• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.671-680
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• 2004

We present numerical and experimental results of the periodic flows inside a rectangular container under a background rotation. In numerical computation, a parallel-computation technique with MPI is implemented. Flow visualization and PIV measurement are also performed to obtain velocity fields at the free surface. Through a series of numerical and experimental works, we aim to clarify the fundamental reasons of discrepancy between the two-dimensional computation and the experimental measurement, which was detected in the previous study for the same flow model. Specifically, we check if the various assumptions prerequisite for the validity of the classical Ekman pumping law are satisfied for periodic flows under a background rotation.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.325-328
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• 2002

We present numerical and experimental result of the rotating flows inside a rectangular container under a background rotation. In numerical computation, a parallel-computation technique with MPI is implemented. Flow visualization and PIV measurement are also performed to obtain velocity fields at the free surface. Through a series of numerical and experimental works, we aim to clarify, if any, the fundamental reasons of discrepancy between the two-dimensional computation and the experimental measurement, which was detected in the previous study for the same flow model. Specifically, we check if the various assumptions prerequisite for the validity of the classical Ekman pumping law are satisfied for periodic flows under a background rotation.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.6
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• pp.548-553
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• 2008

In this paper, we propose a new swing-up control strategy for rotary inverted pendulums with restricted rotation range. The control law is derived from a Lyapunov function. The Lyapunov function is defined as the square of the sum of the absolute value of the total mechanical energy and weighted squares of the arm's angular displacement and velocity. By adjusting the weighting parameters in the Lyapunov function, we can affect the swing-up strategy such that the restriction on rotation range can be satisfied. Finally, we verify the performance of the proposed control law through simulation and experiments.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.84.2-84.2
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• 2011

Astrophysical jets play important roles in many interesting astronomical phenomena, such as star formation, gamma-ray bursts, and active galactic nuclei. The jets are thought to be driven by rotating disks through magneto-centrifugal processes. However, quantitative understanding of the jet-driving mechanism has been difficult because examples showing rotation in both disk and jet are rare. One of the important quantities in the models of jet engine is the size of the jet-launching region. The bipolar jet of the NGC 1333 IRAS 4A2 protostar shows a lateral velocity gradient, which suggests that the SiO jet is rotating around its axis. The jet rotation is consistent with the rotation of the accretion disk. The disk-jet rotation kinematics suggests that the jet-launching region on the disk, or the outflow foot-ring, has a radius of about 2 AU, which supports the disk-wind models.

• Journal of Navigation and Port Research
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• v.30 no.9
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• pp.729-734
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• 2006

The authors aim to establish the theory necessary for developing the free gyroscopic compass and focus on mainly two points. One is to suggest north-finding principle by the angular velocity of the earth's rotation, and the other is to suggest orthogonal coordinate transformations of the motion rate of the spin axis, which transforms the components of motion rate in the free gyro frame into those in the platform frame and that this transformed rate is, in turn, transformed into the NED(north-east-down) navigation frame. Subsequently, ship's heading is obtained by using the fore-aft and athwartship components of the motion rate of the spin axis in the NED frame. In addition it was found how to solve the transformation matrix necessary for transforming each frame.

• Journal of Welding and Joining
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• v.14 no.5
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• pp.78-86
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• 1996

Vision sensor was used to track the weld line of the compressor case. The compressor case was fixed in jig equipped with the rotating system, and two torches having one degree of freedom was applied in automatic welding system. The radius of rotation for the compressor case is varying with each rotating angle, while, the angle velocity is constant Therefore, an algorithm to extract the feature of the compressor case for varying rotation angle is needed. To over come the avove difficulties, the curve fitting and composite curve were used. The experiment to verify the proposed algorithm showed desirable results for tracking the welding line of compressor case.

• Journal of Ocean Engineering and Technology
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• v.13 no.4 s.35
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• pp.124-131
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• 1999

In this paper, we show the numerical and experimental results of two-dimensional fluid motions inside a rectangular container with a vertical plate subjected to a background rotation added by a rotational oscillation. In the PIV experiment we apply a new algorithm, NTSS, to the velocity calculation. In the numerical computation, the linear Ekman-pumping model was used to take the bottom friction effect into account. It was found that it showed good agreement with the experimental results at low ${\epsilon}$ number.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.601-606
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• 1993

The natural frequency measurement of passenger car tire under the load and rotation are studied. In order to obtain theoretical natural frequency and mode shape, the plane vibration of a tire is modeled to that of circular beam. By using the Tickling method based on Hamilton's principle, theoretical results are determined by considering tension force due to tire inflation pressure, rotational velocity and tangential, radial stiffness. Modal parameters varying the inflation pressure, load, rotational velocity are determined experimentally by using frequency response function method. The results show that experimental conditions are parameter for shifting of natural frequency.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.113-116
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• 1998

A numerical study was performed on the fluid flow in the melt of the cold model for Czochralski growth system. The fluid flow in the melt of Woods metal with crucible diameter of 20cm was calculated using a three dimensional finite difference method. Since the crucible size is large, fully turbulent model as well as laminar model was used in the calculation. The effects of crucible rotation rate, crystal rotation rate and wall temperature difference on the velocity and temperature distribution were also investigated. For the purpose of verifying the results of calculation, a cold model experiment using Woods metal was also conducted and the velocity distribution in the melt of the model was measured.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.9-14
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• 2006

The authors aim to establish the theory necessary for developing the free gyrocompass. The following considerations are taken. One is to suggest north-finding principle by the angular velocity of the earth's rotation, and the other is to suggest that the motion rate of the spin axis in the free gyro frame is transformed into the platform fame and this transformed rate is again transformed into the NED navigation frame. After transformation ship's heading is obtained using the fore-aft and athwartship components of the motion rate of the spin axis in the NED frame In addition it was suggested how to solve the transformation matrix necessary for transforming each frame.