Дисертації з теми "Zones of transition"
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1
Hofstra, Menno. "The stratigraphic record of submarine channel-lobe transition zones." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/14264/.
Анотація:
Channel-lobe transition zones (CLTZs) represent critical areas between the submarine slope and basin floor systems, where sediment gravity flows transition from confined to unconfined. In modern systems, this area is characterised by a distinctive assemblage of erosional and depositional features. However, the transfer of the CLTZ into the stratigraphic record is not well constrained. By the detailed study of various well-constrained exhumed base-of-slope systems within the Tanqua and Laingsburg depocentres of the Karoo Basin, South Africa, the sedimentary and stratigraphic record of CLTZs is investigated. The first detailed study of key depositional and erosional bedforms that characterise ancient CLTZs, including sediment waves and giant scour-fills, are presented. Their process record suggests complicated flow-bedform interactions, where both the preservation and sedimentary characteristics are dependent on the evolution of the feeder channel and the lateral position to the channel-mouth. Within the base-of-slope environments, juxtaposition of lobes and channel-fills is common. The lobes in these proximal fan environments are sandstone-prone and differ in facies and architectural characteristics to lobes downdip on the basin floor. The sand-rich nature and juxtaposition of elements in ancient CLTZs means that they are considered attractive hydrocarbon reservoir targets in the subsurface. However, fine-scale reservoir modelling and streamline simulations suggests that the relatively limited sand-volume of channel-fills in comparison to lobe deposits in these environments can have a negative impact on reservoir performance due to its effect on reservoir connectivity. Overall, the stratigraphic record of CLTZs shows high diversity in architecture, facies characteristics and volume, which can be related to three primary controls: a) spatial variability, b) flow efficiency and c) channel evolution. These three controls infer that CTLZs are highly dynamic, migrating and changing in dimensions over time; this needs to be considered when assessing how CLTZs are recorded in the rock record.
2
Schrodt, Franziska Irmela. "Multi-continental biogeochemical comparisons of tropical forest-savanna zones of transition." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545713.
3
Chen, Cheng. "Discrete element modelling of geogrid-reinforced railway ballast and track transition zones." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13399/.
Анотація:
Track deterioration has a serious influence on the safety and efficiency (speed restriction) of train operations. Many expensive, disruptive and frequent repair operations are often required to maintain the ballast characteristics due to the problem of settlement. Because of this, a geogrid solution that has proved to be a simple and economical method of reinforcing track ballast is widely used. This project presents an evaluation of the behaviour of geogrid-reinforced railway ballast. Experimental large box pull-out tests were conducted to examine the key parameters influencing the interaction between ballast and the geogrid. The experimental results demonstrated that the triaxial geogrid with triangular apertures outperforms the biaxial geogrid with square apertures and the geogrid aperture size is more influential than rib profile and junction profile. The discrete element method (DEM) has then been used to model the interaction between ballast and geogrid by simulating large box pull-out tests and comparing with experimental results. The DEM simulation results have been shown to provide good predictions of the pull-out resistance and reveal the distribution of contact forces in the geogrid-reinforced ballast system. The discrete element method has also been used to simulate cyclic loading of geogrid-reinforced ballast under confined and unconfined conditions. For the confined condition, box tests have been simulated on unreinforced samples and reinforced samples with different geogrid positions and geogrid apertures. The response of the ballast layer reinforced with geogrid under repeated loading agrees with experimental results. It was found that the optimum location of geogrid is 100 mm depth from base, and the triaxial geogrid outperforms biaxial geogrid. For the unconfined condition, cyclic loading of a trough of ballast has also been simulated, and the sample with the geogrid at 50mm from the sub-ballast layer performs best. It was also found that the used of two geogrids at both 50mm and 150mm from the sub-ballast gave a smaller settlement than using a single layer geogrid, or the unreinforced ballast. The geogrid reinforcement limits the lateral displacement in reinforced zone, which is approximately 50mm above and below the geogrid. Previous investigations have shown that the abrupt stiffness change in track support is often associated with accelerated rates of deterioration of track geometry, high maintenance demand, and poor ride quality. However, at present, there is no detailed understanding of the mechanisms of track geometry deterioration at transition zones. This work provides insight into the factors that can cause or accelerate track degradation at the transition zones, in order to identify and evaluate appropriate mitigation design. A simple track transition model with dimensions 2.1m x 0.3m x 0.45m was simulated by using PFC3D. In order to identify and evaluate appropriate mitigation methods, two kinds of transition patterns, including a single step change and a multi step-by-step change for subgrade stiffness distribution were tested. The influence of the train direction of travel and speed on the transition were also investigated. In addition, geogrid was used in the ballast layer to examine the effects of geogrid reinforcement.
4
Yamini, Fard Farzam. "Sismotectonique et structure lithosphérique de deux zones de transition dans le Zagros (Iran) : la zone de Minab et la zone de Qatar-Kazerun." Phd thesis, Grenoble 1, 2003. http://tel.archives-ouvertes.fr/tel-00707751.
Анотація:
Les failles importantes en coulissage orientées NS comme la faille du Zendan-Minab-Palami (ZMP) et la faille de Borazjan-Kazerun-Dena séparent des styles différents de déformation au sud de l'Iran. Le ZMP sépare la zone de collision du Zagros à la zone de subduction du Makran. Nous utilisons des données microsismiques et téléséismiques enregistrées par un réseau temporaire de 50 stations qui a fonctionné en novembre et décembre 1999. La microsismicité observée dans cette région montre une activité diffuse entre la faille de Zendan-Minab-Palami et la faille de Jiroft, limitée par la dépression du Jaz-Murian. La distribution de la sismicité en profondeur montre que nos données sont localisées entre 15-35 km, plus profond que dans le Zagros et avec une augmentation des profondeurs vers le NE. L'analyse des mécanismes au foyer montre des mécanismes en coulissage dextre et des mécanismes en chevauchement de pendage faible distribués en profondeur. L'inversion des résidus des séismes locaux montre une anomalie de vitesse plongeant vers le N associée aux séismes. La tomographie téléséismique confirme une variation importante de la structure au passage de la faille zone de Zendan-Minab-Palami, rapide sous le Zagros, lente à proximité du ZMP, qui affecte toute la croûte et le manteau supérieur. L'analyse des fonctions récepteurs montre une structure complexe sous la zone de faille de Zendan-Minab-Palami avec des conversions dans la croûte supérieure à 15 km . En revanche l'interface observée pour la région du Makran se situe à 35 km profondeur. Un réseau temporaire de 29 stations sismologiques a fonctionné en avril et juin 2002 dans la région de Borujen située dans le Zagros nord , au nord du système Qatar-Kazerun. La distribution de la sismicité dans cette région est diffuse et suit approximativement la direction des structures tectoniques, la faille de Dena, d'Ardal (MRF) et le HZF. En revanche le MZT (Main Zagros Thrust) n'est pas sismiquement actif. La sismicité est localisée entre 2-16 km de profondeur et montre des alignements verticaux à proximité de la faille d'Ardal et la faille de Dena. L'analyse des mécanismes au foyer montre des mécanismes en décrochement et des mécanismes en chevauchement. L'étude de la structure de la croûte en utilisant la méthode des fonctions récepteurs montre une conversion claire à 60 km de profondeur sans aucune variation importante au passage de la faille de Dena.
5
Amine, Helmieh. "Évaluation de l'exposition liée à la présence de contaminants organiques dans les zones de transition en Méditerranée." Thesis, Montpellier 1, 2012. http://www.theses.fr/2012MON13521.
Анотація:
De nombreuses familles de polluants organiques en provenance de différentes sources se retrouvent dans les milieux aquatiques continentaux et littoraux. Ces molécules, dont les lipophiles et les persistantes, sont souvent présentes à l'état de trace dans la fraction dissoute. L'utilisation de compartiments concentrateurs comme les sédiments rend alors plus accessible l'évaluation des concentrations ambiantes du milieu. L'objectif de la thèse a été d'évaluer l'exposition en zones côtières aux différentes familles de contaminants organiques « émergents » incluant les filtres UV, les alkylphénols et les alkylphénols polyéthoxylés, ainsi que « persistants-classiques » incluant les hydrocarbures aromatiques polycycliques et les polychlorobiphényles dans les sédiments et, éventuellement, dans les eaux. Un important effort de recherche a été accordé à l'étude des variations spatiales et temporelles des contaminants sélectionnés dans les sédiments, permettant ainsi l'acquisition d'un premier jeu de données nationales (libanais) représentatif pour ces familles de contaminants.Trois rivières en Méditerranée orientale et leur environnement côtier ont été pris comme cas d'étude en plus de la côte d'une petite ville et ses sites portuaires qui ont été sélectionnés afin de compléter l'étude en milieu côtier. Un premier aperçu des niveaux de ces contaminants hydrophobes dans les zones côtières recevant des apports typiques de la Méditerranée orientale est ainsi fourni. Les résultats des analyses chimiques ont clairement montré l'impact des rejets des effluents non traités dans les zones côtières via les entrées des rivières et les déversements directs le long de la côte, en absence des activités récréatives (pour les filtres UV) et de rejets industriels (pour les alkylphénols et les alkylphénols polyéthoxylés). Les zones de transition peuvent être à l'origine de la contamination de l'environnement côtier des trois rivières par ces polluants émergents en absence des apports marins. Des concentrations élevées en hydrocarbures aromatiques polycycliques et en polychlorobiphényles ont été mesurées dans les sédiments prélevés en milieu côtier. Cette contamination a persisté des années après la marée noire qui a envahi la côte Est-Méditerranéenne en 2006. Nos résultats globaux indiquent que les concentrations mesurées dans les sédiments des trois rivières étudiées et du littoral peuvent être classées parmi les niveaux les plus élevés détectés dans le pourtour du bassin méditerranéen et pouvant induire des effets toxiques chez le biota aquatique.Ce travail peut être d'une importance primordiale pour la région Est-Méditerranéenne, et plus particulièrement pour le Liban, un pays qui, malgré d'être parmi les signataires de la convention de Barcelone pour la protection de la mer Méditerranée et qui est, par la suite, impliqué dans la surveillance de la qualité de son milieu marin, souffre jusqu'à présent des rejets de différents types d'effluents non traités le long de ces côtes en absence des stations d'épurationMany organic pollutants issued from different sources are present into freshwater and coastal waters. Since these lipophilic contaminants are present at trace levels in water, accumulator compartments such as sediments can be used to assess their concentration in aquatic systems. The objective of the thesis was to assess the exposure in coastal areas to the various families of organic contaminants namely "emerging pollutants" including UV filters, alkylphenols, alkylphenol polyethoxylates, and "persistent pollutants" including polycyclic aromatic hydrocarbons and polychlorinated biphenyls in sediments and water. A major research effort has been given to the investigation spatial and temporal dynamics of the selected pollutants in sediment, allowing the acquisition of a first set of national data (Lebanese).Three rivers and their coastal environment in the eastern Mediterranean have been taken as a case study in addition to the small coastal city that was selected to complete the study in the coastal environment. A first overview of the levels of these hydrophobic contaminants in coastal areas receiving typical eastern Mediterranean inputs is thus provided. The results of chemical analyzes have clearly shown the impact of discharges of untreated effluents into coastal areas via inputs from rivers and direct discharges along the coast, without recreational activities (for UV filters) and industrial effluents discharges (for alkylphenols and alkylphenol polyethoxylates). Transition zones may act like a source of contamination of the three rivers coastal environment in the absence of marine inputs. Elevated concentrations of polycyclic aromatic hydrocarbons and polychlorinated biphenyls were measured in sediments in coastal environments. This contamination has persisted for years after the oil spill that has invaded the Mediterranean coast in 2006. Our overall results indicate that concentrations in sediments of the three studied rivers and the coastline can be classified among the highest levels detected in the Mediterranean basin and may induce toxic effects in aquatic biota.This work may be of paramount importance for the East-Mediterranean region, and particularly for Lebanon, a country which, despite being a signatory to the Barcelona Convention for the Protection of the Mediterranean Sea and is, subsequently involved in monitoring the quality of its marine environment, suffers far different types of discharges of untreated effluent along its coast in the absence of wastewater treatment plants
6
Trouwborst, Robert Elisa. "Geochemistry of manganese and iron across both stable and dynamic natural oxic-anoxic transition zones." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.64 Mb., 177 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3200548.
