bluuebunny/crossref_metadata_2025_split huggingface dataset:
A visual interpretation rating scale for validation of numerical models
Authors: Coleby D.E. , Duffy A.P. 
Published: January 2007

PurposeThe comparison of large volumes of complex data resulting from numerical modelling in computational electromagnetics is a demanding task, especially when validating the performance of numerical models against experimental results and testing experimental repeatability. “By‐eye” comparisons can lead to inconsistencies and inherent subjectivity. This paper establishes a “visual” benchmark by which comparisons can be made and therefore used to assist in the development of an algorithmic approach to data comparison.Design/methodology/approachThis new method presented here is based on the Cooper‐Harper Rating Scale, which is a test pilot's evaluation‐rating instrument. This has been modified through qualitative research. The assertion that the rating scale will leave the group mean response unaltered but will reduce the variance has been statistically tested.FindingsThe proposed rating scale provides a calibration technique by which to benchmark comparisons. The scale also reduces subjectivity by producing an overall quantitative measure of similarity. The paper concludes with an application of the rating scale to assessment of a candidate algorithmic approach against correlation.Research limitations/implicationsThe research findings are based on small data sets, which is a limit imposed by the industrial environment in which this scale will be used.Practical implicationsThis paper provides a tool to overcome some of the key substantial difficulties in communicating similarity or difference, namely that “similarity” and “difference” have no stand‐alone definition, there is a lack of a shared language for the comparisons and little commonality for a decision‐making framework.Originality/valueThis paper provides modellers and experimentalists in computational electromagnetics (particularly electromagnetic compatibility) with a structured approach to quantifying the quality of comparative results.
The application of polynomial matrix factorization in active network synthesis
Authors: Kandić Dragan B. , Reljin Branimir D. 
Published: January 2007

PurposeTo investigate the general necessary condition for synthesis of square, real rational matrices of complex frequency as admittance matrices of active multiports with resistors, inductors, capacitors and possibly multiport transformers and to prove that this condition is also sufficient for synthesis of stable, square, real rational matrices of complex frequency as admittance matrices of balanced active multiports having only resistors, capacitors and voltage‐amplifiers with sufficiently large amplifications. The main aim of the paper is to provide a new and general method for stable admittance matrices synthesis and to develop strict realization algorithm by active balanced transformerless multiport networks.Design/methodology/approachThe objectives of the paper are achieved by using factorization of regular polynomial matrices in complex frequency with certain degree as products of other regular polynomial matrices with specified degrees. A set of sufficient conditions for such a factorization is presented and derived a pertinent algorithm as the starting point for investigation and solving network synthesis problem and generation of class of equivalent realizations.FindingsTheorem 1 states that sufficient condition for factorization of Pth order, generally regular polynomial matrix P(s) in complex frequency s with degree L, whose determinant has K distinct zeros, in form P(s)=P1(s)·P2(s), where 1≤p2=P20≤L−1 is degree of polynomial matrix P2(s), reads: K>(P−1)·L+p2−1. The coefficient‐matrices of s, s2,… in P1(s) and P2(s) are real or complex depending on whether distinct zeros of det P(s) are real or complex, respectively. Theorem 2 states that: (a) for realization of Pth order matrix of real rational functions in complex frequency s (i.e. RRF matrix) as admittance matrix of active balanced RLC P‐port network with multiport transformers, or without them, P generalized controlled‐sources and P controlling‐ports are necessary, in general; and (b) P balanced voltage‐controlled voltage‐sources (VCVSs) with real and by module greater than unity controlling coefficients (“voltage amplifications”) are sufficient for realization of stable admittance RRF matrix by active, balanced, transformerless, RC P‐port network.Originality/valueThis is a research paper with the following two main contributions (original results). First, a theorem on sufficient conditions for factorization of regular polynomial matrices in complex frequency; and second, a theorem relating to sufficient conditions for synthesis of matrices of real rational functions in complex frequency by active, balanced, transformerless networks. The results may be interesting for network theorists and researchers in the field of electric circuits and systems.
Frequency representations of one‐port networks
Authors: Walczak Janusz , Świszcz Piotr 
Published: January 2007

PurposeAnalysis of harmonics propagation in power systems requires information about models of non‐linear loads which are the main source of harmonics. The purpose of the paper is to present a method of parameter determination of non‐linear loads.Design/methodology/approachA method of parameter determination of a model has been described in the article. This method has been developed assuming that mathematical description of a non‐linear load is known. In order to obtain a harmonic representation of this model for one‐phase loads the theory of harmonic balance method has been used.FindingsParameters of the current or voltage controlled sources can be expressed as a function of any number of voltage or current harmonics. In the case under consideration the network input current is a function of input voltage and its derivatives. Thus, contrary non‐linear element with inertialess characteristics, the first harmonic of the current depends not only on amplitude but also on frequency of the voltage across terminals of one‐ports.Originality/valueThe method presented in the paper enables relatively simple determination of frequency parameters of non‐linear models of one‐port networks.
Calculation of electrical field of spherical and cylindrical gas voids in dielectrics by taking surface conductivity into consideration
Authors: Alisoy G.T. , Alisoy H.Z. , Koseoglu M. 
Published: January 2007

