• Transactions of the Korean hydrogen and new energy society
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• v.31 no.1
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• pp.96-104
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• 2020

A model combustor has been designed and fabricated for studying the combustion characteristics of oxygen (O₂)/hydrogen (H₂) flames under supercritical conditions. The combustor is designed to allow combustion experiments up to 60 bar, the supercritical pressure condition of O₂ and H₂. Injectors can be replaced to study various types of flames and the combustion chamber is designed to visualize flames by installing optical windows. Through the preliminary tests, including a high-pressure (up to 60 bar) test using air and combustion tests for coaxial jet flames of liquid oxygen (LO₂)/gaseous hydrogen (GH₂) at elevated pressure, the reliability of the combustor has been demonstrated.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.59-62
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• 2014

Predicting coal combustion by computational fluid dynamics (CFD) requires a combination of complicated flow and reaction models for turbulence, radiation, particle flows, heterogeneous combustion, and gaseous reactions. There are various levels of models available for each of the phenomena, but the use of advanced models are significantly restricted in a large-scale boiler due to the computational costs and the balance of accuracy between adopted models. In this study, the influence of coal devolatilization model and turbulent mixing rate was assessed in CFD for a commercial boiler at 500 MWe capacity. For coal devolatilization, two models were compared: i) a simple model assuming single volatile compound based on proximate analysis and ii) advanced model of FLASHCHAIN with multiple volatile species. It was found out that the influence of the model was observed near the flames but the overall gas temperature and heat transfer rate to the boiler were very similar. The devolatilization rate was found not significant since the difference in near-flame temperature became noticeable when it was multiplied by 10 or 0.1. In contrast, the influence of turbulent mixing rate (constant A in the Magnussen model) was found very large. Considering the heat transfer rate and flame temperature, a value of 1.0 was recommended for the rate constant.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.171.1-171.1
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• 2016

재료의 표면 강화 방법 중의 하나인 질화공정을 이용하여 탄소강 S45C 소재의 질화 거동에 대하여 연구하였다. $520^{\circ}C$ 온도에서 질화 공정을 진행하여 공정시간에 따른 Kn값을 수소 센서로 측정하여 공정시간에 따른 N-potential의 변화와 그에 따른 화합물층 성장 및 화합물층의 상변화에 대해 관찰하였다. 화합물 층의 미세구조 변화는 광학현미경 및 주사전자현미경을 통해 관찰하였다. 가스 질화 처리 후 표면경도는 약 600Hv의 경도값이 측정되었고, 공정 시간이 늘어남에 따라 화합물층 및 경화깊이가 증가되고 표면 화합물이 성장하여 porous가 감소하는 것을 확인 할 수 있다. 경화깊이는 1440분 일 때 약 0.5mm 경화 깊이를 얻었고, 화합물층의 성장은 ${\varepsilon}$상(Fe2-3N)과 ${\gamma}$'상(Fe4N)으로 두 개의 상으로 형성되는 것을 관찰할 수 있었다. 시험 결과를 바탕으로 S45C 소재의 탄소 함량에 따른 lehrer diagram을 열역학 적으로 계산하고 화합물층의 형성 기구에 대해 비교 분석하였다.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.4
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• pp.437-449
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• 2003

A multi-functional indoor smog chamber was designed and evaluated to investigate photochemical or water vapor reaction mechanisms of air pollutants. Various smog chamber experiments could be conducted using ambient air or purified air in this smog chamber. The smog chamber consisted of a housing, a Teflon bag, blacklights, injection ports, sampling ports, and utility facilities. The characteristics of light source, the wall losses of air pollutants, and the quality of purified air were experimentally investigated. The maximum NO$_2$ photolysis rate was 1.10 min$^{-1}$ . In a 2.5-m$^3$ Teflon bag, the wall losses of ambient $O_3$, NO, and NO$_2$ were 1.2~2.4$\times$10$^{-3}$ min$^{-1}$ , 0.7~2.0$\times$10$^{-3}$ min$^{-1}$ , and 0.4~2.0$\times$10$^{-3}$ min$^{-1}$ , respectively. The wall loss of ambient particles ranging 0.05 to 0.2 ${\mu}{\textrm}{m}$ was 1.8~5.4$\times$10$^{-3}$ min$^{-1}$ , which was slightly higher than those of ambient gaseous species. The purified air supply system provided high quality of air with NO$_{x}$ < 1 ppb, and total hydrocarbons < 5 ppb.b.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.1
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• pp.77-85
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• 2004

In this study, the concentrations of reduced S compounds (including hydrogen sulfide (H$_2$S); methyl mercaptan ($CH_3$SH); dimethyl sulfide (($CH_3$)$_2$S); carbon disulfide (CS$_2$); and dimethyl disulfide (($CH_3$)$_2$S$_2$) were determined from landfill gas (LFG) in three municipal landfill sites in the two cities of Gwang Ju (GJ) and Jeju (JJ), Korea. The S gas concentrations measured in these landfill sites were found to be dominated by H$_2$S with its mean concentration of 850 ppm from 10 LFG samples. Both absolute and relative dominance of H$_2$S was seen to be significant in most LFG samples, except those collected from very old and inactive landfills. Unlike the pattern of H$_2$S, other S gases were typically observed at much reduced concentration levels (a few ppm or less) as follows: DMS (3.5); $CH_3$SH (1.3); CS$_2$(1.2); and DMDS (0.02 ppm). If compared equally in mass concentration unit (mg m$^{-3}$ ), H$_2$S generally explained far above 90% of all S gas masses determined concurrently. Moreover, as its mass concentration commonly exceeds those of the major aromatic VOC components in LFG (like benzene and toluene), it appeared to be one of the most dominant gaseous components emitted as LFG in a quantitative sense.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.1
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• pp.39-50
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• 2001

