Showing papers on "Flow shop scheduling published in 1981"

A Review of Production Scheduling

Abstract: Production scheduling can be defined as the allocation of available production resources over time to best satisfy some set of criteria. Typically, the scheduling problem involves a set of tasks to be performed, and the criteria may involve both tradeoffs between early and late completion of a task, and between holding inventory for the task and frequent production changeovers. The intent of this paper is to present a broad classification for various scheduling problems, to review important theoretical developments for these problem classes, and to contrast the currently available theory with the practice of production scheduling. This paper will highlight problem areas for which there is both a significant discrepancy between practice and theory, and for which the practice corresponds closely to the theory.

Some scheduling techniques and an easily schedulable horizontal architecture for high performance scientific computing

Abstract: Horizontal architectures are attractive for cost-effective, high performance scientific computing. They are, however, very difficult to schedule. Consequently, it is difficult to develop compilers that can generate efficient code for such architectures. The polycyclic architecture has been developed specifically to make the task of scheduling easy. As a result, it has been possible to develop a powerful scheduling algorithm that yields optimal and near-optimal schedules for iterative computations. This novel architecture and this scheduling algorithm are the topic of this paper.

Loading and control policies for a flexible manufacturing system

Abstract: An experimental investigation of operating strategies for a computer-controlled flexible manufacturing system is reported. The system is a real one, consisting of nine machines, an inspection station and a centralized queueing area—all interconnected by an automatic material-handling mechanism. The operating strategies considered involve policies for loading (allocating operations and tooling to machines) and real-time flow control. A detailed simulation was employed to test alternatives. The results are different from those of classical job shop scheduling studies, showing the dependence of system performance on the loading and control strategies chosen to operate this flexible manufacturing system. Loading and control methods are defined that significantly improve the system's production rate when compared to methods which were previously applied to the system. Finally, some conclusions are presented concerning the control of these automated systems.

Minimizing Variation of Flow Time in Single Machine Systems

Abstract: This paper addresses the problem of n jobs to be scheduled on a single machine in such a way that flow time variation is minimized. When the measure of variation is total absolute difference of completion times TADC the problem is shown to be quite simple. Sufficient conditions are shown for minimal TADC and a simple method for generating an optimal solution is provided. When the measure of variation is variance of flow time the problem is much more difficult. For this case a heuristic method for scheduling is proposed. The heuristic is simple and provides solutions which compare favorably with others found in the literature.

A Multiple Objective Nurse Scheduling Model

Abstract: The authors present a model for the nurse scheduling problem which works in two phases. In the first phase, the nurses are assigned their day-on/day-off pattern for the two-week scheduling horizon by a goal programming model which allows for consideration of the multiple conflicting objectives inherent in scheduling a nursing staff. The second phase makes specific shift assignments through the use of a heuristic procedure. The two-phase approach results in considerable reductions in problem size, thus reducing the solution effort. Extensions to the basic model are also examined.

Due Date Assignment for Production Systems

Abstract: This paper is concerned with the study of the constant due-date assignment policy in a dynamic job shop. Assuming that production times are randomly distributed, each job has a penalty cost that is some non-linear function of its due-date and its actual completion time. The due date is found by adding a constant to the time the job arrives to the shop. This constant time allowed in the shop is the lead time that a customer might expect between time of placing the order and time of delivery. The objective is to minimize the expected aggregate cost per job subject to restrictive assumptions on the priority discipline and the penalty functions. This aggregate cost includes 1 a cost that increases with increasing lead times, 2 a cost for jobs that are delivered after the due dates: the cost is proportional to tardiness and 3 a cost proportional to earliness for jobs that are completed prior to the due dates. We present an algorithm for solving this problem and show that the optimal lead time is a unique minimum point of strictly convex functions. The algorithm utilizes analytical procedures; computations can be made manually. No specific distributions are assumed; the distribution of total time a job is in the shop is utilized by the algorithm. This distribution can be theoretical or empirical. An example of a production system is presented.

Preemptive Scheduling of Independent Jobs with Release and Due Times on Open, Flow and Job Shops

Abstract: We study the problem of obtaining feasible preemptive schedules for independent jobs. It is assumed that each job has associated with it a release and due time. No job can begin before its release time. All jobs must be completed by their respective due times. It is shown that determining the existence of feasible preemptive schedules for two processor flow and job shops is NP-hard in the strong sense even when all jobs have the same due time. A linear programming formulation for the open shop problem is obtained. Also, a fast polynomial time algorithm is obtained for a restricted class of open shop problems.

