## 4 Conclusions  
The proposed stationary excitation subsystem (two strong magnets) was placed directly above the tested rebar (with no movement during measurement). Compared to typical MFL systems (Figure 9), this change allows for the magnetizing of only the tested  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Correctness of** & **84\%** & **89\%** & **87\%** & **80\%** & **75\%** & **70\%** & **68\%** & **69\%** & **66\%** \\ \(A\) (\(B_{x}\)) & & & & & & & \\ \(C\) (\(B_{x}\)) & & & & & & & \\ \(O\) (\(B_{x}\)) & & & & & & & \\ \(A\) (\(B_{y}\)) & & & & & & & \\ \(C\) (\(B_{y}\)) & & & & & & & \\ \(O\) (\(B_{y}\)) & & & & & & & \\ \(A\) (\(B_{z}\)) & & & & & & & \\ \(C\) (\(B_{z}\)) & & & & & & & \\ \(O\) (\(B_{z}\)) & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 6: Efficacy of sample models for the identification of the class of alloys.  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **NB** & **C4.5** & **MLP** & **RBF** \\ \hline \(D\) & 81 & 89 & 85 & 86 \\
**CLASS** & 90 & 93 & 94 & 93 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Efficacy of sample models for the identification of class and diameter.  
Figure 24: Regression analysis of ACO parameters in the function of \(h\): (a) \(A\), (b) \(C\), and (c) \(O\).  
rebar. As an effect, the influence of adjacent rebars in the reinforcement grid on measurement results is strongly reduced, allowing for effective measurements for both single rebars and dense reinforced meshes.  
The extraction of association rules can be utilized in the initial stages of any non-destructive testing (NDT) investigation. The presented algorithm enhances the understanding of the underlying processes and can be applied for attribute selection (the obtained results are comparable to those achieved through traditional Infogain filters). Additionally, association rules facilitate the detection of unobvious but significant dependencies and correlations.  
The developed system (both hardware and software components) enables the highly accurate identification of concrete cover thickness and satisfactory precision in determining the reinforcement alloy and rebar diameter class. The decision tree algorithm demonstrated the highest performance compared to other classification methods.  
The developed methodology is universal and can be used in any NDT investigation.  
While the results are promising, further research is warranted to enhance and validate these findings.  
Project management and administration, P.K.F.; concept of the magnetic method, T.C. and P.K.F.; concept of the presented methodology, and algorithms, P.K.F.; concept of the paper, P.K.F.; software development (measuring system), T.C. and P.K.F.; software development (identification), P.K.F.; simulations, T.C.; hardware development, T.C. and P.K.F.; experiments and measurements, P.K.F.; data curation, P.K.F.; formal analysis, P.K.F.; investigation, P.K.F.; resources, T.C. and P.K.F.; visualization, P.K.F. and T.C.; writing--original draft preparation, P.K.F.; writing--review and extensive editing, T.C., P.K.F., P.M., M.M. and T.S.; scientific consultation, T.C.; contribution of the authors in %: P.K.F.--60%, T.C.--20%, P.M.--9%, M.M.--9%, T.S.--2%. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Science Centre (in Polish: NCN--Narodowe Centrum Nauki), program: Preludium, grant number 2021/41/N/ST7/02728 (\"Smart support system for the Magnetic Force Induced Vibration Evaluation (M5)--an electromagnetic, non-destructive method designed for the evaluation of composite materials containing ferromagnetic and conductive elements\").  
Not applicable.  
Data availability Statement: Data are available upon request.  
The authors declare no conflicts of interest.