• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.111-111
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• 2012

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.104-109
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• 2009

In order to apply FBG(Fiber Bragg Grating) sensor as one of reliable sensors in the commercial railway structure, the reliability of FBG sensor in the mechanical strength viewpoint have to be confirmed and the maximum strain should surpass the fracture strain of the host structure to measure the measurands until the host structures fail. In this paper, several factors that influence the mechanical failure strength of fiber Bragg grating sensors were analyzed. A set-up for dynamic tensile testing of optical glass fibers with fiber Bragg gratings was made. To increase the FBG failure strength, techniques relying on the H2 loading treatment and stripping methods were established and testified as a result of the tensile strength test of optical fibers.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.7
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• pp.541-548
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• 2009

Iron coated media (activated carbon, sand and starfish) were prepared at pH 4 and applied for the treatment of landfill leachate containing organic compounds and soluble metal ions such as $Zn^{2+},\;Cu^{2+},\;Mn^{2+}$ in batch and column experiment. The amount of iron coated in media was analyzed with EPA 3050B method. The removal efficiency of metal ions and phenol was compared with iron coated media. The amount of iron coated in Fe-AC and ICS(iron coated sand) were 1,612 mg/kg and 1,609 mg/kg, respectively, while it was higher with 1,768 mg/kg in ICSF(iron coated starfish). The result of batch study represent the highest removal efficiency in the treatment of wastewater using iron coated starfish. In column study, the removal efficiency of phenol and metal ions was higher in multi-layered system of ICS, Fe-AC and ICSF compared to single layered system. Breakthrough time in the effluent was relatively enhanced for $Cu^{2+}$ and $Zn^{2+}$ in multi-layered system while the removal efficiency of $Mn^{2+}$ were not varied much. Therefore, multi-layered system was identified as the better system for the treatment of wastewater containing of metal ions and organic compound.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.6
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• pp.560-567
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• 2009

This paper was designed to estimate the adhesion strength of galvannealed coatings on steel sheets. The adhesion strength were evaluated using single lap - shear tests where the lap joint was bonded by structural adhesive. Tests were performed for overlap length of 5mm, 10mm and 15 mm and three directions (0, 45, 90) of steel sheets used as the adherend of the overlap joint. After the tests, FE simulations of the single lap-shear test were also carried out to observe the stress distribution in the interface between the adhesive and the coated sheet. The results showed that the joint failure loads obtained from the tensile tests of bonded single lap-joints were the same, regardless of overlap lengths and directions of steel sheets. Also, the failure of galvannealed coatings greatly depended on shear stress distribution in the interface and the value was about 30MPa.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.238-243
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• 2007

This paper is designed to estimate the adhesion strength of coating layer on galvannealed steel sheet using lap shear test. The single lap shear test is the most commonly used standard test for determining the strength of medium-strength and high strength bonds. The bond strength of bonded single lap joints on subjecting the substrates to loads is determined by lap shear forces in the direction of the bonded joint. In this study, specimen for adhesion strength test was made to attach coated sheet to cold rolled sheet and were heated in temperature of 180 for 20minutes. After test, detached parts of coatings on coated sheet were observed using SEM and EDX to identify substrate and complete detachment. The tested results showed that adhesive strength of coating is unrelated to anisotropy of sheet and is difficult to be extracted using conventional theory because of fine cracks of coating layers which were created during annealing process.

• Transactions of the Society of Information Storage Systems
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• v.2 no.3
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• pp.178-183
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• 2006

A Blu-ray disc, which has a more than 25GB optical capacity, has been known as a promising next-generation optical disc format. It commonly has a 1.1 mm thick substrate and a 0.1 mm thick cover layer for beam transmitting and the protection of the reflecting surface. The cover layer is generally formed by the spin coating process. However, in conventional spin coating, small bumps are formed along the rim of the disc, which results in the fatal reading error. Numerical simulation of the thin film flow behaviors during spin coating with the commercial solver and optimal spinning conditions was obtained. Thickness distribution of the cover layer according to the variation of substrate's edge shape could be calculated as well. By modifying the shape of the substrate edge shape, the bumps along the disc rim could be minimized, and it was proved that the chamfered edge, around $5{\sim}10$ degree, is the simplest and most effective way to minimize the bumps.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.28-28
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• 2015

