!! Method 4: Vm piece-wise change, i.e. Vm gradually change from Vrest to Vstim
!!           using dynamics tangent angle
!!           The angle is calculated from the previous point of the current point

       IF (tresidue .GE. t_V_stim_start .AND. tresidue .LT. t_V_stim_end) THEN
          Vm = Vm + dt * (V_stim - Vm)/tau_time
       ELSE
          Vm = Vm + dt * (V_rest - Vm) / tau_time
       ENDIF
       INCLUDE "Vm_dependent.inc"  !!kva,kvi
       INCLUDE "dp_args.inc"  !! dp_arg1, dp_arg2


