Operational issues and network effects in vaccine markets

One of the most important concerns for managing public health is the prevention of infectious diseases. Although vaccines provide the most effective means for preventing infectious diseases, there are two main reasons why it is often difficult to reach a socially optimal level of vaccine coverage: (i) the emergence of operational issues (such as yield uncertainty) on the supply side, and (ii) the existence of negative network effects on the consumption side. In particular, uncertainties about production yield and vaccine imperfections often make manufacturing some vaccines a risky process and may lead the manufacturer to produce below the socially optimal level. At the same time, negative network effects provide incentives to potential consumers to free ride off the immunity of the vaccinated population. In this research, we consider how a central policy-maker can induce a socially optimal vaccine coverage through the use of incentives to both consumers and the vaccine manufacturer. We consider a monopoly market for an imperfect vaccine; we show that a fixed two-part subsidy is unable to coordinate the market, but derive a two-part menu of subsidies that leads to a socially efficient level of coverage.     

Supply chain scheduling: Sequence coordination

A critical issue in supply chain management is coordinating the decisions made by decision makers at different stages, for example a supplier and one or several manufacturers. We model this issue by assuming that both the supplier and each manufacturer have an ideal schedule, determined by their own costs and constraints. An interchange cost is incurred by the supplier or a manufacturer whenever the relative order of two jobs in its actual schedule is different from that in its ideal schedule. An intermediate storage buffer is available to resequence the jobs between the two stages. We consider the problems of finding an optimal supplier's schedule, an optimal manufacturer's schedule, and optimal schedules for both. The objective functions we consider are the minimization of total interchange cost, and of total interchange plus buffer storage cost. We describe efficient algorithms for all the supplier's and manufacturers’ problems, as well as for a special case of the joint scheduling problem. The running time of these algorithms is polynomial in both the number of jobs and the number of manufacturers. Finally, we identify conditions under which cooperation between the supplier and a manufacturer reduces their total cost.     

考虑权力结构的产品服务供应链服务渠道选择及协调研究

在制造业服务化转型过程中,传统的产品供应链转变为了产品服务供应链,为顾客提供产品和服务,服务可以由制造商或零售商提供,权力结构会对服务渠道的选择产生影响。本文通过建立博弈模型,研究了制造商为核心、零售商为核心以及制造商与零售商权力均等三种权力结构下最优服务渠道的选择问题,并应用两部定价契约对最优服务渠道的结果进行协调。研究发现,当制造商为核心时,最优的服务渠道为零售商提供服务,当零售商为核心时,最优的服务渠道为制造商提供服务,当制造商与零售商权力均等时,不存在最优的服务渠道。两部定价契约可以实现最优服务渠道的协调,最后通过数值仿真对结论进行了验证。     

自由作业环境下的供应链排序问题

本文研究自由作业环境下的供应链排序问题,研究供应链的上游如何安排工件在自由作业机器上加工,把加工完毕的工件分批发送给下游,使得生产排序费用和发送费用总和最少.这里,生产排序费用是用工件送到时间的函数来表示;发送费用是由发送的固定费用和与运输路径有关的变化费用所组成.本文研究以工件最大送到时间为生产排序费用的自由作业供应链排序问题,在指出问题的NP困难性后,用动态规划算法构造多项式时间近似算法,并分析算法的性能比.本文最后还对特殊情形进行了讨论.     

A disruption recovery model for a single stage production-inventory system

This paper presents a newly developed disruption recovery model for a single stage production and inventory system, where the production is disrupted for a given period of time during the production up time. The model is categorized as a constrained non-linear optimization program which we have solved using an efficient heuristic developed in this paper. The model was also solved using an evolutionary algorithm and a comparison of the results from both methods was performed. The heuristic was able to accurately solve the model with significantly less time compared to the evolutionary algorithm. It can be shown that the optimal recovery schedule is dependent on the shortage cost parameters, as well as the extent of the disruption. The proposed model offers a potentially useful tool to help manufacturers decide on the optimal recovery plan in real time whenever the production system experiences a sudden disruption.     

