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안재혁(Jae-Hyeok Ahn),김정현(Jeong-Hyeon Kim),김정대(Jeong-Dae Kim),박성균(Sungkyun Park),박강현(Kang Hyun Park),이제명(Jae-Myung Lee) 한국해양공학회 2017 韓國海洋工學會誌 Vol.31 No.6
In the present study, silica-aerogel-polyurethane foams were synthesized to improve the mechanical characteristics and insulation performance of the polyurethane foam applied to a liquefied natural gas carrier at a cryogenic temperature of -163℃. A silica-aerogel-polyurethane foam bulk was prepared using a homogenizer by varying the weight ratio of the silica aerogel (0, 1, 3, and 5 wt%), while maintaining the contents of the polyol, isocyanate, and blowing agent constant. Compression tests were performed at room and cryogenic temperatures to compare the mechanical properties of the silica-aerogel polyurethane foams. The internal temperature of the universal testing machine was maintained through the cryogenic chamber. The thermal conductivity of the silica-aerogel-polyurethane foam was measured using a heat flow meter to confirm the insulation performance. In addition, the effect of the silica aerogels on the cells of the polyurethane foam was investigated using FE-SEM and FTIR. From the experimental results, the 1 wt% silica aerogel polyurethane foam showed outstanding mechanical and thermal performances.
NO96타입 LNG 방열시스템 Divinycell의 극저온 압축 강도 평가
최영락(Yeong-Rak Choe),김정현(Jeong-Hyeon Kim),김종민(Jong-Min Kim),박성균(Sungkyun Park),박강현(Kang Hyun Park),이재명(Jae-Myung Lee) 한국해양공학회 2016 韓國海洋工學會誌 Vol.30 No.5
Divinycell, which functions as both insulation and a supporting structure, is generally applied in the NO96-type liquefied natural gas (LNG) insulation system. Polymer-material-based Divinycell, which has a high strength and low weight, has been widely used in the offshore, transportation, wind power generation, and civil engineering fields. In particular, this type of material receives attention as an insulation material because its thermal conductivity can be lowered depending on the ambient temperature. However, it is difficult to obtain research results for Divinycell, even though the component materials of the NO96-type LNG cargo containment system, such as 36% nickel steel (invar steel), plywood, perlite, and glass wool, have been extensively studied and reported. In the present study, temperature and strain-rate dependent compressive tests on Divinycell were performed. Both the quantitative experimental data and elastic recovery are discussed. Finally, the mechanical characteristics of Divinycell were compared to the results of polyurethane foam insulation material.
손영준(Youngjun Son),송세환(Sehwan Song),이지성(Jisung Lee),박홍준(Hongjun Park),한승훈(Seonghoon Han),김지웅(Jiwoong Kim),배종성(Jong-Seong Bae),김송길(Songkil Kim),박성균(Sungkyun Park) 한국물리학회 2022 새물리 Vol.72 No.10
정공을 운반자로 사용하는 p-형 산화물은 깊은 O 2p 준위로 인해 상대적으로 정공 이동도가 낮아 n-형 산화물보다 잠재적인 응용 가능성이 낮다. 최근 밀도범함수이론 연구에 따르면 Bi가 첨가된 In₂O₃는 가전자대 근처에서 새로운 in-gap 상태를 형성하여 받개의 형성 에너지를 낮출 수가 있다고 보고되었다. 또한, 이전 실험에서 Bi가 첨가된 In₂O₃ 세라믹에서 광학적 특성을 통해 in-gap 상태가 형성된 것을 확인하였다. 본 연구에서는 결정성과 in-gap 상태의 상관관계를 이해하기 위하여, 다양한 증착 온도에서 Bi가 첨가된 In₂O₃ 박막을 RF 마그네트론 스퍼터링 방법을 이용하여 제작하였다. 그 결과, 증착 온도가 증가함에 따라 결정립 크기가 증가하였다. 이와 더불어 광학적 특성 측정을 통해 벌크 In₂O₃의 밴드갭(~2.7eV)과 Bi 첨가에 의해 새롭게 형성된 in-gap 준위(~1.9eV) 에너지가 형성되는 것을 확인하였고, 박막의 증착 온도가 증가함에 따라 두 밴드갭이 줄어드는 것을 확인하였다. 이러한 변화는 결정립 크기 증가와 관련이 있는 것으로 생각된다. P-type oxides using holes as carriers exhibit a relatively low hole mobility due to the deep O 2p level; thus, their potential applications are fewer than those of n-type oxides. Recently, a DFT study has reported that Bi-doped In₂O₃ forms a new in-gap state near the valence band, thereby lowering the formation energy of the acceptor and enabling the formation of a new p-type oxide through additional doping. In addition, a previous experiment on the Bi-doped In₂O₃ ceramics revealed the in-gap state. In this study, Bi-doped In₂O₃ films were grown under various conditions to examine the possibility of optical bandgap modulation. Consequently, from a structural viewpoint, the crystalline size grew as the deposition temperature increased; spectroscopically, two optical absorptions were confirmed. While the larger optical bandgap corresponded to bulk In₂O₃, the smaller one was associated with a newly formed in-gap state owing to Bi doping. Furthermore, the bandgap energy decreased as the deposition temperature increased. Therefore, the reduced optical bandgap with an increased deposition temperature was related to the reduced quantum size effect.
