A graph G is a (t, r)-regular graph if every collection of t independent vertices is collectively adjacent to exactly r vertices. If a graph G is (2, r)-regular where p, s, and m are positive integers, and m ≥ 2, then when n is sufficiently large, then G is isomorphic to G = Ks+mKp, where 2(p-1)+s = r. A nested (2,r)-regular graph is constructed by replacing selected cliques with a (2,r)-regular graph and joining the vertices of the peripheral cliques. For example, in a nested 's' graph when n = s + mp, we obtain n = s1+m1p1+mp. The nested 's' graph is now of the form Gs = Ks1+m1Kp1+mKp. We examine the network properties such as the average path length, clustering coefficient, and the spectrum of these nested graphs.

L'expansion des services en ligne, l'avènement du big data, favorisé par l'internet des objets et les terminaux mobiles, a entraîné une croissance exponentielle du nombre de centres de données qui fournissent des divers services de cloud computing. Par conséquent, la topologie du centre de données est considérée comme un facteur d'influence sur la performance du centre de données. En effet, les topologies des centres de données devraient offrir une latence faible, une longueur de chemin moyenne réduite avec une bande passante élevée. Ces exigences augmentent la consommation énergétique dans les centres de données. Dans cette dissertation, différentes solutions ont été proposées pour surmonter ces problèmes. Tout d'abord, nous proposons une nouvelle topologie appelée LCT (Linked Cluster Topology) qui augmente le nombre de nœuds, améliore la connexion réseau et optimise le routage des données pour avoir une faible latence réseau. Une nouvelle topologie appelée VacoNet (Variable connexion Network) a été également présentée. VacoNet offre un nouveau algorithme qui définit le exact nombre de port par commutateur pour connecter le nombre de serveurs requis tout en réduisant l'énergie consommée et les matériaux inutilisés (câbles, commutateurs). En outre, nous _étudions une nouvelle technique pour optimiser la consumation d'énergie aux centres de données. Cette technique peut périodiquement estimer la matrice de trafic et gérer l'_état des ports de serveurs tout en maintenant le centre de données entièrement connecté. La technique proposée prend en considération le trafic réseau dans la décision de gestion des ports. / Data centers (DC) are being built around the world to provide various cloud computing services. One of the fundamental challenges of existing DC is to design a network that interconnects massive number of nodes (servers)1 while reducing DC' cost and energy consumption. Several solutions have been proposed (e.g. FatTree, DCell and BCube), but they either scale too fast (i.e., double exponentially) or too slow. Effcient DC topologies should incorporate high scalability, low latency, low Average Path Length (APL), high Aggregated Bottleneck Throughput (ABT) and low cost and energy consumption. Therefore, in this dissertation, different solutions have been proposed to overcome these problems. First, we propose a novel DC topology called LCT (Linked Cluster Topology) as a new solution for building scalable and cost effective DC networking infrastructures. The proposed topology reduces the number of redundant connections between clusters of nodes, while increasing the numbers of nodes without affecting the network bisection bandwidth. Furthermore, in order to reduce the DCs cost and energy consumption, we propose first a new static energy saving topology called VacoNet (Variable Connection Network) that connects the needed number of servers while reducing the unused materials (cables, switches). Also, we propose a new approach that exploits the correlation in time of internode communication and some topological features to maximize energy saving without too much impacting the average path length.

The Wiener index of a graph G is defined as the sum of the distances between all pairs of vertices in G. In this master thesis we introduce recursive trees, plane oriented recursive trees (PORTs) and simply generated trees. We then present results by Neininger, Janson, and Munsonius and Rüschendorf for the expectation and limiting distribution of the Wiener index of these families. For recursive trees and PORTs the results follow from analysing the recursive structure of the trees and the contraction method, while the results for simply generated trees is based on a limiting object, the continuum random tree.

