基于WPD和CSP的四类运动想象脑电信号分类方法

针对多通道四类运动想象脑电信号分类问题,引入小波包分解(WPD)与共空间模式(CSP)融合的脑电信号特征提取方法.首先利用小波包对训练集的多路脑电信号进行分解,然后用共空间模式算法对不同分解层子带的脑电信号进行特征提取,最后设计了基于支持向量机(SVM)的分类方法.应用提出的方法对四类运动想象脑电信号进行了特征提取和分类,分类正确率达到71.5%;相对于单纯的CSP特征提取,正确率提高了5.8%,说明了该特征提取及分类方法对该数据集的有效性.     

基于共空间模式和神经元网络的脑-机接口信号的识别

提出了一种基于共空间模式和LVQ神经元网络对不同意识的脑电信号进行分类的方法.脑电信号是通过电极在头皮表面采集的脑-机接口的控制信号,提取脑电信号特征并对其进行分类,组成不依赖于正常的由外围神经和肌肉组成的输出通路的通讯系统.首先利用小波包分解对原始脑电信号进行预处理,对分解后特定小波包子带的脑电信号进行共空间模式分解,提取最优的特征;然后利用LVQ网络对不同意识任务特征进行分类,实验结果表明,该方法取得了92.7%的平均分类识别率,已经达到脑-机接口实际应用的标准.     

脑电信号的非线性动力学分析

基于脑电信号的非线性特征,利用LILEY脑电信号动力学模型计算了相关维数和李亚普诺夫指数.计算结果表明,当改变兴奋性神经元集群的兴奋性输入参数时,该EEG模型具有极限环、倍周期分岔、混沌等复杂的动力学行为,得出混沌存在于EEG模型中的结论.     

“模拟阅读”脑-机接口信号的核Fisher分类

采用"模拟阅读"视觉诱发事件相关脑电位的实验模式进行了脑-机接口实验,记录受试者在靶标和非靶标刺激下的脑电信号并进行了模式分类.首先对原始的脑电信号进行预处理、提取最优特征,然后利用核Fisher准则对采集到的脑电信号进行分类.为了验证这种方法的有效性,同时还对信号进行了感知准则和Fisher准则的分类.对5名受试者测试的结果表明:核Fisher准则分类器的正确率分别为92.98%,88.85%,76.32%,78.33%和95.52%,分别高出Fisher准则、感知准则约20%、10%,表明核Fisher准则对含有非线性可分的脑电信号的分类效果比单纯的线性方法更为优越.     

基于近似熵和样本熵的思维脑电信号分析对比

采用近似熵和样本熵,分别对三种不同思维任务产生的脑电信号进行特征提取,并将其特征进行比较分析,结果显示不同思维作业脑电信号的样本熵的变化幅度明显大于近似熵;近似熵和样本熵作为非线性动力学的统计方法为思维作业脑电信号特征提取提供了一种新的途径.     

基于局部均值分解和迭代随机森林的脑电分类

为实现癫痫患者的脑电信号有效识别,进而提高患者的生活质量,针对脑电信号的非平稳、非线性特点, 提出一种基于局部均值分解和迭代随机森林相结合的脑电信号分类方法。首先利用局部均值分解将脑电信号 分解成若干个乘积函数分量和一个残余分量,然后对所有分量进行特征提取,并使用支持向量机、随机森林和 迭代随机森林方法进行分类。实验结果表明,迭代随机森林的分类准确率高于支持向量机和随机森林方法。 此方法为准确识别癫痫脑电信号提供了一个可行有效的途径,具有较好的推广和应用价值。     

EEG信号数学模型与广义非线性动力学方程

从脑电信号与非线性动力学各种物理量之间的对应关系人手,在Van der Pol方程基础上推导了表达脑电信号的广义非线性动力学方程组系统,讨论了该系统的特性和3种求解方法,指出混沌系统内部存在吸引子突然消失(边界激变)或膨胀(内部激变)现象.     

单次运动想象脑电的特征提取和分类

为了实现脑-计算机接口(BCI)系统,对运动想象脑电信号的特征进行了提取和分类.将大脑C3,C4处采集的二路运动想象脑电信号分成4段,分别建立六阶AR参数模型进行功率谱估计,再对每段数据的功率谱求和构造特征矢量,提供给误差反向传播算法进行左右手运动想象脑电模式分类.结果表明,该方法提取的特征向量较好地反应了运动想象脑电信号的事件相关去同步(ERD)和事件相关同步(ERS)的变化时程.另外,该方法识别率高,复杂性低,适合在线脑-计算机接口的应用.     

基于共空间模式和K近邻分类器的脑-机接口信号分类方法

脑-机接口是指在人脑和计算机之间建立的直接的交流和控制通道,它以脑电信号的形式反映人的意识,并转换成控制信号.针对两类运动想象脑电信号的分类问题,提出共空间模式和小波包分解相结合的脑电信号特征提取方法.利用不同小波包对训练集的多路脑电信号进行分解,再用共空间模式算法对不同分解层子带的脑电信号进行特征提取,并采用K近邻分类器对提取到的不同特征进行分类,得到最优小波包函数和小波包子带参数.将结果应用于测试集数据的分类.仿真实验结果表明,选择db4小波包函数和4层小波包分解层,对8个特征点进行分类,可以得到高达96%的正确率.     

基于支持向量机的脑电信号分类方法研究

针对传统支持向量机分类方法在脑电信号处理中存在分类正确率低的问题,将聚类思想与二叉树支持向量机(SVM)结合,构造多类SVM分类器。实验以"BCI Competition 2005"中的Dataset IIIa为例,先对C3/C4导采集的四类运动想象脑电信号应用小波变换进行去噪。再在分析小波包频带划分特点的基础上,利用小波包进行分解与重构,获取相应的能量特征。最后应用改进后的SVM分类方法对特征信号进行分类。结果表明该方法分类正确率,可以达到91.12%;并且有效地减少了分类器的个数,最终达到较好的识别效果。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the