• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.191-194
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• 2009

PtRu based and PtSn based ternary catalysts were prepared by a conventional impregnation method using NaBH4 as reducing agent. The alloy formation, crystalline size and chemical composition of the in-house catalysts were determined by XRD, TEM and EDX, respectively. The chemical compositions of in-house catalysts were quite similar to the nominal value and good alloy formations were also observed. Further, crystalline sizes of ternary catalysts were comparatively smaller than binary catalysts and were approximately 3.5 ~ 5.5 nm. The electrochemical measurements were carried out in the solution 1 M $H_2SO_4$ with 1 M $C_2H_5OH$ at room temperature. LSV results obtained that ternary catalysts were higher current densities and specific activities. Especially, in case of tungsten addition system, Pt5Sn4W/C have the highest specific activities values and was approximately 21.2 and 3.1 times higher than that of PtRu/C and PtSn/C electrocatalyst.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.988-992
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• 2008

A poly(methyl red) film-modified glassy carbon electrode (PMRE) was fabricated for determination of norfloxacin (NFX). The electrochemical behavior of NFX was investigated and a well-defined oxidation peak with high sensitivity was observed at the film electrode. PMRE greatly enhanced the oxidation peak current of NFX owing to the extraordinary properties of poly(methyl red) film. Based on this, a sensitive and simple voltammetric method was developed for measurement of NFX. A sensitive linear voltammetric response for NFX was obtained in the concentration range of $1\;{\times}\;10^{-6}\;-\;1\;{\times}\;10^{-4}$ mol/L and the detection limit was $1\;{\times}\;10^{-7}$ mol/L using linear sweep voltammetry (LSV). The proposed method possessed advantages such as low detection limit, fast response, low cost and simplicity. The practical application of this new analytical method was demonstrated with NFX pharmaceuticals.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.544-544
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• 2008

Metal-CMP 공정시 높은 압력을 가해 줌으로 인하여 금속배선의 디싱 현상과 에로젼 현상이 발생하고 다공성의 하부층에 균열이 생기는 문제점을 개선하고자, 낮은 하력에서 금속막의 광역 평탄화를 이룰 수 있는 ECMP(Electrochemical Chemical Mechanical Polishing)가 생겨나게 되었다. 본 논문에서는 다양한 전해액의 전류-전압 특성 곡선을 비교 분석하여, 패시베이션막이 형성되는 곳을 알 수 있었고, CV와 LSV 법을 통해 전기화학적인 특성을 고찰하였다.

• Journal of Chest Surgery
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• v.34 no.12
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• pp.909-916
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• 2001

Background : Varicose vein is a very common vascular disease and has recently become a matter of concern for thoracic and cardiovascular surgens. Material and Method : We analyzed 209 cases or 269 feet with varicose vein retrospectively, which had been treated in our hospital from April 1999 to December 2000. Result : Male : Female ratio was 1:3(Male : 52 cases, Female : 157 cases), mean age was 42.2$\pm$9.7 years old, mean duration of varicosities was 12.2$\pm$9.7 years, and mean follow up was 14.8$\pm$6.1 months from July 2001. Most common symptom was leg pain(122 cases, 58.4%). Long standing job(44 cases), pregnancy(37 cases), and family history related to varicose vein came to 79.9% as the major predisposing or precipitating factors. Anatomic classifications of main lesion were GSV (greater saphenous vein,126 cases), LSV(lesser saphenous vein,18 cases), and reticular veins and telangiectasias(65 cases). Main treatments were stripping of GSV, stab avulsion, ligation of saphenofemoral junction, sclerotherapy, and conservative treatment. Comparing A group (stripping of GSV) with B group(sclerotherapy of GSV), A group had more complications than B group; however, A group had less recurrences than B group(p 0.05). Comparing C group(stab avulsion of LSV) with D group(sclerotherapy of LSV), there were 2 cases of recurrence in D group; however, there were no statistical differences between the two groups in complication and recurrence(p>0.05). Comparing B group(sclerotherapy of GSV) with E group(sclerotherapy of reticular vein and telangiectasia), there were no differences in complication; however, B group had more recurrences than E group. Post-stripping complications were ankle numbness and tingling(2 cases), ankle pain(2 cases),ankle swelling(2 cases), and wound pain(1 case). Postsclerotherapy complications were thrombophlebitis(1 case) and skin ulcer(1 case). Conclusion: Sclerotherapy for varicose vein involving GSV had more recurrences than stripping for lesions involving GSV. Sclerotherapy for reticular vein and telangiectasia had less recurrences than sclerotherapy for lesion involving GSV. Sclerotherapy is a very convenient method without operation and admission, thus further research is demanded in case of varicose vein involving GSV.

• Journal of the Korean Electrochemical Society
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• v.20 no.2
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• pp.34-40
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• 2017

Electric double layer capacitors (EDLC: electric double layer capacitors) have drew attention as an energy storage device for the next generation because of their outstanding power capability and durability. But their usage is somewhat limited due to low energy density over secondary batteries. One of methods to improve the energy of EDLC is expanding the voltage window of cell operation by increasing the charge cut-off voltage. In this study, $SBP-BF_4$ (spirobipyrrolidinium tetrafluoroborate), $TEA-BF_4$ (tetraethylammonium tetraflouroborate) and $EMI-BF_4$ (1-ethyl-3-methylimidazolium tetrafluoroborate) in AN (acetonitrile) were selected to evaluate the possibility of application at high voltage environment. The LSV (linear sweep voltammetry) measurements showed that the 1.5M SBP-BF4/AN electrolyte was stable over a wide potential window and showed the best electrochemical performance compared to other combinations of electrolytes at high voltage environments (over 3.0 V). Furthermore, TMSP (tris(trimethylsilyl) phosphite) was applied to 1.5M SBP-BF4/AN in order to maintain stable performance at high voltage for the long period of time. The electrolyte with TMSP additive showed the capacity retention of 93% after 10,000 cycles at 3.3 V.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.854-862
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• 2016

