• Polymer(Korea)
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• v.35 no.2
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• pp.157-160
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• 2011

In this paper, poly (dimethyl siloxane) (PDMS) was modified using electron beam irradiation and its property was investigated. PDMS sheets prepared using a conventional thermal curing method were irradiated by electron beams at absorbed doses between 20 and 200 kGy and their properties were characterized using swelling degree and contact angle measurements, universal testing machine (UTM), thermogravimetric analyzer (TGA), and X -ray photoelectron spectrometer (XPS). The results of the swelling degree measurements, UTM, and TGA revealed that the swelling degree of the irradiated PDMS sheets was reduced down to 24% in comparison to the control sheet, and their compression strength and thermal decomposition temperature increased up to maximum 2.5 MFa and $10^{\circ}C$, respectively, due to the increase in crosslinking density by irradiation. In addition, on the basis of the results of contact angle measurements and XPS, the wettability of the PDMS sheets was enhanced up to 24% owing to the generation of hydrophilic functional groups on the PDMS surface by oxidation during electron beam irradiation.

• Elastomers and Composites
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• v.46 no.4
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• pp.277-283
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• 2011

In this study, engineering grade and high intensity reflective sheets were prepared with glass beads and their reflection performance and physical properties were investigated. The reflective sheets prepared by using glass beads are divided into enclosed or encapsulated lens type, depending on whether the glass beads are open in air or not. Because of an extra layer on the glass bead surface, the enclosed lens type reflective sheets show very little change in the properties by bad weather conditions, compared to encapsulated lens type reflective sheets. Optimization of the amount of glass beads on the surface was carried out, which determines the retroreflective properties. Enclosed and encapsulated lens type reflective sheets with various colors were prepared and their coefficients of retroreflection were determined. The encapsulated type reflective sheet with white color shows a coefficient of retroreflection of $210.4cd/1x{\cdot}m^2$, which is higher than the enclosed type ($74cd/1x{\cdot}m^2$). Effect of washing on the reflective property and adhesive power of the reflective sheets was investigated, and it is found that the number of glass beads decreased with washing and the aluminum layer deposited was damaged extensively in the encapsulated lens type reflective sheets.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.787-798
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• 2017

This is a study on characteristics according to the material of sheet-type mask packs being sold on the market. The absorption capacities of water soluble components such as purified water, 1.3-propanediol, 1.3-butylene glycol, glycerine, and hyaluronic acid are compared with that of various oils including cyclomethicone, dimethicone, phytosqualane, caprylic capryl triglyceride, grape seed oil, and macadamia nut oil. As a result, all of the water soluble components except purified water showed higher moisture absorption capacity as the viscosity increased. And in case of oil, all oil showed higher oil absorption capacity according to the viscosity. During this test, the mask sheets with the type of acetic acid fermented bio-cellulose showed 500~1,000 times or more absorption capacity on water soluble wetting agent or all oils, which is due to the fine mesh structure seen in the 5,000x enlarged photograph at surface structure. This mesh structure was well recognized on the cross section and these structural features enhance the absorption capacity of water and oil. It is also believed that largely contained water-soluble components and oils facilitate the discharge over time. In addition, since each mask sheet shows their characteristics according to their material, it is intended to be a basic research for manufacturing mask packs good for skin.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1221-1225
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• 2010

본 연구에서는 스프레드시트를 기반으로 하는 Microsoft EXCEL의 VBA(Visual Bafor Application)를 이용하여, 빗물 유출수 관리가 필요한 지역을 결정하고, 해당 유역에 적용가능한 관리방안을 선정하며, 관리방안 적용에 따른 효과를 분석할 수 있는 시스템을 개발하였다. 모형의 검보정이 완료된 SWAT 모형의 결과를 이용하였으며, 비구조적 관리방안은 모형의 매개변수 및 입력자료 수정을 통해 효과를 분석하였다. 구조적 관리방안은 각 관리방안의 최대 집수면적 및 각 오염물질 별 제거효율을 이용하여 관리방안 효과를 분석하였다. 각 관리방안의 설계규모는 최대 배수면적과 이를 바탕으로 산정된 수질처리용량으로부터 결정하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2007.02a
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• pp.249-250
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• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.729-732
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• 2002

In this paper, poppet valve with cone type poppet and sharp edged seat was studied. In order to develope poppet valve which have a specification of 315(bar) and 3(lpm), effect of design parameter as valve seat diameter, poppet angle, spring stiffness and spring pre-load was evaluated. The validity of simulation was confirmed and basic data far poppet valve design was derived.

• Journal of Animal Environmental Science
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• v.5 no.3
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• pp.197-202
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• 1999

퇴비화 재료를 혼합하는 목적은 재료를 퇴비황에 최적조건으로 조성하여 퇴비화 성능을 향상 시키고 취기발생을 억제하기 위함이다. 퇴비화성능에 미치는 요인으로서는 C/N비, 수분 함량, 산도(pH), 산물밀도, 입자크기 등이 있다. 이 중에서 C/N비는 적정값으로 조성하기 어렵다. 본 자료는 퇴비재료의 적정 수분 함량 및 C/N비를 조성하기 위해 각 요소재료의 혼합비율을 제시하고 있다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.81-86
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• 2016

The valves used to control or shut off the flow through a pipeline can be divided into many different types, including gate valves, globe valves, and check valves. Globe valves, in particular, have excellent properties, and because they can easily control the flow under high-pressure conditions, they are generally used in LNG ship and steam pipelines. In this paper, a method for changing the shape of a seat was suggested to solve the valve leakage problem from a structural perspective. In addition, the stress distribution and directional deformation were compared for each model. The suggested models were thus validated, and the optimized seat structure, which includes a self-supporting capability for decreasing the amount of leakage, was determined.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.414-423
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• 2020

Fiber-reinforced polymer (FRP) laminate sheets, which are lightweight with high strength, are commonly used to reinforce concrete structures. The bonding strength is vital in structural design. Therefore, experiments and analytical studies with differing variables (concrete compressive strength and tensile strength, the elastic modulus of concrete and FRP, thickness of concrete and FRP, width of concrete and FRP, bond length, effective bond length, fracture energy, maximum bond stress, maximum slip) have been conducted to obtain an accurate numerical model of the bond strength between an FRP sheet and concrete. Although many models have been proposed, no validated model has emerged that could be used easily in practice. Therefore, this study analyzed the parameters that influence the bond strength that were used in 23 of the proposed models (Khalifa model, Iso model, Maeda model, Chen model, etc.) and compared them to the test results of 188 specimens via the numerical results of each model. As a result, an easy-to-use practical model with a simple and high degree of expression was proposed based on the Iso model combined with the effective bond length model that was proposed by Holzenkӓmpfer.

• The Journal of the Korea Contents Association
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• v.20 no.12
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• pp.529-536
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• 2020

This paper presents experimental investigations about compressive strength and durability of reinforced concrete compressive members repaired using ductile fiber reinforced cementitious composite (DFRCC) and carbon fiber sheet through freezing and thawing test. Total 24 RC specimens of 100x100x400mm size were tested by compressive strength test and freezing and thawing test by KS F 2456. The specimens were reinforced using 4D10 steels and repaired on 4 sides expect on top cycle. Test results showed that the specimens repaired using fiber carbon sheet revealed about 5% higher values of the compressive strength compared than the cases of DFRCC motar. On the other hand, the resurts did not showed meaningful differences in the aspect of durability. For further research, considerations of the steel interference effect and real old specimens such as taken from real deteriorated structures are needed to be tested after repairing with DFRCC and carbon fiber sheet.