• Korean Journal of Materials Research
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• v.25 no.11
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• pp.607-611
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• 2015

The microstructural evolution of Grade 91 tempered martensite ferritic steels heat treated at $760{\sim}1000^{\circ}C$ for two hours was investigated using scanning electron microscopy(SEM), energy disperse spectroscopy(EDS), electron backscattered diffraction (EBSD), and transmission electron microscopy(TEM); a microhardness tester was also employed, with a focus on the grain and precipitate evolution process as well as on the main hardening element. It was found that an evolution of tempered martensite to ferrite($760{\sim}850^{\circ}C$), and to fresh martensite($900{\sim}1000^{\circ}C$), occurred with the increase of temperature. Simultaneously, the parabolic evolution characteristics of the low angle grain boundary(LAGB) increased with the increase of the heating temperature(highest fraction of LAGB at $925^{\circ}C$), indicating grain recovery upon intercritical heating. The main precipitate, $M_{23}C_6$, was found to be coarsened slightly at $760{\sim}850^{\circ}C$; it then dissolved at $850{\sim}1000^{\circ}C$. Besides this, $M_3C$ cementite was formed at $900{\sim}1000^{\circ}C$. Finally, the experimental results show that the hardness of the steel depended largely on the matrix structure, rather than on the precipitates, with the fresh martensite showing the highest hardness value.

• Textile Coloration and Finishing
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• v.27 no.4
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• pp.318-326
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• 2015

A pre-treatment process is essential for getting high quality of digital textile printing(DTP). In this study, we have studied three kinds of carrageenan polymer(k-, ${\lambda}$-, i-Carrageenan) as a pre-treatment thickening agent for the first time. Alginate polymer was also examined and its results were compared with that of the three kinds of carrageenan polymer. To confirm the performance of each thickening agent, we examined for a sharpness, color strength and fastness(washing, rub, light). The result showed that ${\lambda}$-Carrageenan has superior property in sharpness with low viscosity and i-Carrageenan was excellent in the color strength among the pre-treatment agents. Washing fastness to color change and staining for the all samples were 4 or 4-5 grade. Both dry and wet rubbing fastness of the samples were 4-5 grade. However, ${\lambda}$-Carrageenan coated sample has the lowest grade in light fastness. As a result, we found the possibility of carrageenan polymer as pre-treatment agent.

• Culinary science and hospitality research
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• v.14 no.3
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• pp.123-135
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• 2008

The purpose of this study is to investigate the priority order in the factors influencing college choice of students who are majoring in culinary art in Chungcheong-do. For the study, we set the decision-making factors of upper hierarchies and nineteen bottom hierarchies based on the literature review and employed the analytical hierarchical process(AHP). As a result, the first considering factor among 4 upper hierarchies for college choice was the educational environments of the department(0.378). The next came in the order named as follows: college and university grade(0.263), the educational environments of colleges or universities(0.244), recommendation(0.115). The first considering factor among the educational environments of the department was the aptitude for the major(0.323). The first considering factor in college and university grade was the entrance competitive rate(0.397). The first considering factors among the educational environments of the colleges or universities were scholarships and tuition fees(0.325). The first considering factor in recommendation was the recommendation of a high school teacher(0.295). This results of this study will contribute to the development of colleges and universities under the turbulent changes of educational environments.

• Journal of Korean Elementary Science Education
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• v.30 no.3
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• pp.282-295
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• 2011

Prior research has reported that student epistemological beliefs might affect their participation in learning and the process of conceptual change. The purposes of this study were to investigate the characteristics of sixth grade students epistemological beliefs about science and the relation between their epistemological beliefs about science and factors related their learning. For this research questions, 245 sixth grade students participated and various test instruments were used in this study. Students answered two types of questionnaires on epistemological beliefs about science and three test instruments on factors related students' learning(achievement in science, science inquiry skills, and cognitive levels). The results of this study were as follows. First, a large number of elementary school students believed that the purpose of science to perform activities like simple experiments. A lot of students believed that scientific knowledge was changeable according to the nature of scientific knowledge and that scientific knowledge could be learnt on their own. Also, many students believed experiment results to be basis on which to form personal scientific conceptions. Second, students who believed in more modern epistemology about science represented higher levels of science learning achievement, science inquiry skills, and cognitive levels. Therefore, when developing science curriculum, science educators need to consider how to develop student modern epistemological beliefs about science.

• Journal of Ocean Engineering and Technology
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• v.21 no.1 s.74
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• pp.64-68
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• 2007

Recently, there has been considerable research in the field of application of Laser-Arc hybrid welding for superstructures, such as ship-structures, transport vehicles etc. However, the study on heat distribution and welding residual stress of hybrid weld by numerical simulation leaves much to be desired. Therefore, in this study, an optimized welding condition and numerical simulation for hybrid welding, using previous numerical analysis to calculate the heat source for hybrid welding, has been analyzed. For this purpose, fundamental welding phenomena of the hybrid process, using Laser and, is investigated. In order to calculate temperature and residual stress distribution in hybrid welds, a finite element heat source model is developed on the basis of experimental results and characteristics of temperature. Residual stress distribution in hybrid welds are understood from the result of simulation, and compared with the experimental values.

