用Petri网描述进程的死锁

死锁是操作系统的一个重要概念,本文提出用库所/变迁网直观、动态地描述并发进程的死锁,本人将这一方法用于操作系统有关死锁内容的教学取得了非常好的效果.     

Generalized stochastic Petri nets based models for performance analysis of communication networks of IEC61850 system

1 Introduction a After many years’ research and developments, communication networks have demonstrated more and more important functions in a substation automation system (SAS). In our experience in developing and applying such systems, we have witnessed…     

Education and Colonial Transition: The Hong Kong experience in comparative perspective

While in some respects the nature of Hong Kong's colonial transition seems unique, several parallels exist with transitions elsewhere. This paper begins by identifying major differences and similarities in the macro-framework. It then turns specifically to the education sector, noting that the parallel operation of multiple education systems within the boundaries of a single country is quite common and, therefore, that models already exist for continued plurality of the type that might be envisaged for Hong Kong and the rest of China. Examining changes at various points in time, the paper observes that some reforms were made in Hong Kong's educational provision well ahead of the commencement of colonial transition and far in advance of parallel points in the history in other colonies. The paper then turns to specific changes which occurred during the period 1984-1997 and to commentary on the further changes that may be expected in the continuing period of transition that commenced in 1997. Analysis of the currents and counter-currents makes Hong Kong an important case to study, both in its own right and as a case to compare and contrast with patterns elsewhere.     

Petri nets

Petri nets offer a versatile modeling framework for complex, distributed, concurrent systems and have been used in a wide range of modeling applications. In Part 1 of this two-part article, we have seen important features and representational power of the Petri net model. We have also seen how the application of firing rules enables Petri nets to capture the dynamics or behavior of the modeled system. In this part, we will first understand how important system properties are modeled by Petri nets and then look into the applications of Petri net models.     

On the stochastic dynamics of molecular conformation

An important functioning mechanism of biological macromolecules is the transition between different conformed states due to thermal fluctuation. In the present paper,a biological macromolecule is modeled as two strands with side chains facing each other,and its stochastic dynamics including the statistics of stationary motion and the statistics of conformational transition is studied by using the stochastic averaging method for quasi Hamiltonian systems. The theoretical results are confirmed with the results from Monte Carlo simulation.     

一种分布式层次型校园网络管理模型的研究

伴随高校合并,出现了物理上分布,逻辑上统一的多校区现象,校园网络向大规模、异构方向快速发展,传统网络管理无法满足网络发展的需要。在分析现有网络管理模型的基础上,针对合并高校的特点,构造了一个分布式、层次型的网络管理模型,经过与现有网络管理模型的比较,表明该模型更适合分布式校园网的管理。     

WWW下基于Petri Net的协同编辑模型

工作流管理是一个以业务处理自动化为目标的新兴研究领域。近几年来Internet的发展深刻地影响着工作流管理系统。本文旨在用PetriNet这种非常适合描述离散动态系统的工具建立一个基于WWW环境的期刊协同编辑系统模型 ,使编辑流程规范化 ,也为后期开发提供可靠的理论基础     

AN EQUIVALENCE METHOD FOR COLOURED PETRI NETS AND PLACE/TRANSITION NETS

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Drivability improvements for a single-motor parallel hybrid electric vehicle using robust controls

For a single-motor parallel hybrid electric vehicle, during mode transitions （especially the transition from electric drive mode to engine/parallel drive mode, which requires the clutch engagement）, the drivability of the vehicle will be signifi- cantly affected by a clutch torque induced disturbance, driveline oscillations and jerks which can occur without adequate controls. To improve vehicle drivability during mode transitions for a single-motor parallel hybrid electric vehicle, two controllers are proposed. The first controller is the engine-side controller for engine cranking/starting and speed synchronization. The second controller is the motor-side controller for achieving a smooth mode transition with reduced driveline oscillations and jerks under the clutch torque induced disturbance and system uncertainties. The controllers are all composed of a feed-forward control and a robust feedback control. The robust controllers are designed by using the mu synthesis method. In the design process, control- oriented system models that take account of various parameter uncertainties and un-modeled dynamics are used. The results of the simulation demonstrate the effectiveness of the proposed control algorithms.     

一类离散时滞随机系统的稳定性分析

针对一类不确定随机离散变时滞系统,建立了随机稳定性标准,该系统中随机干扰满足布朗运动。选取合适的李雅普诺夫函数,借助于随机稳定性理论、自由权矩阵和线性矩阵不等式等方法,给出并证明了使得该系统随机稳定的充分条件,所有结果以线性矩阵不等式的形式给出,应用例子和仿真表明所给稳定性标准的有效性。     

《清华大学藏战国竹简(一)》介词考察

《清华简(一)》共有12个介词,主要用来介引处所、时间和对象,也引进工具、方式和原因。出现在谓语后的次数略多于出现在谓语前的次数。介词的使用表现出一定的分工。     

基于扩展Petri网的混合系统建模方法

为了对混合系统进行有效地建模,提出了一种扩展的面向对象混合Petri网(EOHPN)建模方法.针对混合系统的复杂性,在EOHPN模型中融入了面向对象的抽象机制,例如封装和类定义.为了结合混合系统的连续部分和离散部分,减少混合系统的复杂性,引入混合Petri网并用面向对象建模技术作了扩展.在定义EOHPN模型的基础上,拓展了对象模型.最后,用实例描述了基于EOHPN的混合系统建模过程,同时验证了EOHPN模型在处理复杂混合系统建模时是有效的.     

