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 l
evels connected to an infinite quantum wire, using the bosonization method
and phase-shift representation. We show that all previously known results c
an be obtained through our method in a very simple way. Furthermore, the ev
olution of the system from ultraviolet to infrared critical fixed points ap
pears naturally in our method.