• Title/Summary/Keyword: Absorber sheet

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Development of Electromagnetic Wave Absorbers far Mobile Phone Using Sendust (Sendust를 이용한 휴대전화용 전파 흡수체의 개발)

  • Choi Jung-Hyun;Kim Dong-Il;Song Jae-Man;Jung Jae-Hyun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.8 s.99
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    • pp.842-847
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    • 2005
  • In this paper, we fabricated sheet-type EM wave absorbers for mobile phones by using sendusts and tested EM wave absorption of it. The band-width of EM wave absorbers coated with $Al_2O_3$ were larger than non-coated EM wave absorbers. Particle size decreased with increasing milling time, which made the result of increasing of EM wave absorption. The fabricated EM wave absorbers show a reflection coefficient 17.4 dB at 946 MHz for a 4 mm sample and 5 dB at 1.8 GHz for a 1 mm sample.

Electromagnetic Wave Absorbing Properties of FeSiCr and Fe50Ni Flaky Powder-Polymer Composite Sheet (FeSiCr에 Fe50Ni가 첨가된 폴리머 복합 시트의 전자파 흡수 특성)

  • Lee, Seok-Moon;Kim, Sang-Mun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.7
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    • pp.462-467
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    • 2014
  • In this paper, we studied the magnetic composite sheets for electromagnetic wave noise absorber of quasi-microwave band by using soft magnetic FeSiCr and Fe50Ni flakes with the thickness of about $1{\mu}m$ and polymer. The magnetic hysteresis curve including saturation magnetization and residual magnetization and the complex permeability characteristics of the composite sheets were investigated to clarify the mixing effect on electromagnetic wave absorption properties. The saturation magnetization was decreased about 10% while the residual magnetization was increased about 15% and the real parts of complex permeability at below 500 MHz were increased 0.6~4 while those values at above 500 MHz were decreased 0.4~2.5 according to the change of contents of FeSiCr and Fe50Ni powders. As a result, the reflection loss can be moved to the lower frequency from 2~3 GHz to 1~1.5 GHz as the contents of Fe50Ni flaky powder into FeSiCr flaky powder was increased up to 50%.

Electrical and Adhesion Properties of Photoimageable Silver Paste with Glass Addtion

  • Lim, Jong-Woo;Kim, Hyo-Tae;Lee, Eun-Heay;Yoon, Young-Joon;Koo, Eun-Hae;Kim, Jong-Hee;Park, Eun-Tae;Lee, Jong-Myun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.208-208
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    • 2008
  • Micro patterning of conductor line/space on LTCC green sheet in the LTCC module is an important process for miniaturization in 3D integrated circuits. This work presented the effect of inorganic binders on the microstructure, adhesion, electrical resistivity, shrinkage and line/space resolution, which is a part of study in photoimageable conductor paste. The photoimageable conductor paste contains silver powder, polymer binder, monomer, photo-initiator, UV absorber, and solvent. The inorganic binders were furnished with varied weight percentage of anorthite, diopside and MLS-62 glass frits from 0% to 7%. The Line/space sizes thus obtained was under 25 micron.

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An Experimental Study on Optimum Honeycomb Sizes of a Flat-Plate Solar Collector (평판형(平板形) 태양열집열기(太陽熱集熱器)의 최적(最適)하니콤 크기에 관(關)한 연구(硏究))

  • Kim, T.J.;Kim, J.B.
    • Solar Energy
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    • v.8 no.2
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    • pp.3-11
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    • 1988
  • To suppress the natural convection within enclosure spacing it has been shown theoretically and experimentally that the introduction of cell walls will effectively raise the critical Rayleigh number by providing more shear surfaces within the fluid. For a solar collector, a useful solar thermal converter requires effective control of heat losses. It has been reported that the natural convection can be suppressed and the heat performances of the solar collector increased by placing thin, poorly conducting material honeycomb between the absorber plate and the coverglass. The heat performances were measured and compared directly throughout the simultaneous installation of two solar collectors, one with honeycomb structures fabricated from thin poly carbonate sheet and the other without honeycomb structures. Various tilt angles of 30, 45 and 60 deg. from the horizontal and the honeycomb sizes ($W{\times}H$) of $10{\times}10,\;10{\times}20$ and $10{\times}40mm$ were utilized in the present investigation. It is found that the larger the tilt angle are, the greater the heat losses are, and that the smaller the honeycomb size is, the larger suppression effect of heat losses are. Especially, at tilt angles of 30 degree, the heat use ratio of solar collector with the honeycomb sizes of $10{\times}10mm$ improved approximately 29.5% more than that without honeycomb structures.

