• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.389-392
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• 2004

As the integrated circuit device shrinks to the smaller dimension, the chemical mechanical polishing (CMP) process was required for the global planarization of inter-metal dielectric(IMD) layer with free-defect. The effect of alternative commerical slurries pads, and post-CMP cleaning alternatives are discuess, with removal rate, scratch dentisty, surface roughness, dishing, erosion and particulate density used as performance metrics. we investigated the performance of $SnO_2$-CMP process using commonly used silica slurry, ceria slurry, tungsten slurry. This study shows removal rate and non-uniformity of $SnO_2$ thin film used to gas sensor by using Ceria, Silica, W-Slurry after CMP process. This study also shows the relation between particle size and CMP with particle size analysis of used slurry.

• Tuberculosis and Respiratory Diseases
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• v.58 no.2
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• pp.167-173
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• 2005

Background : Airborne particles during Yellow Sand phenomena are known to be associated with the respiratory disease. The purpose of this study was to evaluate the concentration and metal component properties of Yellow Sand particles and compare with airborne microbial concentration and species in non Yellow Sand and Yellow Sand phenomena. Methods : Samplings were carried out in 2002 in Seosan, during non Yellow Sand and Yellow Sand phenomena. Samples were taken using the 8-stage Cascade impactor and metallic elements were analyzed by XRF. Those were culture on the media for bacterial and fungal culture and celline for virus. Results : The concentration of total suspended particulate matter were respectively $80.2{\mu}g/m^3$, $40.3{\mu}g/m^3$ in non Yellow Sand and Yellow Sand phenomena. The concentration of metallic elements such as Ca, Fe, Cu and Zn in Yellow Sand phenomena were higher than its in non Yellow Sand. Two bacteria, Bacillus species and Staphylococcus were grown in two periods. In both periods, several fungal spores(Mucor species, Cladosporum, Alternaria, Aspergillus, Penicillium, and Alternaria species) were identified. The differences of bacteria and fungus species not observed in Yellow Sand and non Yellow Sand. Any viruses were not isolated in between both periods. Conclusions : The concentration of total suspended particulate matter and some metallic elements in Yellow Sand phenomena were higher than its in non Yellow Sand. The difference of bacteria and fungus species was not observed in non Yellow Sand and Yellow Sand phenomena.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.3
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• pp.41-52
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• 2014

In this study, to estimate the biodegradability of sewage discharged intermittently, field scale sampling and analysis was conducted and the results were obtained as follows. According to results of the biodegradability of sewage discharged intermittently, average concentration of TCODcr is 325.5mg/L and ratio of TCOD fraction resulted 100%. Also, average concentration of SCODcr resulted 135.9mg/L and ratio of TCOD fraction resulted 41.8%. Average concentration of Ss showed 74.1mg/L and ratio of TCOD fraction resulted 22.8%. Average concentration of $S_I$ was analyzed to be 61.8mg/L and ratio of TCOD fraction was calculated to 19.0%. Xs which is particulate matter was analyzed to show 27.8mg/L and ratio of TCOD fraction also showed 8.5%. Average concentration of $X_H$ is 103.4mg/L and ratio of TCOD fraction resulted 31.8%. Inert particulate matter showed that average concentration of $X_I$ is 58.5mg/L and ratio of TCOD fraction resulted 18.0%. Accordingly, dissolved biodegradable organic matter showed the ratio of 41.8%, and readily biodegradable matter among this showed 22.8%. Thus intermittent inflow is expected to have less effect with regards equalization by organic loading rate of influent.

• Journal of Environmental Health Sciences
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• v.40 no.1
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• pp.10-16
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• 2014

Objectives: This pilot study assessed secondhand smoke (SHS) exposure in smoking and non-smoking nightclubs in Seoul, Korea by measuring the concentration of particulate matter smaller than $2.5{\mu}m$ ($PM_{2.5}$). Methods: This comparative study was conducted in three nightclubs in Seoul. While one non-smoking nightclub was measured on weekdays and weekends, different smoking nightclubs were measured on weekdays and weekends. The concentration of $PM_{2.5}$ was observed using a real-time monitor over an average of three hours. The number of people in the clubs was also estimated. Settled dust was collected in a smoking and a non-smoking nightclub and analyzed for NNK concentration. Results: The $PM_{2.5}$ concentration in the smoking nightclubs was higher than those found in the non-smoking nightclub by 26 times on weekdays and three times on weekends. Indoor $PM_{2.5}$ concentration was correlated with the number of people in the smoking nightclubs. Relatively high $PM_{2.5}$ concentration was observed in the non-smoking nightclub on weekends. NNK concentration in the smoking nightclub was 7 times higer than in the non-smoking nightclub. Conclusion: Smoking in nightclubs caused high $PM_{2.5}$ concentration. Although the non-smoking nightclub had a lower $PM_{2.5}$ concentration, $PM_{2.5}$ concentration on weekends was higher due to the smoking room. Complete prohibition of smoking in nightclubs can protect patrons from secondhand smoke exposure.

