• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.12
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• pp.2199-2201
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• 2008

Sulfur hexafluoride($SF_6$) is a gaseous dielectric used in high voltage electrical equipment such as an insultor or arc quenching medium in the transmission and distribution of electricity. however, $SF_6$ is one of the greenhouse gases(GHG) with a global warming potential that is 23,900 times greater than that of carbon dioxide($CO_2$). for this reason, $SF_6$ emissions in electric equipment shall be controlled to reduce GHG and improve cost-effective use of $SF_6$ for economical benefits. Until recently there has not been any investigation on $SF_6$ emission characteristics and inventory in Korea. To understand emission characteristics during the use-phase, the scope of this study was limited to the following closed pressure system equipment from 10 substations in Korea. This study highlights (1) the investigation of sampling/analysis methodology for $SF_6$ emissions in high voltage equipment, (2) the estimation of $SF_6$ emissions in the use-phase, and (3) the comparison between the emission ratio and the mass-balance applied to inventory study. According to this study, the majority of emissions were related to electric equipment nameplates and the rest of the emissions were related to the handling of $SF_6$ during operations. from this result, emission ratios estimated from this study were similar; GIS was 14% and GCB was 13%, as maintenance process conditions were the same as manual process conditions for both equipment.

• Journal of Korean Society for Atmospheric Environment
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• v.31 no.1
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• pp.83-91
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• 2015

Biomass burning is known to be one of the main sectors emitting greenhouse gases as well as air pollutants. Unfortunately, the inventory of biomass burning sector has not been established well. We estimated greenhouse gas (GHG) and air pollution (AP) integrated emissions from biomass burning sector in Seoul during year 2010. The data of GHG and AP emissions from biomass burning, classified into open burning, residential fireplace and wood stove, meat cooking, fires, and cremation, were obtained from Statistics Korea and Seoul City. Estimation methodologies and emission factors were gathered from reports and published literatures. Estimated GHG and AP integrated emissions during year 2010 were $3,867tonCO_{2eq}$, and 2,320 tonAP, respectively. Major sources of GHG were forest fires ($1,533tonCO_{2eq}$) and waste open burning ($1,466tonCO_{2eq}$), while those of AP were meat cooking (1,240 tonAP) and fire incidence (907 tonAP). Total emissions by administrative district in Seoul, representing similar patterns in both GHG and AP, indicated that Seocho-gu and Gangseo-gu were the largest emitters whereas Jung-gu was the smallest emitter, ranged in $2{\sim}165tonCO_{2eq}$ and 0.1~8.31 tonAP. GHG emissions per $km^2$ showed different results from total emissions in that Gwanak-gu, Jungnang-gu, Gangdong-gu and Seodaemun-gu were the largest emitters, while Seocho-gu and Gangseo-gu were near-averaged emission districts, ranged in $0.2{\sim}21tonCO_{2eq}/km^2$. However, AP emissions per $km^2$ revealed relatively minor differences among districts, ranged in $2.3{\sim}6.1tonAP/km^2$.

• Journal of Navigation and Port Research
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• v.38 no.6
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• pp.567-575
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• 2014

In recent times, an obvious strategy in liner shipping markets that has come to the fore is slow steaming. Nowadays, most liner shipping companies have decelerated the voyage speed to 15-18 knots on major routes, and some leading liner shipping companies have a plan to reduce it to below 15 knots. Slow steaming is helpful in reducing the operating cost and the amount of greenhouse-gas emissions on a single vessel with lower fuel consumption. However, it also creates various negative effects such as the opportunity cost, additional fixed costs and an in-transit inventory cost on a loop. Hence, the net operating cost on a loop is changing dynamically due to the changes of voyage speed based on various slow steaming effects. The aim of this study is to analyze the slow steaming effects in the liner shipping, and to find the best voyage speed that minimizes the operating cost on a loop. Moreover, this study suggests the recommendable strategy for liner shipping companies. To achieve the aim of this study, a simulation model has been designed using System Dynamics.

• Advances in environmental research
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• v.3 no.4
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• pp.367-377
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• 2014

In this study, we investigated a life cycle assessment (LCA) of six roof-waterproofing systems [asphalt (C1), synthetic polymer-based sheet (C2), improved asphalt (C3), liquid applied membrane (C4), Metal sheet with asphalt sheet (N1), and liquid applied membrane with asphalt sheet (N2)]for reinforced concrete building using an architectural model. To acquire accurate and realistic LCA results, minimum units of material compositions for life cycle inventory and real data for compositions of waterproofing materials were used. Considering only materials and energy demands for waterproofing systems per square meter, higher greenhouse gas (GHG) emissions could be generated in the order of C1 > N2 > C4 > N1 > C2 > C3 during construction phase. However, the order was changed to C1 > C4 > C3 > N2 > N1 > C2, when the actual architecture model was applied to the roof based on each specifications. When an entire life cycle including construction, maintenance, and deconstruction were considered, the amount of GHG emission was in the order of C4 > C1 > C3 > N2 > C2 > N1. Consequently, N1 was the most environmental-friendly waterproofing system producing the lowest GHG emission. GHG emissions from maintenance phase accounted for 71.4%~78.3% among whole life cycle.

