Methods of vendor managed inventory control in supply chain management

By inducing the typical inventory control problem - the bullwhip effect, this paper presents vendor managed inventory (VMI) control methods on the basis of traditional methods of inventory management methods, constructs a VMI mathematics model, and analyzes the influence of VMI on inventory cost and channel profit. Finally, a special case is studied to verify that VMI is an effective supply chain strategy that can not only increase channel profit of supplier and customer but also improve full channel coordination, thereby reducing the bullwhip effect.

Inventory control techniques in medical stores of a tertiary care neuropsychiatry hospital in Delhi

Approximately 35.0% of annual hospitals budget is spent on buying materials and supplies, including medicines. We can bring about substantial improvement in the hospital inventory and expenditures by the inventory control techniques. Objective: To identify the categories of drugs which need stringent management control. Material and Method: The ABC and VED analysis of the medical store of a Neuropsychiatry hospital at Delhi, India was conducted for the year 2008-2009 to identify the categories of items needing stringent management control. Results: The total number of the drugs at the medical store was 145 drugs. The total annual drug expenditure (ADE) on these drug items was Rs. 19219594.79. ABC analysis revealed 3.45%, 6.9% and 89.65% items as A, B and C category items, respectively, accounting for 70.5%, 19.68% and 9.83% of ADE of the medical store. VED analysis showed 32.41%, 61.38% and 6.2% items as V, E, and D category items, respectively, accounting for 70.9%, 28.72% and 0.38% of ADE of the medical store. On ABC-VED matrix analysis, 33.8%, 60% and 6.2% items were found to be category I, II and III items, respectively, accounting for 92.33%, 7.29% and 0.38% of ADE of the medical store. Conclusion: It is suggested by the study that the management of Category I drugs should be done by the top management resulting in stringent control on the annual expenses. The Category II should be managed by the middle management level and Category III at lower managerial level.

Distributed Order-Up-To Inventory Control in Networked Supply Systems With Delay

In this work, the dynamics of networked goods distribution systems subject to the control of a continuous-review order-up-to inventory policy are investigated. In the analytical study, as opposed to the earlier models constrained to the serial and arborescent interconnection structures, an arbitrary multiechelon topology is considered. This external, uncertain demand,following any distribution, may be imposed on all network nodes,not just conveniently selected contact points. As in the physical systems, stock relocation to refill the reserves is subject to nonnegligible delay, which poses a severe stability threat and may lead to cost-inefficient decisions. A state-space model is created and used as the framework for analyzing system properties. In particular, it is formally demonstrated that despite unpredictable demand fluctuations, a feasible(nonnegative and bounded)reserves replenishment signal is generated at all times, and the stock gathered at the nodes does not surpass a finite, precisely determined level. The theoretical content is illustrated with a case study of the Chinese oil supply system.

Inventory control model based on external and interior reverse logistics

To improve the inventory control strategy for enterprise and optimize inventory control parameters of existing external and interior reverse logistics, a multi-resource inventory control model is proposed to better simulate the logistics fact, which is aimed at periodic inventory checking and pull mode of inventory control strategy, based on the return product arrival time obeying Poisson distribution, the return product employing lotsize process and the nonzero lead time of manufaeturinge/remanufacturing. The rational cost function with multiple constraints is employed to describe the inventory model. The genetic algorithm is employed to solve the inventory cost function to obtain the optimal solution of inventory checking periods, safe inventory point, product lot-sizes and process lot-sizes of return product. An example is presented to prove the feasibility and validity of the proposed method. Moreover, the influence of manufacturing/remanufacturing lead time and reuse rate of return production on the inventory control strategy of enterprise is analyzed.

