2018
Autores
Paiva, JS; Cardoso, J; Pereira, T;
Publicação
INTERNATIONAL JOURNAL OF MEDICAL INFORMATICS
Abstract
Objective: The main goal of this study was to develop an automatic method based on supervised learning methods, able to distinguish healthy from pathologic arterial pulse wave (APW), and those two from noisy waveforms (non-relevant segments of the signal), from the data acquired during a clinical examination with a novel optical system. Materials and methods: The APW dataset analysed was composed by signals acquired in a clinical environment from a total of 213 subjects, including healthy volunteers and non-healthy patients. The signals were parameterised by means of 39 pulse features: morphologic, time domain statistics, cross-correlation features, wavelet features. Multiclass Support Vector Machine Recursive Feature Elimination (SVM RFE) method was used to select the most relevant features. A comparative study was performed in order to evaluate the performance of the two classifiers: Support Vector Machine (SVM) and Artificial Neural Network (ANN). Results and discussion: SVM achieved a statistically significant better performance for this problem with an average accuracy of 0.9917 +/- 0.0024 and a F-Measure of 0.9925 +/- 0.0019, in comparison with ANN, which reached the values of 0.9847 +/- 0.0032 and 0.9852 +/- 0.0031 for Accuracy and F-Measure, respectively. A significant difference was observed between the performances obtained with SVM classifier using a different number of features from the original set available. Conclusion: The comparison between SVM and NN allowed reassert the higher performance of SVM. The results obtained in this study showed the potential of the proposed method to differentiate those three important signal outcomes (healthy, pathologic and noise) and to reduce bias associated with clinical diagnosis of cardiovascular disease using APW.
2018
Autores
Ferreira, MS; Novais, S; Pinto, JL;
Publicação
Optics InfoBase Conference Papers
Abstract
A multimode interferometer based on an etched coreless optical fiber tip is proposed for the determination of the thermo-optic coefficient of ethanol-water mixtures, through refractive index and temperature measurements. © OSA 2018 © 2018 The Author(s)
2018
Autores
Barbosa, M; Farshim, P;
Publicação
ADVANCES IN CRYPTOLOGY - CRYPTO 2018, PT I
Abstract
We study Authenticated Encryption with Associated Data (AEAD) from the viewpoint of composition in arbitrary (single-stage) environments. We use the indifferentiability framework to formalize the intuition that a "good" AEAD scheme should have random ciphertexts subject to decryptability. Within this framework, we can then apply the indifferentiability composition theorem to show that such schemes offer extra safeguards wherever the relevant security properties are not known, or cannot be predicted in advance, as in general-purpose crypto libraries and standards. We show, on the negative side, that generic composition (in many of its configurations) and well-known classical and recent schemes fail to achieve indifferentiability. On the positive side, we give a provably indifferentiable Feistel-based construction, which reduces the round complexity from at least 6, needed for blockciphers, to only 3 for encryption. This result is not too far off the theoretical optimum as we give a lower bound that rules out the indifferentiability of any construction with less than 2 rounds.
2018
Autores
Mehrasa, M; Sepehr, A; Pouresmaeil, E; Kyyra, J; Marzband, M; Catalao, JPS;
Publicação
2018 INTERNATIONAL CONFERENCE ON SMART ENERGY SYSTEMS AND TECHNOLOGIES (SEST)
Abstract
In this paper, an angular frequency dynamic-based control technique is proposed to control interfaced converters between the power grid and renewable energy sources. The proposed control technique can guarantee a stable operation of power grid under high penetration of renewable energy resources through providing the required inertia properties. The synchronous generator characteristics combined with the basic dynamic model of the interfaced converter can shape a second order derivative of the grid angular frequency consisting of converter power and virtual mechanical power derivative with embedded virtual inertia to prevent instability from the power grid as well as to generate active and reactive power with appropriate inertia. Simulation analyses are performed in Matlab/Simulink to attest the high performance of the proposed control technique.
2018
Autores
Galdran, A; Alvarez Gila, A; Bria, A; Vazquez Corral, J; Bertalmio, M;
Publicação
2018 IEEE/CVF CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION (CVPR)
Abstract
Image dehazing deals with the removal of undesired loss of visibility in outdoor images due to the presence of fog. Retinex is a color vision model mimicking the ability of the Human Visual System to robustly discount varying illuminations when observing a scene under different spectral lighting conditions. Retinex has been widely explored in the computer vision literature for image enhancement and other related tasks. While these two problems are apparently unrelated, the goal of this work is to show that they can be connected by a simple linear relationship. Specifically, most Retinex-based algorithms have the characteristic feature of always increasing image brightness, which turns them into ideal candidates for effective image dehazing by directly applying Retinex to a hazy image whose intensities have been inverted. In this paper, we give theoretical proof that Retinex on inverted intensities is a solution to the image dehazing problem. Comprehensive qualitative and quantitative results indicate that several classical and modern implementations of Retinex can be transformed into competing image dehazing algorithms performing on pair with more complex fog removal methods, and can overcome some of the main challenges associated with this problem.
2018
Autores
Figueiredo, F; Figueiredo, A; Gomes, MI;
Publicação
Contributions to Statistics - Recent Studies on Risk Analysis and Statistical Modeling
Abstract
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