International Journal of Applied Electromagnetics and Mechanics - Volume 15, issue 1-4

Authors: Lozovan, M. | Cosma, V.M. | Rochat, Monica Cosma | Mihalache, O. | Chiriac, H.

Article Type: Research Article

Abstract: We present in this paper a displacement-frequency sensor including a non-linear resistor with a dynatron-type i(v) dependence, a variable coil and a d.c. voltage source. A general relation is given for the dependence of the period of the oscillations on the coil inductance and on the negative variable resistance of the non-linear resistor respectively. The functioning data of the sensor are presented, for linear and angular displacement respectively. Our sensors could find interesting applications in cardiology.

Keywords: relaxation oscillator, linear and angular displacement sensor

DOI: 10.3233/JAE-2002-449

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 195-200, 2002

Authors: Wu, Y. | Bingham, C.M. | Peel, D.J. | Howe, D.

Article Type: Research Article

Abstract: The performance of electric vehicles may be improved significantly by incorporating a flywheel peak power buffer into the power-train. An annular carbon fibre composite flywheel rim offers a high specific energy capability, although a high rotational speed is necessary for a high stored energy, whilst operation in a vacuum is conducive to a low aerodynamic loss, and necessitates the use of magnetic bearings. The electromagnetic design of such a flywheel system is described, and a dynamic …analysis that predicts the free vibration modes and frequencies, is presented. Finally, the magnetic bearing control system is described, and it is shown that the vibration damping capability of the bearings is such that natural vibration frequencies within the flywheel operating speed range can be accommodated, and performance objectives commensurate with operation in a vehicle drive-train can be achieved. Show more

DOI: 10.3233/JAE-2002-506

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 201-206, 2002

Authors: Haznadar, Z. | Štih, Ž. | Berberović, S.

Article Type: Research Article

Abstract: A procedure for the determination of the distribution of magnetization in an object of interest using measured disturbances of external magnetic field is described in the paper. The object is divided into a finite number of brick-shaped elements and we prescribe uniform distribution of magnetization within each element. The contribution of each element to the total magnetic field may be calculated analytically in terms of unknown coefficients of magnetization distribution. These coefficients are determined …from a set of measured magnetic field values by application of the least square deviations criterion. Such an approach enables a priori analysis of stability of computation. The application of the procedure is illustrated by an example. Show more

DOI: 10.3233/JAE-2002-456

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 207-212, 2002

Authors: Ferrayé, Ralph | Dauvignac, Jean-Yves | Pichot, Christian

Article Type: Research Article

Abstract: A boundary-oriented method for 2D electromagnetic inverse scattering in TM polarization and time-harmonic dependence is presented for perfectly conducting objects [1,2]. Key points of the method include a kinematical description of the contours of the objects, the introduction of pseudo-currents to ensure stability and the use of a level set method for deforming the contours. Level set methods [3] allow to handle automatically the changes of topology and to regularize naturally the contours. In this way, …several objects can be retrieved starting from one single initial guess. The frequency hopping technique turns out to play a very important role in the inversion process. This method gives highly accurate reconstructions within relatively short computational times. Show more

DOI: 10.3233/JAE-2002-457

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 213-218, 2002

Authors: Popella, Hartmut | Henneberger, Gerhard

Article Type: Research Article

Abstract: The mobile usage of a magnetic resonance imaging device commonly known as MRI requires a handy kind of magnetic circuit device for production of the main magnetic field B_0 . This device is called a Mobile Universal Surface Explorer (MOUSE). The requirements of homogeneity and field strength for MRI applications as well as low weight make great demands on the geometrical shape of the magnetic circuit. By genetic optimization of several FEM models of …the MOUSE a suitable solution shall be found which meets the demanded requirements. The paper presents a genetic optimizer for static computation of the MOUSE' field distribution and describes the implementation using object-oriented design patterns. Show more

DOI: 10.3233/JAE-2002-453

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 219-223, 2002

Authors: Kuczmann, Miklós | Iványi, Amália

Article Type: Research Article

Abstract: A neural network (NN) model of scalar hysteresis phenomena has been developed for modeling the behavior of magnetic materials. The function approximation ability of NNs has been applied. The virgin curve and a set of the first order reversal branches can be stored preliminary in a system of three NNs. Different properties of magnetic materials can be simulated by a knowledge-based algorithm. Value of differential susceptibility, dM/dH can be expressed in analytical form. Finally …hysteresis characteristics predicted by the introduced model are compared with the results of the Preisach simulation technique. Show more

DOI: 10.3233/JAE-2002-508

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 225-230, 2002

Authors: Bramanti, A. | Di Barba, P. | Farina, M. | Savini, A.

Article Type: Research Article

Abstract: The reduction of computational cost of evolutionary multiobjective Pareto-optimization algorithms is necessary when time-consuming objective functions evaluation is required. To this end neural network interpolation techniques are used for objective response surface building; evolutionary multiobjective Pareto-optimization is then performed on interpolated functions. Both analytical multiobjective test problems and numerical electromagnetic design problems are considered; the study of Pareto optimal front interpolation accuracy versus neural network training cost is performed.

DOI: 10.3233/JAE-2002-454

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 231-236, 2002

Authors: Ochiai, Hiroyasu | Torii, Susumu

Article Type: Research Article

Abstract: This paper reports about the validity of the numerical model for presuming the internal current of the superconductor that is difficult to measure. The validity of the numerical method is confirmed by the simple analysis model. This model is constituted applying boundary element method and the difficulty of measuring the internal current is solved by the inverse problem from the exterior flux density distribution. Since the application of this model draws the solution of an irreversible …magnetization phenomenon not clarified, the apparatus that uses the superconductor will develop. Show more

DOI: 10.3233/JAE-2002-455

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 237-242, 2002

Authors: Kojima, Fumio | Kubota, Naoyuki | Kobayashi, Futoshi | Takagi, Toshiyuki

Article Type: Research Article

Abstract: This paper is concerned with a shape recovery of natural cracks in steam generator tubes of the PWR nuclear power plant. A three dimensional forward model is developed for analyzing accurate probe response evaluation in eddy current testing. Using the evolutionary programming, an efficient inverse scheme is proposed for recovering natural cracks. The proposed algorithm is tested for stress corrosion cracks of the steam generator tube samples.

DOI: 10.3233/JAE-2002-458

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 243-247, 2002

Authors: Yusa, Noritaka | Chen, Zhenmao | Miya, Kenzo

Article Type: Research Article

Abstract: The present paper presents an inversion scheme that reconstructs crack profile from eddy current signals. The scheme is based upon the genetic algorithm and reconstructs crack profile from the signals obtained by numerical simulations with use of an accelerated FEM-BEM coupling code. The cracks are assumed to have uniform electrical conductivity in order to model natural cracks that occur in steam generator tubes of pressurized nuclear power plants. On the basis of calculated eddy current signals …in the previous generations, the inversion scheme is accelerated by eliminating individuals that are obviously different from the global optimum solution. Reconstruction results are shown in the paper, which reveal that the scheme is very promising. Show more

DOI: 10.3233/JAE-2002-460

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 15, no. 1-4, pp. 249-255, 2002