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Study of Electromagnetic Wave Absorption Properties with Particle Size in Soft Magnetic Alloy Powder (연자성 합금 분말의 입자크기에 따른 전자파 흡수 특성 비교)

  • Hong, S.H.;Sohn, K.Y.;Park, W.W.;Nam, J.M.;Moon, B.G.;Song, Y.S.
    • Journal of Powder Materials
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    • v.14 no.4
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    • pp.261-264
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    • 2007
  • The electromagnetic wave (EM) absorption properties of various particle size have been investigated in a sheet-type absorber using the $Fe_{73}Si_{16}B_{7}Nb_{3}Cu_{1}$ alloy powder. With decreasing the average particle size, the complex permeability (${\mu}_{r}$) and permittivity (${\varepsilon}_{r}$) increased and the matching frequency is shifted toward lower frequency. The fabricated EM wave absorbers showed permeability $2{\sim}6$, permittivity $17{\sim}23$ for a $-325{\sim}+400$ mesh sample, and the calculated power absorption was as high as 80% in the frequency range over 2 GHz.

Processing of a Good Quality Salted and Semi-dried Mackerel by High Osmotic Pressure Resin Dehydration under Cold Condition (저온삼투압탈수법(低溫渗透壓脫水法)에 의한 고품질(高品質)의 반염건(半鹽乾)고등어 제조(製造))

  • Lee, Jung-Suck;Joo, Dong-Sik;Kim, Jin-Soo;Cho, Soon-Yeong;Lee, Eung-Ho
    • Korean Journal of Food Science and Technology
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    • v.25 no.5
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    • pp.468-474
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    • 1993
  • A dehydrating sheet comprises polymeric water absorber. which are packed in a semipermeable cellophane film bag allowing selective permeation of water. This sheet dehydration is quite different from conventional drying method such as sun drying, hot-air blast drying and cold air blast drying in a sense that samples are dried without heat treatment. As a part of the studies to develope a new processing method for effective utilization of dark muscle fishes, the preparation of a good quality salted and semi-dried mackerel by the dehydrating sheet was attempted. The dehydration time for preparation of a salted and semi-dried mackerels containing approximately equal moisture content were revealed $180{\sim}510min$ in conventional drying method and $90{\sim}160min$ in this sheet dehydration, respectively. The moisture and histamine contents of those salted and semi-dried mackerels were $59.4{\sim}62.4%$ and $2.5{\sim}3.6 mg/100g$, respectively. The changes in peroxide value, fatty acid composition, brown pigment formation, myofibrillar protein solubility and Ca-ATPase activity during processing of the salted and semi-dried mackerel prepared by the sheet dehydration were more lower than those of products prepared by conventional drying methods. Therefore, these result showed that the quality of a salted and semi-dried mackerel prepared by the sheet dehydration was imperial to that of those products by conventional drying method.

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Modeling Study on a Circulatory Hollow-Fiber Membrane Absorber for $CO_{2}$ Separation (이산화탄소 분리를 위한 순환식 중공사 막흡수기에 관한 모델링 연구)

  • Chun, Myung-Suk;Lee, Kew-Ho
    • Membrane Journal
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    • v.5 no.1
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    • pp.35-43
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    • 1995
  • For several years lots of attempts have been made to establish the liquid membrane-based techniques for separations of gas mixtures especially containing carbon dioxide. A more effective system to separate $CO_{2}$ from flue gases, a circulatory hollow-fiber membrane absorber(HFMA) consisting of absorption and desorption modules with vacuum mode, has been considered in this study. Gas-liquid mass transfer has been modeled on a membrane module with non-wetted hollow-fibers in the laminar flow regime. The influence of an absorbent flow rate on the separation performance of the circulatory HFMA can be predicted quantitatively by obtaining the $CO_{2}$ concentration profile in a tube side. The system of $CO_{2}/N_{2}$ binary gas mixture has been studied using pure water as an(inert) absorbent. As the absorbent flow rate is increased, the permeation flux(i.e., defined as permeation rate/membrane contact area) also increases. The enhanced selectivity compared to the previous results, on the other hand, shows the decreasing behavior. It has been found obviously that the permeation flux depends on the variations of pressure in gas phase of desorption module. From an accurate comparison with the results of conventional flat sheet membrane module, the advantageous permeability of this circulatory HFMA can be clearly ascertained as expected. Our efforts to the theoretical model will provide the basic analysis on the circulatory HFMA technique for a better design and process.

