• International Journal of Advanced Culture Technology
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• v.9 no.4
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• pp.237-247
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• 2021

The purpose of this study is to investigate the influences on the understanding and academic achievement in general chemistry according to chemical grades in high school and College Scholatic Ability Test. We investigated the difference between the completed subjects in high school and the elective subjects in the Test, degree of understanding of the general chemistry according to the subjects completed in high school, and the effects on the academic achievement of general chemistry by dint of the chemical grades in high school and the Test, etc. By the results of the student's perception survey, most of the students choose Chemistry I at the Test. It was found that the understanding of general chemistry was greatly affected by the chemical elective subjects of high school. Chemical grades in high school and the Test were found to have a significant influence on academic achievement of general chemistry.

• Journal of the Korean Chemical Society
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• v.53 no.6
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• pp.793-804
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• 2009

In this study, high school students' perceptions of chemically ill-defined ‘heavy metals’ were examined through questionnaires. Nineteen classes of 11th graders (N = 611) were divided into two groups according to completion of 'Chemistry I', which were 10 science-classes and 9 liberal art-classes and compared each other. Three terms of students' cognition and definition, impact on the formation of their cognition, and their chemical knowledge of 'heavy metals' were analyzed by SPSS. The findings revealed that most of students recognized ‘the heavy metal’ as the metal which causes to be accumulated on any living thing and is hazardous in human body regardless of different major between liberal art and science. Mass media and school instruction were found to be the greatest impact on the formation of these cognitions. Especially, school instruction had more effects on students majoring in science than students majoring in liberal art, which bring the result that students in science-classes have more misconception about the definition of 'heavy metals' with human toxicant regardless of metal species and its content in human body and physical density due to the ill-defined terminology of the textbook than students in liberal art-classes do. It is interesting that students in science-classes understood hazard and chemical structure of 'heavy metals' better, while students in liberal art-classes answered the question better about hazardous properties of heavy metals.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.300-305
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• 1998

Kinetics of termonomer emulsion polymerization during interval II (i.e, after completion of latex particle formation) were studied through pseudo-homopolymerization (PHP) method. Extended Smith-Ewart equation and equation of instantaneous polymer composition are respectively reduced to the corresponding equation for homopolymerization by defining average rate constants. Average number of radicals per particle and instantaneous polymer compositions were respectively predicted by varying termonomer composition within latex particles for systems containing no more than one growing radical per particle. Styrene-Methyl methacrylate-Acrylonitrile (SMA) system was used for model calculation.

• Elastomers and Composites
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• v.56 no.4
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• pp.254-263
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• 2021

In this study, chitosan obtained after varying extents of deacetylation (i.e., 10%, 30%, and 47%) was employed to introduce antibacterial properties to chitin. The deacetylation reaction completion, wherein the amino group content of chitin was reduced, was ascertained from the FT-IR and NMR analyses. The 47%-deacetylated chitosan exhibited superior antibacterial properties against Bacillus in a disk diffusion test. To further improve these properties, chitosan derivatives were grafted by acrylic acid and acrylamide. The varying concentrations of carboxyl groups, primary amines, and -CH₂-CH₂- with increasing acrylic acid and acrylamide contents were determined by FT-IR and NMR analyses. The enhanced antibacterial properties of the chitosan derivatives, owing to the increased acrylic acid and acrylamide contents, were revealed by the disk diffusion test. In particular, the derivatives with 1.3% acrylic acid and acrylamide showed the highest antibacterial activity, the bacterial reduction rate against Staphylococcus aureus and Escherichia coli being 99.9%, as observed through the ASTM E2149 standard test.

