Derivative of reaction index for formation of H
function U4_der extends Modelica.Icons.Function; input SI.AbsolutePressure p "Pressure"; input SI.Temperature T "Temperature"; input SI.MoleFraction[4] moleFraction "Mole fractions"; input Real p_der "Derivative of pressure"; input Real T_der "Derivative of temperature"; input Real[4] moleFraction_der "Derivative of mole fractions"; output Real u_der "Derivative of reaction index for H"; end U4_der;