International Journal of Applied Electromagnetics and Mechanics - Volume 10, issue 3

Authors: Pantelyat, Michael G.

Article Type: Research Article

Abstract: Peculiarities of the numerical simulation of impulse electromagnetic field distribution in soft ferromagnetic materials are considered. An efficient algorithm has been proposed in order to cause the iterative process to converge quickly. The proposed algorithm is based on the use of the combination of the reluctivities obtained on two previous iterations. The optimal value of the process parameter has been recommended.

DOI: 10.3233/JAE-1999-134

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 10, no. 3, pp. 185-192, 1999

Authors: Sikora, Ryszard | Zeńczak, Michal

Article Type: Research Article

Abstract: The paper presents the problems connected with the selection of frequency for medical equipment using Electrical Impedance Tomography (EIT). The paper considers the problem of electromagnetic compatibility (EMC) between the object under examination and the EIT device. The frequencies of biological signals most often do not exceed few tens of hertz. The problem of EIT system influence on human organism comprises influence of quite weak electric and magnetic fields on the living matters. In some systems may occur the thermal effect. Moreover the optimum selection of frequency has great influence on the resolution of images. The selection of frequency bases …on the maximum of differences in the resistivity of the adjacent tissues. Analysis of the problems points at the range with bottom limit about 10 kHz and top limit about 100 kHz as the optimum range of frequency. Show more

DOI: 10.3233/JAE-1999-136

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 10, no. 3, pp. 193-202, 1999

Authors: Chung, T.Y. | Moon, S.J. | Jang, S.M.

Article Type: Research Article

Abstract: An active control system using a linear oscillatory actuator (LOA) is studied to suppress structural vibration. A voice-coil-type LOA having the moving mass of 23 kg weight is designed and fabricated for good linearity and high-frequency performance. The LOA consists of permanent magnets, a coil-wrapped nonmagnetic hollow rectangular structure, and an iron core for magnetic flux. When the coil is fed with current, changing its polarity, an oscillating force is produced to the moving mass in the magnetic field. Structural vibration is measured by the accelerometer attached to the structure and the level of vibration is reduced by the optimally …controlled motion of the moving mass of the LOA giving anti-phase inertia force to the structure. Among the direct output feedback control methods, the suboptimal control method based on the linear quadratic control is adopted to modify the original control gain. Numerical simulations and experimental tests to verify its performance are carried out on the test structure of about 500 kg subjected to sinusoidal or random base excitation. From these tests, it is confirmed that the acceleration level of the structure is drastically reduced near the resonant region. Show more

DOI: 10.3233/JAE-1999-139

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 10, no. 3, pp. 203-214, 1999

Authors: Lanotte, L. | Iannotti, V. | Müller, M.

Article Type: Research Article

Abstract: On the basis of recent results a new composition for easy rapid quenching production of good magnetoelastic amorphous ribbons was selected. The production was successful and the experimental results in agreements with the predictions. The structural relaxation induced by annealing produces a very high improvement of the magnetoelastic response so that the new alloy results the most promising for magnetoelastic wave application in sensor devices. In particular the amplitude of resonant magnetoelastic wave results the highest still now obtained in an amorphous ribbon.

DOI: 10.3233/JAE-1999-141

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 10, no. 3, pp. 215-220, 1999

Authors: Zhou, Jianwei | Lugg, Martin C. | Collins, Roy

Article Type: Research Article

Abstract: The ACFM technique has been proved to be an extremely practical NDE method for crack detection and sizing. Its original mathematical model is based on a uniform interrogating surface current field. In this paper, the theoretical aspects of the ACFM technique are re-examined. The thin-skin theory of electromagnetic perturbation due to a surface-breaking crack has now been generalised to allow non-uniform interrogating current fields and has then been combined with the theory of electromagnetic induction in a half-space to produce a non-uniform ACFM model. More realistic simulations of many types of ACFM probes are obtained from the new theoretical model.

DOI: 10.3233/JAE-1999-142

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 10, no. 3, pp. 221-235, 1999

Authors: Nagaya, Kosuke | Kanno, Kouichi | Hayashi, Nobuyuki

Article Type: Research Article

Abstract: The high-Tc superconducting levitation system is stable in both radial and axial directions without contacts, so it has been applied as bearings of an energy storage flywheel. To have high efficiency, the rotating speed of the wheel is significantly high, and it is necessary to pass through critical speeds. Rotating tail stocks are often attached at both ends of the shaft, and those are removed after passing through the critical speeds. But the method is complex in practical use. The present article discusses a method for passing through the critical speeds by using magnetic actuators. The analytical results for the …system are first obtained, then a control method for the system is presented. Numerical calculations are carried out for a typical problem, and it is ascertained that the present system and control method are applicable to high-Tc superconducting bearings. Show more

DOI: 10.3233/JAE-1999-143

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 10, no. 3, pp. 237-247, 1999

Authors: Hamamoto, Masaki | Hisada, Toshiaki | Suzumori, Koichi

Article Type: Research Article

Abstract: A computer simulation program based on a finite element interaction analysis method is developed for the design of electrostatic actuators. The simulation program consists of finite element analysis parts for the hyperelastic structure and electrostatic field, and the interaction analysis part. Because the actuator utilizes structural buckling so as to obtain a larger horizontal stroke, the interaction analysis must take the postbuckling problem into consideration. Therefore, the arc-length method is incorporated into the program. It is demonstrated through a numerical example that satisfactory motion of the actuator can be realized by virtue of structural buckling.

DOI: 10.3233/JAE-1999-144

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 10, no. 3, pp. 249-257, 1999

Authors: Leong, M.S. | Li, L.W. | Kooi, P.S. | Yeo, T.S. | Ma, X.

Article Type: Research Article

Abstract: This paper presents a full-wave analysis of the antenna radiation due to an aperture in a ground plane generating a circular waveguide TE_{11} wave, which is covered by a dielectric hemi-spherical radome of multi-layered geometry. Huygen’s equivalence principle and the image theory are utilized to simplify the problem. The dyadic Green’s function technique is applied to analyze the electromagnetic fields due to the circular aperture antenna with TE_{11} field distribution. Following the conventional procedure, the magnetic dyadic Green’s functions for radially three-layered and four-layered geometry are formulated to account for the full-wave contribution due to such …an equivalent magnetic surface current. The coefficients of these dyadics are derived by duality substitution and reduction from the authors’ earlier published work. The Fraunhofer electric fields are obtained using the far-zone approximation. In order to show the applicability of the analysis in this work and demonstrate the effects of the dielectric radome on the radiation patterns, computations of the power patterns, beamwidths, and total transmission losses are made and the results obtained here are compared with the existing results in the literature. Show more

DOI: 10.3233/JAE-1999-145

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 10, no. 3, pp. 259-278, 1999