Spectroscopic properties of Tm3+ in fluorophosphate glasses

The optical properties of Tm³⁺ in a fluorophosphate glass are reported. Oscillator strengths and Ω_λ parameters for Tm³⁺ were calculated. Energy transfer between Ce³⁺ → Tm³⁺, Tm³⁺ → Eu³⁺ and Tm³⁺ → Tb³⁺ were measured at room temperature and interpreted using the Yokota and Tanimoto scheme. Fluorescence decay results seem to support the hypothesis of a diffusion-limited relaxation. The effects of Tb³⁺ and especially Ce³⁺ on the fluorescence of Tm³⁺ ion point out the interest of these dopants for obtaining a better emission of Tm³⁺ at 450 nm.     

Anchoring strength coefficient of a monomer and its dimer at a polymer-coated interface

The dialkoxyphenylbenzoate monomer '5005' (C₅H₁₁OC₆H₄COOC₆H₄OC₅H₁₁) and its dimer were aligned parallel to a buffed polyimide-coated glass substrate. A magnetically induced Freedericksz transition in both thick and thin cells was used in conjunction with a capacitance technique to determine the anchoring strength coefficient Was a function of temperature in the nematic phase. It was found that for both monomer and dimer, Wincreases with decreasing temperature. The anchoring coefficient for the dimer, however, was found to be an order of magnitude larger than for the monomer at comparable reduced temperatures. The splay elastic moduli were also determined for both species, and found to be of comparable magnitude, consistent with previous results.     

Experiments in numerical methods for a problem in combustion modeling

In this paper, we have shown that the numerical method of lines can be used effectively to solve time dependent combustion models in one spatial dimension. By the numerical method of lines (NMOL), we mean the reduction of a system of partial differential equations to a system of ordinary differential equations (ODE's), followed by the solution of this ODE system with an appropriate ODE solver. We used finite differences for the spatial discretization and a variant of the GEAR package for the ODE's.We have presented various solution methods of interest for the nonlinear algebraic system in this setting; that is, in the corrector iteration section of the GEAR package applied to combustion models. These methods include Newton/block SOR (SOR denotes successive over-relaxation), block SOR/Newton, Newton/block-diagonal Jacobian, Newton/kinetics-only Jacobian, and Newton/block symmetric SOR. These methods have in common their lack of frequent use in ODE software and their eady applicability to partial differential equations in more than one spatial dimension.Finally, we have given the results of numerical tests, run on the CDC-7600 and Cray-1 computers. By so doing, we indicate the more promising nonlinear system solvers for the NMOL solution of combustion models.     

Stochastic diffusion models with advertising and word-of-mouth effects

This paper presents a stochastic diffusion model which incorporates advertising word-of-mouth effects. The model defines a 3 variate stochastic process based on explicit assumptions regarding consumer behavior and consumers' response to advertising. The model generalizes a wide variety of advertising models and in addition includes several classes of consumers, interaction effects between these consumers and, of course, a stochastic framework that may be used for assessing the risk implications of advertising policies and for empirical analyses purposes.