• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.1009-1014
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• 2013

In the present study, using a variation of rib height, the transient response and the performance are investigated. The cell voltage is acquired according to the current density change($0.8A/cm^2$ to $1.0A/cm^2$) under same stoichiometry and relative humidity. The different level of undershoots appeared at the different clamping pressure(1.5MPa and 2.0MPa) and different rib height. At 1.5MPa clamping pressure, rib manufactured cut at $100{\mu}m$ height goes to steady state faster than reference plate and has lower maximum undershoot voltage. But performance is lower than reference plate due to increasing contact resistance.

• Journal of Adhesion and Interface
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• v.24 no.3
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• pp.86-94
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• 2023

To fabricate all-solution-processed flexible Organic Light-Emitting Diodes (OLEDs), we demonstrated a bonding technology using a polyethyleneimine (PEI) as an adhesion layer between the two substrates. As the adhesion layer requires not only a high adhesion strength, but also a high current density, we have tried to find out the optimum condition which meets the two requirements at the same time by changing experimental factors such as PEI concentration, thickness of the layer and by mixing some additives into the PEI. The adhesion strength and the electrical current density were investigated by tensile tests and electron only device (EOD) experiments, respectively. The results showed that at higher PEI concentration the adhesion strength showed higher value, but the electrical current through the PEI layer decreased rapidly due to the increased PEI layer thickness. We added Sorbitol and PolyEthyleneGlycohol (PEG) into the 0.1 wt% PEI solution to enhance the adhesion and electrical properties. With the addition of the 0.5 wt% PEG into the 0.1 wt% PEI solution, the device showed an electrical current density of 900 mA/cm² and a good adhesion characteristic also. These data demonstrated the possibility of fabricating all-solution-processed OLEDs using two-substrate bonding technology with the PEI layer as an adhesion layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.294-295
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• 2005

다중 코어를 이용한 대전류 변압기용 Mn-Zn ferrite를 제조하고 전자기적 특성을 분석하였으며, 제조된 자심재료를 이용하여 변압기를 제조하고 전원장치에 탑재하여 효율특성을 분석하였다. ZnO의 몰비가 증가할수록 혼합 스피넬의 형성을 통한 보아 자자의 증가로 인해 투자율은 증가하고 상대적으로 전력손실이 감소하여 $Fe_2O_3$ : MnO : ZnO = 53 : 36 : 11 mo\% 일 때 가장 우수한 특성을 나타냈고, 열처리 공정의 승온 과정에서부터 산소 분압을 제어하고 최적의 대기압 상수를 산출함으로써 Zn-loss 현상을 최소화하여 ZnO 11 mol%, 대기압 상수 7.7일 때 투자율 2350, 밀도 4.9 $g/cm^3$, 비저항 480 ${\Omega}cm$, 300 mT의 최대 자속 밀도 특성을 갖는 우수한 자심 재료를 개발하였다. 그리고 최소 손실 온도를 $90^{\circ}C$ 이하로 감소시켰으며 100 kHz에서 250 $kW/m^3$의 낮은 전력손실을 나타냈다. 또한 개발된 자심재료를 이용하여 제조된 전원장치는 30~80A의 출력 전류에서 85% 이상의 고효율을 얻었다.

• Analytical Science and Technology
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• v.23 no.5
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• pp.505-510
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• 2010

When polybutadiene dissolved in toluene was a binder of carbon powder, the volatility of solvent just after electrode fabrication assured the mechanical solidity of the carbon paste electrode. This characteristic met the qualifications for practical use of carbon paste electrodes. A new enzyme electrode bound with butadiene rubber was constructed. In order to confirm whether it shows quantitative electrochemical behaviors or not, its electrochemical kinetic parameters, e.g. the symmetry factor, the exchange current density, the capacitance of double layer, the time constant, the maximum current, the Michaelis constant and other factors were investigated. These experimental facts showed that butadiene rubber is a recommendable binder for practical use of a carbon paste electrode.

• Resources Recycling
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• v.27 no.5
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• pp.14-22
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• 2018

In this study, scarp of PCB containing copper and precious metals was manufactured as an anode, and electrorefining experiments were conducted on change of $H_2SO_4$ concentration and current density. Through electrolytic refining experiments, the concentration of Cu and slime recovered from each electrode was analyzed, element behavior was confirmed, and current efficiency was also calculated. As the $H_2SO_4$ concentration was increased, the current efficiency and the purity of Cu decreased, but the precious metals in the anode slime were maximally concentrated with 2.0 M $H_2SO_4$. In addition, as the current density was increased, the current efficiency decreased and the purity of Cu showed a tendency to increase, and the precious metals in the anode slime were maximally concentrated with $300A/m^2$. As a result of the pilot scale experiments, the Au content was 8,705 mg/kg, the Ag content was 35,092 mg/kg in the anode slime. As compared with the initial content, Au was concentrated 16 times and Ag concentrated 14 times.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.432-433
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• 2010

