Le transport des particules et de la chaleur dans la zone de bord des tokamaks joue un rôle déterminant à la fois sur les performances du plasma confiné et sur l’extraction de la puissance et ainsi la durée de vie des composants face au plasma. C’est dans ce contexte que s’inscrit ce travail de thèse, qui porte sur le rôle joué par les écoulements transverses au champ magnétique dans l’équilibre entre dynamique parallèle et dynamique perpendiculaire qui régit la région périphérique d’un tokamak. Ces écoulements peuvent produire des asymétries poloïdales du dépôt de chaleur et de particules sur les composants face au plasma, et plus généralement des asymétries des diverses quantités dans le plasma. Les vitesses de dérive radiale sont d’origine électrique (liées à la présence d’un champ électrique radial résultant de l’équilibre des charges) ou liées aux effets de la géométrie toroïdale induisant une inhomogénéité du champ magnétique (vitesse de gradient-courbure). Pour progresser dans la compréhension de ces phénomènes, la modélisation numérique du transport et de la turbulence en géométrie complexe est indispensable. En complément, des outils de diagnostic synthétique permettant de modéliser les processus de mesure dans les plasmas numériques sont développés pour permettre une comparaison réaliste entre modèles et expériences. La modélisation des vitesses de dérive perpendiculaire a été introduite dans le code SOLEDGE2D décrivant le transport de la densité, quantité de mouvement et énergie d’un plasma de tokamak. Nous avons d’abord étudié l’impact d’un champ électrique prescrit sur les équilibres plasma, pour comprendre les mécanismes à l’origine des asymétries du plasma et étudier l’établissement d’écoulement parallèle et d’asymétrie du dépôt de chaleur sur les composants face au plasma. Nous avons ensuite implémenté un modèle auto-consistant de résolution du potentiel électrique dans les équations fluides de SOLEDGE2D afin de comprendre l’équilibre du champ électrique et d’étudier l’effet de la configuration magnétique du tokamak et de la vitesse de gradient-courbure sur ce dernier. Dans la deuxième partie de cette thèse, un diagnostic synthétique permettant de modéliser les mesures expérimentales de rétro-diffusion Doppler a été développé et testé en vue d’être appliqué aux simulations du code fluide 3D turbulent, TOKAM3X. Ce diagnostic permet de mesurer la vitesse perpendiculaire du plasma à partir du mouvement des fluctuations de densité. Il a été utilisé ici pour comparer les asymétries de vitesse observées expérimentalement aux asymétries mesurées dans les simulations numériques. / The transport of heat and particles in the edge of tokamaks plays a key role in both the performance of the confined plasma and the extraction of power and thus the lifetime of the plasma facing components. It’s in this context that this thesis is inscribed, which focuses on the role played by the transverse magnetic field flows in the balance between parallel and perpendicular dynamic that governs the edge region of a tokamak. These flows can produce poloidal asymmetries of heat and particles deposit on plasma facing components and generally asymmetries of various amounts in plasma. The radial drift velocities are due to the presence of a radial electric field resulting from charge balance (electric drift velocity) or related to effects of the toroidal geometry inducing a magnetic field inhomogeneity (curvature drift velocity). To advance the understanding of these phenomena, numerical modeling of transport and turbulence in complex geometries is essential. In addition, synthetic diagnostic tools for modeling the measurement process in numerical plasmas are developed to enable a realistic comparison between models and experiments. Modeling of perpendicular drift velocities was introduced into the SOLEDGE2D code describing the transport of the density, momentum and energy of a tokamak plasma. We first studied the impact of a prescribed electric field on plasma equilibrium to understand the mechanisms behind plasma asymmetries and study the establishment of parallel flows and asymmetry of the heat flux on plasma facing components. Then we implemented a self-consistent model solving the electric potential in SOLEDGE2D fluid equations to understand the equilibrium of the electric field and to study the effect of the magnetic configuration of the tokamak and the curvature drift velocity on it. In the second part of this thesis, a synthetic diagnosis modeling the experimental measurements of Doppler backscattering was developed and tested in order to be applied to simulations of 3D turbulent fluid code TOKAM3X. This diagnosis measures the perpendicular velocity of the plasma from the movement of the density fluctuations. It was used to compare the perpendicular velocity asymmetries observed experimentally to asymmetries measured in numericalsimulations.

