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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

Desenvolvimento de sistema de posicionamento dinâmico com aproamento automático. / Development of an automatic heading dynamic positioning system.

Miyazaki, Michel Rejani 11 April 2013 (has links)
Durante o desenvolvimento dessa dissertação foi criado um novo controlador de navios para aproamento automático de mínima energia (weathervane), de acordo com condições ambientais incidentes, mantendo o posicionamento de um ponto de controle arbitrário. O controlador proposto utiliza a metodologia ZPC (Zero Power Control), empregando o método da integral de realimentação, originalmente proposto para aplicação em sistemas de levitação magnética. Além da análise de estabilidade, também foi utilizado o simulador numérico de sistemas oceânicos TPN (Tanque de Provas Numérico), atestando o funcionamento do controlador sob a influência de diversas condições. Foram simulados casos com agentes ambientais (onda, vento e correnteza) desalinhados, ondas irregulares, posicionamento da popa no navio, dentre outros. O desempenho do controlador desenvolvido foi comparado, através de análise estática, com o desempenho de outras lógicas de controle weathervane, apresentando desempenho igual ou superior. Finalmente, um navio em escala reduzida foi submetido a testes em um tanque físico. Os resultados experimentais foram bastante satisfatórios, validando os resultados numéricos obtidos. Com isto, conclui-se que o controlador projetado atende os propósitos para o qual foi concebido com sucesso, sendo viável e possuindo diversas aplicações práticas imediatas. / A new controller was developed during this thesis, intended to automatically calculate the optimum heading (weathervane) for any given environmental condition. The vessel positioning is kept while this controller adapts the heading. The proposed controller utilizes the Zero Power Control (ZPC) methodology, generally applied to magnetic levitation systems. The chosen ZPC strategy is the integral feedback. A stability analysis was carried, in addition to simulations at the oceanic systems numerical simulator TPN (Numerical Offshore Tank), proving the controller availability under the influence of several environmental conditions. Cases with misaligned environmental agents (wind, waves and current), irregular waves, stern control, among others were simulated. In order to prove its performance, the final controller was compared with existing weathervane controllers through a static analysis, showing that it was equal or superior. Finally, a scale model ship was undergone to tests on a physical tank. The experimental results were pretty good, validating the obtained numerical results. In conclusion, the designed controller attends its design requirements successfully, being viable and having several immediate practical applications.
252

Apport de l’altimétrie satellitale pour l’étude de la variabilité de la circulation de surface dans le canal de Sicile et sur le plateau continental Tunisien / Contribution of satellite altimetry in the study of the surface circulation variability of the Sicilian Channel and over the Tunisian continental shelf

Jebri, Fatma 07 April 2017 (has links)
Ce travail de thèse présente une étude sur la circulation océanique de surface s'écoulantle long des talus continentaux (aux abords de l’isobathe 200 m) de la mer Méditerranée centrale. L'objectif étaitde mieux renseigner le schéma de circulation de surface dans la région et les régimes de variabilité associés ens’appuyant essentiellement sur les observations altimétriques conventionnelles (AVISO/X-TRACK) le longdes traces satellite, disponibles sur la période 1993-2015. Cette étude est également basée sur une utilisationcombinée des données spatiales de SST, de mesures in-situ hydrographiques et de courantométrieconjointement avec l'altimétrie. L'analyse a d'abord permis de caractériser la variabilité saisonnière et deproposer un nouveau schéma de circulation de surface, y compris pour les saisons intermédiaires, incluant unenouvelle branche de courant Atlantique sur le plateau continental Tunisien. Le second point fort de ce travailréside aussi dans la caractérisation du transport de surface et des modes de variations inter-annuelles de l'eauAtlantique à partir de l'altimétrie côtière sur le long terme. L‘observabilité de la méso-échelle océanique de lazone d‘étude est enfin abordée à partir des mesures altimétriques haute résolution (AltiKa). Cela a permis dedétecter des structures physiques à plus fine échelle et d'affiner le détection des variations des courants les pluscôtiers. Au delà des aspects scientifiques, cette thèse a également permis des avancées méthodologiquesimportantes concernant l’utilisation combinée de différents jeux de données spatiaux et in-situ, aisémentapplicables pour les pays du Sud. / This work presents a study on surface ocean circulation flowing along the continentalslopes (near the 200 m isobath) of the central Mediterranean Sea. The aim was to better inform the surfacecirculation patterns in the region and the associated variability regimes based mainly on along-trackconventional altimetry (AVISO / X-TRACK) available over the period 1993-2015. This study is also based onthe combined use of spatial SST data, in-situ hydrographic and current measurements in conjunction withaltimetry. The analysis has first allowed to characterize the seasonal variability and to propose a new surfacecirculation pattern, including the intermediate seasons, and a new branch of Atlantic current on the Tunisiancontinental shelf. The second highlight of this work is the characterization of surface transport and inter-annualvariations of Atlantic water from coastal altimetry over the long term. The observability of the oceanic mesoscaleof the study area is finally addressed from high resolution altimetry measurements (AltiKa). This hasallowed to detect physical structures on a smaller scale and to refine the detection of variations in the mostcoastal currents. Beyond the scientific aspects, this thesis has also allowed important methodological advancesregarding the combined use of different spatial and in-situ data sets, easily applicable for the countries of theSouth.
253

