ERW钢管考虑动态库存和交货期的多阶段生产计划优化方法研究北大核心

多阶段生产计划在钢管制造企业中起着重要的作用,在学术研究中也具有一定的复杂性.由于企业库存与生产及计划密切相关、订单交货期对生产和库存又具有很强的关联性,在研究中将库存的动态性和交货期纳入多阶段生产计划中,试图寻求找到优化的生产计划的方法.根据ERW直缝焊管企业的生产特点,对其生产计划的制订方式进行了优化.针对多阶段生产计划建立了考虑库存和交货期的提前/拖期惩罚数学模型,通过遗传算法对其进行求解及优化,从而得到生产计划的较优解.     

ERW钢管考虑动态库存和交货期的多阶段生产计划优化方法研究

多阶段生产计划在钢管制造企业中起着重要的作用,在学术研究中也具有一定的复杂性.由于企业库存与生产及计划密切相关、订单交货期对生产和库存又具有很强的关联性,在研究中将库存的动态性和交货期纳入多阶段生产计划中,试图寻求找到优化的生产计划的方法.根据ERW直缝焊管企业的生产特点,对其生产计划的制订方式进行了优化.针对多阶段生产计划建立了考虑库存和交货期的提前/拖期惩罚数学模型,通过遗传算法对其进行求解及优化,从而得到生产计划的较优解.     

活动长度有限制的多工序批量加工生产计划研究

当前的化工制造中,有很多工厂使用柔性制造设备,并采用批生产模式来组织生产.由于对设备进行准备和清理的成本比较大,加工的排序一般采用多批次加工同一种产品的活动（campaign）模式.在实际的生产中,由于需要保证产品质量和减少库存,应该考虑限制活动的最大长度.本文针对活动长度有限制的多工序批量加工问题进行研究,利用状态-任务-网络概念和层级模型方法,提出了修正的活动计划模型.该模型是基于混合整数线性规划模型,并且以供应网络内总生产成本和物流成本最小化作为目标函数.最后用一个算例来说明所构建模型的有效性.     

基于系统动力学的多客户供应链库存控制研究

为了研究客户目标库存量变化以及订单方式调整对贸易商供应链库存控制的影响,构建多客户供应链系统动力学模型.在局部信息共享条件下,定量的比较了目标库存量变化对贸易商供应链库存的影响;改变参数设置,模拟了在订单方式调整下供应链库存的波动性.结果表明,客户目标库存量的增加降低贸易商供应链成本;全年订单量给定条件下的多频次小批量订单方式加强供应链库存系统稳定性.     

服装供应链牛鞭效应仿真研究

根据系统动力学建模原理,构建了由S服装公司、直营店和加盟商组成的二级服装供应链系统动力学模型,通过改变模型中S公司的库存调整时间、库存覆盖周期以及运输延迟时间,观察系统模拟仿真运行结果中的订单波动、累计缺货变动情况,提出改善牛鞭效应和削弱累计缺货的措施.研究结果为S服装公司库存控制与优化提供了理论依据,对服装供应链库存控制亦有参考价值.     

面向单产品随机需求的计划期产能决策

国内传统中小生产企业面临的市场需求复杂多变,其生存和发展受到极大挑战.在人工作业系统中,生产线的产能主要取决于工人的数量、掌握技能数及技能水平.在备货型生产模式下,对于只生产单产品的生产线,当计划期内产品需求随机波动性特征明显时,将导致产能与需求的不匹配.考虑工人的薪酬、培训成本,需求工时小于基本产能的库存成本,需求工时处于基本产能与最大产能之间的加班成本,需求工时超过最大产能的加班及外包成本,以员工多技能及各工序生产速率平衡为基础,对计划期初生产线所需的工人数量进行决策,构建总生产成本优化模型,采用极值法对最优解进行求解及分析.通过算例验证了模型的有效性,对员工薪酬、库存成本、加班成本、外包成本系数以及产品单件工时、需求均值及标准差等进行了敏感性分析,得出的结论是:产品单件总工时、需求均值对最优工人数量及总生产成本影响很大,其他各类成本系数对其也有一定影响.尽可能降低单件总工时、提高需求预测准确性等有利于企业控制生产成本.     

