Results 181 to 190 of about 3,974 (207)

A comparative study of Knudsen diffusion in cellular metals

Computational Materials Science, 2011
Abstract This paper addresses Knudsen diffusion in cellular metals. Knudsen diffusivities for air at room temperature are calculated for a representative cross-section of the different types of cellular materials: a sintered fibre structure, a lotus-type porous metal, a sintered metallic hollow sphere structure and a M-Pore® aluminium foam.
Fiedler, T., Belova, I. V., Murch, G. E.
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Knudsen diffusion through thin fibrous films

Journal of Applied Physics, 2007
Variational upper and multiple scattering lower bounds on the Knudsen transport rates are applied to several slab geometries of finite thickness made up of parallel, randomly placed, overlapping long cylindrical fibers, one with fibers aligned perpendicular and a second with fibers parallel to the film edges.
Xiangning Li, William C. Strieder
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Knudsen diffusion in powders. Part I Critical examination of a gas diffusion relationship used in Knudsen flow permeametry

Powder Technology, 1977
Abstract B. V. Derjaguin's treatment of gas diffusion in a porous medium under conditions of Knudsen flow is discussed. A semi-theoretical value obtained for the constant β in the general equation is tested experimentally. In opposition to previous conclusions, molecular diffusion seems best interpreted in terms of elastic collisions against the pore
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Diffusion of Oxygen through Cork Stopper: Is It a Knudsen or a Fickian Mechanism?

Journal of Agricultural and Food Chemistry, 2014
The aim of this work is to identify which law governs oxygen transfer through cork: Knudsen or Fickian mechanism. This is important to better understand wine oxidation during post-bottling aging. Oxygen transfer through cork wafers is measured at 298 K using a manometric permeation technique.
Lagorce-Tachon, Aurélie, Karbowiak, Thomas, Simon, Jean-Marc, Gougeon, Régis, Bellat, Jean-Pierre   +4 more
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The diffusion force in the transition region of knudsen number

Journal of Colloid and Interface Science, 1968
Abstract The free molecule theory of the diffusion Force is reviewed briefly. The theory of the diffusion Force in the transition region is developed for binary mixtures for equimolar counterdiffusion and for diffusion of one component of the mixture through the second stagnant component. The transition region theory of the diffusion Force appears to
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Knudsen diffusivities and properties of structures of unidirectional fibers

AIChE Journal, 1991
AbstractEffective Knudsen diffusion coefficients are presented for fibrous structures consisting of parallel, nonoverlapping or partially overlapping fibers. They are computed by means of a Monte Carlo simulation scheme which is employed to determine the mean square displacement of molecules travelling in the interior of the porous medium for large ...
Manolis M. Tomadakis, Stratis V. Sotirchos   +1 more
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Diffusion approximation of a Knudsen gas model: dependence of the diffusion constant upon the boundary condition

Asymptotic Analysis, 2002
In this article we study a model for the dynamics of particles moving freely between two horizontal plates. Our goal is to characterize the diffusive behavior for such systems in the long‐time and large (horizontal) scale limits.
Boatto, Stefanella, Golse, François
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A dynamic method for measuring tortuosity and Knudsen diffusion contributions to catalyst diffusivities

Journal of Catalysis, 1978
Abstract The Dogu-Smith, dynamic method for measuring catalyst diffusivities was adapted for variable pressure operation. First absolute moment (μ1) data were obtained as a function of pressure and used to evaluate tortuosity and Knudsen and molecular diffusion contributions to effective diffusivities.
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Diffusive limits for the Knudsen gas in a thin channel with accommodation on the boundary

Asymptotic Analysis, 2009
We consider a model for a free molecular flow in a thin channel bounded by two parallel plates on which Maxwellian boundary conditions with (fixed) accommodation and a generic scattering kernel apply. Using functional analytic tools, we show that as the width of the channel vanishes, and on a suitable temporal scale, the evolution of the density is ...
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Knudsen diffusion in ordered sphere packings

AIChE Journal, 1988
Natalie E. Olague, Douglas M. Smith, Muhsin Ciftcioglu   +2 more
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