The m-Center Problem: Minimax Facility Location

The m-Center Problem is to locate a given number of (emergency) facilities anywhere along a road network so as to minimize the maximum distance between these facilities and fixed demand locations assigned to them. Fundamental properties of the m-Center Problem are examined. The problem is modeled using integer programming, and is successfully attacked using a binary search technique and a combination of exact tests and heuristics. Computational results are given.

Note--A Note on El-Shaieb's New Algorithm for Locating Sources Among Destinations

The objective of this note is (i) to identify and briefly review some references not included in [El-Shaieb, A. M. 1973. A new algorithm for locating sources among destinations. Management Sci. 20 221-231.] as well as more recent additions and (ii) to give computational comparisons of three other solution methods with that of El-Shaieb on his 30-city test data.

Choice Matters: Equity and Literacy Achievement

Students’ freedom of choice is critical to promoting equity and literacy in the classroom. When students choose what they read, they are more likely to find books that represent their lives, interests, and personal desires and feel that they are autonomous and can self-regulate learning. Previous research suggests that offering choice during learning activities increases motivation. However, less is known about whether choice is related to reading performance and which factors predict choice. Examining data from fourth-grade students, we found that students’ perception of choice in their reading materials is associated with literacy achievement, even when accounting for the degree to which the teacher reports providing choice of texts in the classroom and student interest. These findings suggest that true choice (i.e., choice that resides within the student) is linked to greater learning than choice that a teacher determines externally. Further, we argue it may be especially important for educators to explore ways to expand the perceived options available to students with the lowest demonstrated in-school literacy competencies.

Efficient Production-Distribution System Design

The production-distribution system design is an integral part of the general supply chain design. This paper proposes a novel solution methodology for this problem that is based on Lagrangean relaxation, interior-point methods, and branch and bound. Unlike classical approaches, Lagrangean relaxation is applied in a two-level hierarchy, branch and bound is based on a Lagrangean lower bound and column generation (branch and price), while interior-point methods are used within a cutting-plane context (analytic centre cutting-plane method---ACCPM). Numerical results demonstrate that the two-level approach outperforms the classical approach and provides a very sharp lower bound that is the (proven) optimal in most cases.production-distribution systems, Lagrangean relaxation, nested decomposition, interior-point cutting-plane methods, branch and price

Testing a Flexible Geographic Information System-Based Network Flow Model for Routing Hurricane Disaster Relief Goods

Recent weather events, particularly in the southeastern United States, have brought issues of hurricane disaster planning to the forefront of public policy. Efficient distribution of relief goods to populations after severe weather events is one of many challenges faced by governing bodies. This paper focuses on provision of hurricane disaster relief and develops a flexible network flow model that provides efficient transport linkages between critical elements of the relief goods supply chain. The model identifies accessible locations in which to place intraurban distribution sites for relief goods. Flexibility inherent in the model structure allows the pursuit of multiple policies, including the ability to trade off the costs paid for constructing various components of the goods supply chain. The model is linked to a geographic information system and can be used to visualize relief planning scenarios. The results of model tests with sample spatial data demonstrate how average population time to relief facilities (accessibility) varies substantially depending on the cost structure input into the model. Conclusions and several suggestions for future research are provided

A Multi-Exchange Heuristic for the Single Source Capacitated Facility Location Problem

We present a very large-scale neighborhood (VLSN) search algorithm for the capacitated facility location problem with single-source constraints. The neighborhood structures are induced by customer multiexchanges and by facility moves. We consider both traditional single-customer multi-exchanges, detected on a suitably defined customer improvement graph, and more innovative multicustomer multi-exchanges, detected on a facility improvement graph dynamically built through the use of a greedy scheme. Computational results for some benchmark instances are reported that demonstrate the effectiveness of the approach for solving large-scale problems. A further test on real data involving an Italian factory is also presented