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Publications

2002

Electrical current metering with a dual interferometric configuration and serrodyne signal processing

Authors
Jorge, PAS; Caldas, P; Ferreira, LA; Ribeiro, ABL; Santos, JL; Farahi, F;

Publication
OFS 2002: 15TH OPTICAL FIBER SENSORS CONFERENCE TECHNICAL DIGEST

Abstract
Theoretical and experimental results were presented which validated a new dual interferometric configuration with serrodyne processing for the remote sensing of electrical current. Linearity and waveform reproduction at 50 Hz were observed and a current resolution (˜22.4 ArmsHz- 1/2) was obtained. The utilization of the proposed interferometric concept to simultaneously perform metering and relaying current measurements was also addressed. © 2002 IEEE.

2002

Micromachined low-finesse Fabry-Pérot interferometer for the measurement of low DC electrical currents

Authors
Heredeor, RL; Santos, JL; De Caleya, RF; Araújo, FM; Ferreira, LA; Guerrero, H;

Publication
2002 15th Optical Fiber Sensors Conference Technical Digest, OFS 2002

Abstract
An optical fiber current sensor based on a permanent magnet fixed on the center of a micromachined Si membrane has been presented. The transducing operation principle is magneto-mechanical and has a linear response. A great improvement of the sensitivity of the microcavities was achieved by the use of a planar coil. Interrogation of the transducer has been carried out using a Fabry-Perot interferometer with an all-fiber detection system to avoid the influence of electromagnetic noise. The effectiveness of a fiber scheme based on the utilization of two fibre Bragg gratings to generate two quadrature phase-shifted interferometric signals has also been reported. © 2002 IEEE.

2002

A study on the optimum order of autoregressive models for heart rate variability

Authors
Boardman, A; Schlindwein, FS; Rocha, AP; Leite, A;

Publication
PHYSIOLOGICAL MEASUREMENT

Abstract
Heart rate variability (HRV) has been used as a non-invasive marker of the activity of the autonomic nervous system and its spectrum analysis gives a measure of the sympatho-vagal balance. If short segments are used in an attempt to improve temporal resolution, autoregressive spectral estimation, where the model order must be estimated, is preferred. In this paper we compare four criteria for the estimation of the 'optimum' model order for an autoregressive (AR) process applied to short segments of tachograms used for HRV analysis. The criteria used were Akaike's final prediction error. Akaike's information criterion, Parzen's criterion of autoregressive transfer function and Rissanen's minimum description length method, and they were first applied to tachograms to verify (i) the range and distribution of model orders obtained and (ii) if the different techniques suggest the same model order for the same frames. The four techniques were then tested using a true AR process of known order p = 6: this verified the ability of the criteria to estimate the correct order of a true AR process and the effect. on the spectrum. of choosing a wrong model order was also investigated. It was found that all the four criteria underestimate the true AR orders specifying a fixed model order was then looked at and it is recommended that an AR order not less than p = 16, should be used for spectral analysis of short segments of tachograms.

2002

Brokerage function in agile virtual enterprise integration - A literature review

Authors
Avila, P; Putnik, GD; Cunha, MM;

Publication
COLLABORATIVE BUSINESS ECOSYSTEMS AND VIRTUAL ENTERPRISES

Abstract
The paper present a review of the brokerage function as it is defined within different Agile and/or Virtual Enterprise (A/V E) models throughout the literature, including the broker's function within the Broker function taxonomy, BM_Virtual Enterprise Architecture Reference Model, as well as their comparison. Many authors see a broker, and the corresponded brokerage function, as one of the principal agents, or a mechanism, for agility as well as for reconfigurability of the A/V E organization structure (by some authors the reconfigurability is the basic function of agility). However, the function of the broker, and its position in the AN E organizational structure, has been defined in different models ranging from entrepreneurship function, resource selection function, through scheduling function etc. The analysis shows that there is a great heterogeneity of the broker functions, or definitions.

2002

Genetic algorithms for the bus driver scheduling problem: a case study

Authors
Dias, TG; de Sousa, JP; Cunha, JF;

Publication
JOURNAL OF THE OPERATIONAL RESEARCH SOCIETY

Abstract
This paper describes an application of genetic algorithms to the bus driver scheduling problem. The application of genetic algorithms extends the traditional approach of Set Covering/Set Partitioning formulations, allowing the simultaneous consideration of several complex criteria. The genetic algorithm is integrated in a DSS but can be used as a very interactive tool or a stand-alone application. It incorporates the user's knowledge in a quite natural way and produces solutions that are almost directly implemented by the transport companies in their operational planning processes. Computational results with airline and bus crew scheduling problems from real world companies are presented and discussed.

2002

Simultaneous UV direct writing of channel waveguides and Bragg gratings in germanium-doped planar silica

Authors
Marques, PVS; Bonar, JR; Leite, AMP; Aitchison, JS;

Publication
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS

Abstract
Channel waveguides incorporating photo-imprinted Bragg gratings were produced in germano-borosilicate glass layers fabricated by flame hydrolysis deposition, through single-and double-step exposure direct writing processes with UV laser irradiation. To our knowledge, this is the first time that UV exposure has been used to simultaneously realize both waveguiding and spectral selectivity functions.

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