• Journal of Korean Society on Water Environment
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• v.20 no.1
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• pp.72-77
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• 2004

Laboratory studies were carried out to find out the characteristics of humic acid treatment by activated carbon and ionized gas, In order to increase oxidation power of ionized gas for treating organic matter, we used granular activated carbon. By using $UV_{254}$, easy analysis method, we calculated humic acid concentration and $SCOD_{cr}$ concentration. For an initial concentration of humic acid, 10, 50 and 100ppm, the reaction rate constant by $UV_{254}$ was $8.98{\times}10^{-3}$/min, $5.62{\times}10^{-3}$/min and $4.8{\times}10^{-3}$/min respectively due to the same flow rate of ionized gas. When we added activated carbon to the ionized gas for humic acid treatment, the reaction rate constant increased in 4.13, 3.65 and 3.15 times. So, by using activated carbon in treating humic acid by ionized gas, oxidation power of organic matter by ionized gas was increased. The hydrophobic fraction constitutes 98% of organic matter for humic acid at the beginning. After the treatment using ionized gas for humic acid, the hydrophobic fraction decreased by 63~65% and the hydrophilic one increased by 35~37%. So, it was proved that the treatment increased the hydrophilic fraction in organic matter.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.390-401
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• 2000

In this study, numerical calculation is carried out to investigate the influence of injection timing, fuel amount, intake $O_2$ concentration, and EGR on Nitric Oxide(NO) formation using a two-zone model in a diesel engine. Results can be summarized as follows. The NO formation is very sensitive to the burned gas temperature, so multi-zone model must be applied to combustion process to predict the burned gas temperature exactly. Since the burned gas temperature increases rapidly during the premixed combustion, most NO is formed within 20 crank angle degrees after ignition. As the injection timing is retarded, the combustion occurs later in the expansion process which causes the decrease of burned gas temperature and, as a result, NO formation decrease. The increase of fuel amount results in the increase of earlier formation of NO in the engine. As the intake $O_2$ concentration increases, the maximum pressure and burned gas temperature increase due to activate combustion. And, [O] mole fraction of equilibrium combustion products also increase. Therefore NO exponentially increases. If exhaust gas is recirculated, the burned gas temperature decreases which results in NO decrease. If exhaust gas is cooled, more NO can be decreased.

• Membrane Journal
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• v.23 no.5
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• pp.384-391
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• 2013

We prepared composite membrane which was made with polysulfone supported hollow fiber membrane coated with Hyflon AD to eliminate $CO_2$ gas from mixed-gases which were generated in DME manufacturing processes. The performance of module about simulated flaring gas was measured by using manufactured composite membrane. 1-stage evaluation result shows $CO_2$ concentration was below 3% at 1.2 MPa and at Stage cut 0.24 above. In addition $CO_2$ removal rate and $CH_4$ recovery rate was 80% respectively at the same condition. 2-stage evaluation result shows, when the $CO_2$ concentration of product gas was fixed at 5%, recycled $CO_2$ at stage cut 0.074 had the same concentration as the feed gas and the recovery rate of $CH_4$ was 99% at the moment.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.4
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• pp.423-434
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• 2012

This study was carried out to develop for the emission factor of greenhouse gas (GHG) from medium and smallscaled incineration facility using RPF which is considering as a part of renewable energy in UNFCC. The actual concentration of the exhaust gas and the fuel composition of RPF were measured for the calculation of GHG emission factor in RPF incinerators, and were compared with the IPCC guideline. The $CO_2$ and $N_2O$ emission factors by the actual concentration of exhaust gas were $2.3575{\pm}1.0070tCO_2/tRPF$ and $0.0014{\pm}0.0014tN_2O/tRPF$ respectively. Also, $CO_2$ emission factor by the RPF composition was $2.7057{\pm}0.0540tCO_2/tRPF$. The GHG emission factor per energy by the actual concentration was $83.0867{\pm}26.0346tCO_2e/TJ$ which showed higher consistency with the GHG emission factor ($80.3967tCO_2e/TJ$) of waste plastic in the IPCC guideline (2006b). The $CO_2$ and $N_2O$ emission factor calculated in this study is considered as a meaningful data for GHG emission factor of RPF incineration facility because of not being developed in ROK.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.412-416
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• 2015

To evaluate the performance and durability of membrane, measurement of hydrogen crossover is needed during PEMFC(Proton Exchange Membrane Fuel Cells) operation. In this work, concentration of hydrogen at cathode was analysed by gas chromatograph during operation suppling with air instead of inert gas into the cathode. The hydrogen permeated through membrane reacted with oxygen at cathode and then the concentration of hydrogen was lower than in case inert gas was supplied. Hydrogen concentration decreased as the flow rate of air increased at cathode. Increase of temperature, humidity and pressure of anode gas enhanced the hydrogen concentration at cathode. The hydrogen concentration was about 5.0 ppm at current density of $120mA/cm^2$ during general PEMFC operation.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2284-2291
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• 2006

