Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 13 of 13 for “"Towed Array"”.
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Performance analysis of subaperture processing using a large aperture planar towed array
… high transmission loss. Large aperture planar arrays have the potential to improve detection performance due to their high resolution and high gain, but are suceptible to two main performance degradation mechanisms: limited spatial coherence of signals and nonstationarity of high bearing rate …
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Target tracking onboard an autonomous underwater vehicle : determining optimal towed array heading in an anisotropic noise field
… vehicle (AUV) towing a horizontal line array. The estimation of the noise directionality is a precursor to another adaptive behavior: optimizing tracking capability of a towed array by choosing a particular heading that minimizes the detection level in the target's direction. In each …
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The effect of towed array orientation on the 3D acoustic picture for sound sources and the vertical ambient noise profile
… underwater vehicle (AUV) equipped with a towed array in a virtual environment to develop an accurate 3D acoustic picture of the undersea environment. While prior towed array experiments are generally limited to the arrays being towed in a horizontal manner, here a "yoyo" maneuver is …
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Beamforming performance enhancement by adaptive hyperbola array shape estimation
… with MIT Lincoln Laboratory, demonstrated that towed array curvature commonly exhibited heading differences up to 100° and never maintained heading differences less than 30° between the forward compass and the aft compass. These deviations reflected a disparity from the underlying assumption …
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Maintaining contact : design and use of acoustic signals in killer whales, Orcinus orca
… gradually separate into different pods. A new towed array beamforming system was developed to identify vocalizing killer whales concurrent with focal behavioral observations. Carefully positioning the array relative to the animals and linking visual observations of whale position with the …
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Spatial variability of the ambient noise field associated with the Marginal Ice Zone and its relationship to environmental parameters
… levels were found along the ice edge using a towed array. Ambient noise levels were obtained on 27 and 28 July using AN/SSQ-57A and AN/SSQ-57XN5 calibrated sonobuoys . The temperature structure of the area was determined using XBT (ship) and AXBT (P3C aircraft) buoys placed inside and outside …
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Localization of Dynamic Acoustic Sources with a Maneuverable Array
… spatial spectrum estimation with maneuverable arrays. Two applications, each having different environmental assumptions and array geometries, are considered: 1) passive broadband source localization with a rigid 2-sensor array in a shallow water, multipath environment and 2) time-varying …
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Evaluation by simulation of an acoustic array composed of multiple autonomous vehicles
Ship-towed arrays have been integral to Navy combatant operations for many decades. The continual advancement of towed array technology has been continually driven by the need for high sensitivity, low self-noise, and response across a wide range of frequencies. Robotic autonomy, as applied to …
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Forward sound propagation around seamounts : application of acoustic models to the Kermit-Roosevelt and Elivs seamounts
… diffraction, and scattering by the seamounts. A towed hydrophone array, with 64 sensors cut for 250Hz (3m spacing), was used to measure the signals transmitted from the aforementioned broadband sources at many locations around the Kermit-Roosevelt and Elvis seamounts. Utilizing the measured …
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Sub-bottom profiling using an Autonomous Underwater Vehicle equipped with a sound source and towed hydrophone array
… underwater vehicle equipped with a source and a towed array is an excellent method to finely survey large areas of the ocean bottom with minimal interference from the water column. This approach has the benefit of being able to determine the range dependence of the sub-bottom on a meter-by-meter …
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Sub-Bottom Profiling Using an Autonomous Underwater Vehicle Equipped With a Sound Source and Towed Hydrophone Array
… underwater vehicle equipped with a source and a towed array is an excellent method to finely survey large areas of the ocean bottom with minimal interference from the water column. This approach has the benefit of being able to determine the range dependence of the sub-bottom on a meter-by-meter …
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Forward sound propagation around seamounts : application of acoustic models to the Kermit-Roosevelt and Elvis seamounts
… diffraction, and scattering by the seamounts. A towed hydrophone array, with 64 sensors cut for 250Hz (3m spacing), was used to measure the signals transmitted from the aforementioned broadband sources at many locations around the Kermit-Roosevelt and Elvis seamounts. Utilizing the measured …
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Sensor Array Processing with Manifold Uncertainty
… realizable source locations for a given array configuration is referred to as the array manifold. In this thesis, array manifold ambiguities for linear arrays of omni-directional sensors in non-dispersive fields are considered. </p><p>First, the problem of underwater a hydrophone array …