• Journal of KSNVE
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• v.10 no.2
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• pp.229-239
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• 2000

To reduce the drag rise on the advancing helicopter rotor blade tips, the tip of the blade is modified to have sweep, anhedral and pretwist. The equations of motion of rotor blade with these tip angles were derived using Hamilton principle, programmed using FORTRAN and named as ARMDAS(Advanced Rotorcraft Multidisplinary Design and Analysis System). Rotating frequency analysis of rotor blades with swept tipe was performed that is necessary in conceptual and preliminary design phases of the helicopter design. Vibration analysis of non-rotating blades was also accomplished and compared with MSC/NASTRAN resutls for the basis of comparison with the vibration test data. The rotating frequency analysis of blades with an actual rotor blade data was also performed to verify coded program and to check the possibility of a resonance of an actual rotor blade at the specific rotating speed.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.6
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• pp.148-158
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• 2001

In this paper, Automatic Dynamic Balancer(ADB) was simulated and investigated to use at the high speed rotating chuck for the friction welding. In the limited computer simulations and experiments that have been presently carried out, several conclusions have been found. Above critical speed of the rotating system, ADB can balance the rotating disk. Therefore, it can be predicted that ADB can make an uniform flash during the friction welding.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.194-201
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• 1998

The beam rotating actuator has been developed. It can be utilized to improve the data transfer rate for the optical disk systems, Newly developed laser beam rotating actuator is applied to put multi-beam spots on more than one track on the optical disk simultaneously. The beam rotating actuator is made of piezoelectric ceramic bimorph as the form of cantilever, Piezoelectric actuators with high resolution, high stiffness and fast frequency response are widely assembled in micropositioning applications. Therefore, the actuator has above 50Hz natural frequency. Beam array is rotated using the dove prism in the end of beamrotator. The dynamic equation of beam rotating actuator is derived theoretically. The actuator is designed on the ground of this analysis. The performance of the beam rotating actuator is verified as the dynamics frequency performance is measured using the dynamic analyzer and sensor.

• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.765-773
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• 2017

The quadratic B-spline finite element method yields mass and stiffness matrices which are half the size of matrices obtained by the conventional finite element method. We solve the free vibration problem of a rotating Rayleigh beam using the quadratic B-spline finite element method. Rayleigh beam theory includes the rotary inertia effects in addition to the Euler-Bernoulli theory assumptions and presents a good mathematical model for rotating beams. Galerkin's approach is used to obtain the weak form which yields a system of symmetric matrices. Results obtained for the natural frequencies at different rotating speeds show an accurate match with the published results. A comparison with Euler-Bernoulli beam is done to decipher the variations in higher modes of the Rayleigh beam due to the slenderness ratio. The results are obtained for different values of non-uniform parameter ($\bar{n}$).

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.150-157
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• 2005

The vibration system in this study is consisted of a rotating cantilever pipe conveying fluid and a tip mass. The equation of motion is derived by using the Lagrange's equation. The influences of the rotating angular velocity and the velocity of fluid flow on the natural frequencies of a cantilever pipe have been studied by the numerical method. The effects of a tip mass on the natural frequencies of a rotating cantilever pipe are also studied. The influences of a tip mass, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the natural frequency of a cantilever pipe are analytically clarified. The natural frequencies of a cantilever pipe conveying fluid are proportional to the angular velocity of the pipe in both axial direction and lateral direction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.1
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• pp.13-19
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• 1995

An experimental investigation has been made for flow in a circular cylinder with a rotating bottom disk. Flow system considered in this paper is a characteristic model of interior flows of an electric washing machine. Flows in a tub of an electric washing machine are driven by a rotating bottom disk called a pulsator. The simple and characteristic model was composed of a circular cylinder with impulsively rotating endwall disk and a viscous fluid in it. Rotational motion of the pulsator is periodic and alternative in rotation direction. The flow field in the interior region is governed by a horizontal boundary layer forms on the impulsively rotating disk. Experimental approach was accomplished by adopting an image processing technique for velocity measurements. Comprehensive details of the flow structure are presented. Also a meridional circulation is obtained by tracking image particles suspended in the fluid. Flow structure and data are successfully procured for this complex rotating flow field.

• Structural Engineering and Mechanics
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• v.30 no.4
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• pp.427-444
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• 2008

A mathematical model for the nonlinear dynamics of a rotating beam with flexible root attached to a rotating hub with elastic foundation is developed. The model is developed based on the large planar and flexural deformation theory and the potential energy method to account for axial shortening due to bending deformation. In addition the exact nonlinear curvature is used in the system potential energy. The Lagrangian dynamics and the assumed mode method is used to derive the nonlinear coupled equations of motion hub rotation, beam tip deflection and hub horizontal and vertical displacements. The derived nonlinear model is simulated numerically and the results are presented and discussed for the effect of root flexibility, hub stiffness, torque type, torque period and excitation frequency and amplitude on the dynamic behavior of the rotating beam-hub and on its stability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.43-49
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• 1997

A rotating rigid disk, attached on a flexible shaft or supported by a torsional spring, experiences precessional whirling due to gyroscopic moment loading. It is well known in rotor dynamics area that, as the rotational speed increases, the precessional mode of the rotating rigid disk starts splitting into two: forward and backward precessional modes. On the other hand, it is also well known in disk vibration area that a rotating flexible disk also shows another kind of mode splitting phenomenon due to the rotation, resulting in forward and backward traveling waves. When rotating multiple flexible disks are coupled in vibration with the supporting Flexible shaft, the associated mode splitting should be compatible with the two seemingly different vibration analysis methods. This paper investigates the possibility of fusing the precessional and traveling wave mode splittings so that the bending coupled disk vibrations in HDD spindle systems can be better understood.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.497-502
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• 2009

The wastewater treatment by photocatalyst decomposes pollutants directly in water, and it is easy to decompose indecomposable organics and inorganic. and Especially, it has an advantage that there is no secondary production of pollutants. However, there will be many problems which are generated depending on the type of photocatalyst. The type of rotating photocatalyst minimizes previous problems, and advanced oxidation processes is possible by the application of rotating disc method. The consideration of the characteristics about various designs and operation factors is needed for the application of rotating photocatalyst system. In this study, rotating photocatalyst was manufactured for rotating disc method by fixing of $TiO_2$. The operation factors were derived for the wastewater treatment by the reaction of rotating photocatalyst. The contained quantity of $TiO_2$ was limited about 70%. The more the contained quantity of $TiO_2$ was increased, the more the treatment rate was continually increased. The optimum rotating photocatalyst was R4, and the contained quantity of $TiO_2$ was 36.8%. The more the exposed amount of UV is increased, the more the decomposition effect of TCODcr was continually increased. However, the adequate strength of light source must be determined by the consideration of economical efficiency. The more the speed of rotating photocatalyst is increased, the more treatment efficiency was increased. When UV lamp was not submerged in reactor, the wastewater treatment was efficient in the order of the depth of water 50%, 30%, 10%, 70%, 100%. This study is a basic research for the development of a system which treats organics in solar light.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1185-1190
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• 2007

In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid. The equation of motion is derived by using the Lagrange's equation. Also, the equation of motion is derived applying a modeling method that employs hybrid deformation variables. Generally, the system of pipe conveying fluid becomes unstable by flutter. So, we studied about the influences of the rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe by the numerical method. The influences of mass ratio, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified. The critical fluid velocity$(u_{cr})$ is proportional to the angular velocity of the cantilever pipe. In this paper Flutter(instability) always occur in the second mode of the system.