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Wyszukujesz frazę "Bjørnø, L." wg kryterium: Autor


Wyświetlanie 1-6 z 6
Tytuł:
Contemporary aspects of the theory and application of nonlinear acoustics
Autorzy:
Bjørnø, L.
Powiązania:
https://bibliotekanauki.pl/articles/176901.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nonlinear acoustics
absorption
diffraction
dispersion
focused fields
underwater applications
second-order nonlinearity parameter
Opis:
The foundations of nonlinear acoustics may be traced nearly 250 years back in time, but only the last 50 years have shown an increasing number of attempts to exploit the research results in nonlinear acoustics. Based upon the fundamental equations of fluid dynamics, the second-order acoustic equations may be derived which can be reduced to a compound equation describing several of the most important and fast developing areas of research in nonlinear acoustics. The relations between this compound equation and Burgers' equation, Korteweg-DeVries equation, the K-Z-K equation, Westervelt's equation and the general second-order wave equation are discussed in depth. Finally, it is shown how the derivatives of the compound equation can be applied to nonlinear acoustic research related to materials characterisation by use of the B/A-ratio, to underwater acoustics by use of the parametric acoustic array and to focused, high-power ultrasonic fields.
Źródło:
Archives of Acoustics; 2005, 30, 1; 73-85
0137-5075
Pojawia się w:
Archives of Acoustics
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:
Scattering of plane acoustic waves at elastic particles with rough surfaces
Autorzy:
Bjørnø, L.
Powiązania:
https://bibliotekanauki.pl/articles/332313.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
ultrasonic waves
acoustic waves
rough surfaces
Opis:
A comprehensive theoretical and numerical study oj the influence oj surface roughness oj elastic particles in water on the scattering oj ultrasonic waves has been carried out. For near spherical shape oj the particles and with small rms-roughness heights a perturbation method has been developed. In this method the first-order perturbation contribution predicts the contribution to the incoherently scattered acoustic field due to surjace roughness, and the second-order perturbation contribution predicts the change in the coherent field and will satisfy the requirement oj energy conservation. The second-order perturbation contribution is evaluated using the concept ojform function, while the first-order perturbation to the total scattered acoustic field is evaluated using the scattering cross-section. As a junction oj the ka-value and jor different rms-roughness heights a numerical study oj the jorward and backward scattering from rough, elastic particles has been carried out and a substantial roughness influence on the scattered field has been verified. Same experimental resultsfrom measurements oj scattering jrom glass and cast iron spheres have given evidence to the numerical predictions.
Źródło:
Hydroacoustics; 2003, 6; 7-18
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anomalous low frequency sea surface reverberation
Autorzy:
Neighbors, T. H.
Bjørnø, L.
Powiązania:
https://bibliotekanauki.pl/articles/332812.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Low frequency sea surface sound backscattering from ̴100 Hz to a few kHz observed from the 1960s [A,B,C] to the 1990s [D,E] is substantially higher than explained by rough sea surface scattering theory. Alternative theories for explaining this difference range from scattering by bubble plumes/clouds formed by breaking waves to stochastic scattering from fluctuating bubble layers. Disparities remain between measurements and predictions [F] as a function of sound incidence angle, wind speed, and whitecap coverage. A first order, two dimensional approach for bubble plume scattering [G] that includes the rough sea surface shows that bubble plume shadowing dominates the backscattered signal strength at shallow grazing angles. To demonstrate the effect, scale model experiments were performed at the Technical University of Denmark [H]. The scattered signal strength fluctuations observed at shallow angles are characteristic of the predicted ocean environment. Shadowing has a first order impact on the scattering strength observed from bubble plumes and clouds.
Źródło:
Hydroacoustics; 2001, 4; 181-192
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of acoustic streaming for improving metal diffusion during electrochemical deposition
Autorzy:
Poćwiardowski, P.
Stepnowski, A.
Bjørnø, L.
Powiązania:
https://bibliotekanauki.pl/articles/332653.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The efficient method of improving diffusion of more noble metal through barrier layer created during electrochemical deposition process, by means of acoustic streaming was investigated. The results obtained from the experiments demonstrates the possibility of controlling the amount of liquid injected to the vicinity of cathode by the change of acoustic intensity. This results in accomplishing the controlled migration inside barrier layer and thus the inspecting of the mass of more noble metal in the plated alloy. The Schlichting type of acoustic streaming was mostly used in investigation.
Źródło:
Hydroacoustics; 2001, 4; 205-208
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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