The 10-mm Dorr-Oliver cyclone separates the oversize dust from the respirable fraction (usually considered to have an aerodynamic diameter of()or less)
A. 10μm
B. 10pm
C. 15 pm
D. 20 pm
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PM10 is defined as particulate matter with a diameter less than or equal to()
A. 10μm
B. 10cm
C. 10mm
D. 10nm
已知伏安法测电阻实验选用直流电压表(C31-V型 a=0.5 量程:0.045-0.075-3-7.5-15-30-75-150-300-600V, 3-600V的电压灵敏度:500Ω/V);如果电压表量程选择30V,那么电压表的内阻是多少()
A. 7500欧姆
B. 37500欧姆
C. 500欧姆
D. 15000欧姆
What is the size of the visual dust()
A. <0.25 μm
B. >0.25 and <10μm
C. >1μm
D. >10μm
将3.26350、3.26451、3.26450、3.26460四个数保留三位小数,结果正确的是()
A. 3.264、3.265、3.265、3.265
B. 3.264、3.265、3.264、3.265
C. 3.263、3.265、3.265、3.265
D. 3.263、3.265、3.264、3