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  • Articles  (637)
  • 1
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    Noise Background Levels and Noise Event Tracking/Characterization Under the Arctic Ice Pack: Experiment, Data Analysis, and Modeling (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: In March 2014, an Arctic Line Arrays System (ALAS) was deployed as part of an experiment in the Beaufort Sea (approximate location 72.323 N, 146.490 W). The water depth was greater than 3500 m. The background noise levels in the frequency range from 1 Hz to 25 kHz were measured. The goal was to have a three-dimensional sparse array that would allow determination of the direction of sound sources out to hundreds of kilometers and both direction and range of sound sources out to 1–2 km from the center of the array. ALAS started recording data at 02:12 on March 10, 2014 (UTC). It recorded data nearly continuously at a sample rate of 50 kHz until 11:04 on March 24, 2014. Background noise spectral levels are presented for low and high floe-drift conditions. Tracking/characterization results for ice-cracking events (with signatures typically in the 10–2000-Hz band), including the initiation of an open lead within about 400 m of the array, and one seismic event (with a signature in the 1–40-Hz band) are presented. Results from simple modeling indicate that the signature of a lead formation may be a combination of both previously hypothesized physics and enhanced emissions near the ice plate critical frequency (where the flexural wave speed equals that of the water sound speed). For the seismic event, the T-wave arrival time results indicate that a significant amount of energy coupled to T-wave energy somewhere along the path between the earthquake and ALAS.
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 2
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    Efficient Use of Space-Time Clustering for Underwater Acoustic Communications (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: Underwater acoustical communication channels are characterized by the spreading of received signals in space (direction of arrival) and in time (delay). The spread is often limited to a small number of space-time clusters. In this paper, the space-time clustering is exploited in a proposed receiver designed for guard-free orthogonal frequency-division multiplexing with superimposed data and pilot signals. For separation of space clusters, the receiver utilizes a vertical linear array (VLA) of hydrophones, whereas for combining delay-spread signals within a space cluster, a time-domain equalizer is used. We compare a number of space-time processing techniques, including a proposed reduced-complexity spatial filter, and show that techniques exploiting the space-time clustering demonstrate an improved detection performance. The comparison is done using signals transmitted by a moving transducer, and recorded on a 14-element nonuniform VLA in sea trials at distances of 46 and 105 km.
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    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 3
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    Power Takeoff Optimization to Maximize Wave Energy Conversions for Oscillating Water Column Devices (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: This paper presents an investigation on how to optimize the power takeoffs (PTOs) to maximize the mean wave energy conversion from seas for floating oscillating water column (OWC) devices. For this purpose, the linear air turbine PTOs are first analytically optimized to maximize the mean energy conversion for regular waves, based on which a simple and fast-turnaround assessment method is proposed to optimize the linear PTO damping coefficient for maximizing the mean energy conversion for the given sea states. Further on, the focus is on how we can reliably assess the maximized mean wave energy conversions if the OWCs are equipped with nonlinear air-turbine PTOs, as frequently seen in practical OWC plants. Conventionally, the time-consuming time-domain analysis is employed for searching the optimized nonlinear damping coefficients which may be both wave-height- and wave-period-dependent for the given sea state. This may not be suitable in the early design stages of the device when many different options may be compared and checked for optimizing the device itself. As such, a reliable fast-turnaround assessment is very desirable for the device performance and for the assessment of energy conversion for the sea states in the deployment site. From the examples in the study, it is shown that the OWC wave energy converters with the optimized linear PTOs have the same energy capture capacities as those with optimized nonlinear PTOs. As such, it can be suggested that the OWC wave energy capture capacity can be analyzed using the fast-turnaround frequency-domain analysis, regardless of whether the linear or nonlinear PTO is used in the wave energy converter.
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 4
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    Normalized Scalar Product Approach for Nearshore Bathymetric Estimation From X-Band Radar Images: An Assessment Based on Simulated and Measured Data (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: This paper investigates the capability of X -band radar systems to estimate nearshore bathymetry fields by considering both simulated and measured radar data. For the first time, a sensitivity analysis is performed to evaluate how sea-state conditions affect bathymetric estimates. For this purpose, sea wave fields generated by means of a numerical model, based on a nonlinear shallow-water equation solver, are used. Starting from the synthetic radar data, which represent the input of the bathymetric estimation algorithm, the bathymetric reconstruction is performed through the normalized scalar product (NSP) estimation strategy, exploiting a spatial partitioning of the radar data. In this way, it is possible to improve the accuracy of the estimates in nearshore areas, where the space-varying behavior of the sea depth and the presence of coastlines or coastal structures typically leads to a spatial inhomogeneity of the wave motion. In this regard, it is shown how the choice of the partitioning settings affects the bathymetric estimates obtained from high-resolution X -band radar images by using the NSP strategy. In addition, an adaptive partitioning strategy that takes into account the wave evolution in nearshore shallow waters is devised. Based on both simulated and measured radar data, the accuracy of the bathymetric estimates achievable through the proposed adaptive partitioning process and that obtained by exploiting the approach using uniform spatial partitioning are compared. The results obtained confirm the robustness of the NSP technique with respect to sea conditions and, moreover, demonstrate that the proposed adaptive partitioning strategy provides more accurate bathymetric estimates than those obtained with the space-invariant partitioning procedure.
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    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 5
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    Special Issue on Verification and Validation of Airgun Source Signature and Sound Propagation Models (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 6
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    Table of Contents (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: Presents the table of contents for this issue of the publication.
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 7
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    Editorial Hello From Your New EIC (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: Presents the introductory editorial for this issue of the publication.
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    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 8
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    Guest Editorial Special Issue on Marine and Maritime Radar Remote Sensing (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 9
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    Editorial Addition of New Material After Peer Review (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: This editorial addresses a serious concern of author misconduct that must be addressed at the editorial level. The problem is not new, but the frequency of occurrences in the last few months has brought the matter to the forefront of our attention. We are talking about the many instances of authors adding new material to their papers after the peer-review process has been completed. To provide the background about the problem, when the paper under review has been recommended for publication by an Associate Editor, the peer-review process has been completed. In the decision letter, the authors are requested to submit a final version that will be sent to the IEEE for typesetting. The final version of the paper is checked carefully at the editorial office as a matter of quality control.
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    Topics: Architecture, Civil Engineering, Surveying , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 10
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    Efficient Seafloor Classification and Submarine Cable Route Design Using an Autonomous Underwater Vehicle (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-01-12
    Description: This work presents an efficient method for designing submarine cable routes using online seafloor classification based on sidescan sonar scanlines, collected by an autonomous underwater vehicle (AUV). Currently, the cable routes are designed manually by experienced experts. Online seafloor classification and an automated route planning method using an AUV can improve the efficiency of construction of submarine cables. Sidescan sonar is a device commonly used for mapping the seafloor and detecting obstacles. An AUV equipped with a sidescan sonar is used to gather sonar scanlines to perform online seafloor classification and mapping. As the AUV operates, the gathered scanlines are analyzed to classify the seafloor using a probabilistic classifier based on Bayes' theorem with the naïve assumption. Based on the seafloor classification map, a probabilistic roadmap is generated. Then, an A * algorithm is applied to determine appropriate cable routes along the cable corridor, using the following five factors: seafloor classification, bathymetry, steepness of slope, angle of change of course, and cable length. Compared with an existing route planning method, the presented method of using an AUV with automatic decision making algorithm can efficiently support submarine cable construction. The favored route determined by the presented method was as acceptable as the route designed by experts.
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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