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 10 of 10 for “"Acoustic holography"”.
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Resolution improvement in acoustic holography using aperture expansion techniques
… main reasons for the restricted application of holography in acoustic imaging is the limited resolution due to the relatively small numerical aperture for a given physical aperture. There is also a lack of suitable acoustic area detectors which provide adequate sensitivity and spatial resolution …
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Development of an Energy-Based Nearfield Acoustic Holography System
Acoustical-based imaging techniques have found merit in determining the behavior of vibrating structures. These techniques are commonly used in numerous applications to obtain detailed noise source information and energy distributions on source surfaces. This thesis focuses on the continued …
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Helmholtz Equation Least Squares Based Near-Field Acoustic Holography With Laser
… normal surface velocity as input in near-field acoustic holography. The conventional HELS based NAH uses acoustic pressure as input to reconstruct sound field quantities, while this modified HELS based NAH with laser utilizes the normal surface velocities measured by LDV to reconstruct the …
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Visualizing Interior And Exterior Jet Aircraft Noise
… Equation Least Squares (HELS) based nearfield acoustic holography will be used to understand noise transmission caused by jet engine and turbulence into the fuselage of a jet aircraft cruising at 30,000 ft. </p> <p>Modern propulsive jet engines produce exterior noise sources with a high …
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Multi-frequency Ultrasound Directed Self-assembly
… directed self-assembly (DSA) relies on the acoustic radiation force associated with a standing ultrasound wave to organize particles dispersed in a fluid medium into specific patterns. State-of-the-art ultrasound DSA methods can only organize particles into (quasi-)periodic patterns, limited …
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Structure Borne Noise Analysis Using Helmholtz Equation Least Squares Based Forced Vibro Acoustic Components
… equation least squares (HELS) based nearfield acoustic holography method. In this study, the HELS formulations derived in spherical co-ordinates using spherical wave expansion functions utilize the input data of acoustic pressures measured in the nearfield of a vibrating object to reconstruct …
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Ultrasound Wave Patterning for Spatiotemporal Control of Acoustic Power Transfer: Pathways from Transmission to Reception
… challenges in understanding and improving how acoustic waves behave as they move through different materials. This dissertation introduces new ways to model and test ultrasound power transfer, helping to boost both output power and efficiency. One focus is on a phenomenon called mode coupling, …
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Multi-functional Holographic Acoustic Lenses for Modulating Low- to High-Intensity Focused Ultrasound
… an essential role in clinical and contactless acoustic energy transfer applications. These applications have critical criteria for the acoustic pressure level, the creation of complex pressure patterns, spatial management of the complicated acoustic field, and the degree of nonlinear waveform …