低速大雷诺数混合飞艇气动性能分析

针对混合飞艇体积巨大同时气动外形复杂使得现有条件的风洞试验很难精确测量其气动性能的问题,开展了适用于混合飞艇气动性能分析的计算流体力学(CFD)的数值分析方法研究。考虑混合飞艇低速大雷诺数的特点,将变分多尺度方法 (VMS)与动态Smagorinsky大涡模拟(LES)模型相结合,提出了组合的VMSLES湍流模型。将基于RANS方法和LES方法的其他三种湍流模型相对比,利用雷诺数相近、实验数据丰富的6:1长椭球飞艇对不同的湍流模型进行了对比验证。结果显示LES方法预测结果与实验结果吻合较好,优于RANS方法,并能显示更多流动细节,而组合的VMS-LES模型能够更精确地捕获实验研究中观察到的二次涡。利用组合的VMS-LES模型对有翼HAV与多囊瓣HAV进行了气动性能分析,并研究了不同部件对飞艇气动特性的影响。结果表明,由于尾翼表面产生的一次涡与二次涡相互作用,尾翼在增加气动升力的同时也增加了阻力。     

Development of cost effective personnel armour through structural hybridization

The objective of the present study is to develop cost effective thermoplastic hybrid laminate using Dyneema® HB50 and Tensylon®HSBD 30A through structural hybridization method. Laminates having 20 mm thickness were fabricated and subjected to 7.62 × 39 mm mild steel core projectile with an impact velocity of 730 ± 10 ms⁻¹. Parameters such as energy absorption, back face deformation and rate of back face deformation were measured as a function of hybridization ratio. It was observed that hybrid laminate with 50:50 ratio (w/w) of Tensylon® and Dyneema® with Tensylon® as front face showed 200% more energy absorption when compared to 100% Tensylon® laminate and showed equal energy absorption as that of expensive 100% Dyneema® laminate. Moreover, hybrid laminate with TD50:50 ratio showed 40% lower in terms of final back face deformation than Dyneema® laminate. Rate of back face deformation was also found to be slow for hybrid laminate as compared to Dyneema® laminate. Dynamic mechanical analysis showed that, Tensylon® laminate has got higher stiffness and lower damping factor than Dyneema® and hybrid laminates. The interface between Tensylon® and Dyneema® layers was found to be separating during the penetration process due to the poor interfacial bonding. Failure behaviour of laminates for different hybridization ratios were studied by sectioning the impacted laminates. It was observed that, the Tensylon® laminate has undergone shear cutting of fibers as major failure mode whereas the hybrid laminate showed shear cutting followed by tensile stretching, fiber pull out and delamination. These inputs are highly useful for body armour applications to design cost effective armour with enhanced performance.     

“It would be impossible to estimate the value of these works...” Mass Production at Springfield Armory during the American Civil War

The U.S. Armory in Springfield, Massachusetts, rarely appears in Civil War histories except perhaps as an unexplained statistical wonder. By late 1863, the Armory was the largest single supplier of rifles to Union forces. Springfield Armory workers out-produced over thirty American contractors, making more Army rifles at less cost while providing contractors with gauges, inspectors, and models, even though there were significant wartime private-sector mechanical innovations. This article identifies and explains the factors in the Armory’s success, provides context on contemporary American arms production and rifle models, and argues that the Armory’s methods and performance were among the first if not the first example of mass production in American small arms manufacture. The relative brevity of the Civil War episode, and the fact that it was not repeated in any comparable way at the Armory until World War II, has obscured its significance in American manufacturing history.     

Is strategic studies narrow? Critical security and the misunderstood scope of strategy

Critical security advocates commonly portray strategic studies as crippled by its narrow focus on Cold War-era military issues, as state-centric and as Western-centric. I argue that this conception of the scope of strategy is flawed and I offer a comprehensive rebuttal by working out the logic of the theories advanced by Carl von Clausewitz and Thomas Schelling. The proponents of critical security overlook the striking expansion of strategy during the Cold War, its longstanding inclusion of competing political actors not just states, as well as its capacity to put Western and non-Western actors in a common analytic frame. By breaking out of the conceptual jails in which strategy has been incarcerated, I seek to reconnect International Relations to strategic thought from which it has become increasingly estranged.     

