New and used temporal models: An issue of time

TheSpecial Issue on Applications of Temporal Models raises many issues of time: What are the important properties of time? How can time be best represented? How can one reason about time-dependent properties? What are the important directions of temporal research? This introductory piece very briefly surveys the current wide variety of temporal models, temporal reasoning methods, and applications to time-varying phenomena. Promising areas of investigation such as the verification of concurrent systems, knowledge-base representation methods, and dealing with theFrame Problem pass in fleeting review. Brief introductions to each of the works in the volume close the section.     

A fuzzy diagnosis approach using dynamic fault trees

By incorporating digraph models, fault trees and fuzzy inference mechanisms in a unified framework, a novel approach for fault diagnosis is developed in this work. To relieve the on-line computation load, the fault origins considered in diagnosis are limited to the basic events in the cut sets of a given fault tree. The symptom occurrence order associated with each root cause is derived from system digraph with the qualitative simulation techniques. The implied candidate patterns are enumerated according to two proposed theorems and then encoded in the inference system with IF-THEN rules. The simulation results show that the proposed approach is not only feasible but also capable of identifying the most likely cause(s) of a hazardous event at the earliest possible time.     

异步时序型PAL解析方法的研究及解析结果分析

本文就异步时序现ＰＡＬ的解析，提出了一种状态图遍历算法。     

Workload Distribution in Fault Simulation

Simulation at the gate level is computationally very expensive.Parallel processing is one technique to reduce simulation time.Possessing knowledge of the distribution of computational activity insimulation can aid in parallelizing it efficiently. We present a newcharacterization of the distribution of the computational workload infault simulation. An empirical analysis shows that the workloaddistribution is circuit specific, and is largely independent of thevector set being simulated. An inexpensive method to predict theworkload distribution is also discussed.     

磁悬浮硬盘转子控制系统中时序电路测试技术

为提高磁悬浮硬盘转子控制系统的可靠性，提出了对时序芯片的测试方法：手工测试和计算机辅助测试；及时时序电路逻辑功能的两种检测技术；基于状态表的测试技术和自动检测技术。对于时序芯片，手工测试方法效率较低，计算机辅助测试方法适用范围更广；对于电路逻辑功能，基于状态表的测试技术操作相对困难，但无须增加额外测试电路；自动检测技术操作简单，且测试速度快，但需要增加辅助检测电路。时序电路测试技术对保证悬浮硬盘转子各组成部分协同工作十分重要。     

气化炉自动建模系统研究

为了减轻建模人员在建模公式推导、逻辑关系推导和编制仿真程序的工作量，设计了气化炉自动建模系统。该系统在反应物为多种气体、多种固体（均考虑为单筛分）的条件下，按照小室模型的框架自动列写相应各个物质的质量、能量平衡方程，并自动生成相应的计算机程序，方便仿真计算。由于该系统避开了工程中常用的纯数值建模的思路，采用了新的数学工具－以符号运算特长的计算机代数系统为计算平台，才使得该系统具有强大的逻辑关系推导能力。该系统在某气化炉的建模过程中得到了验证和示范，事实表明：该系统大大减少了气化炉的建模工作量，特别是减少由于化学反应假定的不同带来的建模复杂性，对于建模与仿真研究新方法的突破有所贡献。     

ispLSI1032E器件及其应用

介绍了Lattice公司的大规模集成电路ispLSI1032E,它是一种在系统复杂可编程逻辑器件(CPLD),借助于EDA设计软件可以随时更改芯片的功能,而且不需要改动印制电路板(PCB)的结构,大大提高了系统设计的效率,并保证了设计的正确性。最后设计了基于该芯片的EDA教学实验系统。     

PLC在葛洲坝大江电厂机组辅助设备控制中的应用

PLC(可编程控制器)在机械工业和电力生产等部门应用广泛。在电力生产部门主要用于集中控制,已有较好的效果。介绍了PLC在葛洲坝水电厂机组辅助设备控制操作功能中的应用回顾及其展望。     

A hybrid PC/PLC architecture for manufacturing-system control—theory and implementation

This paper presents a novel and generic PC/PLC-based software/hardware architecture for the control of flexible manufacturing workcells. The proposed implementation methodology is based on the utilization of any one of the available formal discrete-event-system control theories in conjunction with state-of-the-art industrial programmable-logic controllers (PLCs). The methodology has been illustrated to be a viable technique through its actual implementation in our laboratory using a robotic-workcell testbed. The specific control theory used is a combination of Extended Moore Automata and Ramadge-Wonham Automata that has been developed by our research group. The modular control software architecture has been developed for MS-Windows environments (running on one PC interfaced to the PLCs) and allows the use of different formal control theories as well as different commercial PLC hardware. The effective graphical user interface provides a transparent programming environment, where users are not expected to have a full knowledge of the formal control theory used.     

A real-time road pricing system: The case of a two-link parallel network

A real-time road pricing system in the case of a two-link parallel network is proposed in this paper. The system that is based on a combination of Dynamic Programming and Neural Networks makes “on-line” decisions about road toll values. In the first phase of the proposed model, the best road toll sequences during certain time period are calculated off-line for many different patterns of vehicle arrivals. These toll sequences are computed using Dynamic Programming approach. In the second phase, learning from vehicle arrival patterns and the corresponding optimal toll sequences, neural network is trained. The results obtained during on-line tests are close to the best solution obtained off-line assuming that the arrival pattern is known.