Two‐dimensional failure modeling with minimal repair

In this paper, we discuss two‐dimensional failure modeling for a system where degradation is due to age and usage. We extend the concept of minimal repair for the one‐dimensional case to the two‐dimensional case and characterize the failures over a two‐dimensional region under minimal repair. An application of this important result to a manufacturer's servicing costs for a two‐dimensional warranty policy is given and we compare the minimal repair strategy with the strategy of replacement of failure. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004.     

From management crisis to crisis management? Japan’s post-2012 institutional reforms and Sino-Japanese crisis (In)stability

Since 2012, China’s assertion of its sovereignty claim to the contested Senkaku/Diaoyu Islands has significantly raised the risk of a potentially escalatory political-military crisis with Japan. As circumstances worsen, Japanese Prime Minister Shinzo Abe has championed major institutional reforms aimed at centralizing Japanese security policy decision-making and vastly improving crisis management. This article assesses these reforms’ significance for ameliorating Japan’s long-standing internal crisis management weaknesses, and enhancing its ability to communicate with Beijing promptly under challenging conditions. While significant issues remain, recent developments – especially the establishment of Japan’s first-ever National Security Council – demonstrate significant progress. Bilaterally, however, important firebreaks remain conspicuously absent.     

Size Still Matters: Explaining Sri Lanka’s Counterinsurgency Victory over the Tamil Tigers

The military effectiveness literature has largely dismissed the role of material preponderance in favor of strategic interaction theories. The study of counterinsurgency, in which incumbent victory is increasingly rare despite material superiority, has also turned to other strategic dynamics explanations like force employment, leadership, and insurgent/adversary attributes. Challenging these two trends, this paper contends that even in cases of counterinsurgency, material preponderance remains an essential—and at times the most important—factor in explaining battlefield outcomes and effectiveness. To test this, the paper turns to the case of the Sri Lankan state’s fight against the Tamil Tiger insurgency, a conflict which offers rich variation over time across six periods and over 25 years. Drawing on evidence from historical and journalistic accounts, interviews, memoirs, and field research, the paper demonstrates that material preponderance accounts for variation in military effectiveness and campaign outcomes (including military victory in the final campaign) better than strategic explanations. Additionally, a new quantitative data-set assembled on annual loss-exchange ratios demonstrates the superiority of materialist explanations above those of skill, human capital, and regime type.     

An inventory problem with obsolescence

A stochastic single product convex cost inventory problem is considered in which there is a probability, π_j, that the product will become obsolete in the future period j. In an interesting paper, Barankin and Denny essentially formulate the model, but do not describe some of its interesting and relevant ramifications. This paper is written not only to bring out some of these ramifications, but also to describe some computational results using this model. The computational results show that if obsolescence is a distinct possibility in the near future, it is quite important that the probabilities of obsolescence be incorporated into the model before computing the optimal policies.     

A finite algorithm for concave minimization over a polyhedron

We present a new algorithm for solving the problem of minimizing a nonseparable concave function over a polyhedron. The algorithm is of the branch-and-bound type. It finds a globally optimal extreme point solution for this problem in a finite number of steps. One of the major advantages of the algorithm is that the linear programming subproblems solved during the branch-and-bound search each have the same feasible region. We discuss this and other advantages and disadvantages of the algorithm. We also discuss some preliminary computational experience we have had with our computer code for implementing the algorithm. This computational experience involved solving several bilinear programming problems with the code.     

Heuristics for the multi‐resource generalized assignment problem

The well‐known generalized assignment problem (GAP) involves the identification of a minimum‐cost assignment of tasks to agents when each agent is constrained by a resource in limited supply. The multi‐resource generalized assignment problem (MRGAP) is the generalization of the GAP in which there are a number of different potentially constraining resources associated with each agent. This paper explores heuristic procedures for the MRGAP. We first define a three‐phase heuristic which seeks to construct a feasible solution to MRGAP and then systematically attempts to improve the solution. We then propose a modification of the heuristic for the MRGAP defined previously by Gavish and Pirkul. The third procedure is a hybrid heuristic that combines the first two heuristics, thus capturing their relative strengths. We discuss extensive computational experience with the heuristics. The hybrid procedure is seen to be extremely effective in solving MRGAPs, generating feasible solutions to more than 99% of the test problems and consistently producing near‐optimal solutions. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48: 468–483, 2001     

Attrition modeling in the presence of decoys: An operations-other-than-war motivation

Under various operational conditions, in particular in operations other than war (OOTW) or peacekeeping, an intervening force, here Blue, must occasionally engage in attrition warfare with an opposing force, here Red, that is intermingled with noncombatants. Desirably, Red armed actives are targeted, and not the unarmed noncombatants. This article describes some simple Lanchesterian attrition models that reflect a certain capacity of Blue to discriminate noncombatants from armed and active Red opponents. An explicit extension of the Lanchester square law results: Blue's abstinence concerning the indiscriminate shooting of civilians mixed with Red's is essentially reflected in a lower Blue rate of fire and less advantageous exchange rate. The model applies to other situations involving decoys, and reflects the value of a discrimination capability. © 1997 John Wiley & Sons, Inc. Naval Research Logistics 44 : 507–514, 1997     

Testing or fault-finding for reliability growth: A missile destructive-test example

A new piece of equipment has been purchased in a lot of size m. Some of the items can be used in destructive testing before the item is put into use. Testing uncovers faults which can be removed from the remaining pieces of equipment in the lot. If t < m pieces of equipment are tested, then those that remain, m₁ = m − t, have reduced fault incidence and are more reliable than initially, but m₁ may be too small to be useful, or than is desirable. In this paper models are studied to address this question: given the lot size m, how to optimize by choice of t the effectiveness of the pieces of equipment remaining after the test. The models used are simplistic and illustrative; they can be straightforwardly improved. © 1997 John Wiley & Sons, Inc. Naval Research Logistics 44: 623–637, 1997