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Sample records for model porous materials

  1. Designing and modeling doubly porous polymeric materials

    NASA Astrophysics Data System (ADS)

    Ly, H.-B.; Le Droumaguet, B.; Monchiet, V.; Grande, D.

    2015-07-01

    Doubly porous organic materials based on poly(2-hydroxyethyl methacrylate) are synthetized through the use of two distinct types of porogen templates, namely a macroporogen and a nanoporogen. Two complementary strategies are implemented by using either sodium chloride particles or fused poly(methyl methacrylate) beads as macroporogens, in conjunction with ethanol as a porogenic solvent. The porogen removal respectively allows for the generation of either non-interconnected or interconnected macropores with an average diameter of about 100-200 μm and nanopores with sizes lying within the 100 nm order of magnitude, as evidenced by mercury intrusion porosimetry and scanning electron microscopy. Nitrogen sorption measurements evidence the formation of materials with rather high specific surface areas, i.e. higher than 140 m2.g-1. This paper also addresses the development of numerical tools for computing the permeability of such doubly porous materials. Due to the coexistence of well separated scales between nanopores and macropores, a consecutive double homogenization approach is proposed. A nanoscopic scale and a mesoscopic scale are introduced, and the flow is evaluated by means of the Finite Element Method to determine the macroscopic permeability. At the nanoscopic scale, the flow is described by the Stokes equations with an adherence condition at the solid surface. At the mesoscopic scale, the flow obeys the Stokes equations in the macropores and the Darcy equation in the permeable polymer in order to account for the presence of the nanopores.

  2. On the sensitivity analysis of porous material models

    NASA Astrophysics Data System (ADS)

    Ouisse, Morvan; Ichchou, Mohamed; Chedly, Slaheddine; Collet, Manuel

    2012-11-01

    Porous materials are used in many vibroacoustic applications. Different available models describe their behaviors according to materials' intrinsic characteristics. For instance, in the case of porous material with rigid frame, and according to the Champoux-Allard model, five parameters are employed. In this paper, an investigation about this model sensitivity to parameters according to frequency is conducted. Sobol and FAST algorithms are used for sensitivity analysis. A strong parametric frequency dependent hierarchy is shown. Sensitivity investigations confirm that resistivity is the most influent parameter when acoustic absorption and surface impedance of porous materials with rigid frame are considered. The analysis is first performed on a wide category of porous materials, and then restricted to a polyurethane foam analysis in order to illustrate the impact of the reduction of the design space. In a second part, a sensitivity analysis is performed using the Biot-Allard model with nine parameters including mechanical effects of the frame and conclusions are drawn through numerical simulations.

  3. Modeling heat transfer within porous multiconstituent materials

    NASA Astrophysics Data System (ADS)

    Niezgoda, Mathieu; Rochais, Denis; Enguehard, Franck; Rousseau, Benoit; Echegut, Patrick

    2012-06-01

    The purpose of our work has been to determine the effective thermal properties of materials considered heterogeneous at the microscale but which are regarded as homogenous in the macroscale environment in which they are used. We have developed a calculation code that renders it possible to simulate thermal experiments over complex multiconstituent materials from their numerical microstructural morphology obtained by volume segmentation through tomography. This modeling relies on the transient solving of the coupled conductive and radiative heat transfer in these voxelized structures.

  4. Simplified modeling of transition to detonation in porous energetic materials

    SciTech Connect

    Stewart, D.S. ); Asay, B.W. ); Prasad, K. )

    1994-07-01

    A simplified model that can predict the transitions from compaction to detonation and shock to detonation is given with the aim of describing experiments in beds of porous HMX. In the case of compaction to detonation, the energy of early impact generates a slowly moving, convective-reactive deflagration that expands near the piston face and evolves in a manner that is characteristic of confined deflagration to detonation transition. A single-phase state variable theory is adopted in contrast to a two-phase axiomatic mixture theory. The ability of the porous material to compact is treated as an endothermic process. Reaction is treated as an exothermic process. The algebraic (Rankine--Hugoniot) steady wave analysis is given for inert compaction waves and steady detonation waves in a piston supported configuration, typical of the experiments carried out in porous HMX. A structure analysis of the steady compaction wave is given. Numerical simulations of deflagration to detonation are carried out for parameters that describe an HMX-like material and compared with the experiments. The simple model predicts the high density plug that is observed in the experiments and suggests that the leading front of the plug is a secondary compaction wave. A shock to detonation transition is also numerically simulated.

  5. System level permeability modeling of porous hydrogen storage materials.

    SciTech Connect

    Kanouff, Michael P.; Dedrick, Daniel E.; Voskuilen, Tyler

    2010-01-01

    A permeability model for hydrogen transport in a porous material is successfully applied to both laboratory-scale and vehicle-scale sodium alanate hydrogen storage systems. The use of a Knudsen number dependent relationship for permeability of the material in conjunction with a constant area fraction channeling model is shown to accurately predict hydrogen flow through the reactors. Generally applicable model parameters were obtained by numerically fitting experimental measurements from reactors of different sizes and aspect ratios. The degree of channeling was experimentally determined from the measurements and found to be 2.08% of total cross-sectional area. Use of this constant area channeling model and the Knudsen dependent Young & Todd permeability model allows for accurate prediction of the hydrogen uptake performance of full-scale sodium alanate and similar metal hydride systems.

  6. Advances in design and modeling of porous materials

    NASA Astrophysics Data System (ADS)

    Ayral, André; Calas-Etienne, Sylvie; Coasne, Benoit; Deratani, André; Evstratov, Alexis; Galarneau, Anne; Grande, Daniel; Hureau, Matthieu; Jobic, Hervé; Morlay, Catherine; Parmentier, Julien; Prelot, Bénédicte; Rossignol, Sylvie; Simon-Masseron, Angélique; Thibault-Starzyk, Frédéric

    2015-07-01

    This special issue of the European Physical Journal Special Topics is dedicated to selected papers from the symposium "High surface area porous and granular materials" organized in the frame of the conference "Matériaux 2014", held on November 24-28, 2014 in Montpellier, France. Porous materials and granular materials gather a wide variety of heterogeneous, isotropic or anisotropic media made of inorganic, organic or hybrid solid skeletons, with open or closed porosity, and pore sizes ranging from the centimeter scale to the sub-nanometer scale. Their technological and industrial applications cover numerous areas from building and civil engineering to microelectronics, including also metallurgy, chemistry, health, waste water and gas effluent treatment. Many emerging processes related to environmental protection and sustainable development also rely on this class of materials. Their functional properties are related to specific transfer mechanisms (matter, heat, radiation, electrical charge), to pore surface chemistry (exchange, adsorption, heterogeneous catalysis) and to retention inside confined volumes (storage, separation, exchange, controlled release). The development of innovative synthesis, shaping, characterization and modeling approaches enables the design of advanced materials with enhanced functional performance. The papers collected in this special issue offer a good overview of the state-of-the-art and science of these complex media. We would like to thank all the speakers and participants for their contribution to the success of the symposium. We also express our gratitude to the organization committee of "Matériaux 2014". We finally thank the reviewers and the staff of the European Physical Journal Special Topics who made the publication of this special issue possible.

  7. Modeling adsorption of liquid mixtures on porous materials.

    PubMed

    Monsalvo, Matias A; Shapiro, Alexander A

    2009-05-01

    The multicomponent potential theory of adsorption (MPTA), which was previously applied to adsorption from gases, is extended onto adsorption of liquid mixtures on porous materials. In the MPTA, the adsorbed fluid is considered as an inhomogeneous liquid with thermodynamic properties that depend on the distance from the solid surface (or position in the porous space). The theory describes the two kinds of interactions present in the adsorbed fluid, i.e. the fluid-fluid and fluid-solid interactions, by means of an equation of state and interaction potentials, respectively. The proposed extension of the MPTA onto liquids has been tested on experimental binary and ternary adsorption data. We show that, for the set of experimental data considered in this work, the MPTA model is capable of correlating binary adsorption equilibria. Based on binary adsorption data, the theory can then predict ternary adsorption equilibria. Good agreement with the theoretical predictions is achieved in most of the cases. Some limitations of the model are also discussed. PMID:19243781

  8. Tailored Porous Materials

    SciTech Connect

    BARTON,THOMAS J.; BULL,LUCY M.; KLEMPERER,WALTER G.; LOY,DOUGLAS A.; MCENANEY,BRIAN; MISONO,MAKOTO; MONSON,PETER A.; PEZ,GUIDO; SCHERER,GEORGE W.; VARTULI,JAMES C.; YAGHI,OMAR M.

    1999-11-09

    Tailoring of porous materials involves not only chemical synthetic techniques for tailoring microscopic properties such as pore size, pore shape, pore connectivity, and pore surface reactivity, but also materials processing techniques for tailoring the meso- and the macroscopic properties of bulk materials in the form of fibers, thin films and monoliths. These issues are addressed in the context of five specific classes of porous materials: oxide molecular sieves, porous coordination solids, porous carbons, sol-gel derived oxides, and porous heteropolyanion salts. Reviews of these specific areas are preceded by a presentation of background material and review of current theoretical approaches to adsorption phenomena. A concluding section outlines current research needs and opportunities.

  9. SCDAP/RELAP5 Modeling of Movement of Melted Material Through Porous Debris in Lower Head

    SciTech Connect

    Siefken, Larry James; Harvego, Edwin Allan

    2000-04-01

    A model is described for the movement of melted metallic material through a ceramic porous debris bed. The model is designed for the analysis of severe accidents in LWRs, wherein melted core plate material may slump onto the top of a porous bed of relocated core material supported by the lower head. The permeation of the melted core plate material into the porous debris bed influences the heatup of the debris bed and the heatup of the lower head supporting the debris. A model for mass transport of melted metallic material is applied that includes terms for viscosity and turbulence but neglects inertial and capillary terms because of their small value relative to gravity and viscous terms in the momentum equation. The relative permeability and passability of the porous debris are calculated as functions of debris porosity, particle size, and effective saturation. An iterative numerical solution is used to solve the set of nonlinear equations for mass transport. The effective thermal conductivity of the debris is calculated as a function of porosity, particle size, and saturation. The model integrates the equations for mass transport with a model for the two-dimensional conduction of heat through porous debris. The integrated model has been implemented into the SCDAP/RELAP5 code for the analysis of the integrity of LWR lower heads during severe accidents. The results of the model indicate that melted core plate material may permeate to near the bottom of a 1m deep hot porous debris bed supported by the lower head. The presence of the relocated core plate material was calculated to cause a 12% increase in the heat flux on the external surface of the lower head.

  10. SCDAP/RELAP5 modeling of movement of melted material through porous debris in lower head

    SciTech Connect

    L. J. Siefken; E. A. Harvego

    2000-04-02

    A model is described for the movement of melted metallic material through a ceramic porous debris bed. The model is designed for the analysis of severe accidents in LWRs, wherein melted core plate material may slump onto the top of a porous bed of relocated core material supported by the lower head. The permeation of the melted core plate material into the porous debris bed influences the heatup of the debris bed and the heatup of the lower head supporting the debris. A model for mass transport of melted metallic material is applied that includes terms for viscosity and turbulence but neglects inertial and capillary terms because of their small value relative to gravity and viscous terms in the momentum equation. The relative permeability and passability of the porous debris are calculated as functions of debris porosity, particle size, and effective saturation. An iterative numerical solution is used to solve the set of nonlinear equations for mass transport. The effective thermal conductivity of the debris is calculated as a function of porosity, particle size, and saturation. The model integrates the equations for mass transport with a model for the two-dimensional conduction of heat through porous debris. The integrated model has been implemented into the SCDAP/RELAP5 code for the analysis of the integrity of LWR lower heads during severe accidents. The results of the model indicate that melted core plate material may permeate to near the bottom of a 1m deep hot porous debris bed supported by the lower head. The presence of the relocated core plate material was calculated to cause a 12% increase in the heat flux on the external surface of the lower head.

  11. Porous Organic Molecular Materials

    SciTech Connect

    Tian, Jian; Thallapally, Praveen K.; McGrail, B. Peter

    2012-01-01

    Most nanoporous materials with molecular-scale pores are extended frameworks composed of directional covalent or coordination bonding, such as porous metal-organic frameworks and organic network polymers. By contrast, nanoporous materials comprised of discrete organic molecules, between which there are only weak non-covalent interactions, are seldom encountered. Indeed, most organic molecules pack efficiently in the solid state to minimize the void volume, leading to non-porous materials. In recent years, a significant number of nanoporous organic molecular materials, which may be either crystalline or amorphous, have been confirmed by the studies of gas adsorption and they are surveyed in this Highlight. In addition, the possible advantages of porous organic molecular materials over porous networks are discussed.

  12. Preparation of asymmetric porous materials

    DOEpatents

    Coker, Eric N.

    2012-08-07

    A method for preparing an asymmetric porous material by depositing a porous material film on a flexible substrate, and applying an anisotropic stress to the porous media on the flexible substrate, where the anisotropic stress results from a stress such as an applied mechanical force, a thermal gradient, and an applied voltage, to form an asymmetric porous material.

  13. Porous material neutron detector

    DOEpatents

    Diawara, Yacouba; Kocsis, Menyhert

    2012-04-10

    A neutron detector employs a porous material layer including pores between nanoparticles. The composition of the nanoparticles is selected to cause emission of electrons upon detection of a neutron. The nanoparticles have a maximum dimension that is in the range from 0.1 micron to 1 millimeter, and can be sintered with pores thereamongst. A passing radiation generates electrons at one or more nanoparticles, some of which are scattered into a pore and directed toward a direction opposite to the applied electrical field. These electrons travel through the pore and collide with additional nanoparticles, which generate more electrons. The electrons are amplified in a cascade reaction that occurs along the pores behind the initial detection point. An electron amplification device may be placed behind the porous material layer to further amplify the electrons exiting the porous material layer.

  14. A diffusivity model for predicting VOC diffusion in porous building materials based on fractal theory.

    PubMed

    Liu, Yanfeng; Zhou, Xiaojun; Wang, Dengjia; Song, Cong; Liu, Jiaping

    2015-12-15

    Most building materials are porous media, and the internal diffusion coefficients of such materials have an important influences on the emission characteristics of volatile organic compounds (VOCs). The pore structure of porous building materials has a significant impact on the diffusion coefficient. However, the complex structural characteristics bring great difficulties to the model development. The existing prediction models of the diffusion coefficient are flawed and need to be improved. Using scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) tests of typical porous building materials, this study developed a new diffusivity model: the multistage series-connection fractal capillary-bundle (MSFC) model. The model considers the variable-diameter capillaries formed by macropores connected in series as the main mass transfer paths, and the diameter distribution of the capillary bundles obeys a fractal power law in the cross section. In addition, the tortuosity of the macrocapillary segments with different diameters is obtained by the fractal theory. Mesopores serve as the connections between the macrocapillary segments rather than as the main mass transfer paths. The theoretical results obtained using the MSFC model yielded a highly accurate prediction of the diffusion coefficients and were in a good agreement with the VOC concentration measurements in the environmental test chamber. PMID:26291782

  15. Strong, Lightweight, Porous Materials

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Meador, Mary Ann B.; Johnston, James C.; Fabrizio, Eve F.; Ilhan, Ulvi

    2007-01-01

    A new class of strong, lightweight, porous materials has been invented as an outgrowth of an effort to develop reinforced silica aerogels. The new material, called X-Aerogel is less hygroscopic, but no less porous and of similar density to the corresponding unmodified aerogels. However, the property that sets X-Aerogels apart is their mechanical strength, which can be as much as two and a half orders of magnitude stronger that the unmodified aerogels. X-Aerogels are envisioned to be useful for making extremely lightweight, thermally insulating, structural components, but they may also have applications as electrical insulators, components of laminates, catalyst supports, templates for electrode materials, fuel-cell components, and filter membranes.

  16. Model for the interpretation of nuclear magnetic resonance relaxometry of hydrated porous silicate materials

    NASA Astrophysics Data System (ADS)

    Faux, D. A.; Cachia, S.-H. P.; McDonald, P. J.; Bhatt, J. S.; Howlett, N. C.; Churakov, S. V.

    2015-03-01

    Nuclear magnetic resonance (NMR) relaxation experimentation is an effective technique for probing the dynamics of proton spins in porous media, but interpretation requires the application of appropriate spin-diffusion models. Molecular dynamics (MD) simulations of porous silicate-based systems containing a quasi-two-dimensional water-filled pore are presented. The MD simulations suggest that the residency time of the water on the pore surface is in the range 0.03-12 ns, typically 2-5 orders of magnitude less than values determined from fits to experimental NMR measurements using the established surface-layer (SL) diffusion models of Korb and co-workers [Phys. Rev. E 56, 1934 (1997), 10.1103/PhysRevE.56.1934]. Instead, MD identifies four distinct water layers in a tobermorite-based pore containing surface Ca2 + ions. Three highly structured water layers exist within 1 nm of the surface and the central region of the pore contains a homogeneous region of bulklike water. These regions are referred to as layer 1 and 2 (L1, L2), transition layer (TL), and bulk (B), respectively. Guided by the MD simulations, a two-layer (2L) spin-diffusion NMR relaxation model is proposed comprising two two-dimensional layers of slow- and fast-moving water associated with L2 and layers TL+B, respectively. The 2L model provides an improved fit to NMR relaxation times obtained from cementitious material compared to the SL model, yields diffusion correlation times in the range 18-75 ns and 28-40 ps in good agreement with MD, and resolves the surface residency time discrepancy. The 2L model, coupled with NMR relaxation experimentation, provides a simple yet powerful method of characterizing the dynamical properties of proton-bearing porous silicate-based systems such as porous glasses, cementitious materials, and oil-bearing rocks.

  17. Porous bioactive materials

    NASA Astrophysics Data System (ADS)

    Zhang, Kai

    Bioactive materials chemically bond to tissues through the development of biologically active apatite. Porous structures in biomaterials are designed to enhance bioactivity, grow artificial tissues and achieve better integration with host tissues in the body. The goal of this research is to design, fabricate and characterize novel porous bioactive materials. 3D ordered macroporous bioactive glasses (3DOM-BGs, pore size: 200--1000 nm) were prepared using a sol-gel process and colloidal crystal templates. 3DOM-BGs are more bioactive and degradable than mesoporous (pore size <50 nm) sol-gel BGs in simulated body fluid (SBF). Apatite formation and 3DOM-BG degradation rates increased with the decrease of soaking ratio. Apatite induction time in SBF increased with 3DOM-BG calcination temperature (600--800°C). Apatite formation and 3DOMBG degradation were slightly enhanced for a phosphate containing composition. Large 3DOM-BG particles formed less apatite and degraded less completely as compared with small particles. An increase in macropore size slowed down 3DOM-BG degradation and apatite formation processes. After heating the converted apatite at a temperature higher than 700°C, highly crystalline hydroxyapatite and a minor tri-calcium phosphate phase formed. 3DOM-BGs have potential applications as bone/periodontal fillers, and drugs and biological factors delivery agents. Anchoring artificial soft tissues (e.g., cartilage) to native bone presents a challenge. Porous polymer/bioactive glass composites are candidate materials for engineering artificial soft tissue/bone interfaces. Porous composites consisting of polymer matrices (e.g., polysulfone, polylactide, and polyurethane) and bioactive glass particles were prepared by polymer phase separation techniques adapted to include ceramic particles. Composites (thickness: 200--500 mum) have asymmetric structures with dense top layers and porous structures beneath. Porous structures consist of large pores (>100 mum) in a

  18. Constitutive model for geological and other porous materials under dynamic loading

    SciTech Connect

    Dey, T.N.

    1991-01-01

    An effective stress model is described for use in numerical calculations on porous materials which are partially or fully saturated with water. The flow rule chosen for the shear failure portion of the model is examined and shown to have significant influence on wave propagation results. A flow rule which produces dilatancy results in less attenuation than a rule producing shear-enhanced void collapse. The dilatancy producing rule is less prone to producing liquefaction and results in significantly higher stress levels behind the wave front. 8 refs., 6 figs.

  19. Transfer matrix modeling and experimental validation of cellular porous material with resonant inclusions.

    PubMed

    Doutres, Olivier; Atalla, Noureddine; Osman, Haisam

    2015-06-01

    Porous materials are widely used for improving sound absorption and sound transmission loss of vibrating structures. However, their efficiency is limited to medium and high frequencies of sound. A solution for improving their low frequency behavior while keeping an acceptable thickness is to embed resonant structures such as Helmholtz resonators (HRs). This work investigates the absorption and transmission acoustic performances of a cellular porous material with a two-dimensional periodic arrangement of HR inclusions. A low frequency model of a resonant periodic unit cell based on the parallel transfer matrix method is presented. The model is validated by comparison with impedance tube measurements and simulations based on both the finite element method and a homogenization based model. At the HR resonance frequency (i) the transmission loss is greatly improved and (ii) the sound absorption of the foam can be either decreased or improved depending on the HR tuning frequency and on the thickness and properties of the host foam. Finally, the diffuse field sound absorption and diffuse field sound transmission loss performance of a 2.6 m(2) resonant cellular material are measured. It is shown that the improvements observed at the Helmholtz resonant frequency on a single cell are confirmed at a larger scale. PMID:26093437

  20. SCDAP/RELAP5 Modeling of Movement of Melted Material through Porous Debris in Lower Head (Rev. 2)

    SciTech Connect

    Siefken, Larry James

    1999-10-01

    A model is described for the movement of melted metallic material through a ceramic porous debris bed. The model is designed for the analysis of severe accidents in LWRs, wherein melted core plate material may slump onto the top of a porous bed of relocated core material supported by the lower head. The permeation of the melted core plate material into the porous debris bed influences the heatup of the debris bed and the heatup of the lower head supporting the debris. A model for mass transport of melted metallic material is applied that includes terms for viscosity and turbulence but neglects inertial and capillary terms because of their small value relative to gravity and viscous terms in the momentum equation. The relative permeability and passability of the porous debris are calculated as functions of debris porosity, particle size, and effective saturation. An iterative numerical solution is used to solve the set of nonlinear equations for mass transport. The effective thermal conductivity of the debris is calculated as a function of porosity, particle size, and saturation. The model integrates the equations for mass transport with a model for the two-dimensional conduction of heat through porous debris. The integrated model has been implemented into the SCDAP/RELAP5 code for the analysis of the integrity of LWR lower heads during severe accidents. The results of the model indicate that melted core plate material my permeate in about 120 s to the bottom of a 1 m deep hot porous debris bed supported by the lower head. The presence of the relocated core plate material at the bottom of the debris bed decreases the thermal resistance of the interface between the debris bed and the lower head. This report is a revision of the report with the identifier of INEEL/EXT-98-01178 REV 1, entitled "SCDAP/RELAP5 Modeling of Movement of Melted Material Through Porous Debris in Lower Head."

  1. Macro-meso two-scale model for predicting the VOC diffusion coefficients and emission characteristics of porous building materials

    NASA Astrophysics Data System (ADS)

    Xiong, Jianyin; Zhang, Yinping; Wang, Xinke; Chang, Dongwu

    Through the observation of the pore structure and mercury intruding porosimetry (MIP) experiments of some typical porous building materials, we found that the diffusion coefficient of the material can be expressed by that of a representative elementary volume (REV) in which the pore structure can be simplified as a connection in series of macro and meso pores. Based upon that, a macro-meso two-scale model for predicting the diffusion coefficient of porous building materials is proposed. In contrast to the traditional porous mass transfer model for determining the diffusion coefficient described in the literature [Blondeau, P., Tiffonnet, A.L., Damian, A., Amiri, O., Molina, J.L., 2003. Assessment of contaminant diffusivities in building materials from porosimetry tests. Indoor Air 13, 302-310; Seo, J., Kato, S., Ataka, Y., Zhu, Q., 2005. Evaluation of effective diffusion coefficient in various building materials and absorbents by mercury intrusion porosimetry. In Proceedings of the Indoor Air, Beijing, China, pp. 1854-1859], the proposed model relates the volatile organic compound (VOC) diffusion coefficient of building material not only to the porosity of the building material, but also to the pore size distribution and pore connection modes. To verify the model, a series of experiments of VOC emissions of three types of medium-density board were conducted. The comparison of the model and experimental results shows that the proposed model agrees much better with the experimental results than the traditional models in the literature. More validation for other building materials is needed. The proposed model is useful for predicting the VOC diffusion coefficient of porous building materials and for developing low VOC emission building materials.

  2. Lattice Boltzmann modeling of permeability in porous materials with partially percolating voxels.

    PubMed

    Li, Ruru; Yang, Y Sam; Pan, Jinxiao; Pereira, Gerald G; Taylor, John A; Clennell, Ben; Zou, Caineng

    2014-09-01

    A partial-bounce-back lattice Boltzmann model has been used to simulate flow on a lattice consisting of cubic voxels with a locally varying effective percolating fraction. The effective percolating fraction of a voxel is the total response to the partial-bounce-back techniques for porous media flow due to subvoxel fine structures. The model has been verified against known analytic solutions on two- and three-dimensional regular geometries, and has been applied to simulate flow and permeabilities of two real-world rock samples. This enables quantitative determination of permeability for problems where voxels cannot be adequately segmented as discrete compositions. The voxel compositions are represented as volume fractions of various material phases and void. The numerical results have shown that, for the tight-sandstone sample, the bulk permeability is sensitive to the effective percolating fraction of calcite. That is, the subvoxel flow paths in the calcite phase are important for bulk permeability. On the other hand, flow in the calcite phase in the sandstone sample makes an insignificant contribution to the bulk permeability. The calculated permeability value for the sandstone sample is up to two orders of magnitude greater than the tight sandstone. This model is generic and could be applied to other oil and gas reservoir media or to material samples. PMID:25314558

  3. Acoustic Absorption in Porous Materials

    NASA Technical Reports Server (NTRS)

    Kuczmarski, Maria A.; Johnston, James C.

    2011-01-01

    An understanding of both the areas of materials science and acoustics is necessary to successfully develop materials for acoustic absorption applications. This paper presents the basic knowledge and approaches for determining the acoustic performance of porous materials in a manner that will help materials researchers new to this area gain the understanding and skills necessary to make meaningful contributions to this field of study. Beginning with the basics and making as few assumptions as possible, this paper reviews relevant topics in the acoustic performance of porous materials, which are often used to make acoustic bulk absorbers, moving from the physics of sound wave interactions with porous materials to measurement techniques for flow resistivity, characteristic impedance, and wavenumber.

  4. Finite element modelling approaches for well-ordered porous metallic materials for orthopaedic applications: cost effectiveness and geometrical considerations.

    PubMed

    Quevedo González, Fernando José; Nuño, Natalia

    2016-06-01

    The mechanical properties of well-ordered porous materials are related to their geometrical parameters at the mesoscale. Finite element (FE) analysis is a powerful tool to design well-ordered porous materials by analysing the mechanical behaviour. However, FE models are often computationally expensive. This article aims to develop a cost-effective FE model to simulate well-ordered porous metallic materials for orthopaedic applications. Solid and beam FE modelling approaches are compared, using finite size and infinite media models considering cubic unit cell geometry. The model is then applied to compare two unit cell geometries: cubic and diamond. Models having finite size provide similar results than the infinite media model approach for large sample sizes. In addition, these finite size models also capture the influence of the boundary conditions on the mechanical response for small sample sizes. The beam FE modelling approach showed little computational cost and similar results to the solid FE modelling approach. Diamond unit cell geometry appeared to be more suitable for orthopaedic applications than the cubic unit cell geometry. PMID:26260268

  5. Metal recovery from porous materials

    DOEpatents

    Sturcken, Edward F.

    1992-01-01

    A method for recovering plutonium and other metals from materials by leaching comprising the steps of incinerating the materials to form a porous matrix as the residue of incineration, immersing the matrix into acid in a microwave-transparent pressure vessel, sealing the pressure vessel, and applying microwaves so that the temperature and the pressure in the pressure vessel increase. The acid for recovering plutonium can be a mixture of HBF.sub.4 and HNO.sub.3 and preferably the pressure is increased to at least 100 PSI and the temperature to at least 200.degree. C. The porous material can be pulverized before immersion to further increase the leach rate.

  6. Porous media modeling and micro-structurally motivated material moduli determination via the micro-dilatation theory

    NASA Astrophysics Data System (ADS)

    Jeong, J.; Ramézani, H.; Sardini, P.; Kondo, D.; Ponson, L.; Siitari-Kauppi, M.

    2015-07-01

    In the present contribution, the porous material modeling and micro-structural material parameters determination are scrutinized via the micro-dilatation theory. The main goal is to take advantage of the micro-dilatation theory which belongs to the generalized continuum media. In the first stage, the thermodynamic laws are entirely revised to reach the energy balance relation using three variables, deformation, porosity change and its gradient underlying the porous media as described in the micro-dilatation theory or so-called void elasticity. Two experiments over cement mortar specimens are performed in order to highlight the material parameters related to the pore structure. The shrinkage due to CO2 carbonation, porosity and its gradient are calculated. The extracted values are verified via 14C-PMMA radiographic image method. The modeling of swelling phenomenon of Delayed Ettringite Formation (DEF) is studied later on. This issue is performed via the crystallization pressure application using the micro-dilatation theory.

  7. EQUATION OF STATE AND HUGONIOT LOCUS FOR POROUS MATERIALS: P-ALPHA MODEL REVISITED

    SciTech Connect

    R. MENIKOFF; ET AL

    1999-08-01

    Foams, porous solids and granular materials have a characteristic Hugoniot locus that for weak shocks is concave in the (particle velocity, shock velocity)-plane. An equation of state (EOS) that has this property can be constructed implicitly from a Helmholtz free energy of the form {Psi}{sub s}(V,T,{phi}) = {Psi}{sub s}(V,T)+B({phi}) where the equilibrium volume fraction {phi}{sub eq} is determined by minimizing {Psi}, i.e., the condition {partial_derivative}{sub {psi}} {Psi} = 0. For many cases, a Hayes EOS for the pure solid {Psi}{sub s}(V,T) is adequate. This provides a thermodynamically consistent framework for the P-{alpha} model. For this form of EOS the volume fraction has a similar effect to an endothermic reaction in that the partial Hugoniot loci with fixed {psi} are shifted to the left in the (V,P)-plane with increasing f. The equilibrium volume fraction can then be chosen to match the concavity of the principal Hugoniot locus. An example is presented for the polymer estane. A small porosity of only 1.4 percent is required to match the experimental concavity in the Hugoniot data. This type of EOS can also be used to obtain the so-called ''universal'' Hugoniot for liquids.

  8. Equation of State and Hugoniot locus for porous materials: P--α model revisited

    NASA Astrophysics Data System (ADS)

    Menikoff, Ralph; Kober, Edward

    1999-06-01

    Foams, porous solids and granular materials have a characteristic Hugoniot locus that for weak shocks is concave in the (particle velocity, shock velocity)-plane. An equation of state (EOS) that has this property can be constructed implicitly from a Helmholtz free energy of the form F(V,T,φ) = F_s(V,T) + B(φ) where the equilibrium volume fraction φ_eq is determined by minimizing F, phi.e., the condition partial_φ F = 0. For many cases, a Hayes EOS for the pure solid F_s(V,T) is adequate. This provides a thermodynamically consistent framework for the P--α model. For this form of EOS, we show that the volume fraction has a similar effect to an endothermic reaction in that the partial Hugoniot loci with fixed φ are shifted to the left in the (V,P)-plane with increasing φ. The equilibrium volume fraction can then be chosen to match the concavity of the principal Hugoniot locus. An example is presented for the polymer estane. A small porosity of only 1.4 per cent is required to match the experimental concavity in the Hugoniot data. This type of EOS can also be used to obtain the so-called ``universal'' Hugoniot for liquids.

  9. Ultrasonic Nondestructive Characterization of Porous Materials

    NASA Astrophysics Data System (ADS)

    Yang, Ningli

    2011-12-01

    Wave propagation in porous media is studied in a wide range of technological applications. In the manufacturing industry, determining porosity of materials in the manufacturing process is required for strict quality control. In the oil industry, acoustic signals and seismic surveys are used broadly to determine the physical properties of the reservoir rock which is a porous media filled with oil or gas. In porous noise control materials, a precise prediction of sound absorption with frequency and evaluation of tortuosity are necessary. Ultrasonic nondestructive methods are a very important tool for characterization of porous materials. The dissertation deals with two types of porous media: materials with relatively low and closed porosity and materials with comparatively high and open porosity. Numerical modeling, Finite Element simulations and experimental characterization are all discussed in this dissertation. First, ultrasonic scattering is used to determine the porosity in porous media with closed pores. In order get a relationship between the porosity in porous materials and ultrasonic scattering independently and to increase the sensitivity to obtain scattering information, ultrasonic imaging methods are applied and acoustic waves are focused by an acoustic lens. To verify the technique, engineered porous acrylic plates with varying porosity are measured by ultrasonic scanning and ultrasonic array sensors. Secondly, a laser based ultrasonic technique is explored for predicting the mechanical integrity and durability of cementitious materials. The technique used involves the measurement of the phase velocity of fast and slow longitudinal waves in water saturated cement paste. The slow wave velocity is related to the specimen's tortuosity. The fast wave speed is dependent on the elastic properties of porous solid. Experimental results detailing the generation and detection of fast and slow wave waves in freshly prepared and aged water-saturated cement samples

  10. Metal recovery from porous materials

    DOEpatents

    Sturcken, E.F.

    1991-01-01

    The present invention relates to recovery of metals. More specifically, the present invention relates to the recovery of plutonium and other metals from porous materials using microwaves. The United States Government has rights in this invention pursuant to Contract No. DE-AC09-89SR18035 between the US Department of Energy and Westinghouse Savannah River Company.

  11. Porous heat-insulation material

    SciTech Connect

    Chentemirov, M.G.; Dyachkovsky, F.S.; Enikolopov, N.S.; Gavrilov, J.A.; Gorbachev, J.G.; Kudinova, O.I.; Lukienko, E.P.; Maklakova, T.A.; Novokshonova, L.A.; Parsamian, L.O.; Poluyanov, A.F.

    1980-12-23

    A porous heat-insulation material comprising blocks molded from granules of a porous mineral filler with a polyolefin coating is described. The coating thickness is 1/1000 to 1/25 of the average granule diameter; in contact regions, said granules are spaced from each other at a distance of from 0.5 to 2.0 of the coating thickness, and the mass ratio between said porous mineral filler and said polyolefin is 80-98:20-2, respectively. The material of this invention has a volume mass of from 60 to 250 kg/m/sup 3/. The material features a high plasticity (its flexural strength is as high as 3-4 kgf/cm/sup 2/). The compression strength of the material is 9-1 kgf/cm/sup 2/. The material also has a low thermal conductivity; its thermal conductivity coefficient is 0.03-0.04 kcal/M/h//sup 0/C. The material is substantially non-combustible.

  12. Metal recovery from porous materials

    DOEpatents

    Sturcken, E.F.

    1992-10-13

    A method is described for recovering plutonium and other metals from materials by leaching comprising the steps of incinerating the materials to form a porous matrix as the residue of incineration, immersing the matrix into acid in a microwave-transparent pressure vessel, sealing the pressure vessel, and applying microwaves so that the temperature and the pressure in the pressure vessel increase. The acid for recovering plutonium can be a mixture of HBF[sub 4] and HNO[sub 3] and preferably the pressure is increased to at least 100 PSI and the temperature to at least 200 C. The porous material can be pulverized before immersion to further increase the leach rate.

  13. Lower-bound and Upper-bound Rigid-plastic Constitutive Models for Porous Materials:Comparison and Examination

    NASA Astrophysics Data System (ADS)

    Yin, Yajun; Xue, Mingde; Yu, Shouwen

    A lower bound rigid plastic constitutive model for porous materials has been published recently, but its reliability and accuracy is still kept unknown. Therefore, this paper is confined to examine this model by comparing it with other ones such as the upper bound one and experimental-based one. Under three loading states (i.e. uniaxial stress condition, biaxial equal stress condition and uniaxial strain condition), the sintered copper’s ductility, compressibility, strength property, deformation characteristics, stress˜strain curves and damage evolution process predicted by these models are systematically compared. The advantage of the lower bound model in describing the yield property and its limitations in evaluating the ductility, compressibility, strength variation and damage evolution process of porous materials are clarified. Systematical analysis reveals that these limitations may be attributed to the short of void interaction mechanism in the lower bound model. This discovery lays the foundation for further improvement and modification of the lower bound model in the future research.

  14. Theoretical Equations of State for Porous/Granular Materials

    NASA Astrophysics Data System (ADS)

    Boettger, Jonathan

    2013-06-01

    Although the equation of state (EOS) for a porous/granular material is identical to the EOS for the equivalent non-porous material, the requirement that the EOS must provide a realistic model of the material in its porous/granular state adds additional challenges for EOS modelers. These difficulties can be divided into two broad categories. First, dynamic processes often drive porous/granular materials through regions of thermodynamic phase space that are poorly described by standard wide-ranging tabular EOS. Second, for materials that are only available in a granular form, it can be difficult to accurately measure the material properties/parameters that are routinely used to constrain a theoretical EOS. This talk will attempt to describe in some detail the many challenges posed to EOS modelers by porous/granular materials. Work supported by the U.S. Dept. of Energy under contract DE-AC52-06NA25396.

  15. Uniaxial deformation of a soft porous material

    NASA Astrophysics Data System (ADS)

    MacMinn, Chris; Dufresne, Eric; Wettlaufer, John

    2015-11-01

    Compressing a porous material will decrease the volume of pore space, driving fluid out. Similarly, injecting fluid into a porous material will drive mechanical deformation, distorting the solid skeleton. This poromechanical coupling has applications ranging from cell and tissue mechanics to geomechanics and hydrogeology. The classical theory of linear poroelasticity captures this coupling by combining Darcy's law with linear elasticity and then further linearizing in the strain. This is a good model for very small deformations, but it becomes increasingly inappropriate as deformations grow larger, and moderate to large deformations are common in the context of phenomena such as swelling, damage, and extreme softness. Here, we compare the predictions of linear poroelasticity with those of a rigorous large-deformation framework in the context of two uniaxial model problems. We explore the error associated with the linear model in both steady and dynamic situations, as well as the impact of allowing the permeability to vary with the deformation.

  16. Lattice simulation method to model diffusion and NMR spectra in porous materials.

    PubMed

    Merlet, Céline; Forse, Alexander C; Griffin, John M; Frenkel, Daan; Grey, Clare P

    2015-03-01

    A coarse-grained simulation method to predict nuclear magnetic resonance (NMR) spectra of ions diffusing in porous carbons is proposed. The coarse-grained model uses input from molecular dynamics simulations such as the free-energy profile for ionic adsorption, and density-functional theory calculations are used to predict the NMR chemical shift of the diffusing ions. The approach is used to compute NMR spectra of ions in slit pores with pore widths ranging from 2 to 10 nm. As diffusion inside pores is fast, the NMR spectrum of an ion trapped in a single mesopore will be a sharp peak with a pore size dependent chemical shift. To account for the experimentally observed NMR line shapes, our simulations must model the relatively slow exchange between different pores. We show that the computed NMR line shapes depend on both the pore size distribution and the spatial arrangement of the pores. The technique presented in this work provides a tool to extract information about the spatial distribution of pore sizes from NMR spectra. Such information is difficult to obtain from other characterisation techniques. PMID:25747093

  17. Tensile instabilities for porous plasticity models

    SciTech Connect

    BRANNON,REBECCA M.

    2000-02-29

    Several concepts (and assumptions) from the literature for porous metals and ceramics have been synthesized into a consistent model that predicts an admissibility limit on a material's porous yield surface. To ensure positive plastic work, the rate at which a yield surface can collapse as pores grow in tension must be constrained.

  18. Contaminant tailing in highly heterogeneous porous formations: Sensitivity on model selection and material properties

    NASA Astrophysics Data System (ADS)

    Maghrebi, Mahdi; Jankovic, Igor; Weissmann, Gary S.; Matott, L. Shawn; Allen-King, Richelle M.; Rabideau, Alan J.

    2015-12-01

    Coupled impacts of slow advection, diffusion and sorption were investigated using two heterogeneity models that differ in structure and in the mathematical framework that was used to simulate flow and transport and to quantify contaminant tailing. Both models were built using data from a highly heterogeneous exposure of the Borden Aquifer at a site located 2 km north-west of the Stanford-Waterloo experimental site at Canadian Forces Base Borden, Ontario, Canada. The inclusions-based model used a simplified representation of the different materials found at the site, while the second model was based on transitional probability geostatistics of the formation. These two models were used to investigate sensitivity of contaminant tailing on model selection and on geometric and material properties. While simulations were based on data collected at Borden, models were exercised beyond the geometric and material properties that characterize the site. Various realizations have identified very low conductive silty clay, found at volume fraction of 23.4%, as the material with dominant influence on tailing, and vertical diffusion in and out of low conductive units, affected by sorption, as the dominant transport mechanism causing tailing. The two models yielded almost identical transport results when vertical correlation lengths of silty clay were matched. Several practical implications relevant for characterization of low conductive units were identified and briefly discussed.

  19. SPUTTERING FROM A POROUS MATERIAL BY PENETRATING IONS

    SciTech Connect

    Rodriguez-Nieva, J. F.; Bringa, E. M.; Cassidy, T. A.; Caro, A.; Loeffler, M. J.; Farkas, D.

    2011-12-10

    Porous materials are ubiquitous in the universe and weathering of porous surfaces plays an important role in the evolution of planetary and interstellar materials. Sputtering of porous solids in particular can influence atmosphere formation, surface reflectivity, and the production of the ambient gas around materials in space. Several previous studies and models have shown a large reduction in the sputtering of a porous solid compared to the sputtering of the non-porous solid. Using molecular dynamics simulations we study the sputtering of a nanoporous solid with 55% of the solid density. We calculate the electronic sputtering induced by a fast, penetrating ion, using a thermal spike representation of the deposited energy. We find that sputtering for this porous solid is, surprisingly, the same as that for a full-density solid, even though the sticking coefficient is high.

  20. Sputtering from a Porous Material by Penetrating Ions

    NASA Technical Reports Server (NTRS)

    Rodriguez-Nieva, J. F.; Bringa, E. M.; Cassidy, T. A.; Johnson, R. E.; Caro, A.; Fama, M.; Loeffler, M.; Baragiola, R. A.; Farkas, D.

    2012-01-01

    Porous materials are ubiquitous in the universe and weathering of porous surfaces plays an important role in the evolution of planetary and interstellar materials. Sputtering of porous solids in particular can influence atmosphere formation, surface reflectivity, and the production of the ambient gas around materials in space, Several previous studies and models have shown a large reduction in the sputtering of a porous solid compared to the sputtering of the non-porous solid. Using molecular dynamics simulations we study the sputtering of a nanoporous solid with 55% of the solid density. We calculate the electronic sputtering induced by a fast, penetrating ion, using a thermal spike representation of the deposited energy. We find that sputtering for this porous solid is, surprisingly, the same as that for a full-density solid, even though the sticking coefficient is high.

  1. Microwave impregnation of porous materials with thermal energy storage materials

    DOEpatents

    Benson, D.K.; Burrows, R.W.

    1993-04-13

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  2. Microwave impregnation of porous materials with thermal energy storage materials

    DOEpatents

    Benson, David K.; Burrows, Richard W.

    1993-01-01

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  3. Microwave impregnation of porous materials with thermal energy storage materials

    SciTech Connect

    Benson, D.K.; Burrows, R.W.

    1992-12-31

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  4. Thermal evolution and sintering of chondritic planetesimals. III. Modelling the heat conductivity of porous chondrite material

    NASA Astrophysics Data System (ADS)

    Henke, Stephan; Gail, Hans-Peter; Trieloff, Mario

    2016-04-01

    Context. The construction of models for the internal constitution and temporal evolution of large planetesimals, which are the parent bodies of chondrites, requires as accurate as possible information on the heat conductivity of the complex mixture of minerals and iron metal found in chondrites. The few empirical data points on the heat conductivity of chondritic material are severely disturbed by impact-induced microcracks modifying the thermal conductivity. Aims: We attempt to evaluate the heat conductivity of chondritic material with theoretical methods. Methods: We derived the average heat conductivity of a multi-component mineral mixture and granular medium from the heat conductivities of its mixture components. We numerically generated random mixtures of solids with chondritic composition and packings of spheres. We solved the heat conduction equation in high spatial resolution for a test cube filled with such matter. We derived the heat conductivity of the mixture from the calculated heat flux through the cube. Results: For H and L chondrites, our results are in accord with empirical thermal conductivity at zero porosity. However, the porosity dependence of heat conductivity of granular material built from chondrules and matrix is at odds with measurements for chondrites, while our calculations are consistent with data for compacted sandstone. The discrepancy is traced back to subsequent shock modification of the currently available meteoritic material resulting from impacts on the parent body over the last 4.5 Ga. This causes a structure of void space made of fractures/cracks, which lowers the thermal conductivity of the medium and acts as a barrier to heat transfer. This structure is different from the structure that probably exists in the pristine material where voids are represented by pores rather than fractures. The results obtained for the heat conductivity of the pristine material are used for calculating models for the evolution of the H chondrite

  5. Thermal evolution and sintering of chondritic planetesimals. III. Modelling the heat conductivity of porous chondrite material

    NASA Astrophysics Data System (ADS)

    Henke, Stephan; Gail, Hans-Peter; Trieloff, Mario

    2016-05-01

    Context. The construction of models for the internal constitution and temporal evolution of large planetesimals, which are the parent bodies of chondrites, requires as accurate as possible information on the heat conductivity of the complex mixture of minerals and iron metal found in chondrites. The few empirical data points on the heat conductivity of chondritic material are severely disturbed by impact-induced microcracks modifying the thermal conductivity. Aims: We attempt to evaluate the heat conductivity of chondritic material with theoretical methods. Methods: We derived the average heat conductivity of a multi-component mineral mixture and granular medium from the heat conductivities of its mixture components. We numerically generated random mixtures of solids with chondritic composition and packings of spheres. We solved the heat conduction equation in high spatial resolution for a test cube filled with such matter. We derived the heat conductivity of the mixture from the calculated heat flux through the cube. Results: For H and L chondrites, our results are in accord with empirical thermal conductivity at zero porosity. However, the porosity dependence of heat conductivity of granular material built from chondrules and matrix is at odds with measurements for chondrites, while our calculations are consistent with data for compacted sandstone. The discrepancy is traced back to subsequent shock modification of the currently available meteoritic material resulting from impacts on the parent body over the last 4.5 Ga. This causes a structure of void space made of fractures/cracks, which lowers the thermal conductivity of the medium and acts as a barrier to heat transfer. This structure is different from the structure that probably exists in the pristine material where voids are represented by pores rather than fractures. The results obtained for the heat conductivity of the pristine material are used for calculating models for the evolution of the H chondrite

  6. Interface shear strength and fracture behaviour of porous glass-fibre-reinforced composite implant and bone model material.

    PubMed

    Nganga, Sara; Ylä-Soininmäki, Anne; Lassila, Lippo V J; Vallittu, Pekka K

    2011-11-01

    Glass-fibre-reinforced composites (FRCs) are under current investigation to serve as durable bone substitute materials in load-bearing orthopaedic implants and bone implants in the head and neck area. The present form of biocompatible FRCs consist of non-woven E-glass-fibre tissues impregnated with varying amounts of a non-resorbable photopolymerisable bifunctional polymer resin with equal portions of both bis-phenyl-A-glycidyl dimethacrylate (BisGMA) and triethyleneglycol dimethacrylate (TEGDMA). FRCs with a total porosity of 10-70 vol% were prepared, more than 90 vol% of which being functional (open pores), and the rest closed. The pore sizes were greater than 100 μm. In the present study, the push-out test was chosen to analyse the shear strength of the interface between mechanically interlocked gypsum and a porous FRC implant structure. Gypsum was used as a substitute material for natural bone. The simulative in vitro experiments revealed a significant rise of push-out forces to the twofold level of 1147 ± 271 N for an increase in total FRC porosity of 43%. Pins, intended to model the initial mechanical implant fixation, did not affect the measured shear strength of the gypsum-FRC interface, but led to slightly more cohesive fracture modes. Fractures always occurred inside the gypsum, it having lower compressive strength than the porous FRC structures. Therefore, the largest loads were restricted by the brittleness of the gypsum. Increases of the FRC implant porosity tended to lead to more cohesive fracture modes and higher interfacial fracture toughness. Statistical differences were confirmed using the Kruskal-Wallis test. The differences between the modelled configuration showing gypsum penetration into all open pores and the real clinical situation with gradual bone ingrowth has to be considered. PMID:22098879

  7. Intrinsic flexibility of porous materials; theory, modelling and the flexibility window of the EMT zeolite framework

    PubMed Central

    Fletcher, Rachel E.; Wells, Stephen A.; Leung, Ka Ming; Edwards, Peter P.; Sartbaeva, Asel

    2015-01-01

    Framework materials have structures containing strongly bonded polyhedral groups of atoms connected through their vertices. Typically the energy cost for variations of the inter-polyhedral geometry is much less than the cost of distortions of the polyhedra themselves – as in the case of silicates, where the geometry of the SiO4 tetrahedral group is much more strongly constrained than the Si—O—Si bridging angle. As a result, framework materials frequently display intrinsic flexibility, and their dynamic and static properties are strongly influenced by low-energy collective motions of the polyhedra. Insight into these motions can be obtained in reciprocal space through the ‘rigid unit mode’ (RUM) model, and in real-space through template-based geometric simulations. We briefly review the framework flexibility phenomena in energy-relevant materials, including ionic conductors, perovskites and zeolites. In particular we examine the ‘flexibility window’ phenomenon in zeolites and present novel results on the flexibility window of the EMT framework, which shed light on the role of structure-directing agents. Our key finding is that the crown ether, despite its steric bulk, does not limit the geometric flexibility of the framework. PMID:26634720

  8. Methane storage in advanced porous materials.

    PubMed

    Makal, Trevor A; Li, Jian-Rong; Lu, Weigang; Zhou, Hong-Cai

    2012-12-01

    The need for alternative fuels is greater now than ever before. With considerable sources available and low pollution factor, methane is a natural choice as petroleum replacement in cars and other mobile applications. However, efficient storage methods are still lacking to implement the application of methane in the automotive industry. Advanced porous materials, metal-organic frameworks and porous organic polymers, have received considerable attention in sorptive storage applications owing to their exceptionally high surface areas and chemically-tunable structures. In this critical review we provide an overview of the current status of the application of these two types of advanced porous materials in the storage of methane. Examples of materials exhibiting high methane storage capacities are analyzed and methods for increasing the applicability of these advanced porous materials in methane storage technologies described. PMID:22990753

  9. A modal-based reduction method for sound absorbing porous materials in poro-acoustic finite element models.

    PubMed

    Rumpler, Romain; Deü, Jean-François; Göransson, Peter

    2012-11-01

    Structural-acoustic finite element models including three-dimensional (3D) modeling of porous media are generally computationally costly. While being the most commonly used predictive tool in the context of noise reduction applications, efficient solution strategies are required. In this work, an original modal reduction technique, involving real-valued modes computed from a classical eigenvalue solver is proposed to reduce the size of the problem associated with the porous media. In the form presented in this contribution, the method is suited for homogeneous porous layers. It is validated on a 1D poro-acoustic academic problem and tested for its performance on a 3D application, using a subdomain decomposition strategy. The performance of the proposed method is estimated in terms of degrees of freedom downsizing, computational time enhancement, as well as matrix sparsity of the reduced system. PMID:23145601

  10. Large Deformations of a Soft Porous Material

    NASA Astrophysics Data System (ADS)

    MacMinn, Christopher W.; Dufresne, Eric R.; Wettlaufer, John S.

    2016-04-01

    Compressing a porous material will decrease the volume of the pore space, driving fluid out. Similarly, injecting fluid into a porous material can expand the pore space, distorting the solid skeleton. This poromechanical coupling has applications ranging from cell and tissue mechanics to geomechanics and hydrogeology. The classical theory of linear poroelasticity captures this coupling by combining Darcy's law with Terzaghi's effective stress and linear elasticity in a linearized kinematic framework. Linear poroelasticity is a good model for very small deformations, but it becomes increasingly inappropriate for moderate to large deformations, which are common in the context of phenomena such as swelling and damage, and for soft materials such as gels and tissues. The well-known theory of large-deformation poroelasticity combines Darcy's law with Terzaghi's effective stress and nonlinear elasticity in a rigorous kinematic framework. This theory has been used extensively in biomechanics to model large elastic deformations in soft tissues and in geomechanics to model large elastoplastic deformations in soils. Here, we first provide an overview and discussion of this theory with an emphasis on the physics of poromechanical coupling. We present the large-deformation theory in an Eulerian framework to minimize the mathematical complexity, and we show how this nonlinear theory simplifies to linear poroelasticity under the assumption of small strain. We then compare the predictions of linear poroelasticity with those of large-deformation poroelasticity in the context of two uniaxial model problems: fluid outflow driven by an applied mechanical load (the consolidation problem) and compression driven by a steady fluid throughflow. We explore the steady and dynamical errors associated with the linear model in both situations, as well as the impact of introducing a deformation-dependent permeability. We show that the error in linear poroelasticity is due primarily to kinematic

  11. Light scattering in porous materials: Geometrical optics and stereological approach

    NASA Astrophysics Data System (ADS)

    Malinka, Aleksey V.

    2014-07-01

    Porous material has been considered from the point of view of stereology (geometrical statistics), as a two-phase random mixture of solid material and air. Considered are the materials having the refractive index with the real part that differs notably from unit and the imaginary part much less than unit. Light scattering in such materials has been described using geometrical optics. These two - the geometrical optics laws and the stereological approach - allow one to obtain the inherent optical properties of such a porous material, which are basic in the radiative transfer theory: the photon survival probability, the scattering phase function, and the polarization properties (Mueller matrix). In this work these characteristics are expressed through the refractive index of the material and the random chord length distribution. The obtained results are compared with the traditional approach, modeling the porous material as a pack of particles of different shapes.

  12. Determination of connectivity in porous materials.

    PubMed

    Caccianotti, L; Lucchelli, E; Ramello, S; Spanò, G

    2012-12-01

    A method of practical use was set up to determine the connectivity in a porous material, modelling the physical system as a lattice, whose coordination number is assumed to be an index of connectivity itself. This task was approached through the theory of percolation and input data were provided by two different experimental techniques, that is, adsorption/desorption of nitrogen and mercury porosimetry. The overall procedure is based on the calculation of probability f(P) of occupation of the porous channels and of probability F(P) of percolation. In the framework of the above--mentioned lattice model, the average coordination number Z is calculated through the best fitting of a universal curve to the values found for F(P) and f(P), adopting as fitting parameter the ratio L between the characteristic linear dimension of the whole lattice and the characteristic linear dimension of each of its cells. The procedure described was implemented through a numerical code and applied to three commercial alumina. A simple empirical relationship was found between Z and the percolation threshold, showing an excellent coefficient of statistical correlation. The three products proved different in connectivity, allowing subtle distinctions from each other, despite their hysteresis cycles in the adsorption/desorption process appeared quite similar from a qualitative standpoint. PMID:23447967

  13. Porous polymeric materials for hydrogen storage

    DOEpatents

    Yu, Luping; Liu, Di-Jia; Yuan, Shengwen; Yang, Junbing

    2013-04-02

    A porous polymer, poly-9,9'-spirobifluorene and its derivatives for storage of H.sub.2 are prepared through a chemical synthesis method. The porous polymers have high specific surface area and narrow pore size distribution. Hydrogen uptake measurements conducted for these polymers determined a higher hydrogen storage capacity at the ambient temperature over that of the benchmark materials. The method of preparing such polymers, includes oxidatively activating solids by CO.sub.2/steam oxidation and supercritical water treatment.

  14. Modelling parallel assemblies of porous materials using the equivalent circuit method.

    PubMed

    Pieren, Reto; Heutschi, Kurt

    2015-02-01

    Recently, the accuracy of the parallel transfer matrix method (P-TMM) and the admittance sum method (ASM) in the prediction of the absorption properties of parallel assemblies of materials was investigated [Verdière, Panneton, Elkoun, Dupont, and Leclaire, J. Acoust. Soc. Am. 136, EL90-EL95 (2014)]. It was demonstrated that P-TMM is more versatile than ASM, as a larger variety of different backing configurations can be handled. Here it will be shown that the same universality is offered by the equivalent circuit method. PMID:25698040

  15. Biomass Growth and Clogging in Porous Media: From Microscale and Mesoscale Observations in Silicon Pore Imaging Elements to the Modeling of Aggregates in Network Models Using Material Mechanics

    NASA Astrophysics Data System (ADS)

    Dupin, H. J.; Mccarty, P. L.; Kitanidis, P. K.

    2002-05-01

    An apparatus for non-destructive continuous visualization of biological growth and clogging in porous media has been constructed. Silicon Pore Imaging Elements (micromodels featuring two-dimensional pore networks) were seeded with mixed cultures. A feed solution was then continuously forced through the SPIEs. Subsequently, several forms of biomass developped simultaneously: aggregates, biofilms and filaments ressembling mycellia. Clogging appeared mostly related to the presence of aggregates along preferential flow paths. Due to clogging, mesocale flow paths were modified, and flow was reversed in channels. A novel numerical model was then developped to investigate bioclogging of two-dimensional pore networks by aggregates. Each pore (channel) is seeded with initial biomass that consumes an electron donor and an electron acceptor according to dual Monod kinetics. Biomass is modeled as a continuous uniform isotropic hyperelastic material, whose expansion and deformation are governed by material mechanics stress-strain relations, unlike traditional approaches that use ad hoc empirical schemes. The Stokes flow, the advection-diffusion- reaction mass transport, and the biomass deformation partial differential equations are solved using finite elements. Simple networks are investigated to identify phenomena of interest: four channels of different width operating in parallel to study the effect of local heterogeneity; a periodic network to quantify the effects of distance from the injection point on clogging and substrate utilization; and square lattice 5 x 5 random width networks. Although square-lattice random-width networks are deemed better approximations of porous media, the simpler networks exhibit all the phenomena of interest, with the added advantage of these phenomena being decoupled. Results of numerical simulations for different network types under various boundary conditions show that aggregates have a far greater potential than biofilms to clog a porous

  16. Porous polymeric materials for hydrogen storage

    DOEpatents

    Yu, Luping; Liu, Di-Jia; Yuan, Shengwen; Yang, Junbing

    2011-12-13

    Porous polymers, tribenzohexazatriphenylene, poly-9,9'-spirobifluorene, poly-tetraphenyl methane and their derivatives for storage of H.sub.2 prepared through a chemical synthesis method. The porous polymers have high specific surface area and narrow pore size distribution. Hydrogen uptake measurements conducted for these polymers determined a higher hydrogen storage capacity at the ambient temperature over that of the benchmark materials. The method of preparing such polymers, includes oxidatively activating solids by CO.sub.2/steam oxidation and supercritical water treatment.

  17. Superhydrophobicity on nanostructured porous hydrophilic material

    NASA Astrophysics Data System (ADS)

    Jiang, Hong-Ren; Chan, Deng-Chi

    2016-04-01

    By applying laser oxidation, ablation, and plasma treatment to modify a surface of polydimethylsiloxane, we show that creating hydrophobic sites on an originally superhydrophilic nanostructured porous surface greatly changes the wetting properties of the surface. The modified surface may even become superhydrophobic while the ratio of added hydrophobic site to the surface is relatively low. The relation between the contact angles and the effect of hydrophobic sites is further tested in blade scraping method and a similar result is also obtained. This method to achieve superhydrophobicity on the hydrophilic nanostructured porous material may open possibilities for achieving superhydrophobicity and enable functional superhydrophobic surfaces with heterogeneous components.

  18. Porous graphene materials for water remediation.

    PubMed

    Niu, Zhiqiang; Liu, Lili; Zhang, Li; Chen, Xiaodong

    2014-09-10

    Water remediation has been a critical issue over the past decades due to the expansion of wastewater discharge to the environment. Currently, a variety of functional materials have been successfully prepared for water remediation applications. Among them, graphene is an attractive candidate due to its high specific surface area, tunable surface behavior, and high strength. This Concept paper summarizes the design strategy of porous graphene materials and their applications in water remediation, such as the cleanup of oil, removal of heavy metal ions, and elimination of water soluble organic contaminants. The progress made so far will guide further development in structure design strategy of porous materials based on graphene and exploration of such materials in environmental remediation. PMID:24619776

  19. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2002-01-01

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  20. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2003-12-23

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  1. Filter casting nanoscale porous materials

    DOEpatents

    Hayes, Joel Ryan; Nyce, Gregory Walker; Kuntz, Joshua David

    2012-07-24

    A method of producing nanoporous material includes the steps of providing a liquid, providing nanoparticles, producing a slurry of the liquid and the nanoparticles, removing the liquid from the slurry, and producing a monolith.

  2. Filter casting nanoscale porous materials

    DOEpatents

    Hayes, Joel Ryan; Nyce, Gregory Walker; Kuntz, Jushua David

    2013-12-10

    A method of producing nanoporous material includes the steps of providing a liquid, providing nanoparticles, producing a slurry of the liquid and the nanoparticles, removing the liquid from the slurry, and producing monolith.

  3. Adhesion of liquids to porous materials and fibers

    NASA Astrophysics Data System (ADS)

    Trofimov, Artem

    This research is centered on the analysis of adhesion properties of porous materials and fibers of elliptical shapes. Composites are a unique class of materials having properties, which could not be achieved by either of the constituent materials alone. Composites with porous filler are put into service in buildings, roads, bridges, etc. Fiber-reinforced composites are actively involved in flight vehicles, automobiles, boats, and dozens of other products. In the first part of this study we developed a procedure for evaluation of adhesion of liquids to porous solids, where water, hexadecane and asphalt binder and different rocks were studied to illustrate the methodology. An experimental protocol to evaluate the work of adhesion, a characteristic thermodynamic parameter of the liquid/porous solid pair, was discussed and a mathematical model describing the kinetics of liquid penetration into inhomogeneous porous material was developed and used for interpretation of the experiments. The second part is devoted to the analysis of interactions of liquids with circular and elliptical wires. The behavior of menisci embracing the fiber in the capillary rise experiment was investigated. In particular, we study the profiles of the contact line around cylinders, contact angle, and the work of adhesion of a set of different liquids. Compared to the circular wires, elliptical wires produced taller menisci, hence the wetted area increases. It is expected that the kinetics of resin impregnation into a preforms made of elliptical fibers will significantly change.

  4. Activation of porous MOF materials

    DOEpatents

    Hupp, Joseph T; Farha, Omar K

    2014-04-01

    A method for the treatment of solvent-containing MOF material to increase its internal surface area involves introducing a liquid into the MOF in which liquid the solvent is miscible, subjecting the MOF to supercritical conditions for a time to form supercritical fluid, and releasing the supercritical conditions to remove the supercritcal fluid from the MOF. Prior to introducing the liquid into the MOF, occluded reaction solvent, such as DEF or DMF, in the MOF can be exchanged for the miscible solvent.

  5. Activation of porous MOF materials

    DOEpatents

    Hupp, Joseph T; Farha, Omar K

    2013-04-23

    A method for the treatment of solvent-containing MOF material to increase its internal surface area involves introducing a liquid into the MOF in which liquid the solvent is miscible, subjecting the MOF to supercritical conditions for a time to form supercritical fluid, and releasing the supercritical conditions to remove the supercritical fluid from the MOF. Prior to introducing the liquid into the MOF, occluded reaction solvent, such as DEF or DMF, in the MOF can be exchanged for the miscible solvent.

  6. Dynamic magnetic compaction of porous materials

    SciTech Connect

    1998-10-29

    IAP Research began development of the Dynamic Magnetic Compaction (DMC) process three years before the CRADA was established. IAP Research had experimentally demonstrated the feasibility of the process, and conducted a basic market survey. IAP identified and opened discussions with industrial partners and established the basic commercial cost structure. The purpose of this CRADA project was to predict and verify optimum pressure vs. time history for the compaction of porous copper and tungsten. LLNL modeled the rapid compaction of powdered material from an initial density of about 30% theoretical maximum to more than 90% theoretical maximum. The compaction simulations were benchmarked against existing data and new data was acquired by IAP Research. The modeling was used to perform parameter studies on the pressure loading time history, initial porosity and temperature. LLNL ran simulations using codes CALE or NITO and compared the simulations with published compaction data and equation of state (EOS) data. This project did not involve the development or modification of software code. CALE and NITO were existing software programs at LLNL. No modification of these programs occurred within the scope of the CRADA effort.

  7. (Fracture mechanics of porous materials)

    SciTech Connect

    Gray, L.J.

    1989-09-15

    The primary subject of this trip was the development of a boundary element/finite element analysis system for computational fracture mechanics. The procedures for merging the ORNL/Cornell University boundary element fracture code with the finite element program SESAM were agreed upon, and are currently being implemented. The adopted algorithm relies on the superelement capabilities of the SESAM code. Discussions were held with scientists at the Bergen Scientific Centre on the modeling of fractured rock. A project to develop realistic computer models of naturally occurring fracture patterns is being carried out by a geologist and a physicist; it is expected that these models can be employed in future environmental modeling work. 6 refs.

  8. Deformation Timescales of Porous Volcanic Materials

    NASA Astrophysics Data System (ADS)

    Quane, S.; Friedlander, B.; Robert, G.; Lynn, H.

    2007-12-01

    We describe results from 20 high-temperature, constant strain rate and constant load deformation experiments on natural pyroclastic materials. Experiments were run unconfined and under variable H2O confining pressures at temperatures between 650 and 900 C. Starting materials comprised 4.3 cm diameter, 6 cm length cores of sintered Rattlesnake Tuff rhyolite ash with starting porosities of 70 percent. Experimental displacement was controlled to achieve total strain values between 10 and 90 percent. In thin section, the deformed experimental end products exhibit striking similarities to all facies of natural welded pyroclastic rocks including variably flattened pumice fiamme and systematically deformed bubble wall shards. To quantify the amount of strain accumulation, we placed three manually rounded 1 cm diameter pumice lapilli at different heights in each experimental product. Axial ratios (x-axis dimension/y-axis dimension) of the deformed lapilli (fiamme) show a systematic increase with increased deformation. To further quantify strain, we measured flattening ratios of originally spherical bubble wall shards. These analyses are compared to similar measurements on natural samples to evaluate current methods of quantifying deformation in welded pyroclastic facies. Stress-strain and strain-time experimental results indicate that the glassy, porous aggregates have a strain- dependent rheology; the effective viscosity of the mixture increases non-linearly with decreasing porosity. Temperature, rather than stress is the dominant factor controlling the rheology of these materials. Results also indicate that the presence of moderate H2O pressure allows for viscous deformation (e.g., welding) to occur at significantly lower temperatures than in anhydrous conditions. Results from these experiments are used to develop a constitutive relationship in which the effective viscosity of the experimental cores is predicted using melt viscosity, sample porosity and an empirically

  9. Characterizing He II flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1991-01-01

    An empirical extension of the two-fluid model is used to characterize He II flow through porous materials. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He II flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about +/- 20 percent.

  10. Porous material for protection from electromagnetic radiation

    SciTech Connect

    Kazmina, Olga E-mail: bdushkina89@mail.ru; Dushkina, Maria E-mail: bdushkina89@mail.ru; Suslyaev, Valentin; Semukhin, Boris

    2014-11-14

    It is shown that the porous glass crystalline material obtained by a low temperature technology can be used not only for thermal insulation, but also for lining of rooms as protective screens decreasing harmful effect of electromagnetic radiation as well as to establish acoustic chambers and rooms with a low level of electromagnetic background. The material interacts with electromagnetic radiation by the most effective way in a high frequency field (above 100 GHz). At the frequency of 260 GHz the value of the transmission coefficient decreases approximately in a factor times in comparison with foam glass.

  11. Analysis of acoustic damping in duct terminated by porous absorption materials based on analytical models and finite element simulations

    NASA Astrophysics Data System (ADS)

    Guan Qiming

    Acoustic absorption materials are widely used today to dampen and attenuate the noises which exist almost everywhere and have adverse impact upon daily life of human beings. In order to evaluate the absorption performance of such materials, it is necessary to experimentally determine acoustic properties of absorption materials. Two experimental methods, one is Standing Wave Ratio Method and the other is Transfer-Function Method, which also totally called as Impedance Tube Method, are based on two analytical models people have used to evaluate and validate the data obtained from acoustic impedance analyzers. This thesis first reviews the existing analytical models of previous two experimental methods in the literature by looking at their analytical models, respectively. Then a new analytical model is developed is developed based on One-Microphone Method and Three-Microphone Method, which are two novel experimental approaches. Comparisons are made among these analytical models, and their advantages and disadvantages are discussed.

  12. Acoustical properties of highly porous fibrous materials

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1979-01-01

    Highly porous, fibrous bulk sound absorbing materials are studied with a view toward understanding their acoustical properties and performance in a wide variety of applications including liners of flow ducts. The basis and criteria for decoupling of acoustic waves in the pores of the frame and compressional waves in the frame structure are established. The equations of motion are recast in a form that elucidates the coupling mechanisms. The normal incidence surface impedance and absorption coefficient of two types of Kevlar 29 and an open celled foam material are studied. Experimental values and theoretical results are brought into agreement when the structure factor is selected to provide a fit to the experimental data. A parametric procedure for achieving that fit is established. Both a bulk material quality factor and a high frequency impedance level are required to characterize the real and imaginary part of the surface impedance and absorption coefficient. A derivation of the concepts of equivalent density and dynamic resistance is presented.

  13. Wire Cloth as Porous Material for Transpiration-cooled Walls

    NASA Technical Reports Server (NTRS)

    Eckert, E R G; Kinsler, Martin R; Cochran, Reeves B

    1951-01-01

    The permeability characteristics and tensile strength of a porous material developed from stainless-steel corduroy wire cloth for use in transpiration-cooled walls where the primary stresses are in one direction were investigated. The results of this investigation are presented and compared with similar results obtained with porous sintered metal compacts. A much wider range of permeabilities is obtainable with the wire cloth than with the porous metal compacts considered and the ultimate tensile strength in the direction of the primary stresses for porous materials produced from three mesh sizes of wire cloth are from two to three times the ultimate tensile strengths of the porous metal compacts.

  14. Structure and Thermal Properties of Porous Geological Materials

    NASA Astrophysics Data System (ADS)

    Kirk, Simon; Williamson, David

    2011-06-01

    Understanding the behaviour of porous geological materials is important for developing models of the explosive loading of rock in mining applications. To this end it is essential to first characterise its complex internal structure. Knowing the structure shows how the properties of the component materials relate to the overall properties of rock. The structure and mineralogy of Gosford sandstone was investigated and this information was used to predict its thermal properties. The thermal properties of the material were measured experimentally and compared against these predictions.

  15. Shock compaction of a porous pyrotechnic material

    SciTech Connect

    Lee, L. M.; Schwarz, A. C.

    1980-01-01

    The results of an experimental program to generate Hugoniot data for an unreacted pyrotechnic material are discussed and the data presented. The program included both sample fabrication and experimental determination of stress-particle velocity Hugoniot data for the pyrotechnic, titanium hydride-potassium perchlorate (TiH/sub 2/-KClO/sub 4/), at two densities. The TiH/sub 2/-KClO/sub 4/, which was supplied as a powder mixture, was pressed to the desired bulk sample density and size using a ram and die technique. Samples were produced with nominal 2.02 or 2.27 g/cm/sup 3/ densities. Hugoniot data were generated on the porous pyrotechnic samples using standard flat plate impact techniques. The experimental program provided information defining the shock compaction behavior of porous TiH/sub 2/-KClO/sub 4/ up to 70 kbar. The Hugoniot data for both sample densities indicated full compaction was achieved in the 15 to 20 kbar stress range.

