Yusen Xia

Real-time disruption management in a two-stage production and inventory system

This paper presents a general disruption management approach for a two-stage production and inventory control system. A penalty cost for deviations of the new plan from the original plan is incorporated and the concept of a disruption recovery time window is introduced. We define two classes of problems: one with fixed setup epochs and another with flexible setup epochs. With linear or quadratic penalty functions for production/ordering quantity change and fixed setup epochs, the best recovery plan is obtained by solving a quadratic mathematical programming problem. With convex penalty functions for quantity changes and flexible setup epochs, it is shown that the second stage orders have identical order quantities within each production cycle. Therefore, in a lot-for-lot system, the ordering and production quantities for both stages are the same. As a special case, we consider disruption recovery problems with short time windows spanning one or two production cycles. We also discuss solution procedures for both major and minor disruption problems and give an extension for the case of multiple retailers. Throughout the paper managerial insights are presented that indicate how a company should respond to various types of disruptions during its operations.

A Production-Inventory System with Markovian Capacity and Outsourcing Option

We study the optimal production-inventory-outsourcing policy for a firm with Markovian in-house production capacity that faces independent stochastic demand and has the option to outsource. We find very simple optimal policy forms under fairly reasonable assumptions. In addition, when the capacity Markov process is stochastically monotone, the policy parameters decrease in the firms current capacity level under additional assumptions. All these results extend to the infinite-horizon and undiscounted-cost cases. We analyze comparative statics and the necessity of some technical conditions, and discuss when the outsourcing option is more valuable.

Strategic outsourcing for competing OEMs that face cost reduction opportunities

This paper explores production and outsourcing decisions for two Original Equipment Manufacturers (OEMs) who produce partially substitutable products and have opportunities to invest in reducing the manufacturing cost. In such an environment, competition drives both OEMs to set lower prices and invest more than would maximize their combined profits, particularly when product substitutability is high. However, outsourcing provides a mechanism by which the two OEMs can credibly signal that they will not overinvest in cost reduction, mitigating a mutually destructive cost competition. Our paper explores the role that an external supplier(s) can play in dampening competition between the OEMs when there are opportunities to invest in cost reduction. In particular, we characterize the conditions under which a supplier can profitably enter the market by inducing the OEMs to outsource production. We first examine a basic model of two identical OEMs in which there is a single common supplier and a single component that is a candidate for outsourcing. Later, we extend the basic model to allow for market asymmetry, two suppliers, and more than one component that might be outsourced.

Strategic interactions between channel structure and demand enhancing services

In this paper, we investigate how opportunities to invest in demand enhancing services for a product line affect the interactions between a manufacturer and her dealer. Many demand enhancing services, e.g. after sales support, warranty repair etc. can be provided either by the manufacturer or they can be delegated to the dealer. We first show that when a manufacturer retains control of such services, the dealer will have an incentive to choose a decentralized organizational structure as a means of committing to non-product line pricing since this will encourage the manufacturer to invest more in demand enhancing services. We then consider a game that is played between the manufacturer and the dealer in which the dealer chooses between centralized (product line pricing) or decentralized (non-product line pricing) operations, and the manufacturer chooses between insourcing the services, i.e. providing them herself, or outsourcing them to the dealer. We find that the equilibrium depends on which, if any, channel partner has the ability to act as a Stackelberg leader. If the dealer can move first, then the equilibrium will always be outsourced services and centralized dealer operations. However, if either the manufacturer moves first or if neither partner can move first, then the equilibrium can be either insourced services and decentralized dealer operations or outsourced service and centralized dealer operations.

Sharing demand and supply risk in a supply chain

This article studies two contract mechanisms to share demand and supply risk in a decentralized supply chain. In an option contract, the buyer reserves capacity with a supplier who guarantees delivery up to this limit. This insulates the buyer from any disruption risk, but the supplier faces both demand and supply risk. The second mechanism, the firm order contract, represents a conventional dyadic channel relationship where the buyer places a firm order and the supplier builds capacity but does not guarantee delivery if any disruption occurs. It is shown that the buyers preference for using the different risk-sharing mechanisms switches back and forth (as the probability of disruption increases). Consequently, a supplier with a higher disruption risk may make higher expected profits compared to one with lower risk. In addition, the buyer may benefit from a higher wholesale price since it provides incentive for the supplier to participate without requiring the buyer to use higher order quantities. Two operational mitigation strategies that can be used by the buyer to hedge against the disruption risk are considered: the use of an alternate reliable supplier during a shortage and use of a direct subsidy for the supplier to improve reliability. It is found that the value of the reliable supplier depends on the type of contract with the unreliable supplier: interestingly, it is in the option contract—where supply is guaranteed—that the buyer almost always uses the reliable supplier as well. Also, it is found that offering a subsidy for reliability improvement acts as a strategic alternative to placing large pre-orders as a way to improve supplier operations.

