In this paper, we consider a drift-diffusion system with cross-coupling through the chemical potentials comprising a model for the motion of finite size ions in liquid electrolytes. The drift term is due to the self-consistent electric field maintained by the ions and described by a Poisson equation. We design two finite volume schemes based on different formulations of the fluxes. We also provide a stability analysis of these schemes and an existence result for the corresponding discrete solutions. A convergence proof is proposed for non-degenerate solutions. Numerical experiments show the behavior of these schemes.
As far as indicated by the spectra and the fluorescence time decay law, the properties of the fluorescence of poly(butylene terephthalate) (PBT) are almost identical to those of PET. The groundstate-stable sandwich dimers in the noncrystalline regions of uniaxially-drawn PBT films were used as chainintrinsic fluorescent labels for studying the orientation distribution function. The dimers are formed only in the amorphous regions; concerning the fluorescence signal, "amorphous" includes all the material outside perfect crystallites. During deformation, the orientation coefficient (Pj)F of the dimers follows approximately a superposition curve of crystallite-like orientation, easily separable in the initial range of stretching ratio < 2.5, and of true-amorphous orientation of the affine network type that becomes noticeable at X > 3. The total fluorescence intensity of PBT, if excited at the proper wavelength, is proportional to the concentration of the dimers; it remains constant in the initial range of stretching, i.e. X < 1.5. At higher X, correlated to the increase of amorphous orientation, a strong increase of the dimer concentration, up to a factor of 6, is observed.
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