• 한국소음진동공학회논문집
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• 제18권12호
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• pp.1293-1300
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• 2008

This paper presents an active vibration control of cantilever beams under disturbances by a primary force. A direct velocity feedback control using a pair of PZT actuator and a velocity sensor is considered. Variation of the stability and performance with the locations of the sensor/actuator pair is investigated. It is found that the maximum gain varies with the locations of the sensor/actuator pair significantly. The maximum gain shows a symmetric distribution along the beam length with respect to the center point, although the boundary condition of the beam is unsymmetric. The control performance is affected by the location of the primary force as well as the location of the sensor/actuator pair. The active control system can more effectively reduce the vibration when the primary force is located close to the fixed boundary.

• 한국구조물진단유지관리공학회 논문집
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• 제3권3호
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• pp.195-202
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• 1999

This study present the stability of middle slabs directly supporting train loads in the subway station. According to results of Quality confirmation, mixing and curing conditions are good. But, when effects of hydration heat are analyzed, cracks seems to take place because tensile stress is higher than tensile strength in several points of middle slabs. It is found that vibration by train running don't have an effect on cracks in the structure. The structural analysis shows that there is no problem on the stability of structural body, but the design through 3-dimensional analysis is need to consider columns and opening specially in the subway station structures.

• 터널과지하공간
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• 제28권5호
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• pp.457-475
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• 2018

본 연구에서는 갱내채광장의 발파현상을 보다 현실적으로 수치해석상에서 반영하기 위하여 현장에서의 발파를 통해 획득한 발파진동 파형을 발파지점의 진동속도로 변환하여 이를 동적수치해석의 입력 자료로 직접 활용하였다. 석회석 갱내채광장의 지질특성과 채광단계를 반영한 수치모델을 구성하였으며, 이를 바탕으로 동적수치해석을 수행하여 석회석 갱내광산의 발파작업이 채광장의 안정성에 미치는 영향을 분석하였다. 해석결과와 현장에서 계측된 발파진동의 비교를 통하여 실측발파진동의 적정성을 확인하였으며, 연속되는 채광작업은 응력의 교란에 의한 천반붕락 및 채굴공동 주변의 활동성 파괴영역의 발생을 야기할 수 있는 것으로 분석되었다. 이로부터 연구대상 광산에서의 안정적인 채광활동을 위해서는 추가적인 보강대책이 필요할 것으로 판단된다.

• 한국콘텐츠학회논문지
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• 제9권12호
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• pp.348-356
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• 2009

본 연구는 요부안정화에 도움이 되는 불안정 기저면의 운동인 공운동, 전신진동운동, 매트운동을 선택하여 각 운동조건의 체간과 하지의 근 활성도(%RVC)를 비교한 결과, 배속빗근은 전신진동기조건에서 매트조건보다 유의하게 증가하였고(p<.05), 넙다리곧은근과 장딴지안쪽갈래근은 공과 전신진동기조건에서 매트조건 보다 유의하게 증가하였으며(p<.05), 오금안쪽갈래근은 공조건에서 매트조건 보다 유의하게 증가하였다(p<.05). 세 가지 운동방법으로 4주간 안정화운동프로그램을 진행시킨 결과, 세 운동군 모두 운동전보다 운동 후에 각 방향에서 안정성한계의 유의한 증가가 있었다(p<.05). 각 운동군의 운동 전 후의 안정성한계의 차이 값을 비교한 결과, 각 운동군에서 네 방향(전 후 좌 우)의 안정성한계에 유의한 차이가 없었다(p>.05). 따라서 교각자세에서의 요부안정화 운동방법 중에서 체간근과 하지근육의 근활성도는 공과 전신진동기 운동에서 더 증가되었지만, 안정화운동 4주후에는 세 운동 모두 자세안정성을 증진시키는 것으로 나타났다.

