• 청정기술
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• 제18권3호
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• pp.287-294
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• 2012

본 연구에서는 중고 레이저 복합기의 재제조 과정에서 복합기의 성능에 큰 영향을 미치는 인쇄회로기판(printed circuit board, PCB) 등 전자부품에 대하여 세정공정의 도입 적용 가능성을 분석하고 세정장치 및 최적의 운전조건을 설계하였다. 1단계로 물에 의한 부식의 염려가 없는 건식세정방식으로 플라즈마세정에 의한 세정성을 분석하였다. 플라즈마세정 의한 PCB세정에서는 세정이 어느 정도 이루어졌으나 플라즈마가 전도 될 수 있는 피세정물의 금속 부분 주위에서 피 세정물의 손상을 확인할 수 있었으며 레이저 복합기의 재제조용으로는 생산성 및 경제성이 부족하였다. 2단계에서는 경제성이 있는 초음파세정방식을 위하여 현재 현장에서 사용되고 있는 세정제를 포함하여 세정효율이 우수한 4종의 대체 세정제를 선정하여, 세정제의 물성을 측정하였고 세정성을 평가하였다. 준수계 세정제와 비수계 세정제보다 수계 세정제의 세정력이 우수 하였으며, 초음파 주파수가 작을수록 세정력이 우수하였다. 수계세정제 A를 사용하여 28 kHz의 초음파 세기에서 세정을 한다면 30초~1분 내에 빠른 세정이 가능할 것으로 판단되었다. 3단계에서는 선정된 세정제로 초음파 세정시스템을 구축하고, 실제 부품들을 초음파 세정하여 현장에서 사용이 적합한 최적의 세정조건을 구하였다. PCB 보드 및 대전기에 대하여 최적 세정 조건을 구한 결과, 40 kHz, $50^{\circ}C$에서 1분 30초 및 2분에 세정을 끝낼 수 있었다. 수작업에 의존하거나 외부처리를 하고 있는 중소 재제조 업체들은 본 세정시스템의 도입으로 전자부품 기능의 신뢰성이 확보되며 전체적인 재제조 공정의 생산성 및 경제성 향상에 큰 효과를 볼 수 있을 것으로 기대된다.

• Bulletin of the Korean Chemical Society
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• 제34권7호
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• pp.1985-1989
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• 2013

A simple colorimetric and fluorescent anion sensor 1 based on salicylimine showed a high selectivity and sensitivity for detection of cyanide in aqueous solution. The receptor 1 showed high selectivity toward $CN^-$ ions in a 1:1 stoichiometric manner, which induces a fast color change from colorless to orange and a dramatic enhancement in fluorescence intensity selectively for cyanide anions over other anions. Such selectivity resulted from the nucleophilic addition of $CN^-$ to the carbon atom of an electron-deficient imine group. The sensitivity of the fluorescence-based assay (0.06 ${\mu}M$) is below the 1.9 ${\mu}M$ suggested by the World Health Organization (WHO) as the maximum allowable cyanide concentration in drinking water, capable of being a practical system for the monitoring of $CN^-$ concentrations in aqueous samples.

• 한국응용과학기술학회지
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• 제26권4호
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• pp.422-427
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• 2009

We have investigated the effects of polyols and NaCl on the rheological behaviours of surfactant mixtures. Sodium lauryl ether sulfate (SLES), cocamidopropyl betaine (CAPB), disodium cocoamphodiacetate (DSCA), cocamide DEA (CDEA) and lauroyl/myristoyl DEA (LMDE) were used as surfactants. The polyols added into the surfactant mixture were 1,3-butylene glycol, propylene glycol, glycerin, sorbitol, dipropylene glycol, PEG 1500 and PEG 400. The addition of amphoteric surfactant to SLES aqueous solution lead to increase the height of foam and the viscosity of the system. The addition of nonionic surfactant, LMDE or CDEA to the SLES aqueous solution increased the viscosity and the effect of LMDE was better than that of CDEA. The effect of adding polyols and NaCl into the surfactant mixture aqueous solution lead to increase or decrease the viscosity of the systems depending on the concentration of NaCl and the kinds of polyols. These results can be explained through the salting in or salting out of surfactant of the systems.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3293-3303
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• 1996

Numerical analyses have been performed to estimate the absorption heat and mass transfer coefficients in absorption process of the LiBr aqueous solution and the total heat and mass transfer rates in a vertical tube absorber which is coolING ed by air. Axisymmetric cylindrical coordinate system was adopted to model the circular tube and the transport equations were solved by the finite volume method. Absorption behaviors of heat and mass transfer were analyzed through falling film of the LiBr aqueous solution contacted by water vapor in tube. Effects of film Reynolds number on heat and mass transfer coefficients have been also investigated. Especially, effects of tube diameter have been considered to observe the total heat and mass transfer rates through falling film along the tube. Based on the analysis it has been found that the total mass transfer rate increases rapidly in a region with low film Reynolds number(10 ~ 40) as the film Reynolds number increases, while decreases beyond that region. The total heat and mass transfer rates increase with increasing the tube diameter.

• 청정기술
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• 제13권4호
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• pp.274-280
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• 2007

본 연구에서는 염화 제2철 수용액의 재생 공정에 주로 쓰이고 있는 철환원법을 대체하기 위한 방법으로, 액-액 용매 추출법을 사용하여 수용액 내에 잔존해 있는 중금속인 Fe와 Ni을 분리 회수하는 공정을 개발하였다. Lab 실험을 통해 우선 염화 제2철 수용액으로부터 선택적으로 염화 제2철만을 추출할 수 있는 용매조건을 개발하였고, 그 결과를 사용하여 액-액 추출공정의 상업화 추진을 위한 pilot 공정 및 장치를 개발하였다. 또한 pilot test를 통하여 추출단과 역추출단의 단수를 결정할 수 있었고, 양산 공정에 적용할 수 있는 공정 데이터를 확보하였다.

