• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.23 no.5
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• pp.430-438
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• 2020

Purpose: We investigated the clinical features and factors affecting the choice of treatment modality and the course of pediatric gallstone (GS) disease. Methods: We retrospectively analyzed the medical records of 65 patients diagnosed with GS using imaging studies between January 2009 and December 2017 were included. Results: This study included 65 patients (33 boys and 32 girls; mean age, 8.5±5.3 years; range, 0.2-18 years) who primarily presented with abdominal pain (34%), jaundice (18%), and vomiting (8%). Idiopathic GS occurred in 36 patients (55.4%). The risk factors for GS included antibiotic use, obesity, hemolytic disease, and chemotherapy in 8 (12.3%), 7 (10.8%), 6 (9.2%), and 4 patients (6.2%), respectively. We observed multiple stones (including sandy stones) in 31 patients (47.7%), a single stone in 17 (26.2%), and several stones in 17 (26.2%). GS with a diameter of <5 mm occurred in 45 patients (69.2%). Comorbidities included hepatitis, choledocholithiasis, cholecystitis, and acute pancreatitis in 20 (30.8%), 11 (16.9%), 11 (16.9%), and 4 patients (6.2%), respectively. Ursodeoxycholic acid (UDCA) was administered to 54 patients (83.1%), leading to stone dissolution in 22 patients (33.8%) within 6 months. Cholecystectomy was performed in 18 patients (27.7%) (mean age, 11.9±5.1 years). Most patients treated surgically had multiple stones (83%) and stones measuring <5 mm in size (89%), and 66.7% of patients had cholesterol stones. Conclusion: Cholecystectomy is feasible in patients with small-sized or large numbers of GS and those with persistent abdominal pain and/or jaundice. UDCA administration with close follow-up is recommended in patients with uncomplicated GS.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.11a
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• pp.22-22
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• 2001

전통적으로 초경합금은 무라까미 용액에서 에칭하거나 묽은 염산에 넣고 끓이는 방법에 의해 그 밋구조를 관찰하였다. 그러나 carbide 입자가 suvmicron 크기인 초경합금에서는 전통적인 에칭 방법으 에칭 후에도 입자/기지상, 입자/입자 입계를 동시에 구분시킬 수 있는 SEM 사진을 얻을 수 없다. 본 연구에서는 submicron 크기 초경합금의 고배율 SEM 사진을 얻을 수있는 90H2O2 - 10HNO3 (vol%)의 새로운 에칭 용액을 개발하였다. 경명의 submicron 크기 WC-Co 시편을 샐운 에칭 용액인 90H2O2 - 10HNO3 (vol%)에 넣고 약 6$0^{\circ}C$에서 약 12분 동안 에칭하였다. 에칭에 의해 Co 기지상은 빠르게 제기(dissolution)되었고, 동시에 표면의 WC 입자들은 각각의 결정학적 방향에 따라 천천히(slowly) 다른 속도로 부식(sissolution)되었다. 고배율 SEM을 관찰한 결과 WC/기지상 계면과 WC/WC 입계가 명화갛게 관찰되었다. WC 입자의 성장을 억제시키는입자성장 억제제(Cr3C2, TaC,VC)가 첨가된 WC Co 초경합금을 새로운 에칭 용액인 90H2O2 - 10HNO3 (vol%)에 넣고 약 6$0^{\circ}C$에서 약 12분동안 에칭하였다. 매우 작은 입자를 갖는 미세구조임에도 불구하고 고배율 SEM에서 WC/기지상 계면과 WC/WC 입계가 명확하게 관찰되었다. 90H2O2 - 10HNO3 (vol%)에서 Co 기지상이 빠르게 제거되는 것은 산 (acid)인 HNO3)에서 금속인 Co가 쉽게 녹기 때문이다. 동시에 WC 입자들이 각각 다른 속도로 에칭 된 것은 강력한 산화제인 H2O2가 각각의 WC입자 표면에 얇은 텅스텐 산화물 층을 형성시켰고 이들이 산인 HNO3에서 녹았기 때문이다. 본 연구에서 개발된 새로운 에칭 용액인 90H2O2 - 10HNO3 (vol%)의 에칭 원리가 똑같이 적용 가능한 다른 종류의 초경 합금에서도 사용이 가능할 것으로 판단된다.로 판단된다.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.1
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• pp.22-28
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• 2011

