多种空间关系和时间结合的定性时空推理

空间实体之间存在多种时空关系,主要包含拓扑、方向、距离、尺寸和时间等.以往的研究工作主要集中于3种以下时空关系结合的表示和推理,而3种以上结合的研究很少.但多种时空关系之间是相互统一和相互约束的,所以,将它们全部综合起来研究是时空推理研究发展的必然趋势,也是实际应用的迫切需要.提出了采用矩形关系统一表示多种空间关系,以矩形关系变化次数表示时间的时空统一表示模型,并在此基础上,利用概念邻域图推导空间关系变化和时间变化.据此,结合矩形关系网络和路径一致性算法,提出了检验上述统一模型网络一致性的算法,并分析了算法复杂度.该研究成果提高了空间关系分析方法的准确性,减小了时间信息的冗余,对地理信息系统中空间实体间的空间关系以及时间变化的分析和查询等有一定的理论意义与应用价值.     

线对象邻接关系快速重构算法

给定向量化坐标,计算n个线对象两两邻接关系,普通算法时间复杂度为O(n*n);理论最好时间复杂度为O(C),其中C是邻接关系的基数。基于散列桶,给出了建立线对象邻接关系的快速算法,其平均时间复杂度为O(n(1+1/r)),r为算法分配的桶数量与n的比,空间复杂度为O(n)。证明了若不允许使用额外空间,则不可能使用排序算法解决该问题;给出了允许使用额外空间条件下的两遍排序算法,时间复杂度为O(n(lbn+1+2/r))。应用表明快速算法比普通算法速度提高1~3个数量级。     

快速数据包分流算法研究

基于“流”的数据包分类算法已经在第四层交换等领域中得到了应用,该类算法的特点是流表的容量大,流表的更新速度较快.“快速的数据包分流算法”采用了散列算法的基本思想,并引入了流的局部性原理来加速散列查找的过程,用软件对该算法进行了仿真测试,并在最后从时间复杂度和空间复杂度两个方面对其进行了性能分析.实验结果表明,该算法具有良好的时间复杂度和空间复杂度,可以实现快速的分流.     

一个求解次短和渐次短路径的实用算法

求解第k短路径问题在决策支持系统和咨询系统中具有广泛的用途,本文基于Dijkstra算法,给出了一个求解次短路径和渐次短路径的算法,并且分析了算法的时间复杂度和空间复杂度。     

聚类方法在公共设施选址中的应用研究

对空间数据挖掘聚类技术及其在公共设施选址方面的传统应用方法进行了综述,分析了传统应用方法中有待解决的关键问题,对空间距离代价的表示问题和传统方法的算法时间复杂度进行了初步探讨,运用模拟退火算法和图论对传统方法进行了改进,实现了算法时间复杂度的降低和聚类结果的优化。     

方位关系约束满足问题的推理求解

约束满足问题（Constraint Satisfaction Problems CSP）是人工智能的一个研究领域,诸如空间查找、规划等问题都可转化为约束满足问题。方位关系是空间关系的重要组成部分,用以确定空间对象间的一种顺序。本文研究了空间方位关系模型,给出了方位关系约束的一般表示形式。在此基础上,利用组合表推理给出了方位关系约束满足问题的一个推理求解算法,该算法的时间复杂度为O（n^2）。     

一种高效的层次聚类分析算法

层次聚类算法是一类重要的聚类分析方法。传统的层次聚类算法的时间和空间复杂度很大，这使得聚类分析在大型数据集上的应用受到限制。该文提出一种基于重叠区的3阶段改进算法，该算法将大大减少算法的时间复杂度和空间复杂度。     

确定两个任意简单多边形空间关系的算法

阐述了把简单多边形的边分为奇偶边的新思想,根据一多边形的边与另一多边形的拓朴关系,划分边为5种拓朴类型:内边、外边、重叠边、相交边、复杂边,进而给出了确定两个多边形空间关系的算法,算法的时间复杂度为O((n+m)log(n+m)),其中n、m分别是两输入多边形的顶点数。该算法建立在数学理论基础之上,没有奇异情况需要处理,易于编程实现。算法的主要思想对确定两个简单多面体空间关系亦有参考价值。     

多任务处理环境下的定时器应用算法

本文通过对定时器原理的分析,结合队列数据结构和网络协议中"时间戳"的概念,提出了一种新的、较完善的多任务处理环境下的定时器应期算法,并且给出了主要程序的流程框图.该算法具有较高的效率和可靠性,其时间复杂度及空间复杂度均为O(n).     

