黄土高原降水计算插值与插值计算结果的对比分析

　收集黄土高原及周边地区74 个气象站1952 —2001 年降水数据, 用ArcGIS913 普通克里金(ordinary kriging) 插 值法采用计算插值(calculate then interpolate , CI) 和插值计算(interpolate then calculate , IC) 的方法生成黄土高原地区 1952 —2001 年50 a 平均年降水量和年降水量线性趋势系数空间分布表面, 并对其进行统计分析和地形分析。结果 表明: 1) 从插值结果统计值看, CI、IC 法生成的黄土高原地区50 a 平均年降水量和线性趋势系数空间分布表面平 均值分别为421165、421156 mm和- 01541 0、- 01423 1 mm/ a , 相似系数分别为99178 %和95199 % , 二者一致性良好; 2) 从插值结果表面光滑度看, IC 法稍优于CI 法,借用地形分析对生成表面进行坡度、坡向运算, 可作为评价表面 光滑度、空间数量变化特征和空间方向变化特征的直观方法; 3) 黄土高原地区50 a 平均年降水量具有东南多西北 少、南多北少、东多西少的分布规律, 其中服从东南西北、南北和东西方向递减的地带性分布规律区域占黄土高原 地区面积的89134 % , 非地带性分布规律区域占10166 %; 4) CI 和IC 法计算的黄土高原地区1952 —2001 年降水线 性趋势系数平均- 01541 0 和- 01423 1 mm/ a ,黄土高原地区年降水量有明显减少趋势。

土壤稳定入渗速率空间插值不确定性研究

以黄土丘陵沟壑第三副区的藉河流域为研究区,根据65个实测点数据,采用普通克里格法、反距离权重法、样条函数法等插值方法,分析了测点数量变化、栅格像元尺寸变化及插值方法的差异对土壤稳定入渗速率空间插值结果的影响,剖析了空间插值中的不确定性。结果表明:(1)参与插值站点越多,所得插值结果不确定性越小;(2)像元尺寸在25~800 m间变化对土壤稳定入渗速率的插值结果影响微弱;(3)不同插值方法对插值结果的精度影响较大,说明插值方法的差异对插值结果的不确定性有较大影响。

陕西省水蚀土壤因子指标插值方法比较研究

基于地统计学原理和半变异理论,采用地理信息系统技术定量研究了陕西省水蚀土壤因子指标的空间变异特征。分析比较了反距离权重法、样条函数法与普通克吕格法对陕西省土壤因子指标空间插值的精度。结果表明,研究区土壤抗冲系数具有中等强度的空间相关性,块金系数为32.29%,而稳渗速率、崩解速率、抗剪强度均表现为强烈的空间相关性,块金系数分别为13.19%,11.61%和12.98%。综合考虑平均相对误差、均方差及插值效果,认为普通克吕格法最好,更能反映土壤参数的空间特征并符合区域水土流失模型对数据的要求。对于普通克吕格法,稳渗速率的Lag步长为30 000 m,半方差理论模型为指数模型;抗冲系数、崩解速率、抗剪强度的Lag步长为55 000,半方差理论模型均为高斯模型。在空间分布上,各指标随土壤类型由北到南呈现明显的地带性规律。

Spatial distribution of soil heavy metal pollution estimated by different interpolation methods: Accuracy and uncertainty analysis

Mapping the spatial distribution of contaminants in soils is the basis of pollution evaluation and risk control. Interpolation methods are extensively applied in the mapping processes to estimate the heavy metal concentrations at unsampled sites. The performances of interpolation methods (inverse distance weighting, local polynomial, ordinary kriging and radial basis functions) were assessed and compared using the root mean square error for cross validation. The results indicated that all interpolation methods provided a high prediction accuracy of the mean concentration of soil heavy metals. However, the classic method based on percentages of polluted samples, gave a pollution area 23.54-41.92% larger than that estimated by interpolation methods. The difference in contaminated area estimation among the four methods reached 6.14%. According to the interpolation results, the spatial uncertainty of polluted areas was mainly located in three types of region: (a) the local maxima concentration region surrounded by low concentration (clean) sites, (b) the local minima concentration region surrounded with highly polluted samples; and (c) the boundaries of the contaminated areas. (C) 2010 Elsevier Ltd. All rights reserved.

