Manual classification of sleep stage is a time-consuming but necessary step in the diagnosis and treatment of sleep disorders, and its automation has been an area of active study. The previous works have shown that low dimensional fast Fourier transform (FFT) features and many machine learning algorithms have been applied. In this paper, we demonstrate utilization of features extracted from EEG signals via FFT to improve the performance of automated sleep stage classification through machine learning methods. Unlike previous works using FFT, we incorporated thousands of FFT features in order to classify the sleep stages into 2–6 classes. Using the expanded version of Sleep-EDF dataset with 61 recordings, our method outperformed other state-of-the art methods. This result indicates that high dimensional FFT features in combination with a simple feature selection is effective for the improvement of automated sleep stage classification.

Purple-fleshed sweet potato with high anthocyanins is beneficial to health due to its antioxidant activity. Therefore, 13 promising genotypes of purple-fleshed sweet potato and two improved varieties as checks (Antin 2 and Antin 3) were studied their physical, chemical and sensorial characteristics. The results showed that the flesh colors ranged from red-purple, deep purple to white purplish and their lightness values (L*) negatively correlated with anthocyanin contents (R 2 = 0.65). Six promising genotypes contained anthocyanins >100 mg/100 fw with the highest value observed in RIS 10051-01 (155.47 mg/100 g fw) that was similar to Antin 2. Antin 3 showed the highest content of anthocyanins among all genotypes (177.48 g/100 g fw). MSU 10002-05 and MSU 10010-43 genotypes had higher dry matter contents (33.43% and 37.85%) than Antin 2 and Antin 3, suggesting their promising use for flour processing. High anthocyanins is normally associated with a bitter taste, however the steamed tubers of two deep purple genotypes, namely MSU 10010-43 and Antin 3 and one white purplish genotype (MSU 1000115) were fairly liked for their color, texture and taste attributes, hence they are tailored for steamed food purposes. This information supports the breeder to release a new variety of purple- fleshed sweet potatoes.

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