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A team of Australian researchers used two Maunakea-based observatories – Gemini North and W. M. Keck Observatory – to discover why some galaxies are clumpy rather than spiral in shape and it appears t...
五百米口径射电望远镜(FAST)采用柔性索网作为主要支承结构，根据拟定的变位策略要求，通过促动器连接下拉索控制索网变位实现巡天观测。由于变位观测过程中索网将长期承受高达约500MPa的疲劳载荷，约为目前相关标准规定值的两倍多，故索网结构将是该望远镜中的关键易损部位。为此，该文以索网结构后期运行、监测及维护为背景，通过量纲分析方法明确影响索网变位应力幅值的主导因素，基于大型有限元软件ANSYS建立索...
卫星转发器的时延变化
转发器时延 站间差分 精密定轨 GEO卫星
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2014/7/22
使用转发式测距观测数据对地球静止轨道（Geostationary orbit，GEO）卫星进行精密定轨时，通常认为卫星转发器时延变化很小，可作为常数和卫星轨道一并求解. 事实上这个假定有一定误差，影响了GEO卫星定轨精度. 为了研究转发器时延对GEO卫星精密定轨精度的影响，本文对站间单差消除卫星转发器时延与非差常数解算转发器时延两种定轨方案进行了对比. 结果发现，转发器时延变化对轨道的影响约为1~...
行星际条件如何影响等离子体层和电离层之间的物质传输至今还是一个悬而未决的问题. 我国刚建成的子午工程可以对等离子体层和电离层开展同时监测, 为了解这两个区域之间等离子体的传输特性和耦合机制提供了新的机遇. 我们分析了2011年3月21~27日地磁平静期间等离子体层(L≈2)与电离层物质输运对太阳风脉冲的响应, 发现地磁平静时期等离子体层在太阳风动压脉冲作用下出现削减. 在太阳风动压脉冲作用下, 等...
转发式测距与转发式站间差分的卫星联合定轨
转发式站间差分 重叠弧段 长弧预报
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2013/8/8
从理论上阐明了转发式站间差分数据作为测角观测数据对卫星轨道横向的约束作用, 并综合利用转发式测轨系统对鑫诺1号卫星的自发自收测距数据和站间差分数据进行了联合定轨试验. 结果表明两种数据联合定轨轨道重叠弧段的位置误差小于测距数据单独定轨轨道重叠弧段的位置误差; 测距数据和站间差分数据联合定轨预报5.5天的残差为3.1762 m, 优于测距数据单独定轨预报同样弧段的残差3.5380 m. 试验从轨道重...
由于太阳的真位置无法直接观测, 在实际使用的地球重力固体潮公式中用视位置近似代替真位置. 研究发现, 这种近似相当于隐含了一个假定, 即引力是以光速传播的. 本文从狮泉河站和乌什站的重力固体潮观测数据出发, 作了地球黏弹性相位滞后校正; 用减除月球引力潮理论值的办法从重力固体潮观测数据中提取出准太阳引力潮的观测数据; 推导出并求解了引力传播方程, 得出引力传播速度约为0.93~1.05倍的光速, ...
500m口径射电望远镜(FAST)主要以短程线索网作为反射面支承结构。该文通过对三种短程线分型的索网进行对比分析，建议五轴对称分型方法作为优先选择索网分型方案。同时，该文的优化设计工作进一步减少了主索网与圈梁连接节点的种类及数量，并使索网能满足馈源仓检修升级功能。在此基础上，针对现有两种反射面单元自重情况，优化了索网截面和内力水平，讨论了下拉索节点位置精度对索网变位精度的影响，量化了索网变位过程中...
Revealing the physics of r-modes in low-mass X-ray binaries
Revealing the physics of r-modes in low-mass X-ray binaries
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2011/10/21
We consider the astrophysical constraints on the gravitational-wave driven r-mode instability in accreting neutron stars in low-mass X-ray binaries. We use recent results on superfluid and superconduc...
A 3D radiative transfer framework: XIII. OpenCL implementation
Radiative transfer – Scattering
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2011/10/20
We discuss an implementation of our 3D radiative transfer (3DRT) framework with the OpenCL paradigm for general GPU computing. We implement the kernel for solving the 3DRT problem in Cartesian coordin...
The metallicity distribution of bulge clump giants in Baade's Window
Galaxy: bulge – Galaxy: formation – Galaxy: abundances – Stars: abundances – Stars: atmosphere
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2011/10/20
We seek to constrain the formation of the Galactic bulge by means of analysing the detailed chemical composition of a large sample of red clump stars in Baade's window. We measure [Fe/H] in a sample o...
Precise determination of muon and EM shower contents from shower universality property
shower universality muon signal electromagnetic signal Cherenkov water detectors
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2011/10/17
We present two new aspects of Extensive Air Shower (EAS) development universality allowing to make accurate estimation of muon and electromagnetic (EM) shower contents in two independent ways. In the ...
A 3D Photoionization Model of the Extreme Planetary Nebula NGC 6302
planetary nebulae: individual: NGC 6302, ISM: abundances
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2011/10/13
We present a 3D photoionization model of the PN NGC 6302, one of the most complex objects of its kind. Our Mocassin model is composed of an extremely dense circumstellar disk and a large pair of diffu...
The Kelvin-Helmholtz instability in weakly ionised plasmas: Ambipolar dominated and Hall dominated flows
mhd – instabilities – ISM:clouds – ISM:kinematics and dynamics
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2011/10/12
The Kelvin-Helmholtz instability is well known to be capable of converting well-ordered flows into more disordered, even turbulent, flows. As such it could represent a path by which the energy in, for...