摘要:

Agent technology offers a new way of thinking about many of the classic problems in operations research. Among these are problems such as project scheduling subject to resource constraints. In this paper, we develop and experimentally evaluate eight agent-based algorithms for solving the multimode, resource-constrained project scheduling problem. Our algorithms differ in the priority rules used to control agent access to resources. We apply our approach to a 51-activity project originally published by Maroto and Tormos [1] We solve the problem using two types of agent-based systems: (i) a system of simple, reactive agents that we callbasic agents; and (ii) a system of more complex, deliberative agents that we callenhanced agents. Of the eight priority rules tested, we find that priority based on shortest processing time performs best in terms of schedule quality when applied by basic agents while the priority based on earliest due date performs best when applied by enhanced agents. In comparing agents across priority rules, we find that enhanced agents generate much better schedules (with makespans up to 66% shorter in some cases) and require only slightly more computation time

ISSN:0740-817X    

DOI:10.1080/07408170008963915

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Manufacturing processes and projects often consist of a series of activities with uncertain durations. The resulting uncertainty of the process or project impedes planning and disrupts the supply chain. Suppose that the uncertainty of the duration of individual activities can be reduced at a cost. We wish to minimize the variability of the sum of these durations, i.e., the variability of the project's duration. Using mean-preserving transformations, we derive the optimal budget allocation among individual activities for separable and non-separable cost functions, and also explore the implications of statistical dependence on the allocation

ISSN:0740-817X    

DOI:10.1080/07408170008963916

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper develops two algorithms for computing the average total cost per product and other performance measures for a make-to-order inventory-production system. The two algorithms are developed by using matrix analytic methods. The first algorithm is based on the matrix-geometric solution of the Quasi-Birth-and-Death (QBD) Markov process. The second algorithm is based on the fundamental period of the QBD Markov process. The advantages and disadvantages of the two algorithms are discussed

ISSN:0740-817X    

DOI:10.1080/07408170008963917

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper focuses on manufacturing environments where job processing times are uncertain. In these settings, scheduling decision makers are exposed to the risk that an optimal schedule with respect to a deterministic or stochastic model will perform poorly when evaluated relative to actual processing times. Since the quality of scheduling decisions is frequently judged as if processing times were known apriori, robust scheduling, i.e., determining a schedule whose performance (compared to the associated optimal schedule) is relatively insensitive to the potential realizations of job processing times, provides a reasonable mechanism for hedging against the prevailing processing time uncertainty. In this paper we focus on a two-machine flow shop environment in which the processing times of jobs are uncertain and the performance measure of interest is system makespan. We present a measure of schedule robustness that explicitly considers the risk of poor system performance over all potential realizations of job processing times. We discuss two alternative frameworks for structuring processing time uncertainty. For each case, we define the robust scheduling problem, establish problem complexity, discuss properties of robust schedules, and develop exact and heuristic solution approaches. Computational results indicate that robust schedules provide effective hedges against processing time uncertainty while maintaining excellent expected makespan performance

ISSN:0740-817X    

DOI:10.1080/07408170008963918

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this paper, we consider the maintenance scheduling of a group ofMidentical machines, the performance of which deteriorates with usage. Examples of such situations are frequently found in the heavy machine tooling, petro-chemical and semi-conductor industries among others. Assuming a limited maintenance resource and that the maintenance times are i.i.d., we propose a dynamic maintenance policy which utilities the information about the number of operating machines and their ages. We analyze the system for the special cases of constant and exponentially distributed maintenance times. We investigate the impact of maintenance time variability on system performance and evaluate the performance of various maintenance policies within the proposed policy class when the expected profit rate is maximized

ISSN:0740-817X    

DOI:10.1080/07408170008963919

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We consider a heuristic which has been applied to assign a common due date to a set ofnjobs and schedule them on a set ofmparallel and identical machines so that the weighted sum of the due date, earliness and tardiness is approximately minimized. We alter the heuristic slightly and show that the revised version is asymptotically optimal asn→∞.

ISSN:0740-817X    

DOI:10.1080/07408170008963920

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We introduce unique scheduling problems that arise for multiple spindle machine tools. The ability of these machines to perform simultaneous operations on more than one part creates constraints that are not found in the traditional scheduling literature. Two types of solution procedures are introduced for these problems. The first uses priority dispatching rules and a delay factor concept, while the second uses a genetic algorithm with a random keys encoding. The effectiveness of these methods is demonstrated on test problems with comparisons to lower bounds

ISSN:0740-817X    

DOI:10.1080/07408170008963921

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this paper we analyse the effect of a cutoff transaction size on the average inventory cost in a simple newsboy setting. It is assumed that customers with an order larger than a prespecified cutoff transaction size are satisfied in an alternative way, against additional cost. For compound Poisson demand with discrete order sizes, we show how to determine the average cost and an optimal cutoff transaction size. Because the computational effort to calculate the exact cost is quite large, we also consider an approximate model. By approximating the distribution of the total demand during a period by the normal distribution one can determine an expression for the average cost function that solely depends on the cutoff transaction size. A significant advantage of this approximation is that we can solve problems of any size. The quality of using the normal approximation is evaluated through a number of numerical experiments, which show that the approximate results are satisfactory

ISSN:0740-817X    

DOI:10.1080/07408170008963922

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor