Cette thèse s'inscrit dans le cadre d'une étude polyhédrale des problèmes de conception de réseaux fiables avec forte connexité. En particulier, nous considérons les problèmes dits du sous-graphe k-arête-connexe et de conception de réseau k-arête-connexe avec contrainte de borne lorsque k _>3. Dans un 1er temps, nous étudions le problème du sous-graphe k-arête-connexe. Etant donné un graphe non orienté et valué G = (V, E) et un entier positif k, le problème du sous-graphe k-arête-connexe consiste à déterminer un sous-graphe de G de poids minimum telle qu'il existe k chaînes arête-disjointes entre chaque paire de sommets de V. Nous discutons du polytope associé à ce problème lorsque k _>3. Nous introduisons une nouvelle famille d'inégalités valides pour le polytope et présentons plusieurs familles d'inégalités valides. Pour chaque famille d'inégalités, nous étudions les conditions sous lesquelles ces inégalités définissent des facettes. Nous discutons aussi du problème de séparation associé à chaque famille d'inégalités ainsi que d'opérations de réduction de graphes. En utilisant ces résultats, nous développons un algorithme de coupes et branchements pour le problème et donnons des résultats expérimentaux. Ensuite, nous étudions le problème de conception de réseaux k-arête-connexe avec contrainte de borne. Soient G = (V, E) un graphe valué non orienté, un ensemble de demandes D _C V x V et deux entiers positifs k et L. Le problème de conception de réseaux k-arête-connexe avec contrainte de borne consiste à déterminer un sous-graphe de G de poids minimum telle qu'entre chaque paire de sommets {s, t} E D, il existe k chaînes arête-disjointes de longueur au plus L. Nous étudions ce problème dans le cas où k _>2 et L E {2, 3}. Nous examinons la structure du polytope associé et montrons que, lorsque I D I = 1, ce polytope est complètement décrit par les inégalités dites de st-coupe et de L-chemin-coupe avec les inégalités triviales. Ce résultat généralise ceux de Huygens et al. [75] pour k = 2, L E {2, 3} et Dahl et al. [35] pour k _>2, L = 2. Enfin, nous nous intéressons au problème de conception de réseau k-arête-connexe avec contrainte de borne lorsque k _>2, L E {2, 3} et I D I _> 2. Le problème est NP-difficile dans ce cas. Nous introduisons quatre nouvelles formulations du problème sous la forme de programmes linéaires en nombres entiers. Celles-ci sont basées sur la transformation du graphe G en graphes orientés appropriés. Nous discutons du polytope associé à chaque formulation et introduisons plusieurs familles d'inégalités valides. Pour chacune d'elles, nous décrivons des conditions pour que ces inégalités définissent des facettes. En utilisant ces résultats, nous développons des algorithmes de coupes et branchements et de coupes, génération de colonnes et branchements pour le problème. Nous donnons des résultats expérimentaux et menons une étude comparative entre les différentes formulations.

L'augmentation constante des débits de transmission de données a fait évoluer les réseaux IP vers de nouveaux services. Dans ce contexte, ces travaux de thèse étudient l'influence des nouveaux protocoles dans la conception de réseaux haut débit tolérants aux pannes. Dans un premier temps, nous nous sommes intéressés aux spécificités du routage dans les réseaux MPLS (MultiProtocol Label Switching). Pour limiter la taille des tables de commutation, il est nécessaire de limiter le nombre de routes. Cette contrainte forte sur le support des flux change considérablement la complexité des problèmes de routage. Notre contribution porte principalement sur la modélisation des problèmes de flots k-séparables par des programmes linéaires en nombres entiers adaptés à une résolution exacte. D'autre part nous nous sommes intéressés à la contrainte de délai de bout-en-bout. Nos modèles de flots k-séparables offrent des possibilités intéressantes pour gérer cette contrainte

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Depression has a high prevalence among college students. Because it is a highly private (i.e. experiential) and socially stigmatized mental illness, it often goes undetected in daily life. The basic research question behind this line of research is how students' postings on their social networking websites can be used for the early detection of depression. The current research investigates how well depression can be gauged from MySpace profiles (Study 1) and Facebook profiles (Study 2 & Study 3). Across studies, the results reveal that depression can be assessed with a moderate degree of accuracy. In addition, Study 3 presents evidence that viewing "mini-blogs" allows for similar levels of accuracy compared to viewing an entire profile and the degree to which a person is Extraverted or censors information about themselves (e.g. Impression Management, Public Self-Consciousness) influences the degree of accuracy. Overall, the results speak to the idea that social networking sites can be a cost effective and clinically relevant tool to detecting depression.

No description available.

