Vladimir Arabadzhi - Academia.edu (original) (raw)
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Papers by Vladimir Arabadzhi
BENTHAM SCIENCE PUBLISHERS eBooks, Aug 2, 2011
Radiophysics and Quantum Electronics, Jul 1, 2000
We designed, and studied experimentally, an active system for quenching surface gravity waves in ... more We designed, and studied experimentally, an active system for quenching surface gravity waves in a liquid. This system is based on the cyclic wave gate (CWG) principle. The thickness of the quenching system was about one-tenth of the length of the seiche wave but can also be much smaller than that in accordance with the CWG principle. The use of a high spatio-temporal resolution for parameter control of the waveguiding medium in the active region of the CWG and the opacity of this medium for high-frequency waves make it unnecessary to measure the wave field and generate a quenching wave.
Acoustical Physics, Sep 1, 2006
The problems of suppressing the sound field generated by a vibrating body in a liquid are conside... more The problems of suppressing the sound field generated by a vibrating body in a liquid are considered. For solving these problems, an acoustically thin active coating with a real-time thickness control is proposed. The coating should be placed directly on the surface of the body to be protected. Solutions to the problems of suppressing the radiation and scattering of sound by a body are obtained in the general form on the basis of linear operators, which characterize (i) the sound radiation by a vibrating surface, (ii) the scattering of incident waves by a fixed surface, and (iii) the vibroelastic properties of the body in an acoustic vacuum. Conditions ensuring the stability of the active system are formulated.
The effect of resonant absorption of long waves by the oscillator of little gabarits is investiga... more The effect of resonant absorption of long waves by the oscillator of little gabarits is investigated analytically and numerically. This effect means that absorption cross-section of the oscillator (monopole, dipole...) is defined by wavelength absorbed only, and does not depend on wave dimensions (much smaller, than the wavelength absorbed) of the oscillator. The expression of optimum amplitudes of excitation of the group of degrees of freedom (or oscillators) in the boundary problem of general type is obtained in the form of generalized velocities and generalized forces. Using the linear microstructures (formed by monopoles, which are located on the axis periodically) we investigated the possibility to achieve the maximum absorption cross-section of the acoustic waves by these microstructures of small wave dimensions. We consider the examples of linear microstructures, which provide unlimited logarithmic, linear and square growing of the total absorption cross-section, with growing of the quantity of elements (monopoles) in the linear microstructure with wave dimensions remaining small. The examples of cooperative and the individual strategies of absorbing oscillators are compared too. The results obtained can be used for another waves: for electromagnetic waves, water surface waves, waves of bending in elastic plates, etc.
Acoustical Physics, Nov 1, 2010
The phenomenon of resonance absorption of long waves by small-size oscillators is studied both an... more The phenomenon of resonance absorption of long waves by small-size oscillators is studied both analytically and numerically. The phenomenon consists in that the scattering cross section of an oscillator (a monopole, a dipole, etc.) is determined by the wavelength of the absorbed wave and does not depend on the wave size of the oscillator when this size tends to zero. The expression for the optimal excitation amplitude is derived for a group of oscillators of arbitrary wave size in the framework of the boundary-value problem formulated in the general form in terms of the generalized velocities and generalized forces. Using examples of linear structures (consisting of monopoles equidistantly positioned on the axis), the possibility of obtaining the maximal absorption cross section for sound absorption by such structures with a small wave size is investigated. Examples of linear structures providing unbounded logarithmic, linear, or quadratic growth of the total absorption cross section with an increase in the number of monopoles comprising them are considered for the case of the wave size of the absorbing structures being as small as desired. Characteristic features of the cooperative and individual strategies of absorbing oscillators are described. The results are applicable to waves of various physical natures.
