Deriving the cost function for a class of three-echelon inventory system with N-retailers and one-for-one ordering policy

A three-echelon inventory system with two warehouses and N-retailers is considered in this paper. Transportation times are constant and retailers face independent Poisson demand. Replenishments are one-for-one. The lead time of a retailer is determined not only by the constant transportation time but also by the random delay incurred due to the availability of stock at the warehouses. Axsäter [2] evaluated the value of the expected two-echelon inventory system cost with the same assumptions, but in this paper, we add a warehouse as third echelon and therefore this may lead to having one more delay in shipment which was incurred in the new warehouse. We obtained the cost function for the inventory system and tested it by several examples.     

A multi-item ordering model in the (s, S ) inventory system

The decision variables in the (s,S) inventory system are s (ordering point) and S (maximum inventory level). In this paper, we propose a new ordering model in the (s,S) inventory system for the mixed part transportation problem with multi-item based on the depot system. The order range is introduced and used as decision parameters instead of the order point for ordering multi-item. Finally we test the proposed model with a numerical example and show computational results that verify the effectiveness of the model.     

A particle swarm optimization approach for constraint joint single buyer-single vendor inventory problem with changeable lead time and (r,Q) policy in supply chain

In this paper, the chance-constraint joint single vendor-single buyer inventory problem is considered in which the demand is stochastic and the lead time is assumed to vary linearly with respect to the lot size. The shortage in combination of back order and lost sale is considered and the demand follows a uniform distribution. The order should be placed in multiple of packets, the service rate limitation on each product is considered a chance constraint, and there is a limited budget for the buyer to purchase the products. The goal is to determine the re-order point and the order quantity of each product such that the chain total cost is minimized. The model of this problem is shown to be an integer nonlinear programming type and in order to solve it, a particle swarm optimization (PSO) approach is used. To assess the efficiency of the proposed algorithm, the model is solved using both genetic algorithm and simulated annealing approaches as well. The results of the comparisons by a numerical example, in which a sensitivity analysis on the model parameters is also performed, show that the proposed PSO algorithm performs better than the other two methods in terms of the total supply chain costs.     

制造企业集成库存管理信息化系统研发

根据现代企业库存管理模式,研发了基于多种入出库模式的库存管理信息化系统.该系统采用C/S结构,采用独特且符合实际的设计思想,除了实现物资到货之后的物资分类定义、网上入库、审批、申领、领料、出库、退库的全部操作外,还能自动生成查询报表,能够满足企业内部较为复杂的入出库情况.详细叙述了各功能模块的具体内容,主要包括基础数据处理,库存操作处理,报表生成与查询三大功能模块.对系统突发性事故,如死机、断电等系统异常情况下,进行了安全的数据保护处理.该系统能给库存管理人员提供便捷的操作和准确的数据,方便应对各种复杂的入出库情况,并能对库存管理的业务流程进行控制,采用流水线作业完成任务,并可实现多用户同时访问系统.     

Developing a two-echelon mathematical model for a vendor-managed inventory (VMI) system

Vendor-managed inventory (VMI) system is a mechanism where the supplier creates the purchase orders based on the demand information exchanged by the retailer/customer. In this paper, the performance of the traditional and VMI system is compared. Mathematical modeling is applied and total inventory cost in the supply chain is used as the performance measure. The supply chain is considered in two levels, i.e., buyer and supplier, with the assumption that the supplier faces only one buyer as the contract party. Since none of the previous works quantitatively directed the practitioners to select the traditional or VMI system, the extent point is introduced in which the difference in total cost of both systems is minimal. It is applied to investigate how increasing or reducing the related parameters changes total cost of two systems with respect to each other. A numerical example and sensitivity analysis are provided to illustrate the theory and derive the extent points and percentage of difference in total cost of the traditional and VMI system. The results show that VMI works better and delivers lower cost in all conditions including back order, and as one goes farther from the extent point, the application of VMI is more justified.     