The most widely used protocol for providing reliable service and congestion control in the Internet is the Transmission Control Protocol (TCP). When the Internet is moving towards more use in mobile applications it is getting more important to know how TCP works for this purpose. One of the technologies used for mobile Internet is the Enhanced General Packet Radio Service (EGPRS) extension to the popular GSM system. This thesis presents a low-level analysis of TCP performance in an EGPRS system and an overview of existing TCP, GSM and EGPRS technologies. The bottleneck in an EGPRS system is the wireless link – the connection between the mobile phone and the GSM base station. The data transfer over the wireless link is mainly managed by the complex RLC/MAC protocol. In this thesis, simulations were made to identify some problems with running TCP and RLC/MAC together. The simulations were made using existing EGPRS testing software together with a new TCP module. The simulation software is also briefly described in the thesis. Additionaly, some suggestions are given in order to enhance performance, both by changing the EGPRS system and by modifying the TCP algorithms and parameters.

Au cours de ces dernières décennies, le développement de Systèmes Mobiles de Cartographie, soutenu par un progrès technologique important, est devenu plus apparent. Il a été stimulé par le besoin grandissant de collecte d'informations géographiques précises sur l'environnement. Nous considérons, au sein de cette thèse, des solutions pour l'acquisition des nuages de points mobiles de qualité topographique (précision centimétrique). Il s'agit, dans cette tâche, de mettre au point des méthodes de qualification des données, et d'en améliorer sur les erreurs systématiques par des techniques d'étalonnage et de recalage adéquates.Nous décrivons une démarche innovante d'évaluation de l'exactitude et/ou de la précision des relevés laser mobiles. Celle-ci repose sur l'extraction et la comparaison des entités linéaires de la scène urbaine. La distance moyenne calculée entre les segments appariés, étant la distance modifiée de Hausdorff, sert à noter les nuages par rapport à des références existantes. Pour l'extraction des arêtes, nous proposons une méthode de détection d'intersections entre segments plans retrouvés via un algorithme de RANSAC enrichi d'une analyse de composantes connexes. Nous envisageons également une démarche de correction de relevés laser mobiles à travers un recalage rigide fondé, lui aussi, sur les éléments linéaires. Enfin, nous étudions la pertinence des segments pour en déduire les paramètres de l'étalonnage extrinsèque du système mobile. Nous testons nos méthodes sur des données simulées et des données réelles acquises dans le cadre du projet TerraMobilita. / Over the past few decades, the development of land-based Mobile Mapping Systems (MMS), supported by significant technological progress, has become more prominent. It has been motivated by the growing need for precise geographic information about the environment. In this thesis, we consider approaches for the acquisition of mobile point clouds with topographic quality (centimeter-level accuracy). The aim is to develop techniques for data quality assessment and improvement. In particular, we eliminate the systematic errors inherent to an MMS data using appropriate calibration and registration methods.We describe a novel approach to assess the accuracy and/or the precision of mobile laser point clouds. It is based on the extraction and comparison of line features detected within the urban scene. The computed average distance between corresponding pairs of line segments, taking advantage of a modified Hausdorff distance, is used to evaluate the MMS data with respect to a reference data set. For edge extraction, we propose a method which relies on the intersections between planes modelled via the RANSAC algorithm refined by an analysis of connected components. We also consider an approach to correct point clouds using a line-based rigid registration method. Finally, we study the use of line segments for estimating the boresight angles of a land-based mobile mapping system. We apply our methods to synthetic data and to real data acquired as part of the TerraMobilita project.