DSpace Coleção: Artigos Técnico-científicos na área de Engenharia ElétricaArtigos Técnico-científicos na área de Engenharia Elétricahttps://locus.ufv.br//handle/123456789/117952024-03-28T14:44:05Z2024-03-28T14:44:05ZMultivariate Objective Response Detectors (MORD): Statistical tools for multichannel eeg analysis during rhythmic stimulationFelix, Leonardo BonatoSá, Antonio Mauricio Ferreira Leite Miranda deInfantosi, Antonio Fernando CatelliYehia, Hani Camillehttps://locus.ufv.br//handle/123456789/234772019-02-11T16:18:34Z2007-03-01T00:00:00ZTítulo: Multivariate Objective Response Detectors (MORD): Statistical tools for multichannel eeg analysis during rhythmic stimulation
Autor(es): Felix, Leonardo Bonato; Sá, Antonio Mauricio Ferreira Leite Miranda de; Infantosi, Antonio Fernando Catelli; Yehia, Hani Camille
Abstract: The presence of cerebral evoked responses can be tested by using objective response detectors. They are statistical tests that provide a threshold above which responses can be assumed to have occurred. The detection power depends on the signal-to-noise ratio (SNR) of the response and the amount of data available. However, the correlation within the background noise could also affect the power of such detectors. For a fixed SNR, the detection can only be improved at the expense of using a longer stretch of signal. This can constitute a limitation, for instance, in monitored surgeries. Alternatively, multivariate objective response detection (MORD) could be used. This work applies two MORD techniques (multiple coherence and multiple component synchrony measure) to EEG data collected during intermittent photic stimulation. They were evaluated throughout Monte Carlo simulations, which also allowed verifying that correlation in the background reduces the detection rate. Considering the N EEG derivations as close as possible to the primary visual cortex, if N = 4, 6 or 8, multiple coherence leads to a statistically significant higher detection rate in comparison with multiple component synchrony measure. With the former, the best performance was obtained with six signals (O1, O2, T5, T6, P3 and P4).
Tipo: Artigo2007-03-01T00:00:00ZComparison of univariate and multivariate magnitude-squared coherences in the detection of human 40-Hz auditory steady-state evoked responsesFelix, Leonardo BonatoAntunes, FelipeCarvalho, Jean Antônio da SilvaBarroso, Márcio Falcão dos SantosSá, Antonio Mauricio Ferreira Leite Miranda dehttps://locus.ufv.br//handle/123456789/220722018-10-02T02:00:34Z2018-02-01T00:00:00ZTítulo: Comparison of univariate and multivariate magnitude-squared coherences in the detection of human 40-Hz auditory steady-state evoked responses
Autor(es): Felix, Leonardo Bonato; Antunes, Felipe; Carvalho, Jean Antônio da Silva; Barroso, Márcio Falcão dos Santos; Sá, Antonio Mauricio Ferreira Leite Miranda de
Abstract: Objective response detection (ORD) techniques for evaluating bioelectrical evoked responses in the electroencephalogram (EEG) are based on statistical criteria rather than on visual inspection. Hence, they do not depend on human evaluation, which is often a subjective approach. Furthermore, since such techniques do not involve heuristic approaches, they may be more easily implemented and used in automatic systems. The Magnitude-Squared Coherence (MSC), together with its recently developed multivariate extension (the multiple magnitude-squared coherence – MMSC), have been pointed out as one of the most efficient ORD techniques for detecting steady-state responses in the EEG. In this work, both MSC and MMSC were applied to EEG signals collected during auditory stimulation in order to allow comparison in the detection of auditory steady-state responses (ASSRs). The stimuli consisted of 40 Hz amplitude-modulated tones delivered binaurally in the intensity of 50 dB SPL (sound pressure level). The best result was obtained by using MMSC in the two-electrode set C4 and Fz. This configuration led to a 0.92-detection ratio, within 111.55 s in average to detect each response and kept the false alarm ratio under 0.05. The average improvement in performance was about 11% when compared to the MSC. These results allow concluding that the detection protocol of 40 Hz ASSRs can be improved by using MMSC in multichannel EEG analysis when compared to the traditional univariate MSC approach.
