自聚焦光纤中传导模的场分布     

翁兴涛  余模智  何平安 《武汉大学学报(信息科学版)》1995,(4)

从亥姆霍兹方程出发，导出了自聚焦光纤中传导模在圆柱坐标系中的场分布形式，并给出了几个低阶模的分布图。  相似文献   

1962—1986年JYD1968.0地极坐标的均匀化及其与BIH的比较   总被引：2，自引：0，他引：2  

陆佩珍  须同祺 《测绘学报》1995,24(2):67-72

本文研究了１９６２－１９８６年ＪＹＤ１９６８．０地极坐标均匀中星表系统差，章动系列的变动和光行星常数变动的影响，并将经过改正后的ＪＹＤ１９６８．０地极坐标系统和ＢＩＨ系统作了比较。  相似文献   

Decoupling of the coupled poroelastic equations for quasistatic flow in deformable porous media containing two immiscible fluids   总被引：1，自引：0，他引：1  

Wei-Cheng Lo   《Advances in water resources》2006,29(12):1893-1900

The study of the poroelastic behavior of sedimentary materials containing two immiscible fluids in response to either applied stress or pore pressure change in a quasistatic limit, i.e., negligible second time-derivatives, is of great importance to many hydrogelogical problems, e.g., land subsidence caused by withdrawal of subsurface fluids. The poroelasticity models developed for analyzing these problems feature partial differential equations that are coupled in the terms describing viscous damping and strain field. To determine closed-form analytical solutions for induced volumetric strain (dilatation) of the solid framework and its interaction with fluid flows, the choice of normal coordinates whose transformation can be performed to decouple these poroelastic equations is highly desirable. In this paper, we show that normal coordinates for decoupling these equations are real-valued and equal to three different linear combinations of the dilatations of the solid and the fluids (or equivalently, three different linear combinations of two individual fluid pressures and solid dilatation). In contrast to fully saturated porous media, it is found that the viscous damping effect must be represented in normal coordinates in the presence of the second fluid. The resulting decoupled equations representing independent motional modes are a Laplace equation and two diffusion equations, which can be solved analytically under a variety of initial and boundary conditions. Thus, after inverse transformation of normal coordinates is performed, the closed-form analytical solutions for induced solid volumetric strain and excess pore fluid pressures can be obtained simultaneously from our decoupled partial differential equations.  相似文献   

非结构网格上的三维浅水流动数值模型   总被引：7，自引：3，他引：7       下载免费PDF全文

赖锡军  曲卓杰  周杰  申满斌 《水科学进展》2006,17(5):693-699

针对当前复杂环境水流模拟的需求,建立了新型的基于特征型高分辨率数值算法的三维非结构网格浅水动力模型。模型采用有限体积法离散sigma坐标下的三维浅水方程,运用Roe黎曼近似解评估水平界面通量。模型网格拟合边界能力强,可根据需要局部加密;格式数值性能优良,具有守恒性、单调迎风性、高数值分辨率等特性。同时,应用干湿判别法处理动边界,以适应浅滩地形漫/露过程模拟的需要。封闭水池内部风生环流、干河床上溃坝过程和长江口实际潮流场的模拟从不同侧面展示了模型的特点,结果表明它能够准确地预测水流的三维流动结构,而且计算简单高效,具有良好的数值稳定性。  相似文献   

关于新、旧北京1954坐标系统的转换与应用     

王建国  夏勇  樊朝俊 《现代测绘》2006,29(3):37-37,46

国土部门在北京1954坐标系下,已完成大多数城镇的初始调查工作,并发放了相应的土地证等图件资料。而现在又需要在C级GPS网布设基础控制测量工作,这就产生了它们的坐标转换工作。这里举某市两种坐标转换和比较的实例,以供参考。  相似文献   

地图数字化中基于点位坐标的统一平差模型   总被引：3，自引：0，他引：3  

童小华  杜道生 《武汉大学学报(信息科学版)》2006,31(3):194-198

探讨了地图数字化过程中采用平差方法来建立坐标计算的统一模型。将测得的角度、边长等数据化为方向、距离观测值列立误差方程，通过调用统一的平差迭代计算程序来计算未知点坐标及精度。详细给出了基于平差的11种常用坐标计算方法，并通过实例进行了说明。  相似文献   

高速公路中桩坐标计算及放样方法的探讨     

洪中华  周世健  许亚男  程铭 《北京测绘》2006,(4):50-53

探讨应用Casio-fx4850编程实现现场快速解算任意桩号坐标。最后讨论了实际放样工作中经常遇到的问题与解决办法。  相似文献   

Registration of terrestrial laser scanner data using imagery     

Khalil  Al-Manasir  Clive S.  Fraser 《The Photogrammetric Record》2006,21(115):255-268

  相似文献   

Effect of common point selection on coordinate transformation parameter determination   总被引：2，自引：0，他引：2  

H. S. Kutoglu  P. Vaníček 《Studia Geophysica et Geodaetica》2006,50(4):525-536

The use of satellite positioning techniques commonly requires a transformation from a Conventional Terrestrial coordinate system to a Geodetic coordinate system, or vice versa. For such a transformation, the main problem is the determination of transformation parameters between these coordinate systems. The transformation parameters are estimated by a least-squares process using “common” points, i.e., those points whose coordinates are known in both systems. Therefore, the precision of so estimated transformation parameters is closely related to certain characteristics of the common points. In this contribution, we have formulated some theoretical relations between the transformation parameters and the number and the distribution of common points, and corroborated the theoretical results numerically, using a simulated geodetic network.  相似文献   

WGS-84与地方坐标系转换参数的优化选择     

孙晓光 《测绘与空间地理信息》2007,30(2):152-154

针对GPS动态RTK测量中WGS-84与本地坐标系转换参数的选择进行研究。首先根据稳健估计方法对控制点的精度进行评定,剔除含有粗差的控制点。然后利用概率统计理论对转换参数的优化选择进行分析,确定转换参数最优值。为便于实际应用,编写了转换参数优化选择软件,并将此软件的计算结果应用到实践中,取得较好结果,为证明该方法的可行性提供可靠依据。  相似文献