• Title, Summary, Keyword: Permittivity

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Effects of Size and Permittivity of Rat Brain on SAR Values at 900 MHz and 1,800 MHz

  • Hyun Jong-Chul;Oh Yi-Sok
    • Journal of electromagnetic engineering and science
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    • v.6 no.1
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    • pp.47-52
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    • 2006
  • The objective of this study is to evaluate the effects of size and permittivity on the specific absorption rate(SAR) values of rat brains during microwave exposure at mobile phone frequency bands. A finite difference time domain (FDTD) technique with perfect matching layer(PML) absorbing boundaries is used for this evaluation process. A color coded digital image of the Sprague Dawley(SD) rat based on magnetic resonance imaging(MRI) is used in FDTD calculation with appropriate permittivity values corresponding to different tissues for 3, 4, 7, and 10 week old rats. This study is comprised of three major parts. First, the rat model structure is scaled uniformly, i.e., the rat size is increased without change in permittivity. The simulated SAR values are compared with other experimental and numerical results. Second, the effect of permittivity on SAR values is examined by simulating the microwave exposure on rat brains with various permittivity values for a fixed rat size. Finally, the SAR distributions in depth, and the brain-averaged SAR and brain 1 voxel peak SAR values are computed during the microwave exposure on a rat model structure when both size and permittivity have varied corresponding to different ages ranging from 3 to 10 weeks. At 900 MHz, the simulation results show that the brain-averaged SAR values decreased by about 54 % for size variation from the 3 week to the 10 week-old rat model, while the SAR values decreased only by about 16 % for permittivity variation. It is found that the brain averaged SAR values decreased by about 63 % when the variations in size and permittivity are taken together. At 1,800 MHz, the brain-averaged SAR value is decreased by 200 % for size variation, 9.7 % for permittivity variation, and 207 % for both size and permittivity variations.

Measurement of Complex Permittivity and Permeability for Powder-type Materials (분말재료의 복소 유전율 및 투자율 측정)

  • Park, Sang-Bok;Lee, Jang-Soo;Chong, Young-Seek;Cheon, Chang-Yul
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.12
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    • pp.2196-2201
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    • 2007
  • Materials used at microwave are usually used as a dielectric with a manufacturing purpose of printed circuit boards, etc. Complex permittivity of them can be measured from attenuation constant or propagation constant of a transmission line using a microstrip line with bulk type. But as the technique recently which can manufacture to have complex permittivity and permeability demanded using nonferrous metals for powder-type grows up, we need sensors and methods which can measure characteristics of powder-type materials. So far measuring methods of permittivity and permeability with waveguide or coaxial cable are used but they have faults which have a complex measurement method and are difficult to simultaneously measure permittivity and permeability. In this paper, a simultaneous measuring method of permittivity and permeability with 2-port coaxial cable and a new proposed calculation. The proposed 2-port coaxial cable is designed to be easy to insert materials and to have a wideband. We measure permittivity and permeability of magnetic powder(Ni-Fe-Mo, Ni-Fe) which reveal its characteristic at $0.3{\sim}1.3GHz$ to identify the proposed sensor.

A Measurement of Electromagnetic Property of Illite found in Young-dong Area (영동산 일라이트의 전자기적 특성 측정)

  • Kim, Jin-Chul;Lee, Won-Hui;Koo,K.W.;Hur, Jung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.267-270
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    • 2000
  • This paper describes measurement of relative permittivity of illite found in young-dong area. A measurement of relative permittivity of illite used to cylindrical cavity resonators with moveable cap. A concentric dielectric-rod inserted cylindrical cavity resonator and an exact field representation of travelling wave mode are introduced for measurement of relative permittivity. The exact electromagnetic fields in cylindrical cavity with concentric dielectric rod is analysed. A relative permittivity of dielectric in cavity is calculated by analyzing the characteristic equation. The characteristic equation is solved by using the ContourPlot graph of Mathematica. We know that the field representation of travelling mode is exact. As a result, relative permittivity of dielectric materials were 7.820 at sample-1 and 7.894 at sample-2.

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Effect of Feed Substrate Thickness on the Bandwidth and Radiation Characteristics of an Aperture-Coupled Microstrip Antenna with a High Permittivity Feed Substrate

  • Kim, Jae-Hyun;Kim, Boo-Gyoun
    • Journal of electromagnetic engineering and science
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    • v.18 no.2
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    • pp.101-107
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    • 2018
  • The impedance bandwidth and radiation characteristics of an aperture-coupled microstrip line-fed patch antenna (ACMPA) with a high permittivity (${\varepsilon}_r=10$) feed substrate suitable for integration with a monolithic microwave integrated circuit (MMIC) are investigated for various feed substrate thicknesses through an experiment and computer simulation. The impedance bandwidth of an ACMPA with a high permittivity feed substrate increases as the feed substrate thickness decreases. Furthermore, the front-to-back ratio of an ACMPA with a high permittivity feed substrate increases and the cross-polarization level decreases as the feed substrate thickness decreases. As the impedance bandwidth of an ACMPA with a high permittivity feed substrate increases and its radiation characteristics improve as the feed substrate thickness decreases, the ACMPA configuration becomes suitable for integration with an MMIC.

