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Choi, Seojin,Yoo, Seyeon,Lee, Yongsun,Jo, Yongwoo,Lee, Jeonghyun,Lim, Younghyun,Choi, Jaehyouk IEEE 2019 IEEE journal of solid-state circuits Vol.54 No.4
<P>An ultra-low-jitter, ring-<I>LC</I> -hybrid injection-locked clock multiplier (ILCM) is presented to achieve a high multiplication factor of 114. The proposed hybrid ILCM cascades a ring-type voltage-controlled oscillator (VCO)-based ILCM and an <I>LC</I>-type VCO-based ILCM. Using a dual-purpose frequency calibrator (DPFC) that can continuously calibrate the frequency drifts of the two VCOs, concurrently, the proposed ILCM can maintain excellent jitter performance against process-voltage-temperature (PVT) variations. Since the DPFC eliminates the use of an additional calibrator and operates at a very low frequency, it can reduce the expenditures for silicon and power. The proposed ILCM was fabricated in a 65-nm CMOS process. The RMS jitter of the 22.8-GHz output, integrated from 1 kHz to 100 MHz, was 153 fs, and the DPFC restricted its variations due to variations in temperatures and supply voltages to less than 180 fs. The proposed ILCM achieved the power efficiency of 0.32 mW/GHz. The active area was 0.2 mm<SUP>2</SUP>. The total power consumption was 7.4 mW, but the DPFC consumed only 400 <TEX>$\mu \text{W}$</TEX>.</P>
Choi, Seojin,Yoo, Seyeon,Lim, Younghyun,Choi, Jaehyouk IEEE 2016 IEEE journal of solid-state circuits Vol.51 No.8
<P>A low-jitter, ring-type voltage-controlled oscillator (VCO)-based injection-locked clock multiplier (ILCM) with a continuous frequency-tracking loop (FTL) for process-voltage-temperature (PVT)-calibration is presented. Using a single replica-delay cell of the VCO that provides the intrinsic phase information of the free-running VCO, the proposed FTL can continuously track and correct frequency drifts. Therefore, the proposed ILCM can calibrate real-time frequency drifts due to voltage or temperature variations as well as static frequency deviations due to process variations. Since the FTL provided an additional filtering of in-band VCO noise, the ILCM was able to achieve excellent jitter performance over the PVT variations, while it was based on a ring-VCO. The proposed ILCM was fabricated in a 65 nm CMOS process. When injection locked, the RMS-jitter integrated from 10 kHz to 40 MHz of the 1.20 GHz output signal was 185 fs. The proposed PVT-calibrator regulated the degradations of jitter to less than 5% and 7% over temperatures and supply voltages, respectively. The active area was 0.06 mm(2) and total power consumption was 9.5 mW.</P>
응축 열전달계수 예측을 통한 이종 습윤성을 갖는 액막 채널 표면의 최적설계 및 열전달 성능평가
최영현(Younghyun Choi),한태양(Taeyang Han),정재영(Jaeyoung Jeong),이용남(Yongnam Lee),조항진(HangJin Jo) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
Condensation heat transfer, a heat transfer mechanism utilizing the latent heat, has used in various industrial applications due to its high heat transfer performance. In the case of the dropwise condensation (DWC), the condensate can be quickly removed, so the condensing surface can be exposed to the vapor effectively. This characteristic of DWC is the reason that it has a higher heat transfer coefficient than filmwise condensation (FWC). However, DWC has limitations in use at various applications (e.g. high temperature & pressure) due to the durability issue of the hydrophobic coating layer. To overcome this limitation, at previous study, surface had been developed to enhance heat transfer performance without the hydrophobic coating layer (i.e. water film channeled surface). In this study, prediction of the heat transfer coefficient was carried out to derive the optimal design of this water film channeled surface proposed to increase the heat transfer performance without hydrophobic coating, and heat transfer performance evaluation was performed at pure vapor condition.
