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An important production programming problem arises in paper industries coupling multiple machine scheduling with cutting stocks. Concerning machine scheduling: how can the production of the quantity of large rolls of paper of different types be determined. These rolls are cut to meet demand of items. Scheduling that minimizes setups and production costs may produce rolls which may increase waste in the cutting process. On the other hand, the best number of rolls in the point of view of minimizing waste may lead to high setup costs. In this paper, coupled modeling and heuristic methods are proposed. Computational experiments are presented. [ABSTRACT FROM AUTHOR]

This paper develops a reward model for the optimization of preventive maintenance for a complex production system functioning in any one of k unobservable operating states. The changes of the states are driven by a non-homogeneous Markov (NHM) process X(t) with known characteristics. The system fails according to a point process whose intensity is modulated by the unobservable state. Failures are rectified through minimal repairs (MRs) whose costs are associated with age and the state process X(t). The modeling approach also allows both the revenue stream and the preventive maintenance cost to be characterized by the state process X(t). The paper first formulates the reward model depending on the unobservable state process estimated through the filtering theorem argument by projection on the observed history including failure point process observations. The estimation of the state process allows failure prediction and maximizing revenue stream implemented through scheduling periodic overhauls. A case study is provided to illustrate the proposed method. [ABSTRACT FROM AUTHOR]

In some production processes, the effort associated with a certain activity for its execution can vary over time. In this case, the amount of work per time unit devoted to each activity, so as its duration, is not univocally determined. This kind of problem can be represented by an activity project network with the so-called feeding precedence relations, and activity variable execution intensity. In this paper, we propose a forward recursion algorithm able to find the earliest start and finish times of each activity, in O (m log n) time, with n and m being the number of activities and the number of precedence relations, respectively. In particular, this requires the calculation of the (optimal) execution intensity profile, for each activity, that warrants the earliest start schedule and the minimum completion time of the project. [ABSTRACT FROM AUTHOR]

Critical chain buffer management (CCBM) has been extensively studied in recent years. This paper investigates a new formulation of CCBM, the multimode chance-constrained CCBM problem. A flow-based mixed-integer linear programming model is described and the chance constraints are tackled using a scenario approach. A reinforcement learning (RL)-based algorithm is proposed to solve the problem. A factorial experiment is conducted and the results of this study indicate that solving the chance-constrained problem produces shorter project durations than the traditional approach that inserts time buffers into a baseline schedule generated by solving the deterministic problem. This paper also demonstrates that our RL method produces competitive schedules compared to established benchmarks. The importance of solving the chance-constrained problem and obtaining a project buffer tailored to the desired probability of completing the project on schedule directly from the solution is highlighted. Because of its potential for generating shorter schedules with the same on-time probabilities as the traditional approach, this research can be a useful aid for decision makers. [ABSTRACT FROM AUTHOR]

The generation maintenance scheduling deals with a time sequence of preventive maintenance outages for a given set of generation units in an electricity market subject to power system restrictions. Incorporating a leader–follower structure in generation maintenance scheduling models is essential because of the inherent conflict between the interests of an independent system operator (ISO) and generation companies (GENCOs). The present paper proposes a new preventive maintenance scheduling model for generation companies facing the risk of involving generation units' disruption and demand variations while ensuring the reliability of the power system. Each GENCO proposes the maintenance schedule of its generation units to the ISO in a non-cooperative manner intending to maximize its net profit. Then ISO reacts to the aggregated schedule according to the power system's reliability index. Thus, a new formula is developed to consider all the interactions between the power system's stakeholders. In this regard, a stochastic multi-leader one-follower approach is applied. The GENCOs are considered independent leaders at the upper-level and the ISO is considered a follower at the lower-level. Then an equivalent single-level counterpart model is presented for each leader. So, the whole problem is converted into multiple individual stochastic single-level models, and then the Nash Equilibrium concept is used to determine GENCO equilibrium strategies. The proposed methodology is evaluated using some modified IEEE reliability test systems. The numerical analysis confirms that the proposed model is more effective in cases with higher uncertainties. Moreover, the performed analysis demonstrated the importance of applying a bi-level approach to the problem. Finally, the superiority of the proposed approach compared to the existing one is confirmed. [ABSTRACT FROM AUTHOR]

