• Ocean and Polar Research
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• 제26권2호
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• pp.121-132
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• 2004

Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn were determined in four arctic brown algae (Laminaria saccharina, L. digitata, Alaria esculenta, Desmarestia aculeata) in an attempt to examine for their metal accumulation capacity and also to assess their contamination levels. Macroalgae were collected from shallow subtidal waters (<20m) of Kongsfjorden (Kings Bay) on Spitsbergen during the period of the late July to early August 2003. Metal concentrations highly varied between sampling sites, species and tissue parts. Input of melt-water laden with terrigenous sediment particles seemed to have a large influence on baseline accumulations of some metals (Al, Fe, Mn, Pb etc.) in the macroalgae, causing a significant spatial variation. There were also significant concentration differences between the young and old tissue parts in L. saccharina, L. digitata and A. esculenta. While Al, Fe, Mn, Pb were higher in the perennial parts (stipes and holdfast below meristematic region), Cd and As concentrations were significantly higher in the young blades above the meristematic region. Zn and Cr, on the other hand, showed little differences between the tissue parts. The highest metal concentrations were found in D. aculeata, which seems to be due to its filamentous fine branches leading to high surface/volume ratios. The lowest concentrations were found in the two Laminaria spp., the blades of which are thicker than D. aculeata and A. esculenta. No distinct signs of contamination were detected in the brown algal species analyzed. Added to this, the results of the present studies suggest the potential utility of L. saccharina, L. digitata and A. esculenta as biomonitors for metal pollution monitoring in this area.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.185-188
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• 1999

Biepitaxial Y$_1Ba_2Cu_3O_{7-x}$ (YBCO) and La$_{0.2}Sr_{0.8}MnO_3$ (LSMO) thin films have been prepared on SrTiO$_3$ buffer layer and MgO seed layer grown on Al$_2O_3$(11${\bar{2}}$0)substrates by dc-sputtering with hollow cylindrical targets, respectively. We charaterized Josephson properties and significantly large magnetoresistance in YBCO and LSMO films with 45$^{\circ}$ grain boundary junction, respectively. The observed working voltage (I$_cR_n$) at 77 K in grain boundary junction was below 10${\mu}$V, which is typical I$_cR_n$ value of single biepitaxial Josephson junction. The field magnetoresistance ratio (MR) of LSMO grain boundary juncoon at 77K was enhanced to 13%, which it was significant MR value with high magnetic field sensitivity at a low field of 250 Oe. These results indicate that inserting the insulating layer instead of the grain boundary layer with metallic phase can be possible to apply a new SIS Josephson junction and a novel magnetic device using spin-polarized tunneling junction.

• 마이크로전자및패키징학회지
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• 제11권1호
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• pp.37-42
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• 2004

최근에 3 ㎓이상의 고주파용 전자부품과 소자의 제조에 낮은 저항온도계수(TCR)값과 높은 정밀도를 갖는 박막저항이 사용되고 있다. Ni-Cr 박막저항은 낮은 TCR 값과 저항에 대한 높은 안정성 때문에 저항 물질로 사용되는 가장 일반적인 물질이다. 본 연구에서는 $Ni_{72}Cr_Al_3Mn_4Si$(wt%)이 첨가된 우수한 저항특성을 갖는 S-type의 Evanohm 합금 타겟과 스퍼터링 장비를 이용하여 박막 저항을 제조하였다. 또한 열처리 조건을 $200^{\circ}C$, 300$300^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$로 변화시키면서 고주파 박막 저항의 미세구조와 전기적 특성을 관찰하여 최상의 열처리 조건을 알아보았다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2003년도 기술심포지움 논문집
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• pp.145-150
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• 2003

최근에 3 GHz이상의 고주파용 전자부품과 소자의 제조에 낮은 TCR 값과 높은 정밀도를 갖는 박막저항이 사용되고 있다. Ni-Cr 박막저항은 낮은 TCR 값과 저항에 대한 높은 안정성 때문에 저항 물질로 사용되는 가장 일반적인 물질이다. 본 연구에서는 $Ni_{72}Cr_{20}Al_3Mn_4Si(wt\%)$ 첨가된 우수한 저항특성을 갖는 s-type의 Evanohm 합금 타겟과 스퍼터링 장비를 이용하여 박막 저항을 제조하였다. 또한 열처리 조건을 $200^{\circ}C,\;300^{\circ}C,\;400^{\circ}C,\;500^{\circ}C$로 변화시키면서 고주파 박막저항의 미세구조와 전기적 특성을 관찰하여 최상의 열처리 조건을 알아보았다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권4호
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• pp.31-40
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• 2015

