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    Wyświetlanie 1-11 z 11
    Tytuł:
    Modeling of the acoustic waves propagation in non-homogeneous medium
    Autorzy:
    Baranowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/332534.pdf
    Data publikacji:
    2009
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    acoustic waves
    numerical investigations
    KZK equation
    Opis:
    The aim of the paper is theoretical analysis of acoustic waves propagation in medium which are not homogeneous. The paper presents mathematical model and some results of numerical investigations. The mathematical model was built on the basis of the KZK equation. To solve the problem numerically the finite-difference method was applied. The on-axis pressure and power spectrum density were analysed both in homogeneous and non-homogeneous medium
    Źródło:
    Hydroacoustics; 2009, 12; 1-8
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling of the acoustic waves propagation in non-homogeneous medium
    Autorzy:
    Bjorno, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/332165.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    Research and development in WaterSide Security (WSS) are being carried out in many countries around the World. However, the R & D activities are frequently scattered and uncoordinated from country to country. Therefore, there is still a strong need for a better coordination of development of equipment and procedures for WSS and for exchange of most recent research results in order to obtain a world-wide view over the state-of-the-art in technologies and their applications. To meet this need several conferences have been held over the past decade ranging from its early start in Poland and via 3 international conferences on WaterSide Security held in 2008, 2010 and 2012, to the situation of today. This presentation will comprise an exposition on criminality at sea and its abatement today with a concentration on terror and piracy. What have we learned and what can we do.
    Źródło:
    Hydroacoustics; 2013, 16; 7-10
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical investigations of the nonlinear waves generation in a bubble layer
    Autorzy:
    Baranowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/332403.pdf
    Data publikacji:
    2012
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    The purpose of the paper was to conduct numerical investigations of the nonlinear wave generation in a layer with uniformly distributed mono-size spherical bubbles. The mathematical model and examples of results of theoretical studies of this problem are presented. The mathematical model of the pressure propagation in the bubbly liquid layer is constructed using the linear non-dissipative wave and the Rayleigh-Plesset equations. The Commander and Prosperetti model is employed to compute the phase sound speed in the bubble layer. The spectra of transmitted and reflected waves are studied and the amplitudes of selected frequency harmonics of these waves examined.
    Źródło:
    Hydroacoustics; 2012, 15; 7-12
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modelling of the finite amplitude waves interaction problem inside truncated cone
    Autorzy:
    Baranowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/332087.pdf
    Data publikacji:
    2003
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    amplitude waves
    truncated cone
    Opis:
    The paper presents the results of theoretical investigations of the finite amplitude waves interaction in water. The mathematical model and some results of numerical investigations are presented. The acoustic pressure amplitude changes for different frequency waves (especially difference frequency wave) along the sound beam were investigated. The mathematical model was built on the basis of the KZK equation. It was assumed that a circular piston was the source of two different frequency finite amplitude waves. The problem was considered as an axial symmetric one. The solution of the problem was looked for inside a truncated cone. To solve the problem the finite-difference method was applied.
    Źródło:
    Hydroacoustics; 2003, 6; 131-136
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Theoretical analysis of the finite amplitude waves interactionproblem for two types of piston
    Autorzy:
    Baranowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/331806.pdf
    Data publikacji:
    2002
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    The aim of the paper was the numerical investigations of the finite amplitude waves interaction in water. The problem was considered as an axial symmetric one. It was assumed that circular piston and ring-shaped piston were the source of two different frequency finite amplitude waves. The mathematical model was built on the basis of the Khokhlov - Zabolotskaya - Kuznetsov (KZK) equation. To solve the problem the finite-difference method was applied. The mathematical model and some results of numerical investigations are presented. The spectrum of the wave for fixed distances from the source, the pressure amplitude changes for different frequency waves as a function of distance from the source and pressure amplitude distribution for fixed distances from the piston were investigated.
    Źródło:
    Hydroacoustics; 2002, 5; 1-8
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ambient noise induced by large-amplitude internal waves in the ocean
    Autorzy:
    Serebryany, A.
    Aredov, A.
    Okhrimenko, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/332834.pdf
    Data publikacji:
    2009
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    noise
    Indian Ocean
    South China Sea
    Opis:
    Experimental data on the ambient noise generated by large-amplitude internal waves in the ocean are considered. The data are obtained by us during oceanic expeditions in the Indian Ocean and South China Sea. In both cases the generation of noise was caused by solitary internal waves with 50-m amplitudes. The internal waves were accompanied by strong orbital currents (up to 1.5 m/s) which created intense convergence with choppy surface waves at the sea surface. Simultaneous observations of internal waves and parameters of the ambient noise were carried out from a drifting vessel during calm weather. In both cases, the increase in the level of the ambient noise coincided with the passages of internal waves. The analysis of experimental data and the data of numerically modeling are presented.
