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Publicações

2004

Optical waveguides fabricated by electron-beam irradiation of Ge-doped flame-hydrolysis silica

Autores
Garcia Blanco, S; Aitchison, JS; Marques, PVS; Taylor, RS; Hnatovsky, C;

Publicação
OSA Trends in Optics and Photonics Series

Abstract
The refractive index distribution and birefringence of electron-beam directly-written waveguides in flame-hydrolysis silica have been characterized by means of micro-reflectivity and mode characterization. These results allow the detail design and fabrication of complex optical devices using this fabrication technique. © 2003 Optical Society of America.

2004

Voltage collapse preventive control - A new method

Autores
Andrade, AC; Barbosa, FPM;

Publicação
MELECON 2004: PROCEEDINGS OF THE 12TH IEEE MEDITERRANEAN ELECTROTECHNICAL CONFERENCE, VOLS 1-3

Abstract
Simple performance index for detecting and predicting stability problems such as the voltage collapse are useful analysis tools for planning and operating in power system. A new method for the detection of the point of collapse and a new index for the definition of the distance of the voltage collapse point are proposed. Numerical experiments using standard IEEE 14 and 57 bus systems show that the proposed method can compute the voltage collapse point using several different scenery of load increase. The methodology proposed may be easily implemented in any power flow program.

2004

Intensity-referenced temperature-independent curvature sensing concept based on chirped gratings embedded in a composite laminate

Autores
Romero, R; Frazao, O; Pereira, DA; Salgado, HM; Araujo, FM; Ferreira, LA;

Publicação
SECOND EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS: PROCEEDINGS

Abstract
An intensity-referenced temperature-independent curvature measurement technique using a smart composite comprising two chirped fiber Bragg gratings is demonstrated. The two gratings are embedded on opposite sides of a composite laminate and act simultaneously as curvature sensors and as wavelength discriminators, enabling an unambiguous measurement of the composite radius of curvature.

2004

Electric power systems steady-state security assessment using the rough set theory

Autores
Agreira, CIF; Ferreira, CMM; Pinto, JAD; Barbosa, FPM;

Publicação
2004 INTERNATIONAL CONFERENCE ON PROBABILISTIC METHODS APPLIED TO POWER SYSTEMS

Abstract
In this paper it is proposed an efficient steady-state contingency classification using the Rough Set Theory. The developed methodology produces a classification of the system operating in four possible states: normal, alert, emergency I, and emergency II. The methodology developed by the authors was applied to a test power network and the results obtained were analyzed. Finally, some conclusions that provide a valuable contribution to the understanding of the power system security analysis are pointed out.

2004

Simultaneous measurement of strain and temperature based on polarization loss properties of are-induced long period gratings

Autores
Frazao, O; Rego, G; Araujo, FM; Ferreira, LA; Salgado, HM; Santos, JL;

Publicação
SECOND EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS: PROCEEDINGS

Abstract
A new sensing configuration is proposed for simultaneous measurement of strain and temperature that relies on a single long period grating written by the electric arc technique. The underlying principle is the azimuthal asymmetry induced by the electric arc fabrication technique, which results in a device with polarization dependent insertion loss sensitive to both temperature and strain. With the proposed configuration, resolutions of +/- 2.8 degreesC/rootHz and +/- 13.9 muepsilon/rootHz are obtained for temperature and strain measurements, respectively.

2004

Measurement of the temperature of an optical fiber submitted to an electric arc discharge

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

Publicação
SECOND EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS: PROCEEDINGS

Abstract
The radiation emitted by an optical fiber during heating due to an electric arc discharge was detected using a Cronin spectrometer. The fitting of the emission spectrum to the blackbody radiation, allowed the estimation of the temperature range attained by the fiber.

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