基于全球MGEX数据的北斗导航星座精密轨道确定     

李冉  赵春梅  郑作亚  何正斌 《大地测量与地球动力学》2015,35(4):662-665

利用全球分布的MGEX站观测数据,使用"两步法"以双差方式对北斗卫星进行精密定轨。主要研究北斗卫星轨道确定的处理策略,重点分析轨道确定的流程,并通过实验评价了3种不同类型轨道的精度。结果显示,MEO和IGSO卫星的定轨内符合精度优于0.2m,其中径向优于10cm,外符合精度优于30cm;GEO(以C05号为例)卫星外符合精度优于0.7m,且径向优于10cm。  相似文献   

在SCOUNIX环境下开发实时通信系统     

华英敏 《中国科学院上海天文台年刊》2002,(1)

在SCOUNIX环境下开发实时系统 ,不仅可以利用UNIX的多任务特性 ,建立起高效可靠的系统 ,而且软硬件成本较低 ,还能享有商业软件的技术服务。介绍了基于SCOUNIX环境开发实时通信系统时多路串行通信技术及UDP网络通信技术的应用 ,同时介绍了在系统中如何建立数据日志及监视进程活动  相似文献   

震害现场紧急卫星通讯系统的研究和建设     

张建华  赖锡安  吴亚明  陈文明 《大地测量与地球动力学》1993,(4)

本文研究了应用VSAT技术建立大震现场紧急通讯系统的设计和实施方案,规定了该系统应实现的功能。在此基础上,提出了建立我国未来陆地地震救灾移动卫星通讯计划,并对一些关键技术和为移动用户可能提供的通讯业务进行了讨论。  相似文献   

利用黄河泥沙围出“渤海湖”的初步设想   总被引：1，自引：0，他引：1  

郝戬 《地球信息科学学报》2001,3(3):76-79

本文是一个关于将渤海变成淡水湖的水利工程的构想。让黄河的大量泥沙通过人工导流的方式沿莱州湾南岸与渤海海峡沉积延伸,产生的陆地将渤海封闭并逐渐形成淡水湖。这一工程将陆地连接山东半岛与辽东半岛,并为华北提供巨大淡水库,具有显著的经济、生态效益。具体实施上,可通过两道渔网式围栏促使黄河泥沙定点沉积并阻挡浪潮侵蚀,通过加强汛期水量增加黄河口泥沙。  相似文献   

Theorizing the digital divide: Information and communication technology use frameworks among poor women using a telemedicine system     

Melissa R. Gilbert  Michele Masucci 《Geoforum》2008,39(2):912-925

  相似文献   

室内可见光通信频域均衡技术DSP方法对比分析     

张士灏  汤璇  林邦姜  张敏  李艺伟 《南京气象学院学报》2017,9(2):210-213

对3种室内可见光通信传输技术的数字信号处理方法（DSP）,包括正交频分复用（OFDM）、单载波频域均衡（SCFDE）与单载波频分复用（SCFDM）进行了对比分析.通过峰值功率比（PAPR）和计算复杂度比较了3种方法的优劣.分析结果表明,SCFDE和SCFDM具有较低的PAPR,但SCFDM计算复杂度较高.此外,还使用白光LED灯针对3种调制解调方法建立了实验模型.实验结果表明,在VLC传输系统中,由于低PAPR特性,使得SCFDE和SCFDM在误码率（BER）和Q值方面的性能优于OFDM.  相似文献   

青藏高原史前时期交流路线及其演变     

侯光良  兰措卓玛  朱燕  庞龙辉 《地理学报》2021,76(5):1294-1313

欧亚大陆史前文化交流是当前学术界研究的热点问题,尤其是“一带一路”的国家倡议提出后,青藏高原重要的地理位置确定了其在东西方文化交流中的重要地位。本文基于自然地理因子和不同时期遗址点,在最低成本的控制下实现节点间累积联结的方法,使用GIS（R语言）工具进行空间数值计算,将其结果作为史前时期（新石器—青铜时期)的交流路线。本文重建新石器时期路线27条,总距离约为6000 km;青铜时代30条,总距离约为7800 km。路线的形态由新石器时期的东北—东部—东南—西南边缘呈月牙形环绕发展至青铜时期的由边缘延伸至腹地呈网络化发展的趋势,这是由高原边缘的交流逐步演化成边缘—腹地的交流、并不断强化的表现。重建路线验证了由考古证据支持的农业、驯化动物、彩陶、青铜技术在高原的传播路线,并将其具体化。此外,明确了高原史前交流路线的发展和演变宏观上是受到气候变化的影响,同时受到种植农业技术、驯化动物的传入以及战争等多因素的综合影响。  相似文献   

基于空间几何原理的北斗三频IF-PPP建模和验证     

何劢航  孙付平  肖凯  张伦东  朱新慧 《大地测量与地球动力学》2020,40(12):1290-1293

利用空间几何原理推导三频消电离层参数和最小噪声直线空间表达式,采用5个静态观测站和1组实测跑车北斗三频观测数据,对比分析北斗三频消电离层模型与双频消电离层模型PPP精度和收敛速度。结果表明,静态条件下,三频PPP的位置误差为3.75 cm,标准差为2.06 cm,收敛时间为109.6 min,较双频PPP性能分别提升22.3%、19.8%、22.1%;动态条件下,三频PPP的位置误差为15.21 cm,标准差为12.89 cm,较双频PPP性能分别提升42.4%和26.8%,且收敛速度也更优。  相似文献   

Community‐Derived Standards for LA‐ICP‐MS U‐(Th‐)Pb Geochronology – Uncertainty Propagation,Age Interpretation and Data Reporting          下载免费PDF全文

Matthew S. A. Horstwood  George Gehrels  Simon E. Jackson  Noah M. McLean  Chad Paton  Norman J. Pearson  Keith Sircombe  Paul Sylvester  Pieter Vermeesch  James F. Bowring  Daniel J. Condon  Blair Schoene 《Geostandards and Geoanalytical Research》2016,40(3):311-332

The LA‐ICP‐MS U‐(Th‐)Pb geochronology international community has defined new standards for the determination of U‐(Th‐)Pb ages. A new workflow defines the appropriate propagation of uncertainties for these data, identifying random and systematic components. Only data with uncertainties relating to random error should be used in weighted mean calculations of population ages; uncertainty components for systematic errors are propagated after this stage, preventing their erroneous reduction. Following this improved uncertainty propagation protocol, data can be compared at different uncertainty levels to better resolve age differences. New reference values for commonly used zircon, monazite and titanite reference materials are defined (based on ID‐TIMS) after removing corrections for common lead and the effects of excess ²³⁰Th. These values more accurately reflect the material sampled during the determination of calibration factors by LA‐ICP‐MS analysis. Recommendations are made to graphically represent data only with uncertainty ellipses at 2s and to submit or cite validation data with sample data when submitting data for publication. New data‐reporting standards are defined to help improve the peer‐review process. With these improvements, LA‐ICP‐MS U‐(Th‐)Pb data can be considered more robust, accurate, better documented and quantified, directly contributing to their improved scientific interpretation.  相似文献   

Application of ICTs in Airspace Management and Collaborative Decision-Making—Analyzing the Risk Avoidance in the Condition of Risky Weather as an Example     

Du Xinru  Lu Zi 《地球科学进展》2016,31(3):269-276

The application of ICTs makes structural change of the development and effective utilization of airspace. Next generation air transportation system (NextGen) includes new automation concepts with automated information to support the traffic control decision-making. As a result, in the field of academia and industry, air traffic controllers integrate information automatically while making decisions to change the previous manually integrated and decided pattern. The safety ability of airspace is reduced and airspace system is endangered under risky weather conditions of airspace. So there is an urgent demand for new information and communication technologies. The paper is an overview of the information constitution and support of NextGen and provides the study of the development of technique of airspace collaborative decision-makings to confirm the new features based on ICTs. It contains basic application-the input of data and output of the routes of airspace management and collaborative decision-making, and general application-the choose of probability nets of avoiding risky weather, and special application-the affection in the management of the air routes, which are made up of position and direction. The research shows the accurate schedule characteristics of airspace management and collaborative decision-making based on ICTs, which made the space accurate by time accurate. Second, the visualization of airspace management and collaborative decision-making based on ICTs made the maps of flight path under mobile data quickly generated. This could make the fully development and utilization of national airspace, ensure safety, and reduce air traffic controllers’ workload and the costs in delaying and operating in risky weather.  相似文献