In this thesis, a low bit rate video coding system based on three-dimensional (3-D) wavelet coding is studied. In addition to the initial motivation to make use of the motion compensated wavelet based coding schemes, the other techniques that do not utilize the motion compensation in their coding procedures have also been considered on equal footing. The 3-D wavelet transform (WT) algorithm is based on the &ldquo / group of frames&rdquo / (GOF) concept. The group of eight frames are decomposed both temporally and spatially to their coarse and detail parts. The decomposition process utilizes both orthogonal and bi-orthogonal wavelet analysis filters. The transform coefficients are coded using an embedded image coding algorithm, called the &ldquo / Two-Dimensional Set Partitioning in Hierarchical Trees&rdquo / (2-D SPIHT). Due to its nature, the 2-D SPIHT is applied to the individual subband frames. In the reconstruction phase, the 2-D SPIHT decoding algorithm and the wavelet synthesis filters are employed, respectively. The Peak Signal to Noise Ratios (PSNRs) are used as a quality measure of the reconstructed frames. The investigations reveal that among several factors, the multi-level (de)composition is the dominant one effective both on the signal compression and the PSNR level. The encoded videos compressed to the ratio of 1:9 are reconstructed with the PSNR of about 30 dB in the best cases.

The development of monolithic microwave integrated circuits (MMICs) has enabled the expansion of multiple circuit elements on a single piece of semiconductor, enclosed in a package with connecting leads. Attributable to the widespread use of wireless circuits and sub-systems, MMICs meet stringent demands for smaller chip area, low loss and low cost. These require highly integrated MMICs with compact features. This thesis provides valuable insight into the design of compact multifunctional MMICs using three-dimensional (3-D) multilayer technology. The proposed technology offers compact, hence low-cost solutions, where all active and passive components are fabricated vertically on the same substrate and no expensive via hole or backside processing is required. The substrate used in this work contains pre-fabricated 0.5 µm pseudomorphic High Electron Mobility Transistor (pHEMT) GaAs active devices. The performances of the uncommitted and committed pHEMTs are compared in terms of their DC, small-signal and large-signal RF measurements and modelling results. Committed pHEMT refers to the pHEMT that is connected to multilayer circuit, whereas uncommitted pHEMT is not. The effect of integrating committed pHEMTs with multilayer passive components is studied and the suitability of the multilayer fabrication processing is assessed. Using this technology, two pHEMT Schottky diodes with 120 µm and 200 µm gate widths are designed, fabricated and extensively characterised by I-V, C-V and S-parameter measurements. The information gained from the measurements is then used to extract all unknown equivalent circuit model parameters using high-frequency on-wafer microwave probing. The measured results showed good agreement with the modelled ones over the frequency range up to 40 GHz. Preliminary demonstrations of the use of these pHEMT Schottky diodes in microwave limiter and detector circuit applications are also discussed, showing promising results. Finally, the implementation of 3-D multilayer technology is shown for the first time in single-pole single-throw (SPST) and single-pole double-throw (SPDT) switches design by utilising the pre-fabricated pHEMTs. The design and analysis of the switches are demonstrated first through simulation using TriQuint's Own Model - Level 3 (TOM3). Three optimised SPST and SPDT pHEMT switching circuits which can address applications ranging from L to X bands are successfully fabricated and tested. The performance of the pHEMT switches is comparable to those of the current state-of-the-art, while simultaneously offering compact circuits with the advantages of integration with other MMIC components. All works reported in this thesis should facilitate foundry design engineers towards further development of 3-D multilayer technology.

