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Publicações

2012

Multi-objective Optimization and Meta-learning for SVM Parameter Selection

Autores
Miranda, PBC; Prudencio, RBC; de Carvalho, ACPLF; Soares, C;

Publicação
2012 INTERNATIONAL JOINT CONFERENCE ON NEURAL NETWORKS (IJCNN)

Abstract
Support Vector Machines (SVMs) have become a well succeed technique due to the good performance it achieves on different learning problems. However, the performance depends on adjustments on its model. The automatic SVM parameter selection is a way to deal with this. This approach is considered an optimization problem whose goal is to find suitable configuration of parameters which attends some learning problem. This work proposes the use of Particle Swarm Optimization (PSO) to treat the SVM parameter selection problem. As the design of learning systems is inherently a multi-objective optimization problem, a multi-objective PSO (MOPSO) was used to maximize the success rate and minimize the number of support vectors of the model. Moreover, we propose the combination of Meta-Learning (ML) with MOPSO to the cited problem. ML is used to recommend SVM parameters, to a given input problem, based on well-succeeded parameters adopted in previous similar problems. In this combination, initial solutions provided by ML are possibly located in good regions in the search space. Hence, using a reduced number of candidate search points, the search process, to find an adequate solution, would be less expensive. We highlight that, the combination of search algorithms with ML was just studied in the single objective field and the use of MOPSO in this context has not been investigated. In our work, we implemented a prototype in which MOPSO was used to select the values of two SVM parameters for classification problems. In the performed experiments, the proposed solution (MOPSO using ML or Hybrid MOPSO) was compared to a MOPSO with random initialization, obtaining paretos with higher quality on a set of 40 classification problems.

2012

Vital responder - Wearable sensing challenges in uncontrolled critical environments

Autores
Coimbra, M; Silva Cunha, JP;

Publicação
Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering

Abstract
The goal of the Vital Responder research project is to explore the synergies between innovative wearable technologies, scattered sensor networks, intelligent building technology and precise localization services to provide secure, reliable and effective first-response systems in critical emergency scenarios. Critical events, such as natural disaster or other large-scale emergency, induce fatigue and stress in first responders, such as fire fighters, policemen and paramedics. There are distinct fatigue and stress factors (and even pathologies) that were identified among these professionals. Nevertheless, previous work has uncovered a lack of real-time monitoring and decision technologies that can lead to in-depth understanding of the physiological stress processes and to the development of adequate response mechanisms. Our "silver bullet" to address these challenges is a suite of non-intrusive wearable technologies, as inconspicuous as a t-shirt, capable of gathering relevant information about the individual and disseminating this information through a wireless sensor network. In this paper we will describe the objectives, activities and results of the first two years of the Vital Responder project, depicting how it is possible to address wearable sensing challenges even in very uncontrolled environments. © 2012 ICST Institute for Computer Science, Social Informatics and Telecommunications Engineering.

2012

Long period gratings and rocking filters written with a CO2 laser in highly-birefringent boron-doped photonic crystal fibers for sensing applications

Autores
Carvalho, JP; Anuszkiewicz, A; Statkiewicz Barabach, G; Baptista, JM; Frazao, O; Mergo, P; Santos, JL; Urbanczyk, W;

Publicação
OPTICS COMMUNICATIONS

Abstract
In this work, we demonstrate the possibility of fabricating short-length long-period gratings and rocking filters in highly birefringent Photonic Crystal Fiber using a CO2 laser. In our experiments both kinds of gratings were made in the same Boron doped highly birefringent PCF using similar exposure parameters. We also present the sensing capabilities of both fabricated gratings to temperature, strain and hydrostatic pressure by interrogation of the wavelength shifts at different resonances. Crown Copyright

2012

Time-adaptive quantile-copula for wind power probabilistic forecasting

Autores
Bessa, RJ; Miranda, V; Botterud, A; Zhou, Z; Wang, J;

Publicação
RENEWABLE ENERGY

Abstract
This paper presents a novel time-adaptive quantile-copula estimator for kernel density forecast and a discussion of how to select the adequate kernels for modeling the different variables of the problem. Results are presented for different case-studies and compared with splines quantile regression (QR). The datasets used are from NREL's Eastern Wind Integration and Transmission Study, and from a real wind farm located in the Midwest region of the United States. The new probabilistic prediction model is elegant and simple and yet displays advantages over the traditional QR approach. Especially notable is the quality of the results achieved with the time-adaptive version, namely when evaluated in terms of prediction calibration, which is a characteristic that is advantageous for both system operators and wind power producers.

2012

Integrating Interactive Visualizations of Automatic Debugging Techniques on an Integrated Development Environment

Autores
Riboira, A; Rodrigues, R; Abreu, R; Campos, J;

Publicação
IJCICG

Abstract

2012

Combining a Multi-Objective Optimization Approach with Meta-Learning for SVM Parameter Selection

Autores
de Miranda, PBC; Prudencio, RBC; de Carvalho, ACPLF; Soares, C;

Publicação
PROCEEDINGS 2012 IEEE INTERNATIONAL CONFERENCE ON SYSTEMS, MAN, AND CYBERNETICS (SMC)

Abstract
Support Vector Machine (SVM) is a supervised technique, which achieves good performance on different learning problems. However, adjustments on its model are essentials to the SVM work well. Optimization techniques have been used to automatize this process finding suitable configurations of parameters which attends some learning problems. This work utilizes Particle Swarm Optimization (PSO) applied to the SVM parameter selection problem. As the learning systems are essentially a multi-objective problem, a multi-objective PSO (MOPSO) was used to maximize the success rate and minimize the number of support vectors of the model. Nevertheless, we propose the combination of Meta-Learning (ML) with a modified MOPSO which uses the crowding distance mechanism (MOPSO-CDR). In this combination, solutions provided by ML are possibly located in good regions in the search space. Hence, using a reduced number of successful candidates, the search process would converge faster and be less expensive. In our work, we implemented a prototype in which MOPSO-CDR was used to select the values of two SVM parameters for classification problems. In the performed experiments, the proposed solution (MOPSO-CDR using ML) was compared to the MOPSO-CDR with random initialization, obtaining pareto fronts with higher quality on a set of 40 classification problems.

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