• Nuclear Engineering and Technology
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• v.41 no.8
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• pp.1025-1044
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• 2009

Systematic research has been conducted by KAERI to develop a supercritical carbon dioxide Brayton cycle energy conversion system coupled with a sodium cooled fast reactor. For the development of the supercritical $CO_2$ Brayton cycle ECS, KAERI researched four major fields, separately. For the system development, computer codes were developed to design and analyze the supercritical $CO_2$ Brayton cycle ECS coupled with the KALIMER-600. Computer codes were developed to design and analyze the performance of the major components such as the turbomachinery and the high compactness PCHE heat exchanger. Three dimensional flow analysis was conducted to evaluate their performance. A new configuration for a PCHE heat exchanger was developed by using flow analysis, which showed a very small pressure loss compared with a previous PCHE while maintaining its heat transfer rate. Transient characteristics for the supercritical $CO_2$ Brayton cycle coupled with KALIMER-600 were also analyzed using the developed computer codes. A Na-$CO_2$ pressure boundary failure accident was analyzed with a computer code that included a developed model for the Na-$CO_2$ chemical reaction phenomena. The MMS-LMR code was developed to analyze the system transient and control logic. On the basis of the code, the system behavior was analyzed when a turbine load was changed. This paper contains the current research overview of the supercritical $CO_2$ Brayton cycle coupled to the KALIMER-600 as an alternative energy conversion system.

• Polymer(Korea)
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• v.26 no.6
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• pp.785-791
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• 2002

The effect of the supercritical carbon dioxide (sc$CO_2$) on ion-conductive behaviors for polyether electrolytes based on, both poly (ethylene oxide) (PEO) and poly [oligo (oxyethylene glycol) methacrylate] (PMEO) with lithium triflate, LiCF$_3$SO$_3$, has been investigated. In particular, the present research is a new concept for improving the ionic conductivity of polyether electrolytes. The maximum ionic conductivity ($\sigma$$_{max}$) at room temperature of the PEO electrolyte was more than 100 times higher, and the $\sigma$$_{max}$ at 9$0^{\circ}C$ of the PMEO electrolyte was 30 times improved by the se$CO_2$ treatment, respectively. It was revealed that the penetration of $CO_2$ molecules into the polymer matrix causes the increase of carrier ions by ion-dispersion effect and the decrease of glass transition temperature (T$_{g}$) by plasticizing effect that results in the improvement of the ion transport behaviors.viors.

• Journal of the Society of Disaster Information
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• v.19 no.1
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• pp.184-194
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• 2023

Purpose: The purpose of this study is to identify the characteristics of C02 emissions by road before establishing a policy to reduce greenhouse gas emissions. Method: As for the analysis method, the traffic volume and speed of the road were estimated using the traffic Assignment model targeting 27 arterial road axes in Incheon Metropolitan City. And, after estimating CO2 emissions by road axis by applying this, the characteristics of each group were analyzed through cluster analysis. Result: As a result of cluster analysis using total CO2 emissions, CO2 emissions by truck vehicles, and the ratio of truck vehicle emissions to total carbon dioxide emissions, four clusters were classified. When examining the characteristics of each road included in each group, it was analyzed that the characteristics of each group appeared according to the level of impact by CO2 emissions and truck vehicles. Conclusion: It is judged that it is necessary to establish a plan in consideration of CO2 emission characteristics for road CO2 management for greenhouse gas reduction.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2812-2822
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• 2023

The supercritical carbon dioxide (sCO₂) Brayton power cycle is more effective than the conventional power cycle and is more widely applicable to heat sources. The inlet working conditions of the compressor have a higher influence on their operating performance because the thermophysical properties of the CO₂ vary dramatically close to the critical point. The flow in the sCO₂ compressor is simulated and the compressor performance is analyzed. The results show that the sCO₂ centrifugal compressor operates outside of its intended parameters due to the change in inlet temperature. The sCO₂ compressor requires more power as the inlet temperature increases. The compressor power is 582 kW when the inlet temperature is at 304 K. But the power is doubled when the inlet temperature increases to 314 K, and the change in the isentropic efficiency is within 5%. The increase in the inlet temperature significantly reduces the risk of condensation in centrifugal compressors. When the heat load of the sCO₂ power system changes, the inlet pressure to the turbine can be kept constant by regulating the rotational speed of compressors. With the increase in rotational speed, the incidence loss and condensation risk increase.

