• Polymer(Korea)
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• v.28 no.2
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• pp.135-142
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• 2004

Poly(vinyl acetate) (PVAc) prepared by emulsion polymerization has broad applications for additives such as paint binder, adhesive for wood and paper due to its low glass transition temperature which help to plasticize substrate resins. Since emulsion polymerization has a disadvantage that surfactant and ionic initiator degrade properties of the product polymer, poly(vinyl acetate-co-butyl acrylate) (VVc-BA) was synthesized using potassium persulfate as catalyst and poly(vinyl alcohol) (PVA) as protective colloid to prevent the degradation. The copolymer latex product was internally plasticized and has enhanced colloid stability, adhesion, tensile strength and elongation. During VAc-BA emulsion polymerization, no coagulation and complete conversion occur with the reactant mixture of 0.7wt% potassium persulfate, 15wt% poly(vinyl alcohol) (PVA-217), and the balanced monomer that the weight ratio of vinyl acetate to butyl acrylate is 19. As the concentrations of PVA increase, the copolymerization becomes faster and polymer particles are more stable, resulting in enhanced mechanical stability of the VAc-BA copolymer. However, the size of the polymer particles decreases with increasing PVA contents. Properties of the VAc-BA copolymer, such as minimum film formation temperature, glass transition temperature, surface morphology, molecular weight and molecular weight distribution, tensile strength and elongation, were characterized using differential scanning calorimeter, transmission electron microscope and other instruments.

• Journal of Conservation Science
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• v.27 no.4
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• pp.415-420
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• 2011

Urethane coating agent was made up in order to prevent corrosion on metal relics. This urethane coating agent was designed to solve problems linked to gloss and discoloration caused by existing acrylic coating agent which is mainly applied to metal relics. For the purpose, the urethane coating agent was made up which has lower gloss and slight color change. This coating agent formed thinner coating layer with excellent adhesion compared to the existing agent and has outstanding resistance to the surface oxidization of metal relics and water repellent on the surface. In addition, the agent is considered a stable coating agent replacing current acrylic coating agent with showing easy dissolution in organic solvents such as acetone, toluene and xylene with excellent result in reversible reaction.

• Journal of Adhesion and Interface
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• v.22 no.2
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• pp.63-68
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• 2021

Unsaturated Polyester Resin (UPR) is in general used as a resin to prepare for composite materials with reinforcing materials such as glass fibers. UPR, a thermosetting resin, is used in industry to prepare for sheet molding compound (SMC) molding prepreg that has excellent productivity and is advantageous for mass production among various molding methods of composite materials. The fiber-reinforced composite material using UPR as a matrix material is light and has the advantage of excellent physical properties, but it is weak against impact and is fragile. Four types of polyurethane were synthesized and added to UPR resin to overcome the shortcomings.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.661-673
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• 2007

Rock materials of the three-storied stone pagoda in the Cheongryongsa temple in Korea are mainly composed of gneissose two-mica granite and fine-grained granite. This stone pagoda shows structural instability due to cracks and breaking-out of the stones. The surface properties of the stone is highly degraded by various inorganic pollutants and epilithic biospecies. Therefore, this study carried out comprehensive deterioration diagnosis by non-destructive methods, and some conservation treatments base on the diagnosis were carried out to reduce weathering progress. As the treatments, the biospecies and lichen that covering on the stone surfaces were removed by dry and wet cleaning, and degraded concrete applied to the pagoda for restoration in the past was removed and repaired with epoxy resin. Oxidized iron plates inserted between the rock properties were also substituted titanium stainless steels. After all processes are completed, we sprayed consolidant on the rock surface. Finally, the ground of the stone pagoda was rearranged using small rock aggregates, and the fence was established for control of artificial deterioration by visitors and environmental maintenance.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.4
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• pp.253-262
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• 2006

In this paper, collision analysis is carried out between two FRP fishing boats. A computer simulation with finite element method is used to accomplish this objective. At first, a detailed geometric model of the boat is constructed using 3-D CAD program. The formation of a finite element from a geometric data of the boats is carried out using HYPERMESH that is the commercial software for mesh generation and post processing. Twelve collision configurations are established by combining two kinds of contact angle($90^{\circ},\;135^{\circ}$) and three different speed(5, 10, 15knot) for small and large boats. Collision analysis is accomplished using DYNA3D. Stress distribution and deformation shape are investigated for each collision condition. In general, $90^{\circ}$ collision angle generate larger stress than $135^{\circ}$ case and the collision for two moving boats showed larger maximum stress than the case that one is moving and the other is stationary. When analysis is carried out until 150ms contact parts of two boats are broken for 10 and 15knot collision speed, in which maximum stress is larger than ultimate strength of the material.

