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.     

Recursive Algorithm for Determination of Proximal (Thiessen) Polygons in Any Metric Space

A new and recursive algorithm for determining proximal polygons is based on quadtree concepts. The algorithm can use any distance metric, and produces a quadtree of the image of the proximal polygons. This can be converted to vector form, or be incorporated directly into a quadtree-based geographic information system, in order to solve a number of closest-point problems. The algorithm can also produce the Delaunay triangulation, which is the dual of the proximal polygons. Empirically, the running time of the algorithm is proportional to the number of centers raised to the 1.6 power.     

Culture,technology and policy in the informal sector: attention to endogenous development

243 blacksmiths in Sierra Leone were interviewed in 1984-85 in an effort to focus on both the activities and attitudes of traditional blacksmiths in the country's economy. Due to the fact of an shortage of foreign exchange with which to import and maintain equipment, agriculture using high-technology equipment accounts for less than 15% of total production. Consequently, blacksmiths are vital to the nations' survival, despite prevailing attitudes toward them. The interviews were conducted in 9 of the 12 districts in Sierra Leone. The blacksmith operates not simply in terms of producing and servicing goods; cultural values frame his position in the community. In all of West Africa, and particularly among Mende-related peoples, there historically exists a mystique surrounding a blacksmith. In some societies, blacksmiths were believed to be witches. The arguments that most likely could account for this would probably lie in the fact that the blacksmith made farm tools and weapons of war, means of survival in the community. Thus, his position was vital. Traditionally the importance of the smith's profession lies in the fact that some of the implements he fabricates and the materials he uses are believed to provide elements of social control or to have healing powers. An appreciation of the cultural significance of the blacksmith demonstrates the degree of attachment of the population to this profession as well as the context within which one could relate to possible technological changes in the trade. An attempt was made in the interview to gather some information about levels of production. The figures represent averages, and production capacity varied owing to a number of factors, including the degree of organization of the unit, the capacity of the head of the forge to keep his team busy when work was intensive, and the degree of energy and determination of an operator to get the greatest amount of work done in 1 day. The most obvious factor influencing production levels was the size of the units. Pricing of commodities and the blacksmith's services depended on a combination of factors, but, generally, in semi-urban areas, where more impersonal relationships tended to obtain, prices appeared relatively more fixed than in rural areas. All smiths interviewed complained about the increasing scarcity of scrap iron. As there is every reason to envisage a continued dependence on informal-sector production by blacksmiths, official attitudes need to take these trades more seriously.