• Journal of Magnetics
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• 제18권3호
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• pp.225-229
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• 2013

We report a measurement for the anomalous Nernst effects induced by a temperature gradient in [CoSiB/Pt] multilayer films with perpendicular magnetic anisotropy. The Nernst voltage shows a characteristic hysteresis which reflects the magnetization of the film as in the case of the anomalous Hall effects. With a local heating geometry, we also measure the dependence of the anomalous Nernst voltage on the distance d from the heating element. It is roughly proportional to $1/d^{1.3}$, which can be conjectured from the expected temperature gradient along the sample from the heat equation.

• 한국세라믹학회지
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• 제29권9호
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• pp.695-704
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• 1992

In (Pb, La)(Zr, Ti)O3 ceramic system, the functionally gradient material (FGM) was developed, and its processing and properties were investigated. The FGMs were successfully prepared through doctor blade method with acrylic binder system as well as mold stacking press method. The ultrasonic treatment was very effective for particle dispersion in slurry, and it lead to form clack-free green films. The strain-voltage characteristics of the FGM system was significantly improved which fabricated between a high piezoelectric-low dielectric and a low piezoelectric-high dielectric composition layer.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.691-694
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• 2003

Density gradient method is used to analyze the quantum effect in MOSFET, Quantization effect in the poly gate leads to a negative threshold voltage shift, which is opposed to the positive shift caused by quantization effect in the channel. Quantization effects in the poly gate are investigated using the density gradient method, and the impact on the short channel effect of double gate device is more significant.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 춘계총회,특별강연,심포지움,연구발표회
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• pp.103.2-103.2
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• 2000

• 전기학회논문지
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• 제57권5호
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• pp.845-851
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• 2008

A simple RMRAC (Robust Model Reference Adaptive Control) scheme for the PMSM (Permanent Magnent Synchronous Motor) is proposed in the synchronous frame. A current control of PMSM is the most inner loop of electro-mechanical driving systems and it requires a fast and simple control law to play a foundation role in the control hierarchy. In the proposed synchronous current model, the input signal is composed of a calculated voltage by proposed adaptive laws and real system disturbance. The gains of feed-forward and feedback controllers are estimated by the proposed modified Gradient method respectively, where the system disturbances are assumed as filtered current tracking errors. After the estimation of the system disturbances from the tracking errors, the corresponding voltage is fed forward to control input voltage to compensate for the disturbances. The proposed method is robust against high frequency disturbance and has a fast dynamic response. It also shows a good real-time performance due to it's simplicity of control structure. Through the simulations and real experiments, efficiency of the proposed method is verified.

• Structural Engineering and Mechanics
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• 제66권2호
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• pp.237-248
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• 2018

This study presents the investigation of wave dispersion characteristics of a magneto-electro-elastic functionally graded (MEE-FG) nanosize beam utilizing nonlocal strain gradient theory (NSGT). In this theory, a material length scale parameter is propounded to show the influence of strain gradient stress field, and likewise, a nonlocal parameter is nominated to emphasize on the importance of elastic stress field effects. The material properties of heterogeneous nanobeam are supposed to vary smoothly through the thickness direction based on power-law form. Applying Hamilton's principle, the nonlocal governing equations of MEE-FG nanobeam are derived. Furthermore, to derive the wave frequency, phase velocity and escape frequency of MEE-FG nanobeam, an analytical solution is employed. The validation procedure is performed by comparing the results of present model with results exhibited by previous papers. Results are rendered in the framework of an exact parametric study by changing various parameters such as wave number, nonlocal parameter, length scale parameter, gradient index, magnetic potential and electric voltage to show their influence on the wave frequency, phase velocity and escape frequency of MEE-FG nanobeams.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 추계학술대회
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• pp.454-456
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• 2017

