• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.315.1-315
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• 2002

The piping verification tests were performed in order to verify the structural integrity during initial operation of the reactor coolant systems and the primary heat transportation systems of nuclear power plants by KEPRI in Korea. The tests were conducted at full operating temperature and pressure. The objective is to evaluate the possibility of excessive load generating on piping, piping supports, and reactor structures etc. in the steady normal operation and expected pump transient conditions. (omitted)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.200-203
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• 2005

Ball bearings not only sustain the system, but permit the rotational component to rotate. Excessive radial or axial load and many other reasons can cause faults to be created and grown rapidly in each component. The grown faults make noise and vibration, which can make the system unstable. Therefore, it is important to detect faults as early as possible. For this reason, there have been many researches on fault detection method of early faults in a ball bearing. The fault defection methods can be categorized to several groups by signal processing methods. Not all the methods are efficient for finding early faults. We select representative methods known as efficient for detecting early faults and compare the results for inspecting which method is effective.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.674-681
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• 2008

The main noise source of the BLDC rotary compressor for air conditioner was analyzed by using the measurement of noise and vibration, noise contour, and experimental modal analysis. The source is presumed to the mechanical resonance excited by the electromagnetic attractive force of the BLDC motor. To reduce the excessive noise of the BLDC rotary compressor due to the mechanical resonance, air-gap was enlarged. Its validation was conducted by the analysis of the electromagnetic attractive force which is generated by the BLDC motor. By enlarging the length of air-gap, the noise in the compressor and air conditioner was significantly improved by 2.5dB(A) and 4.5dB(A), respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.593-596
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• 2004

Hub bearings not only sustain the body of a car, but permit wheels to rotate freely. Excessive radial or axial load and many other reasons can cause defects to be created and grown in each component. Therefore, vibration and noise from unwanted defects in outer-race, inner-race or ball elements of a Hub bearing are what we want to detect as early as possible. How early we can detect the faults has to do with how the detection algorithm finds the fault information from measured signal. Fortunately, the bearing signal has periodic impulse train. This information allows us to find the faults regardless how much noise contaminates the signal. This paper shows the basic signal processing idea and experimental results that demonstrate how good the method is.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.42-45
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• 2003

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity impacts. Indentation test was performed with the measurement of optical signal and acoustic emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated by wavelet transform. It was found that damage information of comparable in quality to acoustic emission data could be obtained from the optical fiber vibration sensor signals.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.1013-1017
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• 2003

선박의 진동문제는 고출력 엔진의 채용과 고속화 및 전문화가 되면서 구조의 최적화에 따른 경향화 설계 및 각종 주요 기진원들이 다양화됨에 따라 새로운 진동문제가 많이 발생하게 되었으며 특히 최근 중소형 조선에서 건조중인 특수한 선박들의 경우 비교적 대용량의 출력을 가진 엔진과 긴 추진 축계 시스템 등으로 인하여 과도진동의 발생가능성이 커지고 있다 본 연구에서는 Supply Ship의 시운전 중에 발생한 상부구조물의 과도진동 현상의 원인을 분석하기 위해 다양한 운항 조건에서의 실선 진동 계측 및 분석을 수행하였으며 이를 바탕으로 효과적인 대책방안을 강구하기 위하여 구조의 진동특성 검토 및 진동해석을 수행하였다. 피리고 제시된 진동저감 대책이 적용된 후에 재 시운전시 진동 계측을 수행하여 대책 안의 유용성을 확인하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.207-212
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• 2006

A dynamic analysis of a tilting actuator for projection TV is presented in this study. Generally, an excessive vibration of a tilting actuator is occurred a lowering of video quality of projection TV because of a dynamic unstability of it. Therefore, a dynamic analysis of a tilting actuator system is positively necessary. In this study, a mathematical model about a mirror-reactive type tilting actuator is presented and evidenced by experiment. A FEM model of a lens-transmissive type tilting actuator is presented and we made prototype of it. Then, it is evidenced by experiment. Besides, a design for hinge configuration of it is presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1321-1327
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• 2006

This paper presents the calculation of unbalanced magnetic pull (UMP) that causes rotor misalignment in induction motor. The excessive noise and vibration will be occurred by means of rotor misalignment. Angular misalignment of rotor will produce air-gap permeance wave which is function of axial and circumferential coordinate. In this paper, the UMP is calculated using permeance and magneto motive force (MMF) in the case of static and dynamic misalignment. Based on the percentage of misalignment, the result shows that the UMP and magnetic pressure are increased according to the increasing of misalignment. The UMP is occurred not only in It frequency component but also the others.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.1
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• pp.69-78
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• 1997

Main sources of the vibration in gear driving system are transmission error and backlash. Transmission error is the difference of the rotation between driving and driven gear due to tooth deformation and profile error. Vibro-impacts induced by backlash between meshing gears lead to excessive vibration and noise in many geared rotation systems. Nonlinear dynamic characteristics of the gear driving system due to transmi- ssion error and backlash are investigated. Transmission error is calculated for spur gear. Nonlinear equation of motion for the gear driving system is developed with the calculated transmission error and backlash. Numerical analysis of the equation and the experimental results show the existence of meshing frequency, superharmonic compon- ents. Instability of the gear driving motion is found on the basis of Mathieu equation. Rattle vibration due to backlash is also discussed on the basis if nonlinear jump phenomenon.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.6
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• pp.667-673
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• 2010

Recently, structures are becoming longer and higher because of the developments of new materials and construction techniques. However, such modern structures are more susceptible to excessive structural vibrations which cause deterioration in serviceability and structural safety. A modified probabilistic neural network(MPNN) approach is proposed to reduce the structural vibration. In this study, the global probability density function(PDF) of MPNN is reflected by summing the heterogeneous local PDFs automatically determined in the individual standard deviation of each variable. The proposed algorithm is applied for the vibration control of a three-story shear building model under Northridge earthquake. When the control results of the MPNN are compared with those of conventional PNN to verify the control performance, the MPNN controller proves to be more effective than PNN methods in decreasing the structural responses.