• Journal of Advanced Marine Engineering and Technology
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• 제19권2호
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• pp.81-91
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• 1995

A miniature size electrostatic induction motor has been fabricated and studied with emphasis on the role of the surface resistivity, the relative dielectric constant of the rotor surface materials and the rotor liner materials, which control the charge induction and relaxation on the rotor surface and the field intensity between the rotor and the stator. It is found that the higher resitivity and/or the higher relative dielectric constant, concurrently the longer relaxation time constant of the rotor surface materials make the motor speed get higher speed. In case of discrete coated rotor surface it is found that the motor speed was increased logarithmically as narrow as width of the discrete coated Ti. And the degree of width of discrete coated Ti to the axial direction of the rotor was $60^{\circ}$ and $150^{\circ}$, the motor has got a 125% higher than that at the degree of $0^{\circ}$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권5호
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• pp.385-390
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• 1999

Surface corona discharge characteristics of a dc corona charged ferroelectric pellet barrier have been investigated experimentally. Electric charges stored on the surfaces of the ferroelectric pellets by a dc corona discharge provide partial electric fields on the surfaces of the ferroelectric pellets, which could generate surface corona discharges on the ferroelectric pellets. This system utilizes both the surface discharges on the ferroelectric pellet barrier and the corona discharge between corona tip and mesh electrode. Positive and negative dc voltages were applied to the tip to generate partial discharges, and corona currents were estimated to investigate the buildup charge on ferroelectric pellets as a function of the applied time and the charge relaxation time constants of ferroelectric pellets. As a result, in the case of the negative corona discharge with the ferroelectric pellet barrier, the mean corona current and ozone generation increase greatly, and the surface discharges on the ferroelectric pellets can be fenerated efficiently. It is also found that, charge relaxation time, dielectric constants offerroelectric pellets, polarity of applied voltage and applied time affected to the surface discharges among the ferroelectric pellets.

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.245-249
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• 1999

A new type of nonthermal plasma reactor utilizing ferroelectric pellets is proposed to generate nonthermal plasma efficiently, which is used for simultaneous control of various pollutant gases. Electric charges stored on ferroelctric pellets by corona discharge between a corona tip and a mesh electrode provide partial electrical discharges among ferroelectric pellets. These partial electrical discharges can enhance partial discharges around the surface of ferroelectric pellets. This method utilizes wide reacting area of ferroelectric pellets and partial discharge. Positive and negative dc voltage are applied to the corona tip to generate partial discharges, and corona currents are estimated to investigate charge storage on ferroelectric pellets as function of time and charge relaxation time constants of ferroelectric pellects. As a result, charge relaxationtime, dielectric constants of ferroelectric pellets, polarity of applied voltage and applied time influence partial discharges among ferroelectric pellect.

• 센서학회지
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• 제2권1호
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• pp.65-74
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• 1993

본(本) 연구(硏究)에서는 소형(小型) 정전유도형(靜電誘導型) 모터를 제작하고 이 모터에 인가하는 3상(相) 교류전압(交流電壓) 및 주파수(周波數)를 가변(可變)하였을 때의 회전자(回轉字)의 회전속도(回轉速度)의 특성을 실험적으로 검토하였다. 또한 정전유도형(靜電誘導型) 모터의 작동기구상(作動機構上) 회전자(回轉字) 표층물질(表層物質) 및 내층물질(內層物質)의 표면저항율(表面抵抗率), 비유전율(比誘電率) 및 전하완화시정수(電荷緩和時定數)를 변화시켜 회전자(回轉字) 및 고정자(固定子) 사이의 전계강도(電界强度) 및 회전자(回轉字) 표면물질상(表面物質上)의 표면유기전하(表面誘起電荷)의 분포(分布) 및 유기속도(誘起速度)를 변화시킴으로서 소형(小型) 정전유도형(靜電誘導型) 모터의 회전자의 회전속도에 미치는 영향을 검토하였다. 실험(實驗) 결과(結果), 회전자(回轉字) 표층물질(表層物質)의 비유전율(比誘電率), 표면저항률(表面抵抗率) 및 전하완화시정수(電荷緩和時定數) 및 내층물질(內層物質)의 비저항율(比抵抗率)이 모터의 회전속도(回轉速度)에 매우 큰 영향을 미침이 확인되었다. 또한 모터에 인가하는 3상(相) 전원(電源)의 전압(電壓) 및 주파수(周波數)도 모터의 회전(回轉)에 매우 큰 영향을 주며, 회전속도(回轉速度)는 인가전압(印加電壓) 및 주파수(周波數)에 일차(一次) 비례(比例)하여 증가함을 보여주었다. 회전자의 표층물질(表層物質)이 $BaTiO_{3}$ 80% 내층물질(內層物質)이 Cu 일때 무부하(無負荷) 최대속도(最大速度)는 4.5 kV, 220 Hz에서 5500 rpm이 얻어졌다.