다양한 양자모델(Quantum model)을 적용한 터널 전계 효과 트랜지스터(tunnel field effect transistor; TFET)의 전류 및 커패시턴스(Capacitance)-전압 특성을 조사하였다. 사용된 양자 모델은 density gradient, Bohm Quantum Potential(BQP), Vandort quantum correction 모델을 슈뢰딩거-푸아송 모델과 calibration하여 사용하였다. BQP, Vandort, density gradient 모두 구동전류는 감소하였다. BQP를 단독으로 사용한 경우에 SS(subthreshold swing)와 on-set 전압($V_{onset}$)은 일정하지만 구동전류에서만 약 3배 전류가 감소하였으며, BQP와 Vandort 사용한 경우와 density gradient를 사용한 경우에 모두 $V_{onset}$이 약 0.07 eV 이동하였으며, SS가 40 mV/dec 이상으로 증가하였다.

• 공업화학
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• 제21권2호
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• pp.205-210
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• 2010

본 연구에서는 기체방전관의 과전압 보호 성능과 수명에 미치는 절연파괴 특성을 알아보기 위하여 황동전극을 이용하여 기체방전관을 제조하였다. 황동전극을 이용한 기체방전관의 절연파괴 특성은 인가전압의 기울기와 방전관 내부의 질소기체 압력을 통하여 알아보았다. 방전관 인가전압의 기울기가 증가할수록 절연파괴 전압과 방전 시 소비되는 에너지량이 크게 상승되었고, 절연파괴 시간은 감소되었다. 방전관 내부 질소기체의 압력이 감소할수록 절연파괴 전압과 절연파괴 소요시간, 방전 소비에너지량이 크게 감소되었다. 결과적으로, 방전관의 과전압 보호 성능 및 수명을 증진시키기 위해서는 절연파괴 전압과 절연파괴 소요시간, 방전 시 소비되는 에너지량이 감소되어야 함을 알 수 있었다. 한편, 방전관 내부 질소기체 압력이 방전관의 자체 수명 및 과전압 보호 성능에 영향을 미침을 알 수 있었다.

• Journal of Electrochemical Science and Technology
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• 제10권3호
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• pp.302-312
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• 2019

The voltage produced from the salinity gradient in reverse electrodialysis (RED) increases proportionally with the number of cell pairs of alternating cation and anion exchange membranes. Large-scale RED systems consisting of hundreds of cell pairs exhibit high voltage of more than 10 V, which is sufficient to utilize water electrolysis as the electrode reaction even though there is no specific strategy for minimizing the overpotential of water electrolysis. Moreover, hydrogen gas can be simultaneously obtained as surplus energy from the electrochemical reduction of water at the cathode if the RED system is equipped with proper venting and collecting facilities. Therefore, RED-driven water electrolysis system can be a promising solution not only for sustainable electric power but also for eco-friendly hydrogen production with high purity without $CO_2$ emission. The RED system in this study includes a high membrane voltage from more than 50 cells, neutral-pH water as the electrolyte, and an artificial NaCl solution as the feed water, which are more universal, economical, and eco-friendly conditions than previous studies on RED with hydrogen production. We measure the amount of hydrogen produced at maximum power of the RED system using a batch-type electrode chamber with a gas bag and evaluate the interrelation between the electric power and hydrogen energy with varied cell pairs. A hydrogen production rate of $1.1{\times}10^{-4}mol\;cm^{-2}h^{-1}$ is obtained, which is larger than previously reported values for RED system with simultaneous hydrogen production.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.134-136
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• 1993

This paper presents a novel and efficient method to calculate the critical point of voltage collapse. Conjugate gradient and modified Newton-Raphson methods are employed to calculate two pairs of multiple load flow solutions for two operating conditions, i.e., both +mode and -mode voltages for two loading conditions respectively. Then these four voltage magnitude-load data sets of the bus which is most susceptible to voltage collapse, are fitted to third order polynomial using Lagrangian interpolation in order to represent approximate nose curve (P-V curve). This nose curve locates first estimate of the critical point of voltage collapse. The procedure described above is repeated near the critical point and the new estimate will be very close to the critical point. The proposed method is tested for the eleven bus Klos-Kerner system, with good accuracy and fast computation time.