Modeling and Comparing Vertical Density Profiles


  • Paul M. Winistorfer
  • Timothy M. Young
  • Esteban Walker


Vertical density profile, nonparametric regression, cubic spline, oriented strandboard, furnish moisture content, press closure rate


The vertical density profile of pressed wood panels is influenced by the manufacturing process and is important to panel end-users. Modeling the vertical density profile and making statistical comparisons among profiles resulting from different manufacturing treatments are critical to understanding and improving panel properties. Nonparametric regression analysis was used to model the vertical density profile of aspen (Populus tremuloides) oriented strandboard panels. A methodology is presented to compare vertical density profile curves. Twenty-seven laboratory panels were manufactured at 608 kg/m3 incorporating three levels of furnish moisture content (4%, 8%, 12%) and three levels of press closure rate (20 s, 60 s, 100 s) in a replicated, experimental design.

The nonparametric regression technique called cubic splines was used to fit the data, R2 ranged from 0.985 to 0.998. Detailed discussion is presented that describes the method and interpretation of the nonparametric regression analysis. Statistical comparison of vertical density profile curves among treatment levels revealed that the 4% furnish moisture content level was significantly different (P = 0.015) from the 8% and 12% levels; the 8% level was not significantly different (P > 0.99) from the 12% level. Vertical density profile curves for all press closure rate treatments were significantly different (P < 0.003).


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