• 한국대기환경학회지
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• 제15권6호
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• pp.747-755
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• 1999

Effects of precipitation and cloud cover on high ozone days are examined by investigating the precipitation and average cloud cover before the ozone peak time within a day. High ozone days above 100 ppb in the Greater Seoul Area(GSA) for the ozone season from May to September are chosen for the analyses in terms of the surface meteorological data during 1990~1997. The result shows that the effect of precipitation on the rise of ozone concentration is definitely negative so that ozone concentration could not rise above 100ppb immediately after precipitation. But, the effect of cloud cover is associated with the variations of other meteorological parameters. The number of high ozone days with "zero" cloud cover is rather less than that with cloud cover of 1 to 4 since temperature is usually lower in "zero" cloud cover days. Furthermore, ozone concentration can rise above 100ppb even with full cloud cover when the wind is weak and the temperature is high.temperature is high.

• 한국환경보건학회지
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• 제23권1호
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• pp.105-108
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• 1997

For the removal of heavy metals, Cd, Cu and Cr were used. The initial concentration of Cd and Cu were 1-10 ppm, the removal efficiency of Cd and Cu was 76.2-89.0% and 69.0-79.0%, respectively. The initial concentration of Cr were 1~5 ppm, and the-removal efficiency was low especially at high concentration. In general, the initial concentrations of heavy metals had no relation to the removal efficiency. At the beginning, the removal efficiency was very high, but it was maintained at constant concentration. The trends of accumulations of heavy metals in the stem increased in proportion to the initial concentration. The removal efficiency of heavy metals increased a little bit when nutrients existed in the solution. So that, the initial concentration of Cd and Cu were 1-10 ppm, the removal efficiency of Cd and Cu was 84.8-91.0% and 75.9-82.0%. The initial concentration of Cr were 1-5 ppm, the removal efficiency was 25.0-67.0%.

• 한국산업보건학회지
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• 제24권3호
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• pp.336-344
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• 2014

Objectives: This study was performed to assay the effect of neodymium oxide on the generation of reactive oxygen species and DNA oxidative damage by intratracheal instillation. Methods: Two groups of rats were exposed to neodymium oxide($Nd_2O_3$) via intratracheal instillation with doses of 0.5 mg and 2.0 mg, respectively. At two days and at 12 weeks after exposure, the contents of neodymium oxide in the lung, liver, kidney, heart and brain, leukocyte, olive tail moment, ROS, RNS, lactate dehydrogenase, albumin, cytokine and MDA from BALF were measured. Results: Neodymium oxide contents in the liver, kidney, heart, and brain were detected at less than $1{\mu}g/g$ tissue concentration. However, in the lungs at four weeks the highest amount were detected and then found to be drastically reduced at 12 weeks. ROS and RNS in bronchoalveolar lavage increased in concentration dependently at two days, four weeks and 12 weeks after neodymium oxide instillation. However, ROS and RNS decreased with the passage of time. At two days the total number of WBC in BALF in the high concentration group was significantly increased, and at four weeks the total number of WBC were significantly increased in the low and high concentration groups(p<0.01). At two days after exposure, the LDH of the low and high concentration groups was significantly increased. At 12 weeks, only the LDH of the high concentration group was significantly increased compared to in the control group(p<0.01). As a result of Comet assay, after two days, damage to the DNA of the low and high concentration groups was observed. Conclusions: Intratracheal instillation of neodymium oxide induces the generation of ROS and DNA damage in rats.

• 한국대기환경학회지
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• 제28권1호
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• pp.12-21
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• 2012

The purpose of this study is to understand distribution of ozone concentration in the south coastal region of Korea by evaluating ozone spatial distribution in the upper air using aircraft. Sampling was carried out from May to August in 2009. The average concentration of ozone in the upper air was ranged from 32.3~90.8 ppb with its maximum concentration of 132 ppb. When it comes to the spatial distribution of ozone, ambient concentration was high in the air, 1,000 m and 500 m above the southern sea near the Gwangyang Bay area and emission sources, respectively. Daily mean concentration of NOy was 6.7~24.2 ppb and that of CO was 0.152~0.487 ppm. In addition, the concentration was appeared to be relatively high in the upper air of industrial regions and the southern seas. Meanwhile, the concentration of both $NO_y$ and CO was high in the upper air of the emission sources regardless of latitude. As for PAN, its daily mean concentration ranged between 0.1 and 0.6 ppb with overall mean concentration of 0.2 ppb. The average concentration of VOCs was 48 ppb, and the concentration of toluene and m,p-Xylene were higher than other components.

