\begin{figure}[!h]
\begin{center}
-\includegraphics[width=8cm]{high_to_low_a_e.eps}
+\includegraphics[width=12cm]{high_to_low_a_e.eps}
\caption[Four identical simulation runs with different simulation parameter $p_s$]{} \label{stress}
\end{center}
\end{figure}