• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.557-560
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• 2006

The contact angle of a meniscus and a droplet can be controlled by using electrowetting phenomena. We investigated the dynamic aspect of electrowetting for an oil-electrolyte interface formed inside a closed glass tube. A step input voltage is applied and the subsequent motion of the interface is recorded by a high-speed camera. A kind of capillary instability is observed near the three-phase contact line, which could degrade the reliability of device utilizing electrowetting such as electrowetting liquid lens. The dynamics of interface motion for different input voltages and the fluid viscosities are analyzed and discussed based on the experimental results.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.548-550
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• 2010

The droplet motion on a flat substrate with contact angle hysteresis is studied by solving the equations governing the conservation of mass and momentum. The liquid- gas interface is determined by an level-set method which is based on a sharp-interface representation for accurately imposing the matching or coupling conditions at the interface. The method is modified to treat the dynamic contact angle at the liquid-gas-solid interface. The computations are performed to investigate a droplet impact and merging pattern on a flat substrate to find a optimal condition in a micro-line patterning process. The effects of dynamic contact angles on droplet motion are quantified.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.10a
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• pp.45-50
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• 1997

In recent years the recording density of hard disk has been increasing largely due to the decreasing flying height of head. However, as the flying height is decreased the reliability issue becomes ever more critical. This is because the reliability and durability of hard disk is related to the head/disk interaction as the two components come into partial or full contact. In this work characteristics of friction and stiction in head/disk interface was investigated using constant speed drag test and CSS(contact-start-stop) test. The purpose of this research is to identify the frictional properties of head/disk interface

• The Journal of Korea Robotics Society
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• v.8 no.3
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• pp.206-216
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• 2013

We investigate the role of contact location information on the perception of local features during contour following in a virtual environment. An absolute identification experiment is conducted under force-alone and force-plus-contact-location conditions to investigate the effect of the contact location information. The results show that the participants identify the local features significantly better in terms of higher information transfer for the force-plus-contact-location condition, while no significant difference was found for measures of the efficacy of contour following between the two conditions. Further data analyses indicate that the improved identification of local features with contact location information is due to the improved identification of small surface features.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.278-284
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• 1998

In order to measure the real contact force between head and disk on hard disk drive quantitatively, many technique of measurement have been developed. Acoustic Emission Sensor can be used for detect elastic energy of head/disk contact as arms value. In this study using pencil breaking test is proposed for finding contact force using transfer function between calibrated force and real contact force. And real AE data of subambient and tripad slider shows bending and torsional mode and their energy are dominant in hard disk and head contact.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.404-411
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• 2007

new domain/boundary decomposition method is suggested to perform efficient finite element analyses of contact problems. A penalty method is used for connecting an interface or contact interfaces with neighboring subdomains that satisfy continuity conditions. As a result, the derived effective stiffness matrices are always positive definite, and computational efficiency can be improved to a considerable degree. Moreover, any complex-shaped domain can be divided into independently modeled subdomains without considering the conformity of meshes along the interface. Using a computer code based on the present method, these advantageous features are confirmed through a set of numerical examples.

• Tribology and Lubricants
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• v.17 no.1
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• pp.40-55
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• 2001

Acoustic emission(AE) signal has been widely utilized to monitor the interaction at the head/disk interface. In this work the relationship between the AE signal and the state of contact between the slider and the disk is presented. Results of the FFT(Fast Fourier Transform) analyses of the AE signal could be used to better understand the interfacial interaction. Also, it was found that wear particles affect the AE signal. Therefore, the signal can be used to monitor the wear particle presence at the interface.

• Journal of Sensor Science and Technology
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• v.14 no.2
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• pp.131-135
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• 2005

This paper describes the ohmic contact formation of single crystalline 3C-SiC thin films heteroepitaxially grown on Si(001) wafers. In this work, a TiW (Titanium-tungsten) film as a contact matieral was deposited by RF magnetron sputter and annealed with the vacuum and RTA (rapid thermal anneal) process respectively. Contact resistivities between the TiW film and the n-type 3C-SiC substrate were measured by the C-TLM (circular transmission line model) method. The contact phases and interface the TiW/3C-SiC were evaulated with XRD (X-ray diffraction), SEM (scanning electron microscope) and AES (Auger electron spectroscopy) depth-profiles, respectively. The TiW film annealed at $1000^{\circ}C$ for 45 sec with the RTA play am important role in formation of ohmic contact with the 3C-SiC substrate and the contact resistance is less than $4.62{\times}10^{-4}{\Omega}{\cdot}cm^{2}$. Moreover, the inter-diffusion at TiW/3C-SiC interface was not generated during before and after annealing, and kept stable state. Therefore, the ohmic contact formation technology of single crystalline 3C-SiC using the TiW film is very suitable for high temperature MEMS applications.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.9
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• pp.757-763
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• 2002

A newly designed haptic interface enables an operator to control a remote robot precisely. It transmits position information to the remote robot and feeds back the interaction force from it. A control algorithm of haptic interface has been studied to improve the robustness and stability to uncertain dynamic environments with a proposed contact dynamic model that incorporates human hand dynamics. A simplified hybrid parallel robot dynamic model fur a 6 DOF haptic device was proposed to from a real time control system, which does not include nonlinear components. LQC/LTR scheme was adopted in this paper for the compensation of un-modeled dynamics. The recovery of the farce from the remote robot at the haptic interface was demonstrated through the experiments.

• Structural Engineering and Mechanics
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• v.25 no.1
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• pp.1-20
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• 2007

Dynamic behaviors of the contact surface between ball and raceway in a guideway mechanism vary with the applied loads and hence affect the mechanical responses of machine tools. The study aims to investigate the nonlinear characteristics of dynamic behaviors at the rolling contact interface in linear guideway mechanisms. Firstly, analytical method was introduced to understand the contact behaviors based on Hertz contact theory in a point-to-point way. Then, the finite element approach with a three-dimensional surface-to-surface contact model and appropriate contact stiffness was developed to study the dynamic characteristics of such linear guideways. Finally, experiments with modal test were conducted to verify the significance of both the analytical and the numerical results. Results told that the finite element approach may provide significant predictions. The study results also concluded that the current nonlinear models based on Hertz's contact theory may accurately describe the contact characteristic of a linear guideway mechanism. In the modal analysis, it was told that the natural frequencies vary a little with different loading conditions; however, the mode shapes are changed obviously with the magnitude of applied loads. Therefore, the stiffness of contact interface needs to be properly adjusted during simulation which may affect the dynamic characteristics of the machine tools.