• Journal of the Korean earth science society
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• v.33 no.3
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• pp.269-279
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• 2012

Satellite-retrieved data on Aerosol Optical Depth (AOD) and ${\AA}$ngstr$\ddot{o}$m exponent (AE) using a Moderate Resolution Imaging Spectrometer (MODIS) were used to analyze large-scale distributions of atmospheric aerosols in East Asia. AOD was relatively high in March ($0.44{\pm}0.25$) and low in September ($0.24{\pm}0.21$) in the East Asian region in 2009. Sandstorms originating from the deserts and dry areas in Northern China and Mongolia were transported on a massive scale during the springtime, thus contributing to the high AOD in East Asia. Although $PM_{10}$ with diameters ${\leq}10{\mu}m$ was the highest in February at Anmyon, Cheongwon and Ulleung, which is located leeward about half-way through the Korean Peninsula, AOD rose to a high in May. The growth of hygroscopic aerosols moving with increases in relative humidity prior to the Asian monsoon season contributed to a high AOD level in May. AE typically reaches its highest value ($1.30{\pm}0.37$) in August due to anthropogenic aerosols originating from industrial areas in Eastern China, while AOD stays low in summer due to the removal process caused by rainfall. The linear correlation coefficients of the MODIS AOD and ground-based mass concentrations of $PM_{10}$ at Anmyon, Cheongwon and Ulleung were 0.4-0.6. Four cases (six days) of mineral dustfall from sandstorms and six cases (twelve days) of anthropogenically polluted particles were observed in the central area of the Korean Peninsula in 2009. $PM_{10}$ mass concentrations increased at both Anmyon and Cheongwon in the cases of mineral dustfall and anthropogenically polluted particles. Cases of dustfall from sandstorms and anthropogenic polluted particles, with increasing $PM_{10}$ mass concentrations, exhibited higher AOD values in the Yellow Sea region.

• Journal of the Korean earth science society
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• v.34 no.7
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• pp.681-692
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• 2013

We aimed to evaluate the effectiveness of the Giggenbach bottle method and develop the related pretreatment and analytical methods using artificial fumarolic gases. The artificial fumarolic gases were generated by mixing $CO_2$, CO, $H_2S$, $SO_2$, $H_2$, and $CH_4$ gas streams with a $N_2$ stream sparged through an acidic medium containing HCl and HF, with their compositions varied by adjusting the gas flow rates. The resultant fumarolic gases were collected into an evacuated bottle partially filled with a NaOH absorption solution. While non-condensible gases such as CO, $H_2S$, and $CH_4$ accumulated in the headspace of the bottle, acidic components including $CO_2$, $SO_2$, HCl, and HF that were dissolved into the alkaline solution. Like other acidic components, $H_2S$ also dissolved into the solution, but it reacted with dissolved $Cd^{2+}$ to precipitate as CdS when $Cd(CH_3COO)_2$ was added. The non-condensible gases were analyzed on a gas chromatography. Then, CdS precipitates were separated from the alkaline solution by filtration, and they were pretreated with $H_2O_2$ to oxidize CdS-bound sulfide into sulfate. In addition, a portion of the solution was also pretreated with $H_2O_2$ to oxidize sulfite to sulfate. Following the pretreatment, the resultant samples were analyzed for $SO_4^{2-}$, $Cl^-$ and $F^-$ on an ion chromatography. In the meanwhile, dissolved $CO_2$ was analyzed on a total organic carbon-inorganic carbon analyzer without such pretreatment. According to our experimental results, the measured concentrations of the fumarolic gases were shown to be proportional to the gas flow rates, indicating that the Giggenbach bottle method is adequate for monitoring volcanic gas. The pretreatment and analytical methods employed in this study may also enhance the accuracy and reproducibility of the Giggenbach bottle method.

