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.     

基于承诺交货期的两阶通用件库存模型

在一个两阶段生产系统中,针对第二阶段应用单通用件的情况,引入承诺交货期因素,分别建立了第一阶段无通用件、单通用件、双通用件库存模型,考查了承诺交货期对通用件库存模型总成本的影响,分析了三类模型相应的最优库存水平。通过算例,说明了在一个第二阶段采用单通用件的两阶段生产系统中,当通用件与非通用件的单位采购成本相同时,并非第一阶段使用越多的通用件,总成本就越低。     

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.     

不确定条件下基于三元区间规划的生产计划模型

研究了不确定条件下的生产计划问题,当企业面临多种产品消耗的单位产能、单位生产利润以及企业的总产能和交货期等均为不确定变量时,如何确定出的各种产品的合理的投产量,以使得企业在规定的交货期内获得最大的收益.引入了三元区间数来描述生产计划模型中的各种变量,建立了相应的三元区间线性规划模型;然后利用三元区间线性规划的有关知识简化了该模型,求出了其弱最优解.模型与传统的生产计划模型相比更贴近生产的实际过程,能为生产决策者提供更好的技术支持.     

集中式供应链的生产与库存分配联合决策

考虑一个由单一制造商和多销售点构成的二级集中式供应链,制造商采用积欠订货策略生产和销售产品,因而面临生产、运输和积欠订货型库存分配与补货的联合决策问题.综合考虑了延迟交货成本、库存持有成本、运输成本和生产成本,建立了最大化总利润的非线性混合整数规划模型,以联合优化供应链的生产、运输及库存分配方案.证明了最优的产品生产分配方案应该具有的结构性质:各个销售网点在任意销售间隔期末同时出现缺货或者库存剩余.同时,提出了基于逐级求解策略的分层求解算法,保证了解的全局最优性.最后,敏感性分析表明:单位产品的库存持有成本与延迟交货成本对最优分配次数及生产量的影响作用相反,固定运输成本也会影响制造商的分配方案及生产计划,但三者均不会影响每个间隔期末的产品分配方案(分配量).     

考虑机器调整次数和产品质量的卷烟批量计划和柔性流水车间调度集成问题

针对卷烟企业生产中的批量计划和柔性流水车间调度集成问题,构建了整数规划模型,目标函数由卷烟生产时间、生产线调整次数、卷烟质量、库存成本四部分组成。鉴于该问题的NP-hard性,设计遗传算法进行求解,通过合理设计遗传算子,避免不可行解出现。应用某卷烟企业数据得到优化排产结果,与该企业之前依照经验排产方案进行对比,发现优化排程结果在减少品牌转换次数,提高生产的连续性方面具有明显优势。该算法已作为某卷烟企业排产人员的排产参考,应用于排产决策中,取得了良好的效果,对卷烟企业制定排产计划具有一定的实际指导意义。     

变换核估计在未知需求分布函数条件下多阶段库存控制策略中的应用研究

传统的多阶段库存控制主要致力于库存持有以及过多库存的经济性研究.随机库存模型经常假定需求分布已知,这样可以产生容易解决的方案.但随着销售信息的不断更新,需求分布函数的参数常常未知.这样传统的多阶段库存模型很难产生最优的库存控制策略.当前文献对未知需求分布函数条件下的多阶段库存管理问题研究得不多,当需求分布函数随时间变化,是个多阶段随机规划问题,通常情况难以直接进行求解.针对一般非平稳需求,还缺少有效的库存管理方法.本文致力于变换核估计和优化理论相结合的方法研究未知需求分布函数条件下多阶段库存控制策略,提供一条多阶段库存控制的新思路.可以很好地确定各阶段的最优订货点、最高库存、最低库存等来达到整个系统的最优,从而节省更多的成本,达到营运资本的永久性减少、更高的销售量和客户满意度,从而增加企业的竞争力.     

需求不确定情况下的多周期生产批量决策

针对在市场需求不确定的情况下的中小制造型企业的生产批量决策优化问题进行研究,根据多周期生产情况下需求的不确定性,综合考虑缺货成本、库存成本和期初库存等因素,以多生产周期的总利润最大化为目标,建立生产批量决策模型,通过优化分析,得出其利润最大化下的最优生产批量,并通过敏感性分析讨论最优批量与多周期生产条件下的不确定需求等影响因素之间的关系.     

需求变化的多阶段EOQ订购策略

多阶段库存管理是供应链研究的重要课题,其中独立需求的订购策略问题,现有文献一般设定计划期内各阶段需求且计划执行过程中需求不再变化,给出了相应的算法.本文选择EOQ模型作为基本订购策略,研究下面一类需求变化的多阶段订购策略问题：给定费用参数（物资单价、一次订货费用、单位库存保管费用）的情况下,在订购计划执行过程中,在阶段i（1＜i＜m）需要调整阶段m的需求,而其它阶段的需求不变,订购策略如何调整,使得库存总费用最低.     

