• 한국항해항만학회지
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• 제30권9호
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• pp.763-766
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• 2006

In this paper, the EM wave absorbers were designed and fabricated for X -band sensors using Carbon of dielectric material with CPE. The complex relative permittivity of samples is calculated by using measurement results of S-parameter. We simulated the double-layered type EM wave absorber with broad bandwidth using the measured complex relative permittivity by changing the thickness and layer, which was fabricated based on the simulated design The fabricated EM wave absorber consists of 1 mm first layer sheet facing metal with Carbon composition ratio 70 vol. % and 1.5 mm second layer sheet with Carbon composition ratio 60 vol. %. The measured results showed a good agreement to the simulated ones. It is found toot the optimized absorption ability of double-layered type EM wave absorber with thickness of 2.5 mm is higher than 10 dB from 7.8 GHz to 13.3 GHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.8-11
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• 1997

This study makes SrTiO$_{3}$ with nonpolarity among ferroelectrics by RF sputtering as dielectric layer, produces thin film of Si/SrTiO$_{3}$ and Si/Ti/SrTiO$_{3}$ of MOS structure using Ti as buffer layer, measures and examines the electrical features with optical refractive index, absorption rate, permittivity, photon energy and as a result, ferroelectrics oscillation occurrs by the interaction within a film by light temperature and the absorption of thin film with Ti as buffer layer is increased. It is found that the pea\ulcorner of permittivity value of Ti/SrTiO$_{3}$ thin film has low values and is appeared late and as dipole which is found in dielectric is shown, the experiment satisfies the theory In the nature of permittivity by photon energy, imaginary value is higher and current variation slope of thin film of thickness SrTiO$_{3}$ has lower values in reverse bias.

• 한국수산과학회지
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• 제16권3호
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• pp.247-254
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• 1983

In previous paper (Lee and Kim, 1983) the effect of moisture level and frequency on dielectric properties of sardine starch paste was mentioned. The effect of temperature and starch content of the paste upon dielectric permittivity and activation energy was discussed in this report. Addition of starch affected on dielectric property. Increases of starch in the mixtures resulted in higher complex permittivity and lower critical moisture content (hc) as shown in the mixtures with $20\%$ and $50\%$ starch which were ${\varepsilon}^{\ast}=2.97+j0.36,\;hc=8.0\%;\;{\varepsilon}^{\ast}=3.54+j0.44,\;hc=7.8\%$, respectively while being ${\varepsilon}^{\ast}=2.73+j0.29,\;hc=8.4\%$ for the plain ground sardine meat. When temperature was raised the complex permittivity tended to increase at above the critical moisture content in all cases. The activation energies for plain ground meat and $30\%$ starch added mixture at below the critical moisture of $8.4\%$ were 15.44 kcal/mol and 13.86 kcal/mol while those at the moisture of $12.2\%$ were 10.27 kcal/mol and 9.31 kcal/mol, respectively.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.297-300
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• 2006

In this paper, the EM wave absorbers were designed and fabricated for X-band sensors using Carbon of dielectric material with CPE. The complex relative permittivity of samples is calculated by the measured S-parameter data. We simulated the double-layered type EM wave absorber with broad bandwidth using the measured complex relative permittivity by changing the thickness and layer, which was fabricated based on the simulated design. The fabricated EM wave absorber consist of 1mm first layer sheet facing metal with Carbon composition ratio 70 vol% and 1.5 mm second layer sheet with Carbon composition ratio 60 vol%. The comparisons of simulated and measured results are good agreement. As a result, the optimized absorption ability of double-layered type EM wave absorber with thickness of 2.5 mm is higher than 10 dB from 7.8 GHz to 13.3 GHz.

• 한국항행학회논문지
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• 제23권1호
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• pp.69-76
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• 2019

본 논문에서는 평면 유전체 기판의 유전율 측정을 위해 마이크로스트립 결함 접지구조를 기반으로 한 고감도 마이크로파 센서의 설계 방법에 대하여 연구하였다. 제안된 센서는 H-모양 개구의 리지 구조를 커패시터 기호 모양으로 변형하여 설계하였다. 제안된 센서의 감도를 기존의 이중 링 상보형 분할 링 공진기를 기반으로 한 센서의 감도와 비교하였다. 두 센서는 피 시험 기판이 없는 상태에서 전송 계수가 1.5 GHz에서 공진하도록 0.76 mm 두께의 RF-35 기판 상에 설계하고 제작하였다. 피 시험 기판으로 비유 전율이 2.17에서 10.2 범위에 있는 타코닉 기판 5종을 선택하였다. 실험 결과, 전송계수 공진주파수의 이동으로 측정된 제안된 센서의 감도는 기존 이중 링 상보형 분할 링 공진기를 기반으로 한 센서와 비교할 때 1.31배에서 1.62배 증가하는 것을 확인하였다.

