Browsing by Subject "Social network"
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Item Open Access Consensus as a Nash equilibrium of a dynamic game(IEEE, 2016) Niazi, Muhammad Umar B.; Özgüler, Arif Bülent; Yıldız, AykutConsensus formation in a social network is modeled by a dynamic game of a prescribed duration played by members of the network. Each member independently minimizes a cost function that represents his/her motive. An integral cost function penalizes a member's differences of opinion from the others as well as from his/her own initial opinion, weighted by influence and stubbornness parameters. Each member uses its rate of change of opinion as a control input. This defines a dynamic non-cooperative game that turns out to have a unique Nash equilibrium. Analytic explicit expressions are derived for the opinion trajectory of each member for two representative cases obtained by suitable assumptions on the graph topology of the network. These trajectories are then examined under different assumptions on the relative sizes of the influence and stubbornness parameters that appear in the cost functions.Item Open Access Contagion of network products in small-world networks(Springer, 2019-05-20) İkizler, HüseyinWe formulate a model in which agents embedded in an exogenous social network decide whether to adopt a new network product or not. In the theoretical part of the paper, we characterize the stochastically stable equilibria for complete networks and cycles. For an arbitrary network structure, we develop a novel graph decomposition method to characterize the set of recurrent communication states, which is a superset of stochastically stable equilibria of the adoption game presented in our model. In the simulation part, we study the contagion process of a network product in small-world networks that systematically represent social networks. We simulate a generalization of the Morris (Rev Econ Stud 67(1):57–78, 2000) Contagion model that can explain the chasm between early adopters and early majority. Our numerical analysis shows that the failure of a new network product is less likely in a highly cliquish network. In addition, the contagion process reaches to steady state faster in random networks than in highly cliquish networks. It turns out that marketers should work with mixed marketing strategies, which will result in a full contagion of a network product and faster contagion rates with a higher probability.Item Open Access Finding hidden hierarchy in social networks(2016-06) Kurt, Süreyya EmreStratification among humans is a well studied concept that significantly impacts how social connections are shaped. Given that on-line social networks capture social connections among people, similar structure exist in these networks with respect to the presence of social hierarchies. In this thesis we study the problem of finding hidden hierarchies in social networks, in the form of social levels. The problem is motivated by the need for stratification for social advertising. We formulate the problem into dividing the users of a social network into levels, such that three main metrics are minimized: agony induced by the reverse links in the hierarchy, support disorder resulting from users in higher levels having less impact, and support imbalance resulting from users in the same level having diverse impact. We developed several heuristic algorithms to solve the problem at real-world scales. We present an evaluation that showcases the result quality and running time performance of our algorithms on real-world as well as synthetically generated graphs.Item Open Access Inter-ethnic (In)tolerance between Turks and Kurds: Implications for Turkish Democratisation(Routledge, 2017) Sarigil, Z.; Karakoc, E.Using public opinion survey data, this study investigates the determinants of inter-ethnic (in)tolerance among Turks and Kurds in Turkey. Our empirical analyses show that, compared with Turks, Kurds have a relatively higher level of tolerance towards the ethnic out-group. Our findings also suggest that different dynamics and factors mould Turks’ and Kurds’ tolerance towards ethnic out-group members. Religiosity, (ethno)nationalist orientations, inter-ethnic contact, threat perception and economic factors are the most consistent variables shaping Turks’ tolerance towards Kurds. In contrast, religion-related factors and inter-ethnic social contact do not have a statistically significant effect on Kurds’ tolerance towards Turks. (Ethno)nationalist orientations, however, appear to reduce Kurds’ tolerance. © 2016 Informa UK Limited, trading as Taylor & Francis Group.Item Open Access Link recommendation in P2P social networks(WOSS, 2012) Aytaş, Yusuf; Ferhatosmanoğlu, Hakan; Ulusoy, ÖzgürSocial networks have been mostly based on a centralized infrastructure where the owner hosts all the data and services. This model of “fat server & thin clients” results in many systems and practical problems such as privacy, censorship, scalability, and fault-tolerance. While a P2P infrastructure would be a natural alternative for implementing social networks, it has surprisingly not attracted enough attention yet. Significant research is needed to develop a P2P social network system. From an algorithmic perspective, most graph algorithms for social networks assume that the global graph is available. These need to be revisited in a P2P setting where the nodes have limited information with connectivity to only their neighbors. Following these observations, in this paper, we focus on social network link recommendation problem in a P2P setting. We investigate methods to recommend links to improve social connections as well as the efficiency of the overlay network. We evaluate our methods with respect to measures developed for P2P social networks.Item Open Access Opinion dynamics of stubborn agents under the presence of a troll as differential game(Scientific and Technical Research Council of Turkey - TUBITAK,Turkiye Bilimsel ve Teknik Arastirma Kurumu, 2021-11-30) Yıldız, A.; Özgüler, Arif BülentThe question of whether opinions of stubborn agents result in Nash equilibrium under the presence of troll is investigated in this study. The opinion dynamics is modelled as a differential game played by n agents during a finite time horizon. Two types of agents, ordinary agents and troll, are considered in this game. Troll is treated as a malicious stubborn content maker who disagrees with every other agent. On the other hand, ordinary agents maintain cooperative communication with other ordinary agents and they disagree with the troll. Under this scenario, explicit expressions of opinion trajectories are obtained by applying Pontryagin’s principle on the cost function. This approach provides insight into the social networks that comprise a troll in addition to ordinary agents