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Ferrite-Cored Patch Antenna With Suppressed Harmonic Radiation
Lee, Woncheol,Hong, Yang-Ki,Choi, Minyeong,Won, Hoyun,Lee, Jaejin,Park, Seong-Ook,Bae, Seok,Yoon, Hwan-Sik Institute of Electrical and Electronics Engineers 2018 IEEE Transactions on Antennas and Propagation Vol. No.
<P>We designed and fabricated a multiple-ferrite-cored patch antenna (MFC-PA) to suppress harmonic radiation over the frequency range of 1–10 GHz and obtain wide suppressing bandwidth. Its suppression performance was compared to those of the conventional PA, photonic bandgap PA (PBG-PA), and defected ground structure PA (DGS-PA). Simulated and measured results show that MFC-PA effectively suppresses harmonic radiation up to <TEX>$5.6f_{0}$</TEX>, where <TEX>$f_{0}$</TEX> is 0.9 GHz, while the harmonic radiation of PBG-PA and DGS-PA is suppressed up to <TEX>$3f_{0}$</TEX>. It is suggested by the antenna performance simulation that MFC-PA can further suppress harmonic radiation up to <TEX>$11f_{0}$</TEX>. In principle, the harmonic radiation of MFC-PA is suppressed by dissipating the unwanted signals in ferrite materials, whereas PBG-PA and DGS-PA suppress harmonic radiation by reflecting or redirecting unwanted signals, which is not desired. Ferrite loading is a unique approach to suppress any harmonic radiation.</P>
Long working hours and risk of hypothyroidism in healthy workers: a cohort study
Lee Yesung,Lee Woncheol,김형렬 한국역학회 2022 Epidemiology and Health Vol.44 No.-
OBJECTIVES: Long working hours have been reported to cause various health problems. However, long working hours are currently practiced in many countries. To confirm the consistency with a previous study, the authors aimed to elucidate the causal relationship between long working hours and hypothyroidism through a longitudinal study. METHODS: Data was collected at baseline from 45,259 participants without thyroid disease and with no change in groups of weekly working hours, which were categorized into 36–40, 41–52, 53–60, and > 60 hours, during follow-up period. Hypothyroidism was defined using the reference limits of serum thyroid-stimulating hormone and free thyroxine levels. By estimating hazard ratios (HRs) and 95% confidence intervals (CIs) using Cox proportional hazards regression analyses, the risk of incident hypothyroidism was evaluated with weekly working 36–40 hours as the reference. RESULTS: During 138,261.7 person-years of follow-up, 2,914 participants developed hypothyroidism (incidence density, 2.11 per 102 person-years). Multivariable-adjusted HRs of incident hypothyroidism for weekly working 41–52, 53–60, and > 60 hours compared with the reference group were 1.13 (95% CI 1.03–1.24), 2.53 (95% CI, 2.17–2.95), and 2.57 (95% CI, 2.09– 3.15), respectively. In dose-response analyses, long working hours had an approximately linear relationship with the incidence of hypothyroidism. The risk of incident hypothyroidism in weekly working 53–60 and > 60 hours compared with the reference group were significantly higher among the older age group (≥ 36 years, stratified by median age), men, and daytime workers. CONCLUSIONS: This large-scale cohort study demonstrated the association between long working hours and the increased risk of incident hypothyroidism with a dose-response relationship.
이원철(Woncheol Lee),김연희(Yeonhee Kim) 한국HCI학회 2014 한국HCI학회 학술대회 Vol.2014 No.2
센서 및 하드웨어, 소프트웨어 그리고 통신기술의 융합적인 발달에 힘입어 전에 없던 새로운 문화가 생겨났다. 특히, 스마트기기라 불리고 있는 전화기, 태블릿 PC, 웨어러블 디바이스 등은 다양한 기술이 응집된 인공물로써 인간과 인간, 인간과 사물 그리고 사물과 사물을 끊김없이 연결하고, 정보를 주고받으면서 인간을 둘러싸고 있는 환경과 그에 반응하는 인간 행위의 특징을 체계적으로 분석하기 시작했다. 하지만 지금까지의 상황인지 서비스는 하드웨어 및 통신기술의 한계로 인해 많은 제약이 있었으며 물리적인 데이터 수집에만 그쳤기에 다양한 상황에 처해진 인간의 내면과 그에 따른 행동의 다양성을 제대로 이해하지 못했다. 따라서 본 연구는 인간의 독특한 반응패턴을 추론할 수 있는 대표적 요인인 성격을 6 요인 성격모델 Hexaco 를 통해 분석하고, 각기 다른 상황에 배치된 저전력 블루투스(bluetooth low energy) 기반의 비콘(beacon)을 통해, 성격유형 별 차별화된 상황인지 서비스를 제공하고자 하며 이를 통해 개인의 심리적 요인이 반영된 한층 더 발전된 형태의 상황인지 모델을 제시하고자 한다. Sensors and hardware, software, and communication technologies never before thanks to developmental fusion of the new culture is born. In particular, various techniques have been aggregated artifacts are seamlessly connected to the people and objects, while receiving information to and surrounding the human environment and systematic analysis of the characteristics of human behavior began. But so far, the context-aware services are due to the limitations of hardware and communication technology had many limitations only mere physical data collected in a variety of situations hanged groups and the corresponding behavior of the human inner diversity did not understand properly. In this study the reaction pattern of the human can be inferred unique representation through factor analysis of the nature of the Hexaco, disposed in different situations Low Power Bluetooth based on the beacon and , through the type -specific nature of differentiated to provide a context-aware service. This allows the individual layers of the psychological factors that reflect a more advanced form of context-aware model presented.
Impedance Matching of Electrically Small Antenna with Ni-Zn Ferrite Film
Jaejin Lee,Yang-Ki Hong,Woncheol Lee,Jihoon Park 한국자기학회 2013 Journal of Magnetics Vol.18 No.4
We demonstrate that a partial loading of Ni0.5Zn0.5Fe₂O₄ (Ni-Zn ferrite) film remarkably improves impedance matching of electrically small Ba₃Co₂Fe24O41 (Co₂Z) hexaferrite antenna. A 3 μm thick Ni-Zn ferrite film was deposited on a silicon wafer by the electrophoresis deposition process and post-annealed at 400 ℃. The fabricated Ni-Zn ferrite film has saturation magnetization of 268 emu/cm<SUP>3</SUP> and coercivity of 89 Oe. A partial loading of the Ni-Zn ferrite film on the Co₂Z hexaferrite helical antenna increases antenna return loss to 24.7 dB from 9.0 dB of the Co₂Z antenna. Experimental results show that impedance matching and maximum input power transmission to the antenna without additional matching elements can be realized, while keeping almost the same size as the Co₂Z antenna size.