• 한국정밀공학회지
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• 제11권6호
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• pp.109-116
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• 1994

Quickness and precision are the two most important requirements for an industrial scale used in production lines. In this paper, a new approach, "Dynamic-Mass measurement control System of Acceleration and Displacement(DMS-AD) sensing", is presented to improve some of drowbacks in conventional scales. The system, consisted of acceleration and displace- ment sensors, spring scale and microcomputer, is based on full utilization of dynamic mass measurement of acceleration and displacement via microcomputer-assisted real time monitoring. The rsulting system, when combined with appropriate dynamic mass estimation algorithm software, has shown its effectiveness in terms of two desirable characteristics required. required.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.320-325
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• 2004

The paper deals with the dynamic response of a cantilevered beam under a travelling mass with constant acceleration. Governing equations of motion taking into account all inertia effects of the travelling mass are derived by Galerkin's mode summation method, and Runge-Kutta integration method is applied to solve the differential equations. The effects of the speed, acceleration and the magnitude of the travelling mass on the response of the beam are fully investigated. A variety of numerical results allows us to draw important conclusions for structural design purposes.

• Nuclear Engineering and Technology
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• 제43권4호
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• pp.361-374
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• 2011

Two types of numerical modeling techniques were considered for the dynamic response of a structure subjected to a ground acceleration. One technique is based on the equation of motion relative to ground motion, and the other is based on the equation of absolute motion of the structure and the ground. The analytic background of the former is well established while the latter has not yet been extensively verified. The latter is called a large mass method, which allocates an appropriate large mass to the ground so that it causes the ground to move according to a given acceleration time history. In this paper, through the use of a single degree-of-freedom spring-mass system, the equations of motion of the two techniques were analyzed and useful theorems are provided on the large mass method. Using simple examples, the numerical results of the two modeling techniques were compared with analytic solutions. It is shown that the theorems provide a clear insight on the large mass method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.358-362
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• 2002

The HDD unbalance, with higher rotational speed, is directly influenced by the mechanical assembly allowance between clamping disk and platter disk. The low frequency structural vibration induced by the unbalance force finally gives rise to the structure borne noise of the personal computer. To meet the noise and vibration requirements, the absolute unbalance mass of HDD needs to be measured and adjusted in the disk assembling stage. This study introduces the measurement methods of the absolute magnitude and position of the unbalance mass of HDD based on the mobility and acceleration orbit. The absolute unbalance mass can be obtained by the acceleration responses and the mobility of the mechanical part, while the position of the unbalance mass ran be obtained by the rotation acceleration orbit.

• 센서학회지
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• 제3권1호
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• pp.19-25
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• 1994

KOH와 같은 이방성 식각수용액를 사용하여 직각모양의 볼록한 가장자리를 식각할 때, 언더컷팅에 의해 가장 자리가 뭉개어지는 현상이 나타난다. 그래서 이 현상을 방지하기 위해 mass 패턴을 수정할 필요가 있어 보상법에 관한 실험을 하였다. 가속도센서 소자공간을 고려할 경우 정사각형의 보상구조로 mass를 보상하는 것이 적당하다는 결과를 얻었다. 이 결과를 기초로, SDB 웨이퍼를 이용하여 사각뿔 형태의 mass 보상된 실리콘 압저항형 가속도센서를 제조하였다.

• Earthquakes and Structures
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• 제7권3호
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• pp.385-400
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• 2014

Pounding damage to bridges and buildings is observed in most major earthquakes. The damage mainly occurs in reinforced concrete slabs, e.g. building floors and bridge decks. This study presents the results from pounding of reinforced concrete slabs. A parametric investigation was conducted involving the mass of the pendulums, the relative velocities of impact and the geometry of the contact surface. The effect of these parameters on the coefficient of restitution and peak impact acceleration is shown. In contrast to predictions from numerical force models, it was observed that peak acceleration is independent of mass. The coefficient of restitution is affected by the impact velocity, total participating mass and the mass ratio of striker and struck block.

• 천문학회지
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• 제46권1호
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• pp.41-47
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• 2013

I present a simple scheme for the treatment of gravitational interactions on galactic scales. In anal- ogy with known mechanisms of quantum field theory, I assume ad hoc that gravitation is mediated by virtual exchange particles-gravitons-with very small but non-zero masses. The resulting den- sity and mass profiles are proportional to the mass of the gravitating body. The mass profile scales with the centripetal acceleration experienced by a test particle orbiting the central mass, but this comes at the cost of postulating a universal characteristic acceleration $a_0{\approx}4.3{\times}10^{-12}msec^{-2}$ (or $8{\pi}a_0{\approx}1.1{\times}10^{-10}msec^{-2}$). The scheme predicts the asymptotic flattening of galactic rotation curves, the Tully-Fisher/Faber-Jackson relations, the mass discrepancy-acceleration relation of galaxies, the surface brightness-acceleration relation of galaxies, the kinematics of galaxy clusters, and "Renzo's rule" correctly; additional (dark) mass components are not required. Given that it is based on various ad-hoc assumptions and given further limitations, the scheme I present is not yet a consistent theory of gravitation; rather, it is a "toy model" providing a convenient scaling law that simplifies the description of gravity on galactic scales.

• Smart Structures and Systems
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• 제23권1호
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• pp.71-79
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• 2019

In general, it may be advantageous to measure the pressure pulsation near a valve to detect a valve defect in a linear compressor. However, the acceleration signals are more advantageous for rapid classification in a mass-production line. This paper deals with the performance improvement of fault classification using only the compressor-shell acceleration signal based on the relation between the refrigerant pressure pulsation and the shell acceleration of the compressor. A transfer function was estimated experimentally to take into account the signal noise ratio between the pressure pulsation of the refrigerant in the suction pipe and the shell acceleration. The shell acceleration signal of the compressor was modified using this transfer function to improve the defect classification performance. The defect classification of the modified signal was evaluated in the acceleration signal in the frequency domain using Fisher's discriminant ratio (FDR). The defect classification method was validated by experimental data. By using the method presented, the classification of valve defects can be performed rapidly and efficiently during mass production.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.340.1-340
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• 2002

The unbalance exciting force induced by HDD of lately getting higher speed is directly influenced by the rotational speed and the mechanical assembly allowance between disk and spindle motor, and which gives rise to the structure borne noise of the personal computer. The absolute unbalance mass of HDD needs to be measured and adjusted by the counter mass to control the unbalance exciting force effectively in the stage of assembling the disk and spindle motor. This study introduces the measurement methods of the magnitude of the absolute unbalance mass and the position of HDD by 2 accelerometers. The absolute unbalance mass can be obtained by the acceleration responses and the mobility of the mechanical part, while the position of the unbalance mass can e obtained by the rotation acceleration orbit.

• 한국항공우주학회지
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• 제49권9호
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• pp.739-748
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• 2021

본 연구에서는 모달 질량 가속도 곡선을 이용한 인공위성 탑재품의 설계하중 예측 및 검증에 관해 다룬다. 모달 질량 가속도 곡선을 구성하기 위해 SpaceX의 Falcon 9 발사체 정보를 사용하였으며, 이를 통해 모달 영역에서의 상계가속도 곡선을 도출하고 이를 위성체/발사체 경계하중 및 위성체 모달 정보와 결합하여 위성체 탑재품이 발사환경에서 노출될 최대가속도 하중을 예측하였다. 또한 단순한 인공위성 및 발사체 모델을 이용한 연성하중해석 결과와 비교 검토하여 모달 질량 가속도 곡선이 적절한 상계해를 도출하는 것을 확인하였다.