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Sample records for model porous materials

  1. Modeling of porous elastic viscoplastic material with tensile failure

    SciTech Connect

    Glenn, L A; Rubin, M; Vorobiev, O

    1998-11-01

    This work describes simple but comprehensive constitutive equations that model a number of physical phenomena exhibited by dry porous geological materials and metals. Moreover, formulas have been developed for robust numerical integration of the evolution equations at the element level that can be easily implemented into standard computer programs for dynamic response of materials.

  2. Modeling of shape memory alloys and application to porous materials

    NASA Astrophysics Data System (ADS)

    Panico, Michele

    In the last two decades the number of innovative applications for advanced materials has been rapidly increasing. Shape memory alloys (SMAs) are an exciting class of these materials which exhibit large reversible stresses and strains due to a thermoelastic phase transformation. SMAs have been employed in the biomedical field for producing cardiovascular stents, shape memory foams have been successfully tested as bone implant material, and SMAs are being used as deployable switches in aerospace applications. The behavior of shape memory alloys is intrinsically complex due to the coupling of phase transformation with thermomechanical loading, so it is critical for constitutive models to correctly simulate their response over a wide range of stress and temperature. In the first part of this dissertation, we propose a macroscopic phenomenological model for SMAs that is based on the classical framework of thermodynamics of irreversible processes and accounts for the effect of multiaxial stress states and non-proportional loading histories. The model is able to account for the evolution of both self-accommodated and oriented martensite. Moreover, reorientation of the product phase according to loading direction is specifically accounted for. Computational tests demonstrate the ability of the model to simulate the main aspects of the shape memory response in a one-dimensional setting and some of the features that have been experimentally found in the case of multi-axial non-proportional loading histories. In the second part of this dissertation, this constitutive model has been used to study the mesoscopic behavior of porous shape memory alloys with particular attention to the mechanical response under cyclic loading conditions. In order to perform numerical simulations, the model was implemented into the commercial finite element code ABAQUS. Due to stress concentrations in a porous microstructure, the constitutive law was enhanced to account for the development of

  3. 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.

  4. Modelling dynamic compaction of porous materials with the overstress approach

    NASA Astrophysics Data System (ADS)

    Partom, Y.

    2014-05-01

    To model compaction of a porous material we need 1) an equation of state of the porous material in terms of the equation of state of its matrix, and 2) a compaction law. For an equation of state it is common to use Herrmann's suggestion, as in his Pα model. For a compaction law it is common to use a quasi-static compaction relation obtained from 1) a meso-scale model (as in Carroll and Holt's spherical shell model), or from 2) quasi-static tests. Here we are interested in dynamic compaction, like in a planar impact test. In dynamic compaction the state may change too fast for the state point to follow the quasi-static compaction curve. We therefore get an overstress situation. The state point moves out of the quasi-static compaction boundary, and only with time collapses back towards it at a certain rate. In this way the dynamic compaction event becomes rate dependent. In the paper we first write down the rate equations for dynamic compaction according to the overstress approach. We then implement these equations in a hydro-code and run some examples. We show how the overstress rate parameter can be calibrated from tests.

  5. 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.

  6. Modeling Dynamic Compaction of Porous Materials with the Overstress Approach

    NASA Astrophysics Data System (ADS)

    Partom, Yehuda

    2013-06-01

    To model compaction of a porous material (PM) we need 1) an equation of state (EOS) of the PM in terms of the EOS of its matrix, and 2) a compaction law. For the EOS it is common to use Herrmann's suggestion, as in his P α model. For a compaction law it is common to use a quasi-static compaction relation obtained from 1) a mezzo-scale model (as in Carroll and Holt's spherical shell model), or from 2) quasi-static tests. Here we are interested in dynamic compaction, like in a planar impact test. In dynamic compaction, the state may change too fast for the state point to follow the quasi-static compaction curve. We therefore get an overstress situation. The state point moves out of the quasi-static compaction boundary, and only with time collapses back towards it at a certain rate. In this way the dynamic compaction event becomes rate dependent. In the paper we first write down the rate equations for dynamic compaction according to this overstress approach. We then implement these equations in a hydro-code, and run some examples. We show how the overstress rate parameter can be calibrated from tests.

  7. 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.

  8. DDT modeling and shock compression experiments of porous or damaged energetic materials

    SciTech Connect

    Baer, M.R.; Anderson, M.U.; Graham, R.A.

    1994-05-01

    In this presentation, we present modeling of DDT in porous energetic materials and experimental studies of a time-resolved, shock compression of highly porous inert and reactive materials. This combined theoretical and experimental studies explore the nature of the microscale processes of consolidation, deformation and reaction which are key features of the shock response of porous or damaged energetic materials. The theoretical modeling is based on the theory of mixtures in which multiphase mixtures are treated in complete nonequilibrium allowing for internal boundary effects associated mass/momentum and energy exchange between phases, relative flow, rate-dependent compaction behavior, multistage chemistry and interphase boundary effects. Numerous studies of low-velocity impacts using a high resolution adaptive finite element method are presented which replicate experimental observations. The incorporation of this model into multi-material hydrocode analysis will be discussed to address the effects of confinement and its influence on accelerated combustion behavior. The experimental studies will focus on the use of PVDF piezoelectric polymer stress-rate gauge to precisely measure the input and propagating shock stress response of porous materials. In addition to single constituent porous materials, such as granular HMX, we have resolved shock waves in porous composite intermetallic powders that confirm a dispersive wave nature which is highly morphologically and material dependent. This document consists of viewgraphs from the poster session.

  9. Preparation of asymmetric porous materials

    DOEpatents

    Coker, Eric N [Albuquerque, NM

    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.

  10. A Transverse Dynamic Deflection Model for Thin Plate Made of Saturated Porous Materials

    NASA Astrophysics Data System (ADS)

    Feng-xi, Zhou; Xiao-lin, Cao

    2016-10-01

    In this article, a transverse dynamic deflection model is established for thin plate made of saturated porous materials. Based on the Biot's model for fluid-saturated porous media, using the Love-Kirchhoff hypothesis, the governing equations of transverse vibrations of fluid-saturated poroelastic plates are derived in detail, which take the inertial, fluid viscous, mechanical couplings, compressibility of solid, and fluid into account. The free vibration and forced vibration response of a simply supported poroelastic rectangular plate is obtained by Fourier series expansion method. Through numerical examples, the effect of porosity and permeability on the dynamic response, including the natural frequency, amplitude response, and the resonance areas is assessed.

  11. Porous material neutron detector

    DOEpatents

    Diawara, Yacouba [Oak Ridge, TN; Kocsis, Menyhert [Venon, FR

    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.

  12. 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.

  13. Supersonic flow around a cylinder with front gas-permeable insert which modeled by skeleton of porous material

    NASA Astrophysics Data System (ADS)

    Poplavskaya, T. V.; Kirilovskiy, S. V.; Mironov, S. G.

    2016-10-01

    Experimental data and results of numerical simulation of a supersonic flow around a streamwise aligned cylinder with a frontal gas-permeable insert made of a high-porosity cellular material are presented. The porous material structure is modeled by a system of staggered rings of different diameters (discrete model of a porous medium). The model skeleton of the material corresponds to the pore size (diameter 1mm) and porosity (0.95) of a real cellular porous material. The computed results are compared with the data of wind tunnel experiments performed in a T-327B supersonic continuous-flow wind tunnel at the flow Mach number M∞ = 4.85.

  14. 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.

  15. 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

  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. Analytical Fractal Model for Calculating Effective Thermal Conductivity of the Fibrous Porous Materials.

    PubMed

    Kan, An-Kang; Cao, Dan; Zhang, Xue-Lai

    2015-04-01

    Accurately predicting the effective thermal conductivity of the fibrous materials is highly desirable but remains to be a challenging work. In this paper, the microstructure of the porous fiber materials is analyzed, approximated and modeled on basis of the statistical self-similarity of fractal theory. A fractal model is presented to accurately calculate the effective thermal conductivity of fibrous porous materials. Taking the two-phase heat transfer effect into account, the existing statistical microscopic geometrical characteristics are analyzed and the Hertzian Contact solution is introduced to calculate the thermal resistance of contact points. Using the fractal method, the impacts of various factors, including the porosity, fiber orientation, fractal diameter and dimension, rarified air pressure, bulk thermal conductivity coefficient, thickness and environment condition, on the effective thermal conductivity, are analyzed. The calculation results show that the fiber orientation angle caused the material effective thermal conductivity to be anisotropic, and normal distribution is introduced into the mathematic function. The effective thermal conductivity of fibrous material increases with the fiber fractal diameter, fractal dimension and rarefied air pressure within the materials, but decreases with the increase of vacancy porosity.

  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. Highly porous thermal protection materials: Modelling and prediction of the methodical experimental errors

    NASA Astrophysics Data System (ADS)

    Cherepanov, Valery V.; Alifanov, Oleg M.; Morzhukhina, Alena V.; Budnik, Sergey A.

    2016-11-01

    The formation mechanisms and the main factors affecting the systematic error of thermocouples were investigated. According to the results of experimental studies and mathematical modelling it was established that in highly porous heat resistant materials for aerospace application the thermocouple errors are determined by two competing mechanisms provided correlation between the errors and the difference between radiation and conduction heat fluxes. The comparative analysis was carried out and some features of the methodical error formation related to the distances from the heated surface were established.

  20. Diffusion in porous crystalline materials.

    PubMed

    Krishna, Rajamani

    2012-04-21

    The design and development of many separation and catalytic process technologies require a proper quantitative description of diffusion of mixtures of guest molecules within porous crystalline materials. This tutorial review presents a unified, phenomenological description of diffusion inside meso- and micro-porous structures. In meso-porous materials, with pore sizes 2 nm < d(p) < 50 nm, there is a central core region where the influence of interactions of the molecules with the pore wall is either small or negligible; meso-pore diffusion is governed by a combination of molecule-molecule and molecule-pore wall interactions. Within micro-pores, with d(p) < 2 nm, the guest molecules are always under the influence of the force field exerted with the wall and we have to reckon with the motion of adsorbed molecules, and there is no "bulk" fluid region. The characteristics and physical significance of the self-, Maxwell-Stefan, and Fick diffusivities are explained with the aid of data obtained either from experiments or molecular dynamics simulations, for a wide variety of structures with different pore sizes and topology. The influence of adsorption thermodynamics, molecular clustering, and segregation on both magnitudes and concentration dependences of the diffusivities is highlighted. In mixture diffusion, correlations in molecular hops have the effect of slowing-down the more mobile species. The need for proper modeling of correlation effects using the Maxwell-Stefan formulation is stressed with the aid of examples of membrane separations and catalytic reactors.

  1. Mathematical model of heat and mass transfer in a bidisperse porous material

    NASA Astrophysics Data System (ADS)

    Moshinskii, A. I.

    2009-09-01

    A model of heat and mass processes in a body with two types of pores is considered. This model describes the initial stage of substance penetration into the porous system (or the inverse process, namely, substance extraction from the system) and takes into account convective transport in large channels. A kinetic function of impregnation (extraction) of the porous medium and the substance flux density are found for a problem with additional conditions.

  2. Emergence of molecular recognition phenomena in a simple model of imprinted porous materials

    NASA Astrophysics Data System (ADS)

    Dourado, Eduardo M. A.; Sarkisov, Lev

    2009-06-01

    Polymerization in the presence of templates, followed by their consequent removal, leads to structures with cavities capable of molecular recognition. This molecular imprinting technology has been employed to create porous polymers with tailored selectivity for adsorption, chromatographic separations, sensing, and other applications. Performance of these materials crucially depends on the availability of highly selective binding sites. This parameter is a function of a large number of processing conditions and is difficult to control. Furthermore, the nature of molecular recognition processes in these materials is poorly understood to allow a more systematic design. In this work we propose a simple model of molecularly imprinted polymers mimicking the actual process of their formation. We demonstrate that a range of molecular recognition effects emerge in this model and that they are consistent with the experimental observations. The model also provides a wealth of information on how binding sites form and function in the imprinted structures. It demonstrates the capability to assess the role of various processing conditions in the final properties of imprinted materials, and therefore it can be used to provide some qualitative insights on the optimal values of processing parameters.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. 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.

  5. 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.

  6. Hyper-elastic modeling and mechanical behavior investigation of porous poly-D-L-lactide/nano-hydroxyapatite scaffold material.

    PubMed

    Han, Quan Feng; Wang, Ze Wu; Tang, Chak Yin; Chen, Ling; Tsui, Chi Pong; Law, Wing Cheung

    2017-03-28

    Poly-D-L-lactide/nano-hydroxyapatite (PDLLA/nano-HA) can be used as the biological scaffold material in bone tissue engineering as it can be readily made into a porous composite material with excellent performance. However, constitutive modeling for the mechanical response of porous PDLLA/nano-HA under various stress conditions has been very limited so far. In this work, four types of fundamental compressible hyper-elastic constitutive models were introduced for constitutive modeling and investigation of mechanical behaviors of porous PDLLA/nano-HA. Moreover, the unitary expressions of Cauchy stress tensor have been derived for the PDLLA/nano-HA under uniaxial compression (or stretch), biaxial compression (or stretch), pure shear and simple shear load by using the theory of continuum mechanics. The theoretical results determined from the approach based on the Ogden compressible hyper-elastic constitutive model were in good agreement with the experimental data from the uniaxial compression tests. Furthermore, this approach can also be used to predict the mechanical behaviors of the porous PDLLA/nano-HA material under the biaxial compression (or stretch), pure shear and simple shear.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Mathematical Model of Porous Medium Dynamics

    NASA Astrophysics Data System (ADS)

    Gerschuk, Peotr; Sapozhnikov, Anatoly

    1999-06-01

    Semiempirical model describing porous material strains under pulse mechanical and thermal loadings is proposed. Porous medium is considered as continuous one but with special form of pressure dependence upon strain. This model takes into account principal features of porous materials behavior which can be observed when the material is strained in dynamic and static experiments ( non-reversibility of large strains, nonconvexity of loading curve). Elastoplastic properties of porous medium, its damages when it is strained and dynamic fracture are also taken into account. Dispersion of unidirectional motion caused by medium heterogeneity (porousness) is taken into acount by introducing the physical viscosity depending upon pores size. It is supposed that at every moment of time pores are in equilibrium with pressure i.e. kinetic of pores collapse is not taken into account. The model is presented by the system of differential equations connecting pressure and energy of porous medium with its strain. These equations close system of equations of motion and continuity which then is integrated numerically. The proposed model has been tested on carbon materials and porous copper . Results of calculation of these materials shock compressing are in satisfactory agreement with experimental data. Results of calculation of thin plate with porous copper layer collision are given as an illustration.

  12. 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.

  13. 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.

  14. 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.

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

    SciTech Connect

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

    1991-03-13

    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 tc 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.

  16. 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.

  17. 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.

  18. 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.

  19. Magnetic porous composite material: Synthesis and properties

    NASA Astrophysics Data System (ADS)

    Peretyat'ko, P. I.; Kulikov, L. A.; Melikhov, I. V.; Perfil'ev, Yu. D.; Pal', A. F.; Timofeev, M. A.; Gudoshnikov, S. A.; Usov, N. A.

    2015-10-01

    A new method of obtaining magnetic porous composite materials is described, which is based on the self-propagating high-temperature synthesis (SHS) in the form of solid-phase combustion. The SHS process involves transformation of the nonmagnetic α-Fe2O3 particles (contained in the initial mixture) into magnetic Fe3O4 particles. The synthesized material comprises a porous carbonaceous matrix with immobilized Fe3O4 particles. The obtained composite has been characterized by electron microscopy, X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. The sorption capacity of the porous material has been studied.

  20. 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

  1. Methane storage in advanced porous materials.

    PubMed

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

    2012-12-07

    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.

  2. 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.

  3. 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

  4. 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.

  5. Engineering porous materials for fuel cell applications.

    PubMed

    Brandon, N P; Brett, D J

    2006-01-15

    Porous materials play an important role in fuel cell engineering. For example, they are used to support delicate electrolyte membranes, where mechanical integrity and effective diffusivity to fuel gases is critical; they are used as gas diffusion layers, where electronic conductivity and permeability to both gas and water is critical; and they are used to construct fuel cell electrodes, where an optimum combination of ionic conductivity, electronic conductivity, porosity and catalyst distribution is critical. The paper will discuss these characteristics, and introduce the materials and processing methods used to engineer porous materials within two of the leading fuel cell variants, the solid oxide fuel cell and the polymer electrolyte membrane fuel cell.

  6. 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.

  7. Modelling Assisted Design and Synthesis of Highly Porous Materials for Chemical Adsorbents

    DTIC Science & Technology

    2010-10-01

    Perspectives : On dispose des coordonnées atomiques précises pour les études par modélisation de la sorption des nouveaux matériaux MOF, ainsi que leurs...SURFACE AREA (m2/g) COMMENTS Cu3H3ADTP(OH)·3H2O 200 2800m2/g predicted for N2 absorption by modelling for desolvated MOF SrPTAB 146 Zn(H2DHBP

  8. Parameterization of the Porous-Material Model for Sand with Different Levels of Water Saturation

    DTIC Science & Technology

    2008-01-01

    points in AUTODYN ) was fitted to a polynomial function and modified by: (a) correcting density with a a0b0rw term and (b) introducing a moisture-level...counterparts. All the calculations carried out in this section were done using AUTODYN , a general purpose non-linear dynamics modeling and simulation...software [13]. In this section, a brief overview is given of the basic features of AUTODYN , emphasizing the aspects of this computer program, which

  9. Tuneable porous carbonaceous materials from renewable resources.

    PubMed

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

    2009-12-01

    Porous carbon materials are ubiquitous with a wide range of technologically important applications, including separation science, heterogeneous catalyst supports, water purification filters, stationary phase materials, as well as the developing future areas of energy generation and storage applications. Hard template routes to ordered mesoporous carbons are well established, but whilst offering different mesoscopic textural phases, the surface of the material is difficult to chemically post-modify and processing is energy, resource and step intensive. The production of carbon materials from biomass (i.e. sugars or polysaccharides) is a relatively new but rapidly expanding research area. In this tutorial review, we compare and contrast recently reported routes to the preparation of porous carbon materials derived from renewable resources, with examples of our previously reported mesoporous polysaccharide-derived "Starbon" carbonaceous material technology.

  10. Porous polymeric materials for hydrogen storage

    DOEpatents

    Yu, Luping [Hoffman Estates, IL; Liu, Di-Jia [Naperville, IL; Yuan, Shengwen [Chicago, IL; Yang, Junbing [Westmont, IL

    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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. Templated Electrodeposition of Highly Porous Nanostructured Materials

    NASA Astrophysics Data System (ADS)

    Yang, Han-Chang; Lim, Stephanie; Liu, Jiabin; Wu, Qian; Cheng, X. M.

    2011-03-01

    The fabrication of nanoporous materials has been of great interest for applications such as biosensors, photonic materials and energy storage. Compared to many other methods, the templated electrodeposition method is low cost, fast, and compatible with large-scale production. In this work, we developed a templated electrochemical deposition technique for fabricating highly ordered and highly porous nanostructured materials. The fabrication involves the following steps: self-assembly of monodispersed polystyrene spheres, electrochemical deposition of the desired materials, and sphere removal by a dissolution process. Deposition of Au and Ni layered metallic nanoporous structures were studied using different electrolytes at appropriate potentials. The pore size of the materials was tuned by using different sizes of template polystyrene spheres ranging from 50nm to 1000nm. Scanning electron microscopy images confirmed the highly ordered 3-dimensional hexagonal closed pack (hcp) structures in the samples. The templated electrochemical deposition technique provides a promising alternative approach to preparing highly porous anode materials for battery applications. Work supported by Bryn Mawr K/G fund for faculty research.

  1. Ironless transducer for measuring the mechanical properties of porous materials

    NASA Astrophysics Data System (ADS)

    Doutres, Olivier; Dauchez, Nicolas; Genevaux, Jean-Michel; Lemarquand, Guy; Mezil, Sylvain

    2010-05-01

    This paper presents a measurement setup for determining the mechanical properties of porous materials at low and medium frequencies by extending toward higher frequencies the quasistatic method based on a compression test. Indeed, classical quasistatic methods generally neglect the inertia effect of the porous sample and the coupling between the surrounding fluid and the frame; they are restricted to low frequency range (<100 Hz) or specific sample shape. In the present method, the porous sample is placed in a cavity to avoid a lateral airflow. Then a specific electrodynamic ironless transducer is used to compress the sample. This highly linear transducer is used as actuator and sensor; the mechanical impedance of the porous sample is deduced from the measurement of the electrical impedance of the transducer. The loss factor and the Young's modulus of the porous material are estimated by inverse method based on the Biot's model. Experimental results obtained with a polymer foam show the validity of the method in comparison with quasistatic method. The frequency limit has been extended from 100 Hz to 500 Hz. The sensitivity of each input parameter is estimated in order to point out the limitations of the method.

  2. 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.

  3. Autoignition of combustible fluids in porous insulation materials

    SciTech Connect

    McIntosh, A.C.; Bains, M.; Crocombe, W.; Griffiths, J.F. )

    1994-12-01

    The leakage of combustible fluids into the lagging of pipework in the process engineering industry can be very hazardous because of the increased residence time for oxidation as the liquid resides in the porous medium and also the substantially modified heat and mass transfer rates when compared with ignition at hot surfaces. The exothermic reaction can lead to ignition or at least severe self-heating with the consequent damage of pipework, etc. Experiments have been performed to simulate this hazard. The thermal behavior of a number of combustible liquids placed in porous material has been monitored and evidence is presented in this work that self-heating can indeed take place. It has been found that autoignition occurs at an important watershed oven temperature that is related to the volatility of the combustible fluid. A mathematical model for the autoignition of combustible liquid in an inert porous material is presented. The simple model takes a spatially uniform approach to both the energy equation and the liquid equation for the fluid and predicts a watershed temperature such that for a given concentration of fluid in the porous material, the thermal behavior of the system alters abruptly. For all practical purposes, thermal runaway is predicted beyond this watershed condition even though the classical Semenov theory simply predicts an eventual decay to a stable steady state, with no strict criticality prediction. The watershed temperature is shown to depend on volatility and reactivity.

  4. Mechanical properties of a porous mullite material

    NASA Technical Reports Server (NTRS)

    Viens, Michael J.

    1991-01-01

    Modulus of rupture specimens were used to determine crack growth parameters of a porous mullite material. Strength testing was performed in ambient and moist environments. The power law crack growth rate parameters n and 1n B in 50 percent relative humidity were found to be 44.98 and 0.94, respectively. The inert strength, fracture toughness, and elastic modulus were also determined and found to be 19 MPa, 055 MPa(m) exp 1/2, and 11.6 GPa, respectively.

  5. 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.

  6. 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.

  7. Molecular Rotors Built in Porous Materials.

    PubMed

    Comotti, Angiolina; Bracco, Silvia; Sozzani, Piero

    2016-09-20

    Molecules and materials can show dynamic structures in which the dominant mechanism is rotary motion. The single mobile elements are defined as "molecular rotors" and exhibit special properties (compared with their static counterparts), being able in perspective to greatly modulate the dielectric response and form the basis for molecular motors that are designed with the idea of making molecules perform a useful mechanical function. The construction of ordered rotary elements into a solid is a necessary feature for such design, because it enables the alignment of rotors and the fine-tuning of their steric and dipolar interactions. Crystal surfaces or bulk crystals are the most suitable to adapt rotors in 2D or 3D arrangements and engineer juxtaposition of the rotors in an ordered way. Nevertheless, it is only in recent times that materials showing porosity and remarkably low density have undergone tremendous development. The characteristics of large free volume combine well with the virtually unhindered motion of the molecular rotors built into their structure. Indeed, the molecular rotors are used as struts in porous covalent and supramolecular architectures, spanning both hybrid and fully organic materials. The modularity of the approach renders possible a variety of rotor geometrical arrangements in both robust frameworks stable up to 850 K and self-assembled molecular materials. A nanosecond (fast dynamics) motional regime can be achieved at temperatures lower than 240 K, enabling rotor arrays operating in the solid state even at low temperatures. Furthermore, in nanoporous materials, molecular rotors can interact with the diffusing chemical species, be they liquids, vapors, or gases. Through this chemical intervention, rotor speed can be modulated at will, enabling a new generation of rotor-containing materials sensitive to guests. In principle, an applied electric field can be the stimulus for chemical release from porous materials. The effort needed to

  8. Siloxane treatment by adsorption into porous materials.

    PubMed

    Ricaurte Ortega, D; Subrenat, A

    2009-09-01

    Siloxanes are widely used in different applications: health care, dry cleaning, household products, paints and coatings, paper, personal care, for example. This explains their prevalence in the environment. Because of their volatile nature, most of the time they are dispersed in the atmosphere, but they can also be present in the slurry from landfills. During anaerobic digestion, when the temperature goes up to 60 degrees C, siloxanes are volatilized, forming part of the biogas. Operational problems using biogas to produce energy, heat and hydrogen have been identified. At high temperatures the siloxanes are transformed into silicate dioxide (commonly called sand transmission). These white deposits may adhere to metal or catalytic substrate surfaces, seriously reducing equipment efficiency, and this can be a reason for changing equipment warranties. Consequently, elimination of siloxanes has become very important. Unfortunately, relatively little information can be found on this subject. Nevertheless some authors have described different analytical methods for siloxane quantification, and recent studies have looked at the presence of siloxanes in landfills and the restriction on the energy recovery equipment using the biogas produced. The growing consumption of siloxanes and silicones in industrial processes consequently increase their prevalence in the environment, hampering the use of biogas as a source of 'green energy'. Therefore, the principal focus of this study is the treatment of siloxanes. Their elimination was carried out using an adsorption process with four different porous materials: activated carbon cloths (ACC), granular activated carbon (GAC), zeolite and silica gel. Two representative siloxane compounds were used in this study, hexamethyldisiloxane (L2) and octamethylcyclotetrasiloxane (D4). Adsorption kinetics and isotherms in batch reactors were performed. It was observed that the mass transfer into the porous material was more rapid for the

  9. 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, {\

  10. Development of highly porous carbon and ceramic materials

    NASA Astrophysics Data System (ADS)

    Aoki, Yasuyuki

    The objectives of this thesis were to develop new methods for manufacturing highly porous and low-density carbon and ceramic materials by simple methods using low-cost precursors, which can exhibit high corrosion resistance and high-temperature performance with advantageous porous microstructure. Various types of porous carbon materials were manufactured using different techniques. These materials included porous carbons fabricated by paper making technology, foamed resin based carbons, resin powder based porous carbons and carbon bonded carbon fibre composites. Then, these different forms of porous carbon preforms were converted into lightweight and low-density ceramics by two main fabrication routes. In the first route, porous carbon-ceramic composites were manufactured by infiltration of a mixture of silica sol-gels and a resin carbon source into porous carbon preforms. The silica was subsequently converted into SiC or Si3N4 by carbothermal reduction or nitridation, respectively. Furthermore, boron oxide glass was impregnated in addition to SiC. However, the porous carbon-ceramic composites from this fabrication method exhibited poor high-temperature performance due to low oxidation resistance.In the second route, porous carbon preforms were directly converted into porous SiC materials by a reaction bonding technique with silicon vapour infiltration. The ceramics produced by this route were proved to have high potentiality as lightweight and low-density materials at elevated temperatures and corrosive atmospheres, with modified mechanical properties. Structural and morphological characterizations of the porous materials were carried out using optical and electron microscopy, diffraction and spectroscopic techniques. Mechanical properties were also measured including flexural, tensile and compressive strength, and elastic modulus at room and elevated temperatures, and the results of mechanical properties were analyzed in relation to density/porosity values

  11. Imparting amphiphobicity on single-crystalline porous materials.

    PubMed

    Sun, Qi; He, Hongming; Gao, Wen-Yang; Aguila, Briana; Wojtas, Lukasz; Dai, Zhifeng; Li, Jixue; Chen, Yu-Sheng; Xiao, Feng-Shou; Ma, Shengqian

    2016-10-31

    The sophisticated control of surface wettability for target-specific applications has attracted widespread interest for use in a plethora of applications. Despite the recent advances in modification of non-porous materials, surface wettability control of porous materials, particularly single crystalline, remains undeveloped. Here we contribute a general method to impart amphiphobicity on single-crystalline porous materials as demonstrated by chemically coating the exterior of metal-organic framework (MOF) crystals with an amphiphobic surface. As amphiphobic porous materials, the resultant MOF crystals exhibit both superhydrophobicity and oleophobicity in addition to retaining high crystallinity and intact porosity. The chemical shielding effect resulting from the amphiphobicity of the MOFs is illustrated by their performances in water/organic vapour adsorption, as well as long-term ultrastability under highly humidified CO2 environments and exceptional chemical stability in acid/base aqueous solutions. Our work thereby pioneers a perspective to protect crystalline porous materials under various chemical environments for numerous applications.

  12. Imparting amphiphobicity on single-crystalline porous materials

    NASA Astrophysics Data System (ADS)

    Sun, Qi; He, Hongming; Gao, Wen-Yang; Aguila, Briana; Wojtas, Lukasz; Dai, Zhifeng; Li, Jixue; Chen, Yu-Sheng; Xiao, Feng-Shou; Ma, Shengqian

    2016-10-01

    The sophisticated control of surface wettability for target-specific applications has attracted widespread interest for use in a plethora of applications. Despite the recent advances in modification of non-porous materials, surface wettability control of porous materials, particularly single crystalline, remains undeveloped. Here we contribute a general method to impart amphiphobicity on single-crystalline porous materials as demonstrated by chemically coating the exterior of metal-organic framework (MOF) crystals with an amphiphobic surface. As amphiphobic porous materials, the resultant MOF crystals exhibit both superhydrophobicity and oleophobicity in addition to retaining high crystallinity and intact porosity. The chemical shielding effect resulting from the amphiphobicity of the MOFs is illustrated by their performances in water/organic vapour adsorption, as well as long-term ultrastability under highly humidified CO2 environments and exceptional chemical stability in acid/base aqueous solutions. Our work thereby pioneers a perspective to protect crystalline porous materials under various chemical environments for numerous applications.

  13. 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.

  14. 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.

  15. Studies of acoustical properties of bulk porous flexible materials

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1984-01-01

    Acoustic prediction and measurement of bulk porous materials with flexible frames is investigated. The acoustic properties of Kevlar 29 are examined. Various acoustic tests are employed to determine impedance, sound wave propagation, and wave pressure equations for the highly porous fiber composites. The derivation of design equations and future research goals are included.

  16. A multi-scale Lattice Boltzmann model for simulating solute transport in 3D X-ray micro-tomography images of aggregated porous materials

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoxian; Crawford, John W.; Flavel, Richard J.; Young, Iain M.

    2016-10-01

    The Lattice Boltzmann (LB) model and X-ray computed tomography (CT) have been increasingly used in combination over the past decade to simulate water flow and chemical transport at pore scale in porous materials. Because of its limitation in resolution and the hierarchical structure of most natural soils, the X-ray CT tomography can only identify pores that are greater than its resolution and treats other pores as solid. As a result, the so-called solid phase in X-ray images may in reality be a grey phase, containing substantial connected pores capable of conducing fluids and solute. Although modified LB models have been developed to simulate fluid flow in such media, models for solute transport are relatively limited. In this paper, we propose a LB model for simulating solute transport in binary soil images containing permeable solid phase. The model is based on the single-relaxation time approach and uses a modified partial bounce-back method to describe the resistance caused by the permeable solid phase to chemical transport. We derive the relationship between the diffusion coefficient and the parameter introduced in the partial bounce-back method, and test the model against analytical solution for movement of a pulse of tracer. We also validate it against classical finite volume method for solute diffusion in a simple 2D image, and then apply the model to a soil image acquired using X-ray tomography at resolution of 30 μm in attempts to analyse how the ability of the solid phase to diffuse solute at micron-scale affects the behaviour of the solute at macro-scale after a volumetric average. Based on the simulated results, we discuss briefly the danger in interpreting experimental results using the continuum model without fully understanding the pore-scale processes, as well as the potential of using pore-scale modelling and tomography to help improve the continuum models.

  17. Modulation power of porous materials and usage as ripple filter in particle therapy.

    PubMed

    Printz Ringbæk, Toke; Simeonov, Yuri; Witt, Matthias; Engenhart-Cabillic, Rita; Kraft, Gerhard; Zink, Klemens; Weber, Uli

    2017-04-07

    Porous materials with microscopic structures like foam, sponges, lung tissues and lung substitute materials have particular characteristics, which differ from those of solid materials. Ion beams passing through porous materials show much stronger energy straggling than expected for non-porous solid materials of the same thickness. This effect depends on the microscopic fine structure, the density and the thickness of the porous material. The beam-modulating effect from a porous plate enlarges the Bragg peak, yielding similar benefits in irradiation time reduction as a ripple filter. A porous plate can additionally function as a range shifter, which since a higher energy can be selected for the same penetration depth in the body reduces the scattering at the beam line and therefore improves the lateral fall-off. Bragg curve measurements of ion beams passing through different porous materials have been performed in order to determine the beam modulation effect of each. A mathematical model describing the correlation between the mean material density, the porous pore structure size and the strength of the modulation has been developed and a new material parameter called 'modulation power' is defined as the square of the Gaussian sigma divided by the mean water-equivalent thickness of the porous absorber. Monte Carlo simulations have been performed in order to validate the model and to investigate the Bragg peak enlargement, the scattering effects of porosity and the lateral beam width at the end of the beam range. The porosity is found to only influence the lateral scattering in a negligible way. As an example of a practical application, it is found that a 20 mm and 50 mm plate of Gammex LN300 performs similar to a 3 mm and 6 mm ripple filter, respectively, and at the same time can improve the sharpness of the lateral beam due to its multifunctionality as a ripple filter and a range shifter.

  18. Modulation power of porous materials and usage as ripple filter in particle therapy

    NASA Astrophysics Data System (ADS)

    Printz Ringbæk, Toke; Simeonov, Yuri; Witt, Matthias; Engenhart-Cabillic, Rita; Kraft, Gerhard; Zink, Klemens; Weber, Uli

    2017-04-01

    Porous materials with microscopic structures like foam, sponges, lung tissues and lung substitute materials have particular characteristics, which differ from those of solid materials. Ion beams passing through porous materials show much stronger energy straggling than expected for non-porous solid materials of the same thickness. This effect depends on the microscopic fine structure, the density and the thickness of the porous material. The beam-modulating effect from a porous plate enlarges the Bragg peak, yielding similar benefits in irradiation time reduction as a ripple filter. A porous plate can additionally function as a range shifter, which since a higher energy can be selected for the same penetration depth in the body reduces the scattering at the beam line and therefore improves the lateral fall-off. Bragg curve measurements of ion beams passing through different porous materials have been performed in order to determine the beam modulation effect of each. A mathematical model describing the correlation between the mean material density, the porous pore structure size and the strength of the modulation has been developed and a new material parameter called ‘modulation power’ is defined as the square of the Gaussian sigma divided by the mean water-equivalent thickness of the porous absorber. Monte Carlo simulations have been performed in order to validate the model and to investigate the Bragg peak enlargement, the scattering effects of porosity and the lateral beam width at the end of the beam range. The porosity is found to only influence the lateral scattering in a negligible way. As an example of a practical application, it is found that a 20 mm and 50 mm plate of Gammex LN300 performs similar to a 3 mm and 6 mm ripple filter, respectively, and at the same time can improve the sharpness of the lateral beam due to its multifunctionality as a ripple filter and a range shifter.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

    PubMed

    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.

  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. Characterization of porous construction materials using electromagnetic radar wave

    NASA Astrophysics Data System (ADS)

    Lai, Wallace Wai Lok

    This thesis reports the effort of characterizing three porous construction materials (i.e. concrete, asphalt and soils) and the establishment and formulation of novel unified constitutive models by utilizing electromagnetic (EM) radar wave. An important outcome of this research is that the studied materials were assigned successfully into their rightful positions corresponding to the different regimes governed by three EM wave properties and two engineering/geological properties of the materials. The former refers to the real part of complex dielectric permittivity (epsilon'), energy attenuation and peak-frequency drift. The latter refers to porosity and permeability determined with forward models or conventional testing techniques. In soil and asphalt, the material characterization was achieved by a novel inhouse developed method called Cyclic Moisture Variation Technique (CMVT). The technique is termed cyclic because the porous materials were subjected to change from partially saturated states to fully saturated state (i.e. permeation), and vice versa (i.e. de-watering). With CMVT, water was used as an enhancer or a tracer to differentiate the studied materials which are otherwise difficult when they are dry. Soils and asphalt with different textures were characterized by different curve families exhibited in the relationship between epsilon' and degrees of water saturation (SW). In particular, these curve families were divided into three regions: slow-climbing region in very low SW, fast-climbing region in intermediate SW and another slow-climbing region at high S W. When data obtained from the permeation and de-watering cycles was compared, dielectric hysteresis was observed, but rarely reported in the field of ground penetrating radar (GPR). Different curing histories affect both porosity and pore size distribution within mature concrete. By injecting pressurized water into concrete specimens, different concrete curing histories was back-tracked through the

  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. Dual Control Cell Reaction Ensemble Molecular Dynamics: A Method for Simulations of Reactions and Adsorption in Porous Materials

    DTIC Science & Technology

    2006-09-01

    equilibrium and nonequilibrium transport properties in porous materials such as diffusion coefficients , permeability, and mass flux. Control cells, which...calculation of both equilibrium and nonequilibrium transport properties in porous materials such as diffusion coefficients , permeability, and mass flux...corresponding to dpore max . The second type of membrane model used in this study comprises random configurations of nonoverlapping LJ spheres. The model

  7. Modeling of thermomechanical response of porous shape memory alloys

    NASA Astrophysics Data System (ADS)

    Lagoudas, Dimitris C.; Entchev, Pavlin B.; Vandygriff, Eric L.; Qidwai, Muhammad A.; DeGiorgi, Virginia G.

