• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.9 s.114
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• pp.912-918
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• 2006

A modeling method for the vibration analysis of rotating multi-blade systems considering the coupling stiffness effect is presented in this paper. Blades are assumed as cantilever beams and the coupling stiffness effect originates from disc or shroud between blades. As the angular speed, hub radius ratio, and the coupling stiffness vary, the natural frequencies of the system vary. Numerical results show that the coupling stiffness is very important to estimate the natural frequencies. Along with the natural frequencies, associated mode shapes, critical angular speed, and critical hub radius ratio are obtained through the analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1354-1359
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• 2006

A modeling method for the vibration analysis of rotating multi-blade systems considering the coupling stiffness effect is presented in this paper. Blades are assumed as cantilever beams and the coupling stiffness effect originates from disc or shroud between blades. As the angular speed, hub radius ratio, and the coupling stiffness vary, the natural frequencies of the system vary. Numerical results show that the coupling stiffness is very important to estimate the natural frequencies. Along with the natural frequencies, associated mode shapes, critical angular speed, and critical hub radius ratio are obtained through the analysis.

• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.181-191
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• 2004

For a rigid retaining wall with rough face, the magnitude and distribution of active earth pressure on the wall are affected by the shape of failure surface and arching effect developed in the backfill as well as internal friction angle of the backfill and wall friction angle. Therefore, the practical shape of failure surface and arching effect in the backfill must be considered to acquire accurate magnitude and non-linear distribution of active earth pressure acting on the rigid retaining wall. In this study, a new formulation for calculating the active earth pressure on a rough rigid retaining wall rotating about the top is proposed considering the practical shape of non-linear failure surface and arching effects. Accuracy of the proposed equation is checked through comparisons of calculations from the proposed equations with existing model test results. The comparisons show that the proposed equations produce satisfactory results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.6
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• pp.91-97
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• 2019

Rotating machining unit is a revolutionary product that can process worm shaft or spiral shaft with fast and precise, a rotary type cutting tool, which is attached to automatic lathe and processes spiral groove on outer circumference of round bar. In this work, a study on micro tooth shape modification method of driving gear train in the rotating machining unit was presented. To observe the effect on power transmission characteristics of the driving gear pair, visualize the gear meshing condition and the load distribution on the gear teeth by using the professional gear train analysis program RomaxDesigner. By comparing the repeated analysis results, the effect of micro tooth shape modification on power transmission characteristics on driving gear can be summarized. The optimized gears were fabricated and measured by precision tester as a validation in this research.

• Wind and Structures
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• v.31 no.4
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• pp.373-380
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• 2020

For large-scale 5MW offshore wind turbines, the discrete equation of fluid domain and the motion equation of structural domain with geometric nonlinearity were built, the three-dimensional modeling of the blade considering fluid-structure interaction (FSI) was achieved by using Unigraphics (UG) and Geometry modules, and the numerical simulation and the analysis of the vibration characteristics for wind turbine structure under rotating effect were carried out based on ANSYS software. The results indicate that the rotating effect has an apparent effect on displacement and Von Mises stress, and the response and the distribution of displacement and Von Mises stress for the blade in direction of wingspan increase nonlinearly with the equal increase of rotational speeds. Compared with the single blade model, the blade vibration period of the whole machine model is much longer. The structural coupling effect reduces the response peak value of the blade displacement and Von Mises stress, and the increase of rotational speed enhances this coupling effect. The maximum displacement difference between two models decreases first and then increases along wingspan direction, the trend is more visible with the equal increase of rotational speed, and the boundary point with zero displacement difference moves towards the blade root. Furthermore, the Von Mises stress difference increases gradually with the increase of rotational speed and decreases nonlinearly from the blade middle to both sides. The results can provide technical reference for the safe operation and optimal design of offshore wind turbines.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.213-218
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• 2001

The characteristics of the fluid flow and mass transfer in a vertical atmospheric pressure chemical vapor deposition (APCVD) are numerically studied. In order to get the optimal process parameters for the uniformity of deposition on a substrate, Navier-Stokes and energy equations have been solved for the pressure, mass-flow rate and temperature distribution in a CVD reactor. Results show that the thermal boundary condition at the reactor wall has an important effect in the formation of buoyancy-driven secondary cell when radiation effect is considered. Results also show that reduction of the buoyancy effect on the heated reactor improves the uniformity of deposition.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.628-631
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• 2000

A new control method for precision robust speed control of a PMSM(Permanent Magnet Synchronous Motor) using load torque observer is presented. With this system we can obtain more reliable eye moving singal(nystagmus) Until now rotating chair system which is called 2D-optokinetic stimulator is used to make dizzincess. However an inclined rotating chair system witch is 3D-optokinetic stimulator is needed to obtain the precise dizziness data. This 3D-optokinetic sitimulator include unbalanced load aused by unbalanced center of mass. For this case new compensation method is considered to obtain robust speed control using load torque observer. To reduce the effect of this disturbance we can use dead-beat observer which has high gain. The application of the load torque observer is published in [1] for position control. A problem of using speed information such as amplifying effect of noise is reduce by moving average process. The experimental results are depicted in this paper to show the effect of this proposed algorithm.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.3
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• pp.56-63
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• 1985

The strength of the mounting bolt of a backing plate is investigated with field test to provide the basic data in the safety evaluation of the wheeled vehicle. As a result, during the braking performance test at a vehicle speed of 32km/h, the shearing stress of mounting bolt is 20.5kg/mm$^{2}$ because the translatory mass of the vehicle is increased 21.6 per cent to incorporate the rotating-mass effect of wheels and other permanently engaged rotating parts.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.407-413
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• 2001

A modeling method for the vibration analysis of rotating composite cantilever plates is presented. Explicit mass and stiffness matrices are derived by considering the coupling effects between extensional motions and the bending motion, To confirm the accuracy of the method presented in this study, numerical results are obtained and compared to those of a commercial program. Numerical results show that the coupling effect among the three motions becomes important for the accurate estimation of natural frequencies as laminates are stacked up unsymmetrically. Also, natural frequencies loci veering, loci crossing, and mode shape variations are observed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.236-242
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• 2001

In this paper the effect of bump compliance, load, and the number of pad on the lift-off speed is studied. When the load is greater and bump compliance lower, the shaft is lifted off at higher rotating speed. And when the load is applied near the center of pad, lift-off speed is lower. When the number of pad increases, the lift-off speed is higher. The lift-off characteristics can be used to lengthen the life time of the coating and design the rotating machinery supported by bump bearings.