Dissertations / Theses on the topic 'Texture (Art) Computer simulation'

Computer models of oxide texture and microstructure development and oxidation kinetics have been developed. The first computer model enables the evaluation of the effects of various factors on oxide texture and microstructure development. The second computer model enables the evaluation of the effects of oxide texture and microstructure on oxidation kinetics.
Two examples of Ni single crystal and polycrystalline, Zr-2.5%Nb are used to illustrate the proposed computer models. Simplified oxidation mechanisms on Ni and Zr have been proposed.
In the first system, the simulation of oxide texture and oxidation kinetics on the {100} and {111} oriented single crystal Nickel substrate is analyzed. At the nucleation stage the oxide grain orientation is determined by lattice matching between the oxide and the metal substrate. At the stage of oxide grain growth, oxide surface free energy plays an important role. The simulated oxide textures are in good agreement with experimental results. The observed difference in the oxidation kinetics of the two samples is explained by difference in oxide textures formed on the two single crystal substrates. The high percentage of Sigma3 twin boundaries found in the oxide formed on the {111} substrate indicates that the presence of these boundaries significantly improves oxidation resistance.
In the second system where oxidation on Zr-2.5%Nb is simulated and analyzed, lattice matching between the oxide and the metal substrate is used to determine the oxide orientation at the nucleation stage. At the stage of oxide grain growth, oxide orientation is determined by minimizing the compressive stress that is parallel to the metal/oxide interface. Four samples with different substrate orientations have been used in study. The simulated oxide textures and microstructures are in good agreement with experimental results. During the simulation of oxidation kinetics, it is found that oxygen transport through Zr oxide film takes place mainly through two diffusion paths. The first diffusion path is through oxide grain boundaries formed in the bulk alpha-Zr grain region and the second one is through oxide grain boundaries formed at the alpha-Zr grain boundaries and beta-Zr grain region.

In search of higher speed and integration, the integrated circuit (IC) technology is scaling down. The total on-chip interconnect length is increasing exponentially. In fact, interconnect takes up the most part of the total chip area. The parasitics associated with these interconnect have significant impact on the circuit performance. Some of the effects of parasitics include cross talk, voltage drop and high current density. These issues can result in cross-talk induced functional failure and failures due to IR drop and electro-migration. This has resulted in interconnect- driven design trend in state-of-the-art integrated circuits. Reliability analysis, that includes simulating the effects of parasitics for voltage drop, current density, has become one of the most important steps in the VLSI design flow. Most of the CAD/EDA tools available, map these analysis results two dimensionally. Al- though this helps the designer, providing a three dimensional view of these results is highly desirable when dealing with complex circuits. In pursuit of visualizing reliability analysis results three dimensionally, as a first step, this work presents a tool that can visualize IC interconnect three di- mensionally. Throughout the course of this research open source tools were used to achieve the objective. In this work the circuit layout is stored as an OpenAc- cess database. A C++ program reads the design information using OpenAccess API and converts it to the .OBJ file format. Art of Illusion, an open source 3D modeling and rendering tool, reads this .OBJ file and models the IC interconnect three-dimensionally. In addition, Eclipse, an open source java IDE is used as a development platform. The tool presented has the capability to zoom in, zoom out and pan in real time.

Modern state-of-the-art equation based object oriented modeling languages such as Modelica have enabled easy modeling of large and complex physical systems. When such complex models are to be simulated, simulation tools typically perform a number of optimizations on the underlying set of equations in the modeled system, with the goal of gaining better simulation performance by decreasing the equation system size and complexity. The tools then typically generate efficient code to obtain fast execution of the simulations. However, with increasing complexity of modeled systems the number of equations and variables are increasing. Therefore, to be able to simulate these large complex systems in an efficient way parallel computing can be exploited.

This thesis presents the work of building an automatic parallelization tool that produces an efficient parallel version of the simulation code by building a data dependency graph (task graph) from the simulation code and applying efficient scheduling and clustering algorithms on the task graph. Various scheduling and clustering algorithms, adapted for the requirements from this type of simulation code, have been implemented and evaluated. The scheduling and clustering algorithms presented and evaluated can also be used for functional dataflow languages in general, since the algorithms work on a task graph with dataflow edges between nodes.

Results are given in form of speedup measurements and task graph statistics produced by the tool. The conclusion drawn is that some of the algorithms investigated and adapted in this work give reasonable measured speedup results for some specific Modelica models, e.g. a model of a thermofluid pipe gave a speedup of about 2.5 on 8 processors in a PC-cluster. However, future work lies in finding a good algorithm that works well in general.

Report code: LiU-Tek-Lic-2002:06.

L'objet de cette thèse est de proposer des algorithmes permettant de synthétiser des scènes naturelles complexes, par le nombre des objets qui les composent, par leur forme et par les phénomènes optiques qui peuvent caractériser certains objets ou phénomènes naturels, dans l'eau ou l'atmosphère. Notre objectif est de synthètiser, avec une certaine interactivitl'e, des images simulant leur apparence.

Pour atteindre cet objectif, nous proposons des algorithmes permettant de résoudre divers problèmes. Nous proposons tout d'abord un algorithme qui permet de combiner, pour une image de donnée, des systèmes de visualisation conventionnels et une représentation spectrale. Cette technique permet de simuler visuellement une scène où se produisent partiellement des effets optiques complexes (diffraction, interférence, etc.), en quelques secondes. Nous introduisons ensuite un algorithme permettant de modéliser et visualiser des motifs de couleur, des motifs de fleurs, par exemple. Une application de cet algorithme aux variations saisonnières des feuilles est également présente.

Pour les scènes d'une complexité qui n'est pas à la portée des techniques de simulation et de visualisation, nous présentons un algorithme qui permet de synthétiser des scènes naturelles à l'aide d'échantillons d'images. ous présentons ainsi d'abord une approche dite "Tile-based texture synthesis", fondée sur l'optimisation de la qualité de l'échantillon sélectionné à l'aide de techniques d'intelligence artificielle. Ensuite, nous présentons une technique de génération de textures guidée par des cartes présentant les caractéristiques perceptuelles globales de l'échantillon retenu. Mots-clés: Coulrtus structurelles, motifs de couleur, texture synthétisée, synthétiser des écosystèmes.

Modelling and rendering natural phenomena, such as rain, is an important aspect of creating a realistic driving simulator. Rain is a crucial issue when driving in the real world as it for instance obstructs the driver’s vision. The difficulty is to implement it in a visually appealing way while simultaneously making it look realistic and keeping the computational cost low. In this report, a GPGPU (general-purpose computing on graphical processing units) based approach is presented where the final product is a rain simulation rendered onto a 2D texture, which can then be applied to a surface. The simulated raindrops interact with gravity, wind, a windshield wiper as well as with each other, and are then used to distort the background behind them in a convincing manner. The simulation takes into account multiple physical properties of raindrops and is shown to be suitable to run in real-time. The result is presented in form of a visual demonstration. In conclusion, even though the final simulation is still in its first iteration, it clearly highlights what can be accomplished by utilizing the GPU and the benefits of using a texture-based approach. The appropriate simulation approach will however always depend on the characteristics of the problem and the limitations of the hardware.

