• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.179-189
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• 2001

The determination of trace concentration of U, Th and Pb was carried out for chemical dating of zircon and monazite by electron microprobe. Detection limit and error range should be considered to measure characteristic X-rays of M-line from those minerals, which are low in the ionization of atom and low peak intensity in the spectrum. The element of U, Th and Pb were simultaneously measured with 3 spectrometers equipped with PET crystal to reduce a total counting time and error due to drift of instrumental operating condition. Detection limit could be improved from increase of the peak/background ratio through adjusting pulse height analyzer about 1000 mv baseline. Under permissible maximum analytical conditions, theoretical detection limit of U, Th and Pb is down to 30 ppm (99% confidence level). The analytical result was maintained at a relative error $\pm$10% ($2{\sigma}$) in 800 ppm Pb, $\pm$5% ($2{\sigma}$) in 2330 ppm U and $\pm$10% ($2{\sigma}$) in dating from a single measurement of zircon at 15 keV and 100 nA. However, for the precise dating of zircon and monazite, if it is considered a 3 $\mu\textrm{m}$ spatial resolution, <100 ppm ($3{\sigma}$) detection limit and <$\pm$10% ($2{\sigma}$) relative error, optimum analytical conditions are given as 15~20 keV accelerating voltage, 100~200 nA beam current and 300~1200 sec total counting time. To reduce material damage by high current, there is need to be up to 3~5 $\mu\textrm{m}$ of electron beam diameter, or to use arithmetic average of multiple measuring at a shorter counting time. A younger or relatively low concentration rocks can be dated chemically by lower detection limit and improved precision resulted from increase of current and measuring time.

• Korean Journal of Food Science and Technology
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• v.26 no.3
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• pp.204-212
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• 1994

To estimate the possibility of wine-making with Korean dried persimmon, its homogenized and filtered solution was fermented at $15^{\circ}C$ and $25^{\circ}C$ for 12 weeks with Saccharomyces cerevisiae (Japan Alcoholic Beverage Association N0.7). Sugars of dried persimmon were mainly composed of 27.02% of glucose, 19.81% of fructose and 5.12% of mannose. In the fermentation at $25^{\circ}C$, glucose was almost completely consumed in 8 days, but fructose and mannose were consumed up to 64% and 74%, respectively, in the same period and were not utilized any more afterwards. In the fermentation at $15^{\circ}C$, 75% of glucose, 20% of fructose and 49% of mannose were consumed in 8 days and these sugars were continuously utilized for 12 weeks. Organic acids in the homogenized and filtered solution were levulinic acid (148.6 mg%), 4-methylvaleric acid (73.5 mg%), oxalic acid (28.7 mg%), acetic acid (8.5 mg%), N-butyric acid (8.4 mg%) and succinic acid (6.7 mg%). Irrespective of fermentation temperature, levulinic acid rapidly reduced according to progression of fermentation. Oxalic acid, N-butyric acid and succinic acid decreased at 2nd day of fermentation, and then increased at 4th and 6th days and subsequently decreased again under the levels of the solution. Acetic acid and 4-methylvaleric acid increased with the proceeding of fermentation and at 12th week of fermentation these contents were more than those of the solution. The contents of total free amino acid significantly reduced at 2th day of fermentation and then increased to the level of the solution at 12th week irrespective of fermentation temperature. Ethanol content rapidly increased to the levels of 5.3(v/v) at $15^{\circ}C$ and 9.4%(v/v) at $25^{\circ}C$ to 8th day after fermentation, but at 12th week its content was 14.5%(v/v) at $15^{\circ}C$ and 9.4%(v/v) at $25^{\circ}C$. The higher alcohots identified were 2-methyl-l-propanol, 3-methyl-ibutanol, 2-methyl-l-butanol and 2-methyl-2-propanol and the range of those contents was from 0.001% (v/v) to 0.06%(v/v). The color of the wine fermented at $15^{\circ}C$ was slightly superior but flavor and taste were slightly superior in the wine fermented at $25^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.51 no.3
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• pp.270-278
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• 2007

