• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.421-424
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• 2010

최근 노후한 기존 구조물의 교체 및 건물 증축으로 인하여, 도심지 내 공사 현장 및 주변 지반에 매설된 지중 배관은 차량 이동 하중 및 건설 장비 하중 등의 진동에 노출이 되어있는 실정이다. 이러한 장비하중이 매설배관에 미치는 영향을 분석, 예측하기 위하여 실증 실험 결과를 토대로 모델을 검증하고 수치해석을 수행하였다. 그 결과 최대 발생 응력은 외관은 $270^{\circ}$에서, 내관은 $180^{\circ}$에서 발생 하였으며, 이는 폴리우레탄 보온재의 하중 분산 효과로 설명 할 수 있다.

• Journal of the Korean Society for Railway
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• v.10 no.1 s.38
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• pp.45-50
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• 2007

When the walls and floor of a tunnel are excited by a train, a ground vibration energy is transmitted to the surface and to footing of a nearby buildings. Excessive vibration affected to a building structure causes undesirable effect to the structural safety and the perception on residents in building. In this paper, a simple approach is introduced to predict how much vibration, in terms of level and spectra, is transmitted through the ground from the tunnel vibration excitation. A high rise building on a tunnel is selected as an application example of this case study.

• Journal of Biomedical Engineering Research
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• v.20 no.5
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• pp.625-632
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• 1999

이식형 인공중이에 사용되는 전자트랜스듀서는 압전형 트랜스듀서에 비해 음향특성은 좋으나 부피가 크고 효율이 낮으며 수술시 정밀한 코일-자석 간격 조정이 필요하며, 최근 제안된 FMT 트랜스듀서는 외부 자장의 변화에 민감하다는 문제점이 지적되고 있다. 본 논문에서는 코일-자석 간격조정이 필요 없고 외부자장에 영향을 받지 않는 차동 플로팅메스형 전자 트랜스듀서를 제안하였다. 제안된 방식은 2개의 소형 자석을 같은 극끼리 접합함으로써 외부자장에 대해 영향을 받지 않고 효율이 높은 등의 장점을 가진다. 제안된 트랜스듀서의 진동력 및 효율에 관한 정량적인 해석을 하였으며 기존의 트랜스듀서와 비교분석을 행하였다. 그리고 공급전류에 대해 발생되는 진동력의 크기를 계산함으로서 실제 이식형 인공중이의 제작에 필요한 객관적인 설계데이타를 제시하였다. 한편, 시험 제작된 트랜스듀서의 해석결과 제안한 트랜스듀서는 기존의 FMT 트랜스듀서보다도 효율이 1.5배 정도의 향상됨을 보였으며 무부하시험 및 사체의 이소골 진동실험을 통하여 적절한 진동을 효과적으로 이소골에 전달할 수 있음을 보였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.11
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• pp.847-855
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• 2002

A rotary compressors are used most widely In air-conditioning systems. Noise and vibration of a rotary compressor is an important problems during turning on and off as well as during operating. To estimate the vibration occurring during turning on and off, vibration analysis of a motor-compressor coupled system is required. In this paper, through modeling the motor and solving the forces from the equations of motion of the moving parts, the analysis of vibration of the compressor taking into consideration of the effects of motor and moving parts was performed. The accelerations of accumulator during turning on. turning off and operation are simulated. And simulated accelerations are compared with those of experimental data.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.994-1000
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• 2002

In periodically repeated cyclic structures, small property irregularity of their substructures often causes significant difference in their dynamic responses. which results in unpredicted premature failures. The small irregularity and the resulting phenomenon are called the mistuning and the vibration localization. respectively. In this paper, the vibration localization phenomena due to mistuned coupling effects are investigated. To effectively achieve the objective, a simple coupled multi-pendulum system Is employed. The results show that if there exists some coupling stiffness irregularity, vibration localization may occur and becomes more predominant as the number of substructures increases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1072-1076
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• 2004