• 한국환경복원기술학회지
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• 제25권1호
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• pp.41-55
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• 2022

Social interest in the fine particulate matter has increased significantly since the 2010s, and various efforts have been made to reduce it through environmental plans and policies. To support such environmental planning, in this study, spatial cluster characteristics of fine particulate matter (PM2.5) concentrations were analyzed in the metropolitan area to identify high-risk areas spatially, and the correlation with local environmental characteristics was also confirmed. The PM2.5 concentration for the recent 5 years (2016-2020) was targeted, and representative spatial statistical methods Getis-Ord Gi^* and Local Moran's I were applied. As a result of the analysis, the cluster form was different in Getis-Ord Gi^* and Local Moran's I, but they show high similarity in direction, therefore complementary results could be obtained. In the high concentration period, the hotspot concentration of the Getis-Ord Gi* method increased, but in Local Moran's I, the HH region, the high concentration cluster, showed a decreasing trend. Hotspots of the Getis-Ord Gi^* technique were prominent in the Pyeongtaek-Hwaseong and Yeoju-Icheon regions, and the HH cluster of Local Moran's I was located in the southwest, and the LL cluster was located in the northeast. As in the case of the metropolitan area, in the results of Seoul, there was a phenomenon of division between the northeast and southwest regions. The PM2.5 concentration showed a high correlation with the elevation, vegetation greenness and the industrial area ratio. During the high concentration period, the relation with vegetation greenness increased, and the elevation and industrial area ratio increased in the case of the annual average. This suggests that the function of vegetation can be maximized at a high concentration period, and the influence of topography and industrial areas is large on average. This characteristic was also confirmed in the basic statistics for each major cluster. The spatial clustering characteristics of PM2.5 can be considered in the national land and environmental plan at the metropolitan level. In particular, it will be effective to utilize the clustering characteristics based on the annual average concentration, which contributes to domestic emissions.

• 생태와환경
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• 제38권4호통권114호
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• pp.439-444
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• 2005

The environmental quality of the middle-reach of the Yahagi River has deteriorated in recent years. The nutrient dynamics within the reach were investigated to explain the changes. Seasonal pattern of $NO_3\;^--N$ concentration tended to stay low from April or May through July or August and then increased till winter or early spring, although there were peaks during high flow periods in mid-September, 2000 and late-August, 2001. No clear seasonal changes were observed in $PO_4\;^{3-}-P$ concentration. In the bimonthly records from 1980-2002, the DIN concentrations on January and March were higher than other months whereas the average daily flows on January and March were lower than they were in other months. The mean DIN concentration showed a high negative correlation with the median of average daily flow. In the past 50 years, the average concentration of DIN (excluding nitrite) was 0.21 mg $L^{-1}$ in 1952-1953. The concentration was about twice this high around 1980, and it is about three times this high at present. On the other hand, the average concentration of $PO_4\;^{3-}-P$ was below the limit of detection in 1952-53. However, it increased to almost 0.03 mg $L^{-1}$ around 1980, then decreased to approximately 0.016mg $L^{-1}$ at present. Our results suggest that the increasing DIN concentration is one of the causes of environmental change in the Yahagi River. We conclude that controlling the DIN concentration is essential for improving the river environment.