In this study, we investigated the effects of grouping with respect to the level of students' agreeableness on 6th graders' science achievement, self-efficacy, and science learning motivation in cooperative learning. Three classes (72 students) from an elementary school were randomly assigned to a control group and treatment groups. An agreeableness test, self-efficacy test, and science learning motivation test were administered as pretests. The students of the treatment groups were grouped either homogeneously or heterogeneously on the basis of their agreeableness levels and were taught with a cooperative learning strategy, whereas the students of the control group were randomly grouped and were taught with a traditional method. The cooperative learning intervention lasted for 5 weeks (16 class periods). After the instructions, tests regarding achievement, self-efficacy, and science learning motivation were administered as posttests. The results indicated that the students of the homogeneous and/or the heterogeneous groups significantly outperformed those of the control group in the achievement test. However, students' achievement was not influenced by the grouping method on the basis of students' agreeableness. No significantly differences among the groups were found in the self-efficacy and science learning motivation.

• Journal of The Korean Association For Science Education
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• v.20 no.1
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• pp.43-51
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• 2000

In this study, the effects of extraversion/introversion grouping and the differences between extroverts and introverts in cooperative learning strategy applied to general science class were investigated. Ninety-three 10th-graders were grouped into homogeneous and heterogeneous cooperative groups with respect to extraversion and introversion, and were taught about matter for 10 class periods. Prior to the instructions, three tests regarding the extraversion/introversion, logical thinking, and learning motivation were administered. After the instructions, their achievements, process skills, self-esteem, communication apprehension, and learning motivation were examined. Two-way ANCOVA results revealed that there were no main and interactive effects in the scores of the achievement and the process skills tests. However, significant interactive effect was found in the self-esteem. While the difference in the self-esteem of the introverts and the extroverts was small in the homogeneous group, the self-esteem of the extroverts was higher than that of the introverts in the heterogeneous group. The communication apprehension of the introverts was significantly lower than that of the extroverts. Students' perceptions to their group activities and group members were also studied.

• Korean journal of communication and information
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• v.50
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• pp.50-72
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• 2010

The purpose of this study was to investigate representation of media on Korean controversial historical incidents and its myth and ideology. Especially the authors paid attention to the MBC-TV Documentary which had dealt with many controversial issues in Korean society. Those issues had never been dealt by other Korean media before it began to do. Three episodes about the South-North Korea related issues were selected as main object of this study and were analyzed with various semiotic research methods, especially, paradigmatic analytical method, narrative analytic method and mythical analytic method. As a main result of this study, it was found that the Documentary tended to represent such controversial historical issues very differently from the previous representations of old newspapers'. Th e old newspapers tried to establish old myths; that is, 'myth of national crisis', 'myth of anti-communism', 'myth of scapegoat of college students', 'myth of intelligent agency's monopoly', 'myth of social stablization', etc, while the documentary changed to build up new myths; that is, 'myth of humanities', 'myth of peaceful unification', 'myth of freedom and democracy', 'myth of human rights, etc.' In short, it was concluded that the documentary was able to change some previous myths and ideologies through its changing representations.

• Journal of The Korean Association For Science Education
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• v.35 no.6
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• pp.1063-1074
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• 2015

In this study, we developed an analogy-generating strategy and applied this to a 7th grade science-gifted class. The types of analogies they generated, verbal interactions and analogy-generating patterns, and perceptions of five groups on the analogy-generating strategy were examined. The analyses of the results revealed that there was a higher proportion of the elaborated analogies in terms of quality generated by science-gifted students individually in the analogy-generating strategy than in general analogy-generating activity. After having small group activities, most small groups generated the elaborated analogies. The frequencies and percentages of verbal interactions of each sub-stage were found to be slightly different. Analogy-generating patterns in small groups were categorized into three types; selecting in-depth source, selecting inclusive source, and selecting surficial source. The elaborating patterns of mapping between a target concept and analogies were different among the types. Science-gifted students positively perceived in terms of its values and attitudes toward the analogy-generating strategy, and they responded that the analogy-generating strategy was helpful in generating more elaborated analogies and fostering creative thinking. Therefore the analogy-generating strategy is expected to generate positive impact on the creativity of science-gifted students.