• Journal of the Korean earth science society
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• v.41 no.3
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• pp.248-260
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• 2020

Oceanic current maps introduced in science and earth science textbooks can offer a valuable opportunity for students to learn about rapid climate change and the role of currents associated with the global energy balance problem. Previously developed oceanic current maps in middle and high school textbooks under the 2007 and 2009-revised national curriculum contained various errors in terms of scientific accuracy. To resolve these problems, marine experts have constructed a unified oceanographic map of the oceans surrounding the Korean Peninsula. Since 2010, this process has involved a continuous, long-term consultation procedure. By extensively gathering opinions and through verification process, a representative and scientific oceanic current map was eventually constructed. Based on this, the educational oceanic current maps, targeting the comprehension of middle and high school students, were developed. These maps were incorporated into middle and high school textbooks in accordance with the revised 2015 curriculum. In this study, we analyzed the oceanic current maps of five middle school science textbooks and six earth science textbooks that were published in high school in 2019. Although all the oceanic current maps in the textbooks were unified based on the proposed scientific oceanic current maps, there were problems such as the omission of certain oceanic currents or the use of a combination of dotted and solid lines. Moreover, several textbooks were found to be using incorrect names for oceanic currents. This study suggests that oceanic current maps, produced by integrating scientific knowledge, should be visually accurate and utilized appropriately to avoid students' misconception.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.3
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• pp.290-297
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• 2008

STATEMENT OF PROBLEM: Implant-supported fixed cantilever prostheses are influenced by various biomechanical factors. The information that shows the effect of implant number and position of cantilever on stress in the supporting bone is limited. PURPOSE: The purpose of this study was to investigate the effect of implant number variation and the effect of 2 different cantilever types on stress distribution in the supporting bone, using 3-dimensional finite element analysis. MATERIAL AND METHODS: A 3-D FE model of a mandibular section of bone with a missing second premolar, first molar, and second molar was developed. $4.1{\times}10$ mm screw-type dental implant was selected. 4.0 mm height solid abutments were fixed over all implant fixtures. Type III gold alloy was selected for implant-supported fixed prostheses. For mesial cantilever test, model 1-1 which has three $4.1{\times}10$ mm implants and fixed prosthesis with no pontic, model 1-2 which has two $4.1{\times}10$ mm implants and fixed prosthesis with a central pontic and model 1-3 which has two $4.1{\times}10$ mm implants and fixed prosthesis with mesial cantilever were simulated. And then, 155N oblique force was applied to the buccal cusp of second premolar. For distal cantilever test, model 2-1 which has three $4.1{\times}10$ mm implants and fixed prosthesis with no pontic, model 2-2 which has two $4.1{\times}10$ mm implants and fixed prosthesis with a central pontic and model 2-3 which has two $4.1{\times}10$ mm implants and fixed prosthesis with distal cantilever were simulated. And then, 206N oblique force was applied to the buccal cusp of second premolar. The implant and superstructure were simulated in finite element software(Pro/Engineer wildfire 2.0). The stress values were observed with the maximum von Mises stresses. RESULTS: Among the models without a cantilever, model 1-1 and 2-1 which had three implants, showed lower stress than model 1-2 and 2-2 which had two implants. Although model 2-1 was applied with 206N, it showed lower stress than model 1-2 which was applied with 155N. In models that implant positions of models were same, the amount of applied occlusal load largely influenced the maximum von Mises stress. Model 1-1, 1-2 and 1-3, which were loaded with 155N, showed less stress than corresponding model 2-1, 2-2 and 2- 3 which were loaded with 206N. For the same number of implants, the existence of a cantilever induced the obvious increase of maximum stress. Model 1-3 and 2-3 which had a cantilever, showed much higher stress than the others which had no cantilever. In all models, the von Mises stresses were concentrated at the cortical bone around the cervical region of the implants. Meanwhile, in model 1-1, 1-2 and 1-3, which were loaded on second premolar position, the first premolar participated in stress distribution. First premolars of model 2-1, 2-2 and 2-3 did not participate in stress distribution. CONCLUSION: 1. The more implants supported, the less stress was induced, regardless of applied occlusal loads. 2. The maximum von Mises stress in the bone of the implant-supported three unit fixed dental prosthesis with a mesial cantilever was 1.38 times that with a central pontic. The maximum von Mises stress in the bone of the implant-supported three-unit fixed dental prosthesis with a distal cantilever was 1.59 times that with a central pontic. 3. A distal cantilever induced larger stress in the bone than a mesial cantilever. 4. A adjacent tooth which contacts implant-supported fixed prosthesis participated in the stress distribution.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.2
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• pp.185-194
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• 2018

