As The FA results were confirmed by PCA (Table ), showing that the optimal number of output features is two (an expected result, given that the third output phase results from directly from Eq. 3). Because the output correlation is weakest between δ-Al2O3 and the overreacted fraction, those two features were taken as model output parameters, i.e., y2 and y3. Indeed, for an energetically optimal process, there should be a very strong correlation between the target phase and the underreacted fraction, which should linearly decrease at the same rate as the target fraction increases. There should be no overreacted material whatsoever.