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排序方式: 共有1251条查询结果,搜索用时 15 毫秒
831.
832.
对频率选择表面进行了研究,通过研究不同结构的频率选择表面,在现有介质材料的基础上设计了一种具有带通特性的频率选择表面,并用Ansoft HFSS进行了仿真设计.在20%带宽内实现了垂直照射传输损耗小于-2 dB,并研究了电磁波在不同入射角度下的传输特性. 相似文献
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834.
An availability‐oriented approach has been developed to decide when to replace an aging system. For an existing system, it is optimal to operate another year if and only if the incremental cost per available year is less than the lifetime average cost per available year of a new aircraft. We illustrate our approach using United States Air Force KC‐135 tanker data. In demonstrating our approach, we find it will be optimal to replace the KC‐135 by the end of the decade. 相似文献
835.
Lisa Otto 《African Security Review》2013,22(2):88-95
The 17th Conference of the Parties (COP17) had been anticipated as the ‘African COP’, not only due to the African venue but also due to the opportunity it would afford African countries – with South Africa at the helm – to steer the debate on a global climate change regime. With the conference now over, lobby groups, international organisations, negotiators, observers and commentators alike have been taking stock of its outcome. Despite the litany of developmental and security implications of climate change, COP17 got underway with little hope that much might actually be achieved. In light of the discouraging condition of the global economy, with leading developed economies suffering financially, states were hardly in a mood to be making concessions that would impact their fiscal health. Nonetheless, an agreement was reached. Questions remain, however, about the significance of the outcome of the African COP for the world at large, but ultimately also for Africa. 相似文献
836.
Samuel Oyewole 《Defense & Security Analysis》2013,29(3):253-262
Boko Haram terrorism has been recognized by Nigerian President Jonathan as the most threatening and complex security issue in Nigeria since independence. In response, the Federal Government of Nigeria has committed itself to different counterterrorism measures, which are largely dominated by “hard politics” and military mobilization. Spending heavily on defense to upgrade military hardware and train personnel in a counterterrorism role, Nigeria has also boosted its strategic importance in the “Global War on Terror”. However, this attempt has become unpopular as it has failed to contain Boko Haram within a short time frame and has made insufficient headway against unabated terror, with human rights costs among the host communities and amidst a surge of stakeholders' discordance. As a matter of concern, this article seeks to assess Boko Haram as an opponent in Nigeria's war on terror (WOT) and to ascertain the challenges the country faces, the alternative measures open to it, and possible ways forward. 相似文献
837.
采用胞外聚合物作为生物絮凝剂,开展胞外聚合物复合絮凝剂强化混凝处理微污染原水的研究.研究结果表明,蛋白质是胞外聚合物最主要的成分,多糖次之,腐殖酸和脱氧核糖核酸的含量最低;胞外聚合物含有大量带负电荷的官能团,单独投加胞外聚合物不能有效絮凝和吸附去除原水中的污染物.聚合氯化铝混凝处理微污染水的效果优于氯化铝和聚合硫酸铁,药品较优投加质量浓度为70~80 mg/L.胞外聚合物和聚合氯化铝复合使用能提高对细小颗粒物的去除效果,增强去除有机污染物和氯化消毒副产物前驱体的能力,降低聚合氯化铝的质量浓度.胞外聚合物复合絮凝剂的较优配方:胞外聚合物质量浓度为5 mg/L,聚合氯化铝质量浓度为60 mg/L. 相似文献
838.
《Arms and Armour》2013,10(2):101-153
AbstractThe Sword of Honour (RA IX.1841) presented in 1856 by the Province of Nova Scotia to its native son, General Sir William Fenwick Williams, Bart. for his deeds at Kars, Turkey, is described, illustrated, discussed and placed both in its historical and its design context. Other notable British swords of the Victorian Age (1837–1901), the Age of Empire, are also examined and the various and influential aspects of their designs, ornament and iconography discussed. 相似文献
839.
840.
作战体系具有层次高、规模大,各作战分系统间协调配合密切的特征。在作战任务中,这种多层次、多系统、多决策者、多目标的结构使得对各作战子系统的武器装备分配变得更为复杂。为解决此类复杂结构的优化问题,在层次化多目标分析方法基础之上,将层次系统的风险管理引入到模型中来,形成多目标多决策者资源分配模型多目标多决策者资源分配模型,用以解决在不确定风险环境下进行多目标资源分配的问题。利用MOMDRA模型建模空袭风险下防空反导体系的武器装备分配问题,在求解该模型的过程中采用系统分解的思路,利用权重法,站在不同决策者的角度得到该体系的Pareto最优资源分配方案,并通过一个实例来说明此方法的可行性。 相似文献