具有随机提前期的库存模型中安全因子的优化

建立了一个二级配送系统库存模型,在零售商和供应商库存均采取连续检查控制策略假设下,针对零售商的提前期随供应商的缺货量随机波动这种情形,分析了供应商和零售商关于其安全因子的决策问题.分别求解并研究了双方在分散决策与合作决策的情形下的最优安全因子模型,并通过算例验证了模型的主要结论.     

电力物资复合泊松需求下的最优订货量

以上海电力公司的物资供应体系为背景,给出了（T,Q）库存策略下服从复合泊松分布的电力物资最优订货量的算法。建立复合泊松分布下的库存成本模型,对此模型用闭式算法求得其最小库存成本下的最优订货量,将该算法应用于电力物资进行实证分析。数值结果表明,与传统的报童模型相比,本文提出的最优订货量算法更适用于间断需求。     

A spectral stochastic element free Galerkin method for the problems with random material parameter

This paper presents a spectral stochastic element free Galerkin method (SSEFGM) for the problems involving a random material property. The random material property and resulting system response quantity are represented by a probabilistic spectral expansion techniques (Karhunen–Loeve expansion and Polynomical Chaos series, respectively) and implemented into the element free Galerkin (EFG) analysis. Numerical solutions in 1D linear elastic problem with random elastic modulus are introduced, and compared with those of Monte Carlo simulation (MCS) so as to provide the validation of the proposed approach. The present SSEFGM approach can produce a probabilistic density distribution as well as a first‐ and second‐order statistical moments (mean and variance) of response quantity by a single calculation, which is distinguished from an iterative MCS. Moreover, the method is based on an element free analysis so that there is no need of nodal connectivities, which usually require more time and labourious task than main calculations. Thus the proposed SSEFGM approach can provide an alternative analysis tool for the problems contains a stochastic material property, and demands complex mesh structures. Copyright © 2004 John Wiley & Sons, Ltd.     

Improving Profitability with Quantity Discounts under Fixed Demand

Quantity discount schedules have been studied, in the past, from the retailer's, and not the supplier's, point of view. These studies address the problem of determining the economic order quantities for the retailer, given a quantity discount schedule set by the supplier. In this paper, this problem is addressed from the supplier's point of view, assuming that the retailer always uses his optimal order quantity. It is shown that under certain circumstances, quantity discounts could be of benefit to the supplier (and obviously to the retailer), even when retailer's demand is insensitive to price changes. An algorithm is developed to determine the optimal pricing policy for a linear quantity discount schedule. Numerical examples are provided, and sufficient conditions when no quantity discount should be offered are derived.     

Order Quantity, Product Popularity, and The Location of Stock in a Warehouse

In the assignment of warehouse space to inventory items, the amount of space allocated to each item is traditionally determined on the basis of inventory or production cost considerations. Actual assignment of items to storage locations within the warehouse is then carried out independently, with the space requirements taken as given. Assuming an out-and-back order picking procedure and the simple economic order quantity inventory model, it is demonstrated that the quantity and location problems must be considered simultaneously in order to achieve a minimum total cost (order picking cost plus inventory cost). An iterative solution procedure, based on a gradient search, is developed and applied to a test problem.     

A periodic review inventory model with loss-averse retailer,random supply capacity and demand

This paper studies a periodic review inventory model with random supply capacity and demand, where the retailer is loss-averse. For the single-period problem, it is shown that the retailer will not order unless the initial inventory level is less than a critical value, and the order-up-to level is generally not a constant. Moreover, the critical value and optimal order quantity are only dependent on the random demand and independent on the random capacity. We also investigate the impacts of loss aversion, price and cost on the optimal order quantity and maximum expected utility. Then a dynamic programming approach is used to analyse the retailer’s ordering policy in the multi-period case. In each period, if the initial inventory level is above a given value, an order will not be placed. Otherwise, the upper bound on the optimal order quantity is given. The numerical experiments are conducted to illustrate the optimal ordering policies.     

影响柴油机喷雾数值模拟精度的若干因素分析

为探明影响柴油机喷雾数值模拟精度的若干因素，采用通用商业软件FLUENT对柴油机喷雾特性进行了CFD模拟计算，分别研究了网格尺寸、喷雾粒子数和最大时间步长对油束几何形状及油束贯穿距的影响．结果表明，网格划分的精度和喷雾粒子数量的多少对计算结果的正确性和油束的几何形状有直接的影响，网格尺寸过大或喷雾粒子数过少则喷雾几何形状失真．最大时间步长对数值模拟的精度在一定的范围内影响是比较小的．     

Weibull分布变质物品库存模型研究

研究了变质物品在考虑资金时间价值时的经济订货批量问题.假定物品的变质率服从两参数的Weibull分布,物品的需求率与库存水平有关,且为库存水平的线性函数,计划时域内进行多次订货,订货时间间隔相等,允许缺货且短缺量完全拖后,以库存系统的总费用最小为目标函数,建立了变质物品在存货依赖性需求下考虑资金时间价值时的最优订货批量模型,分析了模型存在唯一的最优解的必要条件,并且给出了在该条件下求解模型最优解的算法,最后给出了一个计算实例.     

