wise current extraction (step-change in current extraction). Step-wise current extraction is a common process done to accommodate a sudden power surge during an operation. Since HT-PEMFCs are capable of handling high impurity of CO, hydrogen fuel that is contaminated with trace amount of CO is usually considered for commercial benefits. Thus, a transient three-dimensional isothermal anodic electro-kinetic numerical model is developed to determine the effect of operating parameters such as fuel cell temperature, CO inlet (initial) concentration, step-change of current density and dwell time on the transport phenomena of CO and adsorption kinetics. In addition, geometrical factors such as the catalyst layer (CL) and gas diffusion layer (GDL) porosity are also varied as well. The results show that the above-mentioned operating parameters can affect the maximum CO concentration at the CL, especially at the outlet of the channel. Specifically, a reduction of fuel cell temperature can significantly increase the CO concentration near the outlet, while increasing CO inlet (initial) concentration, step-change amplitude of current density and current density dwell time can cause an increase in CO concentration at the outlet, albeit to different extent. In addition, the increase in the porosity of CL and GDL, results in the reduction of the maximum CO concentration at the outlet, albeit to different extent. In addition, the CO and hydrogen surface coverage

Robust numerical simulation of porosity evolution in chemical vapor infiltration III: three space dimension

CERN Document Server

Jin Shi

2003-01-01

Chemical vapor infiltration (CVI) process is an important technology to fabricate ceramic matrix composites (CMC's). In this paper, a three-dimension numerical model is presented to describe pore microstructure evolution during the CVI process. We extend the two-dimension model proposed in [S. Jin, X.L. Wang, T.L. Starr, J. Mater. Res. 14 (1999) 3829; S. Jin. X.L. Wang, T.L. Starr, X.F. Chen, J. Comp. Phys. 162 (2000) 467], where the fiber surface is modeled as an evolving interface, to the three space dimension. The 3D method keeps all the virtue of the 2D model: robust numerical capturing of topological changes of the interface such as the merging, and fast detection of the inaccessible pores. For models in the kinetic limit, where the moving speed of the interface is constant, some numerical examples are presented to show that this three-dimension model will effectively track the change of porosity, close-off time, location and shape of all pores.

Impact of cover crops and tillage on porosity of podzolic soil

Science.gov (United States)

Błażewicz-Woźniak, M.; Konopiñski, M.

2013-09-01

The aim of the study was to determine the influence of cover crops biomass, mixed with the soil on different dates and with the use of different tools in field conditions. The cover crop biomass had a beneficial influence on the total porosity of the 0-20 cm layer of the soil after winter. The highest porosity was achievedwith cover crops of buckwheat, phacelia and mustard, the lowest with rye. During the vegetation period the highest porosity of soil was observed in the ridges. Among the remaining non-ploughing cultivations, pre-winter use of stubble cultivator proved to have a beneficial influence on the soil porosity, providing results comparable to those achieved in conventional tillage. The differential porosity of the soil was modified not only by the catch crops and the cultivation methods applied, but also by the sample collection dates, and it did change during the vegetation period. The highest content of macropores after winter was observed for the phacelia cover crop, and the lowest in the case of cultivation without any cover crops. Pre-winter tillage with the use of a stubble cultivator increased the amount of macropores in soil in spring, and caused the biggest participation of mesopores as compared with other non-ploughing cultivation treatments of the soil. The smallest amount of mesopores was found in the ridges.

Solutes transport in unsaturated double-porosity medium. Modelling by homogenization and applications

International Nuclear Information System (INIS)

Tran Ngoc, T.D.

2008-07-01

This Ph.D thesis presents the development of the solute transport models in unsaturated double-porosity medium, by using the asymptotic homogenization method. The obtained macroscopic models concern diffusion, diffusion-convection and dispersion-convection, according to the transport regime which is characterized by the non-dimensional numbers. The models consist of two coupled equations that show the local non-equilibrium of concentrations. The double-porosity transport models were numerically implemented using the code COMSOL Multiphysics (finite elements method), and compared with the solution of the same problem at the fine scale. The implementation allows solving the coupled equations in the macro- and micro-porosity domains (two-scale computations). The calculations of the dispersion tensor as a solution of the local boundary value problems, were also conducted. It was shown that the dispersivity depends on the saturation, the physical properties of the macro-porosity domain and the internal structure of the double-porosity medium. Finally, two series of experiments were performed on a physical model of double-porosity that is composed of a periodic assemblage of sintered clay spheres in Hostun sand HN38. The first experiment was a drainage experiment, which was conducted in order to validate the unsaturated flow model. The second series was a dispersion experiment in permanent unsaturated water flow condition (water content measured by gamma ray attenuation technique). A good agreement between the numerical simulations and the experimental observations allows the validation of the developed models. (author)

Characterization of bentonite pore structure by combining chloride porosity and SAXS measurements

International Nuclear Information System (INIS)

Muurinen, A.

2010-01-01

Document available in extended abstract form only. The total water porosity, chloride porosity and the microstructure were studied in compacted samples prepared from MX-80 and Deponit bentonites equilibrated through filter plates with 0.1 M NaCl solution for 12.5 months. The dry densities of the samples varied approximately from 0.7 to 1.55 g/cm 3 . XRD and SAXS (Small Angle X-ray Scattering) were used to study the microstructure of the bentonites. It was obvious that the chloride porosity was lower than the water porosity in both clays, which indicates the exclusion caused by the negatively charged montmorillonite surfaces. In the XRD and SAXS measurements the measured basal spaces represented by the diffraction peaks were smaller than the theoretical ones assuming a homogenous microstructure. This indicates that there was a substantial amount of water also in the pores, which were not represented by the peaks. This could explain the difference between the measured chloride porosity and the modelling curve obtained with the Donnan model. By combining the information from the SAXS measurements and the chloride exclusion measurements, it was possible to evaluate the volumes of the soft and dense fractions and the pore sizes in each fraction for MX-80. The chloride porosity was mostly caused by the pores in the soft clay where the pore size is larger. The volume of the soft fraction decreased and its density increased with increasing density of the sample. (authors)

The effect of porosity on energetic porous silicon solid propellant micro-propulsion

International Nuclear Information System (INIS)

Churaman, Wayne A; Morris, Christopher J; Ramachandran, Raghav; Bergbreiter, Sarah

2015-01-01

Energetic porous silicon is investigated as an actuator for micro-propulsion based on thrust and impulse measurements for a variety of porous silicon porosity conditions. Porosity of 2 mm diameter, porous silicon microthruster devices was varied by changing the concentration of hydrofluoric acid and ethanol in an etch solution, by changing porous silicon etch depth, and by changing the resistivity of silicon wafers used for the etch process. The porosity varied from 30% to 75% for these experiments. The highest mean thrust and impulse values measured with a calibrated Kistler 9215 force sensor were 674 mN and 271 μN s, respectively, with a 73% porosity, 2 mm diameter porous silicon device etched in a 3 : 1 etch solution on a 3.6 Ω cm wafer to a target etch depth of 30 μm. As a result of changing porosity, a 23×  increase in thrust performance and a 36×  increase in impulse performance was demonstrated. Impulse values were also validated using a pendulum experiment in which the porous silicon microthruster was unconstrained, but several non-linearities in the pendulum experimental setup resulted in less consistent data than when measured by the force sensor for microthrusters at this size scale. These thrust and impulse results complement previous work in determining the effect of porosity on other porous silicon reaction metrics such as flame speed. (paper)

Models for Strength Prediction of High-Porosity Cast-In-Situ Foamed Concrete

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Wenhui Zhao

2018-01-01

Full Text Available A study was undertaken to develop a prediction model of compressive strength for three types of high-porosity cast-in-situ foamed concrete (cement mix, cement-fly ash mix, and cement-sand mix with dry densities of less than 700 kg/m3. The model is an extension of Balshin’s model and takes into account the hydration ratio of the raw materials, in which the water/cement ratio was a constant for the entire construction period for a certain casting density. The results show that the measured porosity is slightly lower than the theoretical porosity due to few inaccessible pores. The compressive strength increases exponentially with the increase in the ratio of the dry density to the solid density and increases with the curing time following the composite function A2ln⁡tB2 for all three types of foamed concrete. Based on the results that the compressive strength changes with the porosity and the curing time, a prediction model taking into account the mix constitution, curing time, and porosity is developed. A simple prediction model is put forward when no experimental data are available.

Measurement of the open porosity of agricultural soils with acoustic waves

Science.gov (United States)

Luong, Jeanne; Mercatoris, Benoit; Destain, Marie-France

2015-04-01

The space between agricultural soil aggregates is defined as structural porosity. It plays important roles in soil key functions that an agricultural soil performs in the global ecosystem. Porosity is one of the soil properties that affect plant growth along with soil texture, aggregate size, aeration and water holding capacity (Alaoui et al. 2011). Water supplies regulation of agricultural soil is related to the number of very small pores present in a soil due to the effect of capillarity. Change of porosity also affect the evaporation of the water on the surface (Le Maitre et al. 2014). Furthermore, soil is a habitat for soils organisms, and most living organisms, including plant roots and microorganisms require oxygen. These organisms breathe easier in a less compacted soil with a wide range of pores sizes. Soil compaction by agricultural engine degrades soil porosity. At the same time, fragmentation with tillage tools, creation of cracks due to wetting/drying and freezing/thawing cycles and effects of soil fauna can regenerate soil porosity. Soil compaction increases bulk density since soil grains are rearranged decreasing void space and bringing them into closer contact (Hamza & Anderson 2005). Drainage is reduced, erosion is facilitated and crop production decreases in a compacted soil. Determining soil porosity, giving insight on the soil compaction, with the aim to provide advices to farmers in their soil optimization towards crop production, is thus an important challenge. Acoustic wave velocity has been correlated to the porosity and the acoustic attenuation to the water content (Oelze et al. 2002). Recent studies have shown some correlations between the velocity of acoustic waves, the porosity and the stress state of soil samples (Lu et al. 2004; Lu 2005; Lu & Sabatier 2009), concluding that the ultrasonic waves are a promising tool for the rapid characterisation of unsaturated porous soils. Propagation wave velocity tends to decrease in a high porous

Measurement of the porosity of amorphous materials by gamma ray transmission methodology

International Nuclear Information System (INIS)

Pottker, Walmir Eno; Appoloni, Carlos Roberto

2000-01-01

In this work it is presented the measurement of the total porosity of TRe soil, Sandstone Berea rocks and porous ceramics samples. For the determination of the total porosity, the Arquimedes method (conventional) and the gamma ray transmission methodology were employed. The porosity measurement using the gamma methodology has a significant advantage respect to the conventional method due to the fast and non-destructive determination, and also for supplying results with a greater characterization in small scales, in relation to the heterogeneity of the porosity. The conventional methodology presents good results only for homogeneous samples. The experimental set up for the gamma ray transmission technique consisted of a 241 Am source (59,53 keV ), a NaI(Tl) scintillation detector, collimators, a XYZ micrometric table and standard gamma spectrometry electronics connected to a multichannel analyser. (author)

3D Membrane Imaging and Porosity Visualization

KAUST Repository

Sundaramoorthi, Ganesh; Hadwiger, Markus; Ben Romdhane, Mohamed; Behzad, Ali Reza; Madhavan, Poornima; Nunes, Suzana Pereira

2016-01-01

Ultrafiltration asymmetric porous membranes were imaged by two microscopy methods, which allow 3D reconstruction: Focused Ion Beam and Serial Block Face Scanning Electron Microscopy. A new algorithm was proposed to evaluate porosity and average pore

Influence of shrinkage porosity on fatigue performance of iron castings and life estimation method

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Wei Liu

2016-01-01

Full Text Available Shrinkage porosity exists more or less in heavy castings, and it plays an important role in the fatigue behavior of cast materials. In this study, fatigue tests were carried out on the QT400-18 cast iron specimens containing random degrees of shrinkage porosity defect. Experimental results showed that the order of magnitude of life scattered from 103 to 106 cycles when the shrinkage percentage ranged from 0.67% to 5.91%. SEM analyses were carried out on the shrinkage porosity region. The inter-granular discontinuous, micro cracks and inclusions interfered with the fatigue sliding or hindering process. The slip in shrinkage porosity region was not as orderly as the ordinary continuous medium. The shrinkage porosity area on fracture surface (SPAFS and alternating stress intensity factor (ASIF were applied to evaluate the tendency of residual life distribution; their relationship was fitted by negative exponent functions. Based on the intermediate variable of ASIF, a fatigue life prediction model of nodular cast iron containing shrinkage porosity defects was established. The modeling prediction was in agreement with the experimental results.

Determination of Porosity in Shale by Double Headspace Extraction GC Analysis.

Science.gov (United States)

Zhang, Chun-Yun; Li, Teng-Fei; Chai, Xin-Sheng; Xiao, Xian-Ming; Barnes, Donald

2015-11-03

This paper reports on a novel method for the rapid determination of the shale porosity by double headspace extraction gas chromatography (DHE-GC). Ground core samples of shale were placed into headspace vials and DHE-GC measurements of released methane gas were performed at a given time interval. A linear correlation between shale porosity and the ratio of consecutive GC signals was established both theoretically and experimentally by comparing with the results from the standard helium pycnometry method. The results showed that (a) the porosity of ground core samples of shale can be measured within 30 min; (b) the new method is not significantly affected by particle size of the sample; (c) the uncertainties of measured porosities of nine shale samples by the present method range from 0.31 to 0.46 p.u.; and (d) the results obtained by the DHE-GC method are in a good agreement with those from the standard helium pycnometry method. In short, the new DHE-GC method is simple, rapid, and accurate, making it a valuable tool for shale gas-related research and applications.

Double porosity model to describe both permeability change and dissolution processes

International Nuclear Information System (INIS)

Niibori, Yuichi; Usui, Hideo; Chida, Taiji

2015-01-01

Cement is a practical material for constructing the geological disposal system of radioactive wastes. The dynamic behavior of both permeability change and dissolution process caused by a high pH groundwater was explained using a double porosity model assuming that each packed particle consists of the sphere-shaped aggregation of smaller particles. This model assumes two kinds of porosities between the particle clusters and between the particles, where the former porosity change mainly controls the permeability change of the bed, and the latter porosity change controls the diffusion of OH"- ions inducing the dissolution of silica. The fundamental equations consist of a diffusion equation of spherical coordinates of OH"- ions including the first-order reaction term and some equations describing the size changes of both the particles and the particle clusters with time. The change of over-all permeability of the packed bed is evaluated by Kozeny-Carman equation and the calculated radii of particle clusters. The calculated result well describes the experimental result of both permeability change and dissolution processes. (author)

Method and apparatus for dual-spaced fast/epithermal neutron porosity measurements

International Nuclear Information System (INIS)

Smith, H.D. Jr.

1986-01-01

A method is described for determining the porosity of earth formations in the vicinity of a well borehole, comprising: (a) irradiating the earth formations in the vicinity of the well borehole with a continuous chemical type source of fast neutrons, (b) detecting the fast neutron population at a first shorter spaced distance from the neutron source in the borehole and generating signals representative thereof, (c) detecting the epithermal neutron population at a second space distance from the neutron source in the borehole and generating signals representative thereof, the second spaced distance being greater than the first spaced distance from the neutron source, (d) forming a ratio of the signals representing the fast and epithermal neutron populations to derive a measurement signal functionally related to the porosity of the earth formations in the vicinity of the borehole, and (e) calibrating the measurement signal according to a predetermined functional relationship to derive a porosity signal quantitatively representative of the porosity of the earth formations in the vicinity of the borehole

Mechanisms and mechanics of porosity formation in ductile iron castings

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M. Perzyk

2007-12-01

Full Text Available Shrinkage defects in ductile iron castings can be of two basic types: shrinkage cavities associated with the liquid contraction prior to the expansion period of the iron as well as the porosity, which may appear even if the liquid shrinkage is fully compensated. In the present paper two possible mechanisms of the porosity are presented and analyzed. The first one is the Karsay’s mechanism based on the secondary shrinkage concept. The second one is the mechanism acting during the expansion period of the iron, first suggested by Ohnaka and co-authors and essentially modified by the present authors. The mechanical interactions between casting and mould are determined for the both mechanisms. Their analysis leads to the conclusion, that porosity forms during expansion period of the melt. The direct cause is the negative pressure which appears in the central part of the casting due to the differences in expansion coefficients of the fast cooling surface layer and slow cooling inner region. Observations concerning feeding behavior of ductile iron castings, based on this mechanism, agree well with industrial practice. The secondary shrinkage is not only needless to induce the porosity, but the corresponding mechanism of its occurrence, proposed by Karsay, does not seem to be valid.

A dual porosity model of nutrient uptake by root hairs

KAUST Repository

Zygalakis, K. C.; Kirk, G. J. D.; Jones, D. L.; Wissuwa, M.; Roose, T.

2011-01-01

Summary: • The importance of root hairs in the uptake of sparingly soluble nutrients is understood qualitatively, but not quantitatively, and this limits efforts to breed plants tolerant of nutrient-deficient soils. • Here, we develop a mathematical model of nutrient uptake by root hairs allowing for hair geometry and the details of nutrient transport through soil, including diffusion within and between soil particles. We give illustrative results for phosphate uptake. • Compared with conventional 'single porosity' models, this 'dual porosity' model predicts greater root uptake because more nutrient is available by slow release from within soil particles. Also the effect of soil moisture is less important with the dual porosity model because the effective volume available for diffusion in the soil is larger, and the predicted effects of hair length and density are different. • Consistent with experimental observations, with the dual porosity model, increases in hair length give greater increases in uptake than increases in hair density per unit main root length. The effect of hair density is less in dry soil because the minimum concentration in solution for net influx is reached more rapidly. The effect of hair length is much less sensitive to soil moisture. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

A dual porosity model of nutrient uptake by root hairs

KAUST Repository

Zygalakis, K. C.

2011-08-09

Summary: • The importance of root hairs in the uptake of sparingly soluble nutrients is understood qualitatively, but not quantitatively, and this limits efforts to breed plants tolerant of nutrient-deficient soils. • Here, we develop a mathematical model of nutrient uptake by root hairs allowing for hair geometry and the details of nutrient transport through soil, including diffusion within and between soil particles. We give illustrative results for phosphate uptake. • Compared with conventional \\'single porosity\\' models, this \\'dual porosity\\' model predicts greater root uptake because more nutrient is available by slow release from within soil particles. Also the effect of soil moisture is less important with the dual porosity model because the effective volume available for diffusion in the soil is larger, and the predicted effects of hair length and density are different. • Consistent with experimental observations, with the dual porosity model, increases in hair length give greater increases in uptake than increases in hair density per unit main root length. The effect of hair density is less in dry soil because the minimum concentration in solution for net influx is reached more rapidly. The effect of hair length is much less sensitive to soil moisture. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

A modeling and numerical algorithm for thermoporomechanics in multiple porosity media for naturally fractured reservoirs

Science.gov (United States)

Kim, J.; Sonnenthal, E. L.; Rutqvist, J.

2011-12-01

Rigorous modeling of coupling between fluid, heat, and geomechanics (thermo-poro-mechanics), in fractured porous media is one of the important and difficult topics in geothermal reservoir simulation, because the physics are highly nonlinear and strongly coupled. Coupled fluid/heat flow and geomechanics are investigated using the multiple interacting continua (MINC) method as applied to naturally fractured media. In this study, we generalize constitutive relations for the isothermal elastic dual porosity model proposed by Berryman (2002) to those for the non-isothermal elastic/elastoplastic multiple porosity model, and derive the coupling coefficients of coupled fluid/heat flow and geomechanics and constraints of the coefficients. When the off-diagonal terms of the total compressibility matrix for the flow problem are zero, the upscaled drained bulk modulus for geomechanics becomes the harmonic average of drained bulk moduli of the multiple continua. In this case, the drained elastic/elastoplastic moduli for mechanics are determined by a combination of the drained moduli and volume fractions in multiple porosity materials. We also determine a relation between local strains of all multiple porosity materials in a gridblock and the global strain of the gridblock, from which we can track local and global elastic/plastic variables. For elastoplasticity, the return mapping is performed for all multiple porosity materials in the gridblock. For numerical implementation, we employ and extend the fixed-stress sequential method of the single porosity model to coupled fluid/heat flow and geomechanics in multiple porosity systems, because it provides numerical stability and high accuracy. This sequential scheme can be easily implemented by using a porosity function and its corresponding porosity correction, making use of the existing robust flow and geomechanics simulators. We implemented the proposed modeling and numerical algorithm to the reaction transport simulator

Fracture toughness of Dy123 low porosity bulks at liquid nitrogen temperature

International Nuclear Information System (INIS)

Murakami, A.; Otaka, K.; Miura, T.; Iwamoto, A.

2011-01-01

Fracture toughness values were measured for Dy123 bulks. Fracture toughness was improved by reducing porosity. Fracture toughness values at 77 K were higher than those at room temperature. Fracture toughness was also improved by Ag addition. In order to evaluate the fracture toughness of DyBa 2 Cu 3 O x (Dy123) low porosity bulks, bending tests of V-notched specimens cut from the bulks were carried out. Fracture toughness evaluations of a conventional Dy123 bulk which had pores were also carried out and effects of elimination of pores on the fracture toughness were investigated. Fracture toughness values at 77 K of the low porosity bulks were higher than those of the porous bulk. These fracture toughness values at 77 K were higher than the values at room temperature. Fracture toughness of the low porosity bulk was improved by Ag addition.

Porosity determination of alumina and boron carbide ceramic samples by gamma ray transmission

International Nuclear Information System (INIS)

Moreira, Anderson Camargo; Appoloni, Carlos Roberto

2009-01-01

The aim of this work is to apply the Gamma Ray Transmission (GRT), a non destructive technique, for structural characterization of ceramic samples. With this technique, the porosity of Alumina (Al 2 O 3 ) and Boron Carbide (B 4 C) ceramic samples, in tablet format, was determined. The equipment employed is constituted by a 241 Am gamma ray source (59.6 keV and 100mCi), a 2''x2'' diameter NaI (Tl) scintillation detector coupled to a standard gamma ray transmission electronic and a micrometric and automated table for sample movement. The porosity profile of the samples shows a homogeneous porosity distribution, within the spatial resolution of the employed transmission system. The mean porosity determined for Al 2 O 3 and B 4 C were 17.8±1.3% and 3.87±0.43%, respectively. A statistical treatment of these results was performed and showed that the mean porosity values determinate by the GRT are the same as those supplied by the manufacturer. (author)

Kinetic study of Chromium VI adsorption onto palm kernel shell activated carbon

Science.gov (United States)

Mohammad, Masita; Sadeghi Louyeh, Shiva; Yaakob, Zahira

2018-04-01

Heavy metal contamination of industrial effluent is one of the significant environmental problems due to their toxicity and its accumulation throughout the food chain. Adsorption is one of the promising methods for removal of heavy metals from aqua solution because of its simple technique, efficient, reliable and low-cost due to the utilization of residue from the agricultural industry. In this study, activated carbon from palm kernel shells has been produced through chemical activation process using zinc chloride as an activating agent and carbonized at 800 °C. Palm kernel shell activated carbon, PAC was assessed for its efficiency to remove Chromium (VI) ions from aqueous solutions through a batch adsorption process. The kinetic mechanisms have been analysed using Lagergren first-order kinetics model, second-order kinetics model and intra-particle diffusion model. The characterizations such as BET surface area, surface morphology, SEM-EDX have been done. The result shows that the activation process by ZnCl2 was successfully improved the porosity and modified the functional group of palm kernel shell. The result shows that the maximum adsorption capacity of Cr is 11.40mg/g at 30ppm initial metal ion concentration and 0.1g/50mL of adsorbent concentration. The adsorption process followed the pseudo second orders kinetic model.

Microstructure and Porosity of Laser-welded Dissimilar Material Joints of HR-2 and J75

Science.gov (United States)

Shen, Xianfeng; Teng, Wenhua; Zhao, Shuming; He, Wenpei

Dissimilar laser welding of HR-2 and J75 has a wide range of applications in high-and low-temperature hydrogen storage. The porosity distributions of the welded joints were investigated at different line energies, penetration status, and welding positions (1G, 2G, and 3G). The effect of the welding position on the welding appearance was evident only at high line energies because of the essential effect of gravity of the larger and longer dwelling molten pool. The porosity of the welded joints between the solutionised and aged J75 and HR-2 at the 3G position and partial penetration was located at the weld centre line, while the porosity at the 2G position with full penetration was distributed at the weld edges, which is consistent with the distribution of floating slag. Full keyhole penetration resulted in minimum porosity, partial penetration resulted in moderate porosity, and periodic molten pool penetration resulted in maximum porosity.

From picture to porosity of river bed material using Structure-from-Motion with Multi-View-Stereo

Science.gov (United States)

Seitz, Lydia; Haas, Christian; Noack, Markus; Wieprecht, Silke

2018-04-01

Common methods for in-situ determination of porosity of river bed material are time- and effort-consuming. Although mathematical predictors can be used for estimation, they do not adequately represent porosities. The objective of this study was to assess a new approach for the determination of porosity of frozen sediment samples. The method is based on volume determination by applying Structure-from-Motion with Multi View Stereo (SfM-MVS) to estimate a 3D volumetric model based on overlapping imagery. The method was applied on artificial sediment mixtures as well as field samples. In addition, the commonly used water replacement method was applied to determine porosities in comparison with the SfM-MVS method. We examined a range of porosities from 0.16 to 0.46 that are representative of the wide range of porosities found in rivers. SfM-MVS performed well in determining volumes of the sediment samples. A very good correlation (r = 0.998, p < 0.0001) was observed between the SfM-MVS and the water replacement method. Results further show that the water replacement method underestimated total sample volumes. A comparison with several mathematical predictors showed that for non-uniform samples the calculated porosity based on the standard deviation performed better than porosities based on the median grain size. None of the predictors were effective at estimating the porosity of the field samples.

Comparison of NBG-18, NBG-17, IG-110 and IG-11 oxidation kinetics in air

Science.gov (United States)

Lee, Jo Jo; Ghosh, Tushar K.; Loyalka, Sudarshan K.

2018-03-01

The oxidation rates of several nuclear-grade graphites, NBG-18, NBG-17, IG-110 and IG-11, were measured in air using thermogravimetry. Kinetic parameters and oxidation behavior for each grade were compared by coke type, filler grain size and microstructure. The thickness of the oxidized layer for each grade was determined by layer peeling and direct density measurements. The results for NBG-17 and IG-11 were compared with those available in the literature and our recently reported results for NBG-18 and IG-110 oxidation in air. The finer-grained graphites IG-110 and IG-11 were more oxidized than medium-grained NBG-18 and NBG-17 because of deeper oxidant penetration, higher porosity and higher probability of available active sites. Variation in experimental conditions also had a marked effect on the reported kinetic parameters by several studies. Kinetic parameters such as activation energy and transition temperature were sensitive to air flow rates as well as sample size and geometry.

Stress history influence on sedimentary rock porosity estimates: Implications for geological CO2 storage in Northern Taiwan

Directory of Open Access Journals (Sweden)

Wen-Jie Wu

2017-01-01

Full Text Available We established a stress-history-dependent porosity model of potential target rocks for CO2 geosequestration based on rock sample porosity measurements under various effective stresses (5 - 120 MPa. The measured samples were collected from shallow boreholes (< 300 m depth drilled at the frontal fold in northern Taiwan. The lithology, density, and the stress-history-dependent porosity derived from shallow boreholes enabled us to predict the porosity-depth relationship of given rock formations at (burial depths of approximately 3170 - 3470 m potential sites for CO2 geosequestration located near the Taoyuan Tableland coastline. Our results indicate that the porosity of samples derived from laboratory tests under atmospheric pressure is significantly greater than the porosity measured under stress caused by sediment burial. It is therefore strongly recommended that CO2 storage capacity assessment not be estimated from the porosity measured under atmospheric pressure. Neglecting the stress history effect on the porosity of compacted and uplifted rocks may induce a percentage error of 7.7% at a depth of approximately 1000 m, where the thickness of the eroded, formerly overlying formation is 2.5 km in a synthetic case. The CO2 injection pressure effect on the porosity was also evaluated using the stress-history-dependent porosity model. As expected, the pore pressure buildup during CO2 injection will induce an increase in the rock porosity. For example, a large injection pressure of 13 MPa at a depth of approximately 1000 m will increase the rock porosity by a percentage error of 6.7%. Our results have implications for CO2 storage capacity injection pressure estimates.

Procedure for Uranium-Molybdenum Density Measurements and Porosity Determination

Energy Technology Data Exchange (ETDEWEB)

Prabhakaran, Ramprashad [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Devaraj, Arun [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Joshi, Vineet V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2016-08-13

The purpose of this document is to provide guidelines for preparing uranium-molybdenum (U-Mo) specimens, performing density measurements, and computing sample porosity. Typical specimens (solids) will be sheared to small rectangular foils, disks, or pieces of metal. A mass balance, solid density determination kit, and a liquid of known density will be used to determine the density of U-Mo specimens using the Archimedes principle. A standard test weight of known density would be used to verify proper operation of the system. By measuring the density of a U-Mo sample, it is possible to determine its porosity.

Analysis of Electrochemical Porosity of Phosphatized Coatings on Galvanized Steel Substrate

Directory of Open Access Journals (Sweden)

Ponte Haroldo de Araújo

2002-01-01

Full Text Available This work refers to the application of a Voltammetric Anodic Dissolution (VAD Technique in the analysis of coating discontinuities, focusing on pores and cracks that exposed the substrate. An evaluation was made of the influence of several parameters, such as the concentration of the passivation solution and sweep rate (SR, on the substrate passivation process and on the porosity indexes of tricationic phosphate coatings of Fe/Zn/Mn. The phosphatization process used was a commercial tricationic Fe/Zn/Mn phosphate bath applied on a galvanized steel (GS substrate. Once the best experimental conditions for the use of the VAD technique had been defined, the grain size and layer weight were related to porosity indexes. The porosity was found to show a tendency to decrease with increasing grain size. The VAD technique consists of the anodic polarization of the substrate/coating system and measurement of the charge density involved in the substrate passivation process. A quantitative porosity index was obtained by comparing the passivation charge density of the substrate without coating (standard passivation charge density and the passivation charge of the coated substrate.

Porosity in fiber laser formation of 5A06 aluminum alloy

Energy Technology Data Exchange (ETDEWEB)

Yu, Yang Chun; Wang, Chun Ming; Hu, Xi Yuan; Wang, Jun; Yu, Sheng Fu [HUST, Wuhan (China)

2010-05-15

The mechanism of porosity formation and its suppression methods in laser formation of aluminum alloy have been studied using a 4kW fiber laser to weld 5A06 aluminum alloy with SAl-Mg5 filler. It was found that the porosity formation is closely related to the stability of the keyhole and fluctuation of the molten pool in the laser welding aluminum alloy. The filling wire increased the instability of the keyhole and weld pool, thus further increasing the amount of gas cavities in the joint. Prefabrication of a suitable gap for the butt joint can provide a natural passage for the flow of the liquid metal, which can weaken, and even completely eliminate the disturbance of the filling wire on the formation of keyhole. The gap can also provide a passage for the escape of the bubble. Thus, this method can greatly decrease the sheet's susceptibility to porosity. Moreover, for a thin sheet, if the power of the laser is sufficient to form a keyhole with stable penetration through the weld sheet, a weld bead without porosity can also be obtained because closing the keyhole is almost impossible

Porosity in fiber laser formation of 5A06 aluminum alloy

International Nuclear Information System (INIS)

Yu, Yang Chun; Wang, Chun Ming; Hu, Xi Yuan; Wang, Jun; Yu, Sheng Fu

2010-01-01

The mechanism of porosity formation and its suppression methods in laser formation of aluminum alloy have been studied using a 4kW fiber laser to weld 5A06 aluminum alloy with SAl-Mg5 filler. It was found that the porosity formation is closely related to the stability of the keyhole and fluctuation of the molten pool in the laser welding aluminum alloy. The filling wire increased the instability of the keyhole and weld pool, thus further increasing the amount of gas cavities in the joint. Prefabrication of a suitable gap for the butt joint can provide a natural passage for the flow of the liquid metal, which can weaken, and even completely eliminate the disturbance of the filling wire on the formation of keyhole. The gap can also provide a passage for the escape of the bubble. Thus, this method can greatly decrease the sheet's susceptibility to porosity. Moreover, for a thin sheet, if the power of the laser is sufficient to form a keyhole with stable penetration through the weld sheet, a weld bead without porosity can also be obtained because closing the keyhole is almost impossible

Optimization and Development of Swellable Controlled Porosity ...

African Journals Online (AJOL)

Purpose: To develop swellable controlled porosity osmotic pump tablet of theophylline and to define the formulation and process variables responsible for drug release by applying statistical optimization technique. Methods: Formulations were prepared based on Taguchi Orthogonal Array design and Fraction Factorial ...

Influence of porosity on cavitation instability predictions for elastic-plastic solids

DEFF Research Database (Denmark)

Tvergaard, Viggo; Vadillo, G.

2007-01-01

, while the high stress levels are reached at some distance from the void, and the interaction of these stress and strain fields determines the porosity evolution. In some cases analysed, the porosity is present initially in the metal matrix, while in other cases voids nucleate gradually during...... the deformation process. It is found that interaction with the neighbouring voids reduces the critical stress for unstable cavity growth....

Study of the porosity of synthetic sandstones by nondestructive nuclear techniques

International Nuclear Information System (INIS)

Marques, Leonardo Carmezini

2008-01-01

In this paper, nuclear techniques have been used to describe structural characteristics of ceramic samples. These samples were produced to serve as simulates of sandstones and their mainly component was silica (SiO 2 ). Three sets of these samples with different characteristics were analyzed with the gamma ray transmission and the X-ray microtomography. They had the function to describe parameters as porosity point to point and total average porosity, for the transmission case, and 2D sections average porosity, total average porosity and size porous distribution for microtomography, as well as to investigate possible irregularities in bulk sample. The experimental set up for the gamma ray transmission technique consisted of: a 2 x 2 crystal NaI(Tl) detector, an 241 Am radioactive source (59.54 keV, 100 mCi), an automatic micrometric table for the sample XZ movement and standard gamma spectrometry electronics. Lead collimators with 2 mm diameter were placed on the source way out and on the detector entrance. The microtomographic measurements were done with a Skyscan system, model 1172, with a X-ray tube with 20-100 kV of voltage range and a CCD camera. Employing gamma ray transmission method was possible to obtain overall porosity values from 25.8 to 34.0 % and from 24.8 to 29.2 % for samples with parallelepiped and cylinder shape, respectively, for ceramic I set; from 58.5 to 61.0 % and from 57.1 to 61.7 % for the same geometric shape of ceramic II set. The samples analyzed by the microtomography achieved resolutions of 1.73 μm, 0.64 μm and 1.28 μm for samples of ceramic set I, II and III, respectively. This methodology provided average total porosity values from 26.6 to 29.4 %, from 48.4 to 51.0 % and from 28.2 to 30.6 % to I, II and III ceramic sets, respectively. The porous size profiles of each ceramic sample were also measured. (author)

Estimation of Fracture Porosity in an Unsaturated Fractured Welded Tuff Using Gas Tracer Testing

International Nuclear Information System (INIS)

B.M. Freifeild

2001-01-01

Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

Estimation of Fracture Porosity in an Unsaturated Fractured Welded Tuff Using Gas Tracer Testing

Energy Technology Data Exchange (ETDEWEB)

B.M. Freifeild

2001-10-18

Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

Estimation of fracture porosity in an unsaturated fractured welded tuff using gas tracer testing

Energy Technology Data Exchange (ETDEWEB)

Freifeld, Barry Mark [Univ. of California, Berkeley, CA (United States)

2001-12-01

Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

Integration of crosswell seismic data for simulating porosity in a heterogeneous carbonate aquifer

Science.gov (United States)

Emery, Xavier; Parra, Jorge

2013-11-01

A challenge for the geostatistical simulation of subsurface properties in mining, petroleum and groundwater applications is the integration of well logs and seismic measurements, which can provide information on geological heterogeneities at a wide range of scales. This paper presents a case study conducted at the Port Mayaca aquifer, located in western Martin County, Florida, in which it is of interest to simulate porosity, based on porosity logs at two wells and high-resolution crosswell seismic measurements of P-wave impedance. To this end, porosity and impedance are transformed into cross-correlated Gaussian random fields, using local transformations. The model parameters (transformation functions, mean values and correlation structure of the transformed fields) are inferred and checked against the data. Multiple realizations of porosity can then be constructed conditionally to the impedance information in the interwell region, which allow identifying one low-porosity structure and two to three flow units that connect the two wells, mapping heterogeneities within these units and visually assessing fluid paths in the aquifer. In particular, the results suggest that the paths in the lower flow units, formed by a network of heterogeneous conduits, are not as smooth as in the upper flow unit.

Characterization of the spatial distribution of porosity in the eogenetic karst Miami Limestone using ground penetrating radar

Science.gov (United States)

Mount, G. J.; Comas, X.; Wright, W. J.; McClellan, M. D.

2014-12-01

Hydrogeologic characterization of karst limestone aquifers is difficult due to the variability in the spatial distribution of porosity and dissolution features. Typical methods for aquifer investigation, such as drilling and pump testing, are limited by the scale or spatial extent of the measurement. Hydrogeophysical techniques such as ground penetrating radar (GPR) can provide indirect measurements of aquifer properties and be expanded spatially beyond typical point measures. This investigation used a multiscale approach to identify and quantify porosity distribution in the Miami Limestone, the lithostratigraphic unit that composes the uppermost portions of the Biscayne Aquifer in Miami Dade County, Florida. At the meter scale, laboratory measures of porosity and dielectric permittivity were made on blocks of Miami Limestone using zero offset GPR, laboratory and digital image techniques. Results show good correspondence between GPR and analytical porosity estimates and show variability between 22 and 66 %. GPR measurements at the field scale 10-1000 m investigated the bulk porosity of the limestone based on the assumption that a directly measured water table would remain at a consistent depth in the GPR reflection record. Porosity variability determined from the changes in the depth to water table resulted in porosity values that ranged from 33 to 61 %, with the greatest porosity variability being attributed to the presence of dissolution features. At the larger field scales, 100 - 1000 m, fitting of hyperbolic diffractions in GPR common offsets determined the vertical and horizontal variability of porosity in the saturated subsurface. Results indicate that porosity can vary between 23 and 41 %, and delineate potential areas of enhanced recharge or groundwater / surface water interactions. This study shows porosity variability in the Miami Limestone can range from 22 to 66 % within 1.5 m distances, with areas of high macroporosity or karst dissolution features

Oxygen plasma treatment of HKUST-1 for porosity retention upon exposure to moisture.

Science.gov (United States)

Bae, Jaeyeon; Jung, Jin-Woo; Park, Hyo Yul; Cho, Chang-Hee; Park, Jinhee

2017-11-07

Despite their remarkable properties, metal-organic frameworks (MOFs) present vulnerable structures that are sensitive to moisture; therefore, their application to real field situations is challenging. Herein, an O 2 plasma technique was introduced as a new method for the activation and protection of porosity in HKUST-1. In an unprecedented manner, O 2 plasma-treated HKUST-1 retains its porosity after a long exposure to moisture as compared to pristine HKUST-1. Porosity retention was examined by N 2 adsorption/desorption measurements of non-activated HKUST-1 after exposure to moisture.

Diffusion-Coefficients of Sulfate and Methane in Marine-Sediments - Influence of Porosity

DEFF Research Database (Denmark)

IVERSEN, N.; JØRGENSEN, BB

1993-01-01

diffusion coefficients can be related to the diffusion coefficient in free solution by D(s) = D(o)/theta2, where theta is the tortuosity of the sediment. The sediment tortuosity calculated from this equation showed a linear relationship with sediment porosity (phi) over the porosity range of 0.4-0.9. From...

Spark plasma sintering and porosity studies of uranium nitride

Energy Technology Data Exchange (ETDEWEB)

Johnson, Kyle D., E-mail: kylej@kth.se; Wallenius, Janne; Jolkkonen, Mikael; Claisse, Antoine

2016-05-15

In this study, a number of samples of UN sintered by the SPS method have been fabricated, and highly pure samples ranging in density from 68% to 99.8%TD – corresponding to an absolute density of 14.25 g/cm{sup 3} out of a theoretical density of 14.28 g/cm{sup 3} – have been fabricated. By careful adjustment of the sintering parameters of temperature and applied pressure, the production of pellets of specific porosity may now be achieved between these ranges. The pore closure behaviour of the material has also been documented and compared to previous studies of similar materials, which demonstrates that full pore closure using these methods occurs near 97.5% of relative density. - Highlights: • UN pellets are fabricated over a wide array of densities using the SPS method. • The sintereing parameters necessary to produce pellets over a wide array of density space are charted. • Pellets of extremely high density (99.9% of TD, absolute density of 14.25 g/cm{sup 3}) are fabricated. • Full-closure of the porosity in this material is obtained at around 2.5% of total porosity.

Computer Based Porosity Design by Multi Phase Topology Optimization

Science.gov (United States)

Burblies, Andreas; Busse, Matthias

2008-02-01

A numerical simulation technique called Multi Phase Topology Optimization (MPTO) based on finite element method has been developed and refined by Fraunhofer IFAM during the last five years. MPTO is able to determine the optimum distribution of two or more different materials in components under thermal and mechanical loads. The objective of optimization is to minimize the component's elastic energy. Conventional topology optimization methods which simulate adaptive bone mineralization have got the disadvantage that there is a continuous change of mass by growth processes. MPTO keeps all initial material concentrations and uses methods adapted from molecular dynamics to find energy minimum. Applying MPTO to mechanically loaded components with a high number of different material densities, the optimization results show graded and sometimes anisotropic porosity distributions which are very similar to natural bone structures. Now it is possible to design the macro- and microstructure of a mechanical component in one step. Computer based porosity design structures can be manufactured by new Rapid Prototyping technologies. Fraunhofer IFAM has applied successfully 3D-Printing and Selective Laser Sintering methods in order to produce very stiff light weight components with graded porosities calculated by MPTO.

Kinetic Monte Carlo simulations of water ice porosity: extrapolations of deposition parameters from the laboratory to interstellar space

Science.gov (United States)

Clements, Aspen R.; Berk, Brandon; Cooke, Ilsa R.; Garrod, Robin T.

2018-02-01

Using an off-lattice kinetic Monte Carlo model we reproduce experimental laboratory trends in the density of amorphous solid water (ASW) for varied deposition angle, rate and surface temperature. Extrapolation of the model to conditions appropriate to protoplanetary disks and interstellar dark clouds indicate that these ices may be less porous than laboratory ices.

Low porosity portland cement pastes based on furan polymers

International Nuclear Information System (INIS)

Darweesh, H.H.M.

2005-01-01

The effect of three different types of Furan polymers on the porosity, mechanical properties, mechanism of hydration and microstructure of Ordinary Portland cement (OPC) pastes was investigated. The results showed that mixing the OPC with Furan polymers, the standard water of consistency of the different cement pastes decreases and therefore the setting times (initial and final) are shortened. The total porosity of the hardened cement pastes decreased, while the mechanical properties improved and enhanced at all curing ages of hydration compared with those of the pure OPC pastes. The hydration process with Furan polymers proceeded according to the following decreasing order: F.ac. > F.ph. > F.alc. > OPC

Relationship between soil aggregate strength, shape and porosity for soils under different long-term management

DEFF Research Database (Denmark)

Munkholm, Lars Juhl; Heck, Richard J; Deen, Bill

2016-01-01

were mouldboard ploughing (MP) and no-tillage (NT). The soil coreswere exposed to a drop shatter test and airdried before separation into different size fractions. Ten aggregates fromthe 4–9.2mmsize fraction per core sample (i.e. 320 in all)were X-ray micro-CT scanned. The size, shape and porosity...... porosity and more rounded aggregates than the continuous corn rotation. Surprisingly, therewas no treatment effect on X-ray micro-CT resolvable porosities. Aggregate strength decreased with both total and X-ray micro-CT resolvable porosity even though the correlations were weak. Significant correlation...

A review on controlled porosity osmotic pump tablets and its evaluation

Directory of Open Access Journals (Sweden)

Chinmaya Keshari Sahoo

2015-12-01

Full Text Available Conventional drug delivery system provides an immediate release of drug which does not control the release of the drug and does not maintain effective concentration at target site for a longer period of time. Hence to avoid the shortcomings there is development of various controlled drug delivery systems. Among these osmotic drug delivery system (ODDS utilizes the principle of osmotic pressure and delivers drug dose in an optimized manner to maintain drug concentration within the therapeutic window and minimizes toxic effects. ODDS releases drug at a controlled rate that is independent of the pH and thermodynamics of dissolution medium. The release of drug from ODDS follows zero order kinetics. The release of drug from osmotic system depends upon various formulation factors such as solubility, osmotic pressure of the core components, size of the delivery orifice and nature of the rate controlling membrane. Controlled porosity osmotic pump (CPOP contains drug, osmogens, excipients in core and a coating of semipermeable membrane with water soluble additives. In CPOP water soluble additives dissolve after coming in contact with water, resulting in an in situ formation of a microporous membrane. The present study gives an idea about osmosis, CPOP, components of CPOP and its evaluation.

Porosity formation in Al-Si casting alloys: role of Sr oxide

International Nuclear Information System (INIS)

Liu, L.; Samuel, A.M.; Samuel, F.H.; Doty, H.W.; Valtierra, S.

2002-01-01

The strength and quality of an Al-Si alloy casting are determined by its microstructure and the amount of porosity present in the casting. Modification is one of the processes used to improve the microstructural quality, where the addition of a modifying agent alters the shape of the eutectic Si from an acicular to a fibrous form that is extremely beneficial to the mechanical properties. Among various modifiers, strontium, although easy to handle and resistant to fading, also causes porosity formation in these alloys, attributed variously to an increase in the hydrogen level of the melt, feedability problems in the mushy zone, changes in the mode of eutectic nucleation, etc. The present study shows how the presence of oxides is responsible for the porosity formation, and that the difference in porosity characteristics with the addition of Sr depends on the amount of Sr oxides present the solidified structure. Both Sr and Al oxides are favourable sites for the nucleation of other microconstituents. A number of experimental (binary Al-Si) and industrial (319 and 356) alloys have been studied, to cover various alloy freezing ranges. Thermal analysis, optical microscopy, SEM/EDX and EPMA analyses were employed to obtain the results. (author)

A comparison of estimated and calculated effective porosity

Science.gov (United States)

Stephens, Daniel B.; Hsu, Kuo-Chin; Prieksat, Mark A.; Ankeny, Mark D.; Blandford, Neil; Roth, Tracy L.; Kelsey, James A.; Whitworth, Julia R.

Effective porosity in solute-transport analyses is usually estimated rather than calculated from tracer tests in the field or laboratory. Calculated values of effective porosity in the laboratory on three different textured samples were compared to estimates derived from particle-size distributions and soil-water characteristic curves. The agreement was poor and it seems that no clear relationships exist between effective porosity calculated from laboratory tracer tests and effective porosity estimated from particle-size distributions and soil-water characteristic curves. A field tracer test in a sand-and-gravel aquifer produced a calculated effective porosity of approximately 0.17. By comparison, estimates of effective porosity from textural data, moisture retention, and published values were approximately 50-90% greater than the field calibrated value. Thus, estimation of effective porosity for chemical transport is highly dependent on the chosen transport model and is best obtained by laboratory or field tracer tests. Résumé La porosité effective dans les analyses de transport de soluté est habituellement estimée, plutôt que calculée à partir d'expériences de traçage sur le terrain ou au laboratoire. Les valeurs calculées de la porosité effective au laboratoire sur trois échantillons de textures différentes ont été comparées aux estimations provenant de distributions de taille de particules et de courbes caractéristiques sol-eau. La concordance était plutôt faible et il semble qu'il n'existe aucune relation claire entre la porosité effective calculée à partir des expériences de traçage au laboratoire et la porosité effective estimée à partir des distributions de taille de particules et de courbes caractéristiques sol-eau. Une expérience de traçage de terrain dans un aquifère de sables et de graviers a fourni une porosité effective calculée d'environ 0,17. En comparaison, les estimations de porosité effective de données de

Porosity of spacer-filled channels in spiral-wound membrane systems: Quantification methods and impact on hydraulic characterization

KAUST Repository

Siddiqui, Amber

2017-04-13

The porosity of spacer-filled feed channels influences the hydrodynamics of spiral-wound membrane systems and impacts the overall performance of the system. Therefore, an exact measurement and a detailed understanding of the impact of the feed channel porosity is required to understand and improve the hydrodynamics of spiral-wound membrane systems applied for desalination and wastewater reuse. The objectives of this study were to assess the accuracy of porosity measurement techniques for feed spacers differing in geometry and thickness and the consequences of using an inaccurate method on hydrodynamic predictions, which may affect permeate production. Six techniques were applied to measure the porosity namely, three volumetric calculations based on spacer strand count together with cuboidal (SC), cylindrical (VCC) and ellipsoidal volume calculation (VCE) and three independent techniques based on volume displacement (VD), weight and density (WD) and computed tomography scanning (CT). The CT method was introduced as an alternative for the other five already existing and applied methods in practice.Six feed spacers used for the porosity measurement differed in filament thickness, angle between the filaments and mesh-size. The results of the studies showed differences between the porosities, measured by the six methods. The results of the microscopic techniques SC, VCC and VCE deviated significantly from measurements by VD, WD and CT, which showed similar porosity values for all spacer types.Depending on the maximum deviation of the porosity measurement techniques from –6% to +6%, (i) the linear velocity deviations were −5.6% and +6.4% respectively and (ii) the pressure drop deviations were –31% and +43% respectively, illustrating the importance of an accurate porosity measurement. Because of the accuracy and standard deviation, the VD and WD method should be applied for the porosity determination of spacer-filled channels, while the CT method is recommended for

The porosity formation mechanism in the laser-MIG hybrid welded joint of Invar alloy

Science.gov (United States)

Zhan, Xiaohong; Gao, Qiyu; Gu, Cheng; Sun, Weihua; Chen, Jicheng; Wei, Yanhong

2017-10-01

The porosity formation mechanism in the laser-metal inter gas (MIG) multi-layer hybrid welded (HW) joint of 19.05 mm thick Invar alloy is investigated. The microstructure characteristics and energy dispersive spectroscopy (EDS) are analyzed. The phase identification was conducted by the X-ray diffractometer (XRD). Experimental results show that the generation of porosity is caused by the relatively low laser power in the root pass and low current in the cover pass. It is also indicated that the microstructures of the welded joints are mainly observed to be columnar crystal and equiaxial crystal, which are closely related to the porosity formation. The EDS results show that oxygen content is significantly high in the inner wall of the porosity. The XRD results indicate that the BM and the WB of laser-MIG HW all are composed of Fe0.64Ni0.36 and γ-(Fe,Ni). When the weld pool is cooled quickly, [NiO] [FeO] and [MnO] are formed that react on C to generate CO/CO2 gases. The porosity of laser-MIG HW for Invar alloy is oxygen pore. The root source of metallurgy porosity formation is that the dissolved gases are hard to escape sufficiently and thus exist in the weld pool. Furthermore, 99.99% pure Argon is recommended as protective gas in the laser-MIG HW of Invar alloy.

Porosity of Lead Agglomerate as Function of CaO and SiO2 Proportion

OpenAIRE

, A. Haxhiaj; , A. Terziqi; , E. Haxhiaj

2016-01-01

Agglomerate porosity is correlated with strength of its pieces and it is main parameter for reductive melting process in Water-jacket furnace. Treatment is oriented toward achieving porosity and optimal strength. The paper deals with the process in te-mperature about 9000C and with less than 10% composition CaO in rapport with lead. In order to achieve optimal results of agglomerate porosity and quality, it is necessary during the roasting process of lead concentration to correlate the conten...

Quality-assured evaluation of effective porosity using fit-for-purpose estimates of clay-mineral volume fraction

Science.gov (United States)

Worthington, Paul F.