Radiophysics and Quantum Electronics, Mar 1, 1981
Nano Progress, Aug 16, 2021
Acoustical Physics, 2005
A spatially one-dimensional model of a plane active double layer between two homogeneous elastic ... more A spatially one-dimensional model of a plane active double layer between two homogeneous elastic half-spaces is studied analytically. The layer synthesizes a preset smooth trajectory of the controlled boundary between the media without any mechanical support. The outer layer of the coating is a piezoelectric, and the inner layer is a polymer that is transparent for low-frequency sound and opaque for high-frequency sound because of dissipation. An algorithm for controlling the piezoelectric elements of the layer on the basis of signals from surface particle-velocity sensors is proposed, and a method for measuring the particle velocity is developed. Conditions of stability and efficiency of the synthesis are formulated. It is shown that the active layer thickness can be much smaller than the wavelength corresponding to the minimal time scale of the boundary trajectory to be formed. The accuracy of the trajectory synthesis depends on the accuracy of measuring, computing, and actuating elements of the system but does not depend on the vibroacoustic characteristics of the half-spaces separated by the active layer or on the presence of smooth waves in these half-spaces. For the synthesis to be efficient, the operating frequency band and the dynamic range of sensors and actuators should be many times greater than the frequency band and the dynamic range of the trajectory to be formed.
Acoustical Physics, 2009
The results of studying the physical characteristics of unidirectional acoustic sources used in a... more The results of studying the physical characteristics of unidirectional acoustic sources used in active sound control systems are presented. A discrete unidirectional source in the form of two phased monopoles and a planar array of such unidirectional sources are considered. One-dimensional boundary-value problems with two (the two-point problem) and three (the three-point problem) controlled parallel planar boundaries between homogeneous media with arbitrary impedances are studied. The boundaries (two or three) are subjected to the action of external forces. The case of the zero sum of external forces applied to the controlled boundaries corresponds to a supportless unidirectional source. It is shown that a unidirectional source can be created within the two-point boundary-value problem, whereas a supportless unidirectional source can be created within the three-point problem. Such parameters as transparency, small size, absence of support, and broad frequency band can be achieved for a unidirectional source in the form of two piezoelectric layers with the same impedance and velocity of sound as those of the surrounding medium.
World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, Jul 20, 2009
Experiments in Fluids, 1996
The effect of resonant absorption of long waves by the oscillator of little gabarits is investiga... more The effect of resonant absorption of long waves by the oscillator of little gabarits is investigated analytically and numerically. This effect means that absorption cross-section of the oscillator (monopole, dipole...) is defined by wavelength absorbed only, and does not depend on wave dimensions (much smaller, than the wavelength absorbed) of the oscillator. The expression of optimum amplitudes of excitation of the group of degrees of freedom (or oscillators) in the boundary problem of general type is obtained in the form of generalized velocities and generalized forces. Using the linear microstructures (formed by monopoles, which are located on the axis periodically) we investigated the possibility to achieve the maximum absorption cross-section of the acoustic waves by these microstructures of small wave dimensions. We consider the examples of linear microstructures, which provide unlimited logarithmic, linear and square growing of the total absorption cross-section, with growing...
Solutions to Problems of Controlling Long Waves with the Help of Micro- Structure Tools, Mar 27, 2012
Acoustical Physics, 2008
An algorithm for the real-time suppression of the fields scattered and radiated by a vibrating sm... more An algorithm for the real-time suppression of the fields scattered and radiated by a vibrating smooth closed surface of an arbitrarily shaped elastic body is developed and examined analytically. The surface of the protected body is assumed to be hard relative to the surrounding compressible medium. The active quenching system under consideration is composed of (a) a subsystem that rapidly forms a given distribution of normal particle velocities on the protected surface and (b) a subsystem that detects the incident waves with the use of a one-layer network of acoustic microphones surrounding the protected surface. It is shown that an acoustically hard body equipped with the proposed active system can be transparent for a certain class of incident wave fields. The statement of an initial-value problem allows a considerable decrease in the number of microphones in the active system for a chosen class of incident waves and, as a consequence, reduces the noise in the control system. The control algorithm includes logical and nonlinear operations, which rules out the conventional description of the quenching system in terms of a combination of linear electric circuits with constant parameters.
