Exact algorithms for scheduling multiple families of jobs on parallel machines

In many practical manufacturing environments, jobs to be processed can be divided into different families such that a setup is required whenever there is a switch from processing a job of one family to another job of a different family. The time for setup could be sequence independent or sequence dependent. We consider two particular scheduling problems relevant to such situations. In both problems, we are given a set of jobs to be processed on a set of identical parallel machines. The objective of the first problem is to minimize total weighted completion time of jobs, and that of the second problem is to minimize weighted number of tardy jobs. We propose column generation based branch and bound exact solution algorithms for the problems. Computational experiments show that the algorithms are capable of solving both problems of medium size to optimality within reasonable computational time. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 823–840, 2003.     

Coercive diplomacy and the Donbas: Explaining Russian strategy in Eastern Ukraine

What were Russia’s objectives in Eastern Ukraine, and why was it seemingly unable to achieve a successful or decisive outcome? In contrast to Russia’s seizure of Crimea, the uprising in Eastern Ukraine was marked by disorganization and chaos. Using proxy and surrogate actors, along with military exercises and the injection of Russian troops, Russia sought to institutionalize a political entity inside Ukraine to influence its domestic politics. In this article, I analyze the mechanisms by which Russia attempted to implement, and later salvage, its strategy. The article contributes to clearer theoretical and practical understanding of limited force in coercive diplomacy, signaling, and a more rigorous treatment of the role and uses of proxy actors.     

Deterrence Beyond Downunder: Australia and US Security Guarantees since 1955

ABSTRACT

From 1944 to 1973 Australia attempted to acquire atomic weaponry. This ambition was driven by the desire to contribute to defending British interests in Asia, fears of invasion by China, Indonesia, and Japan, great-power war, and the belief that nuclear weapons were merely bigger and better conventional weapons, that they would proliferate, and that US security assurances lacked credibility. Although the pursuit of the bomb was eventually abandoned, this was not the result of US assurances. Rather, geopolitical changes in Australia’s environment meant that a major attack on the continent was unlikely to occur outside the context of a confrontation between the US, China, and the Soviet Union. This article argues that Australia may soon have to rethink its policies towards US extended deterrence and instead focus on developing its own deterrent.     

Norms,Military Utility,and the Use/Non-use of Weapons: The Case of Anti-plant and Irritant Agents in the Vietnam War

The role of norms and military utility in the use of weapons is disputed by constructivist and realist scholars. Through an examination of US decision-making regarding anti-plant and irritant agents in the Vietnam War, I advance this debate in three key ways. First, I develop structural realism’s expectations regarding the role of military utility. Second, I demonstrate that social and material factors are at play in our understandings of both ‘norms’ and ‘military utility’, and that both played a role in US decisions. Third, I find that the dominant role – as structural realism expects – was played by military utility.     

动态滑翔运动建模、机理分析与航迹优化

信天翁凭借动态滑翔的飞行技巧从梯度风中获取能量,从而在几乎不拍翅膀的情况下进行长时间、长距离飞行,这种技巧应用于小型无人机上可拓展其完成任务的能力。基于飞行器动力学对梯度风场中的无人机运动方程进行推导和简化处理;利用简化的运动方程,分别从非惯性参考系中的动能定理和机械能变化的角度,对动态滑翔获取能量的机理进行分析;利用微分平坦法,以最小平均控制输入变化率为目标函数,对徘徊模式和平移模式的动态滑翔航迹进行优化计算。分析结果表明:逆风爬升、顺风下滑是动态滑翔基本获能方式。优化结果表明:控制输入变得更加平滑,甚至出现阶段性的常值,使得控制更加简化;徘徊模式下,当风梯度作为决策变量时,优化过程可在[0,0.5 s-1]的区间上找到使得目标函数值最小的风梯度;平移模式下,目标函数值在该区间上单调递减。     

Rising bipolarity in the South China Sea: the American rebalance to Asia and China's expansion

This article synthesizes three elements of power and balancing in the South China Sea (SCS): analytical perspectives on China's behaviour and intentions, the American rebalance to Asia and the dispositions of American allies and partners. Based on extensive interviews and theoretical analysis, it concludes that ‘soft balancing’ backed by American military power provides the optimum chance for resolving the growing dispute. Short to medium-term weakness of Malaysia, Philippines and Vietnam, as well as Japan, means the United States must provide much of the military power while working to build their forces. The most promising alternative is multilateral diplomacy through the Association of Southeast Asian Nations’ Regional Forum, a vehicle for negotiating a Code of Conduct and implementation of the UN Convention on the Law of the Sea. If China remains motivated mainly by defense of realist interests, the costs imposed against expansion will eventually cause recalculation of Beijing's strategy, and soft balancing by the United States and its partners has a chance of working. The constructivist perspective, stressing self-conceptualization of Chinese strategic culture, supports Chinese confidence that patience will eventually bring dominance. If China tries offensively to change the status quo, soft balancing is less likely to influence Beijing. President Xi Jin Ping appears to be offensively asserting power, seeking regional dominance before he is due to step down in 2023. This supports the finding of enhanced risks of unintended escalation in the SCS and the East China Sea.     

Keeping an eye on South Asian skies: America’s pivotal deterrence in nuclearized India–Pakistan crises

Since declaring their nuclear weapons capabilities in 1998, India and Pakistan have engaged in three major crises that each threatened to escalate into war. In each crisis, the USA engaged in active diplomacy to dissuade the South Asian rivals from taking escalatory actions. Previous literature on the crises has described the American role, but has not theorized third-party involvement in a nuclearized regional rivalry. We apply Timothy Crawford’s pivotal deterrence theory to the nuclearized India–Pakistan conflict, and extend the original theory to cover the novel condition of a non-superpower nuclear dyad, in the context of a single-superpower international system. We find that America’s pivotal deterrence generally enhanced stability in the India–Pakistan crises, and unlike in pre-nuclear South Asia, other great powers supported American diplomacy. However, we suggest that future regional crises between nuclear rivals, in South Asia or elsewhere, may present greater challenges for pivotal deterrence.     

The ambivalent coalition: doing the least one can do against the Islamic state

The effort to degrade and defeat the Islamic State is like many other multilateral military efforts – characterized by widely varying contributions to the effort. This article seeks to understand the patterns of contributions. Three sets of explanations are applied: the lessons of Afghanistan and Libya, variations in how potential contributors feel the threat posed by the Islamic State, and domestic political dynamics. While there may be some political processes that overlap with the big lessons and with the threat of the Islamic State, the patterns of contributions thus far suggest that the key drivers of reactions to the Islamic State are the desire not to repeat Afghanistan combined with some impetus provided by Islamic State attacks in the various homelands. The conclusion suggests some policy implications as well as some ideas for future research.