• Progress in Superconductivity and Cryogenics
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• v.26 no.2
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• pp.1-4
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• 2024

We investigated Pb_10-xCu_x(PO₄)₆ (0.9 < x < 1.1) (LK-99) and Cu₂S, presumed to be contained as an impurity in LK-99, in a wide spectral range from far infrared to ultraviolet using optical spectroscopy. The optical conductivity spectra of both samples were obtained from measured reflectance spectra at various temperatures from 80 to 434 K. Both samples showed several infrared-active phonons in the far and mid-infrared regions. LK-99 showed typical insulating features with a band gap of ~1 eV. Cu₂S showed a nonmonotonic temperature-dependent trend and two energy gaps: one energy gap of ~93 meV and a band gap of 2.42 eV. Our results indicate that LK-99 cannot be a superconductor because it is an insulator with a large band gap.

• Environmental Engineering Research
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• v.23 no.1
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• pp.92-98
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• 2018

Suitability of aluminium-based water treatment sludge (WTS), a waste product from water treatment facilities, was assessed for removal of heavy metals from an electroplating wastewater which had high concentrations of copper and chromium along with other heavy metals. Batch tests with simulated wastewater in single- and multi-metal solutions indicated the influence of initial pH and WTS dose on removal of six metals namely Cu(II), Co(II), Cr(VI), Hg(II), Pb(II) and Zn(II). In general, removal of cationic metals such as Pb(II), Cu(II) and Zn(II) increased with increase in pH while that of anionic Cr(VI) showed a reduction with increased pH values. Tests with multi-metal solution showed that the influence of competition was more pronounced at lower WTS dosages. Column test with diluted (100 times) real electroplating wastewater showed complete removal of copper up to 100 bed volumes while chromium removal ranged between 78-92%. Other metals which were present in lower concentrations were also effectively removed. Mass balance for copper and chromium showed that the WTS media had Cu(II) and Cr(VI) sorption capacities of about 1.7 and 3.5 mg/g of dried sludge, respectively. The study thus indicates that WTS has the potential to be used as a filtration/adsorption medium for removal of metals from metal-bearing wastewaters.

• Korean Journal of Environmental Agriculture
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• v.40 no.1
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• pp.60-66
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• 2021

BACKGROUND: The concern over heavy metal(loid)s in arable land and agricultural products increases for public health in recent years. This study aims to identify transition characteristics of heavy metal(loid)s and to assess dietary risk in barley grown at the major producing districts in Korea. METHODS AND RESULTS: The soil and barley samples were collected from 38 locations around the major producing districts at Jeollabuk-do in Korea for the propose of examining the concentrations of heavy metal(loid)s. The 34 barley samples were separately purchased on the market for the same survey. The average concentration and range of arsenic (As), cadmium (Cd) and lead (Pb) in barley grown at the major producing districts in Korea were 0.037 (0.016-0.094), 0.028 (0.004-0.083) and 0.137 (0.107-0.212) mg kg-1, respectively. Currently, the maximum allowable level for barley Pb is set at 0.2 mg kg-1 in Korea, and the monitoring results suggested that some samples exceeded the maximum allowable level and required appropriate farming management. Bio-concentration factor values by heavy metal(loid)s in barley were high at Cd, copper (Cu) and zinc (Zn), similar to other crops, while As and Pb were low, indicating low transferability. CONCLUSION: Human exposure to As, Cd and Pb through dietary intake of barley might not cause adverse health effects due to relatively low concentrations, although the Pb in some barley was detected higher than the maximum allowable level. Further study on uptake and accumulation mechanism of Pb by barley might be required to assess the human health risk associated with soil contamination.