The present study investigates gas residence time and mixing characteristics for various swirl numbers generated by injection of secondary air into a lab-scale cylindrical combustor. Fine dust particles and butane gas were injected into the test chamber to study the gas residence time and mixing characteristics, respectively. The mixing characteristics were evaluated by standard deviation value of trace gas concentration at different measurement points. The measurement points were located 25 mm above the secondary air injection position. The trace gas concentration was detected by a gas analyzer. The gas residence time was estimated by measuring the temporal pressure difference across a filter media where the particles were captured. The swirl number of 20 for secondary air injection angle of 5$^{\circ}$ gave the best condition: long gas residence time and good mixing performance. Numerical calculations were also carried out to study the physical meanings of the experimental results, which showed good agreement with numerical results.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.511-514
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• 2007

Gas hydrate has a unique property that can store a large volume of gas in water as a solid form. Even though investigations for natural gas storage technology have been carried out for several decades, there are still a lot of unsolved problems due to complex formation process, low formation speed, high energy consumption and so on. So, lots of experiments were conducted to overcome these weaknesses and to develop artificial NGH formation technology applicable to industrial-scale storage and commercial transport. In this study, some series of experiments were performed to analyze both stirred and unstirred system especially about the influences of several gas hydrate formation factors such as agitation speed, system temperature, SDS concentration, etc. As a result, optimum range of SDS concentration and temperature that could enhance the storage capacity and shorten the formation time were found. And it is obviously presented that SDS such a kind of surfactant promotes gas hydrate formation dramatically and the quantity of stored gas are proportional to agitation speed in stirred system.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.80-89
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• 1998

The residual gas in an spark-ignition engine is one of important factors on emissions and performance such as combustion stability. With high residual gas fractions, flame speed and maximum combustion temperature are decreased and these are deeply related with combustion stability especially at idle and NOx emission at relatively high engine load. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating load. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating parameters. In the present study, the quantitative measurement technique of residual gas fraction was studied by using Fast Response Flame Ionization Detector(FRFID). The measuring technique and model for estimation of residual gas fraction were reported in this paper. By the assuming that the raw signal from FRFID saturates with the same slope for firing and misfiring cycle, in-cylinder hydrocarbon(HC) concentration can be estimated. Residual gas fraction can be obtained from the in-cylinder HC concentration measured at firing and motoring condition. The developed measurement and calibration procedure were applied to the limited engine operating and design condition such as intake manifold pressure and valve overlap. The results show relevant trends by comparing those from previous studies.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.10
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• pp.912-917
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• 2007

Many electrochemical power devices such as solid state batteries and solid oxide fuel cell have been studied and developed for solving energy and environmental problems. An amperometric gas sensor usually generates sensing signal of electric current along the proportion of the concentration of target gas under the condition of limiting current. For narrow variations of gas concentration, the amperometric gas sensor can show higher precision than a potentiometric gas sensor does. In additional, cross sensitivities to interfering gases can possibly be mitigated by choosing applied voltage and electrode materials properly. In order to improve the sensitivity to $NO_2$, the device was attached with Au reference electrode to form the amperometric gas sensor device with three electrodes. With the fixed bias voltage being applied between the sensing and counter electrodes, the current between the sensing and reference electrodes was measured as a sensing signal. The response to $NO_2$ gas was obviously enhanced and suppressed with a positive bias, respectively, while the reverse current occurred with a negative bias. The way to enhance the sensitivity of $NO_2$ gas sensor was thus realized. It was shown that the response to $NO_2$ gas could be enhanced sensitivity by changing the bias voltage.

• Membrane and Water Treatment
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• v.8 no.1
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• pp.35-50
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• 2017

The theoretical membrane gas absorption module treatments in a hollow fiber gas-liquid membrane contactor using Happel's free surface model were obtained under countercurrent-flow operations. The analytical solutions were obtained using the separated variable method with an orthogonal expansion technique extended in power series. The $CO_2$ concentration in the liquid absorbent, total absorption rate and absorption efficiency were calculated theoretically and experimentally with the liquid absorbent flow rate, gas feed flow rate and initial $CO_2$ concentration in the gas feed as parameters. The improvements in device performance under countercurrent-flow operations to increase the absorption efficiency in a carbon dioxide and nitrogen gas feed mixture using a pure water liquid absorbent were achieved and compared with those in the concurrent-flow operation. Both good qualitative and quantitative agreements were achieved between the experimental results and theoretical predictions for countercurrent flow in a hollow fiber gas-liquid membrane contactor with accuracy of $6.62{\times}10^{-2}{\leq}E{\leq}8.98{\times}10^{-2}$.