Design of wave absorber for small conducting sphere

An electromagnetic wave absorber for a small sized conducting sphere is designed by applying the Newton-Raphson method to the eigenfunction series solution for a coated conducting sphere. The parameters for the perfect absorbing condition are the constitutive parameters and the thickness of coating for a given radius of conducting sphere. The wave absorber designed by this method exhibits a superior absorption performance to that designed using flat plate absorber theory     

Improvement of natural frequency extraction in frequency domain

Natural frequency extraction in the frequency domain using measured frequency responses is an ill-conditioned problem. A method is proposed to improve the accuracy of the previously extracted natural frequencies. It is shown from results that the method can improve the accuracy of the natural frequencies extracted from synthetic and measured frequency response samples     

Scattering analysis of conducting bodies of revolution usingfictitious currents and point-matching

In this paper, a fictitious current model using point-matching is introduced for the electromagnetic scattering problem of a conducting body of revolution. To take advantage of the rotational symmetry of a scatterer, test points and source points are assumed to have φ-dependence of e^jnφ and are grouped into test loops and source loops, respectively. The number of sample points in each loop is determined in proportion to the length of the loop. Thus, the range of orders to be considered in each loop is dependent on the length of the loop. The field components of higher order modes which can arise due to aliasing are removed using appropriate approximations. Since the current sources and the boundary condition testing are of point-form, the numerical evaluation of the matrix elements is simple and fast. Numerical results are compared with other methods, and the numerical efficiencies obtained with this method are discussed     

Fabrication of dye-sensitized solar cells by transplanting highly ordered TiO2 nanotube arrays

Highly ordered TiO₂ nanotube arrays fabricated by anodization are very attractive to dye-sensitized solar cells (DSCs) due to their superior charge percolation and slower charge recombination. However, the efficiency of TiO₂-nanotube-based DSCs is 6.89%, which is still lower than that of TiO₂-nanoparticle-based DSCs. We have suggested the transplanting the highly ordered TiO₂ nanotube arrays to FTO glass to improve the performance of TiO₂-nanotube-based DSCs. DSCs based on transplanted TiO₂ nanotube arrays and TiO₂ nanoparticles were fabricated by same process and materials to exclude the unexpected factors. In TiO₂ thickness of ca. 15 μm, the efficiency of 2.91% in front-side illuminated DSCs based on TiO₂ nanotube arrays was higher than those in back-side illuminated DSCs based on TiO₂ nanotube arrays and in front-side illuminated DSCs based on TiO₂ nanoparticle. Front-side illuminated DSCs based on TiO₂ nanotube arrays having various thicknesses were successfully fabricated. The efficiency in DSCs having 20.0 μm thick TiO₂ nanotube arrays was improved to 5.36% by TiCl₄ treatment.     

Selecting sampling interval of transient response for the improved Prony method

A sampling interval selection scheme for use with the improved Prony method is proposed. Since natural frequency extraction is a numerically ill-conditioned problem, a small change in the sampling interval results in a large change in the extracted natural frequencies. From the perturbation of the eigenvectors of the matrix, the accuracy criterion of the extracted natural frequencies is derived. The proposed scheme is validated using natural frequency extraction from the synthetic response, the method of moments (MM) response, and the measured response.     

Basis function considerations for the method of moments using thefictitious current model

In the method of moments (MoM) using the fictitious current model (FCM), an impulsive basis function is principally employed to expand the fictitious currents for various electromagnetic scattering problems. In this paper, we introduce the subdomain basis functions and consider the dependence of the solution accuracy and computation time of the MoM-FCM on the basis functions by means of a canonical two-dimensional (2-D) scattering problem     

Efficient classification of ISAR images

In this paper, we propose a method to classify inverse synthetic aperture radar images from different targets. Our approach can provide efficient features for classification by the combined use of a polar mapping procedure and a well-designed classifier. The resulting feature vectors are able to meet the requirements that efficient features should have: invariance with respect to rotation and scale, small dimensionality, as well as highly discriminative information. Typical experimental examples of the proposed method are provided and discussed.     

Effect of B2O3 and CuO on the sintering temperature and microwave dielectric properties of the BaTi4O9 ceramics

The effect of B₂O₃ and CuO on the sintering temperature and microwave dielectric properties of BaTi₄O₉ ceramics was investigated. The BaTi₄O₉ ceramics were able to be sintered at 975^∘C when B₂O₃ was added. This decrease in the sintering temperature of the BaTi₄O₉ ceramics upon the addition of B₂O₃ is attributed to the formation of BaB₂O₄ second phase whose melting temperature is around 900^∘C. The B₂O₃ added BaTi₄O₉ ceramics alone were not sintered below 975^∘C, but were sintered at 875^∘C when CuO was added. The formation of BaCu(B₂O₅) second phase could be responsible for the decrease in the sintering temperature of the CuO and B₂O₃ added BaTi₄O₉ ceramics. The BaTi₄O₉ ceramics containing 2.0 mol% B₂O₃ and 5.0 mol% CuO sintered at 900^∘C for 2 h have good microwave dielectric properties of ε_r = 36.3, Q× f = 30,500 GHz and τ_f = 28.1 ppm/^∘C     

Natural frequency extraction using late-time evolutionary programming-based CLEAN

In this paper, we present a novel method for natural frequency extraction. Our algorithm is called late-time evolutionary programming (EP)-based CLEAN, and has many advantages compared to conventional methods. The accuracy of our algorithm is not affected by the false estimation of the number of natural resonance modes. Furthermore, our method is insensitive to random noise. Insensitivity is a very important characteristic in the resonance extraction algorithm since the late-time response usually has small energy. Using synthetic data, we show these characteristics by comparing them to Prony's method and the E-pulse technique. We also applied our method to the numerical data and B-52 measured data which is obtained at Michigan State University (MSU) arch range.     

An asymptotic solution of EM backscattering from a conducting sphere coated with a composite material

An asymptotic high frequency solution for the electromagnetic (EM) backscattered field produced by a plane wave incident on a perfectly conducting sphere coated with a thin composite material is derived in this paper. For the formulation of the incident and the reflected field the characteristics of the wave transformation and the line integral via the stationary phase method were applied, respectively, and the obtained results are cast in the ordinary ray formats of a geometrical optics field. Based on the Watson transform technique, the diffracted field is also formulated from the residue series solution of the problem and presented in a form suitable for the numerical calculation. The numerical results obtained from the derived asymptotic solution show excellent agreement with those from the rigorous eigenfunction solution.