In enterprise project management systems, a program at the tactical level coordinates and manages multiple projects at the operational level. There are close relationships between multiple projects in a program, which are typically manifested as shared resources and precedence relationships. Most research efforts have concentrated on the resource sharing by projects, while the precedence relationships between projects have yet to be comprehensively investigated. In this paper, a bi-objective hierarchical resource-constrained program scheduling problem proposed, where both resource sharing and precedence relationships between projects are considered in a distributed environment. The problem contains two different sub-problems at the operational level and the tactical level, and they are modeled in the same way as two bi-objective multi-mode scheduling problems. Shared resources are allocated from the tactical level to the operational level, and once they are allocated to a project, they can only be re-allocated to other projects once the current project is finished. Subsequently, a two-phase algorithm based on NSGA-III is developed. The algorithm runs at the operational level and the tactical level in turn. According to the Pareto fronts of projects that are submitted from the operational level, the bi-objective program planning at the tactical level is conducted under the constraints of precedence relationships and shared resources. The results of computational simulations demonstrate the satisfactory performance of the improved algorithm. By coordinating the local optimization of projects and the global optimization of the program in a hierarchical framework, the method proposed in this paper provides an effective integrated scheduling method for decision-makers at various levels of a program. [ABSTRACT FROM AUTHOR]

Pre-runtime scheduling of avionic systems is used to ensure that the systems provide the desired functionality at the correct time. This paper considers scheduling of an integrated modular avionic system which from a more general perspective can be seen as a multiprocessor scheduling problem that includes a communication network. The addressed system is practically relevant and the computational evaluations are made on large-scale instances developed together with the industrial partner Saab. A subset of the instances is made publicly available. Our contribution is a matheuristic for solving these large-scale instances and it is obtained by improving the model formulations used in a previously suggested constraint generation procedure and by including an adaptive large neighbourhood search to extend it into a matheuristic. Characteristics of our adaptive large neighbourhood search are that it is made over both discrete and continuous variables and that it needs to balance the search for feasibility and profitable objective value. The repair operation is to apply a mixed-integer programming solver on a model where most of the constraints are treated as soft and a violation of them is instead penalised in the objective function. The largest solved instance, with respect to the number of tasks, has 54,731 tasks and 2530 communication messages. [ABSTRACT FROM AUTHOR]

This paper introduces a novel two-phase framework for designing a proactive–reactive scheduling model in the multi-mode resource-constrained project scheduling problem under disruptions. The proactive phase involves constructing a resilient baseline scheduling model using a mixed-integer linear programming model. This phase contributes to a multi-objective model that minimizes the project completion time and total project cost while maximizing resilience criteria. In this context, resilience refers to allocating float time to project activities to protect their start and finish times against future disruptions as much as possible. The reactive phase involves a bi-objective mathematical model that mitigates the impact of disruptions through preempt-repeat, preempt-resume, and activity-crashing strategies. Real-world projects involve many uncertain parameters that can negatively affect the optimization of rescheduling problems if overlooked. Therefore, for the first time, a scenario-based robust optimization approach is proposed to cope with the uncertainty of the reactive phase. Additionally, a novel hybrid multi-objective method based on goal programming is introduced to solve the proposed multi-objective model. Finally, to demonstrate the capability of the proposed approach, an oil and gas project in Iran is regarded as a real case study. The results indicate that the negative impact of disruptions on the makespan and total cost of the project can be largely mitigated by considering resilience criteria in the proactive phase and preempt-repeat, preempt-resume, and activity-crashing strategies in the reactive phase. [ABSTRACT FROM AUTHOR]