A new continuous model for job-shop scheduling

Abstract: In this paper arguments are presented for the use of a new continuous model for job-shop scheduling. In this model each job is regarded as infinitely divisible. Formulating the job-shop problem in this way leads to optimal control problems of a type which recent work has shown to be efficiently solvable. Solutions to these continuous problems can be used to generate heuristic loading rules. Some simulation results from small job-shops are presented. These demonstrate that loading rules based on the continuous model perform well in practice.

Minimizing Maximum Lateness in a Two-Machine Open Shop

Abstract: We consider the problem of scheduling independent jobs in a two-machine open shop so as to minimize the maximum lateness with respect to due dates for the jobs. For the case in which preemption is allowed, a linear-time algorithm is presented. For the nonpreemptive case, NP-hardness is established.

Combined scheduling system for reducing job tardiness in a job shop

Abstract: Two formulae to give the mean and the standard deviation of job flow-times are derived from the machine number, the load ratio, the required number of operations, and the mean and the standard deviation of processing times, which specify the characteristics of a job shop. On the basis of the two formulae, a method of due-date assignment which contains a due-date adjustment factor is proposed. The assignment method is combined with the sequencing procedure to construct the total scheduling system for reducing job tardiness. Two new dispatching rules are presented as the second phase of the system. The experimental comparison shows that the efficiency of the proposed systems can be better than the conventional scheduling systems

A Vector-Sum Theorem and its Application to Improving Flow Shop Guarantees

Abstract: We prove that if a closed polygonal path in Rd consists of a finite number of line segments of at most unit length, then it is possible to transpose the segments in such a way that the new polygonal path is contained in a ball of radius [ $\frac{3}{2}d$ ]. Using this result we give a near optimal algorithm for the NP-complete flow shop problem. The error of the algorithm cannot exceed a constant depending on the maximal execution time and the number of machines but not depending on the number of jobs. Our theorems improve earlier results of the same type by Belov and Stolin.

An investigation of the advantages of using a man-computer interactive scheduling methodology for job shops

Abstract: Scheduling has been a difficult problem for job shops which manufacture discrete parts. The research described in this paper investigates the hypothesis that interactive man-computer scheduling methodology is more effective in this task than a batch scheduling methodology. This hypothesis is investigated under eight different problem configurations generated by varying three job description parameters. The results have been evaluated statistically and the effectiveness of an interactive schedule compared to the slack-per-remaining-operation heuristic is investigated. Influences of the level of variation in job description parameters on the quality of the interactive schedule have also been analysed in this study. Results show that scheduling interactively is significantly more effective in most problem situations, and that the level of variation of some of the parameters has a significant impact on the quality of the interactive schedule.

Crane Scheduling Problems

Abstract: Crane scheduling problems are introduced together with a descriptive general model. In particular, crane scheduling problems with one operation per job are investigated when arrival patterns are static or dynamic and when the processing times are arbitrary.

A note on the flow‐shop problem without interruptions in job processing

Abstract: This paper deals with a flow-shop problem where the n jobs are being processed uninterrupted by m machines. A comprehensive theory based on “an earliest starting time of a job” concept produced the most efficient solution method for a variety of optimization criteria. The paper also rectifies several known results in this area.

Job shop control

Abstract: The paper defines batch or job shop production and reviews the functions of production planning and production control in a job shop manufacturing situation. It argues that the separation of planning and control has resulted in the artificial isolation of the sequencing problem in job shop research. It attempts to redefine the production control function for a job shop, now called job shop control, and discuss the activities it involves. The major decision-making problems associated with job shop control are highlighted and an objective function of costs to aid in management decision making is evolved.

On J-maximal and J-minimal Flow-Shop Schedules

Abstract: Scheduling problems are considered for a common kind of flow shop where the execuuon Ume for certain tasks in each job is always longer or shorter than that for the other tasks NP-completeness ts shown for some cases, stmple opttmal algorithms are found for the others, and bounds are gtven for the worst cases.

