  In the previous article (S. Matsutani and Y. Shimosako and Y. Wang, Physica A
\bf{391} (2012) 5802-5809) we numerically investigated an electric potential
problem with high contrast local conductivities ($\gamma_0$ and $\gamma_1$,
$0<\gamma_0 \ll \gamma_1$) for a two-dimensional continuum percolation model
(CPM). As numerical results, we showed there that the equipotential curves
exhibit the fractal structure around the threshold $p_c$ and gave an
approximated curve representing a relation between the homogenized conductivity
and the volume fraction $p$ over $[p_c,1]$. In this article, using the duality
of the conductivities and the quasi-harmonic properties, we re-investigate
these topics to improve these results. We show that at $\gamma_0\to0$, the
quasi-harmonic potential problem in CPM is quasiconformally equivalent to a
random slit problem, which leads us to an observation between the conformal
property and the fractal structure at the threshold. Further we extend the
domain $[p_c,1]$ of the approximated curve to $[0,1]$ based on the these
results, which is partially generalized to three dimensional case. These curves
represent well the numerical results of the conductivities.
