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21.
钢丝绳隔振器冲击特性试验研究 总被引:4,自引:0,他引:4
采用气缸式冲击模拟台对钢丝绳隔振器进行了冲击特性试验研究,介绍了试验系统及测量方法。在比较符合舰船实际冲击环境的情况下,获得了钢丝绳隔振器压缩和拉伸方向完整的特性曲线。试验结果分析表明,钢丝绳隔振器表现出明显的冲击软化现象,其冲击刚度特性小于静刚度和动刚度,而且它具有大阻尼耗能特性,是比较理想的抗冲元件。 相似文献
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基于Timoshenko梁理论,提出筒形桅杆首阶固有频率控制设计原理。依据该原理,采用Transfer matrix算法,研究了直壁式、外凸式及双曲式三种构形的桅杆首阶固有频率的变化规律,发现在桅杆高度、质量、顶部及底部截面边长相同的情况下,外凸式构形具有最大的首阶固有频率值。 相似文献
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Antonio Giustozzi 《Small Wars & Insurgencies》2017,28(1):12-33
Although the Taliban insurgency was internally divided and unable to coordinate its activities in 2014–2015, the Afghan security forces were not able to contain it and steadily lost ground throughout 2015. Until 2015, there had been little effort to develop an indigenous Afghan counterinsurgency strategy, but a sense of urgency emerged after a string of Taliban victories. At the beginning of 2016, it was still not clear if and when the National Unity Government would be able to produce a counterinsurgency strategy and, in any case, the need for a coherent counterinsurgency approach became questionable as the Taliban appeared to be transitioning towards conventional warfare. 相似文献
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基于信号循环平稳特性的时延估计算法具有较强的抗干扰和抗噪声能力,但循环频率误差时性能下降严重。针对这一问题,首先分析了循环频率误差对循环时延估计算法中,循环互相关函数相关法估计性能的影响,进而提出了一种对循环频率误差稳健的改进循环时延估计算法。改进算法通过两次搜索确定循环频率的真实值。仿真实验结果表明,改进算法可以有效地校正循环频率误差,最终使时延估计误差与无循环频率误差时基本相同。 相似文献
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Ian Westerman 《Defense & Security Analysis》2017,33(3):276-288
The existing guidelines for security sector reform (SSR) tend to draw on theoretical work in the field of civil–military relations, which in turn has been derived from Western, liberal democratic models of governance. Although guidelines strongly advise that local culture and context need to be considered when drawing up objectives for post-conflict SSR programmes, this is not often reflected in practice. This article considers some of the reasons for this, citing both in-country challenges and donor-related issues, and suggests that one of the biggest problems is a lack of alternative, non-orthodox models of civil–military relations to draw upon. It is further suggested that elements of suitable alternative models may be found in states which possess political structures not entirely dissimilar to the Western, liberal democratic ideal, but which can offer different perspectives. Detailed research of these structures should produce a pool of sub-models which could then be employed to create bespoke, culturally appropriate objectives for use in post-conflict SSR programmes. 相似文献
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Nadine Ansorg 《Contemporary Security Policy》2017,38(1):129-144
Many African states have security sector reform (SSR) programs. These are often internationally funded. But how do such programs account for previously existing security institutions and the security needs of local communities? This article examines SSR all over Africa to assess local ownership and path dependency from a New Institutionalist perspective. It finds that SSR, particularly in post-conflict countries, tends to be driven by ideas and perceptions of international donors promoting generalized blueprints. Often, such programs only account in a very limited way for path-dependent aspects of security institutions or the local context. Hence, the reforms often lack local participation and are thus not accepted by the local community eventually. 相似文献
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针对蚁群算法求解CVRP问题时收敛速度慢、求解质量不高的缺点,提出了一种改进启发式蚁群算法。该算法借鉴蚁群系统和基于排列的蚂蚁系统的优点设计信息素更新策略,既加强了对每次迭代最好解的利用,又避免了陷入局部最优;按一定比例使用基本方法和基于PFIH方法构造路径,扩大了算法的搜索空间;采用一种混合局部搜索算子,增强了算法局部寻优能力。实验结果表明,改进启发式蚁群算法可以大幅度减少车辆运行成本,具有较快的收敛速度。 相似文献