    2000-06-01

    Shape memory alloys (SMAs) have emerged as a class of materials with unique thermal and mechanical properties that have found numerous applications in various engineering areas. While the shape memory and pseudoelasticity effects have been extensively studied, only a few studies have been done on the high capacity of energy dissipation of SMAs. Because of this property, SMAs hold the promise of making high-efficiency damping devices that are superior to those made of conventional materials. In addition to the energy absorption capability of the dense SMA material, porous SMAs offer the possibility of higher specific damping capacity under dynamic loading conditions, du to scattering of waves. Porous SMAs also offer the possibility of impedance matching by grading the porosity at connecting joints with other structural materials. As a first step, the focus of this work, is on establishing the static properties of porous SMA material. To accomplish this, a micromechanics-based analysis of the overall behavior of porous SMA is carried out. The porous SMA is modeled as a composite with SMA matrix, which is modeled using an incremental formulation, and pores as inhomogeneities of zero stiffness. The macroscopic constitutive behavior of the effective medium is established using the incremental More-Tanaka averaging method for a random distribution of pores, and a FEM analysis of a unit cell for a periodic arrangement of pores. Results form both analyses are compared under various loading conditions.

  8. Hierarchically porous materials: synthesis strategies and structure design.

    PubMed

    Yang, Xiao-Yu; Chen, Li-Hua; Li, Yu; Rooke, Joanna Claire; Sanchez, Clément; Su, Bao-Lian

    2017-01-23

    Owing to their immense potential in energy conversion and storage, catalysis, photocatalysis, adsorption, separation and life science applications, significant interest has been devoted to the design and synthesis of hierarchically porous materials. The hierarchy of materials on porosity, structural, morphological, and component levels is key for high performance in all kinds of applications. Synthesis and applications of hierarchically structured porous materials have become a rapidly evolving field of current interest. A large series of synthesis methods have been developed. This review addresses recent advances made in studies of this topic. After identifying the advantages and problems of natural hierarchically porous materials, synthetic hierarchically porous materials are presented. The synthesis strategies used to prepare hierarchically porous materials are first introduced and the features of synthesis and the resulting structures are presented using a series of examples. These involve templating methods (surfactant templating, nanocasting, macroporous polymer templating, colloidal crystal templating and bioinspired process, i.e. biotemplating), conventional techniques (supercritical fluids, emulsion, freeze-drying, breath figures, selective leaching, phase separation, zeolitization process, and replication) and basic methods (sol-gel controlling and post-treatment), as well as self-formation phenomenon of porous hierarchy. A series of detailed examples are given to show methods for the synthesis of hierarchically porous structures with various chemical compositions (dual porosities: micro-micropores, micro-mesopores, micro-macropores, meso-mesopores, meso-macropores, multiple porosities: micro-meso-macropores and meso-meso-macropores). We hope that this review will be helpful for those entering the field and also for those in the field who want quick access to helpful reference information about the synthesis of new hierarchically porous materials and

  9. Porous silicon in drug delivery devices and materials.

    PubMed

    Anglin, Emily J; Cheng, Lingyun; Freeman, William R; Sailor, Michael J

    2008-08-17

    Porous Si exhibits a number of properties that make it an attractive material for controlled drug delivery applications: The electrochemical synthesis allows construction of tailored pore sizes and volumes that are controllable from the scale of microns to nanometers; a number of convenient chemistries exist for the modification of porous Si surfaces that can be used to control the amount, identity, and in vivo release rate of drug payloads and the resorption rate of the porous host matrix; the material can be used as a template for organic and biopolymers, to prepare composites with a designed nanostructure; and finally, the optical properties of photonic structures prepared from this material provide a self-reporting feature that can be monitored in vivo. This paper reviews the preparation, chemistry, and properties of electrochemically prepared porous Si or SiO2 hosts relevant to drug delivery applications.

  10. 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.

  11. Prediction of capillary hysteresis in a porous material using lattice-Boltzmann methods and comparison to experimental data and a morphological pore network model

    NASA Astrophysics Data System (ADS)

    Ahrenholz, B.; Tölke, J.; Lehmann, P.; Peters, A.; Kaestner, A.; Krafczyk, M.; Durner, W.

    2008-09-01

    In this work we use two numerical methods which rely only on the geometry and material parameters to predict capillary hysteresis in a porous material. The first numerical method is a morphological pore network (MPN) model, where structural elements are inserted into the imaged pore space to quantify the local capillary forces. Then, based on an invasion-percolation mechanism, the fluid distribution is computed. The second numerical method is a lattice-Boltzmann (LB) approach which solves the coupled Navier-Stokes equations for both fluid phases and describes the dynamics of the fluid/fluid interface. We have developed an optimized version of the model proposed in [Tölke J, Freudiger S, Krafczyk M. An adaptive scheme for LBE multiphase flow simulations on hierarchical grids, Comput. Fluids 2006;35:820-30] for the type of flow problems encountered in this work. A detailed description of the model and an extensive validation of different multiphase test cases have been carried out. We investigated pendular rings in a sphere packing, static and dynamic capillary bundle models and the residual saturation in a sphere packing. A sample of 15 mm in diameter filled with sand particles ranging from 100 to 500 μm was scanned using X-rays from a synchrotron source with a spatial resolution of 11 μm. Based on this geometry we computed the primary drainage, the first imbibition and the secondary drainage branch of the hysteresis loop using both approaches. For the LB approach, we investigated the dependence of the hysteresis loop on the speed of the drainage and the imbibition process. Furthermore we carried out a sensitivity analysis by simulating the hysteretic effect in several subcubes of the whole geometry with extremal characteristic properties. The predicted hysteretic water retention curves were compared to the results of laboratory experiments using inverse modeling based on the Richards equation. A good agreement for the hysteresis loop between the LB and MPN model

  12. 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 ...

  13. Porous materials produced from incineration ash using thermal plasma technology.

    PubMed

    Yang, Sheng-Fu; Chiu, Wen-Tung; Wang, To-Mai; Chen, Ching-Ting; Tzeng, Chin-Ching

    2014-06-01

    This study presents a novel thermal plasma melting technique for neutralizing and recycling municipal solid waste incinerator (MSWI) ash residues. MSWI ash residues were converted into water-quenched vitrified slag using plasma vitrification, which is environmentally benign. Slag is adopted as a raw material in producing porous materials for architectural and decorative applications, eliminating the problem of its disposal. Porous materials are produced using water-quenched vitrified slag with Portland cement and foaming agent. The true density, bulk density, porosity and water absorption ratio of the foamed specimens are studied here by varying the size of the slag particles, the water-to-solid ratio, and the ratio of the weights of the core materials, including the water-quenched vitrified slag and cement. The thermal conductivity and flexural strength of porous panels are also determined. The experimental results show the bulk density and the porosity of the porous materials are 0.9-1.2 g cm(-3) and 50-60%, respectively, and the pore structure has a closed form. The thermal conductivity of the porous material is 0.1946 W m(-1) K(-1). Therefore, the slag composite materials are lightweight and thermal insulators having considerable potential for building applications.

  14. Migration Mechanism for Atomic Hydrogen in Porous Carbon Materials

    SciTech Connect

    Narayanan, B.; Zhao, Y. F.; Ciobanu, C. V.

    2012-05-14

    To explain the fast kinetics of H in porous carbon, we propose that the migration relies on H hopping from a carbon nanotube (CNT) to another. Using density functional theory, we have found that the barrier for H hopping becomes smaller than that for diffusion along a tube for certain CNT separations, decreasting to less than 0.5 eV for separations of -3.1 {angstrom}. Such significant reduction occurs irrespective of radius, chirality, registry, and orientation of the two CNTs: the diffusion is thus facilitated by the porous nature of the material itself. The mechanism proposed is applicable for any porous carbon-based nanomaterials.

  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. Filling Porous Microspheres With Magnetic Material

    NASA Technical Reports Server (NTRS)

    Chang, Manchium; Colvin, Michael S.

    1990-01-01

    New process produces magnetic microspheres with controllable sizes, compositions, and properties for use in medical diagnostic tests, biological research, and chemical processes. Paramagnetic microspheres also made with process. Porous plastic microspheres prepared by polymerization of monomer in diluent by cross-linking agent. When diluent removed, it leaves tiny pores throughout polymerized spheres. Size and distribution of pores determined by amount and type of diluent and cross-linking agent.

  17. An analytical model for porous single crystals with ellipsoidal voids

    NASA Astrophysics Data System (ADS)

    Mbiakop, A.; Constantinescu, A.; Danas, K.

    2015-11-01

    A rate-(in)dependent constitutive model for porous single crystals with arbitrary crystal anisotropy (e.g., FCC, BCC, HCP, etc.) containing general ellipsoidal voids is developed. The proposed model, denoted as modified variational model (MVAR), is based on the nonlinear variational homogenization method, which makes use of a linear comparison porous material to estimate the response of the nonlinear porous single crystal. Periodic multi-void finite element simulations are used in order to validate the MVAR for a large number of parameters including cubic (FCC, BCC) and hexagonal (HCP) crystal anisotropy, various creep exponents (i.e., nonlinearity), several stress triaxiality ratios, general void shapes and orientations and various porosity levels. The MVAR model, which involves a priori no calibration parameters, is found to be in good agreement with the finite element results for all cases considered in the rate-dependent context. The model is then used in a predictive manner to investigate the complex response of porous single crystals in several cases with strong coupling between the anisotropy of the crystal and the (morphological) anisotropy induced by the shape and orientation of the voids. Finally, a simple way of calibrating the MVAR with just two adjustable parameters is depicted in the rate-independent context so that an excellent agreement with the FE simulation results is obtained. In this last case, this proposed model can be thought as a generalization of the Gurson model in the context of porous single crystals and general ellipsoidal void shapes and orientations.

  18. Tissue engineering scaffold material of porous nanohydroxyapatite/polyamide 66.

    PubMed

    Xu, Qian; Lu, Hongyan; Zhang, Jingchao; Lu, Guoyu; Deng, Zhennan; Mo, Anchun

    2010-05-13

    The aim of the study was to investigate a porous nanohydroxyapatite/polyamide 66 (n-HA/PA66) scaffold material that was implanted into muscle and tibiae of 16 New Zealand white rabbits to evaluate the biocompatibility and osteogenesis and osteoinductivity of the materials in vivo. The samples were harvested at 2, 4, 12 and 26 weeks respectively, and subjected to histological analysis. At 2 weeks, the experiment showed that osteogenesis was detected in porous n-HA/PA66 composite and the density of new bone formation was similar to the surrounding host bone at 12 weeks. The study indicated that three-dimensional pore structures could facilitate cell adhesion, differentiation and proliferation, and help with fibrovascular and nerve colonization. In conclusion, porous n-HA/PA66 scaffold material could be a good candidate as a bone substitute material used in clinics due to its excellent histocompatibility, osteoconductivity and osteoinductivity.

  19. 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).

  20. Imparting amphiphobicity on single-crystalline porous materials

    PubMed Central

    Sun, Qi; He, Hongming; Gao, Wen-Yang; Aguila, Briana; Wojtas, Lukasz; Dai, Zhifeng; Li, Jixue; Chen, Yu-Sheng; Xiao, Feng-Shou; Ma, Shengqian

    2016-01-01

    The sophisticated control of surface wettability for target-specific applications has attracted widespread interest for use in a plethora of applications. Despite the recent advances in modification of non-porous materials, surface wettability control of porous materials, particularly single crystalline, remains undeveloped. Here we contribute a general method to impart amphiphobicity on single-crystalline porous materials as demonstrated by chemically coating the exterior of metal-organic framework (MOF) crystals with an amphiphobic surface. As amphiphobic porous materials, the resultant MOF crystals exhibit both superhydrophobicity and oleophobicity in addition to retaining high crystallinity and intact porosity. The chemical shielding effect resulting from the amphiphobicity of the MOFs is illustrated by their performances in water/organic vapour adsorption, as well as long-term ultrastability under highly humidified CO2 environments and exceptional chemical stability in acid/base aqueous solutions. Our work thereby pioneers a perspective to protect crystalline porous materials under various chemical environments for numerous applications. PMID:27796363

  1. 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.

  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. 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.

  4. 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.

  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. 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

    2015-07-07

    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.

  7. 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.

  8. 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.

  9. Porous graphene materials for advanced electrochemical energy storage and conversion devices.

    PubMed

    Han, Sheng; Wu, Dongqing; Li, Shuang; Zhang, Fan; Feng, Xinliang

    2014-02-12

    Combining the advantages from both porous materials and graphene, porous graphene materials have attracted vast interests due to their large surface areas, unique porous structures, diversified compositions and excellent electronic conductivity. These unordinary features enable porous graphene materials to serve as key components in high-performance electrochemical energy storage and conversion devices such as lithium ion batteries, supercapacitors, and fuel cells. This progress report summarizes the typical fabrication methods for porous graphene materials with micro-, meso-, and macro-porous structures. The structure-property relationships of these materials and their application in advanced electrochemical devices are also discussed.

  10. Modeling and Simulations of Particulate Flows through Functionalized Porous Media

    NASA Astrophysics Data System (ADS)

    Li, Chunhui; Dutta, Prashanta; Liu, Jin

    2016-11-01

    Transport of particulate fluid through a functionalized porous material is of significant interest in many industrial applications, such as earth sciences, battery designs and water/air purifications. The entire process is complex, which involves the convection of fluid, diffusion of reactants as well as reversible chemical reactions at the fluid-solid interface In this work we present a convection-diffusion-reaction model and simulate the transport of particulate fluid through a functionalized porous media. The porous structures are generated and manipulated through the quartet structure generation set method. The Navier-Stokes with convection-diffusion equations are solved using the lattice Boltzmann method. The chemical reactions at the interface are modeled by an absorption-desorption process and treated as the boundary conditions for above governing equations. Through our simulations we study the effects of porous structures, including porosity, pore orientation, and pore size as well as the kinetic rates of surface reactions on the overall performance of removal efficiency of the species from the solution. Our results show that whole process is highly affected by both the porous structures and absorption rate. The optimal parameters can be achieved by proper design. This work is supported by NSF Grants: CBET-1250107 and CBET -1604211.

  11. Modeling of nanostructured porous thermoelastic composites with surface effects

    NASA Astrophysics Data System (ADS)

    Nasedkin, A. V.; Nasedkina, A. A.; Kornievsky, A. S.

    2017-01-01

    The paper presents an integrated approach for determination of effective properties of anisotropic porous thermoelastic materials with a nanoscale stochastic porosity structure. This approach includes the effective moduli method for composite me-chanics, the simulation of representative volumes and the finite element method. In order to take into account nanoscale sizes of pores, the Gurtin-Murdoch model of surface stresses and the highly conducting interface model are used at the borders between material and pores. The general methodology for determination of effective properties of porous composites is demonstrated for a two-phase composite with special conditions for stresses and heat flux discontinuities at the phase interfaces. The mathematical statements of boundary value problems and the resulting formulas to determine the complete set of effective constants of the two-phase composites with arbitrary anisotropy and with surface properties are described; the generalized statements are formulated and the finite element approximations are given. It is shown that the homogenization procedures for porous composites with surface effects can be considered as special cases of the corresponding procedures for the two-phase composites with interphase stresses and heat fluxes if the moduli of nanoinclusions are negligibly small. These approaches have been implemented in the finite element package ANSYS for a model of porous material with cubic crystal system for various values of surface moduli, porosity and number of pores. It has been noted that the magnitude of the area of the interphase boundaries has influence on the effective moduli of the porous materials with nanosized structure.

  12. 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.

  13. Porous low dielectric constant materials for microelectronics.

    PubMed

    Baklanov, Mikhail R; Maex, Karen

    2006-01-15

    Materials with a low dielectric constant are required as interlayer dielectrics for the on-chip interconnection of ultra-large-scale integration devices to provide high speed, low dynamic power dissipation and low cross-talk noise. The selection of chemical compounds with low polarizability and the introduction of porosity result in a reduced dielectric constant. Integration of such materials into microelectronic circuits, however, poses a number of challenges, as the materials must meet strict requirements in terms of properties and reliability. These issues are the subject of the present paper.

  14. 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.

  15. Novel polymeric nanocomposites and porous materials prepared using organogels

    NASA Astrophysics Data System (ADS)

    Lai, Wei-Chi; Tseng, Shen-Chen

    2009-11-01

    We propose a new method for preparing polymeric nanocomposites and porous materials using self-assembled templates formed by 1,3:2,4-dibenzylidene sorbitol (DBS) organogels. DBS is capable of self-assembling into a 3D nanofibrillar network at relatively low concentrations in some organic solvents to produce organogels. In this study, we induced the formation of such physical cross-linked networks in styrene. Subsequently, we polymerized the styrene in the presence of chemical cross-linkers, divinyl benzene (DVB), with different amounts of DBS using thermal-initiated polymerization. The resulting materials were transparent, homogeneous polystyrene (PS) nanocomposites with both physical and chemical cross-links. The porous polymeric materials were obtained by solvent extraction of the DBS nanofibrils from the PS. Brunauer-Emmett-Teller (BET) measurements show that the amounts of DBS and DVB influenced the specific surface area after the removal of the DBS fibrils.

  16. Roughening of porous SiCOH materials in fluorocarbon plasmas

    NASA Astrophysics Data System (ADS)

    Bailly, F.; David, T.; Chevolleau, T.; Darnon, M.; Posseme, N.; Bouyssou, R.; Ducote, J.; Joubert, O.; Cardinaud, C.

    2010-07-01

    Porous SiCOH materials integration for integrated circuits faces serious challenges such as roughening during the etch process. In this study, atomic force microscopy is used to investigate the kinetics of SiCOH materials roughening when they are etched in fluorocarbon plasmas. We show that the root mean square roughness and the correlation length linearly increase with the etched depth, after an initiation period. We propose that: (1) during the first few seconds of the etch process, the surface of porous SiCOH materials gets denser. (2) Cracks are formed, leading to the formation of deep and narrow pits. (3) Plasma radicals diffuse through those pits and the pore network and modify the porous material at the bottom of the pits. (4) The difference in material density and composition between the surface and the bottom of the pits leads to a difference in etch rate and an amplification of the roughness. In addition to this intrinsic roughening mechanism, the presence of a metallic mask (titanium nitride) can lead to an extrinsic roughening mechanism, such as micromasking caused by metallic particles originating form the titanium nitride mask.

  17. Porous silicon based anode material formed using metal reduction

    DOEpatents

    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.

  18. 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.

  19. A multilevel approach to modeling of porous bioceramics

    NASA Astrophysics Data System (ADS)

    Mikushina, Valentina A.; Sidorenko, Yury N.

    2015-10-01

    The paper is devoted to discussion of multiscale models of heterogeneous materials using principles. The specificity of approach considered is the using of geometrical model of composites representative volume, which must be generated with taking the materials reinforcement structure into account. In framework of such model may be considered different physical processes which have influence on the effective mechanical properties of composite, in particular, the process of damage accumulation. It is shown that such approach can be used to prediction the value of composite macroscopic ultimate strength. As an example discussed the particular problem of the study the mechanical properties of biocomposite representing porous ceramics matrix filled with cortical bones tissue.

  20. Zeolitic materials with hierarchical porous structures.

    PubMed

    Lopez-Orozco, Sofia; Inayat, Amer; Schwab, Andreas; Selvam, Thangaraj; Schwieger, Wilhelm

    2011-06-17

    During the past several years, different kinds of hierarchical structured zeolitic materials have been synthesized due to their highly attractive properties, such as superior mass/heat transfer characteristics, lower restriction of the diffusion of reactants in the mesopores, and low pressure drop. Our contribution provides general information regarding types and preparation methods of hierarchical zeolitic materials and their relative advantages and disadvantages. Thereafter, recent advances in the preparation and characterization of hierarchical zeolitic structures within the crystallites by post-synthetic treatment methods, such as dealumination or desilication; and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as (non-reactive as well as reactive) supports are highlighted. Specific advantages of using hierarchical zeolitic catalysts/structures in selected catalytic reactions, such as benzene to phenol (BTOP) and methanol to olefins (MTO) are presented.

  1. Unified water isotherms for clayey porous materials

    NASA Astrophysics Data System (ADS)

    Revil, A.; Lu, N.

    2013-09-01

    We provide a unified model for the soil-water retention function, including the effect of bound and capillary waters for all types of soils, including clayey media. The model combines a CEC-normalized isotherm describing the sorption of the bound water (and the filling of the trapped porosity) and the van Genuchten model to describe the capillary water sorption retention but ignore capillary condensation. For the CEC-normalized isotherm, we tested both the BET and Freundlich isotherms, and we found that the Freundlich is more suitable than the BET isotherm in fitting the data. It is also easier to combine the Freundlich isotherm with the van Genuchten model. The new model accounts for (1) the different types of clay minerals, (2) the different types of ions sorbed in the Stern layer and on the basal planes of 2:1 clays, and (3) the pore size distribution. The model is validated with different data sets, including mixtures of kaolinite and bentonite. The model parameters include two exponents (the pore size exponent of the van Genuchten model and the exponent of the Freundlich isotherm), the capillary entry pressure, and two critical water contents. The first critical water content is the water content at saturation (porosity), and the second is the maximum water content associated with adsorption forces, including the trapped nonbound water.

  2. 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.

  3. 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.

  4. Strain intermittency due to avalanches in ferroelastic and porous materials.

    PubMed

    Soprunyuk, Viktor; Puchberger, Sabine; Tröster, Andreas; Vives, Eduard; Salje, Ekhard; Schranz, Wilfried

    2017-04-06

    The avalanche statistics in porous materials and ferroelastic domain wall systems has been studied for slowly increasing compressive uniaxial stress with stress rates between 0.2 and 17 kPa/s. Velocity peaks vm=dh/dt are calculated from the measured strain drops and used to determine the corresponding Energy distributions N(E = vm2). Power law distributions N(vm2) ~(vm2) have been obtained over 4-6 decades. For most of the porous materials and domain wall systems an exponent ε= 1.5 ± 0.1 was obtained in good agreement with mean-field theory of the interface pinning transition. For charcoal, shale and calcareous schist we found significant deviations of the exponents from mean-field values in agreement with recent acoustic emission experiments.

  5. 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.

  6. Synthesis of Metal Nanoclusters Doped in Porous Materials as Photocatalysts

    DTIC Science & Technology

    2008-04-10

    Ito S. Deactivation of the TiO2 photocatalyst by coupling with WO3 and the electrochemically assisted high photocatalytic activity of WO3 . Langmuir...Synthesis of metal nanoclusters doped in porous materials as photocatalysts 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5d. TASK NUMBER 6...will be performed: Task #1: The development of nanoclusters embedded in zeolites as potential photocatalysts . Task #2: Identify conditions

  7. 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.

  8. 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

  9. 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.

  10. 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.

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

    PubMed

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

    2015-05-15

    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.

  12. Network models of soil porous structure

    NASA Astrophysics Data System (ADS)

    Samec, M.; Santiago, A.; Cardenas, J. P.; Benito, R. M.; Tarquis, A. M.; Mooney, S. J.; Korošak, D.

    2010-05-01

    Soils sustain life on Earth. In times of increasing anthropogenic demands on soils [1] there is growing need to seek for novel approaches to understand the relationships between the soil porous structure and specific soil functions. Recently [2-4], soil pore structure was described as a complex network of pores using spatially embedded varying fitness network model [2] or heterogeneous preferential attachment scheme [3-4], both approaches revealing the apparent scale-free topology of soils. Here, we show, using a large set of soil images of structures obtained by X-ray computed tomography that both methods predict topological similar networks of soil pore structures. Furthermore, by analyzing the node-node link correlation properties of the obtained networks we suggest an approach to quantify the complexity of soil pore structure. [1] R. Lal, Soil science and the carbon civilization, Soil Sci. Soc. Am. J., 71: 1425-1437, 2007. [2] S. J. Mooney, D. Korošak, Using Complex Networks to Model Two- and Three-Dimensional Soil Porous Architecture, Soil Sci. Soc. Am. J., 73: 1094-1100, 2009. [3] A. Santiago, J. P. Cardenas, J. C. Losada, R. M. Benito, A. M. Tarquis, F. Borondo, Multiscaling of porous soils as heterogeneous complex networks, Nonlin. Proc. Geophys., 15: 893-902, 2008. [4] A. Santiago, R. M. Benito, An extended formalism for preferential attachment in heterogeneous complex networks, Eur. Phys. Lett., 82: 58004, 2008.

  13. 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.

  14. 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.

  15. 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.

  16. Mathematical modeling of fines migration and clogging in porous media

    NASA Astrophysics Data System (ADS)

    Kampel, Guido

    2007-05-01

    A porous medium is a material that contains regions filled with fluid embedded in a solid matrix. These fluid filled regions are called pores or voids. Suspensions are fluids with small particles called fines. As a suspension flows through a porous material, some fines are trapped within the material while others that were trapped may be released. Filters are an example of porous media. We model filters as networks of channels. As a suspension flows across the filter, particles clog channels. We assume that there is no flow through clogged channels. In the first part of this thesis, we compute a sharp upper bound on the number of channels that can clog before fluid can no longer flow through the filter. Soil mass is another example of porous media. Fluid in porous media flows through tortuous paths. This tortuosity and inertial effects cause fines to collide with pore walls. After each collision, a particle looses momentum and needs to be accelerated again by hydrodynamic forces. As a result, the average velocity of fines is smaller than that of the fluid. This retardation of the fines with respect to the fluid may lead to an increase of the concentration of fines in certain regions which may eventually result in the plugging of the porous medium. This effect is of importance in flows near wells where the flow has circular symmetry and thus, it is not macroscopically homogeneous. In the second part of this thesis we develop and analyze a mathematical model to study the physical effect described above. In the third and last part of this thesis we study particle migration and clogging as suspension flows through filters by means of numerical simulations and elementary analysis. We model filters as networks of channels. Each channel is either open or clogged. There is no flow through clogged channels. Each particle and each channel is assigned a width. Particles flow with the fluid while inside a wider channel. When reaching an intersection of channels, a particle

  17. 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.

  18. 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.

  19. The Interaction of Sound and Shock Waves with Flexible Porous Materials

    NASA Astrophysics Data System (ADS)

    Abbott, James Fuller

    Several topics are studied which illustrate the role of flexibility in determining the acoustical properties of flexible porous materials. A power balance relation is obtained for the flexible porous material which explicitly identifies two loss mechanisms for sound absorption: the losses due to the irreversible deformation of the structure, and those attributed to the viscous drag between the fluid and the structure. The finite flexible porous layer backed by a rigid wall is then considered. Irreversible deformation of the structure is shown to be the dominant loss mechanism for closed layers. Three departures from the basic model-- a porous layer with anisotropic flow resistance and structure factor, periodic structures consisting of porous layers separated by air gaps, and the porous medium in bulk with mean fluid flow--are considered. The reflection of shock waves is also studied, and a quasi-linear theory is developed which reproduces the principal features of experimental results obtained previously by Ingard. The theory assumes that the propagating pulses in the air and structure are linear and the gross, zeroth order motion of the porous layer is modeled by including its energy and momentum in the conservation equations; these equations compare the system just before and just after the reflection of the incident shock from the front surface of the layer. The substantial motion of the layer and its dragging against a constraining boundary (in this case the walls of the shock tube) are found to introduce a dependence of the front reflection coefficient and maximal layer deformation on the peak pressure of the incident shock. Lastly, we address the question of measurement of the complex compressibility K, a key parameter used to describe the dynamics of a given flexible porous material. The standard long-wavelength assumption used to determine K from experimental measurements of the frequency dependent velocity transfer function across a sample is shown to

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  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. 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.

  7. Solid state NMR of porous materials : zeolites and related materials.

    PubMed

    Koller, Hubert; Weiss, Mark

    2012-01-01

    Solid state NMR spectroscopy applied to the science of crystalline micro- and mesoporous silica materials over the past 10 years is reviewed. A survey is provided of framework structure and connectivity analyses from chemical shift effects of various elements in zeolites including heteroatom substitutions, framework defects and pentacoordinated silicon for zeolites containing fluoride ions. New developments in the field of NMR crystallography are included. Spatial host-guest ordering and confinement effects of zeolite-sorbate complexes are outlined, with special emphasis on NMR applications utilizing the heteronuclear dipolar interaction. The characterization of zeolite acid sites and in situ NMR on catalytic conversions is also included. Finally, the motion of extra-framework cations is investigated in two tutorial cases of sodium hopping in sodalite and cancrinite.

  8. Microplane constitutive model for porous isotropic rocks

    NASA Astrophysics Data System (ADS)

    Baant, Zdenk P.; Zi, Goangseup

    2003-01-01

    The paper deals with constitutive modelling of contiguous rock located between rock joints. A fully explicit kinematically constrained microplane-type constitutive model for hardening and softening non-linear triaxial behaviour of isotropic porous rock is developed. The microplane framework, in which the constitutive relation is expressed in terms of stress and strain vectors rather than tensors, makes it possible to model various microstructural physical mechanisms associated with oriented internal surfaces, such as cracking, slip, friction and splitting of a particular orientation. Formulation of the constitutive relation is facilitated by the fact that it is decoupled from the tensorial invariance restrictions, which are satisfied automatically. In its basic features, the present model is similar to the recently developed microplane model M4 for concrete, but there are significant improvements and modifications. They include a realistic simulation of (1) the effects of pore collapse on the volume changes during triaxial loading and on the reduction of frictional strength, (2) recovery of frictional strength during shearing, and (3) the shear-enhanced compaction in triaxial tests, manifested by a deviation from the hydrostatic stress-strain curve. The model is calibrated by optimal fitting of extensive triaxial test data for Salem limestone, and good fits are demonstrated. Although these data do not cover the entire range of behaviour, credence in broad capabilities of the model is lend by its similarity to model M4 for concrete - an artificial rock. The model is intended for large explicit finite-element programs.

  9. 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

  10. 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

  11. Thick-film humidity sensor based on porous ? material

    NASA Astrophysics Data System (ADS)

    Qu, Wenmin; Meyer, Jörg-Uwe

    1997-06-01

    A new compact, robust, yet fast and highly sensitive ceramic humidity sensor based on the semiconducting metal oxide 0957-0233/8/6/002/img2 has been developed using thick-film technology. The sensor element possesses a novel `sandwich' configuration with a 0957-0233/8/6/002/img3 porous 0957-0233/8/6/002/img2 ceramic layer sandwiched by two 0957-0233/8/6/002/img5 polarity-reversed interdigitated metal films. Instead of traditional glass frits, LiCl powders were used as adhesion promoters. The sintered ceramic layer exhibits a porous structure. The degree of the porosity is controlled by the amount of LiCl added and by the firing conditions for the ceramic. The surfaces of ceramic grains behave like electrolytes and easily adsorb water vapour through the pores. The novel electrode arrangement combines the advantages of humidity sensors in the form of a parallel capacitor with those in the form of an interdigital capacitor. The influence of temperature on the sensor characteristics has been compensated for by integrating a thick-film NTC resistor. The results of studies on the material processing, the fabrication and the characterization of this novel thick-film humidity sensor are described.

  12. Hypercrosslinked porous polymer materials: design, synthesis, and applications.

    PubMed

    Tan, Liangxiao; Tan, Bien

    2017-02-22

    Hypercrosslinked polymers (HCPs) are a series of permanent microporous polymer materials initially reported by Davankov, and have received an increasing level of research interest. In recent years, HCPs have experienced rapid growth due to their remarkable advantages such as diverse synthetic methods, easy functionalization, high surface area, low cost reagents and mild operating conditions. Judicious selection of monomers, appropriate length crosslinkers and optimized reaction conditions yielded a well-developed polymer framework with an adjusted porous topology. Post fabrication of the as developed network facilitates the incorporation of various chemical functionalities that may lead to interesting properties and enhance the selection toward a specific application. To date, numerous HCPs have been prepared by post-crosslinking polystyrene-based precursors, one-step self-polycondensation or external crosslinking strategies. The advent of these methodologies has prompted researchers to construct well-defined porous polymer networks with customized micromorphology and functionalities. In this review, we describe not only the basic synthetic principles and strategies of HCPs, but also the advancements in the structural and morphological study as well as the frontiers of potential applications in energy and environmental fields such as gas storage, carbon capture, removal of pollutants, molecular separation, catalysis, drug delivery, sensing etc.

  13. Design of advanced porous graphene materials: from graphene nanomesh to 3D architectures.

    PubMed

    Jiang, Lili; Fan, Zhuangjun

    2014-02-21

    In order to make full utilization of the high intrinsic surface area of graphene, recently, porous graphene materials including graphene nanomesh, crumpled graphene and graphene foam, have attracted tremendous attention and research interest, owing to their exceptional porous structure (high surface area, and high pore volume) in combination with the inherent properties of graphene, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Interestingly, porous graphene materials and their derivatives have been explored in a wide range of applications in the fields of electronic and photonic devices, energy storage, gas separation/storage, oil absorption and sensors. This article reviews recent progress in the synthesis, characterization, properties, and applications of porous graphene materials. We aim to highlight the importance of designing different porous structures of graphene to meet future challenges, and the trend on future design of porous graphene materials is analyzed.

  14. 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.

  15. A bipotential-based limit analysis and homogenization of ductile porous materials with non-associated Drucker-Prager matrix

    NASA Astrophysics Data System (ADS)

    Cheng, Long; Jia, Yun; Oueslati, Abdelbacet; de Saxcé, Géry; Kondo, Djimedo

    2015-04-01

    In Gurson's footsteps, different authors have proposed macroscopic plastic models for porous solid with pressure-sensitive dilatant matrix obeying the normality law (associated materials). The main objective of the present paper is to extend this class of models to porous materials in the context of non-associated plasticity. This is the case of Drucker-Prager matrix for which the dilatancy angle is different from the friction one, and classical limit analysis theory cannot be applied. For such materials, the second last author has proposed a relevant modeling approach based on the concept of bipotential, a function of both dual variables, the plastic strain rate and stress tensors. On this ground, after recalling the basic elements of the Drucker-Prager model, we present the corresponding variational principles and the extended limit analysis theorems. Then, we formulate a new variational approach for the homogenization of porous materials with a non-associated matrix. This is implemented by considering the hollow sphere model with a non-associated Drucker-Prager matrix. The proposed procedure delivers a closed-form expression of the macroscopic bifunctional from which the criterion and a non-associated flow rule are readily obtained for the porous material. It is shown that these general results recover several available models as particular cases. Finally, the established results are assessed and validated by comparing their predictions to those obtained from finite element computations carried out on a cell representing the considered class of materials.

  16. 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.

  17. Forced imbibition through model porous media

    NASA Astrophysics Data System (ADS)

    Odier, Celeste; Levache, Bertrand; Bartolo, Denis

    2016-11-01

    A number of industrial and natural process ultimately rely on two-phase flow in heterogeneous media. One of the most prominent example is oil recovery which has driven fundamental and applied research in this field for decades. Imbibition occurs when a wetting fluid displaces an immiscible fluid e.g. in a porous media. Using model microfluidic experiment we control both the geometry and wetting properties of the heterogenous media, and show that the typical front propagation picture fails when imbibition is forced and the displacing fluid is less viscous than the non-wetting fluid. We identify and quantitatively characterize four different flow regimes at the pore scale yielding markedly different imbibition patterns at large scales. In particular we will discuss the transition from a conventional 2D-front propagation scenario to a regime where the meniscus dynamics is an intrinsically 3D process.

  18. 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.

  19. The pressure drop in a porous material layer during combustion

    SciTech Connect

    Kondrikov, B.N.

    1995-07-01

    During the combustion of a porous material layer, a manometer, which is attached to the cold end of the charge, records at the bottom of the layer a pressure reduction, which was discovered more than 20 years ago but which remains essentially unexplained up to the present. It is experimentally shown that this effect is similar to the pressure change in the cavities when a light gas (helium, hydrogen) diffuses from (or to) them under isothermal conditions and that it increases during the combustion mainly due to the accompanying Stefan type flow, and probably also as a result of the thermal diffusion. A pressure drop in the cavities is evidently made possible also by the pressure reduction in the flame which follows from the Hugoniot adiabatic theory.

  20. Metal-organic frameworks as functional, porous materials

    NASA Astrophysics Data System (ADS)

    Rood, Jeffrey A.

    The research presented in this thesis investigates the use of metal carboxylates as permanently porous materials called metal-organic frameworks (MOFs). The project has focused on three broad areas of study, each which strives to develop a further understanding of this class of materials. The first topic is concerned with the synthesis and structural characterization of MOFs. Our group and others have found that the reaction of metal salts with carboxylic acids in polar solvents at elevated temperatures often leads the formation of crystalline MOF materials that can be examined by single crystal X-ray diffraction. Specifically, Chapter 2 reports on some of the first examples of magnesium MOFs, constructed from formate or aryldicarboxylate ligands. The magnesium formate MOF, [Mg3(O2CH) 6] was found to be a permanently porous 3-D material capable of selective uptake and exchange of small molecules. Once the synthesis and structures of some of these materials was known, their physical properties were studied. The magnesium formate MOF, [Mg 3(O2CH)6], was found to be permanently porous and able to reversibly adsorb both N2 and H2 gas. Furthermore, the material was also capable of taking up a variety of organic molecules to form new inclusion compounds that were characterized by XRD studies. Size exclusion was shown for cyclohexane and larger molecules. Chapters 3, 5, and 6 attempt to build off of the synthetic findings reported in Chapter 2. Specifically, the ability of these materials to take up guest molecules is expanded by the attempted synthesis of porous, homochiral MOFs using enantiopure carboxylic acids in the synthesis. It was found that under the appropriate synthetic conditions, both L-tartaric acid and (+)-camphoric acid were robust linkers for the formation of homochiral MOFs. Of the compounds synthesized, the most interesting were the set of compounds, [Zn2(Cam) 2(bipy)⊃3DMF] and [Zn2(Cam)2(apyr)⊃2DMF]. These compounds formed isoreticular cubic

  1. 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

  2. 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.

