Two New Location Covering Problems: The Partial P-Center Problem and the Partial Set Covering Problem

Two new covering problems are introduced. The partial covering P-center problem minimizes a coverage distance in such a way that a given fraction of the population is covered. The partial set covering problem seeks the minimum number of facilities needed to cover an exogenously specified fraction of the population within a given coverage distance. The problems are formulated as integer linear programming problems. Bisection search algorithms are outlined for the two problems. The search algorithm repeatedly solves a Lagrangian relaxation of the maximal covering problem. Computational results for the Lagrangian relaxation of the maximal covering problem and for the bisection search algorithms are presented on problems with up to 150 nodes.     

Two New Location Covering Problems: The Partial P-Center Problem and the Partial Set Covering Problem

Two new covering problems are introduced. The partial covering P-center problem minimizes a coverage distance in such a way that a given fraction of the population is covered. The partial set covering problem seeks the minimum number of facilities needed to cover an exogenously specified fraction of the population within a given coverage distance. The problems are formulated as integer linear programming problems. Bisection search algorithms are outlined for the two problems. The search algorithm repeatedly solves a Lagrangian relaxation of the maximal covering problem. Computational results for the Lagrangian relaxation of the maximal covering problem and for the bisection search algorithms are presented on problems with up to 150 nodes.     

Theoretical and Computational Links between the p-Median,Location Set-covering,and the Maximal Covering Location Problem

It has been shown that the p-median problem, the location set-covering and the maximal covering location problems are important facility location models. This paper gives a historical perspective of the development of these models and identifies the theoretical links between them. It is shown that the maximal covering location problem can be structured and solved as a p-median problem in addition to the several approaches already developed. Computational experience for several maximal covering location problems is given.     

Computational Comparison of Five Maximal Covering Models for Locating Ambulances

This article categorizes existing maximum coverage optimization models for locating ambulances based on whether the models incorporate uncertainty about (1) ambulance availability and (2) response times. Data from Edmonton, Alberta, Canada are used to test five different models, using the approximate hypercube model to compare solution quality between models. The basic maximum covering model, which ignores these two sources of uncertainty, generates solutions that perform far worse than those generated by more sophisticated models. For a specified number of ambulances, a model that incorporates both sources of uncertainty generates a configuration that covers up to 26% more of the demand than the configuration produced by the basic model.     

Analysis of Errors Due to Demand Data Aggregation in the Set Covering and Maximal Covering Location Problems

In this paper, we extend the concepts of demand data aggregation error to location problems involving coverage. These errors, which arise from losses in locational information, may lead to suboptimal location patterns. They are potentially more significant in covering problems than in p-median problems because the distance metric is binary in covering problems. We examine the Hillsman and Rhoda (1978) Source A, B, and C errors, identify their coverage counterparts, and relate them to the cost and optimality errors that may result. Three rules are then presented which, when applied during data aggregation, will reduce these errors. The third rule will, in fact, eliminate all loss of locational information, but may also limit the amount of aggregation possible. Results of computational tests on a large-scale problem are presented to demonstrate the performance of rule 3.     

Probabilistic, Maximal Covering Location—Allocation Models forCongested Systems

When dealing with the design of service networks, such as health andemergency medical services, banking or distributed ticket-selling services, the location of servicecenters has a strong influence on the congestion at each of them, and, consequently, on thequality of service. In this paper, several probabilistic maximal coveringlocation—allocation models with constrained waiting time for queue length are presentedto consider service congestion. The first model considers the location of a given number ofsingle-server centers such that the maximum population is served within a standard distance, andnobody stands in line for longer than a given time or with more than a predetermined number ofother users. Several maximal coverage models are then formulated with one or more servers perservice center. A new heuristic is developed to solve the models and tested in a 30-node network.     

On Covering Problems and the Central Facilities Location Problem

A number of variations of facilities location problems have appeared in the research literature in the past decade. Among these are problems involving the location of multiple new facilities in a discrete solution space, with the new facilities located relative to a set of existing facilities having known locations. In this paper a number of discrete solution space location problems are treated. Specifically, the covering problem and the central facilities location problem are shown to be related. The covering problem involves the location of the minimum number of new facilities among a finite number of sites such that all existing facilities (customers) are covered by at least one new facility. The central facilities location problem consists of the location of a given number of new facilities among a finite number of sites such that the sum of the weighted distances between existing facilities and new facilities is minimized. Computational experience in using the same heuristic solution procedure to solve both problems is provided and compared with other existing solution procedures.     

