简述螺旋槽选煤的分选原理。
参考答案:
液流在螺旋槽面上运动的过程中,在螺旋槽横断面上产生
离心力,离心力使液流在横断面上形成从外缘到内缘的横向液面坡降。
According to the new traffic laws, people _______ drive after drinking wine or beer.[ ]
A. wouldn't
B. couldn't
C. needn't
D. mustn't
Alu相当序列基因