전력선통신 종합시험장 구축모델 및 시험기준 설계에 관한 연구
김영현(Younghyun Kim),최문석(Moonseok Choi),최영림(Younglim Choi),정영호(Youngho Jung),이상윤(Sangyun Lee) 전력전자학회 2005 전력전자학술대회 논문집 Vol.- No.-
전력선통신은 다른 통신기술과 달리 표준화 작업이 현재 이루어지지 않고 있으며 타 모뎀과의 호환성이 없다는 단점이 있다. 그러나, 이러한 제약사항들을 극복함으로써 전력선통신의 개발 및 상용화 시기를 앞당길 수 있다. 본 논문에서는 전력선통신의 종합시험장 구축모델 및 시험기준 설계 방안에 관하여 논의하며 전력선통신기기와 관련된 적합성, 성능 및 안정성, 상호운용성에 관한 기준수립 방안에 관하여 고찰하여 전력선통신의 객관적인 성능지표를 마련하고자 한다.
응축 열전달계수 예측을 통한 이종 습윤성을 갖는 액막 채널 표면의 최적설계 및 열전달 성능평가
최영현(Younghyun Choi),한태양(Taeyang Han),정재영(Jaeyoung Jeong),이용남(Yongnam Lee),조항진(HangJin Jo) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
Condensation heat transfer, a heat transfer mechanism utilizing the latent heat, has used in various industrial applications due to its high heat transfer performance. In the case of the dropwise condensation (DWC), the condensate can be quickly removed, so the condensing surface can be exposed to the vapor effectively. This characteristic of DWC is the reason that it has a higher heat transfer coefficient than filmwise condensation (FWC). However, DWC has limitations in use at various applications (e.g. high temperature & pressure) due to the durability issue of the hydrophobic coating layer. To overcome this limitation, at previous study, surface had been developed to enhance heat transfer performance without the hydrophobic coating layer (i.e. water film channeled surface). In this study, prediction of the heat transfer coefficient was carried out to derive the optimal design of this water film channeled surface proposed to increase the heat transfer performance without hydrophobic coating, and heat transfer performance evaluation was performed at pure vapor condition.
기존 메일스캐너 시스템의 비교분석 및 새로운 방안 제안
김영현(Younghyun Kim),윤세안(Sean Yoon),최은정(Eunjung Choi),최주영(Jooyoung Choi),유주영(Jooyoung Yu),김영주(Myuhngjoo Kim) 한국정보과학회 2003 한국정보과학회 학술발표논문집 Vol.30 No.1A
본 논문에서는 정보화 사회에 있어서 E-mail 사용의 확산과 그에 따라 발생하는 컴퓨터 바이러스, 웜, 스팸메일 등의 출현에 따른 문제의 예방책으로써 메일서버스캐너를 제시한다. 이러한 필요성에 기반하여 기존의 개발된 메일스캐너의 개념을 이해하고 기능을 분석한다. 기능 분석을 통해 각각의 메일스캐너의 단점을 개선하고 장점을 강화하는 등의 새롭게 보강된 메일서버스캐너 기술을 제안한다.
보조 자석을 활용한 스포크 타입 IPMSM 출력 향상 연구
최영현(YoungHyun Choi),지태혁(Tae-Hyuk Ji),김용재(Yong-Jae Kim),정상용(Sang-Yong Jung) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.11
스포크 타입 매입형 영구자석 동기기는 희토류를 사용하지 않는 타 매입형 영구자석 동기기에 비해 공극 자속밀도가 높아 고토크 밀도 특성을 가져 많은 연구가 진행되고 있다. 하지만 일반적인 스포크 타입 매입형 영구자석 동기기는 영구자석 자속의 일부가 회전자 내측으로 향해 출력이 저하되어 이를 위한 개선이 필요하다. 본 논문에서는 유한요소 해석을 기반으로 8극 12슬롯 스포크 타입 매입형 영구자석 동기기를 보조 자석 삽입을 통해 자속 경로를 개선하여 동일 극당 자석 사용량으로 토크 밀도를 높이고 기존 모델과의 비출력 비교 및 전자계 해석을 진행하였다.