• Transactions of the Society of Information Storage Systems
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• v.10 no.2
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• pp.39-44
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• 2014

LCD panels are used widely in all sorts of devices. Since glass is the main material used to make the panels, scratch resistance is an important issue in acquiring high quality LCD panels. In this work the wear behaviors of three types of commercially available LCD panel glasses were investigated. A pin-on-reciprocating tribotester was used to perform the wear tests using the glass specimens against a stainless steel ball. The hardness of the specimens was initially obtained. It was shown that the wear amount varied with respect to the applied load as well as the type of glass. The wear pattern of the glass specimen was also characterized using confocal microscopy. It is expected that the results of this work will aid in improving the tribological properties of LCD panel glass.

• Tribology and Lubricants
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• v.29 no.3
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• pp.149-159
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• 2013

In this research, the lubrication characteristics of spool valves with various cross-sectional groove shapes were studied. The validity of using the Reynolds equation for the analysis of spool valves with various groove shapes was also investigated. The cross-sectional shapes for the grooves included a triangle, square, and U shape. The characteristics of the flow in the groove were investigated using streamlines. When the number of grooves was increased, the difference between the results obtained from the Reynolds equation and those obtained from the Navier-Stokes equation increased according to the groove shape. Thus, it was found that the Navier-Stokes equation should be used to investigate the lubrication characteristics of the spool valves in those cases. Moreover, in the case where the cross section of the groove was U-shaped, the groove prevented the small eddy current from occurring in the groove. Therefore, the lateral force and friction force of the spool valve with the U-shaped groove were lower than those of the spool valves with other groove shapes.

• Tribology and Lubricants
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• v.30 no.5
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• pp.278-283
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• 2014

Carbon nanotubes (CNTs) are used in various composite materials to enhance electrical, thermal and mechanical properties of composite materials. In this study, we investigate the wear characteristics of polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends containing multi-walled carbon nanotubes (MWCNTs). PC/ABS blends are commonly used in many industrial applications such as cellular phones and display cases and MWCNTs have been added to the PC/ABS blends to improve their electromagnetic interference shielding (EMS). We performed wear tests on PC/ABS blends containing MWCNTs under reciprocating linear sliding conditions with chrome steel balls as a counterpart material. The normal loads were 10, 30, 50, 70, 100 N, the sliding speed was 10 mm/s, the stroke length was 15 mm, and the tests lasted 900 s. The MWCNTs included in the PC/ABS blends lower the wear volume and friction coefficient of the composites. We analyzed the wear debris collected from the composites during the tests in terms of the MWCNT concentration using inductively coupled plasma optical emission spectroscopy. The results show that the quantity of MWCNTs in the debris is proportional to the concentration of MWCNTs in the composite, indicating that the exposure of the MWCNTs to environments by wear could be increased with their concentration in the composite.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.8
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• pp.689-696
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• 2000

In this paper we propose an eminent controller for wheeled mobile robots. This controller consists of an input-output linearization controller trying to stabilize the system and a neural network controller to compensate for uncertainties. The uncertainties are divided into two parts. First unstructured uncertainties include the elements related with system order such as friction disturbance. Second structure uncertainties are the incorrect system parameters A neural network structure of the proposed overall controller learns structural errors of the wheeled mobile robots with uncertainties and includes the neural network output. This controller learns quickly the model and has good tracking performance Simulation results show that the proposed controller is more efficient than analog controllers.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.604-609
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• 2005

This paper presents an experimental study for optimizing the acceleration of AC servomotor using finite jerk (the first derivative of acceleration). The acceleration optimization with finite jerk aims at generating the smooth velocity profile of AC servomotor by experimentally minimizing vibration resulted from the initial friction of servomotor. The stick-slip motion of AC servomotor induced by initial friction can result in the positional errors that are not good for high-precision devices such as the assembly robot arms to be used in a 300mm wafer or a LCD (Liquid Crystal Display) stocker system. In this paper, experiments were made by using a PM (Permanent Magnet) type AC servomotor with MMC(R) (Multi Motion Controller) programmed in Visual C++(R). The experiments have been performed for finding the optimal duration time of finite jerk in terms of the minimization of vibration displacements when both the magnitude of velocity and the allowable acceleration are given. We have compared the proposed control with the conventional control with trapezoidal velocity profile by measuring vibration displacements. The effectiveness of the proposed control has been verified in that the experimental results showed the decrease of vibration displacement by about 24%.

