• 한국광학회지
• /
• 제4권1호
• /
• pp.57-65
• /
• 1993

용량 이행형 방전여기에 의한 소형 XeCl레이저를 제작하고, 가스 혼합비에 따른 출력특성을 조사하였다. 내자형 capacitor에 의한 자동 예비전리 방식과 2.7 cm 간격의 Chang형상으로 가공된 전극구조의 레이저를 구성하여 2.7cm${\times}$1.5cm 크기의 출력 빔을 얻었고, Xe과 HC1의 농도 변화 및 완충 기체의 종류에 따른 최대 출력 에너지 및 최대 효율 조건을 조사하였다. 최대 레이저 펄스 에너지는 Ne 완충기체를 사용시 230mJ이며, 단위 방전 체적당 1.1 J/l의 에너지를 얻었으며, 최대 에너지 효율은 1.6%이었다. 1:3의 낮은 비율의 피-킹 캐패시턴스의 구성에 의해 레이저 펄스폭은 장펄스 효과를 나타내 foot-to-foot 200 ns로 측정되었다.

• 한국전기전자재료학회논문지
• /
• 제36권4호
• /
• pp.376-384
• /
• 2023

Nitrogen-doped graphene was synthesized by a hydrothermal method using graphene oxide (GO) as the raw material, urea as the reducing agent and nitrogen as the dopant. The morphology, structure, composition and electrochemical properties of the samples are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption analysis, electrical conductivity and electrochemical tests. The results show that urea can effectively reduce GO and achieve nitrogen doping under the hydrothermal conditions. By adjusting the mass ratio of raw materials to dopants, the graphene with different nitrogen doping contents can be obtained; the nitrogen content range is from 5.28~6.08% (atomic fraction percentage).When the ratio of dopant to urea is 1:30, the nitrogen doping content reaches a maximum of 6.08%.The supercapacitor performance test shows that the nitrogen content prepared by the ratio of 6.08% is the best at 0.1 A·g^-1. The specific capacitance is 95.2 F·g^-1.

• Composites Research
• /
• 제33권6호
• /
• pp.336-340
• /
• 2020

본 연구에서는 헥사 메틸렌 테트라민을 촉매로 사용하여 이소프로판올에서 레소시놀과 퍼푸랄을 졸-겔 중축합한 후 이소프로판올 동결 건조 조건에서 유기 겔을 직접 건조시킨 후 질소 분위기에서 탄화시켜 탄소 에어로겔을 제조하였다. 탄소 에어로겔의 제조 조건은 퍼푸랄에 대한 레소시놀의 몰비를 변경하여 조사하였다. 탄소에어로겔의 기공 구조에 대한 제조조건의 영향은 질소 흡착 등온선에 의해 고찰하였다. 탄소 에어로겔의 특성은 주사전자현미경과 적외선 분광법을 가지고 측정하였다. 전기 이중층 커패시터에서 전극으로서의 탄소 에어로겔의 기공 접근성과 성능을 전기 화학적으로 고찰하였다. 결과적으로 BET 표면적과 비용량은 R/C 비율에 따라 증가하였으며, 765 ㎡/g 및 132 F/g의 최대 값은 각각 R/C 비율 200에서 달성되었다. 결론적으로 R/C 비율을 높이면 CA 전극의 평균 기공 크기가 증가하여 시스템의 속도 성능이 향상됨을 확인하였다.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제4C권5호
• /
• pp.193-200
• /
• 2004

In this study, we propose a small high voltage power supply, which uses a half-bridge ZCS resonant and Cockroft-Walton circuit as its ESP (Electrostatic Precipitator). This power supply transfers energy from the ZCS resonant inverter to the step-up transformer. The transformer secondary is then applied to the Cockroft-Walton circuit for generating high voltage as a discharging source of electrodes. It is highly efficient because its amount of switching losses are reduced by virtue of the current resonant half-bridge inverter, and also due to the small size, low parasitic capacitance in the transformer stage owing to the low number of winding turns of the step up transformer secondary combined with the Cockroft-Walton circuit. Using this power supply, experiments have been carried out as a function of the switching frequency and duty ratio in order to investigate the smoke removal characteristics. From these results, the best operational condition is obtained at the switching frequency of 9 kHz and the duty ratio of 50% in this ESP.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
• /
• pp.872-875
• /
• 2003

Carbon nitride($CN_x$) thin films were deposited on quartz substrates using reactive RF magnetron sputtering system at uarious deposition conditions and investigated dielectric characteristics. Samples for capacitance measurements were of the MIM(Metal-Insulator-Metal) type devices. Aluminum film electrodes were prepared by a vacuum thermal evaporation method before and after the deposition of carbon nitride films. Capacitances were measured by a FLUKE PM6306 RCL Meter at room temperature. Current-voltage(I-V) characteristics and resistivity were measured by a CATS CA-EDA semiconductor test and analyzer. The carbon nitride films showed ${\alpha}-C_3N_4$ and ${\beta}-C_3N_4$ etc. peaks through Raman and FTIR. Observed surface of film and side structure using SEM(Scanning Electron Microscope), and measured thickness of film by ${\alpha}-step$. We can find that the dielectric constant was the lowest value in 50% nitrogen ratio and the resistivity was the highest value in 70% nitrogen ratio.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.393-396
• /
• 2008

