Fig. 7.

a, b represent ${\varphi }_s$ versus ${\zeta }^{\ast }$ plot (with $\rho \in (0,0.1])$ and ${\beta }_s$ versus ${\zeta }^{\ast }$ plot (with ${\beta }_s\in (0,2])$. c represent ${\zeta }^{\ast }$ over $({\varphi }_s,{\beta }_s)$ matrix plot, where $({\varphi }_s,{\beta }_s)\in (0.1]\times (0,2]$. The corresponding color bar indicates values of ${\zeta }^{\ast }$. The values of the other parameters are taken as same, shown in Table 1