• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.2
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• pp.200-206
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• 2006

An electric power efficiency of electrodeless fluorescent lamp depens on a big relative property of gas, gas pressure, lamp formation, ingredients of magnetic substance and shape and action frequency etc. in lamp. We used magnetic substance that opens self-examination material of electrodeless fluorescent lamp antenna. We used Mn-Zn type as the Ferrite. We have examined resistance, impedance and Q-factor's frequency characteristic by ferrite. Coil turns were changed from 13 to 15 turns to recognize brightness change of lamp by winding number. Optical equipment (LS-100) was used to measure brightness. We could know Q-factor's difference according to material is important part of antenna design. When an electrodeless fluorescent lamp was made using T company's PE22, it showed the highest brightness. As number of winding is increased the brightness increased, and starting characteristic became good.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.315-318
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• 2001

We are proposing a new mobile phone antenna, which has a specially manufactured Mn-Zn cylindrical ferrite bead inside of the helical coil of the antenna. The extended antenna radiation patters and the spatial peak SAR averaged over 1 gram simulated tissue with and without the ferrite bead insertion were measured at 824 MHz. The results show that the ferrite bead resulted in SAR reduction about 20 %, and reflection coefficient increase about 7 % for the extended antenna. The applicability of this scheme to the antenna mass production is quite feasible.

• Journal of electromagnetic engineering and science
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• v.6 no.1
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• pp.71-75
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• 2006

In this study, EM wave absorbers based on Au coated conductive sheets were prepared, and their reflection and transmission coefficients were investigated. An Au coated conductive sheet showed the transmission loss higher than 40 dB in $1{\sim}18$ GHz. Ba ferrite EM wave absorbers with an Au coated conductive sheet showed enhanced EM wave absorption and shield to compare with Ba ferrite EM wave absorbers without conductive sheets. Proposed EM wave absorbers with conductive sheets are useful to protect EM machines from EM interference by strayfields.

• Journal of the Korean Ceramic Society
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• v.29 no.8
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• pp.639-645
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• 1992

Effects of additives on electromagnetic properties of a Ni-Cu-Zn ferrite for a noise filter in high frequency regions were studied. Both resistivity and permeability were increased with the amount of Mn2O3 up to 1wt%, then decreased with further addition. Addition of Co2O3 decreased the permeability of the ferrite and shifted the resonance frequency to a higher frequency region, which was thought due to the stabilization of domain walls. Therefore it was possible to improve both the permeability and the loss and to control the cut-off frequency by the concurrent addition of Mn2O3 and Co2O3.

• Journal of Environmental Science International
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• v.15 no.6
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• pp.579-586
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• 2006

The purposes of this paper were to monitor the temperature rising courses and spark discharge of the modified granular activated carbon (GAC) by microwave (MW) irradiation and to evaluate absorption of benzene. The GAC coated on $SiO_2$, boron, talc, ferrite was named as the modified GAC. Thermal and spark discharge measurement of virgin GAC and modifed GAC has been carried out using a MW device operating at 2450 MHz under various energy conditions. The results of this paper as follows. First, the modified GAC is more efficient than the virgin GAC in temperature control. Temperature gradient of the modified GAC is more lower than that of virgin GAC. The temperature gradient of GAC was observed in the following order : virgin GAC, Mn-Zn ferrite/GAC, Ni-Zn ferrite,/GAC, $SiO_2/GAC$, Boron/GAC, Talc/GAC. Second, the spark discharge of the modified GAC was diminished, compared with that of virgin GAC. Because of its excellent electrical insulating properties, the coating material prevents the spark discharge. Finally, the benzene adsorption capacity of the modified GAC decreased due to diminishing of adsorption site by the coating material. Considering the temperature gradient and spark discharge of GAC, the GAC coated $SiO_2$ would be appropriate absorbent under irradiation of MW.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2004.12a
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• pp.3-11
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• 2004