2010-05-01

Reservoirs that contain dispersed clay minerals traditionally have been evaluated petrophysically using either the effective or the total porosity system. The major weakness of the former is its reliance on "shale" volume fraction ( Vsh) as a clay-mineral indicator in the determination of effective porosity from well logs. Downhole clay-mineral indicators have usually delivered overestimates of fractional clay-mineral volume ( Vcm) because they use as a reference nearby shale beds that are often assumed to comprise clay minerals exclusively, whereas those beds also include quartzitic silts and other detritus. For this reason, effective porosity is often underestimated significantly, and this shortfall transmits to computed hydrocarbons in place and thence to estimates of ultimate recovery. The problem is overcome here by using, as proxy groundtruths, core porosities that have been upscaled to match the spatial resolutions of porosity logs. Matrix and fluid properties are established over clean intervals in the usual way. Log-derived values of Vsh are tuned so that, on average, the resulting log-derived porosities match the corresponding core porosities over an evaluation interval. In this way, Vsh is rendered fit for purpose as an indicator of clay-mineral content Vcm for purposes of evaluating effective porosity. The method is conditioned to deliver a value of effective porosity that shows overall agreement with core porosity to within the limits of uncertainty of the laboratory measurements. This is achieved through function-, reservoir- and tool-specific Vsh reduction factors that can be applied to downhole estimates of clay-mineral content over uncored intervals of similar reservoir character. As expected, the reduction factors can also vary for different measurement conditions. The reduction factors lie in the range of 0.29-0.80, which means that in its raw form, log-derived Vsh can overestimate the clay-mineral content by more than a factor of three. This

Determination of Meteorite Porosity Using Liquid Nitrogen

Science.gov (United States)

Kohout, T.; Kletetschka, G.; Pesonen, L. J.; Wasilewski, P. J.

2005-01-01

We introduce a new harmless method for porosity measurement suitable for meteorite samples. The method is a modification of the traditional Archimedean method based on immersion of the samples in a liquid medium like water or organic liquids. In our case we used liquid nitrogen for its chemically inert characteristics.

Translating Comprehensive Conservative Care for Chronic Knee Pain Into a Digital Care Pathway: 12-Week and 6-Month Outcomes for the Hinge Health Program

Science.gov (United States)

Erhart-Hledik, Jennifer C; Kinsella, Rose; Hunter, Simon; Mecklenburg, Gabriel; Perez, Daniel

2017-01-01

Background Chronic knee pain (CKP) affects a large number of adults, many of whom do not receive best-practice care and are at high risk for unnecessary surgery. Objective The aim of this study was to investigate the effect of the Hinge Health 12-week digital care program (DCP) for CKP on knee pain and function, with secondary outcomes of surgery interest and satisfaction, at 12 weeks and 6 months after starting the program. Methods Individuals with CKP were recruited onto the 12-week program, comprising sensor-guided physical exercises, weekly education, activity tracking, and psychosocial support such as personal coaching and cognitive behavioral therapy (CBT). We used a single-arm design with assessment of outcomes at baseline, 12 weeks, and 6 months after starting the program. We used a linear mixed effects model with Tukey contrasts to compare timepoints and report intention-to-treat statistics with last observation carried forward. Results The cohort consisted of 41 individuals (32 female, mean age 52 years, SD 9 years). Between baseline and week 12, participants reported clinically significant improvements in the Knee Injury and Osteoarthritis Outcome Score (KOOS) pain and Knee Injury and Osteoarthritis Outcome Score-Physical Function Short Form (KOOS-PS) function scales of 16 points (95% CI 12-21, P<.001) and 10 points (95% CI 6-14, P<.001), respectively. Significant reductions of 57% (mean difference 30, 95% CI 21-38, P<.001) and 51% (mean difference 25, 95% CI 16-33, P<.001) in visual analog scale (VAS) knee pain and stiffness, respectively, were observed at 12 weeks, as well as a 67% reduction in surgery interest (mean reduction 2.3 out of 10, 95% CI 1.5-3.1, P<.001). Average satisfaction at week 12 was 9.2 out of 10. Critically, all improvements were maintained at 6 months at similar or greater magnitude. Conclusions Participants on the Hinge Health DCP for CKP showed substantial clinical improvements that were maintained 6 months after enrolling in the

Optical probe for porosity defect detection on inner diameter surfaces of machined bores

Science.gov (United States)

Kulkarni, Ojas P.; Islam, Mohammed N.; Terry, Fred L.

2010-12-01

We demonstrate an optical probe for detection of porosity inside spool bores of a transmission valve body with diameters down to 5 mm. The probe consists of a graded-index relay rod that focuses a laser beam spot onto the inner surface of the bore. Detectors, placed in the specular and grazing directions with respect to the incident beam, measure the change in scattered intensity when a surface defect is encountered. Based on the scattering signatures in the two directions, the system can also validate the depth of the defect and distinguish porosity from bump-type defects coming out of the metal surface. The system can detect porosity down to a 50-μm lateral dimension and ~40 μm in depth with >3-dB contrast over the background intensity fluctuations. Porosity detection systems currently use manual inspection techniques on the plant floor, and the demonstrated probe provides a noncontact technique that can help automotive manufacturers meet high-quality standards during production.

The effect of limestone aggregate porosity and saturation degree on the interfacial zone

International Nuclear Information System (INIS)

Nguyen, T.D.; Le Saout, G.; Devillers, P.; Garcia-Diaz, E.

2015-01-01

The recycling of concrete wastes concerns the nuclear industry as many nuclear facilities will have to be dismantled and the reduction and reuse of the decommissioning concrete wastes in order to minimize the total waste volume is a key issue. The recycled aggregates have the potential to replace natural resources however it is necessary to assess the effect of recycled aggregates on the final concrete. One important issue to be addressed to achieve the required mechanical properties is the water absorption of the recycled aggregates. As a first step, we have used in this study limestone aggregates with different porosities (total porosity from 2 to 20 %) and have investigated the influence of the porosity and the initial saturation degree of these aggregates on the porosity of the interfacial transition zone (ITZ) using scanning electron microscope. The equation of Feret for the strength-porosity relationship of our mortars was applied σ = K(100-p) 2 where σ is the compressive strength in MPa, p is the capillary pore volume in % and K a constant. Aggregates with lower porosity follow the same law characterized by a K value higher than the value for the more porous aggregate law. The K parameter is not dependent of the humidity degree of the aggregate: for a given aggregate, family mortars made with dry and wet aggregate follow the same law. But for porous aggregates as the meso-porosity of the ITZ for a given time of hydration is higher for mortars made with wet aggregates, the compressive strength of these mortars is less than those of mortars made with dry aggregates. Contrary to the low porous aggregate, it was not possible for porous limestone aggregates, and with a calculation based on the saturated surface dry state as reference state to obtain the same net water to cement ratio with wet and dry aggregates. This study reflects the difficulty to control the amount of efficient water in concrete when using porous aggregates and its influence on compressive

Correlation of Water Frost Porosity in Laminar Flow over Flat Surfaces

Science.gov (United States)

Kandula, Max

2011-01-01

A dimensionless correlation has been proposed for water frost porosity expressing its dependence on frost surface temperature and Reynolds number for laminar forced flow over a flat surface. The correlation is presented in terms of a dimensionless frost surface temperature scaled with the cold plate temperature, and the freezing temperature. The flow Reynolds number is scaled with reference to the critical Reynolds number for laminar-turbulent transition. The proposed correlation agrees satisfactorily with the simultaneous measurements of frost density and frost surface temperature covering a range of plate temperature, ambient air velocity, humidity, and temperature. It is revealed that the frost porosity depends primarily on the frost surface and the plate temperatures and the flow Reynolds number, and is only weakly dependent on the relative humidity. The results also point out the general character of frost porosity displaying a decrease with an increase in flow Reynolds number.

Kinetic modeling of liquefied petroleum gas (LPG) reduction of titania in MATLAB

Science.gov (United States)

Yin, Tan Wei; Ramakrishnan, Sivakumar; Rezan, Sheikh Abdul; Noor, Ahmad Fauzi Mohd; Izah Shoparwe, Noor; Alizadeh, Reza; Roohi, Parham

2017-04-01

In the present study, reduction of Titania (TiO2) by liquefied petroleum gas (LPG)-hydrogen-argon gas mixture was investigated by experimental and kinetic modelling in MATLAB. The reduction experiments were carried out in the temperature range of 1100-1200°C with a reduction time from 1-3 hours and 10-20 minutes of LPG flowing time. A shrinking core model (SCM) was employed for the kinetic modelling in order to determine the rate and extent of reduction. The highest experimental extent of reduction of 38% occurred at a temperature of 1200°C with 3 hours reduction time and 20 minutes of LPG flowing time. The SCM gave a predicted extent of reduction of 82.1% due to assumptions made in the model. The deviation between SCM and experimental data was attributed to porosity, thermodynamic properties and minute thermal fluctuations within the sample. In general, the reduction rates increased with increasing reduction temperature and LPG flowing time.

Porosity Defect Remodeling and Tensile Analysis of Cast Steel

Directory of Open Access Journals (Sweden)

Linfeng Sun

2016-02-01

Full Text Available Tensile properties on ASTM A216 WCB cast steel with centerline porosity defect were studied with radiographic mapping and finite element remodeling technique. Non-linear elastic and plastic behaviors dependent on porosity were mathematically described by relevant equation sets. According to the ASTM E8 tensile test standard, matrix and defect specimens were machined into two categories by two types of height. After applying radiographic inspection, defect morphologies were mapped to the mid-sections of the finite element models and the porosity fraction fields had been generated with interpolation method. ABAQUS input parameters were confirmed by trial simulations to the matrix specimen and comparison with experimental outcomes. Fine agreements of the result curves between simulations and experiments could be observed, and predicted positions of the tensile fracture were found to be in accordance with the tests. Chord modulus was used to obtain the equivalent elastic stiffness because of the non-linear features. The results showed that elongation was the most influenced term to the defect cast steel, compared with elastic stiffness and yield stress. Additional visual explanations on the tensile fracture caused by void propagation were also given by the result contours at different mechanical stages, including distributions of Mises stress and plastic strain.

Report on Evaluation, Verification, and Assessment of Porosity Migration Model in Fast Reactor MOX Fuel

Energy Technology Data Exchange (ETDEWEB)

Novascone, Stephen Rhead [Idaho National Lab. (INL), Idaho Falls, ID (United States); Peterson, John William [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-09-01

Abstract This report documents the progress of simulating pore migration in ceramic (UO₂ and mixed oxide or MOX) fuel using BISON. The porosity field is treated as a function of space and time whose evolution is governed by a custom convection-diffusion-reaction equation (described here) which is coupled to the heat transfer equation via the temperature field. The porosity is initialized to a constant value at every point in the domain, and as the temperature (and its gradient) are increased by application of a heat source, the pores move up the thermal gradient and accumulate at the center of the fuel in a time-frame that is consistent with observations from experiments. There is an inverse dependence of the fuel’s thermal conductivity on porosity (increasing porosity decreases thermal conductivity, and vice-versa) which is also accounted for, allowing the porosity equation to couple back into the heat transfer equation. Results from an example simulation are shown to demonstrate the new capability.

Nano-suspension coating as a technique to modulate the drug release from controlled porosity osmotic pumps for a soluble agent.

Science.gov (United States)

Bahari, Leila Azharshekoufeh; Javadzadeh, Yousef; Jalali, Mohammad Barzegar; Johari, Peyvand; Nokhodchi, Ali; Shokri, Javad

2017-05-01

In controlled porosity osmotic pumps (CPOP), usually finding a single solvent with a capability to dissolve both film former (hydrophobic) and pore former (hydrophilic) is extremely challenging. Therefore, the aim of the present investigation was to tackle the issue associated with controlled porosity osmotic pump (CPOP) system using nano-suspension coating method. In the present study 4-Amino pyridine was used as a highly water soluble drug. In this method, a hydrophilic pore former (sucrose or mannitol) in nano range was suspended in polymeric coating solution using ball-mill. The performance of the prepared formulations was assessed in terms of D 12h (cumulative release percent after 12h), Dev zero (mean percent deviation of drug release from zero order kinetic), t L (lag time of the drug release) and RSQ zero . The results revealed that gelling agent amount (HPMC E 15LV ) in core and pore former concentration in SPM had crucial effect on SPM integrity. All the optimised formulations showed a burst drug release due to fast dissolving nature of the pore formers. Results obtained from scanning electron microscopy demonstrated the formation of nanopores in the membrane where the drug release takes place via these nanopores. Nano suspension coating method can be introduced as novel method in formulation of CPOPs. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrical resistivity and porosity structure of the upper Biscayne Aquifer in Miami-Dade County, Florida

Science.gov (United States)

Whitman, Dean; Yeboah-Forson, Albert

2015-12-01

Square array electrical soundings were made at 13 sites in the Biscayne Aquifer distributed between 1 and 20 km from the shoreline. These soundings were modeled to investigate how resistivity varies spatially and with depth in the upper 15 m of the aquifer. Porosity was estimated from the modeled formation resistivity and observed pore fluid resistivity with Archie's Law. The models were used to interpolate resistivity and porosity surfaces at -2, -5, -8, and -15 m elevations. Modeled resistivity in the unsaturated zone is generally higher than 300 Ω m with the resistivity at sites with thick unsaturated zones greater than 1000 Ω m. Resistivity in the saturated zone ranges from 30 to 320 Ω m. At many sites in the western portions of the study area, resistivity is constant or increases with depth whereas sites in the center of the Atlantic Coastal Ridge exhibit a distinct low resistivity zone (ρ aquifer. The estimated porosity ranges between 14% and 71% with modal values near 25%. The porosity structure varies both with depth and spatially. Western sites exhibit a high porosity zone at shallow depths best expressed in a NE-SW trending zone of 40-50% porosity situated near the western margin of the Atlantic Coastal Ridge. This zone roughly corresponds in depth with the Q5 chronostratigraphic unit of the Miami Fm. which constitutes the upper flow unit of the Biscayne Aquifer. The highest porosity (>50%) is seen at elevations below -5 m at sites in the center of the Atlantic Coastal Ridge and likely corresponds to solution features. The general NE-SW trend of the resistivity and porosity structure suggests a causal connection with the Pleistocene paleogeography and sedimentary environments.

Theoretical models for the muon spectrum at sea level

International Nuclear Information System (INIS)

Abdel-Monem, M.S.; Benbrook, J.R.; Osborne, A.R.; Sheldon, W.R.

1975-01-01

The absolute vertical cosmic ray muon spectrum is investigated theoretically. Models of high energy interactions (namely, Maeda-Cantrell (MC), Constant Energy (CE), Cocconi-Koester-Perkins (CKP) and Scaling Models) are used to calculate the spectrum of cosmic ray muons at sea level. A comparison is made between the measured spectrum and that predicted from each of the four theoretical models. It is concluded that the recently available measured muon differential intensities agree with the scaling model for energies less than 100 GeV and with the CKP model for energies greater than 200 GeV. The measured differential intensities (Abdel-Monem et al.) agree with scaling. (orig.) [de

Porosity determination from 2-D resistivity method in studying the slope failures

Science.gov (United States)

Maslinda, Umi; Nordiana, M. M.; Bery, A. A.

2017-07-01

Slope failures have become the main focus for infrastructures development on hilly areas in Malaysia especially the development of tourism and residential. Lack of understanding and information of the subsoil conditions and geotechnical issues are the main cause of the slope failures. The failures happened are due to a combination of few factors such as topography, climate, geology and land use. 2-D resistivity method was conducted at the collapsed area in Selangor. The 2-D resistivity was done to study the instability of the area. The collapsed occurred because of the subsurface materials was unstable. Pole-dipole array was used with 5 m minimum electrode spacing for the 2-D resistivity method. The data was processed using Res2Dinv software and the porosity was calculated using Archie's law equation. The results show that the saturated zone (1-100 Ωm), alluvium or highly weathered rock (100-1000 Ωm), boulders (1600-7000 Ωm) and granitic bedrock (>7000 Ωm). Generally, the slope failures or landslides occur during the wet season or after rainfall. It is because of the water infiltrate to the slope and cause the saturation of the slope which can lead to landslides. Then, the porosity of saturated zone is usually high because of the water content. The area of alluvium or highly weathered rock and saturated zone have high porosity (>20%) and the high porosity also dominated at almost all the collapsed area which means that the materials with porosity >20% is potential to be saturated, unstable and might trigger slope failures.

Towards the inclusion of open fabrication porosity in a fission gas release model

Energy Technology Data Exchange (ETDEWEB)

Claisse, Antoine, E-mail: claisse@kth.se [KTH Royal Institute of Technology, Reactor Physics, AlbaNova University Centre, 106 91, Stockholm (Sweden); Van Uffelen, Paul [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125, Karlsruhe (Germany)

2015-11-15

A model is proposed for fission product release in oxide fuels that takes into account the open porosity in a mechanistic manner. Its mathematical framework, assumptions and limitations are presented. It is based on the model for open porosity in the sintering process of crystalline solids. More precisely, a grain is represented by a tetrakaidecahedron and the open porosity is represented by a continuous cylinder along the grain edges. It has been integrated in the TRANSURANUS fuel performance code and applied to the first case of the first FUMEX project as well as to neptunium and americium containing pins irradiated during the SUPERFACT experiment and in the JOYO reactor. The results for LWR and FBR fuels are consistent with the experimental data and the predictions of previous empirical models when the thermal mechanisms are the main drivers of the release, even without using a fitting parameter. They also show a different but somewhat expected behaviour when very high porosity fuels are irradiated at a very low burn-up and at low temperature. - Highlights: • We developed a new athermal FGR model based on the porosity. • We present the model, its framework, assumptions and limitations. • We test it out on several irradiation experiments. • Results are comparable to previous models but without using an empirical parameter.

Study of capillary absorption kinetics by X-ray CT imaging techniques: a survey on sedimentary rocks of Sicily

Directory of Open Access Journals (Sweden)

Tiziano Schillaci

2008-04-01

Full Text Available Sedimentary rocks are natural porous materials with a great percent of microscopic interconnected pores: they contain fluids, permitting their movement on macroscopic scale. Generally, these rocks present porosity higher then metamorphic rocks. Under certain points of view, this feature represents an advantage; on the other hand, this can constitute an obstacle for cultural heritage applications, because the porosity grade can lead to a deterioration of the lapideous monument for water capillary absorption. In this paper, CT (Computerized Tomography image techniques are applied to capillary absorption kinetics in sedimentary rocks utilized for the Greek temples as well as baroc monuments, respectively located in western and southeastern Sicily. Rocks were sampled near the archaeological areas of Agrigento, Segesta, Selinunte and Val di Noto. CT images were acquired at different times, before and after the water contact, using image elaboration techniques during the acquisition as well as the post-processing phases. Water distribution into porous spaces has been evaluated on the basis of the Hounsfield number, estimated for the 3-D voxel structure of samples. For most of the considered samples, assumptions based on Handy model permit to correlate the average height of the wetting front to the square root of time. Stochastic equations were introduced in order to describe the percolative water behavior in heterogeneous samples, as the Agrigento one. Before the CT acquisition, an estimate of the capillary absorption kinetics has been carried out by the gravimetric method. A petrographical characterization of samples has been performed by stereomicroscope observations, while porosity and morphology of porous have been surveyed by SEM (Scanning Electron Microscope images. Furthermore, the proposed methods have also permitted to define penetration depth as well as distribution uniformity of materials used for restoration and conservation of historical

Investigation on Porosity and Microhardness of 316L Stainless Steel Fabricated by Selective Laser Melting

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Shahir Mohd Yusuf

2017-02-01

Full Text Available This study investigates the porosity and microhardness of 316L stainless steel samples fabricated by selective laser melting (SLM. The porosity content was measured using the Archimedes method and the advanced X-ray computed tomography (XCT scan. High densification level (≥99% with a low average porosity content (~0.82% were obtained from the Archimedes method. The highest porosity content in the XCT-scanned sample was ~0.61. However, the pores in the SLM samples for both cases (optical microscopy and XCT were not uniformly distributed. The higher average microhardness values in the SLM samples compared to the wrought manufactured counterpart are attributed to the fine microstructures from the localised melting and rapid solidification rate of the SLM process.

Feeding and Distribution of Porosity in Cast Al-Si Alloys as Function of Alloy Composition and Modification

DEFF Research Database (Denmark)

Tiedje, Niels Skat; Taylor, John A.; Easton, Mark A.

2012-01-01

Unmodified, Na-modified, and Sr-modified castings of Al-7 pct Si and Al-12.5 pct Si alloys were cast in molds in which it was possible to create different cooling conditions. It is shown how solidification influences the distribution of porosity at the surface and the center of the castings...... of the casting, while Sr-modified castings solidify in a mushy manner that creates a more homogeneous distribution of porosity in the casting. The amount of porosity was highest in the Sr-modified alloys, lower in the Na-modified alloys, and lowest in the unmodified alloys. The size of the porosity-free layer...... as a function of modification and Si content in sand- and chill-cast samples. Eutectic modification, Si content, and cooling conditions have a great impact on the distribution of porosity. Unmodified and Na-modified castings are more easily fed with porosity tending to congregate near the centerline...

Soil plasticity with a different porosity

Directory of Open Access Journals (Sweden)

Klovanych Sergii

2017-01-01

Full Text Available The model of soils with different porosity in the framework of the associated theory of plasticity is presented The single analytical function describes the loading surface in the stress space. The deformational hardening/softening and the phenomenon of dilatancy during plastic flow are incorporated in the model. The triaxial compression tests are simulated and compared with the experimental results for different values of the void ratio and initial hydrostatic stresses.

Mapping porosity of the deep critical zone in 3D using near-surface geophysics, rock physics modeling, and drilling

Science.gov (United States)

Flinchum, B. A.; Holbrook, W. S.; Grana, D.; Parsekian, A.; Carr, B.; Jiao, J.

2017-12-01

Porosity is generated by chemical, physical and biological processes that work to transform bedrock into soil. The resulting porosity structure can provide specifics about these processes and can improve understanding groundwater storage in the deep critical zone. Near-surface geophysical methods, when combined with rock physics and drilling, can be a tool used to map porosity over large spatial scales. In this study, we estimate porosity in three-dimensions (3D) across a 58 Ha granite catchment. Observations focus on seismic refraction, downhole nuclear magnetic resonance logs, downhole sonic logs, and samples of core acquired by push coring. We use a novel petrophysical approach integrating two rock physics models, a porous medium for the saprolite and a differential effective medium for the fractured rock, that drive a Bayesian inversion to calculate porosity from seismic velocities. The inverted geophysical porosities are within about 0.05 m3/m3 of lab measured values. We extrapolate the porosity estimates below seismic refraction lines to a 3D volume using ordinary kriging to map the distribution of porosity in 3D up to depths of 80 m. This study provides a unique map of porosity on scale never-before-seen in critical zone science. Estimating porosity on these large spatial scales opens the door for improving and understanding the processes that shape the deep critical zone.

Effect of porosity, tissue density, and mechanical properties on radial sound speed in human cortical bone

Energy Technology Data Exchange (ETDEWEB)

Eneh, C. T. M., E-mail: chibuzor.eneh@uef.fi, E-mail: markus.malo@uef.fi, E-mail: janne.karjalainen@boneindex.fi, E-mail: jukka.liukkonen@gmail.com, E-mail: juha.toyras@uef.fi; Töyräs, J., E-mail: chibuzor.eneh@uef.fi, E-mail: markus.malo@uef.fi, E-mail: janne.karjalainen@boneindex.fi, E-mail: jukka.liukkonen@gmail.com, E-mail: juha.toyras@uef.fi; Jurvelin, J. S., E-mail: jukka.jurvelin@uef.fi [Department of Applied Physics, University of Eastern Finland, P.O. Box 1627, Kuopio FI-70211, Finland and Diagnostic Imaging Center, Kuopio University Hospital, P.O. Box 100, Kuopio FI-70029 (Finland); Malo, M. K. H., E-mail: chibuzor.eneh@uef.fi, E-mail: markus.malo@uef.fi, E-mail: janne.karjalainen@boneindex.fi, E-mail: jukka.liukkonen@gmail.com, E-mail: juha.toyras@uef.fi; Liukkonen, J., E-mail: chibuzor.eneh@uef.fi, E-mail: markus.malo@uef.fi, E-mail: janne.karjalainen@boneindex.fi, E-mail: jukka.liukkonen@gmail.com, E-mail: juha.toyras@uef.fi [Department of Applied Physics, University of Eastern Finland, P.O. Box 1627, Kuopio FI-70211 (Finland); Karjalainen, J. P., E-mail: chibuzor.eneh@uef.fi, E-mail: markus.malo@uef.fi, E-mail: janne.karjalainen@boneindex.fi, E-mail: jukka.liukkonen@gmail.com, E-mail: juha.toyras@uef.fi [Bone Index Finland Ltd., P.O. Box 1188, Kuopio FI-70211 (Finland)

2016-05-15

Purpose: The purpose of this study was to investigate the effect of simultaneous changes in cortical porosity, tissue mineral density, and elastic properties on radial speed of sound (SOS) in cortical bone. The authors applied quantitative pulse-echo (PE) ultrasound techniques that hold much potential especially for screening of osteoporosis at primary healthcare facilities. Currently, most PE measurements of cortical thickness, a well-known indicator of fracture risk, use a predefined estimate for SOS in bone to calculate thickness. Due to variation of cortical bone porosity, the use of a constant SOS value propagates to an unknown error in cortical thickness assessment by PE ultrasound. Methods: The authors conducted 2.25 and 5.00 MHz focused PE ultrasound time of flight measurements on femoral diaphyses of 18 cadavers in vitro. Cortical porosities of the samples were determined using microcomputed tomography and related to SOS in the samples. Additionally, the effect of cortical bone porosity and mechanical properties of the calcified matrix on SOS was investigated using numerical finite difference time domain simulations. Results: Both experimental measurements and simulations demonstrated significant negative correlation between radial SOS and cortical porosity (R{sup 2} ≥ 0.493, p < 0.01 and R{sup 2} ≥ 0.989, p < 0.01, respectively). When a constant SOS was assumed for cortical bone, the error due to variation of cortical bone porosity (4.9%–16.4%) was about 6% in the cortical thickness assessment in vitro. Conclusions: Use of a predefined, constant value for radial SOS in cortical bone, i.e., neglecting the effect of measured variation in cortical porosity, propagated to an error of 6% in cortical thickness. This error can be critical as characteristic cortical thinning of 1.10% ± 1.06% per yr decreases bending strength of the distal radius and results in increased fragility in postmenopausal women. Provided that the cortical porosity can be estimated

Effect of porosity, tissue density, and mechanical properties on radial sound speed in human cortical bone

International Nuclear Information System (INIS)

Eneh, C. T. M.; Töyräs, J.; Jurvelin, J. S.; Malo, M. K. H.; Liukkonen, J.; Karjalainen, J. P.

2016-01-01

Purpose: The purpose of this study was to investigate the effect of simultaneous changes in cortical porosity, tissue mineral density, and elastic properties on radial speed of sound (SOS) in cortical bone. The authors applied quantitative pulse-echo (PE) ultrasound techniques that hold much potential especially for screening of osteoporosis at primary healthcare facilities. Currently, most PE measurements of cortical thickness, a well-known indicator of fracture risk, use a predefined estimate for SOS in bone to calculate thickness. Due to variation of cortical bone porosity, the use of a constant SOS value propagates to an unknown error in cortical thickness assessment by PE ultrasound. Methods: The authors conducted 2.25 and 5.00 MHz focused PE ultrasound time of flight measurements on femoral diaphyses of 18 cadavers in vitro. Cortical porosities of the samples were determined using microcomputed tomography and related to SOS in the samples. Additionally, the effect of cortical bone porosity and mechanical properties of the calcified matrix on SOS was investigated using numerical finite difference time domain simulations. Results: Both experimental measurements and simulations demonstrated significant negative correlation between radial SOS and cortical porosity (R"2 ≥ 0.493, p < 0.01 and R"2 ≥ 0.989, p < 0.01, respectively). When a constant SOS was assumed for cortical bone, the error due to variation of cortical bone porosity (4.9%–16.4%) was about 6% in the cortical thickness assessment in vitro. Conclusions: Use of a predefined, constant value for radial SOS in cortical bone, i.e., neglecting the effect of measured variation in cortical porosity, propagated to an error of 6% in cortical thickness. This error can be critical as characteristic cortical thinning of 1.10% ± 1.06% per yr decreases bending strength of the distal radius and results in increased fragility in postmenopausal women. Provided that the cortical porosity can be estimated in vivo

Study of the effects of stress sensitivity on the permeability and porosity of fractal porous media

International Nuclear Information System (INIS)

Tan, Xiao-Hua; Li, Xiao-Ping; Liu, Jian-Yi; Zhang, Lie-Hui; Fan, Zhou

2015-01-01

Flow in porous media under stress is very important in various scientific and engineering fields. It has been shown that stress plays an important role in effect of permeability and porosity of porous media. In this work, novel predictive models for permeability and porosity of porous media considering stress sensitivity are developed based on the fractal theory and mechanics of materials. Every parameter in the proposed models has clear physical meaning. The proposed models are evaluated using previously published data for permeability and porosity measured in various natural materials. The predictions of permeability and porosity show good agreement with those obtained by the available experimental data and illustrate that the proposed models can be used to characterize the flow in porous media under stress accurately. - Highlights: • Predictive models for permeability and porosity of porous media considering stress sensitivity are developed. • The fractal theory and mechanics of materials are used in these models. • The predictions of permeability and porosity show good agreement with those obtained by the available experimental data. • The proposed models can be used to characterize the flow in porous media under stress accurately

Emulsion Inks for 3D Printing of High Porosity Materials.

Science.gov (United States)

Sears, Nicholas A; Dhavalikar, Prachi S; Cosgriff-Hernandez, Elizabeth M

2016-08-01

Photocurable emulsion inks for use with solid freeform fabrication (SFF) to generate constructs with hierarchical porosity are presented. A high internal phase emulsion (HIPE) templating technique was utilized to prepare water-in-oil emulsions from a hydrophobic photopolymer, surfactant, and water. These HIPEs displayed strong shear thinning behavior that permitted layer-by-layer deposition into complex shapes and adequately high viscosity at low shear for shape retention after extrusion. Each layer was actively polymerized with an ultraviolet cure-on-dispense (CoD) technique and compositions with sufficient viscosity were able to produce tall, complex scaffolds with an internal lattice structure and microscale porosity. Evaluation of the rheological and cure properties indicated that the viscosity and cure rate both played an important role in print fidelity. These 3D printed polyHIPE constructs benefit from the tunable pore structure of emulsion templated material and the designed architecture of 3D printing. As such, these emulsion inks can be used to create ultra high porosity constructs with complex geometries and internal lattice structures not possible with traditional manufacturing techniques. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physical Explanation of Archie's Porosity Exponent in Granular Materials: A Process-Based, Pore-Scale Numerical Study

Science.gov (United States)

Niu, Qifei; Zhang, Chi

2018-02-01

The empirical Archie's law has been widely used in geosciences and engineering to explain the measured electrical resistivity of many geological materials, but its physical basis has not been fully understood yet. In this study, we use a pore-scale numerical approach combining discrete element-finite difference methods to study Archie's porosity exponent m of granular materials over a wide porosity range. Numerical results reveal that at dilute states (e.g., porosity ϕ > 65%), m is exclusively related to the particle shape and orientation. As the porosity decreases, the electric flow in pore space concentrates progressively near particle contacts and m increases continuously in response to the intensified nonuniformity of the local electrical field. It is also found that the increase in m is universally correlated with the volume fraction of pore throats for all the samples regardless of their particle shapes, particle size range, and porosities.

Computation of porosity and water content from geophysical logs, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Nelson, P.H.

1996-01-01

Neutron and density logs acquired in boreholes at Yucca Mountain, Nevada are used to determine porosity and water content as a function of depth. Computation of porosity requires an estimate of grain density, which is provided by core data, mineralogical data, or is inferred from rock type where neither core nor mineralogy are available. The porosity estimate is merged with mineralogical data acquired by X-ray diffraction to compute the volumetric fractions of major mineral groups. The resulting depth-based portrayal of bulk rock composition is equivalent to a whole rock analysis of mineralogy and porosity. Water content is computed from epithermal and thermal neutron logs. In the unsaturated zone, the density log is required along with a neutron log. Water content can also be computed from dielectric logs, which were acquired in only a fraction of the boreholes, whereas neutron logs were acquired in all boreholes. Mineralogical data are used to compute a structural (or bound) water estimate, which is subtracted from the total water estimate from the neutron-density combination. Structural water can be subtracted only from intervals where mineralogical analyses are available; otherwise only total water can be reported. The algorithms and procedures are applied to logs acquired during 1979 to 1984 at Yucca Mountain. Examples illustrate the results. Comparison between computed porosity and core measurements shows systematic differences ranging from 0.005 to 0.04. These values are consistent with a sensitivity analysis using uncertainty parameters for good logging conditions. Water content from core measurements is available in only one borehole, yielding a difference between computed and core-based water content of 0.006

Mechanisms of the porosity formation during the fiber laser lap welding of aluminium alloy

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J. Wang

2015-10-01

Full Text Available When joining the aluminum alloys, one of the biggest challenges is the formation of porosity, which deteriorates mechanical properties of welds. In this study, the lap welding was conducted on an aluminum alloy 5754 metal sheets with a thickness of 2 mm. The effects of various laser welding parameters on the weld quality were investigated. The porosity content was measured by X-ray inspections. The key is to control the solidification duration of molten pool. When the solidification duration of molten pool is large enough, more bubbles can escape from the molten pool and less remain as porosity.

Experimental Investigation of Closed Porosity of Inorganic Solidified Foam Designed to Prevent Coal Fires

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Yi Lu

2015-01-01

Full Text Available In order to overcome the deficiency of the existing fire control technology and control coal spontaneous combustion by sealing air leakages in coal mines, inorganic solidified foam (ISF with high closed porosity was developed. The effect of sodium dodecyl sulfate (SDS concentration on the porosity of the foams was investigated. The results showed that the optimized closed porosity of the solidified foam was 38.65 wt.% for an SDS concentration of approximately 7.4×10-3 mol/L. Based on observations of the microstructure of the pore walls after solidification, it was inferred that an equilibrium between the hydration process and the drainage process existed. Therefore, the ISF was improved using three different systems. Gelatin can increase the viscosity of the continuous phase to form a viscoelastic film around the air cells, and the SDS + gelatin system can create a mixed surfactant layer at gas/liquid interfaces. The accelerator (AC accelerates the hydration process and coagulation of the pore walls before the end of drainage. The mixed SDS + gelatin + AC systems produced an ISF with a total porosity of 79.89% and a closed porosity of 66.89%, which verified the proposed stabilization mechanism.

From obc seismic to porosity volume: A pre-stack analysis of a turbidite reservoir, deepwater Campos Basin, Brazil

Science.gov (United States)

Martins, Luiz M. R.

The Campos Basin is the best known and most productive of the Brazilian coastal basins. Turbidites are, by far, the main oil-bearing reservoirs. Using a four component (4-C) ocean-bottom-cable (OBC) seismic survey I set out to improve the reservoir characterization in a deep-water turbidite field in the Campos Basin. In order to achieve my goal, pre-stack angle gathers were derived and PP and PS inversion were performed. The inversion was used as an input to predict the petrophysical properties of the reservoir. Converting seismic reflection amplitudes into impedance profiles not only maximizes vertical resolution but also minimizes tuning effects. Mapping the porosity is extremely important in the development of a hydrocarbon reservoirs. Combining seismic attributes derived from the P-P data and porosity logs I use linear multi-regression and neural network geostatistical tools to predict porosity between the seismic attributes and porosity logs at the well locations. After predicting porosity in well locations, those relationships were applied to the seismic attributes to generate a 3-D porosity volume. The predicted porosity volume highlighted the best reservoir facies in the reservoir. The integration of elastic impedance, shear impedance and porosity improved the reservoir characterization.

Influence of armour porosity on the hydraulic stability of cube armour layers

OpenAIRE

Medina Folgado, Josep Ramón; Molines Llodra, Jorge; GÓMEZ MARTÍN, MARÍA ESTHER

2014-01-01

Armour placement and packing density directly affect construction costs and hydraulic performance of mound breakwaters. In this paper, the literature concerning the influence of armour porosity on the hydraulic stability of single- and double-layer armours is discussed. Qualitative and quantitative estimations for the influence of armour porosity and packing density on the hydraulic stability are given for the most common concrete armour units. The analysis focuses on specific 2D hydraulic st...

Formation of peripheral porosity regions around urania in zirconia-urania mixed oxide powder compact sintering

International Nuclear Information System (INIS)

Das, P.; Choudhury, R.

1992-01-01

Sintering studies of zirconia-urania mixed oxide powder compacts (in stages of 5% urania up to a maximum of 20% addition) were carried out at temperatures between 1000-1400deg C for various soaking periods. The formation of a peripheral porosity region around comparatively coarser urania particle was a characteristic feature in this mixed oxide sintered compact. At even a higher sintering temperature (1800deg C), where extensive solid solution formation takes place, this porosity region demarcates the solutionized particles from the host zirconia apparently acting as a discontinuity in the system. Relative shrinkage difference between the dissimilar particles probably contributes to the porosity regions around the minor second phase at a lower temperature while at higher temperature generation of 'Kirkendall porosity' may be responsible for such an effect. (orig.)

Air filled porosity in composting processes

Energy Technology Data Exchange (ETDEWEB)

Ruggieri, L.; Gea, T.; Artola, A.; Sanchez, A.

2009-07-01

As it is widely known, the composting process consists in the aerobic decomposition of the biodegradable organic matter present in different types of solid wastes. Water and oxygen are necessary for the biological activity of microorganisms involved in the composting process and their availability is directly related to the total and the air filled porosity (AFP). Maintaining adequate AFP level satisfies the oxygen content requirement to achieve the desired composting conditions and thus, tho enhance biological activity. (Author)

Air filled porosity in composting processes

International Nuclear Information System (INIS)

Ruggieri, L.; Gea, T.; Artola, A.; Sanchez, A.

2009-01-01

As it is widely known, the composting process consists in the aerobic decomposition of the biodegradable organic matter present in different types of solid wastes. Water and oxygen are necessary for the biological activity of microorganisms involved in the composting process and their availability is directly related to the total and the air filled porosity (AFP). Maintaining adequate AFP level satisfies the oxygen content requirement to achieve the desired composting conditions and thus, tho enhance biological activity. (Author)

The effects of porosity in friction performance of brake pad using waste tire dust

Directory of Open Access Journals (Sweden)

İbrahim Mutlu

2015-10-01

Full Text Available Abstract This research is focused on the effect of porosity on the friction-wear properties of automotive brake pads. Waste Tire Dust (WTD was used as a new friction material in brake pads. Newly formulated brake pad materials with five different components have been produced by conventional techniques. In the experimental studies, the change of the friction coefficient, the temperature of the friction surface, the specific wear rate, and the hardness, density and porosity were measured. In addition, the micro-structural characterizations of brake pads are determined using Scanning Electron Microscopy (SEM. The mean coefficient of friction, porosity and specific wear are increased due to a WTD rate increases, on the other hand, hardness and density are decreased. As a result, WTD can be considered as an alternative to revalorize this kind of waste products in the brake pads and the amount of porosity of the brake pad affected the friction coefficient and wear behavior of the pad.

Understanding age-induced cortical porosity in women

DEFF Research Database (Denmark)

Andreasen, Christina Møller; Delaisse, Jean-Marie; van der Eerden, Bram C J

2018-01-01

of a histomorphometric analysis of sections of iliac bone specimens from 35 women (age 16-78 years). Firstly, the study shows that the aging-induced cortical porosity reflects an increased pore size rather than an increased pore density. Secondly, it establishes a novel histomorphometric classification of the pores...... initiation of the subsequent bone formation. This article is protected by copyright. All rights reserved....

Simultaneous thermal neutron decay time and porosity logging system

International Nuclear Information System (INIS)

Smith, H.D. Jr.; Smith, M.P.; Schultz, W.E.

1979-01-01

A simultaneous pulsed neutron porosity and thermal neutron capture cross section logging system is provided for radiological well logging of subsurface earth formations. A logging tool provided with a 14 MeV pulsed neutron source, an epithermal neutron detector, and a combination gamma ray and fast neutron detector is moved through a borehole. Repetitive bursts of neutrons irradiate the earth formations; and, during the bursts, the fast neutron and epithermal neutron populations are sampled. During the interval between bursts the thermal neutron capture gamma ray population is sampled in two or more time intervals. The fast and epithermal neutron population measurements are combined to provide a measurement of formation porosity phi. The capture gamma ray measurements are combined to provide a simultaneous determination of the thermal neutron capture cross section Σ

The efficiency of windbreaks on the basis of wind field and optical porosity measurement

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Tomáš Středa

2008-01-01

Full Text Available Windbreaks have been used for many years to reduce wind speed as a wind-erosion control mea­su­re. To assessment of windbreak efficiency two main parameters are using: height of windbreak (H and aerodynamic porosity. In South Moravian Region the total area of windbreaks is approximately 1200 ha. For purposes of horizontal profile measurement of wind speed and wind direction windbreaks with various spices composition, age and construction in cadastral territory Suchá Loz and Micmanice were chosen. Windbreak influence on horizontal wind profile was found out in distance of 50, 100, 150 and 200 m in front and behind windbreak in two-meter height above surface. For the optical porosity measurement the ImageTool program was used. The wind field measurement results of windbreak in Suchá Loz cadastral shows limited effect of windbreak on wind speed. The windbreak is created mainly by Canadian poplars (Populus × canadensis. In dependence on main species foliage stage the effect of windbreak was obvious on leeward side to distance of 100–150 m (c. 5–7 H. Average optical porosity of windbreak in Suchá Loz was 50% (April. Reduction of average wind speed was about 17% maximally in this stage. Optical porosity was 20% and wind speed reduction was about 37% during second measurement (October. The second monitored windbreak (Micmanice had a significant influence on wind speed even to the maximal measured distance (200 m, c. 14 H. This windbreak crea­ted mainly by Acer sp. and Fraxinus excelsior reduced the wind speed about 64%. During first measurement (May the optical porosity of 20% and maximal wind speed reduction of 64% were assessed. For optical porosity of 21% (October the wind speed reduction was about 55%. Close relation between optical porosity and wind speed reduction was found out by statistical evaluation. Correlation coefficient regardless locality for distance of 50 m was −0.80, 100 m −0.92, 150 m −0.76 and for distance of 200 m

The Production of Porous Hydroxyapatite Scaffolds with Graded Porosity by Sequential Freeze-Casting.

Science.gov (United States)

Lee, Hyun; Jang, Tae-Sik; Song, Juha; Kim, Hyoun-Ee; Jung, Hyun-Do

2017-03-31

Porous hydroxyapatite (HA) scaffolds with porosity-graded structures were fabricated by sequential freeze-casting. The pore structures, compressive strengths, and biocompatibilities of the fabricated porous HA scaffolds were evaluated. The porosities of the inner and outer layers of the graded HA scaffolds were controlled by adjusting the initial HA contents of the casting slurries. The interface between the dense and porous parts was compact and tightly adherent. The porosity and compressive strengths of the scaffold were controlled by the relative thicknesses of the dense/porous parts. In addition, the porous HA scaffolds showed good biocompatibility in terms of preosteoblast cell attachment and proliferation. The results suggest that porous HA scaffolds with load-bearing parts have potential as bone grafts in hard-tissue engineering.

Characterizing the turbulent porosity of stellar wind structure generated by the line-deshadowing instability

Science.gov (United States)

Owocki, Stanley P.; Sundqvist, Jon O.

2018-03-01

We analyse recent 2D simulations of the non-linear evolution of the line-deshadowing instability (LDI) in hot-star winds, to quantify how the associated highly clumped density structure can lead to a `turbulent porosity' reduction in continuum absorption and/or scattering. The basic method is to examine the statistical variations of mass column as a function of path length, and fit these to analytic forms that lead to simple statistical scalings for the associated mean extinction. A key result is that one can characterize porosity effects on continuum transport in terms of a single `turbulent porosity length', found here to scale as H ≈ (fcl - 1)a, where fcl ≡ 〈ρ2〉/〈ρ〉2 is the clumping factor in density ρ, and a is the density autocorrelation length. For continuum absorption or scattering in an optically thick layer, we find the associated effective reduction in opacity scales as ˜ 1/√{1+τ_H}, where τH ≡ κρH is the local optical thickness of this porosity length. For these LDI simulations, the inferred porosity lengths are small, only about a couple per cent of the stellar radius, H ≈ 0.02R*. For continuum processes like bound-free absorption of X-rays that are only marginally optically thick throughout the full stellar wind, this implies τH ≪ 1, and thus that LDI-generated porosity should have little effect on X-ray transport in such winds. The formalism developed here could however be important for understanding the porous regulation of continuum-driven, super-Eddington outflows from luminous blue variables.

On the porosity of barrier layers

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J. Mignot

2009-09-01

Full Text Available Barrier layers are defined as the layer between the pycnocline and the thermocline when the latter are different as a result of salinity stratification. We present a revisited 2-degree resolution global climatology of monthly mean oceanic Barrier Layer (BL thickness first proposed by de Boyer Montégut et al. (2007. In addition to using an extended data set, we present a modified computation method that addresses the observed porosity of BLs. We name porosity the fact that barrier layers distribution can, in some areas, be very uneven regarding the space and time scales that are considered. This implies an intermittent alteration of air-sea exchanges by the BL. Therefore, it may have important consequences for the climatic impact of BLs. Differences between the two computation methods are small for robust BLs that are formed by large-scale processes. However, the former approach can significantly underestimate the thickness of short and/or localized barrier layers. This is especially the case for barrier layers formed by mesoscale mechanisms (under the intertropical convergence zone for example and along western boundary currents and equatorward of the sea surface salinity subtropical maxima. Complete characterisation of regional BL dynamics therefore requires a description of the robustness of BL distribution to assess the overall impact of BLs on the process of heat exchange between the ocean interior and the atmosphere.

Incorporating Geochemical And Microbial Kinetics In Reactive Transport Models For Generation Of Acid Rock Drainage

Science.gov (United States)

Andre, B. J.; Rajaram, H.; Silverstein, J.

2010-12-01

diffusion model at the scale of a single rock is developed incorporating the proposed kinetic rate expressions. Simulations of initiation, washout and AMD flows are discussed to gain a better understanding of the role of porosity, effective diffusivity and reactive surface area in generating AMD. Simulations indicate that flow boundary conditions control generation of acid rock drainage as porosity increases.

A 2D double-porosity model for melting and melt migration beneath mid-oceanic ridges

Science.gov (United States)

Liu, B.; Liang, Y.; Parmentier, E.

2017-12-01

Several lines of evidence suggest that the melting and melt extraction region of the MORB mantle is heterogeneous consisting of an interconnected network of high permeability dunite channels in a low porosity harzburgite or lherzolite matrix. In principle, one can include channel formation into the tectonic-scale geodynamic models by solving conservation equations for a chemically reactive and viscously deformable porous medium. Such an approach eventually runs into computational limitations such as resolving fractal-like channels that have a spectrum of width. To better understand first order features of melting and melt-rock interaction beneath MOR, we have formulated a 2D double porosity model in which we treat the triangular melting region as two overlapping continua occupied by the low-porosity matrix and interconnected high-porosity channels. We use melt productivity derived from a thermodynamic model and melt suction rate to close our problem. We use a high-order accurate numerical method to solve the conservation equations in 2D for porosity, solid and melt velocities and concentrations of chemical tracers in the melting region. We carry out numerical simulations to systematically study effects of matrix-to-channel melt suction and spatially distributed channels on the distributions of porosity and trace element and isotopic ratios in the melting region. For near fractional melting with 10 vol% channel in the melting region, the flow field of the matrix melt follows closely to that of the solid because the small porosity (exchange between the melt and the solid. The smearing effect can be approximated by dispersion coefficient. For slowly diffusing trace elements (e.g., LREE and HFSE), the melt migration induced dispersion can be as effective as thermal diffusion. Therefore, sub-kilometer scale heterogeneities of Nd and Hf isotopes are significantly damped or homogenized in the melting region.

Kinetics of YBa2Cu3O6+γ oxidation

International Nuclear Information System (INIS)

Mozhaev, A.P.; Chernyaev, S.V.; Udal'tsova, T.I.; Kotov, N.M.

1992-01-01

Kinetics of the processes taking place during thermal treatment of YBa 2 Cu 3 O 6+γ samples and change in oxygen nonstoichiometry, related to the processes, were studied. The coefficient of oxygen diffusion was determined (D=D 0 x exp x (-E α /RT) a = 118 kJ/mol, D 0 = 4x10 -6 m 2 /s), which gave a satisfactory description of behaviour of powders and ceramics with the density below 5200 kg/m 3 . It is shown that in the course of annealing of denser samples considerable deviations of the calculated curves γ(T) from the experimental ones are observed. The deviations mentioned can be explained by the appearance of closed porosity and additional diffusion impediments

Ultrasonic examination of ceramics and composites for porosities in an automatic scanning system

Energy Technology Data Exchange (ETDEWEB)

Gundtoft, H.E.

1988-05-01

Using a very precise scanning system and computer evaluation, we can get quantitative results from automatic ultrasonic examination. In this paper two examples dealing with nonmetallic materials are presented. In a ceramic plate (>1 inch thick) small spherical prorosities (down to 0.1 mm) would harm the final product. Several artificial defects made in the plate were used for calibration and optimisation of the technique. Areas with with a microscope. Good agreement with the predicted values from the ultrasonic examination was found. From the NDT-examination the exact position of a porosity is known in all 3 coordinates (x, y and z). The size of the defect can also be measured. A single porosity with a diameter of 0.1 mm can be detected. Carbon-reinforced composites were examined. 8 prepregs were stacked and hardened in an autoclave to form a sheet (1 mm thick). Air trapped in the material resulted in porosities in the final product. A double trough transmission-scanning technique was used for the examination. The porosity percentages were determined by the NDT-technique, and agreement with destructivly determined values on samples from the same sheet was found.

Monte Carlo Study on Gas Pressure Response of He-3 Tube in Neutron Porosity Logging

Directory of Open Access Journals (Sweden)

TIAN Li-li;ZHANG Feng;WANG Xin-guang;LIU Jun-tao

2016-10-01

Full Text Available Thermal neutrons are detected by (n,p reaction of Helium-3 tube in the compensated neutron logging. The helium gas pressure in the counting area influences neutron detection efficiency greatly, and then it is an important parameter for neutron porosity measurement accuracy. The variation law of counting rates of a near detector and a far one with helium gas pressure under different formation condition was simulated by Monte Carlo method. The results showed that with the increasing of helium pressure the counting rate of these detectors increased firstly and then leveled off. In addition, the neutron counting rate ratio and porosity sensitivity increased slightly, the porosity measurement error decreased exponentially, which improved the measurement accuracy. These research results can provide technical support for selecting the type of Helium-3 detector in developing neutron porosity logging.

Numerical study on determining formation porosity using a boron capture gamma ray technique and MCNP.

Science.gov (United States)

Liu, Juntao; Zhang, Feng; Wang, Xinguang; Han, Fei; Yuan, Zhelong

2014-12-01

Formation porosity can be determined using the boron capture gamma ray counting ratio with a near to far detector in a pulsed neutron-gamma element logging tool. The thermal neutron distribution, boron capture gamma spectroscopy and porosity response for formations with different water salinity and wellbore diameter characteristics were simulated using the Monte Carlo method. We found that a boron lining improves the signal-to-noise ratio and that the boron capture gamma ray counting ratio has a higher sensitivity for determining porosity than total capture gamma. Copyright © 2014 Elsevier Ltd. All rights reserved.

