• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.704-711
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• 2005

In this study, life cycle assessment(LCA) for the nuclear power generation system and the thermal power generation system, which make a great distribution of the electric power supply in Korea, has been carried out to compare the environmental impact between two power generation systems. In system boundary of this study, the stage of construction, operation and demolition & disposal were included. For life cycle impact assessment(LCIA), three cases were considered; the single environmental impact for the $CO_2$ emissions, the 8 major global environmental impact, and the major global environmental impact categories including radioactive impact. As the results, it was found that the nuclear power generation system is environmentally superior to the thermal power generation system as 10,000 times in the evaluation for the $CO_2$ emissions, 90 times in the evaluation for the 8 major environmental impact categories, and 40 times in the evaluation for the environmental impact categories including radioactive impact.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2200-2205
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• 2007

In order to investigate the variation on a heat transfer coefficient during evaporation of $CO_2$, basic experiment on the evaporation heat transfer characteristics in a horizontal micro-channel tube was performed. Hydraulic diameters of micro-channels were 0.68 and 1.46 mm. The experiment apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiments were conducted for various mass fluxes of 300 to 800 kg/$m^2s$, heat fluxes of 10 to 40 kW/$m^2$ and saturation temperatures of -5 to 5$^{\circ}C$. With the increase heat flux, the evaporation heat transfer coefficient increased. And the significantly change of the heat transfer coefficient was observed at any heat flux and mass flux. As the saturation temperature increased and the hydraulic diameter decreased, the heat transfer coefficient increased.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.8
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• pp.3086-3101
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• 2021

To supply precise marketing and differentiated service for the electric power service department, it is very important to predict the customers with high sensitivity of electric power failure. To solve this problem, we propose a novel grouped 𝑙_1/2 sparsity constrained logistic regression method for sensitivity assessment of electric power failure. Different from the 𝑙₁ norm and k-support norm, the proposed grouped 𝑙_1/2 sparsity constrained logistic regression method simultaneously imposes the inter-class information and tighter approximation to the nonconvex 𝑙₀ sparsity to exploit multiple correlated attributions for prediction. Firstly, the attributes or factors for predicting the customer sensitivity of power failure are selected from customer sheets, such as customer information, electric consuming information, electrical bill, 95598 work sheet, power failure events, etc. Secondly, all these samples with attributes are clustered into several categories, and samples in the same category are assumed to be sharing similar properties. Then, 𝑙_1/2 norm constrained logistic regression model is built to predict the customer's sensitivity of power failure. Alternating direction of multipliers (ADMM) algorithm is finally employed to solve the problem by splitting it into several sub-problems effectively. Experimental results on power electrical dataset with about one million customer data from a province validate that the proposed method has a good prediction accuracy.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.74-83
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• 2017

Coal-fired power plants supply roughly 50 percent of the nation's electricity but produce a disproportionate share of electric utility-related air pollution. Coal combustion technology can facilitate volume reduction of up to 90%, with the inorganic contaminants being captured in furnace bottom ash and fly ash residues. These disposal coal ash residues are however governed by the potential release of constituent contaminants into the environment. Accelerated carbonation process has been shown to have a potential for improving the chemical stability and leaching behavior of bottom ash residues. The aim of this work was to quantify the volume of $CO_2$ that could be sequestrated with a view to reducing greenhouse gas emissions and stabilize the contaminated heavy metals from bottom ash samples. In this study, we used PC boiler bottom ash, Kanvera reactor (KR) slag and calcined waste lime for measuring chemical analysis and heavy metals leaching tests were performed and also the formation of calcite resulting from accelerated carbonation process was investigated by thermo gravimetric and differential thermal analysis (TG/DTA).

