• 한국도로학회논문집
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• 제11권1호
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• pp.95-104
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• 2009

본 연구는 아스팔트 콘크리트의 유전율과 공극률의 상관성을 평가하기 위해 수행되었다. 이를 위해 다양한 범위 $(0%{\sim}20%)$의 공극률을 갖는 아스팔트 콘크리트 시편을 제작하였고, 저주파 유전율 측정법인 parallel plate법을 사용하여 아스팔트 콘크리트 시편의 유전율을 측정하였다. 아스팔트 콘크리트 시편의 경우 주파수가 증가함에 따라 유전율은 감소하는 경향을 나타내었고, 사용한 아스팔트 바인더의 종류에 따라 그 감소폭이 다르게 나타났다. 또한 공극률 $0%{\sim}20%$ 사이에서 공극률이 증가함에 따라 유전율 값은 선형적으로 감소하는 경향을 보였다. 더불어 아스팔트 콘크리트 시편의 유전율에 대한 온도 및 함수량 영향을 보정하여 유전율에 따른 공극률의 상관식을 제시하였다. 본 연구를 통해 제시된 아스팔트 콘크리트의 유전율과 공극률의 상관식은 현재 국내외에서 사용하고 있는 유전율을 활용한 비파괴 밀도 측정장비의 보정모델로 활용 가능하며, 향후 국내에서 개발하고자 하는 아스팔트 포장 비파괴 밀도 측정장비의 기본적인 알고리즘으로 활용이 가능할 것이다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제9권3호
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• pp.1-11
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• 2004

매립지 침출수로 오염된 지반의 오염도 조사에 유전상수 측정기법의 적용성을 평가하기 위하여 매립지 침출수로 오염된 간극수를 포함한 사질토 지반의 유전특성을 분석하였다. 본 연구에서는 75kHz-12MHz 범위의 주파수에서 유전 상수를 실수부와 허수부로 구분하여 분석을 수행하였다. 유전상수 실수부는 공간전하분극과 배향분극의 발현정도에 영향을 받기 때문에 침출수 농도가 증가함에 따라 저주파 영역에서는 유전상수의 실수부 값이 증가하는 경향을 나타내었으나, 고주파 영역에서는 감소하는 경향을 나타내었다. 유전상수 허수부의 경우에는 측정 주파수에 관계없이 침출수의 농도가 증가함에 따라 전류전도에 의한 에너지 손실량이 증대되어 유전상수 허수부가 증가하는 경향을 나타내었다. 유전상수의 실수부와 허수부가 간극수 내 침출수 농도에 따라 변하는 것에 기초하여 유전상수 측정기법이 침출수로 오염된 지반의 오염도 평가에 효과적으로 적용될 수 있음을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.153-156
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• 2001

(Ba$_{0.6-x}$Sr$_{0.4}$Ca$_{x}$)TiO$_3$ (x=0.10, 0.15, 0.20) ceramics were fabricated by the mixed-oxide method and their dielectric properties were investigated with variation of composition ratio, doped ZrO$_2$ (0.5, 1.0, 1.5, 2.0, 3.0 wt%) and sintered at 145$0^{\circ}C$. The dielectric constant and loss of the x=0.10 specimen applied field were 19.86 and 0.302 % at 0 V/cm, and 25.937 and 0.339 % at 300 V/cm, respectively. Dielectric constant were increased with increased applied field and decreased with increased frequency, and dielectric loss were within 0.1% at applied 800 MHz, respectively. all specimens showed fairly good applied field. Although, dielectric constant and loss of all specimen showed to tend of nearly the same. same.

• 한국세라믹학회지
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• 제30권5호
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• pp.365-372
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• 1993

Variation of dielectric constant in PMN-Pyrochlore diphasic mixtures were investigated with grain size of pyrochlore phase. Size of pyrochlore phase was controlled by the numbers of calcining and sedimentation method during powder processing. When grain size of pyrochlore phase is large in the sintered specimen, dielectric constant slowly decreased with increase of amount of pyrochlore phase. On the contary, grain size of pyrochlore phase is small, dielectric constant drastically decreased. It was thought that small sized pyrochlore grains more easily surrounded high dielectric phase (perovskite PMN) than large ones with addition of pyrochlore phase.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.243-247
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• 2000

In this parer, Q-factor measurement method for a dielectric resonator in an MIC environment using the effective dielectric constant is proposed. The effective dielectric constant technique is applied to both radial and axial directions. The proposed method shows that the accuracy of the Q-factor measurement is to be improved with 2% ～ 3% relative error.

