• Journal of Environmental Science International
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• v.14 no.6
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• pp.543-553
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• 2005

In recent days, photochemical smog due to the rapid industry development and vehicle increasement has become a critical pollutant in the metropolitan area and the number of ozone alarm signal has increased every year. This research was performed to evaluate VOCs emission source characteristics and concentration of VOCs in Daegu. The site average concentration was observed in the following order: industrial area > commercial area > residential area. Most of the VOCs species except toluene showed variations with higher concentration during nighttime, and lower concentration during the daytime. The major VOCs of stationary emission source were BTEX(benzene, toluene, ethylbenzene. xylene) and methylene chloride, trichloroethene and styrene. Also, those of automobile exhaust were toluene and benzene. Also, the major VOCs concentration emited by the vehicle fuel was observed in the following order: gasoline > light oil > liquefied petroleum gas (L.P.G). Correlation coefficients values were estimated between major VOCs such as toluene, ethylbenzene, m,p-xylene, o-xylene. Results showed that correlation coefficient values were significant magnitude above 0.76. Also, there showed highly significant correlations among ethyl benzene, m,p-xylene, and o-xylene concentration(Pearson correlation coefficients, r=0.868-0.982). Calculated correlation coefficients among commercial area,industrial area and residential area were 0.934-0.981, they showed high correlation. There showed highly correlation between stationary emission source and industrial area, compared with commercial area and residential area. Also, calculated correlation coefficients among commercial area, industrial area, residential area and automobile exhaust were 0.732, 0.725, 0.777, respectively.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1063-1072
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• 2003

Direct immersion cooling has been considered as one of the promising methods to cool high power density chips. A fluorocarbon liquid such as FC-72, which is chemically and electrically compatible with microelectronic components, is known to be a proper coolant for direct immersion cooling. However, boiling in this dielectric fluid is characterized by its small value of the critical heat flux. In this experimental study, we tried to enhance the critical heat flux by increasing the nucleate boiling area in the heat spreader (Conductive Immersion Cooling Module). Heat nux of 2 MW/㎡ was successfully removed at the heat source temperature below 78$^{\circ}C$ in FC-72. Some modified boiling curves at high heat flux were obtained from these modules. Also, the concept of conduction path length is very important in enhancing the critical heat flux by increasing the heat spreader surface area where nucleate boiling occurs.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.69-78
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• 2009

In order to improve water quality of upper watershed of Paldang reservoir, it is necessary to evaluate non-point source pollution loads and identify critical watershed pollution sources. A GIS based Soil and Water Assessment Tool was applied to evaluate model application and reliability, estimate NPS pollution load, identify critical watershed by NPS pollution sources, and suggest various best management practices for Kyongan Stream watershed. Yearly NPS pollution loads were estimated 30.0% SS, 60.1% TN and 35.4% TP, respectably. The watershed pollution load is mainly decided by precipitation condition and SS and nutrients load have a significant regression relationship. Based on 10-year average yearly NPS pollution load, critical sub-watersheds were identified. The No. 5 and 17 which have lots of relatively intensive agricultural fields and scattered industrial area were vary critical sub-watersheds and under more intensive pollution load. In order to control critical watershed, watershed best management practices such as scientific fertilizer, contour farming and parallel terrace, transferring the sloppy farmland to grass or forest and constructing a buffer zone, and constructing wetlands and retention ponds will be applied. Overall the SWAT model can be efficiently used for identification of critical sub-watersheds in order to develop a priority watershed management plan to reduce water pollutions.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.6
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• pp.65-75
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• 2022

Urban flood management(UFM) strategy ought to consider the connections and interactions between existing and new infrastructures to manage stormwater and improve the capacity to treat water. It is also important to demonstrate strategies that can be implemented to reduce the flow at flooding sources and minimize flood risk at critical locations. Although the general theory of spatial impact is popular, modeling guidelines that can provide information for implementation in real-world plans are still lacking. Under such background, this study conducted a modeling research based on an actual target site to confirm the hypothesis that it is appropriate to install green infrastructure(GI) in the source area and to take structural protection measures in the impact area, as summarized in previous studies. The results of the study proved the hypothesis, but the results were different from the hypothesis depending on which hydrological performance indicators were targeted. This study will contribute to demonstrating the effectiveness of strategies that can be implemented to reduce the flow at flooding sources and minimize the risk of flooding in critical locations in terms of spatial planning and regeneration.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.5
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• pp.145-152
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• 2001

