按频率抽取
decimate in frequency DIF
不等概率抽样
unequal probability sampling
unequal-probability sampling
抽采达标
reaching standards of gas extraction
抽采负压
suction pressure of the drainage system
抽采工艺
gas extraction technology
Gas drainage technology
抽采孔孔距
distance of the gas drainage
抽采利用
gas extraction and utilization