• Journal of the Mineralogical Society of Korea
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• v.27 no.2
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• pp.73-83
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• 2014

In order to investigate selective phase transformations and to determine the maximum Au leaching factors from microwave treated Au-bearing complex sulfides, a microscope, SEM-EDS analysis, and thiocyanate leaching tests were performed. When the Au-bearing complex sulfides were exposed to microwave heating, increasing the microwave exposure time increased temperature and decreased weight. Arsenopyrite was first selectively transformed to hematite, which formed a concentric rim structure. In this hematite, oxygen and carbon was detected and always showed high iron content and low arsenic content due to arcing and oxidation from microwave heating. The results of the leaching test using microwave treated sample showed that the maximum Au leaching parameters was reached with 0.5 g concentration thiocyanate, 2.0 M hydrochloric acid, 0.3 M copper sulfate and leaching temperature at$60^{\circ}C$. Under the maximum Au leaching conditions, 59% to 96.69% of Au was leached from the microwave treated samples, whereas only 24.53% to 92% of the Au was leached from the untreated samples.

• Korean Journal of Environmental Biology
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• v.28 no.4
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• pp.212-217
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• 2010

Soil pollution by heavy metals has become a significant environmental concern due to a variety of human activities. Specially toxicity caused by excessive mercury exposure is now being recognized as a widespread environmental problem and is continuing to attract a great deal of public concerns. The earthworms are very important animals that aerate the soil with their burrowing action and enrich the soil by decomposing organic matters. Especially the earthworm Eisenia fetida is routinely used in ecotoxicological studies. The levels of DNA damage in earthworms treated with HgCl2 and ionizing radiation were investigated in this study. Genotoxic effects were evaluated in the earthworm's coelomocytes using the comet assay (Single Cell Gel Electrophoresis; SCGE). The results showed that the mercury chloride and radiation were responsible for the genotoxic effects on earthworms. The level of DNA damage significantly increased after the treatment of mercury chloride combined with ionizing radiation. The combined treatment of $HgCl_2$ and ionizing radiation had a greater genotoxicity. This study is amenable to further study such as enzyme activation assay.

• Korean Journal of Ichthyology
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• v.23 no.1
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• pp.61-69
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• 2011

Gene and promoter structures of metallothionein(MT) from Miho spine loach (Cobitis choii; Cypriniformes) were characterized, and the transcriptional responses to experimental exposures to heavy metals and heat stress were examined. The C. choii metallothionein displayed well-conserved features of teleostean metallothioneins at gDNA, mRNA and amino acid levels. Bioinformatic analysis predicted that the C. choii MT regulatory region potentially possessed various motifs or elements targeted by various transcription factors associated with metal-coordinating regulation (e.g., metal transcription factor-1), immune responses (e.g., nuclear factor kappa B), and thermal modulations (e.g., heat shock factor). Acute heavy-metal exposures to 0.5 or $1.0\;{\mu}M$ of cadmium (Cd), copper (Cu), manganese (Mn), nickel (Ni) or zinc (Zn) showed that MT transcription was significantly stimulated by Cd (9.6-fold relative to non-exposed control) and Cu (10.4-fold), only moderately by Mn (2.4-fold), but hardly by Ni and Zn. Elevation of water temperature from $25^{\circ}C$ to $31^{\circ}C$ caused a rapid modulation of MT mRNAs toward upregulation to 9.5-fold; however, afterward the elevated mRNA level slightly decreased during further incubation at $31^{\circ}C$ for 6 h. Results from this study suggest that MT-based expression assay could be a useful basis for better understanding the metal- and/or heat-caused stresses in this endangered fish species.