abstract: This thesis investigated two different thermal flow sensors for intravascular shear stress analysis. They were based on heat transfer principle, which heat convection from the resistively heated element to the flowing fluid was measured as a function of the changes in voltage. For both sensors, the resistively heated elements were made of Ti/Pt strips with the thickness 0.12 µm and 0.02 µm. The resistance of the sensing element was measured at approximately 1.6-1.7 kohms;. A linear relation between the resistance and temperature was established over the temperature ranging from 22 degree Celsius to 80 degree Celsius and the temperature coefficient of resistance (TCR) was at approximately 0.12 %/degree Celsius. The first thermal flow sensor was one-dimensional (1-D) flexible shear stress sensor. The structure was sensing element sandwiched by a biocompatible polymer "poly-para-xylylene", also known as Parylene, which provided both insulation of electrodes and flexibility of the sensors. A constant-temperature (CT) circuit was designed as the read out circuit based on 0.6 µm CMOS (Complementary metal-oxide-semiconductor) process. The 1-D shear stress sensor suffered from a large measurement error. Because when the sensor was inserted into blood vessels, it was impossible to mount the sensor to the wall as calibrated in micro fluidic channels. According to the previous simulation work, the shear stress was varying and the sensor itself changed the shear stress distribution. We proposed a three-dimensional (3-D) thermal flow sensor, with three-axis of sensing elements integrated in one sensor. It was in the similar shape as a hexagonal prism with diagonal of 1000 µm. On the top of the sensor, there were five bond pads for external wires over 500 µm thick silicon substrate. In each nonadjacent side surface, there was a bended parylene branch with one sensing element. Based on the unique 3-D structure, the sensor was able to obtain data along three axes. With computational fluid dynamics (CFD) model, it is possible to locate the sensor in the blood vessels and give us a better understanding of shear stress distribution in the presence of time-varying component of blood flow and realize more accurate assessment of intravascular convective heat transfer. / Dissertation/Thesis / M.S. Electrical Engineering 2011

Un système est dit robuste s'il est possible de garantir son bon comportement Le cancer est en passe de devenir la première cause de décès dans le monde avec un nombre de cas de cancer qui a pratiquement doublé sur les trente dernières années. Le diagnostic du cancer est d’autant plus important qu’il est maintenant reconnu que, plus la prise en charge du patient est rapide, plus les traitements thérapeutiques sont efficaces. Ce diagnostic doit être précis, fiable, et établi dans les premiers stades de la maladie afin d’augmenter significativement les chances de succès du/des traitements. Les techniques conventionnelles pour le diagnostic du cancer sont essentiellement basées sur des techniques d’imagerie (radiographies, IRM…) associés à des tests cytologiques et biochimiques. Avec le développement récent des technologies de biologie moléculaire (et notamment en protéomique), de nombreux marqueurs tumoraux ont été identifiés et sont utilisés dans des tests d’immunoassay pour le diagnostic voire pronostic du cancer en oncologie clinique. Cependant, le faible taux de marqueurs tumoraux dans le sérum de patient, ainsi que leur grande diversité, sont un challenge important pour l’établissement d’un diagnostic d’autant plus que les techniques de détection souffrent souvent d’un manque de sensibilité et de sélectivité. De plus, du fait de la diversité et de la variabilité des cancers, aucun marqueur tumoral n’est suffisamment spécifique pour permettre un diagnostic précis. Aussi, afin d’augmenter la fiabilité et la précision du diagnostic, il est nécessaire d’utiliser plusieurs marqueurs tumoraux. Dans ce contexte, grâce à leur capacité d’analyse haut débit en parallèle et le faible volume d’échantillon nécessaire, les technologies de puces à protéines (protein microarray)présentent de nombreux avantages pour l’identification de marqueurs tumoraux associés à la réponse humorale. Comme les marqueurs tumoraux sont souvent présents dans les échantillons en très faible quantité (à l’échelle sub micro-molaire), il y a un besoin urgent de développer des puces à protéines avec une détection ultrasensible de marqueurs tumoraux. La spécificité du diagnostic sera fortement liée au choix des protéines que l’on veut détecter(notées protéines cibles) et par conséquent au choix des protéines sondes que l’on va immobiliser sur le support. Un des paramètres critiques dans le développement de puces à protéines sensibles est la chimie de surface qui détermine le mode d’immobilisation de la protéine sonde sur le support et influence son activité biologique et donc sa capacité à reconnaitre et interagir avec la protéine cible que l’on cherche à détecter. Comme de nombreuses études suggèrent qu’un seul biomarqueur n’est pas suffisamment spécifique et sensible, la recherche d’une combinaison pertinente de biomarqueurs est un axe important pour l’amélioration d’un tel diagnostic. L’objectif de ce travail de thèse est donc le développement d’un outil original basé sur la technologie de puces à protéines fonctionnalisées avec différentes chimies de surface pour la détection sensible et spécifique de biomarqueurs tumoraux afin d’améliorer le diagnostic du cancer. Deux types de puces à protéines seront développés pour des applications différentes. Une première puce, avec comme protéines sondes des anticorps, sera développée pour la détection de biomarqueurs tumoraux impliqués dans le cancer colorectal. Une deuxième puce, où les protéines sondes seront des antigènes, sera étudiée en vue de l’identification de réponses autoimmunes de patientes atteintes