• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.875-879
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• 2008

A method for the depolymerization of polycarbonate waste by glycolysis using ethylene glycol without catalyst was explored in order to get the monomer bisphenol A (BPA). The effect of operation variables such as reaction time, reaction temperature, EG/PC weight ratio and the kinetic of glycolysis were studied. It was found that the polymerization reaction has two different activation energies depending on the reaction temperature. A drop in activation energy with temperature indicates that the reaction mechanism has shifted from one of a succession of elementary steps to another in the series. The maximum yield of BPA of 95.6% was achieved at reaction temperature $220^{\circ}C$ for 85min with EG/PC weight ratio 4.

• Journal of Korean Elementary Science Education
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• v.42 no.3
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• pp.421-433
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• 2023

This study examined the reasoning of gifted elementary science students in a socioscientific issues (SSI) classroom discussion on COVID-19-related trash disposal challenges. This study aimed to understand the characteristics of evidence use and decision-making difficulties in each type of SSI-related reasoning. To this end, the transcripts of 17 gifted students of elementary science discussing SSIs in a classroom were analyzed within the framework of informal reasoning. The analysis framework was categorized into three types according to the primary influence involved in reasoning: rational, emotional, and intuitive. The analysis showed that students exhibited four categories of evidence use in SSI reasoning. First, in the rational reasoning category, students deemed and recorded scientific knowledge, numbers, and statistics as objective evidence. However, students who experienced difficulty in investigating such scientific data were less likely to have factored them in subsequent decisions. Second, in the emotional reasoning category, students' solutions varied considerably depending on the perspective they empathized with and reasoned from. Differences in their views led to conflicting perspectives on SSIs and consequent disagreement. Third, in the intuitive reasoning category, students disagreed with the opinions of their peers but did not explain their positions precisely. Intuitive reasoning also created challenges as students avoided problem-solving in the discussion and did not critically examine their opinions. Fourth, a mixed category of reasoning emerged: intuition combined with rationality or emotion. When combined with emotion, intuitive reasoning was characterized by deep empathy arising from personal experience, and when combined with rationality, the result was only an impulsive reaction. These findings indicate that research on student understanding and faculty knowledge of SSIs discussed in classrooms should consider the difficulties in informal reasoning and decision-making.

• Journal of the Korean Chemical Society
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• v.42 no.2
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• pp.184-189
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• 1998

Tris(pentafluorophenyl)indium acetonitrile complexes have been prepared from the reaction of Indium trihalides (halogen=Cl, Br) and bis(pentafluorophenyl)cadmium in acetonitrile, and characterized by elementary analysis, $^13C{^1H}-,\; ^1H-\;and\; ^{19}F-NMR$ spectroscopy and mass spectrometry. The Indium (III) compounds were formed stable 1:1 adducts with acetonitrile. $In(C_6F_5)_3{\cdot}DMAP$ has been prepared from the ligand exchange reaction of In$(C_6F_5)_3 {\cdot} CH_3CN$ with DMAP in $CH_2Cl_2 {\cdot} DMAP$ has higher donating character and replaced the $CH_3CN$ through the ligand transfer reaction.

• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.410-417
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• 2009

Carbon dioxide was absorbed into GMA solution in a stirred flat cell using mesoporous catalyst Imidazole-CP-MS41, which was synthesized by CP-MCM41 with imidazole. Experiments were carried out at a batch-type absorber with different conditions, varying reaction temperature, concentration of GMA, solvent but maintaining 50 rpm of agitation speed and 2 g of catalyst. Absorption rate of $CO_2$ was used to obtain the kinetics based on the film theory using zwitterion mechanism with 2 elementary reaction and the kinetics were correlated with the solubility parameter of the solvents.

• Journal of the Korean Chemical Society
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• v.43 no.5
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• pp.535-539
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• 1999

1,3-Dimethyllumazine derivatives were synthesized by using Timmis reaction. The reaction of 4-amino-1,3-dimethyl-5-nitrosouracil(1) with 2,4-pentanedione, ethyl cyanoacetate, and ethyl acetoacetate provided 6-acetyl-1,3,7-trimethyllumazine (2), ethyl 7-amino-1,3-dimethyllumazine-6-carboxylate (4), and ethyl 1,3,7-trimethyllumazine-6-carboxylate (5) in good yieId, respectively. The various 1,3-dimethyllumazine derivatives were prepared from the side chain reactions of 6-acetyl and ester group in compound 2,4, and 5. The structure and physical properties of obtained compounds were characterized NMR, UV, IR spectrum, and elementary analysis.

• Journal of the Korean Applied Science and Technology
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• v.12 no.1
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• pp.93-99
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• 1995

As the surfactants that were used in micellar reaction, emulsion polymerization and phase-transfer reaction etc. have the problems, the cleavable surfactant that was converted to inactive compound after such as the reaction was synthesized to above 90% yield. And this surfactant and intermediates were separated through thin layer chromatography and column chromatatography and their molecular structures were confirmed from IR. $^{1}H$-NMR and elementary analysis spectra. And its surface-active properties and acid hydrolysis will be serialized in II.

• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.344-349
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• 2016

Background: Carbon ion therapy has achieved satisfactory results. However, patients have a risk to get a secondary cancer. In order to estimate the risk, it is essential to understand particle transportation and nuclear reactions in the patient's body. The particle transport Monte Carlo simulation code is a useful tool to understand them. Since the code validation for heavy ion incident reactions is not enough, the experimental data of the elementary reaction processes are needed. Materials and Methods: We measured neutron production double-differential cross-sections (DDXs) on a carbon bombarded with 430 MeV/nucleon carbon beam at PH2 beam line of HIMAC facility in NIRS. Neutrons produced in the target were measured with NE213 liquid organic scintillators located at six angles of 15, 30, 45, 60, 75, and $90^{\circ}$. Results and Discussion: Neutron production double-differential cross-sections for carbon bombarded with 430 MeV/nucleon carbon ions were measured by the time-of-flight method with NE213 liquid organic scintillators at six angles of 15, 30, 45, 60, 75, and $90^{\circ}$. The cross sections were obtained from 1 MeV to several hundred MeV. The experimental data were compared with calculated results obtained by Monte Carlo simulation codes PHITS, Geant4, and FLUKA. Conclusion: PHITS was able to reproduce neutron production for elementary processes of carbon-carbon reaction precisely the best of three codes.

• Journal of Elementary Mathematics Education in Korea
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• v.18 no.2
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• pp.211-236
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• 2014

The purpose of this study is to investigate teacher's knowledge of concept of equality and derive implications about proper teaching methods. To solve these study problems, three elementary school teachers are chosen for this study, and a pencil-and paper tests for comprehension of the equality concept targeting 72 students for elementary school that the teachers are in charge of the students was carried out. Also, The semi-structured interview(using a questionnaire) was conducted for analyzing of the teachers' knowledge of the equality concept. The findings are as follows. First, during the lesson, the teachers' reading of equal sign has a decisive effect on the students' the way of reading. Second, teachers tend to interpret the concept of equality as a systematic analysis rather than a relational analysis, and use a equal sign focusing on meaning of 'same result'. So, Students also can't interpret the concept of equality as a relational analysis. Third, under the influence of teacher's feedback or reaction, making the mistake of the using equal sign of students reoccurred continually. Fourth, teachers misjudged some of examples of the nonstandard context equation for teaching elementary school students. Furthermore, during the lesson, they usually used a limited equality context. So, students can't have a chance to learn equality in a plenty of context. Thus, the knowledge of teachers and their lesson has decisive influence on the comprehension of students about the equality concept. So, Teacher has to focus on the meaning of the equality as a relational analysis and teach them in a plenty of context. With this, lots of study and in-service training are needed to enhance knowledge of teachers. And more of lesson programs and materials have to provided on the instruction manual for teaching the meaning of the equality.

• Journal of Science Education
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• v.38 no.2
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• pp.401-414
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• 2014

Overexcitability (OE) and social self-concept are the integral affective characteristics of science-gifted students. Overexcitability refers to sensitivity as an internal disposition to give a more often, longer and more intensive reaction to a wide variety of stimuli, and social self-concept refers to the way of behaving in society, especially at school in the case of students. The purpose of this study was to examine the overexcitability and social self-concept of science-gifted and non-gifted elementary school students. The subjects in this study were 135 gifted elementary students belonged to gifted education centers or gifted classes and 91 ordinary elementary students. An overexcitability test and a social self-concept test were conducted to the subjects, and the collected data were analyzed by SPSS. The findings of the study were as follows: First, the score of the science-gifted was significantly higher than that of the ordinary students in all sub-domain of OE (psychomotor OE, sensual OE, emotional OE, intellectual OE, emotional OE) and social self-concept. Second, the science-gifted students who attended gifted education centers and community gifted classes scored significantly higher than the ordinary students in overexcitability. Based on conclusions, implications for teaching the science-gifted were discussed.

• Design Convergence Study
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• v.14 no.2
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• pp.1-16
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• 2015

As childhood obesity and nutrition imbalance emerge as social issues in South Korea today, the development of education materials on diets and nutrition has become important and has been attempted in diverse ways. The present study was conducted on early elementary school students with the objective of establishing directions for the design of personalized nutrition education materials that can promote a proper, balanced diet for children through application in daily life of knowledge acquired from self-learning linked to nutrition education that is taking place in their schools. For this purpose, a review of previous theoretical literature on nutrition education for early elementary students was performed. Survey questions were formulated based on the advice of field experts in medicine, education, and design and the survey was conducted among 110 children from 1st and 2nd grade in two elementary schools, one in Seoul and the other in Changwon. The results obtained from the user evaluation suggested that the early elementary school students showed positive reaction to nutrition education, had preference for the type of learning using multimedia-based contents and quiz activities, were willing to learn about calorie-adjusted meals, preferred the Gothic typeface and orange and green colors. Furthermore, they showed positive opinion on the use of numerical surveying method and pictorial style similar to actual appearance in connection with nutrition-related information representation. and preferences regarding learning styles and design elements