• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.1
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• pp.64-72
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• 2004

In this paper. we analyse and present electro-mechanical dynamic characteristics of a micro-machined vibrating silicon ring gyroscope which can measure angular velocities about three orthogonal axes. The ring gyroscope has a ring connected to the gyroscope main body by support-ligaments which are arranged with cyclic symmetry. The natural modes of its vibration can be distinguished into the in-plane motion and the out-of-plane motion which are coupled by the gyro-effect due to the rotation of the gyroscope main body. The motions of the ring are electro-statically derived. sensed and balanced by electrodes. The equations of motion are formulated. The measuring method of angular velocities by force-to-rebalance is presented. The dynamic characteristics of a ring gyroscope are calculated and compared.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.921-924
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• 2005

Diesel generator sets with resilient mounts often experience resonances by major excitations which come from diesel engine and their foundation with rigid body modes. Because their natural frequency is determined by moment of inertia and stiffness of resilient mount vibration problems are resolved by changing location and stiffness of resilient mounts. But the calculated natural frequencies are inaccurate due to uncertainty of the inertia and mount stiffness. So this result can be useless on the design stage. In this paper, the stiffness of mount is evaluated on result from mount stiffness test in laboratory and generator set vibration test and a simple calculation method for moment of inertia is proposed. Based on these data, the procedure to select optimized mount stiffness and location on the design stage is set up.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.5
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• pp.491-498
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• 2009

This paper deals with structural analysis and vibration characteristics of scaffolding structures with a hoist according to payloads. In order to analyze the vibrational and structural characteristics for 20-step scaffolding structure, structural and vibrational characteristics for 2-step scaffolding structure were compared with some experimental results. The numerical results for natural frequencies of scaffolding structures have a good agreement with experimental ones. Through the numerical analysis, firstly, it is shown that the maximum stress of scaffolding structures is lower than von-mises yield criteria when four persons with total weight of 280 kgf are working at the top of the scaffolding structures. Secondly, vibration characteristics including natural frequencies and modes for scaffolding structures are shown in case of various kinds of moving masses.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.543-548
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• 2006

This paper presents the vibration characteristics of scaffolding structures with a hoist according to payloads. In order to analyze the vibrational and structural characteristics for 20-step scaffolding structure, structural and vibrational characteristics for 2-step scaffolding structure were compared with some experimental results. The numerical results for natural frequencies of scaffolding structures have a good agreement with experimental ones. Through the numerical analysis, firstly, it is shown that the maximum stress of scaffolding structures is lower than von-mises yield criteria when four persons with total weight of 280kgf are working at the top of the scaffolding structures. Secondly vibration characteristics including natural frequencies and modes for scaffolding structures are shown in case of various kinds of moving masses.

• Journal of Mechanical Science and Technology
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• v.15 no.10
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• pp.1408-1416
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• 2001

It is very important to well understand the dynamic characteristics of damaged structures to successfully develop or to choose a most appropriate structural damage identification method (SDIM) as the means of non-destructive testing. In this pope., the dynamic equation of motion for damaged plates is derived by introducing a damage distribution function, which may characterize the effective state of structural damages. It is found that structural damages may induce the coupling between modal coordinates. The effects of damages on the vibration characteristics of a plate depending on their locations, sizes, and magnitudes are numerically investigated in a systematic way. The numerical investigations are also given to the effects of damage-induced modal coupling on the changes in vibration characteristics and to the minimum number of natural modes required to predict sufficiently accurate vibration characteristics of damaged plates.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.63-71
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• 2000

This paper deals with a systematic approach to GA-PI controller design for static VAR compensator(SVC) using genetic algorithm(GA) to improve system stability. Genetic algorithms(GAs) are search algorithms based on the mechanics of natural selection and natural genetics. To verify the validity of the proposed method, investigated damping ratio of the eigenvalues of the electro-mechanical modes system with and without SVC. Also, we considered dynamic response of terminal speed deviation and terminal voltage deviation by applying a power fluctuation at heavy load, normal load and light to verify the robustness of the proposed. Thus, we proved usefulness of GA-PI controller design to improve the stability of single machine-bus with SVC system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.6
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• pp.36-42
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• 2010

In this study, the deformation and stress are analyzed through modal and harmonic response analysis at resonance on leaf spring. The displacement range of 7 to 14 mm is shown at natural frequencies as 6 kinds of resonance modes. The maximum deformation is shown as 8.8781mm at Mode 2. The maximum displacement and stress at leaf spring are shown as 0.0458 mm and 72.533 MPa respectively on 1200 Hz. The comfortability of passenger becomes better on leaf spring at suspension system by use of this design model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.107-113
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• 2017

The dynamic characteristics including natural frequencies and excitation frequencies are evaluated for a small 10 kW vertical axis wind turbine. Acceleration responses were measured at 12 distributed locations for impact vibration tests, ambient vibration tests during non-operational and operational conditions, and braking tests during operational condition. The natural frequencies for the lowest 2 bending modes and the first torsional mode were estimated and also the excitation frequencies, i.e. 1P, 2P, 4P, were also estimated according to the rotational speed using the responses under operational conditions (i.e. power generation condition).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.7
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• pp.2174-2181
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• 1996

Equations of chordwise and flapwise bending motions of pretwisted rotatin cantilever beams are derived. The two motions are coupled to each other due to the pretwist angle of the beam cross section. As the angular speed, hub radius ratio, and pretwist angle vary, the vibration characteristics of the beam change. It is found that engenvalue loci veering phenomena and associated mode shape variations occur between two vibration modes due to the pretwist angle. The effect of the pretwist angle on the critical angular speed is also investigated.

• Structural Engineering and Mechanics
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• v.63 no.4
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• pp.457-469
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• 2017

This manuscript deals with a novel approach aimed at identifying multiple damaged sites in structural components through finite frequency changes. Natural frequencies, meant as a privileged set of modal data, are adopted along with a numerical model of the system. The adoption of finite changes efficiently allows challenging characteristic problems encountered in damage detection techniques such as unexpected comparison of possible shifted modes and the significance of modal data changes very often affected by experimental/environmental noise. The new procedure extends MDLAC and exploits parallel computing on modern multicore processors. Smart filters, aimed at reducing the potential damaged sites, are implemented in order to reduce the computational effort. Several use cases are presented in order to illustrate the potentiality of the new damage detection procedure.