Factor $c_{shj}$ 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
$c_{shj}$
Formulae
$1.05538 \rho_{ab}^{4} - 33.7582 \rho_{ab}^{3} + 397.204 \rho_{ab}^{2} - 2133.54 \rho_{ab} - 657.704$$0.005 < X_{G2} <= 0.03$
$0.372559 \rho_{ab}^{4} - 11.8278 \rho_{ab}^{3} + 137.785 \rho_{ab}^{2} - 734.738 \rho_{ab} - 1488.81$$0.03 < X_{G2} <= 0.15$
Related
$\rho_{ab}$