Showing papers on "Network theory published in 2004"

Network topology of the interbank market

Abstract: We provide an empirical analysis of the network structure of the Austrian interbank market based on Austrian Central Bank (OeNB) data. The interbank market is interpreted as a network where banks are nodes and the claims and liabilities between banks define the links. This allows us to apply methods from general network theory. We find that the degree distributions of the interbank network follow power laws. Given this result we discuss how the network structure affects the stability of the banking system with respect to the elimination of a node in the network, i.e. the default of a single bank. Further, the interbank liability network shows a community structure that exactly mirrors the regional and sectoral organization of the current Austrian banking system. The banking network has the typical structural features found in numerous other complex real-world networks: a low clustering coefficient and a short average path length. These empirical findings are in marked contrast to the network structures th...

Complex networks: Augmenting the framework for the study of complex systems

Abstract: We briefly describe the toolkit used for studying complex systems: nonlinear dynamics, statistical physics, and network theory We place particular emphasis on network theory—the topic of this special issue—and its importance in augmenting the framework for the quantitative study of complex systems In order to illustrate the main issues, we briefly review several areas where network theory has led to significant developments in our understanding of complex systems Specifically, we discuss changes, arising from network theory, in our understanding of (i) the Internet and other communication networks, (ii) the structure of natural ecosystems, (iii) the spread of diseases and information, (iv) the structure of cellular signalling networks, and (v) infrastructure robustness Finally, we discuss how complexity requires both new tools and an augmentation of the conceptual framework—including an expanded definition of what is meant by a “quantitative prediction”

Network theory and small groups

Abstract: This article describes the network approach to small groups. First, the core constructs that compose social network research are explained. The primary theories that provide the intellectual underpinning of the network approach are described, including theories of self-interest, theories of social exchange or dependency, theories of mutual or collective interest, cognitive theories, and theories of homophily. Highlights of the empirical work examining the internal and external networks of small groups is summarized. Finally, the primary challenges researchers face when applying the network perspective to small groups, and the primary benefits that can accrue to researchers who adopt that perspective, are enumerated.

Three traditions of network research: What the public management research agenda can learn from other research communities

Abstract: This article identifies and describes the development of three parallel streams of literature about network theory and research: social network analysis, policy change and political science networks, and public management networks. Noting that these traditions have sometimes been inattentive to each other's work, the authors illustrate the similarities and differences in the underlying theoretical assumptions, types of research questions addressed, and research methods typically employed by the three traditions. The authors draw especially on the social network analysis (sociological) tradition to provide theoretical and research insights for those who focus primarily on public management networks. The article concludes with recommendations for advancing current scholarship on public management networks.

Scale-free trees: the skeletons of complex networks.

Abstract: We investigate the properties of the spanning trees of various real-world and model networks. The spanning tree representing the communication kernel of the original network is determined by maximizing the total weight of the edges, whose weights are given by the edge betweenness centralities. We find that a scale-free tree and shortcuts organize a complex network. Especially, in ubiquitous scale-free networks, it is found that the scale-free spanning tree shows very robust betweenness centrality distributions and the remaining shortcuts characterize the properties of the original network, such as the clustering coefficient and the classification of scale-free networks by the betweenness centrality distribution.

Network Analysis in Marketing

Abstract: Understanding relationships is fundamental to marketing. Research has moved beyond simple dyadic relations to examine how networks of relations influence behaviour. While network theory is frequently drawn upon in marketing, few researchers apply the formal network analytical techniques developed. The aim here is to make network analysis more accessible. In this paper we discuss the basic data requirements and use a large business-to-business communication network to demonstrate a number of network measures and theories that have been applied in marketing studies.

Emergence of Complexity in Financial Networks

Abstract: We present here a brief summary of the various possible applications of network theory in the field of finance. Since we want to characterize different systems by means of simple and universal features, graph theory could represent a rather powerful methodology. In the following we report our activity in three different subfields, namely the board and director networks, the networks formed by prices correlations and the stock ownership networks. In most of the cases these three kind of networks display scale-free properties making them interesting in their own. Nevertheless, we want to stress here that the main utility of this methodology is to provide new measures of the real data sets in order to validate the different models.

