Selon la méthode utilisée pour construire un modèle structural en trois dimensions et selon l'application à laquelle il est destiné, son maillage, en d'autres termes sa représentation informatique, doit être adapté afin de respecter des critères de type, de nombre et de qualité de ses éléments. Les méthodes de maillage développées dans d'autres domaines que la géomodélisation ne permettent pas de modifier le modèle d'entrée. Ceci est souhaitable en géomodélisation afin de mieux contrôler le nombre d'éléments du maillage et leur qualité. L'objectif de cette thèse est de développer des méthodes de maillage permettant de remplir ces objectifs afin de gérer la complexité géométrique des modèles structuraux définis par frontières. Premièrement, une analyse des sources de complexité géométrique dans ces modèles est proposée. Les mesures développées constituent une première étape dans la définition d'outils permettant la comparaison objective de différents modèles et aident à caractériser précisément les zones plus compliquées à mailler dans un modèle. Ensuite, des méthodes originales de remaillage surfacique et de maillage volumique fondées sur l'utilisation des diagrammes de Voronoï sont proposées. Les fondements de ces deux méthodes sont identiques : (1) une optimisation de type Voronoï barycentrique est utilisée pour globalement obtenir un nombre contrôlé d’éléments de bonne qualité et (2) des considérations combinatoires permettant de construire localement le maillage final, éventuellement en modifiant le modèle initial. La méthode de remaillage surfacique est automatique et permet de simplifier un modèle à une résolution donnée. L'originalité de la méthode de maillage volumique est que les éléments générés sont de types différents. Des prismes et pyramides sont utilisés pour remplir les zones très fines du modèle, tandis que le reste du modèle est rempli avec des tétraèdres / Depending on the specific method used to build a 3D structural model, and on the exact purpose of this model, its mesh must be adapted so that it enforces criteria on element types, maximum number of elements, and mesh quality. Meshing methods developed for applications others than geomodeling forbid any modification of the input model, that may be desirable in geomodeling to better control the number of elements in the final mesh and their quality. The objective of this thesis is to develop meshing methods that fulfill this requirement to better manage the geometrical complexity of B-Rep geological structural models. An analysis of the sources of geometrical complexity in those models is first proposed. The introduced measures are a first step toward the definition of tools allowing objective comparisons of structural models and permit to characterize the model zones that are more complicated to mesh. We then introduce two original meshing methods based on Voronoi diagrams: the first for surface remeshing, the second for hybrid gridding. The key ideas of these methods are identical: (1) the use of a centroidal Voronoi optimization to have a globally controlled number of elements of good quality, and (2) combinatorial considerations to locally build the final mesh while sometimes modifying the initial model. The surface remeshing method is automatic and permits to simplify a model at a given resolution. The gridding method generates a hybrid volumetric mesh. Prisms and pyramids fill the very thin layers of the model while the remaining regions are filled with tetrahedra

在無線網狀網路(Wireless Mesh Network)中，每個節點須幫助相鄰節點轉送資料及提供使用者網路存取，例如WLAN(IEEE 802.11s)、WMAN(IEEE 802.16)等，皆可利用多跳接方式將資料轉送至通訊閘道器(Gateway)。在無線網狀網路中，常利用密集佈建的方式來解決通訊死角的問題。當網路節點的密度增加時，無線訊號的干擾也會增強，並且各節點的效能會顯著下降。 在本研究中，將利用幾何學概念，解決網路干擾問題，並提出拓樸重建演算法來重建路徑，使網路干擾達到最小化。我們試著最小化節點與節點間的干擾，以提升整體無線網狀網路效能。我們將網路問題轉換成幾何問題，並定義在幾何圖形中線段交錯問題，之後驗證在幾何圖形中是否有線段交錯的現象發生。若發生線段交錯時，則將此線段從幾何圖形中移除，並且利用三角化演算法將此區域線段重新規劃，使相鄰節點間的干擾最小。當網路拓樸建立完成後，我們利用標準差公式將干擾較大的連線移除，使得網路效能提升。上述測試線段交錯及三角化多邊形演算法可在時間複雜度O(n log n)內找到干擾最小的解。最後，我們將利用網路模擬器(Network Simulator)驗證所提出的方法是否能達到預期的系統效能指標。 / In wireless mesh networks, such as WLAN (IEEE 802.11s), WMAN (IEEE 802.16), etc., each node should forward packets of neighboring nodes toward gateway using multi-hop routing mechanism. In wireless mesh network, as the density of network nodes increases, the RF interference will increase and the throughput of each node will drop rapidly. In our research, we use the geometry to resolve the RF interference problem by rebuilding network topology. We try to minimize the interference between neighboring nodes and improve the throughput in wireless mesh network. We transform the network topology problem into geometry problem and define the line intersection problem in geometric graph, then check path intersection in the geometric graph. If line intersection occurs in the graph, we remove the intersection line from the graph and re-plan the region by triangulation algorithm. When the network topology is built up, we use a standard deviation formula to improve network performance by removing longer links. The line intersection algorithm and triangulation algorithm, both of time complexity O(n log n), are used to find the minimal interference solution. At the end of our research, we use network simulator to verify if the proposed methods can help to meet all those performance expectations.

