• Atmosphere
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• v.29 no.2
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• pp.183-196
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• 2019

High-quality and high-resolution meteorological information is essential to reduce damages due to disastrous weather phenomena such as flash flood, strong wind, and heat/cold waves. There are many meteorological observation stations operated by Korea Meteorological Administration (KMA) in Seoul Metropolitan Area (SMA). Nonetheless, they are still not enough to represent small-scale weather phenomena like convective storm cells due to its poor resolution, especially over urban areas with high-rise buildings and complex land use. In this study, feasibilities to use additional pre-existing networks (e.g., operated by local government and private company) are tested by investigating the effects of network density on the gridded horizontal distribution of two meteorological variables (temperature and precipitation). Two heat wave event days and two precipitation events are chosen, respectively. And the automatic weather station (AWS) networks operated by KMA, local-government, and SKTechX in Incheon area are used. It is found that as network density increases, correlation coefficients between the interpolated values with a horizontal resolution of 350 m and observed data also become large. The range of correlation coefficients with respect to the network density shows large in nighttime rather than in daytime for temperature. While, the range does not depend on the time of day, but on the precipitation type and horizontal distribution of convection cells. This study suggests that temperature and precipitation sensors should be added at points with large horizontal inhomogeneity of land use or topography to represent the horizontal features with a resolution higher than 350 m.

• Environmental Engineering Research
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• v.20 no.3
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• pp.260-267
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• 2015

The $PM_{10}$, $SO_2$ and $NO_2$ mass concentrations were obtained over five years from monitoring stations across Nanchong, a southwest city in China. Changes in urban air quality over time, as well as the factors influencing that change, were evaluated based on air pollutant concentrations, the Air Pollution Index (API), and the Comprehensive Pollution Index (P). The results showed that the total annual mean $PM_{10}$, $SO_2$ and $NO_2$ concentrations over the five years studied were $61.1{\pm}1.1$, $45.0{\pm}3.9$ and $34.9{\pm}4.9{\mu}g{\cdot}m^{-3}$, respectively. The annual mean concentrations displayed a generally decreasing trend; lower than the annual mean second-level air quality limit. Meanwhile, the annual mean API values were in a small range of 52-53, the air quality levels were grade II, and P values were 1.06-1.21 less than the slight level ($P{\leq}1.31$). Total monthly mean $PM_{10}$, $SO_2$, $NO_2$ concentrations, and API and P values were consistently higher in winter and spring than during autumn and summer. The results of a correlation analysis showed that temperature and pressure were the major meteorological factors influencing pollution levels. Pollution sources included industrial coal and straw burning, automobiles exhaust and road dust, fireworks, and dust storms.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.1
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• pp.77-85
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• 2012

In this study, emission rates (ER) of biogenic volatile organic compounds (BVOCs) were measured by varying levels of photosynthetically active radiation (PAR). An appropriate plan for ozone reduction according to increasing ecology area ratio in future metropolitan areas was suggested. Several trees were selected as representative tree species in urban areas. Emission rates and composition ratios of monoterpene and isoprene emitted from these trees were estimated and compared. As a result, it was found that emission rates of BVOCs were considerably different depending on tree species. Especially, BVOCs emitted from Platanus orientalis and Quercus mongolica could significantly affect ozone increase in the metropolitan area, because the emission rates were several thousands to ten thousand times higher than those emitted from Zelkova serrata and Prunus serrulata. Furthermore, it was observed that emission rates of BVOCs by species increased maximum up to 10 times when PAR, which has close relations with temperature, rose. It was concluded that tree species such as Zelkova serrata et al., was appropriate for metropolitan areas since the species has low ozone potential and good landscape. Suppose this type of trees are planted on purpose in the urban areas, better ambient air quality will be promised in the future.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.6
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• pp.699-707
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• 2007

This study was carried out to investigate the reaction characteristics of corona/catalyst hybrid $DeNO_x$ process. The experiments were performed by using the multi-staged pin-to-hole type corona reactor which is enable to control the pin-to-hole gap and to insert the catalyst. Also, used for this study, were catalysts which commercially used Pt, Pd and $TiO_2$, and oxygen and hydrocarbon ($C_2H_4$) as reagents. In the syn-gas test, at high temperatures in the range of $100{\sim}200^{\circ}C$, the corona-only $DeNO_x$ process did not reduce the $NO_x$ concentration effectively. However in the presence of ethylene and oxygen as reagents, the $NO_x$ removal efficiency was better at these high temperatures than corona-only $DeNO_x$ process. In addition, coronal catalyst hybrid process with $TiO_2$ showed more efficiency of $NO_x$ removal than Pt and Pd catalyst, because the $TiO_2$ catalyst was more active than Pt and Pd catalyst to converse the $NO_2$ to $HNO_3$. Furthermore, at the condition of real diesel exhaust gas, the $DeNO_x$ efficiency of corona/catalyst hybrid process was not good at higher reaction temperature and plasma density.

