• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.323-325
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• 1995

An Inductively Coupled Plasma(ICP) was employed to prepare the Diamond-Like Carbon film with $CH_4$ gas. We observed the changes of mechanical, optical properties and internal stress of the films according to the variation of discharge power and negative-self bias. When weak magnetic field is applied, the properties of film are observed to change drastically. In magnetized case, the micro-hardness and the internal stress increase up to critical point and droped down in marked contrast to unmagnetized case. It suggests that large amount of ion flux exists due to high dissociation rate of the reactive radicals in plasma with magnetic field as reported elsewhere. As a result of FT-IR absorption measurement it could be confirmed that the $CH_x$ bonding and the micro-hardness and the internal stress decreased with the increase of negative-self bias.

• Membrane Journal
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• v.14 no.3
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• pp.192-200
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• 2004

It is an anaerobic germ that Lactobacillus cell concentrated using ceramic membrane has high stability and long lifetime as compared with polymeric membrane. The effects of operating pressure, temperature, crossflow velocity on cell harvesting have been studied. Also the variation of flux and transmembrane pressure (TMP) with increasing concentration ratio and the change of TMP at constant concentration ratio (volumetric concentration factor: VCF) regarding the optimization have been examined. It showed that the permeate flux increased gradually with the increasing of transmembrane pressure, crossflow velocity, and volumetric concentration factor. The higher initial flux was due to the reduction of viscosity at elevated temperature. However, as operating time progressed, the effect of temperature was negligible since the effect of viscosity became minor. As a result, that operate in a constant concentration ratio, decreased degree could know that become slowly although the flux decreases according as operating time progressed. The flux is a very stable in the condition of constant VCF range. The yield of Latobaciilus (PS 406) which was cultivated at $37^{\circ}C$ was concentrated about 4.9{\times}10^9$ after operation.

• Membrane Journal
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• v.26 no.2
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• pp.126-134
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• 2016

To produce renewable biomethane from biogas, the properties of physical absorbents such as water, methanol, 1-methyl-2-pyrrolidone (NMP), poly(ethylene glycol) dimethylether (PEGDME), and propylene carbonate (PC) were studied, and PC was applied to membrane contactor systems. Among physical absorbents, PC exhibited a high contact angle of $58.3^{\circ}$ on polypropylene surface, and a PC/water mixture (5 wt%) increased the contact angle to $90^{\circ}$. Furthermore, the PC/water mixture presented higher $CO_2$ absorption capacities (0.148-0.157 mmol/g) than that of water (0.121 mmol/g), demonstrating a good property as an absorbent for membrane contactors. Actual operations in membrane contactors using the PC/water mixture resulted in $CO_2$ removal of 98.0-97.8% with biomethane purities of 98.5-98.3%, presenting a strong potential for biogas treatment. However, the PC/water mixture yielded moderate improved in $CO_2$ removal and methane recovery, as compared with water in the membrane contactor operation. This is originated from insufficient desorption processes to reuse absorbent and low $CO_2$ flux of the PC/water absorbent. Thus, it is requiring optimizations of membrane contactor technology including development of absorbent and improvement of operation process.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.4
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• pp.271-277
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• 2015

Anaerobic decomposition of organic material in flooded rice fields produces methane, which escapes to the atmosphere primarily by transport through the rice plants. The annual amount of $CH_4$ emitted from a given area of rice is a function of the number and duration of crops grown, water regimes before and during cultivation period, and organic and inorganic soil amendments. Soil type, temperature, and rice cultivar also affect $CH_4$ emissions. The field experiment was conducted for three years to develop methane emission factor for water regime before the cultivation period from the rice fields. It was treated with three different water regimes prior to rice cultivation, namely: non-flooded pre-season < 180 days, non-flooded pre-season > 180 days, flooded per-season in which the minimum flooding interval is set to 30 days. Methane emission increased with days after transplanting and soil redox potential (Eh) decreased rapidly after flooding during the rice cultivation. The average methane emission fluxes were $5.47kg\;CH_4\;ha^{-1}day^{-1}$in flooded pre-season > 30 days, 5.04 in non-flooded pre-season < 180 days and 4.62 in non-flooded pre-season > 180. Methane emission flux was highly correlated with soil temperature and soil Eh. Rice yields showed no difference among treatments with water regime before the cultivation period.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.4
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• pp.436-445
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• 2023

