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

Jong-Chul Hyun,Yisok Oh 한국전자파학회JEES 2006 Journal of Electromagnetic Engineering and Science Vol.6 No.1

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 ㎒, 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 ㎒, 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.

Complex Permittivity and Permeability of Magnesium-Copper Spinel Ferrite under Heat-treatment Conditions

박상훈,지정근,안원기,금준식,김기호,성원모 대한금속·재료학회 2008 ELECTRONIC MATERIALS LETTERS Vol.4 No.4

We studied the complex permittivity and permeability properties of magnesium-copper spinel ferrite under various heat-treatment conditions. We simulated two types of materials: dielectric and magneto-dielectric. Dielectric materials show the miniaturization of the antenna; however, decreases of bandwidth and efficiency are observed. Magneto-dielectric materials show the capability of improvement of bandwidth and efficiency with a miniaturization of the antenna. The target properties were established from simulated results of permittivity and permeability <10, and permittivity/permeability ≈ 1. Magnesium spinel ferrite was shown to increase the permittivity (from 7 to 11.7) and the permeability (from 5.5 to 8.2) with an increase of sintering temperature (from 1,150°C to 1,350°C). However, the high sintering temperature (1,350°C) affected the increase of permittivity more than it did the permeability, and this condition deteriorated the ratio, loss, and resonance frequency. These problems were overcome with the substitution of copper (of formula Mg0.9Cu0.1Fe2O4), the addition of a sintering agent (alginate 1 wt%), and the condition of a lower sintering temperature (1,250°C). The new conditions showed equal value (≈ 9.5) of the permittivity and permeability.

Complex Permittivity and Permeability of Magnesium-Copper Spinel Ferrite under Heat-treatment Conditions

( Sang Hoon Park ),( Jeong Keun Ji ),( Won Ki Ahn ),( Jun Sig Kum ),( Ki Ho Kim ),( Won Mo Seong ) 대한금속재료학회 ( 구 대한금속학회 ) 2008 ELECTRONIC MATERIALS LETTERS Vol.4 No.4

We studied the complex permittivity and permeability properties of magnesium-copper spinel ferrite under various heat-treatment conditions. We simulated two types of materials: dielectric and magneto-dielectric. Dielectric materials show the miniaturization of the antenna; however, decreases of bandwidth and efficiency are observed. Magneto-dielectric materials show the capability of improvement of bandwidth and efficiency with a miniaturization of the antenna. The target properties were established from simulated results of permittivity and permeability <10, and permittivity/permeability □ 1. Magnesium spinel ferrite was shown to increase the permittivity (from 7 to 11.7) and the permeability (from 5.5 to 8.2) with an increase of sintering temperature (from 1,150℃ to 1,350℃). However, the high sintering temperature (1,350℃) affected the increase of permittivity more than it did the permeability, and this condition deteriorated the ratio, loss, and resonance frequency. These problems were overcome with the substitution of copper (of formula Mg0.9Cu0.1Fe2O4), the addition of a sintering agent (alginate 1 wt%), and the condition of a lower sintering temperature (1,250℃). The new conditions showed equal value (□ 9.5) of the permittivity and permeability.

Hakki-Coleman 측정방법에서 공진기의 기하학적 결함과 유전율 측정오차와의 상관관계

김홍오 韓國交通大學校 2013 한국교통대학교 논문집 Vol.48 No.-

Effects of geometric imperfections of dielectric resonator on the permittivity measurement using Hakki-Coleman method were analyzed by computer simulation. Firstly, the S21 spectrum of the sample was calculated by HFSS simulation. Then, the relative permittivity was calculated from the TE011 mode resonant frequency. The relative permittivity is varied by 1% when the sample aspect ratio (D/H) is varied. The relative permittivity is varied by 1~5% when the air-gap was introduced in between the dielectric disk and upper conductor. The tilt angle of the conductor plate also affects the relative permittivity.

