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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.  相似文献   
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Nested multinomial logit models are used to investigate migration behavior during the 1971–74 period for a large sample of the population of Ecuador. The nested form of the model makes it possible to test hypotheses about the importance of destination characteristics in conditioning the odds for out-migration. Our empirical results indicate that the odds for migration from each origin are conditioned by the expected utilities of the available set of destinations, as well as characteristics of the origins and the personal characteristics of potential migrants. The association between destination characteristics and the frequency of out-migration allows the total volumes of migration to be adjusted to interregional differences in place-specific utilities.  相似文献   
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George Woodcock was anarchism's most influential historian and an important public intellectual in Canada. This article focuses on his engagement with Canadian nationalism in the 1960s and 1970s. It argues that a ‘philosophical anarchism’ was at the heart of his intellectual project, and this informed his reading of Canadian cultural development and subsequent political challenge to Pierre Elliott Trudeau's civic nationalism. Woodcock decoupled the concepts of ‘nation’ and ‘state’ in order to develop a radically different model for Canada—the ‘anti-nation’—defined by regionalism, federalism and direct democracy. His reading of Canada's cultural history supporting this position was therefore part of a strategy to repurpose nationalist rhetoric towards anti-state ends.  相似文献   
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