• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.5
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• pp.496-502
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• 2008

In this study, supersonic and hypersonic flutter characteristics have been analyzed for the various typical section shapes of missile fin configurations. Nonlinear flutter analyses are conducted considering the effect of moving shock waves. Computational fluid dynamic method is applied to accurately predict unsteady aerodynamic loads due to structural motions for the solution of aeroelastic governing equations. Commonly used typical section shapes of supersonic and hypersonic launch vehicles are considered in the present numerical study. Detailed flutter responses for four different typical section models are presented and the flutter characteristics are physically investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.131-136
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• 2004

Impact sounds, such as those created by footsteps, the dropping of an object or the moving of furniture, can be a source of great annoyance in residential buildings. The character and level of impact noise generated depends on the object striking the floor, on the basic structure of the floor, and on the floor covering. This study base on the evaluate of isolation performance of impact sound according to the impact noise reduction methods. Reduction methods consist of four ways. First way is increase thickness of bare floor and other ways are using the soft coverings on the floor and ceiling assembles. Last way is make floating floor with shock absorbing materials.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.9 s.90
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• pp.811-818
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• 2004

Impact sounds, such as those created by footsteps, the dropping of an object or the moving of furniture, can be a source of great annoyance in residential buildings. The character and level of impact noise generated depends on the object striking the floor, on the basic structure of the floor, and on the floor covering. This study base on the evaluate of isolation performance of impact sound according to the impact noise reduction methods. Reduction methods consist of four ways. First way is increase thickness of bare floor and other ways are using the soft coverings on the floor and ceiling assembles. Last way is make floating floor with shock absorbing materials.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.314-317
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• 2005

There are many benefits such as increased areal density, reduced power consumption, applied smaller size and improved shock resistance in Load/Unload(L/UL) mechanism. It has been the key technology of developing small form factor hard disk drive used in portable digital devices. The main objectives of L/UL are no slider-disk contact and faster L/UL process. For realizing those, we must consider many design parameters in L/UL systems. In this paper, we focus on the effects of ramp profile. We can investigate dynamic characteristics of suspension tap and slider on ramp during unloading process experimentally. In special, we examine the effects of vortical velocities, ramp slopes and disk vibrations. As the result of these experiments, we propose design criteria of advanced ramp profile for good unloading performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1038-1042
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• 2007

The factors influencing the floor impact sound insulation include floor finishing materials, shock absorbing floors (slabs included), and ceiling structures. The ceilings of the apartment houses, currently built in Korea, are set up with lower parts of slabs and paper finishing, or with double floors for protecting against floor impact sounds in order to improve the sound insulating performance. The most common the method of ceiling structure construction consists of 'wood boarded frames + Gypsum boards + ceiling papers', which is called the wood boarded frame method. This study aimed to measures and evaluates floor impact sound insulation by which the ceiling space are widened according to suppression system is added in apartment house ceiling structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.19-24
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• 2001

In this study, Pb(La Ce)$TiO_3$ composition ceramics were manufactured for 20 MHz resonator application. Electromechanical coupling factor, mechanical quality factor and dynamic range of thickness vibration mode were measured as the variations of L/T(length/thickness) ratio of ceramic substrats. Mechanical quality factor and dynamic range of third overtone thickness vibration mode showed the highest value of 2,773 and 52.22 dB at specimen S4(l/t=12), respectively. The excellent temperature stability of resonant frequency suitable for resonator application was shown, regardless of thermal shock.

• Journal of Power System Engineering
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• v.18 no.2
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• pp.77-82
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• 2014

The air spring is widely used in various fields such as a suspension system and an anti-vibration system because the natural frequency is kept constant regardless of the change in the load, spring constant is easy to change, and, vibration and shock isolation performance are excellent. The purpose of this study is to derive a nonlinear governing equation of an air spring, to analyze the effect of the various parameters on the dynamic stiffness of the air spring, and, to suggest a more efficient design method of an air spring system. In order to do so, this study investigates the impact of all the parameters that could affect the dynamic stiffness of the air spring while changing the excitation amplitude and the frequency with a developed governing equation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.9
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• pp.720-725
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• 2001

In this study, Pb(La,Ce)Ti $O_3$ ceramics were manufactured for 20 MHz resonator application. Electromechanical coupling factor( $k_{t}$, $k_{t3}$, mechanical quality factor( $Q_{mt}$ , $Q_{mt3}$ and dydnamic range (D.R) of thickness vibration mode were measured as the variations of $\ell$/t(length/thickness) ratio of ceramic substrates. Mechanical quality factor( $Q_{mt3}$) and dynamic range of third overtone thickness vibration mode showed the highest value of 2,773 and 52.22dB at specimen S4($\ell$/t=12), respectively. The excellent temperature stability of resonant frequency suitable for resonator application was shown, regardless of thermal shock.k.ock.k.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.163-172
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• 1998

The design fundamentals of the shaking tables are briefly discussed. In order to understand the recent trends in development of the shaking tables, the characteristics and performances of the major seismic testing facilities are investigated. The international standards related to the vibration tests using shaking table are also overviewed. The newly designed multipurpose biaxial shaking table of Hyundai Heavy Industries, Co., Ltd. is introduced. It has the capabilities to perform the vibration, shock and seismic qualification tests in two simultaneous and independent directions (vertical and horizontal directions). Since the shaking table adapts four extremely stiff torque instead of much more expensive hydraulic actuators, these tubes can restrain two undesired rotational motions. Regarding the manufacturing and maintenance costs, two system is more economical since it has only two hydraulic actuators unlike others.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.703-704
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• 2010

The environmental tests simulating the flight condition have been performed to manufacture the high reliable safety and arming device(SAD). A motor assay in preliminary design was reinforced with the structure to resist severe vibration and shock environment, and the design change had been verified by conducting the principal environmental test again.