摘要:

AbstractElectric utilities commonly use econometric modelling for energy and power forecasting. In order to accommodate the uncertainties contained in the input variables, such forecasts are frequently made in three parts: a base forecast, assumed to be the most likely, and a high and a low forecast, often arbitrarily spaced on either side of the base forecast, giving a band of possible values for the forecast. Usually, a single point value forecast is then utilized rather than a distribution of possible forecast values. This paper describes how commercially available spreadsheet software was utilized to convert an econometric energy forecast into probabilistic demand and energy forecasts that incorporate weather variation, as well as other uncertain inputs.

ISSN:0160-5682    

DOI:10.1057/jors.1991.183

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe subject matter is the sustainability of naval forces in combat and the intimate relationships between tactics and logistics. The observation is made that it has been a long time since the United States Navy has worried about logistics in combat and that to some extent combat logistics have become‘somebody else's’responsibility. It is argued that combat logistics is inescapably the force commander's responsibility and its dimensions are sketched. Necessarily, the amount of data and calculation is extensive if an accurate picture of the combat logistics states of the force are to be maintained and predictions of future states are to be made. It is in the predictions of future states that the interactions between tactics and logistics become most apparent. The data storage and retrieval and computational aspects suggest a microprocessor-based support system. BGLCSS (battle group logistics co-ordinator support system) is a program of combat logistics data, event routines, and algorithms designed to allow the logistics co-ordinator to trackand predictforce combat logistics states and provide timely and meaningful insight to the force commander.

ISSN:0160-5682    

DOI:10.1057/jors.1991.184

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe economic trade-off analysis between centralized and decentralized purchasing within the Canadian Forces is examined. A break-even analysis model for slow moving items has been developed. A simple isocost equation has been established relating the difference in item purchase cost, the freight tariff and the quality related costs. The case of the two purchasing modes with and without quality inspections will also be highlighted.

ISSN:0160-5682    

DOI:10.1057/jors.1991.185

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractWe provide two distribution-dependent approximations for the mean waiting time in aGI/G/squeue. Both approximations are weighted combinations of the exact mean waiting times for theGI/M/sandM/D/squeues each of which has the same mean service time and traffic intensity as in the approximatingGI/G/squeue. The weights in the approximations are expressed by the service-time c.d.f. and the first two moments of interarrival and service times. To examine the performance of our approximations, they are numerically compared with exact solutions and previous two-moment approximations for various cases. Extensive numerical comparisons indicate that the relative percentage errors of the approximations are of the order of 5% in moderate traffic and 1% in heavy traffic, except for extreme cases.

ISSN:0160-5682    

DOI:10.1057/jors.1991.186

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThis paper presents a design guideline for netting systems that determine net requirements, for push-type production ordering. Two alternative netting systems (full and single) are formulated in anNstage production and inventory system. The performances of the two alternatives are discussed through numerically analysing production ordering variations and inventory level variations at each stage in the processes. The results obtained suggest that: (1) the full netting system is preferable at the production stages, where variance in the accumulated forecast consumption error by the immediately succeeding stage is smaller than the variance in the accumulated forecast market demand error over a production ordering interval and the lead time for the stage. (2) The single netting system may be preferable at the other stages, particularly in regard to production ordering variations.

ISSN:0160-5682    

DOI:10.1057/jors.1991.188

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractIn this paper, we develop a new heuristic procedure for solving a generalization of the fixed-charge transportation problem in which there are resource losses in addition to the fixed charges. The losses may be evaporation losses when the commodity is a liquid, heat losses in an electrical distribution network, or deterioration losses in distribution networks involving perishable commodities such as, for example, food items. The proposed procedure consists of solving a sequence of pro-rated problems. It is different from heuristic procedures that have been developed for solving the standard fixed charge transportation problem, in that it is not based on extreme point enumeration. We experiment with problems involving up to 2100 arcs with fixed charges and resource losses. The results show that the proposed approach is viable for solving medium-to-large sized problems.

ISSN:0160-5682    

DOI:10.1057/jors.1991.189

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThis paper presents a new and efficient method, referred to as an aggregate constraint method, for the solution of general non-linear programming problems in which a multi-constrained problem is converted to one with a single parametric constraint. This is derived by using the two concepts of constraint surrogation and maximum entropy, and represents a uniform approximation to the original constraint set. An augmented Lagrangean algorithm is then used to solve the resulting problem. Numerical examples are given to show the high efficiency of the present method.

ISSN:0160-5682    

DOI:10.1057/jors.1991.190

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractA heuristic method for PERT analysis is presented, designed in such a way as to keep computational and informational needs to a minimum and to be easy to implement. The procedure is computationally efficient and quite accurate, even though the only information required on activity time distributions is in the form of simple discrete approximations. A numerical study is described which provides guidelines on the number of values to use and the computer time required.

ISSN:0160-5682    

DOI:10.1057/jors.1991.191

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractIn this paper we assume that an oil company haskareas in which to drill and occurrences of undiscovered oilfields are represented by the model of Beale. The company is seeking a strategy for drilling that maximizes its expected return under the constraint that the total amount spent on drilling in all areas must not exceedR. This leads to an integer programming problem. We establish that the expected return functions for the separate areas are concave and that this property can be used to reduce the computational effort required to find an optimal solution.

ISSN:0160-5682    

DOI:10.1057/jors.1991.192

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThis paper deals with a single-period, single-product inventory model with several individual sources of demand. It is a multi-location problem with an opportunity for centralization. Two types of inventory system are considered in this paper: the decentralized system and the centralized system. The aim of this paper is to extend Eppen's model by adding the consideration of transportation cost to constitute a new inventory model. With this new inventory model we prove three theorems that include the results of Eppen's model.

ISSN:0160-5682    

DOI:10.1057/jors.1991.193

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor