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김시진(Sijin Kim),김학철(Hakchul Kim),김계환(Kyehwan Kim),박영훈(Younghoon Park),박선정(Sunjung Park),이동근(Donggeun Lee),김진곤(JinKon Kim),문희장(Heejang Moon),유영준(Youngjun You),권민찬(Minchan Kwon) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5
본 연구는 하이브리드 로켓 모터의 수중추진기관 적용을 위한 초기연구로 Lab-scale 하이브리드 로켓 모터를 이용하여 수중연소시험을 수행하였다. 3 m x 1 m x 1 m 크기의 수조 내 바닥면에서 55 cm 위에 연소기를 위치하여 수중연소시험을 수행하였으며 아크릴판으로 제작된 파열판(rupture disk)을 이용하여 연소실 초기 기밀을 유지하였다. 산화제는 액체아산화질소(LN2O), 연료는 HDPE를 사용하였고 KNSB 추진제를 이용하여 점화하였으며 연소시험은 총 5초간 진행되었다. 수중연소시험 결과 설계 추력에 근접하는 추력을 얻을 수 있음을 확인하였다. In this study, underwater combustion test was performed using a lab-scale hybrid rocket motor. The purpose of this study is to find out the feasibility of underwater propulsion using hybrid rocket system. Combustor was located underwater above 55cm from the bottom of water tank where the size of water tank is 3m X 1m X 1m. The combustor was sealed by installing acrylic plate rupture disk at the nozzle exit. LN2O and HDPE were used as oxidizer and solid fuel respectively, while the KNSB propellant was used as the ignitor source. The combustion duration was set to 5 seconds, and it was confirmed that the measured thrust of underwater combustion test was close to the design thrust.
Antiferromagnetic coupling of van der Waals ferromagnetic Fe<sub>3</sub>GeTe<sub>2</sub>
Kim, Dongseuk,Park, Sijin,Lee, Jinhwan,Yoon, Jungbum,Joo, Sungjung,Kim, Taeyueb,Min, Kil-joon,Park, Seung-Young,Kim, Changsoo,Moon, Kyoung-Woong,Lee, Changgu,Hong, Jisang,Hwang, Chanyong IOP Pub 2019 Nanotechnology Vol.30 No.24
<P>Among two-dimensional (2D) layered van der Waals materials, ferromagnetic 2D materials can be useful for compact low-power spintronic applications. One promising candidate material is Fe<SUB>3</SUB>GeTe<SUB>2</SUB> (FGT), which has a strong perpendicular magnetic anisotropy and relatively high Curie temperature. In this study, we confirmed that an oxide layer (O-FGT) naturally forms on top of exfoliated FGT and that an antiferromagnetic coupling (AFC) exists between FGT and O-FGT layers. From a first-principles calculation, oxide formation at the interface of each layer induces an AFC between the layers. An AFC causes a tailed hysteresis loop, where two-magnetization reversal curves are included, and a negative remanence magnetization at a certain temperature range.</P>
알루미늄 나노입자 첨가량에 따른 케로신 젤의 유변학적 특성 변화
김시진(Sijin Kim),한승주(Seongjoo Han),김진곤(Jinkon Kim),강태곤(Teagon Kang),문희장(Heejang Moon) 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.5
본 연구에서는 젤화제 Thixatrol<SUP>Ⓡ</SUP> 및 100 nm 크기의 알루미늄 입자 첨가량에 따른 케로신 기반 젤 추진제를 제작하여 유변학적 특성을 파악하였다. 케로신 젤 추진제는 젤화제 첨가량 2.5 wt%, 5 wt%, 7.5 wt%의 세 가지 젤을 제작하였으며, 알루미늄이 첨가된 젤은 젤화제 7.5 wt%를 기반으로 입자 첨가량 10 wt%와 20 wt%의 두 가지 블렌딩 알루미늄 젤을 분석하였다. 회전형 rheometer를 이용하여 각 시료의 점도를 측정한 결과, 젤화제 첨가량 증가 및 알루미늄 입자 증가에 따라 점도값이 정성적으로 증가하는 경향을 보였다. 그러나 20 wt%의 높은 금속입자 함유 젤의 경우, 입자간 응집, 고형화로 인해 낮은 전단변형률 구간에서 조차 측정 신뢰도가 낮아 회전형이 아닌 모세관 또는 다양한 방식의 점도계 활용이 요구된다. In this study, the rheological characteristics of kerosene based gel propellants were investigated. For the gelling agent, Thixatrol<SUP>Ⓡ</SUP> has been used with 100 nm nano-sized aluminium particle addition. Three gellant contents of 2.5 wt%, 5 wt% and 7.5 wt% kerosene gels were first investigated where aluminium particles contents of 10 wt% and 20 wt% were added to 7.5 wt% gellant case. The viscosities of each sample measured by rotational rheometer show that the viscosity augments as gellant or aluminium content increases while the 20 wt% aluminum content resulted in failure of measurement due to the agglomerations of aluminum particles.
Nanostructure of core-shell support for enhanced electrochemical activity in PEMFC
김도영(Kim, Doyoung),한상범(Han, Sangbeom),이영우(Lee, Youngwoo),김시진(Kim, Sijin),박경원(Park, Kyungwon) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.11
Nanostructures consisting of TiO₂ particles as a core and carbon as a shell (TiO₂@C) were prepared by heat treatment of TiO₂ nanoparticles at high temperature in a methane atmosphere. X-ray diffraction and transmission electron microscopy showed that a carbon shell layer was formed well. These structures were used as supports for platinum nanoparticles and the hybrid particles exhibit improved catalytic activity and stability toward ORR compared to Pt on a carbon black (Vulcan XC-72R). It is likely that enhanced catalytic properties of the Pt on TiO₂@C could be due to the stability of the core-shell support in comparison with carbon black support.
Observation of variable hybridized-band gaps in Eu-intercalated graphene
Sung, Sijin,Kim, Sooran,Lee, Paengro,Kim, Jingul,Ryu, Mintae,Park, Heemin,Kim, Kyoo,Min, Byung Il,Chung, Jinwook IOP 2017 Nanotechnology Vol.28 No.20
<P>We report europium (Eu)-induced changes in the <I>π</I>-band of graphene (G) formed on the 6H-SiC(0001) surface by a combined study of photoemission measurements and density functional theory (DFT) calculations. Our photoemission data reveal that Eu intercalates upon annealing at 120 °C into the region between the graphene and the buffer layer (BL) to form a G/Eu/BL system, where a band gap of 0.29 eV opens at room temperature. This band gap is found to increase further to 0.48 eV upon cooling down to 60 K. Our DFT calculations suggest that the increased band gap originates from the enhanced hybridization of the graphene <I>π-</I>band with the Eu 4<I>f</I> band due to the increased magnetic ordering upon cooling. These Eu atoms continue to intercalate further down below the BL to produce bilayer graphene (G/BL/Eu) upon annealing at 300 °C. The <I>π</I>-band stemming from the BL then exhibits another band gap of 0.37 eV, which appears to be due to the strong hybridization between the <I>π</I>-band of the BL and the Eu 4<I>f</I> band. The Eu-intercalated graphene thus illustrates an example of versatile band gaps formed under different thermal treatments, which may play a critical role for future applications in graphene-based electronics.</P>
김계환(Kyewhan Kim),김시진(Sijin Kim),한승주(Seungjoo Han),김진곤(Jinkon Kim),문희장(Heejang Moon) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
본 연구에서는 모사젤 추진제의 표면장력을 적환법(Du Noüy Ring Method)을 이용하여 측정하고 젤화제 및 금속입자 첨가량에 따른 표면장력 변화를 분석하였다. 금속입자 첨가에 따른 영향을 파악하기 위해 증류수를 기반유체로 그리고 젤화제는 Carbopol 941을 사용하였으며, 금속입자로는 평균입도 100 nm의 구형 스테인리스 304 입자를 사용하였다. 측정결과, 표면장력은 젤화제의 첨가량 증가에 따라 증가하였으나, 모사젤 추진제 내에 금속입자 첨가에 따른 표면장력은 다른 경향을 나타내었다. In this study, the surface tension of simulant gel propellants was measured by Du Noüy ring method. The variation of the surface tension was investigated with respect to the amount of the gelling agent, and metal particle addition. Distilled water was used as the base fluid for the preparation of the simulant gel propellant where Carbopol 941 was used as a gelling agent and SUS304 spherical metal particles (mean diameter : 100 nm) as simulant energetic particles. As a result of measurements, surface tension increased with increasing gelling agent concentration while, in the presence of metal particle, different behavior of surface tension has been observed.
침치료와 자락치료 위주의 한의 복합 치료로 호전된 장기간 지속된 이명, 이충만감 및 난청 증례 보고
Kang Junhyeok,Kim Sijin,Kim Kwangho,Kim Gyeongchan 대한침도의학회 2024 대한침도의학회지 Vol.8 No.1
Background: The aim of this study is to report the effect of Complex Korean Medicine Treatment, which includes Acupotomy, intranasal bloodletting therapy and soft palate bloodletting therapy on tinnitus and aural fullness. Methods: One patient with tinnitus and aural fullness was treated with Korean medicine therapy, including Acupotomy, intranasal bloodletting therapy, and soft palate acupuncture twice a week. Treatment progress was assessed using the Numeral Rating Scale (NRS) and Automated Micro Audiometer Pure-Tone Audiometry (AMA-PTA). Results: The patient’s symptoms of aural fullness and tinnitus disappeared after the treatment, and an improvement in hearing test results was also observed. Conclusion: These results suggest that Complex Korean Medicine Therapy, which includes Acupotomy, intranasal bloodletting therapy, and soft palate bloodletting therapy, could be an effective treatment for long-term tinnitus, hearing loss, and aural fullness.