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Itier, Vincent. "Nouvelles méthodes de synchronisation de nuages de points 3D pour l'insertion de données cachées." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS017/document.
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Cette thèse aborde les problèmes liés à la protection de maillages d'objets 3D. Ces objets peuvent, par exemple, être créés à l'aide d'outil de CAD développés par la société STRATEGIES. Dans un cadre industriel, les créateurs de maillages 3D ont besoin de disposer d'outils leur permettant de vérifier l'intégrité des maillages, ou de vérifier des autorisations pour l'impression 3D par exemple. Dans ce contexte nous étudions l'insertion de données cachées dans des maillages 3D. Cette approche permet d'insérer de façon imperceptible et sécurisée de l'information dans un maillage. Il peut s'agir d'un identifiant, de méta-informations ou d'un contenu tiers, par exemple, pour transmettre de façon secrète une texture. L'insertion de données cachées permet de répondre à ces problèmes en jouant sur le compromis entre la capacité, l'imperceptibilité et la robustesse. Généralement, les méthodes d'insertion de données cachées se composent de deux phases, la synchronisation et l'insertion. La synchronisation consiste à trouver et ordonner les éléments disponibles pour l'insertion. L'un des principaux challenges est de proposer une méthode de synchronisation 3D efficace qui définit un ordre sur les composants des maillages. Dans nos travaux, nous proposons d'utiliser les sommets du maillage, plus précisément leur représentation géométrique dans l'espace comme composants de base pour la synchronisation et l'insertion. Nous présentons donc trois nouvelles méthodes de synchronisation de la géométrie des maillages basées sur la construction d'un chemin hamiltonien dans un nuage de sommets. Deux de ces méthodes permettent de manière conjointe de synchroniser les sommets et de cacher un message. Cela est possible grâce à deux nouvelles méthodes d'insertion haute capacité (de $3$ à $24$ bits par sommet) qui s'appuient sur la quantification des coordonnées. Dans ces travaux nous mettons également en évidence les contraintes propres à ce type de synchronisation. Nous discutons des différentes approches proposées dans plusieurs études expérimentales. Nos travaux sont évalués sur différents critères dont la capacité et l'imperceptibilité de la méthode d'insertion. Nous portons également notre attention aux aspects sécurité des méthodesThis thesis addresses issues relating to the protection of 3D object meshes. For instance, these objects can be created using CAD tool developed by the company STRATEGIES. In an industrial context, 3D meshes creators need to have tools in order to verify meshes integrity, or check permission for 3D printing for example.In this context we study data hiding on 3D meshes. This approach allows us to insert information in a secure and imperceptible way in a mesh. This may be an identifier, a meta-information or a third-party content, for instance, in order to transmit secretly a texture. Data hiding can address these problems by adjusting the trade-off between capacity, imperceptibility and robustness. Generally, data hiding methods consist of two stages, the synchronization and the embedding. The synchronization stage consists of finding and ordering available components for insertion. One of the main challenges is to propose an effective synchronization method that defines an order on mesh components. In our work, we propose to use mesh vertices, specifically their geometric representation in space, as basic components for synchronization and embedding. We present three new synchronisation methods based on the construction of a Hamiltonian path in a vertex cloud. Two of these methods jointly perform the synchronization stage and the embedding stage. This is possible thanks to two new high-capacity embedding methods (from 3 to 24 bits per vertex) that rely on coordinates quantization. In this work we also highlight the constraints of this kind of synchronization. We analyze the different approaches proposed with several experimental studies. Our work is assessed on various criteria including the capacity and imperceptibility of the embedding method. We also pay attention to security aspects of the proposed methods
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Parisot, Pascaline. "Suivi d’objets dans des séquences d’images de scènes déformables : de l’importance des points d’intérêt et du maillage 2D." Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT012H/document.
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Nous abordons le suivi d’objets dans des séquences d’images de scènes déformables selon deux axes de recherche. Il s’agit de déterminer les transformations d’un objet, d’une image à l’autre, lorsque celui-ci s’est éventuellement déformé ou déplacé et lorsque le point de vue de la caméra a éventuellement été modifié (déplacement, zoom...). Pour cela, nous nous sommes inspirés de l’algorithme de Jurie et Dhome qui permet de suivre un objet plan indéformable. D’une part, nous en améliorons les performances. D’autre part, nous le généralisons au cas d’objets déformables. Le premier axe de recherche consiste à améliorer les performances de l’algorithme de Jurie et Dhome en termes de précision et robustesse. Le suivi s’appuie sur un ensemble de points d’intérêt, dont dépendent fortement les performances. Ces points d’intérêt sont issus d’une sélection des points obtenus par des détecteurs reconnus, à savoir SIFT, KLT, SUSAN, HARRIS et MORAVEC. Nous avons étudié et mis en oeuvre, sur différentes classes d’images, des heuristiques de sélection fondées sur des approches statistique et algébrique. Nous montrons : – qu’il n’existe pas de détecteur universel, – que l’approche statistique est à privilégier dans tous les cas. Le second axe de recherche est une proposition d’un nouvel algorithme de suivi s’appuyant sur le maillage 2D des images de la séquence. Cet algorithme généralise celui de Jurie et Dhome aux scènes déformables. Il repose sur : – des transformations élémentaires (nodales) du maillage, directes et inverses, que nous avons caractérisées tant d’un point de vue géométrique qu’analytique, – l’utilisation des coordonnées barycentriques généralisées pour approcher la composition de deux transformations d’un maillage. Cet algorithme donne des résultats similaires à celui d’appariement hexagonal de Nakaya et Harashima tout en étant plus rapideWe deal with object tracking in videos of non-rigid scenes with two main purposes. We aim at determining the transformations of an object, from one frame to the next, when it may be distorted or moved and when the camera focus may change (movement, zoom...). To do this, we were inspired by the Jurie and Dhome algorithm, which enables the tracking of plane rigid objects. On the one hand, we improve its performance. On the other hand, we generalize it to non-rigid objects. The first goal consists in improving the performance of the Jurie and Dhome algorithm, in terms of accuracy and robustness. The tracking is based on a set of interest points, which has a great effect on the algorithm’s performance. These interest points come from a selection among the points extracted with some common detectors: SIFT, KLT, SUSAN, HARRIS, and MORAVEC.With various pictures classes, we have studied and implemented some selection heuristics based on statistical or algebraic approaches. We show that : • there is no universal detector, • the statistical approach is the best in all cases. The second goal is a proposal of a new tracking algorithm based on a 2D mesh of the video frames. This algorithm generalizes the Jurie and Dhome one for non-rigid scenes. It is based on : • elementary (nodal), direct or inverse, mesh transformations that we geometrically and analytically characterize, • generalized barycentric coordinates to approximate the composition of two mesh transformations. This algorithm gives similar results to the hexagonal matching algorithm of Nakaya and Harashima while being faster
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Loménie, Nicolas. "Interprétation de nuages de points : application à la modélisaion d'environnements 3D en robotique mobile." Phd thesis, Université René Descartes - Paris V, 2001. http://tel.archives-ouvertes.fr/tel-00136113.
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Cette thèse traite de l'analyse de nuages de points 3D désorganisé et s'appuie sur deux outils : un algorithme de partitionnement efficace inspiré des C-moyennes floues d'une part, et des outils de filtrage morphologique de représentation à base de triangulation de Delaunay d'autre part. Le cadre applicatif essentiel est la navigation autonome en robotique mobile en environnement inconnu, c'est-à-dire dans modèle. Mais la méthodologie générique développée a été appliquée à d'autres types d'environnements, notamment plus structurés.
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Akdag, Osman. "Incompressible Flow Simulations Using Least Squares Spectral Element Method On Adaptively Refined Triangular Grids." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614944/index.pdf.
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The main purpose of this study is to develop a flow solver that employs triangular grids to solve two-dimensional, viscous, laminar, steady, incompressible flows. The flow solver is based on Least Squares Spectral Element Method (LSSEM). It has p-type adaptive mesh refinement/coarsening capability and supports p-type nonconforming element interfaces. To validate the developed flow solver several benchmark problems are studied and successful results are obtained. The performances of two different triangular nodal distributions, namely Lobatto distribution and Fekete distribution, are compared in terms of accuracy and implementation complexity. Accuracies provided by triangular and quadrilateral grids of equal computational size are compared. Adaptive mesh refinement studies are conducted using three different error indicators, including a novel one based on elemental mass loss. Effect of modifying the least-squares functional by multiplying the continuity equation by a weight factor is investigated in regards to mass conservation.
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Ben, salah Imeen. "Extraction d'un graphe de navigabilité à partir d'un nuage de points 3D enrichis." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR070/document.
