• 한국연소학회지
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• 제8권3호
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• pp.38-48
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• 2003

OH, CH and NO radical distributions have been measured and compared with the numerical analysis results in methane/air partially premixed laminar flames using 2-D LIF technique. The pick intensity of OH LIF signal is insensitive to fuel equivalence ratio: however, CH LIF intensity decreases as equivalence ratio increases and the NO concentration increases with equivalence ratio. The contribution of the prompt NO, formed near premixed reaction zone, to the total NO formation is evident from the OH, CH, and NO PLIF images in which the dilution effect of nitrogen is minimal for the highest equivalence ratio. Measured OH and NO LIF signals in counterflow flames agree with the computed concentration distributions. Both numerical and experimental results indicate that the structural change in a flame alters the NO formation characteristics of a partially premixed counterflow flame. The nitrogen dilution also changes flame structure, temperature and OH radical distributions and results in the decreased NO concentrations in a flame. The levels of decrease in NO concentrations, however, depends on the premixedness(${\alpha}$) of a flame. The larger change in the flame structure and NO concentrations have been observed in a premixed flame(${\alpha}=1.0$), which implies that the premixedness is likely to be a factor in the dilution effect on NO formation of a flame.

• 한국습지학회지
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• 제15권4호
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• pp.441-451
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• 2013

인천연안 8개 지역 갯벌의 72개 지점의 표층퇴적물과 24개 지점의 주상퇴적물 시료를 2011년 봄 가을 2회에 걸쳐 채취하여, 다환방향족탄화수소(PAHs), 석유계총탄화수소(TPHs) 및 벤젠-톨루엔-에틸벤젠-자일렌(BTEX)의 시 공간적 농도분포 특성을 조사하였다. 또한 PAHs 화합물 구성비에 의한 오염발생기원을 평가하였다. 갯벌 전체의 PAHs 평균농도는 $95.62{\mu}g/kg$으로 조사되었고, 계절별 PAHs 농도분포는 가을철이 봄철보다 낮은 특징을 보였다. 주상퇴적물의 PAHs 농도가 표층퇴적물보다 높았으며, 주상퇴적물의 상부가 하부보다 높은 농도분포를 보였다. 전체 갯벌의 TPHs 평균농도는 46 mg/kg으로 조사되었고, TPHs 평균농도 분포 양상은 봄철보다 가을철이 현저하게 높고, 표층퇴적물이 주상퇴적물보다 높게 나타났다. 갯벌 퇴적물내 PAHs의 오염발생 기원을 평가한 결과, 장화리 갯벌의 표층퇴적물과 소래 및 옥련 갯벌의 주상퇴적물의 PAHs 배출원은 연소와 석유류기원으로 조사되었고, 나머지 모든 갯벌은 연소기원으로 나타났다.

• 천문학회지
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• 제13권1호
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• pp.27-33
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• 1980

Surface density distributions for globular clusters were obtained from photoelectric surface photometry (using centered aperture photometry). These surface brightness profiles were then compared with the theoretical surface density distribution of King's model. From the comparison of the theoretical and observed surface density distributions, we determine he structural parameters of the clusters (the core radius $r_c$, the tidal cut off $r_t$, and the concentration factor C).

• 설비공학논문집
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• 제4권4호
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• pp.253-262
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• 1992

A numerical procedure is introduced to calculate local ventilation effectiveness using the definitions of local decay rate and local mean age. A low Reynolds number $k-{\varepsilon}$ model is implemented to calculate steady state turbulent velocity distributions, and a step-down method is used to calculate transient concentration distributions. Simulations are carried out for several different values of air change rates and several different diffuser angles in a two-dimensional model of a half scale office room. The results show that the local ventilation effectiveness within a room could vary significantly from one location to another. The nominal air change rate based on the assumption of complete mixing of room air does not provide the local ventilation effectiveness information. It is numerically proved that the local mean age distribution obtained from the transient calculation is equivalent to the steady state concentration distribution with homogeneously distributed contaminant sources.

• 전자공학회논문지D
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• 제34D권5호
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• pp.32-44
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• 1997

A three-dimensional (3D) full-dynamic damage model for ion implantation in crystalline silicon was proposed to calculate more accurately point defect distributions and ion-implanted concentration profiles during ion implantation process. The developed model was based on the physical monte carlo approach. This model was applied to simulate B and BF2 implantation. We compared our results for damage distributions with those of the analytical kinchin-pease approach. In our result, the point defect distributions obtained by our new model are less than those of kinchin-pease approach, and the vacancy distributions differ from the interstitial distributions. The vacancy concentrations are higher than the interstitial ones before 0.8 . Rp to the silicon surface, and after the 0.8 . Rp to the silicon bulk, the interstitial concentrations are revesrsely higher than the vacancy ones.The fully-dynamic damage model for the accumulative damage during ion implantation follows all of the trajectories of both ions and recoiled silicons and, concurrently, the cumulative damage effect on the ions and the recoiled silicons are considered dynamically by introducing the distributon probability of the point defect. In addition, the self-annealing effect of the vacancy-interstitial recombination during ion implantation at room temperature is considered, which resulted in the saturation level for the damage distribution.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2008년도 추계학술대회 논문집
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• pp.346-347
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• 2008

