• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.530-534
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• 2011

The synthesis of dimethyl carbonate by liquid phase oxidative carbonylation of methanol was studied under batch reaction system. Reaction factors such as effect on various metals, anion containing in copper catalyst, temperature, carbon monoxide and oxygen molar ratio and copper content were investigated. In particular $CuCl_2{\cdot}2H_2O$ showed the excellent of the methanol conversion 65.2%, DMC selectivity 96.6% reaction condition under 1.0 g, $150^{\circ}C$, MeOH/CO/$O_2$=0.2/0.215/0.05 (molar ratio). $CuCl_2$ led to corrosion of the reactor. Thus, a new catalyst system using supports was investigated to resolve these corrosion problem. Influence on various supports were examined and copper catalyst supported on zeolite Y showed the most excellent activity on the formation of dimethyl carbonate. The amount of Fe dissolved during the reaction using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometer) was compared with catalysts, calcined Cu/zeolite Y showed the lower value below 5% than $CuCl_2-2H_2O$.

• Journal of Korean Society for Atmospheric Environment
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• v.34 no.3
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• pp.373-392
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• 2018

The emission of air pollutants in China has increased rapidly as its economy expanded over the last decades. The Chinese government has recently acknowledged the seriousness of the resulting air pollution and is trying to improve air quality in many ways. Here, we review the air quality control and management policies in China, one of our closest neighbors, because these policies may also influence the air quality in Korea. This study examined the recent policies on $PM_{2.5}$ reduction and analyzed the variation in air quality and air pollutant emissions in China. The ambient air quality and emission standards in China have been strengthened, based on China's Air Pollution Prevention and Control Action Plan of 2013. As a result, the annual mean concentration of $PM_{2.5}$ in 2015 in 74 large Chinese cities declined by 23.6% compared with 2013 values. Coal consumption in China also has been reduced by more than 10% per year since 2013. Furthermore, the laws controlling atmospheric emissions were revised again in 2016, and an air pollution forecasting and warning system was implemented to help manage air pollution problems. At present, the Chinese government is trying to evaluate its policies on $PM_{2.5}$ and find a new paradigm to mitigate ongoing $PM_{2.5}$ pollution. In this context, a joint study between Korea and China has been initiated to investigate the characteristics and sources of ambient $PM_{2.5}$ and to identify factors contributing to the high $PM_{2.5}$ concentrations in northeast China. We expect that this academic collaboration will benefit both countries in their search for new policies for $PM_{2.5}$ reduction.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.3
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• pp.181-188
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• 2013

The increase of carbon dioxide ($CO_2$) emission is known as one of the major causes of global warming, and it has a strong influence on the global environment. Therefore many researchers and politicians have tried to regulate the $CO_2$ emission. In regards to the matter, the IMPACT (Inclusive Marine Pressure Assesment and Classification Technology) committee under the Japan Society of Naval Architects and Ocean Engineers (JASNAOE) has developed an inclusive environmental impact assessment index, so-called "Triple I(III)", in order to assess the environmental impact including economic factors due to the artificial development of marine. In this study, III was applied to compare between the environmental impact of $CO_2$ emitted by container vessels during their life-cycle period and economic benefit due to their operating. Furthermore, III was also applied to assess the comprehensive environmental impact for the cases with various capacities of container vessels and different sailing route. From the results, the case for shortening of the sailing route is more effective to get the advantageous assessment results of III than the case for varying the size of vessels.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.4
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• pp.527-533
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• 2011

Decomposition of compost applied to soils is affected basically by its biological stability; but, many other chemical properties of the compost may also influence compost organic-C mineralization. This study was conducted to investigate the principal substrate quality factors of composts that determine C mineralization of compost with similar stability degree (SD). Three composts samples with similar SD but different chemical properties such as pH, C/N, $K_2SO_4$-extractable C, and molar ratio of $NH_4^+$ to $NO_3^-$ were mixed with an acid loamy soil and $CO_2$ emission was monitored during the laboratory incubation for 100 days. Temporal pattern of cumulative compost organic-C mineralization expressed as % of total organic C ($C_{%\;TOC}$) followed double exponential first order kinetics model and the $C_{%\;TOC}$ ranged from 4.8 to 11.8% at the end of incubation. The pattern of C%TOC among the composts was not coincident with the SD pattern (40.1 to 58.6%) of the composts; e.g. compost with the lowest SD resulted in the least $C_{%\;TOC}$ and vice versa. This result indicates that SD of compost can not serve as a concrete predictor of compost mineralization as SD is subject not only to maturity of compost but also to characteristics of co-composting materials such as rice hull (low SD) and sawdust (high SD). Meanwhile, such pattern of $C_{%\;TOC}$ collaborated with pH, C/N, $K_2SO_4$-extractable C, and molar ratio of $NH_4^+$ to $NO_3^-$ of the composts that are regarded as chemical indices of the progress of composting. Therefore, for better prediction of compost mineralization in soils, it is necessary to consider both SD and other chemical indices (pH, C/N, and molar ratio of $NH_4^+$ to $NO_3^-$).

