http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
NFC의 자기 차폐용 Ni-Zn-Co 페라이트 자성체의 고주파 자기특성
류요한,김성수,Ryu, Yo-Han,Kim, Sung-Soo 한국분말야금학회 2014 한국분말재료학회지 (KPMI) Vol.21 No.6
This study investigated the magnetic properties and frequency dispersion of complex permeability of Ni-Zn-Co ferrites used for magnetic shielding in near field communication (NFC) system. The sintered specimens of $(Ni_{0.7}Zn_{0.3})_{1-x}Co_xFe_2O_4$ composition were prepared by the conventional ceramic processing. The coercive force and saturation magnetization were measured by vibrating sample magnetometer. The complex permeability was measured by RF impedance analyzer in the range of 1 MHz~1.8 GHz. The coercive force increased and saturation magnetization decreased with increasing the Co substitution. The real and imaginary parts of complex permeability decreased and the resonance frequency increased with Co substitution, which was attributed to the increase in crystal anisotropy field and reduction in saturation magnetization. The effect of Co substitution could be found in reducing the magnetic loss to nearly zero at the operating frequency of NFC (13.56 MHz).
류요한,김성수 대한금속·재료학회 2020 대한금속·재료학회지 Vol.58 No.2
Radio frequency identification (RF-ID) uses electromagnetic fields to automatically identify and track tags attached to objects. In response to the need to suppress the electromagnetic interference between adjacent RF-ID equipment or systems, this study aims to achieve a thin and multi-resonance absorber using metamaterials composed of patterned grids on a grounded dielectric substrate in the frequency region of UHF and microwaves. A computational tool (ANSYS HFSS) was used to model and estimate the reflection coefficient and surface current distribution. The samples used to measure reflection loss were fabricated by the printed circuit board (PCB) method in which a copper film was deposited on both sides of a photosensitized board. The reflection loss was measured using a free space measurement system, composed of a pair of horn antennas and network analyzer. The grid-patterned metamaterial absorbers exhibited dual-band absorption peaks at 0.88 GHz and 2.45 GHz with a small substrate thickness (about 3.7 mm) that can be usefully applied to electromagnetic compatibility in RF-ID system. Magnetic coupling is achieved via antiparallel currents in the grid conductor on the top layer and the ground conductor on the bottom layer. Since the magnetic response is influenced by the dimension of the resonators, it is possible to achieve two resonances by scaling the resonating structures. The metamaterial absorbers also exhibited good oblique incidence performance. A high level of absorption (above 10 dB) was maintained at up to 30 degrees of incidence angle for both TE and TM polarization.
NFC의 자기차폐용 Ni-Zn-Cu 페라이트의 자기특성에 미치는 소결온도의 영향
류요한,김성수,Ryu, Yo-Han,Kim, Sung-Soo 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.2
This study investigates the influence of sintering temperature on the magnetic properties and frequency dispersion of the complex permeability of Ni-Zn-Cu ferrites used for magnetic shielding in near-field communication (NFC) systems. Sintered specimens of $(Ni_{0.7}Zn_{0.3})_{0.96}Cu_{0.04}Fe_2O_4$ are prepared by conventional ceramic processing. The complex permeability is measured by an RF impedance analyzer in the range of 1 MHz to 1.8 GHz. The real and imaginary parts of the complex permeability depend sensitively on the sintering temperature, which is closely related to the microstructure, including grain size and pore distribution. In particular, internal pores within grains produced by rapid grain growth decrease the permeability and increase the magnetic loss at the operating frequency of NFC (13.56 MHz). At the optimized sintering temperature ($1225-1250^{\circ}C$), the highest permeability and lowest magnetic loss can be obtained.