본 논문에서는 직렬형 디젤 하이브리드 전기 트럭 구동을 위한 견인 전동기 제어 시스템 개발에 대해 소개한다. 높은 출력 밀도를 요구하는 복합형 전기 차량의 특성을 고려하여 매입형 영구자석 동기전동기를 선정하고, 대전류 고효율 시스템 구성을 위해 수랭식 MCU(Motor Control Unit)를 개발 하였다. 또한 빠른 토크 응답 특성과 넓은 영역의 속도 운전을 위한 약자속 제어 기법을 적용하였으며, 전체 시스템 효율을 향상시키기 위해 단위 전류당 최대 토크 제어 기법(MTPA)이 사용 되었다. 개발 된 제어 시스템 및 제어 기법을 실험을 통해 검증 하였다.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.749-750
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• 2006

대용량 BLDC 모터의 진동과 소음의 원인은 영구자석과 슬롯형상에 의한 코깅토크와 전류 파형에 의한 고주파이다. 특히 대용량 BLDC의 경우 코깅토크에 의한 진동 및 소음의 영향이 상대적으로 큰 값을 가지게 되며, 본 연구는 5MW급 연구자석형 전동기에서 코깅토크 발생원인 중 하나인 영구자석의 형상을 최적화하기 위하여 RSM(Response Surface Method)과 민감도기법을 적용하여 코깅토크 저감을 위한 연구를 하였다. FEM에 의해서 자속밀도분포와 토크를 계산하고, 1개의 목적함수와 3개의 설계변수를 설정하여 최적화 하였다. FEM과 최적화기법(RSM+민감도기법)을 결합하여 영구자석의 형상을 최적화한 결과 코깅토크의 ripple이 최대 20%정도로 감소되었으며, 목적함수와 설계변수의 개수에 따라 더욱 개선될 수 있다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.3
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• pp.113-123
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• 1989

We developed a general algorithm and program to determine nominal value of new optimum geometric parameters of MOSFET when yield satisfying specification of drain current and noise spectral density is maximum. In this paper, the total number of considered devices is 500, and each parameters of geometric parameter was generated randomly within the limits of ${pm}3%$ of nominal value, and the distribution of 500 geometric parameters is gaussian distribution.

• Journal of the Korean Vacuum Society
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• v.15 no.6
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• pp.637-641
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• 2006

We present the DC and RF characteristics of 100 nm gate length InGaAs/InAlAs/GaAs metamorphic high electron mobility transistors (MHEMTs). We fabricated the T-gate with 100 nm foot print by using a positive resist ZEP520/P (MMA-MAA)/PMMA trilayer by double exposure method. The fabricated 100 nm MHEMT with a $70\;{\mu}m$ unit gate width and two fingers were characterized through do and rf measurements. The maximum drain current density of 465 mA/mm and extrinsic transconductance $(g_m)$ of 844 mS/mm were obtained with our devices. From rf measurements, we obtained the current gain cut-off frequency $(f_T)$ of 192 GHz, and maximum oscillation frequency $(f_{max})$ 310 GHz.

• Journal of Astronomy and Space Sciences
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• v.19 no.1
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• pp.75-88
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• 2002

The climatological characteristics of the polar ionosphere is examined in terms of the ionospheric conductance and electric field. For this purpose, 109 days of measurements from the Sondrestrom incoherent scatter radar are utilized. By combining these two quantities, it is possible to deduce the overhead ionospheric current distributions. The ionospheric current density thus obtained is compared with the corresponding ground magnetic disturbance. Also examined is the effect of the field-aligned current on the ground magnetic disturbance, particularly on the D component Several interesting climatological characteristics about the ionosphere over the Sonderstrom are apparent from this study. (1) The conductance distribution is mainly due to solar EUV radiation during day-time On the other hand, the conductance distribution during the night-time is very low. (2) The conductance distribution one. the polar cap region during the day-time is controlled mostly by the solar EUV radiation, while it is extremely low during night-time wish the Hall and Pedersen conductances being 1.6 and 1.2 siemen, respectively (3) The region of the maximum N-S electric field tend to locate in the dayside sector. The E-W component of the electric field is stronger than that over Chatanika (4) The E-W auroal inospheric current (J/sub E/) is more important in the sunlit hemisphere than the night hemisphere. And a strong southward current is noted in the prenoon sector (5) There is a significant correlation between the overhead ionospheric current and the simultaneously observed ground magnetic disturbance. However, the assumption for the infinite sheet current approximation is far from realistic, underestimating the current density. And the correlation between ${\Delta}H$ and J/sub E/ is higher than the one between ${\Delta}D$ and J/sub N/ , indicating that field-aligned current affects significantly ${\Delta}D$.