针对慢跳速跳频信号跳带宽、采样率高数据量大的特点,提出了各跳部分数据拼接的跳频信号快速时差估计方法。同时,针对跳频信号的互相关函数存在周期副峰容易导致错误模糊估计的问题,利用先验信息或单跳信号的时差估计值作为引导值,将最...针对慢跳速跳频信号跳带宽、采样率高数据量大的特点,提出了各跳部分数据拼接的跳频信号快速时差估计方法。同时,针对跳频信号的互相关函数存在周期副峰容易导致错误模糊估计的问题,利用先验信息或单跳信号的时差估计值作为引导值,将最终时差估计的搜索范围限定在一个周期以内,避免模糊估计的产生,有效地提高了跳频信号的时差估计精度。仿真结果表明:在信噪比大于8 d B时,提出的跳频信号时差估计方法能精确地估计时差,并且有效抑制周期副峰的影响。展开更多
Rock is subjected to impact loading during tunnel and subsurface engineering.For understanding the damage evolution of rock under dynamic impact, mechanical research was performed on the carboniferous slate surroundin...Rock is subjected to impact loading during tunnel and subsurface engineering.For understanding the damage evolution of rock under dynamic impact, mechanical research was performed on the carboniferous slate surrounding the Muzhailing tunnel under different influencing factors based on the Split Hopkinson Pressure Bar(SHPB)experimental system. The results show that:(1)carbonaceous slate exhibits a continuous failure process, which develops more rapidly in the presence of joints;simultaneously, a negative correlation was found between the joint density and the dynamic strength of rock;(2) under different impact velocities and wavelengths, the method of using incident energy to represent the dynamic damage threshold of carbonaceous slate under high in situ stress was proposed based on the kinetic energy theorem, and the damage threshold of carbonaceous slate was calculated to be 53 J;(3) impact times is the most critical core variable and negatively correlated with peak strength and positively correlated with strain rate, maximum strain, and cumulative damage. The carbonaceous slate is subjected to repeated load impacts, which is followed by accumulation of damage, continuous strength attenuation, and internal dominant fracture expansion. In particular,when the samples break, there is only one main rupture surface, which is the most significant difference from the single impact rupture form.展开更多
We present an investigation of the optical constants of the near stoichiometric GdN films. Transmission and reflection spectra are collected for the paramagnetic and the ferromagnetic GdN in the photon energy range of...We present an investigation of the optical constants of the near stoichiometric GdN films. Transmission and reflection spectra are collected for the paramagnetic and the ferromagnetic GdN in the photon energy range of 0.5-5.5 eV. In the ferromagnetic phase, behaviors of minority and majority spin states are specifically focussed on, which indicate spin-split joint density of states. The results confirm the LSDA＋U estimates of energy gap associated with the majority-spins and also the magnitude of spin splitting.展开更多
文摘针对慢跳速跳频信号跳带宽、采样率高数据量大的特点,提出了各跳部分数据拼接的跳频信号快速时差估计方法。同时,针对跳频信号的互相关函数存在周期副峰容易导致错误模糊估计的问题,利用先验信息或单跳信号的时差估计值作为引导值,将最终时差估计的搜索范围限定在一个周期以内,避免模糊估计的产生,有效地提高了跳频信号的时差估计精度。仿真结果表明:在信噪比大于8 d B时,提出的跳频信号时差估计方法能精确地估计时差,并且有效抑制周期副峰的影响。
基金the financial support from the Key Special Project of the National Natural Science Foundation of China(Grant No.41941018)the Special Fund of Yueqi Scholars(Grant No.800015Z1207)。
文摘Rock is subjected to impact loading during tunnel and subsurface engineering.For understanding the damage evolution of rock under dynamic impact, mechanical research was performed on the carboniferous slate surrounding the Muzhailing tunnel under different influencing factors based on the Split Hopkinson Pressure Bar(SHPB)experimental system. The results show that:(1)carbonaceous slate exhibits a continuous failure process, which develops more rapidly in the presence of joints;simultaneously, a negative correlation was found between the joint density and the dynamic strength of rock;(2) under different impact velocities and wavelengths, the method of using incident energy to represent the dynamic damage threshold of carbonaceous slate under high in situ stress was proposed based on the kinetic energy theorem, and the damage threshold of carbonaceous slate was calculated to be 53 J;(3) impact times is the most critical core variable and negatively correlated with peak strength and positively correlated with strain rate, maximum strain, and cumulative damage. The carbonaceous slate is subjected to repeated load impacts, which is followed by accumulation of damage, continuous strength attenuation, and internal dominant fracture expansion. In particular,when the samples break, there is only one main rupture surface, which is the most significant difference from the single impact rupture form.
文摘We present an investigation of the optical constants of the near stoichiometric GdN films. Transmission and reflection spectra are collected for the paramagnetic and the ferromagnetic GdN in the photon energy range of 0.5-5.5 eV. In the ferromagnetic phase, behaviors of minority and majority spin states are specifically focussed on, which indicate spin-split joint density of states. The results confirm the LSDA＋U estimates of energy gap associated with the majority-spins and also the magnitude of spin splitting.
