• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.629-633
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• 1998

본 연구에서는 연성손실계수가 구조물의 진동에 미치는 영향을 살펴보았다. 세부시스템의 두께가 동일할 경우 평판으로 이루어진 구조물이 접수되면 연성손실계수가 감소하게 된다. 특히, 저주파수 대역에서 연성손실계수가 크게 낮아졌다. 그 주된 원인은 접수로 인해 평판에서 전파되는 굽힘파의 그룹속도가 줄어들기 때문이며, 접수로 인한 파워투과계수의 변화는 크지 않았다. 내부에 격벽을 가진 steel box에 공기중 연성손실계수와 접수시 연성손실계수를 적용하여 세부시스템의 속도를 구한 결과, 공기중 연성손실계수를 이용하여 구한 속도가 접수시 연성손실계수를 이용하여 구한 속도보다 약 2-3 dB정도 높게 나타났다. 선박과 같은 복잡한 구조물인 경우 연성손실계수에 의한 속도 차이는 더욱 커질 것으로 추정된다. 따라서, SEA를 이용한 접수 구조물의 진동해석에서 해석오차를 줄이기 위해서는 연성손실계수에 접수의 영향을 고려해 주어야 함을 확인하였다. 특히, 접수효과가 고려된 연성손실계수를 사용하면 SEA가 큰 오차를 보이는 중, 저주파수 대역에서 해석 결과에 대한 신뢰성을 높일 것으로 판단된다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.1
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• pp.83-90
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• 2008

A vibration-based monitoring system is newly proposed to predict the loss of prestress forces in prestressed concrete (PSC) girder bridges. Firstly, a global damage alarming algorithm is newly proposed to monitor the occurrence of prestress-loss by using the change in frequency responses. Secondly, a prestress-loss prediction algorithm is selected to estimate the extent of prestress-loss by using the change in natural frequencies. Finally, the feasibility of the proposed system is experimentally evaluated on a scaled PSC girder model for which acceleration responses were measured for several damage scenarios of prestress-loss.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.4
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• pp.399-408
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• 2010

The characteristics of lifted laminar propane flames diluted with nitrogen have been investigated experimentally to elucidate self-excitation and the effects of flame curvature. Flame oscillation modes are classified as follows: oscillation induced by heat loss, a combination of oscillations induced by heat loss and buoyancy, and a combination of the oscillations induced by heat loss and diffusive thermal instability. It is shown that the oscillation induced only by heat loss is not relevant to the diffusive thermal instability and hydrodynamic instability caused by buoyancy; this oscillation is observed under all lift-off flame conditions irrespective of the fuel Lewis number. These experimental evidences are displayed through the analysis of the power spectrum for the temporal variation of lift-off height. The possible mechanism of the oscillation induced by heat loss is also discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.729-738
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• 2010

The characteristics of lifted butane flames diluted with nitrogen have been investigated experimentally in order to elucidate the mechanism of individual flame oscillation modes. Flame oscillations in laminar free-jet lift-off flames are classified into the following five regimes: a stabilized lift-off regime (I), a heat-loss-induced oscillation (II), a buoyancy-induced oscillation along with a heat-loss-induced oscillation (III), a combined form of an oscillation prior to blow-out and a heat-loss-induced oscillation (IV), and a combination of an oscillation prior to blow-out and a buoyancy-induced oscillation along with a heat-loss-induced oscillation (V). The characterization of the individual flame oscillations modes are presented and discussed using Strouhal numbers and their relevant parameters by the analysis of the power spectrum for temporal variation of the lift-off height.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.848-852
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• 2007

Many numerical analysis tools for predicting penetration speed of sheet pile are thought to be unreliable because they overestimate penetration speed for shallow depth of penetration. In order to overcome the defects of numerical analysis, lateral vibration model of sheet pile was suggested and energy consumption due to lateral vibration of sheet pile was estimated. Also, load reduction factor which explains reduction of vibratory driving force due to lateral vibration was introduced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.753-756
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• 2004

최근 전자 부품으로써 널리 사용되는 압전 변압기근 고전계 구동시 야기되는 압전체의 기계적인 진동 손실 및 유전 손실에 의해 높은 온도 상승이 초래된다. 이는 압전 변압기의 동작 특성 변화를 일으키며 결국 안전 변압기의 공진 주파수의 변화 및 효율의 감소 등 비선형성의 원인이 된다. 본 논문에서는 유한 요소법을 이용한 압전 변압기의 공진 특성을 해석하였으며 이를 이용하여 압전 변압기의 기계저인 진동 손실 및 유전 손실을 계산하였다. 또한 유한 요소법을 이용한 3차원 열전달 방정식의 해석을 이용하여 암전 변압기의 온도 분포를 해석하였으며 이를 실험적으로 검증하였다.

• The Journal of the Acoustical Society of Korea
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• v.19 no.6
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• pp.17-22
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• 2000

Statistical Energy Analysis(SEA) is an efficient tool to predict the broadband noise and vibration for the huge and complex structures such as aircraft and ships. To estimate the noise and vibration by using SEA accurately, the characteristics of SEA parameters associated with fluid loading have to be investigated. In this report, the fluid loaded coupling loss factors were calculated for an 'L' and 'T' type line connections and compared to the ones without fluid loading. Then, the vibration levels for steel box model with 'L' and 'T' type line connection were computed using the fluid loaded and no fluid loaded coupling loss factors, respectively. As a result, the calculated vibration levels of the model using the fluid loaded coupling loss factors were lower than those without fluid loading. As a conclusion, it is necessary to use the fluid loaded coupling loss factors for increasing the prediction accuracy on the noise and vibration of immersed structures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.285-286
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• 2011

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.191-196
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• 2000

본 논문에서는 공조용 소음기에 대한 삽입손실 및 압력손실과 같은 음향성능 평가를 위해 필요한 제반 사항을 ISO 7235에 근거하여 소개하였다. 이를 위해 시험설비의 종류 및 구비조건, 측정방법, 측정시 유의사항 등을 기술하였고, 이로서 공조용 소음기의 보다 정확한 음향성능평가가 이루어지도록 검토 하였다.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.07a
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• pp.149-155
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• 2003

우리나라의 농가에서 운반용으로 사용되고 있는 동력경운기와 트랙터 등의 트레일러는 현가장치와 방진장치가 없는 것이 대부분이다. 이런 트레일러를 비포장 된 과수원 등의 농장에서 과채류를 포장되지 않은 상태로 적재물이 트레일러의 바닥에 깔린 채 소량을 적재한 상태로 저속으로 운송될 때 충격, 진동, 마찰 등으로 많은 수송 손실이 예상된다. 이런 수송손실을 줄이기 위해서는 트레일러에 전달되는 진동을 줄여야 한다. (중략)