Global ETD Search

151	Characterization of the Polarization and Frequency Selective Bolometric Detector Architecture Leong, Jonathan Ryan Kyoung Ho 22 January 2009 (has links) No description available. Astrophysics Communication Electrical Engineering Electromagnetism Engineering Optics Physics cosmic microwave background radiation bolometric detectors multimode waveguide polarization sensitive frequency selective PFSB FSB CMBPOL inflation primordial gravity waves galaxy cluster beam map radiation pattern antenna pattern
152	Ondes internes de gravité en fluide stratifié: instabilités, turbulence et vorticité potentielle Koudella, Christophe 08 April 1999 (has links) (PDF) Une étude numérique de la dynamique d'ondes internes de gravité en fluide stablement stratifié est menée. On décrit un algorithme pseudo-spectral<br />parallèle permettant d'intégrer les équations de Navier-Stokes sur une machine paralèele. En deux dimensions d'espace, on analyse la dynamique d'un<br />champ d'ondes internes propagatives, d'amplitude modérée et initialement plan et monochromatique. Le champ d'ondes est instable et déferle. Le déferlement produit une turbulence de petites échelles spatiales influencées par la stratification. L'étude<br />est étendue au cas tridimensionnel, plus réaliste. En trois dimensions, on étudie le même champ d'ondes internes, que l'on perturbe par un bruit infinitésimal ondulatoire tridimensionnel, mais on considère des ondes statiquement stables et<br />instables (grandes amplitudes). On montre que le déferlement d'une onde interne est un processus intrinsèquement tridimensionnel, y compris pour les ondes de faible amplitude. La tridimensionalisation du champ d'ondes s'opère dans les zones de l'espace où le champ de densité devient statiquement instable. L'effondrement gravitationnel d'une zone est de structure transverse au plan de propagation de l'onde. Les effets de la turbulence des petites échelles sur la production de la composante non propagatrice de l'écoulement, le mode de vorticité potentielle et la production d'un écoulement moyen, permet de conclure que seule une petite proportion de l'énergie mécanique initiale est convertie sous ses deux formes, la majeure partie étant dissipée par la dissipation visqueuse et conduction thermique. On reconsidère le mode de vorticiée potentielle par une approche Hamiltonienne non-canonique du fluide parfait stratifié. La dérivation d'un système de dynamique modifiée permet d'étudier la relaxation d'un écoulement stratifié, conservant sa vorticité potentielle et sa densité, vers un état stationnaire d'énergie minimale, correspondant au mode de vorticité potentielle. stratified fluid internal gravity waves hydrodynamic instability wave breaking stratified turbulence potential vorticity non-canonical Hamiltonian dynamics modified dynamics pseudo-spectral algorithm parallel fast Fourier transform
153	Temporal Variations in the Compliance of Gas Hydrate Formations Roach, Lisa Aretha Nyala 20 March 2014 (has links) Seafloor compliance is a non-intrusive geophysical method sensitive to the shear modulus of the sediments below the seafloor. A compliance analysis requires the computation of the frequency dependent transfer function between the vertical stress, produced at the seafloor by the ultra low frequency passive source-infra-gravity waves, and the resulting displacement, related to velocity through the frequency. The displacement of the ocean floor is dependent on the elastic structure of the sediments and the compliance function is tuned to different depths, i.e., a change in the elastic parameters at a given depth is sensed by the compliance function at a particular frequency. In a gas hydrate system, the magnitude of the stiffness is a measure of the quantity of gas hydrates present. Gas hydrates contain immense stores of greenhouse gases making them relevant to climate change science, and represent an important potential alternative source of energy. Bullseye Vent is a gas hydrate system located in an area that has been intensively studied for over 2 decades and research results suggest that this system is evolving over time. A partnership with NEPTUNE Canada allowed for the investigation of this possible evolution. This thesis describes a compliance experiment configured for NEPTUNE Canada’s seafloor observatory and its failure. It also describes the use of 203 days of simultaneously logged pressure and velocity time-series data, measured by a Scripps differential pressure gauge, and a Güralp CMG-1T broadband seismometer on NEPTUNE Canada’s seismic station, respectively, to evaluate variations in sediment