• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.760-763
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• 2002

본 논문은 인체의 머리진동 측정용 Bite-bar에 관한 연구이며, 머리진동의 관심주파수 영역인 0.5∼30Hz 범위의 주파수 범위에서 ICP형 가속도계를 이용한 바이트-바(Bite-bar)의 공진특성에 관한 실험결과와 공진특성의 보상 방법에 관해 기술하고 있다. 또한 바이트-바(Bite-bar)의 회전비교교정에 관한 방법과 절차 그리고 실험결과를 제시하고 바이트-바(Bite-bar) 교정의 중요성과 오차(error)와 설계 제작에 있어서의 주의사항에 관해 간략히 소개한다.

• Transactions of the KSME C: Technology and Education
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• v.5 no.2
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• pp.81-87
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• 2017

315Fr compressor motor exceeds vibration specifications. To find the reason, first a modal impact test with free-free condition is done. Second a modal test with fixed condition is done. Thereafter the test results are compared with FEM simulation results. Using free-free condition modal impact test, FEM simulation conditions (boundary, mesh..) are modified. The motor has rolling motion around 120Hz. FEM simulation also shows same result. FEM simulation will be used to develop other series compressor motors. Using this, manufacturing test model and doing test will be useless.

• The Journal of the Acoustical Society of Korea
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• v.16 no.1
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• pp.16-23
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• 1997

As analysis of the forced dynamic response and vibrational mode for the cantilevered beam is described. Experimental results are compared with the natural frequencies and vibrational modes for the cantilevered beam using the theory of Bernoulli-Euler and finite element method. We have found 1st and 2nd resonance frequency of the cantilevered beam by means of the various external frequencies, $1{\sim}70Hz$, using magnetic transducer. And we have studied the vibrational displacement at obtained resonance frequency of the cantilevered beam. The experimental results for the nodes of cantilevered beam were 0 in 1st mode and 0,0.786 in 2nd mode. close agreement between the theoretically predicted results and experimental result was obtained for the vibrational mode.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.69-74
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• 1998

차량에서 인체가 노출되는 진동환경으로서 좌석과 바닥에서의 진동사이에 위상차가 존재하는 경우에 대한 인체의 반응을 주관평가 실험을 통해 분석하였다. 인체가 진동에 민감하게 반응할 뿐만 아니라 인체와 좌석으로 구성되는 진동시스템의 공진주파수와 관련된 2.5, 3.15, 4, 5, 6.3 Hz의 주파수에서, 진동의 크기를 각각 0.25, 0.4, 0.63, 1.0, 1.6m/s$^{2}$로 변화시켜 가며 위상차가 인체의 안락성에 어떻게 영향을 미치는 지를 분석하였다. 두 진동간의 위상차는 진동량이 적을수록, 또 주파수가 낮을수록 인체의 안락성에 악영향을 미쳤다. 진동의 진폭이 0.25m/s$^{2}$ 일 때 위상차가 180.deg.인 경우의 불편함은 0.deg.인 경우보다 2.5배 정도 큰 것으로 나타났다. 특히 현가장치가 장착된 의자의 경우에는 좌석과 바닥진동의 위상차이가 안락성에 미치는 영향을 정량적으로 파악하여 인체-좌석 시스템의 공진주파수를 선정해야 함을 알 수 있다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.489-494
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• 2013

This study aims to understand the mode characteristics of a droplet under a periodic forced vibration. To predict the resonance frequency of a droplet, theoretical and experimental approaches were employed. A high-speed camera was used to capture the various deformation characteristics of a droplet-mode shape, detachment, separated secondary droplet, and skewed deformation. The comparison between the theoretical and the experimental approaches shows a ~10% discrepancy in the prediction of the resonance frequency, which appears to be caused by the effect of contact line friction, nonlinear wall adhesion, and experimental uncertainty. Owing to contact-line pinning and smaller amplitude, the droplet shape becomes symmetric and the size of each lobe at the resonance frequency exceeds that at the neighbor, which is out of resonance.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.86-93
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• 2002

