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Orbital angular momentum (OAM) is a property of light that is widely used for applications in bioimaging, optical communication and optical manipulation, but is mainly limited to the infrared and visible spectra. Developing a table-top source of Extreme Ultraviolet (XUV) light containing an arbitrary amount of OAM is yet to be achieved. We accomplish this by exploiting high-harmonic generation (HHG), a process whereby an infrared pump beam produces high order harmonics. We experimentally demonstrate the conservation of OAM in HHG by measuring harmonics of order n containing n times the OAM of the pump (n = 11, 13, 15 in our experiment). These results agree with our theoretical model. We also show theoretically how to manipulate the HHG process to impart an arbitrary amount of OAM to the di fferent harmonics. We hence show the way to a table-top and flexible source of XUV light containing orbital angular momentum.

Thesis (M.App.Sc.) - Carleton University, 2002. / Includes bibliographical references (p. 124-130). Also available in electronic format on the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 78-80). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 84-85). Also available via the Internet.

A method of estimating the relative position and orientation of a known target satellite is presented, using only passive imagery. Such a method is intended as a prelude to a system required in future autonomous satellite docking missions. Using a single monocular image, and utilising knowledge of the target spacecraft, estimation of the target's six relative rotation and translation parameters with respect to the camera are found. Pose estimation is divided into modular sections. Each frame is processed to detect the major lines in the image, and correspondence information between detected lines and a-priori target information is estimated, resulting in a list of line-to-model correspondences. This correspondence information is used to estimate the pose of the target required to produce such a correspondence list. Multiple possible pose estimates are generated and tested, where each estimate contains the three rotation and translation parameters. The best estimates go through to the least-squares minimisation phase, which reduces estimation error and provides statistical information for multi-frame filtering. The final estimate vector and covariance matrix is the end result for each frame. Estimates of the target location over time allow the relative orbit parameters of the target to be estimated. Location estimates are filtered to fit an orbit model based on Hill's Equations, and statistical information gathered with each estimate is including in the filter process when estimating the orbit parameters. These orbit parameters allow prediction of the target location with time, which will enable mission planning and safety analysis of potential orbit manoeuvres in close proximity to the target. Testing is carried out by a detailed simulation system, which renders accurate images of the target satellite given the true pose of the target with respect to the inertial reference frame. The rendering software used takes into account lighting conditions, reflections, shadowing, specularity, and other considerations, and further post-processing is involved to produce a realistic image. Target position over time is modelled on orbit dynamics with respect to a defined inertial frame. Transformation between inertial, target, and camera frames of reference are dealt with, to transform a rotating target in the inertial frame to the apparent rotation in the camera frame.

Foram determinadas funções de variáveis como o número atômico e elementos da matriz de densidade que aproximam expoentes variacionalmente otimizados de bases mínimas de orbitais tipo-Slater de átomos em moléculas. Um dos conjuntos de funções corresponde à inclusão de correlação eletrônica (MP2) e potencial efetivo de caroço. No outro conjunto, tais efeitos não foram incluídos. Para a otimização variacional, foram utilizadas cerca de 400 moléculas, contendo átomos do hidrogênio ao argônio, cerca de 2200 expoentes (com potencial efetivo de caroço), e cerca de 3600 expoentes (sem potencial efetivo de caroço). Os orbitais tipo-Slater foram representados por expansões STO-8G. O erro médio na energia molecular devido ao uso dos expoentes aproximados para definir os orbitais atômicos é cerca de mil vezes menor que o erro correspondente devido ao uso da base mínima de orbitais tipo-Slater. / Functions of variables such as density matrix elements and atomic number that give approximate values of variationally optimized exponents for minimal basis sets of Slater-type orbitals were developed. One set of functions includes electronic correlation (MP2) and effective core potential. In the other set such effects are not included. Some 400 molecules, composed of atoms from hydrogen to argon, some 2200 exponents (with effective core potential), and some 3600 exponents (without effective core potential), were used in the variational optimization. Slater-type orbitals were represented by STO-8G expansions. The average molecular energy error due to the use of approximate exponents to define atomic orbitals is close to a thousand times smaller than the corresponding error due to the use of the minimal basis set of Slater-type orbitals.

