  A recent updated version of the Lanzhou quantum molecular dynamics is
reviewed, in which the momentum dependence of symmetry potential and the
effective mass splitting of proton and neutron in nuclear medium are included
in the model. The in-medium nucleon-nucleon (NN) elastic cross sections are
evaluated with the scaling approach according to the effective mass and their
influence on collective flows in heavy-ion collisions are discussed. The
inelastic cross sections, in particular for the process of the channel
N$\Delta\rightarrow$NN, are parameterized in accordance with the available
experimental data. It is found that the in-medium cross sections play a
significant role on isospin emissions and result in a flat distribution for
transverse flows and elliptic flows of free nucleons comparing with the
in-vacuum ones. The rapidity distribution of the difference between neutron and
proton transverse flows is sensitive to the stiffness of nuclear symmetry
energy as a promising observable, which can not be influenced by the in-medium
effect and collision centrality. Furthermore, the elliptic flow of free
energetic nucleons in the case of the mass splitting of
$m_{n}^{\ast}>m_{p}^{\ast}$ is also related to the symmetry energy. However,
the pion flows weakly depend on the symmetry energy and the mass splitting.