Various types of inorganic and organic colloids are present in natural water including groundwater. Previous studies showed that Fe, Mn and Al are colloid-forming elements and dissolved concentrations can be erroneous for these elements if water samples are not properly filtered. Dissolved concentrations of elements including Ca, Na, Mg, K, Fe, Mn, Si and Al in groundwater from alluvial and bedrock aquifers, and surface water near Nakdong River were determined to evaluate effects of colloids on dissolved concentrations in natural water samples using various pore sizes of filters. Groundwater is mostly anoxic and have elevated concentrations of Fe and Mn, which provides a unique opportunity to observe the effects of colloids on dissolved concentrations of colloid-forming elements. Membrane filters with four kinds of pore sizes of 1000 nm, 450 nm, 100 nm, and 15 nm were used for filtration of water samples. Concentrations of dissolved concentrations in each filtrate did not show significant differences from 1000 nm to 100 nm. However, concentrations of all elements considered were decreased in the filtrates obtained using 15 nm pore size filters by 10 to 15% compared to those using 450 nm except for bedrock groundwater. Al in surface water showed a distinct linear decrease with the decrease of filter pore sizes. These results showed that 100 nm pore size had little effect to remove colloidal particles in alluvial groundwater and surface water in our study. In contrast, significant concentration decreases in 15 nm pore size filtrates indicate that the presence of 15 to 100 nm colloidal particles may affect determination of dissolved concentrations of elements in natural water.

• 청정기술
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• 제9권3호
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• pp.125-132
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• 2003

본 연구에서는 이산화탄소 개질반응에 대한 연구의 일환으로 HY-zeolite를 주요 담체로 하여 니켈촉매의 활성화 개선에 대한 연구를 수행하였다. 메탄과 이산화탄소의 전환율은 반응온도가 증가함에 따라 증가하였고, $700^{\circ}C$ 이상이 되었을 때 80% 이상의 전환율을 얻었고, 니켈의 담지량이 증가함에 따라 촉매의 활성이 증가하였으며, 13wt%에서 가정 높은 활성을 보였다. 담체에 대한 영향으로 HY-zeolite 외에 ${\gamma}-Al_2O_3$와 $SiO_2$에 니켈을 담지시켜 반응활성을 비교한 결과 메탄과 이산화탄소의 초기 전환율은 HY-zeolite에 담지된 니켈 촉매를 사용했을 때가 가장 높았으나, 시간이 지남에 따라 ${\gamma}-Al_2O_3$에 담지된 니켈 촉매보다 비활성화가 빨랐지만 24시간 반응 후에도 메탄의 전환율이 80% 이상을 나타내었다. 그리고 13wt%Ni/HY-zeolite 촉매의 성능 향상을 위하여 Mg, Mn, K, Ca을 조촉매로 첨가하여 반응활성을 조사한 결과 Mg을 첨가한 촉매가 높은 활성과 안정성을 나타내었고, Mg의 최적 첨가량이 5wt%임을 확인하였다.

• 한국광물학회지
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• 제11권1호
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• pp.20-31
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• 1998

Adsorption of metal elements onto illite and halloysite was investigated at $25^{\circ}C$ using pollutant water collected from the gold-bearing metal mine. Incipient solution of pH 3.19 was reacted with clay minerals as a function of time: 10 minute, 30 minute, 1 hour, 12 hour, 24 hour, 1 day, 2 day, 1 week, and 2 week. Twenty-seven cations and six anions from solutions were analyzed by AAs (atomic absorption spectrometer), ICP(induced-coupled plasma), and IC (ion chromatography). Speciation and saturation index of solutions were calculated by WATEQ4F and MINTEQA2 codes, indicating that most of metal ions exist as free ions and that there is little difference in chemical species and relative abundances between initial solution and reacted solutions. The adsorption results showed that the adsorption extent of elements varies depending on mineral types and reaction time. As for illite, adsorption after 1 hour-reaction occurs in the order of As>Pb>Ge>Li>Co, Pb, Cr, Ba>Cs for trace elements and Fe>K>Na>Mn>Al>Ca>Si for major elements, respectively. As for halloysite, adsorption after 1 hour-reaction occurs in the order of Cu>Pb>Li>Ge>Cr>Zn>As>Ba>Ti>Cd>Co for trace elements and Fe>K>Mn>Ca>Al>Na>Si for major elements, respectively. After 2 week-reaction, the adsorption occurs in the order of Cu>As>Zn>Li>Ge>Co>Ti>Ba>Ni>Pb>Cr>Cd>Se for trace elements and Fe>K>Mn>Al, Mg>Ca>Na, Si for major elements, respectively. No significant adsorption as well as selectivity was found for anions. Although halloysite has a 1:1 layer structure, its capacity of adsorption is greater than that of illite with 2:1 structure, probably due to its peculiar mineralogical characteristics. According to FTIR (Fourier transform infrared spectroscopy) results, there was no shift in the OH-stretching bond for illite, but the ν1 bond at 3695 cm-1 for halloysite was found to be stronger. In the viewpoint of adsorption, illite is characterized by an inner-sphere complex, whereas halloysite by an outer-sphere complex, respectively. Initial ion activity and dissociation constant of metal elements are regarded as the main factors that control the adsorption behaviors in a natural system containing multicomponents at the acidic condition.

