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Publicações

2007

A multiple scenario security constrained reactive power planning tool using EPSO

Autores
Keko, H; Duque, AJ; Miranda, V;

Publicação
ENGINEERING INTELLIGENT SYSTEMS FOR ELECTRICAL ENGINEERING AND COMMUNICATIONS

Abstract
Evolutionary Particle Swarm Optimization (EPSO) is a robust optimization algorithm belonging to evolutionary methods. EPSO borrows the movement rules from Particle Swarm Optimization (PSO) and uses it as a recombination operator that evolves under selection. This paper presents a reactive power planning approach taking advantage of EPSO robustness, in a model that considers simultaneously multiple contingencies and multiple load levels. Results for selected problems are summarized including a trade-off analysis of results.

2007

VTP-CSMA: A virtual token passing approach for real-time communication in IEEE 802.11 wireless networks

Autores
Moraes, R; Vasques, F; Portugal, P; Fonseca, JA;

Publicação
IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS

Abstract
Currently, there is a trend towards the implementation of industrial communication systems using wireless networks. However, keeping up with the timing constraints of real-time traffic in wireless environments is a hard task. The main reason is that real-time devices must share the same communication medium with timing unconstrained devices. The VTP-CSMA architecture has been proposed to deal with this problem. It considers an unified wireless system in one frequency band, where the communication bandwidth is shared by real-time and non-real-time communicating devices. The proposed architecture is based on a virtual token passing (VTP) procedure that circulates a virtual token among real-time devices. This virtual token is complemented by an underlying traffic separation mechanism that prioritizes the real-time traffic over the non-real-time traffic. This is one of the most innovative aspects of the proposed architecture, as most part of real-time communication approaches are not able to handle timing unconstrained traffic sharing the same communication medium. A ring management procedure for the VTP-CSMA architecture is also proposed, allowing real-time stations to adequately join/leave the virtual ring.

2007

Bt transgenic maize pollen and the silent poisoning of the hive.

Autores
Sabugosa Madeira, B; Abreu, I; Ribeiro, H; Cunha, M;

Publicação
JOURNAL OF APICULTURAL RESEARCH

Abstract

2007

Compositional gossip: A conceptual architecture for designing gossip-based applications

Autores
Riviere, E; Baldoni, R; Li, H; Pereira, J;

Publicação
Operating Systems Review (ACM)

Abstract
Most proposed gossip-based systems use an ad-hoc design. We observe a low degree of reutilization among this proposals. We present how this limits both the systematic development of gossip-based applications and the number of applications that can benefit from gossip-based construction. We posit that these reinvent-the-wheel approaches poses a significant barrier to the spread and usability of gossip protocols. This paper advocates a conceptual design framework based upon aggregating basic and predefined building blocks (B 2). We show how to compose building blocks within our framework to construct more complex blocks to be used in gossip-based applications. The concept is further depicted with two gossip-based applications described using our building blocks.

2007

Emergent structure in unstructured epidemic multicas

Autores
Carvalho, N; Pereira, J; Oliveira, R; Rodrigues, L;

Publicação
37TH ANNUAL IEEE/IFIP INTERNATIONAL CONFERENCE ON DEPENDABLE SYSTEMS AND NETWORKS, PROCEEDINGS

Abstract
In epidemic or gossip-based multicast protocols, each node simply relays each message to some random neighbors, such that all destinations receive it at least once with high probability. In sharp contrast, structured multicast protocols explicitly build and use a spanning tree to take advantage of efficient paths, and aim at having each message received exactly once. Unfortunately, when failures occur, the tree must be rebuilt. Gossiping thus provides simplicity and resilience at the expense of performance and resource efficiency. In this paper we propose a novel technique that exploits knowledge about the environment to schedide payload transmission when gossiping. The resulting protocol retains the desirable qualities of gossip, but approximates the performance of structured multicast. In some sense, instead of imposing structure by construction, we let it emerge from the operation of the gossip protocol. Experimental evaluation shows that this approach is effective even when knowledge about the environment is only approximate.

2007

Recent advances in high-birefringence fiber loop mirror sensors

Autores
Frazao, O; Baptista, JM; Santos, JL;

Publicação
SENSORS

Abstract
Recent advances in devices and applications of high-birefringence fiber loop mirror sensors are addressed. In optical sensing, these devices may be used as strain and temperature sensors, in a separate or in a simultaneous measurement. Other described applications include: refractive index measurement, optical filters for interrogate gratings structures and chemical etching control. The paper analyses and compares different types of high-birefringence fiber loop mirror sensors using conventional and microstructured optical fibers. Some configurations are presented for simultaneous measurement of physical parameters when combined with others optical devices, for example with a long period grating.

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