Optimum ordering policy for an imperfect single-stage manufacturing system with safety stock and planned backorder

Manufacturing industries prefer to produce extra units as safety stock especially when demand for these units varies. The phenomena of producing additional units is also observed when processes are imperfect and production managers are sure that product can be consumed in market. In addition, customer is also willing to wait for demands to be backordered in the case of shortages. However, inventory carrying and backordering costs may play vital role if products are produced in relatively large amount. Therefore, a mathematical model is needed that can define the ordered quantity taking safety stock and planned backordering into consideration with imperfect production setup. This paper is an attempt towards development of such mathematical model that considers safety stock, lot size, and planned backorders for a single-stage imperfect production setup. Mathematical model is developed based on minimization of total average cost function. Three decision variables including order quantity, safety stock, and planned backorders have been optimized simultaneously using classical optimization approach. Numerical examples are used to illustrate the proposed model for calculation of decision variables. Impact of changes in processes imperfection, holding costs, and backordering costs over variables have been numerically computed to highlight model significance in daily industrial life. Results prove that safety stock and planned backorder reduce the total cost significantly.     

大型科学仪器共享系统及安全邮件系统的研究

本文首先描述了大型科学仪器与资源网络共事系统的相关技术和问题．结合光谱成像显微分析系统网络化问题．提出了一种方案的框架结构。提出建设高可靠网络化仪器系统是建设的最高目标．即建立可靠的、可用的、机密的、完整的、安全的系统。邮件系统是大型科学仪器共享系统中的重要组成部分．本文最后介绍了的安全邮件系统设计与实现范例。     

Design and implementation of user information sharing system using location-based services for social network services

Internet takes a role as a place for communication between people beyond a space simply for the acquisition of information.Recently,social network service (SNS) reflecting human's basic desire for talk...     

基于SOA的设备关键备件虚拟联合库存共享平台研究

为解决设备关键备件需求不确定性高导致库存成本高的问题,提出基于虚拟联合库存管理模式的设备关键备件信息共享服务平台,在分析关键备件库存特点的基础上,构建由设备关键备件供应链上各节点企业多方参与的联合库存运作机制,旨在通过资源共享实现关键备件需求的快速响应.平台引入基于服务架构SOA的模型,结合Web Service实现技术,并从用户端虚拟联合库存管理系统、企业总线ESB及Web服务代理模式三方面提供关键支撑技术构建方案,建构畅通的信息共享机制,实践证明具有在组织资源的速度、规模、效率、成本和资源的合理配置方面的优势,为企业解决库存效益背反问题提供了良好的思路.     

Evaluating the value of information sharing in a supply chain using an ARIMA model

This paper considers a two-echelon supply chain, which contains one supplier and one retailer. It studies the quantification of the bullwhip effect and the value of information-sharing between the supplier and the retailer under an autoregressive integrated moving average (ARIMA) demand of (0, 1, q). The results show that with an increasing value of q, bullwhip effects will be more obvious, no matter whether there is information sharing or not. When there exists information sharing, the value of the bullwhip effect is greater than it is without information sharing. With an increasing value of q, the gap between the values of the bullwhip effect in the two cases will be larger.     

Exergy efficiency and irreversibility comparison of R22, R134a, R290 and R407C to replace R22 in an air conditioning system

This work presents an experimental comparison of exergy efficiency (EE), irreversibility at the process 1–2 (evaporator exit to compressor inlet), 2–3 (compressor inlet to condenser inlet), 3–4 (condenser inlet to expansion valve inlet), 4–5 (expansion valve inlet to evaporator inlet) and 5–1 (evaporator), and coefficient of performance (COP) of R22, and its substitutes R134a, R290 and R407C in vapor compression refrigeration system (VCRS) of an air conditioner. In addition, the effects of air temperature in the freezer with reference to environment states on irreversibility and EE have been investigated. At ?18°C air temperature in the freezer, 33°C reference environment state and 42% relative humidity refrigerants R22 and its substitutes R134a, R290 and R407C VCRSs the total irreversibilities are 665.7, 753.5, 582.1 and 677 W, and EEs are 22.9, 14.2, 26.5 and 20.6%, respectively. The refrigerant R290 is the best performer among candidate refrigerants but it suffers from flammability. Thus, R407C can considerably be used to replace R22.     

