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 37 for “"Shear waves"”.
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Velocity of shear waves through unconsolidated materials
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Geology, 1952.
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Mechanism of attenuation of compressional and shear waves for dry, water and benzene satruated rocks
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1985.
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Ultrasound shear wave elastography imaging with external mechanical vibration
Ultrasound shear wave elastography (SWE) imaging is gaining wide acceptance in clinical practice as both a non-invasive and quantitative diagnostic modality. Most commercial SWE systems generate shear waves using acoustic radiation force (ARF), which requires complex hardware and is therefore only …
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System identification and control of a miniature external mechanical vibration device towards clinical ultrasound shear wave elastography
… force (ARF) is commonly used to generate shear waves in ultrasound systems for shear wave elastography (SWE). However, ARF requires complex hardware that produces thermal stresses in tissues and electronic components. External mechanical vibration (EMV) is less power-exhaustive compared to …
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Quantitative estimates of mechanical properties from in vivo tumors of rodent animals
… focuses on using ultrasonic tools to image shear waves generated in spontaneous rodent mammary tumors to estimate the complex shear modulus under realistic conditions, and to assess the sensitivity for relating matrix viscoelasticity to tumor type and stage. Cylindrical, harmonic shear waves …
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Scattering Techniques for the Geophysical Inverse Problem
… inverse problem for the propagation of elastic waves in stratified media. The one-dimensional inverse problem for the propagation of shear waves is studied in the context of spectral theory. We generalize certain inverse scattering methods in quantum mechanics to determine the properties of the …
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Vibrational characteristics of brain magnetic resonance elastography
… non-invasive methodology for the mapping of shear stiffness of the brain. A mechanical actuator shakes the brain and generates shear waves, which are then imaged with a special MRI sequence sensitive to sub-millimeter displacements. This research focuses on exploring the profile of vibrations …
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Shear Wave Elastography Based on Optical Coherence Tomography
… Starting from the numerical model of mechanical waves, the behaviours of shear waves and surface waves in biological tissue is studied. Contact mechanical stimulations, as well as non-contact ultrasound and pulsed lasers are utilised to generate transient waves in biological samples. High speed …
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Ultrasonic stress measurement for evaluating the adequacy of gusset plates
… evaluates normalized variations of polarized shear waves propagating through the plate thickness, which vary proportionally as a function of stress. This thesis discusses exploratory testing to evaluate the potential of the approach as a tool for the condition assessment of gusset plates.
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Development of the Spectral-Analysis-of-Body-Waves (SABW) method for downhole seismic testing with boreholes or penetrometers
… time-domain signals have been used to calculate shear and compression wave velocities in soil and rock layers. This time-domain method requires an operator to pick the first arrival or other reference point of each seismic wave in the time record. Picking these reference points correctly is …
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Seismic performance of single-propped retaining walls
… In order to avoid spurious reflections of shear waves on the vertical boundaries of the finite difference model, the analyses used periodic boundary conditions. The performance of the structure was investigated by considering the wall deflections, bending moments, earth pressures and …
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Seismic reflection moveout for azimuthally anisotropic media
… the reflection moveout for Compressional and Shear waves in horizontally stratified azimuthally anisotropic media. Reflection moveout in common-midpoint (CMP) gathers is generally treated by an azimuthally-isotropic hyperbolic equation. Recently, special treatment for the reflection moveout in …
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A new method to test shear wave splitting: improving statistical assessment of splitting parameters
Shear wave splitting has proved to be a very useful technique to probe for seismic anisotropy in the earth’s interior, and measurements of seismic anisotropy are perhaps the best way to constrain the strain history of the lithosphere and asthenosphere. However, existent methods of shear wave …
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Modeling of acoustic-emission wave propagation in layered media
… and the other as free, fixed or infinite. The AE waves are generated by dislocation over a fault area located in one of the layers or at a layer-to-layer interface. In this study, three-dimensional (3D) wave motion in each homogeneous, isotropic and linearly-elastic layer is solved with the use of …
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MANTLE FLOW AND TRANSITION ZONE DISCONTINUITIES BENEATH THE CARRIBEAN PLATE: CONSTRAINTS FROM SHEAR WAVE SPLITTING AND RECEIVER FUNCTION ANALYSES
… the fast orientations from the two types of shear waves are comparable, but the XKS splitting times are about twice of the local S wave splitting times, suggesting that the observed azimuthal anisotropy has contributions from both above and below the subducting oceanic slab. In the Lesser …
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The earth's interior from both a seismological and petrological perspective
Shear-wave splitting measurements of teleseismic shear waves, such as SKS, have been used to estimate the amount and direction of upper-mantle anisotropy worldwide. One of the basic assumptions in making these measurements is that the anisotropy is confined to a single, homogeneous layer. In this …
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Characterization of Fractures Subjected to Normal and Shear Stress
… specific stiffness, for a fracture subjected to shear and normal stress, are presented and analyzed. The experimental work focuses on the determination of relations between normal and shear fracture specific stiffness and between spatial distribution of fracture specific stiffness and fluid flow …
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Post processing of cone penetration data for assessing seismic ground hazards, with application to the New Madrid seismic zone
… In this thesis, software systems including ShearPro, ClusterPro, and InSituData, are developed to automate post processing of these SCPTu data. ShearPro is developed to automate the post-processing of the shear wave signals. ClusterPro uses the proposed three-dimensional cluster analysis …
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Stiffness characterization of mechanically-compressed cohesive soils using wave propagation
… Due to the difficulty of measuring shear waves through soft cohesive soils with ultrasonic transducers, bender elements are typically used, which couple to the soft clay. Unfortunately, the stress limitation of bender elements precludes it from testing above 1.5 MPa. A novel setup …
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