• International Journal of Control, Automation, and Systems
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• v.6 no.5
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• pp.731-739
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• 2008

The docking and recharging system for a mobile robot must guarantee the ability to perform its tasks continuously without human intervention. This paper proposes two docking mechanisms with localization error-compensation capability for an auto recharging system. The mechanisms use friction forces or magnetic forces between the docking parts of the robot and those of the docking station. It is a structure to improve the allowance ranges of lateral and directional docking offsets, in which the robot is able to dock into the docking station. In this paper, auto-recharging system and the features of the proposed mechanisms are verified with experimental results using simple homing method.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.369-370
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• 2002

To clarify the tribological properties of biodegradable lubricating oils, the four-ball tests were carried out under dip-feed lubrication using a Soda-type four-ball machine. The test balls were lubricated with soybean oil, rapeseed oil, corn oil and turbine oil. From the tests, the coefficient of friction for all the test balls lubricated with biodegradable lubricating oils was lower than that for the test ball lubricated with turbine oil. Further, from the calculation of the pV value, it was clear that the seizure resistance for all the test balls lubricated with biodegradable lubricating oils was higher than that for the test ball lubricated with turbine oil.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.454-461
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• 2001

Dynamic responses of a multi-span simply supported bridge are examined under seismic excitations considering damage of bearings. An idealized mechanical model which can consider components such as pounding, friction at the supports, abutment-soil interaction, rotational and translational motions of foundations, and the nonlinear pier motions, is developed to analyze the effects due to damage of bearings. It is assumed that the bearing's response after failure can be expressed with a sliding model with a friction coefficient between the superstructure and the pier top. It is found that the global seismic behaviors are significantly influenced by the damage of bearings and the damage of bearings may lead to unseating failure at unpredicted supports. Therefore, It can be concluded that detailed seismic response analyses of bridge systems considering damage of bearings is required for the purpose of the seismic safety evaluation.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.197-206
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• 2006

Statement of problem: One of common problems associated with single teeth dental implant prosthetic is the loosening of screws that retain the implants. Purpose: The maintenance of screw joint stability is considered a function of the preload achieved in the screw when the suggested initial tightening torque is applied. The purpose of this study was to investigate acquired preload after initial clamping torque for estimating screw joint stability. Material and methods: A comparative study on the effect of initial clamping of two types of implant systems with different connections was conducted Three dimensional non-linear finite element analysis is adopted to compare the characteristics of screw preloads and stress distributions between two different types of implant systems composed with abutment, screw, and fixture under the same loading and boundary conditions. Results: 1. When the initial clamping torque of 32Ncm was applied to the implant systems, all types of implants generated the maximum effective stress at the first helix region of screw. 2. Morse taper connection types of implants generate lower stress distributions compared to those by butt joint connection types or implants due to large contact surface between abutment and fixture. 3. The internal types of implant systems with friction grip type implant systems have higher resistance to screw loosening than that of the external types of implant systems since the internal types of implant systems generated larger preload than that generated by the external types for the same tightening moments.

• Smart Structures and Systems
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• v.30 no.5
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• pp.479-500
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• 2022

In this study, a new type of isolation bearing is proposed by combining S-shaped steel plate dampers (SSDs) with a spherical steel bearing, and the seismic control effect of a five-span standard high-speed railway bridge is investigated. The advantages of the proposed S-shaped steel damping friction bearing (SSDFB) are that it cannot only lengthen the structural periods, dissipate the seismic energy, but also prevent bridge unseating due to the restraint effectiveness of SSDs in the large relative displacements between the girders and piers. This study first presents a detailed description and working principle of the SSDFB. Then, mechanical modeling of the SSDFB was derived to fundamentally define its cyclic behavior and obtain key mechanical parameters. The numerical model of the SSDFB's critical component SSD was verified by comparing it with the experimental results. After that, parameter studies of the dimensions and number of SSDs, the friction coefficient, and the gap length of the SSDFBs were conducted. Finally, the longitudinal seismic responses of the bridge with SSDFBs were compared with the bridge with spherical bearing and spherical bearing with strengthened shear keys. The results showed that the SSDFB can not only significantly mitigate the shear force responses and residual displacement in bridge substructures but also can effectively reduce girder displacement and prevent bridge unseating, at a cost of inelastic deformation of the SSDs, which is easy to replace. In conclusion, the SSDFB is expected to be a cost-effective option with both multi-stage energy dissipation and restraint capacity, making it particularly suitable for seismic isolation application to high-speed railway bridges.