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Wyświetlanie 1-15 z 18
Tytuł:
Communications underwater
Autorzy:
Zieliński, A.
Powiązania:
https://bibliotekanauki.pl/articles/332121.pdf
Data publikacji:
2004
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This invited contribution is intended for an audience familiar with general underwater acoustics but which wishes to gain more understanding of underwater communication using acoustic waves as a carrier. We will review some basic concepts applicable to any communication system as well as some of the diverse concepts and experimental and commercial systems used for communicating underwater. Topics considered include: acoustic transducers and arrays, some applications of underwater acoustic communications, analogue modulations, multipath, noncoherent and coherent digital transmission schemes including phase modulation, channel equalization, and state of the art. Extensive literature on the subject is provided.
Źródło:
Hydroacoustics; 2004, 7; 235-252
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Coherent underwater acoustic communications - A review
Autorzy:
Yoon, Y.
Zielinski, A.
Powiązania:
https://bibliotekanauki.pl/articles/331947.pdf
Data publikacji:
1997
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Digital communications through the underwater acoustic channel has been an active area of research in recent years. Applications include data transmission from bottom instrumentation, control of autonomous underwater vehicles (AUVs), digital voice and video transmission, etc. The effects of multipath propagation, Doppler frequency shifts due to relative motion of transmitter and receiver, and channel time and space variability which cause intersymbol interference and phase fluctuations of signals impose unique requirements for system design. Most research has been focused on the development of algorithms to cope with intersymbol interference and phase fluctuations. Development of coherent communication systems has improved bandwidth efficiency and reliability. In this paper, the trends and results of recent research on underwater communications, including channel models, equalization, diversity and synchronization, are reviewed. Some of our own research results are presented to illustrate the feasibility and effectiveness of proposed transmission schemes.
Źródło:
Hydroacoustics; 1997, 1; 279-284
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of ship motion on acoustic remote sensing
Autorzy:
Tegowski, J.
Zielinski, A.
Powiązania:
https://bibliotekanauki.pl/articles/332057.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
ship motion
acoustic remote sensing
Opis:
Ship motion affects quality of acoustic data collected by various acoustic remote sensing systems used for bottom and fisheries surveying. The angular position of an acoustic beam changes in time from its nominal position vertical to sea surface. This motion affects the acoustic returns from the bottom and other targets by changing their intensity and arrival times. In this paper we illustrate these effects on bottom returns obtained using single beam sonar.
Źródło:
Hydroacoustics; 2003, 6; 205-214
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Novel equalizer for shallow water acoustic communications
Autorzy:
Yoon, Y.
Zielinski, A.
Powiązania:
https://bibliotekanauki.pl/articles/332566.pdf
Data publikacji:
2000
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The signal transmitted through an underwater acoustic channel is corrupted by multipath propagation caused by surface and bottom reflections. This delay spread causes intersymbol interference (ISI). The surface waves produced by wind affect the signal delay spread at the receiver. The delay spread is large for a calm sea and decreases with rough sea agitated by winds. To compensate for distortion introduced by the multipath channel, adaptive equalizers have been utilized to improve the performance of a communication system. These equalizers have been designed to handle the worst case of a signal delay spread condition associated with a calm sea and have a suitable and fixed number of taps. However, it is known that the power consumed by the processor increases with the number of computations performed per time unit. In this paper, we propose a novel equalizer with a variable number of taps which adaptively changes depending on channel conditions in order to conserve power. The proposed equalizer was tested by computer simulations using a model of an underwater acoustic channel. Results indicate savings in computational load up to 54% for a selected case. Power savings were also obtained when a directional receiver is used together with the proposed equalizer. Lower power consumption is particularly desirable for battery operated systems.
Źródło:
Hydroacoustics; 2000, 3; 185-190
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A novel method for amplitude and phase measurements based on multiple samples
Autorzy:
Xiong, X.
Zieliński, A.
Powiązania:
https://bibliotekanauki.pl/articles/332594.pdf
Data publikacji:
2007
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Precise amplitude and phase measurement of a narrowband signal is required in many practical applications related to underwater sensing, navigation, and positioning. In this paper, we propose a novel method for digital signal acquisition based on multiple signal sampling. This method is an extension of quadrature sampling where amplitude and phase of a harmonic signal can be obtained based on only two samples taken within one period. The advantage of our generalization are reduced errors caused by quantization noise of A/D converters.
Źródło:
Hydroacoustics; 2007, 10; 207-214
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Design considerations for shallow water acoustic communication systems
Autorzy:
Yoon, Y.
Zielinski, A.
Powiązania:
https://bibliotekanauki.pl/articles/332756.pdf
Data publikacji:
1999
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Relevant characteristics of the underwater channel used for acoustic communications are briefly described. There is a trade-off between achievable transmission range and data throughput. Transmission range of several kilometers with carrier frequency of 50kHz and several tens of kilometers with frequency less than 10 kHz might be possible using only 75 watts of acoustic power. Also, we investigated the required acoustic power for certain transmission ranges at given signal-to-noise ratio (SNR) values and the effect of wind speed. A shallow water channel model is proposed to study signal attenuation and arriving angles of the multipath. As the signal time delay increases, the arriving angle of the reflected signals becomes larger, allowing us to limit the number of multipath signals using a directional receiver. We will see that using directional receiver is better suited for a channel with a small range-to-depth ratio (RDR) and that equalization methods are better suited for a channel with a large RDR. Finally hardware complexity for designing shallow water acoustic communication systems is studied using a currently available digital signal processing (DSP) technology.