We consider a non-preemptive single machine scheduling problem for a non-negative penalty function f, where an optimal schedule satisfies the left-shifted property, i.e. in any optimal sequence all executions happen without idle time with a starting time t 0 ≥ 0 . For this problem, every job j has a priority weight w j and a processing time p j , and the goal is to find an order on the given jobs that minimizes ∑ w j f (C j) , where C j is the completion time of job j. This paper explores local dominance properties, which provide a powerful theoretical tool to better describe the structure of optimal solutions by identifying rules that at least one optimal solution must satisfy. We propose a novel approach, which allows to prove that the number of sequences that respect the local dominance property among three jobs is only two, not three, reducing the search space from n! to n ! / 3 ⌈ n / 3 ⌉ schedules. In addition, we define some non-trivial cases for the problem with a strictly convex penalty function that admits an optimal schedule, where the jobs are ordered in non-increasing weight. Finally, we provide some insights into three future research directions based on our results (i) to reduce the number of steps required by an exact exponential algorithm to solve the problem, (ii) to incorporate the dominance properties as valid inequalities in a mathematical formulation to speed up implicit enumeration methods, and (iii) to show the computational complexity of the problem of minimizing the sum of weighted mean squared deviation of the completion times with respect to a common due date for jobs with arbitrary weights, whose status is still open. [ABSTRACT FROM AUTHOR]

In recent years, new resource types have been established in project scheduling. These include so-called partially renewable resources, whose total capacity applies only to a subset of periods in the planning horizon. In this paper, we consider the extension of the resource-constrained project scheduling problem with those partially renewable resources as well as generalized precedence constraints with the objective of minimizing the project duration (RCPSP/max- π ). For this problem it is known that already the determination of a feasible solution is NP-hard in the strong sense. Hence, we present two different generation schemes that are able to find good feasible solutions in short time for most tested instances. The first one is a construction-based heuristic wherein the activities of the project are scheduled iteratively time- and resource-feasibly. The second one is a relaxation-based generation scheme, in which—starting from the schedule consisting of the earliest start times—resource conflicts are identified and resolved by inserting additional resource constraints. [ABSTRACT FROM AUTHOR]

The multi-mode resource constrained project scheduling problem (MRCPSP) is an NP-hard optimisation problem involving scheduling tasks under resource and precedence constraints, while there are several modes for executing each task. In this paper, we propose a novel matheuristic based on relax-and-solve (R &S) algorithm to solve MRCPSP. In addition, a mathematical programming model, which is the generalisation of the multi-dimensional knapsack problem is developed. That model conducts the mode selection process for the purpose of generating an initial feasible solution. We evaluate the performance of the proposed algorithm by solving benchmark instances that are widely used in the literature. The results demonstrate that the proposed R &S algorithm outperforms the state-of-the-art methods for solving the MRCPSP. [ABSTRACT FROM AUTHOR]

This paper deals with a scheduling problem arising at the tactical decision level in aeronautical assembly line. It has the structure of a challenging multi-mode resource-constrained project scheduling problem with incompatibility constraints, a resource leveling objective and also a large number of tasks. We first present a new event-based mixed-integer linear programming formulation and a standard constraint programming formulation of the problem. A large-neighborhood search approach based on the constraint programming model and tailored to the resource leveling objective is proposed. The approaches are tested and compared using industrial instances, yielding significant improvement compared to the heuristic currently used by the company. Moreover, the large-neighborhood search method significantly improves the method proposed in the literature on a related multi-mode resource investment problem when short CPU times are required. [ABSTRACT FROM AUTHOR]

In this paper, the research and development project scheduling problem (RDPSP) under uncertain failure of activities is formulated where an activity's failure results in the project's overall failure. A scenario-based bi-objective model to maximize the expected net present value (eNPV) and to minimize the NPV's risk by conditional value-at-risk (CVaR) measurement is presented. For this purpose, different modes of failure or success of activities have been considered as a stochastic parameter by a set of scenarios. To formulate the problem, a nonlinear model is first presented, then a mixed-integer programming (MIP) model of the problem is developed by piecewise approximation. Some valid inequalities are presented to improve the performance of the MIP model. A sequential sampling procedure is also used to approximate the solution of the MIP model with a large number of scenarios. The experimental results have shown that the sequential sampling procedure attains high-quality solutions in a reasonable CPU time. [ABSTRACT FROM AUTHOR]