배송로봇의 보도 주행 허용을 위한 위험성 평가 모델을 활용한 안전 요구사항 개발에 관한 연구
류요엘(Joel Ryu),백남정(Nam-jeong Baeck),전진우(Jin-Woo Jun),조규선(Guy-Sun Cho) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.9
자율주행을 기반으로 음식을 실외 배송하는 로봇은 보도를 이용하고자 한다. 그러나 국내 현행법상 보도에는 보행자, 유모차, 휠체어 및 의료용 스쿠터만 통행할 수 있다. 따라서 현재 일부 국내기업은 규제샌드박스 제도를 통해 현행법을 적용 받지 않고 특례로 시범 운영 중이다. 배송로봇의 규제 개선을 위해선 제품 안전기준이 명확히 마련되어야 하나, 안전 요구사항 조차 없는 실정이다. 해외의 경우 제조사가 제조물책임법 하에 책임과 권한으로 배송로봇 서비스가 상용화는 되고 있어, 제품 안전기준이나 표준을 참고하기에는 제한적이다. 또한, 배송로봇은 복잡한 도심환경에서 성인, 노약자를 포함해 가로수, 자전거, 킥보드 등을 회피해야해 사고 우려가 높다. 본 연구에서는 첫 단계로 배송로봇 위험성 평가를 통해 안전 요구사항을 정의하고자 하였다. 위험성 평가를 실시한 결과 로봇의 동작, 자율주행 등과 관련한 안전요구사항을 16건 도출하였다. 이를 국제표준 구성을 기준으로 10개의 세부 절로 정리하여 제안하였다. 또한, 제품 안전요구사항 외에 교통 법규 및 안전문화 차원으로 규제되어야 하는 4개 안전요구사항 항목을 제시하였다. 본 연구 결과를 통해 배송로봇의 안전한 활용을 위한 규제 마련과 시장 성장에 기여하기를 기대한다. Robots that autonomously drive and deliver food have the option of using the sidewalks. However, only pedestrians, strollers, wheelchairs, and medical scooters are allowed on sidewalks as per the regulation. Therefore, some companies are piloting tests in the regulatory sandbox systems. However, the relevant product safety criteria must be prepared to improve the regulations, and there exist no safety requirements formulated at present. In overseas, delivery robots are commercialized with greater responsibility and authority under the Product Liability Laws, so the robots are forced to follow the safety criteria. In addition, the risk of using delivery robots anywhere is high, and they must avoid trees, bicycles, etc., in an urban environment. In this study, we define safety requirements for delivery robot usage through a risk assessment As a result of the risk assessment, 16 safety requirements related to the robot operation and autonomous driving were derived. Based on the composition of the international standard, it was proposed to organize these requirements into ten detailed clauses. In addition to the product safety requirements, four safety requirements must be regulated in the traffic laws or safety culture. It is expected that this study will contribute to the establishment of regulations for safety and increase the market for delivery robots.
류요한,임윤철 연세대학교 산업기술연구소 1991 논문집 Vol.23 No.2
In this study, experimental apparatus of repulsive type magnetic bearing has been made and static load characteristics are analyzed. The apparatus consists of aluminium rotor, AC electromagnets, load-cells, and air turbine. The rotational speed of rotor is controlled by compressed air and the forces due to the eddy current induced on an electrically conducting rotor are measured using two load-cells. Results show that levitation force and drag force are found to be strongly dependent with the rotor speed, thickness of the rotor, and input current but slightly influenced by the length of the rotor. Levitation force is almost linearly increased with rotor speed. However, the slope of drag force is found to be decreased as speed increased. Levitation force is proportional to the square of the input current when the rotor speed is zero.
THz 대역에서 Cut Wire로 구성된 메타소재의 자기공진 및 전파흡수특성
류요한(Yo-Han Ryu),김성수(Sung-Soo Kim) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.2
Metamaterials composed of split cut wire (SCW) on grounded polyimide film substrate have been investigated for the aim of electromagnetic wave absorbers operated in THz frequency band. Reflection loss and current density distributions are numerically simulated with variations of the SCW geometries using the commercial software. The minimum reflection loss lower than −20 dB has been identified at 5.5~6.5 THz. The simulated resonance frequency and reflection loss can be explained on the basis of the circuit theory of an inductance-capacitance (L-C) resonator. Dual-band absorption can be obtained by arrangement of two SCWs of different length on the top layer of the grounded substrate, which is due to multiple magnetic resonances by scaling of SCWs. With increasing the side spacing between SCWs, a more enhanced absorption peak is observed at the first resonance frequency that is shifted to a lower frequency.