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IEEE 802.22 시스템을 위한 다중 안테나 기법의 성능 비교, 분석
정호철,박형래,송명선,김창주 한국전자파학회 2006 전자파기술 Vol.17 No.2
본 논문에서는 시공간 블록 코드, 폐회로 송신 다이버시티, V-BLAST 등 대표적인 다중 안테나 기법의 성능을 IEEE 802.22 시스템 환경에서 비교, 분석한다. 먼저, 각 다중 안테나 기법의 복조 알고리즘을 고찰하고 전송 속도에 따라 QPSK, 16 QAM, 64 QAM의 변조 방식을 채택하는 MIMO-OFDM 시스템을 구성한다. IEEE 802.22 시스템의 사용 주파수 대역이 주로 V/UHF 대역이며 또한, 기지국 수신 신호의 angular spread가 매우 작기 때문에 송신 안테나들로부터 전송된 신호 사이에 비교적 큰 코릴레이션이 존재하게 된다. 따라서, 본 논문에서는 송신 안테나 사이의 코릴레이션이 존재하는 환경에서 송신 안테나가 두 개인 경우에 대해서만 MIMO-OFDM 시스템의 성능을 비교, 분석한다. In this paper, we compare the performance of representative MIMO techniques such as space-time block code, closed-loop transmit diversity, and V-BLAST, etc., in IEEE 802.22 environments. We first develope decoding algorithms of the representative MIMO techniques and design a MIMO-OFDM system employing QPSK, 16 QAM, 64 QAM to cover several transmission rates. Since the frequency band used for IEEE 802.22 systems belongs mostly to V/UHF band and the angular spread of the received signal at the base station is very small, there is a significant correlation between the signals from transmit antennas. Thus, in this paper, we compare the performance of MIMO-OFDM systems employing only two Tx antennas in correlated fading environments.
A Simple Static Noise Margin Model of MOS CML Gate in CMOS Processes
정호철,강재현,이강윤,이민재 대한전자공학회 2017 Journal of semiconductor technology and science Vol.17 No.3
This paper presents a simple noise margin (NM) model of MOS current mode logic (MCML) gates especially in CMOS processes where a large device mismatch deteriorates logic reliability. Trade-offs between speed and logic reliability are discussed, and a simple yet accurate NM equation to capture process-dependent degradation is proposed. The proposed NM equation is verified for 130-nm, 110-nm, 65-nm, and 40-nm CMOS processes and has errors less than 4% for all cases.
갑상선 수질암과 갑상선 유두암의 충돌종양: 5예 증례보고
정호철,김제룡,안병현,이진선,장일성,김진만1,Ho Chul Jeong,Je Ryong Kim,Byong Hyon Ahn,Jin Sun Lee,Eil Sung Chang,Jin Man Kim1 대한갑상선-내분비외과학회 2014 The Koreran journal of Endocrine Surgery Vol.14 No.1
Medullary thyroid carcinoma and papillary thyroid carcinoma are different subtypes of thyroid carcinoma. The concomitant occurrence of medullary thyroid carcinoma and papil-lary thyroid carcinoma as a collision tumor is rare. We describe five cases of medullary and papillary thyroid carcinoma as a collision tumor. Four women and one man underwent thyroidectomy for treatment of thyroid cancer. Collision tumor was then detected by histopathologic finding. Genetic testing, point mutation of the BRAF gene or mutation of the RET gene was performed in three cases. However, only one case had point mutation of the BRAF gene. Exact diagnosis of this uncommon event is important because the strategies for treatment of papillary thyroid carcinoma and medullary thyroid carcinoma are different.
셀룰러 이동통신 환경에서STBC-OFDM 시스템의 성능 비교, 분석
정호철,김창주,박형래,장은경,장은영 대한전자공학회 2006 電子工學會論文誌-TC (Telecommunications) Vol.43 No.3
In this paper, we compare the performance of three representative STBC schemes, Alamouti's, Tarokh's and quasi-orthogonal schemes under cellular mobile environments when they are applied to the OFDM system. We first study the encoding algorithms of the STBC schemes along with the development of adequate demodulation algorithms. The OFDM parameters are selected by considering the Wibro system and adequate modulation schemes are assigned for each STBC schemes according to the transmission rate from 2bps/Hz to 4bps/Hz. The STBC-OFDM systems employ Walsh orthogonal codes covered along the frequency domain in order to estimate the channel information for different transmit antennas. We finally compare the performance of the STBC-OFDM systems according to the transmission rate through computer simulations in various mobile channel environments. 본 논문에서는 대표적인 STBC 기법인 Alamouti, Tarokh, quasi-orthogonal 방식을 OFDM 시스템에 적용하여, 셀룰러 이동통신 환경에서 각 기법간의 성능을 비교, 분석한다. 먼저 각 STBC 기법들의 부호화 방식을 고찰하고 각 알고리즘 별로 적절한 복조 알고리즘을 제시한다. OFDM 시스템 파라메타는 Wibro 시스템을 고려하여 설정하며 2bps/Hz에서 4bps/Hz까지의 전송율에 대해서 STBC 기법별로 적절한 변조방식을 채택한다. 또한, 안테나별로 채널 추정이 가능하도록 주파수 영역에서 Walsh 코드를 이용하여 프리앰블을 코딩한다. 끝으로, 여러 가지 이동통신 채널 환경에서 STBC-OFDM 시스템의 전송율에 따른 성능을 시뮬레이션을 통해 비교, 분석한다.
Exploiting virus-like particles as innovative vaccines against emerging viral infections
정호철,성백린 한국미생물학회 2017 The journal of microbiology Vol.55 No.3
Emerging viruses pose a major threat to humans and live-stock with global public health and economic burdens. Vac-cination remains an effective tool to reduce this threat, and yet, the conventional cell culture often fails to produce suf-ficient vaccine dose. As an alternative to cell-culture based vaccine, virus-like particles (VLPs) are considered as a high- priority vaccine strategy against emerging viruses. VLPs repre-sent highly ordered repetitive structures via macromolecular assemblies of viral proteins. The particulate nature allows effi-cient uptake into antigen presenting cells stimulating both innate and adaptive immune responses towards enhanced vaccine efficacy. Increasing research activity and translation opportunity necessitate the advances in the design of VLPs and new bioprocessing modalities for efficient and cost-ef-fective production. Herein, we describe major achievements and challenges in this endeavor, with respect to designing strategies to harnessing the immunogenic potential, produc-tion platforms, downstream processes, and some exemplary cases in developing VLP-based vaccines.