GPSurvey软件利用地方坐标系坐标作为GPS网约束平差条件的探讨

通过在GPSurvey软件中设置投影参数,可以利用地方坐标系坐标作为GPS网约束平差条件,即可直接获得和已知点相统一的地方坐标系坐标。     

THE FORMATION MECHANISM OF CONCENTRIC DOUBLE EYE WALL TYPHOON—PART Ⅰ: DYNAMICAL ANALYSIS*

The strong vortex will mutually adjust the thermodynamic field and dynamic field to a state of gradient balance whilst forced by an external cold source,namely,the gradient adjustment process,in which a linearized two-layer model is dealt with in this paper.The analyses show that on account of the heterogeneous radial distribution of the cold source,the adjustment of the thermodynamic and dynamic fields results in the two-peak tangential wind feature,which is analogous to the character of concentric double eyewalls in the strong typhoon.Consequently,the gradient adjustment may be one possible mechanism for the formation of a concentric double-eye typhoon.     

Impact of hydroelectric power releases on the morphology and sedimentology of the bed of the Warche River (Belgium)

The Butgenbach dam on the Warche River was built in 1932 in order to maintain a suf?cient supply of water to the Robertville reservoir situated 7 km downstream, for the production of hydroelectricity. During winter months, releases are made almost every day from the Butgenbach dam. From a hydrological point of view, this has resulted in signi?cantly reducing the number of discharges that are higher than bankfull. Despite the reduction in peak discharge, there is a signi?cant increase in the number of ef?cient discharges (0·6 bankfull). The impacts of these hydrological modi?cations on the bed morphology and sedimentology below the Butgenbach dam have been studied and the following geomorphological modi?cations have been identi?ed: a doubling of the width of the channel in 45 years, a reduction in the number of rif?es and pools, an increase in the number of gravel bars and islets and an increase in bedrock outcrops in the channel. Moreover, the ?nest bed particles are mobilized by the almost daily releases, inducing a signi?cant increase in bed‐material size sorting. The reduction of sinuosity and the disappearance of bed differentiation and rif?e/pool sequences have produced a diminution of bed roughness and an increase of the competence of the river. Thus relatively small ?oods can remove the armoured layer. Copyright © 2003 John Wiley & Sons, Ltd.     

Flume experiments on the horizontal stream offset by strike‐slip faults

Flume experiments, in which the middle section of an erosion channel is displaced horizontally, have been conducted to assess the response of streams to horizontal displacement by a strike‐slip fault. The experimental erosion channel was developed in a mixture of sand and clay, which provided relatively stable banks with its cohesiveness. Horizontal displacement of a strike‐slip fault perpendicular to the channel is expected to add a ?at section to its longitudinal pro?le along the fault line. The experimental stream eliminated this ?at section with downstream degradation, upstream aggradation, and lateral channel shift. As a result, a roughly continuous longitudinal pro?le was maintained. This maintenance of a continuous longitudinal pro?le along channel is considered to be the principle of stream response to horizontal displacement by a strike‐slip fault. Downstream degradation was the dominant process of this stream response in the overall tendency of erosion without sand supply. When the rate of fault displacement was low (long recurrence interval), the experimental stream eroded the fault surface, jutting laterally into the channel like a scarp, and de?ected the channel within the recurrence interval. This lateral channel shift gave some gradient to the reach created by fault displacement (offset reach), and the downstream degradation occurred as much as completing the remaining longitudinal pro?le adjustment. When the rate of fault displacement was high (short recurrence interval), the lateral erosion on the ?rst fault surface was interrupted by the next fault displacement. The displacement was then added incrementally to the existing channel offset making channel shift by lateral erosion increasingly dif?cult. The channel offset with sharp bends persisted without much modi?cation, and downstream degradation and upstream aggradation became evident with the effect of the offset channel course, which worked like a dam. In this case, a slight local convexity, which was incidentally formed by downstream degradation and upstream aggradation, tended to remain in the roughly continuous longitudinal pro?le, as long as the horizontal channel offset persisted. In either case, once the experimental stream obtained a roughly continuous gradient, further channel adjustment seemed to halt. Horizontal channel offset remained to a greater or lesser extent at the end of each run long after the last fault displacement. Copyright © 2004 John Wiley & Sons, Ltd.     