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Ants belong to a hyperdiverse social insect group with many species used as ecological indicators of their habitat conditions. This study aims to analyze richness, species composition, diversity, evenness, and environmental variables associated to leaf-litter ant fauna of eight forest fragments in the municipality of Santa Maria, Central Depression region of Rio Grande do Sul State, Brazil. The sampling followed standard protocol through a 200-m transect placement by fragment. In order to proceed statistical analyses, the fragments were grouped in two categories, according to their conservation status, preserved or on regeneration. Eighty ant species belonging to 24 genera and nine subfamilies were registered. Myrmicinae, Formicinae and Ponerinae, and Camponotus, Hypoponera and Pheidole were respectively the richest subfamilies and genera and Solenopsis sp. 1 and Gnamptogenys striatula were the most frequent species. Shannon-Wiener and Margalef diversity indexes had the same ordination among fragments, highest at FRJB 01, and lower at FRCE 05. The dominance indexes had the same ordination among higher values but differed among lower ones. FRJB 01 for Simpson and FPMC 06 for Berger-Parker. The fragments separation on two distinct groups was showed by NMDS and confirmed by similarity analyses. The dissimilarity percentage analysis showed that Gnamptogenys striatula and Wasmannia sp. 3 had the highest contribution for conservation status differentiation. The preserved fragments had more similarity among each other than the regeneration ones, highlighting Gnamptogenys striatula and Solenopsis sp. 1 at the first group, and Solenopsis sp. 1 and Hypoponera sp. 4 at the other. Only edge effect showed relationship with species richness among all environmental variables measured. Based on results, the studied ant fauna communities showed noticeably richness and composition partially related to their habitat traits. Although, other factors as adjacent vegetational areas isolation, regeneration time and history and intensity of disturbances could be interfering on these communities structure and their associated biodiversity. / Formigas pertencem a um grupo de insetos sociais hiper-diversos que possuem espécies usadas como indicadores ecológicos das condições dos habitats em que ocorrem. O presente estudo visa analisar riqueza, composição de espécies, diversidade, similaridade e variáveis ambientais associadas à mirmecofauna de serapilheira de oito fragmentos florestais no município de Santa Maria, localizado na região da Depressão Central do Rio Grande do Sul, Brasil. As amostragens seguiram um protocolo padronizado, através do estabelecimento de um transecto de 200 m em cada fragmento. Para fins de análise estatística, os fragmentos foram agrupados em duas categorias, de acordo com seu estado de conservação, preservados ou em regeneração. Foi registrado um total de 80 espécies de formigas, pertencentes a 24 gêneros e nove subfamílias. Myrmicinae, Formicinae e Ponerinae foram as subfamílias mais ricas e Camponotus, Hypoponera e Pheidole, os gêneros com o maior número de espécies. As espécies mais freqüentes foram Solenopsis sp. 1 e Gnamptogenys striatula. Os índices de diversidade de Shannon-Wiener e Margalef tiveram a mesma ordenação entre os fragmentos, sendo maiores em FRJB 01, e menores para FRCE 05. Os índices de dominância apresentaram a mesma ordenação em relação aos valores maiores, mas diferiram em relação aos mínimos, com FRJB 01 menor para Simpson e FPMC 06 para Berger-Parker. O NMDS evidenciou a separação dos fragmentos nos dois grupos distintos, confirmado pela análise de similaridade. A análise de porcentagem de dissimilaridade mostrou que Gnamptogenys striatula e Wasmannia sp. 3 tiveram maior contribuição para a diferenciação dos estados de conservação. Os fragmentos preservados apresentaram maior similaridade entre si do que os em regeneração, destacando-se Gnamptogenys striatula e Solenopsis sp. 1 nos primeiros, e Solenopsis sp. 1 e Hypoponera sp. 4 nos outros. De todas variáveis ambientais mensuradas, apenas tamanho da borda apresentou relação com a riqueza de espécies. Baseado nos resultados encontrados, as comunidades de mirmecofauna estudadas apresentaram riqueza e composição expressivas parcialmente relacionadas com as condições de seus habitats. No entanto, outros fatores como isolamento de áreas de vegetação contíguas, tempo de regeneração e histórico e intensidade das perturbações sofridas podem estar interferindo na estruturação dessas comunidades e sua biodiversidade associada.

Echo state networks represent a special type of recurrent neural networks. Recent papers stated that the echo state networks maximize their computational performance on the transition between order and chaos, the so-called edge of chaos. This work confirms this statement in a comprehensive set of experiments. Afterwards, the best performing echo state network is compared to a network evolved via neuroevolution. The evolved network outperforms the best echo state network, however, the evolution consumes significant computational resources. By combining the best of both worlds, the simplicity of echo state networks and the performance of evolved networks, a new model called locally connected echo state networks is proposed. The results of this thesis may have an impact on future designs of echo state networks and efficiency of their implementation. Furthermore, the findings may improve the understanding of biological brain tissue. 1

