• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.321-324
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• 1999

This paper was presented to BaTiO$_3$-SrTiO$_3$(BST) ceramic capacitor in using high voltage. Structural and electrical properties of BST ceramic capacitor were researched in accordance with SrTiO$_3$ contents. As the result of investigation, the BST1 ceramic capacitor was showed to stable dielectric properties between 25 and 85[$^{\circ}C$]. According as frequency was increased, relative permittivity was decreased because inner spontaneous polarizations were decreased. As supplied voltage was increased, relative permittivity of specimen was varied in 3.04 ~3.98[%].

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.2
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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.

• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.635-641
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• 1995

The effects of A-site substitution with alkaline-earth ions (Ca, Sr and Ba) on the perovskite-phase formation and dielectric properties for Pb1-xMx(Zn1/3Nb2/3)O3 (0.0 x 0.5)-based relaxors were studied. Considerable improvements in the sinterability and the extent fo perovskite formation were observed with increasing the A-site substitution (x) and sintering temperature. The maximum dielectric permittivity appeared at x=0.1 for Sr and Ba substitutiion, while the relative dielectric permittivity was almost invariant in the case of Ca ion substitution. Curie temperature decreased with increasing relative amount of Sr and Ba ions but was almost invariant in case of Ca ion substitution. With increasing the amount of x, the diffuseness parameter ($\delta$) increased but the maximum dielectric constant decreased, demonstrating an enhanced diffuse phase transition (DPT) in the presence of alkaline-earth cations.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.446-449
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• 1988

A spectral inverse technique, which was developed by applying the pulse basis moment method procedure on the direct scattering problem in the reverse sequence for the reconstruction of complex permittivity profiles inside inhomogeneous dielectric objects, is modified to be applicable to the moment method with series-expanded basis. By performing numerical simulations for various type of dielectric objects, it is demonstrated that this inverse technique provides close reconstruction of permittivity profiles. Futhermore, compared to the previous scheme of the pulse basis, the presented method is shown to reduce the computation cost, relative error of reconstructed permittivity profiles by averaging in each cell, and the ill-posedness inherent to this inverse scattering problem.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.3
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• pp.86-90
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• 2003

This paper describes the electrical characteristics of Nomex paper employed as an insulating material for distribution transformers. The relative permittivities (dielectric constants) and tan$\delta$ (dielectric dissipation factors) were measured as dielectric characteristics and the partial discharge inception voltages (PDIVs) and breakdown voltages were also measured as electrical strength characteristics of Nomex paper. As a result, the permittivity and tan $\delta$ of Nomex paper demonstrated both temperature and frequency dependency. Of particular note, the permittivity of 0.18 mm Nomex paper was 2.4 according to the ASTM condition, The PDIVs and breakdown voltages were almost linearly increased with the thickness of Nomex paper. Furthermore, its electrical strength was superior to conventional Kraft paper.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.9
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• pp.565-570
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• 2016

In this work, the complex permittivity of epoxy resins is measured. Epoxy resins, epoxy with micro size fillers and epoxy with micro+nano alumina composites have been evaluated for dielectric properties according to frequency variation. The dielectric spectroscopy measurement and analyses are carried out in the frequency range of $10^{-2}Hz$ to 1MHz and constant to room temperature. The results of dielectric loss suggest that significant improvement in the electrical performance can be expected by using samples containing nano and micro fillers mixture when compared to materials containing only microfillers. As the result, we verified the specific characteristics of dielectric permittivity and dielectric loss namely, relative permittivity become low with improving dispersibility of nano+micro mixture composites and become rise with agglomerate of nano particles.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.5
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• pp.384-394
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• 1996

The propagation properties of square and Gaussian pulse signals on the microstrip line are investigated by using proper conventional models to meet the frequency range of a pulse, accuracy, and geometrical requirements of the microstrip line. Numerical integration technique which has its accuracy and is easily simulated, is used to obtain the time domain response of pulse signals. The dispersion of pulse signals is analyzed regarding to the relative permittivity $\varepsilon_r$, substrate height h, strip width w of the microstrip line and pulse width $\tau$ of signal pulse. The simulation results show that small relative permittivity and small rationale of w/h are advantageous for the dispersion of the pulse signals, and that pulse signals with small bandwidth cause smaller dispersion. The results of this paper are compatible to the trade-off determination of relative permittivity, substrate height, strip width and pulse width of signal pulse when a design of MIC and MMIC is necessary.

• Journal of Korean Society of societal Security
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• v.3 no.1
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• pp.25-32
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• 2010

Detecting rebars in side the concrete structures is one of the important steps in assessing condition of the structure. In order to determine the detection capability of locating rebars inside the concrete, two types of equipments, which use radar system and electromagnetic system each, were tested. Four concrete specimens which have the dimensions of $1,000mm(length){\times}300mm(width)$ with different thickness and diameter of steel bars were applied. A series of testing was achieved after drying in air for 90 days, immersed in water for 3, 24, 48 hour and 28 day. From the experimental outcome, it is shown that error is increased as the diameter of rebar enlarge in case of electromagnetic method. In case of radar method, the detection of embedded rebars in deep is good in the view of reliability. As moisture content increase from 3.6% to 5.5%, the relative permittivity of concrete test specimens show tendency to increase, too. Therefore, it is shown that moisture content is one of the major contributing factors to determine the relative permittivity. And the relative permittivity regression equation is suggested.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1697-1704
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• 2018

As a key component of lighting location system (LLS) for lightning warning, the atmospheric electric field measuring is required to have high accuracy. The Conventional methods of the existent electric field measurement meter can only detect the vertical component of the atmospheric electric field, which cannot acquire the realistic electric field in the thunderstorm. This paper proposed a three dimensional (3D) electric field system for atmospheric electric field measurement, which is capable of three orthogonal directions in X, Y, Z, measuring. By analyzing the relationship between the electric field and the relative permittivity of ground surface, the permittivity is calculated, and an efficiency 3D measurement model is derived. On this basis, a three-dimensional electric field sensor and a permittivity sensor are adopted to detect the spatial electric field. Moreover, the elevation and azimuth of the detected target are calculated, which reveal the location information of the target. Experimental results show that the proposed 3D electric field meter has satisfactory sensitivity to the three components of electric field. Additionally, several observation results in the fair and thunderstorm weather have been presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.117-120
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• 2008

In this paper, we developed the EM wave absorber for eliminating false images in collision-avoidance radar. First of all, we fabricated some samples in different composition ratio of $TiO_2$ and CPE. And the relative permittivities of samples are calculated from S-parameter of samples by using 1-port method. We designed and fabricated the EM wave absorber by using the calculated relative permittivity. As a result, the EM wave absorber with composition of $TiO_2$:CPE=70:30 wt% has thickness of 1.85 mm and absorption ability higher than 20 dB in the frequency range 76-77 GHz.