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 77 for “"Wave speed"”.
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Structural vibration damping using lightweight, low-wave-speed media
Incorporation of a low-density, low-wave-speed medium (LWSM) into a structure yields significant damping if the speed of wave propagation in the medium is low enough for standing waves to arise in it. In this thesis, we characterize wave propagation in low-density granular media and foams for use …
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Vibration damping using low-wave-speed media with applications to precision machines
… widely used. In this thesis, we present a novel wave-based damping approach for the suppression of vibration in machines and structures. Our studies show that significant broad-band damping can be attained with little added mass via dynamic interaction between a structure and a low-density, …
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Compressional wave speed and absorption measurements in a saturated kaolinite-water artificial sediment.
The absorption coefficient for compressional waves in a water-saturated kaolinite clay was measured in the frequency range 100 to 150 kHz using a pulse technique with spherically diverging waves. The measurement also permitted determination of the sound speed, V . For one condition of the clay with …
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The effect of a low density residuum on geoid anomalies and topography
… between surface topography, seismic wave speed, and the geoid (gravitational potential). High seismic wave speed indicates cold material sinking, which pulls the surface downward. Thus, topographic lows are expected to correlate with seismic wave speed highs, contrary to the new …
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Surface wave propagation in 3-D anelastic media
Lateral perturbations in anelasticity (Q) and wave speed together provide important constraints on thermal and chemical structures in the mantle. In present-day tomography studies of global wave speed and anelasticity, the significance of 3-D wave speed and 3-D Q structures on surface wave travel …
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Finite Opening of Propagating Shear Cracks
… when the crack propagated at a sub-Rayleigh speed while the crack opening became negligible when the crack propagated faster than the shear wave speed. On the other hand, the classical linear dynamics theory predicted that there was no crack opening for a pure shear crack. Using the …
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Air-coupled non-destructive evaluation technology for condition assessment of railroad ties
… assessment of railroad ties. Ultrasonic surface waves are generated in railroad ties using an air-coupled ultrasonic sender. Surface waves are sensed at the receiving end using an array of Micro-Electro Mechanical sensors (MEMs). The resulting wave field is visualized in time-space (t-x domain) …
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Airflow limitation in croup
… is that air flow becomes restricted due to wave speed limitation. According to the theory of wave speed limitation, an increase in driving pressure (the intrathoracic pressure) does not increase the flow if the speed of the air particles exceeds the wave speed. In our case the wave speed is …
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Structural Optimization of Regeneratively Cooled Rotating Detonation Rocket Engines
… stresses become significant when the detonation wave speed approaches the elastic wave speed of the hot wall. This effect is important in Nb-C103, GRCop-84, and W25Re combustors, since the detonation wave speed matches the elastic wave speed for cooling channel designs that minimize static …
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Wave propagation in a semi-infinite, cylindrical, orthotropic membrane
… characteristics in the time-space plane, and wave speed equations. Due to the fiber orientation, an extensional disturbance generates a concomitant torsional disturbance, which propagates with a slower wave speed. The solution, thus, involves two sets of superimposed characteristics. The …
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Gravitational waves from a string cusp in Einstein-aether theory
… hopefully observable, in the gravitational waves emitted by cosmic strings. Aspects of cosmic strings are reviewed, in particular how focused bursts of gravitational radiation are emitted when a cusp forms on the string. The same phenomenon is then studied in an effective field theory with …
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Inferring the thermomechanical state of the lithosphere using geophysical and geochemical observables
… I correlate lower crustal rheology with seismic wave speed. Compositional variation is required to explain half of the total variability in predicted lower crustal stress, implying that constraining regional lithology is important for lower crustal geodynamics. In Chapter 2, I utilize …
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Inferring the Thermomechanical State of the Lithosphere Using Geophysical and Geochemical Observables
… I correlate lower crustal rheology with seismic wave speed. Compositional variation is required to explain half of the total variability in predicted lower crustal stress, implying that constraining regional lithology is important for lower crustal geodynamics. In Chapter 2, I utilize …
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Surface and interfacial waves and deformations in pre-stressed elastic materials
… on the propagation of surface and interfacial waves in elastic materials. Following a review of the classical theory of Rayleigh and Stoneley waves for linear elastic materials we consider first the propagation of infinitesimal surface waves on a half-space of incompressible material subject to …
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Travelling waves in Lotka-Volterra competition models
… (diffusion) and competitive strength can cause waves of invasion to be halted and reversed. By establishing rigorous results concerning related degenerate and near-degenerate systems,we build a picture of the dependence of the wave speed on system parameters. Our results lead us to conjecture …
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Clinical Translation of Dynamic OCE for Corneal Biomechanical Assessment
… of corneal elastic modulus. Corneal mechanical waves generated by low-pressure (0.3mmHg) air-pulse stimulation were imaged using high-speed, phase-senstive OCT. Frequency-dependent corneal wave-speed dispersion was measured, and compared to established Rayleigh–Lamb model. Dispersion-independent …
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Analysis of local hemodynamics in central and peripheral arteries
… of the cardiovascular system, the propagation of waves in arteries has to be investigated, since they carry information which can be used for the prevention and diagnosis of cardiovascular diseases. The main goal of this thesis is to improve the understanding of wave propagation in central and …
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Wavefront Healing and Tomographic Resolution of Mantle Plumes
… of the anti-correlation between bulk sound speed and S wave speed imaged in the lowermost mantle, we use a Spectral Element Method (SEM) to simulate global seismic wave propagation in 3-D wavespeed models and measure frequency-dependent P-, S-, Pdiff- and Sdiff-wave traveltime anomalies …
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Travelling Wave Analysis of a Nonlinear Diffusion Equation
… quantities being the width and propagation speed of the proliferating region. In this thesis we consider the continuum limit of a model of an off-lattice, cell-based simulation of a contact-inhibited cell monolayer. Numerical solutions of the continuum model, which can be formulated as a …
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Full waveform inversion of ultrasonic phased array data for the tomographic reconstruction of heterogeneous media for NDT
… work builds upon that work by creating a full waveform inversion framework to build a tomography method that reconstructs spatially heterogeneous wave speeds maps from simulated ultrasonic phased array data. This framework consists of: a Voronoi tessellation to spatially parametrise the wave …
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