Multifractal characteristics of 16-channel hu-man electroencephalogram (EEG) signals under eye-closed rest are analyzed for the first time. The result shows that the EEGs from the different sites on the scalp have different multifractal characteristics and the multifractal strength value a exhibits a kind of interleaving and left-right oppo-site distribution on scalp. This distribution rule is consistent with the localization of function and the lateralization theory in physiology. So Da can become an effective parameter to describe the brain potential character. And such a a stable distribution rule on sites of the scalp means a classic cerebral cortex active state.
强调了激活函数在ANN设计中的重要性,提出一种基于构造性设计及GA的网络结构及神经元激活函数类型自动优化的ANN模型(constructived and GA based activation function,简称为CGBAF),并给出其一般形式和算法.本模型用于多层前向神经网络时,其网络结构及激活函数类型可自动优化,进而可大大提高ANN的泛化能力.通过例子验证了本方法的有效性,并进行了分析.
Vibration acceleration signals are often measured from case surface of a running machine to monitor its condition. If the measured vibration signals display to have periodic impulse components with a certain frequency, there may exist a corresponding local fault in the machine, and if further extracting the periodic impulse components from the vibration signals, the severity of the local fault can be estimated and tracked. However, the signal-to-noise ratios (SNRs) of the vibration acceleration signals are often so small that the periodic impulse components are submersed in much background noises and other components, and it is difficult or inconvenient for us to detect and extract the periodic impulse components with the current common analyzing methods for vibration signals. Therefore, another technique, called singular value decomposition (SVD), is tried to be introduced to solve the problem. First, the principle of detecting and extracting the signal periodic components using singular value decomposition is summarized and discussed. Second, the infeasibility of the direct use of the existing SVD based detecting and extracting approach is pointed out. Third, the approach to construct the matrix for SVD from the signal series is improved largely, which is the key program to improve the SVD technique; Other associated improvement is also proposed. Finally, a simulating application example and a real-life application example on detecting and extracting the periodic impulse components are given, which showed that the introduced and improved SVD technique is feasible.
