Global ETD Search

21	Establishing a sea bottom model by applying a multi-sensor acoustic remote sensing approach Siemes, Kerstin 05 July 2013 (has links) Detailed information about the oceanic environment is essential for many applications in the field of marine geology, marine biology, coastal engineering, and marine operations. Especially, knowledge of the properties of the sediment body is often required. Acoustic remote sensing techniques have become highly attractive for classifying the sea bottom and for mapping the sediment properties, due to their high coverage capabilities and low costs compared to common sampling methods. In the last decades, a number of different acoustic devices and related techniques for analyzing their signals have evolved. Each sensor has its specific application due to limitations in the frequency range and resolution. In practice, often a single acoustic tool is chosen based on the current application, supported by other non-acoustic data where required. However, different acoustic remote sensing techniques can supplement each other, as shown in this thesis. Even more, a combination of complementary approaches can contribute to the proper understanding of sound propagation, which is essential when using sound for environmental classification purposes. This includes the knowledge of the relation between acoustics and sediment properties, the focus of this thesis. Providing a detailed three dimensional picture of the sea bottom sediments that allows for gaining maximum insight into this relation is aimed at.<p><p><p>Chapters 4 and 5 are adapted from published work, with permission:<p>DOI:10.1121/1.3569718 (link: http://asadl.org/jasa/resource/1/jasman/v129/i5/p2878_s1) and<p>DOI:10.1109/JOE.2010.2066711 (link: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=5618582&queryText%3Dsiemes)<p>In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of the Université libre de Bruxelles' products or services.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished Physique Ocean bottom -- Remote sensing Marine sediments -- Acoustic properties Fonds marins -- Télédétection phenomenological approach geoacoustic inversion chirp multibeam echosounder gas seismic profiling fine-grained sediments single-beam echosounder sediment samples acoustic attenuation compressional sound speed density sub-seafloor environmental characterization marine sediment acoustic remote sensing
22	Exploring the feasibility of seawater flush toilets for rural, coastal areas Conroy, Kristen M. 08 September 2022 (has links) No description available. Bioinformatics Ecology Engineering Environmental Engineering Water Resource Management Sustainability Sociology Sanitation Public Health Microbiology Environmental Science seawater toilet flushing urine diversion microbial community intermittent sand bioreactor wastewater treatment saline wastewater ammonia nitrogen diffusion of innovation UDDT ecological sanitation high salt marine sediment coastal sanitation rural sanitation on-site sanitation
23	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
24	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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