列入关注的理由： 20世纪四次最大规模的火山爆发，圣塔玛里亚就占了一次，记录的火山爆发指数(VEI)为6级，留下了一个直径为700-1000米的火山口。
Reasons to worry: Santa María's last big blast was one of the four largest volcaniceruptions in the 20th century, registering a VEI magnitude of 6 and leaving a 700-by-1,000 meter craterbehind.
实践证明，该系统运行稳定可靠，测量精度达到了微米级，可以用于实际的直径测量。
Testing results show that this system runs stably and accurately, the measuring precision is in the range of micron and can be employed in practical diameter measurement.
达到N95等级的口罩可以滤除超过95%的直径大于0.3微米的颗粒物。
A mask rated N95 filters out more than 95% of particles larger than 0.3 microns.
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