Information propagation has attracted increasing attention from sociologists, marketing researchers and Information Technology entrepreneurs. With the rapid developments in online and mobile social applications like Facebook, Twitter, and LinkedIn, large-scale, high-speed and instantaneous information dissemination becomes possible, spawning tremendous opportunities for electronic commerce. It is non-trivial to make an accurate analysis on how information is propagated due to the uncertainty of human behavior and the complexity of the social environment. This dissertation is concerned with exploring models, formulations, and heuristics for the social-network-based information propagation process. It consists of three major parts: information diffusion through online social network, modeling social influence propagation, and social-network-based information spreading in opportunistic mobile networks. Firstly, I consider the problem of maximizing the influence propagation through online social networks. To solve it, I introduce a probabilistic maximum coverage problem, and propose a cluster-based heuristic and a neighbor-removal heuristic for two basic diffusion models, namely, the Linear Threshold Model and the Independent Cascade Model, respectively. Realizing that the selection of influential nodes is mainly based on the accuracy and efficiency in estimating the social influence, I build a framework of up-to-2-hop hierarchical network to approximate the spreading of social influence, and further propose a hierarchy-based algorithm to solve the influence maximization problem. Our heuristic is proved to be efficient and robust with competitive performance, low computation cost, and high scalability. The second part explores the modeling on social influence propagation. I develop an analytical model for the influence propagation process based on discrete-time Markov chains, and deduce a close-form equation to express the n-step transition probability matrix. We show that given any initial state the probability distribution of the converged network state could be easily obtained by calculating a matrix product. Finally, I study the social-network-based information spreading in opportunistic mobile networks by analyzing the opportunistic routing process. I propose three social-network-based communication pattern models and utilize them to evaluate the performance of different social-network-based routing protocols based on several human mobility traces. Moreover, I discuss the fairness evaluation in opportunistic routing, and propose a fair packet forwarding strategy which operates as a plugin for traditional social- network-based routing protocols. My strategy improves the imbalance of success rates among users while maintaining approximately the same system throughput. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Infections frequently occur on both networks of devices and networks of people, and can model not only viruses, but also information, rumors, and product use. However, in many circumstances, the infection process itself is hidden, and only the effects, e.g. sickness or knowledge, can be observed. In addition, this information is likely incomplete, missing many sick nodes, as well as inaccurate, with false positives. To use this data effectively, it is often essential to identify the infection process causing the sickness, or even whether the cause is an infection. For our purposes, we consider the susceptible-infected (SI) infection model. We seek to distinguish between infections and random sickness, as well as between different infection (or infection-like) processes in a limited information setting. We formulate this as a hypothesis testing problem, where (typically) in the null, the sickness affects nodes at random, and in the alternative, the infection is spread through the network. Similarly, we consider the case where the sickness may be caused by one of two infection (or infection-like) processes, and we wish to find which is the causative process. We do this is a setting with very limited information, given only a single snapshot of the infection. Only a small portion of the infected population reports the sickness. In addition, there are several other limitations we consider. There may be false positives, obfuscating the infection. Similarly, there may be a random sickness and epidemic process occurring simultaneously. Knowledge of the graph topology may be incomplete, with unknown edges over which the infection may spread. The graph may also be weighted, affecting the way the infection spreads over the graph. In all these cases, we develop algorithms to identify the causative process of the infection utilizing the fact that infected nodes will be clustered. We demonstrate that under reasonable conditions, these algorithms detect an infection with asymptotically zero error probability as the graph size increases. / text

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This qualitative descriptive inquiry investigates the perceptions and uses of social support of a selected group of adolescents who attended an English school for students with learning disabilities in Montreal, Quebec. I draw on Vygotskian socio-cultural theory as a framework for understanding how the participants access and use people for social support and how these adolescents provide others with social support. I use three Vygotskian concepts, the zone of proximal development, self-regulation and internalization to examine the differences between those who use support well and those who do not. Data collected and analyzed includes audio taped interviews with focus groups, students, parents, teachers and professional staff, school based and classroom based participant observations. A major finding to emerge is that adolescents in this inquiry use or do not use support well based on what they have internalized through previous experiences and social interactions in their home contexts. The students who use support well appear to have had positive demonstrations of social support within their zones of proximal development, thus enabling them to internalize and self regulate how to access and use social support in other contexts. The students who do not use support well do not appear to have experienced positive demonstrations of social support within their zones of proximal development. This latter group experience difficulties in accessing, accepting and using social support both in home and school contexts. However, these adolescents can learn to self regulate, access and use social support when adults, their peers or significant others listen and validate their concerns and move into their zones of proximal development. Implications for teachers include; (a) Creating open and trusting environments in which students feel comfortable in risk-taking and self-disclosure; and (b) Implementing mentoring programs in which a collaborative environment is created and

