About the wave motions in two–layer liquid with surfactant and surface electric charge on the upper border
About the wave motions in two–layer liquid with surfactant and surface electric charge on the upper border
A.V. Kondratieva, D. F. Belonozhko
The wave motion into two-layer conducting liquid with insoluble film of surfactant on the upper electrically charged surface has been investigated. The role of surfactant and charge and also variation of interfacial tension at different mode of wave motion have been considered. Mutual influence of different effects has been analyzed.
Show AbstractThe Gardner equation in weakly dispersive limit: evolution of a pulse with a polarity, opposite to the sign of the quadratic nonlinearity
The Gardner equation in weakly dispersive limit: evolution of a pulse with a polarity, opposite to the sign of the quadratic nonlinearity
E.А. Rouvinskaya, O.E. Kurkina, A.A. Kurkin, A.R. Giniyatullin
We study some peculiarities of the small dispersion limit for the Gardner equation with positive and negative sign of cubic nonlinear term and positive quadratic nonlinear term by numerical modeling of evolution of long bell–shaped pulse with a polarity, opposite to the sign of the quadratic nonlinearity. A statistical and spectral analysis of wave fields is carried out.
Show AbstractThe study of long sine wave’s evolution in the framework of the Gardner equation
The study of long sine wave’s evolution in the framework of the Gardner equation
E.А. Rouvinskaya, O.E. Kurkina, A.A. Kurkin, A.R. Giniyatullin
The purpose of this study is to investigate the possible mechanisms of extreme waves’ generation during degeneration of long sinusoidal (tidal) waves in the framework of the Gardner equation. A statistical analysis of the solitons ensemble formed during the evolution of the undular bore in various possible environmental conditions is done.
Show AbstractExperimental study of geo-hydroacoustic waves in an ice covered shallow sea
Experimental study of geo-hydroacoustic waves in an ice covered shallow sea
D. A. Presnov$^1$, R.A.Zhostkov$^1$, A.S. Shurup$^{1,2}$, A.L. Sobisevich$^1$, D.V. Likhodeev$^1$, D.E. Beloborodov$^1$, F.V. Perederin$^1$
One of the information sources about physical properties of the inhomogeneous medium is a dispersion of surface wave velocity, which amplitude decays exponentially at a depth about the wavelength. In the case of shallow water for the characteristics of the deep bottom recovery the registration of the «bottom» wave propagating along the boundary «elastic bottom–water layer» is required. For this wave registration usually ocean bottom systems are used. The experimental data are accumulated in the memory card that is removed after the measurement with the sensor, or data is transmitted through the satellite transceiver to surface communication channels. In the case of sea covered with ice use of these systems significantly hampered. This paper, based on experimental data shows that the time-frequency analysis of the cross-correlation function of signals, recorded by wideband sensors located on the surface of the ice, allows you to select in the received signal information on the propagation time of the waves between the bottom sensors. The obtained result allows speaking about the possibility of constructing of a sounding of deep inhomogeneous structures in the presence of ice cover with significantly reduced requirements on the practical implementation of this approach.
Show AbstractExperimental identification of the features of sound propagation in a shallow pond with a system of four vertical antennas
Experimental identification of the features of sound propagation in a shallow pond with a system of four vertical antennas
K.V. Dmitriev, A. S. Lipavskiy, I.A. Pankov, S.N.Sergeev, E.A. Fadeev
The experiment of the sound propagation in a shallow pond in a natural environment was made. The pond surface was covered with a layer of ice. The signals were recorded synchronously by the system of four vertical antennas located at different distances from the source. The waves propagating in the water layer and in the pond bottom were detected and its velocities were obtained.
Show AbstractNumerical modeling of axially symmetric focused fields generated by ultrasound surgery transducers using a wide-angle parabolic approximation
Numerical modeling of axially symmetric focused fields generated by ultrasound surgery transducers using a wide-angle parabolic approximation
I. S. Mezdrokhin, P.V. Yuldashev, V. A. Khokhlova
A numerical algorithm for calculating ultrasound fields radiated from axially symmetric focused sources was developed on the basis of a wide-angle parabolic approximation of the Helmholtz equation. A numerical solution for the field of an axially symmetric spherical radiator with an aperture of a = 5cm, focal length F = 9cm, and the frequency f = 1MHz was obtained. The solution was compared to those obtained using the full diffraction formulation and with conventional parabolic equation. The results showed that the relative error in pressure amplitude at the focus was 1–2% for a wide-angle parabolic approximation and 10–12% for the conventional parabolic approximation comparing to the exact Rayleigh integral solution. Calculation time for a wide-angle model was comparable to conventional parabolic model, and was an order of magnitude less than calculating the exact solution using the Rayleigh integral.
Show AbstractComparison of thermal ablation criteria for nonlinear regimes of ultrasound irradiation of biological tissue using a multi-element phased array
Comparison of thermal ablation criteria for nonlinear regimes of ultrasound irradiation of biological tissue using a multi-element phased array
Y. S. Andriyakhina, I.V. Sinilschikov, P.V. Yuldashev, V. A. Khokhlova
In this paper different criteria of thermal ablation induced by high intensity focused ultrasound in clinically significant volumes of biological tissue were compared. Sonications using a multi-element ultrasound array and various nonlinear focusing regimes were considered in numerical experiment. Sonication of tissue was maintained until thermal dose reached a threshold value at the circle of a certain radius. The threshold temperature was chosen so that the sonication stopped at the same time when using the criteria of temperature or dose. Threshold temperatures equivalent to the thermal dose threshold achieved at the end of the heating were obtained. Volumes of thermal lesions in tissue were calculated using both the criteria of thermal dose and temperature. It was shown that the use of the threshold temperature criterion corresponded with good accuracy to the thermal dose criterion in case of the uniform heating of the tissue volume.
Show AbstractMethod to determine maximal values of acousto–optic figure of merit in optically isotropic media
Method to determine maximal values of acousto–optic figure of merit in optically isotropic media
P.A. Nikitin
A method to determine optimal values of acousto-optic (АО) figure of merit was developed. Its advantages are clarity and high performance. Results can be used for development high-efficient AO devices based on optically isotropic media.
Show AbstractQuasi–orthogonal and quasi–collinear acoucto–optic interaction in absorbing medium
Quasi–orthogonal and quasi–collinear acoucto–optic interaction in absorbing medium
P.A. Nikitin, V.B. Voloshinov
A theory of acousto–optic interaction (AOI) in anisotropic medium, taking into account absorption of electromagnetic waves and attenuation of acoustic waves, has been developed. Expressions for optimal length and bandwidth of the AOI were derived. A non–reciprocal effect inherent only in the backward collinear diffraction was discovered.
Show AbstractMathematical model of rectangular waveguide system with impedance wall
Mathematical model of rectangular waveguide system with impedance wall
A. I. Erokhin, I.E. Mogilevsky, V.E. Rodyakin, V.M. Pikunov
Mathematical model for rectangular waveguide with impedance wall on which impedance Schukin–Leontovich boundary conditions are implemented is considered. Using these boundary conditions complete electromagnetic field in the waveguide is not divided into TE and TM fields and hybrids modes have to be taken into account. A new basis to represent components of complete electromagnetic field of a rectangular waveguide is suggested using witch impedance boundary conditions are satisfied exactly. Stiff system ODEs for amplitudes of this representation is a result.
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