基于资源预报的两级并发控制

本文提出了一种新的基于资源预报的并发控制机制，该机制充分考虑了实时事务的功能替代性，将并发控制分为替代级控制和事务级控制，允许多个替代并发执行。每个替代代表一条执行路径，只要其中一个替代成功则该实时事务可以提交；一个替代夭折，不表示该事务夭折，甚至并发执行的所有替代夭折，也不一定表示该实时事务夭折，该事务有可能会从另外的替代重启，这就大大提高了实时事务的成功率，降低了由于硬实时事务超过截止期对系统带来损失的可能性。     

K锁算法—一种数据库上的可适应并发控制策略

本文提出了一种基于悲观和乐观思想的并发控制算法——K锁算法.K锁算法利用K锁机制,在一定程度上允许冲突执程的并发执行.和乐观算法比较,它减少了在系统的执程冲突概率较大时执程的重执次数,和悲观算法比较,它提高了冲突执程的执行并发度.     

并发进程系统正确性的验证图式

并发进程系统正确性的验证,比之顺序进程正确性的验证有其特殊意义。并发系统的运行,在执行序列这一级上是非决定的,通常的调试手段,很难暴露系统中依赖于执行序列的那类错误。因此并发系统正确性的验证,在三种不同水平上都是有价值的:完全形式化的形式演绎系统;半形式化的数学证明;或者有效的检查调试方法。 并发系统运行的非决定性,也极大地增加了验证的复杂性。在证明系统具有某个性质时,粗略地说,就是要证明这个系统的所有执行序列都具有这种性质。一个顺序进程,从给定的初始状态出发,只有一个可能的执行序列;但是多个并发进程的可能执行序列则往往是无穷多个。由于这种复杂性禁锢了人们的智力活动,使得一些简单的事实,人们也很难将其严格证明。系统中存在的问题,事后看来即使是一些很明显的问题,也会被这种复杂性掩盖起来,长时间不被发现。     

协同CAD环境下并发控制问题的研究与解决

实时协同设计是CSCW应用的重要领域。文章在研究经典并发控制策略的基础上，重点分析了基于AutoCAD环境的实时协同设计系统的四种冲突类型；通过考虑响应时间和网络流量，提出了解决这些不同类型冲突的方案和并发控制策略，以确保多个用户对于AutoCAD对象的操作实现准实时传递，为实现原型系统打下良好的基础。     

网格环境下多数据源并发控制的研究

为了有效地控制和实现网格用户的并发操作，提出了一种基于可变周期的任务序列重建的并发控制算法，用来保证网格用户访问的并发性和并行性；同时提出服务一致法和服务跟踪法，用来维护数据源数据的一致性和客户端显示信息与数据源数据的一致性，这也体现了网格数据的易变性和系统的可适应性。     

C程序并发行为控制方法及其测试工具支持

针对由于并发程序的行为不可控而导致难以对其进行测试的问题,提出了一种控制C程序中并发行为的方法。该方法以多线程同步为基础,使用测试序列和测试单位完成对并发行为的控制。在此基础上,实现了对C程序测试活动中并发行为控制的工具支持,以生产者-消费者为例说明了使用此工具进行测试活动,并讨论了其效率。     

带正弦干扰的线性时滞系统的次优控制

研究状态变量含有时滞的线性系统在正弦干扰下的前馈反馈次优减振控制问题，首先构造其解收敛于原时滞系统的无时滞系统序列；然后将时滞系统的最优控制问题化为无时滞系统的最优控制序列问题；最后通过截取最优控制序列解的有限项，得到系统的前馈反馈次优控制律，仿真结果表明，该方法抑制正弦干扰的鲁棒性优于经典反馈最优控制。     

应用共享并发与冲突机制研究

论文分析了应用共享技术“共享显示法”与“事件分发法”中的并发冲突问题,重点探讨了“事件分发法”系统中并发控制机制存在的主要问题,提出了在相容优先方式下“全局序列”与“改进的多版本机制”相结合的并发机制,设计了采用有向图结构存储冲突版本的“事件”序列的方法;设计了非相关”事件”的合并规则。该机制提高了相容优先方式下系统处理冲突的能力,同时节省了空间与时间开销。     

一个基于SQL的并发控制机制

传统的读写事务模型（由ｒｅａｄ（ｘ）和ｗｒｉｔｅ（ｘ）序列组成）不能使调度机制充分利用应用程序的语义信息对事务进行灵活调度，从而不能有效提高系统的并发度．本文根据ＳＱＬ语言的操作语义，给出了基于ＳＱＬ的事务模型．利用这种事务模型并结合２ＰＬ方法，设计了并发控制机制：Ｃｏｎｄｉｔｉｏｎ—ｌｏｃｋｉｎｇ．这个机制可以：（１）避免数据库中的幽灵（ｐｈａｎｔｏｍ）问题，（２）利用应用程序的语义信息和完整性约束提高系统的并发度，（３）减少发生死锁的机会．因此，这是一个实用的并发控制机制．     

一个工在于SQL的并发控制机制

传统的读写事务模型不能使调度机制充分利用应用程序的主义信息对事务进行灵活调度，从而不能有效提高系统的并发度。本根据ＳＱＬ语言的操作语义，给出了基于ＳＱＬ的事务模型。利用这种事务模型并结合２ＰＬ方法，设计了并发控制机制；Ｃｏｎｄｉｔｉｏｎ－ｌｏｃｋｉｎｇ。     

一类受控Petri网的基于管程的广义互斥控制

本文讨论受控Ｐｅｔｒｉ网的广义互斥控制问题。首先，我们给出了此问题存在管程最小约束控制解的充要条件，然后，对一类其不可控 子网为有限状态机的受控Ｐｅｔｒｉ网，证明了其广义互斥控制问题总存在管程最小约束控制解，并给出了综合这一管程的控制的算法。     

信念修正的完全和可操作的方法

给出了命题逻辑上信念修正的两种可操作的完全方法.首先对R-演算的规则进行了修改,使得对任何一个极大协调的子集都通过这组规则得到.然后,给出了求得所有的极小不协调子集的一组规则.最后,给出一个过程,该过程能求得所有的极大协调子集.因为这两种方法都能求得所有的极大协调子集,所以把它们称为完全的.     

