To control reliably the suitable use of curved laminated veneer lumber (LVL) as a structural member of furniture, stress distributions and failure types of curved LVL made from massion pine (Pinus massoniana Lamb.) and fast-growing poplar (Populus euramericana CV. I.) were investigated under end-pull, end-thrust, and transverse loading. The results are summarized as follows: In curved LVL of two wood species, absolute values of the maximum axial stress (
A) occurring at the convex surface are smaller than those (
B) that occurred at the concave surface. The differences between these values decrease with an increase in the radius of curvature. With end-pull loading, there were mainly splitting failures at glue lines near the centroidal axis. With end-thrust loading, there were more fibrous fractures on the tensile side and crushing failures on the compression side. With transverse loading, curved specimens of massion pine exhibited mainly splitting failures. In contrast, for curved LVL of fast-growing poplar, fibrous fractures occurred mainly on the tensile side. Absolute values of
A and
B significantly increased with an increase in the radius of curvature. In contrast, absolute values of the maximum radial stress (
R,) decreased with an increase in the radius of curvature. Absolute values of
A,
B, and
R of curved LVL of massion pine were larger under end-thrust loading than under end-pull and transverse loading. Conversely, absolute values of
A and
B of curved LVL of fast-growing poplar were small under end-thrust loading. However, absolute values of
A and
B of curved LVL of two wood species under end-pull loading were almost similar to those under transverse loading.Part of this study was presented at the 10th annual meeting of Chugoku Shikoku branch of the Japan Wood Research Society, Miki, Kagawa, September 25, 1998 and the 4th Pacific Rim Bio-Based Composites Symposium, Bogor, Indonesia, November 2–5, 1998 相似文献
Two new betaine-type amphoteric surfactants — betaineN,N'-dihydroxyethyl-N-ethyl fatty acid ester and ammoniumN-(fatty acid ester) ethyl-N,N-bis (2-hydroxyethyl)-3-(2-hydroxypropyl) sulfonate — were synthesized using tall oil fatty acids as the raw materials. Processing conditions suitable for synthesizing the intermediates and final products were probed. In addition, the chemical structures of the intermediates and the final products were identified by infrared spectroscopy, hydrogen nuclear magnetic resonance spectroscopy, and elemental analysis. 相似文献
The reactivity of previously prepared antiserum against agatharesinol, a norlignan, was determined by competitive inhibition–ELISA (enzyme-linked immunosorbent assay) using several natural compounds that are representative of plant extractives as competitive inhibitors. The antiserum strongly reacted with some norlignans (i.e., agatharesinol, hinokiresinol, and metasequirin C), each of which has a common chemical-structural unit. This result suggests that the antiserum recognizes the specific chemical-structural unit composing those norlignans. Moreover, differences in the reactivities of the antiserum with agatharesinol derivatives and synthetic chalcones propose the trans-3-p-hydroxyphenyl-1-phenylpropene structural unit as the major antigenic determinant for the antiserum.Part of this paper was presented at the 45th Lignin Symposium, Matsuyama, October 2000 and the 51th Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001 相似文献
We investigated the growth response ofMelaleuca cajuputi Powell to flooding at 3 sites in a tropical swamp in southern Thailand. The relative growth rate (RGR) in height tended to be higher where the water level was higher. The maximumRGR in height was achieved during the flood period at the 2 sites where water levels were higher than at the other site. The
height growth ofM. cajuputi was not reduced by flooding, but enhanced. No decline in growth due to post-anoxic injury was observed after flooding.Melaleuca cajuputi may have mechanisms to tolerate rhizospheric oxygen deficiency and to avoid post-anoxic injury.