• Korean Journal of Animal Reproduction
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• v.25 no.1
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• pp.35-42
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• 2001

This study was performed to elucidate the patho-physiology of copper-poisoned rats after consecutive oral administrations of the copper sulfate. The changes in feed and water intake, gains of body weight, blood pictures and mineral compositions of several organs were observed to measure the effects of copper poisoning. 1. Compared with control group, every experimental group of which 1,000, 2,000, or 4,000 ppm/kg of copper sulfate was administered displayed a gradual decrease in feed intake in dose-dependent manners. 2. After 1,000, 2,000 or 4,000 ppm/kg of copper sulfate administration, water intake seemed to decrease in every experimental group in dose-dependent manners, but there was little statistical significance. 3. After 1,000, 2,000 or 4,000 ppm/kg of copper sulfate administration, body weight decreased in every experimental group in dose-dependent manners. 4. After 1000, 2,000 or 4,000 ppm/kg of copper sulfate administration, the PLT values and numbers of RBC and WBC significantly increased after copper sulfate administration, but the values of Hb and PCV were lower than those of control group's. 5. After 2,000 or 4,000 ppm/kg of copper sulfate administration, the levels of Cu, Mn, Fe, Pb and Zn in the liver were lowered, but the levels of Mn, Fe, Pb and Zn in the kidneys increased except Cu levels.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1200-1204
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• 2003

In this study, in order to develop the low temperature sintering ceramics for multi-layer piezoelectric transformer, PSN-PZT system ceramics were manufactured as a function of CuO addition and their dielectric and piezoelectric characteristics were Investigated. CuO addition facilitated densification at low temperature due to the effect of Cu$_2$O-PbO liquid phase. Through the X-ray diffraction pattern study, absence of second phase unwanted was confirmed. Among the specimen to which CuO was added, the 0.6wt% CuO added specimen sintered at 900$^{\circ}C$ and 920$^{\circ}C$ showed the most excellent mechanical quality factor and electromechanical coupling factor, respectively. Besides the densification accelerator, CuO acted as a accepter and increased mechanical quality. Compared with the specimen with no addition sintered at 1150$^{\circ}C$ , the 0.6wt% CuO added specimen sintered at 920$^{\circ}C$ showed the appropriate dielectric and piezoelectric characteristics for multi-layer piezoelectric transformer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.138-141
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• 2004

[ $MnO_2$ ]가 첨가된 $0.9Pb(Zr_{0.5}Ti_{0.5})O_3-0.2Pb[(Zn_{0.8}Ni_{0.2})_{1/3}Nb_{2/3}]O_3$(0.8PZT-0.2PZNN) 세라믹스는 그 압전특성과 유전특성이 뛰어나지만 $1000^{\circ}C$ 이하의 낮은 소결 온도에서는 소결되지 않는다. $1000^{\circ}C$이하의 낮은 소결온도에서 소결하기 위해 CuO를 첨가한 결과, 소결온도 $920^{\circ}C$에서 소결성은 우수하였으나 그 압전 특성의 저하가 두드러졌다. 이는 XRD에서 확인한 결과에 따르면 CuO의 첨가가 우수한 MPB 조성으로 판명된 $MnO_2$ 가 첨가된 0.8PZT-0.2PZNN 세라믹스의 결정구조를 Rhombohedral 구조로 바꾸기 때문인 것으로 보였으며 이러한 문제는 PZNN의 비율을 조절하여 0.875PZT-0.125PZNN 세라믹스를 선택함으로 인해 해결할 수 있었다. 그러나 여전히 낮은 $Q_m$값을 높이기 위해서 $Al_2O_3$를 첨가하였고 그 결과 시편의 tetragonality 감소와 $Q_m$값의 증가를 확인할 수 있었으나 그 첨가량이 0.2wt% 이상일 경우에는 밀도의 감소로 인한 압전특성의 저하가 나타났다. 밀도의 향상을 위해 Zn and Ni excess 조성을 선택하였고 그 결과 0.5wt% $MnO_2$와 0.2wt% CuO 그리고 0.3wt% $Al_2O_3$를 첨가한 0.875PZT-0.125PZNN 세라믹스(Zn and Ni excess 조성)를 $920^{\circ}C$에서 소결한 경우 $k_p=0.581,\;Q_m=809,\;d_{33}=345\;pC/N\;and\;{\varepsilon}_{33}/{\varepsilon}_0=1345$의 빼어난 압전 및 유전특성과 $330^{\circ}C$의 높은 $T_c$를 보였고 그 조성의 vibration velocity는 약4.5 m/s로 나타났다.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.2
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• pp.275-283
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• 2012

