  An extended quark mass density- and temperature- dependent model which
includes the couplings between quarks and the sigma-mesons, omega-mesons is
suggested. The MIT bag boundary constrain has been given up and the
interactions between quarks and mesons are extended to the whole free space. We
show that the present model is successful to describe both the saturation
properties and the deconfinement phase transition of nuclear matter. When the
effective nucleon masses vanish and the bag radius tends to infinite, the quark
deconfinement takes place. The corresponding QGP phase diagram is addressed.