Digital Rock Physics Aplications: Visualisation Complex Pore and Porosity-Permeability Estimations of the Porous Sandstone Reservoir

Science.gov (United States)

Handoyo; Fatkhan; Del, Fourier

2018-03-01

Reservoir rock containing oil and gas generally has high porosity and permeability. High porosity is expected to accommodate hydrocarbon fluid in large quantities and high permeability is associated with the rock’s ability to let hydrocarbon fluid flow optimally. Porosity and permeability measurement of a rock sample is usually performed in the laboratory. We estimate the porosity and permeability of sandstones digitally by using digital images from μCT-Scan. Advantages of the method are non-destructive and can be applied for small rock pieces also easily to construct the model. The porosity values are calculated by comparing the digital image of the pore volume to the total volume of the sandstones; while the permeability values are calculated using the Lattice Boltzmann calculations utilizing the nature of the law of conservation of mass and conservation of momentum of a particle. To determine variations of the porosity and permeability, the main sandstone samples with a dimension of 300 × 300 × 300 pixels are made into eight sub-cubes with a size of 150 × 150 × 150 pixels. Results of digital image modeling fluid flow velocity are visualized as normal velocity (streamline). Variations in value sandstone porosity vary between 0.30 to 0.38 and permeability variations in the range of 4000 mD to 6200 mD. The results of calculations show that the sandstone sample in this research is highly porous and permeable. The method combined with rock physics can be powerful tools for determining rock properties from small rock fragments.

Investigating textural controls on Archie's porosity exponent using process-based, pore-scale modelling

Science.gov (United States)

Niu, Q.; Zhang, C.

2017-12-01

Archie's law is an important empirical relationship linking the electrical resistivity of geological materials to their porosity. It has been found experimentally that the porosity exponent m in Archie's law in sedimentary rocks might be related to the degree of cementation, and therefore m is termed as "cementation factor" in most literatures. Despite it has been known for many years, there is lack of well-accepted physical interpretations of the porosity exponent. Some theoretical and experimental evidences have also shown that m may be controlled by the particle and/or pore shape. In this study, we conduct a pore-scale modeling of the porosity exponent that incorporates different geological processes. The evolution of m of eight synthetic samples with different particle sizes and shapes are calculated during two geological processes, i.e., compaction and cementation. The numerical results show that in dilute conditions, m is controlled by the particle shape. As the samples deviate from dilute conditions, m increases gradually due to the strong interaction between particles. When the samples are at static equilibrium, m is noticeably larger than its values at dilution condition. The numerical simulation results also show that both geological compaction and cementation induce a significant increase in m. In addition, the geometric characteristics of these samples (e.g., pore space/throat size, and their distributions) during compaction and cementation are also calculated. Preliminary analysis shows a unique correlation between the pore size broadness and porosity exponent for all eight samples. However, such a correlation is not found between m and other geometric characteristics.

The effect of porosity on cell ingrowth into accurately defined, laser-made, polylactide-based 3D scaffolds

Energy Technology Data Exchange (ETDEWEB)

Danilevicius, Paulius; Georgiadi, Leoni [Foundation for Research and Technology Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), N Plastira 100, 70013 Heraklion (Greece); Pateman, Christopher J.; Claeyssens, Frederik [Kroto Research Institute, Department of Materials Science and Engineering, University of Sheffield, Broad Lane, Sheffield S3 7HQ (United Kingdom); Chatzinikolaidou, Maria, E-mail: mchatzin@materials.uoc.gr [Foundation for Research and Technology Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), N Plastira 100, 70013 Heraklion (Greece); Department of Materials Science and Technology, University of Crete, PO Box 2208, 71303 Heraklion (Greece); Farsari, Maria, E-mail: mfarsari@iesl.forth.gr [Foundation for Research and Technology Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), N Plastira 100, 70013 Heraklion (Greece)

2015-05-01

Highlights: • We studied the porosity of laser-made 3D scaffolds on MC3T3-E1 pre-osteoblastic cells. • We made polylactide 3D scaffolds with pores 25–110 μm. - Abstract: The aim of this study is to demonstrate the accuracy required for the investigation of the role of solid scaffolds’ porosity in cell proliferation. We therefore present a qualitative investigation into the effect of porosity on MC3T3-E1 pre-osteoblastic cell ingrowth of three-dimensional (3D) scaffolds fabricated by direct femtosecond laser writing. The material we used is a purpose made photosensitive pre-polymer based on polylactide. We designed and fabricated complex, geometry-controlled 3D scaffolds with pore sizes ranging from 25 to 110 μm, representing porosities 70%, 82%, 86%, and 90%. The 70% porosity scaffolds did not support cell growth initially and in the long term. For the other porosities, we found a strong adhesion of the pre-osteoblastic cells from the first hours after seeding and a remarkable proliferation increase after 3 weeks and up to 8 weeks. The 86% porosity scaffolds exhibited a higher efficiency compared to 82% and 90%. In addition, bulk material degradation studies showed that the employed, highly-acrylated polylactide is degradable. These findings support the potential use of the proposed material and the scaffold fabrication technique in bone tissue engineering.

Effect of keyhole characteristics on porosity formation during pulsed laser-GTA hybrid welding of AZ31B magnesium alloy

Science.gov (United States)

Chen, Minghua; Xu, Jiannan; Xin, Lijun; Zhao, Zuofu; Wu, Fufa; Ma, Shengnan; Zhang, Yue

2017-06-01

This paper experimentally investigates the relationship between laser keyhole characteristics on the porosity formation during pulsed laser-GTA welding of magnesium alloy. Based on direct observations during welding process, the influences of laser keyhole state on the porosity formation were studied. Results show that the porosities in the joint are always at the bottom of fusion zone of the joint, which is closely related to the keyhole behavior. A large depth to wide ratio always leads to the increase of porosity generation chance. Keeping the keyhole outlet open for a longer time benefits the porosity restriction. Overlap of adjacent laser keyhole can effectively decrease the porosity generation, due to the cutting effect between adjacent laser keyholes. There are threshold overlap rate values for laser keyholes in different state.

Cellular Automaton Study of Hydrogen Porosity Evolution Coupled with Dendrite Growth During Solidification in the Molten Pool of Al-Cu Alloys

Science.gov (United States)

Gu, Cheng; Wei, Yanhong; Yu, Fengyi; Liu, Xiangbo; She, Lvbo

2017-09-01

Welding porosity defects significantly reduce the mechanical properties of welded joints. In this paper, the hydrogen porosity evolution coupled with dendrite growth during solidification in the molten pool of Al-4.0 wt pct Cu alloy was modeled and simulated. Three phases, including a liquid phase, a solid phase, and a gas phase, were considered in this model. The growth of dendrites and hydrogen gas pores was reproduced using a cellular automaton (CA) approach. The diffusion of solute and hydrogen was calculated using the finite difference method (FDM). Columnar and equiaxed dendrite growth with porosity evolution were simulated. Competitive growth between different dendrites and porosities was observed. Dendrite morphology was influenced by porosity formation near dendrites. After solidification, when the porosities were surrounded by dendrites, they could not escape from the liquid, and they made pores that existed in the welded joints. With the increase in the cooling rate, the average diameter of porosities decreased, and the average number of porosities increased. The average diameter of porosities and the number of porosities in the simulation results had the same trend as the experimental results.

Compost addition reduces porosity and chlordecone transfer in soil microstructure.

Science.gov (United States)

Woignier, Thierry; Clostre, Florence; Fernandes, Paula; Rangon, Luc; Soler, Alain; Lesueur-Jannoyer, Magalie

2016-01-01

Chlordecone, an organochlorine insecticide, pollutes soils and contaminates crops and water resources and is biomagnified by food chains. As chlordecone is partly trapped in the soil, one possible alternative to decontamination may be to increase its containment in the soil, thereby reducing its diffusion into the environment. Containing the pesticide in the soil could be achieved by adding compost because the pollutant has an affinity for organic matter. We hypothesized that adding compost would also change soil porosity, as well as transport and containment of the pesticide. We measured the pore features and studied the nanoscale structure to assess the effect of adding compost on soil microstructure. We simulated changes in the transport properties (hydraulic conductivity and diffusion) associated with changes in porosity. During compost incubation, the clay microstructure collapsed due to capillary stresses. Simulated data showed that the hydraulic conductivity and diffusion coefficient were reduced by 95 and 70% in the clay microstructure, respectively. Reduced transport properties affected pesticide mobility and thus helped reduce its transfer from the soil to water and to the crop. We propose that the containment effect is due not only to the high affinity of chlordecone for soil organic matter but also to a trapping mechanism in the soil porosity.

Dissolved CO2 Increases Breakthrough Porosity in Natural Porous Materials.

Science.gov (United States)

Yang, Y; Bruns, S; Stipp, S L S; Sørensen, H O

2017-07-18

When reactive fluids flow through a dissolving porous medium, conductive channels form, leading to fluid breakthrough. This phenomenon is caused by the reactive infiltration instability and is important in geologic carbon storage where the dissolution of CO 2 in flowing water increases fluid acidity. Using numerical simulations with high resolution digital models of North Sea chalk, we show that the breakthrough porosity is an important indicator of dissolution pattern. Dissolution patterns reflect the balance between the demand and supply of cumulative surface. The demand is determined by the reactive fluid composition while the supply relies on the flow field and the rock's microstructure. We tested three model scenarios and found that aqueous CO 2 dissolves porous media homogeneously, leading to large breakthrough porosity. In contrast, solutions without CO 2 develop elongated convective channels known as wormholes, with low breakthrough porosity. These different patterns are explained by the different apparent solubility of calcite in free drift systems. Our results indicate that CO 2 increases the reactive subvolume of porous media and reduces the amount of solid residual before reactive fluid can be fully channelized. Consequently, dissolved CO 2 may enhance contaminant mobilization near injection wellbores, undermine the mechanical sustainability of formation rocks and increase the likelihood of buoyance driven leakage through carbonate rich caprocks.

Effect of shelter porosity on downwind flow characteristics

Czech Academy of Sciences Publication Activity Database

Nosek, Štěpán; Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk; Chaloupecká, Hana; Jakubcová, Michala

2016-01-01

Roč. 114, March (2016), 02084-02084 ISSN 2100-014X. [Experimental Fluid Mechanics 2015 /10./. Praha, 17.11.2015-20.11.2015] R&D Projects: GA ČR GA15-18964S Institutional support: RVO:61388998 Keywords : atmospehric boundary layer * porosity * coherent structures * wind tunnel Subject RIV: BK - Fluid Dynamics

In situ detection of porosity initiation during aluminum thin film anodizing

Science.gov (United States)

Van Overmeere, Quentin; Nysten, Bernard; Proost, Joris

2009-02-01

High-resolution curvature measurements have been performed in situ during aluminum thin film anodizing in sulfuric acid. A well-defined transition in the rate of internal stress-induced curvature change is shown to allow for the accurate, real-time detection of porosity initiation. The validity of this in situ diagnostic tool was confirmed by a quantitative analysis of the spectral density distributions of the anodized surfaces. These were obtained by analyzing ex situ atomic force microscopy images of surfaces anodized for different times, and allowed to correlate the in situ detected transition in the rate of curvature change with the appearance of porosity.

Porosity Dependence of Piezoelectric Properties for Porous Potassium Niobate System Ceramics

Energy Technology Data Exchange (ETDEWEB)

Wada, S; Mase, Y; Shimizu, S; Maeda, K; Fujii, I; Nakashima, K; Pulpan, P; Miyajima, N, E-mail: swada@yamanashi.ac.jp [Interdisciplinary Graduate School of Medical and Engineering, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-8510 (Japan)

2011-10-29

Porous potassium niobate (KNbO{sub 3}, KN) system ceramics were prepared by a conventional sintering method using carbon black (CB) nanoparticles. First, KN nanoparticles with a size of 100 nm was mixed with CB nanoparticles and binder using ball milling with ethanol. The mixture was dried, and pressed into pellets using uniaxial pressing. After binder burnout, these ceramics was sintered in air. Their piezoelectric properties were measured and discussed a relationship between porosity and piezoelectric properties. As the results, with increasing porosity, piezoelectric g33 constant increased significantly, which suggested that porous ceramics were effective for stress sensor application.

Porosity Dependence of Piezoelectric Properties for Porous Potassium Niobate System Ceramics

International Nuclear Information System (INIS)

Wada, S; Mase, Y; Shimizu, S; Maeda, K; Fujii, I; Nakashima, K; Pulpan, P; Miyajima, N

2011-01-01

Porous potassium niobate (KNbO 3 , KN) system ceramics were prepared by a conventional sintering method using carbon black (CB) nanoparticles. First, KN nanoparticles with a size of 100 nm was mixed with CB nanoparticles and binder using ball milling with ethanol. The mixture was dried, and pressed into pellets using uniaxial pressing. After binder burnout, these ceramics was sintered in air. Their piezoelectric properties were measured and discussed a relationship between porosity and piezoelectric properties. As the results, with increasing porosity, piezoelectric g33 constant increased significantly, which suggested that porous ceramics were effective for stress sensor application.

Microstructure, porosity and mineralogy around fractures in Olkiluoto bedrock

International Nuclear Information System (INIS)

Kuva, J.; Kelokaski, M.; Ikonen, J.; Siitari-Kauppi, M.; Lindberg, A.; Aaltonen, I.

2012-01-01

3D distributions of minerals and porosities were determined for samples that included waterconducting fractures. The analysis of these samples was performed using conventional petrography methods, electron microscopy, C-14-PMMA porosity analysis and X-ray tomography. While X-ray tomography proved to be a very useful method when determining the inner structure of the samples, combining tomography results with those obtained by other methods turned out to be difficult without very careful sample preparation design. It seems that the properties of rock around a water-conducting fracture depend on so many uncorrelated factors that no clear pattern emerged even for rock samples with a given type of fracture. We can conclude, however, that a combination of different analysis methods can be useful and used to infer novel structural information about alteration zones adjacent to fracture surfaces. (orig.)

Microstructure, porosity and mineralogy around fractures in Olkiluoto bedrock

Energy Technology Data Exchange (ETDEWEB)

Kuva, J. (ed.); Myllys, M.; Timonen, J. [Jyvaeskylae Univ. (Finland); Kelokaski, M.; Ikonen, J.; Siitari-Kauppi, M. [Helsinki Univ. (Finland); Lindberg, A. [Geological Survey of Finland, Espoo (Finland); Aaltonen, I.

2012-01-15

3D distributions of minerals and porosities were determined for samples that included waterconducting fractures. The analysis of these samples was performed using conventional petrography methods, electron microscopy, C-14-PMMA porosity analysis and X-ray tomography. While X-ray tomography proved to be a very useful method when determining the inner structure of the samples, combining tomography results with those obtained by other methods turned out to be difficult without very careful sample preparation design. It seems that the properties of rock around a water-conducting fracture depend on so many uncorrelated factors that no clear pattern emerged even for rock samples with a given type of fracture. We can conclude, however, that a combination of different analysis methods can be useful and used to infer novel structural information about alteration zones adjacent to fracture surfaces. (orig.)

Ultrasonic velocities of North Sea chalk samples: influence of porosity, fluid content and texture

DEFF Research Database (Denmark)

Rogen, B.; Fabricius, Ida Lykke; Japsen, P.

2005-01-01

a porosity-reducing effect and that samples rich in large grains have a relatively low porosity for a given P-wave modulus. The clay content in the samples is low and is mainly represented by either kaolinite or smectite; samples with smectite have a lower P-wave modulus than samples with kaolinite at equal...

High Porosity Alumina as Matrix Material for Composites of Al-Mg Alloys

International Nuclear Information System (INIS)

Gömze, L A; Egész, Á; Gömze, L N; Ojima, F

2013-01-01

The sophisticated industry and technologies require higher and higher assumptions against mechanical strength and surface hardness of ceramic reinforced metal alloys and metal matrix composites. Applying the well-known alumina powders by dry pressing technology and some special pore-forming additives and sintering technology the authors have successfully developed a new, high porosity alumina matrix material for composites of advenced Al-Mg alloys. The developed new matrix material have higher than 30% porosity, with homogenous porous structure and pore sizes from few nano up to 2–3 mm depending on the alloys containments. Thanks to the used materials and the sintering conditions the authors could decrease the wetting angles less than 90° between the high porosity alumina matrix and the Al-Mg alloys. Applied analytical methods in this research were laser granulometry, scanning electron microscopy, and X-ray diffraction. Digital image analysis was applied to microscopy results, to enhance the results of transformation

Effect of the calcining temperature on the porosity of the titanium dioxide powders obtained by Polymeric Precursor Method

International Nuclear Information System (INIS)

Silva, D.W.; Granado, S.R.; Ciola, R.A.; Cavalheiro, A.A.

2011-01-01

Ceramics materials obtained by Polymeric Precursor Method exhibit mechanisms of the pore formation and elimination dependents on the decomposition kinetics of the residual organic matter of the polyester. The mechanism of pore elimination seems to occur by disrupting of the wall among the pores because it leads to the consequent pore coalescence and increasing in pore volume, which posses higher pore diameters. In this case, it was observed that the porosity decreasing occurs by pore wall moving after that the residual organic matter is eliminated from the pore inside. The pore diameter associated to the highest volume desorption occurred for the material obtained after calcining at 450°C is approximately 1,7 nm, what seems to be related to the amorphous carbon accumulated inside the pores, once that the pore volume decreases more effectively for the material obtained by calcining at 550°C, making the maximum volume situates at 2,0 nm. (author)

Benchmark neutron porosity log calculations

International Nuclear Information System (INIS)

Little, R.C.; Michael, M.; Verghese, K.; Gardner, R.P.

1989-01-01

Calculations have been made for a benchmark neutron porosity log problem with the general purpose Monte Carlo code MCNP and the specific purpose Monte Carlo code McDNL. For accuracy and timing comparison purposes the CRAY XMP and MicroVax II computers have been used with these codes. The CRAY has been used for an analog version of the MCNP code while the MicroVax II has been used for the optimized variance reduction versions of both codes. Results indicate that the two codes give the same results within calculated standard deviations. Comparisons are given and discussed for accuracy (precision) and computation times for the two codes

Effect of High Porosity Screen on the Near Wake of a Circular Cylinder

Directory of Open Access Journals (Sweden)

Sahin B.

2013-04-01

Full Text Available The change in flow characteristics downstream of a circular cylinder (inner cylinder surrounded by a permeable cylinder (outer cylinder made of a high porosity screen was investigated in shallow water using Particle Image Velocimetry (PIV technique. The diameter of the inner cylinder, outer cylinder and the water height were kept constant during the experiments as d = 50 mm, D = 100 mm and hw = 50 mm, respectively. The depth-averaged free stream velocity was also kept constant as U = 180 mm/s which corresponded to a Reynolds number of Red = 9000 based on the inner cylinder diameter. It was shown that the outer permeable cylinder had a substantialeffect on the vortex formation and consequent vortex shedding downstream of the circular cylinder, especially in the near wake. The time averaged vorticity layers, streamlines and velocity vector field depict that the location of the interaction of vortices considerably changed by the presence of the outer cylinder. Turbulent statistics clearly demonstrated that in comparison to the natural cylinder, turbulent kinetic energy and Reynolds stresses decreased remarkably downstream of the inner cylinder. Moreover, spectra of streamwise velocity fluctuations showed that the vortex shedding frequency significantly reduced compared to the natural cylinder case.

Development of model hydroxyapatite bone scaffolds with multiscale porosity for potential load bearing applications

Science.gov (United States)

Dellinger, Jennifer Gwynne

2005-11-01

Model hydroxyapatite (HA) bone scaffolds consisting of a latticed pattern of rods were fabricated by a solid freeform fabrication (SFF) technique based on the robotic deposition of colloidal pastes. An optimal HA paste formulation for this method was developed. Local porosity, i.e. microporosity (1--30 mum) and sintering porosity (less than 1 mum), were produced by including polymer microsphere porogens in the HA pastes and by controlling the sintering of the scaffolds. Scaffolds with and without local porosity were evaluated with and without in vitro accelerated degradation. Percent weight loss of the scaffolds and calcium and phosphorus concentrations in solution increased with degradation time. After degradation, compressive strength and modulus decreased significantly for scaffolds with local porosity, but did not change significantly for scaffolds without local porosity. The compressive strength and modulus of scaffolds without local porosity were comparable to human cortical bone and were significantly greater than the scaffolds with local porosity. Micropores in HA disks caused surface pits that increased the surface roughness as compared to non-microporous HA disks. Mouse mesenchymal stem cells extended their cell processes into these microporous pits on HA disks in vitro. ALP expression was prolonged, cell attachment strength increased, and ECM production appeared greater on microporous HA disks compared to non-microporous HA disks and tissue culture treated polystyrene controls. Scaffolds with and without microporosity were implanted in goats bones. Microporous scaffolds with rhBMP-2 increased the percent of the scaffold filled with bone tissue compared to microporous scaffolds without rhBMP-2. Lamellar bone inside scaffolds was aligned near the rods junctions whereas lamellar bone was aligned in a more random configuration away from the rod junctions. Microporous scaffolds stained darkly with toluidine blue beneath areas of contact with new bone. This

Development of сertified reference materials set for opened porosity of solid substances and materials (imitators

Directory of Open Access Journals (Sweden)

E. P. Sobina

2016-01-01

Full Text Available The article deals with data of research for development of certified reference materials set for opened porosity of solid substances and materials (imitators (OPTB SO UNIIM Set Certified Reference Materials GSO 10583-2015. The certified values of opened porosity of metal cylinders were established by the method of hydrostatic weighing before and after boring of holes in. The certified reference materials are intended for calibration and verification of measuring instruments of opened porosity, based on the Boyle - Mariotte's law.

Stochastic modelling of porosity using seismic impedances on a volume of chalk in the Dan Field

Energy Technology Data Exchange (ETDEWEB)

Vejbaek, O.V.

1995-12-31

Seismic impedances calculated from logs show very good correlation to log porosities in wells penetrating the chalk reservoir in the Dan Field, Danish North Sea. This is the basis for an attempt to use seismic impedances derived from inversion as soft data for geostatistical reservoir characterization. The study focusses on porosity description of the Maastrichtian chalk reservoir unit, laterally restricted to an area covered by a subset of a 3D seismic survey. This seismic volume was inverted using the ISIS software producing a volume of seismic impedances. Spatial porosity realizations are produced using a gaussian collocated co-simulation algorithm, where well log porosities constitute the hard data input and seismic impedances are the soft data input. The simulated volume measures 1400 m x 1525 m x 102 m and is oriented parallel to lines and cross lines in the seismic dataset. Simulated blocks measures 25 m x 25 m x 6 m equivalent to twice the line and trace spacing, and approximately equivalent to the seismic sample rate. The correlation coefficient between log porosities and impedances calculated from logs alone are shown to be misleading since they suggest unrealistic high coefficients. However, the actual data used, namely inversion derived impedances and log porosities, still show correlation coefficients in the order of -0,45, which is quite sufficient to make the inversion results very useful. It is remarkable that the calculated correlation coefficient is based on 15 wells, and the inversion is based on only one well. The negative correlation coefficient indicate that high impedances correspond to low porosities and vice-versa. The impedance data indicate the level of average porosities at locations between wells. The fine structure is produced by the geostatistic process, with averages constrained by seismic impedances. The seismic impedances derived from the inversion process are thus shown to constitute useful primary data to constrain reservoir

Porosity development in the Copper Ridge Dolomite and Maynardville Limestone, Bear Creek Valley and Chestnut Ridge, Tennessee

International Nuclear Information System (INIS)

Goldstrand, P.M.; Menefee, L.S.; Dreier, R.B.

1995-12-01

Matrix porosity data from deep core obtained in Bear Creek Valley indicate that porosities in the Maynardville Limestone are lithology and depth dependent. Matrix porosities are greater in the Cooper Ridge Dolomite than in the Maynardville Limestone, yet there is no apparent correlation with depth. Two interrelated diagenetic processes are the major controlling factors on porosity development in the Copper Ridge Dolomite and Maynardville Limestone; dissolution of evaporate minerals and dedolomitization. Both of these diagenetic processes produce matrix porosities between 2.1 and 1.3% in the Copper Ridge Dolomite and upper part of the Maynardville Limestone (Zone 6) to depths of approximately 600 ft bgs. Mean matrix porosities in Zones 5 through 2 of the Maynardville Limestone range from 0.8 to 0.5%. A large number of cavities have been intersected during drilling activities in nearly all zones of the Maynardville Limestone in Bear Creek Valley. Therefore, any maynardville Limestone zone within approximately 200 ft of the ground surface is likely to contain cavities that allow significant and rapid flow of groundwater. Zone 6 could be an important stratigraphic unit in the Maynardville Limestone for groundwater flow and contaminant transport because of the abundance of vuggy and moldic porosities. There are large variations in the thickness and lithology in the lower part of the Maynardville (Zones 2, 3, and 4 in the Burial Grounds region). The direction and velocity of strike-parallel groundwater flow may be altered in this area within the lower Maynardville Limestone

Porosity characterization for heterogeneous shales using integrated multiscale microscopy

Science.gov (United States)

Rassouli, F.; Andrew, M.; Zoback, M. D.

2016-12-01

Pore size distribution analysis plays a critical role in gas storage capacity and fluid transport characterization of shales. Study of the diverse distribution of pore size and structure in such low permeably rocks is withheld by the lack of tools to visualize the microstructural properties of shale rocks. In this paper we try to use multiple techniques to investigate the full pore size range in different sample scales. Modern imaging techniques are combined with routine analytical investigations (x-ray diffraction, thin section analysis and mercury porosimetry) to describe pore size distribution of shale samples from Haynesville formation in East Texas to generate a more holistic understanding of the porosity structure in shales, ranging from standard core plug down to nm scales. Standard 1" diameter core plug samples were first imaged using a Versa 3D x-ray microscope at lower resolutions. Then we pick several regions of interest (ROIs) with various micro-features (such as micro-cracks and high organic matters) in the rock samples to run higher resolution CT scans using a non-destructive interior tomography scans. After this step, we cut the samples and drill 5 mm diameter cores out of the selected ROIs. Then we rescan the samples to measure porosity distribution of the 5 mm cores. We repeat this step for samples with diameter of 1 mm being cut out of the 5 mm cores using a laser cutting machine. After comparing the pore structure and distribution of the samples measured form micro-CT analysis, we move to nano-scale imaging to capture the ultra-fine pores within the shale samples. At this stage, the diameter of the 1 mm samples will be milled down to 70 microns using the laser beam. We scan these samples in a nano-CT Ultra x-ray microscope and calculate the porosity of the samples by image segmentation methods. Finally, we use images collected from focused ion beam scanning electron microscopy (FIB-SEM) to be able to compare the results of porosity measurements

Porosity Gradient at the Surface of Comet 67P/Churyumov-Gerasimenko

Science.gov (United States)

Christou, C.; Dadzie, S. K.; Thomas, N.; Hartogh, P.; Jorda, L.; Kuhrt, E.; Wright, I.; Zarnecki, J.

2017-12-01

The Rosetta mission has provided invaluable and unexpected information about our knowledge and understanding of comets until now. The on-board instruments, ROSINA and VIRTIS showed the non-uniformly outgassing of H2O over the surface of the nucleus. After Philae landing in a small lobe and the attempt to intrude MUPUS into the surface led to estimate the minimum compressive strength of material > 4MPa. This high strength of material (at least locally) along with different porosity ranges that have been presented for the 67P/Churyumov-Gerasimenko (67P) challenge our understanding of the surface and outgassing processes. Here we used the micro computed tomography (micro-CT) technology to represent 3D Earth rock samples with different porosity to investigate outgassing in the near surface boundary layer. The Direct Simulation of Monte Carlo (DSMC) method is used to simulate the rarefied cometary atmosphere. We presented results with H2O outgassing at a maximum production rate near perihelion. We show that an existence of a possible porosity gradient at the surface of the comet may explain some of the structures observed on 67P.

Triple-porosity/permeability flow in faulted geothermal reservoirs: Two-dimensional effects

Energy Technology Data Exchange (ETDEWEB)

Cesar Suarez Arriaga, M. [Michoacan Univ. & CFE, Mich. (Mexico); Samaniego Verduzco, F. [National Autonomous Univ. of Mexico, Coyoacan (Mexico)

1995-03-01

An essential characteristic of some fractured geothermal reservoirs is noticeable when the drilled wells intersect an open fault or macrofracture. Several evidences observed, suggest that the fluid transport into this type of systems, occurs at least in three stages: flow between rock matrix and microfractures, flow between fractures and faults and flow between faults and wells. This pattern flow could define, by analogy to the classical double-porosity model, a triple-porosity, triple-permeability concept. From a mathematical modeling point of view, the non-linearity of the heterogeneous transport processes, occurring with abrupt changes on the petrophysical properties of the rock, makes impossible their exact or analytic solution. To simulate this phenomenon, a detailed two-dimensional geometric model was developed representing the matrix-fracture-fault system. The model was solved numerically using MULKOM with a H{sub 2}O=CO{sub 2} equation of state module. This approach helps to understand some real processes involved. Results obtained from this study, exhibit the importance of considering the triple porosity/permeability concept as a dominant mechanism producing, for example, strong pressure gradients between the reservoir and the bottom hole of some wells.

Characterization of porosity via secondary reactions. Final technical report, 1 September 1991--30 November 1995

Energy Technology Data Exchange (ETDEWEB)

Calo, J.M.; Zhang, L.; Hall, P.J.; Antxustegi, M. [Brown Univ., Providence, RI (United States). Div. of Engineering

1997-09-01

A new approach to the study of porosity and porosity development in coal chars during gasification was investigated. This approach involves the establishment of the relationships between the amount and type of surface complexes evolved during post-activation temperature programmed desorption (TPD), and the porosity, as measured by gas adsorption and small angle neutron scattering (SANS) techniques. With this new method, the total surface area and micropore volume can be determined by the interpretation of post-activation TPD spectra. The primary conclusion of this work is that it is possible to predict total surface area and micropore volume from TPD spectra. From the extended random pore model, additional information about the micropore surface area, the nonmicroporous surface area, and the mean micropore size development as a function of reaction time (or burn-off) can also be predicted. Therefore, combining the TPD technique and the extended random pore model provides a new method for the characterization of char porosity.

Modeling the effectiveness of U(VI) biomineralization in dual-porosity porous media

Science.gov (United States)

Rotter, B. E.; Barry, D. A.; Gerhard, J. I.; Small, J. S.

2011-05-01

SummaryUranium contamination is a serious environmental concern worldwide. Recent attention has focused on the in situ immobilization of uranium by stimulation of dissimilatory metal-reducing bacteria (DMRB). The objective of this work was to investigate the effectiveness of this approach in heterogeneous and structured porous media, since such media may significantly affect the geochemical and microbial processes taking place in contaminated sites, impacting remediation efficiency during biostimulation. A biogeochemical reactive transport model was developed for uranium remediation by immobile-region-resident DMRB in two-region porous media. Simulations were used to investigate the parameter sensitivities of the system over wide-ranging geochemical, microbial and groundwater transport conditions. The results suggest that optimal biomineralization is generally likely to occur when the regional mass transfer timescale is less than one-thirtieth the value of the volumetric flux timescale, and/or the organic carbon fermentation timescale is less than one-thirtieth the value of the advective timescale, and/or the mobile region porosity ranges between equal to and four times the immobile region porosity. Simulations including U(VI) surface complexation to Fe oxides additionally suggest that, while systems exhibiting U(VI) surface complexation may be successfully remediated, they are likely to display different degrees of remediation efficiency over varying microbial efficiency, mobile-immobile mass transfer, and porosity ratios. Such information may aid experimental and field designs, allowing for optimized remediation in dual-porosity (two-region) biostimulated DMRB U(VI) remediation schemes.

Dual detector pulsed neutron logging for providing indication of formation porosity

International Nuclear Information System (INIS)

Hopkinson, E.C.

1980-01-01

A new improved apparatus for determining rock formation porosity was developed which is substantially independent of the formation salinity. The improvements achieved by using differing gating intervals for the two detectors. The rock formations surrounding the earth borehole are first pulse-irradiated with discrete bursts from a high-energy neutron source. The radiations at two different points in the formation are detected and electrical signals are generated. The electrical signals from the first point are gated for a shorter time interval than those from the second point. The gated first and second electrical signals are combined to determine the porosity of the formations. (DN)

Dual detector pulsed neutron logging for providing indication of formation porosity

International Nuclear Information System (INIS)

Hopkinson, E.C.

1979-01-01

A logging instrument contains a pulsed neutron source and a pair of radiation detectors spaced along the length of the instrument. The radiation detectors are gated differently from each other to provide an indication of formation porosity which is substantially independent of the formation salinity. In the preferred embodiment, the electrical signals indicative of radiation detected by the long-spaced detector are gated for almost the entire interval between neutron pulses and the short-spaced signals are gated for a significantly smaller time interval which commences soon after the termination of a given neutron burst. The signals from the two detectors are combined in a ratio circuit for determination of porosity

Quantifying multiscale porosity and fracture aperture distribution in granite cores using computed tomography

Science.gov (United States)

Wenning, Quinn; Madonna, Claudio; Joss, Lisa; Pini, Ronny

2017-04-01

Knowledge of porosity and fracture (aperture) distribution is key towards a sound description of fluid transport in low-permeability rocks. In the context of geothermal energy development, the ability to quantify the transport properties of fractures is needed to in turn quantify the rate of heat transfer, and, accordingly, to optimize the engineering design of the operation. In this context, core-flooding experiments coupled with non-invasive imaging techniques (e.g., X-Ray Computed Tomography - X-Ray CT) represent a powerful tool for making direct observations of these properties under representative geologic conditions. This study focuses on quantifying porosity and fracture aperture distribution in a fractured westerly granite core by using two recently developed experimental protocols. The latter include the use of a highly attenuating gas [Vega et al., 2014] and the application of the so-called missing CT attenuation method [Huo et al., 2016] to produce multidimensional maps of the pore space and of the fractures. Prior to the imaging experiments, the westerly granite core (diameter: 5 cm, length: 10 cm) was thermally shocked to induce micro-fractured pore space; this was followed by the application of the so-called Brazilian method to induce a macroscopic fracture along the length of the core. The sample was then mounted in a high-pressure aluminum core-holder, exposed to a confining pressure and placed inside a medical CT scanner for imaging. An initial compressive pressure cycle was performed to remove weak asperities and reduce the hysteretic behavior of the fracture with respect to effective pressure. The CT scans were acquired at room temperature and 0.5, 5, 7, and 10 MPa effective pressure under loading and unloading conditions. During scanning the pore fluid pressure was undrained and constant, and the confining pressure was regulated at the desired pressure with a high precision pump. Highly transmissible krypton and helium gases were used as

Porosity and wear resistance of flame sprayed tungsten carbide coatings

Science.gov (United States)

Winarto, Winarto; Sofyan, Nofrijon; Rooscote, Didi

2017-06-01

Thermal-sprayed coatings offer practical and economical solutions for corrosion and wear protection of components or tools. To improve the coating properties, heat treatment such as preheat is applied. The selection of coating and substrate materials is a key factor in improving the quality of the coating morphology after the heat treatment. This paper presents the experimental results regarding the effect of preheat temperatures, i.e. 200°C, 300°C and 400°C, on porosity and wear resistance of tungsten carbide (WC) coating sprayed by flame thermal coating. The powders and coatings morphology were analyzed by a Field Emission Scanning Electron Microscope equipped with Energy Dispersive Spectrometry (FE-SEM/EDS), whereas the phase identification was performed by X-Ray diffraction technique (XRD). In order to evaluate the quality of the flame spray obtained coatings, the porosity, micro-hardness and wear rate of the specimens was determined. The results showed that WC coating gives a higher surface hardness from 1391 HVN up to 1541 HVN compared to that of the non-coating. Moreover, the wear rate increased from 0.072 mm3/min. to 0.082 mm3/min. when preheat temperature was increased. Preheat on H13 steel substrate can reduce the percentage of porosity level from 10.24 % to 3.94% on the thermal spray coatings.

A functionally gradient variational porosity architecture for hollowed scaffolds fabrication

Energy Technology Data Exchange (ETDEWEB)

Khoda, A K M [Department of Industrial Engineering, University at Buffalo, Buffalo, NY 14260 (United States); Ozbolat, Ibrahim T [Department of Mechanical and Industrial Engineering, Center for Computer Aided Design, University of Iowa, Iowa City, IA 52242-1527 (United States); Koc, Bahattin, E-mail: bahattinkoc@sabanciuniv.edu [Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956 (Turkey)

2011-09-15

This paper presents a novel continuous tool-path planning methodology for hollowed scaffold fabrication in tissue engineering. A new functionally gradient porous architecture is proposed with a continuous material deposition planning scheme. A controllable variational pore size and hence the porosity have been achieved with a combination of two geometrically oriented consecutive layers. The desired porosity has been achieved with consecutive layers by geometrically partitioning each layer into sub-regions based on the area and the tissue scaffold design constraints. A continuous, interconnected and optimized tool-path for layers has been generated for a three-dimensional biomaterial deposition/printing process. A zigzag pattern tool-path has been proposed for an accumulated sub-region layer, and a concentric spiral-like optimal tool-path pattern has been generated for the successive layer to ensure continuity along the structure. Three-dimensional layers, formed by the proposed tool-path plan, vary the pore size and the porosity based on the biological and mechanical requirements. Several examples demonstrate the proposed methodology along with illustrative results. Also a comparative study between the proposed design and conventional Cartesian coordinate scaffolds has been performed. The results demonstrate a significant reduction in design error with the proposed method. Moreover, sample examples have been fabricated using a micro-nozzle biomaterial deposition system, and characterized for validation.

A functionally gradient variational porosity architecture for hollowed scaffolds fabrication

International Nuclear Information System (INIS)

Khoda, A K M; Ozbolat, Ibrahim T; Koc, Bahattin

2011-01-01

This paper presents a novel continuous tool-path planning methodology for hollowed scaffold fabrication in tissue engineering. A new functionally gradient porous architecture is proposed with a continuous material deposition planning scheme. A controllable variational pore size and hence the porosity have been achieved with a combination of two geometrically oriented consecutive layers. The desired porosity has been achieved with consecutive layers by geometrically partitioning each layer into sub-regions based on the area and the tissue scaffold design constraints. A continuous, interconnected and optimized tool-path for layers has been generated for a three-dimensional biomaterial deposition/printing process. A zigzag pattern tool-path has been proposed for an accumulated sub-region layer, and a concentric spiral-like optimal tool-path pattern has been generated for the successive layer to ensure continuity along the structure. Three-dimensional layers, formed by the proposed tool-path plan, vary the pore size and the porosity based on the biological and mechanical requirements. Several examples demonstrate the proposed methodology along with illustrative results. Also a comparative study between the proposed design and conventional Cartesian coordinate scaffolds has been performed. The results demonstrate a significant reduction in design error with the proposed method. Moreover, sample examples have been fabricated using a micro-nozzle biomaterial deposition system, and characterized for validation.

A functionally gradient variational porosity architecture for hollowed scaffolds fabrication.

Science.gov (United States)

Khoda, A K M; Ozbolat, Ibrahim T; Koc, Bahattin

2011-09-01

This paper presents a novel continuous tool-path planning methodology for hollowed scaffold fabrication in tissue engineering. A new functionally gradient porous architecture is proposed with a continuous material deposition planning scheme. A controllable variational pore size and hence the porosity have been achieved with a combination of two geometrically oriented consecutive layers. The desired porosity has been achieved with consecutive layers by geometrically partitioning each layer into sub-regions based on the area and the tissue scaffold design constraints. A continuous, interconnected and optimized tool-path for layers has been generated for a three-dimensional biomaterial deposition/printing process. A zigzag pattern tool-path has been proposed for an accumulated sub-region layer, and a concentric spiral-like optimal tool-path pattern has been generated for the successive layer to ensure continuity along the structure. Three-dimensional layers, formed by the proposed tool-path plan, vary the pore size and the porosity based on the biological and mechanical requirements. Several examples demonstrate the proposed methodology along with illustrative results. Also a comparative study between the proposed design and conventional Cartesian coordinate scaffolds has been performed. The results demonstrate a significant reduction in design error with the proposed method. Moreover, sample examples have been fabricated using a micro-nozzle biomaterial deposition system, and characterized for validation.

P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

Directory of Open Access Journals (Sweden)

D. Draebing

2012-10-01

Full Text Available P-wave refraction seismics is a key method in permafrost research but its applicability to low-porosity rocks, which constitute alpine rock walls, has been denied in prior studies. These studies explain p-wave velocity changes in freezing rocks exclusively due to changing velocities of pore infill, i.e. water, air and ice. In existing models, no significant velocity increase is expected for low-porosity bedrock. We postulate, that mixing laws apply for high-porosity rocks, but freezing in confined space in low-porosity bedrock also alters physical rock matrix properties. In the laboratory, we measured p-wave velocities of 22 decimetre-large low-porosity (< 10% metamorphic, magmatic and sedimentary rock samples from permafrost sites with a natural texture (> 100 micro-fissures from 25 °C to −15 °C in 0.3 °C increments close to the freezing point. When freezing, p-wave velocity increases by 11–166% perpendicular to cleavage/bedding and equivalent to a matrix velocity increase from 11–200% coincident to an anisotropy decrease in most samples. The expansion of rigid bedrock upon freezing is restricted and ice pressure will increase matrix velocity and decrease anisotropy while changing velocities of the pore infill are insignificant. Here, we present a modified Timur's two-phase-equation implementing changes in matrix velocity dependent on lithology and demonstrate the general applicability of refraction seismics to differentiate frozen and unfrozen low-porosity bedrock.

The Influence of Home Scrap on Porosity of MgAl9Zn1 Alloy Pressure Castings

Directory of Open Access Journals (Sweden)

Konopka Z.

2017-03-01

Full Text Available The work presents the results of examinations concerning the influence of various amounts of home scrap additions on the porosity of castings made of MgAl9Zn1 alloy. The fraction of home scrap in the metal charge ranged from 0 to 100%. Castings were pressure cast by means of the hot-chamber pressure die casting machine under the industrial conditions in one of the domestic foundries. Additionally, for the purpose of comparison, the porosity of specimens cut out directly of the MgAl9Zn1 ingot alloy was also determined. The examinations consisted in the qualitative assessment of porosity by means of the optical microscopy and its quantitative determination by the method of weighting specimens in air and in water. It was found during the examination that the porosity of castings decreases with an increase in the home scrap fraction in the metal charge. The qualitative examinations confirmed the beneficial influence of the increased home scrap fraction on the porosity of castings. It was concluded that the reusing of home scrap in a foundry can be a good way of reduction of costs related to the production of pressure castings.

Porosity, Mineralization, Tissue Type and Morphology Interactions at the Human Tibial Cortex

Science.gov (United States)

Hampson, Naomi A.

Prior research has shown a relationship between tibia robustness (ratio of cross-sectional area to bone length) and stress fracture risk, with less robust bones having a higher risk, which may indicate a compensatory increase in elastic modulus to increase bending strength. Previous studies of human tibiae have shown higher ash content in slender bones. In this study, the relationships between variations in volumetric porosity, ash content, tissue mineral density, secondary bone tissue, and cross sectional geometry, were investigated in order to better understand the tissue level adaptations that may occur in the establishment of cross-sectional properties. In this research, significant differences were found between porosity, ash content, and tissue type around the cortex between robust and slender bones, suggesting that there was a level of co-adaption occurring. Variation in porosity correlated with robustness, and explained large parts of the variation in tissue mineral density. The nonlinear relationship between porosity and ash content may support that slender bones compensate for poor geometry by increasing ash content through reduced remodeling, while robust individuals increase porosity to decrease mass, but only to a point. These results suggest that tissue level organization plays a compensatory role in the establishment of adult bone mass, and may contribute to differences in bone aging between different bone phenotypes. The results suggest that slender individuals have significantly less remodeled bone, however the proportion of remodeled bone was not uniform around the tibia. In the complex results of the study of 38% vs. 66% sites the distal site was subject to higher strains than the 66% site, indicating both local and global regulators may be affecting overall remodeling rates and need to be teased apart in future studies. This research has broad clinical implications on the diagnosis and treatment of fragility fractures. The relationships that

Acoustics of a Mixed Porosity Felt Airfoil

Science.gov (United States)

2016-06-06

NUWC-NPT Technical Report 12,212 6 June 2016 Acoustics of a Mixed Porosity Felt Airfoil Aren M. Hellum Undersea Warfare Weapons...Felt Airfoil 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Aren M. Hellum 5.d PROJECT NUMBER 5e...existing literature. Geyer et al. [5] measured a sound reduction of 5 to 15 dB for airfoils made entirely of porous material. A 1973 patent

Origin of two time-scale regimes in potentiometric titration of metal oxides. A replica kinetic Monte Carlo study

International Nuclear Information System (INIS)

Zarzycki, Piotr P.; Rosso, Kevin M.

2009-01-01

Replica Kinetic Monte Carlo simulations were used to study the characteristic time scales of potentiometric titration of the metal oxides and (oxy)hydroxides. The effect of surface heterogeneity and surface transformation on the titration kinetics were also examined. Two characteristic relaxation times are often observed experimentally, with the trailing slower part attributed to surface non-uniformity, porosity, polymerization, amorphization, and other dynamic surface processes induced by unbalanced surface charge. However, our simulations show that these two characteristic relaxation times are intrinsic to the proton binding reaction for energetically homogeneous surfaces, and therefore surface heterogeneity or transformation do not necessarily need to be invoked. However, all such second-order surface processes are found to intensify the separation and distinction of the two kinetic regimes. The effect of surface energetic-topographic non-uniformity, as well dynamic surface transformation, interface roughening/smoothing were described in a statistical fashion. Furthermore, our simulations show that a shift in the point-of-zero charge is expected from increased titration speed and the pH-dependence of the titration measurement error is in excellent agreement with experimental studies.

Origin of two time-scale regimes in potentiometric titration of metal oxides. A replica kinetic Monte Carlo study.

Science.gov (United States)

Zarzycki, Piotr; Rosso, Kevin M

2009-06-16

Replica kinetic Monte Carlo simulations were used to study the characteristic time scales of potentiometric titration of the metal oxides and (oxy)hydroxides. The effect of surface heterogeneity and surface transformation on the titration kinetics were also examined. Two characteristic relaxation times are often observed experimentally, with the trailing slower part attributed to surface nonuniformity, porosity, polymerization, amorphization, and other dynamic surface processes induced by unbalanced surface charge. However, our simulations show that these two characteristic relaxation times are intrinsic to the proton-binding reaction for energetically homogeneous surfaces, and therefore surface heterogeneity or transformation does not necessarily need to be invoked. However, all such second-order surface processes are found to intensify the separation and distinction of the two kinetic regimes. The effect of surface energetic-topographic nonuniformity, as well dynamic surface transformation, interface roughening/smoothing were described in a statistical fashion. Furthermore, our simulations show that a shift in the point-of-zero charge is expected from increased titration speed, and the pH-dependence of the titration measurement error is in excellent agreement with experimental studies.

Ageing-induced enhancement of open porosity of mesoporous silica films studied by positron annihilation spectroscopy

International Nuclear Information System (INIS)

He Chunqing; Muramatsu, Makoto; Oshima, Nagayasu; Ohdaira, Toshiyuki; Kinomura, Atsushi; Suzuki, Ryoichi

2006-01-01

We show that ageing of the silica sol in a closed vessel enhanced the open porosity of calcined mesoporous silica film studied by positron. Positron annihilation lifetime spectroscopy (PALS) based on a pulsed slow positron beam was used to estimate the mesopore size. 2-dimensional PALS (2D-PALS) and ortho-positronium time-of-flight (Ps-TOF) were used to evaluate the open porosity, interconnectivity and tortuosity of mesopores in the silica films. Results revealed that little change in pore size but significant enhancement of open porosity and/or pore interconnectivity occurred in the silica film deposited after the precursor solution aged for a relative longer time

ELECTRODEPOSITION OF COPPER IONS ON FIXED BED ELECTRODES: KINETIC AND HYDRODYNAMIC STUDY

Directory of Open Access Journals (Sweden)

L.A.M. Ruotolo

2002-03-01

Full Text Available The kinetic and hydrodynamic behaviour of a fixed-bed electrochemical reactor was studied in terms of current efficiency (CE and energy efficiency (EE. In the kinetic experiments the effects of fixed bed thickness (L, current density (i and initial concentration of copper (C0 were studied. In the hydrodynamic experiments the permeability (k of the electrode and the coefficient for inertial forces (c were also studied as functions of the applied current density. At low current densities and bed thicknesses greater than 1.0 cm, negative CE and EE were observed as a consequence of the dissolution of the porous matrix. At high current densities low CE and EE were observed and a powdery deposit was formed on the surface of the particles. From the results of the kinetic study bed thickness and the range of current densities employed in the hydrodynamic experiments were chosen. In these experiments the electrodeposition process continued until the whole electrode had been clogged and no more electrolyte could pass through it. The relationship between pressure drop and flow rate was well described by the Forchheimer equation. It was observed that the reduction in porosity due to copper electrodeposition causes the flow rate to decrease because of the decrease in electrode permeability, but it had no influence on current efficiency.

Low serum vitamin D is associated with higher cortical porosity in elderly men.

Science.gov (United States)

Sundh, D; Mellström, D; Ljunggren, Ö; Karlsson, M K; Ohlsson, C; Nilsson, M; Nilsson, A G; Lorentzon, M

2016-11-01

Bone loss at peripheral sites in the elderly is mainly cortical and involves increased cortical porosity. However, an association between bone loss at these sites and 25-hydroxyvitamin D has not been reported. To investigate the association between serum levels of 25-hydroxyvitamin D, bone microstructure and areal bone mineral density (BMD) in elderly men. A population-based cohort of 444 elderly men (mean ± SD age 80.2 ± 3.5 years) was investigated. Bone microstructure was measured by high-resolution peripheral quantitative computed tomography, areal BMD by dual-energy X-ray absorptiometry and serum 25-hydroxyvitamin D and parathyroid hormone levels by immunoassay. Mean cortical porosity at the distal tibia was 14.7% higher (12.5 ± 4.3% vs. 10.9 ± 4.1%, P vitamin D levels compared to the highest. In men with vitamin D deficiency (6.8 pmol L -1 )], cortical porosity was 17.2% higher than in vitamin D-sufficient men (P vitamin D supplementation and parathyroid hormone showed that 25-hydroxyvitamin D independently predicted cortical porosity (standardized β = -0.110, R 2 = 1.1%, P = 0.024), area (β = 0.123, R 2 = 1.4%, P = 0.007) and cortical volumetric BMD (β = 0.125, R 2 = 1.4%, P = 0.007) of the tibia as well as areal BMD of the femoral neck (β = 0.102, R 2 = 0.9%, P = 0.04). Serum vitamin D is associated with cortical porosity, area and density, indicating that bone fragility as a result of low vitamin D could be due to changes in cortical bone microstructure and geometry. © 2016 The Authors. Journal of Internal Medicine published by John Wiley & Sons Ltd on behalf of Association for Publication of The Journal of Internal Medicine.

Three frequency modulated combination thermal neutron lifetime log and porosity

International Nuclear Information System (INIS)

Paap, H.J.; Arnold, D.M.; Smith, M.P.

1976-01-01

Methods are disclosed for measuring simultaneously the thermal neutron lifetime of the borehole fluid and earth formations in the vicinity of a well borehole, together with the formation porosity. A harmonically intensity modulated source of fast neutrons is used to irradiate the earth formations with fast neutrons at three different modulation frequencies. Intensity modulated clouds of thermal neutrons at each of the three modulation frequencies are detected by dual spaced detectors and the relative phase shift of the thermal neutrons with respect to the fast neutrons is determined at each of the three modulation frequencies at each detector. These measurements are then combined to determine simultaneously the thermal neutron decay time of the borehole fluid, the thermal neutron decay time of surrounding earth formation media and the porosity of the formation media

Establishment of a permeability/porosity equation for salt grit and damming materials

International Nuclear Information System (INIS)

Fein, E.; Mueller-Lyda, I.; Storck, R.

1996-09-01

The flow resistance of stowing and sealing materials hinder the transport of brines in an ultimate storage site in salt rock strata. This effect can be seen when brines flow into the storage areas and when contaminated brines are pressed out of the underground structure. The main variable determining flow resistance is permeability. The convergence process induced by rock pressure reduces the size of the available residual cavern and also the permeability of the stowing and sealing materials. In the long-term safety analyses carried out so far, the interdependence between porosity and permeability in the case of salt grit was commonly described by a power function. The present investigation uses the data available until the end of 1994 to derive an improved relation between permeability and porosity for salt grit stowing material. The results obtained show that the power function used until now is still applicable with only a slight modification of parameters. In addition, the statistical distribution functions of the correlated parameters of the permeability/porosity relation were determined for the first time for a probabilistic safety analysis. (orig./DG) [de

Effects of thermally induced porosity on an as-HIP powder metallurgy superalloy

Science.gov (United States)

Dreshfield, R. L.; Miner, R. V., Jr.