As the demand for a clean energy to replace fossil fuel being depleted increases, hydrogen energy is considered as a promising candidate for future energy source. Water electrolysis which produces hydrogen has high energy efficiency and stability but still has a large overpotential for oxygen evolution reaction (OER). In this study, $Co_3O_4$ catalysts with different morphology were prepared by spray pyrolysis from solutions which contain Co precursor and various organic additives (urea, sucrose, and citric acid), followed by post heat treatment. For the catalysts synthesized, X-ray diffraction (XRD) measurements were performed to identify their crystal structure. Morphology and surface shape of the catalysts were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Surface area and pore volume were examined by nitrogen adsortpion & desorption tests and X-ray photoelectron spectroscopy (XPS) was conducted to confirm nitrogen doping. Linear sweep voltammetry (LSV) was carried out to investigate OER activity of $Co_3O_4$ catalysts. As a result, bare-$Co_3O_4$ which has high surface area and small particle size determined by spray pyrolysis showed high activity toward OER.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.131-137
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• 2011

A simple and rapid electrochemical method for the quantitative analysis of $Mn^{2+}$ ion is demonstrated with a view to examine the $Mn^{2+}$ dissolution behavior of $LiMn_2O_4$. The method described herein is based on the oxidation reaction of $Mn^{2+}$ to $Mn^{4+}(MnO_2)$ in aqueous buffer solution. Under the optimum condition (pH 8.9 0.04 M $NH_3-NH_4Cl$ buffer solution and glassy carbon working electrode), the linear range of $5{\mu}M-100{\mu}M$ (0.275-5.5 ppm) [$Mn^{2+}$] is obtained for the Linear sweep voltammetry(LSV) and $0.2{\mu}M-10{\mu}M$ (0.011-0.55 ppm) [$Mn^{2+}$] for the differential pulse voltammetry (DPV), respectively. It is also noted that the oxidation reaction of $Mn^{2+}$ ion is reduced with increasing amount of the electrolyte ($LiPF_6$, EC, EMC) added to the measuring solution, which is found to be mainly due to $LiPF_6$ and EC rather than EMC.

• Korea Real Estate Review
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• v.28 no.1
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• pp.91-104
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• 2018

In this study, the occurrence and degree of herding behavior as a market participant behavior in a housing market were analyzed. For the analysis method, the actual sales price was applied in the CSAD (Cross-sectional Absolute Deviation) model, which has been used the most of late for herding behavior analysis. For the analysis contents, these were subdivided into region, elapsed year, size, and market condition to analyze the regionality and the internal and external factors. For the study results, first, there was no herding behavior in the entire region of Seoul. By region, herding behavior occurred in the downtown, southeast, and northwest regions, which coincided with the results of the precedent study (Ngene et al., 2017). Second, in the market analysis by elapsed year, herding behavior was captured in dilapidated dwellings. By size, herding behavior was observed in small-scale ($60m^2$ or less) apartments and in $85m^2$ or higher and less than $102m^2$ national housing units. Third, during the time of the global financial crisis, herding behavior was not observed in all the regions, whereas when the market situations were in a boom cycle, it was observed in the northwest region. These results suggest that there is a difference from the stock market, where in a period of recession, herding behavior occurs intensively with the expanding fear of incurring losses. This study is significant in that it analyzed the market participant behaviors in the behavioral economic aspects to better understand the abnormal phenomenon in a housing market, and in that it additionally provides a psychological factor - market participant behavior - in market analysis.

• Resources Recycling
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• v.27 no.6
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• pp.44-52
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• 2018

In this study, copper was recovered from copper containing sludge by selectively controlling electro-refining process conditions in copper sulfate electrolyte solution. Electro-refining process was performed by LSV (Linear Sweep Voltammetry) result according to copper sulfate electrolyte solution concentration, applied current density, additive type and concentration. SEM (Scanning Electron Microscope) and PSA (Particle Size Analyzer) were used to analyze the shape and size of copper powder. In the 0.1 ~ 0.4 M copper sulfate electrolyte solution without organic additives, the copper powder size decreased as the applied current density became closer to the limiting current density and the copper powder size tended to decrease in 0.2 ~ 0.3 M copper sulfate electrolyte solution. In addition, when the shape and size of the copper powder were analyzed by adding various types and concentrations of organic additives to the previous experimental, fine spherical copper powder having the smallest size (nm) was obtained under the condition of cellulose type additive 2,000 ppm.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.344-350
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• 2019

Durability is very important for the commercialization of membranes and electrode assemblies (MEA) developed for proton exchange membrane fuel cells (PEMFC). Durability evaluation of stationary PEMFC MEA has a problem that the voltage change rate should be measured for a long time over 1000 hours under constant current conditions. In this study, the electrochemical durability evaluation protocol of membranes (OCV holding method) using to vehicle MEAs was applied to the stationary MEA for the purpose of shortening the durability evaluation time. After operation of the stationary and automobile MEA for 168 hours under conditions of OCV, cathode oxygen, $90^{\circ}C$ and relative humidity of 30%, I-V, LSV, CV, impedance and FER were measured and compared. When the hydrogen permeability, OCV change, ionic conductivity, and fluorine flow rate, which represent the durability of the membrane after degradation, were all examined, it was shown that durability of stationary MEA membrane was better than that of vehicles MEA membrane. In addition, the electrode degradation of stationary MEA was smaller than that of vehicles MEA after degradation operation. It was possible to evaluate in a short time using automotive protocol that the durability of stationary MEA was superior that of vehicle MEA in terms of membrane and the electrode.