Characteristics of convection and overshooting in RGB and AGB stars

Based on the turbulent convection model (TCM) of Li & Yang, we have studied the characteristics of turbulent convection in the envelopes of 2 and 5M⊙ stars at the red giant branch and asymptotic giant branch phases. The TCM has been successfully applied over the entire convective envelopes, including the convective unstable zone and the overshooting regions. We find that the convective motions become progressively stronger when the stellar models are located farther up along the Hayashi line. In the convect...     

Radioheliograph Observations of Microwave Bursts with Zebra Structures

The so-called zebra structures in radio dynamic spectra, specifically their frequencies and frequency drifts of emission stripes, contain information on the plasma parameters in the coronal part of flare loops. This paper presents observations of zebra structures in a microwave range. Dynamic spectra were recorded by Chinese spectro-polarimeters in the frequency band close to the working frequencies of the Siberian Solar Radio Telescope. The emission sources are localized in the flare regions, and we are able to estimate the plasma parameters in the generation sites using X-ray data. The interpretation of the zebra structures in terms of existing theories is discussed. The conclusion has been arrived at that the preferred generation mechanism of zebra structures in the microwave range is the conversion of plasma waves to electromagnetic emission on the double plasma resonance surfaces distributed across a flare loop.     

日冕物质抛射及其伴生的射电辐射观测特征

统计分析了太阳活动周下降段(2003～2005年)发生的76个共生CME的射电爆发事件.射电爆发资料来自国家天文台和Culgoora的微波和米波频谱仪.在76个事件中有50个快速CME和26个慢速CME.从中发现,快速CME和慢速CME的产率分别随着太阳活动周的降低而下降和上升,这可能说明CME的产率与太阳活动周中日冕磁结构的位形和位置变化有关.同时也发现,射电爆发的类型和寿命有一个变化规律,即随着频率的降低射电爆发的寿命变长,此特征支持了伴生CME的Ⅱ型爆发统一模型的思想.另外还发现在厘米一分米波范围,CME开始前后,容易发生射电Ⅲ型爆发或快速精细结构.这说明射电辐射的精细结构可能是CME的前兆现象或CME早期发展阶段由于磁重联引发的低日冕小尺度磁扰动的结果.     

多相滤波器组谱分析方法的性能讨论与天文观测应用

多相滤波器组(PFB)是均匀数字滤波器组的一种高效实现结构,用于信号的均匀子带分解和抽取,对应用多相滤波器组作为功率谱估计器的统计性能与计算量进行分析,与相关图与周期图方法进行比较,并通过仿真及FAST密云模型21cm中性氢谱线观测检验其应用效果。     

卫星激光测距的电控系统设计与实现

给出的卫星激光测距的二轴系统实现了通过软件控制望远镜coude光路调整、接收系统SPAD和APD的自动切换、视场光阑大小的自动调节、以及发射光束指向的精确控制。该系统是基于MPC07运动控制卡,通过人机交互界面进行实时控制,旨在实现不同功能的调节,提高卫星激光测距的自动化程度。详细介绍了该系统的硬件组成、技术指标及软件工作方式。     

基于贝叶斯模型的器测、古气候重建与气候模拟数据的融合试验

气象部门馆藏的西部最早的器测气象资料始于20世纪30年代,不能满足建立20世纪以来中国气候变化序列的需求,而古气候重建或气候模拟资料则可以延伸到器测时代以前。为了探讨长序列多源气候资料序列融合方法,采用贝叶斯方法对中国北疆地区8条树轮气温重建资料、器测资料与国际耦合模式比较计划第5阶段（CMIP5）模式模拟资料进行了融合试验。首先利用器测资料对气温代用资料进行校验与网格重建,并以此作为贝叶斯模型的先验分布,然后,用泰勒图选出了该区域气候模拟效果最佳的几个模式;最后将网格重建和气候模拟序列用贝叶斯模型进行了融合试验。结果表明,贝叶斯融合模型能有效提取各种数据来源的有用信息进行融合,融合结果的长期变化（线性）趋势更接近器测气候序列,并在一定程度上提高了序列的精度,减小了结果的不确定性;并且,融合结果能够纠正先验分布及气候模拟数据的明显偏差,为长年代气候序列重建提供了一个可行的思路。      

大气中痕量有机胺测量方法的研究进展

作为大气中最重要的含氮有机化合物,有机胺易与硫酸、硝酸气体生成胺盐,促进新颗粒的形成,同时也可与臭氧、OH自由基、NO₃自由基发生氧化反应,是二次气溶胶的前体物.综述了国内外关于大气有机胺检测技术的研究进展,对常规的离线检测技术和在线质谱技术进行了介绍和对比,重点介绍了质谱法工作原理以及测定大气有机胺的优越性,并对其未来发展进行了展望.     

低高度角大气静力学延迟修正的改进

进行低高度角观测是GPS(Global Positioning System)气象学的发展趋势,其中发展高精度的低高度角的大气静力学延迟修正是主要的关键技术.比较了3种计算无线电波从空间到地面接收机的大气静力学延迟修正方法:(1)在大气球对称假设下用探空气球资料路径积分得到大气静力学延迟;(2)在大气球对称假设下用NCEP(National Centers for Environmental Prediction)再分析资料得到大气静力学延迟;(3)用Niell的大气静力学映射函数得到大气静力学延迟.与2001年中国地区89个探空气球站资料计算得到的大气静力学映射函数比较结果显示:NCEP再分析资料路径积分的方法在低高度角(5°以下)的精度好于Niell映射函数模型约5倍.     

The evolution of the z distribution of normal neutron stars in the Galaxy

Under the two initial 1‐D one parameter velocity distribution forms (one is normal, the other is exponential), the z direction scale height evolution of normal neutron stars in the Galaxy is studied by numerical simulation. We do statistics for the cases at different time segments, also do statistics for the cumulative cases made of each time segment. The results show in the cumulative cases the evolution curves of the scale heights are smoother than in the each time segment, i.e., the cumulation improve the signal‐to‐noise ratio. Certainly the evolution cases are different at different Galactic disk locations, which also have very large difference from the average cases in the whole disk. In the initial stages of z evolution of normal neutron stars, after the beginning transient states, the cumulative scale heights increase linearly with time, and the cumulative scale height increasing rates have linear relationship with the initial velocity distribution parameters, which have larger fluctuation in the vicinity of the Sun than in the whole disk. We utilize the linear relationship of the cumulative scale height increasing rates vs. the initial velocity distribution parameters in the vicinity of the Sun to make comparison with the observation near the Sun. The results show if there is no magnetic decay, then the deserved initial velocity parameters are obvious lower than the present well known results from some authors; whereas if introducing magnetic decay, for the 1‐D normal case we can make consistence among concerning results using magnetic decay time values which are supported by some authors, while for the 1‐D exponential case the results show the lackness of young pulsar samples in the larger z in the vicinity of the Sun (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Linear stability for some symmetric periodic simultaneous binary collision orbits in the four-body problem

We apply the analytic-numerical method of Roberts to determine the linear stability of time-reversible periodic simultaneous binary collision orbits in the symmetric collinear four-body problem with masses 1, m, m, 1, and also in a symmetric planar four-body problem with equal masses. In both problems, the assumed symmetries reduce the determination of linear stability to the numerical computation of a single real number. For the collinear problem, this verifies the earlier numerical results of Sweatman for linear stability with respect to collinear and symmetric perturbations.