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최철진(Chul Jin Choi),이기웅(Ki Woong Lee),전동오(Dong-O Jeon) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
A cryogenic refrigeration system is under design by RISP (Rare Isotope Science Project) for a new heavy-ion linear accelerator, RAON, which will be built at Daejeon Korea. RAON will use four types of superconducting cavities which are cooled at 2 K superfluid helium; following IF (In-Flight) separator will utilize HTS and LTS magnets which are cooled at 20-50 K and 4.5 K, respectively. The cryogenic system consists of helium refrigeration system (HRS), helium distribution system (HDS), and cryomodules containing the cavities and magnets. Total capacity of the helium refrigeration system is estimated about 18.6 kW equivalent at 4.5 K. This paper will present current status of the cryogenic refrigeration system for RAON.
열복사를 적용한 드럼 건조기의 건조 메커니즘 분석 및 성능 예측에 관한 연구
최철진(Chul Jin Choi),장정현(Jung Hyun Jang),김종민(Chongmin Kim),김만영(Man Young Kim) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.3
텀블형 드럼 건조기의 적외선 건조 과정동안의 온도 및 수분량의 변화를 예측할 수 있는 2 차원 수학적 모델을 개발하였다. 본 모델에서는 건조대상 물질의 액체 수분의 이동과 건조공기의 유동 및 열전달을 고려하였다. 유체의 유동과 열전달 현상, 그리고 복사열전달은 유한체적법을 이용하여 해석하였다. 텀블건조기의 2 차원 모델을 모사하기 위한 지배방정식을 소개한 후 적외선 히터, 히터의 온도, 그리고 가열 패턴에 따른 수치해석을 수행하였고, 적외선 히터를 도입함으로써 건조시간을 감소시킬 수 있음을 제시하였다. A two-dimensional mathematical model was developed to predict the temperature and moisture-content profiles of a tumble dryer during infrared drying. The model is based on the movements of liquid water and moisture in the object and on the fluid and heat transfer in the drying air. The model was solved by the finite volume analysis for the fluid, temperature, and radiation intensity fields. After deriving the governing equations and developing the twodimensional tumble dryer models, numerical investigations were carried out to examine the effects of various parameters such as the heater temperature and the heating patterns on the drying mechanism of the tumble dryer. All the results show that the drying time can be reduced by using the IR heater.
뫼스바우어 분광법에 의한 Fe - 나노입자의 탄화물 코팅에 관한 연구
오세진(Sei-Jin Oh),최철진(Chul-Jin Choi),김진천(Jin-Chun Kim),권순주(Soon-Ju Kwon),진상호(SangHo Jin) 한국자기학회 2005 韓國磁氣學會誌 Vol.15 No.3
Four nano-sized Fe-nano particle samples synthesized by Chemical Vapor Condensation (CVC) were analyzed using Mossbauer spectroscopy, XRD, BET and TEM. The samples were consisted as functions of carrier gas and decomposition temperature. The synthesized nanoparticles consisted of two- or three-layers with the circular shape. The average particle size was increased with increasing the decomposition temperature. At 500℃ for the decomposition temperature, Fe₃C was formed more under the environment of CO carrier gas than that of CH₄. However, at 1,100℃, almost of Fe-nano particles were transformed into Fe₃C with using both carrier gas.
나노 Fe 분말을 이용하여 사출 성형된 Fe 소결체의 제조
김기현,임재균,최철진,이병택,Kim Ki-Hyun,Lim Jae-Hyun,Choi Chul-Jin,Lee Byong-Taek 한국재료학회 2004 한국재료학회지 Vol.14 No.11
The injection molded Fe sintered bodies were fabricated using two kinds of Fe powders haying 50 nm and $3\sim5{\mu}m$ in diameter. In the using of Fe powder having 50 nm in diameter, the comparatively dense bodies ($94\sim97\%$) were obtained even at low sintering temperature ($600\sim700^{\circ}C$), while in the sintered bodies ($1000^{\circ}C$) using $3\sim5{\mu}m$ Fe powder, their relative densities showed low values about $93\%$, although they were strongly depend on the sintering temperature and volume ratio of Fe powder and binder. In the sintered bodies using of 50 nm Fe powders, the volume shrinkage and grain size increased as the sintering temperature increased, but the values of hardness decreased. In the sample sintered at $650^{\circ}C$, the values of relative density, volume shrinkage and grain size were $96\%,\;37\%\;and\;0.97{\mu}n$, respectively and the minimum value of wear depth was obtained due to combination of fine grain and comparatively high density.
