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.     

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 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.     

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.     

用于微机器人的线切割加工的平行弹性平台

本文给出了具有四个圆形柔性铰链的平行弹性平台的研究结果,并运用材料力学和有限元分析进行了理论仿真,利用线切割加工工艺制造了几个整体式的平台。颈缩截面的厚度为20—100um。对这些结构的刚度进行了精密测量并与理论值进行了比较。这使得能够定性的分析在电加工中产生的在微米级范围内不能忽略的粗糙度和其它表面变形的影响。通过这些实验得到的结果对其它具有几个自由度的复杂柔性机构非常有用。     

无摩擦的空气轴承技术对超精密加工机床进给驱动系统的控制需…

加工过程中随着对精密度和加工环境的要求的不断提高,越来越需要在机床的结构和控制器原理这两者之间进行特殊的组合。近年来,为了补偿进给驱动系统的直接导轨的摩擦造成的影响,人们发明了大量的控制决策,例如［１］－［３］。他们虽然提供了各式各样的功能强大的非线性的机构,但通常又使用相当复杂的计算机算法来耗费系统资源。借助于先进的空气静压轴承技术（ＦＶＭ－空气－轴承）摩擦可以被彻底消除,因而直线导轨也就不存在     

Interactive solution of bi-criteria mathematical programs

In this paper, we develop efficient interactive methods for the solution of bicriteria nonlinear programming problems. The methods do not require trade-off information from the decision maker, pose less cognitive burden and converge to the “best compromise solution” fast. Two methods, called the paired comparison method and comparative trade-off method, are presented with examples. A real application of the interactive method to a bicriteria problem that arose in the planning of the cardiovascular disease control program in the U.S. Air Force is also presented.