湖北省土壤侵蚀景观空间异质性及驱动因子分析     

张志  王少军 《中国地质灾害与防治学报》2004,15(4):49-53

地域分异是地球表层大小不等、内部具有一定相似性地段之间的相互分化以及由此产生的差异。为了研究不同区位土壤侵蚀问题，从土壤生态景观及系统论出发，运用地质学、地理学、景观生态学、环境学的理论和研究方法，研究湖北省土壤侵蚀景观空间格局及其驱动因子，使土壤侵蚀问题研究提高到一个新的水平。湖北省土壤侵蚀景观具有南北分带、东西分区，为一不对称的断块一环组合，土壤流呈现向长江、江汉盆地中心轴带辐聚、单流向特点。景观空间异质性形成的首要驱动因子是大地构造背景，以房县一襄樊一广济断裂带为界，南北两侧地壳物质组成和构造发展史存在较明显的差异，现代气候带、降雨量、温热程度及土地利用等差异，造成了湖北省区域土壤地理、土壤生态的分异，形成湖北省土壤生态带、区具有南北分带，东西分区的宏观格局；其次大兴安岭一武陵山深部构造陡变带两侧新构造运动强度差异、大别造山带构造强烈隆升，导致土壤侵蚀强度的西强东弱、南北强中间弱的态势；成土母岩差异性决定了土壤可蚀性的多变；空间上“土壤侵蚀内城区”分布在湖北省的周边地区，经济贫困、管理落后，这一地区的经济水平与水土流失间形成“自反馈作用”，这一现象在我国水土保持、生态建设工作中应该引起重视。  相似文献   

Methods for Setting up a Three-Dimensional Industrial Surveying System of “Building Blocks Type”     

FENG Wenhao 《地球空间信息科学学报》2004,(3)

1　Methodsfororientatinginitialdirec tioninindustrialsurveyDifferentfromconventionalengineeringsurvey,thedistancebetweenthetwoangle measurementdevicesinindustrialsurveyisnomorethantenmeters.Theaccu racyforthemeasurementofobjectpointsisrequiredtobebetween± ( 0 .0 2～ 0 .0 5～ 0 .2 0 )mm ,sotheaccu racyfortheorientationoftheinitialdirectionoughttobehigh .Theexistingmethodsfororientatingtheinitialdirectionbetweenthetwoangle measurementdevicesincludemethodofusinginnertarget,collimatormethod,metho…  相似文献   

无地面控制GPS辅助光束法区域网平差   总被引：2，自引：4，他引：2  

袁修孝  朱武  武军郦  王瑞幺 《武汉大学学报(信息科学版)》2004,29(10):852-857

介绍了在WGS-84坐标系中进行GPS辅助光束法区域网平差的基本原理以及利用大地水准面拟合方法实施大地高与正常高的变换方法。利用新疆库尔勒地区1：25000和1：50000实际航摄资料验证了理论与程序实现的正确性。试验结果表明，无地面控制GPS辅助光束法区域网平差可用于中小比例尺测图的加密，在WGS-84坐标系中可以获得较高的点定位精度，而在国家80坐标系下，利用大地水；隹面拟合前后的GPS摄站坐标进行GPS辅助光束法区域网平差，加密精度没有明显差异。  相似文献   

导航卫星自主定轨的算法研究及模拟结果   总被引：5，自引：2，他引：5  

刘经南  曾旭平  夏林元  赵齐乐 《武汉大学学报(信息科学版)》2004,29(12):1040-1044

讨论了利用卫星-卫星间的距离观测值建立导航卫星系统自主定轨的数学方法，并用GPS星座模拟星间观测值，采用滤波算法计算卫星的状态参数。模拟结果表明，在空间测距精度一定的情况下，自主定轨精度能高于GPS广播星历，因而能较精确地维持卫星系统的坐标框架。  相似文献   

Stability and accuracy analysis of the central difference method for real‐time substructure testing     

