• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.96-102
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• 2011

Simultaneous measurements using a scanning spectrograph system and transmissometer were performed for the first time over an urban site in Gwangju, Korea, to derive the ambient $NO_2$ volume mixing ratio. The differential slant column densities retrieved from the scanning spectrograph system were converted to volume mixing ratios using the light traveling distance along the scanning line of sight derived from the transmissometer light extinction coefficients. To assess the performance of this system, we compared the derived $NO_2$ volume mixing ratios with those measured by an in situ chemiluminescence monitor under various atmospheric conditions. For a cloudless atmosphere, the linear correlation coefficient (R) between the two data sets (i.e., data derived from the scanning spectrograph and from the in situ monitor) was 0.81; the value for a cloudy atmosphere was 0.69. The two sets of $NO_2$ volume mixing ratios were also compared for various wind speeds. We also consider the measurement errors, as estimated from an error propagation analysis.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.4
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• pp.347-355
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• 2019

As a solution to the growing concern on the global warming, researches are being actively carried out to apply carbon dioxide capture and storage technology to power generation systems. In this study, the integrated gasification combined cycle (IGCC) adopting oxy-combustion carbon capture was modeled and the effect of replacing the conventional air separation unit (ASU) with the ion transport membrane (ITM) on the net system efficiency was analyzed. The ITM-based system was predicted to consume less net auxiliary power owing to an additional nitrogen expander. Even with a regular pressure ratio which is 21, the ITM-based system would provide a higher net efficiency than the optimized ASU-based system which should be designed with a very high pressure ratio around 90. The optimal net efficiency of the ITM-based system is more than 3% higher than that of the ASU-based system. The influence of the operating pressure and temperature of the ITM on system efficiency was predicted to be marginal.

• Membrane and Water Treatment
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• v.10 no.3
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• pp.223-229
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• 2019

Titania modified by 2-ethylimidazole (2-EI) (denoted as $2-EI-TiO_2$) demonstrated visible light photocatalytic activity for the degradation of organic compounds. $2-EI-TiO_2$ was a bright brown powder that exhibited similar crystallinity and morphology with the control $TiO_2$. A diffuse reflectance spectrum indicated that $2-EI-TiO_2$ absorbs visible light of all wavelengths. X-ray photoelectron spectroscopy (XPS) confirmed the cationic state of nitrogen species (e.g. Ti-O-N) on the surface of $2-EI-TiO_2$. Visible light-illuminated $2-EI-TiO_2$ degraded $10{\mu}M$ 4-chlorophenol (4-CP) by approximately 85% in 4 h. The photochemical activity of $2-EI-TiO_2$ was selective in targeting the organic compound. The repeated use of $2-EI-TiO_2$ decreased the photocatalytic activity for the 4-CP degradation. Experiments using radical scavengers and oxidant probes revealed that the oxidation by photogenerated holes is responsible for the degradation of organic compounds by illuminated $2-EI-TiO_2$ and the role of $^{\bullet}OH$ is negligible.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.3
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• pp.256-263
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• 2021

In this study, blending oils of diesel oil and butanol were used as fuel oil for diesel engine to measure combustion pressure, fuel consumption, air ratio and exhaust gas emission due to various operating conditions such as engine revolution and torque. Using these data, the results of analyzing the engine performance, combustion characteristics and exhaust emission characteristics such as NOx (nitrogen oxides), CO₂ (carbon dioxide), CO (carbon monoxide) and soot were as follows. The fuel conversion efficiency at each load was highest when driven in the engine revolution determined by a fixed pitch propeller law. Except 30% butanol blending oil, fuel conversion efficiency of the other fuel oils increased as the load increased. Compared to diesel oil, using 10% and 20% butanol blending oil as fuel oil was advantageous in terms of thermal efficiency, but it did not have a significant impact on the reduction of exhaust gas emissions. On the other hand, future research is needed on the results of the 20% butanol blending oil showing lower or similar levels of smoke concentration and carbon monoxide emission rate other than those types of diesel oil.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.1-7
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• 2021

Restrictions on the emissions of nitrogen oxides, sulfur oxides, carbon dioxide, and particulate matter from marine engines are being tightened. Each of these emissions requires different reduction technologies, which are costly and require many pieces of equipment to meet the requirements. Liquefied natural gas (LNG) fuel has a great advantage in reducing harmful emissions emitted from ships. Therefore, the marine engine application of LNG fuel is significantly increasing in new ship buildings. Accordingly, this study analyzed the internal support structure, insulation type, and fuel supply piping system of a 35 m3 International Maritime Organization C type pressurized storage tank of an LNG-fueled ship. Analysis of the heat transfer characteristics revealed that A304L stainless steel has a lower heat flux than A553 nickel steel, but the effect is not significant. The heat flux of pearlite insulation is much lower than that of vacuum insulation. Moreover, the analysis results of the constraint method of the support ring showed no significant difference. A553 steel containing 9% nickel has a higher strength and lower coefficient of thermal expansion than A304L, making it a suitable material for cryogenic containers.

