• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.173-176
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• 2006

There are many kinds of protection methods for marine structures by using and environmental condition. Coating protection method, one of these methods is being widely adopted to both all ground and marine structures. In this study, by adding some additives such as Zn powder(Zn), carbon black(CB) to epoxy anti-corrosive paint, the effect to promote corrosion resistance was investigated with electrochemical method. Corrosion potentials with additives shifted to negative direction than no additive. However passivity current density increased than no additive except for Zn(20)+CB(10), especially, additive of Zn(20)+CB(10) showed the smallest passivity current density. Polarization resistance of Zn(20)+CB(10) by both cyclic voltammogram and impedance measurement was the largest value than other additives. And also surface phenomenon by adding Zn(20)+CB(10) was observed a good add condition not showing bubbling than other additives.

• 한국정보전자통신기술학회논문지
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• 제1권3호
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• pp.3-8
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• 2008

본 논문에서는 H 평면에서 전방향성 방사패턴을 갖고 저자세를 갖는 평면형 안테나를 제안하였다. 전기적 소형 모노폴 안테나가 갖는 캐패시턴스 성분에 인덕티브 성분의 ENG(Epsilon Negative) 쉘 구조를 부설함으로써 임피던스를 매칭시켰다. ENG 쉘 구조는 4개의 계단형 L-슬롯으로 대칭된 인덕티브 로딩 구조로 이루어져 있다. 실제측정 결과 제안된 안테나의 임피던스 대역폭 ($VSWR{\leq}2$)은 150MHz (2.5 ~ 2.65GHz)를 나타내었고 최대 방사 이득은 중심 주파수 2.56GHz에서 1.12dBi를 나타내었으며 전방향성 방사패턴을 나타내었다. 제안된 안테나는 저자세 높이와 전방향성 방사를 요구하는 시스템에 적용될 수 있을 것으로 사료된다.

• Journal of Power Electronics
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• 제19권6호
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• pp.1467-1476
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• 2019

Grid unbalanced faults can cause core saturation of power transformer and produce lower-order harmonics. These issues increase the electrical stress of power electronic devices and can cause a tripping of an entire HVDC system. In this paper, based on the positive-sequence and negative-sequence impedance model of a VSC-HVDC system as seen from the point of common connection (PCC), the resonance problem is analyzed and the factors determining the resonant frequency are obtained. Furthermore, to suppress over-voltage and over-current during resonance, a novel method using a virtual harmonic resistor is proposed. The virtual harmonic resistor emulates the role of a resistor connected in series with the commutating inductor without influencing the active and reactive power control. Simulation results in PSCAD/EMTDC show that the proposed control strategy can suppress resonant over-voltage and over-current. In addition, it can be seen that the proposed strategy improves the safety of the VSC-HVDC system under unbalanced faults.

• Journal of Advanced Marine Engineering and Technology
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• 제29권5호
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• pp.495-501
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• 2005

Al is a active metal that owes its resistance to a thin, protective, barrier oxide surface layer, which is stable in air and neutral aqueous solution. Thus Al alloys are widely used in architectural trim. cold & hot-water storage vessels and piping. However Al and most of its alloy may corrode with some forms such as pitting corrosion, intergranular corrosion and galvanic corrosion in the case of exposure to various industrial and marine atmosphere. Therefore a correct evaluation of corrosion resistance for their Al and Al alloys may be more important in a economical point of view. In this study. a relative evaluation of corrosion resistance for three kinds of Al alloys such as ALDC2, ALDC3, and ALDC8 series was carried out with electrochemical method. There is a tendency that corrosion potential is shifted to positive or negative direction by alloying components regardless of corrosion resistance. Moreover the data of corrosion properties obtained from cathodic Polarization curve, cyclic voltammogram and AC. DC impedance respectively showed a good correspondence each other against the corrosion resistance but variation of corrosion potential. passivity current density of anodic polarization curve and corrosion current density by Tafel extrapolation and Stern-Geary method didn't correspond with not only each other but also considerably the data of corrosion properties discussed above. Therefore it is suggested that an optimum electrochemical evaluation for corrosion resistance of Al alloy is to calculate the diffusion limiting current density of cathodic polarization curve, impedance of AC or DC and polarization resistance of cyclic voltammogram.

• 조명전기설비학회논문지
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• 제23권12호
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• pp.146-153
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• 2009

최근 대형 건축물들은 접지그리드를 기반으로 한 공통접지방식을 채택하고 있다. 이러한 접지시스템의 성능평가는 접지저항만으로 불충분하므로 접지임피던스의 측정이 요구된다. 대형 접지시스템의 접지임피던스에 대한 측정 방법은 IEEE standard 81.2에 기술되었으나 세부적인 평가방법들은 제시되지 못한 상태이다. 본 논문은 15[m]$\times$15[m] 접지그리드에 대하여 수정된 전위강하법에 기반한 접지임피던스의 정확한 측정방법과 보조전극의 위치에 따른 도전유도 및 전자유도에 의한 측정오차를 기술한다. 그 결과 도전유도에 의한 오차는 보조전극의 거리가 늘어날수록 감소하였다. 전자유도에 의한 오차를 배제하기 위해서 전위측정선은 전류측정선과 90도를 이루어야 한다. 전위측정선과 전류측정선이 예각 또는 둔각을 이루었을 때 전자유도전압은 각각 + 또는 -를 나타내었다. 일반적으로 전자유도에 의한 오차는 예각에 비해서 둔각의 경로가 작게 나타났다.

