Therefore, the dumping-N-R method was used instead. In the method, a dumping factor 𝑓 NR (= 0.01 to 1; 1 for the usual N-R method) was used to calculate the time step, 𝐱 𝐬+𝟏 = 𝐱 𝐬 + 𝑓 NR 𝛿𝐱. The time steps were repeated until that the objective equation substituting 𝐱 𝐬+𝟏 converged within tolerance factor.