用S7-200PLC提高种分槽搅拌装置运行的可靠性

主要阐述了应用西门子S7-200PLC可编程控制器解决种分槽搅拌装置电源自动切换的问题,从方案选择、硬件配置、软件编程等角度对电源自动切换的解决方案进行了论述。实践证明,该系统具有运行稳定、可靠性高、操作维护简单、方便系统扩展和数据采集等许多优点,具有推广价值。     

Sequential Compatibility Effects and Cognitive Control: Does Conflict Really Matter?

Although it is widely accepted that control mechanisms are necessary for human behavior to be adapted, very little is known about how such mechanisms are recruited. A suggestion to fill the gap was put forward by M. M. Botvinick, T. S. Braver, C. S. Carter, D. M. Barch, and J. D. Cohen (2001), who proposed the conflict-loop theory. This theory has been successful in accounting for the reduction of compatibility effects after an incompatible trial: The level of conflict being, on average, higher during an incompatible trial, more control occurs after such a trial. The authors have tested this prediction by sorting the trials on the basis of amount of conflict (quantified by the electromyographic activity) they presented. A reduction of the compatibility effect was observed after incompatible trials, but it was independent of the level of conflict on previous trials, suggesting that the conflict does not trigger changes in executive control. Consequences for the conflict monitoring model are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

可编程控制器(PLC)在泥炮控制中的应用

泥炮是炼钢厂中控制炼钢炉钢水出口的一部分设备，系统较庞大，工序较复杂，用常规控制较难实现，而采用PLC可对其进行控制。该系统共有38点数字量入、33点数字量出、1路模拟信号(压力)，采用三菱公司的FX2系列PLC。由于该系统工艺的复杂性、特殊性，在控制软件的编制上并没有统一采用梯形图编程法，而是采用梯形图编程法与状态转移图编程法相结合的方法，这样大大提高了软件的可编性、可调性、可读性。用状态转移图法编程不用特意考虑就解决了系统在设定压力点附近的抖动问题，而用梯形图法编程则必须特别小心，否则很易使系统在设定点附近抖动起来，通过调试与运行充分体现了这种编程方法的实用性与PLC的可靠性、可维修性、可修改性。     

基于蚂蚁路径的时序电路故障诊断算法

提出了一种VLSI时序电路自动测试型生成(Automatic test pattern generation，ATPG)的新算法。传统ATPG算法采用局部状态转换图或收集门级电路的知识以及提取电路规则来解决时序电路ATPG的困难。本算法引入新的模型，着重解决了ATPG中的计算冗余问题。在蚂蚁路径模型的基础上，前向搜索得到了重建，故障点的前向传输和回溯归结到了单一路径之上．而该路径上可能分布着许多待测的故障点，从而改善了以往时序电路ATPG算法中搜索重复而导致的计算冗余问题，同时，最小测试向量的获取为数学定理所证明。最后在Benchmark电路上进行的与ILP算法的比较试验表明，本算法具备同样的故障覆盖率，且速度更快。     

The constrained longest common subsequence problem

This paper considers a constrained version of longest common subsequence problem for two strings. Given strings S₁, S₂ and P, the constrained longest common subsequence problem for S₁ and S₂ with respect to P is to find a longest common subsequence lcs of S₁ and S₂ such that P is a subsequence of this lcs. An O(rn²m²) time algorithm based upon the dynamic programming technique is proposed for this new problem, where n, m and r are lengths of S₁, S₂ and P, respectively.     

On the Optimality of Randomized Deadlock Avoidance Policies

This paper revisits the problem of selecting an optimal deadlock resolution strategy, when the selection criterion is the maximization of the system throughput, and the system is Markovian in terms of its timing and routing characteristics. This problem was recently addressed in some of our previous work, that (i) provided an analytical formulation for it, (ii) introduced the notion of randomized deadlock avoidance as a generalization of the more traditional approaches of deadlock prevention/avoidance, and detection and recovery, and (iii) provided a methodology for selecting the optimal randomized deadlock avoidance policy for a given resource allocation system (RAS) configuration. An issue that remained open in the problem treatment of that past work, was whether the proposed policy randomization is essential, i.e., whether there exist any RAS configurations for which a randomized deadlock avoidance policy is superior to any other policy that does not employ randomization. The work presented in this paper establishes that for the basic problem formulation where the only concern is the (unconstrained) maximization of the system throughput—or the other typical performance objectives of minimizing the system work-in-process and mean sojourn time—randomization of the deadlock resolution strategy is not essential. However, it is also shown that, sometimes, it can offer an effective mechanism for accommodating additional operational constraints, like the requirement for production according to a specified product mix. Furthermore, the undertaken analysis provides an analytical characterization of the dependence of the aforementioned performance measures on the transition rates relating to the various events of the underlying state space, which can be useful for the broader problem of synthesizing efficient scheduling policies for the considered class of resource allocation systems.     

异步时序电路的功能测试自动生成方法

异步时序电路的测试一直是一个比较困难的问题。该文通过在前人研究的基础上，提出了一种实用、高效的自动测试生成方法。该方法通过使用基于OBDD(有序二元判决图)的布尔特征函数的运算求解来确定电路的状态转换图，然后通过对转换图的强连通图的搜索运算简化状态转换图，最后使用图论的方法求出测试序列。     

一种新的无损小波图像压缩算法

基于Daubechies 5-3旋转小波，本文提出了一种无损图像压缩新算法，这一工作证实了小波压缩的如下问题，小波压缩具有与JPEG那样快的运行速度，在不改变变换系数的条件下，采用序贯处理方法能急剧地减小存储器的需要量，能用小波实现图像的无损压缩，对比实验表明，这种快速，有效的无损图像压缩技术比标准的JBIG和无损的JPEG性能要优越。     

一个基于C/S模式的汉字词属性分析和重组系统的数据模型

随着ＩＳＯ１０６４６的出台，庞大的汉字词集的属性分析是一个迫切需要解决的难题，本文主要阐述了采用Ｃ／Ｓ模式的汉字词属性分析和重组系统的数据模型，并简单介绍了系统的设计要点。     

直线步进电动机单片微机控制与应用

提出利用单片微机作为开发平台，建立了一个测试系统来控制直线步进电机的时序脉冲，向直线电动机提供运行中节拍和方向指令，建立控制运行表格这达到直线步进电机按指定速度向指定方向运行到给定距离的目的。