  A new version of the improved quantum molecular dynamics model has been
developed to include standard Skyrme interactions. Four commonly used Skyrme
parameter sets, SLy4, SkI2, SkM* and Gs are adopted in the transport model code
to calculate the isospin diffusion observables as well as single and double
ratios of transverse emitted nucleons. While isospin diffusion observables are
sensitive to the symmetry energy term, they are not very sensitive to the
nucleon effective mass splitting parameters in the interactions. Our
calculations show that the high energy neutrons and protons and their ratios
from reactions at different incident energies provide a robust observable to
study the momentum dependence of the nucleon effective mass splitting. However
the sensitivity of effective mass splitting effect on the n/p yield ratios
decreases with increasing beam energy, even though high energy proton and
neutron are produced more abundantly at high beam energy. Our calculations show
that the optimum incident energy to study nucleon effective masses is between
100-200 MeV per nucleon.
