different splitting options
type SplitOption = enumeration(out1_over_in "split = Vdot_out1 / V_in", out2_over_in "split = Vdot_out2 / V_in", out2_over_out1 "split = Vdot_out2 / Vdot_out1", Nout1_over_Nin "split = Ndot_out1 / Ndot_in");