Abstract ：

This paper studies the optimization of discretionary after-sales services with spare parts consumption and repairman travel. Discretionary service means that the service quality and spare parts consumption are determined by the service provider. We assume that a long service time enables the service provider to perform a thorough repair, which leads to a high repair quality and low spare parts consumption. Each service encounter comprises both repairman travel and repair service steps. We find that the dual concerns of service quality and spare parts consumption lead to a counterintuitive impact of the spare parts price: the service provider would decrease the consumption of spare parts even if selling the spare parts becomes more profitable. In addition, we show that the repairman travelling time has different impacts on the optimal service time given the maximum sojourn time constraint. In particular, as the repairman travelling time increases, the service provider increases the repair time to keep the repair quality at a high level if no sojourn time is guaranteed; however, if a maximum sojourn time is guaranteed, the service provider decreases the repair time to meet the promise.

Keyword ：

after-Sales services Maximum sojourn time Repairman travelling time Repair time Spare parts consumption

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Abstract ：

Although many firms have deployed Internet of Things (IoT)-based diagnostics to predict equipment failures and maintenance requirements, they receive imperfect demand signals due to inadequate data quality and the use of ineffective predictive tools. A strategic queuing model was developed in this study to investigate a maintenance service provider's optimal capacity allocation and pricing decisions in the presence of imperfect IoT-based diagnostics. In addition, we considered the heterogeneous service rates resulting from the accelerating effect of IoT-based diagnostics. The results of the study revealed that, on the one hand, the optimal service rate always increases with the diagnostic quality; on the other hand, if customer error cost is higher than that of the service provider, the optimal price increases with the diagnostic quality; otherwise, it decreases with the diagnostic quality. Furthermore, we found that the error costs for the two major stakeholders—the service provider and the customer—may affect the equilibrium in different ways. Finally, in the presence of the accelerating effect, we found that although the accelerating effect can improve the average service rate, system congestion actually increases if the effect becomes increasingly obvious; however, the service provider's profit improves in this case. © 2020 Elsevier Ltd

Keyword ：

Costs Internet of things Maintenance Queueing theory

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Abstract ：

COVID-19 has caused massive disruption on the global economy and presents a considerable risk to human lives. Some countries have successfully controlled the pandemic by adopting strict measures, such as lockdown and travel restriction, but such methods are difficult to be applied widely due to their huge costs. To explore available and low-cost solutions, this study proposes an adaptive transmission model on the basis of a complex network, and gives control simulation method of COVID-19. The suggested model considers adaptive changes such as travel network and people's travel intention to form a three-level adaptive network transmission model among cities, communities, and people. The improved susceptible–exposed–infectious–recovered–dead transmission process is integrated into the network. Simulation experiments under high-, low-, and conventional-cost controls are performed. In these experiments, the travel restriction and closing cities are considered, and sensitivity analyses of the parameters are conducted to explore low-cost measures. Meanwhile, time duration and application conditions of different controls are discussed. Results show that lockdown is the most effective way, and the contact and infection rates are the two most important factors to control the pandemic. Low-cost combined control measures are feasible and effective for most countries. Finally, several suggestions are given for national and urban preventions and controls of COVID-19 and other infectious diseases in the future. © 2021 Elsevier Ltd

Keyword ：

Adaptive control systems Adaptive transmission Complex networks Cost benefit analysis Costs Sensitivity analysis

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Abstract ：

This paper studies the impact of partner selection on the value of information sharing in a distribution system with one capacitated make-to-stock manufacturer and two retailers. When the high priority retailer with a higher shortfall cost is the sole partner, in the case that the low priority one places an order, the manufacturer allocates inventory more accurately according to more predictable orders from the high priority retailer. When only the low priority retailer shares information, the manufacturer is better informed about orders from this retailer, which shall trigger rationing decisions. Such intriguing differences in utilizing information from two prioritized retailers further induce different interactions between production and rationing policies and form two distinctive but closely related selective-information sharing systems. We characterize the manufacturer's optimal production and rationing policies under both systems. Through a numerical study, we emphasize the effectiveness of partnering with the high priority retailer. When the manufacturer can establish information sharing links with only one retailer, such a choice usually brings more benefits despite differences in order sizes and/or demand rates of the two retailers. When a selective-information sharing system is the pilot run to full-information sharing, we find that the value of information throughout the implementation process often exhibits second-mover advantage and such a choice also helps the manufacturer create a more balanced return pattern. Finally, we illustrate that the cost-effectiveness of inventory rationing can be significant and optimally rationing inventory is the prerequisite for the superior of the selective-information sharing system with the high priority retailer. (C) 2020 Elsevier B.V. All rights reserved.

Keyword ：

Dynamic programming Information sharing Inventory rationing Production-inventory system Second-mover advantage

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We study a realistic capacitated multimodal transportation planning problem (CMTPP) faced by logistics companies when trying to obtain a cost advantage in a competitive market. This problem simultaneously considers limited vehicle numbers and order consolidation. Given a set of origin-destination transportation orders with a time window, solving the CMTPP involves determining the delivery paths of these orders on a capacitated network as well as selecting the transportation modes used on these paths. Without violating time windows and network capacity constraints, all customers' requests must be satisfied exactly, with minimum overall logistics costs. The CMTPP is formulated as a mixed binary linear program based on which an effective kernel search and dynamic programming hybrid heuristic (HKSDP) is proposed, which repeatedly generates feasible solutions. A column generation approach is also proposed to provide a lower bound for the problem which is then used to evaluate the performance of the proposed heuristics. Numerical experiments for various sizes of random instances (with at most 300 orders in a network and 20 nodes) are conducted. The results demonstrate the effectiveness of column generation in obtaining a tight lower bound as well as the efficiency of the HKSDP in achieving a high-quality near-optimal solution. The average optimality gap is approximately 1.04%. We also provide a practical application of the proposed HKSDP to a logistics network in inland China.