Methane (CH₄) emissions from rice paddies are mainly observed using the closed chamber method or the eddy covariance method. In this study, a new observation technique combining a portable gas analyzer (Model LI-7810, LI-COR, Inc., USA) and an automatic opening/closing chamber (Model Smart Chamber, LI-COR, Inc., USA) was introduced based on the strengths and weaknesses of the existing measurement methods. A cylindrical collar was manufactured according to the maximum growth height of rice and used as an auxiliary measurement tool. All types of measured data can be monitored in real time, and CH₄ flux is also calculated simultaneously during the measurement. After the measurement is completed, all the related data can be checked using the software called 'SoilFluxPro'. The biggest advantage of the new observation technique is that time-series changes in greenhouse gas concentrations can be immediately confirmed in the field. It can also be applied to small areas with various treatment conditions, and it is simpler to use and requires less effort for installation and maintenance than the eddy covariance system. However, there are also disadvantages in that the observation system is still expensive, requires specialized knowledge to operate, and requires a lot of manpower to install multiple collars in various observation areas and travel around them to take measurements. It is expected that the new observation technique can make a significant contribution to understanding the CH₄ emission pathways from rice paddies and quantifying the emissions from those pathways.

• New & Renewable Energy
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• v.16 no.3
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• pp.27-34
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• 2020

This study involved a total budget analysis on the greenhouse gas (GHGs) emissions of landfills, focusing on surface emissions and the effect on emissions reductions of generating landfill gas (LFG) electricity from March 7, 2007 to December 31, 2018. The GHGs reduction effect from the electricity generation using 536.6 × 10³ tCO₂ of CH₄ was only 5.8% of the GHGs from surface emissions of 9,191 × 10³ tCO₂. In the total budget, the collection ratio should be over 95% if the reduction effect is greater than the surface emissions. The correlation coefficient for the relationship between the LFG collection ratio and GHGs reduction was -0.89. An additional effect of lowering CH₄ content may occur if the surface emitting flux of LFG decreased with an increase in the collection ratio. The unit reduction effect of GHGs by suppressing surface emissions was 4174 tCO₂/TJ. This was far greater than that of LFG power generated (54.3 tCO₂/TJ), demonstrating that surface emission control is the most important measure by which to mitigate GHGs emission.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.3
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• pp.261-265
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• 1995

Methane flux from a rice paddy in Korea was measured to study the effects of water management and rice straw application on methane emission under different water managements ; flooding and intermittent irrigation, and with or without rice straw application. Methane emission ranged from 0.066 to $0.455g\;CH_4m^{-2}d^{-1}$. Intermittent irrigation has shown a mitigation effect of methane emission, 70% in NPK plot and 47% in NPK plus rice straw plot, relative to that of flooding. Methane emission from Korean paddy was estimated as 399,590tons per year assuming that paddy fields were managed under intermittent irrigation and rice straw application. This estimation was lower than that of OECD's by 56%, Neue's by 51%, and Matthew's by 62%, while higher than that of Taylor's by 118%.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.1
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• pp.49-56
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• 1993

The net flux of global green house gases such as carbon dioxide($CO_2$), methane($CH_4$), and nitrous oxide($N_2O$) emitted from the rotation of paddy-upland soil during growing sesaon under different cropping system was determined. The results obtained were summarized as follows : 1. The net flux of $CO_2$ during the growing season was the highest from continuous cultivation of rice but the lowest from rotation cultivation of rice-soybean. Under the different cropping system the highst emission was from soil of continuous cultivation of rice, but the lowest from converted system. 2. The net emission of methane was the highest from the sold of continuous cultivation of rice, but the flux was remarkably decreased by differing the cropping system. 3. $N_2O$ was emitted greatly from the every two year rotation of potato-chinese cabbage and the next rank was from continuous cultivation of rice, but was decreased notably from rotation cultivation of rice-soybean and potato-chinese cabbage under rotation of paddy-upland cropping system. 4. The ratio of oxygen and carbon dioxide in the soil air was much different with glowing season, the ratio was varied with 4~10 percents for oxygen and 1~22 percents for carbon dioxide. The ratio of carbon dioxide was dozens or hundreds times to that of air, and the variation was very high also. 5. The emission of global green house gases such as carbon dioxide, methane and nitrous oxide was affected by the moisture, temperature and nutrients of soils and the growth period of crops.

• Journal of the Korean Chemical Society
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• v.63 no.4
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• pp.260-265
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• 2019

Alcohol dehydrogenase (ADH) (EC 1.1.1.1) was selected as the enzyme which will be immobilized on ultrafiltration membrane by fouling with different transmembrane pressure of 1, 2 and 3 bars. ADH will catalyze formaldehyde (CHOH) to methanol ($CH_3OH$) and simultaneously oxidized nicotinamide adenine dinucleotide (NADH) to $NAD^+$. The concentration of enzyme and pH are fixed at 0.1 mg/ml and pH 7.0 respectively. The objective of the study focuses on the effect of different transmembrane pressure (TMP) on enzyme immobilization in term of permeate flux, observed rejection, enzyme loading and fouling mechanism. The results showed that at 1 bar holds the lowest enzyme loading which is 1.085 mg while 2 bar holds the highest enzyme loading which is 1.357 mg out of 3.0 mg as the initial enzyme feed. The permeate flux for each TMP decreased with increasing cumulative permeate volume. The observed rejection is linearly correlated with the TMP where increase in TMP will cause a higher observed rejection. Hermia model predicted that at irreversible fouling with standard blocking dominates at TMP of 3 bar, while cake layer and intermediate blocking dominates at 1 and 2 bar respectively.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.235-250
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• 2021

The overarching question of this study is how a typical rice cultivation system in Gimje, Korea was keeping up with the triple-win challenge of climate-smart agriculture (CSA). To answer this question, we have employed (1) quantitative data from direct measurement of energy, water, carbon and information flows in and out of a rice cultivation system and (2) appropriate metrics to assess production, efficiency, GHG fluxes, and resilience. The study site was one of the Korean Network of Flux measurement (KoFlux) sites (i.e., GRK) located at Gimje, Korea, managed by National Academy of Agricultural Science, Rural Development Administration. Fluxes of energy, water, carbon dioxide (CO₂) and methane (CH₄) were directly measured using eddy-covariance technique during the growing seasons of 2011, 2012 and 2014. The production indicators include gross primary productivity (GPP), grain yield, light use efficiency (LUE), water use efficiency (WUE), and carbon uptake efficiency (CUE). The GHG mitigation was assessed with indicators such as fluxes of carbon dioxide (F_CO2), methane (F_CH4), and nitrous oxide (F_N2O). Resilience was assessed in terms of self-organization (S), using information-theoretic approach. Overall, the results demonstrated that the rice cultivation system at GRK was climate-smart in 2011 in a relative sense but failed to maintain in the following years. Resilience was high and changed little for three year. However, the apparent competing goals or trade-offs between productivity and GHG mitigation were found within individual years as well as between the years, causing difficulties in achieving the triple-win scenario. The pursuit of CSA requires for stakeholders to prioritize their goals (i.e., governance) and to practice opportune interventions (i.e., management) based on the feedback from real-time assessment of the CSA indicators (i.e., monitoring) - i.e., a purpose-driven visioneering.