• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.299-299
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• 2010

In this study, microwave properties with compositions and frequency of the $Ba_3Co_2Fe_{24}O_{41}$ ceramics with Zn substitution for Co were investigated. From the XRD patterns, hexagonal structure of Z-type phase was existed as main phase. Diffraction peaks of Z-type phase were shifted to lower angle by Zn substituted for Co site. The permittivity was increased with Zn additions. In all composition, loss tangent of permittivities were increased with frequency. Permeability and magnetic resonance frequency were increased with Zn additions. Permeability was increased and loss tangent of permeability was decreased rapidly over 600 MHz~800 MHz. The loss tangent of permeability did not changed with composition ratio. In the case of $Ba_3Co_{1.6}Zn_{0.4}Fe_{24}O_{41}$ ceramics sintered at $1250^{\circ}C$ for 3 hours, the permittivity, loss tangent of permittivity, permeability and loss tangent of permeability were 28.277, 0.193, 22.992 and 0.065 at 310 MHz, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.52-59
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• 2006

To construct its complex permittivity from the reflection coefficient of a thin film such as PCB substrate measured by open-ended coaxial probe, an integral equation is formulated using modal analysis and equivalent source. The accuracy of the conversion model based on the integral equation is confirmed in both cases of converted complex permittivities calculated from numerically computed and actually measured reflection coefficients. And the maximum valid frequency of open-ended coaxial probe is limited by the size of its flange.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.690-698
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• 2016

In this paper, a study is carried out to investigate the dielectric, physical and chemical properties of Palm Oil (PO) and Coconut Oil (CO) under open thermal ageing condition. The type of PO used in this study is Refined Bleached and Deodorized Palm Oil (RBDPO) Olein. The ageing experiment was carried out at 85 ℃ and 115 ℃ for 1, 3, 5, 7 and 14 days. Several parameters were measured such as AC breakdown voltage, dielectric dissipation factor, relative permittivity, resistivity, viscosity, moisture and acidity throughout the ageing duration. Based on the study, it is found that there are no significant changes on the AC breakdown voltages and relative permittivities for both RBDPO and CO. At ageing temperature of 115℃, there are clear reduction trends of dielectric dissipation factor for CO and resistivities for most of RBDPO. On the other hand, no clear trends are observed for viscosities, moisture and acidities of RBDPO and CO throughout the ageing duration.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.303.2-303.2
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• 2014

The oxides of group IV transition metals such as titanium, zirconium, hafnium have many important current and future application, including protective coatings, sensors and dielectric layers in thin film electroluminescent (TFEL) devices. Recently, group IV transition metal oxide films have been intensively investigated as replacements for SiO2. Due to high permittivities (k~14-25) compared with SiO2 (k~3.9), large band-gaps, large band offsets and high thermodynamic stability on silicon. Herein, we report the synthesis of new group IV transition metal complexes as useful precursors to deposit their oxide thin films using chemical vapor deposition technique. The complexes were characterized by FT-IR, 1H NMR, 13C NMR and thermogravimetric analysis (TGA). Newly synthesised compounds show high volatility and thermal stability, so we are trying to deposit metal oxide thin films using the complexes by Atomic Layer Deposition (ALD).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.803-808
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• 2003

Several dielectric pipes buried in the lossy half space are reconstructed from the scattered fields measured along the interface between the air and the lossy ground. Iterative inversion method by using the hybrid optimization algorithm combining the genetic and the Levenberg-Marquardt algorithm enables us to find the positions, the sizes, and the medium parameters such as the permittivities and the conductivities of the buried pipes as well as those of the background lossy half space even when the dielectric pipes are close together. Illposedness of the inversion caused by the errors in the measured scattered fields are regularized by filtering the evanescent modes of the scattered fields out.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.1-5
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• 2001

This paper describes the electrical characteristics of Nomex paper employed as an insulating material of distribution transformers. The relative permittivities(dielectric constants) and $tan{\delta}$(dielectric dissipation factors) were measured as a dielectric characteristic and the partial discharge inception voltages(PDIVs) and breakdown voltages were also measured as an electrical strength characteristic of Nomex paper. As a result, the permittivity and $tan{\delta}$ of Nomex paper showed temperature and frequency dependency. Especially, the permittivity of 0.18mm Nomex paper was 2.4 according to the ASTM condition. And the PDIVs and breakdown voltages were, almost linearly increased with the thickness of Nomex paper and its electrical strength was better than conventional kraft paper.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.755-762
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• 2000

In this work, we present the resonant frequencies, Qrad, and impedance bandwidth of rectangular dielectric resonator antenna(DRA)for a broad range of aspect ratios using Dielectric Waveguide Model. These presented data are compared with simulation and measurement. The DRA having relative permittivities of 37.84 and 90 have been fed by a coaxial cable and fed using a aperture-coupled method for comparisions. The approximate resonant frequencies are shown to have the prediction error of about 8% and impedance bandwidth is found to have large prediction variation according to feeding method. The data presented in this paper can be used when the aspect ratios of DRA have to be determined for a given resonant frequency and impedance bandwidth.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.2
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• pp.11-19
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• 1999

The design procedure as well as some test results of a low-cost commercial radome for mobile DBS(Direct Broadcasting Satellite) receiving antenna system are presented in this paper. At first the complex permittivity of dielectric material should be measured in order to select a material for radome design. The complex permittivities of low-cost plastics supplied by domestic vendors are measured and presented. And then the transmission losses of the sheets are calculated. The calculated results are verified by the measurements of wave transmission test of that sheets. Two kinds of radomes, ABS single-layer and A-Sandwich((PET-Foam-ABS), are fabricated and measured practically. The transmission losses of single-layer and A-sandwich radome are 1.5dB and 0.6dB respectively at the maximum wave incident angle of 57 degree. Also the calculated crosspolarization caused by A-sandwich radome is under 20dB.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.77-82
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• 2003

In this paper, as the new type of multi-lines electrode which can formulate strong non-uniform electric field was installed in strong electrolytic water generator, shapes of pre-discharge in bubble and effects of bubble discharge on pH and oxidation/reduction potential change were intended to investigate. Consequently, as multi-lines electrode was installed in side of anode, pre-discharges generated from anode electrode could be observed. This pre-discharge was generated from differences of permittivities between bubble and water in strong non-uniform electric field. And ion concentration in electrolytic water generator was increased by dissolving of ions generated from bubble discharge. So, as generated high concentration ions were separated and assembled to each electrode and reaction of oxidation/reduction was increased, it was shown that strong electrolytic water could be generated.

• Journal of the Korean Geosynthetics Society
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• v.2 no.1
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• pp.47-55
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• 2003

The effects of fiber composition factors of 14 geotextiles which are thickness, porosity, fiber length and diameter etc. on the transmissivity were examined and in-plane permeability of geotextiles under thickness change, transmissivity, confined load were analyzed by the constitutive equations. And the effects of laminar structure on the permittivity of laminar geotextile composites which were manufactured with fiber packing densities were assessed. Transmissivities were increased with thickness of geotextiles and in-plane permeability coefficients were increased with porosity and fiber diameter. The effects of porosity were decreased with normal stress and slightly increased with fiber length. Transmissivities were increased with fiber diameter and showed same tendensy for the same fiber length. Permittivities of laminar geotextile composites were influenced by the waterhead loss in the inner interface and the connection shape of these composites to water path was interpreted as bell mouth type or soft flux pipe type.