  16. Layer like porous materials with hierarchical structure.

    PubMed

    Roth, Wieslaw J; Gil, Barbara; Makowski, Wacław; Marszalek, Bartosz; Eliášová, Pavla

    2016-06-13

    Many chemical compositions produce layered solids consisting of extended sheets with thickness not greater than a few nanometers. The layers are weakly bonded together in a crystal and can be modified into various nanoarchitectures including porous hierarchical structures. Several classes of 2-dimensional (2D) materials have been extensively studied and developed because of their potential usefulness as catalysts and sorbents. They are discussed in this review with focus on clays, layered transition metal oxides, silicates, layered double hydroxides, metal(iv) phosphates and phosphonates, especially zirconium, and zeolites. Pillaring and delamination are the primary methods for structural modification and pore tailoring. The reported approaches are described and compared for the different classes of materials. The methods of characterization include identification by X-ray diffraction and microscopy, pore size analysis and activity assessment by IR spectroscopy and catalytic testing. The discovery of layered zeolites was a fundamental breakthrough that created unprecedented opportunities because of (i) inherent strong acid sites that make them very active catalytically, (ii) porosity through the layers and (iii) bridging of 2D and 3D structures. Approximately 16 different types of layered zeolite structures and modifications have been identified as distinct forms. It is also expected that many among the over 200 recognized zeolite frameworks can produce layered precursors. Additional advances enabled by 2D zeolites include synthesis of layered materials by design, hierarchical structures obtained by direct synthesis and top-down preparation of layered materials from 3D frameworks. PMID:26489452

  17. Porous materials with high negative Poisson’s ratios—a mechanism based material design

    NASA Astrophysics Data System (ADS)

    Kim, Kwangwon; Ju, Jaehyung; Kim, Doo-Man

    2013-08-01

    In an effort to tailor functional materials with customized anisotropic properties—stiffness and yield strain, we propose porous materials consisting of flexible mesostructures designed from the deformation of a re-entrant auxetic honeycomb and compliant mechanisms. Using an analogy between compliant mechanisms and a cellular material’s deformation, we can tailor the in-plane properties of mesostructures; low stiffness and high strain in one direction and high stiffness and low strain in the other direction. An analytical model is developed to obtain the effective moduli and yield strains of the porous materials by combining the kinematics of a rigid link mechanism and deformation of flexure hinges. A numerical technique is implemented with the analytical model for the nonlinear constitutive relations of the mesostructures and their strain-dependent Poisson’s ratios. A finite element analysis (FEA) is used to validate the analytical and numerical models. The designed moduli and yield strain of porous materials with an aluminum alloy are 2 GPa and 0.28% in one direction and 0.2 MPa and 28% in the other direction. These porous materials with mesostructures have high negative Poisson’s ratios, {\

  18. Fabricating porous materials using interpenetrating inorganic-organic composite gels

    DOEpatents

    Seo, Dong-Kyun; Volosin, Alex

    2016-06-14

    Porous materials are fabricated using interpenetrating inorganic-organic composite gels. A mixture or precursor solution including an inorganic gel precursor, an organic polymer gel precursor, and a solvent is treated to form an inorganic wet gel including the organic polymer gel precursor and the solvent. The inorganic wet gel is then treated to form a composite wet gel including an organic polymer network in the body of the inorganic wet gel, producing an interpenetrating inorganic-organic composite gel. The composite wet gel is dried to form a composite material including the organic polymer network and an inorganic network component. The composite material can be treated further to form a porous composite material, a porous polymer or polymer composite, a porous metal oxide, and other porous materials.

  19. Porous silicon as a substrate material for potentiometric biosensors

    NASA Astrophysics Data System (ADS)

    Thust, Marion; Schöning, M. J.; Frohnhoff, S.; Arens-Fischer, R.; Kordos, P.; Lüth, H.

    1996-01-01

    For the first time porous silicon has been investigated for the purpose of application as a substrate material for potentiometric biosensors operating in aqueous solutions. Porous silicon was prepared from differently doped silicon substrates by a standard anodic etching process. After oxidation, penicillinase, an enzyme sensitive to penicillin, was bound to the porous structure by physical adsorption. To characterize the electrochemical properties of the so build up penicillin biosensor, capacitance - voltage (C - V) measurements were performed on these field-effect structures.

  20. METHOD OF IMPREGNATING A POROUS MATERIAL

    DOEpatents

    Steele, G.N.

    1960-06-01

    A method of impregnating a porous body with an inorganic uranium- containing salt is outlined and comprises dissolving a water-soluble uranium- containing salt in water; saturating the intercommunicating pores of the porous body with the salt solution; infusing ammonia gas into the intercommunicating pores of the body, the ammonia gas in water chemically reacting with the water- soluble uranium-containing salt in the water solvent to form a nonwater-soluble uranium-containing precipitant; and evaporating the volatile unprecipitated products from the intercommunicating pores whereby the uranium-containing precipitate is uniformly distributed in the intercommunicating peres of the porous body.

  1. Characterizing He II flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R., Jr.; Vansciver, Steven W.

    1990-01-01

    Proposed space applications, such as the cooling of infrared and x ray telescopes, have generated substantial interest in the behavior of He II flowing in porous materials. For design purposes, classical porous media correlations and room temperature data are often used to obtain order of magnitude estimates of expected pressure drops, while the attendant temperature differences are either ignored or estimated using smooth tube correlations. A more accurate alternative to this procedure is suggested by an empirical extension of the two fluid model. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He II flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about + or - 20 pct.

  2. Characterizing He 2 flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Vansciver, Steven W.; Maddocks, J. R.

    1991-01-01

    Proposed space applications, such as the cooling of infrared and x ray telescopes, have generated substantial interest in the behavior of He(2) flowing in porous materials. For design purposes, classical porous media correlations and room temperature data are often used to obtain order of magnitude estimates of expected pressure drops, while the attendant temperature differences are either ignored or estimated using smooth tube correlations. A more accurate alternative to this procedure is suggested by an empirical extension of the two fluid models. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He(2) flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about + or - 20 percent.

  3. Dynamic mean field theory for lattice gas models of fluids confined in porous materials: Higher order theory based on the Bethe-Peierls and path probability method approximations

    SciTech Connect

    Edison, John R.; Monson, Peter A.

    2014-07-14

    Recently we have developed a dynamic mean field theory (DMFT) for lattice gas models of fluids in porous materials [P. A. Monson, J. Chem. Phys. 128(8), 084701 (2008)]. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable states for fluids in pores and is especially useful for studying system exhibiting adsorption/desorption hysteresis. In this paper we discuss the extension of the theory to higher order by means of the path probability method (PPM) of Kikuchi and co-workers. We show that this leads to a treatment of the dynamics that is consistent with thermodynamics coming from the Bethe-Peierls or Quasi-Chemical approximation for the equilibrium or metastable equilibrium states of the lattice model. We compare the results from the PPM with those from DMFT and from dynamic Monte Carlo simulations. We find that the predictions from PPM are qualitatively similar to those from DMFT but give somewhat improved quantitative accuracy, in part due to the superior treatment of the underlying thermodynamics. This comes at the cost of greater computational expense associated with the larger number of equations that must be solved.

  4. Processing and Modeling of Porous Copper Using Sintering Dissolution Process

    NASA Astrophysics Data System (ADS)

    Salih, Mustafa Abualgasim Abdalhakam

    The growth of porous metal has produced materials with improved properties as compared to non-metals and solid metals. Porous metal can be classified as either open cell or closed cell. Open cell allows a fluid media to pass through it. Closed cell is made up of adjacent sealed pores with shared cell walls. Metal foams offer higher strength to weight ratios, increased impact energy absorption, and a greater tolerance to high temperatures and adverse environmental conditions when compared to bulk materials. Copper and its alloys are examples of these, well known for high strength and good mechanical, thermal and electrical properties. In the present study, the porous Cu was made by a powder metallurgy process, using three different space holders, sodium chloride, sodium carbonate and potassium carbonate. Several different samples have been produced, using different ratios of volume fraction. The densities of the porous metals have been measured and compared to the theoretical density calculated using an equation developed for these foams. The porous structure was determined with the removal of spacer materials through sintering process. The sintering process of each spacer material depends on the melting point of the spacer material. Processing, characterization, and mechanical properties were completed. These tests include density measurements, compression tests, computed tomography (CT) and scanning electron microscopy (SEM). The captured morphological images are utilized to generate the object-oriented finite element (OOF) analysis for the porous copper. Porous copper was formed with porosities in the range of 40-66% with density ranges from 3 to 5.2 g/cm3. A study of two different methods to measure porosity was completed. OOF (Object Oriented Finite Elements) is a desktop software application for studying the relationship between the microstructure of a material and its overall mechanical, dielectric, or thermal properties using finite element models based on

  5. Stochastic modeling of filtrate alkalinity in water filtration devices: Transport through micro/nano porous clay based ceramic materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clay and plant materials such as wood are the raw materials used in manufacture of ceramic water filtration devices around the world. A step by step manufacturing procedure which includes initial mixing, molding and sintering is used. The manufactured ceramic filters have numerous pores which help i...

  6. Modeling Dynamic Ductility: An Equation of State for Porous Metals

    SciTech Connect

    Colvin, J

    2007-07-27

    Enhanced heating from shock compression of a porous material can potentially suppress or delay cracking of the material on subsequent expansion. In this paper we quantify the expected enhanced heating in an experiment in which a sector of a thin cylindrical shell is driven from the inside surface by SEMTEX high explosive ({approx}1 {micro}s FWHM pressure pulse with peak pressure {approx}21.5 GPa). We first derive an analytical equation of state (EOS) for porous metals, then discuss the coupling of this EOS with material elastic-plastic response in a 2D hydrocode, and then discuss the modeling of the HE experiment with both fully dense and 10% porous Ta and a Bi/Ta composite. Finally, we compare our modeling with some recent experimental data.

  7. Adsorption and Separation Modeling of Porous Networks

    NASA Astrophysics Data System (ADS)

    Malanoski, Anthony; van Swol, Frank

    2001-03-01

    With the advent of self-assembly techniques has come the potential to tailor materials for adsorption and separation applications. For example, using surfactants as templating agents it is now feasible to finely control both the three-dimensional (3D) porosity as well as the surface chemistry. With an eye on assisting the emerging materials design we have embarked on a program that focuses on modeling adsorption/desorption, reactions and permeation phenomena in such structures. What makes the modeling particularly challenging is the coupling of length scales. The role of the atomic length scale features such as surface reactions and surface structure must be captured as well as the role of the network connectivity and other larger length scales. The latter include the pore shape and length, and the presence of external surfaces. This paper reports on how we employ refineable lattice models to tackle the modeling problems. We use both equilibrium and non-equilibrium Monte Carlo (MC) and 3D density functional theory (DFT) techniques to study the equilibrium and transport behavior in nanostructured porous materials. We will present 1) results of both adsorption/desorption hysteresis in large regular and random networks and 2) the results of using reactive sites in separation membranes, and compare these with experiments.

  8. Predicting Pressure Drop In Porous Materials

    NASA Technical Reports Server (NTRS)

    Lawing, Pierce L.

    1990-01-01

    Theory developed to predict drop in pressure based on drag of individual fibers. Simple correlation method for data also developed. Helps in predicting flow characteristics of many strain-isolation pad (SIP) glow geometries in Shuttle Orbiter tile system. Also helps in predicting venting characteristics of tile assemblies during ascent and leakage of hot gas under tiles during descent. Useful in study of mechanics of flows through fibrous and porous media, and procedures applicable to purged fiberglass insulation, dialysis filters, and other fibrous and porous media.

  9. Design of energy absorbing materials and composite structures based on porous shape memory alloys (SE)

    NASA Astrophysics Data System (ADS)

    Zhao, Ying

    Recently, attention has been paid to porous shape memory alloys. This is because the alloys show large and recoverable deformation, i.e. superelasticity and shape memory effect. Due to their light weight and potential large deformations, porous shape memory alloys have been considered as excellent candidates for energy absorption materials. In the present study, porous NiTi alloy with several different porosities are processed by spark plasma sintering (SPS). The compression behavior of the porous NiTi is examined with an aim of using it for a possible high energy absorbing material. Two models for the macroscopic compression behavior of porous shape memory alloy (SMA) are presented in this work, where Eshelby's inhomogeneous inclusion method is used to predict the effective elastic and superelastic behavior of a porous SMA based on the assumption of stress-strain curve. The analytical results are compared with experimental data for porous NiTi with 13% porosity, resulting in a reasonably good agreement. Based on the study upon porous NiTi, an energy absorbing composite structure made of a concentric NiTi spring and a porous NiTi rod is presented in this PhD dissertation. Both NiTi spring and porous NiTi rod are of superelastic grade. Ductile porous NiTi cylindrical specimens are fabricated by spark plasma sintering. The composite structure exhibits not only high reversible force-displacement behavior for small to intermediate loading but also high energy absorbing property when subjected to large compressive loads. A model for the compressive force-displacement curve of the composite structure is presented. The predicted curve is compared to the experimental data, resulting in a reasonably good agreement.

  10. TESTING ANTIMICROBIAL EFFICACY ON POROUS MATERIALS

    EPA Science Inventory

    The efficacy of antimicrobial treatments to eliminate or control biological growth in the indoor environment can easily be tested on nonporous surfaces. However, the testing of antimicrobial efficacy on porous surfaces, such as those found in the indoor environment [i.e., gypsum ...

  11. Molecular simulation of adsorption and transport in hierarchical porous materials.

    PubMed

    Coasne, Benoit; Galarneau, Anne; Gerardin, Corine; Fajula, François; Villemot, François

    2013-06-25

    Adsorption and transport in hierarchical porous solids with micro- (~1 nm) and mesoporosities (>2 nm) are investigated by molecular simulation. Two models of hierarchical solids are considered: microporous materials in which mesopores are carved out (model A) and mesoporous materials in which microporous nanoparticles are inserted (model B). Adsorption isotherms for model A can be described as a linear combination of the adsorption isotherms for pure mesoporous and microporous solids. In contrast, adsorption in model B departs from adsorption in pure microporous and mesoporous solids; the inserted microporous particles act as defects, which help nucleate the liquid phase within the mesopore and shift capillary condensation toward lower pressures. As far as transport under a pressure gradient is concerned, the flux in hierarchical materials consisting of microporous solids in which mesopores are carved out obeys the Navier-Stokes equation so that Darcy's law is verified within the mesopore. Moreover, the flow in such materials is larger than in a single mesopore, due to the transfer between micropores and mesopores. This nonzero velocity at the mesopore surface implies that transport in such hierarchical materials involves slippage at the mesopore surface, although the adsorbate has a strong affinity for the surface. In contrast to model A, flux in model B is smaller than in a single mesopore, as the nanoparticles act as constrictions that hinder transport. By a subtle effect arising from fast transport in the mesopores, the presence of mesopores increases the number of molecules in the microporosity in hierarchical materials and, hence, decreases the flow in the micropores (due to mass conservation). As a result, we do not observe faster diffusion in the micropores of hierarchical materials upon flow but slower diffusion, which increases the contact time between the adsorbate and the surface of the microporosity. PMID:23718554

  12. Structural and dynamic properties of confined water in nanometric model porous materials (8 Å⩽∅⩽40 Å)

    NASA Astrophysics Data System (ADS)

    Floquet, N.; Coulomb, J. P.; Dufau, N.; Andre, G.; Kahn, R.

    2004-07-01

    Structural and dynamic properties of confined water have been investigated by ‘‘in situ’’ neutron-scattering experiments. In the medium confinement regime (for MCM-41 host materials: 20 Å⩽∅⩽40 Å) confined water has rather similar properties to bulk (3d) water. The major difference concerns the solidification phase transition. Strong triple-point depression Δ T3t is observed and Δ T3t increases when decreasing the pore diameter ∅ (213 K⩽Δ T3t⩽233 K). Such a confined water behaves as a supercooled liquid phase. The ultra-confinement (AlPO 4-N zeolites: 8 Å⩽∅⩽12 Å), is seen to induce the structuration of the confined water and its stability at room temperature T=300 K due to commensurability effect with the AlPO 4-5 inner surface. No wetting phenomena are observed for both host materials, the silicic MCM-41 samples and the AlPO 4-N zeolite family.

  13. Attenuation of shock waves propagating through nano-structured porous materials

    NASA Astrophysics Data System (ADS)

    Al-Qananwah, Ahmad K.; Koplik, Joel; Andreopoulos, Yiannis

    2013-07-01

    Porous materials have long been known to be effective in energy absorption and shock wave attenuation. These properties make them attractive in blast mitigation strategies. Nano-structured materials have an even greater potential for blast mitigation because of their high surface-to-volume ratio, a geometric parameter which substantially attenuates shock wave propagation. A molecular dynamics approach was used to explore the effects of this remarkable property on the behavior of traveling shocks impacting on solid materials. The computational setup included a moving piston, a gas region and a target solid wall with and without a porous structure. The gas and porous solid were modeled by Lennard-Jones-like and effective atom potentials, respectively. The shock wave is resolved in space and time and its reflection from a solid wall is gradual, due to the wave's finite thickness, and entails a self-interaction as the reflected wave travels through the incoming incident wave. Cases investigated include a free standing porous structure, a porous structure attached to a wall and porous structures with graded porosity. The effects of pore shape and orientation have been also documented. The results indicate that placing a nano-porous material layer in front of the target wall reduced the stress magnitude and the energy deposited inside the solid by about 30 percent, while at the same time substantially decreasing the loading rate.

  14. Chemically modified and nanostructured porous silicon as a drug delivery material and device

    NASA Astrophysics Data System (ADS)

    Anglin, Emily Jessica

    This thesis describes the fabrication, chemical modification, drug release, and toxicity studies of nanostructured porous silicon for the purposes of developing a smart drug delivery device. The first chapter is an introductory chapter, presenting the chemical and physical properties of porous silicon, the concepts and issues of current drug delivery devices and materials, and how porous silicon can address the issues regarding localized and controlled drug therapies. The second chapter discusses chemical modifications of nanostructured porous Si for stabilizing the material in biologically relevant media while providing an extended release of a therapeutic in vitro. This chapter also demonstrates the utility of the porous silicon optical signatures for effectively monitoring drug release from the system and its applications for development of a self-reporting drug delivery device. In chapter three, the concept of providing a triggered release of a therapeutic from porous silicon microparticles through initiation by an external stimulus is demonstrated. The microparticles are chemically modified, and the release is enhanced by a short application of ultrasound to the particulate system. The effect of ultrasound on the drug release and particle size is discussed. Chapter four presents a new method for sustaining the release of a monoclonal antibody from the porous matrix of porous SiO2. The therapeutic is incorporated into the films through electrostatic adsorption and a slow release is observed in vitro. A new method of quantifying the extent of drug loading is monitored with interferometry. The last chapter of the thesis provides a basic in vivo toxicity study of various porous Si microparticles for intraocular applications. Three types of porous Si particles are fabricated and studied in a rabbit eye model. The toxicity studies were conducted by collaborators at the Shiley Eye Center, La Jolla, CA. This work, demonstrates the feasibility of developing a self

  15. Thermal conductivity and electrical resistivity of porous material

    NASA Technical Reports Server (NTRS)

    Koh, J. C. Y.; Fortini, A.

    1971-01-01

    Thermal conductivity and electrical resistivity of porous materials, including 304L stainless steel Rigimesh, 304L stainless steel sintered spherical powders, and OFHC sintered spherical powders at different porosities and temperatures are reported and correlated. It was found that the thermal conductivity and electrical resistivity can be related to the solid material properties and the porosity of the porous matrix regardless of the matrix structure. It was also found that the Wiedermann-Franz-Lorenz relationship is valid for the porous materials under consideration. For high conductivity materials, the Lorenz constant and the lattice component of conductivity depend on the material and are independent of the porosity. For low conductivity, the lattice component depends on the porosity as well.

  16. Advances in monoliths and related porous materials for microfluidics.

    PubMed

    Knob, Radim; Sahore, Vishal; Sonker, Mukul; Woolley, Adam T

    2016-05-01

    In recent years, the use of monolithic porous polymers has seen significant growth. These materials present a highly useful support for various analytical and biochemical applications. Since their introduction, various approaches have been introduced to produce monoliths in a broad range of materials. Simple preparation has enabled their easy implementation in microchannels, extending the range of applications where microfluidics can be successfully utilized. This review summarizes progress regarding monoliths and related porous materials in the field of microfluidics between 2010 and 2015. Recent developments in monolith preparation, solid-phase extraction, separations, and catalysis are critically discussed. Finally, a brief overview of the use of these porous materials for analysis of subcellular and larger structures is given. PMID:27190564

  17. Approach to failure in porous granular materials under compression

    NASA Astrophysics Data System (ADS)

    Kun, Ferenc; Varga, Imre; Lennartz-Sassinek, Sabine; Main, Ian G.

    2013-12-01

    We investigate the approach to catastrophic failure in a model porous granular material undergoing uniaxial compression. A discrete element computational model is used to simulate both the microstructure of the material and the complex dynamics and feedbacks involved in local fracturing and the production of crackling noise. Under strain-controlled loading, microcracks initially nucleate in an uncorrelated way all over the sample. As loading proceeds the damage localizes into a narrow damage band inclined at 30∘-45∘ to the load direction. Inside the damage band the material is crushed into a poorly sorted mixture of mainly fine powder hosting some larger fragments. The mass probability density distribution of particles in the damage zone is a power law of exponent 2.1, similar to a value of 1.87 inferred from observations of the length distribution of wear products (gouge) in natural and laboratory faults. Dynamic bursts of radiated energy, analogous to acoustic emissions observed in laboratory experiments on porous sedimentary rocks, are identified as correlated trails or cascades of local ruptures that emerge from the stress redistribution process. As the system approaches macroscopic failure consecutive bursts become progressively more correlated. Their size distribution is also a power law, with an equivalent Gutenberg-Richter b value of 1.22 averaged over the whole test, ranging from 3 to 0.5 at the time of failure, all similar to those observed in laboratory tests on granular sandstone samples. The formation of the damage band itself is marked by a decrease in the average distance between consecutive bursts and an emergent power-law correlation integral of event locations with a correlation dimension of 2.55, also similar to those observed in the laboratory (between 2.75 and 2.25).

  18. Approach to failure in porous granular materials under compression.

    PubMed

    Kun, Ferenc; Varga, Imre; Lennartz-Sassinek, Sabine; Main, Ian G

    2013-12-01

    We investigate the approach to catastrophic failure in a model porous granular material undergoing uniaxial compression. A discrete element computational model is used to simulate both the microstructure of the material and the complex dynamics and feedbacks involved in local fracturing and the production of crackling noise. Under strain-controlled loading, microcracks initially nucleate in an uncorrelated way all over the sample. As loading proceeds the damage localizes into a narrow damage band inclined at 30°-45° to the load direction. Inside the damage band the material is crushed into a poorly sorted mixture of mainly fine powder hosting some larger fragments. The mass probability density distribution of particles in the damage zone is a power law of exponent 2.1, similar to a value of 1.87 inferred from observations of the length distribution of wear products (gouge) in natural and laboratory faults. Dynamic bursts of radiated energy, analogous to acoustic emissions observed in laboratory experiments on porous sedimentary rocks, are identified as correlated trails or cascades of local ruptures that emerge from the stress redistribution process. As the system approaches macroscopic failure consecutive bursts become progressively more correlated. Their size distribution is also a power law, with an equivalent Gutenberg-Richter b value of 1.22 averaged over the whole test, ranging from 3 to 0.5 at the time of failure, all similar to those observed in laboratory tests on granular sandstone samples. The formation of the damage band itself is marked by a decrease in the average distance between consecutive bursts and an emergent power-law correlation integral of event locations with a correlation dimension of 2.55, also similar to those observed in the laboratory (between 2.75 and 2.25). PMID:24483436

  19. Application of a model of plastic porous materials including void shape effects to the prediction of ductile failure under shear-dominated loadings

    NASA Astrophysics Data System (ADS)

    Morin, Léo; Leblond, Jean-Baptiste; Tvergaard, Viggo

    2016-09-01

    An extension of Gurson's famous model (Gurson, 1977) of porous plastic solids, incorporating void shape effects, has recently been proposed by Madou and Leblond (Madou and Leblond, 2012a, 2012b, 2013; Madou et al., 2013). In this extension the voids are no longer modelled as spherical but ellipsoidal with three different axes, and changes of the magnitude and orientation of these axes are accounted for. The aim of this paper is to show that the new model is able to predict softening due essentially to such changes, in the absence of significant void growth. This is done in two steps. First, a numerical implementation of the model is proposed and incorporated into the SYSTUS® and ABAQUS® finite element programmes (through some freely available UMAT (Leblond, 2015) in the second case). Second, the implementation in SYSTUS® is used to simulate previous "numerical experiments" of Tvergaard and coworkers (Tvergaard, 2008, 2009, 2012, 2015a; Dahl et al., 2012; Nielsen et al., 2012) involving the shear loading of elementary porous cells, where softening due to changes of the void shape and orientation was very apparent. It is found that with a simple, heuristic modelling of the phenomenon of mesoscopic strain localization, the model is indeed able to reproduce the results of these numerical experiments, in contrast to Gurson's model disregarding void shape effects.

  20. Application of porous materials for laminar flow control

    NASA Technical Reports Server (NTRS)

    Pearce, W. E.

    1978-01-01

    Fairly smooth porous materials were elected for study Doweave; Fibermetal; Dynapore; and perforated titanium sheet. Factors examined include: surface smoothness; suction characteristics; porosity; surface impact resistance; and strain compatibility. A laminar flow control suction glove arrangement was identified with material combinations compatible with thermal expansion and structural strain.

  1. Dynamic Compaction Modeling Comparison for Porous Silica Powder

    NASA Astrophysics Data System (ADS)

    Borg, John; Schwalbe, Larry; Chapman, D. J.; Lloyd, Andrew; Ward, Aaron

    2005-07-01

    A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized porous material models, P-lambda and P-alpha, in conjunction with a linear Us-up Hugoniot. Two hydrocodes were used to simulate the compaction event: CTH and KO. CTH is a three-dimensional Eulerian hydrocode developed at Sandia National Laboratory and KO is a one-dimensional Lagrangian hydrocode developed at Lawrence Livermore National Laboratory. A comparison of the advantages and disadvantages, along with a discussion of the salient features, of the two models are presented.

  2. New approach for porous materials obtaining using centrifugal casting

    NASA Astrophysics Data System (ADS)

    Bălţătescu, O.; Axinte, M.; Barbu, G.; Manole, V.

    2015-11-01

    It has been presented different methods for obtaining porous materials, (mainly used for metallic foams) and highlighting a new technology developed in the Faculty of Materials science and engineering, of Iasi. Our technology for obtaining porous materials is called centrifugal casting for porous materials. This technology is included in the method number 8: co-pressing of a metal powder with a leachable powder being in the same time a newer approach in the porous materials field. This technology is currently in the developmental phase. Since now we made experiments on the metallic materials, aluminum alloys. The technology is briefly described in this paper. The obtained parts were used for making samples in order to characterize the properties of the materials. The cellular structure of metallic foams requires special precautions that must be taken in characterization and testing. In this paper we have characterized the samples structurally by its cell topology (open cells, closed cells), relative density, cell size and cell shape and anisotropy. Also it was used scanning electron microscopy (SEM) which is straightforward; the only necessary precaution is that relating to surface preparation.

  3. Study on Solidification of Phase Change Material in Fractal Porous Metal Foam

    NASA Astrophysics Data System (ADS)

    Zhang, Chengbin; Wu, Liangyu; Chen, Yongping

    2015-02-01

    The Sierpinski fractal is introduced to construct the porous metal foam. Based on this fractal description, an unsteady heat transfer model accompanied with solidification phase change in fractal porous metal foam embedded with phase change material (PCM) is developed and numerically analyzed. The heat transfer processes associated with solidification of PCM embedded in fractal structure is investigated and compared with that in single-pore structure. The results indicate that, for the solidification of phase change material in fractal porous metal foam, the PCM is dispersedly distributed in metal foam and the existence of porous metal matrix provides a fast heat flow channel both horizontally and vertically, which induces the enhancement of interstitial heat transfer between the solid matrix and PCM. The solidification performance of the PCM, which is represented by liquid fraction and solidification time, in fractal structure is superior to that in single-pore structure.

  4. Methods for removing contaminant matter from a porous material

    DOEpatents

    Fox, Robert V [Idaho Falls, ID; Avci, Recep [Bozeman, MT; Groenewold, Gary S [Idaho Falls, ID

    2010-11-16

    Methods of removing contaminant matter from porous materials include applying a polymer material to a contaminated surface, irradiating the contaminated surface to cause redistribution of contaminant matter, and removing at least a portion of the polymer material from the surface. Systems for decontaminating a contaminated structure comprising porous material include a radiation device configured to emit electromagnetic radiation toward a surface of a structure, and at least one spray device configured to apply a capture material onto the surface of the structure. Polymer materials that can be used in such methods and systems include polyphosphazine-based polymer materials having polyphosphazine backbone segments and side chain groups that include selected functional groups. The selected functional groups may include iminos, oximes, carboxylates, sulfonates, .beta.-diketones, phosphine sulfides, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, monothio phosphinic acids, and dithio phosphinic acids.

  5. Transient Infrared Measurement of Laser Absorption Properties of Porous Materials

    NASA Astrophysics Data System (ADS)

    Marynowicz, Andrzej

    2016-06-01

    The infrared thermography measurements of porous building materials have become more frequent in recent years. Many accompanying techniques for the thermal field generation have been developed, including one based on laser radiation. This work presents a simple optimization technique for estimation of the laser beam absorption for selected porous building materials, namely clinker brick and cement mortar. The transient temperature measurements were performed with the use of infrared camera during laser-induced heating-up of the samples' surfaces. As the results, the absorbed fractions of the incident laser beam together with its shape parameter are reported.

  6. Strain rate effects in porous materials

    SciTech Connect

    Lankford, J. Jr.; Dannemann, K.A.

    1998-12-31

    The behavior of metal foams under rapid loading conditions is assessed. Dynamic loading experiments were conducted in their laboratory using a split Hopkinson pressure bar apparatus and a drop weight tester; Strain rates ranged from 45 s{sup {minus}1} to 1200 s{sup {minus}1}. The implications of these experiments on open-cell, porous metals, and closed- and open-cell polymer foams are described. It is shown that there are two possible strain-rate dependent contributors to the impact resistance of cellular metals: (i) elastic-plastic resistance of the cellular metal skeleton, and (ii) the gas pressure generated by gas flow within distorted open cells. A theoretical basis for these implications is presented.

  7. In-situ probing of Low Density Porous Materials

    NASA Astrophysics Data System (ADS)

    Hawreliak, James

    2013-06-01

    The shock response of porous materials is of interest in High Energy Density Physics because the PdV heating from void closure allows off principle Hugoniot states for modeling many astrophysical processes. While continuum models exists of shockwave propagation in foams the relevant physical phenomena spans three different length scales: the micro-length scale defined by the pore size and length between solid structures in the foam (10 to 1000 nm), the shock front thickness which determines material and energy flow (0.1 to 100 nm), and the hydrodynamic length scale associated with the expanding spherical wave (>10 μm), all of which impact the shock response of the low density foam. With the advent of new HED experimental facilities for generating shockwaves at x-ray light sources this gives new tools for performing pump probe experiments to understand the microstructural response of low density materials. Currently, we have used x-ray radiograph to make Hugoniot EOS measurements the of shock compressed low density SiO2 and Carbon based foams. We will show recent result of measurements of experiments conducted on the Omega laser facility and discuss imaging shockwaves in low density foams on the soon to be commissioned DCS end station at APS and the MEC end station at LCLS. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  8. Dynamic Compaction Modeling of Porous Silica Powder

    NASA Astrophysics Data System (ADS)

    Borg, John P.; Schwalbe, Larry; Cogar, John; Chapman, D. J.; Tsembelis, K.; Ward, Aaron; Lloyd, Andrew

    2006-07-01

    A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized a linear Us-Up Hugoniot. The compaction events were modeled with CTH, a 3D Eulerian hydrocode developed at Sandia National Laboratory. Simulated pressures at two test locations are presented and compared with measurements.

  9. Gas sensing using porous materials for automotive applications.

    PubMed

    Wales, Dominic J; Grand, Julien; Ting, Valeska P; Burke, Richard D; Edler, Karen J; Bowen, Chris R; Mintova, Svetlana; Burrows, Andrew D

    2015-07-01

    Improvements in the efficiency of combustion within a vehicle can lead to reductions in the emission of harmful pollutants and increased fuel efficiency. Gas sensors have a role to play in this process, since they can provide real time feedback to vehicular fuel and emissions management systems as well as reducing the discrepancy between emissions observed in factory tests and 'real world' scenarios. In this review we survey the current state-of-the-art in using porous materials for sensing the gases relevant to automotive emissions. Two broad classes of porous material - zeolites and metal-organic frameworks (MOFs) - are introduced, and their potential for gas sensing is discussed. The adsorptive, spectroscopic and electronic techniques for sensing gases using porous materials are summarised. Examples of the use of zeolites and MOFs in the sensing of water vapour, oxygen, NOx, carbon monoxide and carbon dioxide, hydrocarbons and volatile organic compounds, ammonia, hydrogen sulfide, sulfur dioxide and hydrogen are then detailed. Both types of porous material (zeolites and MOFs) reveal great promise for the fabrication of sensors for exhaust gases and vapours due to high selectivity and sensitivity. The size and shape selectivity of the zeolite and MOF materials are controlled by variation of pore dimensions, chemical composition (hydrophilicity/hydrophobicity), crystal size and orientation, thus enabling detection and differentiation between different gases and vapours. PMID:25982991

  10. The Uniaxial Tensile Response of Porous and Microcracked Ceramic Materials

    SciTech Connect

    Pandey, Amit; Shyam, Amit; Watkins, Thomas R; Lara-Curzio, Edgar; Lara-Curzio, Edgar; Stafford, Randall; Hemker, Kevin J

    2014-01-01

    The uniaxial tensile stress-strain behavior of three porous ceramic materials was determined at ambient conditions. Test specimens in the form of thin beams were obtained from the walls of diesel particulate filter honeycombs and tested using a microtesting system. A digital image correlation technique was used to obtain full-field 2D in-plane surface displacement maps during tensile loading, and in turn, the 2D strains obtained from displacement fields were used to determine the Secant modulus, Young s modulus and initial Poisson s ratio of the three porous ceramic materials. Successive unloading-reloading experiments were performed at different levels of stress to decouple the linear elastic, anelastic and inelastic response in these materials. It was found that the stress-strain response of these materials was non-linear and that the degree of nonlinearity is related to the initial microcrack density and evolution of damage in the material.

  11. A Two-Phase Model for Shocked Porous Explosive

    NASA Astrophysics Data System (ADS)

    Lambourn, Brian; Handley, Caroline

    2015-06-01

    Mesoscale calculations of hotspots created by a shock wave in a porous explosive show that the hotspots do not cool in times of order at least a microsecond. This suggests that single phase models of porosity like the snowplough model, which assume that a shocked porous explosive jumps to a point on the Hugoniot that is instantaneously in thermodynamic equilibrium, are not correct. A two-phased model of shocked porous explosive has been developed in which a small fraction of the material, representing the hotspots, has a high temperature but the bulk of the material is cooler than the temperature calculated by, for example, the snowplough model. In terms of the mean state of the material, it is shown that the two-phase model only minimally affects the pressure - volume and shock velocity - particle velocity plot of the Hugoniot, but that the mean state lies slightly off the equation of state surface. The results of the model will be compared with two dimensional mesoscale calculations.

  12. Methyl alcohol used as penetrant inspection medium for porous materials

    NASA Technical Reports Server (NTRS)

    Hendron, J. A.

    1971-01-01

    Porous material thoroughly wetted with alcohol shows persistent wet line or area at locations of cracks or porosity. Inspection is qualitative and repeatable, but is used quantitatively with select samples to grade density variations in graphite blocks. Photography is employed to achieve permanent record of results.

  13. Molecules with polymerizable ligands as precursors to porous doped materials

    SciTech Connect

    Hubert-Pfalzgraf, L.G.; Pajot, N.; Papiernik, R.; Parraud, S.

    1996-12-31

    Titanium and aluminum alkoxide derivatives with polymerizable ligands such as 2-(methacryloyloxy)ethylacetoacetate (HAAEMA), oleic acid and geraniol (HOGE) have been obtained. The various compounds have been characterized by FT-IR and NMR {sup 1}H. Copolymerization with styrene and divinylbenzene affords porous doped organic materials which have been characterized by scanning electron microscopy (SEM), elemental analysis, density measurements.

  14. Structure and Stability of Deflagrations in Porous Energetic Materials

    SciTech Connect

    stephen B. Margolis; Forman A. Williams

    1999-03-01

    Theoretical two-phase-flow analyses have recently been developed to describe the structure and stability of multi-phase deflagrations in porous energetic materials, in both confined and unconfined geometries. The results of these studies are reviewed, with an emphasis on the fundamental differences that emerge with respect to the two types of geometries. In particular, pressure gradients are usually negligible in unconfined systems, whereas the confined problem is generally characterized by a significant gas-phase pressure difference, or overpressure, between the burned and unburned regions. The latter leads to a strong convective influence on the burning rate arising from the pressure-driven permeation of hot gases into the solid/gas region and the consequent preheating of the unburned material. It is also shown how asymptotic models that are suitable for analyzing stability may be derived based on the largeness of an overall activation-energy parameter. From an analysis of such models, it is shown that the effects of porosity and two-phase flow are generally destabilizing, suggesting that degraded propellants, which exhibit greater porosity than their pristine counterparts, may be more readily subject to combustion instability and nonsteady deflagration.

  15. SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris

    SciTech Connect

    E. W. Coryell; L. J. Siefken; S. Paik

    1998-09-01

    Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate manner. A design is also described for implementing a model of heat transfer by radiation from debris to the interstitial fluid. A design is described for implementation of models for flow losses and interphase drag in porous debris. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region.

  16. Development of materials and fabrication of porous and pebble bed beryllium multipliers

    NASA Astrophysics Data System (ADS)

    Davydov, D. A.; Solonin, M. I.; Markushkin, Yu. E.; Gorokhov, V. A.; Gorlevsky, V. V.; Nikolaev, G. N.

    2000-12-01

    Beryllium is considered to be a neutron multiplier material for the reference ITER breeding blanket. The main requirements for the porous beryllium multiplier for the breeding blanket are: (1) inherently open porosity within 20 ± 2% for easy removal of radioactive gases; (2) high thermal conductivity; (3) close contact with a stainless steel (SS) shell to provide high heat transfer. A beryllium multiplier can be fabricated by two different techniques: by manufacturing porous or pebble bed beryllium. The method designed (patent 2106931 RU) in SSC RF-VNIINM (Russia) provides for the production of porous beryllium conforming to the requirements mentioned above. For comparative fission tests and the optimization of breeding zone functional capabilities, porous (21.9%) and binary pebble bed (density=78%) beryllium multipliers were fabricated. DEMO breeding blanket models and a mock-up of fission (IVV-2M reactor) tests have been manufactured at SSC RF-VNIINM.

  17. The Tribological Efficiency and the Mechanism of Action of Nano-Porous Composition Base Brake Lining Materials

    NASA Astrophysics Data System (ADS)

    Kutelia, E. R.; Gventsadze, D. I.; Eristavil, B. G.; Maisuradze, N. I.; Tsurtsumia, O. O.; Gventsadze, L. D.; Olofsson, U.; Wahlström, J.; Olander, L.

    2011-12-01

    Based on the comparative analysis of the experimental values determined for the tribological parameters for the three novel nano-porous composition base and two conventional brake lining materials while friction with the grey cast iron disc, it was shown the considerable high tribological efficiency of the novel nano-porous composition base lining materials in comparison with the conventional (from EU and USA market) brake lining materials. The explanation is given to the action mechanism of nano-porous composition base brake lining material and its tribological efficiency basing on the "triple phase" tribo-pair model.

  18. SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris

    SciTech Connect

    Siefken, Larry James; Coryell, Eric Wesley; Paik, Seungho; Kuo, Han Hsiung

    1999-07-01

    Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate manner. Designs are described for models to calculate the flow losses and interphase drag of fluid flowing through the interstices of the porous debris, and to apply these variables in the momentum equations in the RELAP5 part of the code. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region.

  19. Modeling Methane Adsorption in Interpenetrating Porous Polymer Networks

    SciTech Connect

    Martin, RL; Shahrak, MN; Swisher, JA; Simon, CM; Sculley, JP; Zhou, HC; Smit, B; Haranczyk, M

    2013-10-03

    Porous polymer networks (PPNs) are a class of porous materials of particular interest in a variety of energy-related applications because of their stability, high surface areas, and gas uptake capacities. Computationally derived structures for five recently synthesized PPN frameworks, PPN-2, -3, -4, -5, and -6, were generated for various topologies, optimized using semiempirical electronic structure methods, and evaluated using classical grand canonical Monte Carlo simulations. We show that a key factor in modeling the methane uptake performance of these materials is whether, and how, these material frameworks interpenetrate and demonstrate a computational approach for predicting the presence, degree, and nature of interpenetration in PPNs that enables the reproduction of experimental adsorption data.

  20. Wormhole growth in soluble porous materials

    SciTech Connect

    Nilson, R.H.; Griffiths, S.K. )

    1990-09-24

    Analytical solutions are derived for the quasisteady shape and speed of a single wormhole resulting from the coupled processes of Darcian fluid motion and chemical dissolution in a soluble permeable material. For an initially unsaturated medium, two-dimensional solutions are obtained by addressing an inverted free-boundary problem in which the spatial coordinates are treated as dependent variables on the plane of a complex potential. For initially saturated materials, solutions are obtained by analogy to Ivantsov's problem of dendrite growth.

  1. Hydrophobic Porous Material Adsorbs Small Organic Molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Hickey, Gregory S.

    1994-01-01

    Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

  2. A variational constitutive model for porous metal plasticity

    NASA Astrophysics Data System (ADS)

    Weinberg, K.; Mota, A.; Ortiz, M.

    2006-01-01

    This paper presents a variational formulation of viscoplastic constitutive updates for porous elastoplastic materials. The material model combines von Mises plasticity with volumetric plastic expansion as induced, e.g., by the growth of voids and defects in metals. The finite deformation theory is based on the multiplicative decomposition of the deformation gradient and an internal variable formulation of continuum thermodynamics. By the use of logarithmic and exponential mappings the stress update algorithms are extended from small strains to finite deformations. Thus the time-discretized version of the porous-viscoplastic constitutive updates is described in a fully variational manner. The range of behavior predicted by the model and the performance of the variational update are demonstrated by its application to the forced expansion and fragmentation of U-6%Nb rings.

  3. Urothermal Synthesis of Crystalline Porous Materials

    PubMed Central

    Zhang, Jian; Bu, Julia T.; Chen, Shumei; Wu, Tao; Zheng, Shoutian; Chen, Yigang; Nieto, Ruben A.; Feng, Pingyun

    2015-01-01

    Pores from Urea Urea derivatives are shown here to be a highly verstaile solvent system for the synthesis of crystalline solids. In particular, reversible binding of urea derivatives to framework metal sites has been utilized to create a variety of materials integrating both porosity and open-metal sites. PMID:20954225

  4. Nanocomposite Materials - Ferroelectric Nanoparticles Incorporated into Porous Matrix

    NASA Astrophysics Data System (ADS)

    Rysiakiewicz-Pasek, E.; Poprawski, R.; Ciżman, A.; Sieradzki, A.

    The aim of this work is to develop a technique of introducing selected ferroelectric materials (TGS, NaNO2, NaNO3, KNO3, ADP and KDP) into porous glasses with various average pore dimensions. The major efforts have been focused on the investigations of the influence of the pore size on physical properties and phase transition of nanocrystals embedded into porous matrix with different methods. The ferroelectrics have been introduced into porous glasses from the melt and a water solution. The results of electrical (dielectric, pyroelectric) and thermal (dilatometric and calorimetric) measurements have shown that the observed sequences of phase transitions in ferroelectric materials embedded into the porous glasses are similar to that in bulk crystals. The relationship between phase transition and melt temperatures versus average values of pore dimensions has been determined. The experimentally observed shift of phase transition temperatures is the superposition of the size effect and pressure effect created by the difference of thermal expansion coefficients of ferroelectrics nanoparticles and glass matrix.

  5. Porous silicon based anode material formed using metal reduction

    SciTech Connect

    Anguchamy, Yogesh Kumar; Masarapu, Charan; Deng, Haixia; Han, Yongbong; Venkatachalam, Subramanian; Kumar, Sujeet; Lopez, Herman A.

    2015-09-22

    A porous silicon based material comprising porous crystalline elemental silicon formed by reducing silicon dioxide with a reducing metal in a heating process followed by acid etching is used to construct negative electrode used in lithium ion batteries. Gradual temperature heating ramp(s) with optional temperature steps can be used to perform the heating process. The porous silicon formed has a high surface area from about 10 m.sup.2/g to about 200 m.sup.2/g and is substantially free of carbon. The negative electrode formed can have a discharge specific capacity of at least 1800 mAh/g at rate of C/3 discharged from 1.5V to 0.005V against lithium with in some embodiments loading levels ranging from about 1.4 mg/cm.sup.2 to about 3.5 mg/cm.sup.2. In some embodiments, the porous silicon can be coated with a carbon coating or blended with carbon nanofibers or other conductive carbon material.

  6. Bacteria transport through porous material: Final technical report

    SciTech Connect

    Yen, T.F.

    1989-02-13

    The injection and penetration of bacteria into a reservoir is the most problematic and crucial of the steps in microbial enhanced recovery (MEOR). In the last phase of our work valuable information on bacterial transport in porous media was obtained. A great deal of progress was made to determine chemical bonding characteristics between adsorbed bacteria and the rock surfaces. In order to further enhance our knowledge of the effects of surface tensions on bacteria transport through porous media, a new approach was taken to illustrate the effect of liquid surface tension on bacterial transport through a sandpack column. Work in surface charge characterization of reservoir rock as a composite oxide system was also accomplished. In the last section of this report a mathematical model to simulate the simultaneous diffusion and growth of bacteria cells in a nutrient-enriched porous media is proposed.

  7. Combustion Synthesis of Advanced Porous Materials in Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Johnson, D. P.

    1999-01-01

    Combustion synthesis, otherwise known as self-propagating high temperature synthesis (SHS), can be used to produce engineered advanced porous material implants which offer the possibility for bone ingrowth as well as a permanent structure framework for the long-term replacement of bone defects. The primary advantage of SHS is based on its rapid kinetics and favorable energetics. The structure and properties of materials produced by SHS are strongly dependent on the combustion reaction conditions. Combustion reaction conditions such as reaction stoichiometry, particle size, green density, the presence and use of diluents or inert reactants, and pre-heating of the reactants, will affect the exothermicity of the reaction. A number of conditions must be satisfied in order to obtain high porosity materials: an optimal amount of liquid, gas and solid phases must be present in the combustion front. Therefore, a balance among these phases at the combustion front must be created by the SHS reaction to successfully engineer a bone replacement material system. Microgravity testing has extended the ability to form porous products. The convective heat transfer mechanisms which operate in normal gravity, 1 g, constrain the combustion synthesis reactions. Gravity also acts to limit the porosity which may be formed as the force of gravity serves to restrict the gas expansion and the liquid movement during reaction. Infiltration of the porous product with other phases can modify both the extent of porosity and the mechanical properties.

  8. Characterisation of porous materials for bioseparation.

    PubMed

    Barrande, M; Beurroies, I; Denoyel, R; Tatárová, I; Gramblicka, M; Polakovic, M; Joehnck, M; Schulte, M

    2009-10-01

    A set of chromatographic materials for bioseparation were characterised by various methods. Both commercial materials and new supports presenting various levels of rigidity were analysed. The methods included size-exclusion and capillary phenomena based techniques. Both batch exclusion and inverse size-exclusion chromatography were used. Gas adsorption, mercury porosimetry and thermoporometry were applied as well as a new method based on water desorption starting from the saturated state. When the rigidity of adsorbents is high enough, the agreement is reasonable between the values of the structural parameters that were determined (surface area, porosity, and pore size) by various methods. Nevertheless, a part of macroporosity may not be evidenced by inverse size-exclusion chromatography whereas it is visible by batch exclusion and the other methods. When the rigidity decreases, for example with soft swelling gels, where standard nitrogen adsorption or mercury porosimetry are no more reliable, two main situations are encountered: either the methods based on capillary phenomena (thermoporometry or water desorption) overestimate the pore size with an amplitude that depends on the method, or in some cases it is possible to distinguish water involved in the swelling of pore walls from that involved in pore filling by capillary condensation. PMID:19740472

  9. Drying of porous materials in a medium with variable potentials

    SciTech Connect

    Liu, J.Y. )

    1991-08-01

    This paper presents an application of the Luikov system of heat and mass transfer equations in dimensionless form to predict the temperature and moisture distributions in a slab of capillary-porous material during drying. The heat and mass potentials of the external medium in the boundary conditions are assumed to vary linearly with time. The method of solution is illustrated by considering the drying of a slab of lumber. Numerical results based on the estimated thermophysical properties of spruce are presented.

  10. Elastic properties of model 3-D porous ceramics and foams

    NASA Astrophysics Data System (ADS)

    Roberts, Anthony; Garboczi, Edward

    2000-03-01

    The novel properties of many new porous materials are related to their interesting internal microstructure. Apart from simple cases, there exist no theoretical means of predicting the bulk properties of these materials. This limits our ability to guide microstructure optimization for a particular purpose. We use a large scale finite element method to demonstrate the complex relationship between microstructure and the effective properties of realistic three-dimensional model porous ceramics and foams. We find that pore-shape and interconnectivity strongly influence the properties of sintered ceramics. For porous foams we have studied the role of coordination number, random disorder, and strut shape on the Young's modulus and Poisson's ratio. We find that that Voronoi tesselations, commonly used to model solid foams, show unphysical behavior, in particular they are incompressible (rubber-like) at low densities. Deletion of just 10% of the bonds in the model reduces the bulk modulus by 75%, more in line with experimental evidence. The FEM results are generally in good agreement with experimental data for ceramics and foams, and can be used as both a predictive and interpretative tool by experimentalists.

  11. Sound Transmission Through Multi-Panel Structures Lined with Elastic Porous Materials

    NASA Astrophysics Data System (ADS)

    Bolton, J. S.; Shiau, N.-M.; Kang, Y. J.

    1996-04-01

    Theory and measurements related to sound transmission through double panels lined with elastic porous media are presented. The information has application to the design of noise control barriers and to the optimization of aircraft fuselage transmission loss, for example. The major difference between the work described here and earlier research in this field relates to the treatment of the porous material that is used to line the cavity between the two panels of the double panel structure. Here we have used the porous material theory proposed by Biot since it takes explicit account of all the wave types known to propagate in elastic porous materials. As a result, it is possible to use the theory presented here to calculate the transmission loss of lined double panels at arbitrary angles of incidence; results calculated over a range of incidence angles may then be combined to yield the random incidence transmission loss. In this paper, the equations governing wave propagation in an elastic porous material are first considered briefly and then the general forms for the stresses and displacements within the porous material are given. Those solutions are expressed in terms of a number of constants that can be determined by application of appropriate boundary conditions. The boundary conditions required to model double panels having linings that are either directly attached to the facing panels or separated?!from them by air gaps are presented and discussed. Measurements of the random incidence transmission loss of aluminium double-panel structures lined with polyurethane foam are presented and have been found to be in good agreement with theoretical predictions. Both the theoretical predictions and the measured results have shown that the method by which an elastic porous lining material is attached to the facing panels can have a profound influence on the transmission loss of the panel system. It has been found, for example, that treatments in which the lining material

  12. Gravitational Effects on Combustion Synthesis of Advanced Porous Materials

    NASA Technical Reports Server (NTRS)

    Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Thorne, K.

    2000-01-01

    Combustion Synthesis (self-Propagating high-temperature synthesis-(SHS)) of porous Ti-TiB(x), composite materials has been studied with respect to the sensitivity to the SHS reaction parameters of stoichiometry, green density, gasifying agents, ambient pressure, diluents and gravity. The main objective of this research program is to engineer the required porosity and mechanical properties into the composite materials to meet the requirements of a consumer, such as for the application of bone replacement materials. Gravity serves to restrict the gas expansion and the liquid movement during SHS reaction. As a result, gravitational forces affect the microstructure and properties of the SHS products. Reacting these SHS systems in low gravity in the KC-135 aircraft has extended the ability to form porous products. This paper will emphasize the effects of gravity (low g, 1g and 2g) on the SHS reaction process, and the microstructure and properties of the porous composite. Some of biomedical results are also discussed.

  13. A Compaction Model for Highly Porous Silica Powder.

    NASA Astrophysics Data System (ADS)

    Church, P. D.; Tsembelis, K.

    2005-07-01

    This paper describes research to develop an equation of state to describe the behaviour of a highly porous silica powder. It shows that whilst molecular modelling techniques can be readily applied to develop a description of a compact material the description of the compaction process is more problematic. An empirical model, based upon the Lennard-Jones potential, has been shown to be capable of describing the compaction process observed in simple experiments. This development and application of the model in the Eulerian hydrocode GRIM to reproduce experimental plate impact data over a wide range of impact velocities is described and the results compared with experimental data.

  14. Recent Advances on Fractal Modeling of Permeability for Fibrous Porous Media

    NASA Astrophysics Data System (ADS)

    Cai, Jianchao; Luo, Liang; Ye, Ran; Zeng, Xiangfeng; Hu, Xiangyun

    2015-03-01

    Permeability is an important hydraulic parameter for characterizing heat and mass transfer properties of fibrous porous media. However, it is difficult to be quantitatively predicted due to the complex and irregular pore structure of fibrous porous media. Fractal geometry has been verified to be an effective method for determining the permeability of fibrous porous media. In this study, recent works on the permeability of fibrous porous media by means of fractal geometry are reviewed, the advances for each presented fractal model are analyzed and summarized, parameter equations used in available fractal permeability models are also briefly compared and reviewed. Future work for more generalized permeability model of fibrous porous media need to conducted by considering the special characters of fibrous materials, uniform pore structure parameter model and the influence factor of capillary pressure, electrokinetic phenomena, etc.

  15. Coupled hydromechanical and electromagnetic disturbances in unsaturated porous materials

    PubMed Central

    Revil, A; Mahardika, H

    2013-01-01

    A theory of cross-coupled flow equations in unsaturated soils is necessary to predict (1) electroosmotic flow with application to electroremediation and agriculture, (2) the electroseismic and the seismoelectric effects to develop new geophysical methods to characterize the vadose zone, and (3) the streaming current, which can be used to investigate remotely ground water flow in unsaturated conditions in the capillary water regime. To develop such a theory, the cross-coupled generalized Darcy and Ohm constitutive equations of transport are extended to unsaturated conditions. This model accounts for inertial effects and for the polarization of porous materials. Rather than using the zeta potential, like in conventional theories for the saturated case, the key parameter used here is the quasi-static volumetric charge density of the pore space, which can be directly computed from the quasi-static permeability. The apparent permeability entering Darcy's law is also frequency dependent with a critical relaxation time that is, in turn, dependent on saturation. A decrease of saturation increases the associated relaxation frequency. The final form of the equations couples the Maxwell equations and a simplified form of two-fluid phases Biot theory accounting for water saturation. A generalized expression of the Richard equation is derived, accounting for the effect of the vibration of the skeleton during the passage of seismic waves and the electrical field. A new expression is obtained for the effective stress tensor. The model is tested against experimental data regarding the saturation and frequency dependence of the streaming potential coupling coefficient. The model is also adapted for two-phase flow conditions and a numerical application is shown for water flooding of a nonaqueous phase liquid (NAPL, oil) contaminated aquifer. Seismoelectric conversions are mostly taking place at the NAPL (oil)/water encroachment front and can be therefore used to remotely track the

  16. Coupled hydromechanical and electromagnetic disturbances in unsaturated porous materials.

    PubMed

    Revil, A; Mahardika, H

    2013-02-01

    A theory of cross-coupled flow equations in unsaturated soils is necessary to predict (1) electroosmotic flow with application to electroremediation and agriculture, (2) the electroseismic and the seismoelectric effects to develop new geophysical methods to characterize the vadose zone, and (3) the streaming current, which can be used to investigate remotely ground water flow in unsaturated conditions in the capillary water regime. To develop such a theory, the cross-coupled generalized Darcy and Ohm constitutive equations of transport are extended to unsaturated conditions. This model accounts for inertial effects and for the polarization of porous materials. Rather than using the zeta potential, like in conventional theories for the saturated case, the key parameter used here is the quasi-static volumetric charge density of the pore space, which can be directly computed from the quasi-static permeability. The apparent permeability entering Darcy's law is also frequency dependent with a critical relaxation time that is, in turn, dependent on saturation. A decrease of saturation increases the associated relaxation frequency. The final form of the equations couples the Maxwell equations and a simplified form of two-fluid phases Biot theory accounting for water saturation. A generalized expression of the Richard equation is derived, accounting for the effect of the vibration of the skeleton during the passage of seismic waves and the electrical field. A new expression is obtained for the effective stress tensor. The model is tested against experimental data regarding the saturation and frequency dependence of the streaming potential coupling coefficient. The model is also adapted for two-phase flow conditions and a numerical application is shown for water flooding of a nonaqueous phase liquid (NAPL, oil) contaminated aquifer. Seismoelectric conversions are mostly taking place at the NAPL (oil)/water encroachment front and can be therefore used to remotely track the

  17. Supercritical nitrogen processing for the purification of reactive porous materials.

    PubMed

    Stadie, Nicholas P; Callini, Elsa; Mauron, Philippe; Borgschulte, Andreas; Züttel, Andreas

    2015-01-01

    Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml(-1), modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 Å. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride. PMID:26066492

  18. Fundamental problems in porous materials: Experiments & computer simulation

    NASA Astrophysics Data System (ADS)

    Xu, Zhanping

    Porous materials have attracted massive scientific and technological interest because of their extremely high surface-to-volume ratio, molecular tunability in construction, and surface-based applications. Through my PhD work, porous materials were engineered to meet the design in selective binding, self-healing, and energy damping. For example, crystalline MOFs with pore size spanning from a few angstroms to a couple of nanometers were chemically engineered to show 120 times more efficiency in binding of large molecules. In addition, we found building blocks released from those crystals can be further patched back through a healing process at ambient and low temperatures down to -56 °C. When building blocks are replaced with graphenes, ultra-flyweight aerogels with pore size larger than 100 nm were made to delay shock waves. More stable rigid porous metal with larger pores (~um) was also fabricated, and its performance and survivability are under investigation. Aside from experimental studies, we also successfully applied numerical simulations to study the mutual interaction between the nonplanar liquid-solid interface and colloidal particles during the freezing of the colloidal suspensions. Colloidal particles can be either rejected or engulfed by the evolving interface depending on the freezing speed and strength of interface-particle interaction. Our interactive simulation was achieved by programming both simulation module and visualization module on high performance GPU devices.

  19. Method of preparing thin porous sheets of ceramic material

    DOEpatents

    Swarr, Thomas E.; Nickols, Richard C.; Krasij, Myron

    1987-03-24

    A method of forming thin porous sheets of ceramic material for use as electrodes or other components in a molten carbonate fuel cell is disclosed. The method involves spray drying a slurry of fine ceramic particles in liquid carrier to produce generally spherical agglomerates of high porosity and a rough surface texture. The ceramic particles may include the electrode catalyst and the agglomerates can be calcined to improve mechanical strength. After slurrying with suitable volatile material and binder tape casting is used to form sheets that are sufficiently strong for further processing and handling in the assembly of a high temperature fuel cell.

  20. Method of preparing thin porous sheets of ceramic material

    DOEpatents

    Swarr, T.E.; Nickols, R.C.; Krasij, M.

    1984-05-23

    A method of forming thin porous sheets of ceramic material for use as electrodes or other components in a molten carbonate fuel cell is disclosed. The method involves spray drying a slurry of fine ceramic particles in liquid carrier to produce generally spherical agglomerates of high porosity and a rough surface texture. The ceramic particles may include the electrode catalyst and the agglomerates can be calcined to improve mechanical strength. After slurrying with suitable volatile material and binder tape casting is used to form sheets that are sufficiently strong for further processing and handling in the assembly of a high temperature fuel cell.

  1. Solvent extraction of polychlorinated organic compounds from porous materials

    SciTech Connect

    Knowles, V.M.

    1988-07-19

    A method of reducing the level of hexachlorinated organic compounds selected from hexachloroethane, hexachlorobutadiene, hexachlorobenzene, or mixtures thereof to a non-hazardous level in a solid, porous DERAKANE vinyl ester resin, which has been previously used as the material of construction of a cell to produce chlorine, which vinyl ester resin was in contact with chlorine during chlorine manufacture is descried which comprises: (a) contacting the hexachlorinated compound-containing porous vinyl ester resin with an extraction solvent wherein the extraction solvent is selected from chloroform, carbon tetrachloride, trichlorethane, methyl chloroform, tetrachloroethane, perchloroethylene, benzene, toluene, xylene, acetone, methyl ethyl ketone, or mixtures thereof, at a temperature and for a time sufficient to remove the absorbed hexachlorinated organic compound; and (b) separating the hexachlorianated organic compound-containing extraction solvent and vinyl ester resin.

  2. Ceramic porous material and method of making same

    DOEpatents

    Liu, Jun; Kim, Anthony Y.; Virden, Jud W.

    1997-01-01

    The invention is a mesoporous ceramic membrane having substantially uniform pore size. Additionally, the invention includes aqueous and non-aqueous processing routes to making the mesoporous ceramic membranes. According to one aspect of the present invention, inserting a substrate into a reaction chamber at pressure results in reaction products collecting on the substrate and forming a membrane thereon. According to another aspect of the present invention, a second aqueous solution that is sufficiently immiscible in the aqueous solution provides an interface between the two solutions whereon the mesoporous membrane is formed. According to a further aspect of the present invention, a porous substrate is placed at the interface between the two solutions permitting formation of a membrane on the surface or within the pores of the porous substrate. According to yet another aspect of the present invention, mesoporous ceramic materials are formed using a non-aqueous solvent and water-sensitive precursors.

  3. Ceramic porous material and method of making same

    DOEpatents

    Liu, J.; Kim, A.Y.; Virden, J.W.

    1997-07-08

    The invention is a mesoporous ceramic membrane having substantially uniform pore size. Additionally, the invention includes aqueous and non-aqueous processing routes to making the mesoporous ceramic membranes. According to one aspect of the present invention, inserting a substrate into a reaction chamber at pressure results in reaction products collecting on the substrate and forming a membrane thereon. According to another aspect of the present invention, a second aqueous solution that is sufficiently immiscible in the aqueous solution provides an interface between the two solutions whereon the mesoporous membrane is formed. According to a further aspect of the present invention, a porous substrate is placed at the interface between the two solutions permitting formation of a membrane on the surface or within the pores of the porous substrate. According to yet another aspect of the present invention, mesoporous ceramic materials are formed using a non-aqueous solvent and water-sensitive precursors. 21 figs.

  4. Supported metal nanoparticles on porous materials. Methods and applications.

    PubMed

    White, Robin J; Luque, Rafael; Budarin, Vitaliy L; Clark, James H; Macquarrie, Duncan J

    2009-02-01

    Nanoparticles are regarded as a major step forward to achieving the miniaturisation and nanoscaling effects and properties that have been utilised by nature for millions of years. The chemist is no longer observing and describing the behaviour of matter but is now able to manipulate and produce new types of materials with specific desired physicochemical characteristics. Such materials are receiving extensive attention across a broad range of research disciplines. The fusion between nanoparticle and nanoporous materials technology represents one of the most interesting of these rapidly expanding areas. The harnessing of nanoscale activity and selectivity, potentially provides extremely efficient catalytic materials for the production of commodity chemicals, and energy needed for a future sustainable society. In this tutorial review, we present an introduction to the field of supported metal nanoparticles (SMNPs) on porous materials, focusing on their preparation and applications in different areas. PMID:19169462

  5. Porous materials for thermal management under extreme conditions.

    PubMed

    Clyne, T W; Golosnoy, I O; Tan, J C; Markaki, A E

    2006-01-15

    A brief analysis is presented of how heat transfer takes place in porous materials of various types. The emphasis is on materials able to withstand extremes of temperature, gas pressure, irradiation, etc. i.e. metals and ceramics, rather than polymers. A primary aim is commonly to maximize either the thermal resistance (i.e. provide insulation) or the rate of thermal equilibration between the material and a fluid passing through it (i.e. to facilitate heat exchange). The main structural characteristics concern porosity (void content), anisotropy, pore connectivity and scale. The effect of scale is complex, since the permeability decreases as the structure is refined, but the interfacial area for fluid-solid heat exchange is, thereby, raised. The durability of the pore structure may also be an issue, with a possible disadvantage of finer scale structures being poor microstructural stability under service conditions. Finally, good mechanical properties may be required, since the development of thermal gradients, high fluid fluxes, etc. can generate substantial levels of stress. There are, thus, some complex interplays between service conditions, pore architecture/scale, fluid permeation characteristics, convective heat flow, thermal conduction and radiative heat transfer. Such interplays are illustrated with reference to three examples: (i) a thermal barrier coating in a gas turbine engine; (ii) a Space Shuttle tile; and (iii) a Stirling engine heat exchanger. Highly porous, permeable materials are often made by bonding fibres together into a network structure and much of the analysis presented here is oriented towards such materials. PMID:18272456

  6. Measuring static thermal permeability and inertial factor of rigid porous materials (L).

    PubMed

    Sadouki, M; Fellah, M; Fellah, Z E A; Ogam, E; Sebaa, N; Mitri, F G; Depollier, C

    2011-11-01

    An acoustic method based on sound transmission is proposed for deducing the static thermal permeability and the inertial factor of porous materials having a rigid frame at low frequencies. The static thermal permeability of porous material is a geometrical parameter equal to the inverse trapping constant of the solid frame [Lafarge et al., J. Acoust. Soc. Am. 102, 1995 (1997)] and is an important characteristic of the porous material. The inertial factor [Norris., J. Wave Mat. Interact. 1, 365 (1986)] describes the fluid structure interactions in the low frequency range (1-3 kHz). The proposed method is based on a temporal model of the direct and inverse scattering problems for the propagation of transient audible frequency waves in a homogeneous isotropic slab of porous material having a rigid frame. The static thermal permeability and the inertial factor are determined from the solution of the inverse problem. The minimization between experiment and theory is made in the time domain. Tests are performed using industrial plastic foams. Experimental and theoretical data are in good agreement. Furthermore, the prospects are discussed. This method has the advantage of being simple, rapid, and efficient. PMID:22087887

  7. Avalanches in compressed porous SiO(2)-based materials.

    PubMed

    Nataf, Guillaume F; Castillo-Villa, Pedro O; Baró, Jordi; Illa, Xavier; Vives, Eduard; Planes, Antoni; Salje, Ekhard K H

    2014-08-01

    The failure dynamics in SiO(2)-based porous materials under compression, namely the synthetic glass Gelsil and three natural sandstones, has been studied for slowly increasing compressive uniaxial stress with rates between 0.2 and 2.8 kPa/s. The measured collapsed dynamics is similar to Vycor, which is another synthetic porous SiO(2) glass similar to Gelsil but with a different porous mesostructure. Compression occurs by jerks of strain release and a major collapse at the failure point. The acoustic emission and shrinking of the samples during jerks are measured and analyzed. The energy of acoustic emission events, its duration, and waiting times between events show that the failure process follows avalanche criticality with power law statistics over ca. 4 decades with a power law exponent ɛ≃ 1.4 for the energy distribution. This exponent is consistent with the mean-field value for the collapse of granular media. Besides the absence of length, energy, and time scales, we demonstrate the existence of aftershock correlations during the failure process. PMID:25215740

  8. Modeling transport phenomena in porous media

    SciTech Connect

    Bear, J.

    1996-12-31

    The paper reviews the continuum approach to modelling the transport of mass, momentum and energy, of phases and of their components in a porous medium domain. The review begins with the definition of a porous medium, making use of the concept of a Representative Elementary Volume (REV) as a tool for overcoming the effect of the microscopic heterogeneity resulting from the presence of a solid matrix and a void space. The microscopic and macroscopic levels of description are defined. By averaging the description of a transport phenomenon at the microscopic level over an REV, using certain {open_quote}averaging rules{close_quote}, the macroscopic or continuum description of the same phenomenon is obtained. This methodology is first introduced in general terms for any extensive quantity, and then demonstrated for the transport of mass, momentum and energy. In the process of deriving the macroscopic models, expressions are presented also for the advective, dispersive and diffusive fluxes of extensive quantities that appear in them, in terms of averaged, measurable values of state variables.

  9. Biodegradable elastic patch plasty ameliorates left ventricular adverse remodeling after ischemia–reperfusion injury: A preclinical study of a porous polyurethane material in a porcine model

    PubMed Central

    Hashizume, Ryotaro; Fujimoto, Kazuro L.; Hong, Yi; Guan, Jianjun; Toma, Catalin; Tobita, Kimimasa; Wagner, William R.

    2013-01-01

    Objective Myocardial infarction (MI) can lead to irreversible adverse left ventricular remodeling resulting in subsequent severe dysfunction. The objective of this study was to investigate the potential for biodegradable, elastomeric patch implantation to positively alter the remodeling process after MI in a porcine model. Methods Yorkshire pigs underwent a 60-minute catheter balloon occlusion of the left circumflex artery. Two weeks after MI animals underwent epicardial placement of a biodegradable, porous polyurethane (poly(ester urethane)urea; PEUU) patch (MI+PEUU, n = 7) or sham surgery (MI+sham, n = 8). Echocardiography before surgery and at 4 and 8 weeks after surgery measured the end-diastolic area (EDA) and fractional area change (% FAC). All animals were humanely killed 8 weeks after surgery and hearts were histologically assessed. Results At 8 weeks, echocardiography revealed greater EDA values in the MI+sham group (23.6 ± 6.6 cm2 , mean ± standard deviaation) than in the MI+PEUU group (15.9 ± 2.5 cm2) (P < .05) and a lower %FAC in the MI+sham group (24.8 ± 7.6) than in the MI+PEUU group (35.9 ± 7.8) (P < .05). The infarcted ventricular wall was thicker in the MI+PEUU group (1.56 ± 0.5 cm) than in the MI+sham group (0.91 ± 0.24 cm) (P < .01). Conclusions Biodegradable elastomeric PEUU patch implantation onto the porcine heart 2 weeks post-MI attenuated left ventricular adverse remodeling and functional deterioration and was accompanied by increased neovascularization. These findings, although limited to a 2-month follow-up, may suggest an attractive clinical option to moderate post-MI cardiac failure. PMID:23219497

  10. Advanced Porous Coating for Low-Density Ceramic Insulation Materials

    NASA Technical Reports Server (NTRS)

    Leiser, Daniel B.; Churchward, Rex; Katvala, Victor; Stewart, David; Balter, Aliza

    1988-01-01

    The need for improved coatings on low-density reusable surface insulation (RSI) materials used on the space shuttle has stimulated research into developing tougher coatings. The processing of a new porous composite "coating" for RST called toughened unipiece fibrous insulation Is discussed. Characteristics including performance in a simulated high-speed atmospheric entry, morphological structure before and after this exposure, resistance to Impact, and thermal response to a typical heat pulse are described. It is shown that this coating has improved impact resistance while maintaining optical and thermal properties comparable to the previously available reaction-cured glass coating.

  11. MAS PFG NMR Studies of Mixtures in Porous Materials

    NASA Astrophysics Data System (ADS)

    Gratz, Marcel; Hertel, Stefan; Wehring, Markus; Schlayer, Stefan; Stallmach, Frank; Galvosas, Petrik

    2011-03-01

    Pulsed field gradient (PFG) and magic angle spinning (MAS) NMR techniques have been successfully combined for the study of mixture diffusion in porous materials. Using a modular setup of commercially available components, gradient pulses of up to ±2.6 T/m can be applied coinciding with fast sample rotation at the magic angle. Methods for the proper alignment of all components are presented along with protocols for MAS PFG NMR experiments. Finally, first diffusion measurements of n-hexane and benzene being adsorbed together in the metal-organic framework MOF-5 are presented.

  12. Synergistic Carbon Dioxide Capture and Conversion in Porous Materials.

    PubMed

    Zhang, Yugen; Lim, Diane S W

    2015-08-24

    Global climate change and excessive CO2 emissions have caused widespread public concern in recent years. Tremendous efforts have been made towards CO2 capture and conversion. This has led to the development of numerous porous materials as CO2 capture sorbents. Concurrently, the conversion of CO2 into value-added products by chemical methods has also been well-documented recently. However, realizing the attractive prospect of direct, in situ chemical conversion of captured CO2 into other chemicals remains a challenge. PMID:26216701

  13. (De)compaction of porous viscoelastoplastic media: Model formulation

    NASA Astrophysics Data System (ADS)

    Yarushina, Viktoriya M.; Podladchikov, Yuri Y.

    2015-06-01

    A nonlinear viscoelastoplastic theory is developed for porous rate-dependent materials filled with a fluid in the presence of gravity. The theory is based on a rigorous thermodynamic formalism suitable for path-dependent and irreversible processes. Incremental evolution equations for porosity, Darcy's flux, and volumetric deformation of the matrix represent the simplest generalization of Biot's equations. Expressions for pore compressibility and effective bulk viscosity are given for idealized cylindrical and spherical pore geometries in an elastic-viscoplastic material with low pore concentration. We show that plastic yielding around pores leads to decompaction weakening and an exponential creep law. Viscous and plastic end-members of our model are consistent with experimentally verified models. In the poroelastic limit, our constitutive equations reproduce the exact Gassmann's relations, Biot's theory, and Terzaghi's effective stress law. The nature of the discrepancy between Biot's model and the True Porous Media theory is clarified. Our model provides a unified and consistent formulation for the elastic, viscous, and plastic cases that have previously been described by separate "end-member" models.

  14. Basalt fiber reinforced porous aggregates-geopolymer based cellular material

    NASA Astrophysics Data System (ADS)

    Luo, Xin; Xu, Jin-Yu; Li, Weimin

    2015-09-01

    Basalt fiber reinforced porous aggregates-geopolymer based cellular material (BFRPGCM) was prepared. The stress-strain curve has been worked out. The ideal energy-absorbing efficiency has been analyzed and the application prospect has been explored. The results show the following: fiber reinforced cellular material has successively sized pore structures; the stress-strain curve has two stages: elastic stage and yielding plateau stage; the greatest value of the ideal energy-absorbing efficiency of BFRPGCM is 89.11%, which suggests BFRPGCM has excellent energy-absorbing property. Thus, it can be seen that BFRPGCM is easy and simple to make, has high plasticity, low density and excellent energy-absorbing features. So, BFRPGCM is a promising energy-absorbing material used especially in civil defense engineering.

