• 전기의세계
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• 제28권1호
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• pp.53-58
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• 1979

In the microwave heating system, a ferroresonant transformer is used to regulate the magnetron power fluctuation. For the simplification, nonlinear characteristics of the transformer and the magnetron are idealized to be piecewise linear. Dipped peak shape of the magnetron current is explained qualitatively by considering the fundamental and third harmonic frequency components in the circuit. Design equations providing the values of the leakage inductance, turn ratio of the transformer and the capacitance are derived analytically by cosnidering the fundamental frequency component only. The ferroresonant transformer is designed to obtain a required regulation and high input power factor from the derived design equations, and analytical calculations are compared with experimental measurements.

• 한국콘텐츠학회논문지
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• 제18권10호
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• pp.425-430
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• 2018

전기자동차 배터리 시스템은 낮은 온도에서 배터리 출력과 수명이 감소하는 문제가 발생한다. 상온 유지를 목적으로 Positive Temperature Coefficient(PTC) 히터가 사용되고 있다. 하지만 PTC 히터는 복잡한 절연구조로 인해 중량이 크다. 중량이 클수록 전기자동차의 연비가 감소한다. 반면에 인덕션 히터는 단순한 절연 구조로 중량 저감에 효과적이며 빠른 온도 상승 특성을 가지고 있다. 따라서 전기자동차용 히터는 인덕션 히터가 적합하다. 인덕션 히터는 LC공진 회로로 구성된다. 정전용량이 클수록 가격과 중량이 상승하기 때문에 인덕턴스를 높여 정전용량을 감소시켜야한다. 또한 인덕션 히터의 주 발열원은 철손이다. 따라서 전자기장 설계 관점에서 인덕턴스 및 철손의 최적화가 중요하다. 본 논문에서는 인덕션 히터 구조 변경에 따른 인덕턴스 및 철손을 다구찌 기법과 유한요소법(FEM) 시뮬레이션을 통해 분석하고 최적화 설계하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권2호
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• pp.63-68
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• 2005

Total 12 units of high power klystron-modulator systems as microwave source are under operation for 2.5 GeV electron linear accelerator in Pohang Light Source (PLS) linac. The klystron-modulator system has an important role for the stable operation to improve an availability statistics of overall system performance of klystron-modulator system. RF power and beam power of klystron are precisely measured for the effective control of electron beam. A precise measurement and measurement equipment with good response characteristics are demanded for this. Input power of klystron is calculated from the applied voltage and the current on its cathode. Tiny measurement error severely effects RF output power value of klystron. Therefore, special care is needed to measure precise beam voltage. Capacitive voltage divider (CVD), which divides input voltage as capacitance ratio, is intended for the measurement of a beam voltage of 400 kV generated from the klystron-modulator system. Main parameter to determine standard capacitance in the high arm of CVD is dielectric constant of insulation oil. Therefore CVD should be designed to have a minimum capacitance variation due to voltage, frequency and temperature in the measurement range. This paper will be present and discuss the design concept and analysis of capacitive voltage divider for a pulsed high-voltage measurement, and the empirical relations between capacitance effects and oil temperature variation.

• 한국전자파학회논문지
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• 제21권3호
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• pp.262-268
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• 2010

본 논문에서, 부성 저항 특성을 갖는 능동 커패시턴스 회로를 이용한 고출력 능동 가변 대역 통과 여파기는 동축형 유전체 공진기와 버랙터 다이오드를 사용하여 설계하였으며, 셀룰러 TX, RX 대역을 모두 가변할 수 있도록 설계하였다. 능동 커패시턴스 회로의 직렬 피드백 구조는 가변 대역 통과 여파기의 버랙터 다이오드로부터 생기는 손실을 보상함과 동시에 고출력 특성을 갖도록 하기 위해 $P_{1dB}$가 32 dBm인 GaAs HFET을 사용하였다. 버랙터 다이오드는 고선형 특성을 갖도록 하기 위해 back-to-back 구조를 사용하였다. 제작된 2단 능동 가변 대역 통과 여파기는 셀룰러 대역인 800 MHz에서 900 MHz를 가변하며, 각각 25 MHz 대역폭으로 TX 대역 836 MHz에서 0.48 dB 삽입 손실 특성을 나타냈으며, RX 대역 881.5 MHz에서 0.39 dB 삽입 손실 특성을 나타내었다. $P_{1dB}$특성은 TX 및 RX 대역에서 각각 19.5 dBm과 23 dBm을 얻었다.

