In the emerging arena of face-to-face collaboration using large, wall-size screens, a good videoconferencing system would be useful for two locations which both have a large screen. But as screens get bigger, a single camera becomes less than adequate to drive a videoconferencing system for the entire screen. Even if a wide-angle camera is placed in the center of the screen, it's possible for people standing at the sides to be hidden. We can fix this problem by placing several cameras evenly distributed in a grid pattern (what we call a sparse camera array) and merging the photos into one image. With a single camera, people standing near the sides of the screen are viewing an image with a viewpoint at the middle of the screen. Any perspective projection used in this system will look distorted when standing at a different viewpoint. If an orthogonal projection is used, there will be no perspective distortion, and the image will look correct no matter where the viewer stands. As a first step in creating this videoconferencing system, we use stereo matching to find the real world coordinates of objects in the scene, from which an orthogonal projection can be generated. / Master of Science

Susannah is the opera written and composed by American composer Carlisle Floyd in 1955. The opera is based on a story from the Biblical Apocrypha. For the live performance of this opera at the Jefferson Center in Roanoke, I designed the animations that projected onto a screen which was designed and fitted as a part of the set design. I created the series of animations that enhanced the story of the entire length of the opera. This project was in collaboration with Opera Roanoke's 2016-2017 season. Carlisle Floyd's Susannah was performed at the Jefferson Center in Roanoke, Virginia on April 28 and 30, 2017. / Master of Fine Arts / Susannah is the opera written and composed by American composer Carlisle Floyd in 1955. The opera is based on a story from the Biblical Apocrypha. Susannah’s story covers the issues of cultural, social, and religious beliefs. For the live performance of this opera at the Jefferson Center in Roanoke, I designed the animations that projected onto a screen which was designed and fitted as a part of the set design. I created the series of animations that enhanced the story of the entire length of the opera. This project was in collaboration with Opera Roanoke’s 2016-2017 season. Carlisle Floyd’s Susannah was performed at the Jefferson Center in Roanoke, Virginia on April 28 and 30, 2017. Opera Roanoke’s Principal Guest Conductor, Steven White led the Roanoke Symphony Orchestra and an outstanding cast, including Danielle Talamantes, a Virginia Tech grad, under the stage direction of Artistic Director, Scott Williamson.

Yes / Objectives: Unlike the technological advances in cross-sectional imaging, the adoption of CR and DR has been relatively overlooked in terms of the additional radiographer skills and competences required for optimal practice. Furthermore, projection radiography is often referred to as basic, plain or other words suggesting simplicity or entry-level skill requirements. Radiographers’ professional identity is connected with the discourse expressed via the language used in daily practice and consequently, if the perception of projection radiography is regarded as simple practice not requiring much reflection or complex decision-making, apathy and carelessness may arise. The purpose of this narrative review was to raise projection radiography from its longstanding lowly place and re-position it as a specialist imaging field. Key findings: Danish pre-registration radiography curricula contain little mention of projection radiography and a low proportion (n ¼ 17/144; 11.8%) of Danish radiography students chose to focus on projection radiography within publicly available BSc. theses between 2016 and 2020 as compared to topics related to CT and MRI (n ¼ 60/144; 41.7%). Conclusion: By changing how we as the profession perceive the role and position of projection radiography, we can start to rebuild its lost prestige and demand a greater, more detailed and clinically relevant educational offering from academic partners. For this to commence, the language and terminology we use to describe ourselves and tasks undertaken must reflect the complexity of the profession. Implications for practice: Regardless of imaging modality, every patient should be assured that a radiographer with expertise in acquiring images of diagnostic quality undertakes their examination. Reclaiming the prestige of projection radiography may lead students and radiographers to recognize projection radiography as a demanding specialist field for the benefit of the patients.

Ces dernières années ont été marquées par l’adoption en masse de XML comme format d’échange et de représentation des données stockées sur le web. Cette évolution s’est accompagnée du développement de langages pour l’interrogation et la manipulation des données XML et de la mise en œuvre de plusieurs systèmes pour le stockage et le traitement des ces dernières. Parmi ces systèmes, les moteurs mémoire centrale ont été développés pour faire face à des besoins spécifiques d’applications qui ne nécessitant pas les fonctionnalités avancées des SGBD traditionnels. Ces moteurs offrent les mêmes fonctionnalités que les systèmes traditionnels sauf que contrairement à ces derniers, ils nécessitent de charger entièrement les documents en mémoire centrale pour pouvoir les traiter. Par conséquent, ces systèmes sont limités quant à la taille des documents pouvant être traités. Dans cette thèse nous nous intéressons aux aspects liés à l’évolution des données XML et à la gestion de la dimension temporelle de celles-ci. Cette thèse comprend deux parties ayant comme objectif commun le développement de méthodes efficaces pour le traitement des documents XML volumineux en utilisant les moteurs mémoire centrale. Dans la première partie nous nous focalisons sur la mise à jour des documents XML statiques. Nous proposons une technique d’optimisation basée sur la projection XML et sur l’utilisation des schémas. La projection est une méthode qui a été proposée dans le cadre des requêtes afin de résoudre les limitations des moteurs mémoire centrale. Son utilisation pour le cas des mises à jour soulève de nouveaux problèmes liés notamment à la propagation des effets des mises à jour. La deuxième partie est consacrée à la construction et à la maintenance des documents temporels, toujours sous la contrainte d’espace. A cette contrainte s’ajoute la nécessité de générer des documents efficaces du point de vue du stockage. Notre contribution consiste en deux méthodes. La première méthode s’applique dans le cas général pour lequel aucune information n’est utilisée pour la construction des documents temporels. Cette méthode est conçue pour être réalisée en streaming et permet ainsi le traitement de document quasiment sans limite de taille. La deuxième méthode s’applique dans le cas où les changements sont spécifiés par des mises à jour. Elle utilise le paradigme de projection ce qui lui permet en outre de manipuler des documents volumineux de générer des documents temporels satisfaisant du point de vue du stockage. / The last decade has witnessed a rapid expansion of XML as a format for representing and exchanging data through the web. In order to follow this evolution, many languages have been proposed to query, update or transform XML documents. At the same time, a range set of systems allowing to store and process XML documents have been developed. Among these systems, main-memory engines are lightweight systems that are the favored choice for applications that do not require complex functionalities of traditional DBMS such as transaction management and secondary storage indexes. These engines require to loading the documents to be processed entirely into main-memory. Consequently, they suffer from space limitations and are not able to process quite large documents. In this thesis, we investigate issues related to the evolution of XML documents and to the management of the temporal dimension for XML. This thesis consists of two parts sharing the common goal of developing efficient techniques for processing large XML documents using main-memory engines. The first part investigates the optimization of update for static XML documents. We have developed a technique based on XML projection, a method that has been proposed to overcome the limitations of main-memory engines in the case of querying. We have devised for a new scenario for projection allowing the propagation of the updates effects. The second of the thesis investigates building and maintaining time-stamped XML documents under space limitations. Our contribution consists in two methods. The first method can be applied in the general case where no restriction is made on the evolution of the XML documents. This method is designed to be performed in streaming and allows thus processing large documents. The second method deals with the case where the changes are specified by updates. It is based on the projection paradigm which it allows it for processing large documents and for generating time-stamped documents satisfactory from the point of view of storage. We provide a means to comparing time-stamped wrt space occupancy.

My diploma thesis deals with parallel and central projections of surfaces and algorithmization of their creation. It gives information about differential geometry of surfaces. Basic terms are explained as well as methods how to derive parametrization of several types of surfaces. It is also devoted to projections - parallel and central projection. The thesis deals with calculation of projection of surface. The thesis deals with calculation of projection of surface and in special cases with calculation of its silhouette. There is the program documentation of implemented algorithms. The theory of anaglyphs and their creation by programs is included. 3D red cyan glasses are enclosed to the thesis as well as a CD containing the .pdf version of this thesis and file named "mfiles", which contains proposed functions. The thesis is meant to be used by teachers and students in teaching and studying descriptive geometry and mathematics. Powered by TCPDF (www.tcpdf.org)

