适应于极区的惯导系统传递对准技术研究

针对飞机、舰艇全球航行的需求,以及由地球经线在极区收敛而导致的以真北向作为航向参考时的导航算法失效问题,在传统的“速度+姿态”匹配对准及修正算法的基础上,提出了格网导航系下的“速度+姿态”传递对准方法。基于格网导航系下惯性导航算法的编排,建立了格网坐标系的惯导误差模型,推导了格网导航系“速度+姿态”匹配的量测方程,利用卡尔曼滤波器对子惯导的速度、失准角、陀螺漂移、加速度计零偏、主子惯导间的安装误差角等进行了估计与修正。数学仿真及基于极区航行试验数据的半实物仿真结果表明,采用本文提出的格网导航系下的“速度+姿态”匹配传递对准算法,可实现中低精度惯导系统在高纬度地区时间为30s、水平对准精度优于1角分、方位对准精度优于6角分的快速、高精度对准。     

三维复杂腔体的时域有限差分法分析

在计算三维复杂腔体雷达截面的时域有限差分法中，提出了一种简单的计算域设置方法。它由腔壁和腔口面外侧的吸收边界围成，与包围目标的常用计算域设置方法相比，忽略了腔边缘的绕射作用，但具有节省计算机存储空间，无需额外抽取外腔壁对电磁波的散射。数值结果表明该设置方法是合理可行的。     

交叉航路碰撞风险研究

航路上航班的碰撞风险问题是目前空域规划的主要研究问题之一,就交叉航线的碰撞风险问题进行了研究.首先推导出交叉航路碰撞概率计算公式,然后结合概率论和划设保护区的方法对交叉航线的碰撞风险问题进行了研究,最后用自主开发的"空域安全评估方法的研究与应用"软件对上海区域内的某交叉航线的碰撞风险进行了仿真计算.为交叉航路的碰撞风险计算提供了简单易行的方法.     

合成射流激励器阵列实现共轴射流掺混控制研究

文中分别对单列和多列合成射流激励器控制共轴射流掺混流场进行了详细的二维非定常数值模拟,通过对其温度场分布和掺混过程进行分析,探讨激励器阵列进行掺混控制的机理。在研究过程中,考虑了相邻合成射流的影响。结果表明,激励器的采用使得整个流场的非定常性增强、湍流度增大,从而增强了共轴射流及其与周围流体间的掺混;两列激励器较单列激励器相比,前者具有更强的控制能力,这主要是由于相邻合成射流比单个合成射流有着更显著作用力的缘故。     

太阳10.7 cm射电流量中期预报模型研究(Ⅱ)

太阳活动指数中期预报一直是空间环境业务预报的难点之一.本文在自回归方法模型的基础上,利用太阳活动区面积、位置等参数与10.7cm辐射流量之间的定量关系,根据活动区面积衰减规律,建立了一个基于活动区参数及演化规律的改进型太阳活动指数中期预报模型.通过对预报测试实例分析发现,在日面出现较大活动区导致F_(10.7)迅速增长并超过历史数据峰值的情况,在日面活动区消亡导致指数突然出现平静期的情况,新模型的预报准确性相比自回归模型有很大提高,预报的平均相对误差下降约5%～9%.由此可见,新模型在某些特定条件下提高了原有模型的精度.该研究为提高业务型太阳10.7cm射电流量中期预报模型的预报精度奠定了基础.     

Variation of ionospheric electron and ion temperatures during periods of minimum to maximum solar activity by the SROSS-C2 satellite over Indian low and equatorial latitudes

To study the variation of ionospheric electron and ion temperatures with solar activity the data of electron and ion temperatures were recorded with the help of Retarding Potential Analyzer payload aboard Indian SROSS-C2 satellite at an average altitude of ∼500 km. The main focuses of the paper is to see the diurnal, seasonal and latitudinal variations of electron and ion temperatures during periods of minimum to maximum solar activity. The ionospheric temperatures in the topside show strong variations with altitude, latitude, season and solar activity. In present study, the temperature variations with latitude, season and solar activity have been studied at an average altitude ∼500 km. The peak at sunrise has been observed during all seasons, in both electron and ion temperatures. Further, the ionospheric temperatures vary with latitude in day time. The latitudinal variation is more pronounced for low solar activity than for high solar activity.     

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].     

Evidence of change after 2001 in the seasonal behaviour of the mesopause region from airglow data at El Leoncito

Airglow intensities and rotational temperatures of the OH(6-2) and O₂b(0-1) bands acquired at El Leoncito (32°S, 69°W) provide good annual coverage in 1998–2002, 2006, and 2007, with between 192 and 311 nights of observation per year. These data can therefore be used to derive the seasonal variations during each of these seven years, in airglow brightness and temperatures at altitudes of 87 and 95 km. From 1998 to 2001, seasonal variations are similar enough so that they can be well represented by a mean climatology, for each parameter. On the other hand, these climatologies do not agree with what is usually observed at other sites, maybe due to the particular orographic conditions at El Leoncito. With respect to the last three fully documented years (2002, 2006, and 2007), the similarity from year to year deteriorates, and there are greater differences in the seasonal behaviour, more or less in all the parameters. The differences include, e.g., maxima occurring earlier or later than “normal”, by one or two months. All this may suggest the build-up of a new regime of intraseasonal variability, with a possible relationship to corresponding changes in wave activity.     

体-翼干扰区热环境特性分析及预测

高速飞行器的体—翼干扰区热流精确预测对于飞行器生存能力与战术性能的提高具有重要的 意义,是高性能飞行器设计水平的一个重要标志。由于体—翼干扰区流场的复杂性,目前尚 无满足工程设计要求的热环境预测方法,在分析体—翼流场特性的基础上应用文献［1 ］的压力—热流关系式,提出体—翼干扰区的热流预测方法,即压力由N-S数值解给出,热 流应用压力—热流关系式得到,炮风洞的实验结果验证了本文预测方法的可 靠性 。
     

活动区新浮磁流和暗条的激活

用数值计算方法探讨了新浮磁流驱动下暗条运动的基本规律。计算表明,活动区新浮磁流是驱动暗条运动导致暗条激活的有效机制之一,这个过程是通过暗条电流和背景磁场的相互作用来实现的。当选取不同强度的浮现磁流时,暗条可出现周期性振荡、激活上升和闪烁;此外,对同极性磁流浮现,当浮现强度足够强时,暗条一开始就会下沉。