Minimizing maximum lateness in a two-machine unit-time job shop

Abstract: AnO (nlogn)-algorithm is given for the two-machine, job-shop scheduling problem withn unit-time tasks in which maximum lateness is to be minimized. This algorithm generalizes recent results by Hefetz and Adiri for the corresponding makespan problem.

A note on the two machine job shop with exponential processing times

Abstract: Consider two machines, labeled 1 and 2. A set of tasks has to be processed first on machine 1 and after that on machine 2. A second set of tasks has to be processed first on machine 2 and after that on machine 1. All the processing times are exponentially distributed. We present a policy which minimizes the expected completion time of all tasks.

Counterexamples to optimal permutation schedules for certain flow shop problems

Abstract: It is well known that a minimal makespan permutation sequence exists for the n × 3 flow shop problem and for the n × m flow shop problem with no inprocess waiting when processing times for both types of problems are positive. It is shown in this paper that when the assumption of positive processing times is relaxed to include nonnegative processing times, optimality of permutation schedules cannot be guaranteed.

Experimentation with a computerized system for scheduling mass transit vehicles and crews. from the book computer scheduling of public transport

Abstract: An interactive model is proposed for simultaneous solution of the vehicle and driver scheduling problems. A non-interactive version has been programmed and has achieved results which compare favorably on test data with those achieved by manual methods. The model uses a network representation of the problem, and schedules are built up from the network using a series of matching processes.

Myopic heuristics for single machine scheduling problems

Abstract: For many years difficult combinatorial problems, such as scheduling problems, have been solved by the practitioner with heuristics. We suggest in this paper how to determine for which problems heuristics should be developed and, for a class of these problems, how to develop these procedures naturally. These results are motivated by theoretical results in computer science. The suggestion is numerically tested on a particular single machine scheduling problem.

A branch and bound network algorithm for interactive process scheduling

Abstract: A multi-facility multi-product production scheduling problem is considered in terms of a general class of process unit operations scheduling problems which are common in the refining and chemicals processing industries. A generalized network formulation is used to model the conversion of unit processing capacity to finished products. A specialized branch and bound algorithm is used to enforce the restriction that only one operation can be run per unit at any given time. The algorithm minimizes total costs, which consist of unit operating costs, processing costs, inventory holding costs, setup and changeover costs. A procedure is developed by which the setup and changeover costs are used to estimate bounds for the network model in the branch and bound algorithm. All other costs are incorporated in the network formulation. It is shown that the algorithm is more efficient in those problems for which the setup and changeover costs are small, or in problems in which a lower bound for the setup and changeover costs can be accurately estimated. The implementation of the algorithm in an interactive process scheduling system is discussed in terms of the human engineering factors involved.

M/G/1 Queues with Scheduling within Generations and Removable Server

Abstract: Two models of M/G/1 queues with removable server and scheduling within generations are considered in this paper. The scheduling policy considered here is the shortest processing time; the control policies are the multiple vacations policy and N-control policy. The Laplace-Stieltjes transforms of the waiting time distribution, the mean cost rates and the optimal control policies are derived for these two models. Properties of the delayed busy cycle are used in our analysis.

Extreme solutions of the two machine flow‐shop problem

Abstract: The paper provides a new theoretical framework to identify extreme solutions of the two machine flow-shop problem. Some remarkable properties of these solutions have been developed. As a result the problem of generating minimal solutions can be decomposed into a number of smaller subproblems.

A computer based crew scheduling system using a mathematical programming approach. from the book computer scheduling of public transport

Abstract: Two formulations of the bus crew scheduling problems are first set out. The computational difficulties and the inadequacy of the models are then considered. Some relevant aspects of an "optimiser" specially developed for this purpose are discussed. Finally, the data input, the commands and the information flow of the overall system are briefly described.

SPT, Data Analysis, and a Bit of Common Sense in Bus Maintenance Operations: A Case Study

Abstract: A fundamental result in the theory of scheduling is the optimality of the shortest processing time (SPT) rule for minimizing mean flow time in the basic single-machine scheduling problem. The relationship between flow time and inventory also makes this rule an appropriate one to use if the objective is one of rapid turnaround, even when the scheduling environment is dynamic (i.e., where jobs arrive over time). This paper presents a case study where the principle behind SPT sequencing was used for a job shop bus maintenance operation. The results obtained by this implementation are further evidence that the application of SPT sequencing can yield significant improvements in scenarios considerably more complex than the basic single-machine scheduling problem.