Wyniki wyszukiwania - Biblioteka Nauki

1

Diagnostic of intense proton beams by hydroacoustic means

100%

Albul V. I. , Bychkov V. B. , Gusev K. B. , Demidov V. S. , Demidova E. V. , Kurchanov A. F. , Lukijashin V. B. , Vasilijev S. S.

Hydroacoustics

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2003

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tom Vol. 6

293--294

EN

Detecting and parameters' measurement of intense beams of charged particles in accelerators' laboratories is possible to make in water volumes, using conventional measuring hydrophones with applying of new means and algorithms of hydroacoustic signals' processing. The new experimental results is given and discussed.

2

Autonomous hydroacoustic sound velocity profiler

100%

Jedel A. , Marszal J. , Ostrowski Z. , Kilian L.

Hydroacoustics

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2003

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tom Vol. 6

261--266

EN

The paper presents the autonomous hydroacoustic sound velocity profiler collaborating with ordinary PC by small box included interface & battery charger. The measurement and calibration methods and block diagram of the meter are presented as well as principles of operation, data collection, selection and transmission. There are described three versions of this meter - dropped from "normal" ships, installed in the light hull of submarines and casings in the hulls of variable depth sonar antennas.

3

Theoretical problems of the wideband sonar time-spatial filtration

100%

Janowski T. , Kotłowski A. , Porosińska E.

Hydroacoustics

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2003

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tom Vol. 6

221--228

EN

The paper presents the synthesis of the time-spatial matched filtration algorithm. First part specifies base for the algorithm-input data. Successively, the matched filtration for continuous junction is depicted. This leads to the canonical form of the time-spatial filter. Consecutively, the decomposition into series connection of the matched and spatial filtration is realized. The next step is the signals approximation by Fourier series due to equivalence between approximation and interpolation on uniformly distributed discrete sampIes. The equation of the spatial filtration - in frequency domain - results from this mathematical operations. Application of the Bluestein's method to solve this equation provides to the final algorithm version. Advantages of the developed algorithm are presented in conclusions.

4

An acoustic study of zooplankton diel vertical migration in the Black Sea

80%

Pezacki P. D. , Gorska N. , Soloviev V.

Hydroacoustics

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2017

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tom Vol. 20

139--148

EN

Reliable, rapid and non-invasive techniques are important for the monitoring of the ecosystem of the semi-enclosed Black Sea, especially sensitive to the human impact. Hydroacoustic techniques meet these requirements. In the study, the ADCP data (volume backscattering strength and water velocities), collected in the north-east part of the Black Sea in October 2014, were used to understand some biotic and abiotic processes in the environment. The study was motivated by the fact that the used ADCP mounted on the autonomous (moving vertically) platform provided measurements with significantly higher spatial resolution that it was in the previous hydroacoustical studies of Black Sea ecosystem. The main objective of the analysis was to determine the velocity of zooplankton diel vertical migration and understand the processes responsible for the variability of the volume backscattering strength.

5

Influence of microphytobenthos photosynthesis on the spectral characteristics of the signal reflected from Baltic sandy sediments

80%

Jaśniewicz D. , Gorska N.

Hydroacoustics

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2016

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tom Vol. 19

165--171

EN

The use of hydracoustical techniques to classify benthic fauna and flora is one of the important challenges in present marine research. It is crucial to understand the microphytobenthos photosynthesis impact on the backscattering properties of the sea floor in the Baltic Sea, where the techniques are actively developed now. This motivated our study. The data used in the analysis was collected in the multiday laboratory experiment conducted in the frame of the grant of the National Science Centre, Poland (No. N306 773940). In this experiment, during changing light conditions (light/dark photocycles), the hydroacoustical backscattering data was acquired in the aquarium with a sandy bottom. The constant temperature and salinity conditions, typical for the Southern Baltic, were kept, and oxygen content was monitored. In this paper data collected at 280 kHz, was processed. It was studied how the energy of echo and power spectral density of the echo signal, are sensitive to the microphytobenthos photosynthesis.

