A study of colour assessment, using the CIEL*a*b* system, was conducted with samples of Eucalyptus grandis wood thermally treated by the Brazilian industrial process of thermal modification, VAP ...HolzSysteme®, at three different temperatures, i.e. 140, 160 and 180 °C. Previous to the treatment, the samples were classified into three groups according to their distance to the wood pith, on the radial direction. All thermally modified samples presented a noticeable colour change, confirmed by high values of ΔE*. As the intensity of the treatment increased, the eucalypt samples presented an increase of red colour tone (a*) (up to 160 ºC) and a decrease of colour lightness (L*). Significant colour differences were found among the classified groups, for both untreated and thermally modified samples. The eucalypt samples groups showed different colour responses when thermally treated at 140 and 160 ºC. At 180 ºC the groups didn’t show a significant colour response variation.
• Key message
We designed a novel method allowing to automatically detect and measure defects on the surface of trunks including branches, branch scars, and epicormics from terrestrial LiDAR data by ...using only high-density 3D information. We could automatically detect and measure the defects with a diameter as small as 0.5 cm on either oak (Quercus petraea (Matt.) Liebl.) or beech (Fagus sylvatica L.) trees that display either rough or smooth bark.
• Context
Ground-based light detection and ranging (LiDAR) technology describes standing trees with a high level of detail. This provides an opportunity to assess standing tree quality and to use this information in forest inventory. Assuming the availability of a very high level of detail, we could extract information about the surface defects, mainly inherited from past ramification and having a strong impact on wood quality.
• Aims
Within the general framework of the development of a computing method able to detect, identify, and quantify the defects on the trunk surface described from 3D data produced by a terrestrial LiDAR, this study focuses on the relevance of the whole process for two tree species with contrasted bark roughness (
Quercus petraea
(Matt.) Liebl. and
Fagus sylvatica
L.) in terms of detection, identification of the defects, and comparison with measurements performed manually on the bark surface.
• Methods
First, a segmentation algorithm detected singularities on the trunk surface. Next, a Random Forests machine learning algorithm identified the most probable defect type and allowed the elimination of false detections. Finally, we estimated the position, horizontal, and vertical dimensions of each defect from 3D data, and we compared them to those observed directly on the trunk by an operator.
• Results
The defects were detected and classified with a high accuracy with an average
F
1
score (harmonic mean of precision and recall) of 0.74. There were differences in computed and observed defect areas, but a much closer agreement for the number of defects.
• Conclusion
The information about the defects present on the trunk surface measured from terrestrial LiDAR data can be used in an automated procedure for grading standing trees or roundwoods.
Veneers are used as overlaying material for various types of composite substrates for the production of veneered panels and furniture. There is a strong correlation between color and quality for the ...acceptability of a product, which is currently an industrial preoccupation. The aim of the present study was to evaluate the color variability of veneers produced from high-quality European oak logs exhibiting the best production yield. Defect-free logs cut from a Quercus spp. forest in Romania were sliced into veneers. Color measurements were made at various locations on veneer sheets. All data were statistically analyzed. As expected, heartwood highly influenced the final color of decorative oak veneers, in which yellow and red were highlighted. The statistical analysis also revealed the homogeneity of lightness and yellow degree within the veneer collectivity. The color homogeneity within the sectors confirmed the wood quality for veneer production. Therefore, individual veneer sheets can be segregated based on color measurement to provide accurate results for sorting pieces of different colors.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This study develops a high performance grading process based on the analysis of acoustic vibrations in the audible frequency range. The unique feature of the method is that the spectrum is directly ...applied to obtain predictive variables for estimating the modulus of elasticity and modulus of rupture. A partial least squares regression was used. This powerful method represents a compromise between principal component regression and multi-linear regression. Partial least squares regression screens for factors which account for the variance in the predictor variables and achieves the best correlation between factors and predicted variable. The method is based on projections, similar to principle components regression, whereby a set of correlated variables is compressed into a smaller set of uncorrelated factors.
Growth rate, wood relative density and tracheid length variation were examined for three species: black spruce (Picea mariana (Mill.) B.S.P.), white spruce (Picea glauca (Moench) Voss), and tamarack ...(Larix laricina (Du Roi) K. Koch), from two drained wetland sites of north-central Alberta. Increased rates in radial and volume growths were noted for tamarack, white spruce and to a lesser extent, black spruce. The increases were particularly remarkable in younger trees. Accompanying the rapid growth, wood relative density and tracheid length tend to decrease after drainage, at least for a period of several years. In certain trees, the marked decreases in wood relative density might affect the end use of the trees. Key words: drainage, radial growth, volume growth, wood relative density, tracheid length.
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