考虑质量偏好的两阶段服务供应链质量控制策略

研究了一个集成商和一个提供商所组成的服务供应链的质量控制问题。考虑集成商的质量缺陷承诺和提供商的质量偏好,并将提供商的质量活动区分为质量改进和质量保持两个阶段,分别建立了服务供应链成员的效用函数,同时考虑服务供应链成员的竞争与合作,运用博弈理论,优化得到单阶段与两阶段时,集成商的最优服务价格和质量缺陷承诺,以及提供商的最优服务质量改进程度。最后,通过对比分析及数值仿真发现,考虑两阶段质量控制较单阶段情形,更有利于服务供应链较长期限内获得更多效用。其次,服务提供商质量偏好对服务供应链单阶段与两阶段下的最优效用和质量控制策略均产生一定影响。     

Three-level warranty service contract among manufacturer,agent and customer: A game-theoretical approach

A warranty is a service contract between a manufacturer and a customer which plays a vital role in many businesses and legal transactions. In this paper, various three-level service contracts will be presented among the following three participants; a manufacturer, an agent, and a customer. In order to obtain a better result, the interaction between the aforementioned participants will be modeled using the game theory approach. Under non-cooperative and semi-cooperative games, the optimal sale price, warranty period and warranty price for the manufacturer and the optimal maintenance cost or repair cost for the agent are obtained by maximizing their profits. The satisfaction of the customer is also maximized by being able to choose one of the suggested options from the manufacturer and the agent, based on the risk parameter. Several numerical examples and managerial insights are presented and used to illustrate the models presented in this paper.     

Optimal pricing,EOL (end of life) warranty,and spare parts manufacturing strategy amid product transition

We study firm’s strategy to determine its product price and warranty period, and plan the spare parts manufacturing so as to maximize its profit and at the same time to fulfill its commitment to providing the customer with the key part continuously over the relevant decision time horizon, i.e., the product’s life cycle plus its EOL service (warranty) period. To examine the research question, we develop and solve a two-stage optimal control theory model. From the numerical analysis, we infer as follows. It is not always true that the longer the EOL warranty period, the better for the company’s profitability, implying there exists an optimal EOL warranty period that balances all the relevant forces like market demand and cost structures. The relationship between optimal EOL warranty period and failure rate (defect rate) is concave: when the defect rate is moderate, the company has to increase its EOL warranty period as the defect rate increases so as to compensate for the deteriorating quality; but, when the defect rate is beyond a threshold level, the company needs to curtail its EOL warranty commitment as the defect rate increases in order to avoid excessive cost to service the failed parts. By depicting key dynamics in this managerial problem, this paper sheds light on how to make decision for optimal pricing and warranty when the product life cycle is finite and the company is obliged to provide after-sales services to customers for an extended period of time after the current product is no longer produced.     

Optimal maintenance strategy under renewable warranty with repair time threshold

In this paper, we consider a periodic preventive maintenance model, from the manufacturer's perspective, which can be implemented to reduce the maintenance cost of a repairable product during a given warranty period. The product is assumed to deteriorate with age and the warranty policy we adopt in this paper takes into account the two factors of failure time and repair time of the product when the product failure occurs. Under the proposed two-factor warranty, a repair time threshold is pre-determined and if the repair takes more time than that of the threshold, the failed product is replaced with a renewed warranty policy. Otherwise, the product is only minimally repaired to return to the operating state. During such a renewable warranty period, preventive maintenance is conducted to reduce the rate of degradation periodically while the product is in operation. By assuming certain cost structures, we formulate the expected warranty cost during the warranty period from the manufacturer's perspective when a periodic preventive maintenance strategy is adapted. Although more frequent preventive maintenance increases the warranty cost, the chance of product failures would be reduced. The main aim of this paper is to accomplish the optimal trade-off between the warranty cost and the preventive maintenance period by determining the optimal preventive maintenance period that minimizes the total expected warranty cost during the warranty period. Assuming the power law process for the product failures, we illustrate our proposed maintenance model numerically and study the impact of relevant parameters on the optimal preventive maintenance policy.     

On the subject of non optimal play in zero sum extensive games: “The trap phenomenon”

This paper discusses the best reply to be played after a mistake is committed in a zero sum extensive game. First it is shown that the minimax strategies do not, in general, provide specific answers. Two possible criteria are proposed to narrow the set of optimal strategies. Then, a surprising feature of the selected optimal strategy may be observed: it may set the stage in advance so that, if the mistake is committed, the penalty will be maximal. This is called: the “trap phenomenon”.     

Maintenance optimization for second‐hand products following periodic imperfect preventive maintenance warranty period

The maintenance policy for a product's life cycle differs for second‐hand and new products. Although several maintenance policies for second‐hand products exist in the literature, they are rarely investigated with reference to periodic inspection and preventive maintenance action during the warranty period. In this research, we study an optimal post‐warranty maintenance policy for a second‐hand product, which was purchased at age x with a fixed‐length warranty period. During the warranty period, the product is periodically inspected and maintained preventively at a prorated cost borne by the user, while any product failure is only minimally repaired by the dealer. After the warranty expires, the product is self‐maintained by the user for a fixed‐length maintenance period and the costs incurred during this time are fully borne by the user. At the end of the maintenance period, the product is replaced with a product of the user's choice. This study is focused on the determination of an optimal length for the maintenance period after the warranty expiration. As a criterion for the optimality, we adopt the long‐run mean cost during the second‐hand product's life cycle from the user's perspective. Finally, our results are analyzed numerically for sensitive analysis of several relevant factors, assuming that the failure distribution follows a Weibull distribution.     

Optimal maintenance service contract negotiation with aging equipment

In recent years, there has been a growing trend to out-source service operations in which the equipment maintenance is carried out by an external agent rather than in-house. Often, the agent (service provider) offers more than one option and the owners of equipment (customers) are faced to the problem of selecting the optimal option, under the terms of a contract. In the current work, we develop a model and report results to determine the agent’s optimal strategy for a given type of contract. The model derives in a non-cooperative game formulation in which the decisions are taken by maximizing expected profits. This work extends previous models by considering the realistic case of equipments having an increasing failure intensity due to imperfect maintenance, instead of the standard assumption that considers failure times are exponentially distributed (constant failure intensity). We develop a model using a linear function of time to characterize the failure intensity. The main goal, for the agent, is to determine the pricing structure in the contract and the number of customers to service. On the other hand, for the clients, the main goal is to define the period between planned actions for preventive maintenance and the time to replace equipments. In order to give a complete characterization of the results, we also carry out a sensitivity analysis over some of the factors that would influence over the failure intensity.     

考虑衍生需求和粉丝效应的视频服务供应链质量努力策略研究

视频服务作为“互联网+”时代下的新型文化产业模式,日益受到人们的关注。本文构建一个视频服务平台和一个视频服务提供商组成的视频服务供应链,视频服务提供商通过视频服务平台向用户提供基础服务和两阶段衍生服务。考虑视频服务供应链成员的四种行为因素对服务需求的影响,并分别建立平台定价模式和提供商定价模式下服务供应链成员的利润函数,运用博弈理论,优化求解得到两种模式下服务供应链成员最优的质量努力策略和利润。最后,通过数值仿真,探讨了粉丝效应和收益分成比例与最优质量努力策略和最优利润的相关性,并得出相关结论,给出管理启示。     

A Stackelberg Network Game with a Large Number of Followers

We consider a hierarchical network game with multiple links, a single service provider, and a large number of users with multiple classes, where different classes of users enter the network and exit it at different nodes. Each user is charged by the service provider a fixed price per unit of bandwidth used on each link in its route, and chooses the level of its flow by maximizing an objective function that shows a tradeoff between the disutility of the payment to the service provider and congestion cost on the link the user uses, and the utility of its flow. The service provider, on the other hand, wishes to maximize the total revenue it collects. We formulate this problem as a leader-follower (Stackelberg) game, with a single leader (the service provider, who sets the price) and a large number of Nash followers (the users, who decide on their flow rates). We show that the game admits a unique equilibrium, and obtain the solution in analytic form. A detailed study of the limiting case where the number of followers is large reveals a number of interesting and intuitive properties of the equilibrium, and answers the question of whether and when the service provider has the incentive to add additional capacity to the network in response to an increase in the number of users on a particular link.     