6

Principles of computing and displaying the results of detection by underwater systems as part of sound velocity measurements

80%

Raganowicz A. , Kilian L. , Salamon R.

Hydroacoustics

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2003

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tom Vol. 6

267--274

EN

The paper presents the upgraded system for measurements of sound velocity profiles and for computing and imaging the terms of detection in different hydrolocation and hydrocommunication systems. Three types of computations made by the system's processors are discussed. The most interesting task is to link the propagation routes and ray density with the parameters of the hydroacoustic system to obtain the desired display of the conditions to detect the signal from the background noises. Presented discussion of methodology of determining detection conditions using different forms of range equation gives a more detailed description of this task. In the next part of this paper the software's display function and necessary settings are specified and discussed. In the end two examples of computed detection conditions images (for active and passive sonar) are shown.

7

Sensitivity of echo envelope fractal dimension to bottom type and bottom depth - numerical results

80%

Łubniewski Z.

Hydroacoustics

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2003

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tom Vol. 6

195--198

EN

The presented results are a part of those obtained within the author's latest work on application of normal incidence methods in acoustic seafloor characterisation. The work included both theoretical and experimental studies on selection of appropriate methods of seafloor echo processing and feature extraction for characterisation of the bottom type, especially, the study of the usefulness of several echo parameters like fractal dimension or statistical moments of the echo envelope. In this paper, the simulation results of the echo envelope fractal dimension dependence on bottom type and bottom depth are presented. They show that to same extent, fractal dimension of an echo may be useful for bottom identification even in a case of varying depth, however, more detailed, theoretical as well as experimental studies are needed.

8

Bearing errors in passive sonar stationary target location

80%

Schmidt A. , Marszal J. , Salamon R. , Jedel A. , Ostrowski Z.

Hydroacoustics

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2009

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tom Vol. 12

189-200

EN

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.

9

Examination of the co-operation between echosounder and motion sensor during sea trials

80%

Szymczak W. , Buszman K.

Hydroacoustics

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2009

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tom Vol. 12

217-226

EN

Sea trials with parametric echosounder SES-2000 Compact needs precise information about sounded area of the seafloor. Because of narrow beam both in horizontal and vertical surface each change of antenna position have high influence for results and analyze of measured data. Vessel has to be equipped with a special device, such as multibeam echosounder, to obtain more information about seafloor sounding which is an addition for basic measurements units. Information about bottom topography, from where sounding pulse comes, may give many useful data necessary to correct analyze by echosounder user. There are also parameters such as roll, pitch and heave, which have to be complied. These variables have an influence for shape and echo level. The last parameter analyzed in this article is a difference between vessels heading and bearing. This information comes from heading sensor and GPS receiver.

10

Sea floor classification using multibeam sonar

80%

Łubniewski Z. , Chybicki A.

Hydroacoustics

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2009

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tom Vol. 12

127-132

EN

The paper presents the method of seabed identification and classification using multibeam sonar echoes. The proposed approach is based on calculation of a set of parameters of an echo envelope. The parameters are extracted for each consecutive beam allowing the estimation of their dependence on the seafloor incident angle, and then the relation between seabed type and calculated echo parameters and its angular dependence is investigated. The paper concerns the experiment which has been carried out in Gdansk Bay in November 2008, and some comparisons of the results with those obtained during previous experiment in September 2007. The results for several bottom types are presented and discussed. It was confirmed that the information extracted from multibeam seafloor sensing data, e.g. "water column" recordings, may be useful in seafloor characterisation.

11

Acoustic tracking dynamic phenomena in marine ecosystem

80%

Orlowski A.