7
Andersson, Isabella. "Mining for the low-carbon transition : Conflicting discourses of sacrifice zones and win-win narratives." Thesis, Stockholms universitet, Statsvetenskapliga institutionen, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-194328.
Анотація:
To support the transition towards a low-carbon economy, mining companies, international financial institutions and governments are preparing to drastically scale up mineral extraction of energy transition minerals such as cobalt and lithium. Mineral extraction, however, has far-reaching impacts on the biophysical environment and mining-affected communities that may become more severe under a changing climate. In May 2019, the World Bank sought to respond to these challenges with the launch of its climate-smart mining Facility, evoking critique from non-governmental organisations working in solidarity with frontline communities. Drawing on poststructuralist political ecology and discourse analysis, this study examines the conflicting narratives on mining for the energy transition and interrogates the political solutions made conceivable through these narratives. Utilizing documents by proponents and opponents of the climate-smart mining Facility, and semi-structured interviews, the analysis reveals two contrasting discourses on mining for the energy transition, problematising climate change as a problem of rising CO2 emissions, and as a social justice problem rooted in global inequality respectively. These distinct conceptualisations generate three key and overlapping tensions, relating to (i) global versus local priorities, (ii) mitigation and adaptation, and (iii) socio-technical versus socio-political transformations. By highlighting these discursive processes, the results aid our understanding in how mining is made salient in the carbon constrained future, and which actors are likely to benefit and be harmed by the promotion of climate-smart mining.
8
Gallas, Alyssa L. "Lung tumors formed in the TGFΒRII conditional knockout mouse are the result of metastasis from the spontaneous tumor in the anorectal transition zone". University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406808954.
9
Schmidt, Martin [Verfasser], Gunnar [Akademischer Betreuer] Lischeid, Claas [Akademischer Betreuer] Nendel, Gunnar [Gutachter] Lischeid, Claas [Gutachter] Nendel, and Christoph [Gutachter] Thomas. "Fragmentation of landscapes: modelling ecosystem services of transition zones / Martin Schmidt ; Gutachter: Gunnar Lischeid, Claas Nendel, Christoph Thomas ; Gunnar Lischeid, Claas Nendel." Potsdam : Universität Potsdam, 2019. http://d-nb.info/1218405554/34.
10
Schmidt, Martin [Verfasser], Gunnar [Akademischer Betreuer] Lischeid, Claas [Akademischer Betreuer] Nendel, Gunnar Gutachter] Lischeid, Claas [Gutachter] Nendel, and Christoph [Gutachter] [Thomas. "Fragmentation of landscapes: modelling ecosystem services of transition zones / Martin Schmidt ; Gutachter: Gunnar Lischeid, Claas Nendel, Christoph Thomas ; Gunnar Lischeid, Claas Nendel." Potsdam : Universität Potsdam, 2019. http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-442942.
11
Tan, Siwei [Verfasser]. "Wastewater Management in Industrial Zones of the Vietnamese Mekong Delta : A Socio-spatial Analysis of Environmental Management in a Transition Economy / Siwei Tan." Bonn : Universitäts- und Landesbibliothek Bonn, 2015. http://d-nb.info/1077289901/34.
12
Cuppi, Federico. "Analisi dell’efficacia degli interventi di adeguamento e potenziamento della S.P. 3 “DEL RABBI” nel comune di San Lorenzo in Noceto." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Анотація:
In seguito alle esigenze di sviluppo ed espansione delle comunità urbane, negli ultimi decenni sono stati rivisti gli standard in merito alla sicurezza delle infrastrutture stradali. In quest’ottica è estremamente importante tener conto di due aspetti fondamentali che la caratterizzano, quali il comportamento degli utenti alla guida e il ruolo che riveste l’ambiente esterno nel condizionamento degli stessi.
Il problema, in termini di sicurezza stradale, nasce quando si è in presenza di un passaggio tra aree extraurbane e urbane, nel quale gli utenti hanno una scarsa percezione della transizione.
Nasce quindi la necessità di effettuare degli interventi atti ad evidenziare ai conducenti la transizione tra le due zone, facendo in modo che gli stessi possano adattare il loro stile di guida, rendendolo conforme a dei livelli di sicurezza stradale ottimali.
Per raggiungere questi obiettivi, le analisi di sicurezza di un tracciato stradale giocano un ruolo fondamentale, poiché consentono di individuare la presenza di situazioni di rischio per la circolazione, rendendo possibile loro eliminazione o attenuazione prima che si trasformino in siti ad elevata incidentalità.
L’obiettivo di questa tesi è analizzare l’efficacia degli interventi di miglioramento e messa in sicurezza di un’infrastruttura viaria esistente, integrando quanto richiesto dalle "Linee guida per la gestione della sicurezza delle infrastrutture stradali" con metodologie innovative, quali il Mobile Eye ed il V-Box, che rendono possibile una valutazione del comportamento degli utenti durante la guida, in funzione di ciò che cattura la loro attenzione. Questo elaborato descrive lo studio, nato da una convenzione di ricerca tra il DICAM dell’Università di Bologna (Dipartimento di Strade) e la Provincia di Forlì-Cesena, riguardante l’analisi della sicurezza e delle problematiche del tronco stradale della S.P. 3 “DEL RABBI” nel comune di San Lorenzo in Noceto.
13
Lavallez, Catherine. "Territorialisation des politiques énergétiques dans l agglomération franco-valdo-genevoise : la planification énergétique comme opportunité de réaménagement des zones frontières ?" Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAE006/document.
Анотація:
En France comme en Suisse, les collectivités territoriales s'imposent comme des acteurs majeurs de la transition énergétique, une transition dont la mise en œuvre nécessite un important renouvellement des instruments d'intervention publics. Ce sont les enjeux et les conditions d'un tel renouvellement que le présent travail se donne pour objectif d'examiner, à partir des expériences de planification énergétique territoriale menées sur l'agglomération franco-valdo-genevoise. Conçues comme des démarches de relocalisation des filières énergétiques – filières dont nombre de composantes étaient, avec les énergies fossiles, externes aux territoires consommateurs –, ces démarches de planification énergétique sont ici examinées à partir d'une grille de lecture d'inspiration institutionnaliste et pragmatiste.Consistant à appréhender ces démarches comme autant d'enquêtes ayant vocation, à travers un travail collectif de (ré)équipement cognitif du champ d'intervention territorial FVG, à initier et accompagner la reconstruction des modes de coordination des hommes au sujet de leur territoire – territoire entendu dans sa triple dimension matérielle, organisationnelle et politique – , cette grille ouvre vers une double lecture des expériences de planification énergétique. La première se concentre sur la dimension organisationnelle de ces enquêtes en devenir, c'est-à-dire sur les cultures d'action en présence et les modalités d'interaction entre elles, tandis que la seconde porte sur la substance cognitive qui sert de support à ces interactions, c'est-à-dire sur les logiques de réflexion qui président à la mobilisation et à la production des représentations territoriales liées à ces démarches.Cette double lecture permet de tirer des enseignements à différents niveaux. Le premier concerne le champ (cognitif) d'intervention territorial que ces démarches de planification énergétique contribuent à dessiner. Un champ qui, bien que de mieux en mieux appréhendé dans ses dimensions techniques, reste à la fois limité et « déformé » de telle sorte qu'il valorise davantage les filières fossiles, dont on souhaiterait s'affranchir, que les filières renouvelables que l'on souhaiterait leur substituer. Le second niveau d'enseignement porte sur les processus de production de connaissances territoriales (PPCT) qui président à la délimitation et à « l'équipement » de ce champ d'intervention. Appréhendés à travers les normes institutionnelles qui les encadrent, et les cultures d'action dont les interactions peuvent initier des processus de déstabilisation-reconstruction de ces normes, ces PPCT s'avèrent donner naissance à des « zones-frontières » sociocognitives, zones favorables à de telles reconfigurations, mais nécessitant, dans le cas FVG, un travail préalable « d'aménagement ».C'est sur les facteurs les plus déterminants pour la qualité de cet « aménagement » – un aménagement qui n'est plus seulement cognitif mais qui renvoie, plus globalement, aux conditions de mise en œuvre d'enquêtes dont la finalité ultime demeure bien l'action collective territoriale – que se concentre la troisième catégorie d'enseignements. Ouvrant sur les défis comme sur les pistes de renouvellement ouvertes, au niveau des modes d'action publics, par ces démarches de planification énergétique, ces éléments permettent aussi de porter un nouveau regard sur le projet d'agglomération en construction sur ce territoire transfrontalierIn France as in Switzerland, local authorities stand out as leading players of energy transition, a transition that requires an important renewal of public intervention instruments. It is the stakes and the conditions of such a renewal that the present work aims to examine, based on the experiments of territorial energy planning led on the franco-valdo-genevan cross-border territory. Conceived as initiatives of relocation of the energy supply system, these energy planning initiatives are examined through an institutionalist and pragmatic « reading template ».This « reading template » consists of seeing these energy planning initiatives as pragmatist inquiries aiming, through a collective work of cognitive equipment of the territorial franco-valdo-genevan field of intervention, at the reconstruction of the means of coordination between people about their material, organizational and political territory. It opens towards a double reading of the energy planning initiatives. The first one concentrates on the organizational dimension of these inquiries - i.e. on the cultures of action which they gather and the modalities of interaction between them - whereas the second focuses on the cognitive substance which represents the medium of the interactions.This double reading provides insights at various levels. The first one concerns the (cognitive) territorial field of intervention that these energy-planning experiments contribute to draw. A field which, although better and better characterized in its technical dimensions, remains at the same time limited and " deformed " so that it values more the fossil energy systems, from which we want to release ourselves, than the renewable ones, which we would like to replace them with.The second level of teaching concerns the processes of production of territorial knowledge (PPTK) which presides over the demarcation and « equipment » of the territorial field of intervention. Examined through the institutional norms and the culture of action at stake in them, this PPTK turns out to create a sociocognitive "cross-border" area, the kind of area that could shelter the desired reconfigurations…on the condition that they are beforehand correctly “equipped”, in cognitive and also in organizational terms.The determining factor for the quality of this equipment is concentrated in the third category of teaching. Starting with the opportunities created by these energy planning experiments concerning the renewal of public intervention instruments, these elements also allow us to take a new look at the urban area project under construction in this cross-border territory, a project that shows itself closely linked to the energy experiments through a common challenge of territorialisation
14
Saji, Niffy. "Development of a Guide to Lake and Reservoir Zone Determination." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/31587.
Анотація:
Reservoirs are generally created by damming rivers. The upper reaches of any reservoir is generally narrow and winding like the parent river. This is the riverine zone of the reservoir. The reservoir is deepest and widest near the dam. Here, lake-like conditions exist and the water is quiescent. This is the lacustrine zone. The transitional zone separates the lacustrine and riverine zone. It has intermediate characteristics.
There are many characteristics, both physical and chemical, that differentiate between these three zones. Based on the differences in characteristics between the three zones, a method has been developed to successfully divide any reservoir into three zones. The method developed was applied to Lake Manassas and the Occoquan Reservoir located in the Occoquan watershed in Virginia. Both are man-made impoundments.
Analysis of data, based on the method developed, was successfully in dividing both reservoirs into the three zones. This method may therefore be successfully applied to obtain zonation in reservoirs.
