• 전기학회논문지
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• 제64권5호
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• pp.732-738
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• 2015

In ac discharge, emission efficiency shows an time-varying characteristics during discharge. The phenomenon is caused by the potential distribution changes during the discharge, which indicates that a specific potential distribution can contribute to a high improvement of the emission efficiency. To create an artificial environment for a potential distribution favorable to emission efficiency, we used the asymmetric electrode structure and proved the capability. Our results showed that the ratio of the area of anode to cathode became larger, the emission efficacy was greatly improved.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.352-355
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• 2009

The ground resistance has been used as a method of estimating the capability of counterpoise. When transient currents blow through a ground electrode, it is reasonable to evaluate the performance of ground electrode system as a ground impedance instead of ground resistance. However, the measurement method of ground impedance for counterpoise is not clearly presented. This paper describes the measurement method of ground impedance considering the earth mutual resistances and AC mutual coupling. When we measure the ground impedance, the error due to earth mutual resistances depends on the distance between the auxiliary electrodes and the electrode under test. The measurement accuracy of high frequency ground impedance is mainly influenced by the location of the current electrode and the potential electrode.

• 대한치과보철학회지
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• 제31권3호
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• pp.423-446
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• 1993

Titanium and its alloys are finding increasing use in medical devices and dental implants. The strong selling point of titanium is its resistance to the highly corrosive body fluids in which an implant must survive. This corrosion resistance is due to a tenacious passive oxide or film which exists on the metal's surface and renders it passive. Potentiodynamic polarization measurement is one of the most commonly used electro-chemical methods that have been applied to measure corrosion rates. And the potentiodynamic polarization test supplies detailed information such as open circuit, rupture, and passivation potential. Furthermore, it indicates the passive range and sensitivity to pitting corrosion. This study was designed to compare the corrosion resistance of the commonly used dental implant materials such as CP Ti, Ti-6A1-4V, Co-Cr-Mo alloy, and 316L stainless steel. And the effects of galvanic couples between titanium and the dental alloys were assessed for their useful-ness-as. materials for superstructure. The working electrode is the specimen , the reference electrode is a saturated calomel electrode (SCE), and the counter electrode is made of carbon. In $N_2-saturated$ 0.9% NaCl solutions, the potential scanning was performed starting from -800mV (SCE) and the scan rate was 1 mV/sec. At least three different polarization measurements were carried out for each material on separate specimen. The galvanic corrosion measurements were conducted in the zero-shunt ammeter with an implant supraconstruction surface ratio of 1:1. The contact current density was recorded over a 24-hour period. The results were as follows : 1. In potential-time curve, all specimens became increasingly more noble after immersion in the test solution and reached between -70mV and 50mV (SCE) respectively after 12 hours. 2. The Ti and Ti alloy in the saline solution were most resistant to corrosion. They showed the typical passive behavior which was exhibited over the entire experimental range. Therefore no breakdown potentials were observed. 3. Comparing the rupture potentials, Ti and Ti alloy had the high(:st value (because their break-down potentials were not observed in this study potential range ) followed by Co-Cr-Mo alloy and stainless steel (316L). So , the corrosion resistance of titanium was cecellent, Co-Cr-Mo alloy slightly inferior and stainless steel (316L) much less. 4. The contact current density sinks faster than any other galvanic couple in the case of Ti/gold alloy. 5. Ag-Pd alloy coupled with Ti yielded high current density in the early stage. Furthermore, Ti became anodic. 6. Ti/Ni-Cr alloy showed a relatively high galvanic current and a tendency to increase.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.196.2-196.2
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• 2014

Nanostructuring the electrode surface is an emerging technology to improve the performance of supercapacitors since it can facilitate charge transfer, ion diffusion and electron propagation during electrochemical process. Fabrication of the electrode consisting of two or more materials together has also been focused on since it can provide synergetic effect such as broader working potential range and enhanced capacitance. In this work, we have used polyaniline (PANi) and manganese oxide (MnO2) as electrode materials. PANi is one of the promising electrode materials due to its high electrochemical activity, high doping level and stability. MnO2 is also widely studied material for supercapacitors since it is relatively cheap and environmentally friendly. Firstly, we synthesized polystyrene nanospheres on MnO2 nanoparticles. MnO2-incorporated PANi hollow nanospheres were then fabricated by polymerizing aniline monomers on these PS nanospheres and dissolving the inner PS spheres. The surface morphology, electronic absorption and electrical conductivity of the electrode were analyzed using field-emission scanning electron microscope (FE-SEM), UV-visible spectrometer, and sheet resistivity meter, respectively. The electrochemical properties such as capacitance of the supercapacitors were also estimated using cyclic voltammetry.

