• Title/Summary/Keyword: 진동물체

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On the Reconstruction of the Sound Field Using the Regularized Equivalent Source Method (정규화된 등가음원법을 이용한 음장의 재구성)

  • Jeon In-Youl;Ih Jeong-Guon
    • Proceedings of the Acoustical Society of Korea Conference
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    • spring
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    • pp.213-216
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    • 2004
  • 본 연구에서는 복잡한 형상을 가진 음원으로부터 방사하는 음장을 등가음원법 (equivalent source method)을 이용하여 재구성한다. 일반적인 등가음원법의 기본 원리는 진동하는 물체의 표면 또는 내부에 등가음원을 분포시켜서 등가음원의 강도를 계산하는 방법이다. 각 등가음원의 강도는 음원의 경계 조건이나 측정된 음장 음압을 통해서 구할 수가 있으며 사용된 등가음원의 차수, 개수 그리고 위치 등은 고려되어야 할 중요한 변수들이다. 기존의 HELS (Helmholtz equation least square) 방법은 한 곳의 위치에 다양한 차수로 이루어진 등가음원을 사용하여 각 차수의 계수를 구하는 방법으로써 구형에 가까운 음원에 대해서 좋은 결과를 보이나 음장의 결과가 최대 차수의 선택에 따라서 큰 오차를 유발하는 문제점이 있다. 따라서 정규화 기법을 사용하여 음장을 재구성하기 위해 필요한 등가음원의 최적 차수를 구하고, 음원 내부에 최적 차수로 이루어진 등가음원을 여러 개의 점에 위치시켜서 재구성 정확도를 향상시켰다. 정규화된 등가음원법의 타당성 검증을 위하여 표면 일부가 진동하는 구에 대한 수치 해석 및 청소기 모델에 대한 음장 재구성 실험 을 수행하였다.

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Experimental Study of Wall Pressure Fluctuations in the Regions of Flow Transition (천이 경계층 유동의 벽면 변동 압력에 관한 실험적 연구)

  • 홍진숙;전재진;김상윤;신구균
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.4
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    • pp.280-286
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    • 2002
  • It has been long suspected that the transition region may give rise to local pressure fluctuations and radiated sound that are different from those created by the fully-developed turbulent boundary layer at equivalent Reynolds number. Experimental investigation described in this paper concerns the characteristics of pressure fluctuations at the transition. Flush-mounted microphones and hot wires are used to measure the pressure fluctuations and local flow velocities within the boundary layer in the low noise wind tunnel. From this experiment we could observe the spatial and temporal development process of T-S wave using Wigner-Ville method and find the relations between the characteristic frequency of T-S wave and free stream velocity and the boundary layer thickness based on nondimensional pressure spectra scaled on outer variables.

Analysis of Contact and Separation between the Catenary and the Pantograph of a High-speed Electrical Train Considering the Dropper Positions (드롭퍼 위치를 고려한 고속전철 전력선과 급전기의 접촉 분리 해석)

  • Lee, Ki-Su
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.5 s.122
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    • pp.427-436
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    • 2007
  • The catenary of a high-speed electrical train is modeled by the finite elements with the upper suspension wire, lower contact wire, and droppers, and the dynamic contact between the catenary and the pantograph is numerically analyzed by solving the whole equations of motion of the pantograph and the catenary system subjected to the contact condition. For the stability of the numerical solution, with the cubic spline interpolation of the catenary displacement, the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Through the various numerical examples, it is shown that the dropper positions as well as the static deflection are crucial to determine the contact and separation of the pantograph of a high-speed train.

A Study on the Motion Characteristics of the Ultrasonic Transport System using Laser Scanning Vibrometer (레이저 진동 측정기를 이용한 초음파 이송 시스템의 동작특성에 관한 연구)

  • 정상화;신병수;이경형
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.10a
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    • pp.155-158
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    • 2003
  • In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the vibration behavior of flexural beam in the ultrasonic transport system is verified using Laser Scanning Vibrometer. The experiments for verifying vibration are performed in three conditions such as in the maximum transport speed, in the zero speed, and in the change of transport direction.

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Dynamic Contact Analysis of a Wheel Moving on an Elastic Beam with a High Speed (탄성 보 위를 고속 주행하는 바퀴의 동접촉 해석)

  • Lee, Ki-Su
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.5
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    • pp.541-549
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    • 2008
  • The dynamic contact between a high-speed wheel and an elastic beam is numerically analyzed by solving the whole equations of motion of the wheel and the beam subjected to the contact condition. For the stability of the numerical solution, the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Through the numerical examples, it is shown that the acceleration contact constraint including the Coriolis and centripetal accelerations are crucial for the numerical stability.

