Location Science最新文献

Most facilities in today's technological society may be classified as semi-desirable. That is, the facility provides a benefit or service to society, while adversely affecting the quality of life or social values in a number of possible ways. The paper proposes a location model for a new semi-desirable facility that accounts for the service costs by a standard minisum objective with arbitrary travel distance function. The social costs are imputed by specifying around each demand point or population center a convex forbidden region, also defined by an arbitrary distance metric, in which the new facility may not be located. A general solution algorithm is suggested, and the methodology is applied to circular forbidden regions and special travel distance functions.

There are several good reasons to introduce classification schemes for optimization models. For instance, the ability to make concise problem statements, as opposed to verbal, often ambiguous, descriptions. Or the possibility of simple data encoding and information retrieval in bibliographical information systems and software libraries. Therefore, in some branches of optimization, such as scheduling and queuing theory, classification is a widely used tool.

The aim of this paper is to propose a 5-position classification that can be used to describe all location models. We provide a list of currently available symbols and indicate their usefulness in a (necessarily non-comprehensive) list of “classical” location models. The classification scheme has been in use since 1992 and has proven to be helpful in research, software development, classroom teaching, and for overview articles.

Emergency medical services (EMS) systems commonly consist of two types of providers, basic life support (BLS) units and advanced life support (ALS) units, with different capabilities. In contrast to other systems in which multiple vehicle responses are necessary, in EMS systems, the first-arriving unit can begin service prior to the arrival of the second-arriving unit. In this paper, a covering-type model for two-tiered EMS systems is considered. The model, which maximizes the expected number of calls for service that are served adequately, takes server availability into account through a two-dimensional queueing model. Illustrative computational results are provided.

Modeling to support forest management is a complex task. In the public sector, agencies such as the US Forest Service manage millions of acres of land. In the private sector, large forest product companies also own and manage millions of acres. Many countries, like Ireland and Finland, utilize large-scale models to optimize the present value of forest activities and outputs. Forest planning can be viewed as a multi-level management problem. The highest or strategic level involves identifying feasible outputs and goals for long-term operations over decades. The middle or tactical level of analysis is associated with determining specific levels of activities on large tracts of land. At the lowest or operational level, specific stands of timber are slated for harvesting, roads are scheduled to be built or improved, and harvesting systems are designed to minimize the cost of extracting trees across the terrain. Each level of analysis often involves numerous locational decisions. Our objective is to provide a review of forest modeling that highlights many of the locational issues found in forest management.