• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.382-390
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• 2010

In this research hydrogen sulfide, ammonia and toluene were designated as the representative source of malodor and VOC, respectively, frequently generated at the compost manufacturing factory and publicly owned facilities. The optimum operating condition to treat the waste air(2 L/min) containing malodor was constructed using photocatalytic reactor/biofilter process with humidifier composed of fluidized aerobic anf anoxic reactor. The ammonia(300 ppmv) of fed-waste air was removed by 22, 55 and 23% at the stage of photocatalytic reactor, humidifier and biofilter, respectively. The toluene(100 ppmv) of fed-waste air was removed by 20, 10 and 70% at the stage of photocatalytic reactor, humidifier and biofilter, respectively. Therefore the water-soluble ammonia and the water-insoluble toluene were treated mainly at the stage of humidifier and biofilter, respectively. In addition, hydrogen sulfide(10 ppmv) was almost treated at the stage of photocatalytic reactor and its negligible trace was absorbed in humidifier so that it was not detected before biofilter process. The nitrate concentration of the process water from anoxic reactor was found lower by 3 ppm than that from fluidized aerobic reactor. Besides, the dissolved ammonia-nitrogen concentration of the process water from humidifier remained at the high value of 1,500-2,000 ppm, which may be attributed to the existence of ammonium chloride and other source of ammonium nitrogen.

• Journal of Korea Port Economic Association
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• v.36 no.3
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• pp.21-38
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• 2020

Currently, in-port emissions are a serious problem in port cities. However, emissions, especially non-greenhouse gases, from the operation of cargo handling equipment (CHE) have received significant attention from scientific circles. This study estimates the amount of emissions from on-land port diesel-powered CHE in the Port of Incheon. With real-time activity data provided by handling equipment operating companies, this research applies an activity-based approach to capture an up-to-date and reliable diesel-powered CHE emissions inventory during 2017. As a result, 105.6 tons of carbon monoxide (CO), 243.2 tons of nitrogen oxide (NOx), 0.005 tons of sulfur oxide (Sox), 22.8 tons of particulate matter (PM), 26.0 tons of volatile organic compounds (VOCs), and 0.2 tons of ammonia (NH3) were released from the landside CHE operation. CO and NOx emissions are the two primary air pollutants from the CHE operation in the Port of Incheon, contributing 87.71% of the total amount of emissions. Cranes, forklifts, tractors, and loaders are the four major sources of pollution in the Port of Incheon, contributing 84.79% of the total in-port CHE emissions. Backward diesel-powered machines equipped in these CHE are identified as a key cause of pollution. Therefore, this estimation emphasizes the significant contribution of diesel CHE to port air pollution and suggests the following green policies should be applied: (1) replacement of old diesel powered CHE by new liquefied natural gas and electric equipment; (2) the use of NOx reduction after-treatment technologies, such as selective catalytic reduction in local ports. In addition, a systematic official national emission inventory preparation method and consecutive annual in-port CHE emission inventories are recommended to compare and evaluate the effectiveness of green policies conducted in the future.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.2
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• pp.57-62
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• 2011

The energy conversion efficiency of DSSCs (Dye-Sensitized Solar Cells) is dependent on the powder size, the structure, and the morphology of $TiO_2$ electrode. The higher efficiency is obtained with high surface area of the nanoanatase-$TiO_2$ powder adsorbed onto a lot more of the dye. Also, the enhancement of light scattering increases the efficiency with high adsorption of the dye. Powder size, crystalline phase, and shape of $TiO_2$ obtained by hydrothermal method have 15-20 nm, anatase and round. $TiO_2$ electrode has fabricated with the mixture of scattering $TiO_2$ particle with 0.4 ${\mu}m$ in nano-sized powder. Conversion efficiency of series of DSSCs was measured with volume fraction of scattering particle. Photovoltaic characteristics of DSSCs with 10% scattering particles are 3.51 mA for Jsc (short circuit current), 0.79 V for Voc(open circuit potential), filling factor 0.619 and 6.86% for efficiency. Jsc was improved by 11% and enhancement of efficiency by 0.77% compared with that of no scattering particles. The confinement of inserted light by light scattering particles has more increase of the injection of exiton(electron-hole pair) and decrease of moving path in electron. Efficiencies of DSSCs with more than 10% for scattering particles have reduced with increasing the pore in the $TiO_2$ electrode.