• Journal of Climate Change Research
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• v.7 no.3
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• pp.249-256
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• 2016

Porous $Al_2O_3$ hollow fiber membranes were successfully prepared by dry-wet spinning/sintering method. The SEM image shows that the $Al_2O_3$ hollow fiber membrane consists mostly of sponge pore structure. The contact angle and the breakthrough pressure were $126^{\circ}$ and 1.91 bar, respectively. This results indicate that the $Al_2O_3$ hollow fiber membranes were successfully modified to hydrophobic surface. The hydrophobic modified $Al_2O_3$ hollow fiber membranes were assembled into a membrane contactor system to separate $CO_2$ from a model gas mixture of the flue gas at elevated gas velocity. The $CO_2$ absorption flux was enhanced when the gas velocity increased from $1{\times}10^{-3}$ to $6{\times}10^{-3}$ m/s. Whereas the $CO_2$ absorption flux was decreased with the number of hollow fiber membrane of a module because of the concentration polarization. Furthermore, we developed an lab-scale $Al_2O_3$ hollow fiber membrane contactor modules and their system (i.e., $CO_2$ absorption using the $Al_2O_3$ membrane and monoethanolamine (MEA)) that could dispose of over $0.02Nm^3/h$ mixture gas (15% $CO_2$) with the removal efficiency higher than 95%. The results can be useful in a field of the membrane contactor for $CO_2$ separation, helping to design and extend a equipment.

• Journal of Animal Environmental Science
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• v.13 no.1
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• pp.1-12
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• 2007

Stored animal manure is considered as a significant agricultural source of methane $(CH_4)$ and nitrous oxide $(N_2O)$ which have 23 and 297 times higher global warming effect when compared to carbon dioxide $(CO_2)$. Uncertainties caused by lack of understanding physical and biochemical environment in stored animal manure and by errors of emission measurement methods, even though many researches measuring $CH_4\;and\;N_2O$ emissions from stored manure have been conducted for a few decades. In this paper, general information of $CH_4\;and\;N_2O$ generation and emissions from stored animal manure and the measurement methods for quantifying $CH_4\;and\;N_2O$ emissions are discussed.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1195-1206
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• 2011

This study was conducted to apply LCA (Life cycle assessment) methodology to lettuce (Lactuca sativa L.) production systems in Namyang-ju as a case study. Five lettuce growing farms with three different farming systems (two farms with organic farming system, one farm with a system without agricultural chemicals and two farms with conventional farming system) were selected at Namyangju city of Gyeonggi-province in Korea. The input data for LCA were collected by interviewing with the farmers. The system boundary was set at a cropping season without heating and cooling system for reducing uncertainties in data collection and calculation. Sensitivity analysis was carried out to find out the effect of type and amount of fertilizer and energy use on GHG (Greenhouse Gas) emission. The results of establishing GTG (Gate-to-Gate) inventory revealed that the quantity of fertilizer and energy input had the largest value in producing 1 kg lettuce, the amount of pesticide input the smallest. The amount of electricity input was the largest in all farms except farm 1 which purchased seedlings from outside. The quantity of direct field emission of $CO_2$, $CH_4$ and $N_2O$ from farm 1 to farm 5 were 6.79E-03 (farm 1), 8.10E-03 (farm 2), 1.82E-02 (farm 3), 7.51E-02 (farm 4) and 1.61E-02 (farm 5) kg $kg^{-1}$ lettuce, respectively. According to the result of LCI analysis focused on GHG, it was observed that $CO_2$ emission was 2.92E-01 (farm 1), 3.76E-01 (farm 2), 4.11E-01 (farm 3), 9.40E-01 (farm 4) and $5.37E-01kg\;CO_2\;kg^{-1}\;lettuce$ (farm 5), respectively. Carbon dioxide contribute to the most GHG emission. Carbon dioxide was mainly emitted in the process of energy production, which occupied 67~91% of $CO_2$ emission from every production process from 5 farms. Due to higher proportion of $CO_2$ emission from production of compound fertilizer in conventional crop system, conventional crop system had lower proportion of $CO_2$ emission from energy production than organic crop system did. With increasing inorganic fertilizer input, the process of lettuce cultivation covered higher proportion in $N_2O$ emission. Therefore, farms 1 and 2 covered 87% of total $N_2O$ emission; and farm 3 covered 64%. The carbon footprints from farm 1 to farm 5 were 3.40E-01 (farm 1), 4.31E-01 (farm 2), 5.32E-01 (farm 3), 1.08E+00 (farm 4) and 6.14E-01 (farm 5) kg $CO_2$-eq. $kg^{-1}$ lettuce, respectively. Results of sensitivity analysis revealed the soybean meal was the most sensitive among 4 types of fertilizer. The value of compound fertilizer was the least sensitive among every fertilizer imput. Electricity showed the largest sensitivity on $CO_2$ emission. However, the value of $N_2O$ variation was almost zero.

• Journal of Preventive Medicine and Public Health
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• v.35 no.1
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• pp.72-75
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• 2002

Objectives : To evaluate the health hazards in the underground storage facilities of ginger roots. Methods : The authors reviewed the emergency rescue records from the Seosan fire department over the period Jan 1, 1996 to Aug 31, 1999. The atmospheres in 3 different underground storage locations were analyzed for $O_2,\;CO_2,\;CO,\;H_2S\;and\;NH_4$. Results : From the emergency records, we were able to identify 20 individuals that had been exposed to occupational hazards in the underground storage facilities. Among these 20 cases, 13 were due to asphyxiation (resulting in f deaths) and 7 were due to falls. In the first atmospheric tests, peformed on Feb 25, 1998, the O2 level inside the underground storage facility, located about $5{\sim}6$ meters below the surface, was 20.6% and the $CO_2$ level was about 1,000 ppm. CO, $H_2S\;and\;NH_4$ were not detected. In the second tests on Jul 6, 1999, measurements of the $O_2$ level at 3 meters below the surface in two different storage locations were 15.3 and 15.1%. And the $O_2$ levels inside the storage facilities were 12.2 and 12.1%. The $CO_2$ level was above 5,000 ppm (beyond upper limits of measurement). CO, $H_2S\;and\;NH_4$ were not detected. Conclusions : We conclude that asphyxiation in the underground storage facilities for ginger roots was not due to the presence of toxic gases such as CO, $H_2S\;and\;NH_4$, but rather the exclusion of oxygen by carbon dioxide was responsible for causing casualties. For the development of a hazard free working environment, safety education as well as improvements in storage methods are needed.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.304-304
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• 2010

The study on the catalytic oxidation of carbon monoxide (CO) to carbon dioxide ($CO_2$) using the noble metals has long been the interest subject and the recent progress in nanoscience provides the opportunity to develop new model systems of catalysts in this field. Of the noble metal catalysts, we selected ruthenium (Ru) as metal catalyst due to its unusual catalytic behavior. The size of colloid Ru NPs was controlled by the concentration of Ru precursor and the final reduction temperatures. For catalytic activity of CO oxidation, it was found that the trend is dependent on the size of Ru NPs. In order to explain this trend, the surface oxide layer surrounding the metal core has been suggested as the catalytically active species through several studies. In this poster, we show the influence of surface oxide on Ru NPs on the catalytic activity of CO oxidation using chemical treatments including oxidation, reduction and UV-Ozone surface treatment. The changes occurring to UV-Ozone surface treatment will be characterized with XPS and SEM. The catalytic activity before and after the chemical modification were measured. We discuss the trend of catalytic activity in light of the formation of core-shell type oxide on nanoparticles surfaces.

• Journal of Korean Society of Forest Science
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• v.77 no.1
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• pp.92-99
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• 1988

The dark respiration, photosynthesis($CO_2$ refixation), $CO_2$ balance and chlorophyll content of 1st-year conelets and 2nd-year cones of Korean pine(Pinus koraiensis S.et.Z.) were investigated after pollination up to the end of maturation. The results obtained are as follows : 1. The growth of 1st-year conelet was 3.6cm in length. 2.4cm in diameter and 3.058 in dry weighs during the first year. The growth of 2nd-year mature cone was 13.5cm in length, 9.3cm in diameter and 141.0g in dry weight in the late of 2nd-year. 2. The refixation of carbon dioxide released from a cone by the dark respiration was less than 50 percent at light saturation through the growing period. The refixation of carbon dioxide released by dark respiration for one year was 7.3 percent in 1st-year conelets and 8.7 percent in 2nd-year cones. 3. The dark respiration rate of cones by increasing temperature was rapidly increased with increasing temperature up to $25^{\circ}C$. The dark respiration rate of cones was much higher in non-growing season than that in growing season at the same temperature. 4. The rates of dark respiration and $CO_2$ refixation, based on the dry weight, were much higher in 1st-year conelet than that in 2nd-year cone. 5. The $CO_2$ balance for a cone was negative from pollination to the end of maturation. The net dark respiration loss for a cone was 7.23g $CO_2$/year in 1st-year conelet and 164.8g $CO_2$/year in 2nd-year cone. 6. The respiratory loss efficiency for a cone(=$CH_2O$ weight calculated by net dark respiration/dry weight of cone) for one year was 1.61 in 1st-year conelet and 0.81 in 2nd-year cone for one year. 7. The total chlorophyll content of surface scale of the cone was lower than 2mg/g dw through the growing period, and chl. a/b ratio was 2 to 3.