d’un cancer du sein. [...] / Protein microarrays are becoming powerful tools to screen and identify tumor markers for cancer diagnosis, because of the multiplex detection and minute volume of sample requirement. Due to the diversity and variation in different cancers, no single tumor marker is sensitive and specific enough to meet strict diagnostic criteria. Therefore, a combination of tumor markers is required to increase sensitivity and to establish distinct patterns to increase specificity. To obtain reliable tests, the development of reproducible surface chemistry and immobilization procedure are crucial steps in the elaboration of efficient protein microarrays. In this thesis, 3D micro-structured glass slides were functionalized with various surface chemistries like silane monolayer (amino, epoxy and carboxy), and polymer layers of Jeff amine, chitosan, carboxymethyl dextran (CMD), maleic anhydride-alt-methyl vinyl ether copolymer (MAMVE) for physical adsorption or covalent binding with proteins. Surface characterizations, such as X-ray photoelectron spectroscopy (XPS) and Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), confirmed the monolayer/polymer grafting on the glass slides. Colorimetric assay for determining amine density of three aminated surfaces demonstrated that APDMES had more grafting density than Jeffamine and chitosan. Contact angle measurements show that polymer surfaces were more hydrophilic than monolayer surfaces due to the increasing dosages of polar functional groups. Moreover, the parameters such as additives and pH of spotting buffer, probe concentration, blocking procedures etc, were optimized for tumor marker detection. Under the optimized conditions, antibody microarrays were validated with purified tumor antigens. The best analytical performances obtained for each tumor antigen tested were strongly dependent on functionalized surfaces, e.g. MAMVE exhibited best analytical performances for CEA andHsp60 while NHS leads to best results for PDI and CA19-9. Besides, the implemented antibody microarrays were applied to tumor marker detection from colorectal cancer sera. This evaluation shows the interest to combine several tumor markers on the same surface and the combination of tumor markers on their specific surface lead to remarkably increase the positive responses of tested cancer sera (even up to 100 %). A second type of microarrays (tumor-associated antigens - TAA microarrays) was designed to discriminate breast cancer patients from healthy donors through the detection of tumor autoantibodies. This study included a cohort of 29 breast cancer patients’ and 28 healthy donors’ sera. A panel of fiveTAAs (Hsp60, p53, Her2, NY-ESO-1 and Hsp70) immobilized on their respective optimized surface chemistry allowed to specifically detect over 82% of breast cancer patients.

Multiscale computational simulations are performed to investigate how electronic structure and optical absorption characteristics of recently reported nanostructured III-nitride core-shell MQW solar cells are governed by an intricate coupling of size-quantization, atomicity, and built-in structural and polarization fields. The core computational framework, as available in our in-house QuADS 3-D simulator, is divided into four coupled phases: 1) Geometry construction for the wurtzite lattice having hexagonal crystal symmetry and non-conventional crystal orientations; 2) Structural relaxation and calculation of atomistic strain distributions using the VFF Keating molecular-mechanics model, which employs a conjugate gradient energy minimization scheme; 3) Obtaining the induced polarization and internal potential distributions using a 3-D atomistic Poisson solver; 4) Computing the single-particle electronic structure and optical transition rates using a 10- band sp3 s*-spin tight-binding framework; and 5) Using a TCAD toolkit, study the carrier transport and obtain the device terminal characteristics. Special care was taken in incorporating the nonpolar m-plane crystallographic orientation within the simulator via appropriate lattice vectors, rotational matrices, neighboring atom co-ordinates and sp3-hybridized passivation scheme. Numerical calculations of electronic structure properties are generally based on non-primitive rectangular unit cell. The rectangular geometry approximation is still valid and can be considered even in the presence of strain in nanostructures such as quantum wells, nanowires, and even in self-assembled quantum dots with varying composition. With this approximation, atoms are grouped into traditional unit cells resulting in simpler analysis and better storage scheme, which results in more dynamic and easily debugged algorithms. Note that the contribution of the second-order piezoelectric polarization is small in the nonpolar m-plane structure (as compared to the polar c-plane counterpart) and was neglected in this study. Besides, the spontaneous polarization is non-existent in m-plane structure. The polarization fields are incorporated in the Hamiltonian as an external potential within a non-self-consistent approximation. From the simulations, it is found that, even without the inclusion of any internal fields, the crystal symmetry is lowered compared to ideal geometries, which is due mainly to the fundamental atomicity and interface discontinuities. However, with the inclusion of internal polarization fields, although the symmetry is lowered further, the m-plane structure exhibits a stronger overlap and localization of the wavefunctions, as compared to the c-plane counterpart. Importantly, strain, in the m-plane structure, causes a larger splitting of the topmost valence band and the interband transition probability involving the 4th valence band was found to be highest. Overall, the m-plane structure offers higher spontaneous emission rate and internal quantum efficiency (IQE) as well as an improved fill-factor.