This paper studies a two-machine flow shop scheduling problem with availability constraints due to a breakdown on the first machine. The starting time of the breakdown is considered stochastic and follows a known probability distribution. A service-level constraint is introduced to model the guarantee with which the obtained schedule takes into account the stochastic nature of the breakdown's starting time. The objective is to find a solution that minimizes the makespan while satisfying the desired service level. The studied problem is strongly NP-hard. We develop two mixed integer linear models that linearize the non-linear model. Using interval modeling of the breakdown, we propose lower bounds and a valid inequality that are used to strengthen both models. When the lower bounds and the valid inequality are applied, the performance of both models is greatly improved by reducing the gap and reaching optimality for more instances. We also introduced two heuristics that exploit the proposed interval modeling. The computational results indicate that both models are able to reach optimality for the 10-job instances. Moreover, the comparisons results between both models with the two heuristics showed their effectiveness. [ABSTRACT FROM AUTHOR]

In this paper we consider the coupled task scheduling problem with exact delay times on a single machine with the objective of minimizing the total completion time of the jobs. We provide constant-factor approximation algorithms for several variants of this problem that are known to be N P -hard, while also proving N P -hardness for two variants whose complexity was unknown before. Using these results, together with constant-factor approximations for the makespan objective from the literature, we also introduce the first results on bi-objective approximation in the coupled task setting. [ABSTRACT FROM AUTHOR]

Planning and scheduling of operating rooms (ORs) is important for hospitals to improve efficiency and achieve high quality of service. Due to significant uncertainty in surgery durations, scheduling of ORs can be very challenging. In this paper, surgical case scheduling problem with uncertain duration of surgeries in multi resource environment is investigated. We present a two-stage stochastic mixed-integer programming model, named SOS, with the objective of total ORs idle time and overtime. Also, in this paper a two-step approach is proposed for solving the model based on the L-shaped algorithm. Proposing the model in a multi resources environment with considering real-life limitations in academic hospitals and developing an approach for solving this stochastic model efficiently form the main contributions of this paper. The model is evaluated through several numerical experiments based on real data from Hasheminejad Kidney Center (HKC) in Iran. The solutions of SOS are compared with the deterministic solutions in several real instances. Numerical results show that SOS enjoys a better performance in 97% of the cases. Furthermore, the results of comparing with actual schedules applied in HKC reveal a notable reduction of OR idle time and over time which illustrate the efficiency of the proposed model in practice. [ABSTRACT FROM AUTHOR]

This paper provides two new perspectives on single-machine scheduling problems in which the objective involves penalties regarding late work. Both of this perspectives have been neglected in the previous literature. We begin by presenting a parameterized complexity analysis of the N P -hard problem of minimizing the total late work on a single machine. We do so with respect to the following four parameters: (i) the number of different processing times ( υ p ); (ii) the number of different due dates ( υ d ); (iii) the maximal processing time (p max) ; and (iv) the maximal due date ( d max ). We use results from the literature to conclude that the problem is hard with respect to (wrt.) parameter υ d and is tractable (i.e., solvable in FPT time) wrt. p max . We then provide two FPT algorithms showing that the problem is also tractable wrt. to υ p and d max . We continue by analyzing a single-machine scheduling problem with assignable due dates where the cost function to be minimized includes penalties due to weighted early and tardy work. We assume that each job can be assigned a different due-date, the value of which is subject to a job-dependent upper bound. We provide an efficient method to optimally assign due dates for a given job schedule. We then use this result to reduce the problem to a purely combinatorial problem, which we show is N P -hard in general, but solvable in either FPT time or polynomial time for some special cases. [ABSTRACT FROM AUTHOR]

In mass casualty incidents, patients need to be evacuated to nearby hospitals as soon as possible, and a surge in demand for emergency medical services then occurs. It would result in ambulance offload delays, i.e., no emergency operating room is available when the ambulance arrives at a hospital, and thus the patients cannot be treated immediately. In this paper, we aim to solve a combinatorial problem of patient-to-hospital assignment and patient surgery sequence considering patient deterioration and ambulance offload delay during a mass casualty incident. A mixed-integer programming model is proposed. The objective is to minimize the completion time of all patients' surgeries. For solving such a problem, some structural properties of our studied problem are derived, and a heuristic is developed to solve the single operating room scheduling problem considering ambulance offload delay and patient deterioration based on these structural properties. A hybrid Firefly Algorithm-Variable Neighborhood Search algorithm incorporating the heuristic method is proposed to solve it. Our proposed algorithm can solve the problem within a short computation time, and the computational results demonstrate the superiority of our proposed algorithm over the compared algorithms. [ABSTRACT FROM AUTHOR]

