International Journal of Applied Electromagnetics and Mechanics - Volume 21, issue 2

Authors: Chien, Wei | Chiu, Chien-Ching | Li, Ching-Lieh

Article Type: Research Article

Abstract: In this paper we address an inverse scattering problem whose aim is to determine the geometrical and the physical properties of a variable conducting cylindrical body buried in a half-space. The variable conductivity boundary leads to a mathematically ill-posed nonlinear equation. To overcome this difficulty, the attained system of nonlinear integral equations is reformulated into an optimization problem and solved by using the genetic algorithm. The genetic algorithm is employed to search the global extreme of …the object function, such that the shape and the variable conductivity of the scatterer can be reconstructed. Even when the initial guess is far away from the exact one, the genetic algorithm can avoid the local extreme and attain to a global extreme solution sucessfully. In such a case, the gradient-based methods often get stuck in a local extreme. It is found that multiple incident waves from different directions permit good reconstruction of the shape and, to a lesser extent, the conductivity in the presence of noise for the measured data. Numerical results are given to show the effectiveness of the genetic algorithm. Show more

DOI: 10.3233/JAE-2005-670

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 21, no. 2, pp. 51-62, 2005

Authors: Yang, J.S. | Zhou, H.G.

Article Type: Research Article

Abstract: It is shown that the propagation of an interface wave is possible between two ceramic piezoelectric half-spaces as governed by the three-dimensional equations of piezoelectromagnetism with full electromagnetic coupling.

DOI: 10.3233/JAE-2005-671

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 21, no. 2, pp. 63-68, 2005

Authors: Porfiri, M. | dell'Isola, F. | Santini, E.

Article Type: Research Article

Abstract: In the literature collocated or distributed arrays of piezeoelectric patches are employed to actively control structural vibrations. In the present work in order to damp beam vibrations a completely passive electric controller is designed, exploiting distributed piezoelectric transduction. In this way a simultaneous multimodal vibration suppression is obtained. The optimal electric network (interconnecting the piezoelectric transducers) is synthesized as a finite differences approximation of the derived distributed (infinite dimensional) optimal controller. A …prototype of the proposed novel smart structure (Piezo-ElectroMechanical beam) is designed, allowing for appreciating its technical feasibility and effectiveness. Show more

DOI: 10.3233/JAE-2005-672

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 21, no. 2, pp. 69-87, 2005

Authors: Morisaki, Tetsuya | Jiang, Zhongwei

Article Type: Research Article

Abstract: A truss structure consisting of aluminium beams and L-shape joints was used for investigation of the evaluation of the joint connection. Since the fastening state of bolts affects the mechanical impedance in the joint, near which a pair of PZT patches was utilised and embedded on the structure. Therefore, a high accuracy result on the mechanical impedance variation can be obtained by measurement of the electric impedance change in PZT patches. In the experiment, the joint …fastening condition is given by tightening and loosening a bolt with a torque wrench. In order to improve the estimation accuracy whether the joint is in safe or not, two new evaluation indices ε, area difference, and Δ S, template shift distance, are proposed by impedance spectrum curve matching method. The experimental results show that damage overlooking can be improved by the indices ε and Δ S with aid of the impedance peak amplitude ratio δ and the peak frequency shift Δ F, which were proposed in our previous work. Show more

Keywords: structural health monitoring, truss structure, PZT patches, piezoelectric impedance spectrum, joint fastening condition, health estimation indices, healthy factor

DOI: 10.3233/JAE-2005-673

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 21, no. 2, pp. 89-99, 2005

Authors: Di Barba, P.

Article Type: Research Article

Abstract: In the paper the method of gradient balance is revisited from microeconomics and proposed in electromagnetics as an alternative formulation of a design optimisation problem, characterized by two objective functions; this formulation exploits the design space directly. Accordingly, a numerical procedure to approximate a non-dominated solution was implemented; after validating the numerical procedure by means of an analytical benchmark, a field-based case study was developed.

Keywords: multiobjective optimisation, shape design, evolutionary methods, finite elements, inverse magnetostatics

DOI: 10.3233/JAE-2005-674

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 21, no. 2, pp. 101-117, 2005

Authors: Matsuyama, Sawa

Article Type: Research Article

Abstract: A discrete wavelets transform is applied for compressing the image data and extracting the major characteristics from magnetic vector field data which are variable in space and time. Though it always requires a number of target data composed of a power of 2, we propose here a novel approach based on Fourier transform to overcome this difficulty without loosing any original data information. A key idea is simple but effective because it exactly keeps all of …the frequency components comprising the target data. We have tried to compress the magnetic vector field data by the multiresolution analysis using three dimensional discrete wavelets transform. The analysis indicates a high recovery ratio between the raw data and compressed data when the number of the data decreases even one sixty-fourth of number of the original data. As a result, several examples demonstrate the usefulness of our new method to work out the visual communication tools. Show more

DOI: 10.3233/JAE-2005-675

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 21, no. 2, pp. 119-129, 2005

Authors: Yang, J.S. | Zhang, X.

Article Type: Research Article

Abstract: A theoretical analysis is performed on a high voltage piezoelectric transformer operating with thickness-shear modes using the zero-dimensional equations of a piezoelectric parallelepiped. Analytical solutions for the transforming ratio and efficiency of the transformer are obtained. Their dependence on the driving frequency, load impedance and geometric parameters are examined.

DOI: 10.3233/JAE-2005-676

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 21, no. 2, pp. 131-141, 2005