• 폴리머
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• 제28권3호
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• pp.218-224
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• 2004

고분자 생체재료에서 세포부착과 성장은 재료의 적심성, 화학구조, 표면전하 및 거칠기 등의 표면 성질에 의존한다. 본 연구에서는 저밀도 폴리에틸렌 필름 (LDPE)의 표면 적심성과 골수유래 줄기세포의 증식 및 성장성을 측정하기 위하여 플라즈마 처리를 실시하였으며 개질된 필름 표면의 특성을 조사하였다. 또한 LDPE 필름에서의 세포부착과 증식률은 세포수 관찰과 역전사 중합효소 연쇄반응으로 확인하였다. 표면성질의 하나인 물 접촉각 측정 결과 플라즈마 처리 시간이 길어짐에 따라 필름표면의 접촉각이 감소하였으며 암형성 유전자와 암억제 유전자의 발현률이 60∼70$^{\circ}$ 사이에서 높음을 확인할 수 있었다. 또한 세포수 관찰을 통해 접촉각이 60∼70$^{\circ}$인 표면에서 세포 증식률이 우수하여 표면성질이 세포의 성장과 분화에 중요함을 확인하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.963-969
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• 2010

The railway vehicle consists of wires, bodies, bogies and wheelsets, and each part has very complex mechanism. In this paper, wheel-rail contact algorithm is implemented using C++ and inserted into the ODYN which is a dynamic analysis program. To analyze wheel-rail contact mechanism, information such as contact points, contact angle and rolling radius is calculated according to the wheel and rail profile. Using this information, a table for the calculation of the wheel-rail contact analysis is made according to the lateral displacement. And, the creepage and normal force are calculated and a creep force is estimated by the FASTSIM. To verify the reliability of the wheel-rail contact algorithm, results of the program are compared with the ADAMS/Rail and paper. Finally, a wheelset of the railway vehicle is modeled using ODYN and simulated static and dynamic analysis. And, to verify the reliability of the simulation results, a displacement, velocity, acceleration and force are compared with results of ADAMS/Rail.

• Composites Research
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• 제25권3호
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• pp.76-81
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• 2012

대기압 플라즈마 처리를 통해 탄소나노튜브(CNT) 표면은 개질 되며 개질된 입자의 표면과 탄소섬유 강화 CNT 페놀 복합재료간에 계면접착력에 변화를 확인하였다. CNT 표면에 플라즈마 처리에 따라 표면 변화가 발생되고 표면 개질의 결과를 확인하기 위해 FT-IR을 사용하였다. 또한, 정적 접촉각 실험법을 통해 플라즈마 처리에 따른 CNT의 젖음성을 비교 평가하였다. 순수 CNT 입자의 접촉각은 $118^{\circ}$ 였으나, 플라즈마 처리를 할 경우 $60^{\circ}$도로 표면 개질을 통해 젖음성이 향상됨을 확인하였다. 탄소섬유와 CNT-페놀복합재료 간 계면접착력은 플라즈마 처리에 따라 겉보기 강성도가 증가되는 결과를 확인하였으며, 음향방출 실험법과 전기저항 측정법을 병행한 이중기지평가법을 통해 계면전단강도 (IFSS)를 계산하여 계면접착력 향상을 확인하였다.

• 대한금속재료학회지
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• 제50권8호
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• pp.591-597
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• 2012

This paper presents regularly micro-textured glass surfaces ensuring the superhydrophobic properties in the Cassie-Baxter regime. The proposed surfaces were fabricated simply and efficiently by filling the glass material into a silicon micro-mold with periodic micro-cavities based on a thermal-reflow process, resulting in a successful demonstration of the textured glass surface with periodically-arrayed micro-pillar structures. The static and dynamic wetting properties of the micro-textured glass surfaces were characterized by measuring the static contact angle (SCA) and contact angle hysteresis (CAH), respectively. In addition, the surface wettability was estimated theoretically based on Wenzel and Cassie-Baxter wetting theories, and compared with the experimental ones. Through the experimental and theoretical observations, it was clearly confirmed that the proposed micro-textured glass surfaces showed the slippery superhydrophobic behaviors in the Cassie-Baxter wetting mode.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.291-291
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• 2013

The wettability of TiO2 layers is controlled by forming highly ordered arrays of nanocones using nanopatterning, based on self-assembly and dry etching. Nanopatterning of TiO2 layers is achieved via formation of self-assembled monolayers of SiO2 spheres fabricated using the Langmuir-Blodgett technique, followed by dry etching. Compared to a thin film TiO2 layer, the nanopatterned TiO2 samples show a smaller static water contact angle, where the water contact angle decreases as the etching time increases, which is attributed to the Wenzel equation. When TiO2 layers are coated by 1H,1H,2H,2H-perfluorooctyltrichlorosilane, we observed the opposite behavior, exhibiting superhydrophobicity (up to contact angle of $155^{\circ}$) on the nanopatterned TiO2 layers. Self-assembled nanopatterning of the TiO2 layer may provide an advanced method for producing multifunctional transparent layers with self-cleaning properties.