  15. The usable capacity of porous materials for hydrogen storage

    NASA Astrophysics Data System (ADS)

    Schlichtenmayer, Maurice; Hirscher, Michael

    2016-04-01

    A large number of different porous materials has been investigated for their hydrogen uptake over a wide pressure range and at different temperature. From the absolute adsorption isotherms, the enthalpy of adsorption is evaluated for a wide range of surface coverage. The usable capacity, defined as the amount of hydrogen released between a maximum tank pressure and a minimum back pressure for a fuel cell, is analyzed for isothermal operation. The usable capacity as a function of temperature shows a maximum which defines the optimum operating temperature. This optimum operating temperature is higher for materials possessing a higher enthalpy of adsorption. However, the fraction of the hydrogen stored overall that can be released at the optimum operating temperature is higher for materials with a lower enthalpy of adsorption than for the ones with higher enthalpy.

  16. Anomalous reactive transport in porous media: Experiments and modeling

    NASA Astrophysics Data System (ADS)

    Edery, Yaniv; Dror, Ishai; Scher, Harvey; Berkowitz, Brian

    2015-05-01

    We analyze dynamic behavior of chemically reactive species in a porous medium, subject to anomalous transport. In this context, we present transport experiments in a refraction-index-matched, three-dimensional, water-saturated porous medium. A pH indicator (Congo red) was used as either a conservative or a reactive tracer, depending on the tracer solution pH relative to that of the background solution. The porous medium consisted of an acrylic polymer material formed as spherical beads that have pH-buffering capacity. The magnitude of reaction during transport through the porous medium was related to the color change of the Congo red, via image analysis. Here, we focused on point injection of the tracer into a macroscopically uniform flow field containing water at a pH different from that of the injected tracer. The setup yielded measurements of the temporally evolving spatial (local-in-space) concentration field. Parallel experiments with the same tracer, but without reactions (no changes in pH), enabled identification of the transport itself to be anomalous (non-Fickian); this was quantified by a continuous time random walk (CTRW) formulation. A CTRW particle tracking model was then used to quantify the spatial and temporal migration of both the conservative and reactive tracer plumes. Model parameters related to the anomalous transport were determined from the conservative tracer experiments. An additional term accounting for chemical reaction was established solely from analysis of the reactant concentrations, and significantly, no other fitting parameters were required. The measurements and analysis emphasized the localized nature of reaction, caused by small-scale concentration fluctuations and preferential pathways. In addition, a threshold radius for pH-controlled reactive transport processes was defined under buffering conditions, which delineated the region in which reactions occurred rapidly.

  17. High Velocity Impact Interaction of Metal Particles with Porous Heterogeneous Materials with an Inorganic Matrix

    NASA Astrophysics Data System (ADS)

    Glazunov, A. A.; Ishchenko, A. N.; Afanasyeva, S. A.; Belov, N. N.; Burkin, V. V.; Rogaev, K. S.; Tabachenko, A. N.; Khabibulin, M. V.; Yugov, N. T.

    2016-03-01

    A computational-experimental investigation of stress-strain state and fracture of a porous heterogeneous material with an inorganic matrix, used as a thermal barrier coating of flying vehicles, under conditions of a high-velocity impact by a spherical steel projectile imitating a meteorite particle is discussed. Ballistic tests are performed at the velocities about 2.5 km/s. Numerical modeling of the high-velocity impact is described within the framework of a porous elastoplastic model including fracture and different phase states of the materials. The calculations are performed using the Euler and Lagrange numerical techniques for the velocities up to 10 km/s in a complete-space problem statement.

  18. Porous Media Approach for Modeling Closed Cell Foam

    NASA Technical Reports Server (NTRS)

    Ghosn, Louis J.; Sullivan, Roy M.

    2006-01-01

    In order to minimize boil off of the liquid oxygen and liquid hydrogen and to prevent the formation of ice on its exterior surface, the Space Shuttle External Tank (ET) is insulated using various low-density, closed-cell polymeric foams. Improved analysis methods for these foam materials are needed to predict the foam structural response and to help identify the foam fracture behavior in order to help minimize foam shedding occurrences. This presentation describes a continuum based approach to modeling the foam thermo-mechanical behavior that accounts for the cellular nature of the material and explicitly addresses the effect of the internal cell gas pressure. A porous media approach is implemented in a finite element frame work to model the mechanical behavior of the closed cell foam. The ABAQUS general purpose finite element program is used to simulate the continuum behavior of the foam. The soil mechanics element is implemented to account for the cell internal pressure and its effect on the stress and strain fields. The pressure variation inside the closed cells is calculated using the ideal gas laws. The soil mechanics element is compatible with an orthotropic materials model to capture the different behavior between the rise and in-plane directions of the foam. The porous media approach is applied to model the foam thermal strain and calculate the foam effective coefficient of thermal expansion. The calculated foam coefficients of thermal expansion were able to simulate the measured thermal strain during heat up from cryogenic temperature to room temperature in vacuum. The porous media approach was applied to an insulated substrate with one inch foam and compared to a simple elastic solution without pore pressure. The porous media approach is also applied to model the foam mechanical behavior during subscale laboratory experiments. In this test, a foam layer sprayed on a metal substrate is subjected to a temperature variation while the metal substrate is

  19. Effects of grafting on porous metal ingrowth. A canine model.

    PubMed

    Lewis, C G; Jones, L C; Hungerford, D S

    1997-06-01

    Twenty-five mongrel dogs were studied using implantation of autograft, fresh-frozen allograft, and beta-tricalcium phosphate around a porous-coated chrome-cobalt plug in the distal femoral metaphysis; interference-fit and overreamed control specimens were also studied. Over the course of this 4-month study, bone ingrowth through the grouting materials into the center plug was noted for autologous, allograft, and ceramic specimens. Quantitatively, in terms of push-out strength and histology, there were no significant differences between grafted groups; significantly higher push-out strengths were attained in each grafted subgroup compared with nongrafted, overreamed control subjects. In the setting of uncemented revision total hip arthroplasty, bone-grafting is frequently required. Because of the limited availability of autogenous bone and the potential liabilities of allograft material, attention has been given to bone substitutes. On the basis of this preliminary study, bone ingrowth into a porous metal substrate has been documented to occur through autograft, allograft, or ceramic grouting agents. Within the limits of this nonloaded experimental model, it appears that these materials are comparable in terms of their osteoconductive capability. Even in the optimal laboratory situation, bone ingrowth does not appear to occur in a canine model across a nongrafted 2-mm gap with regularity over a 16-week period. PMID:9195322

  20. Freeze fracturing of elastic porous media: a mathematical model

    PubMed Central

    Vlahou, I.; Worster, M. G.

    2015-01-01

    We present a mathematical model of the fracturing of water-saturated rocks and other porous materials in cold climates. Ice growing inside porous rocks causes large pressures to develop that can significantly damage the rock. We study the growth of ice inside a penny-shaped cavity in a water-saturated porous rock and the consequent fracturing of the medium. Premelting of the ice against the rock, which results in thin films of unfrozen water forming between the ice and the rock, is one of the dominant processes of rock fracturing. We find that the fracture toughness of the rock, the size of pre-existing faults and the undercooling of the environment are the main parameters determining the susceptibility of a medium to fracturing. We also explore the dependence of the growth rates on the permeability and elasticity of the medium. Thin and fast-fracturing cracks are found for many types of rocks. We consider how the growth rate can be limited by the existence of pore ice, which decreases the permeability of a medium, and propose an expression for the effective ‘frozen’ permeability. PMID:25792954

  1. Gas-phase diffusion in porous media: Comparison of models

    SciTech Connect

    Webb, S.W.

    1998-09-01

    Two models are commonly used to analyze gas-phase diffusion in porous media in the presence of advection, the Advective-Dispersive Model (ADM) and the Dusty-gas Model (DGM). The ADM, which is used in TOUGH2, is based on a simple linear addition of advection calculated by Darcy`s law and ordinary diffusion using Fick`s law with a porosity-tortuosity-gas saturation multiplier to account for the porous medium. Another approach for gas-phase transport in porous media is the Dusty-Gas Model. This model applies the kinetic theory of gases to the gaseous components and the porous media (or dust) to combine transport due to diffusion and advection that includes porous medium effects. The two approaches are compared in this paper.

  2. Effective permeabilities for model heterogeneous porous media

    SciTech Connect

    Otevo, C.; Rusinek, I. ); Saez, A.E. )

    1990-01-01

    This paper presents a technique to evaluate effective absolute permeabilities for heterogeneous porous media. The technique is based on a perturbation analysis of the equations of motion of a slightly compressible fluid in a homogeneous porous medium at low Reynolds numbers. The effective permeabilities can be calculated once the local geometry of the heterogeneous medium is specified. The technique is used to evaluate two- and three-dimensional effective vertical permeabilities in porous media with shale intercalations, including the case in which the porous matrix is anisotropic.

  3. Characterization of porous carbon fibers and related materials

    SciTech Connect

    Fuller, E.L. Jr.

    1996-07-15

    This program was geared to support the Fossil Energy Material Sciences Program with respect to several areas of interest in efficient production and utilization of energy. Carbon molecular sieves have great potential for economically purifying gases; i.e. removal of carbon dioxide from natural gas without having to resort to cryogenic techniques. Microporous carbons can be tailored to serve as adsorbents for natural gas in on-board storage in automotive applications, avoiding high pressures and heavy storage tanks. This program is a laboratory study to evaluate production methodologies and activation processes to produce porous carbons for specific applications. The Carbon Materials Technology Group of Oak Ridge National Laboratory (ORNL) is engaged in developmental programs to produce activated carbon fibers (ACF) for applications in fixed beds and/or flowing reactors engineering applications.

  4. Porous graphene for high capacity lithium ion battery anode material

    NASA Astrophysics Data System (ADS)

    Wang, Yusheng; Zhang, Qiaoli; Jia, Min; Yang, Dapeng; Wang, Jianjun; Li, Meng; Zhang, Jing; Sun, Qiang; Jia, Yu

    2016-02-01

    Based on density functional theory calculations, we studied the Li dispersed on porous graphene (PG) for its application as Li ion battery anode material. The hybridization of Li atoms and the carbon atoms enhanced the interaction between Li atoms and the PG. With holes of specific size, the PG can provide excellent mobility with moderate barriers of 0.37-0.39 eV. The highest Li storage composite can be LiC0.75H0.38 which corresponds to a specific capacity of 2857.7 mA h/g. Both specific capacity and binding energy are significantly larger than the corresponding value of graphite, this makes PG a promising candidate for the anode material in battery applications. The interactions between the Li atoms and PG can be easily tuned by an applied strain. Under biaxial strain of 16%, the binding energy of Li to PG is increased by 17% compared to its unstrained state.

  5. Moisture storage parameters of porous building materials as time-dependent properties

    NASA Astrophysics Data System (ADS)

    Záleská, Martina; Pavlíková, Milena; Pavlík, Zbyšek

    2016-06-01

    Three different types of bricks and two different types of sandstones are studied in terms of measurement moisture storage parameters for over-hygroscopic moisture area using pressure plate device. For researched materials, basic physical properties as bulk density, matrix density and total open porosity are determined. From the obtained data of moisture storage measurement, the water retention curves and curves of degree of saturation in dependence on suction pressure are constructed. Water retention curve (also called suction curve, capillary potential curve, capillary-pressure function and capillary-moisture relationship) is the basic material property used in models for simulation of moisture storage in porous building materials.

  6. Quantitative properties of complex porous materials calculated from x-ray μCT images

    NASA Astrophysics Data System (ADS)

    Sheppard, Adrian P.; Arns, Christoph H.; Sakellariou, Arthur; Senden, Tim J.; Sok, Rob M.; Averdunk, Holger; Saadatfar, Mohammad; Limaye, Ajay; Knackstedt, Mark A.

    2006-08-01

    A microcomputed tomography (μCT) facility and computational infrastructure developed at the Department of Applied Mathematics at the Australian National University is described. The current experimental facility is capable of acquiring 3D images made up of 2000 3 voxels on porous specimens up to 60 mm diameter with resolutions down to 2 μm. This allows the three-dimensional (3D) pore-space of porous specimens to be imaged over several orders of magnitude. The computational infrastructure includes the establishment of optimised and distributed memory parallel algorithms for image reconstruction, novel phase identification, 3D visualisation, structural characterisation and prediction of mechanical and transport properties directly from digitised tomographic images. To date over 300 porous specimens exhibiting a wide variety of microstructure have been imaged and analysed. In this paper, analysis of a small set of porous rock specimens with structure ranging from unconsolidated sands to complex carbonates are illustrated. Computations made directly on the digitised tomographic images have been compared to laboratory measurements. The results are in excellent agreement. Additionally, local flow, diffusive and mechanical properties can be numerically derived from solutions of the relevant physical equations on the complex geometries; an experimentally intractable problem. Structural analysis of data sets includes grain and pore partitioning of the images. Local granular partitioning yields over 70,000 grains from a single image. Conventional grain size, shape and connectivity parameters are derived. The 3D organisation of grains can help in correlating grain size, shape and orientation to resultant physical properties. Pore network models generated from 3D images yield over 100000 pores and 200000 throats; comparing the pore structure for the different specimens illustrates the varied topology and geometry observed in porous rocks. This development foreshadows a new

  7. Pore-network study of the characteristic periods in the drying of porous materials.

    PubMed

    Yiotis, Andreas G; Tsimpanogiannis, Ioannis N; Stubos, Athanassios K; Yortsos, Yannis C

    2006-05-15

    We study the periods that develop in the drying of capillary porous media, particularly the constant rate (CRP) and the falling rate (FRP) periods. Drying is simulated with a 3-D pore-network model that accounts for the effect of capillarity and buoyancy at the liquid-gas interface and for diffusion through the porous material and through a boundary layer over the external surface of the material. We focus on the stabilizing or destabilizing effects of gravity on the shape of the drying curve and the relative extent of the various drying periods. The extents of CRP and FRP are directly associated with various transition points of the percolation theory, such as the breakthrough point and the main liquid cluster disconnection point. Our study demonstrates that when an external diffusive layer is present, the constant rate period is longer. PMID:16359693

  8. Estimation of moisture transport coefficients in porous materials using experimental drying kinetics

    NASA Astrophysics Data System (ADS)

    Zaknoune, A.; Glouannec, P.; Salagnac, P.

    2012-02-01

    From experimental drying kinetics, an inverse technique is used to evaluate the moisture transport coefficients in building hygroscopic porous materials. Based on the macroscopic approach developed by Whitaker, a one-dimensional mathematical model is developed to predict heat and mass transfers in porous material. The parameters identification is made by the minimisation of the square deviation between numerical and experimental values of the surface temperature and the average moisture content. Two parameters of an exponential function describing the liquid phase transfer and one parameter relative to the diffusion of the vapour phase are identified. To ensure the feasibility of the estimation method, it is initially validated with cellular concrete and applied to lime paste.

  9. Conductive porous scaffolds as potential neural interface materials.

    SciTech Connect

    Hedberg-Dirk, Elizabeth L.; Cicotte, Kirsten N.; Buerger, Stephen P.; Reece, Gregory; Dirk, Shawn M.; Lin, Patrick P.

    2011-11-01

    Our overall intent is to develop improved prosthetic devices with the use of nerve interfaces through which transected nerves may grow, such that small groups of nerve fibers come into close contact with electrode sites, each of which is connected to electronics external to the interface. These interfaces must be physically structured to allow nerve fibers to grow through them, either by being porous or by including specific channels for the axons. They must be mechanically compatible with nerves such that they promote growth and do not harm the nervous system, and biocompatible to promote nerve fiber growth and to allow close integration with biological tissue. They must exhibit selective and structured conductivity to allow the connection of electrode sites with external circuitry, and electrical properties must be tuned to enable the transmission of neural signals. Finally, the interfaces must be capable of being physically connected to external circuitry, e.g. through attached wires. We have utilized electrospinning as a tool to create conductive, porous networks of non-woven biocompatible fibers in order to meet the materials requirements for the neural interface. The biocompatible fibers were based on the known biocompatible material poly(dimethyl siloxane) (PDMS) as well as a newer biomaterial developed in our laboratories, poly(butylene fumarate) (PBF). Both of the polymers cannot be electrospun using conventional electrospinning techniques due to their low glass transition temperatures, so in situ crosslinking methodologies were developed to facilitate micro- and nano-fiber formation during electrospinning. The conductivity of the electrospun fiber mats was controlled by controlling the loading with multi-walled carbon nanotubes (MWNTs). Fabrication, electrical and materials characterization will be discussed along with initial in vivo experimental results.

  10. Theoretical and experimental investigation of acoustic streaming in a porous material

    NASA Astrophysics Data System (ADS)

    Poesio, Pietro; Ooms, Gijs; Schraven, Arthur; van der Bas, Fred

    2002-07-01

    An experimental and theoretical investigation of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material has been made. Particular attention was paid to the phenomenon of acoustic streaming of the liquid in the porous material due to the damping of the acoustic waves. The experiments were performed on Berea sandstone cores. Two acoustic horns were used with frequencies of 20 and 40 kHz, and with maximum power output of 2 and 0.7 kW, respectively. A high external pressure was applied in order to avoid cavitation. A microphone was used to measure the damping of the waves in the porous material and also temperature and pressure measurements in the flowing liquid inside the cores were carried out. To model the acoustic streaming effect Darcy's law was extended with a source term representing the momentum transfer from the acoustic waves to the liquid. The model predictions for the pressure distribution inside the core under acoustic streaming conditions are in reasonable agreement with the experimental data.

  11. Theoretical and experimental investigation of acoustic streaming in a porous material.

    PubMed

    Poesio, Pietro; Ooms, Gijs; Schraven, Arthur; van der Bas, Fred

    2002-07-01

    An experimental and theoretical investigation of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material has been made. Particular attention was paid to the phenomenon of acoustic streaming of the liquid in the porous material due to the damping of the acoustic waves. The experiments were performed on Berea sandstone cores. Two acoustic horns were used with frequencies of 20 and 40 kHz, and with maximum power output of 2 and 0.7 kW, respectively. A high external pressure was applied in order to avoid cavitation. A microphone was used to measure the damping of the waves in the porous material and also temperature and pressure measurements in the flowing liquid inside the cores were carried out. To model the acoustic streaming effect Darcy's law was extended with a source term representing the momentum transfer from the acoustic waves to the liquid. The model predictions for the pressure distribution inside the core under acoustic streaming conditions are in reasonable agreement with the experimental data. PMID:12241483

  12. Impact cratering and ejection of material on porous asteroids

    NASA Astrophysics Data System (ADS)

    Housen, K.; Sweet, W.

    2014-07-01

    increased lithostatic overburden stresses at large scales. When the target material has significant porosity, much of the crater volume forms by permanent compaction of void spaces. This compaction volume depends only on the crushing strength of the material, independent of size scale. The crater volume cannot be less than the volume created by compaction. Therefore, at large size scales, the cratering efficiency for porous materials levels out to a constant value rather than decreasing as in the usual gravity-dominated cratering. The transition to this asymptote represents the onset of compaction-dominated cratering. The presence of a compaction regime of cratering is important because, as our experiments and scaling arguments have shown, the mass of material that is emplaced in a crater's ejecta blanket drops sharply upon transition into the compaction regime. This causes craters to form without ejecting material outside the crater, resulting in an absence of ejecta blankets on porous asteroids, less erosion of existing pre-existing craters, and reduced gardening of the regolith by impacts. Our experiments now allow us to determine the conditions under which this compaction-dominated cratering and suppression of ejecta occur. In the presentation, these experiments will be summarized, we will show how they are consistent with observations of a lack of ejecta around large craters on Mathilde and Hyperion [2--4], and will discuss the mechanics of cratering on porous bodies. by the NASA Planetary Geology and Geophysics program.

  13. SCDAP/RELAP5 modeling of heat transfer and flow losses in lower head porous debris. Revision 1

    SciTech Connect

    Siefken, L.J.; Coryell, E.W.; Paik, S.; Kuo, H.

    1999-05-01

    Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate ma nner. Designs are described for models to calculate the flow losses and interphase drag of fluid flowing through the interstices of the porous debris, and to apply these variables in the momentum equations in the RELAP5 part of the code. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region.

  14. Modeling failure in brittle porous ceramics

    NASA Astrophysics Data System (ADS)

    Keles, Ozgur

    Brittle porous materials (BPMs) are used for battery, fuel cell, catalyst, membrane, filter, bone graft, and pharmacy applications due to the multi-functionality of their underlying porosity. However, in spite of its technological benefits the effects of porosity on BPM fracture strength and Weibull statistics are not fully understood--limiting a wider use. In this context, classical fracture mechanics was combined with two-dimensional finite element simulations not only to account for pore-pore stress interactions, but also to numerically quantify the relationship between the local pore volume fraction and fracture statistics. Simulations show that even the microstructures with the same porosity level and size of pores differ substantially in fracture strength. The maximum reliability of BPMs was shown to be limited by the underlying pore--pore interactions. Fracture strength of BMPs decreases at a faster rate under biaxial loading than under uniaxial loading. Three different types of deviation from classic Weibull behavior are identified: P-type corresponding to a positive lower tail deviation, N-type corresponding to a negative lower tail deviation, and S-type corresponding to both positive upper and lower tail deviations. Pore-pore interactions result in either P-type or N-type deviation in the limit of low porosity, whereas S-type behavior occurs when clusters of low and high fracture strengths coexist in a fracture data.

  15. Freeze-drying of "pearl milk tea": A general strategy for controllable synthesis of porous materials.

    PubMed

    Zhou, Yingke; Tian, Xiaohui; Wang, Pengcheng; Hu, Min; Du, Guodong

    2016-01-01

    Porous materials have been widely used in many fields, but the large-scale synthesis of materials with controlled pore sizes, pore volumes, and wall thicknesses remains a considerable challenge. Thus, the controllable synthesis of porous materials is of key general importance. Herein, we demonstrate the "pearl milk tea" freeze-drying method to form porous materials with controllable pore characteristics, which is realized by rapidly freezing the uniformly distributed template-containing precursor solution, followed by freeze-drying and suitable calcination. This general and convenient method has been successfully applied to synthesize various porous phosphate and oxide materials using different templates. The method is promising for the development of tunable porous materials for numerous applications of energy, environment, and catalysis, etc. PMID:27193866

  16. Porous multi-component material for the capture and separation of species of interest

    DOEpatents

    Addleman, Raymond S.; Chouyyok, Wilaiwan; Li, Xiaohong S.; Cinson, Anthony D.; Gerasimenko, Aleksandr A

    2016-06-21

    A method and porous multi-component material for the capture, separation or chemical reaction of a species of interest is disclosed. The porous multi-component material includes a substrate and a composite thin film. The composite thin film is formed by combining a porous polymer with a nanostructured material. The nanostructured material may include a surface chemistry for the capture of chemicals or particles. The composite thin film is coupled to the support or device surface. The method and material provides a simple, fast, and chemically and physically benign way to integrate nanostructured materials into devices while preserving their chemical activity.

  17. Evaluation and Optimization of Porous and Hierarchically Porous Materials for Applications in Energy Storage and Conversion

    NASA Astrophysics Data System (ADS)

    Petkovich, Nicholas Daniel

    Materials with nm- and mum-scale pores are important in the design of efficient, safe, and versatile energy conversion and storage systems. In the research detailed in this thesis, the synthesis and testing of porous materials for lithium-ion battery anodes and for thermochemical fuel production are explored. The preparation, modification, and performance of various carbon and transition metal oxide composite materials for lithium-ion battery electrodes are discussed in the first part of this work. Of particular interest are TiO 2/carbon composites that possess a three-dimensionally ordered macroporous (3DOM) structure, and, in some instances, additional mesoporosity. By changing the chelating agent used to stabilize the precursor for TiO2, crystallites of TiO2 can either be localized on the surface of the 3DOM structure or buried within the carbon matrix. This positioning has important ramifications for the electrochemical properties of the materials. In addition, the content of carbon in the composite materials can be altered. For carbon-rich composites, improved Li+ insertion/extraction capacities are attained by changing the voltage window used for cycling. Carbon can also be removed altogether, allowing for the formation 3DOM TiO¬2 with good electrochemical properties Conversion of the 3DOM TiO2 to sodium titanate is demonstrated via the ambient pressure treatment of the 3DOM material in sodium hydroxide. Subsequent ion-exchange with H+ results in the formation of hydrogen titanate materials with extremely high surface areas. A remnant of the 3DOM structure remains in these materials. Cerium oxide, praseodymium oxide and perovskite oxide-based catalysts for the thermochemical conversion of solar energy and abundant feedstocks (H2O and CO2) into useable fuels (H2 and CO) are investigated in the second part of this work. All of these materials possess a 3DOM structure and have moderate surface areas intended to improve reaction kinetics. Mixed oxides containing

  18. Enhancement of a dynamic porous model considering compression-release hysteresis behavior: application to graphite

    NASA Astrophysics Data System (ADS)

    Jodar, B.; Seisson, G.; Hébert, D.; Bertron, I.; Boustie, M.; Berthe, L.

    2016-08-01

    Because of their shock wave attenuation properties, porous materials and foams are increasingly used for various applications such as graphite in the aerospace industry and polyurethane (PU) foams in biomedical engineering. For these two materials, the absence of residual compaction after compression and release cycles limits the efficiency of the usual numerical dynamic porous models such as P-α and POREQST. In this paper, we suggest a simple enhancement of the latter in order to take into account the compression-release hysteresis behavior experimentally observed for the considered materials. The new model, named H-POREQST, was implemented into a Lagrangian hydrocode and tested for simulating plate impact experiments at moderate pressure onto a commercial grade of porous graphite (EDM3). It proved to be in far better agreement with experimental data than the original model which encourages us to pursue numerical tests and developments.

  19. Electronically and ionically conductive porous material and method for manufacture of resin wafers therefrom

    DOEpatents

    Lin, YuPo J.; Henry, Michael P.; Snyder, Seth W.

    2011-07-12

    An electrically and ionically conductive porous material including a thermoplastic binder and one or more of anion exchange moieties or cation exchange moieties or mixtures thereof and/or one or more of a protein capture resin and an electrically conductive material. The thermoplastic binder immobilizes the moieties with respect to each other but does not substantially coat the moieties and forms the electrically conductive porous material. A wafer of the material and a method of making the material and wafer are disclosed.

  20. Electronically and ionically conductive porous material and method for manufacture of resin wafers therefrom

    DOEpatents

    Lin, YuPo J.; Henry, Michael P.; Snyder, Seth W.

    2008-11-18

    An electrically and ionically conductive porous material including a thermoplastic binder and one or more of anion exchange moieties or cation exchange moieties or mixtures thereof and/or one or more of a protein capture resin and an electrically conductive material. The thermoplastic binder immobilizes the moieties with respect to each other but does not substantially coat the moieties and forms the electrically conductive porous material. A wafer of the material and a method of making the material and wafer are disclosed.

  1. Use of a porous material description of forests in infrasonic propagation algorithms.

    PubMed

    Swearingen, Michelle E; White, Michael J; Ketcham, Stephen A; McKenna, Mihan H

    2013-10-01

    Infrasound can propagate very long distances and remain at measurable levels. As a result infrasound sensing is used for remote monitoring in many applications. At local ranges, on the order of 10 km, the influence of the presence or absence of forests on the propagation of infrasonic signals is considered. Because the wavelengths of interest are much larger than the scale of individual components, the forest is modeled as a porous material. This approximation is developed starting with the relaxation model of porous materials. This representation is then incorporated into a Crank-Nicholson method parabolic equation solver to determine the relative impacts of the physical parameters of a forest (trunk size and basal area), the presence of gaps/trees in otherwise continuous forest/open terrain, and the effects of meteorology coupled with the porous layer. Finally, the simulations are compared to experimental data from a 10.9 kg blast propagated 14.5 km. Comparison to the experimental data shows that appropriate inclusion of a forest layer along the propagation path provides a closer fit to the data than solely changing the ground type across the frequency range from 1 to 30 Hz. PMID:24116403

  2. Dynamic behavior of particulate/porous energetic materials

    NASA Astrophysics Data System (ADS)

    Nesterenko, Vitali

    2011-06-01

    Dynamic behavior of particulate/porous energetic materials in a broad range of impact conditions and types of deformation (shock, shear) will be discussed. Samples of these materials were fabricated using Cold Isostatic Pressing, sintering and Hot Isostatic Pressing with and without vacuum encapsulation. The current interest in these materials is due to the combination of their high strength with energy efficiency under critical conditions of mechanical deformation. They may exhibit high compressive and tensile strength with the ability to bulk distributed fracture resulting in a small size reactive fragments and possible reaction on later stages. The results of dynamic deformation and fragmentation of these materials in conditions of low velocity (10 m/s), high energy impact, under localized deformation in single and multiple shear bands generated using explosively driven Thick Walled Cylinder method will be discussed. The mechanical properties of these materials are highly sensitive to mesostructure. For example, a dynamic strength of Al-W composites with fine W particles is significantly larger than the strength of composite with the coarse W particles at the same porosity. Morphology of W inclusions had a strong effect on dynamic strength. Samples with W wires arranged in axial direction with the same volume content of components had a highest dynamic strength. Porosity in these materials can provide a strain hardening mechanism effect due to in situ densification which was observed experimentally for cold isostatically pressed Al and Al-coarse W powders. Experimental results will be compared with available numerical data. The support for this project provided by ONR MURI N00014-07-1-0740 (Program Officer Dr. Clifford Bedford).

  3. Modelling the initial stage of porous alumina growth during anodization

    NASA Astrophysics Data System (ADS)

    Aryslanova, E. M.; Alfimov, A. V.; Chivilikhin, S. A.

    2013-05-01

    Artificially on the surface of aluminum there may be build a thick layer of Al2O3, which has a porous structure. In this paper we present a model of growth of porous alumina in the initial stage of anodizing, identifying dependencies anodizing parameters on the rate of growth of the film and the distance between the pores and as a result of the created model equations were found for changes in the disturbance of alumina for the initial stage of anodizing aluminum oxide porous border aluminum-alumina and alumina-electrolyte, with the influence of surface diffusion of aluminum oxide.

  4. Model for high rate gas flows in deformable and reactive porous beds

    SciTech Connect

    Weston, A M

    1985-01-08

    This report presents the development of a one dimensional planar Lagrange hydrodynamic computer model which describes the processes preceding detonation. The model treats gas flow, deflagration, and compaction in a porous bed of reactive material. The early part of deflagration to detonation experiment with porous HMX is simulated. Sensitivity of the simulation calculation to ignition and burn rate parameters is illustrated and discussed. The effects of changing the mean particle size of the porous material are investigated. There is widespread interest in runaway reaction hazards that may be associated with porosity in propellant and explosive materials. Experimentally, such reactions are initiated and observed in long, thick walled hollow tubes, filled with a granular porous bed of reactive material. We will present comparisons with an experiment on porous HMX to illustrate details of the model and to point out what we believe are important features of the observed phenomenon. A geometric finite element cell is devised that allows gas to flow through a compacting matrix. The experimental simulation considers the DDT process from initial squib burn through the onset of general matrix deflagration (convective burning), to the development of a fully dense compaction wave. While this simulation did not calculate turnover to detonation, it did illustrate that the transition occurred as soon as the compaction wave became fully dense. It is shown that deflagration and gas permeation lags compaction at the time of transition. This suggests that the actual transition involves an additional compaction dependent process. 18 references, 20 figures, 3 tables.

  5. Phase field modeling of grain growth in porous polycrystalline solids

    NASA Astrophysics Data System (ADS)

    Ahmed, Karim E.

    The concurrent evolution of grain size and porosity in porous polycrystalline solids is a technically important problem. All the physical properties of such materials depend strongly on pore fraction and pore and grain sizes and distributions. Theoretical models for the pore-grain boundary interactions during grain growth usually employ restrictive, unrealistic assumptions on the pore and grain shapes and motions to render the problem tractable. However, these assumptions limit the models to be only of qualitative nature and hence cannot be used for predictions. This has motivated us to develop a novel phase field model to investigate the process of grain growth in porous polycrystalline solids. Based on a dynamical system of coupled Cahn-Hilliard and All en-Cahn equations, the model couples the curvature-driven grain boundary motion and the migration of pores via surface diffusion. As such, the model accounts for all possible interactions between the pore and grain boundary, which highly influence the grain growth kinetics. Through a formal asymptotic analysis, the current work demonstrates that the phase field model recovers the corresponding sharp-interface dynamics of the co-evolution of grain boundaries and pores; this analysis also fixes the model kinetic parameters in terms of real materials properties. The model was used to investigate the effect of porosity on the kinetics of grain growth in UO2 and CeO2 in 2D and 3D. It is shown that the model captures the phenomenon of pore breakaway often observed in experiments. Pores on three- and four- grain junctions were found to transform to edge pores (pores on two-grain junction) before complete separation. The simulations demonstrated that inhomogeneous distribution of pores and pore breakaway lead to abnormal grain growth. The simulations also showed that grain growth kinetics in these materials changes from boundary-controlled to pore-controlled as the amount of porosity increases. The kinetic growth

  6. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials.

    PubMed

    Félix, V; Jannot, Y; Degiovanni, A

    2012-05-01

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10(-1) to 10(5) Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent. PMID:22667640

  7. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

    NASA Astrophysics Data System (ADS)

    Félix, V.; Jannot, Y.; Degiovanni, A.

    2012-05-01

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10-1 to 105 Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.

  8. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

    SciTech Connect

    Felix, V.; Jannot, Y.; Degiovanni, A.

    2012-05-15

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10{sup -1} to 10{sup 5} Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.

  9. Mechanical properties of sintered meso-porous silicon: a numerical model

    PubMed Central

    2012-01-01

    Because of its optical and electrical properties, large surfaces, and compatibility with standard silicon processes, porous silicon is a very interesting material in photovoltaic and microelectromechanical systems technology. In some applications, porous silicon is annealed at high temperature and, consequently, the cylindrical pores that are generated by anodization or stain etching reorganize into randomly distributed closed sphere-like pores. Although the design of devices which involve this material needs an accurate evaluation of its mechanical properties, only few researchers have studied the mechanical properties of porous silicon, and no data are nowadays available on the mechanical properties of sintered porous silicon. In this work we propose a finite element model to estimate the mechanical properties of sintered meso-porous silicon. The model has been employed to study the dependence of the Young’s modulus and the shear modulus (upper and lower bounds) on the porosity for porosities between 0% to 40%. Interpolation functions for the Young’s modulus and shear modulus have been obtained, and the results show good agreement with the data reported for other porous media. A Monte Carlo simulation has also been employed to study the effect of the actual microstructure on the mechanical properties. PMID:23107474

  10. New Carbon-Based Porous Materials with Increased Heats of Adsorption for Hydrogen Storage

    SciTech Connect

    Snurr, Randall Q.; Hupp, Joseph T.; Kanatzidis, Mercouri G.; Nguyen, SonBinh T.

    2014-11-03

    Hydrogen fuel cell vehicles are a promising alternative to internal combustion engines that burn gasoline. A significant challenge in developing fuel cell vehicles is to store enough hydrogen on-board to allow the same driving range as current vehicles. One option for storing hydrogen on vehicles is to use tanks filled with porous materials that act as “sponges” to take up large quantities of hydrogen without the need for extremely high pressures. The materials must meet many requirements to make this possible. This project aimed to develop two related classes of porous materials to meet these requirements. All materials were synthesized from molecular constituents in a building-block approach, which allows for the creation of an incredibly wide variety of materials in a tailorable fashion. The materials have extremely high surface areas, to provide many locations for hydrogen to adsorb. In addition, they were designed to contain cations that create large electric fields to bind hydrogen strongly but not too strongly. Molecular modeling played a key role as a guide to experiment throughout the project. A major accomplishment of the project was the development of a material with record hydrogen uptake at cryogenic temperatures. Although the ultimate goal was materials that adsorb large quantities of hydrogen at room temperature, this achievement at cryogenic temperatures is an important step in the right direction. In addition, there is significant interest in applications at these temperatures. The hydrogen uptake, measured independently at NREL was 8.0 wt %. This is, to the best of our knowledge, the highest validated excess hydrogen uptake reported to date at 77 K. This material was originally sketched on paper based on a hypothesis that extended framework struts would yield materials with excellent hydrogen storage properties. However, before starting the synthesis, we used molecular modeling to assess the performance of the material for hydrogen uptake

  11. High-intensity sound in air saturated fibrous bulk porous materials

    NASA Technical Reports Server (NTRS)

    Kuntz, H. L., II

    1982-01-01

    The interaction high-intensity sound with bulk porous materials in porous materials including Kevlar 29 is reported. The nonlinear behavior of the materials was described by dc flow resistivity tests. Then acoustic propagation and reflection were measured and small signal broadband measurements of phase speed and attenuation were carried out. High-intensity tests were made with 1, 2, and 3 kHz tone bursts to measure harmonic generation and extra attenuation of the fundamental. Small signal standing wave tests measured impedence between 0.1 and 3.5 kHz. High level tests with single cycle tone bursts at 1 to 4 kHz show that impedance increases with intensity. A theoretical analysis is presented for high-porosity, rigid-frame, isothermal materials. One dimensional equations of motion are derived and solved by perturbation. The experiments show that there is excess attenuation of the fundamental component and in some cases a close approach to saturation. A separate theoretical model, developed to explain the excess attenuation, yields predictions that are in good agreement with the measurements. Impedance and attenuation at high intensities are modeled.

  12. Pore-Scale Simulation for Predicting Material Transport Through Porous Media

    SciTech Connect

    Goichi Itoh; Jinya Nakamura; Koji Kono; Tadashi Watanabe; Hirotada Ohashi; Yu Chen; Shinya Nagasaki

    2002-07-01

    Microscopic models of real-coded lattice gas automata (RLG) method with a special boundary condition and lattice Boltzmann method (LBM) are developed for simulating three-dimensional fluid dynamics in complex geometry. Those models enable us to simulate pore-scale fluid dynamics that is an essential part for predicting material transport in porous media precisely. For large-scale simulation of porous media with high resolution, the RLG and LBM programs are designed for parallel computation. Simulation results of porous media flow by the LBM with different pressure gradient conditions show quantitative agreements with macroscopic relations of Darcy's law and Kozeny-Carman equation. As for the efficiency of parallel computing, a standard parallel computation by using MPI (Message Passing Interface) is compared with the hybrid parallel computation of MPI-node parallel technique. The benchmark tests conclude that in case of using large number of computing node, the parallel performance declines due to increase of data communication between nodes and the hybrid parallel computation totally shows better performance in comparison with the standard parallel computation. (authors)

  13. A simple model of gas flow in a porous powder compact.

    SciTech Connect

    Shugard, Andrew D.; Robinson, David B.

    2014-04-01

    This report describes a simple model for ideal gas flow from a vessel through a bed of porous material into another vessel. It assumes constant temperature and uniform porosity. Transport is treated as a combination of viscous and molecular flow, with no inertial contribution (low Reynolds number). This model can be used to fit data to obtain permeability values, determine flow rates, understand the relative contributions of viscous and molecular flow, and verify volume calibrations. It draws upon the Dusty Gas Model and other detailed studies of gas flow through porous media.

  14. The Evaluation of Hydroxyapatite (HA) Coated and Uncoated Porous Tantalum for Biomedical Material Applications

    NASA Astrophysics Data System (ADS)

    Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

    2014-04-01

    Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

  15. Calibration of thermocouple psychrometers and moisture measurements in porous materials

    NASA Astrophysics Data System (ADS)

    Guz, Łukasz; Sobczuk, Henryk; Połednik, Bernard; Guz, Ewa

    2016-07-01

    The paper presents in situ method of peltier psychrometric sensors calibration which allow to determine water potential. Water potential can be easily recalculated into moisture content of the porous material. In order to obtain correct results of water potential, each probe should be calibrated. NaCl salt solutions with molar concentration of 0.4M, 0.7M, 1.0M and 1.4M, were used for calibration which enabled to obtain osmotic potential in range: -1791 kPa to -6487 kPa. Traditionally, the value of voltage generated on thermocouples during wet-bulb temperature depression is calculated in order to determine the calibration function for psychrometric in situ sensors. In the new method of calibration, the field under psychrometric curve along with peltier cooling current and duration was taken into consideration. During calibration, different cooling currents were applied for each salt solution, i.e. 3, 5, 8 mA respectively, as well as different cooling duration for each current (from 2 to 100 sec with 2 sec step). Afterwards, the shape of each psychrometric curve was thoroughly examined and a value of field under psychrometric curve was computed. Results of experiment indicate that there is a robust correlation between field under psychrometric curve and water potential. Calibrations formulas were designated on the basis of these features.

  16. Analysis of ignition of a porous energetic material

    SciTech Connect

    Telengator, A.M.; Williams, F.A.; Margolis, S.B.

    1998-04-01

    A theory of ignition is presented to analyze the effect of porosity on the time to ignition of a semi-infinite porous energetic solid subjected to a constant energy flux. An asymptotic perturbation analysis, based on the smallness of the gas-to-solid density ratio and the largeness of the activation energy, is utilized to describe the inert and transition stages leading to thermal runaway. As in the classical study of a nonporous solid, the transition stage consists of three spatial regions in the limit of large activation energy: a thin reactive-diffusive layer adjacent to the exposed surface of the material where chemical effects are first felt, a somewhat thicker transient-diffusive zone, and finally an inert region where the temperature field is still governed solely by conductive heat transfer. Solutions in each region are constructed at each order with respect to the density-ratio parameter and matched to one another using asymptotic matching principles. It is found that the effects of porosity provide a leading-order reduction in the time to ignition relative to that for the nonporous problem, arising from the reduced amount of solid material that must be heated and the difference in thermal conductivities of the solid and gaseous phases. A positive correction to the leading-order ignition-delay time, however, is provided by the convective flow of gas out of the solid, which stems from the effects of thermal expansion and removes energy from the system. The latter phenomenon is absent from the corresponding calculation for the nonporous problem and produces a number of modifications at the next order in the analysis arising from the relative transport effects associated with the gas flow.

  17. Quantifying Biofilm in Porous Media Using Rock Physics Models

    NASA Astrophysics Data System (ADS)

    Alhadhrami, F. M.; Jaiswal, P.; Atekwana, E. A.

    2012-12-01

    Biofilm formation and growth in porous rocks can change their material properties such as porosity, permeability which in turn will impact fluid flow. Finding a non-intrusive method to quantify biofilms and their byproducts in rocks is a key to understanding and modeling bioclogging in porous media. Previous geophysical investigations have documented that seismic techniques are sensitive to biofilm growth. These studies pointed to the fact that microbial growth and biofilm formation induces heterogeneity in the seismic properties. Currently there are no rock physics models to explain these observations and to provide quantitative interpretation of the seismic data. Our objectives are to develop a new class of rock physics model that incorporate microbial processes and their effect on seismic properties. Using the assumption that biofilms can grow within pore-spaces or as a layer coating the mineral grains, P-wave velocity (Vp) and S-wave (Vs) velocity models were constructed using travel-time and waveform tomography technique. We used generic rock physics schematics to represent our rock system numerically. We simulated the arrival times as well as waveforms by treating biofilms either as fluid (filling pore spaces) or as part of matrix (coating sand grains). The preliminary results showed that there is a 1% change in Vp and 3% change in Vs when biofilms are represented discrete structures in pore spaces. On the other hand, a 30% change in Vp and 100% change in Vs was observed when biofilm was represented as part of matrix coating sand grains. Therefore, Vp and Vs changes are more rapid when biofilm grows as grain-coating phase. The significant change in Vs associated with biofilms suggests that shear velocity can be used as a diagnostic tool for imaging zones of bioclogging in the subsurface. The results obtained from this study have significant implications for the study of the rheological properties of biofilms in geological media. Other applications include

  18. On wave propagation characteristics in fluid saturated porous materials by a nonlocal Biot theory

    NASA Astrophysics Data System (ADS)

    Tong, Lihong; Yu, Yang; Hu, Wentao; Shi, Yufeng; Xu, Changjie

    2016-09-01

    A nonlocal Biot theory is developed by combing Biot theory and nonlocal elasticity theory for fluid saturated porous material. The nonlocal parameter is introduced as an independent variable for describing wave propagation characteristics in poroelastic material. A physical insight on nonlocal term demonstrates that the nonlocal term is a superposition of two effects, one is inertia force effect generated by fluctuation of porosity and the other is pore size effect inherited from nonlocal constitutive relation. Models for situations of excluding fluid nonlocal effect and including fluid nonlocal effect are proposed. Comparison with experiment confirms that model without fluid nonlocal effect is more reasonable for predicting wave characteristics in saturated porous materials. The negative dispersion is observed theoretically which agrees well with the published experimental data. Both wave velocities and quality factors as functions of frequency and nonlocal parameter are examined in practical cases. A few new physical phenomena such as backward propagation and disappearance of slow wave when exceeding critical frequency and disappearing shear wave in high frequency range, which were not predicted by Biot theory, are demonstrated.

  19. Investigation of using a Porous Media Approximation for Flow and Heat Transfer through the Nuclear Materials Storage Facility Drywell Array

    SciTech Connect

    Bernardin, J.D.; Gregory, W.S.; Owen, A.C.

    1999-04-21

    The Nuclear Materials Storage Facility (NMSF) is being renovated to provide a safe and secure long-term facility at Los Alamos National Laboratory to store nuclear materials. The concept for storage uses vertical tubes that are called drywells that have nuclear bearing canisters inside the tubes. The NMSF facility may use up to 370 of these tubes containing up to 10 canisters producing 15 W each. Analysts at the Laboratory wish to use CFD computer codes to predict the flow and thermal effects of air flow through the facility and the tube array. However, the complexity and large number of storage tubes precludes modeling the facility in enough detail to resolve the boundary layers around each and every tube. Therefore, certain approximations have to be made. A major approximation that has been used in this modeling effort has been to simulate the array of tubes as a porous media, The assumption-in the use of porous media is that the resistance of the drywells can be accounted for in a general way. The purpose of this study is to evaluate the suitability of the porous media approximation for modeling the tube array in the NMSF. In this study we will compare porous media models results with results from models that resolve the boundary layer around tubes. Finally, we offer a compromise modeling approach to address with this problem.

  20. An analytical model for permeability of isotropic porous media

    NASA Astrophysics Data System (ADS)

    Yang, Xiaohu; Lu, Tian Jian; Kim, Tongbeum

    2014-06-01

    We demonstrate that permeability of isotropic porous media e.g., open-cell foams can be analytically presented as a function of two morphological parameters: porosity and pore size. Adopting a cubic unit cell model, an existing tortuosity model from the branching algorithm method is incorporated into a generalized permeability model. The present model shows that dimensionless permeability significantly increases as the porosity of isotropic porous media and unifies the previously reported data in a wide range of porosity (ɛ=0.55-0.98) and pore size (Dp=0.254 mm-5.08 mm).

  1. Examining porous bio-active glass as a potential osteo-odonto-keratoprosthetic skirt material.

    PubMed

    Huhtinen, Reeta; Sandeman, Susan; Rose, Susanna; Fok, Elsie; Howell, Carol; Fröberg, Linda; Moritz, Niko; Hupa, Leena; Lloyd, Andrew

    2013-05-01

    Bio-active glass has been developed for use as a bone substitute with strong osteo-inductive capacity and the ability to form strong bonds with soft and hard tissue. The ability of this material to enhance tissue in-growth suggests its potential use as a substitute for the dental laminate of an osteo-odonto-keratoprosthesis. A preliminary in vitro investigation of porous bio-active glass as an OOKP skirt material was carried out. Porous glass structures were manufactured from bio-active glasses 1-98 and 28-04 containing varying oxide formulation (1-98, 28-04) and particle size range (250-315 μm for 1-98 and 28-04a, 315-500 μm for 28-04b). Dissolution of the porous glass structure and its effect on pH was measured. Structural 2D and 3D analysis of porous structures were performed. Cell culture experiments were carried out to study keratocyte adhesion and the inflammatory response induced by the porous glass materials. The dissolution results suggested that the porous structure made out of 1-98 dissolves faster than the structures made from glass 28-04. pH experiments showed that the dissolution of the porous glass increased the pH of the surrounding solution. The cell culture results showed that keratocytes adhered onto the surface of each of the porous glass structures, but cell adhesion and spreading was greatest for the 98a bio-glass. Cytokine production by all porous glass samples was similar to that of the negative control indicating that the glasses do not induce a cytokine driven inflammatory response. Cell culture results support the potential use of synthetic porous bio-glass as an OOKP skirt material in terms of limited inflammatory potential and capacity to induce and support tissue ingrowth. PMID:23386212

  2. Hierarchical simulator of biofilm growth and dynamics in granular porous materials

    NASA Astrophysics Data System (ADS)

    Kapellos, George E.; Alexiou, Terpsichori S.; Payatakes, Alkiviades C.

    2007-06-01

    A new simulator is developed for the prediction of the rate and pattern of growth of biofilms in granular porous media. The biofilm is considered as a heterogeneous porous material that exhibits a hierarchy of length scales. An effective-medium model is used to calculate the local hydraulic permeability and diffusion coefficient in the biofilm, as functions of the local geometric and physicochemical properties. The Navier-Stokes equations and the Brinkman equation are solved numerically to determine the velocity and pressure fields within the pore space and the biofilm, respectively. Biofilm fragments become detached if they are exposed to shear stress higher than a critical value. The detached fragments re-enter into the fluid stream and move within the pore space until they exit from the system or become reattached to downstream grain or biofilm surfaces. A Lagrangian-type simulation is used to determine the trajectories of detached fragments. The spatiotemporal distributions of a carbon source, an electron acceptor and a cell-to-cell signaling molecule are determined from the numerical solution of the governing convection-diffusion-reaction equations. The simulator incorporates growth and apoptosis kinetics for the bacterial cells and production and lysis kinetics for the EPS. The specific growth rate of active bacterial cells depends on the local concentrations of nutrients, mechanical stresses, and a quorum sensing mechanism. Growth-induced deformation of the biofilms is implemented with a cellular automaton approach. In this work, the spatiotemporal evolution of biofilms in the pore space of a 2D granular medium is simulated under high flow rate and nutrient-rich conditions. Transient changes in the pore geometry caused by biofilm growth lead to the formation of preferential flowpaths within the granular porous medium. The decrease of permeability caused by clogging of the porous medium is calculated and is found to be in qualitative agreement with published

  3. Supercritical adsorption testing of porous silicon, activated carbon, and zeolite materials

    NASA Astrophysics Data System (ADS)

    Harvey, Brendan

    The supercritical adsorption of methane gas on porous silicon, activated carbon, and zeolite materials was studied. An apparatus that utilizes the volumetric adsorption measurement technique was designed and constructed to conduct the experiments. Activated carbon materials consisted of Norit RX3 Extra, Zorflex FM30K woven activated carbon cloth, and Zorflex FM10 knitted activated carbon cloth. Zeolite materials consisted of 3A, 4A, 5A, and 13X zeolites. Porous silicon materials consisted of stain etched and electrochemically etched porous films, and stain etched porous powder. All adsorption tests were conducted at room temperature (approximately 298 K) and pressures up to approximately 5 MPa. Overall, the Norit RX3 Extra granulated activated carbon produced the highest excess adsorption and effective storage capacities. Effective storage and delivery capacities of 109 and 90 stpmlml were obtained at a pressure of 3.5 MPa and a temperature of approximately 298 K.

  4. Idealized radiation efficiency model for a porous radiant burner

    SciTech Connect

    Fu, X.; Viskanta, R.; Gore, J.P.

    1999-07-01

    A simple, highly idealized radiation efficiency model has been developed for a porous radiant burner with or without a screen to assess the thermal performance of an ideal porous burner that yields the highest radiation efficiency and against which test results and/or more realistic model predictions could be benchmarked. The model is based on thermodynamics principles (first law of thermodynamics) with idealizations made for some of the physical processes. Empirical information, where necessary, is then used to close the model equations. The maximum radiation efficiency at a given firing rate is predicted. The effects of input parameters such as the firing rate, the equivalence ratio, and the effective emittance of the burner on the radiation efficiency of the porous radiant burner are reported.

  5. Exploring with simulations the transport properties of multi-scale porous materials

    NASA Astrophysics Data System (ADS)

    Hyväluoma, Jari; Mattila, Keijo; Puurtinen, Tuomas; Timonen, Jussi

    2015-04-01

    The internal structure of many natural porous materials such as soils and carbonate rocks involves multiple length scales. This severely hinders the research relating structure and transport properties: typically laboratory experiments cannot distinguish contributions from individual scales while computer simulations cannot capture multiple scales due to limited computational resources. 3D imaging and image-based fluid flow simulations are increasingly used for studying the pore-scale transport processes. Combining imaging with pore-scale flow simulation techniques, e.g. the lattice Boltzmann method, provides direct means to quantify pore-scale transport processes. However, pore-scale computer simulations have not really been able to capture multiple scales due to the limited size of the simulation system. We show here that the current computational resources and software techniques already allow transport simulations in domains beyond the realms of current imaging techniques, and, more importantly, enable numerical experiments in multi-scale porous materials. We were able to simulate single-phase fluid flow with the lattice Boltzmann method in a synthetic x-ray-tomography image taken from the set of world's largest 3D images of a porous material [1]. The used image has 163843 image voxels and porosity of 0.134 (i.e., 5.9 - 1011 pore voxels) and it represents the microstructure of Fontainebleau sandstone. While the modelled sandstone image is rather homogeneous and therefore does not really represent a multiscale porous material, from a computational point of view it serves the purpose of demonstrating the power of contemporary software and hardware techniques. The simulation was executed at the Edinburgh Parallel Computing Centre on the ARCHER supercomputer ranked number 25 among all supercomputers. ARCHER has 3008 computing nodes each of which has two 12-core Ivy Bridge 2.7 GHz CPUs and 64 GB of memory providing 1.67 Petaflops of theoretical peak performance. The

  6. A fully coupled porous flow and geomechanics model for fluid driven cracks: a peridynamics approach

    NASA Astrophysics Data System (ADS)

    Ouchi, Hisanao; Katiyar, Amit; York, Jason; Foster, John T.; Sharma, Mukul M.

    2015-03-01

    A state-based non-local peridynamic formulation is presented for simulating fluid driven fractures in an arbitrary heterogeneous poroelastic medium. A recently developed peridynamic formulation of porous flow has been coupled with the existing peridynamic formulation of solid and fracture mechanics resulting in a peridynamic model that for the first time simulates poroelasticity and fluid-driven fracture propagation. This coupling is achieved by modeling the role of pore pressure on the deformation of porous media and vice versa through porosity variation with medium deformation, pore pressure and total mean stress. The poroelastic model is verified by simulating the one-dimensional consolidation of fluid saturated rock. An additional porous flow equation with material permeability dependent on fracture width is solved to simulate fluid flow in the fractured region. Finally, single fluid-driven fracture propagation with a two-dimensional plane strain assumption is simulated and verified against the corresponding classical analytical solution.

  7. Modeling microbial processes in porous media

    NASA Astrophysics Data System (ADS)

    Murphy, Ellyn M.; Ginn, Timothy R.

    The incorporation of microbial processes into reactive transport models has generally proceeded along two separate lines of investigation: (1) transport of bacteria as inert colloids in porous media, and (2) the biodegradation of dissolved contaminants by a stationary phase of bacteria. Research over the last decade has indicated that these processes are closely linked. This linkage may occur when a change in metabolic activity alters the attachment/detachment rates of bacteria to surfaces, either promoting or retarding bacterial transport in a groundwater-contaminant plume. Changes in metabolic activity, in turn, are controlled by the time of exposure of the microbes to electron acceptors/donor and other components affecting activity. Similarly, metabolic activity can affect the reversibility of attachment, depending on the residence time of active microbes. Thus, improvements in quantitative analysis of active subsurface biota necessitate direct linkages between substrate availability, metabolic activity, growth, and attachment/detachment rates. This linkage requires both a detailed understanding of the biological processes and robust quantitative representations of these processes that can be tested experimentally. This paper presents an overview of current approaches used to represent physicochemical and biological processes in porous media, along with new conceptual approaches that link metabolic activity with partitioning of the microorganism between the aqueous and solid phases. Résumé L'introduction des processus microbiologiques dans des modèles de transport réactif a généralement suivi deux voies différentes de recherches: (1) le transport de bactéries sous forme de colloïdes inertes en milieu poreux, et (2) la biodégradation de polluants dissous par une phase stationnaire de bactéries. Les recherches conduites au cours des dix dernières années indiquent que ces processus sont intimement liés. Cette liaison peut intervenir lorsqu

  8. Modeling microbial processes in porous media

    NASA Astrophysics Data System (ADS)

    Murphy, Ellyn M.; Ginn, Timothy R.

    The incorporation of microbial processes into reactive transport models has generally proceeded along two separate lines of investigation: (1) transport of bacteria as inert colloids in porous media, and (2) the biodegradation of dissolved contaminants by a stationary phase of bacteria. Research over the last decade has indicated that these processes are closely linked. This linkage may occur when a change in metabolic activity alters the attachment/detachment rates of bacteria to surfaces, either promoting or retarding bacterial transport in a groundwater-contaminant plume. Changes in metabolic activity, in turn, are controlled by the time of exposure of the microbes to electron acceptors/donor and other components affecting activity. Similarly, metabolic activity can affect the reversibility of attachment, depending on the residence time of active microbes. Thus, improvements in quantitative analysis of active subsurface biota necessitate direct linkages between substrate availability, metabolic activity, growth, and attachment/detachment rates. This linkage requires both a detailed understanding of the biological processes and robust quantitative representations of these processes that can be tested experimentally. This paper presents an overview of current approaches used to represent physicochemical and biological processes in porous media, along with new conceptual approaches that link metabolic activity with partitioning of the microorganism between the aqueous and solid phases. Résumé L'introduction des processus microbiologiques dans des modèles de transport réactif a généralement suivi deux voies différentes de recherches: (1) le transport de bactéries sous forme de colloïdes inertes en milieu poreux, et (2) la biodégradation de polluants dissous par une phase stationnaire de bactéries. Les recherches conduites au cours des dix dernières années indiquent que ces processus sont intimement liés. Cette liaison peut intervenir lorsqu

  9. a Fractal Network Model for Fractured Porous Media

    NASA Astrophysics Data System (ADS)

    Xu, Peng; Li, Cuihong; Qiu, Shuxia; Sasmito, Agus Pulung

    2016-04-01

    The transport properties and mechanisms of fractured porous media are very important for oil and gas reservoir engineering, hydraulics, environmental science, chemical engineering, etc. In this paper, a fractal dual-porosity model is developed to estimate the equivalent hydraulic properties of fractured porous media, where a fractal tree-like network model is used to characterize the fracture system according to its fractal scaling laws and topological structures. The analytical expressions for the effective permeability of fracture system and fractured porous media, tortuosity, fracture density and fraction are derived. The proposed fractal model has been validated by comparisons with available experimental data and numerical simulation. It has been shown that fractal dimensions for fracture length and aperture have significant effect on the equivalent hydraulic properties of fractured porous media. The effective permeability of fracture system can be increased with the increase of fractal dimensions for fracture length and aperture, while it can be remarkably lowered by introducing tortuosity at large branching angle. Also, a scaling law between the fracture density and fractal dimension for fracture length has been found, where the scaling exponent depends on the fracture number. The present fractal dual-porosity model may shed light on the transport physics of fractured porous media and provide theoretical basis for oil and gas exploitation, underground water, nuclear waste disposal and geothermal energy extraction as well as chemical engineering, etc.

  10. Sound transmission through double cylindrical shells lined with porous material under turbulent boundary layer excitation

    NASA Astrophysics Data System (ADS)

    Zhou, Jie; Bhaskar, Atul; Zhang, Xin

    2015-11-01

    This paper investigates sound transmission through double-walled cylindrical shell lined with poroelastic material in the core, excited by pressure fluctuations due to the exterior turbulent boundary layer (TBL). Biot's model is used to describe the sound wave propagating in the porous material. Three types of constructions, bonded-bonded, bonded-unbonded and unbonded-unbonded, are considered in this study. The power spectral density (PSD) of the inner shell kinetic energy is predicted for two turbulent boundary layer models, different air gap depths and three types of polyimide foams, respectively. The peaks of the inner shell kinetic energy due to shell resonance, hydrodynamic coincidence and acoustic coincidence are discussed. The results show that if the frequency band over the ring frequency is of interest, an air gap, even if very thin, should exist between the two elastic shells for better sound insulation. And if small density foam has a high flow resistance, a superior sound insulation can still be maintained.

  11. An investigation of the influence of acoustic waves on the liquid flow through a porous material

    NASA Astrophysics Data System (ADS)

    Poesio, Pietro; Ooms, Gijs; Barake, Sander; van der Bas, Fred

    2002-05-01

    An experimental and theoretical investigation has been made of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material. The experiments have been performed on Berea sandstone cores. Two acoustic horns were used with frequencies of 20 and 40 kHz, and with maximum power output of 2 and 0.7 kW, respectively. Also, a temperature measurement of the flowing liquid inside the core was made. A high external pressure was applied in order to avoid cavitation. The acoustic waves were found to produce a significant effect on the pressure gradient at constant liquid flow rate through the core samples. During the application of acoustic waves the pressure gradient inside the core decreases. This effect turned out to be due to the decrease of the liquid viscosity caused by an increase in liquid temperature as a result of the acoustic energy dissipation inside the porous material. Also, a theoretical model has been developed to calculate the dissipation effect on the viscosity and on the pressure gradient. The model predictions are in reasonable agreement with the experimental data.

  12. An investigation of the influence of acoustic waves on the liquid flow through a porous material.

    PubMed

    Poesio, Pietro; Ooms, Gijs; Barake, Sander; van der Bas, Fred

    2002-05-01

    An experimental and theoretical investigation has been made of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material. The experiments have been performed on Berea sandstone cores. Two acoustic horns were used with frequencies of 20 and 40 kHz, and with maximum power output of 2 and 0.7 kW, respectively. Also, a temperature measurement of the flowing liquid inside the core was made. A high external pressure was applied in order to avoid cavitation. The acoustic waves were found to produce a significant effect on the pressure gradient at constant liquid flow rate through the core samples. During the application of acoustic waves the pressure gradient inside the core decreases. This effect turned out to be due to the decrease of the liquid viscosity caused by an increase in liquid temperature as a result of the acoustic energy dissipation inside the porous material. Also, a theoretical model has been developed to calculate the dissipation effect on the viscosity and on the pressure gradient. The model predictions are in reasonable agreement with the experimental data. PMID:12051421

  13. Limit analysis and homogenization of porous materials with Mohr-Coulomb matrix. Part II: Numerical bounds and assessment of the theoretical model

    NASA Astrophysics Data System (ADS)

    Pastor, F.; Anoukou, K.; Pastor, J.; Kondo, D.

    2016-06-01

    This second part of the two-part study is devoted to the numerical Limit Analysis of a hollow sphere model with a Mohr-Coulomb matrix and its use for the assessment of theoretical results. Brief background and fundamental of the static and kinematic approaches in the context of numerical limit analysis are first recalled. We then present the hollow sphere model, together with its axisymmetric FEM discretization and its mechanical position. A conic programming adaptation of a previous iterative static approach, based on a piecewise linearization (PWL) of the plasticity criterion, was first realized. Unfortunately, the resulting code, no more than the PWL one, did not allow sufficiently refined meshes for loss of convergence of the conic optimizer. This problem was solved by using the projection algorithm of Ben Tal and Nemriovski (BTN) and the (interior point) linear programming code XA. For the kinematic approach, a first conic adaptation appeared also inefficient. Then, an original mixed (but fully kinematic) approach dedicated to the general Mohr-Coulomb axisymmetric problem was elaborated. The final conic mixed code appears much more robust than the classic one when using the conic code MOSEK, allowing us to take into account refined numerical meshes. After a fine validation in the case of spherical cavities and isotropic loadings (for which the exact solution is known) and comparison to previous (partial) results, numerical lower and upper bounds (a posteriori verified) of the macroscopic strength are provided. These bounds are used to assess and validate the theoretical results of the companion (part I) paper. Effects of the friction angle as well as that of the porosity are illustrated.

  14. Overlimiting current and water purification in porous materials

    NASA Astrophysics Data System (ADS)

    Deng, Daosheng; Aouad, Wassim; Schlumpberger, Sven; Bazant, Martin Z.

    2012-11-01

    Salt transport in bulk electrolytes occurs by diffusion and convection, but in microfluidic devices and porous media, the presence of charged side walls leads to additional surface transport mechanisms, surface conduction and electro-osmotic flows, which become more important as the bulk salt concentration decreases. As a result, it is possible to exceed the diffusion-limited current to a membrane or electrode. In this work, we present experimental observations of over-limiting current to an ion-exchange membrane through a porous glass frit with submicron pores. Under this operation conditions, we also demonstrate the continuous extraction of depleted solution for water purification, including removing heavy metal ions, filtrating aggregated particles and reducing dye concentration. The porous media pave the way for practical water desalination and purification.

  15. Investigation into the optimal hydrologic design of porous concrete sites using mathematical modeling

    NASA Astrophysics Data System (ADS)

    Syrrakou, C.; Fitch, J.; Eliassen, T.; Ahearn, W.; Pinder, G. F.

    2011-12-01

    Increase in the amount of paved areas as a result of urbanization in modern societies has lead to the need of stormwater best management practices (BMPs). In that direction, porous pavement has been used successfully in regions of warm climate and application in regions of colder climate is an object of ongoing research with encouraging results to date. The significant cost and effort that accompanies the maintenance of porous pavement facilities calls for a design tool that can be used prior construction to facilitate the design process and also post production to evaluate the site's overall performance. Such a tool is a mathematical model which takes into account the different physical processes that can occur in a porous concrete system including recharge from rainfall, runoff from surrounding conventionally paved areas, vertical flow, storage and finally infiltration into the subsurface. In this research a three-dimensional saturated-unsaturated flow and transport model is modified to account for flow through the porous concrete slab and also evaporation. Runoff is accounted by means of a two-dimensional surface flow model which calculates the infiltration into the perimeter porous concrete area. The mathematical model is used to simulate a porous concrete site which operates as a public parking lot facility in Randolph, Vermont. The subgrade soil in the area of interest consists mainly of dense till deposits typically found in New England. Such deposits can result in small infiltration rates. The specific site is unique not only in terms of the underlying geology but also the heavy instrumentation not usually observed in similar sites. The instrumentation includes a number of groundwater wells which are being monitored continuously through a pressure transducer system, temperature probes installed inside the porous concrete and a detailed underdrain system located in the porous concrete's sub-base accumulating infiltrated water. Laboratory research is also

  16. Non-Darcian forced convection analysis in an annulus partially filled with a porous material

    SciTech Connect

    Chikh, S.; Boumedien, A.; Bouhadef, K.; Lauriat, G.

    1995-12-01

    Numerical solutions are presented for fully developed forced convection in concentric annuli partially filled with a porous medium. The porous medium is attached at the inner cylinder, which is maintained at uniform heat flux or at uniform wall temperature while the outer cylinder is adiabatic. The Brinkman-Forchheimer-extended Darcy model was used to model the flow inside the porous medium. The dependence of the fluid flow and heat transfer on several parameters of the problem is thoroughly documented. The inertia coefficient at which the inertial effects reduce the flow rate by 5% is determined as a function of the Darcy number for various thicknesses of the porous substrate. It is also shown that a critical thickness at which the value of the Nusselt number reaches a minimum does not exist if the effective thermal conductivity of the fluid-saturated porous medium is much higher than the fluid conductivity.

  17. A volume-balance model for flow on porous media

    NASA Astrophysics Data System (ADS)

    Malaga, Carlos; Mandujano, Francisco; Becerra, Julian

    2015-11-01

    Volume-balance models are used by petroleum engineers for simulating multiphase and multicomponent flow phenomena in porous media and the extraction process in oil reservoirs. In these models, mass conservation equations and Darcy's law are supplemented by a balance condition for the pore and fluid volumes. This provides a pressure equation suitable for simulating a compressible flow within a compressible solid matrix. Here we present an alternative interpretation of the volume-balance condition that includes the advective transport within a consolidated porous media. We obtain a modified equation for the time evolution of the pressure field. Numerical tests for phase separation under gravity are presented for multiphase three dimensional flow in heterogeneous porous media. The authors acknowledge funding from Fondo Sectorial CONACYT-SENER grant number 42536 (DGAJ-SPI-34-170412-217).

  18. Method for the preparation of ferrous low carbon porous material

    DOEpatents

    Miller, Curtis Jack

    2014-05-27

    A method for preparing a porous metal article using a powder metallurgy forming process is provided which eliminates the conventional steps associated with removing residual carbon. The method uses a feedstock that includes a ferrous metal powder and a polycarbonate binder. The polycarbonate binder can be removed by thermal decomposition after the metal article is formed without leaving a carbon residue.

  19. A comparison of measured and modeled velocity fields for a laminar flow in a porous medium

    NASA Astrophysics Data System (ADS)

    Wood, B. D.; Apte, S. V.; Liburdy, J. A.; Ziazi, R. M.; He, X.; Finn, J. R.; Patil, V. A.

    2015-11-01

    Obtaining highly-resolved velocity data from experimental measurements in porous media is a significant challenge. The goal of this work is to compare the velocity fields measured in a randomly-packed porous medium obtained from particle image velocimetry (PIV) with corresponding fields predicted from direct numerical simulation (DNS). Experimentally, the porous medium was comprised of 15 mm diameter spherical beads made of optical glass placed in a glass flow cell to create the packed bed. A solution of ammonium thiocyanate was refractive-index matched to the glass creating a medium that could be illuminated with a laser sheet without distortion. The bead center locations were quantified using the imaging system so that the geometry of the porous medium was known very accurately. Two-dimensional PIV data were collected and processed to provide high-resolution velocity fields at a single plane within the porous medium. A Cartesian-grid-based fictitious domain approach was adopted for the direct numerical simulation of flow through the same geometry as the experimental measurements and without any adjustable parameters. The uncertainties associated with characterization of the pore geometry, PIV measurements, and DNS predictions were all systematically quantified. Although uncertainties in bead position measurements led to minor discrepancies in the comparison of the velocity fields, the axial and normal velocity deviations exhibited normalized root mean squared deviations (NRMSD) of only 11.32% and 4.74%, respectively. The high fidelity of both the experimental and numerical methods have significant implications for understanding and even for engineering the micro-macro relationship in porous materials. The ability to measure and model sub-pore-scale flow features also has relevance to the development of upscaled models for flow in porous media, where physically reasonable closure models must be developed at the sub-pore scale. These results provide valuable data

  20. Investigations on deflagration to detonation transition in porous energetic materials. Final report

    SciTech Connect

    Stewart, D.S.

    1999-07-01

    The research carried out by this contract was part of a larger effort funded by LANL in the areas of deflagration to detonation in porous energetic materials (DDT) and detonation shock dynamics in high explosives (DSD). In the first three years of the contract the major focus was on DDT. However, some researchers were carried out on DSD theory and numerical implementation. In the last two years the principal focus of the contract was on DSD theory and numerical implementation. However, during the second period some work was also carried out on DDT. The paper discusses DDT modeling and DSD modeling. Abstracts are included on the following topics: modeling deflagration to detonation; DSD theory; DSD wave front tracking; and DSD program burn implementation.

  1. Fluid-Structure interaction modeling in deformable porous arteries

    NASA Astrophysics Data System (ADS)

    Zakerzadeh, Rana; Zunino, Paolo

    2015-11-01

    A computational framework is developed to study the coupling of blood flow in arteries interacting with a poroelastic arterial wall featuring possibly large deformations. Blood is modeled as an incompressible, viscous, Newtonian fluid using the Navier-Stokes equations and the arterial wall consists of a thick material which is modeled as a Biot system that describes the mechanical behavior of a homogeneous and isotropic elastic skeleton, and connecting pores filled with fluid. Discretization via finite element method leads to the system of nonlinear equations and a Newton-Raphson scheme is adopted to solve the resulting nonlinear system through consistent linearization. Moreover, interface conditions are imposed on the discrete level via mortar finite elements or Nitsche's coupling. The discrete linearized coupled FSI system is solved by means of a splitting strategy, which allows solving the Navier-Stokes and Biot equations separately. The numerical results investigate the effects of proroelastic parameters on the pressure wave propagation in arteries, filtration of incompressible fluids through the porous media, and the structure displacement. The fellowship support from the Computational Modeling & Simulation PhD program at University of Pittsburgh for Rana Zakerzadeh is gratefully acknowledged.

