# Investigation of a Precise Control Scheme for Rice Quality
## 3 Results and Discussion
### Drying Time
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Response**} & \multicolumn{2}{c}{**Second-Order Polynomial Model Equation**} & \multicolumn{2}{c}{**R\({}^{2}\)**} & \multicolumn{1}{c}{**CV (\%)**} \\ \cline{2-5}  & Y = \(-319.54457\) \(-4.19846\times\) T \(-5.87506\times\) RH + \(51.29726\times\) MC \(-104.10679\times\) V + \(32.72127\) & \multirow{2}{*}{0.9545} & \multirow{2}{*}{6.03} \\ Dtn & \(\times\) TR \(-0.86797\times\) T*MC \(-2.37116\times\) RH*TR + \(0.21134\times\) T\({}^{2}\) + \(0.21234\times\) RH\({}^{2}\) + \(7.41511\times\) TR\({}^{2}\) & & \\ Dtt & \(\times\) = \(-1362.71399\) \(-3.21407\times\) T \(-52.5745\times\) RH + \(185.21498\times\) MC \(-358.36273\times\) V + & \multirow{2}{*}{0.9399} & \multirow{2}{*}{7.05} \\  & 436.73255 \(\times\) TR\(-3.19833\times\) T*MC \(-8.38511\times\) T*TR + \(0.87549\times\) T\({}^{2}\) + \(0.87649\times\) RH\({}^{2}\) & & \\  & Y = \(87.48851\) \(-0.71122\times\) T \(-0.96706\times\) RH \(-3.62912\times\) MC \(-18.85010\times\) V \(-4.08123\times\) TR + & & \\ ACP & 9.76691 \(\times\)\(10^{-3}\) \(\times\) T*MC \(+0.032925\times\) RH*MC \(+0.03909\times\) RH*TR + \(7.81273\times\)\(10^{-3}\)\(\times\) T\({}^{2}\) + & & \\  & 0.041955 \(\times\) RH\({}^{2}\) + \(18.07766\times\) V\({}^{2}\) + \(0.25390\times\) TR\({}^{2}\) & & \\  & Y = \(108.88074\)\(-0.64910\times\) T \(-0.68473\times\) RH \(-0.14540\times\) MC \(-12.91655\times\) V \(-0.16367\times\) TR & & \\  & \(+4.87314\times\)\(10^{-3}\)\(\times\) T\({}^{2}\) + \(8.87314\times\)\(10^{-3}\)\(\times\) RH\({}^{2}\) + \(10.19643\times\) V\({}^{2}\) + \(0.21658\times\) TR\({}^{2}\) & & \\ \hline \hline \end{tabular} For a significance level of 0.05, the interaction terms T*MC and RH*TR, as well as the quadratic terms T\({}^{2}\), RH\({}^{2}\), and TR\({}^{2}\), exhibit significant effects on Dtn; for Dtt, significant effects were observed for T*MC, T*TR, T\({}^{2}\), and RH\({}^{2}\). To enhance the descriptive power of the model and ensure its simplicity and reliability, insignificant interaction and quadratic terms (\(p\) > 0.05) were eliminated to derive a regression equation for each response variable, and the results are presented in Table 5. The Dtn and Dtt regression models demonstrate a remarkably good agreement between the predicted and measured results, with corresponding R\({}^{2}\) values of 0.9545 and 0.9399, respectively. Additionally, the high reproducibility of these models is evidenced by their low CV values (CV < 10%) [24]. The ANOVA results indicate a strong agreement between the fitted models and experimental data for the regression equation.  
\end{table} 
Table 5: Second-order polynomial equation ignoring non-significant terms. Based on the significant interaction terms identified in the ANOVA results, a subset of factors was chosen for further analysis. Utilizing the Design-Expert software, 3D response surfaces and corresponding contours were generated (Figures 3-6). Factors that remained constant throughout the experimentation were set at a level of zero. Increasing the drying temperature was found to be the most effective method of shortening the net drying time, as demonstrated in Figures 3 and 4. Additionally, Dtn values are superior with lower moisture contents and relative humidities, as well as higher tempering ratios. Notably, varying the moisture content and temperature within the low-drying-time region (lower right corner) does not significantly reduce the Dtn values compared to the high-drying-time region (upper left corner), as shown in Figure 3b. Excessive shortening of the Dtn through process adjustments does not result in significant benefits; rather, it could lead to considerable energy consumption, quality degradation, and other issues. Therefore, it is necessary to comprehensively consider these factors [25; 26; 27]. From Figure 4b, it can be observed that increasing the tempering ratio does not enhance the drying process significantly, particularly at low relative humidities.