Diffusion of penetrants through polymers often does not follow the standard Fickian model. Such anomalous behavior can cause difficulty when designing polymer networks for specific uses. One type of non-Fickian behavior that results is so-called case I1 diffusion, where Fickian-like fronts initially move like fi with a transition to a non-Fickian concentration profile and front speed for modera...

Fick’s law expresses the proportionality of solute flux with respect to concentration gradient. Similar relations are Darcy’s law for the fluid flow in porous media, Ohm’s law for the electric flux and Fourier’s law for heat transfers. When introduced in the corresponding balance equations, these flux laws yield diffusion equations of parabolic character. Different attempts have been made to ob...

The diffusion mechanism of pure component Ar and binary mixtures of Ar/Kr and Ar/Ne confined in single-walled carbon nanotubes (SWNTs) and bundles was investigated by a combined Grand Canonical Monte Carlo and molecular dynamics study. For Ar confined in SWNTs, a crossover from single-file to Fickian diffusion existed when the density of Ar was a minimum as a function of the SWNT diameter. Argo...

In the absence of fractures, methane bubbles in deep-water sediments can be immovably trapped within a porous matrix by surface tension. The dominant mechanism of transfer of gas mass therefore becomes the diffusion of gas molecules through porewater. The accurate description of this process requires non-Fickian diffusion to be accounted for, including both thermal diffusion and gravitational a...

Slow condensed phase diffusion in organic aerosol particles can impede many chemical and physical processes associated with atmospheric (e.g., gas-particle equilibrium partitioning). The characteristic times these high viscosity are typically modelled using a concentration-dependent diffusivity within purely Fickian framework. In that model, the medium which is taking place treated as being inv...

the main objective of present research work is to formulate the clopidogrel fast dissolving tablets. clopidogrel, an antiplatelet drug, belongs to bcs class-ii and used to control heart attack, hypertension by inhibiting platelet activation and aggregation .the fast dissolving tablets of clopidogrel were prepared employing different concentrations of crospovidone and croscarmellose sodium in di...