系统偏差常数弧段估计策略对多系统静态精密单点定位的影响

为探讨系统偏差最优估计策略,利用IGS提供的GPS、BDS、GLONASS和Galileo 四系统的观测数据以及GFZ提供的精密卫星钟差和精密轨道产品,将系统偏差（ISB）按照高斯白噪声、20 min、30 min、1 h、2 h分段常数进行单天静态解,分别获得E、N、U方向上的坐标偏差,分析不同系统偏差求解策略下多系统融合PPP的收敛时间和定位精度。结果表明,在多系统融合静态PPP中,从观测模型强度与定位结果稳定性和可靠性角度综合考虑,对ISB采用20 min分段常数估计策略是最优的,静态PPP收敛时间在30 min左右,收敛后的定位精度E方向优于2 cm、N方向优于1 cm、U方向优于5 cm。     

Visualization and analysis of local and distant population flows on the Qinghai-Tibet Plateau using crowd-sourced data

Human migration between cities is one important aspect of spatial interaction that not only reflects urban attractiveness but also denotes interactions amongst agglomerations.We therefore implemented a web-based visualization system to analyze and interactively explore local and distant population flow patterns between cities on the Qinghai-Tibet Plateau(QTP).We utilized 2017 Tencent population flow data from which we initially constructed inbound and outbound vectors for cities on the QTP.We then used multidimensional scaling to examine and visualize migration patterns and similarities between cities.Results reveal the presence of six local and three distant human mobility patterns on the QTP as well as aver-age summer monthly migrations more than twice the level of those in the winter.     

"7.6"川西川南暴雨天气过程分析

本文利用2006年7月5日到6日的高空资料对7月6日到7日发生在四川省西部、南部的暴雨天气过程成因进行分析,利用24小时降水实况对中尺度雨团的移动做了分析,对数值预报产品的可预报性进行了检验.分析表明:高空低值系统的相互作用、地面冷空气的入侵、中低层能量以及水汽的聚集是这次过程产生的关键.     

"2007.4.1"四川盆地强寒潮天气过程分析

利用T213 1°×1°和欧洲中心实时资料,对2007年4月l～3日四川盆地区域性寒潮天气过程的环流背景及影响系统进行了分析,结果表明:500 hPa乌拉尔山到贝加尔湖以东为宽广深厚的低压带,地面上巴湖附近为冷高压,此冷高压在500 hPa脊前西北气流的引导下东移南压,是造成此次寒潮大风天气的主要原因;而且低空急流也对降温有一定的作用.     

Simultaneous monochromatic and spectral observations of two large loop prominence groups

Using the solar tower telescope of Nanjing University, we observed the two large loop prominence groups of 1982 Dec. 20 and 1983 Feb. 9. Hα photographs and spectra around the Hα and H and K lines were obtained simultaneously. From these data, we derived a line of sight velocity distribution, which agrees perfectly with the distribution for matter falling freely without viscosity. From the widths of the Hα and the K lines, we found the loop material to have a uniform kinetic temperature and a turbulent velocity that increases with height. From the central intensities of the lines we derived a density of n(H) ? 1.3 ? 2.6 × 10¹⁰cm^?3. A possible mechanism of the formation of loop prominence groups and their relation with flares are discussed.     

Automatic Solar Filament Detection Using Image Processing Techniques

We present an automatic solar filament detection algorithm based on image enhancement, segmentation, pattern recognition, and mathematical morphology methods. This algorithm cannot only detect filaments, but can also identify spines, footpoints, and filament disappearances. It consists of five steps: (1) The stabilized inverse diffusion equation (SIDE) is used to enhance and sharpen filament contours. (2) A new method for automatic threshold selection is proposed to extract filaments from local background. (3) The support vector machine (SVM) is used to differentiate between sunspots and filaments. (4) Once a filament is identified, morphological thinning, pruning, and adaptive edge linking methods are used to determine the filament properties. (5) Finally, we propose a filament matching method to detect filament disappearances. We have successfully applied the algorithm to Hα full-disk images obtained at Big Bear Solar Observatory (BBSO). It has the potential to become the foundation of an automatic solar filament detection system, which will enhance our capabilities of forecasting and predicting geo-effective events and space weather.     

The evolution of the Magellanic clouds

The observed maximum luminosities of AGB stars in the Magellanic Cloud clusters were compared with luminosities obtained theoretically in order to estimate the ages of the clusters. Several rates of mass loss by AGB stars are considered. The ages for 10 clusters in the SMC and 25 in the LMC are presented in the tables with the compilations of ages from the literature quoted. The discrepancies between ages derived from the AGB peak luminosities and from the Main-Sequence turn off and maximum luminosity are explained by allowing for intensive mass-loss during the AGB evolutionary phase. The method is useful only if the brightest star is on the thermally pulse AGB phase but not in the early-AGB phase.     

浅析造礁生物演化及生物绝灭事件对礁丘发育的控制作用──以中国南方震旦纪至三叠纪生物礁丘为例

造礁生物演化经历了六个主要发展阶段，具有全球性演化规律特征，其盛衰变化在中国南方礁丘的时代分布上反映较为醒目。早泥盆世至晚泥盆世早期，为生物礁发育的首次鼎盛期，已发现的礁体达９７个，而至今尚未发现晚泥盆世晚期（法门期）的生物礁；二叠纪是第二次鼎盛期，已发现该时期的礁丘达１４８个之多，生物特征明显，而至今也尚未发现早三叠世时期的礁体。中国南方这一礁丘时代分布特征恰好与 Ｆ／Ｆ和Ｔ／Ｐ两次全球性巨大生物绝灭事件相吻合。因此在南方寻找生物礁型油气藏时，除了应当重视本区构造演化的控制作用外，还应极大地注意全球性生物演化规律的控制作用。     

1961-2015年陕西省不同等级降水事件变化特征

利用19612015年陕西省70个气象观测站的逐日降水资料,采用线性倾向估计、趋势分析及Mann Kendall等方法,分析了陕西省不同等级降水量、降水日数及降水强度的气候变化特征。结果表明：无论是降水量、降水日数,还是降水强度,均呈现出南多北少的分布特征,且随着降水级别的逐级增加,地区分布差异逐渐增大;整体上降水量和降水日数呈现出减少趋势,其中降水日数的下降趋势均非常显著,全省年均降水日数的气候倾向率达到了-3.83天·10a-1,通过了0.01的显著性检验,降水强度的增加趋势通过了0.05的显著性检验,每10 a全省年均降水强度增加0.15 mm·d-1;陕西降水量及降水日数的减少主要体现在春秋两季小雨及中雨的减少上,小雨降水强度在夏、秋两季的气候倾向率分别为0.05和0.04 mm·d-1·10a-1,其上升趋势分别通过了0.01和0.1的显著性检验,这是年均降水强度上升的主要原因;陕西年均降水量及降水日数自1984年出现了突变性下降,而降水强度的突变则出现在2004年,之后一直呈现持续的上升趋势。     

等离子发射光谱法测定杜仲中的微量元素

将杜仲样品进行灰化处理,残渣用HNO3、HF、HClO4加热提取,用等离子光谱发射仪测定Co、Ni、Zn、Mn、Cu的含量。实验表明,杜仲中Co、Ni、Zn、Mn、Cu的含量较为丰富。分析方法简便,快速,精确度较好。