• Journal of Korean Society for Atmospheric Environment
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• v.18 no.6
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• pp.465-474
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• 2002

In order to reflect variability due to exposure factors as well as to assess uncertainty associated with cancer risk posed by airborne trace metals, a Monte Calro analysis has been made in this study. Input parameters for Monte Carlo analysis were developed or adjusted using body weight, lifetime, and exposure frequency of Koreans. Ambient distributions of toxic metals were founded to be lognormal distributions for most of them using goodness-of-fit tests. Thus, the 95% UCL and 95% LCL of carcinogenic metals were estimated by H-statistic method for lognormal distribution, respectively. The results of Monte Carlo analysis of 95% UCL showed that the 95th percentile risks for men and women were 1.2 and 1.1 times higher than an acceptable risk of 10$^{-5}$ , respectively. The probabilities which those risks exceed the acceptable risk were estimated to be 8% and 6%, respectively, while to be 95% and 94%, respectively on the basis of the minimum acceptable risk of 10$^{-6}$ , respectively. Approximately 90% of total cancer risk came from human carcinogens such as arsenic and hexavalent chromium. Therefore, it is necessary to properly manage both arsenic and hexavalent chromium emissions in the study area.

• Journal of Welding and Joining
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• v.16 no.4
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• pp.73-82
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• 1998

This paper is especially concerned with the weldment between support beam and square bar that plays important roles in control box of Expansion Joint as a brdige structure. Fatigue strength ({TEX}$$\sigma$_{ult}${/TEX}) of the weldment is dependent on notch factor ({TEX}$K_{f}${/TEX}) become important factors to predict fatigue life. The fatigue notch sensitivity (η) for metals can be divided into two types ; high and low notch sensitivity. In this work, the Expansion Joint weldment was found to have low notch sensitivity. The maximum strain distribution during static loading is similar to the FEM analysis. Fatigue test of real structure was performed up to {TEX}$10^{6}${/TEX} cycles to be compared with predicted endurance limit.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.3
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• pp.42-49
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• 1993

Recently, because the lubricating oil showed a tendency to be emulsified and oxidized by high speed, high output and the extension of maintenance & conservation of marine engine, the cavitation erosion-corrosion at such an environment became a big problem on effective performance of engine. Therefore, there was a need to study the behavior and protection of erosion-corrosion damage, and then applied inhibitor to a protective method of cavitation erosion- corrosion damage. At this time, test environments were marine lubricating oil & various emulsified oil that mixed distilled water and sea water etc., and also used 20KHz, 24.mu.m piezoelectric vibrator as an experimental apparatus of cavitation erosion. With this apparatus, we investigated an influence of the emulsified oil on characteristics of erosion-corrosion and protection for erosion-corrosion by inhibitor at slide bearing metals.

• Transactions of Materials Processing
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• v.9 no.1
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• pp.59-65
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• 2000

Most studies of failure analysis in ductile metals have been based on the classical plasticity theory using the local constitutive relations. These frequently yields a physically unrealistic solution, in which a numerical prediction of the onset of a deformation localization shows an inherent mesh-size sensitivity. A one way to remedy the spurious mesh sensitivity resulted in the unreasonable results is to incorporate the non-local plasticity into the simulation model, which introduce an internal (material) length-scale parameter into the classical constitutive relations. In this paper, a non-local version of the modified Gurson constitutive relation has been introduced into the finite element formulation of the simulation for plane strain compression of the visco elastic-plastic void material. By introducing the non-local constitutive relations we could successfully removed the inherent mesh-size sensitivity for the prediction of the deformation localization. The effects of non-local constitutive relation are discussed in terms of the load-stroke curve and the strain distributions accross the shear band.

• Ocean Science Journal
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• v.40 no.2
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• pp.61-66
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• 2005

Benthic amphipod, Grandidierella japonica widely inhabits the Korean coastal waters and is developed as a standard test species for sediment toxicity tests. We exposed G. japonica to various pollutants including 4 kinds of inorganic metals (Ag, Cd, Cu and Hg), tributyltin [TBT], ammonia and 7 polycyclic aromatic hydrocarbon (PAH) compounds (acenaphthene, chrysene, fluoranthene, fluorene, naphthalene, phenanthrene and pyrene) to estimate the no observed effect concentration (NOEC) and the median lethal concentration (LC50) of each pollutant during the 96-hour acute exposure. Among all tested pollutants, TBT was most toxic to G. japonica, and Rg was most toxic among inorganic metals. The toxicity of pyrene to G. japonica was greatest among PAH compounds, followed by fluoranthene, phenanathrene, acenaphthene, fluorene and naphthalene. The toxicity of PAH compounds was closely related to their physico-chemical characteristics such as $K_ow$ and water solubility. G. japonica responded adequately to pollutant concentrations and exposure durations, and the sensitivity of G. japonica to various inorganic and organic pollutants was generally comparable to other amphipods used as standard test species in ecotoxicological studies, indicating this species can be applied in the assessment of environments polluted by various harmful substances.