This thesis is concerned with creating and evaluating interactive art systems that facilitate emergent participant experiences. For the purposes of this research, interactive art is the computer based arts involving physical participation from the audience, while emergence is when a new form or concept appears that was not directly implied by the context from which it arose. This emergent ‘whole’ is more than a simple sum of its parts. The research aims to develop understanding of the nature of emergent experiences that might arise during participant interaction with interactive art systems. It also aims to understand the design issues surrounding the creation of these systems. The approach used is Practice-based, integrating practice, evaluation and theoretical research. Practice used methods from Reflection-in-action and Iterative design to create two interactive art systems: Glass Pond and +-now. Creation of +-now resulted in a novel method for instantiating emergent shapes. Both art works were also evaluated in exploratory studies. In addition, a main study with 30 participants was conducted on participant interaction with +-now. These sessions were video recorded and participants were interviewed about their experience. Recordings were transcribed and analysed using Grounded theory methods. Emergent participant experiences were identified and classified using a taxonomy of emergence in interactive art. This taxonomy draws on theoretical research. The outcomes of this Practice-based research are summarised as follows. Two interactive art systems, where the second work clearly facilitates emergent interaction, were created. Their creation involved the development of a novel method for instantiating emergent shapes and it informed aesthetic and design issues surrounding interactive art systems for emergence. A taxonomy of emergence in interactive art was also created. Other outcomes are the evaluation findings about participant experiences, including different types of emergence experienced and the coding schemes produced during data analysis.

Dans ce travail nous nous intéressons à l'analyse et l'extraction de l'information 3D (orientation et forme) contenue dans les images de scènes naturelles et des textures homogènes. Pour cela nous adoptons une approche pluridisciplinaire de la modélisation du système visuel.

Nous présentons d'abord des expérimentations psychophysiques où nous avons cherché à évaluer la contribution relative des indices de variation de fréquence et de perspective linéaire pour la perception 3D.
Pour cela nous avons créé des stimuli spécifiques représentant des textures homogènes composées de masques de Gabor disposés sur une surface plane.
Le plan est vu en projection perspective suivant une inclinaison (slant) et une orientation (tilt) particulière.
La fréquence et l'orientation de chaque masque de Gabor sont déterminées en fonction du gradient de fréquence local et de la perspective linéaire locale définis par la projection.
Nous synthétisons ainsi des textures présentant uniquement une variation de fréquence ou une variation d'orientation ou les deux types de variation (en combinaison ou en conflit).

Pour chaque texture, une tâche de discrimination du slant et du tilt est effectuée. L'indice de variation de fréquence apparaît prépondérant dans l'estimation de l'inclinaison d'une surface par rapport à la perspective linéaire.
Par contre les deux indices jouent un role dans l'estimation de l'orientation.
Ces résultats valident l'utilisation de nos stimuli pour la perception 3D et permettent de préciser la décomposition de l'indice de texture en composantes élémentaires.

Basé sur cette approche, nous présentons un modèle biologiquement plausible d'analyse de la variation de fréquence au niveau de V1.
Nous modélisons la réponse des cellules complexes par des filtres log-normaux à variables séparables présentant différents avantages théoriques et pratiques par rapport aux filtres de Gabor classiquement utilisés.i
L'algorithme se compose d'une étape de prétraitement composé d'un filtrage rétinien pour ne conserver que les informations de texture et d'une décomposition de l'image en un ensemble d'imagettes similairement aux champs récepteurs des cellules corticales.
Une technique robuste d'estimation de la fréquence moyenne locale, indépendante de l'information d'orientation et correspondant à une combinaison simple de lensemble des filtres est appliquée à chaque imagette.
La mesure de la variation locale de fréquence entre chaque imagette permet d'estimer le tilt et le slant de la surface étudiée ainsi que sa forme.

La méthode est évaluée sur différentes bases d'images et de textures. Elle s'avère comparable en précision aux autres techniques et s'applique à des textures irrégulières avec une moindre complexité calculatoire.

Orientador: Ramirez Londono, Antonio Jose
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-23T16:20:20Z (GMT). No. of bitstreams: 1 RodriguezFernandez_Johnnatan_D.pdf: 160902949 bytes, checksum: 4744bcf4bff982b6d8a31d0ccb36ea63 (MD5) Previous issue date: 2013
Resumo: Neste trabalho foram realizadas juntas soldadas dissimilares de aço ASTM A516 Gr 60 e da liga de Ni 625, com 6,6 mm de espessura, empregando o processo de soldagem por atrito com pino não consumível (SAPNC) conhecida em inglês como Friction Stir Welding (FSW). Juntas consolidadas foram obtidas com os parâmetros de soldagem de 300 rpm, 100 mm.min-1, 30 kN de força axial e o deslocamento tangencial (DT) de +2,0 mm. Dentre os parâmetros estudados encontrou-se que velocidades de rotação superiores de 300 rpm apresentaram um incremento dos defeitos volumétricos (vazios) e para velocidades menores de 300 rpm, observou-se uma relação entre a oscilação da ferramenta e o incremento das forças axiais. A avaliação da microestrutura foi realizada por meio de microscopia óptica e eletrônica de varredura e transmissão, espectroscopia de raios X dispersiva em energia (XEDS) e difração de elétrons retroespalhados (EBSD). Foi possível estudar a evolução microestrutural e entender as transformações de fases e mecanismos de recuperação e recristalização após o processo de SAPNC. No aço A516, o mecanismo de rearranjo e eliminação de defeitos cristalinos foi por recristalização dinâmica contínua e na liga de Ni observou-se que durante o processo ocorre recristalização dinâmica contínua e descontínua. Na interface entre o aço A516 e a liga Ni 625, com um tamanho de 2 ?m, foi observada a presença de precipitados do tipo NbC o que sugere que estes precipitados foram arrastrados desde a zona misturada. As simulações termodinâmicas dos precipitados durante o processo de soldagem encontram-se de acordo com as observações microestruturais. A análise mostrou texturas de cisalhamento simples em todas as regiões afetadas pela deformação durante o processo de soldagem. Além disso, foi possível determinar por meio das figuras de polo, as rotações das células cristalinas para atingir as orientações cristalográficas finais observadas na junta soldada a partir do estado inicial do material de base
Abstract: Dissimilar 6 mm thick butt joints of steel ASTM A516 Gr 60 and Ni-based alloy 625, were produced by friction stir welding (FSW). Fully consolidated joints were produced using rotational speed of 300 rpm, travel speed of 100 mm.min-1, tangent offset of 2.0 mm, and axial force of 30 kN. Among the parameters studied, it was found that rotational speeds higher than 300 rpm promoted an increase on the macro-voids size. On the other hand, rotational speeds lower than 300 rpm resulted on an undesirable and correlated tool and axial force oscillation. Microstructural characterization was performed using optical microscopy, scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy (XEDS), and electron backscattering diffraction (EBSD). The microstructural evolution, phase transformations, and recovery and recrystallization mechanisms associated to the FSW process were investigated. In the steel A516, continuous dynamic recrystallization characterized by the rearrange and elimination of crystalline defects was identified as the main softening mechanism. In the Ni-based alloy, continuous and discontinuous dynamic recrystallization were the main mechanisms observed, with bulging of the original grain boundaries and progressive subgrain rotation. The NbC precipitates observed at the interface between the steel and the Ni-based alloy are thought to have been dragged from the Nibased alloy stir zone. Thermodynamic/kinetic simulations are in agreement with the above mentioned microstructural observation. The micro-texture analysis showed simple shear textures in all the welding zones affected by deformation during FSW. In addition, it was possible to determine the average crystalline cells rotations undergone by the base material to reach preferential orientations on the stir zone
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica

Military simulation and command and control federations have become large, complex distributed systems that integrate with a variety of legacy and current simulations, and real command and control systems locally as well as globally. As these systems continue to become increasingly more complex so does the data that initializes them. This increased complexity has introduced a major problem in data initialization coordination which has been handled by many organizations in various ways. Service-oriented architecture (SOA) solutions have been introduced to promote easier data interoperability through the use of standards-based reusable services and common infrastructure. However, current SOA-based solutions do not incorporate formal governance techniques to drive the architecture in providing reliable, consistent, and timely information exchange. This dissertation identifies the need to establish governance for common data initialization service development oversight, presents current research and applicable solutions that address some aspects of SOA-based federation data service governance, and proposes a governance reference model for development of SOA-based common data initialization services in military simulation and command and control federations.
ID: 029094323; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2010.; Includes bibliographical references (p. 253-261).
Ph.D.
Doctorate
Department of Modeling and Simulation
Engineering and Computer Science

Les systèmes complexes, naturels et artificiels, ont reçu récemment une attention renouvelée : les systèmes naturels, notamment biologiques, du fait de la nécessité de les appréhender dans une démarche systémique ; les systèmes artificiels, du fait de la dématérialisation de l'ordinateur amorcée avec l'informatique ubiquitaire. L'art, de son côté, explore depuis toujours le détournement des dernières avancées scientifiques et technologiques pour la création d'oeuvres singulières. Le travail mené depuis dix ans se situe à la croisée de ces chemins, dans le cadre unificateur des systèmes multi-agents. Je me suis intéressé plus particulièrement à l'interaction homme-machine dans le contexte de l'informatique ambiante, dans l'idée d'une construction automatique et d'une régulation dynamique de systèmes d'interaction. Ce travail est alimenté par la recherche menée dans le cadre de la simulation à base d'agents, aussi bien du point de vue des concepts et outils développés, que du point de vue de l'inspiration tirée des mécanismes d'auto-organisation et de régulation des systèmes étudiés. L'art fournit quant à lui un cadre expérimental original par la mise en scène métaphorique, dans des performances numériques interactives, des situations étudiées.

Research has shown that students interest in academics declines significantly with age, especially in the areas of math and science (Kahle et al., 1993; Wigfield, 1994; Wigfield and Eccles, 1992). One approach to combating this problem is by using new technologies to engage students who otherwise would not be interested in learning. In the AquaMOOSE project, 3D graphical technology is combined with a constructionist learning philosophy to create an environment where students can creatively explore new mathematical concepts. The AquaMOOSE socio-technical system has been developed using an iterative design process. Three formal studies were conducted to assess the effectiveness of the system, as well as several smaller scale evaluations. The first study was conducted during a six-week summer program where students were able to use the AquaMOOSE system during their free time. The second study explored different learning issues in the context of a comparison-class study at a local high school where one section learned about polar coordinates using standard curriculum materials and an equivalent section learned the same material using a curriculum designed specifically around the AquaMOOSE system. The final study of the AquaMOOSE system was in an eight-week after-school program at a local high school where a balance between structure and creative freedom was explored. In this thesis, the iterative design and evaluation of the AquaMOOSE socio-technical system is presented. Evidence from this process is used to suggest implications of using 3D technology and constructionist philosophy for teaching complex mathematical content. The findings presented address issues of using constructionist learning environments for complex content and the tradeoffs of using 3D technology for educational systems.

Classical force fields are the core of classical simulations, particularly of molecular dynamics (MD), a technique that is changing our view on the structure, flexibility and function of biological macromolecules. Originated from the pioneering work of Lifson’s group in the sixties, force fields have been in continuous evolution, improving in each generation the accuracy in the representation of proteins and nucleic acid. Force field development is tightly connected to the refinement of simulation procedures and to the extension of simulation time scales. Thus, as simulation time passed the microsecond barrier, MD simulations have revealed the existence of some errors in the default force field for DNA simulations, parmbsc0 (developed in the group). The goal of this thesis is to address these problems by a reparameterization of AMBER force field that aims to represent a wide range of DNA structures under physiological and non-physiological conditions. Keeping α/γ parmbsc0 corrections and parm99 non-bonded parameters, we systematically reparameterized sugar puckering, ε, ζ and χ torsions using high level QM calculations both in gas phase and solution. The refined force field has been tested for more than 3 years to an unprecedented level of detail, considering a large variety of DNAs, and analyzing structural, mechanical and dynamical properties of the DNAs resulting from the corresponding MD simulations. The refined force field parameters have been also subjected for more than 1 year of β-testing by different groups, finding to our knowledge no major drawbacks. In the world of RNA simulations, despite the recent efforts to improve the description of RNA in MD simulations, RNA force fields are still far in accuracy from those of DNA. A probable cause could be the incomplete understanding of the mechanism of 2’-OH orientation, which in big extent determines the RNA conformation and most probably serves as the molecular switch. THESIS ORGANIZATION This thesis is compiled of five publications (or in the process of publication) works; first three consider DNA force field development and following validation and benchmark while the last two are focused on RNA efforts. For better understanding of this work Chapter 1 introduces the central concepts related to nucleic acids, their structures and ways to study them. Chapter 2 goes into more details of the methodology employed here, briefly explaining basic QM formalism and MD simulations with an emphasis on force fields. Chapter 3 is a small handbook of methods employed in the analysis in this work. All together first three chapters should provide a solid ground to better understand the details and the relevance of the five publications in the following two chapters. Chapter 4 is based on the development of new force field, called parmbsc1, its further testing on the Drew-Dickerson sequence and benchmarking. Chapter 5 focuses on efforts to understand the mechanism of complexity of RNA structures studying 2’-OH rotation, and computational design of a new RNA dumbbell structure. A summary of the major results and a general discussion that reflects on the five projects and future work are presented in Chapter 6, with the main conclusions at the end of this work.

