Made available in DSpace on 2017-07-21T19:26:05Z (GMT). No. of bitstreams: 1 Marily Aparecida Benicio.pdf: 2662358 bytes, checksum: ba11ae50b21bd9be5feba0d2bf5fd563 (MD5) Previous issue date: 2013-04-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Studies of complex networks help us to understand and model many real world situations. The world abounds in networks that can be found in many real contexts. The term network refers to relations between two sets and can be represented by means of graph theory. The classification of complex networks is given according to the models created to represent them, such as Random networks, networks of Small World, No Scaling networks and hierarchical networks. From the perspective of complex networks, a study which make significant contributions analysis is the phenomenon of diffusion of information in networks, which can be understood through the random walk process, which is characterized by a stochastic used as a mechanism transportation and research in complex networks. A random walk in complex networks can be used to check the behavior of each network model front dissipation. Each network model presents a different behavior with respect to the number of random walkers that pass through the network node over time. The number of walkers will depend on the structure of the networks generated by each model and measures of centrality of each node. Measures of centrality of the vertices of the network are useful for comparing the efficienc of the nodes with respect to receiving and sending information being indicative of the rapidity with which this transport happens. The objective of this work is to study the process of random walk and use it to analyze the efficiency of Centrality measures, inferring the number of random walkers who pass by us in complex networks. Measures of centrality are analyzed centralities Degree, Centrality Intermediation by Minor Roads, Centralization of Random Walk. To compare the efficiency of these measures of centrality in the different network models, numerical simulations were performed. With these, it was noticed that the behavior of the diffusion of walkers varies for each network model. Random network for the flow of walkers from the evenly is not possible to highlight some vertex of utmost importance within the network. It can be observed that the measure of centrality of Random Walk is the one that showed greater efficiency by pointing a greater flow of walkers to the vertices that had a higher value for this measure. / Os estudos sobre redes complexas nos auxiliam a compreender e modelar muitas situações do mundo real. O mundo é abundante em redes que podem ser encontradas em diversos contextos reais. O termo redes faz referência às relações estabelecidas entre dois conjuntos e podem ser representadas por meio da teoria de grafos. A classificação das redes complexas se dá de acordo com os modelos criados para representá-las, tais como as redes Aleatórias, redes de Pequeno Mundo, redes Sem Escala e redes Hierárquicas. Dentro da perspectiva de redes complexas, um estudo que pode trazer contribuições importantes é análise do fenômeno de difusão de informação em redes, os quais podem ser entendidos através do processo da caminhada aleatória, a qual se caracteriza por ser um processo estocástico utilizado como um mecanismo de transporte e pesquisa em redes complexas. A caminhada aleatória nas redes complexas pode ser utilizada para verificar o comportamento de cada modelo de rede frente à dissipação. Cada modelo de rede apresenta um comportamento diferente com relação ao número de caminhantes aleatórios que passam por nó da rede ao longo do tempo. Este número de caminhantes irá depender da estrutura das redes geradas por cada modelo e das medidas de Centralidade de cada nó. As medidas de centralidade dos vértices da rede são úteis para comparar a eficiência dos nós com relação ao recebimento e envio de informações sendo indicativos da rapidez com a qual, este transporte acontece. O objetivo deste trabalho é estudar o processo da caminhada aleatória e utilizá-la para analisar a eficiência das medidas de Centralidade, inferindo o número de caminhantes aleatórios que passam pelos nós nas redes complexas. As medidas de centralidade analisadas são as centralidades do Grau, Centralidade de Intermediação por Menores Caminhos, Centralidade da Caminhada Aleatória. Para comparar a eficiência das referidas medidas de Centralidade nos diferentes modelos de redes, foram realizadas simulações numéricas. Com estas, percebeu-se que o comportamento da difusão de caminhantes varia para cada modelo de rede. Para a rede Aleatória o fluxo de caminhantes se da de maneira uniforme não sendo possível destacar algum vértice de maior importância dentro da rede. Pode-se observar que a medida de Centralidade da Caminhada Aleatória é a que mostrou maior eficiência ao apontar o um maior fluxo de caminhantes aos vértices que possuíam um maior valor para essa medida.