Title: Stereoscopic Projection Author: Jana Vlachová Department: Department of Mathematics Education Supervisor: RNDr. Jana Hromadová, Ph.D. Supervisor's e-mail address: Jana.Hromadova@mff.cuni.cz Abstract: This graduation thesis deals with a special case of a double-central projection - the stereoscopic projection, whereas the position of the centres of projection and the projection plane is adjusted to the conditions of the human vision. The thesis introduces a brief historical development of the imaging and the stereoscopy itself, basic biological and optical characteristics of a human eye and vision and the principles of stereoscopic projection. Furthermore it occupies with the procedures of making stereoscopic drawings and photographs along with the methods of their observation and creating some necessary tools using generally available materials. The end of this thesis is devoted to the possibilities of not only practical usage of the stereoscopy, but mainly of its application in the descriptive geometry teaching. The thesis includes many stereoscopic pictures, some of them are viewable with the lens- glasses or the anaglyph-glasses accompanied in the end of this thesis. Keywords: double-central projection, stereoscopic projection, anaglyph

Reduzir a dimensão de bancos de dados é um passo importante em processos de reconhecimento de padrões e aprendizagem de máquina. Projection Pursuit (PP) tem emergido como uma técnica relevante para tal fim, a qual busca projeções dos dados em espaços de baixa dimensão onde estruturas interessantes sejam reveladas. Apesar do relativo sucesso de PP em vários problemas de redução dimensional, a literatura mostra uma aplicação limitada da mesma em bancos de dados com elevada quantidade de atributos e poucas amostras, tais como os gerados em biologia molecular. Nesta tese, estudam-se formas de aproveitar o potencial de PP em problemas de alta dimensão e poucas amostras a fim de facilitar a posterior construção de classificadores. Entre as principais contribuições deste trabalho tem-se: i) Sequential Projection Pursuit Modified (SPPM), um método de busca sequencial de espaços de projeção baseado em Algoritmo Genético (AG) e operadores de cruzamento especializados; ii) Block Sequential Projection Pursuit Modified (Block-SPPM) e Whitened Sequential Projection Pursuit Modified (W-SPPM), duas estratégias de aplicação de SPPM em problemas com mais atributos do que amostras, sendo a primeira baseada e particionamento de atributos e a segunda baseada em pré-compactação dos dados. Avaliações experimentais sobre bancos de dados públicos de expressão gênica mostraram a eficácia das propostas em melhorar a acurácia de algoritmos de classificação populares em relação a vários outros métodos de redução dimensional, tanto de seleção quanto de extração de atributos, encontrando-se que W-SPPM oferece o melhor compromisso entre acurácia e custo computacional. / Reducing the dimension of datasets is an important step in pattern recognition and machine learning processes. PP has emerged as a relevant technique for that purpose. PP aims to find projections of the data in low dimensional spaces where interesting structures are revealed. Despite the success of PP in many dimension reduction problems, the literature shows a limited application of it in dataset with large amounts of features and few samples, such as those obtained in molecular biology. In this work we study ways to take advantage of the potential of PP in order to deal with problems of large dimensionalities and few samples. Among the main contributions of this work are: i) SPPM, an improved method for searching projections, based on a genetic algorithm and specialized crossover operators; and ii) Block-SPPM and W-SPPM, two strategies of applying SPPM in problems with more attributes than samples. The first strategy is based on partitioning the attribute space while the later is based on a precompaction of the data followed by a projection search. Experimental evaluations over public gene-expression datasets showed the efficacy of the proposals in improving the accuracy of popular classifiers with respect to several representative dimension reduction methods, being W-SPPM the strategy with the best compromise between accuracy and computational cost.

