• 오토저널
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• 제4권3호
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• pp.24-39
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• 1982

It has already been known that quenching effect is influenced greatly by stirring and changing coolant's temperature on quenching. But according to the past investigations its effect has not been taken into consideration quantitatively in the cooling process. The purpose of this study is that the influence of flow rate and temperature on the quenching effect of cooling water as quenching medium is quantitatively examined by using the open channel. The stream of water in this study is turbulent flow. The temperature of the specimen made of pure copper is measured by CA thermocouple in the vicinity of the surface and recorded by an automatic recorder during the quenching process in city water. The results obtained are as follows; 1. The quenching effect of cooling water generally increases with Reynolds Number(characteristic length; specimen diameter)as shown in the experimental formula; but at the realm of Reynolds Number from 1.2 * 10$^{4}$ to 9.2 * 10$^{4}$, the increasing rate of quenching effect shows little increase. 2. The increasing rate of quenching effect was increased under the flow rate of 221 cm/sec. On the other hand, it was decreased below this flow rate. 3. The quenching effect was influenced by the water temperature and the flow rate. But it was rather dependent upon the former than the latter. 4. Although the quenching effect appeared loosely in the water temperature of 50.deg. C, it was shown that the quenching effect increased in the low flow rate of 31 cm/sec. comparing with the still water. 5. It is desirable to design the quenching system to be over 1.2 * 10$^{4}$ in Reynolds Number or over, 3000$cm^{-1}$ / in V/v in order to increase the quenching effect of the system using open channel.annel.

• 대한지하수환경학회지
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• 제1권2호
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• pp.85-89
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• 1994

폐기물 매립지로부터의 침출수의 유출에 의한 지하수와 토양의 오염은 심각한 환경문제중의 하나 이며, 일반적으로 매립지에서는 폐기물의 생화학적 자연분해 또는 강우 침투에 의하여 침출수가 형성된다. 대전시 신대동 일반 폐기물 매립지 역 주변토양의 Cu, Pb와 Zn 함량은 대부분의 우리나라 토양내의 평균 함량보다는 높은 것으로 나타났으나 농작물을 통하여 인류에 해를 끼칠 수 있는 정도는 아닌 것으로 나타났다. 지하수의 경우 Cu, Pb와 Zn이 검출되지는 않았으나 특정 시료의 pH가 5.6으로 나타나 음용수로는 부적합한 것으로 판명되었다. 토양오염이 발견된 지역에서는 심토내의 중금속 원소 함량이 표토보다 높은것으로 나타나 지하수를 통한 오염체의 영향이라고 판단된다. 전기 비저항 탐사를 행한 결과 토양오염이 진행된 지역에 함수층이 존재하고 있었으며 침술수의 배출에 의한 오염체의 이동에 의해 전기 비저항값이 더욱 낮게 나타났다. 한편 침출수의 배출지점에서 멀어질수록 오염물질의 감소에 의해 전기 비저항치가 증가하는 것으로 나타났으며 실제로 토양내의 중금속원소 함량도 감소한다.

• 박물관보존과학
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• 제5권
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• pp.31-36
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• 2004

본 실험은 현재 박물관에서 사용하고 있거나 사용 검토 중이던 목재수종 6종(물푸레나무, 삼나무, 흑호두나무, 솔송나무, 오동나무, 단풍나무)을 대상으로 금속부식 영향을 조사한 것이다. 부식 테스트의 방법으로는 실험하고자 하는 재료와 test 시편(금속시편)을 일정 온습도에서 장시간 노출시키면서 재료가 시편에 미치는 영향을 관찰하는 Oddy test를 사용하였다. 6종의 나무 자재를 대상으로 실시한 Oddy test 결과 수종에 따라 금속부식의 형태가 조금씩 다르게 나타났으며, blank를 제외한 대부분의 철(Fe)과 납(Pb)시편에서는 표면전체에 부식이 발생하였다. 또한 구리(Cu)시편에서도 정도는 다르지만 모든 시편에서 조금씩 변색이 된 것을 관찰할 수 있었다.

