排序方式: 共有9条查询结果,搜索用时 18 毫秒
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1991年3月太阳活动引起的地磁扰动 总被引:2,自引:1,他引:2
利用北京白家疃台和马道峪台的地磁资料分析了1991年3月下旬太阳活动引起的24-27日的磁暴,从中纬记录看,这次磁暴有其特殊的形态:即急始幅度特别大,磁暴最强活动是急始后即刻开始的极区暴影响而产 生的:磁暴过程中多个时段出现脉动,其中以周期为650秒左右的脉动尤为明显;其极化方向主要表现为左旋偏振,同时夹有右旋偏振,有时则无明显规律,谱分析的结果表明,整个磁暴功率谱呈幂律P(f)=f^-2,0分布,对引起这次磁暴可能的行星际扰动进行了讨论。 相似文献
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The flow control of hydraulic transformers is a great challenge.To meet this challenge,a new kind of hydraulic transformer,variable hydraulic transformer(VHT),is proposed in this work.This paper focuses on the power characteristics of the newly proposed VHT,including instantaneous power,average power,power pulsation,and efficiency.In the analyses,the concepts of efficiency,input power,output power,starting angle,and ceasing angle are defined or redefined.To investigate the power characteristics,their models are derived by considering the governing factors such as the control angle of the swash plate and the structure of the port plate.This work highlights that the load flow can be adjusted by adjusting the control angle of the swash plate,and the power characteristics at the B-port produce a remarkable change.In addition,the VHT has a starting angle and a ceasing angle,and these two angles can be adjusted by the influencing factors.The results reveal that the power pulsation and the jump points of the instantaneous power are the primary causes of a less smooth work.Then,it is shown that the control angle of the port plate,the control angle of the swash plate,and the pressures at the ports are the three key elements for a stable operation.The results also reveal that the adjustment of the influencing factors can improve the efficiency. 相似文献
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《中国航空学报》2020,33(1):16-30
The piston pump is the key power component in the civil aircraft hydraulic system, and the most common pump used in the aviation field is the pressure compensated variable displacement type. In this review paper, a basic introduction to the civil aircraft piston pump is presented, including the classification, structure, working principle, design features, and achievements by some research groups. Then, the future directions of the aircraft pump are reported from various perspectives. Further, the critical technologies are analyzed and summarized in detail from six thrust areas: friction couples, noise reduction, inlet boost, thermal management, fault diagnosis and health management, and mechanical seal. Finally, the challenges and limitations of the research on the aircraft pump are discussed to provide valuable insight for future scholars. 相似文献
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Space vehicle in atmosphere travels mostly at supersonic speed and generates a very strong bow shockwave around its blunt nose. Oblique shock and conical separated flow zone generated by a forward disk-tip spike significantly reduce the drag by reducing the high pressure area on the blunt nose. This study employs improved delayed detached eddy simulation to investigate the characteristic flow structures around a spike-tipped blunt nose at Mach number of 3 and Reynolds number(based on the blunt-body diameter) of 2.72x10~8. The calculated time-averaged quantities agree well with experimental data. Characteristic frequencies in different flow regions are extracted using fast Fourier transform. It is found that two distinct instability modes exist: oscillation mode and pulsation mode. The former is related to the foreshock/turbulence interaction with nondimensional frequency at around 0.004. The latter corresponds to the interaction between turbulence and shock structures around the blunt nose, with a typical coherent structure shedding frequency at 0.092. 相似文献
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掌握轻型运动飞机全制造链生产线的核心技术,对提高我国通用飞机产品制造能力具有重要意义和极高的经济价值,同时可完善民机全谱系制造技术体系.通过对某轻型运动飞机的生产实践,掌握了生产线的关键技术,尤其是整机喷漆和试飞的关键技术,具备高速率批产能力且全机零件实现了国产化.同时,建立了先进的质量控制体系、进度计划体系及供应链管理体系,该生产线的建立为国家航空制造领域提供了大量可借鉴的宝贵经验,极大地推动了通用飞机产业在我国的发展. 相似文献
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