| 1. |
- Demin, I.Yu., et al.
(författare)
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The numerical simulation of propagation of intensive acoustic noise
- 2013
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Ingår i: Proceedings of Meetings on Acoustics. - San Francisco : ASA. - 1939-800X.
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Konferensbidrag (refereegranskat)abstract
- The propagation of intensive acoustic noise is of fundamental interest in nonlinear acoustics. Some of the simplest models describing such phenomena are generalized Burgers’ equations for finite amplitude sound waves. An important problem in this field is to find the wave’s behavior far from the emitting source for stochastic initial waveforms. The method of numerical solution of generalized Burgers equation proposed is step-by-step calculation supported on using Fast Fourier Transform of the considered signal. The general idea is to keep only Fourier image of concerned signal and update it recursively (in space). For simulating the wave evolution we used 4096 (212) point realizations and took averaging over 1000 realizations. Also the object of the present study is a numerical analysis of the spectral and bispectral functions of the intense random signals propagating in nondispersive nonlinear media. The possibility of recovering the input spectrum from the measured spectrum and bispectrum at the output of the nonlinear medium is discusses. The analytical estimations are supported by numerical simulation. For two different types of primary spectrum evolution of jet noise were numerically simulates at a short distance and assayed bispectrum and a spectrum analysis of the signals.
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| 2. |
- Gurbatov, S. N., et al.
(författare)
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Behavior of intense acoustic noise at large distances
- 2007
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Ingår i: Acoustical Physics. - 1063-7710 .- 1562-6865. ; 53:1, s. 48-63
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Tidskriftsartikel (refereegranskat)abstract
- Propagation of intense acoustic noise waves is investigated in the case of a nonplanar geometry. It is shown that, at large distances from the source, where the nonlinear effects become negligible, the spectrum of such waves has a universal self-similar shape. The amplitude of the spectrum is determined by a single constant D-infinity= D-infinity(epsilon, R-0) (the spectrum steepness at zero-valued argument) whose value depends on two dimensionless parameters: the inverse acoustic Reynolds number epsilon and the dimensionless radius R-0. It is shown that the plane of dimensionless parameters (epsilon, R-0) can be divided into four regions, so that, within each of them, the quantity D-infinity is described by a universal function of these parameters. The numerical factors of these parameters are found from numerical simulations.
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| 3. |
- Rudenko, Oleg, et al.
(författare)
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Absorption of intense regular and noise waves in relaxing media
- 2014
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Ingår i: Acoustical Physics. - : Maik Nauka/Springer. - 1063-7710 .- 1562-6865. ; 60:5, s. 499-505
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Tidskriftsartikel (refereegranskat)abstract
- An integro-differential equation is written down that contains terms responsible for nonlinear absorption, visco-heat-conducting dissipation, and relaxation processes in a medium. A general integral expression is obtained for calculating energy losses of the wave with arbitrary characteristics-intensity, profile (frequency spectrum), and kernel describing the internal dynamics of the medium. It is shown that for weak waves, the general integral leads to well-known results of a linear approximation. Profiles of stationary solutions are constructed both for an exponential relaxation kernel and for other types of kernels. Energy losses at the front of week shock waves are calculated. General integral formulas are obtained for energy losses of intense noise, which are determined by the form of the kernel, the structure of the noise correlation function, and the mean square of the derivative of realization of a random process
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| 4. |
- Rudenko, Oleg, et al.
(författare)
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Nonlinear noise waves in soft biological tissues
- 2013
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Ingår i: Acoustical Physics. - : Springer. - 1063-7710 .- 1562-6865. ; 59:5, s. 584-589
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Tidskriftsartikel (refereegranskat)abstract
- The study of intense waves in soft biological tissues is necessary both for diagnostics and therapeutic aims. Tissue represents an inherited medium with frequency-dependent dissipative properties, in which waves are described by nonlinear integro-differential equations. The equations for such waves are well known. Their group analysis has been performed, and a number of exact solutions have been found. However, statistical problems for nonlinear waves in tissues have hardly been studied. As well, for medical applications, both intense noise waves and waves with fluctuating parameters can be used. In addition, statistical solutions are simpler in structure than regular solutions; they are useful for understanding the physics of processes. Below a general approach is described for solving nonlinear statistical problems applied to the considered mathematical models of biological tissues. We have calculated the dependences of the intensities of the narrowband noise harmonics on distance. For wideband noise, we have calculated the dependence of the spectral integral intensity on distance. In all cases, wave attenuation is determined both by the specific dissipative properties of the tissue and the nonlinearity of the medium.
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