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The location set-covering problem (LSCP) and the maximal covering location problem (MCLP) have been the subject of considerable interest. As originally defined, both problems allowed facility placement only at nodes. This paper deals with both problems for the case when facility placement is allowed anywhere on the network. Two theorems are presented that show that when facility placement is unrestricted, for either the LSCP or MCLP at least one optimal solution exists that is composed entirely of points belonging to a finite set of points called the network intersect point set (NIPS). Optimal solution approaches to the unrestricted site LSCP and MCLP problems that utilize the NIPS and previously developed solution methodologies are presented. Example solutions show that considerable improvement in the amount of coverage or the number of facilities needed to insure total coverage can be achieved by allowing facility placement along arcs of the network. In addition, extensions to the arc-covering model and the ambulance-hospital model of ReVelle, Toregas, and Falkson are developed and solved. 相似文献
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Archaeology has been firmly embedded in the British planning systems for over a quarter of century, and development-led fieldwork is now by far the largest source of new information available to researchers. Custom and practice in the way that such work is conducted has evolved over this time, yet methodological innovation has been surprisingly limited. Using the data gathered in a major survey of the rural settlement of Roman Britain, this paper explores some themes in the way that commercial work is undertaken and seeks to open up a long-overdue debate about professional practice in a development-led context. 相似文献