水电站厂内经济运行数据库系统的开发与应用

数据库系统是水电站厂内经济运行系统的核心.采用实时数据库和历史数据库相集成的方式,运用可视化语言创建库引擎,开发了水电站厂内经济运行数据库系统.该数据库系统为水电站厂内经济运行系统提供了从数据创建、使用到维护的统一管理,为系统提供了实时的或历史的数据服务.研究结果表明.它具有响应快、扩充性好和使用方便等特点,可以为其他水电站高级应用软件的数据库开发提供借鉴.     

一对多供应链在传统、信息共享和供应商管理库存模式下的绩效比较

比较分析了一对多两阶段供应链在传统、信息共享和供应商管理库存三种供应链管理模式下的供应链绩效,其中绩效指标选取为平均成本.针对三种模式分别构建了供应商、零售商以及供应链整体的运作模型,给出了其成本的解析表达式,最后通过数值实验的方法,比较了三种模式下的供应链绩效.结果表明,对于零售商和整个供应链而言,信息共享模式优于传统模式,并且供应商管理库存模式优于信息共享模式;而对于供应商而言,信息共享和供应商管理库存模式均优于传统模式,但供应商管理库存模式与信息共享模式相比,在一定条件下,有可能带来供应商成本的增加.     

R134a、R123、R23和R14混合工质林德循环的试验研究

提出了一种新的R134a、R123、R23和R14四元混合工质林德制冷循环并做了相关的试验,主要包括制冷剂组分混合比例的确定以及分析不同比例对循环整体性能的影响。通过对不同配比下所得数据的分析比较,总结了此四元混合工质林德循环的运行特点,并提出了整个系统循环的改进方案。     

Eaton(R) Fulle(R) Solo(R)重型离合器的结构原理及使用维修

介绍Eaton Fuller Solo 离合器的结构、自动调整原理,并对其使用与维修中的注意事项进行阐述。     

达芬奇手术机器人系统及其临床应用

手术机器人的发明和应用开创了外科手术的又一新纪元。与传统电视腔镜手术相比,手术机器人系统具有更加精细、微创等优点。本文介绍了达芬奇手术机器人系统的组成原理、手术机器人的特点与临床应用情况,并对手术机器人的发展做了简要探讨。     

基于知识共享重用的智能检测规划系统开发平台IIPDP的研究与实现

本文介绍知识共享和重用技术在建立检测规划知识系统及其知识库模型方面的应用,详细描述了基于知识共享和重用技术的ＩＩＰＤＰ的体系结构,构件库模型及其实现和基于本体论的检测规划知识库模型及其实现,其方法和成果具有普遍意义。     

面对称(CRR)2S-(3R)2R并联机构运动学分析

以一种两移动两转动(2T2R)自由度面对称(CRR)2S-(3R)2R并联机构为研究对象,基于方位特征集理论分析该机构的自由度数目和性质,并对其进行了运动学分析.应用坐标变换法,建立求机构位置正解的非线性方程组,并采用差分进化算法求解该方程组.推导出机构逆解解析表达式,应用数值算例验证机构正解、逆解的正确性.采用矢量法...     

Metaheuristic-based inspection policy for a one-shot system with two types of units

In this paper, we address an inspection policy problem for a one-shot system with two types of units, namely, Type 1 units that fail at random times and Type 2 units that degrade with time. Interval availability and life cycle cost are used as optimization criteria and estimated by simulation. We determine inspection intervals, preventive replacement ages of Type 1 units, and preventive maintenance thresholds of Type 2 units that have minimal life cycle cost and satisfy the target interval availability during inspection periods. A simulation-based optimization procedure using a hybrid genetic algorithm is proposed to find near-optimal solutions. Numerical examples are studied to investigate the effects of model parameters on optimal solutions and compare the hybrid genetic algorithm with the general genetic algorithm.