多工厂环境下考虑个体利益的多目标协同生产计划模型及算法

针对由多个工厂组成的分布式系统,考虑不同工厂的个体利益诉求,构建了多目标协同生产计划模型。在该模型中,以最大化整体收益作为第一个优化目标;同时,基于亚当斯的公平理论,利用偏离系数法,以最小化个体收益平衡偏差作为第二个优化目标。结合模型结构特点,基于快速非支配排序遗传算法,设计了相应的求解过程。最后,通过一个算例验证表明,本文设计的计划模型和求解方法,不仅可以从网络集成角度协调各个工厂的生产、库存和运输活动,而且能够实现整体利益和个体利益非一致性的最小化。     

一类梯形需求且允许缺货的两货栈库存系统的最优补货策略

已有关于梯形需求的产品库存问题多集中在单一货栈的框架内讨论,而这一需求类型的两货栈问题还鲜有被研究.对此,在允许缺货的条件下,考虑租用货栈以及拖后延迟补货的情况,建立了以系统平均成本最小为目标的两货栈库存模型,从而将现有基于梯形需求的库存问题作了进一步扩展.然后分析了此类库存系统最优策略的存在性和唯一性,并提供了求解模型的算法,最后用数值例子和敏感性分析对所建模型进行了说明.     

基于IGA的供应链库存成本优化研究

随着市场竞争的加剧,企业之间的竞争已经演变为了供应链之间的竞争.传统的库存管理主要侧重于单个企业的库存最优,而供应链环境下的库存管理需要最大程度地实现供应链的库存整体最优.本文分析了供应链环境下的库存成本结构和供应链内成本,在此基础上,建立了多个供应商、一个核心制造企业、多个分销商的供应链库存成本模型,在分析免疫遗传算法(IGA)原理的基础上,详细说明基于免疫遗传算法的供应链库存成本模型的求解方法,最后通过算例仿真验证了模型和算法的可行性和有效性.     

基于产品可持续制造过程的多目标决策

研究产品制造过程对经济、环境和社会的影响,使其具有可持续性。以资源约束为主线,考虑产品制造过程中可回收利用材料的使用比例,结合制造过程中安排操作工人的人数,综合优化产品制造过程的生产成本、排放物及单位工人的工作量。建立多目标优化模型,设计专门的非支配遗传算法(NSGA-Ⅱ),获得全局的Pareto最优解集。通过敏感性分析,获得模型中权重系数的合理取值,以及操作工人、可回收利用材料、原始材料的单位成本对模型结果的影响,可以使决策者在制定产品的可持续制造决策时有所依据。文中通过定量分析的方法,对可持续制造的决策理论进行了深入研究。     

Recent developments in Dual Resource Constrained (DRC) system research

Real world manufacturing systems are usually constrained by both machine and human resources. Human operators are often the constraining resource and transfer between workstations to process jobs when required. This kind of system is known as a Dual Resource Constrained (DRC) system and presents additional technical challenges which must be considered during planning and scheduling. These technical challenges can be categorised into the five main dimensions of job release mechanisms, job dispatching, worker flexibility, worker assignment and transfer costs. This paper aims to provide an overview of recent developments in DRC research concerned with each of these areas and also discusses some possible approaches to solving the resource scheduling problem in a DRC system. The focus is on materials published after 1995 and up to 2009. Previous reviews on DRC systems are commented on and followed by a review of recent works associated with each of the five dimensions of DRC system research. Advancements made and new methodologies proposed are discussed and future research directions are identified.     

