Anytime coalition structure generation on synergy graphs

We consider the coalition structure generation (CSG) problem on synergy graphs, which arises in many practical applications where communication constraints, social or trust relationships must be taken into account when forming coalitions. We propose a novel representation of this problem based on the concept of edge contraction, and an innovative branch and bound approach (CFSS), which is particularly efficient when applied to a general class of characteristic functions. This new model provides a non-redundant partition of the search space, hence allowing an effective parallelisation. We evaluate CFSS on two benchmark functions, the edge sum with coordination cost and the collective energy purchasing functions, comparing its performance with the best algorithm for CSG on synergy graphs: DyCE. The latter approach is centralised and cannot be efficiently parallelised due to the exponential memory requirements in the number of agents, which limits its scalability (while CFSS memory requirements are only polynomial). Our results show that, when the graphs are very sparse, CFSS is 4 orders of magnitude faster than DyCE. Moreover, CFSS is the first approach to provide anytime approximate solutions with quality guarantees for very large systems (i.e., with more than 2700 agents

Algorithms for Graph-Constrained Coalition Formation in the Real World

Coalition formation typically involves the coming together of multiple, heterogeneous, agents to achieve both their individual and collective goals. In this paper, we focus on a special case of coalition formation known as Graph-Constrained Coalition Formation (GCCF) whereby a network connecting the agents constrains the formation of coalitions. We focus on this type of problem given that in many real-world applications, agents may be connected by a communication network or only trust certain peers in their social network. We propose a novel representation of this problem based on the concept of edge contraction, which allows us to model the search space induced by the GCCF problem as a rooted tree. Then, we propose an anytime solution algorithm (CFSS), which is particularly efficient when applied to a general class of characteristic functions called $m+a$ functions. Moreover, we show how CFSS can be efficiently parallelised to solve GCCF using a non-redundant partition of the search space. We benchmark CFSS on both synthetic and realistic scenarios, using a real-world dataset consisting of the energy consumption of a large number of households in the UK. Our results show that, in the best case, the serial version of CFSS is 4 orders of magnitude faster than the state of the art, while the parallel version is 9.44 times faster than the serial version on a 12-core machine. Moreover, CFSS is the first approach to provide anytime approximate solutions with quality guarantees for very large systems of agents (i.e., with more than 2700 agents).Comment: Accepted for publication, cite as "in press

Hyperthyroidism in cats, part I : anatomy, physiology, pathophysiology, diagnosis and imaging

In the first part of this review article, thyroid anatomy, physiology and pathophysiology are reviewed to continue more specifically on hyperthyroidism, the most common thyroid disorder in cats. The diagnostic work-up of this disorder is discussed with emphasis on thyroid gland imaging. Scintigraphy is most commonly used and best suited to assess thyroid function, which will be discussed extensively in the second part of this review article. All other available imaging modalities do not offer a functional assessment and are therefore of limited use in the diagnosis and evaluation of hyperthyroidism

Do we need permission to play in public? The design of participation for social play video games at play parties and ‘alternative’ games festivals

Play is a fundamental to being Human. It helps to make sense of the self, to learn, to be creative and to relax. The advent of video games challenged traditional notions of play, introducing a single player experience to what had primarily been a communal social activity. As technology has developed, communal play has found both online and real-world spaces within video games. Online streaming, multiplayer games and built-in spectator modes within games underpin online communal play experiences, whilst ‘alternative’ games festivals, play parties and electronic sports, provide real world spaces for people to meet, play and exchange knowledge relating to both playing and making video games. This article reports the study of social play events which bring people together in the same space to explore video games making and playing. Expert interviews with curators, and event facilitators provides qualitative data from which design processes are formalised into a ‘model of participation’ of social play. Four key areas of balance are proposed as core considerations in supporting participation in event design. The study of these events also suggests that their design and fostering of participation has the potential to evoke cultural change in game making and playing practices

Pteridologist

Index v.2 (1990-1995

Larvae and pupae of New Guinea Tabanidae (Diptera) : 1. Species of Chrysops Meigen

Information on the immature stages of Australasian Tabanidae found in published literature dealt with only 17 species, all so far known only from Australia and none representing the genus Chrysops Meigen. Two of the four Australasian species of Chrysops are found on the island of New Guinea, and both, C. albicinctus Wulp and C. australis Ricardo, are described and illustrated

Results of radar location of planets

Results of radar location and study of planet