How to improve the efficiency of operating rooms (ORs) has always been a challenging problem in the context of healthcare operations management. This paper focuses on the research of operating room scheduling under non-operatingroomanesthesia (NORA) mechanism, in the presence of the uncertainty of emergency arrivals. In particular, we examine the advantages of the NORA mechanism in comparison with traditional surgical anesthesia practice under different operating room settings. Operationally, the process is comprised of two stages: (1) initial scheduling and (2) rescheduling. In the first stage, the initial schedule for elective surgeries under NORA is first performed through our developed model. With experiments, it is shown that for different operating room settings, the NORA mechanism can significantly improve the operating room utilization in comparison with the traditional OR anesthesia process. In the second stage of rescheduling, our experiment results show that the rescheduling model can effectively address the disruptions caused by the random arrival of emergency patients. [ABSTRACT FROM AUTHOR]

This paper addresses a parallel machine scheduling problem with non-anticipatory family setup times and batching, considering the task's stochastic processing times and release dates. The problem arises from a real-life ship scheduling problem in the oil and gas industry. We developed an Iterated Greedy simheuristic with built-in Monte Carlo Simulation to sample the stochastic parameters. We conducted experiments on a set of instances from the literature, considering two simheuristic variants and three uncertainty levels for the stochastic parameters. To highlight the advantages of using simulation to tackle the stochastic problem, the simheuristics are compared against a regular Iterated Greedy metaheuristic, yielding an improvement of up to 16.5% on the objective function's expected values, with a reduced impact on computational times. During a risk analysis, the Pareto set of solutions is generated to illustrate the trade-off between the expected objective value of the solutions and the conditional value at risk, providing decision-makers with a useful tool to select the schedules that better fit their risk profiles. We use an iterative mechanism to build confidence intervals within a certain confidence level during the method's simulation step, interrupting the procedure when it reaches the desired error. This strategy's advantage is highlighted in the computational experiments, which indicates that the number of replications of the simulation is instance and uncertainty level dependent. A periodic re-planning strategy is also used to evaluate the performance of the simheuristic, highlighting the advantages of using the proposed algorithm in a real-life usage situation. [ABSTRACT FROM AUTHOR]

A recent Journal of Scheduling paper by Chen and Zhang (J Sched, 2020. https://doi.org/10.1007/s10951-020-00668-1) proves that the problem of scheduling coupled tasks to minimize total completion time is NP-hard in the strong sense even for the case with all tasks having the same, though not necessarily unit, processing times. This note shows a simpler proof of that result, and strengthens it by proving that the problem is NP-hard in the strong sense even if all tasks are unit-time. [ABSTRACT FROM AUTHOR]

This paper introduces the serial batching scheduling problems with position-based learning effect, where the actual job processing time is a function of its position. Two scheduling problems respectively for single-machine and parallel-machine are studied, and in each problem the objectives of minimizing maximum earliness and total number of tardy jobs are both considered respectively. In the proposed scheduling models, all jobs are first partitioned into serial batches, and then all batches are processed on the serial-batching machine. We take some practical production features into consideration, i.e., setup time before processing each batch increases with the time, regarded as time-dependent setup time, and we formalize it as a linear function of its starting time. Under the single-machine scheduling setting, structural properties are derived for the problems with the objectives of minimizing maximum earliness and number of tardy jobs respectively, based on which optimization algorithms are developed to solve them. Under the parallel-machine scheduling setting, a hybrid VNS-GSA algorithm combining variable neighborhood search (VNS) and gravitational search algorithm (GSA) is proposed to solve the problems with these two objectives respectively, and the effectiveness and efficiency of the proposed VNS-GSA are demonstrated and compared with the algorithms of GSA, VNS, and simulated annealing (SA). This paper demonstrates that the consideration of different objectives leads to various optimal decisions on jobs assignment, jobs batching, and batches sequencing, which generates a new insight to investigate batching scheduling problems with learning effect under single-machine and parallel-machine settings. [ABSTRACT FROM AUTHOR]