• Journal of Environmental Health Sciences
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• v.46 no.2
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• pp.150-158
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• 2020

Objective: This study is designed to measure the concentration of DBPs (disinfection by-products) in pool water and in air and to estimate the carcinogenic potential through the evaluation of inhalation exposure. Methods: The subjects were six indoor swimming pools with many users in Gwangju. Samples of pool water and indoor air were taken every one month from August 2018 to August 2019 and analyzed for eight swimming pool standards. Three-liter air samples were collected and the VOCs were analyzed using GC/MS directly connected to thermal desorption. Results: pH was 6.8-7.5 and the concentration of free residual chlorine in pool water was 0.40-0.96 ?/ℓ. Physicochemical test items such as KMnO₄ consumption and heavy metal items such as Aluminum met existing pool hygiene standards. No VOC materials were detected except for the DBPs. The concentration of THMs in the pool water was 11.05-41.77 ㎍/L and the THMs mainly consist of Chloroform (63-97%) and BDCM (3-31%). The concentration of indoor air THMs is 13.24-32.48 ㎍/㎥ and consists of Chloroform. The results of carcinogenic assessment of chloroform in the indoor swimming pool via inhalation exposure were 2.0 to 6.4 times higher than the 'acceptable risk level' suggested by the US EPA. Conclusions: The concentration of THMs in the pool water is 11.05-41.77 ㎍/L, most of which is chloroform. In addition, the concentration of indoor air THMs is 13.24-32.48 ㎍/㎥. The result of carcinogenic assessment of chloroform was 2.0 to 6.4 times higher than the 'acceptable risk level' suggested by the US EPA.

• Journal of the Korea Convergence Society
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• v.8 no.10
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• pp.249-255
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• 2017

The domestic tourism industry mostly relies on quantitative surveys for customer satisfaction. However, customer participation of the questionnaires is extremely low and the improvement of the dissatisfactory factors is not being performed promptly. In this paper, we propose a new topic map system and prove its empirical effectiveness to improve the accuracy of customer feedback information and the efficiency of the analysis process. The topic map system is a system for analyzing large amounts of customer feedback data in real time. It uses text mining and ontology techniques by integrating data collected over a certain period from real-time SNS and quantitative data obtained from existing survey systems. The effect after improving the analyzed factors of dissatisfaction is also a new and innovative evaluation system for monitoring customer satisfaction in real time. The classification based on this integrated data is a classification system that is specific to the product or the customer. According to this classification, it is possible to measure the effect of the recognition and improvement of the complaint factor in real time on the topic map system. This provides a sophisticated prioritization of the improvement factors and enables customer satisfaction quality control as a PDCA feedback system. In addition, the survey period and costs are greatly shortened, and responses can be more precise to the existing survey method. As a practical application, this system is applied to the largest H travel agency in Korea to prove the accuracy and efficiency of the proposed system.

• Toxicological Research
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• v.26 no.4
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• pp.293-300
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• 2010

tert-Butyl acetate (TBAc) is an organic solvent, which is commonly used in architectural coatings and industrial solvents. It has recently been exempted from the definition of a volatile organic compound (VOC) by the Air Resources Board (ARB). Since the use of TBAc as a substitute for other VOCs has increased, thus its potential risk in humans has also increased. However, its inhalation toxicity data in the literature are very limited. Hence, inhalation exposure to TBAc was carried out to investigate its toxic effects in this study. Adult male rats were exposed to TBAc for 4 h for 1 day by using a nose-only inhalation exposure chamber (low dose, $2370\;mg/m^3$ (500 ppm); high dose, $9482\;mg/m^3$ (2000 ppm)). Shamtreated control rats were exposed to clean air in the inhalation chamber for the same period. The animals were killed at 2, 7, and 15 days after exposure. At each time point, body weight measurement, bronchoalveolar lavage fluid (BALF) analysis, histopathological examination, and biochemical assay were performed. No treatment-related abnormal effects were observed in any group according to time course. Based on those findings, the median lethal concentration ($LC_{50}$) of TBAc was over $9482\;mg/m^3$ in this study. According to the MSDS, the 4 h $LC_{50}$ for TBAc for rats is over $2230\;mg/m^3$. We suggested that this value is changed and these findings may be applied in the risk assessment of TBAc which could be beneficial in a sub-acute study.

