基于快递运输的手机零件供应链改进研究

一些手机零件企业没有设置产品安全库存。他们完全按照客户订单从供应商处采购产品,并使用快递运输。然而供应链中的各种不确定因素造成了频繁的交货延误。作者对这种供应链进行了简单介绍,分析了其中存在的问题,建立了包含安全库存成本和快递运输成本的供应链成本模型．并且以手机扬声器为例计算了安全库存,为企业对快递公司的评价和安全库存的设置提供了参考工具。     

聚集效应对安全库存的影响研究

安全库存是一种额外持有的库存，也是一种缓冲器，它对库存成本有很大影响。本文从分析供应链是怎样运用库存聚集着手，研究在不降低产品供给情况下，聚集效应是怎样影响安全库存量。     

基于期权理论的安全库存管理

设置必要的安全库存是解决供应链上不确定性的重要措施之一。文章首次提出了期权协议下的安全库存调货方案,与传统的设置安全库存方式在管控相同数量的货物上进行对比,在成本核算优化空间问题上做一个探讨,以期为实现构建供应链虚拟安全库存带来全新的思考。     

Quantile forecast optimal combination to enhance safety stock estimation

The safety stock calculation requires a measure of the forecast error uncertainty. Such errors are usually assumed to be Gaussian iid (independently and identically distributed). However, deviations from iid lead to a deterioration in the performance of the supply chain. Recent research has shown that, contrary to theoretical approaches, empirical techniques that do not rely on the aforementioned assumptions can enhance the calculation of safety stocks. In particular, GARCH models cope with time-varying heterocedastic forecast error, and kernel density estimation does not need to rely on a determined distribution. However, if the forecast errors are time-varying heterocedastic and do not follow a determined distribution, the previous approaches are inadequate. We overcome this by proposing an optimal combination of the empirical methods that minimizes the asymmetric piecewise linear loss function, also known as the tick loss. The results show that combining quantile forecasts yields safety stocks with a lower cost. The methodology is illustrated with simulations and real data experiments for different lead times.     

The interchangeability of safety stocks and safety lead time

Due to the uncertainty in estimating both the demand for end products and the supply of components from lower levels, buffering techniques should be included before the loading of a material requirement planning (MRP) system. Safety stocks and safety lead time are two techniques of providing buffering for loading. There have been many studies made concerning the determination of the amount of safety stocks and safety lead time. Some guidelines for choosing between safety stocks and safety lead time for dealing with uncertainty in both demand and supply also have been established. Although these two different methods have been used successfully, it has not been documented that using these two methods in a given situation will yield essentially the same results; that is, the interchangeability of these two buffering techniques has not been explored quantitatively.Since the net influence of safety stocks and safety lead time and their quantitative interchangeability are of major interest, an analytical model is proposed for this study. The lead-time offset procedure for components loading are represented by a matrix model that is based on a lot-for-lot lot-sizing technique. This lead-time offset matrix model is the product of the precedence matrix and the fixed-duration matrix. The precedence matrix is formed according to the total requirement factor matrix and the duration matrix is formed by each component process time. Thus, the lead-time offset matrix will generate the starting period of each component.When the lead-time offset procedure is modeled, the net influence of buffering quantity can be analyzed. The planned safety stock that is normally used to accommodate unexpected demand, shortage in supply, and defects from the operation at each process can be combined with demand to form the master production schedule. The revised lead time due to the integration of the safety stocks can be calculated through the lead-time offset model. The safety lead time may extend the component process time as well as overall production lead time if the designated safety lead time is longer than the available slack time in a fixed lead-time loading system.When the proposed lead-time offset model is further examined, it is found that planned safety stocks at the higher level can buffer the fluctuations of lower level components quantity as well as the fluctuations of same level components quantity. Safety stocks can also buffer shortages that are caused by the delay of raw material and manufacturing processes. Thus, safety stocks can be used to buffer unexpected delay time up to certain limits. A planned safety lead time at higher level component process can buffer the fluctuations of lower level components process time, as well as the same level component process time. The safety lead time can be used to produce additional products to meet unexpected excessive demand up to certain limits under the following conditions: 1. The excessive demand is known before the actual processing of the components in the lowest level. 2. The raw material at the lowest level is available.Although safety stocks and safety lead time are interchangeable in terms of the ability to buffer variations in quantity, the conditions for safety lead time are seldom met in actual practices. Thus, the slack time in a fixed lead-time loading system cannot be considered as an effective measure to substitute safety stocks. However, all or part of the delay in manufacturing processes or the supply from the lower level components can be buffered by the safety stock and the MPS will still be met. From this study, it is obvious that the slack time can be reduced when safety stocks are planned for an MRP system. The reduction of fixed lead-time duration will be beneficial to the overall planning and scheduling in MRP systems.     