We consider a single-machine scheduling problem with two-agents, each with a set of non-pre-emptive jobs, where two agents compete for the use of a single processing resource. A switchover time arises whenever a job of one agent is processed after a job of another agent. Each agent wants to minimize a certain objective function, which depends upon the completion time and switchover time of their own jobs only. This paper considers the minimization of total weighted completion time of the first agent subject to an upper bound on the makespan of the second agent. We introduce some properties to the problem. The properties describe the structure of an optimal solution which is being used for developing an optimal algorithm. We propose an optimal algorithm, a simple heuristic algorithm, and a particle-swarm-based meta heuristic algorithm to solve the problem. The heuristic algorithm is based on the weighted shortest process time-first rule. The performances of the heuristic and particle swarm algorithms are evaluated on randomly generated problem instances. We perform the numerical analysis to reveal the properties of the proposed problem. [ABSTRACT FROM AUTHOR]

Forests are among the most sensitive systems in nature. This is attributed to the fact that, forests are directly affected by fluctuations in price of fossil fuels. Wood products and especially forest fuel products are accessible by anyone, without any prior processing. As forest fuel is a subsidy for fossil fuels (oil) for heating purposes, households turn to forest fuel especially in countries that are heavily impacted by economic recession. The over-exploitation of this natural resource leads the forest to abnormal situation and eventually to deforestation. The exhaust of the natural resource capital has negative impact not only on the local economy, where fuelwood market contributes especially in mountainous regions, but also on the environmental stability of ecosystems. In this paper, two multi-period Linear Programming models are proposed for management of coppice forests. The aim of these models is to maximize the Net Present Value, which is constructed as a function of the revenue from trading fuelwood (price times the logged quantities) minus the transportation cost from the forest to merchants. Two aspects have been investigated in this paper; sustainability and maximum yield. The sustainability aspect is guaranteed by imposing constraints for equalization of non-logged areas at the end of the planning horizon. With maximum yield aspect, the maximization of the logged quantities (and therefore the maximization of the objective function) is guaranteed. The model is solved for various scenarios regarding transportation cost. The applicability of the model is demonstrated through a real-world case study of an even coppice forest in Achladochori–Aggistro–Sidirokastro. The proposed model is easy to be implemented, since it uses only the initial conditions of the forest (area) and can be applied to even and uneven aged forests. [ABSTRACT FROM AUTHOR]

This paper considers an integrated approach to two common problems in a precision agriculture framework: management zone delineation and selective harvest scheduling. Our model minimizes the total costs of harvest operations, establishing planning and scheduling for selective harvest of each selected management zone. Therefore, this tool provides important information for decision making of farmers in the field. Our integrated model is contrasted with the hierarchical approach commonly used in the literature for these cases, where the result of zoning problem is an input to schedule the harvest problem. Both problems were solved through a complete enumeration of all the potential management zones and demonstrated the advantages of our proposed model over the hierarchical approach. Our model reached an average reduction of 10% in harvest operations costs for different instances in a case study. [ABSTRACT FROM AUTHOR]

Over the past couple of centuries, with the increase in the significance of the railways to the economy, the complexity of the railway network and consequently the decision making involved and the number of problems faced has only increased. Among the host of problems in railways management, one of the most important is the locomotive assignment problem (LAP). The LAP is as old as the railways itself. The objective of the LAP is to assign a fleet of locomotives at minimum cost to pre-scheduled trains subject to a host of constraints. Most of the models in literature either work on improving the efficiency of solving the LAP or attempt to solve the three levels of LAP separately. Our attempt in this paper is to arrive at a linear mathematical model that integrates the strategic, tactical and operational level aspects of the LAP. We also demonstrate that by the addition of a valid inequality, the lower bounds can be improved substantially resulting in a substantial reduction in solution times for the problem instances. Further, we develop a Dijkstra's algorithm-based heuristic to test the problem instances and compare the solution times and quality of solutions. Finally, we develop a case based on Southern Zone of the Indian Railways and test the heuristic to solve the LAP for this zone. [ABSTRACT FROM AUTHOR]

