Thiago Lopes Trugillo da Silveira

Automated drowsiness detection through wavelet packet analysis of a single EEG channel

Ratio indices computed from a single EEG channel used as drowsiness indicators.Delta and gamma brain rhythms successfully used for drowsiness detection.Wavelet packet transform as the main tool to localize specific brain frequency ranges.Transition from alert to drowsy state is taken as main event of interest.Wilcoxon signed rank test analysis pointed out the contribution of proposed indices. Advances in materials engineering, electronic circuits, sensors, signal processing and classification techniques have allowed computational systems to interpret biological quantities, recognizing physiological conditions. The next scientific challenge is to turn those technologies portable, wearable or even implantable, above all, being energy efficient. A prospective application for the next generation of portable electroencephalogram (EEG) signal processing systems is hazard prevention in attention-demanding activities. EEG keeps closest connection to the preoptic area where sleep is originated. In this paper, a methodology for assessing alertness level based on a single EEG channel (Pz-Oz) is proposed, allowing the reduction of the required hardware and the computational time of the algorithms, besides being more portable than multi-channel based ones. Two new spectral power-based indices (i) γ/? and (ii) ( γ + β )/( ? + α ) are computed from EEG rhythms through the normalized Haar discrete wavelet packet transform (WPT). The Haar WPT allows precisely resolving the brain rhythms into packets whilst demanding a relatively low computational cost. The effectiveness of the proposed indices in drowsiness detection is evaluated by comparison with five indices originally proposed for multi-channel processing. Statistical Wilcoxon signed rank test is applied to evaluate the performance of the entire set of indices, evidencing the significant changes in the alert-drowsy transitions of 20 subjects of a public database. The proposed indices (ii) and (i) presented the most and second more significant p-Values (p < 0.001 and p?=?0.001), respectively.

Low-complexity 8-point DCT approximation based on angle similarity for image and video coding

The principal component analysis (PCA) is widely used for data decorrelation and dimensionality reduction. However, the use of PCA may be impractical in real-time applications, or in situations were energy and computing constraints are severe. In this context, the discrete cosine transform (DCT) becomes a low-cost alternative to data decorrelation. This paper presents a method to derive computationally efficient approximations to the DCT. The proposed method aims at the minimization of the angle between the rows of the exact DCT matrix and the rows of the approximated transformation matrix. The resulting transformations matrices are orthogonal and have extremely low arithmetic complexity. Considering popular performance measures, one of the proposed transformation matrices outperforms the best competitors in both matrix error and coding capabilities. Practical applications in image and video coding demonstrate the relevance of the proposed transformation. In fact, we show that the proposed approximate DCT can outperform the exact DCT for image encoding under certain compression ratios. The proposed transform and its direct competitors are also physically realized as digital prototype circuits using FPGA technology.

NUMERICAL SIMULATION ANDCONSTRUCTAL DESIGN APPLIED TO THE STUDY OF ELASTIC BUCKLING IN THIN STEEL PLATES WITH OBLONG PERFORATIONS

ABSTRACT Buckling is an instability phenomenon that can happen when a slender plate is subjected to axial compression loads. In addition, perforated plates are often necessary in the engineering field. Throughout this article, the Constructal Design Method, which is based on the Constructal Theory, has been used to evaluate the influence of the hole on thin steel plates under elastic buckling. For that, the different types of holes analyzed were both transversal and longitudinal oblong. They were all placed in the center of the plate. The geometry of the hole varied according to the degree of freedom H 0 /L 0 , which relates the dimensions of each type of different hole. The size of the perforation are varied by means the hole volume fraction (f) parameter, that represents the relation between the volume of the hole and the total volume of the plate (without hole). The main goal is to achieve the greatest critical load for the perforated plates. To do so, the ANSYS software, based on the Finite Element Method (FEM), has been used to numerically analyze the elastic buckling in each case. It has been observed the importance of the geometry when seeking superior performances: through a simple fluctuation of the geometry of the hole, once the volume fraction was kept constant, it was possible to achieve a significant increase on the critical loads. Key words: Buckling; Computational Modeling; Critical Load; Constructal Design.

Classificação de estágios de sono através da aplicação de DWT sobre um único canal de EEG

Este trabalho apresenta uma nova metodologia de apoio a decisao para a classificacao de estagios de sono. No metodo proposto, uma transformada wavelet discreta (DWT) e aplicada a um unico canal de eletroencefalograma (EEG) e sao extraidas, dos coeficientes da DWT, caracteristicas estatisticas de ritmos cerebrais relacionados ao sono que, posteriormente, alimentam um classificador. Diversos algoritmos para classificacao, incluindo florestas aleatorias, sao avaliados em um conjunto de mais de 100.000 instâncias disponiveis em uma base de dados publica. Obtem-se acuracias superiores a 90% e coeficientes kappa maiores que 0.8 para as classificacoes de 2 a 6 estados de estagios de sono. O resultados obtidos sao comparaveis aos de trabalhos no estado da arte.

Experimental evaluation of intersection control policies: A simulation based on ubiquitous computing and VANETs

The growing need for urban mobility implies new challenges for traffic management. Since vehicular networks (VANETs) will be available in future, new solutions can be applied to intersection control, offering more agility to transportation networks. While VANETs are not still widely deployed, this work explores the application of different intersection control policies on urban roads using ubiquitous simulation as support. Implementation of different policies to intersection control were made. Experimental evaluation shown that the deployment of VANETs and the use of other policies - other than those based on signal-timing plans - offer benefits to traffic management.

Improving Public Transport Management: A Simulation Based on the Context of Software Multi-agents

The Simulation is a key element in efficient management and operation of public transport. This activity includes processing of dynamic data possibly obtained through sensors, as well dealing with static information including map digitalization. A fundamental problem is that, although available, systems that perform these activities are proprietary solutions, have high cost of acquisition, are difficult to be used by non-experts, or offer a limited number of features, without considering important aspects such as changes in travel demand and traffic flow. To address this problem, this paper presents a friendly simulation for public transport systems implemented with support of open technologies. Dynamism to modeling bus and travelers behavior is offered by a MAS (multi-agent system). Our simulation was experimentally evaluated using as scenario a medium-sized city with different travel demand and traffic flow.