update papergraph example image

doc/chapter/3ui.tex

@@ -18,7 +18,8 @@ Note that since the application is still under construction, so not all screensh
         \centering
         \includegraphics[width=0.4\linewidth]{img/bk-example-ours}
         \caption[The same graph as~\ref{fig:theirs}, displayed by \appname.]{The same graph as~\ref{fig:theirs}, displayed by \appname.
-        The layouts are leftmost (first column), rightmost (second column), upper (first row) and lower (second row), respectively.}
+        The layouts are leftmost (first column), rightmost (third column), upper (first row) and lower (third row), respectively.
+        The balanced layout is in the center.}
         \label{fig:ours}
     \end{subfigure}\\\vspace{4mm}
     \caption[Comparison with~\cite{brandes_fast_2001}]{Comparison of the implementation with the results of  Brandes and Köpf~\cite{brandes_fast_2001}}