• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1684-1689
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• 2007

Fretting wear is one of the important degradation mechanisms of steam generator tubes in the nuclear power plants. Especially, impact fretting wear occurred between steam generator tubes and tube support plates or anti-vibration bar. Various tests have been carried out to investigate the wear mechanisms and to report the wear coefficients. Those are fruitful to get insight for the wear damage of steam generator tubes; however, most wear researches have concentrated on sliding wear of the steam generator tubes, which may not represent the wear loading modes in real plants. In the present work, impact fretting tests of steam generator tube were carried out. A wear progression model for impact-fretting wear has been investigated and proposed. The proposed wear progression model of impact-fretting wear is as follows; oxide film breaking step at the initial stage, and layer formation step, energy accumulation step and finally particle torn out step which is followed by layer formation in the stable impact-fretting progress. The wear coefficient according to the work-rate model has been also compared with one between tube and support.

• Journal of Korean Elementary Science Education
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• v.32 no.4
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• pp.593-606
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• 2013

The purpose of this study was to examine the effect of science-based STEAM program using a portfolio on elementary students' formation of science concepts and investigate students' opinion about the program. The developed program was applied to 1 experimental class(10 boys and 12 girls) and general science lessons, using a science textbook, was applied to 1 controlled class(11 boys and 13 girls) of $5^{th}$ grade students at S elementary school in Seoul through a total 6 sessions. Concept tests of the solar system were conducted before and after lessons and analysis of covariance was conducted. The results of this study were as follows. First, science-based STEAM program using a portfolio was effective to form science concepts. Second, students opinion about science-based STEAM program using a portfolio was positive. Students think the program was effective in understanding science contents, promoting thinking, self-motivation. It is expected that this study will be basic material to expand STEAM in science education.

• Journal of Korean Elementary Science Education
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• v.32 no.4
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• pp.557-566
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• 2013

The purpose of this study was to investigate the effects of science lesson applying STEAM education on the science learning motivation and science academic achievement of elementary school students. The study subjects were four classes of the 5th grade of M elementary school in B Metropolitan City. Two classes including 64 students were experimental group and the others including 65 students were comparison group. For the purpose of study, the lesson unit 'The human body' were practised, the recomposed unit applying STEAM was applied to experimental group, whereas comparison group was taught traditional science lesson. The results of this study were as follows. First, the science lesson applying STEAM education influenced significantly the improvement of the science learning motivation of elementary school students. Second, the science lesson applying STEAM education influenced significantly the improvement of the science academic achievement of elementary school students.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1397-1405
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• 2009

In recent decades, exergy analysis has been holding spotlight as a useful tool in the design, assessment, optimization, and improvement of energy system. This paper presents the results of the energy and exergy analysis of a steam turbine cogeneration system for industrial complex using two efficiency concepts of conventional one and exergetic one. In order to obtain the destroyed exergy of each component, mathematical analysis is conducted by using exergy balance and the second law of thermodynamics, according as the parameters are changed, such as the ratio of returned process steam, process steam supplied, temperature and pressure of boiler and power. The computer program developed in this study can determine the efficiencies and exergy destroyed at each component of cogeneration system. As a result of this study, a component having the largest destroyed exergy was boiler. And closed and opened feedwater heater had the lowest one. The affects to the cogeneration system due to the variation of process steam flow and return rate of condensed water is shown that the total electric power efficiency(${\eta}_E$) is decreased as increasing the return rate of condensed water under constant process steam flow. As the boiler pressure is increased for the more production of electricity, the efficiency of cogeneration system was decreased.

• International Journal of Contents
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• v.16 no.3
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• pp.101-110
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• 2020

Problem solving in real life is a core competency commonly adopted in several subjects recently. The real-world problems were rarely resolved with only one domain of knowledge. Thus, convergence education is becoming a trend in many countries. As on-line education is revitalized because of COVID-19, the need for changes to STEAM education is emerging. In December 2019, the on-line education systems quickly settled in schools because of COVID-19. During the first semester of 2020, most school education was conducted as virtual/distance learning classes. It is necessary to analyze how much technology has been used in the STEAM classes in Korea. This paper analyzes the research papers related to the STEAM education in Korea conducted in the last 10 years. By doing this, we analyze what kind of edutechs we were interested in, what kind of STEAM education actually occurred, and to whom it was conducted. The previous research papers analyzed in this paper are the papers in the Korea Citation Index accredited journals and candidate journals. Finally, this paper proposes educational changing factors to be considered for future technology-based STEAM education.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.10
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• pp.817-822
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• 2008

