• Journal of the Korean Wood Science and Technology
• /
• v.39 no.2
• /
• pp.132-139
• /
• 2011

This study examined the characteristics of radio-frequency/vacuum dried Korean red pine ($Pinus$ $densoflora$) heavy timbers with 250 ${\times}$ 250 mm (S), 300 ${\times}$ 300 mm (L) in cross section and 300 mm in diameter, and 3,600 mm in length, which were subjected to compressive loading after a kerf pretreatment. The following results were obtained : The drying time was short and the drying rate was high in spite of the large cross section of specimens. The moisture gradient inall specimens was gentle in both longitudinal and transverse directions owing to dielectric heating. The shrinkage of the width in the direction perpendicular to was 21 percent ~ 76 percent of that of the thickness of square timbers in the direction parallel to the mechanical pressure. The casehardening for all specimens was very slight because of significantly reduced ratio of the tangential to radial shrinkage of specimens and kerfing. The surface checks somewhat severely occurred although the occurrence extent of the surface checks on the kerfed specimens was slight compared withthat on the control specimen.

• Journal of the Korean Wood Science and Technology
• /
• v.16 no.1
• /
• pp.9-20
• /
• 1988

Lespedeza species have been widely used not only as plant resources for bark, leaves and honey, but also as erosion control materials. This study was carried out to investigate the structural and wood tiber characteristics in order to obtain basic information for the utilization of the wood. The wood structure was investigated for 10 selected species and the wood fiber, for the 5 selected species among Lespedeza species distributed all over the country. The following results were obtained. In the cross section, campylotropis showed ray diffuse porous wood, L. bicolor, L. cyrtobotrya, L. thunbergii var. intermedia, diffuse porous wood, and L. tomentella, L. angustifolioides. L. maritima, L. robusta, L. patentibicolor, ring porous wood. The maximum diameter of a single vessel ranged 66-123 ${\mu}$ in all species. Campylotropis showed the most number of vessels, L. angustifolioides, the least. The number of ray per mm ranged 7-22, Campylotropis showed the most number of rays, L. angustifolioides, the least. In the radial section the average length of vessel ranged 121-250 ${\mu}$ in all species. L. thunbergii var. intermedia showed the longest vessel, L. tomentella, the shortest. In tangential section the average width of the uniseriate ray ranged 9.2-14.7${\mu}$, that of the multiseriate ray, 19.2-42.1 ${\mu}$. The average height of the uniseriate ray ranged 143.0-1162.0 ${\mu}$. The width of fiber ranged 10.12-13.61 ${\mu}$, L. maximowiezii showed the narrowest tiber, L. thunbergii var. intermedia. the widest, the thickness of fiber wall ranged 2.93-3.71 ${\mu}$ in the five species. L. maximowiezii showed the most thin fiber wall, L. thunbergii var. intermedia, the thickest, L. cyrtobotrya showed the difference in the size of fiber between the shade and the sunny sites but L. maximowiezii showed no difference. There was significant difference in fiber length, fiber width and wall thickness between L. eyrtobotrya and L. maximowiezii.

• Journal of the Korean Wood Science and Technology
• /
• v.40 no.1
• /
• pp.53-59
• /
• 2012

This study used pine wilt disease damaged trees as raw materials. The damaged woods were subjected to soaking treatment using wood vinegar, nematicide and sea water, fumigated treatment using fumigation, and the bending strength and hardness of the timber were measured at different points of time after the treatment. In soaking treatment, the highest bending strength was obtained from wood vinegar (100 fold dilution)-soaked specimens of Pinus densiflora and the nematicide-soaked specimens of Pinus thunbergii. The highest hardness in cross section was gained from the nematicide-soaked specimens of Pinus densiflora and Pinus thunbergii, the highest hardness in radial section was obtained from the nematicide-soaked specimens of Pinus densiflora and wood vinegar (100 fold dilution)-soaked specimens of Pinus thunbergii, and the highest hardness in tangential section was obtained from the nematicide-soaked specimens of Pinus densiflora and Pinus thunbergii, and there were not significantly different among the treatments. When fumigated treatment was applied, bending strength, hardness was somewhat lower in the control but were not significantly different between the treatments.

• Journal of the Korean Wood Science and Technology
• /
• v.44 no.3
• /
• pp.295-301
• /
• 2016

In this study, relationship between seed origin and growth rate of Alnus glutinosa from different seed collection (Yugoslovia, ltaly, United Kingdom, Bulgaria) was investigated with focused on anatomical properties as wood fiber length, vessel element length and diameter. Alnus glutinosa showed diffuse-porous wood with scalariform perforation in alternate pitting. Ray height was 9~11 in tangential section and ray number were 16~26 in cross section. There were no differences on latewood focused on wood fiber length, length and diameter of vessel element, but difference on earlywood. Other than Yugoslavian seed, there was better growth rate with shorter wood fiber and vessel element length on latewood. However, seed from Yugoslovain showed better growth rate with longer wood fiber and vessel element length than other 3 seed orgins.

• Journal of Korean Society of Forest Science
• /
• v.77 no.3
• /
• pp.283-293
• /
• 1988

Anatomical features of the secondary xylem were described in the branches, stems, and roots of Salix glandulosa and Quercus variavilis. In Quercus variavilis, the stem shows ring-porous wood, while the root shows diffuse-porous wood. In both species, it is found that the boundaries between the growth rings are not well defined in the roots. Both vessel elements and fibers are the longest in the roots followed by the sterns and the branches in turn and diameter of vessel elements shows the same trend. In cross section, the number of vessels per unit area are the longest in the branches followed by the stems and the roots in turn as well. Perforation plates are simple in both species and their angles are wide in the root, intermediate in the stems, and narrow in the branches. In tangential section, height of rays is taller in the roots than in the stem and branches.

