Fully polynomial-time approximation scheme for single machine scheduling with proportional-linear deteriorating jobs

This article considers a single machine scheduling problem in which the processing time of a job is a linear increasing function of its starting time. The objective is to minimize the weighted number of tardy jobs. A pseudo-polynomial dynamic programming algorithm and a fully polynomial-time approximation scheme are proposed.     

Online pricing with bundling and coupon discounts

We propose an online pricing strategy by utilising product bundling and coupon discounts. Given customer’s purchase behaviour and preference for bundling and coupon, we propose a nonlinear mixed-integer programming model to determine the most appropriate bundle discount and instant coupon so as to maximise e-tailer’s profit. A fast heuristic algorithm is designed to implement the proposed model online in real time. We investigate the robustness of the proposed method by examining how uncertainties in system parameters affect performance. Through collaborative optimisation, we offer important insights and managerial implications, and show how marketers can attract more purchase and maximise profit by properly integrating marketing tools such as bundling and coupon.     

Integration of promotion and production decisions in sales and operations planning

This paper presents a new modelling framework for developing a sales and operations plan that integrates promotion and production planning decisions. We adopt a rich demand function that captures the dynamics and heterogeneity of consumer response to price promotions by simulating purchase incidence, consumer choice and quantity decisions, as well as household’s inventory level. Our numerical study reveals interesting findings on the benefits of developing an integrated sales and operations plan as well as the optimal timing and number of promotions, and more importantly, how these findings are influenced by the mutual dependence of marketing- and production-related factors.     

The role of social media data in operations and production management

Social media data contain rich information in posts or comments written by customers. If those data can be extracted and analysed properly, companies can fully utilise this rich source of information. They can then convert the data to useful information or knowledge, which can help to formulate their business strategy. This cannot only facilitate marketing research in view of customer behaviour, but can also aid other management disciplines. Operations management (OM) research and practice with the objective to make decisions on product and process design is a fine example. Nevertheless, this line of thought is under-researched. In this connection, this paper explores the role of social media data in OM research. A structured approach is proposed, which involves the analysis of social media comments and a statistical cluster analysis to identify the interrelationships amongst important factors. A real-life example is employed to demonstrate the concept.     

Application of genetic algorithms in production and operations management: a review

Over the last decade, there has been a rapid growth of the use of genetic algorithms in the various areas of production and operations management. This paper provides a review of genetic algorithms research published in twenty-one major production and operations management journals from 1990–2001. More specifically, it identifies research trends and publication outlets of genetic algorithms applications. Our findings show that there are only a handful of production and operations management areas to which genetic algorithms have been applied as the solution approach. Furthermore, we recognize and discuss potential research areas and outlets in which researchers may target their work as well as the need for top ranked POM journals to consider publishing genetic algorithms related papers.     

An ant colony optimization heuristic for an integrated production and distribution scheduling problem

Make-to-order or direct-order business models that require close interaction between production and distribution activities have been adopted by many enterprises in order to be competitive in demanding markets. This article considers an integrated production and distribution scheduling problem in which jobs are first processed by one of the unrelated parallel machines and then distributed to corresponding customers by capacitated vehicles without intermediate inventory. The objective is to find a joint production and distribution schedule so that the weighted sum of total weighted job delivery time and the total distribution cost is minimized. This article presents a mathematical model for describing the problem and designs an algorithm using ant colony optimization. Computational experiments illustrate that the algorithm developed is capable of generating near-optimal solutions. The computational results also demonstrate the value of integrating production and distribution in the model for the studied problem.     

Coordinating continuous-time distribution and sales planning of perishable goods with quality grades

A variety of industries handling perishable goods is faced with the challenge of reducing lead times in order to ensure the best possible freshness of products at the point of sales. Considering a short-term multi-day planning horizon, the implementation of quantitative optimisation approaches with a continuous-time representation is most appropriate for planning and scheduling. However, as the quality measures are usually standardised by discrete grades, coordination take thresholds of maximum delivery times into account. For this purpose, a new mixed-integer linear programming model is developed. It enables to assess complete material flows, whose formal composition originates in a method based on power sets on the one hand, but additionally allows for the exact scheduling of partial material flows between sites. Specific transportation conditions that need to be imposed with respect to shelf-life are included. The efficiency of the model is confirmed by comparison with an equivalent mixed-integer linear formulation that uses path variables for modelling complete material flows. Besides an illustrative example motivated by the real-life problem of a fresh produce company supplying a wholesaler group, both model formulations are validated within a numerical analysis composed of 10 scenarios with different numbers of suppliers, warehouses, markets and product variants. Each scenario includes six instances with randomly generated data. As a result of the computations using high-performance hardware and software, it was shown that the formulation based on power sets was superior in each instance, as it enabled determining optimal solutions within significantly reduced computation times.     

Do horizontal relationships matter to production and operations managers?

