• International Journal of Automotive Technology
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• 제7권1호
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• pp.115-120
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• 2006

On a rotating contact surface of arbitrary shape, the relative velocity of the contact point sliding between the surfaces is computed with the basic geometries of the rotating surfaces, and the acceleration of the contact point between the contact surfaces is computed by using the relative velocity of the contact point. Thus the equation for the acceleration constraint between the contact surfaces in muitibody dynamics is not coupled with the parameters such as the relative velocity of the contact point. In case of the kinematic analysis, the acceleration of the contact point on any specific instant may also be efficiently computed by the present technique because the whole displacement of a full cycle need not be interpolated. Employing a cam-follower mechanism as a verification model, the acceleration of the contact point computed by the present technique is compared with that computed by differentiating the displacement interpolated with a large number of nodal points.

• 한국가시화정보학회지
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• 제22권1호
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• pp.28-33
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• 2024

We visualized the rupturing of liquid films flowing over a disk rotating with large angular velocity. A setup of high speed imaging for liquid flows on dark and reflective surfaces are suggested. From the result, rivulet structures are revealed to be strongly governed by three-dimensional surface structures developed in the film flow. Additionally, unique flow structures including the rivulet sliding and internal meandering are investigated. Generation mechanism of such structures are discussed in terms of the dynamic contact angle theory.

• Journal of Electrochemical Science and Technology
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• 제5권3호
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• pp.82-86
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• 2014

This work presents the variation of formic acid oxidation on Pt depending on hydrodynamic condition using a rotating disk electrode. As the rotating speed increases, the oxidation rate of formic acid decreases under voltammetric and chronoamperometric measurements. The coverages of poison formed from formic acid during the chronoamperomertric investigations decrease when the rotating speed increases. As the roughness factor of Pt electrode surface increases, on the other hand, the current density of formic acid oxidation increases. These observations are discussed in terms of the tangential flow along Pt electrode surfaces generated by the rotating disk electrode, which reduces a contact time between formic acid and a Pt site, thus the formic acid adsorption.

• KSTLE International Journal
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• 제2권2호
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• pp.146-149
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• 2001

Recently, laser printers have been developed to have high-speed laser scanner with hydrodynamic bearings. Among the bearings, herringbone grooved bearing (HGB) produces hydrodynamic pressure by high-speed rotating and so make the surfaces between the shaft and sleeve separated. Accordingly, the bearings with non-contact rotation are suitable to high-speed rotating and have long bearing life and reliability. HGB is a kind of journal bearing and uses oil for a lubricant. HGB has excellent stiffness and load carrying capacity. Also, HGB is leakage-free due to groove pumping action. Consequently, HGB is valuable to be applied to high-performance devices such as hard disk drive, copier, and so on.

• Design & Manufacturing
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• 제14권4호
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• pp.1-10
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• 2020

The seal plays a role in preventing oil leakage when the lip and the rotating shaft come into contact with the fluid and air pressure. Recently, micro dimples or micro pockets are processed and used on the lubrication surfaces of thrust bearings, mechanical bearings, and piston rings. Compared to a smooth surface, micro dimples reduce friction and increase the life of parts. This paper analyzed various kinds of micro dimple shapes on the sealing surface, i.e. circle, rectangle, triangle, and trapezoid. For this purpose, Introduced the design of experiments to work out a micro dimple configuration, unlikely to be damaged from cracks and low in contact stress. As a result, the triangular dimple showed the best results. Optimal factors were dimple size 0.15 mm, dimple depth 0.0383 mm, dimple density 40%, and the maximum equivalent stress was 9.1455 MPa, and the maximum contact pressure was 9.6612 MPa. This paper analyzed the optimal shape of dimples by finite element analysis. As a research project, experiments and comparative analysis of micro dimple shapes are needed.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.433-434
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• 2002

Chemical mechanical polishing refers to a process by which silicon and partially-processed integrated circuits (IC's) built on silicon substrates are polished to produce planar surfaces for the continued manufacturing of IC's. Chemical mechanical polishing is done by pressing the silicon wafer, face down, onto a rotating platen that is covered by a rough polyurethane pad. During rotation, the pad is flooded with a slurry that contains nanoscale particles. The pad deforms and the roughness of the surface entrains the slurry into the interface. The asperities contact the wafer and the surface is polished in a three-body abrasion process. The contact of the wafer with the 'soft' pad produces a unique elastohydrodynamic situation in which a suction force is imposed at the interface. This added force is non-uniform and can be on the order of the applied pressure on the wafer. We have measured the magnitude and spatial distribution of this suction force. This force will be described within the context of a model of the sliding of hard surfaces on soft substrates.

• 한국환경과학회지
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• 제6권6호
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• pp.689-696
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• 1997

This paper discussed effect of the surface roughness and the hydrophobicity of support material on the microbial attachment In a rotating biological contactor. The by- drophoblclty of each support material was determined by the measurement of contact angle of water and the surface roughness was measured by the surface roughness In- strument. Microorganisms have well attached on the surface of more hydrophilic support material like Nylon6 than that of the hydrophobic support material like PE. When the relatively hydrophilic surface was roughen, the microbial attachment was increased but when the relatively hydrophobic surface was roughen, the attachment was slightly In- creased because the hydrophobicity of support material was Increased by roughening the hydrophobic surface. Although both variables, the surface hydrophobicity and the surface roughness, have Influenced the microbial attachment, the influence of the surface roughness overruled that of the surface hydrophobicity. Support material whose surfaces were roughened about 1mm, 6mm and 11mm were allowed for attached 3, 7 and 24hr, but the differences of maximum and minimum attachment of each material gave nearly constant values and similar trend with time.

• 한국컴퓨터그래픽스학회논문지
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• 제9권1호
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• pp.19-27
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• 2003

Most interaction schemes in virtual environment are indirect in one way or another. ln particular, without a haptic device (which introduces its own problems due to its cumbersomeness), users must rely on visual (or/and aural) feedback, and can not directly appreciate the 3Dness of the interaction object even with stereoscopy. This causes a drop in object presence because people are used to, for instance, observing objects in one's hand, rotating and manipulating them with physical contact. To alleviate this problem, this paper proposes a hand-held cubic screen, named TangibleScreen, on which the appearance of the target interaction object is projected. We choose the Relief Texture Mapping as the rendering method to correctly generate the viewer dependent textures to be projected on the non-planar surfaces of the TangibleScreen.