On the 3D structure of the nebula around η-Carinae

The asymmetric shape of the nebula around η-Carinae (Homunculus) can be explained by a spherical expansion in a non-homogeneous medium. Two models are analyzed: an exponential and an inverse power law dependence for the density as a function of distance from the equatorial plane. The presence of a medium with variable density along the polar direction progressively converts the original spherical shell into a bipolar nebula. In the case of the nebula around η-Carinae, we know the time elapsed since the great outburst in 1840. An exact match between observed radii and velocities can be obtained by fine tuning the parameters involved, such as initial radius, initial velocity and the typical scale that characterizes the gradient in density. The observed radius and velocity of the Homunculus as a function of the polar angle in spherical coordinates can be compared with the corresponding simulated data by introducing the efficiency in a single or multiple directions. Once the 3D spatial structure of the Homunculus is obtained, we can compose the image by integrating along the line of sight. In order to simulate the observed image, we have considered a bipolar nebula with constant thickness and an optically thin emitting layer. Some simulated cuts of the relative intensity are reported and may represent a useful reference for the astronomical cuts.     

一类平流层飞艇质量和惯量特性的计算方法与分析

针对一类具有双拼椭球体外形的平流层飞艇,根据适当假设,给出该类飞艇质量和惯量特性的解析计算方法.以飞艇上升过程为例,通过仿真计算给出该过程飞艇质量、质心位置和转动惯量的变化曲线,结合理论分析,验证该计算方法的合理性.最后,简要分析了质量和惯量特性变化对飞艇运动稳定性和能控性的影响.     

基于布局优化的飞行器变质心控制性能研究

研究了变质心再入飞行器的控制性能。对力矩的分析发现活动质量体配置于弹体质心处能降低相对运动对飞行器的影响,且飞行器三通道间的动力学耦合也将减轻。将活动质量体配置在弹体质心以优化变质心控制结构布局,并设计姿态控制律,比较了布局优化和未优化的姿态响应和滑块运动。结果表明:采用布局优化不仅能提高变质心控制的操纵性,改善姿态响应的动态品质,而且滑块的运动品质也得以改进。     

Simultaneous observations of the plasma density on the same field line by the CPMN ground magnetometers and the Cluster satellites

By applying the cross-phase method and the amplitude-ratio method to magnetic field data obtained from two ground stations located close to each other, we can determine the frequency of the field line resonance (FLR), or the field line eigenfrequency, for the field line running through the midpoint of the two stations. From thus identified FLR frequency we can estimate the equatorial plasma mass density (ρ)$(\rho )$ by using the T05s magnetospheric field model [Tsyganenko, N.A., Sitnov, M.I. Modeling the dynamics of the inner magnetosphere during strong geomagnetic storms, J. Geophys. Res. 110, A03208, 2005] and the equation of Singer et al. [Singer, H.J., Southwood, D.J., Walker, R.J., Kivelson, M.G. Alfven wave resonances in a realistic magnetospheric magnetic field geometry, J. Geophys. Res. 86 (A6) 4589–4596, 1981].     

Enhancement of solar wind low-energy energetic particles as precursor of geomagnetic disturbance in operational geomagnetic forecast

A study of the relationship between solar wind low-energy energetic particles using data from the Electron, Proton, and Alpha Monitor (EPAM) onboard the Advanced Compositional Explorer spacecraft (ACE) and geomagnetic activity using data from Canadian magnetic observatories in Canada’s polar cap, auroral zone, and subauroral zone was carried out for a period spanning 1997–2005. Full halo coronal mass ejections (CMEs) were used to gauge the initial particle enhancements and the subsequent geomagnetic activity. It was found that maximum geomagnetic activity is related to maximum particle enhancements in a non-linear fashion. Quadratic fit of the data results in expressions that can be easily used in an operational space weather setting to forecast geomagnetic disturbance quantitatively. A superposed epoch analysis shows increase in particle flux level starts hours before geomagnetic activity attains its peak, affirming the precursory nature of EPAM particles for the impending geomagnetic impact of CME. This can supplement the decision process in formulating geomagnetic warning after the launch of CME from the Sun but before the arrival of shock at Earth. The empirical relationships between solar wind low-energy energetic particles and geomagnetic activity revealed in this statistical study can be easily codified, and thus utilized in operational space weather forecast to appraise the geoeffectiveness of the CME and to provide a quantitative forecast for maximum geomagnetic activity in Canada’s polar cap, auroral zone, and subauroral zone after the occurrence of a CME.     

Study on solar sources and polar cap absorption events recorded in Antarctica

Particularly intense events occurred on the Sun in a period around minimum of solar activity during cycle 23. We investigated the characteristics of September 2005 and December 2006 events and the properties of the correlated observations of ionospheric absorption, obtained by a 30 MHz riometer installed at Mario Zucchelli Station (MZS-Antarctica), and of geomagnetic activity recorded at Scott Base (Antarctica). Solar events are studied using the characteristics of CMEs measured with SoHO/LASCO coronagraphs and the temporal evolution of solar energetic protons in different energy ranges measured by GOES 11 spacecraft.     

航天器密封管路的气态工质与示漏气体 漏率等效关系研究

利用多种气体分析仪,采取四级质谱定量分析技术,分别测定He、N₂、N_e、CF₄、Kr等气体在不同入口压力下通过不同的人造漏孔的漏率;经过对同工况下气体间漏率比对,研究气体间漏率等效关系。试验结果表明:气体在不同工况下处于不同的流动领域,且其漏率与入口压力存在着不同的数值关系,经分析试验结果得出适用于气体全流域的漏率经验公式;气体间漏率的等效关系在低漏率及高漏率端始终呈平滑的线性关系,而在中间的过渡区域呈四或五次多项式关系;但是CF₄与H_e的漏率等效性呈线性关系,显示出多原子分子与单、双原子分子在粒子输运过程中存在着差异。试验结果为示漏工质漏率指标的制定提供了基础数据。     

飞船舱门机构中密封件性能测试方法介绍

文章以某型号飞船的舱门组件中锁紧机构的橡胶密封件的性能试验为背景,介绍了环境模拟试验密封结构设计和密封件密封性能测试的试验过程、结果和漏率测试方法,验证了密封结构设计和密封材料选择的可靠性.     

Promass83A质量流量计在发动机试验中的应用

从原理上解释了Promass83A质量流量计精度高、抗干扰能力强的特性,并通过试验将称重传感器、涡轮流量计和质量流量计测得的数据进行比较,进一步掌握了质量流量计的性能参数,在试车应用中取得了良好的效果。