The Web of Context: Applying Network Theory to the Use of Hyperlinks in Journalism on the Web

Abstract: This study applies emerging network theory to the use of hyperlinks in journalism stories on the Web. A five-year data set, including almost 1,500 Web news stories, is examined. The study concludes...

The corporate boards networks

Abstract: In this work we apply network theory to detect in a quantitative fashion some of the characters of the system composed by companies and their boards of directors. Modelling this as a bipartite graph, we can derive two networks (one for the companies and one for the directors) and apply to them the standard graph analysis instruments. The emerging picture shows an environment where the exchange of information and mutual influences, conveyed by interlocks between boards, is predominant. Such a result should be taken into account when modelling this system.

Network-induced oscillatory behavior in material flow networks and irregular business cycles

Abstract: Network theory is rapidly changing our understanding of complex systems, but the relevance of topological features for the dynamic behavior of metabolic networks, food webs, production systems, information networks, or cascade failures of power grids remains to be explored. Based on a simple model of supply networks, we offer an interpretation of instabilities and oscillations observed in biological, ecological, economic, and engineering systems. We find that most supply networks display damped oscillations, even when their units---and linear chains of these units---behave in a nonoscillatory way. Moreover, networks of damped oscillators tend to produce growing oscillations. This surprising behavior offers, for example, a different interpretation of business cycles and of oscillating or pulsating processes. The network structure of material flows itself turns out to be a source of instability, and cyclical variations are an inherent feature of decentralized adjustments.

Review of uses of network and graph theory concepts within proteomics.

Abstract: The size and nature of data collected on gene and protein interactions has led to a rapid growth of interest in graph theory and modern techniques for describing, characterizing and comparing networks. Simultaneously, this is a field of growth within mathematics and theoretical physics, where the global properties, and emergent behavior of networks, as a function of the local properties has long been studied. In this review, a number of approaches for exploiting modern network theory to help describe and analyze different data sets and problems associated with proteomic data are considered. This review aims to help biologists find their way towards useful ideas and references, yet may also help scientists from a mathematics and physics background to understand where they may apply their expertise.

Intra, Extra, and Internets in Franchise Network Organizations

Abstract: This study integrates thoughts related with electronic communication systems, labeled as Intra, Extra and Internet, with the core concepts of network theory and proposes a conceptual model for business-to-business firms. The context used for this model development is franchise systems. During this process, advantages and disadvantages associated with viewing franchise systems as network organizations as well as incorporating electronic communication systems as a catalyst of movement towards network organization are discussed. We hope that this study forms a basis for future investigation of franchise systems from a network perspective (rather than just a dyadic perspective), with the Intra, Extra, and Internet as a catalyst.

Some centrality results new and old

Abstract: We prove a number of results on betweenness and closeness centrality and centralization. In particular, we prove the much used normalization expression for closeness centrality first given by Freeman (1979), correcting an error in the justification given in his paper. We explore the relationship between betweenness and the cutting number and use these results to prove and correct some centrality and centralization formulae first proposed by Borgatti and Everett (1997).

Power Factor Typology Through Organizational and Network Analysis: Using environmental policy networks as an illustration