  2. Modeling isothermal and non-isothermal flows in porous media

    NASA Astrophysics Data System (ADS)

    Mohseni Languri, Ehsan

    2011-12-01

    A complete understanding of the physics of flow and heat transfer phenomena in porous media is vital for accurate simulation of flow processes in industrial applications. In one such application pertaining to liquid composite molding (LCM) for manufacturing polymer composites, the fiber preforms used in LCM as reinforcements are limited not only to the single-scale porous media in the form of random fiber-mats, but also include dual-scale porous media in the form of woven or stitched fiber-mats. The conventional flow physics is not able to model the resin filling process in LCM involving the dual-scale porous media. In this study, the flow in dual-scale porous media is studied in order to predict the permeability of these fiber mats. The effect of aspect ratio of the fiber preform on the accuracy and flow during permeability estimation in single- and dual-scale porous media is analyzed experimentally and numerically. Flow of liquid in a free channel bounded on one side by porous medium is studied next, and two well-known boundary conditions of stress continuity and stress jump at the interface of the two regions are evaluated numerically. A point-wise solution for Stokes flow through periodic and non periodic porous media (made of cylindrical particles) adjacent to the free channel is presented using the Imite element based CFD software COMSOL. The efficacy of the two interfacial conditions is evaluated after volume averaging the point-wise velocity using a long averaging volume, also called the representative elementary volume or REV, and then comparing such a volume-averaged velocity profile with the available analytical solution. The investigation is carried out for five different porosities at three different Reynolds numbers to cover a wide range of applications. The presence of randomly-placed cylinders during the creation of non-periodic porous media damps out spatial fluctuations in the averaged velocity observed in periodic porous media. The analytical

  3. Synthesis, structure and properties of hierarchical nanostructured porous materials studied by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Chae, Kisung

    For applications of porous materials in many fields of technological importance, such as catalysis, filtration, separation, energy storage and conversion, the efficiency is often limited by chemical kinetics, and/or diffusion of reactants and products to and from the active sites. Hierarchical nanostructured porous materials (HNPMs) that possess both mesopores (2 nm < pore size < 50 nm) and micropores (pore size < 2 nm) have shown great potential for these applications as their bimodal porous structure can provide highly efficient mass transport through mesopores and high electrochemically accessible surface area from micropores. Despite extensive experimental studies, it remains a great challenge to quantify the synthesis-structure-properties relations in HNPMs due to the limitations of existing characterization tools and the difficulty in separating the sum of many effects in experiments. In this thesis work, we carried out a detailed study on the synthesis-structure-property relations in hierarchical nanostructured porous carbons (HNPCs) by using classical molecular dynamics (MD) simulations. We first developed a unique computational nanocasting approach in MD to mimic the synthesis of HNPCs with both mesopores from the templating and micropores from the direct quench of carbon source in MD. Mesoporous structure such as the pore size and the pore wall roughness as well as the microporous structure such as the density and the graphitic pore walls can be independently controlled by synthesis parameters, such as the size of the template, the interaction strength between the template and carbon source, the initial carbon density and the quench rate, respectively. These atomic models allowed us to quantify the structure-mechanical properties relation in aligned carbon nanotubes/amorphous porous carbon nanocomposites. Our study shows that there is an optimum balance between the crystallinity of CNTs and the number bridging bonds between CNTs and the microporous matrix

  4. Estimation of the effects of longitudinal temperature gradients caused by frictional heating on the solute retention using fully porous and superficially porous sub-2μm materials.

    PubMed

    Fekete, Szabolcs; Fekete, Jenő; Guillarme, Davy

    2014-09-12

    In this study, the retention changes induced by frictional heating were evaluated for model small compounds (150-190Da) and a small protein, namely insulin (5.7kDa). For this purpose, the effect of longitudinal temperature gradient caused by frictional heating was experimentally dissociated from the combined effect of pressure and frictional heating, by working either in constant and variable inlet pressure modes. Various columns packed with core-shell and fully porous sub-2μm particles were tested. It appears that frictional heating was less pronounced on the column packed with smallest core-shell particles (1.3μm), compared to the ones packed with core-shell and fully porous particles of 1.7-1.8μm. This observation was attributed to the low permeability of this material and the fact that it can only be employed in a restricted flow rate range, thus limiting the generated heat power. In addition, the thermal conductivity of the solid silica core of superficially porous particles (1.4W/m/K) is known to be much larger than that of fully porous silica. Then, the heat dissipation is improved. However, if systems with higher pressure capability would be available and the mechanical stability of 1.3μm core-shell material was extended to e.g. 2000bar, the retention would be more severely impacted. At 2000bar, ∼4.4W heat power and +30°C increase at column outlet temperature is expected. Last but not least, when analyzing large molecules, the impact of pressure overcomes the frictional heating effects. This was demonstrated in this study with insulin (∼5.7kDa). PMID:25069746

  5. An Overview of Recent Development in Composite Catalysts from Porous Materials for Various Reactions and Processes

    PubMed Central

    Xie, Zaiku; Liu, Zhicheng; Wang, Yangdong; Yang, Qihua; Xu, Longya; Ding, Weiping

    2010-01-01

    Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT), etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts. PMID:20559508

  6. Hydrogen-Bonded Organic Frameworks (HOFs): A New Class of Porous Crystalline Proton-Conducting Materials.

    PubMed

    Karmakar, Avishek; Illathvalappil, Rajith; Anothumakkool, Bihag; Sen, Arunabha; Samanta, Partha; Desai, Aamod V; Kurungot, Sreekumar; Ghosh, Sujit K

    2016-08-26

    Two porous hydrogen-bonded organic frameworks (HOFs) based on arene sulfonates and guanidinium ions are reported. As a result of the presence of ionic backbones appended with protonic source, the compounds exhibit ultra-high proton conduction values (σ) 0.75× 10(-2)  S cm(-1) and 1.8×10(-2)  S cm(-1) under humidified conditions. Also, they have very low activation energy values and the highest proton conductivity at ambient conditions (low humidity and at moderate temperature) among porous crystalline materials, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). These values are not only comparable to the conventionally used proton exchange membranes, such as Nafion used in fuel cell technologies, but is also the highest value reported in organic-based porous architectures. Notably, this report inaugurates the usage of crystalline hydrogen-bonded porous organic frameworks as solid-state proton conducting materials. PMID:27464784

  7. Controlled high-rate-strain shear bands in inert and reactant porous materials

    NASA Astrophysics Data System (ADS)

    Nesterenko, V. F.

    1998-07-01

    Shear localization is considered as one of the main reasons for initiation of chemical reaction in energetic materials under dynamic loading. However despite of widely spread recognition of the importance of rapid shear flow the shear bands in porous heterogeneous materials did not become an object of research. The primary reason for this was a lack of appropriate experimental method. The "Thick-Walled Cylinder" method, which allows to reproduce shear bands in strain controlled conditions, was initially proposed by Nesterenko et al., 1989 for solid inert materials and then modified by Nesterenko, Meyers et al., 1994 to fit porous inert and energetic materials. The method allows to reproduce the array of shear bands with shear strains 10-100 and strain rate 107s-1. Experimental results are presented for inert materials (granular, fractured ceramics) and for reactant porous mixtures (Nb-Si, Ti-Si, Ti-graphite and Ti-ultrafine diamond).

  8. Examining Asphaltene Solubility on Deposition in Model Porous Media.

    PubMed

    Lin, Yu-Jiun; He, Peng; Tavakkoli, Mohammad; Mathew, Nevin Thunduvila; Fatt, Yap Yit; Chai, John C; Goharzadeh, Afshin; Vargas, Francisco M; Biswal, Sibani Lisa

    2016-08-30

    Asphaltenes are known to cause severe flow assurance problems in the near-wellbore region of oil reservoirs. Understanding the mechanism of asphaltene deposition in porous media is of great significance for the development of accurate numerical simulators and effective chemical remediation treatments. Here, we present a study of the dynamics of asphaltene deposition in porous media using microfluidic devices. A model oil containing 5 wt % dissolved asphaltenes was mixed with n-heptane, a known asphaltene precipitant, and flowed through a representative porous media microfluidic chip. Asphaltene deposition was recorded and analyzed as a function of solubility, which was directly correlated to particle size and Péclet number. In particular, pore-scale visualization and velocity profiles, as well as three stages of deposition, were identified and examined to determine the important convection-diffusion effects on deposition. PMID:27532331

  9. Fabrication of porous materials (metal, metal oxide and semiconductor) through an aerosol-assisted route

    NASA Astrophysics Data System (ADS)

    Sohn, Hiesang

    Porous materials have gained attraction owing to their vast applications in catalysts, sensors, energy storage devices, bio-devices and other areas. To date, various porous materials were synthesized through soft and hard templating approaches. However, a general synthesis method for porous non-oxide materials, metal alloys and semiconductors with tunable structure, composition and morphology has not been developed yet. To address this challenge, this thesis presents an aerosol method towards the synthesis of such materials and their applications for catalysis, hydrogen storage, Li-batteries and photo-catalysis. The first part of this thesis presents the synthesis of porous metals, metal oxides, and semiconductors with controlled pore structure, crystalline structure and morphology. In these synthesis processes, metal salts and organic ligands were employed as precursors to create porous metal-carbon frameworks. During the aerosol process, primary metal clusters and nanoparticles were formed, which were coagulated/ aggregated forming the porous particles. Various porous particles, such as those of metals (e.g., Ni, Pt, Co, Fe, and Ni xPt(1-x)), metal oxides (e.g., Fe3O4 and SnO2) and semiconductors (e.g., CdS, CuInS2, CuInS 2x-ZnS(1-x), and CuInS2x-TiO2(1-x)) were synthesized. The morphology, porous structure and crystalline structure of the particles were regulated through both templating and non-templating methods. The second part of this thesis explores the applications of these materials, including propylene hydrogenation and H2 uptake capacity of porous Ni, NiPt alloys and Ni-Pt composites, Li-storage of Fe3O4 and SnO2, photodegradation of CuInS2-based semiconductors. The effects of morphology, compositions, and porous structure on the device performance were systematically investigated. Overall, this dissertation work unveiled a simple synthesis approach for porous particles of metals, metal alloys, metal oxides, and semiconductors with controlled

  10. Modelling of nickel-cadmium batteries using porous electrode theory

    NASA Technical Reports Server (NTRS)

    Timmerman, Paul J.; Di Stefano, Salvador; Glueck, Peter R.; Perrone, David E.

    1991-01-01

    A porous electrode modeling technique is discussed which is considered a viable means for quantitatively predicting Ni-Cd cell performance. The authors describe the integration of the cell model into a battery model useful in the design and operation of aerospace applications. Test data from a sealed boilerplate cell are presented for constant current charge and discharge conditions. Performance predictions for similar cases have been performed, and a comparison to the boilerplate data is made. Areas for further development are also noted.

  11. A General 3-D Methodology for Quasi-Static Simulation of Drainage and Imbibition: Application to Highly Porous Fibrous Materials

    NASA Astrophysics Data System (ADS)

    Riasi, S.; Huang, G.; Montemagno, C.; Yeghiazarian, L.

    2013-12-01

    Micro-scale modeling of multiphase flow in porous media is critical to characterize porous materials. Several modeling techniques have been implemented to date, but none can be used as a general strategy for all porous media applications due to challenges presented by non-smooth high-curvature solid surfaces, and by a wide range of pore sizes and porosities. Finite approaches like the finite volume method require a high quality, problem-dependent mesh, while particle-based approaches like the lattice Boltzmann require too many particles to achieve a stable meaningful solution. Both come at a large computational cost. Other methods such as pore network modeling (PNM) have been developed to accelerate the solution process by simplifying the solution domain, but so far a unique and straightforward methodology to implement PNM is lacking. We have developed a general, stable and fast methodology to model multi-phase fluid flow in porous materials, irrespective of their porosity and solid phase topology. We have applied this methodology to highly porous fibrous materials in which void spaces are not distinctly separated, and where simplifying the geometry into a network of pore bodies and throats, as in PNM, does not result in a topology-consistent network. To this end, we have reduced the complexity of the 3-D void space geometry by working with its medial surface. We have used a non-iterative fast medial surface finder algorithm to determine a voxel-wide medial surface of the void space, and then solved the quasi-static drainage and imbibition on the resulting domain. The medial surface accurately represents the topology of the porous structure including corners, irregular cross sections, etc. This methodology is capable of capturing corner menisci and the snap-off mechanism numerically. It also allows for calculation of pore size distribution, permeability and capillary pressure-saturation-specific interfacial area surface of the porous structure. To show the

  12. Propagation of impact-induced shock waves in porous sandstone using mesoscale modeling

    NASA Astrophysics Data System (ADS)

