• Journal of Adhesion and Interface
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• v.20 no.4
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• pp.140-145
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• 2019

In view of environmental considerations, the control of carbon dioxide (CO₂) and volatile organic compounds (VOCs) is one of important issues in the film and coating industries. Therefore, UV-curable system has been developed due to minimize emissions of VOCs and reduce CO₂ emission due to low energy consumption from fast curing. Also, biodegradable polymers economically are attractive because of environmental and economic concerns associated with huge waste plastics. In this study, UV-curable polyurethane acrylates with different compositions of biodegradable polylactide (PLA) diol and poly(ethylene glycol) as diols were synthesized and curing reaction of their end-capped acrylates was performed by UV exposure. Tensile strength, elongation, and Tg of the UV-cured polyurethane acrylates increased with PLA diol content in the diol while their hydrophilicity and thermal stability increased with the PEG content. These results indicated a property of UV-cured polyurethane acrylates could be controlled by environment-friendly diols.

• Composites Research
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• v.33 no.4
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• pp.213-219
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• 2020

Recently, global facing environmental issues have been raised caused by plastic waste. Hence, increasing the demand for interest in environmentally friendly materials. In this row, research on engineering composite materials also replacing the synthetic reinforcement by introducing natural fibers. However, focus on the strength and interfacial adhesion between matrix and reinforcement is very essential in natural fiber composite, which is insufficient in the literature. There are number of approaches for improving the mechanical strength of the composites, one of the common methods is to reinforce additive nanoparticles. The present investigation, bio-additives were synthesized utilizing bio-waste, cheap, bio-degradable sea-weed powder that could replace expensive nanomaterials and reinforced into the CFRP composite through Hand lay-up followed by a vacuum process. Mechanical properties were evaluated and analyzed through microanalysis. The results concluded that synthesized additives are effective for improving mechanical properties such as tensile, flexural, impact, and shear strength. Overall, the results confirmed that the fabricated composites have potential applications in the field of engineering applications.

• Journal of Welding and Joining
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• v.34 no.2
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• pp.22-29
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• 2016

Recently, Application of composite materials are increased in transport area for weight reduction. Also, Related technical developments have been implemented actively at domestic and abroad. In particular, The carbon fiber has high strength and ultra light property higher than stainless steel, aluminum, GFRP as Eco-friendly material. Carbon fiber contribute to improving the environmental effect such as fuel saving, expansion of loadage, reducing the exhaustion of carbon dioxide through the weight reduction of transport area. In addition, The carbon fiber is applied to the ship in the area of race yacht, luxury cruise boat as weight reduction and high added-value materials, but there is limited application for general boat because price of carbon fiber is very expensive. For the weight reduction of general boat hull, being used as structure materials, glass fiber and carbon fiber are applied to hull with form of hybrid composite materials, but application of domestic and research for development are incomlete. In this study, An evaluations of mechanical strength property and fatigue strength are performed on composite materials by hybrid weaving of glass fiber and carbon fiber and composite materials forming method by hybrid forming.

• Journal of the Korean Applied Science and Technology
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• v.31 no.3
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• pp.486-491
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• 2014

We have been fabricated Thin-walled carbon nanotubes (TWNTs)/amine epoxy additives composite using Eco-friendly solvent system such as supercritical process and dry mixed process. TWNTs/amine epoxy additives composite has used as a curing agent for urethane based bisphenol A type epoxy resin. The thermo-mechanical property of the epoxy resin cured by TWNTs/amine epoxy additives composite is characterized by dynamic mechanical analysis(DMA) and dispersability of the nanotubes in the epoxy matrix is also confirmed by scanning electron microscope(SEM). As a results, the epoxy resin cured by TWNTs/amine epoxy additives composite with supercritical process shows enhanced dispersability of the TWNTs in the matrix and thermo-mechanical property when compare to dry mixed process.

• Journal of the Korean Institute of Gas
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• v.24 no.6
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• pp.55-60
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• 2020

As research and development of eco-friendly vehicles are expanding worldwide, additional devices of vehicles are reduced or deleted to increase the mileage, or research is being conducted to reduce weight. Among them, the multi-stage transmission that was applied to the internal combustion engine vehicle was deleted and replaced with a reducer, and the initial driving power is secured by increasing the torque through the control of the motor output value. However, since frequent motor speed change can result in a load increase, this study attempts to develop a compact and lightweight manual two-stage reducer with a general reducer structure. Therefore, a two-speed transmission with two gear ratio was designed by inserting a large gear and a small gear in a structure with a parallel shaft to connect the gears with a V-belt in the form of a parallel shaft reducer, and setting the gear ratio of the low and high gears respectively. In addition, power performance according to the rotational speed and load of the transmission was checked through a test, and the heat generation characteristics generated during driving were checked to verify the validity of the transmission.

