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조한신(Han-Shin Cho),김성수(Sung-Soo Kim) 한국자기학회 2008 韓國磁氣學會誌 Vol.18 No.4
In this study, the magnetic (static and high-frequency) and microwave absorbing properties have been investigated in Ru-Co substituted M-hexaferrites (BaFe<SUB>12 ? 2x</SUB>Ru<SUB>x</SUB>Co<SUB>x</SUB>O<SUB>19</SUB>). The powders and sintered specimens were prepared by conventional ceramic processing technique. With the calcined powders, the composite specimens were prepared using the silicone rubber as a matrix material. The substitution ratio of Ru-Co to obtain in-plane magnetic anisotropy, thus having the minimum coercivity, is much smaller (about x = 0.3) than the previously reported Ti-Co substituted specimen. Owing to this low substitution, the specimen has a large value of saturation magnetization (Ms= 65 emu/g). Ferromagnetic resonance behavior and microwave absorbing frequency band is strongly influnced by the coercvity which can be controlled by Ru-Co substitution ratio. It is found that the M-hexaferrites with planar magnetic anisotropy by doping Ru-Co in both sintered and composite form have superior microwave absorbing properties in ㎓ frequency range.
철계 연자성 합금 분말을 함유한 고무 복합재의 전파흡수특성
조한신,김성수,Cho, Han-Shin,Kim, Sung-Soo 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.2
Magnetic and dielectric properties of rubber composites are controlled by using two kinds of high-permeability metal particles with different electrical conductivity (Sendust, Permalloy), and their effect on microwave absorbance has been investigated, focusing on the quasi-microwave frequency band (0.8-2 GHz). Noise absorbing sheets are composite materials of magnetic flake particles of high aspect ratio dispersed in polymer matrix with various filler amount of 80-90 wt.%. The frequency dispersion and magnitude of complex permeability is almost the same for Sendust and Permalloy composite specimens. However, the complex permittivity of the Permalloy composite (${{\varepsilon}_r}^{\prime}{\simeq}250$, ${{\varepsilon}_r}^{{\prime}{\prime}}{\simeq}50$) is much greater than that of Sendust composite (${{\varepsilon}_r}^{\prime}{\simeq}70$, ${{\varepsilon}_r}^{{\prime}{\prime}}{\simeq}0$). Due to the large dielectric permittivity of Permalloy composite, the absorbing band is shifted to lower frequency region. However, the investigation of impedance matching reveals that the magnetic permeability is still small to satisfy the zero-reflected condition at the quasi-microwave frequency band, resulting in a small microwave absorbance lower than 10 dB.
한신(Shin Han),조규동(Kyu-dohng Cho),정진우(Jin-Woo Jung) 한국환경교육학회 2010 環境 敎育 Vol.23 No.2
The purposes of this study are to investigate the perception of renewable energy technology among elementary school teachers, and confirm whether elementary school teachers have basic knowledge about renewable energy sources, including solar, wind, and tidal power generation. We conducted preliminary interviews to gather information related to other studies about renewable energy. We developed the last interview question about the perception and knowledge of elementary school teachers regarding renewable energy. This study analyzed the transcribed responses of 10 elementary school teachers in Siheung-city, Gyeonggi-do, following 30-minute interviews. The study's findings are as follows. First, elementary school teachers recognize that they are unfamiliar with concepts and they have only shallow content knowledge about renewable energy. And they tended to distorted to other concepts, and analyze to different meanings. Second, elementary school teachers thought that knowledge about renewable energy should be part of a well-rounded education. And they felt positively about solar energy and wind power energy generation but they had a negative view towards tidal power generation because it destroys tideland. Third, teachers tended to confuse solar heat energy and geothermal energy, they tend to think this two energy sources the same. Teachers had generally correct concepts about wind power energy generation. In the case of tidal power generation, elementary school teachers answered mechanically that it is possible on the western sea, and that 'the difference between the rise and fall of the tide' grows. But they could not talk in depth about 'the difference between the rise and fall of the tide' and the force of waves. This suggests that they are answering by simple memorization and without deep understanding.
