• Korean Journal of Veterinary Research
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• v.37 no.1
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• pp.203-212
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• 1997

Antibacterial efficacy and safety of copper sulfate pentahydrate (5% solution) was evaluated in laboratory and field studies for disinfection of some fish bacterial pathogens in cultured fish, flounder(Paralichthys olivaceus), mirror carp(Cyprinus carpio), gold fish(Carrassius auratus) and eel(Anguilla japonica). Dipping of fishes for acute toxicity was performed for a period of 48h, and the TLm value(median tolerance limit) were 4.0ppm in mirror carp and flounder, 4.4ppm in rainbow trout, and 10.0ppm in gold fish. After exposure below than TLm value for 1 month, no side effects and histopathological changes were observed. The test drug were shown high antibacterial activities against most bacterial pathogens by exposure in the laboratory and field trials. However, Aeromonas salmonicida showed a resistance to the dosage. We can prevent outbreaks of bacterial diseases of fish by the dosage of 1ppm for 6hr and the test drug is thought to be used effectively and widely as a disinfectant against most bacterial fish pathogens.

• Korean Journal of Materials Research
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• v.13 no.8
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• pp.524-530
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• 2003

In order to prepare the uniform copper particles from copper sulfate solution by using hydrazine as a reduction agents, the reduction behavior of copper particles from copper sulfate was investigated in detail at room temperature by the observation of reaction products. The effects of $NH_4$OH and $Na_4$$P_2$$O_{7}$ on the formation of uniform copper particles were discussed. ($NHCu_3$)$_4$$SO_4$was completely formed at over pH 11 by adding $NH_4$OH in copper sulfate solution. The fine $Cu_2$O with the particle size of 50 nm was produced in the initial reduction process of (NH$Cu_3$)$_4$$SO_4$solution with $Na_4$$P_2$$O_{ 7}$ and then the Cu$_2$O was converted into copper particles by inserting additional hydrazine. When Cu(NH$_3$)$_4$SO$_4$solution with $Na_4$$P_2$$O_{ 7}$ was reduced at $80^{\circ}C$ by hydrazine, the highly dispersed copper particles with the particle size of about 0.8 $\mu\textrm{m}$ was obtained.

• Applied Chemistry for Engineering
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• v.22 no.1
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• pp.77-80
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• 2011

In this study, we measured changes in the lignin content of acidified lignocellulosic biomass such as rice straw, saw dust, chestnut shell and peanut hull and analyzed the conversion property to cellulosic ethanol. It turns out that the lignin content increases in chestnut shell, rice straw, saw dust, peanut hull order and the conversion property to cellulosic ethanol is superior in the reverse order. Thus, the removal of lignin by acidification is necessary. In addition, as the concentration of sulfuric acid increases, the lignin content decreases and the yield of cellulosic ethanol increased. The optimum concentration of sulfuric acid is 20 wt%.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.4
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• pp.357-360
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• 1997

To fine out the concentration of $SO_2$ gas in plastic film house, the survey was conducted at 343 sites throughout the nation. The $SO_2$ concentration in plastic film house were similar both heating and non-heating, but $SO_2$ cocentration higher than 0.8ppm was detected at those with heating. The $SO_2$ concentration in plastic film house cultivated red-pepper higher than those of cucumber or tomato cultivation, and it was produced higher amounts at day time than night due to the higher temperature. In plastic film house with heating, $SO_2$ was leaked at brocken parts of heater and joint of stove pipe, sometimes, $SO_2$ discharged from smokestack was resucked with air. $SO_2$ concentration in the plastic film house with and without ventilation were 0.2 and 0.6ppm, respectively.

• Resources Recycling
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• v.26 no.1
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• pp.30-36
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• 2017

Leaching experiments of anode slime were performed with several inorganic acids (HCl, $HNO_3$ and $H_2SO_4$) together with thiourea and thiosulfate solution to recover gold and silver. Gold was not dissolved at all into these inorganic acids in the absence of any oxidizing agents. At the same concentration of inorganic acid, the leaching of percentage of Ag was the highest in the sulfuric acid solution. The leaching percentage of silver increased with the increase of HCl concentration owing to the formation of $AgCl_2{^-}$. Copper, nickel and zinc except tin was almost dissolved in these inorganic acids but no tin was dissolved in nitric acid solution. Most of Au and Ag were dissolved into the mixture of sulfuric acid and thiourea solution. Thiosulfate could dissolve some silver from the anode slime but no gold was dissolved by this agent.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.42-42
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• 2009