A temática da produção de alimentos destaca-se entre as discussões do desenvolvimento sustentável, principalmente por constituir uma das atividades fundamentais para a existência humana, a qual tem sido responsável por inúmeros impactos socioambientais, tais como a destruição das florestas e da biodiversidade genética, a erosão dos solos e a contaminação dos recursos naturais e dos alimentos, bem como o êxodo rural e a concentração de terras. Nesse contexto, a Agroecologia apresenta-se sob um enfoque teórico e metodológico que, agregando diversas disciplinas científicas, se propõe a estudar a atividade agrária sob uma perspectiva ecológica. Sua unidade de análise, portanto, é o agroecossistema, que, a partir de um enfoque sistêmico proporciona as bases científicas para a implantação de agriculturas mais sustentáveis. Assim, percebe-se que a Agroecologia, ao incorporar múltiplas dimensões, promove discussões relacionadas à do desenvolvimento sustentável. Dada a importância de áreas naturais preservadas para a manutenção da biodiversidade e de serviços ecossistêmicos na discussão tanto da Agroecologia como do desenvolvimento sustentável, o objetivo dessa pesquisa foi analisar as diferentes propriedades agroecológicas na área de influência de unidades de conservação do Litoral Norte do estado do Rio Grande do Sul e que fazem parte do Organismo Participativo de Avaliação da Conformidade – OPAC Litoral Norte, a partir do Modelo 3-D de Sustentabilidade de Mauerhofer (2008). Esse modelo foi escolhido porque, além de englobar as três dimensões, ambiental, social e econômica, elas são apresentadas em outro nível de discussão, em um cone, representando uma hierarquia, onde as paredes do cone representam a capacidade de suporte do ambiente, enquanto a base representa o capital ambiental. Interior a esse cone, há outro, em que as paredes representam a capacidade de suporte social e a base o capital social. Da mesma forma, interior a esse segundo cone, há o cone da capacidade econômica e do capital econômico. Os cones estão assim dispostos devido a uma relação de dependência, pois a dimensão social só existe porque há a dimensão ambiental, e a econômica só existe porque há a dimensão social. Portanto, a partir de uma abordagem qualitativa, por meio de entrevistas em profundidade com auxilio de roteiros semiestruturados, a pesquisa foi realizada em seis propriedades agroecológicas do Litoral Norte do Rio Grande do Sul. Uma proposta de operacionalização do modelo 3-D de sustentabilidade de Mauerhofer (2008) foi elaborada, em que os dados coletados resultaram em modelos de triângulo 3-D de sustentabilidade para cada um dos agrossistemas analisados. Um modelo 3- D de sustentabilidade para cada um dos extremos (propriedade sustentável e insustentável) foi também elaborado. Assim, pode-se constatar que os modelos das propriedades rurais analisadas encontram-se bem mais próximos ao modelo da propriedade sustentável, sendo as questões econômicas as que apresentam relações de menor eficiência. Essas propriedades possuem, portanto, inúmeros aspectos que podem contribuir com a efetividade das unidades de conservação. Entre esses aspectos destacam-se a preservação da mata nativa e implantação de sistemas agroflorestais, os quais podem atuar como corredores ecológicos e o envolvimento dos agricultores com os gestores das unidades de conservação, que contribuem para o apoio da população local. / Food production consists in an important topic among the discussions of sustainable development, mainly because of its fundamental role to human existence. However, numerous social and environmental impacts have been generated due to the dominant style of food production, such as the forests destruction and genetic biodiversity lost, soil erosion and contamination of natural resources and food, as well as the rural exodus and the land ownership concentration. In this context, Agroecology is issued as a theoretical and methodological approach that proposes to study the agrarian activity from an ecological perspective, taking into consideration several scientific disciplines for its analysis. The Agroecology unit of analysis is therefore the agroecosystem, which, from a systemic approach, provides the scientific basis for the implementation of more sustainable agriculture. Thus, Agroecology is able to promote discussions related with sustainable development, by incorporating multiple dimensions into its analysis. Given the importance of preserved natural areas for the maintenance of biodiversity and ecosystem services in both discussions, Agroecology and sustainable development, this study aimed to analyze the different agroecological agrosystems located in the influence zone of conservation unities from the North Coast of Rio Grande do Sul which belong to the Participatory Organization for Conformity Assessment (OPAC North Coast) – Organismo Participativo de Avaliação da Conformidade Litoral Norte – from the perspective of 3-D Model of Sustainability of Mauerhofer (2008). This model was chosen because it includes the three sustainable dimensions, environmental, social and economic, which are analyzed through a cone. The cone represents a hierarchy, and its walls mean the carrying capacity of the environment, while the base represents the environmental capital. Inside this cone, there is a second cone, whose walls represent the social carrying capacity and the base represents the social capital. Likewise, inside this second cone, there is a third cone with the economic capacity and economic capital. The cones are arranged through a dependency relationship, since the social dimension only exists because there is the environmental dimension, and economic exists only because there is a social dimension. In order to achieve this purpose, this research had a qualitative approach and it was carried out through in-depth interviews with semi-structured guide in six agroecological farms. An operational proposal of the 3-D sustainability model of Mauerhofer (2008) was elaborated. From that the collected data resulted in models of 3-D sustainability triangle for each agroecosystems. A 3-D sustainability model for each extreme category (sustainable and unsustainable farms) was also elaborated. Thus, the results illustrate that the farms models produced in this research are closer to the sustainable farm model. They also show that economic issues have the lowest efficiency ratios. These farms, however, have many aspects which can contribute to effectiveness of protected areas. Among these aspects, the forest fragments preservation and agroforestry systems implementation can act as ecological corridors and the involvement of these farmers with the protected areas managers can contribute to local population support.

