• 전기화학회지
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• 제16권2호
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• pp.65-69
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• 2013

전기이중층 커패시터용 활성탄의 정전 용량 향상을 위해 우레아를 이용해 활성탄 표면에 펩티드 결합을 유도하였다. 우레아 도입에 따른 활성탄은 소성과정을 거쳐 안정화되었으며, 전기화학적 특성을 순환전류 전압법을 이용하여 정전 용량을 관찰하고, 임피던스를 통해 저항 변화를 관찰하였으며, 충방전 평가를 통해 싸이클 성능을 관찰하였다. 결과적으로 질소성 작용기의 도입으로 정전 용량은 기존 탄소재에 비해 약 22.9%의 향상을 이루었으며, 저항 감소 및 우수한 싸이클 성능을 나타냄을 확인하였다.

• 한국전자파학회논문지
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• 제14권5호
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• pp.479-488
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• 2003

시간영역 유한차분법을 이용하여 2.4 GHz와 5.8 GHz외 ISM 대역을 위한 이중대역 마이크로스트립 안테나를 설계한다. 2개의 구형 패치가 겹쳐진 십자형 패치를 안테나의 방사소자로 제안하고 급전 방식은 개구 결합을 이용한다. 안테나 설계를 위해 개구와 스터브 길이 변화에 따른 입력 임피던스의 변화를 살펴보고, 방사소자의 길이와 폭 변화에 따른 중심 주파수와 -10 dB대역폭을 고찰한다 반사손실에 대한 계산 결과를 IE3D의 해석 결과 및 측정 결과와 비교하여 잘 일치함을 확인하고, 주파수 2.43 GHz와 5.79 GHz에서 안테나의 방사패턴을 측정하여 -3 dB 빔폭, 전후방비 및 최대 이득을 제시한다.

• 한국전기전자재료학회논문지
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• 제22권11호
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• pp.935-940
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• 2009

In this research, the composites (100-x)LCP-xBNT (x = 0, 10, 20, 30, 40 vol.%) were fabricated with thermoplastic LCP(Liquid Crystal Polymer) and BNT($BaNd_2Ti_4O_{12}$) which is a high frequency dielectric material. Their dielectric properties, mechanical strength and microstructure were investigated by Impedance analyser, Instron and SEM. In order to fabricate LCP-BNT composites, LCP resin was put into the twin screw type mixer($310^{\circ}C$), melted by keeping for 10 min. After that, BNT filler was dispersed with melted LCP resin for 15 min. in the mixer. For measuring the dielectric properties and mechanical strength, Composite specimens were made by pressing composite granule (LCP-BNT) with 7 ton in the mold at $310^{\circ}C$. With increasing the BNT content (0~40 vol.%) of the composite, Its dielectric constant increased, dielectric loss and flexural strength decreased. The dielectric constant and flexural strength of composites with 20~30 vol.% of BNT filler are 4.1~6.0 and 35~55 MPa respectively. BNT/LCP composite is the potential substrate material for the high frequency application.

• Transactions on Electrical and Electronic Materials
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• 제15권2호
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• pp.81-86
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• 2014

The process parameter in optimized KOH alkali activation of soft carbon series coke material in high purity was set with DOE experiments design. The activated carbon was produced by performing the activation process based on the set process parameters. The specific surface area was measured and pore size was analyzed by $N_2$ absorption method for the produced activated carbon. The surface functional group was analyzed by Boehm method and metal impurities were analyzed by XRF method. The specific surface area was increased over 2,000 $m^2/g$ as the mixing ratio of activation agent increased. The micro pores in $5{\sim}15{\AA}$ and surface functional group under 0.4 meq/g were obtained. The contents of the metal impurity in activated carbon which is the factor for reducing the electrochemical characteristics was reduced less than 100 ppm through the cleansing process optimization. The electrochemical characteristics of activated carbon in 38.5 F/g and 26.6 F/cc were checked through the impedance measuring with cyclic voltammetry scan rate in 50~300 mV/s and frequency in 10 mHz ~100 kHz. The activated carbon was made in the optimized activation process conditions of activation time in 40 minutes, mixing ratio of activation agent in 4.5 : 1.0 and heat treatment temperature over $650^{\circ}C$.

