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  • Articles  (199)
  • Emerald  (199)
  • American Association for the Advancement of Science (AAAS)
  • American Association of Petroleum Geologists (AAPG)
  • Nature Publishing Group
  • 1995-1999  (199)
  • Mathematics  (199)
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  • Articles  (199)
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  • 1
    Electronic Resource
    Electronic Resource
    Some considerations about the perfectly matched layer for static fields (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 337-347 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper discusses the perfectly matched layer method recently proposed for the computation of static or quasistatic fields in open boundaries. In particular it is shown how the method can be derived by means of a particular co-ordinate transformation applied to a finite-size isotropic domain surrounding the system of interest. The method is therefore equivalent to a trivial truncation from the point of view of both accuracy and computing time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274900
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  • 2
    Electronic Resource
    Electronic Resource
    On the Lorenz gauge (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 323-336 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Although edge elements satisfactorily solve the eddy current problem, formulations allowing the use of standard, node-based elements, are still looked for. But "well-posed" formulations have been elusive up to now. We propose one, based on a particular gauge, div(s a)=-s 2µ v, close to the "Lorenz gauge" of several recent publications, but not identical if one does not assume a piecewise uniform conductivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274892
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  • 3
    Electronic Resource
    Electronic Resource
    The charge-tube method for space-charge simulations (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 548-555 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The charge-tube method is an accurate way of assigning the space-charge of a beam in computational simulations of charged particle systems. The method is described and is compared with the traditional charge-cell method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296528
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  • 4
    Electronic Resource
    Electronic Resource
    Fuzzy control of current in thyristor DC drive (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 675-683 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In the paper an application of fuzzy logic controller (FLC) for control of thyristor DC drive is presented. During synthesis of the FLC a robustness against variation of structure of the current control plant was taken into account. Comparison between the fuzzy control system and an ordinary digital control system, carried out by simulation method, proved that FLC as a robust controller gives better performance in the range where non-linearity and parameter variation is observed. The simulation results were confirmed by the laboratory experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296861
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  • 5
    Electronic Resource
    Electronic Resource
    An approach via the central limit theorem to randomization of Fourier's transform (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 38-42 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: By using the central limit theorem, it is possible to consider the Fourier's transform of a stochastic process with independent increments as a Gaussian random variable of which the mathematical expectation and the variance are respectively integrals of the mean and the variance of this process. One can then use this result to analyze the statistical properties of linear feedback systems in the frequency domain, that is to say in terms of transfer functions. The advantage of this approach is that one can deal with linear systems subject to squared white noises, in a very simple manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910236975
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  • 6
    Electronic Resource
    Electronic Resource
    Reduced-order method for dielectric resonators using FEM and CFH (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 84-94 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper describes an efficient reduced-order method for the analysis of cylindrical dielectric resonators with an inhomogeneous dielectric medium. The field equations are formulated using the Laplace-domain finite element method and are reduced to lower-order models using the complex frequency hopping (CFH) technique. CFH is a moment matching technique which has been used successfully in the circuit simulation area for the solution of a large set of ordinary differential equations. The proposed technique is faster than the conventional approach by one to three orders of magnitude. The results are compared with those of other numerical methods available in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910237019
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  • 7
    Electronic Resource
    Electronic Resource
    Quasi-variational inequality and shape optimization for solution of a free boundary problem (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 143-164 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Electrical potentials in a junction field transistor can be calculated using a simplified model based on a complete depletion assumption. This gives rise to a free boundary problem. We show here how we can approximate this problem with a quasi-variational inequality technique and the shape optimization method. A detailed analysis of these methods is presented. Using some numerical experiments we compare our results with the solution of the discrete drift-diffusion system, accomplished with a Gummel-like algorithm. The numerical results suggest that the methods proposed here work successfully and that the shape optimization technique provides a reasonably free boundary without excessive iterations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264154
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  • 8
    Electronic Resource
    Electronic Resource
    Fast analytical model of induction motor for approaching rotor eccentricity (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 570-586 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Deals with the problem of the electromagnetic torque calculation in the case of either nonuniformity of the air-gap or eccentricity of the rotor. The electromagnetic field distributions have been evaluated for drag-cup motors. An analytical model has been introduced for linear motor based on the variation method for magnetic flux density magnitudes. The total torque and its components have been evaluated for the motors chosen. The decrease of the electromagnetic torque and increase of eddy-current losses have been discussed due to either rotor circular asymmetry or its eccentricity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296582
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  • 9
    Electronic Resource
    Electronic Resource
    Finite element analysis of electromagnetic torque saturation harmonics in a squirrel cage machine (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 619-628 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The electromagnetic torque oscillations caused by saturation harmonics in a squirrel cage machine are analysed. Special attention is paid to the most important saturation harmonic of alternating field that has three times as many poles as fundamental harmonic and three times its frequency. The operations of the machine as a motor and as a self-excited generator have been investigated. The 2D finite element time-stepping method has been applied to the analysis of a particular machine performance. The finite element equations are coupled with circuits equations which describe the winding connections. The skew of the rotor slots is taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296654
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  • 10
    Electronic Resource
    Electronic Resource
    Bispectrum estimation using AR-modelling (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 43-60 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper we present a new autoregressive (AR) method for bispectrum estimation defined in terms of its third-moment sequence. The method is based on the segmentation of data into coupled records, and can be considered to be a modification of the "third order recursion method"(TOR). Its foundation resides in considering the data of the process at the left and the right of each record (needed for the calculation of third moment sequence) as not null and taking them as the data corresponding to the preceding and succeeding record respectively. Several simulated examples show that this method allows model parameters to be obtained with greater precision, most of all when only few data are available per record. The influence of factors such as number of data and records, model order, and added white and coloured Gaussian noise on the parameters' estimation is also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910236984
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  • 11
    Electronic Resource
    Electronic Resource
    The role of the potentials in electromagnetism (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 103-119 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: There are two conflicting views about electromagnetic phenomena. The first is based on the action between stationary and moving particles of electric charge and the second on energy distributions in electric and magnetic fields. The difference between these approaches is seen most clearly in the roles assigned to the potentials. According to the particle view the potentials convey the force from one particle to another, whereas in the field approach the potentials are system parameters related to the field energy. The article compares the two views and concludes that the particle view faces impossible difficulties because it ascribes local significance to quantities which are unobservable and conflicts with the quantum-mechanical understanding of charge as a statistical distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264136
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  • 12
    Electronic Resource
    Electronic Resource
    Application of modified FBT algorithm in induction motor series optimal design (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 165-174 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Some improvements are made for Fast Boundary Tracking algorithm according to the practice of the electric machine design in the paper. As discrete variables play a dominant role in determining the values of the objective function and the constraint functions in the motor optimal design, the algorithm is improved in the paper. From the algorithm, a software is developed and used for the optimal design of the induction motors of Y series. The results show that the algorithm is reliable and efficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264145
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  • 13
    Electronic Resource
    Electronic Resource