• 한국소음진동공학회논문집
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• 제26권6_spc호
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• pp.635-643
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• 2016

안정성 지도(stability map)을 이용하여 부분 종동력(sub-tangentailly follower force)를 받는 외팔 기둥의 동적안정성 이론을 요약한다. Rayleigh 감쇠를 가정하여 내적 및 외적 감쇠효과를 2개의 감쇠비를 통하여 반영하고, 감쇠비 변화에 따른 플러터하중의 변화와 관련된 매개변수 연구를 수행한다. 또한, 종동력을 받는 외팔기둥에 대한 진동수 방정식의 엄밀해를 유도하고, 특정 감쇠비 범위에 대한 안정성 지도를 유한요소 해석결과와 함께 비교/분석한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.262-266
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• 2014

Military vehicle equipped with an antenna and a shelter for operating radar has a vibration exposure during driving time. This vibration would have influence on structure of military vehicle critically. In this paper, driving stability of the military vehicle is obtained through the vibration response analysis. And, vibration level of the military vehicle satisfied the military vibration specification through analysis and comparing the MIL-STD-810G. PSD and Grms data obtained by road test can be used for vibration test specification of cabinets and electronic equipment in shelter.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.875-878
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• 2006

In the case of a vibration sensitive equipment, it require a vibration free environment to provide its proper function, therefore, it is very important to predict precisely vibration environment of microelectronics production facility due to adjacent blast work. However, it is not easy to evaluate a quantitative vibration response of structure due blast because it can be determined by the characteristics of vibration sources, propagation through rock and soil and dynamic properties of building. In this paper, vibration influence evaluation of micro-electronic Production building induced from adjacent blast activity was performed by real measurement data obtained on ground and structure at same time. And blast vibration allowable limit on ground was supposed by measurement data analysis in order to avoid operation error of precision equipments

• Nuclear Engineering and Technology
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• 제42권1호
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• pp.97-108
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• 2010

Fluid-elastic instability and turbulence-induced vibration of steam generator U-tubes of a nuclear power plant are studied numerically to investigate the effect of design changes of support structures in the upper region of the tubes. Two steam generator models, Model A and Model B, are considered in this study. The main design features of both models are identical except for the conditions of vertical and horizontal support bars. The location and number of vertical and horizontal support bars at the middle of the U-bend region in Model A differs from that of Model B. The stability ratio and the amplitude of turbulence-induced vibration are calculated by a computer program based on the ASME code. The mode shape with a large modal displacement at the upper region of the U-tube is the key parameter related to the fretting wear between the tube and its support structures, such as vertical, horizontal, and diagonal support bars. Therefore, the location and the number of vertical and horizontal support bars have a great influence on the fretting wear mechanism. The variation in the stability ratios for each vibrational mode is compared with respect to Model A and Model B. Even though both models satisfy the design criteria, Model A shows substantial improvements over Model B, particularly in terms of having greater amplitude margins in the turbulence-excited vibration (especially at the inner region of the tube bundle) and better stability ratios for the fluid-elastic instability.

• 한국소음진동공학회논문집
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• 제14권3호
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• pp.253-263
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• 2004

The problem considered in this paper is about the collocation of sensor and actuator for the active control of sound and vibration. It is well-known that a point collocated sensor-actuator pair offers an unconditional stability with very high performance when it is used with a direct velocity feedback (DVFB) control, because the pair has strictly positive real (SPR) property. In order to utilize this SPR characteristics, a matched piezoelectric sensor and actuator pair is considered. but this pair suffers from the in-plane motion coupling problem with the out-of-plane motion due to the piezo sensor and actuator interaction. This coupling phnomenon limits the stability and performance of the matched pair with DVFBcontrol. As a new alternative, a point sensor and distributed piezoelectric actuator pair is also considered, which provides SPR property in all frequency range when the pair is implemented on a clamped-clapmed beam. The use of this sensor-actuator pair is highly expected for the applications to more practical active control of sound and vibration systems with the DVFB control strategy.

• Steel and Composite Structures
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• 제23권5호
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• pp.529-541
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• 2017

In the present study, vibration analysis of functionally graded carbon nanotube reinforced composite (FGCNTRC) plate moving in two directions is investigated. Various types of shear deformation theories are utilized to obtain more accurate and simplest theory. Single-walled carbon nanotubes (SWCNTs) are selected as a reinforcement of composite face sheets inside Poly methyl methacrylate (PMMA) matrix. Moreover, different kinds of distributions of CNTs are considered. Based on extended rule of mixture, the structural properties of composite face sheets are considered. Motion equations are obtained by Hamilton's principle and solved analytically. Influences of various parameters such as moving speed in x and y directions, volume fraction and distribution of CNTs, orthotropic viscoelastic surrounding medium, thickness and aspect ratio of composite plate on the vibration characteristics of moving system are discussed in details. The results indicated that thenatural frequency or stability of FGCNTRC plate is strongly dependent on axially moving speed. Moreover, a better configuration of the nanotube embedded in plate can be used to increase the critical speed, as a result, the stability is improved. The results of this investigation can be used in design and manufacturing of marine vessels and aircrafts.