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电路参数随时间变化的介观LC电路的波函数和压缩效应 总被引:2,自引:0,他引:2
本文通过正则变换,采用路径积分的方法,得出了电路参数随时间变化的介观LC电路的严格波函数,研究了含时相干态下电路中电荷和电流的压缩效应。 相似文献
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航空发动机的高温蠕变分析 总被引:6,自引:0,他引:6
详述了航空发动机主要零部件抗蠕变的设计要求 ,综合概括了有关蠕变的设计准则和计算分析方法以及寿命预测方法 相似文献
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B. Spandana S. Srinivasa Rao Adithi R. Upadhya Padmavati Kulkarni V. Sreekanth 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(10):3134-3146
The PM2.5/PM10 ratio (PM2.5 and PM10 are defined as mass concentration of particles having aerodynamic diameter less than 2.5 and 10 µm respectively) is one of the important parameters in understanding the severity of the fine mode surface particulate matter pollution. The present study characterises PM2.5/PM10 ratio estimates from eight Indian urban sites with varying levels of urbanization. Five years (2015–2019) of collocated PM2.5, PM10, and meteorological (ambient temperature, relative humidity (RH), and wind speed) measurements are used to understand the spatial and temporal variability in the PM2.5/PM10 ratio at different scales and to investigate its relationship with meteorological parameters. Over the study sites, the seasonal mean PM2.5/PM10 ratio varied between 0.31 ± 0.08 (mean ± standard deviation) and 0.65 ± 0.13. Seasonally, the highest PM2.5/PM10 ratio was observed during winter and post-monsoon seasons. Sites in the Indo-Gangetic Plain (IGP) exhibited higher PM levels (PM2.5 and PM10) and higher PM2.5/PM10 ratios than the corresponding values recorded at other sites. The seasonal mean PM2.5/PM10 ratio estimated (over the study sites) using MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications, version 2) ranged between 0.25 ± 0.08 and 0.77 ± 0.16, and exhibited consistent overestimation (when compared to values derived from measurements) during winter and pre-monsoon seasons. Grossly, the PM2.5/PM10 ratio exhibited a weak association with meteorological parameters. Interestingly, despite variations in geography, population, anthropogenic activities and PM concentrations across seasons and sites, the PM2.5/PM10 ratio showed low variability. 相似文献
67.
文摘通过引入无机纳米粉体研制了高热导率聚酰亚胺浸渍漆,研究了聚酰亚胺的化学结构、无机粉体的种类、粒径和用量等因素对浸渍漆贮存稳定性以及固化物性能的影响。均苯四甲酸二酐与4,4′-二氨基二苯基醚合成的聚酰亚胺具有高的热导率。在联苯型聚酰亚胺中引入30%~35%、粒径为100~300 nm的α-A l2O3粉体,固化物的热导率可提高到0.65~0.80 W/(m.K),其余性能基本保持原有水平。 相似文献
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S.S. Rao Shweta Sharma P. Galav R. Pandey 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Ionosonde data of a mid latitude station Novosibirsk (Geog. Lat. 54.6°N, Geog. Long. 83.2°E) has been analyzed for the years 1997–2006 that covers the major part of solar cycle 23. Our results show the presence of winter anomaly in the daytime F2 layer critical frequency during different phases of solar activity. Results also reveal a semiannual variation of foF2 with two maxima and a minimum that always appears in summer. While the first maximum is in the spring equinox, the second one is found to shift from autumn to winter with the increase of solar activity. The maximum height of F2 layer during the daytime shows variation with the solar activity. It is higher during the higher activity periods and lower during the periods of low activity. Results of ionosonde observations have been compared with those obtained from IRI-2007 model and it is found that model reproduces gross features of foF2 variation. However, the modeled hmF2 variations during equinoxes are significantly different from the ones derived using the ionosonde data. The model also underestimates the hmF2 values. 相似文献
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Bartley William C. McCracken Kenneth G. Rao U.R. 《IEEE transactions on aerospace and electronic systems》1967,(2):230-235
This paper describes an aspect system flown on PIONEERS VI and VII2 which incorporates an extremely accurate adaptive digital computer in order to define rigorously equal time intervals which are submultiples of the spacecraft spin period. The several submultiples which compose the complete spin period exhibit equality to within 2.5 parts in 105. This system has potential applications in other experiments involving the study of the angular dependence of cosmic radiation and other physical phenomena being measured by a single directional detector mounted on spin-stabilized spacecraft. Included here are the scientific goals for this experiment, system restraints, and the generalized system operation. Some details on specific logic and hardware implementation for the Pioneer experiments are included along with in-flight performance evaluation of the system aboard PIONEER VI. 相似文献
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简要介绍了力矩电机在航空制造设备的应用及控制技术要求。着重介绍了基于西门子611D全数字伺服控制下,力矩电机驱动参数的配置及速度环、位置环的优化,为力矩电机的控制技术应用提供了实践基础。 相似文献