    Numerical investigation of a gas dynamic model for charge transport in semiconductors (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 6-37 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A mathematical gas dynamic model for semiconductor devices is numerically analysed. The well-known ballistic diode problem is taken as an example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910236966
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  • 14
    Electronic Resource
    Electronic Resource
    Remark on Maxwell's divergence equations (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 77-83 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The divergence equations in Maxwell's theory are Gauss law and the statement that magnetic monopoles do not exist; from this point of view these two equations are fundamental. However, from a practical point of view, it is generally believed that Maxwell's divergence equations are redundant and may be ignored provided that they are satisfied at some time t-0. It has been proved recently that this idea is not correct for boundary-initial value problems. To make mathematical arguments more accessible, we analyse here the role of the divergence equations in the framework of 2D-electromagnetism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910237000
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  • 15
    Electronic Resource
    Electronic Resource
    Estimating unique solutions of DC transistor circuits (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 132-142 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: For each natural n let Fn denote the collection of mappings of Rn onto itself defined by: F ?Fn if and only if there exist n strictly monotone increasing functions fk mapping R onto itself such that for each x =[x1, ..., xn]T ? Rn, F(x) = [f1(x1), ..., fn(xn)]T. The following new property of the class P0 of matices is proved: a real n × n matrix A belongs to P0 if and only if for every G, H ? Fn the set S0 = { x ? Rn : - G(x) =Ax = - H(x) } is bounded. As an illustration of this property a method of estimating the unique solution of the nonlinear equation F(x) + A(x) =b describing the large class of DC transistor circuits is developed. This can improve the efficiency of known computation algorithms. Numerical examples of transistor circuits illustrate in detail how the method works in practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264163
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  • 16
    Electronic Resource
    Electronic Resource
    The optimisation of electromagnetic devices using niching genetic algorithms (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 285-297 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The use of niching genetic algorithms can provide a method of a more widespread search of the design space for a device than more conventional methods. It provides, in effect, a breadth first rather than a depth first search. Thus several alternative designs may be evaluated in parallel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274865
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  • 17
    Electronic Resource
    Electronic Resource
    STEP standard's evaluation for modeling in electromagnetism (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 311-323 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The new set of standards ISO 10303 "STEP" makes it possible to give a complete representation of a product, using the description language EXPRESS. A part of STEP is devoted to the finite element analysis. This paper presents a brief overview of the architecture and the methodology of STEP and EXPRESS, with special attention to the part concerning the finite element analysis. The possibility to use it in modelling electromagnetic phenomena will be discussed. An example showing the description of a typical problem in electromagnetism will be implemented using EXPRESS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274883
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  • 18
    Electronic Resource
    Electronic Resource
    Contribution to the finite element analysis of eddy-currents in multi-conductor windings surrounded by magnetically non-linear media (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 668-674 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In the finite element analysis of electrical machines the multi-conductor winding in a stator slot is usually modeled simply by a single conductor with constant current density. The size of a finite element problem due to the precise modeling of eddy currents in the multi-conductor windings can be much larger compared to the single conductor model. The paper investigates a new FEM approach for the consideration of eddy-currents in multi-conductor windings surrounded by nonlinear media, a case typical in electrical machinery. The method, called elimination of inner nodes, is evaluated in the paper as a possible solution for multi conductor eddy current problems. The paper presents examples and concludes in what circumstances the method of elimination is efficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296771
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  • 19
    Electronic Resource
    Electronic Resource
    Voltage ranking using artificial neural network (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 587-599 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Voltage ranking attempts to rank busbar voltage deviations from their normally accepted security margins based on a set of performance indices (PI), without performing a full load flow. Existing methods suffer from either masking effects or long computation time. In this paper, an artificial neural network method is proposed for voltage ranking. Counterpropagation network (CPN) has been employed to overcome the problems listed above. A variety of input features are used with the aim of lowering the dimension of the proposed ANN to make it applicable for large power systems. The method is tested on two example systems, a five-bus system and a 71-bus system with very encouraging results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296618
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  • 20
    Electronic Resource
    Electronic Resource
    Optimizing ferromagnetic characteristics to reduce Newton iterations (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 629-637 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The standard Newton iteration scheme to solve a non-linear system of equations obtained from the finite element methods is based on the updating of the field dependent element reluctivity. Usually, the manufacturer of the ferromagnetic material provides a BH-characteristic as diagram or in the form of a table of data samples. The influence of the material properties, in particular their accurate numerical representation, is significant for the rate of convergence during the Newton iterations. Here, a numerical optimization aiming at a technically smooth non-linear characteristic is performed to obtain a higher rate of convergence of the Newton iteration scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296672
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  • 21
    Electronic Resource
    Electronic Resource
    Models of magnetic circuits and their equivalent electrical diagrams (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 600-610 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents a method of creating electrical equivalent diagrams of magnetic circuits. The method is based on bond-graph techniques, using flux derivative as flow variable. Couplings between magnetic and electric part of the system are represented by gyrators. Simple models of magnetic branches, including non-linear effects due to saturation, hysteresis and eddy currents, are presented. These models can be easily combined into magnetic circuit models, which can be transformed into dual electric equivalent circuit. Various equivalent circuits of transformers are discussed. The proposed models are simple and particularly useful for system-level simulation of power electronic and motion control systems with magnetic elements. These models can be easily developed if needed. Theoretical considerations are illustrated by examples of digital simulation and experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296636
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  • 22
    Electronic Resource
    Electronic Resource
    Highly non-linear field diffusion in HTC superconducting tapes (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 215-224 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents an extension to previous work on modelling AC losses in high-temperature superconducting tapes as a highly non-linear diffusion process. Following successful formulation for a bulk superconductor the presence of silver in a tape has now been included, using a "sandwich" model, to represent more realistically the practical arrangement. The results of the extended 1-D model are included and a new 2-D scheme is described using finite difference formulation. Effects of non-linearity are emphasised.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264217
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  • 23
    Electronic Resource
    Electronic Resource
    Computation of magnetostatic field using second order edge elements in 3D (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 361-371 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: 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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    URL: http://dx.doi.org/10.1108/03321649910274928
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  • 24
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    Non destructive evaluation in the time domain (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 422-435 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper a method is presented for an efficient solution of the direct problem (find the scattered field for a given thin crack and driving field) in the time domain. This is a fundamental step in any non destructive evaluation problem. Two different approaches, one in the time domain and the other based on Fourier analysis, are used and compared with reference to a configuration for which some experimental results are available. The advantages and drawbacks of the two approaches are briefly discussed.
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    URL: http://dx.doi.org/10.1108/03321649910275008
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  • 25
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    Effective reluctivity calculation versus time step calculation of magnetic shielding with ferromagnetic material (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 410-421 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The calculation of magnetic shielding with ferromagnetic material by an effective reluctivity method and a time step method based on the finite element calculation is investigated. The calculation results of both methods are compared with measurement results and with each other in order to check their reliability and accuracy. It turns out that both methods give similar results for the field inside the shielding material, whereas in the surrounding air the effective reluctivity method gives more accurate results than the present time step method.
