• Toxicological Research
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• v.13 no.1_2
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• pp.71-78
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• 1997

The mutational effects of pentachlorophenol (PCP) on the hypoxanthine phosphoribosyl transf erase (hprt) locus in human T-cell were analysed by T-cell clonal assay in vitro. Cells were exposed for 24 hours at primary culture to 0~100 ppm (W/V) PCP in dimethyl sulfoxide. Treated cells were allowed at the same time to stimulate by phytohemagglutinin (PHA) and T-cell growth factor (TCGF) and then seeded in medium containing 6-thioguanine to select for hprt-negative routants. We have also defined the optimal condition for the determination of mutant frequency. The parameters investigated include survival counting, first and second subculture for clonal efficiency plating and mutant plating. Under the optimal conditions, mutant frequencies of high dose-treated cells were significantly higher than those of non-treated or low dose cells. The results indicated a clear dose-effect relationship and showed that mutant frequency in 50 ppm PCP treated cell was 4.31$\times$$10^{-5}$ (background, 8.32$\times$$10^{-6}$). Above data strongly suggest that hprt mutation assay can be used as a biomarker for the environmental risk assessment.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.78-84
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• 2012

An in-situ optical monitoring method for real-time process monitoring of electrochemical copper deposition (CED) is presented. Process variables to be controlled in achieving desired process results are numerous in the CED process, and the importance of the chemical bath conditions cannot be overemphasized for a successful process. Conventional monitoring of the chemical solution for CED relies on the pH value of the solution, electrical voltage level for the reduction of metal cations, and gravity measurement by immersing sensors into a plating bath. We propose a nonintrusive optical monitoring technique using three types of optical sensors such as chromatic sensors and UV/VIS spectroscopy sensors as potential candidates as a feasible optical monitoring method. By monitoring the color of the plating solution in the bath, we revealed that optically acquired information is strongly related to the thickness of the deposited copper on the wafers, and that the chromatic information is inversely proportional to the ratio of $Cu$ (111) and {$Cu$ (111)+$Cu$ (200)}, which can used to measure the quality of the chemical solution for electrochemical copper deposition in advanced interconnection technology.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.7
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• pp.769-776
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• 2011

In order to cope with the requirements of smaller patterns, larger surfaces and lower costs in the fields of displays, optics and energy, greater attentions is now being paid to the development of micro-pattern machining technology. Compared with flat molds, roll molds have the advantages of short delivery, ease of manufacturing larger surfaces, and continuous molding. This paper presents the state-of-the-art of the micro pattern machining technology on the roll molds and introduces some research results on the machining process technology. The copper and nickel-phosphorous-alloy plating process, machining process technology for uniform micro patterns. micro cutting simulation and the real time monitoring system for micro machining are summarized. The developed technologies have led the complete localization of the prism sheets and will be applied to the direct forming process with succeeding research & development.

• New & Renewable Energy
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• v.1 no.1 s.1
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• pp.64-71
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• 2005

The stability of alumina-coated NiO cathodes was studied in $Li_{0.62}/K_{0.38}$ molten carbonate electrolyte. Alumina was effectively coated on the porous Ni plate using galvanostatic pulse plating method. The deposition mechanism of alumina was governed by the concentration of hydroixde ions near the working electrode, which was controlled by the temperature of bath solution. Alumina-coated NiO cathodes were formed to $A1_2O_3-NiO$ solid solution by the oxidation process and their Ni solubilities were were than that of NiO up to the immersion time of 100h. However, their Ni solubilities increased and were similar to that of the bare NiO cathode after 100h. It was because aluminum into the solid solution was segregated to $\alpha-LiAlO_2$ on the NiO and its Product did not Play a role of the Physical barrier against NiO dissolution.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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• pp.81-85
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• 2011

Recently, the electronic parts are to be thinner plate, smaller size, light weight material and CPU, HDD and DRAM in all the parts have been produced on the basis of the high speed and greater capacity. Also, conventional goods have replaced a LED (Light-Emitting Diode) in lighting products so; such industry devices need to have cooling. To maximize all the performance on the heat-radiated products, the area of heat-radiated parts is required to be cooled for keeping the life time extension and performance of product up. Existing cooling systems are using radiant heat plate of aluminum, brass by extrusion molding, heat pipe or hydro-cooling system for cooling. There is a limitation for bringing the light weight of product, cost reduction, molding of the cooling system. So it is proposed that an alternative way was made for bringing to the cooling system. EP (Engineering Plastic) of low-cost ABS (Acrylonitrile butadiene styrene Resin) and PC (Polycarbonate) was coated with brass and the coating made the radiated heat go up. The performance of radiant heat plate is the similar to the existing part. We have studied experimentally on the radiated heat plate for the light-weight, molding improvement and low-cost. From now on, we are going to develop the way to replace the exiting plate with exterior surface of product as a cooling system.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.97-97
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• 2017

This study investigated the corrosion protection by electrodeposited copper layer on AZ31 Mg alloy with and without additional silver layer by immersion test, salt spray test, OCP transient and potentiodynamic polarization experiment. The single electrodeposited Cu layer on AZ31 Mg alloy showed a nodular structure with many imperfections of crevices between the nodules, which resulted in the fast initiation of pitting corrosion within first few hours of immersion. Double-layer coating of Cu and outer Ag layer slightly increased the initiation time for pitting corrosion. Triple-layer coatings of Cu/Ag/Cu exhibited the most efficient corrosion protection of AZ31 Mg alloy, compared to the single- and double-layer coatings. Surface morphology of the outer Cu layer in the triple-layer was changed from the nodular structure to fine particle structure with no crevices due to the presence of an additional Ag layer. Thus, the improved corrosion resistance of AZ31 Mg alloy by electrodeposited Cu/Ag or Cu/Ag/Cu layers is readily ascribed to the decreased number of imperfections in the electrodeposited layers due to the additional silver layer. It is concluded that the additional silver layer provides many nucleation sites for the second Cu plating, resulting in the formation of finer and denser structure than the first Cu electrodeposit.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.174.2-174.2
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• 2016