• 한국재료학회지
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• 제29권12호
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• pp.753-756
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• 2019

Orthorhombic dysprosium manganite DyMnO₃ with single phase is synthesized using solid-state reaction technique and the crystal structure and dielectric properties as functions of temperature and frequency are investigated. Thermally activated dielectric relaxations are shown in the temperature dependence of the complex permittivity, and the respective peaks are found to be shifted to higher temperatures as the measuring frequency increases. In Arrhenius plots, activation energies of 0.32 and 0.24 eV for the high- and low-temperature relaxations are observed, respectively. Analysis of the relationship between the real and imaginary parts of the permittivity and the frequencies allows us to explain the dielectric behavior of DyMnO₃ ceramics by the universal dielectric response model. A separation of the intrinsic grain and grain boundary properties is achieved using an equivalent circuit model. The dielectric responses of this circuit are discerned by impedance spectroscopy study. The determined grain and grain boundary effects in the orthorhombic DyMnO₃ ceramics are responsible for the observed high- and low-temperature relaxations in the dielectric properties.

• The Journal of the Acoustical Society of Korea
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• 제13권1E호
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• pp.5-10
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• 1994

삼층 기판위의 삼중 결합 마이크로스트립 서로의 해석을 위한 수치해석의 일반식이 얻어졌다. 유한차분식을 얻기 위한 방법과 특이점 처리를 위한 최적의 방법이 구해졌다. 홀수 모드와 짝수 모드의 캐패시턴스와 특성 임피이던스의 수치해석 결과를 보였으며 그 결과들은 이층의 두께와 삼층의 마치크로스트립 폭의 비에 따라 구해졌다. 수치해석으로 구한 짝수 모드 캐패시턴스는 다른 수치해석 결과와 비교되었다.

• 한국전기전자재료학회논문지
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• 제21권2호
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• pp.188-193
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• 2008

Epoxy/Organically Modified Layered Silicate Nanocomposites were prepared by dispersing synthetic layered silicate modified with alkyl ammonium ions. In the dispersing process, the organically modified layered silicate were mixed in epoxy resin with shearing, and aggregation of the silicate were removed by centrifugal separation after mixing epoxy resin and silicates. Micrographs taken by transmission electron microscopy(TEM) indicate that the nanocomposites have a mixed morphology including both parallel silicate layers and exfoliated silicate layers area, As the thermal properties, the glass transition temperature of the nanocomposites was shifted to a higher temperature($+6^{\circ}C$)than pure epoxy. Furthermore, dispersion of OMLS will prevented relative permittivity from increasing at a high temperature above the glass transition temperature.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.359.1-359.1
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• 2016

The electromagnetic (EM) properties of media, such as propagation, focusing and scattering, strongly rely on the electric permittivity and the magnetic permeability of media. Recently, artificially-created metamaterials (MMs) composed of periodically-arranged unit cells with tailored electric permittivity and magnetic permeability have drawn wide interest due to their capability of adjusting the EM response. MM absorbers using the conventional sandwich structures usually have very high absorption at a certain frequency, and the absorption properties of MMs can be adjusted simply by changing the geometrical parameters of unit cell. In this work, we suggested an incident-angle-independent broadband perfect absorber based on resistive layers. We analyze the absorption mechanism based on the impedance matching with the free space and the distribution of surface currents at specific frequencies. From the simulation, the absorption was expected to be higher than 96% in 1.4-6.0 GHz. The corresponding experimental absorption was found to be higher than 96% in 1.4-4.0 GHz, and the absorption turned out to be slightly lower than 96% in 4.0-6.0 GHz owing to the irregularity in the thickness of resistive layers.

• 한국전기전자재료학회논문지
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• 제34권5호
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• pp.364-370
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• 2021

In this study, the dielectric properties of flame retardant silicone rubber mixed with the amount of silica 50~65 phr were measured at frequencies ranging from 1 to 2.7 MHz and temperature ranges from 30℃ to 160℃. The permittivity decreased with higher frequencies and higher temperatures, and tanδ are thought to have decreased due to the increased heat oxidation of the methyl group bound to Si, which increased the hardness of silicone rubber. FT-IR analysis of specimen mixed with SiO₂ of 50~65 phr showed oscillations of OH groups bound to SiO₂ between wavenumber 3,600 and 3,300. As a result of analyzing surface components by Energy Dispersive X-ray (EDX) on all specimens mixed with SiO₂ of 50 to 65 phr, all specimens contained Si, and the analysis by field emission scanning electron (FE-SEM) confirmed that about 1~5 ㎛ particles were distributed regularly on the surface of the specimens.