低速率拒绝服务LDoS(Low-rate Denial of Service)攻击是一种基于TCP/IP协议漏洞,采用密集型周期性脉冲的攻击方式.本文针对分布式LDoS攻击脉冲到达目标端的时序关系,提出基于互相关的LDoS攻击检测方法.该方法通过计算构造的检测序列与...低速率拒绝服务LDoS(Low-rate Denial of Service)攻击是一种基于TCP/IP协议漏洞,采用密集型周期性脉冲的攻击方式.本文针对分布式LDoS攻击脉冲到达目标端的时序关系,提出基于互相关的LDoS攻击检测方法.该方法通过计算构造的检测序列与采样得到的网络流量序列的相关性,得到相关序列,采用基于循环卷积的互相关算法来计算攻击脉冲经过不同传输通道在特定的攻击目标端的精确时间,利用无周期单脉冲预测技术估计LDoS攻击的周期参数,提取LDoS攻击的脉冲持续时间的相关性特征,并设计判决门限规则.实验结果表明基于信号互相关的LDoS攻击检测方法具有较好的检测性能.展开更多
广播式自动相关监视(ADS-B)报头检测方法的优劣直接决定着接收机的性能。为了解决脉冲匹配检测方法受脉冲能量影响较大的不足,提出了一种基带归一化的互相关报头检测方法。首先将基带信号根据动态门限进行归一化,然后将其与标准报头作...广播式自动相关监视(ADS-B)报头检测方法的优劣直接决定着接收机的性能。为了解决脉冲匹配检测方法受脉冲能量影响较大的不足,提出了一种基带归一化的互相关报头检测方法。首先将基带信号根据动态门限进行归一化,然后将其与标准报头作互相关,最后通过相关峰检测来判定信号的存在和到达时间。与主流基于脉冲位置和上升沿的检测方法相比,该方法隐含地利用了脉冲位置、上升沿、下降沿、脉冲宽度、非脉冲区等多个信息用于检测报头,且无需进行下行格式(DF)认证。仿真结果表明:该方法在信噪比大于2 d B时检测性能略优,在信噪比小于2 d B时检测性能与主流检测方法相差1 d B。在实际接收实验中,以该方法为基础的信号接收效果良好,在视距内可以形成稳定连续的航迹,证明了该方法的实用性。展开更多
Based on Lamb wave analysis of propagation in plate-like structures, a damage detection method is proposed that not only locates the position of the damage accurately but also estimates its size. Similar damage detect...Based on Lamb wave analysis of propagation in plate-like structures, a damage detection method is proposed that not only locates the position of the damage accurately but also estimates its size. Similar damage detection methods focus only on localization giving no quantitative estimation of extent. To improve detection, we propose two predictive circle methods for size estimation. Numerical simulations and experiments were performed for an aluminum plate with a hole. Two PZT configurations of different sizes were designed to excite and detect Lamb waves. From cross-correlation analysis, the damage location and extent can be determined. Results show that the proposed method enables a better quantitative resolution in detection, the size of the inspection area influences the accuracy of damage identification, and the closer is the inspected area to the damage, the more accurate are the results. The method proposed can be developed into a multiple-step detection method for multi-scale analysis with prospective accuracy.展开更多
设计简易数字控制的微弱信号检测装置,系统主要由信号预处理、参考信号源、互相关检测、ADC采样及STM32处理器控制模块组成。前级通过加法器把微弱待测信号和强噪声信号相加,模拟出信号淹没在强噪声中的微弱信号源;通过带通滤波、程控...设计简易数字控制的微弱信号检测装置,系统主要由信号预处理、参考信号源、互相关检测、ADC采样及STM32处理器控制模块组成。前级通过加法器把微弱待测信号和强噪声信号相加,模拟出信号淹没在强噪声中的微弱信号源;通过带通滤波、程控放大进行预处理后的信号在AD630中进行互相关检测处理;所得信号经过低通滤波后送入ADS1271采样分析,最后得出待测微弱信号的幅度、相位和频率等信息。在强噪声源幅度为2 Vpp的情况下,实现了对20 m Vpp微弱信号的检测。展开更多
文摘低速率拒绝服务LDoS(Low-rate Denial of Service)攻击是一种基于TCP/IP协议漏洞,采用密集型周期性脉冲的攻击方式.本文针对分布式LDoS攻击脉冲到达目标端的时序关系,提出基于互相关的LDoS攻击检测方法.该方法通过计算构造的检测序列与采样得到的网络流量序列的相关性,得到相关序列,采用基于循环卷积的互相关算法来计算攻击脉冲经过不同传输通道在特定的攻击目标端的精确时间,利用无周期单脉冲预测技术估计LDoS攻击的周期参数,提取LDoS攻击的脉冲持续时间的相关性特征,并设计判决门限规则.实验结果表明基于信号互相关的LDoS攻击检测方法具有较好的检测性能.
文摘广播式自动相关监视(ADS-B)报头检测方法的优劣直接决定着接收机的性能。为了解决脉冲匹配检测方法受脉冲能量影响较大的不足,提出了一种基带归一化的互相关报头检测方法。首先将基带信号根据动态门限进行归一化,然后将其与标准报头作互相关,最后通过相关峰检测来判定信号的存在和到达时间。与主流基于脉冲位置和上升沿的检测方法相比,该方法隐含地利用了脉冲位置、上升沿、下降沿、脉冲宽度、非脉冲区等多个信息用于检测报头,且无需进行下行格式(DF)认证。仿真结果表明:该方法在信噪比大于2 d B时检测性能略优,在信噪比小于2 d B时检测性能与主流检测方法相差1 d B。在实际接收实验中,以该方法为基础的信号接收效果良好,在视距内可以形成稳定连续的航迹,证明了该方法的实用性。
基金Project supported by the National Natural Science Foundation of China(Nos.11172003 and 11521202)
文摘Based on Lamb wave analysis of propagation in plate-like structures, a damage detection method is proposed that not only locates the position of the damage accurately but also estimates its size. Similar damage detection methods focus only on localization giving no quantitative estimation of extent. To improve detection, we propose two predictive circle methods for size estimation. Numerical simulations and experiments were performed for an aluminum plate with a hole. Two PZT configurations of different sizes were designed to excite and detect Lamb waves. From cross-correlation analysis, the damage location and extent can be determined. Results show that the proposed method enables a better quantitative resolution in detection, the size of the inspection area influences the accuracy of damage identification, and the closer is the inspected area to the damage, the more accurate are the results. The method proposed can be developed into a multiple-step detection method for multi-scale analysis with prospective accuracy.
文摘设计简易数字控制的微弱信号检测装置,系统主要由信号预处理、参考信号源、互相关检测、ADC采样及STM32处理器控制模块组成。前级通过加法器把微弱待测信号和强噪声信号相加,模拟出信号淹没在强噪声中的微弱信号源;通过带通滤波、程控放大进行预处理后的信号在AD630中进行互相关检测处理;所得信号经过低通滤波后送入ADS1271采样分析,最后得出待测微弱信号的幅度、相位和频率等信息。在强噪声源幅度为2 Vpp的情况下,实现了对20 m Vpp微弱信号的检测。
