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Search Results: 1 - 10 of 231711 matches for " Michael D. Koenig "
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Network Evolution Based on Centrality
Michael D. Koenig,Claudio J. Tessone
Physics , 2009, DOI: 10.1103/PhysRevE.84.056108
Abstract: We study the evolution of networks when the creation and decay of links are based on the position of nodes in the network measured by their centrality. We show that the same network dynamics arises under various centrality measures, and solve analytically the network evolution. During the complete evolution, the network is characterized by nestedness: the neighbourhood of a node is contained in the neighbourhood of the nodes with larger degree. We find a discontinuous transition in the network density between hierarchical and homogeneous networks, depending on the rate of link decay. We also show that this evolution mechanism leads to double power-law degree distributions, with interrelated exponents.
Modeling Evolving Innovation Networks
Michael D. Koenig,Stefano Battiston,Frank Schweitzer
Physics , 2007,
Abstract: We develop a new framework for modeling innovation networks which evolve over time. The nodes in the network represent firms, whereas the directed links represent unilateral interactions between the firms. Both nodes and links evolve according to their own dynamics and on different time scales. The model assumes that firms produce knowledge based on the knowledge exchange with other firms, which involves both costs and benefits for the participating firms. In order to increase their knowledge production, firms follow different strategies to create and/or to delete links with other firms. Dependent on the information firms take into account for their decision, we find the emergence of different network structures. We analyze the conditions for the existence of these structures within a mathematical approach and underpin our findings by extensive computer simulations which show the evolution of the networks and their equilibrium state. In the discussion of the results, particular attention is given to the emergence of direct and indirect reciprocity in knowledge exchange, which refers to the emergence of cycles in the network structure. In order to motivate our modeling framework, in the first part of the chapter we give a broad overview of existing literature from economics and physics. This shows that our framework bridges and extends two different lines of research, namely the study of equilibrium networks with simple topologies and the dynamic approach of hypercycle models.
On Algebraic Graph Theory and the Dynamics of Innovation Networks
Michael D. Koenig,Stefano Battiston,Mauro Napoletano,Frank Schweitzer
Physics , 2007,
Abstract: We investigate some of the properties and extensions of a dynamic innovation network model recently introduced in \citep{koenig07:_effic_stabil_dynam_innov_networ}. In the model, the set of efficient graphs ranges, depending on the cost for maintaining a link, from the complete graph to the (quasi-) star, varying within a well defined class of graphs. However, the interplay between dynamics on the nodes and topology of the network leads to equilibrium networks which are typically not efficient and are characterized, as observed in empirical studies of R&D networks, by sparseness, presence of clusters and heterogeneity of degree. In this paper, we analyze the relation between the growth rate of the knowledge stock of the agents from R&D collaborations and the properties of the adjacency matrix associated with the network of collaborations. By means of computer simulations we further investigate how the equilibrium network is affected by increasing the evaluation time $\tau$ over which agents evaluate whether to maintain a link or not. We show that only if $\tau$ is long enough, efficient networks can be obtained by the selfish link formation process of agents, otherwise the equilibrium network is inefficient. This work should assist in building a theoretical framework of R&D networks from which policies can be derived that aim at fostering efficient innovation networks.
In meiner eigenen Erfahrung
Gottfried Michael Koenig
Musica e Tecnologia , 2010,
Abstract: Gottfried Michael Koenig goes over the terms of the relationship with the technology in relation to his experience, considering the fundamental steps with the objective of establishing some steady points. These considerations lead him to reaffirm the primacy of the compositional idea on the technological means, a principle which he considers even more valid today, where technology certainly can be used, but to which any moral authority cannot be delegated.
Analyzing X-ray variability by Linear State Space Models
Michael Koenig,Jens Timmer
Physics , 1996, DOI: 10.1051/aas:1997104
Abstract: In recent years, autoregressive models have had a profound impact on the description of astronomical time series as the observation of a stochastic process. These methods have advantages compared with common Fourier techniques concerning their inherent stationarity and physical background. However, if autoregressive models are used, it has to be taken into account that real data always contain observational noise often obscuring the intrinsic time series of the object. We apply the technique of a Linear State Space Model which explicitly models the noise of astronomical data and allows to estimate the hidden autoregressive process. As an example, we have analysed the X-ray flux variability of the Active Galaxy NGC 5506 observed with EXOSAT.
Knowledge management: another management fad?
