\begin{table}%t2
\caption{\IZ~NW: model parameters and properties.}\label{tab_mod}
\small%%\centerline
\par
 {
\begin{tabular}{l|c|rrrr}
\hline\hline
&&&&& \\[-8pt]
Parameters            & Run$^a$ & \multicolumn{4}{c}{Model$^b$} \\
of model              & N0--N1    & M1    & M2   &  M3   & M4   \\
                      & 2--3  &  4    &  5   &   6   &  7   \\
\cline{1-6}
\multicolumn{6}{l}{\underline{Central source parameters}}      \\
$T1$/10$^4$~K        &  10.     &  10.  &  8.   &  8.   &  12. \\
$L1$/10$^{41}$\ergs   & 3.5--1.6  & 3.5   & 2.0   & 1.6   & 1.25 \\
$\delta_4$            & .12--.67  & 0.73  & 0.83  & 0.93  &0.24 \\
$T2$/10$^4$~K        &   4.     & 4.    &  4.   &   5.  &  4. \\
$L2$/10$^{41}$\ergs   & 3.5--1.6  &  3.5  & 2.0   &  1.6  &  2.5 \\
log($Q$) $-$ 51.      & 1.04--.71 & 1.054 & 0.829 & 0.779 & 0.734\\ 
$-$log($Q_{\rm He}$/$Q$) &.462--.447 &0.445 &0.523 &0.493 &0.539 \\ 
\multicolumn{6}{l}{\underline{Ionized shell parameters}}        \\
$\epsilon$            &  .0042--.31  & 1.00 & 1.00  & 1.00 & 1.00 \\
$P_{\rm in}/k$/10$^5${\sc cgs} &38.--8.3 & 5.01 & 3.40 & 2.96 & 2.71 \\
$P_{\rm out}/k$/10$^5${\sc cgs} & -- & 23.2 & 21.7 & 25.4 & 26.8 \\
$\tau_{\rm c}$         &     --  & 5.7  &  4.9 & 4.0  & 4.3  \\
$f^{\rm cov}_1$           & 1.--0.43 & 0.20 & 0.26 & 0.23 & 0.29 \\
$f^{\rm cov}_2$           &    --    & --    & 0.30 & 0.50 & 0.60 \\ 
$\tau_{\rm m}$ or $\tau_{\rm m}$(2)     
                      & .96--300.& 270. & 1.21 & 1.46 & 1.00 \\ 
\multicolumn{6}{l}{\underline{Elemental abundances by number (H = 10$^7$)}} \\
C                     &  60--52  & 45.8 & 38.8 & 35.3 & 47.4 \\ 
N                     & 8.1--5.3 &  3.9 &  4.1 &  4.0  & 3.8 \\
O                     & 198--192 & 172. & 168. & 162. & 173. \\ 
Ne                    & 33--30   & 26.4 & 25.7 & 24.8 & 26.9 \\
S (Table~\ref{tab_conv})& 3.4--3.9 &  5.0 & 4.3 & 4.3 &  5.0 \\
Ar                    & .77--.90 & 1.14 & 0.99 &  0.98& 1.13 \\
Fe                    & 4.8--5.8 &  5.8 &  6.1 &  6.0 &  6.5 \\
\multicolumn{6}{l}{\underline{Mean shell properties weighted by \Ne~$\times$ $N_{\rm ion}$, except for \Ne}}\\
$Q_{\rm abs}$/$Q$     & .20--.43   & .200  & .343 & .380 & .426 \\ 
$M_{\rm gas}$/10$^6$\Msun& .15--.92 & 1.02 & 1.52 & 1.74 & 1.79 \\
H$^{+}$/H             & .998--.98  & .957  & .961 & .963 & .948 \\
O$^{0}$/O             & .00--.017  & .041  & .038 & .037 & .052 \\
O$^{+}$/O             & .076--.10  & .122  & .125 & .129 & .131 \\
O$^{2+}$/O            & .910--.85  & .784  & .793 & .790 & .773 \\
O$^{3+}$/O            & .014--.03  & .049  & .043 & .043 & .042 \\
\Te(H$^{+}$)/10$^4$ K  & 1.65--1.73 & 1.873 &1.859 &1.896 &1.839 \\
\Te(O$^{0}$)/10$^4$ K  & 1.61--1.14 & 1.040 &1.013 &1.012 &1.003 \\
\Te(O$^{+}$)/10$^4$ K  & 1.63--1.43 & 1.320 &1.315 &1.309 &1.272 \\ 
\Te(O$^{2+}$)/10$^4$ K & 1.66--1.75 & 1.911 &1.915 &1.961 &1.898 \\
\Te(O$^{3+}$)/10$^4$ K & 1.76--2.1  & 2.576 &2.402 &2.449 &2.479 \\
\Ne(H$^{+}$)/\cc      &    99--18  & 17.3  & 11.1 &  9.8 &  9.4 \\
\Ne(O$^{0}$)/\cc      &   99--8.5  & 46.7  & 34.0 & 37.8 & 41.1 \\
\Ne(O$^{+}$)/\cc      &    99--16  & 62.7  & 48.0 & 54.0 & 54.8 \\
\Ne(O$^{2+}$)/\cc     &    99--18  & 15.4  & 10.2 &  8.9 &  8.5 \\
\Ne(O$^{3+}$)/\cc     &   100--19  & 10.1  & 7.4  &  6.3 &  5.7 \\
$t^2$(H$^{+}$)        & .002--.014 & .032 & .026 & .028 & .030 \\ 
$t^2$(O$^{0}$)        & .001--.018 & .022 & .024 & .023 & .020 \\ 
$t^2$(O$^{+}$)        & .0013--.02 & .021 & .024 & .024 & .023 \\ 
$t^2$(O$^{2+}$)       & .002--.008 & .013 & .010 & .010 & .010 \\ 
$t^2$(O$^{3+}$)       & .0010--05  &.0008 &.0006 &.0007 &.0016 \\
\hline
\end{tabular}}
\medskip
$^a$ Constant \Nh. $N0$: \Nh~= 92\cc; $N1$: \Nh~= 17.0\cc.\\
$^b$ \Nh\ from thermal pressure of Eq.~(1).
\end{table}