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461.
T.V. Kuznetsova A.I. Laptukhov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The paper presents results of our study of dependence of geomagnetic activity from geoeffective parameters taking into account mutual orientation of the interplanetary magnetic field, electric field of the solar wind and geomagnetic moment. We attract a reconnection model elaborated by us made allowance for changes of geometry of the solar wind–magnetosphere interaction during annual and diurnal motions of the Earth. We take as our data base the interplanetary magnetic field and solar wind velocity measured at 1 a.u. at ecliptic plane for the period of 1963–2005 and Kp, Dst, am indices. Taken as a whole a geoeffective parameter suggested by us explains 95% of observed variations of the indices. Changes of the geometric factor determined by mutual orientation of the solar wind electric field and geomagnetic moment explain larger than 75% of observed statistical variations of Dst and am indices. Based on our results we suggest a new explanation of semi-annual and UT variation of geomagnetic activity. 相似文献
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利用自行研制的测力天平在低速风洞中对单个柔性旗帜失稳摆动的受力特性进行了测量,同时还测量了旗帜的振幅、频率等参数。实验结果表明:在实验条件下,宽长比H^*接近1时,旗帜摆动的扭曲变形可以忽略;影响实验的无量纲参数主要是宽长比H^*,质量比M^*和无量纲速度V^*;保持质量比M^*不变、改变宽长比H。时,阻力系数C^*、无量纲振幅A^*和Sf数都随无量纲速度V^*线性增大;保持H^*不变、改变M^*时,C^*、A^*和ST都随V^*先增大后趋于定值。实验证明,在实验参数范围内旗帜受到的阻力与摆动振幅成正比。估算结果表明忽略惯性力对阻力的贡献对结果影响不大。 相似文献
465.
T.I. Pisman 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The paper presents a experimental and mathematical model of interactions between invertebrates (the ciliates Paramecium caudatum and the rotifers Brachionus plicatilis) in the “producer–consumer” aquatic biotic cycle with spatially separated components. The model describes the dynamics of the mixed culture of ciliates and rotifers in the “consumer” component, feeding on the mixed algal culture of the “producer” component. It has been found that metabolites of the algae Scenedesmus produce an adverse effect on the reproduction of the ciliates P. caudatum. Taking into account this effect, the results of investigation of the mathematical model were in qualitative agreement with the experimental results. In the “producer–consumer” biotic cycle it was shown that coexistence is impossible in the mixed culture of invertebrates of the “consumer” component. The ciliates P. caudatum are driven out by the rotifers B. plicatilis. 相似文献
466.
Johan De Keyser 《Space Science Reviews》2005,121(1-4):225-235
The Earth’s magnetosphere is an accessible region for improving our knowledge of the dynamics of collisionless plasmas. We
focus here on the magnetopause a typical plasma discontinuity. We discuss recent developments in describing the structure
of the magnetopause by means of reconstruction techniques, which translate in situ data into spatial information. We review short- and long-duration reconstruction methods and discuss the ideas behind them.
The emphasis is on long-duration reconstruction methods in a multi-spacecraft context. 相似文献
467.
Aerodynamic force can lead to the strong structural vibration of flying aircraft at a high speed. This harmful vibration can bring damage or failure to the electronic equipment fixed in aircraft. It is necessary to predict the structural dynamic response in the design course. This paper presents a new numerical algorithm and scheme to solve the structural dynamics responses when considering fluid–structure interaction(FSI). Numerical simulation for a free-flying structural model in transonic speed is completed. Results show that the small elastic deformation of the structure can greatly affect the FSI. The FSI vibration tests are carried out in a transonic speed windtunnel for checking numerical theory and algorithms, and the wind-tunnel test results well accord with that of the numerical simulation. This indicates that the presented numerical method can be applied to predicting the structural dynamics responses when containing the FSI. 相似文献
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A. Chandran R.L. Collins V.L. Harvey 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
In this review article we summarize recent results in the coupling of the stratosphere–mesosphere during stratospheric sudden warming (SSW) events. We focus on the role of planetary and gravity waves in driving the middle atmosphere circulation and illustrate the stratosphere–mesosphere coupling during undisturbed wintertime circulation, during an SSW event, and after an SSW event during the formation of an elevated stratopause using simulations of past Arctic and Antarctic winters from the Specified Dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM). We illustrate the transition of the polar stratopause from being a gravity wave driven phenomena to a planetary wave driven phenomena during SSW events and its subsequent reestablishment and control by gravity waves. We also examine the synoptic structure of the stratosphere, mesosphere, and lower thermosphere using SD-WACCM data fields that show the structure of the vortex during specific dynamical events in both hemispheres. We illustrate the longitudinal asymmetry in the thermal structure in the stratosphere and mesosphere driven by differences in circulation over the polar cap regions during an SSW event. We complement this analysis of the middle atmosphere circulation with a classification of both the Arctic and Antarctic winters since 1979 into major, minor, elevated stratopause or quiet winters based on the level of disturbance using the Modern Era-Retrospective Analysis for Research and Applications (MERRA) reanalysis data. From the MERRA data we find that the combined occurrences of both major and minor warmings in the Arctic have remained constant over the past three decades while we find a minor increase in their occurrences in the Antarctic. 相似文献
470.
风扇出口导向叶片低噪声设计Ⅱ:数值验证 总被引:1,自引:2,他引:1
作为风扇出口导向叶片(Outlet Guide Vanes,OGV)低噪声设计系列文章的第2篇,本文对气动/声学一体化设计获得的2个OGV低噪声方案的降噪效果进行了数值验证。为了对低噪声优化方案的降噪效果进行详细评估,首先,采用非线性谐波法对优化前后的风扇/增压级开展了数值仿真,对OGV不同截面和叶片表面脉动压力进行了对比分析,发现低噪声优化设计方案有效降低了转/静干涉引起的脉动压力;然后,通过掠形和倾斜的合理组合,改变了叶片表面的相位分布,沿径向的相位变化增加了OGV对尾迹响应相互抵消的机会,从而有利于噪声的降低;最后,采用Wilson的波分解方法开展了对各方案的模态分析,对降噪效果进行了量化评估。结果显示,优化后的低噪声方案除起飞状态1BPF外,降噪量均超过了5 dB。 相似文献