Master of Science
15
Seclaman, Alexandra Catalina. "Chemical and physical behaviour of the trace elements in the silicate melts of the Earth's mantle." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEN004/document.
Анотація:
Nous avons étudié des magmas ferrifères silicatés magnésiens à la pression du manteau terrestre en utilisant la dynamique moléculaire (First Principles Molecular Dynamics). Les résultats de l’équation d’état que nous avons obtenus à partir de nos simulations ont été utilisés pour créer un modèle chimique et minéralogique pour les zones de très basse vitesse sismique (ULVZ, anomalies régionales dans le manteau proche de la limite noyau-manteau). De plus, nous avons étudié le comportement du Ni, du Co et du Fe dans ces magmas et établi la dépendance du spin en fonction de la concentration, de la pression, de la température et du degré de polymérisation du magma silicaté. Nous avons montré qu’une baisse du spin moyen peut être corrélée au changement de pente (kink) observé précédemment pour les coefficients de partage du Ni et du Co. Nous avons analysé la structure du magma pour toutes les compositions étudiées en fonction de la pression. Nos résultats donnent un nouvel aperçu de la coordination des éléments majeurs et traces dans les magmas silicatés de différents degrés de polymérisation. Nous interprétons l’anomalie de coordination Ni-O en fonction de la pression comme un changement d’état de spin. L’effet de la polymérisation du magma silicaté sur les coefficients de partage du Co, du Ni et du W entre le métal et le magma silicaté a été étudié par expériences multi-enclumes en conditions isobares et isothermes. Nous avons réalisé des simulations FPMD de magmas à des degrés de polymérisation similaires aux expériences afin d’expliquer le caractère de plus en plus lithophile du W lorsque le degré de polymérisation du magma silicaté diminue. Nous proposons une explication structurale pour expliquer l’affinité décroissante apparente du W dans les magmas silicatés dépolymérisésWe explore Fe-bearing Mg-silicate melts through the pressure regime of the Earth’s mantle using First Principles Molecular Dynamics (FPMD). The equation of state results we obtained from our simulations are used to create a chemical and mineralogical model for Ultra-Low Velocity Zones (anomalous region on the mantle side of the core-mantle boundary). Furthermore we study the behaviour of Ni, Co, and Fe in these melts, and asses their spin-crossover dependencies on their concentration, pressure, temperature, and the degree of polymerization of the silicate melts. We show that a decrease in the average spin can be correlated with the previously observed kink in the partitioning coefficient of Ni and Co. We investigate the melt structure of all the compositions studied as a function of pressure. Our results provide new insight into the coordination of major and trace elements in silicate melts with different degrees of polymerization. We interpret the anomalous Ni-O coordination trend with pressure as the result of the spin state change. The effect of silicate melt polymerization on the partitioning of Co, Ni, and W between a metal and silicate melt, is investigated at isobaric and isothermic conditions using multi-anvil experiments. We have performed FPMD simulations of melts with similar degrees of polymerization as the experiments in order to explain the increasing lithophile character of W with the decrease in polymerization of the silicate melt. We propose a structural explanation for tungsten’s apparent increased affinity for depolymerized silicate melts
16
Nugroho, Hendro. "GPS Velocity Field In The Transition From Subduction To Collision Of The Eastern Sunda And Banda Arcs, Indonesia." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd885.pdf.
17
Kouame, Brou. "Adéquation de différents modèles globaux pluie-débit pour déterminer les apports en eau dans les zones de transition et de forêt de la Côte - d'Ivoire : essai de régionalisation des paramètres." Montpellier 2, 1992. http://www.theses.fr/1992MON20249.
Анотація:
Dans un but d'evaluation des ressources en eau dans les zones de transition et de foret de la cote d'ivoire, plusieurs modeles globaux pluie-debit sont testes. Ces modeles au pas de temps annuel, mensuel et journalier sont cales sur un ensemble de 90 stations-annees en foret et 54 en zone de transition, reparties en 27 bassins versants de 100 a 7000 km#2. L'analyse des differents calages fait ressortir une adequation satisfaisante du modele au pas de temps mensuel dans la restitution des hydrogrammes. Les modeles au pas de temps journalier ont conduit a des resultats de qualite diverse du fait, d'une part de problemes lies a la qualite des donnees journalieres, issues des reseaux de mesure et souvent entachees d'erreurs, et, d'autre part, des algorithmes eux-memes qui prennent insuffisamment en compte les differences de saturation du sol en saison seche et en saison des pluies. Ce travail permet neanmoins d'offrir un panel complet de methodes d'evaluation des ressources en eau, valide sur l'ensemble du territoire ivoirien
18
Rashid, Shahbaz. "Parametric study of bridge response to high speed trains, ballasted track on concrete bridges." Thesis, KTH, Bro- och stålbyggnad, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-99385.
Анотація:
When a train enters a bridge, passenger sitting inside will feel a sudden bump in the track, which not only affect the riding comfort of the passengers but also put a dynamic impact on the bridge structure. Due to this impact force, we have very serious maintenance problems in the track close to the bridge structure. This sudden bump is produced when train travelling on the track suddenly hit by a very stiff medium like bridge structure. In order to reduce this effect, transition zones are introduced before the bridge so that the change in stiffness will occur gradually without producing any bump. This master thesis examine the effect of track stiffness on the bridge dynamic response under different train speeds from 150 to 350 km/h with interval 5 km/h and also estimate the minimum length of transition zones require to reduce the effect of change in stiffness on the bridge. Study also gives us some guidelines about the choice of loading model of the train, location of maximum vertical acceleration, effect of ballast model on the results and minimum length of transition zone needs to include in the bridge-track FE-model, for dynamic analysis of the concrete bridges. To carry out this research MATLAB is used to produce an input file for the ABAQUS FEM program. ABAQUS will first read this file, model the bridge and then analysis the bridge. MATLAB will again read the result file, process the result data and plot the necessary graphs. The Swedish X2000 train is used for this study, which has been modeled with two different methods: moving load model and sprung mass model, in order to see the difference in results. For verification of the MATLAB-ABAQUS model, a 42m long bridge is analysed and results are compared with known results. In this study, concrete simply supported bridges with spans of 5, 10, 15, 20, 25 m have been analysed.
19
Guerrisi, Burger Catherine. "Intéractions électrolytes 1:1 surfactants non-ioniques polyoxyéthyles et influence sur les zones d'existence de phases microémulsions fluoro-carbonées : Étude de quelques transitions structurales dans ces phases." Nancy 1, 1987. http://www.theses.fr/1987NAN10081.
Анотація:
Étude des transitions structurales dans les microémulsions inverses du type eau/C::(6)F::(13) CH::(2)(EO)::(4)/perfluorodécaline et eau/C::(6)F::(13) CH::(2)(EO)::(5)/C::(8)F::(17) CH=CH::(2), par spectrométrie RMN, par conductimétrie et par la technique du saut de température
20
Arlaud, Elodie. "Modèles dynamiques réduits de milieux périodiques par morceaux : application aux voies ferroviaires." Thesis, Paris, ENSAM, 2016. http://www.theses.fr/2016ENAM0047/document.
Анотація:
Dimensionnée de manière semi-empirique, la voie ferrée est un système mécanique dont le comportement dynamique reste difficile à appréhender et à quantifier. Un outil numérique peut alors être à la fois une aide à la conception, en évaluant la performance de nouvelles structures, et un élément de diagnostic sur les voies existantes, en complément de mesures terrain adaptées.L'outil développé dans ce travail s'appuie sur les techniques de résolution des équations de propagation dans les guides d'ondes dans le domaine des fréquences/nombres d'onde. Sa particularité est l'introduction d'un modèle réduit basé sur une sous-structuration périodique de la structure, en ne conservant, pour la résolution des équations de dispersion, que quelques nombres d'onde judicieusement choisis. En s'appuyant sur cette technique de réduction de modèle et son extension à des modèles temporels avec contact mobile, les coûts de calcul et de stockage sont largement diminués. Cela en fait un outil performant et utilisable dans des études d'ingénierie portant sur la voie ferrée.Des étapes de vérifications numériques sur les hypothèses sous-jacentes à la réduction ont été réalisées en construisant un modèle fréquentiel complet par transformée de Floquet. En parallèle, des campagnes d'essais dynamiques (mesures de réceptance et d'accélération sur traverse au passage des trains) ont été réalisées sur une zone de transition entre voie ballastée et voie sur dalle sur ligne à grande vitesse. Les résultats obtenus expérimentalement permettent de valider les simulations dans les domaines temporel et fréquentiel sur les différentes zones de la transition. Le modèle permet de mieux comprendre l'effet de la sous-structure sur le comportement dynamique. Une des grandes avancées de ce travail est également l'introduction d'une stratégie permettant d'utiliser la méthode de réduction pour coupler des zones présentant des tranches différentes. Des outils de post-traitement ont été développés pour mettre en lumière les effets dynamiques générés par la transitionRailway tracks have evolved over years based on empirical results and their dynamic behavior still can be difficult to assess or to quantify. A numerical model can thus provide assistance in track design by assessing the mechanical performance of new structures, or allowing the diagnostic of existing track parts, as a complement to relevant in-situ measurements.The numerical model developed in this work combines a reduction strategy with numerical techniques used to solve the propagation equations in waveguides in the frequency / wave number domains. The peculiarity of the exposed methodology is the introduction of a model based on a periodic sub structuring of the track, keeping only a few wavelengths carefully chosen to solve dispersion equations. Based on this model reduction technique and its extension to time domain models with moving contact, the computational time and storage capacity required are greatly reduced. Thus, this model is efficient and useful for engineering purposes in railway tracks studies.Numerical validation of the reduction is carried out by building a complete reference model in the frequency domain. In parallel, measurement campaigns (receptance measurement and sleeper acceleration under passing trains) were performed on a transition zone between ballasted and slab tracks on a High Speed Line. These tests are compared to simulation results in both time and frequency domains on different areas of the transition. After successful validation, the model is used to improve understanding of the role of the substructure on the dynamic behavior.The final major development of this work is the introduction of a strategy to extend the reduction to piecewise periodic structures and the development of post-processing tools to highlight the dynamic effects generated by the transition zone
21
Marquart, Nicolas. "Recherche de discriminants polarimétriques dans la diffraction par des objets situés à proximité de l'interface plan entre deux milieux diélectriques à pertes." Phd thesis, Université Rennes 1, 2006. http://tel.archives-ouvertes.fr/tel-00012029.
Анотація:
Le comportement polarimétrique d'un champ électromagnétique diffracté par un cible localisée à l'interface air-sol est analysée pour une onde incidente variant de l'incidence normale à l'incidence rasante.Le champ rétrodiffusé dans le cas monostatique est analysé au moyen de la théorie géométrique de la diffraction (G.T.D) ou la méthode étalon. Dans cette thèse, un modèle de rayon précis a été implémenté. Une attention toute particulière a été portée aux zones de transition, où proches de telles frontières d'ombre, les rayons réfléchis disparaissent et se transforment en rayons rampants sur la cible et sont fortement atténués dans la zone d'ombre. Les études ont montré que les éléments de la matrice de Sinclair [S] et les états de polarisation caractéristiques associés présentent une variation rapide sur la sphère de Poincaré. Les localisations significatives sur la sphère de Poincaré peuvent être exploitées afin d'extraire l'information sur les paramètres géométriques ou les propriétés géophysiques de l'environnement.
22
Calvez, Philippe. "Modélisation d'agencements énergétiques durables dans les zones urbaines intelligentes : une approche pour la réduction de l’emprise énergétique par les pratiques soutenables." Thesis, Paris 1, 2015. http://www.theses.fr/2015PA010056.
