function phaseComposition_duX input Modelica.SIunits.Density d "Density"; input Modelica.SIunits.SpecificInternalEnergy u "Specific internal energy"; input Modelica.SIunits.MassFraction X[nC] = reference_X "Mass fraction"; input Integer phaseIndex "Phase index"; input Properties state; output Real Y[nC]; end phaseComposition_duX;