조한신(Han Shin Cho),지정건(Jeong Geon Ji),나종문(Jong Moon Na),박홍규(Hong Kyu Park) 한국철도학회 2021 한국철도학회 학술발표대회논문집 Vol.2021 No.6
최근 5년간 국내 철도운행장애 통계를 살펴보면 철도차량으로 인한 철도운행장애는 지속 증가추세인 것으로 나타났다. 또한 최근 논의가 있었던 제4차 철도망구축계획 등에 따르면 철도노선의 증가에 따라 국내 철도차량의 전체 보유 현황도 늘어날 것으로 예상된다. 철도차량의 안전성을 확보하는 동시에 체계적인 유지관리를 시행하기 위해서는 철도차량에 대한 종합적인 이력관리 시스템이 요구된다. 이러한 종합적 이력관리시스템의 구축을 위해서는 입력정보에 대한 항목설정과 표준화를 고려하여야 한다. 본 연구에서는 철도차량이력관리시스템 데이터 관리에 필요한 기본 입력정보에 대한 일부 표준화 사례를 도출하였다.
비지상 네트워크와 지상 서비스간 주파수 공유를 위한 DRL 기반 채널 할당 알고리즘
조연기(Cho Yeongi),양우열(Yang Wooyeol),오대섭(Oh Daesub),조한신(Jo Han-Shin) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
저궤도(LEO) 위성은 낮은 지연, 소형화, 다중 위성을 이용한 망 구성 등의 장점을 가지며, 이에 따라 LEO 위성을 이용한 비지상망(NTN) 서비스가 확대되고 있다. 그러나 한정된 주파수 자원으로 인해, 다양한 NTN 서비스의 등장은 기존 지상 서비스와의 간섭 문제를 야기한다. 본 논문은 NTN 상향링크 상황에서, 주어진 서비스 품질(QoS) 조건을 만족하는 동시에 지상 서비스에게 주는 간섭을 최소화하는 멀티에이전트 심층 강화학습 (DRL) 기반 채널 할당 알고리즘을 제안한다. 제안된 알고리즘은 에이전트들이 순차적으로 학습하기 때문에 적은 메모리로도 학습이 가능하며, 간섭이 높은 순서대로 에이전트를 학습하여 간섭 완화효과를 높인다. 시뮬레이션 결과, 제안된 알고리즘은 NTN의 최소 SINR을 만족하는 동시에 최적 할당 방식과 유사한 수준의 간섭 완화 성능을 보임을 확인하였다.
밀리미터파 대역에서 5G 이동통신과 고정위성서비스간 공존 연구
조연기(Yeongi Cho),김현기(Hyun-Ki Kim),조한신(Han-Shin Jo) 한국전자파학회 2019 한국전자파학회논문지 Vol.30 No.9
본 논문에서는 5세대 이동통신(IMT-2020)의 주파수 지정을 위해 국제전기통신연합(international telecommunication union: ITU)에서 제시한 모델링 방법론과 파라미터를 바탕으로 현재 IMT-2020의 밀리미터파 후보대역 중 기존에 할당되어 있는 고정위성서비스(fixed-satellite service: FSS) 상향링크 서비스와 IMT-2020의 동일채널 간섭 분석을 통해 두 서비스의 스펙트럼 공존 가능성을 연구한다. 첫째 기존 서비스의 보호를 위해 FSS 위성이 IMT-2020의 간섭 신호로부터 받는 영향을 분석한다. 그리고 IMT-2020이 FSS 지구국으로부터 간섭을 피하기 위한 최소 이격거리를 제시하며, 최종적으로 이를 통하여 동일대역에서 두 서비스의 공존 가능성을 평가한다. In this paper, the possibility of spectrum coexistence of 5th generation mobile communications(IMT-2020) and Fixed-Satellite Service(FSS) uplink in the millimeter wave band is studied based on modeling approach and considering the parameters proposed by the international telecommunication union(ITU) for the frequency assignment of IMT-2020. First, in order to protect the existing FSS, the interference signal of IMT-2020 received by an FSS satellite is calculated and its influence on the satellite is analyzed. Then, the interference received by the IMT-2020 from the FSS earth station is calculated and the minimum separation distance required to avoid interference is presented. Finally, the feasibility of coexistence of both services is evaluated based on simulation results.