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Article
Publication date: 1 April 1995

T.V. Yioultsis and T.D. Tsiboukis

The importance of vector finite elements for electromagnetic field computation has been extensively demonstrated in the recent literature. In this study we present a systematic…

40

Abstract

The importance of vector finite elements for electromagnetic field computation has been extensively demonstrated in the recent literature. In this study we present a systematic approach to the construction of higher order vector shape functions based on dual vector expansions. The methodology presented results in explicit forms for second order elements. Moreover, it reveals the presence of a whole family of vector finite elements depending on the choice of the degrees of freedom and a set of arbitrary parameters.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 14 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 September 1999

Z. Ren and N. Ida

Several second order edge elements have been applied to solving magnetostatic problems. The performances of these elements are compared through an example of magnetic circuit. In…

201

Abstract

Several second order edge elements have been applied to solving magnetostatic problems. The performances of these elements are compared through an example of magnetic circuit. In order to ensure the compatibility of the system equations and hence the convergence, the current density is represented by the curl of a source field. This avoids an explicit gauge condition which is cumbersome in the case of high order elements.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 18 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 February 1998

N.V. Kantartzis, T.V. Yioultsis and T.D. Tsiboukis

The narrow‐wall inclined‐slot coupling between rectangular waveguides from an H‐plane T‐junction, is numerically analysed, for the first time, via a 3D generalised locally…

221

Abstract

The narrow‐wall inclined‐slot coupling between rectangular waveguides from an H‐plane T‐junction, is numerically analysed, for the first time, via a 3D generalised locally conformed FDTD technique. The structure is excited by a combined pulsed modulated TEmn mode scheme which enables the imposition of higher‐order ABCs or advanced PMLs very close to the slot, thus achieving significant reduction of the computational demands. Numerical results, which are shown to be in very good agreement with those obtained by independent scientific research, indicate that the proposed technique can sufficiently handle this class of problems.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 17 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 June 1998

I.T. Rekanos, T.V. Yioultsis and T.D. Tsiboukis

The evaluation of the conductivity profile of layered metallic structures is performed via the inversion of the impedance of a circular air cored probe coil of rectangular cross…

200

Abstract

The evaluation of the conductivity profile of layered metallic structures is performed via the inversion of the impedance of a circular air cored probe coil of rectangular cross section. The inversion approach is based on the implementation of generalised radial basis function neural networks. The choice of the size of the network and the evaluation of its weights are handled by the orthogonal least squares learning algorithm. The merits of the proposed method are illustrated in the light of two examples concerning non‐destructive testing applications.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 17 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 October 2018

Abhinav Sharma and Sanjay Mathur

The purpose of this paper is to present and solve the problem of adaptive beamforming (ABF) for a uniform linear array (ULA) as an optimization problem. ABF mainly concerns with…

121

Abstract

Purpose

The purpose of this paper is to present and solve the problem of adaptive beamforming (ABF) for a uniform linear array (ULA) as an optimization problem. ABF mainly concerns with estimation of weights of antenna array so as to direct the major lobe in the direction of desired user and nulls in the direction of interfering signals with reduced side lobe level (SLL).

Design/methodology/approach

The potential of gravitational search algorithm is explored to optimize multi-objective fitness function for ABF using MATLAB software.

Findings

The performance of the algorithm has been compared by considering different number of interference signals at different power levels. The proposed algorithm presents good convergence rate and accurate steering of main lobe and nulls with reduced SLL compared to the well-known ABF technique, namely, minimum variance distortionless response (MVDR) and previously reported results. The simulation results are presented in tabular form.

Research limitations/implications

The present work is limited to simulation. The researchers are encouraged to solve the problem of ABF using the proposed approach in hardware.

Originality/value

The application of proposed algorithm is to optimize multi-objective function for ABF with reduced SLL in linear antenna arrays.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 6
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 March 2002

Paolo Fernandes and Mirco Raffetto

From a theoretical point of view the question of spurious modes has been regarded as a closed problem. However, in this paper we show that even a precise definition of…

306

Abstract

From a theoretical point of view the question of spurious modes has been regarded as a closed problem. However, in this paper we show that even a precise definition of spurious‐free approximation was lacking. Hence, a sound definition of spurious‐free finite element method is given and a set of necessary and sufficient conditions ensuring that a finite element method is spurious‐free in the defined sense is stated. A critical comparison between the proposed theory and the currently accepted one is then carried out and existing counterexamples to the latter are pointed out. Comparison with an older theory leads to another set of necessary and sufficient conditions providing a better grasp of the key feature a finite element space must have to rule out spurious modes. The impact of the proposed theory is stressed, showing that Nedelec's tetrahedral edge elements of all orders provide spurious‐free approximations in all conditions of practical interest. Finally, it is shown, for the first time to the best of authors’ knowledge, that also many high‐order edge elements, recently proposed in the engineering literature for the analysis of electromagnetic problems, provide the same kind of reliable approximation.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 21 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 December 2005

N. Canouet, L. Fezoui and S. Piperno

The use of the prominent FDTD method for the time domain solution of electromagnetic wave propagation past devices with small geometrical details can require very fine grids and…

769

Abstract

Purpose

The use of the prominent FDTD method for the time domain solution of electromagnetic wave propagation past devices with small geometrical details can require very fine grids and can lead to very important computational time and storage. The purpose is to develop a numerical method able to handle possibly non‐conforming locally refined grids, based on portions of Cartesian grids in order to use existing pre‐ and post‐processing tools.

Design/methodology/approach

A Discontinuous Galerkin method is built based on bricks and its stability, accuracy and efficiency are proved.

