Global ETD Search

11	Détermination des abondances des éléments chimiques d'étoiles A et F naines membres de deux amas ouverts. Contraintes sur les modèles évolutifs incluant les processus de transport. Gebran, Marwan 14 December 2007 (has links) (PDF) On observe des anomalies d'abondances en surface de nombreuses étoiles A (d'amas et du champ). Ces anomalies d'abondances sont générées par la diffusion microscopique et peuvent etre modulées par l'action d'autres processus de m´elange, incluant la convection, le méange rotationnel, la perte de masse, etc. Ces étoiles désignées chimiquement particulières montrent typiquement des sous-abondances en calcium et/ou en scandium ainsi que des surabondances en éléments du pic du fer et en éléments plus lourds. Les étoiles A non magnétiques de ce type sont classifiées Am.<br />En observant en particulier des étoiles A et F dans des amas ouverts, on peut obtenir des informations additionnelles qui facilitent la comparaison aux mod`eles, soient la composition chimique initiale et l'age de ces étoiles. Ainsi en déterminant la composition chimique des étoiles A/F dans plusieurs amas ouverts d'ages différents, on peut suivre l'évolution de la composition chimique de surface et contraindre les modèles évolutifs au niveau des processus de transport.<br />Dans cette thèse, j'expose l'analyse de la composition chimique d'échantillons d'étoiles A et F dans deux amas ouverts d'ages différents: les Pléiades (100 Myrs) et Coma Berenices (450 Myrs). Ce travail repose sur des observations que j'ai menées avec les trois spectrographes AURELIE, ELODIE et SOPHIE a l'Observatoire de Haute-Provence (OHP). La méthode des spectres synthétiques, basée sur des modèles d'atmosphères d'ATLAS9-12, a été utilisée afin de déterminer les abondances de 22 éléments. Ces observations sont ensuite comparées aux prédictions des modèles évolutifs de Montréal. Les résultats démontrent l'existence de processus hydrodynamiques dans les zones radiatives de ces étoiles et qui contrebalancent les effets de la diffusion microscopique. spectroscopie abondances etoiles A etoiles Am etoiles F diffusion radiative amas ouverts: Coma Berenices Pleiades
12	Studies on K-shell photoionization of nitrogen ions and on valence photoionization of atomic and small molecular ions Alshorman, Mohammad 25 February 2014 (has links) (PDF) In this thesis work, the K-shell photoionization of multi-charged ions has been studied as well as the valence photoionization of atomic and small molecular ions. The K-shell photoionization cross sections were measured for nitrogen iso-nuclear series, from N+ to N4+ ions using the ion-photon merged beam technique and the valence photoionization cross sections for Xe+ and Kr+ ions and the small molecular ions CO_2^+ and N_2^+ using both the merged beam and ion trap techniques at the SOLEIL synchrotron radiation facility in Saint-Aubin, France. Combination of the two techniques allows for the measurement of the pure ground state ionization cross section on an absolute scale.The experimental K-shell photoionization cross sections are compared with theoretical results obtained from the multi-configuration Dirac-Fock (MCDF), R-matrix and the Screening Constant by Unit Nuclear Charge (SCUNC) methods. The interplay between experiment and theory enables the identification and characterization of the strong 1s→2p and 1s→3p resonances observed in the spectra. The experimental valence photoionization cross sections for Xe+ and Kr+ ions are compared with MCDF calculations results obtained for the direct photoionization process. The quality of the absolute cross section measurements using the merged beam techniques is strongly dependent on the performance of Electron Cyclotron Resonance Ion Source (ECRIS). In order to improve the current of ions in the interaction region, the ions extraction system and transport was simulated by using IGUN program and ECRopt. Photoionization Cross section Synchrotron radiation FTICR ECRIS SCUNC R-matrix MCDF MAIA PLEIADES DESIRS SOLEIL
13	CLASSIFYING DOMINANT PARKLAND SPECIES IN A WEST AFRICAN AGROFORESTRY LANDSCAPE USING PLEIADES SATELLITE IMAGERY Lunn, Simon January 2020 (has links) As we move towards a digital based society, technology continues to improve. It is important to take advantage of this to inform and facilitate our sustainable development goals in the most cost-effective and time efficient manner. By utilising the best available technologies, not only can time savings be achieved, but scope of works can be dramatically increased, particularly with ecological data collection. This study will focus on collecting ecological data (tree species) using developing modern technologies (satellites) with the aim of reaching classification accuracies comparable with ground truthed (real life) records. The study area is in central Burkina Faso approximately 30km south of the capital