• Journal of the Korean institute of surface engineering
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• v.56 no.2
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• pp.152-159
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• 2023

The night visibility of pavement is being considered as a global issue in the field of traffic safety. Although the spreading glass beads on the lane paints has been mainly used to secure night-visibility by utilizing the effect of retroreflection, obvious shortcoming of this method is that retroflection does not occur in the range where the headlights do not reach the glass beads. The use of functional paints including phosphorescent constituents could be a solution for overcoming fore-mentioned problem. SrAl₂O₄ based chemicals have not only good phosphorescent property, but also are chemically stable compared to existing ZnS based materials. However, this chemicals also need the improvement due to slightly reduced luminous effect in time. Herein, we developed novel paints showing enhanced phosphorescent properties by putting rare earth elements such as Eu, Dy and Y into SrAl₂O₄. These prepared phosphorescent pigments have displayed improved properties in terms of durability and long afterglow. For instance, the property of afterglow has been persisted after 5 hours with luminace of 20.6 mcd/m².

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.4
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• pp.635-641
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• 2012

The present study evaluated the effect of chitosan on the changes of soil chemical properties, soil microbial population, and yield of red pepper (Capsicum annuum L.) for eco-friendly agriculture in an upland field. We utilized four treatment groups, control, foliar spray, soil drench, and foliar spray + soil drench with chitosan, and analyzed these variations throughout the seven, fourteen, and twenty one days interval. The pH values, organic matter, and available phosphate in the upland soil at the harvesting stage decreased in the chitosan treatment. The populations of bacteria, actinomyces, and fungi in the upland field were increased in plots treated with chitosan. The chlorophyll content of leaves was no significant differences between the control and the chitosan treatments, while calcium content of leaves was significantly higher in the chitosan treatments than in the control. In addition, the nitrogen content of leaves was no significant differences between the foliar spray and the soil drench. The yield of red pepper was significantly higher in the control ($383kg\;10a^{-1}$) than the chitosan treatments and the yield of soil drench with chitosan reached up to 95% of control.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.2
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• pp.61-70
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• 2019

Geopolymer is an eco-friendly construction material that has various advantages such as reduced $CO_2$ emission, fire resistance and low thermal conductivity compared to cement. However, it has not been many studies on the thermal behavior of the surface of the geopolymer panel when flame is applied to the surface. In this study, surface characteristics of hardened geopolymer on flame exposure was investigated to observe its characteristics as heat-resistant architectural materials. External structure changes and crack due to the heat shock were not observed during the exposure on flame. According to the residue of calcite and halo pattern of aluminosilicate gel, decarboxylation and dehydration were extremely limited to the surface and, therefore, it is thought that durability of hardened geopolymer was sustained. Gehlenite and calcium silicate portion was inversely proportional to quartz and calcite and significantly directly proportional to BFS replacement ratio. Microstructure changes due to the thermal shock caused decarboxylation and dehydration of crystallization and it was developed the pore and new crystalline phase like calcium silicate and gehlenite. It is thought that those crystalline phase worked as a densification and strengthening mechanism on geopolymer panel surface.

• Fashion & Textile Research Journal
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• v.14 no.4
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• pp.648-659
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• 2012

This research categorizes fundamental data needed to develop eco-friendly fabrics treated with bamboo leaf & pine leaf extracts. The effect of mordant on those fabrics was analyzed through the measurement of mechanical properties and the estimation of primary hand values for cotton and silk fabrics dyed with bamboo leaf and pine leaf extracts that were later treated with various mordants. When cotton was dyed with bamboo leaves and pine leaves extracts, EM, WT, 2HB, 2HG, 2HG5, LC, T, and W increased however, RT, SMD, and RC decreased compared to raw cotton fabric. The B, G, and MIU increased after mordant treatment to the dyed cotton and resulted in a stiffer and rougher cotton's hand. EM, WT, RT, MIU, WC, T, and W increased (in terms of silk); however, LT, B, 2HB, G, 2HG, 2HG5, MMD, SMD, and LC decreased compared to raw silk fabric. Similar to the dyed cotton, mordant treatment increased the MIU and LC of dyed silk subsequently, the hand became stiffer and rougher. A greater tannin adsorption results in an increased mechanical property and the primary hand value. For both fabrics, mordant treatment made its smoothness drop. However, the scale of drop for cotton was significant, while the scale of the drop for silk was minor. In terms of type of mordant, femordant and natural-mordant treatment influenced the tensile, shear, surface properties of fabrics, and primary hand values more than Cu-mordant and synthetic-mordant in addition, this increased the stiffness, hardness, and roughness of fabrics.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.1
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• pp.38-43
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• 2018

Ceramic membrane has been widely used for water treatment due to its advantages of eco-friendly property and low energy consumption. However, high porosity of ceramic membrane higher than 40 % may cause a problem of strength, when it is applied to a water treatment module. In order to solve this problem, the strength of the membrane edge was improved by using the ceramic glaze. Four different glaze compositions for low temperature sintering was selected to minimize the deformation of the membrane microstructure. After coating with low temperature glaze, cracks were observed due to differences in thermal expansion coefficient between the membrane and glaze. Thus, the thermal expansion coefficient of glaze was controlled by addition of cordierite and petalite. As a results, the compressive strength of the ceramic membrane, which was coated with the optimized glaze composition, was increased from $27N/m^2$ to $117N/m^2$, indicating that the glaze coating can improve the disadvantages of the fragile ceramic membrane.