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 71 for “"phase velocity"”.
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On-chip Group and Phase Velocity Control for Classical and Quantum Optical Devices
We present group and phase velocity control for the photonic integrated circuits with an emphasis on two-dimensional photonic crystal devices in this thesis. We describe the theory, analytical and numerical designs, and experimental characterization of silicon nanophotonic devices both in classical …
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Simultaneous inversion of surface wave phase velocity and attenuation for continental and oceanic paths.
Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences.
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Wideband optical frequency comb generator using a phase velocity-matched lithium tantalate electro-optic modulator
A wideband optical frequency comb generator can be built using an electro-optic modulator that is driven at a frequency of several GHz and that is enclosed in an optical cavity. When light is circulated within the optical cavity, multiple passes through the modulator produce a spectrum centered at …
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A global study on phase velocity, group velocity and attenuation of Rayleigh waves in the period range 20 to 100 seconds
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987.
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Ambient noise interferometry and surface-wave array tomography in southeastern Tibet
… array tomography by combining inter-station phase velocity dispersion measurements from empirical Green's functions (EGFs) recovered from ambient noise interferometry and from traditional teleseismic surface-wave two-station (TS) analysis. The non-stationarity (e.g., seasonal changes) and …
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Surface Wave Propagation and Global Crustal Tomography
… Born sensitivity kernels for Rayleigh-wave phase and amplitude measurements that are valid in regions near seismic stations. Calculations of sensitivity kernels for inter-station measurements show that exact travelling-wave representation of Green tensor is necessary when station spacing is …
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Electrooptic mach-zehnder modulators in gallium arsenide
… of this type of modulator are limited by the velocity mismatch between the microwave and the optical wave, where, in these compound semiconductors, the microwave has the greater phase velocity. To eliminate this problem, a slow-wave electrode structure has been developed in our laboratory in …
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Ultrasonic wave propagation in thick, layered composites containing degraded interfaces
… properties and measured 'values of ultrasonic phase velocity and attenuation are used to represent E-glass and vinyl ester resin fiber-reinforced plastic (FRP) laminate, syntactic foam, and resin putty materials in the model. The ultrasonic phase velocity in all three materials is shown to be …
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Formation of small-scale irregularities in the auroral E region
… is on the theory predictions with respect to the phase velocity of plasma waves. As an expansion of the theory, one new effect in the F-B instability evolution is considered, a secondary instability of a turbulent background of the primary F-B waves. It is shown that in a system of F-B modes the …
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Development of Surface Acoustic Wave Optical Coherence Elastography (SAW-OCE) for Soft Tissue Characterisation
… to induce the SAWs on the specimen surface. Phase-sensitive optical coherence tomography system (PhS-OCT) was employed to image the microstructure of the specimen and to track the transient wave propagation inside the specimen. In a transversely heterogeneous material, the 2D Young’s modulus …
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Characterization of low-frequency electric potential oscillations near the edge of a plasma confined by a levitated magnetic dipole
… has a linear dispersion relation which gives a phase velocity of 2-16 k. This phase velocity is inversely correlated with neutral gas pressure in the vessel. The velocity also has a local maximum at 5 pTorr which is the pressure that produces maximum plasma density. The radial E x B drift …
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1D shallow sedimentary subsurface imaging using ambient noise and active seismic data
… cover. I imaged the seismic 1D shear wave velocity (and possibly the 1D compressional wave velocity). This information is not only required for any seismic risk assessment, geotechnical engineering or microzonation activities, but also for exploration and global seismology where site …
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The Ultrasonic Characterization of Shear Thickening Suspensions
… measurement. Ultrasonic measurement of the group velocity, the frequency-dependent attenuation properties, the frequency-dependent phase velocity, and the frequency-dependent backscatter properties of the suspensions of cornstarch are reported. Initially counterintuitive results including …
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Mass transfer from non-aqueous phase liquids to the aqueous phase in groundwater systems
… a significant portion of non-aqueous phase liquids (NAPL's) is trapped by capillary forces and remains in the subsurface as immobile blobs or ganglia. Residual saturations of NAPL on the order of 5-30 percent have been observed in saturated subsurface systems. The NAPL can partition …
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Investigation of Particle Velocity and Drag with Spherical and Non-Spherical Particles Through a Backward Facing Step
… flow. The large density variation between phases creates the potential for significant differences in velocity known as velocity slip. Flow over a backward facing step provides a well characterized, turbulent, decelerating flow useful for measuring the relative velocities of the solid and …
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Comparison of edge turbulence velocity analysis techniques using Gas Puff Imaging data on Alcator C-Mod
… wavenumber-frequency spectra, from which a phase velocity is computed [1, 2]. The other is based on time-delay cross-correlation of successive images used to track the motion of discrete emission structures [3, 4]. Several Gas-Puff-Imaging experiments were conducted to obtain data taken …
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Measurement of oil-water flows in deviated pipes using thermal anemometry and optical probes
Two phase flow investigations have been undertaken for some time involving either liquid-gas or liquid-liquid flows. In spite of the growing interest in inclined (deviated) oil-water flows, only a small number of experimental data exist. This thesis describes an experimental study into deviated …
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Multistation Methods for Geotechnical Characterization using Surface Waves
… essentially related to the spatial variation of phase velocity. Analyses in the frequency-wavenumber domain and in the frequency-slowness domain are very powerful approaches, still there was a need of studying the effects of the change of scale from geophysical applications to geotechnical ones. …
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Double Negative Metamaterials in Dielectric Waveguide Configurations
… split into two separate modes, one with positive phase velocity and one with negative phase velocity but both with a causal positive group (energy) velocity. Next, the formulation is applied to the five-layer waveguide. New behaviors are observed in this case which are not seen for the three-layer …
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