PurposeTo determine the electrical field E1(t) in spherical and cylindrical gas voids existing in an insulator by considering surface conductivity of gas voids having an electrical permittivity of ε1 and conductivity of γ1 for DC and AC situations.Design/methodology/approachAnalytical expressions satisfying Laplace equation for inside and outside of the cylindrical and spherical gas voids in an insulator located in an external electrical field having a definite time dependent character, have been derived by considering the surface conductivity of the gas void. The coefficients included by these analytical expressions have been determined by utilizing the continuity equation of the current on the surface of the voids.FindingsIt has been demonstrated that the electrical field remains uniform in spherical and cylindrical gas voids when the surface conductivity of gas void has been considered. It has been determined that the contact charging process of different shaped particles has an exponential characteristic, and some expressions have been derived to determine the time constants of this process for practical purposes.Practical implicationsThe results have been applied to the problems about contact charging of semi‐spherical and semi‐cylindrical insulated particles located at a charged surface and problems about the calculation of onset discharging voltage of ionization process in dielectric including gas voids.Originality/valueFor spherical and cylindrical gas voids, the onset discharging voltage corresponding to the ionization process occurring in gas voids has increased by increasing the surface conductivity of the void. For the limit value of the surface conductivity, the voids in the insulator behaves like metal particles distributed into the insulator, for this reason, at the outside of the void, especially in the regions where the voids are close to the electrodes and each other, the electrical field will be non‐uniform and will increase. This situation will cause the ignition of the partial discharge and destroy to the insulator.
Barkhausen instability and its implication in T(x) modelling of hysteresis
Authors: Takacs J. 
Published: January 2007

PurposeThe paper sets out to formulate the intermolecular forces leading to Barkhausen instability. In the approach the known concept of effective field is used within the framework of the T(x) model. The aim is to provide a mathematical tool to theoreticians and applied scientists in magnetism that is easier to use than those of other models. At the same time to demonstrate the easy applicability of the T(x) model to hysteretic phenomena.Design/methodology/approachWith the combination of the effective and the external field the model is applied to hysteresis loops as well as to the anhysteretic state showing in both cases the local development of unstable conditions at beyond a critical point, leading to local hysteresis loops.FindingsThe paper formulates the critical conditions for the hysteretic and the anhysteretic process and calculates the susceptibility as the functions of magnetisation and the applied field.Research limitations/implicationsExperimental verification will be required to prove the applicability to the various magnetic materials and to the accuracy of the model.Practical implicationsThe paper provides an easy mathematical and visual method to show the conditions before and after the Barkhausen instability sets in during the magnetisation process.Originality/valueThe paper provides an easy mathematical tool for theoreticians and experimental scientists with a visual presentation of processes leading to Barkhausen instability and magnetic behaviour beyond that by using the T(x) model.
Analysis of photonic band‐gap structures in stratified medium
Authors: Tong Ming‐Sze , Chen Yinchao , Lu Yilong , Krozer Viktor , Kagoshima Kenichi , Kim Hyeong‐Seok , Chang Tae‐Gyu 
Published: January 2007

PurposeTo demonstrate the flexibility and advantages of a non‐uniform pseudo‐spectral time domain (nu‐PSTD) method through studies of the wave propagation characteristics on photonic band‐gap (PBG) structures in stratified mediumDesign/methodology/approachA nu‐PSTD method is proposed in solving the Maxwell's equations numerically. It expands the temporal derivatives using the finite differences, while it adopts the Fourier transform (FT) properties to expand the spatial derivatives in Maxwell's equations. In addition, the method makes use of the chain‐rule property in calculus together with the transformed space technique in order to make the algorithm flexible in terms of non‐uniform spatial sampling.FindingsThrough the studies of the wave propagation characteristics on PBG structures in stratified medium, it has been found that the proposed method retains excellent accuracy in the occasions where the spatial distributions contain step of up to five times larger than the original size, while simultaneously the flexibility of non‐uniform sampling offers further savings on computational storage.Research limitations/implicationsResearch has been mainly limited to the simple one‐dimensional (1D) periodic and defective cases of PBG structures. Nevertheless, the findings reveal strong implications that flexibility of sampling and memory savings can be realized in multi‐dimensional structures.Practical implicationsThe proposed method can be applied to various practical structures in electromagnetic and microwave applications once the Maxwell's equations are appropriately modeled.Originality/valueThe method validates its values and properties through extensive studies on regular and defective 1D PBG structures in stratified medium, and it can be further extended to solving more complicated structures.
Frequency‐domain analytical investigation of space‐vector modulated PWM waveforms in four‐switch VSI
Authors: Klima Jiri 
Published: January 2007