Based on first principles Density Functional Theory calculations, we have investigated for possible paths for engineering electronic band structure of Transition Metal Dichalco- genides (TMDs). We have considered two approaches which have shown to be promising for engineering electronic bands of TMDs: substitutional chemical doping and heterostruc- turing. All the calculations are done using first principles Density Functional Theory as it is implemented in Quantum Espresso package. Two possible substitutional doping meth- ods for MoS2 are considered in our calculations; cation doping where Mo is substituted by metal atoms and anion doping where Nitrogen and halogen group atoms take the posi- tion of S-sites. We observe the n-type characteristics for halogen group doping and p-type characteristics for Nitrogen group doping at S site. Similarly, we observe these bipolar characteristics when substituted by the transition metal elements (4d elements in the peri- odic table) at Mo site. Our results on doping monolayer MoS2 are in agreement with those results obtained by Dolui et al. for similar systems. Our work is extended to explore the effect of substitutional doping in bilayer MoS2. We observe the promising bipolar char- acteristics on doping while the magnitude of the band gap decreases upon the controlled S-site doping with F and As. In the second part, we considered two types of heterostructuring; Van der Waals heterostructures, and lateral heterostructures. In Van der Waals heterostructures, a direct band gap is observed with a physical separation of charges into two layers from orbital isosurface plots. We present a brief overview of the folding of energy bands in supercell approach. Using heterogeneous supercell approach, we studied the electronic properties of a mixed system of MoS2 -WS2 . The separation of the charges into the two sections shows that our MoS2 -WS2 in-plane heterostructure shows a potential for a pn junction. These systematic studies of the doped and heterostructures of TMDs can be useful for device applications.

L'étude présentée dans ce mémoire traite du perçage orbital de l'alliage de titane Ti6Al4V et du composite à fibres de carbone CFRP sur des structures épaisses. Ce cas d'étude est extrait d'une problématique industrielle, provenant de la société Airbus qui souhaite intégrer à la structure primaire du mât de réacteur des pièces en CFRP afin de diminuer sa masse. Mais l'association de ces deux matériaux aux propriétés antagonistes pose de nombreux problèmes en matière de perçage. C'est la raison pour laquelle de nouvelles alternatives au perçage classique ont été recherchées. Parmi ces alternatives possibles, le perçage orbital avec micro-lubrification a montré des perspectives intéressantes. C'est pourquoi il a été choisi dans cette application industrielle. Mais ce procédé reste encore assez peu étudié et il existe donc peu de retours d'expériences et beaucoup de développements à réaliser. Le procédé de perçage orbital est très différent du perçage axial conventionnel. L'alésage est réalisé avec un outil de diamètre inférieur au trou, qui décrit une trajectoire hélicoïdale dans le matériau. L'ensemble des travaux présentés se focalisent sur la caractérisation en vue de l'optimisation du procédé de perçage orbital. Pour réaliser ceci, plusieurs aspects ont été abordés. Tout d'abord, une modélisation géométrique et cinématique de l'opération a été développée. La prise en compte de la géométrie exacte de l'outil et des conditions de coupe a permis de définir la géométrie du copeau à chaque instant. Cette connaissance est très importante pour la compréhension du mécanisme d'enlèvement de matière réalisé, elle permet d'estimer le chargement de l'outil et les conditions dans lesquelles s'effectue l'usinage. À partir de cette première modélisation géométrique, une modélisation des efforts de coupe a été mise en place. Pour cela, un modèle d'effort de type mécanistique a été utilisé. Son application a été adaptée au perçage orbital, afin de représenter au mieux l'opération. Les efforts ainsi modélisés ont été comparés à ceux observés expérimentalement afin de valider la modélisation proposée. Cela a permis d'envisager l'utilisation de cette modélisation pour une meilleure compréhension du processus d'enlèvement de matière présent. L'influence des entrées du modèle, à savoir les conditions de coupe et la géométrie de l'outil a été étudiée. L'autre apport de ces travaux réside dans la caractérisation du perçage orbital d'empilages CFRP/Ti6Al4V. En effet, de nombreux essais ont été mis en place pour