• 청정기술
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• 제17권3호
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• pp.238-243
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• 2011

본 연구에서는 폴리우레탄을 위한 친환경 폴리올 합성을 위하여 피마자유 기반의 폴리올을 합성하였다. 피마자유의 2차 알콜에 다른 촉매 없이 무수말레산을 이용하여 카르복실기를 도입하고, 이를 1차 알콜로 전환하기 위하여 아미노알콜($H_2N$-R-OH) 유도체를 반응시켜 친환경 폴리올을 제조하였다. 다양한 비율의 피마자유와 무수말레산의 반응이 시험 되었으며, 전체 반응은 상대적으로 낮은 공정온도와 무촉매 반응을 기반으로 수행되었다. 긴 곁가지가 도입되어 유동성을 가지고 있는 피마자유 기반의 천연폴리올이 기존의 합성폴리올과 가장 우수한 상용성을 나타내었다.

• Elastomers and Composites
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• 제49권3호
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• pp.245-252
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• 2014

폴리올, 이소시아네이트, 2-HEMA 및 기타 아크릴레이트 단량체들로부터 제조된 폴리우레탄 접착제의 FT-IR측정과 물성을 검토하였다. 폴리우레탄 접착제의 연화점, 점도, 접착강도 및 기계적 물성들이 각각 링과볼법, Brookfield 점도계 및 만능시험기를 이용하여 검토되었다. 실험 결과에 의하면 PPG 함량 및 부틸아크릴레이트 함량이 증가함에 따라 연화점, 접착강도, 인장강도 및 100% modulus 값 등은 감소하는 것을 보여준다. 하지만 2-HEMA 및 MDI량이 증가할수록 인장강도 및 100% modulus값 등은 증가하였으며 점도와 NCO함량 등도 또한 증가하였다.

• 한국응용과학기술학회지
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• 제33권1호
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• pp.92-99
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• 2016

PPG와 PTMG의 몰비를 달리하면서 첨가하여 합성된 폴리우레탄 수지의 물리적 특성을 SEM, FT-IR, UTM을 이용하여 측정하였다. 본 연구를 통해 4개의 메틸렌기를 포함한 PTMG의 몰비가 증가함에 따라 내마모도(60.26 mg.loss), 인장강도($5.24kgf/mm^2$)가 증가함을 알 수 있었다. 반대로 연신율(297 %)은 감소함을 확인 할 수 있었으며. 톨루엔을 이용한 내용제성 물성측정 결과로부터 PTMG의 반응 몰비 증가에 따른 물성 증감 효과는 없었다. 또한 PTMG의 몰비가 증가함에 따라 점도(4.8 cp)가 상승함을 확인 할 수 있었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.646-651
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• 2007

This study has been conducted to select the suitable refrigeration oil for a $CO_2$ refrigeration system. The oil return is one of the most important characteristics for refrigeration oils. PAG and POE oils are considered as a test fluids in this study. An evaporator model is employed to simulate the evaporator of a $CO_2$ refrigeration system. Oil return characteristics has been investigated for $CO_2$/PAG and $CO_2$/POE mixtures in the range of oil concentration 0 to 5 weight-percent and the mixture temperature range of $0^{\circ}C$ to $15^{\circ}C$. The results obtained indicate that oil return is decreased with an increase in the oil concentration and mixture temperature for both POE and PAG oils. It is also found that POE oil is seen to be superior than PAG oil in terms of oil return in an evaporator of a $CO_2$ refrigeration system.

• Elastomers and Composites
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• 제50권4호
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• pp.297-303
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• 2015

Ammonium polyphosphate-polyurethane foam composite (APP-PUF) was prepared from poly(adipate)diol/ammonium polyphosphate composite (f = 2), polyether polyol (f = 4.6), and PMDI (f = 2.5). As a blowing agent, $H_2O$ was used at various concentrations. The thermal decomposition behavior, morphology, closed-cell content, and density of APP-PUF were characterized. At the $H_2O$ concentrations lower than 3.5 php, the cell size of pure polyurethane foams (PUF) and APP-PUFs were close each other. As the $H_2O$ concentration became greater than 5.0 php, the cell size of the PUFs greatly increased compared to that of APP-PUFs. Addition of 1.5~1.9 wt% ammonium polyphosphate to the PUFs greatly enhanced the thermal stability of the PUFs, so 50 wt% residual temperature of APP-PUFs increased to $380{\sim}488^{\circ}C$, which were $30{\sim}70^{\circ}C$ higher than those of the PUFs. Thermal stability of the PUFs and APP-PUFs increased with $H_2O$ content and then decreased once $H_2O$ content exceeded 5 php.

• 설비공학논문집
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• 제12권2호
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• pp.209-217
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• 2000

The solubility and miscibility measurement apparatus was developed and used to obtain data for refrigerant/oil mixture. The solubility and miscibility data for R-410A/68 ISO VG polyol ester (POE) oil mixture are obtained over the temperature range from -20 to $60^{circ}C\;with\;10^{\circ}C$ intervals and the oil concentration range from 0 to 90 wt%. Using the experimental data, an empirical model was developed to predict the solubility relations for R-410A/POE oil mixture at equilibrium. In the R-410A/Solest 68 oil mixture, the average root-mean-square deviation between measured data and calculated results from the empirical model is 3.4% and in the R-4104/EMKARATE RL 68H oil mixture, that is 2.86%. For R-410A/68 ISO VG POE oil mixture immiscibility was usually observed at the low oil concentrations(5~30 wt%) over the all experimental temperature range($-20~60^{circ}C$) and at the high oil concentrations(50~90 wt%) over the low experimental temperature range($-2O~0^{circ}C$).

