• Journal of the Korean Wood Science and Technology
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• v.39 no.3
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• pp.252-257
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• 2011

Tests were carried out on domestic wood samples to modify the formula which had previously been developed to predict the withdrawal strength of screw on the face of lumber. Screw sizes were No. 6, 8 and 10 used in this study. Predicted equations were fitted to the results of different length of No. 8 wood screw. The withdrawal strength of screws was enabled to predicted as a function of screw diameter, depth of penetration, and specific gravity of wood. Predicted equation was under-predicted the withdrawal strength of 25 and 30 mm length of screw within 5% and over-predicted withdrawal strength of 18 and 38 mm length of screw.

• Journal of the Korean Wood Science and Technology
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• v.30 no.3
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• pp.104-108
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• 2002

Nail withdrawal tests were conducted on clear wood of domestic small diameter logs. Nails were driven into the cross and longitudinal sections of each specimen, then nail withdrawal tests were performed. Nail withdrawal loads are strongly dependent on the direction of nail positions. The average load values for the nail withdrawal both in cross section and longitudinal section are higher in high specific gravity (SG) wood of sawtooth oak (Quercus acutissima Carr.) than those in low SG wood of Korean red pine (Pinus densiflora Sieb. et Zucc.) and pitch pine (Pinus rigida Mill.). The average ratio of the nail withdrawal loads for side-grain and end-grain are higher in the low SG wood than that in the high SG of wood. Both linear and non-linear regression analyses were conducted on nail withdrawal load with SG, good correlations were obtained between nail withdrawal load and SG.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.399-408
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• 2017

Research on the rapid and accurate prediction of physical properties of wood using near-infrared (NIR) spectroscopy has attracted recent attention. In this study, partial least squares analysis was performed between NIR spectra and air-dried specific gravity of five domestic conifer species including larch (Larix kaempferi), Korean pine (Pinus koraiensis), red pine (Pinus densiflora), cedar (Cryptomeria japonica), and cypress (Chamaecyparis obtusa). Fifty different lumbers per species were purchased from the five National Forestry Cooperative Federations of Korea. The air-dried specific gravity of 100 knot- and defect-free specimens of each species was determined by NIR spectroscopy in the range of 680-2500 nm. Spectral data preprocessing including standard normal variate, detrend and forward first derivative (gap size = 8, smoothing = 8) were applied to all the NIR spectra of the specimens. Partial least squares analysis including cross-validation (five groups) was performed with the air-dried specific gravity and NIR spectra. When the performance of the regression model was expressed as $R^2$ (coefficient of determination) and root mean square error of calibration (RMSEC), $R^2$ and RMSEC were 0.63 and 0.027 for larch, 0.68 and 0.033 for Korean pine, 0.62 and 0.033 for red pine, 0.76 and 0.022 for cedar, and 0.79 and 0.027 for cypress, respectively. For the calibration model, which contained all species in this study, the $R^2$ was 0.75 and the RMSEC was 0.37.

• Journal of the Korea Furniture Society
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• v.10 no.1
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• pp.57-63
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• 1999

This study was carried out to analyze the relationship between basic physical properties and acoustical characteristics of imported violin wood and to offer the information on raw material procurement and incoming-material quality control to domestic violin makers which have purchased most raw materials from European exporting countries at high expense. Equilibrium moisture content of European spruce with lower specific gravity after the prolonged storage was rather higher than that of European maple with higher specific gravity. The specific gravity of spruce increased with decreasing annual ring width, however, that of narrower annual ring. Increasement in specific gravity enhanced the dynamic Young's modulus of both wood species, but influenced the vibration energy loss by internal friction differently between two species. For dynamic MOE, qurater-sawn spruce was higher than the flat-sawn, but maple showed the reverse directional characteristics. Consequently, it would be well for violin makers to establish the standard for materials and quality control system to assure the quality of their violin products.

• Journal of the Korean Wood Science and Technology
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• v.14 no.2
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• pp.36-42
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• 1986

Both the control and heated specimen of oak, hornbean, alder, poplar, red pine and pitch pine among domestic commercial species and taun imported were used for radial and tangential shrinkage and movement that occurred on changing the relative humidity of the atmosphere from 90 percent to 60 percent at $25^{\circ}C$. The results of this study were as follows. 1. The radial and tangential shrinkage of the control and heated hornbean and oak wood, except alder, of high specific gravity showed greater than species with low specific gravity. The ratio of tangential to radial shrinkage was 1.46 for taun to 2.70 for alder. Green volume specific gravity of the heated and soaked specimen of all species except poplar decreased 1.5 to 3.1 percent. Shrinkage of the heated specimen increased more than that of the control specimen, and antishrink efficiency of all timbers except alder had negative value. Shrinkage from green to air dry of treated specimens increased more than case of total shrinkage, and radial shrinkage of those specimen increased greater than tangential shrinkage. 3. The movement of the heating specimen for 120 hours decreased than those of the control and the heating specimen for 240 hours. The movement of heating oak, poplar, red pine and pitch pine (or 240 hours increased rather than those of the control specimen.

