• Journal of the Korean institute of surface engineering
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• v.34 no.4
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• pp.289-296
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• 2001

Ni-P electroformed layers were investigated for developing a steam generator tube repair technology in PWRs. The effects of an additive, RPP (Reagent over Pitting Protection) and agitation on mechanical properties and microstructure of the layer were evaluated. The addition of the RPP showed to inhibit the formation of pores, to refine the grain size, and to increase the residual stress in the layer. However, the agitation of the solution during electroforming was observed to increase pores in local regions of the electroformed layer, resulting in decreasing its mechanical properties. The heat treatment of the layer at $343^{\circ}C$ for 1 hr. precipitated the very fine particles of Ni3P in the layer, which inhibited grain growth and increased microhardness.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1454-1459
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• 2024

Researchers have applied theoretical and CFD models for years to analyze the fluidelastic instability (FEI) of tube arrays in steam generators and other heat exchangers. The accuracy of each approach has typically been evaluated using the discrepancy between the experimental critical flow velocity and the predicted value. In the best cases, the predicted critical flow velocity was within an order of magnitude comparable to the measured one. This paper revisits the quasi-steady approach for damping controlled FEI in a normal triangular array with a pitch ratio of P/d = 1.375. The method addresses the fluidelastic frequency at the stability threshold as an input parameter for the approach. The excellent agreement between the estimated stability thresholds and the equivalent experimental results suggests that the fluidelastic frequency must be included in the quasi-steady analysis, which requires minimal computing time and experimental data. In addition, the model allows a simple time delay analysis regarding flow convective and viscous effects.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.117-124
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• 2014

Globally, there are environmental problems due to greenhouse gas emissions. $CO_2$ emissions rate of the cement industry is very high, but the continued demand of cement is needed in the future. In this study, in order to reduce the environmental impact of $CO_2$ emissions from cement production. The experiments were carried out for the development of non-sintered cement (have not undergone firing burning) by granulated ground blast furnace slag. In order to compare the characteristics by curing, an experiment was conducted by changing the curing conditions such as atmospheric steam curing, observe the mechanical properties for the measurement of flexural compressive strength by mortar, observe the chemical properties such as acid resistance, $Cl^-$ penetrate resistance and analyzed the mechanism of hydration by XRD, SEM experiments. From the experimental results, as compared with portland cement usually confirm the mechanical and chemical properties excellent, it is expected be possible to apply to the undersea, underwater and underground structures that require superior durability. In addition, based on the excellent compressive strength by steam curing, it is expected to be possible to utilize as a cement replacement material in the secondary product of concrete. In the future, to solve the problem through continued research, it will be expected to reduce the effect of environmental load and to be excellent economics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.655-662
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• 2014

This study conducted tensile tests on an Alloy 690TT tube at room temperature (RT) and at $343^{\circ}C$ using tube- and ring-type specimens to investigate the stress-strain behavior and tensile properties of a steam generator (SG) tube in the axial and circumferential directions at RT and at the design temperature of a nuclear power plant (NPP). The results of the axial tensile test showed that yield point phenomena appeared at both RT and $343^{\circ}C$, and serrated flow in the stress-strain curve appeared at $343^{\circ}C$. Yield and tensile strengths for both directions were clearly lower at $343^{\circ}C$ compared to RT; however, the elongations were approximately the same at both test temperatures. Regardless of the test temperature, the strengths in the circumferential direction were lower by approximately 5~10 % than those in the axial direction. In addition, the test data revealed that the reduction in the yield and tensile strengths of the Alloy 690TT SG tube with the test temperature was more significant than that estimated by the temperature correction factor of ASME Sec.II.

• Journal of Gifted/Talented Education
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• v.25 no.3
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• pp.363-380
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• 2015

The convergent education such as STEAM education has been implemented in the gifted education institutions in order to resolve the crisis of science and engineering fields caused by the science and engineering avoidance of excellent talents. The purpose of this study was to investigate awareness about science, mathematics and technology/ engineering fields of science gifted students. The subjects were 86 middle school science gifted students at the Science Institute for Gifted Students of a university located in metropolitan city in Korea. The data were collected from the survey that consists of 97 questions in 3 categories. The results were follows: First, the gifted students were aware that science was more interesting than mathematics or technology/engineering. Second, science rated highest in career choice. Third, they were aware that the scientists were more interesting, more imagination, less accuracy and less considering than the mathematicians and the engineers. In addition they responded that the mathematicians were smarter than the scientists and the engineers, and the engineers were more diligent than the scientists and the mathematicians. Finally, the result of the correlational analysis indicated that there were strong correlations between science and mathematics, and between science and technology/engineering. It was recommended that the consolidation of the convergent gifted education, the necessity of systemic career education, and the study of correlation between mathematics and technology/engineering.

• Journal of the Korean Society of Earth Science Education
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• v.9 no.2
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• pp.152-162
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• 2016

This study attempted to present a better direction for the development of STEAM education in science gifted and talented education by making a comparative analysis of the trends date and discussing the implications based on that through Korea Education & Research Information Service(KERIS) The results were as follows: First, the results of the analysis in the order of the published year(2011) showed that since one paper appeared in a journal, the number of the papers has continued to increase. Second, the analysis by research objects found the highest number of the studies on elementary school gifted students; followed by on middle school gifted students; on elementary school gifted students and general school students and teachers; and high school gifted students, middle school gifted students and general school students, and elementary, middle school gifted students, respectively. However, research targeted at infants and college students did not exist. Third, the analysis by research subjects found that science gifted education consists of mainly programming/curriculum and creativity. In addition, the higher number of the researches on creativity suggests that science gifted education is closely associated with not only scientific creativity but science education's nature of increasing the interest and understanding of science and technology. Fourth, the analysis by research methods revealed that the number was the highest regarding development and research studies, followed by experimental research, survey research, qualitative research, and literature research.

