Factor $a_{shj}$ for jacket around each core

The equation for three-core cables with jacket around each core is based on the Jicable paper 'Thermal analysis of 3-core SL-type cables with jacket around each core using the IEC standard' by L.D. Ramirez et al., dated 2019.

Symbol
$a_{shj}$
Formulae
$- 0.00183533 \rho_{ab}^{4} + 0.0633263 \rho_{ab}^{3} - 0.908708 \rho_{ab}^{2} + 8.02417 \rho_{ab} - 52.8651$$0.005 < X_{G2} <= 0.03$
$- 0.0036756 \rho_{ab}^{4} + 0.116068 \rho_{ab}^{3} - 1.34557 \rho_{ab}^{2} + 7.37721 \rho_{ab} - 25.131$$0.03 < X_{G2} <= 0.15$
Related
$\rho_{ab}$