Asymptotic modeling of transport phenomena at the interface between a fluid and a porous layer: Jump conditions.

We develop asymptotic modeling for two- or three-dimensional viscous fluid flow and convective transfer at the interface between a fluid and a porous layer. The asymptotic model is based on the fact that the thickness d of the interfacial transition region Ω_{fp} of the one-domain representation is very small compared to the macroscopic length scale L. The analysis leads to an equivalent two-domain representation where transport phenomena in the transition layer of the one-domain approach are represented by algebraic jump boundary conditions at a fictive dividing interface Σ between the homogeneous fluid and porous regions.

Dynamic effectiveness factor for catalyst particles.

The effectiveness factor (EF) is a nondynamic concept that has been demonstrated to be useful for the analysis and design of reaction-diffusion systems (e.g., catalyst particles).

An approximate solution for a transient two-phase stirred tank bioreactor with nonlinear kinetics.

The derivation of an approximate solution method for models of a continuous stirred tank bioreactor where the reaction takes place in pellets suspended in a well-mixed fluid is presented. It is assumed that the reaction follows a Michaelis-Menten-type kinetics. Analytic solution of the differential equations is obtained by expanding the reaction rate expression at pellet surface concentration using Taylor series.

A method to evaluate the isothermal effectiveness factor for dynamic oxygen into mycelial pellets in submerged cultures.

Several models have been developed simulating O2 transfer in bioreactors, but three limitations are often found: (i) an inadequate kinetic representation of O2 consumption or wrong boundary conditions, (ii) unrealistic parameter values, and (iii) inadequate experimental systems. In our study we minimized those possible sources of error. Oxygen uptake rate, void fraction of the pellet, and external O2 mass transfer coefficient were experimentally obtained from bioreactor studies in which pellets of Gibberella fujikuroi were naturally formed.

Solgel derived tantalum pentoxide films as ultraviolet antireflective coatings for silicon.

A solgel process is described to produce Ta(2)O(5) films as short wavelength antireflective (AR) coatings for silicon. The AR coatings were optimized for 370 nm by controlling the acid catalyzed hydrolysis of Ta(OC(2)H(5))(5), the spin coating parameters, and the heat treatment process (rapid thermal processing (RTP) and muffle furnace). Film thickness uniformity across the wafer was better than 1%, and all the coatings tested passed the standard scotch tape test before and after heat treatment and exhibited no change in optical properties after submersion in liquid N(2).