ter Ejw Jan Maten

Modelling and discretization of circuit problems

Publisher Summary This chapter discusses the modeling aspect of differential-algebraic equations (DAEs). In computational engineering, the network modeling approach forms the basis for computer-aided analysis of time-dependent processes in multibody dynamics, process simulation, or circuit design. Its principle is to connect compact elements via ideal nodes, and to apply some kind of conservation rules for setting up equations. The mathematical model, a set of so-called network equations, is generated automatically by combining network topology with characteristic equations describing the physical behavior of network elements under some simplifying assumptions. Interconnects and semiconductor devices (i.e., transistors) are modeled by multi-terminal elements (multi-ports), for which the branch currents entering any terminal and the branch voltages across any pair of terminals are well-defined quantities. Interconnects and semiconductor devices (i.e., transistors) are modeled by multiterminal elements (multi-ports), for which the branch currents entering any terminal and the branch voltages across any pair of terminals are well-defined quantities.

Simulation of inductive heating

A description is given of a software package for the simultaneous solution of the eddy current and the heat transfer equation for the simulation of inductive heating. Aspects such as velocity effects, Curie temperature transitions, RZ coordinates and enforced current conservation have been taken into account. The use of PDL (Package Designer Language) in the definition phase has proved to be a very flexible way to structure the complex combinatorics of several specialized options and to handle redefinition of the algorithms, because time-consuming items like adapting data structures are handled via PDL. This also resulted in a substantial reduction in development time required for the package. >

Simulation of coupled electromagnetic and heat dissipation problems

A description is given of an integrated simulation environment for the solution of coupled electromagnetic and heat dissipation problems in two dimensions, in particular for the field of induction heating, dielectric heating, and hysteresis heating. The equations are coupled because the most important physical parameters (permeability, conductivity, permittivity) may depend on temperature in a nonlinear way. The software has been constructed with the high level language PDL, using the general Mammy design concept. All heating problems under consideration may involve thermal convection and radiation at the boundaries of the objects. Also, additional temperature dependent heat sources (e.g. resistor heating) can be defined. One can include instantaneous effects of movement in the plane on the temperature transfer. Effects around Curie temperature transitions can be analyzed. >

Splitting methods for fourth order parabolic partial differential equations

In this paper, several splitting methods are discussed which can be used to solve fourth order parabolic partial differential equations that are given in some suitable first order system form. The methods are generalisations of splitting methods for (second order) parabolic PDEs. For all methods which are considered, stability or instability is studied for problems in 2 and in 3 or more spatial dimensions.ZusammenfassungIn dieser Arbeit werden mehrere Splitting-Methoden diskutiert, welche zur Lösung von parabolischen partiellen Differentialgleichungen vierter Ordnung benützt werden können, welche in Form eines Systems erster Ordnung geschrieben sind. Die Methoden sind Verallgemeinerungen von Splitting-Methoden für parabolische Gleichungen zweiter Ordnung. Für alle betrachteten Methoden werden Stabilitätsuntersuchungen angestellt für den Fall von 2, 3 und mehr Raumdimensionen.

Aspects of Multirate Time Integration Methods in Circuit Simulation Problems

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Influence of a temperature gradient on the simple shear now of a nematic liquid crystal

Abstract The influence of a temperature gradient across the channel on the steady-state simple shear flow of a nematic liquid crystal is investigated. The in-plane mean molecular orientation, velocity field and temperature profile are calculated on the basis of the Leslie-Ericksen theory. The dependence of the elasticity and viscosity on the temperature and the anisotropy of the heat conduction are taken into account. Results are obtained for a flow-aligning and a tumbling nematic. By shifting the temperature across the height of the channel so that the Leslie coefficient α 3 changes sign at some point between the two bounding plates, the combination of flow-alignment and tumbling in a simply sheared liquid crystal is evaluated.

Digital Linear Control Theory Applied To Automatic Stepsize Control In Electrical Circuit Simulation

Adaptive stepsize control is used to control the local errors of the numerical solution. For optimization purposes smoother stepsize controllers are wanted, such that the errors and stepsizes also behave smoothly. We consider approaches from digital linear control theory applied to multistep BDF-methods.

Augmented Lagrangian Algorithm for Optimizing Analog Circuit Design

The analog design assistance tool Adapt [5, 6] has been developed to help analog electronic circuit designers tuning design parameters, such that the functional design specifications are met, given process technology constraints. Tuning is based on an optimization process, in which each iteration of the optimization loop implies the evaluation of the circuit by an analog circuit simulator. Considering the simulator as a black box tool, the choice of the optimization technique is restricted, because the simulator does not automatically supply derivatives of the design metrics and numerical noise is inherently present (for instance due to adaptive time stepping). Therefore, optimization algorithms that adopt finite-difference schemes to approximate derivatives cannot be applied straightforwardly.

Optimization of electronic circuits

Several types of parameters influence the behaviour of electronic circuits nand have to be taken into account when optimizing appropriate performance nfunctions : design parameters, manufacturing process parameters, and noperating parameters. nThe performance functions and the constraints can be costly nand are subject to noise. For both the dependency on can be highly nnonlinear. nIn this talk we will describe our in-house developed method nfor optimization and our experiences with that. Also some new directions nfor further research will be described. n n[ DOI : 10.1685/CSC06144] About DOI

DRK methods for time-domain oscillator simulation

This paper presents a new Runge-Kutta type integration method that is well-suited for time-domain simulation of oscillators. A unique property of the new method is that its damping characteristics can be controlled by a continuous parameter.