Hydroacoustics

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2009

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tom Vol. 12

167-180

EN

Acoustic information, collected in the form of measurements of integrated echo energiesrelated to time and 3D space has been applied at the Sea Fisheries Institute since 1981 to examine the rough statistical relationships between clupeoids distribution in the Baltic and the relevant environmental factors. In this paper it is shown that the data collected can be also applied for very detail observation of dynamic phenomena in marine ecosystem. Two differentiated case studies were selected to show new acoustic applications in specific areas of oceanographic research. In the first case spatial characteristics of fish diel vertical migration in the southern Baltic was surveyed and analysed for the period 1994-2007, against the environmental background. In the second case acoustic sounding was applied to quantify ebullition of methane from Baltic sediments. Both phenomena are strongly dependent on climatic variability. For both cases the final characteristics of the phenomenon was given in the form of video frames, expressing the processes in time. Unique method of echo-recording transformation into video frames was described and applied to analyse the process of ebullition of methane from the seabed.

12

Hydroacoustics waves' direct-of-arrival estimation using music algorithm - simulations results

80%

Żak A.

Hydroacoustics

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2009

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tom Vol. 12

249-256

EN

Paper presents simulations results of hydroacoustics waves' direction-of-arrival estimation using MUSIC algorithm. Firstly, the research problem is formulated by general description of studied case and release of simplifying assumption. Next the used to direct-of-arrival estimation MUSIC algorithm was discussed. The mathematical formulations, algorithm of calculation and some computational issues were presented. At the end of the paper the simulations results of estimation of direction-of-arrival using MUSIC algorithm for hypothetical situation were presented.

13

Large-array signal processing in long-range underwater channels: coherence effects and adaptive approach to the multimode signal control

80%

Malekhanov A.

Hydroacoustics

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2009

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tom Vol. 12

141-152

EN

The signal coherence degradation in spatial domain is an intrinsic scenario for large-array signal processing if the array size is greater as compared with the coherence length. For underwater sound, study of this issue is physically motivated by the fact that the discrete spectrum signal-carrying modes lose the mutual covariance at long ranges, so the signal coherence loss at the array inputs can be considerable. This is a case of comparative study of the large-array beamformers, optimal one included, aimed at realistic estimations of the coherence-induced effects on their performance. In this paper, we address the other aspect of the problem, namely, the source array synthesis in a random-inhomogeneous multimode channel under the criteria specified for the signal processor in remote receiving array. The criteria of the output SNR and the array SNR gain are considered to be a reasonable choice. An adaptive approach to the multimode signal control by the use of vertical source array is then formulated as an iterative algorithm for the source excitations and the corresponding modal spectrum of the signal wavefield. Computer simulation is performed for the vertical source and receiving arrays operating in the shallow-water channel from the Barents Sea.

14

Application of non-uniform B-Splines of 2-nd order for description vertical distribution of sound speed in water

80%

Makar A.

Hydroacoustics

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2009

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tom Vol. 12

133-140

EN

Modeling of the vertical distribution of the sound speed in water is useful during determination of the depth on the basis of the acoustic method, modeling refraction phenomena and determination the trajectory of the acoustic wave. For modeling 1D functions (vertical distribution of the sound speed) and 2D (surface of the sea bottom for hydrography) uniform B-Splines was used. In this paper description of uniform B-Splines and description and application of non-uniform B-Splines have been presented.

15

Acoustical observation of internal waves on the shelf of the Black Sea

80%

Mikryukov A. , Popov O. , Serebryany A.

Hydroacoustics

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2009

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tom Vol. 12

153-158

EN

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.

16

Investigation of the pulse reflected from bottom sediments

80%

Nowak Ł. , Szymczak W.

Hydroacoustics

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2009

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tom Vol. 12

159-166

EN

The paper describes method of determining time proceeding of the echo pulse arising as an effect of reflection of sampling pulse given with the known form from layered sea bottom. The main goal of presented model is to afford theoretical data that could be used as a point of reference for the experimental data obtained with SES 2000 Standard parametric echosounder. Basic formulas, computation algorithm with its implementation in Matlab language and examples of obtained results are described. Numerical simulations results are compared with experimental data. The laboratory station enabling computing acoustic impedance of sediments and parameters of sampling and echo pulse in different distances from antenna is presented.