L'architecture actuelle du cloud, reposant sur des datacenters centralisés, limite la qualité des services offerts par le cloud du fait de l'éloignement de ces datacenters par rapport aux utilisateurs. En effet, cette architecture est peu adaptée à la tendance actuelle promouvant l'ubiquité du cloud computing. De plus, la consommation énergétique actuelle des data centers, ainsi que du cœur de réseau, représente 3% de la production totale d'énergie, tandis que selon les dernières estimations, seulement 42,3% de la population serait connectée. Dans cette thèse, nous nous intéressons à deux inconvénients majeurs des clouds centralisés: la consommation d'énergie ainsi que la faible qualité de service offerte. D'une part, du fait de son architecture centralisée, le cœur de réseau consomme plus d'énergie afin de connecter les utilisateurs aux datacenters. D'autre part, la distance entre les utilisateurs et les datacenters entraîne une utilisation accrue du réseau mondial à large bande, menant à des expériences utilisateurs de faible qualité, particulièrement pour les applications interactives. Une approche semi-centralisée peut offrir une meilleur qualité d'expérience aux utilisateurs urbains dans des réseaux clouds mobiles. Pour ce faire, cette approche confine le traffic local au plus proche de l'utilisateur, tout en maintenant les caractéristiques centralisées s’exécutant sur les équipements réseaux et utilisateurs. Dans cette thèse, nous proposons une nouvelle architecture de cloud distribué, basée sur des "microclouds". Des "microclouds" sont créés de manière dynamique, afin que les ressources utilisateurs provenant de leurs ordinateurs, téléphones ou équipements réseaux puissent être mises à disposition dans le cloud. De ce fait, les microclouds offrent un système dynamique, passant à l'échelle, tout en évitant d’investir dans de nouvelles infrastructures. Nous proposons également un exemple d'utilisation des microclouds sur un cas typique réel. Par simulation, nous montrons que notre approche permet une économie d'énergie pouvant atteindre 75%, comparée à une approche centralisée standard. En outre, nos résultats indiquent que cette architecture passe à l'échelle en terme du nombre d'utilisateurs mobiles, tout en offrant une bien plus faible latence qu'une architecture centralisée. Pour finir, nous analysons comment inciter les utilisateurs à partager leur ressources dans les clouds mobiles et proposons un nouveau mécanisme d'enchère adapté à l'hétérogénéité et la forte dynamicité de ces systèmes. Nous comparons notre solution aux autres mécanismes d’enchère existants dans des cas d'utilisations typiques au sein des clouds mobiles, et montrons la pertinence de notre solution. / The current datacenter-centralized architecture limits the cloud to the location of the datacenters, generally far from the user. This architecture collides with the latest trend of ubiquity of Cloud computing. Also, current estimated energy usage of data centers and core networks adds up to 3% of the global energy production, while according to latest estimations only 42,3% of the population is connected. In the current work, we focused on two drawbacks of datacenter-centralized Clouds: Energy consumption and poor quality of service. On the one hand, due to its centralized nature, energy consumption in networks is affected by the centralized vision of the Cloud. That is, backbone networks increase their energy consumption in order to connect the clients to the datacenters. On the other hand, distance leads to increased utilization of the broadband Wide Area Network and poor user experience, especially for interactive applications. A distributed approach can provide a better Quality of Experience (QoE) in large urban populations in mobile cloud networks. To do so, the cloud should confine local traffic close to the user, running on the users and network devices. In this work, we propose a novel distributed cloud architecture based on microclouds. Microclouds are dynamically created and allow users to contribute resources from their computers, mobile and network devices to the cloud. This way, they provide a dynamic and scalable system without the need of an extra investment in infrastructure. We also provide a description of a realistic mobile cloud use case, and the adaptation of microclouds on it. Through simulations, we show an overall saving up to 75% of energy consumed in standard centralized clouds with our approach. Also, our results indicate that this architecture is scalable with the number of mobile devices and provide a significantly lower latency than regular datacenter-centralized approaches. Finally, we analyze the use of incentives for Mobile Clouds, and propose a new auction system adapted to the high dynamism and heterogeneity of these systems. We compare our solution to other existing auctions systems in a Mobile Cloud use case, and show the suitability of our solution.

