2012
Authors
Biazoli, CR; Silva, S; Franco, MAR; Frazao, O; Cordeiro, CMB;
Publication
APPLIED OPTICS
Abstract
Real-time monitoring of the fabrication process of tapering down a multimode-interference-based fiber structure is presented. The device is composed of a pure silica multimode fiber ( MMF) with an initial 125 mu m diameter spliced between two single-mode fibers. The process allows a thin MMF with adjustable parameters to obtain a high signal transmittance, arising from constructive interference among the guided modes at the output end of the MMF. Tapered structures with waist diameters as low as 55 mu m were easily fabricated without the limitation of fragile splices or difficulty in controlling lateral fiber alignments. The sensing device is shown to be sensitive to the external environment, and a maximum sensitivity of 2946 nm/refractive index unit in the refractive index range of 1.42-1.43 was attained. (c) 2012 Optical Society of America
2012
Authors
Bessa, RJ; Costa, IC; Bremermann, L; Matos, MA;
Publication
IET Conference Publications
Abstract
The coordination between wind farms and pumping storage units increases the wind farm's controllability and maximizes the profit. In literature, several optimization algorithms were proposed for deriving the optimal coordination between wind farms and storage units. However, no attention has been given to operational management strategies for following the strategy that results from the optimization phase. This paper presents three possible heuristic strategies for managing the wind-hydro system during the operational day according to a day-ahead optimized strategy. Moreover, a chance-constrained based optimization algorithm, that includes wind power uncertainty, is also described. The algorithms are tested in a real case-study.
2012
Authors
Pinto, T; Sousa, TM; Vale, Z;
Publication
INES 2012 - IEEE 16th International Conference on Intelligent Engineering Systems, Proceedings
Abstract
This paper presents an artificial neural network applied to the forecasting of electricity market prices, with the special feature of being dynamic. The dynamism is verified at two different levels. The first level is characterized as a re-training of the network in every iteration, so that the artificial neural network can able to consider the most recent data at all times, and constantly adapt itself to the most recent happenings. The second level considers the adaptation of the neural network's execution time depending on the circumstances of its use. The execution time adaptation is performed through the automatic adjustment of the amount of data considered for training the network. This is an advantageous and indispensable feature for this neural network's integration in ALBidS (Adaptive Learning strategic Bidding System), a multi-agent system that has the purpose of providing decision support to the market negotiating players of MASCEM (Multi-Agent Simulator of Competitive Electricity Markets). © 2012 IEEE.
2012
Authors
Costa, F; Santos, P; Varajao, J; Pereira, LT; Costa, V;
Publication
4TH CONFERENCE OF ENTERPRISE INFORMATION SYSTEMS - ALIGNING TECHNOLOGY, ORGANIZATIONS AND PEOPLE (CENTERIS 2012)
Abstract
Health care institutions need to implement rigorous clinical management systems. In this context, risk management has an important role aiming to minimize the likelihood of adverse events, thus contributing to improve the quality of provided health care. As the number and complexity of issues that must be addressed in hospitals is quite high and is increasing, it is essential the use of information systems to gather and monitor the hospital data. This paper proposes a new system to support the management of risk indicators, presenting the case of CHTMAD, a Portuguese hospital center. (C) 2012 Published by Elsevier Ltd. Selection and/or peer review under responsibility of CENTERIS/SCIKA - Association for Promotion and Dissemination of Scientific Knowledge
2012
Authors
Nazari, MH; Ilic, M; Lopes, JP;
Publication
CONTROL ENGINEERING PRACTICE
Abstract
This paper investigates small-signal stability and decentralized control design for distribution electric energy systems with a large penetration of distributed generators. Two real world distribution systems are studied in this paper. The first system is the IEEE 30-node distribution system and the second one is the distribution system on Flores Island, one of the western group islands of the Azores Archipelago. The Block Gerschgorin Theorem and Liapunov function-based stability criteria are applied to formally state sufficient conditions for small-signal stability. The results illustrate that when the governor control of distributed generators is designed without considering interactions between generators, small-signal instability could occur in the system and even the sufficient conditions for stability would not be satisfied. In the next step, the paper assesses control design to stabilize potentially unstable distribution systems. The main focus is on designing enhanced decentralized control based on the introduced stability criteria. The findings illustrate that implementing the enhanced decentralized control could ensure stability and support a large penetration of distributed generators.
2012
Authors
Silva, S; Pachon, EGP; Franco, MAR; Jorge, P; Santos, JL; Xavier Malcata, FX; Cordeiro, CMB; Frazao, O;
Publication
JOURNAL OF LIGHTWAVE TECHNOLOGY
Abstract
Singlemode-multimode-singlemode fiber structures (SMS) based on distinct sections of a pure silica multimode fiber (coreless-MMF) with diameters of 125 and 55 mu m, were reported for the measurement of curvature and temperature. The sensing concept relies on the multimode interference that occurs in the coreless-MMF section and, in accordance with the length of the MMF section used, two fiber devices were developed: one based on a bandpass filter (self-image effect) and the other on a band-rejection filter. Maximum sensitivities of 64.7 nm.m and 13.08 pm/degrees C could be attained, for curvature and temperature, respectively, using the band-rejection filter with 55 mu m-MMF diameter. A proof of concept was also explored for the simultaneous measurement of curvature and temperature by means of the matrix method.
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