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- Smart Sock and Resistivity Measurement in Textile MaterialsPublication . Torreblanca González, José; RAUL, GARCIA; Rozas-Izquierdo, Lidia; Silva, Luís Augusto; LEITHARDT, VALDERI
- Fault Prediction Based on Leakage Current in Contaminated Insulators Using Enhanced Time Series Forecasting ModelsPublication . Nemesio Fava Sopelsa Neto; Frizzo Stefenon, Stéfano; Meyer, Luiz Henrique; RAUL, GARCIA; LEITHARDT, VALDERITo improve the monitoring of the electrical power grid, it is necessary to evaluate the influence of contamination in relation to leakage current and its progression to a disruptive discharge. In this paper, insulators were tested in a saline chamber to simulate the increase of salt contamination on their surface. From the time series forecasting of the leakage current, it is possible to evaluate the development of the fault before a flashover occurs. In this paper, for a complete evaluation, the long short-term memory (LSTM), group method of data handling (GMDH), adaptive neuro-fuzzy inference system (ANFIS), bootstrap aggregation (bagging), sequential learning (boosting), random subspace, and stacked generalization (stacking) ensemble learning models are analyzed. From the results of the best structure of the models, the hyperparameters are evaluated and the wavelet transform is used to obtain an enhanced model. The contribution of this paper is related to the improvement of well-established models using the wavelet transform, thus obtaining hybrid models that can be used for several applications. The results showed that using the wavelet transform leads to an improvement in all the used models, especially the wavelet ANFIS model, which had a mean RMSE of 1.58 × 10−3, being the model that had the best result. Furthermore, the results for the standard deviation were 2.18 × 10−19, showing that the model is stable and robust for the application under study. Future work can be performed using other components of the distribution power grid susceptible to contamination because they are installed outdoors.
- Improving Speaker Recognition in Environmental Noise with Adaptive FilterPublication . Almeida Dos Santos, Vinícius; D. Parreira, Wemerson; Fernandes, Anita; RAUL, GARCIA; LEITHARDT, VALDERISpeaker recognition is challenging in real-world environments. Typically, studies approach noises only in an additive manner. However, real environments commonly present everberating conditions that worsen speech processing. When not considering reverberation in the system modeling, the system may not be robust when applied to real-world conditions. In this work, we use a slight different approach to simulate reverberation, considering randomized conditions of the environment. With this approach, each VoxCeleb1 test sample is corrupted by randomly generated conditions, with diversified amplitudes of noise and speech. We generate a corrupted dataset, in which the best model EER degraded from 0.93% to 30.13%. To improve this degradation, we propose using Normalized Kernel Least-Mean-Square (NKLMS) adaptive filter. Through the use of NKLMS, we were able to improve the EER from 30.13% to 1.11%. The results indicate that NKLMS has a great potential for speech enhancement to improve speaker recognition.