• 한국대기환경학회지
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• 제22권4호
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• pp.440-450
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• 2006

PM10, NOx, and $O_3$ were measured at six locations, of which each three is horizontally and vertically distributed respectively, in an apartment complex around the heavily traffic road. Those were measured seven times a day with two hours interval starting from 8 o'clock in the morning for 15 days during May 2005 $\sim$ September 2005. PM10 and NOx showed high concentrations in rush hours while low concentrations in midday due to the direct emissions from automobiles in operation. Temporal variations of 01 showed very much similar trend appeared in normal urban atmospheres. The spatial distributions of PM10, NOx and $O_3$ showed that almost all of concentrations were higher in a row of Roadside > Surface at 130 m apart from the road > Surface at 230 m apart from the road > 3rd floor of apartment building > 15th floor of apartment building > 27th floor of apartment building. Model equations, which can project spatial concentration distributions, were constructed by combining the horizontal and the vertical linear regression equations derived from six mean values corresponding to six measuring locations. According to inter-comparison of PM10, NOx, and $O_3$ with the constructed model equations, concentration gradients were higher in a row of Vertical direction of NOx > Vertical direction of PM10 > Horizontal direction of NOx > Horizontal direction of PMIO > Vertical direction of $O_3$ > Horizontal direction of $O_3$. Why concentration gradient of particulate PM10 is lower than that of gaseous NOx is in question, and should be studied.

• 대한기계학회논문집B
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• 제31권1호
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• pp.21-28
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• 2007

The use of drug-eluting stents has dramatically reduced the incidence of restenosis however, much remains to be teamed about the performance of these stouts. In the present study, we tested the hypothesis that the design of drug-eluting stents influences the efficacy of local drug delivery to the arterial wall and that this effect depends on both arterial geometry and the prevailing flow conditions. We performed computational simulations in which the coupled Navier-Stokes and advection-diffusion equations were solved to determine the flow field and drug concentration in the vicinity of model drug-eluting stouts It is found that the characteristics of flow phenomena can be influenced greatly by the ratio of stent diameter to vessel diameter. The presence of drug-eluting stent may have profound effect on wall shear stresses, recirculation sizes and drug distributions. The results show that recirculation zone is influenced by the imposed flow conditions and stent diameter. In pulsatile flow, the low wall shear stress and high drug concentration occur along the arterial wall during the decelerating flow conditions. These results could provide the guideline for future drug-eluting stent designs toward reducing restenosis by affecting local wall shear stress distributions associated with neointimal hyperplasia.

• 한국대기환경학회지
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• 제9권4호
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• pp.271-277
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• 1993

Indoor radon has been known as one of the notorious carcinogens. However, a safe environmental criterion of radon has not yet been established in Korea, The main objectives of this study were to study concentration distributions of radon, to trace radon sources in subways, and to obtain a strategy for radon reduction in Seoul metropolitan area. Radon concentrations had been extensively determined by several steps. The first step was to survey radon levels in all of 83 subway stations from October to November in 1991. The second step was to select 40 out of 83 stations and then to study seasonal variations in 1991 and 1992. The third step was to monitor radon levels by hourly-basis plans. The fourth step was to seek a radon reduction strategy by altering ventilation at Ankuk station where had the highest radon concentration during the first measurement step. Each underground floor in the station was divided into 10 sites to measure hourly radon variations. The final step of the study was to measure radon concentrations in groundwater that is one of the possible main sources radon place. The result of the various measuring approaches showed short-and long-term radon variation and indicated radon reduction schemes.

• 한국환경과학회지
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• 제15권1호
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• pp.59-66
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• 2006

High concentration of chlorophyll a occurred around the Ulleung Warm Eddy off Ulleung Island in the East Sea of Korea in spring season. The abnormal distributions of chlorophyll a were captured by satellite remote sensing and measured field data. The temporal and spatial scale of the abnormal distributions were around 20days and 50km diameter off Ullung Island. The anomalies were quantified b)'estimated chlorophyll a derived from OCM and SeaWiFS ocean color data from 2000 to 2004. The origin of abnormal hish concentrations was estimated by this study. It was that suspended material discharged from the Nakdong River and the coastal water located in the southeastern part of Korean Peninsula moved to northeastern coast, and then moved to off Ullung island, The high chlorophyll a concentrations including inorganic materials were accumulated by anticyclonic eddy such as the Ullung Warm Eddy around Ullung island in the East Sea of Korea in spring season.