Robert Aboolian

This paper focuses on designing facility networks in the public sector so as to maximize the number of people benefiting from their services. We develop an analytical framework for the maximal accessibility network design problem that involves determining the optimal number, locations, and capacities of a network of public sector facilities. We assume that the time spent for receiving the service from a facility is a good proxy for its accessibility. We provide a generic model that incorporates both the congestion at the facilities and the customer-choice environment that underlies most of the services offered by the public sector. We devise an ɛ-optimal algorithm for the arising nonlinear integer program. The proposed algorithm performs well in tackling fairly large problem instances. Through a realistic example based on the hospital network of Toronto, we demonstrate the model’s capability in providing policy insights.

We consider reliable facility location models in which facilities are subject to unexpected failures, and customers may be reassigned to facilities other than their regular facilities. The objective is to minimize the total expected costs in normal and failure scenarios. We allow facilities to have different failure rates and do not limit the number of facilities that might be assigned to a customer. Lower bounds for reliable uncapacitated fixed-charge location problem (RUFLP) are derived and used to introduce a class of efficient algorithms for solving the RUFLP problem.

In this paper we develop a service network design model that explicitly takes into account the elasticity of customer demand with respect to travel distance and congestion delays. The model incorporates a feedback loop between customer demand and congestion at the facilities. The problem is to determine the number of facilities, their locations, their service capacity, and the assignment of customers to facilities so as to maximize the overall profit of the system. Two versions of the problem are presented. In one, each facility is modeled as an M/M/1 queuing system where the service rate is a decision variable; in the other one, the facility is modeled as an M/M/k queuing model where the service rate is given, but the number k is a decision variable. An exact algorithm and heuristics are developed and tested via computational experiments. Although our model is of the “directed choice” type where the assignment of customers to facilities is controlled by the decision maker, computational results show that in the vast majority of cases the customers are assigned to the utility-maximizing facility, indicating that there is no conflict between the customers' and decision makers' goals. A case study of locating preventive medicine clinics in Toronto, Ontario, illustrates the model.

A massively multiplayer online game often deploys dozens or hundreds of servers to support millions of players around the world. A slow response time stemming from an ill-designed network infrastructure could render the game noncompetitive. To establish an efficient infrastructure, the authors focus on selecting host facilities on backbone network nodes, assigning client clusters to these facilities, and determining the required capacity for each host site. An exact solution approach is obtained from solving a minimum cost set-covering problem. The efficiency of the solution approach, in comparison with a greedy heuristic, is also reported.

Call blockage may incur large losses in areas prone to traffic accidents. We formulate an optimisation problem that chooses base station locations and assign channels to them so as to minimise the overall installation and call blockage costs. Since this problem is a difficult non-linear integer program, we develop an efficient algorithm that finds the optimal solution. The paper features the so-called demand areas that characterise the demand for service of a large number of itinerant cell phone users travelling over a geographic area.

Journal of the Operational Research Society (JORS) is the world's longest established OR journal and an official journal of The OR Society. It is the aim of the Journal to present papers which are relevant to practitioners, researchers, teachers, students and consumers of operational research, and which cover the theory, practice, history or methodology of OR.