Object-oriented DBMS requirements

The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management.     

Windows NT账户管理的二次开发

论述了Window2000账户管理的缺陷以及如何解决这些缺陷。     

基于目录服务的跨平台账户管理

讨论了多重帐户问题在计算机网络管理中诸多弊端。提出以目录服务（Novell NDS）为基础，实现跨平台（NetWare、WindowsNT和Solaris）的帐刻统一管理的方案及详细实施实例。     

电子邮件目录收割攻击的防御

为了更好地解决垃圾邮件的问题,提高对垃圾邮件的防御效果,本文从造成垃圾邮件的其中一个原因———子邮件目录收割攻击(DHA)入手,通过对DHA攻击原理的分析,提出基于黑名单同时以邮件地址阈值和IP地址阈值为锁定条件的防御策略,并在攻击资源有限的条件下对防御策略进行模拟测试。分析结果表明该防御策略能对DHA进行有效的防御,同时得出防御策略中的过滤阈值和锁定时间的设置是防御DHA的关键点。     

一种基于Hadoop的动态树增量更新方法

为适应真实环境中数据量大、流程复杂、计算密集的数据挖掘需求,提高传统树增量更新挖掘效率,改变已有算法的串行执行方式,提出一种基于Hadoop的动态树增量更新方法。介绍云计算、模型与执行流程等基本概念,针对现有Hadoop平台中任务调度的随机分配策略,设计一种动态云平台中的资源调度与分配算法,以期达到成本消耗的最小化,给出树增量更新挖掘算法以及2个并行算法（DeleteFreqTree和FindNewTree）,完成树数据的增量挖掘工作。实验结果表明,该并行算法有效可行,具有高效性与良好的扩展率,能够对海量树数据进行更新挖掘。     

基于EMFP-树的频繁模式挖掘算法

针对MFP-tree挖掘算法的不足,给出了一个频繁模式挖掘算法EMFP。算法通过将事务数据库的每条事务支持度进行裁剪以及为EMFP-树的节点添加子树个数计数器等措施来提高EMFP-树的挖掘算法的效率。实验结果表明,EMFP-树的挖掘算法是一个高效的频繁模式挖掘算法,其性能优于MFP算法。     

基于hash技术的ext3目录索引机制的改进*

针对当前广泛应用的ext3文件系统对超过一定长度的目录进行索引操作时,其性能明显下降的现象,首先对其原因进行了分析,提出一种基于hash技术的ext3目录索引问题的解决方案,并在此基础上给出了实现代码。通过几种测试平台所获得的实验数据证明了该hash技术对解决ext3性能瓶颈的有效性。     

Region-Based Hierarchical Image Matching

This paper presents an approach to region-based hierarchical image matching, where, given two images, the goal is to identify the largest part in image 1 and its match in image 2 having the maximum similarity measure defined in terms of geometric and photometric properties of regions (e.g., area, boundary shape, and color), as well as region topology (e.g., recursive embedding of regions). To this end, each image is represented by a tree of recursively embedded regions, obtained by a multiscale segmentation algorithm. This allows us to pose image matching as the tree matching problem. To overcome imaging noise, one-to-one, many-to-one, and many-to-many node correspondences are allowed. The trees are first augmented with new nodes generated by merging adjacent sibling nodes, which produces directed acyclic graphs (DAGs). Then, transitive closures of the DAGs are constructed, and the tree matching problem reformulated as finding a bijection between the two transitive closures on DAGs, while preserving the connectivity and ancestor-descendant relationships of the original trees. The proposed approach is validated on real images showing similar objects, captured under different types of noise, including differences in lighting conditions, scales, or viewpoints, amidst limited occlusion and clutter.     

OpenLDAP性能测试分析与优化

OpenLDAP是开源的LDAP服务器,在分布式目录服务中得到了广泛应用.详细分析了OpenLDAP目前所采用的独特"线程池"模式.通过比较OpenLDAP在不同模式下的性能差异,发现原模式对LDAP操作存在较大的响应延迟.进一步给出了改进的"线程池"模式,该改进模式能够降低LDAP操作响应延迟.最后通过仿真实验,表明改进模式可以明显改善OpenLDAP的性能.     

防止移动Agent通信失效的方法

通信机制是移动代理系统研究的关键技术之一,但是由于Agent具有移动性,使得Agent在通信过程中会引起通信失效问题.在比较了几种防止通信失效的方法后,结合集中式控制和本地通信,提出了一种新的防止移动Agent通信失效的方法,在有效控制通信开销的同时,保证了消息传递的可靠性.