• The Journal of the Korea Contents Association
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• v.12 no.5
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• pp.323-330
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• 2012

The purpose of this study was to examine the occurrence level of harmful chemical substance and the riskiness caused by it at university laboratory, which had been faintly interested in safe health management. It measured and analyzed indoor pollutants by academic department targeting K university where is located in Seoul Metropolis for 6 days starting from May 26, 2010. As a result, the appearance of being furnished with MSDS, the appearance of installing the exposure-reduction facilities, and the present status of supplying protective equipment in order to grasp the present status of managing harmful chemical substance at university laboratory were relatively good in management at the Dept. of Chemistry, the Dept. of Physics, and the Dept. of Medical Science, which are basic science laboratories. The activity for managing harmful chemical substance in the Dept. of Dental Medicine and the Dept. of Fine Arts was surveyed to be insufficient. Also, the concentration of formaldehyde and TVOCs(total volatile organic compounds) inside laboratory was detected noticeably highly in the Dept. of Fine Arts compared to other laboratories. The concentration of formaldehyde in a group, which was collectivized by similar academic department, was indicated to be higher in other academic departments including the Dept. of Fine Arts and the Dept. of Life Science, thereby having shown significant difference. The concentration of formaldehyde and TVOCs showed significant difference at the laboratory without installation compared to the laboratory with installation of fume hood. Seeing the above results, it could be known that a whole drop in recognition on influence of chemical upon health leads to being able to increase occurrence level of hazardous factor due to being insufficient in activity of protecting exposure to chemical substance.

• Journal of Life Science
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• v.21 no.11
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• pp.1636-1640
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• 2011

Alzheimer's disease (AD) is a progressive neurodegenerative disease, resulting in the loss of cognitive function. Mitochondrial aldehyde dehydrogenase (ALDH2) has been proposed to be a risk factor for the development of AD, but there is still controversy about that. In this study, we demonstrated the role of ALDH2 enzyme activity on amyloid-beta (A${\beta}$) and nuclear factor kappa B (NF-${\kappa}B$) expression in mice brain following ethanol exposure for 8 weeks. Five male Aldh2 (+/+) and Aldh2 (-/-) mice, 8 weeks-old of age (C57BL/6J strain), in each group were exposed to ethanol for 8 weeks (2 g/kg wt./day) using gavage. Those in the control groups received 0.9% saline alone. Results showed a difference in expression level of A${\beta}$ in the hippocampus after ethanol exposure according to the ALDH2 enzyme activity (p<0.05), but not in the level of NF-${\kappa}B$). Our results suggest a possibility that ALDH2 enzyme activity may be an important role in the development of AD.

• The Korean Journal of Malacology
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• v.31 no.1
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• pp.1-8
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• 2015

This study was conducted to investigate the effects of elevated water temperature (WT) on biochemical and immunological factors in the hemolymph of the abalones, Haliotis discus hannai and H. discus discus. The abalone were exposed to various WT; 20, 22, 24, 26 and $28^{\circ}C$ for 4 days. In the control and $20^{\circ}C$, total-protein (TP), glucose and calcium (Ca) in hemolymph of H. discus discus were higher than the values in H. discus hannai. The values of magnesium (Mg), alkaline phosphatase (ALP) and lysozyme in H. discus hannai were similar to the H. discus discus in the control. There were no significant alterations in TP, glucose and Mg levels of hemolymph in H. discus hannai and H. discus discus by WT increases. The values of Ca, ALP and lysozyme were increased in H. discus hannai exposed to the high temperature (26 and $28^{\circ}C$) compared to control, while the values in H. discus discus were not significant difference between the WT groups. The phenoloxidase (PO) activity was increased in hemolymph of H. discus hannai exposed to high temperature (${\geq}24^{\circ}C$) compared to the control (P < 0.05). These physiological and immunological parameters were significantly changed in H. discus hannai. However, these parameters in H. discus discus were barely altered at the high WT (P < 0.05). These results suggested that H. discus hannai is considered to be more sensitive than H. discus discus at the high WT.