基于服务水平的供应链突发事件安全问题研究

提高企业安全库存是一种预防或者减弱供应链内部突发事件对企业冲击的一种有效的办法,但是这样就会增大企业的成本,从而降低企业的利润。文章试图寻找一个控制成本同时能够有效预防突发事件对企业的冲击,在供应链发生突发事件的情况下可以提高服务水平的供应链安全库存模型,通过这个模型进行数值分析,看到企业在控制成本的情况下,服务水平得到明显提高。     

供应链库存优化管理模型研究

供应链库存管理是供应链管理的重要组成部分,如何设置和维持一个合理的订货量和库存水平量,以平衡存货不足带来的短缺风险和损失,以及库存过多所增加仓储成本和资金成本,成为一个企业必须回答的问题。本文从供应链整体角度出发,提出了在缺货费用很小以至于可忽略的前提下,适应供应链模式下,新的库存控制优化模型,并以简单实证加以研究。     

基于JIT的制造商供应链优化模型

JIT思想的主旨是强调生产的无库存与准时,围绕这一思想,将运输商作为供应链上的独立成员,考虑运输商的运输能力、供应商的供应能力、销售商的销售数量等约束以及运输环节诸因素的作用,建立了JIT环境下制造商供应链的优化模型,以实现制造商经营活动的优化,并通过具体的实例说明模型的可行性。     

供应链金融创新下分次赎货模式分析

通过分析现有静态抵质押授信的打款赎货模式和动态抵质押授信的以货易货模式的不足,提出基于应收账款的分次赎货模式。分析了引入应收账款以及核心企业以后,赎货模式流程的改变和各方利益的改变。基于应收账款的分次赎货模式针对处于供应链上游的受流动资金制约的供应商而设计,致力于同时优化供应链上的存货和应收账款两类资产。     

“I’m not hoarding,I’m just stocking up before the hoarders get here.”: Behavioral causes of phantom ordering in supply chains

When suppliers are unable to fill orders, delivery delays increase and customers receive less than they desire. Customers often respond by seeking larger safety stocks (hoarding) and by ordering more than they need to meet demand (phantom ordering). Such actions cause still longer delivery times, creating positive feedbacks that intensify scarcity and destabilize supply chains. Hoarding and phantom ordering can be rational when customers compete for limited supply in the presence of uncertainty or capacity constraints. But they may also be behavioral and emotional responses to scarcity. To address this question we extend Croson et al.’s (2014) experimental study with the Beer Distribution Game. Hoarding and phantom ordering are never rational in the experiment because there is no horizontal competition, randomness, or capacity constraint; further, customer demand is constant and participants have common knowledge of that fact. Nevertheless 22% of participants place orders more than 25 times greater than the known, constant demand. We generalize the ordering heuristic used in prior research to include the possibility of endogenous hoarding and phantom ordering. Estimation results strongly support the hypothesis, with hoarding and phantom ordering particularly strong for the outliers who placed extremely large orders. We discuss psychiatric and neuroanatomical evidence showing that environmental stressors can trigger the impulse to hoard, overwhelming rational decision-making. We speculate that stressors such as large orders, backlogs or late deliveries trigger hoarding and phantom ordering for some participants even though these behaviors are irrational. We discuss implications for supply chain design and behavioral operations research.     