Journal of applied mathematics and computation, Dec 18, 2023
BENTHAM SCIENCE PUBLISHERS eBooks, Aug 2, 2011
Radiophysics and Quantum Electronics, Jul 1, 2000
We designed, and studied experimentally, an active system for quenching surface gravity waves in ... more We designed, and studied experimentally, an active system for quenching surface gravity waves in a liquid. This system is based on the cyclic wave gate (CWG) principle. The thickness of the quenching system was about one-tenth of the length of the seiche wave but can also be much smaller than that in accordance with the CWG principle. The use of a high spatio-temporal resolution for parameter control of the waveguiding medium in the active region of the CWG and the opacity of this medium for high-frequency waves make it unnecessary to measure the wave field and generate a quenching wave.
Acoustical Physics, Sep 1, 2006
The problems of suppressing the sound field generated by a vibrating body in a liquid are conside... more The problems of suppressing the sound field generated by a vibrating body in a liquid are considered. For solving these problems, an acoustically thin active coating with a real-time thickness control is proposed. The coating should be placed directly on the surface of the body to be protected. Solutions to the problems of suppressing the radiation and scattering of sound by a body are obtained in the general form on the basis of linear operators, which characterize (i) the sound radiation by a vibrating surface, (ii) the scattering of incident waves by a fixed surface, and (iii) the vibroelastic properties of the body in an acoustic vacuum. Conditions ensuring the stability of the active system are formulated.
The effect of resonant absorption of long waves by the oscillator of little gabarits is investiga... more The effect of resonant absorption of long waves by the oscillator of little gabarits is investigated analytically and numerically. This effect means that absorption cross-section of the oscillator (monopole, dipole...) is defined by wavelength absorbed only, and does not depend on wave dimensions (much smaller, than the wavelength absorbed) of the oscillator. The expression of optimum amplitudes of excitation of the group of degrees of freedom (or oscillators) in the boundary problem of general type is obtained in the form of generalized velocities and generalized forces. Using the linear microstructures (formed by monopoles, which are located on the axis periodically) we investigated the possibility to achieve the maximum absorption cross-section of the acoustic waves by these microstructures of small wave dimensions. We consider the examples of linear microstructures, which provide unlimited logarithmic, linear and square growing of the total absorption cross-section, with growing of the quantity of elements (monopoles) in the linear microstructure with wave dimensions remaining small. The examples of cooperative and the individual strategies of absorbing oscillators are compared too. The results obtained can be used for another waves: for electromagnetic waves, water surface waves, waves of bending in elastic plates, etc.
Acoustical Physics, Nov 1, 2010
The phenomenon of resonance absorption of long waves by small-size oscillators is studied both an... more The phenomenon of resonance absorption of long waves by small-size oscillators is studied both analytically and numerically. The phenomenon consists in that the scattering cross section of an oscillator (a monopole, a dipole, etc.) is determined by the wavelength of the absorbed wave and does not depend on the wave size of the oscillator when this size tends to zero. The expression for the optimal excitation amplitude is derived for a group of oscillators of arbitrary wave size in the framework of the boundary-value problem formulated in the general form in terms of the generalized velocities and generalized forces. Using examples of linear structures (consisting of monopoles equidistantly positioned on the axis), the possibility of obtaining the maximal absorption cross section for sound absorption by such structures with a small wave size is investigated. Examples of linear structures providing unbounded logarithmic, linear, or quadratic growth of the total absorption cross section with an increase in the number of monopoles comprising them are considered for the case of the wave size of the absorbing structures being as small as desired. Characteristic features of the cooperative and individual strategies of absorbing oscillators are described. The results are applicable to waves of various physical natures.
