where β β i , i = 1 , 2 , … … , 6 are six parameters that have to be determined in the identification process. However, according to Ikhouane et al. (2008), the coefficients β β 2 , β β 3 and β β 6 should be set to zero. Also, according to Aloisio et al. (2020), no investigations concerning the intervals of the admissibility of the β β i parameters have been carried out yet in the light of the second principle of thermodynamics.