La réalité mixte apporte certains avantages aux applications industrielles. Elle peut, entre autres, faciliter la visualisation et validation de projets ou assister des opérateurs durant des tâches spécifiques. Les systèmes de projection (PBS), tels que les CAVE ou la réalité augmentée spatiale, fournissent un environnement de réalité mixte permettant une collaboration directe avec des utilisateurs externes. Dans cette thèse, nous visons à améliorer l'utilisation des systèmes de projection pour des applications industrielles en abordant deux défis majeurs: (1) améliorer les composantes techniques des PBS et (2) augmenter l'expérience utilisateur dans les PBS. En tant que premier défi technique, nous visons à améliorer les systèmes de suivi de mouvements optiques. Nous proposons une approche permettant d’élargir l’espace de travail de ces systèmes grâce à deux méthodes. La première permet de suivre les mouvements à partir d’une seule caméra tandis ce que la deuxième permet de contrôler les caméras et suivre les objets dans l’espace de travail. Le système qui en résulte fournit des performances acceptables pour des applications en réalité mixte tout en augmentant considérablement l'espace de travail. Un tel système de suivi de mouvement peut permettre de mieux exploiter le potentiel des systèmes de projection et d’élargir le champ possible des interactions. En tant que deuxième défi technique, nous concevons un casque « tout-en-un » pour la réalité augmentée spatiale mobile. Le casque rassemble à la fois un système de projection et un système de suivi de mouvements qui sont embarqués sur la tête de l'utilisateur. Avec un tel système, les utilisateurs sont capables de se déplacer autour d'objets tangibles et de les manipuler directement à la main tout en projetant du contenu virtuel par-dessus. Nous illustrons notre système avec deux cas d'utilisation industriels: le prototypage virtuel et la visualisation médicale. Enfin, nous abordons le défi qui vise à améliorer l’expérience utilisateur dans les PBS. Nous proposons une approche permettant d’incarner un personnage virtuel et d’augmenter la perception spatiale des utilisateurs dans les PBS. Pour ce faire, nous ajoutons l’ombre virtuelle des utilisateurs dans les systèmes de projection immersifs. L'ombre virtuelle est directement corrélée aux mouvements des utilisateurs afin qu'ils la perçoivent comme si c'était la leur. Nous avons effectué une expérience afin d'étudier l'influence de la présence de l'ombre virtuelle sur le comportement des utilisateurs. / Mixed reality brings some advantages to industrial applications. It can, among others, facilitate visualizing and validating projects or assist operators during specific tasks. Projection-based Systems (PBS), such as CAVEs or spatial augmented reality provide a mixed reality environment enabling straightforward collaboration with external users. In this thesis, we aim at improving the usage of PBS for industrial applications by considering two main challenges: (1) improving the technical components of PBS and (2) improving the user experience when using PBS. As a first technical challenge, we propose to address the improvement of the tracking component. We introduce an approach that enables increasing the workspace of optical tracking systems by using two methods. As a first method, we propose to use monocular tracking. As a second method, we propose to use controlled cameras that follow the targets across the workspace. The resulting system provides acceptable performances for mixed reality applications while considerably increasing the workspace. Such a tracking system can make it easier to use large projection-based displays and can widen the range of available interactions. As a second technical challenge, we design an “all-in-one” headset for mobile spatial augmented reality on tangible objects. The headset gathers both a projection and a tracking system that are embedded on the user’s head. With such a system, the users are able to move around tangible objects and to manipulate them directly by hand while projecting virtual content over them. We illustrate our system with two industrial use cases: virtual prototyping and medical visualization. Finally, we address the challenge that aims at improving the user experience when using PBS. We introduce a method that provides virtual embodiment and increases the spatial perception of the users when using PBS. To do so we add the user’s virtual shadow in immersive projection-based systems. The virtual shadow is dynamically mapped to users’ movements in order to make them perceive the shadow as if it was their own. We then carry out an experiment to study the influence of the presence of the virtual shadow on the user experience and behavior.

