上游充通大兽 SHANGHAI JIAO TONG UNIVERSITY i 2% R R2 uz 0 u hi hzuz iz h hzuz 1= Ri R H= 07 1 i2=B1+ R 1/R2 33 2 i +  +  R1 R2 1 i 1 i 2 u 1 u 1 11 1 12 2 2 21 1 22 2 u h i h u i h i h u        1 1 1 u  R i 2 1 2 2 1 i i u R    1 2 0 H 1/ R  R        2 i