• 한국정밀공학회지
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• 제31권4호
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• pp.353-358
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• 2014

This paper reports a simple, yet effective 1-step surface modification method for stainless steel. Electrochemical etching in dilute Aqua Regia forms hierarchical micro and nanoscale structure on the surface. The surface becomes highly hydrophobic (${\sim}150^{\circ}$) as a result of the etching in terms of static contact angle (CA). However the liquid drops easily pinned on the surface because of high contact angle hysteresis (CAH), which is called a "petal effect": The petal effect occur because of gap between surface microstructures, despite of intrinsic hydrophobicity of the base material. The pore size and period of surface structure can be controlled by applied voltage during the etching. This method can be applied to wide variety of industrial demand for surface modification, while maintaining the advantageous anti-corrosion property of stainless steel.

• 센서학회지
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• 제22권2호
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• pp.100-104
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• 2013

A superhydrophobic mesh is a unique structure that blocks water, while allowing gases, sound waves, and energy to pass through the holes in the mesh. This mesh is used in various devices, such as gas- and energy-permeable waterproof membranes for underwater sensors and electronic devices. However, it is difficult to fabricate micro- and nano-structures on three-dimensional surfaces, such as the cylindrical surface of a wire mesh. In this research, we successfully produced a superhydrophobic water-repellent mesh with a high contact angle (> $150^{\circ}$) for nanofibrous structures. Conducting polymer (CP) composite nanofibers were evenly coated on a stainless steel mesh surface, to create a superhydrophobic mesh with a pore size of $100{\mu}m$. The nanofiber structure could be controlled by the deposition time. As the deposition time increased, a high-density, hierarchical nanofiber structure was deposited on the mesh. The mesh surface was then coated with Teflon, to reduce the surface energy. The fabricated mesh had a static water contact angle of $163^{\circ}$, and a water-pressure resistance of 1.92 kPa.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.448-448
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• 2011

We investigated the fabrication method of superhydrophobic nanocoating prepared by a simple spin-coating and the chemisorption of fatty acid. The resulting coating showed a tremendous water repellency (static water contact angle = $154^{\circ}$) and the water contact angle can be modulated by changing the number of deposition cycles of ZnO and the carbon length of Self-Assembled Monolayers (SAM). Varying the number of deposition cycles of ZnO controlled the surface roughness, and affected to the superhydrophobicity. This simple coating method can be universally applicable to any substrates including flexible surfaces, papers and cotton fabrics, which can effectively be used in various potential applications. We also observed the thermal and dynamic stabilities of SAM on ZnO nanoparticles. The superhydrophobicic surface maintained its superhydrophobic properties below $250^{\circ}C$ and under dynamic conditions.

• Elastomers and Composites
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• 제33권5호
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• pp.363-369
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• 1998

UV를 이용하여 반응성 모노머인 아크릴아미드를 SBR에 광그라프트 시키는데 있어서 주요한 인자인 모노머 농도, 조사시간 그리고 카본블랙의 함량이 모노머의 그라프트율에 미치는 영향을 살펴보았다. 광개시제로는 benzophenone을 사용하였다. 아크릴아미드의 그라프트율을 측정하기 위하여 FT-IR ATR과 증류수를 이용하여 정접촉각을 측정하였다. 아크릴아미드의 함량과 UV 조사시간이 증가함에 따라 그라프트율은 증가하였으며 또한 접촉각은 감소하는 현상을 나타내었다. SBR중 카본블랙 함량이 증가함에 따라 그라프트율이 증가함을 알 수 있었다.

• Current Optics and Photonics
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• 제8권3호
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• pp.300-306
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• 2024

To solve the nozzle swing angle non-contact measurement problem, we present a nozzle pose estimation algorithm involving weighted measurement uncertainty based on rotation parameters. Firstly, the instantaneous axis of the rocket nozzle is constructed and used to model the pivot point and the nozzle coordinate system. Then, the rotation matrix and translation vector are parameterized by Cayley-Gibbs-Rodriguez parameters, and the novel object space collinearity error equation involving weighted measurement uncertainty of feature points is constructed. The nozzle pose is obtained at this step by the Gröbner basis method. Finally, the swing angle is calculated based on the conversion relationship between the nozzle static coordinate system and the nozzle dynamic coordinate system. Experimental results prove the high accuracy and robustness of the proposed method. In the space of 1.5 m × 1.5 m × 1.5 m, the maximum angle error of nozzle swing is 0.103°.