高维数据空间索引方法的研究

讨论了高维数据空间索引的基本结构、建树算法,重点对几种有代表性的索引方法,如R-Tree,X-Tree,M-tree,VP-tree在重叠、插入原则、分裂原则、再插入等方面进行了比较研究。该文中主要介绍了一些索引结构的特点和一些具有代表性的索引结构。     

RR_tree:多维索引的关系模式实现新方法

为了有效地管理多媒体信息、地理信息及空间数据,提出了多种针对多维数据的索引方法。其中一些索引方法已经在现有的商用数据库系统(DBMS)得以实现,然而学术研究及实际应用中需要更多种的多维乃至高维数据索引方法的支持。有研究提出在关系数据库上利用存储结构、存储过程、触发器来模拟并实现X_tree的多维数据索引功能。在此基础上加以改进,重新设计了模式结构,增加了关键的索引,引入了聚簇存储,以关系模式实现多维索引的创建、插入、查询等操作;并且与现有的商用数据库系统的多维索引Oracle Spatial进行了插入、查询的性能比较。实验结果充分证明这种以关系模式实现多维索引方法的可行性与可用性。     

基于小世界模型的高维索引更新维护算法研究

基于小世界模型的高维索引技术能有效地处理高维数据的检索问题,但对适合该索引结构的插入和删除算法没有进行深入研究,影响了其应用范围。在深入分析该索引结构理论模型的基础上,提出了能够维护索引结构小世界特性的迭代式插入和删除算法。通过将插入算法建模成一种网络增长模型,应用平均场理论分析其度分布,通过实验测得聚集系数及平均路径长度,理论分析和实验结果表明插入和删除算法在完成更新时可以保证索引结构仍然符合小世界特性,扩展了该索引技术的应用范围。     

RAKDB—Tree——一种基于近似区域的多维数据索引结构

多维数据的处理已经成为影响很多领域发展的关键因素,特别是多维数据的相似性查询已经被用在很多领域中。当数据维度很大的时候,大多数索引结构处理的性能下降,这现象被称为“维度灾难”。针对多维度灾难,RAKDB-Tree是本文提出的一种高效处理多维数据的索引结构。该索引结构首先把数据空间划分为子空间,然后使用改进的KDB—Tree对子空间建立索引。RAKDB—Tree的查询、插入、删除等算法使得,索引结构一直保持较优状态。实验结果表明,RAKDB．Tree能够很好解决因为数据维度增加而带来的各种问题。     

CKDB-Tree:一种有效的高维动态索引结构

在高维数据空间中提出了一种新的索引结构:CKDB-Tree(Compact KDB-Tree),该索引结构采用一种新的分裂策略,在进行分裂时,引入插入安全点和删除安全点的概念,不仅考虑到将来的数据,而且对已经进行索引的数据也进行考虑;给出了CK-DB-Tree的定义以及节点结构的特点,针对CKDB-Tree,给出了相应的插入、查找、删除操作的算法;对该索引结构的存储性能进行定量分析和推理;最后经实验证明,CKDB-Tree是高维空间中一种有效的动态索引结构。     

NTFS索引目录B-树结构解析及其应用

针对一些有关NTFS文件系统的书籍和杂志中认为NTFS文件系统对索引目录的管理是采用B+树结构,通过对NTFS文件系统元文件$MFT文件夹记录的90H属性、A0H属性和B0H属性以及索引结点结构的分析,以实验的方式对索引文件进行查找、删除和插入运算来观察NTFS索引目录结构变化. 实验结果表明：NTFS文件系统对索引目录的管理是采用B-树结构,但并非是一棵标准的B-树.     

数据库算法系列讲座（二）

上个月的算法讲座里,我们认识了B—tree。今天,我们一起来学习给B—tree插入键值来进行索引管理。     

多维向量动态索引结构研究

多维向量的索引技术是多媒体数据库系统中的关键技术之一.集中研究基于向量空间模型的动态索引结构,以解决在图像数据库系统中按内容快速检索图像的对象问题.在分析研究R-Tree和R*-Tree的基础上,提出了ER-Tree动态索引结构.该索引树用超球体划分多维向量空间,以有利于计算最近邻;吸取R*-Tree树的重插技术,以增强索引树对数据集整体特征的表达能力,从而提高检索效率;通过引入插入安全点和删除安全点概念,有效地提高建树的效率.同时,给出了基于该结构的特征向量插入算法.实验结果表明,所提出的索引结构建树的     

基于内容的图像检索中多维索引技术研究

基于内容图像检索越来越受到人们的关注,而多维索引技术是基于内容图像检索的关键技术之一.全面分析多维索引的相关技术,主要包括多维索引技术的发展现状、多维数据厦多维索引结构的特点、多维索引结构的查询方式,并且着重分析常见的六种有代表性的索引结构.     

