脑电信号的小波变换和样本熵特征提取方法

针对现有的采用单一的特征提取算法对运动想象脑电信号识别率不高的问题,提出一种结合小波变换和样本熵的特征提取方法.通过小波变换,把脑电信号进行3层分解,抽取出对应于脑电β节律频带的小波系数的能量均值和能量均值差,并结合脑电信号的样本熵组成特征向量,使用支持向量机分类器对左右手运动想象脑电信号进行分类.结果表明,结合小波变换和样本熵的特征提取方法明显优于仅采用小波变换、样本熵以及其他传统的特征提取方法,得到的最高正确识别率为91.43%.     

运动想象脑电信号特征提取与分类算法研究

针对运动想象脑电信号特征提取困难,分类正确率低的问题,提出了利用小波熵进行特征提取并采用支持向量机（SVM）来分类的算法。计算运动想象脑电信号的功率,通过理论分析选择小波包尺度,对信号功率进行小波包分解并计算其小波包熵（WPE）,提取C3、C4导联的小波包熵插值组成特征向量,将特征向量作为分类器的输入送入支持向量机进行分类。采用国际BCI竞赛2003中的Graz数据进行验证,算法的最高分类正确率达97.56%。算法特征向量维数低、数据量小、分类正确率高,对运动想象脑电信号特征提取及分类的任务可以提供参考方法。     

基于改进EMD的运动想象脑电信号识别算法研究

针对现有的单一特征提取算法对运动想象脑电信号识别率不高的问题,提出一种以相关系数改进的经验模态分解(EMD)的特征提取算法。对已有的BCI竞赛数据中C3、C4两个通道脑电数据进行预处理,之后通过EMD对脑电信号进行分解,得到IMF分量。通过计算原始信号与各阶IMF分量之间的相关系数,选择具有较大相关系数的IMF作为特征,由这些IMF分量的能量特征和平均幅值差来组成脑电信号的特征。使用支撑矢量机分类器(SVM)对左右手运动想象脑电信号进行分类。实验结果表明,基于相关系数改进的EMD脑电信号的处理方法明显优于只用EMD的脑电处理方法,得到的最高正确识别率为88.57%。从而证明了该方法的有效性。     

基于样本熵和模式识别的脑电信号识别算法研究

脑-机接口BCI是一种实现人脑和外部设备通信的新兴技术。基于时频特性进行特征提取的传统方法无法体现EEG信号的非线性特征。为了进一步提高分类的准确率,首先采用小波阈值降噪的预处理方法提高了EEG信号的信噪比。然后结合非线性动力学的样本熵参数,对3种想象运动的脑电信号进行特征提取,保留了脑电信号的非线性特征。其中,运动想象MI脑电信号的研究一直都是BCI这一高速发展领域的重点目标。还研究了支持向量机、LVQ神经网络和BP神经网络3种分类器。通过实验结果对比发现,BP神经网络具有较高的识别率,更适用于脑电信号的分类识别。     

基于模糊化符号复杂度的脑电运动想象识别算法

提出一种基于模糊化符号复杂度的运动想象脑电信号特征提取与识别方法。在脑电信号的复杂度细粒化多符号度量中引入模糊算法,用sigmoid函数模糊化处理,逻辑判断得到模糊化符号复杂度。取细粒化指数n为2,提取模糊化符号复杂度作为特征值,最后利用支持向量机对脑电运动想象任务进行分类识别。实验结果表明,以模糊化符号复杂度为特征的分类方法,对左右手运动想象脑电信号的分类识别率最高达88.67%,优于二值化Lempel-Ziv复杂度算法。     

基于局部均值分解与样本熵的脑电信号特征提取与分类

针对运动想象脑电信号的识别问题,提出一种改进的脑电信号特征提取与分类方法。利用局部均值分解算法将原始信号分解为一系列乘积函数(PF)分量,根据μ节律和β节律范围内的脑电信号剔除无意义的PF分量。通过特征时间选择原则,选取4 s~6 s运动想象脑电信号作为分类数据,分别计算C_3,C_4导联信号二阶和三阶PF分量样本熵的和,并将其均值MSampEn(C_3,C_4)作为输入元素构造脑电特征向量,利用支持向量机进行分类预测以识别左右手想象运动。实验结果表明,与经验模态分解以及总体经验模态分解方法相比,该特征提取方法具有更高的分类准确率。     

基于脑机接口的控制器

为实现大脑与设备的通讯,研究基于脑机接口的控制器．本文研究脑电信号（EEG）的特征提取,实验通过E．Prime心理学软件结合Neuroscan公司生产的64导脑电采集设备获取脑电原始信号,利用小波算法对原始脑电信号进行分析,提取感兴趣的频段小波系数作为特征;分析脑电信号的功率谱,基于Fisher准则设计分类器．本文在研究脑机接口（Brine．ComputerInterface,BCI）的基础上通过想象实现了对运动的控制．以轮椅为实际控制对象,仅仅通过两个电极采集脑电信号,设计制作了控制器,理论验证实验成功的通过想象控制轮椅的四个方向的运动．本文最后还探讨了脑机接口的应用前景．     

基于运动想象的脑电小车控制系统设计

为了实时采集并判断和分类人脑运动感知信息,文中基于人脑运动想象脑电信号设计了一套以共空间模式特征提取算法和支持向量机分类算法为核心的采集与判别系统,能够实时采集并分类人脑自发脑电信号,将不同运动想象的结果作为指令表达在智能小车的运动状态上,从而实现脑电实时直接控制小车实物。在此设计中完成了对系统整体的调试并对脑电等相关数据进行采集处理。分析结果表明,该系统稳定,分类准确率高,符合预期的设计要求。     

基于运动想象的脑电信号特征提取研究

基于运动想象脑电信号的脑-机接口系统在医疗领域具有广阔的应用前景,被应用于运动障碍人士的辅助控制以及脑卒的预后康复。由于运动想象的脑电信号信噪比低、不平稳以及差异性显著,对脑电信号识别带来负面影响。一个有效的特征提取算法能够提高脑-机系统的脑电信号识别率。提出一种多通道的脑电信号特征提取方法,将数据矩阵分解为基矩阵与系数矩阵的乘积,以类间离散度做为性能判据对系数矩阵进行特征提取,提取可分性更高、维数更少的特征。结合脑电信号识别领域常见的分类器在2008年BCI竞赛数据集上进行验证,证明所提方法是有效的。     

基于多尺度Lempel-Ziv复杂度的运动想象脑电信号特征分析

运动想象脑电信号特征提取是脑机接口研究领域的重要问题,提出一种基于多尺度Lempel-Ziv复杂度的运动想象脑电信号特征提取算法.该算法是传统二值化Lempel-Ziv复杂度算法的改进,它将脑电信号分成多个不同幅值范围的区域,根据信号在各区域间的上升和下降趋势,对脑电信号进行二值化处理得到Lempel-Ziv复杂度.本...     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

基于AD9626的模拟信号采集存储卡设计

自然界的绝大部分信号都是以模拟的形式存在,因此模拟信号的采集转换存储在数字时代十分关键。文章讨论了在雷达信号处理领域基于AD9626的AD采集存储卡的设计原理、硬件结构和程序设计与芯片配置等问题,为今后相关领域的研究提供了可参考的方案。