• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.7-13
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• 2019

This study aims to develop a FE Model to simulate dissimilar friction stir welding and to address its potential for fundamental analysis and practical applications. The FE model is based on Coupled Eulerian-Lagrangian approach. Multiphysics systems are calculated using explicit time integration algorithm, and heat generations by friction and inelastic heat conversion as well as heat transfer through the bottom surface are included. Using the developed model, friction stir welding between an Al6061T6 plate and an AZ61 plate were simulated. Three simulations are carried out varying the welding parameters. The model is capable of predicting the temperature and plastic strain fields and the distribution of void. The simulation results showed that temperature was generally greater in Mg plates and that, as a rotation speed increase, not the maximum temperature of Mg plate increased, but did the temperature of Al plate. In addition, the model could predict flash defects, however, the prediction of void near the welding tool was not satisfactory. Since the model includes the complex physics closely occurring during FSW, the model possibly analyze a lot of phenomena hard to discovered by experiments. However, practical applications may be limited due to huge simulation time.

• Journal of Life Science
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• v.29 no.8
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• pp.871-878
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• 2019

The aim of this study was to determine the anticancer activities of an 80% methanol extract and various fractions of Rhododendron brachycarpum (RB). The n-hexane fraction of RB showed the highest inhibitory activity (Inhibit concentration $50%=20.2{\pm}1.2{\mu}g/ml$) in HT-29 cells. Colony- and sphereforming abilities were significantly correlated with a decrease in the cell count and size. A TOP/FOP flash reporter assay revealed that the inhibitory activity of the n-hexane fraction of RB ($0.22{\pm}0.02$ fold change) was lower than that of the 80% methanol extract and that of other fractions. The n-hexane and ethyl acetate fractions of RB were predominantly dependent on the expression levels of intracellular ${\beta}-catenin$. Western blotting using $p-GSK3{\beta}$ with only the n-hexane fraction of RB was conducted to examine whether these secondary metabolites reduced ${\beta}-catenin$ degradation. Intracellular ${\beta}-catenin$ regulation resulted in quantitative changes in the nucleus. In summary, these results demonstrate the potential of the n-hexane fraction of RB as a natural anticancer agent.

• Journal of the Society of Disaster Information
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• v.19 no.1
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• pp.117-127
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• 2023

Purpose: The number of Cold Storages at home and abroad is on the rise, fires in large Cold Storages have recently occurred. As fires continue to occur and property damage is on the rise every year, the importance of preventing fires in large Cold Storage is growing. Method: Real Cold Storages were investigated on-site and fire cases were analyzed to derive and analyze fire risk, and the ORS, which is emerging as an adaptive fire prevention technology of Cold Storage, was investigated through FDS. Result: oxygen concentration 21, 15.7% and 17.7, 16.7% were analyzed through FDS, and flashover was reached within 3~4 minutes from 21, 17.7, 16.7%, but if oxygen concentration was lowered to 15.7%, it didn't ignite for 13 minutes. Conclusion: This study understood the concept and general part of the ORS, modeled the freezer through FDS, and analyzed the oxygen concentration to analyze the fire protection adaptability of the ORS. In the future, it is expected that large-scale empirical experiments and related regulations will be prepared to provide solutions for fire prevention in Cold Storages in blind spots of fire.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.427-432
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• 2024

The polymer crystallization process, promoting the formation of ferroelectric β-phase, is essential for developing polyvinylidene fluoride (PVDF)-based high-performance piezoelectric energy harvesters. However, traditional high-temperature annealing is unsuitable for the manufacture of flexible piezoelectric devices due to the thermal damage to plastic components that occurs during the long processing times. In this study, we investigated the feasibility of introducing a flash lamp annealing that can rapidly induce the β-phase in the PVDF layer while avoiding device damage through selective heating. The flash light-irradiated PVDF films achieved a maximum β-phase content of 76.52% under an applied voltage of 300 V and an on-time of 1.5 ms, a higher fraction than that obtained through thermal annealing. The PVDF-based piezoelectric energy harvester with the optimized irradiation condition generates a stable output voltage of 0.23 V and a current of 102 nA under repeated bendings. These results demonstrate that flash lamp annealing can be an effective process for realizing the mass production of PVDF-based flexible electronics.

