• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.299-299
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• 2008

초전도 응용기기 개발을 위해 필수적인 초전도 박막선재는 길이방향으로 임계전류밀도가 균일한 것이 요구되고 있다. 전체 길이에 대해 가장 임계전류 밀도가 낮은 지점에서 선재의 특성이 제한되기 때문이다. 한편 초전도 박막선재의 경우 높은 임계전류 밀도와 함께 과전류 등의 사고발생시를 고려하여 안정화재를 반드시 초전도층 위에 구성하여야 한다. 고가의 은(Ag)을 두껍게 증착할 수 없으므로 보통은 구리도금 또는 솔더링으로 안정화재를 덧댄다. 본 연구에서는 초전도 박막선재의 대전류화와 길이방향의 전류 균일성 향상, 안정화 특성 항상 등의 목적으로 초전도 박막선재간 확산 접합을 시도하였다. 초전도 박막선재 제조 후 안정화재인 은을 증착 후 따로 구리도금이나 솔더링 없이 선재 2가닥을 서로 포개어서 열처리를 하였다. 이때 선재간의 충분한 확산접합을 위하여 선재를 둥근 SUS 디스크에 감고 외부에 다시 SUS판재로 감아서 열처리 도중 압력을 가하였다. 아울러 포개는 방법도 초전도층의 위치에 따라 3 가지로 하였으며 열처리 후 임계전류를 측정하였다. 각 선재한 가닥에 대한 임계전류는 77K에서 50~60 A 정도의 임계전류를 나타내었으며 선재를 접합한 경우 90~120A의 특성을 나타내었으며 특히 초전도층이 설마주보는 형태에서 가장 높은 임계전류 특성을 나타내었다.

• Journal of the Korean Chemical Society
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• v.41 no.4
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• pp.180-185
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• 1997

Zinc, cadmium, lead and copper were simultaneously determined by depositing metals at - 1.200 V vs. a Ag/AgCl(sat. KCl) reference electrode for 150 seconds on a hanging mercury drop electrode(HMDE) or a thin mercury film electrode(TMFE), followed by scanning towards anodic direction using differential pulse voltammetric(DPASV) and square wave voltammetric(SWASV) techniques. The linear calibration curves were obtained for four metal ions simultaneously determined by DPASV with a HMDE in the concentration range between 20 and 100 ppb. However, the linear calibration plots were obtained only for $Cd^{2+}$ and $Pb^{2+}$ in the simultaneous determinations with a TMFE in the concentration range up to 100 ppb using DPASV and up to 10 ppb using SWASV. DPASV with a TMFE was about 15 times more sensitive than DPASV with a HMDE for simultaneous determinations of $Cd^{2+}$ and $Pb^{2+}$. SWASV was about 5 times more sensitive than DPASV at a TMFE. Concentrations of zinc in seven different sediment samples determined by DPASV with a HMDE and inductively coupled plasma-mass spectrometry were compared, resulting with an excellent correlation coefficient of 0.9993 and with no significant difference between two methods after t-test.

• Journal of Wetlands Research
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• v.17 no.3
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• pp.320-324
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• 2015

This study was executed to know the effect of three differently controlled temperature conditions on Huanren brown frog (Rana huanrensis )'s growth in 2013. We've collected nine Huanren brown frog egg's sacs on Mt. Surak ($37^{\circ}40^{\prime}55.86^{{\prime}{\prime}}N$, $127^{\circ}05^{\prime}19.99^{{\prime}{\prime}}E$) in Seoul. We put those nine egg sacs in the controlled growth chambers under low temperature (LT, $5{\pm}2^{\circ}C$), medium temperature (MT, $10{\pm}2^{\circ}C$), and high temperature (HT, $13{\pm}2^{\circ}C$) conditions with three egg sacs, respectively. We measured the eggs' hatching rate, their hatching periods, and the size of the hatched individuals. The hatching rate was higher in MT (95.6%) and the rates of the other treatments were relatively lower but very similar such as LT (82.2%) and HT (82.6%). The three hatching periods were 10 days at HT, 14 days at MT and 23 days at LT. The body sizes of the hatched individuals were biggest at MT ($7.62{\pm}0.11mm$), smallest at LT ($6.82{\pm}0.10mm$) and medium at HT ($7.19{\pm}0.15mm$) (P-value ${\leq}0.0001$). From our results, we found that the various water temperatures could be very effective to Huanren brown frog eggs' hatch and growth including their body sizes. We suggest if we study more about the growth of Huanren brown adult frogs under similar temperature conditions for a long term period, it must be very helpful for conservation study about metamorphosis rate and size of adult frog as well as we could understand about the amphibians who are adapting to the climate change.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.421-433
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• 2023

