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최재화(Jaehwa Choi),공혜란(Hyeran Kong),박형원(HyungWon Park),배중호(Jungho Bae),이광범(Gwangbeom Lee),권해붕(Haebung Gwon) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
Energy consumption of electric vehicle is mainly affected by ambient temperature. While a few electric vehicles is driven in a public institution, a decrease in driving range and a increase in charging time are raised as issues in winter. This study evaluate energy consumption on the basis of vehicle road test in variation of ambient temperature. And we presume driving range in effective using area of battery. Also charging characteristics is researched by in valid of ambient temperature.
납축전지와 리튬전지에 의한 전기모터 출력특성 분석 연구
최재화(Jaehwa Choi),이광범(Kwangbum Lee),최동석(Dongseok Choi),김광일(Kwangil Kim),용기중(Geejoong Yong) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
Compliance tests of electric motor for vehicle driving were performed to characterize performance of the motors by battery types. Two different batteries were used for testing the net power and the maximum 30minute power. One is Pb-battery. The other is Lithium-battery. According to the Korean safety regulation, the electric power analysis was conducted and the temperature inside the motor was measured. It was found that electric driving motor using several kinds of voltage changed net power. If voltage of battery is changes, net power should be reconfirmed.
A Comparison of Different Approaches for Coefficient Alpha for Ordinal Data
최재화(Jaehwa Choi),Maggie Dunlop, Jinsong Chen, 김석우(Sukwoo Kim) 한국교육평가학회 2011 교육평가연구 Vol.24 No.2
이 연구의 목적은 서열자료의 크론바흐 알파계수에 대한 두 가지 추정방법, 즉 요인분석에 기초한 방법과 새롭게 제안된 다항 상관계수 행렬를 이용한 방법을 비교하는 것이다. 또한, 다항 상관계수 행렬방법에서 두 가지 베이지안 추정법 즉, 기대사후확률법과 최대사후확률법을 추가적으로 비교하였다. 이 연구에서는, 최대사후확률법을 이용한 다항상관계수 행렬을 이용한 방법이 다른 방법들에 비하여 추정치를 항상 추정할 수 있는 점과, 모수에 대한 추정치의 정확도가 높다는 점에 있어서 우월한 것으로 밝혀졌다. 연구방법으로는 몬테카를로 시뮬레이션 기법이 이용되었으며, MATLAB과 BayesPCC 프로그램이 사용되었다. This study aims to compare two different estimation methods of coefficient alpha with ordinal data, the factor loading based method and the proposed polychoric correlation matrix based method, under various conditions. Furthermore, for the polychoric correlation matrix based approach, this study also compares two Bayesian estimates, i.e., expected a posteriori (EAP) and maximum a posteriori (MAP) estimates, for the polychoric correlations. A Monte Carlo simulation is used for this comparison by a specialized program code in MATLAB and BayesPCC.