摘要:

It can be difficult to set the reorder point in an inventory system because often one does not have much knowledge of the lead-time demand (LTD)distribution. A frequent practice is to assume a “standard” distribution, such as the Normal. The reorder point is then taken as the p-th fractile of that standard distribution, where (1 −p) is the specified probability of stockout during a replenishment cycle.

ISSN:0740-817X    

DOI:10.1080/07408178908966236

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The most prominently used statistical process control tool is the X¯-chart. Duncan's economic model of Shewhart's original X¯-chart has established its optimal economic application for processes with a Markovian process failure mechanism. However, there are practical situations in which the distribution of the time to failure of the process is not exponential. This paper extends the state of the art in control charting by providing: (1) a generalized dynamic (sample size, sampling frequency, and control limit spread allowed to vary over time) version of Duncan's X¯-chart model and (2) the adoption of the rich Weibull distribution for the failure mechanism. This paper also discusses: (3) a methodology under which control chart parameters may change over time, (4) computational aspects of model implementation, (5) model optimization, and (6) some economic comparisons between the dynamic design and Duncan's design. It is concluded that the choice of process failure mechanism in the cost model is significant; substantial cost savings can result from the use of the dynamic design as compared to Duncan's design.

ISSN:0740-817X    

DOI:10.1080/07408178908966237

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Two 2-stage serial production systems under constant average demand rate and infinite horizon are considered. The first and the simpler system assumes zero final product inventory; while the second assumes it nonzero but with a continuous demand. The stages have finite production rates greater than or equal to the demand rate and operate with periodic start-ups and shutdowns. No stock-outs are allowed in the inventories. Analytical results for determining a cyclic schedule with the minimum sum of set-up and inventory costs are presented. The optimal lot sizing policy for the first system involves integer splitting/merging of lots; however noninteger split/merge policy may be optimal in some instances of the second.

ISSN:0740-817X    

DOI:10.1080/07408178908966238

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

When inspection on the performance variable of interest is destructive or costly, it is attractive to use other variables which are correlated with the performance variable and which are inexpensive to inspect as the screening variables. The idea of using a single correlated variable in a complete screening procedure has drawn much attention recently. In this paper, we extend a previously defined economic model for a screening procedure using more than one correlated variable. The screening specifications are based on a linear combination of the correlated variables, and. if an item fails to conform to the screening specifications, it is rejected and excluded from shipment. The screening specifications are determined so that the total cost, the sum of three components, is minimized.

ISSN:0740-817X    

DOI:10.1080/07408178908966239

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We consider the problem of locating uncapacitated facilities among a set of potential sites to minimize cost of serving a number of demand points each requiring service from two different facilities. This problem has many potential applications. One such application is location of emergency service facilities where it is desirable to have a primary and back-up service facility wthin a certain distance from every district An efficient solution procedure is developed. This procedure is tested on a number of problems and computational results are reported. It is compared to a state of the art commercial linear/integer programming package and found to be around two orders of magnitude faster than this package. It is also compared to a state of the art special purpose agorithm for the simple uncapacitated facility location problem to investigate the computational implications of introducing secondary service requirements. The model is used to illustrate the effect of considering secondary service on the spatial characteristics of the optimal set of locations. The model is further demonstrated on a “real life” example with 625 demand points and 30 potential facility locations.

ISSN:0740-817X    

DOI:10.1080/07408178908966240

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A number of organizations sell products in containers that can be reused. The time from issue to return of an individual container is usually not known with certainty and there is a chance that the container is never returned (because of loss or irrepairable damage). Consequently, even under a level demand pattern new containers must be acquired from time to time. In this paper a purchasing policy of these new containers is determined for a finite time horizon so as to minimize the total purchasing and expected carrying costs under a prescribed service level. The associated stochastic model is reduced to a deterministic, dynamic lot-sizing problem with possible occurrence of negative net demand (demand minus return). A transformation into the usual nonnegative demand case allows us to apply well-known deterministic lot-sizing procedures to obtain the solution.

ISSN:0740-817X    

DOI:10.1080/07408178908966241

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In a steady-state simulation, the initial conditions often bias the estimators, sometimes severely. A common method for ameliorating this is to delete an initial portion of the run, perhaps entailing substantial data loss. We investigate feasible methods for initializing such simulations that lead to lower estimator bias or, alternatively, less requisite deletion. Deterministic and stochastic initialization rules are compared, with appropriately chosen stochastic rules' being preferable in terms of several measures of quality of point estimators and confidence intervals. Forms for the initial distribution are suggested by the maximum entropy principle, the parameters of which may be specified from short pilot runs. These initialization rules are tested on a range of models with analytical tractability varying From complete to none.

ISSN:0740-817X    

DOI:10.1080/07408178908966242

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In this paper, the joint problem of production planning and maintenance schedule is studied under the realistic assumption that the cost of process restoration is a function of the detection delay and the existence of shortages in the system. The detection delay is defined as the elapsed time since the production process has deteriorated until it is identified by some inspection procedure and repaired. Since production planning and maintenance problems have usually been studied as separate problems, this paper is an attempt to develop a formal framework for the joint problem. We have developed sufficient conditions for the optimality of the commonly used equal-interval maintenance schedule. The conditions are found to be a function of parameters such as the cost of defective items, the mean time for system deterioration, and the form of the restoration cost function. For specific restoration cost functions such as linear and exponential, an efficient solution procedure is presented for the simultaneous determination of the number of maintenance inspections in a production run, the length of the production run and consequently the economic manufacturing quantity, and the maximum level of backorders. A numerical example illustrates the use of this procedure and the differences between the optimal cost obtained by this procedure and the cost obtained by using the classical economic manufacturing quantity model.

ISSN:0740-817X    

DOI:10.1080/07408178908966243

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Commonly used learning curve models assume that a repetitive task is performed continuously, disregarding the existence of possible break periods between consecutive repetitions. Since these breaks generate forgetting, actual performance will be inferior to the performance forecasted by typical learning curve models.

ISSN:0740-817X    

DOI:10.1080/07408178908966244

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Duplication in the machine cells formation process is the assignment of one machine type to more than one cell. It is done to reduce the number of intercellular moves. While the existing machine cells formation models employ the duplication process to reduce the machine cells interdependence, none of tem considers its economic consequences. This paper presents a cost-based duplication procedure which uses the duplication cost and the associated reduction in intercellular material handling cost as a basis for decision making in the duplication process.

ISSN:0740-817X    

DOI:10.1080/07408178908966245

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor