Gorshkov's Gambit

This article is a portrait of Admiral Sergei Gorshkov, commander of the Soviet Navy for almost three decades, from 1956–85. The author, a retired US Navy admiral with a Harvard PhD in Russian studies who served as both defense and naval attaché in Moscow, draws on numerous face-to-face interactions with Gorshkov. He also explores Gorshkov's memoirs that were published recently in Russia but have not appeared in an English translation. The paper is not only a first-hand account of an important historical figure, but also a window into the world of military-to-military diplomacy and intelligence during the Cold War.     

A note on scheduling parallel machines subject to breakdown and repair

In this paper we consider n jobs and a number of machines in parallel. The machines are identical and subject to breakdown and repair. The number may therefore vary over time and is at time t equal to m(t). Preemptions are allowed. We consider three objectives, namely, the total completion time, ∑ C_j, the makespan C_max, and the maximum lateness L_max. We study the conditions on m(t) under which various rules minimize the objective functions under consideration. We analyze cases when the jobs have deadlines to meet and when the jobs are subject to precedence constraints. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2004.     

Effect of friction stir processing on mechanical properties and heat transfer of TIG welded joint of AA6061 and AA7075

Tungsten inert gas (TIG) welding is the most commonly used joining process for aluminum alloy for AA6061 and AA7075 which are highly demanded in the aerospace engineering and the automobile sector, but there are some defects occur during TIG welding like micro-crack, coarse grain structure, and porosity. To improve these defects, the TIG welded joint is processed using friction stir processing (FSP). This paper presents the effect of friction stir processing on TIG welding with filler ER4043 and ER 5356 for dissimilar aluminum alloy AA6061 and AA7075. The mechanical characterization, finite element formulation and mathematical equations of heat transfer of TIG + FSP welded joints are investigated using ANSYS Fluent software by adjusting process parameters of FSP. The results show that the maximum compressive residual stress 73 MPa was obtained at the fusion zone (FZ) of the TIG weldment with filler ER4043, whereas minimum compressive residual stress 37 MPa was obtained at stir zone (SZ) of the TIG+FSP with filler 5356. The maximum heat flux 5.33 × 106 W/m2 and temperature 515 ℃ have observed at tool rotation 1600 rpm with a feed rate of 63 mm/min. These results give a satisfactory measure of confidence in the fidelity of the simulation     

A generalization of the weighted set covering problem

We study a generalization of the weighted set covering problem where every element needs to be covered multiple times. When no set contains more than two elements, we can solve the problem in polynomial time by solving a corresponding weighted perfect b‐matching problem. In general, we may use a polynomial‐time greedy heuristic similar to the one for the classical weighted set covering problem studied by D.S. Johnson [Approximation algorithms for combinatorial problems, J Comput Syst Sci 9 (1974), 256–278], L. Lovasz [On the ratio of optimal integral and fractional covers, Discrete Math 13 (1975), 383–390], and V. Chvatal [A greedy heuristic for the set‐covering problem, Math Oper Res 4(3) (1979), 233–235] to get an approximate solution for the problem. We find a worst‐case bound for the heuristic similar to that for the classical problem. In addition, we introduce a general type of probability distribution for the population of the problem instances and prove that the greedy heuristic is asymptotically optimal for instances drawn from such a distribution. We also conduct computational studies to compare solutions resulting from running the heuristic and from running the commercial integer programming solver CPLEX on problem instances drawn from a more specific type of distribution. The results clearly exemplify benefits of using the greedy heuristic when problem instances are large. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2005     