caractériser le procédé de perçage orbital. Des procédures expérimentales ont donc été mises en place. Tout d'abord, le moyen d'essai instrumenté a dû être caractérisé afin qu'il corresponde au mieux aux moyens utilisés par l'industriel et surtout qu'il permette de réaliser des essais fiables et répétitifs. Les plans d'expériences mis en place par la suite ont permis de définir l'influence des paramètres de coupe sur les efforts et sur les diamètres réalisés. Dans cette phase de caractérisation, les défauts présents en perçage ont également été étudiés. Ainsi, des tendances ont pu être observées. Les résultats obtenus dans ces travaux dans ces travaux ont permis enfin d'envisager les voies d'optimisation du procédé, à travers le pilotage des avances, la stratégie de perçage, mais aussi la géométrie de l'outil. Des pistes ont été proposées et doivent faire l'objet d'études complémentaires. la modélisation mise en place et l'identification des phénomènes intervenant pendant l'opération ont d'ailleurs permis de poser les bases d'une surveillance du process. Celle-ci peut s'envisager de façon passive, pour contrôler le bon déroulement de l'opération, mais également de façon active pour agir en temps réel sur le pilotage du procédé, en fonction des phénomènes identifiés, afin de garantir la qualité souhaitée. / The study presented in this thesis deals with the orbital drilling of Ti6Al4V titanium alloy and CFRP carbon fiber composite. This case study is taken from an industrial problem, from the Airbus company wishing to incorporate parts CFRP to reduce its mass. But the combination of these two materials with antagonistic properties poses many problems for drilling. This is why new alternatives to conventional drilling have been sought. Among these alternatives, orbital drilling with micro-lubrication showed interesting prospects. That is why it was chosen in this industrial application. But this process is still relatively unexplored and there is little feedback and many developments to achieve. Orbital drilling process is very different from the conventional axial bore. The bore is machined with a smaller diameter tool than the hole, which describes a helical path in the material. All work presented focus on the characterization for the optimization of the orbital drilling process. To achieve this, several aspects were discussed. First, a geometric modeling and kinematics of operation has been developed. The inclusion of the exact geometry of the tool and cutting conditions helped to define the geometry of the chip at every moment. This knowledge is important for understanding the achieved material removal mechanism, it allows to estimate the loading of the tool and the conditions in which machining is performed. From this first geometric modeling, modeling of cutting forces was established. For this, a model of mechanistic type of effort was used. Its application was adapted to orbital drilling in order to best represent the operation. The thus modeled efforts were compared to those observed experimentally in order to validate the proposed model. This allowed to consider the use of this model for a better understanding of this material removal process. The influence of model inputs, namely the cutting conditions and tool geometry was studied. Another contribution of this work is the characterization of the orbital drilling of CFRP stacks / Ti6Al4V. Indeed, many tests were developed to characterize the orbital drilling process. Experimental procedures have therefore been put in place. First of all, the instrumented test means had to be characterized so that it better corresponds to the means used by the manufacturer and above all it allows to carry out reliable and repeatable testing. The experimental design implemented subsequently helped to define the influence of cutting parameters on the efforts and realized diameters. In this phase of characterization, the bore in errors have also been studied. Thus, the trends have been observed. The results obtained in this work in the meeting helped to consider the process optimization of routes, through the control of advances, the drilling strategy, but also the geometry of the tool. Tracks have been proposed and are subject to further study. modeling implementation and the identification of phenomena occurring during the operation have also laid the foundation for process monitoring. This can be considered passively, to monitor the smooth running of the operation, but also actively to act in real time to the control of the process, based on identified phenomena, to ensure the desired quality.