The aim of this work was to develop and validate a new pre-operative planning in acetabular surgery based on a patient-specific biomechal model. During the first part of this work we brought enhancement in each step of the planning process for acetabular fracture surgery. The first step was to generate 3D models of several acetabular fracture patterns using semi-automatic segmentation methods. In the same time, we showed that the segmented fragments bone could be usefull to correctly classify acetabular fracture by unexperimented residents. The second step was to generate a patient-specific model, in a very simple way, that could be used in clinical practice by surgeons. A literature review of acetabular planning models was performed to identify that a new paradigm was required because of the limitations of the existing models. Once the objectives of patient-specific modelling was identified, a literature review of hips models was performed to record biomechanical properties of the elements that we had to modelize. A compromise between simplicity and realistic behaviour was found to generate patient-specifics biomechanical models, in a limited time, that could be used in clinical practice. Clinical studies on 14 operated cases, then 29 operated cases and finally 39 operated cases, were performed to validate retrospectively the simulations. The results were quite promising. Only open-source softwares with their own weaknesses were used because validity and feasability of the procedure was required before bigger investissment. The proof of concept was done. A prospective clinical study has shown the efficiency of the patient-specific biomechanical simulation and its feasibility in a daily clinical practice. This work opens a door for new approaches in surgical planning and patient-specific modelling
L’objectif de cette thèse est de développer et valider une nouvelle méthode de planification pré-opératoire en chirurgie traumatique de l’acetabulum reposant sur un modèle biomécanique patient-spécifique. La première partie de ce travail a consisté en l’élaboration et l’amélioration progressive de ce nouvel outil de planification. La première étape était de générer des modèles tri-dimensionnels de plusieurs fractures acétabulaires à l’aide d’une méthode de segmentation semi-automatique. Dans le même temps, nous avons démontré que les fragments osseux segmentés pouvaient être utile pour classer correctement les fractures acétabulaires par des internes non expérimentés. La seconde étape était de générer un modèle biomécanique patient-spécifique, le plus simplement possible pour pouvoir être compatible avec une pratique clinique régulière. Une revue de la littérature à propos des différentes méthodes de planifications péri-opératoire en traumatologie de l’acetabulum a été réalisée afin d’identifier qu’un nouveau paradigme était nécessaire du fait des limites des méthodes existantes. Une fois les objectifs d’une modélisation biomécanique patient-spécifique définis, une revue de la littérature des différents modèles biomécanique de la hanche a été réalisée pour définir les propriétés biomécaniques des différents éléments à modéliser. Un compromis entre simplicité et comportement réaliste du modèle a été trouvé pour générer un modèle biomécanique patient-spécifique, dans un temps limité, compatible avec une utilisation courante en pratique clinique. Des études cliniques portant sur 14 cas de fractures acétabulaires opérées, puis 29 et finalement 39 cas ont été réalisées pour valider rétrospectivement les simulations biomécaniques. Les résultats montraient une parfaite adéquation avec la réalité. Seuls des logiciels en libre accès, avec leurs faiblesses, étaient utilisés car la fiabilité et la validité de la simulation étaient nécessaires avant d’envisager plus d’investissements. La preuve de concept était donnée. Enfin, une étude clinique prospective a démontré l’efficacité de la simulation biomécanique patient-spécifique et sa faisabilité en pratique clinique quotidienne. Ce travail ouvre la porte à de nouvelles approches en matière de planification chirurgicale et de modélisation patient-spécifique

Les progrès technologiques ont permis d'abaisser la frontière entre image réelle et image virtuelle à tel point que les différencier devient difficile. Si la réalité virtuelle évolue au rythme des progrès technologiques, la réalité augmentée, passage du virtuel vers le réel, n'en est qu'à ses débuts. Le but de cette thèse est d'assurer la transition entre le monde virtuel et réel grâce à un système procam (projecteur caméra) pour améliorer l'apparence visuelle d'un objet. La position de l'objet est estimée en projetant une mire codée pour déterminer des points de correspondance entre les caméras et le projecteur sur un objet sans texture (les détecteurs classiques de points d'intérêt sont inefficaces sur de tels objets). Nous combinons l'étalonnage du système et ces points pour estimer la position 3D de l'objet, et ensuite le recalons avec un modèle de points plus fin, issu d'un scanner ou d'un modèle de CAO. La synthèse de vue est réalisée et l'image synthétisée est projetée sur l'objet. De tels outils permettent de générer des textures virtuelles, temporaires (il suffit d'éteindre le projecteur pour enlever la texture de l'objet), qui peuvent décrire l'usure de la texture ou l'objet sous son apparence d'origine.

Dans le contexte actuel de diminution des pollutions d'origine agricole, laréduction des apports d'intrants devient un enjeu primordial. En France, laviticulture est l'activité qui possède le taux le plus important de traitementsphytosanitaires par unité de surface. Elle représente, à elle seule, 20% de laconsommation annuelle de pesticides. Par conséquent, il est nécessaire d'étudierle devenir des pesticides appliqués afin de réduire les quantités perduesdans l'environnement. Dans le cadre de la réduction d'apport de produitsphytosanitaires dans les vignes, de nombreux travaux ont été effectués sur lamodélisation du comportement d'un spray de gouttelettes et sa répartitionau niveau de la parcelle et de l'air environnant. Cependant, il est égalementimportant de s'intéresser au comportement de la gouttelette directement auniveau de la feuille. Les progrès dans le domaine de l'imagerie et la diminutiondu coût des systèmes ont rendus ces systèmes beaucoup plus attractifs.Le travail de cette thèse consiste en la mise en place d'un système d'imagerierapide qui permet l'observation du comportement à l'impact de gouttelettesrépondant aux conditions de pulvérisation. Les caractéristiques ainsi que lecomportement associé de chaque gouttelette sont extraits grâce à une méthodede suivi d'objets. Une analyse statistique basée sur un nombre représentatifde résultats permet ensuite d'évaluer de manière robuste le devenir d'unegoutte en fonction de ses caractéristiques. Parallèlement, un paramètre décrivantl'état de surface de la feuille est également étudié grâce à l'imagerie : larugosité qui joue un rôle prédominant dans la compréhension des mécanismesd'adhésion

