• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.5
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• pp.17-24
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• 2000

Complex permittivity of dry sand is measured by using an open-ended coaxial probe, which was self-designed and manufactured. As a simple calibration scheme of the probe, the phase difference between the measured and the calculated reflection coefficients of pure water is subtracted from the phase of the measured reflection coefficient for dry sand. And then the complex permittivity of dry sand is reconstructed by applying its measured reflection coefficient into an improved imaginary transmission-line model. The accuracy of our measurement scheme is verified by showing that its reconstructed complex permittivity approaches the precise value of dry sand.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1848-1850
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• 2004

변압기에 사용되는 절연유의 열화정도를 변압기의 운전정지 없이 실시간으로 측정할 수 있는 전기용량을 이용한 센서를 개발하였다. 개발된 전기용량형 센서는 3-전극형의 구조와 변압기에 센서의 외부상자가 접지 될 때 2중의 정전차폐가 되도록 하여 외부로부터의 잡음에 영향을 받지 않도록 하였다. 또한 변압기에서 절연유의 온도변화에 따른 유전율 변화를 보상하기위하여 기준용 센서와 측정용 센서를 한개의 변압기에 장착함으로 온도보상이 되도록 하였다. 제작된 센서는 변압기에서 절연유의 사용기간에 따른 유전율의 변화를 정확히 측정하였으며, 절연유의 체적저항의 변화도 감지 할 수가 있다. 따라서 센서에서 출력되는 신호를 phase sensitive detector를 사용하여 유전율의 변화로 혹은 체적저항의 변화로도 나타내 보일 수가 있다.

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.252-256
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• 2001

We performed spectroscopic ellipsometry measurement to obtain dielectric function(DF) of ZnSe at room temperature. Proper wet chemical etching procedure was carried out to remove overlayers on top of ZnSe, and our result indicates that the previous reports on the pure DF of ZnSe have inaccurate interpretations. We constructed DF of oxide on ZnSe by using reported DFs of amorphous-Se, $GaAsO_3$, and voids through Bruggeman effective-medium approximation.

• The Journal of Engineering Geology
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• v.14 no.2
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• pp.179-187
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• 2004

This study conducted a laboratory work to determine the change of dielectric constant of saturated soil porous media, which is injecting EML to use Frequency Domain Reflectometry(FDR) system and length 7cm-length measurement sensor. It is purpose of study that estimate a movement path through pore of soil for an ethanol mixing liquid(EML) which have the same specific gravity of water at $20{\;}^{\circ}C$, and determine to a dielectric measuring range for the measurement sensor. As an outflow point of saturated soil column upper part recedes from an EML inject point in EML diffusion test, the diffusion extent of EML through pore of saturated soil was expanded. And results of ail EML flow experiment were measured the change of dielectric constant at all measurement sensors which are placed to constant interval at the same travel time for saturated soil column. Therefore, the displace process of water that exist in pore of saturated soil by EML injection is enough available and confirm together mobility through pores.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.455-458
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• 1998

초음파 산업분야에 널리 사용되고 있는 PZT 압전 세라믹 진동자의 경우 높은 품질계수로 인하여 대역폭이 좁고, 진동 시 두께방향 진동뿐만 아니라 횡방향 진동으로 인하여 초음파 신호를 분석하는데 여러 가지 어려움이 항상 존재하였다. 따라서 본 연구에서는 PZT 세라믹스와 고분자 재료인 Epoxy를 사용하여 1-3 접속도를 갖는 압전 복합재료를 제조하였다. 이를 이용하여 초음파 트랜스듀서를 제작하였고, 이에 대한 전기음향변환능률을 어드미턴스 loop를 측정하여 구하였다. 유전율, 공진 주파수 등을 포함한 기본적인 트랜스듀서의 파라메터들은 공진 부근에서 전기적인 임피던스로부터 측정하였다. 이러한 파라메터들을 적용하여 주파수에 대한 트랜스듀서의 성능을 평가하였다. Pulse-echo법을 이용하여 삽입손실율을 구하고 임펄스 반응을 통하여 주파수 대역폭에 대해서 측정하였다. 그 결과 어드미턴스 loop로부터 두께방향모드를 제외한 횡방향 모드는 거의 나타나지 않았다. 유전율은 5.25㎊m이었고, 공진주파수 1.65MHz에서 -8dB의 최소 손실이 발생하였다. 주파수대역폭은 -6dB에서 64%(Q ; 1.56)의 대역폭이 측정되었고 전기기계 결합계수는 0.54이고 전기기계변환능률은 52%, 기계음향변환능률은 31%로 측정되었다.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.245-251
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• 2013

An impedance of ground electrode for information and communication facilities has a significant relationship with the electrical characteristics of soil where the ground electrode is buried. Especially, the impedance of ground electrode is directly affected by the characteristics of permittivity and conductivity in soil as a function of a frequency of an applied electric field. The program based on the electromagnetic field model was developed in MATLAB. Because both permittivity and conductivity can not be modified in commercial programs. The permittivity of soil was applied with the Debye equation which is a model of dielectric relaxation. And the empirical equation of the conductivity in soil was quoted in other paper. In order to confirm the reliability of proposed program, the impedance measurement of ground electrode was carried out, which were compared with the results of simulation in commercial program. In result, it was confirmed that the impedance and phase different simulated by appling the characteristics of permittivity and conductivity in soil are in good agreement with the measured values than results of NEC.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.5
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• pp.493-498
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• 2004

The complex permittivities of methanol measured from 0.2 to 2.0 ㎓ using an open-ended coaxial probe revealed the large deviation from the given data in literature. In this paper, it was investigated whether the given or measured complex permittivity is similar to the real value of our methanol used for experiment. The FDTD method was applied to confirm the effect of our conversion model excluding the effect of sufficiently small measurement error. The complex permittivities reconverted from the computed reflection coefficient by employing our improved conversion model were not similar to the given value but measured value. These results assured the accuracy and stability of our measurement-and-conversion process.

• Korean Journal of Remote Sensing
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• v.13 no.2
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• pp.151-163
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• 1997

In this paper, an algorithm for retrieving soil moisture from measurement of microwave reflection at the end of a coaxial canble is presented. Because the wave reflection from the boundary between air and soil layers depends on the dielectric constant of the soil layer, the dielectric constant can be obtained from measured reflection coefficient. At first, an equivalent circuit for the coaxial probe contaced on the soil surface was chosen with two unknown circuit elements. Then, the unknown circuit elements are obtained experrmentally by measuring the reflection constants of 20 soil samples, and consequently, an empirical formula for computing the dielectric constant from the reflection coefficient is obtained. The dielectric constant is mainly influenced by the soil moisture, and the soil moisture can be computed from the dielecfic constant using an existing empirical formula. HP Network Analyzer 8510C was used to measure the magnitude and the phase of the reflection coeffcient at 4.65 GHz, and the measured data set were used to obtain an empirical formula for computing the dielectric constant. The empirical formula obtained in this study was proven by other soil samples.

• Proceedings of the Korean Society of Tobacco Science Conference
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• 1998.10a
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• pp.12-12
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• 1998

• 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.