舰船不同位置处的各装备基准面之间的相对水平度测量需要使用相对水平度无线差分系统。分析了相对水平度无线差分测量系统各水平度测量节点对时精度需求,研究阐述了精确时钟同步协议(Procision Time Protocol,PTP)1588协议的工作原理、...舰船不同位置处的各装备基准面之间的相对水平度测量需要使用相对水平度无线差分系统。分析了相对水平度无线差分测量系统各水平度测量节点对时精度需求,研究阐述了精确时钟同步协议(Procision Time Protocol,PTP)1588协议的工作原理、时钟模型和延时测量机制。在该协议分析研究的基础上,结合相对水平度无线差分测量系统的网络特点和对时精度需求,分析了PTP 1588在相对水平度无线差分测量系统网络应用的关键点,选取合适的机制和参数,对报文格式、主从结构等进行针对性设计,构建了针对此特定应用的高精度时间对时方案,并进行了误差因素分析。展开更多
Here we present a cyclicly symmetric non-vacuum spacetime, admitting closed timelike curves(CTCs) which appear after a certain instant of time,i.e.,a time-machine spacetime. The spacetime is asymptotically flat, freef...Here we present a cyclicly symmetric non-vacuum spacetime, admitting closed timelike curves(CTCs) which appear after a certain instant of time,i.e.,a time-machine spacetime. The spacetime is asymptotically flat, freefrom curvature singularities and a four-dimensional extension of the Misner space in curved spacetime. The spacetime is of type Ⅱ in the Petrov classification scheme and the matter field pure radiation satisfy the energy condition.展开更多
文摘舰船不同位置处的各装备基准面之间的相对水平度测量需要使用相对水平度无线差分系统。分析了相对水平度无线差分测量系统各水平度测量节点对时精度需求,研究阐述了精确时钟同步协议(Procision Time Protocol,PTP)1588协议的工作原理、时钟模型和延时测量机制。在该协议分析研究的基础上,结合相对水平度无线差分测量系统的网络特点和对时精度需求,分析了PTP 1588在相对水平度无线差分测量系统网络应用的关键点,选取合适的机制和参数,对报文格式、主从结构等进行针对性设计,构建了针对此特定应用的高精度时间对时方案,并进行了误差因素分析。
文摘Here we present a cyclicly symmetric non-vacuum spacetime, admitting closed timelike curves(CTCs) which appear after a certain instant of time,i.e.,a time-machine spacetime. The spacetime is asymptotically flat, freefrom curvature singularities and a four-dimensional extension of the Misner space in curved spacetime. The spacetime is of type Ⅱ in the Petrov classification scheme and the matter field pure radiation satisfy the energy condition.
