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Publications

2016

Entropy-based discretization methods for ranking data

Authors
de Sá, CR; Soares, C; Knobbe, A;

Publication
INFORMATION SCIENCES

Abstract
Label Ranking (LR) problems are becoming increasingly important in Machine Learning. While there has been a significant amount of work on the development of learning algorithms for LR in recent years, there are not many pre-processing methods for LR Some methods, like Naive Bayes for LR and APRIORI-LR, cannot handle real-valued data directly. Conventional discretization methods used in classification are not suitable for LR problems, due to the different target variable. In this work, we make an extensive analysis of the existing methods using simple approaches. We also propose a new method called EDiRa (Entropy-based Discretization for Ranking) for the discretization of ranking data. We illustrate the advantages of the method using synthetic data and also on several benchmark datasets. The results clearly indicate that the discretization is performing as expected and also improves the results and efficiency of the learning algorithms.

2016

Subspace Algorithm for Identifying Bilinear Repetitive Processes with Deterministic Inputs

Authors
Ramos, JA; Rogers, E; dos Santos, PL; Perdicoúlis, T;

Publication
2016 EUROPEAN CONTROL CONFERENCE (ECC)

Abstract
In this paper we introduce a bilinear repetitive process and present an iterative subspace algorithm for its identification. The advantage of the proposed approach is that it overcomes the "curse of dimensionality", a hurdle commonly encountered with classical bilinear subspace identification algorithms. Simulation results show that the algorithm converges quickly and provides new alternatives for modeling/identifying nonlinear repetitive processes.

2016

Voice recognition in the LabTablet electronic laboratory notebook

Authors
Ventura, S; Amorim, RC; da Silva, JR; Ribeiro, C;

Publication
C3S2E

Abstract
Research institutions are considering data repositories to manage their outputs and ensure their visibility. In many domains, purpose-built tools can help collect data and metadata as they are created. LabTablet is such a tool, designed to provide the functions of a laboratory notebook, and being able to accompany users in either experimental sessions or field trips. In these contexts, the interaction with the device can be problematic, so we experimented with a speech recognition extension for two purposes: to provide commands, such as requesting readings from the built-in sensors, and to record observations such as a dictated note in a field trip.

2016

Using VaR and CVaR Techniques to calculate the Long-term Operational Reserve

Authors
Bremermann, L; Rosa, M; Galvis, P; Nakasone, C; Carvalho, L; Santos, F;

Publication
2016 INTERNATIONAL CONFERENCE ON PROBABILISTIC METHODS APPLIED TO POWER SYSTEMS (PMAPS)

Abstract
Generally, the more Renewable Energy Sources (RES) in generation mix the more complex is the problem of reliability assessment of generating systems, mainly because of the variability and uncertainty of generating capacity. These short-term concerns have been seen as a way of controlling the amount of spinning reserve, providing operators with information on operation system risks. For the medium and long-term assessment, such short-term concerns should be accounted for the system performance [1,2], assuring that investment options will result in more robust and flexible generating configurations that are consequently more secure. In order to deal with the spinning reserve needs, this work proposes the use of a risk based technique, Value-at-Risk and Conditional Value at-Risk, to assist the planners of the Electric Power Systems (EPS) as regards the design of the flexibility of generating systems. This methodology was applied in the IEEE-RTS-96 HW producing adequate results.

2016

An online learning approach to eliminate Bus Bunching in real-time

Authors
Moreira Matias, L; Cats, O; Gama, J; Mendes Moreira, J; de Sousa, JF;

Publication
APPLIED SOFT COMPUTING

Abstract
Recent advances in telecommunications created new opportunities for monitoring public transport operations in real-time. This paper presents an automatic control framework to mitigate the Bus Bunching phenomenon in real-time. The framework depicts a powerful combination of distinct Machine Learning principles and methods to extract valuable information from raw location-based data. State-of-the-art tools and methodologies such as Regression Analysis, Probabilistic Reasoning and Perceptron's learning with Stochastic Gradient Descent constitute building blocks of this predictive methodology. The prediction's output is then used to select and deploy a corrective action to automatically prevent Bus Bunching. The performance of the proposed method is evaluated using data collected from 18 bus routes in Porto, Portugal over a period of one year. Simulation results demonstrate that the proposed method can potentially reduce bunching by 68% and decrease average passenger waiting times by 4.5%, without prolonging in-vehicle times. The proposed system could be embedded in a decision support system to improve control room operations. (C) 2016 Published by Elsevier B.V.

2016

Volatility Leveraging in Heart Rate: health vs disease

Authors
Rocha, AP; Leite, A; Silva, ME;

Publication
2016 COMPUTING IN CARDIOLOGY CONFERENCE (CINC), VOL 43

Abstract
Heart Rate Variability (HRV) data exhibit long memory and time-varying conditional variance (volatility). These characteristics are well captured using Fractionally Integrated AutoRegressive Moving Average (ARFIMA) models with Generalised AutoRegressive Conditional Heteroscedastic (GARCH) errors, which are an extension of the AR models usual in the analysis of HRV. GARCH models assume that volatility depends only on the magnitude of the shocks and not on their sign, meaning that positive and negative shocks have a symmetric effect on volatility. However, HRV recordings indicate further dependence of volatility on the lagged shocks. This work considers Exponential GARCH (EGARCH) models which assume that positive and negative shocks have an asymmetric effect (leverage effect) on the volatility, thus better copping with complex characteristics of HRV. ARFIMA-EGARCH models, combined with adaptive segmentation, are applied to 24 h HRV recordings of 30 subjects from the Noltisalis database: 10 healthy, 10 patients suffering from congestive heart failure and 10 heart transplanted patients. Overall, the results for the leverage parameter indicate that volatility responds asymmetrically to values of HRV under and over the mean. Moreover, decreased leverage parameter values for sick subjects, suggest that these models allow to discriminate between the different groups.

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