  3. 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.

  4. Limit analysis and homogenization of porous materials with Mohr-Coulomb matrix. Part I: Theoretical formulation

    NASA Astrophysics Data System (ADS)

    Anoukou, K.; Pastor, F.; Dufrenoy, P.; Kondo, D.

    2016-06-01

    The present two-part study aims at investigating the specific effects of Mohr-Coulomb matrix on the strength of ductile porous materials by using a kinematic limit analysis approach. While in the Part II, static and kinematic bounds are numerically derived and used for validation purpose, the present Part I focuses on the theoretical formulation of a macroscopic strength criterion for porous Mohr-Coulomb materials. To this end, we consider a hollow sphere model with a rigid perfectly plastic Mohr-Coulomb matrix, subjected to axisymmetric uniform strain rate boundary conditions. Taking advantage of an appropriate family of three-parameter trial velocity fields accounting for the specific plastic deformation mechanisms of the Mohr-Coulomb matrix, we then provide a solution of the constrained minimization problem required for the determination of the macroscopic dissipation function. The macroscopic strength criterion is then obtained by means of the Lagrangian method combined with Karush-Kuhn-Tucker conditions. After a careful analysis and discussion of the plastic admissibility condition associated to the Mohr-Coulomb criterion, the above procedure leads to a parametric closed-form expression of the macroscopic strength criterion. The latter explicitly shows a dependence on the three stress invariants. In the special case of a friction angle equal to zero, the established criterion reduced to recently available results for porous Tresca materials. Finally, both effects of matrix friction angle and porosity are briefly illustrated and, for completeness, the macroscopic plastic flow rule and the voids evolution law are fully furnished.

  5. Modeling Transverse Chemotaxis in Porous Media

    NASA Astrophysics Data System (ADS)

    Porter, M. L.; Valdés-Parada, F. J.; Wood, B. D.

    2009-12-01

    The movement of microorganisms toward a chemical attractant (chemotaxis) has been shown to aid in subsurface contaminant degradation and enhanced oil recovery. However, chemotaxis is inherently a pore scale process that must be upscaled to arrive at continuum scale models for field applications. In this work, the method of volume averaging is used to upscale the microscale chemotactic microbial transport equations in order to obtain the corresponding macroscale models for the mass balance of bacteria and the chemical attractant to which they respond. As a first approach, cellular growth/death and consumption of the attractant by chemical reaction are assumed to be negligible with respect to convective and diffusive transport mechanisms. Two effective medium coefficients are introduced in the model, namely a total motility tensor and a total velocity vector. Under certain conditions, it is shown that the coefficients can differ considerably from the values corresponding to non-chemotactic transport. The model is validated by comparing the predicted transverse motility coefficients and concentration profiles to those measured within an engineered porous medium. For the concentration profiles, we introduced a lag that accounts for the difference between the arrival time of the microorganisms and the their chemotactic response to the attractant.

  6. 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.

  7. 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.

  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. Silicon-based porous nanocomposite thin-films as an active anode material for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Mazaletskiy, L. A.; Rudy, A. S.; Metlitskaya, A. V.

    2016-08-01

    The results of experimental studies of porous silicon nanocomposite materials for future usage as an anode material of lithium-ion batteries are presented. Comparison between original and porous structures in terms of their qualitative and quantitative characteristics is given.

  10. Modeling of a supersonic flow around a cylinder with a gas-permeable porous insert

    NASA Astrophysics Data System (ADS)

    Mironov, S. G.; Maslov, A. A.; Poplavskaya, T. V.; Kirilovskiy, S. V.

    2015-07-01

    Results of an experimental and numerical study of a supersonic (M∞ = 4.85) flow around a streamwise-aligned cylinder with a gas-permeable porous insert on the frontal face in the range of Reynolds numbers Re D = (0.1-2.0) · 105 are presented. The numerical study is performed by using the Ansys Fluent software system and a porous medium model based on a quadratic law of filtration. The parameters of the quadratic dependence are calculated on the basis of experimental data for an air flow in a porous material. Flow fields are obtained, and the wave drag of the model is calculated as a function of the porous insert length and the Reynolds number. Results of numerical simulations are compared with wind tunnel measurements.

  11. Attenuation of intense sinusoidal waves in air-saturated, bulk porous materials

    NASA Technical Reports Server (NTRS)

    Kuntz, Herbert L.; Blackstock, David T.

    1987-01-01

    As intense, initially sinusoidal waves propagate in fluids, shocks form and excess attenuation of the wave occurs. Data are presented indicating that shock formation is not necessary for the occurrence of excess attenuation in nonlinear, lossy media, i.e., air-saturated, porous materials. An empirical equation is used to describe the excess attenuation of intense sinusoids in porous materials. The acoustic nonlinearity of and the excess attenuation in porous materials may be predicted directly from dc flow resistivity data. An empirical relationship is used to relate an acoustic nonlinearity parameter to the fundamental frequency and relative dc nonlinearity of two structurally different materials.

  12. Prediction of Thermophysical and Thermomechanical Characteristics of Porous Carbon-Ceramic Composite Materials of the Heat Shield of Aerospace Craft

    NASA Astrophysics Data System (ADS)

    Reznik, S. V.; Prosuntsov, P. V.; Mikhailovskii, K. V.

    2015-05-01

    A procedure for predicting thermophysical and thermomechanical characteristics of porous carbon-ceramic composite materials of the heat shield of aerospace craft as functions of the type of reinforcement, porosity of the structure, and the characteristics of the material's components has been developed. Results of mathematical modeling of the temperature and stressed-strained states of representative volume elements for determining the characteristics of a carbon-ceramic composite material with account taken of its anisotropy have been given.

  13. 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.

  14. 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

  15. Effect of Moisture Content on Thermal Properties of Porous Building Materials

    NASA Astrophysics Data System (ADS)

    Kočí, Václav; Vejmelková, Eva; Čáchová, Monika; Koňáková, Dana; Keppert, Martin; Maděra, Jiří; Černý, Robert

    2017-02-01

    The thermal conductivity and specific heat capacity of characteristic types of porous building materials are determined in the whole range of moisture content from dry to fully water-saturated state. A transient pulse technique is used in the experiments, in order to avoid the influence of moisture transport on measured data. The investigated specimens include cement composites, ceramics, plasters, and thermal insulation boards. The effect of moisture-induced changes in thermal conductivity and specific heat capacity on the energy performance of selected building envelopes containing the studied materials is then analyzed using computational modeling of coupled heat and moisture transport. The results show an increased moisture content as a substantial negative factor affecting both thermal properties of materials and energy balance of envelopes, which underlines the necessity to use moisture-dependent thermal parameters of building materials in energy-related calculations.

  16. 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.

  17. Small-angle and surface scattering from porous and fractal materials.

    SciTech Connect

    Sinha, S. K.

    1998-09-18

    We review the basic theoretical methods used to treat small-angle scattering from porous materials, treated as general two-phase systems, and also the basic experimental techniques for carrying out such experiments. We discuss the special forms of the scattering when the materials exhibit mass or surface fractal behavior, and review the results of recent experiments on several types of porous media and also SANS experiments probing the phase behavior of binary fluid mixtures or polymer solutions confined in porous materials. Finally, we discuss the analogous technique of off-specular scattering from surfaces and interfaces which is used to study surface roughness of various kinds.

  18. DNA-Templated Fabrication of Arbitrary-Structured Porous Carbon Materials

    DTIC Science & Technology

    2016-07-11

    AFRL-AFOSR-VA-TR-2016-0245 DNA-Templated Fabrication of Arbitrary- Structured Porous Carbon Materials HAITAO LIU UNIVERSITY OF PITTSBURGH 3520 FIFTH...Arbitrary- Structured Porous Carbon Materials 5a. CONTRACT NUMBER FA9550-13-1-0083 5b. GRANT NUMBER FA9550-13-1-0083 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR...3D porous carbon materials with arbitrary structures . We have achieved the original objective of the project. We have coated both 1D and 2D DNA

  19. 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.

  20. Comparison of porous and nonporous materials for methane storage

    SciTech Connect

    Thallapally, Praveen K.; Kirby, Karen A.; Atwood, Jerry L.

    2007-05-10

    Sublimed, low-density p-tert-buytlcalix(4)arene absorbs methane more readily at room temperature and 1 atm pressure than do either single wall carbon nanotubes (SWNT) or a comparaitive porous metal-organic framework (MOF-1).

  1. Dual control cell reaction ensemble molecular dynamics: A method for simulations of reactions and adsorption in porous materials

    NASA Astrophysics Data System (ADS)

    Lísal, Martin; Brennan, John K.; Smith, William R.; Siperstein, Flor R.

    2004-09-01

    We present a simulation tool to study fluid mixtures that are simultaneously chemically reacting and adsorbing in a porous material. The method is a combination of the reaction ensemble Monte Carlo method and the dual control volume grand canonical molecular dynamics technique. The method, termed the dual control cell reaction ensemble molecular dynamics method, allows for the calculation of both equilibrium and nonequilibrium transport properties in porous materials such as diffusion coefficients, permeability, and mass flux. Control cells, which are in direct physical contact with the porous solid, are used to maintain the desired reaction and flow conditions for the system. The simulation setup closely mimics an actual experimental system in which the thermodynamic and flow parameters are precisely controlled. We present an application of the method to the dry reforming of methane reaction within a nanoscale reactor model in the presence of a semipermeable membrane that was modeled as a porous material similar to silicalite. We studied the effects of the membrane structure and porosity on the reaction species permeability by considering three different membrane models. We also studied the effects of an imposed pressure gradient across the membrane on the mass flux of the reaction species. Conversion of syngas (H2/CO) increased significantly in all the nanoscale membrane reactor models considered. A brief discussion of further potential applications is also presented.

  2. Dual control cell reaction ensemble molecular dynamics: a method for simulations of reactions and adsorption in porous materials.

    PubMed

    Lisal, Martin; Brennan, John K; Smith, William R; Siperstein, Flor R

    2004-09-08

    We present a simulation tool to study fluid mixtures that are simultaneously chemically reacting and adsorbing in a porous material. The method is a combination of the reaction ensemble Monte Carlo method and the dual control volume grand canonical molecular dynamics technique. The method, termed the dual control cell reaction ensemble molecular dynamics method, allows for the calculation of both equilibrium and nonequilibrium transport properties in porous materials such as diffusion coefficients, permeability, and mass flux. Control cells, which are in direct physical contact with the porous solid, are used to maintain the desired reaction and flow conditions for the system. The simulation setup closely mimics an actual experimental system in which the thermodynamic and flow parameters are precisely controlled. We present an application of the method to the dry reforming of methane reaction within a nanoscale reactor model in the presence of a semipermeable membrane that was modeled as a porous material similar to silicalite. We studied the effects of the membrane structure and porosity on the reaction species permeability by considering three different membrane models. We also studied the effects of an imposed pressure gradient across the membrane on the mass flux of the reaction species. Conversion of syngas (H2/CO) increased significantly in all the nanoscale membrane reactor models considered. A brief discussion of further potential applications is also presented.

  3. 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

  4. 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

  5. Characterisation of porous carbon electrode materials used in proton exchange membrane fuel cells via gas adsorption

    NASA Astrophysics Data System (ADS)

    Watt-Smith, M. J.; Rigby, S. P.; Ralph, T. R.; Walsh, F. C.

    Porous carbon materials are typically used in both the substrate (typically carbon paper) and the electrocatalyst supports (often platinised carbon) within proton exchange membrane fuel cells. Gravimetric nitrogen adsorption has been studied at a carbon paper substrate, two different Pt-loaded carbon paper electrodes and three particulate carbon blacks. N 2 BET surface areas and surface fractal dimensions were determined using the fractal BET and Frenkel-Halsey-Hill models for all but one of the materials studied. The fractal dimensions of the carbon blacks obtained from gas adsorption were compared with those obtained independently by small angle X-ray scattering and showed good agreement. Density functional theory was used to characterise one of the carbon blacks, as the standard BET model was not applicable.

  6. Impact of physicochemical properties of porous silica materials conjugated with dexamethasone via pH-responsive hydrazone bond on drug loading and release behavior

    NASA Astrophysics Data System (ADS)

    Numpilai, Thanapha; Witoon, Thongthai; Chareonpanich, Metta; Limtrakul, Jumras

    2017-02-01

    The conjugation of dexamethasone (DEX) onto modified-porous silica materials via a pH-responsive hydrazone bond has been reported to be highly efficient method to specifically deliver the DEX to diseased sites. However, the influence of physicochemical properties of porous silica materials has not yet been fully understood. In this paper, the impact of pore sizes, particle sizes and silanol contents on surface functionalization, drug loading and release behavior of porous silica materials conjugated with dexamethasone via pH-responsive hydrazone bond was investigated. The grafting density was found to relate to the number of silanol groups on the surface of porous silica materials. The particle size and macropores of the porous silica materials played an vital role on the drug loading and release behavior. Although the porous silica materials with larger particle sizes possessed a lower grafting density, a larger amount of drug loading could be achieved. Moreover, the porous silica materials with larger particle sizes showed a slower release rate of DEX due to a longer distance for cleaved DEX diffusion out of pores. DEX release rate exhibited pH-dependent, sustained release. At pH 4.5, the amount of DEX release within 10 days could be controlled in the range of 12.74-36.41%, depending on the host material. Meanwhile, less than 1.5% of DEX was released from each of type of the porous silica materials at pH 7.4. The results of silica dissolution suggested that the degradation of silica matrix did not significantly affect the release rate of DEX. In addition, the kinetic modeling studies revealed that the DEX releases followed Korsmeyer-Peppas model with a release exponent (n) ranged from 0.3 to 0.47, indicating a diffusion-controlled release mechanism.

  7. Modeling of coupled hydro-mechanical problem for porous media

    NASA Astrophysics Data System (ADS)

    Koudelka, T.; Krejci, T.; Broucek, M.

    2013-10-01

    The paper deals with numerical modelling of coupled hydro-mechanical problem for porous media. It is focused on coupled hydro-mechanical models for saturated - partially saturated soils. These models were implemented to the SIFEL software package and they were used for numerical simulation of a plate settlement experiment.

  8. Numerical Modelling of Wave Interaction with Porous Structures

    NASA Astrophysics Data System (ADS)

    Gao, F.; M., D.; M., D.; G., C.

    This paper presents a numerical model for simulating wave interaction with porous structures. By using the free surface-capturing approach together with a novel Cartesian cut cell treatment, the Finite Volume Model calculates the two phase flows out side of porous structure based on the Navier-Stokes equations, while the flow in the porous structure is described by Navier-Stokes type model equations. The free surface of water is treated as a contact discontinuity in the density field which is captured automatically as part of the numerical solution by using a time-accurate artificial compressibility method and high resolution Godunov-type scheme. The numerical model is first calibrated by simple test for a steady flow passing through a porous block. Reasonably good agreements with other numerical results are obtained. After that, the numerical model is used to simulate the breaking wave overtopping a caisson breakwater, protected by a layer of armor units. The results show that the porous armor layer is effective in reducing the overtopping rate as well as in protecting the stability of the caisson breakwater.

  9. 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.

  10. Langevin model for reactive transport in porous media

    NASA Astrophysics Data System (ADS)

    Tartakovsky, Alexandre M.

    2010-08-01

    Existing continuum models for reactive transport in porous media tend to overestimate the extent of solute mixing and mixing-controlled reactions because the continuum models treat both the mechanical and diffusive mixings as an effective Fickian process. Recently, we have proposed a phenomenological Langevin model for flow and transport in porous media [A. M. Tartakovsky, D. M. Tartakovsky, and P. Meakin, Phys. Rev. Lett. 101, 044502 (2008)10.1103/PhysRevLett.101.044502]. In the Langevin model, the fluid flow in a porous continuum is governed by a combination of a Langevin equation and a continuity equation. Pore-scale velocity fluctuations, the source of mechanical dispersion, are represented by the white noise. The advective velocity (the solution of the Langevin flow equation) causes the mechanical dispersion of a solute. Molecular diffusion and sub-pore-scale Taylor-type dispersion are modeled by an effective stochastic advection-diffusion equation. Here, we propose a method for parameterization of the model for a synthetic porous medium, and we use the model to simulate multicomponent reactive transport in the porous medium. The detailed comparison of the results of the Langevin model with pore-scale and continuum (Darcy) simulations shows that: (1) for a wide range of Peclet numbers the Langevin model predicts the mass of reaction product more accurately than the Darcy model; (2) for small Peclet numbers predictions of both the Langevin and the Darcy models agree well with a prediction of the pore-scale model; and (3) the accuracy of the Langevin and Darcy model deteriorates with the increasing Peclet number but the accuracy of the Langevin model decreases more slowly than the accuracy of the Darcy model. These results show that the separate treatment of advective and diffusive mixing in the stochastic transport model is more accurate than the classical advection-dispersion theory, which uses a single effective diffusion coefficient (the dispersion

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

    SciTech Connect

    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.

  12. 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.

  13. 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.

  14. High Strain-Rate and Quasi-Static Ductile Failure Mechanisms in Porous Materials

    DTIC Science & Technology

    2007-11-02

    detailed understanding of the interrelated physical mechanisms that can result in ductile material failure in rate-dependent porous crystalline materials subjected...strains and slip-rates, and hydrostatic stresses on failure paths and ligament damage in face centered cubic (f.c.c.) crystalline materials have been

  15. 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

  16. 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

  17. Interaction of a He-Ne laser light with the moist surface zone of porous material

    NASA Astrophysics Data System (ADS)

    Rozniakowski, Kazimierz; Wojtatowicz, Tomasz W.; Drobnik, Antoni; Jeske, I.

    1995-03-01

    The light scattered from the `rough' surface of a porous body illuminated by a narrow laser beam is carrying the information on geometrical micro structure of this surface. It is possible that the water vapor and water droplets in pores will cause changes in scattered light too. The aim of this paper is to present the results of the experimental investigations of the intensity of a helium-neon laser light reflected by a porous and moist gypsum slurry surface. Experiments show that the scattered light intensity increases with the decrease of the moisture content in porous material.

  18. Multiscale modeling of turbulent channel flow over porous walls

    NASA Astrophysics Data System (ADS)

    Yogaraj, Sudhakar; Lacis, Ugis; Bagheri, Shervin

    2016-11-01

    We perform direct numerical simulations of fully developed turbulent flow through a channel coated with a porous material. The Navier-stokes equations governing the fluid domain and the Darcy equations of the porous medium are coupled using an iterative partitioned scheme. At the interface between the two media, boundary conditions derived using a multiscale homogenization approach are enforced. The main feature of this approach is that the anisotropic micro-structural pore features are directly taken into consideration to derive the constitutive coefficients of the porous media as well as of the interface. The focus of the present work is to study the influence of micro-structure pore geometry on the dynamics of turbulent flows. Detailed turbulence statistics and instantaneous flow field are presented. For comparison, flow through impermeable channel flows are included. Supported by the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant agreement No 708281.

  19. 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

  20. 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.

  1. 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

  2. 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

  3. 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

  4. Reconstruction of material properties profiles in one-dimensional macroscopically inhomogeneous rigid frame porous media in the frequency domain.

    PubMed

    De Ryck, L; Lauriks, W; Leclaire, P; Groby, J P; Wirgin, A; Depollier, C

    2008-09-01

    The present paper deals with the inverse scattering problem involving macroscopically inhomogeneous rigid frame porous media. It consists of the recovery, from acoustic measurements, of the profiles of spatially varying material parameters by means of an optimization approach. The resolution is based on the modeling of acoustic wave propagation in macroscopically inhomogeneous rigid frame porous materials, which was recently derived from the generalized Biot's theory. In practice, the inverse problem is solved by minimizing an objective function defined in the least-square sense by the comparison of the calculated reflection (and transmission) coefficient(s) with the measured or synthetic one(s), affected or not by additive Gaussian noise. From an initial guess, the profiles of the x-dependent material parameters are reconstructed iteratively with the help of a standard conjugate gradient method. The convergence rate of the latter and the accuracy of the reconstructions are improved by the availability of an analytical gradient.

  5. 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).

  6. 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.

  7. 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

  8. Applicability of Washburn capillary rise for determining contact angles of powders/porous materials.

    PubMed

    Kirdponpattara, Suchata; Phisalaphong, Muenduen; Newby, Bi-min Zhang

    2013-05-01

    The Washburn capillary rise (WCR) technique has been widely utilized for determining contact angles of powders or porous materials; however, there are concerns regarding powder size and powder packing, especially for materials that exhibit large contact angle hysteresis. In this paper, some of these concerns were addressed. Due to the large water contact angle hysteresis on flat nylon 6/6 films, these films were ground into powders of different sizes and then used as model packing materials. The powders were packed in glass tubes to result in various packing structures that affected the penetration (i.e. advancing) rate of the test liquids. While all advancing contact angles obtained from WCR were found to be overestimated, more reasonable values were resulted when relatively large powders (e.g. 500-2000 μm) were used to pack the tubes. With larger powders, the packing contained bigger voids and consequently lead to slower penetration rates of the liquids, hence a relatively smaller advancing contact angle. The smaller advancing contact angle obtained from the slower advancing rate was also observed by using the sessile drop method. To verify the applicability of using large powders (500-2000 μm) for contact angle determination by using WCR, the advancing water contact angles of a bacterial cellulose/alginate composite sponge (BCA) with and without UV/ozone treatment were measured. The results showed that by using relatively large powders, WCR could be applied to obtain a reasonable advancing contact angle and assess the wettability change of complex porous materials.

  9. On the Acoustic Absorption of Porous Materials with Different Surface Shapes and Perforated Plates

    NASA Astrophysics Data System (ADS)

    CHEN, WEN-HWA; LEE, FAN-CHING; CHIANG, DAR-MING

    2000-10-01

    In architectural acoustic design, perforated plates are often used to protect porous materials from erosion. Although porous materials are usually applied to passive noise control, the effects of their surface shapes are seldom studied. To study the acoustic absorption of porous materials with different surface shapes and perforated plates, an efficient finite element procedure, which is derived by the Galerkin residual method and Helmholtz wave propagation equation, is used in this work. The two-microphone transfer function method and the modified Ingard and Dear impedance tube testing system are employed to measure the parameters deemed necessary for the finite element analysis, such as complex wave propagation constant, characteristic impedance and flow resistivity. For verifying the finite element results, the two-microphone transfer function method is also applied to measure the absorption coefficients of the discussed acoustic absorbers. Four surface shapes of commercially available porous materials, i.e., triangle, semicircle, convex rectangle and plate shapes, are chosen for analysis. The porosity of perforated plates is then evaluated. Finally, the distinct effect of the flow resistivity of porous materials on the acoustic absorption is demonstrated.

  10. Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties.

    PubMed

    Simon, Cory M; Braun, Efrem; Carraro, Carlo; Smit, Berend

    2017-01-17

    Some nanoporous, crystalline materials possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical model of gas adsorption in a porous crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our model captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple model contribute a more intimate understanding of the response and consequence of rotating ligands integrated into porous materials to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our model reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes.

  11. Synthesis and gas adsorption study of porous metal-organic framework materials

    NASA Astrophysics Data System (ADS)

    Mu, Bin

    Metal-organic frameworks (MOFs) or porous 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 materials have some distinct advantages over traditional porous materials 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 porous 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 porous materials 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 porous coordination polymers; (ii) Evaluate porous MOF materials 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 porous MOF materials 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.

  12. Modeling evaporation from porous media influenced by atmospheric processes

    NASA Astrophysics Data System (ADS)

    Mosthaf, K.; Baber, K.; Flemisch, B.; Helmig, R.

    2012-04-01

    Modeling evaporation processes from partially saturated soils into the ambient air is a challenging task. It involves usually a variety of interacting processes and depends on the multitude of properties of the fluids and of the porous medium. Often, the ambient free-flow and the porous-medium compartments are modeled separately with a specification of the evaporation rate as boundary condition. We have developed a coupling concept, which allows the combined modeling of a free-flow and a porous-medium system under non-isothermal conditions with the evaporative fluxes across the soil-atmosphere interface as model output. It is based on flux continuity and local thermodynamic equilibrium at the interface. Darcy's law for multiple phases is used in the porous medium, whereas the ambient air flow is modeled as a compositional single-phase Stokes system. The concept has been implemented in the numerical simulator DuMux. A comparison of simulated and measured data from wind tunnel experiments performed in the group of D. Or (ETH Zürich) will be shown. Furthermore, the impact of several parameters, such as a varying wind velocity, temperature or different soil properties on the evaporation process has been analyzed in a numerical parameter study. The results will be presented and discussed.

  13. Modeling of the mass transport in porous media under laser beam irradiation

    NASA Astrophysics Data System (ADS)

    Wojtatowicz, Tomasz W.

    1995-03-01

    The vaporization of porous materials (especially internal vaporization of skeleton) has been largely ignored in studies of laser heating and processing of materials. The loss of energy associated with the vaporization process would keep the internal temperature of material from rising. In this paper the author presents the results of the computation of the heat losses for two different models of porous media: the sand and the pores' tree model. In his calculation the author uses the thermophysical parameters of gypsum slurry. In the first step a numerical simulation is carried out for the vaporization of solid skeleton and mass transport of vapor (without the viscosity of vapor), only. Then the water on the pore's wall was taken into account.

  14. Multiphase Porous Media Modelling: A novel approach to predicting food processing performance.

    PubMed

    Khan, Md Imran H; Joardder, M U H; Kumar, Chandan; Karim, M A

    2016-07-20

    The development of a physics-based model of food processing is essential to improve the quality of processed food and optimise energy consumption. Food materials, particularly plant-based food materials, are complex in nature as they are porous and have hygroscopic properties. A multiphase porous media model for simultaneous heat and mass transfer can provide a realistic understanding of transport processes and thus can help to optimise energy consumption and improve food quality. Although the development of a multiphase porous media model for food processing is a challenging task because of its complexity, many researchers have attempted it. The primary aim of this paper is to present a comprehensive review of the multiphase models available in the literature for different methods of food processing, such as drying, frying, cooking, baking, heating and roasting. A critical review of the parameters that should be considered for multiphase modelling is presented which includes input parameters, material properties, simulation techniques and the hypotheses. A discussion on the general trends in outcomes, such as moisture saturation, temperature profile, pressure variation and evaporation patterns, is also presented. The paper concludes by considering key issues in the existing multiphase models and future directions for development of multiphase models.

  15. Porous hollow carbon spheres for electrode material of supercapacitors and support material of dendritic Pt electrocatalyst

    NASA Astrophysics Data System (ADS)

    Fan, Yang; Liu, Pei-Fang; Huang, Zhong-Yuan; Jiang, Tong-Wu; Yao, Kai-Li; Han, Ran

    2015-04-01

    Porous 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 material 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.

  16. Pore network model of electrokinetic transport through charged porous media

    NASA Astrophysics Data System (ADS)

    Obliger, Amaël; Jardat, Marie; Coelho, Daniel; Bekri, Samir; Rotenberg, Benjamin

    2014-04-01

    We introduce a method for the numerical determination of the steady-state response of complex charged porous media to pressure, salt concentration, and electric potential gradients. The macroscopic fluxes of solvent, salt, and charge are computed within the framework of the Pore Network Model (PNM), which describes the pore structure of the samples as networks of pores connected to each other by channels. The PNM approach is used to capture the couplings between solvent and ionic flows which arise from the charge of the solid surfaces. For the microscopic transport coefficients on the channel scale, we take a simple analytical form obtained previously by solving the Poisson-Nernst-Planck and Stokes equations in a cylindrical channel. These transport coefficients are upscaled for a given network by imposing conservation laws for each pores, in the presence of macroscopic gradients across the sample. The complex pore structure of the material is captured by the distribution of channel diameters. We investigate the combined effects of this complex geometry, the surface charge, and the salt concentration on the macroscopic transport coefficients. The upscaled numerical model preserves the Onsager relations between the latter, as expected. The calculated macroscopic coefficients behave qualitatively as their microscopic counterparts, except for the permeability and the electro-osmotic coupling coefficient when the electrokinetic effects are strong. Quantitatively, the electrokinetic couplings increase the difference between the macroscopic coefficients and the corresponding ones for a single channel of average diameter.

  17. Averaged model for momentum and dispersion in hierarchical porous media.

    PubMed

    Chabanon, Morgan; David, Bertrand; Goyeau, Benoît

    2015-08-01

    Hierarchical porous media are multiscale systems, where different characteristic pore sizes and structures are encountered at each scale. Focusing the analysis to three pore scales, an upscaling procedure based on the volume-averaging method is applied twice, in order to obtain a macroscopic model for momentum and diffusion-dispersion. The effective transport properties at the macroscopic scale (permeability and dispersion tensors) are found to be explicitly dependent on the mesoscopic ones. Closure problems associated to these averaged properties are numerically solved at the different scales for two types of bidisperse porous media. Results show a strong influence of the lower-scale porous structures and flow intensity on the macroscopic effective transport properties.

  18. 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.

  19. Velocity measurements of inert porous materials driven by infrared-laser-ablated thin-film titanium

    SciTech Connect

    Bedeaux, Brett C.; Trott, Wayne M.; Castaneda, Jaime N.

    2010-02-15

    This article presents and interprets a series of experiments performed to measure the velocity of four inert low-density porous materials that were accelerated by an ablated thin-film titanium metal, created by vaporizing a 250-nm-thick layer of titanium with a high-energy, Q-switched, pulsed, and 1.054 {mu}m neodymium-glass laser. Inert powder materials were chosen to match, among other characteristics, the morphology of energetic materials under consideration for use in detonator applications. The observed behavior occurs near the thin-film titanium ablation layer, through complex physical mechanisms, including laser absorption in the metal layer, ablation and formation of confined plasma that is a blackbody absorber of the remaining photon energy, and vaporization of the remaining titanium metal. One-dimensional hydrodynamic modeling provided a basis of comparison with the measured velocities. We found, as predicted in wave-propagation-code modeling, that an Asay foil can indicate total momentum of the driven material that is mechanically softer (lower in shock impedance) than the foil. The key conclusion is that the specific impulse delivered by the laser transfers a corresponding momentum to soft, organic power columns that are readily compacted. Impulse from the laser is less efficient in transferring momentum to hard inorganic particles that are less readily compacted.

  20. Inclusion of thiazyl radicals in porous crystalline materials.

    PubMed

    Potts, Storm V; Barbour, Leonard J; Haynes, Delia A; Rawson, Jeremy M; Lloyd, Gareth O

    2011-08-24

    The incorporation of benzodithiazolyl (BDTA) and methylbenzodithiazolyl (MBDTA) radicals into porous hybrid frameworks via gas phase diffusion revealed that inclusion appeared selective for the MIL53(Al) framework against a range of other potential hosts. Both PXRD and EPR studies are consistent with retention of a π*-π* dimer motif for BDTA in MIL53(Al)@BDTA whereas MBDTA in MIL53(Al)@MBDTA appears to be monomeric. The guests are readily released by the addition of solvent (CH(2)Cl(2)).

  1. Synthetic vs Natural: Diatoms Bioderived Porous Materials for the Next Generation of Healthcare Nanodevices.

    PubMed

    Rea, Ilaria; Terracciano, Monica; De Stefano, Luca

    2017-02-01

    Nanostructured porous materials promise a next generation of innovative devices for healthcare and biomedical applications. The fabrication of such materials generally requires complex synthesis procedures, not always available in laboratories or sustainable in industries, and has adverse environmental impact. Nanosized porous materials can also be obtained from natural resources, which are an attractive alternative approach to man-made fabrication. Biogenic nanoporous silica from diatoms, and diatomaceous earths, constitutes largely available, low-cost reservoir of mesoporous nanodevices that can be engineered for theranostic applications, ranging from subcellular imaging to drug delivery. In this progress report, main experiences on nature-derived nanoparticles with healthcare and biomedical functionalities are reviewed and critically analyzed in search of a new collection of biocompatible porous nanomaterials.

  2. Characterization of porous materials using combined small-angle X-ray and neutron scattering techniques

    SciTech Connect

    Hu, Naiping; Borkar, Neha; Kohls, Doug; Schaefer, Dale W.

    2014-09-24

    A combination of ultra small angle X-ray scattering (USAXS) and ultra small angle neutron scattering (USANS) is used to characterize porous materials. The analysis methods yield quantitative information, including the mean skeletal chord length, mean pore chord length, skeletal density, and composition. A mixed cellulose ester (MCE) membrane with a manufacturer-labeled pore size of 0.1 {mu}m was used as a model to elucidate the specifics of the method. Four approaches describing four specific scenarios (different known parameters and form of the scattering data) are compared. Pore chords determined using all four approaches are in good agreement with the scanning electron microscopy estimates but are larger than the manufacturer's nominal pore size. Our approach also gives the average chord of the skeletal solid (struts) of the membrane, which is also consistent for all four approaches. Combined data from USAXS and USANS gives the skeletal density and the strut composition.

  3. Effect of the features of functionalized structure on elastic properties and strength of partially-filled brittle porous materials

    NASA Astrophysics Data System (ADS)

    Konovalenko, Igor S.; Shilko, Evgeny V.; Konovalenko, Ivan S.; Vodopjyanov, Egor M.

    2016-11-01

    A two-scale mechanical model of brittle porous material partially filled with plastic filler (inclusions) was developed within the framework of the formalism of movable cellular automaton method. The model was applied to study the mechanical properties of mesoscopic samples with a linear distribution of the local porosity in the depth of the material. Calculation results showed essentially nonlinear dependence of their elastic and strength properties on the degree of pore space filling. It is found that depending on the sign of the gradient of porosity the value of shear strength of partially filled samples can significantly increase or remain constant with increase in the value of the degree of filling.