Tipo: Artigo2018-02-01T00:00:00ZPostos de trabalho e perfil de operadores de máquinas de colheita florestalMinette, Luciano JoséSouza, Amaury Paulo deSilva, Emília Pio daMedeiros, Nathália Magnahttps://locus.ufv.br//handle/123456789/205902018-07-12T02:00:36Z2008-01-01T00:00:00ZTítulo: Postos de trabalho e perfil de operadores de máquinas de colheita florestal
Autor(es): Minette, Luciano José; Souza, Amaury Paulo de; Silva, Emília Pio da; Medeiros, Nathália Magna
Abstract: Este trabalho foi desenvolvido em áreas de colheita de madeira de eucalipto em três empresas de Minas Gerais. O objetivo geral foi caracterizar os operadores de máquinas de colheita de eucalipto e realizar uma análise ergonômica de seus postos de trabalho. Os dados foram coletados mediante o uso de entrevistas, medições e testes. A população pesquisada foi constituída por operadores de máquinas florestais, e 13 máquinas utilizadas na colheita foram avaliadas. Os operadores são jovens de origem urbana, com média do tempo de trabalho na empresa de 46,7 meses, e o número de operadores treinados para a atividade florestal é relativamente pequeno. A avaliação ergonômica das máquinas evidenciou que as variáveis de acesso estavam fora dos valores indicados, destacando as piores situações no feller-buncher e no carregador florestal MJ10070. Apenas os traçadores mecânicos Poclain e Caterpillar tinham o comprimento do assento com dimensões próximas do ideal. De modo geral, os traçadores mecânicos apresentaram os melhores desempenhos ergonômicos.; This work was carried out in areas of eucalyptus harvest belonging to three companies in Minas Gerais. The general objective was to characterize machine operators of of eucalyptus harvest and to perform an ergonomic analysis of their workstations. Data were collected by using interviews, measurements and tests; the studied population consisted of
machine operators, and thirteen machines used in the harvest were evaluated. The operators are youngsters of urban origin. The average work time in the company is 46.7 months and the number of operators for the forest activity was relatively small. The ergonomic evaluation of the machines showed that the access variables did not comply with the recommended values, pointing out the worst situations with the feller-buncher and the log loader MJ10070. Just the Poclain and Caterpillar slachers had the seat length close to the ideal dimensions. In general, the slachers showed the best ergonomic performances.
Tipo: Artigo2008-01-01T00:00:00ZMultivariate evoked response detection based on the spectral F-testRocha, Paulo Fábio F.Felix, Leonardo B.Sá, Antonio Mauricio F.L. Miranda deMendes, Eduardo M.A.M.https://locus.ufv.br//handle/123456789/193712018-05-09T02:00:32Z2016-05-01T00:00:00ZTítulo: Multivariate evoked response detection based on the spectral F-test
Autor(es): Rocha, Paulo Fábio F.; Felix, Leonardo B.; Sá, Antonio Mauricio F.L. Miranda de; Mendes, Eduardo M.A.M.
Abstract: Objective response detection techniques, such as magnitude square coherence, component synchrony measure, and the spectral F-test, have been used to automate the detection of evoked responses. The performance of these detectors depends on both the signal-to-noise ratio (SNR) and the length of the electroencephalogram (EEG) signal.
Recently, multivariate detectors were developed to increase the detection rate even in the case of a low signal-to-noise ratio or of short data records originated from EEG signals. In this context, an extension to the multivariate case of the spectral F-test detector is proposed.The performance of this technique is assessed using Monte Carlo. As an example, EEG data from 12 subjects during photic stimulation is used to demonstrate the usefulness of the proposed detector.The multivariate method showed detection rates consistently higher than those ones when only one signal was used.It is shown that the response detection in EEG signals with the multivariate technique was statistically significant if two or more EEG derivations were used.
Tipo: Artigo2016-05-01T00:00:00Z