Les zéolithes sont des aluminosilicates cristallisés possédant une microporosité organisée et régulière de dimension moléculaire. Plus particulièrement, les zéolithes de type structural FAU sont très employées dans l’industrie comme tamis moléculaires, adsorbants ou catalyseurs grâce à leur faible coût de fabrication, leur grand volume poreux et leur large taille de pores. Cependant, leurs canaux purement microporeux limitent grandement la diffusion de molécules lors de réactions catalytiques ce qui affecte directement les vitesses de réaction et réduit la fraction utile de chaque cristal. L’objectif de cette thèse a été de créer une cavité interne (macroporosité) au sein de chaque cristal de zéolithe Y dont la taille globale et l’épaisseur de parois permettront de réduire les problèmes de diffusion tout en gardant des solides facilement manipulables. Durant cette étude, deux stratégies ont été imaginées et brevetées : la première consiste à préparer des capsules polycristallines de zéolithe Y en faisant croitre des nanocristaux de zéolithe Y en périphérie de cristaux de zéolithe Beta servant directement de nutriment et se détruisant au cours de la synthèse. La seconde stratégie consiste à éliminer le coeur de chaque cristal d’une zéolithe Y par une méthode de dissolution préférentielle. Une méthode multi-étapes alliant désalumination et désilication sélectives a été développée et a permis d’obtenir des monocristaux creux de zéolithe Y. Ensuite, dans le but de tester leurs propriétés diffusionnelles et catalytiques, ces deux nouveaux matériaux ont été imprégnés de nanoparticules de platine puis utilisés dans des réactions modèles d’hydrogénation et d’hydro-isomérisation. Dans le cas des monocristaux creux, ces réactions ont permis de mettre en évidence l’influence positive de la morphologie et plus particulièrement de la longueur de diffusion sur l’activité et l’efficacité catalytiques de ces nouveaux matériaux / Zeolites are crystalline microporous aluminosilicates whose structure contains channels, voids and cavities of molecular dimensions. Zeolites with FAU framework type are extensively used as molecular sieves, adsorbents or catalysts thanks to their low fabrication cost, their high porous volume and their large pore size. However, the intrinsic microporosity of these solids often imposes molecular diffusion limitations due to hindered access and slow intra-crystalline transport. The objective of this PhD thesis was to synthetize hollow Y zeolite crystals with an internal cavity (macroporosity) and walls sufficiently thin to reduce significantly diffusion limitations while preventing handling issues. During the PhD, two strategies have been developed to synthetize these materials. The first one consists in the synthesis of polycrystalline capsules of zeolite Y by overgrowing Y nanocrystals onto Beta zeolite crystals that serve as template as well as nutrients. The second strategy involves the selective removal of the core of each zeolite Y crystals through a multi-step original method combining dealumination and selective desilication. Stating from a standard NaY zeolite, this strategy enables effective preparation of hollow single crystals with well controlled morphology and composition. The influence of the morphology on diffusion and catalytic properties was estimated by comparing the activity of the platinum-impregnated new materials with those of bulk analogs in hydrogenation and hydro-isomerization model reactions. In the case of hollow single crystals, these reactions enable to highlight the positive influence of the morphology and particularly of the diffusion path length on the catalytic efficiency and activity of these new materials

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-03-05T15:35:28Z No. of bitstreams: 2 Dissertação - Micael Oliveira Massula Carvalho de Mello - 2014.pdf: 489311 bytes, checksum: 15900b2c2d82201091cb1f73eeb459f4 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-03-06T10:37:11Z (GMT) No. of bitstreams: 2 Dissertação - Micael Oliveira Massula Carvalho de Mello - 2014.pdf: 489311 bytes, checksum: 15900b2c2d82201091cb1f73eeb459f4 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-03-06T10:37:11Z (GMT). No. of bitstreams: 2 Dissertação - Micael Oliveira Massula Carvalho de Mello - 2014.pdf: 489311 bytes, checksum: 15900b2c2d82201091cb1f73eeb459f4 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-12-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Wireless Mesh Networks (WMNs) are infrastructures with autonomic properties, such as self-organization and self-recovery, which can be developed with widely available technologies and low cost solutions. Besides their current applications, such as community networks and broad-band Internet access, WMNs can offer contributions in the context of the Internet of Things and help to build robust infrastructures to smart energy networks, among other uses. However, WMNs usually have performance issues due to overload in certain parts of the network and interference in wireless links. In this context, it is important that solutions are used to promote load-balancing and to mitigate interference between wireless links. Research in this area shows that one of the most promising approaches are in the subject of the joint routing and channel assignment. However, most of the previous works depends on the knowledge of the network traffic and handle flows with low granularity. In this thesis, we handle the performance problem in WMNs, in particular those having multiple radios and multiple available channels, using a joint approach, but without the mentioned restrictions. Our proposal is a joint heuristic, whose main contribution is the routing, which pursues the compromise between load-balancing and the path length of the network flows. We have developed our proposal in the Network Simulator 3 (ns-3) and have compared it with other works in literature. We found that our heuristic provides throughput improvements in most of the analyzed scenarios, besides promote greater justice between the flows that compete for resources. / Redes em Malha Sem Fio - Wireless Mesh Networks (WMNs) são infraestruturas com propriedades autonômicas, como auto-organização e autorrecuperação, que podem ser implementadas com tecnologias amplamente disponíveis e de custo acessível. Além de suas aplicações atuais, como redes comunitárias e redes de acesso à Internet, as WMNs podem auxiliar na comunicação de Internet das Coisas e constituir infraestruturas robustas para redes inteligentes de energia, dentre outros usos. No entanto, WMNs geralmente apresentam questões relativas a desempenho devido a fatores como sobrecarga em determinadas partes da rede e interferências nos enlaces sem fio. Nesse contexto, é importante que sejam utilizadas soluções que promovam balanceamento de carga na rede e que minimizem as interferências entre os enlaces sem fio. A pesquisa nessa área tem mostrado que uma das abordagens mais promissoras consiste em tratar de maneira conjunta o roteamento e a atribuição de canais. Porém, a maior parte dos trabalhos dependem de conhecimento prévio do tráfego da rede e tratam fluxos com baixa granularidade. Nesta dissertação, tratamos o problema de desempenho em WMNs, em especial as que possuem múltiplos rádios e múltiplos canais disponíveis, utilizando uma abordagem conjunta, mas sem as restrições anteriores. Nossa proposta é uma heurística conjunta, cuja principal contribuição está no roteamento, o qual persegue um compromisso entre o balanceamento de carga e o comprimento dos caminhos seguidos pelos fluxos. Implementamos nossa proposta no Network Simulator 3 (ns-3) e a comparamos com outros trabalhos da literatura. Verificamos que nossa heurística apresenta ganhos de vazão na maior parte dos cenários avaliados, além de promover maior justiça entre os fluxos que concorrem pelos recursos.

