• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.853-856
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• 2004

This study presents a prediction method for sound insulation of sandwich plate which consists of orthotropic plates as skin and mineral wool as core. Prediction by classic theory, which considers orthotropic effects, requires considerably complex and cumbersome process and moreover many assumption. However, experimental results of the sandwich plate with orthotropic plates as skin show that the orthotropic effects are disappeared or fade out. Hence, predictions by using sandwich model are conducted by a simple modelling that substitutes an orthotropic plate into an equivalent flat plate. Comparative results show that sandwich model gives a good agreements with theoretical prediction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.223-226
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• 2004

Vibration analysis of pipe with Elbow subject to internal pressure and temperature is studied through a commercial finite element analysis tool. The natural frequency of Elbow increased very slightly as internal pressure increases. Meanwhile, the frequency of Elbow decreased as temperature increases. It is shown that frequency deviation caused by temperature was greater than that caused by pressure. As the length of Elbows increases, frequency deviation by temperature stew rapidly, but frequency deviation by pressure was not so high. It is concluded that more concern needs to be focused on temperature rather than on pressure in terms of natural frequency.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.597-604
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• 1995

When a pipe bend is modelled with straight beam elements, its stiffness, particularly in bending behavior, is overestimated than its true value. In this paper, we propose a simple and practical beam-modelling technique to estimate its stiffness properly. When this technique, based on the strain energy concept, is employed to modify the beam sectional properties of the bend, quite satisfactory results can be obtained. To verify the validity of this method, we apply the present technique to the free vibration analysis of a center pipe with 2 bends, one of the three components of the automobile exhaust system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.305-308
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• 2002

This paper presents design and analysis of stator which is vibration source of ring-type ultrasonic motor. The stator were designed for 9th flexural vibration mode. Designed stator was simulated by FEA for changing its materials. As results, the resonance frequencies of stators were changed by Poisson's ratio and density. And higher displacement were obtained by using the materials of low Young's modulus. Using the results, can easily design and manufacture the stator of ring type ultrasonic motor. And we suppose that it can save the time and finances.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1053-1060
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• 2006

This paper consider an initially deformed state caused by the pressurized fluid flowing through the pipe at a constant velocity. When the initial forte is neglected in curved pipes, the natural frequencies are reduced as flow velocity increases. However, when the initial tension took into account, the natural frequencies are not changed with the change of the flow velocity. As the internal pipe pressure is increased the natural frequencies are also slightly increased. In free vibrational simulation of piping systems in petrochemical plants, it is necessary to calculate the initial state force due to the velocity and the pressure of the fluid flow from the equilibrium first, then the force should be included in the equation of motion of the systems to get more accurate natural frequencies. In this study, calculate the mass matrix and stiffness matrix of piping system by MATLAB

• Journal of the Korean Institute of Gas
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• v.20 no.6
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• pp.58-64
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• 2016

Vibrational characteristics of curved pipe structures are investigated with respect to the change of inside flow velocities. Based upon the Hamilton's principle, the equations of motions are derived, and the finite element equation is constructed to solve the frequency equation for curved pipe structures. When the initial tension is neglected in cured pipes, the natural frequencies are reduced as flow velocity increases, and the rapid decreases of the natural frequencies take place. However, when the initial tension is taken into account, the natural frequencies are not changed with the change of the flow velocity. In free vibrational simulation of pipe systems, it is necessary to calculate the initial force due to the velocity and the pressure of the fluid flow from the equilibrium. The force should be included in the equation of motion of the systems to get more accurate natural frequencies. The mechanical properties like stiffness or the location of pipe support need to be changed to avoid resonance. The natural frequencies are to be isolated from the frequency range of dominant vibration modes. The angles of elbows do not affect the change of the fundamental natural frequency, but affect the change of the third or higher natural frequencies.

• The Journal of the Acoustical Society of Korea
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• v.17 no.7
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• pp.3-11
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• 1998

본 논문에서는 분포정수선로의 간단한 모델을 이용해서, 외부에서 진동을 가했을 때 에 뼈 표면에서 발생하는 굴곡파의 전파속도와 종파의 전파속도를 구할 수 있는 새로운 측 정원리를 제안했다. 이 측정원리를 이용해서, 봉(brass, polymethylmethacrylate)표면에 발생 하는 정재파에 대한 속도의 공간분포를 laser Doppler법으로 측정해서, 각각의 주파수에 대 한 전파속도를 구했다. 이 새로운 측정방법은 in vivo에서 초음파 Doppler법을 이용해서 뼈 의 이상(골다공증, osteoporosis)진단의 가능성을 제시했다.

• Proceedings of the KSLP Conference
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• 2003.11a
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• pp.162-163
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• 2003

후두의 기능으로는 하기도의 보호, 호흡, 발성, 흉강의 고정 등이 있다. 이 중 발성은 성대의 진동에 의한 성대음이 입술까지의 성도(vocal tract) 및 비강에서의 조음과 공명 과정을 거치면서 이루어진다. 후두 질환을 진단하는 방법으로 간접 후두경, 단순 X-선 검사, 굴곡성 후두경(flexible fiberscope), 후두원시경(telescope), 전산화 단층 촬영, 자기공명영상 등이 사용되어 왔다. (중략)

• Nuclear Engineering and Technology
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• v.23 no.3
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• pp.306-315
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• 1991

This paper considered the out-of-plane motion of the piping system conveying fluid through the elbow connecting two straight pipes. The extended Hamilton's principle is used to derive equations of motion. It is found that dynamic instability does not exist for the clamped-clamped, clamped-pinned and pinned-pinned boundary conditions. The frequency equations for each boundary conditions are solved numerically to find the natural frequencies. The effects of fluid velocity and Coriolis force on the natural frequencies of piping system are investigated. It is shown that buckling-type instability may occur at certain critical velocities and fluid pressures. Equivalent critical velocity, which is defined as a function of flow velocity and fluid pressure, are calculated for various boundary conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.29-32
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• 1998

A plate-type ultrasonic linear motor using longitudinal and bending multi-vibration mode was designed and fabricated for card-forwarding device. The rotor consisted of piezoelectric ceramic plate and elastic materials. The performances of the motor were measured. As the experimental results, no-load speed of the motor was 0.6 m/s at 80 V in applied voltage. Starting torque was 1.4 mNm and maximum efficiency was 1.2 %.