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    URL: http://dx.doi.org/10.1108/03321649910274973
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  • 26
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    Anisotropic vector Preisach model and magnetic field solutions (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 458-468 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The implementation of a vector Preisach model for the modelling of anisotropic hysteretic soft magnetic materials is outlined. Some comparisons with measurements on alternate and rotational magnetic field excitations are shown. The hysteresis model is inserted inside a two-dimensional finite element solver formulated in terms of magnetic vector potential and nonlinear solution is handled by means of the fixed point method with H-scheme. Results obtained on a two-dimensional geometry are described and discussed.
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    URL: http://dx.doi.org/10.1108/03321649910275107
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  • 27
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    Estimation of 3-D eddy currents in conducting laminations by an anisotropic conductivity and a 1-D analytical model (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 494-503 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: To circumvent the high computational costs of modelling each lamination to compute the eddy current distribution in three dimensions in conducting laminations, a simple method has been developed. The laminar nature of the eddy currents due to the magnetic leakage field has been considered by applying an anisotropic conductivity with zero or very low value in the direction normal to the laminations. This yields an overall field distribution serving as basis. In a second step, the much smaller eddy current loops caused by the main magnetic flux parallel to the laminations have been taken into consideration by a one-dimensional analytical model. Nonlinearity is neglected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910275170
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  • 28
    Electronic Resource
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    Numerical modelling of electrodynamic loudspeakers (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 504-514 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A new method for the numerical computation of the dynamic behaviour of electro-dynamic loudspeakers is presented. The numerical scheme, based on the finite element method (FEM), allows the simulation of coupled magnetic, mechanical and acoustic fields. The obtained simulation results are in good agreement with measured data.
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    URL: http://dx.doi.org/10.1108/03321649910275189
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  • 29
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    Identification of 1-D magnetic field profiles in high current plasmas (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 275-284 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The identification of magnetic field profiles is crucial in many applications where a direct measurement is difficult. We discuss here a technique, based on the injection of charged particles in the region under examination, which promises to be an innovative and effective tool in the analysis of 1-D field profiles in high current plasma discharges. After the decription of the inverse problem related to the field construction, we consider a suitable discrete identification scheme, and analyze some properties of the latter. The field map in the interest region is reconstructed via a minimization procedure, which identifies the coefficient of a well-suited expansion for the field. In particular, we discuss the precision and robustness of the identification procedure, with respect to the chosen optimization scheme, the amount of data, the order in the field expansion, and the influence of noise on the data.
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    URL: http://dx.doi.org/10.1108/03321649910274829
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    Comparison of quasi minimal residual and bi-conjugate gradient iterative methods to solve complex symmetric systems arising from time-harmonic magnetic simulations (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 298-310 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Finite element discretizations of low-frequency, time-harmonic magnetic problems lead to sparse, complex symmetric systems of linear equations. The question arises which Krylov subspace methods are appropriate to solve such systems. The quasi minimal residual method combines a constant amount of work and storage per iteration step with a smooth convergence history. These advantages are obtained by building a quasi minimal residual approach on top of a Lanczos process to construct the search space. Solving the complex systems by transforming them to equivalent real ones of double dimension has to be avoided as such real systems have spectra that are less favourable for the convergence of Krylov-based methods. Numerical experiments are performed on electromagnetic engineering problems to compare the quasi minimal residual method to the bi-conjugate gradient method and the generalized minimal residual method.
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    URL: http://dx.doi.org/10.1108/03321649910274874
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    Selected ideas of the theory of non-linear electrical circuits (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 204-214 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper an outline of the development of methods for the analysis of non-linear circuits is presented. Non-inert and inert elements have been discerned and an inertia measure has been proposed. For this purpose, an exponential function with time constant T equal to TR, TL, or TC is formulated for an element of type R, L, or C, respectively. In circuits with the imposed cause, which varies sinusoidally in time with period Te, the following situations are distinguished and considered: Te » T; Te « T; and Te ˜ T. In the first case, the effect changes in time according to the non-linear characteristic of the element. In the second case, the respective circuit is referred to as the "quasi-linear", because for the sinusoidal cause the effect is also sinusoidal. In the third case, the hysteresis occurs and the effect is a two-valued function. The hysteresis effect occurs also in resistive elements.
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    Image reconstruction from real scattering data (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 372-384 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper deals with the inverse scattering problem of reconstructing the material properties of perfectly conducting or dielectric cylindrical objects. The material properties are reconstructed from measured far-field scattering data provided by the Electromagnetics Technology Division, AFRL/SNH, 31 Grenier Street, Hanscom AFB, MA 01731-3010. The measured data have to be calibrated for use in our reconstruction algorithm. The inverse scattering problem formulated as unconstrained nonlinear optimization problem is numerically solved using an iterative scheme with a variable calibration factor which will be determined during the optimization process. Numerical examples show the successful application of the method to the measured data.
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    Computationally efficient rate dependent hysteresis model (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 445-457 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A fast dynamic hysteresis model is constructed based on the classical Preisach model and a differential equation which delays its input with respect to the actual value to encompass dynamic effects such as eddy currents and domain wall displacement. It is applied to describe the magnetic behaviour of both grain oriented and nonoriented electrical steel sheets. The results of numerical simulations are compared to experiment and power loss prediction is performed.
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    B-H characteristic extraction using devices with non-uniform field (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 469-482 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper describes an efficient method to extract the B-H nonlinear characteristic from the experimental flux-current F-I data obtained using a non-uniform magnetic field device. Both functions are monotonically piecewise linear approximated with the same number of breakpoints. The method was successfully applied to characterize the ribbon core material of a fluxset magnetic field sector. In this case the hysteresis loop and the lumped magnetic circuit were extracted. Comparison with experimental results validates the proposed method.
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    Capacitive effect models for a magnetic field sensor (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 515-527 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents an efficient modeling technique for the fluxset magnetic field sensor. Using separate numerical solutions for the electric and magnetic fields, an equivalent SPICE circuit is extracted in the postprocessing phase. The main contribution of the paper is the technique used to model the distributed capacitive effects in insulation between coils, by concentrating them in an "Extended II scheme", an infinite circuit which is optimally reduced to a finite one. The results are in qualitative agreement with the experimental ones.
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    Modelling and computer simulation study of laser-plasma interaction in semiconductor (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 187-203 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Computer simulations were done extensively in order to study non-linear dynamics of laser-plasma interaction in InSb semiconductor. We constructed the modified Duffing kind of non-linear semiconductor plasma oscillator equation. Collision frequency is found to be dominant parameter to influence the bifurcation, chaos, hysteresis and bistable effects of plasma wave. Small windows of higher period cascade above the critical value of laser parameter (a1a2) in the chaos region are observed. Laser-plasma exhibits too much chaotic regime at lower value of laser driving frequency (d). Hysteresis and bistable regions of plasma wave are presented and the conditions for their occurence are identified. The unstable regions completely merge at higher value of effective collision frequency (?).