Origine, évolution et mise en place d'un pluton alcalin récent en contexte intraplaque océanique : exemple du complexe sud de Rallier du Baty, Kerguelen (T.A.A.F.) / Origin, evolution and emplacement of a recent plutonic body in oceanic within-plate settings : example of the south Rallier du Baty igneous complex, Kerguelen (T.A.A.F.)

Ponthus, Léandre 20 March 2018 (has links)
L'étude de ce complexe plutonique alcalin fut multidisciplinaire mêlant, observations et mesures sur le terrain, ASM, pétrographie, minéralogie, géochimie (majeur et traces), géochimie isotopique Rb/Sr et Sm/Nd et géochronologie U-Pb sur zircons. La synthèse des résultats démontre la participation minoritaire de plusieurs sources (manteau métasomatisé et fragments continental) en plus de la source prédominante qui est le manteau typique du panache de Kerguelen. Dans un environnement magmatique ouvert, les magmas contaminés ont formé la plus ancienne série magmatique calcique du complexe. La seconde et plus jeune série magmatique a produit (dans un environnement clos) des roches de plus en plus agpaïtique au cours de la différenciation. La mise en place progressive mais diachrone des intrusions s'est faite entre 11,7 (au sud) et 7,9 Ma (au nord). Enfin, le mode de construction de ce pluton en fait un exemple unique connu de laccolithe en contexte intraplaque océanique. / The study of this alkaline plutonic complex was multidisciplinary, mixing field observations and measurements, AMS, petrography, mineralogy, geochemistry (major and traces), isotopic geochemistry Rb / Sr and Sm / Nd and geochronology U-Pb on zircons. The synthesis of the results shows the minor participation of several sources (metasomatised mantle and continental fragments) in addition to the predominant source which is the typical asthenospheric mantle of the Kerguelen plume. In a dynamic and open magmatic system, the contaminated magmas formed the oldest magmatic and calcic series of the complex. The second and younger magmatic series produced (in a closed environment) more and more agpaitic rocks during differentiation. The incremental emplacement of the intrusions occurred between 11.7 (in the south) and 7.9 Ma (in the north). Finally, the type of construction of this pluton makes it a unique known example of laccolith in oceanic within-plate settings.
254

Ocean views: women's transnational modernism in fiction by Elizabeth Bowen, Hagar Olsson, and Katherine Mansfield

