• Advances in nano research
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• v.8 no.1
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• pp.69-82
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• 2020

In this study, the free and forced vibration analysis of micro sandwich plate with porous core layer and magneto-electric face sheets based on modified couple stress theory and first order shear deformation theory under simply supported boundary conditions is illustrated. It is noted that the core layer is composed from balsa wood and also piezo magneto-electric facesheets are made of BiTiO₃-CoFe₂O₄. Using Hamilton's principle, the equations of motion for micro sandwich plate are obtained. Also, the Navier's method for simply support boundary condition is used to solve these equations. The effects of applied voltage, magnetic field, length to width ratio, thickness of porous to micro plate thickness ratio, type of porous, coefficient of porous on the frequency ratio are investigated. The numerical results indicate that with increasing of the porous coefficient, the non-dimensional frequency increases. Also, with an increase in the electric potential, the non-dimensional frequency decreases, while and with increasing of the magnetic potential is vice versa.

• Journal of the Korean Wood Science and Technology
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• v.35 no.5
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• pp.24-37
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• 2007

The Korean Ministry of Environment started controlling indoor air quality (IAQ) in 2004 through the introduction of a law regulating the use of pollutant emitting building materials. The use of materials with formaldehyde emission levels above $1.25 mg/m^2{\cdot}h$ (JIS A 1901, small chamber method) has been prohibited. This level is equivalent to the $E_2$ grade ($>5.0mg/{\ell}$) of the desiccator method (JIS A 1460). However, the $20{\ell}$ small chamber method requires a 7-day test time to obtain the formaldehyde and volatile organic compound (VOC) emission results from solid building interior materials. As a approach to significantly reduce the test time, the field and laboratory emission cell (FLEC) has been proposed in Europe with a total test time less than one hour. This paper assesses the reproducibility of testing formaldehyde and TVOC emissions from wood-based composites such as medium density fiberboard (MDF), laminate flooring, and engineered flooring using three methods: desiccator, perforator and FLEC. According to the desiccator and perforator standards, the formaldehyde emission level of each flooring was ${\le}E_1$ grade. The formaldehyde emission of MDF was $3.48 mg/{\ell}$ by the desiccator method and 8.57 g/100 g by the perforator method. To determine the formaldehyde emission, the peak areas of each wood-based composite were calculated from aldehyde chromatograms obtained using the FLEC method. Formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde and benzaldehyde were detected as aldehyde compounds. The experimental results indicated that MDF emitted chloroform, benzene, trichloroethylene, toluene, ethylbenzene, m,p-xy-lene, styrene, and o-xylene. MDF emitted significantly greater amounts of VOCs than the floorings did.

• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.70-76
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• 1995

Research was conducted at the Wood Materials and Engineering Laboratory, Washington State University, Pullman, WA to evaluate the effects of the sequence of wax addition, wax level, and wax type on mechanical properties and water resistance performance of isocyanate-bonded particleboard. Mechanical properties and water resistance performance were not influenced significantly by the sequence of wax addition. Internal bond and wet modulus of rupture in bending strength were decreased significantly by increasing the wax emulsion level, but dry modulus of rupture and modulus of elasticity in bending strength were not decreased significantly by increasing the wax emulsion level. Dry internal bond, dry and wet moduli of rupture, and modulus of elasticity were not decreased by increasing the solid wax level except for wet internal bond. The addition of 1.0 and 1.5% wax level did not produce any significant additional water resistance effect when compared to the addition of 0.5% wax level. Internal bond values of boards with solid wax addition showed significantly better results than boards with just a wax emulsion added. Modulus of rupture, modulus of elasticity, and water resistance performance did not show significant difference between solid wax and wax emulsion.

