Effective production control systems are important for any manufacturing plant. In order to obtain effective production control, several different production control systems have been proposed. MRP, Kanban and CONWIP are the most popular systems among these. In this paper, a simulation analysis compares the three control systems implemented in a semi-continuous manufacturing environment: a cold rolling plant. Simulation results show us that the CONWIP production control system is the most effecient of these. It can greatly decrease the WIP (Work-In-Process), average inventory and average inventory costs, while providing a higher throughput rate and facility utilization.

The CONWIP production control system has received a great deal of attention from researchers recently. In this paper, we introduce a method to determine the card number of the CONWIP system for a production line with a bottleneck. The simulation study compares the CONWIP system and the original control system for the four situations in a cold rolling plant. Simulation results show that the CONWIP production control system is very elcient for the production and inventory control of semi-continuous manufacturing, such as that found in the steel rolling plant. It can greatly reduce the work-in-process (WIP), decrease the average inventory and average inventory costs, and guarantee a higher throughput rate and facility utilization.

With the rapid development of Internet and the emerging of global economic, VE (Virtual Enterprise), which is the alliance of stand-alone enterprise and usually organized in project mode, becomes a new paradigm of enterprise operation. On the one hand, VEs can help enterprises to respond rapidly to market demand by sharing capabilities, resources, and so forth. One the other hand, enterprises in a VE face more risks than conventional enterprises. Moreover, the risks in VE are always dynamic. Hence, risk management for VE has received many attentions. Risk evaluation is one of the key phases for the risk management. In this paper, focus on the characteristics of project organization mode and dynamic risk of VE, the evaluation model of dynamic risk for single procedure in VE is presented based on the Markov process. In the VE, the operation of each procedure is composed of different process, and there are many states within each process. The procedure passes these states randomly and the time needed, the quality and the cost needed within each state are different, so the risk is dynamic. The Markov process is used to describe this process, and case study suggests the effective of the method.

Production inventory-control is one of the most important aspects of a flexible manufa Cturing system (FMS) design. CONstant Work In Process (CONWIP), which is a hybrid of push-and-pull type systems, offers an alternative to effective utilization of the expensive FMS equipment while still meeting customer requirements, In the selection of an FMS control method, material handling often becomes one of the capacity-constraints which forms the basis of various resarch interests, In this paper, a structure-based model for a CONWIP-controlled FMS is proposed, and within it, the node type characteristics concept is used to describe the constraints in FMS. Furthemore, simulation is used to determne the card number based on the structure-based model. The simulation results demonstrate that the model is suitable for the design and operation of FMS. The model can be used as a manufacturing execution system of enterprise resources planning. An architecture for this integrated design based on Intemet/Intranet systems is also proposed.

根据电子商务环境下企业风险的特点，在建立企业风险模糊描述机制的基础上，基于模糊ISODATA聚类法，对企业风险管理的关键问题——企业风险分类进行研究。实例表明该方法是有效的。