• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.8
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• pp.689-701
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• 2011

The relations between ambient conditions and ice accretion shapes are quantitatively analyzed by employing self-organization maps and analysis of variance. Liquid water contents(LWC), mean volumetric droplet diameter(MVD), ambient temperature and free-stream velocity are chosen as ambient conditions which change ice accretion shapes. The parameters of ice accretion shape are selected as maximum thickness, icing limits, ice heading, and ice accretion area. Qualitative analysis was conducted by employing self-organization maps which show the qualitative relations between ice shapes and ambient conditions. The quantitative results of analysis of variance yield intensity of ambient conditions to the parameters of ice accretion shapes.

• Journal of Environmental Health Sciences
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• v.18 no.2
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• pp.19-25
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• 1992

The study was carried out to investigate the correlation between the heavy metals emitted by the motor vehicles with the heavy traffic road side environment (soil, leave, bark, ambient air). The Pb, Cu, Zn contents in road side soil sand leaves, barks from Ginkgo, biloba and ambient air adjacent to the heavy traffic road side from June to August, 1992 Suwon city were analyzed by Atomic absorption spectrometry and Inductively coupled plasma emission spectrophotometry. The results were as follows: 1) The high levels of heavy metals concentration were Pb, at city-terminal in soil (186 $\mu$g/g), Cu, at city-terminal in soil (221 $\mu$g/g), Zn, at city-terminal in ambient air (252 $\mu$g/m$^{3}$). 2) The low leves of heavy metals concentration were Pb, at North-gate in ambient air (1.65$\mu$g/m$^{3}$), Cu, at North-gate in ambient air (4 $\mu$g/m$^{3}$), Zn, at North-gate in ambient air (15.31$\mu$g/m$^{3}$). 3) The regional distribution of Pb, Cu, Zn in road side soils, leaves and barks from Ginkgo, biloba, ambient air show high levels in turn, city4erminal, Guan Sean Dong, South gate, North gate. 4) The concentration of heavy metals (Pb, Cu, Zn) in soils, leaves, barks, ambient air was highly correlated with the traffic volume of the sampling sites (r=0.64~0.96). To conclude that the high levels of Pb, Cu, Zn contaminations were positively related to motor vehicles-borne pollutants and road side soils, trees, ambient air adjacent to a high density building area with low road coverage and heavy traffic volume were reflected strongly by the hazardous pollutants emitted by motor vehicles.

• Particle and aerosol research
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• v.8 no.4
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• pp.151-160
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• 2012

Health effects caused by the ultrafine particles in ambient air are great concern to the public health, and the strict measuring and monitoring of the ambient aerosol are required. In this work, the characteristics of the aerosol size distribution in Pohang province are studied. Optical particle counters (Grimm APS 1108 and 1109) were used to measure the aerosol size distribution in the area. Locations near the national monitoring site located in the industrial and the residence area were selected for the measuring sites of this study, and the locations in border area between the industry and the residence were selected for the reference of the comparison. In the industry site, it is found that the concentration of aerosol particles near the size of 5 ${\mu}m$ appear characteristically and the fluctuations in concentration with respect to time are minimal. The mass concentration of the aerosol above 10 ${\mu}m$ in diameter in the industry area was found to fluctuate significantly. The mass portion of $PM_{10}$ and PM2.5 to TSP in the residence area were 83% and 51% respectively. In the industrial regional, it was found that the mass portion of PM10 and $PM_{2.5}$ to TSP were 76% and 35% respectively. In the boundary area the mass portion of $PM_{10}$ and $PM_{2.5}$ to TSP were 78% and 54% respectively.

• Journal of Korean Society of Forest Science
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• v.99 no.5
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• pp.698-705
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• 2010

The concentration of monoterpenes (12 species) was measured from spring to fall in 2008 in ambient air at six different forests located in the southern parts of Korea. Sampling - using a Solid Adsorption Tube - was conducted at 2-hour-interval a day (24 hours) of each season. The highest annual average concentration of total monoterpene was 0.715 ppbv, which occurred at Mt. Baega. ${\alpha}$-Pinene, sabinene and ${\beta}$-pinene were the most abundant compounds throughout the sampling periods and areas. The concentrations of monoterpene were higher in spring than in any other seasons. The compositions and concentrations of monoterpene displayed a distinct pattern by area. Most of monoterpenes had diurnal variations with higher concentrations during the daytime, and lower during the nighttime. This may be due to the fact that the amount of monoterpenes emitted increases at elevated ambient temperatures and increased sunlight intensity. The results of this study showed that each area had distinct monoterpene compositions, which depended on the tree species, topography and local climate at each area.

