解Schr(o)dinger方程的一种修正的Runge-Kutta方法

在经典的四阶Runge-Kutta(简记为RK)方法的基础上,得到一种新的解Schr(o)dinger方程的修正的RK方法,并证明这个方法的代数阶为4.这个方法的稳定性和相性质分析也在本文中给出,新方法的相误差阶为6,耗散误差阶为5,并且通过数值试验证明了新方法的高效性.     

设计与开发大规模倾斜影像数据管理工具

多角度倾斜相机已经成为三维数字城市建设的主要数据获取手段。针对倾斜摄影测量特点,面向海量影像集成处理需求,综合考虑相机成像模型以及影像关联关系,设计与实现了一种大规模倾斜影像数据管理工具,提供了工程管理信息存储、倾斜影像分组浏览、地面覆盖范围计算、目标快速检索等功能。应用实验证明该管理工具能够满足倾斜摄影测量工程管理的实际需求,有效提高了多模式海量影像数据的检索效率。     

基于改进泰勒级数法的总强度磁异常稳健向下延拓

位场向下延拓隶属于经典不适定问题,观测数据中细微的误差在向下延拓过程中都被严重放大,甚至会掩盖真实信息。如何精确地求解总强度磁异常（Bm）在垂直方向的各阶导数,是利用泰勒级数实现稳健向下延拓的关键。为此,本文首先分析了调和函数的相关性质,从理论上证明了Bm为准调和函数的结论,在精确计算各阶垂向导数基础上,提出利用改进泰勒级数实现磁场稳健向下延拓。为降低边界效应对向下延拓计算结果的影响,提出采用半余弦函数对磁场在4个方向上进行平滑扩边处理。通过球体与长方体仿真试验以及航空、船载实测磁场数据对提出方法进行了验证。结论表明,提出的技术方法可实现磁场稳健向下延拓,当观测数据无噪声时,计算结果精度要明显优于现行的FFT法、常规泰勒级数法以及积分-迭代法;当观测数据含有噪声时,本文方法和积分-迭代法计算结果精度相当。     

提高全球导航卫星定位系统精度和稳定性的算法研究

针对地面用户接收机的性能易受各种复杂环境影响的问题,研究了在遮挡、多径等复杂环境下,提高和保持定位精度及稳定性的定位算法。基于RAIM思想,对量测信息进行故障诊断和处理,给出了一种高性能、低复杂度的EKF算法。仿真和试验表明,该算法不但提高了定位的精度,而且具有较强的鲁棒性和较强的工程实用性。     

基于等式的等间隔GM(1,1)模型比较研究

本文归纳了基于等式的2种等间隔GM(1,1)模型,比较了这2种模型与常规模型的精度,算例显示:当发展系数a较小时,3种模型的后验差比值C和小误差概率P的精度一致;当发展系数较大时,基于等式的模型比常规模型的后验差比值C和小误差概率P的精度高,且基于等式的这2种模型的后验差比值C和小误差概率P精度基本相当.     

Computational issues and applications of line-elements to model subsurface flow governed by the modified Helmholtz equation

Two new approaches are presented for the accurate computation of the potential due to line elements that satisfy the modified Helmholtz equation with complex parameters. The first approach is based on fundamental solutions in elliptical coordinates and results in products of Mathieu functions. The second approach is based on the integration of modified Bessel functions. Both approaches allow evaluation of the potential at any distance from the element. The computational approaches are applied to model transient flow with the Laplace transform analytic element method. The Laplace domain solution is computed using a combination of point elements and the presented line elements. The time domain solution is obtained through a numerical inversion. Two applications are presented to transient flow fields, which could not be modeled with the Laplace transform analytic element method prior to this work. The first application concerns transient single-aquifer flow to wells near impermeable walls modeled with line-doublets. The second application concerns transient two-aquifer flow to a well near a stream modeled with line-sinks.     

Estimating evapotranspiration fraction by modeling two-dimensional space of NDVI/albedo and day-night land surface temperature difference: A comparative study

Three simple models estimating the evapotranspiration fraction (EF) were tested, validated and compared with available data from NDVI/albedo and day-night land surface temperature difference (DT). They were analyzed using ground based measurements collected by the energy balance Bowen ratio system at the 11 enhanced facilities located at the Southern Great Planes of the USA between April 2001 and May 2005. One model was superior in predicting the EF. It used an extension of the Priestly-Taylor equation and a relation between the normalized difference vegetation index (NDVI) and DT.     

地震波数值模拟中差分阶数的边界效应

提出了声波正演数值模拟中计算网格间差分阶数(精度)的不衔接而引起的边界反射效应问题,采用不同中心网格有限差分法求解声波波动方程来验证.数值实例分析表明,同差分阶数间不存在任何边界效应,而当差分阶数较低且网格间差分阶数递变较大时,边界效应显著,通过缩小差分网格间的递变阶数并提高相应的离散阶数,可以有效压制该边界效应,并保...     

平移初至点走时动校正反演(英文)

浅层长排列信号在动校正后出现动校拉伸,本文从走时公式的角度深入研究其产生机理,,论证了常规走时公式不能准确描述同一反射子波中所有采样点的走时,建立在子波中心点走时基础上的传统速度分析不能得到准确的动校正速度。通过理论推导重构了同一子波周期中各信号点的走时公式,进而提出基于初至点走时的动校正反演方法,其反演精度相对于传统方法得到了大幅提升。最终采用初至点走时对长排列记录进行整体搬家取得了无拉伸校平的结果,验证了所重构公式的正确性。     

An explicit method for numerical simulation of wave equations: 3D wave motion

In this paper, an explicit method is generalized from 1D and 2D models to a 3D model for numerical simulation of wave motion, and the corresponding recursion formulas are developed for 3D irregular grids. For uniform cubic grids, the approach used to establish stable formulas with 2M-order accuracy is discussed in detail, with M being a positive integer, and is illustrated by establishing second order (M=1) recursion formulas. The theoretical results presented in this paper are demonstrated through numerical testing.