A temática da produção de alimentos destaca-se entre as discussões do desenvolvimento sustentável, principalmente por constituir uma das atividades fundamentais para a existência humana, a qual tem sido responsável por inúmeros impactos socioambientais, tais como a destruição das florestas e da biodiversidade genética, a erosão dos solos e a contaminação dos recursos naturais e dos alimentos, bem como o êxodo rural e a concentração de terras. Nesse contexto, a Agroecologia apresenta-se sob um enfoque teórico e metodológico que, agregando diversas disciplinas científicas, se propõe a estudar a atividade agrária sob uma perspectiva ecológica. Sua unidade de análise, portanto, é o agroecossistema, que, a partir de um enfoque sistêmico proporciona as bases científicas para a implantação de agriculturas mais sustentáveis. Assim, percebe-se que a Agroecologia, ao incorporar múltiplas dimensões, promove discussões relacionadas à do desenvolvimento sustentável. Dada a importância de áreas naturais preservadas para a manutenção da biodiversidade e de serviços ecossistêmicos na discussão tanto da Agroecologia como do desenvolvimento sustentável, o objetivo dessa pesquisa foi analisar as diferentes propriedades agroecológicas na área de influência de unidades de conservação do Litoral Norte do estado do Rio Grande do Sul e que fazem parte do Organismo Participativo de Avaliação da Conformidade – OPAC Litoral Norte, a partir do Modelo 3-D de Sustentabilidade de Mauerhofer (2008). Esse modelo foi escolhido porque, além de englobar as três dimensões, ambiental, social e econômica, elas são apresentadas em outro nível de discussão, em um cone, representando uma hierarquia, onde as paredes do cone representam a capacidade de suporte do ambiente, enquanto a base representa o capital ambiental. Interior a esse cone, há outro, em que as paredes representam a capacidade de suporte social e a base o capital social. Da mesma forma, interior a esse segundo cone, há o cone da capacidade econômica e do capital econômico. Os cones estão assim dispostos devido a uma relação de dependência, pois a dimensão social só existe porque há a dimensão ambiental, e a econômica só existe porque há a dimensão social. Portanto, a partir de uma abordagem qualitativa, por meio de entrevistas em profundidade com auxilio de roteiros semiestruturados, a pesquisa foi realizada em seis propriedades agroecológicas do Litoral Norte do Rio Grande do Sul. Uma proposta de operacionalização do modelo 3-D de sustentabilidade de Mauerhofer (2008) foi elaborada, em que os dados coletados resultaram em modelos de triângulo 3-D de sustentabilidade para cada um dos agrossistemas analisados. Um modelo 3- D de sustentabilidade para cada um dos extremos (propriedade sustentável e insustentável) foi também elaborado. Assim, pode-se constatar que os modelos das propriedades rurais analisadas encontram-se bem mais próximos ao modelo da propriedade sustentável, sendo as questões econômicas as que apresentam relações de menor eficiência. Essas propriedades possuem, portanto, inúmeros aspectos que podem contribuir com a efetividade das unidades de conservação. Entre esses aspectos destacam-se a preservação da mata nativa e implantação de sistemas agroflorestais, os quais podem atuar como corredores ecológicos e o envolvimento dos agricultores com os gestores das unidades de conservação, que contribuem para o apoio da população local. / Food production consists in an important topic among the discussions of sustainable development, mainly because of its fundamental role to human existence. However, numerous social and environmental impacts have been generated due to the dominant style of food production, such as the forests destruction and genetic biodiversity lost, soil erosion and contamination of natural resources and food, as well as the rural exodus and the land ownership concentration. In this context, Agroecology is issued as a theoretical and methodological approach that proposes to study the agrarian activity from an ecological perspective, taking into consideration several scientific disciplines for its analysis. The Agroecology unit of analysis is therefore the agroecosystem, which, from a systemic approach, provides the scientific basis for the implementation of more sustainable agriculture. Thus, Agroecology is able to promote discussions related with sustainable development, by incorporating multiple dimensions into its analysis. Given the importance of preserved natural areas for the maintenance of biodiversity and ecosystem services in both discussions, Agroecology and sustainable development, this study aimed to analyze the different agroecological agrosystems located in the influence zone of conservation unities from the North Coast of Rio Grande do Sul which belong to the Participatory Organization for Conformity Assessment (OPAC North Coast) – Organismo Participativo de Avaliação da Conformidade Litoral Norte – from the perspective of 3-D Model of Sustainability of Mauerhofer (2008). This model was chosen because it includes the three sustainable dimensions, environmental, social and economic, which are analyzed through a cone. The cone represents a hierarchy, and its walls mean the carrying capacity of the environment, while the base represents the environmental capital. Inside this cone, there is a second cone, whose walls represent the social carrying capacity and the base represents the social capital. Likewise, inside this second cone, there is a third cone with the economic capacity and economic capital. The cones are arranged through a dependency relationship, since the social dimension only exists because there is the environmental dimension, and economic exists only because there is a social dimension. In order to achieve this purpose, this research had a qualitative approach and it was carried out through in-depth interviews with semi-structured guide in six agroecological farms. An operational proposal of the 3-D sustainability model of Mauerhofer (2008) was elaborated. From that the collected data resulted in models of 3-D sustainability triangle for each agroecosystems. A 3-D sustainability model for each extreme category (sustainable and unsustainable farms) was also elaborated. Thus, the results illustrate that the farms models produced in this research are closer to the sustainable farm model. They also show that economic issues have the lowest efficiency ratios. These farms, however, have many aspects which can contribute to effectiveness of protected areas. Among these aspects, the forest fragments preservation and agroforestry systems implementation can act as ecological corridors and the involvement of these farmers with the protected areas managers can contribute to local population support.

