• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.2
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• pp.202-210
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• 2015

Objectives: The purpose of this study was to examine clean room(C/R) structure, air conditioning and contamination control systems and to provide basic information for identifying a correlation between the semiconductor work environment and workers' disease. Methods: This study was conducted at 200 mm and 300 mm semiconductor wafer fabrication facilities. The C/R structure and air conditioning method were investigated using basic engineering data from documentation for C/R construction. Furthermore, contamination parameters such as airborne particles, temperature, humidity, acids, ammonia, organic compounds, and vibration in the C/R were based on the International Technology Roadmap for Semiconductors(ITRS). The properties of contamination control systems and the current status of monitoring of various contaminants in the C/R were investigated. Results: 200 mm and 300 mm wafer fabrication facilities were divided into fab(C/R) and sub fab(Plenum), and fab, clean sub fab and facility sub fab, respectively. Fresh air(FA) is supplied in the plenum or clean sub fab by the outdoor air handling unit system which purifies outdoor air. FA supply or contaminated indoor air ventilation rates in the 200 mm and 300 mm wafer fabrication facilities are approximately 10-25%. Furthermore, semiconductor clean rooms strictly controlled airborne particles(${\leq}1,000{\sharp}/ft^3$), temperature($23{\pm}0.5^{\circ}C$), humidity($45{\pm}5%$), air velocity(0.4 m/s), air change(60-80 cycles/hr), vibration(${\leq}1cm/s^2$), and differential pressure(atmospheric pressure$+1.0-2.5mmH_2O$) through air handling and contamination control systems. In addition, acids, alkali and ozone are managed at less than internal criteria by chemical filters. Conclusions: Semiconductor clean rooms can be a pleasant environment for workers as well as semiconductor devices. However, based on the precautionary principle, it may be necessary to continuously improve semiconductor processes and the work environment.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.31-37
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• 2013

Lowering surface reflectance of Si wafers by texturization is one of the most important processes for improving the efficiency of Si solar cells. This paper presents the results on the effect of texturing using acidic solution mixtures containing the catalytic agents to moderate etching rates on the surface morphology of mc-Si wafer as well as on the performance parameters of solar cell. It was found that the treatment of contaminated crystalline silicon wafer with $HNO_3-H_2O_2-H_2O$ solution before the texturing helps the removal of organic contaminants due to its oxidizing properties and thereby allows the formation of nucleation centers for texturing. This treatment combined with the use of a catalytic agent such as phosphoric acid improved the effects of the texturing effects. This reduced the reflectance of the surface, thereby increased the short circuit current and the conversion efficiency of the solar cell. Employing this technique, we were able to fabricate mc-Si solar cell of 16.4% conversion efficiency with anti-reflective (AR) coating of silicon nitride film using plasma-enhanced chemical vapor deposition (PECVD) and Si wafers can be texturized in a short time.

• Economic and Environmental Geology
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• v.53 no.3
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• pp.235-244
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• 2020

Copper (Cu), one of the main contaminants in the mine drainage from the closed mine area, needs to be removed before exposed to environment because of its toxicity even in the low concentration. In this study, passive treatment based field pilot experiments using limestone and compost media were conducted during 9 months for enhancing Cu removal efficiency of the mine water treatment facility of S mine located in Goseong, Gyeongsangnam-do in South Korea. The pH increase and Cu removal efficiency showed high value at Successive Alkalinity Producing System ( SAPS) > Reducing and Alkalinity Producing System (RAPS) > limestone reactor in a sequence. The compost media using in SAPS and RAPS contributed to raise pH by organic material decomposition with generating alkalinity, thus, Cu removal efficiency increased. Also, experimental results showed that Cu removal efficiency was proportional to pH increase, meaning that pH increase is the main mechanism for Cu removal. Moreover, Sulfate Reduction Bacteria (SRB) was identified to be most activated in SAPS. It is inferred that the sulfate reduction reaction also contributed to Cu removal. This study has the site significance in that the experiments were conducted at the place where the mine water generates. In the future, the results will be useful to select the more effective reactive media used in the treatment facility, which is most appropriate to remediate mine water from the S mine.

