• Journal of Digital Convergence
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• v.12 no.8
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• pp.303-308
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• 2014

In this paper, a ferrite sheet at the back of the smartphone by type, pattern, stars, the thickness of the recognition distance by attaching the NFC optimum ferrite sheet simulation was designed. Characterized by patterns rather than the Full-type I-type communication distance of about 1 ~ 2mm more extended. Ferrite sheet metal by applying the NFC antenna is effective in improving the characteristics were confirmed. In the case of the pattern C, the permeability is 140, a thickness of 0.1mm, Full-type ferrite sheet when applied to NFC communication distance than normal electromagnetic absorber is increased from 45 to 59 was confirmed that.

• Journal of Navigation and Port Research
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• v.27 no.1
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• pp.71-74
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• 2003

Electromagnetic wave absorbers with sheet type have been fabricated and their absorption properties are measured. The absorbtion properties of the fabricated ferrite absorbers were improved with decreasing the particle size in the frequency range of 2.4~3.2 GHz.

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.758-763
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• 2002

The various ultrasonic energies (28 kHz, 40 kHz, 70 kHz) were used to improve the magnetic properties of Ba-ferrite as the perpendicular magnetic recording materials. In the sheet formation process, the different orientation hars were used to orientate perpendicularly the dispersed Ba-ferrite to sheet. Throughout these experiments, we have obtained relatively higher value of S. Q. (Squreness Ratio : 0.783) and O. R. (Orientation Ratio : 2.87) magnetic properties at 2 h ultrasonic treatment of 40 kHz ultrasonic energy. With aid of SEM(Scanning Electron Microscopy) images, the obtained sheet with dispersed of Ba-ferrite could be used for perpendicular magnetic recording due to orientated to easy magnetization axis, c-axis. In addition, the value of S. Q. of sheet decreased with increasing applied magnetic field angle during measuring of S. Q. value with changing applied magnetic field angle by VSM (Vibrating Sample Magnetrometer). This result also induced the probability for prependicular magnetic recording.

• Journal of Powder Materials
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• v.15 no.4
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• pp.292-296
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• 2008

The electromagnetic (EM) wave absorption properties of the $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline powder mixed with 5 to 20 vol% of Ni-Zn ferrites has been investigated in a frequency range from 100MHz to 10GHz. Amorphous ribbons prepared by a planar flow casting process were pulverized and milled after annealing at 425 for 1 hour. The powder was mixed with a ferrite powder at various volume ratios to tape-cast into a 1.0mm thick sheet. Results showed that the EM wave absorption sheet with Ni-Zn ferrite powder reduced complex permittivity due to low dielectric constant of ferrite compared with nanocrystalline powder, while that with 5 vol% of ferrite showed relatively higher imaginary part of permeability. The sheet mixed with 5 vol% ferrite powder showed the best electromagnetic wave absorption properties at high frequency ranges, which resulted from the increased imaginary part of permeability due to reduced eddy current.

• 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 Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.781-786
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• 2015

It is necessary for ferrite sheets to be fabricated with high packing density for excellent electrical properties and high strength. In this study, the relationship between the warpage and the packing density of ferrite green sheet, was investigated with amount variation of organic additives. With 0.4 wt% of dispersant, the packing density was about 48% and warpage appeared 0.5~1.3 mm high. With 1.4 wt% of dispersant, the packing density increased up to 57% and warpage appeared 0.8~2.1 mm high. With high packing density, warpage appeared along the edges of specimen, while with low packing density, deformation appeared over whole specimen inhomogeneously. It is thought that inhomogeneous deformation after sintering came from the inhomogeneity in green sheet prepared with badly dispersed slurry. With good homogeneity in green sheet from well-dispersed slurry, isotropic shrinkage is thought to have occurred along the distance from center to edges of specimen during sintering.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.34-34
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• 2006

Ferrite/Varistor 이종재료 동시소성에서 소성 시 두 재료간의 서로 다른 수축률에 의한 휠 거동을 ferrite 하소온도와 sheet 제조 시 binder 함량에 따라 제어하였다. Ferrite의 하소온도를 $750^{\circ}C{\sim}900^{\circ}C$로 변화시켰을 때 하소온도가 $900^{\circ}C$ 일 때 수축률이 varistor의 수축률과 악 1%미만의 차이로 가장 유사하였다. $900^{\circ}C$에서 하소한 ferrite의 slurry 제조 시 binder의 함량을 40wt%~50wt%로 변화시키면서 sheet를 제조하여 varistor와 적층하여 $900^{\circ}C{\sim}1000^{\circ}C$에서 소결하였다. Binder 함량이 40wt%에 ferrite와 varistor를 교대로 적층된 시편에서 동시소성 시 휨을 제거할 수 있었다.

• Journal of electromagnetic engineering and science
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• v.14 no.3
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• pp.317-319
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• 2014

In this letter, a small-loop antenna for a mobile UHF RFID device is proposed. To achieve size reduction, a ferrite sheet optimized for a 900 MHz band is applied. The overall dimensions of the antenna are $46mm{\times}35mm{\times}0.24mm$, and it has a bandwidth of 45 MHz with a return loss of less than -6 dB. The proposed antenna satisfies near and far field UHF EPC global frequency band communications (902-928 MHz).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.2
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• pp.63-68
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• 2007

A number of process problems should be solved in the multi-layered ceramic devices such as EMI filter. In particular, it is essential to control the sintering shrinkage in co-firing of different materials for obtaining defect-free samples such as crack, camber, and delamination which usually occur near the surface and interface. We studied the effect of the powder properties of ferrite on the co-firing behavior of green ceramic layers composed of ferrite and varistor. Three kind of ferrite powder samples as a function of milling time (24, 48, and 72 hr) were prepared. Varistor and ferrite ceramic green sheet were made by means of doctor blade process using slurry (ceramic powder and binder solution). Here, slurry was prepared by mixing 55 wt% powder with 45wt% binder solution. Varistor and ferrite green sheets were laminated at $80 kg/cm^2$, and co-fired at $900^{\circ}C$ and $1000^{\circ}C$ for 3 hr. We obtained the camber-free and co-fired ferrite/varistor layer structure by controlling the milling time and sintering temperature.

• Proceedings of the KWS Conference
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• 1998.05a
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• pp.150-154
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• 1998

The purpose of this paper is to investigate optimum welding conditions of STS 304 thin sheet by GTA welding and control 6 $\delta$--fenite which is harmful in mechanical processing, corrosion problem and can be formed brittle a phase in using long term at high temperature. One series of automatic welds was made using argon plus 10, 20, 30 % nitrogen to ensure a fully austenite deposit. Results obtained were summarized as follows: 1) 6 $\sigma$ferrite content in the weld metals is influenced largely by the nitrogen content. 2) Additions of nitrogen to the shielding gas can significantly reduce the amount of retained delta ferrite and result in an increase in hot cracking. 3) Bead width was increased when Ar + $N_2$ shielding gas was used and travel speed was increased. 4) Ar+$N_2$ shielding gas made weld metal ductile and reduce 6 -$\delta$-ferrite.