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차기구축함 통합마스트에 적용을 위한 전자기파 메타물질 흡수체의 온도 환경 내구성 검증
라영은(Young-Eun Ra),김용준(Yongjune Kim),정현준(Hyun-June Jung),박평원(Pyoungwon Park),조정대(Jeongdai Jo),이준식(Joonsik Lee),김명준(Myungjoon Kim),정준교(Joonkyo Jung),이건민(Gun-Min Lee),이종학(Jong-Hak Lee),이학주(Hak-Joo Lee) 한국전기전자학회 2020 전기전자학회논문지 Vol.24 No.1
본 논문에서는 차기구축함에 탑재될 통합 마스트의 레이더 반사면적을 감소시킬 수 있는 스텔스 기술로 응용하기 위해 해양 환경이 모사된 온도 환경 조건에서 전자기파 메타물질 흡수체의 내구성을 검증하였다. 이를 위해 미국 군사 규격인 MIL-STD-810H의 Method 501.7 중 Procedure I 조건에 따라 주기적으로 온도를 조절할 수 있는 항온 챔버에 저장 후 전자기파 메타물질 흡수체의 반사도를 측정하였다. 고온 환경시험 전과 후 모두 X 밴드 전체에서 스텔스 성능을 충족시킬 수 있는 -10 dB 미만의 반사도가 확인되었다. In this paper, the durability of an electromagnetic metamaterial absorber is verified in a temperature varying condition mimicking a maritime environment for the purpose of applying it to reduce the radar cross section of an integrated mast of the next-generation destroyer. To validate the durability, the reflectance of the electromagnetic metamaterial absorber was measured after storing it in a chamber that can control the temperature according to Procedure I of Method 501.7 included in MIL-STD-810H. Before and after the environmental test, both of the measured reflectances were retained less than -10 dB over the X band, that can guarantee the stealth functionality.
홍준표(Joonpyo Hong),이준식(Joonsik Lee),이기범(Kibum Lee),김준동(Joondong Kim) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.10
EMI (Electromagnetic Interference) has been a big issue regarding device stability. As health problems caused by Electromagnetic waves (EMW) have recently emerged due to the increase in use of electronic devices, a transparent EMI Shielding interface with ensured visibility is required. Herein, ITO/Ag/ITO hybrid structure EMI Shielding film with optical transparency and electrical conductivity has been developed. It showed a high optical transmittance (43%) and a high electrical conductivity (30000 S/m). As a result ITO/Ag/ITO film gives up to 40 ㏈ of EMI SE (Shielding Effectiveness) which is over 20 ㏈, a commercially applicable specification. This transparent EMI-shielding film can invisibly endow the protection from the human electronics and interfaces, such as cell phones, displays, vehicles and residential buildings.
완전 발달 층류 유동에서의 분말 조건에 따른 나노유체의 동적 열전도율
김형준(Hyungjoon Kim),Kenneth David Kihm,이준식(Joonsik Lee) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Many researchers have made desperate efforts to study for thermal characteristic of working fluid. As an idea to obtain higher thermal characteristic than that of existing pure fluid, e.g. water, the nanofluid is contrived and it expanded the research field for thermal properties and method to measure them. Nanofluid is a colloidal system consisting of nano-sized particles (dispersed phase) and a liquid (dispersed medium). The enhanced effective thermal conductivity, one of the representative thermal characteristics, of stationary nanofluid has measured by various ways. As a result, study of effective stationary thermal conductivity of nanofluid settles into shape pretty much and the methods carry conviction to researchers through many papers. In convective flow condition, however, it is hard to convince that we have an index of thermal conductivity for the accurate estimation. In this study, the dynamic conductivity of water-based nanofluids (Al₂O₃, Cu, Si) is measured in a fully developed laminar tube flow under uniformly heating conditions with respect to particle (size, concentration and kind), and then compared with the static conductivity at the mean fluid temperature subject to convective flow conditions.