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 “"Nonlinear acoustics"”.
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Nonlinear Acoustics in a General Waveguide
Until this present work, the acoustics of waveguides has been divided into two broadly distinct fields---linear acoustics in ducts of complex geometry such as those with curvature or varying width, and nonlinear acoustics restricted to simple geometry ducts without curvature or flare. This PhD …
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Nonlinear Acoustics and an Inverse Scattering Problem
… wave propagation problems. The main focus is on nonlinear acoustics, looking at sonic boom propagation in a physically realistic atmosphere, whilst a secondary part will look at the problem of landmine detection and how to improve the target detection rates. The work on nonlinear acoustics …
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Nonlinear Acoustics : what happens when the constraint is challenged?
The Lagrangian formulation for the propagation of sonic disturbances consists of a system of rst order partial di erential equations and an inequality constraint under which the system is hyperbolic. We study the behaviour of solutions when the system is initially at rest but strained under an …
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Strongly nonlinear acoustics of one-dimensional granular sonic vacua
This research is concerned with the nonlinear dynamics and acoustics of one dimensional ordered granular media. In particular the considered granular systems are composed of discrete elastic spherical beads that mutually interact through strongly nonlinear Hertzian force interaction law. In this …
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A dissipative wave packet approach for unified nonlinear acoustics
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994.
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Well-posedness and asymptotic behavior of integro-differential models in linear and nonlinear acoustics
Contains fulltext : 306599.pdf (Publisher’s version ) (Open Access)
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Nonlinear acoustics in the presence of an object with sum or difference frequency sensing
A general and complete second-order theory of nonlinear acoustics in the presence of an object is derived and shown to be consistent with experimental measurements. The total second-order field occurs at sum or difference frequencies of the primary fields and naturally breaks into (A) nonlinear …
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Linear and weakly nonlinear boundary layer acoustics in a lined duct
… look at the effect of boundary layer flow on the acoustics of an acoustic lining. Acoustic linings are used in aircraft engine ducts to reduce the sound they produce. They typically consist of an array of Helmholtz resonators that are characterised by their impedance - a linear relationship …
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Multi-functional Holographic Acoustic Lenses for Modulating Low- to High-Intensity Focused Ultrasound
… complicated acoustic field, and the degree of nonlinear waveform distortion at the focal areas, which have not been met to date. This dissertation focuses on introducing experimentally validated novel numerical approaches, optimization algorithms, and experimental techniques to fill existing …
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Nonlinear acoustic pulse propagation in range-dependent underwater environments
The nonlinear progressive wave equation (NPE) is a time-domain formulation of Euler's fluid equations designed to model low angle wave propagation using a wave-following computational domain. The standard formulation consists of four separate mathematical quantities that physically represent …
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Acoustic non-reciprocity in passive nonlinear waveguides with configurational asymmetry
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2022-11-15 without embargo terms
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Trans-skull Ultrasound for Imaging and Therapy
… including improved targeting for exploitation of nonlinear acoustic effects in the brain, controlling the microbubble dynamics, and super-resolution imaging.
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High data rate acoustic communications with nonideal channels
Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2024-12-01
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Theoretical and experimental studies of the dynamics and acoustics of forced ordered granular networks
… is highly tunable ranging from being strongly nonlinear and non-smooth in the absence of static pre-compression, to reducing to weakly nonlinear and smooth for large static pre-compression. The nonlinearity in uncompressed granular media arises from two sources: First, nonlinear Hertzian …
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The Effect of Nonlinear Propagation on Near-field Acoustical Holography
… equations and finite-amplitude sources imply nonlinear effects, which cause shock formation and consequently an altered spectral shape, a feasibility study is carried out to determine the effect of nonlinear propagation on NAH. Jet and rocket sources typically have a distinct spectral shape …
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Non-destructive quantitative assessment of oxidation in aged and rejuvenated asphalt concrete pavements using a non-collinear wave mixing approach
… need by employing non-collinear wave mixing, a nonlinear acoustic technique, to evaluate the level of oxidation of the pavement. To implement the nonlinear technique, the linear acoustic parameters, i.e., dilatational and shear velocities and attenuations, of asphalt concrete specimens with …
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Hypersound interaction studied by time-resolved inelastic light and x-ray scattering
… amplitude phonon wave packets which can behave nonlinearly, quite similar to shallow water waves which show a steepening of wave fronts or solitons well known as tsunamis. Due to the high amplitude of the acoustic wave packets in the solid, the acoustic properties can change significantly in the …
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Dynamics of Multi-functional Acoustic Holograms in Contactless Ultrasonic Energy Transfer Systems
… which includes the effects of acoustic nonlinearity, diffraction, and absorption of the medium, and entails the problem of several biomedical ultrasound applications. Finally, the design and use of acoustic holograms in microfluidic channels are addressed which opens the door of acoustic …
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Nonlinear Effects in Contactless Ultrasound Energy Transfer Systems
… for radiation effects. The linear models neglect nonlinear effects associated with the nonlinear acoustic wave propagation as well as the receiver's electroelastic nonlinearities on the energy transfer characteristics, which become significant at high source strengths. In this dissertation, we …
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Über Synchronisationsphänomene nichtlinearer akustischer Oszillatoren
In dieser Arbeit werden die Effekte der Synchronisation nichtlinearer, akustischer Oszillatoren am Beispiel zweier Orgelpfeifen untersucht. Aus vorhandenen, experimentellen Messdaten werden die typischen Merkmale der Synchronisation extrahiert und dargestellt. Es folgt eine detaillierte Analyse der …
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