• 한국환경과학회지
• /
• 제25권1호
• /
• pp.163-171
• /
• 2016

We analyzed the characteristics of fog formation in the Gumi Reservoir of Nakdong river with the field observation data for recent 2 years (1 April 2013~31 March 2015) collected by the national institute of meteorological research, KMA. In early morning, we frequently observe the steam rising from the water surface. The fog occurs from adding water vapor into the air. We call the fog as steam fog. Steam fogs occur when cold, dry air mixes with warm, moist air above a water surface. The steam fog appears mainly in autumn under the following conditions; (1) sensible heat is positive values ($10{\sim}20W/m^2$), (2) latent heat is more positive values ($25{\sim}35W/m^2$) than sensible heat, (3) cloudless nights with light winds (about 1.5 m/s), (4) under condition(3), mountainous winds easily blows into the reservoir.

• 한국대기환경학회지
• /
• 제12권1호
• /
• pp.15-21
• /
• 1996

Daily measutements of visibility on 09 LST have been made at a rural site in Chong-won, Chong-book since 1991 to find out a possible influence of emissions of anthropogenic pollutants and water vapout in urban and rural environments. Daily visibility data collected over four-year period were compared with the available visibility and air quality data obtainde from other stations. Detailed examinations of our data showed that the frequency of fog occurrence (visibility .leq. 1 km) at a rural site (KNUE) was at least three times higher (77 days per year) than the frequency of fog both in Chong-ju city (19 days) and at the Air Force Base(AFB) in the rural area. We interpret that the higher frequency of fog at KNUE was due to abundant water vapour in the Mieho River (upstream of the Keum River) area. In Chong-ju city, fog usually continued for a relatively long duration, while it dissipated simewhat faster in the rural environment due to higher solar radiation in the countryside area. The number of misty (.leg. 6 km) days (including foggy days) at KNUE were 235 days as compared with 135 days at the AFB and 67 days in Chong-ju city. In turn the number of days with low visibility (less than 6 km) at KNUE was about 64% per year. Since the moisture alone in a calm morning does not produce a visibility impairment, there must had abundant condensation nuclei including anthropogenic air pollutants. Air pollution was examined, for instance, average values of TSP for November and December 1993 were 115 and 116.mu.g/m$^{3}$, respectively. We conclude that the above mentioned environmental conditions with moisture are favourable for the formation of fog and mist in the rural sampling site at KNUE. Additionally, we found at least 10 days of acid fog at KNUE in September 1994 alone. Measured pH values in the acid for water were in the range of 4.36 .sim. 5.01 with the mean value of 4.51 Our observations suggested that strikingly acid fog do occur occasionally even in the rural environment.

• 한국환경과학회지
• /
• 제25권3호
• /
• pp.405-415
• /
• 2016

We analyzed the micro-meteorological characteristics during typical steam fog over the Gumi Reservoir of Nakdong river with the field observation data for recent 2 year(1 April 2013~31 March 2015) collected by the national institute of meteorological research, KMA. Steam fog occur when the cold drainage flows over the warm water surface. As the sensible and latent heat from water are provided to the air, the instability of lower atmosphere is increased. The resultant vertical mixing of warm, moist air near water surface and cold air aloft causes the formation of status cloud. The convection strengthened by radiative cooling of the upper part of the stratus causes the fog to propagate downward. Also, the temperature at the lowest atmosphere is increased rapidly and the inversion near surface disappear by these processes when the fog forms. The increase of wind speed is observed because the downward transportation of momentum is caused by vertical mixing.

• 대기
• /
• 제23권4호
• /
• pp.443-452
• /
• 2013

The original Fog Stability Index (FSI) is formulated as FSI=$2(T-T_d)+2(T-T_{850})+WS_{850}$, where $T-T_d$ is dew point deficit (temperature-dew point temperature), $T-T_{850}$ is atmospheric stability measure (temperature-temperature at 850 hPa altitude) and $WS_{850}$ is wind speed at 850 hPa altitude. As a way to improve fog prediction at Incheon International Airport (IIA), we develop the modified FSI for IIA, using the meteorological data at IIA for two years from June 2011 to May 2013, the first one year for development and the second one year for validation. The relative contribution of the three parameters of the modified FSI is 9: 1: 0, indicating that $WS_{850}$ is found to be a non-contributing factor for fog formation at IIA. The critical success index (CSI) of the modified FSI is 0.68. Further development is made to consider the fact that fogs at IIA are highly influenced by advection of moisture from the Yellow Sea. One added parameter after statistical evaluation of the several candidate parameters is the dew point deficit at a buoy over the Yellow Sea. The relative contribution of the four parameters (including the new one) of the newly developed FSI is 10: 2: 0.5: 6.4. The CSI of the new FSI is 0.50. Since the developmental period of one year is too short, the FSI should be refined more as the data are accumulated more.

• 한국지구과학회지
• /
• 제38권6호
• /
• pp.395-404
• /
• 2017

본 연구에서는 구미에 위치한 낙동강에서 발생한 안개를 분류하였고 안개 발생 전후의 기상특성을 분석하였다. 안개는 2013년부터 2015년까지 시정계를 이용하여 관측되었다. 안개는 총 74회 발생하였고 대부분 증기안개로 분류되었다. 관측된 증기 안개는 내륙에서 발생한 안개보다 지속시간이 길게 나타났는데 이는 지형적 특징으로 인해 야간 증발이 다른 지역보다 강하게 나타났기 때문이다. 안개 지속시간에 대한 하천 증발 효과를 분석하기 위해 Penman-Monteith(Penman법)와 Bulk aerodynamic (Bulk법) 방법을 사용하여 증발량을 추정하였다. 이 중 Bulk법은 실제 수면에서 측정한 증발량과 유사하게 나타났다. 따라서 Bulk법이 실제 수면 증발량 추정에 적합한 방법임을 확인할 수 있었다. Bulk법으로 추정한 증발량은 안개 비발생일 보다 안개 발생일에 06 LST와 07 LST에 더 높게 나타났다. 안개 발생일에 하천의 증발은 대기에 증발잠열 에너지를 공급하고 안개 내부의 난류를 유지하는 에너지원으로 작용한다. 이와 같은 결과는 안개내부의 풍속, 기온, 그리고 난류운동에너지의 증가를 통해 확인하였다.

• Journal of Information Processing Systems
• /
• 제19권4호
• /
• pp.465-473
• /
• 2023

An image enhancement algorithm and image defogging method are studied in this paper. The formation of fog and the characteristics of fog image are analyzed, and the fog image is preprocessed by histogram equalization method; then the additive white noise is removed by foggy image attenuation model, the atmospheric scattering physical model is constructed, the image detail characteristics are enhanced by image enhancement method, and the visual effect of defogging image is enhanced by guided filtering method. The proposed method has a good defogging effect on the image. When the number of training iterations is 3,000, the peak signal-to-noise ratio of the proposed method is 43.29 dB and the image structure similarity is 0.9616, indicating excellent image defogging effect.

• 한국전기전자재료학회논문지
• /
• 제13권7호
• /
• pp.636-641
• /
• 2000

The purpose of this study is assessing the characteristics of surface aging and recovery of hydrophobicity for silicone rubber which takes a great interest as outdoor insulation recently subjected to the combined stressed of salt fog and AC power. The methods for assessing are contact angle ATR-FRIR, AFM and XRD. In addition salt fog method is adopted as the artificial contamination experiment and AC power is applied 24 hour on and 24 hour off repeatedly for 5 cycles. The results suggest that degraded surface was more rough than virgin but was restored water repellency through the off cycle. It was due to not only the formation of fractal surface but also maintenance of hydrophobic surface by diffusion of low molecular oil. Although surface recovers initial hydropohbicity there are possibilities of decreasing electrical performance due to irreversable changes such as depolymerization of surface and loss of filler particles. This fact is confirmed by surface conductivity measurement showing that the degradation is significant and the recovery of hydrophobicity is imperfect as the energized cycle increases.

• 한국안전학회지
• /
• 제20권3호
• /
• pp.58-63
• /
• 2005

In this research, silicone rubber with additions of inorganic filler, alumina trihydrate$(Al(OH)_3\;:\;ATH)$, was aged acceleratedly and cyclically by the salt-fog and heating. The optimum amount of ATH addition to silicone rubber have been investigated by measurements of leakage current in the change of electrical properties and tensile strength, %elongation in mechanical properties and FT-IR, TG, SEM in the change of the chemical properties. With regard to un-aged silicone rubber, as the ATH addition amount increases, conductive path formation time was shortened in the electrical properties and tensile strength was increased, %elongation was decreased. In case of identical ATH addition amount, as cyclic aging increases, surface resistivity, tensile strength and %elongation were decreased. Considering the cyclic aging, the most effective amount of ATH addition was about 90phr.

• 한국대기환경학회지
• /
• 제32권2호
• /
• pp.131-157
• /
• 2016

A smog chamber has been an effective tool to study air quality, particularly secondary organic aerosol (SOA), which is typically formed by atmospheric oxidation of volatile organic compounds (VOCs). In controlled environments, smog chamber studies have validated atmospheric oxidation by identifying, quantifying and monitoring products with state-of-art instruments (e.g., aerosol mass spectrometer, scanning mobility particle sizer) and provided chemical insights of SOA formation by elucidating reaction mechanisms. This paper reviews types of smog chambers and the current state of smog chamber studies that have accomplished to find pathways of SOA formation, focusing on gas-particle partitioning of semivolatile products of VOC oxidation, heterogeneous reactions on aerosol surface, and aqueous chemistry in aerosol waters (e.g., cloud/fog droplets and wet aerosols). For future chamber studies, then, this paper discusses potential formation pathways of fine particles that East Asia countries (e.g., Korea and China) currently suffer from due to massive formation that gives rise to fatal health problems.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
• /
• pp.866-868
• /
• 1998

Room temperature vulcanizing(RTV)silicone rubber has been widely used to coat porcelain insulators to render water repellency to prevent formation of water filming on the surface and thus to suppress the leakage current and consequent flashover. However, the electrical property and its hydrophobicity of RTV silicone rubber coating under outdoor conditions may be influenced by many environmental factors. In this study various treatments, such as salt-fog, salt water immerging and UV irradiation were applied to samples for investigation the change of the electrical property and hydrophobicity. As a result the leakage current increased and contact angle decreased as the degradation time longer. But the degraded RTV silicone rubber has recovered its hydrophobicity during the drying time in ambient condition because LMW(Low Molecular Weight)silicone fluid diffused from the bulk to the surface.