Jackson, Lisa Marie 01 December 2018 (has links)
This study examines the modernist fiction by three transnational women writers who turned to the ocean in their writing during the first half of the twentieth century to navigate their divided or hyphenated national identities. The Anglo-Irish writer Elizabeth Bowen (1899-1973), the Finland-Swedish author Hagar Olsson (1893-1978), and the New Zealand short story writer of English descent, Katherine Mansfield (1888-1923), use ocean space in their fiction, in the form of both sea imagery and material seascape settings, to unsettle ideologically limiting and culturally anchored categories of identity, gender, class, place and time. The modernist aesthetics and marginal ethics of these white colonial women who existed at a slant to the geographical and cultural center of the British, masculine metropolis pivot on two competing ocean views. First, the sea features in their work as a historically compliant, smooth surface in the service of the establishment, enabling and justifying imperial expansion and colonial settlement, as well as defining and patrolling the uncompromising borders of the land-based modern nation state. Alternately, the ocean comes to disrupt progressive imperial models of history, to inspire fluid and transgressive ideologies, to bear witness to violent histories submerged by official records, and to confound our sense of scale and chronological time through outsized subterranean ecologies that blur the line between land and water, and, as a consequence, throw into question larger fundamental, ontological distinctions, such as that between the ‘human’ and the ‘non-human,’ or ‘more-than-human.’ By bringing postcolonial and ecocritical perspectives to bear on Bowen, Mansfield and Olsson’s literary representations of the ocean, my study contributes to the current expanding reach of modernist studies, ushering into the critical spotlight global regions previously overlooked and misfit writers traditionally dismissed, to locate that which modernity originally defined itself against at the vibrant heart of that construction.
255

Développement et évaluation d'un modèle tridimensionnel de nuage chaud à microphysique détaillée

Leporini, Mathieu 13 May 2005 (has links) (PDF)
Les particules d'aérosols tiennent une position centrale dans la formation des nuages. La description détaillée de l'interaction entre les particules d'aérosols et les nuages réalisée dans une dynamique tridimensionnelle est essentielle. Le modèle de nuage chaud à microphysique détaillée DESCAM est modifié pour permettre son couplage à la dynamique tridimensionnelle du modèle méso-échelle de Clark. DESCAM-3D est ensuite évalué dans le cadre de deux formations nuageuses. D'abord, l'impact sur les précipitations d'une pollution est étudié lors de simulations idéalisées réalisées sur le relief des Cévennes en France. Les résultats montrent qu'une atmosphère riche en noyaux de condensation ralentit considérablement la dynamique convective et réduit la formation de la pluie. Ensuite, le modèle couplé a été évalué à l'aide des mesures de l'expérience ACE-2. Il a montré un accord satisfaisant avec les observations et a aussi mis en évidence l'impact de la pollution sur le champ nuageux.
256

Interaction of Segments along Rifts that Separate Continents and Ridges that Spread Ocean Floors

Tentler, Tatiana January 2004 (has links)
<p>The face of the Earth is constantly renewed by continental rifts that open and allow ridges to spread oceanic floor. Both types of these linear extensional structures are morphologically and structurally segmented. This thesis aims to provide insights into the interaction of such segments as they propagate and mature. It is based on the results of analogue models of evolving rifts and ridges together with field studies of populations of dilational normal faults in the active rift zone of Iceland. Linkage of initially separate segments along rifts and ridges leads to formation of through-going systems operating on a planetary scale. It is argued here that the processes of segment initiation and growth are effectively scale-independent and essentially the same in wide and narrow modes of extension and for shear and dilational failure. Three distinct types of segment coalescence are recognized; these involve tip-to-tip, one tip-to-sidewall and two tips-to-sidewalls segment linkage. The overall structural pattern, particularly the width of the extending domain and the range of displacements and orientations of smaller-scale internal extensional structures, is influenced by both the geometry of extension and the mechanical properties of the extending material. Types of segment linkage appear to be largely independent of localization of dilation or intensity of magmatic accretion. Instead they are controlled mainly by the relative distribution and orientation of interacting segments. A few orders of segmentation along global rift-ridge systems and arrays of dilational normal faults indicate that linear continuous structures accumulate extension in successive increments during which the segments change their geometries in semi-continuous interaction and coalescence.</p>
257

Interaction of Segments along Rifts that Separate Continents and Ridges that Spread Ocean Floors

