한국목재공학회

DOI: JKWST Vol.49(No.2) 1-1, 2021

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한국목재공학회

DOI: JKWST Vol.49(No.2) 3-3, 2021

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Gyu Woong Choi , Seung Min Yang , Hyun Jae Lee , Jun Ho Kim , Kwang Hyeon Choi , Seog Goo Kang

DOI: JKWST Vol.49(No.2) 107-121, 2021

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The purpose of this study is to optimize the bonding method of the plywood suitable for cross-laminated timber (CLT) with plywood as a core by analyzing the flexural performance and failure mode according to the lamina species, the method of bonding plywood in the longitudinal direction, and whether or not adhesive is applied to the joint. In the case of the Douglas fir lamina layer, the modulus of elasticity decreased by about 11.5% due to longitudinal bonding, and the modulus of rupture increased or decreased according to the adhesive application and bonding method. The optimal conditions were derived as the butt joint without adhesive, half lap joint with adhesive, and butt joint. In the case of the larch lamina layer, the modulus of rupture and the modulus of elasticity decreased by about 15% and 40%, respectively. When using the half lab joint and tongue & groove joint, it is believed that it reduces the load transmitted to the middle layer by primarily preventing the failure on flexure at the joint of the plywood layer. From the results of this study, the larch lamina layer used in the manufacturing process of Ply-lam CLT did not show any difference based on the bonding method. Butt joint and half lap joint bonding method are determined to be suitable when using Douglas fir lamina layer.

Ju Yong Lee , Seog Goo Kang

DOI: JKWST Vol.49(No.2) 122-133, 2021

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The radon gas from nature mainly considers a cause of radon problems, and it is closely affect human life cycle. Korean yellow residual soil, Hwangtoh, widely used as a building material, is considered to be one of major sources of indoor radon. However, there have, as yet, been no studies about radon from Hwangtoh in mass market brands. Here, we investigated the indoor radon concentrations and exhalation rates in four Hwangtohs from different brand names and regional features. The Closed Chamber Method (CCM) conducted by a Continuous Radon Monitor (CRM) has been used for the rates of radon exhalation. Based on equations of previous references, the indoor radon concentrations were deducted. As a result, the radon surface exhalation rates resulted in the 1.4208 to 3.0293 Bq·㎡·h^-1 range. Significant differences were found among Hwangtohs according to production regions. Materials with higher radon concentration required a longer time to reach a quasi-steady state in a given environment, in other words, the number of half-life cycles increased from a set starting point. The experimentally identified Hwangtohs demonstrated its safety for construction purposes. There exists, so far, a possibility to exert influence radon emanation due to unidentified factors. Therefore, it is necessary to corroborate with more research by increasing the number of Hwangtohs, considering the other references reported high radon exhalation rates. In addition, it is highly recommended that the radon exhalation rates should be measured for all building materials for preventing human health before the material usage.

Ji Sun Mun , Hwan Chul Kim , Sung Phil Mun

DOI: JKWST Vol.49(No.2) 134-141, 2021

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This study was conducted to investigate the potential of the neutral extract (NE) prepared by treating P. radiata bark with aqueous NaHCO₃ solution as a natural dyestuff. Silk and cotton fabrics were dyed at four different NE concentrations, 0.5%, 1.0%, 1.5%, and 2.0% o.w.b. (on the weight of bath). The fabric to liquid ratio of 1 : 50, dyeing temperature of 90℃, and dyeing time of 90 min were used as the fixed condition. The appropriate NE dyeing concentration of silk and cotton fabrics was 1.5% o.w.b. Colors of the dyed silk and cotton fabrics were brown and light brown, respectively. From colorfastness assessment, both dyed silk and cotton showed good washing and rubbing fastness, but poor light fastness. NE dyed fabrics exhibited excellent ammonia deodorization property and antibacterial activity against Staphylococcus aureus and Klebsiella pneumoniae. Therefore, NE of P. radiata bark could have the potential for use as a functional brown dyestuff.

Jeemin Yoon , Tae-jong Kim

DOI: JKWST Vol.49(No.2) 142-153, 2021

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Candida albicans is a dermal fungus of the human body that is known to cause oral candidiasis, vaginal candidiasis, and bloodstream infections in immunocompromised people or in certain environmental conditions. As cases of strains resistant to antifungal agents in C. albicans have been reported, studies using plant materials as safe antifungal agents are being actively conducted. In this study, a total of 17 edible plant extracts showed antifungal activity against C. albicans as a result of evaluating a 280-plant extract library using paper disk diffusion method. Among them, the four extracts with the strongest antifungal activity (Cinnamomi Cortex, Cinnamomi Ramulus, Magnoliae Cortex, and Syzygii Flos) were selected and evaluated for synergistic antifungal activity against C. albicans. The combination of Magnoliae Cortex and Syzygii Flos showed a synergistic activity. The antifungal activity was evaluated based on the concentrations of magnolol and eugenol, the respective components of Magnoliae Cortex and Syzygii Flos. Magnolol and eugenol showed synergistic antifungal activities at the concentration ratio of 1:25 - 1:61. The antifungal activity of these two compounds contributes 28 to 48% to the synergistic antifungal activity of the combination of Magnoliae Cortex and Syzygii Flos extract. In this study, we propose that a combination of Magnoliae Cortex and Syzygii Flos can effectively inhibit the growth of C. albicans and that magnolol and eugenol are the responsible inhibitory compounds.

