## 3 Results and Discussion
### Multiple Regression Analyses of Tensile Strength  
Multiple regression is used to statistically analyze the influence of the independent variables (\(X\)) on the dependent variables (\(Y\)). \(X\) refers to independent variables that are represented in \(X_{1}\), \(X_{2}\), \(X_{3}\)..., \(X_{n}\), while \(Y\) refers to dependent variable. In this study, the independent variables (\(X_{1}\), \(X_{2}\), \(X_{3}\)..., \(X_{n}\)) are: Contents of Kevlar(r) fibers, immersion periods, and immersion temperatures. The dependent variable (\(Y\)) is the tensile strength of the nonwoven geotextiles after immersion under the specific conditions considered. Table 5 summarizes the results of multiple regression analyses, where \(B\) is the unstandardized regression coefficient that indicates the coefficient of \(X\). \(\beta\) is the standardized regression coefficient that has a value between \(-1\sim+1\). The greater the absolute value of \(\beta\), the higher the influence level of the dependent variable. The \(F\) value is the result of the \(F\) test, and \(p<0.05\) suggests that the multiple regression result has statistical significance. Adjusted \(R^{2}\) stands for the explanatory power of the independent variables for dependent variables. VIF value represents the \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Solutions**} & \multirow{2}{*}{\(T\) (\({}^{\circ}\)C)} & \multirow{2}{*}{\(P\) (**Months**)} & \multicolumn{2}{c}{**Thermal**} & \multirow{2}{*}{\(NS\)} & \multirow{2}{*}{**AV (N)**} & \multicolumn{2}{c}{**SD**} & \multirow{2}{*}{\(t\)**-test**} & \multicolumn{2}{c}{**Scheff’s Test**} \\  & & & & Treatment & & & & (N) & **(N)** \\ \hline \multirow{8}{*}{H\({}_{2}\)O} & \multirow{8}{*}{23} & 0 & No & 5 & 113.70 & 6.07 & \multirow{8}{*}{\(t\)-test} & \multirow{8}{*}{\(p=0.29\) (non-thermal)} \\  & & 1 & No & 5 & 98.40 & 6.63 & & \\  & & 2 & No & 5 & 98.48 & 14.11 & & \\  & & 3 & No & 5 & 105.99 & 13.87 & & \\  & & 4 & No & 5 & 107.70 & 17.99 & & \\  & & 0 & Yes & 5 & 130.10 & 6.41 & & \\  & & 1 & Yes & 5 & 118.30 & 16.86 & & \\  & & 2 & Yes & 5 & 143.73 & 5.92 & & \\  & & 3 & Yes & 5 & 117.73 & 1.77 & & \\  & & 1 & Yes & 5 & 112.64 & 15.27 & & \\ \hline \multirow{8}{*}{H\({}_{2}\)O} & \multirow{8}{*}{50} & 0 & No & 5 & 113.70 & 6.07 & \multirow{8}{*}{\(p=0.84\) (non-thermal)} \\  & & 1 & No & 5 & 118.98 & 21.99 & & \\  & & 2 & No & 5 & 113.48 & 10.72 & & \\  & & 3 & No & 5 & 120.53 & 21.28 & & \\  & & 4 & No & 5 & 110.51 & 10.42 & & \\  & & 0 & Yes & 5 & 130.10 & 6.41 & & \\  & & 1 & Yes & 5 & 119.70 & 3.25 & & \\  & & 2 & Yes & 5 & 150.57 & 8.28 & & \\  & & 3 & Yes & 5 & 148.03 & 16.80 & & \\  & & 4 & Yes & 5 & 140.13 & 29.51 & & \\ \hline \multirow{8}{*}{CH\({}_{3}\)COOH} & \multirow{8}{*}{23} & 0 & No & 5 & 113.70 & 6.07 & \multirow{8}{*}{\(1<0\) (non-thermal)} \\  & & 1 & No & 5 & 87.75 & 13.60 & & \\  & & 2 & No & 5 & 91.63 & 10.95 & & \\  & & 3 & No & 5 & 93.53 & 10.16 & & \\  & & 4 & No & 5 & 90.52 & 10.79 & & \\  & & 0 & Yes & 5 & 130.10 & 6.41 & & \\  & & 1 & Yes & 5 & 109.15 & 11.24 & & \\  & & 2 & Yes & 5 & 101.37 & 13.07 & & 2, 3, 4 \(<0\) (thermal) \\  & & 3 & Yes & 5 & 95.46 & 8.66 & & \\  & & 4 & Yes & 5 & 94.24 & 9.13 & & \\ \hline \multirow{8}{*}{CH\({}_{3}\)COOH} & \multirow{8}{*}{50} & 0 & No & 5 & 113.70 & 6.07 & \multirow{8}{*}{\(1\), \(2\), \(3\), \(4<0\) (non-thermal)} \\  & & 1 & No & 5 & 94.40 & 12.24 & & \\  & & 2 & No & 5 & 81.95 & 10.25 & & \\  & & 3 & No & 5 & 78.60 & 16.74 & & \\ \cline{1-1}  & & 4 & No & 5 & 74.45 & 8.88 & 0.02 & \\ \cline{1-1}  & & 0 & Yes & 5 & 130.10 & 6.41 & & \\ \cline{1-1}  & & 1 & Yes & 5 & 98.98 & 14.68 & & \\ \cline{1-1}  & & 2 & Yes & 5 & 111.50 & 14.87 & & 1, 3, 4 \(<0\) (thermal) \\ \cline{1-1}  & & 3 & Yes & 5 & 82.94 & 11.05 & & \\ \cline{1-1}  & & 4 & Yes & 5 & 86.04 & 7.26 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Tensile strength and statistical analyses of recycled Kevlar®/PET/LPET nonwoven geotextile that are thermally treated, in relation to different solutions and different immersion periods.