Reversibility and dependence in a U-shaped production line

We deal with a U-shaped production line with multiple machines and a multifunction worker. The worker visits machines in a cyclic fashion and operates an item on each machine. The operation consists of detaching the processed item from the machine, sending it to the next machine, putting the new item on the machine and switching it on. Walking times of the worker and processing and operation times are i.i.d. random variables for each machine. We show that the sum of the firstn cycle times is stochastically the same as that in the reversed system where machines are arranged in the reversed order. We give examples where the distributions of waiting and cycle times depend on the machines, called starting ones, where the worker begins operation at time 0. A sufficient condition is derived under which the limiting expected waiting and cycle times do not depend on the starting machines.     

产业结构调整路径优化模型

从动态系统的角度,对产业结构调整过程进行研究.建立了产业结构调整过程优化决策模型,应用动态规划对该模型的求解给予讨论,并根据该模型的特殊性,提出简便算法.     

区域的外环境系统分析

本文分析了区域的外环境系统的影响因素,研究了各因素间相互作用的随机性,利用层次分析方法构造了外环境系统的评价模型,证明了动态排序原理,并给出动态排序权值的计算方法。     

A simulation model for determining variable worker requirements in a service operation with time-dependent customer demand

In a service operation where worker requirements have to be determined for short scheduling time periods with nonstationary customer demand, the assumptions necessary for applying steady-state solutions to elementary queueing models are usually violated. This paper describes a simulation study of the behavior of such a service operation. The results are compared with the steady-state solutions to a queueing model where individual scheduling time periods are assumed to be independent. It is found that if the system utilization is below a derived maximum value (based on a service level criterion), then the steady-state solutions are robust enough to explain the behavior of the system and can be used to schedule worker requirements.     

关于M/M/n排队模型的动态解及稳定性

文章讨论动态 M/M/n排队模型 ,运用算子半群理论证明了该模型动态正解的存在唯一性 .并进一步表明零点是系统的一个本征值 ,相应的本征函数为系统的一个定态正解 ,系统的动态正解强稳定到定态解     

Infinite-horizon minimax control with pointwise cost functional

This paper is devoted to the discussion of a minimax optimal control problem over an infinite-time horizon, where the functional to be minimized is the highest instantaneous cost that may occur under the worst combination of disturbances. The problem is formulated for a general stationary discrete-time dynamic system, and a dynamic programming algorithm is proposed for its solution. The relationship existing between the cost functional associated to a control law and the reachability properties of the resulting controlled system is discussed.     

About the properties of excitability and transparency in positive systems with point delays

In this paper, the properties of positivity, excitability and transparency are discussed in time-invariant time-delay continuous-time systems subject to constant point delays. The properties might be investigated under simple tests on the parameterizations of the given continuous-time positive system and two associated ones. One of these systems is obtained by discretization of the given system while the other one is parameterized with the use of the influence graph of the original system. A dynamic economic Leontief-type model is discussed according to the presented formalism.     

Human resources scheduling to improve the product quality according to exhaustion limit

The role of human resources in manufacturing systems is very significant, and without efficient human resources we encounter high-price products with low quality. To improve the efficiency of human resources, we need to provide an optimal working schedule for each worker in production period. In this paper, we proposed a mixed-integer nonlinear model to find the best working schedule based on product quality cost and workers reliability. In this model, if the worker’s exhaustion level reaches a specific limit, the worker can rest to increase his reliability level and an accommodator should work instead of him. Since the proposed model is NP-hard, we used an artificial immune system to provide the best working schedule. The results indicate that this model can provide efficient and effective human resources schedule in manufacturing systems.     

动力学系统参数辨识问题最优控制解的理论与方法(Ⅱ)——随机系统参数辨识及应用实例

基于文(Ⅰ)(《应用数学和力学》,1998,20(2))的内容和随机最优控制理论,本文首先介绍了随机动力学系统参数辨识问题最优控制解的概念.然后讨论了建立参数辨识问题HJB方程的过程以及参数辨识的算法.最后给出了一个应用实例:解决动力学系统局部非线性参数辨识问题的方法.