\begin{table}%t1
\caption{\label{strucParam}Galactic structure parameters.}            
%\centering
\small
\begin{tabular}{llll}       
\hline\hline \noalign{\smallskip}              
Structure & Set 1 & Set 2 & Set 3 \\
parameter & ~ & ~ & ~ \\ 
\hline                       
   $z_0$ ~ ~ [pc] & 25 & 25 & 27 \\      
   $h_z$ ~ ~ [pc] & 245 & 300 & 330 \\
   $h_r$ ~ ~ [pc] & 2159 & 2600 & 2250 \\
   $n^{\rm thick}$ &  0.13 & 0.12 & 0.0975 \\
   $H_z$ ~~ [pc] &  743 & 900 & 665 \\
   $H_r$ ~~ [pc] &  3261 & 3600 & 3500 \\
   $n^{\rm halo}$ &  0.0051 & 0.0051 & 0.00125 \\
   $\kappa$ & 0.64 & 0.64 & 0.55 \\
   $k$ & 2.77 & 2.77 & 2.5 \\
\hline                                   
\end{tabular}
\end{table}