IEEE 1588标准为新一代智能变电站基于网络的测量和控制系统提供了一种完全基于通信网络的精密时钟协议(Precision Time Protocol,PTP)。该协议支持冗余主钟,并且对于主钟之间的动态切换有比较详尽的规定,但是却没有关于多端口冗余的从...IEEE 1588标准为新一代智能变电站基于网络的测量和控制系统提供了一种完全基于通信网络的精密时钟协议(Precision Time Protocol,PTP)。该协议支持冗余主钟,并且对于主钟之间的动态切换有比较详尽的规定,但是却没有关于多端口冗余的从钟的描述。文章利用PTP的现有技术,提出了一种基于IEEE 1588多端口冗余的从钟同步系统设计方法,实验结果表明,该方法能够快速、择优在从钟之间动态切换,最大限度地保证系统时钟同步的精度和可靠性。展开更多
We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level the...We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level theoretically with the density matrix method.In a steady state,5.8% atoms are at 7S1/2 level and 2.9% at 6P3/2 level,which builds up the population inversion between the two levels.We obtain the fluorescence spectra produced in thermal cesium cell in our experiment.The measured relative intensity of each available fluorescence spectral line in the experiment agrees very well with the theoretical result.The demonstrated population inversion between 7S1/2 and 6P3/2 levels can be used to construct an active optical clock of four-level system with a wavelength of 1469.9 nm.展开更多
文摘IEEE 1588标准为新一代智能变电站基于网络的测量和控制系统提供了一种完全基于通信网络的精密时钟协议(Precision Time Protocol,PTP)。该协议支持冗余主钟,并且对于主钟之间的动态切换有比较详尽的规定,但是却没有关于多端口冗余的从钟的描述。文章利用PTP的现有技术,提出了一种基于IEEE 1588多端口冗余的从钟同步系统设计方法,实验结果表明,该方法能够快速、择优在从钟之间动态切换,最大限度地保证系统时钟同步的精度和可靠性。
基金supported by the National Natural Science Foundation of China (Grant Nos. 10874009 and 11074011)
文摘We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level theoretically with the density matrix method.In a steady state,5.8% atoms are at 7S1/2 level and 2.9% at 6P3/2 level,which builds up the population inversion between the two levels.We obtain the fluorescence spectra produced in thermal cesium cell in our experiment.The measured relative intensity of each available fluorescence spectral line in the experiment agrees very well with the theoretical result.The demonstrated population inversion between 7S1/2 and 6P3/2 levels can be used to construct an active optical clock of four-level system with a wavelength of 1469.9 nm.
