软件配置管理的多级实现

本文介绍了软件配置管理的相关内容,并提出了一种软件配置管理的多级实现方法,该方法在实际应用中取得了良好的效果。     

Extension of the method of auxiliary mapping for three‐dimensional elliptic boundary value problems

In this paper, we extend the method of auxiliary mapping (MAM), introduced by Babuška and Oh, to three dimensions so that the extended MAM (3‐D MAM) can effectively handle three‐dimensional elliptic problems containing the singularities caused by the non‐smooth domains. There are three type of singularities caused by non‐smoothness of domains in R ³: the vertex, the edge, and the vertex–edge combined singularities. To deal with the singularities of these types, we present three auxiliary mappings and formulas for the transformed bilinear forms and the transformed linear functionals by these auxiliary mappings. Then we present 3‐D MAM and constructions of the blending‐type elemental mappings for elements containing singularities. Numerical experiments that show the effectiveness of 3‐D MAM are provided. Copyright © 2001 John Wiley & Sons, Ltd.     

An Installable Version Control File System for Unix

We present a file system named VCFS, a Version Control File System that provides transparent version control of files. VCFS is implemented as an installable file system in the Unix operating system. The facility is transparent to users in the sense that VCFS automatically stores changes between incremental versions of a file without user intervention. Access to the latest version of the file retains traditional Unix semantics, enabling all existing Unix applications to be run modified under VCFS if so desired. VCFS provides system call enhancements and supports application level utilities for version number retrieval, displaying changes between two versions of a file, upgrading to a new release number, and related version control functions. Performance measurements show that VCFS provides a significant increase in version control operations compared to application level change management systems such as SCCS, and that the space utilization is significantly better than of the existing version control systems. The primitives and facilities provided by VCFS can be exploited for use in a wide range of applications, ranging from immutable files, transaction processing and file replication support in a distributed file system, to the development of enhanced change management control systems for software project management. © 1997 John Wiley & Sons, Ltd.     

Efficient Specialization of Relational Concepts

An algorithm is presented for a common induction problem, the specialization of overty general concepts. A concept is too general when it matches a negative example. The particular case addressed here assumes that concepts are represented as conjunctions of positive literals, that specialization is performed by conjoining literals to the overly general concept, and that the resulting specializations are to be as general as possible. Although the problem is NP-hard, there exists an algorithm, based on manipulation of bit vectors, that has provided good performance in practice.     

Learning Conjunctive Concepts in Structural Domains

We study the problem of learning conjunctive concepts from examples on structural domains like the blocks world. This class of concepts is formally defined, and it is shown that even for samples in which each example (positive or negative) is a two-object scene, it is NP-complete to determine if there is any concept in this class that is consistent with the sample. We demonstrate how this result affects the feasibility of Mitchell's version of space approach and how it shows that it is unlikely that this class of concepts is polynomially learnable from random examples alone in the PAC framework of Valiant. On the other hand, we show that for any fixed bound on the number of objects per scene, this class is polynomially learnable if, in addition to providing random examples, we allow the learning algorithm to make subset queries. In establishing this result, we calculate the capacity of the hypothesis space of conjunctive concepts in a structural domain and use a general theorem of Vapnik and Chervonenkis. This latter result can also be used to estimate a sample size sufficient for heuristic learning techniques that do not use queries.     

新版百元币防伪特征与光学鉴别

本文从纸张、油墨、印刷等方面介绍了新版百元币的票面特征、设计特点,并运用配光、显微照相、特种照相等检验手段分析了该币的防伪特征,为鉴别真伪提供了科学依据。     

MIPv6与FMIPv6切换性能分析与优化

随着移动通信的迅速发展,越来越多的移动设备提出了接入互联网的需求。移动IPv6的切换性能是保证移动互联网服务质量的重要因素之一。该文描述了MIPv6及FMIPv6的切换流程,分析了MIPv6及FMIPv6的切换性能及其切换过程中存在的问题,提出和归纳了一些优化思想和改进方法。     

An Enthusiastic Sceptic

Nat Oppenheimer , principal of structural engineers Robert Silman Associates, is a dissenting voice among the advocates of building information modelling (BIM) - an enthusiastic sceptic. Could the quest for integration be leading towards oversimplification rather than customisation and differentiation? Even towards the sort of standardisation adopted with LEED ratings in the quest for sustainability? Copyright © 2009 John Wiley & Sons, Ltd.     

浅谈VRVII型空调在设计中的具体应用

结合VRVII型空调的特点,论述了此种空调形式在工程设计中的选型要点,并对各种VRVII型空调的新风处理方式进行了详细的分析,对不同类型的建筑提出了相应的解决办法．     

一种适合无线环境的IPv6头部压缩方法

头部压缩可以提高链路传输效率,但现有压缩方法基于差分编码方式,压缩效率易受丢包影响,在误码率高的无线链路上反而会降低传输效率。为此,提出一种新的IPv6头部压缩方法SBHC。主要思想是利用IPv6头部变化少的特点,采用基于替换的方式实现压缩行为,克服了差分编码方式存在的弊端。性能测试结果表明,SBHC压缩方法可以有效提高无线链路的传输效率。