• Proceedings of the Mineralogical Society of Korea Conference
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• 1996.10a
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• pp.90-103
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• 1996

식물 양분으로서 유황의 중요성에 관심이 증가되고 있으며 더욱이 대기에서 유래된 유황함량이 감소되고 집약적인 농업으로 유황의 수요가 늘어나고 있다. 호주에서 유황 부족 현상이 1915에 확인된 이래 이 문제를 해결하기 위한 장기적이고 지속적인 연구가 수행되었다. 1980년까지 과석 사용으로 유황의 결핍상황은 나타나지 않았으나 작물 재배가 집약화되고 과석이 고농도비료로 대체되어 사용되면서 유황부족 현상이 증가되었다. 호주의 다우 지역에서 수행된 인광석 시험포장 30군데 중$43\%$가 2년 차에서 효과가 있었다. 토양 유황 검정사업을 통해 유황 분포상황을 파악하게 되었고 시기에 맞는 연구를 통하여 유황 비료 시용으로 유황 결핍을 극복할수 있는 비료정책 발전에 기여하게 되었다. 인도네시아에서는 유황 부족 현상은 과석과 유기질 비료 시용에서 중과석과 요소로 대체되면서 진전되었다. 쌀 생산을 위한 국가 계획에 유안을 질소로서 $25\%$ 포함시킨 효과적인 지도 활동으로 좋은 결과를 얻고 있다. 시비관리로 유황 부족 지역에 유황을 시용하는 노력을 지속하고 있다. 쌀 생산을 위한 유황비료 종류, 시용시기 및 위치 등에 관한 연구가 실용적으로 수행되고 있다. 인도네시아에서의 효과적인 종합 양분으로서의 유황 문제 해결은 연구, 지도, 행정 및 산업계의 상호 밀접한 관계를 요구하고 있다. 중국에서는 유황 부족 토양은 대기로의 유황 방출이 감소되고 고농도 비료, 저유황 비료의 시용으로 급격하게 증가되고 있다. 대부분의 중국 토양은 유황 흡수능이 낮아 생산성은 시용 유황 함량에 따라 결정된다. 유황 결핍과 양분으로서의 수지균형 관계를 이해 하므로서 농업에서의 유황 관리 체계 수립이 무엇보다 중요하다.X>$\mu\textrm{g}$ L$^{-1}$에서는 5.4%로서 가장 낮은 성장을 보였다. 성장률의 전체적인 양상은 노출농도가 증가할수록 성장이 떨어지는 결과를 보였으며, 사료효율과 마찬가지로 노출농도 80 $\mu\textrm{g}$ L$^{-1}$ 이상에서 유의한 감소를 나타냈다.circ}C$에서 각각 3.95-28.9개, 2.9-28.95개 및 1.7-13.6개로 제공된 먹이간에 차이가 현저하였다. 따라서 먹이간 성충 포식량의 현저한 차이는 기주선호성에 따른 것으로 생각된다.군에서 높았으며, elongation index(20:4$\omega$6⇒22:4$\omega$6)는 old군에서 낮았다. 대부분의 elongation과 desaturation 단계는 연령에 따라 유의한 차이를 보이지 못하였으나, $\omega$3계 지방산의 전체적 elongation-desaturation 단계를 나타내는 products-fatty acid($\omega$3)/a-LNA($\omega$3) 비율이 old군에서 young군보다 유의하게 높아, 연령에 따른 PUFA 대사의 변화가 관찰되었다. 이 상에서와 같이, 콩 단백질의 섭취로 흰쥐 혈장 인지질의 ∑MUFA조성은 낮고 ∑SFA 조성은 높아 다른 지질 강화성 분의 섭취와 유사한 결과를 나타내었다. 혈중 콜레스테롤 수준이 높은 old군에서 체내 막조직의 유동성을 유지하기 위해 PUFA의 합성 특히 $\omega$3계 지방산의 elongation-desaturation이 증가하여 총 PUFA 조성이