• Journal of the Korean Wood Science and Technology
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• v.17 no.4
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• pp.26-34
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• 1989

This study was carried out to manufacture bark board from oak bark by new processes and to examine the physical and mechanical properties of the board. This process with no addition of adhesive used higher pressure and temperature than the conventional one and was applied with or without paraformaldehyde. The results are as follows: 1. The new manufacturing process allowed a good bark board with high absorption coefficient. 2. The best manufacturing process for the mechanical properties of bark board was paraformaldehyde 10%-$250^{\circ}C$-100kg/$cm^2$-3 minutes, (bending strength 40kg/$cm^2$, internal bonding strength 2kg/$cm^2$) and the best manufacturing process for both the mechanical properties of bark board and economic point of view was $250^{\circ}C$-100kg/$cm^2$-3 minutes (bending strength 28kg/$cm^2$, internal bonding strength 1.52kg/$cm^2$). 3. Bark board showed specific gravities from 0.94 to 1.03 and air dried moisture content 9.2% to 11.7%, but Bark board needed paraffin wax emusion treatment. 4. The absorption coefficient of bark boards had two peaks along with frequency; one in 200-400 cps, the other 1200-2000 cps. The former was low but the latter great.

• International Journal of Industrial Entomology and Biomaterials
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• v.44 no.1
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• pp.21-27
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• 2022

Different parts of the mulberry plant are described to be potential sources of polyphenolics exhibiting strong antioxidant activity. In this study, we prepared various aqueous extracts of mulberry root bark by subjecting to steam at different temperatures and time intervals (45℃, 15 h; 70℃, 15 h; 95℃, 6 h and 95℃, 15 h) followed by extracting at 80℃ for 1 h. The total polyphenolic content ranged from 66.82-101.20 mg gallic acid equivalent (GE)/g of extract whereas the flavonoids were in the range of 13.03-25.23 mg catechin equivalent (CE)/g of extract. The extracts also exhibited strong antioxidant activities (0.99-1.66 mg trolox equivalent (TE)/g of extract in DDPH assay and 10.65-16.26 mg TE/g of extract in ABTS assay). This study clearly showed an improvement in the antioxidant activity of the water extract of mulberry root bark by the steam treatment, which can be used as a tea or health-promoting materials.

• Journal of Korea Foresty Energy
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• v.20 no.2
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• pp.9-19
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• 2001

This study was carried out to investigate natural insectifuge materials from tree extractives in order to substitute for organic synthetic insecticides for food wrapping corrugated board. Tree samples were collected, extracted, fractionated with hexane, $CH_2Cl_2$, ethylacetate(EtOAc) and $H_2O$, and then freezed dried for further study. EtOAc or $H_2O$ fractions were chromatographed on a Sephadex LH-20 column for isolation and purification, and the isolated compounds were characterized by spectroscopic tools such as NMR and MS. Crude extractives of EtOAc and $H_2O$ fractions were added to the printing ink for corrugated board with the concentration of 2% or 3% based on the weight of the ink, then the prepared ink was printed on the corrugated board to be used for evasion test using larva of indian meal moth(Plodia interpunctella(Hubner)). Robtin, dihydrorobinetin and leucorobinetinidin were isolated from the wood extractives of black locust(Robinia pseudoacacia) and the bark of poplar(Populus alba $\times$ glandulosa) contained many kinds of compounds such as (+)-catechin, naringenin, aromadendrin, eriodictyol, sakuranetin and its glycoside, taxifolin, neosaturanin, salireposide, p-coumaric acid and aesculin. Much of (+)-catechin was isolated from the bark extractives of willow(Salix koreensis) in addition to (+)-gallocatechin and p-coumaric acid and the bark of weeping willow(Salix babylonica) also contained (+)-catechin, (+)-gallocatechin, dihydromyricetin and myricetin.