• Fisheries and Aquatic Sciences
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• v.16 no.3
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• pp.187-194
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• 2013

Microalgae are sensitive indicators of environmental changes, and hence they are widely used in environmental risk assessments and for the development of discharge guidelines. Here we evaluated the toxicity of metals and endocrine-disrupting chemicals (EDCs) to the marine green microalga, Tetraselmis suecica. The toxicants investigated included the metals, Cu, Ni, and Pb; and the EDCs, bisphenol A (BPA), endosulfan (ES), and polychlorinated biphenyl (PCB). The endpoints were variations in cell counts and chlorophyll a levels. T. suecica displayed a varied pattern of sensitivity to the toxicants. Based on the 72-h median effective concentration ($EC_{50}$), ES (0.045 mg/L) was most toxic to T. suecica, followed by PCB (3.96 mg/L) and Pb (9.62 mg/L). Interestingly, T. suecica was relatively tolerant to Cu (43.03 mg/L). The 72-h $EC_{50}$ values of Ni and BPA were approximately 16 mg/L. Our data suggest that this species may be relatively tolerant to most of the chemicals within their permissible limits in the environment.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.211-220
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• 2011

To improve the low ductility and high strain-rate sensitivity in Sn-Bi based solder alloys, the influences of the minor additions of alloying elements (Ag, Mn, In) were investigated. The strain-stress curves of various Sn-40Bi(-X) alloys, including a pre-suggested Sn-40Bi-0.1Cu composition were measured using a tensile testing machine. As a result, the elongation and ultimate tensile strength (UTS) values were compared. The small addition (0.5 wt.%) of Ag significantly enhanced the ductility and high strain-rate sensitivity of the alloys at strain rates of $10^{-4}$ to $10^{-2}\;s^{-1}$ mainly due to the increase and refinement of eutectic lamellar structures. The microstructure change increased the area of grain boundaries, thus ameliorating the grain boundary sliding mode. It was also found that Mn is an effective element in enhancing the ductility, especially at the strain rates of $10^{-3}$ to $10^{-2}\;s^{-1}$ The enhancement is likely attributed to the fine and homogeneous microstructure in the alloys containing Mn.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.574-579
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• 2010

In this study the enzyme inhibition method using dehydrogenase which has been popularly used to estimate ecotoxicity was optimized. When three bacterial strains, Escherichia coli HB101, Enterobacter asburiae KCAD-4, and Aeromonas media KCAD-13, were compared, KCAD-4 was considered as the adequate strain to estimate toxicity because of its sensitivity and reproducibility. The optimal bacterial density was estimated as $5.4{\times}10^9CFU/mL$, at which the maximum sensitivity was observed. The phosphate buffer was suitable for the reaction solution. When the reaction times required for inhibition of enzyme activity by contact of toxicants and for reaction of damaged bacteria and substrate were tested, the optimal value was estimated as 20 min and 2 hrs, respectively. It is expected that the optimized conditions can be used to develop the standardized kits to estimate ecotoxicity of heavy metals in effluent from the industrial wastewater treatment facilities.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.551-557
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• 2013

In the present study, pristine carbon nanotube (p-CNT) and thiolated carbon naotube (t-CNT) electrodes were investigated to improve their detectabilities for cadmium (Cd) and lead (Pb). In addition, we evaluate which reaction mechanism is used when the electrolyte contains both Cd and Pb metals. Square wave stripping was employed for analyzing the sensitivity for the metals. A frequency of 30 Hz, a deposition potential of -1.2 V vs. Ag/AgCl and a deposition time of 300 s were used as optimal SWSV parameters. t-CNT electrodes show the better sensitivity for both Cd and Pb metals than that of p-CNT electrodes. In case of Cd, sensitivities of p-CNT and t-CNT electrodes were $3.1{\mu}A/{\mu}M$ and $4.6{\mu}A/{\mu}M$, respectively, while the sensitivities for Pb were $6.5{\mu}A/{\mu}M$ (p-CNT) and $9.9{\mu}A/{\mu}M$ (t-CNT), respectively. The better sensitivity of p-CNT electrodes is due to the enhancement in the reaction rate of metal ions that are facilitated by thiol groups attached on the surface of CNT. When sensitivity was measured for the detection of Cd and Pb metals present simultaneously in the electrolyte, Pb indicates better sensitivity than Cd irrespective of electrode types. It is ascribed to the low standard electrode potential of Pb, which then promotes the possibility of oxidation reaction of the Pb metal ions. In turn, the Pb metal ions are deposited on the electrode surface faster than that of Cd metal ions and cover the electrode surface during deposition step, and thus Pb metals that cover the large portion of the surface are more easily stripped than that of Cd metals during stripping step.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.115-120
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• 1998

This paper is especially concerned with the weldment between support beam and square bar that plays important roles in control box of Expansion Joint as a bridge structure. Fatigue strength of the weldment is dependent on notch radius from welding defects and material properties. From which, tensile strength($\sigma$ult) and fatigue notch factor(Kf) become important factors to predict fatigue life. The fatigue notch sensitivity(η) for metals can be divided into two types : high and low notch sensitivity. In this work, the Expansion Joint weldment was found to have low notch sensitivity. Fatigue test of real structure was performed up to 106cycles to be compared with predicted endurance limit.