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.1
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• pp.92-111
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• 2021

As fine dust negatively affects disease, industry and economy, the people are sensitive to fine dust. Therefore, if the occurrence of fine dust can be predicted, countermeasures can be prepared in advance, which can be helpful for life and economy. Fine dust is affected by the weather and the degree of concentration of fine dust emission sources. The industrial sector has the largest amount of fine dust emissions, and in industrial complexes, factories emit a lot of fine dust as fine dust emission sources. This study targets regions with old industrial complexes in local cities. The purpose of this study is to explore the factors that cause fine dust and develop a predictive model that can predict the occurrence of fine dust. weather data and fine dust data were used, and variables that influence the generation of fine dust were extracted through multiple regression analysis. Based on the results of multiple regression analysis, a model with high predictive power was extracted by learning with a machine learning regression learner model. The performance of the model was confirmed using test data. As a result, the models with high predictive power were linear regression model, Gaussian process regression model, and support vector machine. The proportion of training data and predictive power were not proportional. In addition, the average value of the difference between the predicted value and the measured value was not large, but when the measured value was high, the predictive power was decreased. The results of this study can be developed as a more systematic and precise fine dust prediction service by combining meteorological data and urban big data through local government data hubs. Lastly, it will be an opportunity to promote the development of smart industrial complexes.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.1
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• pp.45-57
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• 2008

The purpose of this research is to select an appropriate location of water pollution prevention facilities(WPPF) through evaluating location decision factor using environmental geographic information system. To do that, this research reviewed the current location policies of WPPFs and its related researches. And this paper builds water pollutant statistical databases, integrated them with the geographic information system of the administrative areas where water pollutants are generated, and gears it with statistical programs such as correlation and regression analysis in order to figure out the pollution factors which influence on the location decision of WPPF on the real time base. The volume of discharge of industrial wastewater is one of the most important water pollutants on the location decision of WPPF. And the number of industrial facilities also was the most important location decision factor in constructing the WPPFs. In addition, this paper noted that the number of population in each area makes a role to restraint the construction of WPPF. It identified that the disposal facility in Nackdong river upper-middle watersheds was insufficient in treating the livestock pollutants. Therefore, Gyeongbuk should concentrate on the construction of disposal facilities of livestock pollutant in these areas. The results of this research will contribute to decide what kinds of WPPF should be constructed on which watershed in Nackdong River, and to forecast the future water quality of each watershed.

• Analytical Science and Technology
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• v.25 no.5
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• pp.265-272
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• 2012

Okamoto cavity was modified to generate high power (2.45 GHz, 2 kW) He, N2 and Ar plasmas with WR-340 waveguide. Many factors which influence to the plasma generation were optimized and investigated for the spectroscopic properties of the He plasma generated. Some of the important factors are the diameter of the inner conductor, the distance between the inner and outer conductors and the distance between the tip of the inner conductor and the torch. After optimization for the He, two torches (a commercial mini torch for ICP and a tangential flow torch made locally) were compared and showed similar results for the helium plasma gas flow of 25 L/min~30 L/min. A tall torch (extended) was used to block the air in-flow and reduced the background intensity at 340 nm region (NH band). Emission intensity was measured for determination of halogen element in the aqueous solution with power and carrier gas flow rate. Electron number density and the excitation temperature were on the order of $3.67{\times}10^{11}/cm^3$ and 4,350 K, respectively. These values are similar or a bit smaller than other microwave plasmas. It has been possible to analyze aqueous samples. The detection limit for Cl (479.45 nm) was obtained to be 116 mg/L and needs analytical optimization for the better performance.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.45-59
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• 2023

The global focus on mitigating climate change has traditionally centered on carbon dioxide, but recent attention has shifted towards methane as a crucial factor in climate change adaptation. Natural settings, particularly aquatic environments such as wetlands, reservoirs, and lakes, play a significant role as sources of greenhouse gases. The accumulation of organic contaminants on the lake and reservoir beds can lead to the microbial decomposition of sedimentary material, generating greenhouse gases, notably methane, under anaerobic conditions. The escalation of methane emissions in freshwater is attributed to the growing impact of non-point sources, alterations in water bodies for diverse purposes, and the introduction of structures such as river crossings that disrupt natural flow patterns. Furthermore, the effects of climate change, including rising water temperatures and ensuing hydrological and water quality challenges, contribute to an acceleration in methane emissions into the atmosphere. Methane emissions occur through various pathways, with ebullition fluxes-where methane bubbles are formed and released from bed sediments-recognized as a major mechanism. This study employs Biochemical Methane Potential (BMP) tests to analyze and quantify the factors influencing methane gas emissions. Methane production rates are measured under diverse conditions, including temperature, substrate type (glucose), shear velocity, and sediment properties. Additionally, numerical simulations are conducted to analyze the relationship between fluid shear stress on the sand bed and methane ebullition rates. The findings reveal that biochemical factors significantly influence methane production, whereas shear velocity primarily affects methane ebullition. Sediment properties are identified as influential factors impacting both methane production and ebullition. Overall, this study establishes empirical relationships between bubble dynamics, the Weber number, and methane emissions, presenting a formula to estimate methane ebullition flux. Future research, incorporating specific conditions such as water depth, effective shear stress beneath the sediment's tensile strength, and organic matter, is expected to contribute to the development of biogeochemical and hydro-environmental impact assessment methods suitable for in-situ applications.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.73-73
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• 2019

