• Ecology and Resilient Infrastructure
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• 제9권1호
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• pp.36-58
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• 2022

본 연구에서는 제주도의 도시지역을 대상으로 관측이 시작된 2001년부터 2019년까지의 미세먼지 (PM₁₀)와 초미세먼지 (PM_2.5) 악화 빈도에 따른 기상 상황을 분석하였다. PM₁₀과 PM_2.5의 악화는 제주시와 서귀포시 모두 봄>겨울>가을>여름철 순으로 나타났으며, 봄·여름철에는 주간에 가을·겨울철에는 야간에 더 많이 나타났으며, PM₁₀보다 PM_2.5의 피해가 더 심각하게 나타났다. PM₁₀ 악화 시의 기온과 풍속은 제주시와 서귀포시 모두 봄·겨울철에는 각각의 계절평균보다 높게 나왔으나, 여름·가을철에는 반대로 낮게 나왔다. 상대습도는 계절평균보다 모든 계절에 낮게 나타났다. PM_2.5 악화 시 기온은 PM₁₀ 악화 시와 계절별 동일한 경향을 보였으며, 상대습도는 봄·여름철에는 제주시와 서귀포시 모두 평균보다 높았으며, 겨울철에는 평균보다 낮았다. 풍속은 두 도시 동일하게 평균보다 낮게 나왔다. PM_2.5 악화 시가 PM₁₀ 악화 시보다 봄·겨울철에 기온과 풍속이 더 낮을 때 발생 빈도가 높은 것으로 나타났다. PM₁₀과 PM_2.5 악화 시 풍향은 주간에는 북풍과 서풍이, 야간에는 계절별로 다양하게 나타났다. 특히, PM₁₀에 비해 PM_2.5 악화 시 풍속이 낮게 나타나 한라산에서 발생하는 산곡풍의 영향으로 제주시는 남풍이 서귀포시는 북풍이 야간에 자주 발생하였다. 풍속등급별 PM₁₀ 악화 빈도수는 제주시와 서귀포시 모두 주·야간 1.6 - 3.4 ms^-1에서 가장 높았고, 여름철 야간에만 0.3 - 1.6 ms^-1에서 가장 높은 값을 보였다. PM_2.5 악화 빈도수는 제주시에서는 1.6 - 3.4 ms^-1에서 가장 높은 값이 나타났으나, 서귀포시에서는 0.3 - 1.6 ms^-1에서 가장 높은 값이 나타났다. 제주시와 서귀포시 모두 PM₁₀과 PM_2.5 악화 시 3.4 ms^-1이상의 바람이 0.3 ms^-1이하의 바람보다 빈도가 더 높은 것으로 나타나므로, 이는 PM₁₀과 PM_2.5가 바람의 영향으로 도시지역 외부에서 유입된 것이 주요인이라고 할 수 있겠다. 위 자료를 토대로 미세먼지 저감을 위한 도시계획 및 조경식재계획 방안을 마련한다면 효과적일 것으로 판단된다.

• 한국대기환경학회지
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• 제26권3호
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• pp.265-275
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• 2010

Mass and ion concentrations of $PM_{10}$ and $PM_{2.5}$ were measured in Yongin, downwind of the Seoul metropolitan area. Twenty-four hour average samples were collected daily for a month or so in spring and fall of both 2007 and 2008. Asian dust occurred twice in each period except in the fall of 2007. During the Asian dust period, nitrate in fine particles decreased since large amount of cations in coarse particles of Asian dust absorbed it. In spring 2008, sulfate as well as ammonium also increased in coarse particles. In spite of occasional Asian dust events, the influence of secondary formation was dominant over the period. Excessive ammonium over sulfate was enough to neutralize nitrate as well. High correlation coefficients between $K^+$ and sulfate, nitrate, and ammonium indicate a close relationship between secondary formation and biomass burning. Biomass burning and open burning are considered to be important sources of chloride.

