• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.425-430
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• 2015

ZSM-5 crystals grew by hydrothermal synthesis method on the surface of foam type porous silicon carbide ceramics which fabricated by polymer replica method. Oxide layer was developed on the surface of the porous silicon carbide ceramics to induce growth of ZSM-5 from the surface. In this study, hydrothermal synthesis was carried out for 7 h at $150^{\circ}C$ using TEOS, $Al(NO_3){\cdot}9H_2O$ and TPAOH as raw materials in the presence of the porous silicon carbide ceramics. X-ray Powder Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses were confirmed $1{\sim}3{\mu}m$ sized ZSM-5 crystals have grown on the surface of porous silicon carbide ceramics. BET data shows that small pores about $10{\AA}$ size drastically enhanced and surface area increased from $0.83m^2/g$ to $30.75m^2/g$ after ZSM-5 synthesis on the surface of foam type porous silicon carbide ceramics.

• Journal of the Korean Chemical Society
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• v.57 no.3
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• pp.389-397
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• 2013

In this study, the effects of STAD cooperative learning strategy on students' achievement, learning motivation, perceptions of learning environment, and perceived classroom goal structure were investigated in terms of students' collectivism level. Two classes (64 students) from an elementary school were respectively assigned to a control group and a treatment group. A individualism-collectivism test, a learning motivation test, a perceptions of learning environment test, and a perceived classroom goal structure test were administered as pretests. The intervention of cooperative learning lasted for 24 class periods. After instruction, an achievement test, the learning motivation test, the perceptions of learning environment test, and the perceived classroom goal structure test were administered. The results indicated that the students of the treatment group significantly outperformed those of the control group in the achievement test. There was a significant treatment-aptitude interaction effect in the scores of the attention subcategory of the learning motivation. In the perceptions of learning environment, the score of the treatment group was significantly higher than the control group in the cohesiveness subcategory, whereas the score of the treatment group was significantly lower than their counterpart in the competitiveness subcategory. It was also found that the score of the treatment group was significantly higher than the control group in the performance subcategory of the perceived classroom goal structure.

• Journal of The Korean Association For Science Education
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• v.37 no.5
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• pp.813-824
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• 2017

In the previous studies on co-constructing scientific models, students have had various difficulties in constructing their models. As an alternative to compensate for these problems, we introduced smart devices in the modeling process and examined its roles. 60 students from two classes in the fifth grade of an elementary school in Seoul had classes to make up the solar system model in a small group using the smart devices and we examined the roles of smart devices in their classes. The result is as follows; First, students were able to generate their scientific model through various functions of smart devices throughout the modeling process. In particular, smart devices provide highly descriptive and authoritative information that meets the needs of students as well as the opportunity to observe the planets from various perspectives. Moreover, they were not only able to express their models easily as they wanted to express them, but also were able to receive feedbacks from various agents. In order for these smart devices to function properly in the co-construction of scientific models, it is necessary to improve the related environment as well as students' technological literacy.

• Journal of the Korean Institute of Gas
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• v.22 no.1
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• pp.26-36
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• 2018

Conventional nickel-based catalyst processes used for dry reforming reactions have high activation temperatures and problems such as carbon deposition and metal sintering on the active sites of the catalyst surface. In this study, the characteristics of butane dry reforming reaction were investigated by using DBD plasma combined with catalytic process and compared with existing catalyst alone process. The physical and chemical properties of the catalysts were investigated using a surface area & pore size analyzer, XRD, SEM and TEM. Using $10%Ni/{\gamma}-Al_2O_3$ at $580^{\circ}C$, in the case of the catalyst+plasma process, the conversion of carbon dioxide and butane were improved by about 30% than catalyst alone process. When the catalyst+plasma process, the conversion of carbon dioxide and butane and the hydrogen production concentration are enhanced by the influence of various active species generated by the plasma. In addition, it was found that the particle size of the catalyst is decreased by the plasma in the reaction process, and the degree of dispersion of the catalyst is increased to improve the efficiency.

• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.395-402
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• 2005

The most important point when we engage on waterway dredging work is supplying safe navigational passage to the vessels underway by narrowing dredge work area and removing submerged dangers. In order to meet this end it is necessary to use auxiliary equipment for shifting actively and mooring and adopt automation of dredging work by integrating information on real time position, dredging depth, and work information. The dredger with a spud control system in this study, by the way, is able to employed on continuous dredging work with the narrowest working area allowing wide and safe passages to vessels underway, by moving the dredger to the working zone with the spud controlled automatically. Furthermore, it has been improved definitely compared with the existing dredging process management system such that it shows the track of spud and working depth on the electronic navigation chart of window, together with the final outcome of dredging work. The test dredging work at the entrance of Busan North Port for system evaluation showed that actual working time available was twice of the one by the existing anchor system, and that it reduced $38\%$ of time for preparation work and one man power.

• Journal of the Korean association of regional geographers
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• v.22 no.4
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• pp.745-760
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• 2016

The name of a place represents the social and political power relations as well as showing a certain physical space. In particular, the East Sea is not only a representative name of areas represent our country, but also the name of place being in competition with the Sea of Japan internationally. Korea is committed in many ways to spread the name of East Sea in the international community, and gradually expand its name power. The purpose of this study was to investigate the names used in the newspapers and broadcasting in Francophone countries except France by analyzing the newspaper articles and broadcasting contents, and to illuminate how the names of the East Sea produced in France, and the discussion about the names were diffused in Francophone countries and what kind of influence they had on those countries. This study selected Algeria in North Africa, Belgium and Luxembourg in West Europe, and Quebec in Canada for the research areas. As a result, while Algeria in North Africa and Luxembourg are showing inhospitality to the name East Sea, Belgium and Quebec are taking a flexible attitude toward this name. In general, most Francophone countries are provided with press releases from AFP in France. Even in same article provided by AFP, The result shows that some media stick to use the name Sea of Japan solely, and others demonstrate a will to use both name East Sea and Sea of Japan simultaneously. This study was able to show that the diffusion and spread of the place name was significantly influenced by social, political interests and powers, the mess geopolitics in pop cultural materials.

• Journal of Korea Water Resources Association
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• v.51 no.10
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• pp.917-927
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• 2018

Seven heavy metal concentrations (As, Cd, Cr, Cu, Ni, Pb, Zn) were continuously analyzed for twenty rainfall events in 2017~2018 in an urban basin. The overall and dynamic correlations between runoff characteristics and heavy metal concentrations were examined. The peak metal concentration generally appeared in the initial runoff but found to be delayed when the rainfall intensity was low. The rainfall duration had no relationship with either heavy metal concentrations or their total mass. Dynamics of heavy metal mass (load), with the exception of Cu and Zn, showed strong correlation with the 30 minute rainfall intensity (0.60~0.88) and runoff volume (0.74~0.89). While event mean concentration (EMC) showed positive correlation (0.54~0.73) with antecedent dry days (ADD), no significant relationship was found between runoff volume and pollutant concentration. This implies that the pollutants built up on the surface during dry days are washed off even with low rainfall energy. The dynamics of heavy metal and TSS concentrations showed good correlation (0.68~0.87). This result shows that the metals are transported along with solid particles as adsorbate in surface runoff. Regular street sweeping will reduce significant amount of heavy metal loads in urban surface runoff.

