基于候选项目集特性的改进Apriori算法研究

通过对Apriori和1-k-Apriori两种算法进行细致分析和深入研究,结合这两种算法的优点,提出了I1-k-Apriori算法.1-k-Apriori算法中利用Lk-1与L1相连接来得到候选项目集,但是,有些情况下,用这种方法生成的候选k项集数量过大,导致k项集的筛选代价太大.I1-k-Apriori算法根据k-1项集的特性和事务数据库中数据的特性来决定产生k项集的方法,可以有效避免由于Lk项数过多而影响运算效率.实验结果表明,I1-k-Apriori算法较大提高了运算效率.     

FP-growth算法的一种优化实现

研究工作者已经提出了许多对事务数据库中频繁模式、关联规则的挖掘算法.早期算法有Apriori算法,然而该算法利用候选项集找频繁项集,而候选项集的产生往往是非常耗时的.JianweiHan等人提出了一种改进的算法,FP-growth算法.该算法不产生候选项集,效率比Apriori算法提高了近一个数量级.在描述FP-growth算法的基础上,具体讨论了如何优化数据结构,有效的实现该算法.     

基于布尔向量运算的Apriori算法

关联规则挖掘是数据挖掘中的一个重要课题,常用的Apriori 算法要多次扫描数据库,会产生大量的候选项集.利用向量的内积运算和逻辑运算提出了一种关联规则挖掘的改进算法.研究表明,该算法运算简单,只需要扫描一次数据库,不需要产生候选项集,且具有处理大型数据库的优点.     

基于数据挖掘关联规则Apriori改进算法的入侵检测系统的研究

在众多的关联规则挖掘算法中,Apriori算法是最为经典的一个,但Apriori算法有以下缺陷：需要扫描多次数据库、生成大量候选集以及迭代求解频繁项集。因而提出了一种新方法,使Apriori算法产生的候选项集再通过数据库查找是否为频繁项集,从而提高算法的效率。最后针对入侵检测系统形成关联规则。实验结果表明,改进后的算法...     

二项集剪枝技术研究

在现有的关联规则算法的基础上,深入分析了经典算法的内涵,提出了剪枝候选二项集的改进算法,有效的控制候选二项集的生成,得到传统算法中部分候选二项集,从而减少扫描数据库的运算量.与Apriori算法相比,效率明显提高.     

事务约简和2项集支持度矩阵快速剪枝的Apriori改进算法

在Apriori算法的改进算法M-Apriori基础上,为了进一步减少不必要的数据库扫描,引入事务约简技术,提出一种改进的MR-Apriori算法.考虑到M-Apriori算法会产生大量候选项集,为了实现对候选项集快速剪枝,加入一个自定义的2项集支持度矩阵,提出第2种改进的MP-Apriori算法.将事务约简和2项集矩阵快速剪枝一起引入到 M-Apriori算法中,提出第3种改进的MRP-Apriori算法.最后,在mushroom数据集上进行实验.结果表明:加入事务约简的MR-Apriori算法和加入2项集矩阵快速剪枝的MP-Apriori算法,运行时间相比原M-Apriori算法都有较大缩减,而同时结合两种优化策略的MRP-Apriori算法运行时间最短,验证了这两种优化策略的有效性.     

基于十字链表的关联规则改进算法

目的解决在关联规则挖掘中存在大量无用的候选项集和频繁项集以及效率不高的问题。方法提出了一种基于十字链表的关联规则改进算法。结果利用用户给定的条件和剪枝算法减少了候选项集的数量,再遍历十字链表确定频繁项集,结果表明算法提高了挖掘效率。结论基于十字链表的关联规则改进算法避免了重复扫描数据库,提高了挖掘效率。     

FP-growth算法的一种改进

频繁项目集挖掘是多种数据挖掘应用研究的一个重要方面，频繁项目集的快速挖掘算法研究是当前研究的热点，传统Apriori及其改进算法，要多遍扫描数据库并产生大量的候选项目集，针对Apriori算法的缺陷，Han JW(韩家炜)提出FP-growth算法，该算法仅须扫描数据库两遍且无须生成候选项目集，避免了产生“知识的组合爆炸”，提高了频繁项目集的挖掘效率，但FP-growth算法是通过逐步生成条件模式基和条件频繁模式树来挖掘频繁项目集，因而影响了频繁项目集的挖掘效率，为此，在引入F-矩阵概念之后，提出了FP-growth的一种改进算法—IFP-growth，并对改进算法的性能进行了测试，实验结果表明，IFP-growth算法优于FP-growth。     

一种高效相联规则提取算法

在 Ａｐｒｉｏｒｉ 算法基础上, 提出改进算法 Ａｐｒｉｏｒｉ Ｐｒｏ． 利用中间结果对数据库进行过滤,从而加快候选项集的计数速度, 提高了整个算法的效率．     

一种有效的基于约束的关联规则发现算法

基于约束的关联规则挖掘是针对特定约束的规则的挖掘，挖掘的结果有着更好的针对性和实用性，Separate算法是现有的效果较好的算法，但有2点不足：未修剪生成的候选集和候选项重复生成。对此该文提出了改进的SeparateP算法，算法中加入了对候选集的修剪，并且利用了项集重复生成的信息，使候选集的修剪更加有效快捷。实验表明，改进算法显著提高了原算法的效率。     

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.     

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.     

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).     

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.