Optimal lot size and inspection policy for products sold with warranty

This paper develops a mathematical model to jointly determine the optimal lot size and product inspection policy for a deteriorating production system, when products are sold with free minimal repair warranty. Due to system deterioration, a last-K product inspection scheme is proposed, under which the last K products in a production lot are inspected and nonconforming products found are reworked. Based on the model, we show that there exist a unique optimal lot size and a corresponding inspection policy such that the expected total cost per unit time is minimized. Since there is no closed-form expression for the optimal lot size, an upper bound and approximate solutions are obtained to facilitate the search process. Furthermore, an algorithm is provided to efficiently search for the optimal policy and the performance of the optimal policy is evaluated through numerical examples.     

新产品定价决策的影响因素分析

新产品的成功销售取决于两个重要的因素:一是具有生产特性的工程变量,比如产品的可靠性水平;一是具有市场特征的影响因素,比如价格和保障机制。为了实现收益,制造商必须认真审视价格、产品可靠性和保障机制的选择。因此,本文将价格作为外生变量,将保障机制与可靠性作为决策变量,建立了以最大化为目标的收益模型,分析可靠性与保障机制的最优策略。另外,探讨当不同变量的敏感性参数发生变化时,最优保障机制与产品可靠性的变化规律。最后,通过算例分析收益函数的基本特性,结论显示消费者总是从产品保障机制的信号中判断产品的可靠性水平,这对新产品销售有一定的借鉴意义。     

考虑云安全风险的个人云存储服务最优定价策略

针对现有个人云存储服务纷纷关闭的现象,如何根据不同市场时期和云用户特征,制定合理的定价策略已成为个人云存储服务商面临的挑战性问题。本文在考虑云安全风险,云用户感知价值及弹性成本对个人云存储服务定价的影响,建立了基于云安全风险的两阶段定价模型,给出了免费试用时长确定下的最优决策及免费试用时长不确定下的最优免费试用时长及最优价格。借助数值分析,进一步研究了云安全风险系数,云用户感知价值,云安全运营成本系数对最优免费时长,最优利润的影响,结果表明,当云安全风险系数适中时,个人云存储供应商(PCSP)采取两阶段定价策略。另外,最优利润随着云安全风险系数,免费试用时长,单位安全运营成本的增加先增加后减少。     

Joint Determination of Production Cycle and Inspection Intervals in a Deteriorating Production System

This paper considers production-maintenance policy for the deteriorating production system which can go ‘out of control’ while producing items. Once out of control, the production process produces some proportion of defective items. The defective items are reworked at some cost before being shipped, or, if passed to the customer, incur much larger warranty cost. Thus, to operate this system economically, periodic inspection and restoration of the process are needed. A mathematical model representing the expected annual cost is developed to determine the production cycle and process inspection intervals jointly. A case of equally spaced inspection intervals is solved by using an approximation to the cost function.     

Optimal warranty policies for systems with imperfect repair

We investigate a system whose basic warranty coverage is minimal repair up to a specified warranty length. An additional service is offered whereby first failure is restored up to the consumers’ chosen level of repair. The problem is studied under two system replacement strategies: periodic maintenance before and after warranty. It turns out that our model generalizes the model of Rinsaka and Sandoh [K. Rinsaka, H. Sandoh, A stochastic model with an additional warranty contract, Computers and Mathematics with Applications 51 (2006) 179–188] and the model of Yeh et al. [R.H. Yeh, M.Y. Chen, C.Y. Lin, Optimal periodic replacement policy for repairable products under free-repair warranty, European Journal of Operational Research 176 (2007) 1678–1686]. We derive the optimal maintenance period and optimal level of repair based on the structures of the cost function and failure rate function. We show that under certain assumptions, the optimal repair level for additional service is an increasing function of the replacement time. We provide numerical studies to verify some of our results.     