1980-01-01

The effect of thermally induced porosity on the mechanical properties of an as-hot-isostatically pressed and heat-treated pressing made from low carbon Astroloy is examined. Tensile, stress-rupture, creep, and low cycle fatigue tests were performed and the results were compared with industrial acceptance criteria. It is shown that the porous pressing has a porosity gradient from the rim to the bore with the bore having 1-1/2% greater porosity. Mechanical properties of the test ring below acceptance level are tensile reduction in area at room temperature and 538 C and time for 0.1% creep at 704 C. It is also found that the strength, ductility, and rupture life of the rim are slightly inferior to those of the rim of the sound pressings, while those of the bore are generally below the acceptable level. At strain ranges typical of commercial aircraft engines, the low cycle fatigue life of the rim of the porous pressings is slightly lower than that of the sound pressings.

Paleokarst and reservoir porosity in the Ordovician Beekmantown Dolomite of the central Appalachian basin

Science.gov (United States)

Smosna, R.; Bruner, K.R.; Riley, R.A.

2005-01-01

A karst-unconformity play at the top of the Ordovician Beekmantown Dolomite is judged to have great petroleum potential in Ohio and adjacent states; wells have high ultimate reserves and large areas remain untested. To better understand the origin, development, and distribution of Beekmantown porosity, we conducted a petrologic-stratigraphic study of cores and thin sections from 15 oil and gas wells. The massive dolomite, characterized by a hypidiotopic-idiotopic texture, formed by the replacement of stacked peritidal carbonate cycles. Secondary porosity occurs at two scales: (1) mesoscopic - breccia porosity, solution-enlarged fractures, large vugs, and caverns, and (2) microscopic - intercrystalline, intracrystalline, molds, small vugs, and microfractures. Mesoscopic pores (providing the major storage capacity in this reservoir) were produced by intrastratal solution and collapse of carbonate layers, whereas microscopic pores (connecting the larger pores) generally formed by the leaching of individual carbonate grains and crystals. Most pore types developed during periods of subaerial exposure across the carbonate bank, tied to either the numerous, though brief falls of relative sea level during Beekmantown deposition or more importantly the prolonged Knox unconformity at the close of sedimentation. The distribution of reservoir-quality porosity is quite heterogeneous, being confined vertically to a zone immediately below the unconformity and best developed laterally beneath buried hills and noses of this erosion surface. The inferred, shallow flow of ground water in the Beekmantown karst, primarily below topographic highs and above a diagenetic base level close to the water table, led to this irregular distribution of porosity.

Bulk density and porosity distributions in a compost pile

NARCIS (Netherlands)

Ginkel, van J.T.; Raats, P.A.C.; Haneghem, van I.A.

1999-01-01

This paper mainly deals with the description of the initial distribution of bulk density and porosity at the moment a compost pile is built or rebuilt. A relationship between bulk density and vertical position in a pile is deduced from theoretical and empirical considerations. Formulae to calculate

Non-destructive evaluation of porosity and its effect on mechanical properties of carbon fiber reinforced polymer composite materials

Science.gov (United States)

Bhat, M. R.; Binoy, M. P.; Surya, N. M.; Murthy, C. R. L.; Engelbart, R. W.

2012-05-01

In this work, an attempt is made to induce porosity of varied levels in carbon fiber reinforced epoxy based polymer composite laminates fabricated using prepregs by varying the fabrication parameters such as applied vacuum, autoclave pressure and curing temperature. Different NDE tools have been utilized to evaluate the porosity content and correlate with measurable parameters of different NDE techniques. Primarily, ultrasonic imaging and real time digital X-ray imaging have been tried to obtain a measurable parameter which can represent or reflect the amount of porosity contained in the composite laminate. Also, effect of varied porosity content on mechanical properties of the CFRP composite materials is investigated through a series of experimental investigations. The outcome of the experimental approach has yielded interesting and encouraging trend as a first step towards developing an NDE tool for quantification of effect of varied porosity in the polymer composite materials.

On the role of melt flow into the surface structure and porosity development during selective laser melting

International Nuclear Information System (INIS)

Qiu, Chunlei; Panwisawas, Chinnapat; Ward, Mark; Basoalto, Hector C.; Brooks, Jeffery W.; Attallah, Moataz M.

2015-01-01

In this study, the development of surface structure and porosity of Ti–6Al–4V samples fabricated by selective laser melting under different laser scanning speeds and powder layer thicknesses has been studied and correlated with the melt flow behaviour through both experimental and modelling approaches. The as-fabricated samples were investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The interaction between laser beam and powder particles was studied by both high speed imaging observation and computational fluid dynamics (CFD) calculation. It was found that at a high laser power and a fixed powder layer thickness (20 μm), the samples contain particularly low porosity when the laser scanning speeds are below 2700 mm/s. Further increase of scanning speed led to increase of porosity but not significantly. The porosity is even more sensitive to powder layer thickness with the use of thick powder layers (above 40 μm) leading to significant porosity. The increase of porosity with laser scanning speed and powder layer thickness is not inconsistent with the observed increase in surface roughness complicated by increasingly irregular-shaped laser scanned tracks and an increased number of discontinuity and cave-like pores on the top surfaces. The formation of pores and development of rough surfaces were found by both high speed imaging and modelling, to be strongly associated with unstable melt flow and splashing of molten material

Effects of porosity on corrosion resistance of Mg alloy foam produced by powder metallurgy technology

Energy Technology Data Exchange (ETDEWEB)

Aghion, E., E-mail: egyon@bgu.ac.il; Perez, Y.

2014-10-15

Magnesium alloy foams have the potential to serve as structural material for regular light-weight applications as well as for biodegradable scaffold implants. However, their main disadvantage relates to the high reactivity of magnesium and consequently their natural tendency to corrode in regular service conditions and in physiological environments. The present study aims at evaluating the effect of porosity on the corrosion resistance of MRI 201S magnesium alloy foams in 0.9% NaCl solution and in phosphate buffer saline solution as a simulated physiological electrolyte. The magnesium foams were produced by powder metallurgy technology using space-holding particles to control the porosity content. Machined chips were used as raw material for the production of Mg alloy powder by milling process. The microstructure of the foams was examined using optical and scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analysis. The corrosion behavior was evaluated by immersion test and potentiodynamic polarization analysis. The results obtained clearly demonstrate that the porosity has a significant effect on the corrosion resistance of the tested foams. Foams with 14–19% porosity have a corrosion rate of 4–10 mcd and 7–15 mcd in NaCl and phosphate buffer saline solution, respectively, compared to only 0.10 mcd for the same alloy in as cast conditions. This increased corrosion degradation of the Mg foams by more than one order of magnitude compared to the cast alloy may limit their potential application in regular and physiological environments. - Highlights: • Porosity has a detrimental effect on corrosion resistance of MRI 201S Mg foams. • 14–19% porosity increases the corrosion rate by more than one order of magnitude. • Accelerated corrosion limits the use of foams in regular/physiological environments.

Visualization and prediction of porosity in roller compacted ribbonswith near infrared chemical imaging (NIR-CI)

DEFF Research Database (Denmark)

Khorasani, Milad Rouhi; Amigo Rubio, Jose Manuel; Sonnergaard, Jørn

2015-01-01

The porosity of roller compacted ribbon is recognized as an important critical quality attribute which has a huge impact on the final product quality. The purpose of this study was to investigate the use of near-infrared chemical imaging (NIR-CI) for porosity estimation of ribbons produced...... and control of continuously operating roller compaction line....

Porosity influence on UO2 pellet fracture

International Nuclear Information System (INIS)

Quadros, N.F. de; Abreu Aires, M. de; Gentile, E.F.

1976-01-01

Compression tests were made with UO 2 pellets with grain size of 0,01 mm, approximately the same for all pellets, and with different porosities. The strain rate was 5,5 X 10 -5 sec -1 at room temperature. From fractographic studies and observations made during the compression tests, it was suggested that the pores and flaws resulting from sintering at 1650 0 C, play a fundamental role on the fracture mechanism of the UO 2 pellets [pt

Application of a novel cellular automaton porosity prediction model to aluminium castings

International Nuclear Information System (INIS)

Atwood, R.C.; Chirazi, A.; Lee, P.D.

2002-01-01

A multiscale model was developed to predict the formation of porosity within a solidifying aluminium-silicon alloy. The diffusion of silicon and dissolved gas was simulated on a microscopic scale combined with cellular automaton models of gas porosity formation within the growing three-dimensional solidification microstructure. However, due to high computational cost, the modelled volume is limited to the millimetre range. This renders the application of direct modelling of complex shape castings unfeasible. Combining the microstructural modelling with a statistical response-surface prediction method allows application of the microstructural model results to industrial scale casts by incorporating them in commercial solidification software. (author)

Anomalously high porosity in subduction inputs to the Nankai Trough (SW Japan) potentially caused by volcanic ash and pumice

Science.gov (United States)

Huepers, A.; Ikari, M.; Underwood, M.; Kopf, A.

2013-12-01

At convergent margins, the sedimentary section seaward of the trench on the subducting oceanic lithosphere provides the source material for accretionary prisms and eventually becomes the host rock of the plate boundary megathrust. The mechanical properties of the sediments seaward of the subduction zone have therefore a first order control on subduction zone forearc mechanics and hydrogeology. At the Nankai Trough (SW Japan) the majority of sediment approaching the subduction zone is clay-rich. Scientific drilling expeditions in the framework of the Ocean Drilling Program (ODP) and the Integrated Ocean Drilling Program (IODP) have revealed an anomalous zone of high porosity in a major lithologic unit known as the Upper Shikoku Basin facies (USB), which is associated with elevated volcanic ash content and high amounts of silica in the interstitial water. The existence of the high porosity zone has previously been associated with advanced silica cementation, driven by the dual diagenetic transition of opal-A to opal-CT, and opal-CT to quartz. However, temperature estimates from recent drilling expeditions offshore the Kii peninsula reveal different in situ temperatures at the proposed diagenetic boundary in the Shikoku Basin. Furthermore, laboratory measurements using core samples from the USB show that cohesive strength is not elevated in the high porosity zone, suggesting that a process other than cementation may be responsible. The USB sediment is characterized by abundant volcanic ash and pumice, therefore the high porosity zone in the USB may be closely linked to the mechanical behavior of this phase. We conducted consolidation tests in the range 0.1 to 8 MPa effective vertical stress on artificial ash-smectite and pumice-smectite mixtures, as well as intact and remolded natural samples from the IODP Sites C0011 and C0012 to investigate the role of the volcanic constituent on porosity loss with progressive burial. Our results show that both remolded and intact

The Influence of Heat Treatments on the Porosity of Suspension Plasma-Sprayed Yttria-Stabilized Zirconia Coatings

Science.gov (United States)

Ekberg, Johanna; Ganvir, Ashish; Klement, Uta; Creci, Simone; Nordstierna, Lars

2018-02-01

Suspension plasma-sprayed coatings are produced using fine-grained feedstock. This allows to control the porosity and to achieve low thermal conductivity which makes the coatings attractive as topcoats in thermal barrier coatings (TBCs). Used in gas turbine applications, TBCs are exposed to high temperature exhaust gases which lead to microstructure alterations. In order to obtain coatings with optimized thermomechanical properties, microstructure alterations like closing of pores and opening of cracks have to be taken into account. Hence, in this study, TBC topcoats consisting of 4 mol.% yttria-stabilized zirconia were heat-treated in air at 1150 °C and thereafter the coating porosity was investigated using image analysis (IA) and nuclear magnetic resonance (NMR) cryoporometry. Both IA and NMR cryoporometry showed that the porosity changed as a result of the heat treatment for all investigated coatings. In fact, both techniques showed that the fine porosity decreased as a result of the heat treatment, while IA also showed an increase in the coarse porosity. When studying the coatings using scanning electron microscopy, it was noticed that finer pores and cracks disappeared and larger pores grew slightly and achieved a more distinct shape as the material seemed to become more compact.

Assessment of scaffold porosity: the new route of micro-CT.

Science.gov (United States)

Bertoldi, Serena; Farè, Silvia; Tanzi, Maria Cristina

2011-01-01

A complete morphologic characterization of porous scaffolds for tissue engineering application is fundamental, as the architectural parameters, in particular porosity, strongly affect the mechanical and biological performance of the structures. Therefore, appropriate techniques for this purpose need to be selected. Several techniques for the assessment of scaffold porosity have been proposed, including Scanning Electron Microscopy observation, mercury and liquid extrusion porosimetry, gas pycnometry, and capillary flow porometry. Each of these techniques has several drawbacks and, a combination of different techniques is often required so as to achieve an in depth study of the morphologic properties of the scaffold. A single technique is often limited and suitable only for the assessment of a specific parameter. To overcome this limit, the most attractive option would be a single nondestructive technique, yet capable of providing a comprehensive set of data. It appears that micro-computed tomography (micro-CT) can potentially fulfill this role. Initially developed to characterize the 3D trabecular microarchitecture of bone, its use has been recently exploited by researchers for the morphologic characterization of porous biomaterials, as it enables obtaining a full assessment of the porous structures both in terms of pore size and interconnected porosity. This review aims to explore the use of micro-CT in scaffold characterization, comparing it with other previously developed techniques; we also focus on the contribution of this innovative tool to the development of scaffold-based tissue engineering application.

An interlaboratory comparison of methods for measuring rock matrix porosity

International Nuclear Information System (INIS)

Rasilainen, K.; Hellmuth, K.H.; Kivekaes, L.; Ruskeeniemi, T.; Melamed, A.; Siitari-Kauppi, M.

1996-09-01

An interlaboratory comparison study was conducted for the available Finnish methods of rock matrix porosity measurements. The aim was first to compare different experimental methods for future applications, and second to obtain quality assured data for the needs of matrix diffusion modelling. Three different versions of water immersion techniques, a tracer elution method, a helium gas through-diffusion method, and a C-14-PMMA method were tested. All methods selected for this study were established experimental tools in the respective laboratories, and they had already been individually tested. Rock samples for the study were obtained from a homogeneous granitic drill core section from the natural analogue site at Palmottu. The drill core section was cut into slabs that were expected to be practically identical. The subsamples were then circulated between the different laboratories using a round robin approach. The circulation was possible because all methods were non-destructive, except the C-14-PMMA method, which was always the last method to be applied. The possible effect of drying temperature on the measured porosity was also preliminarily tested. These measurements were done in the order of increasing drying temperature. Based on the study, it can be concluded that all methods are comparable in their accuracy. The selection of methods for future applications can therefore be based on practical considerations. Drying temperature seemed to have very little effect on the measured porosity, but a more detailed study is needed for definite conclusions. (author) (4 refs.)

Anisotropic and Hierarchical Porosity in Multifunctional Ceramics

Science.gov (United States)

Lichtner, Aaron Zev

The performance of multifunctional porous ceramics is often hindered by the seemingly contradictory effects of porosity on both mechanical and non-structural properties and yet a sufficient body of knowledge linking microstructure to these properties does not exist. Using a combination of tailored anisotropic and hierarchical materials, these disparate effects may be reconciled. In this project, a systematic investigation of the processing, characterization and properties of anisotropic and isotropic hierarchically porous ceramics was conducted. The system chosen was a composite ceramic intended as the cathode for a solid oxide fuel cell (SOFC). Comprehensive processing investigations led to the development of approaches to make hierarchical, anisotropic porous microstructures using directional freeze-casting of well dispersed slurries. The effect of all the important processing parameters was investigated. This resulted in an ability to tailor and control the important microstructural features including the scale of the microstructure, the macropore size and total porosity. Comparable isotropic porous ceramics were also processed using fugitive pore formers. A suite of characterization techniques including x-ray tomography and 3-D sectional scanning electron micrographs (FIB-SEM) was used to characterize and quantify the green and partially sintered microstructures. The effect of sintering temperature on the microstructure was quantified and discrete element simulations (DEM) were used to explain the experimental observations. Finally, the comprehensive mechanical properties, at room temperature, were investigated, experimentally and using DEM, for the different microstructures.

Densification and grain growth kinetics of Ce_0.9Gd_0.1O_1.95 in tape cast layers: The influence of porosity

DEFF Research Database (Denmark)

Ni, De Wei; Esposito, Vincenzo; Foghmoes, Søren Preben Vagn

2014-01-01

process at the initial sintering stage at T constitutive laws indicate......The sintering behavior of Ce0.9Gd0.1O1.95(CGO) tape cast layers with different porosity was investigated by an extensive characterization of densification, microstructural evolution, and applying the constitutive laws of sintering. The densification of CGO tapes associates with grain coarsening...

Instability of an infiltration-driven dissolution-precipitation front with a nonmonotonic porosity profile

Science.gov (United States)

Kondratiuk, Paweł; Dutka, Filip; Szymczak, Piotr

2016-04-01

Infiltration of a rock by an external fluid very often drives it out of chemical equilibrium. As a result, alteration of the rock mineral composition occurs. It does not however proceed uniformly in the entire rock volume. Instead, one or more reaction fronts are formed, which are zones of increased chemical activity, separating the altered (product) rock from the yet unaltered (primary) one. The reaction fronts propagate with velocities which are usually much smaller than those of the infiltrating fluid. One of the simplest examples of such alteration is the dissolution of some of the minerals building the primary rock. For instance, calcium carbonate minerals in the rock matrix can be dissolved by infiltrating acidic fluids. In such a case the product rock has higher porosity and permeability than the primary one. Due to positive feedbacks between the reactant transport, fluid flow, and porosity generation, the reaction fronts in porosity-generating replacement systems are inherently unstable. An arbitrarily small protrusion of the front gets magnified and develops into a highly porous finger-like or funnel-like structure. This feature of dissolution fronts, dubbed the "reactive-infiltration instability" [1], is responsible for the formation of a number of geological patterns, such as solution pipes or various karst forms. It is also of practical importance, since spontaneous front breakup and development of localized highly porous flow paths (a.k.a. "wormholes") is favourable by petroleum engineers, who apply acidization to oil-bearing reservoirs in order to increase their permeability. However, more complex chemical reactions might occur during infiltration of a rock by a fluid. In principle, the products of dissolution might react with other species present either in the fluid or in the rock and reprecipitate [2]. The dissolution and precipitation fronts develop and and begin to propagate with equal velocities, forming a single dissolution-precipitation front

Rules for Flight Paths and Time of Flight for Flows in Porous Media with Heterogeneous Permeability and Porosity

Directory of Open Access Journals (Sweden)

Lihua Zuo

2017-01-01

Full Text Available Porous media like hydrocarbon reservoirs may be composed of a wide variety of rocks with different porosity and permeability. Our study shows in algorithms and in synthetic numerical simulations that the flow pattern of any particular porous medium, assuming constant fluid properties and standardized boundary and initial conditions, is not affected by any spatial porosity changes but will vary only according to spatial permeability changes. In contrast, the time of flight along the streamline will be affected by both the permeability and porosity, albeit in opposite directions. A theoretical framework is presented with evidence from flow visualizations. A series of strategically chosen streamline simulations, including systematic spatial variations of porosity and permeability, visualizes the respective effects on the flight path and time of flight. Two practical rules are formulated. Rule  1 states that an increase in permeability decreases the time of flight, whereas an increase in porosity increases the time of flight. Rule  2 states that the permeability uniquely controls the flight path of fluid flow in porous media; local porosity variations do not affect the streamline path. The two rules are essential for understanding fluid transport mechanisms, and their rigorous validation therefore is merited.

Effects of Pouring Temperature and Electromagnetic Stirring on Porosity and Mechanical Properties of A357 Aluminum Alloy Rheo-Diecasting

Science.gov (United States)

Guo, An; Zhao, Junwen; Xu, Chao; Li, Hu; Han, Jing; Zhang, Xu

2018-05-01

Semisolid slurry of A357 aluminum alloy was prepared using a temperature-controllable electromagnetic stirrer and rheo-diecast at different temperatures. The effects of pouring temperature and electromagnetic stirring (EMS) on the porosity in rheo-diecast samples, as well as the relation between porosity and mechanical properties, were investigated. The results show that pouring temperature and EMS had minor influences on rheo-diecast microstructure but marked influence on the porosity. With decreasing slurry pouring temperature, the porosity decreased first and then increased, whereas the maximum pore ratio (ratio of shape factor to diameter of the largest pore) increased first and then decreased. The maximum pore ratio determines the level of tensile strength and elongation, and higher mechanical properties can be obtained with smaller and rounder pores in samples. The mechanical properties of the rheo-diecast samples increased linearly with increasing maximum pore ratio. The maximum pore ratio was 1.43 µm-1, and the minimum porosity level was 0.37% under EMS condition for the rheo-diecast samples obtained at a pouring temperature of 608 °C. With this porosity condition, the maximum tensile strength and elongation were achieved at 274 MPa and 4.9%, respectively. It was also revealed that EMS improves mechanical properties by reduction in porosity and an increase in maximum pore ratio.

Dual-porosity Mn₂O₃ cubes for highly efficient dye adsorption

DEFF Research Database (Denmark)

Shao, Yongjiu; Ren, Bin; Jiang, Hanmei

2017-01-01

Dual-porosity materials containing both macropores and mesopores are highly desired in many fields. In this work, we prepared dual-porosity Mn2O3 cube materials with large-pore mesopores, in which, macropores are made by using carbon spheres as the hard templates, while the mesopores are produced...

Bulk substrate porosity verification by applying Monte Carlo modeling and Castaing's formula using energy-dispersive x-rays

Science.gov (United States)

Yung, Lai Chin; Fei, Cheong Choke; Mandeep, Jit Singh; Amin, Nowshad; Lai, Khin Wee

2015-11-01

The leadframe fabrication process normally involves additional thin-metal layer plating on the bulk copper substrate surface for wire bonding purposes. Silver, tin, and copper flakes are commonly adopted as plating materials. It is critical to assess the density of the plated metal layer, and in particular to look for porosity or voids underneath the layer, which may reduce the reliability during high-temperature stress. A fast, reliable inspection technique is needed to assess the porosity or void weakness. To this end, the characteristics of x-rays generated from bulk samples were examined using an energy-dispersive x-ray (EDX) detector to examine the porosity percentage. Monte Carlo modeling was integrated with Castaing's formula to verify the integrity of the experimental data. Samples with different porosity percentages were considered to test the correlation between the intensity of the collected x-ray signal and the material density. To further verify the integrity of the model, conventional cross-sectional samples were also taken to observe the porosity percentage using Image J software measurement. A breakthrough in bulk substrate assessment was achieved by applying EDX for the first time to nonelemental analysis. The experimental data showed that the EDX features were not only useful for elemental analysis, but also applicable to thin-film metal layer thickness measurement and bulk material density determination. A detailed experiment was conducted using EDX to assess the plating metal layer and bulk material porosity.

Numerical modeling of porosity waves in the Nankai accretionary wedge décollement, Japan: implications for aseismic slip

Science.gov (United States)

Joshi, Ajit; Appold, Martin S.

2017-01-01

Seismic and hydrologic observations of the Nankai accretionary wedge décollement, Japan, show that overpressures at depths greater than ˜2 km beneath the seafloor could have increased to near lithostatic values due to sediment compaction and diagenesis, clay dehydration, and shearing. The resultant high overpressures are hypothesized then to have migrated in rapid surges or pulses called `porosity waves' up the dip of the décollement. Such high velocities—much higher than expected Darcy fluxes—are possible for porosity waves if the porous media through which the waves travel are deformable enough for porosity and permeability to increase strongly with increasing fluid pressure. The present study aimed to test the hypothesis that porosity waves can travel at rates (kilometers per day) fast enough to cause aseismic slip in the Nankai décollement. The hypothesis was tested using a one-dimensional numerical solution to the fluid mass conservation equation for elastic porous media. Results show that porosity waves generated at depths of ˜2 km from overpressures in excess of lithostatic pressure can propagate at rates sufficient to account for aseismic slip along the décollement over a wide range of hydrogeological conditions. Sensitivity analysis showed porosity wave velocity to be strongly dependent on specific storage, fluid viscosity, and the permeability-depth gradient. Overpressure slightly less than lithostatic pressure could also produce porosity waves capable of traveling at velocities sufficient to cause aseismic slip, provided that hydrogeologic properties of the décollement are near the limits of their geologically reasonable ranges.

Evolution of porosity in a Portland cement paste studied through positron annihilation lifetime spectroscopy

International Nuclear Information System (INIS)

Consolati, G.; Quasso, F.

2003-01-01

Positron annihilation lifetime spectroscopy experiments were carried out in an ordinary Portland cement paste characterized by a water-to-cement ratio w/c=0.8, in order to monitor the porosity of the paste. It was found that ortho-positronium intensity is a suitable quantity to this purpose, being sensitive to the amount of water contained in the pores. The experimental data show good agreement with the porosity calculated according to the Powers' thin filmsodel

Porosity of natural stone and use of confocal laser scanning microscopy on calcitic marble aged in laboratory

Directory of Open Access Journals (Sweden)

Ana Mladenovič

2008-06-01

Full Text Available Porosity is one of the key characteristics of natural stone, which influences ondurability as well as functionality of stone as building material. Further, deterioration processes themselves are also characterized by change of porosity. Different direct and indirect techniques can be used for porosity determination. In the following paper overview of these methods, as well as their advantages and disadvantages, is given. Confocal laser scanning microscopy (CLSM is indirect (microscopic technique. Despite its numerous advantages, among which 3D visualizationof pore structure is of major importance, this technique is less known in the area of building materials. An example how CLSM can be applied for qualitative and quantitative evaluation of porosity of calcitic polygonal granoblastic marble is given in this paper. Studied marble has been, despite of its poor durability, often used as building material, especially in the case of claddings. It is shown that thermal hydric factors of deterioration can influence porosity significantly,especially formation of intergranular cracks.This kind of deterioration can be successfully evaluated with use of CLSM method, if samples are suitable prepared and if suitable image analysis tools are developed.

Aerogel to simulate delamination and porosity defects in carbon-fiber reinforced polymer composites

Science.gov (United States)

Juarez, Peter; Leckey, Cara A. C.

2018-04-01

Representative defect standards are essential for the validation and calibration of new and existing inspection techniques. However, commonly used methods of simulating delaminations in carbon-fiber reinforced polymer (CFRP) composites do not accurately represent the behavior of the real-world defects for several widely-used NDE techniques. For instance, it is common practice to create a delamination standard by inserting Polytetrafluoroethylene (PTFE) in between ply layers. However, PTFE can transmit more ultrasonic energy than actual delaminations, leading to an unrealistic representation of the defect inspection. PTFE can also deform/wrinkle during the curing process and has a thermal effusivity two orders of magnitude higher than air (almost equal to that of a CFRP). It is therefore not effective in simulating a delamination for thermography. Currently there is also no standard practice for producing or representing a known porosity in composites. This paper presents a novel method of creating delamination and porosity standards using aerogel. Insertion of thin sheets of solid aerogel between ply layers during layup is shown to produce air-gap-like delaminations creating realistic ultrasonic and thermographic inspection responses. Furthermore, it is shown that depositing controlled amounts of aerogel powder can represent porosity. Micrograph data verifies the structural integrity of the aerogel through the composite curing process. This paper presents data from multiple NDE methods, including X-ray computed tomography, immersion ultrasound, and flash thermography to the effectiveness of aerogel as a delamination and porosity simulant.

Pore-level determination of spectral reflection behaviors of high-porosity metal foam sheets

Science.gov (United States)

Li, Yang; Xia, Xin-Lin; Ai, Qing; Sun, Chuang; Tan, He-Ping

2018-03-01

Open cell metal foams are currently attracting attention and their radiative behaviors are of primary importance in high temperature applications. The spectral reflection behaviors of high-porosity metal foam sheets, bidirectional reflectance distribution function (BRDF) and directional-hemispherical reflectivity were numerically investigated. A set of realistic nickel foams with porosity from 0.87 to 0.97 and pore density from 10 to 40 pores per inch were tomographied to obtain their 3-D digital cell network. A Monte Carlo ray-tracing method was employed in order to compute the pore-level radiative transfer inside the network within the limit of geometrical optics. The apparent reflection behaviors and their dependency on the textural parameters and strut optical properties were comprehensively computed and analysed. The results show a backward scattering of the reflected energy at the foam sheet surface. Except in the cases of large incident angles, an energy peak is located almost along the incident direction and increases with increasing incident angles. Through an analytical relation established, the directional-hemispherical reflectivity can be related directly to the porosity of the foam sheet and to the complex refractive index of the solid phase as well as the specularity parameter which characterizes the local reflection model. The computations show that a linear decrease in normal-hemispherical reflectivity occurs with increasing porosity. The rate of this decrease is directly proportional to the strut normal reflectivity. In addition, the hemispherical reflectivity increases as a power function of the incident angle cosine.

Effective porosity and pore-throat sizes of Conasauga Group mudrock: Application, test and evaluation of petrophysical techniques

International Nuclear Information System (INIS)

Dorsch, J.; Katsube, T.J.; Sanford, W.E.; Univ. of Tennessee, Knoxville, TN; Dugan, B.E.; Tourkow, L.M.

1996-04-01

Effective porosity (specifically referring to the interconnected pore space) was recently recognized as being essential in determining the effectiveness and extent of matrix diffusion as a transport mechanism within fractured low-permeability rock formations. The research presented in this report was performed to test the applicability of several petrophysical techniques for the determination of effective porosity of fine-grained siliciclastic rocks. In addition, the aim was to gather quantitative data on the effective porosity of Conasauga Group mudrock from the Oak Ridge Reservation (ORR). The quantitative data reported here include not only effective porosities based on diverse measurement techniques, but also data on the sizes of pore throats and their distribution, and specimen bulk and grain densities. The petrophysical techniques employed include the immersion-saturation method, mercury and helium porosimetry, and the radial diffusion-cell method

From atoms to layers: in situ gold cluster growth kinetics during sputter deposition

Science.gov (United States)

Schwartzkopf, Matthias; Buffet, Adeline; Körstgens, Volker; Metwalli, Ezzeldin; Schlage, Kai; Benecke, Gunthard; Perlich, Jan; Rawolle, Monika; Rothkirch, André; Heidmann, Berit; Herzog, Gerd; Müller-Buschbaum, Peter; Röhlsberger, Ralf; Gehrke, Rainer; Stribeck, Norbert; Roth, Stephan V.

2013-05-01

The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources.The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction

Use of SEM and EDS analysis in the investigation of Al-Si-Cu piston alloy cast porosity

Directory of Open Access Journals (Sweden)

D. Kakaš

2009-07-01

Full Text Available Porosity formation was detected in the casting thinnest section in the proximity of the as cast surface and near the wall centerline. In order to investigate the cause of the porosity formation light microscopy was used to define as cast structure. After initial findings SEM and EDS analyses were performed. Based on the results it is possible to define cause of the observed porosity. A number of pores originates from the mould filling stage and entrainment of the oxide films, while others appear due to insufficient feeding during solidification.

Study of ice formation in the porosity of hydraulic binder based materials

International Nuclear Information System (INIS)

Bejaoui, Syriac

2001-01-01

This work concerns the nuclear waste management problematic, and aims at contributing to a better prediction of concrete freeze / thaw behaviour. Ice formation in the porosity of cement pastes and concrete was studied using differential scanning calorimetry and a thermodynamic model. It is shown that ice formation low temperatures in the pores can't be explained considering only interstitial solution under-cooling induced by crystal size restrictions, dissolved chemical elements, and containment pressures. On the other hand, taking into account the nucleation theory and the porosity division degree, three ice formation mechanisms can be defined, near -10, -25 et -40 deg. C. These results allow to explain freeze / thaw behaviour differences between blended and portland cement based materials, as well as, probably, between some high performance concrete, and allow to consider using differential scanning calorimetry as a tool for testing concrete freeze / thaw behaviour. In addition, this study highlights an irreversible shrinkage for cement pastes and concrete induced by freeze / thaw cycles without provision of water, and, on the basis of small angle neutrons scattering measures, the presence of a fractal surface type porosity in high performance cement pastes. (author) [fr

Porosity structure of green polybag of medium density fiberboard from seaweed waste

Science.gov (United States)

Alamsjah, M. A.; Subekti, S.; Lamid, M.; Pujiastuti, D. Y.; Kurnia, H.; Rifadi, R. R.

2018-04-01

The last decade shown that the needs Medium Density Fibreboard (MDF) rapidly growing in Asia Pacific and Europe up to more 15 % per year. MDF made up of fibers lignoselulosa which combined with synthetic resin or tied other suitable but high temperatures and pressure. Technology engineering for green polybag of MDF from seaweed waste of Kappaphycus alvarezii and Gracilaria verrucosa is an alternative effort for ecosystem stability and technological innovations that is environmentally friendly. Structure porosity from the shape of green polybag shows that performance seaweed waste of K. alvarezii is better than seaweed waste of G. verrucosa. The circulation of water happened more optimal in green polybag formed from MDF of seaweed waste of K. alvarezii with size porosity 3.976 µm, while size porosity of seaweed waste of G. verrucosa measurable 4.794 µm. Structure of green polybag of MDF from seaweed waste showed that C components greater 50 % to K. alvarezii while C components less than 50 % to G. verrucosa. This resulted in the ties to structure of MDF stronger found in green polybag derived from seaweed waste of K. alvarezii than G. verrucosa.

Thermoelectric materials having porosity

Science.gov (United States)

Heremans, Joseph P.; Jaworski, Christopher M.; Jovovic, Vladimir; Harris, Fred

2014-08-05

A thermoelectric material and a method of making a thermoelectric material are provided. In certain embodiments, the thermoelectric material comprises at least 10 volume percent porosity. In some embodiments, the thermoelectric material has a zT greater than about 1.2 at a temperature of about 375 K. In some embodiments, the thermoelectric material comprises a topological thermoelectric material. In some embodiments, the thermoelectric material comprises a general composition of (Bi.sub.1-xSb.sub.x).sub.u(Te.sub.1-ySe.sub.y).sub.w, wherein 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 1.8.ltoreq.u.ltoreq.2.2, 2.8.ltoreq.w.ltoreq.3.2. In further embodiments, the thermoelectric material includes a compound having at least one group IV element and at least one group VI element. In certain embodiments, the method includes providing a powder comprising a thermoelectric composition, pressing the powder, and sintering the powder to form the thermoelectric material.

Study of the influence of agricultural waste on the porosity of clay brick

Directory of Open Access Journals (Sweden)

Chelouah Nasser

2015-02-01

Full Text Available This paper deals with the influence of two organic residues on the porosity of clay bricks. The insulation capacity of the brick increases with increasing the porosity. Combustible organic additions are often used to form pores. The formation of the more homogenous porous structure is favourably impacted by using the crushed rough olive stones containing oil. Plasticity, bulk density and mechanical properties were studied. The additions of organic residues have proved successful to form pores while maintaining the mechanical properties in the limits of the Algerian norms.

The effect of activation agent on surface morphology, density and porosity of palm shell and coconut shell activated carbon

Science.gov (United States)

Leman, A. M.; Zakaria, S.; Salleh, M. N. M.; Sunar, N. M.; Feriyanto, D.; Nazri, A. A.

2017-09-01

Activated carbon (AC) has one of the promising alternative technology for filtration and adsorption process. It inexpensive material because the sources is abundant especially in Malaysia. Main purpose of this project is to develop AC by chemical activation process to improve adsorption capacity by improving porosity of AC. AC developed via carbonization using designed burner at temperature of 650°C to 850 °C and activated by Potassium Hydroxide (KOH) in 12 hour and then dried at temperature of 300°C. Characterization and analysis is conducted by Scanning Electron Microscopy (SEM) for surface morphology analysis, Energy Dispersive Spectroscopy (EDS) for composition analysis, density and porosity analysis. Results shows that uneven surface has been observed both of AC and non-AC and also AC shows higher porosity as compared to non-AC materials. Density value of raw material has lower than AC up to 11.67% and 47.54% and porosity of raw material has higher than AC up to 31.45% and 45.69% for palm shell and coconut shell AC. It can be concluded that lower density represent higher porosity of material and higher porosity indicated higher adsorption capacity as well.

Air-Filled porosity and permeability relationships during solid-waste fermentation

NARCIS (Netherlands)

Richard, T.L.; Veeken, A.H.M.; Wilde, de V.; Hamelers, H.V.M.

2004-01-01

An experimental apparatus was constructed to measure the structural parameters of organic porous media, i.,e. mechanical strength, air-filled porosity, air permeability, and the Ergun particle size. These parameters are critical to the engineering of aerobic bioconversion systems and were measured

Comparison of porosity measurement techniques for porous titanium scaffolds evaluation

International Nuclear Information System (INIS)

Oliveira, M.V.; Ribeiro, A.A.; Moreira, A.C.; Moraes, A.M.C.; Appoloni, C.R.; Pereira, L.C.

2009-01-01

Porous titanium has been used for grafts and implant coatings as it allows the mechanical interlocking of the pores and bone. Evaluation of porous scaffolds for bone regeneration is essential for their manufacture. Porosity, pore size, pore shape and pore homogeneity are parameters that influence strongly the mechanical strength and biological functionality. In this study, porous titanium samples were manufactured by powder metallurgy by using pure titanium powders mixed with a pore former. The quantification of the porosity parameters was assessed in this work by geometric method and gamma-ray transmission, the non-destructive techniques and metallographic images processing, a destructive technique. Qualitative evaluation of pore morphology and surface topography were performed by scanning electron microscopy and optical microscopy. The results obtained and the effectiveness of the techniques used were compared in order to select those most suitable for characterization of porous titanium scaffolds. (author)

Stylolites, porosity, depositional texture, and silicates in chalk facies sediments

DEFF Research Database (Denmark)

Fabricius, Ida Lykke; Borre, Mai K.

2007-01-01

dissolution around 490 m below sea floor (bsf) corresponds to an interval of waning porosity-decline, and even the occurrence of proper stylolites from 830 m bsf is accompanied by only minor porosity reduction. Because opal is present, the pore-water is relatively rich in Si which through the formation of Ca......-silica complexes causes an apparent super-saturation of Ca and retards cementation. The onset of massive pore-filling cementation at 1100 m bsf may be controlled by the temperature-dependent transition from opal-CT to quartz. In the stylolite-bearing chalk of two wells in the Gorm and Tyra fields, the nannofossil...... matrix shows recrystallization but only minor pore-filling cement, whereas microfossils are cemented. Cementation in Gorm and Tyra is thus partial and has apparently not been retarded by opal-controlled pore-water. A possible explanation is that, due to the relatively high temperature, silica has...

Carbonate reservoir characterization with lithofacies clustering and porosity prediction

International Nuclear Information System (INIS)

Al Moqbel, Abdulrahman; Wang, Yanghua

2011-01-01

One of the objectives in reservoir characterization is to quantitatively or semi-quantitatively map the spatial distribution of its heterogeneity and related properties. With the availability of 3D seismic data, artificial neural networks are capable of discovering the nonlinear relationship between seismic attributes and reservoir parameters. For a target carbonate reservoir, we adopt a two-stage approach to conduct characterization. First, we use an unsupervised neural network, the self-organizing map method, to classify the reservoir lithofacies. Then we apply a supervised neural network, the back-propagation algorithm, to quantitatively predict the porosity of the carbonate reservoir. Based on porosity maps at different time levels, we interpret the target reservoir vertically related to three depositional phases corresponding to, respectively, a lowstand system tract before sea water immersion, a highstand system tract when water covers organic deposits and a transition zone for the sea level falling. The highstand system is the most prospective zone, given the organic content deposited during this stage. The transition zone is also another prospective feature in the carbonate depositional system due to local build-ups

Open die forging of large shafts with porosity defects – physical and numerical modelling

DEFF Research Database (Denmark)

Christiansen, Peter; Hattel, Jesper Henri; Bay, Niels

2013-01-01

The aim and scope of this paper is centered to analyze the influence of the geometry of V-shaped dies on the closure of internal centerline porosity defects in ingots during multistep open-die forging. The investigation is performed with small scale physical models made from lead using V-shaped d......The aim and scope of this paper is centered to analyze the influence of the geometry of V-shaped dies on the closure of internal centerline porosity defects in ingots during multistep open-die forging. The investigation is performed with small scale physical models made from lead using V......-shaped dies with 90o and 120o and a reference pair of flat parallel platens. Holes drilled through the center of these preforms are produced to mimic centerline porosity in full scale cast ingots and intermediate rotation of the preforms replicate a multi-stage forging sequence under laboratory testing...

Influence of porosity and groundmass crystallinity on dome rock strength: a case study from Mt. Taranaki, New Zealand

Science.gov (United States)

Zorn, Edgar U.; Rowe, Michael C.; Cronin, Shane J.; Ryan, Amy G.; Kennedy, Lori A.; Russell, James K.

2018-04-01

Lava domes pose a significant hazard to infrastructure, human lives and the environment when they collapse. Their stability is partly dictated by internal mechanical properties. Here, we present a detailed investigation into the lithology and composition of a Rocks with variable porosity and groundmass crystallinity were compared using measured compressive and tensile strength, derived from deformation experiments performed at room temperature and low (3 MPa) confining pressures. Based on data obtained, porosity exerts the main control on rock strength and mode of failure. High porosity (> 23%) rocks show low rock strength (rocks (5-23%) exhibit higher measured rock strengths (up to 278 MPa) and brittle failure. Groundmass crystallinity, porosity and rock strength are intercorrelated. High groundmass crystal content is inversely related to low porosity, implying crystallisation and degassing of a slowly undercooled magma that experienced rheological stiffening under high pressures deeper within the conduit. This is linked to a slow magma ascent rate and results in a lava dome with higher rock strength. Samples with low groundmass crystallinity are associated with higher porosity and lower rock strength, and represent magma that ascended more rapidly, with faster undercooling, and solidification in the upper conduit at low pressures. Our experimental results show that the inherent strength of rocks within a growing dome may vary considerably depending on ascent/emplacement rates, thus significantly affecting dome stability and collapse hazards.

Does nutrition affect bone porosity and mineral tissue distribution in deer antlers? The relationship between histology, mechanical properties and mineral composition.

Science.gov (United States)

Landete-Castillejos, T; Currey, J D; Ceacero, F; García, A J; Gallego, L; Gomez, S

2012-01-01

It is well known that porosity has an inverse relationship with the mechanical properties of bones. We examined cortical and trabecular porosity of antlers, and mineral composition, thickness and mechanical properties in the cortical wall. Samples belonged to two deer populations: a captive population of an experimental farm having a high quality diet, and a free-ranging population feeding on plants of lower nutritive quality. As shown for minerals and mechanical properties in previous studies by our group, cortical and trabecular porosity increased from the base distally. Cortical porosity was always caused by the presence of incomplete primary osteons. Porosity increased along the length of the antler much more in deer with lower quality diet. Despite cortical porosity being inversely related to mechanical properties and positively with K, Zn and other minerals indicating physiological effort, it was these minerals and not porosity that statistically better explained variability in mechanical properties. Histochemistry showed that the reason for this is that Zn is located around incomplete osteons and also in complete osteons that were still mineralizing, whereas K is located in non-osteonal bone, which constitutes a greater proportion of bone where osteons are incompletely mineralized. This suggests that, K, Zn and other minerals indicate reduction in mechanical performance even with little porosity. If a similar process occurred in internal bones, K, Zn and other minerals in the bone may be an early indicator of decrease in mechanical properties and future osteoporosis. In conclusion, porosity is related to diet and physiological effort in deer. Copyright © 2011 Elsevier Inc. All rights reserved.

Modeling of hydrogen production methods: Single particle model and kinetics assessment

Energy Technology Data Exchange (ETDEWEB)

Miller, R.S.; Bellan, J. [California Institute of Technology, Pasadena, CA (United States)

1996-10-01

The investigation carried out by the Jet Propulsion Laboratory (JPL) is devoted to the modeling of biomass pyrolysis reactors producing an oil vapor (tar) which is a precursor to hydrogen. This is an informal collaboration with NREL whereby JPL uses the experimentally-generated NREL data both as initial and boundary conditions for the calculations, and as a benchmark for model validation. The goal of this investigation is to find drivers of biomass fast-pyrolysis in the low temperature regime. The rationale is that experimental observations produce sparse discrete conditions for model validation, and that numerical simulations produced with a validated model are an economic way to find control parameters and an optimal operation regime, thereby circumventing costly changes in hardware and tests. During this first year of the investigation, a detailed mathematical model has been formulated for the temporal and spatial accurate modeling of solid-fluid reactions in biomass particles. These are porous particles for which volumetric reaction rate data is known a priori and both the porosity and the permeability of the particle are large enough to allow for continuous gas phase flow. The methodology has been applied to the pyrolysis of spherically symmetric biomass particles by considering previously published kinetics schemes for both cellulose and wood. The results show that models which neglect the thermal and species boundary layers exterior to the particle will generally over predict both the pyrolysis rates and experimentally obtainable tar yields. An evaluation of the simulation results through comparisons with experimental data indicates that while the cellulose kinetics is reasonably accurate, the wood pyrolysis kinetics is not accurate; particularly at high reactor temperatures. Current effort in collaboration with NREL is aimed at finding accurate wood kinetics.

Shrinkage Porosity Criterion and Its Application to A 5.5 Ton Steel Ingot

Directory of Open Access Journals (Sweden)

Zhang C.

2016-06-01

Full Text Available In order to predict the distribution of shrinkage porosity in steel ingot efficiently and accurately, a criterion R√L and a method to obtain its threshold value were proposed. The criterion R√L was derived based on the solidification characteristics of steel ingot and pressure gradient in the mushy zone, in which the physical properties, the thermal parameters, the structure of the mushy zone and the secondary dendrite arm spacing were all taken into consideration. The threshold value of the criterion R√L was obtained with combination of numerical simulation of ingot solidification and total solidification shrinkage rate. Prediction of the shrinkage porosity in a 5.5 ton ingot of 2Cr13 steel with criterion R√L>0.21 m · °C1/2 · s−3/2 agreed well with the results of experimental sectioning. Based on this criterion, optimization of the ingot was carried out by decreasing the height-to-diameter ratio and increasing the taper, which successfully eliminated the centreline porosity and further proved the applicability of this criterion.

The influence of substrate transport limitation on porosity and methanogenic activity of anaerobic sludge granules

Energy Technology Data Exchange (ETDEWEB)

Alphenaar, P.A. (Agricultural Univ., Wageningen (Netherlands). Dept. of Environmental Technology); Perez, M.C. (Agricultural Univ., Wageningen (Netherlands). Dept. of Environmental Technology); Lettinga, G. (Agricultural Univ., Wageningen (Netherlands). Dept. of Environmental Technology)

1993-05-01

The relationship between porosity, diameter and methanogenic activity of anaerobic granules has been investigated. Experiments with different granular sludges revealed that substrate transport limitations increase with the diameter of the granules. As a consequence, autolysis can occur in the core of the granule, producing hollow granules. The porosity measurements revealed that the hollow centre is not available for substrate transport. Possibly as an effect of bacterial lysis, the porosity decreases in the more interior layers of the granules. This results in a inactive inner part of the large granules, which is not involved in the treatment process; the specific methanogenic activity decreases with granule size. No marked difference in substrate affinity is observed between granules of different sizes, which probably indicates that for large granules only the exterior is biological active. (orig.)

Support vector regression to predict porosity and permeability: Effect of sample size

Science.gov (United States)

Al-Anazi, A. F.; Gates, I. D.

2012-02-01

Porosity and permeability are key petrophysical parameters obtained from laboratory core analysis. Cores, obtained from drilled wells, are often few in number for most oil and gas fields. Porosity and permeability correlations based on conventional techniques such as linear regression or neural networks trained with core and geophysical logs suffer poor generalization to wells with only geophysical logs. The generalization problem of correlation models often becomes pronounced when the training sample size is small. This is attributed to the underlying assumption that conventional techniques employing the empirical risk minimization (ERM) inductive principle converge asymptotically to the true risk values as the number of samples increases. In small sample size estimation problems, the available training samples must span the complexity of the parameter space so that the model is able both to match the available training samples reasonably well and to generalize to new data. This is achieved using the structural risk minimization (SRM) inductive principle by matching the capability of the model to the available training data. One method that uses SRM is support vector regression (SVR) network. In this research, the capability of SVR to predict porosity and permeability in a heterogeneous sandstone reservoir under the effect of small sample size is evaluated. Particularly, the impact of Vapnik's ɛ-insensitivity loss function and least-modulus loss function on generalization performance was empirically investigated. The results are compared to the multilayer perception (MLP) neural network, a widely used regression method, which operates under the ERM principle. The mean square error and correlation coefficients were used to measure the quality of predictions. The results demonstrate that SVR yields consistently better predictions of the porosity and permeability with small sample size than the MLP method. Also, the performance of SVR depends on both kernel function

On the Representation of the Porosity-Pressure Relationship in General Subsurface Flow Codes

Science.gov (United States)

Birdsell, Daniel T.; Karra, Satish; Rajaram, Harihar

2018-02-01

The governing equations for subsurface flow codes in a deformable porous media are derived from the balance of fluid mass and Darcy's equation. One class of these codes, which we call general subsurface flow codes (GSFs), allow for more general constitutive relations for material properties such as porosity, permeability and density. Examples of GSFs include PFLOTRAN, FEHM, TOUGH2, STOMP, and some reservoir simulators such as BOAST. Depending on the constitutive relations used in GSFs, an inconsistency arises between the standard groundwater flow equation and the governing equation of GSFs, and we clarify that the reason for this inconsistency is because the Darcy's equation used in the GSFs should account for the velocity of fluid with respect to solid. Due to lack of awareness of this inconsistency, users of the GSFs tend to use a porosity-pressure relationship that comes from the standard groundwater flow equation and assumes that the relative velocity is already accounted for. For the Theis problem, we show that using this traditional relationship in the GSFs leads to significantly large errors. We propose an alternate porosity-pressure relationship that is consistent with the derivation of the governing equations in the GSFs where the solid velocity is not tracked, and show that, with this relationship, the results are more accurate for the Theis problem. The purpose of this note is to make the users and developers of these GSFs aware of this inconsistency and to advocate that the alternate porosity model derived here should be incorporated in GSFs.

New ANFO explosives made of ammonium nitrate of increased porosity and naphtha

Energy Technology Data Exchange (ETDEWEB)

Kutsarov, B.; Mavrodieva, R.; Ivanov, I.; Stoyanov, V.; Georgiev, N.; Krumov, I.; Katsarski, I.; Vakliev, I.

1990-01-01

Discusses results achieved by the KNIIPPI Niproruda Research Institute and the Osogovo enterprise in improving the quality of ANFO explosives. Ammonium nitrate with increased porosity was treated by water steam and wetting agents and then thermally treated. Naphtha in a quantity of up to 8% was then added to the ammonium nitrate to produce a powerful and stable explosive. The quality of explosive cartridges was tested first in the laboratory using the Schaffler apparatus. Test results were very satisfactory (better porosity, higher detonation velocity (2200-3600 m/s), better stability). Industrial experiments carried out in several underground mines also produced satisfactory results (better output in roadway drivage at lower operating cost and better safety). 8 refs.

Effect of thermally induced porosity on an as-HIP powder metallurgy superalloy

Science.gov (United States)

Dreshfield, R. L.; Miner, R. V., Jr.

1979-01-01

The impact of thermally induced porosity on the mechanical properties of an as-hot-isostatically-pressed and heat treated pressing made from low carbon Astroloy was determined. Porosity in the disk-shape pressing studied ranged from 2.6 percent at the bore to 1.4 percent at the rim. Tensile, yield strength, ductility, and rupture life of the rim of the porous pressing was only slightly inferior to the rim of sound pressings. The strength, ductility, and rupture life of the bore of the porous pressing was severely degraded compared to sound pressings. At strain ranges typical of commercial jet engine designs, the rim of the porous pressing had slightly inferior fatigue life to sound pressings.