• 한국표면공학회지
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• 제49권1호
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• pp.87-91
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• 2016

The development of high performance transparent electrode with flexibility have been required for flexible electronics. Here, we demonstrate the silver nanowire and reduced graphene oxide hybrid transparent electrode for replacing brittle indium-tin-oxide electrode by spray coating technique and plasma reduction. The spray coating system is applied to deposit silver nanowire and over coated graphene oxide films and it has a great potential to scale-up. The resistance of silver nanowire transparent electrode is reduced by 10% and the surface roughness is decreased after graphene oxide coating. The over-coated graphene oxide is successfully reduced by $H_2$ plasma treatment and it is effective in increasing the environmental stability of electrode. The lifetime of silver nanowire and reduced graphene oxide hybrid electrode at $85^{\circ}C$ of Celsius degree of temperature and 85% of relative humidity has much increased.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3253-3256
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• 2013

Lithium is a highly attractive material for high-energy-concentration batteries, since it has low weight and high potential. Rechargeable lithium-ion batteries (LIBs), which have the extremely high gravimetric and volumetric energy densities, are currently the most preferable power sources for future electric vehicles and various portable electronic devices. In order to improve the efficiency and lifetime, new electrode compounds for lithium intercalation or insertion have been investigated for rechargeable batteries. Solid-state nuclear magnetic resonance (NMR) is a very useful tool to investigate the structural changes in electrode materials in actual working lithium-ion batteries. To detect the in-situ microstructural changes of electrode and electrolyte materials, $^7Li-^{19}F$ double-resonance solid-state NMR probe with a static solenoidal coil for a 600-MHz narrow-bore magnet was designed, constructed, and tested successfully.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.295-295
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• 2013

Supercapacitors with higher energy and power density are attracting growing attention for their wide range of potential applications such as portable electronic equipments, hybrid vehicle and cellular devices. In various classes of materials for supercapacitors, the redox pseudocapacitive materials such as conducting polymers and metal oxides have been most widely studied recently. The nanostructuring of the electrode surface has also been focused on since it can provide large surface area and consequently easy diffusion of ions in the capacitors. Among the active materials, in this work, we have used polyaniline (PANi) and manganese oxide ($MnO_2$). PANi is one of the promising electrode and active materials due to its desirable properties such as high electrochemical activity, high doping level and stability. $MnO_2$ is also widely studied material for supercapacitors since it is relatively cheap and environmentally friendly. In this work, we fabricated PANi hollow nanospheres by polymerizing aniline monomers on the polystyrene (PS) nanospheres and then dissolving the inner PS spheres. This nanostructuring of the PANi surface can provide large surface area and hence easy diffusion of electrolyte ions. We also incorporated $MnO_2$ nanoparticles into the PANi hollow nanospheres and investigated its electrochemical properties. It is expected that the combination of these two active materials with slightly different working potential windows show synergetic effects such as broader working potential range and enhanced specific capacitance.

• 전기화학회지
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• 제3권4호
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• pp.235-240
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• 2000

고출력 전기화학 캐패시터를 위한 전극제조공정으로 screen printing과 doctor blade법이 연구되었다. Screen printing에 의해서 제작된 비정질 $MnO_2$전극으로 측정된 CV (cyclic voltammogram)는 이상적인 캐패시터에 가까운 특성을 보여주었다. 50mV/s의 scan rate에서의 CV로부터 계산된 비용량은 $140{\mu}m,\;24{\mu}m,\; 3{\mu}m$의 전극두께에 대해서 각각 5.8F/g과, 81.8F/g, 172.0F/g의 값을 나타내었다. Screen printing전극에서의 $MnO_2$활물질의 이용율을 $100\%$로 하였을 때, paste와 doctor blade법의 이용율은 각각 $3.4\%$와 $47.6\%$이었다. Screen printing은 고출력 응용을 위한 얇은 전극의 코팅 방법으로 우수한 특성을 보였다.

• Journal of Electrochemical Science and Technology
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• 제9권4호
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• pp.292-300
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• 2018

The electrocatalytic oxidative behavior of an antiarrhythmic drug, procainamide hydrochloride (PAH) at the gold electrode surface has been examined using different voltammetric methods like cyclic, linear-sweep and differential pulse voltammetry. Voltammograms obtained in this study reveal that the electrode exhibit excellent electrocatalytic activity towards oxidation of the drug. The parameters that can affect the peak current at different pH, scan rate and concentration were evaluated. The number of electrons transferred was calculated. The current displayed a wide linear response ranging from 0.5 to $30.0{\mu}M$ with a limit of detection of 56.4 nM. The impact of potential interfering agents was also studied. The electrode displayed wide advantages such as simple sample preparation, appreciable repeatability, reproducibility and also high sensitivity. Furthermore, the feasibility of the proposed method was successfully demonstrated by determining PAH in the spiked human biological sample.

• Nuclear Engineering and Technology
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• 제44권8호
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• pp.939-944
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• 2012

Deposition potential, deposition time, square wave frequency, rotation speed of the rotating disc electrode, and palladium concentration were studied on a Glassy Carbon Electrode (GCE) in 0.01M HCl for the determination of palladium in High Level Nuclear Waste (HLNW) by anodic stripping voltammetry. Experimental conditions were optimized for the determination of palladium at two different, $10^{-8}$ and $10^{-7}M$, levels. Error and standard deviation of this method were under 1% for all palladium standard solutions. The developed technique was successfully applied as a subsidiary method for the determination of palladium in simulated high level nuclear waste with very good precision and high accuracy (under 1 % error and standard deviation).