Анотація:
D’un côté, la transition écologique et les enjeux de développement durable sont de nos jours une réalité que l’on ne peut ignorer compte tenu des impacts négatifs des activités humaines sur leurs environnements. De l’autre côté, une numérisation toujours plus importante de ces environnements entraîne la génération de volumes massifs de traces numériques, qui sont autant d’indices sur le monde dans lequel vivent les acteurs de ces activités. Une difficulté non négligeable existe pour comprendre les tenants et aboutissants faisant que d’une activité à une autre, l’impact sur l’environnement mesuré dans ces travaux de recherche à travers le concept d’Emprise Énergétique (EmE) n’est pas le même. Notre approche considère l’identification sur la base de ces traces numériques, d’activité d’entités humaines et non humaines. L’instanciation de ces dernières au sein de pratiques mobilise des ressources (physiques et virtuelles) en plus ou moins grand nombre. Leurs modélisations permettraient de mieux appréhender les enjeux liés à la transition écologique. Identifier sur la base d’indicateurs quantifiables les pratiques ayant un impact réduit sur l’environnement serait une piste permettant de contribuer à cette transition. Ces pratiques, au sens de coordination de multiples entités hétérogènes dans le temps et l’espace, peuvent être formalisées sous forme de structures d’activités multidimensionnelles à l’aide de la théorie de l’Agencement et d’un ensemble d’outils mathématiques (Complexes Simpliciaux, Hypernetworks). Ces travaux de recherche tentent de modéliser le phénomène d’activité humaine et non humaine en s’appuyant sur la caractérisation du contexte de celles-ci à partir de données massives. Ces agencements sont calculés et représentés dans une application (IMhoTEP) ayant pour but de construire ces structures complexes non pas sur des catégorisations faites a priori des entités, mais en se focalisant sur les relations que celles-ci entretiennent dans plusieurs dimensions. L’objectif final est de proposer un outil d’accompagnement à la transition écologique à destination des acteurs participant à des activités induisant la consommation, voire la production de ressources. Ces travaux de recherche en informatique s’appuient sur la numérisation continue des espaces et particulièrement les espaces urbains (Smart City, Internet of Everything)On one hand, the ecological transition and sustainable development issues are today a reality that cannot be ignored given the negative impacts of human activities on their environments. On the other side, an increasingly important digitization of these environments results in the generation of massive volumes of digital traces, which are all signs of actors’ activities. A significant challenge is to understand the ins and outs of environmental impact due activities and considering Emprise of Energy (EmE) as a key indicator and how this indicator can strongly change from an activity to another. Our approach considers the identification of Practice on the basis of these digital traces generated by human and non-human entities during specific activities. Practice (instantiation of activity) uses more or less resources (physical and virtual) during their existence. Be able to identify which one is more resources dependent would help to better understand how to promote ecological transition. Promoting or at least identifying on the basis of quantifiable indicators (i.e Energy Emprise), practices that have a low impact on the environment, could be an innovative approach. These practices, in the sense of coordination of multiple heterogeneous entities in time and space, can be formalized in the form of multidimensional structures activities - Hypergraph of Activities – using the theory of Assemblage (Agencement in french) and using a set of mathematical tool (Simplicial Complexes, Hypernetworks). This research attempts to model the phenomenon of human and not human activity based on the characterization of the context (massive contextual data). These Assemblages are calculated and represented in an research application (IMhoTEP) which aims to build these complex structures not based on a priori entities’ classification, but by focusing on the relationships that they maintain in several dimensions. The main goal is to offer a decision tool which support actors’ ecological transition by understand activities inducing consumption or production of resources. These academic research in the field of computer science is based continuous digitization of physical and virtual spaces, particularly highly connected urban areas (Smart City, Internet of Everything)
23
Aycard, Mylène. "Géochimie des sédiments du bassin de Cariaco (Venezuela) dans le contexte de la dernière transition glaciaire-interglaciaire : processus de sédimentation et préservation de la matière organique." Lille 1, 2004. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2004/50376-2004-Aycard.pdf.
Анотація:
Parce qu'il est directement sous influence de la zone de convergence intertropicale, avec alternance de deux saisons très marquées, un upwelling se développe, pendant 1'hiver boréal, dans les eaux de surface du bassin de Cariaco (Venezuela). La stagnation des eaux de fond associée à une forte production primaire, pendant le fonctionnement optimal de l'upwelling, est à l'origine d'un processus d'eutrophisation conduisant à un dégagement d'H2S dans la colonne d'eau, sensible à partir de 300 m de profondeur. Cette dynamique s'est mise en place au moment de la remontée du niveau marin à la fin du Dernier Maximum Glaciaire et s'est aggravée au début du Younger Dryas, il y a 12600 ans cal. BP avec le développement des conditions anoxiques dans la tranche d'eau. Le bassin de Cariaco est donc actuellement caractérisé par une forte accumulation de matière organique dans ses sédiments. L'objectif était de (1) d'analyser les sédiments dans le but de comprendre l'impact des variations climatiques sur les facteurs qui contrôlent le stockage de la matière organique dans le bassin de Cariaco. Et (2) de caractériser les processus de préservation de la matière organique suivant une approche pluridisciplinaire alliant des observations microscopiques à une étude géochimique détaillée (spectroscopique et pyrolytique). Les échantillons étudiés proviennent de la carotte ODP 165 1O02C 1H prélevés au cours du Leg 165. La première partie de cette thèse est consacrée à une analyse géochimique globale des sédiments dans le but de comprendre les facteurs (océanologiques, climatiques et biogéochimiques) qui contrôlent le stockage de la matière organique dans les sédiments du bassin de Cariaco. Les résultats obtenus nous ont permis de faire une reconstitution paléoclimatique à haute résolution des 16 derniers milliers d'années à partir de l'enregistrement de la teneur et du taux d'accumulation du Corg dans le sédimentLe résultat majeur obtenu est que dans le site exceptionnel du bassin de Cariaco la matière organique se révèle être un marqueur paléoclimatique d'aussi grande qualité que les isotopes stables de l'oxygène. Une étude géochimique détaillée de la matière organique de cinq échantillons révèle l'origine essentiellement phytoplanctonique de la matière organique, ainsi qu'une faible contribution d'origine bactérienne, alors que la matière organique dérivée de végétaux supérieurs est négligeable. Un examen détaillé de la matière organique, par une étude spectroscopique, puis pyrolytique, a permis de montrer que le proto-kérogène, ou matière organique insoluble non hydrolysable, est essentiellement constitué de géomacromolécules, ou mélanoi͏̈dines, formée par une réaction de condensation de matériel dérivé de protéines et de polysaccharides dégradés associées à des lipides fonctionnalisés. Des thermochemolyses TMAH ont également permis de montrer que des protéines avaient été préservées par encapsulation dans la fraction de la matière organique la plus réfractaire. Enfin, le processus de sulfuration naturelle est d'ampleur très modérée, et ce malgré des conditions de sédimentation a priori favorables, i. E. Présence d'une anoxie de la colonne d'eau et intense sulfato-réduction
Cependant, la proportion de composés organo-soufrés tend à augmenter avec le temps. Ainsi, il apparaît que le processus de sulfuration naturelle se produit sur un intervalle de temps long, à l'inverse de la dégradation-recondensation qui paraît finie même pour l'échantillon le plus récent (ca. 800 ans). Une étude détaillée des composés organo-soufrés a permis d'approcher la cinétique de ces processus, et révèle que les polysaccharides incorporent le soufre plus rapidement que les lipides. En effet, la matière organique sulfurée identifiée dans l'échantillon le plus récent est essentiellement dérivée de carbohydrates. En revanche, la proportion de lipides sulfurés dans les proto-kérogènes tend à augmenter dans les échantillons les plus anciens traduisant une meilleure résistance des lipides à la reminéralisation par rapport aux carbohydrates. La combinaison d'une étude géochimique globale des sédiments bruts, couplée à l'étude géochimique moléculaire approfondie de la matière organique permet de proposer un modèle de dépôt de la matière organique dans un cadre climatique parfaitement contraint
24
Sadoudi, Yannis. "Simulation numérique de l'interaction soufflante/nacelle en présence de vent de travers." Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0005/document.
Анотація:
La conception des nacelles doit répondre à des contraintes géométriques d’encombrement mais aussi à des spécifications motoristes qui précisent les niveaux de performance exigés. Au sol, l’une des principales contraintes imposées par le motoriste concerne le niveau de distorsion de pression totale dans le plan fan quand la nacelle est soumise à un vent de travers. Dans le cas le plus limitant, c’est-à-dire lorsque la direction du vent est perpendiculaire à l’axe de la nacelle, il se produit un décollement au niveau de l’entrée d’air côté vent. L’hétérogénéité de l’écoulement crée des efforts instationnaires sur les aubes du fan. Ces efforts peuvent amener à un régime de pompage endommageant ainsi le moteur. De plus, la tendance actuelle est de réaliser des nacelles courtes, réduisant la distance qu’à l’écoulement pour s’homogénéiser avant d’impacter le fan, conduisant à un couplage entre le décollement et le fan. Le but de cette étude est de simuler numériquement l’écoulement intervenant dans une nacelle courte soumise à un vent de travers et d’étudier l’impact de la présence du fan. Tout d’abord, la définition de la distorsion est basée sur les grandeurs totales. Ainsi, la compréhension du comportement des grandeurs totales au voisinage d’une paroi et l’influence des paramètres numériques sur leur évolution est nécessaire. Une approche analytique et numérique sur plaque plane a permis d’évaluer le comportement des grandeurs totales à la frontière externe de la couche limite et l’influence des paramètres numériques RANS sur leur évolution. Cette étude a permis de choisir les paramètres numériques utilisés pour la simulation de la nacelle. Pour faire ressortir l’influence du fan sur la distorsion, deux types de simulations ont été menés : une simulation de nacelle isolée et une simulation de l’ensemble complet nacelle/fan respectivement comparées à un essai en soufflerie sur une maquette de nacelle isolée et à un essai de moteur complet à échelle 1 :1 réalisé en « soufflerie » à veine ouverte. La description correcte de la distorsion nécessite de prendre en compte les phénomènes de transition. Une méthode innovante de prise en compte de la transition par équations de transport est utilisée. Comme le coût de calcul de l’ensemble complet est prohibitif, la question du découplage du calcul en injectant une distorsion, issue d’une simulation de nacelle isolée, dans un calcul de fan isolé est discutée. La distorsion par vent de travers intervient lorsque l’avion est au sol. Par conséquent, l’impact de la présence du sol est étudié dans le cas de la nacelle isolée. Enfin, le critère de distorsion utilisé présente plusieurs défauts importants et peut être remis en cause. Une nouvelle méthode de mesure et de calcul estétudiéeInlet design must fulfill geometrical constraints and engine requirements. One of these requirementsis the homogeneity of the flow impacting the fan which is quantified by the distortionlevels of stagnation pressure. When the airplane is on the ground and ready to take-off, crosswindconditions are critical for the distorsion level. The most critical case is when the wind directionis normal to the engine axis. Subsonic and supersonic separations occur near the inlet lip. Theso-created heterogeneity produces an unsteady stress on the fan blades which can lead to surge.Furthermore, short inlets are designed nowadays reducing the distance available for the flow tohomogenize before the fan leading to a coupling between the fan and the separated flow region.The aim of this study is to numerically predict the flow in a short inlet under crosswind conditionsand to investigate the fan influence on the distortion. First of all, the distortion definition isbased on stagnation quantities. Therefore, the stagnation quantities behavior and the numericalparameters influence must be investigated. The behavior of the stagnation quantities near theboundary layer edge is studied with analytical and numerical approaches. The numerical parameterschosen for the inlet simulation come from the so-obtained results obtained. In order tohighlight the fan influence on the distortion, two kinds of simulations were proceeded and comparedto experimental results : an isolated inlet simulation and a inlet/fan simulation. To correctlypredict the distortion, transition has to be be taken into account. Therefore an innovative solutionusing transport equations is used. As the computation cost for the inlet/fan computation isprohibitive, the decoupling which consists in injecting on a isolated fan the distortion obtainedduring a isolated inlet computation, is discussed. In fact, crosswind conditions occur when theairplane is on the ground, thus, the ground influence over the inlet distortion is studied for anisolated inlet. Finally, the distortion criterion used in this study has evidenced some strong defectsand can be questioned. Another approach of measurement with another criterion definitionis investigated
25
Vasudevan, K. P. "Transition Zone In Constant Pressure Boundary Layer With Converging Streamlines." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/272.