• Restorative Dentistry and Endodontics
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• 제23권1호
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• pp.502-514
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• 1998

The purpose of this study is to observe the corrosion characteristcs of four dental amalgams(CAULK FINE CUT, CAULK SPHERICAL, DISPERSALLOY, TYTIN) and to determine a function of chloride concentration through the anodic polarization curve obtained by using a potentiostat. After each amalgam alloy and Hg being triturated, the triturated mass was inserted into the cylinderical metal mold, and condensed by hydrolic pressure. Each specimen was removed from the metal mold. 24 hours after condensation, specimens were polished with the emery paper and stored at room temperature for 6 months. The anodic polarization curves were employed to compare the corrosion behaviours of the amalgam m KCl and KCl-NaCl solution, which had chlonde concentration of 0.4 g/l, 0.8 g/l, 1.2 gil, and 1.6 gil at $37^{\circ}C$ with 3-electrode potentiostat. After the immersion of specimen in electrolyte for 1 hour, the potential scan was begun. The potential scan range was - 1500mV ~+800mV(vs. S.C.E.) in the working electrode and the scan rate was 50mV/sec. The results were as follows, 1. The corrosion potential. the potential of anodic current peak, and transpassive potential in the solution of high chloride concentration shifted to more cathodic direction than those in the solution of low concentration, and the current density in the solution of high chloride concentration was higher than that in the solution of low concentration. 2. The corrosion potential, the potential of anodic current peak, and transpassive potential for CAULK FINE CUT amalgam were the most cathodic among the others, and the current density were the highest among the others. 3. In the solution of low chloride concentration, the corrosion potential, the potential of anodic current peak, and transpassive potential for DISPERSALLOY were the most anodic among the others, however in the solution of high chloride concentration, those for TYTIN were the most anodic among the others. 4. The anodic polarization curve for CAULK SPHERICAL was similar to that for high copper amalgams.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 춘계학술대회
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• pp.277-279
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• 2021

미세먼지 예측의 경우 농도에 따른 특성으로 인해 예측 모델의 학습이 잘 이루어지지 않는 문제가 있다. 이러한 문제를 해결하기 위해 저농도와 고농도에 대한 개별 예측 모델을 구분하여 설계할 필요가 있다. 따라서 미세먼지 농도를 저농도와 고농도로 구분하기 위한 분류 모델이 필요하다. 본 논문은 미세먼지 농도 80㎍/m³을 기준으로 저농도와 고농도를 구분하기 위한 분류 모델을 제안한다. 분류 모델의 알고리즘은 DNN을 사용하였으며, 하이퍼 파라미터 탐색 후 최적의 파라미터를 적용하여 분류 모델을 설계하였다. 모델의 성능 평가 결과, 저농도 분류의 경우 97.54%, 고농도 분류의 경우 85.51%의 분류 성능을 확인하였다.

• The Korean Journal of Ceramics
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• 제6권2호
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• pp.124-128
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• 2000

Electrical properties of $ZrO_2-TiO_2Yb_2O_3$mixed conductor (Ti-YbSZ) were investigated. This mixed conductor can be applied as a membrane for gas separation at high temperatures. The total conductivity decreased with increasing the $TiO_2$concentration. At high temperatures, the rate of the conductivity degradation became smaller than that at low temperatures. From the oxygen partial pressure dependence of the total conductivity of Ti-YbSZ, the electronic conductivity increased with increasing $TiO_2$concentration at low oxygen partial pressures and at high temperatures. Both 15 and 20 mol% $TiO_2$doped YbSZ showed high oxygen permeability. Mixed conductors, which has high $TiO_2$concentration in YbSZ, are promising materials for using as a membrane for gas separation at high temperatures.

• 한국의상디자인학회지
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• 제19권2호
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• pp.39-48
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• 2017

Transfer printing is a method to combine printing and dyeing technology by the use of sublimation. It is an environmentally-friendly printing method that saves costs, reduces the production processes by the omission of the washing process, and saves time by maintaining quality. Due to the development of transfer printing, a high value added printing technology is available now but color fastness to sublimation of the printing products is still low since there are few dyes that have an affinity to the fabrics and the application technology is still inadequate. Specially, in case of high concentration black dyes, eco-label type black dyes, which is a substitution for general dispersal dyes, have been developed while general dispersal black dyes are still used, creating issues such as color differences on the surface and back side of the fabrics and contamination by friction after transfer printing. There are also some restricted substances such as allergens. To address these issues, high concentration black dyes and application technology that are environmentally-friendly and that have over 16 K/S through the use of single dyes with excellent color fastness, fixation ability, and similar melting temperature were developed for this study.