• Korean Journal of Ecology and Environment
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• v.44 no.2
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• pp.103-112
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• 2011

Aquatic contamination by organic pollutants has been a suspected reason for rapid decrease of amphibian populations whose embryonic and larval stages are in an aquatic environment. Amphibian embryos can be a useful model to study the ecoctoxicologial impacts of aquatic pollutants. The obtained toxicological data are useful references for the management of aquatic pollutants in public health because amphibia share many developmental events with terrestrial vertebrates including humans. Safety guidelines for the toxicological effects of aquatic contaminants of chemicals identified as hazardous should be addressed at multiple endpoints. Alkylphenols have been widely-used in agricultural, industrial, and household activities; they contaminate and can persist in aquatic environments. Exposure to alkylphenols results in endocrine disruption in aquatic animals. In this review, we summarize the developmental toxicities of alkylphenols in amphibian embryos and larva according to the exposure route, chemical concentration, duration of exposure, and affected developmental stage together with mechanisms of toxicity and typical patterns of developmental abnormality. The merits of amphibian embryos as a toxicity test model for mid- to long-term exposure to aquatic pollutants are discussed proposed.

• Journal of the Korean GEO-environmental Society
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• v.15 no.7
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• pp.5-11
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• 2014

Both ultraviolet (UV) and ultrasound (US) systems are used in degrading of organic contaminants and they can thus be applicable simultaneously as an UV/US hybrid system in attempts further to increase the degradation efficiency. The pseudo-first order degradation rate constants with the UV, US and UV/US hybrid irradiation were 2.60, 10.34, and $14.81{\times}10^{-3}min^{-1}$, respectively. It was observed that the synergistic effect of UV/US hybrid system for degrading the bis (2-ethylhexyl) phthalate (DEHP). The highest rate of DEHP degradation was found during UV/US hybrid irradiation and the synergistic effect factor (SEF) was calculated to be 1.15 based on the pseudo-first order degradation rate constants. Results indicate that synergistic effect of UV/US hybrid system is closely correlated to the enhancement of sonochemical reactivity with the UV-US interaction of increasing the formation rate of OHby providing additional $H_2O_2$ production through the pyrolysis of water molecules during UV/US hybrid irradiation.

• Water for future
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• v.24 no.3
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• pp.49-60
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• 1991

As a second part of the study entitled "Field Measurement and Analysis of Fluvial Sediment in the Cheongmi-Strea", this study concerns mineralogical and contaminative characteristics of sediment particles collected at Wonbu-Gyo and Hanpyeong-Gyo in the Cheongmi-Stream. The mineralogical analysis of the bed sediment collected reveals that, in general , quarz is the most abundant mineral found in sands with feldspars and rock fragments in the next, which confirms what is known in the literature. The shape factor of sand particles is about 0.7, which also agrees to what is known in the foreign literature. The analysis also reveals that the clay particles collected are composed mainly of illite, kaolinate, and chlorite. The analysis of contamination reveals that there is no substantial difference between the contents of organic material and heavy metals in the surface water and those in the pore water beneath the river bed. It is because the sampling for this analysis was conducted right after the September flood during which the fresh top soil from the upstream watershed replaced the old bed sediment and pore water that would probably be more contaminated. The contents of geavy metals in the bed sediment of sand particles do not exceed those in the soils adjacent to the river. For fine sediment such as clays, however, the contents of heavy metals, especially of mercury and zinc, far exceed those in the soils adjacent to the river. These fine sediments are transported downstream in the form of wash load and deposited in part on flood plains, which could be a new source of contaminants.taminants.

• Journal of Hydrogen and New Energy
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• v.24 no.1
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• pp.44-49
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• 2013

Hydrogen penetration into a metal leads to damages and mechanical degradations and its content measurement is of importance. For a precise measurement, a sample preparation procedure must be optimized through a series of studies on sample washing and drying. In this study, two-step washing with organic solvents and thermal soaking in inert gas were tried with a rod-shaped, API X65 steel sample. The samples were machined from a steel plate and then washed in acetone and etyl-alcohol for 5 minute each and dried with compressed air. After then, the samples were thermally soaked in a home-made nitrogen gas chamber during 10 minute at different heat gun temperatures from 100 to $400^{\circ}C$ and corresponding temperature range in the soaking chamber was from 77 to $266^{\circ}C$ according to the temperature calibration. Hydrogen residue in the samples was measured with a hot extraction system after each soaking step; hydrogen residue of $0.70{\pm}0.12$ wppm after the thermal soaking at $77^{\circ}C$ decayed with increase of the soaking temperature. By adopting the heat transfer model, decay behavior of the hydrogen residue was fitted into an exponential decay function of the soaking temperature. Saturated value or lower bound of the hydrogen residue was 0.36 wppm and chamber temperature required to lower the hydrogen residue about 95% of the lower bound was $360^{\circ}C$. Furthermore, a thermal desorption spectroscopy was done for the fully soaked samples at $360^{\circ}C$. Weak hydrogen peak was observed for whole temperature range and it means that hydrogen-related contaminants of the sample surface are steadily removed by heating. In addition, a broad peak found around $400^{\circ}C$ means that parts of the hydrogen residue are irreversibly trapped in the steel microstructure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.17-25
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• 2016