The objective of this study was to compare the shear bonding strength of zirconia after cleaning the crown contaminated by saliva or blood and determine the effect of thermocycling. 180 specimens were embedded in acrylic resin. 20 Specimens in the positive control group were bonded with resin cement without contamination. 20 Specimens in the negative control group were washed with water for 20 seconds and then dried for 10 seconds. 120 Specimens contaminated by saliva or blood were cleaned by using three cleaning methods: 37% phosphoric acid gel, commercial cleanse, and 2.5% NaOCl. All samples were bonded with resin cement and divided into two subgroups: One was not aged, and the other was tested with 30,000 thermocycling. In both groups contamination by saliva and blood, no statistically significant difference was not found in control, groups cleansed by commercial cleanser and 2.5% NaOCl. When the groups cleansed with water and 37% phosphate gel were compared with the control, significantly low shear bond strength was shown. Thermocycling group showed statistically significantly low shear bond stress compared to the groups without thermocycling. When zirconia was contaminated by saliva or blood, its original shear bond strength could be obtained if it was cleaned with commercial cleanser or 2.5% NaOCl.

• Journal of The Korean Association For Science Education
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• v.32 no.5
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• pp.805-822
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• 2012

The purpose of this study was to explore the patterns of group model development about blood flow in the heart and reasoning process by small group interaction. The subjects were 14, 8th graders in a Science Gifted Center. The group discussion was made possible by using triggering questions that can be answered based on experiences of hands-on activities such as a siphon pump analogy model activity and a dissection of pigs' hearts. Despite participating in same activities, the groups showed different model development patterns: unchanged, persuasive, and elaborated. Due to the critical revising, the group's explanatory model was elaborated and developed in the added and elaborated pattern. As critical revising is a core element of the developing model, it is important to promote a group interaction so that students become critical and receptive. The pedagogical analogy model and conflict situation enabled students to present elaborated reasoning. The Inquiry activity with the pedagogical analogy model promote students' spontaneous reasoning in relation to direct experience. Therefore offering a pedagogical analogy model will help students evaluate, revise and develop their models of concerned phenomena in science classroom. Conflict situation by rebuttal enable students to justify more solid and elaborate a model close to the target model. Therefore, teachers need to facilitate a group atmosphere for spontaneous conflict situation.

• Journal of The Korean Association For Science Education
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• v.30 no.5
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• pp.576-593
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• 2010

The purpose of this study was to identify the current status of ethics education in science and technology for pre-service science teachers and find out their recognition on the needs for ethics education at school. A survey was administered for this study and a total of 594 pre-service science teachers studying in college/university of education participated. The survey was organized to examine participants' 1) experience in ethics education in science and technology, 2) recognition on the needs of ethics education in science and technology, and 3) the need for it in elementary and secondary school. Each item was responded using either 1 to 5 Likert type scale, multiple choices, or open questionnaires. The results showed that 37.4% of participants obtain science technology information from the mass media, and 23.5% from the school education. Only 8.4% of the participants had the experience of taking class on ethics in science and technology. In terms of level of confidence in understanding the ethical issues in science and technology, the average response was 2.73. However, their perception on the needs of the ethics education ranges from 3.34 to 4.58, which is much stronger than other responses on average. This strong perception on the needs was much higher for pre-service science teachers for elementary school, than those of the secondary school(p<.05). All participants recognized the need for ethics education in science and technology at both elementary and secondary school. In responses for which subject should provide ethical issues on science and technology, science class was most frequently suggested (62.4%), followed by ethics class (29.1%). In responses for the most efficient form of learning, they suggested that case studies (43.5%), followed by discussions (41.4%) would be an efficient way to learn. Even in the responses of open questionnaires asking for efficient ways of learning ethical issues, participants suggested that discussions on various ethical issues on the cases in the science and technology would provide practical and substantial learning.

