Figure 1

For $\mathit{\alpha }\mathbf{=}\mathit{\beta }\mathbf{=}\mathbf{1}$ : exact and approximate solutions (red and blue colored surfaces, respectively) ( $\mathit{u}\mathbf{(}\mathit{x}\mathbf{,}\mathit{t}\mathbf{)}$ and $\mathit{v}\mathbf{(}\mathit{x}\mathbf{,}\mathit{t}\mathbf{)}$ (left- and right-hand sides, respectively)).