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Les caméras sont devenues de plus en plus communes dans les véhicules, les smartphones et les systèmes d'aide à la conduite ADAS (Advanced Driver Assistance Systèmes). Les domaines d'application de ces caméras dans le monde des systèmes intelligents de transport deviennent de plus en plus variés : la détection des piétons, les avertissements de franchissement de ligne, la navigation... La navigation basée sur la vision a atteint une certaine maturité durant ces dernières années grâce à l'utilisation de technologies avancées. Les systèmes de navigation basée sur la vision ont le considérable avantage de pouvoir utiliser directement les informations visuelles présentes dans l'environnement, sans devoir adapter le moindre élément de l'infrastructure. De plus, contrairement aux systèmes utilisant le GPS, ils peuvent être utilisés à l'extérieur ainsi qu'à l'intérieur des locaux et des bâtiments sans aucune perte de précision. C'est pour ces raisons que les systèmes basés sur la vision sont une bonne option car ils fournissent des informations très riches et précises sur l'environnement, qui peuvent être utilisées pour la navigation. Un axe important de recherche porte actuellement sur la cartographie qui représente une étape indispensable pour la navigation. Cette étape engendre une problématique de la gestion de la mémoire assez conséquente requise par ces systèmes en raison de la quantité d'informations importante collectées par chaque capteur. En effet, l'espace mémoire nécessaire pour accueillir la carte d'une petite ville se mesure en dizaines de GO voire des milliers lorsque l'on souhaite couvrir des espaces de grandes dimensions. Cela rend impossible son intégration dans un système mobile tel que les smartphones, les véhicules, les vélos ou les robots. Le défi serait donc de développer de nouveaux algorithmes permettant de diminuer au maximum la taille de la mémoire nécessaire pour faire fonctionner ce système de localisation par vision. C'est dans ce contexte que se situe notre projet qui consiste à développer un nouveau système capable de résumer une carte 3D qui contient des informations visuelles collectées par plusieurs capteurs. Le résumé sera un ensemble des vues sphériques permettant de garder le même niveau de visibilité dans toutes les directions. Cela permettrait aussi de garantir, à moindre coût, un bon niveau de précision et de rapidité lors de la navigation. La carte résumant l'environnement sera constituée d'un ensemble d'informations géométriques, photométriques et sémantiquesCameras have become increasingly common in vehicles, smart phones, and advanced driver assistance systems. The areas of application of these cameras in the world of intelligent transportation systems are becoming more and more varied : pedestrian detection, line crossing detection, navigation ... Vision-based navigation has reached a certain maturity in recent years through the use of advanced technologies. Vision-based navigation systems have the considerable advantage of being able to directly use the visual information already existing in the environment without having to adapt any element of the infrastructure. In addition, unlike systems using GPS, they can be used outdoors and indoors without any loss of precision. This guarantees the superiority of these systems based on computer vision. A major area of {research currently focuses on mapping, which represents an essential step for navigation. This step generates a problem of memory management quite substantial required by these systems because of the huge amount of information collected by each sensor. Indeed, the memory space required to accommodate the map of a small city is measured in tens of GB or even thousands when one wants to cover large spaces. This makes impossible to integrate this map into a mobile system such as smartphones , cameras embedded in vehicles or robots. The challenge would be to develop new algorithms to minimize the size of the memory needed to operate this navigation system using only computer vision. It's in this context that our project consists in developing a new system able to summarize a3D map resulting from the visual information collected by several sensors. The summary will be a set of spherical views allow to keep the same level of visibility in all directions. It would also guarantee, at a lower cost, a good level of precision and speed during navigation. The summary map of the environment will contain geometric, photometric and semantic information
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Vasiliauskienė, Lina. "Prisitaikančiosios baigtinių elementų strategijos plokštuminiams tamprumo teorijos uždaviniams." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2006. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2006~D_20060622_134743-74080.
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The advent of modern computer technologies provided a powerful tool in numerical simulations. One of the most frequently used method for the discretization of the physical domain is Finite element Method (FEM). One of the main problems in a finite element analysis is the adequacy of the finite element mesh. Since the quality of the finite element solution directly depends on the quality of meshes, the additional process to improve the quality of meshes is necessary for reliable finite element approximation. In order to perform quality-assessed numerical simulation, the adaptive finite element strategies have been developed. These strategies integrate the finite element analysis with error estimation and fully automatic mesh modification, user interaction with this process is limited by initial geometry data and possible error tolerance definition. The finite element solution, obtained during adaptive finite element strategy process, approximates quite good different engineering structures. Despite many works in this area the problem of the adequate finite element mesh is not fully solved and additional developments are needed in order to improve adaptive mesh refinement strategy process. The aim and tasks of the work – to obtain methodology for quality assessed discretization to finite elements for complex geometry engineering structures by adaptive finite element strategies. To realize this purpose the following scientific tasks have been dealt: to develop an automatic... [to full text]
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Santoso, Mas Simon. "Simulation d'écoulements fluides à partir de données réelles." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0011.
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Les nuages de points sont des objets mathématiques permettant de décrire de manière discrète des fonctions à plusieurs variables. Ils sont principalement utilisés dans le domaine statistique mais on les retrouve également en géométrie afin de représenter des variétés géométriques complexes. Il est aujourd'hui difficile d'intégrer les objets représentés par ces nuages de points dans des calculs éléments finis car l'intégration de ces nuages de points requiert la reconstruction de la variété ainsi que la génération d'un maillage surfacique qu'il faut intégrer dans un maillage volumique. Ces opérations sont souvent basées sur des processus itératifs et sont extrêmement coûteuses en temps car les nuages de points utilisés sont de très grande taille. La méthodologie développée dans cette thèse permet d'immerger des nuages de points dans un domaine maillé sans passer par les étapes de reconstruction de surface et de génération de maillage. On utilise la technique d'immersion de volume adaptée aux nuages de points. Cette technique est couplée avec une méthode d'adaptation de maillage. Cela nous permettra de générer un maillage anisotropique adapté autour des zones d'intérêt. On utilise ensuite la méthode variationnelle multi-échelle afin de simuler des écoulements fluides. Cette technique est une extension de la méthode éléments finis classique permettant de simuler des écoulements à forte convection et à haut nombre de Reynolds. La dernière partie de ce manuscrit présente quelques cas d'application dans le domaine aérodynamique, hydrodynamique et urbainsPoints clouds are mathematical objects that allows to describe discretely multivariable functions. They are mainly used in the statistical domain but also in geometrical manifolds. It is nowadays a real challenge to immerse the previous manifolds in finite element computation. Indeed, the immersion of those points clouds requires the reconstruction of the surface of the manifold and the generation of a surfacic mesh. As those operations are often based on an iterative process, they are extremely time-consuming as points clouds are usually massive. The method developed in this thesis allows to immerse points clouds in a meshed domain without the surface reconstruction and mesh generations steps. For that purpose, we use the Volume Immersion Method adapted to point clouds. We coupled this method with an adaped mesh generation technique. Then we are able to generate a monolithic anisotropic mesh, adapted around interest zones. We also use the variational multi-scale method to simulate fluid flow. This method is an extension of the classical finite element method and allows to simulate fluid flow. The last part of this thesis introduce some applications cases in the aerodynamic and urbans domains
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El, Sayed Abdul Rahman. "Traitement des objets 3D et images par les méthodes numériques sur graphes." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMLH19/document.
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La détection de peau consiste à détecter les pixels correspondant à une peau humaine dans une image couleur. Les visages constituent une catégorie de stimulus importante par la richesse des informations qu’ils véhiculent car avant de reconnaître n’importe quelle personne il est indispensable de localiser et reconnaître son visage. La plupart des applications liées à la sécurité et à la biométrie reposent sur la détection de régions de peau telles que la détection de visages, le filtrage d'objets 3D pour adultes et la reconnaissance de gestes. En outre, la détection de la saillance des mailles 3D est une phase de prétraitement importante pour de nombreuses applications de vision par ordinateur. La segmentation d'objets 3D basée sur des régions saillantes a été largement utilisée dans de nombreuses applications de vision par ordinateur telles que la correspondance de formes 3D, les alignements d'objets, le lissage de nuages de points 3D, la recherche des images sur le web, l’indexation des images par le contenu, la segmentation de la vidéo et la détection et la reconnaissance de visages. La détection de peau est une tâche très difficile pour différentes raisons liées en général à la variabilité de la forme et la couleur à détecter (teintes différentes d’une personne à une autre, orientation et tailles quelconques, conditions d’éclairage) et surtout pour les images issues du web capturées sous différentes conditions de lumière. Il existe plusieurs approches connues pour la détection de peau : les approches basées sur la géométrie et l’extraction de traits caractéristiques, les approches basées sur le mouvement (la soustraction de l’arrière-plan (SAP), différence entre deux images consécutives, calcul du flot optique) et les approches basées sur la couleur. Dans cette thèse, nous proposons des méthodes d'optimisation numérique pour la détection de régions de couleurs de peaux et de régions saillantes sur des maillages 3D et des nuages de points 3D en utilisant un graphe pondéré. En se basant sur ces méthodes, nous proposons des approches de détection de visage 3D à l'aide de la programmation linéaire et de fouille de données (Data Mining). En outre, nous avons adapté nos méthodes proposées pour résoudre le problème de la simplification des nuages de points 3D et de la correspondance des objets 3D. En plus, nous montrons la robustesse et l’efficacité de nos méthodes proposées à travers de différents résultats expérimentaux réalisés. Enfin, nous montrons la stabilité et la robustesse de nos méthodes par rapport au bruitSkin detection involves detecting pixels corresponding to human skin in a color image. The faces constitute a category of stimulus important by the wealth of information that they convey because before recognizing any person it is essential to locate and recognize his face. Most security and biometrics applications rely on the detection of skin regions such as face detection, 3D adult object filtering, and gesture recognition. In addition, saliency detection of 3D mesh is an important pretreatment phase for many computer vision applications. 3D segmentation based on salient regions has been widely used in many computer vision applications such as 3D shape matching, object alignments, 3D point-point smoothing, searching images on the web, image indexing by content, video segmentation and face detection and recognition. The detection of skin is a very difficult task for various reasons generally related to the variability of the shape and the color to be detected (different hues from one person to another, orientation and different sizes, lighting conditions) and especially for images from the web captured under different light conditions. There are several known approaches to skin detection: approaches based on geometry and feature extraction, motion-based approaches (background subtraction (SAP), difference between two consecutive images, optical flow calculation) and color-based approaches. In this thesis, we propose numerical optimization methods for the detection of skins color and salient regions on 3D meshes and 3D point clouds using a weighted graph. Based on these methods, we provide 3D face detection approaches using Linear Programming and Data Mining. In addition, we adapted our proposed methods to solve the problem of simplifying 3D point clouds and matching 3D objects. In addition, we show the robustness and efficiency of our proposed methods through different experimental results. Finally, we show the stability and robustness of our methods with respect to noise
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Bouchiba, Hassan. "Contributions en traitements basés points pour le rendu et la simulation en mécanique des fluides." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM076/document.