• Journal of the Mineralogical Society of Korea
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• v.28 no.4
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• pp.309-323
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• 2015

This study was initiated to propose the method for human risk assessment suitable to metal mine area. Using a variety of exposure parameters extracted from the investigation of abandoned metal mines, the proposed method was applied to assess the risk of As and heavy metal contamination for inhabitants (male and female adults and child) within an abandoned mine area. Based on the results of risk assessment, in addition, target remediation concentrations of each media (soil, groundwater, and surface water) were estimated. The results indicate that total carcinogenic risk (TCR) and hazard index (HI) representing carcinogenic and non-carcinogenic risks, respectively, were calculated to exceed the tolerable levels (1.00E-6 and 1) with regard to two exposure pathways (groundwater and crop intakes) and As. Thus, the human risk of study area was evaluated to be significant. Based on the target risk (TR) for carcinogens, the remediation concentrations of soil were computed to be 6.83~6.85 mg/kg and 18.41~18.46 mg/kg for As and Pb, respectively. In terms of target hazard index (THI) for non-carcinogens, the remediation concentrations of soil were calculated to be 17.38 mg/kg for Cu and 9.13 mg/kg for As.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.492-498
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• 2022

Process control systems used in most domestic petrochemical corporates today are based on the Windows platforms. As technology leans toward opened environment, the exposure risk of control systems is increasing. However, not many companies are preparing for various cyberattacks due to lack of awareness and misunderstanding of cyber intrusion. This study investigated the extent of how much exposed the petrochemical process control system is to security threats and suggested practical measures to reduce OT cybersecurity vulnerabilities. To identify the cyber threat status of process control systems, vulnerabilities of the Windows platform, a principal cyber threat factor, have been analyzed. For research, three major DCS providers in Korea and the discontinuation of Windows platform of 635 control systems were investigated. It was confirmed that 78% of the survey subjects were still operating in the discontinued windows platforms, and those process control systems were operated in a state vulnerable to cyber intrusions. In order to actively cope with these cyber threats, legal regulations such as designation of critical infrastructure for major petrochemical facilities which is implemented in advanced countries such as the United States are needed. Additionally, it is necessary to take the initiative in eradicating security threats to the process control systems by aggressively introducing security solutions provided from existing DCS suppliers. This paper was submitted to Professor Ko JaeWook's retirement anniversary issue.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5A
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• pp.433-442
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• 2010

A control of chloride diffusion coefficient is very essential for service life of reinforced concrete (RC) structures exposed to chloride attack so that much studies have been focused on this work. The purpose of this study is to derive the intended diffusion coefficient which satisfies intended service life and propose a technique for optimum concrete mixture through genetic algorithm(GA). For this study, 30 data with mixture proportions and related diffusion coefficients are analyzed. Utilizing 27 data, fitness function for diffusion coefficient is obtained with variables of water to binder ratio(W/B), weight of cement, mineral admixture(slag, flay ash, and silica fume), sand, and coarse aggregate. 3 data are used for verification of the results from GA. Average error from fitness function is observed to 18.7% for 27 data for diffusion coefficient with 16.0% of coefficient of variance. For the verification using 3 data, a range of error for mixture proportions through GA is evaluated to 0.3~9.3% in 3 given diffusion coefficients. Assuming the durability design parameters like intended service life, cover depth, surface chloride content, and replacement ratio of mineral admixture, target diffusion coefficient, where exterior conditions like relative humidity(R.H.) and temperature, is derived and optimum design mixtures for concrete are proposed. In this paper, applicability of GA is attempted for durability mixture design and the proposed technique would be improved with enhancement of comprehensive data set including wider range of diffusion coefficients.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.130-137
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• 2023

By using XRF (X-ray fluorescence), this study investigates the variation of chemical properties in cement pastes at elevated temperatures. High-temperature conditions were prepared by using an electric furnace, planning a total of 11 target temperatures ranging from room temperature to 1000 ℃. A standard library of geo-quant basic was applied for the analysis of 12 elements in cement paste, including Ca, Si, Al, Fe, S, Mg, Ti, Sr, P, Mn, Zn and K. The results revealed that, as the temperature increased, the proportion of each element in the cement paste also increased. With the exception of a few elements present in extremely low amounts in the cement pastes, the variation in the composition ratio of most elements exhibited a strong correlation with temperature, with an R-squared value exceeding 0.98. In this study, cement pastes exposed to normal and high-temperature environments were compared. The authors established that the reasons for the different results in this comparison can be explained from the same perspective as when comparing raw cement with cement paste. Furthermore, this study discussed the potentially most dominant parameter when investigating the properties of cement paste using XRF.