    Źródło:
    Hydroacoustics; 2009, 12; 209-216
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Acoustical observation of internal waves on the shelf of the Black Sea
    Autorzy:
    Mikryukov, A.
    Popov, O.
    Serebryany, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/332808.pdf
    Data publikacji:
    2009
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    hydroacoustics
    acoustical observation
    Black Sea
    Opis:
    In October, 2007, the Acoustics Institute performed complex acoustical and oceanological studies on a fixed experimental path in the Black Sea, near the Golubaya Bay. Sound signal with linear frequency modulation were used in the experiment. The processing of the experimental records consisted in computing the envelope of the correlation function of the received and transmitted signals and the time dependence of the correlation maxima. A characteristic change in arrival times of the rays is observed for the period of the income of cold near-bottom waters on the path. The quasi-harmonic variation in the arrival times of the ray groups allows one to correctly define the parameters of short-period internal waves accompanying the bore.
    Źródło:
    Hydroacoustics; 2009, 12; 153-158
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Laser generation and detection of interface waves for the acoustic spectroscopy of liquids
    Autorzy:
    Desmet, C.
    Gusev, V.
    Lauriks, W.
    Thoen, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/332292.pdf
    Data publikacji:
    1997
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    The pulsed heating of the interface between a solid and a liquid leads to the excitation of acoustic interface waves. These interface waves are detected at a variable distance from the generation region by means of a beam deflection setup. By evaluating the amplitude and phase spectra (using a Fast Fourier transform) of two wave pulses at two different source-receiver distances, the velocity of propagation and the attenuation of the interface waves are measured as a function of frequency (bandwidth of 50 MHz). By fitting these experimentally determined results to theory it is possible to determine the acoustic properties of the liquid as a function of frequency.
    Źródło:
    Hydroacoustics; 1997, 1; 295-298
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparison of experimental results and numerical calculations of ultrasonic waves scattering on a model of the artery
    Autorzy:
    Wójcik, J.
    Trawiński, Z.
    Powałowski, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/331649.pdf
    Data publikacji:
    2008
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    ultrasonic waves
    artery model
    transmitted ultrasound
    Opis:
    The aim of this paper is to compare the results of the mathematical modeling and experimental results of the ultrasonic waves scattering in the inhomogeneous dissipative medium. The research was carried out for an artery model (a pipe made of a latex), with internal diameter of 3, 5 and 8 mm and wall thickness of 0.75, 1.25 and 2 mm. The numerical solver was created for calculation of the fields of ultrasonic beams and scattered fields under different boundary conditions, different angles and transversal displacement of ultrasonic beams with respect to the position of the arterial wall. The investigations employed the VED ultrasonic apparatus. The frequency of the transmitted ultrasound was 6.75 MHz. The good agreement between the numerical calculation and experimental results was obtained. The numerical solver is used for verified proposed methods for determining of the IMT in the artery walls.
    Źródło:
    Hydroacoustics; 2008, 11; 449-458
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Theoretical results and numerical study on the nonlinear reflection and transmission of plane sound waves
    Autorzy:
    Wojcik, J.
    Gambin, B.
    Litniewski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/332766.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    theoretical and numerical model
    continuity conditions
    non-linear waves
    lossy media
    Opis:
    The comparison between theoretical and numerical solutions of the reflection/transmission problem for the acoustic plane wave normally incident on the discontinuity surface between two nonlinear lossy media was presented. Numerical calculations made under the assumption that the two media have the same impedance, allow to single out the effect of nonlinearities in the description of the reflection and transmission phenomena, so they agreed with theoretical predictions. It was shown that theoretically obtained and numerically calculated results mutually confirmed themselves.
    Źródło:
    Hydroacoustics; 2015, 18; 181-192
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Diffraction of sound pulses on a spherical target in an oceanic waveguide covered with ice
    Autorzy:
    Grigorieva, N.
    Kupriyanov, M.
    Ostrovskiy, D.
    Stepanova, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/332177.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    diffraction of acoustic waves
    ice-covered homogeneous waveguide
    normal modes of the waveguide
    pulse with a Gaussian envelope
    surface waves
    Franz type
    Whispering Gallery type
    Opis:
    This paper is devoted to modeling of the pulse scattering by a spherical target immersed in a homogeneous waveguide covered with ice. For calculating the echo signal in the frequency domain we have followed Hackman and Sammelmann’s general approach. The arising scattering coefficients of a sphere were evaluated with the use of the normal mode method. The amount of normal modes forming the backscattered field is determined by the given directivity of the source. The emitted signal is a pulse with a Gaussian envelope. Computational results are obtained in a wide frequency range 8 - 12 kHz for water depths equal to several hundreds of m, and distances between the source/receiver and a target from 1 km up to 10 km. The target is assumed to be acoustically rigid or fluid. In particular, the properties of the ice cover and a scatterer may coincide.
    Źródło:
    Hydroacoustics; 2016, 19; 139-144
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-11 z 11

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