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Churilov A.,St. Petersburg State Marine Technical University | Medvedev A.,Uppsala University | Shepeljavyi A.,Saint Petersburg State University
Automatica | Year: 2012

A static gain observer for linear continuous plants with intrinsic pulse-modulated feedback is analyzed. The purpose of the observer is to asymptotically drive the state estimation error to zero and synchronize the sequence of pulse modulation instants estimated by the observer with that of the plant. Conditions on the observer gain matrix locally stabilizing the observer error along an arbitrary periodic plant solution are derived and illustrated by simulation for the case of pulsatile testosterone regulation. © 2012 Elsevier Ltd. All rights reserved.


Libenson B.N.,St. Petersburg State Marine Technical University
Journal of Experimental and Theoretical Physics | Year: 2012

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.


Grigorieva N.S.,St. Petersburg State Marine Technical University | Fridman G.M.,St. Petersburg State Marine Technical University
Acoustical Physics | Year: 2013

The paper is devoted to modeling an acoustic field scattered by an elastic spherical shell. The shell is immersed in a waveguide with a fluid attenuating bottom. Modal analysis is applied to calculations of both the point source field in a free waveguide and the scattering coefficients of the shell. The occurring integrals along a branch cut are expressed via the probability integral. Cases are analyzed when the source frequency differs from the critical frequencies of normal waves and when it coincides with one of them. The method is applied to estimate the effect of the field scattered by a thin elastic shell filled with air with transmission loss of the total acoustic field with distance and its depth distribution. © 2013 Pleiades Publishing, Ltd.


Grigorieva N.S.,St. Petersburg State Marine Technical University | Fridman G.M.,Saint Petersburg State University of Economics
Acoustical Physics | Year: 2014

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.


Kleshchev A.A.,St. Petersburg State Marine Technical University
Acoustical Physics | Year: 2014

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.


Semidetnov N.V.,St. Petersburg State Marine Technical University
Optoelectronics, Instrumentation and Data Processing | Year: 2014

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.


Kleshchev A.A.,St. Petersburg State Marine Technical University
Acoustical Physics | Year: 2012

Various representations of the vector potential of displacement vector in terms of the Debye and Debye-type potentials are considered for elastic (isotropic and anisotropic) bodies and media. On the basis of this artificial approach, three-dimensional diffraction, radiation, and elastic wave propagation prob-lems are solved. In addition to analytic solutions, computer calculations are performed for a three-dimen-sional problem of diffraction by a spheriodal elastic body. © Pleiades Publishing, Ltd., 2012.


Fridman G.,St. Petersburg State Marine Technical University
Journal of Engineering Mathematics | Year: 2011

An analytical solution and corresponding numerical results for the two-dimensional nonlinear problem of the flow past a planing flat plate with stagnation zone in the spoiler vicinity are presented. Chaplygin's method of singular points is applied to derive the exact solution along with the elliptic-theta-functions technique used for numerical implementation. The extreme values of the hydrodynamic coefficients as functions of the length of the stagnation zone are found to correspond to the position of the separation point of the stagnation zone where the Brillouin condition of smooth detachment is satisfied. © 2010 Springer Science+Business Media B.V.


Kleshchev A.A.,St. Petersburg State Marine Technical University
Acoustical Physics | Year: 2011

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.


Grigorieva N.S.,St. Petersburg State Marine Technical University | Fridman G.M.,St. Petersburg State Marine Technical University
Journal of Computational Acoustics | Year: 2013

The paper describes the theory and implementation issues of modeling of the acoustic field scattered by an air-filled spherical elastic shell immersed in a shallow-water waveguide over a homogeneous, fluid half-space. The normal mode evaluation is applied to the source contribution and to the scattering coefficients. The arising branch cut integrals are simplified and expressed via the probability integral. Two cases are analyzed: when a source frequency differs from the critical frequency of a normal mode and when they coincide. The formalism is applied to evaluate the effect of coupling between propagation and scattering on transmission loss. © 2013 IMACS.

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