• Journal of Korean Society for Atmospheric Environment
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• v.31 no.3
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• pp.269-286
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• 2015

24-hr integrated $PM_{2.5}$ measurements were performed between December 2013 and October 2014 at an urban site in Gwangju and the collected samples were analyzed for organic carbon (OC), elemental carbon (EC), ionic species, and elemental species. Objectives of this study were to identify $PM_{2.5}$ pollution episodes, to characterize their chemical components, and to examine their probable origins. Over the course of the study period, average $PM_{2.5}$ concentration was $37.7{\pm}23.6$ $(6.0{\sim}121.5){\mu}g/m^3$. Concentrations of secondary ionic species; $NH_4{^+}$, $NO_3{^-}$, and $SO_4{^{2-}}$ was on average $5.54{\mu}g/m^3$ (0.28~ 20.86), $7.60{\mu}g/m^3$ (0.45~ 33.53), and $9.05{\mu}g/m^3$ (0.50~ 34.98), accounting for 13.7% (4.6~ 22.7), 18.6% (2.9~ 44.8), and 22.9% (4.9~ 55.1) of the $PM_{2.5}$ concentration, respectively. Average OC and EC concentrations were $5.22{\mu}g/m^3$ and $1.54{\mu}g/m^3$, taking possession of 4.6 and 22.2% (as organic mass) of the $PM_{2.5}$, respectively. Frequencies at which 24-hr averaged $PM_{2.5}$ exceeded a 24-hr averaged Korean $PM_{2.5}$ standard of $50{\mu}g/m^3$ (termed as an "episode" in this study) were 30, accounting for 21.3% of total 141 measurements. These pollution episodes were mostly associated with haze phenomenon and weak surface wind speed. It is suggested that secondary formation of aerosol was one important formation mechanism of the episodes. The episodes were associated with enhancements of organic mass, $NO_3{^-}$ and $SO_4{^{2-}}$ in winter, of $NO_3{^-}$ and $SO_4{^{2-}}$ in spring, and of $SO_4{^{2-}}$ in summer. Potential source contribution function results indicate also that $PM_{2.5}$ episodes were likely attributed to local and regional haze pollution transported from northeastern China in winter, to atmospheric processing of local emissions rather than long-range transport of air pollutants in spring, and to the $SO_4{^{2-}}$ driven by photochemistry of $SO_2$ in summer.

• International Commerce and Information Review
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• v.19 no.1
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• pp.155-187
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• 2017

In the US, the Sections 301 of the Trade Act of 1974 are still being used to resolve disputes. The U.S' such unilateral retaliations grounded on the Sections 301 of the Trade Act, in fact, violate the WTO agreements and hinder the development of international trade as the trade partner may assume it as a reprisal move impeding the fair settlement of disputes. Here, this study is going to examine the characteristics and functions of the WTO dispute settlement system briefly and compare the countermeasures recognized to be legitimate by the WTO with the U.S' unilateral retaliation. Also, this author will analyse the US-Japan Automobiles (DS6) and EC-Bananas III (DS27) as one of the typical cases resulted from the unilateral retaliation. According to the result, these cases do not conform to WTO-consistency, and it implies that it is absurd to accept the US' unilateral retaliation internationally. In conclusion, presently, it is a global trend to solidify protectionism, and to vitalize trade and resolve trade disputes efficiently, it is needed to prohibit the recourse to unilateral retaliations and also positively apply the WTO dispute settlement system(DSU) defining rules about how to strengthen the multilateral system.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.374-382
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• 2009

Steam generator(SG) tube, as a barrier isolating primary to the secondary coolant system of nuclear power plants(NPP), must maintain the structural integrity far the public safety and its efficient power generation capacity. And SG tubes bearing defects must be timely detected and taken repair measures if needed. For the accomplishment of these objectives, SG tubes have been periodically examined by eddy current testing(ECT) on the basis of administrative notices and intensified SG management program(SGMP). Stress corrosion cracking(SCC) on the SG tubes is not easily detected and even missed since it has lower signal amplitude and other disturbing factors against its detection. However once SCC is developed, that can cause detrimental affects to the SG tubes due to its rapid propagation rate. Accordingly SCC is categorized as prime damage mechanism challenging the soundness of the SG tubes. In this study, reproduced EDM notch specimens are examined for the detectability and quantitative characterization of the axial ODSCC by +PT MRPC probe, containing pancake, +PT and shielded pancake coils apart in a single plane around the circumference. The results of this study are assumed to be applicable fur providing key information of engineering evaluation of SCC and improvement of confidence level of ECT on SG tubes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.105-114
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• 2018