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Le nuage de points 3D est la donnée obtenue par la majorité des méthodes de numérisation surfacique actuelles. Nous nous intéressons ainsi dans cette thèse à l'utilisation de nuages de points comme unique représentation explicite de surface. Cette thèse présente deux contributions en traitements basés points. La première contribution proposée est une nouvelle méthode de rendu de nuages de points bruts et massifs par opérateurs pyramidaux en espace image. Cette nouvelle méthode s'applique aussi bien à des nuages de points d'objets scannés, que de scènes complexes. La succession d'opérateurs en espace image permet alors de reconstruire en temps réel une surface et d'en estimer des normales, ce qui permet par la suite d'en obtenir un rendu par ombrage. De plus, l'utilisation d'opérateurs pyramidaux en espace image permet d'atteindre des fréquences d'affichage plus élevées d'un ordre de grandeur que l'état de l'art .La deuxième contribution présentée est une nouvelle méthode de simulation numérique en mécanique des fluides en volumes immergés par reconstruction implicite étendue. La méthode proposée se base sur une nouvelle définition de surface implicite par moindres carrés glissants étendue à partir d'un nuage de points. Cette surface est alors utilisée pour définir les conditions aux limites d'un solveur Navier-Stokes par éléments finis en volumes immergés, qui est utilisé pour simuler un écoulement fluide autour de l'objet représenté par le nuage de points. Le solveur est interfacé à un mailleur adaptatif anisotrope qui permet de capturer simultanément la géométrie du nuage de points et l'écoulement à chaque pas de temps de la simulationMost surface 3D scanning techniques produce 3D point clouds. This thesis tackles the problem of using points as only explicit surface representation. It presents two contributions in point-based processing. The first contribution is a new raw and massive point cloud screen-space rendering algorithm. This new method can be applied to a wide variety of data from small objects to complex scenes. A sequence of screen-space pyramidal operators is used to reconstruct in real-time a surface and estimate its normals, which are later used to perform deferred shading. In addition, the use of pyramidal operators allows to achieve framerate one order of magnitude higher than state of the art methods. The second proposed contribution is a new immersed boundary computational fluid dynamics method by extended implicit surface reconstruction. The proposed method is based on a new implicit surface definition from a point cloud by extended moving least squares. This surface is then used to define the boundary conditions of a finite-elements immersed boundary transient Navier-Stokes solver, which is used to compute flows around the object sampled by the point cloud. The solver is interfaced with an anisotropic and adaptive meshing algorithm which refines the computational grid around both the geometry defined by point cloud and the flow at each timestep of the simulation
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Fang, Hao. "Modélisation géométrique à différent niveau de détails d'objets fabriqués par l'homme." Thesis, Université Côte d'Azur (ComUE), 2019. http://www.theses.fr/2019AZUR4002/document.
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La modélisation géométrique d'objets fabriqués par l'homme à partir de données 3D est l'un des plus grands défis de la vision par ordinateur et de l'infographie. L'objectif à long terme est de générer des modèles de type CAO de la manière la plus automatique possible. Pour atteindre cet objectif, des problèmes difficiles doivent être résolus, notamment (i) le passage à l'échelle du processus de modélisation sur des données d'entrée massives, (ii) la robustesse de la méthodologie contre des mesures d'entrées erronés, et (iii) la qualité géométrique des modèles de sortie. Les méthodes existantes fonctionnent efficacement pour reconstruire la surface des objets de forme libre. Cependant, dans le cas d'objets fabriqués par l'homme, il est difficile d'obtenir des résultats dont la qualité approche celle des représentations hautement structurées, comme les modèles CAO. Dans cette thèse, nous présentons une série de contributions dans ce domaine. Tout d'abord, nous proposons une méthode de classification basée sur l'apprentissage en profondeur pour distinguer des objets dans des environnements complexes à partir de nuages de points 3D. Deuxièmement, nous proposons un algorithme pour détecter des primitives planaires dans des données 3D à différents niveaux d'abstraction. Enfin, nous proposons un mécanisme pour assembler des primitives planaires en maillages polygonaux compacts. Ces contributions sont complémentaires et peuvent être utilisées de manière séquentielle pour reconstruire des modèles de ville à différents niveaux de détail à partir de données 3D aéroportées. Nous illustrons la robustesse, le passage à l'échelle et l'efficacité de nos méthodes sur des données laser et multi-vues stéréo sur des scènes composées d'objets fabriqués par l'hommeGeometric modeling of man-made objects from 3D data is one of the biggest challenges in Computer Vision and Computer Graphics. The long term goal is to generate a CAD-style model in an as-automatic-as-possible way. To achieve this goal, difficult issues have to be addressed including (i) the scalability of the modeling process with respect to massive input data, (ii) the robustness of the methodology to various defect-laden input measurements, and (iii) the geometric quality of output models. Existing methods work well to recover the surface of free-form objects. However, in case of manmade objects, it is difficult to produce results that approach the quality of high-structured representations as CAD models.In this thesis, we present a series of contributions to the field. First, we propose a classification method based on deep learning to distinguish objects from raw 3D point cloud. Second, we propose an algorithm to detect planar primitives in 3D data at different level of abstraction. Finally, we propose a mechanism to assemble planar primitives into compact polygonal meshes. These contributions are complementary and can be used sequentially to reconstruct city models at various level-of-details from airborne 3D data. We illustrate the robustness, scalability and efficiency of our methods on both laser and multi-view stereo data composed of man-made objects
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Lee, Kai-wah, and 李啟華. "Mesh denoising and feature extraction from point cloud data." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42664330.
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Cardote, André Amorim de Faria. "WiMax point-to-multipoint and mesh mode network planning." Master's thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/4003.
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Mestrado em Electrónica e TelecomunicaçõesNuma sociedade em que, crescentemente, utilizamos a Internet como meio de trabalho, lúdico ou simplesmente informativo, são necessários novos meios de levar esta tecnologia até todos, de maneira a que possamos tirar partido e evoluir com ela. Sendo a falta de cobertura dos actuais operadores de telecomunicações, em certas partes do território mais recônditas, um dos impedimentos para que toda a população possa ter ligação à Internet a preços acessíveis, o WiMAX surge como uma solução sem fios de banda larga com grande cobertura e baixo custo de implementação, que possibilita tanto o acesso directo por parte dos utilizadores como o funcionamento em modo de backhaul para redes Wi-Fi ou de outro tipo. O objecto de estudo desta dissertação é o planeamento de redes WiMAX ao nível físico, ou seja, a disposição dos diversos elementos constituintes da rede da melhor forma possível para maximizar a cobertura da rede ao menor custo. No âmbito deste trabalho foram efectuados diversos estudos ao nível de propagação de ondas para a tecnologia WiMAX e planeamento de redes ponto-multiponto e em malha. Foram desenvolvidos algoritmos que permitem o planeamento de redes em diversos cenários, tais como: acesso em zonas de grande densidade populacional, acesso em zonas longínquas, até onde se torna difícil a passagem de um cabo, ou mesmo cenários em que seja mais proveitoso utilizar o Wi-Fi como tecnologia de acesso para os utilizadores, ficando o WiMAX como tecnologia de backhaul. Foi também criado um mecanismo de posicionamento automático e optimizado dos componenentes de uma rede em malha. Como resultado do estudo realizado foram desenvolvidas com sucesso, a partir dos algoritmos estudados, duas aplicações para planeamento de redes WiMAX, uma em modo ponto-multiponto e outra em modo de malha, que serão devidamente apresentadas ao longo do texto. Utilizando as aplicações desenvolvidas, foi possível obter vários resultados que permitirão uma melhor compreensão e avaliação de redes WiMAX.
In a society where the Internet is increasingly used for working, playing or simply watching the news, new ways to get this technology to everyone are required, so that each and everyone can take part on this great global community. One of the major barriers for the widespread of the low-cost Internet is the unlikelihood to reach very remote locations of the territory. WiMAX appears as a promising broadband wireless access technology with low deployment cost and high coverage, allowing users to access directly to the network using this technology or providing backhaul connections for other technologies, such as Wi-Fi. The aim of this MSc thesis is the physical WiMAX network planning, i.e. the placement of the various elements of a network in order to maximize de coverage with the lowest cost. In the scope of this work, several studies in wave propagation for the WiMAX technology point-to-multipoint and mesh mode network planning were per- formed. Some algorithms that allow network planning in various scenarios, such as access in highly populated areas, isolated places, where it is hard to run a wire or even in scenarios where it is preferable to make the last mile access in Wi-Fi were developed, as well as a mechanism to select the positions of the elements in a WiMAX mesh network. As a result of this study two applications for WiMAX network planning were successfully developed, based on the formulated algorithms: one for point- to-multipoint mode and the other for mesh mode operation, which will be properly presented through this text. Using the developed applications, it has been possible to perform several essays that will allow a better comprehension and evaluation of WiMAX networks.
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Lee, Kai-wah. "Mesh denoising and feature extraction from point cloud data." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42664330.
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Šuľak, Andrej. "Rekonstrukce povrchu vozovky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401550.
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This thesis presents various approaches for race track surface reconstruction based on different algorithms designated for these purposes. In addition to surface reconstruction it also offers proposals for polygon mesh filling in the unscanned areas around the track.
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Wang, Yawen. "Torque Load Effect on Multi-Point Mesh and Dynamics of Right-angle Geared Drives." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384870250.
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Yanagita, Tamaki. "MESH-FREE MODELING OF ULTRASONIC FIELDS GENERATED BY TRANSDUCERS AND ACOUSTIC MICROSCOPES." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195234.
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With the gain in momentum of the structural health monitoring field in the last two decades, the popularity of ultrasonic nondestructive testing (NDT) has grown. However, ultrasonic NDT requires an expert to perform the testing and can be time consuming and costly when measured wave patterns in testing become extremely complex. A computer simulation of these tests can be utilized as a guide during actual evaluations or as a tool to train technicians. Presented in this dissertation is the development of models which simulate such acoustic phenomena as may arise in NDT. These models were developed using the distributed point source method (DPSM) for its proven capability to represent ultrasonic fields.Four sets of boundary conditions that arise from different types of commonly used acoustic transducers are modeled, enabling the visualization of the ultrasonic fields produced by the transducers. The transducer models exhibit good agreement with existing analytical solutions.In addition, the effect of a small cavity located at or near the focal point of an acoustic microscope is discussed. For this application the DPSM technique is modified so that inversion of a large global matrix is avoided, significantly improving the computational efficiency. The model shows that, as the pressure goes to zero, the velocity increases at the location of a cavity. Simulations demonstrate that the microscope is able to sense changes in position of the cavity by variations in the measured ratio of reflected to incident acoustic force.The field generated by an interferometric acoustic microscope is also presented. Qualitative agreement between the DPSM model and the experimental results of fields generated in a homogeneous fluid are obtained for a three-element lens. In the presence of a solid interface, the pressure on the edges of a converging beam near the fluid-solid interface is greater for a three-element lens than for single-element lens. A multi-element lens is also shown to exhibit oscillations in the pressure slightly above the interface.