Seat inventory control methods for Chinese passenger railways

Railway seat inventory control strategies play a crucial role in the growth of profit and train load factor. The railway passenger seat inventory control problem in China was addressed. Chinese passenger railway operation features and seat inventory control practice were analyzed firstly. A dynamic demand forecasting method was introduced to forecast the coming demand in a ticket booking period. By clustering, passengers' historical ticket bookings were used to forecast the demand to come in a ticket booking period with least squares support vector machine. Three seat inventory control methods: non-nested booking limits, nested booking limits and bid-price control, were modeled under a single-fare class. Different seat inventory control methods were compared with the same demand based on ticket booking data of Train T15 from Beijing West to Guangzhou. The result shows that the dynamic non-nested booking limits control method performs the best, which gives railway operators evidence to adjust the remaining capacity in a ticket booking period.

Modeling and Simulation of Equipment Material Inventory Control Based on System Dynamics

The paper discusses how the inventory control of army equipment material runs sytematically under the two-level maintenance system,and establishes the inventory control model based on system dynamics.On the basis of modeling and simulation,the influence of different inventory upper limit on the whole system is studied,and the optimal inventory control mechanism under the model condition is foud.In addition,through the simulation of two replenishment strategies(s,S) and(T,s,S),the advantages and disadvantages and feasibility of each replenishment strategy are analyzed.

Adaptive Control of a Production-Inventory Model with Uncertain Deterioration Rate

This paper studied a continuous-time model of a production maintenance system in which a manufacturing firm produces a single product selling some and stocking the remaining. The problem of adaptive control of a production-maintenance system with unknown deterioration has been presented. Using Liapunov technique, the production rate and updating rule of deterioration rate are derived as non-linear functions of inventory level perturbation. Numerical analysis for the system has been presented for a set of parameter values and demand rate.

Dynamic Control and Optimization of Capital-Constrained Stochastic Inventory Systems

For most firms,especially the small-and medium-sized ones,the operational decisions are affected by their internal capital and ability to obtain external capital.However,the majority of the current studies on dynamic inventory control ignore the firm’s financial status and financing issues completely.An important question that arises is:what are the dynamic optimal inventory and financing policies for firms with limited capital and limited access to external capital?In this paper,we review some of the latest developments in this area.After a brief review of single period models,we focus on multi-period dynamic control of the firm who aims to optimize its xpected terminal wealth.Two cases are discussed in detail:self-finance and short term finance.In the first case,the firm has to rely on its own capital for all ordering decisions,while in the second,the firm can borrow short term loan from lenders.A detailed characterization of the optimal policy is presented and its managerial insights are discussed.Several possible extensions are suggested.

Impact of Capacity Parameters on Flexible Inventory Control Decision Model

From the mathematical point of view,the flexible inventory control model is proved in the practical problem application and the rationality of the capacity parameter selection and calculation.The purpose is to actively respond to demand fluctuations when there is a demand forecast error or a missing part of the demand information,and to avoid the risk of passive variable demand forecasting to set the immutable inventory capacity.At the same time,the game is controlled by the flexible and variable inventory control strategy and the customer’s willingness to demand.The paper mainly studies the influence of the setting of capacity parameters on the booking-limit decision and its benefits under the control of flexible space with variable total capacity.Through the two trends of capacity increase flexibility and capacity reduction flexibility in the flexible inventory control model,the mathematical performance and marginal utility methods are introduced to change the performance of the booking-limit control decision model under different scenarios.The correlation analysis between the capacity limit level and the return under the optimal Bookinglimit decision,and the above two flexibility parameters are obtained.

Optimal Multiperiodic Control for Inventory Coupled Systems: A Multifrequency Second-Order Test

A complex autonomous inventory coupled system is considered. It can take, for example, the form of a network of chemical or biochemical reactors, where the inventory interactions perform the recycling of by-products between the subsystems. Because of the flexible subsystems interactions, each of them can be operated with their own periods utilizing advantageously their dynamic properties. A multifrequency second-order test generalizing the p-test for single systems is described. It can be used to decide which kind of the operation (the static one, the periodic one or the multiperiodic one) will intensify the productivity of a complex system. An illustrative example of the multiperiodic optimization of a complex chemical production system is presented.