安装、加工和拆卸时间分离的两台机器混合作业问题

混合作业是经典的自由作业和异序作业的一种综合,其中一些工件可以按任意的机器顺序进行处理,而另一些工件必须遵守预先指定的机器顺序.本文研究安装、加工和拆卸时间分离的两台机器混合作业排序问题,该问题已经被知道是强NP困难的,本文把流水作业中的同顺序作业概念推广到混合作业,并得到这个混合作业问题在同顺序意义下的最优解,这个解对于一般情形是3/2近似解,但对于一些有意义的特殊情形是整体最优的.     

Narrowcasting of wireless advertising in malls

Wireless devices are personal, and the advertiser can schedule ads to reach the prospect at the proper time and place, which makes wireless advertising an ideal direct marketing tool. Industry associations, fearing a backlash from uncontrolled spam, have been careful to emphasize opt-ins. Yet the market has been more promise than reality. In spite of the possibilities of personalization, one of the major complaints has been that the ads are not relevant. Proper targeting and scheduling of wireless ads can go a long way to alleviate this problem. In a recent paper [De Reyck, B., Degraeve, Z., 2003. Broadcast scheduling for mobile advertising. Operations Research 51(4), 509–517] discuss a real implementation of wireless advertising in a shopping mall in London, and provide an integer programming model to schedule ads to various segments of prospects over a week. This model was found to be very effective in increasing response rates without saturating the devices with too many ads. We show in this paper that De Reyck and Degraeve’s model can be made more effective by utilizing information that is readily available to the advertiser. Our test runs show an improvement in the sum of ad priority value of about 150%, depending on the type of traffic in the mall. We provide two enhanced integer programming models that incrementally use additional contact history information to better scheduling of ads. Results from extensive runs are presented and managerial insights discussed.     

Single Supplier Scheduling for Multiple Deliveries

The problem of scheduling the production and delivery of a supplier to feed the production of F manufacturers is studied. The orders fulfilled by the supplier are delivered to the manufacturers in batches of the same size. The supplier's production line has to be set up whenever it switches from processing an order of one manufacturer to an order of another manufacturer. The objective is to minimize the total setup cost, subject to maintaining continuous production for all manufacturers. The problem is proved to be NP-hard. It is reduced to a single machine scheduling problem with deadlines and jobs belonging to F part types. An O(NlogF) algorithm, where N is the number of delivery batches, is presented to find a feasible schedule. A dynamic programming algorithm with O(N ^F /F ^F–2) running time is presented to find an optimal schedule. If F=2 and setup costs are unit, an O(N) time algorithm is derived.     

A search heuristic for the sequence-dependent economic lot scheduling problem

Almost all of the research on the economic lot scheduling problem (ELSP) has assumed that setup times are sequence-independent even though sequence-dependent problems are common in practice. Furthermore, most of the solution approaches that have been developed solve for a single optimal schedule when in practice it is more important to provide managers with a range of schedules of different length and complexity. In this paper, we develop a heuristic procedure to solve the ELSP problem with sequence-dependent setups. The heuristic provides a range of solutions from which a manager can choose, which should prove useful in an actual stochastic production environment. We show that our heuristic can outperform Dobson's heuristic when the utilization is high and the sequence-dependent setup times and costs are significant.     

一类自由作业供应链排序的研究

本文研究一类集成工件生产和发送的排序模型.在该模型中,供应链的上游首先将工件安排在自由作业机器上加工,然后把加工完毕的工件分批发送给下游.问题是寻找生产和发送相连的排序,使得生产排序费用和发送费用总和最少.这里,生产排序费用是以工件带权送到时间和表示;发送费用由固定费用和与运输路径有关的变化费用组成.在指出问题的NP困难性后,本文用动态规划算法构造了一致条件下的多项式时间近似算法,并分析算法的性能比.本文最后还讨论了该问题的其它情形.     

