Optimal location of single and multiple obnoxious facilities: Algorithms for the maximin criterion under different norms.

This thesis investigates the computational problem of locating obnoxious (undesirable) facilities in a way that minimizes their effect on a given set of clients (e.g. population centres). Supposing that the undesirable effects of such a facility on a given client are a decreasing function of the distance between them the objective is to locate these facilities as far away as possible from the given set of clients, subject to constraints that prevent location at infinity. Emphasis is given to the MAXIMIN criterion which is to maximize the minimum client-to-facility distance. Distances are measured either in the Euclidean or the rectilinear metric. The properties of the optimal solution to the single facility problem are viewed from different, seemingly unrelated, perspectives ranging from plane geometry to duality theory. In particular, duality results from a mixed integer programming model are used to derive new properties of the optimal solution to the rectilinear problem. A new algorithm is developed for the rectilinear problem where the feasible region is a convex polygon. Unlike previous approaches, this method does not require linear programming at all. In addition to this, an interactive graphical approach is proposed as a site-generation tool used to identify potential locations in realistic problems. Its main advantages are that it requires minimal user intervention and makes no assumptions regarding the feasible region. It has been applied in large scale problems with up to 1000 clients, whereas the largest reported application so far involved 10 clients. Alternative models are presented for the multi-facility problem as well. Each of them is based on different assumptions and is applicable to specific situations. Moreover, an algorithm is established for the two-facility problem based on the properties of the optimal solution. To the best of our knowledge this is the first attempt to address this problem in the plane. Finally, a number of unresolved issues, especially in the multi-facility problem, are outlined and suggested as further research topics

Some Personal Views on the Current State and the Future of Locational Analysis

In this paper a group of participants of the 12th European Summer Institute which took place in Tenerifa, Spain in June 1995 present their views on the state of the art and the future trends in Locational Analysis. The issue discussed includes modelling aspects in discrete, network and continuous location, heuristic techniques, the state of technology and undesirable facility location. Some general questions are stated reagrding the applicability of location models, promising research directions and the way technology affects the development of solution techniques

Some Personal Views on the Current State and the Future of Locational Analysis

In this paper a group of participants of the 12th European Summer Institute which took place in Tenerifa, Spain in June 1995 present their views on the state of the art and the future trends in Locational Analysis. The issue discussed includes modelling aspects in discrete, network and continuous location, heuristic techniques, the state of technology and undesirable facility location. Some general questions are stated reagrding the applicability of location models, promising research directions and the way technology affects the development of solution techniques

A new model for maximal coverage exploiting GIS capabilities

The representation of demand is a key issue which can significantly affect results in several demand covering models. In this paper we concentrate on the well known Maximal Coverage Location Problem and demonstrate that alternative representations of the demand space may lead to largely fluctuating as well as misleading results which seriously overestimate the real coverage achieved by a specified number of servers. We introduce a new model based on the notion of complementary partial coverage and exploit the capabilities of Geographic Information Systems in order to better represent demand. Results of an empirical study indicate that the proposed model is less susceptible to fluctuations for alternative representations of the demand space and that it provides coverage of a larger proportion of demand than traditional models.Demand covering Geographic Information Systems (GIS) Location analysis

Successful Pregnancy and Persistent Polyclonal B Cell Lymphocytosis (PPBL): A Case Study of a Rare Co-Existence

Objective: Unknown etiology Background: Persistent polyclonal B cell lymphocytosis (PPBL) is a benign clinical condition, which is characterized by persistent absolute polyclonal B lymphocytosis (>4.0 K/mu L), with the presence of circulating binucleated lymphocytes on the peripheral blood smear and an extra 3 chromosome long arm i(3q) in most cases. Immunophenotype reveals the polyclonal population of B cell lymphocytes with expression of CD19, CD20, and CD22 antigens, and k and l immunoglobulin light chains. Patients are mostly asymptomatic. Although PPBL has a benign clinical course and does not affect the survival expectancy of most patients, pregnancy seems to be extremely rare in these patients, as only 1 case reported so far. Although the real role of immunologic disorders, possibly PPBL, in recurrent pregnancy losses remains unclear, the rarity of successful pregnancy in PPBL patients could be attributed to the possible association of PPBL with infertility or recurrent miscarriages. Case Report: In the present study we present the second published case of a woman with a typical PPBL and recurrent pregnancy loss with a successful pregnancy outcome. Close clinical and laboratory monitoring in combination with the administration of thromboprophylaxis and the induction of mild immunosuppression with low-dose prednisolone may have contributed to the successful outcome of the pregnancy. Conclusions: In conclusion and taking all these findings into consideration, pregnancy in patients with PPBL seems to be extremely rare and the contribution of PPBL to the 2 previous miscarriages in our case could not be excluded