Il y a une décennie, le contenu numérique virtuel était limité à quelques applications – majoritairementles jeux vidéos, les films en 3D et la simulation numérique. Aujourd’hui, grâce à l’apparition de cartes graphiques performantes et bon marché, les objets 3D sont utilisés dans de nombreuses applications. A peu près tous les terminaux possédant des capacités d’affichage – des clusters de visualisation haute performance jusqu’aux smart phones – intègrent maintenant une puce graphique qui leur permet de faire du rendu 3D. Ainsi, les applications 3D sont bien plus variées qu’il y a quelques années. On citera par exemple la réalité virtuelle et augmentée en temps réel ou les mondes virtuels 3D. Dans ce contexte, le besoin de méthodes efficaces pour la transmission et la visualisation des données 3D est toujours plus pressant. De plus, la taille des maillages 3D ne cesse de s’accroître avec la précision de la représentation. Par exemple, les scanners 3D actuels sont capables de numériser des objets du monde réel avec une précision de seulement quelques micromètres, et génèrent des maillages contenant plusieurs centaines de millions d’´el´ements. D’un autre côté, une précision accrue en simulation numérique requiert des maillages plus fins, et les méthodes massivement parallèles actuelles sont capables de travailler avec des milliards de mailles. Dans ce contexte, la compression de ces données – en particulier la compression de maillages – est un enjeu important. Durant la décennie passée, de nombreuses méthodes ont été développées pour coder les maillages polygonaux. Néanmoins, ces techniques ne sont plus adaptées au contexte actuel, car elles supposentque la compression et la d´ecompression sont des processus sym´etriques qui ont lieu sur un mat´erielsimilaire. Dans le cadre actuel, au contraire, le contenu 3D se trouve cr´e´e, compressé et distribué par des machines de hautes performances, tandis que l’exploitation des données – par exemple, la visualisation – est effectuée à distance sur des périphériques de capacité plus modeste – éventuellement mobiles – qui ne peuvent traiter les maillages de grande taille dans leur int´egralité. Ceci fait de lacompression de maillage un processus intrinsèquement asymétrique.Dans cette thèse, notre objectif est d’étudier et de proposer des méthodes pour la compression de maillages de grande taille. Nous nous intéressons plus particulièrement aux méthodes d’accès aléatoire, qui voient la compression comme un problème intrinsèquement asymétrique. Dans ce modèle, le codeur a accès à des ressources informatiques importantes, tandis que la décompression estun processus temps réel (souple) qui se fait avec du matériel de plus faible puissance. Nous décrivons un algorithme de ce type et l’appliquons au cas de la visualisation interactive. Nous proposons aussi un algorithme streaming pour compresser des maillages hexaèdriques de très grande taille utilisés dans le contexte de la simulation numérique. Nous sommes ainsi capables decompresser des maillages comportant de l’ordre de 50 millions de mailles en moins de deux minutes, et en n’utilisant que quelques mégaoctets de mémoire vive. Enfin, nous proposons, indépendamment de ces deux algorithmes, un cadre théorique général pour améliorer la compression de géométrie. Cet algorithme peut être utilisé pour développer des méthodes de prédiction pour n’importe quel algorithme basé sur un paradigme prédictif – ce qui est la cas dela majorité des méthodes existantes. Nous dérivons ainsi des schémas de prédictions compatibles avec plusieurs méthodes de la littérature. Ces schémas augmentent les taux de compression de 9% enmoyenne. Sous des hypothèses usuelles, nous utilisons aussi ces résultats pour prouver l’optimalité de certains algorithmes existants. / A decade ago, 3D content was restricted to a few applications – mainly games, 3D graphics andscientific simulations. Nowadays, thanks to the development cheap and efficient specialized renderingdevices, 3D objects are ubiquitous. Virtually all devices with a display – from a large visualizationclusters to smart phones – now integrate 3D rendering capabilities. Therefore, 3D applications arenow far more diverse than a few years ago, and include for example real-time virtual and augmentedreality, as well as 3D virtual worlds. In this context, there is an ever increasing need for efficient toolsto transmit and visualize 3D content.In addition, the size of 3D meshes always increases with accuracy of representation. On one hand,recent 3D scanners are able to digitalize real-world objects with a precision of a few micrometers, andgenerate meshes with several hundred million elements. On the other hand, numerical simulationsalways require finer meshes for better accuracy, and massively parallel simulation methods now generatemeshes with billions of elements. In this context, 3D data compression – in particular 3D meshcompression – services are of strategic importance.The previous decade has seen the development of many efficient methods for encoding polygonalmeshes. However, these techniques are no longer adapted to the current context, because they supposethat encoding and decoding are symmetric processes that take place on the same kind of hardware.In contrast, remote 3D content will typically be created, compressed and served by high-performancemachines, while exploitation (e.g. visualization) will be carried out remotely on smaller – possiblyhand held – devices that cannot handle large meshes as a whole. This makes mesh compression anintrinsically asymmetric process.Our objective in this dissertation is to address the compression of these large meshes. In particularwe study random-accessible compression schemes, that consider mesh compression as an asymmetricproblem where the compressor is an off-line process and has access to a large amount of resources,while decompression is a time-critical process with limited resources. We design such a compressionscheme and apply it to interactive visualization.In addition, we propose a streaming compression algorithm that targets the very large hexahedralmeshes that are common in the context of scientific numerical simulation. Using this scheme, we areable to compress meshes of 50 million hexahedra in less than two minutes using a few megabytes ofmemory.Independently from these two specific algorithms, we develop a generic theoretical framework toaddress mesh geometry compression. This framework can be used to derive geometry compressionschemes for any mesh compression algorithm based on a predictive paradigm – which is the case of thelarge majority of compression schemes. Using this framework, we derive new geometry compressionschemes that are compatible with existing mesh compression algorithms but improve compressionratios – by approximately 9% on average. We also prove the optimality of some other schemes underusual smoothness assumptions.

A temática da produção de alimentos destaca-se entre as discussões do desenvolvimento sustentável, principalmente por constituir uma das atividades fundamentais para a existência humana, a qual tem sido responsável por inúmeros impactos socioambientais, tais como a destruição das florestas e da biodiversidade genética, a erosão dos solos e a contaminação dos recursos naturais e dos alimentos, bem como o êxodo rural e a concentração de terras. Nesse contexto, a Agroecologia apresenta-se sob um enfoque teórico e metodológico que, agregando diversas disciplinas científicas, se propõe a estudar a atividade agrária sob uma perspectiva ecológica. Sua unidade de análise, portanto, é o agroecossistema, que, a partir de um enfoque sistêmico proporciona as bases científicas para a implantação de agriculturas mais sustentáveis. Assim, percebe-se que a Agroecologia, ao incorporar múltiplas dimensões, promove discussões relacionadas à do desenvolvimento sustentável. Dada a importância de áreas naturais preservadas para a manutenção da biodiversidade e de serviços ecossistêmicos na discussão tanto da Agroecologia como do desenvolvimento sustentável, o objetivo dessa pesquisa foi analisar as diferentes propriedades agroecológicas na área de influência de unidades de conservação do Litoral Norte do estado do Rio Grande do Sul e que fazem parte do Organismo Participativo de Avaliação da Conformidade – OPAC Litoral Norte, a partir do Modelo 3-D de Sustentabilidade de Mauerhofer (2008). Esse modelo foi escolhido porque, além de englobar as três dimensões, ambiental, social e econômica, elas são apresentadas em outro nível de discussão, em um cone, representando uma hierarquia, onde as paredes do cone representam a capacidade de suporte do ambiente, enquanto a base representa o capital ambiental. Interior a esse cone, há outro, em que as paredes representam a capacidade de suporte social e a base o capital social. Da mesma forma, interior a esse segundo cone, há o cone da capacidade econômica e do capital econômico. Os cones estão assim dispostos devido a uma relação de dependência, pois a dimensão social só existe porque há a dimensão ambiental, e a econômica só existe porque há a dimensão social. Portanto, a partir de uma abordagem qualitativa, por meio de entrevistas em profundidade com auxilio de roteiros semiestruturados, a pesquisa foi realizada em seis propriedades agroecológicas do Litoral Norte do Rio Grande do Sul. Uma proposta de operacionalização do modelo 3-D de sustentabilidade de Mauerhofer (2008) foi elaborada, em que os dados coletados resultaram em modelos de triângulo 3-D de sustentabilidade para cada um dos agrossistemas analisados. Um modelo 3- D de sustentabilidade para cada um dos extremos (propriedade sustentável e insustentável) foi também elaborado. Assim, pode-se constatar que os modelos das propriedades rurais analisadas encontram-se bem mais próximos ao modelo da propriedade sustentável, sendo as questões econômicas as que apresentam relações de menor eficiência. Essas propriedades possuem, portanto, inúmeros aspectos que podem contribuir com a efetividade das unidades de conservação. Entre esses aspectos destacam-se a preservação da mata nativa e implantação de sistemas agroflorestais, os quais podem atuar como corredores ecológicos e o envolvimento dos agricultores com os gestores das unidades de conservação, que contribuem para o apoio da população local. / Food production consists in an important topic among the discussions of sustainable development, mainly because of its fundamental role to human existence. However, numerous social and environmental impacts have been generated due to the dominant style of food production, such as the forests destruction and genetic biodiversity lost, soil erosion and contamination of natural resources and food, as well as the rural exodus and the land ownership concentration. In this context, Agroecology is issued as a theoretical and methodological approach that proposes to study the agrarian activity from an ecological perspective, taking into consideration several scientific disciplines for its analysis. The Agroecology unit of analysis is therefore the agroecosystem, which, from a systemic approach, provides the scientific basis for the implementation of more sustainable agriculture. Thus, Agroecology is able to promote discussions related with sustainable development, by incorporating multiple dimensions into its analysis. Given the importance of preserved natural areas for the maintenance of biodiversity and ecosystem services in both discussions, Agroecology and sustainable development, this study aimed to analyze the different agroecological agrosystems located in the influence zone of conservation unities from the North Coast of Rio Grande do Sul which belong to the Participatory Organization for Conformity Assessment (OPAC North Coast) – Organismo Participativo de Avaliação da Conformidade Litoral Norte – from the perspective of 3-D Model of Sustainability of Mauerhofer (2008). This model was chosen because it includes the three sustainable dimensions, environmental, social and economic, which are analyzed through a cone. The cone represents a hierarchy, and its walls mean the carrying capacity of the environment, while the base represents the environmental capital. Inside this cone, there is a second cone, whose walls represent the social carrying capacity and the base represents the social capital. Likewise, inside this second cone, there is a third cone with the economic capacity and economic capital. The cones are arranged through a dependency relationship, since the social dimension only exists because there is the environmental dimension, and economic exists only because there is a social dimension. In order to achieve this purpose, this research had a qualitative approach and it was carried out through in-depth interviews with semi-structured guide in six agroecological farms. An operational proposal of the 3-D sustainability model of Mauerhofer (2008) was elaborated. From that the collected data resulted in models of 3-D sustainability triangle for each agroecosystems. A 3-D sustainability model for each extreme category (sustainable and unsustainable farms) was also elaborated. Thus, the results illustrate that the farms models produced in this research are closer to the sustainable farm model. They also show that economic issues have the lowest efficiency ratios. These farms, however, have many aspects which can contribute to effectiveness of protected areas. Among these aspects, the forest fragments preservation and agroforestry systems implementation can act as ecological corridors and the involvement of these farmers with the protected areas managers can contribute to local population support.

Three-dimensional (3-D) medical imaging creates notable opportunities as input toward engineering analyses, whether for basic understanding of the normal function or patho-physiology of an organ, or for the simulation of virtual surgical procedures. These analyses most often require finite element (FE) models to be constructed from patient-specific 3-D medical images. However, creation of such models can be extremely labor-intensive; in addition, image processing and mesh generation are often operator-dependent, lack robustness and may be of suboptimal quality. Focusing on the human aorta, the goal of the present work is to create a fast and robust methodology for quadrilateral surface and hexahedral volume meshing from 3-D medical images with minimal user input. By making use of the segmentation capabilities of the 3-D gradient vector flow field combined with original ray-tracing and orientation control algorithms, we will demonstrate that it is possible to incrementally grow a structured quadrilateral surface mesh of the inner wall of the aorta. The process does not only require minimal input from the user, it is also robust and very fast compared to existing methods; it effectively combines segmentation and meshing into one single effort. After successfully testing the methodology and measuring the quality of the meshes produced by it from synthetic as well as real medical image datasets, we will make use of the surface mesh of the inner aortic wall to derive hexahedral meshes of the aortic wall thickness and of the fluid domain inside the aorta. We will finally outline a tentative approach to merge several structured meshes to process the main branches of the aorta.