\begin{equation}
		\begin{aligned}
			& \mathcal{D}(u(\boldsymbol{x}))=f(\boldsymbol{x}), \quad 
			\boldsymbol{x} \in \Omega \\
			& \mathcal{B}(u(\boldsymbol{x}))=g(\boldsymbol{x}), \quad 
			\boldsymbol{x} \in \partial \Omega
		\end{aligned}
\end{equation}
