Optimal algorithms for the single and multiple vertex updating problems of a minimum spanning tree

The vertex updating problem for a minimum spanning tree (MST) is defined as follows: Given a graphG=(V, E _G) and an MSTT forG, find a new MST forG to which a new vertexz has been added along with weighted edges that connectz with the vertices ofG. We present a set of rules that produce simple optimal parallel algorithms that run inO(lgn) time usingn/lgn EREW PRAM processors, wheren=¦V¦. These algorithms employ any valid tree-contraction schedule that can be produced within the stated resource bounds. These rules can also be used to derive simple linear-time sequential algorithms for the same problem. The previously best-known parallel result was a rather complicated algorithm that usedn processors in the more powerful CREW PRAM model. Furthermore, we show how our solution can be used to solve the multiple vertex updating problem: Update a given MST whenk new vertices are introduced simultaneously. This problem is solved inO(lgk·lgn) parallel time using (k·n)/(lgk·lgn) EREW PRAM processors. This is optimal for graphs having (kn) edges.Part of this work was done while P. Metaxas was with the Department of Mathematics and Computer Science, Dartmouth College.     

Web数据库中抽象数据模型及查询语言的研究

WWW实际上是一个巨大的异构分布式数据库系统。为了支持高级的、健壮的和可靠的应用,在WWW上应当加强其数据库的功能。文中引进了新的机制和概念以便将数据库的功能移植到WWW上,并对涉及到的WWW查询处理和数据稳定性的概念进行了探讨。     

不停电作业的低压电源车并机并网系统设计

针对当前低压电源车无法完成不停电并机并网作业问题,分析了不停电作业的低压电源车并机并网工作要求和功能需求;详细介绍了低压电源车并机并网系统硬件构成,设计了并机并网控制系统。经过运行测试,结果表明低压电源车在并网过程电压、电流、频率偏差在允许范围内;其切换过程不影响负荷正常运行,实现了不停机作业的功能。     

三维虚拟火电厂空间数据引擎设计与应用

为了提高火电厂数据存储与管理的效率,考虑到火电厂数据信息复杂、多样和密集度大的特点,以及现有空间数据引擎存在通用性和可移植性的问题,该文针对性设计了一种面向火电厂的空间数据引擎,以此来管理火电厂的数据信息.首先建立了三维虚拟火电厂结构体系和空间数据引擎的架构,然后重点剖析了空间数据模型、空间存储、空间索引、空间查询等空间数据引擎的关键技术,在此基础之上,通过实例验证了所设计的空间数据引擎的可行性和有效性.     

一种工矿企业变电所备用电源自投装置的设计

针对工矿企业变电所,提出了采用可编程控制器实现备用电源自投装置的新技术,在实际应用中具有控制方式灵活、编程简便、抗干扰性强等诸多优点。出口电路中采用微型大功率继电器与特定的程序相结合,解决了烧毁继电器结点的难题,大幅度地降低了设备的运行、维护成本,提高了工矿企业变电所的安全和经济效益。