• Ecology and Resilient Infrastructure
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• v.4 no.4
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• pp.187-192
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• 2017

This study evaluated the reduction performance of ambient temperature and the amount of evaporation that takes place depends on the temperature difference of paving blocks which are used in the sidewalk, roadway, parking lot, park, plaza, and etc. The water-retentive block of the LID (Low Impact Development) practice was compared with the conventional concrete block. For the quantitative performance evaluation, experiments were performed in a climatic environment chamber capable of controlling the climatic environment (solar radiation, temperature, humidity, rainfall, and snowfall). The method for performance evaluation was proposed using temperature, humidity, and ambient air of paving blocks which changes according to the solar radiation and the wind speed after the rainfall. As a result, the evaporation amount of the water-retentive block was 2.6 times higher than that of the concrete block, the surface temperature of water-retentive block was $10^{\circ}C$ lower than the concrete block, and the air temperature of water-retentive block was $4.6^{\circ}C$ lower than the concrete block. Therefore, it is analyzed that the water-retentive block with a large amount of evaporation is more effective in reducing the urban heat island phenomenon as compared with the concrete block.

• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.1
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• pp.28-34
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• 2011

This study was carried out to estimate monthly mean of daily maximum and minimum temperature across North Korea at a 30 m grid spacing for a climatological normal year (1971-2000) and the 4 decadal averages (1971-1980, 1981-1990, 1991-2000, and 2001-2010). A geospatial climate interpolation method, which has been successfully used to produce the so-called 'High-Definition Digital Climate Maps' (HD-DCM), was used in conjunction with the 27 North Korean and 17 South Korean synoptic data. Correction modules including local effects of cold air drainage, thermal belt, ocean, solar irradiance and urban heat island were applied to adjust the synoptic temperature data in addition to the lapse rate correction. According to the final temperature estimates for a normal year, North Korean winter is expected colder than South Korean winter by $7^{\circ}C$ in average, while the spatial mean summer temperature is lower by $3^{\circ}C$ than that for South Korea. Warming trend in North Korea for the recent 40 years (1971-2010) was most remarkable in spring and fall, showing a 7.4% increase in the land area with 15 or higher daily maximum temperature for April.

• Land and Housing Review
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• v.12 no.1
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• pp.129-137
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• 2021

External shading devices are well known solar control devices that can help reduce the cooling load of commercial buildings. For this study, experiments were conducted to examine the feasibility of shading devices in reducing both the cooling and heating loads. The influence of sky radiant cooling during winter was verified for the external shading device, internal roller blind, and window. Results can be summarized as follows. The temperature difference between the inner and outer surfaces of the window with the external shading device was 11.8℃ compared to 14.6℃ for one without the external shading device. This 2.8℃ difference was due to heat exchange by sky radiation when the surface temperature of the shading device was lower than the ambient outdoor air temperature. The roller blind resulted in a lower temperature of 0.8℃ compared to the average temperature of the window's air cavity. This was due to heat exchange by sky radiation of the roller blind surfaces. Without shading devices, the outside surface temperature of the window is about 3℃ higher. The study also found that when external shading devices were installed on both the southwest and southeast sides, the outside surface temperature of the windows were lower on the southwest side than the southeast side.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.35-40
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• 2005

In the present study, the influence of operating conditions on fuel economy for hybrid electric vehicle was analyzed. In order to accomplish this, vehicle speed, engine speed, battery current and voltage, SOC (state of charge),motor speed and torque, generator speed and torque, engine coolant temperature etc. were measured in real time. The tests were carried out under different driving cycles which are urban and highway cycles, KOREA CITY cycle and on-road driving, and also under various operating conditions such as different initial SOC, with or without regenerative braking etc.. Generally, conventional gasoline engines show a poor fuel economy at stop and go driving, because braking energy is wasted and the engine is operated in low thermal efficiency regions. However, in case of hybrid vehicles, higher fuel economy can be obtained because of utilizing the maximum thermal efficiency regions of engine, idling stop of engine, and regenerative braking etc..

• Korean Journal of Ecology and Environment
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• v.53 no.1
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• pp.80-90
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• 2020

In order to understand the stress responses, we measured the concentration of stress hormones by using the fresh feces of wild otters in the Gwangju stream and Seomjin river during summer and winter in 2018. We compared seasonal and regional number of spraints (=otters' feces), temperature, altitude, water width, land cover, and water quality with stress hormones. The stress hormone levels were higher in summer than in winter, and significantly different to season and region. In addition, the number of feces were different according to the season and region, and showed a negative correlation with stress hormone. This study suggested assessing stress hormones as another promising method for the analysis of status of wild otters and it will contribute to establish the management and conservation policy, especially in urban area.

• Journal of the Korean Solar Energy Society
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• v.34 no.1
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• pp.105-116
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• 2014

The objective of this study was to compare and analyze of radiation environment between downtown and suburban area by observation of short, diffuse and long-wave radiation during summer season. The followings are main results from this study. 1) The trends of long-wave radiation is increasing from May to August and the variation of daily range is decreased. It is confirmed that the temperature was closely relevant to long wave radiation. 2) During observation period, suburban area is higher than downtown the value of direct solar radiation. 3) There are much direct solar radiation in suburban area than downtown. But, it was measured much more horizontal solar radiation at the downtown area. From the this result, we can conclude that diffuse radiation play a important role at horizontal solar radiation.