## 6 Discussion  
From the top 10 optimal design parameters (Table 3), it is observed that when the optimization is based only on the averaged reflection coefficient (\(100\%:0\)), minimal reflection is observed when the porous plate is comparatively long around \(l/h=2.0\), with inclined angles of \(6.40^{\circ}\) for \(H/\lambda=0.02\). However, for \(H/\lambda=0.02\) and \(H/\lambda=0.03\), the optimal non-dimensional plate length (\(l/h\)) is reduced to \(1.49\) and \(1.76\) with an optimal inclined angle of \(5.48^{\circ}\) and \(7.82^{\circ}\), respectively. This optimal configuration based on (\(100\%:0\)) might minimize reflection but increase the spatial footprint that a wave absorber occupies. When the optimization significantly prioritizes the reflection coefficient over the spatial footprint (\(80\%:20\%\)), the optimal non-dimensional plate length (\(l/h\)) is substantially reduced to \(1.16\), with a slight decrease in the inclined angle to \(4.79^{\circ}\) for \(H/\lambda=0.01\). This change results in a slight increase in the reflection coefficient but a significant reduction in the spatial footprint. However, for \(H/\lambda=0.02\), the optimal non-dimensional plate length and inclined angle show insignificant change, resulting in minimal changes to both the reflection coefficient and the spatial footprint. For \(H/\lambda=0.03\), the optimal non-dimensional plate length and inclined angle decrease slightly, along with a reduction in the corresponding spatial footprint, while the reflection coefficient increases slightly. When the optimization is performed with a \(20\%\) preference for the reflection coefficient over the spatial footprint (\(60\%:40\%\)), the reduction in the optimal non-dimensional plate length and inclined angle is the same as in the previous weighting ratio for \(H/\lambda=0.01\). Whereas, for \(H/\lambda=0.02\) and \(H/\lambda=0.03\), the optimal non-dimensional plate length (\(l/h\)) is substantially reduced to \(0.52\) and \(0.58\), with an increase in the inclined angle of \(15^{\circ}\) and \(14.93^{\circ}\), respectively. This results in a greater increase in the reflection coefficient but a substantial reduction in the spatial footprint. Based on the observations, the optimal design parameters of weighting factor ratios (\(80\%:20\%\)) appear to be a more reasonable choice, effectively balancing the tradeoff between the reflection coefficient and the spatial footprint criteria. These results provide optimal design parameters based on the relative importance of the criteria, which will facilitate the decision-making process according to specific preferences.  
Based on Figure 10, all reflection coefficients are maintained below 0.2 within the entire range of the wave period. The reflection coefficient of the steeper wave is lower, which implies that wave steepness (or nonlinearity) significantly influences overall performance. The averaged reflection coefficients across the wave period range of 1.0-5.0 s are 0.145, 0.109, and 0.128 in ascending order of wave steepness at \(l/h=1.16\) and \(\theta=4.79^{\circ}\). With another optimal value of \(l/h=1.46\) and \(\theta=5.34^{\circ}\), the averaged reflection coefficients are  
Figure 10: The reflection coefficient of a top-ranked wave absorbing system selected with a weighting factor ratio of (\(80\%\):\(20\%\)) as a function of wave period and wave steepness.  
0.139, 0.084, and 0.083 with increasing wave steepness. The final optimal design parameter of \(l/h=1.64\) and \(\theta=6.27^{\circ}\) gives the averaged reflection coefficients of 0.142, 0.091, and 0.078. Among the three options for optimal design parameters of the wave absorber, \(l/h=1.46\) and \(\theta=5.34^{\circ}\) seems to be the most effective solution.