Network theory

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

Process Network Theory and Implementation for Technology Assessment in Manufacturing

Abstract: This paper describes a theoretical framework called Process Network Theory and its implementation for evaluating the economic, technical and environmental performance of manufacturing systems. Historically, performance of manufacturing enterprises has been measured largely in monetary terms such as cash, value added and net return on investment. Achieving and maintaining a long-term competitive position in a global economy requires looking beyond monetary performance measures and financial accounting systems. It is necessary to evaluate alternative technologies in the context of their economic performance, technical performance and environmental loading. Technical performance, as defined here is the physical performance of manufacturing systems in terms of physical flows of materials, products and energy. Many companies recognize the crucial role of technical performance measures such as defect and scrap rates, yields, throughput time and resource efficiencies in retaining competitive position in the economy. They are experimenting with processes and procedures that stress quality control (TQC), reduce throughput time (JIT), improve process efficiencies, and others. Process network theory provides the ability to determine the technical and economic performance of manufacturing systems by following a two step procedure. As a first step, the physical part of the manufacturing system is represented as a network of elemental processes whose basic function is to transform the technical state of materials using physical energy and skill-specific human time. The models of the elemental processes are parameterized by a set of feasible technologies which are selected based on constraints and opportunities available for the exchange of materials and energies between the manufacturing system and its economic and natural environment. Linear graph theory is used to obtain the overall model of the manufacturing system as a function of the technologies and the network structure. The model is then used to obtain technical, economic and environmental performance as a function of the technologies involved.

Network Games: The Cooperative Approach

Abstract: We survey the recent developments in network games under cooperative framework. Network structures are important in describing and analysing social and economic phenomena through which people interact with each other and are influenced by their peers. Game theory has been successfully applied as a tool for such descriptions and analysis. The corresponding games are called network games. Situations, where people cooperate under binding agreements, are best modelled by cooperative games. One of the primary concerns in the field of social and economic network theory is to design networks on the basis of such binding agreements among the interacting agents. Bi-cooperative games are a special class of cooperative games where people can choose to support or oppose an issue or remain indifferent while making binding agreements. Bi-cooperative network games are network games where agents can make positive or negative links or remain isolated based on their choices of supporting or opposing the issue. We primarily focus on both standard and non-trivial solution concepts of network games under cooperative and bi-cooperative set ups and highlight the recent applications of the theory in dealing with socio-economic issues.

The Inverse Conductivity Problem: Anisotropy, Finite Elements and Resistor Networks

Abstract: EIT is a method of imaging that exists for a century, initially in geophysics and in recent years in medical imaging. Even though the practical applications of EIT go back to the early 20th century the systematic study of the inverse conductivity problem started in the late 1970s, hence many aspects of the problem remain unexplored. In the study of the inverse conductivity problem usually Finite Element Models are used since they can be easily adapted for bodies of irregular shapes. In this work though we use an equivalent approximation, the electrical resistor network, for which many uniqueness results as well as reconstruction algorithms exist. Furthermore resistor networks are important for EIT since they are used to provide convenient stable test loads or phantoms for EIT systems. In this thesis we study the transfer resistance matrix of a resistor network that is derived from n-port theory and review necessary and sufficient conditions for a matrix to be the transfer resistance of a planar network. The so called ?paramountcy? condition may be useful for validation purposes since it provides the means to locate problematic electrodes. In the study of resistor networks in relation to inverse problems it is of a great importance to know which resistor networks correspond to some Finite Element Model. To give a partial answer to this we use the dual graph of a resistor network and we represent the voltage by the logarithm of the circle radius. This representation in combination with Duffin?s non-linear resistor network theory provides the means to show that a non-linear resistor network can be embedded uniquely in a Euclidean space under certain conditions. This is where the novelty of this work lies.

Distributed Assessment of Network Centrality

Abstract: We propose a method for the Distributed Assessment of Network CEntrality (DANCE) in complex networks DANCE attributes to each node a volume-based centrality computed using only localized information, thus not requiring knowledge of the full network topology We show DANCE is simple, yet efficient, in assessing node centrality in a distributed way Our proposal also provides a way for locating the most central nodes, again using only the localized information at each node We also show that the node rankings based on DANCE's centrality and the traditional closeness centrality correlate very well This is quite useful given the vast potential applicability of closeness centrality, which is however limited by its high computational costs We experimentally evaluate DANCE against a state-of-the-art proposal to distributively assess network centrality Results attest that DANCE achieves similar effectiveness in assessing network centrality, but with a significant reduction in the associated costs for practical applicability In contrast to previous work, this outcome allows DANCE to be applied to large-scale networks

Vulnerability of critical infrastructures : identifying critical nodes.

Abstract: The objective of this research was the development of tools and techniques for the identification of critical nodes within critical infrastructures. These are nodes that, if disrupted through natural events or terrorist action, would cause the most widespread, immediate damage. This research focuses on one particular element of the national infrastructure: the bulk power system. Through the identification of critical elements and the quantification of the consequences of their failure, site-specific vulnerability analyses can be focused at those locations where additional security measures could be effectively implemented. In particular, with appropriate sizing and placement within the grid, distributed generation in the form of regional power parks may reduce or even prevent the impact of widespread network power outages. Even without additional security measures, increased awareness of sensitive power grid locations can provide a basis for more effective national, state and local emergency planning. A number of methods for identifying critical nodes were investigated: small-world (or network theory), polyhedral dynamics, and an artificial intelligence-based search method - particle swarm optimization. PSO was found to be the only viable approach and was applied to a variety of industry accepted test networks to validate the ability of the approach to identify sets ofmore » critical nodes. The approach was coded in a software package called Buzzard and integrated with a traditional power flow code. A number of industry accepted test networks were employed to validate the approach. The techniques (and software) are not unique to power grid network, but could be applied to a variety of complex, interacting infrastructures.« less