  We perform a numerical study of a one-dimensional Fermion-Hubbard model in
harmonic traps within the Thomas-Fermi approximation based on the exact
Bethe-ansatz solution. The $\rho-U/t$ phase diagram is shown for the systems of
attractive interactions ($\rho$ is the characteristic density and $U/t$ the
interaction strength scaled in units of the hopping parameter.). We study the
double occupancy, the local central density and their derivatives. Their roles
are discussed in details in detecting the composite phases induced by the
trapping potential.