• E2M - 전기 전자와 첨단 소재
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• 제10권3호
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• pp.239-246
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• 1997

The ZnO is stabilize dielectric constant over a broad temperature range because its addition makes the relaxation time short. In this study, the composite oxide material (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_{3}$ was mixed by ZnO additive material and the dielectric polarization characteristics was studied. The relative density was over 90[%] at all specimen in the structural characteristics. Among of the specimen, the relative density of (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_{3}$ with ZnO (0.4mol) has a 95[%]. The grain size of composite oxide material with an increasing ZnO increased and it was 1.0[.mu.m]-1.22[.mu.m]. In the electrical characteristics, the charge and discharge current was increased by ZnO addition. The dielectric relaxation time was increased by space charge polarization at above 110[.deg. C] and the dielectric relaxation time was fixed by space charge polarization of para-dielectric layer at below 110[.deg. C]. The dielectric relaxation time was maximum when the grain size was small. The dielectric relaxation time is decreased with an additive material ZnO and interface polarization, existing void at the grain and grain boundary. The remnant polarization is increased and the coercive electric field is decreased by ZnO.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권5호
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• pp.543-548
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• 2014

In this paper, the dielectric relaxation and reliability of high capacitance density metal-insulator-metal (MIM) capacitors using $Al_2O_3-HfO_2-Al_2O_3$ and $SiO_2-HfO_2-SiO_2$ sandwiched structure under constant voltage stress (CVS) are characterized. These results indicate that although the multilayer MIM capacitor provides high capacitance density and low dissipation factor at room temperature, it induces greater dielectric relaxation level (in ppm). It is also shown that dielectric relaxation increases and leakage current decreases as functions of stress time under CVS, because of the charge trapping effect in the high-k dielectric.

• 한국수소및신에너지학회논문집
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• 제34권2호
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• pp.178-186
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• 2023

Three activation methods (constant voltage, current cycling, and hydrogen pumping) were applied to investigate the effects on the performance of the membrane electrode assembly (MEA) loaded with PtCo/C catalyst. The current cycling protocol took the shortest time to activate the MEA, while the performance after activation was the worst among the all activation methods. The constant voltage method took a moderate activation time and exhibited the best performance after activation. The hydrogen pumping protocol took the longest time to activate the MEA with moderate performance after activation. According to the distribution of relaxation time analysis, the improved performance after the activation mainly comes from the decrease of charge transfer resistance rather than the ionic resistance in the cathode catalyst layer, which suggests that the existence of water on the electrode is the key factor for activation.

• Rapid Communication in Photoscience
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• 제3권4호
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• pp.85-87
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• 2014

We studied the characteristics of emissive state of the first (p-G1) and second (p-G2) generation of phenylacetylene dendrimers bearing stilbene as a core by using time-resolved fluorescence spectroscopy in cyclohexane (c-Hex) and N, N-dimethylformide (DMF), which are nonpolar and polar solvents, respectively. Time-dependent red-shift of emission spectra p-G2 both in c-Hex and DMF was observed in comparison with p-G1. Besides, the time constant of red-shift of spectra was found to be larger in DMF than in c-Hex. This indicates that the emissive state of p-G2 has a polar character in DMF as a result of charge delocalization from core to peripheral dendrons followed by stabilization of emissive state.

• 한국전기전자재료학회논문지
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• 제24권12호
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• pp.977-981
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• 2011

Non-wovens polyester rayon samples were manufactured, and the electrification properties of electrostatics were measured for three different samples (15 g/$m^2$, 25 g/$m^2$, and 40 g/$m^2$) with the environmental settings of temperature (20~40$^{\circ}C$) and humidity (40~90%). The conclusions are as follows. Heavy sample generated more static electricity when the temperature was constant. The static electricity decreased slowly when the humidity is less than 70%, while it sharply decreased over 70% humidity condition. For non-woven polyester rayon, static charge decreased as temperature and humidity increased. As the weight increased, less time were taken for the electrification voltage to drop to the half.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.699-702
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• 1992

A miniature size electrostatic induction motor have been constructed and studied by applying a three phase ac power source with a maximum voltage of 5 KV and a variable frequency ranged 0.0 - 150 Hz. A maximum no load speed of the motor tested was about 7600 RPM at the applied voltage of 4330 volt and the frequency of 130 Hz for the case of the rotor surface material of polyprophylene sheet screen-printed $TiO_2$ powder on it. It is found that there are 3 different regions of the motor operation, a rotor stop region, a stable operation region and a high speed abnormal region. And it is also found that the motor speed is influenced greatly by the charge relaxation time constant of the rotor surface materials, which however was changed by the means of vapour-deposited Ti or Ni and screen-printed $TiO_2$ powder on the surface of the rotor material, polyprophylene.