• 전기화학회지
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• 제6권2호
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• pp.93-97
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• 2003

[ $RuCI_3{\cdot}xH_2O$ ]로부터 제조한 비정질의 $RuO_2{\cdot}nH_2O$을 사용하여 탄탈륨 집전체상의 수퍼캐패시터 전극을 제조하였다. $RuO_2{\cdot}nH_2O$ 전극과 4.8 M 황산 전해액을 사용하여 $RuO_2$ 수퍼캐패시터를 제조하였다. 탄탈륨 박막은 0.0-1.1 V(vs.SCE)에서 안정적임을 AC impedance로 확인하고 수퍼캐패시터에 적용하였다. 루테늄 산화물 수퍼캐패시터는 약 1.0 V(vs. SCE)이상에서 비가역 가수분해 반응이 진행되었다 수퍼캐패시터를 0.5V(vs. SCE)의 protonation leve을 조정하고, 전압범위를 1V로 하여 충방전 시험할 경우 우수한 특성을 나타내었다. 이때 전극전위는 $-0.004\~0.995V(vs.SCE)$의 범위이고 positive 전극 및 negative 전극의 전위범위는 각각 $-0.004\~0.515V(vs.SCE)$ 및 $-0.515\~0.995V(vs.SCE)$이었다.

• 한국수소및신에너지학회논문집
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• 제6권2호
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• pp.65-73
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• 1995

Negative electrode was prepared by mixing $Ti_{0.7}Zr_{0.3}Cr_{0.3}Mn_{0.3}V_{0.6}Ni_{0.8}$ alloy powder with copper or nickel powder and pressing in the air. The cycled electrodes were analyzed with SEM, potentiostat and electrochemical impedance spectroscopy. It was found that the Cu-compacted electrode showed better low temperature dischargeability and higher rate capability than Ni-compacted electrode. From SEM analysis of the cycled electrode compacted with copper powder, it was observed that the surface of MH particles was covered with copper grains and whisker precipitated from electrolyte after dissolution during cell test. It is found that the improved electrode characteristics are attributed to the copper layer on MH particles deposited by dissolution and precipitation(DP) process.

• Corrosion Science and Technology
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• 제17권2호
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• pp.54-59
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• 2018

The effect of external DC electric field on atmospheric corrosion behavior of zinc under a thin electrolyte layer (TEL) was investigated by measuring open circuit potential (OCP), cathodic polarization curve, and electrochemical impedance spectroscopy (EIS). Results of OCP vs. time curves indicated that the application of external DC electric field resulted in a negative shift of OCP of zinc. Results of cathodic polarization curves measurement and EIS measurement showed that the reduction current of oxygen increased while charge transfer resistance ($R_{ct}$) decreased under the external DC electric field. Variation of OCP negative shift, reduction current of oxygen, and $R_{ct}$ increase with increasing of external DC electric field strength as well as the effect of external DC electric field on double-layer structure in the electrode/electrolyte interface and ions distribution in thin electrolyte layer were analyzed. All results showed that the external DC electric field could accelerate the corrosion of zinc under a thin electrolyte layer.

• 전기화학회지
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• 제6권2호
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• pp.153-157
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• 2003

전기이중층 축전용량(electric double layer capacitance)과 유사축전용량(pseudo-capacitance)을 함께 갖는 하이브리드 전기화학 축전기에 대한 연구를 수행하였다. 양극은 $Ni(OH)_2$ 활성탄소가 복합된 전극을 사용하였으며 음극은 활성탄소를 활물질로 사용하므로써 비대칭 전극 구조를 갖는다. 셀 실험을 위하여 $5\times5cm^2$ 크기인 전극을 제작 사용하였다. Cyclic voltammetry측정 및 교류 임피던스 측정실험을 통하여 각각의 셀들이 갖는 전기화학적 거동을 조사하였고 충 방전 실험을 통하여 양극과 음극의 최적 질량비를 조사하였다.

• 한국수소및신에너지학회논문집
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• 제24권2호
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• pp.179-185
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• 2013

The behavior of surface film formation was greatly dependent on the speed of potential cycling. In $LiClO_4$ / EC + DEC, cyclic voltammetry results showed that the peaks originated from surface film formation on graphite electrode at the high charge-discharge rate was shifted to the lower potentials as the charge-discharge rate decrease. This indicates that surface films with different morphology and thickness were formed by different charge-discharge rate. Transmission electron microscopy (TEM) results indicated that the properties such as thickness and morphology of the surface film were greatly affected by the charge-discharge rate. Electrochemical impedance spectroscopy (EIS) showed that the resistance of surface film was affected by the speed of potential cycling. In addition, the charge transfer resistance was also dependent on the charge-discharge rate indicating that the charge transfer reaction was affected by the nature of surface film. TEM and EIS results suggested that the chemical property as well as the physical property of the surface film was affected by the charge-discharge rate.