  Time-dependent Schroedinger's equation is integrated for a one-dimensional
strongly-correlated electron system driven by large electric fields. For larger
electric fields, many-body Landau-Zener tunneling takes place at anti-crossings
of the many-body energy levels. The nonlinear $I$-$V$ characteristics as well
as the time dependence of the energy expectation value are obtained. The energy
of the Mott insulator in electric fields shows a saturation, which suggests a
dynamical localization in energy space of many-body wave functions.