Radiophysics and Quantum Electronics, Mar 1, 1981
Nano Progress, Aug 16, 2021
Acoustical Physics, 2005
A spatially one-dimensional model of a plane active double layer between two homogeneous elastic ... more A spatially one-dimensional model of a plane active double layer between two homogeneous elastic half-spaces is studied analytically. The layer synthesizes a preset smooth trajectory of the controlled boundary between the media without any mechanical support. The outer layer of the coating is a piezoelectric, and the inner layer is a polymer that is transparent for low-frequency sound and opaque for high-frequency sound because of dissipation. An algorithm for controlling the piezoelectric elements of the layer on the basis of signals from surface particle-velocity sensors is proposed, and a method for measuring the particle velocity is developed. Conditions of stability and efficiency of the synthesis are formulated. It is shown that the active layer thickness can be much smaller than the wavelength corresponding to the minimal time scale of the boundary trajectory to be formed. The accuracy of the trajectory synthesis depends on the accuracy of measuring, computing, and actuating elements of the system but does not depend on the vibroacoustic characteristics of the half-spaces separated by the active layer or on the presence of smooth waves in these half-spaces. For the synthesis to be efficient, the operating frequency band and the dynamic range of sensors and actuators should be many times greater than the frequency band and the dynamic range of the trajectory to be formed.
Acoustical Physics, 2009
The results of studying the physical characteristics of unidirectional acoustic sources used in a... more The results of studying the physical characteristics of unidirectional acoustic sources used in active sound control systems are presented. A discrete unidirectional source in the form of two phased monopoles and a planar array of such unidirectional sources are considered. One-dimensional boundary-value problems with two (the two-point problem) and three (the three-point problem) controlled parallel planar boundaries between homogeneous media with arbitrary impedances are studied. The boundaries (two or three) are subjected to the action of external forces. The case of the zero sum of external forces applied to the controlled boundaries corresponds to a supportless unidirectional source. It is shown that a unidirectional source can be created within the two-point boundary-value problem, whereas a supportless unidirectional source can be created within the three-point problem. Such parameters as transparency, small size, absence of support, and broad frequency band can be achieved for a unidirectional source in the form of two piezoelectric layers with the same impedance and velocity of sound as those of the surrounding medium.
World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, Jul 20, 2009
Experiments in Fluids, 1996
The effect of resonant absorption of long waves by the oscillator of little gabarits is investiga... more The effect of resonant absorption of long waves by the oscillator of little gabarits is investigated analytically and numerically. This effect means that absorption cross-section of the oscillator (monopole, dipole...) is defined by wavelength absorbed only, and does not depend on wave dimensions (much smaller, than the wavelength absorbed) of the oscillator. The expression of optimum amplitudes of excitation of the group of degrees of freedom (or oscillators) in the boundary problem of general type is obtained in the form of generalized velocities and generalized forces. Using the linear microstructures (formed by monopoles, which are located on the axis periodically) we investigated the possibility to achieve the maximum absorption cross-section of the acoustic waves by these microstructures of small wave dimensions. We consider the examples of linear microstructures, which provide unlimited logarithmic, linear and square growing of the total absorption cross-section, with growing...
Solutions to Problems of Controlling Long Waves with the Help of Micro- Structure Tools, Mar 27, 2012
Acoustical Physics, 2008
An algorithm for the real-time suppression of the fields scattered and radiated by a vibrating sm... more An algorithm for the real-time suppression of the fields scattered and radiated by a vibrating smooth closed surface of an arbitrarily shaped elastic body is developed and examined analytically. The surface of the protected body is assumed to be hard relative to the surrounding compressible medium. The active quenching system under consideration is composed of (a) a subsystem that rapidly forms a given distribution of normal particle velocities on the protected surface and (b) a subsystem that detects the incident waves with the use of a one-layer network of acoustic microphones surrounding the protected surface. It is shown that an acoustically hard body equipped with the proposed active system can be transparent for a certain class of incident wave fields. The statement of an initial-value problem allows a considerable decrease in the number of microphones in the active system for a chosen class of incident waves and, as a consequence, reduces the noise in the control system. The control algorithm includes logical and nonlinear operations, which rules out the conventional description of the quenching system in terms of a combination of linear electric circuits with constant parameters.
Journal of applied mathematics and computation, Dec 18, 2023