Formation mechanisms of the powder porosity generated in the neighborhood of the shear plane

International Nuclear Information System (INIS)

Makino, K.; Kuramitsu, K.; Hoshikawa, H.; Mori, H.

1988-01-01

In recent years, the sophisticated technology on the process of powder feeding, packing, mixing, and compacting, by which homogeneous powder products can be manufactured in fine ceramics and electronics industries, is being established. And, in order to develop the technology, it is necessary to make clear the formation mechanism of powder porosity in the neighborhood of shear plane generated in the powder bed. However, this has not yet been sufficiently elucidated. In this paper, a single-plane shear tester which can simultaneously measure three quantities of stress, strain, and the powder porosity in the neighborhood of shear plane, was devised by using an X-ray radiograph system, and these three quantities were systematically measured under various shearing conditions. Next, a formation model of the powder porosity in the neighborhood of shear plane, composed of powder yield locus, critical state line, and Mohr stress semi, was experimentally checked by the three measured quantities mentioned above

Partitioned airs at microscale and nanoscale: thermal diffusivity in ultrahigh porosity solids of nanocellulose

Science.gov (United States)

Sakai, Koh; Kobayashi, Yuri; Saito, Tsuguyuki; Isogai, Akira

2016-02-01

High porosity solids, such as plastic foams and aerogels, are thermally insulating. Their insulation performance strongly depends on their pore structure, which dictates the heat transfer process in the material. Understanding such a relationship is essential to realizing highly efficient thermal insulators. Herein, we compare the heat transfer properties of foams and aerogels that have very high porosities (97.3-99.7%) and an identical composition (nanocellulose). The foams feature rather closed, microscale pores formed with a thin film-like solid phase, whereas the aerogels feature nanoscale open pores formed with a nanofibrous network-like solid skeleton. Unlike the aerogel samples, the thermal diffusivity of the foam decreases considerably with a slight increase in the solid fraction. The results indicate that for suppressing the thermal diffusion of air within high porosity solids, creating microscale spaces with distinct partitions is more effective than directly blocking the free path of air molecules at the nanoscale.

Earth formation porosity log using measurement of neutron energy spectrum

International Nuclear Information System (INIS)

1981-01-01

Methods and apparatus are described for measuring the porosity of subsurface earth formations in the vicinity of a well borehole by means of neutron well logging techniques. All the commercial techniques for measuring porosity currently available are not as accurate as desirable due to variations in the borehole wall diameter, in the borehole fluids (e.g. with chlorine content) in the casings of the borehole etc. This invention seeks to improve accuracy by using a measurement of the epithermal neutron population at one detector and the fast neutron population at a second detector, spaced approximately the same distance from a neutron source. The latter can be detected either by a fast neutron detector or indirectly by an inelastic gamma ray detector. Background correction can be made, and special detectors used, to discriminate against the detection of thermal neutrons or their resultant capture gamma rays. These fluctuations affect the measurement of thermal neutron populations. (U.K.)

Ultra-thin and strong formvar-based membranes with controlled porosity for micro- and nano-scale systems

Science.gov (United States)

Auchter, Eric; Marquez, Justin; Stevens, Garrison; Silva, Rebecca; Mcculloch, Quinn; Guengerich, Quintessa; Blair, Andrew; Litchfield, Sebastian; Li, Nan; Sheehan, Chris; Chamberlin, Rebecca; Yarbro, Stephen L.; Dervishi, Enkeleda

2018-05-01

We present a methodology for developing ultra-thin and strong formvar-based membranes with controlled morphologies. Formvar is a thin hydrophilic and oleophilic polymer inert to most chemicals and resistant to radiation. The formvar-based membranes are viable materials as support structures in micro- and macro-scale systems depending on thinness and porosity control. Tunable sub-micron thick porous membranes with 20%–65% porosity were synthesized by controlling the ratios of formvar, glycerol, and chloroform. This synthesis process does not require complex separation or handling methods and allows for the production of strong, thin, and porous formvar-based membranes. An expansive array of these membrane characterizations including chemical compatibility, mechanical responses, wettability, as well as the mathematical simulations as a function of porosity has been presented. The wide range of chemical compatibility allows for membrane applications in various environments, where other polymers would not be suitable. Our formvar-based membranes were found to have an elastic modulus of 7.8 GPa, a surface free energy of 50 mN m‑1 and an average thickness of 125 nm. Stochastic model simulations indicate that formvar with the porosity of ∼50% is the optimal membrane formulation, allowing the most material transfer across the membrane while also withstanding the highest simulated pressure loadings before tearing. Development of novel, resilient and versatile membranes with controlled porosity offers a wide range of exciting applications in the fields of nanoscience, microfluidics, and MEMS.

Multiscale modelling of dual-porosity porous media; a computational pore-scale study for flow and solute transport

Science.gov (United States)

de Vries, Enno T.; Raoof, Amir; van Genuchten, Martinus Th.

2017-07-01

Many environmental and agricultural applications involve the transport of water and dissolved constituents through aggregated soil profiles, or porous media that are structured, fractured or macroporous in other ways. During the past several decades, various process-based macroscopic models have been used to simulate contaminant transport in such media. Many of these models consider advective-dispersive transport through relatively large inter-aggregate pore domains, while exchange with the smaller intra-aggregate pores is assumed to be controlled by diffusion. Exchange of solute between the two domains is often represented using a first-order mass transfer coefficient, which is commonly obtained by fitting to observed data. This study aims to understand and quantify the solute exchange term by applying a dual-porosity pore-scale network model to relatively large domains, and analysing the pore-scale results in terms of the classical dual-porosity (mobile-immobile) transport formulation. We examined the effects of key parameters (notably aggregate porosity and aggregate permeability) on the main dual-porosity model parameters, i.e., the mobile water fraction (ϕm) and the mass transfer coefficient (α). Results were obtained for a wide range of aggregate porosities (between 0.082 and 0.700). The effect of aggregate permeability was explored by varying pore throat sizes within the aggregates. Solute breakthrough curves (BTCs) obtained with the pore-scale network model at several locations along the domain were analysed using analytical solutions of the dual-porosity model to obtain estimates of ϕm and α. An increase in aggregate porosity was found to decrease ϕm and increase α, leading to considerable tailing in the BTCs. Changes in the aggregate pore throat size affected the relative flow velocity between the intra- and inter-aggregate domains. Higher flow velocities within the aggregates caused a change in the transport regime from diffusion dominated to more

Effect of drying on the porosity of the hydroxyapatite and cellulose nata de coco compositeas bone graft candidate

Science.gov (United States)

Anitasari, S.; Mu’ti, A.; Hutahaean, YO

2018-04-01

Bone graft is used to replace bone parts damaged by illness and accident. As a bone replacement material, the bone graft should be able to stimulate the process of the osteogenesis. The process of osteogenesis is influenced by the osteoconductive properties of a biomaterial, that porosity affects this process. The shells of blood scallop (Anadaragranosa) are producing hydroxyapatite (HAp),having high compressive strength, biocompatibility and osteoconductive properties, but low porosity while cellulose nata de coco (Cnc) have low compressive strength but high porosity. Therefore, the combination of two biomaterials are expected to produce composite that have high osteoconductive properties. The purpose of this research wasknowing the porosity of HAp/Cnc composite which wasbeingprecipitated for 5 hours, 15 hours, 25 hours and wasdried for 24 hours, 48 hours and 72 hours. This research usedwise drop technique to synthesis HAp powder and cellulose immersion technique for synthesis of HAp/Cnc. Results of this research, there was difference in porosity between HAp/Cnc that was precipitated for 5 hours, 15 hours and 25 hours, as well as was dried for 1 day, 2 days and 3 days. The conclusion, the synthesis of HAp/Cncwasuseful as bone graft candidate.

Characterization of zirconium alloy oxidation films by alternating current impedance

International Nuclear Information System (INIS)

Rosecrans, P.M.

1984-01-01

Kinetics of zirconium alloy oxidation are highly nonlinear. The results of electrochemical measurements and electron microscopy support the existence of porosity in oxide films formed on zirconium alloys in high temperature aqueous environments. Analytical treatment is presented relating oxidation kinetics to the thickness and distribution of nonporous elements within the oxide. This analysis illustrates that both the level and distribution of porosity within the oxide factor into oxidation kinetics. The barrier layer model can provide a basis for predicting the effect of environmental changes on oxidation rate. In addition, it demonstrates the need for further research into porosity generation mechanisms in oxide films

Characterization of zirconium alloy oxidation films by alternating current impedance

International Nuclear Information System (INIS)

Rosecrans, P.M.

1983-11-01

Kinetics of zirocnium alloy oxidation are highly nonlinear. The results of electrochemical measurements and electron microscopy support the existence of porosity in oxide films formed on zirconium alloys in high temperature aqueous environments. Analytical treatment is presented relating oxidation kinetics to the thickness and distribution of nonporous elements within the oxide. This analysis illustrates that both the level and distribution of porosity within the oxide factor into oxidation kinetics. The barrier layer model can provide a basis for predicting the effect of environmental changes on oxidation rate. In addition, it demonstrates the need for further research into porosity generation mechanisms in oxide films

A mass transfer based variable porosity model with particle radius change for a Lithium-ion battery

International Nuclear Information System (INIS)

Ashwin, T.R.; McGordon, A.; Jennings, P.A.

2017-01-01

Highlights: • Mass transfer based model to calculate the porosity variation and radius change. • Can be used with any model that calculates Lithium concentration in electrolyte. • Considers SEI as a mass deposition rather than simply an internal resistance. • Brings more accuracy to the volume specific area and the Butler-Volmer kinetics • Practical applicability in pre-lithiation, lithium plating and stress calculation. - Abstract: Micro pore-clogging in the electrodes due to SEI growth and other side reactions can cause adverse effects on the performance of a Lithium-ion battery. The fundamental problem of volume fraction variation and particle radius change during the charge-discharge process in a lithium-ion battery is modelled in this paper with the help of mass transfer based formulation and demonstrated on a battery with LiCoO_2 chemistry. The model can handle the volume fraction change due to intercalation reaction, solvent reduction side reaction and the electrolyte density change due to side reaction contamination in the battery. The entire calculation presented in this paper models particle radius and volume fraction together and therefore gives greater accuracy in calculating the volume-specific-area of the reacting particles which is an important parameter controlling the Butler-Volmer kinetics. The mass deposit on the electrode (or loss of lithium) gives an indication of the amount of pre-lithiation required to maintain cell performance while the amount of mass deposited on the SEI helps to decide the safe operating condition for which the clogging of pores and capacity fade will be minimal. Moreover the model presented in this paper has wide applicability in analysing the stress development inside the battery due to irreversible porous filling.

Influence of Powder Characteristics on Formation of Porosity in Additive Manufacturing of Ti-6Al-4V Components

Science.gov (United States)

Iebba, Maurizio; Astarita, Antonello; Mistretta, Daniela; Colonna, Ivano; Liberini, Mariacira; Scherillo, Fabio; Pirozzi, Carmine; Borrelli, Rosario; Franchitti, Stefania; Squillace, Antonino

2017-08-01

This paper aims to study the genesis of defects in titanium components made through two different additive manufacturing technologies: selective laser melting and electron beam melting. In particular, we focussed on the influence of the powders used on the formation of porosities and cavities in the manufactured components. A detailed experimental campaign was carried out to characterize the components made through the two additive manufacturing techniques aforementioned and the powders used in the process. It was found that some defects of the final components can be attributed to internal porosities of the powders used in the manufacturing process. These internal porosities are a consequence of the gas atomization process used for the production of the powders themselves. Therefore, the importance of using tailored powders, free from porosities, in order to manufacture components with high mechanical properties is highlighted.

Adobe photoshop quantification (PSQ) rather than point-counting: A rapid and precise method for quantifying rock textural data and porosities

Science.gov (United States)

Zhang, Xuefeng; Liu, Bo; Wang, Jieqiong; Zhang, Zhe; Shi, Kaibo; Wu, Shuanglin

2014-08-01

Commonly used petrological quantification methods are visual estimation, counting, and image analyses. However, in this article, an Adobe Photoshop-based analyzing method (PSQ) is recommended for quantifying the rock textural data and porosities. Adobe Photoshop system provides versatile abilities in selecting an area of interest and the pixel number of a selection could be read and used to calculate its area percentage. Therefore, Adobe Photoshop could be used to rapidly quantify textural components, such as content of grains, cements, and porosities including total porosities and different genetic type porosities. This method was named as Adobe Photoshop Quantification (PSQ). The workflow of the PSQ method was introduced with the oolitic dolomite samples from the Triassic Feixianguan Formation, Northeastern Sichuan Basin, China, for example. And the method was tested by comparing with the Folk's and Shvetsov's "standard" diagrams. In both cases, there is a close agreement between the "standard" percentages and those determined by the PSQ method with really small counting errors and operator errors, small standard deviations and high confidence levels. The porosities quantified by PSQ were evaluated against those determined by the whole rock helium gas expansion method to test the specimen errors. Results have shown that the porosities quantified by the PSQ are well correlated to the porosities determined by the conventional helium gas expansion method. Generally small discrepancies (mostly ranging from -3% to 3%) are caused by microporosities which would cause systematic underestimation of 2% and/or by macroporosities causing underestimation or overestimation in different cases. Adobe Photoshop could be used to quantify rock textural components and porosities. This method has been tested to be precise and accurate. It is time saving compared with usual methods.

Non-destructive radiometry inspection technique for locating reinforcements and void/porosity in bridge bearings

International Nuclear Information System (INIS)

Yahaya bin Jafar; Jaafar bin Abdullah; Mohamad Azmi bin Ismail.

1989-01-01

Defects detection in bridge bearings is very important in controlling quality and safety. Typical manufacturing defects include misalligned or bent steel plates and the presence of voids/porosity within the rubber. A non-destructive radiometry inspection technique was used to locate steel plates position and the presence of voids/porosity in bridge bearing samples provided by the Rubber Research Institute of Malaysia (RRIM). Preliminary studies show that the mentioned defects can readily be determined by this technique. Some of the results are also presented. (author)

Initial porosity of random packing : Computer simulation of grain rearrangement

NARCIS (Netherlands)

Alberts, L.J.H.

2005-01-01

The initial porosity of clastic sediments is poorly defined. In spite of this, it is an important parameter in many models that describe the diagenetic processes taking place during the burial of sediments and which are responsible for the transition from sand to sandstone. Diagenetic models are of

Linking air and water transport in intact soils to macro-porosity by combining laboratory measurements and X-ray Computed Tomography

DEFF Research Database (Denmark)

Katuwal, Sheela; Norgaard, Trine; Møldrup, Per

-porosity (R2 = 0.80 for air permeability: R2= 0.61 for 5% arrival time) and macro-porosity of the restricting layer (R2=0.83 for air permeability: R2= 0.71 for 5% arrival time) over air-filled porosity and all the correlations were positive. The high positive correlation these air and water transport...... functions with macro-porosity stressed the importance of continuity and tortuosity of pores in air, water and solute flow and transport through the soils. Negative correlations of air permeability, 5% arrival time of tracer and macro-porosity were obtained with bulk density whereas with other soil physical......With an objective to link the hydraulic properties of soil with the soil structural properties, air permeability and 5% arrival time of a conservative tracer was measured for large undisturbed soil columns from the same agricultural field. The same soil columns were scanned with a medical scanner...

Electrical impedance spectroscopy as a potential tool for recovering bone porosity

International Nuclear Information System (INIS)

Bonifasi-Lista, C; Cherkaev, E

2009-01-01

This paper deals with the recovery of porosity of bone from measurements of its effective electrical properties. The microstructural information is contained in the spectral measure in the Stieltjes representation of the bone effective complex permittivity or complex conductivity and can be recovered from the measurements over a range of frequencies. The problem of reconstruction of the spectral measure is very ill-posed and requires the use of regularization techniques. We apply the method to the effective electrical properties of cancellous bone numerically calculated using micro-CT images of human vertebrae. The presented method is based on an analytical approach and does not rely on correlation analysis nor on any a priori model of the bone micro-architecture. However the method requires a priori knowledge of the properties of the bone constituents (trabecular tissue and bone marrow). These properties vary from patient to patient. To address this issue, a sensitivity analysis of the technique was performed. Normally distributed random noise was added to the data to simulate uncertainty in the properties of the constituents and possible experimental errors in measurements of the effective properties. The values of porosity calculated from effective complex conductivity are in good agreement with the true values of bone porosity even assuming high level errors in the estimation of the bone components. These results prove the future potential of electrical impedance spectroscopy for in vivo monitoring of level and treatment of osteoporosis.

Calcium silicate-based sealers: Assessment of physicochemical properties, porosity and hydration.

Science.gov (United States)

Marciano, Marina Angélica; Duarte, Marco Antonio Hungaro; Camilleri, Josette

2016-02-01

Investigation of hydration, chemical, physical properties and porosity of experimental calcium silicate-based sealers. Experimental calcium silicate-based sealers with calcium tungstate and zirconium oxide radio-opacifiers were prepared by mixing 1g of powder to 0.3 mL of 80% distilled water and 20% propylene glycol. MTA and MTA Fillapex were used as controls. The raw materials and set sealers were characterized using a combination of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Physical properties were analyzed according to ANSI/ADA. The pH and calcium ion release were assessed after 3, 24, 72 and 168 h. The porosity was assessed using mercury intrusion porosimetry. The analysis of hydration of prototype sealers revealed calcium hydroxide as a by-product resulting in alkaline pH and detection of calcium ion release, with high values in initial periods. The radiopacity was similar to MTA for the sealers containing high amounts of radio-opacifiers (p>0.05). Flowability was higher and film thickness was lower for resinous MTA Fillapex sealer (p0.05). The prototype sealers presented adequate hydration, elevated pH and calcium ion release. Regarding physical properties, elevated proportions of radio-opacifiers were necessary to accomplish adequate radiopacity, enhance flowability and reduce film thickness. All the tested sealers presented water sorption and porosity similar to MTA. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Porosity characterization of biodegradable porous poly (L-lactic acid) electrospun nanofibers

Science.gov (United States)

Valipouri, Afsaneh; Gharehaghaji, Ali Akbar; Alirezazadeh, Azam; Ravandi, Seyed Abdolkarim Hosseini

2017-12-01

Poly-L lactic acid (PLLA) is one of the mostly used fibers in biomedical applications as a biodegradable and biocompatible material. Porosity and fiber diameter distribution are governing factors that determine the performance of nanofibers. Present work aims at investigating the process parameters that are affecting porosity and diameter distribution of PLLA nanofibers. PLLA nanofibers were fabricated through electrospinning method using the solution of PLLA polymer/dichloromethane (DCM). Nanofibers with various fiber diameter distribution and porosity were made by changing of process parameters such as spinning distance (5, 10 and 15 cm), voltage (11 and 15 kV), solution concentration (10, 11 and 12 wt%) and feeding rate (0.3, 0.4 and 0.7 ml h-1). Image processing techniques (with Matlab R2017), surface analysis (with Mountainsmap7) and diameter distribution analysis (with Measurement software) were used to examine surface morphology of samples. The results showed that the fiber diameter distribution becomes wider with increasing the applied voltage and reducing the spinning distance. In the other hand, coarse fibers possessed larger pores while having irregular and fewer pores in comparison to fine fibers. The most uniform nano-web with high porous nanofibers was attained by the choice of the process parameters at the voltage of 11 kV, spinning distance of 15 cm, feeding rate of 0.4 ml h-1 and solution concentration of 10 wt%.

Effect of W/C Ratio on Durability and Porosity in Cement Mortar with Constant Cement Amount

Directory of Open Access Journals (Sweden)

Yun-Yong Kim

2014-01-01

Full Text Available Water is often added to concrete placing for easy workability and finishability in construction site. The additional mixing water can help easy mixing and workability but causes increased porosity, which yields degradation of durability and structural performances. In this paper, cement mortar samples with 0.45 of W/C (water to cement ratio are prepared for control case and durability performances are evaluated with additional water from 0.45 to 0.60 of W/C. Several durability tests including strength, chloride diffusion, air permeability, saturation, and moisture diffusion are performed, and they are analyzed with changed porosity. The changing ratios and patterns of durability performance are evaluated considering pore size distribution, total porosity, and additional water content.

Effect of SCM on porosity

DEFF Research Database (Denmark)

Canut, Mariana

Pores are an inherent part of cement-based materials. The pores range from nm to cm varying in shape and distribution. The amount, size and distribution of pores affect the engineering properties. As a first approximation, the total porosity affects the mechanical behavior, whereas the size...... blast furnaces, fly ash from coal fired power stations, and silica fume from ferrosilicon production. Studies suggest that the improvement of the strength and durability using SCMs are governed by refinement of the pores in the cement paste. Both the chemical and physical properties of the SCMs...... and connectivity of pores affect durability. Supplementary cementitious materials (SCMs) are being increasingly used as a substitute for Portland cement in the interests of sustainability and to improve the engineering properties of concrete as strength and durability. SCMs are by-products such as slag from iron...

Etude de la diagraphie neutron du granite de Beauvoir. Effet neutron des altérations et de la matrice du granite. Calibration granite. Porosité totale à l'eau et porosité neutron Analysis of the Beauvoir Granite Neutron Log. Neutron Effect of Alterations and of the Granite Matrix. Granite Calibration. Total Water Porosity and Neutron Porosity

Directory of Open Access Journals (Sweden)

Galle C.

2006-11-01

carottes (n. Nous montrons que, pour le granite de Beauvoir, l'effet neutron de la matrice est important (en moyenne proche de 7% et ne peut être négligé lorsque l'on mesure des porosités voisines de 0,5% sur carottes. La calibration de l'outil neutron dans le granite et non pas dans des calcaires est d'autre part capitale quant à la précision quantitative des résultats. This article describes the research done on the Beauvoir granite (Echassières GPF 1 borehole, French Massif Central range. The aim of this project was to obtain representative values of the water saturation (n total free water porosity of the Beauvoir granite from PorosityN neutron porosity (BRGM neutron log. The exact knowledge of the porosity of a crystalline block is effectively fundamental to determine its possibilities for being used as a waste storage site. With this goal, neutron logging provides indispensable information concerning the characterization of a porous medium. Our procedure was experimental, and we tried to go more deeply into various problems linked to the use of neutron logging in a granitic rock. Two main factors governed the neutron response : (i the hydrogen concentration of the formation (free water and combined water of various minerals and (ii the presence of absorber elements with a large capture cross-section such as gadolinium, cadmium, boron as well as lithium for the Beauvoir granite. After measuring the Beauvoir granite n total (free water porosity on core samples, we evaluated the combined water content of each sample tested on the basis of fire loss tests on rock powder at 900°C. From the hydrogen atoms volumic concentration, we determined a hydrogen index that we directly converted into the PorosityN(OH- neutron porosity, (by definition, pure water at 20°C has a hydrogen index of 1 which is equivalent to a 100% porosity. For the Beauvoir granite, the matrix combined water represents an average neutron porosity (Table 1 of about 4%. In the second phase, we used

Porosity, sorption and diffusivity data compiled for the SKB 91 study

International Nuclear Information System (INIS)

Brandberg, F.; Skagius, K.

1991-04-01

The SKB 91 study is an integrated safety analysis of the KBS-3 concept of a repository located in the Finnsjoen area. For this study, values of important transport parameters in the bentonite backfill and in the rock are proposed. K d -values, diffusivities and diffusion porosity for different elements in compacted MX-80 bentonite are based on experimental data found in the literature. With regard to sorption, both a best estimate and a conservative value is given. Because sorption on bentonite is very much dependent on the conditions prevailing and experimental data are limited and not necessary representative for the conditions expected in the repository, the proposed best estimate values may include large uncertainties. Data proposed for rock are matrix diffusivities, matrix porosity and diffusivity in mobile bulk water. These values are based on experimental results on Finnsjoe rock. (au)

A Study on Porosity Distribution in Nanoporous TiO2 Photoelectrodes for Output Performance of Dye-Sensitized Solar Cells

International Nuclear Information System (INIS)

Wei-Wei, Xu; Xiang-Dong, Luo; Wei-Ping, Jing; Lin-Hua, Hu; Song-Yuan, Dai; Chang-Neng, Zhang

2010-01-01

Porosity as one of the crucial factors to film morphology affects the overall electrical current-voltage characteristics of dye-sensitized solar cell (DSC). We search for the short-circuit current density, the open-circuit voltage and the maximum power output as the main functional parameters of DSC closely related to porosity under different film thickness. The theoretical analyses show some exciting results. As porosity changes from 0.41 to 0.75, the short-circuit current density shows the optimal value when the film thickness is 8–10 μm. The open-circuit voltage presents different variation tendencies for the film thicknesses within 1–8 μm and within 10–30 μm. The porosity is near 0.41 and the film thickness is about 10 μm, DSC will have the maximum power output. The theoretical studies also illustrate that given a good porosity distribution, DSC can obtain an excellent short-circuit current characteristic, which agrees well with the experimental results reported in previous literature. (cross-disciplinary physics and related areas of science and technology)

Black bears with longer disuse (hibernation) periods have lower femoral osteon population density and greater mineralization and intracortical porosity.

Science.gov (United States)

Wojda, Samantha J; Weyland, David R; Gray, Sarah K; McGee-Lawrence, Meghan E; Drummer, Thomas D; Donahue, Seth W

2013-08-01

Intracortical bone remodeling is persistent throughout life, leading to age related increases in osteon population density (OPD). Intracortical porosity also increases with age in many mammals including humans, contributing to bone fragility and fracture risk. Unbalanced bone resorption and formation during disuse (e.g., physical inactivity) also increases intracortical porosity. In contrast, hibernating bears are a naturally occurring model for the prevention of both age-related and disuse osteoporoses. Intracortical bone remodeling is decreased during hibernation, but resorption and formation remain balanced. Black bears spend 0.25-7 months in hibernation annually depending on climate and food availability. We found longer hibernating bears demonstrate lower OPD and higher cortical bone mineralization than bears with shorter hibernation durations, but we surprisingly found longer hibernating bears had higher intracortical porosity. However, bears from three different latitudes showed age-related decreases in intracortical porosity, indicating that regardless of hibernation duration, black bears do not show the disuse- or age-related increases in intracortical porosity which is typical of other animals. This ability to prevent increases in intracortical porosity likely contributes to their ability to maintain bone strength during prolonged periods of physical inactivity and throughout life. Improving our understanding of the unique bone metabolism in hibernating bears will potentially increase our ability to develop treatments for age- and disuse-related osteoporoses in humans. Copyright © 2013 Wiley Periodicals, Inc.

Simultaneous thermal neutron decay time and porosity logging system

International Nuclear Information System (INIS)

Shultz, W.E.

1980-01-01

A method for simultaneously determining the porosity and thermal neutron capture cross-section of earth formations in the vicinity of a well borehole is claimed. It comprises the following steps: passing a well tool into a cased well borehole. The tool has a pulsed source of fast neutrons, a combination fast neutron and gamma ray detector and an epithermal neutron detector; repetitively irradiating the earth formations in the vicinity of the borehole with bursts of fast neutrons; detecting the fast neutron and epithermal neutron populations in the borehole (during the neutron bursts) and generating first and second measurement signals; detecting for second and third time intervals during the time between the neutron bursts, the gamma radiation present in the borehole due to the capture of thermalized neutrons by the nuclei of elements comprising the earth formations and generating third and fourth measurement signals; and combining the first and second measurement signals according to a predetermined relationship to derive an indication of the porosity of the earth formations and combining the third and fourth measurement signals to derive an indication of the thermal neutron capture cross-section of the earth formations

Method and apparatus for epithermal neutron porosity well logging

International Nuclear Information System (INIS)

Hertzog, R.C.; Loomis, W.A.; Wraight, P.

1991-01-01

This patent describes a method for investigating the porosity of a subsurface earth formation surrounding a borehole. It comprises repetitively irradiating the borehole and earth formation with discrete bursts of high energy neutrons from a neutron source, which neutrons interact with nuclei of the materials in the borehole and the formation to produce therein populations of epithermal neutrons; detecting the populations of epithermal neutrons at near and far locations in the borehole spaced apart longitudinally by different distances from the neutron source; generating count signals indicative of the magnitudes of the detected epithermal neutron populations at the respective near and far locations; detecting the decay of the epithermal neutron populations following the neutron bursts at least at one location in the borehole and generating signals representative thereof; deriving from the decay signals a signal indicative of the slowing down time of epithermal neutrons in the formation of the at least one location; and deriving from the near and far count signals and the slowing down time signal a measurement signal representative of the porosity of the formation surrounding the borehole inherently compensated for the effects of tool standoff on the responses of the logging tool

Total and methyl mercury, moisture, and porosity in Lake Michigan surficial sediment

Data.gov (United States)

U.S. Environmental Protection Agency — Total and methyl mercury, moisture content (%), and porosity were measured in Lake Michigan sediment by the U.S. Environmental Protection Agency/Office of Research...

Porous silicon photoluminescence modification by colloidal gold nanoparticles: Plasmonic, surface and porosity roles

International Nuclear Information System (INIS)

Mora, M.B. de la; Bornacelli, J.; Nava, R.; Zanella, R.; Reyes-Esqueda, J.A.

2014-01-01

Metal nanoparticles on semiconductors are of interest because of the tunable effect of the surface plasmon resonance on the physical properties of the semiconductor. In this work, colloidal gold nanoparticles obtained by two different methods, with an average size of 6.1±2.0 nm and 5.0±2.0 nm, were added to luminescent porous silicon by drop casting. The gold nanoparticles interact with porous silicon by modifying its optical properties such as photoluminescence. That being said, plasmon effects are not the only to be taken into account; as shown in this work, surface chemical modification and porosity also play a key role in the final performance of photoluminescence of a porous silicon–gold nanoparticle hybrid system. -- Highlights: • A hybrid material consisting of porous silicon and gold nanoparticles was fabricated. • Porous silicon/gold nanoparticle hybrid material was made by drop casting. • Influence of plasmonics, surface chemical modification and porosity on the optical behavior of our material was analyzed. • Porosity is proposed as a parameter control to obtain the best effects on luminescence of the hybrid plasmonic material

Porous silicon photoluminescence modification by colloidal gold nanoparticles: Plasmonic, surface and porosity roles

Energy Technology Data Exchange (ETDEWEB)

Mora, M.B. de la; Bornacelli, J. [Instituto de Física, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Nava, R. [Centro de Investigación en Energía, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico); Zanella, R. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Reyes-Esqueda, J.A., E-mail: betarina@gmail.com [Instituto de Física, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico)

2014-02-15

Metal nanoparticles on semiconductors are of interest because of the tunable effect of the surface plasmon resonance on the physical properties of the semiconductor. In this work, colloidal gold nanoparticles obtained by two different methods, with an average size of 6.1±2.0 nm and 5.0±2.0 nm, were added to luminescent porous silicon by drop casting. The gold nanoparticles interact with porous silicon by modifying its optical properties such as photoluminescence. That being said, plasmon effects are not the only to be taken into account; as shown in this work, surface chemical modification and porosity also play a key role in the final performance of photoluminescence of a porous silicon–gold nanoparticle hybrid system. -- Highlights: • A hybrid material consisting of porous silicon and gold nanoparticles was fabricated. • Porous silicon/gold nanoparticle hybrid material was made by drop casting. • Influence of plasmonics, surface chemical modification and porosity on the optical behavior of our material was analyzed. • Porosity is proposed as a parameter control to obtain the best effects on luminescence of the hybrid plasmonic material.

The effect of pore size and porosity on thermal management performance of phase change material infiltrated microcellular metal foams

International Nuclear Information System (INIS)

Sundarram, Sriharsha S.; Li, Wei

2014-01-01

The effect of pore size and porosity on the performance of phase change material (PCM) infiltrated metal foams, especially when the pore size reduces to less than 100 μm, is investigated in this study. A three dimensional finite element model was developed to consider both the metal and PCM domains, with heat exchange between them. The pore size and porosity effects were studied along with other system variables including heat generation and dissipation of the PCM-based thermal management system. It is shown that both porosity and pore size have strong effects on the heating of PCM. At a fixed porosity, a smaller pore size results in a lower temperature at the heat source for a longer period of time. The effects of pore size and porosity were more pronounced at high heat generation and low convective cooling conditions, representing the situation of portable electronics. There is an optimal porosity for the PCM-metal foam system; however, the optimal value only occurs at high cooling conditions. The net effective thermal conductivity of a PCM-microcellular metal foam system could be doubled by reducing the pore size from 100 μm to 25 μm. - Highlights: •Pore size and porosity of phase change material-microcellular metal foam were investigated. •A smaller pore size results in a lower temperature at the heat source for a longer period of time. •The effects were more pronounced at high heating and low cooling conditions. •Net thermal conductivity doubled by reducing the pore size from 100 μm to 25 μm

A kinetic study of the replacement of calcite marble by fluorite

Science.gov (United States)

Trindade Pedrosa, Elisabete; Boeck, Lena; Putnis, Christine V.; Putnis, Andrew

2016-04-01

Replacement reactions are relevant in any situation that involves the reequilibration between a solid and an aqueous fluid phase and are commonly controlled by an interface-coupled dissolution-precipitation mechanism (Putnis and Putnis, 2007). These reactions control many large-scale Earth processes whenever aqueous fluids are available, such as during metamorphism, metasomatism, and weathering. An important consequence of coupled dissolution-precipitation is the generation of porosity in the product phase that then allows the infiltration of the fluid within the mineral being replaced. Understanding the mechanism and kinetics of the replacement of carbonates by fluorite has application in earth sciences and engineering. Fluorite (CaF2) occurs in all kinds of rocks (igneous, sedimentary, and metamorphic) and its origin is commonly associated with hydrothermal fluids. Moreover, calcium carbonate has been suggested as a successful seed material for the sequestration of fluoride from contaminated waters (Waghmare and Arfin, 2015). The aim of the present work is to investigate aspects of the replacement of calcium carbonate by fluorite to better understand the mechanism and kinetics of this reaction. Small cubes (˜ 3 × 3 × 3 mm) of Carrara marble (CaCO3 > 99 %) were cut and reacted with a 4 M ammonium fluoride (NH4F) solution for different times (1 to 48 hours) and temperatures (60, 80, 100, and 140 ° C). The microstructure of the product phases was analysed using SEM. The kinetics of replacement was monitored from the Rietveld analysis of X-ray powder diffraction patterns of the products as a function of temperature and reaction time. After reaction, all samples preserved their size and external morphology (a pseudomorphic replacement) and the product phase (fluorite) was highly porous. The activation energy Ea (kJ/mol) of the replacement reaction was empirically determined by both model-fitting and model-free methods. The isoconversional method yielded an

Investigation of porosity and pore structure adjacent to fractures by PMMA method. Samples taken from drill cores at Olkiluoto

International Nuclear Information System (INIS)

Siitari-Kauppi, M.; Ikonen, J.; Kauppi, L.; Lindberg, A.

2010-10-01

The porosity, pore structure and micro fracturing of 18 rock cores from drill holes OLKR4, OL-KR11, OL-KR13, OL-KR14, OL-KR15, OL-KR20 and OL-KR25. The porosity was investigated by the C-14-PMMA autoradiographic method. The main focus was to analyse the changes in porosity and mineralogy adjacent to the typical fractures in the bedrock of Olkiluoto as a mean of porosity profiles. The method makes it possible to study the spatial distribution of the pore space in rock, and the heterogeneity of rock matrices is revealed at the sub micrometre to the centimetre scale. Subsequent autoradiography and digital image analysis make it possible to analyse features limited in size by the range of C-14 beta radiation. The description of the method was given in Posiva working report 2009-03. The samples for this work were chosen in April 2008. The C-14-PMMA method involves the impregnation of centimetre-scale rock cores with C-14 labelled methylmethacrylate (C-14-MMA) in a vacuum, irradiation polymerisation, autoradiography and optical densitometry using digital image-processing techniques. Impregnation with C-14-MMA, a labelled low-molecular-weight and lowviscosity monomer which wets the silicate surfaces well and which can be fixed by polymerisation provides information about the accessible pore space in crystalline rock that cannot be obtained using other methods. The microscopy analyses for mineral identification were done for every PMMA impregnated sample in Geological Survey of Finland. The total porosities of the studied rock cores varied between 0.1 % and 8 %. However, spatially the porosities of 30 - 40 % were determined for the minerals that were strongly altered. The porosity changes were observed adjacent to the fracture surfaces forming from a few to several millimetres porous zones. The heterogeneity of the porosity patterns adjacent to the fracture surfaces was abundant due to mineral alteration. (orig.)

Influence of refining process on the porosity of high pressure die casting alloy Al-Si

Directory of Open Access Journals (Sweden)

A.W. Orlowicz

2009-04-01

Full Text Available This study presents research results of the influence that refining and transfer of AlSi12S alloy on the porosity of high pressure diecastings.Tests were conducted under production conditions of Die-casting Foundry META-ZEL Sp z o.o. The operation of refining was conducted in a melting furnace, with the use of an FDU Mini Degasser. Decay of the refining effect was assessed by evaluating the porosity content and metallographic examination.

Investigations of effective porosity of till by means of a combined soil-moisture/density gauge

International Nuclear Information System (INIS)

Nordberg, L.; Modig, S.

1974-01-01

Effective porosity and processes of saturation and dewatering in till have been investigated. The study was performed in undisturbed till columns, surrounded by ring-shaped excavations filled with sand. The procedure allowed for a raising and lowering of an artificial groundwater level in the till under controlled conditions, which in turn made possible controlled processes of saturation and dewatering. A combined gamma-neutron soil moisture /density gauge was used. The water content was recorded during a period in which water was added to a specially prepared, undisturbed in-situ soil column until a state of saturation was reached. This was followed by a period of induced dewatering by gravity drainage. The drainage was recorded until a steady state> approximately equalling field capacity, was approached (5-16 d). Water contents at saturation are assumed approximately to equal total porosity, having a range of 17.9-32.0% in the investigated till. The intensity of drainage was highest on the first day of dewatering and then diminished with time. A perfectly steady state was never reached. Therefore field capacity is used with indices, indicating the length of time of drainage. Consequently, effective porosity is qualified by the corresponding indices. After 15-16 days of gravity drainage, effective porosity was calculated to be on the average 7.4% at one test plot and 3.4% at another. The difference has been attributed to a corresponding difference in depth to the natural groundwater level; because of the method used a higher groundwater level and capillary fringe may have hampered the complete drainage, resulting in a relatively low value of effective porosity. The investigation is most likely to be applicable in water balance studies, groundwater discharge predictions and various construction and waste-water projects in moraine terrain. (author)

Porosity and liquid absorption of cement paste

DEFF Research Database (Denmark)

Krus, M.; Hansen, Kurt Kielsgaard; Kunzel, H. M.

1997-01-01

be a slowing-down effect which is related to water because the absorption of organic liquids, such as hexane, is quite normal. Measurements of the porosity of hardened cement paste determined by helium pycnometry and water saturation show that water molecules can enter spaces in the microstructure which...... are not accessible to the smaller helium atoms. Considering the results of dilatation tests both before and after water and hexane saturation, it seems possible that a contraction of capillary pores due to moisture-related swelling of the cement gel leads to the non-linear water absorption over the square root...

3D Membrane Imaging and Porosity Visualization

KAUST Repository

Sundaramoorthi, Ganesh

2016-03-03

Ultrafiltration asymmetric porous membranes were imaged by two microscopy methods, which allow 3D reconstruction: Focused Ion Beam and Serial Block Face Scanning Electron Microscopy. A new algorithm was proposed to evaluate porosity and average pore size in different layers orthogonal and parallel to the membrane surface. The 3D-reconstruction enabled additionally the visualization of pore interconnectivity in different parts of the membrane. The method was demonstrated for a block copolymer porous membrane and can be extended to other membranes with application in ultrafiltration, supports for forward osmosis, etc, offering a complete view of the transport paths in the membrane.

A CFD-Model for prediction of unintended porosities in metal matrix composites

DEFF Research Database (Denmark)

Li, Shizhao; Spangenberg, Jon; Hattel, Jesper Henri

2013-01-01

This paper presents a numerical method that simulates the flow through the porous corridors of the preform, which in theory enables the prediction of unintended porosities at the end of the process....

Thermal decomposition and kinetic evaluation of decanted 2,4,6-trinitrotoluene (TNT) for reutilization as composite material

Science.gov (United States)

Ahmed, M. F.; Hussain, A.; Malik, A. Q.

2016-08-01

Use of energetic materials has long been considered for only military purposes. However, it is very recent that their practical applications in wide range of commercial fields such as mining, road building, under water blasting and rocket propulsion system have been considered. About 5mg of 2,4,6-trinitrotoluene (TNT) in serviceable (Svc) as well as unserviceable (Unsvc) form were used for their thermal decomposition and kinetic parameters investigation. Thermogravimetric/ differential thermal analysis (TG/DTA), X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to characterize two types of TNT. Arrhenius kinetic parameters like activation energy (E) and enthalpy (AH) of both TNT samples were determined using TG curves with the help of Horowitz and Metzger method. Simultaneously, thermal decomposition range was evaluated from DTA curves. Distinct diffraction peaks showing crystalline nature were obtained from XRD analysis. SEM results indicated that Unsvc TNT contained a variety of defects like cracks and porosity. Similarly, it is observed that thermal as well as kinetic behavior of both TNT samples vary to a great extent. Likewise, a prominent change in the activation energies (E) of both samples is observed. This in-depth study provides a way forward in finding solutions for the safe reutilization of decanted TNT.

Catalytic valorization of starch-rich food waste into hydroxymethylfurfural (HMF): Controlling relative kinetics for high productivity.

Science.gov (United States)

Yu, Iris K M; Tsang, Daniel C W; Yip, Alex C K; Chen, Season S; Wang, Lei; Ok, Yong Sik; Poon, Chi Sun

2017-08-01

This study aimed to maximize the valorization of bread waste, a typical food waste stream, into hydroxymethylfurfural (HMF) by improving our kinetic understanding. The highest HMF yield (30mol%) was achieved using SnCl 4 as catalyst, which offered strong derived Brønsted acidity and moderate Lewis acidity. We evaluated the kinetic balance between these acidities to facilitate faster desirable reactions (i.e., hydrolysis, isomerization, and dehydration) relative to undesirable reactions (i.e., rehydration and polymerization). Such catalyst selectivity of SnCl 4 , AlCl 3 , and FeCl 3 was critical in maximizing HMF yield. Higher temperature made marginal advancement by accelerating the undesirable reactions to a similar extent as the desirable pathways. The polymerization-induced metal-impregnated high-porosity carbon was a possible precursor of biochar-based catalyst, further driving up the economic potential. Preliminary economic analysis indicated a net gain of USD 43-236 per kilogram bread waste considering the thermochemical-conversion cost and chemical-trading revenue. Copyright © 2017 Elsevier Ltd. All rights reserved.

Non-kinetic capabilities: complementing the kinetic prevalence to targeting

OpenAIRE

Ducheine, P.

2014-01-01

Targeting is used in military doctrine to describe a military operational way, using (military) means to influence a target (or addressee) in order to achieve designated political and/or military goals. The four factors italicized are used to analyse non-kinetic targeting, complementing our knowledge and understanding of the kinetic prevalence. Paradoxically, non-kinetic targeting is not recognized as a separate concept: kinetic and non-kinetic are intertwined facets of targeting. Kinetic tar...

Multi-Scale-Porosity TiO2 scaffolds grown by innovative sputtering methods for high throughput hybrid photovoltaics

Science.gov (United States)

Sanzaro, Salvatore; Smecca, Emanuele; Mannino, Giovanni; Bongiorno, Corrado; Pellegrino, Giovanna; Neri, Fortunato; Malandrino, Graziella; Catalano, Maria Rita; Condorelli, Guglielmo Guido; Iacobellis, Rosabianca; De Marco, Luisa; Spinella, Corrado; La Magna, Antonino; Alberti, Alessandra

2016-12-01

We propose an up-scalable, reliable, contamination-free, rod-like TiO2 material grown by a new method based on sputtering deposition concepts which offers a multi-scale porosity, namely: an intra-rods nano-porosity (1-5 nm) arising from the Thornton’s conditions and an extra-rods meso-porosity (10-50 nm) originating from the spatial separation of the Titanium and Oxygen sources combined with a grazing Ti flux. The procedure is simple, since it does not require any template layer to trigger the nano-structuring, and versatile, since porosity and layer thickness can be easily tuned; it is empowered by the lack of contaminations/solvents and by the structural stability of the material (at least) up to 500 °C. Our material gains porosity, stability and infiltration capability superior if compared to conventionally sputtered TiO2 layers. Its competition level with chemically synthesized reference counterparts is doubly demonstrated: in Dye Sensitized Solar Cells, by the infiltration and chemisorption of N-719 dye (˜1 × 1020 molecules/cm3); and in Perovskite Solar Cells, by the capillary infiltration of solution processed CH3NH3PbI3 which allowed reaching efficiency of 11.7%. Based on the demonstrated attitude of the material to be functionalized, its surface activity could be differently tailored on other molecules or gas species or liquids to enlarge the range of application in different fields.

Pressure and Stress Prediction in the Nankai Accretionary Prism: A Critical State Soil Mechanics Porosity-Based Approach

Science.gov (United States)

Flemings, Peter B.; Saffer, Demian M.

2018-02-01

We predict pressure and stress from porosity in the Nankai accretionary prism with a critical state soil model that describes porosity as a function of mean stress and maximum shear stress, and assumes Coulomb failure within the wedge and uniaxial burial beneath it. At Ocean Drilling Program Sites 1174 and 808, we find that pore pressure in the prism supports 70% to 90% of the overburden (λu = 0.7 to 0.9), for a range of assumed friction angles (5-30°). The prism pore pressure is equal to or greater than that in the underthrust sediments even though the porosity is lower within the prism. The high pore pressures lead to a mechanically weak wedge that supports low maximum shear stress, and this in turn requires very low basal traction to remain consistent with the observed narrowly tapered wedge geometry. We estimate the décollement friction coefficient (μb) to be 0.08-0.38 (ϕb' = 4.6°-21°). Our approach defines a pathway to predict pressure in a wide range of environments from readily observed quantities (e.g., porosity and seismic velocity). Pressure and stress control the form of the Earth's collisional continental margins and play a key role in its greatest earthquakes. However, heretofore, there has been no systematic approach to relate material state (e.g., porosity), pore pressure, and stress in these systems.

A study of porosity of synthetic polymer nanoparticles using PALS

Energy Technology Data Exchange (ETDEWEB)

Pham, B; Smith, S V [Centre for Antimatter-Matter Studies, Australian Nuclear Science and Technology Organisation (ANSTO) NSW 2232 (Australia); Guagliardo, P; Williams, J; Samarin, S, E-mail: binh.pham@ansto.gov.au, E-mail: svs@ansto.gov.au [Centre for Antimatter-Matter Studies, School of Physics, University of Western Australia, WA 6009 (Australia)

2011-01-01

Positron annihilation lifetime spectroscopy (PALS) has been used to study the free volume in dry synthetic polymer nanoparticles of various sizes. A series of poly(styrene/divinyl benzene) particles with diameters in the range of 100 to 500 nm were synthesized and then carefully chemically treated using the sulfonation process, to increase their porosity. The particles were characterised by Scanning Electron Microscopy (SEM), light scattering and PALS. Light scattering gave larger size for the treated particles, reflecting the hydration effect and therefore the increase in porosity. PALS spectra of untreated and treated particles gave four and three life-time components, respectively. Analysis by PAScual version 1.3.0 program indicated there was a reduction in the intensity and the type of the micropores in the treated particles. The data suggest PALS is a sensitive tool for detecting changes in microporosity in particles. The conflicting results obtained for light scattering compared to PALS for chemically treated particles is difficult to resolve and suggests sample preparation of polymeric materials for PALS is the critical factor.

A quantitative comparison of moldic and vuggy porosity structure in karst aquifers using image and geospatial analysis

Science.gov (United States)

Culpepper, A. R.; Manda, A. K.

2011-12-01

Limestone aquifers are vital sources of groundwater for domestic and industrial use throughout the world. To sustain rising population throughout the southeastern United States, aquifers are increasingly exploited to provide the populace clean and reliable water resources. The moldic Castle Hayne and the vuggy Biscayne aquifer systems are two highly productive aquifers that provide critical water resources to millions of citizens in eastern North Carolina and southeastern Florida, respectively. In order to better understand karst aquifers and evaluate the potential for contaminant transport, detailed investigation of 2D porosity and pore geometry using image and geospatial analysis were undertaken. The objective of this study is to compare and contrast the porosity structure of moldic and vuggy karst aquifers by quantifying 2D porosity and pore geometry from images of slabbed core samples and optical televiewer images. Televiewer images and images of painted core samples from the Spring Garden Member of the Castle Hayne aquifer and Miami Limestone Formation of the Biscayne aquifer were acquired for analysis of porosity structure. The procedure for converting images of slabbed core and televiewer images to a GIS useable format consisted of rectification, calibration, image enhancement, classification, recoding and filtering. In GIS, raster or vector formats were used to assess pore attributes (e.g., area and perimeter) and structure. Preliminary results show that both pore area and perimeter for the Spring Garden Member of the Castle Hayne and Miami Limestone Formation of the Biscayne aquifers can be described by exponential distributions. In both sets of slabbed core images the relatively small pores have the highest occurrence, whereas larger pores occur less frequently. However, the moldic Spring Garden Member of the Castle Hayne aquifer has larger pore sizes derived from cores images than the vuggy Miami Limestone Formation of Biscayne aquifer. Total porosity

In silico modeling of structural and porosity properties of additive manufactured implants for regenerative medicine.

Science.gov (United States)

Brünler, Ronny; Aibibu, Dilbar; Wöltje, Michael; Anthofer, Anna-Maria; Cherif, Chokri

2017-07-01

Additive manufacturing technologies are a promising technology towards patient-specific implants for applications in regenerative medicine. The Net-Shape-Nonwoven technology is used to manufacture structures from short fibers with interconnected pores and large functional surfaces that are predestined for cell adhesion and growth. The present study reports on a modeling approach with a particular focus on the specific structural properties. The overall porosities and mean pore-sizes of the digital models are simulated according to liquid-displacement porosity in a tool implemented in the modeling software. This allows adjusting the process parameters fiber length and fiber diameter to generate biomimetic structures with pore-sizes adapted to the requirements of the tissue that is to be replaced. Modeling the structural and porosity properties of scaffolds and implants leads to an efficient use of the processed biomaterials as the trial-and-error method is avoided. Copyright © 2017 Elsevier B.V. All rights reserved.

Reconciling the discrepancies between crystallographic porosity and guest access as exemplified by Zn-HKUST-1.

Science.gov (United States)

Feldblyum, Jeremy I; Liu, Ming; Gidley, David W; Matzger, Adam J

2011-11-16

There are several compounds for which there exists a disconnect between porosity as predicted by crystallography and porosity measured by gas sorption analysis. In this paper, the Zn-based analogue of Cu(3)(btc)(2) (HKUST-1), Zn(3)(btc)(2) (Zn-HKUST-1; btc = 1,3,5-benzenetricarboxylate) is investigated. Conventional analysis of Zn-HKUST-1 by powder X-ray diffraction and gas sorption indicates retention of crystalline structure but negligible nitrogen uptake at 77 K. By using positron annihilation lifetime spectroscopy, a densified surface layer preventing the entry of even small molecular species into the crystal framework is revealed. The material is shown to have inherent surface instability after solvent removal, rendering it impermeable to molecular guests irrespective of handling and processing methods. This previously unobserved surface instability may provide insight into the failure of other microporous coordination polymers to exhibit significant porosity despite crystal structures indicative of regular, interconnected, microporous networks.

Robust automatic high resolution segmentation of SOFC anode porosity in 3D

DEFF Research Database (Denmark)

Jørgensen, Peter Stanley; Bowen, Jacob R.

2008-01-01

Routine use of 3D characterization of SOFCs by focused ion beam (FIB) serial sectioning is generally restricted by the time consuming task of manually delineating structures within each image slice. We apply advanced image analysis algorithms to automatically segment the porosity phase of an SOFC...... anode in 3D. The technique is based on numerical approximations to partial differential equations to evolve a 3D surface to the desired phase boundary. Vector fields derived from the experimentally acquired data are used as the driving force. The automatic segmentation compared to manual delineation...... reveals and good correspondence and the two approaches are quantitatively compared. It is concluded that the. automatic approach is more robust, more reproduceable and orders of magnitude quicker than manual segmentation of SOFC anode porosity for subsequent quantitative 3D analysis. Lastly...

Porosity and adsorption properties of activated carbon derived from palm oil waste

International Nuclear Information System (INIS)

Che Seman Mahmood; Nor Hayati Alias; Choo Thye Foo; Megat Harun Al-Rashid Megat Ahmad

2004-01-01

Activated carbon have extensively been used as adsorbents in industry for the removal of pollutant species from gases for the purpose of purification and recovery of chemicals. The adsorption properties of the carbons depend very much on the porosity and type of pore presents which can be generated and controlled during synthesis and activation steps. This paper reports the effect of chemical activation by ZnCl 3 , KOH and nh 4 OH on the porosity of carbon produced from palm oil industry waste. Type of pores will further be validated by the SEM micrograph. The amount of gas adsorbed, the adsorption capacities can also be estimated based on the BET experiments data. The applicability of the produced carbon materials for the removal and exchange of hazardous incinerator gas is discussed. (Author)

Effect of Etching Parameter on Pore Size and Porosity of Electrochemically Formed Nanoporous Silicon

Directory of Open Access Journals (Sweden)

Pushpendra Kumar

2007-01-01

Full Text Available The most common fabrication technique of porous silicon (PS is electrochemical etching of a crystalline silicon wafer in a hydrofluoric (HF acid-based solution. The electrochemical process allows for precise control of the properties of PS such as thickness of the porous layer, porosity, and average pore diameter. The control of these properties of PS was shown to depend on the HF concentration in the used electrolyte, the applied current density, and the thickness of PS. The change in pore diameter, porosity, and specific surface area of PS was investigated by measuring nitrogen sorption isotherms.

Micro- and macroscopic study on the porosity of marble as a function of temperature and impregnation

Science.gov (United States)

Malaga-Starzec, K.; Akesson, U.; Lindqvist, J. E.; Schouenborg, B.

2003-04-01

The thermal weathering of marble is demonstrated by the progressive granular decohesion that leads to an increased porosity and subsequently to loss of strength. In order to determine how temperature cycling initiates changes in the porosity of fresh and impregnated stones: two chemically and petrographically very different marble types were tested for water absorption and ultrasonic velocity propagation and analysed by fluorescence microscopy and nitrogen adsorption. The influence of the impregnation materials: GypStop P17 and P22, both silica sols with different particle size, on changes of the porosity was also evaluated. A separate long-term study of thermal expansion was additionally performed on fresh unimpregnated samples. The results indicated that inter-granular decohesion was more pronounced for the calictic marble than the dolomitic marble. The impregnation materials had a mitigating effect on the granular decohesion. Use of fluorescence microscopy, among the other methods, appears to give inexpensive and reliable information about internal structure of the marbles. A better understanding of the effect that temperature has on the porosity of marble could be used as a guide for election of suitable stone material for exterior use as well as an indication for appropriate conditioning of the samples before physical properties testing.

Effects of Sintering Temperature on the Density And Porosity of ...

African Journals Online (AJOL)

Effects of sintering temperature on the density and porosity of sodium chloride preforms for alu- minium foam manufacturing have been investigated. Cold pressed salt preforms were sintered at 30, 760 and 790 and di erent times ranging between 6- 18 hours in a carbolite furnace at a heating rate of 5/minute. The Results of ...

Effect of porosity and pore morphology on the low-frequency ...

Indian Academy of Sciences (India)

Effect of porosity and pore size distribution on the low-frequency dielectric response, in the range 0.01-100 kHz, in sintered ZrO2-8 mol% Y2O3 ceramic compacts have been investigated. Small-angle neutron scattering (SANS) technique has been employed to obtain the pore characteristics like pore size distribution, ...

Rayleigh waves in elastic medium with double porosity

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Rajneesh KUMAR

2018-03-01

Full Text Available The present paper deals with the propagation of Rayleigh waves in isotropic homogeneous elastic half-space with double porosity whose surface is subjected to stress-free boundary conditions. The compact secular equations for elastic solid half-space with voids are deduced as special cases from the present analysis. In order to illustrate the analytical developments, the secular equations have been solved numerically. The computer simulated results for copper materials in respect of Rayleigh wave velocity and attenuation coe¢ cient have been presented graphically.

Qualitative and quantitative comparison of geostatistical techniques of porosity prediction from the seismic and logging data: a case study from the Blackfoot Field, Alberta, Canada

Science.gov (United States)

Maurya, S. P.; Singh, K. H.; Singh, N. P.

2018-05-01

In present study, three recently developed geostatistical methods, single attribute analysis, multi-attribute analysis and probabilistic neural network algorithm have been used to predict porosity in inter well region for Blackfoot field, Alberta, Canada, an offshore oil field. These techniques make use of seismic attributes, generated by model based inversion and colored inversion techniques. The principle objective of the study is to find the suitable combination of seismic inversion and geostatistical techniques to predict porosity and identification of prospective zones in 3D seismic volume. The porosity estimated from these geostatistical approaches is corroborated with the well log porosity. The results suggest that all the three implemented geostatistical methods are efficient and reliable to predict the porosity but the multi-attribute and probabilistic neural network analysis provide more accurate and high resolution porosity sections. A low impedance (6000-8000 m/s g/cc) and high porosity (> 15%) zone is interpreted from inverted impedance and porosity sections respectively between 1060 and 1075 ms time interval and is characterized as reservoir. The qualitative and quantitative results demonstrate that of all the employed geostatistical methods, the probabilistic neural network along with model based inversion is the most efficient method for predicting porosity in inter well region.

Hierarchy concepts: classification and preparation strategies for zeolite containing materials with hierarchical porosity.

Science.gov (United States)

Schwieger, Wilhelm; Machoke, Albert Gonche; Weissenberger, Tobias; Inayat, Amer; Selvam, Thangaraj; Klumpp, Michael; Inayat, Alexandra

2016-06-13

'Hierarchy' is a property which can be attributed to a manifold of different immaterial systems, such as ideas, items and organisations or material ones like biological systems within living organisms or artificial, man-made constructions. The property 'hierarchy' is mainly characterised by a certain ordering of individual elements relative to each other, often in combination with a certain degree of branching. Especially mass-flow related systems in the natural environment feature special hierarchically branched patterns. This review is a survey into the world of hierarchical systems with special focus on hierarchically porous zeolite materials. A classification of hierarchical porosity is proposed based on the flow distribution pattern within the respective pore systems. In addition, this review might serve as a toolbox providing several synthetic and post-synthetic strategies to prepare zeolitic or zeolite containing material with tailored hierarchical porosity. Very often, such strategies with their underlying principles were developed for improving the performance of the final materials in different technical applications like adsorptive or catalytic processes. In the present review, besides on the hierarchically porous all-zeolite material, special focus is laid on the preparation of zeolitic composite materials with hierarchical porosity capable to face the demands of industrial application.

Support vector regression for porosity prediction in a heterogeneous reservoir: A comparative study

Science.gov (United States)

Al-Anazi, A. F.; Gates, I. D.

2010-12-01

In wells with limited log and core data, porosity, a fundamental and essential property to characterize reservoirs, is challenging to estimate by conventional statistical methods from offset well log and core data in heterogeneous formations. Beyond simple regression, neural networks have been used to develop more accurate porosity correlations. Unfortunately, neural network-based correlations have limited generalization ability and global correlations for a field are usually less accurate compared to local correlations for a sub-region of the reservoir. In this paper, support vector machines are explored as an intelligent technique to correlate porosity to well log data. Recently, support vector regression (SVR), based on the statistical learning theory, have been proposed as a new intelligence technique for both prediction and classification tasks. The underlying formulation of support vector machines embodies the structural risk minimization (SRM) principle which has been shown to be superior to the traditional empirical risk minimization (ERM) principle employed by conventional neural networks and classical statistical methods. This new formulation uses margin-based loss functions to control model complexity independently of the dimensionality of the input space, and kernel functions to project the estimation problem to a higher dimensional space, which enables the solution of more complex nonlinear problem optimization methods to exist for a globally optimal solution. SRM minimizes an upper bound on the expected risk using a margin-based loss function ( ɛ-insensitivity loss function for regression) in contrast to ERM which minimizes the error on the training data. Unlike classical learning methods, SRM, indexed by margin-based loss function, can also control model complexity independent of dimensionality. The SRM inductive principle is designed for statistical estimation with finite data where the ERM inductive principle provides the optimal solution (the

Regularities in eliminating the porosity in some crystalline and amorphous materials

International Nuclear Information System (INIS)

Betekhtin, V.I.; Kadomtsev, A.G.; Amosova, O.V.

2003-01-01

The results of the number of studies on eliminating the porosity under the effect of increased temperatures and pressures performed on the cast alloys (VT5L; AL2), steels (30KhG5N2A) and amorphous alloys (Co 59 Fe 5 Si 11 Ni 10 B 15 , Fe 61 Co 20 Si 5 B 14 , Fe 77 Ni 1 Si 9 B 13 ) are considered. The change in the porosity parameters was controlled through the small-angle X-ray scattering electron microscopy. It is shown that the effect of the hydrostatic pressure leads to decrease in the excessive free volume in the amorphous alloys, related to the availability of the micropores of about 10 nm dimensions and consequently to the increase in the strength, microhardness and temperature of the viscous-brittle transition. It is noted that the acting forces of the microporosity elimination may be related both to the internal stress and the Laplace pressure conditioned by the pores surface curvature [ru

Porosity and thickness effect of porous silicon layer on photoluminescence spectra

Science.gov (United States)

Husairi, F. S.; Eswar, K. A.; Guliling, Muliyadi; Khusaimi, Z.; Rusop, M.; Abdullah, S.

2018-05-01

The porous silicon nanostructures was prepared by electrochemical etching of p-type silicon wafer. Porous silicon prepared by using different current density and fix etching time with assistance of halogen lamp. The physical structure of porous silicon measured by the parameters used which know as experimental factor. In this work, we select one of those factors to correlate which optical properties of porous silicon. We investigated the surface morphology by using Surface Profiler (SP) and photoluminescence using Photoluminescence (PL) spectrometer. Different physical characteristics of porous silicon produced when current density varied. Surface profiler used to measure the thickness of porous and the porosity calculated using mass different of silicon. Photoluminescence characteristics of porous silicon depend on their morphology because the size and distribution of pore its self will effect to their exciton energy level. At J=30 mA/cm2 the shorter wavelength produced and it followed the trend of porosity with current density applied.

ABSTRACT: CONTAMINANT TRAVEL TIMES FROM THE NEVADA TEST SITE TO YUCCA MOUNTAIN: SENSITIVITY TO POROSITY

International Nuclear Information System (INIS)

Karl F. Pohlmann; Jianting Zhu; Jenny B. Chapman; Charles E. Russell; Rosemary W. H. Carroll; David S. Shafer

2008-01-01

Yucca Mountain (YM), Nevada, has been proposed by the U.S. Department of Energy as a geologic repository for spent nuclear fuel and high-level radioactive waste. In this study, we investigate the potential for groundwater advective pathways from underground nuclear testing areas on the Nevada Test Site (NTS) to the YM area by estimating the timeframe for advective travel and its uncertainty resulting from porosity value uncertainty for hydrogeologic units (HGUs) in the region. We perform sensitivity analysis to determine the most influential HGUs on advective radionuclide travel times from the NTS to the YM area. Groundwater pathways and advective travel times are obtained using the particle tracking package MODPATH and flow results from the Death Valley Regional Flow System (DVRFS) model by the U.S. Geological Survey. Values and uncertainties of HGU porosities are quantified through evaluation of existing site porosity data and expert professional judgment and are incorporated through Monte Carlo simulations to estimate mean travel times and uncertainties. We base our simulations on two steady state flow scenarios for the purpose of long term prediction and monitoring. The first represents pre-pumping conditions prior to groundwater development in the area in 1912 (the initial stress period of the DVRFS model). The second simulates 1998 pumping (assuming steady state conditions resulting from pumping in the last stress period of the DVRFS model). Considering underground tests in a clustered region around Pahute Mesa on the NTS as initial particle positions, we track these particles forward using MODPATH to identify hydraulically downgradient groundwater discharge zones and to determine which flowpaths will intercept the YM area. Out of the 71 tests in the saturated zone, flowpaths of 23 intercept the YM area under the pre-pumping scenario. For the 1998 pumping scenario, flowpaths from 55 of the 71 tests intercept the YM area. The results illustrate that mean

A novel method for biomaterial scaffold internal architecture design to match bone elastic properties with desired porosity.

Science.gov (United States)

Lin, Cheng Yu; Kikuchi, Noboru; Hollister, Scott J

2004-05-01

An often-proposed tissue engineering design hypothesis is that the scaffold should provide a biomimetic mechanical environment for initial function and appropriate remodeling of regenerating tissue while concurrently providing sufficient porosity for cell migration and cell/gene delivery. To provide a systematic study of this hypothesis, the ability to precisely design and manufacture biomaterial scaffolds is needed. Traditional methods for scaffold design and fabrication cannot provide the control over scaffold architecture design to achieve specified properties within fixed limits on porosity. The purpose of this paper was to develop a general design optimization scheme for 3D internal scaffold architecture to match desired elastic properties and porosity simultaneously, by introducing the homogenization-based topology optimization algorithm (also known as general layout optimization). With an initial target for bone tissue engineering, we demonstrate that the method can produce highly porous structures that match human trabecular bone anisotropic stiffness using accepted biomaterials. In addition, we show that anisotropic bone stiffness may be matched with scaffolds of widely different porosity. Finally, we also demonstrate that prototypes of the designed structures can be fabricated using solid free-form fabrication (SFF) techniques.

Root porosity and radial oxygen loss related to arsenic tolerance and uptake in wetland plants

International Nuclear Information System (INIS)

Li, H.; Ye, Z.H.; Wei, Z.J.; Wong, M.H.

2011-01-01

The rates of radial oxygen loss (ROL), root porosity, concentrations of arsenic (As), iron (Fe) and manganese (Mn) in shoot and root tissues and on root surfaces, As tolerances, and their relationships in different wetland plants were investigated based on a hydroponic experiment (control, 0.8, 1.6 mg As L -1 ) and a soil pot trail (control, 60 mg As kg -1 ). The results revealed that wetland plants showed great differences in root porosity (9-64%), rates of ROL (55-1750 mmo1 O 2 kg -1 root d.w. d -1 ), As uptake (e.g., 8.8-151 mg kg -1 in shoots in 0.8 mg As L -1 treatment), translocation factor (2.1-47% in 0.8 mg As L -1 ) and tolerance (29-106% in 0.8 mg As L -1 ). Wetland plants with higher rates of ROL and root porosity tended to form more Fe/Mn plaque, possess higher As tolerance, higher concentrations of As on root surfaces and a lower As translocation factor so decreasing As toxicity. - Research highlights: → There is significant correlation between the porosity of roots and rates of ROL. → The rates of ROL are significantly correlated with tolerance indices and concentrations of As, Fe, Mn on root surface. → The rates of ROL is negatively correlated with As translocation factor. - Wetland plants with high rates of ROL tended to form more Fe plaque on root surfaces and possess higher As tolerance.

Fabrication of slag-glass composite with controlled porosity

Directory of Open Access Journals (Sweden)

Ranko Adziski

2008-06-01

Full Text Available The preparation and performance of porous ceramics made from waste materials were investigated. Slag from thermal electrical plant Kakanj (Bosnia and Herzegovina with defined granulations: (0.500÷0.250 mm; (0.250÷0.125 mm; (0.125÷0.063 mm; (0.063÷0.045 mm and 20/10 wt.% of the waste TV screen glass with a granulation <0.063 mm were used for obtaining slag-glass composites with controlled porosity. The one produced from the slag powder fraction (0.125÷0.063 mm and 20 wt.% TV screen glass, sintered at 950°C/2h, was considered as the optimal. This system possesses open porosity of 26.8±1.0%, and interconnected pores with the size of 250–400 μm. The values of E-modulus and bending strength of this composite were 10.6±0.6 GPa and 45.7±0.7 MPa, respectively. The coefficient of thermal expansion was 8.47·10-6/°C. The mass loss in 0.1M HCl solution after 30 days was 1.2 wt.%. The permeability and the form coefficient of the porous composite were K0=0.12 Da and C0=4.53·105 m-1, respectively. The porous composite shows great potential to be used as filters, diffusers for water aeration, dust collectors, acoustic absorbers, etc.

Integration of porosity and bio-functionalization to form a 3D scaffold: cell culture studies and in vitro degradation

Energy Technology Data Exchange (ETDEWEB)

Mittal, Anupama; Negi, Poonam; Garkhal, Kalpna; Verma, Shalini; Kumar, Neeraj, E-mail: neeraj@niper.ac.i [Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, SAS Nagar-160 062, Punjab (India)

2010-08-01

In this study, porous poly(lactide-co-glycolide) (PLGA) (50/50) microspheres have been fabricated by the gas-foaming technique using ammonium bicarbonate as a gas-foaming agent. Microspheres of different porosities have been formulated by varying the concentration of the gas-foaming agent (0%, 5%, 10% and 15% w/v). These microspheres were characterized for particle size, porosity and average pore size, morphology, water uptake ratio and surface area and it was found that the porosity, pore size and surface area increased on increasing the concentration of the gas-foaming agent. Further, the effect of porosity on degradation behavior was evaluated over a 12 week period by measuring changes in mass, pH, molecular weight and morphology. Porosity was found to have an inverse relationship with degradation rate. To render the surface of the microspheres biomimetic, peptide P-15 was coupled to the surface of these microspheres. In vitro cell viability, proliferation and morphological evaluation were carried out on these microsphere scaffolds using MG-63 cell line to study the effect of the porosity and pore size of scaffolds and to evaluate the effect of P-15 on cell growth on porous scaffolds. MTT assay, actin, alizarin staining and SEM revealed the potential of biomimetic porous PLGA (50/50) microspheres as scaffolds for tissue engineering. As shown in graphical representation, an attempt has been made to correlate the cell behavior on the scaffolds (growth, proliferation and cell death) with the concurrent degradation of the porous microsphere scaffold as a function of time.

Integration of porosity and bio-functionalization to form a 3D scaffold: cell culture studies and in vitro degradation

International Nuclear Information System (INIS)

Mittal, Anupama; Negi, Poonam; Garkhal, Kalpna; Verma, Shalini; Kumar, Neeraj

2010-01-01

In this study, porous poly(lactide-co-glycolide) (PLGA) (50/50) microspheres have been fabricated by the gas-foaming technique using ammonium bicarbonate as a gas-foaming agent. Microspheres of different porosities have been formulated by varying the concentration of the gas-foaming agent (0%, 5%, 10% and 15% w/v). These microspheres were characterized for particle size, porosity and average pore size, morphology, water uptake ratio and surface area and it was found that the porosity, pore size and surface area increased on increasing the concentration of the gas-foaming agent. Further, the effect of porosity on degradation behavior was evaluated over a 12 week period by measuring changes in mass, pH, molecular weight and morphology. Porosity was found to have an inverse relationship with degradation rate. To render the surface of the microspheres biomimetic, peptide P-15 was coupled to the surface of these microspheres. In vitro cell viability, proliferation and morphological evaluation were carried out on these microsphere scaffolds using MG-63 cell line to study the effect of the porosity and pore size of scaffolds and to evaluate the effect of P-15 on cell growth on porous scaffolds. MTT assay, actin, alizarin staining and SEM revealed the potential of biomimetic porous PLGA (50/50) microspheres as scaffolds for tissue engineering. As shown in graphical representation, an attempt has been made to correlate the cell behavior on the scaffolds (growth, proliferation and cell death) with the concurrent degradation of the porous microsphere scaffold as a function of time.

Control of Porosity and Pore Size of Metal Reinforced Carbon Nanotube Membranes

Directory of Open Access Journals (Sweden)

Stephen Gray

2010-12-01

Full Text Available Membranes are crucial in modern industry and both new technologies and materials need to be designed to achieve higher selectivity and performance. Exotic materials such as nanoparticles offer promising perspectives, and combining both their very high specific surface area and the possibility to incorporate them into macrostructures have already shown to substantially increase the membrane performance. In this paper we report on the fabrication and engineering of metal-reinforced carbon nanotube (CNT Bucky-Paper (BP composites with tuneable porosity and surface pore size. A BP is an entangled mesh non-woven like structure of nanotubes. Pure CNT BPs present both very high porosity (>90% and specific surface area (>400 m2/g. Furthermore, their pore size is generally between 20–50 nm making them promising candidates for various membrane and separation applications. Both electro-plating and electroless plating techniques were used to plate different series of BPs and offered various degrees of success. Here we will report mainly on electroless plated gold/CNT composites. The benefit of this method resides in the versatility of the plating and the opportunity to tune both average pore size and porosity of the structure with a high degree of reproducibility. The CNT BPs were first oxidized by short UV/O3 treatment, followed by successive immersion in different plating solutions. The morphology and properties of these samples has been investigated and their performance in air permeation and gas adsorption will be reported.

Industrial waste as a source for fabrication of composite ceramics-glass with a controlled porosity

Directory of Open Access Journals (Sweden)

Adziski R.

2008-01-01

Full Text Available Metallurgical slag with granulation (-0.125+0.063mm and 20 wt% waste TV glass were used for obtaining a glass ceramic composite with a controlled porosity. This material obtained by sintering at 950oC/2h possessed thermal stability, integral porosity of 43.6% and E-modulus and bending strength of 12 GPa and 39 MPa, respectively. The composite was characterized with a permeability of 0.47 Da and generation of air bubbles with size of 1-4 mm in a water medium.

Biot's coefficient as an indicator of strength and porosity reduction: Calcareous sediments from Kerguelen Plateau

DEFF Research Database (Denmark)

Alam, Mohammad Monzurul; Borre, Mai Kirstine; Fabricius, Ida Lykke

2010-01-01

β to fall, even when porosity remains constant. Biot's coefficient correlates with strength-indicating properties: compressional and shear modulus, oedometer modulus, yield strength, strain from direct loading and creep strain. Our data indicate that β may be used for predicting the diagenetic...... Biot's coefficient, β. In calcareous ooze, β is one. Mechanical compaction reduces porosity, but only leads to a minor decrease in β. Recrystallization renders particles smoother, but does not lead to reduction in β unless it gives rise to pore stiffening cementation. Pore stiffening cementation causes...

Enhanced pyroelectric and piezoelectric properties of PZT with aligned porosity for energy harvesting applications.

Science.gov (United States)

Zhang, Yan; Xie, Mengying; Roscow, James; Bao, Yinxiang; Zhou, Kechao; Zhang, Dou; Bowen, Chris R

2017-04-14

This paper demonstrates the significant benefits of exploiting highly aligned porosity in piezoelectric and pyroelectric materials for improved energy harvesting performance. Porous lead zirconate (PZT) ceramics with aligned pore channels and varying fractions of porosity were manufactured in a water-based suspension using freeze-casting. The aligned porous PZT ceramics were characterized in detail for both piezoelectric and pyroelectric properties and their energy harvesting performance figures of merit were assessed parallel and perpendicular to the freezing direction. As a result of the introduction of porosity into the ceramic microstructure, high piezoelectric and pyroelectric harvesting figures of merits were achieved for porous freeze-cast PZT compared to dense PZT due to the reduced permittivity and volume specific heat capacity. Experimental results were compared to parallel and series analytical models with good agreement and the PZT with porosity aligned parallel to the freezing direction exhibited the highest piezoelectric and pyroelectric harvesting response; this was a result of the enhanced interconnectivity of the ferroelectric material along the poling direction and reduced fraction of unpoled material that leads to a higher polarization. A complete thermal energy harvesting system, composed of a parallel-aligned PZT harvester element and an AC/DC converter, was successfully demonstrated by charging a storage capacitor. The maximum energy density generated by the 60 vol% porous parallel-connected PZT when subjected to thermal oscillations was 1653 μJ cm -3 , which was 374% higher than that of the dense PZT with an energy density of 446 μJ cm -3 . The results are beneficial for the design and manufacture of high performance porous pyroelectric and piezoelectric materials in devices for energy harvesting and sensor applications.

Assessment of CO2 Storage Potential in Naturally Fractured Reservoirs With Dual-Porosity Models

Science.gov (United States)

March, Rafael; Doster, Florian; Geiger, Sebastian

2018-03-01

Naturally Fractured Reservoirs (NFR's) have received little attention as potential CO2 storage sites. Two main facts deter from storage projects in fractured reservoirs: (1) CO2 tends to be nonwetting in target formations and capillary forces will keep CO2 in the fractures, which typically have low pore volume; and (2) the high conductivity of the fractures may lead to increased spatial spreading of the CO2 plume. Numerical simulations are a powerful tool to understand the physics behind brine-CO2 flow in NFR's. Dual-porosity models are typically used to simulate multiphase flow in fractured formations. However, existing dual-porosity models are based on crude approximations of the matrix-fracture fluid transfer processes and often fail to capture the dynamics of fluid exchange accurately. Therefore, more accurate transfer functions are needed in order to evaluate the CO2 transfer to the matrix. This work presents an assessment of CO2 storage potential in NFR's using dual-porosity models. We investigate the impact of a system of fractures on storage in a saline aquifer, by analyzing the time scales of brine drainage by CO2 in the matrix blocks and the maximum CO2 that can be stored in the rock matrix. A new model to estimate drainage time scales is developed and used in a transfer function for dual-porosity simulations. We then analyze how injection rates should be limited in order to avoid early spill of CO2 (lost control of the plume) on a conceptual anticline model. Numerical simulations on the anticline show that naturally fractured reservoirs may be used to store CO2.

Effect of Temperature and Age of Concrete on Strength – Porosity Relation

Directory of Open Access Journals (Sweden)

T. Zadražil

2004-01-01

Full Text Available The compressive strengths of unsealed samples of concrete at the age of 180 days and have been measured at temperatures 20 °C, 300 °C, 600 °C and 900 °C. All of tests were performed for cold material. We compared our results with those obtained in [10] for the same type of concrete (age 28, resp. 90 days and measured at temperature ranging from 20 °C to 280 °C. Dependencies of compressive strength and porosity were correlated together and compared for the samples of age 28, 90 and 180 days. Behaviour of concrete of the age 90, resp. 180 days confirms generally accepted hypothesis that with increasing porosity strength of the concrete decreases. It has to be stressed out, howerer, that concrete samples of the age 28 days exhibit totally opposite dependency. 

Determination of the cork bark porosity through the gamma ray transmission technology and electronic scanning microscopy image analysis

International Nuclear Information System (INIS)

Moraes, Antonio M.C.; Moreira, Anderson C.; Appoloni, Carlos R.

2007-01-01

This work applies the gamma transmission techniques (GTR) and imaging by scanning electron microscopy (SEM) for determination of porosity in the sparkling wine bottle corks. The gamma transmission experimental apparatus consists of a micrometric table (ZX) of sample movement automated, a Am-241 source (59,53 keV, 100 mCi), lead collimators, sample-holder, Na I(Tl) detector and appropriated electronics. For the microscopic images an FEI (Quanta 200), electronic microscope with associated electronics was used, and the image analysis was performed with IMAGO software. The average porosity for 22 samples analysed by GTR was of φ=58 +- 4.6 percent. By the imaging technique the found average porosity was φ=60.0 +- 6.2 percent. (author)

Review and statistical analysis of the ultrasonic velocity method for estimating the porosity fraction in polycrystalline materials

International Nuclear Information System (INIS)

Roth, D.J.; Swickard, S.M.; Stang, D.B.; Deguire, M.R.

1990-03-01

A review and statistical analysis of the ultrasonic velocity method for estimating the porosity fraction in polycrystalline materials is presented. Initially, a semi-empirical model is developed showing the origin of the linear relationship between ultrasonic velocity and porosity fraction. Then, from a compilation of data produced by many researchers, scatter plots of velocity versus percent porosity data are shown for Al2O3, MgO, porcelain-based ceramics, PZT, SiC, Si3N4, steel, tungsten, UO2,(U0.30Pu0.70)C, and YBa2Cu3O(7-x). Linear regression analysis produced predicted slope, intercept, correlation coefficient, level of significance, and confidence interval statistics for the data. Velocity values predicted from regression analysis for fully-dense materials are in good agreement with those calculated from elastic properties

Porosity characterization of fiber-reinforced ceramic matrix composite using synchrotron X-ray computed tomography

International Nuclear Information System (INIS)

Zou, C.; Li, B.; Zhang, C.; Wang, S.; Marrow, T.J.; Reinhard, C.

2016-01-01

The pore structure and porosity of a continuous fiber reinforced ceramic matrix composite has been characterized using high-resolution synchrotron X-ray computed tomography (XCT). Segmentation of the reconstructed tomograph images reveals different types of pores within the composite, the inter-fiber bundle open pores displaying a 'node-bond' geometry, and the intra-fiber bundle isolated micropores showing a piping shape. The 3D morphology of the pores is resolved and each pore is labeled. The quantitative filtering of the pores measures a total porosity 8.9% for the composite, amid which there is about 7.1∼ 9.3% closed micropores

Estimation of Dry Fracture Weakness, Porosity, and Fluid Modulus Using Observable Seismic Reflection Data in a Gas-Bearing Reservoir

Science.gov (United States)

Chen, Huaizhen; Zhang, Guangzhi

2017-05-01

Fracture detection and fluid identification are important tasks for a fractured reservoir characterization. Our goal is to demonstrate a direct approach to utilize azimuthal seismic data to estimate fluid bulk modulus, porosity, and dry fracture weaknesses, which decreases the uncertainty of fluid identification. Combining Gassmann's (Vier. der Natur. Gesellschaft Zürich 96:1-23, 1951) equations and linear-slip model, we first establish new simplified expressions of stiffness parameters for a gas-bearing saturated fractured rock with low porosity and small fracture density, and then we derive a novel PP-wave reflection coefficient in terms of dry background rock properties (P-wave and S-wave moduli, and density), fracture (dry fracture weaknesses), porosity, and fluid (fluid bulk modulus). A Bayesian Markov chain Monte Carlo nonlinear inversion method is proposed to estimate fluid bulk modulus, porosity, and fracture weaknesses directly from azimuthal seismic data. The inversion method yields reasonable estimates in the case of synthetic data containing a moderate noise and stable results on real data.

Fuzzy model to predict porosity thought conventional well logs; Modelo Fuzzy para predicao de porosidade via perfis convencionais de poco

Energy Technology Data Exchange (ETDEWEB)

Mimbela, Renzo R.F.; Silva, Jadir C. [Universidade Estadual do Norte Fluminense (UENF), Macae, RJ (Brazil). Lab. de Engenharia e Exploracao do Petroleo (LENEP)

2004-07-01

The well logs have a great applicability in the search and evaluation of hydrocarbon. In this work we calculate porosities of the Namorado field with help of the 'Fuzzy Rule'. This is done segmenting jointly both the neutron ({phi}{sub N}) and density ({phi}{sub d}) porosities logs in groups with better relation of internal linearity. The grouping is processed keeping the best number of groups, which is efficiently chosen by a criterion related to the minimum value of 'Fuzzy Validity' measurement. As a first step, we choose the {phi}{sub N} and {phi}{sub d} values only at that depths where cores exist. To prevent picking measurements errors a previous data filtering is performed by selecting only the and their correspondent values that exhibit a maximum discrepancy with core porosity ({phi}{sub C}) around 5pu (porosity unit). A conventional average porosity {phi}{sub MED}, mixing {phi}{sub N} and {phi}{sub d} is calculated at each point, concerning its own lithological and fluids characteristics. Finally, an inversion algorithm is applied to indicate the best curve curve that fit linearly {phi}{sub C} vs. {phi}{sub MED}, {phi}{sub C} vs. {phi}{sub D} and {phi}{sub C} vs. {phi}{sub N}, and at the same time determines the values of the constants to be extrapolated in order to calculate the porosity of the whole field. (author)

Constrained KP models as integrable matrix hierarchies

International Nuclear Information System (INIS)

Aratyn, H.; Ferreira, L.A.; Gomes, J.F.; Zimerman, A.H.

1997-01-01

We formulate the constrained KP hierarchy (denoted by cKP K+1,M ) as an affine [cflx sl](M+K+1) matrix integrable hierarchy generalizing the Drinfeld endash Sokolov hierarchy. Using an algebraic approach, including the graded structure of the generalized Drinfeld endash Sokolov hierarchy, we are able to find several new universal results valid for the cKP hierarchy. In particular, our method yields a closed expression for the second bracket obtained through Dirac reduction of any untwisted affine Kac endash Moody current algebra. An explicit example is given for the case [cflx sl](M+K+1), for which a closed expression for the general recursion operator is also obtained. We show how isospectral flows are characterized and grouped according to the semisimple non-regular element E of sl(M+K+1) and the content of the center of the kernel of E. copyright 1997 American Institute of Physics

Alternative methods for determination of composition and porosity in abradable materials

Czech Academy of Sciences Publication Activity Database

Matějíček, Jiří; Kolman, Blahoslav Jan; Dubský, Jiří; Neufuss, Karel; Hopkins, N.; Zwick, J.

2006-01-01

Roč. 57, č. 2 (2006), s. 17-29 ISSN 1044-5803 Grant - others:Evropská unie GRD1-2001-40124 “SEALCOAT” (EU) Institutional research plan: CEZ:AV0Z20430508 Keywords : abradable coatings * plasma spraying * structure * porosity * composition Subject RIV: JI - Composite Materials Impact factor: 0.741, year: 2006

Porosity measurement of amorphous materials by gamma ray transmission; Medida de porosidade de materiais amorfos por transmissao de raios gama

Energy Technology Data Exchange (ETDEWEB)

Poettker, Walmir Eno

2000-07-01

In this work it is presented the measurement of the total porosity of TRe soil, Sandstone Berea rocks and porous ceramics samples. For the determination of the total porosity, the Arquimedes method (conventional) and the gamma ray transmission methodology were employed. The porosity measurement using the gamma methodology has a significant advantage respect to the conventional method due to the fast and non-destructive determination, and also for supplying results with a greater characterization in small scales, in relation to the heterogeneity of the porosity. The conventional methodology presents good results only for homogeneous samples. The experimental set up for the gamma ray transmission technique consisted of a {sup 241} Am source (59,53 keV), a NaI (Tl) scintillation detector, collimators, a XYZ, micrometric table and standard gamma spectrometry electronics connected to a multichannel analyser. (author)

Influence of frost damage and sample preconditioning on the porosity characterization of cement based materials using low temperature calorimetry

DEFF Research Database (Denmark)

Wu, Min; Fridh, Katja; Johannesson, Björn

2015-01-01

Low temperature calorimetry (LTC) can be used to study the meso-porosity of cement based materials. The influence of frost damage on the meso-porosity determination by LTC was explored on a model material MCM-41 and two cement pastes by conducting repeated cycles of freezing and melting measureme...

Application of nuclear logging to porosity studies in Itaborai basin

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Milena F.S.; Lima, Inaya; Lopes, Ricardo Tadeu, E-mail: milena@lin.ufrj.br, E-mail: inaya@lin.ufrj.br, E-mail: ricardo@lin.ufrj.br [Coordenacao dos Programas de Pos-Graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Lab. de Instrumentacao Nuclear; Ferrucio, Paula Lucia; Borghi, Leonardo, E-mail: ferrucio@acd.ufrj.br, E-mail: borghi@ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Geociencias. Dept. de Geologia; Abreu, Carlos Jorge, E-mail: jo_abreu@unb.br [Universidade de Brasilia (UnB), DF (Brazil). Inst. de Geociencias

2011-07-01

Nuclear logging provides information on bulk density and porosity variations by measuring the intensity of the scattered radiation induced on the formation by radioactive sources. In this study, nuclear logging was employed to analyze the pore-space system of the 2-ITAB-1-RJ well placed on the Itaborai limestone basin, in the state of Rio de Janeiro. This is one of the smallest sedimentary basin in Brazil and it is formed by clastic deposits and travertine limestone rocks which are fractured. Understanding the pore-space system of carbonate rocks has become important subject for the oil industry, specially in Brazil. A Density Gamma Probe (LSD) and a Neutron Probe (NEUT) were used for data acquisition, which nuclear logging was carried out in part of the well, with continuous detection for about 50 m of deep. The detection speed was 4 m/min for the LSD and 5 m/min for the NEUT. The results obtained by nuclear logging showed that the 2-ITAB-1-RJ well consists of three different intervals with rocks ranging from low to moderate porosity present in travertine, marls and gneisses. (author)

Mechanism of nucleation and growth of hydrogen porosity in solidifying A356 aluminum alloy: an analytical solution

International Nuclear Information System (INIS)

Li, K.-D.; Chang, Edward

2004-01-01

This study derives an analytical solution for the mechanism of nucleation and growth of hydrogen pore in the solidifying A356 aluminum alloy. A model of initial transient hydrogen redistribution in the growing dendritic grain is used to modify the lever rule for the mechanism of nucleation of pore. The model predicts the fraction of solid at nucleation, the temperature range of nucleation, the radius of hydrogen diffusion cell, and the supersaturation of hydrogen needed for nucleation. The role of solidus velocity in nucleation is explained. The parameters calculated from the model of nucleation are used for analyzing the mechanism of kinetic diffusion-controlled growth of pore, in which the mathematical transformations of variables are introduced. With the transformations, it is argued that the diffusion problem involving the liquid and solid phases during solidification could be treated as a classic problem of precipitation in the single-phase medium treated by Ham or Avrami. The analytical solution for the nucleation of pore is compared with the mechanism of macrosegregation. The predicted volume percent of porosity and radius of pore based on the mechanism of growth of pore is discussed with respect to the thermodynamic solution, the published experimental data, the numerical solutions, and the role of interdendritic fluid flow governed by Darcy's law

Evaluation of concrete mechanical strength through porosity

Directory of Open Access Journals (Sweden)

Olivares, M.

2004-03-01

Full Text Available The increasing on voids or pores in any material - if the rest of characteristics remains equal -always causes a decrease in their mechanical strength since the ratio volume/resistant mass is lower Following all these fact a well known conclusion rises: there is a relationship between compacity/porosity and mechanical strengths. The purpose of this research is to establish a new possible correlation between both concrete properties with independence of the proportions, type of cement, size of grain, age, use. etc. So it can be concluded that the results of this research allow the engineer or architect in charge of a restoration or reparation to determine the compression strength of a concrete element. A first step is to determine the porosity through a rather short number of tests. Subsequently, compression strength will be obtained applying just a mathematical formula.

El aumento de huecos o poros de cualquier material, lo mismo que en otras circunstancias, redunda siempre en una merma de sus resistencias mecánicas, al haber menor volumen-masa resistente. En consecuencia, puede deducirse, que hay una relación entre la compacidad/porosidad y las resistencias mecánicas. En el presente trabajo se estudia una posible correlación entre ambas propiedades del hormigón con independencia de su dosificación, tipo de cemento, granulometría, edad, uso, etc. Las conclusiones obtenidas en la presente investigación permiten al técnico, encargado de una restauración o rehabilitación, determinar la resistencia a compresión de un elemento de hormigón, una vez hallada, de una forma sencilla, la porosidad de una muestra no muy voluminosa, mediante la aplicación de una simple fórmula matemática.

Torsion of the bar of the round transverse section from the variable on length and the transverse section porosity

Directory of Open Access Journals (Sweden)

Shlyakhov S.M.

2017-06-01

Full Text Available The present article is devoted to the task of finding of level of the secondary tangent voltages arising in sections because of a variable on porosity length. The decision of such task will allow to consider secondary tangent voltages in case of determination of bearing capacity of a porous bar. Distribution of porosity on a transverse section is set rationally - pro-ceeding from early the solved tasks on selection of porosity in case of torsion of a bar of a round transverse section, on bar length – under the linear law. A research objective is to determine the level of secondary tangent voltages and to evaluate from value.

The effect of porosity on the mechanical properties of porous titanium scaffolds: comparative study on experimental and analytical values

Science.gov (United States)

Khodaei, Mohammad; Fathi, Mohammadhossein; Meratian, Mahmood; Savabi, Omid

2018-05-01

Reducing the elastic modulus and also improving biological fixation to the bone is possible by using porous scaffolds. In the present study, porous titanium scaffolds containing different porosities were fabricated using the space holder method. Pore distribution, formed phases and mechanical properties of titanium scaffolds were studied by Scanning Electron Microscope (SEM), x-ray diffraction (XRD) and cold compression test. Then the results of compression test were compared to the Gibson-Ashby model. Both experimentally measured and analytically calculated elastic modulus of porous titanium scaffolds decreased by porosity increment. The compliance between experimentally measured and analytically calculated elastic modulus of titanium scaffolds are also increased by porosity increment.

Analysis of the Coupled Influence of Hydraulic Conductivity and Porosity Heterogeneity on Probabilistic Risk Analysis

Science.gov (United States)

Libera, A.; Henri, C.; de Barros, F.

2017-12-01

Heterogeneities in natural porous formations, mainly manifested through the hydraulic conductivity (K) and, to a lesser degree, the porosity (Φ), largely control subsurface flow and solute transport. The influence of the heterogeneous structure of K on flow and solute transport processes has been widely studied, whereas less attention is dedicated to the joint heterogeneity of conductivity and porosity fields. Our study employs computational tools to investigate the joint effect of the spatial variabilities of K and Φ on the transport behavior of a solute plume. We explore multiple scenarios, characterized by different levels of heterogeneity of the geological system, and compare the computational results from the joint K and Φ heterogeneous system with the results originating from the generally adopted constant porosity case. In our work, we assume that the heterogeneous porosity is positively correlated to hydraulic conductivity. We perform numerical Monte Carlo simulations of conservative and reactive contaminant transport in a 3D aquifer. Contaminant mass and plume arrival times at multiple control planes and/or pumping wells operating under different extraction rates are analyzed. We employ different probabilistic metrics to quantify the risk at the monitoring locations, e.g., increased lifetime cancer risk and exceedance of Maximum Contaminant Levels (MCLs), under multiple transport scenarios (i.e., different levels of heterogeneity, conservative or reactive solutes and different contaminant species). Results show that early and late arrival times of the solute mass at the selected sensitive locations (i.e. control planes/pumping wells) as well as risk metrics are strongly influenced by the spatial variability of the Φ field.

A Reconciliation of Packed Column Permeability Data: Column Permeability as a Function of Particle Porosity

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Hubert M. Quinn

2014-01-01

Full Text Available In his textbook teaching of packed bed permeability, Georges Guiochon uses mobile phase velocity as the fluid velocity term in his elaboration of the Darcy permeability equation. Although this velocity frame makes a lot of sense from a thermodynamic point of view, it is valid only with respect to permeability at a single theoretical boundary condition. In his more recent writings, however, Guiochon has departed from his long-standing mode of discussing permeability in terms of the Darcy equation and has embraced the well-known Kozeny-Blake equation. In this paper, his teaching pertaining to the constant in the Kozeny-Blake equation is examined and, as a result, a new correlation coefficient is identified and defined herein based on the velocity frame used in his teaching. This coefficient correlates pressure drop and fluid velocity as a function of particle porosity. We show that in their experimental protocols, Guiochon et al. have not adhered to a strict material balance of permeability which creates a mismatch of particle porosity and leads to erroneous conclusions regarding the value of the permeability coefficient in the Kozeny-Blake equation. By correcting the experimental data to properly reflect particle porosity we reconcile the experimental results of Guiochon and Giddings, resulting in a permeability reference chart which is presented here for the first time. This reference chart demonstrates that Guiochon’s experimental data, when properly normalized for particle porosity and other related discrepancies, corroborates the value of 267 for the constant in the Kozeny-Blake equation which was derived by Giddings in 1965.

Root porosity and radial oxygen loss related to arsenic tolerance and uptake in wetland plants

Energy Technology Data Exchange (ETDEWEB)

Li, H. [State Key Laboratory for Bio-control, and School of Life Sciences, Sun Yat-sen University, Guangzhou 510006 (China); Croucher Institute for Environmental Sciences, and Department of Biology, Hong Kong Baptist University, Kowloon Tong (Hong Kong); Ye, Z.H., E-mail: lssyzhh@mail.sysu.edu.c [State Key Laboratory for Bio-control, and School of Life Sciences, Sun Yat-sen University, Guangzhou 510006 (China); Wei, Z.J. [School of Information and Technology, Guangdong University of Foreign Studies, Guangzhou 510275 (China); Wong, M.H., E-mail: mhwong@hkbu.edu.h [Croucher Institute for Environmental Sciences, and Department of Biology, Hong Kong Baptist University, Kowloon Tong (Hong Kong)

2011-01-15

The rates of radial oxygen loss (ROL), root porosity, concentrations of arsenic (As), iron (Fe) and manganese (Mn) in shoot and root tissues and on root surfaces, As tolerances, and their relationships in different wetland plants were investigated based on a hydroponic experiment (control, 0.8, 1.6 mg As L{sup -1}) and a soil pot trail (control, 60 mg As kg{sup -1}). The results revealed that wetland plants showed great differences in root porosity (9-64%), rates of ROL (55-1750 mmo1 O{sub 2} kg{sup -1} root d.w. d{sup -1}), As uptake (e.g., 8.8-151 mg kg{sup -1} in shoots in 0.8 mg As L{sup -1} treatment), translocation factor (2.1-47% in 0.8 mg As L{sup -1}) and tolerance (29-106% in 0.8 mg As L{sup -1}). Wetland plants with higher rates of ROL and root porosity tended to form more Fe/Mn plaque, possess higher As tolerance, higher concentrations of As on root surfaces and a lower As translocation factor so decreasing As toxicity. - Research highlights: There is significant correlation between the porosity of roots and rates of ROL. The rates of ROL are significantly correlated with tolerance indices and concentrations of As, Fe, Mn on root surface. The rates of ROL is negatively correlated with As translocation factor. - Wetland plants with high rates of ROL tended to form more Fe plaque on root surfaces and possess higher As tolerance.

Validation of modeling team solution and matrix porosity of granitic rocks

Czech Academy of Sciences Publication Activity Database

Vaněček, M.; Hanuš, R.; Doležalová, L.; Michálková, J.; Rousová, P.; Sosna, K.; Křížová, H.; Záruba, J.; Navrátil, Tomáš; Nakládal, P.; Brož, M.; Rohovec, Jan; Polák, M.; Milický, M.

2008-01-01

Roč. 34, 4/6 (2008), s. 1343396-1343396 ISSN 0161-6951. [International Geological Congress /33./. 06.08.2008-14.08.2008, Oslo] R&D Projects: GA MPO 1H-PK/31 Institutional research plan: CEZ:AV0Z30130516 Keywords : radioactive waste * granite * hydrogeology * model ing * porosity Subject RIV: DD - Geochemistry

Influence of Fuel Meat Porosity on Heat Capacities of Fuel Element Plate U3Si2-Al

International Nuclear Information System (INIS)

Ginting, Aslina Br.; Supardjo; Sutri Indaryati

2007-01-01

Analyze of heat capacities of Al powder, AIMg 2 cladding, U 3 Si 2 powder and PEB U 3 Si 2 -Al with the meat porosity of 4.9; 5.53 ; 6.25 ; 6.95 %; 7.90; 8.66% have been done. Analysis was conducted by using Differential Scanning Calorimeter (DSC) at temperature 30℃ to 450℃ with heating rate 1℃ /minute in Argon gas media. The purpose of analyze is to know the influence of increasing of fuel meat porosity on heat capacities because increasing of percentage of meat porosity will cause degradation the of heat capacities of PEB U 3 Si 2 -Al. Result of analysis showed that the heat capacities of Al powder, AIMg 2 cladding increase by temperature, while heat capacities of U 3 Si 2 powder was stable with increasing of temperature up to 450℃. Analysis of heat capacities toward PEB U 3 Si 2 -Al indicate that increasing of fuel meat porosity of caused degradation of the heat capacities of PEB U 3 Si 2 -Al. Data obtained were expected to serve the purpose of input to fabricator of research reactor fuel in for design of fuel element type silicide with high loading. (author)

Effect of Porosity and Concentration Polarization on Electrolyte Diffusive Transport Parameters through Ceramic Membranes with Similar Nanopore Size

Directory of Open Access Journals (Sweden)

Virginia Romero

2014-08-01

Full Text Available Diffusive transport through nanoporous alumina membranes (NPAMs produced by the two-step anodization method, with similar pore size but different porosity, is studied by analyzing membrane potential measured with NaCl solutions at different concentrations. Donnan exclusion of co-ions at the solution/membrane interface seem to exert a certain control on the diffusive transport of ions through NPAMs with low porosity, which might be reduced by coating the membrane surface with appropriated materials, as it is the case of SiO2. Our results also show the effect of concentration polarization at the membrane surface on ionic transport numbers (or diffusion coefficients for low-porosity and high electrolyte affinity membranes, which could mask values of those characteristic electrochemical parameters.

Porosity Effect on Thermal Properties of Al-12 wt % Si/Graphite Composites

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José-Miguel Molina

2017-02-01

Full Text Available The effect of porosity on the thermal conductivity and the coefficient of thermal expansion of composites obtained by infiltration of Al-12 wt % Si alloy into graphite particulate preforms has been determined. Highly irregular graphite particles were used to fabricate the preforms. The thermal conductivity of these composites gradually increases with the applied infiltration pressure given the inherent reduction in porosity. A simple application of the Hasselman-Johnson model in a two-step procedure (that accounts for the presence of both graphite particles and voids randomly dispersed in a metallic matrix offers a good estimation of the experimental results. As concerns the coefficient of thermal expansion, the results show a slight increase with saturation being approximately in the range 14.6–15.2 × 10−6 K−1 for a saturation varying from 86% up to 100%. Results lie within the standard Hashin-Strikman bounds.

Porosity Effect on Thermal Properties of Al-12 wt % Si/Graphite Composites.

Science.gov (United States)

Molina, José-Miguel; Rodríguez-Guerrero, Alejandro; Louis, Enrique; Rodríguez-Reinoso, Francisco; Narciso, Javier

2017-02-14

The effect of porosity on the thermal conductivity and the coefficient of thermal expansion of composites obtained by infiltration of Al-12 wt % Si alloy into graphite particulate preforms has been determined. Highly irregular graphite particles were used to fabricate the preforms. The thermal conductivity of these composites gradually increases with the applied infiltration pressure given the inherent reduction in porosity. A simple application of the Hasselman-Johnson model in a two-step procedure (that accounts for the presence of both graphite particles and voids randomly dispersed in a metallic matrix) offers a good estimation of the experimental results. As concerns the coefficient of thermal expansion, the results show a slight increase with saturation being approximately in the range 14.6-15.2 × 10 -6 K -1 for a saturation varying from 86% up to 100%. Results lie within the standard Hashin-Strikman bounds.

Tuning surface porosity on vanadium surface by low energy He{sup +} ion irradiation

Energy Technology Data Exchange (ETDEWEB)

Tripathi, J.K., E-mail: jtripat@purdue.edu; Novakowski, T.J.; Hassanein, A.

2016-08-15

Highlights: • Surface nanostructuring on vanadium surface using novel He{sup +} ion irradiation process. • Tuning surface-porosity using high-flux, low-energy He{sup +} ion irradiation at constant elevated sample temperature (823–173 K). • Presented top-down approach guarantees good contact between different crystallites. • Sequential significant enhancement in surface-pore edge size (and corresponding reduction in surface-pore density) with increasing sample temperature. - Abstract: In the present study, we report on tuning the surface porosity on vanadium surfaces using high-flux, low-energy He{sup +} ion irradiation as function of sample temperature. Polished, mirror-finished vanadium samples were irradiated with 100 eV He{sup +} ions at a constant ion-flux of 7.2 × 10{sup 20} ions m{sup −2} s{sup −1} for 1 h duration at constant sample temperatures in the wide range of 823–1173 K. Our results show that the surface porosity of V{sub 2}O{sub 5} (naturally oxidized vanadium porous structure, after taking out from UHV) is strongly correlated to the sample temperature and is highly tunable. In fact, the surface porosity significantly increases with reducing sample temperature and reaches up to ∼87%. Optical reflectivity on these highly porous V{sub 2}O{sub 5} surfaces show ∼0% optical reflectivity at 670 nm wavelength, which is very similar to that of “black metal”. Combined with the naturally high melting point of V{sub 2}O{sub 5}, this very low optical reflectivity suggests potential application in solar power concentration technology. Additionally, this top-down approach guarantees relatively good contact between the different crystallites and avoids electrical conductivity limitations (if required). Since V{sub 2}O{sub 5} is naturally a potential photocatalytic material, the resulting sub-micron-sized cube-shaped porous structures could be used in solar water splitting for hydrogen production in energy applications.

