• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.921-926
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• 2002

In this study, we investigate the plugging effect on the CE type steam generator tube. The natural frequency and mode shape will be changed due to decrease of the effective mass distribution along the tube. We compared the variation of stability ratio for plugged tube with that for unplugged one. The natural frequency increased because of removing the cooling water inside the steam generator tube, but the stability ratio decreased inversely because of changing the vibrational model shape. We also investigated the turbulent excitation effect.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.95-103
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• 1991

A series of experiments were performed to see the dependence of the response characteristics of vortex-induced vibration of flexible cylinders on mass rations for marine applications. Experiments were conducted in the $60cm{\times}60cm$ test section of the cavitation tunnel at the Korea Research Institute of Ships and Ocean Engineering using 5 test rods of 60cm length and 6mm diameter with different mass ratios. It was confirmed quantitatively from the experiments that the low mass ratio cylinders have much broader flow velocity range of large amplitude vibrations than high mass ratio ones.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.753-756
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• 2013

The demand for sailing yacht is increasing in consonance the improvement of people's live. These yachts can be dually propelled by wind and by diesel engine power. A singing (humming, whistling) phenomenon induced on the propeller was discovered on a 55-foot catamaran sailing yacht. As a result, an increase in the structural vibration of the stern tube room and propulsion system with abnormal noise was detected due to this flow. In this study, the cause of the phenomenon is investigated and its possible countermeasures proposed.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.64-72
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• 1989

A response prediction model is introduced for the non-lockin vibration of a marine riser in sheared flow, where the riser is modelled as linearly varying tensioned-beam. This prediction model is based on the Green's function approach and random vibration theory. This model, of course, can treat general beams having slowly varying spatial system parameters. According to the predicted result of a marine riser by the prediction model proposed in this paper, the dynamic behavior of a marine riser has the mixed characteristics of finite and infinite boundary behavior. Furthermore the velocity response distribution along the riser length is much similar with the sheared flow profile. The predicted response result of a marine riser having linearly varying tension was also compared to that of constant mean tensioned-beam model. It was found that the constant mean tensioned-beam case gives over-estimated responses at the top side of the riser.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.15-22
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• 2016

분자의 진동(특히, 뒤틀림 운동)은 분자의 반응성과 동역학적 특성을 결정하는 중요한 요인이다. 특히, 분자내 메틸기의 뒤틀림 운동은 매우 흔히 관찰되지만, 이 운동을 분광학 실험으로 관찰하고 이론적으로 설명하는 것은 여전히 어려운 과제이다. 여러 양자화학 소프트웨어가 상용화되어 있지만, 뒤틀림 운동과 같은 주기적인 퍼텐셜 에너지를 갖는 운동을 기술하기 위해서는 뒤틀림 운동을 위한 양자화학 솔버가 필요하다. 따라서, 우리는 EDISON의 양자화학 솔버(1차원 슈레딩거 방정식(LagChem), 작은 유기 분자의 분광스펙트럼 분석을 위한 양자 소프트웨어(SGU-QASSO))들을 이용하여 $2-C_3H_5Br$의 ZEKE/MATI (J.Chem.Phys.119,12351(2003),Zero kinetic energy/mass-analyzed threshold ionization)스펙트럼을 이해하고 해석해보았다. $2-C_3H_5Br$ 분자는 메틸기의 강한 뒤틀림 운동을 관찰 할 수 있는 비교적 간단한 분자이기 때문에 뒤틀림 운동 분석을 위한 실험대상으로 적절하다(J.Chem.Phys.119,12352(2003)). $2-C_3H_5Br$ 분자의ZEKE/MATI스펙트럼의 결과는 EDISON양자화학 솔버를 통해 성공적으로 재현되었다. 각 진동 전이의 진동수와 세기는 실험 결과와 일치했으며, 진동 상태에 따른 파동 함수도 구할수 있었다. 이를 바탕으로 thietane 분자와 같은 고리분자의 ring-puckering운동에 대해 이해하려 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.927-932
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• 2002

The stability ratio and vibrational amplitude of each tube inside a steam generator have different values. We estimate the characteristics of flow-induced vibration for CE type steam generator with various column and row number of the tube. To obtain the thermal-hydraulic data and stability ratio we use the ATHOS3-MODI and PIAT-FEI/TE code respectively. It turns out that the steam generator has a bounded central zone with the distributed values of the stability ratio and the vibrational amplitude, and those values across the zone boundary become decreased.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.1
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• pp.36-41
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• 2002

The cause and the elimination method for the chattering phenomena were investigated in a check valve attached to the exit of an auxiliary cooling water pump in a Korean nuclear powerplant. From the site experiment and the numerical calculation, the incident angle of the disk was so small that it was not able to produce the sufficient lifting force to overcome the gravitational component of the disk weight. Moreover, it turned out that the installation position was not symmetric for the secondary vortical flow generated inside the elbow so that the flow structure had strongly unstable flow characteristics. From this study, the tapping noise and the chattering phenomena were eliminated exactly by changing the incidence angle of the valve disk and the installation position of the calve body.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.693-699
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• 2011

The outermost SG tubes have more structural problems than inside tubes. Many studies have used a uniform added mass coefficient for all of the SG tubes during the FIV analysis. The purpose of this study is to find out the added mass coefficients for each tube in a cylindrical shell. When a number of tubes are increased, added mass coefficients are also increased. And added mass coefficients at outermost tubes are less than those of inside tubes. According to gap changes between outermost tube and cylindrical shell, added mass coefficients are decreased with increasing the gap. When the gap has very large value, it shows that the added mass coefficient is asymptotically converged to the value of the tube array in a free fluid field.

• Journal of Korean Association for Spatial Structures
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• v.7 no.1 s.23
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• pp.55-62
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• 2007

The Paper presents three methods for calculating the natural frequencies of cantilevered curved Beams. A summary is given of the development of two techniques: theoretic value and the result of the experiment. Theoretic value of curved beam vibration analysis are derived from complementary variational principles assuming as unknown stress-displacement result fields. In order to perform free vibration analysis of curved beam, Aluminum-made cantilevered curved beam is used in experiment. Experimental input and output signals are derived from the impact hammer and the one accelemeter are amplificated by an amplifier. The validity of the modal analysis method

• Proceedings of the Korean Society of Disaster Information Conference
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• 2017.11a
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• pp.229-230
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• 2017

본 논문에서는 최근 대두되고 있는 지진에 대한 문제를 담고 있다. 우리나라에서는 2016년 발생한 경주지진(진도 5.8)을 계기로 내진설계기준이 한층 강화되고 의무화 되었으며 이로써 내진 성능을 가진 기초 형식이 더욱 필요하게 되었다. 내구성, 경제성, 시공성, 내진 등이 뛰어난 설계기초 공법의 하나로 팽이말뚝 기초공법이 있으나 일반 팽이말뚝기초 공법으로는 지진 시 발생하는 지반 진동으로 인한 구조물 피해를 충분히 감당하기 어렵다. 따라서, 팽이말뚝기초의 장점(경제성, 안정성, 시공성)을 살리면서 구조물과 팽이말뚝 사이에 쇄석층을 두어 진동 전달을 차단하고, 팽이말뚝 상호를 힌지로 연결하여 지반 변형에 따라 유기적으로 변형을 갖게 하고 지반의 지지력 상승과 침하량 감소의 효과를 볼 수 있고 지진시 진동 충격을 흡수하여 지진 시 피해를 줄일 수 있는 내진형 팽이말뚝을 개발하고자 한다.