• Membrane Journal
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• v.24 no.4
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• pp.325-331
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• 2014

We synthesized novel polyimides with high gas permeability and selectivity for application of on board inert gas generation system (OBIGGS). 2,2-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) and two kinds of amines with high permeability and solubility were used to prepare the novel polymide. 2,3,5,6-Tetramethyl-1,4-phenylenediamine (TMPD) was used to improve gas permeability and various kinds of diamines were used to improve the gas selectivity respectively. The polyimide copolymers were synthesized by commercial chemical imidization method and their average molecular weights were over 100,000g/mol. The glass temperature ($T_g$) and the thermal degradation temperature were characterized using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The synthesized copolymers showed high $T_g$ over $300^{\circ}C$ and high thermal degradation temperature over $500^{\circ}C$. The gas permeation properties were measured by time-lag equipment. Although general polyimides showed very low gas permeability, synthesized polyimide copolymer showed high $O_2$ permeability of 36.21 barrer with high $O_2/N_2$ selectivity around 4.1. From this result, we confirm that these membranes have possibility to apply to OBIGGS.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.506-512
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• 2013

Biomass and low-grade coals are known to be better potential sources of energy compared to crude oil and natural gas since these materials are readily available and found to have large reserves, respectively. Gasification of these carbonaceous materials produced syngas for chemical synthesis and power generation. Woodchip, sawdust and lignite were gasified with steam in a thermobalance reactor under atmospheric pressure in order to evaluate their kinetic rate information. The effects of gasification temperature ($600{\sim}900^{\circ}C$) and partial pressure of steam (20~90 kPa) on the gasification rate were investigated. The three different types of gas-solid reaction models were applied to the experimental data to predict the behavior of the gasification reactions. The modified volumetric model predicted the conversion data well, thus the model was used to evaluate kinetic parameters in this study. The observed activation energy of biomass, sawdust and lignite gasification reactions were found to be in reasonable range and their rank was found to be sawdust > woodchip > lignite. The expression of apparent reaction rates for steam gasification of the three solids was proposed to provide basic information on the design of coal gasification processes.

• Journal of the Korean Association of Geographic Information Studies
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• v.2 no.1
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• pp.1-11
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• 1999

The Korean government is developing a systematic plan of integrated coastal management for effective conservation, utilization, and development of coastal areas. For this plan, integrated maps of land maps and nautical charts are indispensable. However, these maps are not made, nor studied yet in terms of integration, although digital maps(DM) on land and electronic nautical charts(ENC) have been recently developed by Korean Geography Institute and National Marine Investigation Institute, respectively. In this study, as preliminary studies to make eventual integrated maps, the concept of coastal areas are defined, specifically, coastal lines from DM and ENC are matched against each other. Issues on map production procedures, coordinate systems, and map projections, are carefully considered. A test coastal area located in Seo-Gu, Pusan, over 14 km of coastal lines is selected for the edge matching of coastal lines. RMS differences are 13.83 m and 4.37 m over man-made coastal lines and natural coast lines, respectively, which are quite larger considering a scale difference and other factors. However, no systematic differences are found.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.302-303
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• 2010

Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

• Membrane Journal
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• v.28 no.6
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• pp.406-413
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• 2018

In OBIGGS, a small amount of ozone in the atmosphere damages the polymer membrane. Therefore, the ozone removal device is installed at the front end to prevent the damage of the membrane by reducing the concentration of ozone in the gas delivered to the membrane. In this study, two hollow fiber membranes, PI and PSf, used to fabrication hollow fiber module with an effective membrane area of $6.37cm^2$ for gas separation in OBIGGS. The ozone concentration in the chamber was maintained at 2-3 ppm. The gas was continuously supplied into the module by using a pump. The gas permeation characteristics and the tensile strength were evaluated as a function of ozone exposure time. The PI-based hollow fiber membrane showed only 20% reduction in the transmittance, and remained its original uniformity without any significant changes. However, when PSf type hollow fiber membranes were used, the permeability decreased by more than 80% and the tensile strength decreased by more than 70%.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.4
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• pp.331-341
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• 2020