• Transactions on Electrical and Electronic Materials
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• 제15권1호
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• pp.24-27
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• 2014

In this study, the effects of Mn-doping and the electrode materials on the memory characteristics of $ZnO_xS_{1-x}$ resistive random access memory (ReRAM) devices on plastic are investigated. Compared with the undoped Al/$ZnO_xS_{1-x}$/Au and Al/$ZnO_xS_{1-x}$/Cu devices, the Mn-doped ones show a relatively higher ratio of the high resistance state (HRS) to low resistance state (LRS), and narrower resistance distributions in both states. For the $ZnO_xS_{1-x}$ devices with bottom electrodes of Cu, more stable conducting filament paths are formed near these electrodes, due to the relatively higher affinity of copper to sulfur, compared with the devices with bottom electrodes of Au, so that the distributions of the set and reset voltages get narrower. For the Al/$ZnO_xS_{1-x}$/Cu device, the ratio of the HRS to LRS is above $10^6$, and the memory characteristics are maintained for $10^4$ sec, which values are comparable to those of ReRAM devices on Si or glass substrates.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권1호
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• pp.19-31
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• 2011

This study had been carried out to investigate spatial and temporal variations of the concentrations of trace metals for contaminated surface water in creek affected by leachate from the tailings impoundment of the Yeonhwa II mine for about 2 years. It was also to ascertain the metal removal efficiency for potentially deleterious metals by the artificial and natural attenuation processes such as retention ponds and hydrologic mixing of uncontaminated tributaries. The concentrations of As, Pb, Cd, and Cu for leachate in the rainy season were not detected. On the other hand, the concentrations of Zn, Fe, Mn, Al, and $SO_4^{2-}$ in the rainy season for leachate were 2-66 times higher than those in the dry season, due to the oxidation of the sulfide minerals and the dissolution of the secondary minerals. The concentrations of Zn and Cd for leachate and surface water of the upper creek in the rainy season exceeded the criteria of River Water Quality and Drinking Water Quality but in the dry season, those of analyzed all the metals (As, Pb, Cd, Cu, Zn, Cd, Fe, Mn, and Al) for surface water sampled at the study area were below the criteria of River Water Quality and Drinking Water Quality. In regard of the attenuation efficiency for the concentrations of metals, Fe, Mn, Al, Zn, Cd, As, and Cu were removed highly at retention ponds, while the removal efficiency for major cations and sulfate ($SO_4^{2-}$) were related to mixing of the uncontaminated tributaries. Therefore, the major attenuation processes of the metal and sulfate contents in creek affected by leachate from a tailing dump were precipitation (accompanied by metal co-precipitation and sorption), water dilution, and neutralization.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.422-422
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• 2010

유기 발광 소자는 전색 디스플레이, 액정디스플레이의 백라이트유닛 및 조명으로의 사용가능성 때문에 많은 관심을 받아 왔고 지속적으로 발전하여 디스플레이 뿐 아니라 조명 시장에서 관심을 갖게 되었다. 그러나 유기 발광 소자의 효율은 무기 발광 소자의 효율보다 낮고 제작하는 데 고비용을 요하기 때문에 조명시장으로의 원활한 진입을 위해서는 지속적인 연구가 필요적이다. 발광층에 삼원색을 혼합하여 백색 유기 발광 소자를 제작하는 방법은 그 제조 공정이 복잡하고 공정 단가가 크게 상승할 우려가 있고 발광 물질의 수명을 동시에 고려해주어야 하는 문제점이 있다. 이 문제를 해결하기 위하여 청색 유기 발광 소자를 제작하고 색변환층으로 적색 형광체를 사용하면 그 단순한 구조에 기인한 간단한 공정으로 인해 가격과 소자성능의 안정성을 가지는 장점을 가질 수 있다. 색변환층의 두께를 통해 유기 발광 소자의 발광 스펙트럼을 아주 용이하게 조절할 수 있어 높은 연색지수를 갖는 백색 발광 유기 소자의 제작이 가능하여 조명으로의 적용 가능성이 아주 크다. 이를 바탕으로 높은 휘도를 갖는 청색 유기 발광 소자의 유리 기판 반대편에 적색 형광체층을 두께별로 도포하여 백색 유기 발광 소자를 제작하였다. 색변환층으로 사용될 적색 형광체는 $CaAl_{12}O_{19}:Mn^{4+}$ 화합물로써 졸-겔 방법을 사용하여 제작하였다. 제작한 $CaAl_{12}O_{19}:Mn^{4+}$ 화합물에 대한 X 선 회절 패턴은 형성된 형광체의 구조임을 알 수 있었다. 각기 다른 형광체의 도포 조건에 따른 구조적 성질과 색변환 효율의 변화를 알아보기 위해 주사전자 현미경 측정으로 확인하였다. 제작된 적색 형광체와 청색 유기 발광 소자는 광루미네센스 스펙트럼과 전계 발광루미네센스 스펙트럼 결과를 사용하여 발광 메커니즘을 분석하였다.