Informacja

Drogi użytkowniku, aplikacja do prawidłowego działania wymaga obsługi JavaScript. Proszę włącz obsługę JavaScript w Twojej przeglądarce.

Wyszukujesz frazę "“target”" wg kryterium: Wszystkie pola


Tytuł:
Indirect fish target strength estimation using adaptive kernel
Autorzy:
Moszyński, M.
Powiązania:
https://bibliotekanauki.pl/articles/332772.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The typical approach to the problem of indirect fish target strength estimation from data collected using single-beam system is based on inversion of probability density function (PDF) of measured fish echo level. Due to ill-conditioning of most inversion algorithms, small errors in input data, and inaccuracies in the assumed form of the kernel, may result in large errors at the output. Therefore, al! modern inversion algorithms use sophisticated techniques to achieve satisfying results, assuming fixed kernel in the inversion procedure. The paper presents different approach, which uses adaptive construction of the kernel, under assumption of non-negative constraints in the obtained estimate of fish target strength PDF. As a result, the more reliable beam pattern PDF is obtained which leads to unbiased and more accurate estimate offish target strength PDF, than in the conventional (fixed kernel) methods.
Źródło:
Hydroacoustics; 2001, 4; 177-180
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Target tracking using multiple passive sonars
Autorzy:
Janowski, T.
Porosińska, E.
Powiązania:
https://bibliotekanauki.pl/articles/331700.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The DOA estimation methods based on the analysis of the noise subspace enable high resolution bearing determination of naval objects emitting hydrouacoustic noise. The knowledge of the objects number is the essential parameter for DOA algorithms. Practically, the number of the objects is unknown. In case of high sea ambient noise to object signal ratio the detection with desired probability is significantly hindered. In the event of system based on the console the detection decision belongs to the operator. The visual analysis of the reception beamformer changes conducts to the intruder detection. Whereas in case of the standalone systems the decision making process is performed by the detection and tracking algorithm. This article describes such algorithm based on the analysis of the machine states.
Źródło:
Hydroacoustics; 2011, 14; 69-74
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Doppler estimation method for moving target location
Autorzy:
Salamon, R.
Marszal, J.
Powiązania:
https://bibliotekanauki.pl/articles/331983.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The article presents an algorithm for target location based solely on Doppler shift of echo acoustic signals of a moving underwater object. The algorithm is designed for use in multi-static systems for protecting bodies of water from terrorist attacks by divers or submerged vehicles. The original source of signals is a transmitter emitting continuous acoustic waves. The echo signals from moving object are received by hydrophones located at fixed and known points in the water. Doppler shifts are determined from discrete Fourier transforms of hydrophone signals. The proposed iterative algorithm for target location calculates the approximate values of target speed vector and target coordinates which correspond to speed vectors as calculated previously.
Źródło:
Hydroacoustics; 2010, 13; 225-234
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of indirect 'in situ' fish target-strength estimation methods
Autorzy:
Stepnowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/331728.pdf
Data publikacji:
1997
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The paper analyzes existing in situ methods of fish target-strength estimation with speciał emphasis on an indirect method that utiłizes statistical manipulation on a backscattered acoustic echoes set. The inverse problem in question requires finding the unknown probability density distribution (PDF) of target strength in the logarithmic "domain" or PDF of a backscattering cross-section in the "domain" of absołute variabłes. These PDFs can be estimated by solving the so called "single-target single-beam integral equation", relating distributions of echo variable, target strength and beam pattem of the echo sounder transducer. In the presented analysis special attention is given to four newly developed TS-estimation methods, viz.: Expectation, Maximization and Smoothing (EMS), Discrete "MeIJin Deconvolution", Windowed Singular Value Decomposition (WSVD) and Regularization. These methods use more sophisticated estimation techniques than conventional deconvolution and related methods. A comparison of the resulting estimates obtained from the analyzed methods (using simulations as well as real data from acoustic surveys) eoneludes the paper.
Źródło:
Hydroacoustics; 1997, 1; 15-26
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Target strength of freshwater fishes at 420 kHz measured in cages
Autorzy:
Godlewska, M.
Powiązania:
https://bibliotekanauki.pl/articles/332061.pdf
Data publikacji:
2004
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The target strength of freshwater fishes was measured in cages using Biosonics 101 dual-beam echosounder. The TS-length and TS-weight relationships were determined for the mixed population of the Dobczyce reservoir and separately for roach, perch, ruffee, bream and pike. The results for small and larger fish suggest that TS for small fish decreases much faster than could be expected from the general 20LogL relationship.
Źródło:
Hydroacoustics; 2004, 7; 55-62
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On a threshold induced bias in fish target strength estimation
Autorzy:
Moszyński, M.
