318,322 research outputs found
Rational production of veneer by IR-heating of green wood during peeling: Modeling experiments
No full textHeating green wood logs by infrared (IR) radiation during peeling for veneer production has been numerically simulated, focusing on the heating kinetics of a green wood cylinder rotating with a decreasing radius. The results confi rm those of previous experiments, that this kind of heating is a promising alternative to soaking wood prior to peeling. The model integrates the green wood parameters such as moisture content, density, distribution and ratios of earlywood and latewood, on the one hand, and the peeling conditions of veneer thickness and peeling speed, on the other. The following heat transfer processes were considered: conduction within the bolt, external heating by the IR source, and convection between the bolt surface and the external environment. The outputs were the temperatures of the bolt surface and of layers several millimeters deep. For maximal heat penetration, the bolt should turn in front of the IR source before cutting starts and the IR source should be positioned at the greatest angular distance ahead of the knife. Several heating scenarios could be simulated by the model, thus it is a useful decision-making tool for the design of an in-line IR heating system installed on the peeling lathe.Institut Carnot ARTS, RYM-TO Doctoral Schoo
Natural weathering of soft- and hardwoods modified by contact and flame charring methods
No full textPublisher Copyright: © 2022, The Author(s).Exterior cladding boards benefit from a known service life that makes planning of maintenance and replacement procedures easier. Among the different wood modification methods, surface charring of wood is expected to increase the lifespan of wooden elements in building façades. This paper reports the properties of surface charred Norway spruce, Scots pine and Silver birch in Southern Finnish climate over a natural weathering period of one year. Several modifications were examined, namely variants of contact and flame charring. These also included oiled and brushed surfaces. The flame charred samples of spruce and birch withstood the weathering well, with some minor flaking and cracking. The thick pine samples cracked extensively regardless of modification, raising questions on suitable density and thickness of wood destined for a charring modification. Contact charring did not seem suitable for outside uses at least in direct sunlight, as the colors faded, and surfaces cracked within all examined groups. The spectroscopical methods employed also revealed degradation of contact charred wood lignin, whereas the flame charred surface consisted mostly of recalcitrant carbon structures rather inert towards weathering. This highlights the importance of sufficient structural degradation of wood components in creating a weathering resistant surface, and also shows that a thicker thermally modified layer does not necessarily improve the weatherability in contact charred wood.Peer reviewe
What share of the wood imports into EU is covered by the EUTR?
No full textIn 2003 the EU proposed the Action Plan on Forest Law Enforcement, Governance and Trade (FLEGT) to combat illegal logging. In March 2013 the European Timber Regulation (EUTR) came into effect as a main mechanism of FLEGT. The objective of this study is to quantify the share of all wood and wood-based product imports into the EU to which the EUTR applies. We defined the scope of the wood-based products based on the definition of the forest-based sector and aggregated them to twelve product groups. We then calculated EUTR coverage ratios for three different reference units: import value (Euro), roundwood eq. and wood fibre eq. Our results show that approximately 90% of total imported wood quantities are covered by the EUTR. This means that 6 million m³ wood fibre eq. (17 million m³ roundwood-eq.) not covered by the EUTR were imported into the EU in 2013. Coverage ratios for product groups differ. Typically raw materials have a higher coverage ratio and finished products a lower coverage ratio. The wood not covered by EUTR is highly concentrated on a few commodities like wood charcoal, articles of wood, n.e.s. and printed books and brochures. The regional import structure of the EU differs between total imports and imports that are not covered by the EUTR. Eastern and South-Eastern Asia and Africa are gaining importance when looking at imports not covered by the EUTR
Land-use regression modeling of wood smoke in Rochester, NY
No full textDuring the last decade, a substantial rise in the use of wood for space and water heating followed the increased cost of fossil fuels in Northern America. The use of this renewable source of energy has many
advantages related to the carbon cycling, greenhouse gas emissions and climate. However, emissions from wood combustion sources may seriously impact air quality. The relationships between wood
smoke exposure and health effects have been studied: epidemiology suggests that the toxicity of wood combustion particles is similar to urban particulate matter. During the 2015/16 heating season, ambient particulate matter (PM) concentrations were measured at 23 sites across the Monroe County using low-cost monitors. Data were corrected based on the results of previous calibration studies. The corrected data were assessed to have good reproducibility, 10% precision and 10 μg/m3 limit of detection. Most of the sites showed clear diurnal patterns with higher concentration in the late afternoon and evening hours. Weekly pattern were more variable, but a general decrease of concentrations was found during the weekends. The hourly and weekly patterns of PM were spatially interpolated. The results show that ambient PM concentrations are generally higher over the more densely urbanized areas of the county. Data were then used as input for a land use regression model. Raster surfaces (spatial resolution 10 x 10 m) were developed for a series of predictors which are potentially related to the concentration of PM, including number of bedroom, fireplaces, kitchens, property value, property year built, road type and road traffic densities, elevation and density of various land cover data features. Circular buffers were calculated around the 23 sampling sites with radius ranging from 50 m to 5000 m (50 m steps) and buffer statistics were computed. Pearson correlation coefficients were calculated between hourly and weekday averages of PM concentrations and the statistics of predictors for all the buffers. In general, the relationships between PM concentrations and the predictors are moderate and comparable with the results of previous studies. A Deletion/Substitution/Addition (D/S/A) algorithm was then used to maximize the prediction accuracy for locations without measurements