현재 인쇄전자 소자 생산을 위해 사용되고 있는 대부분의 그라비아 롤러는 미세 패턴의 보호와 인쇄 중 마찰에 대한 내구성을 향상시키기 위해 경질 크롬 도금 막이 사용되고 있다. 그러나 경질 크롬 도금 막의 경우 구현할 수 있는 경도(~1000 HV)와 이형성, 내마찰(마찰계수: ~ 0.6) 특성 등에 한계가 있다. 이러한 경질 크롬 도금이 적용된 그라비아 롤은 그 수명과 내구성, 구현할 수 있는 인쇄 품질 및 신뢰성 그리고 인쇄처리 속도 등에 있어 여러 문제가 있다. DLC(Diamond Like amorphous Carbon)는 낮은 마찰계수 값인 0.2 이하와 뛰어난 내마모성, 상대재료에 대한 이형성 등을 겸비한 표면강화 기술로 경질 크롬 도금막 대비 우수한 표면 경도(>1,800 HV) 특성을 갖으며, 합성된 DLC 코팅 막의 경우 정밀 인쇄 제판이 요구하는 표면거칠기를 구현할 가능성이 높다는 장점이 있다. 특히 실리콘이 첨가 된 Si-DLC의 경우 표면의 마찰계수를 0.1 이하까지 낮출 수 있는데 닥터블레이드 및 잉크, 인쇄 기재와의 마찰 훼손을 최소화시켜 그라비아 인쇄 롤의 수명을 향상시킬 수 있다. 또한 PECVD 공정을 이용하여 합성한 Si-DLC는 표면거칠기를 10nm 이하의 경면으로 구현할 수 있으며, 높은 접촉각에 의한 우수한 이형성을 통해 미세 패턴 내부에 전자잉크/페이스트가 잔류되는 현상을 억제할 수 있다. 이는 기존 경질 크롬 도금이 적용된 그라비아 롤에서 발생하는 패턴 내 잉크 잔류-고형화와 그에 의한 사용수명 단축현상을 현저히 개선시킬 수 있다.

• Journal of the Mineralogical Society of Korea
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• v.28 no.2
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• pp.95-108
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• 2015

Nano-sized iron colloids are formed as acid mine drainage is exposed to surface environments and is introduced into surrounding water bodies. These iron nanomaterials invoke aesthetic contamination as well as adverse effects on aqueous ecosystems. In order to control them, the characteristics of their behaviour should be understood first, but the cumulative research outputs up to now are much less than the expected. Using zero-valent iron (ZVI) and magnetite, this study aims to investigate the behaviour of iron nanomaterials according to the change in the composition and pH of background electrolyte and the concentration of natural organic matter (NOM). The size and surface zeta potential of iron nanomaterials were measured using dynamic light scattering. Characteristic behaviour, such as aggregation and dispersion was compared each other based on the DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory. Whereas iron nanomaterials showed a strong tendency of aggregation at the pH near point of zero charge (PZC) due to electrostatic attraction between particles, their dispersions became dominant at the pH which was higher or lower than PZC. In addition, the behaviour of iron nanomaterials was likely to be more significantly influenced by cations than anions in the electrolyte solutions. Particularly, it was observed that divalent cation influenced more effectively than monovalent cation in electrostatic attraction and repulsion between particles. It was also confirmed that the NOM enhanced the dispersion nanomaterials with increasing the negative charge of nanomaterials by coating on their surface. Under identical conditions, ZVI aggregated more easily than magnetite, and which would be attributed to the lower stability and larger reactivity of ZVI.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.4
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• pp.471-477
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• 2014

Purpose: We have analyzed the transmittance distribution of the ocular lens using local transmittance microscope to investigate the optical homogeneity of the lens. Methods: The transmittance of the laser which is focused on the surface of the ocular lens was measured by using the photo-detector and lock-in amplifier and analyzed. Multi-coated, uncoated, and progressive lenses were analyzed. Results: In the measurement of the progressive lens and a physical stimulated lens, local transmittance microscopy analysis showed a high degree of match with the measurement results through the optical microscope. In addition, the average value of the transmittance is reduced and the standard deviation was increased in the presence of optical defects. In unstimulated lens, there are a large impact on transmittance whether the anti-reflective coating is presence or absence in both the local transmittance microscopy and general transmittance analysis. Conclusions: The distribution of the transmittance measured by local transmission microscopy were changed when the various stimulus is applied to the lenses. These analyzes by local transmission microscopy can be utilized as a way to evaluate or determine the uniformity of the coating film or lens.

• Journal of the Korean Chemical Society
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• v.52 no.1
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• pp.57-65
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• 2008

are nanometer or micrometer scale vesicles that can be used as drug delivery carriers. However, plain liposomes are plagued by rapid opsonization, making their circulation time in bloodstream be shortened. In this study, model protein, bovine serum albumin (BSA)-coated liposomes were prepared by coating cationic liposomes with BSA molecules at higher pH than isoelectric point of BSA. The BSA molecules coated on the liposomal surface were denatured by thermal treatment at above 60oC. While both plain and cationic liposomes had about mean particle diameter of 1041 nm, BSA-coated cationic liposomes (BCL) had mean particle diameter of 1091 nm. Encapsulation of model drug, doxorubicin (DOX), in liposomes were carried out by using remote loading method and the loading efficiency of DOX to liposomes was about 90%. The mean particle diameter of BCL did not increase in blood plasma and adsorption of plasma protein was much less than plain or cationic liposomes. These results suggest that BCL can be used as a long-circulating liposomes in bloodstream.