• 한국재료학회지
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• 제31권12호
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• pp.710-718
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• 2021

Recently, due to high theoretical capacitance and excellent ion diffusion rate caused by the 2D layered crystal structure, transition metal hydroxides (TMHs) have generated considerable attention as active materials in supercapacitors (or electrochemical capacitors). However, TMHs should be designed using morphological or structural modification if they are to be used as active materials in supercapacitors, because they have insulation properties that induce low charge transfer rate. This study aims to modify the morphological structure for high cycling stability and fast charge storage kinetics of TMHs through the use of nickel cobalt hydroxide [NiCo(OH)₂] decorated on nickel foam. Among the samples used, needle-like NiCo(OH)₂ decorated on nickel foam offers a high specific capacitance (1110.9 F/g at current density of 0.5 A/g) with good rate capability (1110.9 - 746.7 F/g at current densities of 0.5 - 10.0 A/g). Moreover, at a high current density (10.0 A/g), a remarkable capacitance (713.8 F/g) and capacitance retention of 95.6% after 5000 cycles are noted. These results are attributed to high charge storage sites of needle-like NiCo(OH)₂ and uniformly grown NiCo(OH)₂ on nickel foam surface.

• 한국광학회:학술대회논문집
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• 한국광학회 1989년도 제4회 파동 및 레이저 학술발표회 4th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.176-179
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• 1989

The optimization of the monolithic pin-FET receiver is discussed, with emphasis on the sensitivity and bandwidth. The amplifier circuit, bias resistance, total input capacitance, and transconductance of FET for the 2 Gbps transmission are calculated.

• Journal of Electrochemical Science and Technology
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• 제11권2호
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• pp.148-154
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• 2020

Highly ordered mesoporous manganese oxide films were electrodeposited onto indium tin oxide coated (ITO) glass using sodium dodecyl sulfate (SDS) and ethylene glycol (EG) which were used as a templating agent and stabilizer for the formation of micelle, respectively. The manganese oxide films synthesized with surfactant templating exhibited a highly mesoporous structure with a long-range order, which was confirmed by SAXRD and TEM analysis. The unique porous structure offers a more favorable diffusion pathway for electrolyte transportation and excellent ionic conductivity. Among the synthesized samples, Mn₂O₃-SDS+EG exhibited the best electrochemical performance for a supercapacitor in the wide range of scan rate, which was attributed to the well-developed mesoporous structure. The Mn₂O₃ prepared with SDS and EG displayed an outstanding capacitance of 72.04 F g^-1, which outperform non-porous Mn₂O₃ (32.13 F g^-1) at a scan rate of 10 mV s^-1.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권10호
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• pp.687-692
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• 1999

A new technique to measure low level capacitance variations of the gyroscope is proposed and verified by computer simulation. It is based on the new CV(capacitance-voltage) converter circuit biased by dc current source and the peak detector without low pass filter. The CV converter biased by dc current source provides good signal-to-noise ratio and this setup of the detection circuitry without low pass filter makes it possible to provide short settling time, that is, higher speed of measurement and wide operation range if only a few parameters are adjusted. The key parameters that affect the performance of the detection circuitry are illustrated and computer simulation results are presented. The demonstrated detection circuitry shows linear response from 10 fF to 130 fF at 10 kHz and shows good linearity.

• 전자공학회논문지A
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• 제30A권7호
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• pp.82-88
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• 1993

This paper describes fabrication of relative type capacitive pressure sensor to be in great demand for many fields. The fabricated sensor consists of two parts` a sensing diaphragm and a pyrox glass cover. The sensor size is 4.5${\times}3.4mm$^{2})$ and 400$\mu$m thick. To improve the nonlinearity, this sensor is designed a rectangular silicon diaphragm with a center boss structure, and in order to improve the temperature characteristics of the sensor in a packaging process, the sensing element is mounted on the pyrex glass support. Some suggestions toward the design and fabrication of improved sensors have been presented. The zero pressure capacitance, Co of sensor is 26.57pF, and the change of capacitance, ${\Delta}$C is 1.55pF from 0Kgf/Cm$^{2}$ to 1Kgf/Cm$^{2}$ at room temperature. The nonlinearity of the sensor output with center boss diaphragm is 1.29%F.S., and thermal zero shift and thermal sensitivity shift is less than 1.43%F.S./$^{\circ}C$and 0.14% F.S./$^{\circ}C$, respectively.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.703-706
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• 1998

This paper presents an efficient substrate-bias generator(SBG)for low-power, high-density DRAM's The proposed SBG can supply stable voltage with switching the supply voltage of driving circuit, and it can substitude the small capacitance for the large capacitance. The charge pumping circuit of the SBG suffere no VT loss and is to be applicable to low-voltage DRAM's. Also it can reduce the power consumption to make VBB because of it's high pumping efficiency. Using biasing voltage with positive temperature coefficient, VBB level detecting circuit can detect constant value of VBB against temperature variation. VBB level during VBB maintaining period varies 0.19% and the power dissipation during this period is 0.16mw. Charge pumping circuit can make VBB level up to -1.47V using VCC-1.5V, and do charge pumping operation one and half faster than the conventional ones. The temperature dependency of the VBB level detecting circuit is 0.34%. Therefore the proposed SBG is expected to supply a stable VBB with less power consumption when it is used in low power DRAM's.