??12??????????????????6?? (?? ???)12???6??????????,??

???? ?

?????????????????,??,?????????????????:“?????????????????????”??????????????,?????“??????????????????”??,???????,????,????????“??”,???(??)

????????:?? ??“??????”

?? ????:“????”?????????

????:1???????:????Vx

2?????

3????????

4????????????

5????????????

??12??????????????????6?? (?? ???)12???6??????????,??

???? ?

?????????????????,??,?????????????????:“?????????????????????”??????????????,?????“??????????????????”??,???????,????,????????“??”,???(??)

????????:??