• Journal of The Korean Association For Science Education
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• v.32 no.4
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• pp.671-685
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• 2012

In this study, we developed an analogical experimental design strategy emphasizing understanding and checking stages and applied it to four groups consisting of 7th grade science-gifted students. We classified the patterns of experimental design processes and analyzed the verbal interactions among the science-gifted students at the levels of turn and interaction unit. The analyses of the results reveled that three groups were relevant to reinitiated motion and the other to backward-divergent motion. In the analyses of turn and interaction unit, the frequencies of the statements related to the task were high, especially 'making suggestion' and 'elaborated symmetrical interaction'. The analyses for each stage of strategy indicated that the frequencies of 'explain', 'question', and 'cumulative interaction' at understanding stage were high. At designing stage, the frequencies of 'making suggestion', 'cumulative interaction', and 'disputative interaction' were found to be high. At checking stage, 'making suggestion', 'receiving opinion', and 'disputative interaction' were high. In the comparison of the patterns, the qualitative differences among interaction unit were found at all the stages, whereas there were differences only between designing and checking stages in the turn cases. Educational implications of these findings are discussed.

• Journal of The Korean Association For Science Education
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• v.30 no.2
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• pp.304-322
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• 2010

The purpose of this study is to explore the effects of student-centered instruction using analogies for middle school students' learning of the photosynthesis concept. Participants in this study were 8th grade students at a middle school in Seoul (N=132). The students were divided into two groups for implementation. In the experimental group the teaching materials containing analogies were used while the contents of a science textbook were taught in the control group. The results of this study indicated that student-centered instruction using analogies was more effective than traditional methods of instruction for understanding photosynthesis concepts and the students' attitude toward the science class. Analogies were also found to contribute to developing an understanding of the photosynthesis concept through activating students' prior knowledge, focusing on structural features of the target concept and elaborating knowledge. In addition, analogies play an important role in activating small group discussions, improving students' meta-cognitive skills, and revealing and revising of misconceptions about photosynthesis. Moreover, analogies can help improve students' interests and self-efficiency in science classes.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.2
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• pp.116-122
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• 1982

In three diverse wheat and one barley cultivars were used to examine the relation of the spikelet and floret differentiation to fertility and an winter wheat Norin 61 was used to examine the spikelet size gradients in the mature ear in relation to their grain development. The greatest number of grains and florets per spikelet, and the heaviest grains occurred in the low-mid part of the ear. Within the spikelets, the 2nd grain from the base was heavier than the I st or the 3rd one. In this region, the fertility of the 1 st floret was 97%, the 2nd 93%, the 3rd 88%, and 4th floret was 15%. The fertility of the wheat and barley was closely related to spikelet and floret differentiation. Barley spikelets was fertile as their differentiation stage was X that is 25 days before heading. Wheat florets were fertile as their differentiation stage was X that is 15-20 days before heading. But, they were sterile or reduced in fertility if they were not reached to the stage X.

• The Korean Journal of Pesticide Science
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• v.17 no.3
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• pp.145-154
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• 2013

Flonicamid was a water-soluble and systemic insecticide. It was applied to control neonicotinod pesticide-resistant cotton aphid in sweet peppers. However, the residue levels of total flonicamid in sweet pepper exported to Japan in 2009 were exceeded the maximum residue limit (MRL). This study was conducted to elucidate residual properties of flonicamid parent compound and its metabolites in sweet peppers. It was carried out to compare the variation of residues in sweet pepper in three different greenhouses for 21 days after 3 times application with 7 days interval. The mean residues were 0.176, 0.152 and 0.108 mg $kg^{-1}$ and the residue levels in sweet pepper among three greenhouses show significant difference. The maximum residue levels were detected 10 days later after last treatments. The overall residue levels were lower than MRL 2.0 mg $kg^{-1}$ (by Korea) and 0.4 mg $kg^{-1}$ (by Japan in 2009 but now revised MRL is 2.0 mg $kg^{-1}$). But the residue level of total flonicamid at the 21th day after 3 times treatment with 7 days interval was 0.429 mg $kg^{-1}$ restricted by the application of double rate than recommended rate. The amounts of metabolites, TFNA, 4-Trifluoro methyl nicotinic acid and TFNG, N-(4-trifluoro methyl nicotinoyl) glycine were increased while flonicamid parent compound was decreased over time. Therefore the longer trial period should be needed for flonicamid in sweet peppers.