放牧和围封下霸王灌丛对土壤肥力的影响

对阿拉善退化荒漠草地恢复过程中霸王灌丛对土壤肥力的影响进行了研究。结果显示:(1)霸王灌丛对土壤的C、N、P有明显的富集,灌丛下的影响主要发生在0～10cm土层,而灌丛根部对10～20cm的土层也有影响。(2)放牧和围封显著影响着霸王灌丛根部和灌丛下的土壤肥力,土壤有机C、全N、全P均为围封6a>围封2a>自由放牧,pH值为围封6a<围封2a<自由放牧;放牧和围封也显著影响着灌丛根部和灌丛下的土壤养分富集率,土壤有机C、全N、全P的富集率均为围封6a>围封2a>自由放牧。(3)霸王灌丛生物量与灌丛根部、灌丛下土壤有机C、全N和全P的含量呈显著的正相关,与pH值呈显著的负相关,而与灌丛间地的土壤有机C、全N、全P和pH值没有明显的相关关系。     

Evolution of soil properties on stabilized sands in the Tengger Desert, China

The spatial and temporal patterns of pedogenesis on stabilized dunes at Shapotou, northwestern China, were studied on the time sequences of 0, 18, 35 and 43 years. The spatial pattern of soil formation was estimated by measuring the thickness of accumulated sand fractions on the stabilized dune surface and by analyzing the characteristics and properties of soil. The results showed that the environment of soil formation and circulation of soil material were influenced in the processes of shifting-sand fixation, and the mean soil particle size changed from >0.2 to <0.08 mm in 0–20 cm soil depth with the succession from cultivated plants to natural vegetation. The capacity of available soil water increased fivefold. Deep infiltration of water in soil no longer occurred due to the increase in soil water capacity and the change of redistribution of soil water in profiles. Soil microorganisms evolved from simple to complex. Interaction of these processes obviously brought about accumulation of soil fertility, evolution of soil profiles and development of the profiles towards aripsamments. The difference of micro-topography is closely related to redistribution of material and energy in soil formation.     

广义非线性最小二乘测量参数平差的快速差分迭代解算

针对数字化建设中涉及的多类型、多精度、多源、动态非线性最小二乘测量参数平差问题,提出了一种新的解算模型。该模型通过构造适当的差分点列,避免了一阶或二阶导数计算,对于模型复杂或者导数不存在的函数模型而言,具有适应面广、算法简单等特点,为广义非线性数据处理中的参数估计问题的解决开拓了又一新的思路。     

基于星间相对测距的卫星自主定位

利用导航星座卫星之间的无线电测距可实现卫星网整网定位，有效地提高定位精度和减轻地面站的负担，文章对这一方法进行了描述，在此基础上进行数学模型的建立，建模时分别考虑了卫星位置拳数有无验前统计特性两种情况进行网平差处理，在理论上得出了解算结果，对未知参数给出了估计。     

一种GPS网三维平差的数学模型

本文采用带约束条件的间接平差法，给出了取空间直角坐标（Ｘ，Ｙ，Ｚ）为未知参数的ＧＰＳ网三维平差的数学模型。这种模型既便于将ＧＰＳ网的平面部分与高程部分分别处理，又便于对一些理论和实际问题进行分析和研究，此外，文中还对求解方法作了必要的说明，并且简要地介绍了按这各模型研制的软件系统。     

高斯平面上GPS工程网数据处理

结合工程控制网的特点，给出高斯平面上GPS工程网数据处理的数学模型，对提高网的精度进行探讨，编写的软件对某GPS工程网进行数据处理与分析。