三个二次代数曲面的低次拼接

用计算机代数方法，研究了三个二次曲面的光滑拼接，给出了二次拼接曲面存在的判别方法，及计算拼接曲面的Matlab程序。     

二次与三次曲面存在拼接的条件和算法

利用计算机代数的方法，在数学软件的辅助下，初步研究不同次曲面拼接的问题即二次与三次曲面存在拼接的条件和算法，给出它们在不同情况下的存在拼接曲面的条件和算法。     

3个代数曲面的高光滑拼接

利用计算机代数方法，讨论3个代数曲面的高光滑拼接，并将其转化为求解齐次线性方程组的问题，从而给出3个代数曲面GC^2拼接的条件．在数学软件的辅助下，给出具体实例．     

基于CORS的DInSAR大气延迟校正方法研究

针对利用GPS数据改正DInSAR大气延迟误差中存在CORS站点稀疏的问题,给出一种广义曲面拟合插值模型,并基于北京地区的GPS观测数据和SAR影像对比较了反距离加权插值模型（IDW）和曲面拟合插值模型（CSF）用于区域对流层延迟建模的精度,然后对SAR差分干涉图进行大气延迟校正。结果表明,曲面拟合模型比反距离加权模型更能反映区域单差对流层延迟特性,两次实验的插值精度分别达到了7.1和3.5 mm。采用CORS观测数据和曲面拟合内插模型,可有效削弱DInSAR中的大气延迟误差,提高DInSAR测量结果的精度。     

再论DEM精度评定的基本理论问题

数字高程模型(DEM)应用十分广阔。本文通过实际存在的对地面两种不同认识论观点的分析,阐明地面是多个单元曲面,它们是在复杂的地形结构线上拼接而成的确定表面,那种把地面或其局部视为随机曲面的观点不符合人类生活和生产实践;通过对系统误差和偶然误差性质概念和DEM生产过程的分析,指出DEM的总体误差以偶然误差概而论之,完全忽视了内插过程并错判了内插误差的性质;同时,对DEM的偶然误差计算中前提的设置、计算推理链的问题进行一定分析,揭示偶然误差论在实践中难予解脱的困境,并进一步阐述了它对DEM误差检核方法、标准的不良影响和对质量的危害。因此希望重视这一重要理论问题,开展讨论,澄清疑虑,促进问题的解决。     

高精度曲面建模最佳表达形式的数值实验分析

高精度曲面建模的发展过程在理论上可归结为对高斯方程组中单个方程不同组合的数值模拟分析比较和检验过程。数值实验分析结果表明,因有限差分所带来的数值困难,高斯方程组中的交叉项方程是影响高精度曲面建模误差和模拟速度的关键因素,高精度曲面建模的最佳数学表达是除交叉项方程之外的其他两个方程的组合。     

基于Coons曲面的似大地水准面精化算法研究

针对线状或带状GPS水准点控制的似大地水准面,提出Coons曲面内插模型。先将GPS水准点拟合成曲线,再通过曲线构造曲面,尽可能减少传统拟合算法由点直接推面的精度消耗。分别运用最小二乘法、最小二乘配置法、移动内插法和Coons曲面法对线状GPS水准点控制的似大地水准面进行拟合,结果表明,基于Coons曲面的内插模型算法精度最高。     

城市土地信息系统中地籍单元拼接方法探讨

给出了地籍单元拼接的方法,推证了拼接的误差方程式及改化法方程式,总结出了改化法方程式的组成规律。     

偶层位曲面位场数据处理及转换方法

本文在文献［１］［２］的基础上，进一步完善了偶层位曲面位场数据处理及转换方法。克服了三角函数曲面位场数据处理及转换方法不能适应于所有＂强地形＂的弱点。提出了曲面位场处理及转换的两个基本类型（纯位场型和磁力场型）及其相应的计算公式；提出了简单快速的数值积分方法；提出了分块处理技术。编制了相应方法软件，并通过理论模型试算和实际资料处理，检验了方法的正确性和有关技术措施的有效性。该套方法软件具有适应性强，计算速度快和精度高等特点。     

