218,541 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
Carroll D. Wood
No full textPortrait, head and shoulders. On verso: 6''31. ba 1879 deceased. Carroll D. Wood. Supreme Justice (Ark.) [engr. Instr.].Carroll D. Wood (1858-1941) was on the Arkansas Supreme Court for over thirty-five years. He may be best known for his unsuccessful candidacy for Arkansas governor in 1904. He graduated from the University of Arkansas in 1879 and was admitted to the Arkansas bar in 1880. Afterwards, he and one of his brothers practiced law in Monticello, Arkansas. In 1882, he was elected prosecuting attorney for the Tenth District of Arkansas. He assumed the position of circuit court judge in 1886. He was elected to fill the newly created Position No. 4 on the Arkansas Supreme Court in 1893. He served on the court until his retirement in 1929. In 1934, he served as chairman for Arkansas Adjustment Board of the National Recovery Administration
Letter from W. D. Wood, Troy, Alabama, to H. D. Clayton, December 23, 1878
No full textW. D. Wood also enclosed with this letter a letter from, W. Molenty, Elba, Alabama, to W. D. Wood, December 22, 1878
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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[Telegram from Bill Wood to Hermine D. Tobolowsky, December 2, 1959]
No full textTelegram from Bill Wood to Hermine D. Tobolowsky discussing an upcoming meeting regarding constitutional amendments
Chemical Characterisation of Compression Wood in Plantation Grown Pinus Radiata
No full textThe primary objective of this study was to find out if changes in chemistry could be used to quantify Pinus radiata compression wood severity or degree of compression wood development. Basic chemical composition and the lignin structure was assessed for a range of different compression wood samples sourced from juvenile wood, mature wood, earlywood, latewood, branches, knots, 2-year and 1-year old Pinus radiata. Fluorescence microscopy was used as the reference method to assess the degree of compression wood development. Lignin structure of compression wood was studied by thioacidolysis, size exclusion chromatography, and thioacidolysis/31P NMR spectroscopy.
Variation in the basic chemical composition and lignin structure with compression wood severity was ascertained. Results showed that, as the severity of compression wood changed, progressively from normal through mild to severe, all chemical parameters commonly associated with compression wood changed concurrently. With increasing severity lignin and galactose levels increased while glucose and mannose levels decreased.
Lignin structural changes were also associated with changing severity of compression wood. Levels of p-hydroxyphenyl (H) releasable β-ethers increased and guaiacyl (G) releasable β-ethers decreased. Similarly, levels of uncondensed p-hydroxyphenyl units increased, while uncondensed guaiacyl units decreased. Similar proportions of condensed guaiacyl units were present in compression wood and normal wood. Similar trends in chemical composition were observed between the compression wood and related opposite wood in branches, knots and young wood of Pinus radiata.
A number of chemical parameters changed linearly with compression wood severity. They were: the amount of lignin and galactose, the galactose/glucose ratio and p-hydroxyphenyl content in lignin. Parameters based on the p-hydroxyphenyl unit content in lignin, the H/G releasable β-ether ratio, releasable p-hydroxyphenyl β-ether units and uncondensed p-hydroxyphenyl C9 units are most suitable indicators of compression wood severity as they spanned a larger range relative to the normal wood levels and were not influenced by the morphological origin of wood samples. Chemical methods for quantifying compression wood severity should focus on the detection and measurement of these parameters.
Galactan present in Pinus radiata compression wood was isolated and characterised. Structural investigation by methylation analysis and NMR spectroscopy revealed that this galactan was largely composed of (1→4)-linked β-D-galactopyranose residues. No evidence was found to indicate the presence of any branches.
Characterisation of lignin in cell wall fractions of Pinus radiata normal wood revealed that middle lamella lignin has a higher lignin content, a lower amount of releasable β-ethers and a more condensed lignin than the secondary wall lignin. Levels of releasable p-hydroxyphenyl units were not higher in middle lamella lignin.
