• Current Applied Physics
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• v.18 no.12
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• pp.1540-1545
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• 2018

SiGe alloy is widely used thermoelectric materials for high temperature thermoelectric generator applications. However, its high thermoelectric performance has been thus far realized only in alloys synthesized employing mechanical alloying techniques, which are time-consuming and employ several materials processing steps. In the current study, for the first time, we report an enhanced thermoelectric figure-of-merit (ZT) ~ 1.1 at $900^{\circ}C$ in ntype $Si_{80}Ge_{20}$ nano-alloys, synthesized using a facile and up-scalable methodology consisting of rapid solidification at high optimized cooling rate ${\sim}3.4{\times}10^7K/s$, employing melt spinning followed by spark plasma sintering of the resulting nano-crystalline melt-spun ribbons. This enhancement in ZT > 20% over its bulk counterpart, owes its origin to the nano-crystalline microstructure formed at high cooling rates, which results in crystallite size ~7 nm leading to high density of grain boundaries, which scatter heat-carrying phonons. This abundant scattering resulted in a very low thermal conductivity ${\sim}2.1Wm^{-1}K^{-1}$, which corresponds to ~50% reduction over its bulk counterpart and is amongst the lowest reported thus far in n-type SiGe alloys. The synthesized samples were characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy, based on which the enhancement in their thermoelectric performance has been discussed.

• Journal of Korean Elementary Science Education
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• v.39 no.3
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• pp.382-398
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• 2020

This study aims to analyze the relationship between scientific content knowledge of science-gifted elementary students and their expression of scientific creativity, and the characteristics of divided groups according to the levels of their scientific content knowledge and scientific creativity. A science-gifted program was implemented to 33 forth-graders in the Science-Gifted Education Center of an education office in Seoul, Korea. The method of evaluating scientific knowledge was divided into well-structured paper-pencil test (asking specific and limited range of content knowledge of plants) and ill-structured descriptive test (stating all the knowledge they know about plants) to find out which methods were more related to scientific creativity. In addition, in order to find out the characteristics of each group according to the level of scientific content knowledge and scientific creativity, students were required to answer a questionnaire about their own self-perception of scientific knowledge and scientific creativity and how to obtain scientific knowledge. The main results of this study are as follows. First, Both well-structured paper-pencil test (r=.38) and ill-structured descriptive test (r=.51) results of elementary science gifted students were significantly correlated with scientific creativity. Second, As a result of the regression analysis on scientific creativity of science-gifted elementary students, both the knowledge measured by the two evaluation methods have the ability to explain scientific creativity. Third, the students were categorized into four groups according to the levels of their scientific content knowledge and their expression of scientific creativity, and the result showed that the higher the knowledge of science, the higher the scientific creativity. Fourth, the description about self-perception of scientific knowledge revealed that the highest percentage of Type LL students of all 13 students (53.8%, 7 students) answered 'I have little knowledge of plants because I have little interest in them.' Fifth, the description about self-perception of scientific knowledge revealed that the highest percentage of Type HH students of all 15 students (40%, 6 students) answered 'I think my science creativity is high through my experience of scientific creativity. Sixth, the responses to the Questionnaire revealed that 'reading' was the most popular way to obtain scientific knowledge, with 27 out of total 33 students choosing it. In particular, all 18 students from Type HH (high scientific knowledge and high scientific creativity) and Type HL (high scientific knowledge and low scientific creativity) - those with high scientific knowledge - gave that response. On the basis of this research, we should explore practical teaching methods and environment for gifted students to improve their scientific creativity by revealing the nature of the factors that affect scientific creativity and analyzing relationship between knowledge and scientific creativity.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.74.3-74.3
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• 2008

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.74.4-74.4
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• 2008

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.12.1-12.1
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• 2008

• Journal of Korean Elementary Science Education
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• v.37 no.4
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• pp.372-390
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• 2018

The purpose of this research is to know the scientific reasoning ability of elementary students. In order to find it, 320 elementary students wrote a report about germination of the 700 or 2,000 years old seeds. Their writings were analyzed by scientific writing analysis frameworks, Scientific Reasoning Types and Scientific Reasoning Level Criteria developed by Lim (2018). Minto Pyramid Principles was used to show statements and relations of statements related to scientific reasoning. This paper showed scientific reasoning statements of elementary students about germination of seeds. The characteristics of scientific reasoning of elementary students were as follows. In the process of logical writing by the types of scientific reasoning, many students showed various characteristics and different levels. In the writings based on inductive reasoning, they did not distinguish between common features and differences of cases, and did not derive the rules based on common features and differences of the cases. In the writings based on deductive reasoning, there were cases where the major premise corresponding to the principle or rule was omitted and only the phenomenon was described, or the rule was presented but not connected with the case. In the writings based on abductive reasoning, the ability to selectively use the background knowledge related to the question situation was not sufficient, and borrowing of similar background knowledge, which was commonly used in other situations, was very rare.

• Composites Research
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• v.29 no.4
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• pp.173-178
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• 2016

Graphene oxide (GO) was concurrently reduced and functionalized using long alkyl chain dodecyl amine (DA). The DA functionalized GO (DA-G) was assumed to disperse homogenously in linear low density polyethylene (LLDPE). Subsequently, DA-G was used to fabricate DA-G/LLDPE composites by melt mixing technique. Fourier transform infrared spectra analysis was performed to ascertain the simultaneous reduction and functionlization of GO. Field emission scanning electron microscopy analysis was performed to ensure the homogenous distribution and dispersion of DA-G in LLDPE matrix. The enhanced storage modulus value of the composites validates the homogenous dispersion of DA-G and its good interfacial interaction with LLDPE matrix. An increased in tensile strength value by ~ 64% also confirms the generation of good interface between the two constituents, through which efficient load transfer is possible. However, no significant improvement in glass transition temperature was observed. This simple technique of fabricating LLDPE composites following industrially viable melt mixing procedure could be realizable to developed mechanically strong graphene based LLDPE composites for future applications.

• Korean Journal of Childcare and Education
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• v.17 no.1
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• pp.41-63
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• 2021

Objective: The purpose of this research was to examine the effects of an 'Ice' project, a topic chosen based on children's interests to discover the improvement of scientific and mathematical abilities, and creativity of four-year-old children. Methods: For this research, 34 four-year-old children from M childcare center were selected. Seventeen children were placed in the experimental group and the remaining 17 children were placed in the comparison group. After the project was completed, to observe the differences between the two groups, the Mann-Whitney U test was conducted. Results: First, the 'Ice' project had an effect on improving children's scientific abilities and its subfactors. Second, the 'Ice' project hadsignificant effects on improving children's algebraic and geometric mathematical skills. Third, excluding the resistance to premature closure among the subfactors of creativity, the 'Ice' project contributed to improve children's creativity and all sub-factors. Conclusion/Implications: The 'Ice' project activities, a subject chosen from the interests of children, led active play participation from children and brought positive effects in immersion of play and activity. Such effects proved to affect children's scientific abilities, mathematical abilities, and creativity, and suggest this research can be used as base line data in follow-up research on various project activities.

• Carbon letters
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• v.16 no.4
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• pp.275-280
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• 2015

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.73-75
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• 2007

Micro-cell LC film and polymer network liquid crystal (PNLC) film by using continuous compatible process have been developed . A high-contrast micro-cell LC film has a strong potential as a high-performance flexible device. PNLC film has the low driving voltage. Both films show the characteristics of lightness, thinness and mechanical stability.