• 청정기술
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• 제7권1호
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• pp.27-34
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• 2001

CMP공정에서 발생되는 slurry는 다량의 입자성 물질과 중금속을 함유하고 있다. 이 폐 slurry는 응집성과 침강성에 문제가 있어 처리에 어려움이 있다. 따라서, 본 연구에서는 PACI과 Alum을 이용한 Jar-tester를 통하여 용수 재활용을 위한 최적 응집 조건을 도출하고자 하였다. 고형물 함량이 0.1wt%의 경우 PACI을 응집제로 사용할 때 최적 응집 조건은 pH 4 부터 6에서 투여량은 20~50 mg/L 였으며, 0.5 wt%의 경우 pH 4와 5에서 응집제 투여량은 50~100 mg/L였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권2호
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• pp.907-923
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• 2020

For the severe haze situation in the Beijing-Tianjin-Hebei region, conventional fine particulate matter (PM2.5) concentration prediction methods based on pollutant data face problems such as incomplete data, which may lead to poor prediction performance. Therefore, this paper proposes a method of predicting the PM2.5 concentration based on image analysis technology that combines image data, which can reflect the original weather conditions, with currently popular machine learning methods. First, based on local parameter estimation, autoregressive (AR) model analysis and local estimation of the increase in image blur, we extract features from the weather images using an approach inspired by free energy and a no-reference robust metric model. Next, we compare the coefficient energy and contrast difference of each pixel in the AR model and then use the percentages to calculate the image sharpness to derive the overall mass fraction. Furthermore, the results are compared. The relationship between residual value and PM2.5 concentration is fitted by generalized Gauss distribution (GGD) model. Finally, nonlinear mapping is performed via the wavelet neural network (WNN) method to obtain the PM2.5 concentration. Experimental results obtained on real data show that the proposed method offers an improved prediction accuracy and lower root mean square error (RMSE).

• 한국대기환경학회지
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• 제13권6호
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• pp.475-486
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• 1997

The characteristics of atmospheric aerosols were investigated as a function of particle size and water solubility. The atmospheric aerosols were sampled with classifying into 12 size ranges by the use of Andersen low-pressure impactor. Collected aerosol particles were extracted by ultrapure water and filtered to be separated into water-soluble and insoluble components. The concentrations 12 elements in both components were determined by PIXE analysis. And the concentrations of 8 ions in the soluble component were analyzed by ion chromatography. In general, the mass size distribution of particulate matter was represented as a bimodal distribution. The mass size distributions of S$(SO_4^{2-}), K(K^+), Zn and NH_4^+$ skewed to the smaller size range and those of Si, Ca$(Ca^{2+}), Fe, Na^+ and Mg^{2+}$ skewed to the larger size range. They had roughly one peak in the fine and coarse particle region,respectively. On the other hand, the mass size distribution of Ti, Mn, Ni, Cu, $Cl^- and NO_3^-$ were represented as the bimodal distribution. Fe and Si in the aerosol particles extracted into pure water are existing in high insoluble state. Conversely, almost the whole of S is dissolved in water.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.29-33
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• 2001

In the present study, AZ91Mg/$\textrm{Al}_2\textrm{O}_3$ short fiber+SiC particulates hybrid metal matrix composites(MMCs) were fabricated by squeeze casting method. Different particulate sizes of 45, 29 and $9\mu\textrm{m}$ were hybridized with 5% volume fraction to investigate the effect of SiC particulates size on microstructure, mechanical and thermal properties such as hardness, flexural strength, wear resistance and thermal expansion. Results show that the microstructure of the hybrid composites were quite satisfactory, namely revealing relatively uniform distribution of reinforcements. Some aggregation of SiC particulates caused by particle pushing was observed especially in the hybrid composites containing in fine particulates($9\mu\textrm{m}$). The hardness and flexural strength were improved by decreasing particulates size, whereas wear resistance improved by increasing particulates size because of large particulates restricting matrix wear from contacted stress. Regardless of particulates size, thermal expansion of composites was the same. This may be because the content of particulates was in all cases 5 volume fraction.1

• 한국대기환경학회지
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• 제32권3호
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• pp.329-341
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• 2016

Pohang is a well-known industrial city in Korea with a large steel-industrial complexes. The biggest environmental issue in the city is associated with fine particulate matter (hereinafter, $PM_{10}$). The concentration of $PM_{10}$ is generally dependent on the local emission sources and meteorological conditions. Iron and steel industrial complexes are likely serious pollution sources of $PM_{10}$ in Pohang. In this study, daily $PM_{10}$ data from a large database from the year of 2000 to 2012 were statistically analyzed, together with meteorological data. The average concentrations of $PM_{10}$ were evaluated according to the frequency of Asian dust, haze, mist, and fog. The number of days exceeding short-term standard for $PM_{10}$ were also examined, taking into consideration of weather conditions. It was found that the concentration of $PM_{10}$ was reduced about 18% to 26% because of precipitation. In addition, the effects of wind direction and wind speed on the $PM_{10}$ concentrations were investigated.