Abstract: This work is based on a doctoral research. Our main question is: who can be powerful and when. We assume that power is a function of network and organizational (actor-related) characteristics and thus not every actor (organisation) can be powerful in every network. Power and institutional theories will be operationalized, completed and specified by the results. Five types of power factors will be proposed, which are combinations of organizational and network characteristics that combine to produce high power synergy and low inconsistency. The first dimension of power is trust: the trustee leads the one who trusts. The second dimension is financial incentive: the gift giver influences the gift receiver. The third dimension is irreplaceability. This is an operationalization of general system theory which operationalizes the exchange power model. Although the dependent variable (power) will be calculated by the systemic approach, the independent variables will be culled from New Institutionalism. For this purpose, a combination of the Theory of Organized Interests and Network Theory is necessary. These theories will be specified throughout our results. The typology of power factors (organizational and network characteristics) was derived from both inductive and deductive processes. The organizational factors have been deduced from certain theories: the "lawful" type from contingency theory and mobilization of bias, the "trustworthy" from the resource dependence model, the "little brother" from the transaction-cost and resource dependence model, the "omniscient" type from decision- making theory, and the "re-distributor" type from decision-making theory and hypotheses on the role of monitoring information. Afterwards, the deduced organizational factors of each type have functioned as a basis for the induction of network factors, which proved to reach highest power synergy with the organizational factors through stepwise regression.Our methodology is a statistics-based vector algebra. We measured 108 indicators in 234 cases from 12 environmental policy networks in 8 European countries (Denmark, Finland, Germany, Greece, Ireland, Spain, Sweden, UK). In general, "trust" makes up 82% of the power composition, while "financial incentive" is only 8% and "irreplaceability" only 10%. Not all the network characteristics and organized interest models proposed until now have proven relevant to power, rather only some of them in certain combinations. We classified these combinations into five types: The "lawful" type: An actor with a multidisciplinary team that is lawful but not state-controlled has optimal chances in "non crowded" and mono-sectoral networks with intensive state contacts, where the state does not play any important role. The "trustworthy" type: A trustworthy actor with a multidisciplinary team has optimal chances in a "non-crowded" network with intensive state contacts and low importance of state. The "little brother" type: An actor who has powerful partners and various financing resources has optimal chances in a monosectoral network with "equal chances", where many possible contacts remain unexplored. The "omniscient" type: A powerful actor who implements its power by imposing general or scientific information as "important" on a network with little material needs. The "redistributor" type: A powerful actor who receives occasional general information and reconstructs it in order to provide "important" general and scientific information. It has optimal chances in a network with no scientific links.The equilibrium between the advantages and disadvantages of the method of complete network analysis has motivated thoughts about future research questions regarding the quality of regression and the insights of Heckman on the weakness of self-selection. A combined strategy of qualitative and quantitative research is necessary in order to make policy consulting applicable to politics and further theorizing more accurate.

A Durkheimian Network Theory

Abstract: This article sets out, first of all, to reconstruct a Durkheimian network theory that is derived from Durkheim’s own writings, and the sociological literature that considers their relationship to network theory. Secondly, it seeks to show how this Durkheimian network theory is compatible with, and may contribute to, contemporary network theory and fields of inquiry to which network theory has been applied, such as social movements, professions, social capital and organizations. According to this Durkheimian network theory, systemic solidarity flows from dense economic and non-economic relations in local subsystems connected through institutional relations, as are relations in the professions or in the market. If this is not the case, the social system disintegrates into a set of unconnected, or loosely connected, clusters.

Organization of firm networks: six critical points for empirical analysis

Abstract: Network theory has continued to evolve in recent years, but empirical studies are still lagging behind. Complex hybrid forms, meanwhile, are actually being structured in the real world of organizations, leaving a gap to be filled by theoretical and applied research. On the theoretical side some consolidation is necessary, and on the empirical side a research agenda has yet to be properly developed. This paper introduces and analyzes the dyadic perspective and the social embeddedness of networks. It offers a critical analysis challenging the radical social perspective. In addition, the paper introduces the possibility of observing trustless networks and adds six empirical questions in the format of a research agenda.

Dynamics in chains and networks

Abstract: Network theory has continued to evolve in recent years, but empirical studies are still lagging behind. Complex hybrid forms, meanwhile, are actually being structured in the real world of organizations, leaving a gap to be filled by theoretical and applied research. On the theoretical side some consolidation is necessary, and on the empirical side a research agenda has yet to be properly developed. This paper introduces and analyzes the dyadic perspective and the social embeddedness of networks. It offers a critical analysis challenging the radical social perspective of the new institutional approach. In addition, the paper introduces the possibility of observing trustless networks and adds six empirical questions in the format of a research agenda.

