Authors: JungKwon Oh Kugbo Shim KwangMo Kim JunJae Lee
Publish Date: 2009/08/01
Volume: 55, Issue: 4, Pages: 264-272
Abstract
The knot depth ratio KDR evaluation method was designed to quantitatively evaluate the amount of knot in dimension lumber by a singlepass Xray radiation To verify the proposed method KDR values for 38mmthick specimens were predicted and they were compared with the actual measured KDR values The knot is surrounded by the transition zone and the density of the knot and the transition zone is higher than the clear wood Because the average density of the transition zone was similar to the knot density it was found that the proposed method gives the KDR values for the knot area including the transition zone The coefficients of determination between the predicted and measured KDR values were 087 and 083 for Japanese larch and red pine specimens respectively Using the KDR information the ratio of knot area including transition zone to crosssectional area was calculated The presence of latewood and earlywood in the same path of the Xray radiation caused discrepancies in the estimation of KDR values because the density of latewood is much higher than that of earlywood Fortunately latewood and earlywood are repeated in a cross section so the amount of overestimation and underestimation was expected to be nearly identical As expected the relationship between the predicted area ratio and the real area ratio of knot and transition zone was strong with R2 values of 089 and 093 for Japanese larch and red pine specimens respectively
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