A new method based on thioacidolysis and 31P quantitative NMR spectroscopy for estimation of the degree of lignin condensation of the phenolic and etherified C9 units in in situ wood lignin is described. Using this method it was found that phenolic C9 units in in situ lignin were considerably less condensed than etherified C9 units in both compression wood and normal wood
Immunofluorescence Localization of β-(1-4)-d-Galactan and Xylans in Tension Wood and Normal Wood Fibres of Leucaena leucocephala
No full textThe distribution pattern of β-(1-4)-D-galactan and xylans in the fibres of tension wood and normal wood of Leucaena leucocephala was investigated using immunofluorescence microscopy. Light microscopic observation of tension wood fibres revealed that they are characterized by the presence of typical non-lignified, tertiary wall layer. LM-5 labelling of normal fibres showed weak labelling from the cell wall, indicating less concentration of β-(1-4)-D-galactans or masking effect due to co-polymerization of other polymers. Both less substituted (LM-10) and highly substituted (LM-11) xylans found to be distributed more in the secondary wall region, while compound middle lamella showed weak labelling. In tension wood fibres, LM-5 labelling revealed strong signals from tertiary wall layer, indicating that gelatinous layer contains more amount of β-(1-4)-D-galactans. The lignified secondary wall and compound middle lamellae showed weak labelling with LM-5. Labelling of xylans with LM-10 showed intense fluorescence signals from the lignified secondary wall, while gelatinous layer showed weak labelling, indicating less concentration of xylans in the gelatinous layer. In conclusion, in addition to the generalized concept that the G-layer in tension wood fibre is rich in cellulose, our results showed that constitution of pectins and xylans is also different compared to the secondary wall of normal wood fibres.</p
Electrical resistance characteristics of thermally modified wood
No full textThis paper presents electrical resistance characteristics of ThermoWood (R) Thermo-D Norway spruce for wood moisture content measurements below fibre saturation point. Electrical resistance along the grain of small clear wood specimens was measured at various moisture content levels of similar to 4-15% for thermally modified and similar to 5-25% for unmodified spruce. The results show that-similar to unmodified wood-the relationship between wood moisture content and electrical resistance can be well described by a first order polynomial function obtained from simple linear regression. This provides accurate resistance-based predictions of thermally modified wood moisture content. In addition, established temperature corrections derived previously from unmodified wood seem applicable to thermally modified wood
The physical and biological function of wood in New Zealand's forested stream ecosystems
No full textSince the arrival of humans approximately 1000 years before present (B. P.), New Zealand has lost approximately 80% of its forest cover and along with it, the contribution of wood to our aquatic ecosystems. The aim of this thesis was to undertake a large catchment-scale assessment of LW loadings, spatial distribution and morphological influence in an old-growth indigenous forest to provide some understanding on the natural characteristics of wood that would have been present in many river systems of New Zealand prior to human settlement. The second component of the thesis involved the experimental removal of wood from three small streams in order to provide some insight into what that loss of wood may have meant for fish and aquatic invertebrate communities. In the first part of the study, a catchment scale survey of large wood (LW) was completed in a 5thorder, old-growth forest river system. LW volumes ranged from 59-503 m³ ha⁻¹ and declined down the river system along with the number of LW pieces suspended across the channel and LW influence on channel morphology, whereas piece frequency, number of pieces in debris dams and length increased. Nearly half the pieces were influencing channel morphology, particularly wood accumulation, sediment storage, bank armouring, and pool formation. These key pieces were larger, longer and more stable than average. LW contribution to habitat complexity was highest in the middle to upper sections of the river system. Four key zones of wood distribution and influence were identified in the river system. Zonal boundaries were influenced by changes in transport capacity, fluvial processes and channel morphology. In the second part of the study, a field trial was established in three small forested streams to measure the influence of wood and its experimental removal on channel morphology, and indigenous fish and aquatic invertebrate communities. Prior to wood removal there were no significant differences in the total density of fish between wood pools (pools with wood cover), open pools and riffles. Total fish biomass was marginally significant with most of the fish biomass located in wood pools. At the species level, the density and biomass of banded kokopu (Galaxias fasciatus) and the weights of longfin eels (Anguilla dieffenbachii) were significantly higher in wood pools. Species richness, density and biomass of bluegill bullies (Gobiomorphus hubbsi), torrentfish (Cheimarrichthys fosteri) and the density of redfin bullies (Gobiomorphus huttoni) was highest in riffles. Differences in fish community composition were greatest between riffles and pools, whereas there was considerable overlap between the two pool types. Total invertebrate density was 70% higher in debris dams than riffles prior to wood removal, but this difference was not significant. Densities of Trichoptera (caddisfly) and Plecoptera (stonefly), and five aquatic invertebrate taxa were significantly higher in debris dams which also contained greater numbers of less common taxa (< 1% total catch) than riffles. Only Deleatidium sp. (Ephemeroptera) densities were significantly higher in riffles than in debris dams. Aquatic invertebrate communities in debris dams differed significantly from those in riffles and season had a significant influence on aquatic invertebrate community structure. Removal of wood and associated debris dams from the treatment sections in each of the three streams resulted in a simplified channel morphology, significantly increasing the length and area in riffles and reducing the area of pools. The impact on the fish community was greatest for the two larger fish, banded kokopu and large longfin eels, whose abundance declined in the treatment sections. At the reach scale, only banded kokopu biomass showed a significant decline following wood removal. Invertebrates were less affected by wood removal and associated loss of debris dams. Invertebrate composition in the remaining riffles in the treatment sections had a higher proportion of Ephemeroptera and lower proportions of Trichoptera, Plecoptera and Diptera with fewer rare species than remaining debris dams in the control sections, but there were no discernable effects on invertebrate densities and functional feeding groups at the reach scale. Public perception of wood in waterways is mainly negative and wood is managed primarily to reduce flood damage in New Zealand’s streams. With continued research and advocacy on the environmental benefits, careful planning and judicial use, there is the potential to make better use of wood to rehabilitate and enhance New Zealand’s stream environments. This thesis provides some insight into the contribution of wood to forested stream ecosystems in New Zealand and the implicit losses associated with forest removal. It also contributes to our global understanding on the role of wood, its contribution to habitat heterogeneity and influence on biological communities
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