Electrical Engineering Problems Research Articles

An adaptive finite element computation of h-p version for magnetic field problems

In this paper, on the basis of theoretical analysis of hierarchical element structure, an adaptive finite element computation of h-p version for magnetic field problems is presented. Through detailed investigation of three typical problems in electrical engineering with both h-p and h version, two new kinds of efficient adaptive schemes of h-p version are obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Capacitance of disk capacitors

The capacitance of a parallel-plate capacitor is formulated in basic electrostatics, assuming that the separation between the two electrode plates is very narrow and the fringe field of the edges is negligible. However, in practical problems of electrical and electronic engineering there are many cases where the plate separation is wide and the fringe field effect cannot be neglected. In the authors' previously published paper the capacitance of strip capacitor was computed by the boundary element method (BEM) for the case where the separation becomes wide, and a new empirical formula of the capacitance against the plate separation was derived. The empirical formula agreed well with experimental data. A formula for the capacitance of a parallel plate disk capacitor is presented. The formula is valid over a wider separation than formulas presented previously. As a special case of the problem, the capacitance of parallel plate ring capacitors is computed by the BEM. >

Introductory probabilistic and stochastic analysis and design of circuits

The authors introduce the subject of probabilistic and stochastic analysis and design of circuits to nonspecialists and emphasize the need for teaching the subject to senior level undergraduates. It is argued that as this subject area synthesizes ideas from systems theory, electrical circuit analysis and design, matrix methods, probability and stochastic theories, numerical methods, optimization and symbolic algebra, this will be an ideal course to demonstrate the use of most of the background subjects, and relevant computing techniques and software. Problems solved could include electrical engineering problems, and other engineering problems modeled with electrical analogs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

CLP(?) and some electrical engineering problems

The Constraint Logic Programming Scheme defines a class of languages designed for programming with constraints using a logic programming approach. These languages are soundly based on a unified framework of formal semantics. In particular, as an instance of this scheme with real arithmetic constraints, the CLP(ℜ) language facilitates and encourages a concise and declarative style of programming for problems involving a mix of numeric and non-numeric computation. In this paper we illustrate the practical applicability of CLP(ℜ) with examples of programs to solve electrical engineering problems. This field is particularly rich in problems that are complex and largely numeric, enabling us to demonstrate a number of the unique features of CLP(ℜ). A detailed look at some of the more important programming techniques highlights the ability of CLP(ℜ) to support well-known, powerful techniques from constraint programming. Our thesis is that CLP(ℜ) is an embodiment of these techniques in a language that is more general, elegant and versatile than the earlier languages, and yet is practical.

Mechanical Networks Model for Analysis of Elasto-Plastic Truss Systems

The theory and method of mechanical networks model has been used to model, formulate and compute a lot of linear problems in mechanical, electrical and structural engineering. In this paper we will embark on a study of nonlinear problems and demonstrate how to solve a nonlinear system which contains elements with linear and nonlinear properties by the use of the mechanical networks model. A complete program written in the APL programming language, which is used to solve a detailed numerical example of a truss system with ten nonlinear elements, is presented. The principles and concepts proposed are easily understood, and the modelling, formulation and computation of systems can be carried out systematically and consistently. Because of our intensive and limitless desire to analysis and synthesis of a great variety of larger and more sophisticated systems, generality and complexity is a central problem in the design process of modern systems. The main aim of our present work is to develop a general, unified and systematic theory and method which can be employed in the design process to analyze and synthesize a great variety of complex systems, such as mechanical, electrical, fluid, thermal and economic systems, even biological system. The mechanical networks model developed has proved to be ideal for this type of analysis.

Spectral and Inner-Outer Factorizations of Rational Matrices

Spectral factorization and inner-outer factorization are basic techniques in treating many problems in electrical engineering. In this paper, the roblems of doing spectral and inner-outer factorizations via state-space methods are studied when the matrix to be factored is real-rational and surjective on the extended maginary axis. It is shown that our factorization problems can be reduced to solving a certain constrained Riccati equation, and that by examining some invariant ubspace of the associated Hamiltonian matrix there exists a unique solution to this equation. Finally, a state-space procedure to perform the factorization is proposed.

TUTOR301-a successful application of CAI for electrical engineering problem solving

A computer-assisted instruction (CAI) system was developed to teach electrical engineering problem solving at West Point, in an introductory course for nonengineers. The system, known as TUTOR301, takes the place of an individual tutor or coach in problem-solving methods. The simple form of solution text used minimized faculty time required to prepare solution scripts for the computer. The system's basic solution structure and program structure are described along with results gathered from five semesters of using this system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

1987 (39Th) IEEE Annual Conference of Electrical Engineering Problems in the Rubber and Plastics Industries

1987 (39Th) IEEE Annual Conference of Electrical Engineering Problems in the Rubber and Plastics Industries

A numerical method for calculation of transients in electric circuits

The present paper describes a numerical method for calculation of transients in electric circuits, using a step by step approach. For a small interval of times Δt=const, for each branchj of circuit one calculatesa j =R j +L j /Δt+Δt/C j ,β j =R j +Δt/C j andθ=Δt/C j . After that, for each interval Δt the current increments Δi jk , the currentsi jk =i jk−1+Δi jk and the capacitor’s voltageu cjk =u cjk−1+Δu cjk are calculated. The values of Δi jk are the roots of a system of simultaneous linear equations. The results of numerical calculation of transients by the proposed method do not differ from those obtained by analytical ones. The proposed method can be applied to a large number of problems in electrical engineering. A similar approach can be used for the calculation of transients in non-linear electric circuits and in other engineering disciplines (mechanics, thermodynamics, hydraulics etc.). Several numerical examples show how the proposed method can be applied.