• Journal of Environmental Health Sciences
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• v.36 no.4
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• pp.288-293
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• 2010

In this study, exposure to secondhand smoke (SHS) was evaluated in commercial personal computer (PC) rooms with different separation types of non-smoking areas. The particulate matter less than 2.5 ${\mu}m$ ($PM_{2.5}$) level was simultaneously measured by aerosol spectrometers in the non-smoking and smoking areas of these commercial PC rooms. Average $PM_{2.5}$ concentrations in non-smoking and smoking areas were $75\;{\mu}g/m^3$ and $136\;{\mu}g/m^3$, respectively. Although the $PM_{2.5}$ concentrations in non-smoking areas were significantly less than those in smoking areas (p<0.01), the levels still exceeded the US National Ambient Air Quality Standard of $35\;{\mu}g/m^3$. Average $PM_{2.5}$ concentrations in non-smoking areas were not significantly different with regard to area separation type, with $73\;{\mu}g/m^3$ in the no-wall type, $83\;{\mu}g/m^3$ in the wall-type, and $39\;{\mu}g/m^3$ in the separated-floor-type areas (p>0.1). Separation of the non-smoking area thus did not eliminate SHS exposure in commercial PC rooms, regardless of the type of area separation. This study demonstrates that simple separation of non-smoking areas in commercial PC rooms does not protect users from SHS.

• Journal of Preventive Medicine and Public Health
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• v.46 no.1
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• pp.10-18
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• 2013

Objectives: We investigated the association between particulate matter less than $10{\mu}m$ in aerodynamic diameter ($PM_{10}$) exposure and non-accidental mortality in Asian populations by meta-analysis, using both time-series and case-crossover analysis. Methods: Among the 819 published studies searched from PubMed and EMBASE using key words related to $PM_{10}$ exposure and non-accidental mortality in Asian countries, 8 time-series and 4 case-crossover studies were selected for meta-analysis after exclusion by selection criteria. We obtained the relative risk (RR) and 95% confidence intervals (CI) of non-accidental mortality per $10{\mu}g/m^3$ increase of daily $PM_{10}$ from each study. We used Q statistics to test the heterogeneity of the results among the different studies and evaluated for publication bias using Begg funnel plot and Egger test. Results: Testing for heterogeneity showed significance (p<0.001); thus, we applied a random-effects model. RR (95% CI) per $10{\mu}g/m^3$ increase of daily $PM_{10}$ for both the time-series and case-crossover studies combined, time-series studies relative risk only, and case-crossover studies only, were 1.0047 (1.0033 to 1.0062), 1.0057 (1.0029 to 1.0086), and 1.0027 (1.0010 to 1.0043), respectively. The non-significant Egger test suggested that this analysis was not likely to have a publication bias. Conclusions: We found a significant positive association between $PM_{10}$ exposure and non-accidental mortality among Asian populations. Continued investigations are encouraged to contribute to the health impact assessment and public health management of air pollution in Asian countries.

• Asian Journal of Atmospheric Environment
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• v.9 no.4
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• pp.237-246
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• 2015

We conducted intensive observations of ozone, CO, $NO_x$ (=NO and $NO_2$), $NO_y$ (total odd nitrogen species including particulate nitrate) and total nitrate (the sum of gaseous $HNO_3$ and particulate nitrate) at Cape Hedo, Okinawa, Japan, from 19 March to 3 April, 2009, to investigate ozone production during long-range transport from the Asian continent. Ozone production efficiency (OPE) was used to evaluate photochemical ozone production. OPE is defined as the number of molecules of ozone produced photochemically during the lifetime of a $NO_x$ molecule. OPE is calculated by the ratio of the concentration increase of ozone to that of $NO_z$ ($=NO_y-NO_x$). Average OPE during observation was estimated to be $12.6{\pm}0.5$, but concentrations of ozone increased nonlinearly with those of $NO_z$. This non-linearity suggests that OPE depends on air mass origin and $NO_z$ concentrations. There were very different values of OPE for the same air mass origin, so that only the air mass origin alone does not control OPE. OPE was low when $NO_z$ concentration was high. We examined the correlation between $NO_z$ and $CO/NO_y$ ratios, which we used instead of the ratio of non-methane hydrocarbons (NMHCs) to $NO_x$. The $CO/NO_y$ ratios decreased with increasing $NO_z$ concentrations. These results indicate that competition reactions of OH with NMHCs and $NO_2$ are the rate determining steps of photochemical ozone production during long-range transport from the Asian continent to Cape Hedo, for high concentrations of nitrogen oxides.

