International Journal of Applied Electromagnetics and Mechanics - Volume 26, issue 3-4

Authors: Formisano, Alessandro | Martone, Raffaele

Article Type: Editorial

Abstract: Preface to the IXth Workshop on Optimization and Inverse Problems in Electromagnetism, OIPE_Sorrento special issue.

DOI: 10.3233/JAE-2007-920

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 163-165, 2007

Authors: Féron, O. | Duchêne, B. | Mohammad-Djafari, A.

Article Type: Research Article

Abstract: In this paper we propose a stochastic algorithm applied to an electromagnetic inverse scattering problem. The objective is to characterise an unknown object from measurements of the scattered fields at different frequencies and for several illuminations. This inverse problem is known to be nonlinear and ill-posed. It then needs to be regularized by introducing prior information. The particular prior information we account for is that the object is composed of a known finite number of …different materials distributed in compact regions. The algorithm is applied to the inversion of experimental data collected at the Institut Fresnel (Marseille) and has already provided satisfactory results in a 2D-TM configuration. Herein, the goal is to test the same kind of method in a 2D-TE configuration. Show more

Keywords: Microwave imaging, Bayesian estimation, Markov random fields

DOI: 10.3233/JAE-2007-905

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 167-174, 2007

Authors: Abdelli, A. | Sareni, B. | Roboam, X.

Article Type: Research Article

Abstract: In this paper Multiobjective Genetic Algorithms (MOGAs) are used for the design of a small wind turbine generator (WTG) coupled to a DC bus through a diode bridge. The originality of the considered system resides in the suppression of the Maximum Power Point Tracker (MPPT). The poor efficiency of the corresponding passive structure is considerably improved by optimizing the generator characteristics associated with the wind turbine in relation to the wind cycle. The optimized configurations are …capable of matching very closely the behavior of active wind turbine systems which operate at optimal wind powers by using a MPPT control device. Show more

Keywords: Multiobjective optimization, genetic algorithms, wind energy, vertical axis wind turbine

DOI: 10.3233/JAE-2007-906

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 175-182, 2007

Authors: Thomas, D.W.P. | Vukovic, A. | Sewell, P. | Benson, T.M. | McA. McKirdy, D. | Glover, P.

Article Type: Research Article

Abstract: The feasibility of optimising a loaded Magnetic Resonance Imaging RF probe using time reversal analysis and a time domain electromagnetic solver is demonstrated in this paper. It is shown that the geometry of a Magnetic Resonance Imaging RF probe can be refined to improve the field distribution within a sample. In this novel technique the longitudinal electric field is used as the error term for the field within a biological sample and also as the source …function for a time reversal simulation. The output of the time reversal simulation will then indicate how the original probe can be adjusted or supplemented to improve the original field distribution. Two examples are given to demonstrate the utility of this approach. The first is the design of a saddle probe and the second is the design of a microstrip RF coil. Although this approach is limited to lossless structures, the results can still provide a valuable insight for structures and biological loads with significant loss. This is a fast and efficient optimisation method which can lead to novel RF structures. Show more

Keywords: Time reversal, MRI probes, MRI, optimisation, TLM, electromagnetics

DOI: 10.3233/JAE-2007-907

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 183-189, 2007

Authors: Albanese, R. | Artaserse, G. | Mattei, M. | Tudisco, O. | EFDA Contributors, JET

Article Type: Research Article

Abstract: This paper deals with the problem of the equilibrium reconstruction in a tokamak. We firstly describe two approaches for the shape reconstruction: the former based on a nonlinear least square minimization with Finite Element Method modelling taking into account the Grad Shafranov equilibrium equation; the latter based on linear multifilament models accounting for the presence of iron, eddy currents in the passive structures, and plasma. A possible unified treatment for shape and current profile reconstruction using …both internal and external measurements is then discussed: the nonlinear least square minimization procedure used for shape identification is modified to account for internal measurements and profile shape fitting. A linearized approach is finally analysed making use of Singular Value Decomposition theory. Some results on the JET tokamak are shown and discussed. Show more

Keywords: Inverse problems, tokamaks, eddy currents, linearized models

DOI: 10.3233/JAE-2007-908

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 191-199, 2007

Authors: Tran, T.V. | Brisset, S. | Brochet, P.

Article Type: Research Article

Abstract: Two analytical models and two finite element models (2D and 3D) are built and compared in terms of accuracy and computation time. They can be used as a benchmark to compare algorithms for multi-level and combinatorial optimizations. The discrete optimization of the transformer is done using branch and bound methods. The multi-level optimization is performed using one analytical model and the 3D FE model jointly thanks to the space-mapping techniques.

