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Wyświetlanie 1-4 z 4
Tytuł:
Parameters of echo signals originated from a gas seepage site in the Southern Baltic Sea
Autorzy:
Majewski, P.
Klusek, Z.
Powiązania:
https://bibliotekanauki.pl/articles/331854.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Gaseous shallow sediment has been recognized in several areas of the Southern Baltic Sea. The most commonly observed manifestation of the gas in the bottom top layer is an acoustic blanking or shadowing resulting from significant attenuation and scattering of acoustic signals in the regions of gas bubble occurrence at the bottom. The main goal of this publication was to examine whether known methods of acoustic echo parameterization generally used to determine the fraction of the surface deposits would be sufficient in determining the extent of the occurrence of gas saturated sediments and areas with periodic gaseous outflows. To this end, a set of an acoustic echo signals recorded in gas seepage regions by using four different frequencies (12, 70, 120 and 200 kHz) was analyzed. To determine the acoustic features of gaseous sediments, based on the shape of the echo envelope, a few statistical parameters, as well as the parameters resulting from a wavelet transform, were calculated. A comparison of the results allowed for a relatively accurate separation of pockmark areas.
Źródło:
Hydroacoustics; 2014, 17; 143-150
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
CW and CHIRP signals bottom backscattering in the PEZ of the Baltic sea
Autorzy:
Klusek, Z.
Majewski, P.
Dragan, A.
Powiązania:
https://bibliotekanauki.pl/articles/331941.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
High-frequency bottom backscattering experiments were carried out in the Polish Economy Zone of the Southern Baltic Sea. CW and chirp signals were used to determine scattering reverberation as a function of the incident wave grazing angle and at vertical sounding. The chirp signals covered the frequency range from 40 to 80 kHz whilst the CW signals were selected at 40, 60 and 80 kHz. Acoustic data concerning the angular dependence of the backscattering were taken at the points where appropriate investigations of sediment properties had been earlier made by the Polish Geology Institute. The sediment types include not only acoustically hard fine and coarse sand bottom covered with gravel but also a flat muddy bottom. The results present the backscattering as a function of frequency, signal type and sediments properties. Times of reverberation and other statistical properties of returned signal are also discussed. When possible, due to more complete information on the sediments properties the measured backscattering strength was compared to the models developed by Jackson et al.
Źródło:
Hydroacoustics; 2010, 13; 135-142
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
System for bistatic measurements of reverberations in the shallow sea area
Autorzy:
Klusek, Z.
Elminowicz, A.
Majewski, P.
Dragan, A.
Powiązania:
https://bibliotekanauki.pl/articles/331817.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
In the paper a system for measurements of reverberations in the shallow sea environment is presented. The setup operated in 40–80 kHz frequency range with pseudomonochromatic pulses or chirp signal and has possibility to acquire bistatic scattered data. The system is constructed in such manner that depending on an experiment configuration we could perform measurements of the local 3D scattering strength of the bottom and/or far range bistatic reverberations from the sea surface, volume inhomogeneities and sea bottom. The final objective of the system is to give prognosis for probability of target detections when using bior multistatic barriers. Details of the individual blocks are given in the following sections and the technicalities of the design are given. Furthermore, some examples of data gathered during test of the equipment concerning assessment of the reverberation and local bistatic scattering features are presented.
Źródło:
Hydroacoustics; 2011, 14; 83-90
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Preliminary investigations on implementation of technology of broadband signals for marine biology and sediments recognition
Autorzy:
Klusek, Z.
Majewski, P.
Dragan, A.
Psuty, I.
Powiązania:
https://bibliotekanauki.pl/articles/331938.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This paper describes potential applications of broadband acoustic signals for marine biology and fisheries and acoustic precise profiling of the upper layer of sediments. Comparisons of the results of conducted experiments employing the same experimental setup but with different signals are presented. In each of experiments short pulses of CW signals and long pulses of up/down chirp signals were used. The basic theory of FM signals as well as some of the factors that must be considered when implementing this type of signal in actual systems are described.
Źródło:
Hydroacoustics; 2010, 13; 143-152
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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