【作者】 夏海洋；

【导师】 黄培清；

【作者基本信息】 上海交通大学 ， 企业管理， 2009， 博士

【摘要】 进入21世纪后的今天,企业面对着越来越大的竞争压力。随着市场向买方市场转变,客户的要求也不断提升,企业为了保持竞争优势,维持产品的高品质已经成为不可或缺的基本条件。市场竞争的日趋激烈,信息与网络技术的迅猛发展以及全球经济的一体化,也使得企业的竞争模式发生了根本性的转变。过去那种企业与企业之间单打独斗的竞争模式逐渐被供应链与供应链之间的竞争所取代。只有通过供应链管理,整个供应链上成员之间进行信息共享、协同合作,才能满足日益提升的客户需求,在与其他供应链的竞争中占据优势地位。库存模型是供应链管理领域的经典议题,而供应链合约则是最近几年供应链管理领域的研究热点,但在库存模型和供应链合约的研究中考虑产品质量议题的文献还比较缺乏,本文的主要研究工作就是围绕这两个方面来开展的。本文的主要研究工作和结论:(一)在Salameh和Jaber(2000)的基础上,研究了卖方的瑕疵品率为随机变量并且买方检验过程不完美环境下的最优订货策略。除了放宽对买方检验过程的假设之外,我们还分别从订购费用压缩、检验速率可调整、允许缺货以及随机需求等四个方面对Salameh和Jaber(2000)的模型进行了进一步的延伸和拓展。(二)从整个供应链系统的角度出发,研究了卖方瑕疵品率为随机且买方检验过程不完美情形下的整合库存模型。建立了“批对批”生产策略下,买卖双方的联合经济批量公式,然后进一步将卖方的生产设置成本或买方的订货费用作为模型的内生变量,考虑生产设置成本或订货费用压缩的问题。接下来,我们放宽了“批对批”生产策略的假设,考虑了卖方的生产批量是买方订货批量的整数倍的情形,给出了买卖双方如何确定最佳的订货批量和生产批量,从而使整个供应链系统的期望成本达到最低。(三)将田口质量损失的概念引入整合库存模型,运用Li和Maghsoodloo(2000)提出的非对称截断型二次损失函数作为质量损失函数,分别建立了不考虑过程质量改进情形与考虑过程质量改进情形下的买卖双方期望总成本模型,并对其进行优化。在不考虑过程质量改进情形下,我们得到了联合经济批量的解析表达式。但当考虑卖方生产过程的质量改进时,我们发现无法得到联合经济批量和最优投资水平的解析表达式,我们建立了保证买卖双方期望总成本函数凸性的充分条件,并且给出了最优解应满足的等式。(四)研究了供应链上下游企业的质量投资与检验策略之间的博弈。Deming(1982, 1986),Vander Wiel和Vardeman(1994)证明了在质量外生的情况下,满足条件:(1)每批产品中每个产品的质量服从独立同分布(i.i.d.);(2)每个产品的检验成本相同,总检验成本是每个产品检验成本之和,那么all-or-none检验策略是最优检验策略。通过本文的研究,我们发现即使将质量投资作为模型的内生变量,在供应链上下游企业合作的情形下,all-or-none检验策略仍然为最优检验策略。但如果供应链上下游企业不合作,而各自优化其自身的支付函数时,供应链上下游企业之间则构成博弈行为,我们考虑了生产商和零售商之间的Nash博弈,发现Nash均衡解与厂商合约参数的设定密切相关:(1)当合约参数满足αR < C R+Δw时,存在惟一的Nash均衡解;(2)当αR = C R+Δw时,则根据检验成本m取值的不同可能出现惟一Nash均衡和无穷多Nash均衡两种情况;(3)当合约参数满足αR > C R+Δw时,根据检验成本的取值范围,可能出现惟一的Nash均衡解和三个Nash均衡解两种情况。无论是哪种情形,当生产商与零售商之间构成Nash博弈时,all-or-none检验策略则不再是最优检验策略。(五)研究了当卖方的产品质量不完美时,买方的最优合约设计问题。与过去研究如何通过供应链合约来进行质量控制的文献不同,我们研究的是质量外生环境下,买方如何通过合约来对库存水平进行协调,以保证卖方参与的前提下,使买方自身的利益达到最大。首先,作为一个比较的基准,我们研究了买卖双方合作情形下的整合库存模型,随后,我们研究了卖方与买方之间非合作情形下,买方运用合约前的订货决策。在这个部分,我们分了对称信息情形和非对称信息情形两种情况来讨论,区分的标准是买方是否掌握卖方的瑕疵品率信息。有趣的是,我们发现对称信息情形下供应链系统的绩效并不一定高于非对称信息情形下供应链系统的绩效。最后,我们研究了对称信息和非对称信息下买方的最优合约设计。研究结论包括:(1)在对称信息情形下,买方的最优合约可以实现供应链协调,并且买方可以通过转移支付水平的制定使卖方获得的利润水平等于其保留利润水平;(2)在非对称信息下,买方的最优合约可以近似达到供应链协调,此时只要卖方的瑕疵品率低于买方估计的最高值,卖方就可以获得高于其保留利润的利润水平;(3)无论是在对称信息下还是在非对称信息下,通过运用供应链合约可以明显改善供应链系统的效率。本研究的主要创新点:第一,对Salameh和Jaber(2000)的模型进行了修正和推广。在Salameh和Jaber(2000)的模型中,保证检验期间不出现缺货的条件并不充分,我们假设一批产品在检验过程完毕之后方可用于满足需求,并且放宽了检验过程完美性的假设。然后进一步从订购费用压缩、检验速率可调整、允许缺货以及随机需求等四个方面对模型进行了拓展。第二,整合库存模型的研究中通常假设产品的质量是完美的,没有考虑卖方产品中存在瑕疵品的问题,本研究考虑了随机瑕疵品率环境下的整合库存模型,并且放宽了对检验过程完美性的假设,同时我们也将卖方的生产设置成本或买方的订货费用作为模型的内生变量,研究了生产设置成本或订货费用与买卖双方最优经济批量的联合决策问题。第三,采用Li和Maghsoodloo(2000)提出的非对称截断型二次损失函数作为质量损失函数,首次将田口质量损失的观念引入整合库存模型,并且考虑企业可以通过投资来降低生产过程的变异性,分析了买卖双方如何制定订货批量与质量改进投资水平,以实现供应链系统期望利润的最大化。第四,与Deming(1982, 1986),Vander Wiel和Vardeman(1994)等文献将产品的质量水平作为外生变量不同,本研究将质量投资作为模型的内生变量,考虑了供应链上游厂商的质量投资与下游厂商的检验策略之间的互动决策过程。我们建立了生产商和零售商之间的Nash博弈模型并进行了求解,发现根据厂商之间合约参数的设定以及下游厂商检验成本的高低不同,可能存在惟一Nash均衡解、三个Nash均衡解以及无穷多Nash均衡解等几种结果。第五,与过去研究如何通过供应链合约来进行质量控制的文献不同,我们运用委托-代理理论研究了当卖方的产品质量不完美且瑕疵品率为其私有信息时,买方如何通过合约设计激励卖方提供真实的瑕疵品率信息并对库存水平进行协调,以保证卖方参与的前提下,使买方自身的利益达到最大。总之,本文围绕质量议题研究了单个厂商的订货策略,多个厂商的整合库存模型,供应链上下游厂商之间的质量投资与检验策略博弈,以及非对称信息下供应链合约的设计等诸多问题,在对现有的研究进行扩展和延伸的同时,也为企业的生产管理决策提供了理论指导。更多还原

【Abstract】 Today, enterprises are facing increasingly competitive pressure. With buyer’s power increasing, customer’s requirements become more and more demanding. To maintain competitive edge, high quality is an essential factor. More and more fierce competition, rapid development of information and network technology and economic globalization, also change the enterprises’competition paradigm. Competition between single firms has been replaced by supply chains competition. Through supply chain management, information sharing and cooperation among supply chain members, the supply chain can meet customer’s demanding requirement, therefore gain advantage in competition with other supply chains.Inventory model is a classic research issue in supply chain management, while supply chain contracting received extensive attention in