Search results

1 – 10 of 16
To view the access options for this content please click here
Article
Publication date: 1 September 2001

P. Girdinio and M. Nervi

The present work is about the development of automatic techniques for the optimisation of active shields for stationary magnetic fields. An active magnetic shield is…

Abstract

The present work is about the development of automatic techniques for the optimisation of active shields for stationary magnetic fields. An active magnetic shield is basically made by a number of coils, fed with suitably chosen currents. In this way a magnetic field as equal as possible to the disturbing one is generated. The resulting effect is the reduction of the disturbing field in the area of interest. To achieve reasonable results a stochastic optimisation procedure has been used to optimise the non linear part of the problem (i.e. the geometry of shielding coils); the linear part can be optimised “on the fly” in a much more straightforward way through the solution of a least squares problem. The stochastic optimiser used is based on the very fast simulated reannaling (VFSR), allowing to get a good optimum with a much reduced sampling of the objective function. It is used combining it with a deterministic optimiser (Nelder‐Mead simplex method), to get a faster optimisation process as soon as the valley of the global optimum is located. Basically the VFSR has a different point generating function and a different cooling schedule with respect to the standard Boltzmann annealing, but the concept is clearly the same.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 20 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 1 March 2000

P. Alotto, A. Castagnini, P. Girdinio and M. Nervi

An adaptive FEM for 3D magnetostatic problems involving non‐linear materials and permanent magnets is presented. The problems are formulated in terms of scalar potentials…

Abstract

An adaptive FEM for 3D magnetostatic problems involving non‐linear materials and permanent magnets is presented. The problems are formulated in terms of scalar potentials and discretized on a tetrahedral mesh using linear shape functions. Local error is estimated by approximately solving an independent differential problem in each tetrahedral element.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 1 November 2003

Qimi Jiang, Chun‐Hsien Chen and Li Pheng Khoo

Research effort to integrate an analysis module of inductive field into an eddy current NDT system to realise a hybrid technique, which is capable of automatically…

Abstract

Research effort to integrate an analysis module of inductive field into an eddy current NDT system to realise a hybrid technique, which is capable of automatically analysing the inductive field so as to set up the optimum parameters for the system, has not been well addressed. This paper describes the work that leads to the realization of such a hybrid technique. First, two finite element models are described. Next, an analytical algorithm based on these models is proposed. By integrating the algorithm into an eddy current NDT system, a smart hybrid technique can be realized. This is beneficial in setting up relevant parameters such as the working frequencies and the detection distance. Thus, the test precision can be improved. Taking a cylindrical inductive sensor as an example, some calculation results are provided to illustrate the analysis of the inductive field produced in an eddy current NDT system.

Details

Engineering Computations, vol. 20 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 1 February 1996

Jaroslav Mackerle

Presents a review on implementing finite element methods on supercomputers, workstations and PCs and gives main trends in hardware and software developments. An appendix…

Abstract

Presents a review on implementing finite element methods on supercomputers, workstations and PCs and gives main trends in hardware and software developments. An appendix included at the end of the paper presents a bibliography on the subjects retrospectively to 1985 and approximately 1,100 references are listed.

Details

Engineering Computations, vol. 13 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 1 August 2001

Jaroslav Mackerle

Gives a bibliographical review of the error estimates and adaptive finite element methods from the theoretical as well as the application point of view. The bibliography…

Abstract

Gives a bibliographical review of the error estimates and adaptive finite element methods from the theoretical as well as the application point of view. The bibliography at the end contains 2,177 references to papers, conference proceedings and theses/dissertations dealing with the subjects that were published in 1990‐2000.

Details

Engineering Computations, vol. 18 no. 5/6
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 1 October 2006

S. Subramanian and R. Bhuvaneswari

The power transformer is one of the most important pieces of equipment in a power system. The necessity for the optimum design of a power transformer arises because the…

Abstract

Purpose

The power transformer is one of the most important pieces of equipment in a power system. The necessity for the optimum design of a power transformer arises because the design chosen should satisfy all the limitations and restrictions placed on it. This paper presents an improved fast evolutionary programming (IFEP) technique for the optimal design of a three‐phase power transformer.

Design/methodology/approach

The optimization of the transformer design problem is formulated as an NLP problem, expressing the objective and constraint functions in terms of the selected independent variables. Here the cost of the transformer is considered as the objective function and is the sum of material cost of stampings and copper windings, cost of cooling tube arrangements, cost of cooling medium, insulation cost and labour cost. A computer program is written from which the optimal design parameters are obtained. For optimization, the classical evolutionary programming (CEP) technique and its variant the IFEP technique are used and the results are compared.

