• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.784-786
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• 2000

최근에 주목받고 있는 초고속 구동 전기기기의 전자기 설계에 있어서는 일반적 설계법외에 고려하여야 할 상수들이 있다. 10만 rpm급의 고속회전이 필요한 전자기 응용기기들은 물리적 접속이 불가능하며, 초고속 switching이 가능한 전력소자나 높은 주파수에서도 eddy current 및 hysterisis loss를 최소화 할 수 있는 강판 제질의 개발이 선행되어야 가능하다. 본 논문에서는 이러한 초고속 구동을 하는 전자기 응용 기기의 설계에 있어서 고려하여야 하는 유기 기전력, 풍손, 마찰손, eddy current and hysterisis loss 와 같은 철손 그리고 tooth-ripple losse 등에 대한 연구결과를 설명하며, 초고속 전자기 응용기기의 구동 특성과 초고속 회전에서 가장 우려되는 고주파 손실을 최소화하고 고효율을 유지하기 위한 최적형상 설계를 제시한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.905-908
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• 2001

The microstructure and the magnetic properties of Mn-Zn ferrite, which were power loss and saturation magnetic flux density, were investigated as the function of the process before firing. The highest initial permeability and the lowest power loss were attained to the specimen with CaO 400 ppm as a resulted from the highest solubility to SiO$_2$and the creation of liquid phase which improved sintering. The biggest grain size, the highest saturation magnetic flux density and the lowest power loss, which was resulted from that the eddy current loss increased as grain size increased but the hysteresis loss much more decreased and the hysteresis loss strongly influenced on the total power loss rather than the eddy current loss, were obtained to the Mn-Zn ferrite added 2wt% PVA. The power loss was lowest and the saturation magnetic flux density was highest in case of 1 ton/$\textrm{cm}^2$ and the grain size was not influenced.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1134-1136
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• 1993

The mean grain size of sample decreases with increasing the addition of $Al_2O_3$ in the basic composition of YIG. It is mean that the addition of $Al_2O_3$ is helpless the development of magnetic properties in YIG garnet, considering the relation of ${\mu}{\propto}D^{1/3}$. To increase addition of $Al_2O_3$ decreased the area of hysterisis loop. It is known that the addition of $Al_2O_3$ is help the development of magnetic properties in YIG garnet, considering the relation of loss component factor and the area of hysterisis loop. As a results, sample with the addition of $Al_2O_3$ 0.5 mol % among the fabricated samples is must effective in the magnetic properties of YIG Garnet.

• Korean Journal of Materials Research
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• v.13 no.8
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• pp.531-536
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• 2003

The electromagnetic properties and microstructures of the ferrites based on ($Ni_{0.2}$ $Cu_{0.2}$ $Zn_{0.6}$)$_{1.085}$($Fe_2$$O_3$)$_{0.915}$ were investigated by changing the amount of additive SnO$_2$and CaO and the sintering temperatures. Addition of $SnO_2$caused pores in the specimen. There was no variation of grain size by changing the amount of additives. Total loss was reduced when ($Ni_{0.2} $Cu_{0.2}$ $Zn_{ 0.6}$)$_{1.085}$ ($Fe_2$$O_3$)$_{0.915}$ composition was sintered at $1150^{\circ}C$ rather than $1300^{\circ}C$. Addition of CaO was useful to reduce the total loss because it increased the sintering density. The lowest total loss was obtained when 0.06 wt% $SnO_2$and 0.4 wt% CaO were added at the same time.

• Journal of Biosystems Engineering
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• v.16 no.1
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• pp.37-48
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• 1991

Rice plants are subjected to various forces such as natural force of wind and mechanical force of cultivating machines. Rheological behavior of the rice stem can be expressed in terms of three variables : stress, relaxation and time. The objectives of this study are to examine stress relaxation, creep and recovery characteristics on the rice stem in case of axial and radial loading. Stress relaxation with time was studied on three levels of loading rate and on four levels of applied stress. The results were summarized as follows : 1. The hysterisis losses of the rice stem distinctly observed at the radial compression in comparison with axial compression. The hysterisis loss implied that the stem to absorbed energy without being deformed beyond the yield point. 2. Ageneralized Maxwell model consisting of three elements gave a good description of the relaxation behavior of the rice stem. Rate of loading was more significant on the observed relaxation behavior within the short relaxation time, but there were little influences of rate of loading on the relaxation time. 3. The stress relaxation intensity and the residual stress increased in magnitude as the applied stress increased, but the relaxation time was little affected by the applied stress. 4. The coefficients of the stress relaxation model showed much differences in the radial compression and the axial compression, especially the higher relaxation stress of the third element was observed in the radial compression. 5. The behaviors of rice stem in creep and recovery test also might be represented by a four element Burger's model. But the coefficients of the creep model were different from those of the recovery model. 6. The steady-state phenomena of creep appeared at the stress larger than 20 MPa in Samkang and 1.8 MPa in Whajin. 7. The elastic modulus of the stem showed the range from 40 to 60 MPa. It could be considered, as a result, the rice stems had viscoelastic properties.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.197-202
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• 2005

Due to high permeability of the ferrite core, the characteristics of the ICP are expected to be greatly improved. We investigated the effect of the ferrite cores on conventional inductively coupled plasma. It was observed that the current and voltage in ike ICP antenna are slightly decreased and the power transfer efficiency is increased. However, due to eddy current and hysterisis loss, plasma density in the ICP with the ferrite cores is not increased. It seems that the ICP with the ferrite cores at low frequency (${\~}$100kHz) will be greatly improved since the losses at the low frequency can be negligible.