No description available.

No description available.

Thesis (Ph.D.)--University of Tulsa, 1988. / Bibliography: leaves 232-239.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 276-281). Available also in a digital version from Dissertation Abstracts.

The overall focus of this research was to achieve the first detailed understanding of temporal and geographical distributions of inorganic-nitrogen-nutrients within an oligotrophic euphotic zone. In addition to low supply of nutrients, the uptake of nutrients by phytoplankton within the euphotic zone draws the nutrient concentrations down, resulting in very low concentrations of these nutrients and results in these regions being classified as oligotrophic. The site selected for the research was the West Florida Shelf (WFS). There were two main challenges. One was that the detection limits of the standard chemistries used to determine inorganic nitrogen nutrients are not low enough to permit the evaluation of the concentration of these nutrients within an oligotrophic euphotic zone. The other challenge was the adaptation and design of highly sensitive, robust, and simple instrumentation to resolve and evaluate horizontal nutrient distributions within the euphotic zone for both ship-based and Autonomous Underwater Vehicle (AUV) based platforms in near real time. With these obstacles in mind three major goals were set. First was the development of a simple and robust chemistry that could detect nitrite and nitrate with a suitably low detection limit (approximately 10 nanomolar) and could also be coupled with a highly sensitive chemistry previously developed for ammonium with the same characteristics, and incorporate these chemistries into a single laboratory analyzer designed to monitor the surface distribution of these nutrients in the water sampled with a ships flow-through system.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 129-136.

Thesis (M. Eng.), Memorial University of Newfoundland, 1999. / Bibliography: p. 107-109.

Using autonomous underwater vehicles is a popular method of collecting samplesand conducting surveys, but the transportation of this information is not always easy.The underwater vehicle might be unable to transmit the information wirelessly, andsamples may be required to be transported a long distance. A possible solution tothese problems is a hybrid unmanned aerial vehicle, accompanying said underwatervehicle. After a submerged deployment, this vehicle could transport the informationover long distances, or conduct other operations at different locations in air or water.While quadcopters are an increasingly popular type of vehicle, conventional fixed­wingplanes are still superior when it comes to range. This thesis designs, builds and testssuch a vehicle, with the goal of a submerged deployment, performing vertical takeoff,and then transitioning to fixed­wing flight. To minimize the drone’s impact on thevehicle which it accompanies, it is nearly buoyancy neutral by flooding the hull withwater, which enters and exits the vehicle rapidly during dive and egress. To managethe pressure at the underwater vehicle’s operating depth, it utilizes a bladder ratherthan having a heavy rigid compartment. It floats as a tailsitter at the surface, usingtwo motors in a tractor configuration to pull itself out of the water. The vehicle builtproved capable of being submerged and taking off vertically, however there were nofixed­wing flights attempted. / Autonoma undervattensfordon är en populär metod för att samla in prover ochgöra undersökningar, men det är inte alltid uppenbart hur denna informationska transporteras. Undervattensfarkosten kanske inte har kapaciteten att sändainformationen trådlöst, och prover kan krävas att transporteras en lång sträcka. Enmöjlig lösning på dessa problem är en hybrid obemannad flygande farkost som följermed undervattensfordonet. Efter en undervattensstart kan detta fordon transporterainformationen över långa avstånd, alternativt genomföra andra operationer på olikaplatser. Quadcoptrar är en alltmer populär typ av fordon, men konventionella flygplanär fortfarande överlägsna när det gäller räckvidd. Denna avhandling konstruerar,bygger och testar ett sådant fordon, med målet att efter en undervattenstart, genomföravertikal start från vattenytan och sedan övergå till horisontell flygning. För attminimera drönarens inverkan på fordonet som den transporteras med har den nästanneutral flytkraft, detta sker genom att kroppen fylls med vatten, som snabbt kommerin och ut ur fordonet under dykning och vid flygning. För att hantera trycket påundervattensfordonets operationsdjup använder den en blåsa i stället för att ha enstyv behållare. Den flyter med svansen ner på ytan, och använder två motorer ien traktorkonfiguration för att dra sig ur vattnet. Fordonet som byggts visade sigkunna sänkas ned under vattnet och lyfta vertikalt, men det gjordes inga horisontellaflygningar.