A formal model for structuring local perceptions of environmental space

Abstract: The problem of constructing computational models of space that mimic those found in human spatial reasoning is addressed. This paper extends a formal model that addressed point objects in a 2D world to include the presence of line objects and barriers. The problem consists of determining an appropriate global model for the spatial configuration given a sequence of local views or observations. A formal model is proposed based on constraint network theory. The model leads to the identification of stable regions within which perceptual information about the environment changes slowly, and zones of transition within which the perceptual information changes more quickly. A special case of transition zones is a “gateway”, which may be viewed as a kind of discontinuity or singularity in the model. It is expected that the model obtained will be used to mimic human mental representations of navigable outdoor environments.

Response network emerging from simple perturbation

Abstract: In complex networks, an attack on a single node can drastically change the communication pattern between other nodes. To investigate this effect, we measure the betweenness centrality (BC) changes after single node removal. Then we construct a corresponding secondary network based on this response characteristic of the network under perturbation. We find that the changes of BC are proportional to the BC of a removed node. We use a minimal spanning tree and a percolation cluster method for network construction and find that the degree distribution of secondary networks follows a power-law distribution in both cases.

A channel assignment problem in multihop wireless networks and graph theory

Abstract: Multihop wireless networks consist of mobile terminals with personal communication devices. Each terminal can receive a message and then send it to another terminal. In these networks, it is important to assign channels for communications to each terminal efficiently. There are some studies on this assignment problem using a conventional edge coloring in graph theory. In this paper, we propose a new edge coloring problem in graph and network theory on this assignment problem and we discuss the computational complexity of the problem. This edge coloring problem takes the degree of interference into consideration. Therefore, we can reuse the channels more efficiently compared with the conventional method.

Evolving networks : From topology to dynamics

Abstract: A multi-local-world model is introduced to describe the evolving networks that have a localization property such as the Internet. Based on this model, we show that the traffic load defined by “betweenness centrality” on the multi-local-world scale-free networks’ model also follows a power law form. In this kind of network, a few vertices have heavier loads and so play more important roles than the others in the network.

Basic concepts of quantum systems versus classical networks

Abstract: The paper is intended to establish a conceptual bridge between Classical Network Theory and Quantum Mechanics. The concept of time-reversal symmetry is extended from Quantum Mechanics to Network Theory (in the state equations description), while concepts of passivity and losslessness are extended from Network Theory to Quantum Mechanics. Copyright © 2004 John Wiley & Sons, Ltd.

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

Network-Induced Oscillatory Behavior in Material Flow Networks and Business Cycles

Abstract: Network theory is rapidly changing our understanding of complex systems, but the relevance of topological features for the dynamic behavior of metabolic networks, food webs, production systems,information networks, or cascade failures of power grids remains to be explored. Based on a simple model of supply networks, we offer an interpretation of instabilities and oscillations observed in biological, ecological, economic, and engineering systems. We find that most supply networks display damped oscillations, even when their units - and linear chains of these units - behave in a non-oscillatory way. Moreover, networks of damped oscillators tend to produce growing oscillations. This surprising behavior offers, for example, a new interpretation of business cycles and of oscillating or pulsating processes.The network structure of material flows itself turns out to be a source of instability, and cyclical variations are an inherent feature of decentralized adjustments.

Network Theory: A Primer and Questions for Air Transportation Systems Applications

Abstract: A new understanding (with potential applications to air transportation systems) has emerged in the past five years in the scientific field of networks. This development emerges in large part because we now have a new laboratory for developing theories about complex networks: The Internet. The premise of this new understanding is that most complex networks of interest, both of nature and of human contrivance, exhibit a fundamentally different behavior than thought for over two hundred years under classical graph theory. Classical theory held that networks exhibited random behavior, characterized by normal, (e.g., Gaussian or Poisson) degree distributions of the connectivity between nodes by links. The new understanding turns this idea on its head: networks of interest exhibit scale-free (or small world) degree distributions of connectivity, characterized by power law distributions. The implications of scale-free behavior for air transportation systems include the potential that some behaviors of complex system architectures might be analyzed through relatively simple approximations of local elements of the system. For air transportation applications, this presentation proposes a framework for constructing topologies (architectures) that represent the relationships between mobility, flight operations, aircraft requirements, and airspace capacity, and the related externalities in airspace procedures and architectures. The proposed architectures or topologies may serve as a framework for posing comparative and combinative analyses of performance, cost, security, environmental, and related metrics.