• Asian Journal of Atmospheric Environment
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• v.2 no.2
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• pp.116-124
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• 2008

In this study, the Tier 2 method recommended by the Intergovernmental Panel on Climate Change (IPCC) was used to predict the methane generation rate at two landfill sites, designated as Y and C for purposes of this study, in South Korea. Factors such as the average annual waste disposal, methane emissions ($L_0$) and methane gas generation rate constant (k) were estimated by analyses of waste and the historical data for the landfills. The value of k was estimated by field experiments and then the changes in the methane generation rate were predicted through the year 2050, based on the value of k. The Y landfill site, which was in operation until the year 2008, will generate a total of 17, 198.7 tons by the end of 2018, according to our estimations. At the C landfill site, which will not be closed until the end of 2011, the amount of methane gas generated in 2011 will be 3,316 tons and the total amount of gas generated by 2029 will be 61,200 tons. The total production rate of methane gas at the C landfill is higher than that of the Y landfill. This indicates that the capacity of a landfill site affects the production rate of methane gas. However, the interrelation between the generation rate of methane and the value of k is weak. In addition, the generation of methane gas does not cease even when the operations at a landfill site come to a close and the methane gas production rate is at its highest at end of the operating life of a landfill site.

• Journal of the Korean Applied Science and Technology
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• v.27 no.1
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• pp.61-69
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• 2010

This study is focused on the modeling of two phase fluid flow system in the electrode of hydrogen gas generator. The characteristics of hydrogen gas generation was studied in view of efficiency of hydrogen gas generation rate and a tendency of gas flow through the riv of electrode. Since the flow rate of generated gas is the most crucial in determining the efficiency of hydrogen gas generator, we adopted the commercial analytical program of COMSOL $Multiphysics^{TM}$ to calculate the theoretical flow rate of hydrogen gas from the outlet of gas generator.

• Journal of the Korean Applied Science and Technology
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• v.27 no.2
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• pp.152-156
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• 2010

This study is focused on the channel design of bipolar plate in the electrode of hydrogen gas generator. The characteristics of hydrogen gas generation was studied in view of efficiency of hydrogen gas generation rate and a tendency of gas flow through the riv design of electrode. Since the flow rate of generated gas is the most crucial in determining the efficiency of hydrogen gas generator, we adopted the commercial analytical program of COMSOL $Multiphysics^{TM}$ to calculate the theoretical flow rate of hydrogen gas from the outlet of gas generator.

• Journal of the Korean Applied Science and Technology
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• v.27 no.4
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• pp.415-420
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• 2010

This study is focused on the channel design of bipolar plate in the electrode of hydrogen gas generator. The characteristics of hydrogen gas generation was studied in view of efficiency of hydrogen gas generation rate and a tendency of gas flow through the riv design of electrode. Since the flow rate and flow pattern of generated gas in the two phase flow system are the most crucial in determining the efficiency of hydrogen gas generator, we adopted the commercial analytical program of COMSOL MultiphysicsTM to calculate the theoretical flow rate of hydrogen gas from the outlet of gas generator and flow pattern of two phase fluid in the electrode. In this study, liquid electrolyte flows into the bipolar plate and decomposed into gas phase, two phase flow simulation is applied to measure the efficiency of hydrogen gas generation.

• Journal of Environmental Health Sciences
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• v.34 no.6
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• pp.414-422
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• 2008

Methane is a potent greenhouse gas and methane emissions from landfill sites have been linked to global warming. In this study, LandGEM (Landfill Gas Emission Model) was applied to predict landfill gas quantity over time, and then this result was compared with the data surveyed on the site, Cheongju Megalo Landfill. LandGEM allows the input of site-specific values for methane generation rate (k) and potential methane generation capacity $L_o$, but in this study, k value of 0.04/yr and $L_o$ value of $100\;m^3$/ton were considered to be most appropriate for reflecting non-arid temperate region conventional landfilling like Cheongju Megalo Landfill. Relatively high discrepancies between the surveyed data and the predicted data about landfill gas seems to be derived from insufficient compaction of daily soil-cover, inefficient recovery of landfill gas and banning of direct landfilling of food waste in 2005. This study can be used for dissemination of information and increasing awareness about the benefits of recovering and utilizing LFG (landfill gas) and mitigating greenhouse gas emissions.

• Journal of Welding and Joining
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• v.16 no.4
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• pp.63-72
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• 1998

In this study, the effects of the current pulsing conditions, on the spatter generation rate during the $CO_2$ gas metal arc welding (GMAW) were investigated. Normally using the inverter type power supply, of which the welding current waveform was regulated to reduce the spatter generation rate, but in this study pulsing was imposed on the welding current. Observation of the metal transfer phenomena during the pulsed current GMAS indicated that the droplet transfer from the electrode via the short circuit transfer and the repelling transfer mode could be minimized by selecting optimum combinations of pulsing parameters, which include base and peak current, base and pak duration. It was also demonstrated in this study that proper combinations of the pulsing parameters led to reduce generation of spatters during GMAW shielded by $CO_2$ gas.