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    BEM-computation of antenna near field reactions on conducting materials using curvilinear edge elements (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 348-360 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A boundary element method in terms of the field variables is applied to three-dimensional electromagnetic scattering problems. Especially, the influence of a dipole excited field on low conducting materials situated very close to the antenna will be discussed. We use higher order edge elements of quadilateral shape for the field approximation on curved surfaces. The tangential components of the unknown field variables are interpolated by vector element functions. The Galerkin method is implemented to obtain a set of linear equations. The applicability of the proposed edge element is investigated by the comparison of different BEM-formulations and FEM-results.
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    Implementation of a hybrid method for eddy current problems (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 398-409 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper, a hybrid formulation for solving time harmonic eddy current problems in terms of magnetic field h is considered. In particular, we discuss some properties of the implicit boundary condition on the discrete level and the computation of the integral operator exploited in this context. An iterative technique is confirmed to be efficient in solving the arising, partly dense, complex linear system of equations. Furthermore, some test results, including timings for linear solvers are presented.
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    Numerical calibration of fluxset probe for quantitative eddy current testing (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 436-444 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Fluxset type eddy current probes are used for detecting discontinuities in conducting materials. The measurements obtained by such probes can be used for the reconstruction of the parameters of the detected discontinuity if the output signal of the measurement is uniquely related to the measured field. In this paper a calibration method is presented for the establishment of the relation between the measured magnetic field and the output signal of the probe. The relation is obtained by the optimisation of the parameters of the mapping between the calculated magnetic field distribution and the measured output signal. The magnetic field distribution due to the interaction of the probe and an infinitesimally thin crack located in a conducting plate is calculated numerically by the solution of a boundary integral equation.
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    Numerical simulation of induction hardening of steel (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 482-493 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: We discuss a model that is capable of describing the process of induction hardening of steel: induction heating - heat transfer - solid-solid phase transitions in steel. It consists of a reduced system of Maxwell's equations, the heat transfer eqaution and a system of ordinary differential equations for the volume fractions of the occuring phases. The model is applied to simulate surface heat treatments, which play an important role in the manufacturing of steel. The numerical methods are implemented with tools from pdelib, a collection of modular algorithms. We present numerical simulations of surface hardening applied to the steel 42 CrMo 4.
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    Dynamic operation of an electromagnetic actuator taking nonlinearity and eddy currents into account (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 611-622 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper deals with a coupled field-circuit simulation of transient and dynamic states in a non-linear axisymmetrical electromagnetic device. The mathematical model of the dynamic phenomena includes: an equation of transient electromagnetic field in a non-linear conducting and moving medium, equations of the converter electric circuits and the equation of mechanical motion. The numerical implementation of the algorithm is based on the finite element method. The Crank-Nicholson scheme for time discretization has been applied. In order to include nonlinearity, the Newton-Raphson process has been adopted. The influence of the saturation effect on the dynamic characteristics of the device has been investigated.
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    URL: http://dx.doi.org/10.1108/03321649910296645
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    Selected projection methods to improve the convergence of non-linear problems (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 638-646 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Short computation times required for the design and numerical optimisation of electromagnetic devices with the finite element method are obtained using an adaptive mesh refinement algorithm. Less time is spent on the initial mesh generation, while the time needed for refinement is negligible when special data structures are used. But an even more significant reduction in total computation time is achieved with the initialisation of the solution on the generated mesh. Fewer Newton steps are required to solve non-linear problems compared to a zero initial solution, while the time needed for the projection of the solution is far less than the time needed for a Newton step.
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    An energy-transport model for semiconductor heterostructure devices: application to AlGaAs/GaAs MODFETs (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 61-76 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A stationary 3D energy-transport model valid for semiconductor heterostructure devices is derived from a semiclassical Boltznmann equation by the moment method. In addition to the well-known conservation equations, we obtain original interface conditions, which are essential to have a mathematically well-posed problem. An appropriate modelling of the physical parameters appearing in the system of equations is proposed for gallium arsenide. The model being written and its particularities mentioned, we present a novel numerical algorithm to solve it. The discretization of the equations is achieved by means of standard and mixed finite element methods. We apply the model and numerical algorithm to simulate a 2D AlGaAs/GaAs MODFET. Comparisons between expenrimental measurements and calculations are carried out. The influence of the modelling of the physical parameters, especially the electron mobility and the energy relaxation time, is noted. The results show the satisfactory behaviour of our model and numerical algorithm when applied to GaAs heterostructure devices.
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    Finite element analysis of the dynamics of a high bandwidth actuator for a hard disk drive (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 120-131 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper a prototype actuator designed for a high bandwidth servo system is modeled and analyzed using finite elements. Natural frequencies and mode shapes of frequencies below 10kHz are extracted using frequency analysis and compared with the results from an experimental model analysis. The effects of key parameters used in the analysis on the natural frequencies are investigated. The frequency response is calculated using the natural frequencies and mode shapes. The calculated frequency response is compared with experimental results. The comparison of results shows that the numerical results are accurate. From the analysis the mechanical dynamics of the actuator can be understood and characterized. The analysis of the actuator shows that dynamic analysis using finite element modeling is accurate and effective and can be applied to other mechatronic systems.
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    A quasi-variational inequality for the simulation of a MODFET transistor (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 175-186 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: We introduce the drift-diffusion model with appropriate jump conditions at the junction of the MODFET transistor (AlGaAs/GaAs). We propose a quasi-variational inequality (QVI) model for this device. We assume that the electron density is bounded and piecewise constant. These hypotheses imply that the Poisson's equation becomes linear with respect to the electrostatic potential. The QVI model keeps a coupling with the continuity equation. Free boundaries arise in the medium AlGaAs near the Schottky-gate contact and in the high mobility medium (GaAs) under the effect of the electron affinity discontinuity at the junction. Numerical results of the QVI model show their location versus the applied gate voltage V/up〉 and the molar fraction X of the AlXGa(1-X)As medium. The inequality seems to be a reasonable simplification of the non-linear Poisson's equation.
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    Noninvasive cardiac source imaging from potential and magnetic field data (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 236-249 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Ventricular surface activation time maps are estimated from simulated and measured body surface potential (BSP) maps and extra-corporal magnetic field maps. In a first step the transfer matrix, relating the primary cardiac sources to the measured potential and/or magnetic field data, is calculated applying the boundary element method. Activation times are determined by minimizing a cost function which is based on this transfer matrix. This optimization method is solved by a quasi Newton method. The critical point theorem is used in order to estimate the starting column matrix.
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    Dual formulations for the modeling of thin conducting magnetic shells (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 385-398 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Two sets of dual magnetodynamic and magnetostatic finite element formulations taking thin conducting magnetic shells into account are proposed. The abstraction of the thin region from the computational domain is performed by an appropriate treatment of the surface integral terms arising in the weak formulations. Results are presented for two three-dimensional test-problems.