Made available in DSpace on 2014-10-09T12:36:59Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T13:56:24Z (GMT). No. of bitstreams: 1 04491.pdf: 3155069 bytes, checksum: aa854e4a23f31eb334f216ec1ea726c2 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Le clouage est une technique de renforcement des sols en place par des inclusions passives. Dans la première partie de ce rapport, on présente les résultats expérimentaux et théoriques d'une recherche approfondie sur le mécanisme d'interaction sol-renforcement rigide et la mobilisation de la résistance au cisaillement du sol lors du cisaillement direct de la masse du sol cloué. La méthode des éléments finis a été utilisée pour la simulation numérique des essais de cisaillement direct effectués au CERMES en 1980-1981 sur des éprouvettes de grandes dimensions (40 x 60 x 40 cm) de limon argileux renforcé par des inclusions perpendiculaires à la surface de cisaillement. Cette étude a permis de mettre en évidence la mobilisation d'une cohésion apparente et une diminution de l'angle de frottement interne de la masse du sol renforcé et d'étudier l'effet de certains paramètres (contrainte normale appliquée ; rigidité et nombre de renforcements) sur l’effet des inclusions, le comportement de la masse du sol renforcé et la mobilisation de sa résistance globale au cisaillement. La deuxième partie de ce rapport présente une analyse du comportement des ouvrages de soutènement en sol renforcé. On étudie, d'une part, les remblais en Terre Armée, et d'autre part, les soutènements in-situ par clouage. Si la technique de la Terre Armée a fait l'objet de plusieurs recherches et observations sur ouvrages en vraie grandeur, peu d'expérimentations ont été effectuées jusqu'à présent sur des soutènements par clouage. Ces quelques expérimentations montrent une certaine analogie entre le comportement de ces deux types d'ouvrages. Cependant, il existe des différences fondamentales qui concernent en particulier : - Les modes de constructions, - La rigidité des renforcements, - L'inclinaison des renforcements, - La technique de mise en place des renforcements, - La nature du sol. Notre travail a essentiellement pour objectif d'étudier l'influence de ces paramètres sur le comportement global de l'ouvrage sur les efforts mobilisés dans les inclusions ainsi que sur le déplacement de la paroi. On a utilisé une simulation numérique à l'aide d'un programme de calcul en éléments finis, permettant une modélisation phase par phase de ces deux techniques. Pour vérifier cette modélisation on compare les résultats de calculs, d'une part, avec les mesures sur ouvrages réels, et d'autre part, avec observations sur modèles réduits.

The topic of this dissertation is the anatomical, psychological, and cultural examination of a human face in order to effectively construct an anatomy-driven 3D virtual face customization and action model. In order to gain a broad perspective of all aspects of a face, theories and methodology from the fields of art, engineering, anatomy, psychology, and cultural studies have been analyzed and implemented. The computer generated facial customization and action model were designed based on the collected data. Using this customization system, culturally-specific attractive face in Korean popular culture, “kot-mi-nam (flower-like beautiful guy),” was modeled and analyzed as a case study. The “kot-mi-nam” phenomenon is overviewed in textual, visual, and contextual aspects, which reveals the gender- and sexuality-fluidity of its masculinity. The analysis and the actual development of the model organically co-construct each other requiring an interwoven process. Chapter 1 introduces anatomical studies of a human face, psychological theories of face recognition and an attractive face, and state-of-the-art face construction projects in the various fields. Chapter 2 and 3 present the Bezier curve-based 3D facial customization (BCFC) and Multi-layered Facial Action Model (MFAF) based on the analysis of human anatomy, to achieve a cost-effective yet realistic quality of facial animation without using 3D scanned data. In the experiments, results for the facial customization for gender, race, fat, and age showed that BCFC achieved enhanced performance of 25.20% compared to existing program Facegen , and 44.12% compared to Facial Studio. The experimental results also proved the realistic quality and effectiveness of MFAM compared with blend shape technique by enhancing 2.87% and 0.03% of facial area for happiness and anger expressions per second, respectively. In Chapter 4, according to the analysis based on BCFC, the 3D face of an average kot-mi-nam is close to gender neutral (male: 50.38%, female: 49.62%), and Caucasian (66.42-66.40%). Culturally-specific images can be misinterpreted in different cultures, due to their different languages, histories, and contexts. This research demonstrates that facial images can be affected by the cultural tastes of the makers and can also be interpreted differently by viewers in different cultures.

Thesis (MComm)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: Defence forces around the world are experiencing a period of dynamic change with new force structures being combined with new technologies in an effort to enhance effectiveness. Present day resources and technology available to the modern society, have facilitated the evolution of warfare as a technologically advanced enterprise, with the decided emphasis on the digitisation of the battlefield. With rapid development in the field of battlefield digitisation there is an increasing need to address the important issues and challenges facing the military. In order to meet strategic defence guidelines, it is necessary to integrate the capabilities of defence forces with modern technology. In this regard the South African Defence Force is striving towards the digitisation of the battlefield. This digitisation can potentially satisfy the many requirements set for the Defence Force, in a more timely and cost-effective manner than traditional methods of functioning and training would be able to achieve. Effective situational awareness and command and control structures are essential for any military operation, especially with increasingly complex military demands. Key areas of importance are the collection, dissemination and management of information, which if executed skilfully, will result in forces capable of operating more effectively and with greater flexibility. Decision makers on the battlefield continually suffer from information overload due to the extremely rapid inflow of information. This is likely to worsen with the continued introduction of new information technologies. The technology level of any defence force should therefore be appropriate, driven by usefulness and cost-effectiveness. The digitised battlefield allows for the execution of near realistic military exercises, while conserving material and reducing the detrimental impact on environment and personnel, as is the case with traditional exercises. A key issue of focus is the usability and integration of related technologies within the digital battlefield. Promoting optimal usability through continuous and comprehensive user-based evaluation is crucial and will result in increased human performance through interaction with technology. Optimal usability must be engineered into any product (defined as something produced by means of either human or mechanical work) from the inception of the product's life cycle. Within today's technology orientated society, the digitisation of the battlefield and the usability thereof have become increasingly important issues. Most research has investigated the concepts of battlefield digitisation and usability in isolation, and little co-ordinated effort has been made to integrate digitisation and usability, even though the relation is important and necessary. A study of this nature has not hitherto been conducted within the South African military context. The purpose of this study is to provide a theoretical background of the issues of military digitisation and usability, in order to determine the significance of this relation. This research aims specifically to promote the viewpoint that usability is central to military digitisation, as well as to emphasise the importance of user-centred approaches to system development and utilization. The result will be enhanced human performance and satisfaction when interacting with digital battlefield applications. The theoretical perspective is provided by way of a literature review of the relevant military and usability concepts. Military functioning is discussed, highlighting the importance of situational awareness and effective command and control capabilities. The digitisation in the military is examined with specific reference to Virtual Reality and simulation. An overview of usability (within a human-computer interaction and user-centred design context) and usability evaluation methods are provided. This research was conducted during a military exercise conducted by the South African National Defence Force. A usability inquiry approach was followed with questionnaires distributed to participants involved with the Command and Control Digital Battlefield System. Information was obtained concerning participants' characteristics, likes, dislikes, needs, and understanding of the digital battlefield system. The analyses of the information consisted of descriptive statistics as the research aimed to illustrate the attitudes concerning usability and the digital battlefield. The results provide an understanding of the perceptions of the users regarding the digital battlefield system and its usability. Conclusions are drawn from results obtained and recommendations are made for future research.
AFRIKAANSE OPSOMMING: Moderne weermagte deur die wereld ervaar tans 'n peri ode van dinamiese verandering met nuwe magstrukture wat met nuwe tegnologiee gekombineer word ter bevordering van doeltreffendheid. Die hedendaagse hulpbronne en tegnologie tot die moderne samelewing se beskikking, het meegebring dat oorlogvoering ontwikkel het in 'n tegnologies gevorderde aksie met die klem op gevegsterrein-digitalisering. Die betreding van 'n era van tegnologies gevorderde oorlogvoering met die gepaardgaande snelle ontwikkelings in die veld van gevegsterrein digitalisering, het 'n toenemend groeiende behoefte laat ontstaan vir die indringende aanspreking van belangrike strydvrae en uitdagings wat 'n moderne weermag in die gesig staar.Tiit is noodsaaklik dat die vermoens van weermagte geintegreer word met moderne tegnologie ten einde aan strategiese verdedigingsvereistes te kan voldoen. Die Suid-Afrikaanse Nasionale Weermag het digitalisering van die gevegsterrein ten doel. Sodanige digitalisering kan potensieel die talle vereistes gestel aan 'n weermag op 'n meer tydige en koste-effektiewe wyse bevredig as wat met tradisionele metodes van funksionering en opleiding gedoen kan word. Effektiewe situasionele bewustheid en bevel en beheer strukture, is onontbeerlik in enige militere operasie, veral in die lig van toenemende komplekse eise gestel aan die moderne weermag. Sleutelareas van belang is die insameling, disseminasie en bestuur van inligting, wat as dit met die nodige insig en kundigheid uitgevoer word, aanleiding sal gee tot die verhoogde doeltreffendheid en buigsaamheid van 'n weermag. Die tegnologiese vlak van enige weermag behoort dus toepaslik en bruikbaar te wees, sowel as koste-effektief gedrewe. Die gedigitaliseerde gevegsterrein maak vcorsiening vir die uitvoering van bykans-realistiese militere oefeninge met behoud van material en grootskaalse uitskakeling van die negatiewe invloede op die omgewing en personeel, meer so as wat andersins die geval sou wees met tradisionele oefeninge. 'n Sleutel-aspek is die bruikbaarheid en integrasie van verwante tegnologiee in 'n gedigitaliseerde gevegsterrein. Die bevordering van optimale bruikbaarheid deur aaneenlopende en omvattende gebruikersbaseerde evaluasies, is deurslaggewend en sal lei tot verhoogde gebruiker prestasie betreffende interaksie met tegnologie. Optimale bruikbaarheid moet reeds vanaf die aanvang van 'n produk se lewenssiklus, bewerkstellig word. In die hedendaagse tegnologie-gebaseerde moderne same lewing, het digitalisering van die gevegsterrein en die bruikbaarheid daarvan, toenemend belangrik geword. In die meeste navorsmg word gevegsterrein digitalisering, asook bruikbaarheid, afsonderlik ondersoek, onafgesien van die belangrike verwantskap daartussen, en slegs geringe gekoordineerde pogings is van stapel gestuur om digitalisering en bruikbaarheid te integreer. In die Suid-Afrikaanse rnilitere konteks is so 'n studie nog nie uitgevoer nie en derhalwe het hierdie studie ten doel om 'n teoretiese agtergrond te voorsien van militere digitalisering- en bruikbaarheidskwessies, asook die vasstelling van die verwantskap daartussen. Hierdie navorsing het spesifiek ten doel om die standpunt te bevorder dat bruikbaarheid sentraal staan tot militere digitalisering sowel as om die gebruiker-gebaseerde benadering tot sisteem ontwikkeling en benutbaarheid, te bevorder. Die resultaat sal verhoogde gebruikerprestasie en tevredenheid wees wanneer interaksie met gedigitaliseerde gevegsterrein toepassings plaasvind. Die teoretiese perspektief word voorsien deur 'n literatuur-oorsig van die relevante rnilitere- en bruikbaarheidskonsepte. Militere funksionering word bespreek met beklemtoning van die belang van situasionele bewustheid en doeltreffende bevel en beheer vermoens, Militere digitalisering word ondersoek met spesifieke verwysing na virtuele realiteit en simulasie. 'n Oorsig van bruikbaarheid (binne die konteks van mens-rekenaar interaksie en gebruikersgeorienteerde ontwerp) sowel as bruikbaarheidsevaluasie-metodes word voorsien. Hierdie navorsing is uitgevoer tydens 'n militere oefening van die Suid-Afrikaanse Nasionale Weermag. 'n Bruikbaarheidsondersoek-benadering is gevolg deur vraelyste uit te deel aan die deelnemers wat betrokke was by die gedigitaliseerde bevel en beheer stelsel. Informasie is ingewin betreffende die deelnemers se kenmerke, persepsies, voorkeure, afkeure, behoeftes en begrip van die gedigitaliseerde gevegsterrein-stelsel. Die analise van die informasie het beskrywende statistieke behels omdat die navorsing ten doe I gehad het om ingesteldhede betreffende bruikbaarheid en die gedigitaliseerde gevegsterrein, uit te lig. Die resultate voorsien 'n begrip van die persepsies van die gebruikers rakende die gedigitaliseerde gevegsterrein, en die bruikbaarheid daarvan. Gevolgtrekkings word gemaak vanuit die resultate verkry en aanbevelings word voorsien vir verdere toekomstige navorsing.

La capacité à concevoir dans l’abstraction fait appel à la faculté qu’a notre cerveau de combler ce qui n’est pas visible par l’image la plus proche. Cela crée alors une illusion visuelle et l’imagination apporte ensuite à l’esprit des images mentales. Mes recherches consistent à présenter un concept artistique à base d’interférences et d’illusions pour créer des personnages tridimensionnels. Aussi cette thèse est-elle composée de deux parties. La première partie, théorique, est une étude globale sur les propriétés de la lumière, l’optique et la méthode de création des interférences. Dans la deuxième partie j’aborde la pratique en expliquant tout le processus mis en œuvre pour concevoir des personnages tridimensionnels grâce aux illusions visuelles issues des franges d’interférence volontairement perturbées
The ability to conceive in total abstraction calls upon the faculty that has our brain to fill what is not visible by the nearest image. That creates a visual illusion and then our imagination bring forward mental images. My research consists in presenting an artistic concept using interferences and illusions to create three-dimensional characters. Also this thesis is composed in two sections. The first section is a general study on the properties of light, optical and the method to create interferences. The second section is based on my practical work. I explain, step by step, how to conceive three-dimensional characters due to visual illusions obtained through interference rings disturbed on purpose