• Journal of the Korea Furniture Society
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• v.23 no.3
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• pp.324-331
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• 2012

The domestic pine was used to investigate the change of specific gravity, moisture contents, color and anatomical structure by accelerated weathering test (AWT). According to visual inspection, a few knot separation and looseness as well as considerable surface discoloration was found out. However, the crack and split of surface texture have been never occurred till the last step of AWT. On the whole, as the time of accelerated weathering test has increased, the specific gravity has decreased. Finally, after the 9th week of AWT, the specific gravity was 0.38 that reached to 82% compared to the control specimen. In case of moisture content (MC), it showed rising trend in its early stages, however, after 3th week of AWT it have displayed steady state. A deterioration of cell-wall components was not remarkably observed by scanning electron microscope (SEM), however the ray fractures of AWT specimen were observed more than those of control specimen. The full fracture of epithelial cell around resin canal was observed by optical microscope. The fracture of ray of 2th cycle AWT specimen was first, followed by 1th week and control group. A distortion of tracheid for early spring wood and fracture of epithelial cell were generally observed by a similar level, regardless of duration time of AWT. Therefore, it is obvious that increasing duration time of AWT does not affect the deterioration of micro-structure for wood members from this study. Although a considerable change of anatomical properties was not found, there is a need of further research to understand how will the changes of specific gravity and MC on the physical properties of wood member.

• Nuclear Engineering and Technology
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• v.5 no.2
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• pp.150-158
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• 1973

General physical properties and radiation durabilities of some domestic woods and imported lauans were measured and discussed as a preliminary study on the preparation of W. P. C. The data obtained indicate that 1) the hardness of wood is generally proportional to the specific gravity and to the bending strength, 2) the hardness of wood measured in tangential direction to the annual ring increases along with the distance from the center of the annual ring to the peel, 3) the changes of specific gravity under 100 Mrad gamma irradiation are not remarkable, 4) the hardnesses of the soft woods are decreased more -readily than those of the hard woods, but the decreases of hardnesses are not extreme upto 10 Mrad sugges ting that the woods are sufficiently durable to gamma irradiation of below 10 Mard in the preparation of W. P. C.

• Journal of the Korea Furniture Society
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• v.28 no.2
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• pp.111-117
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• 2017

Recently, as people's interest in wood has increased, the use of wood as household and landscape decking materials has increased. As the deck material, imported wood such as synthetic wood, Ipe, and Malas was used in addition to the existing preserved wood, but recently deck use has been activated as part of the activation of domestic materials. As an important quality factor in the selection of such decking materials, various durability along with weatherability for long - term use is required for maintenance. Generally used tropical hardwoods have excellent weatherability and durability without additional preservative treatment. However, the domestic larch is a wood species with a higher specific gravity and durability than ordinary conifers. However, it has not yet been used as a deck material due to lack of comparative studies on its characteristics. Therefore, hardness and durability of wood were measured using six specimens of Ipe, Massaranduba, Malas, Douglas-fir, Larch and Torrefied-Larch. Density Profile was used to measure the density, and Brinell hardness test and resistance test against momentary impact were carried out for the test of resistance to static load. Also, The hardness and durability of wood were measured by castor test with resistance test against dynamic load, as well as, nail down test by experiment on surface hardness and durability. As a result of the experiment, the hardness was increased in proportion to the density, and it was confirmed that the imported lumber was harder and durable than the domestic larch.

• Journal of the Korean Wood Science and Technology
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• v.52 no.1
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• pp.87-100
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• 2024

Wood has different properties depending on the species or growth area. Therefore, in order to use wood efficiently, it is necessary to have a proper understanding of the characteristics of wood depending on the species and the appropriate use for them. In particular, in order to effectively use more than 1,000 species of woody plants in South Korea as wood, it is necessary to evaluate the characteristics of various Korean domestic woods and make a database of them. In this study, the anatomical properties (length and width of tracheid, cell wall thickness), physical properties (specific gravity and shrinkage), mechanical properties (bending strength, compressive strength, tensile strength, shear strength, hardness), and chemical composition (ash, extract, lignin, total sugar content) of Korean red pine which was grown in Pyeongchang-gun, Gangwon-do, South Korea were evaluated.

• Journal of the Korean Wood Science and Technology
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• v.30 no.4
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• pp.41-50
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• 2002

Small clear specimens of Quercus acutissima Carr. and Larix caempferi Carr. were used to measure shrinkage and thermal conductivity for the reasonable and effective use. All samples were conditioned to 18, 12, 5% moisture contents in a humidity chamber of 86, 66, 20% relative humidity(RH), respectively and room temperature(23℃) All specimens were conducted on the shrinkage and thermal conductivity test at each MCs. These processes(cycle) were repeated three times. The radial and tangential shrinkages of Quercus acutissima Carr. and Larix caempferi Carr. decreased at each level of MCs, with the increasing cycles. The radial and tangential shrinkages increased as the specific gravity(on oven-dry weight and volume basis) increased. Thermal conductivities of the radial and tangential direction of Quercus acutissima Carr. and Larix caempferi Carr. increased at each levels of MCs, with increasing cycles. Good correlations were obtained between shrinkages and thermal conductivities of radial and tangential direction, and specific gravity (on oven-dry weight and oven-dry volume basis) and MC.