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 28 for “"acoustic imaging"”.
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An electro-mechanical acoustic imaging scanner assembly.
The design of "a combined electro-mechanical acoustic image scanning assembly is described. Various acoustic imaging system techniques have demonstrated an ability to form underwater images at distances greater than those obtained by optical means. The scanning assembly -utilizes a sixteen element …
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Inverse filtering for virtual acoustic imaging systems
… design and implementation of two-channel virtual acoustic imaging systems that utilise loudspeakers. The basic objective of such systems is to invert the electroacoustic plant between the input to the loudspeakers and the output at the listener’s ears and hence make it possible for a pair of …
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Time-Lapse Acoustic Imaging of the Oceanic Energy Cascade
… reflection records have been used to construct acoustic images of oceanic thermohaline structure. In the water column, acoustic boundaries are produced by variations in temperature and, to a lesser extent, salinity. Acoustic waves generated by an array of airguns suspended behind a vessel are …
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Time-lapse Acoustic Imaging of Oceanic Fronts and Eddies
Seismic reflection surveying is used to generate acoustic images of the water column. This technique employs conventional multi-channel equipment which is used to image the solid Earth. In the water column, acoustic impedance contrasts are produced by variations in temperature and, to some extent, …
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The acoustic imaging, reconstruction and characterization of buried archaeological material
… this thesis aimed to adapt and apply sub-bottom acoustic<br/>techniques to shallowly buried shipwrecks and submerged palaeo-landsurfaces.<br/>The imaging of archaeological sites requires a geophysical source with high resolving power. A<br/>model was developed to determine the vertical resolution …
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Optimization of transmit/receive array topology in 3D acoustic imaging
Acoustic imaging transmit and receive arrays pairs are simulated in the bistatic transmission case using Field II, an industry standard ultrasound toolbox. Analysis of imaging fundamentals, as well as simple transmit and receive array beam patterns reveals desirable beam pattern properties that can …
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Defining and modeling the limits of high-resolution underwater acoustic imaging
… located under water near to interfaces with high acoustic and or magnetic impedance differences and roughness are hard to detect. Today most up to date modern sea mines have a non magnetic hull and a minimum of magnetic materials on board. They preferably hide near interfaces that hinder …
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Investigation of spacecraft cluster autonomy through an acoustic imaging interferometric testbed
… interferometry testbed is developed. Utilizing acoustic sources and sensors as a simplified analog to radio or optical systems, the Acoustic Imaging Testbed's simplest function is that of a Michelson interferometer. Robot arms control the motion of microphones. Through successive measurements an …
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Signal processing in a real-time three-dimensional acoustic imaging system
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.
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A Two -Dimensional Amplitude -Steered Array for Real -Time Volumetric Acoustic Imaging
Real-time volumetric ultrasound imaging is difficult due to problems with array construction and due to the slow speed of data collection. In 1976, a linear amplitude-steered array was introduced that uses reduced electronics to steer a monofrequency beam. The current study examines how the linear …
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A microcomputer-based digital data acquisition controller for a computer aided acoustic imaging system
… microcomputer based controller for an ultrasonic acoustic imaging system. The INTEL 8748 single chip microcomputer was utilized and the associated hardware and software for the system is described in detail. Carefully designed and testing operating instructions are provided along with an …
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NOISE MEASUREMENTS AND EVALUATION OF SOUND SOURCES OF ROAD VEHICLES
… noise at 10, 30, 50 km/h via SoundCam 2.0 acoustic imaging on a quiet road.
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Computational Methods for One-Dimensional Scattering in Non-Smooth Media
… implements various numerical algorithms used for acoustic imaging of layered media: the scattering-based algorithm, the classical Born approximation, the refined impedance transform and the echoes-to-impedance transform. The last three are inverse scattering algorithms that numerically convert …
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Acoustic metamaterial design and applications
… in superlens which allows super-resolution imaging. High-resolution acoustic imaging techniques are the essential tools for nondestructive testing and medical screening. However, the spatial resolution of the conventional acoustic imaging methods is restricted by the incident wavelength of …
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Acoustic Coherence Imaging Through the Atmosphere
"The imaging of acoustic ""scenes"" through the atmosphere is a subject with little treatment in the literature. This thesis strives to set the state of the art in this field by presenting imaging methods and their performance in the turbulent atmosphere. Both narrowband interferometry and wideband …
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Development and deployment of a novel deep-sea in situ bubble sampling instrument for understanding the fate of methane in the water column
… methods of measuring this flux such as acoustic imaging, optical sensors, and modeling suffer from limited information regarding the bubbles’ composition. Studies that attempt to constrain CH4 bubble composition suffer from low spatiotemporal resolution and adaptability. The current …
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Development and deployment of a novel deep-sea in situ bubble sampling instrument for understanding the fate of methane in the water column
… methods of measuring this flux such as acoustic imaging, optical sensors, and modeling suffer from limited information regarding the bubbles' composition. Studies that attempt to constrain CH₄ bubble composition suffer from low spatiotemporal resolution and adaptability. The current …
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Experiments and simulations on a metamaterial based ultrasonic scanner
… individuals. Ultrasonic fingerprint scanners use acoustic waves to obtain the fingerprint image and their performance is invariant to the surface conditions typically found on the finger surface due the ability of ultrasound to penetrate into sub-surfaces. This makes ultrasonic fingerprint …
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