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Publicações

2016

Distinguishing Two Probability Ensembles with One Sample from each Ensemble

Autores
Antunes, L; Buhrman, H; Matos, A; Souto, A; Teixeira, A;

Publicação
THEORY OF COMPUTING SYSTEMS

Abstract
We introduced a new method for distinguishing two probability ensembles called one from each method, in which the distinguisher receives as input two samples, one from each ensemble. We compare this new method with multi-sample from the same method already exiting in the literature and prove that there are ensembles distinguishable by the new method, but indistinguishable by the multi-sample from the same method. To evaluate the power of the proposed method we also show that if non-uniform distinguishers (probabilistic circuits) are used, the one from each method is not more powerful than the classical one, in the sense that does not distinguish more probability ensembles. Moreover we obtain that there are classes of ensembles, such that any two members of the class are easily distinguishable (a definition introduced in this paper) using one sample from each ensemble; there are pairs of ensembles in the same class that are indistinguishable by multi-sample from the same method.

2016

Price forecasting and validation in the Spanish electricity market using forecasts as input data

Autores
Ortiz, M; Ukar, O; Azevedo, F; Mugica, A;

Publicação
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS

Abstract
The electricity sector has been subjected to major changes in the last few years. Previously, there existed a regulated system where electric companies could know beforehand the amount of energy each generator would produce, hence basing their largely operational strategy on cost minimization in order to increase their profits. In Spain, from 1988 till 1997, electricity prices were established by the 'Marco Legal Estable' Stable Legal Framework, where the Ministry of Industry and Energy acknowledged the existence of certain generation costs related to each type of technology. It was an industrial sector with no actual competition and therefore, with very few controllable risks. In the aftermath of the electricity market liberalization competition and uncertainty arose. Electricity spot prices became highly volatile due to the specific characteristics of electricity as a commodity. Long-term contracts allowed for hedge funds to act against price fluctuation in the electricity market. As a consequence, developing an accurate electricity price forecasting model is an extremely difficult task for electricity market agents. This work aims to propose a methodology to improve the limitations of those methodologies just using historical data to forecast electricity prices. In this manner, and in order to gain access to more recent data, instead of using natural gas prices and electricity load historical data, a regression model to forecast the evolution of natural gas prices, and a model based on artificial neural networks (ANN) to forecast electricity loads, are proposed. The results of these models are used as input for an electricity price forecast model. Finally, and to demonstrate the effectiveness of the proposed methodology, several study cases applied to the Spanish market, using real price data, are presented.

2016

Human-Computer Interaction Based on Facial Expression Recognition: A Case Study in Degenerative Neuromuscular Disease

Autores
Matos, A; Filipe, V; Couto, P;

Publicação
Proceedings of the 7th International Conference on Software Development and Technologies for Enhancing Accessibility and Fighting Info-exclusion, DSAI 2016, Vila Real, Portugal, December 1-3, 2016

Abstract
Physical disability can, in certain cases, be a barrier for traditional human-computer interaction based on keyboard and mouse devices. Alternative ways of interaction based on computer vision may be successfully adapted in particular cases of disability. This paper purposes a vision-based assistive technology to help a child with a degenerative neuromuscular disease to interact with the computer through facial expression recognition. The proposed algorithm was evaluated in images extracted from videos of the child and the preliminary results indicate that computer-interaction via facial expression recognition can break down barriers for people with reduced mobility regarding their relation with computers. © 2016 ACM.

2016

Combining Boosted Trees with Metafeature Engineering for Predictive Maintenance

Autores
Cerqueira, V; Pinto, F; Sa, C; Soares, C;

Publicação
ADVANCES IN INTELLIGENT DATA ANALYSIS XV

Abstract
We describe a data mining workflow for predictive maintenance of the Air Pressure System in heavy trucks. Our approach is composed by four steps: (i) a filter that excludes a subset of features and examples based on the number of missing values (ii) a metafeatures engineering procedure used to create a meta-level features set with the goal of increasing the information on the original data; (iii) a biased sampling method to deal with the class imbalance problem; and (iv) boosted trees to learn the target concept. Results show that the metafeatures engineering and the biased sampling method are critical for improving the performance of the classifier.

2016

Effect of Plug-in Electric Vehicles Traffic Behavior on Multi-Energy Demand's Dependency

Autores
Neyestani, N; Damavandi, MY; Mendes, TDP; Catalao, JPS; Chicco, G;

Publicação
2016 IEEE INTERNATIONAL ENERGY CONFERENCE (ENERGYCON)

Abstract
In this paper, a multi energy system (MES) model incorporating the traffic behavior of plug-in electric vehicles (PEVs) is proposed. It is assumed that in a micro MES two charging options are available for the PEVs: the home charging (HC) stations and the PEV parking lot (PL). The operation of these elements within the micro MES concept is studied. The matrix model of the micro MES is adapted to enable the integration of PL and HC. Moreover, the traffic flow of the PEVs is added to the model as an input to the micro MES. The model is tested for various case studies and possible traffic behavior between the PL and HC. The results show that the presence of these two elements leads to effective integration of reduced system operation costs.

2016

Mismatch in the Classification of Linear Subspaces: Sufficient Conditions for Reliable Classification

Autores
Sokolic, J; Renna, F; Calderbank, R; Rodrigues, MRD;

Publicação
IEEE Transactions on Signal Processing

Abstract
This paper considers the classification of linear subspaces with mismatched classifiers. In particular, we assume a model where one observes signals in the presence of isotropic Gaussian noise and the distribution of the signals conditioned on a given class is Gaussian with a zero mean and a low-rank covariance matrix. We also assume that the classifier knows only a mismatched version of the parameters of input distribution in lieu of the true parameters. By constructing an asymptotic low-noise expansion of an upper bound to the error probability of such a mismatched classifier, we provide sufficient conditions for reliable classification in the low-noise regime that are able to sharply predict the absence of a classification error floor. Such conditions are a function of the geometry of the true signal distribution, the geometry of the mismatched signal distributions as well as the interplay between such geometries, namely, the principal angles and the overlap between the true and the mismatched signal subspaces. Numerical results demonstrate that our conditions for reliable classification can sharply predict the behavior of a mismatched classifier both with synthetic data and in a motion segmentation and a hand-written digit classification applications. © 2016 IEEE.

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