• Journal of Biosystems Engineering
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• 제24권2호
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• pp.123-134
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• 1999

The electrical properties such as dielectric constant, dielectric loss factor and AC conductivity of grain were presented to measure the moisture content of grain using RF impedance. At frequency ranging from 1 to 10MHz and room temperature, $20^{\circ}C$, vector network analyzer(HP4195) and coaxial type sample holder were used to analyze the electrical properties of paddy(11∼24%w.b.), brown rice(11∼18%w.b.), barley(11∼21%w.b.) and wheat(11∼23%w.b.) depending on the moisture content, frequency and bulk density. The dielectric constant and AC conductivity of grain samples increased with moisture content and bulk density. The dielectric constants decreased with frequency and could be expressed as function of the moisture density(decimal moisture $content{\times}bulk$ density).

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.387-389
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• 1998

For the continuous and exact measurement of load impedance of AC power system on the electric railway, this paper presents a method to show the load area to resistance(R)-reactance(X) plane of impedance plane. The load area is presented in terms of impedance which is in the ratio of voltage and current continuously measured and impedance plane indicates the protection area of fault locator. The proposed method is verified its reasonability by computer simulation, and using this method we will develop the power system impedance analyser which is available actual application.

• 한국전기전자재료학회논문지
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• 제11권1호
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• pp.18-25
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• 1998

G $d_{0.2}$C $e_{0.8}$ $O_{1.9}$(CGO) for electrolyte and L $a_{0.5}$S $r_{0.5}$Mn $O_3$(LSM50) for cathode in Solid Oxide Fuel Cells(SOFC) were synthesized by citrate process. Specimens were prepared with sintering temperatures at 110$0^{\circ}C$, 120$0^{\circ}C$ and 130$0^{\circ}C$, which were fabricated by slurry coating with citric acid contents. Interfacial resistance was measured between cathode and electrolyte using AC-impedance analyzer. With various citric acid content, the degree of agglomeration for the initial particles changed. Also sintering temperature changed the particle size and the degree of densification of cathode. Factors affecting the interfacial resistance were adherent degree of the electrolyte and cathode, distribution of TPB(three phase boundaries, TPB i.e., electrolyte/electrode/gas phase area) and porosity of cathode. By increasing the sintering temperature, particle size and densification of the cathode were increased. And then, TPB area which occurs catalytic reaction was reduced and so interfacial resistance was increased.sed.sed.d.

• 한국재료학회지
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• 제21권8호
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• pp.468-475
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• 2011

[ $LaMeO_3$ ](Me = Cr, Co) powders were prepared using the polymeric precursor method. The effects of the chelating agent and the polymeric additive on the synthesis of the $LaMeO_3$ perovskite were studied. The samples were synthesized using ethylene glycol (EG) as the solvent, acetyl acetone (AcAc) as the chelating agent, and polyvinylpyrrolidone (PVP) as the polymer additive. The thermal decomposition behavior of the precursor powder was characterized using a thermal analysis (TG-DTA). The crystallization and particle sizes of the $LaMeO_3$ powders were investigated via powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and particle size analyzer, respectively. The as-prepared precursor primarily has $LaMeO_3$ at the optimum condition, i.e. for a molar ratio of both metal-source (a : a) : EG (80a : 80a) : AcAc (8a) inclusive of 1 wt% PVP. When the as-prepared precursor was calcined at $700^{\circ}C$, only a single phase was observed to correspond with the orthorhombic structure of $LaCrO_3$ and the rhombohedral structure of $LaCoO_3$. A solid-electrolyte impedance-metric sensor device composed of $Li_{1.5}Al_{0.5}Ti_{1.5}(PO_4)_3$ as a transducer and $LaMeO_3$ as a receptor has been systematically investigated for the detection of NOx in the range of 20 to 250 ppm at $400^{\circ}C$. The sensor responses were able to divide the component between resistance and capacitance. The impedance-metric sensor for the NO showed higher sensitivity compared with $NO_2$. The responses of the impedance-metric sensor device showed dependence on each value of the NOx concentration.