and is generally described as an agroforestry parklands area. The region suffers greatly from poverty and many people are heavily dependent on the agricultural sector and subsistence farming. As these agroforestry parklands are so critical to many people’s livelihoods, it is important to assess the natural resources available within them to provide the best food security management for the people. Tree species locations were overlayed on two satellite images acquired during different stages of the annual growing periods in the agroforestry parklands of the study area. From these images, segmentation of individual tree crowns was done manually and used as the reference data for an object-based classification model, which were assessed for the classification accuracies that can be achieved. Three satellite image scenarios were assessed for classification accuracy, including two single image scenarios and a multi-imagery dataset combining both images. Results indicate that combined images perform the best in terms of overall classification accuracies, closely followed by the end of the wet season growing period. The image acquisition from the end of the dry season was quite poor in comparison, having an overall classification accuracy more than 10% lower than the other scenarios. Of the focus species assessed in this study, Azadirachta Indica was the clear loser in terms of the number of correctly classified individuals from each model scenario. All other focus species were relatively well classified achieving close to or above 60% accuracies in the multi-imagery classification scenario. Remote Sensing Fjärranalysteknik Miljö- och naturvårdsvetenskap
14	Damage Assessment of the 2018 Swedish Forest Fires Using Sentinel-2 and Pleiades Data / Skadeuppskattning av de svenska skogsbränderna år 2018 med Sentinel-2 och Pleiades data Grenert, Patrik, Bäckström, Linus January 2019 (has links) When a devastating event such as a forest fire occurs, multiple actions have to be taken. The first priority is to ensure people's safety during the fire, then the fire has to be kept under control and finally extinguished. After all of this, what remains is a damaged area in the forest. The objective of this thesis is to evaluate medium and high-resolution satellite imagery for the classification of different burn severities in a wildfire damaged forest. The classification can then be used to plan where to focus restoration efforts after the fire to achieve a safe and economically beneficial usage of the affected area. Trängslet fire in Dalarna and Lillhärdal fire in Härjedalen, the two of the 2018 forest fire sites in Sweden were chosen for this study. Satellite imagery over both study areas at medium spatial resolution from Sentinel-2 were acquired pre-fire in early July, 2018 and post-fire on October 2, 2018 while imagery at high spatial resolution from Pleiades were acquired on September 13, 2018. Image processing, analysis and classification were performed using Google Earth Engine (GEE) and PCI Geomatica. To ensure the quality of the classifications, field data were collected during a field trip to the Lillhärdal area using Open Data Kit (ODK). ODK was used since it is an application that can collect/store georeferenced information and images. The result that this thesis found is that while both the medium and high-resolution classifications achieved accurate results, the Sentinel-2 classification is the most suited method in most cases since it is an easy and automated classification using differential Normalized Burn Ratio (dNBR) compared to the Pleiades classification where a lot of manual work has to be put in. There are however cases where the Pleiades classification would be preferable, such as when the affected area usually is obscured by clouds and Sentinel-2 thus finds it hard to achieve good images and when a good spatial resolution is required to more easily display the classification with the original image. The most accurate result according to the data collected at the site in Lillhärdal also showed that the Pleiades classification had a precise match of 61.54% and a plausible match of 92.31%. This can be compared to the Sentinel-2 classification that had a precise match of 48.72% and a plausible match of 94.87%. These percentages are based on the visual analysis of collected images at the Lillhärdal site compared to the classifications. This thesis could have been improved if more information regarding the groundwork that had been done after the fire, but before the acquiring of the satellite imagery, were available. The result would also most likely be better if a satellite with better spatial resolution than Sentinel-2 but still with near infrared and short-wave infrared bands would have been used. The reason being that dNBR, which gave a good result, only needs those two bands. Damage Assessment Sentinel-2 Pleiades Forest Fire dNBR classification Supervised image classificaiton Sweden 2018 Trängslet Lillhärdal 2018 Other Social Sciences Annan samhällsvetenskap
