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  • 2015-2019  (140)
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  • 1
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-28
    Description: Presents the 2017 subject/author index for this publication.
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 2
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-14
    Description: In this paper, we address the problem of detecting a known signal in snapping shrimp noise. The latter dominates the ambient soundscape at medium-to-high frequencies in warm shallow waters. The noise process is impulsive, exhibits memory and is modeled effectively by stationary $\alpha$ -sub-Gaussian noise with memory order $m$ ( $\alpha$ SGN( $m$ )), which is essentially an impulsive Markov process. Robust detectors have long been used to mitigate the impact of impulsive noise on the performance of digital systems. However, conventional notions of robustness do not assume memory within the noise process. The $\alpha$ SGN( $m$ ) model offers a mathematical model to develop robust detectors that also exploit the mutual information between noise samples. Recent works in this area highlight substantial improvement in detection performance over traditional robust methods in snapping shrimp noise. However, implementing such detectors is a challenge as they are parametric and computationally taxing. To achieve more realizable detectors, we derive the locally optimal detector for $\alpha$ SGN( $m$ ). From it, we introduce the generalized memory-based sign correlator and its variants, all of which offer near-optimal performance in $\alpha$ SGN( $m$ ). The proposed detectors off- r excellent performance in snapping shrimp noise and low computational complexity. These properties make them attractive for use in underwater acoustical systems operating in snapping shrimp noise.
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    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 3
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-11
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    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 4
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-11
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 5
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-11
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 6
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-11
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 7
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-11
    Description: When an aspect-dependent target is insonified by an acoustic source, distinct features are produced in the resulting bistatic scattered field. These features change as the aspect between the source and the target is varied. This paper describes the use of these features for estimation of the target aspect angle using data collected by an autonomous underwater vehicle (AUV). An experiment was conducted in November 2014 in Massachusetts Bay to collect data using a ship-based acoustic source producing 7–9-kHz linear frequency modulation (LFM) chirps insonifying a steel pipe. The true target orientation was unknown, as the target was dropped from the ship with no rotation control. The AUV Unicorn , fitted with a 16-element nose array, was deployed in data collection behaviors around the target, and the ship was moved to create two target aspects. A support vector machine regression model was trained using simulated scattering bistatic field data. This model was then used to estimate the target aspect angle from the data collected during the experiment. The difference between the estimates was consistent with experimental observations of relative source positioning. The simulation-based model appeared successful in estimating the target aspect angle despite uncertainties in target and source location and mismatch between true environment and simulation parameters.
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  • 8
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-11
    Description: Autonomous underwater manipulation has been a topic of interest since the early 1990s. In the past few years, several milestone projects such as SAUVIM and TRIDENT have demonstrated autonomy capabilities for a single underwater vehicle manipulator system (UVMS) in performing simple manipulation tasks, e.g., the recovery of an object from the seafloor. The Italian funded MARIS project aims to extend some of these results to multiple UVMSs performing a cooperative transportation task of a long object such as a pipe. This paper presents the results achieved in developing a unifying architecture for the control of both individually and cooperatively operating UVMSs which explicitly makes use of a limited amount of information exchange between the agents, which is needed due to the severe bandwidth limitations of the underwater acoustic communications. A complete execution of the reference transportation mission is presented to support the proposed distributed algorithm. Furthermore, hydrodynamic simulations of the cooperative transportation phase are presented and an analysis of the achievable performances as different communication schemes are employed is given.
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  • 9
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-11
    Description: An acoustic Digital MONitor (DMON) has been integrated into a Seaglider autonomous underwater vehicle to serve as a general-use tool for passive acoustic sensing of marine mammal vocalizations. The system is being developed as a complement to conventional ship-based cetacean survey methods. The acoustic system includes three omnidirectional hydrophones, one located on centerline of the aft payload hatch and one on each wingtip. An onboard real-time detector has been implemented to record an audio sample if ambient noise has risen above a user-prescribed signal-to-noise ratio (SNR) threshold level. The data size and the number of detections are available in semi-real time, and the acoustic data are retrieved upon recovery of the instrument. Because the DMON system interfaces with the Seaglider firmware, the glider pilot has the capability to modify several operational parameters governing the collection of acoustic data while the glider is deployed to tailor the data recording to the desired mission objectives. This implementation is referred to as the Seaglider Customizable Sampling Configuration (SCSC) DMON and has recorded a wide variety of cetacean vocal activity offshore the Hawaiian Islands.
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  • 10
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    Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 2017-10-11
    Description: A method to generate vehicle maneuvering forces from a propulsor alone has been applied to a generic undersea vehicle. Open and ducted post-swirl propulsors were configured with an upstream rotor and downstream stator row. During normal operation, the downstream stator blades are all situated at the same pitch angle and generate a roll moment to counter the torque produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to generate a mean stator side force that can be used to maneuver the vehicle. In addition, the side force can be increased with increasing thrust producing side forces at very low vehicle velocities enabling low-speed maneuvering capability. The viscous, 3-D Reynolds-averaged Navier–Stokes (RANS) commercial code Fluent was used to predict the vehicle and propulsor component forces as well as the velocity field. Open and ducted geometric configurations were studied and force coefficients computed and compared with currently used control surface forces. Computations predicted that the maneuvering propulsor generated side forces equivalent to those produced by conventional control surfaces with side force coefficients on the order of 0.25 for the open propulsor at the self-propulsion point. This translates to 50% larger forces than can be generated by conventional control surfaces on 21 $^{\prime \prime}$ unmanned undersea vehicles. The ducted configuration produces maximum side force coefficients on the order of 0.15, which is still sufficient for vehicle control. Both configurations produced side forces for the Bollard pull condition indicating low-speed maneuvering capability.
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    Topics: Architecture, Civil Engineering, Surveying , Physics
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