recent years. But we notice that there are few literatures in inventory models and supply chain contracting with consideration of quality issues. With focus on these two areas, we carry out some research work.The main work and conclusions can be concluded in the following five parts:In the first part, based on Salameh and Jaber (2000), investigate the buyer’s optimal ordering strategy when the defective percentage is random and inspection is imperfect. In addition to relaxing the assumption of perfect inspection, we also extend our model to considering setup cost reduction, adjustable inspection rate, shortage permission and stochastic demand.In the second part, we study buyer and vendor’s integrated inventory model under the condition of random defective percentage and imperfect inspection process. Under the assumption of“lot-for-lot”production policy, we obtain the joint economic lot size to optimize the whole supply chain’s benefits. Then we let the vendor’s setup cost or the buyer’s ordering cost be the model’s decision variable, to consider the problem of setup cost or ordering cost reduction in integrated inventory model. Next, we relax the assumption of“lot-for-lot”production policy, and consider the case of vendor’s lot size is an integer number times of the buyer’s ordering quantity. In this case, we develop the vendor’s optimal batch size and the buyer’s optimal ordering quantity to minimize the whole supply chain’s expected cost.In the third part, we introduce Taguchi quality cost into integrated inventory. Using Li and Maghsoodloo’s asymmetrical truncated quadratic quality loss function, we develop the vendor and buyer’s total expected cost function. When the process quality is given, we obtain the closed-form solution of joint economic lot size. While when the process quality is a decision variable, that is the vendor can invest in a process to decrease its variance, we can not obtain closed-form solution. Instead, we develop sufficient condition to assure the convexity of the total expected cost function, and give the condition which the optimal solution should meet.In the fourth part, we study the interaction of upstream firm’s quality investment and downstream firm’s inspection strategy. Traditional models focus on the manufacturer’s inspection decision problem by taking quality as exogenous. Under this assumption, Deming(1982, 1986), Vander Wiel and Vardeman(1994) proved all-or-none inspection policy is optimal if the following two conditions hold: (1) the quality of units in a batch is modeled as i.i.d. random variables; (2) overall inspection cost is a sum of individually and identically determined costs for each of the items encountered. In our study, we found all-or-none inspection policy is still optimal in cooperative supply chain system even taking the quality as endogenous. But in non-cooperative supply chain system things are different. We investigate the Nash game between the manufacturer and the retailer, and found the Nash equilibrium is most related to the contract parameters: (1) ifαR < C R+Δw , there is a unique Nash equilibrium; (2) ifαR = C R+Δw , there may be a unique Nash equilibrium or infinite Nash equilibria depend on the inspection cost; (3) ifαR > C R+Δw , there may be a unique Nash equilibrium or three Nash equilibria depend on the inspection cost. Therefore in non-cooperative supply chain system, when taking the quality as endogenous, the all-or-none inspection policy is no longer optimal.In the last part, we analyze the design of optimal contract for buyer when the vendor’s product quality is imperfect. Different from the past literature which focus on using supply chain contract in quality control, we study on coordinating the inventory by using supply chain contract while taking the quality as exogenous. First, as a benchmark, we investigate the buyer