• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.2
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• pp.99-107
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• 2014

In this study, aerodynamic characteristics of Kline-Fogleman airfoils are numerically investigatied which has been widely used in remote control aircraft operating at low Reynolds numbers. The comparison of aerodynamic characteristics was conducted between NACA4415 and Kline-Fogleman airfoil based on NACA4415. ANSYS Fluent was employed with the incompressible assumption and $k-{\omega}$ SST turbulence model. It was found that lift coefficient was significantly enhanced in the range of Reynolds number from $3{\times}10^3$ to $3{\times}10^6$. Especially in the region of Reynolds number below $2.4{\times}10^5$, the lift-to-drag-ratio was improved by 26% using the Kline-Folgeman airfoil compared with NACA4415 airfoil.

• Journal of Powder Materials
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• v.18 no.1
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• pp.41-48
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• 2011

As a pore precursor, carbon black with different content of 0 to 60 vol% were added to (Ba,Sr)$TiO_3$ powder. Porous (Ba,Sr)$TiO_3$ ceramics were prepared by pressureless sintering at $1350^{\circ}C$ for 1h under air. Effects of carbon black content on the microstructure and PTCR characteristics of porous (Ba,Sr)$TiO_3$ ceramics were investigated. The porosity of porous (Ba,Sr)$TiO_3$ ceramics increased from 6.97% to 18.22% and the grain size slightly decreased from $7.51\;{\mu}m$ to $5.96\;{\mu}m$ with increasing carbon black contents. PTCR jump of the (Ba,Sr)$TiO_3$ ceramics prepared by adding carbon black was more than $10^5$, and slightly increased with increasing carbon black. The PTCR jump in the (Ba,Sr)$TiO_3$ ceramics prepared by adding 40 vol% carbon black showed an excellent value of $9.68{\times}10^5$, which was above two times higher than that in (Ba,Sr)$TiO_3$ ceramics. These results correspond with Heywang model for the explanation of PTCR effect in (Ba,Sr)$TiO_3$ ceramics. It was considered that carbon black is an effective additive for preparing porous $BaTiO_3$ based ceramics. It is believed that newly prepared (Ba,Sr)$TiO_3$ cermics can be used for PTC thermistor.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.705-709
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• 2009

Based on experimental study of lycopodium dust particles' behavior, we suggest the flame propagation model through dust clouds. With dust concentration, flame velocity reaches a maximum value at $170g/m^3$ to exceed the stoichometric concentration for lycopodium-air mixture combustion and decreases slightly in the richer side of $500g/m^3$. At $47{\sim}200g/m^3$, mean velocity of particle increases in proportion to flame velocity. As the sum of burning rate and particle velocity is approximate in flame velocity, the flame propagation velocity with lycopodium dust concentration can be estimated by the calculation and it was found that behavior of particles is useful for better understanding of dust flame propagation velocity.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.118-126
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• 2017

This study was performed to investigate the characteristics of combustion and emissions in pulverized coal fired boiler for using high moisture coal and dry coal through computational fluid dynamics(CFD). We validated this boiler model with performance data of the boiler. The results of flow characteristics showed that climbing speed of gases was increased as blending ratio of high moisture coal was increased. It can decrease a residence time of fuel in the furnace. And it influence coal combustion. The coal burnout and NOx generation in burner level were decreased as increasing blending ratio of high moisture coal. The gas temperature and NOx formation were increased after OFA level due to coal burnout delay.

• Journal of Environmental Health Sciences
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• v.43 no.5
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• pp.382-392
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• 2017

Objectives: The purpose of this study is to obtain basic data on the development of a risk communication model through an investigation of risk perception for radon and identify effective risk communication channels. Methods: A questionnaire was used to evaluate differences in perception level according to respective communication channels. A chi-squared test was used to analyze the difference in pre- and post-risk communication by communication channel. One-way ANOVA was used to analyze the difference in the radon risk perception rate for each communication channel. Results: All of the communication channels resulted in increased radon risk perception, but there was no statistical difference between them in terms of perception (p>0.05). However, based on previous findings that it is effective to use a multi-channel approach, it is considered that communication channels based on duplicate avenues is most appropriate. Conclusions: It is expected that this study will be used as basic data to better understand the formation of public opinion about radon risk and to understand the social reaction to each risk factor.

• Journal of Environmental Health Sciences
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• v.40 no.5
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• pp.346-354
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• 2014

Objectives: Although a number of epidemiologic studies have examined the association between air pollution and mortality, data limitations have resulted in fewer studies of particulate matter with an aerodynamic diameter of ${\leq}2.5{\mu}m$ ($PM_{2.5}$). We conducted a time-series study of the acute effects of particulate matter with an aerodynamic diameter of ${\leq}10{\mu}m$($PM_{10}$) and $PM_{2.5}$ on the increased risk of death for all causes and cardiovascular mortality in Seoul, Korea from 2006 to 2010. Methods: We applied the generalized additive model (GAM) with penalized splines, adjusting for time, day of week, holiday, temperature, and relative humidity in order to investigate the association between risk of mortality and particulate matter. Results: We found that $PM_{10}$ and $PM_{2.5}$ were associated with an increased risk of mortality for all causes and of cardiovascular mortality in Seoul. A $10{\mu}g/m^3$ increase in the concentration of $PM_{10}$ corresponded to 0.44% (95% Confidence Interval [CI]: 0.25-0.63%), and 0.95% (95% CI: 0.16-1.73%) increase of all causes and of cardiovascular mortality. A $10{\mu}g/m^3$ increase in the concentration of $PM_{2.5}$ corresponded to 0.76% (95% CI: 0.40-1.12%), and 1.63% (95% CI: 0.89-2.37%) increase of all causes and cardiovascular mortality. Conclusion: We conclude that $PM_{10}$ and $PM_{2.5}$ have an adverse effect on population health and that this strengthens the rationale for further limiting levels of $PM_{10}$ and $PM_{2.5}$ in Seoul.

• Journal of Environmental Science International
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• v.11 no.7
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• pp.687-696
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• 2002

Air quality monitoring data and meteorology data which had collected from 1995. 1. to 1999. 2. in six areas of Daegu, Manchondong, Bokhyundong, Deamyungdong, Samdukdong, Leehyundong and Nowondong, were investigated to determine the distribution and characteristic of ozone. A equation of multiple regression was suggested after time series analysis of contribution factor and meteorology factor were investigated during the day which had high concentration of ozone. The results show the following; First, 63.6% of high ozone concentration days, more than 60 ppb of ozone concentration, were in May, June and September. The percentage of each area showed that; Manchondong 14.4%, Bokhyundong 15.4%, Deamyungdong 15.6%, Samdukdong 15.6%, Leehyundong 17.3% and Nowondong 21.6%. Second, correlation coefficients of ozone, $SO_2$, TSP, $NO_2$ and CO showed negative relationship; the results were respectively -0.229, -0.074, -0.387, -0.190(p<0.01), and humidity were -0.677. but temperature, amount of radiation and wind speed had positive relationship; the results were respectively 0.515, 0.509, 0.400(p<0.01). Third, $R^2$ of equation of multiple regression at each area showed that; Nowondong 45.4%, Lee hyundong 77.9%, Samdukdong 69.9%, Daemyungdong 78.8%, Manchondong 88.6%, Bokhyundong 77.6%. Including 1 hour prior ozone concentration, $R^2$ of each area was significantly increased; Nowondong 75.2%, Leehyundong 89.3%, Samdukdong 86.4%, Daemyungdong 88.6%, Manchondong 88.6%, Bokhyundong 88.0%. Using equation of multiple regression, There were some different $R^2$ between predicted value and observed value; Nowondong 48%, Leehyundong 77.5%, Samdukdong 58%, Daemyungdong 73.4%, Manchondong 77.7%, Bokhyundong 75.1%. $R^2$ of model including 1 hour prior ozone concentration was higher than equation of current day; Nowondong 82.5%, Leehyundong 88.3%, Samdukdong 80.7%, Daemyungdong 82.4%, Manchondong 87.6%, Bokhyundong 88.5%.

• Korean Journal of Soil Science and Fertilizer
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• v.21 no.1
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• pp.11-14
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• 1988

Field study was conducted to evaluate the relationship between daytime net radiation (Drn) and global solar radiation (Rs) and to develop the empirical equation predicting daytime net radiation above corn canopy from observations of Rs and Ta (mean daily air temperature). The relationship between Drn and Rs under the cloudless day was Drn = 0.6659Rs and that under the cloudy (> 35% of possible sunshine) Drn = 0.729Rs. Thus, Drn/Rs Ratio under cloudless day was found to be lower than that under the cloudy day. Rs and Ta were used in the radiation balance equation to estimate Drn and the empirical model could be expressed as $Drn=[0.9Rs-(352-227{\times}10^{-10}{\times}Ta^4)]$ [1.11Rs/Rso - 0.05].

• Journal of Environmental Science International
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• v.32 no.1
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• pp.67-76
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• 2023

Under constant environmental pollution, the incidence of Atopic Dermatitis (AD) caused by air pollutants and allergens has increased. AD is an allergy inflammatory skin disease characterized by pruritus, eczema, and skin dryness. In herbal medicine, Anemarrhena asphodeloides (Anemarrhenae Rhizoma; AR) has been utilized to treat Alzheimer's disease, osteoporosis, hypertension, and inflammation. The purpose of study evaluated the effect of AR in a mouse model of 2,4-dinitrochlorobenzene (DNCB)-induced AD-like skin lesions. After acclimatization for 5 days, the mice (6-week-old, male Balb/c) were divided into five groups (n=6/group): NC (normal control), DNCB (control), Dex (5 mg·kg-1, p.o.), AR100 (100 mg·kg-1, p.o.), and AR300 (300 mg·kg-1, p.o.). On days 1 and 3, 1% DNCB was applied to the skin and ears. After 4 days, 0.5% DNCB was applied once every 2 days for 2 weeks. Then, skin and ears eczema area and severity index (EASI); skin nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and prostaglandin E2 (PGE2) levels; and plasma immunoglobulin E (IgE) levels were examined. The AR groups showed lower EASI, skin and ear thickness, mast cell count, and IgE levels than the control groups. Moreover, AR reduced iNOS, COX-2, and PGE2 levels. Therefore, AR possesses anti-inflammatory properties and can improve skin damage, indicating its therapeutic potential against AD.

• Journal of Korean Society of Transportation
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• v.23 no.6 s.84
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• pp.31-40
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• 2005

Main airports in the Intra-Asian market have faced competition not only to attract China-bound transshipment cargoes but also to be hub airport in same region. In spite of such a importance, the previous research has been short of evaluation of airport competitiveness. Implication of the previous research has mainly been focused on evaluation of airport critical factor service qualify and efficiency. The aim of this paper is to present critical points that affect airport competitiveness using an algorithm based on reversed fuzzy evaluation and senario method. The results of senario analysis and reversed fuzzy evaluation shows that Incheon international airport needs to enhance service level of 7% as a result of senario analysis and service level of 5% and brand equity level of 10% at the same time as a result of reversed fuzzy evaluation analysis, to ensure competitiveness in same region.