隧道两端在中间相接时，只有几英寸的误差。
When the two ends of the tunnel met in the middle they were only a few inches out.
该锁相环由计算频率误差、更新环路中间变量、输出控制信号组成。
The SPLL consists of calculation frequency error, updating loop middle variable, and output control signal.
基于中间点的渐近性质，获得了数值积分的校正公式及其条件误差估计。
Then Based on the asymptotic properties of the intermediate point, corrective formulas of numerical integral and its conditional errors are obtained.
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