Measurement on the permittivity and propagation velocity of used insulation oil at UHF Band using time domain reflectometry (TDR을 이용한 극초단파 대역에서 사용 절연유의 유전율과 전파속도 측정)

  • Goo, Sun-Geun;Ju, Hyoung-Jun;Park, Ki-Jun;Han, Ki-Seon;Yoon, Jin-Yul
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.11
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    • pp.2011-2014
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    • 2008
  • We measured the permittivity and electromagnetic wave propagation velocity of used insulation oil with wide frequency range including ultra-high frequency by time domain reflectometry. The permittivity or propagation velocity is essential for locating discharge faults of oil filled power transformer. We derived 2.21 as a permittivity and $2.03{\times}10^8 m/s$ as a velocity from the measurement of pulse travelling time along a coaxial line filled with used insulation oil or air. The permittivity measurement system we designed shows high measurement accuracy and the convenience for field use.

Permittivity of Semiconductive Shield Materials in Power Cables by Frequency, Temperature (주파수, 온도에 따른 전력케이블용 반도전 재료의 유전올)

  • Yang, Hoon;Park, Dae-Hee
    • Proceedings of the KIEE Conference
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    • pp.218-219
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    • 2007
  • This paper researched permittivity of carbon nanotube reinforced semiconductive shield materials for power cable in accordance with carbon nanotube content. Permittivity measured 1[Hz], 1[kHz], 1[Mhz] in frequency range, and range of temperature measured to 100$[^{\circ}C]$ from -50$[^{\circ}C]$. It is stable to 100$[^{\circ}C]$ from -50$[^{\circ}C]$ without different gap. But, in case of CNT:CB=100:0, permittivity decreased by temperature increment. Also, in case of CNT:CB=100:0, it shows highest permittivity. Permittivity of change have little no the power of influence by frequency, but in case of 1[Mhz], CNT:CB=100:0 of specimen decreased more than other frequency. This influence thinks phenomenon of induced electricity dispersion.

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Shape Optimization of a Permittivity Graded Solid Insulator in a Gas Insulated Switchgear (가스절연 개폐장치에서 유전율 구배를 갖는 고체 절연물의 형상 최적화)

  • Ju, Heugn-Jin;Kim, Dong-Kyue;Ko, Kwang-Cheol
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.6
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    • pp.467-473
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    • 2012
  • A functionally graded material (FGM) spacer, which the distribution of dielectric permittivity inside an insulator changes spatially, can considerably reduce the electric field concentration around a high-voltage electrode and along the gas-insulator interface when compared to a conventional spacer with a uniform permittivity distribution. In this research, we propose the FGM spacer with an elliptical permittivity distribution instead of that with a distribution of dielectric permittivity varying along a radial direction only in order to improve efficiently the insulation capability. The optimal design of the elliptical FGM spacer configuration is performed by using the response surface methodology (RSM) combined with the steepest descent method (SDM).

Electric double layers interactions under condition of variable dielectric permittivity

  • Payam, Amir Farrokh;Fathipour, Morteza
    • Interaction and multiscale mechanics
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    • v.3 no.2
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    • pp.157-171
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    • 2010
  • In this paper, a theoretical method has been developed for the electric double layer interaction under condition of the variable dielectric permittivity of water. Using Poisson-Boltzmann equation (PBE), for one plate and two plates having similar or dissimilar constant charge or constant potential, we have investigated the electric double layer potential, its gradient and the disjoining pressure as well as the effect of variation of dielectric permittivity on these parameters. It has been assumed that plates are separated by a specific distance and contain a liquid solution in between. It is shown that reduction of the dielectric permittivity near the interfaces results in compression of electric double layers and affects the potential and its gradient which leads to a decreased electrostatic repulsion. In addition, it is shown that variation of dielectric permittivity in the case of higher electrolyte concentration, leads to a greater change in potential distribution between two plates.

Numerical Analysis of the Complex Permittivity of MWNT added Epoxy Depending on Agglomeration Size (에폭시 내부의 MWNT 응집 크기에 따른 복소유전율 변화의 해석적 관찰)

  • Shin, Jae-Hwan;Jang, Hong-Kyu;Choi, Won-Ho;Song, Tae-Hoon;Kim, Chun-Gon;Lee, Woo-Yong
    • Composites Research
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    • v.27 no.5
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    • pp.190-195
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    • 2014
  • This paper predicts the complex permittivity of MWNT added epoxy depending on agglomeration by numerical analysis. 1wt% MWNT added epoxy specimen is prepared using 3-roll-mill method and its complex permittivity is measured in X-band (8.2~12.4 GHz) using freespace measurement system. The analytic model is comprised of cube epoxy and perfect sphere agglomeration. The complex permittivity of the agglomeration model is predicted by complex permittivity mixing rule using the measured complex permittivity of epoxy and 1 wt% MWNT added epoxy. Commercial electromagnetic analysis software, CST, is used to obtain S-parameter of the analytic model and MATLAB code is used to calculate complex permittivity from the S-parameter. It is confirmed that the complex permittivity increases when the agglomeration size decreases.

A study on the rain attenuation prediction model using effective permittivity (실효유전율을 이용한 강우감쇠 예측 모델에 관한 연구)

  • 김혁제;조삼모
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.9 no.1
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    • pp.52-59
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    • 1998
  • We calculated the wave attenuation due to rain using the effective permittivity of the air with raindrops. The effective permittivity depends on the complex permittivity of rain drop and the fractional volume occupied by the raindrops. We calculate the complex permittivity of rain drop and the raindrops' volume using Marshall-Palmer Rain drop size distribution. The rain attenuation calculated by effective permittivity is compared with the results of ITU rain attenuation model, and the two rain attenuation models have a very close agreement. The effetive permittivity model underestimates the rain attenuation under 50 GHz, and overestimate at the frequencies under 50 GHz copmpared with the ITU model.

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