入射频率对高功率微波与等离子体相互作用的影响分析

通过建立等离子体中的波动方程、电子传递方程和重物质传递方程,研究了等离子体对高功率微波传输特性的影响。研究了高功率微波与等离子体相互作用中产生的电子密度和透射电场的变化过程,并重点分析了变化过程中入射波频率产生的影响。研究结果表明,在相互作用过程中,等离子体中的电子密度和透射电场在一定条件下会发生阶跃变化,即等离子体区域平均电子数密度会在极短的时间内由1×10~9m~(-3)增加到1×10~(19)m~(-3),平均电场强度也会由初始场强跃变为零,并且这种变化的产生存在一定的入射阈值场强和最低产生时间。当入射电磁波的频率不同时,产生阶跃变化所需的场强阈值和最低产生时间就会变得不同,高功率微波与等离子体相互作用中存在一定的色散效应。在所考虑的范围内,阈值场强随入射波频率线性增长,而最低产生时间随电磁波频率呈非线性增长变化。     

协方差压缩感知逆合成孔径雷达成像技术

为解决低信噪比条件下短观测时间雷达成像问题,提出一种基于回波协方差矩阵处理的压缩感知逆合成孔径雷达成像技术。该方法构建了回波协方差矩阵层面下的压缩感知问题模型,并通过特定的线性变换降低环境噪声对成像结果的影响。在仿真实验中,通过处理短观测时间和低信噪比条件下的模拟回波数据,该方法获得比传统压缩感知方法像质更好、对比度更强的目标成像结果。同时,其成像结果的目标背景比和背景噪声能量两个雷达图像评价指标都优于传统方法,进一步验证了该方法的有效性。     

稳定特征选择的多目标蚁群优化

为了提高进化算法特征选择稳定性,提出一种面向稳定特征选择的多目标蚁群优化方法。通过抽样策略集成三种特征排序法的输出作为多目标蚁群优化的稳定性指导信息,聚合特征的费舍尔分值和最大信息系数值作为多目标蚁群优化的启发式信息,以分类正确率和扩展昆彻瓦指标值作为两个优化目标,兼顾算法的分类性能与特征选择稳定性。在四个标准数据集上进行对比实验,结果表明,所提方法能够在分类性能与稳定性方面达到较好的平衡。     

Theories of Non-Balancing and Russia’s Foreign Policy

The beginning of the twenty-first century has witnessed the emergence of balancing responses to the US hegemony, among which Russia’s foreign policies stand out as corresponding to what is understood as ‘hard balancing.’ Why is the United States being balanced against? This paper categorizes the existing theories of non-balancing into six conditions that together guarantee the absence of balancing and demonstrates that the current unipolar system can satisfy only one of them. This eases the systemic constraints and makes balancing possible. The paper then presents three cases of balancing with reference to President Putin’s foreign policy. It argues that even though in terms of relative military capabilities unipolarity still holds, the emergence of counter-hegemonic balancing is indicative of important changes in the nature of post-Cold War American domination.     

Effective in battle: conceptualizing soldiers’ combat effectiveness*

How do we understand combat effectiveness – soldiers’ performance in battle? Despite the broad consensus that understanding combat effectiveness is important both for scholars and policymakers, there is widespread disagreement about what combat effectiveness is. More specifically, studies of effectiveness tend to focus on either the skill of soldiers in battle, or their will to fight. Yet both skill and will are essential components of an effective fighting force. This article argues that understanding combat effectiveness requires understanding both of these key components of effectiveness. In other words, combat effectiveness requires both the skill and will to engage the enemy in an organized manner. It then demonstrates the usefulness of this conceptualization by applying it to the cases of British, Indian, and Australian forces fighting the Japanese during the Second World War. Only when scholars are talking about the same concept will our understanding of the conditions under which militaries are effective in battle progress. By comparing different units fighting the same opponent under the same material conditions, I demonstrate that units vary both in their combat skill and their will to fight, and that understanding their effectiveness in battle requires analyzing both of these key factors.     

Nuclear opportunism: A theory of how states use nuclear weapons in international politics

How do states use nuclear weapons to achieve their goals in international politics? Nuclear weapons can influence state decisions about a range of strategic choices relating to military aggression, the scope of foreign policy objectives, and relations with allies. The article offers a theory to explain why emerging nuclear powers use nuclear weapons to facilitate different foreign policies: becoming more or less aggressive; providing additional support to allies or proxies, seeking independence from allies; or expanding the state’s goals in international politics. I argue that a state’s choices depend on the presence of severe territorial threats or an ongoing war, the presence of allies that provide for the state’s security, and whether the state is increasing in relative power. The conclusion discusses implications of the argument for our understanding of nuclear weapons and the history of proliferation, and nonproliferation policy today.     

How durable is the nuclear weapons taboo?

The nuclear weapons taboo is considered one of the strongest norms in international politics. A prohibition against using nuclear weapons has seemingly shaped state behavior for nearly seven decades and, according to some observers, made nuclear use ‘unthinkable’ today or in the future. Although scholars have shown that nuclear aversion has affected decision-making behavior, important questions about the nuclear taboo remain unanswered. This article seeks to answer a basic question: How durable is the taboo? We develop different predictions about norm durability depending on whether the taboo is based primarily on moral logic or strategic logic. We use the comparable case of the norm against strategic bombing in the 20th century to evaluate these hypotheses. The logic and evidence presented in this paper suggest that the norm of nuclear non-use is much more fragile than most analysts understand.     

舰船主动力装置故障隔离与参数估计方法

针对舰船主动力装置结构复杂、故障种类多和系统不确定性等故障诊断问题,提出采用基于双因果键合图模型的定量故障隔离与参数估计方法。根据系统传感器配置方案,建立双因果键合图模型,通过因果路径分析,推导得到系统解析冗余关系,并获得故障特征矩阵。建立系统线性分式变换键合图模型,开展故障仿真,将其与双因果键合图模型耦合,在MATLAB/Simulink环境中进行仿真试验,实现了舰船主动力装置的故障隔离与参数估计。结果表明：对双因果键合图模型因果路径分析,可以避免手动推导系统解析冗余关系的繁杂过程;基于其部件构造方程的分析可以有效实现系统故障隔离与参数估计,实时跟踪和预测故障状态。     

电磁发射用脉冲功率电源放电建模分析

为高效研究电磁发射用脉冲功率电源放电性能,为电磁发射提供技术支持,降低研发成本,电磁发射过程的相关建模与仿真工作需要重点研究。对弹丸在轨道中实际运动物理过程建立数学模型,对脉冲功率电源建立电路模型,采用联合两种模型的方法对脉冲功率电源放电系统进行研究,提出一种基于发射过程多物理现象的脉冲功率电源放电系统仿真模型。通过实验验证了提出方法的有效性,为后续脉冲功率电源放电研究提供了依据。     

Precision cyber weapon systems: An important component of a responsible national security strategy?

Given the advances made in conventional weapon capabilities, precision should by now be the accepted and expected norm in cyberspace as well. In this article I argue that developing precision cyber weapon systems, to be used during a lawful conflict, can be an important part of a responsible national security strategy to reduce the amount of violence and physical destruction in conflicts. I first describe a precision cyber weapon system in a military context. I then present three compelling rationales for the development of precision cyber weapon systems based on ethical, operational, and financial considerations. To support the position, I address several arguments that have been levied against their development. Thereafter I present several recommendations for a way ahead.