Network theory

About: Network theory is a research topic. Over the lifetime, 2257 publications have been published within this topic receiving 109864 citations.

Eigenvector Centrality Based on Shared Research Topics in a Scientific Community

Abstract: In this paper we propose a weighted multi-hypergraph as logical structure to model relationships between researchers and interest groups that join them on the base of shared research topics in a given scientific community. The well known concept of eingenvector centrality for graphs is extended to weighted multi-hypergraphs and we present a model instantiation for centrality analysis in the Pro-VE scientific community.

Evaluating sustainability and resilience of complex systems using network theory

Abstract: This research evaluates sustainability and resilience of integrated human/built/natural systems, or complex Earth systems, using the network theory and approach by case studies of the U.S. book retail market and the 2002 U.S. economy. First, based on the "small-world" model of social networks, the environmental impacts of the U.S. book retail market is simulated using an agent-based modeling technique from a bottom-up perspective. The results show that the future book retail market is primarily dominated by the development of internet penetration. Energy use and carbon dioxide emissions for delivery can be reduced as much as 1.43 million cubic meters and 3.33 million tons, respectively, in the conservative scenario. More broadly, the framework and method used in this case can be easily adapted for studying environmental sustainability of other complex systems in which human components are the primary driver of environmental consequences. Second, the resilience of 2002 U.S. economy is studied by mapping the economic system as an economic input-output (EIO) network. Statistical analysis shows that the distributions of degree of nodes and weight of nodes (or links) of the EIO network generally follow a power law with fat tails in the logarithmic scale. The general power-law distribution suggests the economy's resilience against random failures occurring in nodes and links, while the fat tails in the logarithmic scale represent highly connected clusters consisting of strong nodes which enhance the EIO network's resilience against intentional attacks. More analysis on the network identifies critical sectors for the overall resilience of the economy, such as "wholesale trade", "air transportation", "general state and local government services", or "motor vehicle parts manufacturing". On the other hand, other sectors play less important roles in terms of resilience, such as "veterinary services", "dental laboratories", "logging", or "fishing". Furthermore, the analysis on dependence and similarity between sectors confirms sectors' role in the resilience of the EIO network. Finally, the quantitative tools developed in this research have a wide potential to apply to the evaluation of resilience for systems which contain numerous agents interacting with each other in complex ways.

Modelling economic structures from a Qualitative Input-Output Perspective: Greece in 2005 and 2010

Abstract: The Input-Output model has made extensive use of graph and network theory, methods and conclusions, in order to carry out structural analysis; such extensions have yielded powerful insights on the relationships existing between industries in an economic system. It is customary in the field to take a deterministic perspective when analysing economic structures, using various measures derived from the Input-Output tables; yet the model can include stochastic experiments. This paper takes that course of action, aiming at modelling the Greek economic structure from a qualitative viewpoint for 2005 and 2010; moreover, sectors are divided by groups of differentiated technology intensity. The methodology is based on a model based on families of distributions that allow predicting and analysing network structures. Results are reached by a probabilistic approach, producing interesting insights about the economic structures under study, while revealing different behaviour of the different groups of industries, classified by technological intensity.

Diakoptics-a parallel processing approach for the analysis of large-scale power systems

Abstract: The structure, the quality and the dimension of the power systems are subject to change and to become more complex. For the analysis of such vast power systems the use of computers is indispensable. In the computer-aided power system analysis, the computational cost and the accuracy are two important factors. The computational cost, i.e. computational time and memory needed for the analysis, are related to the dimension of system being analyzed. The increase in the system dimension will directly increase these requirements and creates several difficulties. Some new approaches for the mathematical formulation of power systems have been considered to find a more convenient way to simulate large-scale power systems. However, a literature survey on the analyses of large-scale power systems has shown that the advantages to be gained by the use of the concept of multi-terminal component introduced in network theory have not been fully utilised. This paper deals with the application of the concept of multi-terminal components to the analysis of large-scale power systems. The new approach, which is perfectly general and can be applied to both the analysis of asymmetric and symmetric systems, aims to obtain the coefficient matrix of the system as a block-diagonal-band matrix. Instead of solving the whole matrix by using a processor, blocks representing the sub-networks can be solved simultaneously via parallel processors to speed up the process. >