• Journal of the Korean earth science society
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• v.31 no.4
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• pp.392-402
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• 2010

The purpose of this study is to analyze and evaluate the self-directed learning contents of Earth science area in the basic course of the 7th grade. For this purpose, we applied the 'Cyber Home Study Content Quality Control Tool' presented in 'Elementary Secondary Education e-Learning Quality Management Guidelines (Ver.2.0)' of Korea Education & Research Information Service (2008). The results of contents analysis are as follow: First, it was presented that the study guide introduced the contents which should be studied for one class, properly. And it was not analyzed that the diagnosis assesment was not completed in the initiative study; Second, it was possible to study choosing the contents fitting the learner's level of learning in the main study, it was comprised of about 15 minutes. Third, it was performed without feedback for incorrect answers in the learning assessment, just the number of wrong questions. And the learning arrangement present the important contents learned in that class, summarizing and arranging again. The results of content evaluation are as follows: First, a big difference was not showed against the needs analysis, instructional design, interaction in each class. And the evaluation of the ethics was not included a word or sentence not suitable. The evaluation of copyright, it was analyzed that Work within the content display in compliance with international copyright Second, the evaluation of instructional design presented mainly the description of a simple picture based, the visible resources like flash card were poor. And in the evaluation of Supporting System, it was presented that the contents were installed so that it was freely available for learners. But it was analyzed that there was no memo-function learners were able to jot down something during the studying contents. And in the evaluation for evaluation, the clear valuation basis about the described content was not presented. So there were slightly differences for each class. Third, in the evaluation and analysis for learning content, it was presented that there were some big differences for each class because it was not composed of the latest information, not corrected and complementary.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.4
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• pp.527-532
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• 2014

Purpose: The matching of the optical center and the pupil center was measured by photographs in wearing glasses. In this study, the influences of the induced prism by the mismatching are studied. Methods: 74 subjects (148 eyes) who were spectacles wearer were participated in this study. The mean age was $29.19{\pm}12.22$ years (range 19-55 years). The facial photographs of subjects were taken while wearing spectacles. The matching of the corneal reflected image and optical center of the spectacle lens in the horizontal deviations, and the vertical deviations were measured by the observation of the photo image. The prisms induced in accordance with various frame type were calculated from the mismatching deviations. Results: The binocular horizontal deviations were $1.55{\pm}1.70mm$ for the metal frame, $1.71{\pm}2.21mm$ for the clings type plastic frame, and $1.15{\pm}1.38mm$ for the plastic frame. In the horizontal direction induced prism, the ratio over the tolerance was 23%. The ratio were the 17.6% at the BI prism, and 5.4% at the BO prism. The binocular vertical deviation comparisons were $3.93{\pm}1.91mm$ for the metal frame, $5.79{\pm}1.93mm$ for the clings type plastic frame, and 1$6.01{\pm}2.94mm$ for the plastic frame. In the vertical direction induced prism, the ratio over the tolerance was 44.6%. Based on the refraction power, the ratio were 12.2% at -0.25${\leq}-3.00$, and 32.4% at -3.00${\leq}-12.00D$. Conclusions: The induced prisms in the horizontal direction were much in the BI prism. The binocular vertical deviations of the glasses.

• Journal of Korean Home Economics Education Association
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• v.18 no.2 s.40
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• pp.15-27
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• 2006

The purpose of this research was to develop and analyze the effects of ICT based teaching learning process plans for 'Designing My Home' unit of Technology Home Economics subject in High School. The seven housing contents were selected from 8 textbooks and 8 teaching resources at the analyses stage. A specific homepage(ieduhome.cafe.com) was built to utilize the eight ICT teaching learning process plan as well as many other resources at the planning & development stages. The number of 68 highschool students have participated for the application stage during September 4-26, 2003 and the same number have studied the same contents through regular teaching learning plans as a comparison group. Experimental groups have significantly more increased in the knowledge and understanding of the housing contents than have comparison groups. The same results occurred in the interests in Home Economics, Housing, and Internet utilized study. The Design reports were not statistically differed between two groups based on the objective evaluation criteria. The results of this study generally supported previous research and showed that the In teaching learning plans were more effective in various aspects than were the regular plans.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.201-210
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• 2019

Recently, due to the efforts to mitigate traffic congestion and expansion of space efficiency, the construction of underground roads has been increased in big-scale cities. Since tunnels in the city have a higher chance for a fire leading to a great tragedy during a severe traffic jam than mountain tunnels, it is highly likely that it will be constructed as a tunnel, having a small cross section, for small vehicles. However, if they are constructed as such small-vehicle tunnels, it would be possible to reduce the design fire intensity while the concentration of harmful gases would increase due to a reduction in the small cross sectional area, led by a decrease in the tunnel height. In this study, behaviors of fire smoke by the installation interval and format of large-scale exhaust-gas ports were examined and compared in the analysis of temperatures and CO concentrations of a tunnel and its results were as the following. Although there were no significant differences in the smoke spreading distance between installation intervals, but in this study, 100 m was found to be the most effective installation interval. The smoke exhaustion performance was found to be excellent in the order of $4m{\times}3m$, $6m{\times}2m$, and $3m{\times}2m$ (2 lane) of the smoke spreading distance. Although there was no significant difference in the smoke spreading distance between formats of large-scale exhaust-gas ports, it was found that the smoke spreading distance was larger than other cases when it was $3m{\times}2m$ in the fire growing process. The analysis of smoke spreading distances by the aspect ratio showed that a smoke spreading distance was shorted when its the smoke spreading distance was found to be shorter when its traverse distance was relatively longer than its longitudinal distance.