• Journal of the Korean Society for Heat Treatment
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• v.4 no.1
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• pp.13-18
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• 1991

The formation of high $T_c$ phase is very sluggish and c parameter of unit cell of high $T_c$ phase is about $37{\AA}$. High $T_c$ oxide superconductor with a $T_c$ above 100 K has been successfully prepared by solid state reaction method in BiSrCaCuO system by Pb adding. The microstructure related to the formation of the high $T_c$ phase has been investigated. As compared with YBCO compound, the formation reaction of the high $T_c$ requires long time heat treatment. It is due to the transformation from the low $T_c$ phase to high $T_c$ phase. The sintering just below the melting point of the calcined powder mixture is effective on the formation of the high $T_c$ phase in Pb-added BiSrCaCuO system. The growth of the high $T_c$ superconducting phase has a thin plate shape, which is characterized by the c parameter of $37{\AA}$. The formation of the high $T_c$ phases is delayed by the excessive addition of Pb. The lattice parameter(c) of the unit cell (both the low and high $T_c$ phases) is increased with increase of Pb.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1146-1152
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• 2005

Graft copolymers were synthesized from methylcellulose(MC) and acrylic acid(AA) with active carboxyl groups in the presence of potassium persulfate($K_2S_2O_8$) initiator to enhance adsorption capacity of toxic heavy metal such as $Pb^{2+}$ and $Cu^{2+}$ from wastewater. The resulting grafted copolymers(MC-g-AA/PAA) were mixture of the graft copolymers from MC and AA(MC-g-AA) and polyacrylic acid homopolymers(PAA). The degree of palling was increased with rising concentration of monomer and initiator under the reaction conditions at $60^{\circ}C$, 3 hrs. The water insoluble property of MC-g-AA showed more than 19.7% degree of grafting. So that it could be an adsorbent of heavy metals. Adsorption characteristics of the MC-g-AA were evaluated depending on the degree of grading, pH of wastewater, adsorption time, dosage of MC-g-AA and concentration of heavy metals in the different conditions. Degree of grafting, and initial concentration of heavy metal ions increased, the adsorption amount of $Pb^{2+}$ and $Cu^{2+}$ increased, but added MC-g-AA increased, the adsorption amount per unit weight of $Pb^{2+}$ and $Cu^{2+}$ decreased. The MC-g-AA showed the high $Pb^{2+}$ and $Cu^{2+}$ adsorption amount in the range pH $4{\sim}6$. Also all of $Pb^{2+}$ and $Cu^{2+}$ ions reached in adsorption equilibrium in neighborhood 4 hours. The adsorption of heavy metals described by Freundlich isotherm, it was determined the value of l/n of $Pb^{2+}$ and $Cu^{2+}$ that 0.4294 and 0.3453, respectively.

• Economic and Environmental Geology
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• v.36 no.5
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• pp.357-363
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• 2003

The objective of this study is to investigate background levels of As and heavy metals (Cd, Cu, Pb and Zn) and their dietary intakes from white rice produced at various provinces in Korea during 2000. Except Jeju-do, sixty-three rice grain samples were taken at 8 provinces and analyzed for the elements using ICP-AES after acid digestion. The average contents of hi, Cd, Cu, Pb and Zn in the samples were 0.126, 0.040, 1.96, 0.361 and 16.6 mg/kg(DW), respectively. These levels are within the ranges of worldwide average concentrations in rice grains reported by various research. Assuming the rice consumption of 256 g/day by overall households in Korea, the amount of daily intake of As, Cd, Cu, Pb and Zn by the rice were estimated to be 32.3, 10.2, 502, 92.4 and 4,250 ${\mu}g$/day, respectively. Those amount of daily intakes of the elements by the rice are within the WHO's guide for trace elements, however, rice consumption is one of the most important sources of dietary intake of As and some heavy metals in Korean population.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.1-7
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• 2010

Interfacial reaction characteristics of a Bi-10Cu-20Sb-0.3Ni Pb-free alloy on Cu pad was investigated by reflow soldering at $430^{\circ}C$. The thickness of interfacial reaction layers with respect to the soldering time was also measured. After the reflow soldering, it was observed that a $(Cu,Ni)_2Sb$, a $Cu_4Sb$ intermetallic layer, and a haze layer, which is consisted of Bi and $Cu_4Sb$ phases, were successively formed at the Bi-10Cu-20Sb-0.3Ni/Cu interface. The total thickness of the reaction layers was found to be linearly increased with increasing of the reflow soldering time up to 120 s. As the added Ni element did not participate in the formation of the thickest $Cu_4Sb$ interfacial layer, suppression of the interfacial growth was not observed.

• 보존과학연구
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• s.34
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• pp.102-108
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• 2013

The purpose of this investigation is to Dancheong documentary project of Tangible cultural in Jeollabukdo. The colored pigments of Nahanjeon Hall in Songkwangsa Temple analyzed and composition and repair period for each pigments were compared. The result are that blue color is Ultramarine blue($Na_6Al_6Si_6O_{24}S_4$), green color is Yangrok($Cu(C_2H_3O_2)_2{\cdot}3Cu(AsO_2)_3$), orange color is Jangdan($Pb_3O_4$), yellow color is Chrome yellow($PbCrO_4$). It is difficult to distinguishable from coloring period by analysis of pigments of Nahanjeon Hall.