Glioblastoma multiform (GBM) is an aggressive primary brain tumour. Despite treatment advances in recent years, outcomes remain poor. Disease progression tends to occur adjacent to the original tumour or surgical resection bed, usually within the radiotherapy planning field. This local recurrence and progression is believed to be the result of invasive disease in the surrounding tissue at the time of diagnosis and treatment, which is not currently detectable by conventional non-invasive methods. A number of novel therapies are currently under development which target specific aspects of the tumour behaviour, to try and improve outcomes from this devastating disease. Imaging biomarkers are under development, therefore, in order to provide a non-invasive assessment of tumour extent and behaviour, to provide bespoke image-guided therapies, and detect recurrence or treatment failure at the earliest opportunity. These are also of value in the context of novel therapeutics, which may have a very specific affect on an aspect of tumour behaviour that is not readily apparent on standard clinical imaging. Key to the progression of GBM is the invasion into surrounding white matter. This is followed by a period of tumour growth and subsequent angiogenesis in which microvasculature is produce that is distinct from the highly regulated blood-brain barrier. This thesis covers the development of suite of advanced magnetic resonance imaging (MRI) techniques aimed at characterising those very traits of GBM responsible for the aggressiveness and treatment resistance. Repeatability studies are undertaken to determine the performance of the biomarkers in healthy tissues, and also in a range of gliomas. Dynamic Contrast Enhanced (DCE-) and dynamic susceptibility-enhanced (DSC-)MRI are used to provide estimates of perfusion and permeability in the tumour. In order to address the reasons behind preferential invasion of the corpus callosum, they are used in conjunction with ASL to non-invasively map perfusion territories and watershed regions in the brain through perfusion timing parameters. Diffusion Tensor Imaging (DTI) and quantitative magnetisation transfer (qMT) are used to provide complementary information about white matter integrity, in order to identify changes occurring with glioma invasion as early as possible and direct image-guided treatments at presentation. Their complementary nature is assessed by comparing the two parameters simultaneously in white matter. Additionally, one of the qMT parameters which may be related to tissue pH is shown to be sensitive and specific for the detection of high-grade tumour tissue. Finally, a novel multiparametric imaging biomarker is introduced. Tumour surface mapping assesses the boundary between the solid tumour and surrounding tissue in order to identify areas of potential aggressiveness and invasion. Multiple imaging parameters can be combined to improve specificity and sensitivity. Using the diffusion-weighted imaging parameter, mean diffusivity (MD - also referred to as the apparent diffusion coefficient (ADC)), it is shown to be predictive of clinical outcome in a retrospective and prospective study, while a multiparametric example is given indicating the utility as a predicative biomarker for regions of progression and recurrence, and as potential spatial discriminator for image-guided therapies.

Models are incredibly insidious; they slide undetected into discussions and then dominate the way people think. Since Information Systems (ISs) and particularly Knowledge Management Systems (KMSs) are socio-technical systems, they unconsciously embrace the characteristics of the dominant models of management thinking. Thus, their limitations can often be attributed to the deficiencies of the organizational models they aim to support. Through the case study of a hotel chain, this research suggests that contemporary KMSs in the hospitality sector are still grounded in the assumptions of the mechanistic organizational model which conceives an organization as a rigid hierarchical entity governed from the top. Despite the recent technological advances in terms of supporting dialogue and participation between members, organizational knowledge is still transferred vertically; from the top to the bottom or from the bottom to the top. A number of limitations still exist in terms of supporting effectively the transfer of knowledge horizontally between the geographically distributed units of an organization. Inspired from the key concepts of the more recent complex systems model, referred frequently as complexity theories, a Knowledge Management Architecture (KMA) is proposed aiming to re-conceptualize the existing KMSs towards conceiving an organization as a set self-organizing communities of practice (CoP). In every such CoP, order is created from the dynamic exchange of knowledge between the structurally similar community members. Thus, the focus of the KMA is placed on capturing systematically for reuse the architectural knowledge created upon every initiative for change and share such knowledge with the rest of the members of the CoP. A KMS was also developed to support the dynamic dimensions that the KMA proposes. The KMS was then applied in the case of the hotel chain, where it brought significant benefits which constitute evidence of an improved self-organizing ability. The previously isolated hotel units residing in distant regions could now trace but also reapply easily changes undertaken by the other community members. Top-management’s intervention to promote change was reduced, while the pace of change increased. Moreover, the organizational cohesion, the integration of new members as well as the level of management alertness was enhanced. The case of the hotel chain is indicative. It is believed that the KMA proposed can be applicable to geographically distributed organizations operating in different sectors too. At the same time, this research contributes to the recent discourse between the fields of IS and complexity by demonstrating how fundamental concepts from complexity such as self-organization, emergence and edge-of-chaos can be embraced by contemporary KMSs.

Conservation is costly, and choices must be made about where to best allocate limited resources. I propose a regional evolutionary diversity and endangerment (RED-E) approach to prioritization of endangered species. It builds off of the evolutionary diversity and global endangerment (EDGE) approach, but will allow conservation agencies to focus their efforts on species in specific regions. I used the RED-E approach to prioritize mammal and bird species listed under the U.S. Endangered Species Act (ESA), as well as to make a ranking of species without ESA critical habitat (CH), as a practical application. Regional conservation approaches differ significantly from global approaches. The RED-E approach places a high significance on the level of endangerment of a species, but also allows for very distinct species to have increased prioritization on the RED-E list. Using the CH RED-E list, the U.S. government could begin focusing resources toward endangered and genetically diverse species.

No description available.