• Bulletin of the Korea Photovoltaic Society
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• v.4 no.2
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• pp.45-53
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• 2018

Natural gas demand for power generation continued to increase until 2013 due to the expansion of large-scale LNG power plants after the black-out of 2011. However, natural gas demand for power generation has decreased sharply due to the increase of nuclear power and coal power generation. But demand for power generation has increased again as energy policies have changed, such as reducing nuclear power and coal power plants, and abnormal high temperatures and cold waves have occurred. If the gas pipeline pressure can be properly maintained by predicting these fluctuations, it can contribute to enhancement of operation efficiency by minimizing the operation time of facilities required for production and supply. In this study, we have developed a regression model with daily power demand and base power generation capacity as explanatory variables considering characteristics by day of week. The model was constructed using data from January 2013 to December 2016, and it was confirmed that the error rate was 4.12% and the error rate in the 90th percentile was below 8.85%.

• Korean Business Review
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• v.19 no.2
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• pp.69-94
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• 2006

Landfill gas is a mixture of methane and carbon dioxide produced by the bacterial decomposition of organic wastes, and it is considered to produce bad smells and pollute the environment. Economic trials and the developments of landfill gas, as an alternative energy resource, become known at the recent years. Resource development of landfill gas, which is managed by Korea up to now, is for the most part generation using gas engine. Medium BTU and High BTU are considered for the power generation as well. I\10st income of generation using gas engine is selling charge through a power plant. Expecting to manage the power plant for up to 10 years, the analysis based on revenue and expenditure shows when the unit price is 65.2 Won and the operating rate reaches 90%, it is possible to be into the black in 2012 without considering additional financial expense. It was also analyzed that the profit at a unit price of 85 Won under the anticipated rising unit price by the operating rate of 71% is larger than at the operating rate of 90% under limited unit price of 65.2 Won. It means to manage the power plant at a unit price of 65.2 Won and the operating rate must be higher than 90% for economic logicality. If we assume that the operating rate is 90% and it increases the unit price, the unit price must be higher than 85 Won for the management of a power plant. Analysis of changing a unit price, however, might be expected to have a gradual rise of prices. If there is no price rising and additional income related to CDM(Clean Development Mechanism) and emission trading upon Kyoto protocol, the management of a power plant using gas engine will get financial difficulties because of many operating expenses. However, since landfill gas is considered as a worthy energy resource for the guarantee of sustainable development and for the equity between recent generation and future generation, the development of it must be accomplished by the government's additional supporting and efforts under the interest of all stakeholder who are involved.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6B
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• pp.399-406
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• 2012

The objective of this research is to develop greenhouse gas generation models and estimation method of their parameters for solid waste landfills. Two models obtained by differentiating the Modified Gompertz and Logistic models were employed to evaluate two parameters of a first-order decay model, methane generation potential ($L_0$) and methane generation rate constant (k). The parameters were determined by the statistical comparison of predicted gas generation rate data using the two models and actual landfill gas collection data. The values of r-square obtained from regression analysis between two data showed that one model by differentiating the Modified Gompetz was 0.92 and the other model by differentiating the Logistic was 0.94. From this result, the estimation methods showed that $L_0$ and k values can be determined by regression analysis if landfill gas collection data are available. Also, new models based on two models obtained by differentiating the Modified Gompertz and Logistic models were developed to predict greenhouse gas generation from solid waste landfills that actual landfill generation data could not be available. They showed better prediction than LandGEM model. Frequency distribution of the ratio of Qcs (LFG collection system) to Q (prediction value) was used to evaluate the accuracy of the models. The new models showed higher accuracy than LandGEM model. Thus, it is concluded that the models developed in this research are suitable for the prediction of greenhouse gas generation from solid waste landfills.

• Journal of Korean Society for Atmospheric Environment
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• v.7 no.1
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• pp.31-40
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• 1991

This study shows the correlation between $NO_x$ emission in the exhaust gas and various operation factors of dual fuel engine for Co-generation system. General tendency was shown that the thermal efficiency was lowered by the change of operation factors. However these were not confirmed on this experiment. Increasing T4 temperature (exhaust gas temperature at turbo-charger inlet) reduces $NO_x$ emission rate. The higher T4 temperature requires lower excess air as the excess air ratio is controlled by T4 temperature on gas mode operation. Another tendency was that $NO_x$ emission rate is reduced in case of increasing boost air temperature, quantity of pilot oil or bypassing flue gas through the exhaust gas boiler. The diameter of the fuel injection nozzle was changed smaller than design value and the injection timing was readjusted. Thus $NO_x$ emission rate could be reduced as retarding injection timing and changing hole diameter of fuel injection nozzle, however maxium engine out-put was decreased by changing fuel nozzle on the diesel mode operation.