51,055 research outputs found

    Assessing a Sport/Cultural Events Network: An Application of Social Network Analysis

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    The purpose of this study was to assess the complexity of a sport/cultural events network. To that intent, a social network analysis was conducted in a small community in the US. The study had three main objectives: (1) Examine relationships among organisations involved in planning and implementing sport and cultural events based on their communication, exchange of resources, and assistance; (2) Identify the most important actors within the events network and their relationships; (3) Investigate the structure of the events network and evaluate the community’s capacity to capitalise on their event portfolio via a collaborative events network

    News from the p-process: is the s-process a troublemaker?

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    The most detailed calculations of the p-process call for its development in the O/Ne layers of Type II supernovae. In spite of their overall success in reproducing the solar system content of p-nuclides, they suggest a significant underproduction of the light Mo and Ru isotopes. On grounds of a model for the explosion of a 25 solar mass star with solar metallicity, we demonstrate that this failure might just be related to the uncertainties left in the rate of the 22Ne(alpha,n)25Mg neutron producing reaction. The latter indeed has a direct impact on the distribution of the s-process seeds for the p-process.Comment: 8 pages, 3 figures, Review talk at Nuclei in the Cosmos 2000, Aarhus, June 27 - July 1, 200

    Average Continuous Control of Piecewise Deterministic Markov Processes

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    This paper deals with the long run average continuous control problem of piecewise deterministic Markov processes (PDMP's) taking values in a general Borel space and with compact action space depending on the state variable. The control variable acts on the jump rate and transition measure of the PDMP, and the running and boundary costs are assumed to be positive but not necessarily bounded. Our first main result is to obtain an optimality equation for the long run average cost in terms of a discrete-time optimality equation related to the embedded Markov chain given by the post-jump location of the PDMP. Our second main result guarantees the existence of a feedback measurable selector for the discrete-time optimality equation by establishing a connection between this equation and an integro-differential equation. Our final main result is to obtain some sufficient conditions for the existence of a solution for a discrete-time optimality inequality and an ordinary optimal feedback control for the long run average cost using the so-called vanishing discount approach.Comment: 34 page
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