This paper proposes two models for the Technician Routing and Scheduling Problem (TRSP), which are motivated by a telecom provider based in Saskatchewan, Canada. The proposed TRSP models are distinguished from existing models by their ability to address two key issues: overnight and lunch break scheduling. The models aim to scheduling a set of technicians with homogeneous skill levels and different working hours for the purpose of providing services with different service times and time windows to a diverse set of widely spread communities. As the large-sized experiments of this problem categorized into NP-hard problems, a metaheuristic-based technique, Invasive Weed Optimization, is developed to solve them. A comparative analysis is performed to choose the optimum TRSP model based on two factors which are distance of communities to the main depot and balanced service times during planning horizon. The performance of the models is evaluated through the real-world data obtained from the telecom provider. The results prove that the overnight TRSP model is capable of substantially decreasing travel costs and the number of technicians that are required to perform the same set of services. [ABSTRACT FROM AUTHOR]

Based on a case study, this paper deals with the production planning and scheduling problem of the glass container industry. This is a facility production system that has a set of furnaces where the glass is produced in order to meet the demand, being afterwards distributed to a set of parallel molding machines. Due to huge setup times involved in a color changeover, manufacturers adopt their own mix of furnaces and machines to meet the needs of their customers as flexibly and efficiently as possible. In this paper we proposed an optimization model that maximizes the fulfillment of the demand considering typical constraints from the planning production formulation as well as real case production constraints such as the limited product changeovers and the minimum run length in a machine. The complexity of the proposed model is assessed by means of an industrial real instance. [ABSTRACT FROM AUTHOR]

In this paper a new scheduling problem is presented, which originates from the steel processing industry. The optimal scheduling of a steel forge is investigated with the goal of minimizing setup and storage costs under strict deadlines and special resource constraints. The main distinctive feature of the problem is the deterioration of some equipment, in this case, the so-called forging dies. While the aging effect has been widely investigated in scheduling approaches, where production speed decreases through time, durability deterioration caused by equipment setup has not been addressed yet. In this paper a mixed-integer linear programming model is proposed for solving the problem. The model uses a uniform discrete time representation and resource-balance constraints based on the resource–task network model formulation method. The proposed method was tested on 3-week long schedules based on real industrial scenarios. Computational results show that the approach is able to provide optimal short-term schedules in reasonable time. [ABSTRACT FROM AUTHOR]

In this paper, we study the construction of a cyclic appointment schedule in an outpatient department. In particular, we determine the capacity distribution between elective and urgent patients and the scheduling of the time slots reserved for these patients such that the operational waiting times of elective and urgent patients are minimised. The proposed solution methodology devises a Pareto set of cyclic appointment schedules based on these waiting times with different capacity allocations for urgent patients. An approximation of the Pareto set of non-dominated schedules is obtained using a multi-objective archived simulated annealing heuristic. To accurately validate the cyclic appointment schedules, we incorporate operational decision-making via scheduling individual patients. To this end, we simulate operational variability, i.e., patient arrivals, no-show behaviour, punctuality and scan durations, based on real-life input data. The patients are assigned one-by-one using an online scheduling rule. Computational experiments are conducted with a real-life case study. We compare different appointment scheduling rules and discuss the impact of the capacity distribution between elective and urgent patients and the timing of urgent slots in the cyclic appointment schedules. The results show that the distribution of capacity between patient types, the timing of urgent slots and appointment rules all have significant impacts on patient waiting times. Appointment waiting times improve when urgent slots are spread equally over and throughout the days considered and when the Bailey–Welch rule is used to schedule patients. Trade-offs between elective and urgent waiting times resulting from different capacity distributions or slot timing are exemplified via a Pareto front. The proposed method outperforms relevant single-pass methodologies, and we demonstrate that its performance is strengthened thanks to the integrated optimisation of strategic, tactical and operational decisions. [ABSTRACT FROM AUTHOR]