Objectives: This study was conducted to evaluate perceptions of safety and risk among Korean industrial hygienists and the change between before and after the Sewol Ferry Disaster in 2014. Two surveys with questionnaires composed of 51 questions were completed by attendees of the Korea Industrial Hygiene Association(KIHA) conference. Methods: One was conducted at the 2013 KIHA Fall Conference(N=181) and the other was from the 2014 KIHA Summer Conference(N=123). Between these two surveys was the Sewol Ferry Disaster on April 14, 2014, which was believed to seriously affect safety and risk perceptions in Korea. Results: It was revealed that industrial hygienists' awareness of safety rules strengthened after the Sewol Ferry Disaster(p<0.05). It was apparent that people over the age of 30 were more sensitive to social safety. There was no significant difference in the evaluation and attitude regarding governmental safety policy between the years of 2013 and 2014. The credibility of public organizations responsible for the disaster management system decreased. The self-evaluation of respondents' safety level also decreased. This trend shows mainly in the younger generation. It was evaluated that the overall social safety level decreased and the anxiety level increased. The score on social safety on a ±5 Likert scale was 0.68 in the 2013 survey and -0.33 in the 2014 survey(p<0.05). It was reported that the most serious threat factors for accident or disaster were 'building collapse > illegalities and corruption > side effects of radiation therapy >accidents in normal activity > occupational disease,' in order. They picked 'safety ignorance > hurry-up habits and culture > focusing on short-term benefit > easy-going attitude > insufficient safety education' for the causes of low social safety levels in 2013. In 2014, they were 'safety ignorance > easy-going attitude > focusing on short-term benefit > insufficient safety education > hurry-up habits and culture'. Conclusions: This study has some limitations because it was originally not designed to survey attitudes prior to the Sewol Ferry disaster in 2013. In addition, the survey targets are industrial hygienists who are familiar with occupational disease and injury.

• Resources Recycling
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• v.32 no.3
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• pp.57-67
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• 2023

The treatment of waste plastic has primarily been entrusted to small companies, which has resulted in challenges in obtaining an accurate overview of the current state of affairs and ensuring profitability. Consequently, despite the presence of recycling technology, their practical application has proven to be challenging. In this study, as part of the waste plastic material recycling plan, it is assumed that the PET/OPP laminated waste film is peeled off at the waste film generation site for the second use. The recycling rate of PET/OPP delaminated waste film is assumed to be 2%, 10%, and 30% referring to the figures suggested by "Life-cycle Post Plastic Measures" from the Korean government. In this study, a physical separation method was developed as a recycling approach for waste PET. A result of cost-benefit analysis was conducted to evaluate the economic viability of the recycling process based on changes in the recycling rate. The findings indicated that a recycling rate of waste PET was 30% or higher resulted in a cost-benefit ratio (Benefit-cost ratio, BCR) of 1.32, exceeding the threshold of BCR ≥1, which is considered to meet the minimum requirement for cost-benefit balance. As the government's allocation ratio and unit price are expected to increase in the future, the cost-benefit ratio is expected to increase further. This case is expected to serve as a pilot initiative for waste PET recycling and foster profit creation for businesses in similar industries.

• Journal of Korea Water Resources Association
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• v.55 no.6
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• pp.437-446
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• 2022

In April 2020, the Korean government decided to operate the Hwacheon reservoir, a hydropower reservoir to supply water, and it is currently under pilot operation. Through the pilot operation, the Hwacheon reservoir is the first among the hydropower reservoirs in Korea to make a constant release for downstream water supply. In this study, the water supply capacity of the Hwacheon reservoir was estimated using the inflow data of the Hwacheon reservoir. A simulation model was developed to calculate the water supply that satisfies both the monthly water supply reliability of 95% and the annual water supply reliability of 95%. An optimization model was also developed to evaluate the water supply capacity of the Hwacheon reservoir. The inflow data used as input data for the model was modified in two ways in consideration of the impact of the Imnam reservoir. Calculating the water supply for the Hwacheon reservoir using the two modified inflows is as follows. The water supply that satisfies 95% of the monthly water supply reliability is 26.9 m³/sec and 24.1 m³/sec. And the water supply that satisfies 95% of the annual water supply reliability is 23.9 m³/sec and 22.2 m³/sec. Hwacheon reservoir has a maximum annual water supply of 777 MCM (Million Cubic Meter) without failure in the water supply. The Hwacheon reservoir can supply 704 MCM of water per year, considering the past monthly power generation and discharge patterns. If the Hwacheon reservoir performs a routine operation utilizing its water supply capacity, it can contribute to stabilizing the water supply during dry seasons in the Han River Basin.