An auction model arising from an Internet search service provider

Most search service providers such as Lycos and Google either produce irrelevant search results or unstructured company listings to the consumers. To overcome these two shortcomings, search service providers such as GoTo.com have developed mechanisms for firms to advertise their services and for consumers to search for the right services. To provide relevant search results, each firm who wishes to advertise at the GoTo site must specify a set of keywords. To develop structured company listings, each firm bids for priority listing in the search results that appear on the GoTo site. Since the search results appear in descending order of bid price, each firm has some control over the order in which the firm appears on the list resulting from the search. In this paper, we present a one-stage game for two firms that captures the advertising mechanism of a search service provider (such as GoTo). This model enables us to examine the firm’s optimal bidding strategy and evaluate the impact of various parameters on the firm’s strategy. Moreover, we analyze the conditions under which all firms would increase their bids at the equilibrium. These conditions could be helpful to the service provider when developing mechanisms to entice firms to submit higher bids.     

A simultaneous multi-issue negotiation through autonomous agents

Automated negotiation through autonomous agents has become increasingly important since the advent of e-marketplace. A deadlock may arise in which both negotiators refuse to disclose more information; then, mediation is required. We propose an agent-based sealed-bid design in which both agents simultaneously submit their respective offers to the mediate agent, and construct an efficient negotiation strategy which can reach an agreement aiming to maximize their owner’s utility. An important contribution of this paper is that we consider negotiators not necessarily to conflict over all issues, such as quantity. Our experimental results demonstrate that the proposed automated negotiation strategy is efficient in terms of the Pareto-efficiency of the negotiated contracts, the joint utility obtained, and the equality of both agents. In addition, since disclosure of information is reduced greatly, the design can discourage counter-speculation and effectively control fraud and misrepresentation to a certain extent. The method we proposed is simple and stable in the context of a game and the model could be well suited for practical agent applications.     

Optimal system design considering warranty,periodic preventive maintenance,and minimal repair

This paper presents a cost minimisation model for an optimal design of a mixed series-parallel system with deteriorating components. The model incorporates warranty, periodic preventive maintenance, and minimal repair in the design of system configuration. Imperfect repair is adopted to model the effect of preventive maintenance. Both free and pro-rata warranty policies are considered. A numerical example is given to demonstrate the application of this model.     

基于分类服务机制的可预约排队系统设计和服务定价研究

采取合理有效的服务机制和服务定价是确保服务型企业持续有效运行的重要方式,服务提供商设计合理的服务策略可以使得服务收益达到最优。本文以服务可预约的排队系统为研究背景,对服务提供商分类服务机制选择和服务定价策略进行研究。通过考虑由两种服务策略下顾客之间的平均等待时间的对比和顾客等待厌恶心理参数形成的全新顾客服务效用模型,给出服务提供商在不同服务机制下的最优服务策略以及顾客市场规模对其服务策略选择的影响。研究表明,当预约顾客的市场规模相对较小时,服务提供商可以采取分类服务机制,即同时服务预约顾客和未预约顾客以增加服务收益,反之亦然。此外,预约顾客等待厌恶程度能够显著增大服务提供商的服务定价。     

Pricing of full-service repair contracts

Full-service repair contracts are becoming increasingly popular, especially as an add-on to leasing contracts for technical investment products. This paper presents a model for pricing full-service repair contracts in the presence of risk-averse customers. The model identifies the optimal portfolio of full-service contracts and on-call service agreements to be offered by the service provider. The optimal full-service price is established, with failure arrivals being modeled as Poisson events and the cost of individual failures being stochastic. An existing on-call service business represents the price benchmark. The model is readily applicable for any service provider for small investment products such as special-purpose trucks or printing equipment.     

Optimal decision making in a maintenance service operation

In recent years, there has been a dramatic increase in the out sourcing of equipment maintenance with the maintenance being carried out by an external agent rather than in-house. Often, the agent offers more than one option and the owners of equipment (customers) are faced with the problem of selecting the optimal option. The optimal choice depends on their attitude to risk and the parameters of the different options. The agent needs to take these issues into account in the optimal selection of the parameters for the different options and this requires a game theoretic formulation. The papers deals with one such model formulation to determine the agent's optimal strategy with regards the pricing structure, the number of customers to service and the number of service channels.