• Journal of the Korean Wood Science and Technology
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• v.46 no.2
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• pp.132-142
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• 2018

An elephant digests only around 30~45% of what it consumes; therefore the undigested material mainly passes as intact fibres. Elephant food is usually composed of grass, leaves, twigs, bark, fruit and seed pods. This research aimed to utilize the elephant dung fibers as material for composite board and citric acid as a bonding agent. Citric acid contents in this research were set at 0 wt% (binderless composite board), 10 wt%, 20 wt%, and 30 wt% based on dry weight particles, while the target density was set at $0.8g/cm^3$. Pressing temperatures were set at $180^{\circ}C$ and $200^{\circ}C$ with the pressing time was 10 minutes. Physical and mechanical properties tests were then performed according to Japanese Industrial Standard A 5905. The result showed that elephant dung fibers could be used as potential materials for composite board. Addition of citric acid and pressing temperature significantly increased the quality of composite board. Infrared analysis indicated that the presence of ester linkages much higher with the increasing of citric acid content and pressing temperature. The optimum properties of composite board made from elephant dung fibers could be achieved at pressing temperature of $200^{\circ}C$ and a citric acid content of 20 wt%.

• Journal of the Korean Wood Science and Technology
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• v.11 no.1
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• pp.12-17
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• 1983

The shear strength of plywoods using Douglus-fir bark powder and particlebard sander dust(PSD), abandoned materials in plywood and particleboard industries, as extender to UF resin, was compared with that of plywoods using wheat flour. Extenders were mixed at the rate of 0%, 5%, 10%, 20%, and 30% of UF resin weight. In obtained results, the dry shear strength of all extended plywoods was highest at extending ratio 5% and the wet shear strength was highest at no extending and 5%. Douglas-fir bark powder-and PSD-extended plywoods had as high dry and wet shear strength as wheat flour-extended plywoods up to extending ratio 10% and 20% respectively. But at 300%, wheat flour-extended plywoods had higher shear strength. Douglas-fir bark powder and PSD size should have been reduced (enough to pass through 325 mesh screen) in order to develop the satisfactory mixing, spreading and plywood bond quality. But in this study the powders to pass through 100 mesh screen were used.

• Journal of the Korean Wood Science and Technology
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• v.18 no.4
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• pp.65-78
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• 1990

For the purpose of Improving the sounding boards for the conventional GAYAKUM, I was making approximately 202 specimens of radial board, 371 specimens of tangential board by cutting along the grain and the part of stem and 31 specimens of the disjointed traditional GAYAKUM made in Paulownia coreana. And it was conducted to measure specific gravity, dynamic Young's modulus, internal friction, resonant frequency, velosity of sound and width of annual ring by the method of the frexural vibration in a free-free bar in the audio frequency range. And it confirmed the juvenile wood by measuring wood fiber length of specimens. It was also conducted to investigate dynamic properties and moisture absorption by various heat-treatment and to test dynamic Young's modulus and internal friction for the disjointed conventional GAYAKUM. The results obtained were summarized as follow: 1. The Juvenile wood is located within about 7 annual rings from the pith in Paulownia coreana. 2. As increased with the specific gravity, the dynamic Young's modulus had more and more increased, but the internal friction had slightly decreased. 3. I think that radial board would be good for sounding board wood. because radial board is higher than tangential board in dynamic Young's mudulus and internal friction is lower than tangential board. 4. The value of mean dynamic Young's modulus on the conventional GAYAKUM, radial board and tangential board of 604 samples is $0.4283\pm0.037(\times10^{11}dyne/cm^2)$, $0.4316\pm(\times10^{11}dyne/cm^2)$ and $0.4234\pm0.112(\times10^{11}dyne/cm^2)$ respectively. The value of the radial board showed little higher than that of conventional GAYAKUM, but It had a similar tendency between conventional GAYAKUM and tangential board. 5. The annual ring width by four aspect is more narrow in north and west than that of others. 6. The values of specific gravity and dynamic Young's modulus in the mature wood showed higher than those of juvenile wood. 7. As the grain angle in the butt wood more increased to bark from pith, the dynamic Young's modulus were low. Then it was not good for sounding board. 8. It appeared that the heat-treatment for sounding board wood had a more effect to do the treatment of hotiron on surface after heat-treatment during 24 hours in $60^{\circ}C$ temperature. 9. As increased with the temperature, the rate of moisture absorption of heat-treatment wood had decreased. In conclusion, I thought that the sounding board wood for GAYAKUM would had the most effect to do the treatment of hotiron on surface after heat-treatment during 24 hours in $60^{\circ}C$ temperature using the radial board of mature wood.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.671-674
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• 2007