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Design and Performance Evaluation of Two-Layered Microwave Absorbers(Dielectric/Magnetic) for Wide Oblique Incidence Angles Used for ITS (ITS용 2층형 전파 흡수체(유전체/자성체) 설계 및 경사 입사 흡수 특성 해석)

  • Kim, Jae-Woong;Kim, Sung-Soo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.18 no.11
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    • pp.1217-1223
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    • 2007
  • Advanced microwave absorbers for wide oblique incidence angles are required in many applications including wireless communication or vehicle identification in ITS(Intelligent Transport System) where 5.8 GHz DSRC(Dedicated Short Range Communication) system is applied. In this study, two-layered microwave absorber(with a laminate structure of dielectric/magnetic composites) has been designed for the achievement of low reflection coefficient over wide incidence angles at 5.8 GHz. Iron flake particles are used as the filler in the absorbing layer, and the magnetic composite sheet exhibits high magnetic loss due to ferromagnetic resonance in gigahertz frequencies. The surface layer of low dielectric constant containing small amount of carbon black is used as the impedance transformer. On the basis of transmission line theory, the reflection loss has been calculated for the two-layer structure with variation of incident angles for both TE(Transverse Electric) and TM(Transverse Magnetic) polarizations. At the optimum thickness of the composite layers, a low value of reflection loss(less than -10 dB) has been predicted for wide incidence angles up to $55^{\circ}$ which is in good agreement with the measured value determined by free-space measurement.

Effects of Annealing on Electromagnetic Wave Absorption Characteristics in FeSiCr Flakes/Polymer Composite Sheets (FeSiCr 박편/폴리머 복합 시트의 전자파 흡수 특성에 미치는 합금 어닐링 효과)

  • Kim, Ju-Beom;Noh, Tae-Hwan
    • Journal of the Korean Magnetics Society
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    • v.23 no.3
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    • pp.83-88
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    • 2013
  • The soft magnetic Fe-Si-Cr flakes with the thickness of about 1 ${\mu}m$ were annealed at 500 and $700^{\circ}C$ for 1 h, and the composite sheets for electromagnetic wave noise absorber available for quasi-microwave band were fabricated by using these annealed flakes and polymer. Further the power loss characteristics of the composite sheets was investigated to clarify the annealing effect on electromagnetic wave absorption properties. The power loss decreased in the frequency range of several GHz when the annealed flakes were used as compared to the sheet using the as-milled FeSiCr alloy flakes. Moreover the sheets using annealed flakes exhibited lower value of real and imaginary part of complex permeability. These inferior electromagnetic wave absorption properties of the composite sheets using annealed alloy flakes were considered to be obtained by the enhanced eddy current effect upon annealing-induced recovery of microstructure and resulted low complex permeability.

Electromagnetic Wave Absorption Properties of Fe-based Nanocrystalline P/M sheets with Al2O3 additive (Al2O3 첨가에 따른 Fe계 나노결정립 P/M시트의 전자파 흡수특성)

  • Woo, S.J.;Cho, E.K.;Cho, H.J.;Lee, J.J.;Sohn, K.Y.;Park, W.W.
    • Journal of Powder Materials
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    • v.14 no.4
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    • pp.265-271
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    • 2007
  • Electromagnetic wave absorbing materials have been developed to reduce electromagnetic interference (EMI) for electronic devices in recent years. In this study, Fe-Si-B-Nb-Cu base amorphous strip was pulverized using a jet mill and an attritor and heat-treated to get flake-shaped nanocrystalline powders, and then the powders were mixed, cast and dried with dielectric $Al_{2}O_{3}$ powders and binders. As a result, the addition of $Al_{2}O_{3}$ powders improved the absorbing properties of the sheets noticeably compared with those of the sheets without dielectric materials. The sheet mixed with 2 wt% $Al_{2}O_{3}$ powder showed the best electromagnetic wave absorption, which was caused by the increase of the permittivity and the electric resistance due to the dielectric materials finely dispersed on the Fe-based powder.