# Further Information

The physical parameters ${\epsilon }_{r}{}^{\prime }$ and ${\epsilon }_{r}{}^{\prime \text{​}\prime }$ correspond to the following equation, where represents the conductivity of the material.

(1) ${\underset{_}{\epsilon }}_{r}={\epsilon }_{r}^{\text{'}}-j\cdot {\epsilon }_{r}^{\text{'}\text{'}}={\epsilon }_{r}-j\frac{\sigma }{2\pi f{\epsilon }_{0}}$