摘要:

AbstractSnow removal and disposal are expensive winter activities that affect the quality of life and the environment in cities throughout the world. To facilitate traffic flow in urban regions that receive heavy snowfall, snow is first ploughed from streets and sidewalks and then hauled to disposal sites. A city is typically divided into many sectors that are cleared of snow concurrently. This paper briefly describes urban snow removal and disposal operations and analyses the snow disposal assignment problem for assigning snow removal sectors to snow disposal sites. The snow disposal assignment problem is formulated as a multi-resource generalized assignment problem. A two-phase heuristic solution procedure is developed, and solutions and sensitivity analyses are presented using data for the City of Montreal.

ISSN:0160-5682    

DOI:10.1057/jors.1995.131

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractIn this paper, a new inspection plan for critical multicharacteristic components is presented. A mathematical model that depicts and represents the plan has been developed. An algorithm is proposed to determine the optimal number of repeat inspections and sequence characteristics for inspection that minimizes the expected total cost. The expected total cost consists of the cost of false acceptance (cost of Type II error), cost of false rejection (cost of Type I error), and the cost of inspection. Empirical comparisons with the Raoufet al.model on randomly generated problems have been conducted. The results have shown that the proposed plan performs better in terms of the expected total cost on 82% of the generated problems for the assumed specific parameters. The reduction in the expected total cost ranges from 0.1-10%.

ISSN:0160-5682    

DOI:10.1057/jors.1995.132

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractSensitivity and robustness of efficiency classifications for the additive model and its geometric equivalents in Data Envelopment Analysis (DEA) are addressed. The minimum distance (measured by a Tchebycheff norm) separating an organization from reclassification is computed via linear programming formulations and shown to constitute a generalized‘residual’for each organization. Without this sensitivity information, findings can be distorted when marginally efficient or inefficient units are distinguished solely on the basis of their classification. Analysis of these residuals from an earlier (inconclusive) DEA study further reveals how substantive differences in a sample's underlying groups can be detected. Properties of group efficiency and group proximity to the efficient frontier are investigated using these new indicators.

ISSN:0160-5682    

DOI:10.1057/jors.1995.133

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractAn interactive multiple objective system technique (IMOST) is investigated to improve the flexibility and robustness of multiple objective decision making (MODM) methodologies. The interactive concept provides a learning process about the system, whereby the decision maker can learn to recognize good solutions, the relative importance of factors in the system, and then design a high-productivity and zero-buffer system instead of optimizing a given system. This interactive technique provides integration-oriented, adaptation and dynamic learning features by considering all possibilities of a specific domain of MODM problems which are integrated in logical order. It encompasses the decision-making processes of formulating problems, constructing a model, solving the model, testing/examining its solution, and improving/reshaping the model and its solution in a specific problem domain. Although IMOST deals with multiple objective programming problems, it also provides some valuable orientation of integrated system methodologies.

ISSN:0160-5682    

DOI:10.1057/jors.1995.134

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractThis paper studies Fisk's stochastic user equilibrium (SUE) assignment model in which travellers are assumed not to have perfect knowledge of the traffic system. It is shown that the stochastic properties of this model completely depend on the calibration parameter. After giving the searching method of an‘efficient paths’set, a modified combined algorithm for solving and calibrating Fisk's stochastic traffic assignment model is developed. In this algorithm, the path enumeration is achieved automatically in the preliminary phase and renewed in the iterative processes, and the number of alternative paths generated can be controlled by a predetermined function. Two numerical examples are presented to illustrate the model's properties and the algorithm's efficiencies.

ISSN:0160-5682    

DOI:10.1057/jors.1995.135

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractWe set out a model, algorithms and strategies for the train pathing and timetabling problem for rail lines of the type normally found in Britain and Europe; that is, lines having separate tracks for trains in each direction. As the pathing problem is combinatorially difficult we propose solution heuristics and strategies analogous to those which have enabled‘expert’train pathers to plan large-scale complex rail systems by traditional manual graphical methods. This approach also has the potential advantage of facilitating user interaction, understanding and acceptance. We report computational results for several examples. Without the above strategies we found even very small problems intractable. With these strategies we could solve realistic size problems in acceptable times, while exploring more options and trade-offs than do traditional methods. More work is needed and we suggest natural extensions, and directions for further research and development.

ISSN:0160-5682    

DOI:10.1057/jors.1995.136

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractWe consider a periodic-review inventory replenishment model with an order-up-to-Roperating doctrine for the case of deterministic lead times and a covariance-stationary stochastic demand process. A method is derived for setting the inventory safety stock to achieve an exact desired stockout probability when the autocovariance function for Gaussian demand is known. Because the method does not require that parametric time-series models be fit to the data, it is easily implemented in practice. Moreover, the method is shown to be asymptotically valid when the autocovariance function of demand is estimated from historical data. The effects on the stockout rate of various levels of autocorrelated demand are demonstrated for situations in which autocorrelation in demand goes undetected or is ignored by the inventory manager. Similarly, the changes to the required level of safety stock are demonstrated for varying levels of autocorrelation.

ISSN:0160-5682    

DOI:10.1057/jors.1995.137

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractThis paper studies the optimal operation of anM/Ek/1 queueing system with a removable service station under steady-state conditions. Analytic closed-form solutions of the controllableM/Ek/1 queueing system are derived. This is a generalization of the controllableM/M/1, the ordinaryM/Ek/1, and the ordinaryM/M/1 queueing systems in the literature. We prove that the probability that the service station is busy in the steady-state is equal to the traffic intensity. Following the construction of the expected cost function per unit time, we determine the optimal operating policy at minimum cost.

ISSN:0160-5682    

DOI:10.1057/jors.1995.138

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractThis paper is concerned with a traditional asset allocation of the Markowitz type and develops an efficient algorithm to design an index fund that is a compromise solution to the bicriteria optimization problem. A numerical example is provided to illustrate our algorithm.

ISSN:0160-5682    

DOI:10.1057/jors.1995.139

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

ISSN:0160-5682    

DOI:10.1057/jors.1995.140

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor