基于普通数字相片的土地信息快速巡查技术

本文通过对普通数字相片上比例尺的变化规律进行理论研究,找出比例尺的变化规律,根据变化规律设计实验标志并进行相关实验,提出了一种快速获取土地面积的计算方法,并用实验数据对比例尺变化规律进行了验证,通过现场实验计算土地面积并总结了一些提高精度的方法。研究结果表明该方法对于快速估算土地面积具有一定的实用性。     

基于Erdas软件对InSAR数据提取DEM的方法

重点介绍了InSAR数据处理的一般步骤、生成DEM的原理,以及其利用ERDAS软件系统提取DEM的过程。应用结果显示利用此软件能够快速有效地提取DEM数据,取得较高的工作效率。     

电厂空冷设计中气象观测和分析原理

阐述了空冷技术发展现状和开展空冷气象观测的原因,介绍了空冷气象观测站的组成、要求和观测内容,以及空冷气象参数对比分析研究的思路和方法,并对风、温度对空冷电厂的影响进行了初步分析.空冷电厂必须在厂址处建立临时气象观测站进行1 a以上的气象观测;空冷气象观测站要按标准规范建站,按电力设计的要求进行不同层次多要素的气象观测;通过厂址气象观测站和临近气象站的对比分析,重建电厂厂址近10 a的气象资料,进行分析研究得出电力设计最终所需的各种气象参数和指标;风和温度是对空冷电厂影响最大的2个气象要素.     

基于偏差原则利用MODIS红外资料反演大气廓线以及表层温度

遥感方程或大气辐射传输方程是属于第一类非线性Fredholm积分方程,这类方程的显著特征是不适定的,尤其此类问题解的不稳定性,增加了反演的难度.因此需要研究控制反演不稳定性和提高反演精度的有效方法.为了使解稳定,光滑参数γ作为约束因子是必要的.文中结合牛顿非线性迭代法反演大气廓线,利用偏差原则来最优选择光滑参数γ,即在同步反演大气廓线的同时对γ采用分步迭代的原则.最后利用中分辨率和成像光谱仪(MODIS)红外资料进行反演试验,反演结果表明采用偏差原则选取γ明显优于经验法,反演的表层温度和大气可降水量与美国国家宇航局(NASA)的MOD07产品类似.     

水准式光电测距三角高程的再认识与反思

传统的水准式光电测距方法存在着理论上的缺陷,这种缺陷导致了测量精度的降低.从球面几何学的原理出发,探讨了水准式光电测距三角高程测量的原理,推导出了光电测距三角高程测量的严密计算公式,给出了水准式光电测距三角高程测量的实用计算公式.     

Ambartsumian’s methods in the theory of radiative transfer

The purpose of this article is to provide some insight into Ambartsumian’s methods in the theory of radiative transfer, their applications, and further development. Two of these methods are emphasized--the invariance principle and the method of addition of layers, proposed by Ambartsumian in the 1940’s. The difference between these methods and the classical approach for solving radiative transfer problems is discussed. We discuss only a small portion of the subsequent work by others that we believe reveals, in a more intuitive way, the essence and significance of Ambartsumian’s methods and their efficiency for applications. Thus, for example, a separate section is devoted to applications of the Lagrangian formalism to radiative transfer and it is shown that the invariance principle is a special case of a more general variational principle that reflects an invariance with respect to translational transformation of the optical depth. Our discussion of the method of addition of layers points out its generality and the major role it has played in the later creation of such methods as Bellman’s invariant imbedding method and the method for solving radiative transfer problems in inhomogeneous media. The latter method has yielded a number of new analytic results. The concluding section is a brief summary of Ambartsumian’s results in the nonlinear theory of radiative transfer, where he was a pioneer in the study of the class of multilevel problems. This article also sets out to demonstrate the place and role of Ambartsumian’s methods in the theory of radiative transfer, which, to a great extent, set the path along which this theory developed for many years to come. Translated from Astrofizika, Vol. 52, No. 1, pp. 5–27 (February 2009).     

杜汉莫尔问题的一个新解答

杜汉莫尔(Duhamel)问题在渗流理论与渗流计算中具有重要理论价值和广泛实用价值.本文给出了杜汉莫尔问题一个新解答;从数学与物理的结合上论证了新解的正确性和优越性;举例说明了新公式的实际应用;对杜汉莫尔定理(古典解),从物理意义上提出了点滴商榷     

序贯平差的稳健化处理

本文从最小二乘贝叶斯原理出发,指出了序贯平差的一般原则,据此平差原理,每组观测可以分别处理,从而很客易应用稳健估计方法获得稳健的序贯解。本文算例说明了可行性。     

A conservative, unconditionally stable, second-order three-point differencing scheme for the diffusion–convection equation

A three-point differencing scheme for the diffusion–convection equation is presented that offers all the advantages of both the central and the one-sided ('upwind') differencing scheme without suffering from their drawbacks. Specifically, the scheme is conservative, unconditionally stable, and second-order-accurate in space. It is free of oscillations and over- or undershoots, simple to code, and requires essentially no more computing time than the one-sided scheme. Although known for a relatively long time in numerical mathematics, the scheme apparently has not received sufficient attention from modellers of hydrothermal systems or contaminant transport in the geosciences. In order to fill this gap a comparison is made between this scheme and the widely used one-sided scheme for the transient diffusion–convection equation in different time discretizations. The results are discussed taking into account other approaches towards minimizing numerical diffusion.