Анотація:
The laminar-turbulent transition in viscous fluid flows is one of the most intriguing problems in fluid dynamics today. In view of the enormous applications it has in a variety of fields such as aircraft design, turbomachinery, etc., scientists have now realized the importance of tackling this problem effectively. Three-dimensional flows are usually associated with pressure gradient, streamline curvature, streamline convergence / divergence etc., all acting simultaneously. Towards a better understanding of the transition process and modeling the transition zone, it is important to study the effect of each of these parameters on the transitional flow. The present work aims at studying experimentally the effect of lateral streamline convergence alone on the laminar-turbulent transition zone under constant stream-wise pressure.
The experimental setup consists of a low turbulence wind tunnel with its test section modified to cause lateral streamline convergence under constant pressure. This is achieved by converging the side-walls and appropriately diverging the roof, thus maintaining a constant stream-wise pressure. The half angle of convergence is chosen as 100 , which is approximately the same as the half of the turbulent spot envelope in constant pressure two-dimensional flows.
Experiments are carried out to analyze the development of the laminar and transitional boundary layers, intermittency distribution in the transition zone and the overall characteristics of an artificially induced turbulent spot.
The laminar velocity profiles are found to be of the Blasius type for two-dimensional constant pressure flows. However, the converging streamlines are found to contribute to an increased thickness of the boundary layer as compared to the corresponding two-dimensional flow.
The intermittency distribution in the transition zone is found to follow the universal intermittency distribution for two-dimensional constant pressure flow. A simple linear-combination model for two-dimensional flows is found to perform very well in predicting the measured velocity profiles in the transition zone.
An artificially introduced turbulent spot is found to propagate along a conical envelope with an apex cone angle of 220 which is very nearly the value for a corresponding constant pressure two-dimensional flow. The spot shapes and celerities are also comparable to those in two-dimensional flow.
In summary, the present study brings out many similarities between a constant pressure laterally converging flow and a constant pressure two-dimensional flow.
26
Kay, Christina L. "Coastal architecture design for the transition zone /." Cincinnati, Ohio : University of Cincinnati, 2007. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1179496395.
Анотація:
Thesis (Master of Architecture)--University of Cincinnati, 2007.Title from electronic theses title page (viewed July 9, 2007.) Includes abstract. Keywords: coastal architecture; water and architecture; coast; transition zone; Chesapeake Bay; coastline Includes bibliographic references.
27
Cao, Qin Ph D. Massachusetts Institute of Technology. "Seismic imaging of the mantle transition zone." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70773.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references.
In this thesis, we developed a generalized Radon transform of SS precursors for large-scale, high-resolution seismo-stratigraphy of the upper mantle transition zone. The generalized Radon transform (GRT) is based on the single scattering approximation and maps singularities (reflections) in broad-band data into singularities (reflectors/scatters) in the medium. It is able to detect and characterize mantle discontinuities at a lateral resolution of several hundred kilometers. Synthetic tests with realistic source-receiver distributions demonstrate that the GRT is able to detect and image deep mantle interfaces at correct depths, even in the presence of noise, depth phases, phase conversions, and multiples generated by reverberation within the transition zone. We apply the GRT to ~1,600,000 broadband seismograms to delineate transition zone interfaces beneath distinct tectonic units, including a cross-section in the northwest Pacific Ocean that is far away from known down- and up-wellings, the volcanic islands of Hawaii, and the northwest Pacific subduction system. We account for smooth 3D mantle heterogeneity using first-order perturbation theory and independently derived global tomography models. Through integration with mineral physics data, the GRT seismic sections can put important constraints on the mantle temperature and mineralogy of the transition zone. Our GRT imaging results beneath the Central Pacific (including the Hawaii hotspot) reveal a more complicated mantle convection picture than a thin narrow vertical mantle "plume" passing through the transition zone. We found an 800- to 2000-kilometer-wide thermal anomaly (with a maximum temperature increase of -300 to 400 kelvin) deep in the transition zone west of Hawaii, by explaining the 410 and 660 km discontinuity topographies with olivine and garnet transitions in a pyrolitic mantle. According to our geodynamical modeling study of mantle upwellings, this might suggest that the hot materials feeding the Hawaii volcanoes do not rise from the lower mantle directly through a narrow vertical plume but may accumulate near the base of the transition zone before being entrained in flow toward Hawaii. In the GRT images of the subduction system, we found a deepened 660 km discontinuity in the slab that penetrates directly into the lower mantle according to tomography results. In another cross-section, where tomography results show that the slab is stagnant above the top of the lower mantle, we found broadening of the 660 km discontinuity signals at both edges of the slab. No corresponding uplift of the 410 km discontinuity is found. However, deepening of the 410 km discontinuity is observed beneath the continental side of the subduction system in both cross-sections, indicating hot anomalies at 410 km depth at the continental side if only the thermal effect is playing a role.
by Qin Cao.
Ph.D.
28
KAY, CHRISTINA L. "COASTAL ARCHITECTURE: DESIGN FOR THE TRANSITION ZONE." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1179496395.
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Cambuí, Dorilson Silva. "Dinâmica de Partículas Auto - Propelidas." Universidade Federal da Paraíba, 2011. http://tede.biblioteca.ufpb.br:8080/handle/tede/5701.
Анотація:
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In this work, we study the collective behaviour of living systems whose aggregates form organized groups such as flocks of birds, herds of mamals and schools of fishes. Through numerical simulations, we model the collective movement of a school of fishes using behavioural rules similar to the ones proposed by Couzin et al. [23], that investigates the spatial dynamics of animals groups. The model presents three interaction zones: repulsion, orientation and attraction. Our results for the distributions of nearest neighbour distance, the diference of orientation between the velocities of neighbour fishes and the cooperativeness of the school are in good agreement with experimental measurements. A simpler way to describe the collective motion of several groups of organisms was introduced by Vicsek et al. [10]. This model presents only one interaction region, called orientation zone and considers point particles moving off lattice at constant speed adjusting their direction of motion to that of the average velocity of their neighbors, being subject to some noisy term. A second-order transition between an ordered state and a disordered regime was found. However, Gregoire and Chate [12] contest the nature of such phase transition as being of first order. Indeed, this transition is related to the way of introducing the noise into the system. In this sense, we present a comparative study on noise in two system of self-propelled particle (Vicsek model and Gregoire model) with the aim of understanding the role of the noise on some observables such as polarization, distributions of the nearest neighbour distances, difference of orientations between neighbour particles, the order parameter and the Binder cumulant.
Neste trabalho, estudamos o comportamento coletivo de sistemas vivos cujos agregados formam grupos organizados tais como bandos de pássaros, rebanhos de mamíferos e cardumes de peixes. Através de simulações numéricas, modelamos o movimento coletivo de cardumes de peixes usando regras comportamentais similares áquelas propostas por Cousin et al.[23], que investigam a dinâmica espacial de grupos de animais. O modelo apresenta três zonas de interação: repulsão, orientação e atração. Nossos resultados para as distribuições das distâncias entre vizinhos mais próximos, a diferença de orientação entre as velocidades de peixes vizinhos e a cooperatividade do cardume estão de bom acordo com medidas experimentais. Uma maneira mais simples para descrever o movimento coletivo de vários grupos de organismos foi introduzido por Vicsek et al. [10]. Este modelo apresenta somente uma região de interação, chamada zona de orientação e considera partículas pontuais movendo na rede com uma velocidade constante ajustando sua direção de movimento à velocidade média de seus vizinhos, estando sujeita a algum termo ruidoso. Uma transição de segunda ordem entre um estado ordenado e um regime desordenado foi encontrado. Porém, Gregoire e Chaté [12] contestam a natureza da transição de fase como sendo de primeira ordem. Na verdade, está transição está relacionada à forma de introduzir o ruído no sistema. Neste sentido, apresentamos um estudo comparativo sobre o ruído em dois sistemas de partículas auto-propelidas (modelo de Vicsek e modelo de Gregoire) com o objetivo de compreender o papel do ruído em alguns observáveis tais como a polarização, distribuições das distâncias entre vizinhos mais próximos, diferença de orientação entre partículas vizinhas, o parâmetro de ordem e o cumulante de Binder.
30
Skulski, Thomas. "Magma genesis along an arc-transform transition zone." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74677.
Анотація:
The Wrangell volcanic belt lies in a transpressional zone that results from the oblique convergence between the NE Pacific and North American plates. Transitional lavas predominate in the SE transform regime, whereas a calc-alkaline arc lies to the NW. The geochemical evolution of the St. Clare Creek field (Yukon) reflects changes in mode of crustal interaction and nature of mantle source components. The Wolverine centre (18-16 Ma) consists of alkaline and voluminous transitional lavas overlain by calc-alkaline lavas. The Klutlan centre (16-10 Ma) comprises calc-alkaline and Fe-rich transitional lavas followed by voluminous Fe-poor transitional basalts and more felsic transitional lavas. Primitive Fe-rich Wolverine transitional and alkaline lavas have higher Nb/Y ratios relative to Klutlan lavas, suggesting an enriched lithospheric mantle source with high $ sp{87}$Sr/$ sp{86}$Sr (0.7042) and low K/Nb ratios. Younger Fe-poor transitional lavas have high K/Nb ratios similar to calc-alkaline lavas. The Klutlan calc-alkaline lavas have high K/Nb ratios and low $ sp{87}$Sr/$ sp{86}$Sr ratios ($ sim$0.7035) derived from a slab component. Depleted Klutlan basalts have low La/Yb, low $ sp{87}$Sr/$ sp{86}$Sr (0.7031) and high $ sp{143}$Nd/$ sp{144}$Nd (0.5131) ratios reflecting an origin in the depleted asthenospheric mantle. Mixing between enriched, slab-derived, and depleted mantle components accounts for the trace element and isotopic composition of primitive transitional magmas, whereas different degrees of partial melting of depleted mantle are required to explain the range of Fe contents. Crustal assimilation accompanied the differentiation of early evolved Wolverine alkaline and late Klutlan transitional lavas. Selective contamination resulted in K-enrichment of evolved intervening transitional lavas.
31
Nowicki, Sophie Marie Jeanne. "Modelling the transition zone of marine ice sheets." Thesis, University College London (University of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499076.
32
Halladay, Kate. "Cloud characteristics of the Andes/Amazon transition zone." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.571893.
