Zhi Qi Meng

Image Reconstruction of Two-Dimensional Impenetrable Objects Using Genetic Algorithm

A genetic algorithm (GA) approach to reconstruction of the locations and shapes of two-dimensional impenetrable objects from scattered field data is presented. Local shape function method is used in the forward model, while a GA is used to seek for a solution minimizing the discrepancy between the measured and the estimated scattered fields in the inverse process. Some GA operators appropriate for the 2-D objects are proposed to achieve a high convergence rate. Several numerical results are presented to demonstrate the effectiveness of the GA approach.

Autonomous Genetic Algorithm for Functional Optimization

Genetic algorithm (GA) is effective for global optimizations, but needs the user to define several parameters. Unless these parameters are defined appropriately, search efficiency drops significantly. There are, however, no clear rules for the defining, and almost all users have considerable difficulty to use GA efficiently. A good algorithm must be use-friendly. It should not, if possible, need the user to define such parameters and can play high performance for any optimization problem. This paper proposes an autonomous GA addressing these problems.

Infinite-Series Expressions of Current Generators in Wave Scattering from a Conducting Body

In order to analyze wave scattering from a conducting body surrounded by random media, we defined current generators as an operator that transforms incident waves into surface currents on the body. Current generators are usually expressed in terms of the inverse matrix of which each element is the inner product of basis functions called sometimes modal functions. If the body is a cylinder with circular or elliptic cross-section, the basis functions can be chosen to be orthogonal ones and the inverse matrix becomes diagonal one; consequently, current generators are expressed in infinite series. This paper deals with the infinite-series expressions of current generators for circular and elliptic cylinders by using cylindrical or Mathieu functions according as the circular or elliptic cross-section of cylinders. These explicit expressions are useful for the analysis of scattering problems.

A genetic algorithm with an adaptive chromosome structure for reconstruction of radome parameters using a Gaussian beam

A genetic algorithm with an adaptive chromosome structure for reconstruction of radome parameters using a Gaussian beam

Microwave imaging of conducting cylinders using genetic algorithms

A genetic algorithm (GA) approach to the reconstruction of locations and cross section shapes of conducting cylinders from scattered field data is presented. Some GA operators appropriate for the 2-D objects are proposed to achieve a high convergence rate. Several numerical results demonstrate the effectiveness of the GA approach.

A genetic algorithm for reconstructing electric parameters of planar dielectric layers

A genetic algorithm (GA) approach to the reconstruction of electric parameters of planar dielectric layers is proposed. In order to neglect the complicated scattered waves from edges of the layers with finite size, a Gaussian beam is used as an incident wave. A chromosome structure adjustment technique is used to get a high convergence rate. The reconstructed results agree well with the true values.

Extraction of incident field from total field data

In this paper, an approach based on the field equivalence principle for obtaining the information of the incident field from total field data is presented. In general, the incident field is not easy to know because it is related to not only the impressed source but also the characteristics of the transmitting antenna and the surrounding environment of the source. By using this approach, the incident electric field is calculated from only total field data measured on a closed line, which is very useful for inverse scattering. Preliminary numerical simulations for some two dimensional scatterers show that the fields extracted from total field data are almost equal to the incident fields illuminating a scatterer of interest.

Parallelization performance of robust incomplete factorization preconditioner for real symmetric linear systems arising in magnetic field analyses

This paper investigates the parallelization performance of robust-incomplete-factorization-preconditioned conjugate gradient (RIF-CG) method for linear systems arising in magnetic field analyses using finite element method. A blocked strategy of coefficient matrix is applied to the parallelization of RIF preconditioner. Consequently, it can be seen that the scalability of block RIF is superior to that of block incomplete-Cholesky (IC) preconditioner.

Inquiry into backscattering enhancement phenomenon in random media

Backscattering enhancement phenomenon has attracted considerable attention from radar engineering and remote sensing fields. This paper investigates the phenomenon by analyzing numerically the bistatic radar cross-section (RCS) of a conducting circular cylinder embedded in a continuous random medium. The RCSs of different size cylinders are depicted by changing the fluctuation intensity and thickness of the random medium. As a result, strong backscattering-enhancement and oscillation in the neighborhood of the backward direction are observed for a wavelength-size cylinder embedded in a strong random medium.

Bistatic Scattering Enhancement Phenomenon in a Random Medium

Backscattering enhancement phenomenon in a random medium is studied by numerically analyzing a bistatic radar cross-section of a circular cylinder, under the condition that the spatial coherence length of the incident waves around the cylinder is larger enough than the size of the cylinder. The numerical analysis shows that the phenomenon may occur not only in the backward direction but also in other directions.