考虑供应风险的多源应急物资采购双层规划模型

自然灾害频繁发生,事故灾难不断涌现,公共卫生事件猝不及防,社会安全风险交织叠加,给人们的生产和生活带来了巨大的风险和不确定性。在突发事件背景下,考虑应急物资供应中的各类风险,激励多源应急物资的稳定供给,受到党和政府高度重视。应急物资供应有哪些风险,如何规避这些风险,针对多种渠道的采购,如何优化采购结构。这些问题是本论文关注的重点。本文以政府、制造型企业、受灾地区民众为决策主体的三级供应链为基础,构建了上层以整个供应链系统收益最大化为目标函数、下层以供应风险最小化为目标函数的双层规划模型,对不同情景下物资采购订单的分配进行研究。在此基础上,本文以某市洪涝灾害为例进行分析,证明了模型的可行性,并探究了供应风险变化对物资采购订单分配、以及整个供应链系统收益的影响,以期为政府应急物资采购决策提供参考性建议。     

基于Copula-APD-GARCH模型的投资组合有效前沿分析

根据ES风险度量方法,拓展了马克维茨均值-方差资产组合模型,研究均值-ES准则下的资产组合问题.用APD-GARCH模型刻画风险资产收益率序列,以多元Copula函数描述风险资产间的相关结构信息,构造灵活的Copula-APDG-ARCH模型.利用该模型,借助Monte Carlo模拟,分别研究相关结构是多元正态Copula函数、多元t-Copula函数和多元Clayton Copula函数的风险资产组合的均值一ES有效前沿,并进行比较.实证研究表明,在有效组合范围内,正态Copula函数明显高估了资产的组合风险;当期望收益较小时,t-Copula函数对应的风险值最小,但随着期望收益的增加,多元Clayton Copula函数时应的有效前沿表现最好.     

ASSESSING SOCIAL COSTS OF INEFFICIENT PROCUREMENT DESIGN

This paper considers the social costs implied by inefficient allocation of contracts in a first‐price, sealed‐bid procurement auction with asymmetric bidders. We adopt a constrained (piecewise linear) strategy equilibrium concept and estimate the structural parameters of the bidders' distribution of costs. We estimate social costs defined as the predicted cost difference between the winning firm and the most efficient bidding firm. We also compare the expected procurement costs under two different auction formats. The data is collected from procurement auctions of road painting in Sweden during 1993–1999. The results indicate that the social costs of inefficient contract allocation is about 2% of total potential production cost and that an efficient second‐price auction would lower the expected procurement cost by 2.5%. (JEL: D44, H57, C15)     

多部件采购外包的两阶段均衡投标策略

本文考虑一个由单个制造商和多个供应商群体组成的供应链——该制造商需要采购多个部件,对于每个部件在市场上均存在多个供应商。不同于传统的从各供应商群体分别采购各个部件,制造商考虑将所有部件的采购整体外包给某个供应商。在第一阶段,制造商使用一级价格密封投标的逆向拍卖来确定赢得整体采购合约的供应商。接下来,第一阶段投标的获胜者生产其所能供应的部件,并使用逆向拍卖向第一阶段中未获胜的其他竞标者采购其余部件。我们分析了供应商在两个阶段的均衡竞价策略,并比较了制造商在亲自逐件采购和外包整体采购两种情况下的期望采购成本。我们证明了在两种机制下制造商的总的期望采购成本相等。     

动态均值-方差资产组合的有效性:时变风险容忍度视角

尽管均值-方差模型在静态资产组合优化过程中得到广泛运用并证明是有效的,但在动态情景下,均值-方差模型运用于动态资产组合优化过程中的有效性问题引起人们的质疑：一是常风险规避系数的设定不符合事实;二是投资者偏好设定不符合动态情景下的主流效用函数族。鉴于此,本文假设投资者风险容忍度是资产组合投资期与投资者期望收益率的函数,研究动态均值-方差资产组合的有效性问题。基于均值-方差分析框架构建时变风险容忍度下的动态资产组合模型;运用伊藤定理和拉格朗日乘子法获得最优资产组合封闭解;基于二次效用偏好下的动态资产组合,从资产组合策略、夏普率、确定性等价收益率和有效前沿等视角验证动态均值-方差资产组合策略和业绩,并予以实证。结果表明：动态均值-方差资产组合不但具有同等业绩而且体现了其灵活性和风险对冲价值;尽管动态均值-方差资产组合表现出高杠杆性,但其确定性等价收益率较高,且随投资期的增加呈现倒U型趋势;动态均值-方差资产组合的投资期效应显著,强于投资者期望收益率。研究指出,时变风险容忍度下的动态均值-方差资产组合管理和优化策略有效,但在短投资期（低于12个月）和（或）低期望收益率下并不适用。研究不但拓展了均值-方差模型在动态情境下的应用,而且体现了投资者源于心理和（或）其财富变化的投资行为调整。     