Findings

The application of CEP and IFEP for transformer design has been demonstrated on two test cases. It has been observed that this IFEP outperforms the CEP in obtaining the optimum design of transformers of smaller as well as larger ratings in terms of execution time, convergence rate, quality and success rate.

Originality/value

The proposed method results in the economical design of a three‐phase power transformer which can significantly reduce the cost of manufacturing transformers.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 25 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 1 March 2000

P. Alotto, P. Girdinio, G. Molinari and M. Nervi

Discusses the combined use of a modified version of the global optimization technique simulated annealing and a deterministic optimizer based on Shor’s method. Describes…

Abstract

Discusses the combined use of a modified version of the global optimization technique simulated annealing and a deterministic optimizer based on Shor’s method. Describes the features of the proposed technique and reports on some results regarding a standard benchmark problem.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 1 October 2006

F. Delfino, P. Girdinio, L. Minervini and M. Nervi

To provide a detailed investigation about methods commonly used for the computation of high‐frequency electromagnetic fields in the vicinity of obstacles that can reflect…

Abstract

Purpose

To provide a detailed investigation about methods commonly used for the computation of high‐frequency electromagnetic fields in the vicinity of obstacles that can reflect or diffract them. This is useful to create an elementary block that can be used to evaluate with a high accuracy the propagation of high‐frequency electromagnetic waves in real urban environment.

Design/methodology/approach

The approach is based on a realistic application of the asymptotic theory of the uniform theory of diffraction. Therefore, the effect of material roughness and its electromagnetic properties on the reflection are taken into account.

Findings

Provides information about the mechanisms involved in electromagnetic field propagation in urban environment, and the relative importance of each one.

Research limitations/implications

In urban environment the buildings obviously have finite dimensions. The diffraction equations examined in the paper are strictly valid only in the case of infinite wedges; therefore, the behaviour of real building edges has not been taken rigorously into account.

Practical implications

A source of information for researchers interested in the development of a simulator for the electromagnetic propagation in urban environment.

Originality/value

This paper is aimed at providing to researchers, in a more comprehensive way, all information needed for the study of electromagnetic propagation in an environment containing many close scatterers.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 25 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 1 June 2005

K. Hollaus, B. Wagner and O. Bíró

The aim of the present work is to find an efficient solution concerning the computational effort of quasi‐static electric field (QSEF) problems involving anisotropic…

Abstract

Purpose

The aim of the present work is to find an efficient solution concerning the computational effort of quasi‐static electric field (QSEF) problems involving anisotropic conductivity and permittivity in the frequency domain.

Design/methodology/approach

Numerical simulations are carried out with tetrahedral nodal finite elements of first‐ and second‐order and with Withney elements. The solution of the boundary value problem with the aid of the electric scalar potential approximated by nodal finite elements is compared with those by the electric current vector potential represented by edge finite elements.

Findings

The simulation with an electric current vector potential approximated by the edge elements of first‐order prevail over that by the electric scalar potential approximated by nodal elements of second‐order concerning the memory requirements and the computation time at comparable accuracy.

Originality/value

The application of edge finite elements to solve QSEF problems considering an anisotropic complex conductivity in 3D.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 1 March 2005

Kent R. Davey

The purpose of this paper is to demonstrate how Monte Carlo methods can be applied to the solution of field theory problems.

Abstract

Purpose

The purpose of this paper is to demonstrate how Monte Carlo methods can be applied to the solution of field theory problems.

Design/methodology/approach

This objective is achieved by building insight from Laplacian field problems. The point solution of a Laplacian field problem can be viewed as the solid angle average of the Dirichlet potentials from that point. Alternatively it can be viewed as the average of the termination potential of a number of random walks. Poisson and Helmholtz equations add the complexity of collecting a number of packets along this walk, and noting the termination of a random walk at a Dirichlet boundary.

Findings

When approached as a Monte Carlo problem, Poisson type problems can be interpreted as collecting and summing source packets representative of current or charge. Helmholtz problems involve the multiplication of packets of information modified by a multiplier reflecting the conductivity of the medium.

Practical implications

This method naturally lends itself to parallel processing computers.

Originality/value

This is the first paper to explore random walk solutions for all classes of eddy current problems, including those involving velocity. In problems involving velocity, the random walk direction enters depending on the walk direction with respect to the local velocity.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

1 – 10 of 16