面向“货到人”拣选系统的一种随机调度策略

通过“货到人”拣选系统作业流程分析,提出了在分批下发订单任务的情况下的一种随机调度策略。以AGV (automated guided vehicle)完成所有任务的总时间最短为目标函数,以任务分配为决策变量,考虑进行调度时AGV所处的状态以及在完成任务过程中AGV在拣选台的排队等待时间,建立随机调度策略的数学规划模型。利用遗传算法进行求解,通过实例仿真,验证了随机调度策略较调度空闲AGV策略具有更高的拣选效率,同时解决了AGV调度与拣选序列问题,对AGV数量配置具有指导作用。     

Improving a supplier's quantity discount gain from many different buyers

We consider the pricing and inventory decisions of a vendor who supplies a single product to multiple heterogeneous buyers. The problem is analyzed as a Stackelberg game in which the vendor acts as the leader by announcing its pricing policy to all the buyers in advance and the buyers act as followers by choosing their order quantity and the sassociated purchasing price independently under the vendors' pricing scheme. We propose in this paper a pricing policy for the vendor that offers price discounts based on the percentage increase from a buyers' order quantity before discount. The proposed policy is defined as a discrete all-unit quantity discount schedule with many break points. We show that: (i) the proposed policy offers a higher price discount to a buyer ordering a larger quantity and hence complies with general fair trade laws; (ii) an explicit solution is obtained for the vendors' optimal decision; and (iii) although suppliers in reality normally offer price discounts based on a buyers' unit increase in order quantity, the proposed policy is superior for the vendor when there are many different buyers. Other benefits of the proposed pricing policy are demonstrated by numerical examples.     

白车身生产线规划中设备数量决策问题的Markov模型

提出一个Markov模型,用于解决白车身生产线规划中设备实际需求数量的决策问题.用Markov模型求解设备的故障率,进一步在设备理论生产能力的基础上,考虑设备故障率对生产能力的影响,得出实际生产能力,确定设备实际需求数量,并通过一个算例详细说明了应用过程,重在提出一种方法.     

Determination of economic order quantities (EOQ) in an integrated material flow system

The material flow system is the backbone of a manufacturing system as it provides both physical and operational structure. Each component (material handling, until load size, storage space, layout, etc) is a difficult problem to address on its own; however, it is imperative that components be addressed concurrently due to their interactions. This paper explores the relationships between the components in the material flow system with respect to determining the economic order quantity. This is in contrast to the traditional EOQ model, which considers only order cost, inventory cost, and demand, ignoring other material flow system issues. A multi-item economic order quantity (EOQ) model under a storage space limit is considered with respect to material handling equipment selection and requirements, unit load size, and flow path selection. The integrated material flow system problem is mathematically formulated as a large scale, nonlinear integer programming model and a heuristic solution procedure is developed. The impact of using an integrated approach to determine the EOQ is illustrated and solutions are compared to a lower bound. It is found that an integrated approach provides consistent and significant improvement in the overall solution quality.     

Adaptive finite element approximation of multiphysics problems: A fluid–structure interaction model problem

In this paper we consider finite element simulation of the mechanical response of an elastic solid immersed into a viscous incompressible fluid flow. For simplicity, we assume that the mechanics of the solid is governed by linear elasticity and the motion of the fluid by the Stokes equation. For this one‐way coupled multiphysics problem we derive an a posteriori error estimate using duality techniques. Based on the estimate we propose an adaptive algorithm that automatically constructs a suitable mesh for the fluid and solid computational domains given a specific goal quantity for the elastic problem. Copyright © 2010 John Wiley & Sons, Ltd.     

DISCOUNTING DECISIONS IN A SUPPLIER-BUYER RELATIONSHIP WITH A LINEAR BUYER'S DEMAND

In this paper, we analyze discounting decisions for a supplier with a group of homogeneous customers. We focus on two aspects: the gaming nature of the discount problem and the demand consideration in the process. We use a general quantity discount schedule and start with the Stackelberg equilibrium of the problem. It is shown that, for the seller to gain from quantity discount, he has to set up his quantity discount schedule such that the buyer will order more than his EOQ. Both the seller and the buyer can gain significantly from quantity discount. The incentive for discount is twofold: reducing inventory related cost and attracting more demand from the customers. In addition, quantity discount schedule can be very efficient in obtaining the maximum gain the seller and the buyer can possibly obtain together.     

