tansiying 发表于 2012-5-23 16:01 ' }1 R7 k- n, v/ HQ=V·A 1 {9 V! T9 K4 }. UV=φ(2P/ρ)½ 5 a' R% o& V5 Y8 c0 C6 ]6 c A=π(D/2)²