• Journal of Korean Elementary Science Education
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• v.24 no.5
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• pp.518-530
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• 2005

The purpose of this study was to investigate the characteristics of pre-service primary teachers' justifying their hypotheses about the brightness of electric bulbs. They conducted their experiments and wrote their experimental results and ideas on their worksheets. The worksheets for generating and evaluating scientific hypothesis were analyzed. Most of them generated the consumption hypothesis and designed the experiments to confirm their hypotheses or directly measure without the change of experimental conditions. The responses for valid experimental designs were $74\%$ of total responses. The $62\%$ of total responses was valid prediction for experimental results. The $60\%$ of pre-service teachers described the experimental results correctly. But other teachers described the biased results or inappropriate results. The $54\%$ of them refuted hypotheses and the $36\%$ confirmed their hypotheses. The theory-based responses were $51\%$ and the evidence-based responses were $47\%$. The $64\%$ of them proposed the possibility of the alternative hypothesis after testing their hypotheses. This study also discussed the implications of these findings for teaching and Loaming in science education.

• Journal of Korean Elementary Science Education
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• v.25 no.1
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• pp.70-88
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• 2006

The purpose of this study is to investigate the effect of a multiple cognitive conflict strategy at remedying student's misconceptions. Elementary students have many misconceptions about the brightness of the electric bulb in simple dual circuits. Most of the misconceptions can be summed up as 'the more batteries or the fewer bulbs, the brighter is the output.' The students have learned about the brightness of the electric bulb while connected to a battery in Grade 4 and the brightness of multiple electric bulbs in Grade 5. However, about $50%$ of the students remain with the firm misconception that the brightness of the bulb is related to the number of source batteries. This strong misconception may not lead to a conceptual change in the case of only one cognitive conflict. This study used a multiple conflict strategy while tackling the cognitive conflicts in the students as they solved the problems many times. It involved 160 grade 5 students. The result was they often changed their misconceptions and used more scientific thinking than the same grade students of other schools. It remains to be seen if this success will transfer to other schools and students and we intend on studying further the differences in students regarding this learning process.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.3
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• pp.235-240
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• 2007

Recently, energy saving buildings are interested in many parts and many types of thermal insulating materials have been developed. The temperature and brightness of inside and outside building are influenced by weather change and sun's brightness and location. The location of building considering the natural daylight is an important parameter to build a building. To modeling the natural daylight, we used 342 electric bulbs which mean artificial daylight. All these bulbs are installed on dome shape frame. Especially it is focused on the luminosity control of each bulb in this paper. The luminosity of bulbs is controlled by phase control using several PIC microprocessors and triacs.

• Journal of The Korean Association For Science Education
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• v.19 no.4
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• pp.570-584
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• 1999

The units about electricity in 5th and 6th science curriculum for elementary school was analyzed and the elementary students' understanding of related concepts was investigated. This study was to make connection between the research about alternative concepts and writing textbooks. It was found that students' response had following characteristics. They had strong belief that the + and - ends of battery should be connected. However this belief was not complete because students did not understand that the other circuit elements had to be connected properly. When the circuit involve more than one bulbs or batteries, they counted the number of batteries or bulbs only and paid little attention to the connection of them. In explaining circuits and the brightness of the bulbs in the circuits. students tried to explains the circuit using scientific terms but failed to used them properly. Although the concept of resistance was not dealt explicitly. student had reasonable qualitative understanding about resistance. According to response of students, several suggestions might be made for the curriculum. The structure and the circuit elements and the proper connection needs to be taught. Also more emphasis is necessary to pay attention to the connection in addition to the numbers of bulbs or batteries. Finally, it needs to be investigated carefully if it is better to introduce some qualitative model to explain the amount of current through bulb depending on the connection and the number of bulbs. It might also be better to introduce some terms, such as current and resistance with the model.

• Journal of Korean Elementary Science Education
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• v.24 no.3
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• pp.259-267
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• 2005

This study was to investigate the elementary students' preconception on the brightness of electric bulb and degree of consistency on their preconceptions. Participants were 160 students of fifth graders in Seoul area. They had already teamed about the brightness of series circuit and parallel circuit of batteries. After they solved six problems in the same context, we provided them a pair of circuit which was an anomalous situation. And then they conducted CCLT (Cognitive Conflict Level Test). Elementary school students showed various preconceptions when they explained the light of bulb of two Simple electric Circuits. Many Students Consistently Showed the Scientific misconceptions like 'the light of bulb of two simple electric circuits was that the more batteries and the fewer bulbs were brighter.' The level of consistency that students presented scientific misconceptions was grouped all of four, such as 'high, middle, low, and nothing.' Therefore the higher scientific achievement they have, the higher consistency they have. As the students had high consistency level, they revealed high cognitive conflict level significantly. This high consistency will help them to change their preconception on the brightness of electric bulb and their cognitive conflict.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.358-365
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• 2011

Recently, the LED(Light Emitting Diode) replacing incandescent light bulbs and fluorescent light has great attentions as a most promising candidate for the next generation lighting source due to its environment-friendly characteristics, long life and excellent efficiency. Moreover, since it is a semiconductor device which can convert the electric energy to visible light at a very high speed, it can also used as a communication device. Therefore, the VLC(Visible Light Communication) using the LED can perform the near field communication and lighting function at the same time without additional expenses. However, since the switching device of the conventional LED driver for VLC is operated in the linear region, there exist several drawbacks such as a poor power conversion efficiency and serious heat generation. On the other hand, since the proposed driver is operated in the on/off switching region, it features a higher efficiency and more improved heat generation. To verify the validity of the proposed LED driver, experimental results from a prototype of 20W rated LED driver applied to 3MHz bps broadcasting audio system are given.