  4. 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://www.osti.gov/scitech/servlets/purl/1034349','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1034349"><span>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 [Idaho Falls, ID; Avci, Recep [Bozeman, MT; Groenewold, Gary S [Idaho Falls, ID</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/1163140','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1163140"><span>New Carbon-Based <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Increased Heats of Adsorption for Hydrogen Storage</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Snurr, Randall Q.; Hupp, Joseph T.; Kanatzidis, Mercouri G.; Nguyen, SonBinh T.</p> <p>2014-11-03</p> <p>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 <span class="hlt">porous</span> <span class="hlt">materials</span> that act as “sponges” to take up large quantities of hydrogen without the need for extremely high pressures. The <span class="hlt">materials</span> must meet many requirements to make this possible. This project aimed to develop two related classes of <span class="hlt">porous</span> <span class="hlt">materials</span> to meet these requirements. All <span class="hlt">materials</span> were synthesized from molecular constituents in a building-block approach, which allows for the creation of an incredibly wide variety of <span class="hlt">materials</span> in a tailorable fashion. The <span class="hlt">materials</span> 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 <span class="hlt">modeling</span> played a key role as a guide to experiment throughout the project. A major accomplishment of the project was the development of a <span class="hlt">material</span> with record hydrogen uptake at cryogenic temperatures. Although the ultimate goal was <span class="hlt">materials</span> 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 <span class="hlt">material</span> was originally sketched on paper based on a hypothesis that extended framework struts would yield <span class="hlt">materials</span> with excellent hydrogen storage properties. However, before starting the synthesis, we used molecular <span class="hlt">modeling</span> to assess the performance of the <span class="hlt">material</span> for hydrogen uptake</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6351930','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6351930"><span><span class="hlt">Model</span> of oil ganglion movement 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>Egbogah, E.O.; Wright, R.J.; Dawe, R.A.</p> <p>1981-01-01</p> <p>This paper presents a simple theory of the movement of a discontinuous oil droplet (ganglion) through a <span class="hlt">model</span> <span class="hlt">porous</span> medium. A quantitative description of the ganglion flow in the system was obtained through a tractable solution to the balance of forces controlling ganglion stability during flow of two immiscible fluids within a well-defined geometry. Calculations were based on a constricted conical (divergent-convergent) pore <span class="hlt">model</span>. Experimental data from a tetragonally packed sphere <span class="hlt">model</span> were used interactively with a theoretical static analysis to synthesize the relevant features of the ganglion mechanics into a coherent theory of oil mobilization. The <span class="hlt">model</span> analysis also permits the computation of relative ganglion velocity under various flow conditions. This is an essential parameter for enhanced oil recovery <span class="hlt">modelling</span> which facilitates the prediction of oil bank movements in <span class="hlt">porous</span> media. 34 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.738a2090E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.738a2090E"><span>Potential of Lattice Boltzmann Method to Determine the Ohmic Resistance 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>Espinoza-Andaluz, Mayken; Andersson, Martin; Sundén, Bengt</p> <p>2016-08-01</p> <p>The lattice Boltzmann method (LBM) is a suitable tool for solving transport phenomena that occur in gas- and liquid phases at different length scales, especially when complex geometries such as <span class="hlt">porous</span> media are involved. However, investigations about applications of LBM in the solid electrical conducting <span class="hlt">material</span> have not been carried out yet. Since in fuel cells (FCs) the multifunctional layers play an important role during the energy conversion process, and such layers consist of <span class="hlt">porous</span> <span class="hlt">material</span>, the ohmic resistance of <span class="hlt">porous</span> <span class="hlt">materials</span> represents a crucial characteristic to be studied to predict the internal ohmic losses. The purpose of this paper is to show the feasibility of LBM to determine the ohmic resistance of electrical conducting <span class="hlt">materials</span> whose dimensions are modified considering the crosssectional area and length. Characteristics, limitations and recommendations of LBM applied to solid electrical conducting <span class="hlt">materials</span> calculating the ohmic resistance are presented considering the coupling of the methodology with the Ohm's Law. Additionally, the behavior of the ohmic resistance for a given <span class="hlt">porous</span> <span class="hlt">material</span> is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1340777','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1340777"><span>Coordination Covalent Frameworks: A New Route for Synthesis and Expansion of Functional <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>Elsaidi, Sameh K.; Mohamed, Mona H.; Loring, John S.; McGrail, Bernard. Pete; Thallapally, Praveen K.</p> <p>2016-10-26</p> <p>The synthetic approaches for fine-tuning the structural properties of coordination polymers or metal organic frameworks have exponentially grown during the last decade. This is due to the control over the properties of the resulting structures such as stability, pore size, pore chemis-try and surface area for myriad possible applications. Herein, we present a new class of <span class="hlt">porous</span> <span class="hlt">materials</span> called Covalent Coordination Frameworks (CCFs) that were designed and effectively synthesized using a two-step reticular chemistry approach. During the first step, trigonal prismatic molecular building block was isolated using 4-aminobenazoic acid and Cr (III) salt, subsequently in the second step the polymerization of the isolated molecular building blocks (MBBs) takes place by the formation of strong covalent bonds where small organic molecules can connect the MBBs forming extended <span class="hlt">porous</span> CCF <span class="hlt">materials</span>. All the isolated CCFs were found to be permanently <span class="hlt">porous</span> while the discrete MBB were non-<span class="hlt">porous</span>. This approach would inevitably open a feasible path for the applications of reticular chemistry and the synthesis of novel <span class="hlt">porous</span> <span class="hlt">materials</span> with various topologies under ambient conditions using simple organic molecules and versatile MBBs with different functionalities which would not be possible using the traditional one step approach</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JHyd..543..796K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JHyd..543..796K"><span><span class="hlt">Modelling</span> karst aquifer evolution in fractured, <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>Kaufmann, Georg</p> <p>2016-12-01</p> <p>The removal of <span class="hlt">material</span> in soluble rocks by physical and chemical dissolution is an important process enhancing the secondary porosity of soluble rocks. Depending on the history of the soluble rock, dissolution can occur either along fractures and bedding partings of the rock in the case of a telogenetic origin, or within the interconnected pore space in the case of eogenetic origin. In soluble rocks characterised by both fractures and pore space, dissolution in both flow compartments is possible. We investigate the dissolution of calcite both along fractures and within the pore space of a limestone rock by numerical <span class="hlt">modelling</span>. The limestone rock is treated as fractured, <span class="hlt">porous</span> aquifer, in which the hydraulic conductivity increases with time both for the fractures and the pore spaces. We show that enlargement of pore space by dissolution will accelerate the development of a classical fracture-dominated telogenetic karst aquifer, breakthrough occurs faster. In the case of a pore-controlled aquifer as in eogenetic rocks, enlargement of pores results in a front of enlarged pore spaces migrating into the karst aquifer, with more homogeneous enlargement around this dissolution front, and later breakthrough.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008CRMec.336..176L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008CRMec.336..176L"><span>A theoretical approach of strain localization within thin planar bands in <span class="hlt">porous</span> ductile <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>Leblond, Jean-Baptiste; Mottet, Gérard</p> <p>2008-01-01</p> <p>Propagation of cracks in ductile <span class="hlt">materials</span> is well known to occur through two possible mechanisms: coalescence of cavities and formation of shear bands ('void sheet mechanism'). The classical Gurson-Tvergaard-Needleman (GTN) homogenized <span class="hlt">model</span> for such <span class="hlt">materials</span> incorporates some phenomenological <span class="hlt">modelling</span> of coalescence, but not of formation of shear bands assisted by the presence of microvoids, and this generates a number of shortcomings. In order to solve these difficulties, this paper presents a unified <span class="hlt">model</span> of both coalescence and formation of shear bands in <span class="hlt">porous</span> plastic solids, including the possible couplings between the two. Both phenomena are viewed as expressions of the same basic effect, namely strain localization within thin planar bands, the only difference being the mode of deformation. The <span class="hlt">model</span> is first developed assuming a periodic distribution of cavities, then critically assessed through comparison with some micromechanical numerical simulations based on the same assumption, and finally extended to the case of a random distribution of voids. To cite this article: J.-B. Leblond, G. Mottet, C. R. Mecanique 336 (2008).</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>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://hdl.handle.net/2060/19980001239','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980001239"><span><span class="hlt">Porous</span> and Microporous Honeycomb Composites as Potential Boundary-Layer Bleed <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>Davis, D. O.; Willis, B. P.; Schoenenberger, M.</p> <p>1997-01-01</p> <p>Results of an experimental investigation are presented in which the use of <span class="hlt">porous</span> and microporous honeycomb composite <span class="hlt">materials</span> is evaluated as an alternate to perforated solid plates for boundary-layer bleed in supersonic aircraft inlets. The terms "<span class="hlt">porous</span>" and "microporous," respectively, refer to bleed orifice diameters roughly equal to and much less than the displacement thickness of the approach boundary-layer. A Baseline <span class="hlt">porous</span> solid plate, two <span class="hlt">porous</span> honeycomb, and three microporous honeycomb configurations are evaluated. The performance of the plates is characterized by the flow coefficient and relative change in boundary-layer profile parameters across the bleed region. The tests were conducted at Mach numbers of 1.27 and 1.98. The results show the <span class="hlt">porous</span> honeycomb is not as efficient at removing mass compared to the baseline. The microporous plates were about equal to the baseline with one plate demonstrating a significantly higher efficiency. The microporous plates produced significantly fuller boundary-layer profiles downstream of the bleed region for a given mass flow removal rate than either the baseline or the <span class="hlt">porous</span> honeycomb plates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/949118','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/949118"><span>Stochastic Langevin <span class="hlt">Model</span> for Flow and 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>Tartakovsky, Alexandre M.; Tartakovsky, Daniel M.; Meakin, Paul</p> <p>2008-07-25</p> <p>A new stochastic Lagrangian <span class="hlt">model</span> for fluid flow and transport in <span class="hlt">porous</span> media is described. The fluid is represented by particles whose flow and dispersion in a continuous <span class="hlt">porous</span> medium is governed by a Langevin equation. Changes in the properties of the fluid particles (e.g. the solute concentration) due to molecular diffusion is governed by the advection-diffusion equation. The separate treatment of advective and diffusive mixing in the stochastic <span class="hlt">model</span> has an advantage over the classical advection-dispersion theory, which uses a single effective diffusion coefficient (the dispersion coefficient) to describe both types of mixing leading to over-prediction of mixing induced effective reaction rates. The stochastic <span class="hlt">model</span> predicts much lower reaction product concentrations in mixing induced reactions. In addition the dispersion theory predicts more stable fronts (with a higher effective fractal dimension) than the stochastic <span class="hlt">model</span> during the growth of Rayleigh-Taylor instabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3751908','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3751908"><span>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/2013NRL.....8..266C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NRL.....8..266C"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/23742134','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23742134"><span>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="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Capoen, Bruno; Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bouazaoui, Mohamed</p> <p>2013-06-06</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.osti.gov/scitech/servlets/purl/1038224','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1038224"><span><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('https://www.ncbi.nlm.nih.gov/pubmed/27255561','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27255561"><span>Applications of hierarchically structured <span class="hlt">porous</span> <span class="hlt">materials</span> from energy storage and conversion, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Ming-Hui; Huang, Shao-Zhuan; Chen, Li-Hua; Li, Yu; Yang, Xiao-Yu; Yuan, Zhong-Yong; Su, Bao-Lian</p> <p>2016-06-13</p> <p>Over the last decade, significant effort has been devoted to the applications of hierarchically structured <span class="hlt">porous</span> <span class="hlt">materials</span> owing to their outstanding properties such as high surface area, excellent accessibility to active sites, and enhanced mass transport and diffusion. The hierarchy of porosity, structural, morphological and component levels in these <span class="hlt">materials</span> is key for their high performance in all kinds of applications. The introduction of hierarchical porosity into <span class="hlt">materials</span> has led to a significant improvement in the performance of <span class="hlt">materials</span>. Herein, recent progress in the applications of hierarchically structured <span class="hlt">porous</span> <span class="hlt">materials</span> from energy conversion and storage, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine is reviewed. Their potential future applications are also highlighted. We particularly dwell on the relationship between hierarchically <span class="hlt">porous</span> structures and properties, with examples of each type of hierarchically structured <span class="hlt">porous</span> <span class="hlt">material</span> according to its chemical composition and physical characteristics. The present review aims to open up a new avenue to guide the readers to quickly obtain in-depth knowledge of applications of hierarchically <span class="hlt">porous</span> <span class="hlt">materials</span> and to have a good idea about selecting and designing suitable hierarchically <span class="hlt">porous</span> <span class="hlt">materials</span> for a specific application. In addition to focusing on the applications of hierarchically <span class="hlt">porous</span> <span class="hlt">materials</span>, this comprehensive review could stimulate researchers to synthesize new advanced hierarchically <span class="hlt">porous</span> solids.</p> </li> <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>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> </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('https://www.osti.gov/scitech/biblio/22207389','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22207389"><span>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4872234','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4872234"><span>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://adsabs.harvard.edu/abs/2016NatMa..15..371C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatMa..15..371C"><span><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://pubs.er.usgs.gov/publication/70019031','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70019031"><span>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://hdl.handle.net/2060/19890007948','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890007948"><span>Mechanics of <span class="hlt">materials</span> <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Meister, Jeffrey P.</p> <p>1987-01-01</p> <p>The Mechanics of <span class="hlt">Materials</span> <span class="hlt">Model</span> (MOMM) is a three-dimensional inelastic structural analysis code for use as an early design stage tool for hot section components. MOMM is a stiffness method finite element code that uses a network of beams to characterize component behavior. The MOMM contains three <span class="hlt">material</span> <span class="hlt">models</span> to account for inelastic <span class="hlt">material</span> behavior. These include the simplified <span class="hlt">material</span> <span class="hlt">model</span>, which assumes a bilinear stress-strain response; the state-of-the-art <span class="hlt">model</span>, which utilizes the classical elastic-plastic-creep strain decomposition; and Walker's viscoplastic <span class="hlt">model</span>, which accounts for the interaction between creep and plasticity that occurs under cyclic loading conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MeScT..28a4006S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MeScT..28a4006S"><span>Salinity index determination of <span class="hlt">porous</span> <span class="hlt">materials</span> using open-ended probes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Szypłowska, Agnieszka; Kafarski, Marcin; Wilczek, Andrzej; Lewandowski, Arkadiusz; Skierucha, Wojciech</p> <p>2017-01-01</p> <p>The relations among soil water content, bulk electrical conductivity and electrical conductivity of soil solution can be described by a number of theoretical and empirical <span class="hlt">models</span>. The aim of the paper is to examine the performance of open-ended coaxial probes with and without a short antenna in determination of complex dielectric permittivity spectra, moisture and salinity of <span class="hlt">porous</span> <span class="hlt">materials</span> using the salinity index approach. Glass beads of 0.26 and 1.24 mm average diameters moistened to various water contents with distilled water and KCl solutions were used to <span class="hlt">model</span> the soil <span class="hlt">material</span>. Due to the larger sensitivity zone, only the probe with the antenna enabled determination of bulk electrical conductivity and salinity index of the samples. The relations between bulk electrical conductivity and dielectric permittivity of the samples were highly linear, which was consistent with the salinity index <span class="hlt">model</span>. The slope of the relation between salinity index and electrical conductivity of moistening solutions closely matched the value for 100 % sand presented in literature.</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>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://www.osti.gov/scitech/servlets/purl/485961','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/485961"><span>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/2017JNET...42...79A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JNET...42...79A"><span><span class="hlt">Models</span> for New Corrugated and <span class="hlt">Porous</span> Solar Air Collectors under Transient Operation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adnan Abed, Qahtan; Badescu, Viorel; Ciocanea, Adrian; Soriga, Iuliana; Bureţea, Dorin</p> <p>2017-01-01</p> <p>Mathematical <span class="hlt">models</span> have been developed to evaluate the dynamic behavior of two solar air collectors: the first one is equipped with a V-<span class="hlt">porous</span> absorber and the second one with a U-corrugated absorber. The collectors have the same geometry, cross-section surface area and are built from the same <span class="hlt">materials</span>, the only difference between them being the absorbers. V-corrugated absorbers have been treated in literature but the V-<span class="hlt">porous</span> absorbers <span class="hlt">modeled</span> here have not been very often considered. The <span class="hlt">models</span> are based on first-order differential equations which describe the heat exchange between the main components of the two types of solar air heaters. Both collectors were exposed to the sun in the same meteorological conditions, at identical tilt angle and they operated at the same air mass flow rate. The tests were carried out in the climatic conditions of Bucharest (Romania, South Eastern Europe). There is good agreement between the theoretical results and experiments. The average bias error was about 7.75 % and 10.55 % for the solar air collector with "V"-<span class="hlt">porous</span> absorber and with "U"-corrugated absorber, respectively. The collector based on V-<span class="hlt">porous</span> absorber has higher efficiency than the collector with U-corrugated absorber around the noon of clear days. Around sunrise and sunset, the collector with U-corrugated absorber is more effective.</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>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.dtic.mil/docs/citations/ADA360804','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA360804"><span><span class="hlt">Porous</span> and Cellular <span class="hlt">Materials</span> for Structural Applications; Symposium Held in San Francisco, California on April 13-15, 1998</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1998-04-01</p> <p><span class="hlt">POROUS</span> AERATED AUTOCLAVED CONCRETE Thomas Schneider*, Georg Schober** and Peter Greil* *University of Erlangen-Nuernberg, Department of <span class="hlt">Materials</span> ...Fürstenfeldbruck, Ger- many Abstract Highly <span class="hlt">porous</span> building <span class="hlt">materials</span> like aerated autoclaved concrete are characterized by low- thermal conductivity and...The use of autoclaved aerated concrete (AAC) in constructions requires a high mechanical strength but thermal conductivity. In the production</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4680965','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4680965"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/26671169','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26671169"><span>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="https://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>2015-12-16</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://adsabs.harvard.edu/abs/2015NatSR...518373J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...518373J"><span>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>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('https://www.ncbi.nlm.nih.gov/pubmed/26353534','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26353534"><span>Influence of Environmental Factors on the Adsorption Capacity and Thermal Conductivity of Silica Nano-<span class="hlt">Porous</span> <span class="hlt">Materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Hu; Gu, Wei; Li, Ming-Jia; Fang, Wen-Zhen; Li, Zeng-Yao; Tao, Wen-Quan</p> <p>2015-04-01</p> <p>In this work, the influence of temperature and humidity environment on the water vapor adsorption capacity and effective thermal conductivity of silica nano-<span class="hlt">porous</span> <span class="hlt">material</span> is conducted within a relative humidity range from 15% to 90% at 25 °C, 40 °C and 55 °C, respectively. The experiment results show that both the temperature and relative humidity have significant influence on the adsorption capacity and effective thermal conductivity of silica nano-<span class="hlt">porous</span> <span class="hlt">materials</span>. The adsorption capacity and effective thermal conductivity increase with humidity because of the increases of water vapor concentration. The effective thermal conductivity increases linearly with adsorption saturation capacity at constant temperature. Because adsorption process is exothermic reaction, the increasing temperature is not conducive to the adsorption. But the effective thermal conductivity increases with the increment of temperature at the same water uptake because of the increment of water thermal conductivity with temperature Geometric <span class="hlt">models</span> and unit cell structure are adopted to predict the effective thermal conductivity and comparisons with the experimental result are made, and for the case of moist silica nano-<span class="hlt">porous</span> <span class="hlt">materials</span> with high porosity no quantitative agreement is found. It is believed that the adsorbed water will fill in the nano-pores and gap and form lots of short cuts, leading to a significant reduction of the thermal resistance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1341581-hyper-crosslinked-cyclodextrin-porous-polymer-efficient-co2-capturing-material-tunable-porosity','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1341581-hyper-crosslinked-cyclodextrin-porous-polymer-efficient-co2-capturing-material-tunable-porosity"><span>Hyper-crosslinked cyclodextrin <span class="hlt">porous</span> polymer: An efficient CO2 capturing <span class="hlt">material</span> with tunable porosity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Meng, Bo; Li, Haiyang; East China Univ. of Science and Technology, Shanghai; ...</p> <p>2016-11-11</p> <p>We designed and synthesized the cyclodextrin (CD)-based hyper-crosslinked <span class="hlt">porous</span> polymers (HCPPs) for selective CO2 adsorption and storage. We also explored the effect of monomer size on micropore formation, and determined a feasible way to tailor the porosity of the <span class="hlt">materials</span> during the hyper-crosslinking process.</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><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://www.osti.gov/scitech/servlets/purl/810008','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/810008"><span>Countercurrent Gaseous Diffusion <span class="hlt">Model</span> of Oxidation Through a <span class="hlt">Porous</span> Coating</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Holcomb, G.R.</p> <p>1996-07-01</p> <p>A countercurrent gaseous diffusion <span class="hlt">model</span> was developed to describe oxidation through <span class="hlt">porous</span> coatings and scales. The specific system <span class="hlt">modeled</span> involved graphite oxidized through a <span class="hlt">porous</span> alumina (Al{sub 2}O{sub 3}) overcoat between 570 C (1,058 F) and 975 C (1,787 F). The <span class="hlt">model</span> separated the <span class="hlt">porous</span> Al{sub 2}O{sub 3} coating into two gas diffusion regions separated by a flame front, where oxygen (O{sub 2}) and carbon monoxide (CO) react to form carbon dioxide (CO{sub 2}). In the outer region O{sub 2} and CO{sub 2} counterdiffused. In the inner region, CO{sub 2} and CO counterdiffused. Concentration gradients of each gaseous specie in the pores of the Al{sub 2}O{sub 3} were determined, and the oxidation rate was calculated. The <span class="hlt">model</span> was verified by oxidation experiments using graphite through various <span class="hlt">porous</span> Al{sub 2}O{sub 3} overcoats. The Al{sub 2}O{sub 3} overcoats ranged in fractional porosity and in average pore radius from 0.077 {micro}m (3.0 x 10{sup -6} in., Knudsen diffusion) to 10.0 {micro}m (3.9 x 10{sup -4} in., molecular diffusion). Predicted and measured oxidation rates were shown to have the same dependence upon porosity, pore radius, temperature, and oxygen partial pressure (P{sub O{sub 2}}). Use of the <span class="hlt">model</span> was proposed for other oxidation systems and for chemical vapor infiltration (CVI). This work was part of the U.S. Bureau of Mines corrosion research program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1083394','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1083394"><span>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> </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://hdl.handle.net/2060/19950020938','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950020938"><span>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/abs/2010PhDT.......264M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.......264M"><span><span class="hlt">Modeling</span> imbibition of liquids into rigid and swelling <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>Masoodi, Reza</p> <p></p> <p>In <span class="hlt">porous</span> media studies, imbibition is the spontaneous movement of a liquid into a <span class="hlt">porous</span> medium under the influence of capillary forces. It is also known by the name wicking, and can sometimes be aided by an external pressure, as in the case of forced infiltration of liquid polymers into a bed of fibermats. In this study, the imbibition of liquids into <span class="hlt">porous</span> media in important engineering applications is studied. A relatively new approach of using the single-phase flow behind a clearly-defined liquid front in a <span class="hlt">porous</span> medium has been adopted in this work to <span class="hlt">model</span> imbibition or wicking. Such an approach employs Darcy's law in conjunction with the continuity equation to <span class="hlt">model</span> the liquid flow behind the front. First the <span class="hlt">modeling</span> of liquid flow in polymer wicks is undertaken. A new formula to predict the capillary suction-pressure at the liquid fronts in commercial wicks made of sintering the polymer beads was proposed. Later, a more general formula was derived and verified for estimating the capillary suction pressure in any kind of <span class="hlt">porous</span> substance. We compared the performance of the proposed Darcy's-law based approach with that of the Lucas-Washburn equation; some new methods were suggested to improve the accuracy of these two dominant methods for <span class="hlt">modeling</span> the liquid transport in aforementioned wicks. Our Darcy's law based <span class="hlt">modeling</span> approach is superior to the previous Washburn Equation based approaches as the former can be easily extended to 2-D and 3-D unlike the latter. The 3-D liquid flow in the wicks was studied numerically using PORE-FLOW(c), an in-house computer program to <span class="hlt">model</span> <span class="hlt">porous</span>-media flows. For the first time, the finite element/control volume (FE/CV) algorithm is employed to solve the moving- boundary problem encountered in wicking. A good validation is achieved against the 1-D wicking-flow analytical solution as well as a 3-D wicking experiment involving a wick with two different cross-sections. A special case of wicking, in which both the external</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25983311','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25983311"><span>An explicit formula for the coherent SH waves' attenuation coefficient in random <span class="hlt">porous</span> <span class="hlt">materials</span> with low porosities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Jun; Ye, Wenjing</p> <p>2015-09-01</p> <p>In this paper, the attenuation coefficient of coherent SH waves in random <span class="hlt">porous</span> <span class="hlt">material</span> with uniformly randomly distributed elliptical cavities of different aspect ratios is studied. Based on an analysis of the mechanism for attenuation, a simple macro <span class="hlt">model</span> for the attenuation coefficient is proposed. The macro <span class="hlt">model</span> says that the attenuation coefficient can be expressed as a function of the mean scattering cross section and the number density of cavities at low porosities. Then, large-scale numerical simulations using the pre-corrected Fast Fourier Transform (pFFT) algorithm accelerated Boundary Element Method (BEM) are conducted to specify this macro <span class="hlt">model</span>. Finally, this macro <span class="hlt">model</span> is compared with four theoretical <span class="hlt">models</span> derived for composite/<span class="hlt">porous</span> <span class="hlt">materials</span> with circular inclusions at the porosity p=3.17% and 5%. Results show this macro <span class="hlt">model</span> agree well with three of them. Compared to the existing theoretical <span class="hlt">models</span>, the form of this macro <span class="hlt">model</span> is simple and has a clear physical meaning. In addition, it is applicable to cases with relatively complex cavities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT........94R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT........94R"><span><span class="hlt">Porous</span> grain <span class="hlt">model</span> and equivalent elastic medium approach for predicting effective elastic properties of sedimentary rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruiz, Franklin J.</p> <p></p> <p>This dissertation presents the results of using different inclusion and granular effective medium <span class="hlt">models</span> and poroelasticity to predict the elastic properties of rocks with complex microstructures. Effective medium <span class="hlt">models</span> account for the microstructure and texture of rocks, and can be used to predict the type of rock and microstructure from seismic velocities and densities. We introduce the elastic equivalency approach, using the differential effective medium <span class="hlt">model</span>, to predict the effective elastic moduli of rocks and attenuation. We introduce the <span class="hlt">porous</span> grain concept and develop rock physics <span class="hlt">models</span> for rocks with microporosity. We exploit the <span class="hlt">porous</span> grain concept to describe a variety of arrangements of uncemented and cemented grains with different degrees of hydraulic connectivity in the pore space. We first investigate the accuracy of the differential effective medium and self-consistent estimations of elastic properties of complex rock matrix using composites as analogs. We test whether the differential effective-medium (DEM) and self-consistent (SC) <span class="hlt">models</span> can accurately estimate the elastic moduli of a complex rock matrix and compare the results with the average of upper and lower Hashin-Shtrikman bounds. We find that when the <span class="hlt">material</span> microstructure is consistent with DEM, this <span class="hlt">model</span> is more accurate than both SC and the bound-average method for a variety of inclusion aspect ratios, concentrations, and modulus contrasts. Based on these results, we next pose a question: can a theoretical inclusion <span class="hlt">model</span>, specifically, the differential effective-medium <span class="hlt">model</span> (DEM), be used to match experimental velocity data in rocks that are not necessarily made of inclusions (such as elastics)? We first approach this question by using empirical velocity-porosity equations as proxies for data. By finding a DEM inclusion aspect ratio (AR) to match these equations, we find that the required range of AR is remarkably narrow. Moreover, a constant AR of about 0.13 can be used to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26235127','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26235127"><span>Characterization of <span class="hlt">Porous</span> <span class="hlt">Materials</span> by Fluorescence Correlation Spectroscopy Super-resolution Optical Fluctuation Imaging.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kisley, Lydia; Brunetti, Rachel; Tauzin, Lawrence J; Shuang, Bo; Yi, Xiyu; Kirkeminde, Alec W; Higgins, Daniel A; Weiss, Shimon; Landes, Christy F</p> <p>2015-09-22</p> <p><span class="hlt">Porous</span> <span class="hlt">materials</span> such as cellular cytosol, hydrogels, and block copolymers have nanoscale features that determine macroscale properties. Characterizing the structure of nanopores is difficult with current techniques due to imaging, sample preparation, and computational challenges. We produce a super-resolution optical image that simultaneously characterizes the nanometer dimensions of and diffusion dynamics within <span class="hlt">porous</span> structures by correlating stochastic fluctuations from diffusing fluorescent probes in the pores of the sample, dubbed here as "fluorescence correlation spectroscopy super-resolution optical fluctuation imaging" or "fcsSOFI". Simulations demonstrate that structural features and diffusion properties can be accurately obtained at sub-diffraction-limited resolution. We apply our technique to image agarose hydrogels and aqueous lyotropic liquid crystal gels. The heterogeneous pore resolution is improved by up to a factor of 2, and diffusion coefficients are accurately obtained through our method compared to diffraction-limited fluorescence imaging and single-particle tracking. Moreover, fcsSOFI allows for rapid and high-throughput characterization of <span class="hlt">porous</span> <span class="hlt">materials</span>. fcsSOFI could be applied to soft <span class="hlt">porous</span> environments such hydrogels, polymers, and membranes in addition to hard <span class="hlt">materials</span> such as zeolites and mesoporous silica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AIPC.1034..157L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AIPC.1034..157L"><span>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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>López-Coto, I.; Bolivar, J. P.; Mas, J. L.; García-Tenorio, R.</p> <p>2008-08-01</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 222Rn 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://www.dtic.mil/docs/citations/ADA589783','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA589783"><span>Instrumentation for Nano-<span class="hlt">porous</span>, Nano-particulate Geopolymeric <span class="hlt">Materials</span> Research</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2008-11-04</p> <p>nano-sized high surface area ceramic powders in geopolymers and geopolymeric composites. On the other hand, the Thinky ARE-250 mixer was purchased to...DATES COVERED (From - To) 6/15/07 - 6/14/08 4. TITLE AND SUBTITLE Instrumentation for Nano-<span class="hlt">porous</span>, Nano-particulate Geopolymeric <span class="hlt">Materials</span>... Geopolymers are a new class of ceramic <span class="hlt">materials</span> which are best understood as rigid inorganic, aluminosilicate, hydrated gels, charge-balanced by cations</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20673021','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20673021"><span>The correlation between the internal structure and vascularization of controllable <span class="hlt">porous</span> bioceramic <span class="hlt">materials</span> in vivo: a quantitative study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bai, Feng; Wang, Zhen; Lu, Jianxi; Liu, Jian; Chen, Gongyi; Lv, Rong; Wang, Jun; Lin, Kaili; Zhang, Jinkang; Huang, Xin</p> <p>2010-12-01</p> <p>It is noticeable that <span class="hlt">porous</span> architectural characteristics of the biomaterials play an important role in revascularization of the scaffold. However, there has been no consensus regarding the optimal conditions for vascularization, including macropore size, shape, interconnection, and the arrangement of macropores, due to the failure to accurately control <span class="hlt">porous</span> structure of biomaterials. To investigate the effect of the <span class="hlt">porous</span> structure parameters on vascularization of the biomaterials, an accurate control of these parameters is required. In this study, <span class="hlt">porous</span> β-tricalcium phosphate (β-TCP) with accurately controlled pore parameters is fabricated by using assembled organic microspheres as templates combined with casting technique. Using this technique, we produced a series of disk-type β-TCP with variable pore sizes and variable interconnections to evaluate the influence of macropore size and interconnection on the vascularization of bioceramic <span class="hlt">material</span> in vivo. The vascularization of β-TCP implanted in the rabbit <span class="hlt">model</span> is evaluated by histomorphology and single photon emission computed tomography. The results showed that the pore parameters affect not only the size of the blood vessels growing into the <span class="hlt">porous</span> structure but also the number of blood vessels formed in the pores of the bioceramic. The increase in pore size only resulted in an increase in size of the blood vessels growing into the macroporous of the bioceramic scaffolds. However, with the increase in size of interconnection, both the size and number of the blood vessels formed in the macroporous increased. Therefore, we conclude that the size of the interconnections is more important for vascularization in the scaffold compared with the pore size. On the other hand, there was no significant difference in vascularization in the scaffolds with pores size above 400 μm, and there was no marked increase in extent of vascularization with further increase in pore size above 400 μm, indicating that</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>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://adsabs.harvard.edu/abs/2017NatMa..16..283C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatMa..16..283C"><span><span class="hlt">Porous</span> <span class="hlt">materials</span>: Lining up metal-organic frameworks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Champness, Neil R.</p> <p>2017-02-01</p> <p>A new report demonstrates an innovative approach to aligning crystallites of metal-organic frameworks such that thin films are created with oriented channels -- potentially overcoming one of the major barriers to application of these highly topical <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3767460','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3767460"><span>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('https://www.osti.gov/scitech/biblio/15020420','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/15020420"><span><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/2000PhRvE..62.3891V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhRvE..62.3891V"><span>Rolling of unsaturated <span class="hlt">porous</span> <span class="hlt">materials</span>: Evolution of a fully saturated zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Velten, K.; Best, W.</p> <p>2000-09-01</p> <p>When a roll moves over a partially fluid filled <span class="hlt">porous</span> layer, the degree of saturation in the <span class="hlt">porous</span> layer will change in an a priori unknown area which is affected by the roll. In this work, a mathematical <span class="hlt">model</span> is developed that describes the saturation dynamics in the <span class="hlt">porous</span> layer for moderate rolling velocities. The <span class="hlt">model</span> is based on two-phase flow equations in one dimension. It can be expressed as a nonlinear second order convection-diffusion equation that can be solved by standard (upwind) finite volume techniques. The size of the area affected by the roll, and within this area the degree of saturation, fluid pressures, and fluid velocities, can be predicted. An example is studied where a fully saturated zone evolves between the rolls when the rolling velocity is increased beyond some critical value.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22257906','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22257906"><span>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://hdl.handle.net/2060/19990064146','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990064146"><span>Improved <span class="hlt">Models</span> for the <span class="hlt">Porous</span> Surface with Passive Control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kraushaar, Sandra L.; Chokani, Ndaona</p> <p>1996-01-01</p> <p>A computational investigation of afterbody flow using a passive control method is conducted. The passive control method consists of a <span class="hlt">porous</span> surface placed over a plenum. The purpose of the passive control method is to exploit the adverse pressure gradient present in afterbody flow in an attempt to reduce boundary layer separation and afterbody drag. Four different <span class="hlt">porous</span> wall <span class="hlt">models</span> are used to <span class="hlt">model</span> the transpiration velocity in the region of passive control. A three-dimensional, time-dependent, Reynolds-averaged, simplified Navier-Stokes solver, PAB3D, is used to simulate afterbody flow with and without passive control. Three afterbody configurations with boat-tail angles of 10, 20, and 30 deg. are used to obtain two-dimensional solutions with a freestream Mach number of 0.6 and nozzle pressure ratio of 6. The region of passive control was initially placed from 20-60% of the nozzle length. The effect of the <span class="hlt">porous</span> placement and <span class="hlt">porous</span> extent is also studied. Baseline (no porosity) two-dimensional solutions are qualitatively similar to experimental data but under-predict the magnitude of the pressure recovery. Results for the subsonic solutions show losses in the pressure recovery for some cases with passive control. Three-dimensional effects are also investigated and seen to be very significant. Three-dimensional baseline solutions, for both sub- and super-critical freestream Mach numbers, compare very favorably with the experimental data in comparison to the two-dimensional solution. Future work is required to examine three-dimensional afterbody flows with passive porosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25920830','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25920830"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.774a2055Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.774a2055Z"><span>Experimental study of dynamic properties of <span class="hlt">porous</span> <span class="hlt">materials</span> under shock-wave loading</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zubareva, A. N.; Efremov, V. P.; Mochalova, V. M.; Utkin, A. V.</p> <p>2016-11-01</p> <p>The paper presents new experimental data on properties of <span class="hlt">porous</span> media under shock-wave loading. We considered <span class="hlt">materials</span> with different nature of porosity. The porosity in the silicone rubber and the epoxy resin was produced by glass microspheres filler. Open porosity was realized in a fibrous <span class="hlt">material</span> made from glass fibers with corundum. It was shown that two-wave configuration was formed in <span class="hlt">materials</span> with closed porosity. Such structure of the pulse with a precursor was not observed in samples with open porosity. As a result of analysis of experimental data, Hugoniots for the investigated <span class="hlt">materials</span> were obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24676127','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24676127"><span>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="https://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>2014-07-07</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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27513218','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27513218"><span><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="https://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>.</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>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> </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://www.osti.gov/scitech/servlets/purl/862922','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862922"><span>Method of preparing <span class="hlt">porous</span>, active <span class="hlt">material</span> for use in electrodes of secondary electrochemical cells</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>1977-01-01</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('https://www.ncbi.nlm.nih.gov/pubmed/26456608','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26456608"><span>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="https://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>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22492612','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22492612"><span>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3993991','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3993991"><span><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/abs/2011WRR....47.6518P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011WRR....47.6518P"><span>Multiscale <span class="hlt">modeling</span> of chemotaxis in homogeneous <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>Porter, Mark L.; ValdéS-Parada, Francisco J.; Wood, Brian D.