双螺杆泵Ω形对称型螺杆流场数值分析

由于螺杆泵几何结构及流体流动状态较为复杂,其压力分布和速度等特性很难用数学解析法来分析计算。本文利用参数化设计模块建立双螺杆泵Q形对称型螺杆三维模型,构建双螺杆流道的流场分析模型,运用有限元分析方法得出了双螺杆泵流道内压力场和速度场分布规律。结果表明：流体在流道中的流速分布具有规律性,整个流道的流场速度高低交替变化,在螺杆与衬套间隙处的流动为层流,螺旋面接触区内的流动为复杂的湍流,离螺杆啮合区近的螺旋槽内易发生涡流。本研究结果对于了解双螺杆泵螺杆工况下的性能情况具有重要的参考价值。     

搅拌釜内双层改进型INTER-MIG桨流场实验研究

为得到双层INTER-MIG桨搅拌釜内流场特征,文章采用粒子图像测速技术(PIV)对直径为430 mm的双层改进 型INTER-MIG桨搅拌槽内流场进行了实验研究。分析了搅拌转速、相位角及轴向位置对搅拌槽内流场分布的影响。结 果表明：整个流场表现出较强轴流特性,底桨右端形成一个漩涡;转速增加引起桨叶附近湍动增强,但整体流型变化不 大;当r/R <0.48时,桨叶间轴流效果显著,有利于釜底流体向上抬升,增强整体混合效果;当r/R>0.48时,桨叶右端在 近壁面处会形成上下2股流动流体,有助于形成局部区域循环。实验结果可为工业搅拌过程提供工艺参考。     

论融资约束下企业最优投资时机选择

利用企业投资的三期静态模型,考察了企业投资额、自有资金与外部融资之间的关系。通过比较企业在不同期间即时投资和延迟投资的投资收益,求解得到企业在融资约束下的投资临界值,进而得出了企业在投资可延迟条件下的最优投资时机和投资规则。     

网络环境对财务风险预警系统的影响

近年来，随着网络在财务管理工作中的应用，财务风险发生了显著的变化。建立网络环境下的财务风险预警系统已经迫在眉睫。我国对这一领域的研究无论在理论上还是在实践上都较薄弱，财务预警管理也是我国企业迫切需要解决的问题。     

强化学习型匝道控制模型的研究

高速公路上的交通堵塞造成了道路利用效率低下，并伴随着能源消耗和环境污染问题，因此各种各样的高速公路控制方法应用于缓解交通堵塞。本文提出强化学习型匝道控制模型，该模型以交通流模拟为预测工具，以人工智能的强化学习为最优化选择模型，并具有一定的自主性、有记忆功能和性能反馈功能，且是一种动态的过程。应用JAVA针对不同的交通状态进行模拟再现，模拟结果表明匝道控制模型对于减少交通堵塞具有显著的效果。     

Adaptive agent-based manufacturing control and its application to flow shop routing control

The manufacturing industry is currently facing unprecedented challenges from changes and disturbances. The sources of these changes and disturbances are of different scope and magnitude. They can be of a commercial nature, or linked to fast product development and design, or purely operational (e.g. rush order, machine breakdown, material shortage etc.). In order to meet these requirements it is increasingly important that a production operation be flexible and is able to adapt to new and more suitable ways of operating. This paper focuses on a new strategy for enabling manufacturing control systems to adapt to changing conditions both in terms of product variation and production system upgrades. The approach proposed is based on two key concepts: (1) An autonomous and distributed approach to manufacturing control based on multi-agent methods in which so called operational agents represent the key physical and logical elements in the production environment to be controlled – for example, products and machines and the control strategies that drive them and (2) An adaptation mechanism based around the evolutionary concept of replicator dynamics which updates the behaviour of newly formed operational agents based on historical performance records in order to be better suited to the production environment. An application of this approach for route selection of similar products in manufacturing flow shops is developed and is illustrated in this paper using an example based on the control of an automobile paint shop.     

Improving traceability in continuous processes using flow simulations

Traceability is normally difficult to achieve in continuous processes, since there are no natural batch structures. In this article, we demonstrate flow-based simulation using process data to improve traceability in a continuous pelletising process. Using the simulation model, the engineers could test the impacts of process disturbances, identify cause and effect relations and aid control in case of process disturbances. In a field trial where the chemistry of an additive was varied during production of a special product, the simulation forecasts predicted the level of the chemical content after the plant within the errors that the engineers found acceptable.     

城市供水管网系统工况分析的研究

通过分析实际供水管网系统的特征，对管网工况分析所涉及的几个尚未解决的计算问题进行了研究，提出了用计算机进行工况分析的思路与框架，为管网运行调度及研究管网水质模型打下了良好基础．     

支持MLS的多层次嵌入式高可信软件架构

为增强安全关键系统的高可信能力,在分析高可信保障机制现状的基础上,提出了一种多层次的高可信软件架构。该架构采用时空分离思想、虚拟机技术,为基于MLS的嵌入式安全关键系统提供了一种整体解决方案。基于该架构,研究了多层次的安全和防危策略管理方法、信息流控制机制、可信软件的评估和认证方法,为安全关键嵌入式系统提供可认证的安全服务。     

知识流模型及其在航天企业中的应用

知识管理的理论和实践吸引了众多学者和企业家的关注,但在具体的实施方法上一直没有形成共识。管理的对象是“知识”,对于知识流动的理解、监测乃至控制是顺利实施知识管理项目的基础。已有的研究对知识流的讨论集中于描述概念,或通过统计分析或调查问卷得到对专利、引用等知识流动的描述。把Petri网理论用在对知识流进行刻画中,提出知识流的Petri网模型,能够描述知识分布的拓扑结构、知识存量、一定时期的知识流量和流速,使得管理人员便于监控和管理知识流动,更好地实施知识管理。把基于Petri网的知识流模型应用于航天企业中,通过实证分析说明该知识流模型对知识流动的刻画能力,并通过对现状的分析,为改进知识流动效率,实现知识管理目标提供支持。