In this study, the air quality of underground and overground railway stations was evaluated focusing on the degree of influence of the outside air quality. The measured components were particulate matter ($PM_{10}$), carbon dioxide ($CO_2$), carbon monoxide (CO), nitrogen dioxide ($NO_2$), formaldehyde (HCHO), ozone ($O_3$), total airborne bacteria (TAB), total volatile organic carbon (TVOC), and Radon (Rn), which are included in the maintenance standards and recommended standards of the Indoor Air Quality Management Act. Also, the indoor/outdoor concentration ratios of $PM_{10}$, $NO_2$, and $O_3$ were calculated to estimate the influence of the outdoor air quality. The concentrations of $PM_{10}$ HCHO, TVOC, $NO_2$, and Rn in the underground stations were found to be higher than those in the overground stations. These results indicate that the (present) generation of contaminants are caused by the indoor source of the underground station. The ozone concentration of the overground stations was higher than that of the underground stations, which indicates that the outdoor ozone concentration influenced that of the overground stations directly. Thus, methods of improving the IAQ should take into consideration the types of contamination.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1204-1210
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• 2014

New control methods are proposed for indoor air quality by removing fine airborne dust-particles. As suspended fine dust-particles contain inorganic dust as well as fine organic bacteria, studies for simultaneous control of these contaminants are required. In this study, photocatalytic disinfection of indoor suspended microorganisms such as E. coli and Bacillus subtilis is performed by three types of photocatalysts with UVA irradiation. The UVA irradiation strength was controlled to the minimum $3{\mu}W/cm^2$, and ZnO, $TiO_2$, and ZnO/Laponite ball were used as the catalysts. The results indicate that E. coli was removed over 80 % after about 2 hours of reaction with UVA and all three types of photocatalysts, whereas only with UVA, around 50 % E. coli removal was obtained. Among the catalysts, ZnO/Laponite composite ball was found to have similar sterilizing capacity to $TiO_2$. However, in case of B. subtilis, which has thick cell wall in its spore state, disinfection was not effective under the low UVA irradiation condition, even with the catalysts. Further studies need to figure out the optimal UVA irradiation ranges as well as photocatalysts doses to control airborne dust, to provide healthy clean air environment.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.2
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• pp.313-321
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• 1996

Our laboratoy has been participated in Proficiency Analytical Testing (PAT) program which is operated by the Americal Industrial Hygiene Association in cooperation with the National Institute for Occupational Safety and Health (NIOSH). The program is designed to assist a laboratory improve its analytical performance by providing samples on a quarterly basis, evaluating the results, and providing reports on how well the laboratory performed. Evaluation of the results reported here covers five rounds of the PAT program (round 121~round 125). The way a laboratory is evaluated by PAT program is as follows: 1) There is no overall proficiency rating given to a laboratory. 2) A proficiency rating is given for each type of analyze (i.e., metals, silica, asbestos, solvents) that a laboratory analyzed. 3) Proficiency is rated acceptable ("A") if Z score lies between -3 and +3, and unacceptable if Z score is either higher than +3 ("H") or lower than -3 ("Lo"). Z score = (reported data - reference value) / standard deviation 4) For a laboratory to be rated proficient it must either have had no outliers over the most recent two rounds or of the samples actually analyzed over the past year (past four rounds), 75 % or more of the analyze sample results must be acceptable. According to the above rating criteria of PAT program, performance of metals including cadmium, lead, chromium and zinc, and asbestos sample analyses were rated acceptable ("A"). For silica analyses, all samples except one out of four samples in round 122 was rated high("H") were acceptable showing 95 % of ing 95 % of acceptance rate (19/20) throughout the rounds. Analyses of organic solvents were done on 52 samples in 9 types including methanol(MOH), 1,1,1-trichloroethane(MCM), tetrachloroethylene(PCE), trichloroethylene(TCE), benzene(BNZ), o-xylene(OXY), toluene(TOL), chloroform(CFM), 1,2-dichloroethane(DCE). All samples analyzed were rated acceptable except 2 samples that were rated high; one out of each four MCM and TCE samples in round 121, and one that was low out of four o-xylene analyses in round 122 indicating 94 % of acceptance rate(49/52) throughout the rounds. According to the laboratory rating criteria, our laboratory is rated proficient so far for all types of contaminants.