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- ItemTransient numerical study of termperature gradients during sublimation growth of SiC: Dependence on apparatus design(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2005) Geiser, Jürgen; Klein, Olaf; Philip, PeterUsing a transient mathematical heat transfer model including heat conduction, radiation, and radio frequency (RF) induction heating, we numerically investigate the time evolution of temperature gradients in axisymmetric growth apparatus during sublimation growth of silicon carbide (SiC) bulk single crystals by physical vapor transport (PVT) (modified Lely method). Temperature gradients on the growing crystal's surface can cause defects. Here, the evolution of these gradients is studied numerically during the heating process, varying the apparatus design, namely the amount of the source powder charge as well as the size of the upper blind hole used for cooling of the seed. Our results show that a smaller upper blind hole can reduce the temperature gradients on the surface of the seed crystal without reducing the surface temperature itself.
- ItemFractional-splitting and domain-decomposition methods for parabolic problems and applications(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2006) Daoud, Daoud; Geiser, JürgenIn this paper we consider the first order fractional splitting method to solve decomposed complex equations with multi-physical processes for applications in porous media and phase-transitions. The first order fractional splitting method is also considered as basic solution for the overlapping Schwarz-Waveform-Relaxation method for an overlapped subdomains. The accuracy and the efficiency of the methods are investigated through the solution of different model problems of scalar, coupling and decoupling systems of convection reaction diffusion equation.