Characterization of geo-polymer porosity: temporal evolution and study of the confined water

International Nuclear Information System (INIS)

Benavent, Virginie

2016-01-01

In this study, we have investigated the porous network of geo-polymers. The first step consisted in characterizing the structure of the porous network by the means of both intrusive experimental techniques (water porosimetry, gas sorption and mercury intrusion) and non-intrusive techniques (small-angle X-ray and neutron scattering). By the same time, the evolutions of the porous structure as well as the mechanical properties were followed over time. The second step was to determine the structure, the thermodynamics and the dynamics of water confined in the porosity by differential scanning calorimetry, quasi-elastic neutron scattering and migration tests. Geo-polymer pore structure is a complex multi-scale porosity, a meso- and macroporous network, essentially open and connected. It consists in a vermicular meso-porous network which connects the macro-pores. The meso-pore characteristic size depends on the formulation of the geo-polymer paste and is ranged between about 4 and 10 nm. Geo-polymer have a total pore volume comprised between 40 and 50 %, the meso-porous volume represents between 7 and 15 % of the material global volume. The majority of the pore volume is then attributed to macro-pores. a slight closure of porosity was observed with time and was attributed to a dissolution-precipitation mechanism occurring at pore wall interfaces. The mechanical properties reach a maximum within 10 days, and then are stable over time when the samples were kept from drying and carbonation and at the temperature of 20 C. Besides, three kinds of water were highlighted inside the porosity: (i) an interfacial water linked at the pore surfaces, (ii) free water inside the meso-pores and (iii) free water inside macro-pores. at local time scale, the mobility of water was found close to the one of free water, and at the macroscopic scale, a decrease in diffusion coefficient of one order of magnitude was observed, together with an effect of meso-pore size. (author) [fr

Development of ultrasonic technique for measure of porosity of UO2 pellets

International Nuclear Information System (INIS)

Baroni, Douglas Brandao

2008-01-01

The characterization of nuclear fuel is of great importance to guarantee the efficiency and even the safety in the power stations. At present, the techniques used implicate elevated costs with equipment, materials and installations of radiological protection. Besides, because of being destructive techniques, they impose that the checking of the characteristics of this material is done by sampling. In this work a not destructive technique was developed for measures of porosity in ceramic materials with efficiency and precision. The objective of this work is to this technique will be able to be used in laboratory practice for measures in UO 2 pellets, so it would become viable the inspection of up to 100% of the nuclear fuel, guaranteeing bigger control of the characteristics of the used material, turning in increasing safety, efficiency and economy. The innovation of the technique is due to the fact of analysing the specter of frequency of the ultrasonic wrist, and not his time of course in the material, frequently used. In this work 40 ceramic pellets of alumina were used with values of porosity between 5,09% and 37,30%. A system of recognition of signs using artificial neural networks made possible to distinguish pellets with differences of porosity of 0,04%. It was observed that this technique can be used for several others aims, for example, in the determination of the void fraction in regimen of two-phase flow, what is very important to guarantee the efficiency and safety of nuclear reactors. (author)

Processing and properties of Titanium alloy based materials with tailored porosity and composition

Science.gov (United States)

Cabezas-Villa, Jose Luis; Olmos, Luis; Lemus-Ruiz, Jose; Bouvard, Didier; Chavez, Jorge; Jimenez, Omar; Manuel Solorio, Victor

2017-06-01

This paper deals with powder processing of Ti6Al4V titanium alloy based materials with tailored porosity and composition. Ti6Al4V powder was mixed either with salt particles acting as space holder, so as to provide two-scale porosity, or with hard TiN particles that significantly modified the microstructure of the material and increased its hardness. Finally an original three-layer component was produced. Sample microstructure was observed by SEM and micro-tomography with special interest in pore size and shape, inclusion distribution and connectivity. Compression tests provided elastic modulus and yield stress as functions of density. These materials are representative of bone implants subjected to complex biological and mechanical conditions. These results thus open avenues for processing personalized implants by powder metallurgy.

Electrical Transport Through Micro Porous Track Etch Membranes of same Porosity

Science.gov (United States)

Garg, Ravish; Kumar, Vijay; Kumar, Dinesh; Chakarvarti, S. K.

2012-12-01

Porosity, pore size and thickness of membrane are vital factors to influence the transport phenomena through micro porous track etch membranes (TEMs) and affect the various applications like separations, drug release, flow control, bio-sensing and cell size detection etc. based on transport process. Therefore, a better understanding of transport mechanism through TEMs is required for new applications in various thrust areas like biomedical devices and packaging of foods and drugs. Transport studies of electrolytic solutions of potassium chloride, through porous polycarbonate TEMS having cylindrical pores of size 0.2 μm and 0.4 μm with same porosity of 15%, have been carried out using an electrochemical cell. In this technique, the etched filter is sandwiched between two compartments of cell in such a way that the TEM acts as a membrane separating the cell into two chambers. The two chambers are then filled with electrolyte solution (KCl in distilled water). The current voltage characteristics have been drawn by stepping the voltage ranging 0 to 10 V using Keithley 2400 Series Source Measurement Unit. The results indicate that rate of ion transport through cylindrical pores although is independent of pore size of TEMs of same porosity but there seems to be effect of TEM aperture size exposed to the electrolyte used in conducting cell on ion transport magnitude. From the experimental studies, a large deviation in the conduction through TEMs was observed when compared with theoretical consideration which led to the need for modification in the applicability of simple Ohm's law to the conduction through TEMs. It is found that ion transport increases with increase in area of aperture of TEM but much lower than the expected theoretically value.

Insights into the dolomitization process and porosity modification in sucrosic dolostones, Avon Park Formation (Middle Eocene), East-Central Florida, U.S.A.

KAUST Repository

Maliva,, Robert G.

2011-03-01

The Avon Park Formation (middle Eocene) in central Florida, U.S.A., contains shallow-water carbonates that have been replaced by dolomite to varying degrees, ranging from partially replaced limestones, to highly porous sucrosic dolostones, to, less commonly, low-porosity dense dolostones. The relationships between dolomitization and porosity and permeability were studied focusing on three 305-m-long cores taken in the City of Daytona Beach. Stable-isotope data from pure dolostones (mean δ 18O = +3.91% V-PDB) indicate dolomite precipitation in Eocene penesaline pore waters, which would be expected to have been at or above saturation with respect to calcite. Nuclear magnetic log-derived porosity and permeability data indicate that dolomitization did not materially change total porosity values at the bed and formation scale, but did result in a general increase in pore size and an associated substantial increase in permeability compared to limestone precursors. Dolomitization differentially affects the porosity and permeability of carbonate strata on the scale of individual crystals, beds, and formations. At the crystal scale, dolomitization occurs in a volume-for-volume manner in which the space occupied by the former porous calcium carbonate is replaced by a solid dolomite crystal with an associated reduction in porosity. Dolomite crystal precipitation was principally responsible for calcite dissolution both at the actual site of dolomite crystal growth and in the adjoining rock mass. Carbonate is passively scavenged from the formation, which results in no significant porosity change at the formation scale. Moldic pores after allochems formed mainly in beds that experienced high degrees of dolomitization, which demonstrates the intimate association of the dolomitization process with carbonate dissolution. The model of force of crystallization-controlled replacement provides a plausible explanation for key observations concerning the dolomitization process in the

Insights into the dolomitization process and porosity modification in sucrosic dolostones, Avon Park Formation (Middle Eocene), East-Central Florida, U.S.A.

KAUST Repository

Maliva,, Robert G.; Budd, David A.; Clayton, Edward A.; Missimer, Thomas M.; Dickson, John Anthony D

2011-01-01

The Avon Park Formation (middle Eocene) in central Florida, U.S.A., contains shallow-water carbonates that have been replaced by dolomite to varying degrees, ranging from partially replaced limestones, to highly porous sucrosic dolostones, to, less commonly, low-porosity dense dolostones. The relationships between dolomitization and porosity and permeability were studied focusing on three 305-m-long cores taken in the City of Daytona Beach. Stable-isotope data from pure dolostones (mean δ 18O = +3.91% V-PDB) indicate dolomite precipitation in Eocene penesaline pore waters, which would be expected to have been at or above saturation with respect to calcite. Nuclear magnetic log-derived porosity and permeability data indicate that dolomitization did not materially change total porosity values at the bed and formation scale, but did result in a general increase in pore size and an associated substantial increase in permeability compared to limestone precursors. Dolomitization differentially affects the porosity and permeability of carbonate strata on the scale of individual crystals, beds, and formations. At the crystal scale, dolomitization occurs in a volume-for-volume manner in which the space occupied by the former porous calcium carbonate is replaced by a solid dolomite crystal with an associated reduction in porosity. Dolomite crystal precipitation was principally responsible for calcite dissolution both at the actual site of dolomite crystal growth and in the adjoining rock mass. Carbonate is passively scavenged from the formation, which results in no significant porosity change at the formation scale. Moldic pores after allochems formed mainly in beds that experienced high degrees of dolomitization, which demonstrates the intimate association of the dolomitization process with carbonate dissolution. The model of force of crystallization-controlled replacement provides a plausible explanation for key observations concerning the dolomitization process in the

Simultaneous thermal neutron decay time and porosity logging system

International Nuclear Information System (INIS)

Schultz, W.E.; Smith, H.D.; Smith, M.P.

1980-01-01

An improved method and apparatus are described for simultaneously measuring the porosity and thermal neutron capture cross section of earth formations in situ in the vicinity of a well borehole using pulsed neutron well logging techniques. The logging tool which is moved through the borehole consists of a 14 MeV pulsed neutron source, an epithermal neutron detector and a combination gamma ray and fast neutron detector. The associated gating systems, counters and combined digital computer are sited above ground. (U.K.)

Effect of hierarchical porosity and phosphorus modification on the catalytic properties of zeolite Y

Energy Technology Data Exchange (ETDEWEB)

Li, Wenlin; Zheng, Jinyu; Luo, Yibin; Da, Zhijian, E-mail: dazhijian.ripp@sinopec.com

2016-09-30

Highlights: • Hierarchical zeolite Y was prepared by citric acid treatment and alkaline treatment with NaOH&TBPH. • The addition of TBPH during desilication process transferred the bridge bonded OH− to the terminal P−OH group. • Moderate Brønsted acid sites could be created with phosphorus modification. • Zeolite with hierarchical porosity and appropriated acidities favored high conversion of 1,3,5-TIPB. - Abstract: The zeolite Y is considered as a leading catalyst for FCC industry. The acidity and porosity modification play important roles in determining the final catalytic properties of zeolite Y. The alkaline treatment of zeolite Y by dealumination and alkaline treatment with NaOH and NaOH&TBPH was investigated. The zeolites were characterized by X-ray diffraction, low-temperature adsorption of nitrogen, transmission electron microscope, NMR, NH{sub 3}-TPD and IR study of acidity. Accordingly, the hierarchical porosity and acidity property were discussed systematically. Finally, the catalytic performance of the zeolites Y was evaluated in the cracking of 1,3,5-TIPB. It was found that desilication with NaOH&TBPH ensured the more uniform intracrystalline mesoporosity with higher microporosity, while preserving higher B/L ratio and moderate Brønsted acidities resulting in catalysts with the most appropriated acidity and then with better catalytic performance.

Electromagnetic methods for rapidly characterizing porosity distributions in the upper part of the Biscayne aquifer, southern Florida

Science.gov (United States)

Mount, G. J.; Comas, X.; Cunningham, K. J.

2010-12-01

Gregory J. Mount1, Xavier Comas1, and Kevin J. Cunningham2 1Department of Geosciences, Florida Atlantic University, Boca Raton, Florida 33431 2U.S. Geological Survey, 3110 SW 9th Avenue, Fort Lauderdale, Florida 33315 Although conventional hydrological techniques of aquifer characterization, which rely on data obtained from boreholes and wells can provide very valuable direct information about porosity, storativity and transmissivity, they are invasive and can often become time consuming and relatively expensive. Near-surface electromagnetic techniques, such as ground penetrating radar (GPR), provide indirect measurements of aquifer properties that complement traditional point measurements and provide a laterally continuous subsurface image in an efficient and cost effective manner with a minimal impact on the environment. We investigated the carbonate rocks of the uppermost part (3-5 meters) of the Biscayne aquifer in Everglades National Park to better understand the distribution of karst features that can create concentrated flow of groundwater, nutrients, and contaminants. As the Biscayne aquifer is the primary source of drinking water for millions of people in southern Palm Beach, Broward, and Miami-Dade counties, knowledge about these features could create a more complete understanding of a critical natural resource. These macroporous elements contribute to the overall storage, permeability, and transmissivity of the aquifer and for that reason, delineation of their distribution and areal extent should aid in the development of more accurate groundwater flow models. The macroporous elements create numerous hyperbolic diffractions in GPR common offset profiles, and these diffractions are used directly used to estimate two-dimensional (2D) models of electromagnetic (EM) wave velocity in the subsurface. Such models are further contrasted with one-dimensional (1D) velocity models using GPR common mid-point surveys at selected locations. In order to estimate

Reservoir core porosity in the Resende formation using 3D high-resolution X-ray computed microtomography

International Nuclear Information System (INIS)

Oliveira, Milena F.S.; Lima, Inaya; Lopes, Ricardo T.; Rocha, Paula Lucia F. da

2009-01-01

The storage capacity and production of oil are influenced, among other things, by rocks and fluids characteristics. Porosity is one of the most important characteristics to be analyzed in oil industry, mainly in oil prospection because it represents the direct capacity of storage fluids in the rocks. By definition, porosity is the ratio of pore volume to the total bulk volume of the formation, expressed in percentage, being able to be absolute or effective. The aim of this study was to calculate porosity by 3D High-Resolution X-ray Computed Microtomography using core plugs from Resende Formation which were collected in Porto Real, Rio de Janeiro State. This formation is characterized by sandstones and fine conglomerates with associated fine siliciclastic sediments, and the paleoenviroment is interpreted as a braided fluvial system. For acquisitions data, it was used a 3D high resolution microtomography system which has a microfocus X-ray tube (spot size < 5μm) and a 12-bit cooled X-ray camera (CCD fiber-optically coupled to a scintillator) operated at 100 kV and 100 μA. Twenty-two samples taken at different depths from two boreholes were analyzed. A total of 961 slices were performed with a resolution of 14.9 μm. The results demonstrated that μ-CT is a reliable and effective technique. Through the images and data it was possible to quantify the porosity and to view the size and shape of porous. (author)

Microstructural characterization and grain growth kinetics of atomized Fe-6%Si alloy

Energy Technology Data Exchange (ETDEWEB)

Florio Filho, A.; Bolfarini, C.; Kiminami, C.S. [Dept. de Engenharia de Materiais, Univ. Federal de Sao Carlos, Sao Carlos SP (Brazil)

2001-07-01

The microstructural characterization of the overspray powders is considered an important step to evaluate the as-cast microstructure of preforms fabricated by spray forming process. The particles generated during the high pressure gas atomization fly toward a substrate located at the middle height into the atomization chamber and consolidate to a dense deposit. The solidification process begins already during the flight of the droplets and high cooling rate can be achieved by the droplets of the molten metal during the atomization step. Consequently, the microstructure of the preform has some typical features presented by rapidly solidified metals as low level of porosity and segregation and it is strongly influenced by the thermal history of the droplets during flight. In the present work the microstructure of the particles of the Fe-6%Si alloy was analysed by light microscopy and scanning electron microscopy (SEM). The experimental determination of the kinetic exponent n for grain boundary migration in both powder and preform was determined by isothermal treatment under argon atmosphere. It has been stated that the larger the particle size the greater the grain size in Fe-6%Si alloy. It was observed also that the interface morphology is strongly related to the particle size. Furthermore, the grain growth kinetic in the preform seems to not obey the migration mechanism where the self diffusion of elemental Fe drive the boundary displacement. (orig.)

Numerical analysis of pressure and porosity evolution in lava domes during periodic degassing conditions

Science.gov (United States)

Hyman, D.; Bursik, M. I.; Pitman, E. B.

2017-12-01

The collapse or explosive breakup of growing and degassing lava domes presents a significant hazard due to the generation of dense, mobile pyroclastic flows as well as the wide dispersal of dense ballistic blocks. Lava dome stability is in large part governed by the balance of transport and storage of gas within the pore space. Because pore pressurization reduces the effective stress within a dome, the transient distribution of elevated gas pressure is critically important to understanding dome break up. We combine mathematical and numerical analyses to gain a better understanding of the temporal variation in gas flow and storage within the dome system. In doing so, we develop and analyze new governing equations describing nonlinear gas pressure diffusion in a deforming dome with an evolving porosity field. By relating porosity, permeability, and pressure, we show that the flux of gas through a dome is highly sensitive to the porosity distribution and viscosity of the lava, as well as the timescale and magnitude of the gas supply. The numerical results suggest that the diffusion of pressure and porosity variations play an integral role in the cyclic growth and destruction of small domes.The nearly continuous cycles of lava dome growth, pressurization, and failure that have characterized the last two decades of eruptive history at Volcán Popocatépetl, Mexico provide excellent natural data with which to compare new models of transient dome pressurization. At Popocatépetl, periodic pressure increases brought on by changes in gas supply into the base of the dome may play a role in its cyclic growth and destruction behavior. We compare our model of cyclic pressurization with lava dome survival data from Popocatépetl. We show that transient changes in pore pressure explain how small lava domes evolve to a state of criticality before explosion or collapse. Additionally, numerical analyses presented here suggest that short-term oscillations cannot arise within the dome

Relationship between fiber porosity and cellulose digestibility in steam-exploded Pinus radiata

Energy Technology Data Exchange (ETDEWEB)

Wong, K.K.Y.; Deverell, K.F.; Mackie, K.L.; Clark, T.A.; Donaldson, L.A.

1988-04-05

The use of lignocellulosic materials in bioconversion processes may be improved if the critical factors limiting conversion are better understood. Steam explosion after sulfur dioxide impregnation of wood chips is an effective method for improving the enzymatic digestibility of cellulose in the softwood Pinus radiata. Digestibility of pretreated fiber was progressively increased by altering the conditions of steam explosion. With increasing digestibility, there was an observed increase in fiber porosity as measured by the solute exclusion technique. Accessible pore volume and accessible surface area to a 5-nm dextran probe positively correlated with both 2- and 24-h digestion yields from pretreated fiber. The increase in accessibility was probably the result of hemicellulose extraction and lignin redistribution. A subsequent loss in accessibility, brought about by structural collapse or further lignin redistribution, resulted in a corresponding loss in digestibility. It appears that steam explosion increases cellulose digestibility in P. radiata by increasing fiber porosity.

Energy and exergy analyses of medium temperature latent heat thermal storage with high porosity metal matrix

International Nuclear Information System (INIS)

Kumar, Ashish; Saha, Sandip K.

2016-01-01

Graphical abstract: I. Metal matrix is used as the thermal conductivity enhancers (TCE) in PCM-based TES. II. Time evolution second law analysis is evaluated for different porosities and pore diameters. III. Reduction in fluctuation in HTF temperature is significantly affected by the change in porosity (ε) shown in figure. IV. Maximum energy and exergy efficiencies are obtained for porosity of 0.85. V. Effect of pore diameter on first law and second law efficiencies is found to be marginal. - Abstract: Thermal energy storage system in a concentrating solar plant (CSP) reduces the gap between energy demand and supply caused by the intermittent behaviour of solar radiation. In this paper, detailed exergy and energy analyses of shell and tube type latent heat thermal storage system (LHTES) for medium temperature solar thermal power plant (∼200 °C) are performed to estimate the net useful energy during the charging and discharging period in a cycle. A commercial-grade organic phase change material (PCM) is stored inside the annular space of the shell and the heat transfer fluid (HTF) flows through the tubes. Thermal conductivity enhancer (TCE) in the form of metal matrix is embedded in PCM to augment heat transfer. A numerical model is developed to investigate the fluid flow and heat transfer characteristics using the momentum equation and the two-temperature non-equilibrium energy equation coupled with the enthalpy method to account for phase change in PCM. The effects of storage material, porosity and pore-diameter on the net useful energy that can be stored and released during a cycle, are studied. It is found that the first law efficiency of sensible heat storage system is less compared to LHTES. With the decrease in porosity, the first law and second law efficiencies of LHTES increase for both the charging and discharging period. There is no significant variation in energy and exergy efficiencies with the change in pore-diameter of the metal matrix.

Kinetic Typography

DEFF Research Database (Denmark)

van Leeuwen, Theo; Djonov, Emilia

2014-01-01

After discussing broad cultural drivers behind the development of kinetic typography, the chapter outlines an approach to analysing kinetic typography which is based on Halliday's theory of transitivity, as applied by Kress and Van Leeuwen to visual images.......After discussing broad cultural drivers behind the development of kinetic typography, the chapter outlines an approach to analysing kinetic typography which is based on Halliday's theory of transitivity, as applied by Kress and Van Leeuwen to visual images....

Elastic wave scattering from multiple voids (porosity)

International Nuclear Information System (INIS)

Thompson, D.O.; Rose, J.H.; Thompson, R.B.; Wormley, S.J.

1983-01-01

This paper describes the development of an ultrasonic backscatter measurement technique which provides a convenient way to determine certain characteristics of a distribution of voids (porosity) in materials. A typical ultrasonic sample prepared by placing the ''frit'' in a crucible in an RF induction heater is shown. The results of the measurements were Fourier transformed into an amplitude-frequency description, and were then deconvolved with the transducer response function. Several properties needed to characterize a void distribution are obtained from the experimental results, including average void size, the spatial extent of the voids region, the average void separation, and the volume fraction of material contained in the void distribution. A detailed comparison of values obtained from the ultrasonic measurements with visually determined results is also given

Pore former induced porosity in LSM/CGO cathodes for electrochemical cells for flue gas purification

DEFF Research Database (Denmark)

Skovgaard, M.; Andersen, Kjeld Bøhm; Kammer Hansen, Kent

2012-01-01

In this study the effect of the characteristics of polymethyl methacrylate (PMMA) pore formers on the porosity, pore size distribution and the air flow through the prepared lanthanum strontium manganate/gadolinium-doped cerium oxide (LSM/CGO) cathodes was investigated. Porous cathodes were obtained...... and the highest porosity measured was 46.4% with an average pore diameter of 0.98 μm. The air flow through this cathode was measured to 5.8 ml/(min mm2). Also the effect of exposure time to the solvent was tested for the most promising PMMA pore former and it was found that the average pore diameter decreases...

Change in Soil Porosity under Load

Science.gov (United States)

Dyba, V. P.; Skibin, E. G.

2017-11-01

The theoretical basis for the process of soil compaction under various loading paths is considered in the article, the theoretical assumptions are compared with the results of the tests of clay soil on a stabilometer. The variant of the critical state model of the sealing plastic-rigid environment is also considered the strength characteristics of which depend on the porosity coefficient. The loading surface is determined by the results of compression and stabilometrical tests. In order to clarify the results of this task, it is necessary to carry out stabilometric tests under conditions of simple loading, i.e. where the vertical pressure would be proportional to the compression pressure σ3 = kσ1. Within the study the attempts were made to confirm the model given in the beginning of the article by laboratory tests. After the analysis of the results, the provided theoretical assumptions were confirmed.

Nano-porosity in silica reinforced methyltrimethoxysilane coatings studied by positron beam analysis

NARCIS (Netherlands)

Escobar Galindo, R.; Veen, A. van; Schut, H.; Falub, C.V.; Balkenende, A.R.; With, G. de; Hosson, J.Th.M. De

The porosity in particle reinforced sol-gel coatings has been studied. Silica particles (Ludox-TM40) are introduced into methyl silicate coatings to increase the hardness, the elastic modulus and the fracture toughness. The methyl silicate has a relatively low density (about 1.2 g/cm(2)), while the

Effective diffusion coefficients and porosity values for argillaceous rocks and bentonite: measured and estimated values for the provisional safety analyses for SGT-E2

International Nuclear Information System (INIS)

Van Loon, L.R.

2014-11-01

In Stage 2 of the Sectoral Plan for Deep Geological Repositories, safety analyses have to be performed. Geochemical parameters describing the transport and retardation of radionuclides in the argillaceous rocks considered and in compacted bentonite are required. In the present report, diffusion parameters for all clay host rocks, confining units and compacted bentonite are derived. Diffusion of tritiated water (HTO), "3"6Cl"- and "2"2Na"+ was studied. The measurements gave values for effective diffusion coefficients (D_e) and diffusion accessible porosities. The general observed trend "N"aD_e > "H"T"OD_e > "C"lD_e is in agreement with the expected behaviour of the three species in clay materials: ion exchanging cations show an enhanced mobility due to surface diffusion effects and anions are slowed down due to anion exclusion. Due to the negatively charged clay surfaces, anionic species are repelled from these surfaces resulting in an accessible porosity that is smaller than the total porosity as measured with HTO. The effect of porewater composition on the diffusion of HTO, "3"6Cl"- and "2"2Na"+ in Opalinus Clay was investigated. For ionic strength (IS) values between 0.17 M and 1.07 M, no significant effect on D_e could be observed. In the case of "3"6Cl"-, no effect on the accessible porosity was observed. The anion diffusion accessible porosity equals 50-60 % of the total porosity, independent on the ionic strength of the porewater. The diffusion parameters were measured on sedimentary rocks such as chalk, clay and limestone rocks. All data could be described by one single modified version of Archie's relation (extended Archie's relation). For values of porosity greater than about 0.1, the classical Archie's relation was valid. For values smaller than 0.1, the data deviated from the classical Archie's relation; this can be explained by additional changes of tortuosity with porosity values. At high porosity values (low density rocks), the microfabric of the clay

Microwave-induced porosity and bioactivation of chitosan-PEGDA scaffolds: morphology, mechanical properties and osteogenic differentiation.

Science.gov (United States)

Demitri, Christian; Giuri, Antonella; De Benedictis, Vincenzo Maria; Raucci, Maria Grazia; Giugliano, Daniela; Sannino, Alessandro; Ambrosio, Luigi

2017-01-01

In this study, a new foaming method, based on physical foaming combined with microwave-induced curing, is proposed in combination with a surface bioactivation to develop scaffold for bone tissue regeneration. In the first step of the process, a stable physical foaming was induced using a surfactant (Pluronic) as blowing agent of a homogeneous blend of Chitosan and polyethylene glycol diacrylate (PEGDA700) solutions. In the second step, the porous structure of the foaming was chemically stabilized by radical polymerization induced by homogeneous heating of the sample in a microwave reactor. In this step, 2,2-azobis[2-(2-imidazolin-2yl)propane]dihydrochloride was used as thermoinitiator (TI). Chitosan and PEGDA were mixed in different blends to investigate the influence of the composition on the final properties of the material. The chemical properties of each sample were evaluated by infrared attenuated total reflectance analysis, before and after curing in order to maximize reaction yield and optimize kinetic parameters (i.e. time curing, microwave power). Absorption capacity, elastic modulus, porosity and morphology of the porous structure were measured for each sample. The stability of materials was evaluated in vitro by degradation test in phosphate-buffered saline. To improve the bioactivity and biological properties of chitosan scaffold, a biomineralization process was used. Biological characterization was carried out with the aim to prove the effect of biomineralization scaffold on human mesenchymal stem cells behaviour. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Monte Carlo Simulation on Compensated Neutron Porosity Logging in LWD With D-T Pulsed Neutron Generator

International Nuclear Information System (INIS)

Zhang Feng; Hou Shuang; Jin Xiuyun

2010-01-01

The process of neutron interaction induced by D-T pulsed neutron generator and 241 Am-Be source was simulated by using Monte Carlo method. It is concluded that the thermal neutron count descend exponentially as the spacing increasing. The smaller porosity was, the smaller the differences between the two sources were. When the porosity reached 40%, the ratio of thermal neutron count generated by D-T pulsed neutron source was much larger than that generated by 241 Am-Be neutron source, and its distribution range was wider. The near spacing selected was 20-30 cm, and that of far spacing was about 60-70 cm. The detection depth by using D-T pulsed neutron source was almost unchanged under condition of the same sapcing, and the sensitivity of measurement to the formation porosity decreases. The results showed that it can not only guarantee the statistic of count, but also improve detection sensitivity and depth at the same time of increasing spacing. Therefore, 241 Am-Be neutron source can be replaced by D-T neutron tube in LWD tool. (authors)

Keyhole formation and thermal fluid flow-induced porosity during laser fusion welding in titanium alloys: Experimental and modelling

International Nuclear Information System (INIS)

Panwisawas, Chinnapat; Perumal, Bama; Ward, R. Mark; Turner, Nathanael; Turner, Richard P.; Brooks, Jeffery W.; Basoalto, Hector C.

2017-01-01

High energy-density beam welding, such as electron beam or laser welding, has found a number of industrial applications for clean, high-integrity welds. The deeply penetrating nature of the joints is enabled by the formation of metal vapour which creates a narrow fusion zone known as a “keyhole”. However the formation of the keyhole and the associated keyhole dynamics, when using a moving laser heat source, requires further research as they are not fully understood. Porosity, which is one of a number of process induced phenomena related to the thermal fluid dynamics, can form during beam welding processes. The presence of porosity within a welded structure, inherited from the fusion welding operation, degrades the mechanical properties of components during service such as fatigue life. In this study, a physics-based model for keyhole welding including heat transfer, fluid flow and interfacial interactions has been used to simulate keyhole and porosity formation during laser welding of Ti-6Al-4V titanium alloy. The modelling suggests that keyhole formation and the time taken to achieve keyhole penetration can be predicted, and it is important to consider the thermal fluid flow at the melting front as this dictates the evolution of the fusion zone. Processing induced porosity is significant when the fusion zone is only partially penetrating through the thickness of the material. The modelling results are compared with high speed camera imaging and measurements of porosity from welded samples using X-ray computed tomography, radiography and optical micrographs. These are used to provide a better understanding of the relationship between process parameters, component microstructure and weld integrity.

Integrated Analysis Seismic Inversion and Rockphysics for Determining Secondary Porosity Distribution of Carbonate Reservoir at “FR” Field

Science.gov (United States)

Rosid, M. S.; Augusta, F. F.; Haidar, M. W.

2018-05-01

In general, carbonate secondary pore structure is very complex due to the significant diagenesis process. Therefore, the determination of carbonate secondary pore types is an important factor which is related to study of production. This paper mainly deals not only to figure out the secondary pores types, but also to predict the distribution of the secondary pore types of carbonate reservoir. We apply Differential Effective Medium (DEM) for analyzing pore types of carbonate rocks. The input parameter of DEM inclusion model is fraction of porosity and the output parameters are bulk moduli and shear moduli as a function of porosity, which is used as input parameter for creating Vp and Vs modelling. We also apply seismic post-stack inversion technique that is used to map the pore type distribution from 3D seismic data. Afterward, we create porosity cube which is better to use geostatistical method due to the complexity of carbonate reservoir. Thus, the results of this study might show the secondary porosity distribution of carbonate reservoir at “FR” field. In this case, North – Northwest of study area are dominated by interparticle pores and crack pores. Hence, that area has highest permeability that hydrocarbon can be more accumulated.

An optimized microstructure to minimizing in-plane and through-plane pressure drops of fibrous materials: Counter-intuitive reduction of gas diffusion layer permeability with porosity

Science.gov (United States)

Sadeghifar, Hamidreza

2018-05-01

The present study experimentally investigates the realistic functionality of in-plane and through-plane pressure drops of layered fibrous media with porosity, fiber diameter, fiber spacing, fiber-fiber angles and fiber-flow angles. The study also reveals that pressure drop may increase with porosity and fiber diameter under specific circumstances. This counter-intuitive point narrows down the validity range of widely-used permeability-porosity-diameter models or correlations. It is found that, for fibrous materials, the most important parameter that impacts the in-plane pressure drop is not their porosities but the number of fibers extended in the flow direction. It is also concluded that in-plane pressure drop is highly dependent upon the flow direction (fiber-flow angles), especially at lower porosities. Contrary to in-plane pressure drop, through-plane pressure drop is a weak function of fiber-fiber angles but is strongly impacted by fiber spacing, especially at lower porosities. At a given porosity, low through-plane pressure drops occur if fiber spacing does not change practically from one layer to another. Through-plane pressure drop also, insignificantly, increases with the intersecting angles between fibers. An optimized microstructure of fibrous media resulting in minimal in-plane and through-plane pressure drops is also offered for the first time in this work.

Condensation Enhancement by Surface Porosity: Three-Stage Mechanism.

Science.gov (United States)

Yarom, Michal; Marmur, Abraham

2015-08-18

Surface defects, such as pores, cracks, and scratches, are naturally occurring and commonly found on solid surfaces. However, the mechanism by which such imperfections promote condensation has not been fully explored. In the current paper we thermodynamically analyze the ability of surface porosity to enhance condensation on a hydrophilic solid. We show that the presence of a surface-embedded pore brings about three distinct stages of condensation. The first is capillary condensation inside the pore until it is full. This provides an ideal hydrophilic surface for continuing the condensation. As a result, spontaneous condensation and wetting can be achieved at lower vapor pressure than on a smooth surface.

High Resolution ground penetrating radar (GPR) measurements at the laboratory scale to model porosity and permeability in the Miami Limestone in South Florida.

Science.gov (United States)

Mount, G. J.; Comas, X.

2015-12-01

Subsurface water flow within the Biscayne aquifer is controlled by the heterogeneous distribution of porosity and permeability in the karst Miami Limestone and the presence of numerous dissolution and mega-porous features. The dissolution features and other high porosity areas can create preferential flow paths and direct recharge to the aquifer, which may not be accurately conceptualized in groundwater flow models. As hydrologic conditions are undergoing restoration in the Everglades, understanding the distribution of these high porosity areas within the subsurface would create a better understanding of subsurface flow. This research utilizes ground penetrating radar to estimate the spatial variability of porosity and dielectric permittivity of the Miami Limestone at centimeter scale resolution at the laboratory scale. High frequency GPR antennas were used to measure changes in electromagnetic wave velocity through limestone samples under varying volumetric water contents. The Complex Refractive Index Model (CRIM) was then applied in order to estimate porosity and dielectric permittivity of the solid phase of the limestone. Porosity estimates ranged from 45.2-66.0% from the CRIM model and correspond well with estimates of porosity from analytical and digital image techniques. Dielectric permittivity values of the limestone solid phase ranged from 7.0 and 13.0, which are similar to values in the literature. This research demonstrates the ability of GPR to identify the cm scale spatial variability of aquifer properties that influence subsurface water flow which could have implications for groundwater flow models in the Biscayne and potentially other shallow karst aquifers.

Process of making porous ceramic materials with controlled porosity

Science.gov (United States)

Anderson, Marc A.; Ku, Qunyin

1993-01-01

A method of making metal oxide ceramic material is disclosed by which the porosity of the resulting material can be selectively controlled by manipulating the sol used to make the material. The method can be used to make a variety of metal oxide ceramic bodies, including membranes, but also pellets, plugs or other bodies. It has also been found that viscous sol materials can readily be shaped by extrusion into shapes typical of catalytic or adsorbent bodies used in industry, to facilitate the application of such materials for catalytic and adsorbent applications.

Darboux transformation and explicit solutions for some (2+1)-dimensional equations

International Nuclear Information System (INIS)

Wang Yan; Shen Lijuan; Du Dianlou

2007-01-01

Three systems of (2+1)-dimensional soliton equations and their decompositions into the (1+1)-dimensional soliton equations are proposed. These equations include KPI, CKP, MKPI. With the help of Darboux transformation of (1+1)-dimensional equations, we get the explicit solutions of the (2+1)-dimensional equations

Investigation the effect of porosity on corrosion of macroporous silicon in 1.0 M sodium hydroxide solution using weight loss measurements, electrochemical methods and scanning electron microscope

International Nuclear Information System (INIS)

Lai, Chuan; Xiang, Zhen

2015-01-01

Highlights: • The dissolution of silicon wafers conforms Faraday’s laws of electrolysis. • The porosity effect on macroporous silicon corrosion was investigated. • The corrosion rate increase linearly with porosity increasing. • The porosity effect on activation parameters was obtained. - Abstract: In this study, the macroporous silicon has been fabricated by electrochemical anodization. The dissolution of n-type silicon wafers in etching solution conforms Faraday’s laws of electrolysis. The fabricated macroporous silicon with different porosity corrosion in 1.0 M NaOH was systemically investigated by weight loss measurements, electrochemical methods and scanning electron microscope. Results show that with the porosity increasing, the corrosion rate of macroporous silicon in 1.0 M NaOH increases linearly. In addition, the increase of corrosion rate of macroporous silicon with relative higher porosity was determined by the pre-exponential factor.

How burial diagenesis of chalk sediments controls sonic velocity and porosity

DEFF Research Database (Denmark)

Fabricius, Ida Lykke

2003-01-01

Based on P-wave velocity and density data, a new elastic model for chalk sediments is established. The model allows the construction of a series of isoframe (IF) curves, each representing a constant part of the mineral phase contributing to the solid frame. The IF curves can be related to the pro......Based on P-wave velocity and density data, a new elastic model for chalk sediments is established. The model allows the construction of a series of isoframe (IF) curves, each representing a constant part of the mineral phase contributing to the solid frame. The IF curves can be related.......1 or higher. Upon burial, the sediments lose porosity by mechanical compaction, and concurrently, the calcite particles recrystallize into progressively more equant shapes. High compaction rates may keep the particles in relative motion, whereas low compaction rates allow the formation of contact cement...... this process testifies to the absence of chemical compaction by calcite-calcite pressure dissolution, as well as to the porosity-preserving effect of contact cementation. At sufficient burial stress, the presence of stylolites indicates that pressure dissolution takes place between calcite., and silicates...

The effect of coating patterns with spinel-based investment on the castability and porosity of titanium cast into three phosphate-bonded investments.

Science.gov (United States)

Pieralini, Anelise R F; Benjamin, Camila M; Ribeiro, Ricardo Faria; Scaf, Gulnara; Adabo, Gelson Luis

2010-10-01

This study evaluated the effect of pattern coating with spinel-based investment Rematitan Ultra (RU) on the castability and internal porosity of commercially pure (CP) titanium invested into phosphate-bonded investments. The apparent porosity of the investment was also measured. Square patterns (15 × 15 × 0.3 mm(3)) were either coated with RU, or not and invested into the phosphate-bonded investments: Rematitan Plus (RP), Rema Exakt (RE), Castorit Super C (CA), and RU (control group). The castings were made in an Ar-arc vacuum-pressure machine. The castability area (mm(2) ) was measured by an image-analysis system (n = 10). For internal porosity, the casting (12 × 12 × 2 mm(3) ) was studied by the X-ray method, and the projected porous area percentage was measured by an image-analysis system (n = 10). The apparent porosity of the investment (n = 10) was measured in accordance with the ASTM C373-88 standard. Analysis of variance (One-way ANOVA) of castability was significant, and the Tukey test indicated that RU had the highest mean but the investing technique with coating increased the castability for all phosphate-bonded investments. The analysis of the internal porosity of the cast by the nonparametric test demonstrated that the RP, RE, and CA with coating and RP without coating did not differ from the control group (RU), while the CA and RE casts without coating were more porous. The one-way ANOVA of apparent porosity of the investment was significant, and the Tukey test showed that the means of RU (36.10%) and CA (37.22%) were higher than those of RP (25.91%) and RE (26.02%). Pattern coating with spinel-based material prior to phosphate-bonded investments can influence the castability and the internal porosity of CP Ti. © 2010 by The American College of Prosthodontists.

Investigation on the Accuracy of CT Porosity Analysis of Additive Manufactured Metallic Parts

NARCIS (Netherlands)

Zanini, Filippo; Hermanek, Petr; Rathore, Jitendra; Wits, Wessel W; Carmignato, Simone

2015-01-01

Additive manufacturing (AM) is emerging as an important manufacturing sector, due to its almost unlimited design freedom, the capability to produce personalized parts and the efficient material use. A reliable knowledge about material porosity of manufactured parts is crucial for optimizing AM

Estimating porosity and solid dielectric permittivity in the Miami Limestone using high-frequency ground penetrating radar (GPR) measurements at the laboratory scale

Science.gov (United States)

Mount, Gregory J.; Comas, Xavier

2014-10-01

Subsurface water flow in South Florida is largely controlled by the heterogeneous nature of the karst limestone in the Biscayne aquifer and its upper formation, the Miami Limestone. These heterogeneities are amplified by dissolution structures that induce changes in the aquifer's material and physical properties (i.e., porosity and dielectric permittivity) and create preferential flow paths. Understanding such patterns are critical for the development of realistic groundwater flow models, particularly in the Everglades, where restoration of hydrological conditions is intended. In this work, we used noninvasive ground penetrating radar (GPR) to estimate the spatial variability in porosity and the dielectric permittivity of the solid phase of the limestone at centimeter-scale resolution to evaluate the potential for field-based GPR studies. A laboratory setup that included high-frequency GPR measurements under completely unsaturated and saturated conditions was used to estimate changes in electromagnetic wave velocity through Miami Limestone samples. The Complex Refractive Index Model was used to derive estimates of porosity and dielectric permittivity of the solid phase of the limestone. Porosity estimates of the samples ranged between 45.2 and 66.0% and showed good correspondence with estimates of porosity using analytical and digital image techniques. Solid dielectric permittivity values ranged between 7.0 and 13.0. This study shows the ability of GPR to image the spatial variability of porosity and dielectric permittivity in the Miami Limestone and shows potential for expanding these results to larger scales and other karst aquifers.

Carbon nanotube scaffolds with controlled porosity as electromagnetic absorbing materials in the gigahertz range

Science.gov (United States)

González, M.; Crespo, M.; Baselga, J.; Pozuelo, J.

2016-05-01

Control of the microscopic structure of CNT nanocomposites allows modulation of the electromagnetic shielding in the gigahertz range. The porosity of CNT scaffolds has been controlled by two freezing protocols and a subsequent lyophilization step: fast freezing in liquid nitrogen and slow freezing at -20 °C. Mercury porosimetry shows that slowly frozen specimens present a more open pore size (100-150 μm) with a narrow distribution whereas specimens frozen rapidly show a smaller pore size and a heterogeneous distribution. 3D-scaffolds containing 3, 4, 6 and 7% CNT were infiltrated with epoxy and specimens with 2, 5 and 8 mm thicknesses were characterized in the GHz range. Samples with the highest pore size and porosity presented the lowest reflected power (about 30%) and the highest absorbed power (about 70%), which allows considering them as electromagnetic radiation absorbing materials.Control of the microscopic structure of CNT nanocomposites allows modulation of the electromagnetic shielding in the gigahertz range. The porosity of CNT scaffolds has been controlled by two freezing protocols and a subsequent lyophilization step: fast freezing in liquid nitrogen and slow freezing at -20 °C. Mercury porosimetry shows that slowly frozen specimens present a more open pore size (100-150 μm) with a narrow distribution whereas specimens frozen rapidly show a smaller pore size and a heterogeneous distribution. 3D-scaffolds containing 3, 4, 6 and 7% CNT were infiltrated with epoxy and specimens with 2, 5 and 8 mm thicknesses were characterized in the GHz range. Samples with the highest pore size and porosity presented the lowest reflected power (about 30%) and the highest absorbed power (about 70%), which allows considering them as electromagnetic radiation absorbing materials. Electronic supplementary information (ESI) available: Scheme of hydrogenated derivative of diglycidyl ether of bisphenol-A (HDGEBA) and m-xylylenediamine; X-ray diffractograms of pristine CNT

Eggshell Porosity Provides Insight on Evolution of Nesting in Dinosaurs.

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Kohei Tanaka

Full Text Available Knowledge about the types of nests built by dinosaurs can provide insight into the evolution of nesting and reproductive behaviors among archosaurs. However, the low preservation potential of their nesting materials and nesting structures means that most information can only be gleaned indirectly through comparison with extant archosaurs. Two general nest types are recognized among living archosaurs: 1 covered nests, in which eggs are incubated while fully covered by nesting material (as in crocodylians and megapodes, and 2 open nests, in which eggs are exposed in the nest and brooded (as in most birds. Previously, dinosaur nest types had been inferred by estimating the water vapor conductance (i.e., diffusive capacity of their eggs, based on the premise that high conductance corresponds to covered nests and low conductance to open nests. However, a lack of statistical rigor and inconsistencies in this method render its application problematic and its validity questionable. As an alternative we propose a statistically rigorous approach to infer nest type based on large datasets of eggshell porosity and egg mass compiled for over 120 extant archosaur species and 29 archosaur extinct taxa/ootaxa. The presence of a strong correlation between eggshell porosity and nest type among extant archosaurs indicates that eggshell porosity can be used as a proxy for nest type, and thus discriminant analyses can help predict nest type in extinct taxa. Our results suggest that: 1 covered nests are likely the primitive condition for dinosaurs (and probably archosaurs, and 2 open nests first evolved among non-avian theropods more derived than Lourinhanosaurus and were likely widespread in non-avian maniraptorans, well before the appearance of birds. Although taphonomic evidence suggests that basal open nesters (i.e., oviraptorosaurs and troodontids were potentially the first dinosaurs to brood their clutches, they still partially buried their eggs in sediment

Eggshell Porosity Provides Insight on Evolution of Nesting in Dinosaurs.

Science.gov (United States)

Tanaka, Kohei; Zelenitsky, Darla K; Therrien, François

2015-01-01

Knowledge about the types of nests built by dinosaurs can provide insight into the evolution of nesting and reproductive behaviors among archosaurs. However, the low preservation potential of their nesting materials and nesting structures means that most information can only be gleaned indirectly through comparison with extant archosaurs. Two general nest types are recognized among living archosaurs: 1) covered nests, in which eggs are incubated while fully covered by nesting material (as in crocodylians and megapodes), and 2) open nests, in which eggs are exposed in the nest and brooded (as in most birds). Previously, dinosaur nest types had been inferred by estimating the water vapor conductance (i.e., diffusive capacity) of their eggs, based on the premise that high conductance corresponds to covered nests and low conductance to open nests. However, a lack of statistical rigor and inconsistencies in this method render its application problematic and its validity questionable. As an alternative we propose a statistically rigorous approach to infer nest type based on large datasets of eggshell porosity and egg mass compiled for over 120 extant archosaur species and 29 archosaur extinct taxa/ootaxa. The presence of a strong correlation between eggshell porosity and nest type among extant archosaurs indicates that eggshell porosity can be used as a proxy for nest type, and thus discriminant analyses can help predict nest type in extinct taxa. Our results suggest that: 1) covered nests are likely the primitive condition for dinosaurs (and probably archosaurs), and 2) open nests first evolved among non-avian theropods more derived than Lourinhanosaurus and were likely widespread in non-avian maniraptorans, well before the appearance of birds. Although taphonomic evidence suggests that basal open nesters (i.e., oviraptorosaurs and troodontids) were potentially the first dinosaurs to brood their clutches, they still partially buried their eggs in sediment. Open nests

Characterization of the porosity distribution in the upper part of the karst Biscayne aquifer using common offset ground penetrating radar, Everglades National Park, Florida

Science.gov (United States)

Mount, Gregory J.; Comas, Xavier; Cunningham, Kevin J.

2014-07-01

The karst Biscayne aquifer is characterized by a heterogeneous spatial arrangement of porosity and hydraulic conductivity, making conceptualization difficult. The Biscayne aquifer is the primary source of drinking water for millions of people in south Florida; thus, information concerning the distribution of karst features that concentrate the groundwater flow and affect contaminant transport is critical. The principal purpose of the study was to investigate the ability of two-dimensional ground penetrating radar (GPR) to rapidly characterize porosity variability in the karst Biscayne aquifer in south Florida. An 800-m-long GPR transect of a previously investigated area at the Long Pine Key Nature Trail in Everglades National Park, collected in fast acquisition common offset mode, shows hundreds of diffraction hyperbolae. The distribution of diffraction hyperbolae was used to estimate electromagnetic (EM) wave velocity at each diffraction location and to assess both horizontal and vertical changes in velocity within the transect. A petrophysical model (complex refractive index model or CRIM) was used to estimate total bulk porosity. A set of common midpoint surveys at selected locations distributed along the common-offset transect also were collected for comparison with the common offsets and were used to constrain one-dimensional (1-D) distributions of porosity with depth. Porosity values for the saturated Miami Limestone ranged between 25% and 41% for common offset GPR surveys, and between 23% and 39% for common midpoint GPR surveys. Laboratory measurements of porosity in five whole-core samples from the saturated part of the aquifer in the study area ranged between 7.1% and 41.8%. GPR estimates of porosity were found to be valid only under saturated conditions; other limitations are related to the vertical resolution of the GPR signal and the volume of the material considered by the measurement methodology. Overall, good correspondence between GPR estimates and

Global Characteristics of Porosity and Density Stratification Within the Lunar Crust from GRAIL Gravity and Lunar Orbiter Laser Altimeter Topography Data

Science.gov (United States)

Han, Shin-Chan; Schmerr, Nicholas; Neumann, Gregory; Holmes, Simon

2014-01-01

The Gravity Recovery and Interior Laboratory (GRAIL) mission is providing unprecedentedly high-resolution gravity data. The gravity signal in relation to topography decreases from 100 km to 30 km wavelength, equivalent to a uniform crustal density of 2450 kg/cu m that is 100 kg/cu m smaller than the density required at 100 km. To explain such frequency-dependent behavior, we introduce rock compaction models under lithostatic pressure that yield radially stratified porosity (and thus density) and examine the depth extent of porosity. Our modeling and analysis support the assertion that the crustal density must vary from surface to deep crust by up to 500 kg/cu m. We found that the surface density of mega regolith is around 2400 kg/cu m with an initial porosity of 10-20%, and this porosity is eliminated at 10-20 km depth due to lithostatic overburden pressure. Our stratified density models provide improved fits to both GRAIL primary and extended mission data.

Widespread Neogene and Quaternary Volcanism on Central Kerguelen Plateau, Southern Indian Ocean

Science.gov (United States)

Duncan, R. A.; Falloon, T.; Quilty, P. G.; Coffin, M. F.

2016-12-01

We report new age determinations and compositions for rocks from 18 dredge hauls collected from eight submarine areas across Central Kerguelen Plateau (CKP). Sea knolls and volcanic fields with multiple small cones were targeted over a 125,000 km2 region that includes Heard and McDonald islands. Large early Miocene (16-22 Ma) sea knolls rise from the western margin of the CKP and are part of a NNW-SSE line of volcanic centers that lie between Îles Kerguelen and Heard and McDonald islands. A second group of large sea knolls is aligned E-W across the center of this region. We see evidence of much younger activity (5 Ma to present) in volcanic fields to the north of, and up to 300 km NE of Heard Island. Compositions include basanite, basalt, and trachybasalt, that are broadly similar to plateau lava flows from nearby Ocean Drilling Program (ODP) Site 1138, lower Miocene lavas at Îles Kerguelen, dredged rocks from the early Miocene sea knolls, and Big Ben lavas from Heard Island. Geochemical data indicate decreasing fractions of mantle source melting with time. The western line of sea knolls has been related to hotspot activity now underlying the Heard Island area. In view of the now recognized much larger area of young volcanic activity, we propose that a broad region of CKP became volcanically active in Neogene time due to incubation of plume material at the base of the relatively stationary overlying plateau. The presence of pre-existing crustal faults promotes access for melts from the Heard mantle plume to rise to the surface.

