• 열처리공학회지
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• 제2권4호
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• pp.69-72
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• 1989

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.865-873
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• 2017

Converter transformer is the key equipment of high voltage direct current transmission system. The solid suspending particles originating from the process of installation and operation of converter transformer have significant influence on the insulation performance of transformer oil, especially in presence of DC component in applied voltage. Under high electric field, the particles easily lead to partial discharge and breakdown of insulating oil. This paper investigated copper particle effect on the breakdown voltage of transformer oil at combined AC and DC voltage. A simulation model with single copper particle was established to interpret the particle effect on the breakdown strength of insulating oil. The experimental and simulation results showed that the particles distort the electric field. The breakdown voltage of insulating oil contaminated with copper particle decreases with the increase of particle number, and the breakdown voltage and the logarithm of particle number approximately satisfy the linear relationship. With the increase of the DC component in applied voltage, the breakdown voltage of contaminated insulating oil decreases. The simulation results show that the particle collides with the electrode more frequently with more DC component contained in the applied voltage, which will trigger more discharge and decrease the breakdown voltage of insulating oil.

• 한국환경과학회지
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• 제12권12호
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• pp.1303-1308
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• 2003

This experiment was carried out to investigate the effects of heavy metals (cadmium, chromium, copper and lead) on the seed germination of Arabidopsis thaliana, and examinated the removal effects of biostone and green tea on the heavy metal toxicity. Cadmium and chromium among the four heavy metals had no effect on the seed germination even in the concentration fifty times higher than in the official standard concentration of pollutant exhaust notified by the Ministry of Environment. However, seeds were not germinated in the concentration of copper ten times higher and in the concentration of lead fifty times higher than the official standard concentration. When seeds were sown in the solutions of lead (15, 20, 25 and 30 mg/L) and copper(15 and 20 mg/L), the seed germination rates were 0％ and less than 10％, respectively. However, when biostone(3 g/30 $m\ell$) was added, the seed germination rate was 100％ in all the concentrations. The germination rate was 100％ in distilled water and copper solution (5 mg/L). However, green tea (0.2 g/30 $m\ell$) was added, the seed germination rate was 0％ in both. The results show that cadmiun and chromium had no effect on the seed germination, but lead and copper decreased the rate of seed germination of Arabidopsis thaliana, Biostone removed heavy metal toxicity, but green tea did not removed heavy metal toxicity during germination.

• 한국초지조사료학회지
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• 제20권4호
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• pp.259-264
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• 2000

오차드그래스의 완숙 종자배양에서 배지 내에 첨가되는 copper의 농도가 캘러스 형성과 식물체 재분화율에 미치는 영향을 조사하였다. 캘러스의 유도는 $2\;mg/{\ell}$의 2,4-D와 $0.1-100\;{\mu}mol$의 copper sulfate를 첨가한 MS 배지를 이용하였으며, 식물체 재분화는 $1\;mg/{\ell}$의 NAA, $5\;mg/{\ell}$의 kinetin 및 $0.1-100\;{\mu}mol$의 copper sulfate가 첨가된 N6 배지를 이용하였다.그 결과, copper의 첨가는 캘러스 형성능력에는 유의성있는 차이를 나타내지 않았으나, copper가 첨가된 배지에서 생성된 캘러스에서 백색이면서 조직이 치밀한 즉, 식물체 재분화에 적합한 캘러스의 비율이 높게 나타났다. 식물체 재분화율은 copper가 첨가된 배지에서 생성된 캘러스가 첨가되지 않은 배지에서 생성된 캘러스보다 높게 나타났으며, 특히 $70\;{\mu}mol$의 copper가 첨가된 백지에서 생성된 캘러스가 대구조에 비해 2.5배 이상 증가된 가장 높은 재분화 능력을 나타내었다. 또한, 캘러스당 재분화된 식물체의 수는 $70\;{\mu}mol$의 copper가 첨가된 배지에서 생성된 캘러스에서 대조구에 비해 2.6배 이상 증가된 것으로 나타났다.

• 한국산학기술학회논문지
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• 제7권3호
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• pp.506-511
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• 2006

은은 주조성과 가공성이 뛰어나 장신구 제작에 주된 소재로 채택되어 왔다. 이런 은 소재 자체의 장점을 이용한 전통적인 방법 중 하나인 모꾸메가네는 나뭇결무늬와 같은 자연스러운 금속의 혼합문양을 표현할 수 있어서 부가가치가 높지만 제작 공정이 복잡하고 힘들어서 경제적으로 장신구를 제작하는데 어려움이 있었다. 기존의 모꾸메가네 공정 대신 은과 구리의 융점차를 이용한 변형 주조 방법과 냉간압연으로 구리와 은 두 금속간의 우수한 결합을 유지하면서도 기존의 모꾸메가네와 유사한 표면 장식 효과를 얻을 수 있는 새로운 공정을 제안해 보았다. 직경 3 mm의 구리 그래뉼과 0.5 mm, 1.5 mm 두께의 구리 판재에 순은 용탕을 부어 두 금속간의 확산 접합이 완성된 괴를 만들고, 이후 롤러 압연을 실시하여 두께 1.5 mm의 판재를 만들어서 이를 이용하여 반지 시제품을 제작한 결과, 제안된 공정으로 이종 금속 접합도가 우수하면서 모꾸메가네와 유사한 효과를 성공적으로 낼 수 있었다. 제안된 공정은 기존의 반복된 열간 가공에 의한 복잡한 모꾸메가네 공정에 비해 보다 간단하고 경제적으로 모꾸메가네 효과를 갖는 은 장신구 디자인을 가능하게 함을 확인하였다.