stiffness near Bullseye. The evaluation resulted in a (- 4.49 x10-3± 3.52 x 10-3) % change of the transfer function of 3rd October, 2010 and represents a 2.88% decrease in the stiffness of the sediments over the period. This thesis also outlines a new algorithm for calculating the static compliance of isotropic layered sediments. SEAFLOOR COMPLIANCE GAS HYDRATES BULLSEYE VENT TREND ANALYSIS SENSITIVITY ANALYSIS EIGENPARAMETER ANALYSIS HYDRATE MASS VARIATION LONG TERM TRENDS IN HYDRATE MASS MODIFIED YORK METHOD MARINE GEOPHYISCS MARINE SEDIMENT NEPTUNE CANADA SHEAR MODULUS GAS HYDRATE CONCENTRATIONS CASCADIA MARGIN MARINE GAS HYDRATES INFRA-GRAVITY WAVES SEISMOMETERS SCRIPPS DIFFERENTIAL PRESSURE GAUGE SCRIPPS DPG ODP SITE 889 BROADBAND SEISMOMETER gPhone DGP calibration Bottom Pressure Recorder Guralp CGM-1T Coherence transfer function bounds f-test bootstrapping wave propagation matrix static solution ocean bottom seismometer tsunami earthquakes Modified York least squares temporal variations linear trend in gas hydrates Power spectral densities 1D compliance solution 1D compliance algorithm seafloor compliance instrumentation Micro-g gravitimeter triple phase boundary equation ultra-low frequency seismics seafloor pressure spectrum seafloor gravity spectrum pacific ocean off-shore British Columbia seafloor observatory static compliance of layered structures geophysics gas hydrate characterization 0373
154	Temporal Variations in the Compliance of Gas Hydrate Formations Roach, Lisa Aretha Nyala 20 March 2014 (has links) Seafloor compliance is a non-intrusive geophysical method sensitive to the shear modulus of the sediments below the seafloor. A compliance analysis requires the computation of the frequency dependent transfer function between the vertical stress, produced at the seafloor by the ultra low frequency passive source-infra-gravity waves, and the resulting displacement, related to velocity through the frequency. The displacement of the ocean floor is dependent on the elastic structure of the sediments and the compliance function is tuned to different depths, i.e., a change in the elastic parameters at a given depth is sensed by the compliance function at a particular frequency. In a gas hydrate system, the magnitude of the stiffness is a measure of the quantity of gas hydrates present. Gas hydrates contain immense stores of greenhouse gases making them relevant to climate change science, and represent an important potential alternative source of energy. Bullseye Vent is a gas hydrate system located in an area that has been intensively studied for over 2 decades and research results suggest that this system is evolving over time. A partnership with NEPTUNE Canada allowed for the investigation of this possible evolution. This thesis describes a compliance experiment configured for NEPTUNE Canada’s seafloor observatory and its failure. It also describes the use of 203 days of simultaneously logged pressure and velocity time-series data, measured by a Scripps differential pressure gauge, and a Güralp CMG-1T broadband seismometer on NEPTUNE Canada’s seismic station, respectively, to evaluate variations in sediment stiffness near Bullseye. The evaluation resulted in a (- 4.49 x10-3± 3.52 x 10-3) % change of the transfer function of 3rd October, 2010 and represents a 2.88% decrease in the stiffness of the sediments over the period. This thesis also outlines a new algorithm for calculating the static compliance of isotropic layered sediments. SEAFLOOR COMPLIANCE GAS HYDRATES BULLSEYE VENT TREND ANALYSIS SENSITIVITY ANALYSIS EIGENPARAMETER ANALYSIS HYDRATE MASS VARIATION LONG TERM TRENDS IN HYDRATE MASS MODIFIED YORK METHOD MARINE GEOPHYISCS MARINE SEDIMENT NEPTUNE CANADA SHEAR MODULUS GAS HYDRATE CONCENTRATIONS CASCADIA MARGIN MARINE GAS HYDRATES INFRA-GRAVITY WAVES SEISMOMETERS SCRIPPS DIFFERENTIAL PRESSURE GAUGE SCRIPPS DPG ODP SITE 889 BROADBAND SEISMOMETER gPhone DGP calibration Bottom Pressure Recorder Guralp CGM-1T Coherence transfer function bounds f-test bootstrapping wave propagation matrix static solution ocean bottom seismometer tsunami earthquakes Modified York least squares temporal variations linear trend in gas hydrates Power spectral densities 1D compliance solution 1D compliance algorithm seafloor compliance instrumentation Micro-g gravitimeter triple phase boundary equation ultra-low frequency seismics seafloor pressure spectrum seafloor gravity spectrum pacific ocean off-shore British Columbia seafloor observatory static compliance of layered structures geophysics gas hydrate characterization 0373

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