• 공업화학
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• 제10권5호
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• pp.767-771
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• 1999

내열성 전기 절연 coating에 사용되는 기본 수지인 poly(ester-imide) (PEI)의 1단계 및 2단계 합성법을 비교하였으며 촉매의 영향도 조사하였다. Poly(ester-imide) 수지의 합성에 있어서 trimellitic anhydride(TMA)와 methylene dianiline(MDA)으로부터 imide 반복 단위를 구성하는 N,N'-(4,4'-diphenylmethane)bistrimellitimide(DID)를 먼저 합성하고 에스테르화 반응을 시키는 2단계법과 TMA, MDA, dimethyl terephthalate(DMT) 및 ethylene glycol(EG), 1,3,5-tris-(2-hydroxy ethyl)isocyanurate(THEIC)를 모두 m-cresol 용매에 넣고 반응시키는 1단계법이 동등한 PEI 수지를 생성함을 확인할 수 있었다. 합성된 poly(ester-imide) 수지 용액에 xylene, phenol-formaldehyde 수지인 P-5030K, TDI type blocked isocyanate인 TK-8 및 tetrapropyltitanate(TPT)를 첨가하여 경화 반응을 시키고 생성된 피막의 유연성 및 투명도를 조사한 결과 히드록실기의 함량, DMT의 첨가 및 imide 반복 단위의 함량이 내열성 절연 코팅의 물성에 중요한 인자로 작용함을 알 수 있었다.

• 한국식품저장유통학회지
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• 제18권5호
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• pp.721-728
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• 2011

Camellia oil과 palmitic, 그리고 stearic ethyl ester를 기질로 하고 Lipozyme TLIM을 촉매로 이용하여 interesterification을 통한 POS를 많이 함유한 반응물을 합성하고자 하였다. 반응 조건(반응효소비율, 반응시간, 기질의 비율)을 독립변수로 하여 중심 합성 계획에 의한 반응 표면 분석을 통하여 POS의 함량은 높이고, sn-2 position의 acyl migration을 낮추어 합성하는 최적화 조건을 얻었다. POS를 많이 함유한 반응물의 합성 최적화 조건은 반응 효소양($X_1$)= 5.9%, 반응시간($X_2$)= 60 min, 그리고 기질비율($X_3$)= 1:3(1 mole의 camellia oil: 3 mole의 palmitic ethyl ester + 3 mole의 stearic ethyl ester)이었다. 이와 같은 조건으로 획득된 실재 효소반응 합성물의 TAG-P/O/S(palmitic, stearic과 oleic 지방산을 각각 1 분자씩 어느 위치이던지 함유한 TAG, 즉 POS 및 PSO/OSP/OPS/SPO)의 합성율($Y_1$)은 20.19%이었고, 이때 acyl migration 등에 의하여 sn-2 위치에 결합(이동)한 palmitic과 stearic acid의 양(P/S-sn-2)인 $Y_2$는 12.71% 이었다.

• 공업화학
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• 제25권3호
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• pp.254-261
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• 2014

변압기 내부에서 발생한 열의 냉각과 절연의 목적으로 채워지는 전기절연유는 광유가 널리 이용되고 있지만, 유출 시야기되는 환경오염 문제와 열적 불안정성 등의 문제가 있다. 친환경적이고 넓은 온도 범위에서 사용 가능한 전기절연유를 합성하기 위해, 디글리세롤과 두 종류의 지방산을 반응시켜 diglycerol ester를 합성하였다. 서로 다른 특성을 가진 올레산과 카프릴산의 몰비에 따른 절연특성을 분석한 결과, 지방산의 몰비가 Oleic acid:Caprylic acid = 1:3일 때 유동점은 $-50^{\circ}C$, 인화점은 $306^{\circ}C$로 가장 우수한 절연특성을 보였다. 또한, 합성물은 지방산의 전환율이 상승할수록 인화점은 상승하고 유동점은 감소하였다. $SO_4{^{2-}}/ZrO_2$의 소성온도에 따른 촉매특성 및 전환율을 살펴본 결과, $600^{\circ}C$에서 소성한 $SO_4{^{2-}}/ZrO_2$가 결정성을 가지면서 비표면적 당 산점의 밀도가 높아 가장 높은 전환율을 보였다. 합성한 diglycerol ester는 식물성 절연유와 비교했을 때 전반적으로 식물성 절연유보다 우수한 특성을 보였다.

• 농약과학회지
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• 제2권3호
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• pp.147-150
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• 1998

Ortho치환체로서 ${\alpha}$-diketone 또는 ${\alpha}$-keto ester기를 포함하는 신규한 벤젠 술포닐우레아 유도체들을 2-homophenyl metholernethyl sulfide를 출발물질로 하는 새로운 합성방법을 이용하여 합성하였으며, 이 화합물들은 특히 경엽처리에서 흥미있는 제초활성을 나타내었다.

• 임산에너지
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• 제20권1호
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• pp.42-52
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• 2001

국내에 자생하는 몰푸레, 쇠몰푸레 그리고 들메나무의 수피를 채취하여 아세톤-물(7:3, v/v)로 추출한 후 동결건조시켜서 분말로 제조하였고 Sephadex LH-20 및 TSK 40F로 충진한 칼럼 상에서 메탄올, 에탄올 그리고 에탄올-헥산 혼합액을 용이용매로 상요하여 칼럼크로마토그래키를 실시하였다. 단리된 화합물들은 TLC로 확인한 후 NMR스펙트럼을 상용하여 정확한 구조규명을 하였고 FAB-MS로써 분자량을 측정하였다. 쿠마린 유도체들이 다량으로 포함되어 있었으며 소량의 ester형태의 화합물들도 단리 되었다. 물푸레와 쇠물푸레에서는 aesculetin, aesculin 및 fraxetin과 같은 쿠마린 화합물들과 ligstroside와 oleuropein과 같은 ester형태의 화합무들이 모두 단리 되었으며 들메나무에서는 ester형태의 화합물만 단리 되었다.