평행판 도파관을 이용한 유전율 측정 방법

조규영,박위상 한국인터넷방송통신학회 2012 한국인터넷방송통신학회 논문지 Vol.12 No.2

평행판 도파관에 진행하는 TEM mode를 이용한 평판형 유전체의 유전율을 측정하는 방식을 소개한다. 이는 양 옆이 열린 구조적 장점으로 실험 절차 및 측정 샘플의 가공이 매우 간편한 장점이 있다. 샘플의 유무에 따라 변화하는 도파관 내에서 전파하는 TEM mode의 위상 속도의 차이를 전자기적으로 해석하였고 이를 이용하여 유전체판의 유전율을 측정하였으며, 샘플에 대한 측정 결과는 기존에 알려진 유전율과 일치하였다. This paper introduces a simple new procedure approach to determine the permittivity of dielectric slabs. The method uses a parallel plate waveguide which supports a TEM mode. The presence of the dielectric slab placed at the bottom of the waveguide makes the speed of the TEM wave slower. The relationship between the change of the speed and the permittivity of the dielectric slab allows the determination of the permittivity. The relationship is analyzed electromagnetically, and the results of measurements are in good agreement with the analysis.

Neutron Irradiation, Amorphous Transformation and Agglomeration E®ects on the Permittivity of Nanocrystalline Silicon Carbide (3C-SiC)

Elchin M. Huseynov 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.3

Nanocrystalline 3C-SiC is irradiated by neutron flux (2 x 10 13 n/cm2s) up to 20 h in the TRIGA Mark II type research reactor. At the first stage, silicon carbide nanoparticles were analyzed by scanning electron microscope (SEM) and transmission electron microscope (TEM) devices before and after neutron irradiation. Amorphous transformation and agglomeration effects on the permittivity of nanocrystalline silicon carbide (3C-SiC) were comparisons investigated before and after neutron irradiation. Dielectric spectroscopies of nanocrystalline 3C-SiC have been conducted at the frequency ranges of 0.1Hz–2.5MHz and temperature ranges of 100–400 K. Real and imaginary parts of the permittivity of the nanomaterial were analyzed for comparison before and after neutron irradiation. Neutron irradiation increased dopant elements concentration in the nanocrystalline 3C-SiC particles, and that directly affects dielectric polarization and increased permittivity. All the mechanisms of the observed effects are given in the work.

Reduced Recombination Losses with Enhanced Dielectric Permittivity of Donor Polymers in Polymer Solar Cells

Namchul Cho(조남철),Tae-Dong Kim(김태동),Alex K.-Y. Jen(알렉스 젠) 한국고분자학회 2018 폴리머 Vol.42 No.4

본 연구에서는 나이트릴 그룹을 작용기로 가지는 고분자에 전기장을 가해주어 고분자의 분극도를 높여 고분자의 유전상수를 증가시키는 연구를 진행하였다. 전자주게 고분자의 유전상수를 증가시켜 재결합에 의한 손실을 효과적으로 감소시킬 수 있었고 이로 인해 고분자 태양전지의 개방전압을 증가시킬 수 있음을 보고하였다. 이러한 결과로부터 고분자 태양전지에서 고분자의 유전상수가 가지는 중요성 및 외부 전기장에 의한 고분자의 배열을 이용한 응용분야에 대한 중요성을 밝혔다. In this work, we have demonstrated that the electric field assisted poling of the donor polymer possessing conformationally labile nitrile groups increases dipolar polarization and dielectric permittivity. We find that the enhanced dielectric permittivity of the donor polymer reduces non-geminate recombination losses in bulk-heterojunction (BHJ) solar cells (SCs), resulting in increased open circuit voltage (VOC) compared with unpoled devices. This result reveals the importance of dielectric permittivity of polymers and also signifies the promising applicability of electric field assisted poling for high dielectric polymers in BHJ SCs.

나노결정 Fe₇₃Si₁₆B₇Nb₃Cu₁ 연자성분말과 숯분말 혼합 복합성형체의 전자파흡수 특성

김선이,김미래,손근용,박원욱,Kim, Sun-I,Kim, Mi-Rae,Sohn, Keun-Yong,Park, Won-Wook 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.4

The electromagnetic wave absorption sheets were fabricated by mixing of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline soft magnetic powder, charcoal powder and polymer based binder. The complex permittivity, complex permeability, and scattering parameter have been measured using a network analyzer in the frequency range of 10 MHz$\sim$10 GHz. The results showed that complex permittivity of sheets was largely dependent on the frequency and the amount of charcoal powder : The permittivity was improved up to 100 MHz, however the value was decreased above 1 GHz. The power loss of electromagnetic wave absorption data showed almost the same tendency as the results of complex permittivity. However, the complex permeability was not largely affected by the frequency, and the values were decreased with the addition of charcoal powder. Based on the results, it can be summarized that the addition of charcoal powder was very effective to improve the EM wave absorption in the frequency range of 10 MHz$\sim$1 GHz.

