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Ring VCO를 사용한 UHF 대역 CMOS Fractional-N 주파수합성기 설계
추홍성(H. S. Chu),서희택(H. T. Seo),박상재(S. J. Park),김경환(K. H. Kim),강현철(H. C. Kang),유종근(C. G. Yu) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.10
In this paper, we describe a UHF-band CMOS fractional-N frequency synthesizer using a ring - type VCO. It has been designed using 0.18㎛ CMOS technology. First, The newly designed charge-pump circuit includes an OTA for matching between the upper current and the lower current. In addition, a ring - type VCO is also used for small chip size. The simulation results show that the designed circuit has a phase noise of -109.53㏈c/㎐ at 1㎒ offset and consumes 19.4㎃ from a 1.8V supply. The lock time is less than 30usec and the chip size is 0.45㎜×0.5㎜.
곽지현,김병관,김경환,김지현,Kwag, J.H.,Kim, B.G.,Kim, K.H.,Kim, C.H. 대한의용생체공학회 2009 의공학회지 Vol.30 No.1
Bone remodeling is a continuous process of skeletal renewal during which bone formation is tightly coupled to bone resorption. Mechanical loading is an important regulator of bone formation and resorption. In recent studies, neurotransmitters such as vasoactive intestinal peptide (VIP) were found to be present inside bone tissue and have been suggested to potentially regulate bone remodeling. In this study, our objective was to use a pre-established in vitro oscillatory fluid flow-induced shear stress mechanical loading system to quantify the effect of VIP on bone resorptive activity and investigate its combined effect with mechanical loading. VIP decreased osteoclastogenesis significantly decreased RANKL/OPG mRNA ration by approximately 90%. Combined VIP and mechanical loading further decreased RANKL/OPG ratio to approximately 95%. These results suggest that VIP present in bone tissue may synergistically act with mechanical loading to regulate bone remodeling via suppression of bone resorptive activities.
파력발전 통합성능평가를 위한 WECAN 프로그램 개발방향 고찰
박지용(J.Y. Park),김경환(K.H. Kim),하윤진(Y.J. Ha),박세완(S.W. Park),김길원(K.W. Kim),김정석(J.S. Kim),이정희(J.H. Lee),오재원(J.W. Oh),노찬(C. Roh),최장영(J.Y. Choi),장강현(G.H. Jang),천호정(H.J. Cheon),김재환(J.H. Kim) 한국해양환경·에너지학회 2020 한국해양환경·에너지학회 학술대회논문집 Vol.2020 No.7
본 연구에서는 대표적인 파력발전장치 형태인 진동수주형과 가동물체형 파력발전장치를 대상으로 파력발전 통합성능 평가를 위한 WECAN프로그램 개발에 관한 연구를 수행하였다. 파력발전장치 개발을 위해 각 설치환경을 고려하여 적절한 설계를 진행하고 해당 설계안에 대해 발전성능과 안전성을 평가하게 되는데, 기존 연구에서 각 에너지변환단계를 서로 구분하여 해석함으로써 해당 시뮬레이션 결과가 에너지변환단계가 종합하여 연동된 실험 및 실증시험 결과와 차이를 보여 왔다. 따라서 이러한 문제점을 극복하기 위해 파력발전장치를 시스템기술로 접근하여 각 에너지변환단계를 통합하여 해석하고, 최적설계와 최적제어방안 도출을 위해 WECAN(Wave Energy Converter ANalysis) 프로그램을 개발하려 한다. 본 연구를 통해 WECAN 프로그램 개발을 위한 각 에너지변환단계별 해석기술과 단계별 개발방향을 설명하며, 적용 범위와 구현방안에 대해 언급하였다. 해당 프로그램의 연구개발 이후 단계별로 WECAN-DO, WEC-HILS 등의 프로그램을 개발할 예정이며, 이를 통해 국내 파력발전장치 성능평가 및 설계기술을 한 단계 끌어올리고, 앞선 기술을 통해 파력발전장치의 상용화를 선도하려 한다. In this study, we conducted a study on the development of the WECAN program for the integrated performance analysis of wave energy converter for both the oscillating water column type and activated-body type. The design of wave energy converters is conducted considering each installation environment and then, the power generation performance and safety analysis for the design are evaluated. In this process, existing studies have been analyzed by classifying each energy conversion step by step, and have shown differences from experimental and open sea test results. Therefore, in order to overcome this problem, we are developing a WECAN (Wave Energy Converter ANalysis) program by conducting integrated performance analysis approaching the wave energy converter as a system technology and we will derive an optimal design and an optimal control plan for the wave energy converter. In this study, the analysis technology for each energy conversion step and the development direction for each step are described for the WECAN program, and the application scope and implementation plan are mentioned. We also plan to develop WECAN-DO, WEC-HILS and other programs step by step after the R&D of this program. As a result, the performance evaluation and design technology of the domestic wave energy converter will be taken to the next level, and the commercialization of the wave energy converter will be led by these leading technologies.