\subfigure[The envelope changes in a slow time scale.]
{\resizebox{.9\textwidth}{!}{\input{./Chapters/chapter16/figures/envelope.pdf_t}}
\label{fig:ef2} }
- \caption{Transient envelope-following\index{envelope-following} analysis.
+ \caption[Transient envelope-following\index{envelope-following} analysis.]{Transient envelope-following\index{envelope-following} analysis.
(Both two figures reflect backward Euler\index{Euler!backward Euler} style envelope-following.)}
\label{fig:ef_intro}
\end{figure}