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Publicações

2007

A multiple scenario security constrained reactive power planning tool using EPSO

Autores
Keko, H; Jaramillo Duque, A; Miranda, V;

Publicação
2007 International Conference on Intelligent Systems Applications to Power Systems, ISAP

Abstract
Evolutionary Particle Swarm Optimization (EPSO) is a robust optimization algorithm belonging to evolutionary methods. EPSO borrows the movement rules from Particle Swarm Optimization (PSO) and uses it as a recombination operator that evolves under selection. This paper presents a reactive power planning approach taking advantage of EPSO robustness, in a model that considers simultaneously multiple contingencies and multiple load levels. Results for selected problems are summarized including a trade-off analysis of results.

2007

Fiber optic displacement sensing monitored by an OTDR and referenced by Fresnel reflection and by fiber Bragg gratings

Autores
Mendonca, S; Frazao, O; Baptista, JM; Santos, JL;

Publicação
MICROWAVE AND OPTICAL TECHNOLOGY LETTERS

Abstract
This work presents a stud), of displacement sensing based on a fiber eight geometry shape monitored by an optical time domain reflectometer. The displacement sensor is referenced by Fresnel reflection or by a fiber Bragg grating structure located after the sensor. One of the advantages of the fiber Bragg grating as referencing device is its capability to be multiplexed by a number of displacement sensors in series along the optical fiber. This concept is also demonstrated using two Bragg gratings. (c) 2007 Wiley Periodicals, Inc.

2007

Interface framework to drive an intelligent wheelchair using facial expressions

Autores
Faria, PM; Braga, RAM; Valgode, E; Reis, LP;

Publicação
2007 IEEE INTERNATIONAL SYMPOSIUM ON INDUSTRIAL ELECTRONICS, PROCEEDINGS, VOLS 1-8

Abstract
Many of the physically injured use electric wheelchairs as an aid to locomotion. Usually, for commanding this type of wheelchair, it is required the use of one's hands and this poses a problem to those who, besides being unable to use their. legs, are also unable to properly use their hands. The aim of the work described here, is to create a prototype of a wheelchair command interface that do not require hand usage. Facial expressions. were chosen instead, to provide the necessary visual information for the interface to recognize user commands. The facial expressions are captured by means of a digital camera and interpreted by an application running on a laptop computer on the wheelchair. The software includes digital image processing algorithms for feature detection, such as colour segmentation and edge detection, followed by the application of a neural network that uses these features to detect the desired facial expressions. The results obtained from the framework interface provide strong evidence that it is possible to comfortably drive an intelligent wheelchair using facial expressions.

2007

Strain and temperature discrimination using IF concatenated high-birefringence fiber loop mirrors

Autores
Frazao, O; Santos, JL; Baptista, JM;

Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
In this letter, a new configuration for simultaneous strain and temperature discrimination is, presented using two concatenated high-birefringence (Hi-Bi) fiber loop mirrors. The first loop mirror includes a Hi-Bi photonic crystal fiber, while the second one contains a length of internal elliptical cladding fiber. It is shown that by monitoring the wavelength and optical power of one of the peaks of the system spectral transfer function, it is possible to obtain information that permits the simultaneous measurement of strain and temperature.

2007

Definition of main pollen season using a logistic model

Autores
Ribeiro, H; Cunha, M; Abreu, I;

Publicação
ANNALS OF AGRICULTURAL AND ENVIRONMENTAL MEDICINE

Abstract
This paper proposes a method to unify the definition of the main pollen season based on statistical analysis. For this, an aerobiological study was carried out in Porto region (Portugal), from 2003-2005 using a 7-day Hirst-type volumetric spore trap. To define the main pollen season, a non-linear logistic regression model was fitted to the values of the accumulated sum of the daily airborne pollen concentration from several allergological species. An important feature of this method,is that the main pollen season will be characterized by the model parameters calculated. These parameters are identifiable aspects of the flowering phenology, and determine not only the beginning and end of the main pollen season, but are also influenced by the meteorological conditions. The results obtained with the proposed methodology were also compared with two of the most used percentage methods. The logistic model fitted well with the sum of accumulated pollen. The explained variance was always higher than 97%, and the exponential part of the predicted curve was well adjusted to the time when higher atmospheric pollen concentration was sampled. The comparison between the different methods tested showed large divergence in the duration and end dates of the main pollen season of the studied species.

2007

Temperature-independent strain sensor based on a Hi-Bi photonic crystal fiber loop mirror

Autores
Frazao, O; Baptista, JM; Santos, JL;

Publicação
IEEE SENSORS JOURNAL

Abstract
This work presents an optical sensor based on a highly birefringent photonic crystal fiber (Hi-Bi PCF) loop mirror. The length of the sensing head is 380 mm and its corresponding wavelength spacing between two interferometer minima is 8 nm. The optical sensor was characterized in strain and in temperature with an uncoated Hi-Bi PCF and with an acrylate coated Hi-Bi PCF. Different results for strain and temperature sensitivity were obtained. Relatively to the strain measurement, the sensor with the uncoated Hi-Bi PCF presents slightly less sensitivity (1.11 pm/mu epsilon) when compared with coated Hi-Bi PCF (1.21 pm/mu epsilon). For the temperature measurement and with the uncoated Hi-Bi PCF, the optical sensor is insensitive to temperature (0.29 pm/K).

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