Propellant consumption control for space launch vehicle can be achieved by propellant utilization system (PUS) and tank depletion system (TDS). In the course of developing new space launch vehicles, the main target of design is on reducing of space launch vehicle weight, which results in increasing both specific impulse and payload weight. The weights of space launch vehicles are generally allocated to structure, propulsion system, and propellants loaded. The quantity of propellants filled in propellant tanks may be estimated with the propellants actually consumed by propulsion system to complete its mission and the propellants left on-board at the time of engine shut-off. To minimize the remaining quantity of propellants on-board the supplying propellants' O/F ratio should be controlled from the certain time before engine shutdown. To control an O/F ratio, a control system, which accurately measures and compares the remainder of propellants in tanks and pipes, should be needed. This paper solely dedicates its contents to explore the merits and demerits of various level sensor, which is one of the important elements for PUS and TDS, and the transmission and control of signals within space launch vehicle.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제48권1호
• /
• pp.27-33
• /
• 1999

Compact fluorescent lamps are very sensitive to the variation of ambient temperature. This paper investigates the temperature characteristics of a 15[W] compact fluorescent lamp, and compensates the variation of light output by frequency control of its electronic ballast. Circuit parameters for the inverter of the electronic ballast are obtained by analyzing the R-L-C equivalent circuit for the inverter and the lamp. The optimum ratio of the two capacitance($C_1$/$C_2$), which are connected with the lamp in series and in parallel, respectively, is determined which consideration of the temperature variation within a range of 10~35[$^{\circ}C$]. As a result a value of 10 for the ratio is obtained at an operating frequency of 57[kHz], and with this value the frequency control works well for temperature compensation. Its validity is verified by investigating light output stabilization characteristics resulting from frequency control of the lamp at various temperatures.

• International Journal of Precision Engineering and Manufacturing
• /
• 제9권4호
• /
• pp.3-10
• /
• 2008

Micro-electrical discharge machining (micro-EDM) is an effective method for machining all types of conductive materials regardless of hardness. Since micro-EDM is an electro-thermal process, the energy supplied by the pulse generator is an important factor in determining the effectiveness of the process. In this study, an investigation was conducted on the micro-EDM of tungsten carbide (WC) to compare the performance of transistor and resistance/capacitance (RC) pulse generators in obtaining the best quality micro-hole. The performance was measured by the machining time, material removal rate, relative tool wear ratio, surface quality, and dimensional accuracy. The RC generator was more suited for minimizing the pulse energy, which is a requirement for fabricating micro-parts. The smaller-sized debris formed by the low-discharge energy of RC micro-EDM could be easily flushed away from the machined zone, resulting in a surface free of burrs and resolidified molten metal. The RC generator also required much less time to obtain the same quality micro-hole in WC. Therefore, RC generators are better suited for fabricating micro-structures, producing good surface quality and better dimensional accuracy than the transistor generators, despite their higher relative tool wear ratio.

• 한국세라믹학회지
• /
• 제52권3호
• /
• pp.209-214
• /
• 2015

Silicon nitride films were deposited at $100^{\circ}C$ by using the catalytic chemical vapor deposition technique. The source gas mixing ratio, $R_N=[NH_3]/[SiH_4]$, was varied from 10 to 30, and the hydrogen dilution ratio, $R_H=[H_2]/[SiH_4]$, was varied from 20 to 100. The breakdown field strength reached a maximum value at $R_N=20$ and $R_H=20$, whereas the resistivity decreased in the same sample. The relative permittivity had a positive correlation with the breakdown field strength. The capacitance-voltage threshold curve showed an asymmetric hysteresis loop, which became more squared as $R_H$ increased. The width of the hysteresis window showed a negative correlation with the slope of the transition region, implying that the combined effect of $R_N$ and $R_H$ overides the interface defects while creating charge storage sites in the bulk region.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 하계학술대회 논문집
• /
• pp.852-856
• /
• 2000

In this paper, we investigated the output power, step-up ratio and efficiency properties of piezoelectric transformer with dielectric and piezoelectric characteristics of manufactured ceramics. The piezoelectric transformers with $2.0$\times$10$\times$48[$mm^3$] size were fabricated and its electrical properties were measured. When output power of 6W was constantly maintained, T2 piezoelectric transformer showed the minimum temperature rise of $9(^{\circ}C)$ at $150(K\Omega)$ load resistance. However, T1 piezoelecric transformer showed the temperature rise of $7.2(^{\circ}C)$ at $200(K\Omega)$ load resistance. The 6[w] CCFL (Cold Cathode Fluorescent Lamp) was successfully driven by T1 and T2 piezoelectric transformer but, its temperature rise $\Delta$T[$^{\circ}C)$] was generated more than $20(^{\circ}C)$. It is concluded that we have to design the piezoelectric transformers so that its output impedance correspond to the load impeadance, including any stray capacitance.