• 전기화학회지
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• 제16권1호
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• pp.30-38
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• 2013

In this study, a catalyst slurry was prepared with a Pt/C catalyst, Nafion ionomer solution as a binder, an ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate), deionized water and ethanol as a solvent for the application to polymer electrolyte fuel cells (PEFCs) at high-temperatures. The effect of the IL in the electrode of each design was investigated by performing a cyclic voltammetry (CV) measurement. Electrodes with different IL distributions inside and on the surface of the catalyst electrode were examined. During the CV test, the electrochemical surface area (ESA) obtained for the Pt/C electrode without ILs gradually decreased owing to three mechanisms: Pt dissolution/redeposition, carbon corrosion, and place exchange. As the IL content increased in the electrode, an ESA decrement was observed because ILs leaked from the Nafion polymer in the electrode. In addition, the CVs under conditions simulating leakage of ILs from the electrode and electrolyte were evaluated. When the ILs leaked from the electrode, minor significant changes in the CV were observed. On the other hand, when the leakage of ILs originated from the electrolyte, the CVs showed different features. It was also observed that the ESA decreased significantly. Thus, leakage of ILs from the polymer electrolyte caused a performance loss for the PEFCs by reducing the ESA. As a result, greater entrapment stability of ILs in the polymer matrix is needed to improve electrode performance.

• 한국세라믹학회지
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• 제46권1호
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• pp.16-23
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• 2009

The porous pellets were prepared from porphyry by slurry foaming method. The effect of sintering temperatures on pore structure of porous porphyry pellets with different extension ratio ($E_R$) was investigated by specific surface area, water absorption and porosity, which changed with sintering temperatures. When the sintering temperatures increased from $975^{\circ}C$ to $1075^{\circ}C$, specific surface area and water absorption of the all samples decreased. In case of the sample with an equal sintering temperature, $E_R=3.0$ pellets had little influence on pore structure compared to the $E_R=2.0$ pellets. As a results, it was shown by SEM that facilitated formation of micro pores at $E_R=2.0$ pellets shrunk increasingly after sintering process. At $E_R=3.0$ and sintering temperature at $1025^{\circ}C$, optimum conditions of the porous porphyry porous pellets was found. Also, Escherichia coli removal efficiency of the silver-containing porphoyry porous pellets was measured for the feasibility as a antibacterial media. The antibacterial activity of prepared silver-containing sample was maintained above 90% for 40 days.

• 한국식품과학회지
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• 제39권2호
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• pp.169-174
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• 2007

옥수수전분의 알칼리호화는 NaOH 첨가에 의하여 지수적으로 증가하였으며, 호화도가 급격히 증가하기 시작하는 구간을 알칼리호화 개시점으로 추정하였다. 10%(w/w) 옥수수 전분 현탁액의 $40^{\circ}C$에서 호화개시점은 24.1 meq NaOH/g starch인 반면에 $60^{\circ}C$에서는 9.8 meq NaOH/g starch이었다. 또한 옥수수전분 현탁액의 농도를 40%로 증가시킨 경우 $40^{\circ}C$에서 9.5 meq NaOH/g starch에서 호화가 개시되었다. 이와 같은 결과로부터 전분의 알칼리호화 개시농도가 전분 현탁액의 농도와 온도에 반비례하는 것을 알 수 있었다.

• 한국분말재료학회지
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• 제23권1호
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• pp.49-53
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• 2016

The present study demonstrates the effect of freezing conditions on the pore structure of porous Cu-10 wt.% Sn prepared by freeze drying of $CuO-SnO_2$/camphene slurry. Mixtures of CuO and $SnO_2$ powders are prepared by ball milling for 10 h. Camphene slurries with 10 vol.% of $CuO-SnO_2$ are unidirectionally frozen in a mold maintained at a temperature of $-30^{\circ}C$ for 1 and 24 h, respectively. Pores are generated by the sublimation of camphene at room temperature. After hydrogen reduction and sintering at $650^{\circ}C$ for 2 h, the green body of the $CuO-SnO_2$ is completely converted into porous Cu-Sn alloy. Microstructural observation reveals that the sintered samples have large pores which are aligned parallel to the camphene growth direction. The size of the large pores increases from 150 to $300{\mu}m$ with an increase in the holding time. Also, the internal walls of the large pores contain relatively small pores whose size increases with the holding time. The change in pore structure is explained by the growth behavior of the camphene crystals and rearrangement of the solid particles during the freezing process.

• Asian-Australasian Journal of Animal Sciences
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• 제33권7호
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• pp.1209-1216
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• 2020

Objective: The present study aimed to evaluate the performance of odor abatement by using two different ventilation-biofilter systems with recycled stablized swine wastewater. Methods: The performance of odor removal efficiency was evaluated using two different ventilation-biofilter-recycled wastewater arrangements. A recirculating air-flow ventilation system connected to a vertical biofilter (M1) and a plug-flow ventilation system connected to a horizontal biofilter (M2) were installed. Water dripping over the surface of the biofilter was recycled at a flow rate of 0.83 L/h in summer and 0.58 L/h in winter to reduce odorous compounds and particulate matter (PM). The experiments were performed for 64 days with M1 and M2 to investigate how these two ventilation-biofilter systems influenced the reduction of odor compounds in the model houses. Odorous compounds, NH₃ and volatile organic compounds (VOCs) were analyzed, and microclimatic variables such as temperature, humidity, and PM were monitored. Results: Ammonia concentration inside M1 was about 41% higher on average than that in M2. PM and total suspended particles (TSPs) inside M1 were about 62.2% and 69.9%, respectively, higher than those in M2. TSPs in the model house were positively correlated with the concentration of NH₃ and VOCs. Conclusion: M2 emitted lower concentration of odorous compounds than M1. Moreover, M2 could maintain the optimum temperature condition for a swine house during the cooler season. The plug-flow ventilation-horizontal biofilter system could be used for pig houses to minimize air pollution produced by swine farming activities and maintain optimum microclimate conditions for pigs.

