摘要:

AbstractMathematical modelling of the relationship between acceptable diets and satisfactory nutrition is discussed. The classical minimum-cost diet problem is unsuited to most purposes in human dietetics, since the objective of least monetary cost leads to diets which are unpalatable, both generally and to individuals. In this paper a different approach, using an objective function based on the food preferences of individuals, is described. A computational method, based on this analysis, for constructing individually acceptable diets by means of linear programming is described. Careful use of post-optimal analysis provides invaluable insight to individual patients, and their medical advisors, on the changes to their eating habits which will most readily enable them to meet nutrient intake targets. An example, using data appropriate to a patient with chronic renal failure, demonstrates the usefulness to nutritionists and dietitians of this approach to dietary recommendations.

ISSN:0160-5682    

DOI:10.1057/jors.1994.76

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractA software system is described for the dispatching of buses of different types operated by a public transport organization. The system uses simulated annealing to improve the desirability of the total allocation while satisfying a number of‘hard’dispatching constraints.

ISSN:0160-5682    

DOI:10.1057/jors.1994.77

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe probabilistic changes in certain measurable physical parameters of a lubricant are used to develop a mathematical model of the physical-chemical deterioration process taking place in the crankcase of locomotive diesel engines. A seven-state Markov chain is formulated with actual data taken from the year 1985. Statistical inference is used to establish that the chain is of the first order and that it is applicable across the fleet of locomotives in the study. The Markov model is shown to have the twin advantages of enhancing one's understanding of the deterioration process and of providing a means for predicting future changes. The model also lends itself to the specification of input data.

ISSN:0160-5682    

DOI:10.1057/jors.1994.78

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractA new model of the perishable inventory system is presented, which recognizes and incorporates the effects of consumer-realized product expiration. Such expiration has not been explicitly treated within the perishable inventory literature, and occurs when units are expired at the time of sale or expire within some short period of time subsequent to purchase. The model treats the age at which the vendor outdates units as a decision variable, and allows for analysis of the interaction between inventory ordering and outdate policy for a perishable item with random lifetime. As such, the model represents a synthesis of the fixed versus random lifetime perishable inventory literatures. Sensitivity analysis conducted with respect to the new model provides insight into the trade-offs between the costs of carrying, shortage, outdating, and consumer-realized product expiration.

ISSN:0160-5682    

DOI:10.1057/jors.1994.79

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractOne way of reducing the unit cost of shipment by a motor carrier is to consolidate many LTL (less-than-truck-load) shipments. Explicit information on the route structure is a prerequisite to the understanding of the costs of the services provided and to the planning of the allocation of the equipment and personnel among the terminals. In this paper, an approach for routeing the LTL shipments is presented and is applied to a hypothetical network. Solution results of this example show that the algorithm offers an efficient and reasonably accurate method for the routeing of LTL shipments via the intermediate terminals.

ISSN:0160-5682    

DOI:10.1057/jors.1994.80

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThis paper studies the machine-repair problem consisting ofMoperating machines withSspares, andRservers which themselves are subject to breakdown under steady-state conditions. Spares are considered to be either cold-standby, or warm-standby or hot-standby. Failure and service times of the machines, and breakdown and repair times of the servers, are assumed to follow a negative exponential distribution. Each server is subject to breakdown even if no failed machines are in the system. A profit model is developed in order to determine the optimal values of the number of servers and spares. Numerical results are provided in which several system characteristics are evaluated for all cases under the optimal operating conditions.

ISSN:0160-5682    

DOI:10.1057/jors.1994.81

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractSeveral production and flexible manufacturing systems can naturally be modelled using queueing networks. In this paper, we consider the problem of acquiring servers for the nodes of an open queueing network, so as to optimize the steady-state mean virtual system parameters subject to a budget constraint. A partial enumeration scheme and a heuristic method have been proposed to solve this problem. Empirical results based on randomly generated test problems are used to identify a class of problems for which the heuristic performs well.

ISSN:0160-5682    

DOI:10.1057/jors.1994.82

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe introduction of variability and stochastic processes in health manpower projections may help health planners cope with the inherent problem of uncertainty in the future. However, limited data and the complex nature of health manpower make it very difficult or even impossible to estimate the probability distribution of input variables. In this paper, two statistical methods are discussed and compared for approximating a probability distribution based on imperfect data. The common feature of the two methods is that they use minimum, maximum, and most likely values, which can be estimated by people with little knowledge of statistics and probability. In addition, the methods can be used to analyse variables with a symmetrical as well as non-symmetrical probability distribution. An example is provided of the application of the methods to health manpower projections in China.

ISSN:0160-5682    

DOI:10.1057/jors.1994.83

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractIn this paper we examine a neglected aspect of Data Envelopment Analysis: cross-efficiency. We develop the concept of cross-efficiency in a number of new directions. We ground an intuitive understanding of cross-efficiency in the concept of peer-appraisal, as opposed to self-appraisal implied by simple efficiency, and discuss the relative merits of each. We also present mathematical formulations of, and intuitive meanings for three possible implementations of aggressive and benevolent cross-efficiency. We have implemented two of these formulations in computer programs; their performance is compared empirically on a real data set. Finally, we suggest practical uses for cross-efficiency, illustrated with reference to the same data set.

ISSN:0160-5682    

DOI:10.1057/jors.1994.84

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractMost of the literature dealing with inventory problems assumes lead time as prescribed, whether deterministic or probabilistic. In certain cases, lead time can be reduced but at an added cost. In this article we discuss inventory models where lead time is one of the decision variables.

ISSN:0160-5682    

DOI:10.1057/jors.1994.85

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor