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991.
A simultaneous estimation procedure for the parameters of two functions, i.e., the maximum size–density line and the self-thinning
curve, is presented to predict stand development for fast-growing tropical species. This procedure assumes that the rate of
periodic reduction in stand density with increasing quadratic mean diameter on a logarithmic scale (r) will increase inversely proportionally to the distance from the maximum size–density line and consequently equals the slope
of the line at distance 0. Under this assumption, the maximum size–density line can be incorporated into the self-thinning
curve to form an integrated equation with three parameters: k and m, the slope and constant of the maximum size–density line, and a, the rate of reduction of r of the self-thinning curve. These parameters are estimated simultaneously using measurement data on stand density, quadratic
mean diameter, and the corresponding r. This procedure was evaluated by application to two data sets: 186 measurements of Acacia mangium and 95 measurements of Paraserianthes falcataria, for which the parameters k and m have previously been calculated. The parameters estimated using this procedure were in good agreement with previous ones
based on the A. mangium data set, and the differences found for the P. falcataria data set were also small, within the error variances. Therefore, it is concluded that the proposed procedure would give almost
the same estimates from a single calculation step as the previous procedure that required two separate calculation steps. 相似文献
992.
993.
Takashi Yamasaki Ayumi Enomoto Atsushi Kato Tadashi Ishii Kazumasa Shimizu 《Journal of Wood Science》2011,57(1):76-84
Arabinoglucuronoxylans (AGXs) isolated from the holocellulose of sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa) contained one 4-O-methyl-d-glucopyranosyluronic acid (4-O-Me-d-GlcAp) residue per 6.2 d-xylopyranose (d-Xylp) residues and one 4-O-Me-d-GlcAp residue per 3.8 d-Xylp residues. These AGXs were subjected to partial acid hydrolysis. Analyses by size exclusion chromatography and electrospray-ionization
mass spectroscopy of the neutral sugar fractions in the hydrolysates showed the presence of xylooligosaccharides having a
degree of polymerization of 2-8 in addition to d-Xyl, suggesting that the AGXs from sugi and hinoki contained unsubstituted chains consisting of at least eight d-Xyl residues. The acidic sugars in the hydrolysates were separated into two series of aldouronic acids composed of 4-O-Me-d-GlcAp and d-Xylp by ion-exchange chromatography. The first series included aldouronic acids from aldobiouronic acid (4-O-Me-d-GlcAp-Xyl) to aldopentaouronic acids (4-O-Me-d-GlcAp-Xyl4). The second series were aldouronic acids composed of two 4-O-Me-d-GlcAp residues and 2-4 d-Xyl residues. In these acidic sugars, the uronic acid side chains were located on two contiguous d-Xyl residues. These facts indicated that AGXs from sugi and hinoki had a structural unit containing two 4-O-Me-d-GlcAp residues on two contiguous d-Xyl residues as well as AGXs from spruce and larch. 相似文献
994.
Evaluating the durability of wood-based panels using internal bond strength results from accelerated aging treatments 总被引:1,自引:0,他引:1
In this study, the durability of wood-based panels was evaluated by comparing the internal bond (IB) strength retention after
five different laboratory-based accelerated aging tests with the IB retention after 5 years of outdoor exposure in Shizuoka
City. In each accelerated aging test, the IB retention of MDI-bonded panels showed high retention compared to other panels.
Outdoor exposure in Shizuoka City resulted in an IB retention value for particleboard (PF) and oriented strandboard (aspen)
of less than 10% after the 5-year exposure period. Medium-density fiberboards maintained their initial IB strength over the
same period. Calculation of the mean IB retention for all board types allowed comparison of the severity of aging between
the accelerated test methods and outdoor exposure. The ASTM six-cycle test method was the most severe among the standard treatment
cycles applied. 相似文献
995.
To evaluate windthrow resistance with respect to stem breakage, a nondestructive method for determining the shape of trunk
cross sections was developed. In this method, the coordinates of multiple gauge points set on the perimeter of a trunk are
calculated by measuring the distances between them. The shape between the gauge points is generated with the use of a profile
gauge placed between them. Measurement tests were conducted using profile gauges with lengths of 300 and 900 mm on model specimens
with four shape patterns and four different diameters. The accuracy of the estimation was verified by comparing the section
modulus calculated for the generated image and for the photograph. The average ratio of section modulus (generated/photo)
for all specimens was 0.994, which indicates that the proposed method is highly accurate. The section moduli of hollow trunks
can be evaluated using the profile method together with the drill resistance technique on the condition that 26% of the trunk
diameter could be drilled without skew. 相似文献
996.
Tian-Xiao Meng Shoko Furuta Sayaka Fukamizu Ryoko Yamamoto Hiroya Ishikawa Enos Tangke Arung Kuniyoshi Shimizu Shoji Ohga Ryuichiro Kondo 《Journal of Wood Science》2011,57(5):452-458
Pleurotus citrinopileatus Singer has recently become a popular delicacy in East Asian countries. We prepared a methanol extract, soluble fractions
from the methanol extract, and a hot water extract of the fruiting bodies of P. citrinopileatus. The biological activities such as melanin biosynthesis inhibition, tyrosinase inhibition, antioxidant activities [1,1-diphenyl-2-picrylhydrazyl
(DPPH) radical scavenging, oxygen radical absorbance capacity (ORAC), and superoxide dismutase (SOD)-like activity], antibacterial
activities, and antihyaluronidase activities of these extracts were evaluated. We found that the n-hexanesoluble, diethyl ether-soluble, and ethyl acetate-soluble fractions exhibited melanin biosynthesis inhibition in B16
melanoma cells, as well as antioxidant (ORAC) and antibacterial activities. However, the n-butanol-soluble and water-soluble fractions and the methanol and hot water extracts exhibited antioxidant (DPPH radical scavenging,
SOD-like activity) and antihyaluronidase activities. These results indicate that the fruiting bodies of P. citrinopileatus have the potential to be used as an ingredient in skin cosmetics. 相似文献
997.