The final disposal of spent nuclear fuel(SNF) from nuclear power plants takes place in a deep geological repository. The metal canister encasing the SNF is made of cast iron and copper, and is engineered to effectively isolate radioactive isotopes for a long period of time. The SNF is further shielded by a multi-barrier disposal system comprising both engineering and natural barriers. The deep disposal environment gradually changes to an anaerobic reducing environment. In this environment, sulfide is one of the most probable substances to induce corrosion of copper canister. Stress-corrosion cracking(SCC) triggered by sulfide can carry substantial implications for the integrity of the copper canister, potentially posing a significant threat to the long-term safety of the deep disposal repository. Sulfate can exist in various forms within the deep disposal environment or be introduced from the geosphere. Sulfate has the potential to be transformed into sulfide by sulfate-reducing bacteria(SRB), and this converted sulfide can contribute to the corrosion of the copper canister. Bentonite, which is considered as a potential material for buffering and backfilling, contains oxidized sulfate minerals such as gypsum(CaSO4). If there is sufficient space for microorganisms to thrive in the deep disposal environment and if electron donors such as organic carbon are adequately supplied, sulfate can be converted to sulfide through microbial activity. However, the majority of the sulfides generated in the deep disposal system or introduced from the geosphere will be intercepted by the buffer, with only a small amount reaching the metal canister. Pyrite, one of the potential sulfide minerals present in the deep disposal environment, can generate sulfates during the dissolution process, thereby contributing to the corrosion of the copper canister. However, the quantity of oxidation byproducts from pyrite is anticipated to be minimal due to its extremely low solubility. Moreover, the migration of these oxidized byproducts to the metal canister will be restricted by the low hydraulic conductivity of saturated bentonite. We have comprehensively analyzed and summarized key research cases related to the presence of sulfates, reduction processes, and the formation and behavior characteristics of sulfides and pyrite in the deep disposal environment. Our objective was to gain an understanding of the impact of sulfates and sulfides on the long-term safety of high-level radioactive waste disposal repository.

• Membrane Journal
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• v.30 no.3
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• pp.158-172
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• 2020

In the aspect of saving energy and water, facilitating the separation membrane for the water treatment has been rising recently as one of the possible solutions. However, microbial biofouling effect is the biggest obstacle that hinders reaching higher permeability over a prolonged period of nanofiltration operation. To solve this problem and fully utilize the filtration membranes with enhanced performance, largely two kinds of solutions are studied and the first and the most commonly mentioned type is the one using the silver nanoparticles. Since silver nanoparticles are important to be well tailored on membrane surface, various methods have been applied and suggested. Using silver nanoparticles however also has the drawbacks or possible toxicity risks, raising the need for other types of utilizing non silver particles to functionalize the membrane, such as copper, graphene or zinc oxides, and amine moieties. Each attempt included in either kind has produced some notable results in killing, preventing, or repelling the bacteria while at the same time, left some unsolved points to be evaluated. In this review, the effects of metal nanoparticles and other materials on the antifouling properties of water treatment membranes are summarized.

• Journal of Korean Society of Forest Science
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• v.105 no.2
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• pp.261-267
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• 2016

In this study, the cellulase of Monochamus saltuarius (MsGHF45) gene was introduced in Kluyveromyces lactis, successfully. The molecular weight of recombinant enzyme was determined by SDS-PAGE and western blotting. The enzymatic activity was confirmed by native-PAGE containing carboxymethyl cellulose as a substrate. The optimul pH and temperature of recombinant MsGHF45 was pH5 and $40^{\circ}C$. The barium ($Ba^{2+}$) and ferrous ($Fe^{2+}$) enhanced enzyme activity, and the mercuty ($Hg^{2+}$) inhibited its activity.

• Journal of Internet Computing and Services
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• v.9 no.6
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• pp.117-125
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• 2008

With increase of concern about the Ubiquitous application, the necessity of the computer system which is miniaturized is becoming larger. The ARM processor is showing a high share from embedded system market. In this paper, ideal method for RTD-1000 controller construction and development is described using ARM microcontroller. Existing RTD-1000 measures distance of disconnection or defect of sensing casket by measuring receiving reflected wave which was sent via copper wire inside the leaking sensing rod. Using this RTD-1000, leakage and breakage of water and oil pipe can be sensed and it reports damage results to the networks. But, existing RTD-1000 wastes hardware resources much and costs a great deal to installation. Also, it needs a cooling device because the heating problem, and has some problem of the secondary memory unit such as the hard disk. So, long tenn maintenance has some problems in the outside install place. In this paper, for the resolving the problem of RTD-1000, RTD-1000A embedded system based on ARM is proposed and simulated.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.80-80
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• 2011

