The orienteering problem

Orienteering is a sport in which start and end points are specified along with other locations. These other locations have associated scores. Competitors seek to visit, in a fixed amount of time, a subset of these locations on the way from the start point to the end point in order to maximize the total score. An effective center-of-gravity heuristic is presented that outperforms heuristics from the literature.     

The Needs of Political Policy versus the Reality of Military Operations: Royal Navy Opposition to the Arctic Convoys, 1942

It has become commonplace, especially in the post-Vietnam strategic environment, to quote Clausewitz's dictum that war is the continuation of policy by other means. We are told that military operations are dictated by, and must serve, clear political ends. Such thinking has been invoked to support everything from punitive strikes, to peacekeeping missions, to the ‘Powell’ doctrine and its political ‘exit strategies’, but at times political policy and military operations do not mix. In 1942 the Royal Navy bowed to political pressure and, against its collective better judgement, continued the Arctic convoys to the Soviet Union. These military operations culminated in the destruction of convoy PQ 17 in early July. This conflict between political policy and military strategy provides an object lesson of why in war issues of means and priorities must outweigh the importance of any given political policy.     

A Rejoinder to Peter M. Sales

This analytical article asks the question: to what degree did the media contribute to the Rwandan genocide and what might have been done about it? In examining the historical development of mass media in Rwanda, this paper argues that while hate media clearly contributed to the dynamics that led to genocide, its role should not be overstated. While it is commonly believed that hate media was a major cause of the genocide, instead it was a part of a larger social process. The use of violent discourse was at least as important as, for example, the availability of weapons in carrying out the genocide. Put another way, violent discourse was necessary but not sufficient by itself to cause the genocide of 1994. In arguing this thesis, Rwandan history is examined to demonstrate the processes of communication in the formation of destructive attitudes and behaviour. Next, analysis of the methods and content of propaganda campaigns is discussed. Finally, an overview of the requirements and organizations for third parties to conduct international communication interventions is presented in the last section.     

An advanced dual algorithm with constraint relaxation for all-integer programming

In this article we present an all-integer cutting plane algorithm called the Reduced Advanced Start Algorithm (RASA). The technique incorporates an infeasible advanced start based on the optimal solution to the LP relaxation, and initially discards nonbinding constraints in this solution. We discuss the results of computational testing on a set of standard problems and illustrate the operation of the algorithm with three small examples.     

A bounded dual (all-integer) integer programming algorithm with an objective cut

In this article, we describe a new algorithm for solving all-integer, integer programming problems. We generate upper bounds on the decision variables, and use these bounds to create an advanced starting point for a dual all-integer cutting plane algorithm. In addition, we use a constraint derived from the objective function to speed progress toward the optimal solution. Our basic vehicle is the dual all-integer algorithm of Gomory, but we incorporate certain row- and column-selection criteria which partially avoid the problem of dual-degenerate iterations. We present the results of computational testing.     

The individual station technique for the analysis of cyclic polling systems

Polling systems are used to model a wide variety of real-world applications, for example, telecommunication and material handling systems. Consequently, there is continued interest in developing efficient algorithms to analyze the performance of polling systems. Recent interest in the optimization of these systems has brought up the need for developing very efficient techniques for analyzing their waiting times. This article presents the Individual Station technique for cyclic polling systems. The technique possesses the following features: (a) it allows the user to compute the mean waiting time at a selected station independent of the mean waiting time computations at other stations, and (b) its complexity is low and independent of the system utilization. In addition the technique provides explicit closed-form expressions for (i) the mean waiting times in a system with 3 stations, and (ii) the second moment of the waiting times in a system with 2 stations, for an exhaustive service system. © 1996 John Wiley & Sons, Inc.     

The conjugate gradient technique for certain quadratic network problems

We consider a class of network flow problems with pure quadratic costs and demonstrate that the conjugate gradient technique is highly effective for large-scale versions. It is shown that finding a saddle point for the Lagrangian of an m constraint, n variable network problem requires only the solution of an unconstrained quadratic programming problem with only m variables. It is demonstrated that the number of iterations for the conjugate gradient algorithm is substantially smaller than the number of variables or constraints in the (primal) network problem. Forty quadratic minimum-cost flow problems of various sizes up to 100 nodes are solved. Solution time for the largest problems (4,950 variables and 99 linear constraints) averaged 4 seconds on the CBC Cyber 70 Model 72 computer.     

A semieconomic method for the determination of optimal lot sizes

The construction of lot sizes usually depends upon factors influencing homogeneity. When these factors are not a function of lot quantity, it is possible to determine an optimal lot size. The optimization process balances the cost of sampling against the expected cost of lot rejection for some specified procurement quantity. The rationale for balancing the two costs is contingent upon the fact that rejection criteria waivers frequently occur when the lot size is large. This concept implies that the lot size should be as small as possible, whereas the cost of sampling drives the lot size up. Hence, trade-offs may be made. The formulation is termed a semieconomic one because it combines a pure economic objective function with a pure statistical constraint. This constraint is necessary because the nature of the items under study dictates that the cost of accepting defective material cannot be explicitly stated. The paper presents the formulation, describes when it should be used, derives a good analytical approximation under certain assumptions and gives various ramifications when it is used.