泵喷推进器线谱非定常推力预报方法与试验验证

为预报泵喷推进器转子与周期性前导叶尾流互作用线谱非定常推力,忽略泵喷推进器转子叶片厚度,将泵喷转子简化为环形叶栅,根据片条理论,在半径r处截取泵喷转子分段,忽略流场参数沿分段径向的变化,从而可将该环形叶栅分段视为平面叶栅,在平面叶栅与简谐波互作用的基础上考虑周期性进流,推导得到前导叶分段与转子分段互作用线谱非定常激振力,转子分段周向积分得到非定常推力线谱预报公式,通过数值和试验方法验证公式的有效性。开展设计参数影响分析,得到当前导叶-转子间距与前导叶弦长的比值大于1时,转子-后导叶间距对转子单个叶片的激振力线谱推力几乎不存在影响。     

Kevlar fabric reinforced polybenzoxazine composites filled with silane treated microcrystalline cellulose in the interlayers: The next generation of multi-layered armor panels

The design of astonishing combinations of benzoxazine resins with various fillers is nowadays of great interest for high quality products, especially in ballistic armors. The objective of this study is to investigate a new hybrid material prepared as multi-layered composite plate by hand lay-up technique. Different composites were manufactured from Kevlar fabrics reinforced polybenzoxazine, which was filled with silane treated microcrystalline cellulose (MCC Si) at various amounts in the interlayers. The developed materials were tested for their flexural, dynamic mechanical and ballistic performance. The aim was to highlight the effect of adding different amounts of MCC Si on the behavior of the different plates. Compared to the baseline, the dynamic mechanical and bending tests revealed an obvious decrease of the glass transition of 21 °C and a notable increase in storage modulus and flexural strength of about 180 %and17%, respectively, upon adding 1% MMC Si as filler. Similarly, the ballistic test exhibited an enhancement in kinetic energy absorption for which the composite supplemented with 1% MCC Si had the maximal energy absorption of 166.60 J. These results indicated that the developed panels, with interesting mechanical and ballistic features, are suitable to be employed as raw materials to produce body armor.     

电缆负载射频电磁辐射响应规律研究

采用基于有限积分法的电磁仿真软件CST建立等幅正弦波辐照条件下同轴电缆电磁耦合响应模型,研究终端负载电阻及电缆长度对终端响应电压的影响规律。结果表明,随着终端负载电阻的增大,响应电压逐渐增大,而后趋于稳定;不同频率条件下,电缆长度在一个波长范围内,电缆负载响应电压幅值先是随着电缆长度的增加而变大;达到最大值后,随着长度的增加,响应幅值反而减小。     

邻域加强的并行子空间优化过程

针对基于响应面的并行子空间优化(CSSo-RS)过程的不足,提出了基于邻域加强的改进CSSO-RS优化过程.其主要思路是在子空间优化后,在得到的最优解附近进行全部变量的优化,以更好地协调系统级优化与子空间优化.用经典测试函数及通用航空飞机参数优化问题对该算法进行测试,测试结果表明该算法使CSSO-RS优化效率得到较大的...     

基于能量函数的插值代理模型推广能力评价准则

本文分析了插值型代理模型的特性,提出了影响插值代理模型的推广能力的重要因素是代理模型的振荡特性,分析表明:振荡剧烈的代理模型,其推广能力就弱。为了评价代理模型的推广能力,本文提出基于能量函数方法的评价方法。能量函数方法是通过计算代理模型的一阶和二阶导数,得出代理模型的振荡情况来进行评价。能量函数越高,代理模型的振荡越剧烈,因而其推广能力越差。测试函数表明,能量函数方法在评价代理模型推广能力上是有效的。     

汉语语境下教师对学生冲突性话语的回应策略与面子的语用分析

师生间的言语冲突在课堂教学中时有发生,而这一现象并未引起足够重视。课堂教学中师生间冲突性话语为本文的研究对象,分析其语言表现,并依据Brown&Levinson的面子威胁论,探析教师对于学生不合作话语引发的冲突回应,旨在揭示师生间冲突性话语的面子威胁性特征及语用理据。     

Don't stop with Joint Forces Command … cut AFRICOM too

Abstract

The United States Africa Command (AFRICOM) has been a military success but a strategic messaging failure. The United States’ relationships across Africa cannot be boiled down to military affairs. This paper argues that Africa has many more opportunities than challenges and thus requires a more balanced foreign policy solution from Washington DC than a new military command. For the military engagement that does need to take place, a more low-profile approach would benefit the United States in Africa.     

The Intergovernmental Authority on Development's Conflict Early Warning and Response Mechanism

The Intergovernmental Authority on Development's (IGAD) Conflict Early Warning and Response Mechanism (CEWARN) 2012–2019 Strategy Framework has proposed that the CEWARN mechanism expand its conflict typologies and geographic coverage. The argument advanced in this paper is that the proposed CEWARN expansion should be welcomed. Since its establishment in 2003, CEWARN had restricted itself to dealing with cross-border pastoral conflicts among the member states. However, conceptually and legally, CEWARN was not precluded from dealing with other types of conflict. Firstly, in the past, any conflict, other than cross-border pastoral ones, had been considered by the member states as firmly within their national jurisdiction that mechanisms like CEWARN are precluded from handling. Secondly, CEWARN, which has hitherto been dependent on external donations, just does not have the requisite financial resources to expand its coverage. Thirdly, and most importantly, governments often know the imminence of some, if not all, of the conflicts because they cause them. Thus, they are not interested in reacting to them. In the end, the paper concludes that the proposal to expand CEWARN's conflict portfolio and geographic spread may just remain that – a proposal.     

THE SECURITY IMPLICATIONS OF CHINA'S NUCLEAR ENERGY EXPANSION

Nuclear energy is an integral part of China's energy strategy and will increasingly contribute to China's total energy supply. China has more than twenty civilian facilities, including power reactors, mines, and enrichment plants, to support its nuclear power program. As China operates more nuclear plants, more nuclear materials will be produced and stockpiled, and more nuclear facilities will be spread around the country. To ensure that this expanded network of nuclear facilities does not increase the risk that nuclear materials will be diverted or become the target of attack, China will need to develop more reliable domestic nuclear security strategies. China is also poised to become a major exporter of nuclear energy technology. China has committed to keeping nuclear technologies out of the hands of dangerous states and/or sub-state organizations, but in order to fulfill its nonproliferation obligations as well as its treaty-based commitment to share nuclear technologies, China will need to strengthen nuclear export controls and practices. This report examines and evaluates security measures at Chinese civilian nuclear power plants and suggests ways to improve them. It also reviews current export control policies and systems, identifies likely challenges to the expanding nuclear sector, and proposes possible solutions.