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휴대전화기용 전파흡수체에 있어 페라이트 입자크기와 투자율, 시편제작온도에 따른 전파흡수특성
김동일,옥승민,송재만,김기만,신승재,문상현 한국전자파학회 2004 한국전자파학회논문지 Vol.15 No.4
본 연구에서는 페라이트 입자크기와 시편의 제작온도가 Sheet형 전파홉수체의 전파홉수능에 미치는 영향을 조사한 것으로 분쇄 전 초투자율이 2,500과 10,000인 폐 처리된 MnZn ferrite를 이용하여 휴대전화용 전파홉수체를 제작하고 그 전파흡수능을 조사하였다. 페라이트 입자크기가 증가함에 따라 휴대전화촌 주파수인 1.8 ㎓에서 전파흡수능이 증가하였으며, 시편제작 온도가 증가함에 따라 역시 전파흡수능이 향상되었다. 본 연구에서는 주파수 1.8 ㎓에서 3.8 ㏈의 우수한 홉수능을 나타내는 두께 1 mm인 전파흡수능이 매우 우수하면서도 두께가 얇은 전파흡수체를 개발하였다. In this study, we investigated the reflection coefficient of absorbers fur mobile phone on average Particle size and preparation temperature of specimens. We used recycled MnZn ferrite with initial permeability of 2,500 and 10,000 as starting materials. Absorption ability increased at 1.8 ㎓ which is frequency fur mobile phones with increasing average particle size. We developed a sheet type electromagnetic wave absorber with the thickness of 1 mm which showed reflection coefficient of -3.8 ㏈ at 1.8 ㎓.
김동일,김수정,옥승민,송재만 한국해양대학교 산업기술연구소 2003 연구논문집 Vol.20 No.-
According to mixing rate of Mn-Zn ferrite the absorption ability and frequency band were examined for the electromagnetic wave (EM)absorber. The experiment were carried out to produce the absorber which has excellent absorption ability electromagnetic wave. The natural ceramics, titanium, and graphite are added to Mn-Zn ferrite. Thus the absorber ability was improved. As a result, the EM wave absorber with an ability of 80% absorption was fabricated within the thickness of 3 ㎜.
휴대전화용 전파흡수체에 있어서 페라이트 입자 크기의 제어에 따른 전파흡수특성
송재만,김동일,김수정,옥승민,김보영,박우근,이영구,윤현진,김기만 한국전자파학회 2003 한국전자파학회논문지 Vol.14 No.3
Sheet형 전파흡수체를 제작하여 Mn-Zn페라이트의 입자크기에 따른 전파흡수능의 관계를 조사하였다. 입자 크기가 증가함에 따라 정합주파수는 낮은 쪽으로 이동하였으며, 정합주파수에서 전파흡수능은 감소하였다. 하지만 휴대폰의 사용주파수인 0.8 ㎓와 1.8 ㎓에서는 입자의 크기가 큰 것으로 구성되어 있는 전파흡수체자 작은 입자로 구성되어 있는 전파흡수체보다 우수한 전파흡수능을 나타내었다. 따라서 휴대폰용 전파흡수체를 Mn-Zn 페라이트 파우더로 제작할 경우에는 입자의 크기가 큰 것이 바람직하다고 생각된다. In this study, we investigated the effect of particle size of Mn-Zn ferrite which is used as a material of electromagnetic wave absorber on electromagnetic wave properties. With increasing the particle size, the matching frequency is shifted toward lower frequency and the absorption ability of electromagnetic wave is decreased. We suggest that a sheet-type ferrite absorber composed of Mn-Zn ferrite with large particle is useful to compare with it composed of small particle size for mobile phone.
김동호(Dong Ho Kim),옥승민(Seung Min Ok),박창용(Chang Yong Park) 대한설비공학회 2018 대한설비공학회 학술발표대회논문집 Vol.2018 No.11
An experimental study was performed to measure the flow boiling heat transfer coefficient and pressure drop in multi-ported square channels with 0.5 mm hydraulic diameter. The working fluid was selected as HFE-7100 because of its dielectric fluid characteristics and low saturation pressure. The test section was made of one piece of brass block with carved plenums and mini-channels. In the test section, heat transfer and pressure drop were measured under the conditions at 300 ㎏/㎡s of mass flux, 63℃of saturation temperature, 15 ㎾/㎡ of heat flux, and the vapor quality from 0.3 to 0.55. The measured heat transfer coefficients decreased with the increase of vapor quality and the reason of this trend was estimated as the effect of the early dryout on the channel surface. The measured heat transfer coefficients were compared with the predicted values by several existing correlations and one of the compared correlations showed relatively good agreement including the decreasing trend of heat transfer coefficients with the increase of vapor quality.
Sheet형 전파흡수체에 있어 Ferrite 입자 크기의 제어에 따른 전파흡수체의 특성
김동일(Dong-Il Kim),옥승민(Seung-Min Ok),김수정(Su-Jung Kim),박우근(Woo-Keun Park),송재만(Jae-Man Song) 한국항해항만학회 2003 한국항해항만학회지 Vol.27 No.1
Sheet형 전파흡수체를 제조하고 그들의 전자파 흡수 특성을 조사하였다. 제조된 ferrite 흡수체의 흡수특성은 2.4~3.2 ㎓의 주파수 범위에서 입자크기의 감소에 따라 개선되었다. 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 ㎓.
김동일(Dong Il Kim),최동한(Dong Han Choi),구동우(Dong Woo Ku),김도연(Do Yearn Kim),옥승민(Seung Min Ok),양은정(Eun Jung Yang),김보영(Bo Young Kim) 한국항해항만학회 2002 한국항해항만학회 학술대회논문집 Vol.1 No.-
In this paper, we explain new EM(electromagnetic) wave absorber that mixed NC(Natural Ceramics) and Ferrite with NL(Natural Lacquer). At first, a mixed NC and Ferrite(NC : F = (0.1~30)wt% : (99.9~70)wt%) burn at 950˚~1250˚C. And then, it is comminuted and injected into NL((NC+F) : NL = (30~80)wt% : (70~20)wt%), finally we made Ferrite-NL EM wave absorber. Generally, conventional labor Ferrite covers only 500 MHz to 10 GHz under tolerance limits of 2 to 6 dB in absorption, and Ferrite-NL is over 8~14 dB. However, NCFerrite-NL has superior absorption ability. It is over 16 ro 19 dB through 500 MHz to 10 GHz.