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.     

一类变质物品的最优存贮策略

文章研究了一类变质性物品的最优存贮问题，假定需求率是一个变量，且依赖于库存水平，在瞬时到货和常数变质率的前提下，就允许缺货情形，建立了库存模型，模型解的存在性和唯一性，找到全局最优解，就得到了最优订货策略的求解方法。     

短缺量拖后率与价格折扣相关变质品VMI模型

考虑短缺量拖后率与订货商给予顾客的价格折扣正线性相关,提出一种需求指数时变的变质物品供应商管理库存模型,研究了供应链最优库存策略。数值仿真和主要参数灵敏度分析表明,订货商在缺货期间向顾客提供价格折扣有利于降低丢单损失和系统库存总成本;当需求增长因子变化时,VMI系统应保持库存控制策略不变;当变质系数和拖后率上限变大时,VMI系统则应保持订货商补货次数和价格折扣不变,同时适当降低订货商服务水平。     

基于Weibull函数的易逝品库存优化模型研究

研究了变质率服从Weibull分布的易逝品库存优化问题.在固定订货周期内,针对需求依赖于瞬时库存水平且允许缺货的情况,采取部分延迟订货策略,建立了以单位时间平均总成本最小为目标的易逝品库存优化模型,给出了模型存在唯一最优解的条件,并应用牛顿迭代法对该模型进行了求解.通过实例验证了该模型的有效性和可行性,对模型中的需求率、变质率和延迟订货率等参数进行了灵敏度分析.     

具有有效期易变质品的最优补货策略研究

易变质物品库存管理策略一直是实务界与学术界高度关注的问题,其中具有有效期易变质物品的最优补货策略是研究中的难点。本文研究了有限销售时域内具有有效期易变质物品的库存补货策略,在物品的需求率依赖于物品的库存水平,且物品有效期已知的假设下,本文建立了一个确定易变质物品最优补货策略的优化模型,并给出了具体的求解算法。文章最后给出了数值算例,并对模型中的相关参数作了敏感性分析。     

变库存费且考虑残值的变质性物品最优模型研究

经典的EOQ模型通常假定库存费是不变的,在本文中,我们考虑库存费是可变的．在需求率线性依赖于库存水平的情况下,完善了这个变库存费的EOQ模型．本模型研究物品变质后有残值且经过处理后仍可销售,理论上证明了模型具有唯一的整体最优解,揭示了变库存费对库存系统最优订货策略的影响．     

时滞变质物品库存与运输联合优化模型

针对一类有保鲜期的易腐品——时滞变质物品,考虑需求受价格、广告投入及存货陈列量的影响,在允许缺货和不同的短缺量拖后率下建立该类物品的库存与运输联合优化模型,并针对模型特点设计出一种启发式算法,从而得到最优库存策略及运输策略。给出算例,利用MATLAB7的最优化求解功能容易求出模型的最优解。结果表明:引入由价格、广告和存货陈列量共同决定的需求率,不仅更符合实际,而且有利于将复杂模型转化为关于多项式的问题来处理,大大降低了求解难度,同时节约了求解时间。     

部分短缺量拖后且考虑最终产品变质的VMI模型

在无短缺量拖后或短缺量完全拖后的VMI模型基础上,进一步考虑缺货期间出现短缺量部分拖后的情况,建立了包括一个供应商和多个订货商、从原材料到产成品且最终产品出现变质的供应商管理库存（VMI,Vendor-Managed Inventory）模型,给出了数值算例和主要参数的灵敏度分析,结果表明顾客服务水平、丢单系数及最终产品变质率对供应链各成员的单项成本及集成总成本均有不同程度的影响,为VMI库存系统的管理决策提供了理论依据。     

基于延期支付的非立即变质物品的库存模型

一类短质期变质产品,如生鲜蔬菜、水果等,增加其库存展示量能为顾客提供更多的拣选机会,从而刺激顾客增加购买量.对此,在供应商给予零售商固定延期支付期限且在综合分析已有变质物品的库存模型的基础上,建立了一个更能准确反映当前存货水平和需求率的库存模型.模型中以零售商的年总费用最小为目标讨论了模型的最优解,通过模型的分析求解,得到零售商的最优订货周期及最优订货量的简单判定方法.通过具体算例,结合灵敏度分析,分别分析了物品的固定保鲜期、物品的变质率及供应商给与零售商的延期支付期限对零售商最优订货策略的影响.     

时变变质率产品的订购-定价策略

研究时变变质率产品的订购与定价联合决策问题。以系统平均利润最大化为目标函数且将已变质产品的变质处理成本考虑在内,构建了相应的订购与定价联合决策模型,其中需求同时依赖于价格和库存水平、系统允许缺货且缺货量部分延迟订购。接着,对于已知的定价策略,证明并给出了最优补货策略唯一存在的充分条件;另一方面,对于已知补货策略的情况也证明了最优定价策略的存在性。此外,证明了在联合订购与定价决策下得到的最优销售价格总是大于单独进行定价决策时得到的最优价格。进而,在模型证明和分析的基础上给出一个寻求最优解的算法。最后,通过数值模拟的方法对模型中主要参数的灵敏度进行了分析,并给出相应的管理建议。结果表明：如果零售商忽略库存水平对需求的影响或变质处理成本,制定的销售价格将偏低;对于价格弹性较高的产品,零售商应采取低价销售策略;当顾客的等待耐心较差或产品的替代性较强时,最优策略应该是提高产品的销售定价并缩短缺货期。     

Advance demand information and a restricted production capacity: on the optimality of order base-stock policies

This paper considers the optimality of order aggregation in a single-item production/inventory problem with advance demand information and a restricted production capacity. The advance demand information is modeled by introducing a positive customer order lead time. The paper proves, when customer order lead times are less than a threshold value, it is allowed to aggregate the orders over time when establishing the optimal production decision. This implies the optimality of an order base-stock policy. It shows also that in case of linear inventory cost, the positive effect of advance demand information is equal to a cost reduction that is proportional to idle time and foreknowledge horizon. The results hold for the backlogging case as well as for the lost-sales case.     

