• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1125-1129
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• 1993

A piezoelectric ring type plate, which vibrates in flexural vibration mode, is used for the stator of ultrasonic motor. To design the stator adequately, the force factor of the stator should be estimated in advance. The theoretically calculated force factors for the flexural vibration mode are compared with the measured ones to obtain good agreement. In order to study how to control the force factor, the relation between the shape of the stator and force factor is also considered.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.88-95
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• 2009

Input shaping has been a very effective control method for reducing payload swing in industrial bridge and gantry cranes. However, conventional input shapers often degrade performance when applied to tower cranes because of the nonlinear coupled dynamics between rotational and radial motions in tower cranes. To alleviate this problem, a new input shaper for tower cranes is developed by means of dynamic modeling, analysis and optimization. This work investigates the tower crane dynamics along with parameters of the tower crane varied. A performance index for input shaper design is proposed so as to reduce the coupled residual vibration of a tower crane using only rotational motion of tower crane. The proposed new input shaper is verified to be effective through simulations and experiments.

• Tunnel and Underground Space
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• v.6 no.3
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• pp.267-273
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• 1996

The types of eletric detonators manufactured in korea include instantaneous, decisecond and millisecond delays but number of delay intervals are only limited from No. 1 to No. 20 respectively. It is not sufficient to control accurately millisecond time with these detonators in large surface blasting. But nonelectric system detonators with an unlimited delay time are recently obtained. In this paper the effect of delay time of nonelectric detonator on the level of vibration in surface blasting was studied. A total of 169 data were recorded in the studied area. Blast point-to-measuring point distances ranged from 25 to 100 meter, where charge weight was 1.26 kg per delay.

• Journal of Mechanical Science and Technology
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• v.20 no.6
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• pp.795-805
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• 2006

Tuned Liquid damper and Tuned Liquid Column are kind of passive mechanical damper which relies on the sloshing of liquid in a rigid tank for suppressing structural vibrations. TLD and TLCD are attributable to several potential advantages - low costs ; easy to install in existing structures : effective even for small-amplitude vibrations. In this paper, the shaking table experiments were conducted to investigate the characteristics of water sloshing motion in TLD (rectangular, circular) and TLCD. The parameter obtained from the experiments were wave height, base shear force and energy dissipation. The shaking table experiments show that the liquid sloshing relies on amplitude of shaking table and frequency of tank. The TLCD was more effective control vibration than TLD.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.21-26
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• 2000

This paper describes a positioning system for ultra-precision that will be utilized in semiconductor manufacturing field and precision machinery. This system is composed with laser scale unit with 10nm resolution, ball screw with LM guide, brushless DC servo motor, vibration isolator and is equipped in chamber for continuous measuring environment. The dynamic of table, the problem of servo control and the traceability for micro step motion are described. These data will be applied for getting more stable system with 50nm resolution.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.10a
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• pp.55-59
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• 1993

Interaction between system and disturbance results in system with time-dependent parameter. Parameter variation due to interaction has random characteristics. Most of the randomly varying parameters in control problem is regarded as white noise random process, which is not a realistic model. In real situation those random variation is colored noise random process. Modified F-P-K equation is proposed to get the response of the random parametric system using some correction factor. Proposed technique is employed to obtain the colored noise parametric system response and confirmed via Monte-Carlo Simulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.338-344
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• 1996

In this paper, a semi-active suspension adapting to road variation which also considers the frequency snesitivity of human is proposed. First, a road adapting controller composed of system identification and LQG control is designed. Using the extended least squares method, the road property is estimated by system identification as it varies, and the LQG controller considering the estimated road property and the frequency sensitivity of human is designed. Next, the semi-active suspension is made, which tracks the performance of the active suspension with the road adapting controller. Through numerical simulation, the performance of the proposed semi-active suspension is compared with that of a non-adaptive semi-active suspension with frequency-shaped performance index. As a result, we see that the road adapting semi-active suspension has better performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.138-144
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• 1997

The analysis of lateral hydrodynamic forces from the compressor labyrinth seals is presented. The basic equations are derived using a two-control-volume model for compressible flow. Blasius' wall friction-factor formula and jet flow theory are used for the calculation of the wall shear stresses and the recirculation velocity in the cavity. Linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position by an expansion in the eccentricity ratio. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the labyrinth seal. The rotordynamic analysis for the balance drum labyrinth seal of an ethylene refrigeration compressor is carried out. The results of rotordynamic characteristic of the labyrinth seal and comparisons with other types of seal, honeycomb seal and smooth seal, are presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.244-249
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• 1997

The enclosure with a small opened area is extensively used in power plants to reduce the propagating noise from transformers. The radiation impedance associated with the location and width of the opened area, and the geometric configurations of internal acoustic field is very important to determine the basic acoustic characteristics of this partial enclosure. In this study, two-dimensional rectangular chambers with opened areas are investigated to examine the acoustic properties of the enclosure. The mode expansions of the physical variables defined on boundary surfaces are introduced to derive a simple algebraic equation. The acoustic characteristics can be easily predicted by this analytical approach, and the results well agree with physical grounds. Physical concepts as results of this work will be helpful to use the partial enclosure as a noise control element.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.20-25
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• 1997

Magnetic bearings have been widely used to support rotors without any physical contact. This however, requires the control of five degrees-of-freedom and needs a separate driving motor. This paper introduces selfbearing motors which use the combination of a rotary motor and a magnetic bearing. These motors are suitable for use in high speed rotor or in special circumstances because they are small in size and can replace the contact components. The radial type one has the merit of being small in size and capable of controlling two degrees-of-freedom in x and y directions. The axial type motor controls only one degree-of-freedom in z direction. Theoretical background of the functions, of the motor and magnetic bearing will also be introduced. New research works are reviewed and the application in rotary blood pump is discussed.