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    Approximation of the objective function: multiquadrics versus neural networks (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 250-265 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Global optimization in electrical engineering using stochastic methods requires usually a large amount of CPU time to locate the optimum, if the objective function is calculated either with the finite element method (FEM) or the boundary element method (BEM). One approach to reduce the number of FEM or BEM calls using neural networks and another one using multiquadric functions have been introduced recently. This paper compares the efficiency of both methods, which are applied to a couple of test problems and the results are discussed.
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    The optimisation of electromagnetic devices using a combined finite element/neural network approach with on-line training (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 266-274 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents a novel method of utilising neural networks for optimisation systems. First, a conventional magnetic circuit model of the device is developed to create a set of sensitivity rules which guide the optimisation. The rules are coded in a knowledge-based neural network. Second, an error network is developed to correct the approximations inherent in the magnetic circuit approach and this combines with the first network to generate realistic outputs. Finally, the error network can be trained on-line with a finite element system. Over time, the network replaces the finite element analysis, thus speeding up the optimisation process.
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    Complementary finite element magnetodynamic formulations with enforced magnetic fluxes (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 656-667 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Two complementary 3D finite element formulations, with either the magnetic field or the magnetic vector potential as unknowns, are developed to deal with the modeling of eddy currents in electrical steel laminations. The magnetic flux through the flux gates of the conducting region is imposed via the boundary terms of the weak formulations, in a natural way thanks to the use of edge finite elements. The two formulations are applied to a simple 1D eddy current problem with analytical solution. As a practical 3D application example, a T-joint region of an electrical steel lamination is considered.
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    Investigations of the audible noise of inductors with respect to different ferromagnetic materials (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 647-655 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Fluorescent lamps are one of the most modern light sources. They can be connected to the 230Vac supply without a transformer. To operate them, an inductor and starter are required only. The main disadvantage of this type of light source is the emitted audible noise of a frequency of 100Hz. For this phenomenon the inductor is responsible. Electromagnetic forces and magnetostriction are acting on the body of the device causing the sound emission. Here, the audible noise problem is investigated with respect to different ferromagnetic materials and the range of applied flux densities inside the iron core.
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    Quantum interface conditions for quasi-Fermi levels in an abrupt heterojunction (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 556-569 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: We present a semi-quantum model including tunneling effects across an abrupt heterojunction. The discontinuity of the effective masses and the energy bands are considered. The quantum transmission conditions for the quasi-Fermi levels are obtained using WKB approximation. We use mixed finite element approach and a two dimensional mesh which is double-valued for quasi-Fermi levels at a heterojunction. A GaAs/GaAIAs heterojunction diode is then simulated using both drift-diffusion and semi-quantum model by varying doping density at low temperature.
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    Magnetic modelling and magneto-hydro-dynamic simulations of an aluminium production electrolytic cell (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 528-538 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A simulation of the motion of molten aluminium inside an electrolytic cell is presented. Since the driving term of the aluminium motion is the Lorentz (j × B) body force acting within the fluid,this problem involves the solution of the magneto-hydro-dynamic equations. Different solver modules for the magnetic field computation and for the fluid motion simulation are coupled together. The interactions of all these are presented and discussed.
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    On the use of the FEM and BIE methods in the 3D magnetic field computation of the reactors with air gaps (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 116-120 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The calculation results of the 3D magnetic field in a reactor are examined using the computer packages TRACAL3 as well as OPERA3D. The first own package is based on the boundary integral equations (BIE) and the second commercial package is deduced from finite elements method (FEM). As an example, the magnetic flux density components were calculated. For the reactors with large air gaps, the numerical results obtained by BIE and FEM are relatively close.
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    "Mixed" systems of algebraic equations in computational electromagnetism (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 59-63 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Discusses some general algorithmic problems encountered when solving linear systems in electromagnetism, such as, e.g. the well-known difficulties linked with the curl-curl operator in discrete form. The problem is examined as part of a larger one: solving "mixed" (or as we prefer to say, "constrained") linear systems, with Lagrange multipliers, for which available strategies are reviewed. It is shown that dealing with the mixed system directly, without first getting rid of multipliers, can be a viable proposition.
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    Computational electromagnetics: some conjectures for industrial and teaching requirements (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 36-46 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The purpose of this paper is to examine the current situation in numerical field computation, paying special attention to the role of education in developing new ideas to meet the ever growing demands of industry.
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    Design considerations for claw pole alternators for wind power applications (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 151-154 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents a procedure for the design of claw pole alternators for small scale wind power applications. The method involves a preliminary design stage by means of the classical magnetic circuit analysis and a detailed design stage involving a 3D finite element model. This technique has been implemented in the design of a multiple generation for a small scale gearless autonomous system. The developed model can be implemented for the optimization of the rotor claw geometry through a minimization algorithm.
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    Accelerating the Robin iteration procedure by means of GMRES (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 49-54 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The Robin iteration procedure is a technique for the FEM computation of electromagnetic scattering fields in unbounded domains. It is based on the iterative improvement of the known term of a non-homogeneous Robin condition on a fictitious boundary enclosing the scatterer. In this paper it is shown that the procedure is equivalent to the application of the Richardson method to a reduced system and that the use of GMRES significantly reduces the computational effort.
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    Permanent magnet configuration in repulsive type magnetic bearing for improved radial disturbance attentuation characteristics (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 290-295 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper reports on the development of a repulsive type magnetic bearing system and the importance of permanent magnet (PM) configuration on the attenuation of radial disturbance. A new configuration of the permanent magnet of the bearing system resulting in improved stiffness characteristics in the radial direction has been described. Prototype models have been designed and developed in our laboratory and experiments carried out.
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    Dynamic modelling of a synchronous linear motor with permanent magnet excitation and solid yokes (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 189-195 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A three-axes synchronous torque motor with permanent magnet excitation and solid stator and rotor yoke is used to adjust an air borne telescope and to eliminate oscillations. Hence the motor is part of a complex mechanical system and has to be included in the structural analysis. For this reason the attempt is made to simulate the nonlinear behavior of the motor by a dynamic model considering the eddy current fields and the magnetization characteristic of the iron.
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    Design of RLC circuit for pulse magnetizer of permanent magnets (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 412-417 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The current pulse magnetizing process of permanent magnets is considered. General conditions for the design of a pulse magnetizer are given for the case when the magnetizing process is effected on the magnet put in free space. The boundary-integral analysis of the magnetic field inside the magnet is presented. It concerns both the state corresponding to the maximum value of the magnetizing current pulse and the magnetized state after the full magnetizing.
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    The non-linear characteristics of AC machines based on the calculation of magnetic field co-energy (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 324-328 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Non-linear characteristics, as relations between linked fluxes and currents of individual machine coils, are sought for in the so called circuit models of saturated electrical machines. Their determination can be based on the co-energy of the magnetic field only, which is a multivariable function of all coil currents and rotor position angle. The author proposes the calculation of co-energy values at necessary points by the FEM and the interpolation of the results by a suitable multivariable spline function. The functions of linked fluxes are generated as the first derivatives of the spline. This way could be used to separate the circuit calculation from the field calculation when saturated machines are modelled. An example of a wound rotor induction machine is used to show the elementary problems of the calculation of the non-linear characteristics.
