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http://hdl.handle.net/2445/18700
Title: | Diffusion in spatially and temporarily inhomogeneous media |
Author: | Lehr, Heiner Sagués i Mestre, Francesc Sancho, José M. |
Keywords: | Òptica geomètrica Materials inhomogenis Geometrical optics Inhomogeneous materials |
Issue Date: | 1996 |
Publisher: | The American Physical Society |
Abstract: | In this paper we consider diffusion of a passive substance C in a temporarily and spatially inhomogeneous two-dimensional medium. As a realization for the latter we choose a phase-separating medium consisting of two substances A and B, whose dynamics is determined by the Cahn-Hilliard equation. Assuming different diffusion coefficients of C in A and B, we find that the variance of the distribution function of the said substance grows less than linearly in time. We derive a simple identity for the variance using a probabilistic ansatz and are then able to identify the interface between A and B as the main cause for this nonlinear dependence. We argue that, finally, for very large times the here temporarily dependent diffusion "constant" goes like t-1/3 to a constant asymptotic value D¿. The latter is calculated approximately by employing the effective-medium approximation and by fitting the simulation data to the said time dependence. |
Note: | Reproducció del document publicat a: http://dx.doi.org/10.1103/PhysRevE.54.5028 |
It is part of: | Physical Review e, 1996, vol. 54, num. 5, p. 5028-5036 |
URI: | http://hdl.handle.net/2445/18700 |
Related resource: | http://dx.doi.org/10.1103/PhysRevE.54.5028 |
ISSN: | 1539-3755 |
Appears in Collections: | Articles publicats en revistes (Ciència dels Materials i Química Física) Articles publicats en revistes (Física Quàntica i Astrofísica) |
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