A study of the dispersion of long-period Rayleigh waves was proposed in order to acquire additional knowledge about the lithospheric structure of the Vancouver Island region. Three portable, long-period seismographs were designed and built to operate in field conditions. An array was established with stations at Victoria, Vancouver and Quadra Island; during six weeks of operation, several earthquakes were recorded, of which two were aligned conveniently with the array. Another network with stations at Ucluelet, Quadra Island and Victoria was set up later; no usable data were recorded. the earthquake record was chosen for analysis, and group-velocity dispersion calculations were begun. Echo resolution on these data and a lack of ether usable records prevented the continuation of the data processing. No conclusions are drawn about the lithospheric structure; however, recommendations are made regarding possible future experimentation with the existing apparatus. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Desde su introducción, los motores de combustión interna alternativos han sido desarrollados con el fin de reducir el consumo y mejorar el rendimiento y facilidad de conducción. Con el tiempo, la contaminación se ha convertido en un factor crítico para los gobiernos y como consecuencia se han introducido regulaciones para reducir las emisiones contaminantes de los motores. Con el constante progreso tecnológico requerido por las normas contra la contaminación, la inyección directa se ha vuelto indispensable en cuanto a los motores Diesel. La introducción de combustible en la cámara de combustión permite un alto nivel de control sobre la liberación de energía del proceso de combustión. Con las novedosas estrategias de combustión empleadas, el proceso de inyección se ha convertido en el tema principal y el chorro es el factor principal. El trabajo realizado a lo largo de este estudio para analizar el proceso de mezcla aire-combustible se basa en el desarrollo de técnicas láser de diagnóstico. Inicialmente, la inyección de Diesel se ha estudiado en una atmósfera isoterma para evitar la evaporación del combustible (dodecano) a través del uso de una iluminación estructurada para medir la distribución de la mezcla mediante el control de la dispersión de Mie. La aplicación de la dispersión de Rayleigh en la parte evaporada del chorro inyectado en una cámara a alta temperatura ha permitido la obtención de la distribución de combustible en una situación equivalente a la existente en un motor real. El análisis y comparación de los distintos parámetros del chorro inyectado en condiciones de baja o alta temperatura da la posibilidad de entender mejor lo que es el proceso de mezcla en los motores Diesel. Por otra parte, según el estado del fluido inyectado, líquido o gaseoso, las condiciones experimentales tendrán diferentes efectos y la mezcla aire-combustible también tendrá un comportamiento distinto. / Manin ., JL. (2011). ANALYSIS OF MIXING PROCESSES IN LIQUID AND VAPORIZED DIESEL SPRAYS THROUGH LIF AND RAYLEIGH SCATTERING MEASUREMENTS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/10189 / Palancia

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Thesis. 1977. Sc.D.--Massachusetts Institute of Technology. Dept. of Meteorology. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Vita. / Bibliography : leaves 136-139. / Sc.D.

