were designated for the variables as 1, 0, and −1, respectively. Thecoded and actual levels of the independent variables in the BBD experimental design matrix are listed in Table 1.Statistical analysis of variance (ANOVA) and regression modelanalysis were performed, and two-dimensional contour plots weredrawn. It can be seen from pareto chart (Fig. 5), that two interac-tion coefficients (X3X4) and (X2X3) and one linear term coefficient(X2) were significant. Data analysis at 95% confidence level, permit-ted to obtain the following semi-empirical expression in terms ofsignificant coded factors:Y