• 한국식물학회:학술대회논문집
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• 한국식물학회 1987년도 식물생명공학 심포지움 논문집 Proceedings of Symposia on Plant Biotechnology
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• pp.157-167
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• 1987

The have been many reports that phenoloxidase are correlated with development in many fungi. C. congregatus, one of nushroom-forming basidiomycetes, which requires light for its development also has phenoloxidases. In C. congragatus, there are two sets of membrane-associated phenoloxidase (PHO I and PHO II) which are differentiated by their isozyme patterns, and each enzyme set consists of two different subtrate specific enzyme protein; o-tolidine reacting enzyme, and DOPA reacting enzyme. PHO I which is localized by a protoplast-concanavalin A technique by using a new solidifying agent, Pluronic Polyol F 127, instead of agar appears in the vegetative hyphae, and PHO II appears at the early primordial stage on agar and at the sclerotial stage of liquid shake cultures. Inhibition of PHO I with the enzyme inhibitors inhibits mushroom formation as well as melanization of the vegetative hyphae at concentrations which do not inhibit the vegetative growth. PHO I deficient mutants do not form mushrooms or melanins, and the mutants show abnormal nuclear migration patterns. PHO II has roles; possibly cementing the adjacent hyphae during the actual three dimensonal structure formation, and melanizing mushrooms and sclerotia. The possible roles of PHO I in the light reception complex and in melanin formation, the function of malanin, and possible roles of postulated post translational modifying enzymes which regulate the phenoloxidases, nuclear migration pattern, and self-nonself recognition mechanism are discussed.

• Advances in nano research
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• 제3권2호
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• pp.55-66
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• 2015

Crystalline $Ce^{3+}$ co-doped $LaPO_4$:RE ($RE=Dy^{3+}$, $Tb^{3+}$, $Eu^{3+}$, $Sm^{3+}$) and mix doped rare earth ions of $Dy^{3+}$, $Tb^{3+}$ and $Eu^{3+}$ were prepared by the polyol method at $150^{\circ}C$. Strongly enhance luminescence intensity is obtained with the co-doping of $Ce^{3+}$ with $LaPO_4$:$Dy^{3+}$ and $LaPO_4$:$Tb^{3+}$ due to charge transfer (CT) occurring from $Ce^{3+}$ to $Dy^{3+}$ and $Ce^{3+}$ to $Tb^{3+}$, where as there is no significant changes in luminescence intensity of $Ce^{3+}$ co-doped $Eu^{3+}$ and $Sm^{3+}$ doped $LaPO_4$ samples. The luminescence color can be tuned from green to white by varying the excitation wavelength for the mix ions $Ce^{3+}$, $Dy^{3+}$, $Tb^{3+}$ and $Eu^{3+}$ doped with $LaPO_4$.

• The Korean Journal of Physiology and Pharmacology
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• 제5권3호
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• pp.271-278
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• 2001

Oxidative stress and methylglyoxal (MG), a reactive dicarbonyl metabolites produced by enzymatic and non-enzymatic reaction of normal metabolism, induced aldose reductase (AR) expression in rat aortic smooth muscle cells (SMC). AR expression was induced in a time-dependent manner and reached at a maximum of 4.5-fold in 12 h of MG treatment. This effect of MG was completely abolished by cyclohemide and actinomycin D treatment suggesting AR was synthesized by de novo pathway. Pretreatment of the SMC with N-acetyl-L-cysteine significantly down-regulated the MG-induced AR mRNA. Furthermore, DL-Buthionine-(S,R)-sulfoximine, a reagent which depletes intracellular glutathione levels, increased the levels of MG-induced AR mRNA. These results indicated that MG induces AR mRNA by increasing the intracellular peroxide levels. Aminoguanidine, a scanvenger of dicarbonyl, significantly down-regulated the MG-induced AR mRNA. In addition, the inhibition of AR activities with statil, an AR inhibitor, enhanced the cytotoxic effect of MG on SMC under normal glucose, suggesting a protective role of AR against MG-induced cell damages. These results imply that the induction of AR by MG may contribute to an important cellular detoxification of reactive aldehyde compounds generated under oxidative stress in extrahepatic tissues.

• 한국산업보건학회지
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• 제22권3호
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• pp.209-216
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• 2012

Objectives: Polyurethanes are usually formed by the reactions of liquid diisocyanate components with liquid polyol resin components. Although polyurethanes have advantageous properties, such as their versatility, the manufacturing process generates diisocyanates, which can cause asthma and respiratory irritation in exposed workers. This study compared the differences in diisocyante concentrations between two different (molded foam and slabstock foam) polyurethane foam manufacturing methods. Materials and Methods: Active samples and direct reading samples of diisocyanates (MDI, TDI) were collected in five polyurethane foam manufacturing companies. Results: Workers' exposure concentrations of diisocyanate (GM: 4.078 ppb, range: 1.190~23.770 ppb) in a slabstock foam manufacturing company were much higher than those (GM: 0.011 ppb, range: 0.001~0.055 ppb) in molded foam manufacturing companies. The results of the direct reading samples of diisocyanate indicated that the rapid reaction zone of the slabstock foam processes emitted large amounts of diisocyanates. Conclusions: The exposure levels of diisocyanates for all molded foam workers were much lower than the occupational exposure standard (5 ppb); however, exposure levels for many slabstock foam workers exceeded the standard.