• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.5
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• pp.101-106
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• 2019

Carbon deposition on the turbine nozzle throat of a LOx/kerosene gas generator cycle(open cycle) engine causes performance reduction of the engine. Estimation methods for a turbine nozzle throat area are proposed. The discharge coefficient of the turbine nozzle was estimated with the turbine gas properties such as gas constant, specific heat ratio, and temperatures. The pressure ratio and temperature ratio of the turbine nozzle throat, was utilized to estimate the discharge coefficient also. Estimated discharge coefficient of turbine nozzle throat of KSLV-II 1st stage engine shows the carbon deposition effects on the turbine nozzle throat of a LOx/kerosene open cycle engine.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.1-7
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• 2019

To overcome the limitations of existing rainwater drainage systems, we compared and analyzed a newly developed eco-friendly channel-type rainwater drainage system. We also developed an integrated evaluation index to quantify the improvement of the new system. The concept of Life Cycle Assessment (LCA) was applied to calculate and compare the costs of each process and to develop the integrated evaluation index, which considers the carbon emissions by each process. As a result, the cost was reduced by 53% overall compared to an O-type system and by 63% compared to a U-type system. In addition, when applying the integrated evaluation index, the new system was evaluated to be over 80% in the four processes compared to the existing systems. When applying the evaluation index to sites in Anyang and Incheon, the new system was improved by 35-100% compared to existing systems.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.1
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• pp.13-22
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• 2022

This study proposes a low-cycle fatigue life derived from measurement points on pipe elbows, which are components that are vulnerable to seismic load in the interface piping systems of nuclear power plants that use seismic isolation systems. In order to quantitatively define limit states regarding leakage, i.e., actual failure caused by low-cycle fatigue, in-plane cyclic loading tests were performed using a sine wave of constant amplitude. The test specimens consisted of SCH40 6-inch carbon steel pipe elbows and straight pipes, and an image processing method was used to measure the nonlinear behavior of the test specimens. The leakage lines caused by low-cycle fatigue and the low-cycle fatigue curves were compared and analyzed using the relationship between the relative deformation angles, which were measured based on each of the measurement points on the straight pipe, and the moment, which was measured at the center of the pipe elbow. Damage indices based on the combination of ductility and dissipation energy at each measurement point were used to quantitatively express the time at which leakage occurs due to through-wall cracking in the pipe elbow.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.3
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• pp.237-246
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• 1995

Larvae of the freshwater shrimp, Macrobrachium nipponense were reared in the laboratory at constant condition $(25^{\circ}C,\;7\%o)$, and their feeding rate, oxygen consumption rate, and growth rate were measured in regular intervals of time during larval development. Regression equations describing rates of feeding, growth and respiration as functions of time during individual larval molt cycles were inserted in a simulation model in order to analyse time-dependent patterns of variation as well as in bioenergetic efficiencies. Absolute values for feeding, growth, respiration and assimilation showed clear changes during the molt cycle, The absolute and specific values of respiration (R: R/C) showed small variation during the individual molt cycles. Significance of respiration in relation to growth (G) increased within the carbon budget, respiration rate (R/C) outbalanced growth rate (G/C) in late premolt. When the portion of metabolizable carbon is respired (R/G), metabolic coefficient was < 1 (i.e. R$(K_2)$ decreased concurrently, In cumulative carbon budget, total feeding was $491.54\;{\mu}g$ C/ind., assimilation was $85.3\%$, respiration was $47.7\%$, and growth was $37.6\%$ from hatching to postlarval stage.

• Environmental and Resource Economics Review
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• v.27 no.1
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• pp.67-104
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• 2018

In this paper, we compare the spread effects of the carbon tax imposition method using the real business cycle model considering the productivity and energy price shocks. Scenario 1 sets the carbon tax rate that encourages the representative firm to maintain a constant $CO_2$ reduction ratio in accordance with its green house gas reduction targets for each period. Scenario 2 sets the method of imposing the steady state value of the carbon tax rate of Scenario 1 during the analysis period. The impulse response analysis shows that the responses of $CO_2$ emissions to external shocks are relatively sensitive in scenario 2. And simulation results show that the cost of $CO_2$ abatement is more volatile in scenario 1, and $CO_2$ emissions and $CO_2$ stock are more volatile in scenario 2. In particular, the percentage changes in volatility between the two scenarios of $CO_2$ emissions and $CO_2$ stock increase as the green house gas reduction target is harder. When the green house gas reduction target is 60% and over, the percentage changes(absolute value) between the two scenarios exceed the percentage change(absolute value) of the $CO_2$ reduction cost between them.

• Journal of Ecology and Environment
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• v.43 no.4
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• pp.390-399
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• 2019

Background: The Northern Hemisphere forest ecosystem is a major sink for atmospheric carbon dioxide, and the subalpine zone stores large amounts of carbon; however, their magnitude and distribution of stored carbon are still unclear. Results: To clarify the carbon distribution and carbon budget in the subalpine zone at volcanic Jeju Island, Korea, we report the C stock and changes therein owing to vegetation form, litter production, forest floor, and soil, and soil respiration between 2014 and 2016, for three subalpine forest ecosystems, namely, Abies koreana forest, Taxus cuspidata forest, and Juniperus chinensis var. sargentii forest. Organic carbon distribution of vegetation and NPP were bigger in the A. koreana forest than in the other two forests. However, the amount of soil organic carbon distribution was the highest in the J. chinensis var. sargentii forest. Compared to the amount of organic carbon distribution (AOCD) of aboveground vegetation (57.15 t C ha^-1) on the subalpine-alpine forest in India, AOCD of vegetation in the subalpine forest in Mt. Halla was below 50%, but AOCD of soil in Mt. Halla was higher. We also compared our results of organic carbon budget in subalpine forest at volcanic island with data synthesized from subalpine forests in various countries. Conclusions: The subalpine forest is a carbon reservoir that stores a large amount of organic carbon in the forest soils and is expected to provide a high level of ecosystem services.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.134-134
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• 2010

Recently, the interest of the study about IGCC(Integrated Gasification Combined Cycle), one of New & Renewable Energy technologies, bas been increased due to the United Nations Framework Convention on Climate Change, the Low Carbon Green Growth policy, etc. Also, with this interest of IGCC, the study on the gas turbine utilizing the synthetic gas is performing actively. In the study of the gas turbine characteristic, the power performance and the combustion efficiency are mainly discussed and also the concern about the exhaust gas is being taken care of due to the increasing awareness of the environment. With this, we would like to go over the exhaust gas emission characteristic by the synthetic gas inflow in this test. In order to conduct such a test, we constructed a synthetic gas supplying system to supply the synthetic gases ($H_2$: hydrogen, $N_2$: nitrogen, CO: carbon monoxide, $CO_2$: carbon dioxide, and $H_2O$: steam) quantitatively and this combustion test was conducted by controlling the supplied synthetic gases artificially. The concentration of the exhaust gases appeared variously depending on the differences of the inflow nitrogen amount and the steam amount, whether or not the carbon dioxide flow in and so on. The results of the test can be able to be utilized for the IGCC study by understanding the exhaust gas emission characteristic of the coal gas turbine by synthetic gas composition.

• Transactions on Electrical and Electronic Materials
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• v.8 no.1
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• pp.41-45
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• 2007

Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. Carbon black was added to enhance the electrical conductivity of $LiFePO_4$. The structural and morphological performance of $LiFePO_4$ and $LiFePO_4$-C powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). $LiFePO_4$/Li and $LiFePO_4$-C/Li cells were characterized electrochemically by cyclic voltammogram (CV), charge/discharge experiments and ac impedance spectroscopy. The results showed that the discharge capacity of $LiFePO_4$/Li cell was 147 mAh/g at the first cycle and 118 mAh/g after 30 cycles, respectively. The discharge capacity of $LiFePO_4$-C/Li cell with 5 wt% carbon black was the largest among $LiFePO_4$-C/Li cells, 133 mAh/g at the first cycle and 128 mAh/g after 30 cycles, respectively. It was demonstrated that cycling performance of $LiFePO_4$-C/Li cell with 5 wt% carbon black was better than that of $LiFePO_4$/Li cell.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.898-902
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• 2008

Prepared are three types of composite supercapacitor electrode, such as electroactive polyaniline(PAN), PAN/multi-walled carbon nanotube(CNT), and $CNT/PAN/RuO_2$. Cyclic voltammetry was performed to investigate the supercapacitive properties of these electrodes in an electrolyte solution of 1.0M $H_2SO_4$. The $CNT/PAN/RuO_2$ electrode showed the highest specific capacitance at all scan rates(e.g., 441 and $392F\;g^{-1}$ at 100 and $1,000mV\;s^{-1}$, respectively). In cycle performance, however, the PAN/CNT electrode demonstrated the best capacitance retention (66%) at $10^4th$ cycle.

• Journal of Korean Society of Forest Science
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• v.98 no.1
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• pp.33-48
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• 2009

Forests store carbon dioxide ($CO_2$), one of the major factors of global warming, in vegetation and soils through photosynthesis process. In addition, woods deposit $CO_2$ for a long term until the harvested wood is decomposed or burned, and deforested areas could be expanded the carbon sinks through reforestation. Forests are a lso able to decrease temperature through transpiration and contribute to control the micro climate in global climate systems. Consequently, forests are considered as one of major sinks of greenhouse gases for mitigating global warming. It is very important to develop a Korea specific forest carbon flux model for preparing adaptation measures to climate change. In this study, we compared the climate change impact models in forests developed in foreign countries and analyzed the applicability of the models to Korean forest. Also we selected models applicable to Korean forest and suggested approaches for developing Korean specific model.