Controllability and control-invariance in discrete-event systems

Recently, for discrete-event systems modelled by automata, Ramadge and Wonham (1987 a, b) have proposed two control techniques called ‘supervisory control’ and ‘state feedback logic’. If control specifications are given in terms of predicates on the set of states, both techniques are applicable. This paper discusses the relationship between these techniques. It is shown that the language accepted by the discrete-event system with maximally permissive feedback is equal to the supremal controllable language if the predicate is control invariant. Moreover, it is shown that the predicate is control invariant if there exists a controllable language with a certain condition on the set of reachable states, but the converse does not hold in general     

The real-time supervisory control of an experimental manufacturing system based on a hybrid method

In this paper, the real-time supervisory control of an experimental manufacturing system is reported based on a recently proposed hybrid (mixed PN/automaton) approach. Assuming that an uncontrolled bounded Petri net (PN) model of a (plant) discrete event system (DES) and a set of forbidden state specifications are given, the proposed approach computes a maximally permissive and nonblocking closed-loop hybrid model. The method is straightforward logically, graphically and technologically. This paper particularly shows the applicability of a hybrid (mixed PN/automaton) approach to low-level real-time DES control. To do this, programmable logic controller (PLC) based real-time control of an experimental manufacturing system is considered.     

Deadlock-free Supervisor Design for Robotic Manufacturing Cells With Uncontrollable and Unobservable Events

In this paper,a deadlock prevention policy for robotic manufacturing cells with uncontrollable and unobservable events is proposed based on a Petri net formalism.First,a Petri net for the deadlock control of such systems is defined.Its admissible markings and first-met inadmissible markings(FIMs)are introduced.Next,place invariants are designed via an integer linear program(ILP)to survive all admissible markings and prohibit all FIMs,keeping the underlying system from reaching deadlocks,livelocks,bad markings,and the markings that may evolve into them by firing uncontrollable transitions.ILP also ensures that the obtained deadlock-free supervisor does not observe any unobservable transition.In addition,the supervisor is guaranteed to be admissible and structurally minimal in terms of both control places and added arcs.The condition under which the supervisor is maximally permissive in behavior is given.Finally,experimental results with the proposed method and existing ones are given to show its effectiveness.     

一类离散事件系统的监控器综合

前向无同步前向无冲突网是每个变迁有且只有一个输入库所并且每个库所最多有一个输入变迁的受限Petri网.针对不可控影响子网为前向无同步前向无冲突网的广义互斥约束,显式地给出了最大允许控制策略的计算方法.并用一个例子给予了说明.     

Controller design and performance evaluation for deadlock avoidance in automated flexible manufacturing cells

In this paper, the design of a deadlock avoidance controller is described. The uncontrolled system is modeled using colored Petri nets. The system controller is based on a restrictive (not maximally permissive) deadlock avoidance policy to resolve deadlocks and control the real-time resource allocation decisions in the system. Performance evaluation of systems controlled by not maximally permissive algorithms is essential in determining the applicability and effectiveness of the control algorithms. The performance of the controlled system is compared with performance of optimal control policies to quantify the effects of the restrictiveness of the deadlock avoidance policy on system performance.     

On maximally distant spanning trees of a graph

A set ofk spanning trees of a graphG is calledmaximally distant if their union contains the maximum number of edges ofG. We present a necessary and sufficient condition for a set of spanning trees to be maximally distant. We also give an efficient algorithm which actually findsk maximally distant spanning trees in a given graph.     

A method for forming program control for velocity regime of motion of underwater vehicles along arbitrary spatial trajectories with given dynamic accuracy

An approach to precise control of motion of an underwater vehicle is proposed; this approach consists in an automatic correction of program motion signals such that the execution of these new program signals provides precise motion of the underwater vehicle along a given spatial trajectory with maximum possible velocity irrespective of dynamic error of the control system of this underwater vehicle. The program signals of motion of the underwater vehicle are corrected by shifting the target point specifying the desired position of the underwater vehicle on a given trajectory by a value proportional to the vector of deviation of the underwater vehicle from this trajectory and simultaneous adjustment of the desired velocity of the underwater vehicle. The results of mathematical simulation have shown that the application of the proposed method provides exact and maximally fast motion of the underwater vehicle along the given spatial trajectory using simple standard linear controllers in the control system of this underwater vehicle.     

Propelling a torque controlled baton to a maximum height

Recent applications of optimal control theory to the analysis of human and animal locomotion have resulted in optimal control problems that are too complex for analytic solution. Furthermore, these problems involve unusual constraints and dynamics. In order to provide a clearer understanding of the problems involved, the much simpler but related problem of causing a baton to "jump" maximally has been completely solved via elementary methods. The solution is given in feedback form. The state space divides into several regions according to the form of the optimal control. There exist regions where many controls are globally optimal, regions where a locally optimal control and a globally optimal control both exist, and regions where a unique globally optimal control exists. Finally, some relations between these results and experimental observations in both human and animal jumping are discussed.