• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2329-2333
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• 2022

Base metal corrosion forms a significant issue during the chemical decontamination of the primary coolant loop in nuclear power plants as it is directly related to the economic and safety viability of decommissioning. In this technical note, potentiodynamic evaluations of several base metals (304 stainless steel, SA106 Grade B carbon steel, and alloy 600) were performed to determine their corrosion behavior during the hydrazine (N₂H₄)-based reductive ion decontamination (HyBRID) process. The results suggested that N₂H₄ protected the surface of the base metals in the HyBRID solution, which is primarily composed of H₂SO₄. The corrosion resistance of the carbon steel was further improved through the addition of CuSO₄ to the solution. The corrosion rate of carbon steel in the H₂SO₄-N₂H₄-CuSO₄ solution was lower than that exhibited in an oxalic acid solution, a commonly used reaction medium during commercial decontamination processes. These results indicate the superiority of the HyBRID process with respect to the base metal stability.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.16-23
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• 2016

This study was carried out to investigate how grade level and experiences when taking courses affect the creativity of engineering students in a Korean college. The sample group consisted of 372 engineering students of which 49.5% were first graders, 15.6% second graders, 22.6% third graders, and 12.4% fourth graders. They conducted self-report measures on a domain-general and domain-specific view of creativity. The engineering creativity test, developed by Kang and Yune (2015), is based on the domain-specific view of creativity and consists of four sub-factors: creative attitude, knowledge research, interest in engineering, and team work ability. The domain-general creativity test consists of three sub-factors. Analysis of the results led to the following conclusions: First, we found significant differences in engineering creativity between students depending on experiences in taking courses and tests; and, second, we discovered significant differences in integrative creativity among students depending on experiences in taking courses and tests, and/or grade level. These conclusions suggest that we should develop and apply appropriate strategies to enhance creativity in engineering education.

• The Korean Journal of Community Living Science
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• v.15 no.2
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• pp.83-92
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• 2004

The purpose of this research is to determine the influence of affectionate child-rearing behavior on children's self esteem. The sample group was composed of 200 forth and sixth grade elementary school students. The statistics used for this data were frequency, percentile, averages, standard deviation, Cronbach's alpha, t-test, Pearson's correlation, and stepwise multiple regression analysis. The major findings of the research were as follows: First, the scores of affectionate child-rearing behavior(3.60), global self-worth(3.58), social acceptance(3.46) and behavior conduct(3.28) were higher than the mean scores. On the contrary the scores of cognitive ability(2.95), physical ability(2.94) and physical appearance(2.85) were lower than the mean scores. Second, there were significant differences in cognitive ability based on gender(p＜.01) and global self-worth based on grade(p<.05). Third, the influence of affectionate child-rearing behavior on children's self esteem was found to be significant due to the sub-areas of self-esteem. Affectionate child-rearing behavior affects all sub-areas of self-esteem. Affectionate child-rearing behavior affects cognitive ability(p<.001), physical ability(p＜.01), physical appearance(p＜.01), social acceptance(p＜.001), behavior conduct(p＜.01) and global self-worth(p＜.001). In addition, gender(p＜.01) affects cognitive ability and grade(p＜.05) affects global self-worth.

• Advances in Energy Research
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• v.7 no.2
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• pp.147-166
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• 2020

Industrial cooling towers are often ageing infrastructure that is expensive to maintain and operate. A novel approach is introduced in which a heat pump circuit is incorporated to reduce the load upon the towers by extracting low-grade energy from the stream sent to the towers and repurposing in on-site processing operations. To demonstrate the concept, a model was constructed, which uses industrial data on cooling towers linked to a smelter's sulphuric acid plant, to allow direct economic and environmental impact comparison between different heat recovery and repurposing scenarios. The model's results showed that implementing a heat pump system would significantly decrease annual operating costs and achieve a payback period of 3 years. In addition, overall CO₂ emissions could be reduced by 42% (430,000 kg/year) and a 5% heat load reduction on the cooling towers achieved. The concept is significant as the outcomes introduce a new way for energy intensive industrial sectors, such as mineral processing, to reduce energy consumption and improve long-term sustainable performance.

• Korean Journal of Child Studies
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• v.28 no.6
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• pp.1-16
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• 2007

In this study of mathematics anxiety, mathematical learning style, and grade in school, 1,264 elementary students completed the Mathematics Anxiety Scale(Lee, 2005) and the Mathematical Learning Style Scale(Yang & Whang, 2005) for elementary school students. Analysis of their responses showed that anxiety about mathematics increased with grade in school. Among sub-factors of mathematics anxiety, the subject itself, learners' attitude, and learning environment increased the anxiety of upper grade students. Motivation, initiative, and regulation styles of learning mathematics were found to be important factors in the mathematics anxiety of elementary school students.

