  We investigate the nucleosynthesis process in high-entropy ($s/k_{\rm
B}\gtrsim100$) and very fast-expanding ($\tau_{\rm exp}\sim10^{-3}\ {\rm s}$)
materials. In such a material with the electron fraction near 0.5, an
interesting nucleosynthesis process occurs. In this process, the abundance
distribution of heavy-nuclei of $A>100$ achieve quasi-statistical equilibrium
(QSE) at high temperature and the abundances are frozen at the end of the
nucleosynthesis. We explain this abundance distribution using the
"alpha-constrained QSE" abundances formulated in this paper. We demonstrate
that this nucleosynthesis would occur in neutrino-driven winds from massive
proto-neutron stars in hypernovae, where $A\sim140$ $p$-nuclei are synthesized.
