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적외선 열화상법 및 FE-SEM을 활용한 마그네슘 연소특성에 관한 실험적 연구
이준식,남기훈,Lee, Jun-Sik,Nam, Ki-Hun 한국산업융합학회 2020 한국산업융합학회 논문집 Vol.23 No.6
Magnesium powder has been widely used in various industries because it is light weight and extremely high mechanical strength including aeronautics and chemicals. However, magnesium, as a combustible metal, poses serious safety issues such as fires and explosions if it is not managed properly. Especially, magnesium's max adiabatic flame temperature is 3,340℃ and it is impossible to extinguish it by using water, CO2 and Halonagents. The aim of this study is to identify the combustion characteristics of magnesium powder. We carried out a combustion experiment, using 1 kg of magnesium (purity > 99 %, particle < 150 ㎛). The features of the magnesium burning process were scrutinized using infrared thermal image analysis. Also, a field-emission scanning electron microscope (FE-SEM) were used employed to analyze particulate composites and properties. It concludes the significant tendency of magnesium fire and light, combustion carbide's particle characteristics. This study contributes to make better prevention and response manners to magnesium fires, as well as fire investigation measures.
비정렬 고정격자계를 이용한 쌍롤 박판주조에서의 유동장 및 열전달 해석
이준식,이주명,정재동,Lee, Jun-Sik,Lee, Ju-Myeong,Jeong, Jae-Dong 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.5
This paper presents a numerical analysis on the solidification characteristics in twin-roll strip casting. Unstructured fixed-grid system was employed to deal with phase change. Melting of pure gallium was analyzed to confirm the validity of present program in both structured and unstructured grid systems. An algorithm for simultaneous calculation of the temperature in the roll and the molten metal pool was developed. The flow field in the pool and heat transfer features between pool and roll were shown. The effect of process parameters was also studied. Since the geometry of the molten metal Pool significantly deforms along the casting direction, unstructured grid system is more efficient. The unstructured grid system gives almost the same accuracy, even though the number of grids is only 60% of the structure done.
이준식,Lee Joon Sik 대한설비공학회 1987 설비저널 Vol.16 No.1
The heat transfer processes taking place in the side wall of a thermocline enclosure have been analyzed for idealized conditions based on the assumption that, at any instant time, side wall heat transfer processses are independent of the thermocline bulk motion. However, the axial tempera-ture distribution in the thermocline core provides the means for specifying the liquid medium-side boundary condition to the enclosure side wall. A picture is drawn which reflects the side wan response to thermocline bulk motion within the frame work of a quasi-steady analytic approach. For valves of the parameters typical of systems of engineering interest, the analysis shows that a significant amount of heat transfer short - circuiting can take place along the side wall enclosure. This phenomenon is favored by high values of $H_l$ and low values of P and $H_g$ respec-tively. The location of the point of zero normal heat flux on the side wan can be expected to mark, approximately, the region of confluence of two sidewall boundary flows respectively driven by the buoyant effects.
경화촉매 분말의 입도조절 및 표면코팅에 의한 에폭시 레진 기반 혼합조성의 상온 보관특성 개선
이준식,현창용,이종현,Lee, Jun-Sik,Hyun, Chang-Yong,Lee, Jong-Hyun 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.2
To increase pot life in the formulation mixed with bisphenol F epoxy resin, anhydride-based curing agent, and imidazole-based curing accelerator powders as a paste material for high-speed RFID chip bonding, size variation of the imidazole-based powders and a coating method of the powders were adopted in this study. In experiment with regard to the size variation, the pot life was not outstandingly increased. Through the idea using the coating method, however, the pot life was increased up to 4.25 times in comparison with the addition of initial imidazole-based powders. Consequently, successive bonding of RFID chip could be performed with very short time of 5sec using the suggested formulation having improved pot life.
SGCMG를 이용한 단축 불안정 시스템의 안정화 제어 기법 개발
이준식,이준용,유지훈,김지철,전동익,오화석,Lee, Junsik,Yi, Junyong,Yoo, Jihoon,Kim, Jichul,Cheon, Dongik,Oh, Hwa-Suk 항공우주시스템공학회 2013 항공우주시스템공학회지 Vol.7 No.4
Control Moment Gyroscope(CMG) is one of the most efficient momentum exchange devices for satellite attitude control and essential device for agile maneuver system. This paper presents the details of a designed Single Gimbal CMG with a constant speed momentum wheel and single axis attitude control unstable to stable. In order to keep the naturally unstable equivalent point, it should be controlling the gimbal constantly. The experimental data are compared with theoretical result and requirements are used to verify their performance specifications.