Анотація:
This research is motivated by the need to conserve tropical montane cloud forests (TMCFs) as a biodiversity hotspot threatened by environmental change. A defining feature ofTMCFs is frequent cloud immersion, which also provides moisture to the ecosystem in the dry season. Therefore, TMCFs may be sensitive to any changes in the height or frequency of cloud. The thesis consists of four papers using a combination of field and satellite-based estimations of cloud heights and frequencies with reanalysis data to investigate cloud climatology, trends and variability for a TMCF in SE Peru. The first paper uses satellite-based cloud observations from the International Satellite Cloud Climatology Project (ISCCP) (1983 to 2008), MODIS (Moderate Resolution Imaging Spectroradiometer) (2000 to 2009) and ground-based o~i'rvations to characterise cloud frequency at local and regional scales. The study area is divided into highlands (or puna), eastern slope and lowland zones to investigate spatial variability in the seasonal/diurnal cycles. Greater amplitude annual cycles and an early dry season minimum were found for the puna. For the lowlands, the minimum occurred in the late dry season except in the early morning. The second paper examines differences in interannual variability of cloud frequency between the three zones and its relationship with SSTs. Cloud frequencies are correlated with SSTs areas in the Pacific, Indian Ocean and tropical Atlantic, revealing differences between zones in the SST region of highest correlation, which also varies with season. Composites of cloud frequency, circulation and moisture flux for four combinations of high and low SSTs in the tropical North Atlantic and tropical Pacific suggest that high(low) SST anomalies in these regions are associated with reduced(increased) cloud frequency in all zones in both MAM and SON. Significant decreasing trends are found for the lowlands in January, March and September and in March on the eastern slope. The third uses radiosonde observations from the field site with station data from four elevations and cloud top heights from MODIS to investigate seasonal, diurnal and intra-seasonal variability of atmospheric structure and its relationship with cloud height and frequency. On a seasonal basis the cloud base height varies by approximately 400 m and top height by approximately 4000 m resulting in a minimum relative humidity in September at lower elevations but in June at higher elevations on the slope. Diurnal variability is dominated by daytime upslope and night-time downslope flows. The direction of mid to upper level winds are a dominant feature of intra-seasonal variability and influence inversion frequency, cloud height and frequency in all zones. The final paper compares direct observational methods (photographs, infrared thermometer and disappearance time of the radiosonde), with profile-based methods using relative humidity or temperature thresholds or gradients to estimate the positions of cloud boundaries. Methods to estimate cloud base height using the MODIS Cloud Product were also tested but potential applications were found to be limited. A method is proposed for cloud base height estimation involving consensus estimates from three methods that could be applied on long time scales. 11
33
Deyzel, (Shaun) Herklaas Phillipus. "Mesozooplankton dynamics in a biogeographical transition zone estuary." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1007901.
Анотація:
This thesis presents the first intensive community-level investigation of the mesozooplankton from a biogeographical transition zone estuary. The Mgazana Estuary is located along a rural, semi-undeveloped part of South Africa’s east coast, believed to represent a transition zone between the subtropical and warm-temperate biogeographical zones. The research represented in this thesis involves data collected over a five year period between 2002 and 2006, with additional data collection made in 2008. The study focussed on five areas of investigation, the first of which investigated the physico-chemical dynamics of the Mgazana Estuary. The Mgazana Estuary exhibited marked vertical, horizontal and regional structures in the hydrological environment. Prominent vertical and horizontal stratification characterised summer months. A substantial turbidity front was observed in the lower estuary during summer and winter. The upper estuary was marked by considerable variation in multiple variables but especially salinity. These structures appeared to have shifted in position over the horizontal plane, which was attributed to variation in freshwater flow. The second study focused on the spatial dynamics of mesozooplankton in the Mgazana Estuary. The zooplankton was rich and in terms of composition typical of mangrove systems. The Copepoda were dominant, numerically and in terms of taxonomic representation. Calanoids Acartiella natalensis and Pseudodiaptomus hessei characterised middle and upper reaches in summer and mostly upper reaches in winter. On community level, a highly structured assemblage arrangement was observed during summer and winter months. These trends were further scrutinised under the theoretical framework of ecological boundaries. In so doing, an agreeable spatial association emerged between specific assemblages and their environments. These trends were concluded to reflect ecoclinal as well as ecotonal properties, the latter describing interactions over narrow spatial bands of marked changes in turbidity. The third study investigated flooding events as short-lived extreme meteorological events and the influence on zooplankton. Within this regard, second-stage multivariate statistics was used to assess year-to-year variability in assemblage structures on whole-system and regional scales. The impact of two major flooding events that flushed the estuary some days prior to sampling could clearly be elucidated. Flooding emerged as a significant source of inter-annual variability in the zooplankton of the Mgazana Estuary. Second-stage multivariate analysis proved to be an effective analytical strategy for investigating inter-annual variability in species assemblage structures. Results from the preceding study prompted a detailed investigation into the spatio-temporal dynamics of Acartiella natalensis, the most important zooplankton species of the system aimed at elucidating flood responses. Acartiella natalensis showed indication of temporal arrest in association with flooding events in a similar fashion as is observed in seasonal variation trends in estuaries towards its geographical distribution limit south of the study area. It was concluded that A. natalensis was severely affected by floods and the possibility exist for entrainment of entire populations from the estuary during flooding events. The final study tested the hypothesis of post-flood propagation from a resting egg bank in the sediments of the Mgazana Estuary. Preliminary data revealed that numerous eggs were present in the sediments. Nauplii hatched from eggs under laboratory conditions were identified as belonging to the family Acartiidae. The preliminary mode of diapause is presented as a schematic model, emphasising the role of freshwater flow and specific environmental variables. This was the first discovery of resting eggs from a subtropical estuary from South Africa. It is hoped that the findings of this study would give rise to new research initiatives investigating the importance of resting stages in estuarine and coastal Copepoda species and the role such reproductive strategies may play in estuarine functioning.
34
Schaeffer, Andrew John. "Nature of a low-velocity zone atop the transition zone in northwestern Canada." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/11762.
Анотація:
Seismic studies over the past decade have identified a S-wave low-velocity zone (LVZ) above the transition zone at various locations around the globe. This layer is hypothesized to be a lens of dense, fluid-rich silicate melt ponding atop the 410 km discontinuity, beneath the silicate melt-density crossover predicted to exist within the upper mantle. We have assembled a P- and S-receiver function (PRF and SRF, respectively) dataset from the CNSN Yellowknife Array (YKA), the CANOE array, and the POLARIS-Slave array, to quantify the physical properties and geographical extent of the layer in Northwestern Canada. In order to compute the Poisson's ratio, an important discriminant of possible composition and/or fluid content, we generated a suite of 1-D velocity models based on IASP91, but with varying thicknesses and velocity ratios for a hypothetical layer above the 410 km discontinuity. From these models we computed moveout curves for the range of slowness represented in the YKA data. A grid search was performed over the model space of interval thickness and Poisson's ratio to obtain an estimate of the model that best accounts for the data. In addition, we performed a linearized inversion of transmission coefficient amplitudes to estimate the shear velocity contrast at the bounding interfaces of the LVZ. Results indicate a LVZ of thickness 36 km with a shear velocity contrast of -7.8%, and Poisson's ratio of 0.42. In combination, these two results require an associated increase in compressional velocity into the LVZ. The Poisson's ratio lies well above the IASP91 average of 0.29-0.3 for this depth range and favours the presence of high melt or fluid fractions. Geographic profiles of PRFs and SRFs 1-D migrated to depth from CANOE and POLARIS-Slave arrays reveal 410 km and 660 km discontinuities at nominal depths with little variation in transition zone thickness. PRF results from the Slave craton indicate a potential LVZ beneath many stations at an average nominal depth of 340 km, highlighted by events from the northwest. The CANOE array SRF profile images an emergent LVZ beginning at 280 km depth dipping eastwards to 310 km approaching YKA.
35
Su, Kemin. "Performance of Texas bluegrass hybrids in the transition zone." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/483.
36
Rospabé, Mathieu. "Etude pétrologique, géochimique et structurale de la zone de transition dunitique dans l'ophiolite d'Oman : identification des processus pétrogénétiques à l'interface manteau/croûte." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30071/document.
Анотація:
L'origine de la zone de transition dunitique (DTZ) à l'interface manteau-croûte est mal connue, ainsi que les processus physico-chimiques impliqués dans sa genèse. Pour aborder cette question, ce travail a porté sur l'étude pétrologique, géochimique et structurale de 20 coupes (600 échantillons) levées dans la DTZ du massif de Sumail (ophiolite d'Oman), épaisse de plus de 400 mètres à l'aplomb d'un paléo-diapir mantellique. Au-delà des données in situ sur minéraux (microsonde, LA-ICP-MS) et des compositions en éléments majeurs des roches totales, le développement d'une procédure analytique a permis l'acquisition des compositions en éléments en traces des dunites dont les teneurs sont de l'ordre du ng.g-1. La DTZ est faite de dunites pures (olivine et chromite) et de dunites imprégnées, contenant une quantité variable de minéraux interstitiels ayant cristallisé à partir d'un magma percolant. Ces faciès renferment des minéraux d'une variété insoupçonnée incluant, en plus de ceux clairement issus d'un MORB (clinopyroxène et plagioclase), de l'orthopyroxène, amphibole, grenat, et des diopsides témoignant d'un processus d'hybridation entre le MORB et des fluides hydratés. Les forts rapports Mg# et teneurs en TiO2 des orthopyroxènes et amphiboles ainsi que la composition des clinopyroxènes, intermédiaire entre clinopyroxènes magmatiques et diopsides hydrothermaux, a permis de contraindre la composition du magma hybride qui résulterait du mélange entre un magma d'affinité tholéiitique et un fluide supercritique riche en silice, voire trondhjémitique issu de la fusion incongruente hydratée des orthopyroxènes mantelliques, similaire au produit de fusion hydratée des roches environnantes (péridotites serpentinisées, troctolites, gabbros). Ces minéraux sont observés en position interstitielle et en inclusion dans les chromites, témoignant de leur origine précoce et du fait que les magmas hybrides ont participé à la formation de la DTZ. La combinaison des interprétations des données in situ et des données roches totales a permis la déconvolution du message polyphasé enregistré par les dunites : la signature du protolithe, celles de la dunitisation et du rééquilibrage de la matrice d'olivine avec un MORB percolant (métasomatisme cryptique), la signature de refertilisation par la cristallisation des minéraux interstitiels (métasomatisme modal), ainsi que les effets de la serpentinisation. Il apparaît que les dunites pures, caractérisées par un spectres de terres rares en forme de U ou de V, semblent avoir acquis cette signature très précocement, probablement lors de la phase initiale de leur genèse sous l'effet de rééquilibrages avec des liquides très riches en éléments incompatibles (REE, Th, U, HFSE) et pouvant correspondre au magma hybride. L'étude structurale de la DTZ dans le massif de Sumail a montré l'influence de la tectonique synmagmatique sur la structuration de la DTZ, se traduisant par l'alternance d'horizons imprégnés ou non ainsi que par l'évolution verticale sur plusieurs dizaines de mètres des compositions chimiques à l'approche des zones de failles. On l'observe notamment pour les teneurs en éléments immobiles dans les fluides tels que le Ti, les REE ou le Th. La DTZ semble s'être développée dans un environnement transtensif dont les deux systèmes de failles principaux N130 et N165-180 ont accommodé la percolation des magmas et fluides responsables de la dunitisation ainsi que l'introduction des fluides hydrothermaux pouvant conditionner les échanges globaux avec les enveloppes externes.La comparaison avec les DTZ d'autres massifs en Oman ou à Trinity (Californie), ayant évolué dans un contexte magmatique différent, montre également l'importance des failles synmagmatiques dans la structuration de la DTZ. Les liquides qui ont percolé dans ces DTZ apparaissent systématiquement sous-saturés en Al et saturés en H2O, amenant à interpréter le caractère hydraté comme une condition critique pour la genèse des dunitesThe origin of the dunitic transition zone (DTZ) between the mantle and the crust is still largely unknown, as well as the physical and chemical processes involved in its genesis. To address this topic, this thesis focused on the petrological, geochemical and structural study of 20 cross-sections (600 samples) collected along the DTZ from the Sumail massif, Oman ophiolite, 400 meters thick and located above a former paleo-mantle diapir. In addition to mineral compositions acquired using in situ methods (microprobe, LA-ICP-MS) and to whole rock major elements, the development of an analytical procedure permitted to determine trace element contents in dunites that display low concentrations (regularly about one ng.g-1). The DTZ is made of pure dunites (olivine and minor chromites), and of impregnated ones, containing a variable amount of interstitial minerals that crystallized from a percolating melt. These latter rocks contain an unexpected mineralogical variety with, in addition to clinopyroxene and plagioclase showing a MORB affinity, the presence of orthopyroxene, amphibole, garnet and diopsides that highlights a hybridization process between the MORB and hydrated fluids. The high Mg# ratio and TiO2 content in orthopyroxene and amphibole together with the clinopyroxene composition, intermediate between igneous clinopyroxene and pure hydrothermal diopside, allow deciphering the nature of the parent melt as the result of the mixing between tholeiitic melt and a supercritical water enriched in silica, or trondhjemitic fluid issued from the hydrated incongruent melting of mantle orthopyroxene, similar to melts produced by the hydrated melting of country rocks (serpentinized peridotites, troctolites, gabbros). All these minerals are observed both in interstitial position and as inclusions in chromite, showing that they crystallized early and that hybrid melts participated to the genesis of the DTZ. The comparison between mineral and whole rock compositions permitted to highlight the different processes that led to the observed chemical signatures of dunites: the protolithe signature, the dunitization process, chemical reequilibration between the olivine matrix and the percolating MORB, refertilization following the crystallization of interstitial minerals, as well as the effects of later serpentinization. Pure dunites, characterized by U or V-shaped REE patterns, seem to have acquired early the LREE-enriched signature that probably results from the reequilibration with silica- and incompatible trace elements-rich fluids (REE, Th, U, HFSE) generated through the harzburgite orthopyroxenes incongruent melting and probably reflecting the hybrid melt that crystallized interstitial hydrous minerals. The structural study of the DTZ in Sumail highlights the effect of synmagmatic faults on the DTZ development, resulting in the alternation between pure and impregnated horizons as well as in the vertical chemical structuration with compositions evolving on few tens of meters until fault zones. This is particularly true for chemical species expected as immobile during weathering as Ti, REE or Th. The DTZ seems to have been developed in a transtensional environment structured by two main faults systems, oriented N130 and N165-180. These faults spatially constrained both the melt flow, thus the dunitization, and the introduction of hydrothermal fluids probably oceanic in origin. This meeting zone between igneous and hydrothermal fluids can strongly influence the chemical exchanges and distribution between the deep lithosphere and the surface. The comparison between the Sumail DTZ and other ones from Oman or Trinity (California) ophiolites, which evolved in a different magmatic setting, shows the systematic role of synmagmatic faults. Melts that percolated these other DTZ were under-saturated in Al and saturated in water, allowing to interpret the hydrated component as an essential condition for dunites genesis at the mantle-crust transition
37
Matthews, John David. "Geological and physical assessment of the oil reservoir transition zone." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412713.
