Wyniki wyszukiwania - BazTech

1

Modeling of performance of a AUV vehicle towards limiting the hydro-acoustic field

Gerigk M. K.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2018

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Vol. 12, no. 4

687--692

EN

Some results of research devoted to the modeling of a AUV-Stealth vehicle performance towards limiting its hydro-acoustic field are presented in the paper. At the beginning the AUV-Stealth autonomous underwater vehicle concept is described. Then the method of research is introduced. Next the key design drivers of the AUV-Stealth vehicle are presented. Between them are the AUV-Stealth hull form, arrangement of internal spaces, materials, hull covers, energy supply and propulsion system, etc. Some results of the hydrodynamic and stealth characteristics of the AUV-Stealth vehicle are briefly described. It is presented in the paper that the hull form, construction materials including the covers may affect the AUV-Stealth vehicle boundary layer and wake. This may create some problems of identification of the AUV-Stealth vehicle using a sonar or hydrophone. The final conclusions are presented.

2

Development of a coupled numerical and experimental approach to hydrodynamic noise estimation

Felicjancik J., Gatz M., Badur J.

Transactions of the Institute of Fluid-Flow Machinery

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2017

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nr 138

89--105

EN

The hydroacoustic signatures of ship propellers can be identiﬁed experimentally through measurements of cavitation-induced pressure ﬂuctuations and the accompanying noise distribution at model scale. These measurements have to be performed in a cavitation tunnel at the propellers operating conditions and with suﬃcient accuracy. In comparison, the numerical approach can be used to present a good general idea of the predicted results. Numerical methods can provide highly accurate tools for noise level and propagation prediction, as well as giving insight into the ﬂow ﬁeld and other key aspects. They are also not inﬂuenced by signal conditioning or disturbance sources present in a physical environment. So we trade scope and precision of the results for time and cost reduction. In this paper, we described both experimental and numerical methods currently in use and present advantages and limitations of the practical application of both.

3

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

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

Hydroacoustics

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2017

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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.

4

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

Jaśniewicz D., Gorska N.

Hydroacoustics

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2016

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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.

5

Historyczny przegląd rozwoju systemów akustyki podwodnej

Grelowska G., Kozaczka S.

Logistyka

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2015

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nr 4

1649--1652, CD2

PL

W artykule przedstawiono informacje o początkach hydroakustyki, gałęzi nauki i techniki niezastąpionej jako narzędzie eksploracji i eksploatacji mórz i oceanów. Zaprezentowano najważniejsze odkrycia naukowe, dzięki którym powstać mogły urządzenia i systemy hydroakustyczne, a także pierwsze doświadczenia i pierwsze systemy obserwacji podwodnej.

EN

The article presents information about the origins of hydroacoustics, branches of science and technology as a irreplaceable tool for exploration and exploitation of the seas and oceans. Paper presents major scientific discoveries in the field of hydroacoustic devices and systems, as well as first experiences and the first underwater observation systems.

6

Impact of Microphytobenthos Photosynthesis on the Characteristics of the Echo Signal from Baltic Sandy Sediments

Gorska N., Kowalska-Duda E., Marszal J., Schmidt J., Klusek Z.

Archives of Acoustics

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2015

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Vol. 40, No. 3

395--405

EN

The understanding the influence of biological processes on the characteristics of the signals backscattered by the sea floor is crucial in the development of the hydroacoustical benthic habitat classification techniques. The impact of the microphytobenthos photosynthesis on the acoustical backscattering properties of the Atlantic sandy sediments was previously demonstrated by Holliday et al. (2004) and Wildman and Huettel (2012). To account for the sensitivity of the hydroacoustical classification techniques to the backscattering properties of local marine sediments, it is important to understand the microphytobenthos photosynthesis impact for the Baltic Sea where the techniques are being actively developed now. This is the main motivation of the paper. In the paper the influence of the microphytobenthos photosynthesis on the characteristics of the echo signals reflected by sandy sediments in the typical Baltic temperature and the salinity conditions is discussed. The interdisciplinary multiday laboratory experiment was conducted to study the impact of benthic microalgal photosynthesis on the characteristics of the echo signal reflected by sandy sediments. Hydroacoustical data were collected under controlled constant light, temperature and salinity conditions. The oxygen content at different levels of the water column was simultaneously monitored.

7

Szumy podwodne małej jednostki

Dudziak S.

Zeszyty Naukowe Akademii Marynarki Wojennej

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2013

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R. 54 nr 3 (194)

39--51

PL

Artykuł przedstawia wyniki badań in situ przeprowadzone na akwenie Zatoki Gdańskiej w celu pomiaru i analizy szumów generowanych przez jednostkę morską. Otrzymane wyniki są wstępem do opracowania metod opisu dźwięków generowanych przez jednostki, a także fazy ich przejścia względem obiektu pomiarowego.

EN

The paper presents the results of investigations carried out in the Bay of Gdańsk in order to measure and analyze noise generated by a maritime vessel. The results obtained are the initial stage in developing methods for describing sounds generated by vessels, as well as phases of their passage with regard to the object measured.

8

Investigation of the underwater noise produced by ships by means of intensity method

Kozaczka E., Domagalski J., Gloza I.

Polish Maritime Research

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2010

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nr 3

26-36

EN

This paper presents results of research on spectral structure of underwater noise acoustic field radiated into water by selected ships moving in shallow waters. Underwater acoustic field of ships in motion is associated with acoustic activity of ship mechanisms and equipment under work. Vibration energy radiated by the mechanisms and devices is transmitted by ship structural elements to surrounding water where it is propagated in the form of acoustic waves of a wide frequency band. In this paper are presented results of the research on propagation of energy of acoustic waves in the near fiel, obtained from acoustic pressure measurements by means of two sensors located close to each other.

9

Identification of hydroacoustic wave sources of ship in motion

Kozaczka E., Domagalski J.

Polish Maritime Research

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2010

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nr 4

64-71

EN

This paper deals with results of identification tests of acoustic field spectrum of underwater noise generated by ship in motion. The field is connected with acoustic activity of ship mechanisms and devices in operation. Vibration energy generated by the mechanisms and devices is transferred through ship structural elements to surrounding water where it propagates in the form of acoustic waves of a broad band of frequencies. In the publication results of identification tests of underwater noise generated by a ship in motion, are presented.

10

Sea floor classification using multibeam sonar

Łubniewski Z., Chybicki A.

Hydroacoustics

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2009

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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

Monitoring of ocean current perturbations using acoustic phase variations

Zieliński A., Butowski M., Kraeutner P.

Hydroacoustics

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2009

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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.

12

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

Malekhanov A.

Hydroacoustics

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2009

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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.

13

Investigation of the pulse reflected from bottom sediments

Nowak Ł., Szymczak W.

Hydroacoustics

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2009

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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.

14

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

Żak A.

Hydroacoustics

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2009

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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.

15

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

Szymczak W., Buszman K.

Hydroacoustics

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2009

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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.

16

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

Secomski W., Klimonda Z.

Hydroacoustics

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2009

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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.

17

Bearing errors in passive sonar stationary target location

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

Hydroacoustics

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2009

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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.

18

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

Makar A.

Hydroacoustics

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2009

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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.

19

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

Mikryukov A., Popov O., Serebryany A.

Hydroacoustics

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2009

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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.

20

Acoustic tracking dynamic phenomena in marine ecosystem

Orlowski A.

Hydroacoustics

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2009

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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.