• Toxicological Research
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• v.24 no.3
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• pp.207-212
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• 2008

Pesticide residues play several key roles as environmental and food pollutants and it is crucial to develop a method for the rapid determination of pesticide residues in environments. In this study, a simple, effective, and sensitive method has been developed for the quantitative analysis of methoxyfenozide in water and soil when kept under laboratory conditions. The content of methoxyfenozide in water and soil was analyzed by first purifying the compound through liquid-liquid extraction and partitioning followed by florisil gel filtration. Upon the completion of the purification step the residual levels were monitored through high performance liquid chromatography(HPLC) using a UV absorbance detector. The average recoveries of methoxyfenozide from three replicates spiked at two different concentrations and were ranged from 83.5% to 110.3% and from 98.1% to 102.8% in water and soil, respectively. The limits of detection(LODs) and limits of quantitation(LOQs) were 0.004 vs. 0.012 ppm and 0.008 vs. 0.024 ppm, respectively. The method was successfully applied to evaluate the behavioral fate of a 21% wettable powder(WP) methoxyfenozide throughout the course of 14 days. A first-order model was found to accurately fit the dissipation of methoxyfenozide in water with and a $DT_{50}$ value of 3.03 days was calculated from the fit. This result indicates that methoxyfenozide dissipates rapidly and does not accumulate in water.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.109-114
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• 2020

This work presents the results of laboratory scale tests of the CARBOFLUOREX (CARBOnate FLUORide EXtraction) process - a novel technology for the recovery of U and Pu from the solid fluorides residue (fluorination ash) of Fluoride Volatility Method (FVM) reprocessing of spent nuclear fuel (SNF). To study the oxidative leaching of U from the fluorination ash (FA) by Na₂CO₃ or Na₂CO₃-H₂O₂ solutions followed by solvent extraction by methyltrioctylammonium carbonate in toluene and purification of U from the fission products (FPs) impurities we used a surrogate of FA consisting of UF₄ or UO₂F₂, and FPs fluorides with stable isotopes of Ce, Zr, Sr, Ba, Cs, Fe, Cr, Ni, La, Nd, Pr, Sm. Purification factors of U from impurities at the solvent extraction refining stage reached the values of 10⁴-10⁵, and up to 10⁶ upon the completion of the processing cycle. Obtained results showed a high efficiency of the CARBOFLUOREX process for recovery and separating of U from FPs contained in FA, which allows completing of the FVM cycle with recovery of U and Pu from hardly processed FA.

• Journal of The Korean Association For Science Education
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• v.40 no.2
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• pp.217-226
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• 2020

The purpose of this research is to draw suggestions on the settling of the 2015 revised curriculum and the direction of science curriculum improvement by identifying the current status of science general elective courses for high school sophomores, and examining teachers' perception. To this end, with 12 city and provincial education offices' cooperation, we analyzed the status of science elective subjects that freshmen took in 2018 by school year, school type and region. In addition, in-depth interviews were conducted with nine science teachers of the focus group to discuss ways to improve curriculum operation and implementation of science general elective courses, and ways to raise the selection rate. The number of science general elective courses for high school students in 12 municipal and provincial education offices was confirmed to be 163,710 for Physics I, 216,754 for Chemistry I, 290,736 for Bioscience I, and 200,861 for Earth Science I. By school type, autonomous high schools have the highest completion rate, while specialized schools and vocational schools have very low rates. Units completed per semester for general elective courses were mostly three units (61.5%) and two units (28.7%). High school science teachers suggested reconstruction of three-unit elective courses that can be completed in one semester, content development focused on competences rather than knowledge, and the need for a teacher community to improve teachers' teaching competences. Based on the results of the research, ways to operate high school science elective curriculum in preparation for the high school credit system were suggested.

• Journal of Science Education
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• v.43 no.2
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• pp.195-206
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• 2019

The study aims to find a way to guarantee high school students choose science subjects by exploring its necessity as a prerequisite for admission to university science and engineering major courses. For this purpose, a survey was administered to 516 science & engineering college students to investigate their cognition and completion of the prerequisite science subjects related to their major, department adjustment, and influence on their major of study. Among nine major clusters, Physics was identified as a science domain with a high relevance to majors in five major clusters, and Chemistry in three. The students who completed both science I and II subjects related to their majors responded most positively to the usefulness of prerequisite subjects to their studies. Suggestions include conditions for the opening of science II subjects, strengthening the connection between science subjects and IT, promotion of linkage between the prerequisite subject and major studies to assert students' choice of science subjects in high school.