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김철환,박배훈,정창현 ( C . H . Kim,B . H . Park,C . H . Jung ) 한국수학교육학회 1988 수학교육 Vol.26 No.2
Mathematics education is generally to cultivate mathematical thought. Most meaningful thought is to solve a certain given situation, that is, a problem. The aim of mathematics education could be identified with the cultivation of mathematical problem-salving ability. To cultivate mathematical problem-solving ability, it is necessary to study the nature of mathematical ability and its aspects pertaining to problem-solving ability. The purpose of this study is to investigate the relation between problem-solving ability and classificational viewpoint of mathematical verbal problems, and between the detailed abilities of problem-solving procedure and classificational viewpoint of mathematical verbal problems. With the intention of doing this work, two tests were given to the third-year students of middle school, one is problem-solving test and the other classificational viewpoint test. The results of these two tests are following. 1. The detailed abilities of problem-solving procedure are correlated with each other : such as ability of understanding, execution and looking-back. 2. From the viewpoint of structure and context, students classified mathematical verbal problems. 3. The students who are proficient at problem-solving, understanding, execution, and looking-back have a tendency to classify mathematical verbal problems from a structural viewpoint, while the students who are not proficient at the above four abilities have a tendency to classify mathematical verbal problems from a contextual viewpoint. As the above results, following conclusions can be made. 1. The students have recognized at least two fundamental dimensions of structure and context when they classified mathematical verbal problems. 2. The abilities of understanding, execution, and looking-back effect problem-solving ability correlating with each other. 3. The instruction emphasizing the importance of the structure of mathematical problems could be one of the methods cultivating student`s problem-solving ability.
송전선 상시 운전 시 통신선 유도전압 계산 시뮬레이터 개발
한웅(Woong Han),권오상(O. S. Kwon),허정용(J. Y. Heo),김철환(C. H. Kim),정창수(C. S. Jung),유연표(Y. P. Yoo) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
본 논문에서는 송전선 상시 운전 시 통신선에 미치는 유도전압 계산 시뮬레이터를 개발 하였다. 본 시뮬레이터는 Visual C++를 이용하여 개발되었으며, 송전탑 및 도선의 데이터들을 입력함으로써 통신선 유도전압을 계산할 수 있다. 또한, 본 시뮬레이터는 EMTP 프로그램을 내장하여 동작하며 GUI 방식으로 설계되어 보다 손쉽게 유도전압을 계산할 수 있다.
김철환(C.H.Kim),전광민(K.M.Chun),이진호(J.H.Lee) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.11_1
In this study, numerical calculation is carried out to investigate the influence of injection timing and fuel amount on Nitric Oxide(NO) formation using a two-zone model in a diesel engine. Results can be summarized as follows.<br/> The NO formation is very sensitive to burned gas temperature, so multi-zone model must be applied to combustion process to predict burned gas temperature exactly. Since burned gas temperature increase rapidly during the premixed combustion. Most NO is formed within 20 degree crank angle after ignition. As the injection timing is retarded, the combustion occurs later in the expansion process which causes the decrease of burned gas temperature and, as a result. NO formation decrease. The increase of fuel amount results in the increase of earlier formation of NO in the engine<br/>