从孙子“静以幽，正以治”谈军校学员领导力培养

坚强的领导力是确保军事行动成功的关键。军校学员领导力不同于普通意义上的领导力。孙子“静以幽,正以治”的论述,揭示了军校学员领导力培养的基本内容、基本标准和各内容之间的辩证关系,对军校学员领导力培养具有重要的启迪意义。军校必须将培养超常的心质作为学员领导力的基础,把提升思维的广度和深度作为学员领导力的保障,将培养强烈的感召力作为学员领导力的核心,将培养坚强的执行力作为学员领导力的支撑。     

The essence of war: French armies and small war in the Low Countries (1672–1697)

In the late seventeenth century during the Dutch War (1672–1678) and the Nine Years War (1688–1697), French armies relied on small war for the accomplishment of essential tasks and as part of an overall strategy of exhausting their opponents in the Low Countries. The purposes of small war included the imposition of contributions on enemy populations, the destruction of the enemy base of operations, blockades of fortresses, and the general support of campaign armies. The expression ‘small war’ in the French language appeared with growing frequency in the 1690s. Small war can be viewed as both a cause and consequence of the characteristics of these wars. The limited policy goals of Louis XIV the king of France required a strategy that minimised risk and accomplished the goal of reducing if not eliminating the Spanish presence in the Low Countries that bordered the north of France. As French armies increased in size during this period, the demand for specialists at small increased in order to provide security and ensure supply. Small war in the late seventeenth century was thus not ideologically motivated insurgency, but in the minds of French commanders an essential component of strategy and the nature of war.     

The prospects of combined action: Lessons from Vietnam

Military commanders, policymakers, and analysts have recently embraced the concept of combined action as a powerful tool to improve the effectiveness of Afghan security forces in the fight against the Taliban. In doing so, they explicitly draw inspiration from the Combined Action Program employed by US Marines during the Vietnam War. This program is widely considered to have greatly improved the effectiveness of South Vietnamese government forces and contributed to increased population security in its area of operations and is considered a model worthy of emulation. This study finds that the success of the Vietnam-era Combined Action Program was more qualified than contemporary proponents argue. It argues that successes were tempered, and conditioned, by the choice of junior commanders, the level of operational control enjoyed by the US Marines, and the way the local forces were recruited and deployed. These conditions offer valuable lessons for those seeking to employ combined action not only in present-day Afghanistan, but also in future counterinsurgency campaigns.     

Book reviews

This paper defines the global economic costs of conflict and suggests two key criteria, namely comprehensiveness and consistency, which are necessary for a valid calculation of such costs. A critical review of the literature reveals that most studies focus on national income losses, using counterfactual regression models, finding a negative impact on growth both for conflict countries themselves and for their neighbors. However, the debate is quite fragmented and the literature fails to combine these insights in a comprehensive and consistent manner. Furthermore, there is little work thus far on integrating aggregate and micro‐level estimates of the costs of conflict.     

THE FATE OF DISPUTED TERRITORIES: AN ECONOMIC ANALYSIS

This paper presents a simple model to characterize the outcome of a land dispute between two rival parties using a Stackelberg game. Unlike Gershenson and Grossman (2000 Gershenson, D. and Grossman, H.I. 2000. Civil conflict: ended or never ending?. Journal of Conflict Resolution, 44(6): 807–821.  [Google Scholar]), we assume that the opposing parties have access to different technologies for challenging and defending in conflict. We derive the conditions under which territorial conflict between the two parties is less likely to persist indefinitely. Allowing for an exogenous destruction term as in Garfinkel and Skaperdas (2000 Garfinkel, M. and Skaperdas, S. 2000. Conflict without misperceptions or incomplete information: how the future matters. Journal of Conflict Resolution, 44(6): 793–807. [Crossref], [Web of Science ®] , [Google Scholar]), we show that, when the nature of conflict becomes more destructive, the likelihood of a peaceful outcome, in which the territory’s initial possessor deters the challenging party, increases if the initial possessor holds more intrinsic value for the disputed land. Following Siqueira (2003 Siqueira, K. 2003. Conflict and third‐party intervention. Defence and Peace Economics, 14(6): 389–400. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]), our model has policy implications for peace through third‐party intervention.     

The only choice is both choices: balancing assurance and coercion in nonproliferation-focused alliance-management strategies

ABSTRACT

Conventional theories of alliance management often overemphasize the utility of either assurance or coercion in preventing allied nuclear proliferation. Historical analysis reveals that prioritizing either of these two tactics to the exclusion of the other is inadvisable. A strategy that focuses solely on security guarantees or coercive threats is likely to encourage an allied state to pursue a hedging strategy, in which the client state continues to clandestinely develop its own nuclear capabilities while remaining underneath its patron’s defensive “umbrella.” This article introduces a new framework for understanding the effectiveness of nonproliferation-focused alliance-management strategies. By exploring the cases of West Germany and South Korea, the article concludes that the best way to prevent allies from pursuing nuclear weapons is to combine assurance with coercion. This establishes an incentive–punishment relationship that limits an ally’s motivation to develop nuclear weapons. These conclusions have particular salience today, as conversations over nuclear-weapons development have become increasingly normalized in Germany and particularly in South Korea. The United States’s capacity to influence its allies’ nuclear behavior is currently being eroded through the degradation of both patron credibility and client dependence, weakening the long-term viability of the global nonproliferation regime.