The objective of the Patrol Boat Scheduling Problem with Complete Coverage (PBSPCC) is to find a minimum size patrol boat fleet to provide continuous coverage at a set of maritime patrol regions, ensuring that there is at least one vessel on station in each patrol region at any given time. The requirement for continuous patrol coverage is complicated by the need for vessels to be replenished on a regular basis. This combinatorial optimization problem contains both routing and scheduling components and is known to be NP-hard. In this paper, we show how recent theoretical insights can be used in conjunction with specially tailored heuristics to accelerate a column generation solution approach over a resource-space-time network construct. We show how the column generation approach can be used within a branch-and-price framework and combined with various reduction techniques to find cyclic and long-term scheduling solutions on a range of test problems. [ABSTRACT FROM AUTHOR]

It has been proposed that if replacement time is planned too early prior to failure, a waste of operation cost, i.e., excess costs, would incur because the system might run for an additional period of time to complete critical operations, and if replacement time is too late after failure, a great failure cost, i.e., shortage cost, is incurred due to the delay in time of the carelessly scheduled replacement. In order to make the preventive replacement policies perform in a more general way, the above two variable types of costs are taken into considerations for periodic replacement policies in this paper. We firstly take up a standard model in which the unit is replaced preventively at periodic times. Secondly, the modeling approaches of whichever occurs first and last are applied into periodic and random models, and replacement first and last policies are discussed to find optimum periodic replacement times for a random working time. Furthermore, optimum working numbers are obtained for the extended models. We give analytical discussions of the above replacement policies, and finally, numerical examples are illustrated. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of open shop scheduling on two machines with resources constraints. In the context of our study, in order to be executed, a job requires first, for its preparation for a given period of time, a number of resources which cannot exceed a given resource capacity. Then, it goes onto its execution while the resources allocated to it become available again. We seek a schedule that minimizes the makespan. We first prove the $\mathcal{N}\mathcal{P}$ -hardness of several versions of this problem. Then, we present a well solvable case, lower bounds, and heuristic algorithms along with an experimental study. [ABSTRACT FROM AUTHOR]

This paper presents a model to support planning decisions in the engineering methodology referred to as value analysis. A goal programming model incorporating elements of critical path method and concurrent engineering is proposed as a means to augment the planning of value analysis projects. The modeling approach builds and extends prior goal programming research by uniquely incorporating both timing and cost information to ease modeling complexity and reveal scheduling resource tradeoffs. An illustrative example is presented to demonstrate the modeling approach informational efficacy. [ABSTRACT FROM AUTHOR]

Most scheduling papers consider flexible machining and assembly systems as being independent. In this paper, a heuristic two-level scheduling algorithm for a system consisting of a machining and an assembly subsystem is developed. It is shown that the upper level problem is equivalent to the two machine flow shop problem. The algorithm at the lower level schedules jobs according to the established product and part priorities. Related issues, such as batching, due dates, process planning and alternative routes, are discussed. The algorithm and associated concepts are illustrated on a number of numerical examples. [ABSTRACT FROM AUTHOR]

Multi-position refining furnaces are a critical strategy for energy-intensive industries to meet its demands of fast-paced production. In most literature, however, they serve only as a buffer, holding up to at most two ladles to maintain the proper temperature of ladles. These studies do not take full advantage of them, nor do they study the production scheduling of energy-intensive enterprises with multi-position refining furnaces under time-of-use (TOU) tariffs. Therefore, this paper presents a steelmaking-continuous casting (SCC) scheduling problem with multi-position refining furnaces under TOU tariffs. We firstly develop a mixed integer nonlinear programming (MINLP) model with the goals of minimizing jobs completion time, machines idle time, and total electricity costs, which subjects to the double-position characteristics and other process constraints. Owing to the complexity between the time-slots of TOU tariffs and the processing cycles of jobs, we design an intermediate function to calculate objectives efficiently. Furthermore, a Lagrangian relaxation (LR) algorithm based on a subgradient algorithm is utilized to solve the proposed model, and an interior point algorithm is adopted to solve sub-problems obtained by job-level and batch-level decomposition, whose solution approximates optimality comparing to GUROBI solver. The computational results demonstrate that the solution of job-level decomposition algorithm approximates the optimal scheduling scheme in an acceptable time and is superior to that of GUROBI solver. In addition, double-position instance can find a better scheduling scheme than nondouble-position one. [ABSTRACT FROM AUTHOR]