基于K-Means和Apriori算法的多层特征提取方法

根据科技文献的结构特点,论文提出了一种四层挖掘模式,并结合K-means算法和Apriori算法,构建一个新的特征词提取方法——MultiLM-FE方法.该方法首先依据科技文献的结构将其分为4个层次,然后通过K-means聚类对前3层逐层实现特征词提取,最后再使用Aprori算法找出4层的最大频繁项集,并作为4层的特征词集合.该方法能够解决K-means算法不能自动确定最佳聚类初始点的问题,减少了聚类过程中信息损耗,这使得该方法能够在文献语料库中更加准确地找到特征词,较之以前的方法有很大提升,尤其是在科技文献方面更为适用.实验结果表明,该方法是可行有效的.     

基于空间分布优选初始聚类中心的改进K-均值聚类算法

针对海量数据聚类过程中,经典的K-均值聚类算法对其K个初始聚类中心点的选择以及数据集噪声十分敏感的问题,提出了一种针对海量数据考虑初始聚类中心点选择的聚类算法.该算法首先采用冒泡排序法对数据集进行排序,获取数据集的各维中心值组成第一个初始聚类中心点.其次,通过计算与第一个初始聚类中心点的欧式距离,对剩余候选初始聚类中心点进行优化选择,保证所有的聚类中心点均匀地分布在数据集密度较大的空间上,以此减少聚类过程中的迭代次数和提高聚类算法效率.最后,基于UCI(University of California,Irvine)中多个数据集,进行聚类算法对比实验.结果表明,在不降低聚类效果的前提下,该聚类算法的迭代次数平均降低到50％,所需的时间降低平均达10％,由实验结果还能推出,当点集的数目越多时,该算法就能表现出越明显的聚类优势效果.     

基于密度的改进聚类算法比较

针对传统K-means算法的聚类结果依赖初始聚类中心的缺陷,提出了一种基于密度的改进K-means聚类算法,该算法选择位于数据集样本密集区且相距较远的数据对象作为初始聚类中心,实现K-means聚类。针对PAM算法时间复杂度高,且不利于大数据集处理的缺陷,提出了一种基于密度的改进K-medoids聚类算法,在选取初始中心点时根据数据集样本的分布特征选取,使得初始中心点位于不同类簇。UCI机器学习数据库数据集和随机生成的带有噪音点的人工模拟数据集的实验测试证明,基于密度的改进K-means算法和基于密度的改进Kmedoids算法都具有很好的聚类效果,运行时间短,收敛速度快,有抗噪性能。     

最大判别特征选择算法在文本分类的优化研究

采用朴素贝叶斯分类器进行文本分类时,特征选择方法的好坏直接影响到分类器的性能.本文提出一种最大判别(MD)特征选择算法,由训练得到N个类的概率分布后,通过对样本进行测试并得到其特征向量d中每个特征词区分类别的能力,并构造出了一个新的特征向量ε用于分类,使得从中选取的部分特征词具有最大的类别区分能力.仿真结果表明,与cMFD,CSFS和CMFS三种特征选择算法相比,MD特征选择算法能在选取较少特征词情况下,获得更高的分类精度.     

基于方差优化谱聚类的热点区域挖掘算法

为改善交通拥堵的情况,本文利用聚类分析方法对移动轨迹数据进行挖掘,识别居民出行的热点区域。传统的Ng-Jordan-Weiss （NJW）谱聚类算法常使用K-means聚类算法来实现最后的聚类操作,然而K-means聚类算法存在对初始值敏感、容易陷入局部最优的缺陷,影响对热点区域的挖掘结果。因此,本研究将方差优化初始中心的K-medoids聚类算法运用到谱聚类算法最后聚类阶段,提出基于方差优化谱聚类的热点区域挖掘算法（Hot Region Mining algorithm based on improved K-medoids Spectral Clustering,HRM-KSC）,然后在真实的轨迹数据集上进行试验。试验结果发现,HRM-KSC算法聚类结果的轮廓系数更高,表明HRM-KSC算法改善了NJW谱聚类算法,提高了聚类质量。     

基于文本最小相似度的中心选取方法

基于划分的聚类算法是一种局部最优算法.聚类初始中心的选择对该聚类算法的收敛速度和聚类的性能都有很大的影响.初始中心点应该选择来自不同的类并且初始中心点文本之间的相似度应尽量小,为此提出了一种新的基于最小相似度的中心选取方法,该方法选择相似度最小的两个样本分别作为初始的两个中心,然后依次选择到已知中心相似度最小的样本作为其他类的中心.实验表明该方法能够选出来自不同类的样本作为聚类的初始中心,同其他初始中心选择方法比较,聚类算法的性能有明显提高.     

基于局部与全局信息的自动文摘算法

采用平均特征词频率策略计算特征词权重,用快速n-grims算法对各特征词所处的概念体进行加权,用一种改进的K-means聚类算法进行段落聚类,提出一种基于局部与全局信息的自动文摘算法并给出算法评估.该算法不仅能够自适应获得k值,而且有效防止了初始点的随机选择对聚类结果的影响.评测结果表明该算法对经济类和科技类文章的准确率和召回率都明显高于新闻类和文学类文章,利用机器文摘进行分类的准确率明显高于使用原文本进行分类.该算法所得到的文摘,在各项指标上都优于传统方法生成的文摘.     

采用八方向Gabor滤波的指纹识别算法

采用指纹增强算法与复滤波器中心点定位结合的方法,有效地解决低质量指纹图像中心点定位问题,实现了平移不变.同时,采用基于结构的指纹特征提取算法,用八方向Gabor滤波提取指纹的全局特征和局部脊线特征,实现了旋转不变.在FVC2004指纹库上的仿真实验表明:该算法取得较好的识别效果,优于基于单Finger Code特征和基于点模式的指纹识别算法.     

一种改进禁忌搜索的K-medoids聚类算法

针对传统K-medoids聚类算法初始聚类中心随机选择、聚类精度不高、全局搜索能力较差以及禁忌搜索算法对初始值随机选取等问题,提出了一种粒计算与最大距离积法相结合的初始化禁忌搜索初始值算法,将改进后的禁忌搜索算法用来优化K-medoids,以提高聚类算法的性能。通过仿真试验论证了该算法具有较高的效率和准确率以及较强的稳定性。     

基于影响空间的初始中心点优化K-means聚类算法

针对K-means聚类算法依赖初始点、聚类结果受初始点的选取影响较大的缺陷,给出了一种稳定的基于影响空间的初始点优化K-means聚类算法。该算法借助了影响空间数据结构和定义的加权距离吸引因子,将特殊中心点合并为K个微簇,并对微簇中的数据点加权平均得到K个初始中心点,然后执行K-means算法;最后,理论分析和实验结果表明,该初始点优化K-means聚类算法能够有效降低噪声数据对聚类结果的影响,在聚类结果、聚类过程效率方面有较大优势。     

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.     

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…     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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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。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

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