Tentler, Tatiana January 2004 (has links)
The face of the Earth is constantly renewed by continental rifts that open and allow ridges to spread oceanic floor. Both types of these linear extensional structures are morphologically and structurally segmented. This thesis aims to provide insights into the interaction of such segments as they propagate and mature. It is based on the results of analogue models of evolving rifts and ridges together with field studies of populations of dilational normal faults in the active rift zone of Iceland. Linkage of initially separate segments along rifts and ridges leads to formation of through-going systems operating on a planetary scale. It is argued here that the processes of segment initiation and growth are effectively scale-independent and essentially the same in wide and narrow modes of extension and for shear and dilational failure. Three distinct types of segment coalescence are recognized; these involve tip-to-tip, one tip-to-sidewall and two tips-to-sidewalls segment linkage. The overall structural pattern, particularly the width of the extending domain and the range of displacements and orientations of smaller-scale internal extensional structures, is influenced by both the geometry of extension and the mechanical properties of the extending material. Types of segment linkage appear to be largely independent of localization of dilation or intensity of magmatic accretion. Instead they are controlled mainly by the relative distribution and orientation of interacting segments. A few orders of segmentation along global rift-ridge systems and arrays of dilational normal faults indicate that linear continuous structures accumulate extension in successive increments during which the segments change their geometries in semi-continuous interaction and coalescence.
258

Linkages between environmental conditions and recreational king mackerel catch off west-central FLorida

Wall, Carrie C 01 June 2006 (has links)
The objective of this study was to determine if fronts sustained up to three days will result in an aggregation of kingfish due to the anticipated accumulation of forage, increasing fishing success at these locations. Automated algorithms to detect frontal features in satellite-derived sea surface temperature, chlorophyll concentration, water clarity, and fluorescence images were successfully adapted for the coastal waters off west-central Florida. The surface ocean fronts were used to study the linkages between environmental conditions and recreational catch statistics of king mackerel (Scomberomorus cavalla) during 19 seasonal tournaments held in April to May and October to November of 2004 and 2005. The local winds estimated from a USF Coastal Ocean Monitoring and Prediction System observing station were analyzed with the frontal data to examine factors that influence oceanic frontal formation and stability. The front detection algorithms were also applied to high-r esolution bathymetry data which serves as a new technique for analyzing bottom topography. The spatial relationships between catch data collected through 415 angler interviews, frontal boundaries and stability, bathymetric gradients, bottom structure, and baitfish presence were identified using ESRI ArcGIS.Fishing success and fishing effort were highly variable regarding the distance of fishing activity to the nearest front. This was attributed to non-persistent winds. Intermediate water clarity (0.7 to 1.0 mW cm-2 microm-1 sr-1), the presence of baitfish, and the side of the front with relatively less chlorophyll showed the greatest influence on the king mackerel catch rates. Fishing success was found to be significantly higher at fishing locations where baitfish were reported present compared to where they were not reported. Concurrent with the 2005 harmful algal bloom event, a significant decrease in king mackerel catch occurred in the fall of 2005 (208 fish) compared to fall 20 04 (818) and spring 2005 (538). Additionally, fishing locations with baitfish present were observed about 15% less often during the fall of 2005 than the preceding seasons. From this, a model can be developed to diagnose the environmental conditions that can be used by resource managers to better understand variations in catch, which result from naturally occurring phenomena or man-induced overfishing.
259

THE EAST PACIFIC RISE CRUSTAL THICKNESS, MOHO TRANSITION ZONE CHARACTER AND OFF-AXIS MAGMA LENS MELT CONTENT FROM 9°37.5’N TO 9°57’N: RESULTS FROM THREE-DIMENSIONAL MULTICHANNEL SEISMIC DATA ANALYSIS

