## 3 Results and Discussion
### Multi-Objective Optimization  
The MOO problem formulated in Equation (9) was solved with the genetic algorithm using the initial population size of 40. Table 3 shows the controlled parameters of NSGA II. The optimization problem converged to the Pareto optimum set after 146 genetic algorithm generations. In the study, the probability of mutation and crossover and were 0.15 and 0.85, respectively. One hundred and eighty design points formed Pareto set given in Table A1. Figure A1 presents the impact of \(T_{d}\) and \(v_{a}\) on EC, CD, and quality parameters (A\({}_{\text{loss}}\), TAC\({}_{\text{loss}}\), TEC\({}_{\text{loss}}\), TPC\({}_{\text{loss}}\)) of the _Echium amoneum_ petals (data from Table A1). Figure 4 shows the Pareto fronts for EC and CD, A\({}_{\text{loss}}\), TAC\({}_{\text{loss}}\), TEC\({}_{\text{loss}}\), TPC\({}_{\text{loss}}\), respectively. The smallest values of EC were obtained for ID134, ID132, and ID131 (278.3, 288.8, and 295.5 MJ/kg, respectively). It corresponds to the following drying parameters: \(T_{d}\) = 60.00 \({}^{\circ}\)C and \(v_{d}\) = 0.50 m/s, \(T_{d}\) = 59.84 \({}^{\circ}\)C and \(v_{d}\) = 0.50 m/s, \(T_{d}\) = 59.77 \({}^{\circ}\)C and \(v_{d}\) = 0.50 m/s, respectively. However, due to the very small differences between the individual values of drying parameters obtained and the lack of such precise settings, it can be assumed that the best parameters due to energy savings are the following: \(T_{d}\) = 60 \({}^{\circ}\)C and \(v_{d}\) = 0.5 m/s. Assuming that the temperature and velocity of the drying air can be set (in the dryer) with an accuracy of 0.5 \({}^{\circ}\)C and 0.02 m/s, drying at \(T_{d}\) = 60.0 \(\pm\) 0.5 \({}^{\circ}\)C and \(v_{d}\) = 0.5 \(\pm\) 0.02 m/s allows for obtaining _Echium amoneum_ petals with the following parameters: TAC\({}_{\text{loss}}\), TEC\({}_{\text{loss}}\), A\({}_{\text{loss}}\), TPC\({}_{\text{loss}}\), CD, EC: 45.5%, 28.0%, 47.3%, 29.8%, 36.7, and 328.8 MJ/kg, respectively (average values for mentioned ranges of \(T_{d}\) and \(v_{d}\)). \begin{table}
\begin{tabular}{c c c c} \hline
**i** & **D\({}_{\text{i1}}\)** & **D\({}_{\text{i2}}\)** & **D\({}_{\text{i3}}\)** \\ \hline
1 & \(-\)35.560371 & 1.530375 & 35.746782 \\
2 & 5.264209 & \(-\)34.088544 & 9.816984 \\
3 & 22.479106 & \(-\)27.444875 & 6.052853 \\
4 & \(-\)17.140856 & \(-\)32.840889 & 30.725816 \\
5 & 21.678617 & 31.658204 & \(-\)31.391203 \\
6 & \(-\)23.550824 & 28.269281 & \(-\)7.366114 \\
7 & 39.790524 & 16.976584 & \(-\)38.393101 \\
8 & 28.398313 & \(-\)24.399395 & 1.949355 \\ \hline \end{tabular}
\end{table} 
Table 5: Constants (weights and biases) \(D_{\bar{y}}\) in Equation (17). However, additionally taking into account the quality parameters of the obtained dried material, it should be noted that these solutions (as mentioned above, for ECmin.ID134, ID132, and ID131) CD are 36.16, 36.65 and 36.87, respectively, and they are very different from CDmin = 19 (1.90, 1.93, and 1.94 times higher, respectively). Thus, the dried petals obtained at low-energy expenditure (long drying time) are characterized by significant petal color changes (large CD) (see Figure 4b). Pareto front (Figure 4b) indicates the following solutions: ID70, ID75 and ID84, for which EC is 835.6, 804.8, and 766.4 MJ/kg, respectively, and CD are 30.7, 31.6, and 31.8, respectively. These solutions are obtained for the following drying process parameters: air drying temperature 44.47, 45.42, and 45.41 \({}^{\circ}\)C, and air-drying velocity 0.50, 0.51, and 0.50 m/s. However, due to the very small differences between each value of \(T_{d}\) and \(v_{d}\) obtained and the inability to set these parameters so precisely (adjustment by 0.02 \({}^{\circ}\)C and 0.01 m/s), it can be assumed that the best parameters due to the simultaneous energy-saving and color preservation are the following: \(T_{d}\) = 45.5 \({}^{\circ}\)C and \(v_{d}\) = 0.5 m/s.