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Lee J.H.,Korea Testing and Research Institute | Kim S.J.,Mokpo Maritime University
Acta Physica Polonica A

The cavitation damage characteristics of austenitic stainless steel with different concentrations of Ti were investigated. The microstructure of the alloys was observed with optical microscope to identify its correlation with cavitation resistance. Hardness of the alloys was measured to examine its contribution to cavitation damage. It was found that the microstructure played a more significant role in cavitation damage behavior of austenitic stainless steel with Ti than the hardness. The findings in this study revealed that Ti addition in austenitic stainless steel may present either a beneficial or detrimental effect on cavitation damage behavior, depending on the microstructural characteristics. In particular, Ti content of 1.0% represented the most deteriorated cavitation characteristics due to the formation of relatively coarse precipitates. Therefore, control of Ti concentration is essential for marine application of austenitic stainless steel. Source

Yi B.,Sookmyung Womens University | Kim C.,Korea Testing and Research Institute | Yang M.,Sookmyung Womens University
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences

Biological monitoring is a necessary process for risk assessment of endocrine disrupting chemicals (EDCs), particularly, bisphenol A (BPA), in breast milk, because its human risks are not clear yet, and infants, who feed on breast milk, are highly susceptible for EDCs. Concerning biological monitoring of BPA, the HPLC/FLD has been widely used before the LC/MS/MS. However, there was no report, which simultaneously evaluated the two methods in real analyses. Therefore, we analyzed BPA with LC/MS/MS and HPLC/FLD in human breast milk and conducted comparison of two methods in analyzed BPA levels. After establishing optimal condition, e.g. linearity, recovery, reproducibility and free BPA system, we analyzed BPA levels in human breast milk samples (N=100). The LOQs were similar in the two methods, i.e. 1.8 and 1.3ng/mL for the HPLC/FLD and LC/MS/MS assays, respectively. There were strong associations between total BPA levels with the two methods (R2=0.40, p<0.01), however, only 11% of them were analyzed as similar levels with 15% CVs. In addition, the detection range of BPA was broader in the HPLC method than the LC/MS/MS method. However, the BPA levels in the HPLC/FLD analysis were lower than those in the LC/MS/MS analysis (p<0.01). Thus, the differences in BPA levels between the two methods may come from mainly over-estimation with the LC/MS/MS method in low BPA samples and some of poor resolution with the HPLC/FLD in high BPA samples. © 2010 Elsevier B.V. Source

Park D.W.,Korea Testing and Research Institute
Transactions of the Korean Society of Mechanical Engineers, B

A centrifuge works on the principle that particles with different densities will separate at a rate proportional to the centrifugal force during high-speed rotation. Dense particles are quickly precipitated, and particles with relatively smaller densities are precipitated more slowly. A decanter-type centrifuge is used to remove, concentrate, and dehydrate sludge in a water treatment process. This is a core technology for measuring the sludge conveyance efficiency improvement. In this study, a smoothed particle hydro-dynamic analysis was performed for a decanter centrifuge used to convey sludge to evaluate the efficiency improvement. This analysis was applied to both the original centrifugal model and the design change model, which was a ball-plate rail model, to evaluate the sludge transfer efficiency. © 2015 The Korean Society of Mechanical Engineers. Source

Lee J.-H.,Pusan National University | Lee J.-H.,Korea Testing and Research Institute | Oh J.-E.,Pusan National University
Science of the Total Environment

A comprehensive examination of nitrosamines was conducted in a water system, which included sewage treatment plants (STPs), river water, and seawater to understand their characteristic occurrence and fates in whole real water system. The concentrations of nitrosamines were highest in the STP influent (1440-29,100 ng/L), followed by the river water (26.0-5180 ng/L), the STP effluent (9.58-310 ng/L), and seawater (44.2-155 ng/L). The samples were especially affected by proximity to the industrial zone and the samples collected near industrial complex had much higher levels than others with different distribution patterns. In the STPs, nitrosamines were mostly eliminated during biological treatment processes (86.7-95.0%), while they were formed through chlorination processes (-. 59.6 to -. 27.7%), which is consistent with previous surveys. The primary clarifier showed insignificant elimination tendencies (5.6-28.2%). Although removal by ultraviolet light was effective (73.2-94.1%), more surveys may be needed because of conflicting results in other studies. Among water quality parameters, nitrosamines in waste water were linked with organic carbon and nitrogen levels. © 2016 Elsevier B.V. Source

Kim J.,Korea University | Nam S.M.,Korea Testing and Research Institute | Hyun S.,Korea University
Science of the Total Environment

The removal of Zn, As(V), and Cd during the leachate seepage process was measured in single, binary, and ternary solute systems by batch sorption and 1-column flow experiments, followed by a sequential extraction procedure (SEP). In single-solute systems, sorption (Kd *) occurred in the order of As(V) > Zn ≫ Cd, and this sequence did not change in the presence of other solutes. In multi-solute systems, the sorption of Zn (~20%) and Cd (~27%) was enhanced by As(V), while Zn and Cd suppressed the sorption of each other. In all cases, As(V) sorption was not affected by the cations, indicating that As(V) is prioritized by sorption sites to a much greater degree than Zn and Cd. Element retention by column soils was strongly correlated (r2 = 0.77) with Kd *. Across column segments, mass retention was in the order of inlet (36-54%) > middle (26-35%) > outlet (20-31%), except for Cd in the Zn-Cd binary system. The result of SEP revealed that most of the retained Cd (98-99%) and Zn (56-71%) was in the labile fraction (e.g., the sum of F1 and F2) while only 9-12% of As(V) was labile and most (>55%) was specifically adsorbed to Fe/Al oxides. Plots of the labile fraction (flabile) and the fast sorption fraction (ffast) suggested that the kinetics of specific As(V) sorption occur rapidly (ffast > flabile), whereas labile Zn and Cd sorption occurs slowly (flabile > ffast), indicating the occurrence of kinetically limited labile sorption sites, probably due to Zn-Cd competition. In conclusion, the element leaching potential of mine leachate can be greatly attenuated during downgradient soil seepage. However, when assessing the soil attenuation process, the impact of sorption competitors and the lability of adsorbed elements should first be considered. © 2016 Elsevier B.V. Source

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