MCM-41(Mobil's Composition of Matter-41) and expanded graphite(EG) were investigated as potential adsorbents for heavy metal ions including Pb(II), Cu(II) and Ni(II) in various aqueous chemistries. MCM-41 showed shorter equilibrium times and higher adsorption capacities for all three heavy metal ions compared to expanded graphite. The adsorption of three heavy metal ions was significantly affected by the solution pH due to the competition with $H_{3}O^{+}$ at lower pH and precipitation at neutral or higher pH. Adsorptions of heavy metal ions onto MCM-41 and expanded graphite were successfully described with the pseudo-second-order model. During the competitive adsorption of three heavy metal ions, the selectivity of Pb(II) was highest and almost same selectivity was observed with Cu(II) and Ni(II) when MCM-41 was used as an adsorbent, while the expanded graphite exhibited the highest selectivity to Pb(II), followed by Ni(II) and Cu(II).

• Advances in environmental research
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• v.6 no.4
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• pp.281-299
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• 2017

Single (0.005 M DTPA), sequential (six-step) and kinetic (0.05 M EDTA) extractions were performed to assess Cd, Cr, Cu, Ni, Pb, and Zn mobilization and their potential ecological risks in Abuja (Nigeria) water (WTS) and wastewater (WWTS) treatment sludges. Total metal levels (mg/kg) in WTS and WWTS, respectively were: Cd(3.67 and 5.03), Cr(5.70 and 9.03), Cu(183.59 and 231.53), Ni(1.33 and 3.23), Pb(13.43 and 17.87), Zn(243.45 and 421.29). DTPA furnished metal extraction yields (%) in WTS and WWTS, respectively as: Cd(11 and 6), Cr (15 and 7), Cu(17 and 13), Ni(23 and 3), Pb(11 and 12), and Zn(37 and 33). The metals were associated with the soluble/exchangeable, carbonate, Mn/Fe-oxide, organic matter and residual forms to varying degrees. Kinetic extractions cumulatively leached metal concentrations akin to the mobilizable fractions extracted sequentially and the leaching data fitted well into the Elovich model. Metal mobilities were concordant for the three leaching procedures and varied in the order:WTS>WWTS. Calculated ecological risk indices suggested moderate and considerable metal toxicity in WTS and WWTS, respectively with Cd as the worst culprit. The findings may be useful in predicting heavy metals bioavailability and risks in the sludges to guide their disposal and use in land applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.6
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• pp.522-531
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• 2003

Samples with the nominal composition, B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+{\delta}}$ high- $T_{c}$ superconductors containing MgO as an additive were fabricated by a solid-state reaction method. Samples with MgO of 5~30 wt% each were sintered at 820~86$0^{\circ}C$ for 24 hours. The structural characteristics, critical temperature, grain size and image of mapping with respect to MgO contents were analyzed by XRD(X-Ray Diffraction), SEM(Scanning Electron Microscope) and EDS(Energy dispersive X-ray spectrometer) respectively. As MgO contents increased, intensity of MgO Peaks and ratio of Bi-2212 phase in superconductors intensified and the proportion of the phase transition from Bi-2223 to Bi-2212 was increased.

• Electrical & Electronic Materials
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• v.7 no.4
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• pp.306-311
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• 1994

In this study, the influence of the powder sintering, the 2nd sinteiing and the grinding time on the Superconducting properties in the Bi(Pb)SiCaCuO Superconductor has been studied. From the analysis of SEM and XRD patterns, it was known that the sample prepared by the process of powder sintering has a porous microstructure with the critical temperature(Tc) below 77K, while the sample prepared by the 2nd sintering has a highly oriented microstructure with the Tc above 100K. The Critical Current Density(Jc) of the sample prepared by the 2nd sintering was better than the sample prepared by the process of powder sinteiing, but it's Jc, was low in practical use. Also, the effect of grinding time from 0[min] to 120[min] was investigated. As the grinding time is increased, the samples degraded from high-Tc phase to low-Tc phase and nonsuperconducting phases.