Experiments with a fast string searching algorithm

Consider the problem of finding the first occurrence of a particular pattern in a (long) string of characters. Boyer and Moore (1977) found a fast algorithm for doing this. Here we consider how this algorithm behaves when executed on a multiprocessor. It is shown that a simple implementation performs very well. This claim is based on experiments performed on the Multi-Maren multiprocessor by the present authors (1982).     

A comparison of three string matching algorithms

Three string matching algorithms—straightforward, Knuth-Morris-Pratt and Boyer-Moor—re examined and their time complexities discussed. A comparison of their actual average behaviour is made, based on empirical data presented. It is shown that the Boyel-Moore algorithm is extremely efficient in most cases and that, contrary to the impression one might get from the analytical results, the Knuth-Morris-Pratt algorithm is not significantly better on the average than the straightforward algorithm.     

大跨度张弦梁结构若干问题的探讨

张弦梁结构是近年来大跨空间结构领域兴起的一种新的结构类型,并在我国大型工程中有所应用,但对该种结构设计和施工过程的理论研究并不完善,文中对大跨度张弦梁结构设计和施工中的若干问题进行较深入的探讨,以促进其合理应用。     

A control matching model predictive control approach to string stable vehicle platooning

A predictive control strategy for vehicle platoons is presented in this paper, accommodating both string stability and constraints (e.g., physical and safety) satisfaction. In the proposed design procedure, the two objectives are achieved by matching a model predictive controller (MPC), enforcing constraints satisfaction, with a linear controller designed to guarantee string stability. The proposed approach neatly combines the straightforward design of a string stable controller in the frequency domain, where a considerable number of approaches have been proposed in literature, with the capability of an MPC-based controller enforcing state and input constraints.A controller obtained with the proposed design procedure is validated both in simulations and in the field test, showing how string stability and constraints satisfaction can be simultaneously achieved with a single controller. The operating region that the MPC controller is string stable is characterized by the interior of feasible set of the MPC controller.     

浅谈江汉油区井下管柱防腐技术

矿化度、二氧化碳、硫化氢、溶解氧等是造成井管柱腐蚀的主要因素。经过两年的现场实验,形成了以油井井筒连续投加缓蚀荆技术、井下管柱阴极防护技术、井下油管防磨蚀技术等为主的配套防护工艺。综合数据统计显示,油井腐蚀速度由（0.091-0．4147）mm／a降低到（0．0006-0．0026）mm／a,腐蚀油井免修期平均延长197天,年减少腐蚀作业井次28井次,年节约成本775万元,取得了显著的经济效益。     

一种轮腿式悬垂绝缘子检测机器人机构分析

在输电线路维护中,采用绝缘子检测机器人带电检测输电线路不良绝缘子的应用越来越广泛。基于轮腿式移动机构,针对500kV超高压交流输电线路悬垂绝缘子串的线路环境和绝缘子带电检测作业任务要求,提出了一种悬垂绝缘子检测机器人机构,介绍了其运动原理并确定了机构的尺度参数。运动学分析指出了机器人在运动过程中存在速度冲击的问题,分析了产生速度冲击的原因,并通过合理的运动规划消除了速度冲击。仿真结果表明,运动规划后的机器人冲击减小,运动平稳。     

Acquisition of 2D Shape Models from Scenes with Overlapping Objects using String Matching

In this paper we describe a system that is able to acquire models of 2D shapes from cluttered scenes. The input of the system is a sequence of images, each of which shows an unknown number of overlapping unknown 2D objects. The system identifies matching partial shapes across different images and combines them into complete 2D shape models, thus giving a complete interpretation of the input scenes. The identification of partial shapes is based on string matching, whereas a graph search procedure is used for shape model generation. The system has been fully implemented and tested on images containing parts of a jigsaw puzzle. Received: 20 November 1998?Received in revised form: 24 December 1998?Accepted: 4 January 1999     

Constructing a Tree from Homeomorphic Subtrees, with Applications to Computational Evolutionary Biology

This paper discusses how to count and generate strings that are ``distinct' in two senses: p -distinct and b -distinct. Two strings x on alphabet A and x' on alphabet A' are said to be p -distinct iff they represent distinct ``patterns'; that is, iff there exists no one—one mapping from A to A' that transforms x into x' . Thus aab and baa are p -distinct while aab and ddc are p -equivalent. On the other hand, x and x' are said to be b -distinct iff they give rise to distinct border (failure function) arrays: thus aab with border array 010 is b -distinct from aba with border array 001 . The number of p -distinct (resp. b -distinct) strings of length n formed using exactly k different letters is the [k,n] entry in an infinite p' (resp. b' ) array. Column sums p[n] and b[n] in these arrays give the number of distinct strings of length n . We present algorithms to compute, in constant time per string, all p -distinct (resp. b -distinct) strings of length n formed using exactly k letters, and we also show how to compute all elements p'[k,n] and b'[k,n] . These ideas and results have application to the efficient generation of appropriate test data sets for many string algorithms. Received December 21, 1995; revised April 28, 1997.     

钻柱应力波频谱分析技术的应用

钻柱应力波频谱分析技术是一个崭新的技术领域。该文针对石油钻井中在线识别钻头工况和地层岩性的客观需要,叙述了钻柱应力波的成因、其各频段的特征、应力波各频段信息的分离技术、以及频谱技术在石油工程中的应用。着重阐述了频谱高频段岩性信息的分离技术,提供了一个能量归一化公式,对井深、井径和钻进措施等干扰因素进行了分析和排除,并给出了用人工神经网络识别岩性的初步方法。     

基于“弓弦箭”模型的产业竞争力提升策略研究：以广州市为例

在新一轮产业革命的背景下,如何加快产业转型升级,提升产业竞争力是当前亟待解决的问题. 以广州市为例,基于“弓弦箭”模型,围绕广州产业发展的新理念和新定位,为区域竞争力水平提供全面科学的评价模型,并得出以下结论：（1）传统的“弓弦箭”模型,在弓、弦、箭,即硬要素、软要素以及主要抓手的基础上,标靶与靶心、弓弦箭的协同以及运动员的专业素养也是不可缺少的三大要素,即发展定位、产业协同发展、管理部门的治理水平;（2）为促进广州新时期产业发展,需要构建以文化为基础,生态协同和创新引领的“内力驱动机制”;（3）广州区域竞争力的发展需要借助互联网和国际产能优势,以新型研发机构和颠覆性技术为突破口,创建特色城镇,促进产业整合.