Present day email is provided by centralized services running in the cloud. The services transparently connect users behind middleboxes and provide backup, redundancy, and high availability at the expense of user privacy. In present day mobile environments, users can access and modify email from multiple devices with updates reconciled on the central server. Prioritizing updates is difficult and may be undesirable. Moreover, legacy email protocols do not provide optimal email synchronization and access. Recent phenomena of the Internet of Things (IoT) will see the number of interconnected devices grow to 27 billion by 2021. In the first part of my dissertation I am proposing a decentralized email architecture which takes advantage of user's a IoT devices to maintain a complete email history. This addresses the email reconciliation issue and places data under user control. I replace legacy email protocols with a synchronization protocol to achieve eventual consistency of email and optimize bandwidth and energy usage. The architecture is evaluated on a Raspberry Pi computer. There is an extensive body of research on Social Network Analysis (SNA) based on email archives. Typically, the analyzed network reflects either communication between users or a relationship between the email and the information found in the email's header and the body. This approach discards either all or some email attachments that cannot be converted to text; for instance, images. Yet attachments may use up to 90% of an email archive size. In the second part of my dissertation I suggest extracting the network from email attachments shared between users. I hypothesize that the network extracted from shared email attachments might provide more insight into the social structure of the email archive. I evaluate communication and shared email attachments networks by analyzing common centrality measures and classication and clustering algorithms. I further demonstrate how the analysis of the shared attachments network can be used to optimize the proposed decentralized email architecture.

O processo de reestruturação produtiva envolveu implicações tanto na morfologia, quanto dinâmica de vida em inúmeras cidades, gerando consideráveis mudanças nos fluxos interurbanos. É sobre eles que assentamos nossas análises. No Brasil, as dinâmicas que definiram nosso recorte temporal implantaram-se mais incisivamente através de uma série de reformulações políticas que caracterizaram o início da década de 1990. Elas implicaram, entre outras coisas, no acirramento da concorrência entre empresas e em sua maior liberdade de deslocamento pelo território, sendo a indústria a força impulsionadora de inúmeras transformações espaciais. Para compreender a relação entre reestruturação produtiva e mudanças na rede urbana, definimos como recorte territorial as cidades de Itu, Salto e Sorocaba. A análise dos fluxos interurbanos dessas cidades fornece elementos que reafirmam a ideia de que as mudanças espaciais geradas a partir da reestruturação produtiva não implicaram em uma perda de importância da capital do Estado, São Paulo. Ao invés disso, houve um reforço de sua centralidade, bem como de outras que lhe dão suporte, como é o caso de Sorocaba, em torno da qual um novo aglomerado se conformou. Essa cidade ampliou suas funções na rede urbana e atualmente integra o amplo conjunto metropolitano formado pela expansão da metrópole paulistana, a cidade-região. Concomitantemente a essa reafirmação de determinadas centralidades, há também o aumento da importância de fluxos que se estabelecem entre cidades de mesmo nível hierárquico, o que, atrelado a outros aspectos, assinala o desenvolvimento de uma rede urbana mais complexa, pela multiplicidade de interações que se estabelecem. Essa aparente contradição no contexto da rede urbana e sua relação com o processo de reestruturação produtiva é outro ponto que buscamos entender. Ela nos remete à análise das mudanças econômicas e nas estratégias empresariais para a concentração capitalista durante as últimas décadas. Isso porque consideramos os fluxos econômicos como os principais definidores da rede urbana. / The restructuring process involved implications so much in the morphology, as much in the dynamics of life in many cities, generating considerable changes in intercity flows. Its about them that we seat our analysis. In Brazil, the dynamics that defined our time frame established themselves more sharply through a series of reformulations policies that characterized the early 1990s. They led, among other things, to the increased of the competition between companies and their greater freedom of movement throughout the territory, being the industry the driving force of numerous spatial transformations. To understand the relation between changes in industrial structure and urban network, we defined as territorial clipping the cities of Itu, Salto and Sorocaba. The analysis of the intercity flows of these cities provides elements that reaffirm the idea that the spatial changes generated from the productive restructuring did not result in a loss of importance of the state capital, São Paulo. Instead, there was an increase of its centrality, as well as others that give support to it, as is the case of Sorocaba, around which a new agglomerate has been conformed. This city strengthened its functions in urban network and, currently, integrates the broad metropolitan set formed by the expansion of the paulistana metropolis, the city-region. Concomitantly with this reaffirmation of certain centralities, there is also the increasing importance of flows established between cities of the same hierarchical level, which, linked to other aspects, marks the development of a more complex urban network, due the multiplicity of interactions that take place. This apparent contradiction in the context of the urban network and its relation with the restructuring process is another point that we seek to understand with this research. It remits us to the analysis of the economic and business strategies changes for the capitalist concentration during the recent decades. This is because we consider the economic flows as the main delineaters of the urban network.