Leonard J. Ponzi,Michael Koenig
Information Research: an international electronic journal , 2002,
Abstract: Knowledge management is a subject of a growth body of literature. While capturing the interest of practitioners and scholars in the mid-1990s, knowledge management remains a broadly defined concept with faddish characteristics. Based on annual counts of article retrieved from Science Citation Index, Social Science Citation Index, and ABI Inform referring to three previous recognized management fad, this paper introduces empirical evidence that proposes that a typical management movement generally reveals itself as a fad in approximately five years. In applying this approach and assumption to the case of knowledge management, the findings suggest that knowledge management is at least living longer than typical fads and perhaps is in the process of establishing itself as a new aspect of management. To further the understanding of knowledge management's development, its interdisciplinary activity and breadth are reported and briefly discussed.
On Exchangeable Continuous Variable Systems
Robert Koenig,Michael M. Wolf
Mathematics , 2008, DOI: 10.1063/1.3043788
Abstract: We investigate permutation-invariant continuous variable quantum states and their covariance matrices. We provide a complete characterization of the latter with respect to permutation-invariance, exchangeability and representing convex combinations of tensor power states. On the level of the respective density operators this leads to necessary criteria for all these properties which become necessary and sufficient for Gaussian states. For these we use the derived results to provide de Finetti-type theorems for various distance measures.
Conceptualising spirituality for medical research and health service provision
Michael B King, Harold G Koenig
BMC Health Services Research , 2009, DOI: 10.1186/1472-6963-9-116
Abstract: A consideration of patients' spirituality is now regarded as an important component in compassionate service delivery in a number of medical specialities in the United Kingdom[1] (see for example http://www.dh.gov.uk/en/News/Speeches/Speecheslist/DH_4000737 webcite) and the United States. [2-6]. However, research into the role of spirituality and health has been hampered by poorly designed studies and lack of agreement on definitions[7,8]. In this review we aim to provide a concise summary of critical thinking that might form the basis for a useful definition of spirituality for research and clinical work. We first review how the terms spirituality and religion relate to each other. We then consider varieties of spirituality and spiritual experience. Finally, we suggest that our understanding of the word spirituality must be embedded in its use by ordinary speakers rather than based on an abstraction of its meaning. In this way we arrive at a definition that might aid clinicians and researchers to address these issues.Religion and spirituality were regarded as one and the same thing until recent times[9]. The advent of the twentieth century saw a gradual distinction between religion as practices and beliefs about the sacred or divine and spirituality which came to mean something more closely related to emotional experience. The psychologist William James reflected this evolution in his view of religious experience as "the feelings, acts and experiences of individual men in their solitude, so far as they apprehend themselves to stand in relation to the divine"[10]. James was influenced by Emerson's view of religion[11] when he interpreted the 'divine' as anything that is god-like[10]. In so doing, he anticipated the descriptions of spirituality that are common today. Over 50 years later Wach described spiritual (or mystical) experience as one in which there is 1) a response to a "given" that lies beyond one's everyday self; 2) total involvement; 3) a sense of somethi
Linear State Space Modeling of Gamma-Ray Burst Lightcurves
David Band,Michael Koenig,Anton Chernenko
Physics , 1997, DOI: 10.1063/1.55324
Abstract: Linear State Space Modeling determines the hidden autoregressive (AR) process in a noisy time series; for an AR process the time series' current value is the sum of current stochastic ``noise'' and a linear combination of previous values. We present preliminary results from modeling a sample of 4 channel BATSE LAD lightcurves. We determine the order of the AR process necessary to model the bursts. The comparison of decay constants for different energy bands shows that structure decays more rapidly at high energy. The resulting models can be interpreted physically; for example, they may reveal the response of the burst emission region to the injection of energy.
Sex Allocation in California Oaks: Trade-Offs or Resource Tracking?
Johannes M. H. Knops, Walter D. Koenig
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043492
Abstract: Trade-offs in sex resource allocation are commonly inferred from a negative correlation between male and female reproduction. We found that for three California oak species, aboveground annual net productivity (ANP) differences among individuals were primarily correlated with water availability and soil fertility. Reproductive biomass increased with ANP, but the relative allocation to reproduction was constant, indicating that reproduction tracked productivity, which in turn tracked site quality. Although there was a negative correlation between male and female reproduction, this was not the result of a resource investment trade-off, but rather a byproduct of the positive correlation between female reproductive biomass and ANP combined with the greater overall resource allocation to female, compared to male, function. Thus, we reject the hypothesis of a trade-off between these key life-history components within individuals of these species. For long-lived individuals, a plastic resource tracking response to environmental fluctuations may be more adaptive than directly linking life-history traits through trade-offs.
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