Left panel shows example of broad Hα with double-peaked profile (in blue) expected by the circular accretion-disk plus spiral-arm model with smaller R_out, but with single-peaked profile (in red) expected by the model with larger R_out2. The applied model parameters, except the R_out and R_out2 marked in the top left corner, are marked in the top right corner. The other panels show the distributions of the model parameters of the 1825 cases that have profiles changed from double-peaked to single-peaked, through the circular accretion-disk plus spiral-arm model.