</p> <p>2011-06-01</p> <p>We present a predictive, multiscale <span class="hlt">modeling</span> framework for chemotaxis in <span class="hlt">porous</span> media. This <span class="hlt">model</span> results from volume averaging the governing equations for bacterial transport at the microscale and is expressed in terms of effective medium coefficients that are predicted from the solution of the associated closure problems. As a result, the averaged chemotactic velocity is an explicit function of the attractant concentration field and diffusivity, rather than an empirical effective chemotactic sensitivity coefficient. The <span class="hlt">model</span> was validated by comparing the transverse bacterial concentration profiles with experimental measurements for Escherichia coli HCB1 in a T-sensor. The averaged chemotactic velocity predicted by the <span class="hlt">model</span> was found to be within the range of values reported in the literature. Reasonable agreement (approximately 10% mean absolute error) between theory and experiments was found for several flow rates. In order to assess the potential for decreasing the computational demands of the <span class="hlt">model</span>, the macroscale domain was divided into subdomains for the coupling of bacterial transport to that of the attractant. Sensitivity analysis was performed regarding the number of subdomains chosen, and the results indicate that bacterial transport (as measured by concentration profiles) was not highly affected by this choice. Overall, these results suggest that the predictive, multiscale <span class="hlt">modeling</span> framework is reliable for <span class="hlt">modeling</span> chemotaxis in <span class="hlt">porous</span> media when chemotactic transport is significant compared to convective transport.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20005633','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20005633"><span>A new method for evaluation of heat transfer between solid <span class="hlt">material</span> and fluid in a <span class="hlt">porous</span> medium</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ichimiya, K.</p> <p>1999-11-01</p> <p>Technological applications in which <span class="hlt">porous</span> <span class="hlt">materials</span> are utilized include thermal energy storage, geophysical fluid engineering, thermal insulation, heat transfer enhancement, and heat exchangers. The author proposes a new method to estimate the heat transfer between fluid gas and solid <span class="hlt">material</span> in a <span class="hlt">porous</span> medium. In the first stage, the local Nusselt numbers on the heated wall of a flow passage with a <span class="hlt">porous</span> medium are numerically obtained in advance for the parameter H{sub a}, including the volumetric heat transfer coefficient, h{sub {nu}}, between the fluid and the solid <span class="hlt">material</span> in a <span class="hlt">porous</span> medium. In the second stage, the experimental Nusselt numbers on the heated wall are obtained by measuring wall temperatures and heat flux. The volumetric heat transfer coefficient, h{sub {nu}}, is evaluated by comparing experimental Nusselt numbers with numerical ones. This method also gives the longitudinal characteristics of the heat transfer in a <span class="hlt">porous</span> medium.</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>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> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1616405K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1616405K"><span>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/2015EGUGA..1712831R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712831R"><span><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://adsabs.harvard.edu/abs/2015AGUFM.H21A1320H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H21A1320H"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/23743266','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23743266"><span><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="https://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>.</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>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://adsabs.harvard.edu/abs/2016AIPA....6l1605J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPA....6l1605J"><span>Broadband quasi perfect absorption using chirped multi-layer <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>Jiménez, N.; Romero-García, V.; Cebrecos, A.; Picó, R.; Sánchez-Morcillo, V. J.; Garcia-Raffi, L. M.</p> <p>2016-12-01</p> <p>This work theoretically analyzes the sound absorption properties of a chirped multi-layer <span class="hlt">porous</span> <span class="hlt">material</span> including transmission, in particular showing the broadband unidirectional absorption properties of the system. Using the combination of the impedance matching condition and the balance between the leakage and the intrinsic losses, the system is designed to have broadband unidirectional and quasi perfect absorption. The transfer and scattering matrix formalism, together with numerical simulations based on the finite element method are used to demonstrate the results showing excellent agreement between them. The proposed system allows to construct broadband sound absorbers with improved absorption in the low frequency regime using less amount of <span class="hlt">material</span> than the complete bulk <span class="hlt">porous</span> layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3344220','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3344220"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/22605984','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22605984"><span>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="https://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.</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>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('https://www.ncbi.nlm.nih.gov/pubmed/26568472','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26568472"><span>A convenient process to fabricate gelatin modified <span class="hlt">porous</span> PLLA <span class="hlt">materials</span> with high hydrophilicity and strength.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yin, Guangzhong; Zhao, Donglin; Ren, Ye; Zhang, Lianwei; Zhou, Zheng; Li, Qifang</p> <p>2016-02-01</p> <p>PLLA <span class="hlt">porous</span> <span class="hlt">materials</span> with high porosity were prepared by a gradual precipitation method and further modified by using different concentrations of gelatin aqueous solutions. Therefore, <span class="hlt">porous</span> <span class="hlt">materials</span> with different contents of gelatin coating were obtained. The micro morphology, crystallization, thermal performance, hydrophilicity and mechanical properties of the <span class="hlt">materials</span> were evaluated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), thermogravimetric analysis (TGA), water uptake ability tests and compression tests. It was found that the modified <span class="hlt">materials</span> were formed by the stacking of nanosheets. The <span class="hlt">materials</span> can maintain more than 80% porosity, high water uptake abilities and fast water uptake rates after modification. The compressive moduli of the <span class="hlt">materials</span> were significantly improved from the initial sample with a value of 0.57 MPa to 46.41 MPa with gelatin modification. Due to the high porosity of <span class="hlt">materials</span>, interconnected pore structures, and good surface hydrophilicity, the <span class="hlt">materials</span> were expected to be widely used in the field of tissue engineering scaffolds, especially for bone substitutes, mainly due to their tunable and excellent mechanical properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......116T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......116T"><span>Bio-inspired Supramolecular Assemblies and <span class="hlt">Porous</span> <span class="hlt">Materials</span> for the Degradation of Organophosphate Nerve Agents</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Totten, Ryan K.</p> <p></p> <p>This thesis reports the synthesis of bio-inspired supramolecular assemblies and <span class="hlt">porous</span> <span class="hlt">materials</span> that are catalytically active in the degradation of organophosphate nerve agents. The first catalysts described are a series of cofacial metalloporphyrin dimers <span class="hlt">modeled</span> after the active site of phosphotriesterase that were modularly prepared from a single porphyrin building block and shown to catalyze the methanolysis of p-nitrophenyl diphenyl phosphate (PNPDPP), a simulant for nerve agents. Notably, tuning the active sites inside the cavities of these dimers, from ZnII metal centers to Al-OMe moieties, affords an enhanced nucleophilic environment where a high concentration of methoxy ligands becomes available for reaction with encapsulated phosphate triesters. Up to a 1300-fold rate acceleration over the uncatalyzed reaction can be achieved via a combination of cavity-localized Lewis-acid activation and methoxide-induced methanolysis. Based on the design principles learned from the aforementioned solution-phase Al(porphyrin) dimers, a heterogeneous <span class="hlt">porous</span> organic polymer (POP) catalyst was synthesized by incorporating an Al(porphyrin) functionalized with a large axial ligand into a POP using a cobalt-catalyzed acetylene trimerization strategy. Removal of the axial ligand afforded a microporous <span class="hlt">material</span> that is capable of encapsulating and solvolytically degrading PNPDPP. Supercritical CO 2 processing of the Al(porphyrin)-based POP dramatically increased the pore size and volume, allowing for significantly higher catalytic activities. The syntheses of porphyrin-based POPs with tunable pore diameters and volumes have also been attempted. SnIV(porphyrins) functionalized with bulky trans-diaxial ligands can be incorporated into POPs. Post-synthesis removal of the ligands reveal POPs with a tunable range of micro- and mesopores as well as tunable pore volumes. Expanding upon the idea that active sites that can both bind substrates and deliver nucleophiles should be active</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...5E7910M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...5E7910M"><span>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4300473','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4300473"><span>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> </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://adsabs.harvard.edu/abs/2015IJAME..20..385S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJAME..20..385S"><span>Mathematical <span class="hlt">Modeling</span> of Magneto Pulsatile Blood Flow Through a <span class="hlt">Porous</span> Medium with a Heat Source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharma, B. K.; Sharma, M.; Gaur, R. K.; Mishra, A.</p> <p>2015-05-01</p> <p>In the present study a mathematical <span class="hlt">model</span> for the hydro-magnetic non-Newtonian blood flow in the non-Darcy <span class="hlt">porous</span> medium with a heat source and Joule effect is proposed. A uniform magnetic field acts perpendicular to the <span class="hlt">porous</span> surface. The governing non-linear partial differential equations have been solved numerically by applying the explicit finite difference Method (FDM). The effects of various parameters such as the Reynolds number, hydro-magnetic parameter, Forchheimer parameter, Darcian parameter, Prandtl number, Eckert number, heat source parameter, Schmidt number on the velocity, temperature and concentration have been examined with the help of graphs. The present study finds its applications in surgical operations, industrial <span class="hlt">material</span> processing and various heat transfer operations.</p> </li> <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>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('https://www.ncbi.nlm.nih.gov/pubmed/18452318','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18452318"><span>Click chemistry in mesoporous <span class="hlt">materials</span>: functionalization of <span class="hlt">porous</span> silicon rugate filters.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ciampi, Simone; Böcking, Till; Kilian, Kristopher A; Harper, Jason B; Gooding, J Justin</p> <p>2008-06-03</p> <p>In this paper we report the use of the optical properties of <span class="hlt">porous</span> silicon photonic crystals, combined with the chemical versatility of acetylene-terminated SAMs, to demonstrate the applicability of "click" chemistry to mesoporous <span class="hlt">materials</span>. Cu(I)-catalyzed alkyne-azide cycloaddition reactions were employed to modify the internal pore surfaces through a two-step hydrosilylation/cycloaddition procedure. A positive outcome of this catalytic process, here performed in a spatially confined environment, was only observed in the presence of a ligand-stabilized Cu(I) species. Detailed characterization using Fourier transform infrared spectroscopy and optical reflectivity measurements demonstrated that the surface acetylenes had reacted in moderate to high yield to afford surfaces exposing chemical functionalities of interest. The <span class="hlt">porous</span> silicon photonic crystals modified by the two-step strategy, and exposing oligoether moieties, displayed improved resistance toward the nonspecific adsorption of proteins as determined with fluorescently labeled bovine serum albumin. These results demonstrate that "click" immobilization offers a versatile, experimentally simple, and modular approach to produce functionalized <span class="hlt">porous</span> silicon surfaces for applications as diverse as <span class="hlt">porous</span> silicon-based sensing devices and implantable biomaterials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA622573','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA622573"><span>A Family of Reference Hugoniots for Two-phase <span class="hlt">Porous</span> <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2015-06-01</p> <p>UNCLASSIFIED UNCLASSIFIED A Family of Reference Hugoniots for Two-phase <span class="hlt">Porous</span> <span class="hlt">Materials</span> A.D. Resnyansky Weapons and Combat...of Australia 2015 AR-016-394 June 2015 APPROVED FOR PUBLIC RELEASE UNCLASSIFIED UNCLASSIFIED A Family of Reference Hugoniots for...EOS [4] is based on a constitutive consideration. The latter approach specifies Hugoniot states from a family of non-equilibrium Hugoniot for a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017HMT...tmp...42Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017HMT...tmp...42Z"><span>A dynamic experimental study on the evaporative cooling performance of <span class="hlt">porous</span> building <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>Zhang, Yu; Zhang, Lei; Meng, Qinglin; Feng, Yanshan; Chen, Yuanrui</p> <p>2017-03-01</p> <p>Conventional outdoor dynamic and indoor steady-state experiments have certain limitations in regard to investigating the evaporative cooling performance of <span class="hlt">porous</span> building <span class="hlt">materials</span>. The present study investigated the evaporative cooling performance of a <span class="hlt">porous</span> building <span class="hlt">material</span> using a special wind tunnel apparatus. First, the composition and control principles of the wind tunnel environment control system were elucidated. Then, the meteorological environment on a typical summer day in Guangzhou was reproduced in the wind tunnel and the evaporation process and thermal parameters of specimens composed of a <span class="hlt">porous</span> building <span class="hlt">material</span> were continuously measured. Finally, the experimental results were analysed to evaluate the accuracy of the wind tunnel environment control system, the heat budget of the external surface of the specimens and the total thermal resistance of the specimens and its uncertainty. The analysis results indicated that the normalized root-mean-square error between the measured value of each environmental parameter in the wind tunnel test section and the corresponding value input into the environment control system was <4%, indicating that the wind tunnel apparatus had relatively high accuracy in reproducing outdoor meteorological environments. In addition, the wet specimen could cumulatively consume approximately 80% of the shortwave radiation heat during the day, thereby reducing the temperature of the external surface and the heat flow on the internal surface of the specimen. Compared to the dry specimen, the total thermal resistance of the wet specimen was approximately doubled, indicating that the evaporation process of the <span class="hlt">porous</span> building <span class="hlt">material</span> could significantly improve the thermal insulation performance of the specimen.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA580696','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA580696"><span>Instrumentation for Nano-<span class="hlt">porous</span>, Nano-particulate Geopolymeric <span class="hlt">Materials</span> Research</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2008-11-04</p> <p>surface area ceramic powders in geopolymers and geopolymeric composites. On the other hand, the Thinky ARE-250 mixer was purchased to assist with...3. DATES COVERED (From - To) 6/15/07 – 6/14/08 4. TITLE AND SUBTITLE Instrumentation for Nano-<span class="hlt">porous</span>, Nano-particulate Geopolymeric ...STATEMENT 13. SUPPLEMENTARY NOTES 14. ABSTRACT -- Geopolymers are a new class of ceramic <span class="hlt">materials</span> which are best understood as rigid</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA148528','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA148528"><span>Response of Saturated <span class="hlt">Porous</span> Nonlinear <span class="hlt">Materials</span> to Dynamic Loadings</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1984-05-31</p> <p>the following section a bilinear hysteretic skeleton was <span class="hlt">modeled</span>, followed by calculations on an actual sand from Enewetak Atoll . In this section...the response of saturated sand from Enewetak Atoll . The skeleton properties are taken from laboratory data reported in the second volunie of this study...with an actual saturated sand from Enewetak Atoll . In Section 2, the theoretical background and numerical code, TPDAP, used in this study are described</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23945102','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23945102"><span><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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/162928','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/162928"><span>High surface area electrode <span class="hlt">materials</span> by direct metallization of <span class="hlt">porous</span> substrates</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chyan, O.; Chen, J.J.; Liu, M.; Richmond, M.G.; Yang, K.</p> <p>1995-12-31</p> <p>Recent advances in high surface area (HSA) electrode <span class="hlt">materials</span> have played an important role in the development of high-performance batteries and fuel cells. HSA electrodes can significantly increase the power-density of batteries and fuel cells by enhancing the heterogeneous electrochemical reaction rate and concurrently reducing battery and fuel cell size and weight. The compactness of HSA electrodes can also reduce the ohmic potential drop, which has the clear advantage of reducing power losses. This paper reports results on utilizing direct metallization of <span class="hlt">porous</span> substrates to prepare new HSA electrode <span class="hlt">materials</span>. Specifically, Nickel HSA electrode <span class="hlt">materials</span>, relevant to the Ni-Cd and metal-hydride rechargeable batteries, were prepared on <span class="hlt">porous</span> carbon substrates by direct thermolysis of organometallic precursors and/or electroless Ni plating. SEM and XPS characterization results indicate a Ni metallic film was conformally coated over the <span class="hlt">porous</span> carbon skeleton. The real electroactive areas were determined electrochemically in NaOH solution and results will be discussed in correlation with the metallization conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28199096','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28199096"><span>Why <span class="hlt">Porous</span> <span class="hlt">Materials</span> Have Selective Adsorptions: A Rational Aspect from Electrodynamics.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Qiang; Ma, Yuguang; Song, Wei-Chao; Chang, Ze; Li, Jian-Rong; Zhang, Jun; Sun, Hong-Wei; Balbuena, Perla B; Bu, Xian-He</p> <p>2017-03-06</p> <p>Gas storage/separation is a typical application of <span class="hlt">porous</span> <span class="hlt">materials</span> such as metal organic frameworks (MOFs). The adsorption/separation behavior results from the host-guest and/or guest-guest interaction and equilibration (host, <span class="hlt">porous</span> <span class="hlt">material</span>; guest, adsorbates). Although the driving forces for gas adsorption have been investigated, a detailed picture of interactions between gas molecules and MOFs has not clearly emerged. Herein, a new cobalt microporous MOF [Co(tipb)(adc)](DMF)3(H2O)1.5, which possesses a rare self-interpenetrated gra topology, has been prepared with both tipb and H2adc ligands (tipb = 1,3,5-tris(p-imidazolylphenyl)benzene, adc = 9,10-anthracenedicarboxylate). This MOF shows high stability and exceptional selective adsorption of CO2 over N2, O2, and CH4. In particular, a theoretical assumption of a "regional dynamic electric field effect" is proposed to clarify the selective adsorption. Moreover, we suggest that the proposed effect may be one of the most important factors impacting gas separation and storage in <span class="hlt">porous</span> <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003WRR....39.1072D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003WRR....39.1072D"><span><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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5238682','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5238682"><span>Organoclay hybrid <span class="hlt">materials</span> as precursors of <span class="hlt">porous</span> ZnO/silica-clay heterostructures for photocatalytic applications</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Akkari, Marwa; Aranda, Pilar; Ben Haj Amara, Abdessalem</p> <p>2016-01-01</p> <p>In this study, ZnO/SiO2-clay heterostructures were successfully synthesized by a facile two-step process applied to two types of clays: montmorillonite layered silicate and sepiolite microfibrous clay mineral. In the first step, intermediate silica–organoclay hybrid heterostructures were prepared following a colloidal route based on the controlled hydrolysis of tetramethoxysilane in the presence of the starting organoclay. Later on, pre-formed ZnO nanoparticles (NP) dispersed in 2-propanol were incorporated under ultrasound irradiation to the silica–organoclay hybrid heterostructures dispersed in 2-propanol, and finally, the resulting solids were calcinated to eliminate the organic matter and to produce ZnO nanoparticles (NP) homogeneously assembled to the clay–SiO2 framework. In the case of montmorillonite the resulting <span class="hlt">materials</span> were identified as delaminated clays of ZnO/SiO2-clay composition, whereas for sepiolite, the resulting heterostructure is constituted by the assembling of ZnO NP to the sepiolite–silica substrate only affecting the external surface of the clay. The structural and morphological features of the prepared heterostructures were characterized by diverse physico-chemical techniques (such as XRD, FTIR, TEM, FE-SEM). The efficiency of these new <span class="hlt">porous</span> ZnO/SiO2-clay heterostructures as potential photocatalysts in the degradation of organic dyes and the removal of pharmaceutical drugs in water solution was tested using methylene blue and ibuprofen compounds, respectively, as <span class="hlt">model</span> of pollutants. PMID:28144545</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28144545','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28144545"><span>Organoclay hybrid <span class="hlt">materials</span> as precursors of <span class="hlt">porous</span> ZnO/silica-clay heterostructures for photocatalytic applications.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Akkari, Marwa; Aranda, Pilar; Ben Haj Amara, Abdessalem; Ruiz-Hitzky, Eduardo</p> <p>2016-01-01</p> <p>In this study, ZnO/SiO2-clay heterostructures were successfully synthesized by a facile two-step process applied to two types of clays: montmorillonite layered silicate and sepiolite microfibrous clay mineral. In the first step, intermediate silica-organoclay hybrid heterostructures were prepared following a colloidal route based on the controlled hydrolysis of tetramethoxysilane in the presence of the starting organoclay. Later on, pre-formed ZnO nanoparticles (NP) dispersed in 2-propanol were incorporated under ultrasound irradiation to the silica-organoclay hybrid heterostructures dispersed in 2-propanol, and finally, the resulting solids were calcinated to eliminate the organic matter and to produce ZnO nanoparticles (NP) homogeneously assembled to the clay-SiO2 framework. In the case of montmorillonite the resulting <span class="hlt">materials</span> were identified as delaminated clays of ZnO/SiO2-clay composition, whereas for sepiolite, the resulting heterostructure is constituted by the assembling of ZnO NP to the sepiolite-silica substrate only affecting the external surface of the clay. The structural and morphological features of the prepared heterostructures were characterized by diverse physico-chemical techniques (such as XRD, FTIR, TEM, FE-SEM). The efficiency of these new <span class="hlt">porous</span> ZnO/SiO2-clay heterostructures as potential photocatalysts in the degradation of organic dyes and the removal of pharmaceutical drugs in water solution was tested using methylene blue and ibuprofen compounds, respectively, as <span class="hlt">model</span> of pollutants.</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>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/abs/2015AGUFMNG33A1857G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNG33A1857G"><span>Thermal conductivity <span class="hlt">modeling</span> in 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>Ghanbarian, B.; Daigle, H.</p> <p>2015-12-01</p> <p><span class="hlt">Modeling</span> effective thermal conductivity under variably saturated conditions is essential to study heat transfer in natural sediments, soils, and rocks. The effective thermal conductivity in completely dry and fully saturated <span class="hlt">porous</span> media is an integrated quantity representing the complex behavior of two conducting phases, i.e., pore fluid (either air or water) and solid matrix. Under partially saturated conditions, however, the effective thermal conductivity becomes even more complicated since three phases (air, water, and solid matrix) conduct heat simultaneously. In this study, we invoke an upscaling treatment called percolation-based effective-medium approximation to <span class="hlt">model</span> the effective thermal conductivity in fully and partially saturated <span class="hlt">porous</span> media. Our theoretical porosity- and saturation-dependent <span class="hlt">models</span> contain endmember properties, such as air, solid matrix, and saturating fluid thermal conductivities, a percolation exponent t, and a percolation threshold. Comparing our theory with 216 porosity-dependent thermal conductivity measurements and 25 saturation-dependent thermal conductivity datasets indicate excellent match between theory and experiments. Our results show that the effective thermal conductivity under fully and partially saturated conditions follows nonuniversal behavior. This means the value of t changes from medium to medium and depends not only on topological and geometrical properties of the medium but also characteristics of the saturating fluid.</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>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('https://www.osti.gov/scitech/biblio/21442691','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21442691"><span>Interaction of a high-power laser pulse with supercritical-density <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>Gus'kov, Sergei Yu; Rozanov, Vladislav B; Caruso, A; Strangio, C</p> <p>2000-03-31</p> <p>The properties of a nonequilibrium plasma produced by high-power laser pulses with intensities I{sub L} {approx} 10{sup 14}-10{sup 15} W cm{sup -2} irradiating plane targets made of a <span class="hlt">porous</span> <span class="hlt">material</span> are investigated. The mean density of matter in targets was substantially higher than the critical plasma density corresponding to a plasma resonance. The density of <span class="hlt">porous</span> <span class="hlt">material</span> was {rho}{sub a} {approx} 1 - 20 mg cm{sup -3}, whereas the critical density at the wavelength of incident radiation was {rho}{sub cr} {approx} 3 mg cm{sup -3}. An anomalously high absorption (no less than 80%) of laser radiation inside a target was observed. Within the first 3 - 4 ns of interaction, the plasma flow through the irradiated target surface in the direction opposite of the direction of the laser beam was noticeably suppressed. Only about 5% of absorbed laser energy was transformed into the energy of particles in this flow during the laser pulse. Absorbed energy was stored as the internal plasma energy at this stage (the greenhouse effect). Then, this energy was transformed, similar to a strong explosion, into the energy of a powerful hydrodynamic flow of matter surrounding the absorption region. The specific features of the formation and evolution of a nonequilibrium laser-produced plasma in <span class="hlt">porous</span> media are theoretically analysed. This study allows the results of experiments to be explained. In particular, we investigated absorption of laser radiation in the bulk of a target, volume evaporation of <span class="hlt">porous</span> <span class="hlt">material</span>, the expansion of a laser-produced plasma inside the pores, stochastic collisions of plasma flows, and hydrothermal energy dissipation. These processes give rise to long-lived oscillations of plasma density and lead to the formation of an internal region where laser radiation is absorbed. (invited paper)</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>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('https://www.ncbi.nlm.nih.gov/pubmed/16853195','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16853195"><span><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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/287533','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/287533"><span>Analytical <span class="hlt">model</span> for heterogeneous reactions in mixed <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hatfield, K.; Burris, D.R.; Wolfe, N.L.</p> <p>1996-08-01</p> <p>The funnel/gate system is a developing technology for passive ground-water plume management and treatment. This technology uses sheet pilings as a funnel to force polluted ground water through a highly permeable zone of reactive <span class="hlt">porous</span> media (the gate) where contaminants are degraded by biotic or abiotic heterogeneous reactions. This paper presents a new analytical nonequilibrium <span class="hlt">model</span> for solute transport in saturated, nonhomogeneous or mixed <span class="hlt">porous</span> media that could assist efforts to design funnel/gate systems and predict their performance. The <span class="hlt">model</span> incorporates convective/dispersion transport, dissolved constituent decay, surface-mediated degradation, and time-dependent mass transfer between phases. Simulation studies of equilibrium and nonequilibrium transport conditions reveal manifestations of rate-limited degradation when mass-transfer times are longer than system hydraulic residence times, or when surface-mediated reaction rates are faster than solute mass-transfer processes (i.e., sorption, film diffusion, or intraparticle diffusion). For example, steady-state contaminant concentrations will be higher under a nonequilibrium transport scenario than would otherwise be expected when assuming equilibrium conditions. Thus, a funnel/gate system may fail to achieve desired ground-water treatment if the possibility of mass-transfer-limited degradation is not considered.</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://adsabs.harvard.edu/abs/2016APS..DFDD40007A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDD40007A"><span>Diffuse-Interface <span class="hlt">Modelling</span> of 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>Addy, Doug; Pradas, Marc; Schmuck, Marcus; Kalliadasis, Serafim</p> <p>2016-11-01</p> <p>Multiphase flows are ubiquitous in a wide spectrum of scientific and engineering applications, and their computational <span class="hlt">modelling</span> often poses many challenges associated with the presence of free boundaries and interfaces. Interfacial flows in <span class="hlt">porous</span> media encounter additional challenges and complexities due to their inherently multiscale behaviour. Here we investigate the dynamics of interfaces in <span class="hlt">porous</span> media using an effective convective Cahn-Hilliard (CH) equation recently developed in from a Stokes-CH equation for microscopic heterogeneous domains by means of a homogenization methodology, where the microscopic details are taken into account as effective tensor coefficients which are given by a Poisson equation. The equations are decoupled under appropriate assumptions and solved in series using a classic finite-element formulation with the open-source software FEniCS. We investigate the effects of different microscopic geometries, including periodic and non-periodic, at the bulk fluid flow, and find that our <span class="hlt">model</span> is able to describe the effective macroscopic behaviour without the need to resolve the microscopic details.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/889373','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/889373"><span>A pore network <span class="hlt">model</span> for adsorption 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>Satik, Cengiz; Yortsos, Yanis C.</p> <p>1995-01-26</p> <p>Using a pore network <span class="hlt">model</span> to represent <span class="hlt">porous</span> media we investigate adsorption-desorption processes over the entire range of the relative pressure, highlighting in particular capillary condensation. The <span class="hlt">model</span> incorporates recent advances from density functional theory for adsorption-desorption in narrow pores (of order as low as 1 nm), which improve upon the traditional multi-layer adsorption and Kelvin's equation for phase change and provide for the dependence of the critical pore size on temperature. The limited accessibility of the pore network gives rise to hysteresis in the adsorption-desorption cycle. This is due to the blocking of larger pores, where adsorbed liquid is allowed to but cannot desorb, by smaller pores containing liquid that may not desorb. By allowing for the existence of supercritical liquid in pores in the nm range, it is found that the hysteresis area increases with an increase in temperature, in agreement with experiments of water adsorption-desorption in rock samples from The Geysers. It is also found that the hysteresis increases if the <span class="hlt">porous</span> medium is represented as a fractured (dual porosity) system. The paper finds applications to general adsorption-desorption problems but it is illustrated here for geothermal applications in The Geysers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22392371','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22392371"><span>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5043355','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5043355"><span>Europium (III) Organic Complexes in <span class="hlt">Porous</span> Boron Nitride Microfibers: Efficient Hybrid Luminescent <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>Lin, Jing; Feng, Congcong; He, Xin; Wang, Weijia; Fang, Yi; Liu, Zhenya; Li, Jie; Tang, Chengchun; Huang, Yang</p> <p>2016-01-01</p> <p>We report the design and synthesis of a novel kind of organic-inorganic hybrid <span class="hlt">material</span> via the incorporation of europium (III) β-diketonate complexes (Eu(TTA)3, TTA = 2-thenoyltrifluoroacetone) into one-dimensional (1D) <span class="hlt">porous</span> boron nitride (BN) microfibers. The developed Eu(TTA)3@BN hybrid composites with typical 1D fibrous morphology exhibit bright visible red-light emission on UV illumination. The confinement of Eu(TTA)3 within pores of BN microfibers not only decreases the aggregation-caused quenching in solid Eu(TTA)3, but also improves their thermal stabilities. Moreover, The strong interactions between Eu(TTA)3 and <span class="hlt">porous</span> BN matrix result in an interesting energy transfer process from BN host to TTA ligand and TTA ligand to Eu3+ ions, leading to the remarkable increase of red emission. The synthetic approach should be a very promising strategy which can be easily expanded to other hybrid luminescent <span class="hlt">materials</span> based on <span class="hlt">porous</span> BN. PMID:27687246</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>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('https://www.osti.gov/scitech/biblio/1028052','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1028052"><span>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://adsabs.harvard.edu/abs/2016PhRvE..93c3006P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvE..93c3006P"><span>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/2016FML.....950032L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016FML.....950032L"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/24611543','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24611543"><span>In silico design of <span class="hlt">porous</span> polymer networks: high-throughput screening for methane storage <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martin, Richard L; Simon, Cory M; Smit, Berend; Haranczyk, Maciej</p> <p>2014-04-02</p> <p><span class="hlt">Porous</span> polymer networks (PPNs) are a class of advanced <span class="hlt">porous</span> <span class="hlt">materials</span> that combine the advantages of cheap and stable polymers with the high surface areas and tunable chemistry of metal-organic frameworks. They are of particular interest for gas separation or storage applications, for instance, as methane adsorbents for a vehicular natural gas tank or other portable applications. PPNs are self-assembled from distinct building units; here, we utilize commercially available chemical fragments and two experimentally known synthetic routes to design in silico a large database of synthetically realistic PPN <span class="hlt">materials</span>. All structures from our database of 18,000 <span class="hlt">materials</span> have been relaxed with semiempirical electronic structure methods and characterized with Grand-canonical Monte Carlo simulations for methane uptake and deliverable (working) capacity. A number of novel structure-property relationships that govern methane storage performance were identified. The relationships are translated into experimental guidelines to realize the ideal PPN structure. We found that cooperative methane-methane attractions were present in all of the best-performing <span class="hlt">materials</span>, highlighting the importance of guest interaction in the design of optimal <span class="hlt">materials</span> for methane storage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25350718','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25350718"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1030875','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1030875"><span>NUMERICAL <span class="hlt">MODELING</span> OF CATHODE CONTACT <span class="hlt">MATERIAL</span> DENSIFICATION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Koeppel, Brian J.; Liu, Wenning N.; Stephens, Elizabeth V.; Khaleel, Mohammad A.</p> <p>2011-11-01</p> <p>Numerical <span class="hlt">modeling</span> was used to simulate the constrained sintering process of the cathode contact layer during assembly of solid oxide fuel cells (SOFCs). A finite element <span class="hlt">model</span> based on the continuum theory for sintering of <span class="hlt">porous</span> bodies was developed and used to investigate candidate low-temperature cathode contact <span class="hlt">materials</span>. Constitutive parameters for various contact <span class="hlt">materials</span> under investigation were estimated from dilatometry screening tests, and the influence of processing time, processing temperature, initial grain size, and applied compressive stress on the free sintering response was predicted for selected candidate <span class="hlt">materials</span>. The densification behavior and generated stresses within a 5-cell planar SOFC stack during sintering, high temperature operation, and room temperature shutdown were predicted. Insufficient constrained densification was observed in the stack at the proposed heat treatment, but beneficial effects of reduced grain size, compressive stack preload, and reduced thermal expansion coefficient on the contact layer densification and stresses were observed.</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>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5255619','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5255619"><span>Statistical mechanical <span class="hlt">model</span> of gas adsorption in <span class="hlt">porous</span> crystals with dynamic moieties</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Braun, Efrem; Carraro, Carlo; Smit, Berend</p> <p>2017-01-01</p> <p>Some nanoporous, crystalline <span class="hlt">materials</span> possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical <span class="hlt">model</span> of gas adsorption in a <span class="hlt">porous</span> crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our <span class="hlt">model</span> captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple <span class="hlt">model</span> contribute a more intimate understanding of the response and consequence of rotating ligands integrated into <span class="hlt">porous</span> <span class="hlt">materials</span> to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our <span class="hlt">model</span> reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes. PMID:28049851</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><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('https://www.ncbi.nlm.nih.gov/pubmed/27870246','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27870246"><span><span class="hlt">Materials</span> Informatics: Statistical <span class="hlt">Modeling</span> in <span class="hlt">Material</span> Science.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yosipof, Abraham; Shimanovich, Klimentiy; Senderowitz, Hanoch</p> <p>2016-12-01</p> <p><span class="hlt">Material</span> informatics is engaged with the application of informatic principles to <span class="hlt">materials</span> science in order to assist in the discovery and development of new <span class="hlt">materials</span>. Central to the field is the application of data mining techniques and in particular machine learning approaches, often referred to as Quantitative Structure Activity Relationship (QSAR) <span class="hlt">modeling</span>, to derive predictive <span class="hlt">models</span> for a variety of <span class="hlt">materials</span>-related "activities". Such <span class="hlt">models</span> can accelerate the development of new <span class="hlt">materials</span> with favorable properties and provide insight into the factors governing these properties. Here we provide a comparison between medicinal chemistry/drug design and <span class="hlt">materials</span>-related QSAR <span class="hlt">modeling</span> and highlight the importance of developing new, <span class="hlt">materials</span>-specific descriptors. We survey some of the most recent QSAR <span class="hlt">models</span> developed in <span class="hlt">materials</span> science with focus on energetic <span class="hlt">materials</span> and on solar cells. Finally we present new examples of <span class="hlt">material</span>-informatic analyses of solar cells libraries produced from metal oxides using combinatorial <span class="hlt">material</span> synthesis. Different analyses lead to interesting physical insights as well as to the design of new cells with potentially improved photovoltaic parameters.</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>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('https://www.osti.gov/scitech/biblio/126354','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/126354"><span>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4730847','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4730847"><span>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('https://www.osti.gov/scitech/biblio/22420594','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22420594"><span>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> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17891422','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17891422"><span>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="https://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> </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/2016Nanos...813507H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Nanos...813507H"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/28322439','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28322439"><span><span class="hlt">Modeling</span> multidimensional and multispecies biofilms in <span class="hlt">porous</span> media.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tang, Youneng; Liu, Haihu</p> <p>2017-03-21</p> <p><span class="hlt">Modeling</span> multidimensional and multispecies biofilm in <span class="hlt">porous</span> media at the pore scale is challenging due to the need to simultaneously track the microbial community in the biofilms and the interfaces between the biofilms and the fluid. Therefore, researchers usually assume that the <span class="hlt">model</span> has only one dimension in space or has only one microbial species. This work uses bioremediation of U(VI)-contaminated groundwater as the context to develop a two-dimensional and multispecies biofilm <span class="hlt">model</span>. The <span class="hlt">model</span> simulates the transverse mixing zone in which U(VI) is mixed with propionate, a nutrient externally supplied to stimulate the growth of microorganisms. The <span class="hlt">model</span> considers multiple interactions among fluid flow, transport and reaction of chemical species, and growth of biofilm. The biofilm consists of two types of active biomass (syntrophs and dissimilatory metal reducing bacteria) and inert biomass. The two types of active biomass collaboratively remove U(VI). The <span class="hlt">model</span> outputs biomass distribution, chemical species concentrations, and fluid flow at the pore scale to fundamentally study the multiple interactions. The <span class="hlt">model</span> also outputs the contaminant removal rate that can be potentially used for up-scaling studies. The simulated results are generally consistent with experimental observations from other studies in trend. The trend can be explained by the multiple interactions based on thermodynamics and microbial kinetics. This article is protected by copyright. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27381910','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27381910"><span>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="https://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>.</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>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://adsabs.harvard.edu/abs/1980WRR....16..201G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980WRR....16..201G"><span>Percolation Theory and <span class="hlt">Models</span> of Unsaturated <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>Golden, J. M.</p> <p>1980-02-01</p> <p>Concepts from percolation theory (Broadbent and Hammersley, 1957) are applied to a <span class="hlt">model</span> of unsaturated flow through <span class="hlt">porous</span> media. This approach in principle allows one to build into the <span class="hlt">model</span> aspects of the topological structure of pore space. At a very general level the input of results from percolation theory gives a relationship between minimum and maximum saturation values for a medium which should be experimentally checkable, though probably not without sophisticated techniques. Also, it gives some qualitative insight into known properties of unsaturated flow. Furthermore, there emerges a way of looking at the phenomenon of hysteresis that is quite different from the standard approach. This aspect is explored in some detail, and two possible new <span class="hlt">models</span> are presented. A subsidiary result obtained from the detailed <span class="hlt">model</span> used is that in a simple pore <span class="hlt">model</span> the inclusion of a pore length parameter, statistically correlated with pore radius, is equivalent, at least in a restricted sense, to incorporating into the <span class="hlt">model</span> the concept of tortuosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25096091','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25096091"><span>Experimental observation of a hydrodynamic mode in a flow duct with a <span class="hlt">porous</span> <span class="hlt">material</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Aurégan, Yves; Singh, Deepesh Kumar</p> <p>2014-08-01</p> <p>This paper experimentally investigates the acoustic behavior of a homogeneous <span class="hlt">porous</span> <span class="hlt">material</span> with a rigid frame (metallic foam) under grazing flow. The transmission coefficient shows an unusual oscillation over a particular range of frequencies which reports the presence of an unstable hydrodynamic wave that can exchange energy with the acoustic waves. This coupling of acoustic and hydrodynamic waves becomes larger when the Mach number increases. A rise of the static pressure drop in the lined region is induced by an acoustic excitation when the hydrodynamic wave is present.