L’indice de surface foliaire (Leaf Area Index, LAI), défini comme la moitié de la surface foliaire par unité de surface de sol, est un paramètre clé du cycle écologique de la Terre, et sa précision d'acquisition a toujours la nécessité et la possibilité d'amélioration. La technologie du scanner laser actif offre une possibilité d'obtention cohérente du LAI à plusieurs échelles, car le scanner laser terrestre et le scanner laser aéroporté fonctionnent sur le même mécanisme physique. Cependant, les informations tridimensionnelles du scanner laser ne sont pas complètement explorées dans les méthodes actuelles et les théories traditionnelles ont besoin d'adaptation. Dans cette thèse, le modèle de distribution de longueur de trajet est introduit pour corriger l'effet d’agrégation, et il est appliqué aux données du scanner laser terrestre et du scanner laser aéroporté. La méthode d'obtention de la distribution de longueur de trajet de différentes plates-formes est étudiée et le modèle de récupération cohérent est établi. Cette méthode permet d’améliorer la mesure du LAI des arbres individuels dans les zones urbaines et la cartographie LAI dans les forêts naturelles, et ses résultats sont cohérents à différentes échelles. Le modèle devrait faciliter la détermination cohérente de l'indice de surface foliaire des forêts à l'aide de données au sol et aéroportées. / Leaf Area Index (LAI), defined as one half of the total leaf area per unit ground surface area, is a key parameter of vegetation structure for modeling Earth's ecological cycle and its acquisition accuracy always has the need and opportunity for improvement. Active laser scanning provides an opportunity for consistent LAI retrieval at multiple scales because terrestrial laser scanning (TLS) and airborne laser scanning (ALS) have the similar physical mechanism. However, the three-dimensional information of laser scanning is not fully explored in current methods and the traditional theories require adaptation. In this thesis, the path length distribution model is proposed to model the clumping effect, and it is applied to the TLS and ALS data. The method of obtaining the path length distribution of different platforms is studied, and the consistent retrieval model is established. This method is found to improve the individual tree measurement in urban areas and LAI mapping in natural forest, and its results at consistent at different scales. The model is expected to facilitate the consistent retrieval of the forest leaf area index using ground and airborne data.

