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We present two frameworks for designing random search methods for discrete simulation optimization. One of our frameworks is very broad (in that it includes many random search methods), whereas the other one considers a special class of random search methods called point‐based methods, that move iteratively between points within the feasible region. Our frameworks involve averaging, in that all decisions that require estimates of the objective function values at various feasible solutions are based on the averages of all observations collected at these solutions so far. Also, the methods are adaptive in that they can use information gathered in previous iterations to decide how simulation effort is expended in the current iteration. We show that the methods within our frameworks are almost surely globally convergent under mild conditions. Thus, the generality of our frameworks and associated convergence guarantees makes the frameworks useful to algorithm developers wishing to design efficient and rigorous procedures for simulation optimization. We also present two variants of the simulated annealing (SA) algorithm and provide their convergence analysis as example application of our point‐based framework. Finally, we provide numerical results that demonstrate the empirical effectiveness of averaging and adaptivity in the context of SA. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012 相似文献
663.
Robert R. Tomes 《Defense & Security Analysis》2012,28(4):303-315
Facing nearly half a billion dollars in spending cuts over the next five years, US defense planners and strategists must simultaneously rebuild a war-weary Army weakened from over a decade of war, build new sea and air capabilities for the Pacific theater, and reduce manpower, procurement, and contractor budgets while promoting innovation. The US defense department is embarking on what may be the most sweeping period of defense transformation in recent memory. This article reviews the history of American defense transformation, focusing on an important but largely overlooked period of military innovation that began in the shadow of Vietnam and ended with troops fighting through blinding sandstorms at night on the road to Baghdad. The multifaceted transformation strategy conceived in the 1970s paved the way for a military revolution in the 1990s and enabled unprecedented battlefield adaptation in the 2000s. After reviewing the revolutionary changes that led to American dominance in conventional warfare in the 1990s, the article examines US transformation policies in the 2000s to inform defense strategy and planning efforts in the 2010s. 相似文献
664.
Explosive welding technique is widely used in many industries. This technique is useful to weld different kinds of metal alloys that are not easily welded by any other welding methods. Interlayer plays an important role to improve the welding quality and control energy loss during the collision process. In this paper, the Ti6Al4V plate was welded with a copper plate in the presence of a commercially pure titanium interlayer. Microstructure details of welded composite plate were observed through optical and scanning electron microscope. Interlayer-base plate interface morphology showed a wavy structure with solid melted regions inside the vortices. Moreover, the energy dispersive spectroscopy analysis in the interlayer-base interface reveals that there are some identified regions of different kinds of chemical equilibrium phases of Cu–Ti, i.e. CuTi, Cu2Ti, CuTi2, Cu4Ti, etc. To study the mechanical properties of composite plates, mechanical tests were conducted, including the tensile test, bending test, shear test and Vickers hardness test. Numerical simulation of explosive welding process was performed with coupled Smooth Particle Hydrodynamic method, Euler and Arbitrary Lagrangian-Eulerian method. The multi-physics process of explosive welding, including detonation, jetting and interface morphology, was observed with simulation. Moreover, simulated plastic strain, temperature and pressure profiles were analysed to understand the welding conditions. Simulated results show that the interlayer base plate interface was created due to the high plastic deformation and localized melting of the parent plates. At the collision point, both alloys behave like fluids, resulting in the formation of a wavy morphology with vortices, which is in good agreement with the experimental results. 相似文献
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Craig A. Deare 《Small Wars & Insurgencies》2019,30(1):14-30
ABSTRACTMexico’s defeat in the war that (in the U.S.) takes the country’s name resulted as much from the strategic context created by unrealized nation-building that followed independence as it did from American tactical supremacy. Three centuries of Spanish empire did not translate into national military excellence due to the decades of revolutionary upheaval that followed the sudden decapitation occasioned by Napoleon’s ouster of the monarchy in Madrid. That the occupation which followed major combat provided salutary lessons learned in dealing with guerrillas rather than a Vietnam-like litany of quagmire eventuated from the conscious designs of military leadership steeped in the same Napoleonic dynamic that had produced our opponent. The United States wisely chose to leave issues of state-building and governance to the Mexicans themselves, while annexing the sparsely populated northern remnant of Spanish empire. 相似文献
667.
Robert Czulda 《Defense & Security Analysis》2020,36(2):201-217
ABSTRACTThe paper’s goal is to analyses the potential of the Iranian defence industry, including both research-and-development and production capabilities. It is argued that, despite official statements about the great power and sophistication of the Iranian defence industry, in reality its capabilities are very limited and cannot meet the operational needs of the Iranian armed forces. At the same time, it is argued that many official releases, which are abundantly available in the Iranian press and often unthinkingly repeated by the Western media, do not present the real and value of military products, but are rather a tool for deception and propaganda. 相似文献
668.