• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.598-601
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• 2005

Plastic parts are molded for the purpose of mass production in multi-cavity system. Therefore, designer is usually designing molds that has geometrically balanced runner lay-out for filling balance at each cavities. Although, mold is manufactured with geometrically balanced runner lay-out, there are actually filling imbalances in cavities. These filling imbalances phenomenon are caused by complicated interaction between melt and mold. In this study, based on previous studies for filling imbalances in cold-runner mold, filling imbalances in hot-runner mold were investigated by CAE and injection molding experiments. ABS, PMMA as amorphous polymer and PA, PP as crystalline polymer were used to compare the filling imbalances. The filling imbalances decreased as injection rate increased without regard to kind of resins and were lower than the one of cold-runner.

• The Korean Journal of Rheology
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• v.7 no.3
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• pp.237-249
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• 1995

폴리우레탄 미세포 포움의 가공에 대한 연구를 수행하였으며 기체 과포화 수지 내 의 핵생성율을 증진시키기 위하여 폴리올과 이소시아네이트의 혼합물에 초음파 가진을 적용 하였다. 미세포 구조는 고압에서 질소 가스로 폴리올을 과포화ㅣ키고 폴리우레탄의 두 성분 을 충돌혼합시킨 직후 초음파에 의해 기포를 생성시켜 이루어진다. 낮은 포화 압력에서 질 소에 의해 포화된수지의 핵생성율을 증가시키기위하여 초음파 가진을 적용하였다. 확산에 의해 기포의 성장이 조절된다고 가정하고 금형이 충전되는 동안에 금형 내부에서의 기포성 장기구를 이해하기 위하여 수치적인 방법으로 이론적 연구를 수행하였다. 경화 시간과 확산 경계를 고려하여 최종적인 기포의 크기를 계산하였으며 반응속도론을 고려하여 중합반응 동 안의 폴리우레탄의 점도의 변화를 예측하고 경화 시간을 결정하였다. 이론적 및 실험적으로 결정된 기포의 수를 기준으로 하여 확산 경계를 예측하였다.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1053-1058
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• 1998

Poly(vinyl butyral)s (PVB) with different butyral content were synthesized from poly(vinyl alcohol)(PVA) and n-butylaldehyde with acid catalyst. Bound butyral unit in PVB was determined by elemental analysis. Synthesized PVBs were reacted with p-azidobenzaldehyde to give photosensitive polymer with azidobenzene group(PVB-AZ). Bound photosensitive azidobenzene group in PVB-AZ was determined by UV spectrophotometry. The photosensitivity of PVB-AZ was compared with that of PVB/2,6-bis(p-azidobenzylidene)cyclohexanone(BAC) photosensitizer mixture system by gray scale method. Photosensitivity of PVB-AZ was higher than that of PVB/BAC mixture system. The photosensitivity of PVB-AZ was dependent on the developer used due to the solubility of PVB-AZ in a developer solvent.

• Elastomers and Composites
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• v.43 no.1
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• pp.39-48
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• 2008

Peel strength of epoxy adhesives can be increased by adding some amounts of XNBR. In this case, thermal resistance of the adhesive will be decreased by decrease of glass transition temperature of the adhesive. Epoxy resin modified with siloxane-imide was synthesized to improve thermal resistance and peel strength of the adhesive, after that the properties of modified epoxy resin were compared with the commercial epoxy resin. When 5% XNBR was added to 30% modified epoxy resin, this adhesive showed 0.42 N/mm of peel strength and $155^{\circ}C$ of glass transition temperature. These properties are enough compared to the required properties by the industry, i.e., 0.3 N/mm and $150^{\circ}C$, respectively. Weight loss of the modified epoxy resin by the treatment of nitric acid and 0.1N NaOH was reduced, but weight gain by the humid condition was increased by the presence of benzene ring and imide ring. 30% modified epoxy resin blended with 5% XNBR showed 220% improvement in tensile strength and elongation compared to the case of common epoxy resin. This is due to the flexibility of the siloxane in the modified epoxy resin.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.2
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• pp.447-450
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• 2004

Overall migration through epoxy layer coated wood was investigated to estimate the coating thickness satisfying the regulatory limit. As an index of overall migration, KMnO$_4$ oxidizable extractives by the food simulant water solution was used. Migration pattern in interest range could described by a simple diffusion model and the temperature dependence of the permeability index could be explained by Arrhenius equation. The thickness of epoxy coating greater than 0.004 mm was analyzed to be required for satisfying the regulatory guideline.