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    Identification of thermal parameters in a coupled magnetic-thermal model with the experimental designs method (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 331-336 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In analysing coupled electromagnetic thermal behaviours in electrical devices one of the main difficulties is related to the uncertainties of thermal parameters. The authors present, in this work, a technique using the method of experimental designs for the identification of thermal parameters necessary for a coupled finite element model analysing the magneto-thermal behaviour of an electromagnetic device.
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    Numerical modeling of transient heating of solid plate 3D structure (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 337-341 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The heating of flat metal products has an increasing importance in different technical applications. One of the most advanatageous heating methods is induction heating. The heat is generated within the workpiece itself. It provides high power densities and high productivity. For induction heating of flat metal products two methods are applied: the longitudinal and the tranverse magnetic flux heating. In our case we have applied tranverse flux heating. This paper presents certain results of electromagnetic field obtained by means of finite element method and transient thermal field obtained by finite difference method. The analysis is made by simulating the heating phenomenon while the sophisticated software has been employed.
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    Computational electromagnetics in Poland: a review (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 427-438 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents a historical review, the state of the art and recent advances in the field of computational electromagnetics at leading universities and research institutes in Poland. Contributions made by Polish scientists to the development of fundamental electromagnetism, as well as to computational methods, are emphasized, and some conclusions are drawn regarding expected future developments.
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    Analytical approximation of the dependence of magnetic material properties on temperature (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 402-406 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Temperature dependence of magnetic susceptibility has been approximated by the extension of Curie-Weiss law to ferromagnetic states. Application of similar relations to other properties and corresponding model parameters of magnetic materials would enable thermal analysis of circuits containing ferromagnetic cores.
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    Benchmark problems for optimal shape design for 2D eddy currents (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 448-459 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Two new benchmark inverse problems for eddy currents are proposed. The first originates in the optimal design of the tubular inductive heater. The authors' goal is to offer a simple problem which will check whether new software is able to minimize a multimodal objective function. The second benchmark is a simplified model of a hardening device. The purpose of this problem is to test the ability of the software to deal with different design parameters. This benchmark can be easily extended for more complicated, coupled fields problems. For both benchmarks reference standard solutions are presented. They were obtained using a finite element package for electromagnetics, developed by the authors.
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    Fluxoid dynamics methods for electromagnetic phenomena of superconductors (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 541-566 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this study the numerical method was developed to simulate behavior of the fluxoids in NbTi and Bi-2212. The method was named the Fluxoid Dynamics (FD) method, and is based on a combination of two concepts : the Molecular Dynamics (MD) and Ginzburg-Landau (G-L) theory. Several macroscopic electromagnetic phenomena were predicted by these methods, and the results were compared with the well-known empirical ones.
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    Separation of crackles and squawks from vesicular sounds using a wavelet-based filtering technique (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 649-657 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: An automated way of revealing the diagnostic character of discontinuous adventitious sounds (DAS), i.e. crackles and squawks, by isolating them from vesicular sounds (VS), based on their nonstationarity, is presented in this paper. The proposed algorithm combines multiresolution analysis with hard thresholding in order to compose a wavelet-based stationary-non-stationary filter (WTST-NST). Applying the WTST-NST filter to fine/coarse crackles and squawks, selected from three lung sound databases, the coherent structure of the DAS is revealed and they are separated from VS. When compared to other separation tools, in noiseless case, the WTST-NST filter performed more accurately, objectively, and with lower computational cost. Owing to its simple implementation it can easily be used in clinical medicine.
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    Recent experiences on mixed finite elements for 2D simulations of magnetic fields (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 674-681 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A mixed formulation of two-dimensional magnetostatic problems, where both B and H are unknowns, is considered. The solution is obtained by minimizing the residual of the constitutive law, imposing Maxwell's equations as constraints by means of Lagrange multipliers. When a finite element discretization involving face and edge elements is applied, we have to solve a linear system whose algebraic treatment presents some difficulties. In the paper, the attention is focused on the computational aspects of the proposed methodology with special emphasis on the choice of algebraic solvers and of possible preconditioning techniques. A case study, concerning the field analysis of a magnetic screen, is presented and discussed.
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    Three-dimensional coupled thermo-magnetic analysis of toroidal field coils of resistive high field tokamaks by FEM (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 576-584 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper a code for the solution of nonlinear thermo-magnetic problems, arising in the transient analysis of thermal and electromagnetic fields in resistive toroidal field coils of tokamak devices, is presented. A formulation based on the electric vector potential T and the magnetic total scalar potential ? for the analysis of the thermo-magnetic skin effect phenomenon in the toroidal field coils of proposed tokamaks has been used, and the results obtained are reported, reviewed and discussed.
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    Irreversible thermodynamics and thermal noise of non-linear networks (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 635-648 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The conventional treatment of thermal noise is based on Nyquist's theorem. This theorem has only been derived for linear, reciprocal (we define "reciprocal networks" as networks that are built of reciprocal network elements) networks. In this paper a description of thermal noise in reciprocal non-linear RLC networks is presented. This description is derived from first principles, i.e. from a direct application of non-equilibrium thermodynamics (irreversible thermodynamics) to electrical networks. As an example, the class of "complete" non-linear networks is considered. Using the idea of equivalent n-ports, the theory's extension to certain classes of transistor circuits should be possible.
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    Evaluation of the high voltage transmission line inductance and capacitance using the finite element approach (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 313-317 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper the per phase inductance and the capacitance to neutral of a 220kV three-phase overhead transmission line are calculated using a 2D finite element formulation. This study was performed considering the phase conductors transposition as well as the effect of the earth wires in the capacitance. The results produced by the finite element approach are compared with the analytical solutions showing a close agreement. Finally some conclusions are presented.
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    Effect of the non-linearity of demagnetization curves on the torque of hybrid stepping motors with permanent magnets in slots (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 318-323 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The recent achievements in electronic control as well as the higher performance of advanced permanent magnets have brought about a change in the general strategy for design and development of new types of small electrical machines. A special application of permanent magnets (PM) is represented by hybrid stepping motors (HSM). The latter are a sort of combination of variable reluctance-motors and permanent magnet-motors. The influence of various PM inserts into the magnetic circuits of electromechanical converters on field and force distribution has been already investigated by the authors (1996). Promising results for HSM have been reported, especially when rare-earth PMs are used. The main aim of PM inserting, when they are put into slots of slotted pole shoes with radial N-S polarization, is to focus magnetic field lines in the corresponding teeth. As a result, the reluctance stepping torque can be increased depending on the material used. Now a further step is made by extending the analysis from the case of linear to that of non-linear demagnetization curves of permanent magnets.