• 공업화학
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• 제8권4호
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• pp.704-707
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• 1997

카올린에서 추출된 황산알루미늄 용액을 이용하여 정밀화학 분야에서 많은 이용이 기대되고 있는 알루미나 졸의 제조에 대하여 연구하였다. 교반을 하면서 황산알루미늄용액에 암모니아수를 첨가하여 비정질의 일수산화알루미늄(AlO(OH))를 제조하고, 제조된 입자의 표면에 전기이중층을 형성하기 위해서 초산($CH^3COOH$)을 투입하여 안정한 알루미나 졸을 제조하였다. 안정한 알루미나 졸의 제조에 미치는 반응온도, 반응시간, 초산의 농도 등의 영향을 조사하였다. 반응온도 $50{\sim}90^{\circ}C$, A/C(건조된 알루미나 량/첨가된 초산의 량) 1.6 (몰비)에서 안정한 졸의 합성이 가능하였으며, 반응시간에는 거의 영향을 받지않았다. 또한, 알루미나의 함량이 1~5vol%까지의 범위에서 안정한 졸이 제조되었고, 이때 졸의 입자크기는 약 5~10nm 정도이었다.

• Journal of Microbiology and Biotechnology
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• 제24권11호
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• pp.1484-1489
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• 2014

A novel esterase gene, est01, was successfully unearthed from a biogas digester microbiota metagenomic library. The 1,194 bp est01 gene encodes a protein of 44,804 Da (designated Est01). The amino acid sequence of Est01 shows only moderate (33%) identity to a lipase/esterase. Phylogenetic analysis and biochemical characterization confirmed that Est01 is a new member of family VIII esterases. The purified Est01 from recombinant Escherichia coli BL21 (DE3) showed high hydrolytic activity against short-chain fatty acid esters, suggesting that it is a typical carboxylesterase rather than a lipase. Furthermore, the Est01 was even active at $10^{\circ}C$ (43% activity remained), with the optimal temperature at $20^{\circ}C$, and had a broad pH range from 5.0 to 10.0, with the optimal pH of 8.0. These properties suggest that Est01 is a cold-adaptive esterase and could have good potential for low-temperature hydrolysis application.

• 한국식품영양과학회지
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• 제36권8호
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• pp.1094-1097
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• 2007

주파수 20 Hz와 0.18 g의 가속도에 해당하는 진동을 1L 유리병에 담겨진 600 g의 물김치에 가하였다. $-3^{\circ}C$와 $-6^{\circ}C$에서 동결의 진행정도를 관찰하였고, $10^{\circ}C$에서는 총산과 $CO_{2}$ 발생을 측정하여 발효진행 정도를 측정하였다. 진동이 없는 대조구를 같은 온도조건에서 두어서 진동의 효과를 비교하였다. $-3^{\circ}C$와 $-6^{\circ}C$에서의 진동은 동결의 과정을 지연시키고, 계속되는 저장에서 작은 얼음결정의 혼합체를 유지하는 데에 있어서 긍정적인 결과를 보였다. $10^{\circ}C$에서 진동은 산의 생성과 $CO_{2}$ 발생을 촉진하여 숙성시간을 단축시키고 시원한 맛을 주는 데 긍정적인 역할을 할 수 있는 것으로 평가되었다.

• 대한화학회지
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• 제31권1호
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• pp.110-117
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• 1987

선형저밀도폴리에틸렌(LLDPE)의 제조를 위해 여러가지 티탄알콕시드-알킬알루미늄 화합물을 촉매로 하여 에틸렌과 1-부텐을 슬러리 상태로 공중합하였다. 이때 촉매성분의 종류 및 농도, 숙성시간, 중합시간과 중합온도 등이 촉매활성과 공중합체 조성에 미치는 영향을 연구하였다. 그리고 공중합체의 성질과 1-부텐 함량과의 관계를 조사하였다. 그 결과 티탄사노르말부톡시드-염화디에틸알류미늄의 촉매를 사용하였을 때 가장 큰 촉매활성, 보다 많은 1-부텐 함량 및 가장 작은 가용성 부분의 LLDPE를 얻을 수 있었다. 얻은 공중합체의 밀도, 유리전이온도, 녹는점 및 녹음열 등은 1-부텐의 함량이 증가함에 따라 감소하였다.

• 한국세라믹학회지
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• 제44권9호
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• pp.529-535
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• 2007

Calcium oxide has been used as a demolition agent in fracturing rocks and old concrete structures, etc. With the agent, demolition work can be done in safety without a noise, vibration and any other pollution, since high expansive pressure is obtained gradually by only mixing the agents with water and pouring the slurry into boreholes. But application of the non-explosive demolition agent is a time-consuming job, especially in winter. Essentially, this problem is related to the reaction rate of calcium oxide with water. This study examines the influence of additives such as cement and anhydrite on expansion pressure of calcium oxide at different curing temperatures. The expansion pressure of calcium oxide began to increase steadily with the rise of the curing temperature. When mixing calcium oxide alone with water, blown-out shot occurred. But as additives were added to calcium oxide, the reaction of calcium oxide delayed and the expansion pressure showed gradual increment. Especially, anhydrite showed a superior delaying effect than cement on the reaction of calcium oxide.