</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>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.; Rübel, Oliver; Haranczyk, Maciej; Smit, Berend</p> <p>2012-05-08</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/2015EPJST.224.1749C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJST.224.1749C"><span>A comprehensive multiscale moisture transport analysis: From <span class="hlt">porous</span> reference silicates to cement-based <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>Chemmi, H.; Petit, D.; Tariel, V.; Korb, J.-P.; Denoyel, R.; Bouchet, R.; Levitz, P.</p> <p>2015-07-01</p> <p>Natural and manufactured disordered systems are ubiquitous and often involve hierarchical structures. This structural organization optimizes defined physical properties at several scales from molecular to representative volumes where the usual homogenization approach becomes efficient. For studying a particular physical property on these systems it is thus required to use a general method of analysis based on the joint application of complementary techniques covering the whole set of time-and length-scales. Here we review a comprehensive multiscale method presented for analyzing the three-dimensional moisture transport in hierarchical <span class="hlt">porous</span> media such as synthesized reference silicates and cement-based <span class="hlt">materials</span>. Several techniques (NMR spectroscopy, relaxometry, diffusometry, X-ray micro-tomography, conductivity…) have been used to evidence the interplay between the different scales involved in this transport process. This method allows answering the general opened questions concerning the scale dependence of such a moisture transport in cement-based <span class="hlt">materials</span>. We outline the main results of the multiscale techniques applied on reference <span class="hlt">porous</span> silicates allowing separating the impact of geometry, hydric state and wettability on the moisture transport. Based on this approach, we prove that this transport at micro- and meso-scale is determinant to modify the moisture at macro-scale during setting or for hardened cement-based <span class="hlt">materials</span>.</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>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/2016WRR....52.9390F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52.9390F"><span>A travel time-based approach to <span class="hlt">model</span> kinetic sorption in highly heterogeneous <span class="hlt">porous</span> media via reactive hydrofacies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Finkel, Michael; Grathwohl, Peter; Cirpka, Olaf A.</p> <p>2016-12-01</p> <p>We present a semianalytical <span class="hlt">model</span> for the transport of solutes being subject to sorption in <span class="hlt">porous</span> aquifers. We couple a travel time-based <span class="hlt">model</span> of advective transport with a spherical diffusion <span class="hlt">model</span> of kinetic sorption in nonuniform <span class="hlt">material</span> mixtures. The <span class="hlt">model</span> is formulated in the Laplace domain and transformed to the time domain by numerical inversion. By this, three-dimensional transport of solutes undergoing mass transfer between aqueous and solid phases can be simulated very efficiently. The <span class="hlt">model</span> addresses both hydraulic and reactive heterogeneity of <span class="hlt">porous</span> aquifers by means of hydrofacies, which function as homogeneous but nonuniform subunits. The total exposure time to each of these subunits controls the magnitude of sorption effects, whereas the particular sequence of facies through which the solute passes is irrelevant. We apply the <span class="hlt">model</span> to simulate the transport of phenanthrene in a fluvio-glacial aquifer, for which the hydrofacies distribution is known at high resolution, the lithological composition of each facies has been analyzed, and sorption properties of the lithological components are available. Taking the fully resolved hydrofacies <span class="hlt">model</span> as reference, we evaluate different approximations referring to lower information levels, reflecting shortcomings in typical <span class="hlt">modeling</span> projects. The most important feature for a good description of both the main breakthrough and tailing of phenanthrene is the nonuniformity of the <span class="hlt">porous</span> medium. While spatial heterogeneity of chemical properties might be neglected without introducing a large error, an approximation of the facies' composition in terms of a uniform substitute <span class="hlt">material</span> considerably compromises the quality of the <span class="hlt">modeling</span> result.</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>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://adsabs.harvard.edu/abs/2007APS..DFD.AQ007G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007APS..DFD.AQ007G"><span>A <span class="hlt">model</span> for ion transport during drying of 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>Guglielmini, Laura; Gontcharov, Alexandre; Aldykiewicz, Antonio; Stone, Howard</p> <p>2007-11-01</p> <p>Salt crystallization at the surface or in the body of a <span class="hlt">porous</span> medium has been recognized as a major mechanism in the deterioration of construction <span class="hlt">materials</span> and historical monuments. Crystal formations on the surface of bricks, concrete, stones, called efflorescences, lead to fast obsolescence of building and monuments finishing, while crystal growth inside the <span class="hlt">material</span>, called subflorescences, causes crack formation, which may lead to major structural damages. A number of studies have been devoted to the analysis of crystal growth in an elementary pore and aim at explaining the stress generated by crystallization. From a fluid mechanical point of view the physics of water transport and salt distribution in the <span class="hlt">porous</span> medium turns out to be quite complex, since it is a function of the pore structure and wettability characteristics, of granule size and of the thermal properties of the <span class="hlt">material</span>. It also depends on the transient environmental conditions the surface is exposed to and on the effective diffusivity of salt at different saturation conditions. We present here a simple theoretical <span class="hlt">model</span> of the first phase of the drying process, during which water is uniformly distributed throughout the medium and often efflorescences occurs, which aims at characterizing the physics involved in the process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1335981','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1335981"><span>Hysteretic Four-Step Spin Crossover within a Three-Dimensional <span class="hlt">Porous</span> Hofmann-like <span class="hlt">Material</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Clements, John E.; Price, Jason R.; Neville, Suzanne M.; Kepert, Cameron J.</p> <p>2016-10-21</p> <p><span class="hlt">Materials</span> that display multiple stepped spin crossover (SCO) transitions with accompanying hysteresis present the opportunity for ternary, quaternary, and quinary electronic switching and data storage but are rare in existence. Herein, we present the first report of a four-step hysteretic SCO framework. Single-crystal structure analysis of a <span class="hlt">porous</span> 3D Hofmann-like <span class="hlt">material</span> showed long-range ordering of spin states: HS, HS<sub>0.67</sub>LS<sub>0.33</sub>, HS<sub>0.5</sub>LS<sub>0.5</sub>, HS<sub>0.33</sub>LS<sub>0.67</sub>, and LS. These detailed structural studies provide insight into how multistep SCO <span class="hlt">materials</span> can be rationally designed through control of host–host and host–guest interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JSV...329..866K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JSV...329..866K"><span>Acoustic absorption <span class="hlt">modeling</span> of <span class="hlt">porous</span> concrete considering the gradation and shape of aggregates and void ratio</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, H. K.; Lee, H. K.</p> <p>2010-03-01</p> <p>The results of acoustic absorption <span class="hlt">modeling</span> of <span class="hlt">porous</span> concrete considering the gradation and shape of aggregates and void ratio are presented. To <span class="hlt">model</span> the void texture of <span class="hlt">porous</span> concrete, the multi-layered micro-perforated rigid panel <span class="hlt">model</span> considering air gaps [1,2] is adopted. The parameters used in this acoustic absorption <span class="hlt">modeling</span> are determined by a geometrical and experimental approach considering the gradation and shape of aggregates and void ratio. The predicted acoustic absorption spectra are compared with experimental results to verify the proposed acoustic absorption <span class="hlt">modeling</span> approach. Finally, a parametric study is conducted to investigate the influence of design factors on the acoustic absorption properties of <span class="hlt">porous</span> concrete.</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>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('https://www.ncbi.nlm.nih.gov/pubmed/25871080','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25871080"><span>Bottom-up <span class="hlt">model</span> of adsorption and transport in multiscale <span class="hlt">porous</span> media.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boţan, Alexandru; Ulm, Franz-Josef; Pellenq, Roland J-M; Coasne, Benoit</p> <p>2015-03-01</p> <p>We develop a <span class="hlt">model</span> of transport in multiscale <span class="hlt">porous</span> media which accounts for adsorption in the different porosity scales. This <span class="hlt">model</span> employs statistical mechanics to upscale molecular simulation and describe adsorption and transport at larger time and length scales. Using atom-scale simulations, which capture the changes in adsorption and transport with temperature, pressure, pore size, etc., this approach does not assume any adsorption or flow type. Moreover, by relating the local chemical potential μ(r) and density ρ(r), the present <span class="hlt">model</span> accounts for adsorption effects and possible changes in the confined fluid state upon transport. This <span class="hlt">model</span> constitutes a bottom-up framework of adsorption and transport in multiscale <span class="hlt">materials</span> as it (1) describes the adsorption-transport interplay, (2) accounts for the hydrodynamics breakdown at the nm scale, and (3) is multiscale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1413856D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1413856D"><span>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://adsabs.harvard.edu/abs/2010PhDT.........3V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.........3V"><span>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://hdl.handle.net/2060/19720010302','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720010302"><span>Experimental investigation of the flow, oxidation, cooling, and thermal-fatigue characteristics of a laminated <span class="hlt">porous</span> sheet <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>Hickel, R. O.; Warren, E. L.; Kaufman, A.</p> <p>1972-01-01</p> <p>The basic flow and oxidation characteristics of a laminated <span class="hlt">porous</span> <span class="hlt">material</span> (Lamilloy) are presented. The oxidation characteristics of Lamilloy are compared to a wireform-type <span class="hlt">porous</span> <span class="hlt">material</span> for the case when both <span class="hlt">materials</span> are made from Hastelloy-X alloy. The cooling performance of an air cooled vane made from Lamilloy, as determined from cascade tests made at gas temperatures ranging from 1388 to 1741 C (2350 to 3165 F) is also discussed, as well as of a cascade-type thermal fatigue test of the Lamilloy vane.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22398914','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22398914"><span>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> </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://adsabs.harvard.edu/abs/2016JPS...329..339Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPS...329..339Y"><span>Natural sisal fibers derived hierarchical <span class="hlt">porous</span> activated carbon as capacitive <span class="hlt">material</span> in lithium ion capacitor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Zhewei; Guo, Huajun; Li, Xinhai; Wang, Zhixing; Yan, Zhiliang; Wang, Yansen</p> <p>2016-10-01</p> <p>Lithium-ion capacitor (LIC) is a novel advanced electrochemical energy storage (EES) system bridging gap between lithium ion battery (LIB) and electrochemical capacitor (ECC). In this work, we report that sisal fiber activated carbon (SFAC) was synthesized by hydrothermal treatment followed by KOH activation and served as capacitive <span class="hlt">material</span> in LIC for the first time. Different particle structure, morphology, specific surface area and heteroatoms affected the electrochemical performance of as-prepared <span class="hlt">materials</span> and corresponding LICs. When the mass ratio of KOH to char precursor was 2, hierarchical <span class="hlt">porous</span> structured SFAC-2 was prepared and exhibited moderate specific capacitance (103 F g-1 at 0.1 A g-1), superior rate capability and cyclic stability (88% capacity retention after 5000 cycles at 1 A g-1). The corresponding assembled LIC (LIC-SC2) with optimal comprehensive electrochemical performance, displayed the energy density of 83 Wh kg-1, the power density of 5718 W kg-1 and superior cyclic stability (92% energy density retention after 1000 cycles at 0.5 A g-1). It is worthwhile that the source for activated carbon is a natural and renewable one and the synthesis method is eco-friendly, which facilitate that hierarchical <span class="hlt">porous</span> activated carbon has potential applications in the field of LIC and other energy storage systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24016841','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24016841"><span><span class="hlt">Porous</span> graphitic carbon nanosheets as a high-rate anode <span class="hlt">material</span> for lithium-ion batteries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Long; Wang, Zhiyuan; He, Chunnian; Zhao, Naiqin; Shi, Chunsheng; Liu, Enzuo; Li, Jiajun</p> <p>2013-10-09</p> <p>Two-dimensional (2D) <span class="hlt">porous</span> graphitic carbon nanosheets (PGC nanosheets) as a high-rate anode <span class="hlt">material</span> for lithium storage were synthesized by an easy, low-cost, green, and scalable strategy that involves the preparation of the PGC nanosheets with Fe and Fe3O4 nanoparticles embedded (indicated with (Fe&Fe3O4)@PGC nanosheets) using glucose as the carbon precursor, iron nitrate as the metal precursor, and a surface of sodium chloride as the template followed by the subsequent elimination of the Fe and Fe3O4 nanoparticles from the (Fe&Fe3O4)@PGC nanosheets by acid dissolution. The unique 2D integrative features and <span class="hlt">porous</span> graphitic characteristic of the carbon nanosheets with high porosity, high electronic conductivity, and outstanding mechanical flexibility and stability are very favorable for the fast and steady transfer of electrons and ions. As a consequence, a very high reversible capacity of up to 722 mAh/g at a current density of 100 mA/g after 100 cycles, a high rate capability (535, 380, 200, and 115 mAh/g at 1, 10, 20, and 30 C, respectively, 1 C = 372 mA/g), and a superior cycling performance at an ultrahigh rate (112 mAh/g at 30 C after 570 charge-discharge cycles) are achieved by using these nanosheets as a lithium-ion-battery anode <span class="hlt">material</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT........85T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT........85T"><span>Supported Intrinsically <span class="hlt">Porous</span> Oligomers as Hybrid <span class="hlt">Materials</span> for Separations, Storage, and Sensing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, Anthony Boone</p> <p></p> <p>Adsorption-desorption phenomena are often difficult to study at the molecular level because the surfaces on which they occur can be heterogeneous, giving a wide distribution of adsorption sites and associated energies. Considering that these phenomena underlie an incredibly wide variety of industrially important processes, a better understanding could aid in the development of more efficient methods. In this work, we describe an approach to designing <span class="hlt">materials</span> with well-defined adsorption sites by covalently attaching intrinsically <span class="hlt">porous</span> molecules to solid surfaces by a rigid multidentate linker. These cup-shaped molecules are intended to act as adsorption sites on the <span class="hlt">material</span>, whereas the rigid attachment to the solid support serves to prevent movement and conformational changes of the sites, leading to better understanding of adsorption phenomena. As a proof-of-concept application, <span class="hlt">materials</span> were used for adsorption of n-butanol biofuel and related compounds from dilute aqueous solution. The <span class="hlt">materials</span> were thermally and hydrolytically stable, and adsorption phenomena were reversible. Adsorption sites containing more hydrophobic molecular area led to stronger adsorption, suggesting that it is driven by weak van der Waals forces. Likewise, adsorption sites that were strongly polarized performed poorly, possibly reflecting a greater energy penalty of removing water molecules from the cavity. Upon placing a Lewis acidic metal at the bottom of the cavity, an enhancement was seen only with the most acidic metal, which may indicate weak guest coordination. Observing that hydrophobic interactions dominate adsorption on these <span class="hlt">materials</span>, efforts were made to develop hybrid <span class="hlt">materials</span> with large hydrophobic area for adsorption. Glaser coupling of diethynylbenzene was used to grow oligo(phenylene butadiynylene)s from the surface of silica, resulting in <span class="hlt">materials</span> that were more than 25% organic by weight. In addition to their potential use as adsorbents, these <span class="hlt">materials</span> may</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25179786','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25179786"><span>Breath Figures of Nanoscale Bricks: A Universal Method for Creating Hierarchic <span class="hlt">Porous</span> <span class="hlt">Materials</span> from Inorganic Nanoparticles Stabilized with Mussel-Inspired Copolymers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Saito, Yuta; Shimomura, Masatsugu; Yabu, Hiroshi</p> <p>2014-09-01</p> <p>High-performance catalysts and photovoltaics are required for building an environmentally sustainable society. Because catalytic and photovoltaic reactions occur at the interfaces between reactants and surfaces, the chemical, physical, and structural properties of interfaces have been the focus of much research. To improve the performance of these <span class="hlt">materials</span> further, inorganic <span class="hlt">porous</span> <span class="hlt">materials</span> with hierarchic <span class="hlt">porous</span> architectures have been fabricated. The breath figure technique allows preparing <span class="hlt">porous</span> films by using water droplets as templates. In this study, a valuable preparation method for hierarchic <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> is shown. Hierarchic <span class="hlt">porous</span> <span class="hlt">materials</span> are prepared from surface-coated inorganic nanoparticles with amphiphilic copolymers having catechol moieties followed by sintering. Micron-scale pores are prepared by using water droplets as templates, and nanoscale pores are formed between the nanoparticles. The fabrication method allows the preparation of hierarchic <span class="hlt">porous</span> films from inorganic nanoparticles of various shapes and <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JPhD...41u2002H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JPhD...41u2002H"><span>FAST TRACK COMMUNICATION: Sodium sulfate heptahydrate: direct observation of crystallization in a <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>Hamilton, Andrea; Hall, Christopher; Pel, Leo</p> <p>2008-11-01</p> <p>It is well known that sodium sulfate causes salt crystallization damage in building <span class="hlt">materials</span> and rocks. However since the early 1900s the existence of the metastable heptahydrate has been largely forgotten and almost entirely overlooked in scientific publications on salt damage mechanics and on terrestrial and planetary geochemistry. We use hard synchrotron x-rays to detect the formation of this metastable heptahydrate on cooling a <span class="hlt">porous</span> calcium silicate <span class="hlt">material</span> saturated with sodium sulfate solution. The heptahydrate persists indefinitely and transforms to mirabilite only below 0 °C. At the transformation, which is rapid, the solution is highly supersaturated with respect to mirabilite. We estimate that crystallization of the heptahydrate and of mirabilite have associated Correns pressures of about 9 and 19 MPa, respectively, exceeding the tensile strength of building stones. We detect lattice strains in the salts from x-ray measurements consistent with these values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1128993','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1128993"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/26996258','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26996258"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24591265','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24591265"><span>Pumping through <span class="hlt">porous</span> hydrophobic/oleophilic <span class="hlt">materials</span>: an alternative technology for oil spill remediation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ge, Jin; Ye, Yin-Dong; Yao, Hong-Bin; Zhu, Xi; Wang, Xu; Wu, Liang; Wang, Jin-Long; Ding, Hang; Yong, Ni; He, Ling-Hui; Yu, Shu-Hong</p> <p>2014-04-01</p> <p>Recently, <span class="hlt">porous</span> hydrophobic/oleophilic <span class="hlt">materials</span> (PHOMs) have been shown to be the most promising candidates for cleaning up oil spills; however, due to their limited absorption capacity, a large quantity of PHOMs would be consumed in oil spill remediation, causing serious economic problems. In addition, the complicated and time-consuming process of oil recovery from these sorbents is also an obstacle to their practical application. To solve the above problems, we apply external pumping on PHOMs to realize the continuous collection of oil spills in situ from the water surface with high speed and efficiency. Based on this novel design, oil/water separation and oil collection can be simultaneously achieved in the remediation of oil spills, and the oil sorption capacity is no longer limited to the volume and weight of the sorption <span class="hlt">material</span>. This novel external pumping technique may bring PHOMs a step closer to practical application in oil spill remediation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1342699-ultra-tunable-platform-molecular-engineering-high-performance-crystalline-porous-materials','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1342699-ultra-tunable-platform-molecular-engineering-high-performance-crystalline-porous-materials"><span>An ultra-tunable platform for molecular engineering of high-performance crystalline <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Zhai, Quan -Guo; Bu, Xianhui; Mao, Chengyu; ...</p> <p>2016-12-07</p> <p>Metal-organic frameworks are a class of crystalline <span class="hlt">porous</span> <span class="hlt">materials</span> with potential applications in catalysis, gas separation and storage, and so on. Of great importance is the development of innovative synthetic strategies to optimize porosity, composition and functionality to target specific applications. Here we show a platform for the development of metal-organic <span class="hlt">materials</span> and control of their gas sorption properties. This platform can accommodate a large variety of organic ligands and homo- or hetero-metallic clusters, which allows for extraordinary tunability in gas sorption properties. Even without any strong binding sites, most members of this platform exhibit high gas uptake capacity. Asmore » a result, the high capacity is accomplished with an isosteric heat of adsorption as low as 20 kJ mol–1 for carbon dioxide, which could bring a distinct economic advantage because of the significantly reduced energy consumption for activation and regeneration of adsorbents.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5180166','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5180166"><span>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://adsabs.harvard.edu/abs/2016NatCo...713645Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...713645Z"><span>An ultra-tunable platform for molecular engineering of high-performance crystalline <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>Zhai, Quan-Guo; Bu, Xianhui; Mao, Chengyu; Zhao, Xiang; Daemen, Luke; Cheng, Yongqiang; Ramirez-Cuesta, Anibal J.; Feng, Pingyun</p> <p>2016-12-01</p> <p>Metal-organic frameworks are a class of crystalline <span class="hlt">porous</span> <span class="hlt">materials</span> with potential applications in catalysis, gas separation and storage, and so on. Of great importance is the development of innovative synthetic strategies to optimize porosity, composition and functionality to target specific applications. Here we show a platform for the development of metal-organic <span class="hlt">materials</span> and control of their gas sorption properties. This platform can accommodate a large variety of organic ligands and homo- or hetero-metallic clusters, which allows for extraordinary tunability in gas sorption properties. Even without any strong binding sites, most members of this platform exhibit high gas uptake capacity. The high capacity is accomplished with an isosteric heat of adsorption as low as 20 kJ mol-1 for carbon dioxide, which could bring a distinct economic advantage because of the significantly reduced energy consumption for activation and regeneration of adsorbents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1342699','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1342699"><span>An ultra-tunable platform for molecular engineering of high-performance crystalline <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>Zhai, Quan -Guo; Bu, Xianhui; Mao, Chengyu; Zhao, Xiang; Daemen, Luke; Cheng, Yongqiang; Ramirez-Cuesta, Anibal J.; Feng, Pingyun</p> <p>2016-12-07</p> <p>Metal-organic frameworks are a class of crystalline <span class="hlt">porous</span> <span class="hlt">materials</span> with potential applications in catalysis, gas separation and storage, and so on. Of great importance is the development of innovative synthetic strategies to optimize porosity, composition and functionality to target specific applications. Here we show a platform for the development of metal-organic <span class="hlt">materials</span> and control of their gas sorption properties. This platform can accommodate a large variety of organic ligands and homo- or hetero-metallic clusters, which allows for extraordinary tunability in gas sorption properties. Even without any strong binding sites, most members of this platform exhibit high gas uptake capacity. As a result, the high capacity is accomplished with an isosteric heat of adsorption as low as 20 kJ mol<sup>–1</sup> for carbon dioxide, which could bring a distinct economic advantage because of the significantly reduced energy consumption for activation and regeneration of adsorbents.</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>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5150645','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5150645"><span>An ultra-tunable platform for molecular engineering of high-performance crystalline <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>Zhai, Quan-Guo; Bu, Xianhui; Mao, Chengyu; Zhao, Xiang; Daemen, Luke; Cheng, Yongqiang; Ramirez-Cuesta, Anibal J.; Feng, Pingyun</p> <p>2016-01-01</p> <p>Metal-organic frameworks are a class of crystalline <span class="hlt">porous</span> <span class="hlt">materials</span> with potential applications in catalysis, gas separation and storage, and so on. Of great importance is the development of innovative synthetic strategies to optimize porosity, composition and functionality to target specific applications. Here we show a platform for the development of metal-organic <span class="hlt">materials</span> and control of their gas sorption properties. This platform can accommodate a large variety of organic ligands and homo- or hetero-metallic clusters, which allows for extraordinary tunability in gas sorption properties. Even without any strong binding sites, most members of this platform exhibit high gas uptake capacity. The high capacity is accomplished with an isosteric heat of adsorption as low as 20 kJ mol−1 for carbon dioxide, which could bring a distinct economic advantage because of the significantly reduced energy consumption for activation and regeneration of adsorbents. PMID:27924818</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060041352&hterms=Sodium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DSodium','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060041352&hterms=Sodium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DSodium"><span>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://www.osti.gov/scitech/servlets/purl/10197006','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10197006"><span>Nonequilibrium multiphase mixture <span class="hlt">modeling</span> of energetic <span class="hlt">material</span> response</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baer, M.R.; Hertel, E.; Bell, R.</p> <p>1995-12-31</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. Foundation for this multiphase <span class="hlt">model</span> is based on a continuum mixture formulation given by Baer and Nunziato. In this nonequilibrium approach, multiple thermodynamic and mechanics fields are resolved including the effects of <span class="hlt">material</span> relative motion, rate-dependent compaction, drag and heat transfer interphase effects and multiple-step combustion. 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 which are key features to describe shock initiation and self-accelerated deflagration-to-detonation combustion behavior. To complement one-dimensional simulation, two dimensional numerical simulations are presented which indicate wave curvature effects due to the loss of wall confinement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Fract..2202001C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Fract..2202001C"><span>An Introduction to Flow and Transport in Fractal <span class="hlt">Models</span> of <span class="hlt">Porous</span> Media: Part I</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Jianchao; San José Martínez, Fernando; Martín, Miguel Angel; Perfect, Edmund</p> <p>2014-09-01</p> <p>This special issue gathers together a number of recent papers on fractal geometry and its applications to the <span class="hlt">modeling</span> of flow and transport in <span class="hlt">porous</span> media. The aim is to provide a systematic approach for analyzing the statics and dynamics of fluids in fractal <span class="hlt">porous</span> media by means of theory, <span class="hlt">modeling</span> and experimentation. The topics covered include lacunarity analyses of multifractal and natural grayscale patterns, random packing's of self-similar pore/particle size distributions, Darcian and non-Darcian hydraulic flows, diffusion within fractals, <span class="hlt">models</span> for the permeability and thermal conductivity of fractal <span class="hlt">porous</span> media and hydrophobicity and surface erosion properties of fractal structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24337222','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24337222"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007TSE....15...39M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007TSE....15...39M"><span>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://adsabs.harvard.edu/abs/2007PhDT........24N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhDT........24N"><span>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> </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://adsabs.harvard.edu/abs/2015WRR....51.8182H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015WRR....51.8182H"><span><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> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24511248','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24511248"><span>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="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Daly, K R; Roose, T</p> <p>2014-02-08</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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24483554','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24483554"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1048491','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1048491"><span>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://adsabs.harvard.edu/abs/2016ChPhB..25i0202Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ChPhB..25i0202Y"><span>Statistical second-order two-scale analysis and computation for heat conduction problem with radiation boundary condition 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>Yang, Zhi-Qiang; Liu, Shi-Wei; Sun, Yi</p> <p>2016-09-01</p> <p>This paper discusses a statistical second-order two-scale (SSOTS) analysis and computation for a heat conduction problem with a radiation boundary condition in random <span class="hlt">porous</span> <span class="hlt">materials</span>. Firstly, the microscopic configuration for the structure with random distribution is briefly characterized. Secondly, the SSOTS formulae for computing the heat transfer problem are derived successively by means of the construction way for each cell. Then, the statistical prediction algorithm based on the proposed two-scale <span class="hlt">model</span> is described in detail. Finally, some numerical experiments are proposed, which show that the SSOTS method developed in this paper is effective for predicting the heat transfer performance of <span class="hlt">porous</span> <span class="hlt">materials</span> and demonstrating its significant applications in actual engineering computation. Project supported by the China Postdoctoral Science Foundation (Grant Nos. 2015M580256 and 2016T90276).</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>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/abs/2013ApSS..265....4W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApSS..265....4W"><span>Fabrication, characterization, and application in nanoenergetic <span class="hlt">materials</span> of uncracked nano <span class="hlt">porous</span> silicon thick films</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Shouxu; Shen, Ruiqi; Yang, Cheng; Ye, Yinghua; Hu, Yan; Li, Chuangxin</p> <p>2013-01-01</p> <p>The <span class="hlt">porous</span> silicon (PS) film has gained increasing attention in recent years as advanced nanoenergetic <span class="hlt">materials</span> (nEMs). A simple fabrication method to prepare uncracked PS thick films was successfully realized with precisely controlled electrochemical etching, and the relationship between the current density and the concentration of electrolytes was found in its fabrication. Additionally, the capillary stresses resulted from the liquids in nanopores of PS films was another factor resulted in its crack. The nanopores composed of uncracked PS thick films distributed regularly and their diameters ranged from 2 nm to 6 nm. Its Sa (average roughness) of PS film surface was 6.53 nm, and its thickness ranged from 102.41 μm to 205.75 μm. The specific surface area was 587 m2/g and the average diameter of nanopores was 4.3 nm. The PS film was found to be monocrystal and it was same as the substrate. The crack mechanism of PS films was discussed: the <span class="hlt">porous</span> structure reduced the strength of PS films comparing the silicon bulk and the capillary effect hastened the crack of PS films. PS films filling with sodium percholorate in nanopores were ignited by laser and the stable combustion showed that they were advantageous to be applied as micro-electromechanical systems (MEMS) compatible devices, such as silicon-based chips of mircothruster and microigniter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005SPIE.5724..183T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005SPIE.5724..183T"><span>Hybrid solar cells based on organic <span class="hlt">material</span> embedded into <span class="hlt">porous</span> silicon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tokranova, Natalya; Levitsky, Igor A.; Xu, Bai; Castracane, James; Euler, William B.</p> <p>2005-04-01</p> <p>Solar cells based on organic and inorganic <span class="hlt">materials</span> are an emerging technology for a new generation of photovoltaics (PV). Hybrid solar cells, which use both organic and inorganic components, have advantages such as cost-effective processing and the ability to fabricate devices on flexible substrates. The combination of organic <span class="hlt">materials</span> with semiconductor nanostructures allows enhancement of the conversion efficiency due to the fast electron transport in semiconductors and a high interface area between organic and inorganic components. In our work, anodized <span class="hlt">porous</span> Si (PSi) was chosen as a host matrix filled with Copper Phthalocyanine (CuPC) molecules. The resulting nanocomposite can yield high performance novel <span class="hlt">materials</span> for solar cells. The fabrication of PSi was completed using electrochemical etching of Si in diluted hydrofluoric acid (HF). Also, this process, with some modifications, can be applied to produce free-standing PSi films of desired thickness. PSi layer was filled with CuPC dissolved in concentrated sulfuric acid. The top contact was made by sputtering of Au or ITO. A power conversion efficiency (PCE) of 3% (33 mW/cm2) was obtained for 12 um thick n-type pSi layer with pore sizes of approximately 15 nm filled with CuPC. The electrochemical etching of Si under different conditions was carried out to optimize the photovoltaic parameters. A detailed investigation of the solar cell performance depending on <span class="hlt">porous</span> layer thicknesses and pore sizes is presented. The use of free-standing films of PSi can lead to the fabrication of novel PV solar cells on flexible substrates with high conversion efficiency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24411347','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24411347"><span>Effect of sintering conditions on the microstructural and mechanical characteristics of <span class="hlt">porous</span> magnesium <span class="hlt">materials</span> prepared by powder metallurgy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Čapek, Jaroslav; Vojtěch, Dalibor</p> <p>2014-02-01</p> <p>There has recently been an increased demand for <span class="hlt">porous</span> magnesium <span class="hlt">materials</span> in many applications, especially in the medical field. Powder metallurgy appears to be a promising approach for the preparation of such <span class="hlt">materials</span>. Many works have dealt with the preparation of <span class="hlt">porous</span> magnesium; however, the effect of sintering conditions on <span class="hlt">material</span> properties has rarely been investigated. In this work, we investigated <span class="hlt">porous</span> magnesium samples that were prepared by powder metallurgy using ammonium bicarbonate spacer particles. The effects of the purity of the argon atmosphere and sintering time on the microstructure (SEM, EDX and XRD) and mechanical behaviour (universal loading machine and Vickers hardness tester) of <span class="hlt">porous</span> magnesium were studied. The porosities of the prepared samples ranged from 24 to 29 vol.% depending on the sintering conditions. The purity of atmosphere played a significant role when the sintering time exceeded 6h. Under a gettered argon atmosphere, a prolonged sintering time enhanced diffusion connections between magnesium particles and improved the mechanical properties of the samples, whereas under a technical argon atmosphere, oxidation at the particle surfaces caused deterioration in the mechanical properties of the samples. These results suggest that a refined atmosphere is required to improve the mechanical properties of <span class="hlt">porous</span> magnesium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22318047','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22318047"><span><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('https://www.ncbi.nlm.nih.gov/pubmed/19948552','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19948552"><span>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="https://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.</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><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://adsabs.harvard.edu/abs/2016AIPC.1718j0002D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1718j0002D"><span><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://adsabs.harvard.edu/abs/2015Fract..2302001C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Fract..2302001C"><span>An Introduction to Flow and Transport in Fractal <span class="hlt">Models</span> of <span class="hlt">Porous</span> Media: Part II</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Jianchao; San José Martínez, Fernando; Martín, Miguel Angel; Hu, Xiangyun</p> <p>2015-03-01</p> <p>This is the second part of the special issue on fractal geometry and its applications to the <span class="hlt">modeling</span> of flow and transport in <span class="hlt">porous</span> media, in which 10 original research articles and one review article are included. Combining to the first part of 11 original research articles, these two issues summarized current research on fractal <span class="hlt">models</span> applied to <span class="hlt">porous</span> media that will help to further advance this multidisciplinary development. This whole special issue is published also to celebrate the 70th birthday of Professor Boming Yu for his distinguished researches on fractal geometry and its application to transport physics of <span class="hlt">porous</span> media.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..DFDD29010B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..DFDD29010B"><span>Oil drainage in <span class="hlt">model</span> <span class="hlt">porous</span> media by viscoelastic fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beaumont, Julien; Bodiguel, Hugues; Colin, Annie</p> <p>2012-11-01</p> <p>Crude oil recovery efficiency has been shown to depend directly on the capillary number (Ca). If the capillary phenomenon is well described for Newtonian fluids, the consequences of non linear rheology and viscoelasticity require more experimental work at the pore scale. In this work we take advantage of microfluidic to revisit this field. We carried out oil drainage experiments through a micromodel made up with photoresist resin. The wetting phase trapped is a <span class="hlt">model</span> oil. The invading phases used are aqueous solutions of high molecular weight hydrolyzed polyacrylamide (HPAM) and surfactant. Qualitatively, we observed a transition between a capillary fingering at low flow rates and a stable front at high flow rates for the drainage experiments with HPAM and surfactant solutions as it happened for drainage with Newtonian fluids. From movies of the filling of the device, we determine the local velocity of all menisci in the <span class="hlt">porous</span> media. Thus, we quantify the capillary fingering. Surprisingly, local velocities are not significantly different from those measured using water, whereas the HPAM solutions are much more viscous. With betaine solutions, we observed an emulsification of the oil clusters trapped during the invasion leading to a very high oil recovery after percolation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.H51H1452K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.H51H1452K"><span><span class="hlt">Modeling</span> coupled Thermo-Hydro-Mechanical processes including plastic deformation in geological <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>Kelkar, S.; Karra, S.; Pawar, R. J.; Zyvoloski, G.</p> <p>2012-12-01</p> <p>There has been an increasing interest in the recent years in developing computational tools for analyzing coupled thermal, hydrological and mechanical (THM) processes that occur in geological <span class="hlt">porous</span> media. This is mainly due to their importance in applications including carbon sequestration, enhanced geothermal systems, oil and gas production from unconventional sources, degradation of Arctic permafrost, and nuclear waste isolation. Large changes in pressures, temperatures and saturation can result due to injection/withdrawal of fluids or emplaced heat sources. These can potentially lead to large changes in the fluid flow and mechanical behavior of the formation, including shear and tensile failure on pre-existing or induced fractures and the associated permeability changes. Due to this, plastic deformation and large changes in <span class="hlt">material</span> properties such as permeability and porosity can be expected to play an important role in these processes. We describe a general purpose computational code FEHM that has been developed for the purpose of <span class="hlt">modeling</span> coupled THM processes during multi-phase fluid flow and transport in fractured <span class="hlt">porous</span> media. The code uses a continuum mechanics approach, based on control volume - finite element method. It is designed to address spatial scales on the order of tens of centimeters to tens of kilometers. While large deformations are important in many situations, we have adapted the small strain formulation as useful insight can be obtained in many problems of practical interest with this approach while remaining computationally manageable. Nonlinearities in the equations and the <span class="hlt">material</span> properties are handled using a full Jacobian Newton-Raphson technique. Stress-strain relationships are assumed to follow linear elastic/plastic behavior. The code incorporates several plasticity <span class="hlt">models</span> such as von Mises, Drucker-Prager, and also a large suite of <span class="hlt">models</span> for coupling flow and mechanical deformation via permeability and stresses</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhyA..389.3140C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhyA..389.3140C"><span>Adsorption of molecular gases on <span class="hlt">porous</span> <span class="hlt">materials</span> in the SAFT-VR approximation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Castro, M.; Martinez, R.; Martinez, A.; Rosu, H. C.</p> <p>2010-08-01</p> <p>A simple molecular thermodynamic approach is applied to the study of the adsorption of gases of chain molecules on solid surfaces. We use a <span class="hlt">model</span> based on the Statistical Associating Fluid Theory for Variable Range (SAFT-VR) potentials [A. Gil-Villegas, A. Galindo, P.J. Whitehead, S.J. Mills, G. Jackson, A.N. Burgess, J. Chem. Phys. 106 (1997) 4168] that we extend by including quasi-two-dimensional approximation to describe the adsorption properties of these types of real gas [A. Martínez, M. Castro, C. McCabe, A. Gil-Villegas, J. Chem. Phys. 126 (2007) 074707]. The <span class="hlt">model</span> is applied to ethane, ethylene, propane, and carbon dioxide adsorbed on activated carbon and silica gel, which are <span class="hlt">porous</span> media of significant industrial interest. We show that the adsorption isotherms obtained by means of the present SAFT-VR <span class="hlt">modeling</span> are in fair agreement with the experimental results provided in the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25528691','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25528691"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/206497','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/206497"><span>Combustion of <span class="hlt">porous</span> energetic <span class="hlt">materials</span> in the merged-flame regime</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Margolis, S.B.; Williams, F.A.; Telengator, A.M.</p> <p>1996-02-01</p> <p>The structure and burning rate of an unconfined deflagration propagating through a <span class="hlt">porous</span> energetic <span class="hlt">material</span> is analyzed in the limit of merged condensed and gas-phase reaction zones. A global two-step reaction mechanism, applicable to certain types of degraded nitramine propellants and consisting of sequential condensed and gaseous steps, is postulated. Taking into account important effects due to multiphase flow and exploiting the limit of large activation energies, a theoretical analysis based on activation energy asymptotics leads to explicit formulas for the deflagration velocity in a specifically identified regime that is consistent with the merged-flame assumption. The results clearly indicate the influences of two-phase flow and the multiphase, multi-step chemistry on the deflagration structure and the burning rate, and define conditions that support the intrusion of the primary gas flame into the two-phase condensed decomposition region at the propellant surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1188868','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1188868"><span>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_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/abs/2016WRR....52..315R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52..315R"><span>Percolating length scales from topological persistence analysis of micro-CT images 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>Robins, Vanessa; Saadatfar, Mohammad; Delgado-Friedrichs, Olaf; Sheppard, Adrian P.