public override OOPTools_Math.Vector IntegralArgument_Fe(OOPTools_Math.Vector Xi) { int NNPE = ElementNodes.Length; double Det_Jac; Vector X; Vector N; Vector B = new Vector(2); Interpolator.Calculate_X_N_DetJacobian(Xi, ElementNodes, out X, out N, out Det_Jac); B = b(X); Vector F_Arg = new Vector(NNPE * 2); for (int i = 0; i < NNPE; i++) { F_Arg.Values[2 * i] = N.Values[i] * B.Values[0] * rho(X); //nodes at x direction F_Arg.Values[2 * i + 1] = N.Values[i] * B.Values[1] * rho(X); //nodes at y direction } return(F_Arg); }