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Publications

2014

Double four-quadrants single-phase current source converter sharing the same DC-bus

Authors
Vitorino, MA; Correa, MBR; Costa, LC; Hartmann, LV; Fernandes, DA;

Publication
2014 IEEE Energy Conversion Congress and Exposition (ECCE)

Abstract

2014

Dynamics of blueshifted floating pulses in gas-filled hollow-core photonic crystal fibers

Authors
Facao, M; Carvalho, MI;

Publication
APPLIED PHYSICS B-LASERS AND OPTICS

Abstract
Frequency blueshifting was recently observed in light pulses propagating on gas-filled hollow-core photonic crystal fibers where a plasma has been produced due to photoionization of the gas. One of the propagation models that is adequate to describe the actual experimental observations is here investigated. It is a nonlinear Schrodinger equation with an extra term, to which we applied a self-similar change of variables and found its accelerating solitons. As in other NLS-related models possessing accelerating solitons, there exist asymmetrical pulses that decay as they propagate in some parameter region that was here well defined.

2014

Remote curvature fiber sensors using core mismatch structures and OTDR based interrogation

Authors
Fernandes, CS; Rocco Giraldi, MTMR; Gouveia, CJ; Sousa, MJ; Costa, JCWA; Frazao, O; Jorge, PAS;

Publication
SECOND INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS

Abstract
In this work, a remote curvature sensor using a standard OTDR as the interrogation system is presented. This approach uses a core diameter mismatch sensor which is formed by a short section of a multimode fiber, with a length of 3 mm, sandwiched between two singlemode fibers. In this case, the attenuation of the optical signal will vary as the fiber is bent allowing interrogating the sensor with OTDR technology. Preliminary results indicate a resolution range of similar to 0.0003 cm(-1), sensitivity in the range of similar to-208.46 dB/cm(-1) and a variation of 2.67 dB in the OTDR trace within the bend radius range.

2014

Overall survival prediction for women breast cancer using ensemble methods and incomplete clinical data

Authors
Abreu, PH; Amaro, H; Silva, DC; Machado, P; Abreu, MH; Afonso, N; Dourado, A;

Publication
IFMBE Proceedings

Abstract
Breast Cancer is the most common type of cancer in women worldwide. In spite of this fact, there are insufficient studies that, using data mining techniques, are capable of helping medical doctors in their daily practice. This paper presents a comparative study of three ensemble methods (TreeBagger, LPBoost and Subspace) using a clinical dataset with 25% missing values to predict the overall survival of women with breast cancer. To complete the absent values, the k-nearest neighbor (k-NN) algorithm was used with four distinct neighbor values, trying to determine the best one for this particular scenario. Tests were performed for each of the three ensemble methods and each k-NN configuration, and their performance compared using a Friedman test. Despite the complexity of this challenge, the produced results are promising and the best algorithmconfiguration (TreeBagger using 3 neighbors) presents a prediction accuracy of 73%. © Springer International Publishing Switzerland 2014.

2014

A computerized system for maintenance management of assembly lines

Authors
Costa, R; Lopes, I; Machado, C; Cabral, JM;

Publication
SAFETY, RELIABILITY AND RISK ANALYSIS: BEYOND THE HORIZON

Abstract
Organizations are increasingly seeking to improve their efficiency and effectiveness to obtain reliable and high quality product at a lower cost. To achieve this objective, the use of tools that facilitate the acquisition of knowledge about processes is a valuable support. In maintenance, recording data about corrective actions is essential to define proactive actions that aim to avoid or mitigate the effects of future failures. Several computer systems are commercially available for maintenance management. However, the degree of suitability of these systems is low, once they do not consider organizations particularities. This paper presents a computer system for collecting and analyzing data from the machines of the production lines of a semiconductor company. This project aims to provide the company with a tool adapted to its needs, able to perform a behavioral analysis of all the machines of the production lines based on the systematic record of failures occurrence and maintenance activities.

2014

A compositional model to reason about end-to-end QoS in Stochastic Reo connectors

Authors
Moon, YJ; Silva, A; Krause, C; Arbab, F;

Publication
SCIENCE OF COMPUTER PROGRAMMING

Abstract
In this paper, we present a compositional semantics for the channel-based coordination language Reo that enables the analysis of quality of service (QoS) properties of service compositions. For this purpose, we annotate Reo channels with stochastic delay rates and explicitly model data-arrival rates at the boundary of a connector, to capture its interaction with the services that comprise its environment. We propose Stochastic Reo Automata as an extension of Reo automata, in order to compositionally derive a QoS-aware semantics for Reo. We further present a translation of Stochastic Reo Automata to Continuous-Time Markov Chains (CTMCs). This translation enables us to use third-party CTMC verification tools to do an end-to-end performance analysis of service compositions. In addition, we discuss to what extent Interactive Markov Chains (IMCs) can serve as an alternative semantic model for Stochastic Reo. We show that the semantics of Stochastic Reo cannot be specified compositionally using the product operator provided by IMCs.

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