• 전기학회논문지
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• 제58권6호
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• pp.1186-1193
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• 2009

Wearable ECG monitoring is regarded as one of the most essential part in the ubiquitous healthcare environment and subsequently day-life monitoring of a heart condition has been pursued especially for the elder people. However, there are many problems to accomplish this task such as; i) implementation of long-term monitoring device, ii) development of non-irritating electrode on skin and iii) stable signal acquisition. With these aims, we have focused on implementing a non-irritating electrode with an endurable monitoring device for day-life. To accomplish our tasks, we basically developed four different types of textile electrodes that are adapted by both shape and the composed material; flat or convex shape and Ag-conductive paste material or not. It turns out to be that a convex shape and Ag-paste textile electrode has the best performance in terms of both signal-to-noise ratio (SNR) and Impedance/Phase characteristics. Furthermore, ECG amplifier (35 ${\times}$ 35 mm) has developed to resolve the ECG signal and transfer the signal to desktop computing device or portable one by RF serial communication.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.295-298
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• 2009

Oxygen ionic conductors of CeScSZ electrolyte in SOFC unit cell are applied to anode and cathode as well as electrolyte to have the triple-phase-boundaries of electrochemical reaction, and it is required to decrease the sintering temperature of anode-supported electrolyte by the nanoscale of CeScSZ electrolyte powder. In this report, nanoscale CeScSZ electrolyte powder was synthesized by chemical synthesis method. The particle size, surface area and morphology of the powder were observed by SEM and BET. Thin film electrolyte of under $10{\mu}m$ was fabricated by tape casting using the synthesized CeScSZ electrolyte powder, and ionic conductivity and gas permeability of electrolyte film were evaluated. Finally the SOFC unit cell was fabricated using the anode-supported electrolyte prepared by a tape casting method and co-sintering, in which the active layer, measuring $20{\mu}m$, was introduced in the anode layer to provide a more efficient reaction. Electrochemical evaluations of the SOFC unit cell, including measurements such as power density and impedance, were performed and analyzed.

• 조명전기설비학회논문지
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• 제27권8호
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• pp.30-35
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• 2013

This paper describes the assessment method of deterioration condition for a power transformer using SFRA. Frequency Response Analysis(FRA) is a method to evaluate the mechanical and geometrical integrity of the core and windings within a power transformer by measuring the electrical transfer functions over a wide frequency range. SFRA is sweep frequency response analyzer for power transformer winding diagnosis. The FRA is a comparative method, that evaluates the transformer condition by comparing the obtained set of FRA results to reference results on the same, or a similar, unit. FRA techniques were widely used and much more sensitive than the traditional and internationally accepted method of impedance measurements, but that work was required on standardization and interpretation. In order to analyze the deterioration condition for power transformer, overvoltage test and mechanical distortion test were carried out. The deterioration condition for power transformer was evaluated by SFRA. It is intended to present the elemental technology of assessment method for power transformer using SFRA.

• 전력전자학회논문지
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• 제17권6호
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• pp.546-552
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• 2012

This paper presents an active anti-islanding detection method using negative sequence voltage injection to the grid through a three-phase photovoltaic inverters. Because islanding operation mode can cause a variety of problems, the islanding detection of grid-connected photovoltaic inverter is the mandatory feature. The islanding mode is detected by measuring the magnitude of negative sequence impedance calculated by the negative sequence voltage and current at the point of common coupling. Simulation and experimental test are performed to verify the effectiveness of the proposed method which can detect the islanding mode in the specified time. The test has been done in accordance with the condition on IEEE Std 929-2000.

• 한국전자파학회논문지
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• 제14권10호
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• pp.1024-1029
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• 2003

본 논문에서는 시간영역의 전자계 측정에 사용하기 위한 원판 부착형 모노폴 안테나의 복소 안테나 인자를 검토하고 있다. 이론 해석으로서는 가상 전기벽을 설정하여 각 영역에서의 전자계를 고유함수로 전개하고 모드 정합법을 적용하여 안테나의 입력 임피던스 및 안테나 인자 등을 계산하고 있다. 이론 해석의 결과, 모노폴 안테나에 원판을 부착하면 저주파수 대역에서의 안테나 인자 절대치는 발산하지 않으며 일반적인 모노폴 안테나에 비교하여 광대역 특성이 있음을 알 수 있었다. 모드 정합법에 의한 이론 해석의 타당성을 확인하기 위하여 입력 임피던스의 이론치와 측정치를 비교하여 양자가 잘 일치함을 확인하고 있다.

• 한국전자파학회논문지
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• 제25권9호
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• pp.879-885
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• 2014

논문에서는 전자파(EMFs) 측정을 위한 광대역 3축 등방성 안테나를 설계 및 제작하였다. 제안된 3축 안테나의 각축에 따른 개별 안테나는 등방성 특성을 가지며, 임의의 안테나 축을 선택하기 위하여 RF 스위치를 사용하였다. 또한, 안테나의 이득 개선 및 잡음성분을 억제하기 위하여 각 축에 저항을 삽입하였고, 각 다이폴 안테나의 포트 임피던스는 발룬을 사용하여 정합하였다. 안테나의 성능 검증을 위하여, 표준전자기장을 만들어주는 GTEM Cell를 사용하여 antenna factor 및 수신감도를 도출하였다. 결과적으로, 제작된 3축 등방성 안테나는 0.03~3 GHz의 넓은 동작주파수 범위 내에서 수신감도 0.12~4.2 mV/m, VSWR(typical)은 3.3:1 이하이다.