低产低压油井关井后，井筒内出现段塞流，测试资料表现出很长的早期段。
To low production and low pressure wells, low pressure makes liquid depth in bore hole to be low before it closed.
板子沟、桃关沟和彻底关沟均为低频率泥石流或高含沙洪水，平均20～50年发生一次；
The debris flow gullies of Banzi, Taoguan and Chediguan generate low frequency and low viscous debris flows or hyper-concentrated flows with an average interval of 20~50 years.
ZD B型直流电源变换器是工作在直流600v供电系统的变流装置。该装置以新颖电力器件IGBT作为开、关器件并采用PWM控制技术。
Working in a 600v DC power supply system, the type ZDB battery charger USES new power electronic insulated-gate bipolar transistors (IGBT) as switching device and adopts PWM control technics.
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