• Journal of the Korean Chemical Society
• /
• v.32 no.6
• /
• pp.581-587
• /
• 1988

The solvolysis of substituted benzyl bromides was studied in binary solvent mixtures of acetone-water and ethanol-water at $25^{\circ}C$ and $45^{\circ}C$. The rate constants increase with electron-donating substituents in benzene ring and increasing of water contents in both of solvent mixtures. The sensitivity parameter (m) of the solvolysis of substituted benzyl bromides to solvent ionizing power (Y) was decreased in going from the electron-donating group to electron-withdrawing one, whereas their nucleophilic sensitivity increased continuously in going to above same substituents. It was shown that electron-donating (electron-withdrawing) groups make the transition state looser (tighter). The above results were consisted with the account for the potential energy surface model and the quantum mechanical approach.

• Elastomers and Composites
• /
• v.48 no.3
• /
• pp.190-194
• /
• 2013

In this study, sebacic acid made from castor oil was used as monomer with isophthalic acid and glycols for polyester polyol synthesis. Polyurethane adhesive was synthesized from the various polyester polyol. From the result of adhesion strength test, polyester polyol made from sebacic acid showed better adhesive force than that of adipic acid due to higher cohesive energy. Branched glycol containing methyl group represented better adhesion than linear glycol. In the chain extender, adhesion strength increased going from PG, EG, BD. From the measurement of TGA, BD showed the best heat stability, and followed by PG, EG. Glass transition temperature increased in the order PG, EG, BD by the result of DMA.

• Geomechanics and Engineering
• /
• v.21 no.4
• /
• pp.357-369
• /
• 2020

Different from the conventional planar fracture and simplified Newton model, for power-law slurries with a lower water-cement ratio commonly used in grouting engineering, flow model in geological rough fractures is built based on ten standard profiles from Barton (1977) in this study. The numerical algorithm is validated by experimental results. The flow mechanism, grout superiority, and water plugging of pseudo plastic slurry are revealed. The representations of hydraulic grouting properties for JRCs are obtained. The results show that effective plugging is based on the mechanical mechanisms of the fluctuant structural surface and higher viscosity at the middle of the fissure. The formulas of grouting parameters are always variable with the roughness and shear movement, which play a key role in grouting. The roughness can only be neglected after reaching a threshold. Grouting pressure increases with increasing roughness and has variable responses for different apertures within standard profiles. The whole process can be divided into three stationary zones and three transition zones, and there is a mutation region (10 < JRCs < 14) in smaller geological fractures. The fitting equations of different JRCs are obtained of power-law models satisfying the condition of -2 < coefficient < 0. The effects of small apertures and moderate to larger roughness (JRCs > 10.8) on the permeability of surfaces cannot be underestimated. The determination of grouting parameters depends on the slurry groutability in terms of its weakest link with discontinuous streamlines. For grouting water plugging, the water-cement ratio, grouting pressure and grouting additives should be determined by combining the flow conditions and the apparent widths of the main fracture and rough surface. This study provides a calculation method of grouting parameters for variable cement-based slurries. And the findings can help for better understanding of fluid flow and diffusion in geological fractures.

• Journal of Practical Engineering Education
• /
• v.9 no.2
• /
• pp.167-174
• /
• 2017

The purpose of this paper is to review the effects of the $4^{th}$ Industrial Revolution on job competency development by the Transitional Labor Market(TLM) model, and suggest job competency development policiy in the rea of the $4^{th}$ Industrial Revolution. The $4^{th}$ Industrial Revolution will create new jobs, destroy many current jobs, and will fundamentally change employment pattern, contents of jobs and ways of works. In these circumstances, we will confront more risks in each stage of labor market transition. To minimize the risks of TLM, we should reform education and develop life time career and job competency. We have to train high level talented persons to lead the $4^{th}$ Industrial Revolution. We have to retrain employed people to adjust new technology and to enhance employability and adaptability. We have to train vulnerable groups so that they may adjust new circumstance. Government should develop life time job competency development open platform.

• Nuclear Engineering and Technology
• /
• v.53 no.6
• /
• pp.1821-1833
• /
• 2021

The gas-liquid counter-current flow limitation (CCFL) is closely related to efficient and safety operation of many equipment in industrial cycle. Air-water countercurrent flow experiments were performed in a tube with diameter of 25 mm to understand the triggering mechanism of CCFL. A parallel electrode probe was utilized to measure film thickness whereby the time domain and frequency domain characteristics of liquid film was obtained. The amplitude of the interface wave is small at low liquid flow rate while it becomes large at high liquid flow rate after being disturbed by the airflow. The spectral characteristic curve shows a peak-shaped distribution. The crest exists between 0 and 10 Hz and the amplitude decreases with the frequency increase. The analysis of visual observation and characteristic of film thickness indicate that two flooding mechanisms were identified at low and high liquid flow rate, respectively. At low liquid flow rate, the interfacial waves upward propagation is responsible for the formation of CCFL onset. While flooding at high liquid flow rate takes place as a direct consequence of the liquid bridging in tube due to the turbulent flow pattern. Moreover, it is believed that there is a transition region between the low and high liquid flow rate.

