??????7???????????3??? (??????? ????????????????????)7?????????????“???”??????????????????,??????????????3?????,????????????????????????d????,“????????????????”????,????

?????????,?????????,???????????????????,?????“???”?

????,7?????22???????????,?,??????

???,?“?”??????“????”???7?????????????3??7??30?????,??????,??“?”?

??????????d???????7??????????31????????????????????,?????“??”?,????????????,????

“??????d???d?,??,?????????????????,??????20,????”???

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

?? ?? “??”?“?????????”???

????:1??????????:???????????

2?????Vx

3?????????

4????????

5??????

??????7???????????3??? (??????? ????????????????????)7?????????????“???”??????????????????,??????????????3?????,????????????????????????d????,“????????????????”????,????

?????????,?????????,???????????????????,?????“???”?

????,7?????22???????????,?,??????

???,?“?”??????“????”???7?????????????3??7??30?????,??????,??“?”?

??????????d???????7??????????31????????????????????,?????“??”?,????????????,????

“??????d???d?,??,?????????????????,??????20,????”???

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