PurposeTo provide a new method and methodology for researches and academic members which can help them to develop scientific work.Design/methodology/approachThe paper presents closed‐form expressions for the harmonic components of the space‐vector pulsewidth modulated (PWM) waveforms under inverter fault‐mode operations. The main method that is used is the Laplace transform and Fourier series expansion theorem.FindingsProvides information about harmonic sources and its influence on the behavior of the induction machine.Practical implicationsThe calculated harmonics show a very close agreement with measured harmonics from an experimental digital signal processor (DSP) based modulator. It provides a very useful source of theoretical and practical information for scientific and research area.Originality/valueThe method is original and has not been published before. The new and original approach is given by the use of the Laplace transform of space‐vectors in the complex plane. This will help to understand harmonics which are formed in four‐switch voltage source inverter.
Time step truncation in direct simulation Monte Carlo for semiconductors
Authors: Muscato Orazio , Wagner Wolfgang 
Published: January 2007

PurposeTo provide an accurate analysis of the systematic error introduced by the constant time technique free flight mechanism, due to the choice of the time step and number particles.Design/methodology/approachA homogeneous (bulk) silicon semiconductor is studied by using direct simulation Monte Carlo (DSMC).FindingsThe systematic error turns out to be of the first order with respect to the time step. The efficiency of the method is tackled.Research limitations/implicationsThe analysis is limited to the bulk case. Future researches will consider non homogeneous devicesOriginality/valueAn accurate analysis of an “old” free flight mechanism has been performed, and its limits have been stated.
Discontinuous Galerkin time‐domain solution of Maxwell's equations on locally‐refined nonconforming Cartesian grids
Authors: Canouet N. , Fezoui L. , Piperno S. 
Published: January 2007

PurposeThe use of the prominent FDTD method for the time domain solution of electromagnetic wave propagation past devices with small geometrical details can require very fine grids and can lead to very important computational time and storage. The purpose is to develop a numerical method able to handle possibly non‐conforming locally refined grids, based on portions of Cartesian grids in order to use existing pre‐ and post‐processing tools.Design/methodology/approachA Discontinuous Galerkin method is built based on bricks and its stability, accuracy and efficiency are proved.FindingsIt is found to be possible to conserve exactly the electromagnetic energy and weakly preserves the divergence of the fields (on conforming grids). For non‐conforming grids, the local sets of basis functions are enriched at subgrid interfaces in order to get rid of possible spurious wave reflections.Research limitations/implicationsAlthough the dispersion analysis is incomplete, the numerical results are really encouraging it is shown the proposed numerical method makes it possible to handle devices with extremely small details. Further investigations are possible with different, higher‐order discontinuous finite elements.Originality/valueThis paper can be of great value for people wanting to migrate from FDTD methods to more up to date time‐domain methods, while conserving existing pre‐ and post‐processing tools.
Multiobjective optimal design of three‐phase induction motor using simulated annealing technique
Authors: Subramanian S. , Bhuvaneswari R. 
Published: January 2007

PurposeThis paper presents a novel multiobjective optimal design of three phase induction motor using simulated annealing (SA) technique for minimizing annual material cost and annual loss cost as two objectives.Design/methodology/approachThe design problem of a three‐phase induction motor is presented as a nonlinear multicriterion optimization problem on the basis of minimizing the annual cost of the motor. The annual cost referred is the sum of the annual interest and depreciation of motor active material costs, annual cost of active power loss of the motor and the annual energy cost required to supply such power loss. A computer package is built which generates initial values of motor parameters and gives the optimal values of these parameters with more than one objective function and nonviolated constraints. The problem is solved by giving weights which reflect the priority of objective functions. The SA technique is used as a tool to solve the problem.FindingsTo verify the validity, the proposed method is applied to a three‐phase induction motor design. From the results, it is found that the proposed method is fast and efficient and hence it is useful for multiobjective design of an induction motor.Originality/valueThis method is particularly useful in satisfying the needs of motor producer and consumer by prioritizing their needs and finally arriving at a best compromise solution.
Minimal positive realizations for discrete‐time systems with state time‐delays
Authors: Kaczorek Tadeusz 
Published: January 2007

PurposeAims to formulate and solve the minimal positive realization problem for discrete‐time linear single‐input, single‐output systems with many state time‐delays.Design/methodology/approachA conceptual discussion and approach are taken.FindingsSufficient conditions for the existence of positive realizations of a given proper rational function are established. A procedure for computation of minimal positive realizations is presented and illustrated by an example.Originality/valueExtends an earlier method for positive discrete‐time systems with many state time‐delays.
Steady‐state modeling of a phase‐shift PWM parallel resonant converter
Authors: İskender İres , Üçtug˘ Yıldürüm , Bülent Ertan H. 
Published: January 2007