김기현,윤형철,최철진,이병택,Kim Ki-Hyun,Yoon Hyeong-Chul,Choi Chul-Jin,Lee Byong-Taek 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.6
The Fe-Ni compact bodies were fabricated using Fe-Ni mixed powders with 50 nm in diameter by injection molding process. The relationship between microstructure and material properties was characterized with respect to the volume ratio of powder/binder and sintering temperature with SEM and TEM. In the compact body having the volume percent ratio of 45(Fe-Ni) : 55(binder), which was sintered at $900^{\circ}C$ the values of relative density and hardness were low about 97.7% and 277.1 Hv, respectively. Using the composition of 50(Fe Ni) : 50(binder) and sintered at $900^{\circ}C$, the values of relative density and hardness were 98.5%, 294.4 Hv, respec-tively. The grain size of sintered bodies strongly depended on the sintering temperature. In both samples sintered at $600^{\circ}C$ and $900^{\circ}C$, the average grain sizes were about 150 nm and 500 nm in diameter, respectively.
환원-확산법에 의한 Sm-Fe 합금분말 제조시 Sm<sub>2</sub>O<sub>3</sub> 첨가량의 영향
곽훈,이정구,최철진,Kwak, Hun,Lee, Jung-Goo,Choi, Chul-Jin 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.5
To produce alloy powders with only Sm$_2$Fe$_{17}$ single phase by reduction-diffusion (R-D) method, the effect of excess samarium oxide on the preparation of Sm-Fe alloy powder during R-D heat treatment was studied. The quantity of samarium oxide was varied from 5% to 50% whereas iron and calcium were taken 0% and 200% in excess of chemical equivalent, respectively. The pellet type mixture of samarium, iron powders and calcium granulars was subjected to heat treatment at 1100$^{\circ}C$ for 5 hours. The R-D treated pellet was moved into deionized water and agitated to separate Sm-Fe alloy powders. After washing them in deionized water several times, the powders were washed with acetic acid to remove the undesired reaction products such as CaO. By these washing and acid cleaning treatment, only 0.03 wt% calcium remained in Sm-Fe alloy powders. It was also confirmed that the content of unreacted $\alpha$-Fe in Sm$_2$Fe$_{17}$ matrix gradually decreased as the percentage of samarium oxide is increased. However, there was no significant change above 40% excess samarium oxide.
김진천,하국현,최철진,김병기,Kim Jin-Chun,Ha Gook-Hyun,Choi Chul-Jin,Kim Byoung-Kee 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.4
1990년도 초반에 개발되어 나노분말의 제조 공정으로 집중적으로 연구되어온 화학기상응축공정은 고강도용 나노분말 소재이외에 기능성 자성재료로의 응용에 주로 이용되어 왔다. 최근에는 이러한 응용이외에 나노분말의 표면을 다양한 이종 소재로 응용하고자하는 나노캡슐(혹은 core/shell)화 제조 공정으로 진보되어 다양한 합금 시스템으로 발전하게 되었다. 특히 최근 Particles 2005, Surface Modification in Particle Technology 학회에서는 나노금속 혹은 세라믹 분말에 PMMA, PE등 polymer의 유기화합물의 코팅하여, DNA나 RNA를 부착하거나 추출해내는 나노캡슐화 공정 연구가 매우 활발하게 진행됨을 보여주고 있으며, 이들 나노 캡슐의 개발은 약물전달계(Drug delivery system), 온열치료용 및 MRI 조영제 등의 바이오재료로의 응용가능성이 크게 기대되어 이에 대한 연구들이 활발하게 진행될 것으로 예상된다.