• The Journal of the Acoustical Society of Korea
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• v.41 no.2
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• pp.192-198
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• 2022

As an effective weapon system for anti-submarine warfare, DIrectional Frequency Analysis and Recording (DIFAR) sonobuoy detects underwater targets via beamforming with three channels composed of an omni-direcitonal and two directional channels. However, ambient noise degrades the detection performance of DIFAR sonobouy in specific direction (0°, 90°, 180°, 270°). Thus, an ambient noise redcution technique is proposed for performance improvement of acoustic target detection of DIFAR sonobuoy. The proposed method is based on OTA (Order Truncate Average), which is widely used in sonar signal processing area, for ambient noise estimation and Wiener filtering, which is widely used in speech signal processing area, for noise reduction. For evaluation, we compare mean square errors of target bearing estmation results of conventional and proposed methods and we confirmed that the proposed method is effective under 0 dB signal-to-noise ratio.

• Journal of Environmental Impact Assessment
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• v.19 no.1
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• pp.59-74
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• 2010

The trend of the PM10 concentrations in the Seoul Metropolitan Area (SMA) is reviewed and relative contributions of major contributors (paved road emissions and long-range transport from outside the SMA) are discussed. It was shown that the PM10 concentrations in the SMA have generally decreased except Incheon between 1999 and 2005. Further, it was identified that the difference of the PM10 mass concentration between the roadside stations and urban ambient stations has decreased between 2004 and 2008. Based on the emission estimates, it was suggested that the reduction of resuspension of aerosols on the road is the major reason for that. Based on the modeling results, it was identified that outside effects be about 30% of the ambient PM10 concentration in the SMA. Further research and policy issues to identify major sources of PM10 in the SMA are discussed.

• Structural Engineering and Mechanics
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• v.3 no.6
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• pp.569-581
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• 1995

In this paper, the seismic behavior of a 10-story building equipped with viscoelastic dampers is analyzed. The effects of ambient temperature, the thickness, the total area, and the position of the viscoelastic dampers are studied. Results indicate that the energy-absorbing capacity of viscoelastic damper decreases with increasing the ambient temperature. The thickness and the total area of viscoelastic dampers also affect the seismic mitigation capacity. The thickness cannot be too small, which is not effective in vibration reduction, nor can it be too large, which not only increases the cost but also reduces the seismic resistance. The total area of viscoelastic dampers should be determined properly for optimum damper performance at the most economical design. The mounting position of viscoelastic dampers also influences the structure's seismic performance. Numerical results show that, if properly equipped, the VE dampers can reduce the structural response both floor displacement and story shear force and increase the overall level of damping in structures during earthquakes.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.443-445
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• 2005

• Journal of Sensor Science and Technology
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• v.16 no.6
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• pp.395-400
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• 2007

Ambient drying sol-gel processing was used for monolithic silica ambigels in the temperature range of $130-250^{\circ}C$. A new method of mesopore ambigels, which mean the aerogels prepared by ambient pressure drying process synthesis, is suggested at first. This method includes two important approaches. The first point is that $SiO_{2}$ surface modification of wet gel was performed by trimethylchlorosilane in n-butanol solution. This procedure is provided the silica gel mesopore structure formation. The second point is a creation of the ternary azeotropic mixture water/n-butanol/octane as porous liquid, which is effectively provided removing of water such a low temperature by 2 step drying condition under ambient pressure. The silica aerogels, which were prepared by ambient pressure drying from azeotropic mixture of water/n-butanol/octane, are transparent, crack-free and mesoporous (pore size ${\sim}$ 5.6 nm) with surface area of ${\sim}$ $923{\;}m^2/g$, bulk density of $0.4{\;}g/cm^3$ and porosity of 85 %.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.1
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• pp.61-68
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• 2010

In this study, we investigated the concentrations of volatile organic compounds (VOCs) in Shiwha area and compared the characteristics of both industrial area and residential area. The passive samplers were set 6 times each for a month in 21 locations at industrial and residential area to obtain 6 VOCs including benzene, trichlorobenzene, toluene, ethyl benzene, xylene and stylene. Above all, toluene was the most abundant VOCs in the ambient air both in industrial and residential area. Average TVOC concentration of industrial area was 1.86 times higher than that of residential area, and it was greatly reduced in winter compared with summer. Furthermore, the average BTEX concentrations showed that all concentrations of industrial area were 1.94~5.39 times higher than those of residential area except benzene which were similar to each other. In winter, the concentration of ethyl benzene and xylene were significantly decreased by comparing with summer: but benzene concentrations were increased. Also, BTEX relative ratio was as follows: toluene>benzene>ethylbenzene>xylene. Correlation coefficients among VOCs were confirmed that VOCs in ambient air of industrial area were generally more related to each other than that of residential area. On the whole, the concentrations of VOCs in industrial area were higher, and it seems to be potential that industrial area affects the distribution of VOCs to residential area.