As advances in thin films are made there is a parallel requirement to develop equipment capable of measuring their properties accurately and consistently. In addition there is a need to understand the parameters that are measured. Typical DPI measurements allow both the refractive index (related to density) and the thickness of the adsorbed layer to be calculated with relatively few assumptions, to a very high precision in real time. This thesis presents the research undertaken to develop multiple path length dual polarisation interferometry (MPL-DPI) and absorption enhanced dual polarisation interferometry (AE-DPI). In addition research is presented that can be used to improve the interpretation of the measured parameters for inhomogeneous films and uniaxial films. The new Interferometric technique MPL-DPI allows the thickness and refractive index of in situ and ex-situ coated ultra-thin films to be measured. The procedures and the mathematics required to calculate the properties of films have been described and the technique verified. The technique was demonstrated using films of PMMA, where good agreement was found with complementary techniques. Furthermore, some key features of MPL-DPI were demonstrated using the measurements of interfacially grafted acrylic acid. The absorption enhanced DPI uses the attenuation of the light within the waveguide, due to the light absorbing properties of a film on its surface. As the composition of a film changed, it was shown that the refractive index and extinction coefficients could be used to separate the mass of the components of the film that absorbed light, from the components of the film that did not. With the use of a semi-uniaxial model, the extra data from the attenuation in two polarisations was used to fit the extraordinary and ordinary extinction coefficients. The extraordinary and ordinary extinction coefficients were used to demonstrate that molecular orientation could be implied. The influence that an inhomogeneous film has on the measured thickness, refractive index and extinction coefficient fitted by homogeneous models were investigated. Formulas are presented to explain the thickness, refractive index and extinction coefficient of the measured film. A formula for the total mass per unit area that uses the refractive index was created to account for films that contain molecules of different refractive index increments (dn/dc's). To separate the mass of the individual molecular species from the total mass per unit area, formulas that use the extinction coefficient were derived so molecules that absorb light could be separated from those that do not. The mass calculated from the refractive index and the mass calculated from the extinction coefficient were also examined for uniaxial films. For uniaxial films both measures of the adsorbed mass were found to be relatively accurate and benefited from a partial cancellation of errors. The accuracy of the measurements made by dual polarisation interferometry technology is systematically examined throughout this thesis. Improvements in the calibration routines are suggested and a procedure for the identification and reduction of errors in the phase and contrast is demonstrated.

La construction d’un NSOM, dans ce manuscrit de thèse, est décrite en détail. Lacombinaison du système NSOM construit avec un interféromètre est proposée afin d’accéderà des mesures de phase, à la fois de ultra-haute sensibilité mais également de très granderésolution spatiale. Le nom de l’instrument développé est un interferomètre optique àbalayage en champ proche (NSOI, pour l’acronyme en anglais). Le principe est basé surl’utilisation d’un diapason accordable en cristal de quartz, sur lequel se trouve une pointe,afin de sonder le matériau étudié. La mesure de la force de cisaillement de la pointe sondeau voisinage de la surface permet d’assurer la régulation et la stabilité de la distance depositionnement de la pointe par rapport à la surface considérée. Le dispositif est construit encombinant différents éléments électroniques pilotés par un logiciel développé en langageLab-VIEW. Le bruit de la mesure en NSOI est supprimé par un calcul simple basé sur lathéorie de l’optique ondulatoire et des interférences associées. Le système permet deréaliser des mesures optiques en champ proche ainsi que la détermination en hauterésolution de la phase du champ optique. L’échantillon SNG01 (l’un des réseaux utilisés pourcaractériser notre microscope à balayage en champ proche), ainsi que des disques optiques(CD, DVD and disques blu-ray) ont été utilisés pour tester la faisabilité et les performancesde notre système.Dans ce manuscrit de thèse, le graphène et les monocouches de MoS2 sont étudiés. Nous montrons qu’une épaisseur à l’échelle atomique peut être résolue par notresystème NSOI, avec l’utilisation de l’algorithme de suppression du bruit de mesure. Lesjoints de grain du graphène sont observés à grande échelle, via la technique d’imagerie parcollection en champ proche et par la réalisation de cartographies de phase. En particulier,les tensions internes à une couche de graphène sont observées, uniquement dans le casd’une imagerie de phase. / In this thesis, near-field scanning optical interferometry (NSOI), which combinesNSOM with interferometer, is proposed for the phase measurement. The shear-forcedetection scheme is applied for distance regulation. The hardware of the systemis constructed by combining various electronic devices, and the operating softwareis coded by LabVIEW. Unwanted background signal is removed by simple calculationbased on interference theory. By using this, the near-field optical measurementand the ultra-sensitive phase investigation of nano-materials are performed. 2D materialssuch as graphene and monolayer MoS2 are investigated. It is shown thatatomic-scale thickness can be resolved by the NSOI. Especially, the grain boundariesof graphene and the seed of MoS2 can be found by phase detection. In addition,direct laser writing (DLW) on silver-containing glass is observed by using NSOM,and NSOI. For the first time, the writing threshold is correlatively observed in thefluorescence imaging and the near-field phase image.