    GÜLdemeister, Nicole; WÜNnemann, Kai; Durr, Nathanael; Hiermaier, Stefan

    2013-01-01

    Abstract-Generation and propagation of shock waves by meteorite impact is significantly affected by <span class="hlt">material</span> properties such as porosity, water content, and strength. The objective of this work was to quantify processes related to the shock-induced compaction of pore space by numerical <span class="hlt">modeling</span>, and compare the results with data obtained in the framework of the Multidisciplinary Experimental and <span class="hlt">Modeling</span> Impact Research Network (MEMIN) impact experiments. We use mesoscale <span class="hlt">models</span> resolving the collapse of individual pores to validate macroscopic (homogenized) approaches describing the bulk behavior of <span class="hlt">porous</span> and water-saturated <span class="hlt">materials</span> in large-scale <span class="hlt">models</span> of crater formation, and to quantify localized shock amplification as a result of pore space crushing. We carried out a suite of numerical <span class="hlt">models</span> of planar shock wave propagation through a well-defined area (the "sample") of <span class="hlt">porous</span> and/or water-saturated <span class="hlt">material</span>. The <span class="hlt">porous</span> sample is either represented by a homogeneous unit where porosity is treated as a state variable (macroscale <span class="hlt">model</span>) and water content by an equation of state for mixed <span class="hlt">material</span> (ANEOS) or by a defined number of individually resolved pores (mesoscale <span class="hlt">model</span>). We varied porosity and water content and measured thermodynamic parameters such as shock wave velocity and particle velocity on meso- and macroscales in separate simulations. The mesoscale <span class="hlt">models</span> provide additional data on the heterogeneous distribution of peak shock pressures as a consequence of the complex superposition of reflecting rarefaction waves and shock waves originating from the crushing of pores. We quantify the bulk effect of porosity, the reduction in shock pressure, in terms of Hugoniot data as a function of porosity, water content, and strength of a quartzite matrix. We find a good agreement between meso-, macroscale <span class="hlt">models</span> and Hugoniot data from shock experiments. We also propose a combination of a porosity compaction <span class="hlt">model</span> (ɛ-α <span class="hlt">model</span>) that was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011PhDT.......205M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011PhDT.......205M&link_type=ABSTRACT"><span id="translatedtitle">Synthesis and gas adsorption study of <span class="hlt">porous</span> metal-organic framework <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mu, Bin</p> <p></p> <p>Metal-organic frameworks (MOFs) or <span class="hlt">porous</span> coordination polymers (PCPs) have become the focus of intense study over the past decade due to their potential for advancing a variety of applications including air purification, gas storage, adsorption separations, catalysis, gas sensing, drug delivery, and so on. These <span class="hlt">materials</span> have some distinct advantages over traditional <span class="hlt">porous</span> <span class="hlt">materials</span> such as the well-defined structures, uniform pore sizes, chemically functionalized sorption sites, and potential for postsynthetic modification, etc. Thus, synthesis and adsorption studies of <span class="hlt">porous</span> MOFs have increased substantially in recent years. Among various prospective applications, air purification is one of the most immediate concerns, which has urgent requirements to improve current nuclear, biological, and chemical (NBC) filters involving commercial and military purposes. Thus, the major goal of this funded project is to search, synthesize, and test these novel hybrid <span class="hlt">porous</span> <span class="hlt">materials</span> for adsorptive removal of toxic industrial chemicals (TICs) and chemical warfare agents (CWAs), and to install the benchmark for new-generation NBC filters. The objective of this study is three-fold: (i) Advance our understanding of coordination chemistry by synthesizing novel MOFs and characterizing these <span class="hlt">porous</span> coordination polymers; (ii) Evaluate <span class="hlt">porous</span> MOF <span class="hlt">materials</span> for gasadsorption applications including CO2 capture, CH4 storage, other light gas adsorption and separations, and examine the chemical and physical properties of these solid adsorbents including thermal stability and heat capacity of MOFs; (iii) Evaluate <span class="hlt">porous</span> MOF <span class="hlt">materials</span> for next-generation NBC filter media by adsorption breakthrough measurements of TICs on MOFs, and advance our understanding about structureproperty relationships of these novel adsorbents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1145..941G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1145..941G"><span id="translatedtitle">Towards a Dynamical Collision <span class="hlt">Model</span> of Highly <span class="hlt">Porous</span> Dust Aggregates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Güttler, Carsten; Krause, Maya; Geretshauser, Ralf; Speith, Roland; Blum, Jürgen</p> <p>2009-06-01</p> <p>In the recent years we have performed various experiments on the collision dynamics of highly <span class="hlt">porous</span> dust aggregates and although we now have a comprehensive picture of the micromechanics of those aggregates, the macroscopic understanding is still lacking. We are therefore developing a mechanical <span class="hlt">model</span> to describe dust aggregate collisions with macroscopic parameters like tensile strength, compressive strength and shear strength. For one well defined dust sample <span class="hlt">material</span>, the tensile and compressive strength were measured in a static experiment and implemented in a Smoothed Particle Hydrodynamics (SPH) code. A laboratory experiment was designed to compare the laboratory results with the results of the SPH simulation. In this experiment, a mm-sized glass bead is dropped into a cm-sized dust aggregate with the previously measured strength parameters. We determine the deceleration of the glass bead by high-speed imaging and the compression of the dust aggregate by x-ray micro-tomography. The measured penetration depth, stopping time and compaction under the glass bead are utilized to calibrate and test the SPH code. We find that the statically measured compressive strength curve is only applicable if we adjust it to the dynamic situation with a ``softness'' parameter. After determining this parameter, the SPH code is capable of reproducing experimental results, which have not been used for the calibration before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JPS...280...30F&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JPS...280...30F&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Porous</span> hollow carbon spheres for electrode <span class="hlt">material</span> of supercapacitors and support <span class="hlt">material</span> of dendritic Pt electrocatalyst</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fan, Yang; Liu, Pei-Fang; Huang, Zhong-Yuan; Jiang, Tong-Wu; Yao, Kai-Li; Han, Ran</p> <p>2015-04-01</p> <p><span class="hlt">Porous</span> hollow carbon spheres (PHCSs) are prepared through hydrothermal carbonization of alginic acid and subsequent chemical activation by KOH. The porosity of the alginic acid derived PHCSs can be finely modulated by varying activation temperature in the range of 600-900 °C. The PHCSs activated at 900 °C possess the largest specific surface area (2421 m2 g-1), well-balanced micro- and mesoporosity, as well as high content of oxygen-containing functional groups. As the electrode <span class="hlt">material</span> for supercapacitors, the PHCSs exhibit superior capacitive performance with specific capacitance of 314 F g-1 at current density of 1 A g-1. Pt nanodendrites supported on the PHCSs are synthesized by polyol reduction method which exhibit high electrocatalytic activity towards methanol oxidation reaction (MOR). Moreover, CO-poisoning tolerance of the Pt nanodendrites is greatly enhanced owing to the surface chemical property of the PHCSs support.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPS...295..254S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPS...295..254S"><span id="translatedtitle">Template-assisted formation of <span class="hlt">porous</span> vanadium oxide as high performance cathode <span class="hlt">materials</span> for lithium ion batteries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Su, Yanhui; Pan, Anqiang; Wang, Yaping; Huang, Jiwu; Nie, Zhiwei; An, Xinxin; Liang, Shuquan</p> <p>2015-11-01</p> <p>Similar to carbonaceous <span class="hlt">materials</span>, <span class="hlt">porous</span> metal oxides have attracted wide attention in energy storage and conversion systems because of their structural advantages, including high activity and electrolyte accessibility. In this work, we report the novel preparation of <span class="hlt">porous</span> vanadium pentoxide (V2O5) as high performance cathode <span class="hlt">material</span> for lithium ion batteries. Ketjen black (KB), a <span class="hlt">porous</span> carbon <span class="hlt">material</span>, has been employed as hard templates to host precursor species in their <span class="hlt">porous</span> structures. The <span class="hlt">porous</span> V2O5 electrode <span class="hlt">material</span> is prepared after removing the KB carbon framework by calcinating the composites in air. As cathode <span class="hlt">materials</span> for lithium ion batteries, the <span class="hlt">porous</span> V2O5 electrodes exhibit high capacity, good cycling stability and rate capability. An initial discharge capacity of 141.1 mA h g-1 is delivered at a current density of 100 mAg-1, very close to the theoretical capacity of 147 mA h g-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27198674','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27198674"><span id="translatedtitle">Pore chemistry and size control in hybrid <span class="hlt">porous</span> <span class="hlt">materials</span> for acetylene capture from ethylene.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cui, Xili; Chen, Kaijie; Xing, Huabin; Yang, Qiwei; Krishna, Rajamani; Bao, Zongbi; Wu, Hui; Zhou, Wei; Dong, Xinglong; Han, Yu; Li, Bin; Ren, Qilong; Zaworotko, Michael J; Chen, Banglin</p> <p>2016-07-01</p> <p>The trade-off between physical adsorption capacity and selectivity of <span class="hlt">porous</span> <span class="hlt">materials</span> is a major barrier for efficient gas separation and purification through physisorption. We report control over pore chemistry and size in metal coordination networks with hexafluorosilicate and organic linkers for the purpose of preferential binding and orderly assembly of acetylene molecules through cooperative host-guest and/or guest-guest interactions. The specific binding sites for acetylene are validated by <span class="hlt">modeling</span> and neutron powder diffraction studies. The energies associated with these binding interactions afford high adsorption capacity (2.1 millimoles per gram at 0.025 bar) and selectivity (39.7 to 44.8) for acetylene at ambient conditions. Their efficiency for the separation of acetylene/ethylene mixtures is demonstrated by experimental breakthrough curves (0.73 millimoles per gram from a 1/99 mixture). PMID:27198674</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27195990','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27195990"><span id="translatedtitle">Tailoring of the <span class="hlt">porous</span> structure of soft emulsion-templated polymer <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kovalenko, Artem; Zimny, Kévin; Mascaro, Benoit; Brunet, Thomas; Mondain-Monval, Olivier</p> <p>2016-06-21</p> <p>This paper discusses the formation of soft <span class="hlt">porous</span> <span class="hlt">materials</span> obtained by the polymerization of inverse water-in-silicone (polydimethylsiloxane, PDMS) emulsions. We show that the initial state of the emulsion has a strong impact on the <span class="hlt">porous</span> structure and properties of the final <span class="hlt">material</span>. We show that using a surfactant with different solubilities in the emulsion continuous phase (PDMS), it is possible to tune the interaction between emulsion droplets, which leads to <span class="hlt">materials</span> with either interconnected or isolated pores. These two systems present completely different behavior upon drying, which results in macroporous air-filled <span class="hlt">materials</span> in the interconnected case and in a collapsed <span class="hlt">material</span> with low porosity in the second case. Finally, we compare the mechanical and acoustical properties of these two types of bulk polymer monoliths. We also describe the formation of micrometric polymer particles (beads) in these two cases. We show that <span class="hlt">materials</span> with an interconnected macroporous structure have low mechanical moduli and low sound speed, and are suitable for acoustic applications. The mechanical and acoustical properties of the <span class="hlt">materials</span> with a collapsed <span class="hlt">porous</span> structure are similar to those of non-<span class="hlt">porous</span> silicone, which makes them acoustically inactive. PMID:27195990</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.4833W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.4833W"><span id="translatedtitle">An electrical conductivity <span class="hlt">model</span> for fractal <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, Wei; Cai, Jianchao; Hu, Xiangyun; Han, Qi</p> <p>2015-06-01</p> <p>Archie's equation is an empirical electrical conductivity-porosity <span class="hlt">model</span> that has been used to predict the formation factor of <span class="hlt">porous</span> rock for more than 70 years. However, the physical interpretation of its parameters, e.g., the cementation exponent m, remains questionable. In this study, a theoretical electrical conductivity equation is derived based on the fractal characteristics of <span class="hlt">porous</span> media. The proposed <span class="hlt">model</span> is expressed in terms of the tortuosity fractal dimension (DT), the pore fractal dimension (Df), the electrical conductivity of the pore liquid, and the porosity. The empirical parameter m is then determined from physically based parameters, such as DT and Df. Furthermore, a distinct interrelationship between DT and Df is obtained. We find a reasonably good match between the predicted formation factor by our <span class="hlt">model</span> and experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015RMRE...48..223X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015RMRE...48..223X"><span id="translatedtitle">An Experimental Study and Constitutive <span class="hlt">Modeling</span> of Saturated <span class="hlt">Porous</span> Rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, S. Y.; Shao, J. F.</p> <p>2015-01-01</p> <p>This paper is devoted to the experimental characterization and constitutive <span class="hlt">modeling</span> of saturated <span class="hlt">porous</span> rocks. A typical <span class="hlt">porous</span> chalk is investigated. Drained hydrostatic and triaxial compression tests are first performed to characterize the basic mechanical behavior of chalk. Drained triaxial tests with constant interstitial pressure are then carried out to study the effects of interstitial pressure on the plastic deformation and failure criterion. Finally, undrained triaxial compression tests are performed to investigate poromechanical coupling in saturated conditions. Based on the experimental data and some relevant micromechanical considerations, a micromechanics-based plastic <span class="hlt">model</span> is proposed and extended to poroplastic coupling using the effective stress concept. The proposed <span class="hlt">model</span> is verified through comparisons between the numerical results and experimental data for both drained and undrained tests.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..DFDD31010A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..DFDD31010A"><span id="translatedtitle">Mathematical <span class="hlt">modeling</span> heat and mass transfer processes in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Akhmed-Zaki, Darkhan</p> <p>2013-11-01</p> <p>On late development stages of oil-fields appears a complex problem of oil-recovery reduction. One of solution approaches is injecting of surfactant together with water in the form of active impurities into the productive layer - for decreasing oil viscosity and capillary forces between ``oil-water'' phases system. In fluids flow the surfactant can be in three states: dissolved in water, dissolved in oil and adsorbed on pore channels' walls. The surfactant's invasion into the reservoir is tracked by its diffusion with reservoir liquid and mass-exchange with two phase (liquid and solid) components of <span class="hlt">porous</span> structure. Additionally, in this case heat exchange between fluids (injected, residual) and framework of <span class="hlt">porous</span> medium has practical importance for evaluating of temperature influences on enhancing oil recovery. Now, the problem of designing an adequate mathematical <span class="hlt">model</span> for describing a simultaneous flowing heat and mass transfer processes in anisotropic heterogeneous <span class="hlt">porous</span> medium -surfactant injection during at various temperature regimes has not been fully researched. In this work is presents a 2D mathematical <span class="hlt">model</span> of surfactant injections into the oil reservoir. Description of heat- and mass transfer processes in a <span class="hlt">porous</span> media is done through differential and kinetic equations. For designing a computational algorithm is used modify version of IMPES method. The sequential and parallel computational algorithms are developed using an adaptive curvilinear meshes which into account heterogeneous <span class="hlt">porous</span> structures. In this case we can evaluate the boundaries of our process flows - fronts (``invasion'', ``heat'' and ``mass'' transfers), according to the pressure, temperature, and concentration gradient changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1034349','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1034349"><span id="translatedtitle">Systems and strippable coatings for decontaminating structures that include <span class="hlt">porous</span> <span class="hlt">material</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Fox, Robert V.; Avci, Recep; Groenewold, Gary S.</p> <p>2011-12-06</p> <p>Methods of removing contaminant matter from <span class="hlt">porous</span> <span class="hlt">materials</span> include applying a polymer <span class="hlt">material</span> to a contaminated surface, irradiating the contaminated surface to cause redistribution of contaminant matter, and removing at least a portion of the polymer <span class="hlt">material</span> from the surface. Systems for decontaminating a contaminated structure comprising <span class="hlt">porous</span> <span class="hlt">material</span> include a radiation device configured to emit electromagnetic radiation toward a surface of a structure, and at least one spray device configured to apply a capture <span class="hlt">material</span> onto the surface of the structure. Polymer <span class="hlt">materials</span> that can be used in such methods and systems include polyphosphazine-based polymer <span class="hlt">materials</span> having polyphosphazine backbone segments and side chain groups that include selected functional groups. The selected functional groups may include iminos, oximes, carboxylates, sulfonates, .beta.-diketones, phosphine sulfides, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, monothio phosphinic acids, and dithio phosphinic acids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1038224','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1038224"><span id="translatedtitle"><span class="hlt">Modeling</span> reactive transport in deformable <span class="hlt">porous</span> media using the theory of interacting continua.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Turner, Daniel Zack</p> <p>2012-01-01</p> <p>This report gives an overview of the work done as part of an Early Career LDRD aimed at <span class="hlt">modeling</span> flow induced damage of <span class="hlt">materials</span> involving chemical reactions, deformation of the <span class="hlt">porous</span> matrix, and complex flow phenomena. The numerical formulation is motivated by a mixture theory or theory of interacting continua type approach to coupling the behavior of the fluid and the <span class="hlt">porous</span> matrix. Results for the proposed method are presented for several engineering problems of interest including carbon dioxide sequestration, hydraulic fracturing, and energetic <span class="hlt">materials</span> applications. This work is intended to create a general framework for flow induced damage that can be further developed in each of the particular areas addressed below. The results show both convincing proof of the methodologies potential and the need for further validation of the <span class="hlt">models</span> developed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/485961','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/485961"><span id="translatedtitle">In situ bioremediation: A network <span class="hlt">model</span> of diffusion and flow in granular <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Griffiths, S.K.; Nilson, R.H.; Bradshaw, R.W.</p> <p>1997-04-01</p> <p>In situ bioremediation is a potentially expedient, permanent and cost- effective means of waste site decontamination. However, permeability reductions due to the transport and deposition of native fines or due to excessive microorganism populations may severely inhibit the injection of supplemental oxygen in the contamination zone. To help understand this phenomenon, we have developed a micro-mechanical network <span class="hlt">model</span> of flow, diffusion and particle transport in granular <span class="hlt">porous</span> <span class="hlt">materials</span>. The <span class="hlt">model</span> differs from most similar <span class="hlt">models</span> in that the network is defined by particle positions in a numerically-generated particle array. The <span class="hlt">model</span> is thus widely applicable to computing effective transport properties for both ordered and realistic random <span class="hlt">porous</span> media. A laboratory-scale apparatus to measure permeability reductions has also been designed, built and tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMagR.269....1K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMagR.269....1K"><span id="translatedtitle">Diffusion-mediated nuclear spin phase decoherence in cylindrically <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knight, Michael J.; Kauppinen, Risto A.</p> <p>2016-08-01</p> <p>In NMR or MRI of complex <span class="hlt">materials</span>, including biological tissues and <span class="hlt">porous</span> <span class="hlt">materials</span>, magnetic susceptibility differences within the <span class="hlt">material</span> result in local magnetic field inhomogeneities, even if the applied magnetic field is homogeneous. Mobile nuclear spins move though the inhomogeneous field, by translational diffusion and other mechanisms, resulting in decoherence of nuclear spin phase more rapidly than transverse relaxation alone. The objective of this paper is to simulate this diffusion-mediated decoherence and demonstrate that it may substantially reduce coherence lifetimes of nuclear spin phase, in an anisotropic fashion. We do so using a <span class="hlt">model</span> of cylindrical pores within an otherwise homogeneous <span class="hlt">material</span>, and calculate the resulting magnetic field inhomogeneities. Our simulations show that diffusion-mediated decoherence in a system of parallel cylindrical pores is anisotropic, with coherence lifetime minimised when the array of cylindrical pores is perpendicular to B0. We also show that this anisotropy of coherence lifetime is reduced if the orientations of cylindrical pores are disordered within the system. In addition we characterise the dependence on B0, the magnetic susceptibility of the cylindrical pores relative to the surroundings, the diffusion coefficient and cylinder wall thickness. Our findings may aid in the interpretation of NMR and MRI relaxation data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27208416','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27208416"><span id="translatedtitle">Diffusion-mediated nuclear spin phase decoherence in cylindrically <span class="hlt">porous</span> <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Knight, Michael J; Kauppinen, Risto A</p> <p>2016-08-01</p> <p>In NMR or MRI of complex <span class="hlt">materials</span>, including biological tissues and <span class="hlt">porous</span> <span class="hlt">materials</span>, magnetic susceptibility differences within the <span class="hlt">material</span> result in local magnetic field inhomogeneities, even if the applied magnetic field is homogeneous. Mobile nuclear spins move though the inhomogeneous field, by translational diffusion and other mechanisms, resulting in decoherence of nuclear spin phase more rapidly than transverse relaxation alone. The objective of this paper is to simulate this diffusion-mediated decoherence and demonstrate that it may substantially reduce coherence lifetimes of nuclear spin phase, in an anisotropic fashion. We do so using a <span class="hlt">model</span> of cylindrical pores within an otherwise homogeneous <span class="hlt">material</span>, and calculate the resulting magnetic field inhomogeneities. Our simulations show that diffusion-mediated decoherence in a system of parallel cylindrical pores is anisotropic, with coherence lifetime minimised when the array of cylindrical pores is perpendicular to B0. We also show that this anisotropy of coherence lifetime is reduced if the orientations of cylindrical pores are disordered within the system. In addition we characterise the dependence on B0, the magnetic susceptibility of the cylindrical pores relative to the surroundings, the diffusion coefficient and cylinder wall thickness. Our findings may aid in the interpretation of NMR and MRI relaxation data. PMID:27208416</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NRL.....8..266C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NRL.....8..266C"><span id="translatedtitle">Laser-induced growth of nanocrystals embedded in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Capoen, Bruno; Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bouazaoui, Mohamed</p> <p>2013-06-01</p> <p>Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated <span class="hlt">porous</span> xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in <span class="hlt">porous</span> silica xerogels, which allows</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3751908','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3751908"><span id="translatedtitle">Laser-induced growth of nanocrystals embedded in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2013-01-01</p> <p>Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated <span class="hlt">porous</span> xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in <span class="hlt">porous</span> silica xerogels, which allows</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H14A..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H14A..01L"><span id="translatedtitle"><span class="hlt">Modelling</span> the Complex Conductivity of Charged <span class="hlt">Porous</span> Media using The Grain Polarization <span class="hlt">Model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leroy, P.; Revil, A.; Jougnot, D.; Li, S.</p> <p>2015-12-01</p> <p>The low-frequency complex conductivity response of charged <span class="hlt">porous</span> media reflects a combination of three polarization processes occuring at different frequency ranges. One polarization process corresponds to the membrane polarization phenomenon, which is the polarization mechanism associated with the back-diffusion of salt ions through different pore spaces of the <span class="hlt">porous</span> <span class="hlt">material</span> (ions-selective zones and zones with no selectivity). This polarization process generally occurs at the lowest frequency range, typically in the frequency range [mHz Hz] because it involves polarization mechanism occurring over different pore spaces (the relaxation frequency is inversely proportional to the length of the polarization process). Another polarization process corresponds to the electrochemical polarization of the electrical double layer coating the surface of the grains. In the grain polarization <span class="hlt">model</span>, the diffuse layer is assumed to not polarize because it is assumed to form a continuum in the <span class="hlt">porous</span> medium. The compact Stern layer is assumed to polarize because the Stern layer is assumed to be discontinuous over multiple grains. The electrochemical polarization of the Stern layer typically occurs in the frequency range [Hz kHz]. The last polarization process corresponds to the Maxwell-Wagner polarization mechanism, which is caused by the formation of field-induced free charge distributions near the interface between the phases of the medium. In this presentation, the grain polarization <span class="hlt">model</span> based on the O'Konski, Schwarz, Schurr and Sen theories and developed later by Revil and co-workers is showed. This spectral induced polarization <span class="hlt">model</span> was successfully applied to describe the complex conductivity responses of glass beads, sands, clays, clay-sand mixtures and other minerals. The limits of this <span class="hlt">model</span> and future developments will also be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19760055232&hterms=porous+burner&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dporous%2Bburner','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19760055232&hterms=porous+burner&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dporous%2Bburner"><span id="translatedtitle">Composite propellant combustion <span class="hlt">modeling</span> with a <span class="hlt">porous</span> plate burner</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kumar, R. N.; Strand, L. D.; Mcnamara, R. P.</p> <p>1976-01-01</p> <p>A burner is designed to <span class="hlt">model</span> on a large scale (millimeters) the complex vapor phase processes that take place on awkwardly small scales (about a hundred microns) in the combustion of practical AP/ composite propellants at conventional pressures. Binder vapor evolution is <span class="hlt">modeled</span> with gaseous fuel (ethane in the experiments reported) flow through a <span class="hlt">porous</span> plate and oxidizer vapor with the flow of a gaseous oxidizer (air and enriched air in the experiments reported) through discrete holes in the <span class="hlt">porous</span> plate. Measured flame standoff distance and surface temperature variations are consistent with theoretical predictions at atmospheric pressure. Data obtained at several atmospheres are discussed in the light of the current theories of propellant burning that place varying emphasis on the roles of chemical kinetics and fluid dynamic diffusion/mixing in the vapor phase of a burning composite propellant. The potential and proposed future applications of the burner are indicated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950020938','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950020938"><span id="translatedtitle">A probabilistic <span class="hlt">model</span> of a <span class="hlt">porous</span> heat exchanger</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Agrawal, O. P.; Lin, X. A.</p> <p>1995-01-01</p> <p>This paper presents a probabilistic one-dimensional finite element <span class="hlt">model</span> for heat transfer processes in <span class="hlt">porous</span> heat exchangers. The Galerkin approach is used to develop the finite element matrices. Some of the submatrices are asymmetric due to the presence of the flow term. The Neumann expansion is used to write the temperature distribution as a series of random variables, and the expectation operator is applied to obtain the mean and deviation statistics. To demonstrate the feasibility of the formulation, a one-dimensional <span class="hlt">model</span> of heat transfer phenomenon in superfluid flow through a <span class="hlt">porous</span> media is considered. Results of this formulation agree well with the Monte-Carlo simulations and the analytical solutions. Although the numerical experiments are confined to parametric random variables, a formulation is presented to account for the random spatial variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004AGUFM.H53A1235C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004AGUFM.H53A1235C&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Modeling</span> Multi-process Transport of Pathogens in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheng, L.; Brusseau, M. L.</p> <p>2004-12-01</p> <p>The transport behavior of microorganisms in <span class="hlt">porous</span> media is of interest with regard to the fate of pathogens associated with wastewater recharge, riverbank filtration, and land application of biosolids. This interest has fomented research on the transport of pathogens in the subsurface environment. The factors influencing pathogen transport within the subsurface environment include advection, dispersion, filtration, and inactivation. The filtration process, which mediates the magnitude and rate of pathogen retention, comprises several mechanisms such as attachment to <span class="hlt">porous</span>-medium surfaces, straining, and sedimentation. We present a mathematical <span class="hlt">model</span> wherein individual filtration mechanisms are explicitly incorporated along with advection, dispersion, and inactivation. The performance of the <span class="hlt">model</span> is evaluated by applying it to several data sets obtained from miscible-displacement experiments conducted using various pathogens. Input parameters are obtained to the extent possible from independent means.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1083394','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1083394"><span id="translatedtitle">Dissipative particle dynamics <span class="hlt">model</span> for colloid transport in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pan, W.; Tartakovsky, A. M.</p> <p>2013-08-01</p> <p>We present that the transport of colloidal particles in <span class="hlt">porous</span> media can be effectively <span class="hlt">modeled</span> with a new formulation of dissipative particle dynamics, which augments standard DPD with non-central dissipative shear forces between particles while preserving angular momentum. Our previous studies have demonstrated that the new formulation is able to capture accurately the drag forces as well as the drag torques on colloidal particles that result from the hydrodynamic retardation effect. In the present work, we use the new formulation to study the contact efficiency in colloid filtration in saturated <span class="hlt">porous</span> media. Note that the present <span class="hlt">model</span> include all transport mechanisms simultaneously, including gravitational sedimentation, interception and Brownian diffusion. Our results of contact efficiency show a good agreement with the predictions of the correlation equation proposed by Tufenkji and EliMelech, which also incorporate all transport mechanisms simultaneously without the additivity assumption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AIPC.1738U0047K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AIPC.1738U0047K&link_type=ABSTRACT"><span id="translatedtitle">Numerical <span class="hlt">modeling</span> of fresh concrete flow through <span class="hlt">porous</span> medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kolařík, F.; Patzák, B.; Zeman, J.</p> <p>2016-06-01</p> <p>The paper focuses on a numerical <span class="hlt">modeling</span> of a non-Newtonian fluid flow in a <span class="hlt">porous</span> domain. It presents combination of a homogenization approach to obtain permeability from the underlying micro-structure with coupling of a Stokes and Darcy flow through the interface on the macro level. As a numerical method we employed the Finite Element method. The results obtained from the homogenization approach are validated against fully resolved solution computed by direct numerical simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H53H..01R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H53H..01R"><span id="translatedtitle">Pore Topology Method: A General and Fast Pore-Scale <span class="hlt">Modeling</span> Approach to Simulate Fluid Flow in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riasi, M. S.; Huang, G.; Montemagno, C.; Yeghiazarian, L.</p> <p>2014-12-01</p> <p>Micro-scale <span class="hlt">modeling</span> of multiphase flow in <span class="hlt">porous</span> media is critical to characterize <span class="hlt">porous</span> <span class="hlt">materials</span>. Several <span class="hlt">modeling</span> techniques have been implemented to date, but none can be used as a general strategy for all <span class="hlt">porous</span> media applications due to challenges presented by non-smooth high-curvature and deformable solid surfaces, and by a wide range of pore sizes and porosities. Finite approaches like the finite volume method require a high quality, problem-dependent mesh, while particle-based approaches like the lattice Boltzmann require too many particles to achieve a stable meaningful solution. Both come at a large computational cost. Other methods such as pore network <span class="hlt">modeling</span> (PNM) have been developed to accelerate the solution process by simplifying the solution domain, but so far a unique and straightforward methodology to implement PNM is lacking. Pore topology method (PTM) is a new topologically consistent approach developed to simulate multiphase flow in <span class="hlt">porous</span> media. The core of PTM is to reduce the complexity of the 3-D void space geometry by working with its medial surface as the solution domain. Medial surface is capable of capturing all the corners and surface curvatures in a <span class="hlt">porous</span> structure, and therefore provides a topologically consistent representative geometry for <span class="hlt">porous</span> structure. Despite the simplicity and low computational cost, PTM provides a fast and straightforward approach for micro-scale <span class="hlt">modeling</span> of fluid flow in all types of <span class="hlt">porous</span> media irrespective of their porosity and pore size distribution. In our previous work, we developed a non-iterative fast medial surface finder algorithm to determine a voxel-wide medial surface of the void space of <span class="hlt">porous</span> media as well as a set of simple rules to determine the capillary pressure-saturation curves for a <span class="hlt">porous</span> system assuming quasi-static two-phase flow with a planar w-nw interface. Our simulation results for a highly <span class="hlt">porous</span> fibrous <span class="hlt">material</span> and polygonal capillary tubes were in excellent agreement</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70019031','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70019031"><span id="translatedtitle">Determination of water retention in stratified <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Constantz, J.</p> <p>1995-01-01</p> <p>Predicted and measured water-retention values, ??(??), were compared for repacked, stratified core samples consisting of either a sand with a stone-bearing layer or a sand with a clay loam layer in various spatial orientations. Stratified core samples were packed in submersible pressure outflow cells, then water-retention measurements were performed between matric potentials, ??, of 0 to -100 kPa. Predictions of ??(??) were based on a simple volume-averaging <span class="hlt">model</span> using estimates of the relative fraction and ??(??) values of each textural component within a stratified sample. In general, predicted ??(??) curves resembled measured curves well, except at higher saturations in a sample consisting of a clay loam layer over a sand layer. In this case, the <span class="hlt">model</span> averaged the air-entry of both <span class="hlt">materials</span>, while the air-entry of the sample was controlled by the clay loam in contact with the cell's air-pressure inlet. In situ, avenues for air-entry generally exist around clay layers, so that the <span class="hlt">model</span> should adequately predict air-entry for stratified formations regardless of spatial orientation of fine versus coarse layers. Agreement between measured and predicted volumetric water contents, ??, was variable though encouraging, with mean differences between measured and predicted ?? values in the range of 10%. Differences in ?? of this magnitude are expected due to variability in pore structure between samples, and do not indicate inherent problems with the volume averaging <span class="hlt">model</span>. This suggets that explicit <span class="hlt">modeling</span> of stratified formations through detailed characterization of the stratigraphy has the potential of yielding accurate ??(??) values. However, hydraulic-equilibration times were distinctly different for each variation in spatial orientation of textural layering, indicating that transient behavior during drainage in stratified formations is highly sensitive to the stratigraphic sequence of textural components, as well as the volume fraction of each textural</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H13B1318Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H13B1318Q"><span id="translatedtitle"><span class="hlt">Modeling</span> of Multiphase Flow through Thin <span class="hlt">Porous</span> Layers: Application to a Polymer Electrolyte Fuel Cell (PEFC)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qin, C.; Hassanizadeh, S.</p> <p>2013-12-01</p> <p>Multiphase flow and species transport though thin <span class="hlt">porous</span> layers are encountered in a number of industrial applications, such as fuel cells, filters, and hygiene products. Based on some macroscale <span class="hlt">models</span> like the Darcy's law, to date, the <span class="hlt">modeling</span> of flow and transport through such thin layers has been mostly performed in 3D discretized domains with many computational cells. But, there are a number of problems with this approach. First, a proper representative elementary volume (REV) is not defined. Second, one needs to discretize a thin <span class="hlt">porous</span> medium into computational cells whose size may be comparable to the pore sizes. This suggests that the traditional <span class="hlt">models</span> are not applicable to such thin domains. Third, the interfacial conditions between neighboring layers are usually not well defined. Last, 3D <span class="hlt">modeling</span> of a number of interacting thin <span class="hlt">porous</span> layers often requires heavy computational efforts. So, to eliminate the drawbacks mentioned above, we propose a new approach to <span class="hlt">modeling</span> multilayers of thin <span class="hlt">porous</span> media as 2D interacting continua (see Fig. 1). Macroscale 2D governing equations are formulated in terms of thickness-averaged <span class="hlt">material</span> properties. Also, the exchange of thermodynamic properties between neighboring layers is described by thickness-averaged quantities. In Comparison to previous macroscale <span class="hlt">models</span>, our <span class="hlt">model</span> has the distinctive advantages of: (1) it is rigorous thermodynamics-based <span class="hlt">model</span>; (2) it is formulated in terms of thickness-averaged <span class="hlt">material</span> properties which are easily measureable; and (3) it reduces 3D <span class="hlt">modeling</span> to 2D leading to a very significant reduction of computation efforts. As an application, we employ the new approach in the study of liquid water flooding in the cathode of a polymer electrolyte fuel cell (PEFC). To highlight the advantages of the present <span class="hlt">model</span>, we compare the results of water distribution with those obtained from the traditional 3D Darcy-based <span class="hlt">modeling</span>. Finally, it is worth noting that, for specific case studies, a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1683b0020B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1683b0020B"><span id="translatedtitle">A mesomechanical analysis of the deformation and fracture in polycrystalline <span class="hlt">materials</span> with ceramic <span class="hlt">porous</span> coatings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Balokhonov, R. R.; Zinoviev, A. V.; Romanova, V. A.; Batukhtina, E. E.</p> <p>2015-10-01</p> <p>The special features inherent in the mesoscale mechanical behavior of a <span class="hlt">porous</span> ceramic coating-steel substrate composite are investigated. Microstructure of the coated <span class="hlt">material</span> is accounted for explicitly as initial conditions of a plane strain dynamic boundary-value problem solved by the finite difference method. Using a mechanical analogy method, a procedure for generating a uniform curvilinear finite difference computational mesh is developed to provide a more accurate description of the complex grain boundary geometry. A modified algorithm for generation of polycrystalline microstructure of the substrate is designed on the basis of the cellular automata method. The constitutive equations for a steel matrix incorporate an elastic-plastic <span class="hlt">model</span> for a <span class="hlt">material</span> subjected to isotropic hardening. The Hall-Petch relation is used to account for the effect of the grain size on the yield stress and strain hardening history. A brittle fracture <span class="hlt">model</span> for a ceramic coating relying on the Huber criterion is employed. The <span class="hlt">model</span> allows for crack nucleation in the regions of triaxial tension. The complex inhomogeneous stress and plastic strain patterns are shown to be due to the presence of interfaces of three types: coating-substrate interface, grain boundaries, and pore surfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatMa..15..371C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatMa..15..371C"><span id="translatedtitle"><span class="hlt">Materials</span> <span class="hlt">modelling</span> in London</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ciudad, David</p> <p>2016-04-01</p> <p>Angelos Michaelides, Professor in Theoretical Chemistry at University College London (UCL) and co-director of the Thomas Young Centre (TYC), explains to Nature <span class="hlt">Materials</span> the challenges in <span class="hlt">materials</span> <span class="hlt">modelling</span> and the objectives of the TYC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Nanos...7.5826G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Nanos...7.5826G"><span id="translatedtitle">Graded <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> derived from self-assembled block copolymer templates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gu, Yibei; Werner, Jörg G.; Dorin, Rachel M.; Robbins, Spencer W.; Wiesner, Ulrich</p> <p>2015-03-01</p> <p>Graded <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> directed by macromolecular self-assembly are expected to offer unique structural platforms relative to conventional <span class="hlt">porous</span> inorganic <span class="hlt">materials</span>. Their preparation to date remains a challenge, however, based on the sparsity of viable synthetic self-assembly pathways to control structural asymmetry. Here we demonstrate the fabrication of graded <span class="hlt">porous</span> carbon, metal, and metal oxide film structures from self-assembled block copolymer templates by using various backfilling techniques in combination with thermal treatments for template removal and chemical transformations. The asymmetric inorganic structures display mesopores in the film top layers and a gradual pore size increase along the film normal in the macroporous sponge-like support structure. Substructure walls between macropores are themselves mesoporous, constituting a structural hierarchy in addition to the pore gradation. Final graded structures can be tailored by tuning casting conditions of self-assembled templates as well as the backfilling processes. We expect that these graded <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> may find use in applications including separation, catalysis, biomedical implants, and energy conversion and storage.Graded <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> directed by macromolecular self-assembly are expected to offer unique structural platforms relative to conventional <span class="hlt">porous</span> inorganic <span class="hlt">materials</span>. Their preparation to date remains a challenge, however, based on the sparsity of viable synthetic self-assembly pathways to control structural asymmetry. Here we demonstrate the fabrication of graded <span class="hlt">porous</span> carbon, metal, and metal oxide film structures from self-assembled block copolymer templates by using various backfilling techniques in combination with thermal treatments for template removal and chemical transformations. The asymmetric inorganic structures display mesopores in the film top layers and a gradual pore size increase along the film normal in the macroporous sponge</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...626438Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...626438Z"><span id="translatedtitle">Freeze-drying of “pearl milk tea”: A general strategy for controllable synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Yingke; Tian, Xiaohui; Wang, Pengcheng; Hu, Min; Du, Guodong</p> <p>2016-05-01</p> <p><span class="hlt">Porous</span> <span class="hlt">materials</span> have been widely used in many fields, but the large-scale synthesis of <span class="hlt">materials</span> with controlled pore sizes, pore volumes, and wall thicknesses remains a considerable challenge. Thus, the controllable synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span> is of key general importance. Herein, we demonstrate the “pearl milk tea” freeze-drying method to form <span class="hlt">porous</span> <span class="hlt">materials</span> with controllable pore characteristics, which is realized by rapidly freezing the uniformly distributed template-containing precursor solution, followed by freeze-drying and suitable calcination. This general and convenient method has been successfully applied to synthesize various <span class="hlt">porous</span> phosphate and oxide <span class="hlt">materials</span> using different templates. The method is promising for the development of tunable <span class="hlt">porous</span> <span class="hlt">materials</span> for numerous applications of energy, environment, and catalysis, etc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22207389','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22207389"><span id="translatedtitle">Effect of crystallization time on the physico-chemical and catalytic properties of the hierarchical <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xu, Ling; Ma, Yuanyuan; Ding, Wenli; Guan, Jingqi; Wu, Shujie; Kan, Qiubin</p> <p>2010-09-15</p> <p>A series of hierarchical <span class="hlt">porous</span> <span class="hlt">materials</span> were prepared by a dual template method. The effect of different crystallization time on the channel architecture, morphology, acid performance of the hierarchical <span class="hlt">porous</span> <span class="hlt">materials</span> was investigated. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption and {sup 27}Al nuclear magnetic resonance were performed to obtain information on the physico-chemical properties of the <span class="hlt">materials</span>. It was shown that the change in crystallization time could influence the structure/texture and surface acid properties of the hierarchical <span class="hlt">porous</span> <span class="hlt">materials</span>. In addition, alkylation of phenol with tert-butanol reaction was carried out to investigate the catalytic performance of the hierarchical <span class="hlt">porous</span> <span class="hlt">materials</span>. The results showed that the catalytic activity of the hierarchical <span class="hlt">porous</span> <span class="hlt">materials</span> and the selectivity to the bulkly product 2,4-di-tert-butyl-phenol decreased with processing time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4872234','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4872234"><span id="translatedtitle">Freeze-drying of “pearl milk tea”: A general strategy for controllable synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhou, Yingke; Tian, Xiaohui; Wang, Pengcheng; Hu, Min; Du, Guodong</p> <p>2016-01-01</p> <p><span class="hlt">Porous</span> <span class="hlt">materials</span> have been widely used in many fields, but the large-scale synthesis of <span class="hlt">materials</span> with controlled pore sizes, pore volumes, and wall thicknesses remains a considerable challenge. Thus, the controllable synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span> is of key general importance. Herein, we demonstrate the “pearl milk tea” freeze-drying method to form <span class="hlt">porous</span> <span class="hlt">materials</span> with controllable pore characteristics, which is realized by rapidly freezing the uniformly distributed template-containing precursor solution, followed by freeze-drying and suitable calcination. This general and convenient method has been successfully applied to synthesize various <span class="hlt">porous</span> phosphate and oxide <span class="hlt">materials</span> using different templates. The method is promising for the development of tunable <span class="hlt">porous</span> <span class="hlt">materials</span> for numerous applications of energy, environment, and catalysis, etc. PMID:27193866</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/868855','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/868855"><span id="translatedtitle">Process of making <span class="hlt">porous</span> ceramic <span class="hlt">materials</span> with controlled porosity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Anderson, Marc A.; Ku, Qunyin</p> <p>1993-01-01</p> <p>A method of making metal oxide ceramic <span class="hlt">material</span> is disclosed by which the porosity of the resulting <span class="hlt">material</span> can be selectively controlled by manipulating the sol used to make the <span class="hlt">material</span>. 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 <span class="hlt">materials</span> can readily be shaped by extrusion into shapes typical of catalytic or adsorbent bodies used in industry, to facilitate the application of such <span class="hlt">materials</span> for catalytic and adsorbent applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4680965','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4680965"><span id="translatedtitle">Dimpled elastic sheets: a new class of non-<span class="hlt">porous</span> negative Poisson’s ratio <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C.; Shanian, Ali; Weaver, James C.; Bertoldi, Katia</p> <p>2015-01-01</p> <p>In this study, we report a novel periodic <span class="hlt">material</span> with negative Poisson’s ratio (also called auxetic <span class="hlt">materials</span>) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic <span class="hlt">materials</span> are either <span class="hlt">porous</span> or comprise at least two phases, the <span class="hlt">material</span> proposed here is non-<span class="hlt">porous</span> and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic <span class="hlt">materials</span> that significantly expand their design space and possible applications. PMID:26671169</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26671169','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26671169"><span id="translatedtitle">Dimpled elastic sheets: a new class of non-<span class="hlt">porous</span> negative Poisson's ratio <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C; Shanian, Ali; Weaver, James C; Bertoldi, Katia</p> <p>2015-01-01</p> <p>In this study, we report a novel periodic <span class="hlt">material</span> with negative Poisson's ratio (also called auxetic <span class="hlt">materials</span>) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic <span class="hlt">materials</span> are either <span class="hlt">porous</span> or comprise at least two phases, the <span class="hlt">material</span> proposed here is non-<span class="hlt">porous</span> and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic <span class="hlt">materials</span> that significantly expand their design space and possible applications. PMID:26671169</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...518373J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...518373J"><span id="translatedtitle">Dimpled elastic sheets: a new class of non-<span class="hlt">porous</span> negative Poisson’s ratio <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C.; Shanian, Ali; Weaver, James C.; Bertoldi, Katia</p> <p>2015-12-01</p> <p>In this study, we report a novel periodic <span class="hlt">material</span> with negative Poisson’s ratio (also called auxetic <span class="hlt">materials</span>) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic <span class="hlt">materials</span> are either <span class="hlt">porous</span> or comprise at least two phases, the <span class="hlt">material</span> proposed here is non-<span class="hlt">porous</span> and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic <span class="hlt">materials</span> that significantly expand their design space and possible applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040084809','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040084809"><span id="translatedtitle">Measurements of Acoustic Properties of <span class="hlt">Porous</span> and Granular <span class="hlt">Materials</span> and Application to Vibration Control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Park, Junhong; Palumbo, Daniel L.</p> <p>2004-01-01</p> <p>For application of <span class="hlt">porous</span> and granular <span class="hlt">materials</span> to vibro-acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The primary goal of this study was to investigate structural vibration damping through this frame wave propagation for various poroelastic <span class="hlt">materials</span>. A measurement method to investigate the vibration characteristics of the frame was proposed. The measured properties were found to follow closely the characteristics of the viscoelastic <span class="hlt">materials</span> - the dynamic modulus increased with frequency and the degree of the frequency dependence was determined by its loss factor. The dynamic stiffness of hollow cylindrical beams containing <span class="hlt">porous</span> and granular <span class="hlt">materials</span> as damping treatment was measured also. The data were used to extract the damping <span class="hlt">materials</span> characteristics using the Rayleigh-Ritz method. The results suggested that the acoustic structure interaction between the frame and the structure enhances the dissipation of the vibration energy significantly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3767460','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3767460"><span id="translatedtitle">A <span class="hlt">Porous</span> Media <span class="hlt">Model</span> for Blood Flow within Reticulated Foam</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ortega, J.M.</p> <p>2013-01-01</p> <p>A <span class="hlt">porous</span> media <span class="hlt">model</span> is developed for non-Newtonian blood flow through reticulated foam at Reynolds numbers ranging from 10−8 to 10. This empirical <span class="hlt">model</span> effectively divides the pressure gradient versus flow speed curve into three regimes, in which either the non-Newtonian viscous forces, the Newtonian viscous forces, or the inertial fluid forces are most prevalent. When compared to simulation data of blood flow through two reticulated foam geometries, the <span class="hlt">model</span> adequately captures the pressure gradient within all three regimes, especially that within the Newtonian regime where blood transitions from a power-law to a constant viscosity fluid. PMID:24031095</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/15020420','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/15020420"><span id="translatedtitle"><span class="hlt">Modeling</span> of Biomass Plug Development and Propagation in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stewart, Terri L.; Kim, Dong-Shik</p> <p>2004-02-01</p> <p>Biomass accumulation and evolution in <span class="hlt">porous</span> media were simulated using a combination of biofilm evolution <span class="hlt">model</span> and a biofilm removal <span class="hlt">model</span>. Theses <span class="hlt">models</span> describe biomass plug development, removal, and propagation in biological applications such as microbial enhanced oil recovery, in situ bioremediation, and bio-barrier techniques. The biofilm evolution <span class="hlt">model</span> includes the cell growth rate and exopolymer production kinetics. The biofilm removal <span class="hlt">model</span> was used for describing the biomass plug propagation and channel breakthrough using Bingham yield stress of biofilm, which represents the stability of biofilm against shear stress. Network <span class="hlt">model</span> was used to describe a <span class="hlt">porous</span> medium. The network <span class="hlt">model</span> consists of pore body and pore bond of which the sizes were determined based on the pore size distribution of ceramic cores. The pressure drop across the network is assumed to be generated from pore bonds only, and the cell growth and biomass accumulation took place in pore bonds. The simulation results showed that the biofilm <span class="hlt">models</span> based on Bingham yield stress predicted the biomass accumulation and channel breakthrough well. The pressure oscillation (or, permeability oscillation) was also demonstrated well indicating the process of biomass accumulation and breakthrough channel formation. In addition, the effects of cell and biofilm sucrose concentration were significant on the biomass plug development and permeability reduction rates. The <span class="hlt">modeling</span> elucidated some deficiencies in our knowledge of the biomass yield stress that enables us to predict the stability of biomass plug against shear stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AIPC.1453...69D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AIPC.1453...69D"><span id="translatedtitle">Towards a <span class="hlt">porous</span> media <span class="hlt">model</span> of the human lung</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>DeGroot, Christopher T.; Straatman, Anthony G.</p> <p>2012-05-01</p> <p>In this article, progress towards building a complete <span class="hlt">porous</span> media <span class="hlt">model</span> of the human lung is discussed. While the recent trend in computational fluid dynamics studies of airflow in the human lung has been to continually increase the size and detail of the airway tree under consideration, it is proposed in this work that simulating flow in the human lung as a coupled fluid-<span class="hlt">porous</span> system is an effective method to simulate the flow in the whole lung. Under the proposed <span class="hlt">modeling</span> paradigm, a truncated airway tree constitutes a fluid region which is coupled to a <span class="hlt">porous</span> region that represents the remainder of the lung volume, containing small airways and alveoli. The first part of this work describes pore-level simulations conducted in an alveolated duct geometry, which are present in large quantities in the human lung, to determine its permeability. Next, volume-averaged simulations incorporating the results of the pore-level simulations and using a realistic lung geometry based on computed tomography images are discussed along with future directions for this work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JPS...156..700R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JPS...156..700R"><span id="translatedtitle"><span class="hlt">Porous</span> structured vanadium oxide electrode <span class="hlt">material</span> for electrochemical capacitors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reddy, Ravinder N.; Reddy, Ramana G.</p> <p></p> <p>A nano <span class="hlt">porous</span> vanadium oxide (V 2O 5) was prepared by sol-gel method. The preparation involved elutriation of aqueous sodium meta vanadate over a cation exchange resin. The product was characterized using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, surface area analysis and thermogravimetric analysis. Electrochemical characterization was done using cyclic voltammetry in a three electrode system consisting of a saturated calomel electrode as reference electrode, platinum mesh as a counter electrode, and V 2O 5 mounted on Ti mesh as the working electrode. Two molars of aqueous KCl, NaCl and LiCl were used as electrolytes. A maximum capacitance of 214 F g -1 was obtained at a scan rate of 5 mV s -1 in 2 M KCl. The effect of different electrolytes and the effect of concentration of KCl on the specific capacitance of V 2O 5 were studied. Specific capacitance faded rapidly over 100 cycles in 2 M KCl at a 5 mV s -1 scan rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27059168','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27059168"><span id="translatedtitle">Hierarchical <span class="hlt">Porous</span> Carbon <span class="hlt">Materials</span> Derived from Sheep Manure for High-Capacity Supercapacitors.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Caiyun; Zhu, Xiaohong; Cao, Min; Li, Menglin; Li, Na; Lai, Liuqin; Zhu, Jiliang; Wei, Dacheng</p> <p>2016-05-10</p> <p>3 D capacitance: Hierarchical <span class="hlt">porous</span> carbon-based electrode <span class="hlt">materials</span> with a composite structure are prepared from a biomass waste by a facile carbonization and activation process without using any additional templates. Benefiting from the composite structure, the ions experience a variety of environments, which contribute significantly to the excellent electrochemical properties of supercapacitors. PMID:27059168</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ThEng..57..516P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ThEng..57..516P"><span id="translatedtitle">Generalization of experimental data on heat transfer in permeable shells made of <span class="hlt">porous</span> reticular <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polyakov, A. F.; Strat'ev, V. K.; Tret'yakov, A. F.; Shekhter, Yu. L.</p> <p>2010-06-01</p> <p>Heat transfer from six samples of <span class="hlt">porous</span> reticular <span class="hlt">material</span> to cooling gas (air) at small Reynolds numbers is experimentally studied. The specific features pertinent to heat transfer essentially affected by longitudinal heat conductivity along gas flow are analyzed. The experimental results are generalized in the form of dimensionless empirical relations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997APS..SHK..M201N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997APS..SHK..M201N"><span id="translatedtitle">Controlled High-Rate-Strain Shear Bands in Inert and Reactant <span class="hlt">Porous</span> <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nesterenko, Vitali</p> <p>1997-07-01</p> <p>Shear localization was considered as one of the main reasons for initiation of chemical reaction in energetic <span class="hlt">materials</span> under dynamic loading (Dremin and Breusov 1968, Winter and Field 1975, Frey 1981, Kipp 1985, Iyer, Bennet et al., 1994) and for particles bonding during shock compaction (Nesterenko 1985). However despite of wide spread recognition of the importance of rapid shear flow the shear bands in <span class="hlt">porous</span> heterogeneous <span class="hlt">materials</span> did not become an object of research. The primary reason for this was a lack of appropriate experimental method. The "Thick-Walled Cylinder" method, which allows to reproduce shear bands in controlled conditions, was initially proposed by Nesterenko et al., 1989 for solid inert <span class="hlt">materials</span> and then modified by Nesterenko, Meyers et al., 1994 to fit <span class="hlt">porous</span> inert and energetic <span class="hlt">materials</span>. The method allows to reproduce the array of shear bands with shear strains 10 - 100 and strain rate 107 s-1. Experimental results will be presented for inert <span class="hlt">materials</span> (granular, fractured ceramics) and for reactant <span class="hlt">porous</span> mixtures (Nb-Si, Ti-Si, Ti-C). Mechanisms of <span class="hlt">material</span> deformation and shear induced chemical reactions inside shear localization zone as well as conditions for the initiation of the chemical reaction in the bulk of energetic <span class="hlt">material</span> by array of shear bands will be considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3993991','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3993991"><span id="translatedtitle"><span class="hlt">Modeling</span> Analyte Transport and Capture in <span class="hlt">Porous</span> Bead Sensors</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chou, Jie; Lennart, Alexis; Wong, Jorge; Ali, Mehnaaz F.; Floriano, Pierre N.; Christodoulides, Nicolaos; Camp, James; McDevitt, John T.</p> <p>2013-01-01</p> <p><span class="hlt">Porous</span> agarose microbeads, with high surface to volume ratios and high binding densities, are attracting attention as highly sensitive, affordable sensor elements for a variety of high performance bioassays. While such polymer microspheres have been extensively studied and reported on previously and are now moving into real-world clinical practice, very little work has been completed to date to <span class="hlt">model</span> the convection, diffusion, and binding kinetics of soluble reagents captured within such fibrous networks. Here, we report the development of a three-dimensional computational <span class="hlt">model</span> and provide the initial evidence for its agreement with experimental outcomes derived from the capture and detection of representative protein and genetic biomolecules in 290μm <span class="hlt">porous</span> beads. We compare this <span class="hlt">model</span> to antibody-mediated capture of C-reactive protein and bovine serum albumin, along with hybridization of oligonucleotide sequences to DNA probes. These results suggest that due to the <span class="hlt">porous</span> interior of the agarose bead, internal analyte transport is both diffusion- and convection-based, and regardless of the nature of analyte, the bead interiors reveal an interesting trickle of convection-driven internal flow. Based on this <span class="hlt">model</span>, the internal to external flow rate ratio is found to be in the range of 1:3100 to 1:170 for beads with agarose concentration ranging from 0.5% to 8% for the sensor ensembles here studied. Further, both <span class="hlt">model</span> and experimental evidence suggest that binding kinetics strongly affect analyte distribution of captured reagents within the beads. These findings reveal that high association constants create a steep moving boundary in which unbound analytes are held back at the periphery of the bead sensor. Low association constants create a more shallow moving boundary in which unbound analytes diffuse further into the bead before binding. These <span class="hlt">models</span> agree with experimental evidence and thus serve as a new tool set for the study of bio-agent transport processes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JMPSo..94..230S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JMPSo..94..230S&link_type=ABSTRACT"><span id="translatedtitle">Phase field <span class="hlt">modeling</span> of partially saturated deformable <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sciarra, Giulio</p> <p>2016-09-01</p> <p>A poromechanical <span class="hlt">model</span> of partially saturated deformable <span class="hlt">porous</span> media is proposed based on a phase field approach at <span class="hlt">modeling</span> the behavior of the mixture of liquid water and wet air, which saturates the pore space, the phase field being the saturation (ratio). While the standard retention curve is expected still^ to provide the intrinsic retention properties of the <span class="hlt">porous</span> skeleton, depending on the <span class="hlt">porous</span> texture, an enhanced description of surface tension between the wetting (liquid water) and the non-wetting (wet air) fluid, occupying the pore space, is stated considering a regularization of the phase field <span class="hlt">model</span> based on an additional contribution to the overall free energy depending on the saturation gradient. The aim is to provide a more refined description of surface tension interactions. An enhanced constitutive relation for the capillary pressure is established together with a suitable generalization of Darcy's law, in which the gradient of the capillary pressure is replaced by the gradient of the so-called generalized chemical potential, which also accounts for the "force", associated to the local free energy of the phase field <span class="hlt">model</span>. A micro-scale heuristic interpretation of the novel constitutive law of capillary pressure is proposed, in order to compare the envisaged <span class="hlt">model</span> with that one endowed with the concept of average interfacial area. The considered poromechanical <span class="hlt">model</span> is formulated within the framework of strain gradient theory in order to account for possible effects, at laboratory scale, of the micro-scale hydro-mechanical couplings between highly localized flows (fingering) and localized deformations of the skeleton (fracturing).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25573031','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25573031"><span id="translatedtitle">Diffusion <span class="hlt">model</span> to describe osteogenesis within a <span class="hlt">porous</span> titanium scaffold.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schmitt, M; Allena, R; Schouman, T; Frasca, S; Collombet, J M; Holy, X; Rouch, P</p> <p>2016-01-01</p> <p>In this study, we develop a two-dimensional finite element <span class="hlt">model</span>, which is derived from an animal experiment and allows simulating osteogenesis within a <span class="hlt">porous</span> titanium scaffold implanted in ewe's hemi-mandible during 12 weeks. The cell activity is described through diffusion equations and regulated by the stress state of the structure. We compare our <span class="hlt">model</span> to (i) histological observations and (ii) experimental data obtained from a mechanical test done on sacrificed animal. We show that our mechano-biological approach provides consistent numerical results and constitutes a useful tool to predict osteogenesis pattern. PMID:25573031</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014EGUGA..1616405K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014EGUGA..1616405K&link_type=ABSTRACT"><span id="translatedtitle">P-adic <span class="hlt">model</span> of transport in <span class="hlt">porous</span> disordered media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khrennikov, Adrei Yu.; Oleschko, Klaudia</p> <p>2014-05-01</p> <p>The soil porosity and permeability are the most important quantitative indicators of soil dynamics under the land-use change. The main problema in the <span class="hlt">modeling</span> of this dynamic is still poor correlation between the real measuring data and the mathematical and computer simulation <span class="hlt">models</span>. In order to overpassed this deep divorce we have designed a new technique, able to compare the data arised from the multiscale image analices and time series of the basic physical properties dynamics in <span class="hlt">porous</span> media studied in time and space. We present a <span class="hlt">model</span> of the diffusion reaction type describing transport in disordered <span class="hlt">porous</span> media, e.g., water or oil flow in a complex network of pores. Our <span class="hlt">model</span> is based on p-adic representation of such networks. This is a kind of fractal representation. We explore advantages of p- adic representation, namely, the possibility to endow p-adic trees with an algebraic structure and ultrametric topology and, hence, to apply analysis which have (at least some) similarities with ordinary real analysis on the straight line. We present the system of two diffusion reaction equations describing propagation of particles in networks of pores in disordered media. As an application, one can consider water transport through the soil pore Networks, or oil flow through capillaries nets. Under some restrictions on potentials and rate coefficients we found the stationary regime corresponding to water content or concentration of oil in a cluster of capillaries. Usage of p-adic analysis (in particular, p-adic wavelets) gives a possibility to find the stationary solution in the analytic form which makes possible to present a clear pedological or geological picture of the process. The mathematical <span class="hlt">model</span> elaborated in this paper (Khrennikov, 2013) can be applied to variety of problems from water concentration in aquifers to the problem of formation of oil reservoirs in disordered media with <span class="hlt">porous</span> structures. Another possible application may have real practical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.5162F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.5162F"><span id="translatedtitle">Numerical <span class="hlt">Modelling</span> of The Response of <span class="hlt">Porous</span> Sensors of The Matric Potential of Soil Water</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferraris, S.; Whalley, R.</p> <p></p> <p><span class="hlt">Porous</span> sensors are used to give an indirect estimate of the matric potential of soil water. In these sensors the water content of a <span class="hlt">porous</span> matrix in equilibrium with the soil can be used to calculate the matric potential, provided that moisture retention characteristic of the <span class="hlt">porous</span> matrix is known. The original design of these sensors used a plaster of Paris matrix and AC resistance electrodes to estimate its water content. More recently a ceramic matrix has been used with a dielectric measurement of its water content (e.g. Or and Wraith 1999; Whalley et al. 2001). The advantage of the more recent designs is that they can be used at relatively high water potentials in comparison with plaster of Paris based sensors which have application in dry soils. However, the development of the sensors that are designed to be used in wetter soils, raises the question of the sensor response time. In this paper we use an axial-symmetric 3D numerical solution of the Richards equation to investigate the effect of sensor geometry on the time taken for it to equilibrate with the potential of the soil water. We consider the sensor to have a cylindrical ceramic <span class="hlt">porous</span> matrix. The effect of the shape of the <span class="hlt">porous</span> matrix on the equilibration time after changes in soil water potential is <span class="hlt">modelled</span>. We view the shape of the <span class="hlt">porous</span> matrix in terms of the ratio of diameter to length and also the volume. The results are discussed in terms of the design requirements of a <span class="hlt">porous</span> sensor for soil water matric potential. Or, D. &Wraith, J.M. 1999. A new soil matric-potential sensor based on time-domain- reflectometry. Water Resources Research, 35: 3399-3407. Whalley W.R., Watts C.W., Hilhorst M.A., Bird N.R.A., Balendonck J. &Longstaff D. J. 2001. The design of <span class="hlt">porous</span> <span class="hlt">material</span> sensors to measure matric potential of water in soil. European Journal of Soil Science, 53: 511-519.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1684g0006S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1684g0006S"><span id="translatedtitle">Mathematical <span class="hlt">modeling</span> of deformation of a <span class="hlt">porous</span> medium, considering its strengthening due to pore collapse</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sadovskii, V. M.; Sadovskaya, O. V.</p> <p>2015-10-01</p> <p>Based on the generalized rheological method, the mathematical <span class="hlt">model</span> describing small deformations of a single-phase <span class="hlt">porous</span> medium without regard to the effects of a fluid or gas in pores is constructed. The change in resistance of a <span class="hlt">material</span> to the external mechanical impacts at the moment of pore collapse is taken into account by means of the von Mises-Schleicher strength condition. In order to consider irreversible deformations, alongside with the classical yield conditions by von Mises and Tresca- Saint-Venant, the special condition <span class="hlt">modeling</span> the plastic loss of stability of a <span class="hlt">porous</span> skeleton is used. The random nature of the pore size distribution is taken into account. It is shown that the proposed mathematical <span class="hlt">model</span> satisfies the principles of thermodynamics of irreversible processes. Phenomenological parameters of the <span class="hlt">model</span> are determined on the basis of the approximate calculation of the problem on quasi-static loading of a cubic periodicity cell with spherical voids. In the framework of the obtained <span class="hlt">model</span>, the process of propagation of plane longitudinal waves of the compression in a homogenous <span class="hlt">porous</span> medium, accompanied by the plastic deformation of a skeleton and the collapse of pores, is analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492612','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492612"><span id="translatedtitle">Mathematical <span class="hlt">modeling</span> of deformation of a <span class="hlt">porous</span> medium, considering its strengthening due to pore collapse</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sadovskii, V. M. Sadovskaya, O. V.</p> <p>2015-10-28</p> <p>Based on the generalized rheological method, the mathematical <span class="hlt">model</span> describing small deformations of a single-phase <span class="hlt">porous</span> medium without regard to the effects of a fluid or gas in pores is constructed. The change in resistance of a <span class="hlt">material</span> to the external mechanical impacts at the moment of pore collapse is taken into account by means of the von Mises–Schleicher strength condition. In order to consider irreversible deformations, alongside with the classical yield conditions by von Mises and Tresca– Saint-Venant, the special condition <span class="hlt">modeling</span> the plastic loss of stability of a <span class="hlt">porous</span> skeleton is used. The random nature of the pore size distribution is taken into account. It is shown that the proposed mathematical <span class="hlt">model</span> satisfies the principles of thermodynamics of irreversible processes. Phenomenological parameters of the <span class="hlt">model</span> are determined on the basis of the approximate calculation of the problem on quasi-static loading of a cubic periodicity cell with spherical voids. In the framework of the obtained <span class="hlt">model</span>, the process of propagation of plane longitudinal waves of the compression in a homogenous <span class="hlt">porous</span> medium, accompanied by the plastic deformation of a skeleton and the collapse of pores, is analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006IJNMF..50.1085M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006IJNMF..50.1085M"><span id="translatedtitle">Computational <span class="hlt">modelling</span> of variably saturated flow in <span class="hlt">porous</span> media with complex three-dimensional geometries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McBride, D.; Cross, M.; Croft, N.; Bennett, C.; Gebhardt, J.</p> <p>2006-03-01</p> <p>A computational procedure is presented for solving complex variably saturated flows in <span class="hlt">porous</span> media, that may easily be implemented into existing conventional finite-volume-based computational fluid dynamics codes, so that their functionality might be geared upon to readily enable the <span class="hlt">modelling</span> of a complex suite of interacting fluid, thermal and chemical reaction process physics. This procedure has been integrated within a multi-physics finite volume unstructured mesh framework, allowing arbitrarily complex three-dimensional geometries to be <span class="hlt">modelled</span>. The <span class="hlt">model</span> is particularly targeted at ore heap-leaching processes, which encounter complex flow problems, such as infiltration into dry soil, drainage, perched water tables and flow through heterogeneous <span class="hlt">materials</span>, but is equally applicable to any process involving flow through <span class="hlt">porous</span> media, such as in environmental recovery processes. The computational procedure is based on the mixed form of the classical Richards equation, employing an adaptive transformed mixed algorithm that is numerically robust and significantly reduces compute (or CPU) time. The computational procedure is accurate (compares well with other methods and analytical data), comprehensive (representing any kind of <span class="hlt">porous</span> flow <span class="hlt">model</span>), and is computationally efficient. As such, this procedure provides a suitable basis for the implementation of large-scale industrial heap-leach <span class="hlt">models</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050217168','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050217168"><span id="translatedtitle">Mechanically Strong, Lightweight <span class="hlt">Porous</span> <span class="hlt">Materials</span> Developed (X-Aerogels)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leventis, Nicholas</p> <p>2005-01-01</p> <p>Aerogels are attractive <span class="hlt">materials</span> for a variety of NASA missions because they are ultralightweight, have low thermal conductivity and low-dielectric constants, and can be readily doped with other <span class="hlt">materials</span>. Potential NASA applications for these <span class="hlt">materials</span> include lightweight insulation for spacecraft, habitats, and extravehicular activity (EVA) suits; catalyst supports for fuel cell and in situ resource utilization; and sensors for air- and water-quality monitoring for vehicles, habitats, and EVA suits. Conventional aerogels are extremely fragile and require processing via supercritical fluid extraction, which adds cost to the production of an aerogel and limits the sizes and geometries of samples that can be produced from these <span class="hlt">materials</span>. These issues have severely hampered the application of aerogels in NASA missions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21152430','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21152430"><span id="translatedtitle">Characterization of <span class="hlt">Porous</span> <span class="hlt">Materials</span> as Radon Source and its Radiological Implications</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lopez-Coto, I.; Bolivar, J. P.; Mas, J. L.; Garcia-Tenorio, R.</p> <p>2008-08-07</p> <p>In this work, a magnitude is proposed in order to compare the potential radiological risk due to radon exposition generated by different <span class="hlt">materials</span>, and a method based in the {sup 222}Rn accumulation technique is presented for its determination. The obtained results indicate that the proposed magnitude and their corresponding measurement methodology are useful in order to take decisions about the management of different kinds of <span class="hlt">porous</span> <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712831R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712831R"><span id="translatedtitle"><span class="hlt">Modeling</span> of Multi-Scale Channeling Phenomena in <span class="hlt">Porous</span> Flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Räss, Ludovic; Omlin, Samuel; Yarushina, Viktoriya; Simon, Nina; Podladchikov, Yuri</p> <p>2015-04-01</p> <p>Predictive <span class="hlt">modeling</span> of fluid percolation through tight <span class="hlt">porous</span> rocks is critical to evaluate environmental risks associated with waste storage and reservoir operations. To understand the evolution of two-phase mixtures of fluid and solid it is insufficient to only combine single-phase fluid flow methods and solid mechanics. A proper coupling of these two different multi-scales physical processes is required to describe the complex evolution of permeability and porosity in space and in time. We conduct numerical <span class="hlt">modeling</span> experiments in geometrically simple but physically complex systems of stressed rocks containing self-focusing <span class="hlt">porous</span> flow. Our <span class="hlt">model</span> is physically and thermodynamically consistent and describes the formation and evolution of fluid pathways. The <span class="hlt">model</span> consists of a system of coupled equations describing poro-elasto-viscous deformation and flow. Nonlinearity of the solid rheology is also taken into account. We have developed a numerical application based on an iterative finite difference scheme that runs on mutli-GPUs cluster in parallel. In order to validate these <span class="hlt">models</span>, we consider the largest CO2 sequestration project in operation at the Sleipner field in the Norwegian North Sea. Attempts to match the observations at Sleipner using conventional reservoir simulations fail to capture first order observations, such as the seemingly effortless vertical flow of CO2 through low permeability shale layers and the formation of focused flow channels or chimneys. Conducted high-resolution three-dimensional numerical simulations predict the formation of dynamically evolving high porosity and permeability pathways as a natural outcome of <span class="hlt">porous</span> flow nonlinearly coupled with rock deformation, which may trigger leakage through low permeability barriers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22257906','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22257906"><span id="translatedtitle">Potential of hybrid functionalized meso-<span class="hlt">porous</span> <span class="hlt">materials</span> for the separation and immobilization of radionuclides</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Luca, V.</p> <p>2013-07-01</p> <p>Functionalized meso-<span class="hlt">porous</span> <span class="hlt">materials</span> are a class of hybrid organic-inorganic <span class="hlt">material</span> in which a meso-<span class="hlt">porous</span> metal oxide framework is functionalized with multifunctional organic molecules. These molecules may contain one or more anchor groups that form strong bonds to the pore surfaces of the metal oxide framework and free functional groups that can impart and or modify the functionality of the <span class="hlt">material</span> such as for binding metal ions in solution. Such <span class="hlt">materials</span> have been extensively studied over the past decade and are of particular interest in absorption applications because of the tremendous versatility in choosing the composition and architecture of the metal oxide framework and the nature of the functional organic molecule as well as the efficient mass transfer that can occur through a well-designed hierarchically <span class="hlt">porous</span> network. A sorbent for nuclear applications would have to be highly selective for particular radio nuclides, it would need to be hydrolytically and radiolytically stable, and it would have to possess reasonable capacity and fast kinetics. The sorbent would also have to be available in a form suitable for use in a column. Finally, it would also be desirable if once saturated with radio nuclides, the sorbent could be recycled or converted directly into a ceramic or glass waste form suitable for direct repository disposal or even converted directly into a <span class="hlt">material</span> that could be used as a transmutation target. Such a cradle-to- grave strategy could have many benefits in so far as process efficiency and the generation of secondary wastes are concerned.This paper will provide an overview of work done on all of the above mentioned aspects of the development of functionalized meso-<span class="hlt">porous</span> adsorbent <span class="hlt">materials</span> for the selective separation of lanthanides and actinides and discuss the prospects for future implementation of a cradle-to-grave strategy with such <span class="hlt">materials</span>. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25920830','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25920830"><span id="translatedtitle">Acoustical properties of air-saturated <span class="hlt">porous</span> <span class="hlt">material</span> with periodically distributed dead-end pores.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Leclaire, P; Umnova, O; Dupont, T; Panneton, R</p> <p>2015-04-01</p> <p>A theoretical and numerical study of the sound propagation in air-saturated <span class="hlt">porous</span> media with straight main pores bearing lateral cavities (dead-ends) is presented. The lateral cavities are located at "nodes" periodically spaced along each main pore. The effect of periodicity in the distribution of the lateral cavities is studied, and the low frequency limit valid for the closely spaced dead-ends is considered separately. It is shown that the absorption coefficient and transmission loss are influenced by the viscous and thermal losses in the main pores as well as their perforation rate. The presence of long or short dead-ends significantly alters the acoustical properties of the <span class="hlt">material</span> and can increase significantly the absorption at low frequencies (a few hundred hertz). These depend strongly on the geometry (diameter and length) of the dead-ends, on their number per node, and on the periodicity along the propagation axis. These effects are primarily due to low sound speed in the main pores and to thermal losses in the dead-end pores. The <span class="hlt">model</span> predictions are compared with experimental results. Possible designs of <span class="hlt">materials</span> of a few cm thicknesses displaying enhanced low frequency absorption at a few hundred hertz are proposed. PMID:25920830</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..MARZ10004A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..MARZ10004A"><span id="translatedtitle">Optical second-harmonic generation measurements of <span class="hlt">porous</span> low-k dielectric <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Atkin, Joanna; Shaw, Thomas; Laibowitz, Robert; Heinz, Tony</p> <p>2009-03-01</p> <p>Low-k dielectric <span class="hlt">materials</span> based on <span class="hlt">porous</span> carbon-doped oxides, with relative dielectric constants as low as 2.1, are widely used as thin insulating films in the microelectronics industry. Knowledge of these <span class="hlt">materials</span>' basic electronic properties, such as energy gaps, barrier heights, and trap states, is essential for <span class="hlt">modeling</span> their electrical leakage and stability characteristics. We use femtosecond laser pulses to probe the dynamics of charge-carrier transfer processes across Si/LKD interfacial barriers by optical second harmonic generation (SHG). Larger electric fields from multiphoton injection can be developed in Si/LKD systems compared to Si/SiO2, indicating a significantly higher density of traps in the LKD. This is consistent with previously reported measurements of trap density by photoinjection techniques^*. We will also discuss results on the dynamics of discharging and on the dependence of charging phenomena on layer thickness. ^*J. M. Atkin, D. Song, T. M. Shaw, E. Cartier, R. B. Laibowitz, and T. F. Heinz, J. Appl. Phys. 103, 094104 (2008).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JOM...tmp..322K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JOM...tmp..322K"><span id="translatedtitle">Low-Temperature Synthesis of <span class="hlt">Porous</span> <span class="hlt">Materials</span> from Mortar Sands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kazmina, O. V.; Volland, S. N.; Dushkina, M. A.</p> <p>2015-08-01</p> <p>It is established that the eliminations of construction sand with the content of SiO2 about 70 wt.% and particle size less than 60 μm are suitable for the production of a foam-glass-crystal <span class="hlt">material</span> on the basis of the low-temperature frit, which was synthesized at the temperature of 900°C. The obtained foam-glass-crystal <span class="hlt">material</span> exceeds foam-glass (by 3.0 times) and clayite (by 1.5 times) by strength and is characterized by the low value of water absorption (0.1%).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT.......420M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.......420M"><span id="translatedtitle">Computing the Seismic Attenuation in Complex <span class="hlt">Porous</span> <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masson, Yder Jean</p> <p></p> <p>The present work analyzes seismic attenuation due to wave-induced flow in complex poroelastic <span class="hlt">materials</span> containing an arbitrary amount of heterogeneity and fully or partially saturated with a mixture of fluids. In the first part, two distinct finite-difference (FDTD) numerical schemes for solving Biot's poroelastic set of equations are introduced. The first algorithm is designed to be used in the seismic band of frequencies; i.e., when the permeability of the medium doesn't depend on frequency. The second algorithm accounts for viscous boundary layers that appear in the pores at high frequencies (in this case, the permeability depends on frequency) and can be used across the entire band of frequencies. An innovative numerical method is presented in the second part allowing computation of seismic attenuation due to wave-induced flow for any poroelastic <span class="hlt">material</span>. This method is applied to study the attenuation associated with different classes of <span class="hlt">materials</span> saturated with a single fluid (water). For a <span class="hlt">material</span> having a self-affine (fractal) distribution of elastic properties, it is demonstrated that frequency dependence in the attenuation is controlled by a single parameter that is directly related to the fractal dimension of the <span class="hlt">material</span>. For anisotropic <span class="hlt">materials</span>, a relation is established between the attenuation levels associated with waves propagating in different directions and the geometrical aspect ratio of the heterogeneities present within the <span class="hlt">material</span>. The third part concerns the study of attenuation associated with <span class="hlt">materials</span> having a homogeneous solid skeleton saturated with a mixture of immiscible fluids. The special case where the distribution of fluids is the result of an invasion-percolation process is treated in detail. Finally, the last part presents a novel experimental setup designed to measure fluctuations of the elastic properties in real rock samples. This device performs automated micro-indentation tests at the surface of rock samples and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27160665','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27160665"><span id="translatedtitle">Dynamics of H2 adsorbed in <span class="hlt">porous</span> <span class="hlt">materials</span> as revealed by computational analysis of inelastic neutron scattering spectra.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pham, Tony; Forrest, Katherine A; Space, Brian; Eckert, Juergen</p> <p>2016-06-29</p> <p>The inelastic scattering of neutrons from adsorbed H2 is an effective and highly sensitive method for obtaining molecular level information on the type and nature of H2 binding sites in <span class="hlt">porous</span> <span class="hlt">materials</span>. While these inelastic neutron scattering (INS) spectra of the hindered rotational and translational excitations on the adsorbed H2 contain a significant amount of information, much of this can only be reliably extracted by means of a detailed analysis of the spectra through the utilization of <span class="hlt">models</span> and theoretical calculations. For instance, the rotational tunneling transitions observed in the INS spectra can be related to a value for the barrier to rotation for the adsorbed H2 with the use of a simple phenomenological <span class="hlt">model</span>. Since such an analysis is dependent on the <span class="hlt">model</span>, it is far more desirable to use theoretical methods to compute a potential energy surface (PES), from which the rotational barriers for H2 adsorbed at a particular site can be determined. Rotational energy levels and transitions for the hindered rotor can be obtained by quantum dynamics calculations and compared directly with experiment with an accuracy subject only to the quality of the theoretical PES. In this paper, we review some of the quantum and classical mechanical calculations that have been performed on H2 adsorbed in various <span class="hlt">porous</span> <span class="hlt">materials</span>, such as clathrate hydrates, zeolites, and metal-organic frameworks (MOFs). The principal aims of these calculations have been the interpretation of the INS spectra for adsorbed H2 along with the extraction of atomic level details of its interaction with the host. We describe calculations of the PES used for two-dimensional quantum rotation as well as rigorous five-dimensional quantum coupled translation-rotation dynamics, and demonstrate that the combination of INS measurements and computational <span class="hlt">modeling</span> can provide important and detailed insights into the molecular mechanism of H2 adsorption in <span class="hlt">porous</span> <span class="hlt">materials</span>. PMID:27160665</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24676127','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24676127"><span id="translatedtitle">Recent advances in <span class="hlt">porous</span> polyoxometalate-based metal-organic framework <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Du, Dong-Ying; Qin, Jun-Sheng; Li, Shun-Li; Su, Zhong-Min; Lan, Ya-Qian</p> <p>2014-07-01</p> <p>Polyoxometalate (POM)-based metal-organic framework (MOF) <span class="hlt">materials</span> contain POM units and generally generate MOF <span class="hlt">materials</span> with open networks. POM-based MOF <span class="hlt">materials</span>, which utilize the advantages of both POMs and MOFs, have received increasing attention, and much effort has been devoted to their preparation and relevant applications over the past few decades. They have good prospects in catalysis owing to the electronic and physical properties of POMs that are tunable by varying constituent elements. In this review, we present recent developments in <span class="hlt">porous</span> POM-based MOF <span class="hlt">materials</span>, including their classification, synthesis strategies, and applications, especially in the field of catalysis. PMID:24676127</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/863064','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/863064"><span id="translatedtitle">Electrode including <span class="hlt">porous</span> particles with embedded active <span class="hlt">material</span> for use in a secondary electrochemical cell</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Vissers, Donald R.; Nelson, Paul A.; Kaun, Thomas D.; Tomczuk, Zygmunt</p> <p>1978-04-25</p> <p>Particles of carbonaceous matrices containing embedded electrode active <span class="hlt">material</span> are prepared for vibratory loading within a <span class="hlt">porous</span> electrically conductive substrate. In preparing the particles, active <span class="hlt">materials</span> such as metal chalcogenides, solid alloys of alkali or alkaline earth metals along with other metals and their oxides in powdered or particulate form are blended with a thermosetting resin and particles of a volatile to form a paste mixture. The paste is heated to a temperature at which the volatile transforms into vapor to impart porosity at about the same time as the resin begins to cure into a rigid, solid structure. The solid structure is then comminuted into <span class="hlt">porous</span>, carbonaceous particles with the embedded active <span class="hlt">material</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22350935','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22350935"><span id="translatedtitle">Dark-field X-ray imaging of unsaturated water transport in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yang, F. E-mail: michele.griffa@empa.ch; Di Bella, C.; Lura, P.; Prade, F.; Herzen, J.; Sarapata, A.; Pfeiffer, F.; Griffa, M. E-mail: michele.griffa@empa.ch; Jerjen, I.</p> <p>2014-10-13</p> <p>We introduce in this Letter an approach to X-ray imaging of unsaturated water transport in <span class="hlt">porous</span> <span class="hlt">materials</span> based upon the intrinsic X-ray scattering produced by the <span class="hlt">material</span> microstructural heterogeneity at a length scale below the imaging system spatial resolution. The basic principle for image contrast creation consists in a reduction of such scattering by permeation of the porosity by water. The implementation of the approach is based upon X-ray dark-field imaging via Talbot-Lau interferometry. The proof-of-concept is provided by performing laboratory-scale dark-field X-ray radiography of mortar samples during a water capillary uptake experiment. The results suggest that the proposed approach to visualizing unsaturated water transport in <span class="hlt">porous</span> <span class="hlt">materials</span> is complementary to neutron and magnetic resonance imaging and alternative to standard X-ray imaging, the latter requiring the use of contrast agents because based upon X-ray attenuation only.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......168L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......168L"><span id="translatedtitle">Computational study of <span class="hlt">porous</span> <span class="hlt">materials</span> for gas separations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Li-Chiang</p> <p></p> <p>Nanoporous <span class="hlt">materials</span> such as zeolites, zeolitic imidazolate frameworks (ZIFs), and metal-organic frameworks (MOFs) are used as sorbents or membranes for gas separations such as carbon dioxide capture, methane capture, paraffin/olefin separations, etc. The total number of nanoporous <span class="hlt">materials</span> is large; by changing the chemical composition and/or the structural topologies we can envision an infinite number of possible <span class="hlt">materials</span>. In practice one can synthesize and fully characterize only a small subset of these <span class="hlt">materials</span>. Hence, computational study can play an important role by utilizing various techniques in molecular simulations as well as quantum chemical calculations to accelerate the search for optimal <span class="hlt">materials</span> for various energy-related separations. Accordingly, several large-scale computational screenings of over one hundred thousand <span class="hlt">materials</span> have been performed to find the best <span class="hlt">materials</span> for carbon capture, methane capture, and ethane/ethene separation. These large-scale screenings identified a number of promising <span class="hlt">materials</span> for different applications. Moreover, the analysis of these screening studies yielded insights into those molecular characteristics of a <span class="hlt">material</span> that contribute to an optimal performance for a given application. These insights provided useful guidelines for future structural design and synthesis. For instance, one of the screening studies indicated that some zeolite structures can potentially reduce the energy penalty imposed on a coal-fired power plant by as much as 35% compared to the near-term MEA technology for carbon capture application. These optimal structures have topologies with a maximized density of pockets and they capture and release CO2 molecules with an optimal energy. These screening studies also pointed to some systems, for which conventional force fields were unable to make sufficiently reliable predictions of the adsorption isotherms of different gasses, e.g., CO2 in MOFs with open-metal sites. For these systems, we</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26456608','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26456608"><span id="translatedtitle">Preparation of steel slag <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> using coal powder as pore former.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Peng; Guo, Zhancheng</p> <p>2015-10-01</p> <p>The aim of the study was to prepare a <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> using steel slag and fly ash as the main raw <span class="hlt">material</span>, with coal powder and sodium silicate used as a pore former and binder respectively. The influence of the experimental conditions such as the ratio of fly ash, sintering temperature, sintering time, and porosity regulation on the performance of the <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> was investigated. The results showed that the specimens prepared by this method had high sound absorption performance and good mechanical properties, and the noise reduction coefficient and compressive strength could reach 0.50 and 6.5MPa, respectively. The compressive strength increased when the dosage of fly ash and sintering temperature were raised. The noise reduction coefficient decreased with increasing ratio of fly ash and reducing pore former, and first increased and then decreased with the increase of sintering temperature and time. The optimum preparation conditions for the <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> were a proportion of fly ash of 50% (wt.%), percentage of coal powder of 30% (wt.%), sintering temperature of 1130°C, and sintering time of 6.0hr, which were determined by analyzing the properties of the sound-absorbing <span class="hlt">material</span>. PMID:26456608</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1211169','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1211169"><span id="translatedtitle">Water Adsorption in <span class="hlt">Porous</span> Metal-Organic Frameworks and Related <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Furukawa, H; Gandara, F; Zhang, YB; Jiang, JC; Queen, WL; Hudson, MR; Yaghi, OM</p> <p>2014-03-19</p> <p>Water adsorption in <span class="hlt">porous</span> <span class="hlt">materials</span> is important for many applications such as dehumidification, thermal batteries, and delivery of drinking water in remote areas. In this study, we have identified three criteria for achieving high performing <span class="hlt">porous</span> <span class="hlt">materials</span> for water adsorption. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the <span class="hlt">material</span>. In search of an excellently performing <span class="hlt">porous</span> <span class="hlt">material</span>, we have studied and compared the water adsorption properties of 23 <span class="hlt">materials</span>, 20 of which are metal organic frameworks (MOFs). Among the MOFs are 10 zirconium(IV) MOFs with a subset of these, MOF-801-SC (single crystal form), -802, -805, -806, -808, -812, and -841 reported for the first time. MOF-801-P (microcrystalline powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examined for water adsorption because it is a byproduct of MOF-841 synthesis. All the new zirconium MOFs are made from the Zr6O4(OH)(4)(-CO2)(n) secondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl organic linkers to make extended <span class="hlt">porous</span> frameworks. The permanent porosity of all 23 <span class="hlt">materials</span> was confirmed and their water adsorption measured to reveal that MOF-801-P and MOF-841 are the highest performers based on the three criteria stated above; they are water stable, do not lose capacity after five adsorption/desorption cycles, and are easily regenerated at room temperature. An X-ray single-crystal study and a powder neutron diffraction study reveal the position of the water adsorption sites in MOF-801 and highlight the importance of the intermolecular interaction between adsorbed water molecules within the pores.