• 전기학회논문지
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• 제60권3호
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• pp.674-679
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• 2011

In this paper, we experimented and analyzed about electric fire risk assessment methods of LED lightings for outdoor. LED lighting is composed of AC power lines, AC/DC converter, DC power lines and LED lamps. There are some risk factors of electric fire in LED lighting such as short circuit between power lines or power line and ground, dielectric breakdown, leakage current, abnormal voltage inflow, poor contacts(connections), etc. As a result of this study, insulation coverings of wire was ignited due to dielectric breakdown between power lines and molten marks were formed in copper conductor. LED lighting was blown out while short circuit, beside that, electrical disorder did not occur. When abnormal voltage was inflowed, electronic components such as varistor, condenser were damaged. Partial heating was produced and insulation was melted and carbonized by arc and heating while poor contacts were happened. We expect that the results of this study would be helpful for electrical safety of LED lightings for outdoor.

• 한국세라믹학회지
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• 제21권4호
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• pp.341-348
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• 1984

$BaTiO_3$ and $SrTiO_3$ were mixed with the mole ratio of 35:65， 50:50 and 65:35 and heated at 1100~120$0^{\circ}C$ for 1~64 hours. The dielectrics of $BaTiO_3$-$SrTiO_3$ system were investigated as a function of amount of solid solution formed. The dielectric constant was increased and Curie temperature was shifted to higher temperature with increasing of heating of soaking time for the same composition and heating temperature. This can be explained by the homogeneous distribution of $Ba^{2+}$ and $Sr^{2+}$ ion in the $BaTiO_3$ system. The Curie temperature was shifted to lower temperature with increasing $SrTiO_3$ in the $BaTiO_3$-$SrTiO_3$system because of decreasing the lattice constant.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기물성,응용부문
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• pp.134-136
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• 2002

유리기판 위에서 제작된 다결정 실리콘 TFT(Thin Film Transistor) 에서는 열전도율이 낮은 실리콘 산화막 같은 물질이 사용되기 때문에 열에 대해서 낮은 임계점을 갖는다. 이로 인하여. 게이트와 드레인에 높은 전압이 걸리는 조건에서 동작시킬 경우에는 다결정 실리콘 TFT에서의 열화 현상이 두드러지게 나타나게 된다. 그러나, 열전도율이 실리콘 산화막(SiO2) 보다 열배 이상 높은 실리콘 질화막(SiNx)을 ILD(inter-layer dielectric) 재료로 사용했을 때 같은 스트레스 조건에서 다결정 실리콘의 신뢰성이 개선되는 것을 확인할 수 있었다.

• Carbon letters
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• 제24권
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• pp.62-72
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• 2017

The aim of this work was to evaluate the dielectric properties of impregnated and activated palm kernel shells (PKSs) samples using two activating agents, potassium carbonate ($K_2CO_3$) and sodium hydroxide (NaOH), at three impregnation ratios. The materials were characterized by moisture content, carbon content, ash content, thermal profile and functional groups. The dielectric properties were examined using an open-ended coaxial probe method at various microwave frequencies (1-6 GHz) and temperatures (25, 35, and $45^{\circ}C$). The results show that the dielectric properties varied with frequency, temperature, moisture content, carbon content and mass ratio of the ionic solids. PKSK1.75 (PKS impregnated with $K_2CO_3$ at a mass ratio of 1.75) and PKSN1.5 (PKS impregnated with NaOH at a mass ratio of 1.5) exhibited a high loss tangent ($tan{\delta}$) indicating the effectiveness of these materials to be heated by microwaves. $K_2CO_3$ and NaOH can act as a microwave absorber to enhance the efficiency of microwave heating for low loss PKSs. Materials with a high moisture content exhibit a high loss tangent but low penetration depth. The interplay of multiple operating frequencies is suggested to promote better microwave heating by considering the changes in the materials characteristics.

• 한국세라믹학회지
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• 제42권1호
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• pp.33-36
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• 2005

저온 소결용 PMN-PT-BT분말을 $850^{circ}C/2h$ 소결할 때 승온 속도를 분당 5, 10, $20^{circ}C$로 변화하며 물성에 미치는 영향을 조사하였다. PbO(응점 $886^{circ}C$)의 휘발이 미미한 소결온도에서는 분당 $5^{circ}C$로 승은하여 소결한 것이 승온 속도 $10^{circ}C$나 $20^{circ}C$의 경우에 비하여 보다 균일한 미세구조를 나타내며, 소결밀도 $7.93g/cm^{3}$, 실온 유전을 15300, 유전손실 $0.92\%의 우수한 유전 특성을 나타내었다.

