• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.174-186
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• 2019

This paper reviews the development condition of nanomaterials used in concrete over years. The definitions of nanomaterial, nanotechnology, and nano-concrete are reviewed. The impacts of nanomaterials on cementitious material in the point of advantages and disadvantages are analyzed. Moreover, this paper analyzes and classifies the nanomaterials into the extra quality enhancement and modification to plain cementitious composite. Indeed, the outstanding properties of the embedded nanomaterials can be introduced to concrete such as the mechanical improvement, pore structure refinement, hydrate acceleration, and smartness modifying of self-cleaning, and/or self-sensing. Before the full potential of nanotechnology can be realized in concrete applications, various techniques have to be solved including proper dispersion, compatibility of the nanomaterials in cement, processing, manufacturing, safety, handling issues, scale-up, cost, the impact on the environment and human health.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.231-235
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• 1986

MNDO and ab initio calculations for gas phase reactions of alkoxide-exchange at silicon and carbon centers have been performed. Results show that MNDO values of ${\Delta}$E's of these reactions closely parallel those of the STO-3G method. The alkoxide-exchange at silicon is shown to be facile due to the formation of stable five-coordinate intermediate while the reaction at carbon is predicted to proceed with high barrier; the difference in this substitution behavior between carbon and silicon is shown to be due to an easy valence shell expansion of silicon in accommodating an extra bond in the formation of stable five-coordinate intermediates.

• Advances in nano research
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• v.14 no.3
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• pp.235-246
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• 2023

Nanotechnology, like any other revolutionary innovation in materials science, has significantly influenced the level of competition in sports. Nanotechnology provides various benefits and enormous potential to enhance athletic equipment, making players safer, more comfortable, and more agile. Various sporting equipment is being infused with nanomaterials, including carbon nanotubes (CNTs), silica nanoparticles (SNPs), nanoclays fullerenes, etc., to enhance athlete and equipment performance. Each of these nanomaterials gives athletic equipment an extra benefit like high strength and stiffness, longevity, decreased weight, abrasion resistance, etc. This paper mechanically analysis the structural strength of tennis equipment to avoid injury. As a result, the bending forces are applied to the reinforced structures to investigate their durability.

• Journal of Gastric Cancer
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• v.6 no.4
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• pp.237-243
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• 2006

Purpose: This study was conducted to evaluate the treatment outcomes and the prognosis for gastric cancer patients with hepatic metastasis. Materials and Methods: This retrospective study was based on the medical records of 85 gastric cancer patients with hepatic metastasis (62 synchronous and, 23 metachronous) who received chemotherapy with or without resectional therapy from March 1990 to March 2006. The survival rate was analyzed according to clinicopathologic factors and therapeutic factors, such as whether or not a gastrectomy, a hepatic resection, and/or chemotherapy had been performed. Results: The median survival of gastric cancer patients with hepatic metastasis was 11 months (synchronous: 11 months and metachronous: 17 months). The rates of gastrectomies and hepatic resections in the synchronous group were 24.1% and 16.1%, respectively A 23.5% prevalence of extra-hepatic metastasis was observed. The median survivals of patients who underwent a gastrectomy with a hepatic resection, a gastrectomy alone, and non-surgical treatment were 60, 18, and 9 months, respectively (P<0.05). The disease-free median survival of the metachronous group was 8 ($3{\sim}39$) months. There was no difference in initial pathologic stage and frequency of hepatic metastasis after the gastrectomy in the metachronous group. In the synchronous group, extra-hepatic metastasis, a gastrectomy as the operative procedure, a hepatic resection as the operative procedure and the response to chemotherapy were statistically significant in the univariate analysis, and a hepatic resection as the operative procedure, the response to chemotherapy, and extra-hepatic metastasis were independant prognostic factors identified by the multivariate analysis. In the metachronous group, extra-hepatic metastasis, the response to chemotherapy and differentiation were statistically significant in the univariate analysis, and extra-hepatic metastasis was an independent prognostic factor identified by the multivariate analysis. Conclusion: An aggressive surgical therapy and effective chemotherapy are necessary in the treatment of gastric cancer patients with hepatic metastasis. (J Korean Gastric Cancer Assoc 2006;6:237-243)

• Korean Journal of Community Nutrition
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• v.13 no.5
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• pp.630-639
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• 2008

The purpose of this study was to develop children-friendly comic books and animation for dietary education of 3rd or 4th grade elementary students. Through a literature review on current dietary problems and dietary education for children, 15 educational themes were chosen on both healthy eating and safe dietary life. Comic books and animation were developed based on the themes by the brainstorming and help of professional animators, and they were applied and evaluated in the field. The developed comic books and animation, with its own characters, proved to be of high quality and effective educational materials for children's healthy and safe eating. Compared with the reference group, the tested group has shown a significant improvement in dietary knowledge and attitude (p < 0.05). And both parents (level of understanding 4.29, level of interest 4.49, level of usefulness 4.46, level of design satisfaction 3.95 in 5-point Likert scale) and children (level of understanding 4.63, level of interest 4.57, level of usefulness of 1st comic book 4.44, 2nd comic book 4.49, level of design satisfaction 4.06, level of usefulness for knowledge pages 4.22 in 5-point Likert scale) have shown high levels of interests and satisfaction. Therefore, these materials could be utilized as effective educational materials for elementary students in school lunch time, extra-curricular activities, or after school programs.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.213-213
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• 2013