Este estudo problematiza a produção espacial de um bairro mediante os caminhos que nele chegam, como a ferrovia e a rodovia. Procura discutir como os caminhos que favoreceram o processo de industrialização e urbanização, sendo resultado das relações de produção de uma sociedade. Assim, o estabelecimento de uma sociedade num dado local advém também da importância dos caminhos criados e elaborados socialmente para esse fim, dando uma continuidade e interferindo nas relações de produção em seu sentido mais amplo: da vida, de mercadorias, de espaços. Esse movimento possibilita a reprodução das esferas produtivas, fazendo parte da sociedade urbana e industrial. Num tempo próprio do bairro, no caso o Bairro Barcelona na cidade de Sorocaba-SP, este tem seu cotidiano transformado ao mesmo tempo em que essa escala do lugar faz parte de um movimento de reprodução do capital que articula outras escalas. Entender esse processo exige que se discuta a expansão da cidade, bem como de sua centralidade e como, ao mesmo tempo, se fragmentam e articulam os espaços, transformando a realidade local. / This study shows the problem in the space production of a neighborhood by means of the roads that arrive in it, as the railroad and the highway. It tries to discuss as the roads that favored the industrialization process and urbanization, being resulted of the relationships of production of a society. Thus, the establishment of a society in a dice local came also of the roads servants\' importance and elaborated socially for that end, giving a continuity and interfering in the production relationships in its wider sense: of the life, of goods, of spaces. That movement facilitates the reproduction of the productive spheres, being part of the urban and industrial society. In an own time of the neighborhood, in the case the Barcelona Village in the city of Sorocaba-SP, this has its daily one transformed at the same time in that that scale from the position is part of a movement of reproduction of the capital that articulates other scales. To understand that process demands to discusses the expansion of the city, as well as of its centrality and as, at the same time, how the spaces are fragmented and articulated, transforming the local reality.

Esta dissertação tem como objetivo central a análise das transformações do espaço urbana metropolitano a partir do estudo de um fragmento de São Paulo, o Largo da Batata, no bairro de Pinheiros. Entende-se que, por ter passado por intensas transformações socioespaciais, encaminhadas na relação entre o Estado e o Setor Privado, o lugar possa apontar para as transformações mais amplas do capitalismo, principalmente no período atual, em que a reprodução do capital passa, inequivocamente, pela reprodução do espaço. Este fragmento, constituído como centralidade comercial, na mobilidade e na vida cotidiana ao longo do século XX, foi inserido na Operação Urbana Faria Lima, a partir da reconversão urbana do Largo da Batata. Desde 2001, quando foi lançado o edital para o Projeto, até 2013, quando as principais obras foram finalizadas o Largo foi transformado em um imenso canteiro de obras: desapropriações, mudanças viárias, construção das estações do metrô e a metamorfose do próprio espaço do Largo da Batata, tornado uma explanada. Estas transformações, encaminhadas pelo Estado interferiram profundamente na dinâmica de todo o entorno, com destaque para o aumento significativo da verticalização trazida pela expansão imobiliário-financeira, o que gerou uma valorização que, em menos de uma década, mudou o padrão do comércio e o perfil dos moradores do lugar. O comércio popular, característico das últimas décadas do século XX, foi trocado por atividades do setor terciário superior, apesar de algumas permanências. O uso residencial, transformado por edifícios de alto padrão, trouxe para o entorno uma população de maior renda. Com isso, houve um aumento significativo de restaurantes, comércios em geral e serviços voltados a esta população. Observa-se um processo de homogeneização e fragmentação deste espaço que, com sua centralidade voltada aos setores mais modernos da economia, alcança outro patamar na hierarquia dos lugares na metrópole. Desde que as obras iniciaram, coletivos e movimentos questionam as imposições da Prefeitura e o avanço do mercado imobiliário. Estes coletivos, em geral, são responsáveis por atuar no Largo como incentivadores e viabilizadores de uma série de atividades políticas, culturais, artísticas e esportivas que visam o uso e a apropriação do espaço público. Nesse sentido, o Largo torna-se também, sobretudo a partir de 2013, um lugar privilegiado nas manifestações políticas na metrópole de São Paulo, indicando que de fato o lugar ganhou centralidade na escala metropolitana e, mesmo com ação direta das forças homogeneizantes, o espaço é usado e apropriado de forma a apontar seu caráter público. / This dissertation has as main objective the analysis of the transformations of the metropolitan urban space from the study of a fragment of São Paulo, Largo da Batata, in the district of Pinheiros. It is understood that, because it has undergone intense socio-spatial transformations, rooted in the relationship between the State and the Private Sector, the place may point to the broader transformations of capitalism, especially in the present period, when the reproduction of capital unequivocally, by the reproduction of space. This fragment, constituted as a commercial center, in mobility and in daily life throughout the 20th century, was inserted in Operation Faria Lima Urban, from the urban reconversion of the Largo da Batata. Since 2001, when the project was published, until 2013, when the main works were completed, Largo was transformed into an immense construction site: expropriations, road changes, construction of subway stations and the metamorphosis of Largo da Batata\'s own space, made an esplanade. These transformations, driven by the State, deeply interfered in the dynamics of the whole environment, with emphasis on the significant increase in verticalization brought by the real estate-financial expansion, which generated a valuation that, in less than a decade, changed the pattern of commerce and the profile of the locals. Popular trade, characteristic of the last decades of the twentieth century, was replaced by activities of the higher tertiary sector, despite some permanence. The residential use, transformed by buildings of high standard, brought to the surroundings a population of greater income. With this, there was a significant increase of restaurants, commerce in general and services directed to this population. It is observed a process of homogenization and fragmentation of this space that, with its centrality directed to the most modern sectors of the economy, reaches another level in the hierarchy of places in the metropolis. These processes, however, did not occur continuously and without embargos. Since the works began, collectives and movements question the impositions of the City Hall and the advance of the real estate market. These collectives, in general, are responsible for acting in the Largo as incentive and enablers of a series of political, cultural, artistic and sports activities that aim at the use and appropriation of the public space. In this sense, the Largo also becomes, especially from 2013, a privileged place in the political manifestations in the metropolis of São Paulo, indicating that in fact the place has gained centrality in the metropolitan scale and, even with direct action of the homogenizing forces, the space is used and appropriate in order to point out its public character.