• 대기
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• 제27권4호
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• pp.499-509
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• 2017

Possible links among cosmic ray, cloud, and climate have scientific uncertainties. The reputed topics have been highly controversial during several decades. A link between the atmospheric ionization by galactic cosmic rays (GCR), which is modulated by solar activities, and global cloud cover was firstly proposed in 1997. Some researchers suggested that the GCR can stimulate the formation of cloud condensation nuclei (CCN) in the atmosphere, and then the higher CCN concentrations may lead to an increase of cloud cover, resulting in a cooling of the Earth's climate, and vise versa. The CLOUD (Cosmic leaving outdoor droplets) experiment was designed to study the effect of GCR on the formation of atmospheric aerosols and clouds under precisely controlled laboratory conditions. A state-of-the-art chamber experiment has greatly advanced our scientific understanding of the aerosol formation in early stage and its nucleation processes if the GCR effect is considered or not. Many studies on the climate-GCR (or space weather) connection including the CLOUD experiment have been carried out during the several decades. Although it may not be easy to clarify the physical connection, the recent scientific approaches such as the laboratory experiments or modeling studies give some implications that the research definitively contributed to reduce the scientific uncertainties of natural and anthropogenic aerosol radiative forcing as well as to better understand the formation processes of fine particulate matters as an important parameter of air quality forecast.

• 한국분말재료학회지
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• 제5권4호
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• pp.334-339
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• 1998

In purpose of introducing the inverse magnetostrictive properties into the structural ceramics, $Al_2O_3$ based nanocomposites dispersed with nano-sized Ni-Co particles were studied. The composites were fabricated by the hydrogen reduction and hot-pressing of $Al_2O_3$ and NiO-CoO mixed powders. The mixtures were prepared by using Ni- and Co-nitrate $(Ni(NO_3)_2\;{\cdot}\;6H_2O\;and\;Co(NO_3)_2\;{\cdot}\6H_2O)$ as source materials for the Ni-Co particles. Microstructural observations revealed that nano-sized Ni-Co particles were dispersed homogeneously at $Al_2O_3$ grain boundaries. High strength above 1 GPa was obtained for the $Al_2O_3/10$ wt% Ni-Co nanocomposite fabricated by a controlled powder preparation process. The inverse magnetostrictive response to applied stress was obtained due to the presence of dispersed Ni-Co particles, which indicates a possibility to incorporate new functions into the structural ceramics without loosing the mechanical properties.

• Asian Journal of Atmospheric Environment
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• 제4권2호
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• pp.72-79
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• 2010

In this study, the ionic composition of volcanogenically derived particles and their temporal and spatial distributions have been investigated to evaluate the impact of the volcanic eruption on the local ecosystem and residents. To this end, an intensive field study was conducted to measure the size-segregated particulate matters at the east part of Sakurajima in Japan. Fractionated sampling of particles into > $PM_{10}$, $PM_{10-2.5}$, and $PM_{2.5}$ was made by a multi nozzle cascade impactor (MCI). The concentration of various ions present in the size-resolved particles was determined by Ion chromatography. The time dependent 3-dimensional Volcanic Ash Forecast Transport And Dispersion (VAFTAD) model developed by the NOAA Air Resources Laboratory (ARL) indicated that the sampling site of this work was affected by the volcanic aerosol particles plume. The temporal distributions of sulfate and $PM_{2.5}$ during the field campaign were significantly variable with important contributions to particle mass concentration. The chlorine loss, suspected to be caused by acidic components of volcanic gases, occurred predominantly in fine particles smaller than $10\;{\mu}m$.