A high-speed image sensing technique with adjustable frame rate based on an ordinary CCD

In the sinusoidal phase modulating interferometer technique, the high-speed CCD is necessary to detect the interference signals. The reason of ordinary CCD's low frame rate was analyzed, and a novel high-speed image sensing technique with adjustable frame rate based on ail ordinary CCD was proposed. And the principle of the image sensor was analyzed. When the maximum frequency and channel bandwidth were constant, a custom high-speed sensor was designed by using the ordinary CCD under the control of the special driving circuit. The frame rate of the ordinary CCD has been enhanced by controlling the number of pixels of every frame; therefore, the ordinary of CCD can be used as the high frame rate image sensor with small amount of pixels. The multi-output high-speed image sensor has the deficiencies of low accuracy, and high cost, while the high-speed image senor with small number of pixels by using this technique can overcome theses faults. The light intensity varying with time was measured by using the image sensor. The frame rate was LIP to 1600 frame per second (f/s), and the size of every frame and the frame rate were adjustable. The correlation coefficient between the measurement result and the standard values were higher than 0.98026, and the relative error was lower than 0.53%. The experimental results show that this sensor is fit to the measurements of sinusoidal phase modulating interferometer technique. (c) 2007 Elsevier GmbH. All rights reserved.

农田土壤特性的空间变异性及Kriging估值法

以自相关和半方差函数对 40 m× 45m面积内的 90个点进行了土壤容重、田间持水量的空间变异性研究。结果表明 ,土壤特性表现出空间变异结构 ,但不是完全的随机变异 ,在一定范围内存在着空间相关现象 ,且空间结构无明显的方向 ,并对以空间变异结构为基础的 Kriging估值法作了探讨 ,其较普通平均法估值精度高。

The cellular structure of a two-dimensional H2/O2/Ar detonation wave

In this paper, the cellular structure of a two-dimensional detonation wave in a low pressure H2/O2/Ar mixture calculated with a detailed chemical reaction model, high order scheme and high resolution grids is investigated. The regular cellular structure is produced about 1 ms after introducing perturbations in the reaction zone of a steady one-dimensional detonation wave. It is found from the present resolution study that the discrepancies concerning the structure type arising from the coarser grid employed can be resolved using a sufficiently fine grid size of 0.05 mm and below and shows a double-Mach-like strong-type configuration. During the structure evolution process, the structure configuration does not change much in the periods before and after the triple point collision. Through the triple point collision, three regular collision processes are observed and are followed by a quick change to the double-Mach-like configuration. The simulated structure tracks show that there are three different tracks associated with different triple points or the kink on the transverse wave. Comparisons with previous work and experiments indicate the presence of a strong structure for an ordinary detonation.

The Structure and Evolution of a Two-Dimensional H2/O2/Ar Cellular Detonation

This paper reports on two-dimensional numerical simulation of cellular detonation wave in a / / mixture with low initial pressure using a detailed chemical reaction model and high order WENO scheme. Before the final equilibrium structure is produced, a fairly regular but still non-equilibrium mode is observed during the early stage of structure formation process. The numerically tracked detonation cells show that the cell size always adapts to the channel height such that the cell ratio is fairly independent of the grid sizes and initial and boundary conditions. During the structural evolution in a detonation cell, even as the simulated detonation wave characteristics suggest the presence of an ordinary detonation, the evolving instantaneous detonation state indicates a mainly underdriven state. As a considerable region of the gas mixture in a cell is observed to be ignited by the incident wave and transverse wave, it is further suggested that these two said waves play an essential role in the detonation propagation.

Experimental Study on the Thermal Argon Plasma Generation and Jet Length Change Characteristics at Atmospheric Pressure

The generation, jet length and flow-regime change characteristics of argon plasma issuing into ambient air have been experimentally examined. Different torch structures have been used in the tests. Laminar plasma jets can be generated within a rather wide range of working-gas flow rates, and an unsteady transitional flow state exists between the laminar and turbulent flow regimes. The high-temperature region length of the laminar plasma jet can be over an order longer than that of the turbulent plasma jet and increases with increasing argon flow rate or arc current, while the jet length of the turbulent plasma is less influenced by the generating parameters. The flow field of the plasma jet has very high radial gradients of plasma parameters, and a Reynolds number alone calculated in the ordinary manner may not adequately serve as a criterion for transition. The laminar plasma jet can have a higher velocity than that of an unsteady or turbulent jet. The long laminar plasma jet has good stiffness to withstand the impact of laterally injected cold gas and particulate matter. It could be used as a rather ideal object for fundamental studies and be applied to novel materials processing due to its attractive stable and adjustable properties.