Studying the internal characteristics of a network using measurements obtained from endhosts is known as network tomography. The foremost challenge in measurement-based approaches is the large size of a network, where only a subset of measurements can be obtained because of the inaccessibility of the entire network. As the network becomes larger, a question arises as to how rapidly the monitoring resources (number of measurements or number of samples) must grow to obtain a desired monitoring accuracy. Our work studies the scalability of the measurements with respect to the size of the network. We investigate the issues of scalability and performance evaluation in IP networks, specifically focusing on fault and congestion diagnosis. We formulate network monitoring as a machine learning problem using probabilistic graphical models that infer network states using path-based measurements. We consider the theoretical and practical management resources needed to reliably diagnose congested/faulty network elements and provide fundamental limits on the relationships between the number of probe packets, the size of the network, and the ability to accurately diagnose such network elements. We derive lower bounds on the average number of probes per edge using the variational inference technique proposed in the context of graphical models under noisy probe measurements, and then propose an entropy lower (EL) bound by drawing similarities between the coding problem over a binary symmetric channel and the diagnosis problem. Our investigation is supported by simulation results. For the congestion diagnosis case, we propose a solution based on decoding linear error control codes on a binary symmetric channel for various probing experiments. To identify the congested nodes, we construct a graphical model, and infer congestion using the belief propagation algorithm. In the second part of the work, we focus on the development of methods to automatically analyze the information contained in electron tomograms, which is a major challenge since tomograms are extremely noisy. Advances in automated data acquisition in electron tomography have led to an explosion in the amount of data that can be obtained about the spatial architecture of a variety of biologically and medically relevant objects with sizes in the range of 10-1000 nm A fundamental step in the statistical inference of large amounts of data is to segment relevant 3D features in cellular tomograms. Procedures for segmentation must work robustly and rapidly in spite of the low signal-to-noise ratios inherent in biological electron microscopy. This work evaluates various denoising techniques and then extracts relevant features of biological interest in tomograms of HIV-1 in infected human macrophages and Bdellovibrio bacterial tomograms recorded at room and cryogenic temperatures. Our approach represents an important step in automating the efficient extraction of useful information from large datasets in biological tomography and in speeding up the process of reducing gigabyte-sized tomograms to relevant byte-sized data. Next, we investigate automatic techniques for segmentation and quantitative analysis of mitochondria in MNT-1 cells imaged using ion-abrasion scanning electron microscope, and tomograms of Liposomal Doxorubicin formulations (Doxil), an anticancer nanodrug, imaged at cryogenic temperatures. A machine learning approach is formulated that exploits texture features, and joint image block-wise classification and segmentation is performed by histogram matching using a nearest neighbor classifier and chi-squared statistic as a distance measure.

Cette thèse porte sur la modélisation du comportement humain dans les simulations de combat naval. Au sein de l'entreprise DCNS, les simulations de combat naval permettent d'évaluer les performances opérationnelles des navires militaires, dans un scénario donné. Les simulations actuelles ne permettent pas de prendre en compte l'analyse et la décision d'un opérateur, qui peuvent parfois conduire à des réactions inattendues. Le but de cette thèse est donc de modéliser le comportement d'un opérateur pour les simulations de combats navals.Pour représenter les connaissances, la logique non monotone la plus employée a été utilisée: la logique des défauts. Une prise en compte du temps a été ajoutée à cette logique des défauts. La logique des défauts va permettre de calculer des extensions. Chaque extension correspond à une action possible pour l'opérateur.Une méthode qui permet de choisir une extension a été définie. Cette méthode simule la décision de l'opérateur et elle prend en compte le caractère de l'opérateur.

Les problèmes étudiés dans cette thèse relèvent du cadre général de la modélisation des tunnels profonds. Ce travail traite essentiellement de l'interaction complexe entre massif et soutènement. Initialement, on réalise une approche expérimentale portant sur l'optimisation du dimensionnement des soutènements des galeries dans des roches viscoplastiques. Une modélisation numérique fine de ce problème d'interaction massif viscoplastique-soutènement plastique est mise en oeuvre et permet de bien interpréter le comportement de la galerie expérimentale de Mol (Belgique). Ensuite, on s'intéresse à l'aspect 3D du creusement des tunnels a l'aide de la méthode numérique d'activation/désactivation des éléments en axisymétrie. On montre, par la réalisation d'abaques, que l'équilibre des tunnels dans les milieux viscoplastiques dépend largement de la rigidité et de la distance de pose du revêtement ainsi que de la vitesse de creusement de l'ouvrage. Dans la dernière partie, on compare les résultats donnés par notre méthode numérique d'une part, et par la méthode cv-cf d'autre part: on met en évidence les imprécisions de la méthode approchée cv-cf sous sa forme actuelle. Finalement, on propose une nouvelle méthode approchée en élasticité, qui conserve le formalisme de la méthode cv-cf, mais permet de mieux prendre en compte l'effet de la rigidité du soutènement sur la valeur de la convergence avant pose. Cette nouvelle méthode approchée conduit à des résultats tout a fait acceptables.

Les argiles raides sont généralement rencontrées à grande profondeur (plus de 300 mètres). Ces matériaux se caractérisent par leur teneur en eau relativement faible. De nombreux projets industriels justifient l'intérêt récent porté à ces matériaux. La thèse traite en particulier d'argiles raides susceptibles de répondre à des sollicitations par des déformations élastiques, plastiques et viscoplastiques. C'est la prise en compte simultanée d'une rupture engendrant des déformations plastiques et des déformations différées de types viscoplastiques qui font l'originalité de cette thèse. Cette nouvelle approche constitue une amélioration indispensable dans la description du comportement mécanique d'argiles raides. Ce travail est présenté en trois parties : la première partie est consacrée à l'étude expérimentale et à la modélisation du comportement mécanique des argiles raides. Dans cette partie, nous décrivons les matériaux considérés, et les essais réalisés. Nous discutons les résultats et élaborons un modèle viscoplastique avec rupture. La deuxième partie, « Application du modèle VPR au calcul d'un tunnel de section circulaire », est consacrée à l'élaboration d'une solution originale semi analytique et d'un algorithme implanté dans GEOMEC91. La troisième partie, « Application du modèle VPR au calcul 2d axisymétrique des tunnels soutenus et étude paramétrique », montre très clairement l'influence du modèle VPR sur la convergence du tunnel au moment de la pose du soutènement, et par conséquent sur les sollicitations de ce dernier. Les résultats des calculs montrent une forte influence de la cohésion à court terme sur la convergence du tunnel.