• 한국분말재료학회지
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• 제13권6호
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• pp.455-461
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• 2006

High temperature dielectric constants of the various ceramic materials have been measured using cavity perturbation method. The measurements were applied to refractory, traditional and fine ceramic powder compacts from room temperature to $1200^{\circ}C$. Calibration constant in the equation suggested by Hutcheon et al., was determined from the dielectric constants of reference specimen (teflon and alumina) at room temperature. From these results, informations on the refectory materials were obtained for the microwave kiln design and understanding of the microwave heating effects of ceramics have been improved.

• 한국식품저장유통학회지
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• 제8권3호
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• pp.331-337
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• 2001

가열우지의 산화 안정성을 연구하기 위하여 우지를 130, 150 및 18$0^{\circ}C$의 세가지 튀김온도 조건에서 하루에 10시간씩 총 240시간 가열하였을 때 가열시간에 따라 지방질의 산화정도를 나타내는 각종 이화학적 특성치들(산값, 과산화물값, 요오드값, 유전상수, 극성화합물 및 중합물의 함량, 굴절률, 발연점 및 점도)과 색도의 변화를 연구하였다. 가열한 우지의 산값, 유전상수, 굴절률, 점도, 극성화합물 및 중합물의 함량은 가열시간의 경과에 따라 계속 증가하였고, 과산화물 값은 가열시간의 경과에 따라 증가와 감소를 반복적으로 나타냈다. 요오드값과 발연점은 가열시간의 경과에 따라 계속 감소하였으며, 이러한 이화학적 특성치들의 변화는 가열온도가 높을수록 심하였다. 색도는 가열시간이 경과함에 따라 황색도와 적색도가 증가하여 전체의 색깔은 착색화되는 경향을 나타냈고, 그 착색의 정도는 시료의 산화정도와 밀접한 관계가 있어 고온에서 가열할수록 심하였다. 따라서 높은 온도에서 튀기면 각종 이화학적 향수들의 변화가 일어나므로 튀김유의 열화는 물론 가공식품의 품질에 영향을 미칠 것이다.

• 한국재료학회지
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• 제21권9호
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• pp.477-481
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• 2011

Composites of insulating polyethylene and carbon black are widely used in switching elements, conductive paint, and other applications due to the large gap of resistance value. This research addresses the critical exponent of dielectric breakdown strength of polymer matrix composites (PMC) made with carbon black and polyethylene below the percolation threshold (Pt) for the first time. Here, Pt means the volume fraction of carbon black of which the resistance of the PMC is transferred from its sharp decrease to gradual decrease in accordance with the increase of carbon-black-filled content. First, the Pt is determined based on the critical exponents of resistivity and relative permittivity. Although huge cohesive bodies of carbon black are formed in case of being less than the Pt, a percolation path connecting the conducting phases is not formed. The dielectric breakdown strength (Dbs) of the PMC below Pt is measured by using an impulse voltage in the range from 10 kV to 40 kV to avoid the effect of joule heating. Although the observed Dbs data seems to be well fitted to a straight line with a slope of 0.9 on a double logarithm of (Pt-$V_{CB}$) and Dbs, the least squares method gives a slope of 0.97 for the PMC. It has been found that finite carbon-black clusters play an important role in dielectric breakdown.

• 한국세라믹학회지
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• 제44권5호
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• pp.179-183
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• 2007

BCB $Resin-BaNd_2Ti_4O_{12}$(BNT) composites with BNT contents were prepared by tape casting method and epoxy resin-BNT composites were prepared by using heating press. Their dielectric properties and microstructures were investigated. The dielectric properties such as dielectric constant and dielectric loss at 1 MHz for epoxy resin-BNT composites and BCB resin-BNT composites are improved with an increase of BNT volume fraction. The dielectric constant of the Epoxy-BNT composite increased from 5.9 to 7.8 as the volume fraction of BNT increased from 15 to 25. The dielectric constant of the BCB-BNT composite increased from 9.1 to 15.5 as the volume fraction of BNT increased from 30 to 50. The dielectric behavior of BCB-BNT system can be explained by Lichtenecker's equation. The dielectric constant of epoxy resin-BNT composite is smaller than that of BCB resin-BNT composite. These results are considered to be related with the dispersion of BNT filler in polymer matrix from the result of SEM photograph.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.247-250
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• 1998

Ferroelectric PZT(10/90)PZT(90/10) heterolayered thin films were fabricated by spin-coating method on the Pt/Ti/SiO$^2$/Si substrate alternately using PZT(10/90) and PZT(90/10) metal alkoxide solutions. The coating and heating procedure was repeated six times to form PZT heterolayered films. The surface, cross-sectional microstructures and thickness of the films were observed using scanning electron microscope(SEM). The relative dielectric constant and dielectric loss of the 5-coated PZT heterolayered films were 1331 and 4.8% respectively.