网上拍卖销售与逆向拍卖采购下的库存管理

以电子商务为背景研究网上拍卖销售与逆向拍卖采购下的库存管理。在该问题中,零售商一方面利用网上拍卖销售产品,另一方面利用逆向拍卖进行采购。对于单阶段情形,证明网上拍卖下零售商的期望收益函数是采购量的严格递增的凹函数,从而得到零售商的最优采购策略和供应商的最优投标策略。对于多阶段情形,利用马尔可夫决策过程理论建立该问题的最优控制模型,得到零售商的最优采购策略和供应商的贝叶斯-纳什均衡投标策略均与基本库存策略相类似。     

Common benchmarking and ranking of units with DEA

This paper develops a common framework for benchmarking and ranking units with DEA. In many DEA applications, decision making units (DMUs) experience similar circumstances, so benchmarking analyses in those situations should identify common best practices in their management plans. We propose a DEA-based approach for the benchmarking to be used when there is no need (nor wish) to allow for individual circumstances of the DMUs. This approach identifies a common best practice frontier as the facet of the DEA efficient frontier spanned by the technically efficient DMUs in a common reference group. The common reference group is selected as that which provides the closest targets. A model is developed which allows us to deal not only with the setting of targets but also with the measurement of efficiency, because we can define efficiency scores of the DMUs by using the common set of weights (CSW) it provides. Since these weights are common to all the DMUs, the resulting efficiency scores can be used to derive a ranking of units. We discuss the existence of alternative optimal solutions for the CSW and find the range of possible rankings for each DMU which would result from considering all these alternate optima. These ranking ranges allow us to gain insight into the robustness of the rankings.     

现货价格和需求关联时期权组合合约模式下采购风险管理策略

在现货价格和客户端需求关联的情形下,本文引用期权组合合约建立现货市场供应量有限时的两阶段采购风险管理模型,以期最大化零售商的期望收益。文中先用逆向归纳法列出零售商第二阶段的最优策略,采用标准扰动定理得出有效合约应满足的最优性条件,并将原模型转化为单调的最短路径问题,应用动态规划求解最优的采购策略。最后用算例分析了现货价格与需求的相关系数及现货市场的供应量对最优策略的影响,发现当供应量一定时,各有效合约的最优预订量及有效合约的总预订量都随着相关系数的增大而提高,并且有效合约受相关系数的影响大小取决于合约的灵活性;并且,当相关系数一定时,有效合约的总预订量及执行价格最低的有效合约的最优预订量都随着供应量的增加而单调减少。     

基于数量柔性契约的双源应急物资采购定价模型

针对灾害事件发生的不确定性以及灾害发生后应急物资需求量的爆发式增长，本文设计了一个政府主导的基于数量柔性契约的双源应急物资采购模型。在存在一个现货市场的情况下，政府除了常规采购外，还会与供应方签订一份数量柔性契约，用以建立政企联合储备应急物资的合作关系。通过数理推导，本文发现灾害事件发生概率，政府自身储备量，现货市场采购价格会对双方决策产生重要影响，并给出三个影响因素在满足不同条件时政企双方的最优决策，同时进一步分析了这三个因素对政府采购成本与供应方利润的影响。最后，通过数值模拟的方式对所得结论进行了验证。本文的研究为政府与企业构建联合储备应急物资的合作关系提供了指导与依据。     

基于财政补贴的拥挤定价下公交收费策略研究

交通拥挤是目前世界上多数大中城市普遍面临的问题,公交优先和拥挤定价是针时该问题的有效管理措施.巨额的公交财政补贴,往往是我国城市推行公交优先政策的障碍.本文采用交通行为科学的理论和方法,从系统科学的角度将财政补贴、拥挤定价和公交收费等问题结合起来,设计了基于财政补贴的拥挤定价下的公交收费策略,解释了如何通过拥挤定价和公交收费等手段实现缓解交通压力减少公交财政补贴的管理目标.本文以广州市为典型,进行了相应的策略分析.     