• Journal of Environmental Science International
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• v.32 no.5
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• pp.303-313
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• 2023

In this study, the hydraulic gradient was calculated using the groundwater level and rainfall observed in the Hyogyo-ri area for a year, and the change in the hydraulic gradient according to the rainfall was analyzed. It was found that the groundwater level increased as the rainfall increased in all groundwater wells in the research site, and the groundwater level rise decreased as the altitude of the groundwater well increased. The hydraulic gradient in the research site ranged from 0.016 to 0.048, decreasing during rainfall and increasing after the end of the rainfall. As the rainfall increased, the groundwater level rise in the low-altitude area was more than the high-altitude area, and the hydraulic gradient decreased due to the difference in groundwater level rise according to the altitude. Through this study, it was found that the influence of rainfall is dominant for the fluctuation of the hydraulic gradient in the unconfined aquifer.

• Journal of Environmental Science International
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• v.32 no.4
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• pp.267-276
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• 2023

In this study, we analyzed seasonal variations in carbon dioxide fluxes, concentrations, and soil temperatures over three years in unvegetated tidal flats in the Beolgyo area. We also investigated the correlations between carbon dioxide fluxes and influencing factors. The average carbon dioxide flux was positive in summer and autumn but negative in winter and spring. A positive correlation was observed between carbon dioxide flux and soil temperature in spring whereas a negative correlation was noted in summer. In summer and autumn, as the soil temperature increased, the carbon dioxide flux decreased. In contrast, in spring and winter, as the soil temperature decreased, the carbon dioxide flux increased. Overall, this study reveals the significant influence of soil temperatures on carbon dioxide fluxes between the surface layer of the tidal flat and atmosphere.

• Journal of Environmental Science International
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• v.32 no.3
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• pp.181-189
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• 2023

In this study, sediment cores from unvegetated tidal flats in the Hampyeong Bay (west coastal wetland) and Dongdae Bay (south coastal wetland) were sampled, the blue carbon stock in the sediments was calculated, and the characteristics of the blue carbon stock were analyzed based on particle size of the sediments. The sediments in the Hampyeong Bay tidal flat had large particle size and low mud content, and the Dongdae bay tidal flat had small particle size and high mud content. The organic carbon content and blue carbon stock in the sediments were higher in the Dongdae tidal flat than in the Hampyeong Bay tidal flat. As a result of the regression function, in both the Hampyeong Bay and Dongdae Bay tidal flats, the sediments had the smaller particle size and higher mud contents the higher the organic carbon content and blue carbon stock. The sediments with smaller particle size had the larger specific surface area, so were feasible to adsorb and store more organic matters.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.4
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• pp.280-287
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• 2012

The sources of greenhouse gases (GHG) at Hanyang University Ansan campus, including direct sources, indirect sources, and others, were investigated in order to establish the GHG inventory. Emission of GHG was calculated with the energy use from each source from 2007 and 2009. The indirect emission (56.7%) due to the electricity significantly contributed to total GHG emission. The scenario for the GHG reduction was designed for both campus administration and members. The reduction potential of GHG was simulated from 2007 to 2020 using Long-range Energy Alternatives Planning (LEAP) model. In case of GHG reduction scenario by campus administration, the GHG can be reduced by 63.34 ton $CO_{2eq}/yr$ for stationary combustion in the direct source, by 221.1 ton $CO_{2eq}/yr$ for mobile combustion in the direct source, and by 4,637.34 ton $CO_{2eq}/yr$ for lighting in the indirect source, compared to 2020 Business As Usual (BAU). In case of GHG reduction action scenario by campus members, the reduction potential of GHG was 1293.76 ton $CO_{2eq}/yr$. Overall, the total GHG emissions in 2020 by the both scenarios can be decreased by 24% compared to 2020 BAU.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.7
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• pp.506-513
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• 2014

The objective of this study is to establish the greenhouse gases (GHG) inventories and estimate the GHG reduction plans for Daegu University from 2009 to 2011. The annual average of GHG emissions in Daegu University was estimated to be 19,413 ton $CO_2$ eq during the study period. Emissions of electricity usage in Scope 2 most contributed about 55.4% of the total GHG emissions. Also, GHG emissions of Scope 2, Scope 1, and Scope 3 contributed 60.4%, 22.6%, and 17.0%, respectively. In order to estimate reduction potential of GHG, the Long-range Energy Alternatives Planning (LEAP) model was calculated using three scenarios such as sensor installation, LED replacement, and solar facility. The GHG will be reduced by 1,656 ton $CO_2$ eq for LED scenario, by 1,041 ton $CO_2$ eq for sensor scenario, and by 737 ton $CO_2$ eq for solar scenario compared to 2020 business as usual (BAU). Therefore, the total GHG emissions in 2020 apply three scenarios can be reduced by 15% compared with 2020 BAU.

• Journal of Climate Change Research
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• v.4 no.3
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• pp.235-244
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• 2013

Carbon dioxide emission estimation methods consist of four tiers according to the IPCC guideline. In this study, estimated results by tier 3 and tier 4 were compared with the theoretically calculated $CO_2$ emissions based on the mass balance approach for a gas fired power plant between March and May 2011. It was found that the relative differences were upto 17% between the measured emissions by tier 4 and theoretically estimated emissions, while the results of tier 3 were similar to those from theoretically estimated ones. The comparisons suggested the possibility of misestimation due to replacing missing, abnormal, or invalid data in continuous emissions monitoring system. When using only the data without those missing, abnormal, or invalid data, the relative differences decreased somewhat but still showed consistent differences depending on the stack. It is suggested that this differences might be due to the accuracy of the measurement instruments for the tier 4, especially, for the flow rate measurement instrument.