Weidong Cheng Xueqing Xing Dehong Wang Kunhao Zhang Quan Cai Guang Mo Zhongjun Chen Zhonghua Wu 《Journal of Wood Science》2011,57(6):470-478
Wood is a highly sophisticated and multihierarchical material. The nanoscale structures in natural cell walls of red pine,
American pine, and white ash specimens were investigated using the small-angle X-ray scattering (SAXS) technique. A tangent-by-tangent
method was used to analyze the SAXS data. The results demonstrate that the multihierarchical scatterers in the three specimens
can be divided into two dominant components, i.e., a sharp component and a wide component. The sharp component mainly corresponds
to the contribution of cellulose microfibrils, and its size is almost unaffected by the water content. However, the wide component
includes voids or microcracks and cellulose microfibril aggregates; its size changes, reflecting swelling and water accumulation
in the voids or microcracks. Because of the different morphological features of the cell walls, softwood (red pine and American
pine) displays different tendencies from hardwood (white ash) in terms of changes in the wide component with water content:
the average scatterer size of the wide component has an incremental tendency with the water content in softwood, but it has
a descending tendency in hardwood. Fractal analysis further revealed that in white ash the surface of scatterers is coarser
and the scatterers form more compact nanostructures than in the two pine woods. All this nanostructural information can be
used to explain well the difference of swelling behaviors between the two pines and the white ash. 相似文献
998.
An air-injection press, which has holes punched in the heating plates, injects high-pressure air through the holes of one
plate into boards during press heating. The air-injection press can manufacture boards from high-moisture-content particles
by controlling blowouts of the boards. In this study, boards were manufactured from particles that had a moisture content
of 25% by using the air-injection press, which reduced the required pressing time. Boards manufactured by injecting air through
holes of 5 mm in diameter were of poor quality with a low internal bond strength of only 0.31 MPa. When the hole diameter
was reduced to 1 mm, the internal bond strength increased to 0.44 MPa. A high air-injection pressure of 0.55 MPa also resulted
in improved board properties over those for boards manufactured at lower pressures. This was probably because a large amount
of binder was released from boards through the 5-mm holes, together with water vapor, during air injection; the small-diameter
holes reduced the release of binder, resulting in better board properties. 相似文献
999.
The dependence of the acidolysis reaction of a C6-C3 dimeric nonphenolic β-O-4 type lignin model compound, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl) propane-1,3-diol (veratrylglycerol-β-guaiacyl ether, VG), on the type of acid applied was examined using three different acids [0.2 mol/l HCl, 0.2 mol/l HBr,
and 0.1 mol/l (0.2 N) H2SO4 in 82% aqueous 1,4-dioxane at 85°C]. In the HCl system, the major reaction modes of the corresponding benzyl cation-type
intermediate (BC), which is produced by protonation of the α-hydroxyl group of VG and successive release of the water molecule, are the abstraction of the β-proton and hydride transfer from the β-to the α-position. The liberation of formaldehyde from the γ-hydroxymethyl group of BC is the predominant reaction mode in the H2SO4 system. Apparently, an unknown reaction mode or modes is operative in the early stage of the HBr system that causes rapid
disappearance of VG accompanied by the quantitative formation of 2-methoxyphenol without affording the common counterpart
of a Hibbert’s ketone, 1-hydroxy-3-(3,4-dimethoxyphenyl) propan-2-one. The reaction mode in the HBr system changes with the
progress of the reaction and is the same as that in the HCl system after the early stage. 相似文献
1000.
Chihiro Kayo Seiji Hashimoto Atsunori Numata Masanori Hamada 《Journal of Wood Science》2011,57(3):234-240
We compared the greenhouse gas (GHG) emissions from a log pile (LP) to those from a sand compaction pile (SCP) and from cement
deep mixing (CDM) as measures against soil liquefaction, assuming that forest and waste management scenarios influence the
GHG (CO2, CH4, and N2O) balance of wood. We found little difference between the LP and SCP methods with respect to GHG emissions from fossil fuel
and limestone consumption. However, GHG emissions from the CDM method were seven times higher than emissions from the LP method.
In the GHG balance of wood, when the percentage of CH4 emissions from carbon in underground wood was lower than 3.3%, permanent storage in the log achieved greater reductions in
GHG emissions than using the waste log as fuel in place of coal or heavy oil. In order to obtain reductions in GHG emissions
by replacing SCPs or CDM with LPs, sustainable forest management with reforestation and prevention of CH4 emissions from the underground log are essential. Using reforestation, permanent storage of the log, no CH4 emission from the log, and using logging residues instead of coal, the LP can achieve reductions in GHG emissions of 121
tonnes of CO2 per 100 m2 of improvement area by replacing CDM. 相似文献