Even weak van der Waals (vdW) adhesion between two-dimensional solids may perturbtheir various materials properties owing to their low dimensionality. Although the electronic structure of graphene has been predicted to be modified by the vdW interaction with other materials, its optical characterization has not been successful. In this report, we demonstrate that Raman spectroscopy can be utilized to detect a few % decrease in the Fermi velocity ($v_F$) of graphene caused by the vdW interaction with underlying hexagonal boron nitride (hBN). Our study also establishes Raman spectroscopic analysis which enables separation of the effects by the vdW interaction from those by mechanical strain or extra charge carriers. The analysis reveals that spectral features of graphene on hBN are mainly affected by change in vF and mechanical strain, but not by charge doping unlike graphene supported on $SiO_2$ substrates. Graphene on hBN was also found to be less susceptible to thermally induced hole doping.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.4
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• pp.185-192
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• 2022

Variations in the microstructure and mechanical properties of API X70 steel processed by piping, electrical resistance welding (ERW), and post seam annealing (PSA) are investigated in this study. In the welding zone, some elongated pearlites are formed and grains coarsening occurs due to extra heat caused by the ERW and PSA processes. After the piping, the base metal shows continuous yielding behavior and a decrease in yield and impact strengths because mobile dislocation and back stress are introduced during the piping process. On the other hand, the ERW and PSA processes additionally decreased the impact strength of welding zone at room and low temperatures because some elongated pearlites easily act as crack initiation site and coarse ferrite grains facilitate crack propagation. As a result, the fracture surface of the welding zone specimen tested at low temperature revealed mostly cleavage fracture unlike the base metal specimen.

• Journal of Sensor Science and Technology
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• v.31 no.2
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• pp.102-106
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• 2022

Currently, the demand for real-time monitoring of water quality has increased dramatically. Total organic carbon (TOC) analysis is a suitable method for real-time analysis compared with conventional biochemical oxygen demand (BOD) and chemical oxygen demand (COD) methods in terms of analysis time. However, this method is expensive because of the complicated internal processes involved. The photocatalytic titanium dioxide (TiO2)-based TOC method is simpler as it omits more than three preprocessing steps. This is because it reacts only with organic carbon (OC) without extra processes. We optimized the rate between the TiO2 photocatalyst and binder solution and the TiO2 concentration. The efficiency was investigated under 365 nm UV exposure onto a TiO2 coated substrate. The optimized conditions were sufficient to apply a real-time monitoring system for water quality with a short reaction time (within 10 min). We expect that it can be applied in a wide range of water quality monitoring industries.

• The Mathematical Education
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• v.48 no.3
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• pp.303-328
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• 2009

In this study, we developed the teaching methods using manipulative materials to teach regular polytopes, and applied these to first-year student of middle school who is attending the extra math class. In that class, we focused on the change of the mathematical representations -especially verval, visual and symbolic representations- and mathematical behavioral. By analyzing characterstics the students' work sheets, we obtained affirmative results as follows. First, manipulative materials played an important role on drawing a development figure of regular polyhtopes describing the verval representation definition of regular polytopes. Second, classes utilizing manipulative materials changed students verbalism level of representations the definition of regular polytopes. For example, in the first class about 60% of students are in the $0{\sim}2$ vervalism level, but in the third class, about 65% of students are in the $6{\sim}7$ level. Third, classes utilizing manipulative materials improved visual representation about development figure. After experiences making several development figures about regular octahedron directly, and discussion, students found out key points to be considered for draws development figure and this helped to draw development figures about other regular polytopes. Fourth, students were unaccustomed to make symbolic representations of regular polytopes. But, they obtained same improvement in symbolic representations, so in fifth the class some students try to make symbol about something in common of whole regular polytopes. Fifth, after the classes, we have significant differences in the students, especially behavioral characteristics in II items such as mind that want to study own fitness, interest, attachment, spirit of inquiry, continuously mathematics posthumously. This means that classes using manipulative materials. Specially, 'mind that want to study mathematics continuously' showed the biggest difference, and it may give positive influence to inculcates mathematics studying volition while suitable practical use of manipulative materials. To conclude, classes using manipulative materials may help students enhance the verbal, visual representation, and gestates symbol representation. Also, the class using manipulative materials may give positive influence in some part of mathematical behavioral characteristic. Therefore, if we use manipulative materials properly in the class, we have more positive effects on the students cognitive perspect and behavioral cteristics.

• Journal of Korean Home Economics Education Association
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• v.20 no.3
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• pp.215-230
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• 2008

Activity materials in textbook could facilitate students' oriented self-help learning. The purpose of this paper is to find out characteristics of activity materials in the housing area of middle school Technology and Home Economics and teacher's perception of them. The data were collected from 253 middle school teachers who had ever taught the housing unit in any of 6 textbooks. The results showed that the number of activity materials were differed by the characteristics of the materials such as type of materials, feature of non sentence materials, and type of activity, depend on authors as well as textbooks. In general, teachers interests in the materials were higher than those of students even the trends of the interests were the same. Adequacy of activity contents and related knowledge of teachers were higher than adequacy of level. Teachers thought time and extra search beyond class were barrier to full the interests of students. Further research is suggested to find out whether higher interests in the materials are related to the higher activating rate of them.