非均质多孔介质特征参数的描述方法及应用

用地质统计学中有代表性的普通Kriging法和对数正态Kriging法对某油田P油层的渗透率、孔隙度和有效厚度等特征参数进行了分析。通过比较两种计算方法的特征参数结果，发现这两种地质统计学方法在描述油藏多孔介质的非均质性方面各有各的适用范围。普通Kriging法更适合于特征参数呈正态分布关系的情况，对数正态Kriging法更适合于特征参数呈非正态分布关系的情况。这为非均质油藏的油藏描述方法提供了合理的判据，为非均质多孔介质中流体流动规律的研究提供了有力基础。

Water Content Distribution in the Surface Layer of Maoping Slope

The water content distribution in the surface layer of Maoping slope has been studied by testing the water content at 31 control sites. The water content profiles at these sites have also been determined. The water content distributions at different segments have been obtained by using the Kriging method of geostatistics. By comparing the water content distributions with the landform of the slope, it was shown that the water content is closely dependent on the landform of the slope. The water content distribution in the surface layer provided a fundamental basis for landslide predication and treatment.

Computation of stress intensity factors by the sub-region mixed finite element method of lines

Based on the sub-region generalized variational principle, a sub-region mixed version of the newly-developed semi-analytical 'finite element method of lines' (FEMOL) is proposed in this paper for accurate and efficient computation of stress intensity factors (SIFs) of two-dimensional notches/cracks. The circular regions surrounding notch/crack tips are taken as the complementary energy region in which a number of leading terms of singular solutions for stresses are used, with the sought SIFs being among the unknown coefficients. The rest of the arbitrary domain is taken as the potential energy region in which FEMOL is applied to obtain approximate displacements. A mixed system of ordinary differential equations (ODEs) and algebraic equations is derived via the sub-region generalized variational principle. A singularity removal technique that eliminates the stress parameters from the mixed equation system eventually yields a standard FEMOL ODE system, the solution of which is no longer singular and is simply and efficiently obtained using a standard general-purpose ODE solver. A number of numerical examples, including bi-material notches/cracks in anti-plane and plane elasticity, are given to show the generally excellent performance of the proposed method.

The mixed-type integral equations for transient elastodynamic plane crack problems

In the present paper, by use of the boundary integral equation method and the techniques of Green fundamental solution and singularity analysis, the dynamic infinite plane crack problem is investigated. For the first time, the problem is reduced to solving a system of mixed-typed integral equations in Laplace transform domain. The equations consist of ordinary boundary integral equations along the outer boundary and Cauchy singular integral equations along the crack line. The equations obtained are strictly proved to be equivalent with the dual integral equations obtained by Sih in the special case of dynamic Griffith crack problem. The mixed-type integral equations can be solved by combining the numerical method of singular integral equation with the ordinary boundary element method. Further use the numerical method for Laplace transform, several typical examples are calculated and their dynamic stress intensity factors are obtained. The results show that the method proposed is successful and can be used to solve more complicated problems.

Magnetohydrodynamics equilibrium of a self-confined elliptic plasma ball

A variational principle is applied to the problem of magnetohydrodynamics (MHD) equilibrium of a self-contained elliptical plasma ball, such as elliptical ball lightning. The principle is appropriate for an approximate solution of partial differential equations with arbitrary boundary shape. The method reduces the partial differential equation to a series of ordinary differential equations and is especially valuable for treating boundaries with nonlinear deformations. The calculations conclude that the pressure distribution and the poloidal current are more uniform in an oblate self-confined plasma ball than that of an elongated plasma ball. The ellipticity of the plasma ball is obviously restricted by its internal pressure, magnetic field, and ambient pressure. Qualitative evidence is presented for the absence of sighting of elongated ball lightning.