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우리나라와 인도의 수학 교과서 과제 비교: 정수와 유리수를 중심으로
김재헌(Kim Jaehun),이아란(Lee Ahran),권오남(Kwon Oh Nam) 학습자중심교과교육학회 2019 학습자중심교과교육연구 Vol.19 No.17
본 연구는 정수와 유리수 단원의 과제에 대한 시사점을 도출하기 위하여 우리나라와 인도의 중학교 수학 교과서 과제를 비교하였다. 이를 위해 우리나라 교과서 종, 인도 교과서 종을 선정하여 년 월부터 약 개월 동안 과제의 인지적 노력수준(cognitive demands)을 분석한 후 대수적 사고(algebraic thinking)를 비교하였다. 그 결과 우리나라 교과서에는 낮은 인지적 노력수준의 과제가 인도보다 많고, 높은 인지적 노력수준의 과제가 인도보다 적은 것으로 나타났다. 대수적 사고와 관련하여 인도 교과서는 연산의 기본 성질을 모든 인지적 노력수준의 과제에서 다루고 있다. 또한 실생활 문제로부터 양적 관계를 표현하거나, 공변추론을 요구하는 과제는 인도 교과서에만 있는 것으로 나타났다. 이러한 연구 결과를 바탕으로 정수와 유리수의 교과서 과제에 대한 향후 시사점을 제언하였다. This study compared the tasks in middle school mathematics textbooks used in Korea with those used in India, focused on integers and rational numbers. The purpose of this work is to propose implications for the tasks in mathematics textbooks, focused on integers and rational numbers. For this study, the tasks in Korean textbooks and Indian textbook were analyzed for months starting from June to investigate levels of cognitive demands. Also, algebraic thinking required in those tasks was compared for each level of cognitive demands. This study shows that, first, there are fewer high level tasks (PWC task, DM task) in the Korean textbooks than in their Indian counterpart. Second, with respect to algebraic thinking, the Indian textbook presents tasks which can help students understand fundamental properties in all cognitive level tasks. Also, the tasks in the Indian textbook require students’ quantitative reasoning in real situations and covariational reasoning. Based on these results, this study suggests some implications for the tasks focused on integers and rational numbers.
윤성민(Sungmin Yoon),김재헌(Jaehun Kim),서정민(Jungmin Seo),이중훈(Joonghoon Lee),송두삼(Doosam Song) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7
Airflow in building caused by stack-effect may have a significant impact on heating load in high-rise residential buildings under winter season in Korea. While, building load caused by airflow is considered as infiltration only in a conventional building load calculation. However, with the building height is higher and higher and the outdoor air temperature is colder and colder, the airflow caused by stack-effect in a high-rise building seriously affects on building load. Therefore, it is necessary to consider the airflow caused by stack-effect in calculation of the building load. In this paper, the effect of airflow caused by stack-effect on heating load in a high-rise residential building will be analyzed by measurement and whole building simulation method.
전동식 과급시스템을 이용한 HEV전용 고효율/고성능 밀러싸이클 엔진 연구
홍승우(Seungwoo Hong),한동희(Donghee Han),이관희(Kwanhee Lee),강현진(Hyunjin Kang),김재헌(Jaehun Kim),구자언(Jaeon Gu),임종석(Jongsuk Lim),박한용(Hanyong Park),김도완(Dowan Kim),팽용석(Yongsuk Pang),박귀열(Guiyeol Park) 한국자동차공학회 2020 한국자동차공학회 부문종합 학술대회 Vol.2020 No.7
A Miller Cycle engine based on a hybrid electric vehicle (HEV) dedicated boosting system, working in great synergy with a HEV abundant in electric power capacity, has been studied to improve the efficiency and performance of the HEV. Conventional turbocharged boosting system in an internal combustion engine dedicated vehicle grants fuel economy benefits thanks to engine downsizing. In a HEV, an electric motor governs the operating region of the engine, limiting the fuel economy benefits of said downsizing approach. Moreover, turbocharging reduces exhaust energy for the catalytic converter while increasing the back pressure, leading to adverse effects on emissions and fuel economy. This paper discusses the HEVdedicated Miller Cycle engine, which can boost the intake pressure without increasing the back pressure. In addition, the energy of the exhaust gas can be used in its entirety for the catalytic converter, thus favorable for emission reduction. An intake manifold integrated with a water-cooled intercooler was used, lowering the volumetric efficiency while realizing high charge cooling effects. The HEV-dedicated Miller Cycle engine was tested in a vehicle for fuel consumption in various drive cycles. In comparison to the base HEV, a similar level of fuel economy was achieved for the FTP-75 and HWFET combined drive cycle. For the more aggressive US-06 drive cycle, a 4.1% fuel economy improvement was realized. Furthermore, a 20% improvement in vehicle dynamic performance was observed in various conditions; a result of both engine output increase by the HEV-dedicated boosting system and the fast response of the electric supercharger.