• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.103-112
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• 1999

This is study to estimate the pump induced vibration in time and frequency domain by frequency response function between two points in case of 20Hp and 50Hp centrifugal pumps. The frequency response function has real and imaginary information of signals, and response function has also real and imaginary information. So the vibration force can be obtained from the response function and frequency response function by complex calculation. And it is compared with the theoretically estimated values and it is suggested that the amplitude of vibration with main frequency is about 10~25% of pump and motor weight, and the magnitude of unbalanced mass is about 30~60% of pump and motor weight to estimated vibration force in time domain. There are the other kinds of vibration components with different frequency values of 2~3 times of its main frequency, and these kinds of information are used to control the tuning ratio between operating frequency of pump and structural frequency of concrete slab.

• Explosives and Blasting
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• v.20 no.3
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• pp.73-81
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• 2002

본 연구에서는 국내의 발파 자료를 이용하여 지반진동을 무차원적으로 예측하는 경험식을 도출하였다. 또 지반진동에 의한 구조물진동의 증폭계수를 산정하여 구조물 예상 응답스펙트럼을 작도할 수 있도록 하였다.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.852-856
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• 1998

Effects of packing materials on the pressure fluctuations in a fluidized bed have been analysed using statistical method to interpret fluidized bed behavior. The experiments were carried out in a fluidized bed of 6.7cm - ID, and the experimental variables were particle size and its distributions, fluidizing velocity, aspect ratio, and packing materials, etc. Screen packings are used as packing material, the properties of the pressure fluctuations in the fluidized bed were measured by a differential pressure transducer. The measured properties for the pressure fluctuations were the mean, the standard deviation, and the major frequency of the power spectral density functions, etc. The standard deviations of the pressure fluctuations have been slightly affected in the radial directions of fluidized bed, and almost constant in axial directions the height above 4.5cm of the distributor of fuidized bed without packing materials. The major frequency decreased with increaing packing size, whereas it showed maximum at 10% of packing materials. It has been found that the standard deviation of the pressure fluctuations can effectively explain the fluidized phenomena, and the packing materials severely affected the properties of the pressure fluctuations.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.327-333
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• 2003

Characteristics of vibration propagation of borehole blasting were analyzed with 578 borehole vibration data obtained from 23 sites which were used in tunnel and underground space design, and 221 tunnel vibration data fron 4 sites of tunnel under construction. Analysis results on the damping of vibration velocity show that site factors in borehole blasting were higher than those in tunnel blasting. And the critical charge calculated from regression equations at large scaled distance was lower in borehole blasting. Dominant frequency was in the range of 30∼60Hz for the borehole blasting and 60∼90Hz for the tunnel blasting. As a conclusion, the borehole blasting data should not be used on the tunnel blasting design without careful statistical analysis.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.1237-1240
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• 2010

본 연구에서는 유동층반응기를 이용하여 왕겨의 탄화반응을 수행하였다. 탄화반응은 내경 40mm, 높이 1.8m의 유동층을 사용하였으며, 분산판은 다공성 스테인레스스틸을 사용하였다. 탄화반응은 질소를 이용하여 수행하였다. 왕겨 주입입자 크기는 직경 2.0mm, 0.715mm, 0.359mm, 0.194mm를 각각 사용하였으며, 유동층의 온도는 $400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$, $700^{\circ}C$에서 탄화특성을 측정하였다. 또한 유동층의 매질로는 직경 1.0mm의 Co-Mo-Fe/$Al_2O_3$ 촉매를 사용하였으며, 탄화물은 유동층상부에 설치된 사이크론에 의하여 포집분리되었다. 탄화시 유동층 내부의 현상을 압력요동을 이용하여 해석하였으며, 압력신호로부터 평균압력, 압력요동의 표준편차, 주진동수, power spectrum density function을 계산하여 층내현상을 해석하였다. 층내온도, 유동화속도, 공급 입자크기에 따른 층내현상을 압력요동특성치를 이용하여 해석할 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.10-16
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• 2003

The unsteady supersonic flow over tandem cavities has been analyzed by the integration of Navier-Stokes equations with the k-$\varepsilon$ turbulence model. The unsteady flow is characterized by the periodicity due to the mutual relation between the shear layer and the internal flow in cavities. The upwind TVD scheme based on the flux vector split with the van Leer limiters is used. The results show the principal frequency is very reasonable. The principal frequency of the rear cavity due to the front cavity has been analyzed by the combination of the several aspect ratios of cavities. In the case of the front cavity of low aspect ratio, the frequencies of tandem cavities are almost same, because two shear layers developed from each cavity are mixed and developed to one shear layer. However, in the case of the front cavity of high aspect ratio, the characteristis of frequency are very different, because the second shear layer is developed in the diffused first shear layer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3274-3279
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• 2009

The elutriation characteristics of particle size distribution were investigated in a gas-solid fluidized bed. Experiments were carried out with the mulit-sized particles of Gaussian distributions. The elutriation rate constant obtained from the experiment was correlated with the standard deviation of particle size and the dimensionless group of the velocity ratio. The standard deviation of pressure fluctuation, mean pressure, major frequency and power spectrum density function were calculated by pressure fluctuation properties. Size distribution of elutriated particles and pressure fluctuations were measured for the particle size distribution of particle system depended largrly on the size distribution. Characteristics of fluidization and elutriation were greatly influenced by the particle size distribution and these characteristics could be interpreted with pressure fluctuation properties.