• 한국재료학회지
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• 제23권9호
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• pp.477-482
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• 2013

We investigated the detection properties of nitrogen monoxide (NO) gas using transparent p-type $CuAlO_2$ thin film gas sensors. The $CuAlO_2$ film was fabricated on an indium tin oxide (ITO)/glass substrate by pulsed laser deposition (PLD), and then the transparent p-type $CuAlO_2$ active layer was formed by annealing. Structural and optical characterizations revealed that the transparent p-type $CuAlO_2$ layer with a thickness of around 200 nm had a non-crystalline structure, showing a quite flat surface and a high transparency above 65 % in the range of visible light. From the NO gas sensing measurements, it was found that the transparent p-type $CuAlO_2$ thin film gas sensors exhibited the maximum sensitivity to NO gas in dry air at an operating temperature of $180^{\circ}C$. We also found that these $CuAlO_2$ thin film gas sensors showed reversible and reliable electrical resistance-response to NO gas in the operating temperature range. These results indicate that the transparent p-type semiconductor $CuAlO_2$ thin films are very promising for application as sensing materials for gas sensors, in particular, various types of transparent p-n junction gas sensors. Also, these transparent p-type semiconductor $CuAlO_2$ thin films could be combined with an n-type oxide semiconductor to fabricate p-n heterojunction oxide semiconductor gas sensors.

• 한국안전학회지
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• 제14권3호
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• pp.93-100
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• 1999

Decomposition efficiency, power consumption, and applied voltage of CFC(Chlorofluorocatbon) were investigated by SPCP(surface induced discharge plasma chemical processing) reactor to obtain optimum process variables and maximum decomposition efficiencies. Decomposition efficiency of CFC-12 with various electric frequencies(5~50kHz). flow rates (100~1,000mL/min), initial concentrations(100~1,000ppm), electrode materials(W, Cu, Al). electrode thickness(1, 2, 3mm) and reference gases($N_2$, $O_2$, air) were measured and the products were analyzed with FT-IR. Experimental results showed that at the frequency of 10kHz, the highest decomposition efficiency of 92.7% for CFC-12 were observed at the power consumptions of 29.6W. respectively, and that decomposition efficiency decreased with increasing frequency above 20kHz and decomposition efficiency per unit power were 3.13%/W for CFC-12. Decomposition efficiency was increased with increasing residence times and with decreasing initial concentration of pollutants. Decomposition efficiency was increased with increasing thickness of discharge electrode and the highest decomposition efficiency was obtained for the electrode diameter of 3m. As the electrode material, decomposition efficiency was in order that tungsten(W), copper(Cu), aluminum (Al). Decomposition of CFC-12 in the reference gas of $N_2$ showed the highest efficiency among three reference gases, and then the effect of reference gas on the decomposition efficiency decreased in order of air and $O_2$. The optimum power for the maximum decomposition efficiency was 25.3W for CFC.

• 유기물자원화
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• 제15권2호
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• pp.81-88
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• 2007

톱밥을 이용한 중금속 제거에 관한 연구가 수행되어졌다. 납, 구리, 카드뮴 이온들 중에서 납의 흡착능이 pH 4에서 0.22 mmol/g-dry mass로서 가장 높았다. 톱밥의 표면상태와 납이온의 존재 여부는 FT-IR, SEM(Scanning Electron Microscopy) 그리고, EDX(Energy Dispersive X-ray)에 의해서 확인되어졌다. 초기 납 농도가 100ppm일때 0.5g의 톱밥으로 약 90%의 납 이온을 제거할 수 있었다. Langmuir model 식을 이용하여 납 이온에 대한 등온흡착선을 묘사하였으며 실험결과는 모델식에서 얻어진 결과와 잘 부합되었다. 또한 대부분의 흡착은 60분 내에 이루어졌으며 납 이온 용액의 pH는 5.8에서 4.5로 시간에 따라 감소하였다.

• Progress in Superconductivity
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• 제13권2호
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• pp.127-132
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• 2011

Many research groups have been manufacturing coated conductor by various processes such as PLD, MOD, and MOCVD, but the methods with production cost suitable for wide and massive application of coated conductor did not develop yet. Spray pyrolysis method adopting ultrasonic atomization was tried as one of the possible option. GdBCO precursor films have been deposited on IBAD substrate by spray pyrolysis method at low temperature and converted to GdBCO by post heat treatment. Ultrasonic atomization was used to generate fine droplets from precursor solution of Gd, Ba, and Cu nitrate dissolved in water. Primary GdBCO films were deposited at $500^{\circ}C$ and oxygen partial pressure of 1 torr. After that, the films were converted at various temperatures and low oxygen partial pressures. C-Axis oriented films were obtained IBAD substrates at conversion temperature of around $870^{\circ}C$ and oxygen partial pressures of 500 mtorr ~ 1 torr in a vacuum. Thick c-axis epitaxial film with the thickness of 0.4 ~ 0.5 ${\mu}m$ was obtained on IBAD substrate. C-axis epitaxial GdBCO films were successfully prepared by ex-situ methods using nitrate precursors on IBAD metal substrate. Converted GdBCO films have very dense microstructures with good grain connectivity. EDS composition analysis of the film showed a number of Cu-rich phase in surface. The precursor solution having high copper concent with the composition of Gd : Ba : Cu = 1 : 2 : 4 showed the better grain connectivity and electrical conductivity.

