Panel (a): Examples of the simulated double-peaked broad emission lines in different phases according to the elliptical accretion disk model. The solid lines in different colors show the line profiles in different phases with different orientation angles ω, as shown in the legend in the top right corner. Panels (b) and (c): Dependence of the first moment λ₀ and the second moment σ on the orientation angle ω for the case shown in panel (a). The solid blue circles show the λ₀ and σ calculated through simulated results with 30 randomly collected values of ω, and the solid red line shows the best descriptions of λ₀(ω) and σ(ω) based on applications of a sine function plus a linear trend. Panels (d), (e), and (f): Corresponding results according to the circular accretion disk plus arms model.