• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.9
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• pp.817-823
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• 2017

In the past, research has been conducted on the development of an adaptive cruise control algorithm considering fuel efficiency, and an adaptive cruise control system considering fuel efficiency have been developed. However, research on optimizing vehicle and adaptive cruise control parameters in order to maximize performances is insufficient. In this study, the design optimization of vehicle and control parameters considering fuel efficiency, trackability, ride comfort and safe distance is performed. This paper proposes performance measures of vehicle behavior and develops an adaptive cruise control system. In addition, based on the screening of vehicle parameters that significantly influence performances, kriging surrogate models are constructed through a sequential design of experiment, and kriging surrogate model-based design optimization is performed to maximize fuel efficiency and satisfy target performances.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.172-175
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• 2010

본 논문에서는 GaN HEMT를 이용하여 Jamming용 System에 사용될 수 있는 고효율 및 고출력 특성을 가지는 광대역 Amplifier를 제작하였다. Jamming System에서 핵심이 되는 Amplifier는 넓은 범위의 주파수에서 통상적으로 사용되는 출력 신호에 비해 보다 높은 출력의 신호를 구현하는 것이 중요하다. 본 논문에서는 GaN HEMT에 안정적인 전원 공급을 위한 음 전원 Bias 제어 회로와 Sequence 회로 및 온도에 따른 Gain 보상 회로를 구현하였으며, 500~2500MHz의 광대역에서 동작하면서 50W 이상의 출력을 낼 수 있도록 설계하였다. 출력 전력이 향상과 안정적인 동작을 위해 Main 출력 단은 60Watt 급의 GaN HEMT 소자와 광대역 Coupler를 이용하여 Balanced Structure로 설계하였다. 제작된 광대역 Amplifier는 30V 단일 전원에서 동작하도록 설계되었고, 크기는 140*90mm이다. 동작주파수 대역(500~2500MHz)에서 Small Signal Gain 63dB와 Gain Flatness ${\pm}$2dB, -10dB 이하의 Input Return Loss를 가진다. CW(Continuous Wave) Signal을 이용하여 측정하였으며, 50Watt 이상의 Saturation Power에서 최대 45%, 최소 28% 정도의 효율 특성을 보였다.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.49-53
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• 2007

The direct methanol fuel cell (DMFC) is a promising power source for portable applications due to many advantages such as simple construction, compact design, high energy density, and relatively high energy-conversion efficiency. In this work, an electrochemical methanol sensor for monitoring the methanol concentration in direct methanol fuel cells was fabricated using a thin composite nafion membrane as the electrolyte. We have analyzed the I-V characteristic of the fabricated methanol sensor as a function of methanol concentration, catalyst electrode and platinum(Pt) thickness. The fabricated sensor was analyzed by I-V measurement with various methanol concentration. When we measured the sensor characteristics with 10nm Pt and at 1V, the current value was $1.30{\times}10^{-6}A,\;1.96{\times}10^{-6}A\;and\;2.80{\times}10^{-6} A$ for three methanol concentration of 1M, 2M and 3M, respectively. When the methanol concentration was fixed at 2M, the current value of the fabricated device with Pt layers of 5, 10 and 15 nm thickness was $3.06{\times}10^{-6}A,\;1.96{\times}10^{-6}A\;and\;1.00{\times}10^{-6}A$, respectively. These results lead us to the conclusion that when the methanol concentration increases, the output current increases and when the catalyst electrode become thinner, the current increase more. It showed that, the thinner the catalyst electrode, the more electrochemistry become activation.