Finding subgroups within social networks is important for understanding and possibly influencing the formation and evolution of online communities. This thesis addresses the problem of finding cohesive subgroups within social networks inferred from online interactions. The dissertation begins with a review of relevant literature and identifies existing methods for finding cohesive subgroups. This is followed by the introduction of the SCAN method for identifying subgroups in online interaction. The SCAN (Social Cohesion Analysis of Networks) methodology involves three steps: selecting the possible members (Select), collecting those members into possible subgroups (Collect) and choosing the cohesive subgroups over time (Choose). Social network analysis, clustering and partitioning, and similarity measurement are then used to implement each of the steps. Two further case studies are presented, one involving the TorCamp Google group and the other involving YouTube vaccination videos, to demonstrate how the methodology works in practice. Behavioural measures of Sense of Community and the Social Network Questionnaire are correlated with the SCAN method to demonstrate that the SCAN approach can find meaningful subgroups. Additional empirical findings are reported. Betweenness centrality appears to be a useful filter for screening potential subgroup members, and members of cohesive subgroups have stronger community membership and influence than others. Subgroups identified using weighted average hierarchical clustering are consistent with the subgroups identified using the more computationally expensive k-plex analysis. The value of similarity measurement in assessing subgroup cohesion over time is demonstrated, and possible problems with the use of Q modularity to identify cohesive subgroups are noted. Applications of this research to marketing, expertise location, and information search are also discussed.

Finding subgroups within social networks is important for understanding and possibly influencing the formation and evolution of online communities. This thesis addresses the problem of finding cohesive subgroups within social networks inferred from online interactions. The dissertation begins with a review of relevant literature and identifies existing methods for finding cohesive subgroups. This is followed by the introduction of the SCAN method for identifying subgroups in online interaction. The SCAN (Social Cohesion Analysis of Networks) methodology involves three steps: selecting the possible members (Select), collecting those members into possible subgroups (Collect) and choosing the cohesive subgroups over time (Choose). Social network analysis, clustering and partitioning, and similarity measurement are then used to implement each of the steps. Two further case studies are presented, one involving the TorCamp Google group and the other involving YouTube vaccination videos, to demonstrate how the methodology works in practice. Behavioural measures of Sense of Community and the Social Network Questionnaire are correlated with the SCAN method to demonstrate that the SCAN approach can find meaningful subgroups. Additional empirical findings are reported. Betweenness centrality appears to be a useful filter for screening potential subgroup members, and members of cohesive subgroups have stronger community membership and influence than others. Subgroups identified using weighted average hierarchical clustering are consistent with the subgroups identified using the more computationally expensive k-plex analysis. The value of similarity measurement in assessing subgroup cohesion over time is demonstrated, and possible problems with the use of Q modularity to identify cohesive subgroups are noted. Applications of this research to marketing, expertise location, and information search are also discussed.