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In this thesis, I analyze seismic signals collected during two passive-source broadband seismic deployments that instrumented tectonic boundaries with opposing plate motion—the heavily sedimented forearc of the obliquely convergent Indo-Burman subduction zone and the Malawi rift of the divergent East African rift system—as part of the BIMA and SEGMeNT experiments. These two settings provide unprecedented opportunities to broaden the extent of our understanding of tectonic processes and linkages between atmosphere-to-solid earth seismic coupling, respectively. The Indo-Burman forearc represents an extreme endmember system for sedimentary accretion underneath Earth’s largest delta, while the Malawi rift contains one of the widest and deepest freshwater bodies and one of the first to be instrumented by a seismic array from lake bottom to lake shore. Collectively, this work represents a diverse set of seismic observations that improve our understanding of environmental and tectonic systems across a range of scales, from oblique convergence under heavy sedimentation to energy transfer between the atmosphere and the solid earth. Using the BIMA dataset, we investigate the seismic shear-velocity structure across the extensive sediment blanket, crust, and uppermost mantle of the Indo-Burman forearc margin to robustly constrain subsurface structure and lithology. We construct a comprehensive three- dimensional survey of seismic shear velocity across the region using a joint-inversion of surface- and scattered-wave constraints that explicitly parameterizes key boundary layers. We extract measurements of Rayleigh-wave phase velocities from (1) interstation Rayleigh wavefields produced from the cross-correlation and spectral waveform fitting of ambient seismic noise between 12-25 s period and (2) intra-array Rayleigh-wave phase variations form regional and teleseismic earthquakes propagating across the array between 20-80 s period, in order to constrain absolute shear velocities throughout the model. To constrain the depths to and amplitudes of significant velocity interfaces, we also develop a generalized-Radon-transform migration image across the array and incorporate the resulting scattered-wave measurements into the joint inversion. Together, these measurements complement each other’s individual limitations and allow for a comprehensive modeling analysis. Overall, the Bengal basin appears markedly slower than other heavily sedimented basins observed globally. East-west dispersion variations highlight a deepening slow structure to the east, which suggests a basin geometry primarily controlled by a down-dipping slab interface as opposed to central basin loading. Scattered-wave imaging captures three important interfaces in the velocity architecture underlying the region. Within the joint-inversion modeling, we observe two model classes that emblemize the evolution of consolidation and stress state within the uppermost sediments and metasediments along a predominantly northeast-southwest trend. We interpret variations in deeper seismic structure under two proposed scenarios: (1) a Moho at ~21-26 km underlying a package of metasediments and a thin oceanic crust, with a slow mantle lithosphere that may contain retained melt from the onset of India-Antarctica seafloor spreading; or (2) a Moho at ~50-59 km underlying a package of metasediments and a thick slug of mafic material, which may correspond to significant underplating from the Kerguelen hotspot at the time of creation of the subducting crust. These findings improve our understanding of sediment evolution and tectonic architecture across the Indo-Burman forearc margin. Using the amphibious SEGMeNT data at Lake Malawi, we explore variations in the spectral character of lake-generated microseisms to investigate the dominant parameters controlling seismic coupling between water and the solid earth. We document clear evidence for two spectral peaks in the lake microseism band, and relate variations in spectral behavior as a function of recording depth and proximity to steep lake-floor slopes and shorelines to suggest that these spectral bands may correspond to single- and double-frequency generation processes, akin to primary and secondary ocean microseisms. Some observations are otherwise complex and inconsistent with traditional microseism theory, indicating that signals may alternatively reflect interactions between differing source regions within separate basins of the lake under exclusively double-frequency generation processes, an ambiguity that might have been resolved with the availability of colocated wind and wave-state data sets. This dissertation work highlights the value of array-based seismic deployments and the incorporation of complementary data types for exploring the detailed structure and evolution of systems, especially in high-noise settings.

The intent of this thesis is to simulate the effect of a background magnetic field on Rayleigh-Taylor (RT) instability morphology and evolution in support of a Discovery Science campaign at the National Ignition Facility. The RT instability is relevant in High Energy Density (HED) systems including supernova remnants such as the Crab Nebula and inertial fusion confinement (ICF). Magnetic fields affect RT evolution and can suppress small-scale fluid motion. Thus far no experimental work has quantified the effect of a B-field on RT evolution morphology. RT evolution under a B-field was examined in three-dimensional magnetohydrodynamic (MHD) simulations using the hydrocode ARES, developed by Lawrence Livermore National Laboratory. The parameter space of the experiment is explored to determine the parameters that yield a visible effect on RT evolution. The effect of resistive MHD and conductivity is examined to further establish the desired parameter space to observe the suppression of RT morphology.

No description available.

No description available.

Thesis: M.S., Massachusetts Institute of Technology, Department of Civil Engineering, 1976 / Bibliography: leaf 139. / M.S. / M.S. Massachusetts Institute of Technology, Department of Civil Engineering