This study was supported by a Grant-in-Aid for Basic Research (No. 09NP0901) from the Ministry of Education, Science, Sports,
and Culture of Japan. 相似文献
The formaldehyde off-gassing properties of various wood products were evaluated under environment conditions that simulate
conditions of mobile home. The formaldehyde concentrations observed in the chamber were correlated to the 24-h desiccator
formaldehyde potentials. It was found that 24-h desiccator values did correlate to formaldehyde levels in the chamber at a
given temperature, relative humidity, air change rate, and sample loading. The 24-h desiccator method correlated to each other
for a given wood product. Formaldehyde levels of wood products tested in combination reflected the levels of the highest single
emitter. Formaldehyde concentrations from combinations of particleboards and plywood panels may be predicted from their single
chamber K factor using the modified Hoetjer equation. Double loading of a single wood product did not double the chamber concentration
at the low air change rate and sample loading. Finally, the formaldehyde concentrations observed in the chamber under conditions
that simulated mobile loadings of wood product, air change rate, temperature, and humidity relate to real wood formaldehyde
levels. 相似文献
We quantified structural features and the aboveground biomass of the deciduous conifer, Metasequoia glyptostroboides (Hu and Cheng) in six plantations in central Japan. In order to derive biomass estimates we dissected 14 M. glyptostroboides trees into three structural components (stem wood, branch wood and foliage) to develop allometric equations relating the mass of these components and of the whole tree to diameter at breast height (DBH). We found robust relationships at the branch and whole tree level that allow accurate prediction of component and whole tree biomass. Dominant tree height was similar within five older (>40 years) plantations (27–33 m) and shorter in a 20-year-old plantation (18 m). Average stem diameter varied from 12.8 cm in the youngest stand to greater than 35 cm in the oldest stand.
Metasequoia have relatively compact crowns distributed over the top 30% of the tree although the youngest stand had the deepest crown relative to tree height (up to 38%). At the individual tree level in older stands, 87% of the aboveground biomass was allocated to the stem, 9% to branch wood and 4% to foliage. We found little difference in the relative distribution of above ground biomass among the stands with the exception of lower foliage biomass in larger diameter trees. Total aboveground biomass of the older stands varied twofold, ranging from a maximum of 450 Mg ha−1 in a 42-year-old stand to a minimum of 196 Mg ha−1 in a 48-year-old stand. Total above ground biomass of the 20-year-old stand was 176 Mg ha−1. 相似文献
To clarify the biosynthesis of syringyl lignans and lignan formation by stereoselective coupling of monolignols, formation of (+)-syringaresinol and (+)-pinoresinol inLiriodendron tulipifera were investigated by means of feeding experiments. Following individual administration ofl-[U-14C]phenylalanine and [8-14C]sinapyl alcohol to excised shoots ofL. tulipifera and their subsequent metabolism for 3h, free [14C] lignans and [14C] lignan glucosides were extracted from both of the stems and leaves with methanol and divided into an ether fraction and an aqueous one, respectively. The glucosides were hydrolyzed by a combination of cellulase and-glucosidase to liberate [14C]lignans as aglycones.l-[U-14C]Phenylalanine was incorporated into free (+)-[14C]syringaresinol and its glucosides; the (+)-[14C]syringaresinols in the stems and leaves had 52% enantiomeric excess (% e.e.) and 42% e.e., respectively; and the (+)-[14C]syringaresinol aglycones from the glucosides in the stems and leaves had 20% e.e. and 22% e.e., respectively. Furthermore, [8-14C]sinapyl alcohol was incorporated into (+)-[14C]syringaresinol and its glucosides in the stems. These results suggest that the (+)-enantiomer of syringaresinol was enantioselectively formed from two molecules of sinapyl alcohol inL. tulipifera followed by transformation into the (+)-syringaresinol glucosides, accompanying the formation of racemic syringaresinol by nonselective coupling and the subsequent transformation of the racemate into their glucosides.l-[U-14C]Phenylalanine was incorporated also into free (+)-[14C]pinoresinol and its glucosides with 12%–42% e.e.Part of this paper was presented at the 47th Annual Meeting of the Japan Wood Research Society, Kochi, April 1997 相似文献