Line formation in accretion disks. 3D comoving frame calculations

The 3D radiative transfer equation is written in O(#nu#/c) in the comoving frame and solved by a short characteristics method for a two-level atom with complete redistribution. An Approximate-#LAMBDA# operator and various other acceleration techniques are applied to improve the rate of convergence. Line profiles and source functions are calculated for accretion disk models of cataclysmic variables (CV) and active galactic nuclei (AGN) homogeneous in density and temperature. We find that the velocity gradient in the disks makes it necessary for line transfer problems to use the full 3D radiative transfer equation. (orig.)Available from TIB Hannover: RR 1606(94-57) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Efficient techniques for the optimization of complex chemical processes

Efficient and robust techniques for the optimization of complex chemical processes are presented. In particular, we address the solution of large, multistage optimal control problems for processes described by DAE models. Our boundary value problem approach (a simultaneous solution strategy) is based on a piecewise representation of the control functions and a multiple shooting discretization of the DAEs, combined with a specifically tailored SQP technique. The inherent problem structure is exploited on various levels, leading to an extremely efficient overall method. A reliable and easy-to-use implementation of this strategy is provided by the recently developed modular optimal control package MUSCOD-II. Two real-life applications of MUSCOD-II are discussed: 1. Optimal control of a fed-batch fermentation for the production of Nikkomycin. 2. Optimization of a hydrogen-air combustion process in a 1D steady-state tube reactor. The first application provides a realistic bioprocess optimization problem, and our method is shown to be so fast that it could be even used for the online optimization of such processes. The second problem demonstrates the suitability of our approach for the stiff differential equation models that are common in chemical kinetics applications. (orig.)SIGLEAvailable from TIB Hannover: RR 1606(96-40) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Stationary Marangoni convection: a free boundary value problem for the Navier Stokes equations

The author considers a stationary free boundary problem for the Navier Stokes system and the heat equation. The system is considered as a model for the motion of a fluid drop in a zero gravity field. The shape of the drop and the flow resp. pressure inside are determined by surface forces (at least in the case f = 0) and they act via a variable surface tension on the fluid inside. More precisely, a force on the surface (in our case it will be the gradient of a temperature field) changes the surface tension and the boundary conditions tell us how this causes an onset of a motion of the fluid inside. The system is written here in dimensionless form. In this paper the author proves existence and regularity of a solution of the stationary system. He decomposes the system in two systems. The first system contains the physical equations and the geometry is given, while the second one determines the geometry and the physical quantities are given. The paper is based on results, obtained by different authors in the last few years. (orig./AKF)SIGLEAvailable from TIB Hannover: RR 1606(94-41) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Decomposition numbers for generic Iwahori-Hecke algebras of non-crystallographic type

In this note we compute the #PHI#_e-modular decomposition matrices for the generic Iwahori-Hecke algebras of type I_2(m) for m element of N, m>2, H_3, and H_4, for all e element of N leading to non-trivial decomposition maps. The results are obtained by a combined use of different ideas from computational representation theory and by application of the computer algebra systems GAP, CHEVIE, Vector Enumerator, and MeatAxe. (orig.)Available from TIB Hannover: RR 1606(96-33) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Discrete models for the morphogenesis of neurites regulated by attraction-diffusion-depletion

SIGLEAvailable from TIB Hannover: RR 1606(2001,12) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Computing invariants of reductive groups in positive characteristic

SIGLEAvailable from TIB Hannover: RR 1606(2002,6) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Genralized Harish-Chandra theory

SIGLEAvailable from TIB Hannover: RR 1606(97-42) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

On American derivatives and related obstacle problems

SIGLEAvailable from TIB Hannover: RR 1606(2002,9) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

The graphics program cnom2.0. User manual

Available from TIB Hannover: RR 1606(95-32) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Computational invariant theory

SIGLEAvailable from TIB Hannover: RR 1606(98-07) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman