A modified mix-differenced approach for estimating multi-GNSS real-time satellite clock offsets

A modified mixed-differenced approach for estimating multi-GNSS real-time clock offsets is presented. This approach, as compared to the earlier presented mixed-differenced approach which uses epoch-differenced and undifferenced observations, further adds a satellite-differenced process. The proposed approach, based on real-time orbit products and a mix of epoch-differenced and satellite-differenced observations to estimate only satellite clock offsets and tropospheric zenith wet delays, has fewer estimated parameters than other approaches, and thus its implementing procedure is efficient and can be performed and extended easily. To obtain high accuracy, the approach involves three steps. First, the high-accuracy tropospheric zenith wet delay of each station is estimated using mixed-differenced carrier phase observations. Second, satellite clock offset changes between adjacent epochs are estimated using also mixed-differenced carrier phase observations. Third, the satellite clock offsets at the initial epoch are estimated using satellite-differenced pseudorange observations. Finally, the initial epoch clock results and clock offset changes are concatenated to obtain the clock results of the current epoch. To validate the real-time satellite clock results, multi-GNSS post-processing clock products from IGS ACs were selected for comparison. From the comparison, the standard deviations of the GPS, GLONASS, BeiDou and Galileo systems clock results are approximately 0.1–0.4 ns, except for the BeiDou GEO satellites. The root mean squares are about 0.4–2.3 ns, which are similar to those of other international real-time products. When the clock estimates were assessed based on a pseudo-kinematic PPP procedure, the positioning accuracies in the East, North and Up components reach 5.6, 5.5 and 7.6 cm, respectively, which meet the centimeter level and are comparable to the application of other products.     

塔里木盆地塔中志留系柯坪塔格组物源示踪:碎屑锆石U-Pb年代学证据

目前对塔中志留系物源的认识仍存在不确定性.利用LA-ICP-MS分析技术对塔里木盆地塔中地区志留系柯坪塔格组2件样品开展碎屑锆石U-Pb年代学研究.结果表明塔中志留系碎屑锆石主要为岩浆结晶成因,锆石年龄主要分布在早古生代460~490 Ma、新元古代760~1 000 Ma、古元古代1 600~2 200 Ma及新太古代晚期-古元古代早期2 400~2 600 Ma四个时期,其中新元古代760~1 000 Ma碎屑锆石年龄占绝对优势（56.8%）,峰值~850 Ma.结合志留纪时期塔里木板块南北缘的板块动力学背景,通过盆内构造演化及地貌特征的分析以及和潜在源区锆石年龄的详细对比,确定塔中志留系碎屑锆石主要来源于塔里木盆地西南缘的铁克里克隆起构造带.      

Variations of methane stable isotopic values from an Alpine peatland on the eastern Qinghai-Tibetan Plateau

Acta Geochimica - Isotopic signature is a powerful tool to discriminate methane (CH4) source types and constrain regional and global scale CH4 budgets. Peatlands on the Qinghai-Tibetan Plateau are...     

Investigation of the penetration characteristics of snake skin-inspired pile using DEM

Acta Geotechnica - Snake can perfectly utilize its scales to move. Inspired by the snake scales, this study investigated the characteristics of the snake skin-inspired pile penetration process. Six...     

河南省人工防雹作业指挥系统研发及应用

利用河南省历史气象资料,结合先进的防雹理论与技术,系统分析和总结了河南省冰雹过程的天气尺度与中尺度概念模型,并根据三维冰雹云数值模式及雷达探测、闪电定位、卫星、自动站数据,研发出河南省人工防雹作业指挥系统。该系统包括天气形势分析子系统和作业决策指挥子系统。天气形势分析子系统可根据大尺度形势背景、中尺度系统特征及三维冰雹云数值模式和卫星、闪电、自动站资料,对可能降雹区进行预测。作业决策指挥子系统通过对雷达数据产品的二次开发,完成雷达资料处理、产品生成及风暴自动识别、分类、预警,并根据参数的变化和雹云的移动方向,对下游作业区进行预警及输出作业方案。整个系统基于VS2005开发平台,使用c++开发语言,利用图层分层管理将地理信息、雷达实时观测资料、雷达二次产品、高空资料、火箭和高炮作业点等信息分层显示。系统自动化程度高,操作简便,为河南省冰雹天气预报预警提供了可参考的技术指标体系。     

基于ERA5的快速辐射传输模式与FY-4A成像仪观测结果的偏差分析

2016年12月发射升空的FY-4A是中国第二代静止轨道气象卫星,该星上搭载了可提供东半球近实时高分辨率卫星观测数据的扫描辐射成像仪——AGRI（Advanced Geostationary Radiation Imager）。在其观测数据应用于大气参数反演或同化前,数据偏差的定量化分析是一个必要环节。采用快速辐射传输模式RTTOV（Radiative Transfer for the TIROS Operational Vertical Sounder）,基于欧洲中期天气预报中心（ECMWF）第5个全球再分析数据产品（ERA5）对AGRI的7个红外通道（通道08—14）进行了模拟,并利用MODIS云检测产品对模拟结果进行了晴空筛选,以期得到一些对AGRI的定量应用有价值的偏差分析结果。观测-模拟（O-B）的偏差分析结果显示:海洋和陆地上,通道10（7.1 μm）存在明显大于其他红外通道的系统性偏差,这很可能来源于ERA5在对流层中层对水汽的高估。通道08为近红外短波通道,地表反射作用影响强烈,陆地上存在较大的平均偏差,而海洋上平均偏差小于0.4 K。通道14在ERA5近地层气温偏高及定标偏差的影响下,海洋存在接近1 K的平均偏差;陆地上存在2 K左右的平均偏差。其余各红外通道在海洋和陆地上的平均偏差分别在0.6和1.3 K以下。偏差影响因子分析结果显示:地表海拔高度、观测天顶角对偏差也存在一定程度的影响;海洋上偏差分布存在季节变化可能来源于再分析资料中海表温度估算的季节性误差。      

Variations in annual winter mean temperature in South China since 1736

Modern meteorological observations in South China from 1960 to 2009 show a strong correlation between winter temperatures and two snowfall parameters, the southern boundary of the snow and the number of snowy days. Based on this relationship, the variation in annual winter mean temperature in South China from 1736 to 2009 was reconstructed using data acquired from Chinese historical documents dating from the Qing dynasty, such as memos and local gazettes. The reconstructed time series were used to analyse variations in winter temperature in South China. Significant interannual and interdecadal changes were found. The maximum temperature difference between neighbouring years was 3.1 °C for 1958–2009 and 3.0 °C for 1736–1957, whereas the maximum temperature difference between adjacent decades was 0.8 °C for the 1960s–2000s and 0.6 °C for the 1740s–1950s. The 2000s was the warmest decade; the mean temperature was 1.6 °C higher than that of the 1870s, which was the coldest decade between the 1740s and the 2000s. The mean winter temperature was warmer in the 18th and 20th centuries and coldest in the 19th century.     

Lateral dynamic response of a pipe pile in saturated soil layer

This paper presents an analytical solution for the lateral dynamic response of a pipe pile in a saturated soil layer. The wave propagations in the saturated soil and the pipe pile are simulated by Biot's three‐dimensional poroelastic theory and one‐dimensional elastic theory, respectively. The governing equations of soil are solved directly without introducing potential functions. The displacement response and dynamic impedances of the pipe pile are obtained based on the continuous conditions between the pipe pile and both the outer and inner soil. A comparison with an existing solution is performed to verify the proposed solution. Selected numerical results for the lateral dynamic responses and impedances of the pipe pile are presented to reveal the lateral vibration characteristics of the pile‐soil system. Copyright © 2015 John Wiley & Sons, Ltd.     

钴—5—Br—PADNm络合物的光度性质研究及其应用

本文研究了钴(Ⅱ)-5-Br-PADNm络合物的光度性质。在pH5.0缓冲溶液中,有TritonX-100存在时,Co~(2 )与5-Br-PADNm形成1:2红色络合物,λ_(max)为547nm,ε为1.35×10~5l·mol~(-1)·cm~(-1)。所提出的方法用于矿石及茶叶中Co的测定,得到满意结果。