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1

Ground Penetrating Radar investigation of limestone karst objects in the Botanical Garden in Kielce

Zielinski A., Łyskowski M., Mazurkiewicz E.

Geology, Geophysics and Environment

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2016

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Vol. 42, no. 1

31--38

EN

Ground Penetrating Radar (GPR) is one of the most effective and rapid types of geophysical survey methods. The present study was carried out in the Botanical Garden in Kielce, which is currently undergoing a second stage of infrastructure development. This object is located in the Świętokrzyskie (Holy Cross) Region, characterized by large scale deformations in the development of karst origins. Those structures threaten existing buildings and can be obstacles to newly constructed ones. Radargrams presented in this paper show significant potential of the GPR method in mapping of karst phenomena. Proper acquisition parameters and optimal processing of raw data resulted in a clear image of the structure of rock mass under the Botanical Garden, along acquired profile lines. Additionally, precise GPS coordinate links and established researchers’ experience of conducting this type of surveys helped in the process of mapping the anomalies in the limestone. Under these conditions, the survey minimized the need for a second method and resulted in high quality data acquisition. The study provided information about underlying rock mass structure development and registered anomalies whose origins include voids or caves of karst genesis. The area studied covers a large part of the Botanical Garden. Described anomalies can be dynamic in origin.

2

Underwater terrain aided navigation based on acoustic imaging

Song Z., Bian H., Zielinski A.

Hydroacoustics

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2015

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Vol. 18

153-160

EN

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.

3

Acoustic and laser bathymetry systems

Gupta S. D., Zielinski A.

Hydroacoustics

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2013

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Vol. 16

77--88

EN

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.

4

On the characteristics of sound generated by bubbles injected underwater

Lohrasbipeydeh H., Zielinski A., Gulliver T. A.

Hydroacoustics

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2012

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Vol. 15

111-122

EN

The transient oscillation of an air bubble injected underwater is investigated. This oscillation generates a decaying acoustic signal that can be remotely received and analyzed. The narrowband spectrum of this signal is centered at the bubble oscillation frequency. These results are extended to a plume of bubbles generated by a linear array of nozzles. This models bubble behavior in applications such as passive diver localization, bubble depth measurement, detection of ocean gases, and gas pipe leakage. The results presented show that these bubbles can generate a sufficiently strong acoustic signal that can be utilized for passive remote sensing.

5

High-voltage amplifier with DC adaptive capability for piezoelectric acoustic transmitter/actuator

Niebergal J., Caputa K., Zielinski A.

Hydroacoustics

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2012

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Vol. 15

153-162

EN

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.

6

From deformable mirror pointing at sky to underwater acoustics

Niebergal J., Zielinski A., Caputa K.

Hydroacoustics

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2011

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Vol. 14

171-180

EN

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.

7

Large Eddy Simulation of transitional flows in rotor/stator cavity

Tuliszka-Sznitko E., Zielinski A., Majchrowski W.

Archives of Mechanics

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2009

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Vol. 61, nr 2

95-120

EN

An algorithm for the Large Eddy Simulation, with subgrid modelling based on the spectral Chebyshev-Fourier approximation, is developed for the investigation of 3D turbulent and transitional non-isothermal flows within a rotor/stator cavity. In LES we use a version of the dynamic Smagorinsky eddy viscosity model in which the Smagorinsky coefficient at a given position x depends on the history of the flow along the fluid particle pathline. Computations are based on the efficient pseudo-spectral Chebyshev-Fourier method (S. HUGUES, A. RANDRIAMAMPIANINA, An improved projection scheme applied to pseudospectral methods for the incompressible Navier-Stokes equations, Int. J. Numer. Methods Fluids, 28, 501, 1998). To demonstrate the effectiveness of the proposed algorithm, computations were performed for the cavity of aspect ratio L = 5 and results were compared favorably with the experimental data taken from literature.

8

Effects of ship motion on acoustic remote sensing

Tegowski J., Zielinski A.

Hydroacoustics

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2003

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Vol. 6

205--214

EN

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.

9

Novel equalizer for shallow water acoustic communications

Yoon Y., Zielinski A.

Hydroacoustics

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2000

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Vol. 3

185--190

EN

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.

10

Design considerations for shallow water acoustic communication systems

Yoon Y., Zielinski A.

Hydroacoustics

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1999

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Vol. 2

179--184

EN

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.

11

Coherent underwater acoustic communications - A review

Yoon Y., Zielinski A.

Hydroacoustics

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1997

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Vol. 1

279--284

EN

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.