• 전기화학회지
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• 제6권2호
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• pp.145-152
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• 2003

전해 캐패시터와 supercapacitor의 특성을 함께 가지는 하이브리드 캐패시터의 용량은 표면이 산화물로 피복된 양극에 의해서 좌우된다 본 연구에서는 고전압 하이브리드 슈퍼캐패시터의 제조를 위해 양극의 용량 최적화를 수행하였다. $40{\mu}m$의 입자경을 갖는 알루미늄 분말과 NaCl분말을 4:1의 무게비로 혼합하여 디스크 형태의 전극을 만들고 열처리를 하였다. 열처리 후 $50^{\circ}C$의 증류수에서 NaCl을 용해시켜 열처리 온도에 따른 용량과 저항을 비교하였다. 최적의 열처리 과정을 거친 후 electropolishing 및 화학처리, 1차 및 2차 에칭을 단계별로 행하였고 각각의 단계에서 최적의 조건을 조사하였다 각각의 단계에서의 용량과 저항은 ac impedance analyzer를 사용하여 측정하였으며 전극의 표면은 SEM을 이용하여 관찰하였다. 2차 에칭 후 내전압이 300V급인 전극으로 만들기 위하여 365V로 양극산화 시켰으며, 산화된 알루미늄 디스크 전극을 사용하여 단위 셀을 제조하여 주파수에 따른 용량과 저항 특성을 기존의 300V급 알루미늄 전해 캐패시터와 비교하였다.

• 한국결정성장학회지
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• 제4권1호
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• pp.21-32
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• 1994

Bridgman법에 의해 성장속도를 변화시키면서 $CaF_2$ 결정을 육성시켰으며, 각 성장속도에 따른 이온전도도의 변화를 알아보기 위하여 AC Impedance Analyzer를 사용하여 그 전기적 특성을 고찰하였다. 성장속도가 증가함에 따라 $CaF_2$ 결정은 단결정에서 다결정으로 육성되었으며, 그로인한 여러가지 결함 및 계면의 변화에 따라 이온 전도도는 크게 변화하였다. 또한, $CaF_2$ 결정을 더욱 무질서(disorder)화 시키고 여분의 불소 이온 carrier와 공공(vacancy)을 증가시키기 위하여 $YF_3$를 첨가하여 $Ca_{1-x}Y_XF_{2+X}$ 결정을 얻었으며, $YF_3$의 첨가량의 변화에 따른 $Ca_{1-x}Y_XF_{2+X}$ 결정의 이온전도도의 변화를 조사하였다. $CaF_2$ 결정과 $Ca_{1-x}Y_XF_{2+X}$ 결정의 온도변화에 따른 이온전도도의 변화를 비교하여 결함 clustering이 고체전해질의 전기적 성질에 미치는 영향을 조사하였다.

• 한국재료학회지
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• 제22권2호
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• pp.61-65
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• 2012

A $Li_2O-2SiO_2$ ($LS_2$) glass was investigated as a lithium-ion conducting oxide glass, which is applicable to a fast ionic conductor even at low temperature due to its high mechanical strength and chemical stability. The $Li_2O-2SiO_2$ glass is likely to be broken into small pieces when quenched; thus, it is difficult to fabricate a specifically sized sample. The production of properly sized glass samples is necessary for device applications. In this study, we applied spark plasma sintering (SPS) to fabricate $LS_2$ glass samples which have a particular size as well as high transparency. The sintered samples, $15mm\phi{\times}2mmT$ in size, ($LS_2$-s) were produced by SPS between $480^{\circ}C$ and $500^{\circ}C$ at 45MPa for 3~5mim, after which the thermal and dielectric properties of the $LS_2$-s samples were compared with those of quenched glass ($LS_2$-q) samples. Thermal behavior, crystalline structure, and electrical conductivity of both samples were analyzed by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and an impedance/gain-phase analyzer, respectively. The results showed that the $LS_2$-s had an amorphous structure, like the $LS_2$-q sample, and that both samples took on the lithium disilicate structure after the heat treatment at $800^{\circ}C$. We observed similar dielectric peaks in both of the samples between room temperature and $700^{\circ}C$. The DC activation energies of the $LS_2$-q and $LS_2$-s samples were $0.48{\pm}0.05eV$ and $0.66{\pm}0.04eV$, while the AC activation energies were $0.48{\pm}0.05eV$ and $0.68{\pm}0.04eV$, respectively.