与月球上相同，那些巨大陨石坑的范围（例如，那些巨大到自形成后尚未被尘埃填满的陨石坑）标志着火星表面的年龄。
As on the Moon, the extent of large impact cratering (i.e. craters too big to have been filled in by erosion since they were formed) serves as an age indicator for the Martian surface.
即将爆炸或着火的粉末粒子和空气的比率范围。
Range of the ratio of powder particles to air which the mixture will explode or ignite.
对所采集煤尘样品进行实验分析，测定了不同粒径范围下煤尘层和煤尘云的最低着火温度。
Analyzed the coal dust samples we collected, mensurated the minimum ignition temperature of coal dust layer and coal dust cloud in different diameter range.
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