• Korean Journal of Ecology and Environment
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• v.52 no.3
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• pp.192-201
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• 2019

While a fairly large amount of organic matter is produced daily via phytoplankton photosynthesis in Lake Paldang, South Korea, knowledge of the role of algal-derived organic matter (OM) as a refractory OM source is not adequate. To understand the contribution of algal-derived OM to the refractory pool, biodegradation experiment and $KMnO_4$ oxidation experiment were conducted for 60 days using $^{13}C$ and $^{15}N$ labeled natural phytoplankton assemblage. The assemblage was collected from Lake Paldang on May 20, 2010. The photosynthetically produced total organic carbon ($TO^{13}C$), particulate organic carbon ($PO^{13}C$), and particulate nitrogen ($P^{15}N$) remained at 26%, 20%, and 17% of the initial concentrations, respectively, in the form of non-biodegradable organic matter. In addition, 12% and 38% of $PO^{13}C$ remained after $KMnO_4$ treatment on Day 0 and 60, respectively. These results indicate that photosynthetic products could be an important source of refractory organic matter after microbial degradation. Moreover, the microbially transformed algal-derived OM could contribute to the oxidation rate of the chemical oxygen demand.

• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.29-35
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• 2020

To manage the non-point source pollution and restore the water circulation, many technologies including infiltration or reservoir systems were installed in the urban area. These facilities have many problems regarding maintenance as their operation period becomes lengthier. The purpose of this study was to estimate the optimal maintenance timing through a long-term load test on the infiltration trench as one of the low impact development techniques. An infiltration trench was installed in the demonstration test facility, and stormwater was manufactured by Manual on installation and operation of non-point pollution management facilities from the Ministry of Environment, Korea and entered into the infiltration trench. Particle size distribution (PSD), suspended solids (SS) removal efficiency, and infiltration rate change tests were performed on inflow and outflow water. In case of the PSD, the maximum particulate size in the outflow decreased from 64 ㎛ to 33 ㎛ as the operating duration elapsed. The SS removal efficiency improved from 97 % to 99 %. The infiltration rate changed from 0.113 L/sec to 0.015 L/sec during the operation duration. The maintenance timing was determined based on the stormwater runoff requirements with these changes in water quality and infiltration rate. The methodologies in this study could be used to estimate the timing of maintenance of other low impact development techniques.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.6
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• pp.719-731
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• 2003

In order to maintain and manage ambient air quality, it is necessary to identify sources and to apportion its sources for ambient particulate matters. The receptor methods were one of the statistical methods to achieve reasonable air pollution strategies. Also, receptor methods, a field of chemometrics, is based on manifold applied statistics and is a statistical methodology that analyzes the physicochemical properties of gaseous and particulate pollutant on various atmospheric receptors, identifies the sources of air pollutants, and quantifies the apportionment of the sources to the receptors. The objective of this study was 1) after obtaining results from the PMF modeling, the existing sources of air at the study area were qualitatively identified and the contributions of each source were quantitatively estimated as well. 2) finally efficient air pollution management and control strategies of each source were suggested. The PMF model was intensively applied to estimate the quantitative contribution of air pollution sources based on the chemical information (128 samples and 25 chemical species). Through a case study of the PMF modeling for the PM-10 aerosols, the total of 11 factors were determined. The multiple linear regression analysis between the observed PM-10 mass concentration and the estimated G matrix had been performed following the FPEAK test. Finally the regression analysis provided quantitative source contributions (scaled G matrix) and source profiles (scaled F matrix). The results of the PMF modeling showed that the sources were apportioned by secondary aerosol related source 28.8 ％, soil related source 16.8％, waste incineration source 11.5%, field burning source 11.0%, fossil fuel combustion source 10%, industry related source 8.3％, motor vehicle source 7.9%, oil/coal combustion source 4.4％, non-ferrous metal source 0.3％. and aged sea- salt source 0.2％, respectively.