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1.
为合理利用异叶南洋杉人工林木材,通过排水法、质量法和数值法对异叶南洋杉人工林的生材性质展开研究,结果表明,异叶南洋杉人工林木材树皮体积百分率、质量百分率、生材密度、基本密度和生材含水率的平均值分别为11.39%、13.78%、0.842 g/cm3、0.394 g/cm3和121.43%。随异叶南洋杉树高的增加,树皮体积百分率和质量百分率总体呈增大趋势;生材密度和基本密度总体呈下降趋势;生材含水率总体呈先升高后降低的趋势。以期为异叶南洋杉人工林木材的合理利用提供数据支持和理论支撑。 相似文献
2.
The purpose of this study was to use images from a microwave sensor on a pixel level for simultaneous prediction of moisture
content and density of wood. The microwave sensor functions as a line-scan camera with a pixel size of 8mm. Boards of Scots
pine (Pinus sylvestris), 25 and 50mm thick, were scanned at three different moisture contents. Dry density and moisture content for each pixel were
calculated from measurements with a computed tomography scanner. It was possible to create models for prediction of density
on a pixel level. Models for prediction of moisture content had to be based on average values over homogeneous regions. Accuracy
will be improved if it is possible to make a classification of knots, heartwood, sapwood, etc., and calibrate different models
for different types of wood. The limitations of the sensor used are high noise in amplitude measurements and the restriction
to one period for phase measurements. 相似文献
3.
Angela LO MONACO Luigi TODARO Mara SARLATTO Raffaello SPINA Luca CALIENNO Rodolfo PICCHIO 《中国林学(英文版)》2011,13(4):276-284
This study aims to investigate wood density at different levels of moisture, basic density and shrinkage of timber from Turkey oak (Quercus cerris L.) coppice forests growing in Central Italy. We also studied the variability in density in the trees within and among sites. Density shows no significant statistical differences in the tested population. A higher variability in the shrinkage than in the density was found. Wood moisture is referred to as dry mass and fresh mass, which is related to many performance characteristics of wood, i.e., energy production. Trends in moisture and water content were studied because these physical parameters play an important role in the specific area of firewood which requires an accurate estimation of mass, volume and energy content. This work is a contribution to improve xylo-energy estimates of small and medium forestry issues. 相似文献
4.
Roger E. Hernández 《Wood Science and Technology》2007,41(3):249-265
Wood samples of nine tropical hardwoods from Peru and sugar maple wood from Quebec were selected to perform moisture sorption
tests associated with parallel-to-grain and tangential compression tests using a multiple step procedure at 25°C. Cold-water
and hot-water extractives, sequential cyclohexane (CYC), acetone (ACE) and methanol (MET) extracts, ash content (ASH), wood
density and interlocked grain (IG) were evaluated on matched samples too. Wood density corrected for the accessory substances
was by far the major factor positively affecting the compressive properties of tropical hardwoods. The total amount of accessory
substances is required in order to establish better relationships between physico–mechanical properties and density of tropical
hardwoods. For a given wood density, the ultimate stress in parallel-to-grain compression was higher in tropical hardwoods
than in temperate hardwoods. However, the compliance coefficients for both types of woods were quite similar. Sequential extraction
with organic solvents was the most suitable method for evaluating the effect of extractives on compressive properties of tropical
hardwoods. The CYC and ACE fractions did not contribute to variation in these mechanical properties. The substances dissolved
in MET affected positively the compliance coefficient s
11 in parallel-to-grain compression and negatively the compliance coefficient s
33 in tangential compression. The IG decreased the compliance coefficient s
11 but also decreased the ultimate stress in parallel-to-grain compression. Finally, variations in compressive properties that
were due to changes in equilibrium moisture content (EMC) were clearly influenced by wood density; denser woods were more
sensitive to changes in EMC than lighter woods. 相似文献
5.
Julian Moreno Chan John C. Walker Carolyn A. Raymond 《Wood Science and Technology》2011,45(4):609-626
The effects of moisture content from 17 to 159% MC and temperatures from −71°C to +58°C on resonance-based acoustic velocity
and dynamic modulus of elasticity (DMOE) were investigated using 36 boards of radiata pine sapwood. Acoustic velocity decreased
with increasing moisture content and temperature, although effects differed noticeably below and above fibre saturation point
(FSP). Below FSP, acoustic velocity decreased rapidly and linearly with increasing moisture; whereas above FSP changes in
velocity were rather gradual and curvilinear with marked differences in velocity patterns between temperatures below and above
freezing. Acoustic velocity decreased linearly with increasing temperature but there was an abrupt discontinuity at the freezing
point for wood above FSP. Changes in moisture content and temperature affecting wood density and acoustic velocity led to
changes in DMOE, although this relationship was not straightforward because changes of velocity with moisture were linear
or curvilinear and depended on whether wood was frozen or unfrozen, whereas changes of density with moisture content were
invariably linear. For practical work, it is important to estimate the relative effect of changing moisture content or temperature
with respect to standard conditions on DMOE, thus general guidelines were devised to account for significant changes. 相似文献
6.
为了解邓恩桉的木材性质,本研究采用排水法和《GB/T 1930-2009》方法测定邓恩桉的生材含水率、年轮宽度以及木材密度。结果表明：全树生材含水率、年轮宽度、生材密度和基本密度均值分别为114.61%、4.73 mm、1.164 g·cm-3、0.522 g·cm-3。随着树高的增加,年轮宽度、木材密度呈-大-小-大‖趋势,生材含水率呈-小-大-小‖趋势;由髓心向外,木材密度逐渐减小,生材含水率逐渐增大,年轮宽度先增加后减小。4个材性指标在树干径向不同位置间差异极显著,在不同树高间差异不显著（除年轮宽度外）。基本密度与3个材性指标间存在极显著或显著相关。 相似文献
7.
《Wood material science & engineering》2013,8(3):119-127
Abstract This study evaluated the capability of nuclear magnetic resonance (NMR) technology based on small portable magnets for in situ studies of the local moisture content in wood. Low-field and low-resolution [1H]NMR with a unilateral permanent magnet was used to monitor and map the moisture content of wood cladding materials of various types in a spatially resolved manner. The results show that portable NMR equipment based on small open-access permanent magnets can be successfully used for non-invasive monitoring of the moisture content in various extended wood specimens. The moisture content was measured with a depth resolution of 0.2 mm and a maximum penetration depth of 3 mm. This makes the technique suitable for in situ local moisture content measurements beneath a coating layer in the cladding, for example, and it is also possible to relate the moisture level to specific properties of the wood material. 相似文献
8.
《Scandinavian Journal of Forest Research》2012,27(1):14-29
Genetic parameters were estimated for wood and growth traits in two 19-yr-old clonal trials and a 40-yr-old full-sib progeny trial of Norway spruce [Picea abies (L.) Karst.]. In the clonal trials high (>0.4) broad-sense heritabilities were found for wood density traits, lignin content, number of internal cracks, growth traits, spiral grain and number of resin canals. Moderate (0.2–0.4) heritabilities were found for tracheid lumen diameter and cell wall thickness, microfibril angle and tracheid length, while low heritabilities (<0.2) were found for pulp yield, fibre strength, wood stiffness and wood colour. Lignin content and pulp yield showed low genetic variation, whereas the genotypic coefficient of variation for most other traits ranged between 5 and 15%. Most traits showed low levels of genotype by environment interaction. Among the wood properties, latewood proportion, earlywood density and ring density showed significant, adverse correlations with volume in both clonal trials. 相似文献
9.
Steam conditioning of softwood boards after kiln drying is of critical importance for relief of residual drying stresses
and to improve distribution of final moisture content. The conditioning practice in New Zealand includes two steps: immediately
after high temperature (HT) drying the load is cooled until the core wood temperature is 75 to 90°C, and then the stack is
steam conditioned for a period of 1 to 4 hours depending on the lumber thickness and moisture content after drying. In this
work, experimental and theoretical studies were performed to better understand the conditioning process and to investigate
factors which influence its effectiveness. In the experiment, 50 mm thick Pinus radiata sapwood boards were first dried at 120/70°C for 11, 12, 13, 16 and 18 hours, respectively, to varying moisture contents,
and then cooled and steam conditioned for 1 hour. To assess the effectiveness of conditioning, moisture pick-up, moisture
gradient, and transverse residual drying stress (indicated by cup and strain) were measured. It was found that drying wood
to a low moisture content (below 6%) increased the conditioning effectiveness. A separate matched stack was conditioned for
4 hours after 13 hours drying which showed better results than 1 hour conditioning. A mathematical model for wood drying was
extended to include both the cooling and conditioning phases. The model was numerically solved to examine the wood temperature
and moisture content changes during the whole process of drying, cooling and final steam conditioning. Increase in wood temperature,
moisture pickup and moisture gradient during steam conditioning were predicted and validated by the experimental data. This
information is currently being used at the New Zealand Forest Research Institute in simulation of stress development and relief
for drying of Pinus radiata lumber.
Received 6 July 1998 相似文献
10.
J. A. Fuwape 《Agroforestry Systems》1993,22(3):175-179
Charcoal was produced from short rotation tropical species ofLeucaena leucocephala andTectona grandis. The combustion-related properties, moisture content, specific gravity and percentage element composition of carbon, hydrogen, oxygen, nitrogen, sulphur and ash in wood and charcoal from the two species were determined. The gross heat of combustion of wood and charcoal was also determined.There were significant differences in the moisture content, specific gravity and percentage element composition between wood and charcoal from the two species. The carbon and ash content of charcoal were higher than those of wood. The average heat of combustion of charcoal 25.25 MJKg–1 was higher than that of wood 13.75 MJKg–1. 相似文献
11.
In this research, technological properties of glulam beams made from hydrothermally treated poplar (Populus deltoides) wood were investigated. Poplar wood blocks with dimensions of 6 (r)?×?10 (t)?×?73 (l)?cm3 were cut and hydrothermally treated in a stainless steel reactor at temperatures of 140 and 160°C for a holding time of 30?min. The treated wood blocks were initially air seasoned and then they were dried in a semi-pilot scale vacuum dryer to achieve moisture content (MC) of 12%. Conditioning of the treated and the untreated wood blocks was done prior to adhesive bonding. Afterwards the glulam beams (4 ply) were manufactured using polyurethane. In order to evaluate the physico-mechanical properties of the beams, density, equilibrium moisture content, water repellent effect (WRE), anti-swelling effect (ASE), mass loss (ML), wettability as well as surface roughness due to the hydrothermal treatment were determined in the treated wood and delamination, bond shear strength, tensile strength, MC and moisture-induced stresses as well as strains in cross-section of the beams were determined in the glulam beams. The results revealed that density, ML, ASE, WRE, modulus of elasticity, modulus of rupture and delamination were increasing and the others were decreased due to the hydrothermal treatment. 相似文献
12.
Guillermo Riesco Muñoz Marcos Barrio Anta 《European Journal of Forest Research》2010,129(6):1037-1045
Forty young trees from a stand of maritime pine in the southern mountains of Galicia, Spain (42°21′N: 8°01′W) were felled
to obtain the material required for studying density and shrinkage in clear and small wood specimens. The wood ranged from
light to moderately heavy, and the dimensions remained reasonably stable with varying moisture content. The results were consistent
with those obtained in previous studies of adult trees, except for axial shrinkage, which was very high and variable in this
study. The between-tree variation in wood properties was high considering that the sampled trees came from the same stand.
However, the relationships between density and height in the stem were similar in all trees. A general model for the prediction
of volumetric shrinkage was developed, with oven-dry density and ring width as predictor variables. The model is feasible
for estimation of wood quality in living trees. It is applicable to tree selection for thinning and for genetic improvement
of stock. 相似文献
13.
Yutaka Ishimaru Kazutoshi Arai Masato Mizutani Katsuhito Oshima Ikuho Iida 《Journal of Wood Science》2001,47(3):185-191
Some properties of wood (hinoki:Chamaecyparis obtusa) moisture-conditioned by an adsorption process from a dry state and by two desorption processes (from a water-saturated state and from a state with a moisture content slightly below the fiber saturation point) were investigated. The moisture contents of wood conditioned by the adsorption process and by the desorption process continued to approach to one another for the moisture-conditioning period of over 50 weeks. Accordingly, sorption hysteresis should be regarded as a transitional phenomenon that occurs during the process of approaching the true equilibrium, which requires a long time. The wood conditioned by the desorption process beginning from a water-saturated state showed slightly smaller dimensions than those conditioned by the adsorption process with the same moisture content; however, the wood conditioned by the desorption process from a moisture content below the fiber saturation point showed slightly larger dimensions than those conditioned by the adsorption process. The wood conditioned by the adsorption process from a dry state showed a higher modulus of elasticity and modulus of rupture than did the wood conditioned from a water-saturated state with the same moisture content. The mechanical properties of the wood also varied based on the states at which the desorption process was started. This is a notable characteristic of the relation between the drying condition and the mechanical properties of wood. 相似文献
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Context
Australian blackwood (Acacia melanoxylon), is a fast-growing, high-quality, appearance-grade timber species native to eastern Australia. Some of its key wood properties are percentage heartwood, heartwood colour, basic density, wood stiffness and green moisture content. Variation in these properties affects log value, processing and marketing. 相似文献17.