구부러진 슬롯이 추가된 고감도 마이크로스트립 패치 유전율 센서 안테나 설계

여준호,이종익 한국항행학회 2019 韓國航行學會論文誌 Vol.23 No.5

In this paper, a design method for a high-sensitivity microstrip patch sensor antenna (MPSA) loaded with a bent-slot was studied for the permittivity measurement. The bent-slot similar to a single-ring complementary split ring resonator was added along a radiating edge of the patch in order to enhance the sensitivity to the permittivity. The sensitivity of the proposed MPSA was compared with that of a conventional rectangular MPSA and a thin rectangular-slotted MPSA. Three MPSAs were designed and fabricated on a 0.76-mm-thick RF-35 substrate so that the input reflection coefficient would resonate at 2.5 GHz in the absence of the superstrate under test. When five different Taconic substrates with a relative permittivity ranging from 2.17 to 10.2 were used as the superstrate under test, experiment results show that the sensitivity of the proposed MPSA, which is measured by the shift in the resonant frequency of the input reflection coefficient, is 4.1 to 6.1 times higher than that of the conventional MPSA. 본 논문에서는 유전율 측정을 위한 구부러진 슬롯이 추가된 고감도 마이크로스트립 패치 센서 안테나의 설계 방법에 대하여 연구하였다. 유전율에 대한 감도를 향상시키기 위해 단일 링 CSRR 구조와 유사한 구부러진 슬롯이 패치의 한쪽 방사면에 추가되었다. 제안된 마이크로스트립 패치 센서 안테나의 감도를 기존의 직사각형 마이크로스트립 패치 센서 안테나와 얇은 직사각형 슬롯이 추가된 마이크로스트립 패치 센서 안테나와 비교하였다. 세 마이크로스트립 패치 센서 안테나는 피 시험 상판이 없는 상태에서 전송 계수가 2.5 GHz에서 공진하도록 0.76 mm 두께의 RF-35 기판 상에 설계하고 제작하였다. 피 시험 상판으로 비유전율이 2.17에서 10.2 범위에 있는 타코닉 기판 5종을 사용하여 실험한 결과, 입력 반사계수의 공진 주파수의 이동으로 측정된 제안된 마이크로스트립 센서 안테나의 감도는 기존의 직사각형 마이크로스트립 패치 센서 안테나와 비교할 때 4.1배에서 6.1배 증가하는 것을 확인하였다.

Dielectric resonance effect with negative permittivity in a La1.5Sr0.5NiO4+δ ceramic

Tran Dang Thanh,Nguyen Van Dang,Le Van Hong,The-Long Phan,Seong-Cho Yu 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.10

A polycrystalline sample of La1.5Sr0.5NiO4+δ was prepared by using a solid-state reaction. Xraydiffraction proved the sample to be a single phase with a tetragonal structure (space group:I4/mmm). By using an iodometric titration method to determine the non-stoichiometric oxygenconcentration (δ) in La1.5Sr0.5NiO4+δ, we found δ = −0.017, which corresponds to a doping level ofnh = x + 2δ = 0.466. Also, a strong increase of the magnetization in theM(T) curve at temperaturesbelow the spin-ordering temperature (TSO 100 K) was observed. The M(H) curves show verysmall magnetic moments, which proves the weak ferromagnetic nature of La1.5Sr0.5NiO4+δ. Thedependences of the dielectric constant on the frequency and the temperature, "(!, T) = "0(!, T) +i"00(!, T), was investigated in the frequency range of 1 − 13 MHz. At temperatures around roomtemperature, the maximum of the real part ("0) was higher than 105. Particularly, an abnormaldependence of the permittivity on frequency was observed. Depending on temperature, a dielectricresonance was observed at about 500 kHz or 8 MHz. Interestingly, we observed the dielectricresonanceeffect with a negative permittivity. Such a feature is very similar to that observed inleft-handed materials. The fitting of the experimental data for the dielectric constant at frequenciesaround the resonance frequency to the equations associated with an equivalent RLC series circuitproves that La1.5Sr0.5NiO4+δ belongs to the class of multiferroic materials.