The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Andrew L. Zydney - One of the best experts on this subject based on the ideXlab platform.
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Pore Size Distribution effects on electrokinetic phenomena in semipermeable membranes
Journal of Membrane Science, 1995Co-Authors: Skand Saksena, Andrew L. ZydneyAbstract:Electrokinetic phenomena occurring in charged ultrafiltration membranes can significantly influence the transport characteristics of these membranes. Theoretical calculations have been performed to evaluate the effects of different log-normal Pore Size Distributions on the solvent flow rate, the induced streaming potential, and the membrane zeta potential. The solvent flow rate increased with an increase in the breadth of the Pore Size Distribution, with this effect being much more pronounced for pressure-driven flow than for electrically-driven flow. The streaming potential induced by the convective fluid flow significantly alters the flow profiles through the membrane due to the very different dependence of the pressure-driven and counter-electroosmotic flow on the Pore radius. This causes a relatively large negative (reverse) flow to develop through the smallest Pores in the Distribution. The membrane zeta potential was also a function of the Pore Size Distribution, even for membranes having the same hydraulic permeability and surface charge density. These results provide important insights into the effects of different Pore Size Distributions on membrane transport and on the proper interpretation of these electrokinetic phenomena.
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Theoretical analysis of Pore Size Distribution effects on membrane transport
Journal of Membrane Science, 1993Co-Authors: Seiichi Mochizuki, Andrew L. ZydneyAbstract:Abstract The membrane selectivity can be critically affected by the Pore Size Distribution. We examined the effect of different Pore Size Distributions on the asymptotic membrane sieving coefficient, the hindered solute diffusivity, and the membrane hydraulic permeability by averaging the solute and solvent transport rates over specific Pore Size Distributions. Although the calculated sieving coefficients and hindered diffusivities both increased significantly with an increase in the breadth of the Distribution, the relationship between these two membrane transport parameters was relatively unaffected by the Pore Size Distribution, allowing for reasonably accurate predictions of the hindered diffusivity from sieving data (or vice versa). These detailed calculations were also compared with predictions of a recently developed analytical model which implicitly accounts for the Pore Size Distribution by evaluating the effective solute to Pore Size ratio using an expression for the solute partition coefficient in a random porous media. Model predictions were in good agreement with the detailed integral results for a membrane with a log-normal Distribution with geometric standard deviation of around two, which is consistent with the observed Pore Size Distribution for many ultrafiltration membranes. Model calculations also examined the effects of protein adsorption on membrane transport, with very different behavior seen for different adsorption mechanisms.
Seiichi Mochizuki - One of the best experts on this subject based on the ideXlab platform.
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Theoretical analysis of Pore Size Distribution effects on membrane transport
Journal of Membrane Science, 1993Co-Authors: Seiichi Mochizuki, Andrew L. ZydneyAbstract:Abstract The membrane selectivity can be critically affected by the Pore Size Distribution. We examined the effect of different Pore Size Distributions on the asymptotic membrane sieving coefficient, the hindered solute diffusivity, and the membrane hydraulic permeability by averaging the solute and solvent transport rates over specific Pore Size Distributions. Although the calculated sieving coefficients and hindered diffusivities both increased significantly with an increase in the breadth of the Distribution, the relationship between these two membrane transport parameters was relatively unaffected by the Pore Size Distribution, allowing for reasonably accurate predictions of the hindered diffusivity from sieving data (or vice versa). These detailed calculations were also compared with predictions of a recently developed analytical model which implicitly accounts for the Pore Size Distribution by evaluating the effective solute to Pore Size ratio using an expression for the solute partition coefficient in a random porous media. Model predictions were in good agreement with the detailed integral results for a membrane with a log-normal Distribution with geometric standard deviation of around two, which is consistent with the observed Pore Size Distribution for many ultrafiltration membranes. Model calculations also examined the effects of protein adsorption on membrane transport, with very different behavior seen for different adsorption mechanisms.
Victor G. J. Rodgers - One of the best experts on this subject based on the ideXlab platform.
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Sieving variations due to the choice in Pore Size Distribution model
Journal of Membrane Science, 2002Co-Authors: S. Derjani-bayeh, Victor G. J. RodgersAbstract:The effect of the choice of the standard probabilistic model to describe the Pore Size Distribution was theoretically studied on predicting membrane performance parameters, area average water flux and area average membrane sieving coefficient. Preliminary discrete Pore Size Distributions were generated from rejection profiles of dextran and PEG for 10,000, 30,000 and 100,000 molecular weight cutoff (MWCO) polysulfone and cellulose acetate membranes. The standard probability Distribution functions (PDF), gamma, lognormal, normal, Weibel and Rayleigh were used to fit the resulting Pore Size Distribution data. It was observed that the area averaged sieving coefficients are sensitive to the choice of the PDF. These results implied that an uncertainty in the choice of Distribution in describing the membrane morphology could lead to a propagated uncertainty in predicting overall membrane performance.
Bishwajit Bhattacharjee - One of the best experts on this subject based on the ideXlab platform.
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porosity Pore Size Distribution and in situ strength of concrete
Cement and Concrete Research, 2003Co-Authors: Rakesh Kumar, Bishwajit BhattacharjeeAbstract:In this study, in situ strength of concrete was determined through compression test of cores drilled out from laboratory cast beams. The apparent porosity and Pore Size Distribution of the same concrete were determined through mercury intrusion porosimetry, performed on small-drilled cores. The normal-strength concrete mixes used in the experimental investigation were designed to exhibit a wide variation in their strengths. To ensure further variation in porosity, Pore Size Distribution and strength, two modes of compaction, two varieties of coarse aggregates, different levels of age, curing period and exposure condition of concrete were also introduced in experimental scheme. With the data so generated, an appraisal of the most frequently referred relationships involving strength, porosity and Pore Size of cement-based materials was carried out. Finally, a new empirical model relating the in situ strength of concrete with porosity, Pore Size characteristics, cement content, aggregate type, exposure conditions, etc., is presented.
Guoping Zhang - One of the best experts on this subject based on the ideXlab platform.
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Statistical modelling of compressive strength controlled by porosity and Pore Size Distribution for cementitious materials
Cement and Concrete Composites, 2019Co-Authors: Dong-wei Hou, Peicheng Hua, Junda Jiang, Guoping ZhangAbstract:Abstract The compressive strength of cementitious materials is significantly affected by its Pore system inherent in the matrix of cement paste, not only porosity but also Pore Size Distribution. In present work, by deconvolution analysis, the total Pore Size Distribution of cement paste is represented by a multiple Distribution consisting of two single Distributions for the capillary Pores and the macro Pores respectively. In this way, the widely accepted Raleigh-Ritz (R-R) function is challenged and the lognormal Distribution is found to be best to approximate the Pore Size Distribution for cementitious materials. With Pore Size Distributions, a statistical model based on probability principle and fracture criterion is proposed to reveal the physical mechanism of reduction in compressive strength induced by porous structures. Parameters in the model, e.g. fracture toughness of cement paste matrix, fracture mode, volume of specimen, porosity and Pore Size Distributions, are further discussed and examined quantitatively.