• Toxicological Research
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• v.29 no.1
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• pp.69-79
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• 2013

The purpose of this study was to investigate the current status of metal pollution in the sediment from rivers, lakes, and streams in active gold mining districts in Ghana. Two hundred and fifty surface sediment samples from 99 locations were collected and analyzed for concentrations of As, Hg, Cr, Co, Cu, Fe, Zn, Pb, Cd, Ni, and Mn using inductively coupled plasma-mass spectroscopy (ICP-MS). Metal concentrations were then used to assess the human health risks to resident children and adults in central tendency exposure (CTE) and reasonable maximum exposure (RME) scenarios. The concentrations of Pb, Cd, and As were almost twice the threshold values established by the Hong Kong Interim Sediment Quality Guidelines (ISQG). Hg, Cu, and Cr concentrations in sediment were 14, 20, and 26 times higher than the Canadian Freshwater Sediment Guidelines for these elements. Also, the concentrations of Pb, Cu, Cr, and Hg were 3, 11, 12, and 16 times more than the Australian and New Zealand Environment and Conservation Council (ANZECC) sediment guideline values. The results of the human health risk assessment indicate that for ingestion of sediment under the central tendency exposure (CTE) scenario, the cancer risks for child and adult residents from exposure to As were $4.18{\times}10^{-6}$ and $1.84{\times}10^{-7}$, respectively. This suggests that up to 4 children out of one million equally exposed children would contract cancer if exposed continuously to As over 70 years (the assumed lifetime). The hazard index for child residents following exposure to Cr(VI) in the RME scenario was 4.2. This is greater than the United States Environmental Protection Agency (USEPA) threshold of 1, indicating that adverse health effects to children from exposure to Cr(VI) are possible. This study demonstrates the urgent need to control industrial emissions and the severe heavy metal pollution in gold mining environments.

• Journal of Korean Society on Water Environment
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• v.31 no.3
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• pp.304-312
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• 2015

In this study, we tried to determine the vertical variation of sediment structure and geochemical characteristics, core sediment was collected in the Nakdong River midstream on August, 2014. Core sediment mainly composed of sand (51.48%) and silt (46.21%) and coarsing upward changed from sM to mS facies. IL and TOC were decreased from lower to upper layer. C/N ratio was lower than 10 so the organic matters were originated from underwater creatures and C/S ratio was decreased from lower to upper layer. Heavy metal (Al, Fe, Zn, Cr, Pb, Ni, Cu, Cd) content were decreased from lower to upper layer and seriously polluted condition is not. These results are thought to be due to the effect of natural and anthropogenic in the fluctuation of flow.

• 한국해양학회지
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• v.13 no.2
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• pp.11-16
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• 1978

The contents of heavy metals were studied on sediments collected from the southeastern coastal area of Korea.Concentrations of the elements showed Cu 14∼ 48ppm (av. 18ppm), Pb 14∼49ppm (av. 28ppm), Zn 79∼187ppm (av. 11ppm), Co 11∼ 15ppm (av. 13ppm), Ni 22∼32ppm (av. 29ppm), Fe 3.1∼5.3% (av. 4.3%) and Mn 333 ∼1010ppm (av. 499ppm). When these values are compared with those of the unpolluted near-shore sediments from other countries,there seems to be little environmental contamination of heavy metals in the sediments of the study area. However, from the fact that the nearer to harbor the stations are, the higher the contents of copper, lead and zinc are in the sea off Pusan Bay, it is suggested that heavy metals in the sediments are starting to show some contamination from man's activities.

• Journal of the Mineralogical Society of Korea
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• v.14 no.1
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• pp.58-72
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• 2001