Dynamic Modeling of Planar System Consisting of Two Flexible Links and Experiment (두 개의 유연 링크로 이루어진 2차원 구조물의 동적 모델링 및 실험)

  • Choi, Min Seop;Kwak, Moon K.
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.7
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    • pp.865-874
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    • 2016
  • This research is concerned with the experimental investigation on the vibrations of a flexible two-link system for verifying the theoretical result from simplified equations of motion for the system along with the kinematical synthesis are proposed to simulate the elastic vibrations of a previous study. The structure consists of flexible two-links; The link 2 is attached to the end of the link 1. The link 1 is made of composite fiber reinforced polymer and the link 2 is an aluminum beam. In order to verify the theoretical result, a flexible two-link system operated by the AC and RC servo motors was constructed. Experimental results show that the dynamic modeling approach and the kinematical synthesis proposed in this paper are effective.

Walking Assistance Robot Design and Development (보행 보조 로봇의 설계 및 개발)

  • Lee, Min-Gyu;Lee, Yong-Hoon;Yim, Hong-Jae;Lee, Yong-Kwun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.585-592
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    • 2008
  • The aging society comes, the number of the old people expended. Technical aids allow elderly and handicapped people to live independently in their private homes as long as they wish. As a contribution to these required technological solutions, a demonstrator platform for a walking assistance robot. robot which has the capability to perform fetch and carry and various other supporting tasks. In this study, we addresses the development of a walking assistance robot system. We execute static analysis, vibration analysis and flexible dynamics to reserve stability at the design. Each motion of the robot uses a linear actuator and gears. Motion can be distinguished into 3 parts depending on the up & down, rotation, and cushion trans. In each motion, we compare the displacement of the case to be rigid with the case to be flexible. As a result, manufactured and feasibility of the walking assistance robot is validated through preliminary experiments.

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Prediction of Strouhal Number of the Triangular Cylinder Bluff Bodies (삼각주형 와 발생체의 스트로우할 수의 예측)

  • 김창호
    • The Journal of the Acoustical Society of Korea
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    • v.17 no.2
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    • pp.71-78
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    • 1998
  • 와(vortex) 박리는 고형물체가 유동내에서의 유체의 흐름을 방해할 때 발생하는 전 형적인 주기적 진동 현상이다. 본 연구에서는 삼각주형 실린더가 유동내에 유발하는 와 발 리 특성을 가시화 기법, 와에 의해 변조된 초음파의 파워 스펙트럼 및 유동관에서의 진동측 정 등을 통해 연구하였다. 가시화 관찰과 유동측정 실험 결과, 발생 와는 발생체 전면으로부 터 3d와 5d 사이에서 가장 안정성이 유지됨을 발견하였다. 넓은 레이놀즈 수(104≤Re≤106) 의 유동영역에서 액체와 기체원형유동의 측정 실험결과로부터 스트로우할(Strouhal) 수가 와발생체 폭(d)과 형상비(d/D)의 증가함수이며, 삼각주 단면의 높이에 반비례함을 알 수 있 었다. 또한 실험 결과로부터 실린더의 기하학적 치수로 삼각주형 실린더의 스트로우할 수를 예측할 수 있는 경험식을 제시하였다.

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A Study on Motion Characteristics of the Ultrasonic Transporting System according to the change of Flexural Beam Shape (Flexural Beam의 형태 변화에 따른 초음파 이송시스템의 동작특성에 관한 연구)

  • 정상화;신병수;차경래
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.696-699
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    • 2003
  • In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. There systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The relationship of transporting speed according to the change of flexural beam shape is verified and the system performance for practical use is evaluated.

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Dynamic Analysis and Experimental Verification of Brake Judder considering Quality (품질을 고려한 브레이크 저더의 동역학 해석 및 시험 검증)

  • 김효식;임홍재
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.365-370
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    • 2003
  • The problem of brake judder is typically caused by quality defects in manufacturing. This quality problem, however, can't be controlled deterministically and requires analyses and designs considering uncertainties. This paper presents a method for dynamic analysis of a brake judder considering uncertainties. Firstly, quality defects, which come from the uncertainties, are determined by examination of symptoms of the brake judder quality problem. Effective quality defects are selected by investigation of process capability and comparison of sensitivity of each quality defects and noise levels of the effective quality defects are determined. Secondly, flexible multibody dynamic analysis and finite element analysis according to the proposed method are carried out. Finally, The analysis results are compared with the test results with noise levels of the effective quality defects.

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