• Journal of the Korean Chemical Society
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• v.58 no.1
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• pp.126-129
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• 2014

Concerning the difficulty of learning science and reduced interest in science, the authors of this study searched for potential threshold concepts which are portals or gateways in the field of science (particularly chemistry). The nature of these concepts and how to overcome their troublesomeness were further questioned. For this study, 239 high school students completed chemistry II provided information about what difficult concepts and potential threshold concepts in high school chemistry are and how they affect learning chemistry. In particular, the mastery experience of the threshold concepts was explored in detail. Two, "mole and atomic structure" were selected as threshold concepts in chemistry. Not only as important but also as threshold, this study emphasized the importance of the two concepts in terms of features characterizing them as threshold concepts. In particular, the features objectify subjective experiences of students and provide information describing the scientific meaning and distinctive nature of threshold concepts in science. Along with the data from teachers, this study shows the integrative feature as key criteria for students to make meaningful understanding of the two threshold concepts.

• Journal of the Korean Chemical Society
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• v.53 no.4
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• pp.445-452
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• 2009

In this study, the influences of the context of discrepant events on the conceptual change process using cognitive conflict strategy were investigated in terms of students' cognitive and motivational variables such as cognitive conflict, situational interest, attention, effort, conceptual understanding. A preconception test was administered to 536 seventh graders. A test of response to a discrepant event and a situational interest questionnaire were then administered. The context of discrepant events, either scientific or everyday, was randomly presented to the subjects. After learning the concept of density, the tests of attention, effort, and conceptual understanding were administered. The reponses of 194 students who had been found to possess the target misconception were analyzed. The results revealed that the scientific-context discrepant event induced higher cognitive conflict than everyday-context one. The context of discrepant events, however, did not show significant correlations with situational interest, attention, effort, and/or conceptual understanding. The result of path analysis indicated that the context of discrepant events both directly influenced cognitive conflict and indirectly influenced conceptual understanding via cognitive conflict.

• Analytical Science and Technology
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• v.30 no.6
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• pp.319-328
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• 2017

The identification of explosive residues on specimens obtained from an explosion event is a crucial factor for assessing the cause of the explosion. In order to detect the components of explosives, the explosive residues deposited on surfaces are commonly extracted using swabbing materials pre-wetted with an organic solvent. The residues are then analyzed with analytical instruments such as LC/MS and CE/MS. Most conventionally used swabbing media such as cotton swabs or cotton tip swabs seem unsuitable for extracting explosive residues from the surface of a large area of clothes because the swabbing materials tend to be damaged easily, and because only a relatively small amount of explosives is collected. To overcome these problems, we have introduced a novel wiper ($215{\times}210mm$, single layer, Yuhan-Kimberly, Republic of Korea) as a swabbing material to recover representative organic explosives, namely, TNT, RDX, tetryl, HMX, PETN, and NG, from a large area of clothes. Different sides of the wiper, which was folded in half five times, was used to swab the surface of a clothing. We compared this novel wiper with a cotton swab and a cotton tip swab in terms of the recovery efficiency for the aforementioned organic explosives by pre-wetting with methanol, acetone, and acetonitrile, respectively. We identified that this novel wiper collected a significantly higher amount of organic explosive residues than a cotton swab or a cotton tip swab when using methanol as an extracting solvent.

• Journal of The Korean Association For Science Education
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• v.25 no.6
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• pp.678-688
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• 2005

The main objective of this study was to investigate Korean university students' understanding of the structure of the atom based on a Lakatosian view. In this study, we examined twenty-three Korean university students' understandings of atomic structure using an open-ended questionnaire. The participants were all junior students majoring in chemistry education in Korea. The characteristics of students' understanding were categorized into three philosophical stances based on the classification criteria. Assertions were constructed concerning students' written descriptions of the development of scientific knowledge with respect to atomic structure: (a) characteristics of positivist response; (b) characteristics of transitional response; (c) characteristics of Lakatosian response; and (d) tendencies in students' responses.

• Journal of Environmental Science International
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• v.6 no.3
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• pp.213-218
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• 1997

The question style In high school enoronmental science textbook was examined in terms of the placement, frequency, and type of question, and then analyzed the kind of scientific Inquiry process elicited by the question In the topic of textbook using the Tektbook guestioning Strategy Assessment Instrument (TQSAI). The average number of question per topic was only 0.6. The number of all Question In the high school enororunental science textbook was very little : the number of non-experiential Question was 8 and that of experiential one was 3. The total number of sentence was 1,236 and the ratio of the number of Question to that of sentence was 0.9% . The frequency of non-experlential question was higher than that of experiential one. In action part of the textbook, there were more kinds of Question styles than In the matin part.