and vendor’s integrated inventory model. Then we study the buyer’s optimal ordering strategy when the buyer and vendor do not cooperate with symmetric information and asymmetric information individually. Interestingly, we found that in symmetric information case the performance of supply chain may not necessarily superior to the performance of supply chain with asymmetric information. Finally, we investigate the design of the buyer’s optimal contract in symmetric and asymmetric information cases individually. The conclusions include: (1) in symmetric information case, the buyer’s optimal contract can coordinate the whole channel, while the vendor can only obtain her reservation profit in this case; (2) in asymmetric information case, the buyer’s optimal contract can almost achieve channel coordination, and the vendor’s profit can be higher than her reservation profit if her defective percentage below the upper bound of the buyer’s estimation; (3) using supply chain contract can improve the supply chain’s efficiency both in symmetric and asymmetric information case.The main innovations of this study are as follows:First, in Salameh and Jaber (2000)’s model the sufficient condition to ensure that shortage will not occur in inspection period may not really prevent their occurrence. To avoid shortage occur in inspection period, in our model when finishing the inspection of the whole batch, the product in this batch can be used to meet demand. We also relax the assumption of perfect inspection process, and allow the buyer’s inspection process make type I mistake, i.e. accepting an item that is defective. In the following, we extend basic model to four cases: ordering cost reduction, adjustable inspection rate, shortage permission and random demand.Second, it is generally assumed that all units produced are of perfect quality in integrated inventory models. In this dissertation we investigate the integrated model with consideration of random defective rate and imperfect inspection process. Also in our model we take the vendor’s setup cost or the buyer’s ordering cost as endogenous variable and analyze the joint optimal decision-making problem of setup cost, ordering cost and economic lot size.Third, using Li and Maghsoodloo’s asymmetrical truncated quadratic quality loss function, we first introduce Taguchi quality loss into integrated inventory model. Also in our model, the vendor can invest in a process to decrease its variance. We analyze how the vendor and the buyer make their decisions to optimize the whole supply chain’s profit.Fourth, in Deming (1982, 1986), Vander Wiel and Vardeman (1994), they take product quality as exdogenous variable. In this dissertation, we take the quality investment as endogenous variable and found all-or-none inspection policy is still optimal when the vendor and buyer cooperate. When the vendor and buyer do not cooperate, we study the Nash game between them and found there may be one unique Nash equilibrium, three Nash equilibria and infinite Nash Equilibria depends on the contract parameters and the buyer’s inspection cost.Last, different from the past literatures which focus on using supply chain contract to control supplier’s quality, in this dissertation by use of principle-agent theory we investigate the design of buyer’s optimal contract to simulate the vendor provide true information and coordinate the inventory level to maximize the buyer’s profit.To sum up, in this dissertation around quality issues we study single firm’s optimal order strategy, multiple firms’integrated inventory model, the interaction between quality investment and inspection strategy and supply chain contracting with asymmetric information. Our work extends the current research in the related areas, and also provides theoretical guidance to production management decision-making.更多还原