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Publications

1995

REFERENCING TECHNIQUE FOR INTENSITY-BASED SENSORS USING FIBER OPTIC BRAGG GRATINGS

Authors
CAVALEIRO, PM; RIBEIRO, ABL; SANTOS, JL;

Publication
ELECTRONICS LETTERS

Abstract
An all-optical fibre referencing scheme for intensity based sensors which uses two identical fibre Bragg gratings is described. It provides a general and simple miniature sensor design with referencing effectiveness against system power fluctuations. The concept is demonstrated for a reflective-type displacement sensing cavity, and its potential for simultaneous measurand and temperature evaluation is evaluated.

1995

Connection Oriented Isochronous Services in a DQDB Network: Specification of a Service-protocol pair and a Bandwidth Allocation Scheme

Authors
Juanole, G; Carmo, RLR; Vasques, F;

Publication
Local and Metropolitan Communication Systems

Abstract

1995

Cancellation of third-order intermodulation distortion in a directly modulated DFB laser and optical discriminator

Authors
Castro, JCS; Salgado, HM; O'Reilly, JJ; Todd, CJ;

Publication
Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS

Abstract
This work uses Volterra kernels to model the distortion of complex optical systems using both frequency and intensity modulation of a DFB laser and an optical discriminator. The laser's IM and FM complex responses and also the laser's intrinsic FM distortion are shown to be crucial to model accurately the system's third-order intermodulation product (IMP3) performance. The results show that it is possible to achieve a large reduction of the third-order IMP3 in some frequency ranges by off-setting the bias of the discriminator from the point of maximum slope. Furthermore, at high frequencies the system's IMP3 performance can be better than in the case of a purely intensity modulated laser without a discriminator.

1995

Characterization of Classification Algorithms

Authors
Gama, J; Brazdil, P;

Publication
Progress in Artificial Intelligence, 7th Portuguese Conference on Artificial Intelligence, EPIA '95, Funchal, Madeira Island, Portugal, October 3-6, 1995, Proceedings

Abstract
This paper is concerned with the problem of characterization of classification algorithms. The aim is to determine under what circumstances a particular classification algorithm is applicable. The method used involves generation of different kinds of models. These include regression and rule models, piecewise linear models (model trees) and instance based models. These are generated automatically on the basis of dataset characteristics and given test results. The lack of data is compensated for by various types of preprocessing. The models obtained are characterized by quantifying their predictive capability and the best models are identified. © Springer-Verlag Berlin Heidelberg 1995.

1995

ELECTROOXIDATION OF D-SORBITOL ON PLATINUM IN PERCHLORIC MEDIUM - A VOLTAMMETRIC STUDY

Authors
FONSECA, I; LOPES, MIS; SANTOS, JL; PROENCA, L;

Publication
ELECTROCHIMICA ACTA

Abstract
The electrocatalytic oxidation of D-sorbitol on a polycrystalline platinum electrode, in perchloric aqueous medium, was studied by cyclic voltammetry under varying sweep rate, potential limits, stirring, temperature, pH and concentration of D-sorbitol. A value of about 50 kJ mol(-1) was obtained for the apparent activation enthalpy of the oxidation reaction at 0.1 V vs. sme. The experimental rate equation is i = kC(D-sorb)(0.4) C-H+(-0.3).exp[0.4 FE/RT], valid for [D-sorbitol] < 0.1 mol dm(-3) and pH < 1.

1995

FIBER OPTIC INTERFEROMETRIC SENSOR-BASED ON SOURCE COHERENCE SYNTHESIS BY DYNAMICAL SPECTRAL FILTERING OF A SUPERLUMINESCENT SOURCE

Authors
FERREIRA, LA; SANTOS, JL;

Publication
OPTICS COMMUNICATIONS

Abstract
Interferometric sensors based on source coherence synthesis have been reported for measurement of quasistatic parameters. An absolute sensing technique has been demonstrated based on fringe visibility modulation using a frequency modulated laser. In this Letter, a technique is described which allows to perform absolute displacement measurements in the range from tens to several hundreds of micrometers. It is based on dynamical spectral filtering of a superluminescent source which provides frequency modulation amplitudes up to 3000 GHz. The principle is described and experimentally verified for displacement measurement

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