• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.139-139
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• 2018

최근 자동차 산업을 중심으로 한 수송용 기기의 경량화 추세에 따라 대표적인 경량금속 소재인 알루미늄 합금에 대한 수요가 증가하고 있으며 이에 따라 알루미늄 합금 표면에 다양한 특성을 부여할 수 있는 표면개질 기술에 대한 필요성이 부각되고 있다. 알루미늄 합금의 대표적인 표면처리기술인 아노다이징과 유사한 원리로 표면에 세라믹 코팅층을 형성할 수 있는 기술인 플라즈마 전해 산화(Plasma electrolytic oxidation, PEO)가 주목을 받고 있다. PEO 코팅법은 전해액 내에 소재를 침지시키고 400 ~ 600V에 이르는 고전압을 인가시켜 마이크로 방전을 유도하여 표면에 치밀한 세라믹 층을 형성시키는 기술이다. 본 연구에서는 PEO법으로 표면 개질된 Al 합금 표면의 표면 조직 특성과 전기화학 특성을 평가하고, 코팅층 특성에 미치는 공정 변수의 영향을 분석하고자 하였다. PEO 처리를 위해 사용된 소재는 상용 Al 합금 판재(Al 5083-O)로서 $2cm{\times}2cm$로 절단하여, 에머리페이퍼로 1000번까지 연마하여 사용하였다. 시험을 위한 PEO 처리 시스템은 전해액 수조, 일정 온도 유지를 위한 열교환기와 칠러, 전원 발생을 위한 전원공급기(power supply)로 구성되었다. 전해액은 약 알칼리 수용액을 이용하였으며, 전원 공급기를 통해 시험편에 펄스 전류를 인가하였다. PEO 처리 후 시편에 대하여 SEM, EDS, XRD 등을 이용한 표면 특성 평가를 실시하였다. 또한 코팅층의 전기화학적 부식 특성 평가를 위해 해수용액에서 동전위분극실험을 실시하였다. 시험 결과, Al 합금의 PEO 처리 시 내식성은 개선되는 것으로 확인되었으며, 공정변수는 표면의 미세조직 및 전기화학적 특성에 큰 영향을 미치는 것으로 나타났다.

• The Journal of Engineering Geology
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• v.33 no.3
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• pp.371-388
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• 2023

A stratum with a complex composition and a distributed low-permeability soil layer is difficult to remediate quickly because the soil remediation does not proceed easily. For efficient purification, the permeability should be improved and the soil remediation agent (H₂O₂) should be injected into the contaminated section to make sufficient contact with the TPH (Total petroleum hydrocarbons). This study analyzed a method for crack formation and effective delivery of the soil remediation agent based on pneumatic fracturing, plasma blasting, and vacuum suction (the PPV method) and compared its improvement effect relative to chemical oxidation. A demonstration test confirmed the effective delivery of the soil remediation agent to a site contaminated with TPH. The injection amount and injection time were monitored to calculate the delivery characteristics and the range of influence, and electrical resistivity surveying qualitatively confirmed changes in the underground environment. Permeability tests also evaluated and compared the permeability changes for each method. The amount of soil remediation agent injected was increased by about 4.74 to 7.48 times in the experimental group (PPV method) compared with the control group (chemical oxidation); the PPV method allowed injection rates per unit time (L/min) about 5.00 to 7.54 times quicker than the control method. Electrical resistivity measurements assessed that in the PPV method, the diffusion of H₂O₂2 and other fluids to the surface soil layer reduced the low resistivity change ratio: the horizontal change ratio between the injection well and the extraction well decreased the resistivity by about 1.12 to 2.38 times. Quantitative evaluation of hydraulic conductivity at the end of the test found that the control group had 21.1% of the original hydraulic conductivity and the experimental group retained 81.3% of the initial value, close to the initial permeability coefficient. Calculated radii of influence based on the survey results showed that the results of the PPV method were improved by 220% on average compared with those of the control group.

• The Korean Journal of Pesticide Science
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• v.5 no.1
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• pp.12-18
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• 2001

The effects of organophosphorus were examined with inhibition of the cholinesterase activity on tile chicken plasma in vivo and in vitro. The cholinesterase activity in chicken plasma determined by tile Ellman mettled was $23{\mu}mol$/min/g protein. After oral administration with 0.2 and 0.5 times of organophosphorus terbufos $LD_{50}$(1.81 mg/kg), cholinesterase activity were inhibited to 36% and 96% of control after 15min in vivo, respectively. After oral administration with 0.2 and 0.5 times of terbufos $LD_{50}$(1.81 mg/kg), then the recovery of cholinesterase activity followed to 99% and 56% of control after 11hr, respectively. Ki of phosphorodithioate and phosphorothioate with P=S was $74{\sim}322\;mole^{-1}min^{-1}$ in vitro. Ki of phosphate and phosphorothiolate with P=O was $13898{\sim}79610\;mole^{-1}min^{-1}$. Toxicology of organophosphorus with P=S was higher than that of organophosphorus with P=S by oxidation. $pI_{50}$ of phosphorodithioate and phosphorothioate with P=S was $21{\sim}102$ mg/L. $pI_{50}$ of phosphate and phosphorothiolate with P=O was $0.519{\sim}0.071$ mg/L. Enzyme-Inhibition method with cholinesterase was the rapid bioassay method to detect the organohpophorus pesticides in vitro.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.9
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• pp.681-684
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• 2010

