b U=E1·t+|E,t (n b-Ina)+.(nc-In b) 2m1 2丌y →I 2TY1n2Uo r2In(b/a)+r, In(c/b) nira a<7<C In2 In(6/a)+n,In(c/b]r n2 n In, In(b/a)+r, In(c/ b)]r a<7< E r, lr, In(b/a)+r, In(c/b]r (6<r<c) E、·r (6<r<c) E,dr+ E dr (a<r<b)1 2 b c a b U E dr E dr = +   1 2 (ln ln ) (ln ln ) 2 2 I I b a c b   = − + − 1 2 0 2 1 2 ln( / ) ln( / ) U I b a c b      = + 1 2 0 2 1 ( ) [ ln( / ) ln( / )] U J a r c b a c b r      =   + 2 0 1 1 2 1 ( ) [ ln( / ) ln( / )] r J U E e a r b b a c b r     = =   + 1 0 2 2 2 1 ( ) [ ln( / ) ln( / )] r J U E e b r c b a c b r     = =   + 2 2 ( ) c r  = =   E dr b r c  1 1 2 ( ) b c r b  = + =   E dr E dr a r b  