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 20 of 21 for “"Active sonar"”.
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High Resolution Continuous Active Sonar
… and signal processing methods for continuous active sonar (CAS). The work presented focuses on methods for achieving high range, Doppler, and angular resolution, while maintaining a high signal-to-interference plus noise ratio (SINR).</p><p>CAS systems transmit at or near 100\% duty cycle for …
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Low frequency active sonar performance in the Arctic Beaufort Lens
… Beaufort Sea in the Arctic has a major effect on active acoustic transmissions. This work performs an in depth analysis of how the lower duct impacts the propagation of various active signals used commonly for acoustic communications or active sonar. First, this thesis performs a thorough modal …
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Low frequency active sonar performance in the Arctic Beaufort Lens
… Beaufort Sea in the Arctic has a major effect on active acoustic transmissions. This work performs an in depth analysis of how the lower duct impacts the propagation of various active signals used commonly for acoustic communications or active sonar. First, this thesis performs a thorough modal …
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Real time active sonar simulation in a deep ocean environment
… power is very limited. A new module called uSimActiveSonar has been developed in order to simulate an active sonar system with hydrophone data acquisition. This has been done through the use of middleware Mission Oriented Operating Suite (MOOS), ray tracing code BELLHOP as well as using the …
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Target Tracking in Multi-Static Active Sonar Systems Using Dynamic Programming and Hough Transform
… in the track hypothesis. The multi-static active sonar scenario is an example for such systems where multiple source-receiver combinations are deployed. Due to the nature of the underwater environment and sound propagation characteristics, tracking targets in the underwater environment …
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Input of Factor Graphs into the Detection, Classification, and Localization Chain and Continuous Active SONAR in Undersea Vehicles
… localization (DCL) of underwater objects using active SOund Navigation And Ranging (SONAR). A factor graph is a bipartite graphical representation of the decomposition of a particular function. Messages are passed along the edges connecting factor and variable nodes, on which, a message passing …
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Dynamics of Multi-Agent Systems with Bio-Inspired Active and Passive Sensing
Active sensors, such as radar, lidar and sonar, emit a signal into the environment and gather information from its reflection. In contrast, passive sensors such as cameras and microphones rely on the signals emitted from the environment. In the current application of active sensors in multi-agent …
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Soundscape Ecology of Hawaiian Spinner Dolphin Resting Bays
… vessel sound and military mid-frequency active sonar. During one recorded mid-frequency active sonar event in August 2011, sound pressure levels in the 3.15 kHz 1/3rd-octave band were as high as 45.8 dB above median ambient noise levels. Human activity both inside (vessels) and outside …
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Investigating Real-Time Sonar Performance Predictions Using Beowulf Clustering
<p>Predicting sonar performance, critical to using any sonar to its maximum effectiveness, is computationally intensive and typically the results are based on data from the past and may not be applicable to the current water conditions. This paper discusses how Beowulf clustering techniques were …
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Room reconstruction and navigation using acoustically obtained room impulse responses and a mobile robot platform
… of a robot that uses a combination of active sonar and a pseudo-random acoustic signal to navigate and reconstruct an unknown environment. The robot sends the pseudo-random signal into the environment and records the resulting response. This response is processed to gain information on …
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Remote sensing of submerged objects and geomorphology in continental shelf waters with acoustic waveguide scattering
… in continental shelf waters using an active sonar system is explored experimentally and theoretically. A unified model for 3-D object scattering and reverberation that takes into account the coupling between propagation and scattering in a stratified medium is developed from wave …
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Performance Analysis Of Active and Passive Multi-Array Sonar Networks
… the results these networks obtain using active and passive sonar. These results determine the ideal sensor placement for optimal parameter detection and estimation of targets. This work's first part focuses on active sonar networks with a fixed number of sensors in a differing number of …
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A code-division, multiple beam sonar imaging system
In this thesis, a new active sonar imaging concept is explored using the principle of code-division and the simultaneous transmission of multiple coded signals. The signals are sixteen symbol, four-bit, non-linear, block Frequency-Shift Keyed (FSK) codes, each of which is projected into a different …
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Diel vertical migration and frontal variability of acoustic backscatter in the Balearic Sea
Acoustic Doppler current profilers (ADCPs) use active sonar to measure current velocities by measuring the sound returned by scatterers (most often zooplankton) in the water column. The volume of scatterers, or echo intensity, has been used to measure the abundance of zooplankton and characterize …
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Diel vertical migration and frontal variability of acoustic backscatter in the Balearic Sea
Acoustic Doppler current profilers (ADCPs) use active sonar to measure current velocities by measuring the sound returned by scatterers (most often zooplankton) in the water column. The volume of scatterers, or echo intensity, has been used to measure the abundance of zooplankton and characterize …
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An investigation of the roles of geomagnetic and acoustic cues in whale navigation and orientation
… beaked whale to playbacks of Navy mid-frequency active sonar and orca predation calls. Navy sonar exercises have been linked to beaked whale strandings, and identifying whether these are the result of a mistaken predator avoidance reaction may help prevent future strandings.
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Understanding and utilizing waveguide invariant range-frequency striations in ocean acoustic waveguides
… be utilized for applications such as passive and active sonar, time-reversal mirrors, and array processing, even when the SSP or the seafloor properties are not well known. This thesis develops a framework for understanding and calculating the waveguide invariant, and uses that framework to …
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Understanding and utilizing waveguide invariant range-frequency striations in ocean acoustic waveguides
… be utilized for applications such as passive and active sonar, time-reversal mirrors, and array processing, even when the SSP or the seafloor properties are not well known. This thesis develops a framework for understanding and calculating the waveguide invariant, and uses that framework to …
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An investigation of the roles of geomagnetic and acoustic cues in whale navigation and orientation
… beaked whale to playbacks of Navy mid-frequency active sonar and orca predation calls. Navy sonar exercises have been linked to beaked whale strandings, and identifying whether these are the result of a mistaken predator avoidance reaction may help prevent future strandings.
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Dynamic Emission Baffle Inspired by Horseshoe Bat Noseleaves
… of two key innovations - powered flight and biosonar - that are unique among mammals. Bats still outperform engineered systems in both capabilities by a large margin. Bat biosonar stands out for its ability to encode and extract sensory information using various mechanisms such as adaptive beam …
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