농촌유역하천에서 수집된 수질측정자료를 이용하여 주요 오염원을 규명하였다. 분석에 이용된 수질항목은 BOD, COD. EC, pH. TN, TP,$NO_3-N,PO_4-P$ 등으로서 하천 본류내 구간별로 쌍대비교를 통해서 항목별 차이에 대한 유의성 검정을 하였다. 유의성 검정에 이용된 방법은 쌍대비교를 위한 비모수검정법인 Wilcoxon 순위검정법을 이용하였다. 검정결과, 유기성 오염물질의 지표로 이용되는 BOD와 COD가 상승하는 구간은 주로 생활하수가 유입되는 구간으로 나타났다. 인구밀도가 매우 높으나 생활하수가 처리장으로 배제되는 지역의 하천구간에서는 이들 농도변화는 없었다. 유역 내 축산농가가 밀집되어 있는 지역의 하천구간에서도 농도의 변화 또한 존재하지 않았다. 본 연구에서 조사된 유역에서와 같이 축산분뇨를 퇴비화 및 농지환원하는 경우에는 하천수질에 거의 영향을 미치지 않는다는 것을 알 수 있었다. 따라서 농촌지역의 하천 수질을 개선하기 위해서는 생활하수에 대한 처리가 선행되어야 한다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.3
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• pp.183-195
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• 2012

This study conducted comparative analysis to estimate critical velocity in tunnel fire under variation of grid number and the location and size of the fire source using three-dimensional computational fluid dynamics. In the target tunnel, by one-dimensional way, the calculated critical velocity in the tunnel, 2.22 m/s was estimated, if appling hydraulic diameter, instead of the tunnel height. According to six numerical analysis, each grid number has different position, temperature, and CO concentration of back-layering. In the case of the subject, the case 1 with 0.84 million grid was found to be the most ideal. According to the location and size of the fire source, after three cases for three-dimensional numerical analysis was performed, it is resulted that the location and size of the fire source affect the critical velocity, because air velocity distribution, temperature distribution and CO concentration distribution showed different each case. This is due to the difference of heat exchange area and locations. Therefore, it is necessary to decide appropriate grid number, and the location and size of the fire source for processing techniques through comparison with actual experiment results and three-dimensional analysis.

• The KIPS Transactions:PartD
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• v.11D no.4
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• pp.799-808
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• 2004

Well documented, simplified and clarified source code is required for the mission critical application software area in which C programing language is generally used. We suggest an XML_based comment management system for C source code. The comment management system is composed of 6 modules including comment user module, reviewer module, comment extraction module, comment traceability link module, comment tag definition module and storage management module. The XML comment tags defined in this paper cover categories of the development process activities applying the IEEE standard 1028 and IEEE standard 1012. The XML Schema Is used to insert comments into C source code and to extract XML tags from C source code and the XSL-FO is used fur the visual display professing o( comment extraction results.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.177-186
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• 2006

Flame surface area is a critical parameter determining turbulent flame speed. Three-dimensionaldirect numerical simulations (DNS) were conducted to figure out the evolution process of flame surface area. Fully compressible Navier-Stokes equations are solved to reproduce premixed flame embedded in isotropic decaying turbulent flow. The tangential straining and curvature of propagating surface affect development of flame area. In this study, four different turbulent intensity flows and three different Le number flames are investigated to force changes in straining and curvature effects. Consistent results are obtained for the probability density functions (PDF) of strain and curvature with previous researches. It is revealed that displacement speed, which is a speed of flame surface relative to unburnt flow, controls the balance between sink and source of flame surface area.

• Journal of the Korean Society of Combustion
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• v.12 no.2
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• pp.10-19
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• 2007

Flame surface area is a critical parameter determining turbulent flame speed. Three-dimensional direct numerical simulations(DNS) were conducted to figure out the evolution process of flame surface area. Fully compressible Navier-Stokes equations are solved to reproduce premixed flame embedded in isotropic decaying turbulent flow. The tangential straining and curvature of propagating surface affect development of flame area. In this study, four different turbulent intensity flows and three different Le number flames are investigated to force changes in straining and curvature effects. Consistent results are obtained for the probability density functions (PDF) of strain and curvature with previous researches. It is revealed that displacement speed, which is a speed of flame surface relative to unburnt flow, controls the balance between sink and source of flame surface area.

• Spatial Information Research
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• v.14 no.4 s.39
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• pp.363-377
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• 2006

Mean annual soil loss was calculated and critical soil erosion areas were identified for the Congaree River Basin in South Carolina, USA using the Revised Universal Soil Loss Equation (RUSLE) model. In the RUSLE model, the mean annual soil loss (A) can be calculated by multiplying rainfall-runoff erosivity (R), soil erodibility (K), slope length and steepness (LS), crop-management (C), and support practice (P) factors. The critical soil erosion areas can be identified as the areas with soil loss amounts (A) greater than the soil loss tolerance (T) factor More than 10% of the total area was identified as a critical soil erosion area. Among seven subwatersheds within the Congaree River Basin, the urban areas of the Congaree Creek and the Gills Creek subwatersheds as well as the agricultural area of the Cedar Creek subwatershed appeared to be exposed to the risk of severe soil loss. As a prototype model for examining future effect of human and/or nature-induced changes on soil erosion, the RUSLE model customized for the area was embedded into ESRI ArcGIS ArcMap 9.0 using Visual Basic for Applications. Using the embedded model, users can modify C, LS, and P-factor values for each subwatershed by changing conditions such as land cover, canopy type, ground cover type, slope, type of agriculture, and agricultural practice types. The result mean annual soil loss and critical soil erosion areas can be compared to the ones with existing conditions and used for further soil loss management for the area.