基于FFT的自适应频率估计算法

为了解决FFT算法中因能量泄露和栅栏效应而导致的算法估计性能下降的问题,提出了一种基于FFT的自适应频率估计算法.分析了Rife算法,指出当信号频率位于量化频率附近时,由于插值方向错误,会导致频率估计性能下降;对于分段FFT相位差频率估计算法,当2段信号最大谱线处对应的相位相差比较大时,容易产生相位模糊,从而增大估计误差.基于FFT的自适应频率估计算法将2种算法进行了综合,既保留了2种算法的优点,又对算法性能有所改进.仿真结果表明:该算法的估计精度、稳定性和抗噪能力都有显著提高.     

Security sector stabilisation in counterinsurgency operations: the case of Afghanistan

This article argues that the debate on security sector reform (SSR) needs to be taken further by taking into consideration the fact that, even though the SSR concept was not originally developed as an element in stabilising states undergoing an insurgency, it is very much being used for exactly that. When conducting counterinsurgency with a focus on the creation of stability, the baseline will ultimately have to be security sector stabilisation (SSS) as a precondition for complete SSR implementation. However, the two must be connected to avoid them undermining each other. This is important if a comprehensive approach to programme implementation and especially sustainability is to guide the programme, and not just isolated ‘train and equip’ stand-alone projects that do not solve either the initial need for stabilisation or the long-term need for accountable security forces. Currently, in Afghanistan the surge for security by the international military is in danger of overtaking the other elements of the SSR, thereby undermining the primary end state and thus risking laying the wrong foundation for the long-term process of SSR.     

基于区间数理论的空战目标威胁评估

针对空战目标威胁评估问题,提出了一种新的基于区间数理论的评估方法。在分析了现有的目标威胁评估方法中距离威胁模型存在不足的基础上,提出了改进的距离威胁模型。给出了区间数特征向量法求解威胁指标权重的计算步骤,建立了基于区间数理论的空战目标威胁评估的数学模型。最后给出了仿真算例,仿真结果表明该方法是合理和有效的。