The $TiO_2$/ZnS/Ag/ZnS/$TiO_2$ multilayered structure for the transparent electrodes in plasma display panel was designed by essential macleod program (EMP) and the multilayered film was deposited on a glass substrate by direct-current (DC)/radio-frequency (RF) magnetron sputtering system. During film deposition process, the Ag layer in $TiO_2$/Ag/$TiO_2$ structure became oxidized and the filter characteristic was degraded easily. In this study, ZnS layer was adopted as a diffusion blocking layer between $TiO_2$ and Ag to prevent the oxidation of Ag layer efficiently in $TiO_2$/ZnS/Ag/ZnS/$TiO_2$ structure. Based on the AES depth profiling analysis, the Ag layer was effectively protected by the ZnS layer as compared with the $TiO_2$/Ag/$TiO_2$ multilayered films without ZnS as an antioxidant layer. The 3 times stacked $TiO_2$/ZnS/Ag/ZnS/$TiO_2$ films have low sheet resistance of $1.22{\Omega}/{\square}$ and luminous transmittance was as high as 62% in the visible ranges.

• Anatomy and Cell Biology
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• v.56 no.4
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• pp.538-551
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• 2023

Exposure to environmental pollutants such as carbon tetrachloride (CCL₄) causes liver damage. This study aimed to compare the ameliorative activity of the dates flesh extract (DFE) and selenium-nanoparticles (SeNPs) on CCL₄-induced hepatotoxicity and if DFE could be a useful alternative supplement. Twenty-four male albino rats were enrolled and randomly divided into four equal groups (6 rats in each group): control group received only basal diet with no medications. Group II received CCL₄ in a dose of 0.5 mg/kg intraperitoneal injection twice weekly for four weeks. Group III rats were pretreated with SeNPs in a dose of 2.5 mg/kg once a day orally three times/wk for four weeks alone then combined with the previously described dose of CCL₄ for another four weeks. Group IV rats were pretreated with DFE in a dose of 8 ml of the aqueous extract/kg/d orally for four weeks alone then combined with the previously described dose of CCL₄ for another four weeks. The liver damage was assessed by estimation of plasma concentration of albumin and enzymes activities of alanine aminotransferase and tissue genes expression. Liver oxidation levels were assessed by measuring the tissue concentration of the malondialdehyde, superoxide dismutase, and the total glutathione. Additionally, inflammatory mediators tumour necrosis factor--α and interleukin-6 were estimated. Detecting the liver's cellular structural damage was done by histopathological and immunohistochemical examination. This study suggests that CCL₄-induced liver damage in rats can be protected by administration whether the costly SeNPs or the economical DFE.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.189-195
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• 2001

We prepared TMR junctions of NiFe(170 )/CoFe(48 )/Al(13 )-O/CoFe(500 )/Ta(50 ) structure on 2.5$\times$2.5 $\textrm{cm}^2$ area Si/SiO$_2$ substrates in order to investigate the uniformity of magnetoresistance(MR) value using a ICP magnetron sputter. Each layer was deposited by the ICP magnetron sputter and tunnel barrier was formed by the plasma oxidation method. We measured MR ratio and resistance of TMR devices with four-terminal probe system by applying external magnetic field. Although we used ICP sputter which is known as superior to make uniform films, the standard variation of MR ratio was 2.72. The variation was not dependent on the TMR devices location of a substrate. We found that MR ratio and spin-flip field (H's) increased as the resistance increased, which may be caused by local interface irregularity of the insulating layer. The variation of resistance value was 64.19 and MR ratio was 2.72, respectively. Our results imply that to improve the insulating layer fabrication process including annealing process to lessen interface modulation in order to mass produce the TMR devices.

• Tuberculosis and Respiratory Diseases
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• v.51 no.3
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• pp.211-223
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• 2001

Background : Rhinovirus infection of the airways results in increased permeability of the airway vascular endothelium with the influx of plasma proteins, including lipids such as LDL. In vitro studies on the effect of oxLDL on leukocytes has shown many pro inflammatory effects on multiple leukocytes. We hypothesized that oxLDL is one mechanism for recruiting granulocytes to the airways during a RV infection. Therefore, chemotaxis and transendothelial migration, in response to nLDL, was determined for these granulocytes. Methods : nLDL was oxidized with 5mM Cu2S04 for 20-24 hours. 3-5 105 cells were loaded into the Transwell filter while the chemotatic agonists were placed in the lower well for chemotaxis. Confluent monolayers on HPMEC were grown on Transwell filters for transendothelial migration. The filters were washed and eosinophils and neutrophils loaded on to the filter with the chemotatic agonist was were placed in the lower well. The wells were incubated for 3 hours. The number of migrating cells was counted on a hemocytometer. Results : OxLDL, but not nLDL, is chemotatic for eosinophils and neutrophils. The level of granulocytes chemotaxis was dependent on both the concentration of LDL and its degree of oxidation. OxLDL stimulates eosinophil and neutrophils migration across HPMEC monolayers (+/-IL-$1{\beta}$ preactivation) in a dose dependent manner. Conclusion : Increased vascular permeability during a RV infection may lead to the influx and oxidation of LDL. The resulting oxLDL. is one possible mechanism for the recruitment of neutrophils and eosinophils to the airway interstitial matrix. Once in the airways, granulocytes can further interact with oxLDL to promote airway inflammation.