• Journal of The Korean Association For Science Education
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• v.34 no.7
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• pp.613-624
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• 2014

The aim of this study is to explore why Korean 4th graders' interest in science was not connected to career aspirations in science using the perspective of science identity. Forty-five students with a high interest in science but with low science-related aspirations have been chosen from 488 elementary school students who have completed a questionnaire exploring students' interest and career aspirations in science. Among them, 19 who have received parental permission participated in in-depth interviews examining students' science identities (interest, competence, and recognition by others in science) and their experiences and perceptions of science-related activities. The results showed that most students have limited or situational interest in science, a gap between the perception of their competence in science and their competence for a science-related career, and negative recognition by others in science. Also, participants' science identities and low aspirations for a science-related career constrained their attention and participation in science-related activities. Students' negative science identities and low aspirations for science-related careers were based on the high standards of science-related careers. It seems that these erroneous perceptions and expectations led them to differentiate themselves from students pursuing science-related careers, as well as to perceive that their interest, competence, and recognition by others in science were not enough to pursue a science-related career. This study has implications for understanding the current condition of young students with low aspirations for science careers and exploring desirable objectives and strategies to promote activities to raise their aspirations for science-related careers.

• Journal of The Korean Association For Science Education
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• v.37 no.3
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• pp.507-521
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• 2017

The purpose of this study is to investigate a meaningful path model among the components of students' positive experiences about science and science learning to understand the interactive relationships among different variables of affective domains. Positive Experiences about Science (PES) means whole experiences that have positive effects on students' affectional achievement related with science learning, which consists of science academic emotion, science-related self-concept, science learning motivation, science-related attitude, and science-related career aspiration. We conducted an online survey with 1,841 students consisting of 4th, 6th, 8th, and 10th graders from 17 provinces and cities using Test for Indicators of Positive Experiences about Science (TIPES). To explore the structural relationships among variables, we selected and analyzed an optimal structural equation model and then conducted multigroup analyses among groups. According to the analysis of the structural equation model, 'positive as well as negative science academic emotion' has effects on science learning motivation, science-related attitude, and science-related career aspiration via science-related self-concept. According to the independent t-test results for TIPES scores by participants' characteristics, there were statistically significant differences in the average scores of five sub-components of PES depending on gender, school-level, school location, and participation in science-related activities. According to the multi-group analysis results, the difference of path coefficients by gender and school-level were statistically significant, whereas the difference of path coefficients by school location and participation were not significant. Discussed in the conclusion are the implications of this research for science education research and ways to help students' affectional achievement related with science learning.

• Journal of The Korean Association For Science Education
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• v.38 no.1
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• pp.57-68
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• 2018

The purpose of this study is to categorize learning style groups and to analyze students' learning interest and self-regulated learning abilities, according to their learning style and giftedness. One hundred and twenty-three (123) science-gifted student and 296 regular students participated in this study, responding to learning style, self-regulated learning, and learning interest questionnaires. Data were analyzed, using 2-stage cluster analysis, $x^2$ test, two way-MANOVA test, and $Scheff{\acute{e}}$ test. The results are as follows: First, by 2-stage cluster analysis, four groups were categorized: 'high-score thinking style,' 'external-liberal,' 'executive-conservative,' and 'low-score thinking style.' In the gifted group, high-score thinking style (51.2%) was the most popular, then executive-conservative (30.2%), external-liberal (17.1%), and low-score thinking style (1.6%); in the regular student group, the executive-conservative group was the biggest, then high-score thinking style (20.6%), external-liberal (11.6%), and then the low-score thinking style (8.7%). Second, in terms of learning interest, the analysis by thinking style showed that the high-score thinking style group had higher learning interest compared to the executive-conservative and the low-thinking style group. The high-thinking style group's thoughtful interest also scored the highest compared with the others. The gifted students' thoughtful interest and investigative interest also were higher than regular students '. Third, in terms of the self-regulated learning, the analysis by thinking style showed that the high-score thinking style group showed higher scores on all sub-variances than other groups, especially having highest control-belief scores. Also, gifted students had higher scores on control-belief and searching information. Based on these results, the ways for effective education and support were discussed.