• 한국전산유체공학회지
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• 제21권4호
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• pp.1-10
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• 2016

The analysis of characteristics of turbulent flow and thermal boundary layer for natural convection caused by fire along vertical wall is performed. The 4m-high vertical copper plate is heated and kept at a uniform surface temperature of $60^{\circ}C$ and the surrounding fluid (air) is kept at $16.5^{\circ}C$. The flow and temperature is solved by large eddy simulation(LES) of FDS code(Ver.6), in which the viscous-sublayer flow is calculated by Werner-Wengle wall function. The whole analyzed domain is assumed as turbulent region to apply wall function even through the laminar flow is transient to the turbulent flow between $10^9$<$Gr_z$<$10^{10}$ in experiments. The various grids from $7{\times}7{\times}128$ to $18{\times}18{\times}128$ are applied to investigate the sensitivity of wall function to $x^+$ value in LES simulation. The mean velocity and temperature profiles in the turbulent boundary layer are compared with experimental data by Tsuji & Nagano and the results from other LES simulation in which the viscous-sublayer flow is directly solved with many grids. The relationship between heat transfer rate($Nu_z$) and $Gr_zPr$ is investigated and calculated heat transfer rates are compared with theoretical equation and experimental data.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.598-602
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• 2018

석유정제공장에서 사용된 폐촉매의 특성을 조사하여 바나듐 레독스 흐름전지용 소재인 전해액의 제조에 대하여 연구하였다. 석유정제공정에서 사용된 폐촉매의 총공극 부피, 비표면적 및 평균 기공크기는 BET법과 BJH법으로 계산하여 각각 3.96cc/g, 13.81m2/g, 1.15A 구하여 폐촉매에서 바나듐을 회수하여 전해액으로 제조 할 수 있음을 확인하였다. 폐촉매를 TG-DTA분석결과, $25^{\circ}C$부터 $700^{\circ}C$ 범위에서 중량손실이 약 23wt%였다. 폐촉매의 성분을 ICP 장비를 분석하여 황, 바나듐, 니켈, 알루미늄, 망간 철 구리 등의 원소를 확인하였다. 또한 TEM 장비로 측정한 결과 바나듐 외 다른 원소들이 결정성 클러스터가 밝은 점으로 명백하게 드러남을 알 수 있었다. 액액 추출법을 사용하여 폐촉매로 부터 바나듐을 99.25%로 분리하여 추출한 바나듐용액의 전기화학적 특성분석을 위해 CV(cyclic votammetry)측정한 결과, 산화/환원피크가 나타남으로서 전해질 용액으로서의 가능성을 보여주고 있다. 또한 폐촉매로 부터 추출된 바나듐 용액의 순도를 더욱 높여 전해질 용액을 제조하면 기존 상용화된 전해질 성능과 같은 것을 제조 할 것으로 사료된다.

• Environmental Analysis Health and Toxicology
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• 제28권
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• pp.17.1-17.3
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• 2013

The fact that hazardous metals do not bio-degrade or bio-deteriorate translates to long-lasting environmental effects. In the context of evidently rapid global industrialization, this ought to warrant serious caution, particularly in developing countries. In the Republic of Fiji, a developing country in the South Pacific, several different environmental studies over the past 20 years have shown levels of lead, copper, zinc and iron in sediments of the Suva Harbor to be 6.2, 3.9, 3.3 and 2.1 times more than the accepted background reference levels, respectively. High levels of mercury have also been reported in lagoon shellfish. These data inevitably warrant thorough assessment of the waste practices of industries located upstream from the estuaries, but in addition, an exposure and health impact assessment has never been conducted. Relevant government departments are duty-bound, at least to the general public that reside in and consume seafood from the vicinities of the Suva Harbor, to investigate possible human effects of the elevated hazardous metal concentrations found consistently in 20 years of surface sediment analysis. Furthermore, pollution of the intermediate food web with hazardous metals should be investigated, regardless of whether human effects are eventually confirmed present or not.