The Influence of Data Aggregation on the Stability of p-Median Location Model Solutions

Location planning often makes use of data in an aggregate form without a clear understanding of the consequences. Although research has been directed toward addressing aggregate data usage in location planning, there have been conflicting findings on the stability of location model solutions obtained using aggregated data. This paper analyzes the question of location model solution stability from a somewhat different perspective than previous researchers in that locational configurations identified for aggregate data are evaluated using the original disaggregate data. Analytical results demonstrate that a high level of solution stability does exist when aggregated data are utilized. Further, this analysis is based upon the use of what can be expected to be worst case aggregation approaches. This suggests that the use of aggregate data is adequate for conducting locational studies.     

Results of a New Approach to Solving the p-Median Problem with Maximum Distance Constraints

Considerable interest has been directed in the past to developing approaches for solving the p-median problem with maximum distance constraints. All current solution techniques consider potential facilities to be located only at nodes of the network. This paper deals with the solution of this problem under the condition where facility placement is not restricted to nodes. The examples given show that improvement in weighted distance can be obtained by solving the unrestricted site problem. In addition, feasible solutions can be obtained for smaller numbers of facilities than possible by all nodal facility placement.     

Theoretical and Computational Links between the p-Median,Location Set-covering,and the Maximal Covering Location Problem

It has been shown that the p-median problem, the location set-covering and the maximal covering location problems are important facility location models. This paper gives a historical perspective of the development of these models and identifies the theoretical links between them. It is shown that the maximal covering location problem can be structured and solved as a p-median problem in addition to the several approaches already developed. Computational experience for several maximal covering location problems is given.     

A Note on Applying the Gravity Rule to the Airline Hub Problem

In this note we propose a new model for the airline hub selection problem. Passengers use a hub on the way to their destination. We apply the objective of minimizing the total miles traveled by passengers. This formulation can be used as the basis for other objectives also.     

Elimination of Source A and B Errors in p-Median Location Problems

The p-median problem is a powerful tool in analyzing facility location options when the goal of the location scheme is to minimize the average distance that demand must traverse to reach its nearest facility. It may be used to determine the number of facilities to site, as well as the actual facility locations. Demand data are frequently aggregated in p-median location problems to reduce the computational complexity of the problem. Demand data aggregation, however, results in the loss of locational information. This loss may lead to suboptimal facility location configurations (optimality errors) and inaccurate measures of the resulting travel distances (cost errors). Hillsman and Rhoda (1978) have identified three error components: Source A, B, and C errors, which may result from demand data aggregation. In this article, a method to measure weighted travel distances in p-median problems which eliminates Source A and B errors is proposed. Test problem results indicate that the proposed measurement scheme yields solutions with lower optimality and cost errors than does the traditional distance measurement scheme.     

中外文明比较研究中的方法论问题

本文主要探讨中外文化比较研究中的方法论问题,提出应将中国古代文明作为世界古代文明的一部分,在研究方法上要破除传统的地域界限,扩大横向比较范围,改进理论建设,建立规范的学术交流机制,积极参与国际合作,大力扶持中青年学者,加强学术监督和学术评论,使我们的比较研究真正在方法上有所变化,有所创新,赶上科技发展的时代潮流。     

A Generalization of the Utility Theory Approach To the Problem of Spatial Interaction

The derivation of the gravity model from utility theory is reformulated and generalized in order to show (1) how both the number of trips to individual destinations and the total travel budget may be determined simultaneously, and (2) how the effect of both distance and destination quality on trip distribution and total budget may be analyzed. Results are compared with the revealed space preference approach and are found to be superior in dealing theoretically with trip frequency and the effects of spatial context. For empirical applications, however, the revealed preference approach is advantageous.     

Note Concerning the Problem of Samson the Nazirite in the Biblical Studies

Apparently, some biblical scholars prefer to consider Samson only as a biblical character, rather than as a mythical hero too, and they think falsely that his title of Nazir has its explanation in the law text of Numbers.     

A Note from the Editor

Abstract

This paper presents results of research conducted during the summer of 2006 at the South Flats Earthwork (20MU2) along the Muskegon River in western Michigan. The site was first identified and excavated by George Irving Quimby in the 1930s. Our objectives included assessing the condition of the earthwork, systematically testing the area both within and outside the earthwork, developing data on earthwork construction, and considering alternative hypotheses for understanding the function of this earthwork in the context of recent discussions of earthworks in Michigan and the Midwest.