Źródło:
Hydroacoustics; 1999, 2; 179-184
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Precision acoustic navigation for remotely operated vehicles (ROV)
Autorzy:
Zieliński, A.
Zhou, L.
Powiązania:
https://bibliotekanauki.pl/articles/985799.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The ability to navigate a ROV to exact bottom locations or along a precise path is essential to many scientific and engineering tasks. Bottom and water column surveys along a precise and repeatable trajectory allow the monitoring of chemical and physical variables, and the study of sedimentation processes and biological phenomena. Precise navigation is also required for high-resolution synthetic sonar observations and for placement and retrieval of various devices on the bottom. This paper reviews principles behind acoustic navigation and provides a survey of commercially available Ultra-Short Baseline (USBL) navigation systems. A novel high precision navigation system is proposed that offers several advantages over the surveyed systems. Specifically, the precise position and trajectory of a ROV tethered by a cable to a bottom node is obtained using sensitive phase measurement of an acoustic signal. Proof of this concept through shallow-water and deep-water prototypes will be carried out shortly at the University of Victoria.
Źródło:
Hydroacoustics; 2005, 8; 255-264
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quadrature phase detection in an acoustic positioning system
Autorzy:
Zieliński, A.
Shi, Y.
Powiązania:
https://bibliotekanauki.pl/articles/332319.pdf
Data publikacji:
2006
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
A novel acoustic navigation method is described. The method is based on a continuous waveform transmitted from a tethered object being tracked and received by a bottom node. Accurate range and bearing measurements are made by differential phase detection and phase unwrapping of the received signals. Phase detection is performed using a quadrature phase sensitive detector (QPSD). The paper investigates, using computer simulation, the performance of the system in the presence of noise. The RMS error in the phase estimate was found to be 14o for range estimation and 17o for angle estimation even with a poor SNR of 0 dB. These estimates represent a theoretical equivalent range error of 5.8 mm and angle error of 0.5o, respectively, for an operating frequency of 10 kHz and 5ë hydrophone separation. These results indicate potentially a much better accuracy than that offered by the conventional ultra-short baseline system.
Źródło:
Hydroacoustics; 2006, 9; 227-238
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis and wavelet analysis of side-scan sonar sea bottom imagery
Autorzy:
Tęgowski, J.
Zieliński, A.
Powiązania:
https://bibliotekanauki.pl/articles/332396.pdf
Data publikacji:
2006
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
A backscattered side-scan sonar signal contains indirect information about the scattering surface, namely, the bottom sediment, character of bottom surface, and seafloor relief. This paper presents a method of automatic estimation of height of seafloor characteristic objects and micro relief reconstruction applying the measured shadow length. The proposed method utilises coefficients of two-dimensional discrete wavelet decomposition of a side-scan sonar image as the input to the self-organised neural network classification algorithm. The heights of seafloor characteristic objects were the basis for synthesis of a three-dimensional map of the bottom surface. The computations were conducted for data recorded in Hornsund Fjord (Spitsbergen Island, Svalbard Archipelago) during a habitat mapping experiment and for synthetic data. The verification of the proposed algorithm was made by comparison of computed results with calibrated video recordings.
Źródło:
Hydroacoustics; 2006, 9; 199-208
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic and laser bathymetry systems
Autorzy:
Gupta, S. D.
Zielinski, A.
Powiązania:
https://bibliotekanauki.pl/articles/332055.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
This paper discusses acoustic and lasers based bathymetric systems in terms of their applicability in diverse circumstances. The advantages and disadvantages of each method are compared in terms of capabilities, cost and accuracy. None of these systems can provide full bottom coverage in all circumstances but could be supplementary to each other. Information has been presented in support of this conclusion. Acoustic bathymetry is suitable at deeper waters whereas laser bathymetry may be used in shallow clear coastal waters. A hybrid option has been suggested with the mix of these systems for higher survey efficiency and lesser costs. This paper is of interest to persons involved in ocean acoustics study and survey projects planners as well as to the developers of laser instruments for study ocean water and bottom properties and object detection such as wracks, boulders and other objects.
Źródło:
Hydroacoustics; 2013, 16; 77-88
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
From deformable mirror pointing at sky to underwater acoustics
Autorzy:
Niebergal, J.
Zielinski, A.
Caputa, K.