• Journal of the Korea Institute of Building Construction
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• v.14 no.2
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• pp.156-162
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• 2014

This study aims to develop a rapidly hardening type of concrete to achieve the removal of form intensity (more than 10MPa) using the method of curing at room temperature in order to solve some economic environmental problems by omitting the steam curing process involved in producing PC (Precast Concrete). Therefore, this study evaluated a rapidly hardening cement containing a high amunt of C3S, which is very responsive in expressing early intensity, and a rapidly hardening type of concrete which uses some hardening accelerator to increase thehydration reaction of $C_3S$. The results of the experiment on concrete using some hardening accelerator are asfollows. In the slump flow experiment for identifying the liquidity and the air test, the desired values were met. The compression strength showed rapid expression response by 12 hours, and met the desired value within 6~9 hours. Its drying shrinkage value and Autogenous shrinkage value were measured as below ($-754.5{\times}10^{-6}$),and satisfied the requirements. In addition, in the Semi-Adiabatic Temperature Test, it was found that the concrete rose to its peak temperature within 24 hours and then its temperature dropped.

• The Journal of Korean Obstetrics and Gynecology
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• v.28 no.3
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• pp.21-29
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• 2015

Objectives This study aimed to investigate therapeutic effect of Korean Medicine Steam Therapy (KMST) for leukorrhea patients. Methods From December 1st 2013 to Nov 31st 2014, 16 leukorrhea outpatients treated with KMST filled out questionnaire before and after treatments. The questionnaire was composed of 8 question items such as sleep, appetite & digestion, urination, defecation, emotion, cold hypersensitivity, menstrual pain, leukorrhea and patients were told to evaluate their symptoms as NRS score. We analyzed mean NRS score of each question item before and after KMST by using Wilcoxon's signed rank test of SPSS ver. 19. Results Mean age of participants was 40.8±13.0 years and mean value of treatment numbers per person was 3.8±1.8 times. 43.75% (n=7) of the patients had history of vaginitis caused by gardnella vaginalis, ureaplasma urealyticum or candida albicans. All patients were treated with acupuncture, moxibustion and Korean medicine. In addition, there was no side effect reported by participants. NRS score of quantity, odor of leukorrhea, perineal unpleasant sensation such as itching, dryness, burning sensation remarkably decreased (p<0.01, p<0.05, p<0.01 each). NRS score of symptoms including sleep, urination, cold hypersensitivity, menstrual pain also remarkably decreased (p<0.05). Conclusions Symptoms of leukorrhea patients including sleep, urination, cold hypersensitivity, menstrual pain, leukorrhea showed significant decrease after treated with concurrent KMST.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.6
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• pp.559-569
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• 2018

Catalytic supports made of carbon have many advantages, such as high coking resistance, tailorable pore and surface structures, and ease of recycling of waste catalysts. Moreover, they do not require pre-reduction. In this study, ash-free coal (AFC) was obtained by the thermal extraction of carbonaceous components from raw coal and its performance as a carbon catalytic support was compared with that of well-known activated carbon (AC). Nickel was dispersed on the carbon supports and the resulting catalysts were applied to the steam reforming of toluene (SRT), a model compound of biomass tar. Interestingly, nickel catalysts dispersed on AFC, which has a very small surface area (${\sim}0.13m^2/g$), showed higher activity than those dispersed on AC, which has a large surface area ($1,173A/cm^2$). X-ray diffraction (XRD) analysis showed that the particle size of nickel deposited on AFC was smaller than that deposited on AC, with the average values on AFC ${\approx}11nm$ and on AC ${\approx}23nm$. This proved that heteroatomic functional groups in AFC, such as carboxyls, can provide ion-exchange or adsorption sites for the nano-scale dispersion of nickel. In addition, the pore structure, surface morphology, chemical composition, and chemical state of the prepared catalysts were analyzed using Brunauer-Emmett-Taylor (BET) analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and temperature-programmed reduction (TPR).

• Korea Science and Art Forum
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• v.21
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• pp.437-449
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• 2015

The research aims to verify the effects of preference for science and self-directed learning ability of the science puppet show program that the researcher has developed as a STEAM education model. The results for conducting the survey with the same questionnaire before and after the program targeting the students showed that the science puppet show had effects on increasing the science related assignment performance will of the behavioral will among the three sub-dimensions including emotional respond, value cognition and behavioral will, but there was no effect on overall aspects of science preference. It can be interpreted as reflecting the characteristics of the scientific talents who already have a high level of preference for science. In addition, the three sub-dimensions including the cognitive regulation, motivational regulation and behavioral regulation had effects on the self-directed learning ability. Especially it had great effects on the directed learning ability of cognitive regulation, learning motivation of motivational regulation, tool application of behavioral regulation, and cooperation capacity which were greater for female students than male students. It is judged that the three-staged science puppet show program including the 'content integrating stage' that the students integrate the curriculum contents, 'integrated mission stage' of solving the visualization, auralization and performance missions by themselves, and 'process integration stage' of making the stage piece all together.