• Journal of the Korean Wood Science and Technology
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• v.45 no.6
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• pp.682-688
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• 2017

Fresh japanese anise (Illicium anisatum L.) tree leaves were collected and ground after drying. The essential oils of the leaves were analyzed by gas chromatography-mass spectrometry (GC-MS) using headspace (HS) and solid phase-microextra (SPME) methods. Volatile components of the leaves were identified 21 and 65 components in HS and SPME, respectively. The main components of the essential oils obtained by HS method were eucalyptol (36.7%), (+)-sabinene (15.61%), ${\delta}$-3-carene (6.87%), ${\alpha}$-pinene (6.07%), ${\gamma}$-terpinen (5.72%), ${\alpha}$-limonene (5.26%), ${\beta}$-myrcene (4.13%), ${\alpha}$-terpinene (4.04%) and ${\beta}$-pinene (3.73%). The other components were less than 3.5%. SPME method also showed that eucalyptol (17.88%) was main. The other were 5-allyl-1-methoxy-2 (13.29%), caryophyllene (6.09%), (+)-sabinene (5.60%), ${\alpha}$-ocimene (4.89%) and ${\beta}$-myrcene (3.73%), and the rest were less amounts than 3.5%. This work indicated that many more volatile components were isolated, comparing to the previous literature data and that SPME method was much more effective than HS method in the analysis of the volatile components.

• Journal of the Korean Wood Science and Technology
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• v.40 no.6
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• pp.424-430
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• 2012

In this study, laccase activity, rate of weight loss and degree of lignin degradation of pine wood chips were determined during the liquid and solid state incubation with Polyporus brumalis. The results showed that laccase enzyme activity at untreated wood chip was gradually decreased after 20 days, but enzyme activity with wood chip treatment showed 10 times higher than untreated ones at 60 incubation days. Rate of weight losses of pine chip and rate of lignin loss were 23.4% and 6.3% by P. brumalis during 80 incubation days. Gene expression of pblac1 from P. brumalis was 3 times increased under pine chip treatment at 40 incubation days. Consequently, laccase activity of white rot fungi, P. brumalis, was increased at incubation with wood chip and pblac1 gene was important factor of lignin degradation. Therefore, to regulate lignin degrading enzyme gene expression by using the tools of biotechnology will be able to develop superior strains and it will be useful for pretreatment of lignocellulosic biomass at bioethanol production.

• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.691-699
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• 2014

In order to improve the dimensional stability and durability of wood, this study attempted to impregnate bismuth (Bi) - tin (Sn) alloy metal with low melting temperature into solid woods of three species such as radiata pine, red oak and white oak, and investigated to determine an optimum condition of manufacturing the metal alloy-wood composites with natural wood grains. These Bi-Sn alloys were chosen for this study because they were harmless to human and melting at low temperatures. The composites resulted in high dimensional stability and low thickness swelling, and also showed much improved performance such as high bending strength, high hardness, high electric conductivity, and high thermal conductivity as floor materials. A proper impregnating condition of all specimens was determined as 10 minutes of the preliminary vacuum time, and $185^{\circ}C$ of the heating temperature. The proper processing condition for radiata pine wood was 2.5 minutes of the pressuring time at the pressure of $10kgf/cm^2$. For red oak wood, 10 minutes of the pressuring time at the pressure of $30kgf/cm^2$ were the proper condition. The proper manufacture conditions for white oak wood was determined as 10 minutes of the pressuring time at the pressure of $50kgf/cm^2$.

• Journal of Conservation Science
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• v.33 no.1
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• pp.35-42
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• 2017

The Yeongheungdo shipwreck was excavated in the sea of Seomeopbeol, Ongjin-gun, Incheon, Korea. Chemical characterization of timbers from the shipwreck occurred via maximum moisture content, chemical composition, FT-IR, solid state $^{13}C$ NMR, and XRD analyses. As maximum moisture content of the outer part of the timbers averaged 623%, a phenomenon in that lignin increased relatively, according to the decrease in cellulose, and the ash content increased, which is typical of waterlogged archaeological wood was shown. The results from the FT-IR and solid state $^{13}C$ NMR analyses showed that the cellulose band of the outer part had disappeared or had remarkably decreased. In addition, the bands assigned to lignin dramatically increased. However, regarding the inner part of the timbers, hemicellulose and some crystalline cellulose and amorphous cellulose bands decreased. Therefore, a large difference exists between the degradation levels of the outer and inner parts of the timbers of the Yeongheungdo shipwreck.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.57-66
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• 2016