基于贝叶斯网络的工程项目进度完工概率分析

针对传统计划评审技术(Program Evaluation and Review Technique,PERT)在计算完工概率时假设条件的局限性(假设条件与工程实际存在偏差,导致完工概率偏大),提出了基于贝叶斯网络的施工进度完工概率分析方法.首先,分析了贝叶斯网络与进度计划网络之间的相似性,将两者结合起来构建了贝叶斯进度网络;在此基础上,综合考虑贝叶斯网络在节点取值及概率计算方面的优越性,并结合工程项目的不确定性及复杂性特点,建立了基于贝叶斯网络的施工进度完工概率分析模型.最后,将该模型应用于具体工程进行实例分析,验证了模型的可行性与有效性.研究结果表明:基于贝叶斯网络的进度完工概率模型充分考虑了工程施工中的风险因素,其结果能更客观地反映工程实际,可为工程项目决策者提供可靠的依据.     

Trade deals and/or on-package coupons

The selection of either a pull or a push price promotion has mainly been investigated in contexts where manufacturers offer deals to consumers at the time of purchase or offer trade deals to retailers. This paper extends this framework to where manufacturers can offer either trade deals or rebate-like promotions to consumers such as on-pack coupons that stimulate the first and second purchases or a combination of the two promotion vehicles. It is demonstrated that the decision to implement either of the three promotion options critically depends, among other factors, on the percentage of first-time buyers who redeem their coupons at the second purchase. Particularly, a necessary condition to simultaneously offer both a trade deal and coupons is to have a positive coupon redemption rate. When possible, manufacturers prefer on-pack coupons over trade deals to take advantage of slippage and to further increase the overall demand via coupon-induced repeat purchase. Manufacturers are more likely to take the lion’s share of channel profits.     

基于资源约束的突发事件应急救援鲁棒性调度优化

突发事件应急救援的调度优化,对于救援活动的顺利实施及应急资源的有效使用具有至关重要的作用。本文研究资源约束下的突发事件应急救援鲁棒性调度优化问题,其中,鲁棒性定义为各活动的时间缓冲与其权重系数乘积的总和,目标是在资源可用量及救援期限的约束下,安排活动开始时间和执行模式以最大化应急救援计划的鲁棒性。作者构建了问题的0-1规划优化模型,针对其NP-hard属性,基于问题特征设计双环路禁忌搜索启发式算法。通过对一个算例的计算分析,得到如下结论:给定网络结构及时间参数,利用权重系数的定义可以将时间缓冲分配到重要活动上,由此提高应急救援计划的鲁棒性;随着资源可用量的增加,计划的鲁棒性呈上升趋势,而当救援期限延长时,计划的鲁棒性单调增加。本文研究可为突发事件应急救援基准计划的制定提供决策支持。     

System dynamics modelling of mixed recycling mode based on contract: a case study of online and offline recycling of E-waste in China

ABSTRACT

As the pace of global sustainable economic development accelerates, increasing attention has been brought to the reutilization of waste electronic resources (E-waste). As the leading manufacturer and consumer of electronic products, China has now become the largest producer of E-waste around the world. Considering the current state of recycling mode in China, Huawei Technologies Co. Ltd. (Huawei) took the lead in implementing a blended operation model of manufacturer-led recycling model (offline recycling, OffR) and retailer-led recycling model (online recycling, OnR). In order for the improvement of recycling efficiency for Huawei and other telecommunication companies, this paper constructs a closed-loop network model of mixed recycling (MR) between manufacturers and retailers based on contract, where manufacturers and retailers jointly recycle E-waste for the provision of E-waste to manufacturers for remanufacturing. In this paper, the MR model is compared against the OffR model and OnR model to evaluate the recycling allocation mechanism run by both manufacturer and retailer and then a contract-based, closed-loop network model of mixed recycling between manufacturers and retailers is developed on the basis of obtaining the optimal MR model. By means of simulation analysis, the optimal recycling allocation ratio between manufacturer and retailer is determined. The results obtained from this study are expected to help manufacturers and retailers with effective negotiation and cooperation, so as to improve the efficiency of E-waste recycling while promoting sustainable development and reducing the economic losses caused by price competition to the minimum. This research contributes to not only the waste management studies but also the recycling of E-waste in China and other countries.     