工作流响应时间概率分布分析

提出了一种基于流体随机Petri网的工作流响应时间概率分布计算方法.首先讨论了利用随机工作流网建模的一些相关问题,然后描述了如何将随机工作流网模型转化为流体随机Petri网模型,最后给出了该种流体随机Petri网模型的动态方程,说明工作流响应时间的概率分布可直接由流体随机Petri网模型的暂态解得到.该方法对工作流模型的结构没有提出任何限制,且工作流任务的处理时间可取任意概率分布,通过递归地使用网化简技术可有效地处理大型工作流模型.     

基于混沌模拟退火算法的BPNN模型的随机混沌系统辨识

文章针对随机混沌系统辨识引入贝叶斯正则化方法的BPNN模型,使神经网络具有自适应性和推广能力;并交替使用贝叶斯正则化算法和混沌退火算法对网络参数进行优化,使系统具有最佳参数．以Logistic系统为例进行仿真分析,结果表明辨识模型不仅能够拟合原混沌系统,而且训练后的网络对含噪声的随机混沌系统有很好的辨识能力,精度良好．为下一步的设计控制器对混沌系统进行控制消除混沌,奠定了良好的基础．     

Information Systems Education in the USA

Fast changing information technology (IT) has posed tremendous challenges to information systems (IS) educational programmes. One question frequently asked by IS educators has been: ‘Are we doing the right thing?’ This article presents information about the current state of IS educational programmes in the USA based on a survey of 193 higher education institutions conducted at the end of 1996. The results indicate that IS educational programmes are prevalent in the higher educational institutions. These programmes have a highly qualified faculty: 92% or more holding terminal degrees, more than two-thirds having tenure, with evidence of an increasing amount of time being devoted to research activities. It is also found that the most popular programming languages taught in both graduate and undergraduate programmes are C/C++, SQL and COBOL, and dominant operating systems are Windows/OS2 and UNIX. The most profound change over the last five years in the content of IS programmes has been the transition from text-based and centralized mainframe environment to the graphical and decentralized network based client–server architecture. This survey provides a snapshot of IS programmes, serving both to improve our understanding of current programmes and to provide a frame of reference for future studies.     

From higher education to work patterns of labor market entry in Germany and the US

Comparative studies describing the transition from higher education to work have often simplified the complex transition processes involved. In this paper we extend previous research by taking into account several steps that comprise labor market entry, e.g., recurrent education leading to more than one instance of labor market entry. By comparing Germany and the United States we also examine how the tertiary education systems influence these transitions via the mode of stratification (parallel tracks in Germany vs. consecutive tracks in the US), the coordination mechanism (state-controlled vs. market-based) and the degree of standardization in educational programs. In our empirical analyses using large-scale longitudinal survey data we find that transitions in the US are less standardized and regulated than in Germany. Furthermore, differences between students from lower- and higher-tier institutions are less marked than expected, both within and between the two countries.     

Stochastic averaging of quasi partially integrable Hamiltonian systems under fractional Gaussian noise

A stochastic averaging method for predicting the response of quasi partially integrable and non-resonant Hamiltonian systems to fractional Gaussian noise (fGn) with the Hurst index 1/2<H<1 is proposed. The averaged stochastic differential equations (SDEs) for the first integrals of the associated Hamiltonian system are derived. The dimension of averaged SDEs is less than that of the original system. The stationary probability density and statistics of the original system are obtained approximately from solving the averaged SDEs numerically. Two systems are worked out to illustrate the proposed stochastic averaging method. It is shown that the results obtained by using the proposed stochastic averaging method and those from digital simulation of original system agree well, and the computational time for the former results is less than that for the latter ones.     

A minimax optimal control strategy for uncertain quasi-Hamiltonian systems

A minimax optimal control strategy for quasi-Hamiltonian systems with bounded parametric and/or external disturbances is proposed based on the stochastic averaging method and stochastic differential game. To conduct the system energy control, the partially averaged Ito stochastic differential equations for the energy processes are first derived by using the stochastic averaging method for quasi-Hamiltonian systems. Combining the above equations with an appropriate performance index, the proposed strategy is searching for an optimal worst-case controller by solving a stochastic differential game problem. The worst-case disturbances and the optimal controls are obtained by solving a Hamilton-Jacobi-Isaacs （HJI） equation. Numerical results for a controlled and stochastically excited DulTlng oscillator with uncertain disturbances exhibit the efficacy of the proposed control strategy.     

韩国学生不同句法位“在＋处所”短语习得考察

“在＋处所”短语在句中可作状语、补语和定语,占据五种句法位：主语前、谓语动词前（无主语）、主语后谓语动词前、谓语动词后以及定语中心语前。对韩国学生来说,几种句法位中以谓语动词后的句法位最难,其使用规则也影响学生对其他句法位的习得,应加强“在＋处所”短语后置于谓语动词的规则教学。另外,几乎所有句法位都存在方位词的误代、误加和遗漏,“在”的遗漏及与其他相关介词的误代;主语前和主语后动词前两种句法位存在较多错序：定语中心语前“的”的遗漏较严重。这些在对韩汉语教学中都应加以注意。     

From Green to Red Tomatoes or Is there a Shortcut by which to Change the Conceptions of Teaching and Learning of College Teachers?

No general shift from a teaching to a learning paradigm in higher education is possible without a parallel change in the conceptions that college and university teachers have of teaching and learning‐‐from teaching, conceived as transmission and reception of knowledge, to teaching as facilitation of student learning. Staff development and action research can play a useful role in “defreezing” the existing conceptions and attitudes. But for a substantial change in teaching practices in the direction of learning of high quality to occur, more substantial changes in organization, curricula, funding, staff recruitment, and professional development policies are needed. The international academic community can play an important role in this paradigm shift by presenting models of good practice as well as exchanges of experiences and incentives. Such assistance is especially important for small countries in transition, like Slovenia.