Unique influences of reboiler inventory control on the operation of totally reboiled reactive distillation columns

In this work,the dynamics and operation of the totally reboiled reactive distillation columns are visualized in terms of transfer function based process models.This kind of processes is found to be characterized by underdamped step responses due to the special topological configuration and the intricate interplay between the reaction operation and the separation operation involved.The under-dampness can be substantially alleviated through the tight inventory control of bottom reboiler and this presents beneficial effects to process dynamics and operation.Two totally reboiled reactive distillation columns,separating,respectively,a hypothetical synthesis reaction from reactants A and B to product C,and a real decomposition reaction from 1,4-butanediol to tetrahydrofuran and water,are employed to demonstrate these uncommon behaviors.The results obtained give full support to the above qualitative interpretation.Despite the strong influences of reaction kinetics and thermodynamic properties of the reacting mixtures,the totally reboiled reactive distillation columns are generally considered to present such unique behaviors and require tight inventory control of bottom reboiler to facilitate their control system development.

Study on Inventory Cost Control under JIT System

Traditional inventory control methods generally emphasize minimizing costs. Under current thinking, we not only consider cost control, but also tie inventory management directly into production scheduling. This system, called ＂Just-in-Time delivery＂, is based on having inventory arrive at the factory door just as it is needed on the assembly line. This inventory management technique of essential zero raw material inventory speeds inventory turnover rate and greatly reduces holding cost. This paper analyzes and compares all aspects related to both traditional and JIT systems, and explores ways of reducing inventory costs. The result is the elimination of waste, the speed-up of inventory turnover and the increase in productivity, all with the objective of maximizing profitability. Using advanced logistics （physical distribution methods） will enhance the business image, strengthen international competitive ability and contribute greatly to increase gross domestic product.

Robust solutions of Uncertain Capacity inventory control

This paper analyzes the uncertainties of air cargo and applies revenue management to solve the problem of air cargo capacity control.A robust capacity allocation model for a multiple-leg with multiple shipment types is established,which describe uncertainty of these parameters as a number of discrete scenarios,and obtain the optimal allocation with Mutation Particle Swarm Optimization.Simulation experiments show that this method can balance uncertainty of the model effectively and accord with actual situation.

基于EOQ模型传统涉外制造企业物料库存管理研究

库存成本管理水平高低对企业经营成本有着直接影响,提高库存管理水平,有助于降低库存成本和经营成本。文章基于EOQ模型,以传统涉外制造企业DJ公司为例,选取物料面浆作为研究对象,通过对EOQ模型使用前后库存成本对比分析,发现采用EOQ模型后,面浆的库存量和库存总成本比原来有所降低。研究表明,科学合理采用EOQ模型有助于实现订货成本与维持成本最小化,降低企业经营成本,促进企业可持续发展。

基于实时交通流的上海市机动车碳污同源排放清单

为满足交通碳污减排政策多样化、差别化和精细化发展需求,扩大交通排放测算范围、提高测算准确度和时空分辨力,提出了一种基于实时交通流的高时空分辨力机动车碳污同源排放清单构建方法,综合交通模型、IVE模型和相关算法建立了覆盖上海全市的机动车碳污同源排放清单。结果显示,二氧化碳、氮氧化物周排放规律相近,呈现出明显的周末低工作日高的特征;二氧化碳分时变化规律呈现明显的双峰,而氮氧化物受重型车影响,峰值出现在夜间;由于各车型的碳污分担率不同且活动区域不同造成了上海市机动车二氧化碳和氮氧化物排放的空间分布差异明显;碳污同源排放清单中,NOx、PM、CO、VOCs、CO_(2)的月均排放量分别为5160t、440t、1.7×10^(4)t、732t和2.46×10^(6)t;排放分担率表明,NOx、PM等污染物主要来自重货车及大货车排放;CO、VOCs和CO_(2)排放来源以小客车排放占比最高。