• Journal of the Korean earth science society
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• v.35 no.7
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• pp.562-571
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• 2014

In the celebration of the $50^{th}$ anniversary of the Korean Earth Science Society, the whole articles published in Journal of the Korean Earth Science Society (JKESS) were quantitatively analyzed. JKESS has played a major role in exchanging academically among earth science education specialists and in educating next generation for the last 36 years since it was founded in 1979. The total number of 1544 articles in thirty five volumes about the earth sciences and the earth science pedagogy has been published by August, 2014, and the number of the yearly published articles has been increasing. Regarding the research area, 69.3% was published in earth sciences and the other 30.7% was in earth science education; the percentage of research articles in geology, atmospheric science, environmental science, oceanography, and astronomy was 55.2, 17.6, 16.0, 6.0, and 5.2%, respectively. The number of research articles on atmospheric science and environmental science has recently been increasing, whereas, earth science education research articles have been" decreasing, which was similar to the pattern seen fifteen years ago. We thought that one of the reasons was related to a new journal named, "Journal of the Korean Society of Earth Science Education" started to publish in December, 2008. The number of articles authored or co-authored with foreigner scholars was totaled 53, which is only 3.4% of the entire number of published articles. It suggests that international advertisement via public relations as well as the development of English homepage be necessary. In order to become an excellent registered academic journal, it is the time to comprehensively discuss how to improve both the quality growth and the quantity of JKESS. According to the Ministry of Education, it is now in its planning stage to convert the current registration system of the academic journals to the autonomous evaluation system in academia. Therefore, we recommend that Journal of the Korean Earth Science Society be prepared for the upcoming future change.

• Tuberculosis and Respiratory Diseases
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• v.45 no.4
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• pp.846-860
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• 1998

Background: Endotoxin (LPS : lipopolysaccharide), a potent activator of immune system, can induce acute and chronic inflammation through the production of cytokines by a variety of cells, such as monocytes, endothelial cells, lymphocytes, eosinophils, neutrophils and fibroblasts. LPS stimulate the mononucelar cells by two different pathway, the CD14 dependent and independent way, of which the former has been well documented, but not the latter. LPS binds to the LPS-binding protein (LBP), in serum, to make the LPS-LBP complex which interacts with CD14 molecules on the mononuclear cell surface in peripheral blood or is transported to the tissues. In case of high concentration of LPS, LPS can stimulate directly the macrophages without LBP. We investigated to detect the generation of proinflammatory cytokines such as interleukin 1 (IL-1), IL-6 and TNF-$\alpha$ and fibrogenic cytokine, TGF-$\beta$, by peripheral blood mononuclear cells (PBMC) after LPS stimulation under serum-free conditions, which lacks LBPs. Methods : PBMC were obtained by centrifugation on Ficoll Hypaque solution of peripheral venous bloods from healthy normal subjects, then stimulated in the presence of LPS (0.1 ${\mu}g/mL$ to 100 ${\mu}g/mL$ ). The activities of IL-1, IL-6, TNF, and TGF-$\beta$ were measured by bioassaies using cytokines - dependent proliferating or inhibiting cell lines. The cellular sources producing the cytokines was investigated by immunohistochemical stains and in situ hybridization. Results : PBMC started to produce IL-6, TNF-$\alpha$ and TGF-$\beta$ in 1 hr, 4 hrs and 8hrs, respectively, after LPS stimulation. The production of IL-6, TNF-$\alpha$ and TGF-$\beta$ continuously increased 96 hrs after stimulation of LPS. The amount of production was 19.8 ng/ml of IL-6 by $10^5$ PBMC, 4.1 ng/mL of TNF by $10^6$ PBMC and 34.4 pg/mL of TGF-$\beta$ by $2{\times}10^6$ PBMC. The immunoreactivity to IL-6, TNF-$\alpha$ and TGF-$\beta$ were detected on monocytes in LPS-stimulated PBMC. Some of lymphocytes showed positive immunoreactivity to TGF-$\beta$. Double immunohistochemical stain showed that IL-1$\beta$, IL-6, TNF-$\alpha$ expression was not associated with CD14 postivity on monocytes. IL-1$\beta$, IL-6, TNF-$\alpha$ and TGF-$\beta$mRNA expression were same as observed in immunoreactivity for each cytokines. Conclusion: When monocytes are stimulated with LPS under serum-free conditions, IL-6 and TNF-$\alpha$ are secreted in early stage of inflammation. In contrast, the secretion of TGF-$\beta$ arise in the late stages and that is maintained after 96 hrs. The main cells releasing IL-1$\beta$, IL-6, TNF-$\alpha$ and TGF-$\beta$ are monocytes, but also lymphocytes can secret TGF-$\beta$.