The taper ring's irregular section shape decide the unequal forming of the ring metal when rolling ring, which is the main cause of irregular wide spread and draw concave on the symmetry face of ring.

This mining technology combined the fully mechanized mining with orthodox working face, and it layoutted irregular form and double unit face, adopted the rotational adjustment mining.

Chorea is an aimless and irregular, fast and involuntary movement of head and face, and four extremities.