Takaaki Fujimoto Kazuhito Kita Kazuko Uchiyama Makoto Kuromaru Hisashi Akutsu Kazuyuki Oda 《Journal of Forest Research》2006,11(3):157-163
Age trends in variance components and heritability of overall wood density, earlywood and latewood density, and latewood proportion
were investigated in 29-year-old trees of 19 full-sib families of hybrid larch (Larix gmelinii var. japonica × Larix kaempferi) F1. The age–age correlation and optimum selection age for these traits were also estimated and genetic and phenotypic correlations
between wood density and radial growth rate were calculated for each growth ring. Intraring wood density data were obtained
using X-ray densitometry. The coefficient of additive genetic variance was stable over all ages, whereas the coefficient of
environmental variances gradually decreased with increasing age, resulting in increases in heritability estimates with age
for overall density. The latewood proportion had the highest heritability estimates at all ages, ranging from 0.44 to 0.66.
Overall density and its various components at 28 years of age showed strong genetic correlations with their respective traits
at all younger ages. Optimum selection ages for the wood density traits ranged from 8 to 14 years, at which point maximum
gain efficiencies per year were obtained. There were negative correlations between wood density and radial growth rate at
early ages, although these relationships tended to be weaker with increasing age. These results suggest that selection at
a young age is effective for wood density, but particular care must be taken in selecting trees with an improved radial growth
rate because rapid growth will result in a low-density wood product, especially in the early growth period. 相似文献
18.
A literature study on the feasibility of treating wood with aqueous solutions at high moisture levels revealed a positive indication. The objective of the present study was to determine treatability of Pinus radiata and P. pinaster lumber at high moisture levels with commercial CCA in controlled experiments. The wood samples were treated at levels of moisture content ranging from 20 to 100%. A statistical analysis of the data showed that specific gravity and moisture content influence solution-absorption, the effect being different for different species. Chemical analyses showed a screening out of copper- and arsenic compounds. The effect of higher moisture contents on screening out was negligible. The results indicated that certain wood species can be treated satisfactorily with CCA at moisture levels higher than 25%. 相似文献
19.
《Scandinavian Journal of Forest Research》2012,27(1-4):403-419
Seventy‐four half‐sib families of lodgepole pine (Pinus contorta ssp. latifolia Engelm.) plus trees were measured for vigour, height growth, stem diameter, wood density and ring width in two Swedish field trials at age 9. Height growth, wood density and ring width differed between families within provenances with variance components of 3–8 %. Coefficients of variation were highest for height growth and lowest for ring width. Heritabilities were similar for height growth and wood density but lower for ring width. These genetic parameters seemed to be equal for all provenances. Indirect selection for high dry stem biomass was more effective using height growth than wood density, and a correlated response in wood density of 2.1 % of mean by selecting the 15 highest parent trees was indicated. Juvenile wood density looks uncertain as a selection criterion for mature wood density. 相似文献
20.
Understanding the green moisture content and wood density is important for effective forest management. Radial distribution
patterns in the green moisture content (MC) and basic density (BD) in stems of red cypress (Chamaecyparis formosensis) were investigated in 69 plantation trees that were 46 years old. An increment core was collected from each sample tree at
breast height (1.3 m). Five radial positions were defined: pith piece (Pith), inner heartwood (IHW), outer heartwood (OHW),
intermediate wood (TSH), and sapwood (SW). Results showed that the average MC was highly dependent on the individual tree. Average values of the MC obtained from the TSH were significantly lower than those for the other positions. The MC of heartwood was higher than that of SW. Distribution patterns of the MC in the radial direction varied among trees. Radial variations in MC and BD were greater than in between-tree variations. Six types of radial distribution patterns of MC were detected for sample trees. MC values increased with decreasing BD (except for the TSH). Positive correlations were found between adjacent sampling positions in both MC and BD. 相似文献