Made available in DSpace on 2016-08-29T15:36:37Z (GMT). No. of bitstreams: 1 tese_7192_Franciane Louzada.pdf: 3423474 bytes, checksum: 8d995c834302f420f1480045227459b6 (MD5) Previous issue date: 2016-02-29 / CAPES / A precipitação é importante para calcular a disponibilidade hídrica de uma região e a qualidade desses dados pode afetar os resultados do balanço hídrico. Portanto, dados com melhor cobertura espacial são necessários. O satélite Tropical Rainfall Measuring Mission TRMM, produto 3B43-v7, estima a precipitação com resolução espacial de 0,25° x 0,25°. O objetivo deste trabalho foi avaliar os dados de precipitação estimados pelo 3B43-v7 e seu potencial uso na elaboração do balanço hídrico climatológico para a bacia hidrográfica do rio Doce. Foi gerado o mapeamento da disponibilidade hídrica pixel-a-pixel com boa cobertura espacial. Os dados do satélite foram comparados com os dados dos postos meteorológicos. Os erros relativos na estação chuvosa apresentaram melhores resultados do que na estação seca, que apresentou maiores porcentagens de erro. O satélite estimou adequadamente a precipitação, apresentando ótima correlação com os postos meteorológicos e respondendo a sazonalidade do clima da região nas estações de seca e chuvosa. Entretanto, apresentou tendência a superestimar a precipitação. O balanço hídrico climatológico com o 3B43-v7 apresentou correlação acima de 0,82. Os maiores erros percentuais foram encontrados em postos na região sudeste e nordeste da bacia (no Baixo Doce e Médio Doce). Os dados do 3B43-v7 caracterizou o balanço hídrico climatológico de forma semelhante aos dados observados pelos postos meteorológicos. A precipitação estimada pelo 3B43-v7 proporcionou a realização do balanço hídrico climatológico dessa bacia com boa cobertura. A utilização dos dados de precipitação estimados pelo 3B43-v7 pode ser uma ferramenta importante na caracterização de disponibilidade hídrica regional, contribuindo para o planejamento e manejo agrícola, principalmente por preencher as lacunas deixadas devido à ausência de postos meteorológicos nessa bacia, disponibilizando um produto com boa cobertura espacial. / Rainfall is important to calculate water availability of a region and its quality may affect the results of the water balance. Therefore data source with better spatial coverage is needed. The Tropical Rainfall Measuring Mission satellite -TRMM 3B43-v7 product estimated precipitation with spatial resolution of 0.25 ° x 0.25 °. The objective of this study was to evaluate the rainfall data estimated by 3B43-v7 and its impact on climatic water balance, by Thornthwaite method and Mather (1955), to the watershed of the river Doce. Mapping was generated pixel-by-pixel water availability with good spatial coverage. Satellite data were compared with data from weather stations. The errors in the rainy season showed better results than in the dry season that had the highest error percentages. The satellite performed well, properly estimated the rainfall, showed excellent correlation with weather stations, said the seasonal climate of the area, but tended to overestimate precipitation. The climatic water balance with the 3B43-v7 showed good correlation with the observed. Errors may have had an influence of cold air masses that predominate in this period and the higher regions. The largest percentage errors were found in stations in the southeast and northeast of the basin (in the Baixo Doce and Médio Doce). The 3B43-v7 data characterized the climatic water balance in a manner similar to data collected by the meteorological stations. The rainfall estimated by 3B43-v7 provided the realization of climatic water balance of the basin with good coverage. The use of estimated rainfall data by 3B43-v7 can be an important tool in the characterization of regional water availability, contributing to the planning and agricultural management, mainly to fill the gaps left by the absence of weather stations in this basin, providing a product with good spatial coverage.