</p> <p>2016-01-01</p> <p>Topological persistence is a powerful and general technique for characterizing the geometry and topology of data. Its theoretical foundations are over 15 years old and efficient computational algorithms are now available for the analysis of large digital images. We explain here how quantities derived from topological persistence relate to other measurements on <span class="hlt">porous</span> <span class="hlt">materials</span> such as grain and pore-size distributions, connectivity numbers, and the critical radius of a percolating sphere. The connections between percolation and topological persistence are explored in detail using data obtained from micro-CT images of spherical bead packings, unconsolidated sand packing, a variety of sandstones, and a limestone. We demonstrate how persistence information can be used to estimate the percolating sphere radius and to characterize the connectivity of the percolating cluster.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..182a2013W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..182a2013W"><span>Activated <span class="hlt">porous</span> carbon wrapped sulfur sub-microparticles as cathode <span class="hlt">materials</span> for lithium sulfur 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, Y.; Yan, Y. L.; Ren, B.; Yang, R.; Zhang, W.; Xu, Y. H.</p> <p>2017-03-01</p> <p>The lithium-sulfur batteries holds a high theoretical capacity and specific energy, which is 4-5 times larger than that of today’s lithium-ion batteries, yet the low sulfur loading and large particles in the cathode greatly offset its advantage in high energy density. In the present paper, a liquid phase deposition method was introduced to synthesize sub-micro sulfur particles, which utilized as cathode <span class="hlt">materials</span> after composed with activated <span class="hlt">porous</span> carbon. Compared with common sublimed sulfur cathodes, as-obtained composite cathode shows an enhanced initial discharge capacity from 840.7 mAh/g to 1093 mAh/g at C/10. The reversible specific capacity after 50 cycles increased from 383 mAh/g to 504 mAh/g. The developed method has the advantages of simple process, convenient operation and low cost, and is suitable for the industrial preparation of lithium/sulfur batteries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AtmEn..42.2300K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AtmEn..42.2300K"><span>Removal of VOCs from indoor environment by ozonation over different <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>Kwong, C. W.; Chao, Christopher Y. H.; Hui, K. S.; Wan, M. P.</p> <p></p> <p>Ozonation of toluene over NaX, NaY and MCM-41 adsorbents was studied targeting for indoor air purification. The combined use of ozone and the various micro- or meso-<span class="hlt">porous</span> adsorbents aimed to take advantage of the strong oxidizing capability of ozone. At the same time the residual ozone would be minimized due to the enhanced catalytic reaction in the <span class="hlt">porous</span> structure. To lower the residual ozone level is a crucial issue as ozone is itself an indoor pollutant. The Lewis acid sites in the adsorbents were believed to decompose ozone into atomic oxygen, and the subsequent reactions would then convert the adsorbed toluene into CO 2 and H 2O. In the dry conditions, the MCM-41 required the smallest amount of <span class="hlt">material</span> to achieve the 90% reduction target, followed by NaY and NaX. In the more humid environment (50% RH), extra amounts of MCM-41 and NaX adsorbents were required to reach the target as compared with the dry conditions. Desorption experiments were also conducted to study the amounts of various major species held in the adsorbents during the catalytic process. A <span class="hlt">material</span> balance analysis of the major species in both the effluents and the adsorbents showed that within our experimental conditions, about 20-40% of the removed toluene was carried out via catalytic ozonation while adsorption covered the rest. Trace amount of intermediate species such as aldehydes and organic acids were identified in the desorbed gas indicating that they were withheld by the adsorbents during the air purification process and those in the effluent were below detection levels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1812444J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1812444J"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/28372521','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28372521"><span>Bone response to <span class="hlt">porous</span> polymethylmethacrylate cement loaded with hydroxyapatite particles in a rabbit mandibular <span class="hlt">model</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sa, Yue; Yu, Na; Wolke, Joop G C; Chanchareonsook, Nattharee; Goh, Bee Tin; Wang, Yining; Yang, Fang; Jansen, John A</p> <p>2017-04-03</p> <p>The aim of the current study was to evaluate bone formation and tissue response to <span class="hlt">porous</span> polymethylmethacrylate (PMMA) cement with or without hydroxyapatite (HA) in a rabbit mandibular <span class="hlt">model</span>. Therefore, fourteen New Zealand white rabbits were randomly divided into two groups of seven according to the designed study end points of 4 and 12 weeks. For each rabbit, two decorticated defects (6 mm in height and 10 mm in width for each) were prepared at both sides of the mandible. Subsequently, the defects were filled with respectively <span class="hlt">porous</span> PMMA and <span class="hlt">porous</span> PMMA-HA cement. After reaching the designated implantation period, the rabbits were euthanized and the mandibles were retrieved for histological analysis. Results showed that both <span class="hlt">porous</span> PMMA and <span class="hlt">porous</span> PMMA-HA supported bone repair. Neither of the bone cements caused significant inflammation to nerve or other surrounding tissues. After implantation of 12 weeks, majority of the porosity was filled with newly formed bone for both cements, which supports the concept that a <span class="hlt">porous</span> structure within PMMA can enhance bone ingrowth. Histomorphometrical evaluation, using histological grading scales, demonstrated that, at both implantation times, the presence of HA in the PMMA enhanced bone formation. Bone was always in direct contact with the HA particles, while intervening fibrous tissue was present at the PMMA-bone interface. On the basis of results, it was concluded that injectable <span class="hlt">porous</span> PMMA-HA cement might be a good candidate for craniofacial bone repair, which should be further evaluated in a more clinically relevant large animal <span class="hlt">model</span>.</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>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('https://www.ncbi.nlm.nih.gov/pubmed/23890630','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23890630"><span>Detection of anionic energetic <span class="hlt">material</span> residues in enhanced fingermarks on <span class="hlt">porous</span> and non-<span class="hlt">porous</span> surfaces using ion chromatography.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Love, Catherine; Gilchrist, Elizabeth; Smith, Norman; Barron, Leon</p> <p>2013-09-10</p> <p>The ability to link criminal activity and identity using validated analytical approaches can be of great value to forensic scientists. Herein, the factors affecting the recovery and detection of inorganic and organic energetic <span class="hlt">material</span> residues within chemically or physically enhanced fingermarks on paper and glass substrates are presented using micro-bore anion exchange chromatography with suppressed conductivity detection. Fingermarks on both surfaces were enhanced using aluminium powder or ninhydrin after spiking with <span class="hlt">model</span> test mixtures or through contact with black-powder substitutes. A quantitative study of the effects of environmental/method interferences, the sweat matrix, the surface and the enhancement technique on the relative anion recovery of forensically relevant species is presented. It is shown that the analytical method could detect target analytes at the nanogram level even within excesses of enhancement reagents and their reaction products when using solid phase extraction and/or microfiltration. To our knowledge, this work demonstrates for the first time that ion chromatography can detect anions in energetic <span class="hlt">materials</span> within fingermarks on two very different surfaces, after operational enhancement techniques commonly used by forensic scientists and police have been applied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1044688','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1044688"><span>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://adsabs.harvard.edu/abs/2014MSSP...42..115Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MSSP...42..115Y"><span>Nonlinear transient response analysis for double walls with a <span class="hlt">porous</span> <span class="hlt">material</span> supported by nonlinear springs using FEM and MSKE method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamaguchi, Takao; Hozumi, Hiroaki; Hirano, Yuta; Tobita, Kazuhiro; Kurosawa, Yoshio</p> <p>2014-01-01</p> <p>In this paper, we newly propose a fast computation method for the nonlinear transient responses including coupling between nonlinear springs and sound proof structures having <span class="hlt">porous</span> <span class="hlt">materials</span> using FEM. In this method, we extend our numerical method named as Modal Strain and Kinetic Method (i.e. MSKE method proposed previously by Yamaguchi who is one of the authors) from linear damping analysis to nonlinear dynamic analysis. We assume that the restoring force of the spring has cubic nonlinearity and linear hysteresis damping. To calculate damping properties for soundproof structures including elastic body, viscoelastic body and <span class="hlt">porous</span> body, displacement vectors as common unknown variable are solved under coupled condition. The damped sound fields in the <span class="hlt">porous</span> <span class="hlt">materials</span> are defined by complex effective density and complex bulk modulus. The discrete equations in physical coordinate for this system are transformed into nonlinear ordinary coupled differential equations using normal coordinates corresponding to linear natural modes. Further, using MSKE method, modal damping can be derived approximately under coupled conditions between hysteresis damping of viscoelastic <span class="hlt">materials</span>, damping of the springs and damping due to flow resistance in <span class="hlt">porous</span> <span class="hlt">materials</span>. The modal damping is used for the nonlinear differential equation to compute nonlinear transient responses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25025228','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25025228"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1341581','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1341581"><span>Hyper-crosslinked cyclodextrin <span class="hlt">porous</span> polymer: An efficient CO<sub>2</sub> capturing <span class="hlt">material</span> with tunable porosity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Meng, Bo; Li, Haiyang; Mahurin, Shannon Mark; Liu, Honglai; Dai, Sheng</p> <p>2016-11-11</p> <p>We designed and synthesized the cyclodextrin (CD)-based hyper-crosslinked <span class="hlt">porous</span> polymers (HCPPs) for selective CO<sub>2</sub> adsorption and storage. We also explored the effect of monomer size on micropore formation, and determined a feasible way to tailor the porosity of the <span class="hlt">materials</span> during the hyper-crosslinking process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27709208','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27709208"><span>Hierarchical <span class="hlt">porous</span> carbon <span class="hlt">materials</span> prepared using nano-ZnO as a template and activation agent for ultrahigh power supercapacitors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Haoran; Yu, Shukai; Xu, Bin</p> <p>2016-09-20</p> <p>Hierarchical <span class="hlt">porous</span> carbon <span class="hlt">materials</span> with high surface areas and a localized graphitic structure were simply prepared from sucrose using nano-ZnO as a hard template, activation agent and graphitization catalyst simultaneously, which exhibit an outstanding high-rate performance and can endure an ultrafast scan rate of 20 V s(-1) and ultrahigh current density of 1000 A g(-1).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28069940','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28069940"><span>All-carbon-based <span class="hlt">porous</span> topological semimetal for Li-ion battery anode <span class="hlt">material</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Junyi; Wang, Shuo; Sun, Qiang</p> <p>2017-01-24</p> <p>Topological state of matter and lithium batteries are currently two hot topics in science and technology. Here we combine these two by exploring the possibility of using all-carbon-based <span class="hlt">porous</span> topological semimetal for lithium battery anode <span class="hlt">material</span>. Based on density-functional theory and the cluster-expansion method, we find that the recently identified topological semimetal bco-C16 is a promising anode <span class="hlt">material</span> with higher specific capacity (Li-C4) than that of the commonly used graphite anode (Li-C6), and Li ions in bco-C16 exhibit a remarkable one-dimensional (1D) migration feature, and the ion diffusion channels are robust against the compressive and tensile strains during charging/discharging. Moreover, the energy barrier decreases with increasing Li insertion and can reach 0.019 eV at high Li ion concentration; the average voltage is as low as 0.23 V, and the volume change during the operation is comparable to that of graphite. These intriguing theoretical findings would stimulate experimental work on topological carbon <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27791352','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27791352"><span>Manganese Dioxide Supported on <span class="hlt">Porous</span> Biomorphic Carbons as Hybrid <span class="hlt">Materials</span> for Energy Storage Devices.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gutierrez-Pardo, Antonio; Lacroix, Bertrand; Martinez-Fernandez, Julian; Ramirez-Rico, Joaquin</p> <p>2016-11-16</p> <p>A facile and low-cost method has been employed to fabricate MnO2/C hybrid <span class="hlt">materials</span> for use as binder-free electrodes for supercapacitor applications. Biocarbon monoliths were obtained through pyrolysis of beech wood, replicating the microstructure of the cellulosic precursor, and serve as 3D <span class="hlt">porous</span> and conductive scaffolds for the direct growth of MnO2 nanosheets by a solution method. Evaluation of the experimental results indicates that a homogeneous and uniform composite <span class="hlt">material</span> made of a carbon matrix exhibiting ordered hierarchical porosity and MnO2 nanosheets with a layered nanocrystalline structure is obtained. The tuning of the MnO2 content and crystallite size via the concentration of KMnO4 used as impregnation solution allows to obtain composites that exhibit enhanced electrochemical behavior, achieving a capacitance of 592 F g(-1) in electrodes containing 3 wt % MnO2 with an excellent cyclic stability. The electrode <span class="hlt">materials</span> were characterized before and after electrochemical testing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PNAS..114..651L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PNAS..114..651L"><span>All-carbon-based <span class="hlt">porous</span> topological semimetal for Li-ion battery anode <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>Liu, Junyi; Wang, Shuo; Sun, Qiang</p> <p>2017-01-01</p> <p>Topological state of matter and lithium batteries are currently two hot topics in science and technology. Here we combine these two by exploring the possibility of using all-carbon-based <span class="hlt">porous</span> topological semimetal for lithium battery anode <span class="hlt">material</span>. Based on density-functional theory and the cluster-expansion method, we find that the recently identified topological semimetal bco-C16 is a promising anode <span class="hlt">material</span> with higher specific capacity (Li-C4) than that of the commonly used graphite anode (Li-C6), and Li ions in bco-C16 exhibit a remarkable one-dimensional (1D) migration feature, and the ion diffusion channels are robust against the compressive and tensile strains during charging/discharging. Moreover, the energy barrier decreases with increasing Li insertion and can reach 0.019 eV at high Li ion concentration; the average voltage is as low as 0.23 V, and the volume change during the operation is comparable to that of graphite. These intriguing theoretical findings would stimulate experimental work on topological carbon <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017OptSp.122...79D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017OptSp.122...79D"><span><span class="hlt">Modeling</span> of the optical properties of <span class="hlt">porous</span> silicon photonic crystals in the visible spectral range</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dovzhenko, D. S.; Martynov, I. L.; Kryukova, I. S.; Chistyakov, A. A.; Nabiev, I. R.</p> <p>2017-01-01</p> <p>Optical devices based on photonic crystals are of great interest because they can be efficiently used in laser physics and biosensing. Photonic crystals allow one to control the propagation of electromagnetic waves and to change the emission characteristics of luminophores embedded into photonic structures. One of the most interesting <span class="hlt">materials</span> for developing one-dimensional photonic crystals is <span class="hlt">porous</span> silicon. However, an important problem in application of this <span class="hlt">material</span> is the control of the refractive index of layers by changing their porosity, as well as the refractive index dispersion. In addition, it is important to have the possibility of <span class="hlt">modeling</span> the optical properties of structures to choose precisely select the fabrication parameters and produce one-dimensional photonic crystals with prescribed properties. In order to solve these problems, we used a mathematical <span class="hlt">model</span> based on the transfer matrix method, using the Bruggeman <span class="hlt">model</span>, and on the dispersion of silicon refractive index. We fabricated microcavities by electrochemical etching of silicon, with parameters determined by the proposed <span class="hlt">model</span>, and measured their reflection spectra. The calculated results showed good agreement with experimental data. The <span class="hlt">model</span> proposed allowed us to achieve a microcavity Q-factor of 160 in the visible region.</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><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('https://www.ncbi.nlm.nih.gov/pubmed/24480405','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24480405"><span>A constitutive <span class="hlt">model</span> of <span class="hlt">porous</span> SMAs considering tensile-compressive asymmetry behaviors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Bingfei; Dui, Guansuo; Xie, Benming; Xue, Lijun</p> <p>2014-04-01</p> <p>A constitutive <span class="hlt">model</span> of the macroscopic behaviors of <span class="hlt">porous</span> shape memory alloys (SMA) is developed in this work. A yield function for <span class="hlt">porous</span> SMAs considering both the effect of hydrostatic stress and the tensile-compressive asymmetry is proposed. Combining the constitutive <span class="hlt">model</span> of dense SMAs and the macroscale and microscale analysis, the evolution equation for the overall transformation strain is then derived. Examples for the response of both dense SMA and <span class="hlt">porous</span> Ni-Ti SMA subjected to uniaxial tension and compression loads are supplied. Good agreement between the numerical prediction results and the published experimental data is observed. Numerical result shows that the yielding stresses, loop width and length, strain-hardening behaviors of <span class="hlt">porous</span> SMAs under pure tensile and pure compressive are different. Importantly, the transformation initiation stress is much closer to the experiment result than simulated by Zhao et al. (2005).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApPhL..99v2110Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApPhL..99v2110Z"><span>Role of copper in time dependent dielectric breakdown of <span class="hlt">porous</span> organo-silicate glass low-k <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>Zhao, Larry; Pantouvaki, Marianna; Croes, Kristof; Tőkei, Zsolt; Barbarin, Yohan; Wilson, Christopher J.; Baklanov, Mikhail R.; Beyer, Gerald P.; Claeys, Cor</p> <p>2011-11-01</p> <p>The role of copper in time dependent dielectric breakdown (TDDB) of a <span class="hlt">porous</span> low-k dielectric with TaN/Ta barrier was investigated on a metal-insulator-metal capacitor configuration where Cu ions can drift into the low-k film by applying a positive potential on the top while they are not permitted to enter the low-k dielectric if a negative potential is applied on the top. No difference in TDDB performance was observed between the positive and negative bias conditions, suggesting that Cu cannot penetrate TaN/Ta barrier to play a critical role in the TDDB of <span class="hlt">porous</span> low-k <span class="hlt">material</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27524006','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27524006"><span><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="https://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.</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/2016JAP...119a4906B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAP...119a4906B"><span>Experimental determination of the viscous flow permeability of <span class="hlt">porous</span> <span class="hlt">materials</span> by measuring reflected low frequency acoustic waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berbiche, A.; Sadouki, M.; Fellah, Z. E. A.; Ogam, E.; Fellah, M.; Mitri, F. G.; Depollier, C.</p> <p>2016-01-01</p> <p>An acoustic reflectivity method is proposed for measuring the permeability or flow resistivity of air-saturated <span class="hlt">porous</span> <span class="hlt">materials</span>. In this method, a simplified expression of the reflection coefficient is derived in the Darcy's regime (low frequency range), which does not depend on frequency and porosity. Numerical simulations show that the reflection coefficient of a <span class="hlt">porous</span> <span class="hlt">material</span> can be approximated by its simplified expression obtained from its Taylor development to the first order. This approximation is good especially for resistive <span class="hlt">materials</span> (of low permeability) and for the lower frequencies. The permeability is reconstructed by solving the inverse problem using waves reflected by plastic foam samples, at different frequency bandwidths in the Darcy regime. The proposed method has the advantage of being simple compared to the conventional methods that use experimental reflected data, and is complementary to the transmissivity method, which is more adapted to low resistive <span class="hlt">materials</span> (high permeability).</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>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://www.osti.gov/scitech/servlets/purl/1347598','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1347598"><span>Metal-organic framework templated synthesis of <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> as novel sorbents</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Taylor-Pashow, Kathryn M. L.; Lin, Wenbin; Abney, Carter W.</p> <p>2017-03-21</p> <p>A novel metal-organic framework (MOF) templated process for the synthesis of highly <span class="hlt">porous</span> inorganic sorbents for removing radionuclides, actinides, and heavy metals is disclosed. The highly <span class="hlt">porous</span> nature of the MOFs leads to highly <span class="hlt">porous</span> inorganic sorbents (such as oxides, phosphates, sulfides, etc) with accessible surface binding sites that are suitable for removing radionuclides from high level nuclear wastes, extracting uranium from acid mine drainage and seawater, and sequestering heavy metals from waste streams. In some cases, MOFs can be directly used for removing these metal ions as MOFs are converted to highly <span class="hlt">porous</span> inorganic sorbents in situ.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10166650','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10166650"><span>Effects of two-phase flow on the deflagration of <span class="hlt">porous</span> energetic <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Margolis, S.B.; Williams, F.A.</p> <p>1994-07-01</p> <p>Theoretical analyses are developed for the multi-phase deflagration of <span class="hlt">porous</span> energetic solids, such as degraded nitramine propellants, that experience significant gas flow in the solid preheat region and are characterized by the presence of exothermic reactions in a bubbling melt layer at their surfaces. Relative motion between the gas and condensed phases is taken into account in both regions, and expressions for the mass burning rate and other quantities of interest, such as temperature and volume-fraction profiles, are derived by activation-energy asymptotics. The <span class="hlt">model</span> extends recent work by allowing for gas flow in the unburned solid, and by incorporating pressure effects through the gas-phase equation of state. As a consequence, it is demonstrated how most aspects of the deflagration wave, including its structure, propagation speed and final temperature, depend on the local pressure in the two-phase regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvE..91c3004C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvE..91c3004C"><span>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://adsabs.harvard.edu/abs/2016NatSR...631233R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...631233R"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/16530942','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16530942"><span>Preparation and sorption properties of <span class="hlt">porous</span> <span class="hlt">materials</span> from refuse paper and plastic fuel (RPF).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kadirova, Z; Kameshima, Y; Nakajima, A; Okada, K</p> <p>2006-09-01</p> <p><span class="hlt">Porous</span> <span class="hlt">materials</span> consisting of activated carbon and amorphous CaO-Al(2)O(3)-SiO(2) (CAS) compound were prepared from refuse paper and plastic fuel (RPF), (a mixture of old paper and plastic) by carbonizing and/or activating treatments. Samples formed by chemical activation using K(2)CO(3) showed a high specific surface area (S(BET)) of 1330 m(2)/g but a lower ash content due to being washed after activation. By contrast, samples prepared by physical activation using steam showed rather lower S(BET) (510 m(2)/g) due to higher ash contents. The physically activated samples showed much higher uptake properties for Ni(2+) (a representative heavy metal) and phosphate ions (a representative of a harmful oxyanion) than the chemically activated samples because of the higher content of amorphous CAS in the former samples. By contrast, the chemically activated samples showed higher uptake for methylene blue (MB, a representative organic <span class="hlt">material</span>) than the physically activated samples because of the higher activated carbon content of higher surface area. Although differences in the sorption properties for Ni(2+), phosphate ion and MB were found between the physically and chemically activated samples, both samples show excellent multiple sorption properties for cation-anion combinations and inorganic-organic sorbents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21366761','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21366761"><span>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4606457','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4606457"><span><span class="hlt">Porous</span> Structures in Stacked, Crumpled and Pillared Graphene-Based 3D <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>Guo, Fei; Creighton, Megan; Chen, Yantao; Hurt, Robert; Külaots, Indrek</p> <p>2015-01-01</p> <p>Graphene, an atomically thin <span class="hlt">material</span> with the theoretical surface area of 2600 m2g−1, has great potential in the fields of catalysis, separation, and gas storage if properly assembled into functional 3D <span class="hlt">materials</span> at large scale. In ideal non-interacting ensembles of non-<span class="hlt">porous</span> multilayer graphene plates, the surface area can be adequately estimated using the simple geometric law ~ 2600 m2g−1/N, where N is the number of graphene sheets per plate. Some processing operations, however, lead to secondary plate-plate stacking, folding, crumpling or pillaring, which give rise to more complex structures. Here we show that bulk samples of multilayer graphene plates stack in an irregular fashion that preserves the 2600/N surface area and creates regular slot-like pores with sizes that are multiples of the unit plate thickness. In contrast, graphene oxide deposits into films with massive area loss (2600 to 40 m2g−1) due to nearly perfect alignment and stacking during the drying process. Pillaring graphene oxide sheets by co-deposition of colloidal-phase particle-based spacers has the potential to partially restore the large monolayer surface. Surface areas as high as 1000 m2g−1 are demonstrated here through colloidal-phase deposition of graphene oxide with water-dispersible aryl-sulfonated ultrafine carbon black as a pillaring agent. PMID:26478597</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27501762','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27501762"><span>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="https://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>2016-08-09</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('https://www.ncbi.nlm.nih.gov/pubmed/21361434','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21361434"><span>Measurement of the resistivity of <span class="hlt">porous</span> <span class="hlt">materials</span> with an alternating air-flow method.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dragonetti, Raffaele; Ianniello, Carmine; Romano, Rosario A</p> <p>2011-02-01</p> <p>Air-flow resistivity is a main parameter governing the acoustic behavior of <span class="hlt">porous</span> <span class="hlt">materials</span> for sound absorption. The international standard ISO 9053 specifies two different methods to measure the air-flow resistivity, namely a steady-state air-flow method and an alternating air-flow method. The latter is realized by the measurement of the sound pressure at 2 Hz in a small rigid volume closed partially by the test sample. This cavity is excited with a known volume-velocity sound source implemented often with a motor-driven piston oscillating with prescribed area and displacement magnitude. Measurements at 2 Hz require special instrumentation and care. The authors suggest an alternating air-flow method based on the ratio of sound pressures measured at frequencies higher than 2 Hz inside two cavities coupled through a conventional loudspeaker. The basic method showed that the imaginary part of the sound pressure ratio is useful for the evaluation of the air-flow resistance. Criteria are discussed about the choice of a frequency range suitable to perform simplified calculations with respect to the basic method. These criteria depend on the sample thickness, its nonacoustic parameters, and the measurement apparatus as well. The proposed measurement method was tested successfully with various types of acoustic <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4977488','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4977488"><span>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4214099','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4214099"><span>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('https://www.osti.gov/scitech/biblio/1130683','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1130683"><span><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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3618403','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3618403"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/12616634','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12616634"><span>Behavior of silica aerogel networks as highly <span class="hlt">porous</span> solid solvent media for lipases in a <span class="hlt">model</span> transesterification reaction.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>El Rassy, H; Perrard, A; Pierre, A C</p> <p>2003-03-03</p> <p>Highly <span class="hlt">porous</span> silica aerogels with differing balances of hydrophobic and hydrophilic functionalities were studied as a new immobilization medium for enzymes. Two types of lipases from Candida rugosa and Burkholderia cepacia were homogeneously dispersed in wet gel precursors before gelation. The <span class="hlt">materials</span> obtained were compared in a simple <span class="hlt">model</span> reaction: transesterification of vinyl laurate by 1-octanol. To allow a better comparison of the hydrophobic/hydrophilic action of the solid, very open aerogel networks with traditional organic hydrophobic/hydrophilic liquid solvents, this reaction was studied in mixtures containing different proportions of 2-methyl-2-butanol, isooctane, and water. The results are discussed in relation to the <span class="hlt">porous</span> and hydrophobic nature of aerogels, characterized by nitrogen adsorption. It was found that silica aerogels can be considered as "solid" solvents for the enzymes, able to provide hydrophobic/hydrophilic characteristics different from those prevailing in the liquid surrounding the aerogels. A simple mechanism of action for these aerogel networks is proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6265264','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6265264"><span>Flow of polymer solutions in <span class="hlt">porous</span> media: inadequacy of the capillary <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Duda, J.L.; Klaus, E.E.; Hong, S.A.</p> <p>1983-08-01</p> <p>Experimental measurements show that conventional capillary <span class="hlt">models</span> are inadequate for the description of the flow of nonlinear purely viscous solutions in <span class="hlt">porous</span> media. A theoretical analysis indicates that any <span class="hlt">model</span> for the flow of purely viscous polymer solutions in <span class="hlt">porous</span> media must meet 2 criteria. First, the <span class="hlt">model</span> must include expansion and contraction regions where excess pressure drops occur. Secondly, the rheologic <span class="hlt">model</span> for the fluid must include the characteristic transition from Newtonian behavior at low shear rates to shear-thinning behavior at high shear rates. 17 references.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22399300','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22399300"><span>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/2015JPS...283..289W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPS...283..289W"><span><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> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApPhA.116.1525L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApPhA.116.1525L"><span>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> </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://www.osti.gov/scitech/servlets/purl/771502','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/771502"><span>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://adsabs.harvard.edu/abs/2013EGUGA..1512719A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1512719A"><span>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://adsabs.harvard.edu/abs/2012PhDT.......151K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......151K"><span>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://adsabs.harvard.edu/abs/2014AGUFMMR23A4320C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMMR23A4320C"><span>3-D Numerical Simulation of Hydrostatic Tests of <span class="hlt">Porous</span> Rocks Using Adapted Constitutive <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>Chemenda, A. I.; Daniel, M.</p> <p>2014-12-01</p> <p>The high complexity and poor knowledge of the constitutive properties of <span class="hlt">porous</span> rocks are principal obstacles for the <span class="hlt">modeling</span> of their deformation. Normally, the constitutive lows are to be derived from the experimental data (nominal strains and stresses). They are known, however, to be sensitive to the mechanical instabilities within the rock specimen and the boundary (notably friction) conditions at its ends. To elucidate the impact of these conditions on the measured mechanical response we use 3-D finite-difference simulations of experimental tests. <span class="hlt">Modeling</span> of hydrostatic tests was chosen because it does not typically involve deformation instabilities. The ends of the cylindrical 'rock sample' are in contact with the 'steel' elastic platens through the frictional interfaces. The whole system is subjected to a normal stress Pc applied to the external <span class="hlt">model</span> surface. A new constitutive <span class="hlt">model</span> of <span class="hlt">porous</span> rocks with the cap-type yield function is used. This function is quadratic in the mean stress σm and depends on the inelastic strain γp in a way to generate strain softening at small σm and strain-hardening at high σm. The corresponding <span class="hlt">material</span> parameters are defined from the experimental data and have clear interpretation in terms of the geometry of the yield surface. The constitutive <span class="hlt">model</span> with this yield function and the Drucker-Prager plastic potential has been implemented in 3-D dynamic explicit code Flac3D. The results of an extensive set of numerical simulations at different <span class="hlt">model</span> parameters will be presented. They show, in particular, that the shape of the 'numerical' hydrostats is very similar to that obtained from the experimental tests and that it is practically insensitive to the interface friction. On the other hand, the stress and strain fields within the specimen dramatically depend on this parameter. The inelastic deformation at the specimen's ends starts well before reaching the grain crushing pressure P* and evolves heterogeneously with Pc</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/51604','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/51604"><span>Properties and characterization of <span class="hlt">porous</span> <span class="hlt">material</span> prepared by hydrothermal treatment of kaolin</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Malla, P.B.; Arrington-Webb, L.A.</p> <p>1994-12-31</p> <p>A kaolin was hydrothermally treated with various amounts of NAOH and KOH at 150 C for 15 min to chemically aggregate the kaolin plates in a structured configuration. X-ray powder diffraction analysis indicated that kaolin was the only crystalline phase present. Chemical analyses showed that about 0.25--1.1% Na{sub 2}O and 1.2--5.0% K{sub 2}O were trapped in the solid phase depending on the reaction conditions. Mercury porosimetry indicated a highly <span class="hlt">porous</span> nature with pore volumes of 0.3--1.4 ml/g and median pore sizes of 0.06--0.3 {mu}m. Scanning electron micrographs showed that the aggregation was achieved by surface modification and random association (edge to edge and face to edge, face to face) of the particles. Measurement of light scattering coefficient of the coating showed an increase of {approximately}350% in scattering compared to that of the precursor kaolin. These <span class="hlt">materials</span> are useful in imparting highly pacifying properties to paper and paint. They are also potentially useful as catalysts, catalyst supports, and in other applications which demand a high light scattering ability and macroporous nature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20905365','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20905365"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/23853114','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23853114"><span>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="https://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>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21074162','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21074162"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhST..159a4065M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhST..159a4065M"><span>Thermo-chemical fuel removal from <span class="hlt">porous</span> <span class="hlt">materials</span> by oxygen and nitrogen dioxide</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Möller, S.; Alegre, D.; Kreter, A.; Petersson, P.; Esser, H. G.; Samm, U.</p> <p>2014-04-01</p> <p>Thermo-chemical removal (TCR), or baking in reactive gases, is a candidate method to control the co-deposit related tritium inventory in fusion devices. TCR can be understood as reaction-diffusion processes in a <span class="hlt">porous</span> <span class="hlt">material</span>. O2-TCR was applied to 150-550 nm thick a-C:D layers with similar textures. A linear relation between the integral TCR rate and the layer thickness, as predicted by the understanding, was observed in the experiment, i.e. the time to remove the hydrogen inventory is independent of its initial amount. TCR with nitrogen dioxide (NO2) at temperatures of 200-350 °C was conducted with a set of a-C:D and W-C-H layers. At 350 °C NO2 removed ˜ 15% porosity a-C:D within 3 min. The O retention in remaining a-C:D was ≈ 1017 O cm-2. An activation energy of ≈ 0.78 eV for reactions of NO2 with D and C was determined. The results were applied for predictions of the TCR effectivity in ITER. The treatment of W-C-H led to O uptake (O/W ≈ 2-3), while W and C contents remained unchanged.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H43F1317E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H43F1317E"><span>A Physically-based <span class="hlt">Model</span> for Surface and Subsurface Drainage from <span class="hlt">Porous</span> Pavement Overlays</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eck, B. J.; Barrett, M.; Charbeneau, R. J.</p> <p>2010-12-01</p> <p>A thin layer of <span class="hlt">porous</span> asphalt is commonly overlain on regular impermeable pavement to reduce splash and spray and improve visibility in wet weather. The <span class="hlt">porous</span> layer often has a large hydraulic conductivity (>1cm/s) to encourage infiltration and drainage and therefore contains runoff when the rainfall intensity is low. However, under high rainfall intensity, the layer’s capacity is exceeded and drainage occurs both within and on top of the <span class="hlt">porous</span> pavement. The problem is analogous to hill-slope hydrology of a thin aquifer where infiltration occurs rapidly and sheet flow is generated only when the aquifer is full. Common roadway features such as slope transitions and curvature make the drainage two-dimensional. A computer <span class="hlt">model</span> was developed to study this coupled, unsteady process. The <span class="hlt">porous</span> layer is <span class="hlt">modeled</span> using the Boussinesq equation. The diffusion wave <span class="hlt">model</span> is used for sheet flow over the pavement surface. This presentation summarizes the model’s development, shows that <span class="hlt">model</span> results compare favorably to field measurements, and gives a case study in which the <span class="hlt">porous</span> layer reduces the maximum sheet flow depth by 25% compared to conventional pavement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21951321','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21951321"><span>A new approach to <span class="hlt">model</span> the spatiotemporal development of biofilm phase in <span class="hlt">porous</span> media.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bozorg, Ali; Sen, Arindom; Gates, Ian D</p> <p>2011-11-01</p> <p>Bacteria can exist within biofilms that are attached to the solid matrix of a <span class="hlt">porous</span> medium. Under certain conditions, the biomass can fully occupy the pore space leading to reduced hydraulic conductivity and mass transport. Here, by treating biofilm as a growing, high-viscosity phase, a novel macroscopic approach to <span class="hlt">model</span> biofilm spatial expansion and its corresponding effects on <span class="hlt">porous</span> medium hydraulic properties is presented. The separate yet coupled flow of the water and biofilm phases is handled by using relative permeability curves that allow for biofilm movement within the <span class="hlt">porous</span> medium and bioclogging effects. Fluid flow is governed by Darcy's law and component transport is set by the convection-diffusion equation reaction terms for each component. Here, the system of governing equations is solved by using a commercial multiphase flow reservoir simulator, which is used to validate the <span class="hlt">model</span> against published laboratory experiments. A comparison of the <span class="hlt">model</span> and experimental observations reveal that the <span class="hlt">model</span> provides a reasonable means to predict biomass development in the <span class="hlt">porous</span> medium. The results reveal that coupled flow of water and movement of biofilm, as described by relative permeability curves, is complex and has a large impact on the development of biomass and consequent bioclogging in the <span class="hlt">porous</span> medium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDG15003B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDG15003B"><span><span class="hlt">Modelling</span> Cerebral Blood Flow and Temperature Using a Vascular <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>Blowers, Stephen; Thrippleton, Michael; Marshall, Ian; Harris, Bridget; Andrews, Peter; Valluri, Prashant</p> <p>2016-11-01</p> <p>Macro-<span class="hlt">modelling</span> of cerebral blood flow can assist in determining the impact of temperature intervention to reduce permanent tissue damage during instances of brain trauma. Here we present a 3D two phase fluid-<span class="hlt">porous</span> <span class="hlt">model</span> for simulating blood flow through the capillary region linked to intersecting 1D arterial and venous vessel trees. This combined vasculature <span class="hlt">porous</span> (VaPor) <span class="hlt">model</span> simulates both flow and energy balances, including heat from metabolism, using a vasculature extracted from MRI data which are expanded upon using a tree generation algorithm. Validation of temperature balance has been achieved using rodent brain data. Direct flow validation is not as straight forward due to the method used in determining regional cerebral blood flow (rCBF). In-vivo measurements are achieved using a tracer, which disagree with direct measurements of simulated flow. However, by <span class="hlt">modelling</span> a virtual tracer, rCBF values are obtained that agree with those found in literature. Temperature profiles generated with the VaPor <span class="hlt">model</span> show a reduction in core brain temperature after cooling the scalp not seen previously in other <span class="hlt">models</span>.</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>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('https://www.ncbi.nlm.nih.gov/pubmed/18683958','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18683958"><span>Use of fluorescence spectroscopy to study polymeric <span class="hlt">materials</span> with <span class="hlt">porous</span> structure based on imprinting by self-assembled fibrillar networks.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Burguete, M Isabel; Galindo, Francisco; Gavara, Raquel; Izquierdo, M Angeles; Lima, João C; Luis, Santiago V; Parola, A Jorge; Pina, Fernando</p> <p>2008-09-02</p> <p>Different polymeric <span class="hlt">materials</span> have been prepared from the organogels formed by a polymerizable methacrylic mixture (methyl methacrylate/ethylene glycol dimethacrylate, 1:1, w/w) and the macrocyclic pseudopeptide 1. The use of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide as a very efficient radical initiator allows polymeric <span class="hlt">materials</span> in which the structure of the fibrils formed by self-assembly of the organogelator 1 is truly preserved to be obtained. Removal of the pseudopeptidic molecule provides <span class="hlt">materials</span> with a <span class="hlt">porous</span> structure reflecting that of the original self-assembled fibrils. The use of fluorescent probes such as rhodamine B and pyrene greatly facilitate the study of the <span class="hlt">porous</span> structures formed and, accordingly, that of the morphology of the original fibrils. Those studies reveal the presence of a permanent porosity and the organization of the substructures as a <span class="hlt">porous</span> network. This confirms the existence of a nucleation and growth mechanism for the generation of the fibrils, giving rise to the formation of spherulitic structures. Those spherulites are additionally linked by connections of variable size. A series of diffusion experiments allowed establishment of a direct dependence of the inner porosity of the <span class="hlt">materials</span> on the amount of self-organizing template used for their preparation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9434E..0OC','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9434E..0OC"><span>AC magnetic field-assisted method to develop <span class="hlt">porous</span> carbon nanotube/conducting polymer composites for application in thermoelectric <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>Chuang, Chun-Yu; Yang, Shu-Chian; Chang, Su-Hua; Yang, Ta-I.