Time-frequency analysis of EEG signals evoked by voluntary,stimulated and imaginary motions

In order to investigate the characteristics of sensorimotor cortex during motor execution(ME), voluntary, stimulated and imaginary finger flexions were performed by ten volunteer subjects. Electroencephalogram(EEG) data were recorded according to the modified 10-20 International EEG System. The patterns were compared by the analysis of the motion-evoked EEG signals focusing on the contralateral(C3) and ipsilateral(C4) channels for hemispheric differences. The EEG energy distributions at alpha(8—13 Hz), beta(14—30 Hz) and gamma(30—50 Hz) bands were computed by wavelet transform(WT) and compared by the analysis of variance(ANOVA). The timefrequency(TF) analysis indicated that there existed a contralateral dominance of alpha post-movement event-related synchronization(ERS) pattern during the voluntary task, and that the energy of alpha band increased in the ipsilateral area during the stimulated(median nerve of wrist) task. Besides, the contralateral alpha and beta event-related desynchronization(ERD) patterns were observed in both stimulated and imaginary tasks. Another significant difference was found in the mean power values of gamma band(p0.01)between the imaginary and other tasks. The results show that significant hemispheric differences such as alpha and beta band EEG energy distributions and TF changing phenomena(ERS/ERD) were found between C3 and C4 areas during all of the three patterns. The largest energy distribution was always at the alpha band for each task.     

双基地SAR成像系统时频同步设计与试验

双基地SAR成像具有常规单基地SAR成像难以实现的一些优点。常规单基地SAR成像收发一体,很容易实现SAR成像孔径合成时间内收发信号相位相参的基本要求,但该要求却是双基地SAR成像的难点。时频同步是双基地SAR成像的关键技术,文章简述了时频同步的常用方法,提出了采用GPS＋高精度原子钟的时频同步设计方法,通过同步试验静态测试、微波暗室测试和动态同步试验的验证,表明该同步设计方法能够满足双基地SAR成像的需求。     

论余华先锋小说中的时间意识

余华的先锋小说集中体现着他的时间意识,他用错乱的时序构造人性的真实,以时间作为叙述节奏推动情节发展,同时也用时空交错的方式提升文本的叙事魅力等。余华用自己独特的时间意识实现了对传统时间观念的颠覆,进行了前所未有的小说形式的革新与试验,使先锋小说攀登到了一个新的高峰。     

基于数字相关法的多通道DAC同步算法

针对多通道MUXDAC系统的同步问题,采用数字相关法进行反馈时钟鉴相,提出一种适于FPGA的低采样率反馈算法.对算法原理、实现方法及影响算法精度的各参数进行了分析.该算法在雷达双通道信号发生器系统中得以应用,证明了其正确性.算法简单易行,提高了系统可靠性.     

离散混沌系统的参量驱动同步

介绍利用驱动参量法实现混沌同步的过程，用该法成功实现了离散混沌系统Logistic映象与Henon映象的同步。     

Hénon混沌系统的自适应预测控制与同步

提出了一种Hénon混沌系统的自适应预测控制与同步快速算法。该方法以不确定非线性差分方程为预测模型,预测模型的参数采用递推最小二乘法在线辨识得到。该控制算法占用内存小,计算速度快,具有较强的跟踪给定信号和抑制系统参数摄动和随机噪声的能力。仿真结果验证了该方法的有效性。     

一个新自治系统的混沌同步

研究了一个新的自治系统的混沌同步问题,设计了一个非线性控制器,实现了该系统的自同步,借助Lyapunov稳定性定理,从理论上证明保证了混沌同步的稳定性,Matlab数值仿真结果证明了该方法的有效性.     

Synchronization criteria based on a general complex dynamical network model

Many complex dynamical networks display synchronization phenomena. We introduce a general complex dynamical network model. The model is equivalent to a simple vector model of adopting the Kronecker product. Some synchronization criteria, including time-variant networks and time-varying networks, are deduced based on Lyapunov＇s stability theory, and they are proven on the condition of obtaining a certain synchronous solution of an isolated cell. In particular, the inner-coupling matrix directly determines the synchronization of the time-invariant network; while for a time-varying periodic dynamical network, the asymptotic stability of a synchronous solution is determined by a constant matrix which is related to the fundamental solution matrices of the linearization system. Finally, illustrative examples are given to validate the results.     

虚拟参考咨询系统中FAQ功能的改进——以北京师范大学图书馆虚拟参考咨询系统为例

本文以北京师范大学图书馆虚拟参考咨询系统为例分析了FAQ功能模块存在的两个问题,并提出了改进措施与实现方案。     

一种新的基于数字语音教室的音频与文本同步方法

音频与文本同步是设计开发数字语音教室的一个关键问题。通过对多媒体同步方法的研究，结合基于嵌入式技术的数字语音教室的实际情况，提出了一种新的应用于数字语音教室的音频与文本同步的方法。