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Oceanic Engineering, IEEE Journal of

Issue 2 • Date Apr 1995

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Displaying Results 1 - 6 of 6
  • Detection of transient signals in multipath environments

    Page(s): 131 - 138
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    This research examines methods for detecting unknown transient waveforms that are contaminated by noise. The sensitivity of the performance levels of the energy detector and the lack of knowledge about the structure of the transient waveform motivate the examination of other moment- or spectra-based detection techniques. We examine the performance of a bispectral energy detector and show that its performance will degrade if the bispectra is smoothed and that signals with no bispectral content can be detected if the bispectra is not smoothed. Further, it is shown that the performance levels of the bispectral detector are slightly better, and slightly less sensitive, than those of the energy detector for the multipath linear frequency modulated signal. Finally, the performance levels of narrowband implementations of the energy and bispectral energy detectors are compared. It is shown that for a large enough sample, the performance levels of the bispectral detector are nearly as good as those of the optimal energy detector for the single narrowband signal case. However, when the received waveform contains multiple narrowband components, the narrowband bispectral detector performs slightly better than the energy detector View full abstract»

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  • A novel flow visualization technique using bioluminescent marine plankton II. Field studies

    Page(s): 147 - 149
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    The broad scope of this study is to investigate whether the flow induced stimulation of naturally occurring luminescent plankton can be effectively utilized as a method of flow visualization in the field. The primary goal is to determine the nature of flow around a moving dolphin based on the luminescent response of in situ plankton to hydrodynamic stimulation View full abstract»

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  • Parametric estimation of ocean surface currents with HF radar

    Page(s): 139 - 144
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    Ocean surface currents can be estimated, over a large coastal area, by utilizing the backscatter of high frequency (HF) radar waves from ocean gravity waves. Although the overall backscatter mechanism is complicated, the surface current information is contained within the spectral characteristics of two dominant Bragg components. The accuracy of the current estimate, following the usual FFT-based spectral estimate, is limited by the frequency resolution of the FFT and the time-varying characteristics of the Bragg components. This paper describes a high resolution parametric estimation of the ocean currents based on a recently proposed technique for analyzing time-varying signals. This technique, together with a time-domain ocean clutter model, allows all the Bragg signal information to be extracted from the two dominant eigenvalues and eigenvectors of a matrix constructed from the radar data. Using signals from an operational coastal surveillance radar, current estimates made using this technique are compared with those estimated by the conventional FFT-based method View full abstract»

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  • Simulation of backscattering of high frequency sound from complex objects and sand sea-bottom

    Page(s): 119 - 130
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    This paper describes the simulation of backscattering of high frequency sound from complex objects and sand sea-bottom. Backscattering data from complex objects and seabottom were generated using a Universal High Resolution Imaging Sonar Simulation Toolkit (UHRISST) developed by the authors. Our approach here involves the approximation of objects and the sea-bottom through a series of facets that are small compared to the wavelength. The Target Strength of standard objects like the sphere, cylinder, and cone predicted by our model have been compared with various high frequency approximation formulations and produced a good fit. For the prediction of the backscattering strength from the sea-bottom, we have taken into account most of the small-scale features that represent the sand grain properties, intermediate features that represent seabottom roughness and large features that block propagation. Sea-bottom backscattering predictions made using this model were compared with high frequency scattering strength values measured off Panama City, FL, USA, and produced a moderate fit. Nonparametric statistical analysis was carried out on the bottom backscattering signals from a flat isotropic sea-bottom. The probability distribution function and probability of false alarm function of the bottom backscattering data was measured and found to largely follow the normal distribution View full abstract»

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  • Passive Doppler-bearing tracking using a pseudo-linear estimator

    Page(s): 114 - 118
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    In this paper an explicit pseudo-linear estimator for Doppler-bearing tracking is proposed. It overcomes the problems with the bias of earlier pseudo-linear estimators and with the nonlinear frequency measurement equation by using another representation than the Cartesian one and by using the logarithm of the frequency, respectively. It is fast, inherently stable, and easy to implement. The Doppler shift is, for a nonmoving own-ship, determined by the target velocities, while the bearing rate is determined by the same velocities divided by the range. The special representation in this paper uses this difference in behavior to give fast and bias free estimation of the range. Instead of iterating a weighted feast squares problem using bearing and frequency measurements simultaneously, the true bearings and the course are estimated in a bearings only step followed by a frequency only step, which estimates range and frequency. The range estimate then gives the speed estimate. Modifications for scenarios with multiple emitted frequency lines and/or for frequency lines that disappear during parts of a scenario are shown View full abstract»

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  • Standard definitions for sound levels in the ocean

    Page(s): 109 - 113
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    Measurements and calculations in underwater and bio-acoustics should use for the units of the primary reference quantities the International System of Units commonly referred to as SI metric. Relative levels are important quantities provided the reference is clearly specified and the modifier to the term level is consistent with the units of the reference quantity. In particular it is necessary to distinguish between pressure, power, and energy references. These reference quantities should have clearly defined SI-metric (mks) units. The absolute value of the power or intensity should be parenthetically included View full abstract»

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Aims & Scope

The IEEE Journal of Oceanic Engineering (ISSN 0364-9059) is published quarterly by the IEEE Oceanic Engineering Society (IEEE OES). The scope of the Journal is the field of interest of the IEEE OES, which encompasses all aspects of science, engineering, and technology that address research, development, and operations pertaining to all bodies of water. This includes the creation of new capabilities and technologies from concept design through prototypes, testing, and operational systems to sense, explore, understand, develop, use, and responsibly manage natural resources.

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Meet Our Editors

Editor-in-Chief
N. Ross Chapman
School of Earth & Ocean Sciences
University of Victoria
3800 Finnerty Road
Victoria, BC V8P 5C2 Canada
chapman@uvic.ca