• Journal of Korean Elementary Science Education
• /
• v.40 no.2
• /
• pp.210-226
• /
• 2021

The purpose of this study was to understand what orientations elementary school teachers have related to their science classes, what realities they encounter in real classes, how they overcome their frustrations and failures they experience. We employed a narrative inquiry method and analyzed the experiences of two early career elementary school teachers (Miss Park and Mr. Choi). Miss Park wanted to conduct students-driven inquiry classes, in which students become active investigators, but in reality, she faced herself who conducted teacher-driven classes. Mr. Choi wanted to conduct science classes based on constructivism, but in reality, he encountered himself as a knowledge giver rather than scaffolder. However, rather than giving up their orientations, the two teachers tried to keep them in their own way. It was expected that by understanding what strategies beginner teachers take when their theoretical orientation and ideals are not well implemented in actual educational reality, we could find a clue that will lead to a more successful transition from pre-service teacher to teacher.

• The Journal of the Korea Contents Association
• /
• v.22 no.3
• /
• pp.121-133
• /
• 2022

The main purpose of this paper is to examine the efficacy and future potential of a newly-emerging concept of a metaverse in online education environment. In order to achieve this goal, this paper showcases various scenes that happened in the metaverse classes using the ifland app. Through an in-depth analysis of theoretical grounds and preliminary survey findings of 32 university students, this study suggests that as students in a metaverse space are engaged in the interactive learning process and environment with an avatar that projects oneself, it can be an effective educational platform coming from the benefits of gamification and edutainment. In addition, a metaverse space provides existential encounters and hands-on experiences, which in turn increases the level of 3D learning immersion. It may overcome the shortcomings of online live streaming platforms such as Zoom or Webex that provide 2D experiences. Based on the findings, this paper further suggests a blueprint for online education suitable for the transition to a digital society.

• Korean Journal of Childcare and Education
• /
• v.11 no.4
• /
• pp.189-210
• /
• 2015

This study's aim was to find a patterns of network dynamics focused on multicultural education contents within the teacher's guide books which are based on national kindergarten curriculum. It was analysed that the 43 guidebooks(2009 Educational activities and materials guidebooks for kindergarten, 11 and the Nuri curriculum teacher guidebooks for the age of 3-5, 32) were analysed using the UCINET 6 program with multicultural education contents frameworks. The findings were as follows: First, multicultural contents' density is connected to life theme of the Nuri curriculum was higher than the 2009 kindergarten curriculum. And life theme with high connectivity was 'I and my family' in the 2009 kindergarten curriculum and 'animals, plants and nature'(3 years old), 'kindergarten and friends' & 'I and my family'(4-5 years old) in the Nuri curriculum. Second, the highest connection content was 'having interests in culture' & 'knowing similarities and differences' in the 2009 kindergarten curriculum, and 'having interests in culture' & 'promoting a sense of community' in the Nuri curriculum. Finally, multicultural education for young children according to the national educational curriculum transition was changed from 'identity' to 'interaction and cooperation'. It means that the Nuri curriculum is more focused on international knowledges and competencies as a world citizen. It suggests the directions for multicultural education for young children in the future.

• Molecules and Cells
• /
• v.37 no.12
• /
• pp.873-880
• /
• 2014

In our previous study, miRNA-183, a miRNA in the miR-96-182-183 cluster, was significantly over-expressed in esophageal squamous cell carcinoma (ESCC). In the present study, we explored the oncogenic roles of miR-183 in ESCC by gain and loss of function analysis in an esophageal cancer cell line (EC9706). Genome-wide mRNA micro-array was applied to determine the genes that were regulated directly or indirectly by miR-183. 3'UTR luciferase reporter assay, RT-PCR, and Western blot were conducted to verify the target gene of miR-183. Cell culture results showed that miR-183 inhibited apoptosis (p < 0.05), enhanced cell proliferation (p < 0.05), and accelerated G1/S transition (p < 0.05). Moreover, the inhibitory effect of miR-183 on apoptosis was rescued when miR-183 was suppressed via miR-183 inhibitor (p < 0.05). Western blot analysis showed that the expression of programmed cell death 4 (PDCD4), which was predicted as the target gene of miR-183 by microarray profiling and bioinformatics predictions, decreased when miR-183 was over-expressed. The 3'UTR luciferase reporter assay confirmed that miR-183 directly regulated PDCD4 by binding to sequences in the 3'UTR of PDCD4. Pearson correlation analysis further confirmed the significant negative correlation between miR-183 and PDCD4 in both cell lines and in ESCC patients. Our data suggest that miR-183 might play an oncogenic role in ESCC by regulating PDCD4 expression.

• 대한공업교육학회지
• /
• v.31 no.2
• /
• pp.155-176
• /
• 2006

The purpose of this study was to explore the strategies for applying TRIZ to technology education. This study was carried out through literature review on contradiction, 40 principles, 76 standard solutions, multi screen method, effects, the law of technology evolution, and ARIZ, and questionnaire survey to investigate the validity. Through this study the strategies for applying TRIZ to technology education were proposed and the validity was identified. Only the '40 Principles' was appropriate to technology education of elementary and middle school. The results of this study were as follows; In elementary school technology education, segmentation, extraction, local quality, asymmetry, consolidation, universality, counterweight, do it in reverse, mediator, self service, dispose, flexible membranes or thin films, changing the color, homogeneity, rejecting and regenerating parts, and composite materials were suitable. And in middle school technology education, segmentation, extraction, local quality, asymmetry, consolidation, universality, counterweight, prior counteraction, prior action, cushion in advance, do it in reverse, dynamicity, partial or excessive action, continuity of useful action, convert harm into benefit, mediator, self service, dispose, flexible membranes or thin films, changing the color, homogeneity, rejecting and regenerating parts, transformation of properties, phase transition, thermal expansion, and composite materials were suitable.