Membrane fouling in EC-MBR (Electro-Coagulation aided Membrane Bio-Reactor) processes was evaluated according to the operating parameters, such as current density and contact time. In addition, the fouling mechanism was investigated. Compared to the control (i.e., no electro-coagulation), membrane fouling for filtration of the activated sludge suspension after electro-coagulation was reduced significantly. Membrane fouling was improved further when the contact time was doubled under a low current density of $2.5A/m^2$. On the other hand, membrane fouling was not mitigated further, as expected, even though the contact time was doubled from 12 to 24 hr. at a current density of $10A/m^2$. This indicates that the overall decrease in membrane fouling is a function of the product of the current density and contact time. The particle size of the activated sludge flocs after electro-coagulation was changed slightly, which means that the membrane fouling reduction was not attributed to a larger particle size resulting from electro-coagulation. The experimental confirmed that the dynamic membrane made from aluminum hydroxide, Al(OH)3, and/or aluminum phosphate, Al(PO4), which had been formed during the electro-coagulation, played a key role on the reduction of membrane fouling. The dynamic membrane prevents the particles in the feed solution from deposition to the membrane pores and cake layers. Dynamic membrane formation as a result of electro-coagulation plays a critical role in the mitigation of membrane fouling in EC-MBR.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.11
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• pp.1087-1094
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• 2008

Diazinon is a phosphorothiate insecticide widely used in the world including Korea. This study investigates the feasibility of photolysis and photocatalysis processes for the degradation of diazinon in water. Both photolysis and photocatalysis reactiosn were effective in degrdading diazinon, however lower TOC removals were achieved. In case of photocatalysis, approximately 40% of nitrogen from diazinon was recovered as NO$_3^-$, and less than 5% of phosphorus as PO$_4{^{3-}}$. However, the sulfur in diazinon molecule was completely recovered to SO$_4{^{2-}}$ from photocatalysis reaction, and the recovery from photolysis was 50%, indicating that P=S bond easily breaks first during photolysis and photocatalysis. The poor recoveries of ionic byproducts and TOC from photolysis and photocatalysis indicate the presence of other organic intermediates during reactions. The formation of organic intermediates were identified during reactions using GC/MS and LC/MS/MS, and the main degradation products were diazoxon, and 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMP), respectively. Finally, the acute 48-hr toxicity test using Daphnia magna were employed to measure the toxicity reduction during photocatalysis of degradation. The results showed that the toxicity increased until 180 min of the photocatalysis reaction (from EC$_{50}$ (%) of 69.6 to 13.2%), however, acute toxicity completely disappeared (>100%) after 360 min. The toxicity results showed that the intermediates from photocatalysis such as diazoxon were more toxic than diazinon itself, however these intermediates can be degraded or mineralized with further reaction.

• Journal of the Korean Electrochemical Society
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• v.5 no.3
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• pp.111-116
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• 2002

Electrochemical scanning tunneling microscopy was employed to study the evolution of surface morphology during electrochemical preparation of Si(111)-H from Si(111) oxide. Anodic dark current of cyclic voltammogram in 0.2M $NH_4F$ solution (pH 4.7) decreased as the number of cycles increased and remained nearly constant after the second cycle. Then, the Si(111) oxide was entirely stripped, which was followed by H termination on the Si(111) surface. Hydrides at kink and step sites were etched more rapidly than on the terrace, which remained triangle pits with [112] oriented steps where existed stable monohydride. Then, triangle pits deepened. During chronomamperometry at 0.4V anodic dark current shoulder appeared and decreased slowly, indicated the stripping of Si(111) oxide and the formation of stable (112) oriented steps with monohydride. Additionally, the etching mechanism of Si(111)-H in 0.2M $NH_4F(pH 4.7)$ solution at +0.4V was discussed.

• Journal of Life Science
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• v.28 no.1
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• pp.1-8
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• 2018

To confirm the function of lactate dehydrogenase (LDH) (EC 1.1.1.27, LDH), its metabolism was studied by activity, kinetics, and isozyme analysis in tissues of Ldh testis-specific C expressing mice (Mus musculus) maintained in a state of starvation for 48 hr and 96 hr. In skeletal muscle, liver, and eye tissues, LDH and LDH $A_4$ activity increased and anaerobic metabolism predominated. While LDH activity in the heart and kidney tissues decreased, LDH $B_4$ activity increased and aerobic metabolism predominated, producing pyruvic acid. In the testis tissue, LDH $C_4$ activity decreased. In the brain tissue, LDH activity increased, but the isozyme change was small and the amount of pyruvic acid decreased. $K{_m}^{PYR}$ increased in tissues other than kidney tissue, and the affinity for pyruvic acid decreased. Consequently, in Ldh-A and B-expressing tissues, the activities of isozymes with higher concentrations increased. However, in Ldh-A, B, and C-expressing tissue, $C_4$ decreased and the function of the tissue also decreased. In particular, LDH in brain tissue played a role as a pyruvate reductase. Therefore, this process might be the mechanism for producing energy in the state of starvation.