</p> <p>2015-04-01</p> <p>Thermoelectric <span class="hlt">materials</span> are very effective in converting waste heat sources into useful electricity. Researchers are continuing to develop new polymeric thermoelectric <span class="hlt">materials</span>. The segregated-network carbon nanotube (CNT)- polymer composites are most promising. Thus, the goal of this study is to develop novel <span class="hlt">porous</span> CNT -polymer composites with improved thermoelectric properties. The research efforts focused on modifying the surface of the CNT with magnetic nanoparticles so that heat was released when subjecting to an AC magnetic field. Subsequently, polymers covered on the surface of the CNT were crosslinked. The <span class="hlt">porous</span> CNT -polymer composites can be obtained by removing the un-crosslinked polymers. Polydimethylsiloxane polymer was utilized to investigate the effect of porosity and electrical conductivity on the thermoelectric properties of the composites. This AC magnetic field-assisted method to develop <span class="hlt">porous</span> carbon nanotube/polymer composites for application in thermoelectric <span class="hlt">materials</span> is introduced for the first time. The advantage of this method is that the electrical conductivity of the composites was high since we can easily to manipulate the CNT to form a conducting path. Another advantage is that the high porosity significantly reduced the thermal conductivity of the composites. These two advantages enable us to realize the polymer composites for thermoelectric applications. We are confident that this research will open a new avenue for developing polymer thermoelectric <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JAP...102g3533M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JAP...102g3533M"><span>Geometrical <span class="hlt">modeling</span> of fibrous <span class="hlt">materials</span> under compression</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maze, Benoit; Vahedi Tafreshi, Hooman; Pourdeyhimi, Behnam</p> <p>2007-10-01</p> <p>Many fibrous <span class="hlt">materials</span> such as nonwovens are consolidated via compaction rolls in a so-called calendering process. Hot rolls compress the fiber assembly and cause fiber-to-fiber bonding resulting in a strong yet <span class="hlt">porous</span> structure. In this paper, we describe an algorithm for generating three dimensional virtual fiberwebs and simulating the geometrical changes that happen to the structure during the calendering process. Fibers are assumed to be continuous filaments with square cross sections lying randomly in the x or y direction. The fibers are assumed to be flexible to allow bending over one another during the compression process. Lateral displacement is not allowed during the compaction process. The algorithm also does not allow the fibers to interpenetrate or elongate and so the mass of the fibers is conserved. Bending of the fibers is <span class="hlt">modeled</span> either by considering a constant "slope of bending" or constant "span of bending." The influence of the bending parameters on the propagation of compression through the <span class="hlt">material</span>'s thickness is discussed. In agreement with our experimental observations, it was found that the average solid volume fraction profile across the thickness becomes U shaped after the calendering. The application of these virtual structures in studying transport phenomena in fibrous <span class="hlt">materials</span> is also demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28235741','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28235741"><span>Different effects of surface heterogeneous atoms of <span class="hlt">porous</span> and non-<span class="hlt">porous</span> carbonaceous <span class="hlt">materials</span> on adsorption of 1,1,2,2-tetrachloroethane in aqueous environment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Weifeng; Ni, Jinzhi</p> <p>2017-05-01</p> <p>The surface heterogeneous atoms of carbonaceous <span class="hlt">materials</span> (CMs) play an important role in adsorption of organic pollutants. However, little is known about the surface heterogeneous atoms of CMs might generate different effect on adsorption of hydrophobic organic compounds by <span class="hlt">porous</span> carbonaceous <span class="hlt">materials</span> - activated carbons (ACs) and non-<span class="hlt">porous</span> carbonaceous <span class="hlt">materials</span> (NPCMs). In this study, we observed that the surface oxygen and nitrogen atoms could decrease the adsorption affinity of both ACs and NPCMs for 1,1,2,2-tetrachloroethane (TeCA), but the degree of decreasing effects were very different. The increasing content of surface oxygen and nitrogen ([O + N]) caused a sharper decrease in adsorption affinity of ACs (slope of lg (kd/SA) vs [O + N]: -0.098∼-0.16) than that of NPCMs (slope of lg (kd/SA) vs [O + N]: -0.025∼-0.059) for TeCA. It was due to the water cluster formed by the surface hydrophilic atoms that could block the micropores and generate massive invalid adsorption sites in the micropores of ACs, while the water cluster only occupied the surface adsorption sites of NPCMs. Furthermore, with the increasing concentration of dissolved TeCA, the effect of surface area on adsorption affinity of NPCMs for TeCA kept constant while the effect of [O + N] decreased due to the competitive adsorption between water molecule and TeCA on the surface of NPCMs, meanwhile, both the effects of micropore volume and [O + N] on adsorption affinity of ACs for TeCA were decreased due to the mechanism of micropore volume filling. These findings are valuable for providing a deep insight into the adsorption mechanisms of CMs for TeCA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhFl...28g2003Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhFl...28g2003Z"><span>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/abs/2016JPhCS.735a2010A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.735a2010A"><span><span class="hlt">Modelling</span> the growth of <span class="hlt">porous</span> alumina matrix for creating hyperbolic media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aryslanova, E. M.; Alfimov, A. V.; Chivilikhin, S. A.</p> <p>2016-08-01</p> <p><span class="hlt">Porous</span> aluminum oxide is a regular self-assembled structure. During anodization it is possible to control nano-parameters of the structure using macroscopic parameters of anodization. <span class="hlt">Porous</span> alumina films can be used as a template for the creation of hyperbolic media. In this work we consider the anodization process, our <span class="hlt">model</span> takes into account the influence of layers of aluminum and electrolyte on the rate of growth of aluminum oxide, as well as the effect of surface diffusion. As a result of our <span class="hlt">model</span> we obtain the minimum distance between centers of alumina pores in the beginning of anodizing process. We also present the results obtained by numerical <span class="hlt">modelling</span> of hyperbolic media based on <span class="hlt">porous</span> alumina film.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1207..957W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1207..957W"><span>Numerical simulation on forced convection heat transfer in <span class="hlt">porous</span> media using Gibson-Ashby constitutive <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>Wang, J. X.; Jia, P. Y.; Wang, Y. S.; Jiang, L.</p> <p>2010-03-01</p> <p>In this article, using Gibson-Ashby constitutive <span class="hlt">model</span>, we suggest a new method for numerical investigation of forced convection heat transfer in <span class="hlt">porous</span> foam metal, and try to consolidate the study for mechanical property and that for thermal characteristic. By available experimental data, we simulated to two cases, namely as the transfer in <span class="hlt">porous</span> media for diameter is 0.6 mm and porosity is 0.402, and for diameter is 1.6 mm and porosity is 0.462. The result, from our constitutive <span class="hlt">model</span> for single forced convection heat transfer, corresponds well with the experimental data. As for pressure drop prediction in <span class="hlt">porous</span> is in good agreement with experiment, and the error is only 5% to 10%, but for transfer is less accurate, the error is about 20%, which is acceptable in practice. So it is done that constitutive <span class="hlt">model</span> is used to simulate the transfer property.</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>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/2014AIPC.1591..246N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1591..246N"><span>Novel synthesis of highly <span class="hlt">porous</span> spinel cobaltite (NiCo2O4) electrode <span class="hlt">material</span> for supercapacitor applications</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>2014-04-01</p> <p>High performing <span class="hlt">porous</span> nickel cobaltite (NiCo2O4) nanomaterial is prepared using novel cost effective auto combustion technique. Physical characterization reveals the formation of nickel rich spinel cobaltitie with average crystallite size of 17 nm. Electrochemical evaluation of the sample is carried using cyclic voltammetry (CV), chronopotentiometry (CP) and AC impedance techniques. The Pseudocapacitive nature of the <span class="hlt">material</span> is observed from CV and CP studies exhibiting a high specific capacitance of 772 Fg-1 at a current density of 1 Ag-1. The low resistive behavior of the <span class="hlt">material</span> is seen from the impedance spectra, projecting nickel cobaltite as promising <span class="hlt">material</span> for supercapcitor applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23446349','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23446349"><span><span class="hlt">Porous</span> <span class="hlt">materials</span> with optimal adsorption thermodynamics and kinetics for CO2 separation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nugent, Patrick; Belmabkhout, Youssef; Burd, Stephen D; Cairns, Amy J; Luebke, Ryan; Forrest, Katherine; Pham, Tony; Ma, Shengqian; Space, Brian; Wojtas, Lukasz; Eddaoudi, Mohamed; Zaworotko, Michael J</p> <p>2013-03-07</p> <p>The energy costs associated with the separation and purification of industrial commodities, such as gases, fine chemicals and fresh water, currently represent around 15 per cent of global energy production, and the demand for such commodities is projected to triple by 2050 (ref. 1). The challenge of developing effective separation and purification technologies that have much smaller energy footprints is greater for carbon dioxide (CO2) than for other gases; in addition to its involvement in climate change, CO2 is an impurity in natural gas, biogas (natural gas produced from biomass), syngas (CO/H2, the main source of hydrogen in refineries) and many other gas streams. In the context of <span class="hlt">porous</span> crystalline <span class="hlt">materials</span> that can exploit both equilibrium and kinetic selectivity, size selectivity and targeted molecular recognition are attractive characteristics for CO2 separation and capture, as exemplified by zeolites 5A and 13X (ref. 2), as well as metal-organic <span class="hlt">materials</span> (MOMs). Here we report that a crystal engineering or reticular chemistry strategy that controls pore functionality and size in a series of MOMs with coordinately saturated metal centres and periodically arrayed hexafluorosilicate (SiF(2-)(6)) anions enables a 'sweet spot' of kinetics and thermodynamics that offers high volumetric uptake at low CO2 partial pressure (less than 0.15 bar). Most importantly, such MOMs offer an unprecedented CO2 sorption selectivity over N2, H2 and CH4, even in the presence of moisture. These MOMs are therefore relevant to CO2 separation in the context of post-combustion (flue gas, CO2/N2), pre-combustion (shifted synthesis gas stream, CO2/H2) and natural gas upgrading (natural gas clean-up, CO2/CH4).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870001779','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870001779"><span>Constitutive <span class="hlt">modeling</span> for isotropic <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>Ramaswamy, V. G.; Vanstone, R. H.; Dame, L. T.; Laflen, J. H.</p> <p>1984-01-01</p> <p>The unified constitutive theories for application to typical isotropic cast nickel base supperalloys used for air-cooled turbine blades were evaluated. The specific <span class="hlt">modeling</span> aspects evaluated were: uniaxial, monotonic, cyclic, creep, relaxation, multiaxial, notch, and thermomechanical behavior. Further development of the constitutive theories to <span class="hlt">model</span> thermal history effects, refinement of the <span class="hlt">material</span> test procedures, evaluation of coating effects, and verification of the <span class="hlt">models</span> in an alternate <span class="hlt">material</span> will be accomplished in a follow-on for this base program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23858922','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23858922"><span><span class="hlt">Porous</span> LiFePO4/C microspheres as high-power cathode <span class="hlt">materials</span> for lithium ion batteries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Bing; Wang, Ying; Wang, Bei; Kim, Hyun-Soo; Kim, Woo-Seong; Wang, Guoxiu</p> <p>2013-05-01</p> <p><span class="hlt">Porous</span> LiFePO4/C microspheres were synthesized by a novel hydrothermal reaction combined with high-temperature calcinations. The morphology of the prepared <span class="hlt">material</span> was investigated by field-emission scanning electron microscopy. <span class="hlt">Porous</span> microspheres with diameters around 1-3 microm were obtained, which consisting of primary LiFePO4 nanoparticles. The electrochemical performances of the as-prepared LiFePO4 microspheres were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge cycling. The carbon coated LiFePO4 microspheres showed lower polarization, higher rate capability, and better cycling stability than that of pristine LiFePO4 microspheres, indicating the potential application as the cathode <span class="hlt">material</span> for high-power lithium ion batteries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=267574','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=267574"><span><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('https://www.ncbi.nlm.nih.gov/pubmed/10991521','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10991521"><span>Pipe network <span class="hlt">model</span> for scaling of dynamic interfaces in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lam; Horvath</p> <p>2000-08-07</p> <p>We present a numerical study on the dynamics of imbibition fronts in <span class="hlt">porous</span> media using a pipe network <span class="hlt">model</span>. This <span class="hlt">model</span> quantitatively reproduces the anomalous scaling behavior found in imbibition experiments [Phys. Rev. E 52, 5166 (1995)]. Using simple scaling arguments, we derive a new identity among the scaling exponents in agreement with the experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24635718','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24635718"><span>Selective ultrathin carbon sheath on <span class="hlt">porous</span> silicon nanowires: <span class="hlt">materials</span> for extremely high energy density planar micro-supercapacitors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alper, John P; Wang, Shuang; Rossi, Francesca; Salviati, Giancarlo; Yiu, Nicholas; Carraro, Carlo; Maboudian, Roya</p> <p>2014-01-01</p> <p>Microsupercapacitors are attractive energy storage devices for integration with autonomous microsensor networks due to their high-power capabilities and robust cycle lifetimes. Here, we demonstrate <span class="hlt">porous</span> silicon nanowires synthesized via a lithography compatible low-temperature wet etch and encapsulated in an ultrathin graphitic carbon sheath, as electrochemical double layer capacitor electrodes. Specific capacitance values reaching 325 mF cm(-2) are achieved, representing the highest specific ECDL capacitance for planar microsupercapacitor electrode <span class="hlt">materials</span> to date.</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>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('https://ntrs.nasa.gov/search.jsp?R=19870040441&hterms=material+flow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmaterial%2Bflow','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870040441&hterms=material+flow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmaterial%2Bflow"><span>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://www.dtic.mil/docs/citations/ADA202494','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA202494"><span>Aerospace <span class="hlt">Materials</span> Process <span class="hlt">Modelling</span></span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1988-08-01</p> <p>des phdnombnes physico - chimiques , slors sal connus, notamment des rdactions do phase as produisant dana l intorvalle do solidification, par des...connaissance do donndos theraiques, sinai qua du comportement e~canique, physico - chimique at mdtaliurgique des pibees & order maim aussi des moules. des...W.T.Sbs 16 A NUMERICAL <span class="hlt">MODEL</span> OF DIRECTIONAL SOLIDIFICATION OF CAST TURBINE BLADES by G,.Lammndu and L -Veruiot des Roches 17 Paper IS withdrawn Pape 19</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24802130','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24802130"><span>Nitrogen-doped <span class="hlt">porous</span> carbon/Co3O4 nanocomposites as anode <span class="hlt">materials</span> for lithium-ion batteries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Li; Zheng, Yaolin; Wang, Xiaohong; Chen, Shouhui; Xu, Fugang; Zuo, Li; Wu, Jiafeng; Sun, Lanlan; Li, Zhuang; Hou, Haoqing; Song, Yonghai</p> <p>2014-05-28</p> <p>A simple and industrially scalable approach to prepare <span class="hlt">porous</span> carbon (PC) with high surface areas as well as abundant nitrogen element as anode supporting <span class="hlt">materials</span> for lithium-ion batteries (LIBs) was developed. Herein, the N-doped PC was prepared by carbonizing crawfish shell, which is a kind of food waste with abundant marine chitin as well as a naturally <span class="hlt">porous</span> structure. The <span class="hlt">porous</span> structure can be kept to form the N-doped PC in the pyrolysis process. The N-doped PC-Co3O4 nanocomposites were synthesized by loading Co3O4 on the N-doped PC as anode <span class="hlt">materials</span> for LIBs. The resulting N-doped PC-Co3O4 nanocomposites release an initial discharge of 1223 mA h g(-1) at a current density of 100 mA g(-1) and still maintain a high reversible capacity of 1060 mA h g(-1) after 100 cycles, which is higher than that of individual N-doped PC or Co3O4. Particularly, the N-doped PC-Co3O4 nanocomposites can be prepared in a large yield with a low cost because the N-doped PC is derived from abundant natural waste resources, which makes it a promising anode <span class="hlt">material</span> for LIBs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AdWR...56...61Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AdWR...56...61Z"><span>An improved gray lattice Boltzmann <span class="hlt">model</span> for simulating fluid flow in multi-scale <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>Zhu, Jiujiang; Ma, Jingsheng</p> <p>2013-06-01</p> <p>A lattice Boltzmann (LB) <span class="hlt">model</span> is proposed for simulating fluid flow in <span class="hlt">porous</span> media by allowing the aggregates of finer-scale pores and solids to be treated as 'equivalent media'. This <span class="hlt">model</span> employs a partially bouncing-back scheme to mimic the resistance of each aggregate, represented as a gray node in the <span class="hlt">model</span>, to the fluid flow. Like several other lattice Boltzmann <span class="hlt">models</span> that take the same approach, which are collectively referred to as gray lattice Boltzmann (GLB) <span class="hlt">models</span> in this paper, it introduces an extra <span class="hlt">model</span> parameter, ns, which represents a volume fraction of fluid particles to be bounced back by the solid phase rather than the volume fraction of the solid phase at each gray node. The proposed <span class="hlt">model</span> is shown to conserve the mass even for heterogeneous media, while this <span class="hlt">model</span> and that <span class="hlt">model</span> of Walsh et al. (2009) [1], referred to the WBS <span class="hlt">model</span> thereafter, are shown analytically to recover Darcy-Brinkman's equations for homogenous and isotropic <span class="hlt">porous</span> media where the effective viscosity and the permeability are related to ns and the relaxation parameter of LB <span class="hlt">model</span>. The key differences between these two <span class="hlt">models</span> along with others are analyzed while their implications are highlighted. An attempt is made to rectify the misconception about the <span class="hlt">model</span> parameter ns being the volume fraction of the solid phase. Both <span class="hlt">models</span> are then numerically verified against the analytical solutions for a set of homogenous <span class="hlt">porous</span> <span class="hlt">models</span> and compared each other for another two sets of heterogeneous <span class="hlt">porous</span> <span class="hlt">models</span> of practical importance. It is shown that the proposed <span class="hlt">model</span> allows true no-slip boundary conditions to be incorporated with a significant effect on reducing errors that would otherwise heavily skew flow fields near solid walls. The proposed <span class="hlt">model</span> is shown to be numerically more stable than the WBS <span class="hlt">model</span> at solid walls and interfaces between two <span class="hlt">porous</span> media. The causes to the instability in the latter case are examined. The link between these two GLB <span class="hlt">models</span> and a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25248700','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25248700"><span>Promotion of maltose fermentation at extremely low temperatures using a cryotolerant Saccharomyces cerevisiae strain immobilized on <span class="hlt">porous</span> cellulosic <span class="hlt">material</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ganatsios, Vassilios; Koutinas, Athanasios A; Bekatorou, Argyro; Kanellaki, Maria; Nigam, Poonam</p> <p>2014-11-01</p> <p>Advantages in maltose fermentation at extremely low temperatures (5-10°C) using an alcohol resistant and cryotolerant yeast strain (Saccharomyces cerevisiae AXAZ-1) immobilized on <span class="hlt">porous</span> cellulosic <span class="hlt">material</span> (or tubular cellulose, TC), produced by delignification of wood sawdust, are reported. Pure maltose and glucose media (80, 100 and 140 g/l) were examined as <span class="hlt">model</span> substrates to evaluate the potential effect of TC on the rate of fermentation of maltose containing substrates. The use of TC sharply accelerated the rate of maltose fermentation compared to free cells (FC) in suspension. Fermentation at 5°C by immobilized cells was complete, while FC were unable to ferment maltose at this temperature, in contrast to glucose, which was completely fermented. From the results of maltose and glucose fermentations at 5 and 10°C, it was concluded that the effect of TC was higher at lower fermentation temperature and that its promotional effect on fermentation rate had to be at the step of maltose uptake. Specifically, it is suggested that the presence of TC increased maltose uptake rate by the immobilized cells due to attraction by hydrogen bonding on the TC surface and continuous pumping of maltose towards the cells. Calculation of the activation energy of maltose fermentations at 5, 10 and 15°C showed that it was reduced by an average 42% when cells immobilized on TC were used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1121534','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1121534"><span><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://adsabs.harvard.edu/abs/2011JMiMi..21i5029G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JMiMi..21i5029G"><span><span class="hlt">Porous</span> ceramics for multistage Knudsen micropumps—<span class="hlt">modeling</span> approach and experimental evaluation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gupta, Naveen K.; Gianchandani, Yogesh B.</p> <p>2011-09-01</p> <p>This paper describes the evaluation of four types of <span class="hlt">porous</span> ceramics for use as thermal transpiration <span class="hlt">materials</span> in Knudsen pumps that operate at atmospheric pressure. Knudsen pumps are motionless gas pumps that utilize thermal transpiration along a channel or a set of channels; the channels must have a temperature gradient and must constrain the flow to remain within the free molecular or transitional flow regimes. Of the ceramics evaluated, a clay-based, 15 bar synthetic ceramic (15PC) presents the most favorable properties for Knudsen pumps. For an input power of 3.4 W, a 25 × 25 mm2 nine-stage Knudsen pump that uses this <span class="hlt">material</span> provides a maximum pressure head of 12 kPa and a maximum gas flow rate of ≈3.7 µL min-1. Reliability tests demonstrate more than 11 750 h of continuous operation without any deterioration in their gas pumping capabilities. A fitted <span class="hlt">model</span> suggests that the temporal evolution of pressure at the sealed outlet of a Knudsen pump can be captured adequately using four parameters. These parameters correspond to various nonidealities that play dominant roles in the transient response of these pumps.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4348457','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4348457"><span>A review on solar cells from Si-single crystals to <span class="hlt">porous</span> <span class="hlt">materials</span> and quantum dots</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Badawy, Waheed A.</p> <p>2013-01-01</p> <p>Solar energy conversion to electricity through photovoltaics or to useful fuel through photoelectrochemical cells was still a main task for research groups and developments sectors. In this article we are reviewing the development of the different generations of solar cells. The fabrication of solar cells has passed through a large number of improvement steps considering the technological and economic aspects. The first generation solar cells were based on Si wafers, mainly single crystals. Permanent researches on cost reduction and improved solar cell efficiency have led to the marketing of solar modules having 12–16% solar conversion efficiency. Application of polycrystalline Si and other forms of Si have reduced the cost but on the expense of the solar conversion efficiency. The second generation solar cells were based on thin film technology. Thin films of amorphous Si, CIS (copper–indium–selenide) and t-Si were employed. Solar conversion efficiencies of about 12% have been achieved with a remarkable cost reduction. The third generation solar cells are based on nano-crystals and nano-<span class="hlt">porous</span> <span class="hlt">materials</span>. An advanced photovoltaic cell, originally developed for satellites with solar conversion efficiency of 37.3%, based on concentration of the solar spectrum up to 400 suns was developed. It is based on extremely thin concentration cells. New sensitizer or semiconductor systems are necessary to broaden the photo-response in solar spectrum. Hybrids of solar and conventional devices may provide an interim benefit in seeking economically valuable devices. New quantum dot solar cells based on CdSe–TiO2 architecture have been developed. PMID:25750746</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25750746','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25750746"><span>A review on solar cells from Si-single crystals to <span class="hlt">porous</span> <span class="hlt">materials</span> and quantum dots.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Badawy, Waheed A</p> <p>2015-03-01</p> <p>Solar energy conversion to electricity through photovoltaics or to useful fuel through photoelectrochemical cells was still a main task for research groups and developments sectors. In this article we are reviewing the development of the different generations of solar cells. The fabrication of solar cells has passed through a large number of improvement steps considering the technological and economic aspects. The first generation solar cells were based on Si wafers, mainly single crystals. Permanent researches on cost reduction and improved solar cell efficiency have led to the marketing of solar modules having 12-16% solar conversion efficiency. Application of polycrystalline Si and other forms of Si have reduced the cost but on the expense of the solar conversion efficiency. The second generation solar cells were based on thin film technology. Thin films of amorphous Si, CIS (copper-indium-selenide) and t-Si were employed. Solar conversion efficiencies of about 12% have been achieved with a remarkable cost reduction. The third generation solar cells are based on nano-crystals and nano-<span class="hlt">porous</span> <span class="hlt">materials</span>. An advanced photovoltaic cell, originally developed for satellites with solar conversion efficiency of 37.3%, based on concentration of the solar spectrum up to 400 suns was developed. It is based on extremely thin concentration cells. New sensitizer or semiconductor systems are necessary to broaden the photo-response in solar spectrum. Hybrids of solar and conventional devices may provide an interim benefit in seeking economically valuable devices. New quantum dot solar cells based on CdSe-TiO2 architecture have been developed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813599M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813599M"><span>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> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017RSPTA.37560025M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RSPTA.37560025M"><span>Flue-gas and direct-air capture of CO2 by <span class="hlt">porous</span> metal-organic <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>Madden, David G.; Scott, Hayley S.; Kumar, Amrit; Chen, Kai-Jie; Sanii, Rana; Bajpai, Alankriti; Lusi, Matteo; Curtin, Teresa; Perry, John J.; Zaworotko, Michael J.</p> <p>2017-01-01</p> <p>Sequestration of CO2, either from gas mixtures or directly from air (direct air capture), is a technological goal important to large-scale industrial processes such as gas purification and the mitigation of carbon emissions. Previously, we investigated five <span class="hlt">porous</span> <span class="hlt">materials</span>, three <span class="hlt">porous</span> metal-organic <span class="hlt">materials</span> (MOMs), a benchmark inorganic <span class="hlt">material</span>, Zeolite 13X and a chemisorbent, TEPA-SBA-15, for their ability to adsorb CO2 directly from air and from simulated flue-gas. In this contribution, a further 10 physisorbent <span class="hlt">materials</span> that exhibit strong interactions with CO2 have been evaluated by temperature-programmed desorption for their potential utility in carbon capture applications: four hybrid ultramicroporous <span class="hlt">materials</span>, SIFSIX-3-Cu, DICRO-3-Ni-i, SIFSIX-2-Cu-i and MOOFOUR-1-Ni; five microporous MOMs, DMOF-1, ZIF-8, MIL-101, UiO-66 and UiO-66-NH2; an ultramicroporous MOM, Ni-4-PyC. The performance of these MOMs was found to be negatively impacted by moisture. Overall, we demonstrate that the incorporation of strong electrostatics from inorganic moieties combined with ultramicropores offers improved CO2 capture performance from even moist gas mixtures but not enough to compete with chemisorbents. This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: <span class="hlt">materials</span> by design'.</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('https://www.ncbi.nlm.nih.gov/pubmed/27895255','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27895255"><span>Flue-gas and direct-air capture of CO2 by <span class="hlt">porous</span> metal-organic <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Madden, David G; Scott, Hayley S; Kumar, Amrit; Chen, Kai-Jie; Sanii, Rana; Bajpai, Alankriti; Lusi, Matteo; Curtin, Teresa; Perry, John J; Zaworotko, Michael J</p> <p>2017-01-13</p> <p>Sequestration of CO2, either from gas mixtures or directly from air (direct air capture), is a technological goal important to large-scale industrial processes such as gas purification and the mitigation of carbon emissions. Previously, we investigated five <span class="hlt">porous</span> <span class="hlt">materials</span>, three <span class="hlt">porous</span> metal-organic <span class="hlt">materials</span> (MOMs), a benchmark inorganic <span class="hlt">material</span>, ZEOLITE 13X: and a chemisorbent, TEPA-SBA-15: , for their ability to adsorb CO2 directly from air and from simulated flue-gas. In this contribution, a further 10 physisorbent <span class="hlt">materials</span> that exhibit strong interactions with CO2 have been evaluated by temperature-programmed desorption for their potential utility in carbon capture applications: four hybrid ultramicroporous <span class="hlt">materials</span>, SIFSIX-3-CU: , DICRO-3-NI-I: , SIFSIX-2-CU-I: and MOOFOUR-1-NI: ; five microporous MOMs, DMOF-1: , ZIF-8: , MIL-101: , UIO-66: and UIO-66-NH2: ; an ultramicroporous MOM, NI-4-PYC: The performance of these MOMs was found to be negatively impacted by moisture. Overall, we demonstrate that the incorporation of strong electrostatics from inorganic moieties combined with ultramicropores offers improved CO2 capture performance from even moist gas mixtures but not enough to compete with chemisorbents.This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: <span class="hlt">materials</span> by design'.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H43M1147D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H43M1147D"><span>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://adsabs.harvard.edu/abs/2011PhRvE..84d6305R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhRvE..84d6305R"><span>Experiments and network <span class="hlt">model</span> of flow of oil-water emulsion 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>Romero, Mao Illich; Carvalho, Marcio S.; Alvarado, Vladimir</p> <p>2011-10-01</p> <p>Transport of emulsions in <span class="hlt">porous</span> media is relevant to several subsurface applications. Many enhanced oil recovery (EOR) processes lead to emulsion formation and as a result conformance originating in the flow of a dispersed phase may arise. In some EOR processes, emulsion is injected directly as a mobility control agent. <span class="hlt">Modeling</span> the flow of emulsion in <span class="hlt">porous</span> media is extremely challenging due to the complex nature of the associated flows and numerous interfaces. The descriptions based on effective viscosity are not valid when the drop size is of the same order of magnitude as the pore-throat characteristic length scale. An accurate <span class="hlt">model</span> of emulsion flow through <span class="hlt">porous</span> media should describe this local change in mobility. The available filtration <span class="hlt">models</span> do not take into account the variation of the straining and capturing rates with the local capillary number. In this work, we present experiments of emulsion flow through sandstone cores of different permeability and a first step on a capillary network <span class="hlt">model</span> that uses experimentally determined pore-level constitutive relationships between flow rate and pressure drop in constricted capillaries to obtain representative macroscopic flow behavior emerging from microscopic emulsion flow at the pore level. A parametric analysis is conducted to study the effect of the permeability and dispersed phase droplet size on the flow response to emulsion flooding in <span class="hlt">porous</span> media. The network <span class="hlt">model</span> predictions qualitatively describe the oil-water emulsion flow behavior observed in the experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ThCFD..29....1S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ThCFD..29....1S"><span>A lattice Boltzmann-Saltation <span class="hlt">model</span> and its simulation of aeolian saltation at <span class="hlt">porous</span> fences</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shi, Xiao Fei; Xi, Ping; Wu, Jian Jun</p> <p>2015-04-01</p> <p>This paper introduces a 2D lattice Boltzmann-Saltation (LBM-Saltation) <span class="hlt">model</span> for numerical simulation of velocity profiles of windblown sand particles. The <span class="hlt">model</span> is based on the LBM equations for transient, incompressible viscous flow. We first introduced a lattice Boltzmann subgrid <span class="hlt">model</span>, which was used to predict the turbulent wind field. Two-way coupling was then used to describe the interaction between wind and the saltating sand particles. The correctness of the <span class="hlt">model</span> was verified by comparing the simulated results of several important variables of wind-sand flow with that of experiment over a flat bed surface. To show the feasibility of this <span class="hlt">model</span> with complex boundary conditions, we used it to simulate the wind-sand flow at <span class="hlt">porous</span> wind fences and mainly discussed the particle velocity profiles. Single <span class="hlt">porous</span> wind fence case was computed first and compared with the measurement. Two tandem <span class="hlt">porous</span> wind fences cases were simulated next. Different distance and porosity of the fences were considered to quantitatively investigate the variation of the shelter effect. The simulated results achieved additional conclusions: The wind speed and the velocity of sand particles are obviously weakened because of the fence; reduction of the particle velocity by <span class="hlt">porous</span> fence varies with the fence distance and porosity; the larger the distance or the porosity (significantly larger than the 0.3), the worse the shelter effect, and the weaker the reduction of particle velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10147898','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10147898"><span>Micromechanical <span class="hlt">modeling</span> of advanced <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Silling, S.A.; Taylor, P.A.; Wise, J.L.; Furnish, M.D.</p> <p>1994-04-01</p> <p>Funded as a laboratory-directed research and development (LDRD) project, the work reported here focuses on the development of a computational methodology to determine the dynamic response of heterogeneous solids on the basis of their composition and microstructural morphology. Using the solid dynamics wavecode CTH, <span class="hlt">material</span> response is simulated on a scale sufficiently fine to explicitly represent the <span class="hlt">material`s</span> microstructure. Conducting {open_quotes}numerical experiments{close_quotes} on this scale, the authors explore the influence that the microstructure exerts on the <span class="hlt">material`s</span> overall response. These results are used in the development of constitutive <span class="hlt">models</span> that take into account the effects of microstructure without explicit representation of its features. Applying this methodology to a glass-reinforced plastic (GRP) composite, the authors examined the influence of various aspects of the composite`s microstructure on its response in a loading regime typical of impact and penetration. As a prerequisite to the microscale <span class="hlt">modeling</span> effort, they conducted extensive <span class="hlt">materials</span> testing on the constituents, S-2 glass and epoxy resin (UF-3283), obtaining the first Hugoniot and spall data for these <span class="hlt">materials</span>. The results of this work are used in the development of constitutive <span class="hlt">models</span> for GRP <span class="hlt">materials</span> in transient-dynamics computer wavecodes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RScI...87i4903B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RScI...87i4903B"><span>A simple AC calorimeter for specific heat measurement of liquids confined in <span class="hlt">porous</span> <span class="hlt">materials</span>: A study of hydrated Vycor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonetti, Marco; Zanotti, Jean-Marc</p> <p>2016-09-01</p> <p>Nanometric confinement of fluids in <span class="hlt">porous</span> media is a classical way to stabilize metastable states. Calorimetric studies give insight on the behavior of confined liquids compared to bulk liquids. We have developed and built a simple quasi-adiabatic AC calorimeter for heat capacity measurement of confined liquids in <span class="hlt">porous</span> media in a temperature range between 150 K and 360 K. Taking the fully hydrated <span class="hlt">porous</span> medium as a reference, we address the thermal behavior of water as a monolayer on the surface of a <span class="hlt">porous</span> silica glass (Vycor). For temperature ranging between 160 K and 325 K, this interfacial water shows a surprisingly large heat capacity. We describe the interfacial Hbond network in the framework of a mean field percolation <span class="hlt">model</span>, to show that at 160 K interfacial water experiences a transformation from low density amorphous ice to a heterogeneous system where transient low and high density water patches coexist. The fraction of each species is controlled by the temperature. We identify the large entropy of the interfacial water molecules as the cause of this behaviour.</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>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://adsabs.harvard.edu/abs/2016APS..DFDL40007K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDL40007K"><span><span class="hlt">Model</span> of fluid flow and internal erosion of a <span class="hlt">porous</span> fragile medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kudrolli, Arshad; Clotet, Xavier</p> <p>2016-11-01</p> <p>We discuss the internal erosion and transport of particles leading to heterogeneity and channelization of a <span class="hlt">porous</span> granular bed driven by fluid flow by introducing a <span class="hlt">model</span> experimental system which enables direct visualization of the evolution of porosity from the single particle up to the system scale. Further, we develop a hybrid hydrodynamic-statistical <span class="hlt">model</span> to understand the main ingredients needed to simulate our observations. A uniqueness of our study is the close coupling of the experiments and simulations with control parameters used in the simulations derived from the experiments. Understanding this system is of fundamental importance to a number of geophysical processes, and in the extraction of hydrocarbons in the subsurface including the deposition of proppants used in hydraulic fracturing. We provide clear evidence for the importance of curvature of the interface between high and low porosity regions in determining the flux rate needed for erosion and the spatial locations where channels grow. This <span class="hlt">material</span> is based upon work supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences program under DE-SC0010274.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27412621','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27412621"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AIPC.1453..111V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AIPC.1453..111V"><span>Numerical <span class="hlt">modeling</span> of ground water flow and contaminant transport in a saturated <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>Valipour, Mohammad S.; Sadeghi, Masoomeh; Mahmoudi, Amir H.; Shahi, Mina; Gandaghi, Hadi</p> <p>2012-05-01</p> <p>In this paper, numerical <span class="hlt">modeling</span> and experimental testing of the distribution of pollutants along the water flow in a <span class="hlt">porous</span> medium is discussed. Governing equations including overall continuity, momentum and species continuity equations are derived for <span class="hlt">porous</span> medium. The governing equations have been solved numerical using the Finite Volume Method based on collocated grids. The SIMPLE algorithm has been adopted for the pressure _ velocity linked equations. In order to validate the numerical results, experimental data from laboratory apparatus are applied and there is a good agreement among numerical results and experimental test. Finally, the main affecting parameters on the distribution and transport of pollutants <span class="hlt">porous</span> medium were investigated. Results indicate that, the domain of pollution rises with increasing dispersion coefficient and the dispersion phenomenon overcomes on pollutant transfer. Reduction of porosity has decreased the pollutant transfer and increased velocity has result in the increasing pollutant transport phenomenon but has reduced the domain of the pollution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17822109','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17822109"><span>An ion diffusion <span class="hlt">model</span> in semi-permeable clay <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Chongxuan</p> <p>2007-08-01</p> <p>Clay <span class="hlt">materials</span> typically contain negative surface charges that induce electrostatic fields (or diffuse double layers) in electrolytes. During ion diffusion in a <span class="hlt">porous</span> medium of clay <span class="hlt">materials</span>, ions dynamically interact with the electrostatic fields associated with individual clay grains by depressing or expanding the electrostatic double layers, which subsequently affects ionic fluxes. Current theory of ion transport in <span class="hlt">porous</span> media, however, cannot explicitly account for the dynamic interactions. Here we proposed a <span class="hlt">model</span> by coupling electrodynamics and nonequilibrium thermodynamics (EDNT) to describe ion diffusion in clay <span class="hlt">materials</span> as a complex function of factors including clay surface charge density, tortuosity, porosity, chemicoosmotic coefficient, and ion self-diffusivity. The <span class="hlt">model</span> was validated by comparing the calculated and measured apparent ion diffusion coefficients in clay <span class="hlt">materials</span> as a function of ionic strength. At transitional states, ion diffusive fluxes are dynamically related to the electrostatic fields, which shrink or expand as ion diffusion occurs. At steady states, the electrostatic fields are time-invariant and ion diffusive fluxes conform to flux and concentration gradient relationships; and apparent diffusivity can be approximated by the ion diffusivity in bulk electrolytes corrected by a tortuosity factor and macroscopic concentration discontinuities at the interfaces between clay <span class="hlt">materials</span> and bulk solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=130232&keyword=equilibrium+AND+constants&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=85806401&CFTOKEN=56966520','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=130232&keyword=equilibrium+AND+constants&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=85806401&CFTOKEN=56966520"><span><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://www.osti.gov/scitech/servlets/purl/60553','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/60553"><span><span class="hlt">Modeling</span> of strongly heat-driven flow in partially saturated fractured <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pruess, K.; Tsang, Y.W.; Wang, J.S.Y.</p> <p>1984-10-01</p> <p>We have performed <span class="hlt">modeling</span> studies on the simultaneous transport of heat, liquid water, vapor, and air in partially saturated fractured <span class="hlt">porous</span> media, with particular emphasis on strongly heat-driven flow. The presence of fractures makes the transport problem very complex, both in terms of flow geometry and physics. The numerical simulator used for our flow calculations takes into account most of the physical effects which are important in multi-phase fluid and heat flow. It has provisions to handle the extreme non-linearities which arise in phase transitions, component disappearances, and capillary discontinuities at fracture faces. We <span class="hlt">model</span> a region around an infinite linear string of nuclear waste canisters, taking into account both the discrete fractures and the <span class="hlt">porous</span> matrix. From an analysis of the results obtained with explicit fractures, we develop equivalent continuum <span class="hlt">models</span> which can reproduce the temperature, saturation, and pressure variation, and gas and liquid flow rates of the discrete fracture-<span class="hlt">porous</span> matrix calculations. The equivalent continuum approach makes use of a generalized relative permeability concept to take into account for fracture effects. This results in a substantial simplification of the flow problem which makes larger scale <span class="hlt">modeling</span> of complicated unsaturated fractured <span class="hlt">porous</span> systems feasible. Potential applications for regional scale simulations and limitations of the continuum approach are discussed. 27 references, 13 figures, 2 tables.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=128645&keyword=cho&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=89976288&CFTOKEN=74674448','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=128645&keyword=cho&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=89976288&CFTOKEN=74674448"><span>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> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26352212','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26352212"><span><span class="hlt">Porous</span> Silicon Nanotube Arrays as Anode <span class="hlt">Material</span> for Li-Ion Batteries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tesfaye, Alexander T; Gonzalez, Roberto; Coffer, Jeffery L; Djenizian, Thierry</p> <p>2015-09-23</p> <p>We report the electrochemical performance of Si nanotube vertical arrays possessing thin <span class="hlt">porous</span> sidewalls for Li-ion batteries. <span class="hlt">Porous</span> Si nanotubes were fabricated on stainless steel substrates using a sacrificial ZnO nanowire template method. These <span class="hlt">porous</span> Si nanotubes are stable at multiple C