• Journal of the Korean earth science society
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• v.43 no.1
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• pp.77-90
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• 2022

Despite the decreasing trend of anthropogenic emissions in East Asia in recent years, haze days still frequently occur in spring. Atmospheric blocking, which occurs frequently in the northeastern Pacific, leads to persistent changes in large-scale circulation and blocks westerly flow in the East Asian region. During March 2019, frequent warm and stagnant synoptic meteorological conditions over East Asia were accompanied 6-7 days later by the Alaskan atmospheric blocking. The Alaskan atmospheric blocking over the period of March 18-24, 2019 led to high particulate matter (PM₁₀) severe haze days exceeding a daily average of 50 ㎍ m^-3 over the period of March 25-28, 2019 in South Korea. Although the high-PM₁₀ severe haze days were caused by warm and stagnant meteorological conditions, the regional contribution of anthropogenic emissions in eastern China was calculated to be 30-40% using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). The major regional contributions of PM₁₀ aerosols in the period of high-PM₁₀ severe haze days were as follows: nitrates, 20-25%; sulphates, 10-15%; ammonium, 5-10%; and other inorganics, 15-20%. Ammonium nitrate generated via gas-to-aerosol conversion in a warm and stagnant atmosphere largely contributed to the regional transport of PM₁₀ aerosols in the high-PM₁₀ severe haze days in South Korea.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.145-151
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• 2014

This paper proposes an image haze removal algorithm for a single image. The conventional Dark Channel Prior(DCP) algorithm estimates a transmission map using the dark information in an image, and the haze regions are then detected using a matting algorithm. However, since the DCP algorithm uses block-based processing, block artifacts are invariably formed in the transmission map. To solve this problem, the proposed algorithm generates a modified transmission map using a Hidden Markov Random Field(HMRF) and Expectation-Maximization(EM) algorithm. Experimental results confirm that the proposed algorithm is superior to conventional algorithms in image haze removal.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.340-340
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• 2016

We have prepared alumina (Al2O3) doped zinc oxide (AZO) films by DC magnetron sputtering (MS) technique and obtained higher self surface texturing at a high target angle (f). We have characterized the films and applied it as a front electrode of a single junction amorphous silicon solar cell. At a lower f the deposited films show higher values of optical gap (Eg), charge carriers mobility & concentration, crystallite grain size and wider wavelength range of transmission. At higher target angle the sheet resistance, surface roughness, haze factor etc for the films increase. For f=72.5o the haze factor for diffused transmission becomes 6.46% at 540 nm wavelength. At f=72.5o the material shows a reduction in crystallinity and evolution of a hemispherical-type sub-micron surface textures. A Monte Carlo method (MCM) of simulation of the AZO film deposition shows that such an enhanced self-surface texturing of the films at higher f is possible.

• Journal of IKEEE
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• v.24 no.2
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• pp.492-496
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• 2020

The visibility deteriorates in hazy weather and it is difficult to accurately recognize information captured by the camera. Research is being actively conducted to remove haze so that camera-based applications such as object localization/detection and lane recognition can operate normally even in hazy weather. In this paper, we propose a nonlinear model for depth map estimation through an extensive analysis that the difference between brightness and saturation in hazy image increases non-linearly with the depth of the image. The quantitative evaluation(MSE, SSIM, TMQI) shows that the proposed haze removal method based on the nonlinear model is superior to other state-of-the-art methods.

• Journal of Environmental Science International
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• v.29 no.7
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• pp.761-772
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• 2020

This research investigated the meteorologically relevant characteristics of high PM_2.5 episodes in Busan. The number of days when daily mean PM₁₀ concentration exceeded 100 ㎍/㎥ and the PM_2.5 concentration exceeded 50 ㎍/㎥ over the last four years in Busan were 24 and 58, respectively. Haze occurrence frequency was 37.6% in winter, 27.4% in spring, 18.6% in fall, and 16.4% in summer. Asian dust occurrence frequency was 81.8% in spring, 9.1% in fall and winter, and 0% in summer. During summer in Busan, high PM_2.5 episode occurred under the following meteorological conditions. 1) Daytime sea breeze. 2) Mist and haze present throuout the day. 3) Anti-cyclone located around the Korean peninsula. 4) Stable layer formed in the lower atmosphere. 5) Air parcel reached Busan by local transport rather than by long-range transport. These results indicate that understanding the meteorological relevance of high PM_2.5 episodes could provide insight for establishing a strategy to control urban air quality.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.289-292
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• 2015