Fretting wear is one of the important degradation mechanisms of steam generator tubes in the nuclear power plants. Especially, impact fretting wear occurred between steam generator tubes and tube support plates or anti-vibration bar. Various tests have been carried out to investigate the wear mechanisms and to report the wear coefficients. Those are fruitful to get insight for the wear damage of steam generator tubes; however, most wear researches have concentrated on sliding wear of the steam generator tubes, which may not represent the wear loading modes in real plants. In the present work, impact fretting tests of steam generator tube were carried out. A wear progress model for impact-fretting wear has been investigated and proposed. The proposed wear progress model of impact-fretting wear is as follows; oxide film breaking step at the initial stage, and layer formation step, energy accumulation step and finally particle torn out step which is followed by layer formation in the stable impact-fretting progress. The wear coefficient according to the work-rate model has been also compared with one between tube and support.

• Journal of Hydrogen and New Energy
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• v.28 no.5
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• pp.570-576
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• 2017

Gas turbine system with steam injection has shown outstanding advantages such as high specific power and NOx reduction. In the present work, a comparative exergetic analysis was carried out for Steam Injected Gas Turbine (STIG), Regenerative Steam Injected Gas Turbine (RSTIG), and Regenerative After Fogging Gas Turbine (RAF). Effects of pressure ratio, steam injection ratio and steam injection method on the system performance was theoretically investigated. The results showed that the order of the highest exergy efficiency is RSTIG, RAF, and STIG for low pressure ratios but STIG, RSTIG, and RAF for high pressure ratios. In each arrangement, the combustion chamber has the highest exergy destruction and the compressor has the second one.

• Journal of Fisheries and Marine Sciences Education
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• v.23 no.3
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• pp.445-460
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• 2011

Recently, worldwide attention has been placed on being able to develop a person with interdisciplinary abilities. Specifically, there has been an emphasis on the integration of the previous STEM education and the arts, as well as the role of IT in technology and engineering education. Therefore, for this study, our goal is to help pave the way for the increased use of the teaching-learning methods of the IT-based STEAM education in developing people with interdisciplinary abilities. Firstly, we searched through domestic and foreign papers for example related to the recent trend towards the STEAM and integrative IT education models. In this study, we also presented a realistic teaching model based on STEAM education, applied mainly in the U.S., and on the teaching-learning methods of science and technology. The method we suggested is rated by expert assessments as a highly effective teaching-learning method for science and math. The use of educational IT technology in the STEAM education method is also analyzed with positive results.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1669-1679
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• 2017

Background: Steam generator (SG) is one of the significant components in the nuclear steam supply system. A variety of SGs have been designed and used in nuclear reactor systems. Every SG has advantages and disadvantages. A brief account of some of the existing SG designs is presented in this study. A high surface to volume ratio of a SG is required in small modular reactors to occupy the least space. In this paper, performance improvement for SGs of integral small modular reactor is proposed. Aims/Methods: For this purpose, cross-grooved microfins have been incorporated on the inner surface of the helical tube to enhance heat transfer. The primary objective of this work is to investigate thermal-hydraulic behavior of the proposed improvements through modeling in RELAP5-3D. Results and Conclusions: The results are compared with helical-coiled SGs being used in IRIS (International Reactor Innovative and Secure). The results show that the tube length reduces up to 11.56% keeping thermal and hydraulic conditions fixed. In the case of fixed size, the steam outlet temperature increases from 590.1 K to 597.0 K and the capability of power transfer from primary to secondary also increases. However, these advantages are associated with some extra pressure drop, which has to be compensated.

• Clean Technology
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• v.12 no.4
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• pp.217-223
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• 2006

The operating variables of a desorption step were experimentally investigated tor the cycle of the process made up of benzene adsorption, steam desorption, and drying step. The effect of adsorbent regeneration depending on existence and nonexistence of drying step was studied by breakthrough curves obtained in the adsorption step of the second cycle. The duration of drying step was determined by the experimental results. In case that the amount of nitrogen gas was fixed, the regeneration efficiency increased with the amount of steam. However, the effect of steam decreased as the amount of nitrogen increased. Therefore, it would be possible to predict the optimum amount of steam comparing the amount of nitrogen gas with amount of steam in economic view.