• Journal of Adhesion and Interface
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• v.21 no.3
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• pp.93-100
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• 2020

3D printing technology enables proper objects to be made through an additive manufacturing method, but resulting in dimension deviation of the product due to contraction phenomenon as cooling melted filament resin injected from high-temperature use environment. In this research, we studied on acrylic adhesives for 3D printer build sheet in order to fabricate high-quality products with a precise shape and to well-mount without distortion. The solvent-free UV-curable acrylic adhesive formulation was designed by adding 4-acryloylmorpholine (ACMO) with high adhesion, toughness, glass transition temperature so that adhesion properties are stable at high temperature and products are easily mounted/detached from the adhesives. The designed formulation was polymerized through two-steps using post-addition of monomers. Using this, the acrylic adhesive was coated to make a film and then analyzed using various experimental techniques. As a result, the fabricated adhesive exhibited high glass transition temperature and there was little gap in peel strength before and after thermal treatment. Moreover, it was confirmed by rheological analysis that this adhesive can provide great bonding/debonding ability without distortion. We demonstrated the fabrication of a rectangular product using a 3D printing method using our acrylic adhesive as a build sheet. Mounting ability and workability were satisfactory and dimension deviation of the product was tiny. Because the product is easily detachable from the acrylic adhesive developed here than conventional build sheets, it is expected that this will provide work convenience to users who use the 3D printer.

• Journal of Environmental Health Sciences
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• v.32 no.5 s.92
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• pp.404-411
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• 2006

이 연구의 목적은 유치원에서 총 휘발성 유기화합물의 농도를 평가하고, 총 휘발성 유기화합물 농도와 대표적인 8개 방향족 화합물의 상관관계를 조사하는데 있다. 도시에 위치한 11개 유치원의 실내와 실외에서 각각 30개, 11개의 지역시료를, 시골에 위치한 4개 유치원에서는 각각 10개, 4개의 시료를 테낙스 튜브를 이용하여 오전에 1-2시간 채취하였다. 채취한 시료는 열탈착하여 가스크로마토그래피-질량분석기로 분석하였다. 13가지 물질을 각각의 표준물질로 개별 정량하여 이중 빈번히 발견되는 8가지 방향족 유기화합물은 상관관계 평가에 사용하였다. 총 휘발성 유기화합물은 톨루엔을 기준으로 정량하였다. 도시에 위치한 유치원 실내의 총 휘발성 유기화합물 농도가 높았고, 조사 건수의 50%가 환경부 및 교육인적자원부의 가이드라인($400{\mu}g/m^{3}$)을 초과하였다. 도시지역의 유치원 실내 및 실외의 기하평균은 각각 $387.9{\mu}g/m^{3}$과 $134.9{\mu}g/m^{3}$이었고, 시골지역 유치원에서는 각각 $189.6{\mu}g/m^{3},;74.4{\mu}g/m^{3}$이었다. 톨루엔, 크실렌, 에틸벤젠, 정량한 유기 화합물 총합, 총 휘발성 유기화합물은 기하정규분포를 하였다. 벤젠, 톨루엔, 에틸벤젠, 크실렌(BTEX)은 도시에 위치한 유치원에서 농도도 높고, 총 휘발성 유기화합물중 함량도 높았고, 시골지역에서는 농도와 상대적 함량이 낮았다. 도시지역에서는 총 휘발성 유기화합물 중 BTEX의 비중이 25.2%였고 정량한 13가지 유기화합물 중에서는 35.6%를 차지하였다. BTEX 각각 개별물질은 미국 환경보호청이 제시하는 일일 노출 기준량(Reference Concentration; RfC) 보다는 현저히 낮았다. 총 휘발성 유기화합물읜 농도는 실내가 실외 보다 높았다(I/O ratio 2.5). BTEX의 상대적 함량도 실내가 실외보다 높아 실내에도 발생원이 있음을 암시하고 있다. 자료 분석결과 유치원 실내의 벤젠은 실외로부터 유입되고 있었고, 톨루엔, 에틸벤젠, 크실렌은 실외뿐 아니라 실내에서도 발생하고 있었다. 정량한 8개 화합물 각각과 총 휘발성 유기화합물의 스피어만 상관계수는 벤젠을 제외하고는 모두 유의하였다. 이중 톨루엔과 크실렌은 총 휘발성 유기화합물과 좋은 상관성 (톨루엔 0.76, 크실렌, 0.87)을 나타내었다. 이 연구는 톨루엔과 크실렌이 총 휘발성 유기화합물의 좋은 지표를 사용될 있고, 톨루엔, 에틸벤젠, 크실렌 등 많은 휘발성 유기화합물의 발생원은 실외뿐 아니라 실내에도 있음을 나타내고 있다.