Keywords: Combinatorial optimization, multi-level optimization, space-mapping, safety isolating transformer

DOI: 10.3233/JAE-2007-909

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 201-208, 2007

Authors: Cavaliere, V. | Cioffi, M. | Delli Colli, V. | Formisano, A. | Marignetti, F. | Martone, R. | Scarano, M.

Article Type: Research Article

Abstract: Air-core superconducting transformers incorporate the function of shunt reactors, thus they can be used in high-voltage high-capacity applications. They result lighter than their traditional counterpart while requiring heavy metallic shields. However they may represent an effective alternative to traditional transformers only if the weight and clearance reduction is accompanied by acceptable values of magnetizing current and leakage fluxes. The reduction of the leakage fluxes allows the reduction of the metallic shield size …leading to an enhancement of the weight advantage. In addition the value of the mutual inductance should fit the shunt reactor action requirement. These objectives can be achieved by the active shielding technique. The paper proposes to properly design both the transformer and its active shield by means of a combined optimization stochastic algorithm. The procedure outlined is applied to a three-phase transformer layout. Show more

Keywords: Multi-objectives optimization, particle swarm optimization, superconducting devices

DOI: 10.3233/JAE-2007-910

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 209-215, 2007

Authors: Arunachalam, Kavitha | Udpa, Lalita | Udpa, Satish S.

Article Type: Research Article

Abstract: The concept of using adaptive optics based deformable mirror for near field microwave imaging of penetrable objects is presented in this paper. The deformable mirror microwave tomography technique proposed for inverse scattering applications relies on the use of an adaptive mirror to steer the electromagnetic (EM) field for multi-view irradiation of an unknown dielectric object using a fixed EM source. The deformable mirror tomography method offers higher degrees of freedom in that a large number of …field measurements can be recorded by adaptively changing the mirror shape during data acquisition. In this paper, the potential of a deformable mirror to yield useful field measurements for reliable permittivity reconstruction is investigated via computer simulations for TM^z polarization. The investigation also includes the robustness of the novel imaging technique in recovering the unknown permittivity distribution in the presence of noise. Show more

Keywords: Deformable mirror, near field, inverse scattering, microwave imaging

DOI: 10.3233/JAE-2007-911

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 217-223, 2007

Authors: Dilettoso, Emanuele | Gagliano, Salvina | Salerno, Nunzio | Tina, Giuseppe Marco

Article Type: Research Article

Abstract: The paper proposes a new method for the optimized design of grid-connected Hybrid Solar Wind Power Systems (HSWPS). The optimization objectives are maximization of the economic efficiency and performance of the system. Evaluation of the objectives, related to assessment of the long-term performance of the system, is performed by means of a probabilistic model. Two different stochastic algorithms proved to be suitable for the optimization: Particle Swarm Optimization and Genetic Algorithms. The proposed strategy was …applied to real systems, obtaining good solutions at low computational costs. Show more

Keywords: Hybrid Solar Wind Power Systems, multi-objective optimization, Genetic Algorithm (GA), Particle Swarm Optimization (PSO)

DOI: 10.3233/JAE-2007-912

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 225-231, 2007

Authors: Moussouni, F. | Brisset, S. | Brochet, P.

Article Type: Research Article

Abstract: The sequential quadratic programming and genetic algorithms are finely tuned on the optimal design of a brushless DC wheel motor. Combining both methods, a hybrid approach is tested. Multiobjective optimizations are performed using Nondominated Sorting Genetic Algorithm, Strength Pareto Evolutionary Algorithm, and a variable weighted sum of objectives with the sequential quadratic programming. The Pareto fronts are compared in term of accuracy, uniformity, and coverage criteria using some quality indicators.

Keywords: Sequential quadratic programming, genetic algorithms, mixed-integer optimization, multiobjective optimization

DOI: 10.3233/JAE-2007-913

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 233-241, 2007

Authors: Micu, Dan D. | Ceclan, Andrei | Micu, Dan O. | Simion, Emil

Article Type: Research Article

Abstract: It is proposed a synthesis method of designing an inductive position sensor with Tikhonov regularization procedure. Details about the mathematical modeling and numerical solutions obtained are discussed.

