• Korean Journal of Environmental Agriculture
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• v.31 no.2
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• pp.104-112
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• 2012

BACKGROUND: Agricultural inputs (fertilizer and organic inputs) and water conditions can influence $CH_4$ and $CO_2$ emission from agricultural soils. This study was conducted to investigate the effects of agricultural inputs (fertilizer and organic inputs) under changing water regime on $CH_4$ and $CO_2$ emission from a soil in a laboratory incubation experiment. METHODS AND RESULTS: Four treatments were laid out: control without input and three type of agricultural inputs ($(NH_4)_2SO_4$, AS; pig manure compost, PMC; hairy vetch, HV). Fertilizer and organic inputs were mixed with 25 g of soil at 2.75 mg N/25 g soil (equivalent to 110 kg N/ha) in a bottle with septum, and incubated for 60 days. During the first 30-days incubation, the soil was waterlogged (1 cm of water depth) by adding distilled water weekly, and on 30 days of incubation, excess water was discarded then incubated up to 60 days without addition of water. Based on the redox potential, water regime could be classified into wetting (1 to 30 days), transition (31 to 40 days), and drying periods (41 to 60 days). Across the entire period, $CH_4$ and $CO_2$ flux ranged from 0 to 13.8 mg $CH_4$/m/day and from 0.4~1.9 g $CO_2$/m/day, and both were relatively higher in the early wetting period and the boundary between transition and drying periods. During the entire period, % loss of C relative to the initial was highest in HV (16.4%) followed by AS (8.1%), PMC (7.5%), and control (5.4%), indicating readily decomposability of HV. Accordingly, both $CH_4$ and $CO_2$ fluxes were greatest in HV treatment. Meanwhile, the lower $CH_4$ flux in AS and PMC treatments than the control was ascribed to reduction in $CH_4$ generation due to the presence of oxidized compounds such as ${SO_4}^{2-}$, $Fe^{3+}$, $Mn^{4+}$, and ${NO_3}^-$ that compete with precursors of $CH_4$ for electrons. CONCLUSION: Green manure such as HV can replace synthetic fertilizer in terms of N input, however, it may increase $CH_4$ emission from soils. Therefore, co-application of green manure and livestock manure compost needs to be considered in order to achieve satisfactory N supply and to mitigate $CH_4$ and $CO_2$ emission.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.101-103
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• 2012

Characteristic of aluminum ignition under high temperature and high pressure is studied using lasers. The laser ablation method is used to generate aluminum particles exposed to a high pressure by using a nanosecond pulsed laser where the range of ablation pressure varies between 0.35 and 2.2 GPa. A $CO_2$ laser is used to supply radiative heat to the aluminum target surface for providing high temperature ranging between 5000~9300 Kelvin. The ignition is confirmed using spectroscopy analysis of AlO vibronic band 484 nm wavelength. Also the radiative temperature is measured in various high pressure range for tracing the ignition temperature in high pressure conditions.

• Journal of Animal Environmental Science
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• v.5 no.2
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• pp.101-106
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• 1999

This study was conducted to develop a lignite coal heater which can be used to livestock facilities and to test performance of the heater developed. Experimental results are as following: 1. Heating capacity of the heater was 85,000 kcal/h. 2. The concentrations of CO gas in the exhaust gas were the maximum of 759 ppm and the average of 319 ppm; for the concentrations of NOx, the maximum of 212 ppm and the average of 57 ppm ; for the concentrations of SO2 gas, the maximum of 302 ppm and the average of 99 ppm. As the values were less than the allowable concentration limites, they did not violate the air environment law. 3. Problems such as frequent interruption of fuel supply and bridge state were happened. Therefore, it was required that these should be resolved in the future.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.226-233
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• 1999

A transmitting antenna mounted on the naval vessels can be easily exited by exogenous disturbances such as wave and impact. Gimbal system need for the controller to maintain the robust performance against various modeling uncertainties and disturbances. PI controller, however, cannot supply good robust performance under situation. Thus a robust $H_{\infty}$ control scheme is used to ensure a specified dynamic response under above conditions. Gimbal system controlled simplified as 2 DOF system that ignored coordinate co-relations of each direction and hydraulic system is linearly modelled. In this paper, we compared those of simulation to the results of experiment and H$_{\infty}$ controller, proposed, showed the good response and stability than PI controller.