• 한국재료학회지
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• 제16권11호
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• pp.710-714
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• 2006

The purpose of this study is to identify the effect of additives and composition on copper surface morphology and mechanical characteristics by copper electrodeposition. Additives such as hydroxy ethyl cellulose(HEC), chloride ion were used in this study. Electrochemical experiments allied to SEM, XRD, AFM and four- point probe were performed to characterize the morphology and mechanical characters of copper in the presence of additives. Among various electrodeposition conditions, the minimum surface roughness of copper foil was obtained when electrodeposited at the current density of 200 mA/$cm^2$ for 68 seconds with 2 ppm of HEC. The minimum value of surface roughness(Rms) was 107.6 nm. It is copper foil is good for electromigration inhibition due to preferential crystal growth of Cu (111) deposited in the electrolyte containing chloride ions(10 ppm) and HEC(1 ppm).

• Molecules and Cells
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• 제39권3호
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• pp.195-203
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• 2016

Copper is an essential element required for a variety of functions exerted by cuproproteins. An alteration of the copper level is associated with multiple pathological conditions including chronic ischemia, atherosclerosis and cancers. Therefore, copper homeostasis, maintained by a combination of two copper ions ($Cu^+$ and $Cu^{2+}$), is critical for health. However, less is known about which of the two copper ions is more toxic or functional in endothelial cells. Cubic-shaped $Cu_2O$ and CuO crystals were prepared to test the role of the two different ions, $Cu^+$ and $Cu^{2+}$, respectively. The $Cu_2O$ crystal was found to have an effect on cell death in endothelial cells whereas CuO had no effect. The $Cu_2O$ crystals appeared to induce p62 degradation, LC3 processing and an elevation of LC3 puncta, important processes for autophagy, but had no effect on apoptosis and necrosis. $Cu_2O$ crystals promote endothelial cell death via autophagy, elevate the level of reactive oxygen species such as superoxide and nitric oxide, and subsequently activate AMP-activated protein kinase (AMPK) through superoxide rather than nitric oxide. Consistently, the AMPK inhibitor Compound C was found to inhibit $Cu_2O$-induced AMPK activation, p62 degradation, and LC3 processing. This study provides insight on the pathophysiologic function of $Cu^+$ ions in the vascular system, where $Cu^+$ induces autophagy while $Cu^{2+}$ has no detected effect.

• 환경영향평가
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• 제17권2호
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• pp.143-151
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• 2008

As the NOAFL of copper based on liver toxicity in the human body is set and the TDI of copper is lower, it is necessary to strengthen the drinking water standard of copper according to toxic effects and the TDI of copper in humans. It is difficult to calculate the accurate drinking water standard because of the part of uncertainty for chronic effects of acute human with Wilson's disease and baby in the current studies. In order to improve the drinking water standard of copper considering of liver toxicity, it is desired to set the drinking water standard with concerning of the revising tendency in the foreign countries such as US, EC and WHO.

• 한국레이저가공학회지
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• 제16권2호
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• pp.7-11
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• 2013

Recently advanced laser processing is widely introduced to improve the efficiency of micro part production and to reduce the rate of inferior goods. In this paper the trend of delamination of single layer with both thin copper and polyimide according to the variation of copper thickness was investigated using the coupled thermal-structural analysis of ANSYS. From these analyses results, some conclusions were obtained. Firstly, the maximum temperature was increasing with respect to decrease of copper thickness. Secondly the maximum strain which was in general estimation the main effect of the delamination was observed in case of the copper thickness of $5{\mu}m$. Finally the trend of the delamination was decreasing with increasing the thickness of copper layer.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 춘계학술발표 개요집
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• pp.6-9
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• 1996

The Joining of copper rod and zirconia tube was carried out in Ar gas atmosphere. There are two type of the joining. The one is the reaction bond consisting of Cu and zirconia was dominated by surface reaction wi th a undetctable very thin layer. It was found that copper elements were diffused to zirconia side, but that most of Z $r^{4+}$ ions were not diffused to copper side. This result means application of a DC voltage to migrate oxygen to the copper/zirconia interface can oxidize metal at the copper /zirconia interface, and the bonding reaction between zirconia and copper oxide may occur. The other is the reaction bonding was dominated by interdiffusion with a very thick interface layer. This result means application of a DC voltage can reduce zirconia at the interface. The bonding reaction is to be an alloying between Zr and Cr.