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Wood density and fiber length in young populus stems: relation to clone, age, growth rate, and pruning
No full textCross-sectional disks were cut at two stem heights (1.5 m and 3.0 m) from 9-year-old trees of three Populus clones grown in an intensively-cultured plantation in western Washington. At age 1.5 years, when the trees averaged 3.4 m tall, half of the trees were pruned by removing all branches below 1.8 m. Ring width, wood density, and fiber length were measured for each ring. Pruning had no effect on mean ring width or wood properties, averaged over the entire disk or on rings produced during the 2nd through the 4th years. Averaged over all trees, wood density of the 1.5 m sample was 0.37 g cm-3 during the first 3 years, decreased somewhat at age 4 or 5, and then increased to an average of 0.45 g cm-3 at age 9. Fiber length increased from 0.57 mm at age 1 to nearly 1.0 mm at age 9. Averaged over all disks at 1.5 m, clones differed significantly in ring width, wood density, and fiber length. Mean values for the two wood properties at 3.0 m were slightly lower than those at 1.5 m and did not differ significantly among clones. Within clone correlations between ring width and wood density or fiber length or between wood properties were low, and generally non significant or inconsistent.Keywords: clones, fiber length, pruning, ring width, wood density, populus, sampling heigh
Heritage Society (Houston)
No full textTranscript of Letter from William B. Wood to William M. Rice discussing his difficulties with finding enough labor to work his land. He asks if Mr. Rice could provide enough labor or help him sell his land (if he cannot do the former)
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Do Douglas-fir branches and roots have juvenile wood?
No full textWe sampled boles, branches, and roots of four Douglas-fir (Pseudotsuga menziesii var. menziesii) trees to learn a) whether branches and roots have a zone of juvenile wood, defined as a zone with progressive changes in wood density and/or tracheid length from the pith outward at successively greater cambial
ages, and if so, b) whether the radial patterns in branches and roots are similar to those in boles. Samples came from the following positions: bole, 30 cm aboveground; branch, 30 cm outward on the lowest live branch, and root, 1–3 m from the bole. Average sample cambial ages were bole, 60 years; branch, 30
years; and root, 48 years. Roots and branches had higher density wood than did the bole at the positions studied, and roots had the longest tracheids followed by the bole and then the branches. All three positions exhibited juvenile wood but with different radial patterns. All positions had their highest density near the
pith, which was followed by a steep decline in the boles and a more gradual decline in the roots and branches. Boles and roots, but not branches, then showed an increase in density after this decline. Boles and branches had short tracheids near the pith followed by a gradual increase to an asymptotic value. In
contrast, tracheid length in roots was relatively constant from pith to bark, although there was a dip of about 20% from about cambial ages 14 to 24. This study shows that the vascular cambium of this species is not constrained to produce one sole radial pattern of wood properties as it matures. The presence of
different radial patterns in boles, branches, and roots supports the hypothesis that juvenile wood in the bole is an adaptive feature rather than an unavoidable developmental consequence. Further work should investigate more fully the different physiological or mechanical roles of the various wood types within the context of the position in the tree at which they occur.Keywords: root, branch, density, juvenile wood, specific gravity, tracheid length, Douglas-fi
Mid-infrared absorption properties of green wood
No full textThere is a lack of quantitative data on the penetration depth and the amount of energy absorbed by green wood under infrared (IR) radiation. This lack of knowledge is a potential barrier to the development of IR heating as an alternative to soaking as a means of warming logs prior to peeling in the manufacture of plywood. Experimental measurements of normal hemispherical spectral reflectance and transmittance over the range 550–5,500 cm-1 wavenumbers on four wood species, beech, birch, Douglas-fir and spruce have brought new knowledge on mid-infrared absorption properties of green wood and removed some uncertainties. For instance, it is not possible to deliver energy deeper than up to 0.3 mm below the wood surface because 70–90 % of all incident IR radiation on the wood surface is absorbed in this layer. Some wood features, such as surface quality, the presence of knots and of free water in wood (the latter two having a more significant effect) influence the amount of energy absorbed. These results illustrate that IR radiation can heat the surface layers, but then heat penetrates deeper into the inside layers of wood by conduction.Institut Carnot ARTS, RYM-TO Doctoral Schoo
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