Avec la croissance importante du besoin d'analyser une grande masse de données structurées tels que les composés chimiques, les structures de protéines ou même les réseaux sociaux, la fouille de sous-graphes fréquents est devenue un défi réel en matière de fouille de données. Ceci est étroitement lié à leur nombre exponentiel ainsi qu'à la NP-complétude du problème d'isomorphisme d'un sous-graphe général. Face à cette complexité, et pour gérer cette taille importante de l'espace de recherche, les méthodes classiques de fouille de graphes ont exploré des heuristiques de recherche basées sur le support, le langage de description des exemples (limitation aux chemins, aux arbres, etc.) ou des hypothèses (recherche de sous-arborescence communes, de chemins communs, etc.). Dans le cadre de cette thèse, nous nous basons sur une méthode d'appariement de graphes issue du domaine de la programmation par contraintes, nommée AC-projection, qui a le mérite d'avoir une complexité polynomiale. Nous introduisons des approches de fouille de graphes permettant d'améliorer les approches existantes pour ce problème. En particulier, nous proposons deux algorithmes, FGMAC et AC-miner, permettant de rechercher les sous-graphes fréquents à partir d'une base de graphes. Ces deux algorithmes profitent, différemment, des propriétés fortes intéressantes de l'AC-projection. En effet, l'algorithme FGMAC adopte un parcours en largeur de l'espace de recherche et exploite l'approche par niveau introduite dans Apriori, tandis que l'algorithme AC-miner parcourt l'espace en profondeur par augmentation de motifs, assurant ainsi une meilleure mise à l'échelle pour les grands graphes. Ces deux approches permettent l'extraction d'un type particulier de graphes, il s'agit de celui des sous-graphes AC-réduits fréquents. Dans un premier temps, nous prouvons, théoriquement, que l'espace de recherche de ces sous-graphes est moins important que celui des sous-graphes fréquents à un isomorphisme près. Ensuite, nous menons une série d'expérimentations permettant de prouver que les algorithmes FGMAC et AC-miner sont plus efficients que ceux de l'état de l'art. Au même temps, nous prouvons que les sous-graphes AC-réduits fréquents, en dépit de leur nombre sensiblement réduit, ont le même pouvoir discriminant que les sous-graphes fréquents à un isomorphisme près. Cette étude est menée en se basant sur une évaluation expérimentale de la qualité des sous-graphes AC-réduits fréquents dans un processus de classification supervisée de graphes. / With the important growth of requirements to analyze large amount of structured data such as chemical compounds, proteins structures, social networks, to cite but a few, graph mining has become an attractive track and a real challenge in the data mining field. Because of the NP-Completeness of subgraph isomorphism test as well as the huge search space, frequent subgraph miners are exponential in runtime and/or memory use. In order to alleviate the complexity issue, existing subgraph miners have explored techniques based on the minimal support threshold, the description language of the examples (only supporting paths, trees, etc.) or hypothesis (search for shared trees or common paths, etc.). In this thesis, we are using a new projection operator, named AC-projection, which exhibits nice complexity properties as opposed to the graph isomorphism operator. This operator comes from the constraints programming field and has the advantage of a polynomial complexity. We propose two frequent subgraph mining algorithms based on the latter operator. The first one, named FGMAC, follows a breadth-first order to find frequent subgraphs and takes advantage of the well-known Apriori levelwise strategy. The second is a pattern-growth approach that follows a depth-first search space exploration strategy and uses powerful pruning techniques in order to considerably reduce this search space. These two approaches extract a set of particular subgraphs named AC-reduced frequent subgraphs. As a first step, we have studied the search space for discovering such frequent subgraphs and proved that this one is smaller than the search space of frequent isomorphic subgraphs. Then, we carried out experiments in order to prove that FGMAC and AC-miner are more efficient than the state-of-the-art algorithms. In the same time, we have studied the relevance of frequent AC-reduced subgraphs, which are much fewer than isomorphic ones, on classification and we conclude that we can achieve an important performance gain without or with non-significant loss of discovered pattern's quality.

Dans cette étude, la technologie de la projection à froid a été utilisée pour réaliser des projections de bronze et ses composites de manière à obtenir un revêtement qui possède bonnes performances en frottement. Les recherches suivantes ont été exécutées dans ce travail à savoir : -la fabrication, la sélection et le post-traitement des poudres de bronzes et de quasicrystaux : -la réalisation de revêtements de bronze et ses composites ; -l'analyses des performances en frottement des revêtements fabriqués ; -la comparaison des caractéristiques et des comportements en frottement entre les revêtements fabriqués par la projection à froid et par la projection thermique conventionnelle. Les résultats montrent que la projection à froid peut être une technologie fiable pour réaliser des revêtements composites à base de bronze, la transformation de phase et l'oxydation qui sont associées aux revêtements fabriqués par les autres techniques de projection thermique conventionnelle peuvent être évitées ou atténuées efficacement par utilisation du procédé de projection à froid, le revêtement composite présente une meilleure propriété tribologique par rapport aux revêtements de bronzes seuls. Les performances en frottement des revêtements fabriqués par projection à froid sont comparables à celles des revêtements fabriqués par projection thermique.