On s'intéresse à la modélisation des matériaux granulaires composé d'agrégats non convexes et cohésifs en vue d'application à la rhéologie des poudres d'UO2 . L'influence du degré de non-convexité des particules est analysé en termes de grandeurs macroscopiques (frottement interne et cohésion de Coulomb) et de paramètres micro-mécaniques tels que l'anisotropie de la texture et la transmission des efforts. Il apparaît en particulier que la compacité évolue d'une manière complexe avec la non-convexité et que la résistance au cisaillement augmente mais sature sous l'effet d'imbrication entre agrégats. Des modèles simples sont introduits pour décrire ces comportements en termes de paramètres micro-mécaniques. De même, des études systématiques par cisaillement, compaction uniaxiale et compression simple montrent que la cohésion interne augmente avec la non-convexité mais est fortement contrôlée par les conditions aux limites et l'apparition de bandes de cisaillement ou de concentrations de contraintes.

Le réalisme des objets en infographie exige de simuler adéquatement leur apparence sous divers éclairages et à différentes échelles. Une solution communément adoptée par les chercheurs consiste à mesurer avec l’aide d’appareils calibrés la réflectance d’un échantillon de surface réelle, pour ensuite l’encoder sous forme d’un modèle de réflectance (BRDF) ou d’une texture de réflectances (BTF). Malgré des avancées importantes, les données ainsi mises à la portée des artistes restent encore très peu utilisées. Cette réticence pourrait s’expliquer par deux raisons principales : (1) la quantité et la qualité de mesures disponibles et (2) la taille des données. Ce travail propose de s’attaquer à ces deux problèmes sous l’angle de la simulation. Nous conjecturons que le niveau de réalisme du rendu en infographie produit déjà des résultats satisfaisants avec les techniques actuelles. Ainsi, nous proposons de précalculer et encoder dans une BTF augmentée les effets d’éclairage sur une géométrie, qui sera par la suite appliquée sur les surfaces. Ce précalcul de rendu et textures étant déjà bien adopté par les artistes, il pourra mieux s’insérer dans leurs réalisations. Pour nous assurer que ce modèle répond aussi aux exigences des représentations multi-échelles, nous proposons aussi une adaptation des BTFs à un encodage de type MIP map.
The realism of objects in computer graphics requires adequate simulation of their appearence under different light/view directions and at various scales. A solution commonly adopted by researchers consists in measuring the reflectance of a real surface by means of calibrated devices. The measured data is encoded in the form of a reflectance model (BRDF) or a texture of reflectance (BTF). Despite significant progress in this area, the measured appearence data remain very infrequently used. This reluctance could be explained by two main reasons: (1) the limited number of high-quality measured materials and (2) the huge storage space required by the data. In this work, we suggest resolving these two problems from the angle of simulation. We consider that the level of realism in rendered images already produces satisfactory results with current techniques. Therefore, we propose to precompute and encode the effects of lighting on a completely synthetic micro-geometry, which will be applied on surfaces. This production pipeline being already well adopted by artists, it should better fit into their realizations. To ensure that this model also respects the requirements of multi-scale representations, we also propose an adaptation of the BTF to a MIP map encoding.

碩士
國立成功大學
物理學系碩博士班
90
Applying a high/low voltage pulse, we can switch a bistable reflective polymer-stabilized cholesteric texture (PSCT) device between the reflective and transparent states. These two states are stable for years in the absence of voltage. In addition, this device is operated under the reflective mode without a polarizer. No backlight is required. As a result, it has potential for use as a display. This thesis researches this PSCT device. Tasks include the fabrication of PSCT devices and the measurements of their reflection characteristics. In addition, using Berreman’s 4x4 matrix, we simulate the reflection characteristics of PSCT devices. It shows that the simulated results fit well with the measured ones. Thus this simulation provides us a good approach to predict the properties of PSCT devices, and save us not only money but also effort and time. Finally in Chapter 5, I propose some ideas which deserve to carry out further with PSCT devices.

碩士
國立屏東師範學院
視覺藝術教育研究所
91
There are four purposes of the study : 1. to investigate the problems associated with current methods of painting instruction. 2. to investigate functions and contents where computer-image-processing technology can be used to simulate painting, 3. to develop a teaching model that uses computer-image-processing technology to simulate the tools, materials, strokes, styles and other techniques of painting. 4. to assess the feasibility of a teaching model which uses computer-image-processing technology to simulate painting, and to assess the effects of this model on the learning attitude and motivation of students. Data was collected by interviewing naïve participants and the amended “equivalent-time-sample design” quasi-experimental study method was used to analyze results. The participants were 91 pre-service teachers from National Ping-Tung Teachers College. Five senior art teachers were also interviewed in order to obtain their opinions about the instructional model. The findings and conclusions of the study are as follows : 1.Problems associated with current painting instruction include insufficient equipment, lack of resources, few painting teachers continue to learn, and painting teachers seldom use the information media in their teaching works. 2.The functions and contents which computer-image-processing technology can be used to simulate: a.functions include the tools, strokes, techniques, styles, materials and special effects. b.the contents : no need to prepare the paraphernalia and materials, save a lot of time and energy, can complete the simulation immediately, can deal with the special effects, and can simulate at any time. 3.Instructional model: a.Preparation for teaching is comprised of getting the sample files, using computer image-processing technology to create image files, using word-processing software to arrange the files based on teaching order, creating computer files of “teaching topics”, testing the working situation of computer and projector and arranging the classroom. b.Teaching activities include brief instruction, introduction of topics, presentation of examples, explaining, presentation of different painting effects, phased test and conclusion. 4.Feasibility study and effects on students : a.The feasibility : The contents and functions were accepted by the senior art teachers. These teachers thought students will be anxious but also liked the concept. They feel students will be highly confidential and have more worthiness in their learning attitude. The senior art teachers also expressed the belief that the concept will have positive effects on students’ learning motivation and will improve overall learning outcomes. b.Effects of this model on learning attitude of students were less positive. The model also can not give rise to students’ learning motivation; a relatively higher score only appeared in the aspects of “ inter-object orientation”, “work value”, and “controlling belief of learning”. c.The opinions of students and senior art teachers : （1）In learning attitude, it appeared that the senior art teachers were more confident than the students. The senior art teachers thought that although the teaching model will cause anxiety, it would be worthwhile to popularize. （2）In learning motivation, the senior art teachers thought the teaching model more worthy than the students did. Both the senior art teachers and the students, however, thought that the work worthiness in the learning motivation can not guarantee that students can achieve learning goals.

M.Sc (Computer Science)
Facial modelling and animation is considered one of the most challenging areas in the animation world. Since Parke and Waters’s (1996) comprehensive book, no major work encompassing the entire field of facial animation has been published. This thesis covers Parke and Waters’s work, while also providing a survey of the developments in the field since 1996. The thesis describes, analyses, and compares (where applicable) the existing techniques and practices used to produce the facial animation. Where applicable, the related techniques are grouped in the same chapter and described in a chronological fashion, outlining their differences, as well as their advantages and disadvantages. The thesis is concluded by exploratory work towards a talking head for Northern Sotho. Facial animation and lip synchronisation of a fragment of Northern Sotho is done by using software tools primarily designed for English.
Computing