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AIPC..898..193J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AIPC..898..193J"><span id="translatedtitle">Hydrothermal Synthesis of Meso-<span class="hlt">porous</span> <span class="hlt">Materials</span> using Diatomaceous Earth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jing, Z.; Kato, S.; Maeda, H.; Ishida, E. H.</p> <p>2007-03-01</p> <p>In order to sustain the inherent properties of diatomaceous earth (DE), a low-temperature synthesis of mesoporous <span class="hlt">material</span> from DE was carried out using a hydrothermal processing technique under saturated steam pressure at 200 °C for 12 h. The experimental results showed that the most important strength-producing constituent in the solidified specimens was tobermorite formed by hydrothermal processing, and the addition of slaked lime was favorable to tobermorite formation. At Ca/Si ratio around 0.83 in the starting <span class="hlt">material</span>, tobermorite appeared to form readily. A high autoclave curing temperature (200 °C), or a longer curing time (12 h) seemed to accelerate the tobermorite formation, thus leading to a higher strength development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/814269','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/814269"><span id="translatedtitle">Characterization of <span class="hlt">Porous</span> Carbon Fibers and Related <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fuller, E.L., Jr.</p> <p>1993-01-01</p> <p>A one-year subcontract sponsored by the Carbon <span class="hlt">Materials</span> Technology Group of the Oak Ridge National Laboratory (ORNL) with the Department of Geological Sciences, University Of Tennessee, has been completed. A volumetric sorption system has been upgraded, in cooperation with commercial vendor, to allow the acquisition of data relevant to the program for the production of activated carbon molecular fiber sieves (ACFMS). The equipment and experimental techniques have been developed to determine the pore structure and porosity of reference <span class="hlt">materials</span> and <span class="hlt">materials</span> produced at ORNL as part of the development of methods for the activation of carbon fibers by various etching agents. Commercial activated coconut shell charcoal (ACSC) has been studied to verify instrument performance and to develop methodology for deducing cause and effects in the activation processes and to better understand the industrial processes (gas separation, natural gas storage, etc.). Operating personnel have been trained, standard operating procedures have been established, and quality assurance procedures have been developed and put in place. Carbon dioxide and methane sorption have been measured over a temperature range 0 to 200 C for both ACFMS and ACSC and similarities and differences related to the respective structures and mechanisms of interaction with the sorbed components. Nitrogen sorption (at 77 K) has been used to evaluate ''surface area'' and ''porosity'' for comparison with the large data base that exists for other activated carbons and related <span class="hlt">materials</span>. The preliminary data base reveals that techniques and theories currently used to evaluate activated carbons may be somewhat erroneous and misleading. Alternate thermochemical and structural analyses have been developed that show promise in providing useful information related both to the activation process and to industrial applications of interest in the efficient and economical utilization of fossil fuels in a manner that is</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/956632','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/956632"><span id="translatedtitle">Ensemble phase averaging equations for multiphase flows in <span class="hlt">porous</span> media, part I: the bundle-of-tubes <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yang, Dali; Zhang, Duan; Currier, Robert</p> <p>2008-01-01</p> <p>A bundle-of-tubes construct is used as a <span class="hlt">model</span> system to study ensemble averaged equations for multiphase flow in a <span class="hlt">porous</span> <span class="hlt">material</span>. Momentum equations for the fluid phases obtained from the method are similar to Darcy's law, but with additional terms. We study properties of the additional terms, and the conditions under which the averaged equations can be approximated by the diffusion <span class="hlt">model</span> or the extended Darcy's law as often used in <span class="hlt">models</span> for multiphase flows in <span class="hlt">porous</span> media. Although the bundle-of-tubes <span class="hlt">model</span> is perhaps the simplest <span class="hlt">model</span> for a <span class="hlt">porous</span> <span class="hlt">material</span>, the ensemble averaged equation technique developed in this paper assumes the very same form in more general treatments described in Part 2 of the present work (Zhang 2009). Any <span class="hlt">model</span> equation system intended for the more general cases must be understood and tested first using simple <span class="hlt">models</span>. The concept of ensemble phase averaging is dissected here in physical terms, without involved mathematics through its application to the idealized bundle-of-tubes <span class="hlt">model</span> for multiphase flow in <span class="hlt">porous</span> media.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H23R..06G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H23R..06G"><span id="translatedtitle">Colloid Transport in <span class="hlt">Porous</span> Media: A Continuing Survey of Conceptual <span class="hlt">Model</span> Developmen</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ginn, T. R.; Nelson, K.; Kamai, T.; Massoudieh, A.; Nguyen, T. H.; Le Borgne, T.; Meheust, Y.; Turuban, R.; Benjamin, A.; Palomino, A.</p> <p>2014-12-01</p> <p>The grand challenge problem of understanding colloid transport and filtration processes in <span class="hlt">porous</span> media continues to defy fundamental solution, limiting progress of engineering science in in fields ranging from human health to water quality to <span class="hlt">materials</span> engineering to energy production to microbiology. Focused experimental and <span class="hlt">modeling</span> studies continue to chip away at our ignorance, in particular as regards colloid interactions with surfaces and colloid motion. In this continuing survey we give an updated overview of some of the currently active research areas with a focus on the exciting new conceptual <span class="hlt">model</span> development and testing, with reference to pore-to-continuum scale experiments and simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003WRR....39.1072D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003WRR....39.1072D&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Modeling</span> of contaminants mobility in underground domains with multiple free/<span class="hlt">porous</span> interfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Das, D. B.; Nassehi, V.</p> <p>2003-03-01</p> <p>Existing simulation techniques for subsurface water quality management remain inadequate despite the phenomenal progress made in the computing capabilities in the past 2 decades. One major lacunas found in mathematical <span class="hlt">models</span> for groundwater hydrodynamics in combined free flow zones (zones that are devoid of <span class="hlt">porous</span> <span class="hlt">materials</span>) and <span class="hlt">porous</span> domains (e.g., soil water regions) in the subsurface is that these <span class="hlt">models</span> impose continuity of all flow/transport parameters to describe the flow behavior at the intermediate surfaces between the two zones. Prescription of such interfacial conditions cannot always be physically justified and, in general, result in ill-posed mathematical formulations. The present paper aims to remove the above limitations of the mathematical <span class="hlt">models</span> by imposing well-posed mathematical formulations of mass and momentum transfer across the boundaries between free and <span class="hlt">porous</span> zones underground for simulating subsurface flow. The possibility of the existence of a multiple number of pervious boundaries in the domain across which water may flow is considered in this work, as it represents the most realistic scenario for the subsurface transport processes. The hydrodynamics of coupled fluid flow and behavior of contaminants transport are described. Combined effects of Darcy and Reynolds numbers on the subsurface transport of contaminants are discussed. Sensitivity of the flow variables to a coefficient of the permeability and porosity of interfacial boundary, which is determined by its structural properties, is also considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21520022','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21520022"><span id="translatedtitle">Pore-network <span class="hlt">modeling</span> of biofilm evolution in <span class="hlt">porous</span> media.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ezeuko, C C; Sen, A; Grigoryan, A; Gates, I D</p> <p>2011-10-01</p> <p>The influence of bacterial biomass on hydraulic properties of <span class="hlt">porous</span> media (bioclogging) has been explored as a viable means for optimizing subsurface bioremediation and microbial enhanced oil recovery. In this study, we present a pore network simulator for <span class="hlt">modeling</span> biofilm evolution in <span class="hlt">porous</span> media including hydrodynamics and nutrient transport based on coupling of advection transport with Fickian diffusion and a reaction term to account for nutrient consumption. Biofilm has non-zero permeability permitting liquid flow and transport through the biofilm itself. To handle simultaneous mass transfer in both liquid and biofilm in a pore element, a dual-diffusion mass transfer <span class="hlt">model</span> is introduced. The influence of nutrient limitation on predicted results is explored. Nutrient concentration in the network is affected by diffusion coefficient for nutrient transfer across biofilm (compared to water/water diffusion coefficient) under advection dominated transport, represented by mass transport Péclet number >1. The <span class="hlt">model</span> correctly predicts a dependence of rate of biomass accumulation on inlet concentration. Poor network connectivity shows a significantly large reduction of permeability, for a small biomass pore volume. PMID:21520022</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..DFD.AH009D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..DFD.AH009D"><span id="translatedtitle">Droplet impact on a <span class="hlt">porous</span> substrate: a capillary tube <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ding, Hang; Theofanous, Theo</p> <p>2009-11-01</p> <p>The dynamics of impacting (spreading, penetrating) a droplet on a <span class="hlt">porous</span> substrate, <span class="hlt">modeled</span> by an array of capillary tubes, is studied numerically using diffuse interface methods. The absorption rate depends on the diameter ratio of the capillary tube to the droplet, wettability, and liquid properties. The flow dynamics is resolved by solving the Navier-Stokes equations and interface capturing is governed by the Cahn-Hilliard equation. Contact-angle hysteresis is included (Ding&Spelt 2008) and the stress singularity at moving contact lines is relieved using a diffuse interface <span class="hlt">model</span> (Seppecher 1996; Jaqcmin 2000). The <span class="hlt">model</span> is validated by studying the evolution of a droplet initially resting on a <span class="hlt">porous</span> substrate and by comparison to drop-impact experiments involving just one capillary tube (Kogan et al 2008). Comparisons with analytical solutions and results available in the literature (e.g. Hilpert & Ben-David 2009) are presented. Through parametric simulations over relevant ranges of Reynolds and Ohnesorge numbers and contact angles, impact regime maps are derived.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.H21A1320H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.H21A1320H&link_type=ABSTRACT"><span id="translatedtitle">Pore-scale <span class="hlt">Modelling</span> of Capillarity in Swelling Granular <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hassanizadeh, S. M.; Sweijen, T.; Nikooee, E.; Chareyre, B.</p> <p>2015-12-01</p> <p>Capillarity in granular <span class="hlt">porous</span> media is a common and important phenomenon in earth <span class="hlt">materials</span> and industrial products, and therefore has been studied extensively. To <span class="hlt">model</span> capillarity in granular <span class="hlt">porous</span> media, one needs to go beyond current <span class="hlt">models</span> which simulate either two-phase flow in <span class="hlt">porous</span> media or mechanical behaviour in granular media. Current pore-scale <span class="hlt">models</span> for two-phase flow such as pore-network <span class="hlt">models</span> are tailored for rigid pore-skeletons, even though in many applications, namely hydro-mechanical coupling in soils, printing, and hygienic products, the <span class="hlt">porous</span> structure does change during two-phase flow. On the other hand, <span class="hlt">models</span> such as Discrete Element Method (DEM), which simulate the deformable <span class="hlt">porous</span> media, have mostly been employed for dry or saturated granular media. Here, the effects of porosity change and swelling on the retention properties was studied, for swelling granular <span class="hlt">materials</span>. A pore-unit <span class="hlt">model</span> that was capable to construct the capillary pressure - saturation curve was coupled to DEM. Such that the capillary pressure - saturation curve could be constructed for varying porosities and amounts of absorbed water. The study <span class="hlt">material</span> was super absorbent polymer particles, which are capable to absorb water 10's to 200 times their initial weight. We have simulated quasi-static primary imbibition for different porosities and amounts of absorbed water. The results reveal a 3 dimensional surface between capillary pressure, saturation, and porosity, which can be normalized by means of the entry pressure and the effective water saturation to a unique curve.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23743266','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23743266"><span id="translatedtitle"><span class="hlt">Porous</span> carbon <span class="hlt">material</span> containing CaO for acidic gas capture: preparation and properties.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Przepiórski, Jacek; Czyżewski, Adam; Pietrzak, Robert; Toyoda, Masahiro; Morawski, Antoni W</p> <p>2013-12-15</p> <p>A one-step process for the preparation of CaO-containing <span class="hlt">porous</span> carbons is described. Mixtures of poly(ethylene terephthalate) with natural limestone were pyrolyzed and thus hybrid sorbents could be easily obtained. The polymeric <span class="hlt">material</span> and the mineral served as a carbon precursor and CaO delivering agent, respectively. We discuss effects of the preparation conditions and the relative amounts of the raw <span class="hlt">materials</span> used for the preparations on the porosity of the hybrid products. The micropore areas and volumes of the obtained products tended to decrease with increasing CaO contents. Increase in the preparation temperature entailed a decrease in the micropore volume, whereas the mesopore volume increased. The pore creation mechanism is proposed on the basis of thermogravimetric and temperature-programmed desorption measurements. The prepared CaO-containing <span class="hlt">porous</span> carbons efficiently captured SO2 and CO2 from air. Washing out of CaO from the hybrid <span class="hlt">materials</span> was confirmed as a suitable method to obtain highly <span class="hlt">porous</span> carbon <span class="hlt">materials</span>. PMID:23743266</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1177074','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1177074"><span id="translatedtitle">Enhancing activated-peroxide formulations for <span class="hlt">porous</span> <span class="hlt">materials</span> :</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krauter, Paula; Tucker, Mark D.; Tezak, Matthew S.; Boucher, Raymond</p> <p>2012-12-01</p> <p>During an urban wide-area incident involving the release of a biological warfare agent, the recovery/restoration effort will require extensive resources and will tax the current capabilities of the government and private contractors. In fact, resources may be so limited that decontamination by facility owners/occupants may become necessary and a simple decontamination process and <span class="hlt">material</span> should be available for this use. One potential process for use by facility owners/occupants would be a liquid sporicidal decontaminant, such as pHamended bleach or activated-peroxide, and simple application devices. While pH-amended bleach is currently the recommended <U+2018>low-tech<U+2019> decontamination solution, a less corrosive and toxic decontaminant is desirable. The objective of this project is to provide an operational assessment of an alternative to chlorine bleach for <U+2018>low-tech<U+2019> decontamination applications <U+2013> activated hydrogen peroxide. This report provides the methods and results for activatedperoxide evaluation experiments. The results suggest that the efficacy of an activated-peroxide decontaminant is similar to pH-amended bleach on many common <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRG..119.1418J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRG..119.1418J"><span id="translatedtitle">Mechanistic <span class="hlt">models</span> of biofilm growth in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaiswal, Priyank; Al-Hadrami, Fathiya; Atekwana, Estella A.; Atekwana, Eliot A.</p> <p>2014-07-01</p> <p>Nondestructive acoustics methods can be used to monitor in situ biofilm growth in <span class="hlt">porous</span> media. In practice, however, acoustic methods remain underutilized due to the lack of <span class="hlt">models</span> that can translate acoustic data into rock properties in the context of biofilm. In this paper we present mechanistic <span class="hlt">models</span> of biofilm growth in <span class="hlt">porous</span> media. The <span class="hlt">models</span> are used to quantitatively interpret arrival times and amplitudes recorded in the 29 day long Davis et al. (2010) physical scale biostimulation experiment in terms of biofilm morphologies and saturation. The <span class="hlt">model</span> pivots on addressing the sediment elastic behavior using the lower Hashin-Shtrikman bounds for grain mixing and Gassmann substitution for fluid saturation. The time-lapse P wave velocity (VP; a function of arrival times) is explained by a combination of two rock <span class="hlt">models</span> (morphologies); "load bearing" which assumes the biofilm as an additional mineral in the rock matrix and "pore filling" which assumes the biofilm as an additional fluid phase in the pores. The time-lapse attenuation (QP-1; a function of amplitudes), on the other hand, can be explained adequately in two ways; first, through squirt flow where energy is lost from relative motion between rock matrix and pore fluid, and second, through an empirical function of porosity (φ), permeability (κ), and grain size. The squirt flow <span class="hlt">model</span>-fitting results in higher internal φ (7% versus 5%) and more oblate pores (0.33 versus 0.67 aspect ratio) for the load-bearing morphology versus the pore-filling morphology. The empirical <span class="hlt">model</span>-fitting results in up to 10% increase in κ at the initial stages of the load-bearing morphology. The two morphologies which exhibit distinct mechanical and hydraulic behavior could be a function of pore throat size. The biofilm mechanistic <span class="hlt">models</span> developed in this study can be used for the interpretation of seismic data critical for the evaluation of biobarriers in bioremediation, microbial enhanced oil recovery, and CO2</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3344220','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3344220"><span id="translatedtitle">Fly Ash <span class="hlt">Porous</span> <span class="hlt">Material</span> using Geopolymerization Process for High Temperature Exposure</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Abdullah, Mohd Mustafa Al Bakri; Jamaludin, Liyana; Hussin, Kamarudin; Bnhussain, Mohamed; Ghazali, Che Mohd Ruzaidi; Ahmad, Mohd Izzat</p> <p>2012-01-01</p> <p>This paper presents the results of a study on the effect of temperature on geopolymers manufactured using pozzolanic <span class="hlt">materials</span> (fly ash). In this paper, we report on our investigation of the performance of <span class="hlt">porous</span> geopolymers made with fly ash after exposure to temperatures from 600 °C up to 1000 °C. The research methodology consisted of pozzolanic <span class="hlt">materials</span> (fly ash) synthesized with a mixture of sodium hydroxide and sodium silicate solution as an alkaline activator. Foaming agent solution was added to geopolymer paste. The geopolymer paste samples were cured at 60 °C for one day and the geopolymers samples were sintered from 600 °C to 1000 °C to evaluate strength loss due to thermal damage. We also studied their phase formation and microstructure. The heated geopolymers samples were tested by compressive strength after three days. The results showed that the <span class="hlt">porous</span> geopolymers exhibited strength increases after temperature exposure. PMID:22605984</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1107637','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1107637"><span id="translatedtitle">Ordered <span class="hlt">porous</span> mesostructured <span class="hlt">materials</span> from nanoparticle-block copolymer self-assembly</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Warren, Scott; Wiesner, Ulrich; DiSalvo, Jr., Francis J</p> <p>2013-10-29</p> <p>The invention provides mesostructured <span class="hlt">materials</span> and methods of preparing mesostructured <span class="hlt">materials</span> including metal-rich mesostructured nanoparticle-block copolymer hybrids, <span class="hlt">porous</span> metal-nonmetal nanocomposite mesostructures, and ordered metal mesostructures with uniform pores. The nanoparticles can be metal, metal alloy, metal mixture, intermetallic, metal-carbon, metal-ceramic, semiconductor-carbon, semiconductor-ceramic, insulator-carbon or insulator-ceramic nanoparticles, or combinations thereof. A block copolymer/ligand-stabilized nanoparticle solution is cast, resulting in the formation of a metal-rich (or semiconductor-rich or insulator-rich) mesostructured nanoparticle-block copolymer hybrid. The hybrid is heated to an elevated temperature, resulting in the formation of an ordered <span class="hlt">porous</span> nanocomposite mesostructure. A nonmetal component (e.g., carbon or ceramic) is then removed to produce an ordered mesostructure with ordered and large uniform pores.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAP...119l5901N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAP...119l5901N"><span id="translatedtitle">Explicit accounting of electronic effects on the Hugoniot of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nayak, Bishnupriya; Menon, S. V. G.</p> <p>2016-03-01</p> <p>A generalized enthalpy based equation of state, which includes thermal electron excitations explicitly, is formulated from simple considerations. Its application to obtain Hugoniot of <span class="hlt">materials</span> needs simultaneous evaluation of pressure-volume curve and temperature, the latter requiring solution of a differential equation. The errors involved in two recent papers [Huayun et al., J. Appl. Phys. 92, 5917 (2002); 92, 5924 (2002)], which employed this approach, are brought out and discussed. In addition to developing the correct set of equations, the present work also provides a numerical method to implement this approach. Constant pressure specific heat of ions and electrons and ionic enthalpy parameter, needed for applications, are calculated using a three component equation of state. The method is applied to <span class="hlt">porous</span> Cu with different initial porosities. Comparison of results with experimental data shows good agreement. It is found that temperatures along the Hugoniot of <span class="hlt">porous</span> <span class="hlt">materials</span> are significantly modified due to electronic effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27159626','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27159626"><span id="translatedtitle">Synthetic Methodology for the Fabrication of <span class="hlt">Porous</span> Porphyrin <span class="hlt">Materials</span> with Metal-Organic-Polymer Aerogels.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhao, Xin; Yuan, Lin; Zhang, Zeng-Qi; Wang, Yong-Song; Yu, Qiong; Li, Jun</p> <p>2016-06-01</p> <p>A promising fabrication strategy used for designing <span class="hlt">porous</span> porphyrin <span class="hlt">materials</span> and a group of rigid carboxyl porphyrins based metal-organic-polymer aerogels (MOPAs) has been proposed recently. These newly synthesized MOPAs were exemplarily characterized by FT-IR, UV-vis-DRS, EDS, PXRD, TGA, SEM, TEM, and gas sorption measurements. A gelation study has shown that solvents, molar ratio, temperature, and peripheral carboxyl number in porphyrins all affect gel generation. The MOPA series exhibit eminent thermal stability, high removal efficiency in dye adsorption, versatile morphologies, and permanent tunable porosity; also the BET surface areas fall within the range 249-779 m(2) g(-1). All of the mentioned properties are significantly superior to some other <span class="hlt">porous</span> <span class="hlt">materials</span>, which enable these compounds to be potential candidates for dye uptake, gas storage, and separation. PMID:27159626</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22605984','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22605984"><span id="translatedtitle">Fly ash <span class="hlt">porous</span> <span class="hlt">material</span> using geopolymerization process for high temperature exposure.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Abdullah, Mohd Mustafa Al Bakri; Jamaludin, Liyana; Hussin, Kamarudin; Bnhussain, Mohamed; Ghazali, Che Mohd Ruzaidi; Ahmad, Mohd Izzat</p> <p>2012-01-01</p> <p>This paper presents the results of a study on the effect of temperature on geopolymers manufactured using pozzolanic <span class="hlt">materials</span> (fly ash). In this paper, we report on our investigation of the performance of <span class="hlt">porous</span> geopolymers made with fly ash after exposure to temperatures from 600 °C up to 1000 °C. The research methodology consisted of pozzolanic <span class="hlt">materials</span> (fly ash) synthesized with a mixture of sodium hydroxide and sodium silicate solution as an alkaline activator. Foaming agent solution was added to geopolymer paste. The geopolymer paste samples were cured at 60 °C for one day and the geopolymers samples were sintered from 600 °C to 1000 °C to evaluate strength loss due to thermal damage. We also studied their phase formation and microstructure. The heated geopolymers samples were tested by compressive strength after three days. The results showed that the <span class="hlt">porous</span> geopolymers exhibited strength increases after temperature exposure. PMID:22605984</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014FrMS....8...46K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014FrMS....8...46K"><span id="translatedtitle">Preparation and application of highly <span class="hlt">porous</span> aerogel-based bioactive <span class="hlt">materials</span> in dentistry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuttor, Andrea; Szalóki, Melinda; Rente, Tünde; Kerényi, Farkas; Bakó, József; Fábián, István; Lázár, István; Jenei, Attila; Hegedüs, Csaba</p> <p>2014-03-01</p> <p>In this study, the possibility of preparation and application of highly <span class="hlt">porous</span> silica aerogel-based bioactive <span class="hlt">materials</span> are presented. The aerogel was combined with hydroxyapatite and β-tricalcium phosphate as bioactive and osteoinductive agents. The porosity of aerogels was in the mesoporous region with a maximum pore diameter of 7.4 and 12.7 nm for the composite <span class="hlt">materials</span>. The newly developed bioactive <span class="hlt">materials</span> were characterized by scanning electron microscopy. The in vitro biological effect of these modified surfaces was also tested on SAOS-2 osteogenic sarcoma cells by confocal laser scanning microscopy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16853195','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16853195"><span id="translatedtitle"><span class="hlt">Modeling</span> heating curve for gas hydrate dissociation in <span class="hlt">porous</span> media.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dicharry, Christophe; Gayet, Pascal; Marion, Gérard; Graciaa, Alain; Nesterov, Anatoliy N</p> <p>2005-09-15</p> <p>A method for <span class="hlt">modeling</span> the heating curve for gas hydrate dissociation in <span class="hlt">porous</span> media at isochoric conditions (constant cell volume) is presented. This method consists of using an equation of state of the gas, the cumulative volume distribution (CVD) of the <span class="hlt">porous</span> medium, and a van der Waals-Platteeuw-type thermodynamic <span class="hlt">model</span> that includes a capillary term. The proposed method was tested to predict the heating curves for methane hydrate dissociation in a mesoporous silica glass for saturated conditions (liquid volume = pore volume) and for a fractional conversion of water to hydrate of 1 (100% of the available water was converted to hydrate). The shape factor (F) of the hydrate-water interface was found equal to 1, supporting a cylindrical shape for the hydrate particles during hydrate dissociation. Using F = 1, it has been possible to predict the heating curve for different ranges of pressure and temperature. The excellent agreement between the calculated and experimental heating curves supports the validity of our approach. PMID:16853195</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22409622','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22409622"><span id="translatedtitle">Maintaining the structure of templated <span class="hlt">porous</span> <span class="hlt">materials</span> for reactive and high-temperature applications.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rudisill, Stephen G; Wang, Zhiyong; Stein, Andreas</p> <p>2012-05-15</p> <p>Nanoporous and nanostructured <span class="hlt">materials</span> are becoming increasingly important for advanced applications involving, for example, bioactive <span class="hlt">materials</span>, catalytic <span class="hlt">materials</span>, energy storage and conversion <span class="hlt">materials</span>, photonic crystals, membranes, and more. As such, they are exposed to a variety of harsh environments and often experience detrimental morphological changes as a result. This article highlights <span class="hlt">material</span> limitations and recent advances in <span class="hlt">porous</span> <span class="hlt">materials</span>--three-dimensionally ordered macroporous (3DOM) <span class="hlt">materials</span> in particular--under reactive or high-temperature conditions. Examples include systems where morphological changes are desired and systems that require an increased retention of structure, surface area, and overall <span class="hlt">material</span> integrity during synthesis and processing. Structural modifications, changes in composition, and alternate synthesis routes are explored and discussed. Improvements in thermal or structural stability have been achieved by the isolation of nanoparticles in <span class="hlt">porous</span> structures through spatial separation, by confinement in a more thermally stable host, by the application of a protective surface or an adhesive interlayer, by alloy or solid solution formation, and by doping to induce solute drag. PMID:22409622</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4300473','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4300473"><span id="translatedtitle">Hierarchically <span class="hlt">porous</span> silicon–carbon–nitrogen hybrid <span class="hlt">materials</span> towards highly efficient and selective adsorption of organic dyes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Meng, Lala; Zhang, Xiaofei; Tang, Yusheng; Su, Kehe; Kong, Jie</p> <p>2015-01-01</p> <p>The hierarchically macro/micro-<span class="hlt">porous</span> silicon–carbon–nitrogen (Si–C–N) hybrid <span class="hlt">material</span> was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid <span class="hlt">material</span> was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp2-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir <span class="hlt">model</span>, the adsorption capacity is 1327.7 mg·g−1 and 1084.5 mg·g−1 for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid <span class="hlt">materials</span> do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically <span class="hlt">porous</span> Si–C–N hybrid <span class="hlt">material</span> from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants. PMID:25604334</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015NatSR...5E7910M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015NatSR...5E7910M&link_type=ABSTRACT"><span id="translatedtitle">Hierarchically <span class="hlt">porous</span> silicon-carbon-nitrogen hybrid <span class="hlt">materials</span> towards highly efficient and selective adsorption of organic dyes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meng, Lala; Zhang, Xiaofei; Tang, Yusheng; Su, Kehe; Kong, Jie</p> <p>2015-01-01</p> <p>The hierarchically macro/micro-<span class="hlt">porous</span> silicon-carbon-nitrogen (Si-C-N) hybrid <span class="hlt">material</span> was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid <span class="hlt">material</span> was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir <span class="hlt">model</span>, the adsorption capacity is 1327.7 mg.g-1 and 1084.5 mg.g-1 for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid <span class="hlt">materials</span> do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically <span class="hlt">porous</span> Si-C-N hybrid <span class="hlt">material</span> from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..DFDD16006O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..DFDD16006O"><span id="translatedtitle">A <span class="hlt">Porous</span> Media <span class="hlt">Model</span> for Blood Flow within Reticulated Foam</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ortega, Jason</p> <p>2013-11-01</p> <p>A <span class="hlt">porous</span> media <span class="hlt">model</span> is developed for non-Newtonian blood flow through reticulated foam at Reynolds numbers ranging from 10-8 to 10. This empirical <span class="hlt">model</span> effectively divides the pressure gradient versus flow speed curve into three regimes, in which either the non-Newtonian viscous forces, the Newtonian viscous forces, or the inertial fluid forces are most prevalent. When compared to simulation data of blood flow through two reticulated foam geometries, the <span class="hlt">model</span> adequately captures the pressure gradient within all three regimes, especially that within the Newtonian regime where blood transitions from a power-law to a constant viscosity fluid. This work was supported by the National Institutes of Health/National Institute of Biomedical Imaging and Bioengineering Grant R01EB000462 and partially performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1028052','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1028052"><span id="translatedtitle">Hybrid <span class="hlt">Models</span> of Reactive Transport in <span class="hlt">Porous</span> and Fractured Media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Battiato, Ilenia; Tartakovsky, Daniel M.; Tartakovsky, Alexandre M.; Scheibe, Timothy D.</p> <p>2011-02-02</p> <p>Darcy-scale <span class="hlt">models</span> of flow and transport in <span class="hlt">porous</span> media often fail to describe experimentally observed phenomena, while their pore-scale counterparts are accu- rate but can be computationally prohibitive. Most numerical multi-scale <span class="hlt">models</span>, which seek to combine these two descriptions, require empirical closures and/or assumptions on the behavior of pore-scale quantities at the continuum (Darcy) scale. We present a general formulation of an iterative hybrid numerical method that links these two scales without resorting to such approximations. The algorithm treats the fluxes exchanged at the internal boundaries between the pore- and continuum-scale domains as unknown, and allows for iteratively determined boundary conditions to be applied at the pore-scale in order to guarantee their continuity. While the algorithm proposed is general, we use it to <span class="hlt">model</span> Taylor dispersion in a fracture with chemically reactive walls. Results show significant improvement upon standard continuum-scale formulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11350000','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11350000"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">material</span> characterization--ultrasonic method for estimation of tortuosity and characteristic length using a barometric chamber.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moussatov, A; Ayrault, C; Castagnède, B</p> <p>2001-04-01</p> <p>An ultrasonic method of acoustic parameter evaluation for <span class="hlt">porous</span> <span class="hlt">materials</span> saturated by air (or any other gas) is discussed. The method is based on the evolution of speed of sound and the attenuation inside the <span class="hlt">material</span> when the static pressure of the gas saturating the <span class="hlt">material</span> is changed. Asymptotic development of the equivalent fluid <span class="hlt">model</span> of Johnson-Allard is used for analytical description. The method allows an estimation of three essential parameters of the <span class="hlt">model</span>: the tortuosity, and the viscous and thermal characteristic lengths. Both characteristic lengths are estimated individually by assuming a given ratio between them. Tests are performed with industrial plastic foams and granular substances (glass beads, sea sand) over a gas pressure range from 0.2 to 6 bars at the frequencies 30-600 kHz. The present technique has a number of distinct advantages over the conventional ultrasonic approach: operation at a single frequency, improved signal-to-noise ratio, possibility of saturation the <span class="hlt">porous</span> media by different gases. In the case when scattering phenomena occur, the present method permits a separate analysis of scattering losses and viscothermal losses. An analytical description of the method is followed by a presentation of the set-up and the measurement procedure. Experimental results and perspectives are discussed. PMID:11350000</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JMMM..320E.189L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JMMM..320E.189L"><span id="translatedtitle"><span class="hlt">Porous</span> manganese-based magnetocaloric <span class="hlt">material</span> for magnetic refrigeration at room temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lozano, J. A.; Kostow, M. P.; Brück, E.; de Lima, J. C.; Prata, A. T.; Wendhausen, P. A. P.</p> <p></p> <p>The powder metallurgy technique has been exploited as a means to prepare <span class="hlt">porous</span> magnetocaloric <span class="hlt">materials</span>. The alloy Mn 1.1Fe 0.9P 0.46As 0.54 was previously synthesized by mechanical alloying followed by a solid-state reaction for crystallization and homogenization. Subsequently, the alloy was comminuted and sintered at 1298 K. The obtained sintered product is aimed to be tested in a magnetic regenerator of a prototype machine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/242525','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/242525"><span id="translatedtitle">Preparation of <span class="hlt">porous</span> nickel-titania cermets and their application to anode <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Taimatsu, H.; Kudo, K.; Kaneko, H.; Matsukaze, N.; Iwata, T.</p> <p>1995-12-31</p> <p><span class="hlt">Porous</span> nickel-titania cermets have been prepared as new-type anode <span class="hlt">materials</span> for solid oxide fuel cells using the solid-state displacement reaction method. The microstructures of the cermets were interwoven aggregate-type, differently from those of conventional nickel-YSZ cermets: nickel and titania phases three-dimensionally entangled each other. These cermets revealed good properties in compatibility of thermal expansion with YSZ, strength, gas permeation and electrical conduction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/256817','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/256817"><span id="translatedtitle">A three-phase homogeneous <span class="hlt">model</span> for <span class="hlt">porous</span> electrodes in molten-carbonate fuel cells</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Prins-Jansen, J.A.; Hemmes, K.; Wit, J.H.W. de; Fehribach, J.D.</p> <p>1996-05-01</p> <p>In this paper a new <span class="hlt">model</span> for <span class="hlt">porous</span> electrodes in molten-carbonate fuel cells (MCFC) is presented. The <span class="hlt">model</span> is based on an averaging technique commonly used in <span class="hlt">porous</span>-media problems. Important disadvantages of the existing agglomerate <span class="hlt">model</span> caused by geometric assumptions and restrictions are eliminated in this new <span class="hlt">model</span>. Unlike the agglomerate <span class="hlt">model</span>, the new <span class="hlt">model</span> is suitable for studying three-dimensional and anisotropic problems and incorporating the degree of electrolyte fill. Different reaction mechanisms can easily be incorporated. The validity of the new <span class="hlt">model</span> is checked and compared with the agglomerate <span class="hlt">model</span> by fitting the two <span class="hlt">models</span> to ac-impedance spectra recorded from <span class="hlt">porous</span> MCFC cathodes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H14C..01G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H14C..01G"><span id="translatedtitle">A novel approach to <span class="hlt">model</span> hydraulic and electrical conductivity in fractal <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghanbarian, B.; Daigle, H.; Sahimi, M.</p> <p>2014-12-01</p> <p>Accurate prediction of conductivity in partially-saturated <span class="hlt">porous</span> media has broad applications in various phenomena in <span class="hlt">porous</span> media, and has been studied intensively since the 1940s by petroleum, chemical and civil engineers, and hydrologists. Many of the <span class="hlt">models</span> developed in the past are based on the bundle of capillary tubes. In addition, pore network <span class="hlt">models</span> have also been developed for simulating multiphase fluid flow in <span class="hlt">porous</span> media and computing the conductivity in unsaturated <span class="hlt">porous</span> media. In this study, we propose a novel approach using concepts from the effective-medium approximation (EMA) and percolation theory to <span class="hlt">model</span> hydraulic and electrical conductivity in fractal <span class="hlt">porous</span> media whose pore-size distributions exhibit power-law scaling. In our approach, the EMA, originally developed for predicting electrical conductivity of composite <span class="hlt">materials</span>, is used to predict the effective conductivity, from complete saturation to some intermediate water content that represents a crossover point. Below the crossover water content, but still above a critical saturation (percolation threshold), a universal scaling predicted by percolation theory, a power law that expresses the dependence of the conductivity on the water content (less a critical water saturation) with an exponent of 2, is invoked to describe the effective conductivity. In order to evaluate the accuracy of the approach, experimental data were used from the literature. The predicted hydraulic conductivities for most cases are in excellent agreement with the data. In a few cases the theory underestimates the hydraulic conductivities, which correspond to <span class="hlt">porous</span> media with very broad pore-size distribution in which the largest pore radius is more than 7 orders of magnitude greater than the smallest one. The approach is also used to predict the saturation dependence of the electrical conductivity for experiments in which capillary pressure data are available. The results indicate that the universal scaling of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21752539','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21752539"><span id="translatedtitle">Adsorption characteristics of haloacetonitriles on functionalized silica-based <span class="hlt">porous</span> <span class="hlt">materials</span> in aqueous solution.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Prarat, Panida; Ngamcharussrivichai, Chawalit; Khaodhiar, Sutha; Punyapalakul, Patiparn</p> <p>2011-09-15</p> <p>The effect of the surface functional group on the removal and mechanism of dichloroacetonitrile (DCAN) adsorption over silica-based <span class="hlt">porous</span> <span class="hlt">materials</span> was evaluated in comparison with powdered activated carbon (PAC). Hexagonal mesoporous silicate (HMS) was synthesized and functionalized by three different types of organosilanes (3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and n-octyldimethysilane). Adsorption kinetics and isotherm <span class="hlt">models</span> were used to determine the adsorption mechanism. The selective adsorption of five haloacetonitriles (HANs) in the single and mixed solute systems was also studied. The experiments revealed that the surface functional groups of the adsorbents largely affected the DCAN adsorption capacities. 3-Mercaptopropyl-grafted HMS had a high DCAN adsorption capacity compared to PAC. The adsorption mechanism is believed to occur via an ion-dipole electrostatic interaction in which water interference is inevitable at low concentrations of DCAN. In addition, the adsorption of DCAN strongly depended on the pH of the solution as this related to the charge density of the adsorbents. The selective adsorption of the five HANs over PAC was not observed, while the molecular structure of different HANs obviously influenced the adsorption capacity and selectivity over 3-mercaptopropyl-grafted HMS. PMID:21752539</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000Natur.404..982S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000Natur.404..982S"><span id="translatedtitle">A homochiral metal-organic <span class="hlt">porous</span> <span class="hlt">material</span> for enantioselective separation and catalysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seo, Jung Soo; Whang, Dongmok; Lee, Hyoyoung; Jun, Sung Im; Oh, Jinho; Jeon, Young Jin; Kim, Kimoon</p> <p>2000-04-01</p> <p>Inorganic zeolites are used for many practical applications that exploit the microporosity intrinsic to their crystal structures. Organic analogues, which are assembled from modular organic building blocks linked through non-covalent interactions, are of interest for similar applications. These range from catalysis, separation and sensor technology to optoelectronics, with enantioselective separation and catalysis being especially important for the chemical and pharmaceutical industries. The modular construction of these analogues allows flexible and rational design, as both the architecture and chemical functionality of the micropores can, in principle, be precisely controlled. <span class="hlt">Porous</span> organic solids with large voids and high framework stability have been produced, and investigations into the range of accessible pore functionalities have been initiated. For example, catalytically active organic zeolite analogues are known, as are chiral metal-organic open-framework <span class="hlt">materials</span>. However, the latter are only available as racemic mixtures, or lack the degree of framework stability or void space that is required for practical applications. Here we report the synthesis of a homochiral metal-organic <span class="hlt">porous</span> <span class="hlt">material</span> that allows the enantioselective inclusion of metal complexes in its pores and catalyses a transesterification reaction in an enantioselective manner. Our synthesis strategy, which uses enantiopure metal-organic clusters as secondary building blocks, should be readily applicable to chemically modified cluster components and thus provide access to a wide range of <span class="hlt">porous</span> organic <span class="hlt">materials</span> suitable for enantioselective separation and catalysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26256356','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26256356"><span id="translatedtitle">Fabrication of interpenetrating polymer network chitosan/gelatin <span class="hlt">porous</span> <span class="hlt">materials</span> and study on dye adsorption properties.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cui, Li; Xiong, Zihao; Guo, Yi; Liu, Yun; Zhao, Jinchao; Zhang, Chuanjie; Zhu, Ping</p> <p>2015-11-01</p> <p>One kind of adsorbent based on chitosan and gelatin with interpenetrating polymer networks (IPN) and <span class="hlt">porous</span> dual structures was prepared using genipin as the cross-linker. These dual structures were demonstrated by means of Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Adsorptions of acid orange II dye from aqueous solution were carried out at different genipin contents, adsorption times and pH values. The results showed that this <span class="hlt">material</span> was put up the largest adsorption capacity when the genipin content is 0.25 mmol/L, meanwhile, the lower the solution pH value the greater the adsorption capacity. The chitosan/gelatin interpenetrating polymer networks <span class="hlt">porous</span> <span class="hlt">material</span> displayed pH-sensitive and rapidly response in adsorption and desorption to pH altered. It is indicated that the cross-linked chitosan/gelatin interpenetrating polymer networks <span class="hlt">porous</span> <span class="hlt">material</span> could be used as a recyclable adsorbent in removal or separation of anionic dyes as environmental pH condition changed. PMID:26256356</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23945102','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23945102"><span id="translatedtitle"><span class="hlt">Porous</span> coordination polymers as novel sorption <span class="hlt">materials</span> for heat transformation processes.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Janiak, Christoph; Henninger, Stefan K</p> <p>2013-01-01</p> <p><span class="hlt">Porous</span> coordination polymers (PCPs)/metal-organic frameworks (MOFs) are inorganic-organic hybrid <span class="hlt">materials</span> with a permanent three-dimensional <span class="hlt">porous</span> metal-ligand network. PCPs or MOFs are inorganic-organic analogs of zeolites in terms of porosity and reversible guest exchange properties. Microporous water-stable PCPs with high water uptake capacity are gaining attention for low temperature heat transformation applications in thermally driven adsorption chillers (TDCs) or adsorption heat pumps (AHPs). TDCs or AHPs are an alternative to traditional air conditioners or heat pumps operating on electricity or fossil fuels. By using solar or waste heat as the operating energy TDCs or AHPs can significantly help to minimize primary energy consumption and greenhouse gas emissions generated by industrial or domestic heating and cooling processes. TDCs and AHPs are based on the evaporation and consecutive adsorption of coolant liquids, preferably water, under specific conditions. The process is driven and controlled by the microporosity and hydrophilicity of the employed sorption <span class="hlt">material</span>. Here we summarize the current investigations, developments and possibilities of PCPs/MOFs for use in low-temperature heat transformation applications as alternative <span class="hlt">materials</span> for the traditional inorganic <span class="hlt">porous</span> substances like silica gel, aluminophosphates or zeolites. PMID:23945102</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPS...261..156K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPS...261..156K"><span id="translatedtitle">Hierarchical meso-macro structure <span class="hlt">porous</span> carbon black as electrode <span class="hlt">materials</span> in Li-air battery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kang, Jun; Li, Oi Lun; Saito, Nagahiro</p> <p>2014-09-01</p> <p>A new class of hierarchical structure <span class="hlt">porous</span> carbon black, carbon nanoballs (CNBs), was generated by solution plasma process (SPP) with benzene. The structural characterization revealed that CNBs have excellent meso-macro hierarchical pore structure, with an averaged diameter size of 14.5 nm and a total pore volume of 1.13 cm3 g-1. The CNBs are aggregated forming inter-connected pore channels in different directions on both the meso- and macrometer length scales. The discharge capacity of CNBs reached 3600 mAh g-1, which exceeded the capacity of Ketjen Black EC-600JD (a commercial carbon black with highest cell performance) by 30-40%. The excellent discharge capacity was contributed by the co-existence of high pore volume and meso-macro hierarchical <span class="hlt">porous</span> structure. This new class carbon <span class="hlt">material</span> exhibited higher discharge capacity compared to commercial <span class="hlt">porous</span> carbon <span class="hlt">materials</span>, and is possible to apply as the next generation of electrode <span class="hlt">materials</span> in lithium-air (Li-air) battery. The structural and electrochemical properties accompanied with the synthesis mechanism of CNBs were discussed in details.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1230814-sandia-material-model-driver','SCIGOV-ESTSC'); return false;" href="http://www.osti.gov/scitech/biblio/1230814-sandia-material-model-driver"><span id="translatedtitle">Sandia <span class="hlt">Material</span> <span class="hlt">Model</span> Driver</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech/">Energy Science and Technology Software Center (ESTSC)</a></p> <p></p> <p>2005-09-28</p> <p>The Sandia <span class="hlt">Material</span> <span class="hlt">Model</span> Driver (MMD) software package allows users to run <span class="hlt">material</span> <span class="hlt">models</span> from a variety of different Finite Element <span class="hlt">Model</span> (FEM) codes in a standalone fashion, independent of the host codes. The MMD software is designed to be run on a variety of different operating system platforms as a console application. Initial development efforts have resulted in a package that has been shown to be fast, convenient, and easy to use, with substantialmore » growth potential.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1510181L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1510181L"><span id="translatedtitle">Electrokinetic induced solute dispersion in <span class="hlt">porous</span> media; pore network <span class="hlt">modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Shuai; Schotting, Ruud; Raoof, Amir</p> <p>2013-04-01</p> <p>Electrokinetic flow plays an important role in remediation process, separation technique, and chromatography. The solute dispersion is a key parameter to determine transport efficiency. In this study, we present the electrokinetic effects on solute dispersion in <span class="hlt">porous</span> media at the pore scale, using a pore network <span class="hlt">model</span>. The analytical solution of the electrokinetic coupling coefficient was obtained to quantity the fluid flow velocity in a cylinder capillary. The effect of electrical double layer on the electrokinetic coupling coefficient was investigated by applying different ionic concentration. By averaging the velocity over cross section within a single pore, the average flux was obtained. Applying such single pore relationships, in the thin electrical double layer limit, to each and every pore within the pore network, potential distribution and the induced fluid flow was calculated for the whole domain. The resulting pore velocities were used to simulate solute transport within the pore network. By averaging the results, we obtained the breakthrough curve (BTC) of the average concentration at the outlet of the pore network. Optimizing the solution of continuum scale advection-dispersion equation to such a BTC, solute dispersion coefficient was estimated. We have compared the dispersion caused by electrokinetic flow and pure pressure driven flow under different Peclet number values. In addition, the effect of microstructure and topological properties of <span class="hlt">porous</span> media on fluid flow and solute dispersion is presented, mainly based on different pore coordination numbers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080022430','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080022430"><span id="translatedtitle"><span class="hlt">Modeling</span> of Fixed-Exit <span class="hlt">Porous</span> Bleed Systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Slater, John W.; Saunders, John D.</p> <p>2008-01-01</p> <p>A <span class="hlt">model</span> has been developed to simulate a fixed-exit <span class="hlt">porous</span> bleed system for supersonic inlets. The fixed-exit <span class="hlt">model</span> allows the amount of bleed flow to vary according to local flow conditions and fixed-exit characteristics of the bleed system. This variation is important for the control of shock-wave/boundary-layer interactions within the inlet. The <span class="hlt">model</span> computes the bleed plenum static pressure rather than requiring its specification. The <span class="hlt">model</span> was implemented in the Wind-US computational fluid dynamics code. The <span class="hlt">model</span> was then verified and validated against experimental data for bleed on a flat plate with and without an impinging oblique shock and for bleed in a Mach 3.0 axisymmetric, mixed-compression inlet. The <span class="hlt">model</span> was able to accurately correlate the plenum pressures with bleed rates and simulate the effect of the bleed on the downstream boundary layer. Further, the <span class="hlt">model</span> provided a realistic simulation of the initiation of inlet unstart. The results provide the most in-depth examination to date of bleed <span class="hlt">models</span> for use in the simulation of supersonic inlets. The results also highlight the limitations of the <span class="hlt">models</span> and aspects that require further research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000APS..SES.LA002B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000APS..SES.LA002B"><span id="translatedtitle"><span class="hlt">Modeling</span> Granular <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brackbill, J. U.</p> <p>2000-11-01</p> <p>Granular <span class="hlt">materials</span> are often cited as examples of systems with complex and unusual properties. Much of this complexity is captured by computational <span class="hlt">models</span> in which the actual <span class="hlt">material</span> properties of individual grains are idealized and simplified. Because <span class="hlt">material</span> properties can be important under extreme conditions, we consider assemblies of grains with more realistic properties. Our <span class="hlt">model</span> grains may deform, their resulting stresses are computed from elastic / plastic constitutive <span class="hlt">models</span>, and their interactions with each other include Coulomb friction and bonding. Our <span class="hlt">model</span> equations are solved using a particle-in-cell (PIC) method, which combines a Lagrangian representation of the <span class="hlt">materials</span> with an adaptive grid [1]. Our contact <span class="hlt">model</span> between grains is linear in the number of grains, and we <span class="hlt">model</span> assemblies with statistically significant numbers of grains. With our <span class="hlt">model</span>, we have studied the response of dense granular <span class="hlt">material</span> to shear, with especial attention to the probability density function governing the volume distribution of stress for mono- and poly-disperse samples, circular and polygonal grains, and various values of microscopic friction coefficients, yield stresses, and packing fractions [2]. Remarkably, PDF's are similar in form for all cases simulated, and similar to those observed in experiments with granular <span class="hlt">materials</span> under both compression and shear. Namely, the simulations yield an exponential probability of large stresses above the mean, and there is a finite chance that a few grains in a large assembly are subjected to extreme stresses at any given time, even at low strain rates. For energetic <span class="hlt">materials</span>, such as explosives, this is a signficant finding. We have also studied the relationship between distributions of boundary tractions and volume distributions of stress. The ratio of normal and tangential components of traction on the boundary defines a bulk frictional response, which we find increases with the inter-granular friction coefficient</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/873832','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/873832"><span id="translatedtitle">Method and apparatus for measuring surface changes, in <span class="hlt">porous</span> <span class="hlt">materials</span>, using multiple differently-configured acoustic sensors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Hietala, Susan Leslie; Hietala, Vincent Mark; Tigges, Chris Phillip</p> <p>2001-01-01</p> <p>A method and apparatus for measuring surface changes, such as mass uptake at various pressures, in a thin-film <span class="hlt">material</span>, in particular <span class="hlt">porous</span> membranes, using multiple differently-configured acoustic sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25725857','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25725857"><span id="translatedtitle">Small angle scattering methods to study <span class="hlt">porous</span> <span class="hlt">materials</span> under high uniaxial strain.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Le Floch, Sylvie; Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso</p> <p>2015-02-01</p> <p>We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly <span class="hlt">porous</span> <span class="hlt">materials</span>. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of <span class="hlt">porous</span> <span class="hlt">materials</span> by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar <span class="hlt">porous</span> systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells. PMID:25725857</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015RScI...86b3901L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015RScI...86b3901L"><span id="translatedtitle">Small angle scattering methods to study <span class="hlt">porous</span> <span class="hlt">materials</span> under high uniaxial strain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Floch, Sylvie; Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso</p> <p>2015-02-01</p> <p>We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly <span class="hlt">porous</span> <span class="hlt">materials</span>. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of <span class="hlt">porous</span> <span class="hlt">materials</span> by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar <span class="hlt">porous</span> systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22392371','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22392371"><span id="translatedtitle">Small angle scattering methods to study <span class="hlt">porous</span> <span class="hlt">materials</span> under high uniaxial strain</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Le Floch, Sylvie Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso</p> <p>2015-02-15</p> <p>We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly <span class="hlt">porous</span> <span class="hlt">materials</span>. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of <span class="hlt">porous</span> <span class="hlt">materials</span> by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar <span class="hlt">porous</span> systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013CPL...561...68S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013CPL...561...68S"><span id="translatedtitle">Hierarchical <span class="hlt">porous</span> nickel oxide-carbon nanotubes as advanced pseudocapacitor <span class="hlt">materials</span> for supercapacitors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Su, Aldwin D.; Zhang, Xiang; Rinaldi, Ali; Nguyen, Son T.; Liu, Huihui; Lei, Zhibin; Lu, Li; Duong, Hai M.</p> <p>2013-03-01</p> <p>Hierarchical <span class="hlt">porous</span> carbon anode and metal oxide cathode are promising for supercapacitor with both high energy density and high power density. This Letter uses NiO and commercial carbon nanotubes (CNTs) as electrode <span class="hlt">materials</span> for electrochemical capacitors with high energy storage capacities. Experimental results show that the specific capacitance of the electrode <span class="hlt">materials</span> for 10%, 30% and 50% CNTs are 279, 242 and 112 F/g, respectively in an aqueous 1 M KOH electrolyte at a charge rate of 0.56 A/g. The maximum specific capacitance is 328 F/g at a charge rate of 0.33 A/g. <!--Q2: Please provide highlights.--></p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvE..93c3006P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvE..93c3006P"><span id="translatedtitle">Record-breaking events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pál, Gergő; Raischel, Frank; Lennartz-Sassinek, Sabine; Kun, Ferenc; Main, Ian G.</p> <p>2016-03-01</p> <p>An accurate understanding of the interplay between random and deterministic processes in generating extreme events is of critical importance in many fields, from forecasting extreme meteorological events to the catastrophic failure of <span class="hlt">materials</span> and in the Earth. Here we investigate the statistics of record-breaking events in the time series of crackling noise generated by local rupture events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span>. The events are generated by computer simulations of the uniaxial compression of cylindrical samples in a discrete element <span class="hlt">model</span> of sedimentary rocks that closely resemble those of real experiments. The number of records grows initially as a decelerating power law of the number of events, followed by an acceleration immediately prior to failure. The distribution of the size and lifetime of records are power laws with relatively low exponents. We demonstrate the existence of a characteristic record rank k*, which separates the two regimes of the time evolution. Up to this rank deceleration occurs due to the effect of random disorder. Record breaking then accelerates towards macroscopic failure, when physical interactions leading to spatial and temporal correlations dominate the location and timing of local ruptures. The size distribution of records of different ranks has a universal form independent of the record rank. Subsequences of events that occur between consecutive records are characterized by a power-law size distribution, with an exponent which decreases as failure is approached. High-rank records are preceded by smaller events of increasing size and waiting time between consecutive events and they are followed by a relaxation process. As a reference, surrogate time series are generated by reshuffling the event times. The record statistics of the uncorrelated surrogates agrees very well with the corresponding predictions of independent identically distributed random variables, which confirms that temporal and spatial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009MPLB...23..501L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009MPLB...23..501L"><span id="translatedtitle">Numerical Simulation for Effects of Microcapsuled Phase Change <span class="hlt">Material</span> (mpcm) Distribution on Heat and Moisture Transfer in <span class="hlt">Porous</span> Textiles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Fengzhi</p> <p></p> <p>In recent years, the use of phase change <span class="hlt">materials</span> (PCM) to improve heat and moisture transfer properties of clothing has gained considerable attention. The PCM distribution in the clothing impacts heat and moisture transfer properties of the clothing significantly. For describing the mechanisms of heat and moisture transfer in clothing with PCM and investigating the effect of the PCM distribution, a new dynamic <span class="hlt">model</span> of coupled heat and moisture transfer in <span class="hlt">porous</span> textiles with PCM was developed. The effect of water content on physical parameters of textiles and heat transfer with phase change in the PCM microcapsules were considered in the <span class="hlt">model</span>. Meanwhile, the numerical predictions were compared with experimental data, and good agreement was observed between the two, indicating that the <span class="hlt">model</span> was satisfactory. Also the effects of the PCM distribution on heat transfer in the textiles-PCM microcapsule composites were investigated by using the <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/126354','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/126354"><span id="translatedtitle">Colloid release and transport processes in natural and <span class="hlt">model</span> <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Roy, S.B.; Dzombak, D.A.</p> <p>1995-12-01</p> <p>Colloidal particles present in <span class="hlt">porous</span> media may be released and transported over significant distances when contacted with water at low ionic strength. An understanding of this process is of environmental interest because suspended colloidal particles in groundwater may enhance the subsurface transport of contaminants that are sorbed on their surfaces. This research focused on the processes of colloid release and transport in natural <span class="hlt">porous</span> media of interest in contaminant transport, i.e., high permeability <span class="hlt">materials</span> with low fines contents. Our objective in this study was to examine the mechanisms of colloid release and transport in a natural sand, and two <span class="hlt">model</span> systems: latex particles attached on glass beads, and kaolinite particles attached on glass beads. For the appropriate electrolyte conditions, the release of attached colloids from all three <span class="hlt">porous</span> media was found to be substantial. The total amount of colloids released depended upon the electrolyte composition and concentration. Column effluent data could be described with an advective-dispersive transport equation for colloidal particles with first-order terms for colloid release and deposition rates, by changing the mass of colloids available for release at each electrolyte concentrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016FML.....950032L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016FML.....950032L"><span id="translatedtitle">Superior supercapacitor electrode <span class="hlt">material</span> from hydrazine hydrate modified <span class="hlt">porous</span> polyacrylonitrile fiber</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Ying; Lu, Chunxiang; Wang, Junzhong; Yan, Hua; Zhang, Shouchun</p> <p>2016-03-01</p> <p>A hierarchical <span class="hlt">porous</span> carbon fiber with high nitrogen doping was fabricated for high-performance supercapacitor. For the purpose of high nitrogen retention, the <span class="hlt">porous</span> polyacrylonitrile fiber was treated by hydrazine hydrate, and then underwent pre-oxidation, carbonization, and activation in sequence. The resulted <span class="hlt">material</span> exhibited high nitrogen content of 7.82 at.%, large specific surface area of 1963.3m2 g‑1, total pore volume of 1.523cm3 g‑1, and the pores with size range of 1-4nm were account for 49.1%. Due to these features, the high reversible capacitance of 415F g‑1 and the good performance in heavy load discharge were obtained. In addition, the amazing cyclability was observed after 10,000 circles without capacitance fading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26406996','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26406996"><span id="translatedtitle">Sponge-Like Behaviour in Isoreticular Cu(Gly-His-X) Peptide-Based <span class="hlt">Porous</span> <span class="hlt">Materials</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martí-Gastaldo, Carlos; Warren, John E; Briggs, Michael E; Armstrong, Jayne A; Thomas, K Mark; Rosseinsky, Matthew J</p> <p>2015-11-01</p> <p>We report two isoreticular 3D peptide-based <span class="hlt">porous</span> frameworks formed by coordination of the tripeptides Gly-L-His-Gly and Gly-L-His-L-Lys to Cu(II) which display sponge-like behaviour. These <span class="hlt">porous</span> <span class="hlt">materials</span> undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2 O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbone, can be post-synthetically modified to produce urea-functionalised networks by following methodologies typically used for metal-organic frameworks built from more rigid "classical" linkers. PMID:26406996</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4676333','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4676333"><span id="translatedtitle">Sponge-Like Behaviour in Isoreticular Cu(Gly-His-X) Peptide-Based <span class="hlt">Porous</span> <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Martí-Gastaldo, Carlos; Warren, John E; Briggs, Michael E; Armstrong, Jayne A; Thomas, K Mark; Rosseinsky, Matthew J</p> <p>2015-01-01</p> <p>We report two isoreticular 3D peptide-based <span class="hlt">porous</span> frameworks formed by coordination of the tripeptides Gly-l-His-Gly and Gly-l-His-l-Lys to CuII which display sponge-like behaviour. These <span class="hlt">porous</span> <span class="hlt">materials</span> undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbone, can be post-synthetically modified to produce urea-functionalised networks by following methodologies typically used for metal–organic frameworks built from more rigid “classical” linkers. PMID:26406996</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21043421','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21043421"><span id="translatedtitle">Dynamic mean field theory of condensation and evaporation processes for fluids in <span class="hlt">porous</span> <span class="hlt">materials</span>: application to partial drying and drying.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Edison, J R; Monson, P A</p> <p>2010-01-01</p> <p>We study the dynamics of evaporation for lattice gas <span class="hlt">models</span> of fluids in <span class="hlt">porous</span> <span class="hlt">materials</span> using a recently developed dynamic mean field theory. The theory yields a description of the dynamics that is consistent with the mean field theory of the thermodynamics at equilibrium. The nucleation processes associated with phase changes in the pore are emergent features of the dynamics. Our focus is on situations where there is partial drying or drying in the system, associated with weakly attractive or repulsive interactions between the fluid and the pore walls. We consider two systems in this work: (i) a two-dimensional slit pore geometry relevant to the study of adsorption/desorption or intrusion/extrusion dynamics for fluids in <span class="hlt">porous</span> <span class="hlt">materials</span> and (ii) a three dimensional slit pore <span class="hlt">modeling</span> a pair of square plates in a bath of liquid as used in recent theoretical studies of dewetting processes between hydrophobic surfaces. We assess the theory by comparison with a higher order approximation to the dynamics that yields the Bethe-Peierls or quasi-chemical approximation at equilibrium. PMID:21043421</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17891422','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17891422"><span id="translatedtitle">Effect of Hydroxyapatite <span class="hlt">porous</span> characteristics on healing outcomes in rabbit posterolateral spinal fusion <span class="hlt">model</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Motomiya, Makoto; Ito, Manabu; Takahata, Masahiko; Kadoya, Ken; Irie, Kazuharu; Abumi, Kuniyoshi; Minami, Akio</p> <p>2007-12-01</p> <p>Hydroxyapatite (HA) has been commonly used as a bone graft substitute in various kinds of clinical fields. To improve the healing capability of HA, many studies have been performed to reveal its optimal structural characteristics for better healing outcomes. In spinal reconstruction surgery, non-interconnected <span class="hlt">porous</span> HAs have already been applied as a bone graft extender in order to avoid autogenous bone harvesting. However, there have been few experimental studies regarding the effects of the structural characteristics of HA in posterolateral lumbar intertransverse process spine fusion (PLF). The aims of this study were to investigate the effect of HA <span class="hlt">porous</span> characteristics on healing outcomes in a rabbit PLF <span class="hlt">model</span> in order to elucidate appropriate structural characteristics of HA as a bone graft extender. Thirty-six adult female Japanese White rabbits underwent bilateral intertransverse process fusion at the level of L5-6 without internal fixation. We prepared three types of HA with different porosities: HA with 15% porosity (HA15%), HA with 50% porosity (HA50%), and HA with 85% porosity (HA85%), all of which were clinically available <span class="hlt">materials</span>. The HA15% and HA50% had few interconnecting pores, whereas the HA85%, which was a recently developed <span class="hlt">material</span>, had abundant interconnecting pores. All rabbits were randomly divided into the following four groups according to the grafted <span class="hlt">materials</span>: (1) HA15% + autogenous bone, (2) HA50% + autogenous bone, (3) HA85% + autogenous bone, (4) pure autogenous bone graft. The animals were euthanized at 5 weeks after surgery, and post-mortem analyses including biomechanical testing, radiographical and histological evaluations were performed. There was no statistically significant difference in either fusion rate and/or bending stiffness among the three HA groups. However, in histological and radiological analyses, both bone ingrowth rate and direct bone bonding rate in the HA85% group were significantly higher than those in the HA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26257095','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26257095"><span id="translatedtitle">From spent Mg/Al layered double hydroxide to <span class="hlt">porous</span> carbon <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Laipan, Minwang; Zhu, Runliang; Chen, Qingze; Zhu, Jianxi; Xi, Yunfei; Ayoko, Godwin A; He, Hongping</p> <p>2015-12-30</p> <p>Adsorption has been considered as an efficient method for the treatment of dye effluents, but proper disposal of the spent adsorbents is still a challenge. This work attempts to provide a facile method to reutilize the spent Mg/Al layered double hydroxide (Mg/Al-LDH) after the adsorption of orange II (OII). Herein, the spent hybrid was carbonized under the protection of nitrogen, and then washed with acid to obtain <span class="hlt">porous</span> carbon <span class="hlt">materials</span>. Thermogravimetric analysis results suggested that the carbonization could be well achieved above 600°C, as mass loss of the spent hybrid gradually stabilized. Therefore, the carbonization process was carried out at 600, 800, and 1000°C, respectively. Scanning electron microscope showed that the obtained carbon <span class="hlt">materials</span> possessed a crooked flaky morphology. Nitrogen adsorption-desorption results showed that the carbon <span class="hlt">materials</span> had large BET surface area and pore volume, e.g., 1426 m(2)/g and 1.67 cm(3)/g for the sample carbonized at 800°C. Moreover, the pore structure and surface chemistry compositions were tunable, as they were sensitive to the temperature. Toluene adsorption results demonstrated that the carbon <span class="hlt">materials</span> had high efficiency in toluene removal. This work provided a facile approach for synthesizing <span class="hlt">porous</span> carbon <span class="hlt">materials</span> using spent Mg/Al-LDH. PMID:26257095</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DFDD24005S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DFDD24005S"><span id="translatedtitle">Tear film dynamics: <span class="hlt">modeling</span> the glycocalyx as a <span class="hlt">porous</span> medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siddique, Javed; Mastroberardinob, , Antonio; Braun, Richard; Anderson, Daniel</p> <p>2015-11-01</p> <p>The human tear film is a complex fluid structure composed of multiple layers: an aqueous layer that comprises most of the film and an outermost thinner lipid layer coat a forest of large transmembrane mucins at the epithelial surface. The glycocalyx helps provide stability to the ocular surface by assisting the tear film to wet it. It is also permeable to water, but less so to ions. We formulate a thin film <span class="hlt">model</span> based on lubrication theory in order to understand the dynamics between the aqueous layer and the glycocalyx, which we treat as a rigid <span class="hlt">porous</span> medium. We present numerical solutions for the evolution of the tear film and discuss the roles played by the key parameters of the system. This work was supported by the Simons Foundation Grant No. 281839.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/102194','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/102194"><span id="translatedtitle">Multidimensional DDT <span class="hlt">modeling</span> of energetic <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baer, M.R.; Hertel, E.S.; Bell, R.L.</p> <p>1995-07-01</p> <p>To <span class="hlt">model</span> the shock-induced behavior of <span class="hlt">porous</span> or damaged energetic <span class="hlt">materials</span>, a nonequilibrium mixture theory has been developed and incorporated into the shock physics code, CTH. The foundation for this multiphase <span class="hlt">model</span> is based on a continuum mixture formulation given by Baer and Nunziato. This multiphase mixture <span class="hlt">model</span> provides a thermodynamic and mathematically-consistent description of the self-accelerated combustion processes associated with deflagration-to-detonation and delayed detonation behavior which are key <span class="hlt">modeling</span> issues in safety assessment of energetic systems. An operator-splitting method is used in the implementation of this <span class="hlt">model</span>, whereby phase diffusion effects are incorporated using a high resolution transport method. Internal state variables, forming the basis for phase interaction quantities, are resolved during the Lagrangian step requiring the use of a stiff matrix-free solver. Benchmark calculations are presented which simulate low-velocity piston impact on a propellant <span class="hlt">porous</span> bed and experimentally-measured wave features are well replicated with this <span class="hlt">model</span>. This mixture <span class="hlt">model</span> introduces micromechanical <span class="hlt">models</span> for the initiation and growth of reactive multicomponent flow that are key features to describe shock initiation and self-accelerated deflagration-to-detonation combustion behavior. To complement one-dimensional simulation, two-dimensional numerical calculations are presented which indicate wave curvature effects due to the loss of wall confinement. This study is pertinent for safety analysis of weapon systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25350718','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25350718"><span id="translatedtitle">Hierarchical ZnO-Ag-C composite <span class="hlt">porous</span> microspheres with superior electrochemical properties as anode <span class="hlt">materials</span> for lithium ion batteries.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xie, Qingshui; Ma, Yating; Zeng, Deqian; Zhang, Xiaoqiang; Wang, Laisen; Yue, Guanghui; Peng, Dong-Liang</p> <p>2014-11-26</p> <p>Hierarchical ZnO-Ag-C composite <span class="hlt">porous</span> microspheres are successfully synthesized by calcination of the preproduced zinc-silver citrate <span class="hlt">porous</span> microspheres in argon. The carbon derives from the in situ carbonization of carboxylic acid groups in zinc-silver citrate during annealing treatment. The average particle size of ZnO-Ag-C composite <span class="hlt">porous</span> microspheres is approximate 1.5 μm. When adopted as the electrode <span class="hlt">materials</span> in lithium ion batteries, the obtained composite <span class="hlt">porous</span> microspheres display high specific capacity, excellent cyclability, and good rate capability. A discharge capacity as high as 729 mA h g(-1) can be retained after 200 cycles at 100 mA g(-1). The excellent electrochemical properties of ZnO-Ag-C are ascribed to its unique hierarchical <span class="hlt">porous</span> configuration as well as the modification of silver and carbon. PMID:25350718</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.8795D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.8795D"><span id="translatedtitle">New hydrologic <span class="hlt">model</span> of fluid migration in deep <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dmitrievsky, A.; Balanyuk, I.</p> <p>2009-04-01</p> <p>The authors present a new hydrological <span class="hlt">model</span> of mantle processes that effect on formation of oil-and-gas bearing basins, fault tectonics and thermal convection. Any fluid migration is initially induced by lateral stresses in the crust and lithosphere which result from global geodynamic processes related to the mantle convection. The global processes are further transformed into regional movements in weakness zones. <span class="hlt">Model</span> of <span class="hlt">porous</span> media in deep fractured zones and idea of self-oscillation processes in mantle layers and fractured zones of the crust at different depths was used as the basis for developed concept. The content of these notions resides in the fact that there are conditions of dynamic balance in mantle layers originating as a result of combination and alternate actions of compaction and dilatance mechanisms. These mechanisms can be manifested in different combinations and under different conditions as well as can be complemented by other processes influencing on regime of fluid migration. They can act under condition of passive margin, ocean rift and ocean subduction zones as well as in consolidated platform and sheet. Self-oscillation regime, sub vertical direction of fluid flows, anomalously high layer pressure, and high level of anomalies of various geophysical fields are common for them. A certain class of fluid dynamic <span class="hlt">models</span> describing consolidation of sedimentary basins, free oscillation processes slow and quick (at the final stage) fluid dynamic processes of the evolution of a sedimentary basin in subduction zones is considered for the first time. The last <span class="hlt">model</span> of quick fluid dynamic processes reflects the process of formation of hydrocarbon deposits in the zones of collision of lithosphere plates. The results of numerical simulation and diagrams reflecting consecutive stages of the gas-fluid dynamic front propagation are assessed of the Pri-Caspian depression as the example. Calculations with this <span class="hlt">model</span> will simultaneously be carried out for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27381910','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27381910"><span id="translatedtitle">A Simplified <span class="hlt">Model</span> of Moisture Transport in Hydrophilic <span class="hlt">Porous</span> Media With Applications to Pharmaceutical Tablets.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Klinzing, Gerard R; Zavaliangos, Antonios</p> <p>2016-08-01</p> <p>This work establishes a predictive <span class="hlt">model</span> that explicitly recognizes microstructural parameters in the description of the overall mass uptake and local gradients of moisture into tablets. <span class="hlt">Model</span> equations were formulated based on local tablet geometry to describe the transient uptake of moisture. An analytical solution to a simplified set of <span class="hlt">model</span> equations was solved to predict the overall mass uptake and moisture gradients with the tablets. The analytical solution takes into account individual diffusion mechanisms in different scales of porosity and diffusion into the solid phase. The time constant of mass uptake was found to be a function of several key <span class="hlt">material</span> properties, such as tablet relative density, pore tortuosity, and equilibrium moisture content of the <span class="hlt">material</span>. The predictions of the <span class="hlt">model</span> are in excellent agreement with experimental results for microcrystalline cellulose tablets without the need for parameter fitting. The <span class="hlt">model</span> presented provides a new method to analyze the transient uptake of moisture into hydrophilic <span class="hlt">materials</span> with the knowledge of only a few fundamental <span class="hlt">material</span> and microstructural parameters. In addition, the <span class="hlt">model</span> allows for quick and insightful predictions of moisture diffusion for a variety of practical applications including pharmaceutical tablets, <span class="hlt">porous</span> polymer systems, or cementitious <span class="hlt">materials</span>. PMID:27381910</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1684g0005S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1684g0005S"><span id="translatedtitle">Numerical implementation of mathematical <span class="hlt">model</span> of the dynamics of a <span class="hlt">porous</span> medium on supercomputers of cluster architecture</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sadovskaya, O. V.; Sadovskii, V. M.</p> <p>2015-10-01</p> <p>The parallel computational algorithm for analysis of the processes of elastic-plastic deformation of a <span class="hlt">porous</span> medium under the action of external dynamic loads is developed. This algorithm is based on the mathematical <span class="hlt">model</span> taking into account threshold nature of change in the strength of a <span class="hlt">material</span> under the collapse of pores. The algorithm is implemented in Fortran by means of functions of the MPI library. The parallel program system has been tested on clusters in computations of the propagation of plane longitudinal shock waves of the compression and in computations of the expansion of a cylindrical cavity in an infinite <span class="hlt">porous</span> medium. The comparison of numerical results and exact solutions has shown their good qualitative and quantitative correspondence. Using the obtained algorithm, the process of propagation of elastic-plastic waves of the compression in a homogenous <span class="hlt">porous</span> medium, accompanied by the deformation of a skeleton and the collapse of pores, is analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/751012','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/751012"><span id="translatedtitle">Ignition analysis of a <span class="hlt">porous</span> energetic <span class="hlt">material</span>. 2. Ignition at a closed heated end</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Alexander M. Telegentor; Stephen B. Margolis; Forman A. Williams</p> <p>1998-11-01</p> <p>A continuation of an ignition analysis for <span class="hlt">porous</span> energetic <span class="hlt">materials</span> subjected to a constant energy flux is presented. In the first part, the analysis was developed for the case of an open-end, semi-infinite <span class="hlt">material</span> such that gas flow, generated by thermal expansion, flowed out of the <span class="hlt">porous</span> solid, thereby removing energy from the system. In the present study, the case of a closed end is considered, and thus the thermally-induced gas flow is now directed into the solid. In these studies, an asymptotic perturbation analysis, based on the smallness of the gas-to-solid density ratio and the largeness of the activation energy, is utilized to describe the inert and transition stages leading to thermal runaway. In both cases it is found that the effects of porosity provide a leading-order reduction in the time to ignition relative to that for the nonporous problem, arising from the reduced amount of solid <span class="hlt">material</span> that must be heated and the difference in thermal conductivities of the solid and gaseous phases. A correction to the leading-order ignition-delay time, however, is provided by the convective flow of gas through the solid, and the sign of this correction is shown to depend on the direction of the gas flow. Thus, gas flowing out of an open-end solid was previously shown to give a positive correction to the leading-order time to ignition. Here, however, it is demonstrated that when the flow of gas is directed into the <span class="hlt">porous</span> solid, the relative transport effects associated with the gas flow serve to preheat the <span class="hlt">material</span>, resulting in a negative correction and hence a decrease in the ignition-delay time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4730847','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4730847"><span id="translatedtitle">Bioinspired large-scale aligned <span class="hlt">porous</span> <span class="hlt">materials</span> assembled with dual temperature gradients</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bai, Hao; Chen, Yuan; Delattre, Benjamin; Tomsia, Antoni P.; Ritchie, Robert O.</p> <p>2015-01-01</p> <p>Natural <span class="hlt">materials</span>, such as bone, teeth, shells, and wood, exhibit outstanding properties despite being <span class="hlt">porous</span> and made of weak constituents. Frequently, they represent a source of inspiration to design strong, tough, and lightweight <span class="hlt">materials</span>. Although many techniques have been introduced to create such structures, a long-range order of the porosity as well as a precise control of the final architecture remain difficult to achieve. These limitations severely hinder the scale-up fabrication of layered structures aimed for larger applications. We report on a bidirectional freezing technique to successfully assemble ceramic particles into scaffolds with large-scale aligned, lamellar, <span class="hlt">porous</span>, nacre-like structure and long-range order at the centimeter scale. This is achieved by modifying the cold finger with a polydimethylsiloxane (PDMS) wedge to control the nucleation and growth of ice crystals under dual temperature gradients. Our approach could provide an effective way of manufacturing novel bioinspired structural <span class="hlt">materials</span>, in particular advanced <span class="hlt">materials</span> such as composites, where a higher level of control over the structure is required. PMID:26824062</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24601731','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24601731"><span id="translatedtitle"><span class="hlt">Porous</span> TiO₂ <span class="hlt">materials</span> through Pickering high-internal phase emulsion templating.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Xiaodong; Sun, Guanqing; Li, Yecheng; Yu, Jimmy C; Wu, Jie; Ma, Guang-Hui; Ngai, To</p> <p>2014-03-18</p> <p>We report a facile method for preparing <span class="hlt">porous</span> structured TiO2 <span class="hlt">materials</span> by templating from Pickering high-internal phase emulsions (HIPEs). A Pickering HIPE with an internal phase of up to 80 vol %, stabilized by poly(N-isopropylacrylamide)-based microgels and TiO2 solid nanoparticles, was first formulated and employed as a template to prepare the <span class="hlt">porous</span> TiO2 <span class="hlt">materials</span> with an interconnected structure. The resultant <span class="hlt">materials</span> were characterized by scanning electron microscopy, X-ray diffraction, and mercury intrusion. Our results showed that the parent emulsion droplets promoted the formation of macropores and interconnecting throats with sizes of ~50 and ~10 μm, respectively, while the interfacially adsorbed microgel stabilizers drove the formation of smaller pores (~100 nm) throughout the macroporous walls after drying and sintering. The interconnected structured network with the bimodal pores could be well preserved after calcinations at 800 °C. In addition, the photocatalytic activity of the fabricated TiO2 was evaluated by measuring the photodegradation of Rhodamine B in water. Our results revealed that the fabricated TiO2 <span class="hlt">materials</span> are good photocatalysts, showing enhanced activity and stability in photodegrading organic molecules. PMID:24601731</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18481790','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18481790"><span id="translatedtitle">A novel nano-<span class="hlt">porous</span> alumina biomaterial with potential for loading with bioactive <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Walpole, Andrew R; Xia, Zhidao; Wilson, Crispian W; Triffitt, James T; Wilshaw, Peter R</p> <p>2009-07-01</p> <p>Nano-<span class="hlt">porous</span> alumina, with the potential for being loaded with bioactive <span class="hlt">materials</span>, has been proposed as a novel <span class="hlt">material</span> for coating implants. In this study, the shear strength of the interface between such nano-<span class="hlt">porous</span> anodic aluminium oxide (AAO) coatings and titanium substrates, their biocompatibility, and their potential for pore loading have been investigated. An interface shear strength in excess of 29 MPa was obtained which is comparable with that of conventional plasma sprayed hydroxyapatite implant coatings. The viability and differentiation of MG63 osteoblastic cells co-cultured on the coating was found to be broadly comparable to that of similar cells co-cultured on conventional bioinert implant <span class="hlt">materials</span> such as titanium and fully dense alumina. Extensive pore loading with silica nano-particles of different sizes and in different combinations was demonstrated throughout the thickness of AAO layers 1 microm and 60 microm thick. This work has demonstrated, that with suitable choice of pore filling <span class="hlt">materials</span>, this novel coating might simultaneously combat infection, encourage bone regeneration, and secure fixation of the implant to bone. PMID:18481790</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22420594','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22420594"><span id="translatedtitle">Infiltrating sulfur into a highly <span class="hlt">porous</span> carbon sphere as cathode <span class="hlt">material</span> for lithium–sulfur batteries</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhao, Xiaohui; Kim, Dul-Sun; Ahn, Hyo-Jun; Kim, Ki-Won; Cho, Kwon-Koo; Ahn, Jou-Hyeon</p> <p>2014-10-15</p> <p>Highlights: • A highly <span class="hlt">porous</span> carbon (HPC) with regular spherical morphology was synthesized. • Sulfur/HPC composites were prepared by melt–diffusion method. • Sulfur/HPC composites showed improved cyclablity and long-term cycle life. - Abstract: Sulfur composite <span class="hlt">material</span> with a highly <span class="hlt">porous</span> carbon sphere as the conducting container was prepared. The highly <span class="hlt">porous</span> carbon sphere was easily synthesized with resorcinol–formaldehyde precursor as the carbon source. The morphology of the carbon was observed with field emission scanning electron microscope and transmission electron microscope, which showed a well-defined spherical shape. Brunauer–Emmett–Teller analysis indicated that it possesses a high specific surface area of 1563 m{sup 2} g{sup −1} and a total pore volume of 2.66 cm{sup 3} g{sup −1} with a bimodal pore size distribution, which allow high sulfur loading and easy transportation of lithium ions. Sulfur carbon composites with varied sulfur contents were prepared by melt–diffusion method and lithium sulfur cells with the sulfur composites showed improved cyclablity and long-term cycle life.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27513218','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27513218"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">Materials</span> with Tunable Structure and Mechanical Properties via Templated Layer-by-Layer Assembly.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ziminska, Monika; Dunne, Nicholas; Hamilton, Andrew R</p> <p>2016-08-31</p> <p>The deposition of stiff and strong coatings onto <span class="hlt">porous</span> templates offers a novel strategy for fabricating macroscale <span class="hlt">materials</span> with controlled architectures at the micro- and nanoscale. Here, layer-by-layer assembly is utilized to fabricate nanocomposite-coated foams with highly customizable properties by depositing polymer-nanoclay coatings onto open-cell foam templates. The compressive mechanical behavior of these <span class="hlt">materials</span> evolves in a predictable manner that is qualitatively captured by scaling laws for the mechanical properties of cellular <span class="hlt">materials</span>. The observed and predicted properties span a remarkable range of density-stiffness space, extending from regions of very soft elastomer foams to very stiff, lightweight honeycomb and lattice <span class="hlt">materials</span>. PMID:27513218</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016Nanos...813507H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016Nanos...813507H&link_type=ABSTRACT"><span id="translatedtitle">Strengthening of polymer ordered <span class="hlt">porous</span> <span class="hlt">materials</span> based on a layered nanocomposite internal structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heng, Liping; Guo, Xieyou; Guo, Tianqi; Wang, Bin; Jiang, Lei</p> <p>2016-07-01</p> <p>Ordered <span class="hlt">porous</span> polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered <span class="hlt">porous</span> polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on.Ordered <span class="hlt">porous</span> polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered <span class="hlt">porous</span> polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on. Electronic supplementary information (ESI) available: SEM image of hexagonal silicon pillar templates, AFM images of clay platelets on a silicon substrate, photographs of free-standing gels, X-ray diffraction profiles for dried <span class="hlt">materials</span>, FTIR and TGA of the samples, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JEPT...87.1362O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JEPT...87.1362O"><span id="translatedtitle">Regular Heat Regime of Heating of Moist Capillary-<span class="hlt">Porous</span> <span class="hlt">Materials</span> in the Process of Their Drying</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ol'shanskii, A. I.</p> <p>2014-11-01</p> <p>Results of investigation of the drying of plane samples of different capillary-<span class="hlt">porous</span> <span class="hlt">materials</span> by the method of regular heat regime are presented. Experimental empirical dependences defining the kinetics of drying of these <span class="hlt">materials</span> have been obtained. The dependences of the rate of heating of a moist capillary-<span class="hlt">porous</span> <span class="hlt">material</span> and the rate of decrease in the moisture content in it on different factors determining the drying process were investigated. The influence of these factors on the rate of heating of such a <span class="hlt">material</span> and the rate of removal of moisture from it were determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994uamd.rept.....M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994uamd.rept.....M"><span id="translatedtitle">The use of acoustic methods to determine the parameters of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Malecki, Ignacy; Ranachowski, Jerzy</p> <p></p> <p><span class="hlt">Porous</span> media are a subject of research in a variety of scientific disciplines, including physics, mechanics, electrical engineering, <span class="hlt">materials</span> science, and acoustics. The subject of this article is a comparison of the methods used in theoretical mechanics with standard acoustic methods. The authors start by examining the method of static averaging of the mechanical properties of <span class="hlt">porous</span> media. This method makes it possible to determine substitute static moduli of elasticity, which, however, does not meet the needs of acoustics. More suitable methods include the dynamic methods developed in the works of J. Lewandowski, among others. These methods are based on a motion equation in which the tensor of elasticity is assigned a complex value which accounts for the medium's dynamic properties and losses. The transition from a complex tensor of elasticity to the velocity and damping of an acoustic wave poses no particular problems. On the backdrop of the theory of <span class="hlt">porous</span> <span class="hlt">materials</span> used in mechanics, the authors present their own theory for the acoustic properties of these <span class="hlt">materials</span>. They call it the theory of 'compound obstacles', which initially examines the interference offered by a solitary inclusion in a homogeneous medium to the propagation of an acoustic wave. This is followed by the calculation of the interference caused by a group of inclusions using the concept of the density of obstacles. In turn, this leads to general formulas for acoustic wave velocity and damping as functions of obstacle density. The authors consider examples of a spherical inclusion in a liquid and a hollow spheroidal inclusion in a solid. The article also contains the results of experiments conducted to verify the 'compound obstacles' theory. The authors measured the velocity of an ultrasound wave in electrical engineering porcelain with varying degrees of porosity and in glycerine in which glass balls were suspended.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11601726','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11601726"><span id="translatedtitle">A linear viscoelastic biphasic <span class="hlt">model</span> for soft tissues based on the Theory of <span class="hlt">Porous</span> Media.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ehlers, W; Markert, B</p> <p>2001-10-01</p> <p>Based on the Theory of <span class="hlt">Porous</span> Media (mixture theories extended by the concept of volume fractions), a <span class="hlt">model</span> describing the mechanical behavior of hydrated soft tissues such as articular cartilage is presented. As usual, the tissue will be <span class="hlt">modeled</span> as a <span class="hlt">materially</span> incompressible binary medium of one linear viscoelastic <span class="hlt">porous</span> solid skeleton saturated by a single viscous pore-fluid. The contribution of this paper is to combine a descriptive representation of the linear viscoelasticity law for the organic solid matrix with an efficient numerical treatment of the strongly coupled solid-fluid problem. Furthermore, deformation-dependent permeability effects are considered. Within the finite element method (FEM), the weak forms of the governing <span class="hlt">model</span> equations are set up in a system of differential algebraic equations (DAE) in time. Thus, appropriate embedded error-controlled time integration methods can be applied that allow for a reliable and efficient numerical treatment of complex initial boundary-value problems. The applicability and the efficiency of the presented <span class="hlt">model</span> are demonstrated within canonical, numerical examples, which reveal the influence of the intrinsic dissipation on the general behavior of hydrated soft tissues, exemplarily on articular cartilage. PMID:11601726</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JHyd..486..246J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JHyd..486..246J"><span id="translatedtitle">A novel architecture for pore network <span class="hlt">modelling</span> with applications to permeability of <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jivkov, Andrey P.; Hollis, Cathy; Etiese, Friday; McDonald, Samuel A.; Withers, Philip J.</p> <p>2013-04-01</p> <p>SummaryNetwork <span class="hlt">models</span> of <span class="hlt">porous</span> media are beneficial for predicting the evolution of macroscopic mass transport properties. This work proposes a novel bi-regular network <span class="hlt">model</span> based on truncated octahedral support. With the <span class="hlt">model</span>, pore systems with different pore coordination spectra for a given average coordination number can be constructed to match experimental data. This feature and the maximum allowed pore coordination of 14 make the proposed <span class="hlt">model</span> more realistic and flexible than the existing <span class="hlt">models</span> based on cubic supports. Limestone is used as a study <span class="hlt">material</span> to illustrate the <span class="hlt">model</span> performance. Experimental pore space data for this <span class="hlt">material</span> obtained by X-ray tomography (CT) are used for constructing microstructure-informed <span class="hlt">model</span> realisations. It is demonstrated that with these realisations the experimentally measured permeability of the <span class="hlt">material</span> can be predicted. The <span class="hlt">model</span> is further used to assess the effects of pore connectivity and porosity on the permeability. It is shown that the effect of pore connectivity is substantially stronger than the effect of porosity. A strategy for calculating the evolution of permeability with damage-related pore space changes is also described. The results reveal the effects of the mechanical properties of the medium on the permeability evolution as a function of damage evolution. Developments of this strategy are suggested for deriving mechanism-based constitutive laws for engineering applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010010295','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010010295"><span id="translatedtitle">Cryogenic <span class="hlt">Model</span> <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kimmel, W. M.; Kuhn, N. S.; Berry, R. F.; Newman, J. A.</p> <p>2001-01-01</p> <p>An overview and status of current activities seeking alternatives to 200 grade 18Ni Steel CVM alloy for cryogenic wind tunnel <span class="hlt">models</span> is presented. Specific improvements in <span class="hlt">material</span> selection have been researched including availability, strength, fracture toughness and potential for use in transonic wind tunnel testing. Potential benefits from utilizing damage tolerant life-prediction methods, recently developed fatigue crack growth codes and upgraded NDE methods are also investigated. Two candidate alloys are identified and accepted for cryogenic/transonic wind tunnel <span class="hlt">models</span> and hardware.