• 한국표면공학회지
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• 제36권3호
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• pp.277-283
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• 2003

Electrochemical techniques were used to study the surface treatment for improving the pitting corrosion resistance of 304L stainless steel by inhibitors in chloride medium. Sodium molybdate (in concentration range : 0.005-80 g/l) , sodium nitrite (in concentration range : 0.001-50 g/l) and their mixture were used for this study. It was found that, molybdate and nitrite were good passivators for 304L stainless steel, but molybdate was not able to prohibit the pitting ; nitrite prevented pitting corrosion of 304L stainless steel only at the concentration more than 25 g/l. The relationship between pitting potentials and concentrations of inhibitors in the logarithm expression obeyed the linear function. It was found that the surface treatment by mixture of two inhibitors enables stainless steel to have increased the corrosion resistance , the pitting corrosion of 304L stainless steel was completely prohibited by the mixtures of molybdate and nitrite in ratio min, with $m\;\geq\;3\;and\;n\;\geq\;10$. The interesting cases on electrochemical measurement of threshold of inhibitors concentration combination for optimum surface treatment were described.

• 콘크리트학회논문집
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• 제17권2호
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• pp.303-309
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• 2005

This study aims the evaluation of the corrosion of steel bar embedded in antiwashout underwater concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed on three series of steel bar-reinforced antiwashout underwater concrete specimens manufactured with different admixtures. The three series of antiwashout underwater concrete were: concrete constituted exclusively with ordinary portland cement (OPC), concrete composed of ordinary portland cement mixed with fly-ash in $20\%$ ratio (FA20), and concrete with ground granulated blast furnace slag mixed in $50\%$ ratio (BFS50). The environment of manufacture was in artificial seawater. Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below -350mv after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as $30{\mu}A/mm^2$ and $0.258\%$. On the other hand, for the other specimens that are FA20 and BFS50, potential values below -350mV were observed later at 18 and 20 cycles, respectively. Results confirmed the hypothesis that mineral admixtures may be more effective on delay the development of steel bar corrosion in antiwashout underwater concrete.

• 한국분말재료학회지
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• 제15권2호
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• pp.148-155
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• 2008

Nano magnetite particles have been prepared by two step reaction consisting of urea hydrolysis and ammonia addition at certain ranges of pH. Three different concentrations of aqueous solution of ferric ($Fe^{3+}$) and ferrous ($Fe^{2+}$) chloride (0.3 M-0.6 M, and 0.9 M) were mixed with 4 M urea solution and heated to induce the urea hydrolysis. Upon reaching at a certain pre-determined pH (around 4.7), 1 M ammonia solution were poured into the heated reaction vessels. In order to understand the relationship between the concentration of the starting solution and the final size of magnetite, in-situ pH measurements and quenching experiments were simultaneous conducted. The changes in the concentration of starting solution resulted in the difference of the threshold time for pH uprise, from I hour to 3 hours, during which the akaganeite (${\beta}$-FeOOH) particles nucleated and grew. Through the quenching experiment, it was confirmed that controlling the size of ${\beta}$-FeOOH and the attaining a proper driving force for the reaction of ${\beta}$-FeOOH and $Fe^{2+}$ ion to give $Fe_3O_4$ are important process variables for the synthesis of uniform magnetite nanoparticles.

• 한국지하수토양환경학회지:지하수토양환경
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• 제17권5호
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• pp.49-55
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• 2012