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Brown, Steven W. "Interactive Part Selection for Mesh and Point Models Using Hierarchical Graph-cut Partitioning." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2420.pdf.
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Mbayi, Charles K. "Efficient Variable Mesh Techniques to solve Interior Layer Problems." University of Western Cape, 2020. http://hdl.handle.net/11394/7324.
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Philosophiae Doctor - PhDSingularly perturbed problems have been studied extensively over the past few years from different perspectives. The recent research has focussed on the problems whose solutions possess interior layers. These interior layers appear in the interior of the domain, location of which is difficult to determine a-priori and hence making it difficult to investigate these problems analytically. This explains the need for approximation methods to gain some insight into the behaviour of the solution of such problems. Keeping this in mind, in this thesis we would like to explore a special class of numerical methods, namely, fitted finite difference methods to determine reliable solutions. As far as the fitted finite difference methods are concerned, they are grouped into two categories: fitted mesh finite difference methods (FMFDMs) and the fitted operator finite difference methods (FOFDMs). The aim of this thesis is to focus on the former. To this end, we note that FMFDMs have extensively been used for singularly perturbed two-point boundary value problems (TPBVPs) whose solutions possess boundary layers. However, they are not fully explored for problems whose solutions have interior layers. Hence, in this thesis, we intend firstly to design robust FMFDMs for singularly perturbed TPBVPs whose solutions possess interior layers and to improve accuracy of these approximation methods via methods like Richardson extrapolation. Then we extend these two ideas to solve such singularly perturbed TPBVPs with variable diffusion coefficients. The overall approach is further extended to parabolic singularly perturbed problems having constant as well as variable diffusion coefficients.
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Liu, Yong-Jin. "Complex shape modeling with point sampled geometry /." View abstract or full-text, 2003. http://library.ust.hk/cgi/db/thesis.pl?MECH%202003%20LIUY.
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Joshi, Shriyanka. "Reverse Engineering of 3-D Point Cloud into NURBS Geometry." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1595849563494564.
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Azeredo, Daniel Mendes. "Simulação numérica de uma função indicadora de fluidos tridimensional empregando refinamento adaptativo de malhas." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/45/45132/tde-15082013-160020/.
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No presente trabalho, utilizou-se o Método da Fronteira Imersa, o qual utiliza dois tipos de malhas computacionais: euleriana (utilizada para o fluido) e lagrangiana (utilizada para representar a interface de separação de dois fluidos). O software livre GMSH foi utilizado para representar um sólido por meio da sua superfície externa e também para gerar uma malha triangular, bidimensional e não estruturada para discretizar essa superfície. Essa superfície foi utilizada como condição inicial para a malha lagrangiana (fronteira imersa). Os dados da malha lagrangiana são armazenados em uma estrutura de dados chamada Halfedge, a qual é largamente utilizada em Computação Gráfica para armazenar superfícies fechadas e orientáveis. Uma vez que a malha lagrangiana esteja armazenada nesta estrutura de dados, passa-se a estudar uma hipotética interação dinâmica entre a fronteira imersa e o escoamento do fluido. Esta interação é estudada apenas em um sentido, considera-se apenas a condição de não deslizamento, isto é, a fronteira imersa acompanhará passivamente um campo de velocidades pré-estabelecido (imposto), sem exercer qualquer força ou influência sobre ele. Foi utilizado um campo de distância local com sinal (função indicadora de fluidos) para identificar o interior e o exterior da superfície que representa a interface entre os fluidos. Este campo de distância é atualizado a cada passo no tempo utilizando idéias de Geometria Computacional, o que tornou o custo computacional para calcular esse campo otimal independente da complexidade geométrica da interface. Esta metodologia mostrou-se robusta e produz uma definição nítida das distintas fases dos fluidos em todos os passos no tempo. Para acompanhar e visualizar de forma mais precisa o comportamento dos fluidos na vizinhança da superfície que representa a interface de separação dos fluido, foi utilizado um algoritmo chamado de Refinamento Adaptativo de Malhas para fazer um refinamento dinâmico da malha euleriana na vizinhança da malha lagrangiana.The scientific motivation of the present work is the mathematical modeling and the computational simulation of multiphase flows. Specifically, the equations of a two-phase flow are written by combining the Immersed Boundary Method with a suitable fluid indicator function. It is assumed that the fluid equations are discretized on an Eulerian mesh covering completely the flow domain and that the interface between the fluid phases is discretized by a non-structured Lagrangian mesh formed by triangles. In this context, employing tools commonly found in Computational Geometry, the computation of the fluid indicator function is efficiently performed on a block-structured Eulerian mesh bearing dynamical refinement patches. Formed by a set of triangles, the Lagrangian mesh, which is initally generated employing the free software GMSH, is stored in a Halfedge data structure, a data structure which is widely used in Computer Graphics to represent bounded, orientable closed surfaces. Once the Lagrangian mesh has been generated, next, one deals with the hipothetical situation of dealing with the one-way dynamical interaction between the immersed boundary and the fluid flow, that is, considering the non-slip condition, only the action of the flow on the interface is studied. No forces arising on the interface affects the flow, the interface passively being advect with the flow under a prescribed, imposed velocity field. In particular, the Navier-Stokes equations are not solved. The fluid indicator function is given by a signed distance function in a vicinity of the immersed boundary. It is employed to identify interior/exterior points with respect to the bounded, closed region which is assumed to contain one of the fluid phases in its interior. The signed distance is update every time step employing Computational Geometry methods with optimal cost. Several examples in three dimensions, showing the efficiency and efficacy in the computation of the fluid indicator function, are given which employ the dynamical adaptive properties of the Eurlerian mesh for a moving interface.
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Raška, Martin. "Mobile IP v sítích MANET." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218096.
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This thesis discuss about the problem with mobility of stations in IP networks, concretely protocol Mobile IP and about the problems with this protocol in MANET networks, with the scope on Motorola MESH. First part is about design integration of protocol Mobile IP in this networks with usage Tropos 5210 MetroMesh routers and Cisco components (router, switch) to design and configure wireless MESH network, than connect this network with Cisco components and try to implement Mobile IP into this network. Second part is about design and configure wireless network from Cisco Wireless Access Points and about succesfully implementation of Mobile IP protocol into this network. In the last part is some tests of the function and quality of this topology.
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Ellyson, Laura Jean. "Resource Intensification of Small Game Use at Goodman Point, Southwestern Colorado." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699883/.
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This analysis of faunal remains from eleven archaeological sites in the northern San Juan region, extensively occupied by the Ancestral Pueblo people until they leave the region by AD 1300, explores the effects of resource intensification of small wild and domestic resources leading up to this regional depopulation. By examining multiple lines of evidence, in addition to faunal abundance, causal factors are identified to address changes in abundances through time. In particular, age- and sex-based mortality are examined for lagomorphs (jackrabbits and cottontails) and domesticated turkey, respectively, to test hypotheses generated using the prey and patch choice models. Analyses of these resources follow a systematic paleontology which provides explicit identifications made of five sites from a large study area, Goodman Point Pueblo Unit. These data are integrated with those from large village sites from the encompassing central Mesa Verde region. The results of both analyses help clarify why the Ancestral Pueblo people left southwestern Colorado. During the final twenty-year occupation period, the results of this study support a shift from reliance on turkey husbandry to intense exploitation of locally available garden resources (i.e. cottontails).
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Mojžyšek, Tomáš. "Možnosti vytvoření mračna bodů a síťového modelu místa dopravní nehody z fotografií." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-399590.
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The thesis focuses on creating point cloud and mesh model of chosen intersections and their applications in forensic-engineering praxis. In the first part, we describe a workflow for creating point cloud and mesh model of intersection by digital photogrammetry. In the second part, we applied these at chosen intersections. Which leads us to the comparison of three digital photogrammetric programs which we used to make point clouds and mesh models. At the end of thesis, we use our mesh models in forensic-engineering praxis and we decide about barriers in sign conditions at intersections.
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Kolářová, Eva. "Vliv přídavku vícesměrně orientované výztuže na mechanické vlastnosti materiálu pro přípravu celkově snímatelných náhrad." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-217087.
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Tato Diplomová práce se zabývá vlivem vyztužení na mechanické vlastnosti materiálu pro přípravu snímatelných náhrad. Pro testování byly použity tři sady vzorků: PMMA pryskyřice, PMMA pryskyřice s Dentapreg Mesh výztuží a PMMA pryskyřice vyztužena zesilující síťkou z nerezové oceli.Pro měření chování vzorků při statickém a dynamickém namáhání byl použit třibodový ohybový test a Charpy rázové kladivo. Viskoelastické vlastnostzi byly měřeny dynamicko-mechanickou analýzou (DMA). Skenovací elektronová mikroskopie (SEM) byla použita k charakterizaci lomových ploch. Během statického namáhání vzorků výztuž nehraje důležitou roli v porovnání s nevyztuženou pryskyřicí. Nicméně byl pozorován opačný trend při dymanickém namáhání, kde efekt výzruže rostl v řadě PMMA pryskyřice – síťka z nerezové oceli – Dentapreg Mesh.
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Lounsbury, Robert Lee. "Optimum antenna configuration for maximizing access point range of an IEEE 802.11 wireless mesh network in support of multi-mission operations relative to hastily formed scalable deployments." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Sep%5FLounsbury.pdf.
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Thesis (M.S. in Systems Technology (Command, Control, and Communications (C3)))--Naval Postgraduate School, September 2007.Thesis Advisor(s): Ehlert, James. "September 2007." Description based on title screen as viewed on Oct. 23, 2007. Includes bibliographical references (p. 85-86). Also available in print.
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Lounsbury, Jr Robert L. "Optimum Antenna Configuration for Maximizing Access Point Range of an IEEE 802.11 Wireless Mesh Network in Support of Multi-Mission Operations Relative to Hastily Formed Scalable Deployments." Ft. Belvoir : Defense Technical Information Center, 2007. http://handle.dtic.mil/100.2/ADA474138.