有限供应的现货市场与期权合约下的采购策略

在随机现货价格与随机需求相独立的情况下,当现货市场供应量有限时,本文采用期权组合合约建立两阶段采购风险管理模型,以期最大化零售商的期望利润.文中提供了甄别有效合约的算法,得到零售商的最优采购策略,并进一步用算例分析了现货市场的供应量、现货价格和客户需求的波动性对最优采购策略的影响,发现当现货市场的供应量增加时,零售商应...     

风险资产组合的均值—M有效前沿及其实证分析

本文基于由Carlo Acerbi(2002)提出的一类一致性风险度量—谱风险测度M,给出了谱风险测度的一些性质及构造谱密度的一种具体形式;重点讨论了正态情形下风险资产组合的均值—M有效前沿,探讨了其经济含义,并与经典的均值—方差有效前沿进行了对比研究,获得了若干深入的结果。由于期望短缺ES是特殊的谱风险测度,因此其对应的有效前沿是本文结果的特例。最后,本文利用前面的结论对深市和沪市的风险资产组合的均值—M有效前沿作了实证分析。     

SHORT‐TERM E‐PROCUREMENT STRATEGIES VERSUS LONG‐TERM CONTRACTS

In this paper we compare the following procurement strategies based on their expected costs: strategic partnership, which is based on a long‐term relationship with a single supplier; online search, which is a short‐term strategy; and a combined strategy, which is some combination of the first two strategies. In addition, we determine for the online search and combined strategy the optimal number of suppliers to contact for a price quote, and analyze how it depends on the various cost and demand parameters. The main contribution of this paper is that it does not assume a single procurement strategy, but rather compares three alternatives.     

基于流动性风险的资本资产定价模型

在现有的资产定价理论基础上,研究了考虑流动性风险因素的风险资产定价问题。首先在无套利下对流动性风险进行定价,得到流动性风险的市场价格,进而给出了无风险资产和风险资产的有效前沿。再从风险构成的角度给出了流动性风险的测度和市场价格,推导出两种形式的基于流动性风险的资本资产定价模型(以相对量表示风险的LBCAPM和以绝对量表示风险的LBCAPM)并揭示了资产期望回报的形成过程。最后,介绍了定价模型的应用前景。     

感知的创业激情、 信任与员工创新行为关系研究

实践中, 制造商可通过商业保险策略降低因零部件质量问题造成的经济损失.然而, 商业保险购买成本较高且可能导致供应商轻视质量问题, 放弃质量改进.为此, 本文基于完全信息下单周期两级供应链的采购合约决策模型, 研究制造商如何利用商业保险管理供应链质量风险的问题.通过比较研究, 找出商业保险策略的实施条件, 并给出最优采购合约及商业保险策略.研究结果表明: (1) 当供应商的企业规模较小、抗风险能力较低时, 商业保险策略可完全消除风险承受能力对双方交易的制约, 促进双方达成交易; (2) 当供应商的企业规模较大、抗风险能力较高时, 制造商可利用商业保险策略降低零部件采购价格, 提高期望利润; (3) 在商业保险策略下, 制造商的最优商业保险策略是全额投保; (4) 商业保险的实施不一定造成零部件质量水平的下降.当质量成本或供应商的风险承受能力较低时, 商业保险策略与质量改进之间具有互补效应.当风险承受能力和质量成本均比较高时, 商业保险策略与质量改进之间具有替代效应.     