The power loss analysis was carried out for Ni-Cu-Zn ferrite samples with different content of NiO and ZnO. The power loss, Pcv decreases monotonically wi increasing temperature and attains to a certain value at around $100\~120$ degrees Celsius. The frequency dependence of Pcv can be explained by $Pcv\~f^n$', and n is independent of the frequency, f up to 1MHz. The Pcv decreases with an increase in ZnO/NiO. The Pcv was separated to hysteresis loss, Ph and residual loss, (Pcv-Ph). The temperature characteristics and compositional dependence of Pcv can be attributed to the Ph, while (Pcv-Ph) is not affected by both temperature and ZnO/NiO. By analyzing temperature and composition dependence of Ph and initial permeability, ${\mu}^i$ following equations could be formularized. $${\mu}_i{\mu}o=I_x\;^2/(K_1+bs_ol_s)\;\;\;\;(1)$$ $Wh=13.5(I_s\;^2/{\mu}_i{\mu}_o)\;\;\;\;(2)$$ Were ${\mu}_o$ is permeability of vacuum, $I_s$ saturation magnetization, $K_1$ anisotropy constant, $S_o$ internal heterogeneous stress, $I_s$, magnetostriction constant, b unknown constant. Wh hysteresis loss per one cycle of excitation (Ph: Wh*f). Steinmetz constant of Ni-Cu-Zn ferrites, $m=1.64\~2.2$ is smaller than the one of Mn-Zn ferrites, which suggests the difference of loss mechanism between these materials.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.3-7
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• 2004

An electric power efficiency of electrodeless fluorescent lamp has big relativie property of gas in lamp, gas pressure, lamp formation, ingredients of magnetic substance and shape and action frequency etc. We used magnetic substance that open self-examination material of electrodeless fluorescent lamp antenna. Ferrite that is used in this experiment was Mn-Zn type. We have examined resistance kind, impedance, Q-factor's frequency characteristic by ferrite. Impedance, resistance and capacitance did not show difference in start frequency 2.65 [MHz] but there was difference quantity. We could know Q-factor's difference according to material, and Q-factor's is important part of antenna design.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.607-610
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• 2004

An electric power efficiency of electrodeless fluorescent lamp has big relativie propertye of gas in lamp, gas pressure, lamp formation, ingredients of magnetic substance and shape and action frequency etc. We used magnetic substance that open self-examination material of electrodeless fluorescent lamp antenna. Ferrite that is used in this experiment was Mn-Zn type. Coill turn was changed from 13th to 13th turn to recognize brightness change of lamp by winding number. Optical equipment that used in an experiment was used to measure brightness (LS-100). When an electrodeless fluorescent ]amp was made using and T company's PE22, was it showed the highest brightness. As number of winding is increased the brightness increased, and starting characteristic became good.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1123-1130
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• 1995

In the preparation of manganese zinc ferrite powders by alcoholic dehydration of citrate/formate solution. The effect of pH change on precipitation was investigated. The pH range for obtaining stable precipitates was studied. The glassy phase was obtained when the pH value of solution is higher than 5, and the formation mechanism of glassy phase was suggested. Below pH 5, the stable precipitates were formed, and the optimal pH was 2. Formation of glassy phase was accounted for the change of surface charge by pH change. The change of surface charge is caused by the interparticular agglomeration. The precipitate was redissolved into the water on the surface of precipitate itself and through the polymerization, it agglomerated. This mechanism is tought to be similar to that of viscous flow.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.248-250
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• 1996

VTR 자기헤드의 핵심소재로 사용되는 ferrite는 VTR 의 주기능인 영상의 기록 및 재생역할에 가장 중요한 소재이다. 이러한 종류의 head는 지금까지 mask wet chemical etching과 mechanical Process 에 의해 제작 되어왔다. 그러나 기록용량의 중가로 자기장치의 recording density를 높일것이 요구됨에 따라 자기헤드의 gap width를 줄일 필요가 있게 되었다. 본 연구는 mask와 photoresist를 사용하지 않고 ferrite를 직접 미세가공 하는 laser-induced wet etching을 이용하여 자기헤드의 기록용량을 높이고자 하였다. $Ar^+$ laser ( 파장 514 nm )를 빔 확장기와 렌즈를 사용 하여 직경 $1.8{\mu}m$ 로 집속하고, $100{\sim}500\;mW$의 출력 변화를 주어 실험을 하였다. 인산 수용액 (45, 65, 85 %)을 etchant로 사용하여 $5{\sim}30{\mu}m/sec$의 주사속도로 etching 하여, 미세선폭과 high aspect ratio를 갖는 groove를 얻을 수 있었다.