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이성철,김기태,Lee, Seong-Cheol,Kim, Gi-Tae 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.1
Densification behavior of aluminum alloy(A16061) powder was investigated under cold compaction. Experimental data were obtained under triaxial compression with various loading conditions. A special form of the Cap model was proposed from experimental data of A16061 powder under triaxial compression. The proposed yield function and several yield functions in the literature were implemented into a finite element program (ABAQUS) to compare with experimental data for densifcation behavior of A16061 powder under cold isostatic pressing and die compaction. The agreement between finite element calculations from the proposed yield function and experimental data is very good under cold isostatic pressing and die compaction.
Exergy Analysis of Cryogenic Air Separation Process for Generating Nitrogen
이성철,문흥만,용평순 한국공업화학회 2002 Journal of Industrial and Engineering Chemistry Vol.8 No.6
A cryogenic air separation process that generates nitrogen has different process configurations depending on the utilization of either a cold heat supply method or a distillation method. Each method presents different initial investment costs, operating costs and energy efficiencies. Therefore, an accurate estimation of the energy efficiency as well as the cost is an important factor in selecting an appropriate process and in designing the most efficient equipment. Accordingly, the current study formulated criteria that can be applied to select the most efficient process. Processes using liquid nitrogen and an expansion turbine representing different cold heat supply methods were analyzed and evaluated to compare the exergy efficiency. In addition, the exergy efficiency of structure packing and sieve tray distillation method was also compared based on the experimental results.
이성철,박기현,정행근 대한전자공학회 1996 전자공학회논문지-B Vol.b33 No.3
An optical transmitter, which is a key component of the optical transmission system, converts the electrical signal to optical signal and consists of a high-speed current-pulse driver for laser diode and low-speed feedback loops that stabilize optical power against aging, power supply voltage fluctuations, and ambient temperature changes. In this paper, the power-stabilizing part, which forms the bulk of the optical transmitter circuitry was designed in integrted circuits. Operational amplifiers and reference voltage generation circuits, which were identified as key building blocks for the power-stabilizing feedback loops, were designed and were subsequently verified through HSPICE simulations. The designed operational amplifier consists of a two-stage folded cascode amplifier and class AB output stage, whereas the reference voltage is obtained by bandgap reference circuits. Finally the power-stabilizing circuitry was laid out based on 3\mu$m CMOS design rules for fabrication.
이성철,장재훈,정석진 경희대학교 산학협력기술연구원 2003 산학협력기술연구논문집 Vol.9 No.-
The catalyst formation is important step in chemical industries. Therefore, information on the influence of preparation methods on catalytic performances are very important for developing an industrial catalyst. However, very little information is available in the literature, mainly due to the pre-conception that such information counts as technical arts or trade secrets. The study is focused on investigating catalytic behavior of catalysts using extruding method and wetting method in CO2 hydrogenation. It was found that Fe-K/-Al2O3, which is prepared as wetting method, had excellent capability of CO2hydrogenation, whereas Fe-K/-Al2O3 with PVA binder showed decreased capability compared with those of other catalysts.
Preparation and stabilization of iron oxide nanoparticles using polymers
이성철,Se Chan Jang,김창영 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.3
Spherical Fe2O3 nanoparticles were prepared by the polyol process of organometallic precursor (Fe(acac)3) in the presence of a reducing agent with a stabilizing agent. These were then heat- treated to make crystalline of Fe2O3 nanoparticles. Also, a seedmediated growth technique was used to make them larger. TEM images of Fe2O3 nanoparticles made by the polyol process showed that the average particle size is 2.265 nm in diameter and the overall particle size distribution is narrow. It was confirmed that the diameter of Fe2O3 nanoparticles re-treated through the seed-mediated growth method had doubled by analyzing TEM images and the UV-visible spectrum. From XRD analysis, Fe2O3 nanoparticles transformed from amorphous to the hematite (α-Fe2O3) phase above 500 oC.