Roof falling and rib spalling occurred in any times. To predict roof falling, AE field tests have been conducted and AE monitor holes are laid out based on the block analysis.

为了预报冒落事故，开展了声发射（AE）现场试验，并在块体分析的基础上布置了AE监测孔。

youdao

To predict roof falling AE field tests have been conducted and AE monitor holes are laid out based on the block analysis.

为了预报冒落事故，开展了声发射(AE)现场试验，并在块体分析的基础上布置了AE监测孔。

youdao

Last year, the U.S. Embassy installed an air monitor on the roof of one of its buildings, and every hour it posts the results to a Twitter feed, with a score ranging from 1, which is the cleanest air, to 500, the dirtiest.

NEWYORKER: Green Giant