Keywords: Synthesis, regularization, condition number, numerical precision, achievability

DOI: 10.3233/JAE-2007-914

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 243-249, 2007

Authors: Lattarulo, Francesco

Article Type: Research Article

Abstract: The observed deposition, on a collector placed in the drift region outside the source, of unipolar ion flow in corona discharges is strongly dependent on the current density distribution in the ionisation sheath (source's region of support) enveloping the active electrode. Such a distribution, whose knowledge is the prerequisite for an optimal design of corona-based electrostatic devices and corona-free systems, results still undetermined. Therefore, an inverse source problem has been adopted for …reconstructing corona source features. To this end, a universal law governing the ion flow distribution in the drift region has been discovered long after an intense experimental activity. The value of the present law consists in being virtually interpretable as the boundary condition, at the source, needed for successfully resolving a forward space-charge-dominated field problem by a method based on Deutsch's hypothesis. Show more

Keywords: Corona discharge, unipolar ion flow, forward electric field problem, inverse source problem, universal boundary condition, Deutsch's hypothesis

DOI: 10.3233/JAE-2007-915

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 251-255, 2007

Authors: Kuilekov, M. | Ziolkowski, M. | Brauer, H.

Article Type: Research Article

Abstract: The paper deals with a regularization technique applied to the reconstruction of the interface between two conducting fluids. The reconstruction is performed using a simple genetic algorithm or an evolution strategy. However, both algorithms can give ambiguous results with low cost function values and bad quality interfaces which are far away from optically observed shapes. For avoiding such situations it is implemented a regularization procedure by including in the cost function additional terms …depending on the interface parameters. The results of the new approach and the comparison with the previous one are also presented. Show more

Keywords: Inverse field problems, interface reconstruction, regularization

DOI: 10.3233/JAE-2007-916

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 257-264, 2007

Authors: La Foresta, F. | Cacciola, M. | Mammone, N. | Morabito, F.C. | Versaci, M.

Article Type: Research Article

Abstract: It is well know that the evaluation of the bioelectric field generated by the human heart allows an accurate monitoring of the cardiac activity. In fact the human heart can be assimilated to an electric dipole that changes its amplitude and its orientation during the depolarization and repolarization processes of the heart muscle cell: this is the theoretic basis of the modern electrocardiogram (ECG). In fact the ECG is a recording of the electric potential, generated …by the electric activity of the heart, on the surface of the thorax. Thus, it is used in cardiological diagnosis, like tachycardia, arrhythmia and other disorders in the heart activation. Recent works have shown that the ECG technique could be employed to evaluate the effects of the bioelectric field generated by a fetal heart muscle in order to obtain the so-called fetal electrocardiogram (fECG). The fECG could be a very efficient way for in utero fetal heart monitoring and pathology detection during the pregnancy. In the last years many authors have studied signal processing techniques in order to obtain the fECG in a non-invasive way, but no-reflection has been shown about the bioelectric field generated by the fetal heart. The goal of this paper is to discuss the bioelectric potential distribution that the fetal heart produces on the mother abdomen during the pregnancy. The authors also show that the electrodes placement on the mother abdomen can be optimized to evaluate the fECG using blind source separation technique. Show more

Keywords: Inverse problems, ICA, fECG, bioelectromagnetic fields

DOI: 10.3233/JAE-2007-917

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 265-271, 2007

Authors: Polak, M. | Kvitkovic, J. | Formisano, A. | Martone, R.

Article Type: Research Article

Abstract: The determination of the current distribution in full-size cable-in-conduit conductor is a relevant research activity in the framework of the International Thermonuclear Experimental Reactor, aimed at optimizing the performance of the superconducting cables to be used for the machine magnets. The direct measurement of current in the cable is not possible, and inverse techniques must be used, providing only rough estimates due to the severe ill conditioning of the problem. The measurement of magnetic field in …the neighbourhood of superconducting cables is the first step in the estimation of the current distribution inside them. Uncertainties in this early phase may very adversely impact the reliability of the problem solution. In this paper we study the impact on current reconstruction of possible errors in the measurement of magnetic field of superconducting cables of Cable in Conduit Conductor type, at low temperatures, close to 4.2 K, due to a number of physical and geometrical effects. Show more

Keywords: Magnetic field measurement, source inverse problems

DOI: 10.3233/JAE-2007-918

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 273-283, 2007

Authors: Tomek, Jiří | Platil, Antonín | Ripka, Pavel

Article Type: Research Article

Abstract: To obtain unknown source distribution and magnetic moments of discrete magnetized ferromagnetic elementary volumes in our lung phantom we have chosen neural network inverse model. The simplified task was solved by regression multiple-layer perceptron network taught on data generated by multi-pole discrete forward model of the lungs. Magnetic fields corresponding to numerous possible sources were processed. The results are quite promising though more complex cases and especially in-vivo measurements would require much …more measuring nodes over the patient/phantom to get enough data for reasonable inversion. Show more

Keywords: Magnetopneumography, inversion, modeling, neural networks

DOI: 10.3233/JAE-2007-919

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 26, no. 3-4, pp. 285-290, 2007