• Journal of ILASS-Korea
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• v.17 no.1
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• pp.14-19
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• 2012

The present study conducts experimental investigation on spreading and deposition characteristics of a $4.3{\mu}l$ de-ionized (DI) water droplet impacting upon aluminum (Al 6061) flat and textured surfaces. The micro-textured surface consisted the micro-hole arrays (hole diameter: $125{\mu}m$, hole depth: $125{\mu}m$) fabricated by the conventional micro-computer numerical control (${\mu}$-CNC) milling machine process. We examined the surface effect of texture area fraction ${\varphi}_s$ ranging from 0 to 0.57 and impact velocity of droplet ranging from 0.40 m/s to 1.45 m/s on spreading and deposition characteristics from captured images. We used a high-speed camera to capture sequential images for investigate spreading characteristics and the image sensor to capture image of final equilibrium deposition droplet for analyze spreading diameter and contact angle. We found that the deposition droplet on textured surfaces have different wetting states. When the impact velocity is low, the non-wetting state partially exists, whereas over 0.64 m/s of impact velocity, totally wetting state is more prominent due to the increase kinetic energy of impinging droplet.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.521-525
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• 1996

An attempt is made to characterize and synthesize engineered surfaces. The proposed method is not only an analytical tool to characterize but alsoto generate/synthesize three-dimensional surfaces. The developed method expresses important engineered surface characteristics such as the autocorrelation or pwoer spectrum density functions in terms of the two-dimensional autoregressive coefficients.

• Tribology and Lubricants
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• v.18 no.5
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• pp.339-344
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• 2002

Whenever moving surfaces of machine driving elements interact in air and lubricating oil, oxidization film on the surfaces are generated. It is effect to prevent friction and wear on contact area. Since the electronic current progress the oxidization of metal, if the electronic flow be regulated, the thickness of oxidization film can be regulated and friction characteristics can be improved. But the electronic current can deteriorate friction characteristics, so various characteristics must be investigated on transforming of electronic current. Therefor, using the Norton equation in this study, short current were transformed between frictional materials using ball on disk type tester. It was studied on effect of electronic current for friction characteristics.

• KSBB Journal
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• v.7 no.4
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• pp.318-324
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• 1992

The adsorption characteristics of bovine serum albumin(BSA) on the modified carbon fiber and cellulose surfaces were investigated. In order to define the effects of solid surface characteristics on protein adsorption, surfaces of carbon fiber and cellulose were modified by physical and chemical treatment. The amounts of BSA adsorbed onto various solid surfaces were evaluated by batch method under various pH and ionic strength. The amount of adsorbed BSA was highly dependent on pH as well as surface functional groups.

• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1942-1949
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• 2006

Typically, condensate forms as droplets on the fin surfaces and may bridge the space between the fin surfaces. This is due to the dry characteristics inherent to the fin surface. The droplets increase the air-side pressure drop. In the case of high air velocities, these droplets may be blown off the fins and entrained in the air stream. To minimize the formation of condensate droplet, the wet ability of the fins must be improved. The carry-over velocity is affected by fin surface characteristics. To avoid carry-over in the air conditioner having the highest air velocity of 1.5 m/sec, the dynamic contact angle (DCA) should be at least lowly under $60^{\circ}$.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.436-441
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• 2003

The present study investigates heat/mass transfer characteristics in rotating two-pass ducts of three different aspect ratios with 90-ribbed surfaces. The results show that the flows generated by the 180-turn, rib turbulators, and duct rotation. The curvature of the 180-turn produces Dean vortices causing high heat/mass transfer in the turning region and in the upstream region of the second-pass. The rib turbulators disturb the main flow by producing reattachment and separation near the ribbed surfaces, and increase heat/mass transfer in the region between the ribs. As the rotation number increases, the heat/mass transfer discrepancy between the leading and the trailing surfaces become larger.

• Electrical & Electronic Materials
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• v.10 no.10
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• pp.1011-1015
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• 1997

In this paper we investigated the electro-optical characteristics of amorphous (a)- twisted nematic (TN)-liquid crystal display(LCD) on polymide (PI) surfaces with different molecular structure. It was found that the domaine size of a-TN-LCD on PI with high polarization is small compared to a-TN-LCD on PI with medium polarization. It is considered that the response time of a-TN-LCd contributes to surface effect between the substrate surfaces and the LC molecules. Finally we obtained that the viewing angle of a-TN-LCD on PI surfaces increases with decreasing the domain size.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.3
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• pp.233-238
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• 2010

In this paper, we have proposed discrete ray tracing method (DRTM) for numerical analysis of characteristics of electromagnetic propagation along 2D random rough surfaces. The point of the present method is to discretize not only rough surface but also ray tracing. The former helps saving computer memories and the latter does simplifying ray searching algorithm resulting in saving computation time. Numerical calculations are carried out for 2D random rough surfaces, and electric field distributions are shown to check the effectiveness of the proposed DRTM.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.401-406
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• 2008

This paper proposes a method to calculate the static characteristics of the FDBs with the curved surface. The general Reynolds equations are derived for the curved surfaces in the ${\theta}s$ plane. And the Reynolds equation is transformed to the finite element equations by considering the continuity of pressure and flow at the interface between the curved, journal and the thrust bearings. It also includes the Reynolds boundary condition in the numerical analysis to simulate the cavitation phenomenon. The static characteristics of the coupled journal and conical bearings were investigated due to the variation of conical angle. It shows that the conical angle is one of the important design parameters affecting the static and dynamic characteristics of FBBs.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.227-228
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• 2002

One of the serious challenges in developing rotary compressor with HFC refrigerant is the prediction of scuffing times and wear amounts between vane and roller surface. In this study, the tribological characteristics of sliding surfaces using roller-vane geometry of rotary compressor were investigated. The sliding tests were carried out under various sliding speeds, normal loads and surface roughness. During the tests, friction force, wear scar width, time to failure, surface temperature, and surface roughness were monitored. Because severe wear was occurred on vane surface, TiN coating was applied on sliding surfaces to prolong the wear-life of vane-roller interfaces. From the sliding tests, it was found that there was the optimum initial surface roughness to break in and to prolong the wear life of sliding surfaces. Depending on load and speed, the protective layers, which were composed of metallic oxide and organic compound, were formed on sliding surfaces. Those would play an important role in the amount of friction and wear between roller and vane surfaces.