• Korean Journal of Childcare and Education
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• v.17 no.5
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• pp.43-61
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• 2021

Objective: This study aimed to examine the sequential mediating effects of children's perceived maternal acceptance and peer acceptance in the relationship between maternal warmth and first grade children's school adjustment. Methods: Participants in this study were 979 seven-year-old children(498 boys, 481 girls) recruited for the Korea Child Panel Study. Data were analyzed by analyzing descriptive statistics, correlations, and significance of serial mediation pathways using SPSS 18.0 and PROCESS Macro 3.4. Results: Maternal warmth at age five effected perception of maternal acceptance at age six. Perceived maternal acceptance at age six effected perceived peer acceptance at age six. Perceived peer acceptance at age six effected school adjustment at age seven. Lastly, perceived maternal acceptance and peer acceptance at age six had a serial mediation effect between maternal warmth at age five and school adjustment at age seven. Conclusion/Implications: Perceived social acceptance during preschool years should be emphasized in order to promote school adjustment for first grade children. Parent education for promoting better parent child relationships should be considered and teachers should encourage peer play interaction to help children perceive acceptance from their peers.

• Journal of the Korea Safety Management & Science
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• v.25 no.3
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• pp.55-62
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• 2023

Public institutions have a responsibility to ensure the safety of their employees and the public. One way to do this is to implement a systematic safety inspection system based on risk assessments and continuous improvements. This study developed a systematic safety inspection system for public institutions that are ordered construction projects. The proposed system in this study consists of a three-step process: (1) developing safety grade evaluation tables, (2) preparing and conducting safety inspections, and (3) evaluating and improving safety management grades. The first step is to develop safety grade evaluation tables by analysis and diagnosis of the construction site's work type, disaster statistics, and related laws. The second step is to conduct safety inspections using the developed evaluation tables. The third step is to determine the safety management grade based on the results of the safety inspection, and to improve risk factors found during the safety evaluation. The proposed system was implemented in highway construction projects carried out by public institutions. The results showed that the proposed system has two major effects: (1) reducing accident-related deaths and injuries, (2) improving safety management levels by continuous evaluation and improvement. The proposed system can be utilized in construction projects ordered by public institutions to improve the level of occupational safety and health.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.443-450
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• 2008

Efficient use of low rank coals (LRC) have been investigated as a method to cope with recent high oil price. Among the coals used in industry, lignite and sub-bituminous coals are belong to the LRC, and have abundant deposit and are distributed worldwide, but high moisture contents and self ignition properties inhibits their utilization. In this paper, chemical coal cleaning to produce ash-free coal from LRC has been investigated. Two technologies, that is, UCC(Ultra Clean Coal) process removing ash from coal and Hyper Coal process extracting combustibles from coal were compared with. UCC process has merits of simple and reliable when it compared with Hyper Coal process, but the remaining ash contents werehigher than Hyper Coal. Hyper Coal has ash contents under the 200ppm when raw coal is treated with appropriate solvent and ion exchange materials to remove alkali materials in extracted solution. The ash-free coal which is similar grade with oil can be used as alternate oil in the industry, and also used as a high grade fuel for IGCC, IGFC and other advanced combustion technology.

• The Mathematical Education
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• v.57 no.3
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• pp.289-309
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• 2018

There has been a gradually increasing focus on adopting mathematical modeling techniques into school curricula and classrooms as a method to promote students' mathematical problem solving abilities. However, this approach is not commonly realized in today's classrooms due to the difficulty in developing appropriate mathematical modeling problems. This research focuses on developing reformulation strategies for those problems with regard to mathematical modeling. As the result of analyzing existing textbooks across three grade levels, the majority of problems related to the real-world focused on the Operating and Interpreting stage of the mathematical modeling process, while no real-world problem dealt with the Identifying variables stage. These results imply that the textbook problems cannot provide students with any chance to decide which variables are relevant and most important to know in the problem situation. Following from these results, reformulation strategies and reformulated problem examples were developed that would include the Identifying variables stage. These reformulated problem examples were then applied to a 7th grade classroom as a case study. From this case study, it is shown that: (1) the reformulated problems that included authentic events and questions would encourage students to better engage in understanding the situation and solving the problem, (2) the reformulated problems that included the Identifying variables stage would better foster the students' understanding of the situation and their ability to solve the problem, and (3) the reformulated problems that included the mathematical modeling process could be applied to lessons where new mathematical concepts are introduced, and the cooperative learning environment is required. This research can contribute to school classroom's incorporation of the mathematical modeling process with specific reformulating strategies and examples.

• Resources Recycling
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• v.18 no.2
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• pp.30-38
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• 2009

In this research, we studied the scale-up triboelectrostatic process for separation of PVC from higher gravity fraction of plastic wastes produced from wet gravity separation process. High density polyethylene (HDPE) was found to be the most effective materials for a tribo-charger in the separation of plastic tailings. In a commercial scale triboelelctrostatic separator unit, using the HDPE pipe-line charger, a grade of 99.1% with PET, PS and others and a recovery of 86% was obtained under optimum conditions at over 250 kV/m electric field, a splitter position of -8 cm from the center, and less than 40% relative humidity. The developed unit can process the plastic wastes at a 300 kg/h, and the product can be utilized as RPF or RDF of over grade 2.