The study applied for a social network analysis tool and HLM method to analysis cross level dataset which will specify an integrated ¡¥meso¡¦ framework of linking diversified relationships and employees¡¦ attitudes and behavior within the work group settings. The effective sample size of this study collected by whole completed survey involved 317 employees within 26 different workgroups representing diversified industries in Taiwan. This study provided evidence that density of informal development network (informal network, advice network, and mentoring network) are related to both employees¡¦ intention to stay and individual job performance. As hypothesized, both In-degree centrality of advice network was positively related to individual job performance. Perceived career success was positively related to in-degree centrality of advice network. In-degree centrality of friendship network was negatively related to intention to stay. Furthermore, Density of mentoring network will be positively related to intention to stay and individual job performance. Density of advice network was related negatively to individual job performance and density of friendship was related positively to individual job performance. The effect of in-degree centrality of advice network on individual job performance will be partially mediated by mediating variable - perceived career success as well as the effect of in-degree centrality of friendship network will be partially mediated by mediating variable - perceived career success.

As Internet communities such as question-answer (Q&A) forums and online social networks (OSNs) grow in prominence as knowledge sources, traditional editorial filters are unable to scale to their size and pace. This absence hinders the exchange of knowledge online, by creating an understandable lack of trust in information. This mistrust can be partially overcome by a forum by consistently providing reliable information, thus establishing itself as a reliable source. This work investigates how algorithmic approaches can contribute to building such a community of voluntary experts willing to contribute authoritative information. This work identifies two approaches: a) reducing the cost of participation for experts via matching user queries to experts (question recommendation), and b) identifying authoritative contributors for incentivization (authority estimation). The question recommendation problem is addressed by extending existing approaches via a new generative model that augments textual data with expert preference information among different questions. Another contribution to this domain is the introduction of a set of formalized metrics to include the expert's experience besides the questioner's. This is essential for expert retention in a voluntary community, and has not been addressed by previous work. The authority estimation problem is addressed by observing that the global graph structure of user interactions, results from two factors: a user's performance in local one-to-one interactions, and their activity levels. By positing an intrinsic authority 'strength' for each user node in the graph that governs the outcome of individual interactions via the Bradley-Terry model for pairwise comparison, this research establishes a relationship between intrinsic user authority, and global measures of influence. This approach overcomes many drawbacks of current measures of node importance in OSNs by naturally correcting for user activity levels, and providing an explanation for the frequent disconnect between real world reputation and online influence. Also, while existing research has been restricted to node ranking on a single OSN graph, this work demonstrates that co-ranking across multiple endorsement graphs drawn from the same OSN is a highly effective approach for aggregating complementary graph information. A new scalable co-ranking framework is introduced for this task. The resulting algorithms are evaluated on data from various online communities, and empirically shown to outperform existing approaches by a large margin. / text

Nearshore populations have been depleted and some have not yet recovered. Therefore, theoretical studies focus on improving fisheries management and designing marine protected areas (MPAs). Depleted populations may be undergoing an Allee effect, i.e. a decrease in fitness at low densities. Here, I constructed a marine metapopulation model that included pre- and post-dispersal Allee effects using a network theory approach. Networks represent metapopulations as groups of nodes connected by dispersal paths. With this model I answered four questions: What is the role of Allee effects on habitat occupancy? Are MPAs effective in recovering exploited populations? What is the importance of larval dispersal patterns in preventing local extinctions due to exploitation and Allee effects? Can exploitation fragment nearshore metapopulations? When weak Allee effects are included, habitat occupancy drops as larval retention decreases because more larvae are lost to unsuitable habitat. With strong Allee effects habitat occupancy also drops at high larval retention because more larvae are needed to overcome the Allee effect. Post-dispersal Allee effects seem more detrimental for nearshore metapopulations. MPA effectiveness seems also lower in a post-dispersal Allee effect scenario. In overexploited systems, local populations that go extinct are also less likely to recover even after protecting the whole coastline. In exploited nearshore metapopulations with Allee effects, local occupancy or the recovery of local populations depends not only on larval inflow from neighbor populations, but also on larval inflow for these neighbors. Nearshore metapopulations with intense fishing mortality and Allee effects may also suffer a decrease in dispersal strength and fragmentation. Population fragmentation occurs when large populations are split into smaller groups. A tool for detecting partitioning in a network is modularity. The modularity analysis performed for red abalone in the Southern California Bight showed that exploitation increases partitioning through time before the entire metapopulation collapses. These findings call for research effort in estimating the strength of potential Allee effects to prevent stock collapse and assess MPA effectiveness, evaluating the predictability of local occupancy by centrality metrics to help identify important sites for conservation, and using modularity analysis to quantify the health of exploited metapopulations to prevent their collapse. / text