With the increasing cultivation of acid-loving plants such as blueberries, the artificial acidification of soils is frequently required. This research was conducted to determine the application rates of elemental sulfur (S) required in the soil acidification for blueberry cultivation. Laboratory incubation experiment was conducted to acidify three arable soils (pH 6-7) of different texture to pH 4.5-5.0 by the addition of varying amounts of elemental S. All rates of elemental S addition reduced soil pH, although the efficacy of acidification was related to the application rate and soil characteristics. pH reduction was slow in sandy loam soil, and the final equilibrium pH was obtained after 60, 43, and 30 days of incubation in sandy loam, loam, and silty clay, respectively. Although the final pHs obtained after 93 days of incubation were not significantly different among the three soils, the equilibrium pH was relatively higher in soil of higher clay content in the application rates of 1.5-2.0 g S $kg^{-1}$ soil. The estimated amounts of elemental S required in lowering pH to 4.5-5.0 were 0.59-1.01, 0.67-1.03, and 0.53-0.88 g S $kg^{-1}$ for sandy loam, loam, and silty clay, respectively. The lowest estimated amount of elemental S in the acidification of silty clay soil was attributable to the low organic matter content. For clay soils containing optimum level of organic matter, the application rates of elemental S should be much higher than those values estimated in this research. Soil acidification did not significantly increase the available concentrations of Ca, Mg and K. Extractable Cu and Zn was not greatly affected by the acidification, but extractable Fe, Mn, and Al in the acidified soils were higher than those found in non-acidified soils. Such increases in solubility are attributable to the dissolution of oxides and hydroxides of the elements.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.1
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• pp.222-224
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• 2004

This study was performed to analyze the contents of titanium dioxide in commercial foods by UV/VIS spectrophotometry. This method incorporated foods reducing to ashes, dissolution of the ash in sulfuric acid and color development using hydrogen peroxide. The UV/VIS spectrophotometric response was compared to a standard solution. The contents of titanium dioxide in commercial foods were 1.56∼7.74 g/kg in chocolate, 0.27∼1.74 g/kg in health food, 0.48∼2.96 g/kg in chewing gum and 0.34∼2.34 g/kg in candy, respectively. Recoveries of titanium dioxide in foods were 88.46∼104.75％ accordingly.

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.368-378
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• 2020

In the paper, corrosion behavior of T91 steel in different concentrations of NaHSO₃ solution was studied in combination with scanning electron microscope (SEM) and electrochemical measurements. The results showed that the steel exhibited active anodic dissolution characteristics in the solution, and NaHSO₃ concentration affected both cathodic and anodic behaviors. The steel surface was covered by intact corrosion products in the solutions, but the compactness and mechanical properties of the corrosion products degraded with the increase of NaHSO₃ concentration. In low-concentration NaHSO₃ solution the steel tended to undergo uniform corrosion with slight corrosion pits, but its corrosion mode gradually transited to localized corrosion as the NaHSO₃ concentration increased. The mechanical property degradation of the corrosion products caused by sulfur compounds and the pH decrease of the solution are the important factors to accelerating its corrosion process.

• The Journal of the Petrological Society of Korea
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• v.2 no.2
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• pp.130-138
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• 1993

Kyeonggi Gneiss complex forming Korean Precambrian basement is mainly composed of high-grade metasedimentary rocks, which are generally difficult to determine their absolute ages. We examined the feasibility of successive absolute age determination method for the marbles from this basement. We used hydrochloric acid for the selective dissolution of carbonate minerals from the marbles. Trace element analysis shows that most of Zr and Rb are concentrated in the residues. U in the residue is more abundant than that in HC1-dissolved parts. Pb, Sr, Sm, and Nd are somewhat evenly distributed between HC1-dissolved parts and the residues. }Th shows rather complex behavior. Sr isotopic compositions of the HC1-dissolved parts reveal mixing with Sr from non-carbonate minerals having much higher $^{87}Sr/^{86}Sr$ ratios. We suggest that the most reliable method in the age determination for the marbles of this area is measuring Pb isotopic ratios of the pieces of pure marbles.