Development of an integrated medical supply information system

The integrated medical supply inventory control system introduced in this study is a hybrid system that is shaped by the nature of medical supply, usage and storage capacity limitations of health care facilities. The system links demand, service provided at the clinic, health care service provider's information, inventory storage data and decision support tools into an integrated information system. ABC analysis method, economic order quantity model, two-bin method and safety stock concept are applied as decision support models to tackle inventory management issues at health care facilities. In the decision support module, each medical item and storage location has been scrutinised to determine the best-fit inventory control policy. The pilot case study demonstrates that the integrated medical supply information system holds several advantages for inventory managers, since it entails benefits of deploying enterprise information systems to manage medical supply and better patient services.     

供应链中的安全库存优化管理的探讨

安全库存是一种额外持有的库存,也是一种缓冲器,它对库存成本有很大影响。本文通过分析供应链上如何利用聚集效应和提前期优化着手,探讨在不降低产品供给水平的情况下,如何通过聚集效应和提前期优化来减少安全库存量。     

供应链共享信息准确度研究

信息共享在供应链协调过程中发挥着重要的作用,而共享信息准确度是关键。基于一个供应商和一个零售商组成的两层供应链模型,比较两者非信息共享与信息共享状态下的收益,得出信息共享准确度对于整个供应链绩效的影响,提出了提高共享信息准确度的措施。     

Short-term institutions’ information advantage and overvaluation

Prior literature has documented that institutions which trade more frequently are better able to forecast future returns and have an informational advantage. This study examines a proximate explanation for the differences in performance based on institutions’ investment horizon – short-term institutions are better informed because they are better able to identify overvalued stocks that are short-sale constrained and overvalued in the context of Miller’s (1977) overvaluation hypothesis. Analysis is conducted on 6330 unique firms from 1996 to 2014 using the calendar-time portfolio approach where abnormal returns are estimated from the Fama-French-Carhart four-factor regression model. The results provide evidence that stocks which are extremely overvalued due to short-sale constraints have the greatest decline in short-term institutional ownership, consistent with the notion that short-term institutions are able to correctly assess the components for stock overvaluation.     

Application and research on the complex dynamics behaviour under price-discount promotion policy in inventory control system

In this paper, we study the inventory control system of the apparel industry supply chain in which the products are fast-fashion and mass-consuming goods. Retailers tend to promote by price-discount policy to regulate overstock situation caused by fluctuated demand, frequent product upgrading, etc. Here, we discuss the impact of fluctuated demand triggered by price-discount promotion policy on the comprehensive inventory control system in which the final inventory and supply line stock are considered and weighted differently according to corresponding practical operation situations. In this model, stock returns are permissible. Then we calculated the Lyapunov stable region of the decision parameters based on the state space model. These conclusions present the managers a big picture to inspect the inventory control system and serve as reliable references to make correct decisions.     

Supply chain finance schemes in the procurement of agricultural products

Product, information, and finance flows are all interrelated within the modern supply chain; thus, it is now more than ever of paramount importance for practitioners to integrate procurement and financial decisions. This challenge is exemplified in many agricultural supply chains, where operational risks are significant and access to capital differs sharply across firms. We study three management tactics that some large food/beverage manufacturers – situated downstream in these chains – have used to meet the challenge: ordinary fixed price contracts (or soft tolling) with direct suppliers, hard tolling and contract farming where the manufacturer intervenes upstream, providing capital, and coordinating procurement decisions. We place these upstream intervention schemes in the theoretical context of supply chain finance (SCF) and model their application to a three-echelon agricultural supply chain. We perform a numerical study in order to understand how the structure of capital constraints in the chain may influence the manufacturer's choice of SCF scheme. The numerical study is based on a business case that reflects the barley–malt supply chain of Heineken N.V. Despite greater coordination opportunities, we show that upstream intervention is not necessarily preferable for the manufacturer. Nevertheless, the preferred SCF scheme can be inferred on the basis of relatively simple characterization of the capital constraints in the supply chain.     

