Browsing by Author "Freitas, Diamantino Silva"
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- Accoustical characterisation of accented syllable in portuguese; a contribution to the naturalness of speech synthesisPublication . Teixeira, João Paulo; Paulo, Elisabete R.; Freitas, Diamantino Silva; Pinto, Maria da GraçaText-to-Speech systems require control of the prosodic parameters of the produced speech waveform in order to achieve a higher naturalness and degree of perception. Amongst the several dimensions into which prosody can be unfolded, the accented syllable realisation brings the basic problem of producing a set of comprehensive rules for accurate control of the acoustic realisation of the syllable parameters, which remains to be solved. In particular, for the Portuguese language, in Europe, a set of comprehensive quantitative characterisation data and rules is absolutely lacking. The present paper is intended, as a quantitative contribution, as far as we know the first, to the solution of this problem. The duration Intensity, and variation of F0 were modelled in the tonic syllable according to its position in the word and the position of the word in the sentence.
- Acoustic characterisation of the tonic syllable in portuguesePublication . Teixeira, João Paulo; Freitas, Diamantino SilvaA particular problem for the automatic prediction of prosody in speech synthesis is the realisation of accented syllables since these are affected by many parameters and are perceptually very salient. For the Portuguese language, in Europe, a set of comprehensive quantitative characterisation data and rules is totally lacking. The present paper is intended to be a quantitative contribution to the solution of this problem. In this paper, a preliminary modelling of duration, intensity and variation of F0 in the tonic syllable will be presented. The dependencies of the model with the syllable position in the word and the word position in the phrase are also presented.
- Alzheimer electroencephalogram temporal events detection by K-meansPublication . Rodrigues, Pedro Miguel; Freitas, Diamantino Silva; Teixeira, João PauloAlzheimer Disease (AD) is a chronic progrcssive and irrevcrsible ncurodegencrative brain disorder. Ils diagnostic accuracy is rclatively low and lhere is nol a biomarkcr able lo detcct AD without invasive tcsts. This study is a ncw approach to obtuined clectroencephalogram (EEG) temporal cvenls in crder lo improve Lhe AD diagnosis. For that, K-means were used and the rcsults suggcsted that thcre are scquences af EEG cnergy variation tbat appear more frequently in AO patients lhan in Health subject.
- Alzheimer electroencephalogram temporal events detection by K-meansPublication . Rodrigues, Pedro Miguel; Freitas, Diamantino Silva; Teixeira, João PauloAlzheimer Disease (AD) is a chronic progressive and irreversible neurodegenerative brain disorder. Its diagnostic accuracy is relatively low and there is not a biomarker able to detect AD without invasive tests. This study is a new approach to obtained electroencephalogram (EEG) temporal events in order to improve the AD diagnosis. For that, K-means were used and the results suggested that there are sequences of EEG energy variation that appear more frequently in AD patients than in Health subject.
- Alzheimer’s early prediction with electroencephalogramPublication . Rodrigues, Pedro Miguel; Teixeira, João Paulo; Garrett, Carolina; Alves, Dílio; Freitas, Diamantino SilvaAlzheimer's disease (AD) is currently an incurable illness that causes dementia and patienfs condition is progressively worse and it represents one ofthe greatest public health challenges worldwide. The main objective ofthis work was to develop a classificatiwmethodology for EEG signals to improve discrimination amongst patients at varying stages ofthe illness, Mitd Cognitive Impairment (MCI) patients and non-patients either in order to obtain a more reliable methodology to identify AD in early stages.
- Alzheimer's Early Prediction with ElectroencephalogramPublication . Rodrigues, Pedro Miguel; Teixeira, João Paulo; Garrett, Carolina; Alves, Dílio; Freitas, Diamantino SilvaAlzheimer’s disease (AD) is currently an incurable illness that causes dementia and patient’s condition is progressively worse and it represents one of the greatest public health challenges worldwide. The main objective of this work was to develop a classification methodology for EEG signals to improve discrimination amongst patients at varying stages of the illness, Mild Cognitive Impairment (MCI) patients and non-patients either in order to obtain a more reliable methodology to identify AD in early stages. For this purpose, a surrogate decision tree classifier was used with 2 different ways of cross-validation (leave-one-out-crossvalidation and 10-fold-cross validation). The EEG studied features were the values of maxima (NMax) and minima (NMin), the zero-crossing (Zcr) rate, the mean derivative value at a point (Mdif), the Relative Power (RP) in each of the conventional bands and finally the spectral ratios (r). The best classification was obtained with vectors of 10 features as classifier entries in a leaveone- out-cross validation process, reaching 0.934 AUC, a sensitivity of 86.19%, a specificity of 99.35%, an accuracy of 94.88%, with a low out-of-sample classification error of 6.98% which indicates that the classifier generalizes fairly well.
- Alzheimer’s electroencephalogram event scalp and source localizationPublication . Rodrigues, Pedro Miguel; Teixeira, João Paulo; Freitas, Diamantino SilvaAlzheimer’s disease is the most common cause of dementia which causes a progressive and irreversible impairment of several cognitive functions. The aging population has been increasing significantly in recent decades and this disease affects mainly the elderly. Its diagnostic accuracy is relatively low and there is not a biomarker able to detect AD without invasive tests. Despite the progress in better understanding the disease there remains no prospect of cure at least in the near future. The electroencephalogram (EEG) test is a widely available technology in clinical settings. It may help diagnosis of brain disorders, once it can be used in patients who have cognitive impairment involving a general decrease in overall brain function or in patients with a located deficit. This study is a new approach to improve the scalp localization and the detection of brain anomalies (EEG temporal events) sources associated with AD by using the EEG.
- Alzheimer's electroencephalogram event scalp localizationPublication . Rodrigues, Pedro Miguel; Freitas, Diamantino Silva; Teixeira, João PauloAlzheimer’s disease (AD) is a neurodegenerative and incurable illness that causes intellectual functions decrease. This study is a new approach to improve the scalp brain anomalies localization associated with Electroencephalogram (EEG) energy variations of EEG threads (subsegments) sequencies sets found in AD patients by unsupervised learning techniques, called AD EEG temporal events. This study showed that AD patients have less brain dynamics than controls, because the AD EEG events propagation time over the scalp is higher and statistically different from control subjects (p < 0.0022)
- Alzheimer's electroencephalogram event scalp localizationPublication . Rodrigues, Pedro Miguel; Freitas, Diamantino Silva; Teixeira, João PauloAlzheimer’s disease (AD) is a neurodegenerative and incurable illness that causes intellectual functions decrease. This study is a new approach to improve the scalp brain anomalies localization associated with Electroencephalogram (EEG) energy variations of EEG threads (subsegments) sequencies sets found in AD patients by unsupervised learning techniques, called AD EEG temporal events. This study showed that AD patients have less brain dynamics than controls, because the AD EEG events propagation time over the scalp is higher and statistically different from control subjects (p<0.0022).
- An integrated test bench for research, study or demonstration of variable speed drives of induction motorsPublication . Teixeira, Henrique José Alves; Leite, Vicente; Batista, José; Araújo, Rui Esteves; Freitas, Diamantino SilvaThis paper presents an integrated and low cost test bench for teaching and R&D purposes in variable speed drives of induction motors. The test bench is composed by different integrated sub-systems and the resulting platform is suitable for control, parameter estimation and condition monitoring of induction machines controlled by electrical drives