• Applied Microscopy
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• v.47 no.3
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• pp.121-125
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• 2017

This study deals the prediction of temperature effect on low-frequency dispersion of alternating current (AC) conductivity spectra of composite materials based on copolymer reinforced with carbon black (CB) particles. A sample of ethylene butylacrylate loaded with 13% of CB particles were prepared and investigated using the impedance spectroscopy representation in the frequency range from 40 Hz to 0.1 MHz and temperature range from $20^{\circ}C$ to $125^{\circ}C$. The dielectric constant, ${\varepsilon}^{\prime}$, and dielectric losses, ${\varepsilon}^{{\prime}{\prime}}$, were found to decrease with increasing frequency. The frequency dependence of the AC conductivity follows the universal power law with a large deviation in the high frequency region, the positive temperature coefficient in resistivity effect has been observed below the melting temperature which makes this composite potentially remarkable for industrial applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1142-1148
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• 1999

In this paper, the characteristics of frequency dependent dispersion are analyzed for the phase shifters in Ku-band phased array antenna system using full-wave method, SDA(Spectral Domain Approach).The design technique of asymmetric coupled-line phase shifter with dielectric overlay is proposed. The compared results of phase responses are shown with conventional symmetric coupled-line Schiffman phase shifter. The experimental results verify the improvement of broadband characteristics by the increasing bandwidths and the decreasing phase deviations.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.548-553
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• 2007

Ceramic green sheets consisting Bi-based glass frit were fabricated for an application to PDP transparent dielectric front panel. The dispersion condition of the slurry for tape casting was pre-examined, and two kinds of hinder and plasticizer were used in the non-aqueous slurry system. In the fabrication process for the frit film, the properties such as dry and firing shrinkage, elongation, and transmittance were examined at the condition of various mixing ratio of plasticizers. In the mixing ratio of polyethylene glycol to dibutyl phthalate of 3:5wt%, a good adhesion, elongation and transmittance were observed at the firing temperature of $580^{\circ}C$. The photograph for the cross section of the interface was also showed a dense microstructure.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.11
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• pp.1-7
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• 2000

Surface wave scattering by periodic grooves of arbitrary profile in a grounded dielectric slab is investigated for the TE surface wave incidence. Both the finite and infinite periodic geometries are considered. The former case is analyzed by using of hybrid FEM/MOM and the latter by using of full MOM procedure. Some numerical results for the reflected and transmitted powers in a grounded dielectric slab, radiation power into the free space, and radiation patterns in case of finite structure and for the dispersion diagram in case of infinite structure are presented. And some descriptions on the relationship between the finite and infinite structure such as the maximum beam angle are given.

• Journal of the Speleological Society of Korea
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• no.78
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• pp.9-15
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• 2007

The materials showing high structure dispersion with functional properties were developed on the quartz base and those were obtained by mechano-chemical reaction technology. Depending on the processing conditions and subsequent applications the materials produced by mechano-chemical reaction show concurrently magnetic, dielectric and electrical properties. The obtained magnetic-electrical powders classified by aggregate complex of their features as segnetomagnetics, containing a dielectric material as a carrying nucleus, particularly the quartz on that surface one or more layers of different compounds were synthesized having thickness up to 1050nm showing magnetic, electrical properties and others. The similarity of the structure of surface layers of quartz particles subjected to mechano-chemical processing and nano-structure cluspol (clusters in a polymer matrics) material was alsoconfirmed by the fact that the characteristics of ferromagnetic quartz of insulating nano-composite powder were changed with time, after its preparing process was completed.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.2
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• pp.114-121
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• 1996

Thin film Ba$^{0.7}Sr^{0.3}TiO^{3}$ (BST) capacitors were fabricated on SiO$_{2}$/Si substrates by RF magnetron sputtering method and characterized at microwave frequencies ranging from 40 MHz to 1GHz to examine the dielectric dispersion of the capacitors. The BST thin films were electrode material of BST thin films capacitor which is known as one of the best electrode materials for BST films. 50$\AA$-thick titanium (Ti) layers were introduced to increase adhesion between bottom Pt and SiO$_{2}$. The leakage current density of the capacitors was about 1.7${\times}10^{7}A/cm^{2}$ at 1.5V and the dielectric constant was about 140 at 1MHz. Microwave measurement patterns having a coplanar waveguide type were fabricated and their S parameters were measured using network analyzer. After de-embedding parasitic components in microwave measurement patterns nearly frequency-invariant dielectric constant of about 120 was extracted in the measurement range of 40 MHz to 1 GHz.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.231-236
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• 2017

The space harmonics generated by a plane-wave incident upon a multi-layered dielectric grating can undergo strong resonance scattering variations known as GMR(guided-mode resonance). To clarify these effects, we examine the field propagation and dispersion curve inside the grating region by using a rigorous equivalent transmission-line theory(RETT). The results show that, at the peak of a scattering resonance, the reflected mode is almost identical to a leaky wave that can be supported by the grating structure. Thus, we confirm and generalize previous research that has occurred GMR effect associated with the free-resonant character of leaky waves at multi-layered dielectric gratings. Quantitative simulation results illustrating the behavior of typical gratings are given, and the special case of normal incidence is discussed for TM mode.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2819-2827
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• 1997

A dielectric waveguide structure using rectangular dielectic strip is analyzed directly in terms of the wave equation for quasi TE and quasi TE and quasiTM modes. This problem can be solved, with no approximation in the wave equation for the electric field $\vec{E}$ and magnetic field $\vec{H}$ inside and outside the dielectric rectangular waveguide matching the boundary conditions between interfaces. This leads to an eigenvalue problem where spurious modes do not appear. Dispersion characeristic examples are presented for square and rectangular waveguides. The formulation is general and can be used for compuarison with ogher methods such as FDM or FEM in various structures.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1236-1239
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• 2004

We developed a new cholesteric material for bistable LCDs. The material consists of dispersion of sub-micron ferroelectric particles in cholesteric host. We found that the doping of the cholesteric with ferroelectric particles in small concentration (< 1% by weight) strongly improved basic characteristics of the transition between poly-domain planar texture and focal conic texture. Decrease of the driving voltage, increase of the reflection contrast and the steepness of the transition is associated with giant steady dipole and dielectric constant of the ferroelectric particles.

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.342-345
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• 1987