38
Haynes, Ronald. "Eulerian and Lagrangian observations in the Iberian coastal transition zone." Thesis, Bangor University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358594.
39
Gugliotta, Marcello. "The fluvial to marine transition zone and its stratigraphic significance." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-fluvial-to-marine-transition-zone-and-its-stratigraphic-significance(c9a2baf3-7ba0-46fb-a589-77d4f0f48578).html.
Анотація:
The seaward end of modern rivers is characterized by the interactions of marine and fluvial processes within a tract known as the fluvial to marine transition zone (FMTZ), which varies between systems due to the relative strength of fluvial, tidal and wave processes. River deltas also show a range of different morphologies and architectures linked to the balance between these depositional processes. However sedimentological interpretations of fluvial to shallow-marine deposits from the rock record commonly relate sedimentary structures to single depositional processes and give greater importance to facies-based observations rather than to architectural style. To better understand how fluvial and tidal process interactions are preserved and distributed in the rock record, deltaic deposits of the Middle Jurassic Lajas Formation (Neuquén Basin, Argentina) have been investigated in large-scale outcrops. The degree of tidal influence has been evaluated using both facies-scale observations and architecture analysis, and critically testing the application of the FMTZ concept in ancient deposits. The characteristics of the reconstructed FMTZ together with the architectural elements described from the Lajas Formation are consistent with an interpretation of a fluvial-dominated, tide-influenced delta, rather than a tide-dominated system, as previously proposed. The results presented herein suggest that highstand systems tract progradational deltas of the Lajas Fm. accumulated largely under microtidal conditions. Comparison of facies and architecture between modern tide dominated deltas and published examples from ancient successions shows a fundamental mismatch; modern systems are mud-dominated with laterally accreting tidal bars while ancient examples are sand-rich and dominated by forward accreting deposits. This thesis argues that the majority of ancient sand-rich successions interpreted as tide-dominated deltas might have formed in large parts in a fluvial-dominated, tide-influenced delta system and that tide-dominated deltas may have not been adequately described from the rock record yet. The improved identification of process interactions presented in this study is crucial to refining classifications of shallow-marine successions and to understanding the recorded spatial and temporal evolution of ancient depositional systems. This can have fundamental implications in refining reservoir models and predicting correct geometries in hydrocarbon-bearing successions.
40
Chollet, Mélanie. "Cinétiques de transition de phase dans le manteau terrestre." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10149.
Анотація:
L’évolution des assemblages pétrologiques avec l’augmentation de pression et de température est couramment perçue à l’équilibre et figée dans le temps. Le développement des sources synchrotron de rayons X permet à présent de mesurer in situ et en temps résolu les vitesses de transformations minéralogiques à haute pression (HP), haute température (HT). Cette thèse présente l’utilisation de cette technologie dans 2 contextes géologiques. (i) Le potentiel sismogène de la déstabilisation des minéraux hydratés dans les plaques en subduction est vérifié. Les cinétiques de déshydratation du talc, de la phase à 10Å et de l’antigorite ont été mesurées à HP-HT en système clos. Nous avons identifié que l’antigorite se déshydrate en passant par un stade intermédiaire. Toutes les vitesses de libération de fluides associées sont plus rapides que la déformation visqueuse des roches et sont donc compatibles avec le déclenchement de rupture. (ii) Les cinétiques de transition olivine-ringwoodite ont été déterminées dans la loupe de costabilité pour des compositions riches en Fe. Elles mettent en évidence une amorphisation partielle de l'olivine en début de transformation. Cela pourrait perturber de manière significative la vitesse des ondes sismiques lors de leur passage au niveau de la zone de transition mantellique. Par ailleurs, les temps caractéristiques de réaction et la réduction conséquente de la taille des grains, indiquent qu’une telle transition de phase induit une atténuation sismique importante. Ces résultats expérimentaux in situ HP-HT révèlent des mécanismes originaux de transition de phase et contribuent ainsi à une meilleure compréhension des modèles géodynamiquesThe evolution of petrological assemblies with increasing pressure and temperature is commonly perceived at equilibrium and fixed within time. The development of X-ray synchrotron sources now enable to measure in situ, time-resolved rates of mineralogical transformations at high pressure (HP), high temperature (HT). This thesis presents the application of this technology in two geological settings. (i) The seismogenic ability of breakdown of hydrated minerals within the subducting slab is checked. The dehydration kinetics of talc, 10Å phase and antigorite were measured at HP-HT in a closed system. We have found that antigorite dehydrates through an intermediate stage. All associated rates of released fluids are faster than the viscous deformation of rocks and are therefore compatible with the trigger of rupture. (ii) The kinetics of olivineringwoodite transition were determined within the co-stability loop for Fe-rich compositions. They show a partial amorphization of olivine at the beginning of the transformation. This could significantly affect the velocities of seismic waves when crossing the mantle transition zone. Moreover, the characteristic times of this reaction and the substantial reduction in grain size, indicate that such a phase transition may induce a significant seismic attenuation. These in situ HP-HT experimental results reveal novel mechanisms of phase transition and thus contribute to a better understanding of geodynamic models
41
Wise, Erika Kristine. "Streamflow and the Climate Transition Zone in the Western United States." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195178.
Анотація:
Hydroclimatic variability in the western United States (the West) is characterized by a north-south dipole pattern of precipitation and streamflow variance, with centers of opposite association in the Pacific Northwest and the Desert Southwest. These dipole centers tend to react in opposite fashion to tropical Pacific Ocean conditions, and the resulting contrast in precipitation variability is an important component of Western climate. Teleconnection impacts are not as well understood in the transition zone separating the centers of opposite association, located primarily within the semi-arid Intermountain West. This leads to low hydroclimatic predictive capacity in the transition zone region, an area that is extremely important for water supply in the West. In this dissertation, I examine paleohydroclimatic variability in this region using dendrochronology, investigate recent variability through a synoptic climatology approach, and assess future conditions based on climate change projections.Overall, this dissertation's findings confirm that the transition zone region is highly vulnerable to extremes in hydroclimatic variability and underscore the need for improved predictive capacity in the region. In the Snake River headwaters, low- to mid-elevation Pseudotsuga menziesii trees are the strongest recorders of winter precipitation, a vital component of water supply, and the season of precipitation impacting growth is a major component of the overall variability between tree-ring sites in the region. The 415-year reconstruction of Snake River streamflow indicates that extended droughts, more severe than those recorded in the instrumental period, have occurred in the pre-instrumental past. Streamflow in the upper Snake River is strongly linked to Pacific Ocean conditions and sensitive to storm track position. The West's precipitation dipole has a surprisingly narrow transition zone that has shifted in its location over time in some areas but has remained remarkably stationary across Nevada and Utah. Projected climate changes - including warmer temperatures, changing seasonality, reduced snowpack, and changes in the storm track position - highlight the importance of understanding climate-water linkages for future water resource management.
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Palazzin, Giulia. "Transition-fragile ductile en zone de subduction : le rôle du quartz." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2001/document.
Анотація:
La transition d’un comportement séismique/instable à un comportement aséismique/stable est observée dans la partie en aval des zones sismogéniques (12-15 km de profondeur). Cette transition est supposée être contrôlée par l’activation de la plasticité de basse température du quartz à ~350°C. À cause de la grande profondeur à laquelle cette transition a lieu, le seul moyen pour étudier les processus physiques qui agissent en ces contestés, est l’étude des anciens prismes d’accrétion exhumés actuellement dans des chaines de montagnes. Le mélange tectonique de Hyuga et l’unité de Morotsuka appartiennent au prisme fossile de Shimanto et sont des unités metasédimentaires déformées à des températures peu inférieures ou égales à la limite fragile/ductile (~250 et ~340°C respectivement). Les résultats des observations de microstructures en microscopie optique et en microscopie électronique à balayage (diffraction des électrons rétrodiffusés) confirment que 1) la pression dissolution et une intense microfracturation sont les mécanismes de déformation principaux du quartz dans le mélange de Hyuga et localement l’activation de la plasticité du quartz est aussi observée; 2) dans l’unité de Morotsuka la recristallisation dynamique du quartz est pleinement active. Ces considérations indiquent que la température n’est pas le seul paramètre qui control l’activation de la plasticité du quartz, et laisse supposer la participation de l’effet adoucissant de l’eau. Avec le but de mieux comprendre le rôle de l’eau sur la rhéologie quartz, des expériences en Presse Griggs ont été menées, le matériel du départ étant de porphyroclasts de quartz (immergés dans une matrice sec) à la fois très riches en eau (provenant du mélange tectonique de Hyuga) et secs (quartz du Brésil). Ces expériences montrent l’effet très adoucissant de l’eau, qui à parité de conditions de déformation, favorise la migration de joint des grains dans le quartz de Hyuga tandis que le quartz du Brésil reste indéformé à exceptions de ses bordures extérieures. L’eau « en excès » est expulsée dans la matrice pour le quartz de Hyuga et stockée dans des bandes de cisaillement C’; l’eau incorporée par le quartz de Brésil n’est pas suffisantes pour favoriser la recristallisation dynamiqueThe trasition from instable seismic to stable aseismic behaviour is observed in at the lower limit of the seismogenic zones in subduction zones (12-15 km). This transition is supposed to be controlled by the onset of quartz low grade plasticity at about 350°C. Due to inaccessibility of these geodynamic contests, the only way to study the physical processes acting at these depth are exhumed accretionary prisms exposed in mountain chains. The Hyuga tectonic mélange and the Foliated Morotsuka are metasedimentary units constituting the Shimanto accretionary prism (Japan). They were deformed at temperatures of ~250°C and ~340°C respectively, so slightly lower or equal to the temperature transition. Results by optical microscopy and EBSD reveal that 1) quartz deformation mechanisms active in Hyuga Tectonic Mélange are pressure solution and microfracturation accompanied by local quartz low grade plasticity; 2) dynamic recrystallization is totally active in quartz of the Foliated Morotsuka. These considerations allow to consider the role of water in triggering quartz plasticity especially in such water-rich contest as subduction zones. With the aim to better understand the role played by water on quartz rheology, we deformed high hydrated (from Hyuga unit) and dry (classic Brazil) quartz porphyroclasts within a quartz matrix, with the Griggs apparatus. These experiments show the weakening water effect on quartz strength. At the same deformation conditions, the high hydrated Hyuga quartz show recrystallization by grain boundary migration while the dry Brazil porphyroclasts are mostly undeformed, at exception of the outer recrystallized rims. The exceeding water expulsed from Hyuga quartz is stored in C’ shear bands in the matrix; water absorbed by dry Brazil porphyroclasts is not enough to promote dynamic recrystallization
43
Wu, Yu. "Development zones the making of new industrial spaces in transitional China : a case of Suzhou /." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40687491.