• Journal of Electrochemical Science and Technology
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• v.11 no.1
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• pp.60-67
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• 2020

In this study, copper (II) oxide powder for electroplating was prepared by recovering CuCl₂ from NaClO₃ type etching wastes via recovered non-sintering two step chemical reaction. In case of alkali copper carbonate [mCuCo₃·nCu(OH)₂], first reaction product, CuCo₃ is produced more than Cu(OH)₂ when the reaction molar ratio of sodium carbonate is low, since m is larger than n. As the reaction molar ratio of sodium carbonate increased, m is larger than n and Cu(OH)₂ was produced more than CuCO₃. In the case of m has same values as n, the optimum reaction mole ratio was 1.44 at the reaction temperature of 80℃ based on the theoretical copper content of 57.5 wt. %. The optimum amount of sodium hydroxide was 120 g at 80℃ for production of copper (II) oxide prepared by using basic copper carbonate product of first reaction. At this time, the yield of copper (II) oxide was 96.6 wt.%. Also, the chloride ion concentration was 9.7 mg/L. The properties of produced copper (II) oxide such as mean particle size, dissolution time for sulfuric acid, and repose angle were 19.5 mm, 64 second, and 34.8°, respectively. As a result of the hole filling test, it was found that the copper oxide (II) prepared with 120 g of sodium hydroxide, the optimum amount of basic hydroxide for copper carbonate, has a hole filling of 11.0 mm, which satisfies the general hole filling management range of 15 mm or less.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.339-342
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• 2003

The corrosion characteristics of Copper by oxidizers in Cu CMP slurry has been investigated. Key experimental variables that has been investigate are the corrosion rate by different oxidizers containing slurry of Cu CMP. Oxidizers in Cu CMP slurry reacts with Cu surfaces to raise the oxidation state of the metal via a reduction-oxidation reaction, resulting in either dissolution of the Cu or the formation of Ta surface film on the metal.[1] When Cu films were corroded adding each oxidizer, corrosion rate increased as much as higher Icorrosion. The corrosion rate of Cu was the largest as added $(NH_4)_2S_2O_8$. The higher content of Urea Hydrogen peroxide was, the higher corrosion rate was measured. Putting in tartaric acid as complexing agent, the corrosion rates of the compounds(Urea hydrogen peroxide+$H_2O_2$) are uniformly. As a result of Cu corrosion by $Cu(NO_3)_2$, the high corrosion rate was determined by even small amounts of $Cu(NO_3)_2$. Consequently, this can be explained by assuming that corrosion by oxidizers has primary effects on the removal rate of Cu and the proper oxidizer needs to be chosen in accordance with relationship of each slurry agent.

• Resources Recycling
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• v.27 no.3
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• pp.93-99
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• 2018

Effective extraction of platinum group elements by dissolving waste platinum scrap from the display industry and solvent extraction, was studied. The extracted platinum solution was prepared as a precursor solution for diesel automotive exhaust gas purification catalyst and its catalytic activity was tested. The behavior of aqueous species of platinum was investigated through solution chemistry and based on the existence and behavior of these chemical species, the possibility of extraction and separation was established. By dissolving waste scrap by electrochemical method, the dissolution time of scrap was shortened and the extraction efficiency was increased. Through separation and removal of rhodium component, solvent extraction by TBP, and stripping by hydrochloric acid, Pt-Chloride-$H_2O$ solution was prepared. And then, an platinum amine complex solution through amination reaction with this solution as a raw material was prepared. The possibility of producing high-value platinum compounds from platinum group waste scrap was investigated by preparing platinum amine complex solution and then examining the catalytic activity with this amine precursor on the combustion reaction of carbon black.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.686-693
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• 1992

In order to investigate the mechanism of dissolutin of nickel from a matte composed essentially of heazlewoodite and ferronickel, the leaching in an aqueous solution of hydrochloric was carried out at $50-90^{\circ}C$, 0.5-3.ON HCl, and with the particle sizes between $100-160{\mu}m$ and $400-500{\mu}m$. The leaching rate of heazlewoodite was much rapider than that of ferronickel, and the two components were simultaneously dissolved with different reaction rates. Within the experimental range, NiS, an intermediate, was not formed. However a possibility to form a thin layer of NiS on particle surface upon saturating the reaction mixture with $H_2S$ was not excluded. At the initial stage, the activation energy was about 10 kcal/g mol. The reaction occurred at the particle surface, and consequently the particle size decreased with time. The rate of dissoultion for nickel was linearly proportional to the concentration of HCl up to 1.0N.