The etching processes of glass in aqueous hydrofluoric acid (HF) solutions were used to improve the current density of solar cell. In this study, the textured glass substrate has been etched by solution and the $TiO_2$ thin films have been prepared on this textured glass. After the $TiO_2$ film deposition the surface has been etched by HF under different concentration and the etched $TiO_2$ thin films had a longer electron lifetime and higher haze ratio as well as light scattering, resulting in 1.7 times increment of dye-sensitized solar-cell(DSSC) efficiency. Increases in the surface root-mean-square roughness of glass substrates from 80 nm to 1774 nm enhanced haze ratio in above 300 nm wavelength. In particular, haze ratio of etched $TiO_2$ films on textured glass showed gradually increasing tendency at 550 nm wavelength by increasing of HF concentration up to 10M, suggesting a formation of crater with various sizes on its surface.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.82.1-82.1
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• 2019

Recent analyses of spectro-images of Saturn observed by Visual and Infrared Mapping Spectrometer (VIMS)/Cassini revealed altitudinal distributions of the spectral structure of haze in Saturn's south-polar regions (Kim et al., 2018) and at $55^{\circ}N$ latitude (Kim et al., 2012). However, other regions of Saturn still have not been investigated. We derived series of high-spatial resolution VIMS images of Saturn's limb at various latitudes. Using our developed code, the altitudinal intensity profiles of $3.3-{\mu}m$ emission and H3+ through different latitudes were plotted. Then we obtained the averaged vertical spectra of $3.3-{\mu}m$ emission which is all blended with fluorescent methane and hydrocarbon haze. The vertically-resolved spectra were measured from the limb of Saturn in 50km intervals to see altitudinal variance. We will present a comparison of spectral structures of $3.3-{\mu}m$ emission with different latitudes. Further investigation using radiative transfer to extract adjacent fluorescent CH4, C2H6, and H3+ is needed to derive spectral structure of pure haze. We look forward to a better understanding of aging process in a global view.

• Journal of Broadcast Engineering
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• v.18 no.2
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• pp.159-166
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• 2013

In this paper, we propose a transmission rate compensation method to remove a haze of an image by using edge information of a haze image and image segmentation. With a hazed image, it is difficult not only to recognize objects in the image but also to use an image processing method. One of the famous defogging algorithm named 'Dark Channel Prior'(DCP) is used to predict fog transmission rate using dark area of an image, and eliminates fog from the image. But there is a big possibility to calculate a wrong transmission rate if the area of high RGB values is larger than the area of the reference area. Therefore we eliminate color distortion area to calculate transmission rate by using the propose method, and obtain a natural clean image from a hazed image.

• Atmosphere
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• v.28 no.2
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• pp.175-185
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• 2018

Characteristics of precipitation response to enhanced aerosols have been investigated during the severe haze events observed in Korea for 2011 to 2016. All 6-years haze events are classified into long-range transported haze (LH: 31%), urban haze (UH: 28%), and yellow sand (YS: 18%) in order. Long-range transported one is mainly discussed in this study. Interestingly, both LH (68%) and YS (87%) appear to be more frequently accompanied with precipitation than UH (48%). We also found out the different timing of precipitation for LH and YS, respectively. The variations of precipitation frequency for the LH event tend to coincide with aerosol variations specifically in terms of temporal covariation, which is in contrast with YS. Increased aerosol loadings following precipitation for the YS event seems to be primarily controlled by large scale synoptic forcing. Meanwhile, aerosols for the LH event may be closely associated with precipitation longevity through changes in cloud microphysics such that enhanced aerosols can increase smaller cloud droplets and further extend light precipitation at weaker rate. Notably, precipitation persisted longer than operational weather forecast not considering detailed aerosol-cloud interactions, but the timescale was limited within a day. This result demonstrates active interactions between aerosols and meteorology such as probable modifications of cloud microphysics and precipitation, synoptic-induced dust transport, and precipitation-scavenging in Korea. Understanding of aerosol potential effect on precipitation will contribute to improving the performance of numerical weather model especially in terms of precipitation timing and location.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.11
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• pp.165-173
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• 2014

This paper presents a fast and high-quality haze removal method by the modification of the conventional transmission estimation process. In the conventional haze removal method, the halo and blocking artifacts arises while estimating the transmission. In order to effectively reduce the artifacts, the proposed method employs the maximum filter after the calculation of the dark channel. Because of the reduction of the artifacts, the proposed method can simplify the transmission refinement process without sacrificing the quality of the results: this paper proposes to use the single-channel guided filter instead of the multi-channel guided filter. The experimental results demonstrate that the quality of the dehazed results by the proposed transmission correction process is improved and the haze removal speed is increased by up to 59.6%, when compared to the conventional ones.