• Journal of Drive and Control
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• v.18 no.4
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• pp.28-34
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• 2021

Among the currently available types of fuel, LNG emits a relatively small amount of nitrogen oxide and carbon dioxide when it burns in the engine. However, since LNG is a flammable material, leakage during bunkering can lead to accidents, such as fires. Therefore, it is necessary to install a remote operation emergency shut-down (ESD) valve to block the flow and leakage of LNG in an emergency situation that occurs during bunkering. The ESD valve uses a hydraulic driving device consisting of a hydraulic control valve and a hydraulic motor to control globe valve disc displacement, which regulates the flow path for LNG transfer. At this time, there are various nonlinearities in hydraulic driving devices; hence, it is necessary to design a controller with robust control performance against these uncertainties. In this study, modeling of the ESD valve was carried out, and a sliding mode controller to control the displacement of the globe valve disc was designed. As a result, it was confirmed that the designed control performance could be achieved by overcoming nonlinearity characteristics using the designed controller.

• Tuberculosis and Respiratory Diseases
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• v.85 no.4
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• pp.313-319
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• 2022

Environmental exposure to air pollution is known to have adverse effects on various organs. Air pollution has greater effects on the pulmonary system as the lungs are directly exposed to contaminants in the air. Here, we review the associations of air pollution with the development, morbidity, and mortality of pulmonary diseases. Short-and long-term exposure to air pollution have been shown to increase mortality risk even at concentrations below the current national guidelines. Ambient air pollution has been shown to be associated with lung cancer. Particularly long-term exposure to particulate matter with a diameter <2.5 ㎛ (PM_2.5) has been reported to be associated with lung cancer even at low concentrations. In addition, exposure to air pollution has been shown to increase the incidence risk of chronic obstructive pulmonary disease (COPD) and has been correlated with exacerbation and mortality of COPD. Air pollution has also been linked to exacerbation, mortality, and development of asthma. Exposure to nitrogen dioxide (NO₂) has been demonstrated to be related to increased mortality in patients with idiopathic pulmonary fibrosis. Additionally, air pollution increases the incidence of infectious diseases, such as pneumonia, bronchitis, and tuberculosis. Furthermore, emerging evidence supports a link between air pollution and coronavirus disease 2019 transmission, susceptibility, severity and mortality. In conclusion, the stringency of air quality guidelines should be increased and further therapeutic trials are required in patients at high risk of adverse health effects of air pollution.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.18-24
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• 2022

Hydrogen is a clean fuel and is used in many applications in power systems such as fuel cells. It has unique properties such as wide flammability, high burning velocity, and difficulty to liquefy, which lead to critical safety issues. Fire and explosion are the most frequently occurring accidents and one of the major reasons is autoignition. In the ignition process, the chemistry of hydrogen combustion depends mainly on radical pools, and the temperature at which chain-branching and terminating rates are equal is called the crossover temperature. This study addresses the homogeneous autoignition of diluted hydrogen-air mixtures to investigate the effects of dilution on the crossover temperature to prevent explosions in the future. The new criterion for crossover temperature is introduced by only hydrogen radicals to adjust more simply. The detailed calculations indicate that the crossover temperatures are low at high dilutions of carbon dioxide and nitrogen because the concentrations of active radicals are reduced when an inert gas is added. This result is expected to contribute to hydrogen safety and realize a hydrogen society in the future.

• Corrosion Science and Technology
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• v.21 no.6
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• pp.514-524
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• 2022

Carbon emissions from fuel consumption have been pointed by scientists as the cause of global warming. In particular, fossil fuels are known to emit more carbon when burned than other types of fuels. In this regard, International Maritime Organization has announced a regulation plan to reduce carbon dioxide emissions. Therefore, recently, Liquefied Natural Gas propulsion ships are responding to such carbon reduction regulation. However, from a long-term perspective, it is necessary to use carbon-free fuels such as hydrogen and ammonia. Nitrogen oxides might be generated during ammonia combustion. There is a possibility that incompletely burned ammonia is discharged. Therefore, rather than being used as a direct fuel, Ammonia is only used to reduce NO_X such as urea solution in diesel vehicle Selective Catalyst Reduction. Currently, LPG vehicle fuel feed system studies have evaluated the durability of combustion injectors and fuel tanks in ammonia environment. However, few studies have been conducted to apply ammonia as a ship fuel. Therefore, this study aims to evaluate corrosion damage that might occur when ammonia is used as a propulsion fuel on ships.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4204-4212
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• 2023

Background: Storage reservoirs of radioactive waste could be the source of atmospheric pollution due to the efflux of aqueous aerosol from their water areas. The main mechanism of formation of aqueous aerosols is the collapse of gas bubbles at the water surface. In this paper, we discuss the potential influence of biological factors on gas ebullition in the water areas of the radioactively contaminated industrial reservoirs R-9 (Lake Karachay) and R-4 (Metlinsky pond) of the Mayak PA. The emission of the released non-dissolved gases captured with gas traps in reservoir R-9 was (88-290) ml/m² per day (2015) and in reservoir R-4 (270-460) ml/m² per day (2016). The analysis of gas composition in reservoir R-4 (60% methane, 35% nitrogen, 2.4% oxygen, 1.5% carbon dioxide) confirms their biological origin. It is associated with the processes of organic matter destruction in bottom sediments. The major source of organic matter in bottom sediments is the dying phytoplankton developing in these reservoirs. Conclusion: The obtained results form the basis to set a task to quantify the relationship between the phytoplankton development, gases ebullition and radioactive atmosphere contamination.