空间圆心确定模型及精度分析

介绍了三点确定圆心和多点平差确定圆心的数学模型方法,提出了数学模型中的一些不足和相应的解决办法,最后通过模拟的数据分析不同的点位分布对三点确定圆心的影响,有利于在实际工作中应用合理的点位分布提高精度。所有的数学模型都经过了VC 编程实现。     

A STORABE PROCESS OF THE MAGNETIC ENERGY RESULTS FROM THE UNSTEADY PLASMA FLOW FIELD IN THE DISTURBANCE REGIONS OF COMETARY TAIL AND ATMOSPHERE

In this paper we discuss coupling processes between a magnetic field and an unsteady plasma motion, and analyze the features of energy storage and conversions in the cometary disturbance regions.     

Improvement of the empirical thermospheric model DTM: DTM94 – a comparative review of various temporal variations and prospects in space geodesy applications

The Drag Temperature Model (1978) has been improved to respond better to the actual requirements of space geodesy, especially under extreme solar and geomagnetic conditions. Extended data and an improved algorithm have been considered, leading to valuable improvements. Temporal variations of temperature of the thermopause, total density and major chemical constituent density are reviewed and compared to the DTM94, DTM78 and MSIS86 models. A comparison with data is performed, giving the mean ratios between observed and model values with their root mean squares for different physical and geometric conditions. This comparison is made for the three models and includes data used in the modelling as well as external data. The limits of the thermosphere modelling are discussed. Received: 3 December 1996 / Accepted: 4 August 1997     

基于剖分的三维拓扑ER模型研究

本文首先分析评述了目前三维ＧＩＳ空间拓扑数据模型研究状况,指出了Ｍａｒｔｉｅｎ Ｍｏｌｅｎｎａｒ的３Ｄ ＦＤＳ．,Ｍｏｒａｋｏｔ Ｐｉｌｏｕｋ等人的基于四面体的三维矢量数据模型等的局限性。继而根据笔者在三维空间实体及其相互间拓扑关系形式化描述方面的研究结果,分析研究了三维空间实体点、线、面、体与构成这些空间实体的ｋ－单纯形（０≤ｋ≤３）之间的实体关系,给出了相应的实体－关系（ＥＲ）图,提出了一个顾     

空间测边交会的直接解法、精度及应用条件

给出空间测边交会的一种无需初值、迭代和多值判断的直接解法 ,证明了现有两个精度估算公式的一致性。提出的空间测边交会取得最优构形的两个必要条件及对其应用条件研究所得的结论对实际工作应用有重要指导意义     

Heating of beam ions by ion acoustic waves

Satellite measurements show that ion beams above the auroral acceleration region are heated to hundreds of eV in a direction perpendicular to the magnetic field. We show that ion acoustic waves may be responsible for much of this heating. Even in the absence of a positive slope in the velocity distribution of the beam ions, ion acoustic waves can be generated by a fan instability. We present analytical estimates of the wave growth rate and ion beam heating rate. These estimates, which are confirmed by particle simulations, indicate that the perpendicular temperature of the beam ions will increase by 30 eV/s, or by 1 eV in 20–25 km. From the simulations we also conclude that the heating saturates at a perpendicular temperature around 200 eV, which is consistent with observations.     

空间物理学的回顾和展望

空间物理学是一门重要的迅速发展的学科。回顾了过去百年中发生的重大空间物理学事件。空间物理学已成功地迈过了探索阶段 ,未来是要搞清一些基本的科学问题。这些问题的解决需要观测研究、理论分析、数值模拟和环境预报的紧密合作 ,才能促成空间物理学的飞跃发展。     

大华北地区地震活动的周期性时空演化特征

本文在对比分析大华北地区第３，４活动期地震时序分布相似性的基础上，提出了活动集的概念。分析认为：这两个活动期在总的时序结构上存在期、集、幕３个层次的相似和对应关系；每个活动期都由前后两个彼此联系密切、又相对完整、演化过程类似的地震活动集组成；两活动期的前集进程一致，但第４活动期的后集要明显比第３活动期的进程快。文中指出，研究区第３，４活动期总的地震空间分布呈一个椭圆环形带，其中第４活动期的环带偏东     

Causal and functional relations in fluvial geomorphology

The concept of causality has been a fundamental principle of scientific investigation for many centuries. Recently, however, there has been a significant reappraisal of the philosophical basis of the concept of causality and this has important implications for future geomorphological research. It is now recognized that there are two approaches to the study of relations between variables. Conventionally knowledge was divided into classes and, on the basis of time precedence, causal relations were defined. While this approach enables static systems to be analysed it does not apply to dynamic systems which exhibit mutual causality. This traditional view of knowledge became obsolete with the introduction of the concept of the continuum. Algebraic techniques now enable the solution of systems of simultaneous equations, provided that there are as many equations as unknowns. Significantly this approach applies to dynamic as well as static systems. Further advances in fluvial geomorphological research are dependent on the adoption of mathematical reasoning. This will concentrate research on the mode and rate of operation of channel processes and feedback mechanisms. Given this information it will be possible to develop a static process-response model to explain and predict channel response to a set of input conditions, and a dynamic model to simulate channel development through time and space.     

等价观测与GPS差分法定位

本文首先利用空间和投影算子的概念证明了等价观测中的部分等价性定理，然后从该定理出发讨论了各种GPS差分定位法的等价性问题并给出了其相应的等价条件。