不同突发事件下进口原油采购策略

石油对经济生活的重要性不言而喻,中国原油的高对外依存度及集中的进口来源区域引起我们对能源安全的广泛关注,如何有效最小化国际原油价格波动和供应短缺或中断带来的风险,制定突发事件影响下的最佳采购策略是我们必需关注的焦点,但目前结合突发事件的采购策略研究还不足。论文通过采用符合中国原油进口习惯的月度数据,建立了突发事件下的CVaR模型,综合考虑价格波动、供应中断造成的GDP冲击和战略石油储备因素,分析三种不同突发事件情景下的原油进口采购策略。研究表明：当预期中东区域出现危机时,非洲和欧洲/俄罗斯是增加采购量的理想选择,若迪拜价格波动不剧烈,亚太采购量也可适当增加;对于仅仅只有价格变动,动用战略石油储备降低风险有限,只有当供给中断时,动用战略储备才能发挥巨大的降低风险,更好的减少对国民经济冲击的作用。本文在最小化原油进口风险值且同时考虑进口来源多样化、风险、成本及价格变动率的情况下,构建的基于CVaR的应急原油进口采购策略模型,丰富了该领域的研究成果,为中国原油进口采购策略提供了具体可操作的参考。     

制造商流程改进与采购合同联合优化

如何降低供应风险是供应链管理中的热点问题。本文考虑供应商拥有关于初始可靠性的私有信息,且制造商流程改进可提高初始可靠性,运用委托代理理论,研究了制造商流程改进和采购策略联合优化下的最优合同设计。通过对比对称和不对称信息下制造商的最优采购合同,发现信息不对称的存在降低了制造商向低初始可靠性供应商订货的概率,还可能导致过度努力。信息不对称的存在不一定造成社会福利损失,也不一定产生信息租金。当供应商的初始可靠性水平和纳什谈判力满足一定条件时,相比与制造商的最优采购合同,供应商披露私有信息会使供应链实现帕累托改进。最后通过算例验证了模型的结论。本文对供应风险下的采购实践有很好的参考价值和指导意义。     

A Multi‐Supplier Sourcing Problem with a Preference Ordering of Suppliers

We study a sourcing problem faced by a firm that seeks to procure a product or a component from a pool of alternative suppliers. The firm has a preference ordering of the suppliers based on factors such as their past performance, quality, service, geographical location, and financial strength, which are commonly included in a supplier scorecard system. Thus, the firm first uses available inventory from supplier 1, if any, then supplier 2, if any, and so on. The suppliers differ in costs and prices. The buyer firm seeks to determine which suppliers to purchase from and in what quantities to maximize its total expected profit subject to the preference ordering constraint. We present the optimal solution to this problem, and show that it has a portfolio structure. It consists of a sub‐set of suppliers that are ordered by their underage and overage costs. This portfolio achieves a substantial profit gain compared to sourcing from a unique supplier. We present an efficient algorithm to compute the optimal solution. Our model applies to component sourcing problems in manufacturing, merchandizing problems in retailing, and capacity reservation problems in services.     

Managing stochastic demand in an Inventory Routing Problem with transportation procurement

We study an Inventory Routing Problem in which the supplier has a limited production capacity and the stochastic demand of the retailers is satisfied with procurement of transportation services. The aim is to minimize the total expected cost over a planning horizon, given by the sum of the inventory cost at the supplier, the inventory cost at the retailers, the penalty cost for stock-out at the retailers and the transportation cost. First, we show that a policy based just on the average demand can have a total expected cost infinitely worse than the one obtained by taking into account the overall probability distribution of the demand in the decision process. Therefore, we introduce a stochastic dynamic programming formulation of the problem that allows us to find an optimal policy in small size instances. Finally, we design and implement a matheuristic approach, integrating a rollout algorithm and an optimal solution of mixed-integer linear programming models, which is able to solve realistic size problem instances. Computational results allow us to provide managerial insights concerning the management of stochastic demand.     

Updating Inventories of Substitutable Resources in Response to Forecast Updates

We show simple yet optimal results to update the inventory/capacity levels, expected profit, fill rates, and service levels of substitutable resources in response to an updating of the mean demand forecasts for the resources. We find that a change in the mean demand of one resource does not affect the optimal inventory level of any other resource. The results are obtained for demands with location‐scale distribution, and for a revenue structure satisfying a triangle property such that the manager will always use the inventory of a resource to meet her own demand first before using it for substitution. The results for updating the performance measures also extend to managers who maintain non‐optimal inventory/capacity levels. Implications for procurement, sales and operational planning, and multi‐store operations are discussed.