17

Estimation and measurements of resonance scattering on the gas filled polymer microspheres

80%

Secomski W. , Klimonda Z.

Hydroacoustics

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2009

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tom Vol. 12

201-208

EN

The gas filled polymer spheres are used either as an ultrasonic contrast agents or controlled drug delivery microcapsules. The power spectrum of the ultrasonic backscattered signal was calculated from the resonance scattering theory for the gas bubbles surrounded by elastic shield. The size distribution of the measured microspheres was included in the calculations. In experiment, the backscattered power spectrum of measured sample was recorded by Siemens Antares ultrasonic scanner. Radio frequency (RF) data was recorded for 2.5 - 6.7 MHz transmitted ultrasonic frequencies. The backscattered spectra were calculated by Matlab software and subtracted from the transmitter spectrum, recorded as an echo from the perfect reflector. The particle size in measured sample was 12 µm mean š 8 µm sd. The resonance frequency, measured under the microscope, was 0.60 MHz for 45 µm diameter microsphere which corresponds to 2.25 MHz for 12 µm sphere. The sample volume was 10cm? and the mean quantity of scatterers was 6ź103/cm?. In conclusion, measured spectra matched those calculated from theory. The use of ultrasonic scanner with RF data output and the high sensitivity, wide bandwidth ultrasonic transducer allows to measure backscattered signal from the very small quantity of resonance scatterers with satisfactory results at 40 dB signal to noise ratio.

18

Monitoring of ocean current perturbations using acoustic phase variations

80%

Zieliński A. , Butowski M. , Kraeutner P.

Hydroacoustics

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2009

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tom Vol. 12

237-248

EN

In this paper, we review an acoustic method for measuring both average ocean current speed and sound speed along an acoustic path. The method requires two or more stations on the sea floor, synchronized through a connecting underwater electric cable, that can transmit and receive an acoustic signal and The method is based on reciprocal acoustic transmissions to determine time of flight in both the forward and reverse directions. A specific implementation of this method is proposed. We also consider a novel method for monitoring ocean current perturbations through acoustic phase measurements. In simplest form, a continuous sinusoidal signal is transmitted from one station to a second station. Any variations in ocean current speed will introduce a phase shift in the received signal proportional to the time derivative of the current speed. This effect has been demonstrated through ultrasonic in-air experiments. Finally, the two methods are combined into a single system that continuously measures small-scale ocean current velocity changes.

19

Identification of hydro-acoustic waves emitted from floating units during mooring tests

80%

Kozaczka E. , Domagalski J. , Grelowska G. , Gloza I.

Polish Maritime Research

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2007

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tom nr 4

40-46

EN

Measurements of hydro-acoustic noise emitted from vessels are a.o. a subject of the tests carried out in the control measurement ranges of the Navy. The measurements are performed both on anchored and floating vessels. Acoustic field of vessels is changing along with their speed changing and is associated with acoustic activity of wave sources installed in vessel’s hull (main engines, electric generating sets, reduction gears, pumps, shaft-lines, piping, ventilating ducts etc) as well as hydro-dynamic sources such as screw propellers and water flow around the hull [5, 7]. Vibration energy generated by the onboard devices is transferred through ship structural elements to water where it propagates in the form of hydro-acoustic waves of a wide frequency band.

20

Hydroacoustic activity of the ship propeller operation

80%

Szantyr J. A. , Koronowicz T.

Archives of Acoustics

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2006

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tom Vol. 31, No. 4

481-487

EN

The paper presents ship propellers as the source of a variable pressure field in water. The frequency spectrum of this field covers the entire audible range and beyond this range. This pressure field is generated by several physical mechanisms: the rotating hydrodynamic loading of the blades, the displacement effect of the rotating blades, the boundary layer effect, and, first of all, various forms of cavitation. The relative importance of these mechanisms is analysed and the methods of the theoretical prediction of the propeller generated variable pressure field are briefly presented. The results of the prediction are compared with experimental data.