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1.
应用一维混合模拟方法数值研究了高密度等离子体团和行星际激波与准平行无碰撞激波的相互作用.结果表明,由于推平行无碰撞激波上游的大振幅低频波动的散射,除了在通过激波过渡区时稍有压缩外,等离子体团从激波的上游开始就一直是不断弥散的.行星际激波在向准平行无碰撞激波靠近的过程中,会在其上游产生大振幅的低频波动,同时行星际激波的强度不断增加,最后和准平行无碰撞激波会并成一个新的激波,在新激波前继续有大振幅的低频波动产生 相似文献
2.
Timothy G. Hawarden Robert Crane Harley A. Thronson Jr. Alan J. Penny Anna H. Orlowska Thomas W. Bradshaw 《Space Science Reviews》1995,74(1-2):45-56
The designs of cold space telescopes, cryogenic and radiatively cooled, are similar in most elements and both benefit from orbits distant from the Earth. In particular such orbits allow the anti-sunward side of radiatively-cooled spacecraft to be used to provide large cooling radiators for the individual radiation shields. Designs incorporating these features have predictedT
tel near 20 K. The attainability of such temperatures is supported by limited practical experience (IRAS, COBE). Supplementary cooling systems (cryogens, mechanical coolers) can be advantageously combined with radiative cooling in hybrid designs to provide robustness against deterioration and yet lower temperatures for detectors, instruments, and even the whole telescope. The possibility of such major additional gains is illustrated by the Very Cold Telescope option under study forEdison, which should offerT
tel5 K for a little extra mechanical cooling capacity. 相似文献
3.
An efficient hyper-elastic model that can reflect the primary mechanical behaviors of Carbon-Kevlar hybrid woven reinforcement was developed and implemented with VUMAT constitutive code for preforming simulation. The model parameters were accurately determined through the uniaxial and bias-extension tests. To calibrate the simulation code, preforming experiments of hybrid woven reinforcement over the hemisphere mold and tetrahedron mold were respectively conducted to validate the proposed hyper-... 相似文献
4.
提出并设计了一种基于混杂非对称复合材料层合板的新型自适应对日定向器。该对日定向器采用混杂非对称复合材料层合板作为驱动元件,利用在轨光照条件的变化引起复合材料层合板温度变化,进而使其产生热变形并驱动太阳翼发生偏转。提出的自适应对日定向器结合传统的单自由度对日定向机构,能够实现太阳能帆板的双自由度对日定向。介绍了自适应对日定向器的基本原理,并结合地球静止轨道的光照条件进行了具体设计。利用能量变分原理建立了混杂非对称复合材料的热变形模型,分析其热变形特点,并利用有限元方法对定向器在地球静止轨道上的温度场特性、热变形及对日定向转动角度进行分析。有限元分析结果表明,通过合理设计,自适应对日定向器的转角能够随太阳光入射角变化呈线性变化,定向精度可达±1°。 相似文献
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在野外等一些环境下的无线数据采集系统中,由于地理环境恶劣、节点数量多等原因很难更换电源电池,因此有效地降低系统各层的功耗、提高系统的生命周期尤为重要.文中在论述传感器节点结构的基础上,分析如何对传感器节点的动态电压调度、MCU能量消耗控制、动态功率管理、收发模块节能等硬件电路以及对MAC层、网络层的软件协议降低系统耗能. 相似文献
7.
认知无线电Ad Hoc网络中,吞吐量最大化是一个关键的挑战.为了实现这一目标,协同传输是前景看好的技术,利用在每个空间节点的多样性中继链路以增加性能,特别是在无线环境中由于不同的信道质量、有限的能源和带宽资源,这种想法是有吸引力的.文章在分布式动态环境下,研究了联合动态路由.中继分配和频谱分配分布式和本地算法,提出了一... 相似文献
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《中国航空学报》2016,(1):1-14
The precision forming of thin-walled components has been urgently needed in aviation and aerospace field. However, the wrinkling induced by the compressive instability is one of the major defects in thin-walled part forming. The initiation and growth of the wrinkles are interac-tively affected by many factors such as stress states, mechanical properties of the material, geometry of the workpiece and boundary conditions. Especially when the forming process involves compli-cated boundary conditions such as multi-dies constrains, the perturbation of clearances between workpiece and dies and the contact conditions changing in time and space, etc., the predication of the wrinkling is further complicated. In this paper, the current prediction methods were summa-rized including the static equilibrium method, the energy method, the initial imperfection method, the eigenvalue buckling analysis method, the static-implicit finite element method and the dynamic-explicit finite element method. Then, a systematical comparison and summary of these methods in terms of their advantages and limitations are presented. By using a combination of explicit FE method, initial imperfection and energy conservation, a hybrid method is recommended to predict plastic wrinkling in thin-walled part forming. Finally, considering the urgent requirements of com-plex thin-walled structures’ part in aviation and aerospace field, the trends and challenges in wrin-kling prediction under complicated boundary conditions are presented. 相似文献
10.