In automotive industry, all passenger vehicles are treated with damping materials to reduce structure borne noise. The effectiveness of damping treatments depends upon design parameters such as choice of damping materials. locations and size of the treatment. Generally, the CAE method uses modal strain-energy information of the bare structural panels to identify flexible regions, which in turn facilitates optimization of damping treatments with respect to location and size. This paper proposes a design of the damping material with a CAE(Computer Aided Engineering) methodology based on finite element analysis and DOE(Design Of Experiments) to optimize damping treatments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.257-260
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• 2004

This study aims to evaluate factors of ceiling structure influencing to the floor impact sound. For this reasons, we measured the vibration of ceiling and the floor impact sound by ceiling structure. The main results from this study are that ceiling structure makes worse to non-ceiling structure for an effect of air layer in heavy-weight floor impact sound. But it has an effect on light-weight floor impact sound about $2\sim8dB$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.670-676
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• 2004

In this paper, a modeling method for the vibration analysis of rotating structures composed of beams and shells employing multi-reference frames is presented. The rotary inertia effect and the geometric stiffening effect that results from centrifugal inertia force we considered for beams and shells with lumped mass model. In most previous studies, single reference frame has been employed for the vibration analysis. In the present study, a modeling method employing multi-reference frames is presented and the effects of employing multi-reference frames on the analysis accuracy are investigated through solving numerical examples.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.8
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• pp.8-18
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• 2003

An experimental study is carried out to investigate the Reynolds number effects on the near-wake of an airfoil oscillating in pitch. An NACA 4412 airfoil is sinusoidally pitched about the quarter chord point between the angle of attack -6$^{\circ}$ and +6$^{\circ}$. A hot-wire anemometer is used to measure the turbulent intensity in the near-wake region of an NACA 4412 airfoil. The freestream velocities of present work are 3.4, 12.4, 26.2 m/s, and the corresponding Reynolds numbers are $5.3{\times}10^4,\;1.9{\times}10^5,\;4.1{\times}10^5$ and the reduced frequency is 0.1. Axial turbulent intensity profiles are presented to show the Reynolds number effects on the near-wake region behind an airfoil oscillating in pitch. All the cases in these measurements show that the turbulent intensities by the change of the Reynolds number are very large at the lowest Reynolds number $R_N=5.3{\times}10^4$; and are small at the other Reynolds number $(R_N=1.9{\times}10^5\;and\;4.1{\times}10^5)$ in the near-wake region. The significant difference of turbulent intensity between $R_N=5.3{\times}10^4,\;and\;1.9{\times}l0^5$ is observed. A critical value of the Reynolds number in the near-wake of an oscillating NACA 4412 airfoil which indicates laminar separation, no separation or turbulent separation exists in the range between $R_N=5.3{\times}10^4\;and\;1.9{\times}10^5$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.21-32
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• 2013

This is a preliminary study for the real-time feedback vibration control of building structures. The study developed a wireless acceleration sensor system based on authentic technology capacities, to integrate with the Prototype AMD system and ultimately construct the feedback vibration control system. These systems were used to evaluate the basic performance levels of the control systems within model building structures. For this purpose, the study first developed a wireless acceleration sensor unit that integrates an MEMS sensor device and bluetooth communication module. Also, the study developed an operating program that enables control output based on real-time acceleration response measurement and control law. Furthermore, the Prototype AMD and motor driver system were constructed to be maneuvered by the AC servo-motor. Eventually, all these compositions were used to evaluate the real-time feedback vibration control system of a 2-story model building, and qualitatively measure the extent of vibrational reduction of the target structure within the laboratory validation tests. As a result of the tests, there was a definite vibrational reduction effect within the laboratory validation tests. As a result of the tests, there was a definite vibrational reduction effect within 1st and 2nd resonance frequency as well as the random frequency of the model building structure. Ultimately, this study confirmed the potential of its wireless acceleration sensor system and AMD system as an effective tool that can be applied to the active vibration control of other structures.