In this study, numerical experiments were performed to decide the proper size off finite element for the analysis of harbor resonance problems. Various sizes of finite elements were considered from 1/3 to 1/60 of wavelength to model a fully opened rectangular harbor. Through the numerical results, the proper number of finite elements per wavelength were revealed to be nine within two percents errors allowed in resonant period and amplification ratio, while twelve within one percent error. It was fecund that error rates of resonant periods decrease linearly, while those of amplification ratio decrease with oscillating form as the size of an element decreases. The error of amplification ratio increases more rapidly than that of resonant period in case of element numbers below nine.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1096-1103
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• 1990

A finite element method is used for analyzing the resonant characteristics of three- dimensional wind tunnel with circular cross section. The resonant frequencies of wind tunnel is nearly constant in Mach number range of 0.0-0.2. The resonant frequencies and modes of three-dimensional low speed wind tunnel have been calculated. The 20-node isoparametric element gives accurate results compared with the experimental results.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.1-16
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• 1999

Differential equations and its numerical solution program using Turbo-C were formulated to describe the radical distribution and average displacement amplitude of vibrating dehydrated contact lens(HEMA) driven by sinusoidal or rectangular pressure. The natural resonant frequency of the lens diaphram(thickness 0.08mm, diameter 14mm, curvature radius 8mm) was measured to be 5730 Hz from the extrapolation of frequency vs addedmass to the diaphram curve. The Young's modulus of the lens was measured to be $4{\times}10^9$ Pa with altering the original shape. The effect of parameters such as thickness, effective radius, damping coeff., amplitude of driving pressure on the vibration characteristics was illustrated by the computer simulation of the derived program. When the frequency of driving pressure coincides with the integral multiple of fundamental resonance frequency of the lens the wave pattern changes from arc to bell-shape along the radial position of the diaphram. If this happens to the contact lens on the cornea in vivo, it might create the feel of pull of the lens due to the increased rise of central part of the lens.

• Resources Recycling
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• v.29 no.1
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• pp.25-34
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• 2020

Electrochemical Quartz Crystal microbalance is a tool that is capable of measuring nanogram-scale mass change on electrode surface. When applying alternating voltage to the quartz crystal with metal electrode formed on both sides, a resonant frequency by inverse piezoelectric effect depends on its thickness. The resonant frequency changes sensitively by mass change on its electrode surface; frequency increase with metal dissolution and decrease with metal deposition on the electrode surface. The relationship between resonant frequency and mass change is shown by Sauerbrey equation so that the mass change during metal dissolution can be measured in real time. Especially, it is effective in the case of reaction mechanism and rate studies accompanied by precipitation, volatilization, compound formation, etc. resulting in difficulties on ex-situ AA or ICP analysis. However, it should be carefully considered during EQCM experiments that temperature, viscosity, and hydraulic pressure of solution, and stress and surface roughness can affect on the resonant frequency. Application of EQCM was shown as a case study on leaching of platinum using aqueous chlorine for obtaining activation energy. A platinum electrode of quartz crystal oscillator with 1000 Å thickness exposed to solution was used as leaching sample. Electrogenerated chlorine as oxidant was purged and its concentration was controlled in hydrochloric acid solution. From the experimental results, platinum dissolution by chlorine is chemical reaction control with activation energy of 83.5 kJ/mol.

• The Journal of the Acoustical Society of Korea
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• v.15 no.6
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• pp.52-58
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• 1996

Using the acoustic resonances and oscillatory pulsations considered as the branch of wave technologies, the concept of the acoustic resonance diffusers for waste water treatment which maximize the oxygen transfer efficiency in gas-liquid two phase medium have been proposed, and studies for the principles and performance tests were accomplished. Besides, the design concepts for the low pressure Helmholtz resonator, cylinder and annular type reflection resonator and combined type resonance system have been implemented. The acoustic resonance energy which can speed up the mass transfer process increase the oxygen transfer efficiency, and periodic pulsations generated from the instability of air jet from nozzle make very small air bubbles. Then, the annular type jet resonator(AJR) applying these two principles successfully was evalulated as the most promising device and also the efficiency showing $20{\sim}30%$ better than conventional diffusers has been verified experimentally.