Optimal Expediting Policies for a Serial Inventory System with Stochastic Lead Time

In recent supply chains, often operating multiple delivery modes such as standard freight shipping and air is an effective way of addressing both delivery lead time uncertainties and service rates. We propose a model on how to optimally operate multiple delivery modes. We consider a serial supply chain and an expediting option from intermediate installations to the downstream of the chain. The goods move stochastically among the installations and the system faces a stochastic demand. We identify systems that yield simple optimal policies, in which both regular ordering and expediting follow a variant of the base stock policy. Expediting allows the system to be leaner due to the reduced regular order amount. In addition, we provide managerial insights linking expediting, base stock levels, and expediting costs based on analytical and numerical results.     

技术创新网络中企业间依赖、企业开放度对合作绩效的影响

技术创新网络中企业的合作绩效受到企业间依赖关系与企业开放度的影响。本文在对相关文献梳理的基础上,提出了网络内企业间依赖与开放度对合作绩效影响的理论假设,利用我国企业技术创新合作过程中的实际数据,对其进行了实证检验。结果表明,技术创新网络中企业间联合依赖与不对称依赖的程度会影响到企业在合作过程中的开放度,同时也会影响到企业的合作绩效。进而,作为企业间依赖与企业合作绩效间重要的中介,开放度也显著影响着企业合作的绩效。     

Two remarks on order statistics

Let X₍₁₎,…,X_(n) be the order statistics of n iid distributed random variables. We prove that (X_(i)) have a certain Markov property for general distributions and secondly that the order statistics have monotone conditional regression dependence. Both properties are well known in the case of continuous distributions.     

A note on closure of the ILR and DLR classes under formation of coherent systems

In this paper, we give the closure of the class of increasing likelihood ratio (ILR) life distributions under the formation of certain coherent systems with independent and identically distributed components, and particularly in k-out-of-n systems. Some possible definitions of its dual class (DLR) are discussed and results about the closure are given. Furthermore, we include examples which show that these two aging classes are not closed under formation of special coherent systems. This work has been supported by Ministerio de Ciencia y Tecnologia, Grants PB96-1105 and BFM2000-0362.     

Dispersive ordering—Some applications and examples

A basic concept for comparing spread among probability distributions is that of dispersive ordering. Let X and Y be two random variables with distribution functions F and G, respectively. Let F ⁻¹ and G ⁻¹ be their right continuous inverses (quantile functions). We say that Y is less dispersed than X (Y≤ _disp X) if G ⁻¹(β)−G ⁻¹(α)≤F ⁻¹(β)−F ⁻¹(α), for all 0<α≤β<1. This means that the difference between any two quantiles of G is smaller than the difference between the corresponding quantiles of F. A consequence of Y≤ _disp X is that |Y ₁−Y ₂| is stochastically smaller than |X ₁−X ₂| and this in turn implies var(Y)≤var(X) as well as E[|Y ₁−Y ₂|]≤E[|X ₁−X ₂|], where X ₁, X ₂ (Y ₁, Y ₂) are two independent copies of X(Y). In this review paper, we give several examples and applications of dispersive ordering in statistics. Examples include those related to order statistics, spacings, convolution of non-identically distributed random variables and epoch times of non-homogeneous Poisson processes. This work was supported in part by KOSEF through Statistical Research Center for Complex Systems at Seoul National University. Subhash Kochar is thankful to Dr. B. Khaledi for many helpful discussions.     

Disability and the promises of technology: Technology, subjectivity and embodiment within an order of the normal

The topic of this article is the promises of technology for disabled people. The starting point is that disabled is not something one is but something one becomes, and, further, that disability is enacted and ordered in situated and quite specific ways. The question, then, is how people become, and are made, disabled - and, in particular, what role technologies and other material arrangements play in enabling and or disabling interactions. Drawing on a study of the uses of new technologies in the lives of disabled people in Norway, and recent work in disability studies as well as social studies of science and technology, this article explores precisely what positions and capacities are enabled; how these are made possible in practice; the specific configuration of subjectivity, embodiment and disability that emerges; and the limits to this mode of ordering disability and its technologies. The argument is that in this context the mobilization of new technologies works to build an order of the normal and turn disabled people into competent normal subjects. However, this strategy based on compensation achieves its goals only at a very high price: by continuing to reproduce boundaries between abled and disabled, and normal and deviant, which constitute some people as disabled in the first place. There are thus limits to normalization. And so, notwithstanding their generative and transformative power, technologies working within an order of the normal are implicated in the (re)production of the asymmetries that they and it seek to undo.     

Dependence in the 2001 one-number census project

Summary.  The one-number census approach was developed by the Office for National Statistics to adjust the counts from the 2001 census of England and Wales for underenumeration. The method is underpinned by an assumption of independence between the count of the population that was given by the 2001 census and the count that was given by the Census Coverage Survey. Some dependence was, however, detected, and the paper describes the strategy that was used to measure dependence and to adjust the 2001 census population estimates.     

Selling with Money‐Back Guarantees: The Impact on Prices,Quantities, and Retail Profitability

In this paper, we consider a retailer adopting a “money‐back‐guaranteed” (MBG) sales policy, which allows customers to return products that do not meet their expectations to the retailer for a full or partial refund. The retailer either salvages returned products or resells them as open‐box items at a discount. We develop a model in which the retailer decides on the quantity to procure, the price for new products, the refund amount, as well as the price of returned products when they are sold as open‐box. Our model captures important features of MBG sales including demand uncertainty, consumer valuation uncertainty, consumer returns, the sale of returned products as open‐box items, and consumer choice between new and returned products and possibility of exchanges when restocking is considered. We show that selling with MBGs increases retail sales and profit. Furthermore, the second‐sale opportunity created by restocking returned products enables the retailer to generate additional revenues. Our analysis identifies the ideal conditions under which this practice is most beneficial to the retailer. Offering an MBG without restocking increases the new product price. We show that if the retailer decides to resell the returned items as open‐box, the price of the new product further increases, while open‐box items are sold at a discount. On the other hand, customers enjoy more generous refunds along with lower restocking fees. The opportunity to resell returned products also generally decreases the initial stocking levels of the retailer. Our extensive numerical study substantiates the analytical results and sharpens our insights into the drivers of performance of MBG policies and their impact on retail decisions.     

考虑策略型消费者行为的零售商订货及忠诚计划联合决策研究

顾客忠诚计划是零售商的重要销售策略之一. 本文针对两期折扣问题中零售商的订货和积分回馈计划投入的联合决策问题,基于完全理性假设,并结合问题的实际情况,考虑了全价期单期以及全价期和折扣期两期的积分回馈计划,构建了基于这两种积分回馈计划下的策略型消费者决策模型. 分析了不同积分回馈计划对策略型消费者行为的影响,进而讨论了零售商在不同决策下的收益情况,探索了零售商订货和积分回馈计划联合决策的制定. 研究发现：(1)积分回馈计划会对策略型消费者行为产生影响,从而影响零售商的决策和收益;(2)订货和忠诚计划制定的联合决策有利于零售商提高收益;(3)对于单位成本低的商品,面向全价期的积分回馈计划的最优收益提升较大;(4)对于商品价值与实际价格差异较小的商品,积分回馈计划对最优收益的提升作用较大. 具体而言,如果商品单位成本小于等于折扣价,则面向全价期的积分回馈计划的最优收益提升较大,反之,则面向全价期和折扣期的积分回馈计划的最优收益提升较大.