Optimal joint replenishment policy for multiple non-instantaneous deteriorating items

In this paper, we deal with the problem of determining the optimal economic operating policy when a number of non-instantaneous deteriorating items are jointly replenished. We establish a multi-item joint replenishment model for non-instantaneous deteriorating items under constant demand rate allowing full backlogging. This problem is challenging, in particular, the cost function is a piecewise function with exponential parts, which makes the problem more complicated. To solve this problem, an approximation method is used to simplify the objective function and a bound-based heuristic algorithm is developed to solve the model. Numerical examples illustrate the effectiveness of the proposed method and the quality of the approximation. Experimental results on a real-life case study show that the proposed model can achieve substantial cost savings compared to the individual replenishment policy for non-instantaneous deteriorating items. Furthermore, sensitivity analysis of key parameters is carried out and the implications are discussed in detail.     

Optimal control of a stochastic production–inventory system under deteriorating items and environmental constraints

In this paper, we present an optimal control model of a stochastic production–inventory with deteriorating items, emission tax and pollution abatement investment. In our model, the emission tax is levied on the firm’s environmental obsolescence rate of technology rather than the total amount of the environmental externality. Our objective is to apply Hamilton–Jacobi–Bellman (HJB) equation to solve the stochastic production–inventory system with deteriorating items, emission tax and pollution abatement investment; and derive the optimal production rate and pollution abatement investment rate that maximise the objective function value. The results are discussed with some illustrative examples for different demand rate functions, and sensitivity analysis is conducted to study the effect of changing the parameters and coefficients on the objective function value.     

可控制前置时间需求分布未知的部分缺货待补混合库存策略

同时考虑可控制前置时间与货币时间价值两项因素,假设前置时间内需求量的概率分布未知,建立了部分缺货欠待补混合库存模型,并对混合库存模型进行了数值验证.研究证明,混合库存模型的总变动成本函数为凸函数,然而由于前置时间内的随机性需求量会造成无法求取期望缺货量的精确值,因此采用最小最大准则找出具有最大期望总成本的现值函数,进而求取使得期望总成本现值为最小的最优值,以确定最优订购策略.     

Joint inventory-and-pricing strategy for a stochastic continuous-review system

We analyze an infinite-horizon continuous-review stochastic inventory system in which the selling price and inventory replenishment are determined simultaneously. The demand process is Poisson with a price-dependent arrival rate. The ordering cost includes a fixed setup cost and a variable cost proportional to the order quantity. We obtain closed-form solutions for the optimal inventory control strategy and optimal pricing strategy, which provide managerial insights as well as quantitative and qualitative relationships between decision rules and system parameters. We show that the optimal price is a unimodal function of the inventory level. We also develop efficient algorithms to compute the optimal strategies and present numerical examples.     

基于需求依赖库存的变质性商品最优库存-配送模型

超市型销售终端中商品展示水平的“选择效应”和“广告效应”,使得商品需求在很大程度上依赖其库存展示水平。针对这一实际情形,假设销售商在此类终端销售某一变质性商品,其中需求线性依赖于该商品当前库存水平,当库存水平下降到一定量时,立即从配送中心运送商品对超市库存进行补充。以单位平均利润最大化为目标构造相应的库存-配送模型,使用最优化理论讨论了模型最优解的存在性及唯一性,并提供寻求模型整体最优解的算法,以此求出最优的库存与配送方案。最后给出了数值例子,分析了模型参数变化对系统最优策略和利润的影响。     

Economic ordering model for deteriorating items with random demand and deterioration

In modern marketplaces, competitive products frequently face volatile demand. In particular, the majority of deteriorating items are frequently subject to dual uncertainty, simultaneously suffering from demand and deterioration. Accordingly, this study attempts to develop an economic ordering model for a newsboy-style deteriorating item with lognormal demand and Poisson-type deterioration. Finally, an effective and practical economic ordering model involving deteriorating inventory is developed for optimising the order quantity of a given deteriorating item during an upcoming selling period to maximise expected profits of retailers. Numerical examples demonstrate that, as expected, the proposed economic ordering model can obtain an optimal solution for the inventory problem involving deteriorating items under uncertain and random demand and deterioration.     

Economic production quantity models for deteriorating items with rework and stochastic preventive maintenance time

Economic production quantity (EPQ) models for deteriorating inventory have been investigated by many researchers in recent years. In this paper, we develop EPQ models for deteriorating items with rework and stochastic preventive maintenance time. The models are solved using a search method, since a closed form solution cannot be derived. A numerical example and sensitivity analysis are provided to evaluate the models. The sensitivity analysis shows that the deteriorating cost has a significant effect on the optimal inventory cost; however, the production and the demand rate have the most significant effect on the optimal total cost and the optimal production up-time period.