• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.103-108
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• 2001

The structure of hard disk drive(HDD) is excited by dynamic motion of a disk-spindle motor, and it makes sound noise. Therefore, the cover and the base of HDD should be designed to reduce noise and vibration induced by spindle motor. The prediction technique of sound pressure level(SPL) of a given structural shape enables us to design a cover and a base with much less vibration and noise. In this paper, we measured the force of disk-spindle motor and predicted SPL from HDD by computational simulation. To get a SPL of HDD by computational simulation, modal analysis and forced vibration analysis were performed with ANSYS, and sound radiation was computed using SYSNOISE. The calculated results were compared with experimental results and a good agreement was obtained. With this computer simulation procedure and design of experiment(DOE), optimal thickness of noise barrier and damper was calculated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.356.1-356
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• 2002

A satellite shipping container must afford the satellite a relatively benign thermal, vibration, and particle environment that is oblivious to the extreme temperatures, sand, dust, vibrations, and shock that can accompany the transportation. Korea Aerospace Research Institute has developed a new shipping container system that will be used to transport KOMPSAT-2(Korea Multi-Purpose SATellite) from Tae-jon to launch site. (omitted)

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.251-257
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• 2007

This paper describes the variation of the critical speed of an urban railway vehicle according to the change of suspension characteristics. Suspensions of a railway vehicle are composed of primary and secondary suspensions. Generally, main focus of the stability analysis has been the primary suspension. However, secondary suspension has large effects on the stability as well as the ride quality of a vehicle. In this paper, stability of an urban railway vehicle is discussed in relation to the variation of characteristics of both primary and secondary suspension. For this, modal analysis is carried out using a linear dynamic model of a half vehicle and a polynomial fit for Kalker's creep coefficients. Stability along with change of the effective conicity of a wheel is also investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.476-481
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• 2012

A plant's generator system under operating condition has been suffered the vibration from the excitation force with 120Hz. The vibration is generated in the stator end windings. For analyze dynamic characteristics of the generator's stator, its finite element model were obtained using ANSYS software package for modal and harmonic analysis. we compare the analysis result with experimental data. The results show that the resonance frequency, which is related with second ecliptical mode on the stator end windings 129Hz. The experimental results are good agreement with the FEA model.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.35-42
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• 1998

Response spectrum analysis method(RSA) rather than time history analysis method(THA) continues to e used by the profession for evaluating maximum dynamic responses of structures subjected to earthquake excitations. Nevertheless, this simple and practical method can cause significant errors in some cases with unproper modal combination method and so on. To obtain more exact responses based n RSA many studies have been carried out considering displacement of top story, base shear and overturning moment. The purpose of this study is to verify error characteristics in RSA with respect to various responses including displacement shear force and overturning moment of each story. It's shown that RSA appears to yield underestimated responses when compared to THA calculations. Also, errors involved in RSA computations grow with an increase in total number of stories.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.273-280
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• 1999

The base shear and the veritcal distribution of shears along the height of a building are two fundamental measures that define the design seismic load. But the method specified in Korean building code does not give an appropriate distribution for buildings of tall or longer period because it roughly account for the contributions of the higher modes. several methods to give a better distribution of seismic forces have been proposed. But they have not been introduced into the seismic codes yet probably because they cannot solve all the above-mentioned problems. This paper deals with the distribution of lateral seismic forces along the height of a building to account for the contribution of the higher modes. After reviewing some existing distributions in seismic codes and literatures moment-resisting frames with various stories were studied by modal analysis for a wide range of fundamental period and the stiffness ratio of the buiding. As a result of the analysis a new expression for the distribution of seismic forces is proposed and compared with those of some codes and dynamic analysis.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.10
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• pp.1062-1069
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• 2012

This paper suggests a computational modeling to reflect static/dynamic characteristics of LM bearings. A theoretical study for modeling LM bearings is elucidated by using the Hertz contact theory, the Lagrange's equation of motion, normal mode analysis and a calculation of equivalent moment center. The complex geometry of LM bearings is replaced by a simplified model with eight springs only. The suggested model reflects static and dynamic characteristics of LM bearings without any consideration for the shape of the bed or stages on the LM bearings. The modal experimental results are compared to the simulation results with the suggested computational modeling. The difference between the experiments and simulation is calculated less than 8%.

• Structural Monitoring and Maintenance
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• v.5 no.2
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• pp.243-260
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• 2018

Detection of damages in fibre reinforced plastic (FRP) composite structures is important from the safety and serviceability point of view. Usually, damage is realized as a local reduction of stiffness and if dynamic responses of the structure are sensitive enough to such changes in stiffness, then a well posed inverse problem can provide an efficient solution to the damage detection problem. Usually, such inverse problems are solved within the framework of pattern recognition. Support Vector Machine (SVM) Algorithm is one such methodology, which minimizes the weighted differences between the experimentally observed dynamic responses and those computed using the finite element model- by optimizing appropriately chosen parameters, such as stiffness. A damage detection strategy is hereby proposed using SVM which perform stepwise by first locating and then determining the severity of the damage. The SVM algorithm uses simulations of only a limited number of damage scenarios and trains the algorithm in such a way so as to detect damages at unknown locations by recognizing the pattern of changes in dynamic responses. A rectangular fiber reinforced plastic composite plate has been investigated both numerically and experimentally to observe the efficiency of the SVM algorithm for damage detection. Experimentally determined modal responses, such as natural frequencies and mode shapes are used as observable parameters. The results are encouraging since a high percentage of damage cases have been successfully determined using the proposed algorithm.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.7
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• pp.555-561
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• 2003

An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported Euler-Bernoulli beams with the moving masses. The influences of the velocities of moving masses, the distance between the moving masses and a crack have been studied on the dynamic behavior of a simply supported beam system by numerical method. The Presence of crack results In large deflection of beam. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. This flexibility matrix defines the relationship between the displacements and forces across the crack section and is derived by applying fundamental fracture mechanics theory. Totally, as the velocity of the moving masses and the distance between the moving masses are increased, the mid-span deflection of simply supported beam with the crack is decreased.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.12
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• pp.1246-1253
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• 2007

The recent issue of optical pickup actuators is to apply optical storage devices to mobile devices such as a cellular phone and PDA. It requires actuators to become smaller than conventional types. As the size becomes smaller, the magnetic force is reduced and the assembly of optical pickup actuators becomes more difficult. In addition, its dynamic characteristics are changed. In this paper, methods to improve magnetic forces and dynamic characteristics are suggested and the optimal result of the plate spring design is obtained. A diamond shape magnet and the fine pattern coil (FPC) are used to improve magnetic forces and damping elements are attached to decrease the peak magnitude of the mode instead of using structural damping, mostly for the purpose of improving the accuracy of the finite element simulation. To get more stable dynamic characteristics than conventional ones, a plate spring is applied to the optical pickup actuator and it is optimized with topology and parameter optimization to obtain the concept and the detail design, respectively.