Gönenç Yücel

Impact of Homophily on Diffusion Dynamics Over Social Networks

The purpose of this study is to analyze the impact of homophily on diffusion over social networks. An agent-based simulation model is developed to serve as the experimental ground for this analysis. Diffusion dynamics of a nonsticky innovation is investigated by varying homophily levels in the social network depicted in the model as the primary control variable. First of all, the results show that homophily is self-reinforcing. Second, starting from a nonhomophilous network, early increases in the level of homophily have a positive effect on the extent of diffusion, whereas further increases have a negative impact. Finally, several local minima and maxima are observed in the relation between the homophily level and the extent of diffusion. Our analysis focuses on node properties such as connectedness and average degrees in order to explain the observed regular relationship between homophily and diffusion. We argue that (i) homophily increases the connectedness of different status groups separately and (ii) increasing levels of homophily decreases the marginal importance of a single homophilous tie by increasing the sources of valuable information. Future research involves investigating the coevolution of social behavior and networks by allowing the adopted innovation to lead to value homophily, exploration of different diffusion initiation types, and different adoption heuristics.

Studying transition dynamics via focusing on underlying feedback interactions

The emerging need for societal transitions raises the need for a better understanding of the dynamic nature of large scale societal systems, and therefore the development of an analytical approach for drawing dynamic conclusions based on system’s dynamic mechanisms, feedback relationships and interacting components.The objective of this study is to explore the degree to which System Dynamics as an approach enhances the process of understanding transition dynamics in socio-technical systems. In other words, it is aimed to reveal the type of insights that can be developed about such systems and their dynamic behaviour using the approach, as well as the shortcomings of the approach in this challenging task. In order to do so, a modeling study aiming to understand the underlying mechanisms of the waste management transition in the Netherlands is conducted.The quantitative model developed is based on the historical case of the waste management transition of the Netherlands, and it portrays issues as the dynamics of actors’ preferences, development of infrastructure and environmental consequences of dominant mode of functioning and provides an instance for demonstrating and evaluating the feedback-focused perspective discussed in this paper.Finally, the paper discusses a set of points regarding the utilized approach, System Dynamics, observed during this study both in general and in the specific context of transitions. In short, System Dynamics stands as a promising approach mainly due to its strength in explaining the source of complex dynamics based on interacting feedback loops, but it also has certain drawbacks in the context of transitions.

A Simulation-Based Analysis of Electricity Access in Uganda

Access to power is tied to a countrys development. It facilitates improved social welfare, education, health and income generating opportunities. Ugandas economy is stifled by its low electrification rates-16% nationally. This study builds a working theory on the internal setup of Ugandas power sector utilizing this theory to surface influential behavior modes as they pertain to power generation and supply and how these ultimately affect electricity access. Based on this working theory a System Dynamics simulation model is built. The model simulations show how Ugandas power sector is expected to evolve over 80 years in terms of power supply and demand given existing market structure and prevailing conditions. The study finds major problems in the nature of power accessed specifically an insufficient and unreliable power supply. The root cause is found in the nature of the existing capacity planning process in terms of how future capacity requirements are determined and the agreements made with generators as to how and when they fulfill their investment obligations.

Influence maximization based on partial network structure information: A comparative analysis on seed selection heuristics

In this study, the problem of seed selection is investigated. This problem is mainly treated as an optimization problem, which is proved to be NP-hard. There are several heuristic approaches in the literature which mostly use algorithmic heuristics. These approaches mainly focus on the trade-off between computational complexity and accuracy. Although the accuracy of algorithmic heuristics are high, they also have high computational complexity. Furthermore, in the literature, it is generally assumed that complete information on the structure and features of a network is available, which is not the case in most of the times. For the study, a simulation model is constructed, which is capable of creating networks, performing seed selection heuristics, and simulating diffusion models. Novel metric-based seed selection heuristics that rely only on partial information are proposed and tested using the simulation model. These heuristics use local information available from nodes in the synthetically created networks. The performances of heuristics are comparatively analyzed on three different network types. The results clearly show that the performance of a heuristic depends on the structure of a network. A heuristic to be used should be selected after investigating the properties of the network at hand. More importantly, the approach of partial information provided promising results. In certain cases, selection heuristics that rely only on partial network information perform very close to similar heuristics that require complete network data.

The Actor-Option Framework: A General Framework for Modelling Socio-Technical Systems in Transition

A very fundamental need in transition studies is a general modelling framework that allows representing the state of different systems, as well as the change processes related to reinforcing or counteracting their transitions. Such a framework is needed in order to be able to benchmark different transition cases and to integrate case-specific insights for developing general understanding. This chapter briefly presents a general modelling framework, Actor-Option Framework (AOF), for modelling transitional change processes of socio-technical systems. The framework provides a toolbox with conceptual components and a structure about the way these components can be combined for representing a particular system of concern. AOF is based on an extensive set of empirical cases on technological change and socio-technical transitions. The general applicability and appropriateness for developing quantitative and qualitative models of change is assessed through a set of modelling exercises.

Impact Of Homophily On Diffusion Dynamics Over Social Networks.

The purpose of this study is to find out under what conditions homophily reinforce the diffusions over social networks or undermines them. To realize this aim, formal modeling approach is utilized and an Agent-Based Model is constructed. Afterwards, diffusion of a non-sticky innovation is investigated with the experiments having varying homophily levels in a social network with two distinct kinds of agents as the primary control variable. The results show that (i) homophily reinforces itself (ii) looking at the macrobehavior of the diffusion, initial increases in the level of homophily has a positive effect on adopted fraction of the population whereas further increases have a negative impact, and (iii) looking at the micro-behavior of the diffusion, increasing homophily can result in local maxima even the macro trend is decreasing. Connectedness and average degrees interacting with social persuasion are the two explanatory remarks in the course of investigating the impact of homophily. As a by-product, the model is also capable of capturing the segregation dynamics over social networks. Future research involves allowing the adopted innovation to lead to value homophily, exploration of the different diffusion initiation types and adoption heuristics.