A generalized assignment model for dynamic supply chain capacity planning

We consider a generalization of the well‐known generalized assignment problem (GAP) over discrete time periods encompassed within a finite planning horizon. The resulting model, MultiGAP, addresses the assignment of tasks to agents within each time period, with the attendant single‐period assignment costs and agent‐capacity constraint requirements, in conjunction with transition costs arising between any two consecutive periods in which a task is reassigned to a different agent. As is the case for its single‐period antecedent, MultiGAP offers a robust tool for modeling a wide range of capacity planning problems occurring within supply chain management. We provide two formulations for MultiGAP and establish that the second (alternative) formulation provides a tighter bound. We define a Lagrangian relaxation‐based heuristic as well as a branch‐and‐bound algorithm for MultiGAP. Computational experience with the heuristic and branch‐and‐bound algorithm on over 2500 test problems is reported. The Lagrangian heuristic consistently generates high‐quality and in many cases near‐optimal solutions. The branch‐and‐bound algorithm is also seen to constitute an effective means for solving to optimality MultiGAP problems of reasonable size. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

A mathematical programming approach for improving the robustness of least sum of absolute deviations regression

This paper discusses a novel application of mathematical programming techniques to a regression problem. While least squares regression techniques have been used for a long time, it is known that their robustness properties are not desirable. Specifically, the estimators are known to be too sensitive to data contamination. In this paper we examine regressions based on Least‐sum of Absolute Deviations (LAD) and show that the robustness of the estimator can be improved significantly through a judicious choice of weights. The problem of finding optimum weights is formulated as a nonlinear mixed integer program, which is too difficult to solve exactly in general. We demonstrate that our problem is equivalent to a mathematical program with a single functional constraint resembling the knapsack problem and then solve it for a special case. We then generalize this solution to general regression designs. Furthermore, we provide an efficient algorithm to solve the general nonlinear, mixed integer programming problem when the number of predictors is small. We show the efficacy of the weighted LAD estimator using numerical examples. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

Emulating US Counterinsurgency Doctrine: Barriers for Developing Country Forces,Evidence from Peru

ABSTRACT

Recent US advances in counterinsurgency doctrine have been adopted by developing country armed forces. Nevertheless, no systematic study has examined the barriers they face to implementing highly involved counterinsurgency strategy. Tracing the evolution of Peruvian doctrine demonstrates that Peru was able to quickly improve the unity of effort, intelligence capacity, and military basing to meet the demands of a population-centric hearts-and-minds approach to counterinsurgency. Nevertheless, the limited tactical initiative and flexibility of Peruvian forces remains a challenge. The Peruvian experience is instructive for other militaries undergoing similar transitions. However, given the diversity of insurgent conflicts, this doctrine is not universally appropriate.     

Fostering nonviolent elections in Africa through conflict-sensitive reportage of elections

Given that most Africans view political aspirants in terms of their ethnic and religious lineage rather than political ideology, and since most Africans rely on the media for information, there is a tendency to fall prey to biased and insensitive reportage, capable of inciting violence elicited by the prejudiced information often presented as news, features, commentaries, documentaries, etc. This article hypothesises that with appropriate training on conflict-sensitive reportage, journalists can foster peaceful and nonviolent elections through their reportage. The article recommends the adoption of an alternative method of news reportage using the peace-journalism model. The model, developed by Jake Lynch and Annabel McGoldrick, encourages journalists to report social issues in ways that create opportunities for a society to consider and value nonviolent responses toward conflict by using the insights from conflict analysis and transformation to update concepts of balance, fairness and accuracy in reporting. It also provides a new route map that traces the connections between journalists, their sources, the stories they cover and the consequences of their reportage. In addition, it builds awareness of nonviolence and brings creativity into the practical job of everyday editing and reporting. This article holds theoretical significance in that it explicitly identifies conditions that encourage journalists to apply conflict sensitivity to their reportage, thereby promoting societal peace, particularly during elections.     

Understanding armed groups and party politics

Abstract

Political parties with an armed history are not unusual, yet how these groups function in politics after the transition has largely been ignored. This special issue examines armed groups in party politics, using single and comparative case studies. The introduction forwards five recommendations for future research: (1) We need to see more comparisons across taken for granted boundaries; (2) the consequences for democracy should figure more prominently in our analysis of armed groups; (3) think more critically about standards and conceptual tools; (4) critically examine the interaction between levels of analysis; and (5) methodological pluralism would enrich the field.