On Improving Silver's Algorithm for the Joint Replenishment Problem

In this paper a general algorithm is proposed for improving Silver's algorithm for determining the economic packaging policy for jointly replenished items.     

An Improvement of Silver's Algorithm for the Joint Replenishment Problem

Silver's algorithm for the joint replenishment problem is modified and improved. Computational requirements due to this modification are relatively very small. Extensive experimentation shows that the errors of Silver's algorithm can, on the average, be reduced by an order of magnitude.     

基于总金额折扣的多物品联合订购模型

为了更好地模拟现实情况,将传统的基于总量折扣模型修正至基于总金额折扣的多物品联合订购情形。针对修正后的模型,给出了具体的求解过程和算法,给出了数值例子和参数敏感性分析。研究得出,在供应商提供总金额折扣时,部分订购的策略并不总是优于全部订购,而是随着不同的参数的变化而变化的。模型更符合实际,更容易运用于实际的生产销售的多产品订货中。     

车载可补货无人配送小车配送路径研究

无人配送小车由于不适合长距离运输,可与货车搭配完成“最后一公里”配送任务以增加服务范围,这对车辆路径优化问题提出了新的挑战。针对配送小车数量有限、城市配送货物量大且货车停靠限制的特点,提出无人配送小车可补货的大车-小车路径优化问题,即一辆货车搭载多台无人配送小车,由无人配送小车给客户送货,无人配送小车可在货车处补充货物并执行多行程配送。构建以总配送距离最短为目标的整数规划模型,针对此模型设计混合遗传大邻域搜索算法,在遗传算法基础上增加大邻域搜索算法对个体优化。在算法优化过程中先优化小车路径,再在小车路径基础上优化大车路径。数值实验表明,对于小规模问题,所提算法最多花费CPLEX求解时间的6%便获得最优解;在改造的Solomon数据上,所提算法相对于遗传算法平均有95.5%的计算结果优势,相对于大邻域搜索算法平均有7.2%的计算结果优势,且数据量越大,优势越大。     

考虑运输能力约束的VMI补货发货动态批量研究

考虑由一个供应商和多个零售商构成的VMI供应链,在供应商运输能力有限、可采用外包策略的情况下,研究了动态需求环境下供应链补货及发货批量策略问题.分析得出供应商最优补货及发货期结构满足"零库存补货"性质,进而利用动态规划方法提出一个多项式算法优化补货及发货策略,其计算复杂度为O(T3),且通过平衡各种成本,可得每个发货周...     

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。     

斜坡需求下延迟补货的高科技产品EOQ模型

高科技产品是科技发展的产物,对发展国家经济和提高人民群众的生活水平起着重要的作用。考虑高科技产品斜坡需求和延迟补货受时间和价格影响的特点,将顾客分为价格偏好者和时间偏好者,构造了2种不同的延迟函数,建立了相应的经济订货批量模型,采用数值仿真分析了系统主要参数对高科技产品订货策略和总利润的影响。研究结果表明：需求增长因子、价格敏感因子以及资金贴现率对订货次数和服务水平的影响比其它因素大;需求增长期长度、价格偏好者比例对服务水平的影响比订货次数大;计划期长度对服务水平的影响比订货次数小。     

整数比时间协调的VMI补货策略

针对确定性需求下单供应商两分销商的VMI供应链,运用整数比时间协调方法,即供应商的补货周期分别是两个分销商的补货周期的整数倍,建立了使供应商和两个分销商订单处理成本、生产准备成本、库存持有成本等总成本最小的系统优化模型,并对模型进行了求解,获得了供应商的最优补货策略组合。最后,用算例验证了理论建模与求解。     

分散协调VMI&TPL模式下的补货决策

提出分散协调供应商管理库存(VMI)与第三方物流(TPL)集成供应链管理模式。与传统VMI不同,该模式下的供应商拥有库存决策权,但将物流具体作业外包给TPL。从供应商角度出发探讨了该模式下的补货决策问题。本模型引入供应商与制造商之间的需求信息共享,同时考虑供应商与TPL之间的运费契约,运费是与补货量有关的分段函数。供应商根据制造商滚动计划期内的需求量、运费契约以及制造商线边仓库的存储能力等进行补货决策。通过将模型转化为动态网络规划问题,分析了模型的计算复杂性。由于该模型问题是NPC问题,给出了模型的模拟退火遗传算法。算例验证了模拟退火遗传算法解决该问题的有效性。     

易逝品联合采购订货决策分析

采购联盟成员间的信息不完全,彼此均以对方的期望需求作为对方实际需求的估计.针对易逝品的特点,提出了调剂价格的特殊约束条件并建立了联盟期望利润模型,最后进行了数值仿真.研究表明:联合采购使联盟总体利润得到改善,但不能使联盟成员的利润都得到改善.     

The Fixed-Charge Transportation Problem: A Computational Study with a Branch-and-Bound Code

This paper presents the computational experience obtained with an experimental branch-and-bound code for the fixed-charged transportation problem. The code calculates simple penalties and uses a modern transportation routine to solve the linear programming relaxation. The findings of the investigation are as follows: (i) the solution times for problems with similar variable and fixed arc costs are highly variable, but performance definately worsens as fixed costs increase relative to variable costs with demands remaining constant, (ii) computational times decrease as total supply increases if other variables are held constant, (iii) computational times tend to vary inversely with the ratio of number of destinations to number of sources for ratios greater than unity if other variables are held constant, and (iv) problems with about 200 arcs may be solved if the fixed costs do not play too large a role, while problems with fewer than 100 arcs may blow up. We found no way to predict solution time as a function of problem characteristics.     

带有横向调度的易变质商品两级库存系统分析与优化

在对库存控制策略研究的基础上,针对一对多的易变质商品两级库存系统,在需求率、变质率随时间变化和二级库存之间存在横向调度的情况下,建立了一对多的易变质商品两级库存优化数学模型,提出了基于牛顿法的求解算法,得出了在一定时间水平上的两级库存系统的最优控制策略。通过算例仿真验证了模型的正确性和求解算法的有效性。分析了两级库存控制参数与补货周期、系统总成本的关系,结果表明:在二级库存之间的横向调度不仅可以缩短补货周期,还可以有效降低库存系统的总成本;变质率的增加使得极大库存水平的波动加剧。     

Replenishment policy for a purchase-to-order seller: a tradeoff between ordering cost and delay cost

We consider replenishment decisions on when and how many goods to purchase for a seller under a purchase-to-order mode where there is no inventory and the seller purchases goods to fulfil orders already placed. For each purchase, there is a constant ordering cost. For each order, delay cost will be incurred if it is not fulfilled timely. Generally, the more frequent the replenishment, the higher the ordering cost but the lower the delay cost. Consequently, there is a tradeoff between the ordering cost and the delay cost for the seller to make replenishment decisions minimising the total cost. In this paper, we study three cases of the problem and investigate both offline versions and online versions according to the seller's knowledge about information of future orders. For offline versions with perfect information, we either develop an optimal policy, or prove it is NP-hard and develop an approximation policy. For online versions without any information about future orders, from the perspective of competitive analysis we prove the lower bound of competitive ratio for any possible online policy and present a 10-competitive online policy for the general case and a 2-competitive online policy for each of two special cases.     

含铰间隙的曲柄摇杆机构动力学研究

本文研究了含间隙的两个铝材料构件的碰撞动力学问题.通过ADAMS软件中的CONTACT工具建立相连接的两个构件之间的联系.通过设置不同间隙尺寸大小和曲柄旋转速度来研究转速和间隙对曲柄摇杆机构动力学的影响.结果表明:间隙越大、曲柄转速越高,机构的碰撞越严重.     

The Passage Problem for a Stationary Markov Chain

A Monte Carlo simulation experiment was performed to compare the resulting mean square error of two different Weibull estimation methods. It was found that the MSE for both methods was quite high in relation to the Rao-Cramer lower bound. Some suggestions are offered for reducing the MSE of estimates.     

The Flow-Shop Problem with Mean Completion Time Criterion

This paper discusses the mean flow-time flow-shop problem. Several new properties have been developed that provide the reader with a better understanding of this model. A class of solvable cases is defined that includes the known solvable cases.     

Problem of image superresolution with a negative-refractive-index slab

By means of the angular spectrum representation of wave fields, a discussion is given on the propagation and restoration of the wave-front structure in a slab of a left-handed medium (or negative-index medium) whose surface impedance matches that of vacuum, namely, one whose effective optical parameters are n = epsilon = mu = -1. This restoration was previously discussed [Phys. Rev. Lett. 85, 3866 (2000)] in regard to whether it may yield superresolved images. The divergence of the wave field in the slab, and its equivalence with that of the inverse diffraction propagator in free space, is addressed. Further, the existence of absorption, its regularization of this divergence, and the trade-off of a resulting limited superresolution are analyzed in detail in terms of its effect on the evanescent components of the wave field and hence on the transfer function width.     

间隙约束悬臂梁振动系统动力行为研究

运用分段线性系统分析理论，研究间隙约束的悬臂梁振动系统在简谐激励下系统稳态响应的动力学行为。首先建立间隙约束的一般线性系统动态响应分析的理论模型，以传递函数为基础，推导系统的动力学分析方程及其求解方法。然后对系统进行数值求解分析，得到该系统稳态响应随激励频率、幅值以及间隙接触刚度和阻尼变化的一般规律。研究结果对于间隙振动系统分析和间隙型减振结构设计都有重要意义。     

The Two-Inspector Problem

Reinspection is often used in industrial quality control as a final means of ensuring higher outgoing quality. Effectiveness is limited by the fault rate effect, which shows decreasing defect detection performance with successive stages of reinspection. This paper uses a model of the human inspector as a conservative signal detector to examine the various ways in which two inspectors can be combined to achieve enhanced system performance. An optimization program was used to select the optimum payoff matrix for each inspector and, given this optimum payoff matrix, various options were evaluated. It was concluded, as expected, that two inspectors are better than one and that better inspectors give better system performance. Other results were not so obvious. The method of combining the inspectors had only a 5% to 10% effect on system performance and the degree of conservatism of the two inspectors gave even smaller differences. The choice of inspection strategy was robust to changes in incoming product quality, provided the payoff matrix was optimized for each inspector.     

带缓冲区的基于时间延迟的可修设备联合优化

考虑到设备停机时间较长对企业经济效益的影响,在设备间设置缓冲区;同时考虑到设备单目标维修决策模型的不足,以及故障次数表达的精确程度对决策的影响,借用了时间延迟理论,建立了可修复设备的联合决策模型。为了满足设备的生产要求,以及最优化缓冲区生产系统的费用水平,将分别以平均单位时间的总停机时间、平均单位时间的总费用作为目标函数,来进行研究。通过时间延迟理论,分析了故障形成的过程,并表达出故障次数。借用更新报酬定理,来表达两目标函数。由离散迭代算法,求解得到：最优的检查周期和额定库存分别为25 d、1 195件时,总费用率在停机时间率为0.199时最小为22 739.95元。另外,进行了敏感性分析来验证最优解,最后由求解结果来指导生产线维修管理。