非均匀复合材料中裂纹扩展过程的数值模拟

应用有限单元法和最大正应力准则,引入楔形界面过渡层模型,求解相应的特征函数,准确地确定界面裂纹第一步开裂角,模拟了裂纹在非均匀复合材料中的扩展过程。结果表明:裂纹扩展初期呈波浪式前进,并最终沿着与最大正应力垂直的方向前进。这对此类结构的防断控制具有指导意义。     

基于DSPACE的高功率密度柴油机智能化冷却系统控制策略验证

为了验证高功率密度柴油机智能化控制冷却系统控制策略是否正确,以DSPACE为基础搭建了半实物仿真试验平台;通过仿真试验平台验证,控制策略符合柴油机冷却系统工作要求,电控阀、传感器、驱动电路等部件工作可靠,节省了研制时间、经费,降低了研制风险。     

基于动态模型的机场配电网潮流计算新方法

机场配电网因非常情况成为孤立电力系统后,配电系统的电压、潮流和频率等发生巨大变化,传统的潮流计算方法往往会出现收敛性差、计算结果与实际不相符的情况。提出的机场配电网动态潮流计算模型能有效解决此类问题,阐述了机场配电网动态潮流计算模型的构成原理、算法并给出相应算例。通过算例计算证明了动态潮流计算模型适用于计算机场配电网的潮流。     

预失真技术在C波段功率放大器中的应用

文章设计了一个工作在C波段的功率放大器,并针对此放大器设计了模拟预失真电路。选用Agilent公司的ATF-21170砷化镓场效应晶体管作为模拟预失真器的非线性器件,所设计的预失真器具有结构简单、易实现、插入损耗小、三阶互调失真补偿性能较好的特点。仿真结果表明,在输出功率为1dB压缩点时,三阶互调比改善了13dB。     

Deviant globalization: the application of strategic landpower*

In both Afghanistan and Iraq, US landpower was able to gain control rapidly over terrain. However, that control ebbed as US presence weakened. Non-state actors, such as the Taliban, the Haqqani network, the Islamic State, and Al Qaeda, gained control of segments of the population. Transnational Criminal Organizations capitalized on this permissive environment to strengthen their networks, often eroding the legitimacy of the host nation government, fueling regional instability, and, ultimately, undermining US policy objectives. The proliferation of deviant globalization, or the connectedness of subversive elements, is a key indicator of future conflict. Strategic landpower is uniquely positioned to influence the physical, psychological, economic, and social interactions of various non-state actors and their association with deviant globalization. It is no longer enough to seize and hold terrain. Landpower must also have the capability to influence the actions and attitudes of populations on that terrain wherever and whenever these interactions occur.     

利用镁金属化学还原法制备多孔Si/Si-O-C负极材料机理研究

以二乙烯基苯和聚硅氧烷为原料经先驱体转化法制备了Si-O-C材料,利用镁金属在惰性气氛保护下高温还原制备了多孔的Si/Si-O-C负极材料。Si/Si-O-C负极材料的首次放电与充电容量分别为547.2和450.7mAh?g-1,第二次放电与充电容量分别为487.4和422.9mAh?g-1,库伦效率分别为82.3%、86.8%,材料具有较好的循环性能。利用X射线衍射(XRD)、能谱分析(EDX)、元素分析和场发射扫描电镜(FE-SEM)分析了多孔Si/Si-O-C负极材料的组成、结构、形貌,从而研究利用镁金属化学还原法制备多孔Si/Si-O-C负极材料的机理。结果表明,镁金属在还原过程中生成MgO和Mg2SiO4等产物,经HCl洗涤后可形成多孔的Si/Si-O-C负极材料。Si/Si-O-C材料中的单质硅分布于多孔的Si-O-C相中,一定程度上可缓解Si在循环过程中产生的体积效应。利用镁金属还原Si-O-C材料制备多孔Si/Si-O-C材料是一种可行的制备方法。     

用于卫星干扰源定位的压缩感知DOA估计方法

针对传统测向方法的实际应用性能较差,提出一种基于压缩感知(CS)的卫星干扰源定位方法。根据干扰信号方位角的空间稀疏性,建立了压缩感知波达方向(DOA)估计模型。通过协方差矩阵的高阶幂逼近信号子空间和矩阵的共轭对称特征,利用高阶幂矩阵的主对角线下左下角列向量进行波达方向估计。仿真实验验证,该方法不需要已知干扰源数,具有较高的精度和较好的分辨力,且能满足对相干干扰信号的估计。对压缩感知DOA估计在卫星干扰源定位中的应用具有一定参考意义。     

军用电传动车辆混合动力系统能量管理技术

混合动力系统是军用电传动车辆具有优越性能的基础,能量管理技术则负责实现负载需求在系统中各动力源间的合理分流及部件的优化控制,是军用车辆混合动力系统研究的关键技术之一。分析了军用车辆混合动力系统的特点,研究了其对系统能量管理的影响,总结了当前能量管理技术研究现状,最终,针对当前能量管理技术存在的问题提出了相应的解决方案。     

AFRICOM: hard or soft power initiative?

The United States (US) Africa Command (AFRICOM) was launched in 2007, ostensibly to foster African security. Rather than focusing on traditional military operations, AFRICOM also embraces non-military activities such as humanitarian aid and African development. This begs the question as to what type of power (hard or soft) the US intends to wield through AFRICOM. Several US official statements have emphasised the soft power attributes of this military project. To this end, this article seeks to respond to two fundamental questions. First, is AFRICOM a soft power project? Second, how, if at all, has AFRICOM enhanced perceptions of the US in Africa? The article concludes that sceptical and negative perceptions of AFRICOM inhibit its soft-power objective of winning the hearts and minds of the African people.     

The EU Global Strategy and diplomacy

The new EU Global Strategy has significant implications for EU diplomacy, in terms of both goals and means. This article first analyses the timing of the strategy as an exercise in diplomacy in its own right. Second, it argues that the strategy outlines a more expansive and noticeably more smart power-oriented approach to diplomacy in practical terms. Finally, it notes that the strategy has a new meta-narrative for EU diplomacy, which seeks to project a blend of both realistic assessment and idealistic aspiration.