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5G 이동통신을 위한 GaN RF 전자소자 및 집적회로 기술 동향
이종민,민병규,장우진,지홍구,조규준,강동민,Lee, J.M.,Min, B.G.,Chang, W.J.,Ji, H.G.,Cho, K.J.,Kang, D.M. 한국전자통신연구원 2021 전자통신동향분석 Vol.36 No.3
As the 5G service market is expected to grow rapidly, the development of high-power, high-efficiency power amplifiers for the 5G communication infrastructure is indispensable. Gallium nitride (GaN) is attracting great interest as a key device in power devices and integrated circuits due to its wide bandgap, high carrier concentration, high electron mobility, and high-power saturation characteristics. In this study, we investigate the technology trends of Ka-band GaN radio frequency (RF) power devices and integrated circuits for operation in the millimeter-wave band of recent 5G mobile communication services. We review the characteristics of GaN RF high electron mobility transistor (HEMT) devices to implement power amplifiers operating at frequencies around 28 GHz and compare the technology of foreign companies with the device characteristics currently developed by the Electronics and Telecommunication Research Institute (ETRI). In addition, the characteristics of Ka-band GaN monolithic microwave integrated circuit (MMIC) power amplifiers manufactured using various GaN HEMT device technologies are reviewed by comparing characteristics such as frequency band, output power, and output power density of integrated circuits. In addition, by comparing the performance of the power amplifier developed by ETRI, the current status and future direction of domestic GaN power devices and integrated circuit technology will be discussed.
Experimental Study on the Evaluation of Fatigue Life in a Double-lap Bolted Joint
J. M. Lee(이종민),N. G. Jun(전남규),K. B. Park(박기범),C. S. Seok(석창성) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
Double-lap bolted joint in bracket structure has been used in various fields including vehicle industry to connect mechanical components. There is huge risk of bolt loosening in the structure as vehicle is exposed to external factors such as static load, fatigue load, vibration or thermal shock. Cyclic load reduces clamping force formed in the structure, which leads to the instability of the joint and even serious industrial accidents. Therefore, the fatigue life of the double-lap bolted joint according to operating condition, such as cyclic load and tightening torque, has to be quantitatively evaluated to understand the progress of the loosening state and reduce the possibility of the accidents. In this study, fatigue tests were conducted for the bolted joint according to the cyclic load and tightening torque. Clamping force-cycle graph for each condition was obtained by developing a measurement technique to record the data in real time. By analyzing the clamping force-cycle graphs according to the test condition, the fatigue characteristic of the structure is evaluated. Finally, a method to select proper clamping force to prevent bolt loosening in the structure is suggested based on the evaluation of the fatigue life.
대한민국 서남해 갯벌내 유기탄소 저장량 및 연간 탄소침적률 산정
이종민(Jongmin Lee),권봉오(Bong-Oh Kwon),류종성(Jongseong Ryu),박진순(Jinsoon Park),홍성진(Seongjin Hong),이숙희(Sukhui Lee),김성길(Seong-Gil Kim),손수진(Sujin Son),윤훈주(Hoon Joo Yoon),남정호(Jungho Nam),최경식(Kyungsik Choi),김종성(J 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.5
블루카본 연구에서 퇴적물 내 유기탄소 저장량과 연간 유기탄소 침적률의 산정은 필수적이나, 현재 한국 갯벌에서의 국가적 규모의 연구는 부족한 실정이다. 본 연구에서는 현장조사 자료와 원격탐사기법을 이용하여 서남해 갯벌의 유기탄소 저장량과 연간 유기탄소 침적률을 추산하였다. 조사지역은 서남해 6개 시도(경기, 인천, 충남, 전북, 전남, 경남)내 20개 지역이었으며, 2017년부터 2019년까지 총 289개의 코어퇴적물(깊이=0.6-1.0m)을 채취 및 분석하였다. 그리고 원격탐사기법을 통해 서남해 갯벌의 퇴적물 성상과 면적을 추산하였다. 코어퇴적물 분석결과, 니질함량은 전 지역에 걸쳐 퇴적물 내 유기탄소 함량을 예측하는 주요한 환경 변수였으며, 총 유기탄소 함량과 양의 상관관계(p < 0.05)를 나타냈다. 염습지에서는 염생식물의 일차생산을 통한 높은 탄소고정 능력으로 인해, 비식생 갯벌보다 상대적으로 높은 유기탄소 저장량을 보였다. 또한, 인공위성 영상분석을 통한 퇴적물 성상분류는 니질함량 분석에 의한 퇴적물 성상분류 결과와 대체적으로 유사하였다(p < 0.05). 현장조사와 인공위성 분석을 통해 서남해 갯벌의 총 유기탄소 저장량 13,939,020 Mg C, 연간 유기탄소 침적률 75,367 Mg C yr<sup>-1</sup>을 추산하였다. 본 자료는 처음으로 한국 서남해 갯벌의 블루카본 잠재량을 국가 규모로 조사하였으며, 향후 한국 조간대 퇴적물 내 탄소순환 연구에 대한 중요한 기초자료로써 활용될 수 있을 것으로 사료된다. Blue carbon studies require estimates of organic carbon stocks and sequestration rates; however, holistic data analyses remain limited in South Korea, particularly at national scale. The present study reports current organic carbon stocks and sequestration rates in the coastal areas of Korea, encompassing the entire tidal flats, by long-term field survey combined with remote sensing approach. Target areas included 20 intertidal flats across five provinces in South Korea (Gyeonggi, Chungnam, Jeonbuk, Jeonnam, Gyeongnam). Out of the evaluated environmental parameters, mud content represented a significant factor controlling sedimentary organic carbon stocks across target areas, and was significantly positively correlated to total organic carbon (p < 0.05). Organic carbon stocks measured in the salt marshes, say upper intertidal zone, reflected the high carbon fixation capacity of halophytes through primary production. Sediment textural types were classified using remotely sensed imagery, and was closely correlated with the experimental classification results (p < 0.05). Using field and satellite measurements, we could estimate total organic carbon stocks (13,939,020 Mg C) and sequestration rates (75,637 Mg C yr<sup>-1</sup>) in South Korea at national scale. The present study first report the blue carbon potentials of the Korean tidal flats at national scale and provides baseline information on the carbon dynamics of intertidal sediments in Korea and elsewhere.