This paper shifts the focus of production, operations and supply chain management business relationships from the vertical to the horizontal side and calls for more research on this issue. The main intent is to provide managerially oriented arguments regarding the linkages between the achievement of operations-related goals and decisions related to horizontal business relationships. Specifically, we address the following research question: Does a linkage exist between production and operations objectives and the decisions a company makes about horizontal agreements, particularly horizontal governance mode choice? To answer this research question, we develop literature-based hypotheses and collect data from 4316 agreements of mergers and acquisitions and alliances and joint venture announced and completed between 2000 and 2010 by 88 of the first 100-ranked members of the Fortune 500 in the year 2000. We then test the hypotheses through a binary logistic regression model. This study brings interesting results and findings in terms of how and why production management considerations should play a crucial role in the type of strategic decisions that are usually reserved for finance and strategy managers. Operations managers should be fully involved in such decisions if they are to be well acquainted about how their choices impact on operational objectives.     

Scheduling with non-decreasing deterioration jobs and variable maintenance activities on a single machine

There is a situation found in many manufacturing systems, such as steel rolling mills, fire fighting or single-server cycle-queues, where a job that is processed later consumes more time than that same job when processed earlier. The research finds that machine maintenance can improve the worsening of processing conditions. After maintenance activity, the machine will be restored. The maintenance duration is a positive and non-decreasing differentiable convex function of the total processing times of the jobs between maintenance activities. Motivated by this observation, the makespan and the total completion time minimization problems in the scheduling of jobs with non-decreasing rates of job processing time on a single machine are considered in this article. It is shown that both the makespan and the total completion time minimization problems are NP-hard in the strong sense when the number of maintenance activities is arbitrary, while the makespan minimization problem is NP-hard in the ordinary sense when the number of maintenance activities is fixed. If the deterioration rates of the jobs are identical and the maintenance duration is a linear function of the total processing times of the jobs between maintenance activities, then this article shows that the group balance principle is satisfied for the makespan minimization problem. Furthermore, two polynomial-time algorithms are presented for solving the makespan problem and the total completion time problem under identical deterioration rates, respectively.     

Single-machine scheduling and common due date assignment with potential machine disruption

This paper studies a single-machine due date assignment and scheduling problem in a disruptive environment, where a machine disruption may occur at a particular time that will last for a period of time with a certain probability, and the job due dates are determined by the decision-maker using the popular common due date assignment method. The goal is to determine jointly the optimal job sequence and the common due date so as to minimise the expected value of an integrated cost function that includes the earliness, tardiness and due date assignment costs. We analyse the computational complexity status of various cases of the problem, and develop pseudo-polynomial-time solution algorithms, randomised adaptive search algorithms, and fully polynomial-time approximation schemes for them, if viable. Finally, we conduct extensive numerical testing to assess the performance of the proposed algorithms.     

Group scheduling with deteriorating jobs and allotted resource under limited resource availability constraint

This study considers a single machine group scheduling problem with deteriorating jobs and resource allocation (controllable processing times). The objective is to have the resource availability limited within a given range, and to minimize the maximum completion time (i.e. the makespan). For two special cases, it is proved that the problem can be solved in polynomial time. For the general case, an heuristic algorithm and a branch-and-bound algorithm are proposed. Computational results show that the proposed heuristic algorithm is generally effective.     

Coordinated scheduling of customer orders with decentralized machine locations

We consider a scheduling model with two machines at different locations. Each job is composed of two tasks where each task must be processed by a specific machine. The finished tasks are shipped to a distribution center in batches before they are bundled together and delivered to customers. The objective is to minimize the sum of the delivery cost and customers' waiting costs. This model attempts to coordinate the production and delivery schedules on the decentralized machines while taking into consideration the shipping cost as well as the waiting time of the customers. We develop polynomial-time heuristic algorithms for this problem and analyze their worst-case performance. Computational experiments are conducted to test the effectiveness of the heuristics and to evaluate the benefits obtained by coordinating the production and delivery of the two decentralized machines.     

Beyond the trade-off and cumulative capabilities models: alternative models of operations strategy

Organisations are expected to develop sound strategies relating to their core operations capabilities of cost efficiency, quality, delivery, flexibility and innovation, to gain and maintain competitive advantage. However, there is a paucity of specific models that can be used to explain and predict how organisations combine and use these capabilities. Previous research has primarily focused on the ‘trade-off’ and the ‘cumulative capabilities’ models. In this study, data from an international sample of 1438 manufacturing plants are used to explore other models that organisations are using in addition to the two predominant models. This analysis shows that, in practice, the trade-off model is not used, but the cumulative capabilities model is used extensively. Further, our proposed new models, the ‘threshold’, ‘average’ and ‘multiple’, are prevalent in many plants. Also, a small proportion of the plants have in place the ‘uncompetitive’ model. In terms of relative effectiveness, there are no significant differences between the models with respect to several measures of operational performance. Overall, this study provides empirical evidence that there are other operations strategy models beyond the trade-off and cumulative capabilities dichotomy that organisations deploy.     