The Cretaceous granite, andesite and sedimentary rocks are widely distributed in the northern Pusan area. The present study investigates mineralogical and geochemical charateristics of residual and cultivated soils derived from these rocks. The soils of granite area contain a large amount of quartz relative to clay minerals, whereas the soils of the andesite area contain more clay minerals than quartz. Clay minerals consist mainly of kaolin minerals illite hydroxy interlayered vermiculite interstratified mica/vermiculite and chlorite. Kaolin minerals are abundant in paddy soils while illite is abundant in less weathered soils. Si and K are major elements in the soils of granite area while Fe and Al in the soils of andesite area. In all the soils Ca, Mg and Na were generally depleted in comparison to those in parent rocks. Analysis data of trace element show that the enrichment pattern in soils depends on parent rock type with high oncentration of some elements over 100 ppm: Ba and Rb in granite area Zn, Bn, and V in andesite area, and Ba and V in sedimentary rock. In granite area, Rb and Th were greatly enriched in soil than in parent rocks. However, Cr, Ni and Sr commonly decrease, whereas Pb increases in all the soils. Exchangeable cation capacity(CEC) is relatively high in the soils of andesite are including abundant clay minerals. Collective evidences prove that the mineralogical and chemical compositions of soils are strongly dependent on the parent rock type. The mineralogy and chemistry of long cultivated soils are not significantly different from those of residual soils.

• Journal of Life Science
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• v.20 no.6
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• pp.902-906
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• 2010

A producer of thermophilic extracellular lipase, Geobacillus kaustophilus DSM 7263, was selected from various microorganisms of the Geobacillus genus. We investigated optimum conditions for mass production of G. kaustophilus lipase. Among the different natural oil media, olive oil was optimal for enzyme production. The maximum amount of enzyme production was obtained when G. kaustophilus was grown in a medium containing 0.5% olive oil as a carbon source. The pH and temperature for optimal growth were pH 8.0 and $55^{\circ}C$, respectively, while the optimum pH and temperature for lipase production were pH 6.0 and $50^{\circ}C$, respectively. In the presence of $Mg^{2+}$ and $Mn^{2+}$, lipase production was dramatically enhanced by 247% and 157%, respectively, whereas enzyme production was inhibited by $Zn^{2+}$, $Cu^{2+}$, and $Cd^{2+}$. The addition of 0.1% (v/v) triton X-100 increased lipase production and cell growth when compared to the negative control.

• Corrosion Science and Technology
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• v.11 no.3
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• pp.96-102
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• 2012

Outer diameter stress corrosion cracking (ODSCC) has occurred for Alloy 600 (Ni 75 wt%, Cr 15 wt%, Fe 10 wt%) as a heat exchanger tube of the steam generator (SG) in nuclear power plants (NPP) during long term operation. Among many causes for SCC, lead (Pb) is known to be one of the most deleterious species in the secondary system. In the present work, the oxide formed on Alloy 600 was characterized as a function of the PbO content in 0.1 M NaOH at $315^{\circ}C$ by using an electrochemical impedance spectroscopy (EIS), a transmission electron microscopy (TEM), equipped with an energy dispersive x-ray spectroscopy (EDS). The oxide property was analyzed in view of SCC susceptibility.

• Corrosion Science and Technology
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• v.17 no.4
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• pp.154-165
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• 2018

During the process of sulfur dioxide removal, flue gas desulfurization equipment provides a serious internal corrosion environment in creating sulfuric acid dew point corrosion. Therefore, the utilities must use the excellent corrosion resistance of steel desulfurization facilities in the atmosphere. Until now, the trend in developing anti-sulfuric acid steels was essentially the addition of Cu, in order to improve the corrosion resistance. The experimental alloy used in this study is Fe-0.03C-1.0Mn-0.3Si-0.15Ni-0.31Cu alloys to which Ru, Zn and Ta were added. In order to investigate the effect of $H_2SO_4$ concentration and the alloying elements, chemical and electrochemical corrosion tests were performed. In a low concentration of $H_2SO_4$ solution, the major factor affecting the corrosion rate of low alloy steels was the exchange current density for $H^+/H_2$ reaction, while in a high concentration of $H_2SO_4$ solution, the major factors were the thin and dense passive film and resulting passivation behavior. The alloying elements reducing the exchange current density in low concentration of $H_2SO_4$, and the alloying elements decreasing the passive current density in high concentration of $H_2SO_4$, together play an important role in determining the corrosion rate of Cu-bearing low alloy steels in a wide range of $H_2SO_4$ solution.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.417-421
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• 2008

