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铁磁谐振是中性点非有效接地系统经常发生的一种不正常运行现象,如果不加以治理任其发展,可能引发熔断器熔断、电压互感器烧毁、绝缘击穿、母线闪络等严重后果。文章就鹤岗矿业集团热电厂35kV供电系统的一次铁磁谐振,结合热电厂35kV供电系统结构、运行方式、事故处理程序以及谐振期间发生的现象,通过理论分析找出了发生此次铁磁谐振的原因,并提出了改进措施和运行管理的注意事项。 相似文献
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Approximate formulas are obtained for various parameters of a piezoelectric material in the form of a disk, which do not require the calculation of the least (first) root of the frequency equation. To calculate approximately the planar electromechanical coupling coefficient, one can simplify the measurement procedure because it is not necessary to measure the first overtone frequency and determine Poisson's ratio. 相似文献
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各类大功率非线性、时变性用电设备的广泛应用,使农村电网的谐波污染日益严重,电能质量下降,通过对农村地方电力用户谐波治理措施的调查研究,提出改变现在实行的针对自身的谁污染谁治理的点治方法,改之以更为经济有效的全面系统综合整治的谐波治理策略. 相似文献
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应用新的温度补偿方法研制了100.450MHz五次泛音温度补偿晶体振荡器,该振荡器由450kHz陶瓷振荡器,100MHz五次泛音晶体振荡器,混频器,晶体滤波器组成。450kHz陶瓷振荡器的输出频率与100MHz晶体振荡器的输出频率混频,滤波,取其和频。直接利用450kHz陶瓷振荡器输出频率对100MHz晶体振荡器进行温度补偿。实验结果表明,在0~70℃该振荡器的频率-温度稳定度<±7×10-7,初步测量相位噪声为-119dBc@1kHz。 相似文献
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Glass transitions in polyvinylbutyral (PVB) films deposited on a gold substrate have been studied using a quartz crystal resonator technique by measuring the resonant frequency shift and resonant peak broadening of the quartz crystal coated with a PVB film. Using the measured frequency shift and peak broadening of the resonance of the quartz crystal due to changes in the coated PVB film, the storage moduli of the film were derived. The results show rapid drops in the storage moduli of the PVB films at temperature closer to that of glass transition of bulk PVB. The transitions at different frequencies were assessed by simultaneously measuring the resonance of the quartz crystal at multiple harmonics. No significant change in the glass transition temperature at multiple harmonics was observed. The results of the storage moduli for PVB films of different thickness show that glass transition temperatures in the films decrease with the film thickness; the decrease become more noticeable as the film thickness is less than 500 nm where the characteristic of changing of storage moduli become distinctly different from that in thicker film and in bulk materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45433. 相似文献
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In this work we provide direct evidence of hydrogen, carbon and oxygen contamination of poly-crystalline diamond surfaces from ambient conditions and their thermal stability upon vacuum annealing. Deuterated diamond films were exposed to ambient conditions for ~ 3 months and then studied by high-resolution electron energy loss spectroscopy and X-ray photoelectron spectroscopy. Hydrocarbon contaminations posses at least two different binding states which desorb upon annealing to ~ 300 °C and ~ 600 °C. Oxygen contaminations gradually desorb upon annealing to 700–800 °C. It is shown that thermal desorption of contaminations creates sp2 carbon atoms on the diamond film surface. 相似文献
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Tomio Satoh Ruzaini Izyan Binti Ruslan Masahide Marumo Tetsuya Akitsu 《IEEJ Transactions on Electrical and Electronic Engineering》2012,7(1):81-90
A novel design is proposed for a low‐frequency quartz crystal oscillator circuit. Negative resistance in a low‐frequency CMOS‐inverter quartz oscillator was reviewed for the fundamental mode at 32 kHz and the overtone oscillation at 200 kHz. Suppression of the overtone oscillation, appropriate gain, and drive current reduction are realized by adding only three circuit components. Experimental results and an estimate of the absolute value of the negative resistance are presented for the conventional Colpitts circuit and two types of the quartz crystal oscillator circuit. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献