2 o df df adl x Bo p=此=B,=（BB)(月+B】 dl Ho 2 1(B2-B,2) 2l0 ENDdd Blf 0 rr r α ×= 2 )()( d d 21 0 21 0 BBBB B l f p − + === μ α 0 21 μ α − BB , = 2 21 0 BB B rr r + = END )( 21 22 21 0 −= BB μ