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A High Efficiency Boost Converter For TFT-LCD Bias Supply
Hyunseok Nam,Inseok Kim,Youngkook Ahn,Jeongjin Roh 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
In this paper, a high efficiency boost converter is designed using a 0.5-㎛ 5V, 3.5-㎛ 30-V CMOS process for TFT-LCD Bias supply. The boost converter can be adjusted with external resistors. The boost converter’s input power supply range is 2.5V ∼ 5V, the output voltage range is 10V-20V and the clock frequency is 1.3 ㎒. The maximum load current is 120㎃ at an input power supply of 3V, output voltage of 20V and the maximum efficiency is 92% with input power supply at 5V, output voltage of 12V, and load current of 120㎃. The simulation results show the successful operation of the boost converter.
Hyunseok Nam,Youngkook Ahn,Jeongjin Roh IEEE 2012 IEEE TRANSACTIONS ON POWER ELECTRONICS - Vol.27 No.1
<P>A high-voltage-tolerant buck converter with a novel adaptive power transistor driver is proposed in this paper. In order to minimize the <I>R</I><SUB>ON</SUB> of the cascode power transistor, the proposed scheme uses optimized and separated driving voltages for bias of the pMOS and nMOS power transistors. This increases not only the conversion efficiency, but also the maximum allowable load current for the transistor driver with small layout size, when compared to the buck converter with the earlier scheme. The measurements show that when the supply voltage is 2.5 V and the load current is 150 mA, the efficiency of the buck converter with the earlier scheme is 82%, whereas the efficiency of the buck converter with the proposed scheme is 92%, showing a maximum improvement of 10%. The designed buck converter uses the 0.35- μm-thick gate oxide CMOS process, and at 2.5-5 V of voltage, can supply up to 380 mA of load current. The total chip size is 2.7 mm<SUP>2</SUP>.</P>
Green Tea Consumption and Stomach Cancer Risk
Hyunseok Kang,Sun Young Rha,Kyung Won Oh,Chung Mo Nam 한국역학회 2010 Epidemiology and Health Vol.32 No.-
OBJECTIVES: Green tea has been suggested to have a chemopreventive effect against various cancers including stomach cancer. The aim of this study is to elucidate the relationship between green tea consumption and stomach cancer risk by meta-analysis. METHODS: Eighteen observational studies were identified using MEDLINE, THE COCHRANE LIBRARY, RISS, and a manual search. Summary relative risks/odds ratios (RR/ORs) for the highest versus non/lowest green tea consumption levels were calculated on the basis of fixed and random effect models. Subgroup analyses were used to examine heterogeneity across the studies. RESULTS: The combined results indicate a reduced risk of stomach cancer with intake of green tea (RR/OR=0.86, 95% CI: 0.74-1.00). Subgroup analysis with six studies that reported differences between the highest and lowest consumption levels equal to or greater than five cups/day revealed a statistically significant protective effect (RR/OR=0.68, 95% CI: 0.53-0.87). CONCLUSION: Green tea appears to play a protective role against the development of stomach cancer. The results also suggest that a higher level of green tea consumption might be needed for a clear preventive effect to appear. This conclusion, however, should be interpreted with caution because various biases can affect the results of a meta-analysis.
차량 네트워크에서 차량의 이동성 정보를 이용한 차량 클라우드 서비스 안정성 향상을 위한 차량 클라우드 관리 방안
최현석(Hyunseok Choi),남영주(Youngju Nam),신용제(Yongje Shin),Mugerwa Dick,이의신(Euisin Lee) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2
본 논문은 차량 네트워크에서 차량들의 이동 정보를 이용하여 차량 클라우드를 유지하는 방안을 제시한다. 최근 사용자가 요구하는 데이터의 급격한 증가로 인하여 기지국이 부담해야할 트래픽이 거대해지고 있다. 따라서, 주변에 있는 차량을 이용하여 클라우드를 생성하는 방안으로 기지국의 부담을 완화시키는 연구가 진행 중이다. 본 논문에서는 클라우드가 붕괴되는 상황을 예측하여 미리 재구성함으로서 클라우드를 유지하는 방안을 제시한다. 시뮬레이션은 NS-3로 진행되었으며 성능 결과에서 기지국이 감당하는 패킷 수가 현저히 감소하였다.
An implicit Multi-hop Communication scheme based on Overhearing in IoT LoRa Networks
Mugerwa Dick,Hyunseok Choi(최현석),Youngju Nam(남영주),Yongje Shin(신용제),Euisin Lee(이의신) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2
The advent of Low Power Wide Area Networks (LPWAN) culminated in a quest for innovative low power, low cost and long-range transmission network solutions promoted by the Internet of Things (IoT). With wide coverage, low energy and openness of LoRa technology, has attracted attention from both industry and academia. However, this technology suffers from several challenges. In this work, an innovative implicit multi hop scheme takes advantage of overhearing to extend both uplink and downlink data to the gateway for only weak signals and un demodulated data packets. Implementation of this scheme not only improves the packet delivery ratio but also minimizes packet delay, thus a longer lifetime of the LoRa network.