In this paper we re-examine the problem of electronic transports through a
system consisting of a quantum dot which has well-defined discrete energy
levels connected to an infinite quantum wire, using the bosonization method and
phase shift representation, we show that all previously known results can be
obtained through our method in a very simple way. Furthermore, the evolution of
the system from ultraviolet to infrared critical fixed points appears naturally
our method.Comment: latex, 26 pages, to appear in Phys. Rev. B61, January 15/200