The efficient synthesis of four mesitylene-based receptors 1-4 and their potentiometric response characteristics to alkali metal, alkaline earth metal, and transition metal ions, under various pH conditions are outlined. Receptor 1-based electrode exhibited more sensitive response to Ag+ ion (49 mV/decade of range from 10-6 to 10-2 M) than the 2-based electrode (47 mV/decade of range from 3 ´ 10-5 to 10-2 M), while the 3- and 4-based ones revealed sub-Nernstian below 40 mV/pAg+. All electrodes showed substantial responses to Ag+ ion under acidic condition, but there was almost nil-response to other transition metal ions (Fe2+, Co2+, Zn2+, Ni2+, Pb2+, Cd2+, Cu2+ and Hg2+). The association constant of receptor 1 toward Ag+ ion, measured by 1H NMR titration, showed the largest value (200 M-1) among the tested receptors. The results were interpreted with semi empirically-modeled structures.

• Journal of the Korean Magnetics Society
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• v.4 no.4
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• pp.319-325
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• 1994

Permalloy films were deposited by an RF magnetron sputtering method using several different targets which had been cold-rolled and annealed at various temperatures to give different microstructure and texture. The grain refinement occurs at high temperature annealing due to recrystallization and subsequently the initial (110) target texture transforms to the random texture. The coercive forces of thin films fabricated using targets which are not recrystallized are below 0.2 Oe in the AI pressure range of 1~5 mTorr and the lowest coercive force achieved is 0.07 Oe. The low value of coercive force, 0.25 Oe, is only obtained at the sputtering conditions of 400 W and 1 mTorr, and 300 W and 5 mTorr when recrystallized targets are used. The internal stress changes from compressive to tensile as the Ar pressure increases, the stress-free being at 5 mTorr. The changes of coercive force and permeability can be well interpreted by the differences from the composition and the internal stress.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.95-95
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• 2013

박막 공정 기술은 반도체 및 디스플레이뿐만 아니라 대부분의 전자소자에 적용되는 매우 중요한 기술이다. 그 중, 마그네트론 스퍼터링 공정은 플라즈마를 이용하여 금속 및 세라믹 등의 벌크 물질을 박막으로 증착 가능한 가장 널리 사용되는 방법 중의 하나이다. 하지만, Fe, Co, Ni 같은 강자성체 재료는 공정이 불가능하며, 스퍼터링 타겟 효율이 40% 이하이고, 제한적인 방전압력 범위 및 전류 상승에 의한 높은 전압 인가 제한이 있다는 단점이 있다. 본 연구에서 사용된 고밀도 플라즈마 소스를 적용한 고효율 스퍼터링 시스템은 할로우 음극을 이용한 원거리에서 고밀도 플라즈마를 생성하여 전자석 코일을 통해 자석이 없는 음극으로 이온을 수송시켜 스퍼터링을 일으킨다. 따라서 강자성체 재료의 스퍼터링이 가능하며, 90% 이상의 타겟 사용 효율 구현 및 기존 마그네트론 스퍼터링 대비 고속 증착이 가능하다. 또한, $10^{-4}$ Torr 압력영역에서 방전 및 스퍼터링이 가능하다. 타겟 이온 전류를 타겟 인가 전압과 관계없이 0~4 A까지, 타겟 이온 전류와 상관없이 타겟 인가 전압을 70~1,000 V 이상까지 독립적으로 제어가능하다. 또한 TiN과 같은 질소 반응성 공정에서 반응성 가스인 질소를 40%까지 넣어도 타겟에 수송되는 이온의 양에 영향이 없다. 할로우 음극 방전 전류 40 A에서 발생된 플라즈마의 이온에너지 분포는 55 eV에서 가우시안 분포를 보였으며, 플라즈마 포텐셜인 sheath drop은 74 V 였다. OES를 통한 광학적 진단 결과, 전자석에 의한 이온빔 초점에 따라 플라즈마 이온화율을 1.8배까지 증가시킬 수 있으며, 할로우 음극 방전 전류가 60~100 A로 증가하면서 플라즈마 이온화율을 6배까지 증가 가능하다. 또한, 타겟 이온 전류와 관계없이 타겟 인가 전압을 300~800 V로 증가시킴에 따라 Ar 이온 밀도의 경우 1.4배 증가, Ti 이온 밀도의 경우 2.2배 증가시킬 수 있었으며, TiN의 경우 증착 속도도 16~44 nm/min으로 제어가 가능하다.