• Advances in Traditional Medicine
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• 제10권2호
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• pp.111-115
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• 2010

The flowers of Nyctanthes arbor-tristis Linn. of Oleaceae widely used in Ayurvedic system of medicine for the treatment of diuresis, liver disorder, spleen enlargement sciatica, bitter, stomachic, carminative and tonic to hair. The aim of the present study was to evaluate the alcoholic and aqueous extracts of the flowers of Nyctanthes arbor-tristis for hepatoprotective effect against carbontetrachloride induced liver damage in rats. Administration of alcoholic and aqueous extracts of the leaves of Nyctanthes arbor-tristis protect the liver from toxic effects of carbontetrachloride by reducing the elevated levels of Serum glutamate pyruvate transaminase, Serum glutamate oxaloacetate transaminase, Alkaline phosphatase and serum bilirubin. Results revealed that both the alcoholic and aqueous extracts showed significant hepatoprotective activity by reducing the elevated levels of biochemical parameters at a dose of 200 mg/kg body weight. The results were supported by histopathological studies of liver samples which showed regeneration of hepatocytes by the extracts.

• Korea-Australia Rheology Journal
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• 제17권2호
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• pp.79-85
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• 2005

Aqueous mixtures of hyaluronic acid and poly(vinyl alcohol) system and hydrogels thereof were introduced to obtain new bioartificial materials that have excellent mechanical properties, biocompatibility and enhanced rheological properties. The interactions between hyaluronic acid and poly(vinyl alcohol) and/or borax were investigated by rheological measurements. Preparation parameters of the aqueous mixtures were mixture composition, the degree of hydrolysis of poly(vinyl alcohol) and borax concentration. From the rheological behavior, it could be deduced that the key factor of the interaction between hyaluronic acid and poly(vinyl alcohol) was the hydrogen bonding between them and the effect was pronounced with borax. Enhanced viscosity was observed at the composition of $20wt\%$ of hyaluronic acid solution and $80wt\%$ of poly(vinyl alcohol) and borax solution. Rheological properties were influenced by the degree of hydrolysis of poly(vinyl alcohol) and borax concentration. As the degree of hydrolysis and borax concentration increased, rheological properties increased due to the increased hydrogen bonding and networking of hyaluronate aggregates. Physical hydrogels from hyaluronic acid and poly(vinyl alcohol) were prepared and the composition dependence of the gels was rheologically investigated as well.

• 한국재료학회지
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• 제28권2호
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• pp.82-88
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• 2018

Stable slurries of YSZ in aqueous suspension with added polymer dispersants, namely, poly-methacrylic acid ammonium salt (PMMA), poly-acrylic acid (PAA) and poly-acrylic-co-maleic acid (PAMA), were mixed with the monomolecular dispersants citric acid and oxalic acid. The dispersion properties of the suspension were investigated using PSA, viscosity, sedimentation, and FT-IR. The polymer dispersants and monomolecular dispersants were attached to the YSZ surface by the carboxylic group, as shown by the FTIR results. A stabilized aqueous suspension was obtained when the polymer dispersant and citric acid were mixed and compared to the use of citric acid alone as a dispersant agent. When the polymer dispersant and citric acid were mixed and milled through attrition milling, there was a smaller particle size compared to when the polymer dispersant alone was used as a dispersant agent. This study determined that the particle size of the mixed dispersant was affected by the properties of the monomolecular dispersant and that the stability of the suspension was affected by the polymer dispersant. However, when slurries of YSZ were mixed with oxalic acid, the particle bridging behavior was the result of the high degree of viscosity and the small sedimentation height.

• 미생물학회지
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• 제46권3호
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• pp.291-295
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• 2010

Streptococcus parauberis Z49가 생산하는 새로운 bacteriocin의 특성을 조사하고 수성 이상계를 사용하여 발효배양액에서 효율적으로 추출하였다. Nisin과 유사한 S. parauberis Z49의 bacteriocin은 $121^{\circ}C$에서 15 min 열처리해도 활성이 있었으며, 넓은 범위의 pH (pH 2-12)에서 안정하며, M. luteus, Lactobacillus sp., L. fermentum, E. faecium, L. monocytogenes, and P. fluorescens의 생육을 억제하였다. S. parauberis Z49의 발효배양액에 있는 bacteriocin을 간편하게 분리하기 위한 PEG 600/$Na_2SO_4$ 수성 이상계의 최적조건은 PEG 600 15%, $Na_2SO_4$ 30%, NaCl 8% 이었으며, bacteriocin은 PEG층에서 농축이 되었다.

• 설비공학논문집
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• 제18권7호
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• pp.596-602
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• 2006

Ice adhesion and blockage problems have been issued in continuous ice slurry making process. So we composed continuous ice slurry making device using a commercial small plate heat exchanger (PHX), and investigated character of ice formation. An experiment of ice formation was peformed with an aqueous solution of ethylene glycol 7 mass%. In the experiment, the effect of the pressurization on ice slurry formation during the cooling process was investigated. The pressurization test for the aqueous solution was performed by setting valves at the PHX inlet and outlet. At the results, the time of continuous ice formation increased as the pressure of the plate heat exchanger increased for cooling temperature of $-5^{\circ}C$. Also continuous ice formation at the cooling temperature of $-7^{\circ}C$ showed a possibility. It was found that the pressurization may contribute to suppress the dissolution of supercooled aqueous solution in the PHX.