• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.916-922
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• 2018

Recently, power plant effluent condensers received a Renewable Energy Certificate as components of hydrothermal energy (weighted 1.5 times) as one target item of the Renewable Portfolio Standard (RPS) policy. Accordingly, more attention is being paid to the value of thermal wastewater as a heat source. However, for utilization of thermal wastewater from power plants in high-turbidity areas like the West Sea of Korea, a turbidity reducing system is required to reduce system contamination. In this study, an experimental test was performed over a month on thermal wastewater from power plants located in the West Sea of Korea. It was found that water turbidity was reduced by more than 80 % and that the concentration of organic materials and nutrient salts was partially reduced due to the reduction of floating/drifting materials. To conduct a comparative analysis of the level of contamination of the heat exchanger when thermal wastewater flows in through a turbidity reducing system versus when the condenser effluent flows in directly without passing through the turbidity system, we disassembled and analyzed heat exchangers operated for 30 days. As a result, it was found that the heat exchanger without a turbidity reducing system had a higher level of contamination. Main contaminants (scale) that flowed in to the heat exchanger included minerals such as $SiO_2$, $Na(Si_3Al)O_8$, $CaCO_3$ and NaCl. It was estimated that marine sediment soil flowed in to the heat exchanger because of the high level of turbidity in the water-intake areas.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.742-749
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• 2002

Numerical Study with detailed chemistry has been conducted to investigate the flame structure and NOx formation characteristics in oxygen -enhanced(CH$_4$/O$_2$-$N_2$) and oxygen-enhanced-EGR(CH$_4$/O$_2$-$CO_2$) counter diffusion flame with various strain rates. A small amount of $N_2$is included in oxygen-enhanced-EGR combustion, in order to consider the inevitable $N_2$contamination by $O_2$production process or air infiltration. The results are as follows : In CH$_4$/O$_2$-$CO_2$flame it is very important to adopt a radiation effect precisely because the effect of radiation changes flame structure significantly. In CH$_4$/O$_2$-$N_2$flame special strategy to minimize NO emission is needed because it is very sensitive to a small amount of $N_2$. Special attention is needed on CO emission by flame quenching, because of increased CO concentration. Spatial NO production rate of oxygen-enhanced combustion is different from that of air and oxygen-enhanced-EGR combustion in that thermal mechanism plays a role of destruction as well as production. In case CH$_4$/O$_2$-$CO_2$flame contains more than 40% $CO_2$it is possible to maintain the same EINO as that of CH$_4$/Air flame with accomplishing higher temperature than that of CH$_4$/Air flame. EINO decreases with increasing strain rate, and those effects are augmented in CH$_4$/O$_2$flame.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.185-190
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• 2001

Numerical Study with detailed chemistry has been conducted to investigate the flame structure and NOx formation characteristics in oxygen-enhanced$(CH_4/O_2-N_2)$ and oxygen-enhanced-EGR$(CH_4/O_2-CO_2)$ counter diffusion flame with various strain rates. A small amount of $N_2$ is included in oxygen-enhanced-EGR combustion, in order to consider the inevitable $N_2$ contamination by $O_2$ production process or air infiltration. The results are as follows : In $CH_4/O_2-CO_2$ flame it is very important to adopt a radiation effect precisely because the effect of radiation changes flame structure significantly. In $CH_4/O_2-N_2$ flame special strategy to minimize NO emission is needed because it is very sensitive to a small amount of $N_2$. Special attention is needed on CO emission by flame quenching, because of increased CO concentration. Spatial NO production rate of oxygen-enhanced combustion is different from that of air and oxygen-enhanced-EGR combustion in that thermal mechanism plays a role of destruction as well as production. In case $CH_4/O_2-CO_2$ flame contains more than 40% $CO_2$ it is possible to maintain the same EINO as that of $CH_4/Air$ flame with accomplishing higher temperature than that of $CH_4/Air$ flame. EINO decreases with increasing strain rate, and those effects are augmented in $CH_4/O_2$ flame. Complementary study is needed with extending the range of strain rate variation.

• Journal of the Korea Organic Resources Recycling Association
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• v.17 no.3
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• pp.40-47
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• 2009

Coinjection of alcohol and air or alcohol flooding only were evaluated with 3-D soil tank for removal of nonaqueous phase liquid (NAPL) contaminant from soil. 70%-ethanol and 40%-isopropanol were used for non-NAPL-swelling alcohol and NAPL-swelling alcohol, respectively. 729 ml-benzene was placed in the 37 liter soil tank. Alcohols were respectively injected from the injection well placed near the bottom of the tank and mobilized free phase NAPL and aqueous phases were then recovered from the extraction well placed in the upper part of the soil tank. Approximately 50% of removed NAPLs were free-phase in all experiments. The results were completely different to the previous soil column experiment results and also implied that alcohol properties did not affect the NAPL removal efficiency in the 3-D soil tank experiment. Air was also co-injected with alcohol to evaluate co-injection effects on NAPL removal. Enhanced NAPL removal effect of co-injection of 70%-ethanol and air was also found even in the 3-D soil tank evaluation. However, co-injection effect of 40%-iso-propanol and air was less apparent. This study determined that the most important parameter governing alcohol flooding for NAPL removal would be extraction capacity to recover NAPL and aqueous phase flowing in the soil. More researches are required for improving recovery efficiency of extraction well in real soil contamination conditions.

• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.1-6
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• 2014

Recent international environmental regulations are focused on reducing pre-contamination and on sustainable development prior to the usage stage of a product. The Environmental Performance Declaration is being used as a tool for quantifying the environmental performance of products, to reduce contamination in advance, and for advertising the results of railway vehicles in Europe. In this study, a life cycle assessment of the tilting train was conducted, the first such case study in Korea, according to the ISO 14025 standard and Korea EDP (Environmental Declaration of the Product) rule. As a result of the LCA, the life cycle carbon emission of the tilting train was determined to be $3.54{\times}10^7kgCO_2eq.$ which is higher than that of a European train. Also, the amount of $CO_2$ emission of the Mcp and car body is higher than that of the other car and bogie.

• Journal of the Korean earth science society
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• v.24 no.8
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• pp.711-720
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• 2003

To study characteristics of the heavy metal pollution, sediment samples were collected at 67 sites on the roadside of Jeonju city during summer and winter, 2002. The total concentration of metals including Cd, Co, Cr, Cu, Ni, Pb, Zn, and Mn in the sediment samples were determined. The results indicate that the roadside sediments in Jeonju city have lower (1/2 to 1/7 times) concentrations of Zn, Cu, Pb and Cd than the metal concentrations previously reported for roadside soil, dust and sewage sludges in Seoul. However, the metal concentrations are higher than environmental quality criteria in soil suggested from several countries, and Zn, Cu, Pb and Cd contents are usually 2-7 times higher than the world average contents of the metals in natural soil. Although pollution index and concentrations of Cr, Ni, Pb and Zn in the roadside sediments at industrial area were usually higher than those of downtown and residential area, the metal having small vehicle- and steel-related industries had high concentrations of metals. The results of chemical partitioning analysis showed that Pb, Zn and Mn are mainly associated with carbonate/adsorbed and Fe-Mn oxide phases but that Cu is largely associated with the organic and sulfide fractions. It thus indicates that both large and small (vehicle- and steel-related) industries are main sources of heavy metal contamination. Due to high solubility of the carbonate phases by natural leaching episodes, the carbonate/adsorbed Cd, Co, Ni, Pb, Zn and Mn in the roadside sediments may serve as a potential source of contamination.

• Economic and Environmental Geology
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• v.38 no.4 s.173
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• pp.451-462
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• 2005

In order to examine the extent of environmental contamination at abandoned Samsanjeil Cu mines in Kosung-kun, Kyeongsangnam-do, we have investigated the contaminations and mobility of toxic trace elements from mine wastes including about 280,000 tonnages of tailings by chemical experiments (total extraction, partial extraction by 0.1N HCI and sequential extraction procedure). Total concentrations of trace elements showed that Cu, As, Co, Zn, Pb, and Cd concentrations in tailings were 14.0, 3.6, 3.1, 2.1, 2.1 and 1.6 times greater than those in background soil, respectively. From the proportion of metals bound to the exchangeable and carbonate fractions, the comparative mobility of metals decrease in order of $Zn(29.0\%)>Cu(12.3\%)Pb(9.6\%)>Cd(3.0\%)>As=Co(0.0\%)$. Based on the concentrations, chemical speciations of tailings, waste rock and nearby soil, it was revealed that Cu and Zn were the most possible elements to contaminate the surrounding environment in Samsanjeil mine area. In addition, the tailings had total trace metal concentrations below Dutch guideline values except Cu, and they might not affect adverse impact on environment.

• Journal of the Korean Chemical Society
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• v.42 no.5
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• pp.526-530
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• 1998

Analysis of trace impurities in the gases has been very important with the development of semi-conductor related industry. Particularly, the contamination of the gas handling systems in a semi-conductor plant by the air has been a trouble to the manufacturers. Thus, the analysis of the air components in the system has been a task to the analysts. In this study, we report the analysis data with a expanded uncertainty for the trace impurities of nitrogen and argon in the bulk helium and hydrogen. All data show a good correspondence, exhibiting reliable statistical error ranges.

• Safety and Health at Work
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• v.11 no.3
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• pp.372-377
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• 2020

Infection risks of handling specimens associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by public health laboratory services teams were assessed to scrutinize the potential hazards arising from the work procedures. Through risk assessments of all work sequences, laboratory equipment, and workplace environments, no aerosol-generating procedures could be identified except the procedures (mixing and transfer steps) inside biological safety cabinets. Appropriate personal protective equipment (PPE) such as surgical masks, protective gowns, face shields/safety goggles, and disposable gloves, together with pertinent safety training, was provided for laboratory work. Proper disinfection and good hand hygiene practices could minimize the probability of SARS-CoV-2 infection at work. All residual risk levels of the potential hazards identified were within the acceptable level. Contamination by gloved hands was considered as a major exposure route for SARS-CoV-2 when compared with eye protection equipment. Competence in proper donning and doffing of PPE accompanied by hand washing techniques was of utmost importance for infection control.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.210.2-210.2
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• 2014

Recently, molybdenum disulfide (MoS2) nanostructures have been investigated for applications of lithium-ion batteries, solar cell, and gas sensors. In this regard, we have studied atomic and electronic properties of MoS2 nanostructures with adsorbed atoms and molecules using density functional theory calculations. Our calculations reveal that the several atoms such as H, C, N, and F are chemically bound to several sites on the two-dimensional (2D) MoS2 surface. On the other hand, various contamination molecules such as CO, CO2, NO, NO2, and NH3 do not bind to the surface. Next, adsorption of various molecules on the one-dimensional (1D) armchair MoS2 nanoribbon is investigated. Contrary to the case of 2D MoS2 monolayer surface, some molecules (CO and NO) are bound well to the edge of the MoS2 nanoribbon. We find that the molecular states due to adsorption are located near the Fermi level, which makes the band gap narrower. Therefore, we suggest that monolayer MoS2 nanoribbons be used as the gas sensors or detectors.