The Sahelian Problem

Abstract

Philosophy of engineering is an area of study that is still in its infancy – attracting a growing number of researchers but still far behind the established field of philosophy of science. This essay reports on a series of seminars held on the topic at the Royal Academy of Engineering which have demonstrated that it is an area rich with problems for both philosophers and engineers to tackle. These problems can shed light on existing philosophical questions, raise new ones and even have practical value for the engineer.     

The Postmodern Problem

Abstract

Mormon political theology must reconcile two distinct projects: the care for the Church's concrete, temporal existence in the World, and the welcoming of the future Kingdom of God on earth. Because of this duality, political theology finds itself highlighting the distinction between the World and the Kingdom of God and at the same time pointing out common ground and attempting to establish peace between the Church and the World. The alleged contradictions of Mormon political thought are, according to this conception, to be understood not as confrontations between idealism and brute reality (or “utopianism” and “assimilation”), but rather as the bringing together of the two goals of Mormon political reflection, pursued by two sides of political theology. These two sides, apologetic and prophetic political theology, are distinguished not by their political content, but rather by their particular kinds of political rhetoric.     

Protecting Critical Assets: The r-Interdiction Median Problem with Fortification

Many systems contain bottlenecks, critical linkages, and key facilities. Such components, when lost due to a man-made or natural disaster, may imperil a system in performing its intended function. This article focuses on reducing the impact of an intentional strike against a supply system where supply facilities can be fortified in order to prevent such events. It is assumed that fortification resources are limited and must be used in the most efficient manner. In a recent article, Church, Scaparra, and Middleton (2004) introduced the r-interdiction median problem, which can be used to identify the most important facilities in a supply system. In this article, we extend that model to address the option of fortifying such sites against possible interdiction. We present a new integer-linear programming model that optimally allocates fortification resources in order to minimize the impact of interdiction. Computational results are presented in using this model for several hypothetical problems. We also discuss the general properties of fortification and demonstrate that the presence of fortification can impact which system elements are considered critical.     

The Negative Effects of Insufficient Support Systems on Kuwaiti Mothers of Children with Disabilities

Parents raising a child with a physical or cognitive disability are often faced with the negative stigma against disabilities that exist in several Arab countries. This puts extra pressure on the parents and can lead to negative outcomes for the children. The purpose of this study was to investigate the effects of parenting stress and varying levels of support for mothers of children with disabilities and the effects of these pressures on their relationship with their disabled child. We surveyed 85 Kuwaiti mothers of children with disabilities. The participants filled out an online survey with questions regarding parenting related stress, perceived social support, feelings of social isolation, self‐efficacy, and attachment to their child. Results indicate that mothers who feel unsupported by their families, community, and government experience more parenting stress and greater social isolation. These in turn lead them to feel less competent in their parenting abilities, and ultimately they feel less emotionally connected to their child. Implications of these findings are discussed.     

The Regionally Constrained p-Median Problem

In many applications involving the location of public facilities, the activity that is being located is added to the landscape of existing public facilities and services. Further, there also exists a political and behavioral landscape of differing jurisdictions, representations, and perceptions. This paper presents a new form of the p-median problem which addresses two types of “regional” constraints that can arise in public facilities planning. A formulation is given for this specially constrained median problem along with a solution approach. Several examples are presented with computational results which indicate that this type of constrained problem could lead to better facilities planning.     

Stuck in a Rut: The Problem with Australia's Electoral Apparatus

The origins of the distinguishing features of the Australian Electoral Commission can be found in nineteenth-century South Australia, when that colony led the world in electoral administration. It was the first jurisdiction to develop a professional, permanent, independent election management body, with salaried electoral officials, and to pursue continuous, State-initiated enrolment. South Australia evolved this way because, to extend path dependence terminology, it was ‘locked out’ of inefficient British practices. After Federation in 1901, the new Australian Electoral Office, largely based on the South Australian model, continued the tradition. One unique and defining feature was the strong, permanent role of divisional returning officers –‘Electoral Kings’, in the words of the first Australian Chief Electoral Officer. The ‘Kings’ were an integral component of much that was good about Australia's way of running elections. However, this structure is no longer the most appropriate for an organisation such as the AEC. It has long outlived its usefulness and is holding the Commission back. And, perhaps ironically for an organisation with a long record of resistance to political interference, it is House of Representatives politicians, of all major parties, who are restraining the AEC from adopting sensible arrangements. The AEC is now, in path dependence terms, ‘locked in’ to inefficient practices.     