• The Korean Journal of Ecology
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• v.26 no.3
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• pp.109-114
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• 2003

To investigate ecophysiological characteristics of plants species adapted to moor habitat, we selected 22 species plants and analyzed inorganic cations (K, Ca, Mg), heavy metals (Al, Fe, Mn) and total nitrogen and phosphorus quantitatively. Moojechi moor indicated typical acidic and oligotrophic conditions with pH of 5.0∼5.6 (pH 4.3∼5.1 in soil) and EC of 15∼30μ S/cm, and contained very low contents of soil divalent cation such as Ca and Mg but high contents of heavy metals (esp. Al). With respect to inorganic cation contents, investigated plants species showed remarkable interspecific difference. Plant species belonging to J. effusus var. decipiens, M. japonica, I. globosa, M. sacchariflorus, R. mucronulatum, R. yedoense var. poukhanense, H. micrantha, D. rotundifolia showed very low contents of inorganic cation below 400 μ M/g DW, but plant species of C. palustris var. spontanea, L. sessilifolia, P. mandarinorum, C. lineare, S. austriaca sub. glabra, V. mandshurica, A. decursiva showed high cation contents in leaves. Especially, S. austriaca sub. glabra (Compositae) and V. mandshurica (Violaceae) showed pattern accumulating Ca and Mg with plant growth, but I. ensata var. spontanea (Iridaceae) and S. officinalis (Rosaceae) showed decreasing tendency. Meanwhile, most plant species showed low contents of soluble metal ions in leaves in spite of high heavy metal contents on soil, and indicated remarkable interspecific differences in the total contents and composition of heavy metals accumulated. Despite low contents of N and P on soil, most plant species indicated relatively high contents of N and P in leaves at the early stage of growth, and showed slowly decreasing pattern according to growth. Consequently, it seems that plant species inhabited on Moojechi moor cope with acidic-oligotrophic conditions, accumulating inorganic cations and nitrogen at the early growing stage and reutilizing them in the course of growth, and developing heavy metal excluding mechanism.

• Biomolecules & Therapeutics
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• v.22 no.6
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• pp.510-518
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• 2014

Chronic (>24 h) exposure of arsenite, an environmental toxicant, has shown the decreased nitric oxide (NO) production in endothelial cells (EC) by decreasing endothelial NO synthase (eNOS) expression and/or its phosphorylation at serine 1179 ($eNOS-Ser^{1179}$ in bovine sequence), which is associated with increased risk of vascular diseases. Here, we investigated the acute (<24 h) effect of arsenite on NO production using bovine aortic EC (BAEC). Arsenite acutely increased the phosphorylation of $eNOS-Thr^{497}$, but not of $eNOS-Ser^{116}$ or $eNOS-Ser^{1179}$, which was accompanied by decreased NO production. The level of eNOS expression was unaltered under this condition. Treatment with arsenite also induced reactive oxygen species (ROS) production, and pretreatment with a ROS scavenger N-acetyl-L-cysteine (NAC) completely reversed the observed effect of arsenite on $eNOS-Thr^{497}$ phosphorylation. Although protein kinase C (PKC) and protein phosphatase 1 (PP1) were reported to be involved in $eNOS-Thr^{497}$ phosphorylation, treatment with PKC inhibitor, Ro318425, and overexpression of various PKC isoforms did not affect the arsenite-stimulated $eNOS-Thr^{497}$ phosphorylation. In contrast, treatment with PP1 inhibitor, calyculin A, mimicked the observed effect of arsenite on $eNOS-Thr^{497}$ phosphorylation. Lastly, we found decreased cellular PP1 activity in arsenite-treated cells, which was reversed by NAC. Overall, our study demonstrates firstly that arsenite acutely decreases NO production at least in part by increasing $eNOS-Thr^{497}$ phosphorylation via ROS-PP1 signaling pathway, which provide the molecular mechanism underlying arsenite-induced increase in vascular disease.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.148-158
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• 2022

The electrochemical CO₂ reduction (ECR) to produce value-added fuels and chemicals using clean energy sources (like solar and wind) is a promising technology to neutralize the carbon cycle and reproduce the fuels. Presently, the ECR has been the most attractive route to produce carbon-building blocks that have growing global production and high market demand. The electrochemical CO₂ reduction could be extensively implemented if it produces valuable products at those costs which are financially competitive with the present market prices. Herein, the electrochemical conversion of CO₂ obtained from flue gases of a power plant to produce diesel and formic acid using a consistent techno-economic approach is presented. The first scenario analyzed the production of diesel fuel which was formed through Fischer-Tropsch processing of CO (obtained through electroreduction of CO₂) and hydrogen, while in the second scenario, direct electrochemical CO₂ reduction to formic acid was considered. As per the base case assumptions extracted from the previous outstanding research studies, both processes weren't competitive with the existing fuel prices, indicating that high electrochemical (EC) cell capital cost was the main limiting component. The diesel fuel production was predicted as the best route for the cost-effective production of fuels under conceivable optimistic case assumptions, and the formic acid was found to be costly in terms of stored energy contents and has a facile production mechanism at those costs which are financially competitive with its bulk market price. In both processes, the liquid product cost was greatly affected by the parameters affecting the EC cell capital expenses, such as cost concerning the electrode area, faradaic efficiency, and current density.