Keyword ：

Column generation Dynamic programming Kernel search Multimodal transportation

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Abstract ：

As modern machines are always highly customised, it is important to diagnose the specific maintenance requirement of each machine before performing regular maintenance tasks. However, the diagnosis cannot always be accurate. In this study, we focus on a diagnostic service design problem considering imperfect diagnosis with uncertain error cost, which increases in the inaccuracy of the diagnosis. The service system is modelled as a multiple server queue, with servers performing a sequential diagnosis and customers deciding whether or not to use the service. We consider the case where the expert skill level is exogenous, uncertain and endogenous, respectively. The results suggests that (1) when the expert skill level is exogenous, the congestion of the system increases in expert skill level. In addition, the error costs for the two major stakeholders-the service centre and the customer-may affect the optimal service time and number of experts in different ways; (2) when expert skill level becomes more uncertain, the service centre should improve the optimal service time further and will see a further erosion of the profit; and (3) different from the exogenous expert skill level, high skill level experts always accompany with long service time when expert skill level is endogenous.

Keyword ：

expert skill level imperfect diagnosis service time the number of experts uncertain error cost

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Abstract ：

To improve profitability and reduce demand uncertainty, lateral transshipment is employed in this study to reallocate inventory with updated demand information. A decentralized inventory system with two retailers ordering from one common supplier is analyzed. Each retailer places the order independently before the selling season begins based on original demand forecast. As lead time elapses, more information is collected to update the demand forecast and transshipment is examined. This study constructs a two-stage model and applies backward induction to solve the problem. A threshold transshipment policy is proposed at stage 2. The existence of unique Nash equilibrium is proven at stage 1. Both the centralized system with transshipment and the newsvendor-like system without transshipment are studied as benchmarks to evaluate the performance of transshipment in the decentralized system. Extensive numerical examples are conducted to provide some valuable management implications. The results show that transshipment can lead to profit increase, especially in the system with high informative value of demand forecast updates.

Keyword ：

Decentralized inventory system Forecast updates Lateral transshipment Nash equlibrium

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This paper studies a periodic-review, infinite-horizon, backlogging inventory model with two demand classes and a constant lead time, where inventory replenishment follows a base-stock policy. We consider an anticipated rationing policy which reserves inventory for future high-priority demands with higher backlogging costs by taking the coming delivery of the next period into consideration. Due to the lack of nice properties such as convexity, both the optimal base-stock level and the optimal critical level when minimising inventory costs have to be found by an exhaustive search. Instead, we study a single-period problem truncated from the original infinite-horizon problem and derive its optimal reservation level with a closed-form expression. Surprisingly, the solution form of the single-period problem coincides exactly with the anticipated rationing policy and hence this solution serves as a good approximation for the optimal critical level of the infinite-horizon problem. An empirical study further demonstrates that our closed-form approximation is quite attractive in both solution accuracy and computation efficiency based on spare parts inventory data from a petrochemical plant in China.

Keyword ：

backlogging closed-form expressions dynamic rationing inventory two demand classes

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This paper studies price and promised delivery lead time (PDL) competition between two e-tailers in the context of e-commerce. Product returns are considered, which are affected by late and early delivery inaccuracies, i.e., the delay and early arrival of random actual delivery time relative to PDL. The goal is to examine whether the Nash Equilibrium exists in the competition, and to explore the impact of product returns on equilibrium solutions. We consider two cases where the sensitivities of the return rate to late delivery inaccuracy and early delivery inaccuracy are symmetric/asymmetric. The results suggest that (1) firms with lower basic return rates or lower return rate sensitivities, always quote higher prices and shorter PDLs; (2) it is not always profitable for firms whose competitors’ return parameters increase. © 2018 Elsevier Ltd

Keyword ：

Delivery lead time Delivery time Early arrival Equilibrium solutions Nash equilibria Online retailing Product returns Rate sensitivity

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Abstract ：

Should complementary firms offer online personalization services to their customers, and how does the differentiated quality of personalization services affect product prices and profits? To answer these questions, we investigate a two-dimensional model of both vertically differentiated product preferences and horizontally differentiated personalization services. The asymmetric quality of basic and complementary personalization services offered by firms is examined in three cases. The quality asymmetry of basic and complementary personalization services, and the complementarity of products lead to several interesting findings regarding firms' prices and profits. We find that when differentiated personalization services are offered by firms, the profits for both firms increase in complementarity. Given the presence of complementary personalization services offered by firm 1, both firms are worse off with the quality of complementary personalization services. When quality asymmetry exists for both basic and complementary personalization services, there are win-lose, win-win, and lose-win scenarios, which depend on the level of quality differentiation in the basic personalization services offered by firm 2. Furthermore, by comparing the profits in three cases, we find that firms' profits rest in complementarity. (C) 2017 Elsevier B.V. All rights reserved.

Keyword ：

Complementary firms Horizontal differentiation Personalization services Quality differentiation Two-dimensional model

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