Abstract
Modeling competition in the future European Electricity Market (EEM) suggests considering new perspectives of leadership between the participant generators. EEM models should then be able to represent the possible existence of leaders and followers, and Conjectural Stackelberg equilibriums could be a powerful approach to do so. These asymmetric equilibriums can represent several types of competitive advantages among the market participants, though existing literature approaches generally assume single-leader-follower games. In addition, the complexity of the resolution methodologies sometimes compromises their applicability, especially if large-scale problems have to be solved. In this paper, a multi-leader-follower conjectural Stackelberg equilibrium model is presented. A simple convex quadratic optimization problem is proposed for its resolution, and the conditions for the equilibrium existence are discussed. A case study is presented to validate the model, and to analyze how market competition changes with the number of leaders or followers. The main conclusion is that if leadership spreads and Stackelberg models are used for its representation, regulatory policies should be oriented to increase the number of followers. However, there exists a maximum number of followers for which Stackelberg equilibriums does not exist, suggesting a deeper analysis for these cases to understand that matter and to decide the possible use of other market models. © 2012 IEEE.

Abstract
In this paper we will maintain that cultural institutions are increasingly facing the inevitability of a profound revision in their traditional parameters of unidirectional communication. Given the increasing availability of tools for audiovisual production as well as the diversity of networked communication contexts, the roles of the user and the audience have come to assume a participatory potential in the content they consume and attend; this will dictate their repositioning in relation to the universe of institutions' work. In order to communicate new messages, media narratives, views or perspectives on the same reality are constantly constructed, deconstructed and reconstructed. In this age of 'Consumer- Generated Media', identities and representations are constantly changing. The idea and the concept of a brand now extends far beyond its own limits, taking on important emotional values, and people enjoy being a part of that brand's mythology. The Serralves Foundation, along with its Museum of Contemporary Art, in Porto, Portugal, was the subject of a first study of an empirical nature: a series of audio-visual objects were developed, in order to generate material for analysis and proposition. In this subsequent stage, we aim at the identification of new procedures and practices that may be effectively implemented within the institutional universe. We intend to establish more efficient communication contexts, including the maximizing of a set of relationships between institutions and audiences regarding dimensions that are traditionally outside the institutional radar: identity, narrative and affection. By referring to key examples, we will posit that in order to achieve more success in their missions, cultural institutions should focus on participatory education and communication processes regarding contemporary issues. By doing this, they will strengthen their engagement with their audiences and bring them into the institutions' projects. This project is currently undertaking a wide inventory and taxonomy of the various institutional paradigms in regards to communication practices. We aim at producing a map of vocations and positions within the institutional world in regards to the aforementioned issues that require participatory communication. © Berg 2012 Printed In The UK.

Abstract
Many or-parallel Prolog computational models exploiting implicit parallelism have been proposed in the past. The Muse and YapOr systems are arguably two of the most efficient systems exploiting or-parallelism on shared memory architectures, both based on the environment copying model. Stack splitting emerged as an alternative model specially geared to distributed memory architectures as it basically splits the computation in such a way that no further, or just minimal, synchronization is required. With the new multicore architectures, it just makes sense to recover the body of knowledge there is in this area and reengineer prior computational models to evaluate their performance on newer architectures. In this paper, we focus on the design and implementation of stack splitting in the YapOr system. Our aim is to take advantage of its robustness to efficiently implement stack splitting support using shared memory, and then be able to directly compare the original YapOr with the YapOr using stack splitting. We consider two splitting models, vertical splitting and half splitting, and have adapted data structures, scheduling and incremental copy procedures in YapOr to cope with the new models. Experimental results, on a multicore machine with 24 cores, show that YapOr using stack splitting is, in general, comparable to the original YapOr, obtaining in some cases better performance than with only environment copying. Copyright © 2012 ACM.

Abstract
In this article we describe a system that is capable of self-organizing news clips collected by readers, into a personal digital library. The system then uses this information to provide a rich set of inferred relations between the clips and clusters of clips to the producers. The inferred information is in the form of news with the 'hot' topics, the relations between clips content and the interests of their readers. We describe the Breadcrumbs system which features an online news collecting tool, an inference engine and a social graph. We discuss the outcomes of our system, which allows for a better understanding of the news consumption and trends. Finally, we describe how we can use these outcomes to create a business model. © 2012 IEEE.

Abstract
Camera-enabled sensor nodes deployed for visual monitoring can considerably enlarge the applicability of wireless sensor networks. Due to the stringent requirements of visual data transmission and processing, when compared with scalar wireless sensor networks, quality assessment becomes a relevant issue. Although academic investigation has been focused on QoS parameters such as end-to-end delay, throughput and packet error rate, what is being seen by source nodes may be more important for the application than the quality of received data. In such way, we propose the novel concept of Quality of Viewing (QoV) to be employed as an important QoS parameter when assessing the monitoring quality in visual sensor networks. Some issues for the establishment of the QoV of monitoring applications will be presented, as well as practical exploitation of this parameter for dynamic verification, control and management of wireless sensor networks composed of camera-enabled source nodes. © 2012 IEEE.

Abstract
Gossip, or epidemic, protocols have emerged as a highly scalable and resilient approach to implement several application level services such as reliable multicast, data aggregation, publish-subscribe, among others. All these protocols organize nodes in an unstructured random overlay network. In many cases, it is interesting to bias the random overlay in order to optimize some efficiency criteria, for instance, to reduce the stretch of the overlay routing. In this paper, we propose X-BOT, a new protocol that allows to bias the topology of an unstructured gossip overlay network. X-BOT is completely decentralized and, unlike previous approaches, preserves several key properties of the original (nonbiased) overlay (most notably, the node degree and consequently, the overlay connectivity). Experimental results show that X-BOT can generate more efficient overlays than previous approaches independently of the underlying physical network topology.