## 3 Results and Discussion
### EMI SE Statistical Analysis  
The weight percentage of GNP, ZrO\({}_{2}\), and BC are the input parameters, while EMI Shielding Effectiveness is the output parameter. The DOE tool was an RSM model, the central composite design approach. Table 6 depicts the various levels of input parameters used. Using Minitab software, ANOVA was used to determine the effects of the weight percentage of GNP, ZrO\({}_{2}\), and BC on the EMI shielding effectiveness of flexible bio-based polyurethane foam. Table 7 represents the ANOVA findings, and the \(p\)-value is 0.6, indicating that all the data and the model are statistically significant and fit the experimental results. As shown by the findings, the model may be used to predict the results with a 95% confidence level. In Figure 6, the contour plots indicate the interaction between the input parameters and output response. Figure 6a shows a maximum EMI value greater than 26 dB for the composition of GNP with a weight of 0.1-0.5 percent and ZrO\({}_{2}\) with a weight of 0.1-0.17. Figure 6b shows a maximum EMI value greater than 26.5 dB for the composition of GNP with a weight of 0.45-0.5 percent and BC with a weight of 0.5-0.6 percent. Finally, Figure 6c shows a maximum EMI value greater than 27.5 dB for the composition of BC with a weight of 2.3-2.5 percent and ZrO2 with a weight of 0.45-0.5 percent. The regression equation produced using ANOVA is Equation(8). In Equation(8), A, B, and C represent the weight percent of GNP, ZrO\({}_{2}\), and BC, respectively. It forecasts EMI values by substituting the corresponding weight percent from Table 6. Table 8 compares the actual EMI values acquired through the experimental investigation with the expected EMI values obtained from Equation (8). The Electromagnetic Interference value has been employed for numerical analysis, since it is directly related to the EMI SE. Table 8 demonstrates that the highest error % between the real and statistically predicted electromagnetic interference is less than 5%, demonstrating the regression equation's validity. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Code**} & \multirow{2}{*}{**Parameters**} & \multicolumn{5}{c}{**Levels**} \\ \cline{3-6}  & & \(-\)**2** & \(-\)**1** & **0** & **1** & **2** \\ \hline A & Graphite nanoplates (wt.\%) & 0.1 & 0.2 & 0.3 & 0.4 & 0.5 \\ \hline B & Zirconium Oxide (wt.\%) & 0.1 & 0.2 & 0.3 & 0.4 & 0.5 \\ \hline C & Bamboo Charcoal (wt.\%) & 0.5 & 1 & 1.5 & 2 & 2.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Different levels of nanoparticles worn in flexible bio-based polyurethane foam. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Source** & **DF** & **Sum of Squares** & **Mean Square** & **F-Value** & \(p\)**-Value** \\ \hline Model & 9 & 2.17432 & 0.241591 & 0.78 & 0.644 \\ \hline Linear & 3 & 0.59970 & 0.199900 & 0.64 & 0.605 \\ \hline A & 1 & 0.01921 & 0.019208 & 0.06 & 0.809 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: ANOVA for electromagnetic interference (dB). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Specimen** & **Reflection Coefficient (R) (dB)** & **SE Reflection (SEref) (dB)** \\ \hline Free Air Medium & 2.73–20.25 & \(-\)2.38\(\sim\)\(-\)12.84 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Diagnostic calculation of Reflection Coefficient (R) and Shielding Effectiveness Reflection (SEref) from Equations (1) and (4).