多旋翼无人机减振分析与实验

针对多旋翼无人机机身系统振动过大导致飞行状态不稳的问题,基于有限元仿真技术与实验方法,进行了减振分析。通过频率分析,确定系统振动过大的原因为固有频率与激励频率耦合导致的共振现象,且共振频点的模态振型包含一阶挥舞、一阶摆振和二阶摆振振型。提出了优化机身壳体截面形状的设计方案,在不增加额外质量的情况下,将一阶挥舞、一阶摆振和二阶摆振振型对应的频点分别提高37.23%、22.47%和18.43%,有效规避了机身共振现象。仿真实验证明,提出的有限元仿真与实验结合的减振分析思〖BHDWG8,WK10YQ,DK1*2,WK1*2D〗〖XCMWL.TIF;%129%129〗听语音 聊科研与作者互动 路及优化设计方法,可为旋翼无人机减振设计提供参考依据。     

The year of the drone misinformation

This paper challenges the widely held view in the research communities around the world that US drone strikes on the Pakistan's north-western border area with Afghanistan lead to large-scale civilian casualties and are unpopular in that tribal area. As an example of that view the author analyses a recent research report, ‘The Year of the Drone’, produced by the New American Foundation, and argues that sources of the report are questionable and doubtful. The author, who is a native of the border area with Afghanistan and has lived almost all of her lifetime in the area, informs that the drone attacks are popular in the region and the reports about large-scale civilian casualties are baseless. She provides some evidence in support of her argument and cautions the researchers against the uncritical acceptance of the notions, like the drone attacks are unpopular or have killed civilians.     

Modern Irregular Warfare: The ISIS Case Study

ISIS (the Islamic State of Iraq and Syria) has become a key political and military actor in the Middle East and in North Africa. This essay aims at outlining ISIS warfare through an analysis of its operations in the frame of hybrid warfare theory proposed by Frank Hoffman. Therefore, the paper deals with: the role of terrorist tactics in ISIS warfare and the relationship between terrorism and insurgency; ISIS use of technology, mainly with regard to suicide attacks and to drones; and the relevance of urban warfare. Finally, the paper highlights how ISIS operates and the most threatening features of its warfare.     

基于十字靶标的人控交会对接仿真

为了减轻航天员的负担,提高人控对接成功率,建立人控交会对接仿真系统是很有必要的。通过对追踪飞行器和目标飞行器的动力学模型分析,建立了人控交会对接仿真系统的基本框架,并基于十字靶标进行了相应的仿真实验。实验结果表明航天员经过一定的训练后,可以通过操作手柄控制追踪飞行器的位置和姿态,实现航天器的交会对接。为降低操作的复杂程度,航天员可以只进行位置控制,而把姿态控制交给自控系统,这样手控对接的成功率会更高。     

Indications and warning in Belgium: Brussels is not Delphi

The terrorist attacks in France and Belgium of 2015–2016 that occurred while these countries were in a heightened state of alert raise questions about indications and warning methodology as well as effectiveness of the blanket-protection deployment of security services assisted even by the military. Response and perhaps even more anticipation may require strategic rethinking in light of the predatory attacks that target the most vulnerable spots of the public space. This study looks at threat analysis in Belgium as conducted through her intelligence fusion centre Coordination Unit for Threat Analysis (CUTA)?????? since its inception in 2006. With a special focus on what is known, at the time of writing, about the terrorist attacks in Paris and Brussels, this study hopes to put into context how the system (mal)functions and will also consider the preventive measures that respond to the threat, and the international aspects which have implications far beyond Belgian borders. Therefore, a case is made for not just a Belgian homeland security framework, but one that fits into an EU-wide security concept.     

我国反恐怖斗争对策研究

随着以美国为首的国际反恐怖战争在全球的迅速展开 ,以基地组织为代表的国际恐怖组织实施恐怖袭击的行动能力受到一定的削弱和限制。但同时 ,在世界各地尤其是中东、中亚等热点地区的恐怖事件却愈演愈烈 ,并且恐怖袭击的目标、采用的方式更趋于多样化、复杂化 ,造成的危害更加严重。     

From elite consumption to popular opinion: framing of the US drone program in Pakistani newspapers

The United States has conducted armed drone strikes in Pakistan since 2004. While there has been some recent work on Pakistani public opinion about drones, there is very little research on how Pakistan’s media characterize the US drone program. This is an important gap in understanding the determinants of Pakistani popular perceptions of this program. Decades of research has shown that “news framing”, a process by which certain aspects of a complex concept are emphasized in political communications with others played down, influences individual cognition while forming political opinions. In this essay, we address this lacuna by assembling an unprecedented sample of editorials about the drone program from three English newspapers and one Urdu newspaper and analyzing the news frames within them. We next compare the trends in these news frames to public opinion data collected by Pew between the spring of 2009 and 2014. Initially, most Pakistanis were unaware of the drone program, media coverage of the program expanded as drone strikes increased in frequency. While Pakistanis became more cognizant of the US drone strikes, even by 2014 large minorities remained unaware. Pakistani public opinion strongly reflected the top media frames, particularly those that are negative. This is an important finding suggesting that newspaper editorials are a good barometer of Pakistani opinions despite the fact that only information elites rely upon newspapers for political information.     

不可能差分分析时间复杂度通用计算公式的改进

研究Boura等和Derbez分别提出的不可能差分分析时间复杂度计算公式,根据实际攻击过程优化密钥排除的步骤,给出不可能差分分析实际攻击的时间复杂度计算的改进公式,进而利用两个分组密码算法模型将改进后公式计算的实际结果分别与Boura等的公式和Derbez的公式的计算结果进行对比,结果表明Boura等的公式计算结果既可能高于优化公式的实际分析计算的结果,也可能低于优化公式的实际分析计算的结果,而在轮子密钥独立时改进后公式的实际计算结果是Derbez公式的计算结果的2-1.2倍。     

析印度孟买11·26反恐作战的得与失

2008年11月26日,印度孟买市遭到了境外不明身份恐怖分子的突然袭击,面对突如其来的打击,虽然政府态度坚定,参战人员勇敢,武器装备也较先进,但由于平时思想麻痹、准备不足,以致反应较慢,战术运用不够灵活,给国家和人民造成了极大的损失。总结这次震惊世界的恐怖事件,其中最值得反思的是反恐战术运用的经验和教训。     

针对OpenSSL的RSA实现算法的计时攻击

通过对OpenSSL中的RSA算法的研究,发现RSA算法在解密过程中会发生Montgomery约简,从而导致对于不同的密文产生不同的解密时间差异,由该时间差异信息能够提取密钥的信息,进行密钥破解。为了能够产生更加明显的时间差异,提高攻击执行效率,提出了添加临近值的改进方法,并设计了计时攻击的流程。实验结果表明,改进的方法能够提高计时攻击的效率和准确性。