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Fier, Jeffrey Michael Keller Herbert Bishop Keller Herbert Bishop. "Part I. Fold continuation and the flow between rotating, coaxial disks. : Part II. Equilibrium chaos. Part III. A mesh selection algorithm for two-point boundary value problems /." Diss., Pasadena, Calif. : California Institute of Technology, 1985. http://resolver.caltech.edu/CaltechETD:etd-03262008-150456.
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Nyman, Jonas. "Faster Environment Modelling and Integration into Virtual Reality Simulations." Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-19800.
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The use of virtual reality in engineering tasks, such as in virtual commissioning, has increased steadily in recent years, where a robot, machine or object of interest can be simulated and visualized. Yet, for a more immerse experience, an environment for the object in question needs to be constructed. However, the process for creatingan accurate environment, for a virtual simulation have remained a costly and a long endeavour. Because of this, many digital simulations are performed, either with no environment at all, or present a very basic and abstract representation of an intended environment.The aim of this thesis is to investigate if technologies such as LiDAR and digital photogrammetry could shorten the environment creation process. Therefore, a demonstrative virtual environment was created and analysed, in which the different technologies was investigated and presented in the form of a comprehensive review of the current state of the technologies with in digital recreation. Lastly, a technique specific evaluation of the time requirement, cost and user difficulty was conducted. As the field of LiDAR and digital photogrammetry is too vast to investigate all forms thereof within one project, this thesis is limited to the investigation of static laser scanners and wide lens camera photogrammetry. A semi industrious locale was chosen for digital replication, which through static laser scans and photographs would generate semi-automated 3D models.The resulting 3D models leave much to be desired, as large holes were present throughout the 3D models, sincecertain surfaces are not suitable for neither replication processes. Transparent and reflective surfaces lead to ripple effects within the 3D models geometry and textures. Moreover, certain surfaces, as blank areas for photogrammetry or black coloration for laser scanners led to missing features and model distortions.Yet despite the abnormalities, the majority of the test environment was successfully re-created. An evaluation of the created environments was performed, which list and illustrate with tables and figures the attributes, strengths and weaknesses of each technique. Moreover, technique specific limitations and a spatial analysis was carried out. With the result, seemingly illustrating that photogrammetry creates more visually accurate 3D models in comparison to the laser scanner, yet the laser scanner produces a more spatially accurate result. As such, a selective combination of the techniques can be suggested.Observations and interviews seem to point towards the full scale application, in which an accurate 3D model is re-created without much effort, to currently not exist. As both photogrammetry and static laser scanning require great effort, skill and time in order to create a seemingly perfect solid model. Yet, utilizing either, or both techniques as a template for 3D object creation could reduce the time to create an environment significantly.Furthermore, methods such as digital 3D sculpting could be used in order to remove imperfections and create what is missing from the digitally constructed 3D models. Thereby achieving an accurate result.
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Ruest-Paquette, Anne-Sophie. "Le poids des représentations sociales: Les répercussions identitaires et sociales de mes expériences socioscolaires." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28103.
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Ce voyage autonarratif fait état des répercussions identitaires et sociales de mes expériences à titre de cible d'intimidation à l'école élémentaire (1986 à 1994) et secondaire (1994 à 1999), lesquelles étaient imbriquées des représentations sociales de la beauté féminine et des orientations sexuelles alternatives. La théorie de l'expérience de Dewey (1947/1968) en est l'encre puisqu'elle englobe tous les éléments qui sont essentiels à ma recherche: l'interaction et l'environnement social qui assurent la production, le développement et la reproduction des représentations sociales et des normes socioculturelles, l'expérience, dans laquelle s'inscrit l'intimidation, et la continuité de l'expérience qui renvoie aux processus que constituent la socialisation et la construction identitaire. Mes données (documents personnels, souvenirs, entretiens) ont fait l'objet d'une analyse de discours et témoignent de la multitude et de la complexité des enjeux liés à l'intimidation. Elles me permettent également d'approfondir notre compréhension du concept des marginalités multiples (Misa, 2006).
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Hoffman, Amy Susan. "Faunal Exploitation during the Depopulation of the Mesa Verde Region (A. D. 1300): A Case Study of Goodman Point Pueblo (5MT604)." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc84216/.
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This analysis of faunal remains from Goodman Point Pueblo (5MT604), a large village occupied just before the ancestral Puebloans permanently left southwestern Colorado at the end of the thirteenth century, explores the effect of dietary stress during abandonment in the Four Corners region. As archaeologists, we interpret what these former cultures were like and what resources they used through what they left behind. By specifically looking at faunal remains, or remains from food resources, environmental change and dietary stress can be assessed. Identifications of taxa identified at Goodman Point are made explicit via a systematic paleontology. This is followed by site-level taxonomic abundances and spatial analysis. Then, effects of technological innovations, environmental change, and sample quality are examined as alternate explanations of shifts in foraging efficiency, particularly related to animal hunting. Analyzing why and if the availability of faunal resources changes over time helps to clarify why the ancestral Puebloans left southwestern Colorado.
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Kjellén, Kevin. "Point Cloud Registration in Augmented Reality using the Microsoft HoloLens." Thesis, Linköpings universitet, Datorseende, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-148901.
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When a Time-of-Flight (ToF) depth camera is used to monitor a region of interest, it has to be mounted correctly and have information regarding its position. Manual configuration currently require managing captured 3D ToF data in a 2D environment, which limits the user and might give rise to errors due to misinterpretation of the data. This thesis investigates if a real time 3D reconstruction mesh from a Microsoft HoloLens can be used as a target for point cloud registration using the ToF data, thus configuring the camera autonomously. Three registration algorithms, Fast Global Registration (FGR), Joint Registration Multiple Point Clouds (JR-MPC) and Prerejective RANSAC, were evaluated for this purpose. It was concluded that despite using different sensors it is possible to perform accurate registration. Also, it was shown that the registration can be done accurately within a reasonable time, compared with the inherent time to perform 3D reconstruction on the Hololens. All algorithms could solve the problem, but it was concluded that FGR provided the most satisfying results, though requiring several constraints on the data.
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Winstead, Christy. "The Use of Faunal Remains for Identifying Shifts in Pit Structure Function in the Mesa Verde Region: a Case Study From Goodman Point." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc804909/.
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The archaeofaunal remains left by the Ancestral Puebloan people of Goodman Point Unit provides a valuable, yet underutilized resource into pit structure function. This thesis explores temporal changes in pit structure use and evaluates if a final feast occurred during a kiva decommissioning. The results from zooarchaeological analyses of a pithouse and two great kivas suggest that changes in pit structures at Goodman Point mimic the regional trend toward specialization until late Pueblo III. Cross-cultural studies on feasts, southwest ethnographies and previous zooarchaeological work established methods for identifying a feast. The analysis of differences in faunal remains from a great kiva and multiple room block middens imply that the remains in the kiva were from a final feast prior to a decommissioning ceremony and were not fill. Spatially and temporally the great kiva appears to be a unique, specialized structure in the cultural development of the Goodman Point community.
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Kroupa, Ondřej. "Digitální model reliéfu v areálu Admas." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-390213.
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The goal of this thesis is to scan part of the complex research center AdMaS using terrestrial laser scanner, from obtained data draw up a 3D terrain model and compare the height accuracy with conventional terrestrial measurement. The thesis is focused to software, which allow processing of point clouds and prepare the 3D model. The output of this work is the 3D terrain model and two transverse profiles for vertical comparison of two measurement methods.
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Silva, Alysson Alexander Naves. "Simulação numérica de escoamentos bidimensionais com superfícies livres e linhas de contato dinâmicas." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-22062010-145307/.
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Um método lagrangeano-euleriano arbitrário para a resolução de escoamentos dominados por tensão superficial é apresentado neste trabalho. Tais escoamentos são importantes em muitas aplicações, especialmente em canais capilares que frequentemente aparecem em escoamentos em microescala. A resolução deste tipo de escoamento apresenta vários desafios que são abordados neste trabalho. O escoamento é resolvido somente para a fase líquida, com condições de contorno apropriadas para a superfície livre que delimita o líquido e o gás, que é representada por arestas e vértices da malha computacional. Esta se move e se deforma, sendo que sua qualidade é mantida sob controle para não degradar a solução numérica. As equações de Navier-Stokes são discretizadas pelo método de elementos finitos em um referencial arbitrário. O método de incorporação dos efeitos de tensão superficial e linha de contato é explicado em detalhes. Validações comprovam a precisão do método proposto, com comparações através de soluções pseudo-analíticas para casos simples. Finalmente alguns resultados sobre escoamentos em capilares são apresentadosAn arbitrary lagrangian-eulerian finite element method to solve surface tension dominated flows is presented. Such flows are important in many applications, particularly in capillary channels, that appear in microscale flows. The resolution of such flows presents several challenges that are addressed in this work. The flow is solved only in the liquid phase, and proper boundary conditions are applied on the free-surface, bounding the liquid and gas, which is explicitly represented by vertices and edges of the computational mesh. The mesh is moved and deformed, but its quality is kept under control in order to control errors in the numerical solution. The Navier-Stokes equations are discretized by standard Galerkin finite element method in an arbitrary reference. Details of the computation of surface tension and contact line effects are presented. The methodology is validated for a number of simple test cases against known pseudo-analytical solutions, and numerical results are presented, showing the robustness and accuracy of the methodology. Finally, some results about surface-tension-driven flows in capillaries are presented
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Vitula, Marek. "Dokumentace části hradu Rokštejn pomocí laserového skenování." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-390174.
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The goal of this thesis is to scan part of castle Rokštejn using terrestrial laser scanner and from obtained data draw up a 3D model. Model is made with a method using meshing. In this work I also deal with the software, which supports meshing, and evaluating pros and cons of each program. The output of this work is 3D model which will serve to better representation of the current state of the castle and its better documentation.
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Brown, Andrew D. "Looking Outward from the Village: The Contingencies of Soil Moisture on the Prehistoric Farmed Landscape near Goodman Point Pueblo." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc862755/.