• Journal of Forest and Environmental Science
• /
• v.21 no.1
• /
• pp.98-103
• /
• 2005

Anatomical properties of kenaf cultivated in Korea was investigated using light microscopy. Bast fiber, phloem ray and cortex parenchyma cell were observed in bast, and vessel, wood fiber and ray in core. A lot of solitary and multiple radial pores in core existed. The cell type of ray parenchyma in radial section was procumbent, upright and square cells. Uniseriate and multiseriate rays existed in tangential section. The layer of bast fiber in bast increased with increasing the growth period.

• Journal of the Korean Wood Science and Technology
• /
• v.30 no.2
• /
• pp.95-101
• /
• 2002

Physical and mechanical properties of major Korean ash species were examined. For Fraxinus rhynchophylla and Fraxinus sieboldiana, green moisture content of sapwood was almost the same value as heartwood. Heartwood of Fraxinus mandshurica, however, had slightly higher moisture content than sapwood. Green and oven dry densities of F. mandshurica were lower than those of F. rhynchophylla and F. sieboldiana. Swelling and shrinkage of sapwood in F. sieboldiana showed somewhat higher value than those of F. rhynchophylla. Longitudinal compressive strength and modulus of elasticity in F. sieboldiana were lower values than those in the other species. Shearing strength in radial section was higher than that in tangential section of all samples. It could be noted that shearing strength of F. sieboldiana demonstrated higher value than that of the other species. Three species had excellent bending properties in MOR and MOE. Impact bending absorbed energy for F. rhynchophylla and F. mandshurica did not show any significant differences.

• Journal of the Korean Wood Science and Technology
• /
• v.17 no.2
• /
• pp.26-33
• /
• 1989

The acoustic absorption coefficient and acoustic impedance of 5 species of softwood(sonamoo, sam namoo, gusang namoo, hwaback, sitka spruce) and 5 species of hardwood (Mulgusul namoo, Italian popular, white meranti, red meranti, kalantas) were measured by the standing wave method. which is simple in the setup and gives more accurate result than does any other measuring method. The dependence of the absorption coefficient and complex acoustic impedance on the wood sections. thickness of the sample itself and the back air gap was investigated experimentally in the frequency range from 200Hz to 1800Hz, and the result are as follows: 1. The acoustic absorption coefficient of wood sections was higher on the cross section than radial and tangential sections. 2) The acoustic absorption coefficient were higher in the frequency range from 400Hz to 600Hz, but decreased in the frequency above 600Hz. 3. The genenal tendency of the variation of the normal acoustic impedance was increased according to the frequency. 4. The acoustic absortion coefficient was increased in the to 7mm-thick sample and decreased in 9mm-thick sample. 5. The higher acoustic absorption coefficient was shown in the case with the backing an gap than in the case without the gap.

• Advances in aircraft and spacecraft science
• /
• v.2 no.4
• /
• pp.427-443
• /
• 2015

The present paper is the follow-on of a former work in which the influence of the gas-surface interaction models was evaluated on the aerodynamic coefficients of an aero-space-plane and on a section of its wing. The models by Maxwell and by Cercignani-Lampis-Lord were compared by means of Direct Simulation Monte Carlo (DSMC) codes. In that paper the diffusive, fully accommodated, semi-specular and specular accommodation coefficients were considered. The results pointed out that the influence of the interaction models, considering the above mentioned accommodation coefficients, is pretty strong while the Cercignani-Lampis-Lord and the Maxwell models are practically equivalent. In the present paper, the comparison of the same models is carried out considering the dependence of the accommodation coefficients on the angle of incidence (or partial accommodation coefficients). More specifically, the normal and the tangential momentum partial accommodation coefficients, obtained experimentally by Knetchel and Pitts, have been implemented. Computer tests on a NACA-0012 airfoil have been carried out by the DSMC code DS2V-64 bits. The airfoil, of 2 m chord, has been tested both in clean and flapped configurations. The simulated conditions were those at an altitude of 100 km where the airfoil is in transitional regime. The results confirmed that the two interaction models are practically equivalent and verified that the use of the Knetchel and Pitts coefficients involves results very close to those computed considering a diffusive, fully accommodated interaction both in clean and flapped configurations.

• Journal of the Korean Wood Science and Technology
• /
• v.42 no.1
• /
• pp.58-67
• /
• 2014

We investigated the mechanical properties of Korean red pine (Geumgangsong, Pinus densiflora forma erecta Uyeki) of Uljin province in Korea as a basic research to investigated the material properties. Compressive strength of Korean red pine was $36.2N/mm^2$, which was slightly lower than the pine (Pinus densiflora S. et Z.) in Korea. The compressive strength of Korean red pine showed the maximum value at a distance of 60 mm from the pith. Bending strength of Korean red pine was $76.5N/mm^2$, which was slightly higher than the pine (Pinus densiflora S. et. Z.) and nut pine (Pinus koraiensis) in Korea. Similar to the compressive strength, bending strength of Korean red pine showed the maximum value at a distance of 60 mm from the pith. On the other hand, the shearing strength showed the maximum value at part of including the pith. This result does not coincide with the results of compressive and bending strength, in consideration of the specific gravity, which is consistent. Surface hardness of Korean red pine was $43.7N/mm^2$ in cross section, $12.0N/mm^2$ in radial section and $13.7N/mm^2$ in tangential section respectively. The mechanical properties of Korean red pine were similar to the pine and nut pine having a similar specific gravity. The mechanical properties were greatly affected on the specific gravity than the annual ring width.