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ZaMP...65..377A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ZaMP...65..377A"><span id="translatedtitle">Solvability of a quasi-steady rolling problem for <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Angelov, T. A.</p> <p>2014-04-01</p> <p>A quasi-steady rolling problem with nonlocal friction, for <span class="hlt">porous</span> rigid-plastic, strain-rate-sensitive and strain hardening <span class="hlt">materials</span>, is considered. A variational formulation is derived, consisting of a variational inequality and two evolution equations, coupling the velocity, strain hardening and relative density variables. The convergence of a variable stiffness parameters method is proved, and existence and uniqueness results are obtained. An algorithm, combining this method with the finite element method, is proposed and used for solving an illustrative rolling problem.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ZaMP..tmp...50A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ZaMP..tmp...50A"><span id="translatedtitle">Solvability of a quasi-steady rolling problem for <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Angelov, T. A.</p> <p>2013-05-01</p> <p>A quasi-steady rolling problem with nonlocal friction, for <span class="hlt">porous</span> rigid-plastic, strain-rate-sensitive and strain hardening <span class="hlt">materials</span>, is considered. A variational formulation is derived, consisting of a variational inequality and two evolution equations, coupling the velocity, strain hardening and relative density variables. The convergence of a variable stiffness parameters method is proved, and existence and uniqueness results are obtained. An algorithm, combining this method with the finite element method, is proposed and used for solving an illustrative rolling problem.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25314657','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25314657"><span id="translatedtitle">Cost-effective synthesis of amine-tethered <span class="hlt">porous</span> <span class="hlt">materials</span> for carbon capture.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lu, Weigang; Bosch, Mathieu; Yuan, Daqiang; Zhou, Hong-Cai</p> <p>2015-02-01</p> <p>A truly cost-effective strategy for the synthesis of amine-tethered <span class="hlt">porous</span> polymer networks (PPNs) has been developed. A network containing diethylenetriamine (PPN-125-DETA) exhibits a high working capacity comparable to current state-of-art technology (30 % monoethanolamine solutions), yet it requires only one third as much energy for regeneration. It has also been demonstrated to retain over 90 % capacity after 50 adsorption-desorption cycles of CO2 in a temperature-swing adsorption process. The results suggest that PPN-125-DETA is a very promising new <span class="hlt">material</span> for carbon capture from flue gas streams. PMID:25314657</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B13A0450J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B13A0450J"><span id="translatedtitle">Rock Physics <span class="hlt">Models</span> of Biofilm Growth in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaiswal, P.; alhadhrami, F. M.; Atekwana, E. A.</p> <p>2013-12-01</p> <p>Recent studies suggest the potential to use acoustic techniques to image biofilm growth in <span class="hlt">porous</span> media. Nonetheless the interpretation of the seismic response to biofilm growth and development remains speculative because of the lack of quantitative petrophysical <span class="hlt">models</span> that can relate changes in biofilm saturation to changes in seismic attributes. Here, we report our efforts in developing quantitative rock physics <span class="hlt">models</span> to biofilm saturation with increasing and decreasing P-wave velocity (VP) and amplitudes recorded in the Davis et al. [2010] physical scale experiment. We adapted rock physics <span class="hlt">models</span> developed for <span class="hlt">modeling</span> gas hydrates in unconsolidated sediments. Two distinct growth <span class="hlt">models</span>, which appear to be a function of pore throat size, are needed to explain the experimental data. First, introduction of biofilm as an additional mineral grain in the sediment matrix (load-bearing mode) is needed to explain the increasing time-lapse VP. Second, introduction of biofilm as part of the pore fluid (pore-filling mode) is required to explain the decreasing time-lapse VP. To explain the time-lapse VP, up to 15% of the pore volume was required to be saturated with biofilm. The recorded seismic amplitudes, which can be expressed as a function of porosity, permeability and grain size, showed a monotonic time-lapse decay except on Day 3 at a few selected locations, where it increased. Since porosity changes are constrained by VP, amplitude increase could be <span class="hlt">modeled</span> by increasing hydraulic conductivity. Time lapse VP at locations with increasing amplitudes suggest that these locations have a load-bearing growth style. We conclude that permeability can increase by up to 10% at low (~2%) biofilm saturation in load-bearing growth style due to the development of channels within the biofilm structure. Developing a rock physics <span class="hlt">model</span> for the biofilm growth in general may help create a field guide for interpreting porosity and permeability changes in bioremediation, MEOR and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1082201','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1082201"><span id="translatedtitle">High-throughput Characterization of <span class="hlt">Porous</span> <span class="hlt">Materials</span> Using Graphics Processing Units</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kim, Jihan; Martin, Richard L.; Ruebel, Oliver; Haranczyk, Maciej; Smit, Berend</p> <p>2012-03-19</p> <p>We have developed a high-throughput graphics processing units (GPU) code that can characterize a large database of crystalline <span class="hlt">porous</span> <span class="hlt">materials</span>. In our algorithm, the GPU is utilized to accelerate energy grid calculations where the grid values represent interactions (i.e., Lennard-Jones + Coulomb potentials) between gas molecules (i.e., CH$_{4}$ and CO$_{2}$) and <span class="hlt">material</span>'s framework atoms. Using a parallel flood fill CPU algorithm, inaccessible regions inside the framework structures are identified and blocked based on their energy profiles. Finally, we compute the Henry coefficients and heats of adsorption through statistical Widom insertion Monte Carlo moves in the domain restricted to the accessible space. The code offers significant speedup over a single core CPU code and allows us to characterize a set of <span class="hlt">porous</span> <span class="hlt">materials</span> at least an order of magnitude larger than ones considered in earlier studies. For structures selected from such a prescreening algorithm, full adsorption isotherms can be calculated by conducting multiple grand canonical Monte Carlo simulations concurrently within the GPU.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJMPB..2950015W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJMPB..2950015W"><span id="translatedtitle">Simulations on the gelling process of particle suspension systems for in-situ preparing <span class="hlt">porous</span> <span class="hlt">materials</span> in a capillary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, J.; Xu, J. J.; Yang, Y.; Wang, X. J.; Luo, X.; Zhang, L.; Jiang, G.</p> <p>2015-10-01</p> <p>The gelling process of particle suspension in a capillary which is crucial for in-situ preparing small size foam products has been simulated with an off-lattice diffusion limited cluster aggregation (DLCA) <span class="hlt">model</span> by the three-dimensional Monte Carlo simulations. The effects of the <span class="hlt">model</span> parameters, such as the interaction between capillary wall and particles, particle volume fraction, capillary size etc. on the density distribution of the system have been fully explored. And the aggregation kinetics process over a broad range of volume fractions and interactions have also been discussed. The results show that the geometric constraint of capillary can be analogous to a weak repulsive interaction between capillary wall and particles. And we found that as the capillary size or particle volume fraction increase, particle concentration distribution will be more uniform with other parameters constant. <span class="hlt">Porous</span> network with relatively uniform density distribution can be also obtained through controlling the interaction between capillary wall and particles. In addition, by analyzing the aggregation kinetics process, we found that the attraction of capillary wall dramatically reduces the probability of gelation in the small-scale capillary. The obtained results will be of great importance in controlling the density distribution of <span class="hlt">porous</span> <span class="hlt">materials</span> prepared by in-situ methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3530947','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3530947"><span id="translatedtitle">Fibrin-Loaded <span class="hlt">Porous</span> Poly(Ethylene Glycol) Hydrogels as Scaffold <span class="hlt">Materials</span> for Vascularized Tissue Formation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jiang, Bin; Waller, Thomas M.; Larson, Jeffery C.; Appel, Alyssa A.</p> <p>2013-01-01</p> <p>Vascular network formation within biomaterial scaffolds is essential for the generation of properly functioning engineered tissues. In this study, a method is described for generating composite hydrogels in which <span class="hlt">porous</span> poly(ethylene glycol) (PEG) hydrogels serve as scaffolds for mechanical and structural support, and fibrin is loaded within the pores to induce vascularized tissue formation. <span class="hlt">Porous</span> PEG hydrogels were generated by a salt leaching technique with 100–150-μm pore size and thrombin (Tb) preloaded within the scaffold. Fibrinogen (Fg) was loaded into pores with varying concentrations and polymerized into fibrin due to the presence of Tb, with loading efficiencies ranging from 79.9% to 82.4%. Fibrin was distributed throughout the entire <span class="hlt">porous</span> hydrogels, lasted for greater than 20 days, and increased hydrogel mechanical stiffness. A rodent subcutaneous implant <span class="hlt">model</span> was used to evaluate the influence of fibrin loading on in vivo response. At weeks 1, 2, and 3, all hydrogels had significant tissue invasion, but no difference in the depth of invasion was found with the Fg concentration. Hydrogels with fibrin loading induced more vascularization, with a significantly higher vascular density at 20 mg/mL (week 1) and 40 mg/mL (weeks 2 and 3) Fg concentration compared to hydrogels without fibrin. In conclusion, we have developed a composite hydrogel that supports rapid vascularized tissue ingrowth, and thus holds great potential for tissue engineering applications. PMID:23003671</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1112021Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1112021Y"><span id="translatedtitle"><span class="hlt">Modelling</span> of reactive fluid transport in deformable <span class="hlt">porous</span> rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yarushina, V. M.; Podladchikov, Y. Y.</p> <p>2009-04-01</p> <p>One outstanding challenge in geology today is the formulation of an understanding of the interaction between rocks and fluids. Advances in such knowledge are important for a broad range of geologic settings including partial melting and subsequent migration and emplacement of a melt into upper levels of the crust, or fluid flow during regional metamorphism and metasomatism. Rock-fluid interaction involves heat and mass transfer, deformation, hydrodynamic flow, and chemical reactions, thereby necessitating its consideration as a complex process coupling several simultaneous mechanisms. Deformation, chemical reactions, and fluid flow are coupled processes. Each affects the others. Special effort is required for accurate <span class="hlt">modelling</span> of the porosity field through time. Mechanical compaction of <span class="hlt">porous</span> rocks is usually treated under isothermal or isoentropic simplifying assumptions. However, joint consideration of both mechanical compaction and reactive porosity alteration requires somewhat greater than usual care about thermodynamic consistency. Here we consider the <span class="hlt">modelling</span> of multi-component, multi-phase systems, which is fundamental to the study of fluid-rock interaction. Based on the conservation laws for mass, momentum, and energy in the form adopted in the theory of mixtures, we derive a thermodynamically admissible closed system of equations describing the coupling of heat and mass transfer, chemical reactions, and fluid flow in a deformable solid matrix. Geological environments where reactive transport is important are located at different depths and accordingly have different rheologies. In the near surface, elastic or elastoplastic properties would dominate, whereas viscoplasticity would have a profound effect deeper in the lithosphere. Poorly understood rheologies of heterogeneous <span class="hlt">porous</span> rocks are derived from well understood processes (i.e., elasticity, viscosity, plastic flow, fracturing, and their combinations) on the microscale by considering a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CompM..54.1129B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CompM..54.1129B"><span id="translatedtitle">Multi-physics computational grains (MPCGs) for direct numerical simulation (DNS) of piezoelectric composite/<span class="hlt">porous</span> <span class="hlt">materials</span> and structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bishay, Peter L.; Dong, Leiting; Atluri, Satya N.</p> <p>2014-11-01</p> <p>Conceptually simple and computationally most efficient polygonal computational grains with voids/inclusions are proposed for the direct numerical simulation of the micromechanics of piezoelectric composite/<span class="hlt">porous</span> <span class="hlt">materials</span> with non-symmetrical arrangement of voids/inclusions. These are named "Multi-Physics Computational Grains" (MPCGs) because each "mathematical grain" is geometrically similar to the irregular shapes of the physical grains of the <span class="hlt">material</span> in the micro-scale. So each MPCG element represents a grain of the matrix of the composite and can include a pore or an inclusion. MPCG is based on assuming independent displacements and electric-potentials in each cell. The trial solutions in each MPCG do not need to satisfy the governing differential equations, however, they are still complete, and can efficiently <span class="hlt">model</span> concentration of electric and mechanical fields. MPCG can be used to <span class="hlt">model</span> any generally anisotropic <span class="hlt">material</span> as well as nonlinear problems. The essential idea can also be easily applied to accurately solve other multi-physical problems, such as complex thermal-electro-magnetic-mechanical <span class="hlt">materials</span> <span class="hlt">modeling</span>. Several examples are presented to show the capabilities of the proposed MPCGs and their accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012EGUGA..1413856D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012EGUGA..1413856D&link_type=ABSTRACT"><span id="translatedtitle">Optimization and Use of 3D sintered <span class="hlt">porous</span> <span class="hlt">material</span> in medical field for mixing fibrin glue.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delmotte, Y.; Laroumanie, H.; Brossard, G.</p> <p>2012-04-01</p> <p>In medical field, Mixing of two or more chemical components (liquids and/or gases) is extremely important as improper mixing can affect the physico-chemical properties of the final product. At Baxter Healthcare Corporation, we are using a sintered <span class="hlt">porous</span> <span class="hlt">material</span> (PM) as a micro-mixer in medical device for mixing Fibrinogen and Thrombin in order to obtain a homogeneous polymerized Fibrin glue clot used in surgery. First trials were carried out with an interconnected PM from Porvair® (made of PE - porosity: 40% - permeability: 18Darcy). The injection rate is very low, usually about 10mL/min (Re number about 50) which keeps fluids in a laminar flow. Such a low flow rate does not favour mixing of fluids having gradient of viscosity if a mixer is not used. Promising results that were obtained lead the team to understand this ability to mix fluids which will be presented in the poster. Topology of <span class="hlt">porous</span> media (PM) which associates a solid phase with interconnected (or not) <span class="hlt">porous</span> structure is known and used in many commodity products. Researches on PM usually focus on flows inside this structure. By opposition to transport and filtration capacity, as well as mechanic and thermic properties, mixing is rarely associated with PM. However over the past few years, we shown that some type of PM have a real capacity to mix certain fluids. Poster will also describe the problematic of mixing complex biological fluids as fibrinogen and Thrombin. They indeed present a large viscosity difference (ratio about 120) limiting the diffusion and the interaction between the two solutions. As those products are expensive, we used Water (1cPo) and Glycerol 87% (120cPo) which are matching the viscosities of Thrombin and Fibrinogen. A parametric investigation of the "<span class="hlt">porous</span> micro-mixer" as well as a scale up investigation was carried out to examine the influence of both diffusion and advection to successful mix fluids of different viscosity. Experiments were implemented with Planar Laser</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1015419','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1015419"><span id="translatedtitle">Methods of using structures including catalytic <span class="hlt">materials</span> disposed within <span class="hlt">porous</span> zeolite <span class="hlt">materials</span> to synthesize hydrocarbons</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Rollins, Harry W.; Petkovic, Lucia M.; Ginosar, Daniel M.</p> <p>2011-02-01</p> <p>Catalytic structures include a catalytic <span class="hlt">material</span> disposed within a zeolite <span class="hlt">material</span>. The catalytic <span class="hlt">material</span> may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite <span class="hlt">material</span> may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic <span class="hlt">material</span> may include copper and zinc oxide. The zeolite <span class="hlt">material</span> may include a first plurality of pores substantially defined by a crystal structure of the zeolite <span class="hlt">material</span> and a second plurality of pores dispersed throughout the zeolite <span class="hlt">material</span>. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite <span class="hlt">material</span> at least partially around a template structure, removing the template structure, and introducing a catalytic <span class="hlt">material</span> into the zeolite <span class="hlt">material</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3896057','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3896057"><span id="translatedtitle">Multiscale <span class="hlt">modelling</span> of hydraulic conductivity in vuggy <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Daly, K. R.; Roose, T.</p> <p>2014-01-01</p> <p>Flow in both saturated and non-saturated vuggy <span class="hlt">porous</span> media, i.e. soil, is inherently multiscale. The complex microporous structure of the soil aggregates and the wider vugs provides a multitude of flow pathways and has received significant attention from the X-ray computed tomography (CT) community with a constant drive to image at higher resolution. Using multiscale homogenization, we derive averaged equations to study the effects of the microscale structure on the macroscopic flow. The averaged <span class="hlt">model</span> captures the underlying geometry through a series of cell problems and is verified through direct comparison to numerical simulations of the full structure. These methods offer significant reductions in computation time and allow us to perform three-dimensional calculations with complex geometries on a desktop PC. The results show that the surface roughness of the aggregate has a significantly greater effect on the flow than the microstructure within the aggregate. Hence, this is the region in which the resolution of X-ray CT for image-based <span class="hlt">modelling</span> has the greatest impact. PMID:24511248</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015WRR....51.8182H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015WRR....51.8182H"><span id="translatedtitle"><span class="hlt">Modeling</span> NAPL dissolution from pendular rings in idealized <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Junqi; Christ, John A.; Goltz, Mark N.; Demond, Avery H.</p> <p>2015-10-01</p> <p>The dissolution rate of nonaqueous phase liquid (NAPL) often governs the remediation time frame at subsurface hazardous waste sites. Most formulations for estimating this rate are empirical and assume that the NAPL is the nonwetting fluid. However, field evidence suggests that some waste sites might be organic wet. Thus, formulations that assume the NAPL is nonwetting may be inappropriate for estimating the rates of NAPL dissolution. An exact solution to the Young-Laplace equation, assuming NAPL resides as pendular rings around the contact points of <span class="hlt">porous</span> media idealized as spherical particles in a hexagonal close packing arrangement, is presented in this work to provide a theoretical prediction for NAPL-water interfacial area. This analytic expression for interfacial area is then coupled with an exact solution to the advection-diffusion equation in a capillary tube assuming Hagen-Poiseuille flow to provide a theoretical means of calculating the mass transfer rate coefficient for dissolution at the NAPL-water interface in an organic-wet system. A comparison of the predictions from this theoretical <span class="hlt">model</span> with predictions from empirically derived formulations from the literature for water-wet systems showed a consistent range of values for the mass transfer rate coefficient, despite the significant differences in <span class="hlt">model</span> foundations (water wetting versus NAPL wetting, theoretical versus empirical). This finding implies that, under these system conditions, the important parameter is interfacial area, with a lesser role played by NAPL configuration.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24483554','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24483554"><span id="translatedtitle">Fractal continuum <span class="hlt">model</span> for tracer transport in a <span class="hlt">porous</span> medium.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Herrera-Hernández, E C; Coronado, M; Hernández-Coronado, H</p> <p>2013-12-01</p> <p>A <span class="hlt">model</span> based on the fractal continuum approach is proposed to describe tracer transport in fractal <span class="hlt">porous</span> media. The original approach has been extended to treat tracer transport and to include systems with radial and uniform flow, which are cases of interest in geoscience. The <span class="hlt">models</span> involve advection due to the fluid motion in the fractal continuum and dispersion whose mathematical expression is taken from percolation theory. The resulting advective-dispersive equations are numerically solved for continuous and for pulse tracer injection. The tracer profile and the tracer breakthrough curve are evaluated and analyzed in terms of the fractal parameters. It has been found in this work that anomalous transport frequently appears, and a condition on the fractal parameter values to predict when sub- or superdiffusion might be expected has been obtained. The fingerprints of fractality on the tracer breakthrough curve in the explored parameter window consist of an early tracer breakthrough and long tail curves for the spherical and uniform flow cases, and symmetric short tailed curves for the radial flow case. PMID:24483554</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060041352&hterms=sodium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsodium','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060041352&hterms=sodium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsodium"><span id="translatedtitle">A Quantitative <span class="hlt">Model</span> for the Exchange Current of <span class="hlt">Porous</span> Molybdenum Electrodes on Sodium Beta-Alumina in Sodium Vapor</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Williams, R. M.; Ryan, M. A.; LeDuc, H.; Cortez, R. H.; Saipetch, C.; Shields, V.; Manatt, K.; Homer, M. L.</p> <p>1998-01-01</p> <p>This paper presents a <span class="hlt">model</span> of the exchange current developed for <span class="hlt">porous</span> molybdenum electrodes on sodium beta-alumina ceramics in low pressure sodium vapor, but which has general applicability to gas/<span class="hlt">porous</span> metal electrodes on solid electrolytes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT.........3V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.........3V"><span id="translatedtitle">Mechanical behavior of concrete and related <span class="hlt">porous</span> <span class="hlt">materials</span> under partial saturation: The effective stress and the viscous softening due to movement of nanometer-scale pore fluid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vlahinic, Ivan</p> <p></p> <p>It has been said that <span class="hlt">porous</span> <span class="hlt">materials</span> are like music: the gaps are as important as the filled-in bits. In other words, in addition to the solid structure, pore characteristics such as size and morphology play a crucial role in defining the overall physical properties of the <span class="hlt">porous</span> <span class="hlt">materials</span>. This work goes a step further and examines the behaviors of some <span class="hlt">porous</span> media that arise when the pore network is occupied by two fluids, principally air and water, as a result of drying or wetting. Such a state gives rise to fluid capillarity which can generate significant negative fluid pressures. In the first part, a constitutive <span class="hlt">model</span> for drying of an elastic <span class="hlt">porous</span> medium is proposed and then extended to derive a novel expression for effective stress in partially saturated media. The <span class="hlt">model</span> is motivated by the fact that in a system that is saturated by two different fluids, two different pressure inherently act on the surfaces of the pore network. This causes a non-uniform strain field in the solid structure, something that is not explicitly accounted for in the classic formulations of this problem. We use some standard micromechanical homogenization techniques to estimate the extent of the 'non-uniformity' and on this basis, evaluate the validity of the classic Bishop effective stress expression for partially saturated <span class="hlt">materials</span>. In the second part, we examine a diverse class of <span class="hlt">porous</span> <span class="hlt">materials</span> which behave in an unexpected (and even counterintuitive) way under the internal moisture fluctuations. In particular, during wetting and drying alike, the solid viscosity of these <span class="hlt">materials</span> appears to soften, sometimes by an order of magnitude or more. Under load, this can lead to significantly increased rates of deformations. On account of the recent experimental and theoretical findings on the nature of water flow in nanometer-size hydrophillic spaces, we provide a physical explanation for the viscous softening and propose a constitutive law on this basis. To this end, it also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhDT........24N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhDT........24N"><span id="translatedtitle">Interaction of pressure and momentum driven flows with thin <span class="hlt">porous</span> media: Experiments and <span class="hlt">modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naaktgeboren, Christian</p> <p></p> <p>Flow interaction with thin <span class="hlt">porous</span> media arise in a variety of natural and man-made settings. Examples include flow through thin grids in electronics cooling, and NOx emissions reduction by means of ammonia injection grids, pulsatile aquatic propulsion with complex trailing anatomy (e.g., jellyfish with tentacles) and microbursts from thunderstorm activity over dense vegetation, unsteady combustion in or near <span class="hlt">porous</span> <span class="hlt">materials</span>, pulsatile jet-drying of textiles, and pulsed jet agitation of clothing for trace contaminant sampling. Two types of interactions with thin <span class="hlt">porous</span> media are considered: (i) forced convection or pressure-driven flows, where fluid advection is maintained by external forces, and (ii) inertial or momentum-driven flows, in which fluid motion is generated but not maintained by external forces. Forced convection analysis through thin permeable media using a <span class="hlt">porous</span> continuum approach requires the knowledge of <span class="hlt">porous</span> medium permeability and form coefficients, K and C, respectively, which are defined by the Hazen-Dupuit-Darcy (HDD) equation. Their determination, however, requires the measurement of the pressure-drop per unit of <span class="hlt">porous</span> medium length. The pressure-drop caused by fluid entering and exiting the <span class="hlt">porous</span> medium, however, is not related to the <span class="hlt">porous</span> medium length. Hence, for situations in which the inlet and outlet pressure-drops are not negligible, e.g., for short <span class="hlt">porous</span> media, the definition of Kand C via the HDD equation becomes ambiguous. This aspect is investigated analytically and numerically using the flow through a restriction in circular pipe and parallel plates channels as preliminary <span class="hlt">models</span>. Results show that inlet and outlet pressure-drop effects become increasingly important when the inlet and outlet fluid surface fraction φ decreases and the Reynolds number Re increases for both laminar and turbulent flow regimes. A conservative estimate of the minimum <span class="hlt">porous</span> medium length beyond which the core pressure-drop predominates over the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22398914','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22398914"><span id="translatedtitle">Multi-contrast 3D X-ray imaging of <span class="hlt">porous</span> and composite <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sarapata, Adrian; Herzen, Julia; Ruiz-Yaniz, Maite; Zanette, Irene; Rack, Alexander; Pfeiffer, Franz</p> <p>2015-04-13</p> <p>Grating-based X-ray computed tomography allows for simultaneous and nondestructive determination of the full X-ray complex index of refraction and the scattering coefficient distribution inside an object in three dimensions. Its multi-contrast capabilities combined with a high resolution of a few micrometers make it a suitable tool for assessing multiple phases inside <span class="hlt">porous</span> and composite <span class="hlt">materials</span> such as concrete. Here, we present quantitative results of a proof-of-principle experiment performed on a concrete sample. Thanks to the complementarity of the contrast channels, more concrete phases could be distinguished than in conventional attenuation-based imaging. The phase-contrast reconstruction shows high contrast between the hardened cement paste and the aggregates and thus allows easy 3D segmentation. Thanks to the dark-field image, micro-cracks inside the coarse aggregates are visible. We believe that these results are extremely interesting in the field of <span class="hlt">porous</span> and composite <span class="hlt">materials</span> studies because of unique information provided by grating interferometry in a non-destructive way.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1211220','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1211220"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">materials</span> with pre-designed single-molecule traps for CO2 selective adsorption</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Li, JR; Yu, JM; Lu, WG; Sun, LB; Sculley, J; Balbuena, PB; Zhou, HC</p> <p>2013-02-26</p> <p>Despite tremendous efforts, precise control in the synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span> with pre-designed pore properties for desired applications remains challenging. Newly emerged <span class="hlt">porous</span> metal-organic <span class="hlt">materials</span>, such as metal-organic polyhedra and metal-organic frameworks, are amenable to design and property tuning, enabling precise control of functionality by accurate design of structures at the molecular level. Here we propose and validate, both experimentally and computationally, a precisely designed cavity, termed a 'single-molecule trap', with the desired size and properties suitable for trapping target CO2 molecules. Such a single-molecule trap can strengthen CO2-host interactions without evoking chemical bonding, thus showing potential for CO2 capture. Molecular single-molecule traps in the form of metal-organic polyhedra are designed, synthesised and tested for selective adsorption of CO2 over N-2 and CH4, demonstrating the trapping effect. Building these pre-designed single-molecule traps into extended frameworks yields metal-organic frameworks with efficient mass transfer, whereas the CO2 selective adsorption nature of single-molecule traps is preserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JMagR.208..235V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JMagR.208..235V"><span id="translatedtitle">One-dimensional scanning of moisture in heated <span class="hlt">porous</span> building <span class="hlt">materials</span> with NMR</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Heijden, G. H. A.; Huinink, H. P.; Pel, L.; Kopinga, K.</p> <p>2011-02-01</p> <p>In this paper we present a new dedicated NMR setup which is capable of measuring one-dimensional moisture profiles in heated <span class="hlt">porous</span> <span class="hlt">materials</span>. The setup, which is placed in the bore of a 1.5 T whole-body scanner, is capable of reaching temperatures up to 500 °C. Moisture and temperature profiles can be measured quasi simultaneously with a typical time resolution of 2-5 min. A methodology is introduced for correcting temperature effects on NMR measurements at these elevated temperatures. The corrections are based on the Curie law for paramagnetism and the observed temperature dependence of the relaxation mechanisms occurring in <span class="hlt">porous</span> <span class="hlt">materials</span>. Both these corrections are used to obtain a moisture content profile from the raw NMR signal profile. To illustrate the methodology, a one-sided heating experiment of concrete with a moisture content in equilibrium with 97% RH is presented. This kind of heating experiment is of particular interest in the research on fire spalling of concrete, since it directly reveals the moisture and heat transport occurring inside the concrete. The obtained moisture profiles reveal a moisture peak building up behind the boiling front, resulting in a saturated layer. To our knowledge the direct proof of the formation of a moisture peak and subsequent moisture clogging has not been reported before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27078440','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27078440"><span id="translatedtitle">Record-breaking events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pál, Gergő; Raischel, Frank; Lennartz-Sassinek, Sabine; Kun, Ferenc; Main, Ian G</p> <p>2016-03-01</p> <p>An accurate understanding of the interplay between random and deterministic processes in generating extreme events is of critical importance in many fields, from forecasting extreme meteorological events to the catastrophic failure of <span class="hlt">materials</span> and in the Earth. Here we investigate the statistics of record-breaking events in the time series of crackling noise generated by local rupture events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span>. The events are generated by computer simulations of the uniaxial compression of cylindrical samples in a discrete element <span class="hlt">model</span> of sedimentary rocks that closely resemble those of real experiments. The number of records grows initially as a decelerating power law of the number of events, followed by an acceleration immediately prior to failure. The distribution of the size and lifetime of records are power laws with relatively low exponents. We demonstrate the existence of a characteristic record rank k(*), which separates the two regimes of the time evolution. Up to this rank deceleration occurs due to the effect of random disorder. Record breaking then accelerates towards macroscopic failure, when physical interactions leading to spatial and temporal correlations dominate the location and timing of local ruptures. The size distribution of records of different ranks has a universal form independent of the record rank. Subsequences of events that occur between consecutive records are characterized by a power-law size distribution, with an exponent which decreases as failure is approached. High-rank records are preceded by smaller events of increasing size and waiting time between consecutive events and they are followed by a relaxation process. As a reference, surrogate time series are generated by reshuffling the event times. The record statistics of the uncorrelated surrogates agrees very well with the corresponding predictions of independent identically distributed random variables, which confirms that temporal and spatial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhDT........82S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhDT........82S"><span id="translatedtitle">Open flow hot isostatic pressing assisted synthesis of highly <span class="hlt">porous</span> <span class="hlt">materials</span> and catalysts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siadati, Mohammad Hossein</p> <p></p> <p>Open-flow hot isostatic pressing (OFHIP) technique is applied for synthesizing molecular sieves and highly <span class="hlt">porous</span> catalytic <span class="hlt">materials</span>. First, the isostatic pressure is applied to the starting <span class="hlt">material</span>/catalyst precursor, and then heat is applied. Under this condition, as the organic components gradually decompose and leave the <span class="hlt">material</span>, the voids left behind are immediately filled/replaced by the gas (pressure medium) in flow. This substitution warrants the preservation as well as the uniformity of the voids/pores. The result is a very <span class="hlt">porous</span> <span class="hlt">material</span> with very uniform pore size distribution. Another advantage is the production of the catalyst directly from the precursor, in the absence of solvent (neat), rendering the process simpler and less costly than previous processes. The entire process takes place under flow of the gas that is used as medium to develop the isostatic pressure. Consequently, the entire process, as well as the final product produced, is devoid of any undesirable residues. This endeavor also introduces a viable technique for mass-producing <span class="hlt">porous</span> <span class="hlt">materials</span>/catalysts. The resulting <span class="hlt">materials</span> are termed "amorphous sulfide sieves" to reflect their unique properties that include high surface area, narrow pore size distribution and high activity. The catalysts are potentially licensable to all petroleum and petroleum chemical companies for a wide variety of environmental and product improvement purposes. The results obtained on unpromoted samples synthesized at 300°C indicate that as the synthesis pressure is increased, both surface area and catalytic activity of the <span class="hlt">materials</span> produced increase. The increase in activity k value from 3 to 6 x 10-7 mol/g.s corresponds to increase in pressure from 100 to 800 psi, respectively. The N2 gas used as pressure medium results in highly <span class="hlt">porous</span> <span class="hlt">materials</span> but low activity. H 2 seems to be the ideal gas for both pressure medium and reducing agent. Co-promoted catalysts synthesized at 1400 psi and 300°C show</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGE....12..210E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGE....12..210E"><span id="translatedtitle">Seismic attenuation in fractured <span class="hlt">porous</span> media: insights from a hybrid numerical and analytical <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ekanem, A. M.; Li, X. Y.; Chapman, M.; Main, I. G.</p> <p>2015-04-01</p> <p>Seismic attenuation in fluid-saturated <span class="hlt">porous</span> rocks can occur by geometric spreading, wave scattering or the internal dissipation of energy, most likely due to the squirt-flow mechanism. In principle, the pattern of seismic attenuation recorded on an array of sensors contains information about the medium, in terms of <span class="hlt">material</span> heterogeneity and anisotropy, as well as <span class="hlt">material</span> properties such as porosity, crack density, and pore-fluid composition and mobility. In practice, this inverse problem is challenging. Here we provide some insights into the effects of internal dissipation by analysing synthetic data produced by a hybrid numerical and analytical <span class="hlt">model</span> for seismic wave propagation in a fractured medium embedded within a layered geological structure. The <span class="hlt">model</span> is made up of one anisotropic and three isotropic horizontal layers. The anisotropic layer consists of a <span class="hlt">porous</span>, fluid-saturated <span class="hlt">material</span> containing vertically aligned inclusions representing a set of fractures. This combination allows squirt-flow to occur between the pores in the matrix and the <span class="hlt">model</span> fractures. Our results show that the fluid mobility and the associated relaxation time of the fluid-pressure gradient control the frequency range over which attenuation occurs. This induced attenuation increases with incidence angle and azimuth away from the fracture strike-direction. Azimuthal variations in the induced attenuation are elliptical allowing the fracture orientations to be obtained from the axes of the ellipse. These observations hold out the potential of using seismic attenuation as an additional diagnostic in the characterisation of rock formations for a variety of applications including hydrocarbon exploration and production, subsurface storage of CO2, and geothermal energy extraction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22318047','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22318047"><span id="translatedtitle"><span class="hlt">Modeling</span> precursor diffusion and reaction of atomic layer deposition in <span class="hlt">porous</span> structures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Keuter, Thomas Menzler, Norbert Heribert; Mauer, Georg; Vondahlen, Frank; Vaßen, Robert; Buchkremer, Hans Peter</p> <p>2015-01-01</p> <p>Atomic layer deposition (ALD) is a technique for depositing thin films of <span class="hlt">materials</span> with a precise thickness control and uniformity using the self-limitation of the underlying reactions. Usually, it is difficult to predict the result of the ALD process for given external parameters, e.g., the precursor exposure time or the size of the precursor molecules. Therefore, a deeper insight into ALD by <span class="hlt">modeling</span> the process is needed to improve process control and to achieve more economical coatings. In this paper, a detailed, microscopic approach based on the <span class="hlt">model</span> developed by Yanguas-Gil and Elam is presented and additionally compared with the experiment. Precursor diffusion and second-order reaction kinetics are combined to identify the influence of the <span class="hlt">porous</span> substrate's microstructural parameters and the influence of precursor properties on the coating. The thickness of the deposited film is calculated for different depths inside the <span class="hlt">porous</span> structure in relation to the precursor exposure time, the precursor vapor pressure, and other parameters. Good agreement with experimental results was obtained for ALD zirconiumdioxide (ZrO{sub 2}) films using the precursors tetrakis(ethylmethylamido)zirconium and O{sub 2}. The derivation can be adjusted to describe other features of ALD processes, e.g., precursor and reactive site losses, different growth modes, pore size reduction, and surface diffusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JAP...105b4908P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JAP...105b4908P"><span id="translatedtitle">Nanocrystal characterization by ellipsometry in <span class="hlt">porous</span> silicon using <span class="hlt">model</span> dielectric function</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petrik, Peter; Fried, Miklos; Vazsonyi, Eva; Basa, Peter; Lohner, Tivadar; Kozma, Peter; Makkai, Zsolt</p> <p>2009-01-01</p> <p><span class="hlt">Porous</span> silicon layers were prepared by electrochemical etching of p-type single-crystal Si (c-Si) of varying dopant concentration resulting in gradually changing morphology and nanocrystal (wall) sizes in the range of 2-25nm. We used the <span class="hlt">model</span> dielectric function (MDF) of Adachi to characterize these <span class="hlt">porous</span> silicon thin films of systematically changing nanocrystal size. In the optical <span class="hlt">model</span> both the surface and interface roughnesses have to be taken into account, and the E0, E1, and E2 critical point (CP) features are all described by a combination of several lineshapes (two-dimensional CP, excitonic, damped harmonic oscillator). This results in using numerous parameters, so the number of fitted parameters were reduced by parameter coupling and neglecting insensitive parameters. Because of the large number of fitted parameters, cross correlations have to be investigated thoroughly. The broadening parameters of the interband transitions in the measured photon energy range correlate with the long-range order in the crystal. The advantage of this method over the robust and simple effective medium approximation (EMA) using a composition of voids and c-Si with a nanocrystalline Si reference [Petrik et al., Appl. Surf. Sci. 253, 200 (2006)] is that the combined EMA +MDF multilayer method of this work provides a more detailed description of the <span class="hlt">material</span> and layer structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19948552','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19948552"><span id="translatedtitle">A partially open <span class="hlt">porous</span> media flow with chaotic advection: towards a <span class="hlt">model</span> of coupled fields.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Metcalfe, Guy; Lester, Daniel; Ord, Alison; Kulkarni, Pandurang; Trefry, Mike; Hobbs, Bruce E; Regenaur-Lieb, Klaus; Morris, Jeffery</p> <p>2010-01-13</p> <p>In nature, dissipative fluxes of fluid, heat and/or reacting species couple to each other and may also couple to deformation of a surrounding <span class="hlt">porous</span> matrix. We use the well-known analogy of Hele-Shaw flow to Darcy flow to make a <span class="hlt">model</span> <span class="hlt">porous</span> medium with porosity proportional to local cell height. Time- and space-varying fluid injection from multiple source/sink wells lets us create many different kinds of chaotic flows and chemical concentration patterns. Results of an initial time-dependent potential flow <span class="hlt">model</span> illustrate that this is a partially open flow, in which parts of the <span class="hlt">material</span> transported by the flow remain in the cell forever and parts pass through with residence time and exit time distributions that have self-similar features in the control parameter space of the stirring. We derive analytically the existence boundary in stirring control parameter space between where isolated fluid regions can and cannot remain forever in the open flow. Experiments confirm the predictions. PMID:19948552</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PlST...15..521J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PlST...15..521J"><span id="translatedtitle">The Effect of Plasma Surface Treatment on a <span class="hlt">Porous</span> Green Ceramic Film with Polymeric Binder <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeong, Woo Yun</p> <p>2013-06-01</p> <p>To reduce time and energy during thermal binder removal in the ceramic process, plasma surface treatment was applied before the lamination process. The adhesion strength in the lamination films was enhanced by oxidative plasma treatment of the <span class="hlt">porous</span> green ceramic film with polymeric binding <span class="hlt">materials</span>. The oxygen plasma characteristics were investigated through experimental parameters and weight loss analysis. The experimental results revealed the need for parameter analysis, including gas <span class="hlt">material</span>, process time, flow rate, and discharge power, and supported a mechanism consisting of competing ablation and deposition processes. The weight loss analysis was conducted for cyclic plasma treatment rather than continuous plasma treatment for the purpose of improving the film's permeability by suppressing deposition of the ablated species. The cyclic plasma treatment improved the permeability compared to the continuous plasma treatment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26996258','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26996258"><span id="translatedtitle">Production of nanotubes in delignified <span class="hlt">porous</span> cellulosic <span class="hlt">materials</span> after hydrolysis with cellulase.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koutinas, Αthanasios Α; Papafotopoulou-Patrinou, Evgenia; Gialleli, Angelika-Ioanna; Petsi, Theano; Bekatorou, Argyro; Kanellaki, Maria</p> <p>2016-08-01</p> <p>In this study, tubular cellulose (TC), a <span class="hlt">porous</span> cellulosic <span class="hlt">material</span> produced by delignification of sawdust, was treated with a Trichoderma reesei cellulase in order to increase the proportion of nano-tubes. The effect of enzyme concentration and treatment duration on surface characteristics was studied and the samples were analyzed with BET, SEM and XRD. Also, a composite <span class="hlt">material</span> of gelatinized starch and TC underwent enzymatic treatment in combination with amylase (320U) and cellulase (320U) enzymes. For TC, the optimum enzyme concentration (640U) led to significant increase of TC specific surface area and pore volume along with the reduction of pore diameter. It was also shown that the enzymatic treatment did not result to a significant change of cellulose crystallinity index. The produced nano-tubular cellulose shows potential for application to drug and chemical preservative delivery systems. PMID:26996258</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..MAR.V1256L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..MAR.V1256L"><span id="translatedtitle">Superstructured Carbon Nanotube/<span class="hlt">Porous</span> Silicon Hybrid <span class="hlt">Materials</span> for Lithium-Ion Battery Anodes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Jun-Ki; Kang, Shin-Hyun; Choi, Sung-Min</p> <p>2015-03-01</p> <p>High energy Li-ion batteries (LIBs) are in great demand for electronics, electric-vehicles, and grid-scale energy storage. To further increase the energy and power densities of LIBs, Si anodes have been intensively explored due to their high capacity, and high abundance compared with traditional carbon anodes. However, the poor cycle-life caused by large volume expansion during charge/discharge process has been an impediment to its applications. Recently, superstructured Si <span class="hlt">materials</span> were received attentions to solve above mentioned problem in excellent mechanical properties, large surface area, and fast Li and electron transportation aspects, but applying superstructures to anode is in early stage yet. Here, we synthesized superstructured carbon nanotubes (CNTs)/<span class="hlt">porous</span> Si hybrid <span class="hlt">materials</span> and its particular electrochemical properties will be presented. Department of Nuclear and Quantum Engineering</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5180166','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5180166"><span id="translatedtitle">Liners of natural <span class="hlt">porous</span> <span class="hlt">materials</span> to minimize pollutant migration. Final report, Oct. 1975 - Sep. 1977</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fuller, W.H.</p> <p>1981-07-01</p> <p>The use of natural low-cost <span class="hlt">materials</span> as barriers for minimizing pollution migration out of landfills by retaining contaminants from liquids was investigated. The relative effectiveness of natural low-cost liners of crushed limestone, clayey soil, hydrous oxides of iron, and crushed pecan hulls for minimizing the migration of Be, Cd, Cr, Fe, Ni, Zn, and total organic carbon constituents of municipal solid waste landfill leachates was evaluated. Several leachate variables such as aqueous dilution, aeration, pH, and flux were also studied for their effect on movement of metals through 11 representative U.S. soils. Laboratory investigations using soil columns as a first step in screening for potential liners and manipulation practices are described. Limestone and hydrous iron oxide were found to be potentially useful as <span class="hlt">porous</span> liners for retention of metallic leachate constituents. The amounts of these <span class="hlt">materials</span> in natural soil were also found to be useful predictors of contaminant removal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1128993','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1128993"><span id="translatedtitle">Short time proton dynamics in bulk ice and in <span class="hlt">porous</span> anode solid oxide fuel cell <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Basoli, Francesco; Senesi, Roberto; Kolesnikov, Alexander I; Licoccia, Silvia</p> <p>2014-01-01</p> <p>Oxygen reduction and incorporation into solid electrolytes and the reverse reaction of oxygen evolution play a cru-cial role in Solid Oxide Fuel Cell (SOFC) applications. However a detailed un derstanding of the kinetics of the cor-responding reactions, i.e. on reaction mechanisms, rate limiting steps, reaction paths, electrocatalytic role of <span class="hlt">materials</span>, is still missing. These include a thorough characterization of the binding potentials experienced by protons in the lattice. We report results of Inelastic Neutron Scattering (INS) measurements of the vibrational state of the protons in Ni- YSZ highly <span class="hlt">porous</span> composites (75% to 90% ), a ceramic-metal <span class="hlt">material</span> showing a high electrical conductivity and ther mal stability, which is known to be most effectively used as anodes for solid ox ide fuel cells. The results are compared with INS and Deep Inelastic Neutron Scattering (DINS) experiments on the proton binding states in bulk ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3083698','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3083698"><span id="translatedtitle">Development of a Chitosan-Based Biofoam: Application to the Processing of a <span class="hlt">Porous</span> Ceramic <span class="hlt">Material</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mathias, Jean-Denis; Tessier-Doyen, Nicolas; Michaud, Philippe</p> <p>2011-01-01</p> <p>Developing biofoams constitutes a challenging issue for several applications. The present study focuses on the development of a chitosan-based biofoam. Solutions of chitosan in acetic acid were dried under vacuum to generate foams with high-order structures. Chitosan concentration influenced significantly the morphology of developed porosity and the organization of pores in the <span class="hlt">material</span>. Physico-chemical characterizations were performed to investigate the effects of chitosan concentration on density and thermal conductivity of foams. Even if chitosan-based biofoams exhibit interesting insulating properties (typically around 0.06 W·m−1·K−1), it has been shown that their durabilities are limited when submitted to a wet media. So, a way of application consists to elaborate a ceramic <span class="hlt">material</span> with open porosity from a slurry prepared with an organic solvent infiltrating the <span class="hlt">porous</span> network of the foam. PMID:21541051</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014IJMPC..2550086Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014IJMPC..2550086Z"><span id="translatedtitle"><span class="hlt">Porous</span> Substrate Effects on Thermal Flows Through a Rev-Scale Finite Volume Lattice Boltzmann <span class="hlt">Model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zarghami, Ahad; Francesco, Silvia Di; Biscarini, Chiara</p> <p>2014-09-01</p> <p>In this paper, fluid flows with enhanced heat transfer in <span class="hlt">porous</span> channels are investigated through a stable finite volume (FV) formulation of the thermal lattice Boltzmann method (LBM). Temperature field is tracked through a double distribution function (DDF) <span class="hlt">model</span>, while the <span class="hlt">porous</span> media is <span class="hlt">modeled</span> using Brinkman-Forchheimer assumptions. The method is tested against flows in channels partially filled with <span class="hlt">porous</span> media and parametric studies are conducted to evaluate the effects of various parameters, highlighting their influence on the thermo-hydrodynamic behavior.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007TSE....15...39M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007TSE....15...39M&link_type=ABSTRACT"><span id="translatedtitle">Rapid Generation of Superheated Steam Using a Water-containing <span class="hlt">Porous</span> <span class="hlt">Material</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mori, Shoji; Okuyama, Kunito</p> <p></p> <p>Heat treatment by superheated steam has been utilized in several industrial fields including sterilization, desiccation, and cooking. In particular, cooking by superheated steam is receiving increased attention because it has advantages of reducing the salt and fat contents in foods as well as suppressing the oxidation of vitamin C and fat. In this application, quick startup and cut-off responses are required. Most electrically energized steam generators require a relatively long time to generate superheated steam due to the large heat capacities of the water in container and of the heater. Zhao and Liao (2002) introduced a novel process for rapid vaporization of subcooled liquid, in which a low-thermal-conductivity <span class="hlt">porous</span> wick containing water is heated by a downward-facing grooved heating block in contact with the upper surface of the wick structure. They showed that saturated steam is generated within approximately 30 seconds from room-temperature water at a heat flux 41.2 kW⁄m2. In order to quickly generate superheated steam of approximately 300°C, which is required for cooking, the heat capacity of the heater should be as small as possible and the imposed heat flux should be so high enough that the <span class="hlt">porous</span> wick is able to dry out in the vicinity of the contact with the heater and that the resulting heater temperature becomes much higher than the saturation temperature. The present paper proposes a simple structured generator to quickly produce superheated steam. Only a fine wire heater is contacted spirally on the inside wall in a hollow <span class="hlt">porous</span> <span class="hlt">material</span>. The start-up, cut-off responses and the rate of energy conversion for input power are investigated experimentally. Superheated steam of 300°C is produced in approximately 19 seconds from room-temperature water for an input power of 300 W. The maximum rate of energy conversion in the steady state is approximately 0.9.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1256902-two-dimensional-model-analysis-contaminant-transport-fractured-porous-medium','SCIGOV-ESTSC'); return false;" href="http://www.osti.gov/scitech/biblio/1256902-two-dimensional-model-analysis-contaminant-transport-fractured-porous-medium"><span id="translatedtitle">A Two-Dimensional <span class="hlt">Model</span> for the Analysis of Contaminant Transport in a Fractured <span class="hlt">Porous</span> Medium.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech/">Energy Science and Technology Software Center (ESTSC)</a></p> <p></p> <p>1991-03-05</p> <p>CHAINT-MC is a two-dimensional finite element <span class="hlt">model</span> applicable to the transport of a dissolved radionuclide in a fractured <span class="hlt">porous</span> medium along with radioactive chain decay and subsequent transport of the dissolved daughters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27064740','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27064740"><span id="translatedtitle">Excellent cycling stability and superior rate capability of a graphene-amorphous FePO4 <span class="hlt">porous</span> nanowire hybrid as a cathode <span class="hlt">material</span> for sodium ion batteries.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yang, Gaoliang; Ding, Bing; Wang, Jie; Nie, Ping; Dou, Hui; Zhang, Xiaogang</p> <p>2016-04-28</p> <p>A <span class="hlt">porous</span> nanowire <span class="hlt">material</span> consisting of graphene-amorphous FePO4 was investigated as an advanced cathode <span class="hlt">material</span> for sodium ion batteries for large-scale applications. This hybrid cathode <span class="hlt">material</span> showed excellent cycling performance and superior rate capability, which were attributed to the <span class="hlt">porous</span> nanowire structure and the existence of graphene. PMID:27064740</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24337222','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24337222"><span id="translatedtitle">Atmospheric methane removal by methane-oxidizing bacteria immobilized on <span class="hlt">porous</span> building <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ganendra, Giovanni; De Muynck, Willem; Ho, Adrian; Hoefman, Sven; De Vos, Paul; Boeckx, Pascal; Boon, Nico</p> <p>2014-04-01</p> <p>Biological treatment using methane-oxidizing bacteria (MOB) immobilized on six <span class="hlt">porous</span> carrier <span class="hlt">materials</span> have been used to mitigate methane emission. Experiments were performed with different MOB inoculated in building <span class="hlt">materials</span> at high (~20 % (v/v)) and low (~100 ppmv) methane mixing ratios. Methylocystis parvus in autoclaved aerated concrete (AAC) exhibited the highest methane removal rate at high (28.5 ± 3.8 μg CH₄ g⁻¹ building <span class="hlt">material</span> h⁻¹) and low (1.7 ± 0.4 μg CH₄ g⁻¹ building <span class="hlt">material</span> h⁻¹) methane mixing ratio. Due to the higher volume of pores with diameter >5 μm compared to other <span class="hlt">materials</span> tested, AAC was able to adsorb more bacteria which might explain for the higher methane removal observed. The total methane and carbon dioxide-carbon in the headspace was decreased for 65.2 ± 10.9 % when M. parvus in Ytong was incubated for 100 h. This study showed that immobilized MOB on building <span class="hlt">materials</span> could be used to remove methane from the air and also act as carbon sink. PMID:24337222</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25528691','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25528691"><span id="translatedtitle">A 3-D constitutive <span class="hlt">model</span> for pressure-dependent phase transformation of <span class="hlt">porous</span> shape memory alloys.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ashrafi, M J; Arghavani, J; Naghdabadi, R; Sohrabpour, S</p> <p>2015-02-01</p> <p><span class="hlt">Porous</span> shape memory alloys (SMAs) exhibit the interesting characteristics of <span class="hlt">porous</span> metals together with shape memory effect and pseudo-elasticity of SMAs that make them appropriate for biomedical applications. In this paper, a 3-D phenomenological constitutive <span class="hlt">model</span> for the pseudo-elastic behavior and shape memory effect of <span class="hlt">porous</span> SMAs is developed within the framework of irreversible thermodynamics. Comparing to micromechanical and computational <span class="hlt">models</span>, the proposed <span class="hlt">model</span> is computationally cost effective and predicts the behavior of <span class="hlt">porous</span> SMAs under proportional and non-proportional multiaxial loadings. Considering the pressure dependency of phase transformation in <span class="hlt">porous</span> SMAs, proper internal variables, free energy and limit functions are introduced. With the aim of numerical implementation, time discretization and solution algorithm for the proposed <span class="hlt">model</span> are also presented. Due to lack of enough experimental data on multiaxial loadings of <span class="hlt">porous</span> SMAs, we employ a computational simulation method (CSM) together with available experimental data to validate the proposed constitutive <span class="hlt">model</span>. The method is based on a 3-D finite element <span class="hlt">model</span> of a representative volume element (RVE) with random pores pattern. Good agreement between the numerical predictions of the <span class="hlt">model</span> and CSM results is observed for elastic and phase transformation behaviors in various thermomechanical loadings. PMID:25528691</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1048491','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1048491"><span id="translatedtitle">Computational <span class="hlt">modeling</span> of composite <span class="hlt">material</span> fires.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brown, Alexander L.; Erickson, Kenneth L.; Hubbard, Joshua Allen; Dodd, Amanda B.</p> <p>2010-10-01</p> <p>Composite <span class="hlt">materials</span> behave differently from conventional fuel sources and have the potential to smolder and burn for extended time periods. As the amount of composite <span class="hlt">materials</span> on modern aircraft continues to increase, understanding the response of composites in fire environments becomes increasingly important. An effort is ongoing to enhance the capability to simulate composite <span class="hlt">material</span> response in fires including the decomposition of the composite and the interaction with a fire. To adequately <span class="hlt">model</span> composite <span class="hlt">material</span> in a fire, two physical <span class="hlt">model</span> development tasks are necessary; first, the decomposition <span class="hlt">model</span> for the composite <span class="hlt">material</span> and second, the interaction with a fire. A <span class="hlt">porous</span> media approach for the decomposition <span class="hlt">model</span> including a time dependent formulation with the effects of heat, mass, species, and momentum transfer of the <span class="hlt">porous</span> solid and gas phase is being implemented in an engineering code, ARIA. ARIA is a Sandia National Laboratories multiphysics code including a range of capabilities such as incompressible Navier-Stokes equations, energy transport equations, species transport equations, non-Newtonian fluid rheology, linear elastic solid mechanics, and electro-statics. To simulate the fire, FUEGO, also a Sandia National Laboratories code, is coupled to ARIA. FUEGO represents the turbulent, buoyantly driven incompressible flow, heat transfer, mass transfer, and combustion. FUEGO and ARIA are uniquely able to solve this problem because they were designed using a common architecture (SIERRA) that enhances multiphysics coupling and both codes are capable of massively parallel calculations, enhancing performance. The decomposition reaction <span class="hlt">model</span> is developed from small scale experimental data including thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) in both nitrogen and air for a range of heating rates and from available data in the literature. The response of the composite <span class="hlt">material</span> subject to a radiant heat flux boundary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27250142','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27250142"><span id="translatedtitle">Asymptotic limits of some <span class="hlt">models</span> for sound propagation in <span class="hlt">porous</span> media and the assignment of the pore characteristic lengths.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Horoshenkov, Kirill V; Groby, Jean-Philippe; Dazel, Olivier</p> <p>2016-05-01</p> <p><span class="hlt">Modeling</span> of sound propagation in <span class="hlt">porous</span> media requires the knowledge of several intrinsic <span class="hlt">material</span> parameters, some of which are difficult or impossible to measure directly, particularly in the case of a <span class="hlt">porous</span> medium which is composed of pores with a wide range of scales and random interconnections. Four particular parameters which are rarely measured non-acoustically, but used extensively in a number of acoustical <span class="hlt">models</span>, are the viscous and thermal characteristic lengths, thermal permeability, and Pride parameter. The main purpose of this work is to show how these parameters relate to the pore size distribution which is a routine characteristic measured non-acoustically. This is achieved through the analysis of the asymptotic behavior of four analytical <span class="hlt">models</span> which have been developed previously to predict the dynamic density and/or compressibility of the equivalent fluid in a <span class="hlt">porous</span> medium. In this work the <span class="hlt">models</span> proposed by Johnson, Koplik, and Dashn [J. Fluid Mech. 176, 379-402 (1987)], Champoux and Allard [J. Appl. Phys. 70(4), 1975-1979 (1991)], Pride, Morgan, and Gangi [Phys. Rev. B 47, 4964-4978 (1993)], and Horoshenkov, Attenborough, and Chandler-Wilde [J. Acoust. Soc. Am. 104, 1198-1209 (1998)] are compared. The findings are then used to compare the behavior of the complex dynamic density and compressibility of the fluid in a <span class="hlt">material</span> pore with uniform and variable cross-sections. PMID:27250142</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1812444J&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1812444J&link_type=ABSTRACT"><span id="translatedtitle">A visco-poroelastic damage <span class="hlt">model</span> for <span class="hlt">modelling</span> compaction and brittle failure of <span class="hlt">porous</span> rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jacquey, Antoine B.; Cacace, Mauro; Blöcher, Guido; Milsch, Harald; Scheck-Wenderoth, Magdalena</p> <p>2016-04-01</p> <p>Hydraulic stimulation of geothermal wells is often used to increase heat extraction from deep geothermal reservoirs. Initiation and propagation of fractures due to pore pressure build-up increase the effective permeability of the <span class="hlt">porous</span> medium. Understanding the processes controlling the initiation of fractures, the evolution of their geometries and the hydro-mechanical impact on transport properties of the <span class="hlt">porous</span> medium is therefore of great interest for geothermal energy production. In this contribution, we will present a thermodynamically consistent visco-poroelastic damage <span class="hlt">model</span> which can deal with the multi-scale and multi-physics nature of the physical processes occurring during deformation of a <span class="hlt">porous</span> rock. Deformation of a <span class="hlt">porous</span> medium is crucially influenced by the changes in the effective stress. Considering a strain-formulated yield cap and the compaction-dilation transition, three different regimes can be identified: quasi-elastic deformation, cataclastic compaction with microcracking (damage accumulation) and macroscopic brittle failure with dilation. The governing equations for deformation, damage accumulation/healing and fluid flow have been implemented in a fully-coupled finite-element-method based framework (MOOSE). The MOOSE framework provides a powerful and flexible platform to solve multiphysics problems implicitly and in a tightly coupled manner on unstructured meshes which is of interest for such non-linear context. To validate and illustrate the <span class="hlt">model</span>, simulations of the deformation behaviour of cylindrical <span class="hlt">porous</span> Bentheimer sandstone samples under different confining pressures are compared to experiments. The first experiment under low confining pressure leads to shear failure, the second for high confining pressure leads to cataclastic compaction and the third one with intermediate confining pressure correspond to a transitional regime between the two firsts. Finally, we will demonstrate that this approach can also be used at the field</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...5E8781W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...5E8781W"><span id="translatedtitle">Monodisperse <span class="hlt">Porous</span> Silicon Spheres as Anode <span class="hlt">Materials</span> for Lithium Ion Batteries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S.</p> <p>2015-03-01</p> <p>Highly monodisperse <span class="hlt">porous</span> silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g-1. In particular, reversible Li storage capacities above 1500 mAh g-1 were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing <span class="hlt">porous</span> Si-based LIB anode <span class="hlt">materials</span> by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25740298','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25740298"><span id="translatedtitle">Monodisperse <span class="hlt">porous</span> silicon spheres as anode <span class="hlt">materials</span> for lithium ion batteries.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S</p> <p>2015-01-01</p> <p>Highly monodisperse <span class="hlt">porous</span> silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g(-1). In particular, reversible Li storage capacities above 1500 mAh g(-1) were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing <span class="hlt">porous</span> Si-based LIB anode <span class="hlt">materials</span> by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures. PMID:25740298</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4350083','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4350083"><span id="translatedtitle">Monodisperse <span class="hlt">Porous</span> Silicon Spheres as Anode <span class="hlt">Materials</span> for Lithium Ion Batteries</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S.</p> <p>2015-01-01</p> <p>Highly monodisperse <span class="hlt">porous</span> silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g−1. In particular, reversible Li storage capacities above 1500 mAh g−1 were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing <span class="hlt">porous</span> Si-based LIB anode <span class="hlt">materials</span> by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures. PMID:25740298</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1254..242B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1254..242B"><span id="translatedtitle">Test Method To Quantify The Wicking Properties Of <span class="hlt">Porous</span> Insulation <span class="hlt">Materials</span> Designed To Prevent Interstitial Condensation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Binder, Andrea; Zirkelbach, Daniel; Künzel, Hartwig</p> <p>2010-05-01</p> <p>Applying an interior insulation often is the only option for a thermal retrofit, especially when heritage buildings are concerned. In doing so, the original construction becomes colder in winter and interstitial condensation may occur. The common way to avoid harmful condensation beneath the interior insulation of the external wall is the installation of a vapor barrier. Since such a barrier works both ways, it may adversely affect the drying potential of the wall during the warmer seasons. One way to avoid the problems described is the installation of an interior insulation system without a vapor barrier to the inside. Here, the effect of capillary transport in <span class="hlt">porous</span> hydrophilic media is used to conduct condensing moisture away from the wall/insulation interface back to the surface in contact with the indoor air. Following an increasing demand, several water wicking insulation <span class="hlt">materials</span> (e.g. Calcium-silicate, Autoclave Aerated Concrete based mineral foam, hydrophilic Glass fiber, Cellulose fiber) have appeared on the market. In the past, different methods have been developed to measure and describe the liquid transport properties of hydrophilic <span class="hlt">porous</span> media. However, the evaluation of the moisture transport mechanisms and their efficiency in this special field of implementation is very complex because of the interacting vapor- and liquid moisture transfer processes. Therefore, there is no consensus yet on its determination and quantification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT........47Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT........47Y"><span id="translatedtitle">Micro- and Nano- <span class="hlt">Porous</span> Adsorptive <span class="hlt">Materials</span> for Removal of Contaminants from Water at Point-of-Use</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yakub, Ismaiel</p> <p></p> <p>Water is food, a basic human need and a fundamental human right, yet hundreds of millions of people around the world do not have access to clean drinking water. As a result, about 5000 people die each day from preventable water borne diseases. This dissertation presents the results of experimental and theoretical studies on three different types of <span class="hlt">porous</span> <span class="hlt">materials</span> that were developed for the removal of contaminants from water at point of use (household level). First, three compositionally distinct <span class="hlt">porous</span> ceramic water filters (CWFs) were made from a mixture of redart clay and sieved woodchips and processed into frustum shape. The filters were tested for their flow characteristics and bacteria filtration efficiencies. Since, the CWFs are made from brittle <span class="hlt">materials</span>, and may fail during processing, transportation and usage, the mechanical and physical properties of the <span class="hlt">porous</span> clays were characterized, and used in <span class="hlt">modeling</span> designed to provide new insights for the design of filter geometries. The mechanical/physical properties that were characterized include: compressive strength, flexural strength, facture toughness and resistance curve behavior, keeping in mind the anisotropic nature of the filter structure. The measured flow characteristics and mechanical/physical properties were then related to the underlying porosity and characteristic pore size. In an effort to quantify the adhesive interactions associated with filtration phenomena, atomic force microscopy (AFM) was used to measure the adhesion between bi-<span class="hlt">material</span> pairs that are relevant to point-of-use ceramic water filters. The force microscopy measurements of pull-off force and adhesion energy were used to rank the adhesive interactions. Similarly, the adsorption of fluoride to hydroxyapatite-doped redart clay was studied using composites of redart clay and hydroxyapatite (C-HA). The removal of fluoride from water was explored by carrying out adsorption experiments on C-HA adsorbents with different ratios of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014Nanot..25p5402X&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014Nanot..25p5402X&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Porous</span>-structured Cu2O/TiO2 nanojunction <span class="hlt">material</span> toward efficient CO2 photoreduction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Hua; Ouyang, Shuxin; Liu, Lequan; Wang, Defa; Kako, Tetsuya; Ye, Jinhua</p> <p>2014-04-01</p> <p><span class="hlt">Porous</span>-structured Cu2O/TiO2 nanojunction <span class="hlt">material</span> is successfully fabricated by a facile method via loading Cu2O nanoparticles on the network of a <span class="hlt">porous</span> TiO2 substrate. The developed Cu2O/TiO2 nanojunction <span class="hlt">material</span> has a size of several nanometers, in which the p-type Cu2O and n-type TiO2 nanoparticles are closely contacted with each other. The well designed nanojunction structure is beneficial for the charge separation in the photocatalytic reaction. Meanwhile, the <span class="hlt">porous</span> structure of the Cu2O/TiO2 nanojunction can facilitate the CO2 adsorption and offer more reaction active sites. Most importantly, the gas-phase CO2 photoreduction tests reveal that our developed <span class="hlt">porous</span>-structured Cu2O/TiO2 nanojunction <span class="hlt">material</span> exhibits marked photocatalytic activity in the CH4 evolution, about 12, 9, and 7.5 times higher than the pure TiO2, Pt-TiO2, and commercial Degussa P25 TiO2 powders, respectively. The greatly enhanced activity can be attributed to the well designed nanojunction structure combined with the <span class="hlt">porous</span> structure, which can simultaneously enhance the charge separation efficiency and facilitate the CO2 adsorption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT........85Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT........85Z"><span id="translatedtitle">Investigation on thermo-mechanical instability of <span class="hlt">porous</span> low dielectric constant <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zin, Emil Hyunbae</p> <p></p> <p>This study investigates the structural stability of <span class="hlt">porous</span> low dielectric constant <span class="hlt">materials</span> (PLK) under thermal and mechanical load and the influence of contributing factors including porosity as intrinsic factor and plasma damage and moisture absorption as extrinsic factors on thermo-mechanical instability of PLK in advanced Cu/PLK interconnects. For this purpose, a ball indentation creep test technique was developed to examine the thermal and mechanical instability of PLK at relevant load and temperature conditions in the interconnect structure. Our exploration with the ball indentation creep test found that PLK films plastically deforms with time, indicating that viscoplastic deformation does occur under relevant conditions of PLK processing. On the basis of the results that the increase of the indentation depth with time shows more noticeable difference in PLK films with higher porosity, plasma exposure, and moisture absorption, it is our belief that PLK stability is greatly affected by porosity, plasma damage and moisture. Viscous flow was found to be mechanism for the viscoplastic deformation at the temperature and load of real PLK integration processing. This finding was obtained from the facts that the kinetics of the indentation creep fit very well with the viscous flow <span class="hlt">model</span> and the extracted stress exponent is close to unity. Based on the results of temperature dependence in all PLK films, the activation energy(~1.5eV) of the viscosity back calculated from the experimental value of the kinetics was found to be much small than that of a pure glass (> 4eV). This suggests that the viscous flow of PLK is controlled by chemical reaction happening in PLK matrix. The FT-IR measurement for the examination of chemical bond reconfiguration shows that the intensity of Si-OH bonds increases with the flow while that of Si-O-Si, -CHX and Si-CH 3 bonds decreases, indicating that chemical reactions are involved in the deformation process. From these findings, it is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1718j0002D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1718j0002D"><span id="translatedtitle"><span class="hlt">Porous</span> carbon <span class="hlt">materials</span> synthesized using IRMOF-3 and furfuryl alcohol as precursor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deka, Pemta Tia; Ediati, Ratna</p> <p>2016-03-01</p> <p>IRMOF-3 crystals have been synthesized using solvothermal method by adding zinc nitrate hexahydrate with 2-amino-1,4-benzenedicarboxylic acid in N'N-dimethylformamide (DMF) at 100°C for 24 (note as IR-24) and 72 h (note as IR-72). The obtained crystals were characterized using X-ray Diffraction (XRD), SEM (Scanning Electron Microscopy) and Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), FTIR and Isothermal adsorption-desorption N2. The diffractogram solids synthesized show characteristic peak at 2θ 6.8, 9.6 and 13.7°. SEM micrograph show cubic shape of IRMOF-3 crystal. Based on FTIR characterization, IRMOF-3 appear at wavelength (1691,46; 1425,3; 1238,21; 1319,22 dan 3504,42)cm-1. The Isotherm of crystal IRMOF-3 at heating time 24 h and 72 h are type IV. The surface area of IR-24 and IR-72 are respectively 24,758 m2/g and 29,139 m2/g with its dominant mesopores. Carbonaceous <span class="hlt">materials</span> has been successfully synthesized using IR-24, IR-72 and furfuryl alcohol (FA) as second carbon precursor with variation of carbonation temperature 550, 700 and 850°C. The XRD result from both carbonaceous <span class="hlt">materials</span> show formation of amorphous carbon and caharacteristic peak of ZnO oxide. Micrograph SEM show that carbonaceous <span class="hlt">materials</span> have cubic shape as IRMOF-3 and SEM-EDX result indicate Zn and nitrogen content of these <span class="hlt">materials</span> has decrease until temperature 850°C. <span class="hlt">Porous</span> carbon using IR-24 and FA (notes as C-24) has increased surface area with higher carbonation temperature. The highest surface area is 1495,023 m2/g. Total pore volume and pore size of C-24 from low to high temperature respectively as (0,338; 0,539 and 1,598) cc/g; (0,107; 0,152 and 0,610) cc/g. <span class="hlt">Porous</span> carbon using IR-72 and FA (notes as C-72) has smaller surface area than C-24 but its also increased during higher carbonation heating. The highest surface area is 1029,668 m2/g.The total pore volume and pore size of these carbon <span class="hlt">materials</span> from low to high temperature respectively as (0,390; 0</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5788155','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5788155"><span id="translatedtitle">Percolation <span class="hlt">models</span> for boiling and bubble growth in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yortsos, Y.C.</p> <p>1991-05-01</p> <p>We analyze the liquid-to-vapor phase change in single-component fluids in <span class="hlt">porous</span> media at low superheats. Conditions typical to steam injection in <span class="hlt">porous</span> media are taken. We examine nucleation, phase equilibria and their stability, and the growth of vapor bubbles. Effects of pore structure are emphasized. It is shown that at low supersaturations, bubble growth can be described as a percolation process. In the absence of spatial gradients, macroscopic flow properties are calculated in terms of nucleation parameters. A modification of gradient percolation is also proposed in the case of spatial temperature gradients, when solid conduction predominates. 22 refs., 10 figs., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1213488','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1213488"><span id="translatedtitle"><span class="hlt">Materials</span> Analysis and <span class="hlt">Modeling</span> of Underfill <span class="hlt">Materials</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wyatt, Nicholas B; Chambers, Robert S.</p> <p>2015-08-01</p> <p>The thermal-mechanical properties of three potential underfill candidate <span class="hlt">materials</span> for PBGA applications are characterized and reported. Two of the <span class="hlt">materials</span> are a formulations developed at Sandia for underfill applications while the third is a commercial product that utilizes a snap-cure chemistry to drastically reduce cure time. Viscoelastic <span class="hlt">models</span> were calibrated and fit using the property data collected for one of the Sandia formulated <span class="hlt">materials</span>. Along with the thermal-mechanical analyses performed, a series of simple bi-<span class="hlt">material</span> strip tests were conducted to comparatively analyze the relative effects of cure and thermal shrinkage amongst the <span class="hlt">materials</span> under consideration. Finally, current knowledge gaps as well as questions arising from the present study are identified and a path forward presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140006525','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140006525"><span id="translatedtitle">Ballistic Performance <span class="hlt">Model</span> of Crater Formation in Monolithic, <span class="hlt">Porous</span> Thermal Protection Systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miller, J. E.; Christiansen, E. L.; Deighton, K. D.</p> <p>2014-01-01</p> <p><span class="hlt">Porous</span> monolithic ablative systems insulate atmospheric reentry vehicles from reentry plasmas generated by atmospheric braking from orbital and exo-orbital velocities. Due to the necessity that these <span class="hlt">materials</span> create a temperature gradient up to several thousand Kelvin over their thickness, it is important that these <span class="hlt">materials</span> are near their pristine state prior to reentry. These <span class="hlt">materials</span> may also be on exposed surfaces to space environment threats like orbital debris and meteoroids leaving a probability that these exposed surfaces will be below their prescribed values. Owing to the typical small size of impact craters in these <span class="hlt">materials</span>, the local flow fields over these craters and the ablative process afford some margin in thermal protection designs for these locally reduced performance values. In this work, tests to develop ballistic performance <span class="hlt">models</span> for thermal protection <span class="hlt">materials</span> typical of those being used on Orion are discussed. A density profile as a function of depth of a typical monolithic ablator and substructure system is shown in Figure 1a.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1188868','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1188868"><span id="translatedtitle">Separation of C2 Hydrocarbons by <span class="hlt">Porous</span> <span class="hlt">Materials</span>: Metal Organic Frameworks as Platform</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Banerjee, Debasis; Liu, Jun; Thallapally, Praveen K.</p> <p>2014-12-22</p> <p>The effective separation of small hydrocarbon molecules (C1 – C4) is an important process for petroleum industry, determining the end price of many essential commodities in our daily lives. Current technologies for separation of these molecules rely on energy intensive fractional distillation processes at cryogenic temperature, which is particularly difficult because of their similar volatility. In retrospect, adsorptive separation using solid state adsorbents might be a cost effective alternative. Several types of solid state adsorbents (e.g. zeolite molecular sieves) were tested for separation of small hydrocarbon molecules as a function of pressure, temperature or vacuum. Among different types of plausible adsorbents, metal organic frameworks (MOFs), a class of <span class="hlt">porous</span>, crystalline, inorganic-organic hybrid <span class="hlt">materials</span>, is particularly promising. In this brief comment article, we discuss the separation properties of different types of solid state adsorbents, with a particular emphasis on MOF based adsorbents for separation of C2 hydrocarbon molecules.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986aiaa.confQ....B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986aiaa.confQ....B"><span id="translatedtitle">Sound transmission through double panel constructions lined with elastic <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bolton, J. S.; Green, E. R.</p> <p>1986-07-01</p> <p>Attention is given to a theory governing one-dimensional wave motion in elastic <span class="hlt">porous</span> <span class="hlt">materials</span> which is capable of reproducing experimental transmission measurements for unfaced polyurethane foam layers. Calculations of the transmission loss of fuselage-like foam-lined double panels are presented and it is shown that the foam/panel boundary conditions have a large effect on the panel performance; a hybrid arrangement whereby the foam is bonded directly to one panel and separated from the other by a thin air gap appears to be the most advantageous under practical circumstances. With this configuratiom, the mass-air-mass resonance is minimized and increased low-frequency performance is offered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApSS..257.4643K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApSS..257.4643K"><span id="translatedtitle">Electrochemical synthesis of ZnO nanoflowers and nanosheets on <span class="hlt">porous</span> Si as photoelectric <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kou, Huanhuan; Zhang, Xin; Du, Yongling; Ye, Weichun; Lin, Shaoxiong; Wang, Chunming</p> <p>2011-03-01</p> <p>Well-aligned ZnO nanoflowers and nanosheets were synthesized on <span class="hlt">porous</span> Si (PS) at different applied potentials by electrodeposition approach. The deposits were grown using the optimized program and were characterized by means of cyclic voltammetry (CV), amperometry I-t (I-t), open-circuit potentiometry. X-ray diffraction (XRD) analysis proved a strong preferential orientation (1 0 0) on PS. Scanning electronic microscopy (SEM) observation showed the deposits consist of nanoflowers with uniform grain size of about 100 nm in diameter and nanosheets, which may have potential applications in nanodevices and nanotechnologies. Thus, ZnO grown on PS can be used as photoelectric <span class="hlt">materials</span> due to its larger photoelectric effect compared to Si wafer according to open-circuit potential (OCP) study. Optical band gap measurements were made on samples using UV-visible spectrophotometer thus giving a band gap of 3.35 eV.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1084692','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1084692"><span id="translatedtitle"><span class="hlt">Modeling</span> and Diagnostics of Fuel Cell <span class="hlt">Porous</span> Media for Improving Water Transport</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Allen, Jeff; M'edici, Ezequiel</p> <p>2011-07-01</p> <p>When a fuel cell is operating at high current density, water accumulation is a significant cause of performance and component degradation. Investigating the water transport inside the fuel cell is a challenging task due to opacity of the components, the randomness of the <span class="hlt">porous</span> <span class="hlt">materials</span>, and the difficulty in gain access to the interior for measurement due to the small dimensions of components. Numerical simulation can provide a good insight of the evolution of the water transport under different working condition. However, the validation of those simulations is remains an issue due the same experimental obstacles associated with in-situ measurements. The discussion herein will focus on pore-network <span class="hlt">modeling</span> of the water transport on the PTL and the insights gained from simulations as well as in the validation technique. The implications of a recently published criterion to characterize PTL, based on percolation theory, and validate numerical simulation are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013MeScT..24j5005A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MeScT..24j5005A"><span id="translatedtitle">Measuring sound absorption properties of <span class="hlt">porous</span> <span class="hlt">materials</span> using a calibrated volume velocity source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arenas, Jorge P.; Darmendrail, Luis</p> <p>2013-10-01</p> <p>Measurement of acoustic properties of sound-absorbing <span class="hlt">materials</span> has been the source of much investigation that has produced practical measuring methods. In particular, the measurement of the normal incidence sound absorption coefficient is commonly done using a well-known configuration of a tube carrying a plane wave. The sound-absorbing coefficient is calculated from the surface impedance measured on a sample of <span class="hlt">material</span>. Therefore, a direct measurement of the impedance requires knowing the ratio between the sound pressure and the volume velocity. However, the measurement of volume velocity is not straightforward in practice and many methods have been proposed including complex transducers, laser vibrometry, accelerometers and calibrated volume velocity sources. In this paper, a device to directly measure the acoustic impedance of a sample of sound-absorbing <span class="hlt">material</span> is presented. The device uses an internal microphone in a small cavity sealed by a loudspeaker and a second microphone mounted in front of this source. The calibration process of the device and the limitations of the method are also discussed and measurement examples are presented. The accuracy of the device was assessed by direct comparison with the standardized method. The proposed measurement method was tested successfully with various types of commercial acoustic <span class="hlt">porous</span> <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=231115','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=231115"><span id="translatedtitle">Fractal and Multifractal <span class="hlt">Models</span> Applied to <span class="hlt">Porous</span> Media - Editorial</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Given the current high level of interest in the use of fractal geometry to characterize natural <span class="hlt">porous</span> media, a special issue of the Vadose Zone Journal was organized in order to expose established fractal analysis techniques and cutting-edge new developments to a wider Earth science audience. The ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C43D0423S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C43D0423S"><span id="translatedtitle">Acoustic Wave Propagation in Snow Based on a Biot-Type <span class="hlt">Porous</span> <span class="hlt">Model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sidler, R.</p> <p>2014-12-01</p> <p>Despite the fact that acoustic methods are inexpensive, robust and simple, the application of seismic waves to snow has been sparse. This might be due to the strong attenuation inherent to snow that prevents large scale seismic applications or due to the somewhat counterintuitive acoustic behavior of snow as a <span class="hlt">porous</span> <span class="hlt">material</span>. Such <span class="hlt">materials</span> support a second kind of compressional wave that can be measured in fresh snow and which has a decreasing wave velocity with increasing density of snow. To investigate wave propagation in snow we construct a Biot-type <span class="hlt">porous</span> <span class="hlt">model</span> of snow as a function of porosity based on the assumptions that the solid frame is build of ice, the pore space is filled with a mix of air, or air and water, and empirical relationships for the tortuosity, the permeability, the bulk, and the shear modulus.We use this reduced <span class="hlt">model</span> to investigate compressional and shear wave velocities of snow as a function of porosity and to asses the consequences of liquid water in the snowpack on acoustic wave propagation by solving Biot's differential equations with plain wave solutions. We find that the fast compressional wave velocity increases significantly with increasing density, but also that the fast compressional wave velocity might be even lower than the slow compressional wave velocity for very light snow. By using compressional and shear strength criteria and solving Biot's differential equations with a pseudo-spectral approach we evaluate snow failure due to acoustic waves in a heterogeneous snowpack, which we think is an important mechanism in triggering avalanches by explosives as well as by skiers. Finally, we developed a low cost seismic acquisition device to assess the theoretically obtained wave velocities in the field and to explore the possibility of an inexpensive tool to remotely gather snow water equivalent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23496613','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23496613"><span id="translatedtitle">Reactive transport in <span class="hlt">porous</span> media: pore-network <span class="hlt">model</span> approach compared to pore-scale <span class="hlt">model</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Varloteaux, Clément; Vu, Minh Tan; Békri, Samir; Adler, Pierre M</p> <p>2013-02-01</p> <p>Accurate determination of three macroscopic parameters governing reactive transport in <span class="hlt">porous</span> media, namely, the apparent solute velocity, the dispersion, and the apparent reaction rate, is of key importance for predicting solute migration through reservoir aquifers. Two methods are proposed to calculate these parameters as functions of the Péclet and the Péclet-Dahmköhler numbers. In the first method called the pore-scale <span class="hlt">model</span> (PSM), the <span class="hlt">porous</span> medium is discretized by the level set method; the Stokes and convection-diffusion equations with reaction at the wall are solved by a finite-difference scheme. In the second method, called the pore-network <span class="hlt">model</span> (PNM), the void space of the <span class="hlt">porous</span> medium is represented by an idealized geometry of pore bodies joined by pore throats; the flow field is computed by solving Kirchhoff's laws and transport calculations are performed in the asymptotic regime where the solute concentration undergoes an exponential evolution with time. Two synthetic geometries of <span class="hlt">porous</span> media are addressed by using both numerical codes. The first geometry is constructed in order to validate the hypotheses implemented in PNM. PSM is also used for a better understanding of the various reaction patterns observed in the asymptotic regime. Despite the PNM approximations, a very good agreement between the <span class="hlt">models</span> is obtained, which shows that PNM is an accurate description of reactive transport. PNM, which can address much larger pore volumes than PSM, is used to evaluate the influence of the concentration distribution on macroscopic properties of a large irregular network reconstructed from microtomography images. The role of the dimensionless numbers and of the location and size of the largest pore bodies is highlighted. PMID:23496613</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhRvE..91c3004C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhRvE..91c3004C&link_type=ABSTRACT"><span id="translatedtitle">Generalized lattice Boltzmann <span class="hlt">model</span> for flow through tight <span class="hlt">porous</span> media with Klinkenberg's effect</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Li; Fang, Wenzhen; Kang, Qinjun; De'Haven Hyman, Jeffrey; Viswanathan, Hari S.; Tao, Wen-Quan</p> <p>2015-03-01</p> <p>Gas slippage occurs when the mean free path of the gas molecules is in the order of the characteristic pore size of a <span class="hlt">porous</span> medium. This phenomenon leads to Klinkenberg's effect where the measured permeability of a gas (apparent permeability) is higher than that of the liquid (intrinsic permeability). A generalized lattice Boltzmann <span class="hlt">model</span> is proposed for flow through <span class="hlt">porous</span> media that includes Klinkenberg's effect, which is based on the <span class="hlt">model</span> of Guo et al. [Phys. Rev. E 65, 046308 (2002), 10.1103/PhysRevE.65.046308]. The second-order Beskok and Karniadakis-Civan's correlation [A. Beskok and G. Karniadakis, Microscale Thermophys. Eng. 3, 43 (1999), 10.1080/108939599199864 and F. Civan, Transp. <span class="hlt">Porous</span> Med. 82, 375 (2010), 10.1007/s11242-009-9432-z] is adopted to calculate the apparent permeability based on intrinsic permeability and the Knudsen number. Fluid flow between two parallel plates filled with <span class="hlt">porous</span> media is simulated to validate the <span class="hlt">model</span>. Simulations performed in a heterogeneous <span class="hlt">porous</span> medium with components of different porosity and permeability indicate that Klinkenberg's effect plays a significant role on fluid flow in low-permeability <span class="hlt">porous</span> media, and it is more pronounced as the Knudsen number increases. Fluid flow in a shale matrix with and without fractures is also studied, and it is found that the fractures greatly enhance the fluid flow and Klinkenberg's effect leads to higher global permeability of the shale matrix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25871199','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25871199"><span id="translatedtitle">Generalized lattice Boltzmann <span class="hlt">model</span> for flow through tight <span class="hlt">porous</span> media with Klinkenberg's effect.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Li; Fang, Wenzhen; Kang, Qinjun; De'Haven Hyman, Jeffrey; Viswanathan, Hari S; Tao, Wen-Quan</p> <p>2015-03-01</p> <p>Gas slippage occurs when the mean free path of the gas molecules is in the order of the characteristic pore size of a <span class="hlt">porous</span> medium. This phenomenon leads to Klinkenberg's effect where the measured permeability of a gas (apparent permeability) is higher than that of the liquid (intrinsic permeability). A generalized lattice Boltzmann <span class="hlt">model</span> is proposed for flow through <span class="hlt">porous</span> media that includes Klinkenberg's effect, which is based on the <span class="hlt">model</span> of Guo et al. [Phys. Rev. E 65, 046308 (2002)]. The second-order Beskok and Karniadakis-Civan's correlation [A. Beskok and G. Karniadakis, Microscale Thermophys. Eng. 3, 43 (1999) and F. Civan, Transp. <span class="hlt">Porous</span> Med. 82, 375 (2010)] is adopted to calculate the apparent permeability based on intrinsic permeability and the Knudsen number. Fluid flow between two parallel plates filled with <span class="hlt">porous</span> media is simulated to validate the <span class="hlt">model</span>. Simulations performed in a heterogeneous <span class="hlt">porous</span> medium with components of different porosity and permeability indicate that Klinkenberg's effect plays a significant role on fluid flow in low-permeability <span class="hlt">porous</span> media, and it is more pronounced as the Knudsen number increases. Fluid flow in a shale matrix with and without fractures is also studied, and it is found that the fractures greatly enhance the fluid flow and Klinkenberg's effect leads to higher global permeability of the shale matrix. PMID:25871199</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1044688','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1044688"><span id="translatedtitle">Ionic Liquids as Versatile Precursors for Functionalized <span class="hlt">Porous</span> Carbon and Carbon-Oxide Composite <span class="hlt">Materials</span> by Confined Carbonization</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dai, Sheng; Wang, Xiqing</p> <p>2010-01-01</p> <p>Thermolysis of an ionic liquid (IL) gives no char residue, whereas heating the same IL trapped within an oxide framework affords high carbonization yields (see picture). This confinement method allows incorporation of heteroatoms from the parent IL in the final products, for the development of functionalized <span class="hlt">porous</span> carbon and carbon-oxide composite <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25625943','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25625943"><span id="translatedtitle"><span class="hlt">Porous</span> graphene-based <span class="hlt">material</span> as an efficient metal free catalyst for the oxidative dehydrogenation of ethylbenzene to styrene.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Diao, Jiangyong; Liu, Hongyang; Wang, Jia; Feng, Zhenbao; Chen, Tong; Miao, Changxi; Yang, Weimin; Su, Dang Sheng</p> <p>2015-02-25</p> <p>Reduced <span class="hlt">porous</span> graphene oxide as a metal free catalyst was selected for the oxidative dehydrogenation of ethylbenzene to styrene. It showed the best catalytic performance compared with other carbon <span class="hlt">materials</span> (routinely reduced graphene oxide, graphite powder and oxidized carbon nanotubes) and commercial iron oxide. PMID:25625943</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25025228','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25025228"><span id="translatedtitle">Novel hierarchically <span class="hlt">porous</span> carbon <span class="hlt">materials</span> obtained from natural biopolymer as host matrixes for lithium-sulfur battery applications.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Bin; Xiao, Min; Wang, Shuanjin; Han, Dongmei; Song, Shuqin; Chen, Guohua; Meng, Yuezhong</p> <p>2014-08-13</p> <p>Novel hierarchically <span class="hlt">porous</span> carbon <span class="hlt">materials</span> with very high surface areas, large pore volumes and high electron conductivities were prepared from silk cocoon by carbonization with KOH activation. The prepared novel <span class="hlt">porous</span> carbon-encapsulated sulfur composites were fabricated by a simple melting process and used as cathodes for lithium sulfur batteries. Because of the large surface area and hierarchically <span class="hlt">porous</span> structure of the carbon <span class="hlt">material</span>, soluble polysulfide intermediates can be trapped within the cathode and the volume expansion can be alleviated effectively. Moreover, the electron transport properties of the carbon <span class="hlt">materials</span> can provide an electron conductive network and promote the utilization rate of sulfur in cathode. The prepared carbon-sulfur composite exhibited a high specific capacity and excellent cycle stability. The results show a high initial discharge capacity of 1443 mAh g(-1) and retain 804 mAh g(-1) after 80 discharge/charge cycles at a rate of 0.5 C. A Coulombic efficiency retained up to 92% after 80 cycles. The prepared hierarchically <span class="hlt">porous</span> carbon <span class="hlt">materials</span> were proven to be an effective host matrix for sulfur encapsulation to improve the sulfur utilization rate and restrain the dissolution of polysulfides into lithium-sulfur battery electrolytes. PMID:25025228</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..GECLW1090S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..GECLW1090S"><span id="translatedtitle">Gold Nanoparticle Synthesis by 3D Integrated Micro-solution Plasma in a 3D Printed Artificial <span class="hlt">Porous</span> Dielectric <span class="hlt">Material</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sotoda, Naoya; Tanaka, Kenji; Shirafuji, Tatsuru</p> <p>2015-09-01</p> <p>Plasma in contact with HAuCl4 aqueous solution can promote the synthesis of gold nanoparticles. To scale up this process, we have developed 3D integrated micro-solution plasma (3D IMSP). It can generate a large number of argon microplasmas in contact with the aqueous solution flowing in a <span class="hlt">porous</span> dielectric <span class="hlt">material</span>. The <span class="hlt">porous</span> dielectric <span class="hlt">material</span> in our prototype 3D IMSP reactor, however, consists of non-regularly arranged random-sized pores. These pore parameters may be the parameters for controlling the size and dispersion of synthesized gold nanoparticles. We have hence fabricated a 3D IMSP reactor with an artificial <span class="hlt">porous</span> dielectric <span class="hlt">material</span> that has regularly arranged same-sized pores by using a 3D printer. We have applied the reactor to the gold- nanoparticle synthesis. We have confirmed the synthesis of gold nanoparticles through the observation of a plasmon resonance absorption peak at 550 nm in the HAuCl4 aqueous solution treated with 3D IMSP. The size and distribution of the synthesized gold nanoparticles are under investigation. We expect that these characteristics of the gold nanoparticles can be manipulated by changing pore size and their distribution in the <span class="hlt">porous</span> dielectric <span class="hlt">material</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24307432','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24307432"><span id="translatedtitle">Nitrogen-doped <span class="hlt">porous</span> graphitic carbon as an excellent electrode <span class="hlt">material</span> for advanced supercapacitors.