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Kleshchev A.A.,St. Petersburg State Marine Technical University
Acoustical Physics

The resonances of spheroidal elastic bodies (prolate and oblate) in the form of solid bodies and shells are determined using dynamic elasticity theory and Debye potentials. In addition to analytic solutions, results of computer calculations are presented for the angular characteristics and scattering cross sections of spheroidal elastic bodies. © 2014 Pleiades Publishing, Ltd. Source

Grigorieva N.S.,St. Petersburg State Marine Technical University | Fridman G.M.,Saint Petersburg State University of Economics
Acoustical Physics

The paper is devoted to simulating an acoustic field scattered by an elastic spherical shell placed in a waveguide with a fluid attenuating bottom. The emitted signal is a wideband pulse with a Gaussian envelope. The normal wave method is used in the frequency domain for calculating the field of a point source in a free waveguide and the shell scattering coefficients. Movement of the receiver along a vertical straight line located behind the shell makes it possible to obtain a "three-dimensional" image of the field scattered by the shell. In this representation, the horizontal axis is time; the vertical axis is the submersion depth of the receiver; the intensity shows the amplitude of the received signal. Such three-dimensional structures make it possible to analyze the dependence of the complex diffraction structure of the acoustic field on receiver depth. In the considered numerical example, a thin, elastic, spherical shell is located near the attenuating fluid bottom. © 2014 Pleiades Publishing, Ltd. Source

Semidetnov N.V.,St. Petersburg State Marine Technical University
Optoelectronics, Instrumentation and Data Processing

The effects of local interaction of light with a particle used for diagnostics of the dispersed phase of flows are usually well described by the laws of geometrical optics. For forward scattering, geometrical optics is complemented by Fraunhofer diffraction by an opaque disk. Accurate calculations using Mie theory reveal an additional intensity of the radiation scattered in a direction close to the the direction of illumination. This additional contribution is attributed to the edge wave. The components of forward scattered light, namely, diffraction, reflection, and edge wave are studies in order to refine the contribution to the scattered intensity and locality of the interaction with the particle. It is shown that localization of the interaction with the particle occurs for all of these components. The distributions of the intensity of the individual components in forward scattering are obtained. © 2014, Allerton Press, Inc. Source

Libenson B.N.,St. Petersburg State Marine Technical University
Journal of Experimental and Theoretical Physics

The Green's function of the electric field of plasmons is determined in a semi-infinite medium with an abrupt plasma boundary where nonequilibrium conduction electrons either undergo elastic reflection from the boundary or "stick" to it and give rise to a stationary surface charge. The angular reflection of elastically scattered electrons can be either specular or diffuse. The Green's function is used to find the single event spectrum of energy loss by a fast electron moving parallel to the boundary. The effect of electron- boundary scattering parameters on the structure of bulk and surface plasmon resonances is analyzed. The probability of transition radiation of bulk plasmon by an electron moving in vacuum is examined. A new type of surface resonance is found under conditions of perfectly elastic scattering of conduction electrons from the plasma boundary, similar in structure to a tangential surface plasmon. © Pleiades Publishing, Inc., 2012. Source

Kleshchev A.A.,St. Petersburg State Marine Technical University
Acoustical Physics

A method and experimental setup intended for measuring the amplitude and phase of acoustic field in the near zone of a scatterer are described. The results of measuring the scattering characteristics of low-frequency sound signals scattered by elastic cylindrical shells are analyzed. © 2011 Pleiades Publishing, Ltd. Source

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