• Journal of Environmental Health Sciences
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• v.12 no.1
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• pp.69-78
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• 1986

In order to determine the content levels of trace metals in cow's milk, 79 market milk samples were collected from markets in major cities of Korea from July to August, 1985 and analyzed for content levels of Cu, Fe, Zn, Mn, Pb, Cd. The Results were as follows Cu, average 43.5 $\mu$g/l range 14 ~ 172.7 $\mu$g/l Fe, average 398.4 $\mu$g/l range 35 ~ 1,873 $\mu$g/l Zn, average 2.917 mg/l range 1.233 ~ 7.46 mg/l Mn, average 26.74 $\mu$g/l range 7.6 ~ 102 $\mu$g/l Pb, average 33.9 $\mu$g/l range N.D. ~ 105 $\mu$g/l Cd, average 1.73 $\mu$g/l range N.D. ~ 5.4 $\mu$g/l

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.446-450
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• 2001

In this study, microstructural and electrical properties of (Pb)(La,Nd)TiO$_3$ ceramics were investigated as a function of CuO addition. Taking into consideration Tc of 3$25^{\circ}C$, dynamic range of 49dB( at the wafer form) and density of 7.71g/㎤, it can be concluded that the specimen S2 sintered at 120$0^{\circ}C$ is the best for the resonator application. Dynamic characteristics of energy-trapped 20MHz SMD type resonator as a function of internal dot size variation were also investigated. Dynamic range characteristics showed the highest value of 60.72dB at S2-4(dot size 1.13mm).

• Journal of Soil and Groundwater Environment
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• v.16 no.1
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• pp.42-50
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• 2011

Potential risk of heavy metals to various receptors including humans depends on the bioavailability of the heavy metals in soil. In this study, the heavy metal extraction methods using 0.1N HCl and aqua regia were compared with the Tessier's sequential extraction method to assess whether these two methods can be used to determine the plant-available heavy metal concentrations. The contamination characteristics of copper (Cu), cadmium (Cd), lead (Pb), and arsenic (As) found in soils collected from 75 sites around the closed Janghang smelter were analyzed by extracting heavy metals using 0.1 N HCl, aqua regia, and the Tessier's sequential extraction method. The portion of metals bioavailable to plants is considered as the sum of the fraction 1 (exchangeable) and the fraction 2 (carbonates binding) of the Tessier's 5-step sequential extraction method, which were determined to be 3.1 ${\pm}$ 3.82, 0.6 ${\pm}$ 0.15, 20.6 ${\pm}$ 18.78, and 7.0 ${\pm}$ 6.48 mg/kg for Cu, Cd, Pb, and As, respectively, in this study. When the extraction using aqua regia and the Tessier's extraction method were compared, the extracted Cu and Pb concentrations did not show significant differences, whereas the extracted Cd and As concentrations showed significant differences. These results indicate that the portion of Cd and As in the fraction 5 of the Tessier's sequential extraction can not be extracted using aqua regia. Using aqua regia, which is the official test method, higher concentrations of Cu, Cd, Pb and As were extracted than the sum of the fraction 1 and 2. The results show that only 9, 40, 39 and 10% of Cu, Cd, Pb and As using aqua regia can be uptaken by plants (i.e., plant-available). Using 0.1N HCl, the portion of Cd equivalent to about 66% the fraction 1 could be extracted, while, with Pb, the portion of the fraction 1 and about 90% of the fraction 2 could be extracted. With As, the portion equivalent to the fraction 1, 2 and 79% of the fraction 3 was extracted, while with Cu, the portion equivalent to the fraction 1, 2, 3 and 20% of the fraction 4 was extracted using 0.1N HCl.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.25-36
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• 2016

Heavy metals in the stream sediments around Shihwa Lake were studied not only to investigate the characteristics of spacio-temporal distribution but also to assess the pollution degree and ecological risk using various pollution indices. Among metals, Zn had the highest values (1,311 mg/kg) and Hg showed the lowest value (0.261 mg/kg). The order of mean concentrations (mg/kg) of metals was Zn>Cu>Pb>Cr>Ni>Co>As>Cd>Hg in stream sediments around Shihwa Lake. Metal concentrations showed different pollution pattern with industrial region, indicating that these metals originated from different sources and industrial region had higher metal concentration than rural/urban regions. The results of geoaccumulation index (Igeo) showed that the stream sediments were significantly polluted with Cd, Cu, Zn and Pb, indicating moderately to highly polluted by these metals. According to PLI consideration, industrial region was more seriously polluted by metals whereas an rural/urban region was not polluted. About 85% of sampling site for Cr, Ni, Cu, Zn and Pb from industrial regions were exceeded the PEL values. The mPELQ and SQI values derived from PEL of industrial region were classified as 'highly toxic' and 'very poor' and metal pollution level tend to be worse in wet season. This indicates that the industrial activities and stromwater runoff represents an important sources of heavy metals around Shihwa Lake.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.4
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• pp.56-64
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• 2000

Behavior of trace metals in Masan Bay, Korea was studied in August 1998 when the oxygen deficient condition occurred. Dissolved Cd and Zn concentration in the surface waters decreased with increasing distance from Masan Harbor. Dissolved concentrations of Cd, Cu Pb and Zn in the surface waters were higher than bottom waters. Particulate(acid-teachable fraction) concentrations of Cu, Cd and Pb in the surface waters of Masan Bay decreased with increasing distance from Masan Harbor. Bottom waters contained higher concentrations of particulate Cd, Cu, Pb and Zn than surface waters. Distribution coefficients between dissolved and particulate phase (K/sub d/) of Cu and Cd decreased with the increasing distance from the Harbor, possibly due to reaction of these elements with sewage-derived particulate matter Al, Zn, Cu, Cd, and Pb in the surface sediment showed relatively high concentration in the inner Masan Bay.