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Publicações

2006

A maintenance float system with periodic overhauls

Autores
Lopes, IS; Leitao, ALF; Pereira, GAB;

Publicação
Safety and Reliability for Managing Risk, Vols 1-3

Abstract
In this work, a maintenance float system is considered. Equipments in workstation are submitted to overhauls carried out at regular time intervals. A mathematical model has been constructed to find out the best combination of three parameters: the number of standby units, R, the number of maintenance crews in the maintenance centre, L and the time between overhauls, T. The strategy to construct the model involved: the development of differential equations in order to determine system state probabilities; the definition of an operating cycle; the calculation of the cycle duration and respective total maintenance system cost incurred; and the utilization of a search method to find out the combination of parameters that minimizes the total cost of a specific system.

2006

Reconstructed high frame rate sequences quality measurement tool

Autores
Costa, MI; Tavares, C; Barroso, J; Soares, S;

Publicação
Working Group Reports on ITiCSE on Innovation and Technology in Computer Science Education 2006

Abstract
In this paper, we presented an application developed to measure the quality of a set of reconstructed high frame rate sequences. The main goal of the developed application is to allow the simultaneous visualization of both original and reconstructed sequences and measure the quality of the reconstructed frames.

2006

Polarization dependent loss of arc-induced long-period fibre gratings

Autores
Rego, GM; Santos, JL; Salgado, HM;

Publicação
OPTICS COMMUNICATIONS

Abstract
We have investigated the polarization properties of long-period fibre gratings fabricated using the electric arc technique. It was found that the choice of the fabrication parameters (electric current, arc duration and pulling tension) affects the polarization dependent loss of the produced gratings. In particular, a non-monotonic dependence on the external pulling tension was obtained.

2006

Low-Depth Witnesses are Easy to Find

Autores
Antunes, L; Fortnow, L; Pinto, A; Souto, A;

Publicação
Electronic Colloquium on Computational Complexity (ECCC)

Abstract

2006

Ambience and mobility

Autores
Doherty, GJ; Du Bousquet, L; Campos, JC; El Atifi, EM; Falquet, G; Massink, M; Santoro, C;

Publicação
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Abstract

2006

Estimation of the fibre temperature during the inscription of arc-induced long-period gratings

Autores
Rego, GM; Marques, PVS; Santos, JL; Salgado, HM;

Publicação
OPTICS COMMUNICATIONS

Abstract
The underlying formation mechanisms and the properties of long-period gratings produced through arc discharges are intrinsically related to the temperature reached by the fibre during arc exposure. In this work, the determination of the fibre temperature was based on Plank's blackbody radiation law. The radiation emitted by the optical fibre during heating due to an electric arc discharge, detected using a Cronin spectrometer, was fitted to the emission spectrum of the blackbody radiation, allowing the estimation of the temperature range attained by the fibre. A peak temperature of 1400 +/- 50 degrees C was obtained.

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