Pinpointing the sources and measuring the lengths of the principal rivers of the world

Abstract

Cultures throughout the world are associating with the rivers. People depend upon the rivers and their tributaries for food, water, transport, and many other aspects of their daily lives. Unfortunately, human beings have not calculated the accurate lengths for the great rivers even today. The lengths of the rivers are very different in popular textbooks, magazines, atlases and encyclopedias, etc. To accurately determine the lengths of the principal rivers of the world, the combination of satellite image analysis and field investigations to the source regions is proposed in this paper. The lengths of the Nile, Amazon, Yangtze, Mississippi, Yellow, Ob, Yenisey, Amur, Congo and Mekong, with lengths over or close to 5000 km, were calculated using the proposed method. The results may represent the most reliable and accurate lengths of the principal rivers of the world that are currently achievable.     

世纪之交的沉思--论21世纪软科学的发展

软科学这一术语是70年代在国外提出的.然而30多年以来,它在国外不仅未得到普遍的承认,而且对软科学的定义也还未能达成大体上一致的共识.而在改革开放后的中国,出于决策科学化和民主化的需要,经过一些领导人的提倡和支持,特别是通过1986年召开的软科学座谈会及1994年召开的全国软科学工作会议,软科学事业得到了蓬勃的发展.据初步统计,截止1998年底全国共有软科学研究机构1224个,研究人员32655人,初步形成了一支较为强大的研究队伍,并取得了数百项覆盖多个领域的研究成果,为支持各级各类的决策发挥了一定的作用.     

Improving the modeling of the atmospheric delay in the data analysis of the Intensive VLBI sessions and the impact on the UT1 estimates

The very long baseline interferometry (VLBI) Intensive sessions are typically 1-h and single-baseline VLBI sessions, specifically designed to yield low-latency estimates of UT1-UTC. In this work, we investigate what accuracy is obtained from these sessions and how it can be improved. In particular, we study the modeling of the troposphere in the data analysis. The impact of including external information on the zenith wet delays (ZWD) and tropospheric gradients from GPS or numerical weather prediction models is studied. Additionally, we test estimating tropospheric gradients in the data analysis, which is normally not done. To evaluate the results, we compared the UT1-UTC values from the Intensives to those from simultaneous 24-h VLBI session. Furthermore, we calculated length of day (LOD) estimates using the UT1-UTC values from consecutive Intensives and compared these to the LOD estimated by GPS. We find that there is not much benefit in using external ZWD; however, including external information on the gradients improves the agreement with the reference data. If gradients are estimated in the data analysis, and appropriate constraints are applied, the WRMS difference w.r.t. UT1-UTC from 24-h sessions is reduced by 5% and the WRMS difference w.r.t. the LOD from GPS by up to 12%. The best agreement between Intensives and the reference time series is obtained when using both external gradients from GPS and additionally estimating gradients in the data analysis.     

Movements of the protoplanetary superconducting particles in the magnetic field of the Saturn lead to the origin of the rings

In this letter, we are trying to resolve the electromagnetic problem for the movements of the superconducting particles of the protoplanetary cloud in the magnetic field of Saturn. The force of levitation (Meissner-Ochsenfeld phenomenon) is introduced to the field of planetary science for the first time. It is shown from our theoretical analysis that rings of Saturn might have a superconducting origin, and rings might levitate within magnetic equator plane of the planet.     

省直管市（县）体制下建设用地监管技术研究

面向解决省直体制下市（县）建设用地管理业务监管难度大问题,研究建设用地全过程监管关键技术,设计该模式下的监管模式、技术架构、业务模型和数据模型,实现省直管市（县）模式下的建设用地批前、批中、批后＂批-供-用-补-查-登＂全过程监管。     

GPS整周模糊度确认中残差二次型次小与最小之差的分布问题

根据残差二次型次小与最小之差进行整周模糊度确认的关键是差值的分布,只有得到了合理的差值分布才可确定合理的界值.文中基于原有的两种方法及这两种方法的不足,从理论上导出了满足条件的差值分布,并作了一定的说明.     

跟踪世界发展动态 致力地球重力场研究

比较系统、扼要地叙述了笔者所在单位40余年来坚持跟踪世界发展动态，致力于地球重力场理论和方法的研究，并从教学和生产需要出发，在地球重力场研究方面所获得的一些有理论意义和实用价值的成果。     

国家一等水准网复测高程变化分析及其成果使用

分析国家一等水准网点复测高程的变化量值与分布特征以及导致高程变化的原因，对现有国家水准网点高程的使用提出建议。     

试论高技术局部战争条件下的军事地理研究

本文以现代战争的特点、军事思想和军事理论的发展变化为指导，对高技术局部战争条件下军事地理研究内容、技术手段、方法等方面的变化和发展方向进行了探索性研究。     

工程摄影测量中交向摄影的精度分析

本文从理论上推导了工程摄影测量中交向摄影方式各元素影响物点坐标精度的严密公式,并根据理论分析的结果,采用先进的数码相机和量测相机进行了一定的试验,在仔细分析试验结果的基础上,找出了工程摄影测量中交向摄影最佳的交向角、摄影基线、摄影距离和摄影比例尺等参数,对物点坐标总精度的影响规律。实际作业中,要使最佳交向摄影方式获得最理想的点位精度,所总结出的结论是可行的。     

圆形标志及其椭圆构像间中心偏差的确定

当目标面与像片平面不平行时,圆形标志的像将为椭圆,椭圆的中心与标志中心的像存在偏差。当标志较大时,此偏差将显著影响求解的精度。揭示了偏差的方向性,导出了求解偏差的方程,给出了偏差的解算步骤     

论柴达木盆地成图的数学基础

本文从柴达木盆地石油地质勘探成图的实际需要出发,提出用兰勃脱正轴等角割圆锥投影取代高斯投影,从而解决了柴达木盆地成图坐标系统不统一的矛盾,有利于盆地的石油地质勘探的整体设计规划。     

On the rotation of the Earth and the terrestrial reference system

The Working Group on the Rotation of the Earth was established in 1978 and developed a programme of international collaboration to Monitor Earth-Rotation and Intercompare the Techniques of observation and analysis (MERIT). The MERIT Short Campaign was held in 1980 to test and develop the organisational arrangements required during the MERIT Main Campaign in 1983–4. The Working Group on the Terrestrial Reference System was established in 1980 to prepare a proposal for the establishment and maintenance of a new Conventional Terrestrial Reference System (COTES) that would be based on the new techniques of space geodesy. The Working Groups collaborated closely and organised two intensive campaigns in 1984 and 1985 that were aimed primarily at determining the relationships between the reference systems of the six different techniques that were used to determine earth-rotation parameters. Observational data were obtained from 35 countries; analyses and intercomparisons of the results were carried out in 7 countries. The Working Groups reviewed the results at the Third MERIT Workshop and recommended that a new International Earth Rotation Service be set up in 1988 and that it be based on the use of very-long-baseline radio interferometry and both satellite and lunar laser ranging.     

多边形直角房屋外墙体一半面积计算模型的研究

在不动产测量中,计算外墙体一半面积的数学模型,只有针对四边形直角房屋的数学模型,而对于多边形直角房屋计算外墙体一半面积的数学模型还没有发现,这给分析多边形直角房屋外墙体一半面积的精度带来困难,本文通过研究分析,推导出了多边形直角房屋外墙体一半面积的数学模型,供研究面积精度者参考。