도금은 크게 전해 도금과 무전해 도금으로 나눌 수 있다. 전기적 에너지를 사용하여 이온 상태의 금속을 환원시켜 석출함으로써 도금을 진행하는 전해 도금과는 달리 무전해 도금은 도금액 내의 환원제에 의해 금속 이온을 환원시켜 도금을 진행한다. 무전해 도금법은 전해 도금에 비해 전류 인가 장비가 필요하지 않아 도금 공정이 간단하고, 피도금체에 따른 인가 전류, 전압, 금속의 환원 전위 등을 계산하지 않아도 되기 때문에 전문적인 지식이 없어도 도금을 할 수 있다. 하지만 무전해 도금은 도금이 진행 될수록 도금액 내 금속 이온, 환원제의 농도 등이 수시로 변화하기 때문에 도금액의 조성을 파악하여 원하는 두께의 도금층을 형성하는 방법에 대한 연구가 필요하다. 본 연구에서는 무전해 도금액 내 환원제, 도금액 온도, 도금 시간을 변경하여 Ni 무전해 도금을 형성 하였고 그 특성을 평가하였다. 도금은 각각 플라스틱, RF module 유리 등 다양한 기판에 진행 하였으며, 도금 후 밀착성, 도금 두께 및 microstructure를 분석하였다. 도금 후 밀착성을 분석하기 위해 열처리 후 박리정도를 테스트를 하였고, 도금 두께 및 microstructure를 분석하기 위해 field emission scanning electron microscope (FE-SEM), energy-dispersive spectroscopy (EDS)를 사용하였다. 실험 결과, 두께 $3{\sim}5{\mu}m$ 급의 균일한 도금층이 형성된 것을 확인하였으며, $260^{\circ}C$에서 3회 열처리 후 박리성 평가 결과, 결함 없는 양호한 표면을 나타내었다.

• BMB Reports
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• v.37 no.4
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• pp.487-492
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• 2004

The extent of codon usage in the protein coding genes of the mycobacteriophage, Bxz1, and its plating bacteria, M. smegmatis, were determined, and it was observed that the codons ending with either G and / or C were predominant in both the organisms. Multivariate statistical analysis showed that in both organisms, the genes were separated along the first major explanatory axis according to their expression levels and their genomic GC content at the synonymous third positions of the codons. The second major explanatory axis differentiates the genes according to their genome type. A comparison of the relative synonymous codon usage between 20 highly- and 20 lowly expressed genes from Bxz1 identified 21 codons, which are statistically over represented in the former group of genes. Further analysis found that the Bxz1- specific tRNA species could recognize 13 out of the 21 over represented synonymous codons, which incorporated 13 amino acid residues preferentially into the highly expressed proteins of Bxz1. In contrast, seven amino acid residues were preferentially incorporated into the lowly expressed proteins by 10 other tRNA species of Bxz1. This analysis predicts for the first time that the Bxz1-specific tRNA species modulates the optimal expression of its proteins during development.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.15-16
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• 2008

In case manufacturing COF, through hole should be made to be used for a pathway connecting the conductive layers of its both faces. In case Cu-plating inside of through hole with electroless plating way, contact between Cu and PI film gets bad to be fell apart from PI by the impact of applying to the electric devices. Therefore, after sputtering is applying on inner through hole, then a method to perform electroplating process. In this study, after changing sputtering condition to manufacture FCCL, we looked the changeability of the upper PI and inner hole Cu layers. Making use of RF Magnetron sputtering equipment, we coated Cu thin film and Cu-plated on it through electroplating. After cold-mounting the completed FCCL, we examined hole section through an optical microscope. From the result of test, with parameters deposition pressure and deposition time, both the thickness of the hole plated layer and PI plated upper layer increased at regular rate, increasing the thickness of Cu sputter layer. However, from the result of test in increasing RF-power, we could know the increment rate of hole plated layer is considerably greater than that of PI plated upper layer. Therefore, we finally acquired good result; if you want only to increase the plated layer of inner hole, it's much better to increase RF-power.

• Korean Journal of Metals and Materials
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• v.48 no.5
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• pp.462-468
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• 2010

Carbon Nanotubes (CNTs) have recently emerged as a material with outstanding properties. It has shown promising potential for applications in many engineering fields as electronic devices, thermal conductors, and light-weight composites. Researchers have investigated their use as reinforcements in themetal matrix composites of CNTs. In the present work, we decorated CNTs with Ni particles by electroless plating. The CNTs were wet-ball milled for various milling times with a nickel sulfate solution. The precipitated Ni particles were observed mainly by FESEM. In this study, the dispersion of the CNTs and Ni particles was improved with the addition of the surfactant. Also, as the CNTs were shortened and widened by an increased ball milling time, the size of the precipitated Ni particles increased. It was estimated that the CNTs were deformed and caused some defects on their surface during the ball milling process. Those defects were assumed to be heterogeneous nucleation sites for the Ni particles.