The spatial distribution characteristics of airborbe mercury(Hg) were investigated used its concentration data from six measurement sites selected to represent:(1) three terminal sites with heavy traffic loads in urban area, (2) one urban residential site and (3) two mountainous sites in Korea. The measurement data obtained during September 1997 through May 1998 indicated that the mean concentration of Hg from different study sites were comparably high with the mean values spanning from 5-9ng./㎥. The concentration from all those sites were systmatically high compared to those of most background sites around world or to other Korean sites investigaed previously. When results of correlation analysis between Hg and relevant parameters were compared among different study sites. temperature was most frequently found out to be in strong correlation with Hg concentrations. Results of factor analysis also indicated that Hg concentrations could be affected simultaneously by th factors affecting such parameters as ozone, temperature, ozone, carbon monoxide, and PM. The findings of enhanced Hg levels from Ji-Ri Mountain relative to terminal site suggest that is distributions may be rather homogeneous not enough to clearly distinguish areal differences and the associated source signatures between urban and rural area. The existence of systmatically high concentrations from all investigated sites also indicate that the impact of its source processes should be quite ubiquitous, while highly variable in relatively long term scale.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.7
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• pp.841-848
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• 1997

Combustion of gaseous fuel combustor in a high temperature vitiated air stream was studied with computer simulation. It is for application to afterburner of gas turbine engine which the exact mechanism is not yet clarified. As the jet velocity from fuel nozzle is very high and the geometry of combustor is three dimensional complex structure, many time and money are required to have good results. To consider this demerit, it is simplified to 2-dimensional and modified with the nozzle hole area to same area of annual status. As the thickness of annual is too thin, it is to divide with the many grids for reasonable results. Accordingly, new method which injected fuel mass, momentum and energy are added to source terms of each governing conservation equation as a source terms is introduced like as two phase analysis. Reaction rate is determined by taking into account the Arrhenius reaction based on a single step reaction mechanism. It is focused to temperature and product concentration distribution at each equivalence ratio of inlet hot product.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.271-279
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• 2004

The aroma component of Hallabong peel has been characterized by GC-MS with two different extraction techniques: solid-phase trapping solvent extraction (SPTE) and headspace solid-phase microextraction (HSSPME). Aroma components emitted from Hallabong peel were compared with those of other citrus varieties: lemon, orange and grapefruit by SPTE and GC-MS. d-Limonene (96.98%) in Hallabong was the main component, and relatively higher peaks of cis- ${\beta}$-ocimene, valencene and -farnesene were observed. Other volatile aromas, such as sabinene, isothujol and ${\delta}$-elemene were observed as small peaks. Also, principal components analysis was employed to distinguish citrus aromas based on their chromatographic data. For HSSPME, the fiber efficiency was evaluated by comparing the partition coefficient ($K_{gs}$Kgs) between the HS gaseous phase and HS-SPME fiber coating, and the relative concentration factors (CF) of the five characteristic compounds of the four citrus varieties. 50/30 ${\mu}$m DVB/CAR/PDMS fiber was verified as the best choice among the four fibers evaluated for all the samples.

• Journal of Environmental Science International
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• v.15 no.2
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• pp.133-139
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• 2006

Soil biofiltration is an environmentally-sound technology for elimination of VOCs, odorous and NOx compounds from a low concentration, high volume waste gas streams because of its simplicity and cost-effectiveness. This study was performed to evaluate effect of removal of gaseous NOx using a soil and a yellow soil. Over $60\%\;and\;48\%$ of NOx from a soil and a yellow soil was removed at the inlet NO concentrations of $423\~451$ppb, respectively. The bio-filter using a soil media was capable of purifying NOx with a different natural processes. Although some of the processes are quite complex, they can broadly be summarized as adsorption into soil pore water, and biochemical transformations by soil bacteria. When the filteration bio-reactor was applied to a soil and a yellow soil, effective NOx removal was obtained for several times and months. These results show that a soil biofilter can be of use as an alternative advanced NOx treatment system.

• Journal of environmental and Sanitary engineering
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• v.21 no.1 s.59
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• pp.1-11
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• 2006

This study was to investigate concentration characteristics of atmospheric PCBs in soil sample and pine needle at rural area. Profiles of PCB congener detected in pine needle and soil sample have a difference that low molecular PCBs mainly existed in pine needle, whereas high molecular PCBs were mainly existed in soil sample because of their different vapor pressure and octanol-air partitioning coefficient($K_{OA}$) of each congeners. Correlation coefficients(r) of PCB congeners simultaneously detected in soil and pine needle were significant (r>0.71, p<0.01), which showed that PCB congeners patterns of atmosphere could be estimated in using pine needle and soil sample indirectly. The contributions(%) of higher molecular PCBs(>penta-CB) to total PCBs in soil sample were higher than those of pine needle and the contribution of lower molecular PCBs(