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Publicações

2015

Many-Objective PSO PID Controller Tuning

Autores
Freire, HF; de Moura Oliveira, PBD; Solteiro Pires, EJS; Bessa, M;

Publicação
CONTROLO'2014 - PROCEEDINGS OF THE 11TH PORTUGUESE CONFERENCE ON AUTOMATIC CONTROL

Abstract
Proportional, integral and derivative controller tuning can be a complex problem. There are a significant number of tuning methods for this type of controllers. However, most of these methods are based on a single performance criterion, providing a unique solution representing a certain controller parameters combination. Thus, a broader perspective considering other possible optimal or near optimal solutions regarding alternative or complementary design criteria is not obtained. Tuning PID controllers is addressed in this paper as a many-objective optimization problem. A Multi-Objective Particle Swarm Optimization algorithm is deployed to tune PID controllers considering five design criteria optimized at the same time. Simulation results are presented for a set of four well known plants.

2015

Construction and validation of a scale of assessment of self-care behaviors with arteriovenous fistula in hemodialysis

Autores
Sousa, CN; Alves Apostolo, JLA; Jesus Silva Figueiredo, MHJS; Ferreira Dias, VFF; Teles, P; Martins, MM;

Publicação
HEMODIALYSIS INTERNATIONAL

Abstract
Several guidelines recommend the importance of educating the patient about the care of vascular access. Nurses have a key role in promoting the development of self-care behaviors by providing the necessary knowledge to patients, so that they develop the necessary skills to take care of the arteriovenous fistula (AVF). This article describes the process of building a scale of assessment of self-care behaviors with arteriovenous fistula in hemodialysis (ASBHD-AVF). This is a cross-sectional study in which the development, construction, and validation process followed the directions of the authors Streiner and Norman. This is a convenience sample, sequential, and nonprobabilistic constituted by 218 patients. The study was conducted in two stages during 2012-2014. The first phase corresponds to the scale construction process, 64 patients participated, while the second corresponds to the evaluation of metric properties and 154 patients participated. The principal component analysis revealed a two-factor structure, with factorial weights between 0.805 and 0.511 and between 0.700 and 0.369, respectively, explaining 39.12% of the total variance of the responses. The Cronbach's alpha of the subscale management of signs and symptoms is 0.797 and from the subscale prevention of complications is 0.722. The ASBHD-AVF revealed properties that allow its use to assess the self-care behaviors in the maintenance and conservation of the AVF.

2015

Links between Scores, Real Default and Pricing: Evidence from the Freddie Mac’s Loan-Level Dataset

Autores
Rocha Sousa, M; Gama, J; Brandão, E;

Publicação
Journal of Economics, Business and Management

Abstract

2015

SPR Microstructured D-Type Optical Fiber Sensor Configuration for Refractive Index Measurement

Autores
Santos, DF; Guerreiro, A; Baptista, JM;

Publicação
IEEE SENSORS JOURNAL

Abstract
This paper presents the performance analysis of a sensing configuration of refractive index, based on surface plasmon resonance (SPR) in microstructured D-type optical fiber with a thin gold layer, using the finite-element method. The configuration is analyzed in terms of the loss and distribution Poynting vector. The results are compared with a conventional SPR D-type optical fiber sensor for refractive index measurement. The simulation results show an improvement of the sensitivity and resolution (10 x 10(3) nm/RIU and 9.8 x 10(-6) RIU, respectively, when considering an accurately spectral variation detection of 0.1 nm).

2015

Periocular Recognition under Unconstrained Settings with Universal Background Models

Autores
Monteiro, JC; Cardoso, JS;

Publicação
BIOSIGNALS

Abstract
The rising challenges in the fields of iris and face recognition are leading to a renewed interest in the area. In recent years the focus of research has turned towards alternative traits to aid in the recognition process under less constrained image acquisition conditions. The present work assesses the potential of the periocular region as an alternative to both iris and face in such scenarios. An automatic modeling of SIFT descriptors, regardless of the number of detected keypoints and using a GMM-based Universal Background Model method, is proposed. This framework is based on the Universal Background Model strategy, first proposed for speaker verification, extrapolated into an image-based application. Such approach allows a tight coupling between individual models and a robust likelihood-ratio decision step. The algorithm was tested on the UBIRIS.v2 and the MobBIO databases and presented state-of-the-art performance for a variety of experimental setups.

2015

Distributed Forest Fire Monitoring Using Wireless Sensor Networks

Autores
Serna, MA; Casado, R; Bermudez, A; Pereira, N; Tennina, S;

Publicação
INTERNATIONAL JOURNAL OF DISTRIBUTED SENSOR NETWORKS

Abstract
Disaster management is one of the most relevant application fields of wireless sensor networks. In this application, the role of the sensor network usually consists of obtaining a representation or a model of a physical phenomenon spreading through the affected area. In this work we focus on forest firefighting operations, proposing three fully distributed ways for approximating the actual shape of the fire. In the simplest approach, a circular burnt area is assumed around each node that has detected the fire and the union of these circles gives the overall fire's shape. However, as this approach makes an intensive use of the wireless sensor network resources, we have proposed to incorporate two in-network aggregation techniques, which do not require considering the complete set of fire detections. The first technique models the fire by means of a complex shape composed of multiple convex hulls representing different burning areas, while the second technique uses a set of arbitrary polygons. Performance evaluation of realistic fire models on computer simulations reveals that the method based on arbitrary polygons obtains an improvement of 20% in terms of accuracy of the fire shape approximation, reducing the overhead in-network resources to 10% in the best case.

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