Solar wind origins in coronal holes and in the quiet Sun

Coronal hole (CH) and the quiet Sun (QS) are considered to account for sources of fast and slow solar wind streams, respectively. The differences between the solar wind streams flowing out from the CH and the QS are thought to be related with different plasma generation and acceleration mechanisms in the respective source regions. Here we review recent studies on the solar wind origin in the CH and the QS, compare the possible flow geometries and magnetic structures in these two kinds of solar regions, and summarize the physics associated with two different origin scenarios.     

新型狭缝节流球形静压气体陀螺轴承的动态特性

针对新型结构气浮陀螺,对其中的狭缝节流球形静压气体轴承,采用小扰动法进行动态特性分析,通过相容性条件将狭缝气膜与球形支撑气膜统一,建立动态Reynolds方程的伽辽金余量弱解公式,有限元求解有关弱解公式的耦合非线性方程组,得到动态特性系数,进行仿真并分析了该结构球形静压气体轴承的动态特性系数随扰动频率v(挤压数σ),转子转速ω(压缩数Λ)以及偏心率Eh的变化规律,从而在理论上确定了该结构气体轴承动态特性系数的影响因素及变化规律。     

Testing the no-hair theorem with observations of black holes in the electromagnetic spectrum

According to the no-hair theorem, astrophysical black holes are uniquely described by their mass and spin. In this paper, we review a new framework for testing the no-hair hypothesis with observations in the electromagnetic spectrum. The approach is formulated in terms of a Kerr-like spacetime containing a quadrupole moment that is independent of both mass and spin. If the no-hair theorem is correct, then any deviation from the Kerr metric quadrupole has to be zero. We show how upcoming VLBI imaging observations of Sgr A∗ as well as spectroscopic observations of iron lines from accreting black holes with IXO may lead to the first astrophysical test of the no-hair theorem.     

Short term topological changes of coronal holes associated with prominence eruptions and subsequent CMEs

We study the short-term topological changes of equatorial and polar coronal hole (CH) boundaries, such as a variation of their area and disintegration, associated to reconnection with nearby (within 15° distance) quiescent prominence magnetic fields leading to eruptions and subsequent Coronal Mass Ejections (CMEs). The examples presented here correspond to the recent solar minimum years 2008 and 2009. We consider a temporal window of one day between the CH topological changes and the start and end times of prominence eruptions and onset of CMEs. To establish this association we took into account observational conditions related to the instability of prominence/filaments, the occurrence of a CME, as well as the subsequent evolution after the CME. We found an association between short-term local topological changes in CH boundaries and the formation/disappearance of bright points near them, as well as, between short-term topological changes within the whole CH and eruptions of nearby quiescent prominences followed by the appearance of one or more CMEs.     

层板椭圆孔自由边缘效应

 复合材料层板的直边和圆孔自由边缘效应的三维应力分析,国内外已有不少的数值解和近似解析解。Rybicki等提出了各向异性板椭圆孔2维问题变换为圆孔问题的方法,本文论证了这种变换方法的3维情形,从而可根据圆孔自由边缘效应结果来估计椭圆孔自由边缘效应。     

固体火箭发动机气体动力学发展的现状和方向

提纲式地阐述固体火箭发动机气体动力学,特别是二相流的发展和应用.认为气体动力学是固体火箭发动机理论设计、性能计算和专题研究的重要基础,流场计算已成为固体火箭发动机设计和研究中众所瞩目的中心问题.提出了固体火箭发动机流场计算一体化的观点.反应湍流边界层理论是固体火箭发动机气体力学的新领域.轴对称二相流的理论和实验研究已取得显著成果,但有必要继续进行和不断完善.工程应用迫切要求从速建立许多研究专题的二相模型.三维、二相、计算气体动力学是今后发展的方向;它与固体火箭发动机一体化工作过程的计算机图象显示相结合,将成为本世纪90年代及21世纪初的新水平.     

航天飞机用LACE方案的发展及其参数分析

研究了应用于空天飞机的液体空气循环发动机。介绍了提高空气液化比的几种方法，如：液氢，液氧储箱循环，液氧喷洒，液态空气喷洒。以能量平衡为基础，计算了液体循环发动机的循环参数。结果表明综合采用以上方法可以使液化比提高约６５％。     

高反压环境中空气雾化喷嘴的雾化性能

使用美国Ｐｕｒｄｕｅ大学“热力科学及推进研究中心”的高反压喷嘴试验设备，试验研究了空气雾化喷嘴在高反压环境中的雾化性能，试验中对一种典型空气雾化喷嘴，使用粘度分别为０．００１，０．０５０和０．１００Ｐａ．ｓ的三种液体，在０．１－１．８ＭＰａ反压范围内，用Ｍａｌｖｅｒｎ粒度分析仪，测量了喷雾的液滴平均直径及液滴尺寸分布。试验结果表明，在试验的环境压力和液体粘度范围内，提高喷嘴的气液比总是起着改善雾化     

垂直射流混合的三维湍流数值模拟

采用三维ＳＩＭＰＬＥ程序和ｋ－ε双方程湍流模型对三维受限垂直射流进行数值模拟,研究了不同的几何变量和流动参数对射流穿透和混合的影响。模拟结果表明,三维垂直射流最显著的流动特征是形成了流向旋涡。射流与来流的混合程度取决于旋涡的位置、作用范围和强弱。单股射流随动量比、旋涡强度和尺度的增加,混合增强。对于单排多股射流,喷孔间距直接影响旋涡涡心位置。密排射流,旋涡过于靠近下壁面,旋涡无法影响上面来流;但喷孔排列也不能过于稀疏,否则涡对靠的太近,旋涡对侧面影响不大。Ｓ／Ｈ和动量比不变,改变孔径Ｄ对射流穿透几乎无影响。这一重要结论说明Ｓ／Ｈ和Ｊ是决定多股受限射流穿透深度的最重要的量。     

降低含多孔带板应力集中的有限元研究

在飞机和船体结构设计中,由于管路穿行、电缆布置等总体布局要求,在机翼梁的腹板上的指定位置开有多个孔,引发多个孔应力互相干扰。利用ANSYS有限元软件分别对圆孔间距、圆孔数和方形孔圆角半径对含孔带板应力集中系数的影响进行了分析,并与特定情况的试验值进行了对比,两者基本一致。研究结果表明:在孔数一定时,对于不同的孔间距,存在不同的最佳值,使应力集中系数得到最有利的缓和,且板宽对该最佳值的影响不大;对于方形孔, 当圆角半径为1/14方形孔边长时,对缓和应力集中系数最有利。文中并给出了特定情况下最有利于降低应力集中系数的孔的个数。