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Tarleton, Edmund. "Dislocation-dynamics modelling of crack-tip plastic zones and brittle-ductile transitions in BCC metals." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526123.
45
Lapart, Jean-André. "Identification et caractérisation de nouvelles protéines de la zone de transition des cils et des flagelles." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1108/document.
Анотація:
Les cils et les flagelles sont des organites conservés chez les eucaryotes où ils jouent des rôles essentiels et variés comme la motilité et la signalisation cellulaire. La zone de transition (ZT) est une structure complexe, localisée à la base des cils, indispensable à leur assemblage et pour la sélection des constituants ciliaires. Chez l'Homme, de nombreuses pathologies appelées ciliopathies sont associées à des défauts d'assemblage ou de fonctionnement des cils. Les plus sévères sont liées à des défauts de protéines de la ZT. Cette dernière est composée principalement de trois complexes protéiques nommés MKS, NPHP et CEP290 interagissant étroitement entre eux. D'autres protéines, dont CBY conservée des mammifères à la drosophile, s'ajoutent à ces modules mais leur interconnections ne sont pas connues Deux modes d'assemblage ciliaire ont été décrits : la ciliogenèse compartimentée et cytosolique. La fonction de la ZT au cours de la ciliogenèse compartimentée a fait l'objet de nombreuses études mais son rôle dans la ciliogenèse cytosolique reste peu connu. Au cours de ma thèse j'ai analysé la fonction de nouvelles protéines de la ZT en utilisant le modèle de la drosophile qui présente les 2 types de ciliogenèse. J'ai d'une part réalisé un crible protéomique en cellules murine IMCD3 et caractérisé le module protéique CBY, composé de CBY, FAM92A et DZIP1L. Ce module est conservé chez la drosophile à la ZT. Il est nécessaire à la ciliogenèse notamment pour l'assemblage de la ZT et pour l'ancrage du corps basal à la membrane plasmique. L'absence de ces protéines entraine des défauts ciliaires importants dans l'assemblage des flagelles de spermatozoïde et des cils des neurones sensoriels chez les drosophiles.En conclusion, ce travail apporte de nouvelles connaissances sur l'assemblage de la ZT et sur le rôle de CBY dans les mécanismes qui contrôlent la ciliogenèseCilia and flagella are highly conserved organelles among eukaryotes species. They are composed of a microtubular cytoskeleton and play essential functions during development and in numerous physiological processes. As a result, in humans, cilia dysfunction leads to a wide range of pathologies, called ciliopathies.At the ciliary base, the transition zone (TZ), a complex structure, is required for proper cilia assembly and regulates the traffic of ciliary components in and out cilia. Defects in TZ proteins lead to severe ciliopathies. The TZ is composed of 3 protein complexes, MKS, NPHP et CEP290 that closely interact. Additional proteins, like CBY, conserved between mammals and Drosophila, have been described at the TZ but their precise role and relationships with the other TZ complexes are unknown. Two modes of cilia assembly have been described: compartmentalized and cytosolic ciliogenesis. Whereas the function of the TZ in compartmentalized ciliogenesis is well documented, its role in cytosolic ciliogenesis remains poorly characterized. During my PhD, I characterized new TZ proteins conserved in mammals and Drosophila and analyzed their function during cilia assembly in Drosophila. First, I performed a proteomic screen in murine IMCD3 cells and characterized the CBY module composed of CBY, FAM92A1 and DZIP1L. This complex is conserved in Drosophila and locates at the TZ. Moreover, I showed that this module is necessary for TZ assembly and centriolar docking to the plasma membrane and hence required for cilia and flagella assembly. In absence of these proteins, Drosophila show severe ciliogenesis defects both in sperm cells and in sensory neurons.In conclusion, this work brings new insights into the understanding of TZ assembly and of the mechanisms, that control ciliogenesis
46
Nono, nguendjio Franck Laurel. "Caractérisation polyphasique de la zone de transition dans un réservoir pétrolier carbonaté." Thesis, Paris, ENSAM, 2014. http://www.theses.fr/2014ENAM0012/document.
Анотація:
Dans cette thèse, nous nous sommes intéressés à la mesure et à la modélisation des propriétés d'écoulements diphasiques (perméabilités relatives) dans des milieux poreux carbonatés représentatifs de la zone de transition de réservoirs pétroliers carbonatés. Notre étude expérimentale a porté sur deux roches carbonatées de même minéralogie mais de propriétés pétrophysiques différentes (unimodale et bimodale). Les fluides utilisés sont une saumure, une huile minérale pour les expériences en mouillabilité franche à l'eau et une huile brute pour les expériences en mouillabilité altérée (obtenue par macération). Durant les expériences en « écoulements permanents », la perte de charge est mesurée continûment et le champ de saturation locale est mesuré en fin d'expérience par atténuation gamma. Les principaux résultats expérimentaux de cette étude sont les suivantes :- La mouillabilité dépend de la saturation initiale en huile et donc de la hauteur de la zone de transition. Elle a une influence sur les perméabilités relatives à l'huile ET à l'eau.- L'hystérésis des perméabilités relatives à l'eau est d'autant plus prononcée que la saturation initiale en huile augmente. Une observation similaire est faite sur la courbure des perméabilités relatives à l'huile.- Les évolutions des Sorw en fonction des Soi ne vérifient pas toutes, une loi monotone de type Land. Leur évolution dépend aussi de la structure poreuse.- Les deux types de roches carbonatés présentent une altération de mouillabilité différente, la structure vacuolaire favorisant l'altération de mouillabilité. Nos données expérimentales ont été interprétées en utilisant différents modèles d'hystérésis de la littérature. Il apparait clairement des différences entre les prédictions numériques et nos données expérimentales car ces modèles ne prennent pas en compte l'évolution de la mouillabilité. Nous avons proposé un modèle de calcul des perméabilités relatives qui décrit nos données expérimentales de manière satisfaisanteIn this work, we take an interest in measuring and modeling the multiphase flow properties (relative permeabilities) in different carbonate rock types that are representative of the transition zone of carbonate reservoirs. Our experimental study focused on two different carbonate rock types, with almost the same mineralogy, but different petrophysical properties (bimodal and unimodal). The system of fluids used is composed of brine, a mineral oil (for experiments at water-wet conditions), and a crude oil (for experiments including wettability alteration after an ageing process at high temperature). During the experiments performed by the steady-state core flooding method, the pressure drop is continuously measured along the core, and the saturation profiles are obtained at the end of the flooding, by gamma ray measurements. The main results of this study are as follows:- Wettability depends on the initial oil saturation and hence the heights above the oil-water contact. It affects the oil relative permeabilities AND water relative permeabilities- The hysteresis observed on water relative permeability is even more pronounced that the initial oil saturation increases. A similar observation is made on the curvatures of the oil relative permeability.- The evolution of Sorw as function of Soi does not always follow a classical Land correlation. Their evolution also depends on the pore structure.- The two rock types exhibit different responses to wettability alteration. The vuggy structure might promote oil-wetness.Our experimental data were interpreted using different hysteretic models of the literature. We observed significant differences between the results predicted by the models and our experimental observations which are attributed mainly to the failures to take into account the change in wettability. We proposed an improved hysteresis model, which described our experimental data satisfactorily
47
Braun, Ross. "Cultural strategies to improve zoysiagrass acceptability and performance in the transition zone." Thesis, Kansas State University, 2014. http://hdl.handle.net/2097/18257.
Анотація:
Master of ScienceDepartment of Horticulture, Forestry, and Recreation Resources
Jack Fry
Zoysiagrass (Zoysia spp.) is more heat and drought resistant and requires fewer cultural inputs than cool-season (C3) turfgrasses; however, its widespread use may be limited by an extended period of winter dormancy, the disease Rhizoctonia large patch (Rhizoctonia solani Kühn AG-2-2 LP), and lack of cold hardiness. Objectives of these 2012-2014 field studies were to evaluate: 1) turfgrass colorants and overseeding for color enhancement; 2) three colorant application volumes on color persistence; 3) colorants applied at two volumes, once or sequentially, on buffalograss (Buchloë dactyloides) and zoysiagrass; 4) the impact of nitrogen source and application timing on large patch severity; and 5) winter hardiness and turf quality of new experimental lines. The colorants Ultradwarf Super and Green Lawnger provided acceptable lawn-height ‘Chisholm’ zoysiagrass color for 7 to 9 and 19 to 24 weeks after treatment (WAT), respectively. Chisholm receiving a sequential application of either product in mid-winter (14 WAT) maintained an acceptable color level after that point until mid-May (28 WAT). Overseeding with annual ryegrass did not provide acceptable color for more than 4 weeks. Evaluation of the colorants Green Lawnger, Endurant, and Wintergreen Plus showed that acceptable Chisholm color at lawn-height occurred for 8 to 14 WAT at 80 gallons per acre (GPA) and 16 to 26 WAT at 240 GPA. Buffalograss at lawn-height receiving a single autumn colorant application had acceptable color for 8 to 12 WAT at 100 GPA or 8 to 14 WAT at 160 GPA. ‘Meyer’ zoysiagrass maintained at a 0.5 inch height receiving a single autumn colorant application had acceptable color for 8 to 18 WAT at 100 GPA or 14 to 18 WAT at 160 GPA. No differences in large patch occurred between spring and fall applications of ammonium sulfate and calcium nitrate, nor between those treatments and summer-applied urea. Applying fertilizer in spring when soils reached 21 ºC increased green cover on some rating dates compared to applications in fall when soil temperatures fell to 21 ºC but differences were minimal. Out of 985 experimental zoysiagrass lines planted in the field, about 25 were identified for further evaluation for cold hardiness, large patch resistance, and turf quality.
48
Hinojosa-Prieto, Hector R. "Subduction zone-related Nonvolcanic Tremor in Oaxaca, Mexico." Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1242326095.
49
Campfield, Patrick Anthony. "Ichthyoplankton community structure and feeding ecology in the Patuxent River estuarine transition zone." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1751.
Анотація:
Thesis (M.S.) -- University of Maryland, College Park, 2004.Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
50
Bazzi, Hussein. "Étude numérique de l'écoulement transitoire dans une zone flottante la transition axisymétrique/oscillatoire." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0034/NQ67092.pdf.