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Ancestral Pueblo communities of the central Mesa Verde region (CMVR) became increasingly reliant on agriculture for their subsistence needs during Basketmaker III (BMIII) through Terminal Pueblo III (TPIII) (AD 600–1300) periods. Researchers have been studying the Ancestral Pueblo people for over a century using a variety of methods to understand the relationships between climate, agriculture, population, and settlement patterns. While these methods and research have produced a well-developed cultural history of the region, studies at a smaller scale are still needed to understand the changes in farming behavior and the distribution of individual sites across the CMVR. Soil moisture is the limiting factor for crop growth in the semi-arid region of the Goodman Watershed in the CMVR. Thus, I constructed the soil moisture proxy model (SMPM) that is on a local scale and focuses on variables relevant to soil moisture – soil particle-size, soil depth, slope, and aspect. From the SMPM output, the areas of very high soil moisture are assumed to represent desirable farmland locations. I describe the relationship between very high soil moisture and site locations, then I infer the relevance of that relationship to settlement patterns and how those patterns changed over time (BMIII – TPIII). The results of the model and its application help to clarify how Ancestral Pueblo people changed as local farming communities. The results of this study indicates that farmers shifted away from use of preferred farmland during Terminal Pueblo III, which may have been caused by other cultural factors. The general outcome of this thesis is an improved understanding of human-environmental relationships on the local landscape in the CMVR.
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Yogeswaran, Arjun. "3D Surface Analysis for the Automated Detection of Deformations on Automotive Panels." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19992.
Full textAbstract:
This thesis examines an automated method to detect surface deformations on automotive panels for the purpose of quality control along a manufacturing assembly line.
Automation in the automotive manufacturing industry is becoming more prominent, but quality control is still largely performed by human workers. Quality control is important in the context of automotive body panels as deformations can occur along the assembly line such as inadequate handling of parts or tools around a vehicle during assembly, rack storage, and shipping from subcontractors. These defects are currently identified and marked, before panels are either rectified or discarded. This work attempts to develop an automated system to detect deformations to alleviate the dependence on human workers in quality control and improve performance by increasing speed and accuracy.
Some techniques make use of an ideal CAD model behaving as a master work, and panels scanned on the assembly line are compared to this model to determine the location of deformations. This thesis presents a solution for detecting deformations of various scales without a master work. It also focuses on automated analysis requiring minimal intuitive operator-set parameters and provides the ability to classify the deformations as dings, which are deformations that protrude from the surface, or dents, which are depressions into the surface.
A complete automated deformation detection system is proposed, comprised of a feature extraction module, segmentation module, and classification module, which outputs the locations of deformations when provided with the 3D mesh of an automotive panel. Two feature extraction techniques are proposed. The first is a general feature extraction technique for 3D meshes using octrees for multi-resolution analysis and evaluates the amount of surface variation to locate deformations. The second is specifically designed for the purpose of deformation detection, and analyzes multi-resolution cross-sections of a 3D mesh to locate deformations based on their estimated size. The performance of the proposed automated deformation detection system, and all of its sub-modules, is tested on a set of meshes which represent differing characteristics of deformations in surface panels, including deformations of different scales. Noisy, low resolution meshes are captured from a 3D acquisition, while artificial meshes are generated to simulate ideal acquisition conditions. The proposed system shows accurate results in both ideal situations as well as non-ideal situations under the condition of noise and complex surface curvature by extracting only the deformations of interest and accurately classifying them as dings or dents.
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Noreikis, Marius. "Image Based Indoor Navigation." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177344.
Full textAbstract:
Over the last years researchers proposed numerous indoor localisation and navigation systems. However, solutions that use WiFi or Radio Frequency Identification require infrastructure to be deployed in the navigation area and infrastructureless techniques, e.g. the ones based on mobile cell ID or dead reckoning suffer from large accuracy errors. In this Thesis, we present a novel approach of infrastructure-less indoor navigation system based on computer vision Structure from Motion techniques. We implemented a prototype localisation and navigation system which can build a navigation map using area photos as input and accurately locate a user in the map. In our client-server architecture based system, a client is a mobile application, which allows a user to locate her or his position by simply taking a photo. The server handles map creation, localisation queries and pathnding. After the implementation, we evaluated the localisation accuracy and latency of the system by benchmarking navigation queries and the model creation algorithm. The system is capable of successfully navigating in Aalto University computer science department library. We were able to achieve an average error of 0.26 metres for successfully localised photos. In the Thesis, we also present challenges that we solved to adapt computer vision techniques for localisation purposes. Finally we observe the possible future work topics to adapt the system to a wide use.Forskare har de senaste åren framfört olika inomhusnavigations- och lokaliseringssystem. Dock kräver lösningar som använder WiFi eller radiofrekvens identifikation en utbyggdnad av stödjande infrastruktur i navigationsområdena. Även teknikerna som används lider av precisionsfel. I det här examensarbetet redovisar vi en ny taktik för inomhusnavigation som använder sig av datorvisualiserings Structure from Motion-tekniker. Vi implementerade en navigationssystemsprototyp som använder bilder för att bygga en navigationskarta och kartlägga användarens position. I vårt klient-server baserat system är en klient en mobilapplikation som tillåter användaren att hitta sin position genom att ta en bild. På server-sidan hanteras kartor, lokaliseringsförfrågor och mättningar av förfrågorna och algoritmerna som används. Systemet har lyckats navigera genom Aalto Universitets datorvetenskapsbiblioteket. Vi lyckades uppnå en felmarginal pa 0.26 meter för lyckade lokaliseringsbilder. I arbetet redovisar vi utmaningar som vi har löst för att anpassa datorvisualiseringstekniker for lokalisering. Vi har även diskuterat potentialla framtida implementationer for att utvidga systemet.
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Tournier, Nicolas. "Synchronisation pour l'insertion de données dans des maillages 3D." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20221/document.
Full textAbstract:
De nos jours la protection des données numériques est un problème très important. Que ce soit pour des applications de confidentialité, de communication, de traçabilité ou d'identification par exemple, il est nécessaire de développer des techniques adaptées. Dans le cadre de cette thèse en collaboration avec la société STRATEGIES S.A., la méthode choisie pour la protection de maillages 3D est l'insertion de données cachées, également appelée tatouage numérique. Pour des données 3D, un des problèmes les plus importants est la phase de synchronisation qui intervient dans les algorithmes d'insertion et d'extraction des données. Cette phase permet de repérer, de sélectionner et d'ordonner les « zones » qui sont privilégiées pour la dissimulation d'information. Nous avons choisi d'orienter le manuscrit sur cette phase. Ainsi, nous proposons une classification des méthodes de tatouages en fonction de leur méthode de synchronisation. Puis en se basant sur des techniques de synchronisation par des structures de données, telle que les arbres couvrants de poids minimum, nous proposons une analyse théorique de cette structure. Dans un premier temps nous expliquons les raisons de la sensibilité des arbres à la mobilité des points. Puis connaissant ses faiblesses, nous proposons une autre technique de synchronisation toujours basée sur les arbres couvrants de poids minimumData security is one of the main issue in computer science. We need to develop solutions for confidentiality, communication, fingerprinting or identification applications for exemple. In this thesis made with STRATEGIES S.A., the chosen method to protect 3D meshes is watermarking.Watermarking is divided in two steps, the embedding and the extraction. In both of them a synchronization phase is needed. It is one of the most important step for 3D mesh because it permits to look for areas available to embed information, and order them. All the thesis is devoted to the synchronization step. First of all, we propose a classification of watermarking techniques based on the type of synchronization method instead of evaluation criterions such as robustness or capacity.Then, from methods based on Euclidean minimum spanning tree, we propose a theoritical analysis of the mobility of the vertices in that kind of structure. First, we explain the reasons of the sensibility of the structure. Secondly, we propose another scheme based on the Euclidean minimum spanning tree knowing its fragility
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Neeli, Yeshwanth Sai. "Use of Photogrammetry Aided Damage Detection for Residual Strength Estimation of Corrosion Damaged Prestressed Concrete Bridge Girders." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99445.
Full textAbstract:
Corrosion damage reduces the load-carrying capacity of bridges which poses a threat to passenger safety. The objective of this research was to reduce the resources involved in conventional bridge inspections which are an important tool in the condition assessment of bridges and to help in determining if live load testing is necessary. This research proposes a framework to link semi-automated damage detection on prestressed concrete bridge girders with the estimation of their residual flexural capacity. The framework was implemented on four full-scale corrosion damaged girders from decommissioned bridges in Virginia. 3D point clouds of the girders reconstructed from images using Structure from Motion (SfM) approach were textured with images containing cracks detected at pixel level using a U-Net (Fully Convolutional Network). Spalls were detected by identifying the locations where normals associated with the points in the 3D point cloud deviated from being perpendicular to the reference directions chosen, by an amount greater than a threshold angle. 3D textured mesh models, overlaid with the detected cracks and spalls were used as 3D damage maps to determine reduced cross-sectional areas of prestressing strands to account for the corrosion damage as per the recommendations of Naito, Jones, and Hodgson (2011). Scaling them to real-world dimensions enabled the measurement of any required dimension, eliminating the need for physical contact.