Tae-gwang Nam , Hun-suk Kim

DOI: JKWST Vol.49(No.2) 154-168, 2021

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Various types of wooden relics are being unearthed following the full-scale excavation in Wolseong palace site, Gyeongju in Korea. In particular, a large number of relics were found in the moat surrounding the Wolseong Fortress. This study attempted to secure basic data on the shields of the Silla era through species identification, radiocarbon dating, and shape analysis of the two wooden shields excavated from the Wolseong moat. As a result of the radiocarbon dating, it was confirmed that the shields were made of wood procured in the period between the mid-4th century and the early 5th century. The species identification confirmed that the body of the relic was made with Pinus soft pine group and the handle with Zelkova serrata. It was also confirmed that the excavated wooden shield was made by first marking a thin line on a flat grain board, then marking double concentric circles and perforating small holes. The distance between the division lines is constant at about 6cm, and spaces between them are colored in red and black. The shape analysis estimated that two artifacts were more than 50cm and 36cm in width, respectively.

Seongsu Park , Byung-dae Park

DOI: JKWST Vol.49(No.2) 169-180, 2021

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Inherent crystalline domains present in low formaldehyde to urea (F/U) molar ratio urea-formaldehyde (UF) resins are responsible for their poor adhesion in wood-based composite panels. To modify the crystallinity of low molar ratio (LMR) UF resins, this study investigates the additional effect of cellulose nanomaterials (CNMs), such as cellulose microfibrils (CMFs), cellulose nanofibrils (CNFs), and TEMPO-oxidized CNFs (TEMPO-CNFs) on the crystallinity of modified LMR UF resins. First, two modification methods (post-mixing and in situ) were compared for modified LMR UF resins with TEMPO-CNFs. The modified UF resins with TEMPO-CNFs decreased the nonvolatile solid contents, while increasing the viscosity and gel time. However, the in situ modification of UF resins with TEMPO-CNFs showed lower crystallinity than that of post-mixing. Then, the in situ method was compared for all CNMs to modify LMR UF resins. The modified UF resins with CMFs using the in situ method increased nonvolatile solid contents and viscosity but decreased the gel time. The crystallinity of UF resins modified with TEMPO-CNFs was the lowest even though the crystalline domains were not significantly changed for all modified UF resins. These results suggest that these CNMs should be modified to prevent the formation of crystalline domains in LMR UF resins.

Hyung Woo Lee , Sang Sik Jang , Chun-won Kang

DOI: JKWST Vol.49(No.2) 181-190, 2021

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Screw-type fasteners are widely used to make connections between wood members or between wood and steel connectors because they can tolerate the applied loads by withdrawal or shearing. In this study, we evaluated the withdrawal resistances of the screw-type fasteners and analyzed the effects of the lead-hole size, relative grain direction (tangential, radial, and cross-sections) of the wood member, screw diameter, screw type, and species. Two wood species, including domestic larch and imported spruce, and three screw-type fasteners, including domestic lag screws (diameters of 9.46, 7.79, and 6.27 mm), domestic tapping screw (diameter, 6.3 mm), and imported Sherpa screw (diameter, 8.0 mm) were used. To assess the effect of lead-hole size, the lead holes with diameters corresponding to 68.7%, 70.8%, and 74.0% of the shank diameter of the lag screw were predrilled. The lead hole corresponding to 74% of the shank diameter was selected for this study because the smaller lead holes required higher rotational force for installation, which may cause damage in the screw neck, although there was no significant difference in the withdrawal resistance depending on the lead-hole sizes applied in this study. The lag screws installed on the tangential and radial surfaces showed similar withdrawal resistances to each other, which were greater than those installed on the cross-sectional surface. As the lag screw diameter increased from 6.27 mm to 9.46 mm, the withdrawal resistance also increased proportionally. The withdrawal resistance of the tapping screw having a diameter of 6.3 mm was almost 1.6 times higher than that of the lag screw having a similar diameter of 6.27 mm, while that of Sherpa screw having a diameter of 8.0 mm was around 1.4 times higher than that of the lag screw having a similar diameter of 7.79 mm.

Ros Syazmini Mohd Ghani , Man Djun Lee

DOI: JKWST Vol.49(No.2) 191-209, 2021

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Australia has significant wood resources in its native forest, but the resource available for harvest becomes lesser due to the conversion of native forest to conservation reserves. The natural occurrences of bushfires, droughts, and cyclones are highly destructive, making the situation worse. The shortage of wood resources is having a significant negative impact on Australia because wood is so scarce that they cannot meet domestic demands, especially durable wood. Australia cleared approximately 100 million hectares of its land to establish forest plantations, and two million trees were planted. However, most of these plantations are for pulpwood production; however, their application for high-value products is limited due to their undesirable properties. Wood modification is a process of improving unfavorable wood properties to be utilized for a wide range of applications. Australia has not adopted any of these modification processes; it still depends on the less toxic wood preservative to treat wood. This study focuses on the recent advancement in industrial wood modification worldwide and how it may be used to modify Eucalyptus wood for high-value applications. The opportunities and suggestions for Eucalyptus wood modification in Australia will be discussed. Before the study concludes, the future of commercial wood modification for Eucalyptus plantation in Australia will also be presented.

한국목재공학회

DOI: JKWST Vol.49(No.2) 210-211, 2021

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한국목재공학회

DOI: JKWST Vol.49(No.2) 212-212, 2021

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한국목재공학회

DOI: JKWST Vol.49(No.2) 213-213, 2021

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