15	Etude tectonique et géomorphologique du système de failles de Longriba (Est Tibet, Chine) Ansberque, Claire 11 April 2016 (has links) Ce manuscrit concerne l'analyse tectonique et géomorphologique du système de failles de Longriba (LFS), localisé à l'Est du plateau tibétain à environ 200 km au Nord-ouest de la chaîne des Longmen Shan. Le LFS est constitué de deux zones de failles décrochantes dextres, parallèles et d'orientation N55°E : la faille de Longriqu, au Nord, et la faille de Maoergai, au Sud. Le rôle géodynamique de ce système est primordial puisqu'il accommode 5 ± 1 mm/an de la composante décrochante induite par la convergence oblique du bloc Aba, elle-même liée à la collision Inde-Asie. De plus, le LFS partitionne la déformation de la marge Est tibétaine; les structures des Longmen Shan étant essentiellement chevauchantes. Cependant l'histoire long-terme du LFS est mal contrainte. L'objectif de cette thèse est donc d'apporter des informations spatio-temporelles sur l'activité du système à l'échelle du Cénozoïque. Pour cela trois études ont été réalisées. La première a permis de mieux contraindre le comportement sismogénique des deux zones de failles à l'aide d'images satellites de basse (90m) et très haute résolution (50cm). L'analyse des déplacements cumulés le long de la faille de Maoergai a permis de proposer que celle-ci était active vers ~15Ma. La seconde étude a mis en évidence un contrôle du système sur la répartition des taux de dénudation au travers de la marge Est tibétaine à l'échelle de l'Holocène. Enfin, les données de thermochronologie basse température suggèrent que la faille de Maoergai a accommodé un mouvement vertical vers ~10Ma. Ce mouvement est probablement lié au rebond isostatique de la marge, découplé du mouvement décrochant qu'elle accommode à la même période. / This manuscript concerns the tectonic and geomorphic analysis of the Longriba fault system (LFS), located in the eastern Tibetan plateau at about 200 km north-west of the Longmen Shan. The LFS consists of two dextral strike-slip fault zones, parallel and N55 °-trending: the Longriqu fault to the north and the Maoergai fault the south. The geodynamic role of the system is essential as accommodates 5 ± 1 mm / year of the slip component induced by the oblique convergence of the Aba block, itself linked to the India-Asia collision. In addition, the LFS partitions the deformation of the east Tibetan margin; the structures of the Longmen Shan are mainly thrust faults. However the long-term history of LFS is poorly constrained. The objective of this thesis is to bring spatial and temporal information on system activity throughout the Cenozoic. To do so, three studies were performed. The first led to better constrain the seismogenic behavior of the two fault zones with low resolution (90m) and very high resolution satellite images (50cm). The analysis of cumulative displacements along the Maoergai fault allowed to propose that it was active at ~ 15 Ma. The second study showed that the system controls the distribution of the denudation rates over the EastTibetan margin throughout the Holocene. Finally, the low-temperature thermochronology data suggest that, in particular, the Maoergai fault has accommodated a vertical movement at ~ 10 Ma. This movement is probably related to the isostatic rebound of the margin, decoupled from the strike-slip movement it accommodates at the same period. Failles décrochantes Comportement sismogénique Images Pléiades Radionucléides Taux de dénudation Thermochronologie Taux d'exhumation Bassin de Ruoergai Paléoclimat. Strike-Slip faults Seismogenic behavior Pleiades images Cosmogenic nuclides Denudation rates Thermochronology Exhumation rates Ruoergai basin Paleo-Climate
16	Contribution des technologies satellitaires Pléiades à l'étude des trames vertes urbaines : entre maintien des connectivités écologiques potentielles et densification des espaces urbains / Contribution of Pléiades-HR images to the assessment of urban green infrastructures : dealing with urban ecological network issues and urban densification Crombette, Pauline 13 May 2016 (has links) En milieu urbain, la concurrence entre les enjeux de préservation de la biodiversité et de la densification du territoire est particulièrement développée. Dans une optique d’aide à la décision, une meilleure connaissance des zones les plus conflictuelles est requise. Face au constat d’insuffisance et d’inadéquation des données et des méthodes nécessaires à la cartographie des Trames vertes urbaines, notre travail s’intègre en premier lieu dans une démarche technique. Celle-ci est centrée sur la mise en place d’une méthode de traitement d’images satellitaires Très Haute Résolution Spatiale Pléiades (THRS) pour