• Journal of Korean Medical Science
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• v.33 no.53
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• pp.298.1-298.10
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• 2018

Background: The renal function of individuals is one of the reasons for the variations in therapeutic response to various drugs. Patients with renal impairment are often exposed to drug toxicity, even with drugs that are usually eliminated by hepatic metabolism. Previous study has reported an increased plasma concentration of indoxyl sulfate and decreased plasma concentration of $4{\beta}$-hydroxy (OH)-cholesterol in stable kidney transplant recipients, implicating indoxyl sulfate as a cytochrome P450 (CYP) inhibiting factor. In this study, we aimed to evaluate the impact of renal impairment severity-dependent accumulation of indoxyl sulfate on hepatic CYP3A activity using metabolic markers. Methods: Sixty-six subjects were enrolled in this study; based on estimated glomerular filtration rate (eGFR), they were classified as having mild, moderate, or severe renal impairment. The plasma concentration of indoxyl sulfate was quantified using liquid chromatography-mass spectrometry (LC-MS). Urinary and plasma markers ($6{\beta}$-OH-cortisol/cortisol, $6{\beta}$-OH-cortisone/cortisone, $4{\beta}$-OH-cholesterol) for hepatic CYP3A activity were quantified using gas chromatography-mass spectrometry (GC-MS). The total plasma concentration of cholesterol was measured using the enzymatic colorimetric assay to calculate the $4{\beta}$-OH-cholesterol/cholesterol ratio. The correlation between variables was assessed using Pearson's correlation test. Results: There was a significant negative correlation between MDRD eGFR and indoxyl sulfate levels. The levels of urinary $6{\beta}$-OH-cortisol/cortisol and $6{\beta}$-OH-cortisone/cortisone as well as plasma $4{\beta}$-OH-cholesterol and $4{\beta}$-OH-cholesterol/cholesterol were not correlated with MDRD eGFR and the plasma concentration of indoxyl sulfate. Conclusion: Hepatic CYP3A activity may not be affected by renal impairment-induced accumulation of plasma indoxyl sulfate.

• Korean Journal of Social Welfare Studies
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• v.48 no.2
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• pp.233-266
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• 2017

The problem of excessive job burdens and high turnover rates in the social welfare area has been dealt with for a long time. However, there is a lack of discussions on the issue of voluntary turnover of medical social workers. The purpose of this study is to examine the effect of job demands on medical social workers' turnover intentions and to verify the mediating effect of job satisfaction on the relationship between job demands and turnover intentions. Among the medical social workers registered in the Korean Association of Medical Social Workers, 188 respondents currently working in hospitals were used for data analysis. As research methods, frequency, descriptive statistics, correlate analysis, and logistic regression analysis were conducted by SPSS 22.0 version and SPSS Macro Process v.2.16. Finally, bootstrap was conducted to verify the significant mediating effect of job satisfaction. The findings are follows: extrinsic job satisfaction was found to have the full mediating effect between job demands and turnover intentions of medical social workers. In other words, job demands of medical social workers affect turnover intentions through extrinsic job satisfaction, but there is no direct effect of the job demand on the turnover intention. On the other hand, intrinsic job satisfaction did not mediate the relationship between job demands and turnover intentions. Based on the results, we suggested organizational and institutional implications for improving the job demands affected to low job satisfaction and turnover intention of medical social workers.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.75-80
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• 2019

Silicon solar cells have been widely used as a most promising renewable energy source due to eco-friendliness and high efficiency. As modules of silicon solar cells are connected in series for a practical electricity generation, a large voltage of 500-1,500 V is applied to the modules inevitably. Potential-induced degradation (PID), a deterioration of the efficiency and maximum power output by the continuously applied high voltage between the module frames and solar cells, has been regarded as the major cause that reduces the lifetime of silicon solar cells. In particular, the migration of the $Na^+$ ions from the front glass into Si through the anti-reflection coating and the accumulation of $Na^+$ ions at stacking faults inside Si have been reported as the reason of PID. In this research, the thickness effect of $SiO_x$ layer that can block the migration of $Na^+$ ions on the reduction of PID is investigated as it is incorporated between anti-reflection coating and p-n junction in p-type PERC solar cells. From the measurement of shunt resistance, efficiency, and maximum power output after the continuous application of 1,000 V for 96 hours, it is revealed that the thickness of $SiO_x$ layer should be larger than 7-8 nm to reduce PID effectively.