Computing Only Minimal Answers in Disjunctive Deductive Databases

A method is presented for computing minimal answers of the form in disjunctive deductive databases under the disjunctive stable model semantics. Such answers are constructed by repeatedly extending partial answers. Our method is complete (in that every minimal answer can be computed) and does not admit redundancy (in the sense that every partial answer generated can be extended to a minimal answer), thus no non-minimal answer is generated. The method does not (necessarily) require the computation of models of the database in their entirety. A partitioning of the database into extensional and intensional components is employed in order to overcome the problems caused by the possible non-existence of disjunctive stable models, and a form of compilation is presented as a means of simplifying and improving the efficiency of the run-time computation, which then reduces to relatively trivial processing within the extensional database. In addition, the output from this compilation process has the significant advantage of being immune to updates to the extensional database. Other forms of database pre-processing are also considered, and three transformations are presented mapping a database onto an equivalent positive database, non-disjunctive database, and set of conditional facts.     

Finding a minimal cover for binary images: An optimal parallel algorithm

Given a black-and-white image, represented by an array of n × n binary-valued pixels, we wish to cover the black pixels with aminimal set of (possibly overlapping) maximal squares. It was recently shown that obtaining aminimum square cover for a polygonal binary image with holes is NP-hard. We derive an optimal parallel algorithm for theminimal square cover problem, which for any desired computation timeT in [logn,n] runs on an EREW-PRAM with (n/T) processors. The cornerstone of our algorithm is a novel data structure, the cover graph, which compactly represents the covering relationships between the maximal squares of the image. The size of the cover graph is linear in the number of pixels. This algorithm has applications to problems in VLSI mask generation, incremental update of raster displays, and image compression.The research reported here forms part of the author's doctoral dissertion, submitted to Cornell University in May 1989. This work was partially supported by NSF Grant DC1-86-02256, IBM Agreement 12060043, and ONR Contract N00014-83-K-0640. A preliminary version of this paper was presented at the 26th Annual Allerton Conference on Communications, Control, and Computing, Monticello, IL, September 28–30, 1988.     

现浇单向板肋梁楼盖结构实荷试验

通过某工程实例,介绍了用水加载的方式对某框架结构现浇单向板肋梁楼盖进行结构实荷试验的全过程．     

Surjections and coverings

This paper determines the necessary and sufficient condition under which a collection of sequence covers on a finite set can be induced by a surjection. The relationship of sequence covers and surjections to generalized decomposition of an automaton allowing feedback, is the same as the relationship of partitions and bijections to series-parallel decompositions. The condition determined is a natural, but complex generalization of the known condition for the series-parallel case.     

基于C++Builder的不规则图形动画的实现

结合原图及掩图的处理,介绍了在C Builder中如何利用双缓冲技术,实现不规则图形的逼真动画技术的原理及方法,并给出了程序的部分源代码.     

新型旋转式分盖装置的设计与分析

目的介绍一种封口机上的新型旋转式分盖装置。方法首先通过对分盖动作的介绍,详尽分析该装置的结构组成及工作原理。然后对刀盘进行设计,确定其关键参数。最后对装置进行运动仿真,验证其是否满足设计要求。结果经过仿真分析,上下刀盘边缘切刀切入点在分盖过程中始终相距约10°,与刀盘边缘切刀外形设计相符,能够成功地实现分盖功能。结论该装置稳定性好、结构简单,经实际使用证明达到了设计要求。     

四面体有限单元覆盖的三维数值流形方法

构造三维流形单元的覆盖函数和总体位移函数,基于最小势能原理建立四面体有限单元覆盖的三维数值流形方法分析格式,详细推导了三维流形单元的刚度矩阵、初应力矩阵、荷载矩阵、惯性矩阵、位移约束矩阵和接触矩阵,并给出了相应的公式和算例。