摘要:

AbstractThis paper addresses a cutting-stock problem which arises in the manufacture of furniture. An heuristic has been developed to schedule the cutting of worktops of varying shapes and sizes from available raw material.The work was carried out for a local manufacturing company. Interface software written at that company allows the program to be integrated into their computer system in such a way that it can easily be run by the user.Details of the heuristic are given, together with results of some numerical experiments designed to test the robustness of the algorithm and to give some guidance as to the optimal batch size and dimensions of the raw material.Performance of the algorithmin situsupports the results of numerical experiments, the computer solution giving some improvements over the previously obtained manual solution with respect to trim loss without incurring an unacceptable build-up of offcuts.

ISSN:0160-5682    

DOI:10.1057/jors.1984.77

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

AbstractCardiac pacemaker malfunctions are of continuous concern to the medical profession as well as to the electronics industry. Certain failures in cardiac pacemaker performance are critical and can result in patient deaths. Cardiac pacemakers are vulnerable to certain malfunctions in the electrode, batteries and the electronic circuit. This paper focuses on failures and reliability of the electronic circuit and how they affect its choice and design. The paper discusses the issues of balancing the various failure modes by considering both failure rates and failure outcomes.As the choice of an appropriate pacemaker is a decision problem under conditions of uncertainty, we employ decision analysis as the analytical and conceptual framework. Use of utility theory enables a systematic quantitative evaluation of such seeming intangibles as the various failure outcomes. Probabilities are assessed using specific engineering and reliability literature. The method is demonstrated on a choice problem between two specific electronic circuit designs.The methodology can be useful in designing the electronic circuit to meet certain reliability specifications, deciding whether or not to introduce redundancy, decisions affecting components and technology, and establishing minimal reliability standards, with regard not only to cardiac pacemakers but to other electronics as well.

ISSN:0160-5682    

DOI:10.1057/jors.1984.78

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

AbstractAlthough material requirements planning (M.R.P.) allows managers to better plan hierarchical production and inventory systems, much is still left to the planner's intuition and experience in devising realistic master production schedules, selecting appropriate lot sizes for components, and changing capacity levels. Decisions are made sequentially, rather than simultaneously, with no real assurance of satisfactory performance.This research proposes an integrated model for facilitating these decisions. A mixed-integer nonlinear programming model is formulated such that it can be solved by a heuristic procedure. Several versions of this procedure are tested in a research design controlling for nine variables on shop and cost structure. Preliminary research results show that the procedure gives good solutions to the situations represented by the experimental variables. Computational results are also encouraging.

ISSN:0160-5682    

DOI:10.1057/jors.1984.79

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

AbstractThe technique of delay time analysis is here extended to problems of industrial plant maintenance. A basic model of inspection maintenance is presented, along with models of some of the variations which have been observed in practice. Numerical examples indicate both the nature and sensitivity of the output from the models.

ISSN:0160-5682    

DOI:10.1057/jors.1984.80

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

AbstractMany vehicle scheduling situations require careful monitoring and control of the time a vehicle is on the road. Setting time limits as rigid constraints on a vehicle scheduling problem is usually not appropriate since minor violations of such constraints do not really imply that a solution is infeasible. An heuristic method for solving vehicle scheduling problems in which time is an important factor has been developed. The heuristic creates routes based on a "time density function" which identifies clusters of stops and chooses stops from these clusters to form a route. Important considerations balancing overtime costs, overnight route costs and travel costs to and from far clusters of stops are part of the heuristic. The method has been tested on 10 days of data from a large food distributor in the midwestern United States and found to affect significantly both variable and fixed costs in these commercial problems. The smallest of these problems had 110 stops, while the largest had 223. A modest amount of computer time (under 15 seconds in every case) was required to generate the assignment of stops to trucks and produce routes for the vehicles.

ISSN:0160-5682    

DOI:10.1057/jors.1984.81

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

AbstractPredictions of the tender price of proposed buildings are needed during early design. Conventionally, these are prepared manually and based on limited data.A computer system was produced which prepares estimates using a library of data containing rate, quantity and date for the constituent elements of previous buildings, inflation indices and statistical models.Because the scatter of the rate vs quantity data for each element in a sample of buildings was so variable between samples, no one model was adequate. Thirty two different models were included, together with a criterion for selecting the most appropriate. This ensured the most precise prediction possible.The co-efficient of variation of the ratio forecast to actual price measured for a set of system-produced estimates grouped by building type ranged from 10 to 19%. Current manual practice ranges from 6 to 21%, but this is only achieved much later when design is complete and more reliable data is available.

ISSN:0160-5682    

DOI:10.1057/jors.1984.82

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

AbstractUsing convex analysis and a characterization of the entire family of optimal solutions to an L.P., we show that in order to obtain shadow prices, one has to solve a much smaller L.P. derived from any optimal tableau. We then show that positive as well as negative shadow prices for any constraint or for any combination of constraints can easily be computed by parametric linear programming. Some examples exhibiting the method are also included.

ISSN:0160-5682    

DOI:10.1057/jors.1984.83

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

AbstractGiven a set ofnjobs with deterministic processing times and the same ready times, the problem is to find the optimal processing-time multiplek* for the T.W.K. due-date assignment method, and the optimal sequenceσ* to minimize the total amount of missed due-dates. It is found thatk* is a constant for a given job set andσ* should be in S.P.T. sequence. After the theoretical treatment, a numerical example is given for discussion. The optimal results can readily be extended to situations in which the processing times are random variables with known means and having the same coefficient of variation. From a practical point of view, the main merit of this paper is that it demonstrates how, under certain production environments in which completion times of the jobs can be anticipated, to determine the optimal due-dates and obtain the optimal sequence.

ISSN:0160-5682    

DOI:10.1057/jors.1984.84

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

摘要:

AbstractThis paper considers the infinite server queue with arrivals generated by a non-homogeneous compound Poisson process. In such a system, customers arrive in groups of variable size, the arrival epochs of groups being points of a non-homogeneous Poisson process, and they are served without delay. The service times of customers who belong to the same group need not be independent nor identically distributed. Assuming that the system is initially empty, the transient distribution of the queue size and of the counting departure process is obtained. Also the limiting queue size distribution (when it exists) is determined and it is found to be insensitive to the form the service time distribution functions.

ISSN:0160-5682    

DOI:10.1057/jors.1984.85

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor

ISSN:0160-5682    

DOI:10.1057/jors.1984.86

出版商:Taylor&Francis    

年代:1984

数据来源: Taylor