基于Vensim的汽车零部件供应链管理研究

利用系统动力学和Vensim软件搭建汽车零部件供应链模型,分析“牛鞭效应”在供应链中需求变异放大现象对供应链库存的影响。通过绘制因果关系图,建立三级零部件供应链模型,对时间延迟、期望库存持续时间、库存调整时间、移动平均时间节点进行分析,研究发现这4个辅助变量都会加剧“牛鞭效应”。根据汽车零部件供应链的特点,提出针对性策略来弱化“牛鞭效应”,优化企业库存管理,提高库存利用率、最小化库存支出,改善企业现金流。

基于数据分析的低值耗材三级库管理优化探讨

为解决低值耗材三级库管理中存在的盘点困难等问题、减少三级库库存损耗、提高医务人员使用耗材的准确性,文章从三级库库存上下限设置、零库存校验和超耗提醒、三级库使用行为分析等方面进行功能优化,探讨基于SPD(Supply-Processing-Distribution)模式的低值耗材三级库管理,为实现低值耗材三级库管理的规范性、溯源性及提高落地应用性提供管理思路。

《香港公约》规则解读与影响分析

为了帮助船舶业界实施《香港公约》,对《香港公约》规则要求,以及国际海事组织(International Maritime Organization,IMO)和国际标准化组织(International Organization for Standardization, ISO)制定的相关配套实施文件进行梳理,对《香港公约》对当前船舶有害物质控制以及拆船厂的可能影响进行分析,并提出相应建议。研究成果可为船舶业界实施《香港公约》提供一定参考。

考虑零件库存的两机器装配线性能评估与库存控制

对于面向大批量生产的装配线而言,其产出能力不仅受到设备不可靠性和缓冲有限性的限制,还受到外部零件供给不确定性的影响。以考虑零件库存的两机器装配线为研究对象,研究了(s,S)库存控制策略作用下装配线的性能评估与库存控制问题。首先,针对由一台装配机器和零件库存组成的装配工站,分析了(s,S)库存控制策略对系统状态转移过程的影响,利用马尔可夫链建立了装配工站的性能评估模型,求得了系统稳态概率分布的闭集表达式。其次,针对由两个装配工站组成的装配线,将一个装配工站等效为一台独立机器,进而利用马尔可夫链求得了主要性能指标的解析表达式。再次,以最小化库存相关成本为目标,以产出率满足市场需求为约束条件,构建了(s,S)库存控制阈值优化模型,并利用自适应遗传算法对模型进行了求解。最后,通过数值实验验证了所提性能评估方法的准确性,并分析了性能指标关于库存控制阈值的单调性以及最优控制阈值随装配机器参数的变化趋势。实验结果表明,本研究为考虑零件库存的装配线提供了一种有效的性能评估与库存控制方法。

场地土壤镉污染排放清单与溯源——以铜冶炼厂为例

以华东地区某铜冶炼厂为例,采用“四大排放途径”函数定量描述Cd通过“废气沉降、废水排放、固废淋滤、跑冒滴漏”进入土壤的通量.结合AERMOD废气沉降模型,计算废气携带的Cd沉降于场地边界内部和外部的分布,明确各途径对场地内土壤Cd污染的贡献.结果表明,企业在2000~2002年在产期间主要通过废气(1411kg,50.05%)和固废淋滤(1327kg,47.05%)排放Cd,而废水及跑冒滴漏途径影响很小(共81.74kg,2.90%).但所排废气中的Cd沉降于场地内的仅0.68kg(0.05%),场地内土壤Cd主要由固废淋滤途径贡献.空间排放清单显示其主要分布于堆料区和废气处理区等生产区域.研究结果对加强冶炼行业的精细化源头管控有重要指导作用,且本文提出的方法可拓展至其他行业和多种污染物的排放量溯源.