Economic Batch-Size Determination for Multi-Product Scheduling

In the determination of batch-sizes in batch production, different criteria can be used as guiding principles, depending on the specified objectives. In a production schedule consisting of several products, an optimum solution for the whole production schedule is sought. At the same time it is necessary to ensure that the total production costs of each individual product will not exceed a certain pre-determined value. Solutions for overall optimization of the schedule with respect to maximum profit per batch, or with respect to maximum return on the total cost of production of the batch, have already been published. This paper suggests a method for determining the economic batch-sizes when it is desirable to maximize the rate of return per unit time for a multi-product schedule.     

Coordination of supply chains by option contracts: A cooperative game theory approach

Manufacturer–retailer supply chains commonly adopt a wholesale price mechanism. This mechanism, however, has often led manufacturers and retailers to situations of conflicts of interest. For example, due to uncertain market demand, retailers prefer to order flexibly from manufacturers so as to avoid incurring inventory costs and to be able to respond flexibly to market changes. Manufacturers, on the other hand, prefer retailers to place full orders as early as possible so that they can hedge against the risks of over- and under-production. Such conflicts between retailers and manufacturers can result in an inefficient supply chain. Motivated by this problem, we take a cooperative game approach in this paper to consider the coordination issue in a manufacturer–retailer supply chain using option contracts. Using the wholesale price mechanism as a benchmark, we develop an option contract model. Our study demonstrates that, compared with the benchmark based on the wholesale price mechanism, option contracts can coordinate the supply chain and achieve Pareto-improvement. We also discuss scenarios in which option contracts are selected according to individual supply chain members’ risk preferences and negotiating powers.     

Human resources scheduling to improve the product quality according to exhaustion limit

The role of human resources in manufacturing systems is very significant, and without efficient human resources we encounter high-price products with low quality. To improve the efficiency of human resources, we need to provide an optimal working schedule for each worker in production period. In this paper, we proposed a mixed-integer nonlinear model to find the best working schedule based on product quality cost and workers reliability. In this model, if the worker’s exhaustion level reaches a specific limit, the worker can rest to increase his reliability level and an accommodator should work instead of him. Since the proposed model is NP-hard, we used an artificial immune system to provide the best working schedule. The results indicate that this model can provide efficient and effective human resources schedule in manufacturing systems.     

Prices, promotions, and channel profitability: Was the conventional wisdom mistaken?

Because of the lack of empirical evidence supporting the shift of economic power from manufacturers to retailers, it has been claimed that the conventional wisdom that retailers benefit more from the use of consumer promotions was mistaken. This paper assesses this claim and examines how two different pricing approaches during manufacturers’ instant price promotions targeted at consumers impact on channel profits in a bilateral monopoly. We found that manufacturers should only offer rebates when they keep their prior-to-promotion wholesale prices unchanged. Consistent with the conventional wisdom, retailers do indeed take the lion’s share of the promotion incremental profits. Surprisingly, however, we found that in the largest part of the parameter space, manufacturers still earn more total channel profits than retailers over time. The theoretical and managerial implications of these findings are discussed.     

Retailer’s optimal pricing and lot-sizing policies for deteriorating items with partial backlogging

Pricing is a major strategy for a retailer to obtain its maximum profit. Therefore, in this paper, we establish an economic order quantity model for a retailer to determine its optimal selling price, replenishment number and replenishment schedule with partial backlogging. We first prove that the optimal replenishment schedule not only exists but also is unique, for any given selling price. Next, we show that the total profit is a concave function of p when the replenishment number and schedule are given. We then provide a simple algorithm to find the optimal selling price, replenishment number and replenishment timing for the proposed model. Finally, we use a couple of numerical examples to illustrate the algorithm.     

Single machine scheduling with general job-dependent aging effect and maintenance activities to minimize makespan

This paper considers single machine scheduling with an aging effect in which the processing time of a job depends on its position in a sequence. It is assumed that aging ratios are job-dependent and machine can be maintained some times in a schedule. After a maintenance activity, machine will be restored to its initial condition. The processing of jobs and the maintenance activities of machine are scheduled simultaneously. The objective is to schedule the jobs and the maintenance activities, so as to minimize the makespan. We provide a polynomial time algorithm to solve the problem.