The flexural capacities of a box beam and an I-beam estimated using strain compatibility analysis were validated with the actual capacities at failure sections determined from four destructive tests conducted by Al Rufaydah (2020). Along with the reduction in the cross-sectional areas of strands, limiting the ultimate strain that heavily corroded strands can develop was explored as a possible way to improve the results of the analysis. Strain compatibility analysis was used to estimate the ultimate rupture strain, in the heavily corroded bottommost layer prestressing strands exposed before the box beam was tested. More research is required to associate each level of strand corrosion with an average ultimate strain at which the corroded strands rupture. This framework was found to give satisfactory estimates of the residual strength. Reduction in resources involved in current visual inspection practices and eliminating the need for physical access, make this approach worthwhile to be explored further to improve the output of each step in the proposed framework.Master of Science
Corrosion damage is a major concern for bridges as it reduces their load carrying capacity. Bridge failures in the past have been attributed to corrosion damage. The risk associated with corrosion damage caused failures increases as the infrastructure ages. Many bridges across the world built forty to fifty years ago are now in a deteriorated condition and need to be repaired and retrofitted. Visual inspections to identify damage or deterioration on a bridge are very important to assess the condition of the bridge and determine the need for repairing or for posting weight restrictions for the vehicles that use the bridge. These inspections require close physical access to the hard-to-reach areas of the bridge for physically measuring the damage which involves many resources in the form of experienced engineers, skilled labor, equipment, time, and money. The safety of the personnel involved in the inspections is also a major concern. Nowadays, a lot of research is being done in using Unmanned Aerial Vehicles (UAVs) like drones for bridge inspections and in using artificial intelligence for the detection of cracks on the images of concrete and steel members. Girders or beams in a bridge are the primary longitudinal load carrying members. Concrete inherently is weak in tension. To address this problem, High Strength steel reinforcement (called prestressing steel or prestressing strands) in prestressed concrete beams is pre-loaded with a tensile force before the application of any loads so that the regions which will experience tension under the service loads would be subjected to a pre-compression to improve the performance of the beam and delay cracking. Spalls are a type of corrosion damage on concrete members where portions of concrete fall off (section loss) due to corrosion in the steel reinforcement, exposing the reinforcement to the environment which leads to accelerated corrosion causing a loss of cross-sectional area and ultimately, a rupture in the steel. If the process of detecting the damage (cracks, spalls, exposed or severed reinforcement, etc.) is automated, the next logical step that would add great value would be, to quantify the effect of the damage detected on the load carrying capacity of the bridges. Using a quantified estimate of the remaining capacity of a bridge, determined after accounting for the corrosion damage, informed decisions can be made about the measures to be taken. This research proposes a stepwise framework to forge a link between a semi-automated visual inspection and residual capacity evaluation of actual prestressed concrete bridge girders obtained from two bridges that have been removed from service in Virginia due to extensive deterioration. 3D point clouds represent an object as a set of points on its surface in three dimensional space. These point clouds can be constructed either using laser scanning or using Photogrammetry from images of the girders captured with a digital camera. In this research, 3D point clouds are reconstructed from sequences of overlapping images of the girders using an approach called Structure from Motion (SfM) which locates matched pixels present between consecutive images in the 3D space. Crack-like features were automatically detected and highlighted on the images of the girders that were used to build the 3D point clouds using artificial intelligence (Neural Network). The images with cracks highlighted were applied as texture to the surface mesh on the point cloud to transfer the detail, color, and realism present in the images to the 3D model. Spalls were detected on 3D point clouds based on the orientation of the normals associated with the points with respect to the reference directions. Point clouds and textured meshes of the girders were scaled to real-world dimensions facilitating the measurement of any required dimension on the point clouds, eliminating the need for physical contact in condition assessment. Any cracks or spalls that went unidentified in the damage detection were visible on the textured meshes of the girders improving the performance of the approach. 3D textured mesh models of the girders overlaid with the detected cracks and spalls were used as 3D damage maps in residual strength estimation. Cross-sectional slices were extracted from the dense point clouds at various sections along the length of each girder. The slices were overlaid on the cross-section drawings of the girders, and the prestressing strands affected due to the corrosion damage were identified. They were reduced in cross-sectional area to account for the corrosion damage as per the recommendations of Naito, Jones, and Hodgson (2011) and were used in the calculation of the ultimate moment capacity of the girders using an approach called strain compatibility analysis. Estimated residual capacities were compared to the actual capacities of the girders found from destructive tests conducted by Al Rufaydah (2020). Comparisons are presented for the failure sections in these tests and the results were analyzed to evaluate the effectiveness of this framework. More research is to be done to determine the factors causing rupture in prestressing strands with different degrees of corrosion. This framework was found to give satisfactory estimates of the residual strength. Reduction in resources involved in current visual inspection practices and eliminating the need for physical access, make this approach worthwhile to be explored further to improve the output of each step in the proposed framework.
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Chater, Rabah. "Etude des antimonites MeSb 2 O 4 à basse température : évolution structurale, thermodynamique, propriétés élastiques et magnétiques anisotropes ; modélisation." Paris 6, 1986. http://www.theses.fr/1986PA066219.
Full textAbstract:
Etude par diffraction des RX et de neutrons, spectroscopie Raman et IR, chaleur massique, susceptibilité magnétique des antimonites (MNNifezn)sb2o4. Interprétation quantitative des anomalies de dilatation liées à Tltn dans le cas des composés de Ma et Fe. Définition d'un champ de force cohérent avec un potentiel de paires simplifié.
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Doležal, Jan. "Minimalizace vlivu rušení na bezdrátovou síť." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217521.
Full textAbstract:
This thesis is concerned the technology with technologies of transfer through wireless devices. It is about possibilities of optimization of transfer in wireless net, especially of the reduction of interference influence. The first part is about theory and the standards development of wireless technology. There are methods and principles used in wireless technologies. The second part is a practical measuring and testing of an internal wireless net, with the emphasis being on the source of interference influence. Measuring was focused on interference between access points and was not about meteorological influence. It continues with theory and testing of interference of the microwave oven in our wireless net. Then, it is a practical demonstration of interference in an external environment. There are practical examples of interference between different providers’ nets on the same area and solutions to prevent or to cancel this interference. In next part of work the wireless net is parsed and described in a given territory. Here is described the way how to precede the reciprocal interference and eventually how this mutual disturbance suppress. Consequently, our net is optimized for customer growth and for today’s options of newer and more powerful components for wireless transfer. Finally there are two laboratory tasks. The first one is about practical measuring and testing of wireless net’s parameters and the second one is about simulation of wireless networks in the Opnet program.
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Diouf, Abdoulaye. "Influence du régime des feux d'aménagement sur la structure ligneuse des savanes nord-soudaniennes dans le Parc du W, Sud Ouest Niger." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209610.
Full textAbstract:
L'équilibre arbre-herbe dans la savane tropicale est reconnu comme l'une des principalesénigmes de l'écologie des plantes. Les origines du difficile équilibre entre ces formes de vie
sur des dizaines de millions de kilomètres carrés à l'échelle mondiale sont en partie attribuées
aux perturbations fréquentes induites par les feux de végétation dont les effets varient dans
l'espace et dans le temps selon les conditions environnementales. Les résultats de recherche
dépendent de l’échelle et les conclusions tirées d’études locales sont rarement transposables à
d’autres échelles. La question du transfert d'échelle s’avère donc cruciale dans l'étude des
effets du feu, et nécessite une approche transdisciplinaire.
En raison de la variété des échelles couvertes, cette étude constitue une première dans la
confrontation de données sur l’historique des feux dérivé de l'imagerie satellitaire à des
données de terrain incluant des mesures détaillées sur la structure et la composition de
végétation, ainsi que des propriétés édaphiques et topographiques. Elle s’est focalisée sur la
composante ligneuse de par son caractère pérenne et son influence sur les processus
écologiques majeurs. Sur une zone de plus de 2000 km², le Parc National du W du Niger
(PNWN), où le feu est utilisé comme outil pour la gestion et la conservation des écosystèmes
semi-arides, une carte de l'historique des feux a été élaborée à partir d'images MODIS de 250
m de résolution spatiale et de résolution temporelle journalière couvrant une période de sept
années (2002-2009). Pour comprendre la variabilité, à la fois dans l'espace et le temps, de la
propagation du feu dans la végétation, nous avons étudié les caractéristiques de distribution
des feux en termes de régime du feu (i.e. période d'occurrence et fréquence) et de structure
spatiale (métriques paysagères). Les relations causales plausibles entre les régimes du feu, les
conditions édaphiques et topographiques à l'échelle régionale comme locale, et les
caractéristiques de la végétation ligneuse (composition et structure) ont été examinées à
travers des analyses multivariées et des modèles d'équations structurales. Nous avons aussi
examiné plus en détails les stratégies adaptatives mises en oeuvre par les ligneux, et les
interactions biologiques qui sous-tendent l'organisation spatiale des ligneux à travers une
approche des processus ponctuels.
Les résultats montrent que l'activité du feu dans le PNWN se caractérise par une hétérogénéité
spatio-temporelle induite principalement par les conditions édapho-topographiques via la
structure de la végétation ligneuse. Les feux précoces de gestion créent des pare-feux
efficaces, limitant une large extension des feux de saison tardifs. Cependant, ces feux tardifs
pourraient ne pas être aussi destructifs comme qu’on le suppose généralement. En effet,
l'adaptation des espèces aux différents régimes defeu correspond à des stratégies de croissance
contrastées. Dans le cas des feux tardifs, les surfaces terrières et hauteurs moyennes les plus
fortes sont rencontrées, permettant aux arbres de résister au feu. Quant aux zones non
affectées par les feux l'analyse "patron-processus" désigne clairement la facilitation entre
ligneux comme un processus fondamental de l'organisation spatiale périodique du couvert, une
structure émergente qui empêche le passage du feu. Bien qu’ils ne se substituent pas aux
études expérimentales, ces résultats basés sur une expérimentation naturelle à large échelle
apportent des informations nouvelles précieuses tant au niveau fondamental que pour la mise
en place d'une gestion raisonnée du PNWN.
The tree-grass equilibrium in tropical savanna is recognized as one of plant ecology's main
conundrums. The origins of the difficult balance between these life forms over tens of millions
of square kilometers worldwide are in part attributed to the frequent disturbances caused by
vegetation fires effects of which vary in space and time depending on local environmental
factors. Research results are scale-dependent and findings from local studies are rarely
transposable to higher levels of ecosystem organization. The question of scaling (scale
transfer) is therefore crucial in the study of fire effects, and requires a multidisciplinary
approach.
Because of the variety of scales covered, this study is a premiere in the confrontation of
satellite-imagery derived fire history data with detailed field data including measurements of
vegetation parameters (structure and composition), as well as soil and topographic properties.
The study focuses on the woody component, because of its perennial character and its
influence on major ecological processes. On an area of more than 2000 km², the W National
Park of Niger (WNPN) where fire is used as a tool for the management and conservation of
semi-arid ecosystems, a fire history map was elaborated from MODIS images with a 250 m
spatial resolution and a daily temporal resolution over a period of seven years (2002-2009). To
understand the variability, both in space and time, of fire propagation in vegetation, we studied
the fire distribution characteristics in terms of fire regime (i.e. timing and frequency) and
spatial structure (landscape metrics). Plausible causal relationships at regional and local scales
between fire regimes, edaphic and topographic conditions, and the woody vegetation
(composition and structure) characteristics were examined through multivariate analyses and
structural equations models. We also examined in detail the woody species adaptive strategies
as well biological interactions, which underlie their spatial organization, using point statistics.