随机需求下多供应商和多零售商的生产-库存-运输联合优化模型

考虑随机需求下多供应商和多零售商的生产-库存-运输联合优化问题.在联合优化时,首先利用最近邻算法将各零售商分成不同区域,分区后问题转化为随机需求下单供应商对多零售商的生产-库存-运输联合优化问题.在每个分区内,由供应商统一决策其分区内各零售商的送货量和送货时间.利用粒子群算法和模拟退火算法相结合的两阶段算法求出最优送货量、最优运输路径和最大期望总利润.然后采用收入共享契约将增加的利润合理分配给各供应商和各零售商,使各方利润都得到增加,从而促使各方愿意合作.通过数值算例验证了联合优化模型优于独立决策模型.     

Formulating an objective for an economy

This paper is dedicated to the memory of E.M.L. Beale. Not a small part of Martin Beale's success in developing and solving large-scale mathematical programs is attributed to the care he took in properly formulating his models.Our presentation concerns our efforts to also properly formulate a model. Our model is an economic model used for technology assessment. In order for it to be useful, it is important that the dual variables represent as realistically as possible real world prices. This required us to formulate the model as a time-staged economic equilibrium model. Our main result is a proof that an equilibrium formulation using expected aggregate demand can under certain conditions be replaced by one in which the economy is driven by an aggregate utility or objective function, one that promotes economic growth subject to physical flow constraints. We show that such an objective function always exists except for populations consisting of significantly large classes of people whose consumption patterns differ radically one from another. Assuming that the latter is not the case, this equivalent formulation means that mathematical programming software can be applied to efficiently solve the model. This paper summarizes an extensive paper entitled Deriving a Utilty Function for the U.S. Economy [3]. The main theorems are stated without proof.The authors wish to thank Kenneth Arrow, Gerard Debreu, Robert Dorfman, Dale Jorgenson and Lawrence J. Lau for their helpful comments.Research of this report was partially supported by the National Science Foundation Grants DMS-8420623, SES-8518662 and ECS-8617905; U.S. Department of Energy Grant DE-FG03-87ER25028; Office of Naval Research Contract N0004-85-K-0343, Electric Power Research Institute Contract RP 5006-01, and the Center for Economic Policy Research at Stanford University.     

用L-预远域系算子、L-预外部算子或L-预边界算子确定L-预拓扑

给定集合X，设T（X）是X上的L-预拓扑的全体。本文证明了可以在R（X）（X上的L-预远域系算子的全体）、E（X）（X上的L-预外部算子的全体）和B（X）（X上的L-预边界算子的全体）上定义适当的序关系，使它们在一定条件下成为与（T（X），包含）同构的完备格。因此一个给定集合X上的L-预拓扑可以由X上的L-预远域系算子、L-预外部算子或L-预边界算子确定。     

Similarity of an operator to an isometric operator

Leningrad State University. Translated from Funktsional'nyi Analiz i Ego Prilozheniya, Vol. 23, No. 2, pp. 77–78, April–June, 1989.     

Numerical realization of an algorithm for reconstructing an inhomogeneous medium in an X-ray tomography problem

Under study is the X-ray tomography problem that is an inverse problem for the transport differential equation. We take into account the absorption of particles by the medium and their single scattering. The statement of the problem corresponds to multiple probing. The medium is unknown; while the densities of the outcoming flux averaged over energy are given. The object in question is the discontinuity surfaces of the coefficients of the equation. This corresponds to searching for the boundaries between various substances contained in the medium that we probe. The solution is constructive, and a numerical realization of the obtained algorithm is presented.     

An Embedding of an Ordered Groupoid into an le-Groupoid

In this paper we prove that each ordered groupoid (resp. semigroup) S embeds in a complete distributive le-groupoid (resp. le-semigroup) using the ordered groupoid (resp. semigroup) arising from S by the adjunction of a zero element.     

Estimating an interaction parameter of an infinite particle system

This article deals with the estimation of a parameter in the stochastic motion affecting an infinite number of particles. An estimator, based on a nonstationary time-series is considered and shown to be consistent. A comparison with more well-known estimates, via asymptotic variances, is also carried out.     

A case of an intervention in an outpatients department

This paper is an account of a case intervention, undertaken at a National Health Service hospital outpatients department. The intervention utilised a soft systems approach, to address gaps between the customers' and providers' expectations, and simulation was used within this framework. A procedure to reduce unexpected non–attendance of patients has been implemented. Patient bookings are now scheduled according to simple rules, with the result that in–clinic waiting times have been reduced. A model of the intervention process has been accepted by the key stakeholders as a sensible framework for continuing investigations. More widely, the participants increased their knowledge of their own systems. The results from the case suggest that the time spent following this approach may be worthwhile in some interventions, but there are concerns relating to the time needed, and the cost of such an approach. The paper provides a critique of the framework and the intervention, and concludes that this approach is probably viable in unpaid, collaborative, investigations where there is little or no cost. However, time and cost may prove prohibitive in the case of paid consultancy.     

Entropic repulsion of an interface in an external field

We consider an interface above an attractive hard wall in the complete wetting regime, and submitted to the action of an external increasing, convex potential, and study its delocalization as the intensity of this potential vanishes. Our main motivation is the analysis of critical prewetting, which corresponds to the choice of a linear external potential. We also present partial results on critical prewetting in the two dimensional Ising model, as well as a few (weak) results on pathwise estimates for the pure wetting problem for effective interface models.Mathematics Subject Classification (2000): 60K35, 82B41, 82B27