Browsing by Subject "social network"
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Item Distributed Control Approaches to Network Optimization(2010-07-14) Sah, SankalpThe objective of this research is to develop distributed approaches to optimizing network traffic. Two problems are studied, which include exploiting social networks in routing packets (coupons) to desired network nodes (users in the social network), and developing a rate based transport protocol, which will guarantee that all the flows in a network (e.g. Internet) meet a delay constraint per packet. Firstly, we will study social networks as a means of obtaining information about a system. They are increasingly seen as a means of obtaining awareness of user preferences. Such awareness could be used to target goods and services at them. We consider a general user model, wherein users could buy different numbers of goods at a marked and at a discounted price. Our first objective is to learn which users would be interested in a particular good. Second, we would like to know how much to discount these users such that the entire demand is realized, but not so much that profits are decreased. We develop algorithms for multihop forwarding of such discount coupons over an online social network, in which users forward coupons to each other in return for a reward. Coupling this idea with the implicit learning associated with backpressure routing (originally developed for multihop wireless networks), we would like to demonstrate how to realize optimal revenue. We will then propose a simpler heuristic algorithm and try to show, using simulations, that its performance approaches that of backpressure routing. As the second problem, we look at the traditional formulation of the total value of information transfer, which is a multi-commodity flow problem. Here, each data source is seen as generating a commodity along a fixed route, and the objective is to maximize the total system throughput under some concept of fairness, subject to capacity constraints of the links used. This problem is well studied under the framework of network utility maximization and has led to several different distributed congestion control schemes. However, this idea of value does not capture the fact that flows might associate value, not just with throughput, but with link-quality metrics such as packet delay, jitter and so on. The traditional congestion control problem is redefined to include individual source preferences. It is assumed that degradation in link quality seen by a flow adds up on the links it traverses, and the total utility is maximized in such a way that the quality degradation seen by each source is bounded by a value that it declares. Decoupling source-dissatisfaction and link-degradation through an ?effective capacity? variable, a distributed and provably optimal resource allocation algorithm is designed, to maximize system utility subject to these quality constraints. The applicability of our controller in different situations is illustrated, and results are supported through numerical examples.Item Emergent Leadership Structures in Organizations(2010-01-14) Slaughter, AndrewA social network approach was used to investigate the structural features of various emergent leadership systems in a large financial organization (n = 137), including transactional and transformational-style leadership relations. Results indicate that macro-level patterns of leadership nominations may be explained by a small number of underlying structural features, some of which vary across types of leadership networks. Leadership nominations were shown to be less hierarchical, more reciprocal, and more triadic than traditionally thought. On top of effects associated with individual differences in sex, supervisor status, tenure, and physical location, leadership networks displayed tendencies towards reciprocity and loose core-periphery structures based on transitive hierarchies. There was also some evidence that transformational leadership networks tended to be slightly less centralized and more transitive than transactional leadership networks. Implications for bridging leadership theory across levels of analysis are discussed.Item Is Everyone Created Equal? A Social Network Perspective on Personality in Teams(2012-10-19) Li, NingOne important research topic in team research concerns how team composition (i.e., the configuration of team member attributes such as personality factors) affects team effectiveness. To date, researchers have almost exclusively focused on the role of team members' attributes (e.g., extraversion) without considering team members' status in the team. Yet, according to social network theory, a team member who occupies a central position in a team network (e.g., has numerous social ties to others) will have a greater impact on the team than other members who occupy peripheral positions. As a result, the effects of team composition on team effectiveness are not influenced exclusively by an attribute, but also determined by who possesses the attribute. To remedy this limitation and account for member "centrality" effects on personality in teams, I conceptualize team composition in the form of personality from a social network perspective. Using 584 team members of 84 teams in China, I test the effects of various operationalizations of team personality traits on team processes and performance. Specifically, the results indicate that team overall personality traits fail to display superior predictive validity over team mean personality traits in predicting team processes. However, I report that the most central member's conscientiousness and agreeableness have meaningful impacts on team processes. Finally, team maximum extraversion and openness interact with team member centrality in predicting team processes such that the personality traits have stronger effects on team processes when the traits are possessed by central members. In doing so, I help to clarify the construct of team composition and gain a better understanding of how team composition affects team outcomes.Item Types and Gender Composition of Social Networks: Their Influence on Adolescent Substance Use(2015-01-22) Jacobs, Wuraola OThis dissertation presents three separate studies designed to examine how the different factors and determinants known to influence adolescent alcohol and tobacco use and the gender compositions of different adolescent network types are associated with alcohol and tobacco use among adolescents. Additionally, the similarities and/or differences in networks of adolescent substance users and non-users are also examined. First, a systematic review of empirical studies (n=48) employing social network analysis to examine adolescents? alcohol, tobacco, and other drugs (ATOD) use behavior will be presented discussing: (a) how this body of literature examined gender differences in ATOD use, (b) whether these network studies examine the gender composition of these adolescents? networks, and (c) what network affiliation types are used to characterize adolescent networks. Secondly, descriptive characteristics and network analysis of the social networks of 10th grade substance using and non-using adolescents will be presented. Employing a bounded whole network approach, data was collected from 1,707 10th graders in a school district in Los Angeles, California. The students were asked different network questions in order to generate different network types. The network types elicited from these network questions are: Friendship, Admiration, Succeed, Popularity, and Romantic networks. Attributes and network characteristics of users and non-users across these five different networks are presented and the commonalities and/or differences are described also. Lastly, using data from the same students, a quantitative analysis of the associations between interpersonal (e.g. age, gender) and interpersonal (e.g. parent and sibling substance use) factors, network measures, and gender composition of the networks and their alcohol and tobacco use will be discussed. These associations are then further examined across the five different types of networks mentioned above. Prior to this study, research studies employing social network analysis did not attempt to examine the gender composition of the networks in which adolescents are embedded; and only a few other studies used networks other than friendship networks to characterize adolescent social networks. Thus, this study represents the first step towards addressing these limitations associated with examining how adolescents? social networks facilitate or constrain their substance use behavior and filling these apparent conceptual gaps.