Design and Synthesis of Hybrid Ceramic Foams with Tailored Porosity

OpenAIRE

Capasso, Ilaria

2017-01-01

Alkali activated ceramic foams have been produced by using metakaolin and/or diatomite as aluminosilicate source, an aqueous sodium silicate solution as alkali activator and Na2SiF6 as a catalyst that promotes the gelification of the entire system. Two different techniques of direct foaming have been coupled, one based on chemical reactions with gas production and the other one based on a mechanical foaming. Then, other levels of hierarchical porosity (nanometric and macrometric scale) have b...

Sintered ceramics having controlled density and porosity

International Nuclear Information System (INIS)

Brassfield, H.C.; DeHollander, W.R.; Nivas, Y.

1980-01-01

A new method was developed for sintering ceramic uranium dioxide powders, in which ammonium oxalate is admixed with the powder prior to being pressed into a cylindrical green body, so that the end-point density of the final nuclear-reactor fuel product can be controlled. When the green body is heated, the ammonium oxalate decomposes and leaves discrete porosity in the sintered body, which corresponds to the ammonium oxalate regions in the green body. Thus the end-point density of the sintered body is a function of the amount of ammonium oxalate added. The final density of the sintered product is about 90-97% of the theoretical. The addition of ammonium oxalate also allows control of the pore size and distribution throughout the fuel. The process leaves substantially no impurities in the sintered strucuture. (DN)

Examining the social porosity of environmental features on neighborhood sociability and attachment.

Directory of Open Access Journals (Sweden)

John R Hipp

Full Text Available The local neighborhood forms an integral part of our lives. It provides the context through which social networks are nurtured and the foundation from which a sense of attachment and cohesion with fellow residents can be established. Whereas much of the previous research has examined the role of social and demographic characteristic in relation to the level of neighboring and cohesion, this paper explores whether particular environmental features in the neighborhood affect social porosity. We define social porosity as the degree to which social ties flow over the surface of a neighborhood. The focus of our paper is to examine the extent to which a neighborhood's environmental features impede the level of social porosity present among residents. To do this, we integrate data from the census, topographic databases and a 2010 survey of 4,351 residents from 146 neighborhoods in Australia. The study introduces the concepts of wedges and social holes. The presence of two sources of wedges is measured: rivers and highways. The presence of two sources of social holes is measured: parks and industrial areas. Borrowing from the geography literature, several measures are constructed to capture how these features collectively carve up the physical environment of neighborhoods. We then consider how this influences residents' neighboring behavior, their level of attachment to the neighborhood and their sense of neighborhood cohesion. We find that the distance of a neighborhood to one form of social hole-industrial areas-has a particularly strong negative effect on all three dependent variables. The presence of the other form of social hole-parks-has a weaker negative effect. Neighborhood wedges also impact social interaction. Both the length of a river and the number of highway fragments in a neighborhood has a consistent negative effect on neighboring, attachment and cohesion.

Influence of lactose addition to gentamicin-loaded acrylic bone cement on the kinetics of release of the antibiotic and the cement properties.

Science.gov (United States)

Frutos, Gloria; Pastor, José Ygnacio; Martínez, Noelia; Virto, María Rosa; Torrado, Susana

2010-03-01

The purpose of this study was to characterize a poly(methyl methacrylate) bone cement that was loaded with the antibiotic gentamicin sulphate (GS) and lactose, which served to modulate the release of GS from cement specimens. The release of GS when the cement specimens were immersed in phosphate-buffered saline at 37 degrees Celsius was determined spectrophotometrically. The microstructure, porosity, density, tensile properties and flexural properties of the cements were determined before and after release of GS. A kinetics model of the release of GS from the cement that involved a coupled mechanism based on dissolution/diffusion processes and an initial burst effect was proposed. Dissolution assay results showed that drug elution was controlled by a diffusion mechanism which can be modulated by lactose addition. Density values and mechanical properties (tensile strength, flexural strength, elastic modulus and fracture toughness) were reduced by the increased porosity resulting from lactose addition, but maintained acceptable values for the structural functions of bone cement. The present results suggest that lactose-modified, gentamicin-loaded acrylic bone cements are potential candidates for use in various orthopaedic and dental applications. Copyright 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The effects of porosity and angle of inclination on the deflection of ...

African Journals Online (AJOL)

The effects of porosity and angle of inclination on the deflection of fluid flow in porous media. ... a helpful Frequently Asked Questions about PDFs. Alternatively, you can download the PDF file directly to your computer, from where it can be opened using a PDF reader. To download the PDF, click the Download link above.

Cesium removal and kinetics equilibrium: Precipitation kinetics

International Nuclear Information System (INIS)

Barnes, M.J.

1999-01-01

This task consisted of both non-radioactive and radioactive (tracer) tests examining the influence of potentially significant variables on cesium tetraphenylborate precipitation kinetics. The work investigated the time required to reach cesium decontamination and the conditions that affect the cesium precipitation kinetics

Critically Tapered Wedges and Critical State Soil Mechanics: Porosity-based Pressure Prediction in the Nankai Accretionary Prism.

Science.gov (United States)

Flemings, P. B.; Saffer, D. M.

2016-12-01

We predict pore pressure from porosity measurements at ODP Sites 1174 and 808 in the Nankai Accretionary prism, offshore Japan. For a range of friction angles (5-30 degrees), we estimate that the pore pressure ratio (λ*) ranges from 0.5 to 0.8: the pore pressure supports 50% to 80% of the overburden. Higher friction angles result in higher pressures. For the majority of the scenarios, pressures within the prism parallel the lithostat and are greater than the pressures beneath it. Our results support previous qualitative interpretations at Nankai and elsewhere suggesting that lower porosity above the décollement than below reflects higher mean effective stress there. By coupling a critical state soil model (Modified Cam Clay), which describes porosity as a function of mean and deviator stress, with a stress model that considers the difference in stress states above and below the décollement, we quantitatively show that the prism porosities record significant overpressure despite their lower porosity. As the soil is consumed by the advancing prism, changes in both mean and shear stress drive overpressure generation. Even in the extreme case where only change in mean stress is considered (a vertical end cap model), significant overpressures are generated. The high pressures we predict require an effective friction coefficient (µb') at the décollement of 0.023-0.038. Assuming that the pore pressure at the décollement lies between the values we report for the wedge and the underthrusting sediments, these effective friction coefficients correspond to intrinsic friction coefficients of µb= 0.08-0.38 (f = 4.6 - 21°). These values are comparable to friction coefficients of 0.1-0.4 reported for clay-dominated fault zones in a wide range of settings. By coupling the critical wedge model with an appropriate constitutive model, we present a systematic approach to predict pressure in thrust systems.

A new powder morphology for making high-porosity nickel structures

International Nuclear Information System (INIS)

Cormier, Elena; Yang, Quan Min; Charles, Doug; Wasmund, Eric Bain; Renny, Les V.

2007-01-01

Nickel powders with a special branched chain microstructure such as CVRD Inco Limited's Type 255 trademark have been used for more than 50 years as the basis for making porous metal monoliths for applications such as the electrical backbone of nickel electrode batteries by the sinter/slurry process. The classic trade-off when making these structures is that the strength and porosity are inversely correlated. A number of adaptations to the sinter/slurry making process have been proposed to address this problem. The current approach proposes another solution, optimization of the particle microstructure. The strength and porosity relationship of battery plaques made from Type 255 trademark is compared with plaques made with the new powder and it is statistically verified that plaques made from the new powder have an improved combination of structural properties. A comparison of the rheological characteristics of metal powder slurries suggests ways that the new powder can be incorporated into existing processes. Finally, it is shown that properties such as the slurry apparent viscosity can be used as the basis for measuring and predicting the characteristics of particle microstructure that impute these benefits to the sinter/slurry process. An analysis of battery plaques made with the new powder on an industrial battery sinter/slurry production line confirms that the laboratory results are valid. (author)

SEPARATION OF THE INTER- AND INTRA-PARTICLE POROSITY IN IMAGES OF POWDER COMPACTS

Directory of Open Access Journals (Sweden)

Jacques Lacaze

2011-05-01

Full Text Available Powder metallurgy is a highly developed and cheap method of manufacturing reliable materials, either metallic, ceramic or composite. This process was used to make green compacts of iron powders with a high porosity level. This study is part of a project aimed at describing the relationships between mechanical properties and morphological features of such compacts, with particular attention paid to the shape of the grains and the compaction pressure. In this report, a method is proposed to separate the intra grain porosity from the cavities located between particles. The approach is based on the covariogram of images obtained from the surface of the compacts by means of a laser roughometer. To achieve this separation, a model of the structure is proposed which assumes that the distributions of the grains and of the intra-particle cavities are random and independent. Each distribution is characterized by two parameters. A satisfactory agreement is obtained between experimental and calculated covariograms after identification of these parameters.

The influence of porosity on the thermal conductivity of irradiated UO2 fuel

International Nuclear Information System (INIS)

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

1994-12-01

The influence of porosity on the thermal conductivity of irradiated UO 2 fuel has been determined with the Finite Element Method (FEM). Light-microscopy photographs were made of the fuel. The pore shape and the pore distribution are entered in the FEM program from these photographs. The two dimensional (2D) thermal conductivity in the plane of the photograph is obtained from the FEM calculations. The 2D thermal conductivity, that has no physical meaning itself, is the lower limit of the three dimensional (3D) thermal conductivity. For three well defined pore shapes the relation is determined between the 2D thermal conductivity and the 3D thermal conductivity. From these computations a simple relation is obtained that transfers the 2D thermal conductivity into the 3D thermal conductivity, independent of the pore shape. The influence of porosity on the 3D thermal conductivity of irradiated UO 2 fuel and UO 2 fuel doped with Nb 2 O 5 was computed with the FEM. (orig.)

THE EFFECT OF VOLUME VARIATION OF SILVER NANOPARTICLE SOLUTION TOWARDS THE POROSITY AND COMPRESSIVE STRENGTH OF MORTAR

Directory of Open Access Journals (Sweden)

W.S.B. Dwandaru

2016-10-01

Full Text Available As the world is growing rapidly, people need better building materials such as mortar. The aim of this research is to determine the effect of adding silver nanoparticle solution towards the porosity and compressive strength of mortar. This research was started by making silver nanoparticle solution from nitrate silver (AgNO3. The solution is then characterized using Uv-Vis spectrophotometer. 5 mM silver nanoparticle is added in the process of mortar production with volume variation of the silver nanoparticle solution. The porosity, compressive strength, and the content of mortar were determined by digital scale, universal testing machine, and X-ray diffraction, respectively. For silver nanoparticle solution volumes of (in mL 0, 5, 10, 15, 20, and 25 the porosity obtained are (in % 20.38, 19.48, 19.42, 18.9, 17.8, and 17.5, respectively. The best increase in compressive strength is obtained for (in MPa 29,068, 29,308, and 31,385, with nanoparticle solution volumes of (in mL 5, 10, and 15   Keywords: mortar, silver nanoparticle, compressive strength

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

Science.gov (United States)

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

2014-02-01

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

Porosity and pore size distribution determination of Tumblagooda formation sandstone by X-ray microtomography

International Nuclear Information System (INIS)

Fernandes, Jaquiel S.; Appoloni, Carlos R.; Moreira, Anderson C.

2007-01-01

Microstructural parameters evaluations of reservoir rocks are very important to petroleum industry. This work presents total porosity and pore size distribution measurement of a sandstone sample from the Tumblagooda formation, collected at Kalbarri National Park in Australia. Porosity and pores size distribution were determined using X-Ray microtomography and imaging techniques. For these measurements, it was employed a micro-CT (μ-CT) Skyscan system model 1172 with conical beam, operated with a 1 mm Al filter at 80 kV and 125 μA, respectively, and a 2000 x 1048 pixels CCD camera. The sample was rotated from 0 deg to 180 deg, in step of 0.5 deg. For the considered sample, this equipment provided images with 2.9 μm spatial resolution. Six hundreds 2-D images where reconstructed with the Skyscan NRecon software, which were analyzed with the aid of Imago software, developed at the Laboratory of Porous Media and Thermophysical Properties (LMPT), Department of Mechanical Engineering, Federal University of Santa Catarina, Brazil, in association with the Brazilian software company Engineering Simulation and Scientific Software (ESSS), and Petroleo Brasileiro SA (PETROBRAS) Research and Development Center (CENPES). The determined average porosity was 11.45 ±1.53 %. Ninety five percent of the porous phase refers to pores with radius ranging from 2.9 to 85.2 μm, presenting the larger frequency (7.7 %) at 11.7 μm radius. (author)

Long-term flow/chemistry feedback in a porous medium with heterogenous permeability: Kinetic control of dissolution and precipitation

International Nuclear Information System (INIS)

Bolton, E.W.; Lasaga, A.C.; Rye, D.M.

1999-01-01

The kinetics of dissolution and precipitation is of central importance to understanding the long-term evolution of fluid flows in crustal environments, with implications for problems as diverse as nuclear waste disposal and crustal evolution. The authors examine the dynamics of such evolution for several geologically relevant permeability distributions (models for en-echelon cracks, an isolated sloping fractured zone, and two sloping high-permeability zones that are close enough together to interact). Although the focus is on a simple quartz matrix system, generic features emerge from this study that can aid in the broader goal of understanding the long-term feedback between flow and chemistry, where dissolution and precipitation is under kinetic control. Examples of thermal convection in a porous medium with spatially variable permeability reveal features of central importance to water-rock interaction. After a transient phase, an accelerated rate of change of porosity may be used with care to decrease computational time, as an alternative to the quasi-stationary state approximation (Lichtner, 1988). Kinetic effects produce features not expected by traditional assumptions made on the basis of equilibrium, for example, that cooling fluids are oversaturated and heating fluids are undersaturated with respect to silicic acid equilibrium. Indeed, the authors observe regions of downwelling oversaturated fluid experiencing heating and regions of upwelling, yet cooling, undersaturated fluid. When oscillatory convection is present, the amplitudes of oscillation generally increase with time in near-surface environments, whereas amplitudes tend to decrease over long times near the heated lower boundary. The authors examine the scaling behavior of characteristic length scales, of terms in the solute equation, and of the typical deviation from equilibrium, each as a function of the kinetic rate parameters

High Structural Stability of Textile Implants Prevents Pore Collapse and Preserves Effective Porosity at Strain

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Uwe Klinge

2015-01-01

Full Text Available Reinforcement of tissues by use of textiles is encouraged by the reduced rate of recurrent tissue dehiscence but for the price of an inflammatory and fibrotic tissue reaction to the implant. The latter mainly is affected by the size of the pores, whereas only sufficiently large pores are effective in preventing a complete scar entrapment. Comparing two different sling implants (TVT and SIS, which are used for the treatment of urinary incontinence, we can demonstrate that the measurement of the effective porosity reveals considerable differences in the textile construction. Furthermore the changes of porosity after application of a tensile load can indicate a structural instability, favouring pore collapse at stress and questioning the use for purposes that are not “tension-free.”

Impact of gamma irradiation on porosity and pore distribution of poly [ethylene-oxide] films: correlation with dielectric and microstructural properties

Science.gov (United States)

Saha, Mou; Mukhopadhyay, Madhumita; Ray, Ruma

2018-03-01

The structure and morphology of polymers are significantly altered upon exposure to high energy gamma irradiation either through bond breakage i.e. scission or cross-linkage. The present article reports the influence of gamma radiation (1-20 kGy) on the distribution of molecular weight and porosity of the films prepared using irradiated and unirradiated poly-[ethylene oxide] (PEO) powder. The PEO films exhibit pore dimension in the range of 20-500 nm. Selective irradiation is capable of tailoring the pore-size and reducing the multimodal trait to uni-or bimodal upon high energy perturbation. The porosity of PEO films is determined from both 2D-pore surface calculation from SEM images and compared with 3D-BET porosity. Correlation is established among dielectric constant (ɛ') and porosity. The magnitude of ɛ' increases sharply towards low frequency due to electrode polarization effects. Relaxation time is found to be highest and comparable for 1 and 10 KGy. With increase in irradiation dose, scission is predominant, owing to which smaller polymer fragments are produced which are able to follow fast frequency regime and thereby relax at lesser time.

Heparin kinetics

International Nuclear Information System (INIS)

Swart, C.A.M. de.

1983-01-01

The author has studied the kinetics of heparin and heparin fractions after intravenous administration in humans and in this thesis the results of this study are reported. Basic knowledge about the physico-chemical properties of heparin and its interactions with proteins resulting in anticoagulant and lipolytic effects are discussed in a review (chapter II), which also comprises some clinical aspects of heparin therapy. In chapter III the kinetics of the anticoagulant effect are described after intravenous administration of five commercial heparin preparations. A mathematical model is presented that fits best to these kinetics. The kinetics of the anticoagulant and lipolytic effects after intravenous injection of various 35 S-radiolabelled heparin fractions and their relationship with the disappearance of the radiolabel are described in chapter IV. Chapter V gives a description of the kinetics of two radiolabels after injection of in vitro formed complexes consisting of purified, 125 I-radiolabelled antithrombin III and various 35 S-radiolabelled heparin fractions. (Auth.)

Passively Aerated Composting of Straw-Rich Pig Manure : Effect of Compost Bed Porosity

NARCIS (Netherlands)

Veeken, A.H.M.; Wilde, de V.; Hamelers, H.V.M.

2002-01-01

Straw-rich manure from organic pig farming systems can be composted in passively aerated systems as the high application of straw results in a compost bed with good structure and porosity. The passively aerated composting process was simulated in one-dimensional reactors of 2 m3 for straw-rich

POROSITY OF THE WALL OF A NEUROLAC (R) NERVE CONDUIT HAMPERS NERVE REGENERATION

NARCIS (Netherlands)

Meek, Marcel F.; Den Dunnen, Wilfred F. A.

2009-01-01

One way to improve nerve regeneration and bridge longer nerve gaps may be the use of semipermeable/porous conduits. With porosity less biomaterial is used for the nerve conduit. We evaluated the short-term effects of porous Neurolac (R) nerve conduits for in vivo peripheral nerve regeneration. In 10

Porosity of Self-Compacting Concrete (SCC) incorporating high volume fly ash

Science.gov (United States)

Kristiawan, S. A.; Sunarmasto; Murti, G. Y.

2017-02-01

Degradation of concrete could be triggered by the presence of aggressive agents from the environment into the body of concrete. The penetration of these agents is influenced by the pore characteristics of the concrete. Incorporating a pozzolanic material such as fly ash could modify the pore characteristic of the concrete. This research aims to investigate the influence of incorporating fly ash at high volume level on the porosity of Self-Compacting Concrete (SCC). Laboratory investigations were carried out following the ASTM C642 for measuring density and volume of permeable pores (voids) of the SCC with varying fly ash contents (50-70% by weight of total binder). In addition, a measurement of permeable voids by saturation method was carried out to obtain an additional volume of voids that could not be measured by the immersion and boiling method of ASTM C642. The results show that the influence of fly ash content on the porosity appears to be dependent on age of SCC. At age less than 56 d, fly ash tends to cause an increase of voids but at 90 d of age it reduces the pores. The additional pores that can be penetrated by vacuum saturation method counts about 50% of the total voids.

Design and development of controlled porosity osmotic tablet of diltiazem hydrochloride

Directory of Open Access Journals (Sweden)

Sadhana R Shahi

2012-01-01

Full Text Available The present work aims towards the design and development of extended release formulation of freely water-soluble drug diltiazem hydrochloride (DLTZ based on osmotic technology by using controlled porosity approach. DLTZ is an ideal candidate for a zero-order drug delivery system because it is freely water-soluble and has a short half-life (2-3 h. Sodium chloride (Osmogen was added to the core tablet to alter the solubility of DLTZ in an aqueous medium. Cellulose acetate (CA and sorbitol were used as semipermeable membrane and pore former, respectively. The effect of different formulation variables namely concentration of osmogen in the core tablet, % pore former, % weight gain, pH of the dissolution medium and agitation intensity on the in vitro release was studied. DLTZ release was directly proportional to % pore former and inversely proportional to % weight gain. The optimized formulation (F8 delivered DLTZ independent of pH and agitation intensity for 12 h at the upper level concentration of % pore former (25% w/w and middle level concentration of % weight gain (6% w/w. The comparative study of elementary osmotic pump (EOP and controlled porosity osmotic pump revealed that it superior than conventional EOP and also easier and cost effective to formulate.

Comparing flows to a tunnel for single porosity, double porosity and discrete fracture representations of the EDZ

International Nuclear Information System (INIS)

Hawkins, I.; Swift, B.; Hoch, A.; Wendling, J.

2010-01-01

transfer between the continua. The MINC model is an extension of double continuum models. Double continuum models assume that the flow between the fractures and matrix blocks is 'quasi-steady' (i.e. proportional to the local difference in average pressure between the fractures and matrix blocks). In contrast, the MINC model treats this flow in a fully transient way; it resolves the gradients that drive the flow by discretizing the matrix blocks into a nested sequence of volume elements. DFN models were implemented using the computer program NAPSAC. The program uses an efficient finite-element method that allows the flow through many thousands of fractures to be calculated accurately. Amongst its capabilities, NAPSAC is able to: calculate the effective continuum permeability tensor; calculate the porosity and the inter-fracture matrix block size; simulate steady-state and transient inflows to tunnels; and simulate unsaturated flow in fractured rocks. Continuum models were implemented using the computer program TOUGH2v2. TOUGH2v2 can be used to simulate multiphase flows in single continuum, double continuum or MINC models. A DFN model of the EDZ was developed. The model includes three classes of fractures. - Chevron fractures are curved, flowing surfaces, which cut perpendicular to the tunnel axis and have a variable spacing. - Oblique fractures are planar, and cut into the side of the tunnel at a defined angle. - Random fractures are small, planar features, which lie in a narrow region close to the tunnel wall. - Additionally, lattices of fractures were included in the DFN model to represent the undamaged clay and the concrete lining of the tunnel. NAPSAC was used to calculate effective continuum permeability tensors and porosities for sub-regions of the DFN model. These permeability tensors and porosities were used to parameterize both single continuum and MINC models of the EDZ. For each of the models (i.e. DFN, single continuum and MINC), desaturation of the

Lattice Boltzmann simulation of dissolution-induced changes in permeability and porosity in 3D CO2 reactive transport

Science.gov (United States)

Tian, Zhiwei; Wang, Junye

2018-02-01

Dissolution and precipitation of rock matrix are one of the most important processes of geological CO2 sequestration in reservoirs. They change connections of pore channels and properties of matrix, such as bulk density, microporosity and hydraulic conductivity. This study builds on a recently developed multi-layer model to account for dynamic changes of microporous matrix that can accurately predict variations in hydraulic properties and reaction rates due to dynamic changes in matrix porosity and pore connectivity. We apply the model to simulate the dissolution and precipitation processes of rock matrix in heterogeneous porous media to quantify (1) the effect of the reaction rate on dissolution and matrix porosity, (2) the effect of microporous matrix diffusion on the overall effective diffusion and (3) the effect of heterogeneity on hydraulic conductivity. The results show the CO2 storage influenced by factors including the matrix porosity change, reaction front movement, velocity and initial properties. We also simulated dissolution-induced permeability enhancement as well as effects of initial porosity heterogeneity. The matrix with very low permeability, which can be unresolved on X-ray CT, do contribute to flow patterns and dispersion. The concentration of reactant H+ increases along the main fracture paths where the flow velocity increases. The product Ca++ shows the inversed distribution pattern against the H+ concentration. This demonstrates the capability of this model to investigate the complex CO2 reactive transport in real 3D heterogeneous porous media.

Nonstationary porosity evolution in mixing zone in coastal carbonate aquifer using an alternative modeling approach.

Science.gov (United States)

Laabidi, Ezzeddine; Bouhlila, Rachida

2015-07-01

In the last few decades, hydrogeochemical problems have benefited from the strong interest in numerical modeling. One of the most recognized hydrogeochemical problems is the dissolution of the calcite in the mixing zone below limestone coastal aquifer. In many works, this problem has been modeled using a coupling algorithm between a density-dependent flow model and a geochemical model. A related difficulty is that, because of the high nonlinearity of the coupled set of equations, high computational effort is needed. During calcite dissolution, an increase in permeability can be identified, which can induce an increase in the penetration of the seawater into the aquifer. The majority of the previous studies used a fully coupled reactive transport model in order to model such problem. Romanov and Dreybrodt (J Hydrol 329:661-673, 2006) have used an alternative approach to quantify the porosity evolution in mixing zone below coastal carbonate aquifer at steady state. This approach is based on the analytic solution presented by Phillips (1991) in his book Flow and Reactions in Permeable Rock, which shows that it is possible to decouple the complex set of equation. This equation is proportional to the square of the salinity gradient, which can be calculated using a density driven flow code and to the reaction rate that can be calculated using a geochemical code. In this work, this equation is used in nonstationary step-by-step regime. At each time step, the quantity of the dissolved calcite is quantified, the change of porosity is calculated, and the permeability is updated. The reaction rate, which is the second derivate of the calcium equilibrium concentration in the equation, is calculated using the PHREEQC code (Parkhurst and Apello 1999). This result is used in GEODENS (Bouhlila 1999; Bouhlila and Laabidi 2008) to calculate change of the porosity after calculating the salinity gradient. For the next time step, the same protocol is used but using the updated porosity

Application of finite difference method in the study of diffusion with chemical kinetics of first order

Directory of Open Access Journals (Sweden)

Beltrán-Prieto Juan Carlos

2016-01-01

Full Text Available The mathematical modelling of diffusion of a bleaching agent into a porous material is studied in the present paper. Law of mass conservation was applied to analize the mass transfer of a reactant from the bulk into the external surface of a solid geometrically described as a flat plate. After diffusion of the reactant, surface reaction following kinetics of first order was considered to take place. The solution of the differential equation that described the process leaded to an equation that represents the concentration profile in function of distance, porosity and Thiele modulus. The case of interfacial mass resistance is also discused. In this case, finite difference method was used for the solution of the differential equation taking into account the respective boundary conditions. The profile of concentration can be obtained after numerical especification of Thiele modulus and Biot number.

A Porosity Method to Describe Complex 3D-Structures Theory and Application to an Explosion

Directory of Open Access Journals (Sweden)

M.-F. Robbe

2006-01-01

Full Text Available A theoretical method was developed to be able to describe the influence of structures of complex shape on a transient fluid flow without meshing the structures. Structures are considered as solid pores inside the fluid and act as an obstacle for the flow. The method was specifically adapted to fast transient cases.The porosity method was applied to the simulation of a Hypothetical Core Disruptive Accident in a small-scale replica of a Liquid Metal Fast Breeder Reactor. A 2D-axisymmetrical simulation of the MARS test was performed with the EUROPLEXUS code. Whereas the central internal structures of the mock-up could be described with a classical shell model, the influence of the 3D peripheral structures was taken into account with the porosity method. 

Multiple technologies applied to characterization of the porosity and permeability of the Biscayne aquifer, Florida

Science.gov (United States)

Cunningham, K.J.; Sukop, M.C.

2011-01-01

Research is needed to determine how seepage-control actions planned by the Comprehensive Everglades Restoration Plan (CERP) will affect recharge, groundwater flow, and discharge within the dual-porosity karstic Biscayne aquifer where it extends eastward from the Everglades to Biscayne Bay. A key issue is whether the plan can be accomplished without causing urban flooding in adjacent populated areas and diminishing coastal freshwater flow needed in the restoration of the ecologic systems. Predictive simulation of groundwater flow is a prudent approach to understanding hydrologic change and potential ecologic impacts. A fundamental problem to simulation of karst groundwater flow is how best to represent aquifer heterogeneity. Currently, U.S. Geological Survey (USGS) researchers and academic partners are applying multiple innovative technologies to characterize the spatial distribution of porosity and permeability within the Biscayne aquifer.

Detection of wood cell wall porosity using small carbohydrate molecules and confocal fluorescence microscopy.

Science.gov (United States)

Donaldson, L A; Kroese, H W; Hill, S J; Franich, R A

2015-09-01

A novel approach to nanoscale detection of cell wall porosity using confocal fluorescence microscopy is described. Infiltration of cell walls with a range of nitrophenyl-substituted carbohydrates of different molecular weights was assessed by measuring changes in the intensity of lignin fluorescence, in response to the quenching effect of the 4-nitrophenyl group. The following carbohydrates were used in order of increasing molecular weight; 4-nitrophenyl β-D-glucopyrano-side (monosaccharide), 4-nitrophenyl β-D-lactopyranoside (disaccharide), 2-chloro-4-nitrophenyl β-D-maltotrioside (trisaccharide), and 4-nitrophenyl α-D-maltopentaoside (pentasaccharide). This technique was used to compare cell wall porosity in wood which had been dewatered to 40% moisture content using supercritical CO2, where cell walls remain fully hydrated, with kiln dried wood equilibrated to 12% moisture content. Infiltration of cell walls as measured by fluorescence quenching, was found to decrease with increasing molecular weight, with the pentasaccharide being significantly excluded compared to the monosaccharide. Porosity experiments were performed on blocks and sections to assess differences in cell wall accessibility. Dewatered and kiln dried wood infiltrated as blocks showed similar results, but greater infiltration was achieved by using sections, indicating that not all pores were easily accessible by infiltration from the lumen surface. In wood blocks infiltrated with 4-nitrophenyl α-D-maltopentaoside, quenching of the secondary wall was quite variable, especially in kiln dried wood, indicating limited connectivity of pores accessible from the lumen surface. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Porosity dependence of positive magnetoconductance in n-type porous silicon

Energy Technology Data Exchange (ETDEWEB)

Chouaibi, Bassem; Radaoui, Moufid; Benfredj, Amel; Bouchriha, Habib [Laboratoire Materiaux Avances et Phenomenes Quantiques, Faculte des Sciences de Tunis, Universite El Manar, 2092 Campus universitaire, Tunis (Tunisia); Romdhane, Samir [Laboratoire Materiaux Avances et Phenomenes Quantiques, Faculte des Sciences de Tunis, Universite El Manar, 2092 Campus universitaire, Tunis (Tunisia); Faculte des Sciences de Bizerte, 7021 Zarzouna, Bizerte, Universite de Carthage (Tunisia); Bouaicha, Mongi [Laboratoire de Photovoltaique, Centre de Recherches et des Technologies de l' Energie, BP 95, Hammam-Lif 2050 (Tunisia)

2012-10-15

Positive magnetoconductance (MC) on n-type porous silicon (PS) based devices was observed at room temperature for low static magnetic field (under 6000 G). We found that the measured MC decreases when the film porosity is increased. Obtained results were analyzed by means of the quasi-1D weak localization (WL) theory. From the dependence of the MC vs. applied magnetic field, we determine the phase coherence length L{sup {phi}}. Good agreement between theoretical and experimental results was found (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Early age compressive strength, porosity, and sorptivity of concrete using peat water to produce and cure concrete

Science.gov (United States)

Olivia, Monita; Ismeddiyanto, Wibisono, Gunawan; Sitompul, Iskandar R.

2017-09-01

Construction in peatland has faced scarce water sources for mixing and curing concrete. It is known that peat water has high organic content and low pH that can be harmful to concrete in the environment. In some remote areas in Riau Province, contractors used peat water directly without sufficient treatments to comply with SKSNI requirements of concrete mixing water. This paper presents a study of compressive strength, porosity and sorptivity of Ordinary Portland Cement (OPC) and blended OPC-Palm Oil Fuel Ash (OPC-POFA) concrete. The specimens were mixed using natural water and peat water, then some of them were cured in fresh water and peat water. Six mixtures were investigated using a variation of cement, mixing water and curing water. Tap water is used as control mixing and curing water for all specimens. The compressive strength, porosity and sorptivity were calculated at seven and 28 days. Results indicate that the use of peat water will cause low compressive strength, high porosity and sorptivity for both OPC and OPC-POFA concrete. Using peat water and curing the specimens in tap water could improve the early strength, porosity and sorptivity of OPC concrete; however, it has an adverse effect on OPC-POFA specimens. The properties of early age concrete of both types (OPC and OPC-POFA) using peat water were as good as those with tap water. Therefore, it is suggested that peat water should be considered as mixing and curing water for concrete where tap water resources are scarce. Investigation of its long-term properties, as well as extending the observed age of concrete is recommended before any use of peat water.

Radioactive wastes storage rock porosity study using neutron radiography

International Nuclear Information System (INIS)

Peterka, F.

1995-01-01

Neutron radiography and neutron transmission analysis application to porosity study was mainly dealing with the building industry, the art protection and the basic research. Cooperation with the building industry has produced the solution of number of problems. Cement hydratation, concrete material, red brick sample, roofing tiles protection and epoxy resin efficiency for sand stones sculpture protection, can be cited as example. Many valuable experiences (like samples thickness, penetrating substances, detection techniques for the different experiments) were achieved. These can be used in the rockies formation studies too. Resolution is the proposal to JAERI and PNC for the cooperation, which can even be on the international basis. (J.P.N.)

Analysis of the porosity distribution of mixed oxide pins

International Nuclear Information System (INIS)

Lieblich, M.; Lopez, J.

1987-01-01

In the frame of the Joint Irradiation Program IVO-FR2-Vg7 between the Centre of Nuclear Research of Karlsruhe (KfK), the irradiation of 30 mixed-oxide fuel rods in the FR2 experimental reactor was carried out. The pins were located in 10 single-walled NaK capsules. The behaviour of the fuel during its burnup was studied, mainly, the rest-porosity and cracking distribution in the pellet, partial densification, etc. In this work 3 pins from the capsule No. 165 were analyzed. The experimental results (pore and cracking profiles) were interpreted by the fuel rod code SATURN. (Author) 20 refs

Three-dimensional (3D) visualization of reflow porosity and modeling of deformation in Pb-free solder joints

International Nuclear Information System (INIS)

Dudek, M.A.; Hunter, L.; Kranz, S.; Williams, J.J.; Lau, S.H.; Chawla, N.

2010-01-01

The volume, size, and dispersion of porosity in solder joints are known to affect mechanical performance and reliability. Most of the techniques used to characterize the three-dimensional (3D) nature of these defects are destructive. With the enhancements in high resolution computed tomography (CT), the detection limits of intrinsic microstructures have been significantly improved. Furthermore, the 3D microstructure of the material can be used in finite element models to understand their effect on microscopic deformation. In this paper we describe a technique utilizing high resolution (< 1 μm) X-ray tomography for the three-dimensional (3D) visualization of pores in Sn-3.9Ag-0.7Cu/Cu joints. The characteristics of reflow porosity, including volume fraction and distribution, were investigated for two reflow profiles. The size and distribution of porosity size were visualized in 3D for four different solder joints. In addition, the 3D virtual microstructure was incorporated into a finite element model to quantify the effect of voids on the lap shear behavior of a solder joint. The presence, size, and location of voids significantly increased the severity of strain localization at the solder/copper interface.

The effects of bauxite, metakaolin, and porosity on the thermal properties of prepared Iraqi clays refractory mortars

Science.gov (United States)

Zaidan, Shihab A.; Omar, Mustafa H.

2018-05-01

One of the most important requirements for the manufacture of refractory mortars, especially those used in the construction of thermal systems (building or plastering), is the balance between thermal insulation properties and porosity. Where, increasing porosity of mortar to a large amount may be always undesirable, because the absorption of liquid and gases emitted from industrial system is decline the bonded with bricks and structural properties of mortars. Refractory mortars prepared from either fired bauxite or metakaolin clays with different percentages of kaolin (10, 20, 30, and 40 wt%). Bauxite rocks were fired at 1200 °C and metakaolin was obtained by firing kaolin up to 700 °C then crushed and grinded. Grog was added to mixture to reduce the shrinkage. Cylindrical specimens are prepared and then sintered at 1200 °C. All mixtures maintained a low thermal conductivity within the limits of thermal insulation material (less than 0.5 W/m K); it was done by controlling the porosity which reached a maximum value approximately 25%. The volumetric heat capacity and thermal diffusivity was ranged between (1-10 MJ/m3 K), (0.06-0.2 mm2/s), respectively.

Computational intelligence models to predict porosity of tablets using minimum features

Directory of Open Access Journals (Sweden)

Khalid MH

2017-01-01

Full Text Available Mohammad Hassan Khalid,1 Pezhman Kazemi,1 Lucia Perez-Gandarillas,2 Abderrahim Michrafy,2 Jakub Szlęk,1 Renata Jachowicz,1 Aleksander Mendyk1 1Department of Pharmaceutical Technology and Biopharmaceutics, Faculty of Pharmacy, Jagiellonian University Medical College, Krakow, Poland; 2Centre National de la Recherche Scientifique, Centre RAPSODEE, Mines Albi, Université de Toulouse, Albi, France Abstract: The effects of different formulations and manufacturing process conditions on the physical properties of a solid dosage form are of importance to the pharmaceutical industry. It is vital to have in-depth understanding of the material properties and governing parameters of its processes in response to different formulations. Understanding the mentioned aspects will allow tighter control of the process, leading to implementation of quality-by-design (QbD practices. Computational intelligence (CI offers an opportunity to create empirical models that can be used to describe the system and predict future outcomes in silico. CI models can help explore the behavior of input parameters, unlocking deeper understanding of the system. This research endeavor presents CI models to predict the porosity of tablets created by roll-compacted binary mixtures, which were milled and compacted under systematically varying conditions. CI models were created using tree-based methods, artificial neural networks (ANNs, and symbolic regression trained on an experimental data set and screened using root-mean-square error (RMSE scores. The experimental data were composed of proportion of microcrystalline cellulose (MCC (in percentage, granule size fraction (in micrometers, and die compaction force (in kilonewtons as inputs and porosity as an output. The resulting models show impressive generalization ability, with ANNs (normalized root-mean-square error [NRMSE] =1% and symbolic regression (NRMSE =4% as the best-performing methods, also exhibiting reliable predictive

Modifying the Hierarchical Porosity of SBA-15 via Mild-Detemplation Followed by Secondary Treatments

NARCIS (Netherlands)

Zhang, Zheng; Melian-Cabrera, Ignacio

2014-01-01

Fenton-chemistry-based detemplation combined with secondary treatments offers options to tune the hierarchical porosity of SBA-15. This approach has been studied on a series of SBA-15 mesophases and has been compared to the conventional calcination. The as-synthesized and detemplated materials were

X-ray tomography studies on porosity and particle size distribution in cast in-situ Al-Cu-TiB{sub 2} semi-solid forged composites

Energy Technology Data Exchange (ETDEWEB)

Mathew, James; Mandal, Animesh [School of Minerals, Metallurgical and Materials Engineering, Indian Institute of Technology, Bhubaneswar (India); Warnett, Jason; Williams, Mark A. [WMG, University of Warwick, Coventry CV4 7AL (United Kingdom); Chakraborty, Madhusudan [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur (India); Srirangam, Prakash, E-mail: p.srirangam@warwick.ac.uk [WMG, University of Warwick, Coventry CV4 7AL (United Kingdom)

2016-08-15

X-ray computed tomography (XCT) was used to characterise the internal microstructure and clustering behaviour of TiB{sub 2} particles in in-situ processed Al-Cu metal matrix composites prepared by casting method. Forging was used in semi-solid state to reduce the porosity and to uniformly disperse TiB{sub 2} particles in the composite. Quantification of porosity and clustering of TiB{sub 2} particles was evaluated for different forging reductions (30% and 50% reductions) and compared with an as-cast sample using XCT. Results show that the porosity content was decreased by about 40% due to semi-solid forging as compared to the as-cast condition. Further, XCT results show that the 30% forging reduction resulted in greater uniformity in distribution of TiB{sub 2} particles within the composite compared to as-cast and the 50% forge reduction in semi-solid state. These results show that the application of forging in semi-solid state enhances particle distribution and reduces porosity formation in cast in-situ Al-Cu-TiB{sub 2} metal matrix composites. - Highlights: •XCT was used to visualise 3D internal structure of Al-Cu-TiB{sub 2} MMCs. •Al-Cu-TiB{sub 2} MMC was prepared by casting using flux assisted synthesis method. •TiB{sub 2} particles and porosity size distribution were evaluated. •Results show that forging in semi-solid condition decreases the porosity content and improve the particle dispersion in MMCs.

Um problema de corte com padrões compartimentados

Directory of Open Access Journals (Sweden)

Robinson Hoto

2003-01-01

Full Text Available Neste artigo apresentaremos a aplicação do Problema da Mochila Compartimentada (PMC no Problema de Corte de Bobinas de Aço (PCBA, que é um problema de corte em duas etapas com restrições especiais de agrupamento dos itens. O PMC consiste em construir compartimentos de capacidades desconhecidas em uma mochila de capacidade conhecida, tendo em vista que os itens de interesse estão agrupados em subconjuntos, de modo que, itens de um agrupamento não podem ser combinados com itens de outro. Para entender melhor o PMC admita que a mochila de um alpinista deve ser composta por um número ideal de compartimentos com itens de quatro categorias (remédios, alimentos, ferramentas, roupas, porém, itens de categorias distintas não podem ser combinados para formar um mesmo compartimento, além do mais, são desconhecidas as capacidades ideais de cada compartimento da mochila.In this paper we will present the application of the Compartmented Knapsack Problem (CKP in the Cut Problem of Steel Rolls (CPSR, that it is a problem of cut in two stages with restrictions special of grouping of items. The CKP consists of constructing compartments of unknown capacities in a knapsack of known capacity, in view of that items of interest is grouped in subgroups, in mode that, items of a grouping cannot be matched with items of another one. To understand the CKP more good it admits that the knapsack of a alpinist must be composite for an ideal number of compartments with items of four categories (remedies, foods, tools, clothes, however, items of distinct categories cannot be matched to form one same compartment, in addition, is unknown the ideal capacities of each compartment of the knapsack.

In-line monitoring of Li-ion battery electrode porosity and areal loading using active thermal scanning - modeling and initial experiment

Science.gov (United States)

Rupnowski, Przemyslaw; Ulsh, Michael; Sopori, Bhushan; Green, Brian G.; Wood, David L.; Li, Jianlin; Sheng, Yangping

2018-01-01

This work focuses on a new technique called active thermal scanning for in-line monitoring of porosity and areal loading of Li-ion battery electrodes. In this technique a moving battery electrode is subjected to thermal excitation and the induced temperature rise is monitored using an infra-red camera. Static and dynamic experiments with speeds up to 1.5 m min-1 are performed on both cathodes and anodes and a combined micro- and macro-scale finite element thermal model of the system is developed. It is shown experimentally and through simulations that during thermal scanning the temperature profile generated in an electrode depends on both coating porosity (or area loading) and thickness. It is concluded that by inverting this relation the porosity (or areal loading) can be determined, if thermal response and thickness are simultaneously measured.

Saturation and porosity measurements of different soil samples by gamma ray transmission

International Nuclear Information System (INIS)

Akbal, S.; Filiz Baytas, A.

2000-01-01

Gamma-ray transmission methods have been used accurately for the study of the properties of soil samples. In this study, the soil samples were collected from various regions of Turkey and a Nal (TI) detector measured the attenuation of strongly collimated monoenergetic gamma beam (from Cs-137) through soil samples. The water saturation and porosity were therefore calculated from the transmission measurements for each soil sample. (authors)

Workplace Injuries And Safety Practice Among Nurses In A Nigerian ...

African Journals Online (AJOL)

AA Nasir, OO Ajide, LO Abdur-Rahman, T Adebola, CY Ijagbemi, GH Ibraheem, CKP Ofoegbu, BA Solagberu. Abstract. Click on the link to view the abstract. The Tropical Journal of Health Sciences Vol 20 No 2 (July 2013). AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors ...

Transformation of seismic velocity data to extract porosity and saturation values for rocks

International Nuclear Information System (INIS)

Berryman, James G.; Berge, Patricia A.; Bonner, Brian P.

2000-01-01

For wave propagation at low frequencies in a porous medium, the Gassmann-Domenico relations are well-established for homogeneous partial saturation by a liquid. They provide the correct relations for seismic velocities in terms of constituent bulk and shear moduli, solid and fluid densities, porosity and saturation. It has not been possible, however, to invert these relations easily to determine porosity and saturation when the seismic velocities are known. Also, the state (or distribution) of saturation, i.e., whether or not liquid and gas are homogeneously mixed in the pore space, is another important variable for reservoir evaluation. A reliable ability to determine the state of saturation from velocity data continues to be problematic. It is shown how transforming compressional and shear wave velocity data to the (ρ/λ,μ/λ)-plane (where λ and μ are the Lame parameters and ρ is the total density) results in a set of quasi-orthogonal coordinates for porosity and liquid saturation that greatly aids in the interpretation of seismic data for the physical parameters of most interest. A second transformation of the same data then permits isolation of the liquid saturation value, and also provides some direct information about the state of saturation. By thus replotting the data in the (λ/μ, ρ/μ)-plane, inferences can be made concerning the degree of patchy (inhomogeneous) versus homogeneous saturation that is present in the region of the medium sampled by the data. Our examples include igneous and sedimentary rocks, as well as man-made porous materials. These results have potential applications in various areas of interest, including petroleum exploration and reservoir characterization, geothermal resource evaluation, environmental restoration monitoring, and geotechnical site characterization. (c) 2000 Acoustical Society of America

The influence of mesoscale porosity on cortical bone anisotropy. Investigations via asymptotic homogenization

Science.gov (United States)

Parnell, William J; Grimal, Quentin

2008-01-01

Recently, the mesoscale of cortical bone has been given particular attention in association with novel experimental techniques such as nanoindentation, micro-computed X-ray tomography and quantitative scanning acoustic microscopy (SAM). A need has emerged for reliable mathematical models to interpret the related microscopic and mesoscopic data in terms of effective elastic properties. In this work, a new model of cortical bone elasticity is developed and used to assess the influence of mesoscale porosity on the induced anisotropy of the material. Only the largest pores (Haversian canals and resorption cavities), characteristic of the mesoscale, are considered. The input parameters of the model are derived from typical mesoscale experimental data (e.g. SAM data). We use the method of asymptotic homogenization to determine the local effective elastic properties by modelling the propagation of low-frequency elastic waves through an idealized material that models the local mesostructure. We use a novel solution of the cell problem developed by Parnell & Abrahams. This solution is stable for the physiological range of variation of mesoscopic porosity and elasticity found in bone. Results are computed efficiently (in seconds) and the solutions can be implemented easily by other workers. Parametric studies are performed in order to assess the influence of mesoscopic porosity, the assumptions regarding the material inside the mesoscale pores (drained or undrained bone) and the shape of pores. Results are shown to be in good qualitative agreement with existing schemes and we describe the potential of the scheme for future use in modelling more complex microstructures for cortical bone. In particular, the scheme is shown to be a useful tool with which to predict the qualitative changes in anisotropy due to variations in the structure at the mesoscale. PMID:18628200

Development and prevention of porosity in the fusion welding of thick titanium alloys

International Nuclear Information System (INIS)

Kulikov, F.R.; Redchits, V.V.; Khokhlov, V.V.

1975-01-01

This article describes the results of experimental investigations of the mechanics of formation of porosity in electron-beam welding, single-pass and multipass welding in argon with a consumable and non-consumable electrode, and also in the electroslag welding of alloys VT14 and VT22 from 10 to 60mm thick. It was established that nuclei of gas phase form at the moment of fusion of the edges of the parts being welded, the end surfaces of which have machining defects. The weld metal porosity can be prevented by: careful machining of the faying surfaces of the parts to be welded immediately before welding; the use of welding conditions ensuring long pool existence time, sufficient for hydrogen bubbles to float up and escape; intensification of the weld pool degassing process by using fluxes based on metal fluorides and chlorides, applied to the ends of the root part of the faying edges, and on the filler wire; reduction of the gas pressure in the beam channel by making gas-escape paths

Modeled near-field environment porosity modifications due to coupled thermohydrologic and geochemical processes

International Nuclear Information System (INIS)

Glassley, W. E.; Nitao, J. J.

1998-01-01

Heat deposited by waste packages in nuclear waste repositories can modify rock properties by instigating mineral dissolution and precipitation along hydrothermal flow pathways. Modeling this reactive transport requires coupling fluid flow to permeability changes resulting from dissolution and precipitation. Modification of the NUFT thermohydrologic (TH) code package to account for this coupling in a simplified geochemical system has been used to model the time- dependent change in porosity, permeability, matrix and fracture saturation, and temperature in the vicinity of waste-emplacement drifts, using conditions anticipated for the potential Yucca Mountain repository. The results show, within a few hundred years, dramatic porosity reduction approximately 10 m above emplacement drifts. Most of this reduction is attributed to deposition of solute load at the boiling front, although some of it also results from decreasing temperature along the flow path. The actual distribution of the nearly sealed region is sensitive to the time- dependent characteristics of the thermal load imposed on the environment and suggests that the geometry of the sealed region can be engineered by managing the waste-emplacement strategy

The Monte Carlo calculation of gamma family

International Nuclear Information System (INIS)

Shibata, Makio

1980-01-01

The method of the Monte Carlo calculation for gamma family was investigated. The effects of the variation of values or terms of parameters on observed quantities were studied. The terms taken for the standard calculation are the scaling law for the model, simple proton spectrum for primary cosmic ray, a constant cross section of interaction, zero probability of neutral pion production, and the bending of the curve of primary energy spectrum. This is called S model. Calculations were made by changing one of above mentioned parameters. The chamber size, the mixing of gamma and hadrons, and the family size were fitted to the practical ECC data. When the model was changed from the scaling law to the CKP model, the energy spectrum of the family was able to be expressed by the CKP model better than the scaling law. The scaling law was better in the symmetry around the family center. It was denied that primary cosmic ray mostly consists of heavy particles. The increase of the interaction cross section was necessary in view of the frequency of the families. (Kato, T.)

Porosity and reservoir potentiality of the Cherahil Formation limestone (middle-upper Eocene) in the Gulf of Gabes (Tunisia)

Science.gov (United States)

Njahi, Zahra; Kassabi, Nadhem; Touir, Jamel

2017-07-01

During the middle and upper Eocene, the deposits in the Gulf of Gabes correspond to the Cherahil Formation, which is sub-divided into three units, which are as follows from base to top: the Lower Cherahil A, the Siouf and the Upper Cherahil B members. The Siouf member has a lateral equivalent in the Souar Formation named Reineche member. The Cherahil Formation has never been considered by oil companies as a particular drilling target in the Gulf of Gabes (offshore east Tunisia) despite the presence of hydrocarbon at the bottom of Cherahil Formation in Sidi Behara and Sidi Litayem oil fields in Sfax Area (onshore east Tunisia) and in its equivalent carbonate beds in Jebel Trozza (Central Tunisia). Therefore, the evaluation of porosity in the carbonate levels of Cherahil Formation in 20 drilling wells were performed on well logging by applying Wyllie method. The obtained results show that the studied carbonates are characterized by an economically important total porosity average ranging between 5% and 55%, and both vertical and lateral variations. The vertical porosity variation was controlled by the sea-level fluctuation that, in turn, controlled the evolution of carbonate sedimentary environments and relative facies. The lateral porosity variation followed the Tunisian middle-upper Eocene paleogeography changes controlled by NW-SE synsedimentary tectonic trends. Considering the important features of the Cherahil Formation and the coexistence of components of an oil system in the Gulf of Gabes, this formation can be an important potential reservoir and subsequently a new petroleum exploration target in the Gulf of Gabes.

Using decomposition kinetics to model the removal of mine water pollutants in constructed wetlands

Energy Technology Data Exchange (ETDEWEB)

Tarutis, W J; Unz, R F [Pennsylvania State University, University Park, PA (United States)

1994-01-01

Although numerous mathematical models have been used to describe decomposition, few, if any, have been used to model the removal of pollutants in constructed wetlands. A steady state method based on decomposition kinetics and reaction stoichiometry has been developed which simulates the removal of ferrous iron entering wetlands constructed for mine drainage treatment. Input variables for the model include organic matter concentration, reaction rate coefficient, porosity and dry density, and hydraulic detection time. Application of the model assumes complete anaerobic conditions within the entire substrate profile, constant temperature, no additional organic matter input, and subsurface flow only. For these ideal conditions, model simulations indicate that wetlands constructed with readily decomposable substrates rich in organic carbon are initially capable of removing far greater amounts of iron than wetlands built with less biodegradable substrates. However, after three to five years of operation this difference becomes negligible. For acceptable long-term treatment performance, therefore, periodic additions of decomposable organic matter will be required.