International Journal of Applied Electromagnetics and Mechanics - Volume 40, issue 3

Authors: Yang, Fan | Jiang, Yan | Shi, Qinyan | Chen, Tao | He, Wei

Article Type: Research Article

Abstract: When the current distribution changes due to the breakage in the grounding grid, the magnetic field in the vicinity of the grounding grid will change, hence the magnetic field on the ground above the grounding can be used to detect the breakage of the grounding. In the paper, the magnetic field forward problem of the grounding grid is described firstly, and simulations were carried out when the breakage was located at different position. Results indicate that …the maximum change of the magnetic flux density occurs at different measuring point when the breakage was located at different position. To achieve a more convenient method to detect the grounding grid fault, the magnetic field inverse problem of the grounding grid is presented, which is the process to calculate the current flowing in the grounding grid according to the magnetic field strength, and the method based on the global regularization and Damped Gauss-Newton method to solve the inverse problem is described, with which the ill-posed and ill-conditioning characteristic of the inverse problem can be diminished. Then the fault state of the grounding grid can be confirmed in the following way. Firstly, inject a 10∼30A current into the grounding grid, measure the magnetic field strength or the magnetic flux density at the measuring points on the ground above the grounding grid, then the current distribution can be obtained by solving the inverse problem. If the parameters of the soil are known, the resistance distribution can be obtained, with which the fault state of the grounding grid and the location of the fault can be confirmed. An equivalent model to verify the inverse problem was set up, and results indicate that the global regularization can diminish the ill-posed and ill-conditioning characteristic of the inverse problem. Show more

Keywords: Grounding grid, magnetic field, forward problem, inverse problem

DOI: 10.3233/JAE-2012-1580

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 40, no. 3, pp. 173-183, 2012

Authors: Rybin, Oleg

Article Type: Research Article

Abstract: The complex effective relative permeability of a two-component ferrite-like metamaterial was studied for the two cases of electromagnetic wave propagation with respect to direction of dc magnetic bias field, namely, parallel and transverse. The metamaterial of interest is the host dielectric with periodically embedded ferric cylindrical or spherical inclusions. The inclusions are saturated with the biasing magnetic field and the magnetic losses are taken into account. The analysis was performed utilizing the …Microwave Effective Medium Theory for two-component artificial composite materials with saturated lossless ferric inclusions [1]. Computations revealed that low values of refractive index as well as negative values of permeability can be achieved. Show more

Keywords: Metamaterials, metaferrites, negative permeability, enhancement of permeability, ultra-low refractive index, Microwave Effective Medium Theory

DOI: 10.3233/JAE-2012-1582

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 40, no. 3, pp. 185-193, 2012

Authors: Chiu, Chien-Ching | Huang, Chung-Hsin

Article Type: Research Article

Abstract: A time-domain inverse scattering technique for reconstructing a buried homogeneous cylinder with arbitrary cross section in a slab medium is proposed. For the forward scattering, the FDTD method is employed to calculate the scattered E fields. Base on the scattering fields, these inverse scattering problems are transformed into optimization problems. The non-uniform steady state genetic algorithm (NU-SSGA) is applied to reconstruct the location shape and permittivity of the two-dimensional homogeneous dielectric cylinder. …The NU-SSGA is a population-based optimization approach that aims to minimize the objective function between measurements and computer-simulated data. A set of representative numerical results is presented for demonstrating that the proposed approach is able to efficiently reconstruct the electromagnetic properties of homogeneous dielectric scatterer even when the initial guess is far away from the exact one. In addition, the effects of Gaussian noises on the image reconstruction are also investigated. Show more

Keywords: Time domain inverse scattering, microwave imaging, FDTD, subgridding FDTD, NU-SSGA

DOI: 10.3233/JAE-2012-1584

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 40, no. 3, pp. 195-204, 2012

Authors: Zhang, Bo | Peng, Tao | Chen, Qiao | Cao, Quan-Liang | Ji, Kai | Shuang, Bo | Ye, Jun-Jie | Li, Liang

Article Type: Research Article

Abstract: An accurate 3-D nonlinear transient finite-element model of an eddy current brake (ECB) has been developed, with consideration of the skin effect, eddy current distribution, nonlinear magnetization-saturation and rotation. Based on the analysis of the eddy current path (ECP) and penetration depth, the influence of principal parameters related to the braking process is analyzed. After analysis and comparison with the common round pole, a novel pole with sector shape has been developed, which brings about a …significant increase of braking torque. An eight-pole ECB device with a peak torque of 4220 N · m under an excitation current of 88 A has been designed and tested for use in high-speed trains. The test results agree well with simulations. Show more

Keywords: 3-D nonlinear transient analysis, eddy current brake, eddy current path, skin effect

DOI: 10.3233/JAE-2012-1585

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 40, no. 3, pp. 205-214, 2012

Authors: Chien, Wei | Chiu, Chien-Ching | Li, Ching-Lieh | Sun, Chi-Hsien

Article Type: Research Article

Abstract: In this paper, we investigate the imaging problem to determine both the shape and the conductivity of a partially immersed non-uniform conducting cylinder from the knowledge of scattered far-field pattern of TM waves by solving the ill-posed nonlinear equation. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the inverse problem is reformulated into an optimization one. The steady-state genetic algorithm is then employed to find …out the global extreme solution of the object function. As a result, the shape and the conductivity of the conductor can be obtained. Numerical results are given to demonstrate that even in the presence of noise, good reconstruction can be obtained. Show more

Keywords: Inverse problem, partially immersed, non-uniform conducting cylinder, steady-state genetic algorithm

DOI: 10.3233/JAE-2012-1586

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 40, no. 3, pp. 215-225, 2012

Authors: Yang, Wan'an | Zhou, Gang | Gong, Kai | Li, Yan

Article Type: Research Article

Abstract: Based on the theory of molecular current hypothesis, the model of the magnetic flux intensity at a point around the cylindrical magnet is established, and a numeric method for the solution of the model is proposed. Compared with the dipole model, this method doesn't need the precondition that the distance from the magnet to the evaluation point is much larger than the maximum dimension of the magnet. At the same time, a group of the parametric …values and experiment results are illustrated. Show more

Keywords: Magnetic flux intensity, cylindrical magnet, dipole, numeric approach

DOI: 10.3233/JAE-2012-1587

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 40, no. 3, pp. 227-235, 2012

Authors: Han, Yong | Zhao, Yongping | Chai, Xin

Article Type: Research Article

Abstract: A mathematical analytical modeling of induced current for electronic anti-fouling technology is deduced in the present study, which can directly measure induced electric field generated by excitation coil. Based on the analytical expression of induced current, average power density is presented to measure the force of electronic anti-fouling system acting on the aqueous solution, and the functional relationship between average power density and electronic anti-fouling system parameters is established, which can be made as …the basis of the system parameters optimizing. By discussing the functional relationship it can be found: 1 when excitation signal frequency is higher than a certain frequency value, the increase of excitation signal frequency can't help increasing average power density effectively; 2 the coil radius is shorter or coil turns are less then the average power becomes larger. Furthermore, for proving the correctness of the proposed analytical model of induced current, an exact 2D finite element method is used to calculate induced current in a real electronic anti-fouling system, and the finite element calculation results can fit well with the results calculated by the proposed analytical model of induced current. Show more

Keywords: Electronic anti-fouling (EAF) system, induced current, average power density, system parameters optimizing

DOI: 10.3233/JAE-2012-1588

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 40, no. 3, pp. 237-250, 2012