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Publications

Publications by Hélder Filipe Oliveira

2011

Development of a BCCT Quantitative 3D Evaluation System through Low-Cost Solutions

Authors
Oliveira, HP; Patete, P; Baroni, G; Cardoso, JS;

Publication
Proceedings of the 2nd International Conference on 3D Body Scanning Technologies, Lugano, Switzerland, 25-26 October 2011

Abstract

2009

A new method for the detection of singular points in fingerprint images

Authors
Magalhaes, F; Oliveira, HP; Campilho, AC;

Publication
2009 Workshop on Applications of Computer Vision, WACV 2009

Abstract
Automatic biometric identification based on fingerprints is still one of the most reliable identification method in criminal and forensic applications. A critical step in fingerprint analysis without human intervention is to automatically and reliably extract singular points from the input fingerprint images. These singular points (cores and deltas) not only represent the characteristics of local ridge patterns but also determine the topological structure (i.e., fingerprint type) and largely influence the orientation field. Poincaré Index-based methods are one of the most common for singular points detection. However, these methods usually result in many spurious detections. Therefore, we propose an enhanced version of the method presented by Zhou et al. [13] that introduced a feature called DORIC to improve the detection. Our principal contribution lies in the adoption of a smoothed orientation field and in the formulation of a new algorithm to analyze the DORIC feature. Experimental results show that the proposed algorithm is accurate and robust, giving better results than the best reported results so far, with improvements in the range of 5% to 7%. © 2009 IEEE.

2007

A nonlinear model predictive control of an omni-directional mobile robot

Authors
Conceicao, AS; Oliveira, HP; e Silva, AS; Oliveira, D; Moreira, AP;

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

Abstract
This paper presents a nonlinear model based predictive controller (NMPC) for trajectory tracking of a mobile robot. Methods of numerical optimization to perform real time nonlinear minimization of the cost function are used. The cost function penalizes the robot position error, the robot orientation angle error and the control effort. Experimental results of the trajectories following and the performance of the methods of optimization are presented.

2010

An Accurate and Interpretable Model for BCCT.core

Authors
Oliveira, HP; Magalhaes, A; Cardoso, MJ; Cardoso, JS;

Publication
2010 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC)

Abstract
Breast Cancer Conservative Treatment (BCCT) is considered nowadays to be the most widespread form of locor-regional breast cancer treatment. However, aesthetic results are heterogeneous and difficult to evaluate in a standardized way. The limited reproducibility of subjective aesthetic evaluation in BCCT motivated the research towards objective methods. A recent computer system (BCCT. core) was developed to objectively and automatically evaluate the aesthetic result of BCCT. The system is centered on a support vector machine (SVM) classifier with a radial basis function (RBF) used to predict the overall cosmetic result from features computed on a digital photograph of the patient. However, this classifier is not ideal for the interpretation of the factors being used in the prediction. Therefore, an often suggested improvement is the interpretability of the model being used to assess the overall aesthetic result. In the current work we investigate the accuracy of different interpretable methods against the model currently deployed in the BCCT. core software. We compare the performance of decision trees and linear classifiers with the RBF SVM currently in BCCT. core. In the experimental study, these interpretable models shown a similar accuracy to the currently used RBF SVM, suggesting that the later can be replaced without sacrificing the performance of the BCCT.core.

2010

Value of Photographic Side-Views in the Objective Evaluation of the Aesthetic Result of Breast Cancer Conservative Treatment

Authors
Magalhaes, AT; Oliveira, HP; Costa, S; Cardoso, JS; Cardoso, MJ;

Publication
CANCER RESEARCH

Abstract

2011

Feature Selection with Complexity Measure in a Quadratic Programming Setting

Authors
Sousa, R; Oliveira, HP; Cardoso, JS;

Publication
PATTERN RECOGNITION AND IMAGE ANALYSIS: 5TH IBERIAN CONFERENCE, IBPRIA 2011

Abstract
Feature selection is a topic of growing interest mainly due to the increasing amount of information, being an essential task in many machine learning problems with high dimensional data. The selection of a subset of relevant features help to reduce the complexity of the problem and the building of robust learning models. This work presents an adaptation of a recent quadratic programming feature selection technique that identifies in one-fold the redundancy and relevance on data. Our approach introduces a non-probabilistic measure to capture the relevance based on Minimum Spanning Trees. Three different real datasets were used to assess the performance of the adaptation. The results are encouraging and reflect the utility of feature selection algorithms.

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