Este trabalho trata da aplicação de técnicas de identificação de sistemas dinâmicos a ensaios com veículos submarinos não tripulados ou com modelos em escala auto-propelidos de veículos submarinos. Complementa-se, desta forma as investigações que vêm sendo realizadas no Laboratório de Veículos Não Tripulados, LVNT, voltadas à estimativa de parâmetros hidrodinâmicos de veículos autônomos submarinos, AUVs. Estas têm utilizado os métodos pertencentes a outras classes de abordagens para a estimativa de modelos de manobras para veículos submarinos como os métodos CFD e ASE (de BARROS, et. al., 2004, 2006, 2008a, 2008b; de BARROS e DANTAS, 2012). Outras atribuições deste trabalho dizem respeito à compreensão e desenvolvimento na modelagem linear da dinâmica de manobra de veículos submarinos, teoria e implementação de métodos de identificação de sistemas aplicados a resultados de ensaios com modelos auto-propelidos. As atividades de estudo foram divididas de acordo com os temas relativos à dinâmica de veículos submarinos, conceitos físicos envolvidos nas derivadas hidrodinâmicas de estabilidade, técnicas de identificação de sistemas e aspectos tecnológicos e experimentais da utilização de ensaios com modelos auto-propelidos. As atividades voltadas ao atendimento de tais metas envolveram, durante o programa de pesquisa, estudos de modelos analíticos, simulação numérica do movimento, realização de experimentos em piscina e campo com um AUV, e a implementação de ferramentas numéricas de análise de dados e estimação de parâmetros de manobra. / This paper is related to the application of techniques for identifying dynamic systems testing scale models of underwater vehicles or even unmanned underwater vehicles in real scale. Complementing in this way the investigations that have been conducted in the Laboratory of Unmanned Vehicles, LVNT, aimed to estimate the hydrodynamic parameters of autonomous underwater vehicles, AUVs. They have used the methods belonging to the three other classes mentioned (of Barros, et. Al., 2004, 2006, 2008a, 2008b; Barros and the DANTAS, 2012). Other tasks of this work relates to the understanding and development in modeling linear dynamic manoeuvring underwater vehicles, theory and implementation of identification methods applied to systems test results with self-propelled models. The study activities were divided according to themes related to the dynamics of underwater vehicles, physical concepts derived in the hydrodynamic stability, system identification techniques and technological aspects and experimental trials with use of self-propelled models. The activities aimed at meeting those goals involved during the research program, studies of analytical models, numerical simulation of the movement, performing experiments with a swimming pool and AUV, and implementation of numerical tools for data analysis and parameter estimation maneuver.

Plataformas semi-submersíveis, utilizadas como estruturas flutuantes na prospecção e exploração de petróleo em águas profundas, têm sua geometria composta basicamente por elementos horizontais totalmente submersos (pontoons), pelo convés, e por elementos verticais que cruzam a superfície livre (colunas), estes últimos ligando os pontoons ao convés. Tal geometria é eficaz para manter reduzidas as oscilações sob a ação de ondas, mormente o heave, bem como para prover flutuação, área de convés e estabilidade estática compatíveis com a missão. Neste trabalho aplicam-se modelos bastante simplificados para representação de características geométricas e dos atributos acima mencionados. De fato, pontoons e colunas são representados por trechos de cilindros, enquanto que as oscilações sob ondas são determinadas a partir de formulação semelhante à Equação de Morison. Tais modelos compõem um processo de otimização para determinar dimensões principais e proporções que satisfaçam certos requisitos quanto ao peso, à área de convés, à estabilidade estática e ao heave. Resultados numéricos para as oscilações sob ondas são confrontados com dados experimentais obtidos para plataformas em escala reduzida ensaiadas no canal de ondas do Laboratório de Engenharia Naval e Oceânica da EPUSP, observando-se boa aproximação. O processo de otimização é aplicado a situações descritas na literatura, chegando-se a resultados compatíveis com aqueles publicados, com a vantagem da simplicidade dos modelos analítico-numéricos aqui adotados. / Semi-submersible platforms, which are used as floating structures for oil production and exploration in deep waters, have their geometry composed basically of totally submerged horizontal elements (pontoons), the deck, and vertical elements that cross the free surface, these latter linking the pontoons to the deck. This geometry is efficient for keeping the oscillations due to wave excitation at small levels, specially the heave, as well to provide floatation, deck area and static stability compatible to the platform?s mission. In the present work, rather simplified models are applied for the representation of the geometric characteristics and of the other above mentioned attributes. In fact, pontoons and columns are represented by cylinders, and oscillations due to waves are determined by a formulation similar to Morison?s equation. These models take part in an optimization process for the determination of the main dimensions and proportions that satisfy certain requirements concerning weight, deck area, static stability and the heave. Numerical results for the oscillations due to waves are compared to experimental data obtained for scaled platforms tested in the wave channel of the Naval and Oceanic Engineering Laboratory of EPUSP, leading to reasonable approximations. The optimization process is applied to some cases described in the Literature, leading to results compatible with the published ones, but with the advantage of the simplicity of the analytic-numerical models here adopted.