Dans cette thèse, nous étudions les problèmes de reconstruction statique et dynamique à partir de vues multiples et texturation, en s'appuyant sur des applications réelles et pratiques. Nous proposons trois méthodes de reconstruction destinées à l'estimation d'une représentation d'une scène statique/dynamique à partir d'un ensemble d'images/vidéos. Nous considérons ensuite le problème de texturation multi-vues en se concentrant sur la qualité visuelle de rendu..

This thesis investigates the problem of robot navigation using only landmark bearings. The proposed system allows a robot to move to a ground target location specified by the sensor values observed at this ground target posi- tion. The control actions are computed based on the difference between the current landmark bearings and the target landmark bearings. No Cartesian coordinates with respect to the ground are computed by the control system. The robot navigates using solely information from the bearing sensor space. Most existing robot navigation systems require a ground frame (2D Cartesian coordinate system) in order to navigate from a ground point A to a ground point B. The commonly used sensors such as laser range scanner, sonar, infrared, and vision do not directly provide the 2D ground coordi- nates of the robot. The existing systems use the sensor measurements to localise the robot with respect to a map, a set of 2D coordinates of the objects of interest. It is more natural to navigate between the points in the sensor space corresponding to A and B without requiring the Cartesian map and the localisation process. Research on animals has revealed how insects are able to exploit very limited computational and memory resources to successfully navigate to a desired destination without computing Cartesian positions. For example, a honeybee balances the left and right optical flows to navigate in a nar- row corridor. Unlike many other ants, Cataglyphis bicolor does not secrete pheromone trails in order to find its way home but instead uses the sun as a compass to keep track of its home direction vector. The home vector can be inaccurate, so the ant also uses landmark recognition. More precisely, it takes snapshots and compass headings of some landmarks. To return home, the ant tries to line up the landmarks exactly as they were before it started wandering. This thesis introduces a navigation method based on reflex actions in sensor space. The sensor vector is made of the bearings of some landmarks, and the reflex action is a gradient descent with respect to the distance in sensor space between the current sensor vector and the target sensor vec- tor. Our theoretical analysis shows that except for some fully characterized pathological cases, any point is reachable from any other point by reflex action in the bearing sensor space provided the environment contains three landmarks and is free of obstacles. The trajectories of a robot using reflex navigation, like other image- based visual control strategies, do not correspond necessarily to the shortest paths on the ground, because the sensor error is minimized, not the moving distance on the ground. However, we show that the use of a sequence of waypoints in sensor space can address this problem. In order to identify relevant waypoints, we train a Self Organising Map (SOM) from a set of observations uniformly distributed with respect to the ground. This SOM provides a sense of location to the robot, and allows a form of path planning in sensor space. The navigation proposed system is analysed theoretically, and evaluated both in simulation and with experiments on a real robot.

My master´s thesis deals with use of astronomical levelling for creation of quasigeoid models. The basic input dates are componets of astronomical-geodetic deflections of the vertical in points, which are determined on AGNES and VEVEŘÍ nets. The dates are adjust for determination of relative quasigeoid. In literature [4], there is simplified solution for adjustment of this dates. The thesis looks for the most comprehensive solutions of adjustment without simplification. The solutions are compared.

The focus of this thesis is on facial biometrics; specifically in the problems of face detection and face recognition. Despite intensive research over the last 20 years, the technology is not foolproof, which is why we do not see use of face recognition systems in critical sectors such as banking. In this thesis, we focus on three sub-problems in these two areas of research. Firstly, we propose methods to improve the speed-accuracy trade-off of the state-of-the-art face detector. Secondly, we consider a problem that is often ignored in the literature: to decrease the training time of the detectors. We propose two techniques to this end. Thirdly, we present a detailed large-scale study on self-updating face recognition systems in an attempt to answer if continuously changing facial appearance can be learnt automatically. / L'objectiu d'aquesta tesi és sobre biometria facial, específicament en els problemes de detecció de rostres i reconeixement facial. Malgrat la intensa recerca durant els últims 20 anys, la tecnologia no és infalible, de manera que no veiem l'ús dels sistemes de reconeixement de rostres en sectors crítics com la banca. En aquesta tesi, ens centrem en tres sub-problemes en aquestes dues àrees de recerca. En primer lloc, es proposa mètodes per millorar l'equilibri entre la precisió i la velocitat del detector de cares d'última generació. En segon lloc, considerem un problema que sovint s'ignora en la literatura: disminuir el temps de formació dels detectors. Es proposen dues tècniques per a aquest fi. En tercer lloc, es presenta un estudi detallat a gran escala sobre l'auto-actualització dels sistemes de reconeixement facial en un intent de respondre si el canvi constant de l'aparença facial es pot aprendre de forma automàtica.