In order to develop materials with a low environmental load for restoring the destroyed forest, seven types of wood-concrete hybrid laminated materials were manufactured with four softwoods, three hardwoods and concrete, and the effect of wood density on bending creep property was investigated. The bending creep curves showed a shape to considerably increase at the upper right side, and the curves were found to show a linear behavior beyond about 30 min - 1 hour, as behaviors of solid woods and wood-based materials. The initial compliances of wood-concrete hybrid-laminated materials decreased with an increase in the wood density, and those values showed 0.9 - 1.2 times of the concrete one. The creep compliances of hybrid laminated materials showed very low values, which were 0.4 - 0.8 times of the concrete ones. The relative creep were very low with a range from 8.2% to 17.0% range, which were 0.3 - 0.7 times of the concrete ones. These results indicate that these materials can be applied for restoring the destroyed forest to reduce creep deformation of the conventional concrete materials by hybrid-laminating concrete and woods.

• Journal of the Korean Wood Science and Technology
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• v.48 no.3
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• pp.303-314
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• 2020

Gambir is a non-wood forest product with a potential of being used as wood adhesive, due to about 33% catechin in it. Meanwhile, catechins and sucrose have not been studied as adhesives. Therefore, basic characteristics of gambir-sucrose adhesives were investigated. In this research, adhesives were prepared by dissolving gambir and sucrose in distilled water, at different blending ratios of the gambir/sucrose such as 100/0, 75/25, 50/50, and 25/75 wt%. Furthermore, gas chromatography-mass spectrometry (GC-MS) was employed to determine the gambir chemical compositions, and Fourier transform-infrared (FTIR) spectroscopy was carried out to identify chemical bonds. Particleboards with a target density of 0.8 g/㎤ were then manufactured by hot-pressing for 10 min at 200℃. The internal bond (IB) strength of particleboard was subsequently measured. Based on the GC-MS analysis, 31.11% of catechin was identified. In addition, the viscosity, density, solid content, and gelation time of the adhesives, and insoluble matter content (IMC) in boiling water were 7.30~33.24 mPa.s, 1.2~1.3 g/㎤, 25.56~28.44%, 73~420 min, and 29.75~62.10%, respectively. Adding sucrose to the adhesive was observed to raise the IMC from 49.05 to 62.10%, at 180℃ and 200℃. FT-IR analysis showed that the gambir absorption peaks occurred at approximately 1620 cm^-1, assigned to the C=O stretching of 5-hydroxymethylfurfural, which tended to increase with the addition of sucrose. The reaction between gambir and sucrose was observed in the form of the dimethylene ether bridge. The 25/75 wt% gambir-sucrose adhesives and 200℃ hot-pressed temperature resulted in the highest IB strength (0.89 MPa), and met the requirement of JIS A5908-2003 type 18. Consequently, the gambir-sucrose adhesive could be used as a particleboard adhesive.

• The Plant Pathology Journal
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• v.35 no.6
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• pp.674-683
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• 2019

Some species of the Trichoderma genus are reported as the major problem in oak wood mushroom production in Korea. In spite of economic loss by the fungi, scientific information on airborne Trichoderma species is not much available. To generate information for disease management development we analyzed airborne Trichoderma. A total of 1,063 fungal isolates were purely obtained from indoor air sampling of cultivation houses used for oak wood mushroom using sawdust media. Among the obtained isolates, 248 isolates were identified as Trichoderma fungi including T. harzianum, T. atroviride, T. citrinoviride, and T. pseudokoningii, by morphological and molecular analysis. T. harzianum was dominant among the four identified species. All the four Trichoderma species grew fast on solid nutrient media tested (potato dextrose agar [PDA], malt extract agar [MEA], Czapek's Dox + yeast extract agar [CYA] and cornmeal dextrose agar). Compact mycelia growth and mass spore production were better on PDA and CYA. In addition, T. harzianum and T. citrinoviride formed greenish and yellowish mycelium and spores on PDA and CYA. Greenish and yellowish pigment was saturated into PDA only by T. pseudokoningii. These four Trichoderma species could produce extracellular enzymes of sawdust substrate degradation such as β-glucosidase, avicelase, CM-cellulase, amylase, pectinase, xylanase, and protease. Their mycelia inhibited the growth of oak wood mushroom mycelia of two tested cultivars on dual culture assay. Among of eleven antifungal agents tested, benomyl was the best to inhibit the growth of the four Trichoderma species. Our results demonstrate that the airborne Trichoderma fungi need to be properly managed in the cultivation houses for safe mushroom production.