The explicit inverses of general tridiagonal matrices and some applications

Tridiagonal or Jacobi matrices arise in several problems in electrical engineering as well as in different areas of mathematics. — However, there is little known on the inverses of such matrices. The explicit inverses of general tridiagonal matrices are presented in this paper. The method is based on an efficient implementation of Cramer's rule or Coate's flow graph technique and the theory of continuants. The technique is well suited to computer programming and is extremely efficient in symbolical analysis of electrical networks. It could also be efficiently implemented on a parallel computer. — Sensitivity studies or modern optimization techniques used in iterative network synthesis often require the computation of partial derivatives. The proposed technique permits these to be calculated analytically with great case.

Physical and geometric singularities modelling techniques for electrostatics and electromagnetism problems

Singularities appear in many problems in electrical engineering. They may be geometric (for example peaks, corners or ridges in Electrostatics) or physical (for example, changes in electromagnetic properties on thin depths). Classical numerical methods like finite elements technique are badly adapted to the simulation of these singularities. The authors present the techniques that they have developed to take these singularities into account. It consists of crack elements in eddy current non destructive testing, and of bilinear elements to control insulating materials. The particularity of these techniques is the association of a numerical resolution using finite elements technique, with an analytical resolution using singular elements. The authors recall, moreover, the techniques introduced in their Boundary Integral Equations package, in order to take into account geometrical singularities in electrostatic problems.

Multipole analysis of biomagnetic signals from the human leg

Computationally tractable solutions of the "inverse problem," the calculation of source currents from magnetic field data, are an essential component of biomagnetic studies. A multipole analysis suitable for any system that may be modeled as having all currents oriented along a given axis but not depending on the value of position coordinate on that axis is described. The lowest nonvanishing term is dipolar, and we specify a "best fit" criterion that estimates from data the dipole's magnitude and orientation together with its location in the transverse plane. The dipolar term is seen to give good fits to fields measured outside the normal relaxed lower human leg, even though the field data varies with position along the leg-axis. Reasons for this success are considered. The analysis is not specific to biomagnetic systems and may be useful in electrical engineering or geophysical problems.

1984 Thirty-Sixth Annual Conference on Electrical Engineering Problems in the Rubber and Plastics Industries

1984 Thirty-Sixth Annual Conference on Electrical Engineering Problems in the Rubber and Plastics Industries

Typical Applications of Microcomputer Spreadsheets to Electrical Engineering Problems

This paper describes typical applications of a popular spreadsheet program, SuperCalc, to a variety of electrical engineering problems using the IBM Personal Computer. The problems selected are series resonance in ac circuits, loop analysis of dc circuits, uniform plane wave propagation in conducting media, and the Runge-Kutta fourth-order numerical integration routine for initial value problems. These examples amply demonstrate how SuperCalc exploits the power of the microcomputer to automate many time-consuming "what if" computational chores by functioning as a visible processor with a "scrollable" on-line window on the machine-stored worksheet. The templates created for the application examples cited in the paper clearly underscore the fact that problem solving with SuperCalc is data-oriented rather than program-oriented, unlike problem solving with computers using the conventional approach. The paper also shows the integral relationship between spreadsheet and graphics software packages by using Micrograph (a graphics software) to extract graphic displays from the SuperCalc-generated numbers. Because of their versatility, visible numeric processors like SuperCalc offer interesting and exciting potential as important user-friendly tools in electrical engineering education.

1983 Thirty-Fifth Annual Conference of Electrical Engineering Problems in the Rubber and Plastics Industries

1983 Thirty-Fifth Annual Conference of Electrical Engineering Problems in the Rubber and Plastics Industries

Potential field of a stationary electric current in a stratified medium with a three-dimensional perturbing body

The potential of the electric field of a stationary current in a two-layered Earth is calculated by applying Green's formula in the case where a three-dimensional inhomogeneity of different conductivity is located in the basement of the layer. It is proved that the potential outside and inside the perturbing body can be calculated from the potential of an electric double-layer distributed on the surface of this body. An integral equation of the Fredholm type is derived for the surface density of the double-layer, together with some of its integral properties. A similar procedure can be applied to computing the magnetic anomalies of three-dimensional magnetized bodies, geothermal anomalies due to three-dimensional inhomogeneities of different heat conductivity, as well as to potential problems of theoretical electrical engineering.

A new iteration technique for solving stationary eddy-current problems using the method of finite differences

The paper describes a special block-successive overrelaxation technique for the numerical solution of 2-dimensional stationary eddy-current problems. The method proposed converges at least 10 times better than the complex point-SOR iteration which is usually used in solving large complex systems of equations. Numerical experience is given as well as application of the method to some problems of electrical engineering.

On the numerical analysis of eddy-current problems

Starting from Maxwell's equations, we derive a general variational formulation suitable for eddy-current problems in non-magnetic, non-moving conductors disposed in an arrangement of closed multiply-connected circuits. The related problem of open circuits is considered and the validity of the notion of impedance is discussed. A finite element approach is described and illustrated by two examples, one of them from a real problem in electrical engineering.

The Joint European Torus

The aim of the Joint European Torus (JET), now under construction near Abingdon, Oxfordshire, is to extend the study of magnetically-confined plasma to conditions similar to those needed in a power-producing fusion reactor. JET is much the largest single experiment in the European programme of nuclear-fusion research, and its design and construction have required a major effort of multinational collaboration, and the solution of many novel problems in mechanical and electrical engineering

Conservation Laws in Circuit Theory

This article presents a method for determining first integrals for nonlinear second-order differential equations arising in electrical engineering problems. It is based on finding a set of transformations under which the variational problem associated with the given differential equation is invariant. An example involving a simple R-C-L circuit is presented.