Wn,2(u,ξ)=ξ1/2Kν(uξ1/2)s=0n1As(ξ)u2sξKν+1(uξ1/2)s=0n2Bs(ξ)u2s+1+ξ1/2Kν(uξ1/2)O(1u2n1).