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.     

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.     

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。     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.