Electromagnetic scattering of metallic cylinders of arbitrary shape by using asynchronous particle swarm optimization and non-uniform steady state genetic algorithm

[[abstract]]Two techniques for the shape reconstruction of multiple metallic cylinders from scattered fields are investigated in this paper, in which two-dimensional configurations are involved. After an integral formulation, the method of moment (MoM) is applied to solve it numerically. Two separate perfect-conducting cylinders of unknown shapes are buried in one half-space and illuminated by the transverse magnetic (TM) plane wave from the other half space. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equation is derived and the imaging problem is reformulated into optimization problem. The non-uniform steady state genetic algorithm (NU-SSGA) and asynchronous particle swarm optimization (APSO) are employed to find out the global extreme solution of the object function. Numerical results demonstrate even when the initial guesses are far away from the exact shapes, and the multiple scattered fields between two conductors are serious, good reconstruction can be obtained. In addition, the effect of Gaussian noise on the reconstruction results is investigated and the numerical simulation shows that the reconstruction results are good and acceptable, as long as the SNR is greater than 20 dB.[[incitationindex]]SCI[[booktype]]電子版[[booktype]]紙

Image reconstruction for the partially immersed conductor by dynamic differential evolution

[[abstract]]The application of one technique for the reconstruction of shape reconstruction of a metallic cylinder from scattered field measurements is studied in this paper. Considering that the microwave imaging is recast as a nonlinear optimization problem, a cost functional is defined by the norm of a difference between the measured scattered electric field and that calculated for an estimated the shape of metallic cylinder. Thus, the shape of metallic cylinder can be obtained by minimizing the cost function. In order to solve this inverse scattering problem, dynamic differential evolution (DDE) is employed. The technique has been tested in the case of simulated measurement contaminated by additive white Gaussian noise. Numerical results demonstrate that, even when the initial guess is far away from the exact one, good reconstruction can be obtained.[[notice]]需補地點及國別[[conferencetype]]國際[[conferencedate]]20110527~2011052

Inverse problem of a buried metallic object

[[abstract]]In this paper we address an inverse scattering problem whose aim is to discuss the CPU time for recovering a perfectly conducting cylindrical object buried in a half-space. First, we use Fourier-series or cubic-spline methods to describe the shape and reformulate the inverse problem into an optimization one. Then we solved it by the improved steady state genetic algorithm (SSGA) and simple genetic algorithm (SGA) respectively and compare the cost time in finding out the global extreme solution of the objective function. It is found the searching ability of SSGA is much powerful than that of the SGA. Even when the initial guess is far away from the exact one, the cost time for converging to a global extreme solution using by SSGA is much less than that by SGA. Numerical results are given to show that the inverse problem by using SSGA is much better than SGA in time costing.[[notice]]需補地點及國別[[conferencetype]]國際[[conferencedate]]20051004~2005100

Microwave imaging of a partially immersed non-uniform conducting cylinder

[[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.[[notice]]補正完畢[[incitationindex]]SCI[[booktype]]電子

Inverse Problem of Multiple Conductors Buried in a Half-Space

[[abstract]]Electromagnetic imaging of buried multiple conductors by using genetic algorithm has been presented. Two separate perfectly conducting cylinders of unknown shapes are immersed in one half-space and illuminated by transverse magnetic (TM) polarization plane wave from the other half-space. Based on the boundary condition and the measured scattered field, we have derived a set of nonlinear integral equations, and the imaging problem is reformulated into an optimization problem. For describing the shapes of conductors, the Fourier series is selected to expanding the shape functions. In inverse algorithms, the improved steady state genetic algorithm is employed to search for the global extreme solution of objective function. Numerical results have demonstrated that the powerful performance of the inverse algorithm. The reconstructed shapes are considerably accurate even when the initial guesses are far away from the exact ones and the buried depths of the conductors are large compared to wavelength.[[conferencetype]]國際[[conferencedate]]20070816~20070818[[booktype]]紙本[[iscallforpapers]]Y[[conferencelocation]]Xi'an, Chin