지구 표면의 약 2%에 해당하는 담수에서 육상계 전체가 흡수하는 탄소의 50%가 배출되며, 이는 토양표면에서 배출되는 탄소량에 비해 더 큰 수치로 전 지구적 탄소순환 해석에 중요한 역할을 한다. 특히, 내륙수역과 대기의 경계면에서 $CO_2$ 이동은 전 지구적 탄소순환의 중요한 구성요소로 평가되고 있다. 호수와 저수지 같은 담수 저류시설은 육상에서 기인한 탄소의 운송 및 처리 역할을 한다. 하지만, 저수지에서 온실가스배출량을 평가할 수 있는 명확한 방법론이 부족하며, 전지구 규모 GHGs배출량에 대한 추정에 대한 불확실성이 상당히 큰 상황이다. 본 연구에서는 몬순기후대에 위치한 인공저수지를 대상으로 보다 신뢰도있는 온실가스 배출량 추정을 위해 $CO_2$ NAF 산정하고, 산정에 영향을 미치는 인자들을 분석 하였다. 분석을 위해 $CO_2$ NAF 산정에 필요한 수리 및 수질 인자들을 2017년부터 2018년까지 수집하고, 기초통계량 및 상관분석을 실시하였다. 또한, 주성분분석(PCA) 및 다중선형회귀모델(MLR)과 랜덤포레스트(RF) 기법을 사용해 변수 중요도를 평가하였으며, $CO_2$ NAF 산정 주요인자인 기체교환 계수를 경험적 모델 3종(Cole and Caraco, Crusius, Vachon), 표면갱신형 모델 4종(Heiskanen, Maclntyre, Read, Soloviev)을 비교, 검토하였다. 조사기간 동안 기체교환계수 산정 결과 Crusius 모델 예측값이 평균 $0.342(0.047{\sim}4.323)cm\;hr^{-1}$으로 검토한 모델중 가장 낮은 평균값을 보였으며, Heiskane 모델이 $2.135(0.337{\sim}5.152)cm\;hr^{-1}$으로 가장 큰 평균값을 보였다. 대상 수체는 연주기로 완전혼합되며 수온성층이 약화되는 시기에 저수지 표층 아래에 축적된 탄소가 표층으로 전달되어 높은 수준의 p$CO_2$를 보이며, 수표면에 큰 난류 강도가 작용하는 기간에 대기중으로 배출(pulse emission) 기작이 나타난다. NAF 산정결과 경험적 모델의 NAF값($-1246.0{\sim}6510.3mg-CO_2m^{-2}day^{-1}$)은 표면갱신형 모델 NAF값($-1436.1{\sim}8485.7mg-CO_2m^{-2}day^{-1}$)보다 낮은 수준을 보였으며, 풍속의 함수만을 이용하는 경험적 모델보다 부력 플럭스와 난류 혼합의 영향을 고려하는 Macintyre, Heiskanen모델이 성층 저수지의 $CO_2$ NAF 산정에 적합한 것으로 나타났다. $CO_2$ NAF 산정의 주요인자로 MLR모델은 Tw, EC, pH, Chla, TOC, Alk, RF모델은 EC, DO, TOC가 중요 변수로 평가되었다. PCA 분석결과, 수온이 낮고 성층이 약화되며 pH가 낮은 상태에서 NAF가 큰 것으로 나타났다.

• Journal of Korean Society of Forest Science
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• v.100 no.2
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• pp.149-153
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• 2011

This study was conducted to examine the uncertainty analysis of the stem density and biomass expansion factor for Pinus rigida in Korea. A total of 57 representative sample trees were harvested. The age class in Pinus rigida forests was divided into two, which were stands with less than 20 years and more than 21 years. The influence of stand ages on biomass expansion factor showed that it was statistically significant (p=0.0001), but it was not significant on stem density (p=0.8070). The results of this study based on the uncertainty evaluation method which were suggested by IPCC guide line indicated that stem density of the stand with less than 20 years were 30.92%, while were 25.12% the stands with more than 21years. The uncertainty in biomass expansion factor of less than 20 years and more than 21 years were 60.32% and 22.42%, respectively. The uncertainty of less than 20 years was higher compared to those stands with more than 21 years. In the case of old stand, it showed the lowest uncertainty results but younger stands showed the highest uncertainty results. This study could be applied to our country's emission factor by using stem density and biomass expansion factors which were less than 20 years and more than 21 years for Pinus rigida in Korea.