Evolutionary dynamics of supervision-compliance game on optimal pre-positioning strategies in relief supply chain management

Emergency supply reserves are indispensable material bases in relief supply chain management. However, limited in-kind relief resources stockpiled in government-managed depositories may fail to meet the surging demand following the disaster. This paper develops an optimal pre-positioning strategy for emergency supplies with pre-purchasing contracts between local governments (LGs) and emergency supply manufacturers (ESMs) to properly address demand uncertainty in different disaster scenarios. Physical materials and production capacity are integrated into a holistic and hybrid reserve model to mitigate overstock or stock-out risks. Applying an evolutionary game-theoretic framework, contract enforcement has been extensively analyzed to avoid LGs dereliction of duty and ESMs’ breach of contract. A novel dynamic penalty mechanism is proposed to control the fluctuations in strategy choices and effectively improve ESMs’ compliance without LGs’ excessive inputs on supervision. The numerical simulation results, along with sensitivity analyses on major cost-accounting, demand characteristics, and environmental parameters, show that safety stock is the primary guarantee in most cases, while reactive stock acts as an important supplement for disasters with long-term consequences. The joint reserve policy (except for no action strategy) outperforms the price-only contract on the total reserved quantity of emergency supplies at a lower long-term average cost. The initial state and cost-benefit structures dominate the complex interplay and periodical fluctuations in the supervision-compliance game. The doomed cycle of order, disorder, and reorder in contract performance management can be well managed under the proposed dynamic penalty mechanism, which appears much more efficient and incentive-compatible in promoting both parties to fulfill their obligations.     

The effect of operational slack,diversification, and vertical relatedness on the stock market reaction to supply chain disruptions

This paper empirically examines whether operational slack, business diversification, geographic diversification, and vertical relatedness influence the stock market reaction to supply chain disruptions. The results are based on a sample of 307 supply chain disruptions announced by publicly traded firms during 1987–1998. Our analysis shows that firms with more slack in their supply chain experience less negative stock market reaction. The extent of business diversification has no significant effect on the stock market reaction. Firms that are more geographically diversified experience a more negative stock market reaction. We find that firms with a high degree of vertical relatedness experience a less negative stock market reaction. These results have important implications on how firms design and operate their supply chains to mitigate the negative effect of supply chain disruptions.     

Common inventory modeling assumptions that fall short: Arborescent networks, Poisson demand, and single-echelon approximations

Traditional multi-echelon inventory theory focuses on arborescent supply chains that use a central warehouse which replenishes remote warehouses. The remote warehouses serve customers in their respective regions. Common assumptions in the academic literature include use of the Poisson demand process and instantaneous unit-by-unit replenishment. In the practitioner literature, single-echelon approximations are advised for setting safety stock to deal with lead time, demand, and supply variations in these settings. Using data from a U.S. supplier of home improvement products, we find that neither the assumptions from the academic literature nor the approximations from the practitioner literature necessarily work well in practice.In a variation of the strictly arborescent supply chain, the central warehouse at our real company not only replenishes other warehouses but also meets demand from customers in the region near the central warehouse. In this paper, we study this dual-role central warehouse structure, which we believe is common in practice. Using high and low volume product demand data from this company, we use Monte Carlo simulations to study the impact of (1) the use of a dual-role centralized warehouse, (2) common demand assumptions made in multi-echelon research, and (3) single-echelon approximations for managing a multi-echelon supply chain. We explore each of these under both centralized and decentralized control logic. We find that the common assumptions of theoretical models impede their usefulness and that heuristics that ignore the actual supply chain structure fail to account for additional opportunities to utilize safety stock more effectively. Researchers should be aware of the gap between standard assumptions in traditional literature and actual practice, and critically evaluate their assumptions to find a reasonable balance between tractability and relevance.     

基于供应链管理的成本控制优化

企业的利润与其成本密切相关,成本控制历来是企业最关注的问题之一。本文从基于供应链的成本控制特点出发,分别从采购、库存和交易三个关键环节,分析了供应链管理对成本控制的意义,最后提出了基于供应链管理的四种成本控制策略。