A branch-and-bound algorithm for the concave cost supply problem

Effective supplier selection and allocation of order quantity among multiple suppliers are indispensable to the success of a manufacturing company. While companies have begun to turn into a comprehensive multi-criteria approach, most buyers still consider purchasing cost to be their primary concern in selecting their suppliers. In this paper, we consider the concave cost supply problem where a manufacturer seeks to select the suppliers and simultaneously procure the quantity of material/component required for production at the minimum total cost during a standard production period. We provide and validate an effective and efficient branch-and-bound algorithm that is finite and that finds the global optimal solution of the problem without any restrictions on the cost functions or on the set of input parameters used in the problem. Numerical experiments are conducted to evaluate the performance of the proposed algorithm.     

Statistical modelling of Poisson/log normal data

In statistical data fitting, self consistency is checked by examining the closeness of the quantity chi(2)/NDF to 1, where chi(2) is the sum of squares of data minus fit divided by standard deviation, and NDF is the number of data minus the number of fit parameters. In order to calculate chi(2) one needs an expression for the standard deviation. In this note several alternative expressions for the standard deviation of data distributed according to a Poisson/log-normal distribution are proposed and evaluated by Monte Carlo simulation. Two preferred alternatives are identified. The use of replicate data to obtain uncertainty is problematic for a small number of replicates. A method to correct this problem is proposed. The log-normal approximation is good for sufficiently positive data. A modification of the log-normal approximation is proposed, which allows it to be used to test the hypothesis that the true value is zero.     

A solution to the multiple set-up problem

This note finds the optimal order quantity for the multiple set-up problem. The solution is obtained by a direct method.     

Risk intermediation in supply chains

This paper demonstrates that an important role of intermediaries in supply chains is to reduce the financial risk faced by retailers. It is well known that risk averse retailers when faced by the classical single-period inventory (newsvendor) problem will order less than the expected value maximizing (newsboy) quantity. We show that in such situations a risk neutral distributor can offer a menu of mutually beneficial contracts to the retailers. We show that a menu can be designed to simultaneously: (i) induce every risk averse retailer to select a unique contract from it; (ii) maximize the distributor's expected profit; and (iii) raise the order quantity of the retailers to the expected value maximizing quantity. Thus inefficiency created due to risk aversion on part of the retailers can be avoided. We also investigate the influence of product/market characteristics on the offered menu of contracts.     

Evaluation of performance measures for multi-part,single-product kanban controlled assembly systems with stochastic acquisition and production lead times

We consider the following kanban-controlled, multi-stage production assembly system. A number of raw parts are acquired from various suppliers and assembled into a single product. The raw-part acquisition lead times, the production lead time and demand arrival are all random variables. The raw-part acquisition order is made when the inventory level of the common part buffer, consisting of a number of sets of raw parts where a set of raw parts forms a single product, depletes to a reorder point. A production stage consists of the input queue, the output buffer, and the kanban board. The finished product can be backordered with a given allowable quantity. The problem is to evaluate the various system performance measures for a given set of design parameters: the raw-part batch order size, the common buffer size, the reorder point, the number of kanbans circulating in each production stage. A system is decomposed into a number of semi-autonomous Markov processes. A mathematical model is formulated and an iterative algorithm is proposed to evaluate system performance measures. Extensive numerical experiments with simulation analyses show that the computational time is very short and the model proposed is reasonably accurate. Thus, resorting to a genetic algorithm we can find an optimal set of system design parameters.     

DVD在线租赁问题

考虑到客户租赁DVD的具体时刻和租赁时长的概率分布,并根据其相互关联关系,对其概率分布进行修正.在对租赁过程进行详细分析的基础上,得到了保有量与DVD租赁周期的公式,建立了保有量的概率模型,根据实际数据和相关参数可以得出具体问题的数值解.此外,对不同周期下的DVD保有量进行了测算,并对不同周期分布、不同时间跨度下的保有量进行了分析. 对于给定定单租赁的优化问题,建立了具有现有存量限制条件下的0-1规划模型,并运用Lingo软件对问题进行了求解.对于给定定单的情况下的保有量优化问题,在没有限制存量的条件下,可以根据每份定单分别充分满足贪婪策略,得到用户满意度最大的DVD租赁的日需求量,进而给出日定单的保有量最优策略和满足给定用户群的分配策略.