• Journal of the Korean Chemical Society
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• v.65 no.6
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• pp.455-467
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• 2021

The purpose of this study was to investigate the impact of negotiation-based peer and self-assessment activities on science-gifted students' modeling and students' perceptions of the impact of these assessment activities on modeling. For this purpose, 92 students in the 11th grade of a science high school, in a metropolitan city, were selected to conduct peer assessment, self-assessment, and science writing activities with four topics of Advanced Chemistry. The students' modeling was analyzed in terms of 'structuring scientific concepts', 'logic', 'multiple representations' and 'communication'. Based on the results, the mean scores of modeling increased for each element of evaluation according to the progress of assessment activities. Students' responses in the survey and interviews showed that students perceived the results of student assessment activities as valid, students also recognized the benefit of these assessment activities by referring to the assessment results before their next writing assignment.

• Journal of the Korean Chemical Society
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• v.43 no.6
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• pp.699-706
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• 1999

The purpose of this study was to investigate high school students' conceptions and conceptual types on molecular kinetic theory of gases. Data was collected by a series of semi-structured and in-depth interviews, and has been analyzed. This study showed that the students came to science classes with various prior conceptions of many disciplinary topics. Their conceptual types of their prior knowledge were distinguished as superficial terms-speaking, partial sense-making, and causal sense-making by the degrees of organization and elaboration of conceptual networks. These conceptual types had influence on the ways students understand and think of science, a stability of their conceptions, a tendency to distinguish school science from everyday science, and building a meaning of concept in contexts. It was referred that the students didn't have proper understanding on the nature of scientific knowledge and had been limited their participations as active learners. Therefore, in order for students to experience conceptual change, they must have opportunities of manifesting their own thinking, taking part in discussions, and promoting their motivations and metacognition of knowing and learning science.

• Journal of The Korean Association For Science Education
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• v.31 no.4
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• pp.491-504
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• 2011

We investigated science-gifted students' conceptions on science learning. The inventory instruments used for our study were a questionnaire on the conceptions of learning science (COLS) and a questionnaire on the approaches to learning science (ALS). Our analysis of the questionnaires showed that there are differences in the conceptions of science learning between the science-gifted and ordinary students. Science-gifted students perceive science learning as storing up of scientific knowledge, expansion of knowledge structure and achievement of a new view. There are no differences in the conceptions of science learning between male and female science-gifted students. There are also no differences in the conceptions of science learning in terms of subject preference such as physics, chemistry, biology and earth science. Our analysis offer assistance to teaching material and teaching method for science courses.

• Journal of Powder Materials
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• v.8 no.3
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• pp.157-162
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• 2001

An optimum route to fabricate the ferrous alloy dispersed $Al_2O_3$ nanocomposites such as $Al_2O_3$/Fe-Ni and $Al_2O_3$/Fe-Co with sound microstructure and desired properties was investigated. The composites were fabricated by the sintering of powder mixtures of $Al_2O_3$ and nano-sized ferrous alloy, in which the alloy was prepared by solution-chemistry routes using metal nitrates powders and a subsequent hydorgen reduction process. Microstructural observation of reduced powder mixture revealed that the Fe-Ni or Fe-Co alloy particles of about 20 nm in size homogeneously surrounded $Al_2O_3$, forming nanocomposite powder. The sintered $Al_2O_3$/Fe-Ni composite showed the formation of Fe$Al_2O_4$ phase, while the reaction phases were not observed in $Al_2O_3$/Fe-Co composite. Hot-pressed $Al_2O_3$/Fe-Ni composite showed improved mechanical properties and magnetic response. The properties are discussed in terms of microstructural characteristics such as the distribution and size of alloy particles.

• Korean Journal of Agricultural Science
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• v.49 no.4
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• pp.919-926
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• 2022

Fertigation, which has been introduced in agricultural fields since 1990, has been widely practiced in upland fields as well as in plastic film houses as part of the crop production system. In accordance with demands in the agricultural sector, a huge number of scientific studies on fertigation have been conducted worldwide. Moreover, with a combination of advanced technologies such as big-data, machine learning, etc., fertigation is positioned as an indispensable tool to achieve sustainable crop production and to enhance nutrient and water use efficiency. In this review, we focused on providing valuable information in terms of crop production and nutrient/water use efficiency. A variety of fertigation studies have described that enhancement of crop production did not differ relative to conventional method or slightly increased. In contrast, fertigation significantly improved nutrient/water use efficiency, with a reduction in use ranging from 20 to 50%. Water-soluble organic resources such as livestock manure and agricultural byproducts also have been identified as useful resources like chemical fertilizers. Furthermore, the initial irrigation point was generally recommended in a range of -10 - -40 kPa, although the point differed according to the crop and crop growth stage. From this review, we suggest that fertigation, which is closely integrated with advanced technology, could be a leading technology to attain not only food security but also carbon neutrality via improvement of nutrient/water use efficiency.