What Determines the Composition of SEPs in Gradual Events?

Gradual solar energetic particle (SEP) events are evidently accelerated by coronal/interplanetary shocks driven by coronal mass ejections. This talk addresses the different factors which determine the composition of the accelerated ions. The first factor is the set of available seed populations including the solar wind core and suprathermal tail, remnant impulsive events from preceding solar flares, and remnant gradual events. The second factor is the fractionation of the seed ions by the injection process, that is, what fraction of the ions are extracted by the shock to participate in diffusive shock acceleration. Injection is a controversial topic since it depends on the detailed electromagnetic structure of the shock transition and the transport of ions in these structured fields, both of which are not well understood or determined theoretically. The third factor is fractionation during the acceleration process, due to the dependence of ion transport in the turbulent electromagnetic fields adjacent to the shock on the mass/charge ratio. Of crucial importance in the last two factors is the magnetic obliquity of the shock. The form of the proton-excited hydromagnetic wave spectrum is also important. Finally, more subtle effects on ion composition arise from the superposition of ion contributions over the time history of the shock along the observer’s magnetic flux tube, and the sequence of flux tubes sampled by the observer.     

氙离子推力器束流分布特性研究

建立了离子推力器束流分布的高斯模型,以200mm氙离子推力器为例,在不同工作环境下对推力器束流分布进行了数值模拟,并通过试验测量了推力器引出切面不同位置(轴向z=50mm,z=100mm)下的径向束电流密度和束离子密度分布。通过对数值模拟结果与试验测量结果的比较,误差为17%,认为数值模拟结果与试验测量结果吻合较好。表明离子推力器引出束流呈轴对称分布,在推力器出口附近,束离子密度很大,越往下游,密度越小且束流出现发散。     

SOME RESULTS OF UPPER ATMOSPHERIC COMPOSITION MEASUREMENTS BY A MASS-SPECTROMETER ON BOARD "SZ-2":CHANGE OF COMPOSITIONS DURING SOLAR AND GEOMAGNETIC DISTURBANCES

Upper atmosphere composition data were obtained for the last half year with a quadruple mass spectrometer on board spacecraft "SZ-2" launched on 10 Jan uary 2001. Based on the analysis of these data, the variations of atmospheric compositions in solar and geomagnetic quiet conditions are reported first, then a detailed discussion on the atmospheric composition variations under the so lar and geomagnetic disturbed conditions is given. The results show that near the altitude of 400 km the variations of main atmospheric compositions corre sponding to solar disturbances are more remarkable in the sunlit area than in the shade area. On the contrary, in geomagnetic disturbance events the corre sponding variations are more obvious in the shade area, an evident increase of N2 density at relatively higher latitudes was observed.     

弓激波前内透射离子动力学横场流静电不稳定性

本文讨论了地球弓激波前内背景电子速度分布函数为平顶形式时的透射离子横场流静电不稳定性.结果表明,在超临界(Alfvén Mach数M_A>3)准垂直激波区(激波法向与行星际磁场之间的夹角75°)情况下,透射离子流产生的静电不稳定性增长率峰值要比电子速度为Maxwell分布时更加显著,并满足动力学性质.     

非硅氧化物的滤出及其机理探讨

 采用B核磁共振仪,激光拉曼光谱仪,隧道扫描显微镜及各种化学分析等方法,较系统地研究了沥滤温度、时间和酸液浓度对拉制的钠硼硅玻璃纤维纯度的影响。结果表明,高钝超细SiO_2,纤维可以用酸沥滤法获得;揭示了纤维中非硅氧化物沥出的规律;并初步探讨了沥滤机理,认为沥滤过程主要是B~(3+)和N~+与H~+发生交换扩散的过程。     

H_∞滤波算法及其在GPS/SINS组合导航系统中的应用

 在对 H∞ 估计问题进行数学描述的基础上,建立了一种 H∞ 次优滤波算法的迭代方程。定性讨论了H∞滤波算法与传统 Kalman滤波器的关系,通过在 GPS/SINS组合系统中的实际应用进一步从精度、鲁棒性等性能指标方面对 H∞ 滤波和 Kalman滤波算法进行了比较。仿真结果表明,在理想条件下,Kalman滤波方法具有较高的精度;但是,当系统模型和外部干扰统计特性发生变化时,H∞ 滤波算法明显具有良好的鲁棒性能,同时,估计精度也较高,有效地克服了 Kalman滤波器存在的局限性。     

离子注入抑制摩擦温升的研究

 离子注入抑制摩擦表面的温升,是减少粘着磨损、提高摩擦副耐磨性的新途径。本文采用离子注入技术抑制航空柱塞泵配流副试件摩擦表面的温升,获得显著的效果。当逐级改变负载时,离子注入试件摩擦表面的温度平均下降３５℃；当逐级改变润滑油流率时,试件表面温度平均下降４６℃。并初步探讨了离子注入抑制摩擦温升的机理。     

铜基高温钎料中钴作用机制的研究

探讨了Cu-Zn-Mn-Co钎料中钴的变质剂作用机理,为高温钎料的研制提供了实验基础研究。     

混粉电火花加工表面的研究

分析了混粉电火花加工工件表面的组成成分,探讨了混粉电火花加工获得低的表面粗糙度的机理。     

Electrolytic Passivation of Nitinol Shape Memory Alloy in Different Electrolytes

The corrosion behavior of the nitinol alloy was studied in various corrosion media of different Cl–ion concentrations. The results demonstrate that the Cl–ion concentration has significant influences on the corrosion behavior of the nitinol alloy. In order to enhance the corrosion resistance, protective films were generated on the surface of the nitinol alloy by means of the electrochemical passivation method, for which five different electrolytic solutions were investigated. The surface analysis indicates full growth of all samples pas-sivated in the different electrolytic solutions with layers, however, showing different morphological features. Without any defects like micro-cracks and pores, the surface of the samples passivated in the molybdate solution turns out smoother and denser than those pas-sivated in other solutions. It is shown that the electro-chemical passivation will reduce Ni content but increase Ti content in the surface, reaching the Mole ratio of Ti:Ni=9.01:1 on the outermost surface. Potentiodynamic polarization test demonstrates that the samples electrochemically passivated in the molybdate solution present a significant increase in breakdown potential due to titanium enrichment on the outermost surface.