• KDI Journal of Economic Policy
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• v.16 no.1
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• pp.93-117
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• 1994

이론적으로, 국가경제에 있어서 인구구조(人口構造)의 변화(變化)는 인적자본(人的資本) 형성 및 노동공급(勞動供給), 각 주체들의 소비(消費) 저축행위(貯蓄行爲) 등의 장기적(長期的) 추세(趨勢)를 결정짓는 중요한 요인으로 인식되어 왔다. 본 논문에서는 우리나라의 연령별(年齡別) 인구구조 변화가 거시경제변수인 가계소비(家計消費), 금리(金利) 및 경상수지(經常收支)에 미치는 영향에 대하여 이론적(理論的)인 모형(模型) 제시(提示)와 함께 실증분석(實證分析)을 시도하였다. 이론적 모형에서는 인구구조 변화와 이러한 거시경제변수들간의 관계를 평생소득가설(平生所得假說)에 의거하여 설정하였으며, 실증분석 결과는 실제로 인구구조 변화의 거시경제적 효과가 통계적(統計的)으로 유의성(有意性)이 매우 높게 나타나고 있음을 보여주고 있다. 그러나 가계소비와 경상수지의 경우, 장년층인구(壯年層人口)의 상대적(相對的) 증가(增加)는 경제전체의 평균소비성향(平均消費性向)을 낮추고 경상수지(經常收支)를 개선(改善)하는 요인인 것으로 분석되어 평생소득가설에 잘 부합하고 있는 반면, 금리(金利)의 경우에는 장년층인구 증가가 금리를 상승(上昇)시키는 요인으로 나타나고 있어 평생소득가설에 상반(相反)되는 모습을 나타내고 있다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.1
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• pp.124-129
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• 2010

When a phenolic resin is carbonized by the leakage current flowing along its surface, the carbonization pattern is one of the most important factors to determine its carbonization characteristics. However, the typical carbonization pattern of a phenolic resin is too complicated to be analyzed by conventional Euclidean geometry. In most cases, such a complicated shape shows a fractal structure. It is possible, therefore, to examine the characteristics of the carbonization pattern regarding a given phenolic resin. In order to quantitatively investigate the carbonization pattern of the phenolic resin carbonized by a leakage current, in this paper, the fractal dimension of the carbonization pattern has been calculated as a function of the magnitude of a leakage current and the distance between two electrodes. For reliability of calculation, the correlation function as well as the box counting method has been used to calculate the fractal dimension. According to the result of calculation, the fractal dimension increases as the current increases at the constant electrode gap distance. However, there is no significant relation between the fractal dimension and the electrode gap distance at a constant current.

• Journal of Adhesion and Interface
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• v.16 no.1
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• pp.29-34
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• 2015

Hydrocarbon resins, which are defined as low molecular weight, amorphous, and thermoplastic polymers, are widely used as tackifier for various types of adhesives, as processing aids in rubber compounds, and as modifiers for plastics polymers such as isotactic polypropylene. Typically, hydrocarbon resins are non-polar, and thus highly compatible with non-polar rubbers and polymer. However, they are poorly compatible with polar system, such as acrylic copolymer, polyurethanes, and polyamides. Moreover, recently the raw materials of hydrocarbon resin from naphtha cracking had been decreased because of light feed cracking such as gas cracking. To overcome this problem, in this study, novel hydrocarbon resins were designed to have a highly polar chemical structure which material is sustainable. And, it was successfully synthesized by Diels-Alder reaction of dicyclopentadiene monomer and sorbic acid from blueberry as renewable resources. Acrylic resins were formulated with various tackifiers solution including sorbic acid grafted hydrogenated dicyclopentadiene hydrocarbon resins in acrylic adhesive and rolling ball tack, loop tack, $180^{\circ}$ peel adhesion strength, and shear adhesion strength were measured. The properties depend on the softening point and polar content of tackifiers.

• The Journal of the Korea Contents Association
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• v.13 no.1
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• pp.456-466
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• 2013

The most important thing to develop real estate asset would be a feasibility study. To secure feasibility of development projects, reducing and minimizing the cost of land and construction also would be the important thing. To analyze optimal land-value for real estate development projects, I have collected 204 balance sheets of development projects in South Korea. With the help of statistical technology, I could have selected useful data from those balance sheets. After detailed analysis of statistical data, I could have reached conclusion that the most important factor to earning rate would be land cost per unit ground area under the constraint of given sale price. So far the main pattern of feasibility study of development projects was land cost and construction cost. However, by this study, I have found a new fact that construction cost has little effect to earning rate and land cost per unit ground area is the most effect to earning rate especially in residential facilities rather than commercial ones.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.44-51
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• 2020

The basic catalyst 1-benzyl-3-methyl-imidazolium hexafluoroantimonate (BMH) was synthesized and analyzed by FT-IR and ¹H-NMR. A crystalized biphenyl-based epoxy was synthesized by using tetramethyl biphenol (TMBP) and epichlorohdrine. In order to consider the curing tendency of the synthesized BMH, the mass ratio was changed to 0.5, 1.0, 2.0 wt.% under heated conditions and the curing tendency was analyzed by differential scanning calorimeter (DSC). As a result, the BMH catalyst showed a fast curing result in the stepwise heating pr℃ess of the biphenol-A epoxy and the cationic polymer. From these results, the BMH catalyst showed excellent thermal stability as a potential heat curing catalyst. In addition, we considered the application possibility of epoxy molding compound (EMC) which required a skeleton structure and a high heat resistance because the synthesized biphenyl epoxy had a characteristic of rapidly lowering viscosity at a constant temperature and a rigid skeleton structure of biphenol. As a result, it was confirmed that the TMBP-based epoxy developed in this study was composed of a crystalline structure, and a curing reaction was observed with a Novolac resin at a high temperature. In the presence of a catalyst, a curing reaction was observed around 150 ℃ and thus TMBP-based epoxy was successfully applied as a raw material of EMC.