• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.270-276
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• 2013

We have been unwittingly exposed to magnetic field. Biological effects due to electromagnetic field exposure has been studied over the past several decades. There has been epidemiological studies and laboratory studies. In the case of laboratory studies, the effect has been observed through the cell stimulation of an artificial magnetic field. The used frequency and waveform are various in the cell experiment, but the intensity of the magnetic field is usually around 10G. Intensity of Earth's magnetic field is about 300-400mG. Although this intensity is not much higher than artificial magnetic field as 3-4% amplitude, we can't ignore the effect because every living thing on earth has already adapted for long time ago. In this study, we have designed and implemented the 3-axis magnetic field generation system in oder to remove the static magnetic field in the real-time and kept its intensity less than ${\pm}5mG({\pm}0.5uT)$ using 3-axis helmholtz coil.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.139-144
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• 2015

Recently, to realize sound-absorbing structures, we have to insert sound-absorbing materials into wall. These shapes are taken limitations because sound-absorbing materials should be fixed. Therefore, the sound absorption is changed by environment that used the sound-absorbing materials. On the other hand, we will take same effect without sound-absorbing material, if we change the shape of wall to sound absorbing structure. If we use this sound absorbing structure, we can get benefits by removing limitation of materials. Therefore we suggest perforated plate for effective sound-absorbing structure. We confirmed the function of sound-absorption of this structure using equivalent property. Then, we found the similarity between perforated plate and resonator. Also, we verify these theories through computer simulation by FEM(Finite Element Method). Finally, we validated that perforated plate has function of sound absorption without sound-absorbing material. This perforated plate is used for sound-absorbing material of buildings and transportations such as vehicle, train etc. Also, these results could be further used basic tool for design of sound-absorption structure.