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Li; Tian, Chungui; Fu, Yu; Yang, Ying; Yin, Jie; Wang, Lei; Fu, Honggang</p> <p>2014-01-01</p> <p>An advanced supercapacitor <span class="hlt">material</span> based on nitrogen-doped <span class="hlt">porous</span> graphitic carbon (NPGC) with high a surface area was synthesized by means of a simple coordination-pyrolysis combination process, in which tetraethyl orthosilicate (TEOS), nickel nitrate, and glucose were adopted as porogent, graphitic catalyst precursor, and carbon source, respectively. In addition, melamine was selected as a nitrogen source owing to its nitrogen-enriched structure and the strong interaction between the amine groups and the glucose unit. A low-temperature treatment resulted in the formation of a NPGC precursor by combination of the catalytic precursor, hydrolyzed TEOS, and the melamine-glucose unit. Following pyrolysis and removal of the catalyst and porogent, the NPGC <span class="hlt">material</span> showed excellent electrical conductivity owing to its high crystallinity, a large Brunauer-Emmett-Teller surface area (SBET =1027 m(2)  g(-1) ), and a high nitrogen level (7.72 wt %). The unusual microstructure of NPGC <span class="hlt">materials</span> could provide electrochemical energy storage. The NPGC <span class="hlt">material</span>, without the need for any conductive additives, showed excellent capacitive behavior (293 F g(-1) at 1 A g(-1) ), long-term cycling stability, and high coulombic efficiency (>99.9 % over 5000 cycles) in KOH when used as an electrode. Notably, in a two-electrode symmetric supercapacitor, NPGC energy densities as high as 8.1 and 47.5 Wh kg(-1) , at a high power density (10.5 kW kg(-1) ), were achieved in 6 M KOH and 1 M Et4 NBF4 -PC electrolytes, respectively. Thus, the synthesized NPGC <span class="hlt">material</span> could be a highly promising electrode <span class="hlt">material</span> for advanced supercapacitors and other conversion devices. PMID:24307432</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25158688','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25158688"><span id="translatedtitle"><span class="hlt">Porous</span> ovalbumin scaffolds with tunable properties: a resource-efficient biodegradable <span class="hlt">material</span> for tissue engineering applications.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Luo, Baiwen; Choong, Cleo</p> <p>2015-01-01</p> <p>Natural <span class="hlt">materials</span> are promising alternatives to synthetic <span class="hlt">materials</span> used in tissue engineering applications as they have superior biocompatibility and promote better cell attachment and proliferation. Ovalbumin, a natural polymer found in avian egg white, is an example of a nature-derived <span class="hlt">material</span>. Despite the availability and reported biocompatibility of ovalbumin, limited research has been carried out to investigate the efficacy of ovalbumin-based scaffolds for adipose tissue engineering applications. Hence, the current study was carried out to investigate the effect of different crosslinkers on ovalbumin scaffold properties as first step towards the development of ovalbumin-based scaffolds for adipose tissue engineering applications. In this study, highly <span class="hlt">porous</span> three-dimensional scaffolds were fabricated by using three different crosslinkers: glutaraldehyde, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 1,4-butanediol diglycidyl ether. Results showed that the overall scaffold properties such as morphology, pore size and mechanical properties could be modulated based on the type and concentration of crosslinkers used during the fabrication process. Subsequently, the efficacy of the different scaffolds for supporting cell proliferation was investigated. In vitro degradation was also carried on for the best scaffold based on the mechanical and cellular results. Overall, this study is a demonstration of the viability of ovalbumin-based scaffolds as cell carriers for soft tissue engineering applications. PMID:25158688</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25945394','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25945394"><span id="translatedtitle">Giant Negative Area Compressibility Tunable in a Soft <span class="hlt">Porous</span> Framework <span class="hlt">Material</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cai, Weizhao; Gładysiak, Andrzej; Anioła, Michalina; Smith, Vincent J; Barbour, Leonard J; Katrusiak, Andrzej</p> <p>2015-07-29</p> <p>A soft <span class="hlt">porous</span> <span class="hlt">material</span> [Zn(L)2(OH)2]n·Guest (where L is 4-(1H-naphtho[2,3-d]imidazol-1-yl)benzoate, and Guest is water or methanol) exhibits the strongest ever observed negative area compressibility (NAC), an extremely rare property, as at hydrostatic pressure most <span class="hlt">materials</span> shrink in all directions and few expand in one direction. This is the first NAC reported in metal-organic frameworks (MOFs), and its magnitude, clearly visible and by far the highest of all known <span class="hlt">materials</span>, can be reversibly tuned by exchanging guests adsorbed from hydrostatic fluids. This counterintuitive strong NAC of [Zn(L)2(OH)2]n·Guest arises from the interplay of flexible [-Zn-O(H)-]n helices with layers of [-Zn-L-]4 quadrangular puckered rings comprising large channel voids. The compression of helices and flattening of puckered rings combine to give a giant piezo-mechanical response, applicable in ultrasensitive sensors and actuators. The extrinsic NAC response to different hydrostatic fluids is due to varied host-guest interactions affecting the mechanical strain within the range permitted by exceptionally high flexibility of the framework. PMID:25945394</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.B11A0405Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.B11A0405Z"><span id="translatedtitle">A new <span class="hlt">model</span> for the spectral induced polarization signature of bacterial growth in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, C.; Revil, A.; Atekwana, E. A.; Jardani, A.; Smith, S.</p> <p>2012-12-01</p> <p>Recent biogeophysics studies demonstrated the sensitivity of complex conductivity to bacterial growth and microbial mediated mineral transformations in <span class="hlt">porous</span> media. Frequency-domain induced polarization is a minimally invasive manner to measure the complex conductivity of a <span class="hlt">material</span> over a broad range of frequencies. The real component of complex conductivity is associated with electromigration of the charge carriers, and the imaginary component represents reversible energy storage of charge carriers at polarization length scales. Quantitative relationship between frequency-domain induced polarization responses and bacterial growth and decay in <span class="hlt">porous</span> media is analyzed in this study using a new developed <span class="hlt">model</span>. We focus on the direct contribution of bacteria themselves to the complex conductivity in <span class="hlt">porous</span> media in the absence of biomineralization. At low frequencies, the induced polarization of bacteria (α-polarization) is related to the properties of the electrical double layer surrounding the membrane surface of bacteria. Surface conductivity and α-polarization are due to the Stern layer of the counterions occurring in a brush of polymers coating the surface of the bacteria, and can be related to the cation exchange capacity of the bacteria. From the <span class="hlt">modeling</span> results, at low frequencies (< 10 Hz), the mobility of the counterions (K+) in the Stern layer of bacteria is found to be extremely small (4.7×10-10 m2s-1 V-1 at 25°C), and is close to the mobility of the same counterions along the surface of clay minerals (Na+, 1.5×10-10 m2s-1 V-1 at 25°C). This result is in agreement with experimental observations and it indicates a very low relaxation frequency for the α-polarization of the bacteria cells (typically around 0.1 to 5 Hertz). By coupling this new <span class="hlt">model</span> with reactive transport <span class="hlt">modeling</span> in which the evolution of bacterial populations are usually described by Monod kinetics, we show that the changes in imaginary conductivity with time can be used to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/993681','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/993681"><span id="translatedtitle">Considerations for <span class="hlt">Modeling</span> Bacterial-Induced Changes in Hydraulic Properties of Variably Saturated <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rockhold, Mark L.; Yarwood, R. R.; Niemet, Michael R.; Bottomley, Peter J.; Selker, John S.</p> <p>2002-07-26</p> <p>Bacterial-induced changes in the hydraulic properties of <span class="hlt">porous</span> media are important in a variety of disciplines. Most of the pervious research on this topic has focused on liquid-saturated <span class="hlt">porous</span> media systems that are representative of aquifer sediments. Unsaturated or variably saturated systems such as soils require additional considerations that have not been fully addressed in the literature. This paper reviews some of the earlier studies on bacterial-induced changes in the hydraulic properties of saturated <span class="hlt">porous</span> media, and discusses characteristics of unsaturated or variably saturated <span class="hlt">porous</span> media that may be important to consider when <span class="hlt">modeling</span> such phenomena in these systems. New data are presented from experiments conducted in sand-packed columns with initially steady unsaturated flow conditions that show significant biomass-induced changes in pressure heads and water contents and permeability reduction during growth of a Pseudomonas fluorescens bacterium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AdWR...25..477R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AdWR...25..477R"><span id="translatedtitle">Considerations for <span class="hlt">modeling</span> bacterial-induced changes in hydraulic properties of variably saturated <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rockhold, M. L.; Yarwood, R. R.; Niemet, M. R.; Bottomley, P. J.; Selker, J. S.</p> <p></p> <p>Bacterial-induced changes in the hydraulic properties of <span class="hlt">porous</span> media are important in a variety of disciplines. Most of the previous research on this topic has focused on liquid-saturated <span class="hlt">porous</span> media systems that are representative of aquifer sediments. Unsaturated or variably saturated systems such as soils require additional considerations that have not been fully addressed in the literature. This paper reviews some of the earlier studies on bacterial-induced changes in the hydraulic properties of saturated <span class="hlt">porous</span> media, and discusses characteristics of unsaturated or variably saturated <span class="hlt">porous</span> media that may be important to consider when <span class="hlt">modeling</span> such phenomena in these systems. New data are presented from experiments conducted in sand-packed columns with initially steady unsaturated flow conditions that show significant biomass-induced changes in pressure heads and water contents and permeability reduction during growth of a Pseudomonas fluorescens bacterium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27524006','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27524006"><span id="translatedtitle"><span class="hlt">Porous</span> biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective <span class="hlt">materials</span> for bone implants.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gryshkov, Oleksandr; Klyui, Nickolai I; Temchenko, Volodymyr P; Kyselov, Vitalii S; Chatterjee, Anamika; Belyaev, Alexander E; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit</p> <p>2016-11-01</p> <p><span class="hlt">Porous</span> and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO2) composite are <span class="hlt">materials</span> with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, <span class="hlt">porous</span> and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application. PMID:27524006</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPS...315....9J&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPS...315....9J&link_type=ABSTRACT"><span id="translatedtitle">Facile synthesis of reduced graphene oxide-<span class="hlt">porous</span> silicon composite as superior anode <span class="hlt">material</span> for lithium-ion battery anodes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiao, Lian-Sheng; Liu, Jin-Yu; Li, Hong-Yan; Wu, Tong-Shun; Li, Fenghua; Wang, Hao-Yu; Niu, Li</p> <p>2016-05-01</p> <p>We report a new method for synthesizing reduced graphene oxide (rGO)-<span class="hlt">porous</span> silicon composite for lithium-ion battery anodes. Rice husks were used as a as a raw <span class="hlt">material</span> source for the synthesis of <span class="hlt">porous</span> Si through magnesiothermic reduction process. The as-obtained composite exhibits good rate and cycling performance taking advantage of the <span class="hlt">porous</span> structure of silicon inheriting from rice husks and the outstanding characteristic of graphene. A considerably high delithiation capacity of 907 mA h g-1 can be retained even at a rate of 16 A g-1. A discharge capacity of 830 mA h g-1 at a current density of 1 A g-1 was delivered after 200 cycles. This may contribute to the further advancement of Si-based composite anode design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPS...315....9J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPS...315....9J"><span id="translatedtitle">Facile synthesis of reduced graphene oxide-<span class="hlt">porous</span> silicon composite as superior anode <span class="hlt">material</span> for lithium-ion battery anodes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiao, Lian-Sheng; Liu, Jin-Yu; Li, Hong-Yan; Wu, Tong-Shun; Li, Fenghua; Wang, Hao-Yu; Niu, Li</p> <p>2016-05-01</p> <p>We report a new method for synthesizing reduced graphene oxide (rGO)-<span class="hlt">porous</span> silicon composite for lithium-ion battery anodes. Rice husks were used as a as a raw <span class="hlt">material</span> source for the synthesis of <span class="hlt">porous</span> Si through magnesiothermic reduction process. The as-obtained composite exhibits good rate and cycling performance taking advantage of the <span class="hlt">porous</span> structure of silicon inheriting from rice husks and the outstanding characteristic of graphene. A considerably high delithiation capacity of 907 mA h g-1 can be retained even at a rate of 16 A g-1. A discharge capacity of 830 mA h g-1 at a current density of 1 A g-1 was delivered after 200 cycles. This may contribute to the further advancement of Si-based composite anode design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JCoPh.306..199N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JCoPh.306..199N"><span id="translatedtitle">Improved PISO algorithms for <span class="hlt">modeling</span> density varying flow in conjugate fluid-<span class="hlt">porous</span> domains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nordlund, M.; Stanic, M.; Kuczaj, A. K.; Frederix, E. M. A.; Geurts, B. J.</p> <p>2016-02-01</p> <p>Two modified segregated PISO algorithms are proposed, which are constructed to avoid the development of spurious oscillations in the computed flow near sharp interfaces of conjugate fluid-<span class="hlt">porous</span> domains. The new collocated finite volume algorithms modify the Rhie-Chow interpolation to maintain a correct pressure-velocity coupling when large discontinuous momentum sources associated with jumps in the local permeability and porosity are present. The Re-Distributed Resistivity (RDR) algorithm is based on spreading flow resistivity over the grid cells neighboring a discontinuity in <span class="hlt">material</span> properties of the <span class="hlt">porous</span> medium. The Face Consistent Pressure (FCP) approach derives an auxiliary pressure value at the fluid-<span class="hlt">porous</span> interface using momentum balance around the interface. Such derived pressure correction is designed to avoid spurious oscillations as would otherwise arise with a strictly central discretization. The proposed algorithms are successfully compared against published data for the velocity and pressure for two reference cases of viscous flow. The robustness of the proposed algorithms is additionally demonstrated for strongly reduced viscosity, i.e., higher Reynolds number flows and low Darcy numbers, i.e., low permeability of the <span class="hlt">porous</span> regions in the domain, for which solutions without unphysical oscillations are computed. Both RDR and FCP are found to accurately represent <span class="hlt">porous</span> media flow near discontinuities in <span class="hlt">material</span> properties on structured grids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1512719A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1512719A"><span id="translatedtitle">A numerical <span class="hlt">model</span> of controlled bioinduced mineralization in a <span class="hlt">porous</span> medium to prevent corrosion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Afanasyev, Michael; van Paassen, Leon; Heimovaara, Timo</p> <p>2013-04-01</p> <p>This paper presents a numerical <span class="hlt">model</span> of controlled bioinduced mineralization in a <span class="hlt">porous</span> medium as a possible corrosion protection mechanism. Corrosion is a significant economic problem - recent reports evaluate the annual cost of metal corrosion as 3-4% of the gross domestic product (GDP), in both developed and developing countries. Corrosion control methods currently used are costly and unsustainable as they require the use of larger volumes of <span class="hlt">materials</span>, hazardous chemicals and regular inspections. As an alternative corrosion control method, bioinduced deposition of protective mineral layers has been proposed. Bioinduced precipitation of calcite has already been investigated for CO2 geological sequestration and soil improvement. To our knowledge, though, no numerical study of biomineralization for corrosion protection has been described yet. Our <span class="hlt">model</span> includes three phases - solid, biofilm and mobile water. In the latter the reactive elements are dissolved, which are involved in the precipitation and the biofilm growth. The equations that describe the pore water flow, chemical reactions in the mobile water, consumption of substrate and expulsion of metabolic products by the biofilm are briefly presented. Also, the changes in porosity and permeability of the <span class="hlt">porous</span> medium through biofilm growth and solids precipitation are included. Our main assumptions are that the biofilm is uniform, has a constant density and composition, that all chemical reactions except for substrate consumption occur in the mobile water, and that the precipitates are uniformly distributed on the surface of the solids. We validate the <span class="hlt">model</span> with simple analytical solutions and against experimental data. The metabolism of the micro-organisms introduces changes in the physical and chemical characteristics of the environment, such as concentrations of chemicals and pH levels. As an extension to the <span class="hlt">model</span>, we couple these changes to the rates of biofilm growth and precipitation rates. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/771502','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/771502"><span id="translatedtitle">The Consistent Kinetics Porosity (CKP) <span class="hlt">Model</span>: A Theory for the Mechanical Behavior of Moderately <span class="hlt">Porous</span> Solids</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>BRANNON,REBECCA M.</p> <p>2000-11-01</p> <p>A theory is developed for the response of moderately <span class="hlt">porous</span> solids (no more than {approximately}20% void space) to high-strain-rate deformations. The <span class="hlt">model</span> is consistent because each feature is incorporated in a manner that is mathematically compatible with the other features. Unlike simple p-{alpha} <span class="hlt">models</span>, the onset of pore collapse depends on the amount of shear present. The user-specifiable yield function depends on pressure, effective shear stress, and porosity. The elastic part of the strain rate is linearly related to the stress rate, with nonlinear corrections from changes in the elastic moduli due to pore collapse. Plastically incompressible flow of the matrix <span class="hlt">material</span> allows pore collapse and an associated macroscopic plastic volume change. The plastic strain rate due to pore collapse/growth is taken normal to the yield surface. If phase transformation and/or pore nucleation are simultaneously occurring, the inelastic strain rate will be non-normal to the yield surface. To permit hardening, the yield stress of matrix <span class="hlt">material</span> is treated as an internal state variable. Changes in porosity and matrix yield stress naturally cause the yield surface to evolve. The stress, porosity, and all other state variables vary in a consistent manner so that the stress remains on the yield surface throughout any quasistatic interval of plastic deformation. Dynamic loading allows the stress to exceed the yield surface via an overstress ordinary differential equation that is solved in closed form for better numerical accuracy. The part of the stress rate that causes no plastic work (i.e-, the part that has a zero inner product with the stress deviator and the identity tensor) is given by the projection of the elastic stressrate orthogonal to the span of the stress deviator and the identity tensor.The <span class="hlt">model</span>, which has been numerically implemented in MIG format, has been exercised under a wide array of extremal loading and unloading paths. As will be discussed in a companion</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27501762','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27501762"><span id="translatedtitle">A Versatile and Scalable Approach toward Robust Superhydrophobic <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Excellent Absorbency and Flame Retardancy.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui</p> <p>2016-01-01</p> <p>The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for <span class="hlt">materials</span> that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic <span class="hlt">porous</span> <span class="hlt">materials</span>, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications. PMID:27501762</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4977488','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4977488"><span id="translatedtitle">A Versatile and Scalable Approach toward Robust Superhydrophobic <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Excellent Absorbency and Flame Retardancy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui</p> <p>2016-01-01</p> <p>The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for <span class="hlt">materials</span> that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic <span class="hlt">porous</span> <span class="hlt">materials</span>, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications. PMID:27501762</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24411389','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24411389"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">material</span> based on spongy titanium granules: structure, mechanical properties, and osseointegration.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rubshtein, A P; Trakhtenberg, I Sh; Makarova, E B; Triphonova, E B; Bliznets, D G; Yakovenkova, L I; Vladimirov, A B</p> <p>2014-02-01</p> <p>A <span class="hlt">porous</span> <span class="hlt">material</span> has been produced by pressing spongy titanium granules with subsequent vacuum sintering. The <span class="hlt">material</span> with porosity of more than 30% has an open system of interconnecting pores. The Young's modulus and 0.2% proof strength have been measured for the samples having 20-55% porosity. If the porosity is between 30 and 45%, the mechanical properties are determined by irregular shape of pores, which is due to spongy titanium granules. The experiment in vivo was performed on adult rabbits. Before surgery the implants were saturated with adherent autologous bone marrow cells. The implants were introduced into the defects formed in the condyles of tibias and femurs. Investigations of osseointegration of implants having 40% porosity showed that the whole system of pores was filled with mature bone tissue in 16 weeks after surgery. Neogenic bone tissue has an uneven surface formed by lacunas and craters indicative of active resorption and subsequent rearrangement (SEM examination). The bone tissue is pierced by neoformed vessels. Irregular-shaped pores with tortuous walls and numerous lateral channels going through the granules provide necessary conditions for the formation of functional bone tissue in the implant volume and the periimplant region. PMID:24411389</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...631233R&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...631233R&link_type=ABSTRACT"><span id="translatedtitle">A Versatile and Scalable Approach toward Robust Superhydrophobic <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Excellent Absorbency and Flame Retardancy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui</p> <p>2016-08-01</p> <p>The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for <span class="hlt">materials</span> that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic <span class="hlt">porous</span> <span class="hlt">materials</span>, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMuMo...650011W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMuMo...650011W"><span id="translatedtitle">Probabilistic Prediction of Homogenized Property and Update of Prediction for Spherical <span class="hlt">Porous</span> <span class="hlt">Material</span> Considering Microstructural Uncertainties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wen, Pin; Yokota, Kenichiro; Takano, Naoki</p> <p>2015-02-01</p> <p>The purpose of this work is to simulate uncertainties existing in microscopic field of spherical <span class="hlt">porous</span> <span class="hlt">material</span> so that the homogenized property of interest can be predicted with high reliability. Moreover, the final goal is to build a bridge of feedback between microstructure design and fabrication to predict microstructure morphology by limited measurement data of macroscopic property. The uncertainties are identified as parametric variables in constituent <span class="hlt">material</span> property and nonparametric variables in morphological fluctuation such as disordering and clustering in microstructure. First-order perturbation, based stochastic homogenization (FPSH) method together with mixture distribution technique is employed for probabilistic prediction. Furthermore, the update of prediction is accomplished in the case of an assumed virtual experimental trial. Two numerical examples show that the probabilistic prediction has given a better decision in microstructure design than deterministic prediction. The main conclusion coming from the new method derived by gap between measured data and prediction showed that, when the update is used for morphology prediction of microstructure, it is almost perfect agreement with parameters’ setup of virtual experiment. After it is applied for update of probabilistic homogenized property, it could make the updated homogenized property closer to measurement data so that it becomes more realistic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21366761','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21366761"><span id="translatedtitle">Investigation of Sintering Temperature on Attrition Resistance of Highly <span class="hlt">Porous</span> Diatomite Based <span class="hlt">Material</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Garderen, Noemie van; Clemens, Frank J.; Scharf, Dagobert; Graule, Thomas</p> <p>2010-05-30</p> <p>Highly <span class="hlt">porous</span> diatomite based granulates with a diameter of 500 mum have been produced by an extrusion method. In order to investigate the relation between microstructure, phase composition and attrition resistance of the final product, the granulates were sintered between 800 and 1300 deg. C. Mean pore size of the granulates was evaluated by Hg-porosimetry. An increase of the pore size is observed in the range of 3.6 nm to 40 mum with increasing sintering temperature. Higher mean pore radii of 1.6 mum and 5.7 mum obtained by sintering at 800 and 1300 deg. C respectively. X-ray diffraction shows that mullite phase appears at 1100 deg. C due to the presence of clay. At 1100 deg. C diatomite (amorphous silicate) started to transform into alpha-cristobalite. Attrition resistance was determined by evaluating the amount of ground <span class="hlt">material</span> passed through a sieve with a predefined mesh size. It was observed that a <span class="hlt">material</span> sintered at high temperature leads to an increase of attrition resistance due to the decrease of total porosities and phase transformation. Due to the reason that attrition resistance significantly increased by sintering the granulates at higher temperature, a so called attrition resistance index was determined in order to compare all the different attrition resistance values. This attrition resistance index was determined by using the exponential component of the equation obtained from attrition resistance curves. It permits comparison of the attrition behaviour without a time influence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4214099','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4214099"><span id="translatedtitle">A <span class="hlt">Porous</span> TiAl6V4 Implant <span class="hlt">Material</span> for Medical Application</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ebel, Thomas; Willumeit, Regine</p> <p>2014-01-01</p> <p>Increased durability of permanent TiAl6V4 implants still remains a requirement for the patient's well-being. One way to achieve a better bone-<span class="hlt">material</span> connection is to enable bone “ingrowth” into the implant. Therefore, a new <span class="hlt">porous</span> TiAl6V4 <span class="hlt">material</span> was produced via metal injection moulding (MIM). Specimens with four different porosities were produced using gas-atomised spherical TiAl6V4 with different powder particle diameters, namely, “Small” (<45 μm), “Medium” (45–63 μm), “Mix” (90% 125–180 μm + 10% <45 μm), and “Large” (125–180 μm). Tensile tests, compression tests, and resonant ultrasound spectroscopy (RUS) were used to analyse mechanical properties. These tests revealed an increasing Young's modulus with decreasing porosity; that is, “Large” and “Mix” exhibit mechanical properties closer to bone than to bulk <span class="hlt">material</span>. By applying X-ray tomography (3D volume) and optical metallographic methods (2D volume and dimensions) the pores were dissected. The pore analysis of the “Mix” and “Large” samples showed pore volumes between 29% and 34%, respectively, with pore diameters ranging up to 175 μm and even above 200 μm for “Large.” <span class="hlt">Material</span> cytotoxicity on bone cell lines (SaOs-2 and MG-63) and primary cells (human bone-derived cells, HBDC) was studied by MTT assays and highlighted an increasing viability with higher porosity. PMID:25386191</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3618403','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3618403"><span id="translatedtitle">Effective conductivity and permittivity of unsaturated <span class="hlt">porous</span> <span class="hlt">materials</span> in the frequency range 1 mHz–1GHz</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Revil, A</p> <p>2013-01-01</p> <p>A <span class="hlt">model</span> combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp, which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd, the quadrature conductivity is generally well described by a plateau when clay minerals are present in the <span class="hlt">material</span>. Clay-free <span class="hlt">porous</span> <span class="hlt">materials</span> with a narrow grain size distribution are described by a Cole-Cole <span class="hlt">model</span>. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the <span class="hlt">material</span>. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd, the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified <span class="hlt">model</span> is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone. PMID:23576823</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1130683','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1130683"><span id="translatedtitle"><span class="hlt">Porous</span> Chromatographic <span class="hlt">Materials</span> as Substrates for Preparing Synthetic Nuclear Explosion Debris Particles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harvey, Scott D.; Liezers, Martin; Antolick, Kathryn C.; Garcia, Ben J.; Sweet, Lucas E.; Carman, April J.; Eiden, Gregory C.</p> <p>2013-06-13</p> <p>In this study, we investigated several <span class="hlt">porous</span> chromatographic <span class="hlt">materials</span> as synthetic substrates for preparing surrogate nuclear explosion debris particles. The resulting synthetic debris <span class="hlt">materials</span> are of interest for use in developing analytical methods. Eighteen metals, including some of forensic interest, were loaded onto <span class="hlt">materials</span> by immersing them in metal solutions (556 mg/L of each metal) to fill the pores, applying gentle heat (110°C) to drive off water, and then treating them at high temperatures (up to 800°C) in air to form less soluble metal species. High-boiling-point metals were uniformly loaded on spherical controlled-pore glass to emulate early fallout, whereas low-boiling-point metals were loaded on core-shell silica to represent coated particles formed later in the nuclear fallout-formation process. Analytical studies were applied to characterize solubility, <span class="hlt">material</span> balance, and formation of recalcitrant species. Dissolution experiments indicated loading was 1.5 to 3 times higher than expected from the pore volume alone, a result attributed to surface coating. Analysis of load solutions before and after filling the <span class="hlt">material</span> pores revealed that most metals were passively loaded; that is, solutions filled the pores without active metal discrimination. However, niobium and tin concentrations were lower in solutions after pore filling, and were found in elevated concentrations in the final products, indicating some metals were selectively loaded. High-temperature treatments caused reduced solubility of several metal species, and loss of some metals (rhenium and tellurium) because volatile species were formed. Sample preparation reproducibility was high (the inter-batch relative standard deviation was 7.8%, and the intra-batch relative standard deviation was 0.84%) indicating that this <span class="hlt">material</span> is suitable for use as a working standard for analytical methods development. We anticipate future standardized radionuclide-loaded <span class="hlt">materials</span> will find use in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAP...117l5901Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAP...117l5901Y"><span id="translatedtitle">Mesoscopic deformation features of shocked <span class="hlt">porous</span> ceramic: Polycrystalline <span class="hlt">modeling</span> and experimental observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Yin; Wang, Wenqiang; He, Hongliang; Jiang, Tailong; Huan, Qiang; Zhang, Fuping; Li, Yongqiang; Lu, Tiecheng</p> <p>2015-03-01</p> <p>To prevent functional failure, the macroscopic shock response of ceramics needs to be understood. We explored the mesoscopic deformation features of <span class="hlt">porous</span> ceramics, which are responsible for the measured macroscopic "plastic" wave profiles, using polycrystalline <span class="hlt">modeling</span> and experiments. A polycrystalline <span class="hlt">model</span> is established that considers the influence of two major microstructures (multi-voids and grain boundaries) in the <span class="hlt">porous</span> ceramics. Shock experiments with the recovery of shocked <span class="hlt">porous</span> lead zirconate titanate ceramics were conducted. The computational results show that shear cracks nucleate around voids under shock because of severe shear stress concentrations. Broken fragments fill the voids and lead to void collapse. Representative long-distance extended cracks and thick crevices are observed in the recovered sample subjected to 3.3 GPa compression. These representative features are reproduced by the polycrystalline <span class="hlt">model</span>. An initial transgranular crack translates into an intergranular crack after a certain propagation range to form a long-distance extended crack. Intergranular cracks branch from the main transgranular crack during main crack propagation to form a thick crevice. The simultaneous propagation of main and branching cracks results in a more effective shock energy dissipation. Slippage and rotation deformation induced by multi-cracks allows the shocked <span class="hlt">porous</span> ceramic to deform even after all the voids have collapsed. Mesoscopic deformations of <span class="hlt">porous</span> ceramics induce significant stress relaxations and lead to macroscopic "plastic" wave profiles. The polycrystalline <span class="hlt">model</span> will aid microstructures design and provide guidance for preventing the shock failure of functional ceramics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ApSS..256.5210G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ApSS..256.5210G"><span id="translatedtitle">Influence of elastic strains on the adsorption process in <span class="hlt">porous</span> <span class="hlt">materials</span>. Thermodynamics and experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grosman, A.; Ortega, C.</p> <p>2010-06-01</p> <p>If we disregard the shape of the boundary hysteresis loop, H1 for SBA-15, MCM-41 and KIT-6, H2 for p +-type <span class="hlt">porous</span> silicon and <span class="hlt">porous</span> glass, the hysteretic features inside the loop are qualitatively the same for all these systems and show that none of them are composed of independent pores whether the pores are interconnected or not. We hence believe that the physical parameter which couples the pores is not the interconnectivity but the elastic deformation of the <span class="hlt">porous</span> matrix. The thermodynamic approach we develop includes the elastic energy of the solid. We show that the variation of the surface free energy, which is proportional to the deformation of the <span class="hlt">porous</span> matrix, is an important component of the total free energy. With <span class="hlt">porous</span> silicon, we experimentally show that a stress external to the <span class="hlt">porous</span> matrix exerted by the substrate on which it is supported significantly increases the total free energy and the adsorbed amount and decreases the condensation pressure compared to that of the same <span class="hlt">porous</span> matrix detached from its substrate which is the relaxed state of the supported layer. This stress can be partly relaxed by making thicker <span class="hlt">porous</span> layers due to the breaking of Si-Si bonds. This results in the shift of the isotherms towards that of the membrane. We propose a new interaction mechanism occurring through the pore wall elastic deformation in which the external mechanical stress is imposed on a given pore by its neighbours.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhFl...28g2003Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhFl...28g2003Z&link_type=ABSTRACT"><span id="translatedtitle">General slip regime permeability <span class="hlt">model</span> for gas flow through <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Bo; Jiang, Peixue; Xu, Ruina; Ouyang, Xiaolong</p> <p>2016-07-01</p> <p>A theoretical effective gas permeability <span class="hlt">model</span> was developed for rarefied gas flow in <span class="hlt">porous</span> media, which holds over the entire slip regime with the permeability derived as a function of the Knudsen number. This general slip regime <span class="hlt">model</span> (GSR <span class="hlt">model</span>) is derived from the pore-scale Navier-Stokes equations subject to the first-order wall slip boundary condition using the volume-averaging method. The local closure problem for the volume-averaged equations is studied analytically and numerically using a periodic sphere array geometry. The GSR <span class="hlt">model</span> includes a rational fraction function of the Knudsen number which leads to a limit effective permeability as the Knudsen number increases. The mechanism for this behavior is the viscous fluid inner friction caused by converging-diverging flow channels in <span class="hlt">porous</span> media. A linearization of the GSR <span class="hlt">model</span> leads to the Klinkenberg equation for slightly rarefied gas flows. Finite element simulations show that the Klinkenberg <span class="hlt">model</span> overestimates the effective permeability by as much as 33% when a flow approaches the transition regime. The GSR <span class="hlt">model</span> reduces to the unified permeability <span class="hlt">model</span> [F. Civan, "Effective correlation of apparent gas permeability in tight <span class="hlt">porous</span> media," Transp. <span class="hlt">Porous</span> Media 82, 375 (2010)] for the flow in the slip regime and clarifies the physical significance of the empirical parameter b in the unified <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008PhDT.......228C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008PhDT.......228C&link_type=ABSTRACT"><span id="translatedtitle">Design, synthesis, and characterization of <span class="hlt">materials</span> for controlled line deposition, environmental remediation, and doping of <span class="hlt">porous</span> manganese oxide <span class="hlt">material</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calvert, Craig A.</p> <p></p> <p>This thesis covers three topics: (1) coatings formed from sol-gel phases, (2) environmental remediation, and (3) doping of a <span class="hlt">porous</span> manganese oxide. Synthesis, characterization, and application were investigated for each topic. Line-formations were formed spontaneously by self-assembly from vanadium sol-gels and other metal containing solutions on glass substrates. The solutions were prepared by the dissolution of metal oxide or salt in water. A more straightforward method is proposed than used in previous work. Analyses using optical microscopy, atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and infrared spectroscopy showed discreet lines whose deposition could be controlled by varying the concentration. A mechanism was developed from the observed results. Microwave heating, the addition of graphite rods, and oxidants, can enhance HCB remediation from soil. To achieve remediation, a TeflonRTM vessel open to the atmosphere along with an oxidant, potassium persulfate (PerS) or potassium hydroxide, along with uncoated or aluminum oxide coated, graphite rods were heated in a research grade microwave oven. Microwave heating was used to decrease the heating time, and graphite rods were used to increase the absorption of the microwave energy by providing thermal centers. The results showed that the percent HCB removed was increased by adding graphite rods and oxidants. Tungsten, silver, and sulfur were investigated as doping agents for K--OMS-2. The synthesis of these <span class="hlt">materials</span> was carried out with a reflux method. The doping of K--OMS-2 led to changes in the properties of a tungsten doped K--OMS-2 had an increased resistivity, the silver doped <span class="hlt">material</span> showed improved epoxidation of trans-stilbene, and the addition of sulfur produced a paper-like <span class="hlt">material</span>. Rietveld refinement of the tungsten doped K--OMS-2 showed that the tungsten was doped into the framework.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EML....11..815K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EML....11..815K"><span id="translatedtitle">Poly L-lysine (PLL)-mediated <span class="hlt">porous</span> hematite clusters as anode <span class="hlt">materials</span> for improved Li-ion batteries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Kun-Woo; Lee, Sang-Wha</p> <p>2015-09-01</p> <p><span class="hlt">Porous</span> hematite clusters were prepared as anode <span class="hlt">materials</span> for improved Li-ion batteries. First, poly-L-lysine (PLL)-linked Fe3O4 was facilely prepared via cross-linking between the positive amine groups of PLL and carboxylate-bound Fe3O4. The subsequent calcination transformed the PLL-linked Fe3O4 into <span class="hlt">porous</span> hematite clusters (Fe2O3@PLL) consisting of spherical α-Fe2O3 particles. Compared with standard Fe2O3, Fe3O4@PLL exhibited improved electrochemical performance as anode <span class="hlt">materials</span>. The discharge capacity of Fe2O3@PLL was retained at 814.7 mAh g-1 after 30 cycles, which is equivalent to 80.4% of the second discharge capacity, whereas standard Fe2O3 exhibited a retention capacity of 352.3 mAh g-1. The improved electrochemical performance of Fe2O3@PLL was mainly attributed to the <span class="hlt">porous</span> hematite clusters with mesoporosity (20-40 nm), which was beneficial for facilitating ion transport, suggesting a useful guideline for the design of <span class="hlt">porous</span> architectures with higher retention capacity. [Figure not available: see fulltext.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPS...283..289W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPS...283..289W"><span id="translatedtitle"><span class="hlt">Porous</span> carbon nanotubes decorated with nanosized cobalt ferrite as anode <span class="hlt">materials</span> for high-performance lithium-ion batteries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Lingyan; Zhuo, Linhai; Cheng, Haiyang; Zhang, Chao; Zhao, Fengyu</p> <p>2015-06-01</p> <p>Generally, the fast ion/electron transport and structural stability dominate the superiority in lithium-storage applications. In this work, <span class="hlt">porous</span> carbon nanotubes decorated with nanosized CoFe2O4 particles (p-CNTs@CFO) have been rationally designed and synthesized by the assistance of supercritical carbon dioxide (scCO2). When tested as anode <span class="hlt">materials</span> for lithium-ion batteries, the p-CNTs@CFO composite exhibits outstanding electrochemical behavior with high lithium-storage capacity (1077 mAh g-1 after 100 cycles) and rate capability (694 mAh g-1 at 3 A g-1). These outstanding electrochemical performances are attributed to the synergistic effect of <span class="hlt">porous</span> p-CNTs and nanosized CFO. Compared to pristine CNTs, the p-CNTs with substantial pores in the tubes possess largely increased specific surface area and rich oxygen-containing functional groups. The <span class="hlt">porous</span> structure can not only accommodate the volume change during lithiation/delithiation processes, but also provide bicontinuous electron/ion pathways and large electrode/electrolyte interface, which facilitate the ion diffusion kinetics, improving the rate performance. Moreover, the CFO particles are bonded strongly to the p-CNTs through metal-oxygen bridges, which facilitate the electron fast capture from p-CNTs to CFO, and thus resulting in a high reversible capacity and excellent rate performance. Overall, the <span class="hlt">porous</span> p-CNTs provide an efficient way for ion diffusion and continuous electron transport as anode <span class="hlt">materials</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/918780','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/918780"><span id="translatedtitle">A finite element formulation for <span class="hlt">modeling</span> dynamic wetting on flexible substrates and in deformable <span class="hlt">porous</span> media.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schunk, Peter Randall; Cairncross, Richard A.; Madasu, S.</p> <p>2004-03-01</p> <p>This report summarizes research advances pursued with award funding issued by the DOE to Drexel University through the Presidential Early Career Award (PECASE) program. Professor Rich Cairncross was the recipient of this award in 1997. With it he pursued two related research topics under Sandia's guidance that address the outstanding issue of fluid-structural interactions of liquids with deformable solid <span class="hlt">materials</span>, focusing mainly on the ubiquitous dynamic wetting problem. The project focus in the first four years was aimed at deriving a predictive numerical <span class="hlt">modeling</span> approach for the motion of the dynamic contact line on a deformable substrate. A formulation of physical <span class="hlt">model</span> equations was derived in the context of the Galerkin finite element method in an arbitrary Lagrangian/Eulerian (ALE) frame of reference. The formulation was successfully integrated in Sandia's Goma finite element code and tested on several technologically important thin-film coating problems. The <span class="hlt">model</span> equations, the finite-element implementation, and results from several applications are given in this report. In the last year of the five-year project the same physical concepts were extended towards the problem of capillary imbibition in deformable <span class="hlt">porous</span> media. A synopsis of this preliminary <span class="hlt">modeling</span> and experimental effort is also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRB..120.2179L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRB..120.2179L"><span id="translatedtitle">Visco-poroelastic damage <span class="hlt">model</span> for brittle-ductile failure of <span class="hlt">porous</span> rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lyakhovsky, Vladimir; Zhu, Wenlu; Shalev, Eyal</p> <p>2015-04-01</p> <p>The coupling between damage accumulation, dilation, and compaction during loading of sandstones is responsible for different structural features such as localized deformation bands and homogeneous inelastic deformation. We distinguish and quantify the role of each deformation mechanism using new mathematical <span class="hlt">model</span> and its numerical implementation. Formulation includes three different deformation regimes: (I) quasi-elastic deformation characterized by <span class="hlt">material</span> strengthening and compaction; (II) cataclastic flow characterized by damage increase and compaction; and (III) brittle failure characterized by damage increase, dilation, and shear localization. Using a three-dimensional numerical <span class="hlt">model</span>, we simulate the deformation behavior of cylindrical <span class="hlt">porous</span> Berea sandstone samples under different confining pressures. The obtained stress, strain, porosity changes and macroscopic deformation features well reproduce the laboratory results. The <span class="hlt">model</span> predicts different rock behavior as a function of confining pressures. The quasi-elastic and brittle regimes associated with formation of shear and/or dilatant bands occur at low effective pressures. The <span class="hlt">model</span> also successfully reproduces cataclastic flow and homogeneous compaction under high pressures. Complex behavior with overlap of common features of all regimes is simulated under intermediate pressures, resulting with localized compaction or shear enhanced compaction bands. Numerical results elucidate three steps in the formation of compaction bands: (1) dilation and subsequent shear localization, (2) formation of shear enhanced compaction band, and (3) formation of pure compaction band.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22399300','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22399300"><span id="translatedtitle">The efficacy of post porosity plasma protection against vacuum-ultraviolet damage in <span class="hlt">porous</span> low-k <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lionti, K.; Volksen, W.; Darnon, M.; Magbitang, T.; Dubois, G.</p> <p>2015-03-21</p> <p>As of today, plasma damage remains as one of the main challenges to the reliable integration of <span class="hlt">porous</span> low-k <span class="hlt">materials</span> into microelectronic devices at the most aggressive node. One promising strategy to limit damage of <span class="hlt">porous</span> low-k <span class="hlt">materials</span> during plasma processing is an approach we refer to as post porosity plasma protection (P4). In this approach, the pores of the low-k <span class="hlt">material</span> are filled with a sacrificial agent prior to any plasma treatment, greatly minimizing the total damage by limiting the physical interactions between plasma species and the low-k <span class="hlt">material</span>. Interestingly, the contribution of the individual plasma species to the total plasma damage is not fully understood. In this study, we investigated the specific damaging effect of vacuum-ultraviolet (v-UV) photons on a highly <span class="hlt">porous</span>, k = 2.0 low-k <span class="hlt">material</span> and we assessed the P4 protective effect against them. It was found that the impact of the v-UV radiation varied depending upon the v-UV emission lines of the plasma. More importantly, we successfully demonstrated that the P4 process provides excellent protection against v-UV damage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994WRR....30.2785D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994WRR....30.2785D"><span id="translatedtitle"><span class="hlt">Modeling</span> water infiltration in unsaturated <span class="hlt">porous</span> media by interacting lattice gas-cellular automata</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>di Pietro, L. B.; Melayah, A.; Zaleski, S.</p> <p>1994-10-01</p> <p>A two-dimensional lattice gas-cellular automaton fluid <span class="hlt">model</span> with long-range interactions (Appert and Zaleski, 1990) is used to simulate saturated and unsaturated water infiltration in <span class="hlt">porous</span> media. Water and gas within the <span class="hlt">porous</span> medium are simulated by applying the dense and the light phase, respectively, of the cellular automaton fluid. Various wetting properties can be <span class="hlt">modeled</span> when adjusting the corresponding solid-liquid interactions. The lattice gas rules include a gravity force step to allow buoyancy-driven flow. The <span class="hlt">model</span> handles with ease complex geometries of the solid, and an algorithm for generating random <span class="hlt">porous</span> media is presented. The results of four types of simulation experiments are presented: (1) We verified Poiseuille's law for steady and saturated flow between two parallel plates. (2) We analyzed transient water infiltration between two parallel plates of varying degrees of saturation and various apertures. (3) Philip's infiltration equation was adequately simulated in an unsaturated <span class="hlt">porous</span> medium. (4) Infiltration into an aggregated medium containing one vertical parallel crack was simulated. Further applications of this lattice gas method for studying unsaturated flow in <span class="hlt">porous</span> media are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=267574','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=267574"><span id="translatedtitle"><span class="hlt">Modeling</span> colloid transport and retention in saturated <span class="hlt">porous</span> media under unfavorable attachment conditions</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>A mathematical <span class="hlt">model</span> is presented for colloid transport and retention in saturated <span class="hlt">porous</span> media under unfavorable attachment conditions. The <span class="hlt">model</span> accounts for colloid transport in the bulk aqueous phase and adjacent to the solid surface, and rates of colloid collision, interaction, release and imm...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=204510','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=204510"><span id="translatedtitle">Fractional Advective-Dispersive Equation as a <span class="hlt">Model</span> of Solute Transport in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Understanding and <span class="hlt">modeling</span> transport of solutes in <span class="hlt">porous</span> media is a critical issue in the environmental protection. The common <span class="hlt">model</span> is the advective-dispersive equation (ADE) describing the superposition of the advective transport and the Brownian motion in water-filled pore space. Deviations from...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6211567','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6211567"><span id="translatedtitle">Empirical correction of a hydraulic <span class="hlt">model</span> of mutual displacement of solutions in a <span class="hlt">porous</span> bed</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kuznetskii, R.S.</p> <p>1986-09-10</p> <p>This paper seeks to experimentally verify and correct a hydraulic <span class="hlt">model</span> for the forced displacement of a homogeneous solution in a <span class="hlt">porous</span> or granular bed or in a pipe by calibrating the <span class="hlt">model</span> against empirical data for the hydraulic behavior of sulfonated coal, an ion exchange resin, calcium carbonate, and diatomite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014ApPhA.116.1525L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014ApPhA.116.1525L&link_type=ABSTRACT"><span id="translatedtitle">Anti-graffiti nanocomposite <span class="hlt">materials</span> for surface protection of a very <span class="hlt">porous</span> stone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Licchelli, Maurizio; Malagodi, Marco; Weththimuni, Maduka; Zanchi, Chiara</p> <p>2014-09-01</p> <p>The preservation of stone substrates from defacement induced by graffiti represents a very challenging task, which can be faced by applying suitable protective agents on the surface. Although different anti-graffiti <span class="hlt">materials</span> have been developed, it is often found that their effectiveness is unsatisfactory, most of all when applied on very <span class="hlt">porous</span> stones, e.g. Lecce stone. The aim of this work was to study the anti-graffiti behaviour of new nanocomposite <span class="hlt">materials</span> obtained by dispersing montmorillonite nanoparticles (layered aluminosilicates with a high-aspect ratio) into a fluorinated polymer matrix (a fluorinated polyurethane based on perfluoropolyether blocks). Polymeric structure was modified by inducing a cross-linking process, in order to produce a durable anti-graffiti coating with enhanced barrier properties. Several composites were prepared using a naturally occurring and an organically modified montmorillonite clay (1, 3, and 5 % w/w concentrations). <span class="hlt">Materials</span> were applied on Lecce stone specimens, and then their treated surfaces were soiled by a black ink permanent marker or by a black acrylic spray paint. Several repeated staining/cleaning cycles were performed in order to evaluate anti-graffiti effectiveness. Colorimetric measurements were selected to assess the anti-graffiti performance. It was found that the presence of 3 % w/w organically modified montmorillonite in the polymer coating is enough to induce a durable anti-graffiti effect when the stone surface is stained by acrylic paint. Less promising results are obtained when staining by permanent marker is considered as all the investigated treatments afford a reasonable protection from ink only for the first staining/cleaning cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......151K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......151K"><span id="translatedtitle">Effects of Temperature, Oxygen Partial Pressure, and <span class="hlt">Materials</span> Selection on Slag Infiltration into <span class="hlt">Porous</span> Refractories for Entrained-Flow Gasifiers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kaneko, Tetsuya Kenneth</p> <p></p> <p>The penetration rate of molten mineral contents (slag) from spent carbonaceous feedstock into <span class="hlt">porous</span> ceramic-oxide refractory linings is a critical parameter in determining the lifecycle of integrated gasification combined cycle energy production plants. Refractory linings that withstand longer operation without interruption are desirable because they can mitigate consumable and maintenance costs. Although refractory degradation has been extensively studied for many other high-temperature industrial processes, this work focuses on the mechanisms that are unique to entrained-flow gasification systems. The use of unique feedstock mixtures, temperatures from 1450 °C to 1600 °C, and oxygen partial pressures from 10-7 atm to 10-9 atm pose engineering challenges in designing an optimal refractory <span class="hlt">material</span>. Experimentation, characterization, and <span class="hlt">modeling</span> show that gasifier slag infiltration into <span class="hlt">porous</span> refractory is determined by interactions between the slag and the refractory that either form a physical barrier that impedes fluid flow or induce an increased fluid viscosity that decelerates the velocity of the fluid body. The viscosity of the slag is modified by the thermal profile of the refractory along the penetration direction as well as reactions between the slag and refractory that alter the chemistry, and thereby the thermo-physical properties of the fluid. Infiltration experiments reveal that the temperature gradient inherently present along the refractory lining limits penetration. A refractory in near-isothermal conditions demonstrates deeper slag penetration as compared to one that experiences a steeper thermal profile. The decrease in the local temperatures of the slag as it travels deeper into the refractory increases the viscosity of the fluid, which in turn slows the infiltration velocity of fluid body into the pores of the refractory microstructure. With feedstock mixtures that exhibit high iron-oxide concentrations, a transition-metal-oxide, the oxygen</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070018065','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070018065"><span id="translatedtitle">An Initial Non-Equilibrium <span class="hlt">Porous</span>-Media <span class="hlt">Model</span> for CFD Simulation of Stirling Regenerators</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tew, Roy; Simon, Terry; Gedeon, David; Ibrahim, Mounir; Rong, Wei</p> <p>2006-01-01</p> <p>The objective of this paper is to define empirical parameters (or closwre <span class="hlt">models</span>) for an initial thermai non-equilibrium <span class="hlt">porous</span>-media <span class="hlt">model</span> for use in Computational Fluid Dynamics (CFD) codes for simulation of Stirling regenerators. The two CFD codes currently being used at Glenn Research Center (GRC) for Stirling engine <span class="hlt">modeling</span> are Fluent and CFD-ACE. The <span class="hlt">porous</span>-media <span class="hlt">models</span> available in each of these codes are equilibrium <span class="hlt">models</span>, which assmne that the solid matrix and the fluid are in thermal equilibrium at each spatial location within the <span class="hlt">porous</span> medium. This is believed to be a poor assumption for the oscillating-flow environment within Stirling regenerators; Stirling 1-D regenerator <span class="hlt">models</span>, used in Stirling design, we non-equilibrium regenerator <span class="hlt">models</span> and suggest regenerator matrix and gas average temperatures can differ by several degrees at a given axial location end time during the cycle. A NASA regenerator research grant has been providing experimental and computational results to support definition of various empirical coefficients needed in defining a noa-equilibrium, macroscopic, <span class="hlt">porous</span>-media <span class="hlt">model</span> (i.e., to define "closure" relations). The grant effort is being led by Cleveland State University, with subcontractor assistance from the University of Minnesota, Gedeon Associates, and Sunpower, Inc. Friction-factor and heat-transfer correlations based on data taken with the NASAlSunpower oscillating-flow test rig also provide experimentally based correlations that are useful in defining parameters for the <span class="hlt">porous</span>-media <span class="hlt">model</span>; these correlations are documented in Gedeon Associates' Sage Stirling-Code Manuals. These sources of experimentally based information were used to define the following terms and parameters needed in the non-equilibrium <span class="hlt">porous</span>-media <span class="hlt">model</span>: hydrodynamic dispersion, permeability, inertial coefficient, fluid effective thermal conductivity (including themal dispersion and estimate of tortuosity effects}, and fluid-solid heat transfer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Nanos...8.8495Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Nanos...8.8495Y"><span id="translatedtitle">Excellent cycling stability and superior rate capability of a graphene-amorphous FePO4 <span class="hlt">porous</span> nanowire hybrid as a cathode <span class="hlt">material</span> for sodium ion batteries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Gaoliang; Ding, Bing; Wang, Jie; Nie, Ping; Dou, Hui; Zhang, Xiaogang</p> <p>2016-04-01</p> <p>A <span class="hlt">porous</span> nanowire <span class="hlt">material</span> consisting of graphene-amorphous FePO4 was investigated as an advanced cathode <span class="hlt">material</span> for sodium ion batteries for large-scale applications. This hybrid cathode <span class="hlt">material</span> showed excellent cycling performance and superior rate capability, which were attributed to the <span class="hlt">porous</span> nanowire structure and the existence of graphene.A <span class="hlt">porous</span> nanowire <span class="hlt">material</span> consisting of graphene-amorphous FePO4 was investigated as an advanced cathode <span class="hlt">material</span> for sodium ion batteries for large-scale applications. This hybrid cathode <span class="hlt">material</span> showed excellent cycling performance and superior rate capability, which were attributed to the <span class="hlt">porous</span> nanowire structure and the existence of graphene. Electronic supplementary information (ESI) available: Experimental section; SEM images, BET, XPS spectrum, TG curve and EIS spectra of the samples; the comparison of electrochemical performance with the reported results. See DOI: 10.1039/c6nr00409a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26752728','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26752728"><span id="translatedtitle">Oxygen-doped <span class="hlt">porous</span> silicon carbide spheres as electrode <span class="hlt">materials</span> for supercapacitors.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Myeongjin; Ju, Hyun; Kim, Jooheon</p> <p>2016-01-28</p> <p>Oxygen-containing functional groups were introduced onto the surface of the micro- and meso-<span class="hlt">porous</span> silicon carbide sphere (MMPSiC) in order to investigate the relationship between the electric double layer properties and pseudo-capacitive properties; the degree of oxidation of MMPSiC was also optimized. Although the oxygenated surface functionalities can lead to a decrease in the surface area of MMPSiC, the oxygen functional groups attached to the external surface can participate in the redox reaction, resulting in the enhancement of the total super-capacitive performance. The MMPSiC electrode oxidized for 24 h exhibits a high charge storage capacity with a specific capacitance of 301.1 F g(-1) at a scan rate of 5 mV s(-1), with 86.8% rate performance from 5 to 500 mV s(-1) in 1 M KCl aqueous electrolyte. This outstanding capacitive performance of the MMPSiC electrode oxidized for 24 h can be attributed to the harmonious synergistic effect between the electric double layer capacitive contribution of MMPSiC and the pseudo-capacitive contribution of the oxygen-containing functional groups. These encouraging results demonstrate that the MMPSiC electrode oxidized for 24 h is a promising candidate for high performance electrode <span class="hlt">materials</span> for supercapacitors. PMID:26752728</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26415132','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26415132"><span id="translatedtitle">Oil saturation effects in lead metaniobate <span class="hlt">porous</span> piezoceramic: transient <span class="hlt">material</span> characteristics.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mezheritsky, Alex</p> <p>2015-09-01</p> <p>Lead metaniobate PbNb2O6 (PN) has a unique combination of high piezoelectric anisotropy; relatively low dielectric permittivity and high Curie temperature; and a low Q-factor, near 20. The very low Q-factor is the most intriguing PN property among the piezoelectric <span class="hlt">materials</span>, and as shown in this research, this internal high dissipation and damping effect is directly related to the presence of silicon oil in the <span class="hlt">porous</span> PN structure; consequently, it is dependent on the oil properties. To the contrary, the quality factor of PN not saturated with oil was found to be as high as nearly 400. Full sets of PN electro-mechanical constants, transient resonance and dissipation characteristics, and their temperature dependencies were determined under both conditions: PN conventionally saturated with oil and PN not saturated with oil. As was experimentally shown, at higher temperatures particularly after a 260°C soak for several days, a transition from the "with oil" state to the "no oil" state takes place in the conventional PN properties; this effect is a consequence of the phase transition in the silicon oil from liquid to solid state. PMID:26415132</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23853114','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23853114"><span id="translatedtitle">Sericin-carboxymethyl cellulose <span class="hlt">porous</span> matrices as cellular wound dressing <span class="hlt">material</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nayak, Sunita; Kundu, S C</p> <p>2014-06-01</p> <p>In this study, <span class="hlt">porous</span> three-dimensional (3D) hydrogel matrices are fabricated composed of silk cocoon protein sericin of non-mulberry silkworm Antheraea mylitta and carboxymethyl cellulose. The matrices are prepared via freeze-drying technique followed by dual cross-linking with glutaraldehyde and aluminum chloride. The microstructure of the hydrogel matrices is assessed using scanning electron microscopy and biophysical characterization are carried out using Fourier transform infrared spectroscopy and X-ray diffraction. The transforming growth factor β1 release from the cross-linked matrices as a growth factor is evaluated by immunosorbent assay. Live dead assay and 3-[4,5-dimethylthiazolyl-2]-2,5-diphenyl tetrazolium bromide assay show no cytotoxicity of blended matrices toward human keratinocytes. The matrices support the cell attachment and proliferation of human keratinocytes as observed through scanning electron microscope and confocal images. Gelatin zymography demonstrates the low levels of matrix metalloproteinase 2 (MMP-2) and insignificant amount of MMP-9 in the culture media of cell seeded matrices. Low inflammatory response of the matrices is indicated through tumor necrosis factor alpha release assay. The results indicate that the fabricated matrices constitute 3D cell-interactive environment for tissue engineering applications and its potential use as a future cellular biological wound dressing <span class="hlt">material</span>. PMID:23853114</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20905365','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20905365"><span id="translatedtitle">Evaluation of the acid properties of <span class="hlt">porous</span> zirconium-doped and undoped silica <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fuentes-Perujo, D.; Santamaria-Gonzalez, J.; Merida-Robles, J.; Rodriguez-Castellon, E.; Jimenez-Lopez, A.; Maireles-Torres, P. . E-mail: maireles@uma.es; Moreno-Tost, R.</p> <p>2006-07-15</p> <p>A series of <span class="hlt">porous</span> silica and Zr-doped silica molecular sieves, belonging to the MCM-41 and MSU families, were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N{sub 2} adsorption at 77 K. Their acid properties have been evaluated by NH{sub 3}-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FT-IR spectroscopy and the catalytic tests of isopropanol decomposition and isomerization of 1-butene. The acidity of purely siliceous solids were, in all cases, very low, while the incorporation of Zr(IV) into the siliceous framework produced an enhancement of the acidity. The adsorption of basic probe molecules and the catalytic behaviour revealed that Zr-doped MSU-type silica was more acidic than the analogous Zr-MCM-41 solid, with a similar Zr content. This high acidity observed in the case of Zr-doped silica samples is due to the presence of surface zirconium atoms with a low coordination, mainly creating Lewis acid sites. - Graphical abstract: The adsorption of basic probe molecules and the catalytic behaviour have revealed that MSU-type <span class="hlt">materials</span> are more acidic than the analogous MCM-41 solids, mainly after the incorporation of zirconium into the silica framework.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006EPJAP..33...35P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006EPJAP..33...35P"><span id="translatedtitle">Determination of the thermophysical properties of evolutive <span class="hlt">porous</span> media: application to Civil Engineering <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Poullain, P.; Mounanga, P.; Bastian, G.; Coué, R.</p> <p>2006-01-01</p> <p>The purpose of this paper is to describe the development and the use of two measurement techniques especially adapted to the rapid determination of the thermophysical properties of evolutive <span class="hlt">porous</span> media. The first technique exploits the method of the “heated and non-heated wires” and is validated on wet clay by comparison with previous works [Mounanga et al., Eur. Phys. J. Appl. Phys. 26, 65 (2004)]. It is then used to quantify the evolution of both thermal conductivity and volumetric heat capacity of hardening cement pastes maintained at 294 ± 1 K. The second technique is based on the classical method of the “heating film” and a data treatment using forward calculation. This technique is first used to measure the properties of well-known <span class="hlt">materials</span> (hardened mortars, wet sand [Mounanga et al., Eur. Phys. J. Appl. Phys. 26, 65 (2004); Delacre, Ph.D. thesis, University of Artois, 2000] and glass [Bastian, Rev. Phys. Appl. 22, 431 (1987)] and then applied to media whose properties evolve both over time and through space (drying sand).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21074162','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21074162"><span id="translatedtitle">Preparation and characterization of <span class="hlt">porous</span> carbon <span class="hlt">material</span>-coated solid-phase microextraction metal fibers.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhu, Fang; Guo, Jiaming; Zeng, Feng; Fu, Ruowen; Wu, Dingcai; Luan, Tiangang; Tong, Yexiang; Lu, Tongbu; Ouyang, Gangfeng</p> <p>2010-12-10</p> <p>Two kinds of <span class="hlt">porous</span> carbon <span class="hlt">materials</span>, including carbon aerogels (CAs), wormhole-like mesoporous carbons (WMCs), were synthesized and used as the coatings of solid-phase microextraction (SPME) fibers. By using stainless steel wire as the supporting core, six types of fibers were prepared with sol-gel method, direct coating method and direct coating plus sol-gel method. Headspace SPME experiments indicated that the extraction efficiencies of the CA fibers are better than those of the WMC fibers, although the surface area of WMCs is much higher than that of CAs. The sol-gel-CA fiber (CA-A) exhibited excellent extraction properties for non-polar compounds (BTEX, benzene, toluene, ethylbenzene, o-xylene), while direct-coated CA fiber (CA-B) presented the best performance in extracting polar compounds (phenols). The two CA fibers showed wide linear ranges, low detection limits (0.008-0.047μgL(-1) for BTEX, 0.15-5.7μgL(-1) for phenols) and good repeatabilities (RSDs less than 4.6% for BTEX, and less than 9.5% for phenols) and satisfying reproducibilities between fibers (RSDs less than 5.2% for BTEX, and less than 9.9% for phenols). These fibers were successfully used for the analysis of water samples from the Pearl River, which demonstrated the applicability of the home-made CA fibers. PMID:21074162</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1665h0004N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1665h0004N"><span id="translatedtitle">Rapid synthesis of monodispersed highly <span class="hlt">porous</span> spinel nickel cobaltite (NiCo2O4) electrode <span class="hlt">material</span> for supercapacitors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naveen, A. Nirmalesh; Selladurai, S.</p> <p>2015-06-01</p> <p>Monodispersed highly <span class="hlt">porous</span> spinel nickel cobaltite electrode <span class="hlt">material</span> was successfully synthesized in a short time using combustion technique. Single phase cubic nature of the spinel nickel cobaltite with average crystallite size of 24 nm was determined from X-ray diffraction study. Functional groups present in the compound were determined from FTIR study and it further confirms the spinel formation. FESEM images reveal the <span class="hlt">porous</span> nature of the prepared <span class="hlt">material</span> and uniform size distribution of the particles. Electrochemical evaluation was performed using Cyclic Voltammetry (CV) technique, Chronopotentiometry (CP) and Electrochemical Impedance Spectroscopy (EIS). Results reveal the typical pseudocapacitive behaviour of the <span class="hlt">material</span>. Maximum capacitance of 754 F/g was calculated at the scan rate of 5 mV/s, high capacitance was due to the unique <span class="hlt">porous</span> morphology of the electrode. Nyquist plot depicts the low resistance and good electrical conductivity of nickel cobaltite. It has been found that nickel cobaltite prepared by this typical method will be a potential electrode <span class="hlt">material</span> for supercapcitor application.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/238563','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/238563"><span id="translatedtitle">Global nuclear <span class="hlt">material</span> control <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dreicer, J.S.; Rutherford, D.A.</p> <p>1996-05-01</p> <p>The nuclear danger can be reduced by a system for global management, protection, control, and accounting as part of a disposition program for special nuclear <span class="hlt">materials</span>. The development of an international fissile <span class="hlt">material</span> management and control regime requires conceptual research supported by an analytical and <span class="hlt">modeling</span> tool that treats the nuclear fuel cycle as a complete system. Such a tool must represent the fundamental data, information, and capabilities of the fuel cycle including an assessment of the global distribution of military and civilian fissile <span class="hlt">material</span> inventories, a representation of the proliferation pertinent physical processes, and a framework supportive of national or international perspective. They have developed a prototype global nuclear <span class="hlt">material</span> management and control systems analysis capability, the Global Nuclear <span class="hlt">Material</span> Control (GNMC) <span class="hlt">model</span>. The GNMC <span class="hlt">model</span> establishes the framework for evaluating the global production, disposition, and safeguards and security requirements for fissile nuclear <span class="hlt">material</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1813599M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1813599M&link_type=ABSTRACT"><span id="translatedtitle">Adaptive multiresolution <span class="hlt">modeling</span> of groundwater flow in heterogeneous <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Malenica, Luka; Gotovac, Hrvoje; Srzic, Veljko; Andric, Ivo</p> <p>2016-04-01</p> <p>Proposed methodology was originally developed by our scientific team in Split who designed multiresolution approach for analyzing flow and transport processes in highly heterogeneous <span class="hlt">porous</span> media. The main properties of the adaptive Fup multi-resolution approach are: 1) computational capabilities of Fup basis functions with compact support capable to resolve all spatial and temporal scales, 2) multi-resolution presentation of heterogeneity as well as all other input and output variables, 3) accurate, adaptive and efficient strategy and 4) semi-analytical properties which increase our understanding of usually complex flow and transport processes in <span class="hlt">porous</span> media. The main computational idea behind this approach is to separately find the minimum number of basis functions and resolution levels necessary to describe each flow and transport variable with the desired accuracy on a particular adaptive grid. Therefore, each variable is separately analyzed, and the adaptive and multi-scale nature of the methodology enables not only computational efficiency and accuracy, but it also describes subsurface processes closely related to their understood physical interpretation. The methodology inherently supports a mesh-free procedure, avoiding the classical numerical integration, and yields continuous velocity and flux fields, which is vitally important for flow and transport simulations. In this paper, we will show recent improvements within the proposed methodology. Since "state of the art" multiresolution approach usually uses method of lines and only spatial adaptive procedure, temporal approximation was rarely considered as a multiscale. Therefore, novel adaptive implicit Fup integration scheme is developed, resolving all time scales within each global time step. It means that algorithm uses smaller time steps only in lines where solution changes are intensive. Application of Fup basis functions enables continuous time approximation, simple interpolation calculations across</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/970919','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/970919"><span id="translatedtitle">Mechanical <span class="hlt">modeling</span> of <span class="hlt">porous</span> oxide fuel pellet A Test Problem</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nukala, Phani K; Barai, Pallab; Simunovic, Srdjan; Ott, Larry J</p> <p>2009-10-01</p> <p>A poro-elasto-plastic <span class="hlt">material</span> <span class="hlt">model</span> has been developed to capture the response of oxide fuels inside the nuclear reactors under operating conditions. Behavior of the oxide fuel and variation in void volume fraction under mechanical loading as predicted by the developed <span class="hlt">model</span> has been reported in this article. The significant effect of void volume fraction on the overall stress distribution of the fuel pellet has also been described. An important oxide fuel issue that can have significant impact on the fuel performance is the mechanical response of oxide fuel pellet and clad system. Specifically, <span class="hlt">modeling</span> the thermo-mechanical response of the fuel pellet in terms of its thermal expansion, mechanical deformation, swelling due to void formation and evolution, and the eventual contact of the fuel with the clad is of significant interest in understanding the fuel-clad mechanical interaction (FCMI). These phenomena are nonlinear and coupled since reduction in the fuel-clad gap affects thermal conductivity of the gap, which in turn affects temperature distribution within the fuel and the <span class="hlt">material</span> properties of the fuel. Consequently, in order to accurately capture fuel-clad gap closure, we need to account for fuel swelling due to generation, retention, and evolution of fission gas in addition to the usual thermal expansion and mechanical deformation. Both fuel chemistry and microstructure also have a significant effect on the nucleation and growth of fission gas bubbles. Fuel-clad gap closure leading to eventual contact of the fuel with the clad introduces significant stresses in the clad, which makes thermo-mechanical response of the clad even more relevant. The overall aim of this test problem is to incorporate the above features in order to accurately capture fuel-clad mechanical interaction. Because of the complex nature of the problem, a series of test problems with increasing multi-physics coupling features, <span class="hlt">modeling</span> accuracy, and complexity are defined with the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPS...261..363A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPS...261..363A"><span id="translatedtitle"><span class="hlt">Porous</span> carbon <span class="hlt">materials</span> for Li-S batteries based on resorcinol-formaldehyde resin with inverse opal structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agrawal, Mukesh; Choudhury, Soumyadip; Gruber, Katharina; Simon, Frank; Fischer, Dieter; Albrecht, Victoria; Göbel, Michael; Koller, Stefan; Stamm, Manfred; Ionov, Leonid</p> <p>2014-09-01</p> <p>This study reports on a novel approach to fabrication of carbon-sulfur composite <span class="hlt">material</span> and demonstrates its application as cathode for Li-S batteries. Firstly, highly <span class="hlt">porous</span> carbon <span class="hlt">material</span> has been prepared by exploiting PMMA colloidal crystal arrays as sacrificial template and subsequently mixing with elemental sulfur at 155 °C. The resulting carbon-sulfur composite cathode <span class="hlt">material</span> possess very high intrinsic surface area, conductivity and has been found to demonstrate as high as 1600 mAh g-1 capacity in 1st discharge cycle and about 300-400 mAh g-1 in 50th discharge cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhyA..437...12W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhyA..437...12W"><span id="translatedtitle">A permeability <span class="hlt">model</span> for power-law fluids in fractal <span class="hlt">porous</span> media composed of arbitrary cross-section capillaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Shifang; Wu, Tao; Qi, Hongyan; Zheng, Qiusha; Zheng, Qian</p> <p>2015-11-01</p> <p>The fractal theory and technology has been applied to determine the flow rate, the average flow velocity, and the effective permeability for the power-law fluid in <span class="hlt">porous</span> media composed of a number of tortuous capillaries/pores with arbitrary shapes, incorporating the tortuosity characteristic of flow paths. The fractal permeability and average flow velocity expressions are found to be a function of geometrical shape factors of capillaries, <span class="hlt">material</span> constants, the fractal dimensions, microstructural parameters. The effects of the porosity, the tortuosity fractal dimension, <span class="hlt">material</span> constants, and geometrical shape factors on the effective permeability are also analyzed in detail. To verify the validity of the present <span class="hlt">model</span>, our proposed <span class="hlt">model</span> is compared with the available macroscopic <span class="hlt">model</span> and experimental data and there is good agreement between them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JPS...213..229S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JPS...213..229S"><span id="translatedtitle">Magnesiothermically reduced diatomaceous earth as a <span class="hlt">porous</span> silicon anode <span class="hlt">material</span> for lithium ion batteries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Lanyao; Guo, Xianwei; Fang, Xiangpeng; Wang, Zhaoxiang; Chen, Liquan</p> <p>2012-09-01</p> <p>Three-dimensional <span class="hlt">porous</span> silicon has been prepared by magnesiothermically reducing diatomaceous earth. BET surface area analysis shows that the specific surface area of the obtained <span class="hlt">porous</span> silicon is about 96 m2 g-1, much higher than that of the diatomaceous earth (6 m2 g-1). The silicon products after HCl immersion have a <span class="hlt">porous</span> structure similar to that of the diatomaceous earth, with pore sizes around 200 nm. Galvanostatic cycling tests show that the initial charge and discharge capacities of the <span class="hlt">porous</span> silicon are 1321 mAh g-1 and 1818 mAh g-1, respectively. A reversible capacity of 633 mAh g-1 is retained after 30 cycles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6751500','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6751500"><span id="translatedtitle">Calculation of shocks in oil reservoir <span class="hlt">modeling</span> and <span class="hlt">porous</span> flow</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Concus, P.</p> <p>1982-03-01</p> <p>For many enhanced recovery methods propagating fronts arise that may be steep or discontinuous. One example is the waterflooding of a petroleum reservoir, in which there is forced out residual oil that remains after outflow by decompression has declined. In this paper high-resolution numerical methods to solve <span class="hlt">porous</span> flow problems having propagating discontinuities are discussed. The random choice method can track solution discontinuities sharply and accurately for one space dimension. The first phase of this study adapted this method for solving the Buckley-Leverett equation for immiscible displacement in one space dimension. Extensions to more than one space dimension for the random choice method were carried out subsequently by means of fractional splitting. Because inaccuracies could be introduced for some problems at dicontinuity fronts propagating obliquely to the splitting directions, efforts are currently being directed at investigating alternatives for multidimensional cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPS...309..238W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPS...309..238W"><span id="translatedtitle">Scalable preparation of <span class="hlt">porous</span> micron-SnO2/C composites as high performance anode <span class="hlt">material</span> for lithium ion battery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Ming-Shan; Lei, Ming; Wang, Zhi-Qiang; Zhao, Xing; Xu, Jun; Yang, Wei; Huang, Yun; Li, Xing</p> <p>2016-03-01</p> <p>Nano tin dioxide-carbon (SnO2/C) composites prepared by various carbon <span class="hlt">materials</span>, such as carbon nanotubes, <span class="hlt">porous</span> carbon, and graphene, have attracted extensive attention in wide fields. However, undesirable concerns of nanoparticles, including in higher surface area, low tap density, and self-agglomeration, greatly restricted their large-scale practical applications. In this study, novel <span class="hlt">porous</span> micron-SnO2/C (p-SnO2/C) composites are scalable prepared by a simple hydrothermal approach using glucose as a carbon source and Pluronic F127 as a pore forming agent/soft template. The SnO2 nanoparticles were homogeneously dispersed in micron carbon spheres by assembly with F127/glucose. The continuous three-dimensional <span class="hlt">porous</span> carbon networks have effectively provided strain relaxation for SnO2 volume expansion/shrinkage during lithium insertion/extraction. In addition, the carbon matrix could largely minimize the direct exposure of SnO2 to the electrolyte, thus ensure formation of stable solid electrolyte interface films. Moreover, the <span class="hlt">porous</span> structure could also create efficient channels for the fast transport of lithium ions. As a consequence, the p-SnO2/C composites exhibit stable cycle performance, such as a high capacity retention of over 96% for 100 cycles at a current density of 200 mA g-1 and a long cycle life up to 800 times at a higher current density of 1000 mA g-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFM.H43M1147D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AGUFM.H43M1147D&link_type=ABSTRACT"><span id="translatedtitle">Smoothed Particle Hydrodynamics <span class="hlt">Modeling</span> of Gravity Currents on a Dry <span class="hlt">Porous</span> Medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Daly, E.; Grimaldi, S.; Bui, H.</p> <p>2014-12-01</p> <p>Gravity currents flowing over <span class="hlt">porous</span> media occur in many environmental processes and industrial applications, such as irrigation, benthic boundary layers, and oil spills. The coupling of the flow over the <span class="hlt">porous</span> surface and the infiltration of the fluid in the <span class="hlt">porous</span> media is complex and difficult to <span class="hlt">model</span>. Of particular interest is the prediction of the position of the runoff front and the depth of the infiltration front. We present here a <span class="hlt">model</span> for the flow of a finite volume of a highly viscous Newtonian fluid over a dry, homogenous <span class="hlt">porous</span> medium. The Navier-Stokes equations describing the runoff flow are coupled to the Volume Averaged Navier-Stokes equations for the infiltration flow. The numerical solution of these equations is challenging because of the presence of two free surfaces (runoff and infiltration waves), the lack of fixed boundary conditions at the runoff front, and the difficulties in defining appropriate conditions at the surface of the <span class="hlt">porous</span> medium. The first two challenges were addressed by using Smoothed Particle Hydrodynamics, which is a Lagrangian, mesh-free particle method particularly suitable for <span class="hlt">modelling</span> free surface flows. Two different approaches were used to <span class="hlt">model</span> the flow conditions at the surface of the <span class="hlt">porous</span> medium. The Two Domain Approach (TDA) assumes that runoff and infiltration flows occur in two separate homogenous domains; here, we assume the continuity of velocity and stresses at the interface of the two domains. The One Domain Approach (ODA) <span class="hlt">models</span> runoff and infiltration flows as occurring through a medium whose hydraulic properties vary continuously in space. The transition from the hydraulic properties of the atmosphere and the <span class="hlt">porous</span> medium occur in a layer near the surface of the <span class="hlt">porous</span> medium. Expressions listed in literature were used to compute the thickness of this transition layer and the spatial variation of porosity and permeability within it. Our results showed that ODA led to slower velocities of the runoff</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23225752','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23225752"><span id="translatedtitle">Nitrogen-doped <span class="hlt">porous</span> carbon nanosheets as low-cost, high-performance anode <span class="hlt">material</span> for sodium-ion batteries.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Heng-guo; Wu, Zhong; Meng, Fan-lu; Ma, De-long; Huang, Xiao-lei; Wang, Li-min; Zhang, Xin-bo</p> <p>2013-01-01</p> <p>Between the sheets: Sodium-ion batteries are an attractive, low-cost alternative to lithium-ion batteries. Nitrogen-doped <span class="hlt">porous</span> carbon sheets are prepared by chemical activation of polypyrrole-functionalized graphene sheets. When using the sheets as anode <span class="hlt">material</span> in sodium-ion batteries, their unique compositional and structural features result in high reversible capacity, good cycling stability, and high rate capability. PMID:23225752</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19870040441&hterms=Media+transport&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMedia%2Btransport','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19870040441&hterms=Media+transport&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMedia%2Btransport"><span id="translatedtitle">Effect of flow oscillations on axial energy transport in a <span class="hlt">porous</span> <span class="hlt">material</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Siegel, R.</p> <p>1987-01-01</p> <p>The effects of flow oscillations on axial energy diffusion in a <span class="hlt">porous</span> medium, in which the flow is continuously disrupted by the irregularities of the <span class="hlt">porous</span> structure, are analyzed. The formulation employs an internal heat transfer coefficient that couples the fluid and solid temperatures. The final relationship shows that the axial energy transport per unit cross-sectional area and time is directly proportional to the axial temperature gradient and the square of the maximum fluid displacement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014EGUGA..16.3148G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014EGUGA..16.3148G&link_type=ABSTRACT"><span id="translatedtitle">Fate and Transport of Graphene Oxide in Granular <span class="hlt">Porous</span> Media: Experimental Results and <span class="hlt">Modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, Bin</p> <p>2014-05-01</p> <p>Although graphene oxide (GO) has been used in many applications to improve human life quality, its environmental fate and behavior are still largely unknown. In this work, a range of laboratory experiments were conducted to explore the aggregation, deposition, and transport mechanisms of GO nano-sheets in <span class="hlt">porous</span> media under various conditions. Stability experimental data showed that both cation valence and pH showed significant effect on the aggregation of GO sheets. The measured critical coagulation concentrations were in good agreement with the predictions of the extended Schulze-Hardy rule. Sand column experimental results indicated that deposition and transport of GO in <span class="hlt">porous</span> media were strongly dependent on solution ionic strength. Particularly, GO showed high mobility under low ionic strength conditions in both saturated and unsaturated columns. Increasing ionic strength dramatically increased the retention of GO in <span class="hlt">porous</span> media, mainly through secondary-minimum deposition. Recovery rates of GO in unsaturated sand columns were lower than that in saturated columns under the same ionic strength conditions, suggesting moisture content also played an important role in the retention of GO in <span class="hlt">porous</span> media. Findings from the bubble column experiments showed that the GO did not attach to the air-water interface, which is consistent with the XDLVO predictions. Additional retention mechanisms, such as film straining, thus could be responsible to the reduced mobility of GO in unsaturated <span class="hlt">porous</span> media. The breakthrough curves of GO in saturated and unsaturated columns could be accurately simulated by an advection-dispersion-reaction <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/973182','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/973182"><span id="translatedtitle">Mesoscopic <span class="hlt">modeling</span> of multi-physicochemical transport phenomena in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kang, Qinjin; Wang, Moran; Mukherjee, Partha P; Lichtner, Peter C</p> <p>2009-01-01</p> <p>We present our recent progress on mesoscopic <span class="hlt">modeling</span> of multi-physicochemical transport phenomena in <span class="hlt">porous</span> media based on the lattice Boltzmann method. Simulation examples include injection of CO{sub 2} saturated brine into a limestone rock, two-phase behavior and flooding phenomena in polymer electrolyte fuel cells, and electroosmosis in homogeneously charged <span class="hlt">porous</span> media. It is shown that the lattice Boltzmann method can account for multiple, coupled physicochemical processes in these systems and can shed some light on the underlying physics occuning at the fundamental scale. Therefore, it can be a potential powerful numerical tool to analyze multi-physicochemical processes in various energy, earth, and environmental systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24348161','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24348161"><span id="translatedtitle">Mathematical <span class="hlt">model</span> and solution for fingering phenomenon in double phase flow through homogeneous <span class="hlt">porous</span> media.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mistry, Piyush R; Pradhan, Vikas H; Desai, Khyati R</p> <p>2013-01-01</p> <p>The present paper analytically discusses the phenomenon of fingering in double phase flow through homogenous <span class="hlt">porous</span> media by using variational iteration method. Fingering phenomenon is a physical phenomenon which occurs when a fluid contained in a <span class="hlt">porous</span> medium is displaced by another of lesser viscosity which frequently occurred in problems of petroleum technology. In the current investigation a mathematical <span class="hlt">model</span> is presented for the fingering phenomenon under certain simplified assumptions. An approximate analytical solution of the governing nonlinear partial differential equation is obtained using variational iteration method with the use of Mathematica software. PMID:24348161</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/118383','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/118383"><span id="translatedtitle"><span class="hlt">Modeling</span> added compressibility of porosity and the thermomechanical response of wet <span class="hlt">porous</span> rock</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rubin, M.B.; Elata, D.; Attia, A.V.</p> <p>1995-06-01</p> <p>This paper concerned with <span class="hlt">modeling</span> the response of a <span class="hlt">porous</span> brittle solid whose pores may be dry or partially filled with fluid. A form for the Helmholtz free energy is proposed which incorporated known Mie-Grueneisen constitutive equations for the nonporous solid and for the fluid, and which uses an Eilnstein formulation with variable specific heat. In addition, a functional form for porosity is postulated which <span class="hlt">porous</span> rock. Restrictions on constitutive assumptions for the composite of <span class="hlt">porous</span> solid ad fluid are obtained which ensure thermodynamic consistency. Examples show that although the added compressibility of porosity is determined by fitting data for dry Mt. Helen Tuff, the predicted responses of saturated and partially saturated tuff agree well with experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1121534','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1121534"><span id="translatedtitle"><span class="hlt">Model</span> simulation and experiments of flow and mass transport through a nano-<span class="hlt">material</span> gas filter</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yang, Xiaofan; Zheng, Zhongquan C.; Winecki, Slawomir; Eckels, Steve</p> <p>2013-11-01</p> <p>A computational <span class="hlt">model</span> for evaluating the performance of nano-<span class="hlt">material</span> packed-bed filters was developed. The <span class="hlt">porous</span> effects of the momentum and mass transport within the filter bed were simulated. For the momentum transport, an extended Ergun-type <span class="hlt">model</span> was employed and the energy loss (pressure drop) along the packed-bed was simulated and compared with measurement. For the mass transport, a bulk dsorption <span class="hlt">model</span> was developed to study the adsorption process (breakthrough behavior). Various types of <span class="hlt">porous</span> <span class="hlt">materials</span> and gas flows were tested in the filter system where the mathematical <span class="hlt">models</span> used in the <span class="hlt">porous</span> substrate were implemented and validated by comparing with experimental data and analytical solutions under similar conditions. Good agreements were obtained between experiments and <span class="hlt">model</span> predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27412621','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27412621"><span id="translatedtitle">Illuminating solid gas storage in confined spaces - methane hydrate formation in <span class="hlt">porous</span> <span class="hlt">model</span> carbons.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Borchardt, Lars; Nickel, Winfried; Casco, Mirian; Senkovska, Irena; Bon, Volodymyr; Wallacher, Dirk; Grimm, Nico; Krause, Simon; Silvestre-Albero, Joaquín</p> <p>2016-07-27</p> <p>Methane hydrate nucleation and growth in <span class="hlt">porous</span> <span class="hlt">model</span> carbon <span class="hlt">materials</span> illuminates the way towards the design of an optimized solid-based methane storage technology. High-pressure methane adsorption studies on pre-humidified carbons with well-defined and uniform porosity show that methane hydrate formation in confined nanospace can take place at relatively low pressures, even below 3 MPa CH4, depending on the pore size and the adsorption temperature. The methane hydrate nucleation and growth is highly promoted at temperatures below the water freezing point, due to the lower activation energy in ice vs. liquid water. The methane storage capacity via hydrate formation increases with an increase in the pore size up to an optimum value for the 25 nm pore size <span class="hlt">model</span>-carbon, with a 173% improvement in the adsorption capacity as compared to the dry sample. Synchrotron X-ray powder diffraction measurements (SXRPD) confirm the formation of methane hydrates with a sI structure, in close agreement with natural hydrates. Furthermore, SXRPD data anticipate a certain contraction of the unit cell parameter for methane hydrates grown in small pores. PMID:27412621</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=40458&keyword=porous+AND+media+AND+permeability&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=74019873&CFTOKEN=66954595','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=40458&keyword=porous+AND+media+AND+permeability&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=74019873&CFTOKEN=66954595"><span id="translatedtitle">PARAMETRIC <span class="hlt">MODEL</span> FOR CONSTITUTIVE PROPERTIES GOVERNING MULTIPHASE FLOW IN <span class="hlt">POROUS</span> MEDIA</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>A parametric <span class="hlt">model</span> is developed to describe relative permeability-saturation-fluid pressure functional relationships in two- or three-fluid phase <span class="hlt">porous</span> media systems subject to monotonic saturation paths. All functions are obtained as simple closed-form expressions convenient fo...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Fract..2350017L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Fract..2350017L"><span id="translatedtitle">a Novel Fractal <span class="hlt">Model</span> for Two-Phase Relative Permeability in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lei, G.; Dong, P. C.; Mo, S. Y.; Gai, S. H.; Wu, Z. S.</p> <p>2015-03-01</p> <p>Multiphase flow in <span class="hlt">porous</span> media is very important in various scientific and engineering fields. It has been shown that relative permeability plays an important role in determination of flow characteristics for multiphase flow. The accurate prediction of multiphase flow in <span class="hlt">porous</span> media is hence highly important. In this work, a novel predictive <span class="hlt">model</span> for relative permeability in <span class="hlt">porous</span> media is developed based on the fractal theory. The predictions of two-phase relative permeability by the current mathematical <span class="hlt">models</span> have been validated by comparing with available experimental data. The predictions by the proposed <span class="hlt">model</span> show the same variation trend with the available experimental data and are in good agreement with the existing experiments. Every parameter in the proposed <span class="hlt">model</span> has clear physical meaning. The proposed relative permeability is expressed as a function of the immobile liquid film thickness, pore structural parameters (pore fractal dimension Df and tortuosity fractal dimension DT) and fluid viscosity ratio. The effects of these parameters on relative permeability of <span class="hlt">porous</span> media are discussed in detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=40971&keyword=ass&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=76765574&CFTOKEN=70444695','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=40971&keyword=ass&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=76765574&CFTOKEN=70444695"><span id="translatedtitle"><span class="hlt">MODELING</span> MULTICOMPONENT ORGANIC CHEMICAL TRANSPORT IN THREE-FLUID-PHASE <span class="hlt">POROUS</span> MEDIA</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>A two dimensional finite-element <span class="hlt">model</span> was developed to predict coupled transient flow and multicomponent transport of organic chemicals which can partition between NAPL, water, gas and solid phases in <span class="hlt">porous</span> media under the assumption of local chemical equilibrium. as-phase pres...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=130232&keyword=Fluid+AND+Density&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=64965664&CFTOKEN=31477349','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=130232&keyword=Fluid+AND+Density&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=64965664&CFTOKEN=31477349"><span id="translatedtitle"><span class="hlt">MODELING</span> MULTICOMPONENT ORGANIC CHEMICAL TRANSPORT IN THREE FLUID PHASE <span class="hlt">POROUS</span> MEDIA</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>A two-dimensional finite-element <span class="hlt">model</span> was developed to predict coupled transient flow and multicomponent transport of organic chemicals which can partition between nonaqueous phase liquid, water, gas and solid phases in <span class="hlt">porous</span> media under the assumption of local chemical equilib...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=128645&keyword=science+AND+fair&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=77683884&CFTOKEN=77837203','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=128645&keyword=science+AND+fair&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=77683884&CFTOKEN=77837203"><span id="translatedtitle">A KINETIC <span class="hlt">MODEL</span> FOR CELL DENSITY DEPENDENT BACTERIAL TRANSPORT IN <span class="hlt">POROUS</span> MEDIA</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>A kinetic transport <span class="hlt">model</span> with the ability to account for variations in cell density of the aqueous and solid phases was developed for bacteria in <span class="hlt">porous</span> media. Sorption kinetics in the advective-dispersive-sorptive equation was described by assuming that adsorption was proportio...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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