Powiązania:
https://bibliotekanauki.pl/articles/332238.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
fisheries acoustics
marine organisms
Opis:
In fisheries acoustics the bias introduced by a system threshold in the integration of echoes from fish and other marine organisms has long been recognized. Some simple methods for evaluating such a bias uses Rayleigh assumption applied to fish backscattering length distribution. More adequate methods require that the target strength distribution of the fish and directivity pattern of the transducer be known. The method proposed here uses statistical approach for correction of target strength probability density function (PDF). The theory of conditional target strength PDF and conditional beam pattern PDF is derived. It provides correction not only for mean value of target strength but for whole distribution. The data obtained from simulations are presented and compared with those obtained from single-beam inverse processing.
Źródło:
Hydroacoustics; 2003, 6; 49-52
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The beam pattern PDF in target strength estimation - theoretical and practical approach
Autorzy:
Moszyński, M.
Stepnowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/331912.pdf
Data publikacji:
1997
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The knowledge of beam pattem probability density function (PDF) plays a crucial role in target strength estimation when using indirect methods. The paper describes the theoretical and practical aspects of approximations applied in calculating the PDF of this deterministic function from a probabilistic point of view. The solution of differential equation presented in the paper leads to a unified approach to approximations and has a elear interpretation.
Źródło:
Hydroacoustics; 1997, 1; 31-26
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Using single-beam observations off fish echoes from sidelobe in fish target strength estimation
Autorzy:
Moszynski, M.
Hedgepeth, J. B.
Powiązania:
https://bibliotekanauki.pl/articles/332246.pdf
Data publikacji:
1999
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Fish target estimation when using single-beam echosounder data is based on solving integral equation by inverse technique with probability density functions (PDFs) of echo envetope and heam pattern as known variabies. Typically - by setting threshold on echo level - only main-tobe observation are used due to difficulties in beam pattern PDF evaluation and signal-to-noise ratio constraints. This paper presents a method that uses side-tobe observations in the beam pattern probability density function and all collected echo peak values. These side-tobe echo observations indifferentiable when using single-beam system are combined with those from main-tobe. The smoothed Expectation Maximization metbod (EMS) is used to estimate densities and acoustic sizes of fish main-tobe with side-tobe observations.
Źródło:
Hydroacoustics; 1999, 2; 21-26
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Receiver of Doppler multistatic system for moving target detection and tracking
Autorzy:
Ostrowski, Z. J.
Powiązania:
https://bibliotekanauki.pl/articles/332810.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
positioning system
Doppler shift
homodyne detection
Opis:
The article presents a method for solving major structural problems that occur in the receiver used in the multistatic Doppler system, aimed at determination of the trajectory and velocity of a moving target. In the system two transmitters emit acoustic continuous sinusoidal waves at different frequencies. The signals, scattered from a moving target are received by four hydrophones. Beside of the echoes, much larger signals coming directly from transmitters are recorded. It has been proved that in the presence of the direct high-amplitude signal, using currently available A/D converters, there is no possibility to detect the Doppler shift of small signals. The proposed approach is based on the homodyne frequency conversion of the received signals. Subsequently, the constant component and other unwanted products of the frequency conversion are filtered. The results of computer simulation have shown the effectiveness of the adopted design solution.
Źródło:
Hydroacoustics; 2015, 18; 141-152
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling multistatic of target detection
Autorzy:
Klusek, Z.
Elminowicz, A.
Tęgowski, J.
Szczucka, J.
Dragan, A.
Powiązania:
https://bibliotekanauki.pl/articles/331565.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
Gdansk Gulf
chirp signals
hydroacoustic
Opis:
The paper presents a numerical approach to modelling the detection of underwater targets with a bi- or multistatic active sonar systems in the shallow water areas using different waveform signals. The results of the numerical modelling of surface, bubble clouds and bottom reverberation for CW and using up and down time-varying instantaneous frequency of chirp signals are presented. Some suggestions are made on the basis of the development and practicality for the shallow sea modeling techniques and approaches to existing sonar models. The paper reports the literature of the model components required for active sonar modelling for different propagation conditions. Some examples of scattering of CW and chirp source signals at bubble clouds and corrugated surfaces, and coherence are given. Active propagation and the system performance are surveyed and modelled adaptable to the specific environmental condition of the shallow sea area of the Gdansk Gulf.
Źródło:
Hydroacoustics; 2008, 11; 131-138
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental evidence for enhanced target detection by sonar in bubbly water
Autorzy:
Leighton, T.
Finfer, D.
White, P.
Powiązania:
https://bibliotekanauki.pl/articles/331582.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
bubbly water
sonars
hydroacoustic
Opis:
A sonar system has been developed which allows one to discriminate targets from scattered energy from bubbles. The underlying theory and experimental testing of this system are presented. The effectiveness of this sonar system is demonstrated through experimentation within a large fresh water tank in which bubble clouds are generated. Some of the practical requirements associated with such an experiment are detailed.