Findings

It is found to be possible to conserve exactly the electromagnetic energy and weakly preserves the divergence of the fields (on conforming grids). For non‐conforming grids, the local sets of basis functions are enriched at subgrid interfaces in order to get rid of possible spurious wave reflections.

Research limitations/implications

Although the dispersion analysis is incomplete, the numerical results are really encouraging it is shown the proposed numerical method makes it possible to handle devices with extremely small details. Further investigations are possible with different, higher‐order discontinuous finite elements.

Originality/value

This paper can be of great value for people wanting to migrate from FDTD methods to more up to date time‐domain methods, while conserving existing pre‐ and post‐processing tools.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 16 April 2020

Stamatis A. Amanatiadis, Theodoros Zygiridis and Nikolaos V. Kantartzis

The coupling characteristics between adjacent circuits are crucial for their efficient design in terms of electromagnetic compatibility features. Specifically, either the wireless…

107

Abstract

Purpose

The coupling characteristics between adjacent circuits are crucial for their efficient design in terms of electromagnetic compatibility features. Specifically, either the wireless power transfer can be enhanced or the interference can be limited. This paper aims to the extraction of the coupling characteristics of surface plasmon polariton waves propagating onto graphene layers to facilitate the telecommunication system design for advanced THz applications.

Design/methodology/approach

The surface conductivity of graphene is described at the far-infrared spectrum and modelled accurately by means of a properly modified finite-difference time-domain) scheme. Then, a series of numerical simulations for different coupling setups is conducted to extract an accurate generalised parametric coupling model that is dependent explicitly on the fundamental propagation features of graphene.

Findings

The coupling coefficients of two basic waveguiding setups are examined thoroughly. The initial one includes two parallel graphene layers of infinite dimensions, and it is observed that the coupling is influenced via the ratio between their distances to the confinement of the surface wave. The second scenario is composed of graphene microstrips that are parallel to their small edge, namely, microstrip width. The extracted numerical results indicate that the coupling coefficient depends on the ratio between widths to wavelength.

Originality/value

The accurate extraction of the generalised coupling coefficients for graphene surface wave circuits is conducted in this work via an adjustable numerical technique for a novel family of plasmonic couplers. It is derived that only the fundamental propagation features of graphene, such as the wavelength and the confinement of the surface waves, have an effect on the coupling calculation, thus enabling a consistent electromagnetic compatibility study.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 39 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 4 September 2017

Jennifer Susanne Dutiné, Markus Clemens and Sebastian Schöps

Discretizing the magnetic vector potential formulation of eddy current problems in space results in an infinitely stiff differential algebraic equation system that is integrated…

125

Abstract

Purpose

Discretizing the magnetic vector potential formulation of eddy current problems in space results in an infinitely stiff differential algebraic equation system that is integrated in time using implicit time integration methods. Applying a generalized Schur complement to the differential algebraic equation system yields an ordinary differential equation (ODE) system. This ODE system can be integrated in time using explicit time integration schemes by which the solution of high-dimensional nonlinear algebraic systems of equations is avoided. The purpose of this paper is to further investigate the explicit time integration of eddy current problems.

Design/methodology/approach

The resulting magnetoquasistatic Schur complement ODE system is integrated in time using the explicit Euler method taking into account the Courant–Friedrich–Levy (CFL) stability criterion. The maximum stable CFL time step can be rather small for magnetoquasistatic field problems owing to its proportionality to the smallest edge length in the mesh. Ferromagnetic materials require updating the reluctivity matrix in nonlinear material in every time step. Because of the small time-step size, it is proposed to only selectively update the reluctivity matrix, keeping it constant for as many time steps as possible.

Findings

Numerical simulations of the TEAM 10 benchmark problem show that the proposed selective update strategy decreases computation time while maintaining good accuracy for different dynamics of the source current excitation.

Originality/value

The explicit time integration of the Schur complement vector potential formulation of the eddy current problem is accelerated by updating the reluctivity matrix selectively. A strategy for this is proposed and investigated.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 5 May 2015

Łukasz Knypiński, Lech Nowak and Cezary Jedryczka

The purpose of this paper is to elaborate the methodology and software for the optimization of rotor structure of the line-start permanent magnet synchronous motor (LSPMSM). To…

304

Abstract

Purpose

The purpose of this paper is to elaborate the methodology and software for the optimization of rotor structure of the line-start permanent magnet synchronous motor (LSPMSM). To prove usefulness of presented approach the case study problem has been solved.

Design/methodology/approach

The modified particle swarm optimization (PSO) algorithm has been employed for the optimization of LSPMSM. The optimization solver has been elaborated in Delphi environment. The software consists of two modules: an optimization solver and a numerical model of LSPMSM. The model of the considered machine has been developed in the ANSYS Maxwell environment. In the optimization procedure the objective function has been based on maximizing efficiency and power factor.

Findings

Obtained results show that modified PSO algorithm can be successfully applied for the optimization of the rotor structure of LSPMSM. This software can be used as a design tool to improve the performance of LSPMSM. The results of studied case problem illustrate that it is possible to optimize rotor of LSPMSM to achieve good self-starting properties with simultaneous minimization of usage of permanent magnet material.

Research limitations/implications

Both, the simpler lumped parameters model and more advanced field model of the motor were tested. Presented comparison to the results of the finite element analysis (FEA) shows that for considered in the paper the case study problem the accuracy of circuit model is acceptable.

Practical implications

Presented approach and developed software can be used as an effective design tool to improve the performance of LSPMSM.

Originality/value

The paper offers appropriate approach for optimizing the permanent magnet synchronous motors having ability to start by direct connection to the grid.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 3
Type: Research Article
ISSN: 0332-1649

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