이정란(Jungran Lee),강희석(Heeseog Kang),김정한(Jeonghan Kim),박성균(Sungkyun Park) 한국정보기술학회 2020 한국정보기술학회논문지 Vol.18 No.11
Electronic attack systems against radar use wideband high power noise jamming to neutralize enemy radar or false target signals to improve survivability and operability of friendly combat system. To improve the deception performance in the radar jamming system, it is necessary to estimate the scan period of the radar as well as analyzing the basic parameters. This paper presents the method of estimating the scan period of search radar using Kalman Filter based on the basic parameters such as frequency, pulse width, pulse repetition interval, pulse amplitude and time of arrival of search radar. This paper presents the method of generating the deception signal based on estimated scan period, and test results using HILS are presented to show the performance of the proposed method.
아크 융해로를 이용한 β-Ti<SUB>3</SUB>O<SUB>5</SUB> 및 λ-AlxTi<SUB>3-x</SUB>O<SUB>5</SUB>의 합성
공민식(Minsik Kong),김서희(Seohee Kim),김민재(Min Jae Kim),강명준(Myeongjun Kang),지광철(Gwangcheol Ji),박성욱(Seonguk Park),이지성(Jisung Lee),손영준(Yeongjun Son),박성균(Sungkyun Park),옥종목(Jong Mok Ok) 한국물리학회 2024 새물리 Vol.74 No.1
마그넬리(Magneli)상 티타늄 산화물인 Ti₃O<SUB>5</SUB>는 514 K에서 β상에서 λ상으로 변화하며 절연체에서 도체로 변화하는 금속-절연체 전이(metal-insulator transition; MIT)를 보인다. Ti<SUB>5</SUB>O<SUB>5</SUB>의 MIT는 큰 저항 변화와 높은 열에너지 저장 특성을 동반하는 것으로 알려져있어 높은 응용성을 가지고 있다. 이러한 Ti₃O<SUB>5</SUB>의 전기적 혹은 열적 특성을 활용하기 위해선 균일한 시료의 합성과 상전이 온도의 제어가 우선되어야 한다. 본 연구에서는 아크 융해로(arc melting furnace)를 이용한 티타늄 환원법으로 Ti₃O<SUB>5</SUB>를 합성하였고, 그 구조를 탄소 환원법으로 제조한 Ti₃O<SUB>5</SUB>와 비교하였다. 또한, 티타늄 환원법을 이용해 Al이 도핑된 AlxTi₃−xO<SUB>5</SUB>를 합성하고 Al 도핑 비율에 따른 구조, 상전이 온도 및 잠열량을 확인함을 통해 아크 융해법이 Ti₃O<SUB>5</SUB>를 합성하고 상전이를 온도를 제어하는데 효과적인 합성법임을 확인하였다. Ti₃O<SUB>5</SUB> exhibits a metal-insulator transition (MIT) accompanied by a structural change from β- phase to λ-phase at 514 K. During the transition, Ti₃O<SUB>5</SUB> demonstrates significant resistance changes and high thermal energy storage characteristics. To harness the beneficial characteristics of Ti₃O<SUB>5</SUB>, it is essential to develop a growth method that yields homogeneous samples and to control the phase transition temperature. In this study, we successfully synthesized high-quality β-Ti₃O<SUB>5</SUB> and λ-AlxTi₃−xO5 polycrystalline samples using an arc melting method. Furthermore, the structural and physical properties of β-Ti₃O<SUB>5</SUB> and λ-AlxTi₃−xO<SUB>5</SUB> were investigated as a function of the Al doping ratio. Our results suggest that the arc melting method provides an effective way to synthesize high-quality Ti₃O<SUB>5</SUB> and control the transition temperature of the MIT.