Inverse scattering of an embedded inhomogeneous dielectric cylinders coated on a conductor

[[abstract]]In this paper, the inverse problem of an embedded inhomogeneous dielectric cylinders coated on a conductor by TM wave illumination is investigated. Inhomogeneous dielectric cylinders coated on a conductor embedded in a slab scatters a group of unrelated incident waves from outside. The scattered field is recorded outside the slab. By proper arrangement of the various unrelated incident field, the difficulties of ill-posedness and nonlinearity are circumvented, and the permittivity distribution can be reconstructed through simple matrix operations. The algorithm is based on the moment method and the unrelated illumination method. Numerical results are given to demonstrate the capability of the inverse algorithm. They also show that the permittivity distribution of the cylinders can be successfully reconstructed even when the permittivity is fairly large. Good reconstructed is obtained even in the presence of additive Gaussian noise in measured data. In addition, the effect of noise on the reconstruction result is also investigated.[[notice]]需補地點及國別[[conferencetype]]國際[[conferencedate]]20060903~2006090

Cubic-spline expansion for a two-dimensional periodic conductor in free space

[[abstract]]This paper presents a computational approach to the imaging of a two-dimensional periodic conductor. Both cubic-spline method and trigonometric series for shape description are used and compared. A periodic conducting cylinder with unknown shape in free space and the scattered field is recorded outside. Based on the boundary condition and the recorded scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. The genetic algorithm is employed to find out the global extreme solution of the object function. It is found that the shape described by cubic-spline can be reconstructed. In such a case, Fourier series expansion will fail. Even when the initial guess is far away from the exact one, the cubic-spline expansion and genetic algorithm can avoid the local extreme and converge to a global extreme solution. Numerical results are given to show that the shape description by using cubic-spline method is much better than that by the Fourier series. In addition, the effect of Gaussian noise on the reconstruction is investigated.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SCI[[incitationindex]]EI[[booktype]]紙本[[countrycodes]]NL

Self-adapting control parameters in dynamic differential evolution on inverse scattering problems: SADDE for inverse scattering

[[abstract]]The application of two techniques for the reconstruction of shape reconstruction of the perfectly conducting cylinder from scattered field measurements is studied in the present paper. These approaches are applied to two-dimensional configurations. After an integral formulation, a discretization using the method of moment (MoM) is applied. The inverse scattering problems are transformed into optimization problems. Considering that the microwave imaging is recast as a nonlinear optimization problem, an objective function is defined by the norm of a difference between the measured scattered electric field and that calculated for an estimated the shape of the perfectly conducting cylinder. Thus, the shape of metallic cylinder can be obtained by minimizing the objective function. In order to solve this inverse scattering problem, two techniques are employed. The first is based on a dynamic differential evolution (DDE). The second is a new version of the DDE algorithm with self-adaptive control parameters (SADDE). Numerical results indicate that the self-adaptive dynamic differential evolution algorithm (SADDE) outperforms the DDE in terms of reconstruction accuracy.[[conferencetype]]國際[[conferencedate]]20110926~20110930[[conferencelocation]]Seoul, Kore

Inverse scattering of a two-dimensional periodic conductor

[[abstract]]The image reconstruction of a two-dimensional periodic conductor by the genetic algorithm is investigated. A periodic conducting cylinder of unknown periodic length and shape scatters the incident wave in free space and the scattered field is recorded outside. Based on the boundary condition and measured scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. The genetic algorithm is then employed to find out the global extreme solution of the cost function. As a result, the shape and the periodic length of the conductor can be obtained. Numerical results are given to demonstrate that even in the presence of noise, good reconstruction has been obtained[[notice]]需補地點及國別[[conferencetype]]國際[[conferencedate]]20011015~2001101