Results show that the WNPN fire's activity is characterized by spatial and temporal
heterogeneity induced mainly by edaphic and topographic conditions via the structure of the
ligneous component. Prescribed early season fires create effective firewalls, limiting wide late
season fires. However, these late fires might not be as destructive as is commonly assumed.
Indeed, species adaptation to different fire regimes corresponds to contrasting growth
strategies. In the case of late fires, increased basal areas and mean tree heights were
encountered, enabling trees to resist fire and escape flames. As for the unburned areas, the
"pattern-process" analysis clearly indicates that facilitation between shrubs is a fundamental
process determining the woody cover periodic spatial organization, an emergent structure that
prevents fire spread.
Although they do not replace experimental studies, these results based on a large-scale natural
experiment provide valuable new information both on a fundamental level and for setting up
the rational management of the WNPN.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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"Robust and parallel mesh reconstruction from unoriented noisy points." 2009. http://library.cuhk.edu.hk/record=b5896897.
Full textAbstract:
Sheung, Hoi.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references (p. 65-70).
Abstract also in Chinese.
Abstract --- p.v
Acknowledgements --- p.ix
List of Figures --- p.xiii
List of Tables --- p.xv
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Main Contributions --- p.3
Chapter 1.2 --- Outline --- p.3
Chapter 2 --- Related Work --- p.5
Chapter 2.1 --- Volumetric reconstruction --- p.5
Chapter 2.2 --- Combinatorial approaches --- p.6
Chapter 2.3 --- Robust statistics in surface reconstruction --- p.6
Chapter 2.4 --- Down-sampling of massive points --- p.7
Chapter 2.5 --- Streaming and parallel computing --- p.7
Chapter 3 --- Robust Normal Estimation and Point Projection --- p.9
Chapter 3.1 --- Robust Estimator --- p.9
Chapter 3.2 --- Mean Shift Method --- p.11
Chapter 3.3 --- Normal Estimation and Projection --- p.11
Chapter 3.4 --- Moving Least Squares Surfaces --- p.14
Chapter 3.4.1 --- Step 1: local reference domain --- p.14
Chapter 3.4.2 --- Step 2: local bivariate polynomial --- p.14
Chapter 3.4.3 --- Simpler Implementation --- p.15
Chapter 3.5 --- Robust Moving Least Squares by Forward Search --- p.16
Chapter 3.6 --- Comparison with RMLS --- p.17
Chapter 3.7 --- K-Nearest Neighborhoods --- p.18
Chapter 3.7.1 --- Octree --- p.18
Chapter 3.7.2 --- Kd-Tree --- p.19
Chapter 3.7.3 --- Other Techniques --- p.19
Chapter 3.8 --- Principal Component Analysis --- p.19
Chapter 3.9 --- Polynomial Fitting --- p.21
Chapter 3.10 --- Highly Parallel Implementation --- p.22
Chapter 4 --- Error Controlled Subsampling --- p.23
Chapter 4.1 --- Centroidal Voronoi Diagram --- p.23
Chapter 4.2 --- Energy Function --- p.24
Chapter 4.2.1 --- Distance Energy --- p.24
Chapter 4.2.2 --- Shape Prior Energy --- p.24
Chapter 4.2.3 --- Global Energy --- p.25
Chapter 4.3 --- Lloyd´ةs Algorithm --- p.26
Chapter 4.4 --- Clustering Optimization and Subsampling --- p.27
Chapter 5 --- Mesh Generation --- p.29
Chapter 5.1 --- Tight Cocone Triangulation --- p.29
Chapter 5.2 --- Clustering Based Local Triangulation --- p.30
Chapter 5.2.1 --- Initial Surface Reconstruction --- p.30
Chapter 5.2.2 --- Cleaning Process --- p.32
Chapter 5.2.3 --- Comparisons --- p.33
Chapter 5.3 --- Computing Dual Graph --- p.34
Chapter 6 --- Results and Discussion --- p.37
Chapter 6.1 --- Results of Mesh Reconstruction form Noisy Point Cloud --- p.37
Chapter 6.2 --- Results of Clustering Based Local Triangulation --- p.47
Chapter 7 --- Conclusions --- p.55
Chapter 7.1 --- Key Contributions --- p.55
Chapter 7.2 --- Factors Affecting Our Algorithm --- p.55
Chapter 7.3 --- Future Work --- p.56
Chapter A --- Building Neighborhood Table --- p.59
Chapter A.l --- Building Neighborhood Table in Streaming --- p.59
Chapter B --- Publications --- p.63
Bibliography --- p.65
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Liu, L., Y. Sheng, G. Zhang, and Hassan Ugail. "Graph Cut Based Mesh Segmentation Using Feature Points and Geodesic Distance." 2015. http://hdl.handle.net/10454/8220.
Full textAbstract:
NoBoth prominent feature points and geodesic distance are key factors for mesh segmentation. With these two factors, this paper proposes a graph cut based mesh segmentation method. The mesh is first preprocessed by Laplacian smoothing. According to the Gaussian curvature, candidate feature points are then selected by a predefined threshold. With DBSCAN (Density-Based Spatial Clustering of Application with Noise), the selected candidate points are separated into some clusters, and the points with the maximum curvature in every cluster are regarded as the final feature points. We label these feature points, and regard the faces in the mesh as nodes for graph cut. Our energy function is constructed by utilizing the ratio between the geodesic distance and the Euclidean distance of vertex pairs of the mesh. The final segmentation result is obtained by minimizing the energy function using graph cut. The proposed algorithm is pose-invariant and can robustly segment the mesh into different parts in line with the selected feature points.
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Lee, Pai-Feng, and 李白峰. "Reconstruct Object Triangular Mesh by Using Spatial Points Cluster characteristics on Surface." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/7xt9bh.
Full textAbstract:
碩士中原大學
資訊工程研究所
91
Recently, the fast progress of computer technology and cost down of prices progressively, “Virtual Reality” becomes so popular. Many scenes of objects are displayed by 3D’s form, there are almost real effect, such as 3D (three dimension) architecture 、the introduction and trial of merchandise on line. Many object models are necessary to display a scene. Unfortunately, only a little objects of the real world have built its digital form. Therefore users must create digital objects by themselves. To create a digital object, user can use surface reconstruction. It be first proposed on the reconstruction problem by Hoppe in 1992 ; The input is a set of unorganized vertices in 3D, and the output is triangulation mesh models. In this dissertation, we present a proved surface reconstruction algorithm. At first, we stand on the spatial points cluster characteristic on surface to compute every point’s neighbor boundary. To find out the candidate neighbor which can possibly form triangles and do some test to ensure there can’t have narrow triangles. The point which referenced will be called complete point, and we will continue reconstruct along the boundary point. Therefore we use breadth first search to generate triangles progressively.
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Lun, Huang-Kuan, and 黃冠綸. "Optical Design and Simulation for UV Curing Mesh Points on Light Guide Plate." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/86180206234567689677.
Full textAbstract:
碩士國立中興大學
精密工程學系所
102
The thesis focuses on developing a high-luminance and thin light guide plate. The research studies a light guide plate in a size of 8 inches with a thickness of 0.6mm and provided with a superficial microstructure of mesh point. The research hereof mainly discusses the optical effect caused by alight guide plate under a back light module in the manufacturing method of Roll-to-Roll with continuous UV curing, while the light guide plate is made of a substrate with high light guidance PC material and processed with an UV coating having different refractive index. In the simulation of Trace Pro, when the UV coating refractive index increases by 0.02, the overall luminance increases by 9% to 11%. When the UV coating refractive index by 1.6, the overall luminance reaches the maximum value; however, if the UV coating refractive index continues to increase, the overall luminance decreases. In the experiment, when the UV coating refractive index by 0.02time to time and does not surpass the value of 1.56, the overall luminance increases by 3% to 4% time to time accordingly. The curve chart presenting the increasing or decreasing phenomenon is constant with the result of the simulation. Therefore, it is proved that the increase of the UV coating refractive index actually causes the increase of overall luminance of the light guide plate.
49
Han, Jiajia. "Point-to-Point Traffic in Wireless Mesh Networks." Thesis, 2010. http://hdl.handle.net/10012/5319.
Full textAbstract:
Although most work on Wireless Mesh Networks (WMNs) has focused on traffic flowing in and out of the network via gateways, traffic within the WMN may also be significant in many environments. This point-to-point (P2P) traffic between the nodes within WMN can be handled in different ways, particularly in WMNs containing multiple gateways. The approach used affects the performance of both the P2P flows and other traffic in the network.
This work studies the impact of handling P2P traffic in the presence of gateways and gateway traffic. Through mathematical analysis of the resulting traffic patterns, along with extensive simulations, the need to route P2P traffic appropriately is demonstrated. While direct routing yields considerable performance improvements in small networks, it can actually decrease capacity in larger networks.
Consequently, we extend the Hybrid Wireless Mesh Protocol (HWMP) proposed in IEEE 802.11s by adding two new message types to obtain more information useful for choosing the best route. Through simulations on different networks, HWMP shows better average delivery ratio and end-to-end delay than the original gateway-based and the P2P routing mechanisms in the simulation settings.
50
Wang, Sheng-Wen, and 王聖文. "Regular Mesh Reconstruction from Unorganized Point Cloud." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/44093762722330302491.
Full textAbstract:
碩士中原大學
資訊工程研究所
98
For a regular mesh model, typically constructing a model that usually using two steps model reconstruction and remesh. First unorganized point cloud can be created by 3D scanner. Through point-based reconstruction technique, we can make a model approximate the original object. But the mesh of model always be irregular. Therefore, the second step remesh, adjusting the mesh of model and resampling the point cloud to make the final mesh more regular. For mesh, not only model reconstruction but also remesh, both of them would create a mesh model finally. The difference between model reconstruction and remesh is shape of triangles and degree of vertices in mesh. Therefore, our paper presents a technique about mesh model reconstruction from unorganized points set. This technique can construct a regular mesh model from points set directly, and comparing with original object by eyes the features can be preserved. The most important concept is that regular mesh model reconstructing from unorganized point cloud directly, and no need two steps method to finish model reconstruction.