The social preferences of local citizens and spontaneous volunteerism during disaster relief operations*

Existing studies on disaster relief operations pay limited attention to acts of spontaneous volunteerism by local citizens in the aftermath of disasters. The purpose of this paper is to explore how social preferences motivate citizens to help during post-disaster situations; above and beyond their own self-regarding interests. The paper begins by synthesising the literature on social preferences from the field of behavioural economics and social psychology with the discourse surrounding behavioural operations management and humanitarian operations management. By doing so, we identify the motivators, enablers and barriers of local citizen response during disaster relief operations. These factors inform a theoretical framework of the social preferences motivating spontaneous volunteerism in post-disaster situations. We evidence facets of the framework using archival and unstructured data retrieved from Twitter feeds generated by local citizens during the floods that hit Chennai, India in 2015. Our model highlights the importance of individual-level action during disaster relief operations and the enabling role of social media as a coordination mechanism for such efforts.     

Field services design and management of natural gas distribution networks: a class of vehicle routing problem with time windows approach

Service operations management of metropolitan gas networks at operational level implies the optimisation of decisions related to logistic activities, taking into account multi-objectives and operational constraints. This paper proposes a metaheuristic approach for the operational planning of the daily logistic activities based on vehicle routing with time window model. Experimental results for a real planning case in a gas distribution network demonstrate the approach effectiveness.     

Worker coordination policies in parallel station systems: performance models for a set of jobs and for continuous arrival of jobs

Varying workloads and uncertain processing times in parallel assembly cause idle times for skilled, high-cost workers. This idleness can be avoided and the utilisation of the workers improved by allowing workers to move between the stations to help each other. Worker movement between assembly stations needs efficient and feasible coordination, and therefore, this paper compares four different worker coordination policies: no helping, floater, pairs and complete helping. The dynamics of the policies are modelled by studying the parallel assembly as a continuous-time Markov process. The system is studied with two different job release cases for non-identical jobs (customised products). In the first case, a given number of jobs have to be completed by the entire system. In the second case, new jobs arrive with a Poisson-distributed rate. The models assume that when one worker helps another, their collaborative inefficiency reduces the productivity. The models are used in numerical experiments to compare the performances of worker coordination policies as average job cycle times. The main conclusions from the results suggest the use of the complete helping policy in minor collaborative inefficiency conditions, especially with a given set of jobs. The pairs policy is a reasonable alternative in major inefficiency conditions with the continuous arrival of jobs.     

双方不完全信息下政府引导的逆向供应链协调研究

讨论双方不完全信息下政府引导一个制造商和两个零售商组成的逆向供应链的协调问题。运用信号甄别和委托代理理论,分别从政府不参与、政府奖励零售商和政府奖励制造商三个方面得到零售商和制造商的协调策略。研究表明:定价合同可有效避免逆向选择,实现逆向供应链协调;高市场需求状态下低成本零售商获得收益较高;政府对企业的合理奖励,尤其是对零售商的奖励,可以促进逆向供应链协调,提高收益。     

Dielectric characteristics of vacuum circuit breakers with CuCr and CuBi contacts before and after short-circuit breaking operations

This paper presents the results of the degree of irreversible changes of dielectric properties of vacuum circuit breakers with CuCr and CuBi contacts before and after short-circuit breaking operations. Tests of dielectric properties were performed on four different types of switching vacuum chamber with RMF electrodes in the form of a spiral disk with slots. The paper describes the configuration of measuring system for determining the dielectric properties of circuit breakers with DC, AC and pulse voltage. It also describes the measuring procedure. The results were analyzed and the experimentally obtained random variable breakdown voltage is found to belong to Weibull distribution in all cases. Based on these results it was found that for the vacuum circuit breakers with CuCr contacts and CuBi breakdown occurs by the emission mechanism after stopping of diffuse arc with the initial breakdown at the anode. It was also found that significant reduction of the breakdown voltage occurs only after a short-circuit current breaking for a constricted arc. Only in this case, the significant difference between circuit breakers with CuBi and CuCr contacts is observed. This difference is explained by the fact that breakdown voltage for a constricted arc strongly depends on the shape of the applied voltage by the action mechanism of micro particles generated during the breaking of the arc current for the vacuum circuit breakers with CuBi contacts and it is caused by material of contacts. The results confirm the lower degree of irreversible changes of dielectric properties of vacuum circuit breakers with CuCr contacts in operation.     

An empirical study of impacts of production mix,product route efficiencies on operations performance and profitability: a reverse logistics approach

This research studies the impact of two reverse logistics business strategies on profitability of the firm through operations management (OM). The study is employed on scrap steel industry. The first strategy is production mix efficiency (PME), which is involved in the process of producing goods. The second strategy is product route efficiency (PRE), which engages in the transportation of goods. Our finding indicates that OM alone does not have a positive impact on profitability. However, the two strategies have a positive effect on profitability, which provides a potential answer to firms trying to improve profitability.