Źródło:
Hydroacoustics; 2008, 11; 181-203
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Seasonal differences in situ measurements of the target strength of vendace (Coregonus albula L.) in lake Pluszne
Autorzy:
Świerzowski, A.
Doroszczyk, L.
Powiązania:
https://bibliotekanauki.pl/articles/332127.pdf
Data publikacji:
2004
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The subject of the study was vendace Coregonus albula L. This species is a typical planktivore and inhabits the pelagic zone of Lake Pluszne (area - 903 ha, 51 m - maximum depth) located in northeastern Poland. Acoustic measurements were taken with a Simrad EY-500 type split beam echosounder at a frequency of 120 kHz, with beam divergence of 7x7 degrees and a pulse duration of 0.3 ms. The data were analyzed using the trace tracking method with the EP 500 program and 5696 fish traces. A total of 3092 vendace individuals were caught in various water layers with a pelagic trawl during control fishing. The study involved determining the dependence between the acoustic size of vendace TS in dB, body length L in cm and specimen weight. The measurements were carried out in June and October 2003 under varied environmental conditions that limited spatial distribution, density and the condition of the examined fish. The dependencies of TS (dB) on fish body length L (cm) were determined for the average values of TSS.A. = 20 log L –65.4 š 0.1 SE and TSmax = 20 log L –63.8 š 0.1 SE.
Źródło:
Hydroacoustics; 2004, 7; 217-226
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
In Situ measurements of acoustic target strengths of siphonophores
Autorzy:
Warren, J. D.
Stanton, T. K.
Benfield, M. C.
Wiebe, P. H.
Chu, D.
Powiązania:
https://bibliotekanauki.pl/articles/331586.pdf
Data publikacji:
1999
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Measurements were made of the acoustic target strengths of siphonophores swimming freely in the ocean. The measurements were made possible by use of a remotely operated vehicle (ROV) on which both acoustics and video camera equipment were mounted. The acoustic transducers and camera were aimed at the same volume of water and data jrom che two sets of devices were co-registered. The cameras were used to help search for and identify the animais and to direct the path of the ROV; sa that ance the animals were jound they would be in or near the acoustic beams. The data show that these gas-bearing zooplankton have relatively high target strengths due to the presence of the gas inclusion. These data are essential in the use of acoustics for quantitatively surveying zooplankton for twa reasons: 1) lt suggests that a relatively small number of siphonophores can dominate che echo in an acoustic survey while other species present may dominate the biomass. 2) Siphonophores are very fragile and, as a result, cannot be reliably captured by use of nets. These data can help in making acoustics a quantitative survey tool for these important animals.
Źródło:
Hydroacoustics; 1999, 2; 11-13
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bearing errors in passive sonar stationary target location
Autorzy:
Schmidt, A.
Marszal, J.
Salamon, R.
Jedel, A.
Ostrowski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/332830.pdf
Data publikacji:
2009
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
bearing errors
passive sonar
hydroacoustics
Opis:
The paper presents a method for determining the coordinates of stationary targets using passive sonar bearing. It identifies the requirements sonar movements must meet to keep the incorrect determination of coordinates to a minimum. It gives the relations, which help determine coordinate errors analytically. Numerical experiments are used to demonstrate the success of the analysis.
Źródło:
Hydroacoustics; 2009, 12; 189-200
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling of acoustic backscattering by southern Baltic herring
Autorzy:
Idczak, J.
Gorska, N.
Powiązania:
https://bibliotekanauki.pl/articles/331977.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
acoustic biomass estimation
Baltic herring
target strength
modelling approach
X-ray images
Opis:
Assessment of Baltic herring abundance can be carried out using acoustic techniques. Analysis of the relationship between the Baltic herring individual target strength, TS, and the total fish length, L, important for the acoustic assessment, showed the relationship to be dependent on the location of the study area. This finding motivated a detailed analysis of the relationship for the herring occurring in the southern Baltic ICES subdivisions 24, 25, and 26, in which Poland is responsible for the acoustic herring abundance assessment. The paper addresses the numerical analysis of the backscattering properties of the southern Baltic herring. The modelling approach used to study the backscattering was based on the Modal Series-Based Deformed Cylinder Model approximation. Details of the individual herring swimbladders were taken into account. Morphometric data necessary for the analysis was obtained from X-ray images of herring from the Polish coastal zone (ICES subdivision 26).
Źródło:
Hydroacoustics; 2016, 19; 145-152
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł

Ta witryna wykorzystuje pliki cookies do przechowywania informacji na Twoim komputerze. Pliki cookies stosujemy w celu świadczenia usług na najwyższym poziomie, w tym w sposób dostosowany do indywidualnych potrzeb. Korzystanie z witryny bez zmiany ustawień dotyczących cookies oznacza, że będą one zamieszczane w Twoim komputerze. W każdym momencie możesz dokonać zmiany ustawień dotyczących cookies