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Figure14. Difference in surface profiles between P&W11 (uncoated) and P&W12 (coated) in the same scan length. 4. Conclusions MAD parameters, such as RMAD and FMAD , exhibit lower variability in surface roughness and friction characterization. In general, surface parameters such as Ra , Rq , and MIU are highly dependent on profilometry measurement conditions. However, MAD parameters for surface roughness and friction provide stable and robust information. The correlation between surface roughness and friction was investigated. The results indicate that surface roughness and friction are independent, with an R² value of 0.264. Even when surfaces have the same average roughness and deviation, frictional resistance varies depending on the contour shape. FD values were successfully calculated using the PSD technique, ranging from 1.13 to 1.27. These values were distinguishable from those obtained using the variogram method for FD analysis of printing paper surfaces. FD values were independent of surface roughness and friction, showing weak correlations with R 2 values of 0.342 and 0.016, respectively. This suggests that FD provides additional information on surface complexity and autocorrelation properties beyond what conventional surface parameters can offer. The roles of surface parameters were confirmed by comparing uncoated and coated paper samples. FD analysis offers a comprehensive understanding of coating effects on printing paper surfaces that is not possible using conventional surface parameters. Future research will focus on FD analysis of tissue products and the separation of roughness scales, including macro-, sub-micro-, and micro-scales. The findings will be reported in a future study. Author Contributions: Y.J.L.: Writing—original draft, Visualization, Formal analysis, Data curation. G.-W.K.: Investigation, Data curation. T.-J.L.: Writing—review & editing, Validation. H.J.K.: Supervi- sion, Conceptualization, Funding Acquisition. All authors have read and agreed to the published version of the manuscript. Funding: This research has been supported by the Ministry of Science and ICT (Information and Communication Technology) of the Korean government and the National Research Foundation of Korea (Grant No. RS-2023-00301889). Data Availability Statement: The raw data supporting the conclusions of this article will be made available by the authors on request. Conflicts of Interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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