A Polynomial Algorithm for Computing Elementary Siphons in a Class of Petri Nets

A set of elementary siphons plays a key role in the development of deadlock prevention policies for automated manufacturing systems. This paper addresses the computation problem for elementary siphons in a subclass of Petri nets which are basic systems of simple sequential processes with resources (BS³PR) and can model many automated manufacturing systems. An algorithm for enumerating elementary siphons is established by the one‐to‐one relationship between maximal perfect resource‐transition circuits (MPCs) and strict minimal siphons. A set of MPCs is first computed, followed by a set of elementary siphons in a BS³PR. The presented algorithm is proved to have polynomial‐time complexity. An example is used to illustrate the algorithm.     

Group technology based adaptive cell formation using predator-prey genetic algorithm

In recent years, there has been a considerable growth of application of group technology in cellular manufacturing. This has led to investigation of the primary cell formation problem (CFP), both in classical and soft-computing domain. Compared to more well-known and analytical techniques like mathematical programming which have been used rigorously to solve CFPs, heuristic approaches have yet gained the same level of acceptance. In the last decade we have seen some fruitful attempts to use evolutionary techniques like genetic algorithm (GA) and Ant Colony Optimization to find solutions of the CFP. The primary aim of this study is to investigate the applicability of a fine grain variant of the predator-prey GA (PPGA) in CFPs. The algorithm has been adapted to emphasize local selection strategy and to maintain a reasonable balance between prey and predator population, while avoiding premature convergence. The results show that the algorithm is competitive in identifying machine-part clusters from the initial CFP matrix with significantly less number of iterations. The algorithm scaled efficiently for large size problems with competitive performance. Optimal cluster identification is then followed by removal of the bottleneck elements to give a final solution with minimum inter-cluster transition cost. The results give considerable impetus to study similar NP-complete combinatorial problems using fine-grain GAs in future.     

稀土钕对激光快速成形TC4合金组织及性能的影响

针对氢化脱氢钛合金粉末氧含量较高的问题，研究了添加稀土钕对激光快速成形TC4合金组织及性能的影响。结果发现，添加稀土Nd后，激光快速成形TC4合金的宏观晶粒尺寸变化不大；但随稀土添加量的增加，初始β列状晶逐渐转化为全β等轴晶，晶粒内部的魏氏α组织逐渐转变为网篮α，粗化α条不断增多，呈现团束聚集趋势，晶界α集束体积分数也不断增大；随稀土添加量的增加，激光快速成形TC4合金的室温塑性先大幅度提高，然后急剧降低；稀土添加量为0．1％～0．2％（质量分数，下同）时，氧含量为0．26％的氢化脱氢TC4合金粉末激光快速成形件沉积态的抗拉强度达975MPa，延伸率9．5％，满足锻件标准要求。     

火车车轮成形新工艺的开发研究

在比较分析技术先进国家的火车车轮成形工艺流程后，采用试验研究和数值模拟相结合方法，研究开发出优化的新工艺。钢坯先在一台水压机上预成形制坯，再在另一台压机上模锻，经轧制扩径后冲孔压弯。这样的生产线效益最好     

铸态及快淬态无钴AB5型贮氢合金的循环稳定性

对AB5型LaxMm1-x(NiMnSiAlFe)49(x=0,0.45,0.75,1.00,摩尔分数)贮氢合金进行了快淬处理,研究了La含量及快淬工艺对合金微观结构及电化学循环稳定性的影响.结果表明:La含量的增加对铸态合金的循环稳定性没有明显影响,但使快淬态合金的循环稳定性下降,且快淬处理能显著提高合金的循环稳定性.当La替代量从0增加到1.00时,经300次充放循环后,铸态合金的容量保持率(Rh)从59.2%增加到59.8%;16 m/s淬速快淬态合金的容量保持率从83.9%下降到65.0%.对于x=0.45的合金,当淬速从0(铸态被定义为淬速等于0)增加到28 m/s时,容量保持率从59.8%增加到75.8%.     

快速凝固Al—Li—Mg—Zr合金粉末粒度对组织和性能影响

研究超音雾化快速凝固Al—Li—Mg—Zr合金粉末粒度对组织和性能的影响中发现,粉末粒度越细,组织越细,合金强度越大;但粒度太细,又会导致塑性变差。试验合金粒度范围选用40—100μm为佳。     

电机智能制造发展现状及推进策略

随着电机制造要求逐步提高、自动化逐渐普及,智能制造将成为未来主流的生产制造模式。基于对传统电机制造现状和发展趋势的分析,厘清智能制造优势及智能制造推进误区,概括智能制造推进内容及策略。以江苏大中电机股份有限公司相关项目为例,介绍智能制造的侧重内容、实施步骤、原则及实施成果。结果表明：总体生产效率提高了35.75%,生产运营成本降低了26.21%,产品不良率降低了75.84%。在此基础上概括电机行业智能制造推进参考战略,为中小型电机行业发展提供支持。     

模具敏捷制造系统研究

针对模具设计制造过程复杂、条件苛刻和单件或小批量生产的特点 ,论述了模具产业发展敏捷制造技术的必要性。提出了模具敏捷制造系统框架和基于STEP与特征技术实现信息集成与过程集成的运行机制。阐述了基于Internet/Intranet的开放式可视化协同工作平台的模具敏捷制造实施方案。     

基于多代理的制造执行系统的研究

制造执行系统作为连接计划管理系统（ERP/MRPⅡ）和生产控制系统的桥梁与纽带，对车间层生产调度的优化，生产过程的改进等方面起了重要的作用，文章对制造执行系统的制造模式进行研究的基础上，提出了基于多Agent的制造执行系统的应用框架结构，并对基于多Agent的制造执行系统的调度系统进行了研究，最后给出了制造执行系统的调度算法结构。     

银基电接触材料改性及制备工艺

概述了银基电接触材料的发展,介绍了Ag-Ni、Ag-C、Ag-WC和Ag-MO4个主要系列的银基电接触材料的特点及其改性方法,比较了不同银基电接触材料改性前后的优缺点。同时,叙述了粉末冶金法、合金内氧化法及预氧化合粉末法等银基电接触材料的制备工艺。最后指出,提高银基电接触材料的性能、发展新型的节银触头材料和复合触头材料是今后银基电接触材料的发展方向。