• Journal of The Korean Association For Science Education
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• v.32 no.5
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• pp.991-1006
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• 2012

The purpose of this research is to find factors that affect high school science teachers' class compositions. In this research, we developed the class composing factor analysis framework and we observed teachers' class to figure out the class composing factors. The results from this research were as follows: First, the class composing factor was classified with 'positive motive factor' and 'negative motive factor'. It is the positive motive factor that teachers' voluntary motives operate to teacher for class compositions. It is the negative motive factor that outer demands operate to teacher for class compositions. Second, both positive and negative motive factors were shown in all the steps, which included preparing a class, progressing a class, and after a class. Also, according to the circumstances, each factor changed. Minimizing and overcoming negative motive factors will lead to positive interaction between the teacher and students. It will also increase a teachers' achievements in class and maximize the effectiveness of class. Therefore, it is expected that this will be a great help for teachers to enhance their teaching professionalism.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.34-40
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• 2006

This paper proposed power system for new DC 49[V] telecommunication using forward three-phase PWM rectifier power factor and efficiency for improvement of ripple voltage. Proposed power system for DC 48[V] telecommunication that consists of power conversion devices including switch, inductor and condenser were made between each line, in power inverter device of each switch control turn-on in period of continuity time control to get power factor '1' of sine wave current and on-off of switch lessens peak current that was happened and got conversion efficiency 92.1[%] composing in PWM rectifier of forward form instead of general PWM rectifier. Also, harmonic input regulation value(IEC61000-3-2 Class-As) satisfy input current and reduce ripple factor of output voltage in state that distortion of three-phase supply is overlapped each other.