마찰교반접합 (Friction Stir Welding)은 1991년 영국 TWI에서 개발된 접합 법으로서 회전하는 툴이 재료내부에 삽입되면 툴과 재료사이에서 발생하는 마찰열에 의하여 온도가 상승하게 되어 재료는 연화되고, 이러한 재료 내부에서 회전하는 툴이 이동하게 되면 재료 내부는 기계적 교반에 의해 소성변형이 일어남과 동시에 접합이 이루어진다. 마찰교반접합은 동적 재결정에 의한 접합부의 미세한 결정립 형성으로 인하여 기계적 특성이 향상되며 보호 가스가 필요 없어 친환경적임과 동시에 용융 용접 법에 비해 접합 시 에너지 소모가 적으며 또한 접합 후 접합부에서의 변형이 상대적으로 적다는 장점이 있다. 이러한 장점을 가진 마찰교반접합은 알루미늄 합금, 마그네슘 합금 그리고 동 합금과 같은 저 융점 비철재료에 많은 연구와 적용 사례들이 있어왔다. 하지만 최근에는 일반 탄소강, 연강, 오스테나이트계 스테인리스강, 니켈 합금, 티타늄 합금과 같은 고융점 재료에도 연구 및 적용이 진행되고 있는 추세이다. 페라이트계 스테인리스강은 가격이 비싼 Ni을 함유하지 않아 오스테나이트계 스테인리스강에 비하여 강재의 가격은 낮으면서도 고온특성 및 내식성이 우수하여 건축용, 자동차 배기계용으로 널리 사용되고 있다. 하지만 이런 장점을 가진 페라이트계 스테인리스강을 기존의 용융 용접 법으로 접합 시 용접부 및 열영향부에서의 결정립의 조대화로 인한 인성 및 연성이 저하되며, 특히 예민화된 열영향부 입계 내에 Cr 탄화물이 석출되어 입계주변에 Cr 결핍 층을 형성되어 입계부식이 발생되는 문제점이 발생된다. 본 연구에서는 마찰교반접합을 이용하여 두께 3mm의 409 스테인리스강에 대해 맞대기 접합을 실시하였다. 접합 변수를 툴의 재료 (WC-12wt%Co, $Si_3N_4$)로 하여 접합을 실시하였고 접합 후 외관상태 점검, 광학 현미경과 주사 전자 현미경을 통하여 미세조직을 관찰하였으며 황산-황산동 부식 시험을 실시하여 접합부의 부식 특성을 평가하였다.

• Resources Recycling
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• v.26 no.6
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• pp.84-90
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• 2017

The electro-refining process was performed to recovery high purity copper from low grade copper containing sludge in sulfuric acid. The surface morphologies and roughness of electro-refining copper were analyzed with variation of the type and concentration of organic additives, the best surface morphology was obtained 5 ppm of the gelatin type and 5 to 10 ppm of the thiol type organic additive. The crude metal consisted of copper with 86.635, 94.969 and 99.917 wt.%, several impurity metals of iron, nickel, cobalt and tin by pyro-metallurgical process. After electro-refining process, the purity of copper increases to 3N or 4N grade. The impurity concentrations and copper purities of copper crude metals, electrolyte and electro-refining copper were analyzed using ICP-OES, the electro-refining time and purity of copper crude metal to recover 4N grade copper were deduced.

• Journal of the Mineralogical Society of Korea
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• v.27 no.1
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• pp.53-62
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• 2014

In order to remove Fe impurity from low-grade pyrophyllite ore, the effect of certain variables such as particle size, concentration of sulfuric acid, amount of ammonium sulfate, added hydrogen peroxide, and temperature were studied. The euhedral cubic pyrites were observed in the low-grade pyrophyllite ore by reflected light microscopy, and quartz and dickite were identified in the sample by XRD analysis. The results of the Fe removal experiments showed that the best Fe removal parameters were when the particle size was at -325 mesh, the addition of $H_2SO_4$, $(NH_4)_2SO_4$ and $H_2O_2$ was at a 2.0 M, 10.0 g/l, and 3.0 M concentration, respectively, and at a $70^{\circ}C$ leaching temperature. In the dissolution kinetics analysis, the dissolution of Fe from the pyrite surface was a controlled chemical reaction, and the Fe dissolution reaction was proportioned to 0.066/R, $[H_2SO_4]^{1.156}$, $[(NH_4)_2SO_4]^{0.745}$, $[H_2O_2]^{0.428}$.

• Journal of Conservation Science
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• v.26 no.4
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• pp.437-443
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• 2010

The influence of noxious corrosive gas, which is the product of fossil fuel, and the acidic descent material, which becomes the reason for such reaction, on wax which protects the cultural assets, and the habitat factor were researched. It could be viewed that corrosion occurred rapidly due to the acidic descent material, which have the long staying on the material, rather than harmful corrosive gas. Also, it could be figured out that such corrosion began from whitening phenomenon of coated wax. As the acidity increased, more whitening phenomenon occurred, and eventually, it could be found out that whitening effect began due to the acidic descent material, corrosive gas and various 0.1 M acid solution, which lead to the exposure of internal metal, and corrosion occurred. The wax with the greatest resistance to the acidity due to its least changing aspect seemed to be Renaissance wax, except sulfuric acid.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.233-234
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• 2003

부유 분진의 입경에 따른 물리, 화학적 특성은 대기질 및 인체의 건강 측면에서 중요한 변수로 작용되고 있으며, 호흡기내 침착 및 가시도의 영향에도 밀접한 관련이 있다. 거대입자는 주로 자연적 발생원에서 방출되고 호흡시 구강이나 코에서 대부분 제거된다. 미세입자는 인위적인 배출원에서 주로 방출되며 입경이 10$\mu\textrm{m}$이하인 것으로 보고되고 있다. 이들 1차 생성분진과는 달리 대기중에서 황산가스나 휘발성유기화합물 등이 응축과정을 거쳐 가스상에서 입자상으로 변환되어 생성된 입자도 환경학적으로 매우 중요한 의미를 갖는다. (중략)