命题μ-演算局部模型检测高效算法设计

命题μ-演算局部模型检测算法中,目前最好的算法的时间复杂度与不动点算子交替嵌套深度d呈指数关系。针对命题μ-演算局部模型检测算法的计算过程进行分析,得到迭代计算的中间迭代值间满足的一组偏序关系,然后利用该偏序关系设计了一个局部模型检测算法,算法时间复杂度的指数部分为d/2,大大提高了算法的计算效率。     

The complexity of constraint satisfaction problems for small relation algebras

Andréka and Maddux [Notre Dame J. Formal Logic 35 (4) 1994] classified the small relation algebras—those with at most 8 elements, or in other terms, at most 3 atomic relations. They showed that there are eighteen isomorphism types of small relation algebras, all representable. For each simple, small relation algebra they computed the spectrum of the algebra, namely the set of cardinalities of square representations of that relation algebra.In this paper we analyze the computational complexity of the problem of deciding the satisfiability of a finite set of constraints built on any small relation algebra. We give a complete classification of the complexities of the general constraint satisfaction problem for small relation algebras. For three of the small relation algebras the constraint satisfaction problem is NP-complete, for the other fifteen small relation algebras the constraint satisfaction problem has cubic (or lower) complexity.We also classify the complexity of the constraint satisfaction problem over fixed finite representations of any relation algebra. If the representation has size two or less then the complexity is cubic (or lower), but if the representation is square, finite and bigger than two then the complexity is NP-complete.     

基于广义归结的定理机器证明系统

本文使用Ｃ—ＰＲＯＬＯＧ语言在ＳＵＮ工作站上设计实现了基于广义归结和基于归结的两个定理机器证明系统ＧＲＭ,ＲＭ,证明了《数学原理》中Ｐａｒｔ１：ｍａｔｈｅｍａｔｉｃａｌｌｏｇｉｃ中ＳｅｃｔｉｏｎＡ与ＳｅｃｔｉｏｎＢ中全部定理（３５０个）．讨论ＧＲＭ和ＲＭ的时、空复杂性,并在实现设计中提出新的全局调度策略及归结式的化简、排序策略,以单子句恒真、恒假的判断代替了广义归结中的自归结,实现了带ＯＣＣＵＲ检查的模式匹配．     

Divide and Conquer: EKF SLAM in $O(n)$

In this paper, we show that all processes associated with the move-sense-update cycle of extended Kalman filter (EKF) Simultaneous Localization and Mapping (SLAM) can be carried out in time linear with the number of map features. We describe Divide and Conquer SLAM, which is an EKF SLAM algorithm in which the computational complexity per step is reduced from $O(n^2)$ to $O(n)$, and the total cost of SLAM is reduced from $O(n^3)$ to $O(n^2)$. Unlike many current large-scale EKF SLAM techniques, this algorithm computes a solution without relying on approximations or simplifications (other than linearizations) to reduce computational complexity. Also, estimates and covariances are available when needed by data association without any further computation. Furthermore, as the method works most of the time in local maps, where angular errors remain small, the effect of linearization errors is limited. The resulting vehicle and map estimates are more precise than those obtained with standard EKF SLAM. The errors with respect to the true value are smaller, and the computed state covariance is consistent with the real error in the estimation. Both simulated experiments and the Victoria Park dataset are used to provide evidence of the advantages of this algorithm.      

On the futility of blind search: an algorithmic view of "no free lunch"

The paper is in three parts. First, we use simple adversary arguments to redevelop and explore some of the no-free-lunch (NFL) theorems and perhaps extend them a little. Second, we clarify the relationship of NFL theorems to algorithm theory and complexity classes such as NP. We claim that NFL is weaker in the sense that the constraints implied by the conjectures of traditional algorithm theory on what an evolutionary algorithm may be expected to accomplish are far more severe than those implied by NFL. Third, we take a brief look at how natural evolution relates to computation and optimization. We suggest that the evolution of complex systems exhibiting high degrees of orderliness is not equivalent in difficulty to optimizing hard (in the complexity sense) problems, and that the optimism in genetic algorithms (GAs) as universal optimizers is not justified by natural evolution. This is an informal tutorial paper--most of the information presented is not formally proven, and is either "common knowledge" or formally proven elsewhere. Some of the claims are intuitions based on experience with algorithms, and in a more formal setting should be classified as conjectures.     

基于水印的XML文档完整性保护算法

数字签名是一种传统的用于XML文档完整性保护的方法,为XML文档的完整性保护,提出了一种新的基于水印技术的解决方案。实验表明,相比数字签名机制,提出的算法在时间复杂度和空间复杂度有所降低。     

计算机应用课程中任务驱动式教学的“任务”设计

任务驱动式教学是指在整个教学过程中,以完成一个个具体的任务为线索,把教学内容巧妙地隐含在每个任务之中。在计算机应用课程的"任务"设计中,应使用"单刀直入法"化繁为简,既要使各任务能较好地涵盖课程知识点,又要能使学生在愉快的情景下完成学习任务。     

基于可控蠕虫的W-A-W传播模型研究

利用良性蠕虫来对抗蠕虫是一种新的蠕虫对抗技术。本文针对WAW模型中对抗蠕虫状态不可控、产生流量过大等问题提出了可控蠕虫的概念,给出了可控蠕虫的定义、分布式框 架结构和工作流程,并将可控蠕虫用作W-A-W中的对抗蠕虫,给出了可控蠕虫对抗蠕虫传播模型。经验证明,和已有良性蠕虫相比,用可控蠕虫对抗蠕虫产生流量影响更小状态更易控制,在不影响模型效果的情况下降低了模型的复杂度。     

一种基于“是一个”模式的下位概念获取方法

在文本知识获取中，上下位关系的获取是一个基本而又关键的问题。针对基于模式上下位关系获取中遇到的下位概念获取问题，本文结合我们的研究工作，给出一种从符合“是一个”模式的句子中获取下位概念的方法，这里主要利用半自动获取的词典和句型对“是一个”模式进行分析，然后根据不同的规则，分流获取下位概念。在实验分析中，此方法显示了较好的效果。     

Prioritized assertional-based removed sets revision of <Emphasis Type="Italic">DL</Emphasis>-<Emphasis Type="Italic">Lite</Emphasis> belief bases

In real world applications, information is often provided by multiple sources having different priority levels reflecting for instance their reliability. This paper investigates ”Prioritized Removed Sets Revision” (PRSR) for revising stratified DL-Lite knowledge bases when a new sure piece of information, called the input, is added. The strategy of revision is based on inconsistency minimization and consists in determining smallest subsets of assertions (prioritized removed sets) that should be dropped from the current stratified knowledge base in order to restore consistency and accept the input. We consider different forms of input: A membership assertion, a positive or a negative inclusion axiom. To characterize our revision approach, we first rephrase Hansson’s postulates for belief bases revision within a DL-Lite setting, we then give logical properties of PRSR operators. In some situations, the revision process leads to several possible revised knowledge bases where defining a selection function is required to keep results within DL-Lite fragment. The last part of the paper shows how to use the notion of hitting set in order to compute the PRSR outcome. We also study the complexity of PRSR operators, and show that, in some cases, the computational complexity of the result can be performed in polynomial time.