• Composites Research
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• 제30권5호
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• pp.303-309
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• 2017

Organo-montmorillonite (OMMT) has attracted much attention for fiber-reinforced polymer composites as a filler material due to high aspect ratio and low charge density. The present study focused on the fabrication of nanocomposites using Vinyl ester and Jute fabric as matrix and reinforcement respectively. The OMMT was uniformly dispersed in vinyl ester resin at 1, 2 and 3 wt%, loading through high speed mechanical stirrer at room temperature and further nanocomposites were manufactured through vacuum assisted resin infusion (VARI) technique. Effects of OMMT on the mechanical properties of vinyl ester/Jute composites were carefully investigated through tensile, bending and Izod impact tests, which revealed significant improvement in mechanical properties. The morphology of the nanocomposites after tensile test was investigated by SEM which affirmed that OMMT filled nanocomposites has improved interactions with the host matrix than the pure composites. Based on the nature and flame retardancy mechanism, the OMMT slightly improved the flammability property which was clearly explained by horizontal burning test.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.820-829
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• 2017

Vegetable oil dielectrics have been used in transformers as green alternatives to mineral insulating oils for about twenty years, because of their advantages of non-toxic, biodegradability, and renewability. However, the viscosity of vegetable oils is more than 3 times of mineral oils, which means a poor heat dissipation capacity. To get low-viscosity dielectrics, transesterification and purification were performed to prepare vegetable oil methyl esters in this study. Electrical and physical properties were determined to investigate their potential as dielectrics. The results showed that the methyl ester products had good dielectric strengths, high water saturation and enough fire resistance. The viscosities (at $40^{\circ}C$) were 0.2 times less than FR3 fluid, and 0.7 times less than mineral oil, which indicated superior cooling capacity as we expected. With the assistance of 0.5 wt% pour point depressants, canola oil methyl ester exhibited the lowest pour point ($-26^{\circ}C$) among the products which was lower than FR3 fluid ($-21^{\circ}C$) and 25# mineral oil ($-23^{\circ}C$). Thus, canola oil methyl ester was the best candidate as a low-viscosity vegetable oil-based dielectric. The low-viscosity fluid could extend the service life of transformers by its better cooling capacity compared with nature ester dielectrics.

• 한국응용과학기술학회지
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• 제15권3호
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• pp.55-60
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• 1998

The sodium ${\alpha}-sulfo$ fatty acid vinyl ester oligomers, which are oligomer type surfactants were prepared by polymerization with fatty acid vinyl acetate. The ${\alpha}-sulfonation$ of fatty acid vinyl ester oligomers were carried by direct addition of sulfur trioxide. The dispersing performance of oligomer type anionic surfactants and sodium dodecyl sulfate(SDS) in the aqueous suspension of iron oxide and titanium dioxide particles was evaluated by particle size distribution and zeta-potential measurement. As results, the particles of iron oxide and titanium dioxide were flocculated by addition of small amount of oligomer type anionic surfactants and sodium dodecyl sulfate(SDS), then the flocks redispersed by more addition of oligomer type anionic surfactants and SDS. The flocculation, redispersion process was observed in lower concentration range of oligomer type anionic surfactants than SDS. Especially, the dispersing action of sodium ${\alpha}-sulfo$ palmitic acid vinyl ester oligomer was better than sodium ${\alpha}-sulfo$ lauric acid vinyl ester oligomer.

• Journal of Pharmaceutical Investigation
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• 제23권2호
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• pp.61-69
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• 1993

Prodrug of cefazolin (CFZ) was prepared with the objective of improving its oral bioavailability. Cefazolin phthalidyl ester (CFZ-PT) was synthesized and evaluated as potential prodrug form. The successful synthesis of CFZ-PT was identified by spectroscopic analysis. Partition coefficient studies showed that CFZ-PT is more lipophilic than CFZ and the ester was hydrolyzed enzymatically into the parent drug in blood, liver and intestinal homogenates. The pharmacokinetic characteristics of CFZ-PT and CFZ were compared following oral administrations to rabbits. Serum CFZ concentration was determined by HPLC method and the ester compound (prodrug) was not detected in serum following oral administration of CFZ-PT. CFZ-PT did not have antimicrobial activity in vitro against Bacillus subtilis ATCC 6633, whereas CFZ-PT in serum after oral administration to rabbits had antimicrobial activity. From above observations, it was noted that CFZ-PT is rapidly hydrolyzed to CFZ in the body and the bioavailability of CFZ-PT was increased by 3.5-fold than that of CFZ. From these results of this study, it was concluded that CFZ-PT may be a novel prodrug of CFZ which can improve the oral absorption of CFZ.

• 전기학회논문지P
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• 제64권4호
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• pp.236-240
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• 2015

Natural ester has a higher biodegradability, flash and fire points, and a greater permittivity compared to conventional mineral oils. However, natural ester also has a higher pour point, viscosity, and water content. These characteristics hamper circulation and the electrical properties of oil-filled transformer. Thus, this paper applied electromagnetic-thermal-flow coupled analysis method to predict temperature distribution inside 154kV single phase power transformer using natural ester. It modeled in the actual appearance for the tank and winding of the power transformer to improve the accuracy of analysis and applied heat flow analysis that considered hydromechanics and heat transfer at the same time. It calculated the power loss, the main cause of temperature rise, from winding and core with electromagnetic analysis then used for the heat source for the heat flow analysis. It then compared the reasonability of result of measurement analysis based on the result acquired from temperature rise test using FBG sensor on the power transformer.