基于路网的移动对象索引机制研究

本文基于FNR-Tree的思想提出了一种新的索引算法FNR-Tree，该算法可以实现基于轨迹的查询，而这正是FNR-Tree索引结构所欠缺的，接着给出了FNR-Tree的数据结构和插入算法，查询算法，最后给出了两种索引结构的试验对比结果。     

度量空间中高维索引结构回顾

1 引言近年来,高维数据库的应用得到快速的发展,如海量的多媒体数据库、大规模的文本数据以及生物信息学中庞大的DNA数据库等,这些信息一般使用特征抽取等方法映射为高维数据,然后通过计算这些高维数据之间距离实现相似性查询。例如,对于图像数据,往往采用颜色直方图来表征一幅图像,当需要从数据集查找与给定图像相似的图像时,通过计算     

基于Rough集的成人招生系统评价指标体系的获取

主要讨论了基于粗糙集 (Rough Set,RS)理论 ,在成人招生系统的编制中系统复杂 ,变量繁多 ,评价指标的数量过细过多的情况下 ,如何不影响其代表性和决策功能 ,选出最重要的且尽可能少的评价指标 ,即在大量约简中求解最小约简 ,从而科学地形成了成人招生指标体系。     

Qualitative representation of spatial knowledge in two-dimensional space

Various relation-based systems, concerned with the qualitative representation and processing of spatial knowledge, have been developed in numerous application domains. In this article, we identify the common concepts underlying qualitative spatial knowledge representation, we compare the representational properties of the different systems, and we outline the computational tasks involved in relation-based spatial information processing. We also describesymbolic spatial indexes, relation-based structures that combine several ideas in spatial knowledge representation. A symbolic spatial index is an array that preserves only a set of spatial relations among distinct objects in an image, called the modeling space; the index array discards information, such as shape and size of objects, and irrelevant spatial relations. The construction of a symbolic spatial index from an input image can be thought of as a transformation that keeps only a set of representative points needed to define the relations of the modeling space. By keeping the relative arrangements of the representative points in symbolic spatial indexes and discarding all other points, we maintain enough information to answer queries regarding the spatial relations of the modeling space without the need to access the initial image or an object database. Symbolic spatial indexes can be used to solve problems involving route planning, composition of spatial relations, and update operations.     

指挥自动化系统综合效能评估系统设计

本文旨在研究如何建立一个具备科学性、灵活性和较强重用性的指挥自动化系统综合效能评估系统。根据指挥自动化系统的特点,研究了评估原则、指标体系和评估方法,在此基础上提出了评估系统的设计方案,给出了典型的综合效能评估方案,完成了评估系统的实现。     

数字图像处理在顶点识别中的应用研究

图像检测中对2D图像的长度，面积测量，以及工件的某些指标的计算，常常会遇到顶点识别问题,锯齿型工件的锯齿顶点坐标的测量，是数字图像顶点识别中比例典型的例子，利用数字图像处理技术检测锯齿工件顶点，对图像进行了边缘检测，二值化，顶点识别处理，在顶点识别中还需剔除异常点，以减少识别错误率，描述了数字图像处理技术用于非接触精确测量的原理，对整个顶点识别过程做了详细的探讨，给出满意的识别结果。     

A methodology for transferring principles of plant movements to elastic systems in architecture

In architecture, kinetic structures enable buildings to react specifically to internal and external stimuli through spatial adjustments. These mechanical devices come in all shapes and sizes and are traditionally conceptualized as uniform and compatible modules. Typically, these systems gain their adjustability by connecting rigid elements with highly strained hinges. Though this construction principle may be generally beneficial, for architectural applications that increasingly demand custom-made solutions, it has some major drawbacks. Adaptation to irregular geometries, for example, can only be achieved with additional mechanical complexity, which makes these devices often very expensive, prone to failure, and maintenance-intensive.Searching for a promising alternative to the still persisting paradigm of rigid-body mechanics, the authors found inspiration in flexible and elastic plant movements. In this paper, they will showcase how today’s computational modeling and simulation techniques can help to reveal motion principles in plants and to integrate the underlying mechanisms in flexible kinetic structures. By using three case studies, the authors will present key motion principles and discuss their scaling, distortion, and optimization. Finally, the acquired knowledge on bio-inspired kinetic structures will be applied to a representative application in architecture, in this case as flexible shading devices for double curved facades.     

Saint venant's principle in sandwich strip

The Saint Venant's principle is generally accepted to be valid in most problems in structural mechanics. But some earlier studies have drawn attention to the fact that routine application of Saint Venant's principle in the solution of elasticity problems of sandwich type structures is not justified in general. The aim of the investigation reported herein is to study the applicability of Saint Venant's principle to the problem of a sandwich strip quantitatively in detail. A simple finite element model, with linear strain triangles representing the core and bar elements representing the thin faces, is used for the analysis. Four different load cases are studied, and representative numerical results are presented. In all cases it is observed that significant edge disturbances do exist at relatively large distances from the load point, compared to homogeneous type of construction. Strength of Materials solutions are valid only beyond a distance of “4h” from the loaded end in the case of very soft cores, the distance being less for more rigid cores. Also very high values of face to core modulus ratio do not influence the solution significantly.     

Stress propagation in sandwich strips

The St. Venant's principle is generally accepted to be valid in most of the problems in structural mechanics. Earlier researchers have drawn attention to the fact that routine application of this principle in the analysis of sandwich type structures is not justified in general. In an earlier paper, the authors have reported results of detailed numerical experiments on sandwich strips, using a finite element model. The aim of the investigation reported herein is to study the applicability of St. Venant's principle to the problem of a sandwich strip quantitatively, using a theory of elasticity solution with a stress function approach. Infinitely long three-layered sandwich strip, subjected to two equal and opposite line loadings, is considered. Three face-to-core modulus ratios are considered and representative numerical results are presented. In all cases it is observed that significant edge disturbances do exist at relatively large distances from the load point, compared to homogeneous type of construction.The edge disturbance becomes negligible only at a distance of about ‘5h’ the load point in the case of very soft cores, the distance being less for more rigid cores.