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    An easy and fast 2D finite element program for studying the fields in three-phase transformers (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 342-346 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: All the algorithms introduced by the authors in their finite-element computational program for studying fields easily and quickly are described in the paper. Moreover, an application of the analysis of the thermal field to a three-phase transformer is proposed. This analysis gives a valid help to designing transformers having to provide services to satisfy some particular needs.
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    Loss evaluation of non-magnetic tie-plates in transformers (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 347-351 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper tests the eddy current analysis methods based on TEAM benchmark model, evaluates the engineering effectiveness of the eddy current codes through product-based test models, and proposes an engineering-oriented loss solver to deal with the eddy current loss problems concerning the core tie-plates in large power transformers.
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    3D coupled field-circuit simulation of electromechanical converter dynamics (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 439-447 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: An algorithm for simultaneous solution of equations describing transient 3D magnetic field coupled to the Kirchhoff's equations and the equation of motion has been presented. The nonlinearity and anisotropy of the magnetic core have been taken into account. Numerical implementation of the algorithm is based on the finite element method. In order to solve the 3D problem a special iterative procedure, in which the 3D task is substituted with a sequence of 2D problems, has been proposed. The time-stepping backward difference algorithm for the time-discretization of the electric circuit equations has been applied. To determine the moving armature position, an implicit procedure, which is unconditionally stable has been proposed. For the sake of example, the calculations of dynamic operation of the E-type electromagnetic actuator equipped with the shading coil have been performed.
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    Bi-scalar boundary-integral approach to modelling electromagnetic fields (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 475-488 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A bi-scalar boundary-integral approach to the static and monoharmonic electromagnetic field
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    Identification of flaws using eddy current testing (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 516-527 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The eddy current method of non-destructive testing uses an alternating current excitation to induce secondary currents in a specimen under test. Flaws within the specimen affect the induced currents, causing changes in the impedance of a test coil. In this paper we present a method for obtaining a solution of inverse problems, in which the parameters of defects are unknown and the excitation function and the eddy current system response are given. The method is based on the use of artificial neural networks, which are trained using measurements. Illustrative examples are given.
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    3D eddy current computation with edge elements in terms of the electric intensity (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 667-673 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A finite element formulation for the solution of 3D eddy current problems in terms of the electric intensity E is presented. A weak formulation, based on a Galerkin weighted residual procedure, is presented and edge elements, that impose only tangential continuity across element interfaces of the approximated field, are employed for the discretization of the problem with the finite element method. The reliability and validity of the suggested method is verified by its application to the calculation of the 3D eddy current distribution in two conducting systems.
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    Time harmonic eddy currents in non-linear media (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 567-575 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: One way to deal with non-linearity in the case of time harmonic excitation of the electric and magnetic fields in ferromagnetic media is to introduce an effective material to model the ferromagnetic region. This fictitious material is constant throughout a period but inhomogeneous and it takes into account the non-linear relationship between the field quantities. Several methods to create an effective magnetization curve are presented and different finite element formulations are applied to these. Some of these methods are known from the literature for 1D and 2D problems but not for 3D ones and they have only be used for a magnetic vector potential formulation so far. In the present paper they are extended for general vector and scalar potential formulations. Further possible ways to introduce such an effective material to take into account saturation effects are shown. All these different methods are investigated on a non-linear 3D time harmonic eddy current problem using complex formalism.
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    Examination of optimal design method using die press model (problem 25) (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 595-601 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Factors affecting convergence of the simulated annealing method are investigated using an actual model. The convergence characteristics of various optimization methods are examined using the contour line of objective function. Two kinds of combination methods with the simulated annealing method and the Rosenbrock's method are investigated.
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    Integral boundary conditions in FEM approaches with the minimization of constitutive error (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 612-619 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A method based on the minimization of the constitutive error has been successfully applied to finite element formulations of Maxwell equations. Error based techniques present a number of appealing characteristics, including the possibility of providing an estimation of the error distribution and to split the equation system in two decoupled subsystems. However, except for very simple cases, a direct numerical translation of the boundary conditions can cause a number of drawbacks: on one side the lack of symmetry and positive definition of the matrix, on the other side the impossibility of splitting the unknowns. This paper is aiming to discuss the problem and to propose a technique to effectively impose a wide class of boundary conditions within the framework of error based formulations. To show the performance of the technique, some examples are proposed.
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    Hysteresis modeling (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 682-689 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In the modeling of transducers, especially magnetic transducers, hysteresis may affect performance. Hysteresis models have been improved greatly and are capable of modeling a large variety of rate-independent phenomena, and are capable of describing minor loops. Of these, the most useful are: the Preisach model, the play model, and the stop model. Coupling these purely magnetic models with other phenomena, such as magnetostriction, enhances the model's usefulness for transducer applications. This paper will discuss the conditions under which these models may be inverted, and for the invertible media, a technique for inverting them.
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    Infinite elements for axisymmetric electrical field problems with open boundaries (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 781-788 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents infinite elements for axisymmetric electrical field problems with open boundaries. The formulation of the elements is so simple that closed-form expressions for the infinite element matrix are obtained. In order to test the infinite elements, a simple problem, for which an analytical solution exists, is analysed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810221413
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  • 86
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    Neural network simulation of a pulse magnetiser for magnetising permanent magnets (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 697-707 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper is concerned with a design and a validation of a neurocontroller for a pulse magnetiser for magnetising permanent magnets. The goal is to register the peak time and crest current in order to pick up an optimal intermittent duty conditions regime for the magnetiser. This is usually done by solving a set of coupled ordinary differential equations describing current waveforms and the temperature rise in the magnetising winding. The neurocontroller is based on a one-layer feedforward neural network which is trained using the Levenberg-Marquardt learning rule. We present the results produced by the neurocontroller and we compare them with the numerical and measurement results. The neurocontroller is intended to serve later as a part of a global optimising algorithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810221242
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  • 87
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    Influence of the sampling period on sinusoidal steady-state operations of inverter-fed asynchronous motors (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 219-224 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Inverter-fed asynchronous motors represent today a source of disturbance in electric drives, because they irradiate outside their frames electromagnetic waves with different frequencies. Knowledge of the disturbances generated inside the drive is necessary. In the paper the influence of the sampling time on the distortion between predicted and actual armature current is evaluated on the basis of an analytical calculus procedure, that allows for an easy evaluation of the harmonic contents of the currents. This is the first step towards the evaluation of the causes of environmental electromagnetic disturbances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810369393
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  • 88
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    Field and power loss distribution on covers of power transformers (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 302-306 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Heavy current bushings passing through steel cover plates and housing walls of power transformers, generators and other large power equipment are thermally hazardous elements of construction and a source of additional power losses. Safety and reliability of such expensive objects and safety of power delivery often depend on the proper design of these elements. In the paper a computer analysis, based on Maxwell equations and analytical representation of electromagnetic field was carried out. Non-linear permeability of solid steel was considered with the help of analytical approximation. Eddy current losses have been calculated and compared using different methods of calculation and experiments. The method of forecasting possible excessive heating and hot spot with the help of electromagnetic criteria was used. Various constructional means of loss and hot spot reduction were proposed and examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810369456
