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Yayın Influence of the velocity on the energy patterns of moving scatterers(Taylor & Francis, 2004) İdemen, Mehmet Mithat; Alkumru, AliParallel to the developments in the communication through space vehicles achieved during the last two decades, the scattering problems connected with moving objects became more and more important from both theoretical and practical points of view. Same problems are also arisen in point of space science, radio astronomy, radar techniques and particle physics. The earlier investigations available in the open literature concern the analysis of the scattered field pattern and, hence, treat the polarization, frequency shift (Doppler effect), aberration, etc, which are all important from both pure scientific and technological points of view. But, another issue which is also important in regard to the communication, antennas and particle physics is the influence of the motion on the scattered energy patterns which involves the radar cross-section and scattering coefficient. This paper is devoted to this purpose and aims to study the influence of the velocity on the received and scattered energies. Notice that the scattered wave is not time-harmonic even though the incident wave is so because the Lorentz transformation formulas interrelate the space coordinates and time, which makes impossible to extend the notion of radar cross-section to moving bodies. For the sake of simplicity of the mathematical manipulations, only two-dimensional case is taken into account but the method can be adapted by straightforward extensions to other types of scatterer.Yayın Diffraction of two-dimensional high-frequency electromagnetic waves by a locally perturbed two-part impedance plane(2004) İdemen, Mehmet Mithat; Alkumru, AliAmong the wave propagation problems, those connected with half-spaces bounded by sectionally homogeneous boundaries take important place because they are motivated by microwave applications. If the boundary are of three or more parts, then the problem results, very frequently, in functional equations involving unknown functions, say Ψ+ (v), Ψ- (v) and P(v), which are regular in the upper half, lower half and whole of the complex v-plane, respectively, except at the point of infinity. A local (non-homogeneous) perturbation on a two-part boundary, which is of extreme importance from engineering point of view, gives also rise to a problem of this type. The aim of the present paper is to establish a method which is based on the elimination of the unknown functions Ψ+ (v) and Ψ- (v) to obtain an integral equation of the Fredholm type for the entire function P(v), which can be solved rather easily by numerical methods. The functions Ψ+ (v) and Ψ- (v) are then determined by the classical Wiener-Hopf technique.