Production-Inventory Systems with Lost Sales and Compound Poisson Demands

This paper considers a continuous-review, single-product, production-inventory system with a constant replenishment rate, compound Poisson demands, and lost sales. Two objective functions that represent metrics of operational costs are considered: 1 the sum of the expected discounted inventory holding costs and lost-sales penalties, both over an infinite time horizon, given an initial inventory level; and 2 the long-run time average of the same costs. The goal is to minimize these cost metrics with respect to the replenishment rate. It is, however, not possible to obtain closed-form expressions for the aforementioned cost functions directly in terms of positive replenishment rate PRR. To overcome this difficulty, we construct a bijection from the PRR space to the space of positive roots of Lundbergs fundamental equation, to be referred to as the Lundberg positive rootLPR space. This transformation allows us to derive closed-form expressions for the aforementioned cost metrics with respect to the LPR variable, in lieu of the PRR variable. We then proceed to solve the optimization problem in the LPR space and, finally, recover the optimal replenishment rate from the optimal LPR variable via the inverse bijection. For the special cases of constant or loss-proportional penalty and exponentially distributed demand sizes, we obtain simpler explicit formulas for the optimal replenishment rate.

Private labels: Facilitators or impediments to supply chain coordination

We consider a retailer’s decision of whether to develop an internally produced, private label version of a national brand and the role that this decision plays in coordinating the supply chain. Our model assumes that the perceived quality of the private label is lower than that of the national brand, and we allow for the two products to have different marginal costs. We further allow for a fixed development cost that the retailer must incur to develop private label capability, and distinguish two types of private labels depending upon whether they would or would not be developed as product line extensions by a vertically integrated supply chain. We refer to these two types as first-best (FB) and non-first-best (NFB) product line extensions, respectively. When the private label can be characterized as a NFB product line extension, its development creates adverse cannibalization effects, yet it also helps to mitigate the effects of double marginalization with respect to the national brand. We characterize the conditions under which the retailer will develop private label capability, and distinguish among the conditions under which this is either beneficial or detrimental to the overall performance of the supply chain.

An Interactive Goal Programming Procedure for Operational Recovery Problems

We propose an interactive Goal Programming (GP) for operational recovery problems that are present in diverse areas of application. After defining the problem we discuss its relevance to scenarios taken from airline scheduling, supply chain management and call centers operations. We then construct the GP procedure for operational recovery decision making and illustrate the mechanics of the proposed procedure through two examples: an abstract example based on a minimum spanning tree problem and a more practical example of a production-inventory problem.

Strategic outsourcing decisions for manufacturers competing on product quality

This article examines strategic outsourcing decisions for two competing manufacturers whose key components have quality improvement (QI) opportunities. We consider the effects of vertical and horizontal product differentiation on demand. In deriving the Subgame Perfect Nash Equilibria (SPNE), it is shown that either a symmetric outsourcing strategy (i.e., both manufacturers outsource) or an asymmetric sourcing strategy profile (i.e., manufacturers use different sourcing strategies) can be an SPNE. Insights are provided into how sourcing strategies are affected by the factors such as fixed setup cost, unit production cost, QI efficiency, and horizontal and vertical differentiations. It is found that larger horizontal differentiation expands the range over which symmetric outsourcing is an equilibrium. In addition, the outsourcing manufacturer may provide a higher QI level, produce a higher quantity, and offer a lower retail price than the insourcing one in the asymmetric sourcing setting. On the other hand, the insourcing manufacturer should pay more attention to the effect of the rivals sourcing strategy on the QI level than the outsourcing one. Finally, it is shown that all players have an incentive to determine sourcing partner relationships before the wholesale price contract is offered.

Revenue management for a supply chain with two streams of customers

In this paper, we consider revenue management for a service supply chain with one supplier and one retailer. The supplier has a limited capacity of a perishable product and both the supplier and the retailer face customers. Each customer may choose to buy a product from either the supplier or the retailer by considering prices and the cost associated with switching. For the centralized model, the supplier determines the selling prices for both herself and the retailer, and the retailer simply collects a commission fee for each product sold. We derive monotone properties for the revenue functions and pricing strategies. Further, we show that the commission fee increases the retailers price while decreasing the suppliers and leads to efficiency loss of the chain. For the decentralized decision-making model, the supplier and the retailer compete in price over time. Two models are considered. In the first, the retailer buys products from the supplier before the selling season and in the second the retailer shares products with the supplier in retailing. For both models, we discuss the existence of the equilibrium and characterize the optimal decisions. Numerical results are presented to illustrate properties of the models and to compare the supply chain performance between the centralized and the decentralized models.