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  • 89
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    Design of GIS insulators including small metal particle influence (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 141-145 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The influence of accidentally left metal particles inside high voltage gas insulated switchgear was investigated using 3D finite element method for transient electric field with slightly non-linear permittivity and floating potential of moving particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203062
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  • 90
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    Field modelling and characteristics simulation in electromechanical transducers (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 146-150 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The main purpose of this paper is to discuss ways in which magnetic performance of electromechanical transducers can be simulated accurately using a series of finite-element models. Of particular interest is the usage of multivariable interpolation techniques which enable significant reduction of the number of finite-element computations necessary to fully model all relevant cases. This is particularly important in the case when a shift of the zero position of the coil occurs. Moreover, this type of modelling provides a good insight into the physical behaviour of the device and aids understanding of its performance characteristics. Finally, the paper presents briefly how a significant reduction in harmonic content has been achieved by improving the linearity of the magnetic circuit. These improvements have been confirmed experimentally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810369357
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  • 91
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    Optimal design by means of material derivative (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 155-159 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Deals with the method of shape optimisation that belongs to the class of methods called continuous gradient methods. The approach in question is based on the concept of the material derivative. The main definitions and the features of the method are presented. In order to validate the method, an example is solved: a two-variable problem (cylindrical capacitor with the distribution of potential fixed).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810369366
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  • 92
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    A 3D design optimisation of electromagnetic low-voltage linear actuators based on FE force computation (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 166-170 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Experience and exploring the linear AC and DC actuators confirm the necessity of the computation of forces distribution as the step preceding their optimal design. This paper expresses an approach to computations of different forces of low-voltage linear actuators acting on both mechanical and/or electrical parts. The computations are based on magnetic coenergy concept associated with virtual work method and simulated by step displacement of the armature from the total open through total closed position. The magnetic coenergy is numerically computed through the flux-linkage approach, where the magnetic field distribution is obtained by applying the finite element method in 3D-domain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203099
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  • 93
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    An integral approach for 3D magnetostatic field calculation (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 55-58 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper shows a method for 3D magnetic field calculation. The method was developed from previously published 2D method of current sheets. The method is based on magnetic homogenisation of the space. Only one permeability appears inside all magnetic problem space after the homogenisation and so the Biot-Savart low can be applied. All calculations are made without any kind of potentials. The main advantages of the current sheet methods are: simple model building, direct magnetic field density calculation, no need to know boundary conditions and easy calculation of open boundary problems. The method has similar properties to the boundary element method and is suitable for problems with unknown boundary conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810202973
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  • 94
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    A new probe for eddy current testing of low conductivity materials (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 393-397 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In the paper a new probe for eddy current testing of low conductivity materials is presented. The new probe has been applied for eddy current testing of H2SO4 water solution. Results of measurements are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203332
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  • 95
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    Limitation of the electric field effects in a cylindrical tank by a system of grounding rods (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 280-284 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The results of calculation of the 3D electrostatic field in a cylindrical tank provided with a system of vertical grounding rods are presented. The field intensities of the original tank without the grounding rods are very large, which may cause a spark discharge, even at a relatively small space-charge density. The presented results involving the grounding rod system can be used to eliminate or reduce fire and/or explosion hazards.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810369438
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  • 96
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    Analysis of drifting charged aerosols from HVDC ionizers via a hybrid CSM-FD method (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 620-627 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper are summarized our research activities dealing with the theoretical and experimental analysis of high voltage direct current (HVDC) ionizers. We present here the basic principle of a hybrid charge simulation-finite difference method, that has been used to simulate the electric behaviour of these devices, by computing the electric field strength and the ionic current density distribution, therefore the efficiency of emission. We have realized an experimental ion counter and we have used it to verify the values predicted by means of this numerical technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810220919
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  • 97
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    Application of higher-order spectra for signal processing in electrical power engineering (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 602-611 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: During recent years, higher order statistics (HOS) have found a wide applicability in many diverse fields, e.g. biomedicine, harmonic retrieval and adaptive filtering. In power spectrum estimation, the signal under consideration is processed in such a way that the distribution of power among its frequency is estimated and phase relations between the frequency components are suppressed. Higher order statistics and their associated Fourier transforms reveal not only amplitude information about a signal, but also phase information. If a non-Gaussian signal is received along with additive Gaussian noise, a transformation to higher order cumulant domain eliminates the noise. These are some methods for estimation of signal components, based on HOS. In the paper we apply the MUSIC method both for the correlation and the fourth order cumulant, to investigate the state of asynchronous running of synchronous machines and the fault operation of inverter-fed induction motors. When the investigated signal is distorted by a coloured noise, more exact results can be achieved by applying cumulants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810220892
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  • 98
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    Topology and performance of superconducting magnetic bearings (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 628-634 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents different topologies of inherent stable magnetic support systems consisting of monolithic high temperature superconductors (HTSC) and permanent magnets (PM). They may be used as contactless magnetic bearings for high speed rotating machines. Depending on the application, cylindric, conic or disk shaped HTSC-PM arrangements with increased both radial and/or axial forces and stiffnesses are proposed. The dependencies of optimal pole pitch on the air gap are given including the effects of limited current densities associated with the behaviour of real monolithic superconductors. Furthermore, the effect of zero field and maximum field frozen HTSCs on the performance of magnetic HTSC bearings are represented. To compute the magnetic HTSC-PM interaction a new extended finite element (EFEM) program is applied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810220946
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  • 99
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    A boundary element analysis of magnetic shielding for electron microscopes (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 585-594 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper describes a boundary element analysis of magnetic shieldings for electron microscopes. Since the thickness of the shielding layer is considerably small compared with its overall size, numerical analysis of electromagnetic fields inside the layer leads to an ill-conditioned matrix. This problem can be overcome by analytical evaluation of the interior electromagnetic field, which yields the impedance boundary condition (IBC) valid for static and eddy current fields, which expresses the relationship between the electromagnetic fields on both surfaces of the layer. In this paper the magnetic fields around a shielding layer are analyzed by the boundary element method under the IBC on the shielding layer. Two-dimensional and axisymmetric magnetic fields are analyzed to evaluate the shielding efficiency of shielding immersed in an ac magnetic field. It is shown that magnetic disturbances can be reduced to less than one-hundredth inside a shielding consisting of double shielding layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810220883
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  • 100
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    Complementarity by "local corrections" (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 717-725 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: By using complementarity (solving for both potentials, scalar and vector), one often can provide bilateral bounds for some quantities of interest, like for instance the reluctance of a circuit. However, the vector potential method is expensive, and does not make use of information acquired in the first phase of solving for the scalar potetential. We show how to improve on this by a "local correction" process which, starting from h = grad ?, yields a divergence-free b, close to µh, by a series of local and independent (parallel) problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810221279
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