\begin{figure*}[!htbp]
\centering
\setcounter{figure}{3} %编号为4
\subfigure[case 1 with LHS]{
\includegraphics[width=0.25\linewidth]{case1_k_LHS}
}
\subfigure[case 2 with LDS]{
\includegraphics[width=0.25\linewidth]{case2_k_LDS}
}
\subfigure[case 3 with GS]{
\includegraphics[width=0.25\linewidth]{case3_k_GS}
}
\caption{The historical MAEs of the PINN-TFI method over three cases with different thermal conductivities under 2 000 iterations.}
\label{fig:different_k}
\end{figure*}