• 한국도로학회:학술대회논문집
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• 2006.10a
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• pp.467-472
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• 2006

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.392-398
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• 2020

Producing solar grade silicon using an inexpensive method is a key factor in lowering silicon solar cell costs; the direct electrochemical reduction of SiO₂ in molten salt is one of the more promising candidates for manufacturing this silicon. In this study, SiO₂ granules were electrochemically reduced in molten CaCl₂ (850℃) using Ag-Si eutectic droplets that catalyze electrochemical reduction and purify the Si product. When Ag is used as the working electrode, the Ag-Si eutectic mixture is formed naturally during SiO₂ reduction. However, since the Ag-Si eutectic droplets are liquid at 850℃, they are easily lost during the reduction process. To minimize the loss of liquid Ag-Si eutectic droplets, a cylindrical graphite container working electrode was introduced and Ag was added separately to the working electrode along with the SiO₂ granules. The graphite container working electrode successfully prevented the loss of the Ag-Si eutectic droplets during reduction. As a result, the Ag-Si eutectic droplets acted as stable catalysts for the electrochemical reduction of SiO₂, thereby producing one-dimensional Si rods through a mechanism similar to that of vapor-liquid-solid growth.

• Korean Journal of Human Ecology
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• v.9 no.4
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• pp.5-14
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• 2006

The purpose of this study was to identify the effect of social support and self-efficacy on career decision level among female university students. Data was collected by questionnaires from 380 students at 3 universities in Jeonnam province and Gwangju city, Korea. The results were as follows. First, the average levels of social support, self-efficacy and career decision were over middle point(2.5point). The best of them was self-efficacy. Second, the lowest level of them by grade was commonly freshman female students. But there were no significant differences by major except for soczzzzzial support. Third, the effective sub-variables of social support which have influenced on career decision level were self-esteem support and evaluated support. Forth, the impactive sub-variables of self-efficacy which have influenced on career decision level showed general self-efficacy. Fifth, the significant sub-variables of social support which have influenced on self-efficacy were self-esteem support and material support. This study suggested that the high levels of self esteem social support and general self-efficacy led students to improve in career decision level. Here showed that the effect by grade or group on study was more clear than that by major.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1876-1889
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• 2013

Packet-based mobile multimedia services for the Internet differ with respect to their resource requirements, performance objectives, and resource usage efficiencies. Nonetheless, each mobile terminal should support a variety of multimedia services, sometimes even simultaneously. This paper proposes a sub-channel allocation scheme based on multi-level priority for supporting mobile multimedia services in an Orthogonal Frequency Division Multiple Access (OFDMA) system. We attempt to optimize the system for satisfying the Quality of Service (QoS) requirements of users and maximize the capacity of the system at the same time. In order to achieve this goal, the proposed scheme considers the Signal-to-Interference-plus-Noise Ratio (SINR) of co-sub-channels in adjacent cells, the Signal-to-Noise Ratio (SNR) grade of each sub-channel in the local cell on a per-user basis, and the characteristics of the individual services before allocating sub-channels. We used a simulation to evaluate our scheme with the performance measure of the outage probabilities, delays, and throughput.

• Journal of Korean Elementary Science Education
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• v.35 no.2
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• pp.181-193
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• 2016

We examined the inquiry activities in the material domain of the elementary science textbooks and experimental workbooks based on 2009 revised curriculum. The analysis framework was SEP (Science and Engineering Practices) - 'Asking questions and defining problems', 'developing and using models', 'planning and carrying out investigations', 'analyzing and interpreting data', 'using mathematics and computational thinking', 'constructing explanations and designing solutions', 'engaging in argument from evidence', and 'obtaining, evaluating, and communicating information'. Sub-SEP of each grade band were also used. The results showed that the $3^{rd}{\sim}5^{th}$ grade science textbooks and workbooks mainly emphasized 'make observations and/or measurements', 'represent data in tables and/or various graphical displays', or 'use evidence to construct or support an explanation or design a solution to a problem' among around 40 sub-SEP. In the case of the inquiry activities for $6^{th}$ grade, majority of sub-SEP included were also only 'collect data to produce data to serve as the basis for evidence to answer scientific questions or test design solutions', 'analyze and interpret data to provide evidence for phenomena' or 'construct a scientific explanation based on valid and reliable evidence obtained from sources'. The type of 'asking questions and defining problems', 'using mathematics and computational thinking' or 'obtaining, evaluating, and communicating information' were little found out of 8 SEP. Educational implications were discussed.