l’extraction de la végétation arborée et herbacée à l’échelle fine d’une emprise urbaine. D’abord appliquée à des données fictives, cette méthode est ensuite déployée sur quatre territoires (Toulouse, Muret, Pierrefite-Nestalas et Strasbourg). Bien que fondée sur une approche pixel, la simplicité de la méthode, qui s’appuie sur des outils libres, et les résultats obtenus (indice Kappa supérieur à 85 %) garantissent sa reproductibilité sur de vastes territoires plus ou moins urbanisés. Cette donnée de végétation est ensuite exploitée pour modéliser les connectivités écologiques potentielles du paysage urbain et périurbain toulousain. L’approche mobilise la théorie des graphes et permet d’évaluer l’impact d’un aménagement urbain sur la biodiversité. Le cas du Boulevard Urbain Nord de Toulouse est étudié. La cartographie proposée des réservoirs de biodiversité, hiérarchisés à l’aide de métriques de connectivité, est avant tout indicative. Elle est finalement confrontée à des documents d’urbanisme (Plans Locaux d’Urbanisme) afin d’obtenir une meilleure visibilité des territoires à enjeux environnementaux et urbanistiques. En fonction des enjeux fixés par les acteurs du territoire et à travers le filtre applicatif, cette thèse propose un outil robuste d’analyse et d’aide à la décision pour la gestion et la planification du territoire. / In urban areas, competition between land development and ecological conservation is intense. To assist decision making, a better knowledge of those areas of interest is required. Regarding inadequacy data and methods needed for ecological network mapping in urban areas, the aim of our study is to develop a method for semi-automatic vegetation extraction with Very High Spatial Resolution Pleiades imagery (VHSR). Initially applied to training samples, the process is then be deployed to four French study areas (Toulouse, Muret, Pierrefite-Nestalas and Strasbourg). The reproducibility of this method over large urbanized areas is ensured by its simplicity and the results of a pixel-based classification (kappa coefficient higher than 85 %). This extraction workflow uses free or open-source software. This vegetation data is then used in order to model potential ecological connectivity in Toulouse’s urban and peri-urban areas. Impacts on biodiversity due to urban planning are assessed using graph theory. The “Boulevard Urbain Nord de Toulouse” project, a road infrastructure, is studied. Graph metrics have been calculated to assess the level of connectivity at habitat patches and landscape scales. We classified the importance of the patches which is cross-tabulated with planning documents (PLU, a local town planning) in order to locate conflict urban areas: between biodiversity preservation and urbanization. Depending on the issues set out by local actors and through the application filter, this thesis proposes a robust analytical tool and decision-making aid for landscape management and land planning. Trame verte urbaine Aménagement du territoire Milieu urbain et périurbain Graphes paysagers Outils libres Urban green infrastructure Land planning Urban and peri-Urban areas Landscape graphs Open-Source software
17	The Pleiadic Age of Stuart Poesie: Restoration Uranography, Dryden's Judicial Astrology, and the Fate of Anne Killigrew Brown, Morgan Alexander 30 April 2010 (has links) The following Thesis is a survey of seventeenth-century uranography, with specific focus on the use of the Pleiades and Charles's Wain by English poets and pageant writers as astrological ciphers for the Stuart dynasty (1603-1649; 1660-1688). I then use that survey to address the problem of irony in John Dryden's 1685 Pindaric elegy, "To the Pious Memory of Mrs. Anne Killigrew," since the longstanding notion of what the Pleiades signify in Dryden's ode is problematic from an astronomical and astrological perspective. In his elegiac ode, Dryden translates a young female artist to the Pleiades to actuate her apotheosis, not for the sake of mere fulsome hypberbole, but in such a way that Anne (b. 1660-d. 1685) signifies for the reign of Charles II (1660-1685) in her Pleiadic catasterism. The political underpinnings of Killigrew's apotheosis reduce the probability that Dryden's hyperbole reserves pejorative ironic potential. Hevelius Restoration prodigies Restoration prodigy birth star Pleiads Pleiades Tycho Brahe Restoration Anne Killigrew Ursa Major Charles's Wain judicial astrology Dryden Charls his wain William Bradford Gardner Edward Matthew irony Arcturus Laura Brown Howard Weinbrot Pindar uranography William Lilly Charles I Charles II uranology septentrional Polaris Ben Jonson Virgil Taygete Electra Astronomica Hyginus Fasti Ovid coronation James I vernal equinox septem triones seven stars 1660 star waine Ursa Minor Flamsteed Halley David Vieth English Language and Literature

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