Catálogo de publicaciones - libros

Some propositions for approximation of the controllability and observability gramians for nonlinear systems are presented. This enables a balancing type model reduction to be performed for nonlinear systems in the same manner as for linear systems.

The distribution of electromagnetic fields, forces and source term of temperature induced by an alternating axially-symmetric system of electric current in a cylinder of a finite length with 6 electrodes has been investigated and calculated in [2, 1].

In this paper the three-phase alternating current with phase shift 120 degree is fed to every of 9 discreate circular conductors-electrodes, which are placed on the internal wall of the cylinder. The motion of electrolyte and temperature distribution in a cylinder has been calculated in dependence of the arrangement of electrodes.

Numerical aspects for solving of certain problem arising in gyrotron theory are discussed. Particularly, finite-difference schemes using quasistationarization and method of lines were applied and the relevant results analyzed.

A deterministic solution method for the coupled Boltzmann-Poisson system regarding spatially two-dimensional problems is presented. The method is based on a discontinuous piecewise polynomial approximation of the carrier distribution function. The conduction band of silicon is modelled by a non-parabolic six-valley model. In particular, we applied the multicell method to simulate the transients of a silicon MESFET. The results are compared to Monte Carlo simulations.

(VF) is an iterative technique to construct rational approximations based on multiple frequency domain samples, introduced by Gustavsen and Semlyen [1, 3]. VF is nowadays widely investigated and used in the and communities. Numerical experiments show that VF has favorable convergence properties. However, so far, no theoretical proof for its convergence, or conditions to guarantee convergence, have been published. This paper gives a description of a general iterative Least-Squares framework for rational approximation and shows that VF fits into this framework.

Krylov subspace methods are well-known for their nice properties, but they have to be implemented with care. In this article the mathematical consequences encountered during implementation of Krylov subspace methods in an existing layout-simulator are discussed. Briey, the representation in a circuit is visited and two methods to avoid parts of the redundancy are drawn.

Several iterative methods have been tested in nonlinear DC analysis of industrial electronic circuits.

The efficient implementation of the FDTD algorithm in C, particularly the data types and nested loops required, is discussed. The different constructs were run on four computer platforms indicating significant performance improvement with proper implementation. The extent of the improvement depends on the data type, compiler and computer used.

Finite element approximation in space and Crank-Nicolson approximation in time are used to model incompressible creeping flow of molten glass with temperature dependent viscosity. Iso-P triangle elements and second degree approximation of temperature and velocity fields are applied. Localized thermal behavior is captured with adaptively refined unstructured mesh.

The simulation of circuits including signals with widely separated time scales can easily become very time-consuming. To avoid this, a multidimensional signal model was developed. The resulting system of network equations can be solved very efficiently by a method of characteristics. We investigate the applicability of this method to circuits including digital signal structures. Moreover, systems given in linear-implicit form are solved using the multidimensional approach.