Alberto Yoshihiro Nakano

O consumo global de combustíveis fósseis é um fator que contribui para a geração de gases de efeito estufa e eventos climáticos extremos, como secas, inundações, incêndios florestais e ondas de calor em todo o mundo. Embora o mundo ainda precise do petróleo como fonte de energia, é importante olhar para o futuro e tentar reduzir seu consumo. Uma maneira é priorizar a produção de energia elétrica através de fontes limpas e renováveis, visto que há uma tendência de usá-la para atividades cotidianas, desde o preparo de alimentos até o transporte veicular. Exemplos dessas fontes são eólica, hidráulica e solar, mas este estudo se concentra naquelas que dependem de máquinas rotativas, baseadas em ímãs permanentes, cuja construção e aspectos dinâmicos podem influenciar no seu desempenho. Assim, este artigo investiga os efeitos relacionados à inclinação de ímãs permanentes de neodímio alojados no rotor de um microgerador trifásico, sem escovas e de fluxo radial. A análise dos dados coletados durante os ensaios realizados no microgerador demonstram a influência direta da inclinação relativa desses ímãs na distorção harmônica total no sinal de tensão trifásica de saída do dispositivo, o que tem como consequência o impacto direto em um dos parâmetros de análise da qualidade de energia elétrica propostos pela ANEEL.

A small Brazilian speech corpus was created for educational purposes to study a state-of-the-art speaker recognition system. The system uses the Gaussian Mixture Model (GMM) as a statistical model for speakers and employs the Mel-frequency cepstral coefficients (MFCC) as acoustic features. The results using clean and noisy speech are compatible with the expected results, showing that the bigger the mismatch between training and test conditions, the worse the results. The results also improve with the increase in the utterance length. Finally, the obtained results can be used as baselines to compare with other speaker statistical models created with different acoustic features in different acoustic conditions.

An acoustic emitter based on electrical–mechanical transduction is designed to have a projected emission pattern. However, due to constructive features, design flaws, and different material qualities, the final device does not match project specifications which may cause, among other things, the reduction of performance, loss of emission power, and undesirable noise. In this work, an apparatus for acoustic characterization comprising a turntable and an arc is developed to estimate the emission power of acoustic emitters. The time-stretched pulse method is used as a test signal to obtain the emission power for each emitter's azimuth and elevation angles. Processing the acquired signals gives an estimated radiation pattern in the three-dimensional space, which visually allows the analysis of the emission characteristics of the acoustic source.

Due to the clinkerization process during the Portland cement production, large amounts of CO2 are emitted, increasing the effects related to climate change (approximately 5-10% of global CO2 emissions come from cement production), consequently, the seek for alternatives to mitigate these high emissions are necessary. The use of supplementary cementitious materials (SCM) to partial replace of Portand clinker/cement has been the subject of different research, including the use of LC3 cements (Limestone Calcined Clay Cements), where up to 50% of Portland clinker can be replaced, however, cement industry has already used othersupplementary cementitious materials with pozzolanic activities in commercial cements. In this sense, this work evaluates the performance of concretes containing LC3 mixtures with the presence of different SCM (silica fume, fly ash, sugarcane bagasse ash and açaí stone ash) regarding durability issues by carbonation. The results showed that all concretes with LC3 presented higher carbonation fronts in relation to the reference concrete, with Portland cement, due to the lower availability of calcium to react with the CO2 that penetrates into the concrete pores, so the adoption of curing procedures and coatings are recommended.