• Asian Journal of Atmospheric Environment
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• v.6 no.4
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• pp.288-303
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• 2012

In this study, real time measurements of particle number size distribution in urban Gwangju, coastal Taean, and industrial Yeosu in Korea were conducted in 2008 to understand the occurrence of ultrafine particle (UFP) (<100 nm) events, the variation of its concentration among different sampling sites, and UFP formation pathways. Also, to investigate seasonal and long-term variation of the UFP number concentration, data were collected for the period of 5 years (2007, 2008, 2010, 2011, and 2012) in urban Gwangju. Photochemical and combustion events were found to be responsible for the formation of UFP in the urban Gwangju site, whereas only photochemical event led to the formation of UFP in the coastal Taean site. The highest UFP concentration was found in industrial Yeosu (the average UFP number fractions were 79, 59 and 58% in Yeosu, Gwangju, and Taean, respectively), suggesting that high amount of gas pollutants (e.g., $NO_2$, $SO_2$, and volatile organic carbon (VOC)) emitted from industries and their photochemical reaction contributed for the elevated UFP concentration in the industrial Yeosu site. The UFP fraction also showed a seasonal variation with the peak value in spring (61.5, 54.5, 50.5, and 40.7% in spring, fall, summer, and winter, respectively) at urban Gwangju. Annual average UFP number concentrations in urban Gwangju were $5.53{\times}10^3\;cm^{-3}$, $4.68{\times}10^3\;cm^{-3}$, $5.32{\times}10^3\;cm^{-3}$, $3.99{\times}10^3\;cm^{-3}$, and $2.16{\times}10^3\;cm^{-3}$ in the year 2007, 2008, 2010, 2011, and 2012, respectively. Comparison of the annual average UFP number concentration with urban sites in other countries showed that the UFP concentrations of the Korean sites were lower than those in other urban cities, probably due to lower source strength in the current site. TEM/EDS analysis for the size-selected UFPs showed that the UFPs were classified into various types having different chemical species. Carbonaceous particles were observed in both combustion (soot and organics) and photochemical events (sulfate and organics). In the photochemical event, an internal mixture of organic species and ammonium sulfate/bisulfate was identified. Also, internal mixtures of aged Na-rich and organic species, aged Ca-rich particles, and doughnut shaped K-containing particles with elemental composition of a strong C with minor O, S, and K-likely to be originated from biomass burning nearby agricultural area, were observed. In addition, fly ash particles were also observed in the combustion event, not in the photochemical event.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.490.2-490.2
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• 2014

Since the general solar cells accept sun light at the front side, excluding the electrode area, electrons move from the emitter to the front electrode and start to collect at the grid edge. Thus the edge of gridline can be important for electrical properties of screen-printed silicon solar cells. In this study, the improvement of electrical properties in screen-printed crystalline silicon solar cells by contact treatment of grid edge was investigated. The samples with $60{\Omega}/{\square}$ and $70{\Omega}/{\square}$ emitter were prepared. After front side of samples was deposited by SiNx commercial Ag paste and Al paste were printed at front side and rear side respectively. Each sample was co-fired between $670^{\circ}C$ and $780^{\circ}C$ in the rapid thermal processing (RTP). After the firing process, the cells were dipped in 2.5% hydrofluoric acid (HF) at room temperature for various times under 60 seconds and then rinsed in deionized water. (This is called "contact treatment") After dipping in HF for a certain period, the samples from each firing condition were compared by measurement. Cell performances were measured by Suns-Voc, solar simulator, the transfer length method and a field emission scanning electron microscope. According to HF treatment, once the thin glass layer at the grid edge was etched, the current transport was changed from tunneling via Ag colloids in the glass layer to direct transport via Ag colloids between the Ag bulk and the emitter. Thus, the transfer length as well as the specific contact resistance decreased. For more details a model of the current path was proposed to explain the effect of HF treatment at the edge of the Ag grid. It is expected that HF treatment may help to improve the contact of high sheet-resistance emitter as well as the contact of a high specific contact resistance.