Aghaei, Omid 20 November 2013 (has links)
This thesis discusses the results from the first multi-source and multi-streamer three-dimensional multichannel seismic experiment conducted over a mid-ocean ridge environment. Prestack time migration was applied to the dataset resulting in the most detailed reflection images of a spreading center and its flanks to date. The key products from this work are maps of crustal velocities, crustal thickness, and Moho transition zone (MTZ) reflection character for a section of the fast-spreading East Pacific Rise (EPR) from 9°37.5’N to 9°57’N, excluding the area from 9°40’N to 9°42’N where no data were collected. Moho reflections were imaged within ~92% of the study area. The derived average crustal thickness and average crustal velocity for the investigated ~880 km2 area are 5920±320 m and 6320±290 m/s, respectively. The average crustal thickness varies little from Pacific to Cocos plate suggesting mostly uniform crustal production in the last ~180 Ka. Detailed analysis of the crustal thickness and MTZ reflection character shows that the third-order segmentation is governed by melt extraction processes within the uppermost mantle while the fourth-order ridge segmentation arises from mid- to upper-crustal processes. This analysis also suggests that both the mechanism of lower-crustal accretion and the volume of melt delivered to the crust vary along the investigated section of the EPR. More efficient mantle melt extraction is inferred at latitudes from 9°42’N to 9°51.5’N, with greater proportion of the lower crust accreted from the AML than for the rest of the study area. Larger volume of melt is delivered to the crust from 9°37.5’N to 9°40’N than to the investigated crust further north. At some locations, the Moho reflections are for the first time unambiguously imaged below the AML away from any ridge discontinuity suggesting that the Moho is formed at zero age at least at some sections of the spreading centers. The first study of the melt content of mid-crustal off-axis magma lenses (OAML), done using amplitude variation with offset technique calibrated for a magmatic plumbing system, shows that these magma bodies contain 0 to 20% melt. This suggests that OAMLs likely contribute little to the overall crustal formation.
260

Marae: a whakapapa of the Maori marae

Bennett, Adrian John Te Piki Kotuku January 2007 (has links)
A whakapapa of the marae Whakapapa, a Maori word, is often abstracted to the English language as the word genealogy. Whakapapa however has a more subtle and comprehensive meaning in Maori. In that language it has complex connotations of genealogical lines, yes, but also the history of the people involved and perhaps most importantly, the inter-relationships between those people. Degrees of consanguinity are all important when establishing relationships within Te Ao Maori - the Maori world. Marae, the basis of this thesis, is another Maori word. A marae, at its simplest, might be referred to as an agglomeration of separated, functional buildings on an area of reserved land, usually deemed to be sacral to some extent. Marae have an ancient history both in New Zealand Maori culture, but really originating at least in part, in the older cultures from which our Maori culture was eventually derived, from other, earlier settled, Pacific Islands. This thesis then is a genealogy, a sort of cultural history of marae, but is based on the idea and Maori sense of the whakapapa and so partakes of the nuances involved. It is these additional complexities that are referred to by the use of the word whakapapa in the title of this thesis. This thesis investigates the lineage of the marae, tracing it back to legendary roots, but it also examines the relationships between the components of the marae and also the place the marae has established within Maori (and other) communities. Beyond the historical forms of the marae that this thesis investigates are the other aspects that delineate what a marae really is. It is not simply a group of buildings at all, although this is a common non-Maori understanding of its disposition. A marae is a tapu or sacred space, and within or nearby that space are buildings whose form, function and meaning have only come to their present conjunction in (written) historic times. What makes the marae is the combination of the people and the ritual that is involved on a marae, the marae space and lastly, the physical buildings. The buildings, particularly carved houses, have additional meaning that they lend to the thread of the story. They themselves represent the whakapapa of the marae, and specifically of the hapu (or sub-tribe) who inhabit that marae. They do this by direct representation, but also by analogy and by spiritual means that are little dealt with in most literature. Ancestors in Te Ao Maori are deemed to exist within the very fabric of the building and have a renewed or continuing existence that is created in the first instance by a melange of ritual and belief. This thesis discusses both the usage of ritual to create such physical interjacence, utilised in modern times within whare (houses), and the continued use of regular ritual on marae for human functions. It is only together that a complete modern marae is created. With any of these elements missing the marae form is truncated or lessened and diminished in some ways. So, marae which have been recreated in preserved forms, such as those in museums, are discussed at length in this thesis, by contrast with marae in regular usage for 'traditional' purposes. In essence then, this is an investigation of the marae, but in terms, manners and ways, which have not always been fully or comprehensively dealt with before.

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