With increasing concerns of indoor air quality, $CO_2$ concentration in the public transportation, such as train, bus, and subway, draws big interests. The $CO_2$ concentration in the indoor air is regarded as index of ventilation status rather than that of adverse health effect. In this study, we measured the time-series of $CO_2$ concentrations in the subway saloon at the Subway line 1 (Suwon-station to Cheongyangri-station) with the number of passengers on board. At the same time, the concentration of particulate matter (PM), temperature, and humidity were monitored. It was found that the $CO_2$ concentration was correlated linearly with number of passengers and the relation function is suggested for the prediction of $CO_2$ conecntration by the number of passengers.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.192-195
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• 2006

With increasing concerns of indoor air quality, $CO_2$ concentration in the public transportation, such as train, bus, and subway, draws big interests. The $CO_2$ concentration in the indoor air is regarded as index of ventilation status rather than that of adverse health effect. In this study, we measured the time-series of $CO_2$ concentrations in the KTX cabin during the journey of Gyongbu-line (Seoul-Busan) and Honam-line (Seoul-Mokpo) with the number of passengers on board. At the same time, the concentration of particulate matter (PM), temperature, humidity and gaseous pollutants including HCHO and VOCs were monitored. It is found that the $CO_2$ concentration was correlated linearly with number of passengers and was highly correlated with tunnel regions where the ventilation unit (flap) was closed.

• Journal of Fisheries and Marine Sciences Education
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• v.16 no.2
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• pp.163-170
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• 2004

The rapid exchanges of mobile computing environment and development of wireless communication are providing many effects for learning activity of students. Recently, PDA system developers which are studying memory capacity, communication speed and size of screen support techniques to be capable of learning from students in the wireless or moving environment. In this viewpoints, this paper has a purpose to design multimedia learning system to be able to do with sound lecture contents. The implemented system largely consists of two parts which have the teacher module and students module. The one manages learning progress of students, class management, bulletin board and etc. The other is capable of using studying and bulletin functions. The main idea of this research is focus to upgrade the effect of learning without almost treating the existing studies, which can be listening sound lecture and also seeing text and image at the same time.

• Journal of the Korean Wood Science and Technology
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• v.27 no.2
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• pp.31-37
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• 1999

This study was carried out to develop the Korean paper(Hanji) sludge-wood fiber composite boards utilizing the relinquished sludges occurring from the making process of Korean classic paper Hanji. The bark of paper mulberry(Broussonetia kazinoki Sieb.) has been used as a raw material since past hundreds and thousands years. Korean paper(Hanji) sludge was divided into two kinds, the one was the white sludge from the first stage and the other was the black sludge occurring from the final stage of Korean paper(Hanji) making. Four levels of the mixed ratio of each white or black sludge to wood fiber(10:90, 20:80, 30:70 and 40:60), three levels of the resin adhesives(PMDI, urea and phenol resin) and three levels of the density(0.60, 0.75 and 0.90) were designed to investigate the mechanical properties of Korean paper(Hanji) sludge-wood fiber composite boards. From the results and discussion, it could be concluded as follows : 1. In the white and black sludge-wood fiber composite boards, bending modulus of rupture showed the clear decreasing tendency according to the increase of sludge additive, but it was clearly increased with the increase of specific gravity. Modulus of elasticity showed the same tendency as in the modulus of rupture, and also tensile and internal bonding strength had the same tendencies as in these bending properties. 2. Among the resin adhesives, PMDI or urea resin showed great values in MOR of white sludge-wood fiber composite board, but urea resin was greater than PMDI in MOR and MOE of black sludge-wood fiber composite board. Tensile and internal bonding strength showed the same tendencies as in white sludge-wood fiber composite board. 3. It is suggested that the white sludge-wood fiber composite boards bonded with PMDI or black sludge-wood fiber composite boards bonded with urea resin were able to made similar boards to general fiberboard by the mixed ratio 20:80 of sludge to wood fiber.