• 한국도로학회논문집
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• 제18권4호
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• pp.55-61
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• 2016

PURPOSES : The objective of this study was to determine the relationship between the dielectric characteristics of asphalt mixtures and the air voids present in them using ground penetrating radar (GPR) testing. METHODS : To measure the dielectric properties of the asphalt mixtures, the reflection coefficient method and the approach based on the actual thickness of the asphalt layer were used. An air-couple-type GPR antenna with a center frequency of 1 GHz was used to measure the time for reflection from the asphalt/base layer interface. A piece of aluminum foil was placed at the interface to be able to determine the reflection time of the GPR signal with accuracy. An asphalt pavement testbed was constructed, and asphalt mixtures with different compaction numbers were tested. After the GPR tests, the asphalt samples were cored and their thicknesses and number of air voids were measured in the laboratory. RESULTS : It was found the dielectric constant of asphalt mixtures tends to decrease with an increase in the number of air voids. The dielectric constant values estimated from the reflection coefficient method exhibited a slight correlation to the number of air voids. However, the dielectric constant values measured using the approach based on the actual asphalt layer thickness were closely related to the asphalt mixture density. Based on these results, a regression equation to determine the number of air voids in asphalt mixtures using the GPR test method was proposed. CONCLUSIONS : It was concluded that the number of air voids in an asphalt mixture can be calculated based on the dielectric constant of the mixture as determined by GPR testing. It was also found that the number of air voids was exponentially related to the dielectric constant, with the coefficient of determination, $R^2$, being 0.74. These results suggest that the dielectric constant as determined by GPR testing can be used to improve the construction quality and maintenance of asphalt pavements.

• 대한전기학회논문지
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• 제34권8호
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• pp.323-330
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• 1985

Dielectric loss tangent and ac dielectric strength of GFRP (Glass Fiber Reinforced Plastics, G-10)was investigated as parameters of mechanical and thermal stresses, in order to study the basic dielectrical characteristics of composite insulating materials. The dielectric loss tangent was increased and the ac dielectric strength was decreased with increase in the mechanical stresses beyond the mechanical yield point on account of fiber-matrix debonding, but the dielectric constant was not varied sigificantly. the dielectric strength of G-10 was about 2 MV/cm and the dielectric constant was about 4.8.

• 대한전자공학회논문지
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• 제25권12호
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• pp.1582-1585
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• 1988

A cavity perturbation technique is employed to determine the dielectric property of thin samples. Substrates in microwave integrated circuits are fabricated in sheet form and are expected to have a dielectric constant less than 10 and a dielectric loss better than 10**-3. This research aimed to determine both dielectric constant and dielectric loss with good accuracy. The tecynique makes use of thin circular disk samples placed in a right circular cylindrical cavity. The accuracy of measurements is within \ulcorner% for dielectric constnat and 3x10**-4 for dielectric loss.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.135-138
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• 2007

A novel technique to estimate the dielectric constant of ground material by means of air launching GPR is proposed. The technique is an application of SAR algorithm. A laboratory experiment was conducted to examine the technique.

• Transactions on Electrical and Electronic Materials
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• 제16권6호
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• pp.338-341
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• 2015

Epoxy/micro-sized alumina composite was prepared, and the effects of alumina content on the dielectric properties were investigated in order to develop an insulation material for gas-insulated switchgears (GIS). Nano-sized alumina (average particle size: 30 nm) was also incorporated into the epoxy/micro-sized alumina composite. Dielectric tests were carried out in ASTM D 150, and capacitance (Cp) and dielectric loss (tanδ) were measured. The dielectric constant increased with increasing alumina content in the epoxy/micro-alumina system and the epoxy/micro-alumina/nano-alumina system. As 1,3-diglycidyl glyceryl ether (DGE) content increased, the dielectric constant decreased and dielectric loss increased. This ocurred as a result of the weak electric field enhancement due to homogeneous dispersion of micro- and nano-sized alumina particles in an epoxy composite.