• Clean Technology
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• v.20 no.3
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• pp.218-225
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• 2014

Catalytic gasification of raw coals at mild condition is not realized yet mainly due to deactivation of catalysts via their irreversible interaction with mineral matters in coal. In this work, the gasification behavior of ash-free coal (AFC) was compared with that of the parent raw coal. In order to modify the gasification conditions, the raw coal gasified with fixed variables (water supply, space velocity, temperature, catalysts) in a fixed bed reactor. When catalysts are added by physical mixing method with coal, $K_2CO_3$ was the most effective additives for steam gasification of coal. However, the activity of ash-free coal (AFC) was much less reactive than raw coal due to high temperature extraction in a 1-methylnaphthalene under 30bar at $370^{\circ}C$ for 1 h, almost removed oxygen functional groups, and increased carbonization. The addition of $K_2CO_3$ in AFC achieved higher conversion rate at low temperature ($700^{\circ}C$). At that time, the molar ratio of gases ($H_2/CO$ and $CO_2/CO$) was increased because of water-gas shift reaction (WGSR) by addition of catalysts. This shows that catalytic steam gasification of AFCs is achievable for economic improvement of gasification process at mild temperature.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.181-184
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• 2001

The biological fixation of carbon dioxide using microalgae have many advantages over chemicals and remove carbon dioxide simultaneously. A ketocarotenoid astaxanthin is hyper-accumulated in the green freshwater microalga, Haematococcus pluvialis. In the present study, the combine effects of carbon dioxide concentration and light intensity on the growth of H. pluvilais were investigated. The carbon dioxide concentration above 10% caused a severe inhibition and around 5% is optimal for growth. Adaptation to high concentration of carbon dioxide enhanced the $CO_2$ tolerance. Specific growth rate calculated differently based upon cell number or dry weight because of the distinctive life cycle patterns of H. pluvialis : small-sized motile green cell and thick cell walled red cyst cell. Based on the light dependence of H. pluvialis, internally illuminated air-lift photobioreactor was designed and operated. Gradual increase of light supply gave more active growth and more effective productivity of astaxanthin than constant light supply.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1103-1111
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• 2011

This paper is developed to Energy Balance Flow show the flow of total energy resource be used nationally. The Energy Balance Flow is applicable of demand management factor through the analysis of foreign energy model of supply and demand and energy statistic data in the country. This study is based on and developed to Energy system management model is able to appraisal efficient of energy cost cutting, CO2 emission reduction and Energy saving at the national level calculated effect reached amount of primary energy to change of energy flow followed application of demand side management factor is able to appraisal quantitatively at the total energy to model of demand and supply.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.679-680
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• 2011

This paper is developed to Energy Balance Flow show the flow of total energy resource be used nationally. The Energy Balance Flow is applicable of demand management factor through the analysis of foreign energy model of supply and demand and energy statistic data in the country. This study is based on and developed to Energy system management model is able to appraisal efficient of energy cost cutting, CO2 emission reduction and Energy saving at the national level calculated effect reached amount of primary energy to change of energy flow followed application of demand side management factor is able to appraisal quantitatively at the total energy to model of demand and supply.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.580-582
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• 2008

The object of this paper is develope the PC based controlled high voltage power supply and studies 1.2kW(120kV, 10mA) pulse power X-ray generator possible to adapt fluoroscopy of Dental CT X-ray generator and industrial X-ray pulse power equipment. The developed pulse power X-ray generator consisted of mono-block tank include X-ray tube and high voltage X-ray power supply circuit and high voltage control unit with RS232C/422 communication port. The PC control program of pulse power X-ray generator uses LabVIEW, and the size of high voltage transformer and high voltage generator is minimized by high voltage high frequency inverter has 100kHz switching frequency. Also this paper shows result of X-ray tube voltage and tube current correspond to variable load.

• KSTLE International Journal
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• v.10 no.1_2
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• pp.37-42
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• 2009

This paper presents the characteristics of volumetric efficiency of an axial type piston pump considering the piston tilting. A numerical analysis is carried out in order to obtain the pressure distribution considering the fluid inertia at the notch of the valve plate. The cylinder pressure variation and the discharge flow rate are measured experimentally according to the operating conditions such as supply pressure, rotational speed, and viscosity of the working fluid by using the cam type test apparatus. Leakage is also measured considering piston tilting. The characteristics of the volumetric efficiency are analyzed with respect to various operating conditions and leakage is also analyzed according to the piston tilting angle. Results are applicable to improve the design of an axial type piston pump.