• Proceedings of the Korean Society of Food Science and Nutrition Conference
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• 2001.12a
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• pp.38-47
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• 2001

L-theanine is a unique amino acid, found almost solely in tea plants. It is the main component responsible for the exotic taste of green tea. In our studies of L-theanine, we have found a variety of biological activities including relaxation and the alleviation of PMS. In general, animals generate very weak electric pulses on the surface of the brain, called brain waves. Brain waves are classified into four types, namely $\alpha$, $\beta$, $\delta$ and $\theta$-waves, based on their frequency. Brain waves correlate with individual mental conditions. For example, generation of $\alpha$-waves is considered an index of relaxation. In human volunteers, $\alpha$-waves were generated on the occipital and parietal regions of the brain surface within 40 minutes after the oral administration of 50 or 200 mg Suntheanine$^{TM}$ without causing drowsiness. Premenstrual Syndrome (PMS) is a symptom unique to women which appears in the luteal phase from the ovulation period through the first day of menstruation. It possesses characteristics of having a peak just prior to menstruation and disappearing 1 - 2 days following the start of menstruation. Symptoms of PMS are generally categorized as mental, physical and social symptoms. When comparing the reported Symptoms of PMS by the methods of MDQ score, the Suntheanine$^{TM}$ group was found to have a lower incidence of PMS symptoms, including physical, mental and social symptoms. Overall, a significant alleviation of PMS symptoms by the administration of 200 mg Suntheanine$^{TM}$ was observed. With the successful industrial production of L-theanine, we are now able to supply Suntheanine$^{TM}$, offering a tremendous opportunity for designing functional foods targeting relaxation and the alleviation of PMS.

• Journal of Power System Engineering
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• v.16 no.4
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• pp.30-36
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• 2012

A scroll expander has been designed to produce a shaft power from a R134a Rankine cycle for electricity generation. Heat was supplied to the Rankine cycle through a heat exchanger, which received heat from another cycle of water. In the water cycle, water was heated up in a boiler using biogenic solid fuel. The designed scroll expander was a horizontal type, and a trochoidal oil pump was employed for oil supply to bearings and Oldham-ring keys. For axial compliance, a back pressure chamber was created on the backside of the orbiting scroll base plate. Numerical study has been carried out to estimate the performance of the designed scroll expander. The expander was estimated to produce the shaft power of about 2.9 kW from a heat supply of 36 kW, when the temperature of R134a was $80^{\circ}C$ and $35^{\circ}C$ at the evaporator and condenser of the Rankine cycle, respectively. The expander efficiency was about 70.5%. When the amount of heat supply varied in the ranges of 7.5~55 kW, the expander efficiency changed in the range of 45.6~70.5%, showing a peak efficiency of 70.5% at the design shaft speed.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.225-232
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• 2024

The reduction of CO₂ emissions in the energy production sector, which accounts for 86.8% of total greenhouse gas emissions, is important to achieve carbon-neutrality. At present, 60% of total power generation in South Korea is coal and natural gas. Replacing fossil fuel with renewable energy such as wind and solar has disadvantages of unstable energy supply and high costs. Therefore, this study was conducted through the co-firing of natural gas, ammonia and hydrogen utilizing the natural gas combined cycle process. The results demonstrated reduction in CO₂ emissions and 34%~238% of the power production compared to using only natural gas. Case studies on mass fractions of natural gas, ammonia and hydrogen indicated that power production and NO_x emissions were inversely proportional to the ammonia ratio and directly proportional to the hydrogen ratio. This study provides guidelines for the use of various fuel mixtures and economic analysis in co-firing power generation.

• New & Renewable Energy
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• v.7 no.2
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• pp.10-17
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• 2011

Korea is the 11th largest energy consumption country and 96% of its total energy consumption depends on imports from overseas. Therefore it is a very important task to secure renewable energy sources which can reduce both the carbon-dioxide emission and dependency on overseas energy imports. Among the various renewable energy sources, organic wastes are important sources. In Korea, 113 million toe of methane is generated from organic wastes annually, but only 3.7% is effectively used for energy conversion. Thus, it is very important to make better use of organic wastes, especially for power generation. The goals of this project are to develope the fuel supplying system of Bio Gasturbine (GT) for 5MW-class co-generation system. The fuel supplying system mainly consists of $H_2S$ removal system, Bio Gas compression system, Siloxane removal system and moisture separating systems. The fuel requirement of 5MW-class GT is at around 60% of $CH_4$, $H_2S$ (<30 ppm), Siloxane(<10 mg/$nm^3$) and supply pressure (> 25 bar) from biogas compressor. Main mechnical charateristics of Bio Gasturbine system have the specific performance; 1) high speed turbine speed (12,840 rpm) 2) very clean emmission NOx (<50 ppm) 3) high efficiency of energy conversion rate. This paper focuses on the development of design technology for food waste biogas pretreatment system for 5MW-class biogas turbine. The study also has the plan to replace the fuel of gas turbine and other distributed power systems. As the increase of bioenergy, this system help to contribute to spread more New & Renewable Energy and the establishment of Renewable Portfolio Standards (RPS) for Korea.

• Korean Journal of Materials Research
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• v.19 no.8
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• pp.452-456
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• 2009

In high-efficiency Cu(In,Ga)$Se_2$ solar cells, Na is doped into a Cu(In,Ga)$Se_2$ light-absorbing layer from sodalime-glass substrate through Mo back-contact layer, resulting in an increase of device performance. However, this supply of sodium is limited when the process temperature is too low or when a substrate does not supply Na. This limitation can be overcome by supplying Na through external doping. For Na doping, an NaF interlayer was deposited on Mo/glass substrate. A Cu(In,Ga)$Se_2$ absorber layer was deposited on the NaF interlayer by a three-stage co-evaporation process As the thickness of NaF interlayer increased, smaller grain sizes were obtained. The resistivity of the NaF-doped CIGS film was of the order of $10^3{\Omega}{\cdot}cm$ indicating that doping was not very effective. However, highest conversion efficiency of 14.2% was obtained when the NaF thickness was 25 nm, suggesting that Na doping using an NaF interlayer is one of the possible methods for external doping.

• Journal of Environmental Science International
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• v.25 no.4
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• pp.473-481
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• 2016

We examined the effects of ocean acidification (OA) and eutrophication on the physiology of a red alga, Gracilariopsis chorda, using specimens collected at Wando Island, Korea, in July of 2015. The samples were transported to a laboratory and placed on growth media for treatments involving low or high levels of ammonium ($4{\mu}M$ or $60{\mu}M\;NH_4{^+}$) and low or high pH(7.5 or 8.2). The control treatment used filtered seawater (pH 8.2 and $4{\mu}M\;NH_4{^+}$). All experiments were conducted at $20^{\circ}C$ and under a lighting intensity of $80{\mu}mol\;photons\;m^{-2}\;s^{-1}$, with or without an injection of $CO_2$ (pH 7.5). In addition, we calculated rates of respiration under darkness, at a pH of 7.5 and $60{\mu}M\;NH_4{^+}$. Fluctuations in pH as well as the evolution of photosynthetic oxygen and $NH_4{^+}$ uptake rates were monitored for 6 h. The greatest increase in pH levels, from 7.50 to 8.65, occurred in response to $60{\mu}M\;NH_4{^+}$, whereas the largest decrease, from 7.50 to 7.42, was associated with elevated respiration rates. At a pH of 7.5, rates of oxygen evolution were higher (236% saturation) for samples treated with $60{\mu}M\;NH_4{^+}$ than for the control (121% saturation). Ammonium uptake was highest at pH 7.5 and $60{\mu}M\;NH_4{^+}$, with a rate of $0.526{\pm}0.002{\mu}mol\;g^{-1}\;FW\;h^{-1}$, followed in order by the treatments of $pH\;8.2/60{\mu}\;NH_4{^+}$, $pH\;7.5/4{\mu}M\;NH_4{^+}$, and the control ($pH\;8.2/4{\mu}M\;NH_4{^+}$). We speculated that the rates of photosynthesis and $NH_4{^+}$ uptake could be enhanced at a higher ammonium concentration and lower pH because $CO_2$ concentrations were increased through greater photosynthetic activity. Therefore, these findings suggest that the physiology of G. chorda populations can be improved by the interaction of optimized $CO_2$ concentrations and an adequate supply of essential nutrients such as ammonium.