运用Geomagic Studio实现点云数据的曲面重建及误差分析

曲面重建是逆向工程的关键,为了评定曲面重建的精度要进行相应的误差分析。研究基于三维激光扫描仪获取得到的某塑像表面完整点云数据,运用Geomagic Studio软件对点云数据经过三角网格化、曲面划分等处理构建精确曲面,从而实现此塑像表面的重建。为对重建的曲面进行误差分析,通过平面拟合方程系数以及平面拟合的中误差,验证Geomagic Studio软件中的标准偏差即是测量中由残差计算得到的中误差,进而通过Geomagic Studio软件得到所建模型与点云的标准偏差,实现曲面重建的误差分析。     

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基于移去-恢复法的局部似大地水准面精化模型对比研究

针对似大地水准面在精化过程中不同移去-恢复高程转换模型的适用性和选取问题,基于二次曲面和EGM2008重力场模型,分别构建了RBF神经网络、多面函数和Shepard等3种类型的移去-恢复模型,结合平原和高原山区两个工程实例,通过调整高程拟合点数目进行似大地水准面拟合与精度对比。结果表明,在平原地区,EGM2008-多面函数高程模型精度略优于其他模型;在高原山区,当拟合点数较少时,基于EGM2008的移去-恢复模型精度高于基于二次曲面的移去-恢复模型,其中,EGM2008-多面函数和EGM2008-Shepard较优,而随着拟合点数目的增加,二次曲面-Shepard高程转换模型的精度优于其他模型。     

On the existence of an optimal control of ship automatic steering instruments

The existence of linear quadratic optimal control of ship automatic steering instruments is studied. Firstly, the sufficient conditions for the quadratic integrability of the solutions of linear second order time-variant differential equations are developed. Secondly, the optimal control form of the ship automatic steering instrument is obtained by using the dynamic programming method, which guarantees a minimal ship sway range, during long-distance navigation, by using as little energy as possible. Finally, based on the above mentioned sufficient conditions, the conditions for the realization of optimal control are obtained, which provides a foundation for choosing the weighted coefficients for optimal control in engineering.     

Review of Global Ocean Intermediate Water Masses： 1. Part A, the Neutral Density Surface （the ＇McDougall Surface＇ ） as a Study Frame for Water-Mass Analysis

This review article commences with a comprehensive historical review of the evolution and application of various density surfaces in atmospheric and oceanic studies. The background provides a basis for the birth of the neutral density idea. Attention is paid to the development of the neutral density surface concept from the nonlinearity of the equation of state of seawater. The definition and properties of neutral density surface are described in detail as developed from the equations of state of seawater and the buoyancy frequency when the squared buoyancy frequency N2 is zero, a neutral state of stability. In order to apply the neutral density surface to intermediate water-mass analysis, this review also describes in detail its practical oceanographic application. The mapping technique is focused for the first time on applying regularly gridded data in this review. It is reviewed how a backbone and ribs framework was designed to flesh out from a reference cast and first mapped the global neutral surfaces in the world＇s oceans. Several mapped neutral density surfaces are presented as examples for each world ocean. The water-mass property is analyzed in each ocean at mid-depth. The characteristics of neutral density surfaces are compared with those of potential density surfaces.     

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Review of Global Ocean Intermediate Water Masses: 1.Part A, the Neutral Density Surface (the ‘McDougall Surface’) as a Study Frame for Water-Mass Analysis

1Preface Todescribeoceanicintermediatewatermasses,itis necessarytohaveawell definedstudyframeorsurfacebecauseofthefluctuationnatureofintermediatewa ters.Itiswellunderstoodthatoceanicwater mass mixingdoesnotalignwitheitheraconstantgeopoten tialdepthorapropertysurfacesuchastemperature,salinity,pressureanddensitysurfacesbutfollowsa neutraldensitysurface.Thisisbecauseawaterparcelmovesasmalldistanceisentropicallyandadiabaticallyontheneutraldensitysurfacewithoutdoingworka gainstabuoyantrestoringforc…     

Modeling all-sky global solar radiation using MODIS atmospheric products: A case study in Qinghai-Tibet Plateau

The surface solar radiation(SSR) is of great importance to bio-chemical cycle and life activities.However,it is impossible to observe SSR directly over large areas especially for rugged surfaces such as the Qinghai-Tibet Plateau.This paper presented an improved parameterized model for predicting all-sky global solar radiation on rugged surfaces using Moderate Resolution Imaging Spectroradiometer(MODIS) atmospheric products and Digital Elevation Model(DEM).The global solar radiation was validated using 11 ob...