基于可编程逻辑阵列的RS232至RS422的串行口扩展电路

介绍了利用可编程逻辑阵列把1路RS232扩展至4路RS422的串行口电路设计方法。该扩展电路不占用PC系统资源，同时具有结构简单，使用方便，通用性和可补性强等特点，可广泛应用于主从式多机通讯系统中。     

近年西方国家通信网发展动态

首先说明西方国家通信网近年发展变迁情况，然后对IP与WDM的结合使用、光数据网的发展、密集波分多路的应用和光网中通路的保护4个主要方面作了具体说明。     

GPRS业务模型和无线网络的研究

根据GPRS业务及业务发展情况，对GPRS业务模型进行深入研究，并对GPRS无线网络进行了更深入的探讨。     

Markov analysis of qualitative dynamics1

Common sense sometimes predicts events to be likely or unlikely rather than merely possible. We extend methods of qualitative reasoning to predict the relative likelihoods of possible qualitative behaviors by viewing the dynamics of a system as a Markov chain over its transition graph. This involves adding qualitative or quantitative estimates of transition probabilities to each of the transitions and applying the standard theory of Markov chains to distinguish persistent states from transient states and to calculate recurrence times, settling times, and probabilities for ending up in each state. Much of the analysis depends solely on qualitative estimates of transition probabilities, which follow directly from theoretical considerations and which lead to qualitative predictions about entire classes of systems. Quantitative estimates for specific systems are derived empirically and lead to qualitative and quantitative conclusions, most of which are insensitive to small perturbations in the estimated transition probabilities. The algorithms are straightforward and efficient.     

Extracting Modes of Constrained Structure with Elastic Supports from Free Test Data

The dynamic flexibility (DF) and improved dynamic flexibility (IDF) methods can be applied to extract constrained structural modes from free-free modal test data. The residual flexibility method is also good for boundaries of constrained structure with rigid supports. Under elastic support boundary conditions both the DF and residual flexibility methods cannot produce accurate results. This paper expands the previously published IDF method to become a more general approach for structural design engineers. A new method called the general dynamic flexibility (GDF) method has been developed in this paper to extract constrained structural modes from free test data. The GDF method can always be applied as follows: (1) when the boundary support stiffness is very stiff, the GDF method can accurately obtain results from rigid support as by Liu et al. in 2001 and Zhang and Wei in 2003; (2) when the support stiffness is soft, the present method can produce results similar to those free-free modal parameters measured by hanging structures using rubber band; (3) when the support stiffness is zero, the method can reproduce true free-free modal parameters; and (4) when the support stiffness has any finite values, the GDF method can also achieve satisfactory results for engineering use. The algorithm included in the GDF method converges rapidly and is numerically stable in the analysis. This feature is very practical for many engineering applications for using the GDF method.     

Real-Time Three-Dimensional Occupancy Grid Modeling for the Detection and Tracking of Construction Resources

Awareness of the construction environment can be improved by automatic three-dimensional (3D) sensing and modeling of job sites in real time. Commercially available 3D modeling approaches based on range scanning techniques are capable of modeling static objects only, and thus cannot model dynamic objects in real time in an environment comprised of moving humans, equipment, and materials. Emerging prototype video range cameras offer an alternative by facilitating affordable, wide field of view, dynamic object tracking at frame rates better than 1?Hz (real time). This paper describes a methodology to model, detect, and track the position of static and moving objects in real time, based on data obtained from video range cameras. Experiments with this technology have produced results that indicate that video rate 3D data acquisition and analysis of construction environments can support effective modeling, detection, and tracking of project resources. This approach to job site awareness has inherent value and broad application. In combination with effective management practices and other sensing techniques, this technology has the potential to significantly improve safety on construction job sites.     

CIMS环境中的数据模式转换

本文在分析CIMS环境中数据模式冲关类型的基础上，提出一种互连数据库系统模式结构，论述了在异构数据库集成中解决模式冲突的基本方法．在这种方法体系中，不需要建立整个企业的全局数据模式，各局部DBA以简单的方式定义应用所需的模式变换，系统根据这种定义自动完成各种转换，使用户看到的模式和数据结果与应用要求的一致．     

CRC计算方法的研究

本文丛面地介绍了ＣＲＣ的基本原理和计算方法，并给出了编程实例。     

Testing of multi-output circuits by means of signature analyzer

Let a circuit havem outputs,m>1. There are two ways to test this circuit by means of a signature analyzer: use a single input analyzer for each output or use anm-input analyzer to test all outputs simultaneously. The main goal of this letter is to demonstrate that for fault output sequences with small multiplicity of errors and long length the second approach is more effective.     

反应堆材料热物性数据库管理系统

衡量一个数据库的质量，不以要看其所包含的数据还应考虑数据库管理系统的使用功能。为了更有效地实施ＩＡＥＡ的ＣＲＰ（ＣｏｏｒｄｉｎａｔｅｄＲｅｓｅａｒｃｈＰｒｏｇｒａｍｍｅ）中有关建立反应堆材料热物性数据库的计划，并考虑到能使所收集的数据方便地为用户服务和进行广泛的国际交流，为此设计并编制了该数据库的软件管理系统ＴＰＳＹＳ。这个系统可在ＩＢＭ－ＰＣ（３８６，４８６）等兼容机上运行，采用人机对话、菜单提示、全屏幕操作。其主要功能有：数据库维护、数据检索、与大型计算程序ＭＡＴ－ＰＲＯ接口和与国际上现有的数据库ＴＨＥＲＳＹＳＴ接口。