\({-\varepsilon}_{i}E_{z}\frac{\partial^{2}c_{b}}{\partial z^{2}}+v_{l}\frac{\partial c_{b}}{\partial z}{+\varepsilon}_{i}\frac{\partial c_{b}}{\partial t}-(1{-\varepsilon}_{i})\sum_{\begin{matrix}k=1\\ k\neq b\\ \end{matrix}}^{\text{nc}}J_{k}=0,\) (1)