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최정길,홍준표 ( Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.3
주철의 중력금형주조에서 반복작업에 따른 응고과정의 변화를 3차원의 수치해석적 방법에 의하여 컴퓨터해석을 하였다. 수치해석적 방법으로는 차분법을 채택하였다. 반본작업과정에 따라 변화되어지는 주물의 응고시간과 미세조직, 기계적성질과의 관계가 조사 되어졌다. 컴퓨터에 의해 계산된 각싸이클의 냉각속도로 부터 주물의 공정셀의 수, 경도, 인장강도등의 변화를 예측하였으며 또한 반복싸이클에 따른 금형 및 주물의 온도분포와 최종응고부위등을 예측하였고 이들은 실제주조시험에서 얻어진 결과와 비교적 잘일치하였다. 중력금형주조에서 회주철의 응고시간, 공정셀, 기계적성질 및 응고속도에 미치는 냉각수의 영향이 또한 컴퓨터해석에 의하여 잘예측되었으며 컴퓨터해석에 의한 냉각수 라인의 적절한 설계에 의하여 주물의 미세조직 및 기계적성질과 결함발생 가능위치를 효과적으로 제어할수 있음을 확인하였다. N/A
최정길,김성빈,홍준표 ( Jeong Kil Choi,Seoung Bin Kim,Chun Pyo Hong ) 한국주조공학회 1992 한국주조공학회지 Vol.12 No.1
N/A A computer simulation of mold filling has been performed in order to analyze the fluid flow pattern in a mold cavity since casting defects such as cold shut formation, entrapment of air or gas, and inclusions are closely related to the fluid flow phenomena. The flow of molten metal entering the mold cavity with free surface has been modeled by SMAC(Simplified Marker and Cell) method. Two dimensional analysis was carried out on plate shape castings with two types of gate system. The calculation results were compared with those of water modeling experiments and showed relatively good agreement.
최정길,김동옥 ( Jeong Kil Choi,Dong Ok Kim ) 한국주조공학회 1986 한국주조공학회지 Vol.6 No.1
The gating design of gray cast iron was programmed in a Personal computer. By this program, casting test was done. The results obtained are as follows. 1. Gating design that can calculate the velocity of metal flow and size in each gate section by knowing the loss coefficient caused by friction loss and bend loss was programmed. 2. In the test casting, the gating ratio was changed into 1.1:1.3:1, 1:2:2, 1:4:4. And sound casting, free of sand washing defect, was obtained at the velocity of 35.5㎝/sec in ingate.
국내자원을 활용한 가탄재의 (加炭材) 개발에 관한 연구 (2)
최정길,김동옥 ( J . K . Choi,D . O . Kim ) 한국주조공학회 1982 한국주조공학회지 Vol.2 No.3
N/A For the purpose of development of domestic carburizer, when the basicity of ash in carburizer was changed from Na₂O/Al₂O₃+ SiO₂; 0.06 to Na₂O/Al₂O₃+SiO₂: 0,196wt%, using Na₂O as flux for domestic graphite resource (Bong Myung armorphous graphite), carburizing efficiency was improved as basicity increased, optimum basicity value was Na₂O/Al₂O₃+ SiO₂; 0.151. This means that Na₂O contributed to lower viscosity of slag and raise occurence probability of specific reaction surface between molten iron and carburizer. The experiment of effect of general characteristics offecting carburizing ability of this carburizer was performed, the result is that 10/30 mesh was optimum size of the carburizer and as carbon equivalent of molten iron was higher, carburizing ratio was lowered, but when si concentration was below 1.8% in general cast iron melting region, recovery showed 75-85%. As agitation rate of molten iron and temperature interval were higher, Carburizing ratio was increased and showed max, 94%. Desulfurizing phenomena of molten iron by Na₂O in carburizer didn`t appear.
최정길(Jungkil Choi),김태하(Teaha Kim),이효진(Hyojin Lee) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.5
최근 선박을 이용한 국제교역의 증가로 항만 및 선박의 규모가 대형화되었다. 선박은 벙커C와 MDO(Marine Diesel Oil)를 연소하여 전기를 생산한다. 선박에서 배출되는 NOx, SOx, PM, CO는 대기오염의 원인이고, 항만 노동자와 인근 주민들의 건강에도 상당한 영향을 미친다. 국제적으로 대기오염물질 저감에 관한 배출규제가 진행됨에 따라 선박과 하역장비, 물류수송 트럭, 기관차에서 배출하는 대기오염물질의 양을 산정하는 연구가 국외에서 수행되었다. 하지만 한국은 선박에 의한 대기오염물질 배출에 관한 연구가 미흡하다. 본 연구는 우리나라 주요 항만인 인천, 광양, 부산, 울산을 대상으로 입항하는 선박의 배기가스 배출량을 산정하였다. 또한 배출된 배기가스에 의한 사회적 비용도 산정하였다. 그 결과, 선박의 입항횟수가 많은 부산에서 배기가스 배출량과 사회적 비용 부담이 높았다. 선종별로는 4개 항에 입항횟수가 많았던 유조선이 배출량과 사회적 비용 부담이 높았다. The recent increase in international trade using vessels has increased the size of ports and vessels. The ship produces electricity by burning bunker C and Marine Diesel Oil (MDO). NOx, SOx, PM, and CO emitted when ships burn fuel cause air pollution and have a significant impact on the health of port workers and neighbors. As international regulations on air pollutant reduction have been carried out, studies to estimate the amount of air pollutants emitted by ships, cargo handling equipment, logistics transportation trucks, and locomotives have been conducted abroad. However, Korea has insufficient research on the emission of air pollutants by ships. This study estimates the exhaust gas emissions of ships entering Incheon, Gwangyang, Busan and Ulsan, the major ports in Korea. In addition, the social cost of the exhaust gas was calculated. As a result, exhaust gas emissions and social cost burdens in Busan were high. By ship type, the tankers that frequently entered four ports had high emissions and social cost burden.
최정길(Choi, Jeong-Gil) 한국신재생에너지학회 2013 신재생에너지 Vol.9 No.1
Tantalum carbide crystallites which is to be used for H₂ fuel cell has been synthesized via a temperature-programmed reduction of Ta₂O<sub>5</sub> with pure CH₄. The resultant Ta carbide crystallites prepared using two different heating rates and space velocity exhibit the different surface areas. The O₂ uptake has a linear relation with surface area, corresponding to an oxygen capacity of 1.36{times}10^{13};O;cm^{-2}. Tantalum carbide crystallites are very active for hydrogen production form ammonia decomposition reaction. Tantalum carbides are as much as two orders of magnitude more active than Pt/C catalyst (Engelhard). The highest activity has been observed at a ratio of C_1/Ta^{{delta}+}=0.85, suggesting the presence of electron transfer between metals and carbon in metal carbides.