The Aggregation Problem in Location-Allocation

Location-allocation solutions based on aggregate estimates of demand are subject to error because of a loss of locational information during aggregation. It is shown that any method to remove or reduce uncertainty must be solution-specific and therefore impractical, for both median and center classes of problems. The significance of the error is illustrated by simulation of solutions to a number of artificial and real problems. It is suggested that aggregation problems be specifically addressed in applications of location-allocation models, and possible methods are proposed.     

美国历史上的黑白混血儿问题

黑白混血儿问题是美国黑、白种族关系史上一个很有意思的话题。在以混血为特征的美国社会,黑白混血儿不完全同于纯血黑人、也完全不同于其他混血儿的独特历史命运以及冒充白人的现象,既是对美国白人自认为血统纯正的讽刺,又揭示了建立在肤色基础上的种族歧视制度的脆弱性和荒谬性。     

The Problem of Diffusion: Rejoinders

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HERBERT JENNINGS ROSE, 1883–1961. By W. L. LORIMER, Oxford University Press. 3s. net. Reviewed by E. O. James.

THE CULT OF THE CAT. By PATRICIA DALE-GREEN. London, William Heinemann. Pp. 189; 39 plates. Price 30s. Reviewed by Theo Brown.

DIE SAGEN DER MONATHLICHEN UNTERREDUNGEN OTTO VON GRABENS ZUM STEIN. Edited by W. E. PEUCKERT. Corpus Fabulorum I. Berlin, W. de Gruyter &; Co., 1961. Pp. xix, 327. Reviewed by E. Ettlinger.

GÖTTER UND GÖTTERTIERE DER MAYA. By WOLFGANG CORDAN. Bern, Francke Verlag, 1963. Pp. 75; 50 text figs. Reviewed by Ellen Ettlinger.

THE REGIONAL VOCABULARY OF TEXAS. By E. Bagby Atwood. University of Texas Press, 1962. Pp. 273, xiii. $5.75. Reviewed by C. A. Burland.

LAPP LIFE AND CUSTOMS. By ØRNULF VORREN and ERNST MANKER, (translated by Kathleen McFarlane). London, 1962. Pp. 183.38s. Reviewed by W. R. Mead.

FOLK TALES FROM RAJASTHAN. Retold by L. N. BIRLA. Illustrated by PHANI BHUSHAN. London, Asia Publishing House, 1964. Pp. 60. 20s. Reviewed by L. P. Elwell-Sutton.

DRAMA AND IMAGERY IN ENGLISH MEDIEVAL CHURCHES. By M. D. ANDERSON. C.U.P., 1963. Pp. 248. 45s. Reviewed by Alex Helm.

BRETON FOLK DANCES. By JEAN-MICHAEL GUILCHER. Paris, School of Higher Studies, Sorbonne. Reviewed by Douglas Kennedy.

THE LAST DAYS OF THE SIOUX NATION. By ROBERT M. UTLEY. Yale University Press, 1961. Pp. 314; 24 plates. 56s. net. Reviewed by C. A. Burland.

STUDIES IN JAPANESE FOLKLORE. By RICHARD M. DORSON. Indiana University Press, 1963. Pp. 247. Reviewed by W. H. Hudspeth.

THE MEDIEVAL HISTORY OF THE COAST OF TANGANYIKA. By G. S. P. FREEMAN-GRENVILLE. Oxford University Press. Pp. 238; maps, plates. 50s. Reviewed by W. H. Whiteley.

DIE VOLKSERZÄHLUNG. By LEOPOLD SCHMIDT. Berlin, Erich Schmidt Verlag, 1963. Pp. 448; 4 maps. Reviewed by Ellen Ettlinger.

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SONGS OF THE CIVIL WAR. Compiled and edited by IRWIN SILBER, Piano and Guitar Accompaniment by Garry Silverman. Columbia University Press, 1960; Oxford University Press, 1961. Reviewed by K. M. Briggs.