Most theoretical and methodological research addressing victimization, social support, and loneliness has focused on early childhood and adulthood. The purpose of this study was to investigate the link between victimizing behavior and lack of social support that may lead to loneliness in adolescents. / A cross sectional survey with 152 students ages 12-16 years from grades 8-10 was conducted in a Montreal public secondary school in September 2004. Three empirically validated tools were used: the UCLA Loneliness Scale (Russell et al., 1980), the Multidimensional Scale of Perceived Social Support (Zimet et al., 1988), and the Bullying - Fighting and Victimization Scale (Espelage and Holt, 2001). Results of regression analysis indicated that absence of family and friends' support and victimization are highly significant predictors of adolescent loneliness (p ≤ .001). / There remains a need to increase support available for victimized and lonely adolescents at school, at home, and in the community.

Friend, family and global social support, peer deviance and gambling frequency were examined as predictors of gambling involvement. Analyses focused on the predictors of gambling involvement with the covariate, drug-use, removed. For the 962 college student (mean age 18.5) participants, global social support, peer deviance and gambling frequency were the best predictors of gambling involvement with drug-use removed. Although males and females both reported diminished perceived supports globally and increased peer deviance as their reported level of gambling involvement increased, females reported less perceived support from all three networks. Males did not perceive less support from friends and family as their gambling involvement increased. The social support construct provides a social contextualization for future gambling involvement investigations. One important implication of this research is that diminished global social support will need to be recognized as a significant risk factor predicting problem gambling by researchers, clinicians and politicians alike. Peer deviance will need to be recognized as a significant risk-factor for males as well as females. Males reported more gambling-related problems than females. Although peer deviance significantly increased for both males and females with greater gambling involvement, peer deviance was higher among males than females. Males perceived no diminished sense of family and friend support. However, this shift for females appears to be evidence of diminished perceived support from all sources: family and friends as well as globally. Researchers, clinicians and politicians need to be aware that adolescents and young adults are at increased risk for encountering gambling problems as gambling frequency and peer deviance affiliation increases, and social support perceived to be available globally diminishes.

For ethnic entrepreneurs, it is vitally important to be able to move fluidly through boundaries between ethno-racial groups. Social activities on both sides of a boundary increase access to opportunities, needed resources and advantageous contacts in mainstream marketplaces. In Canada, men of European descent disproportionately hold positions of advantage and authority in mainstream marketplaces. Entrepreneurs wishing to do business in these markets must foster ties with well placed European Canadians, yet research shows that ethnic minorities are typically shut out of these important and advantageous networks. Through three publishable papers, this dissertation considers the unique case and place of Indigenous entrepreneurs in Toronto, Canada. They are a population discriminated against for centuries, while at the same time a fundamental part of the creation of Canadian society. This dissertation asks whether and how Indigenous entrepreneurs can move effectively across ethnic boundaries and participate in multiple groups and settings. More specifically, these three papers explore the factors and macro social structures that contribute to the development of diverse networks and cultural capital within Indigenous and Euro-Canadian worlds, and the effects of social and cultural capitals on performance in Toronto's mainstream marketplace. While current theory explores the ability of some individuals to move between groups and across boundaries, research does not exist to test these assertions. This dissertation provides then, an initial case study of boundary spanning behaviour and the first effort at exploring Indigenous entrepreneurs in that role. Findings do indeed show that respondents instrumentally develop and maintain diverse cultural and social capital. Further, some forms of social capital contribute substantially to successful performance in Toronto's mainstream marketplace.

For ethnic entrepreneurs, it is vitally important to be able to move fluidly through boundaries between ethno-racial groups. Social activities on both sides of a boundary increase access to opportunities, needed resources and advantageous contacts in mainstream marketplaces. In Canada, men of European descent disproportionately hold positions of advantage and authority in mainstream marketplaces. Entrepreneurs wishing to do business in these markets must foster ties with well placed European Canadians, yet research shows that ethnic minorities are typically shut out of these important and advantageous networks. Through three publishable papers, this dissertation considers the unique case and place of Indigenous entrepreneurs in Toronto, Canada. They are a population discriminated against for centuries, while at the same time a fundamental part of the creation of Canadian society. This dissertation asks whether and how Indigenous entrepreneurs can move effectively across ethnic boundaries and participate in multiple groups and settings. More specifically, these three papers explore the factors and macro social structures that contribute to the development of diverse networks and cultural capital within Indigenous and Euro-Canadian worlds, and the effects of social and cultural capitals on performance in Toronto's mainstream marketplace. While current theory explores the ability of some individuals to move between groups and across boundaries, research does not exist to test these assertions. This dissertation provides then, an initial case study of boundary spanning behaviour and the first effort at exploring Indigenous entrepreneurs in that role. Findings do indeed show that respondents instrumentally develop and maintain diverse cultural and social capital. Further, some forms of social capital contribute substantially to successful performance in Toronto's mainstream marketplace.