세계 기후 변화와 불안정한 유가 변화에 대응하고 국내산업의 저탄소 녹색성장을 위해 신재생에너지 개발이 활발하게 이루어지고 있다. 해양에너지 중에서 조류발전은 대규모 댐을 건설할 필요가 없어 비용이 적게 소요되고 특히 날씨 변화나 계절에 관계가 없고, 발전량이 예측 가능하므로 신뢰성 있는 에너지원으로 적용이 가능하다. 조류발전기 블레이드에 폴리머계 복합재료와 스테인리스강이 대부분인데, 이 재료는 특정 회사에서만 제작 가능하며, 충격에 약하고, 균열전파 속도가 빠르며, 대단히 고가이며, 수입에 의존하고 있는 실정이다. 이러한 조류발전에 사용되는 블레이드는 가혹한 부식, 캐비테이션 그리고 침식환경에 노출되어 있어 내구성이 우수한 제품개발이 대단히 중요하며, 조류발전 블레이드를 동합금으로 제작시, 내식성이 뛰어나며 구리의 특성상 해양생물 서식을 방지할 수 있고, 내캐비테이션 특성, 내구성, 가공성 및 유지보수가 용이한 장점이 있다. 이러한 동합금에 WC-27NiCr와 WC-10Co4Cr를 초고속 화염용사(HVOF)를 이용하여 코팅층의 캐비테이션 특성 및 전기화학적 거동을 연구하였다. 본 연구에서는 조류발전용 블레이드의 재료로 사용하려는 동합금에 WC-27NiCr와 WC-10Co4Cr이 용사코팅된 시험편을 사용하였다. 다채널 부식시험기인 WonA-tech WMPG-1000을 이용하여, 자연전위를 측정하였으며, 분극실험은 자체 제작한 홀더를 사용하여 $0.3318cm^2$를 노출 시켜 실험하였다. 기준전극은 은/염화은 전극을, 대극은 백금 전극을 사용하였다. 양분극과 음분극 실험을 통해 개로전위에서의 부식거동을 확인하였고, 정전위 실험도 실시하였다. 실험 종료 후 3D현미경 및 전자주사현미경(SEM)을 사용하여 코팅층 표면의 손상거동을 관찰하였다. 캐비테이션 실험은 ASTM-G32 규정에 의거하여 압전효과를 용한 진동발생 장치(RB 111-CE)를 사용하였다. 수조는 전기화학적 부식의 영향을 고려하여 아크릴로 제작하였고, 시험편은 실험장비에 맞게 파인커팅머신을 이용하여 $20mm{\times}20mm$로 절단하여 사용하였으며 혼과 대향하도록 하여 1mm 간격을 두어 실험하였다. 실험 실시 전, 미소전자저울을 사용하여 무게감소량을 측정하였으며 표면관찰을 통하여 캐비테이션 거동을 관찰하였다.

• Resources Recycling
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• v.26 no.4
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• pp.9-18
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• 2017

Recently, the amount of electronic scrap is rapidly increasing due to the rapid growth of the electronics industry. Among the components of electronic scrap, the printed circuit board(PCB) is an important recycling target which includes common metals, precious metals, and rare metals such as gold, silver, copper, tin, nickel and so on. In Korea, however, PCB recycling technologies are mainly commercialized by some major companies, and other process quantities are not accurately counted. According to present situation, several urban mining companies, research institutes, and universities are conducting research on recovery of valuable metals from PCBs and/or reusing them as raw materials that is different from existing commercialization process developed by major companies. In this study, we analyzed not only current status of collection/disposal process and recycling of waste PCBs in Korea but also the trend of recycling technologies in order to help resource circulation from waste PCBs become more active.

• Korean Journal of Environment and Ecology
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• v.33 no.2
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• pp.178-186
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• 2019

This study used the probit analysis to evaluate the toxicity of three chemicals - benomyl (Germicide), carbofuran (insecticide), and thiobencarb (herbicide) - with the FETAX (Frog Embryo Teratogenesis Assay-Xenopus) protocol using the incubated embryos of tree frog, Hyla japonica. The results showed that the larval body length decreased while the mortality and malformation rates increased as the concentrations of benomyl, carbofuran, and thiobencarb increased. The teratogenic concentration ($EC_{50}$) of benomyl, carbofuran, and thiobencarb were 1.00, 0.58, 4.75 mg/L, respectively, indicating that the malformation of larvae was the most sensitive to carbofuran. The embryo lethal concentration ($LC_{50}$) was 7.04, 28.71, and 16.12mg/L, respectively, indicating that benomyl showed the lowest embryo lethal concentration. The teratogenic index (TI) was 7.04 in Benomyl, 49.50 in Carbofuran, and 3.39 in Thiobencarb, indicating that the TI values were above 1.5, which is the criterion of teratogenicity, for all three chemicals. All three pesticides examined by this study were considered to be the most teratogenic substances, and the carbofuran was the most potent teratogen.