A 1.28 L-batch reactor and continuous-flow stirred tank reactor (CFSTR) fed with formate and trichloroethene (TCE) were operated for 120 days and 56 days, respectively, to study the effect of formate as electron donor on anaerobic reductive dechlorination (ARD) of TCE to cis-1,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethylene (ETH). In batch reactor, injected 60 ${\mu}mol$ TCE was completely degraded in the presence of 20% hydrogen gas ($H_2$) in less than 8 days by anaerobic dechlorination mixed-culture (300 mg-soluble protein), Evanite Culture with ability to completely degrade tetrachloroethene (PCE) and -TCE to ETH under anaerobic conditions. Once the formate was used as electron donor instead of hydrogen gas in batch or chemostat system, the TCE-dechlorination rate decreased and acetate production rate increased. It indicates that the concentration of hydrogen produced in both systems is possibly more close to threshold for homoacetogenesis process. Soluble protein concentration of Evanite culture during the batch test increased from 300 mg to 688 mg for 120 days. Through the protein monitoring, we confirmed an increase of microbial population during the reactor operation. In CFSTR test, TCE was fed continuously at 9.9 ppm (75.38 ${\mu}mol/L$) and the influent formate feed concentration increased stepwise from 1.3 mmol/L to 14.3 mmol/L. Injected TCE was accumulated at 18 days of HRT, but TCE was completely degraded at 36 days of HRT without accumulation of the injected-TCE during the left of experiment period, getting $H_2$ from fermentative hydrogen production of injected formate. Although c-DCE was also accumulated for 23 days after beginning of CFSTR operation, it reached steady-state in the presence of excessive formate. We also evaluated microbial dynamic of the culture at different chemical state in the reactor by DGGE (denaturing gradient gel electrophoresis).

• 한국토양비료학회지
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• 제36권6호
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• pp.399-406
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• 2003

배추와 무 직파재배시 토양중 치환성 칼륨의 생육 저해 한계 농도를 밝히기 위하여 $1m^2$ 무저 pot에서 주로 농가에서 사용하는 염화칼리비료를 처리하여 토양의 치환성 칼륨행동과 작물의 생육과 발아특성을 조사하여 다음과 같은 결과를 얻었다. 배추와 무의 최고 수량은 토양내 치환성 칼륨 함량이 각각 $0.96cmol_c\;kg^{-1}$, $1.28cmol_c\;kg^{-1}$에서 있었으며, 이때의 염화칼리 비료의 시용량은 봄 배추 $370(K_2O:\;222)\;kg\;ha^{-1}$, 가을 무 $517(K_2O:\;310)\;kg\;ha^{-1}$이었다. 이 이상에서는 토양의 치환성 칼륨함량이 높아짐에 따라 수량은 낮아지는 경향을 보였다. 토양의 치환성 칼륨 함량과 작물의 발아율과의 관계를 보면 배추는 치환성 칼륨 함량이 $0.54cmol_c\;kg^{-1}$이하에서는 정상적인 발아가 되었으나 $1.29cmol_c\;kg^{-1}$은 83%, $2.30cmol_c\;kg^{-1}$은 67%의 발아율을 보였고, 무의 경우에는 $1.29cmol_c\;kg^{-1}$ 이하에서는 정상적 생육, $2.30cmol_c\;kg^{-1}$에서는 83%의 발아율을 보였다. 발아장해를 받는 토양의 전기전도도 값은 배추는 $1.29dS\;m^{-1}$, 무는 $2.30dS\;m^{-1}$이었다. 따라서 작물 재배전에 다량의 염화칼리비료 시용은 전기전도도의 증가로 염류장해를 받을 우려가 있기 때문에 이를 고려하여 시비관리를 해야할 필요가 있는 것으로 판단되었다.

• 한국식품과학회지
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• 제12권3호
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• pp.150-157
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• 1980

관능검사법(官能檢査法)에 의한 식품(食品)의 품질(品質) 평가(評價)를 위하여 관능(官能) 파넬을 선발(選拔)하여 우유에 대한 차이(差異) 식별(識別) 시험(試驗)을 실시하여 다음과 같은 결과(結果)를 얻었다. 1. 파넬원 선발(選拔)의 일반(一般) 기준(基準), 감도(感度) 시험(試驗)및 차이(差異) 식별(識別) 능력(能力) 시험(試驗)을 통하여 40명의 관능(官能) 파넬을 선발(選拔)하였으며 또한 그들이 우유 품질(品質)의 관능적(官能的) 평가(評價)에 있어서 정상 능력을 갖도록 훈련(練訓)을 실시하였다. 2. 파넬원의 기본(基本) 맛에 대한 감도(感度) 시험(試驗) 결과(結果) 짠맛, 신맛, 쓴맛 및 단맛의 평균 최소(最小) 감도(感度)양(量)은 각각 0.0128M sodium chloride, 0.008M citric acid, 0.0016M caffeine 및 0.0256 M sucrose이었다. 3. 시판(市販) 5개(個) 회사(會社) 제품(製品)의 우유 시료(試料) 간(間)에 단일시료법(單一試料法), 2점(點) 대비법(對比法), 1 2 점(點) 시험법(試驗法) 및 3점(點) 시험법(試驗法)에 의한 차이(差異) 식별(識別) 시험(試驗)을 통하여 1% 수준(水準)이상에서 유의적(有意的)인 차이(差異)가 인정(認定)되었다.

• 한국식품과학회지
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• 제9권2호
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• pp.123-130
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• 1977

동방유량(東邦流糧)에서 공급(供給)받은 저변성(低變成) 탈지대두박(脫脂大豆粕)을 0.02N NaOH액(液)으로 추출(抽出)하여 Soy Protein Isolate (SPI)의 수율(收率)을 증류수나 염용액(鹽溶液)으로 추출(抽出)할때 보다 높이는 과정(過程)(84 % 수율(收率))을 확립(確立)하였으며 제조(製造)된 SPI는 92.1 %의 단백질(蛋白質)을 함유(含有)하였다. SPI를 $70^{\circ}C$에서 moisture heat를 하면 80분간(分間)에 5 %의 변성(變性)이 일어났으나 $95^{\circ}C$에서는 20분(分) 처리(處理)에 의(依)하여 95 %의 변성(變性)이 일어났다. SPI의 alkali 현탄액 (dope solution)은 SPI의 농도(濃度) 15 %, NaOH 농도(濃度) 0.6 %일때 7분(分)만에 60 poises를 나타내고 계속 안정(安定)된 점도(粘度)를 유지하였다. NaOH의 농도(濃度)가 0.9 %일 때는 시간(時間)이 경과(經過)함에 따라 점도(粘度)는 증가(增加)하였다가 감소(減少)하는 경향(傾向)을 보였다. syringe needle (dia. 0.3 mm)로서 모의(模擬) 실험(實驗) 결과(結果) 점도(粘度)가 $28^{\circ}C$에서 60 Poises일때 가장 적합한 단백질섬유(蛋白質纖維)의 texture를 보여주었다. 가열(加熱)에 의(依)한 SPI의 gelation은 8 %이상(以上)의 SPI농도(濃度)일 때 gel이 형성(形成)되기 시작하였으며 $100^{\circ}C$까지 안정(安定)한 gel을 형성(形成)하였고 SPI의 농도(濃度)가 12 %일때 $120^{\circ}C$에서 30분(分) 가열(加熱)에 의(依)하여 20,000 Poises의 좋은 점도(粘度)를 가졌으나 $120^{\circ}C$이상에서는 gel의 continuity가 떨어져 과립상(果粒上)의 gel이 생성(生成)되었다. SPI의 유화력(乳化力)은 pH가 8.7, NaCl의 농도(濃度)가 2 %일때 가장 큰 유화력(乳化力)을 나타냈다. milk casein과 비교(比較) 실험(實驗) 결과(結果) 유화력(乳化力)은 약간 낮았으나 염(鹽)이 존재(存在)하는 경우는 근사한 유화력(乳化力)을 보였다. 그러나 SPI의 foaming capacity는 foaming stability 면(面)에서 egg albumin이나 milk casein과 비교(比較)하여 양호(良好)한 결과(結果)를 보여주었다.