Peer-to-peer streaming has emerged as a killer application in today's Internet, delivering a large variety of live multimedia content to millions of users at any given time with low server cost. Though successfully deployed, the efficiency and optimality of the current peer-to-peer streaming protocols are still less than satisfactory. In this thesis, we investigate optimizing solutions to enhance the performance of the state-of-the-art mesh-based peer-to-peer streaming systems, utilizing both theoretical performance modeling and extensive real-world measurements. First, we model peer-to-peer streaming applications in both the single-overlay and multi-overlay scenarios, based on the solid foundation of optimization and game theories. Using these models, we design efficient and fully decentralized solutions to achieve performance optimization in peer-to-peer streaming. Then, based on a large volume of live measurements from a commercial large-scale peer-to-peer streaming application, we extensively study the real-world performance of peer-to-peer streaming over a long period of time. Highlights of our measurement study include the topological characterization of large-scale streaming meshes, the statistical characterization of inter-peer bandwidth availability, and the investigation of server capacity utilization in peer-to-peer streaming. Utilizing in-depth insights from our measurements, we design practical algorithms that advance the performance of key protocols in peer-to-peer live streaming. We show that our optimizing solutions fulfill their design objectives in various realistic scenarios, using extensive simulations and experiments.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / Discover how it is now possible to memory-link all man-in-the-loop and machine-in-the-loop elements, as global resources that share information at memory-access speeds, to provide a unified system paradigm that avows: "the data is there, on time, every time." Regardless of configuration, if your past, present, or future system consists of more than one computer, and it interactively mixes information sources and destinations (e.g. Telemetry data streams, I/O interfaces, information processors, etc.) to achieve a highly integrated system, then the critical path to real-time success mandates a high performance, reliable, and deterministic communications methodology. This softwareless, future technology is already successfully sharing information in other real-time markets and applications, and is ready for more challenging applications.

<p>We are witnessing a paradigm shift in computing---people are increasingly using Web-based software for tasks that only a few years ago were carried out using software running locally on their computers. The increasing use of mobile devices, which typically have limited processing power, is catalyzing the idea of offloading computations to the cloud. It is within this context of cloud computing that this thesis attempts to address a few key questions: (a) With more computations moving to the cloud, what is the state of the Internet's core? In particular, do routing changes and consistent congestion in the Internet's core affect end users' experiences? (b) With software-defined networking (SDN) principles increasingly being used to manage cloud infrastructures, are the software solutions robust (i.e., resilient to bugs)? With service outage costs being prohibitively expensive, how can we support network operators in experimenting with novel ideas without crashing their SDN ecosystems? (c) How can we build a large-scale passive IP geolocation system to geolocate the entire IP address space at once so that cloud-based software can utilize the geolocation database in enhancing the end-user experience? (d) Why is the Internet so slow? Since a low-latency network allows more offloading of computations to the cloud, how can we reduce the latency in the Internet?</p> / Dissertation

Social network sites are online spaces that can be used for interaction between young people and youth work practitioners. The focus of this thesis is social network site interaction that falls outside the guidance of the local authority, through unsanctioned interaction on practitioners’ personal but also work profiles. Twenty one practitioners and fourteen young people were interviewed, using a semi-structured interview guide. Three inter-linked themes emerged through the research process; space and place; trust development and boundary management. Young people wanted to interact with some practitioners through the practitioners' personal profiles but the majority of practitioners would rather interact with young people through work profiles. Young people viewed and trusted these practitioners as friends and were willing to share their personal, but also socially intimate information with them. Most practitioners viewed their relationship with young people as a professional relationship and aimed to maintain personal and professional boundaries. However, practitioners did not extend this same awareness to the boundaries of young people. This was further confirmed by the practice of client searching through a variety of profiles to access socially intimate information of young people. Where practitioners and volunteers lived and worked in the same geographical spaces, these multiple relationships increased uncertainty with regards to unsanctioned SNS interaction. Other practitioners were either fearful or opportunistic of these relationships and used them to gain further socially intimate information about young people or turned a blind eye to these relationships due to uncertainty of how to respond. This thesis extends knowledge and theory concerning youth work practice at a time of change, and also new spaces for interaction online. Civic courage and incentives that outweigh deterrents lead to unsanctioned connections for practitioners. For young people this interaction was based on the type of friendship they perceived they had with practitioners. Studying perceptions regarding this interaction revealed cycles of perpetual negative practice, personal and socially intimate boundaries and different views on the type of relationship that young people and practitioners developed with each other.

This study explored attributes of a Facebook brand page (FBP). Seven variables were derived from the framework and applied to FBPs. The goals of this research were to discover which attributes contribute to a successful FBP, determine which attributes increase purchase intentions, and help marketers determine where to focus their efforts. A total of 421 surveys were gathered from men and women ages 18 and older. The methods of this research included factor analysis and multiple regression analysis. Results yielded two loading factors for the trustworthiness variable and supported hypotheses of trustworthiness increasing purchase intentions. It was also discovered that participation positively influences purchase intentions. It is advised that information content be monitored to avoid information overload.