PurposeTo derive an analytical model for a dc‐ac‐dc parallel resonant converter operating in lagging power factor mode based on the steady‐state operation conditions and considering the effects of a high‐frequency transformer.Design/methodology/approachA range of published works relevant to dc‐ac‐dc converters and their control methods based on pulse‐width‐modulation technique are evaluated and their limitations in output measurement of higher output voltage converters are indicated. The circuit diagram of the converter is described and the general mathematical model of the system is obtained by deriving and combining the mathematical models of the different converter blocks existing in the system. The derived mathematical model is used to study the steady‐state and transient performance of the converter. The deriving procedure of the analytical model for a parallel resonant converter is extensively given and the analytical model obtained is verified by simulation results achieved using MATLAB/SIMULINK and the program written by the authors.FindingsThe paper suggests an analytical model for dc‐ac‐dc parallel resonant converters. The model can be used in the output voltage estimation of a converter in terms of its phase‐shift angle and the dc‐link voltage.Research limitations/implicationsThe resources in the library of the authors' university and also the English resources relative to dc‐ac‐dc converters reachable through the internet were researched.Practical implicationsThe analytical model suggested can be used in estimating the output voltage of the converters used in high‐voltage applications or where there are difficulties in employing sensors in measurement of the output voltage due to high price or implementation problems.Originality/valueThe originality of the paper is to present an analytical model for dc‐ac‐dc parallel resonant converters. Using this model makes it possible to estimate the output voltage of the converter using the dc‐link voltage and the phase‐shift angle. The proposed model provides researchers to regulate the output voltage of the converters using feed‐forward control technique.
Efficient computation of the periodic steady state solution of nonlinear electric systems applying parallel processing techniques
Authors: Medina Aurelio , Ramos‐Paz Antonio , Rubén Fuerte‐Esquivel Claudio 
Published: January 2007

PurposeTo introduce an efficient methodology for the computation of the periodic steady state solution of power systems with nonlinear and time‐varying components which combines a Newton method based on a numerical differentiation procedure to obtain a fast steady state solution in the time domain and parallel process techniques.Design/methodology/approachNonlinear electric systems are represented by a set of differential equations, the conventional solution in the time domain is accelerated by a Newton method based on a numerical differentiation procedure for the convergence of state variables to the limit cycle and thus to the network periodic steady state solution. The efficiency of the solution is further enhanced with the application of parallel processing technology based on parallel virtual machine (PVM) and multi‐threading (MT).FindingsThe periodic steady state solution of nonlinear electric systems, even of large‐scale, can be efficiently obtained in the time domain with the application of Newton methods for the fast converge of state variables to the limit cycle. The efficiency of the computer solution can be dramatically enhanced with the application of parallel processing technology. The potential of the PVM and MT platforms is shown in the investigation. A comparison of advantages and disadvantages associated with each parallel processing platforms is given; a quantitative comparison between PVM and MT is provided.Practical implicationsThe steady state solution of nonlinear electric systems can be efficiently obtained with a combination of Newton methods for the convergence acceleration to the limit cycle and parallel processing techniques.Originality/valueThe steady state solution of nonlinear electric systems using a Newton method based on a numerical differentiation procedure for the convergence acceleration to the limit cycle and parallel processing based on the PVM and MT platforms has not, to the authors' knowledge, reported before.
Improved fast evolutionary program for optimum design of power transformer
Authors: Subramanian S. , Bhuvaneswari R. 
Published: January 2007

PurposeThe power transformer is one of the most important pieces of equipment in a power system. The necessity for the optimum design of a power transformer arises because the design chosen should satisfy all the limitations and restrictions placed on it. This paper presents an improved fast evolutionary programming (IFEP) technique for the optimal design of a three‐phase power transformer.Design/methodology/approachThe optimization of the transformer design problem is formulated as an NLP problem, expressing the objective and constraint functions in terms of the selected independent variables. Here the cost of the transformer is considered as the objective function and is the sum of material cost of stampings and copper windings, cost of cooling tube arrangements, cost of cooling medium, insulation cost and labour cost. A computer program is written from which the optimal design parameters are obtained. For optimization, the classical evolutionary programming (CEP) technique and its variant the IFEP technique are used and the results are compared.FindingsThe application of CEP and IFEP for transformer design has been demonstrated on two test cases. It has been observed that this IFEP outperforms the CEP in obtaining the optimum design of transformers of smaller as well as larger ratings in terms of execution time, convergence rate, quality and success rate.Originality/valueThe proposed method results in the economical design of a three‐phase power transformer which can significantly reduce the cost of manufacturing transformers.