Powiązania:
https://bibliotekanauki.pl/articles/331766.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Due to air density variations, turbulence, eddies, and cross winds in the atmosphere, ground-based telescopes record temporal and spatial fluctuations of phase and amplitude of received stellar light. For astronomical imaging, the effects of the atmosphere result in aberrations of received light leading to blurring and other undesired affects. Using a complex optical system called adaptive optics, aberrations can be effectively reversed resulting in improved imaging quality. Similarities between the atmosphere and ocean are apparent when considered as a propagation medium for light or sound, respectively; both media are turbulent and governed by similar dynamic processes involving temperature gradients, pressure differentials, and other factors. Similarities also exist in the distortions that the changing medium produces on each wavefront. In presenting the adaptive optics solution that has improved ground-based astronomical imaging, this paper will propose that similar strategies could be utilized in underwater acoustics.
Źródło:
Hydroacoustics; 2011, 14; 171-180
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Extraction of seabed geomorphologic features of Svalbard fjords using high-resolution side scan sonar
Autorzy:
Tęgowski, J.
Giżejewski, J.
Zieliński, A.
Powiązania:
https://bibliotekanauki.pl/articles/331637.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
Svalbard fjords
side scan sonar
sea bed
Opis:
This paper presents results of a study on the relationship between features of side scan sonar acoustic imagery of zones with active bedforms and geomorphologic seafloor characteristics. Acoustic measurements were conducted in Hornsund, a Svalbard fjord representing a periglacial environment with great intensity of morphodynamic processes and rapidly progressing changes of tidewater glaciers. Due to the intensity of these processes, Arctic fjords are the most promising areas to study the effects of climate change on the ecosystem. Acoustic identification of sedimentary structures and morphological forms created by currents and iceberg transport of glacier sediment away from the ice margin was performed. The spectral and fractal features of the recorded signals were analysed. The proposed analysis scheme allows identification of the morphodynamic active zones in the changing Arctic fjord environments. Measurements of acoustical features of seafloor surface were made during the 2006 Arctic cruise of r/v Oceania.
Źródło:
Hydroacoustics; 2008, 11; 401-411
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ocean average current measurement using acoustic phase monitoring
Autorzy:
Zieliński, A.
Zhou, L.
Butowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/331688.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
ocean-related activities
acoustic phase monitoring
hydroacoustic
Opis:
Knowledge of water currents is important in several ocean-related activities. Typically, current speed and direction are measured at a certain fixed location and depth (or depth profile) by a suitable current meter. In this paper, we propose a novel method for average current speed measurement along a path, based on acoustic phase monitoring. In this method, a transmitter and a receiver are installed at the ends of a designated path. A transmitted sinusoidal signal propagates along the path to the receiver. Intervening currents will introduce Doppler frequency shifts that can be measured as a rate of phase change in the received signal. The phase is recovered by means of a phase detector and unwrapping techniques. The desirable feature of the proposed method is that average current speed is monitored along the entire path. Moreover, the estimated frequency shift via the phase measurement achieves a higher accuracy in current measurement than does a measure of frequency directly by an FM demodulator.
Źródło:
Hydroacoustics; 2008, 11; 459-467
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Underwater terrain aided navigation based on acoustic imaging
Autorzy:
Song, Z.
Bian, H.
Zielinski, A.
Powiązania:
https://bibliotekanauki.pl/articles/331702.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
3D terrain model
multi-beam bathymetry
Opis:
Underwater terrain aided navigation is applicable to underwater vehicles during long missions. It relies on a prior known ocean bathymetric map and collected in-situ sonar data to determine the position of the vehicle. The performance of the navigation system depends on the sea floor characteristics and algorithms that are used to match those two sets of data. In this paper, a novel idea was proposed to treat bathymetric maps and in-situ sonar data as images. A variety of existing algorithms developed for image processing can be applied to obtain position fixes. Textual features extraction, image interpolation and image registration were tested using available bathymetric data and synthesized sonar data as collected in-situ. Simulation results indicate that the chosen image analysis methods are capable of providing robust position fixes. The image characteristics extracted from the underwater terrain data are shown to be rotation and scale invariant. As the resolution of multi-beam bathymetry sonars keeps improving with technology advances, the use of image analysis techniques facilitates underwater terrain aided navigation for a wide range of new applications.
Źródło:
Hydroacoustics; 2015, 18; 153-160
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High-voltage amplifier with DC adaptive capability for piezoelectric acoustic transmitter/actuator
Autorzy:
Niebergal, J.
Caputa, K.
Zielinski, A.
Powiązania:
https://bibliotekanauki.pl/articles/331894.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The piezoelectric element of an acoustic transducer requires a high voltage drive signal. This paper describes the development of a compact high-voltage amplifier (HVA) capable of driving piezoelectric elements and providing the additional capability of a DC response. This opens the possibility to control the DC displacement of an active array of transducers, which would not be possible using a step-up transformer due to the lack of a DC response. This HVA is particularly suited for low frequency operation, where the elimination of the transformer will provide the greatest benefit due to its large size, cost and weight at these frequencies. The HVA is very compact allowing large-scale integration, and therefore can be utilized for driving large arrays of transducers. Such an array could facilitate an active correction system driven by the DC signal from the amplifier. Considering the target application for large multi-element transducer arrays, design goals have been to minimize the size and cost. The features and benefits of the HVA will be presented.
Źródło:
Hydroacoustics; 2012, 15; 153-162
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 18

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