B. Wu  H. Bao  J. Ou  S. Tian 《地震工程与结构动力学》2005,34(7):705-718

The central difference method (CDM) that is explicit for pseudo‐dynamic testing is also believed to be explicit for real‐time substructure testing (RST). However, to obtain the correct velocity dependent restoring force of the physical substructure being tested, the target velocity is required to be calculated as well as the displacement. The standard CDM provides only explicit target displacement but not explicit target velocity. This paper investigates the required modification of the standard central difference method when applied to RST and analyzes the stability and accuracy of the modified CDM for RST. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Incorporating Spatial Dependence in Predictive Vegetation Models: Residual Interpolation Methods*     

Jennifer Miller 《The Professional geographer》2005,57(2):169-184

Predictive vegetation modeling can be used statistically to relate the distribution of vegetation across a landscape as a function of important environmental variables. Often these models are developed without considering the spatial pattern that is inherent in biogeographical data, resulting from either biotic processes or missing or misspecified environmental variables. Including spatial dependence explicitly in a predictive model can be an efficient way to improve model accuracy with the available data. In this study, model residuals were interpolated and added to model predictions, and the resulting prediction accuracies were assessed. Adding kriged residuals improved model accuracy more often than adding simulated residuals, although some alliances showed no improvement or worse accuracy when residuals were added. In general, the prediction accuracies that were not increased by adding kriged residuals were either rare in the sample or had high nonspatial model accuracy. Regression interpolation methods can be an important addition to current tools used in predictive vegetation models as they allow observations that are predicted well by environmental variables to be left alone, while adjusting over‐ and underpredicted observations based on local factors.  相似文献   

Correcting the Smoothing Effect of Ordinary Kriging Estimates   总被引：2，自引：0，他引：2  

Jorge Kazuo Yamamoto 《Mathematical Geology》2005,37(1):69-94

The smoothing effect of ordinary kriging is a well-known dangerous effect associated with this estimation technique. Consequently kriging estimates do not reproduce both histogram and semivariogram model of sample data. A four-step procedure for correcting the smoothing effect of ordinary kriging estimates is shown to be efficient for the reproduction of histogram and semivariogram without loss of local accuracy. Furthermore, this procedure provides a unique map sharing both local and global accuracies. Ordinary kriging with a proper correction for smoothing effect can be revitalized as a reliable estimation method that allows a better use of the available information.  相似文献   

Snow model sensitivity analysis to understand spatial and temporal snow dynamics in a high‐elevation catchment          下载免费PDF全文

Michael Engel  Claudia Notarnicola  Stefano Endrizzi  Giacomo Bertoldi 《水文研究》2017,31(23):4151-4168

In this paper, we addressed a sensitivity analysis of the snow module of the GEOtop2.0 model at point and catchment scale in a small high‐elevation catchment in the Eastern Italian Alps (catchment size: 61 km²). Simulated snow depth and snow water equivalent at the point scale were compared with measured data at four locations from 2009 to 2013. At the catchment scale, simulated snow‐covered area (SCA) was compared with binary snow cover maps derived from moderate‐resolution imaging spectroradiometer (MODIS) and Landsat satellite imagery. Sensitivity analyses were used to assess the effect of different model parameterizations on model performance at both scales and the effect of different thresholds of simulated snow depth on the agreement with MODIS data. Our results at point scale indicated that modifying only the “snow correction factor” resulted in substantial improvements of the snow model and effectively compensated inaccurate winter precipitation by enhancing snow accumulation. SCA inaccuracies at catchment scale during accumulation and melt period were affected little by different snow depth thresholds when using calibrated winter precipitation from point scale. However, inaccuracies were strongly controlled by topographic characteristics and model parameterizations driving snow albedo (“snow ageing coefficient” and “extinction of snow albedo”) during accumulation and melt period. Although highest accuracies (overall accuracy = 1 in 86% of the catchment area) were observed during winter, lower accuracies (overall accuracy < 0.7) occurred during the early accumulation and melt period (in 29% and 23%, respectively), mostly present in areas with grassland and forest, slopes of 20–40°, areas exposed NW or areas with a topographic roughness index of ?0.25 to 0 m. These findings may give recommendations for defining more effective model parameterization strategies and guide future work, in which simulated and MODIS SCA may be combined to generate improved products for SCA monitoring in Alpine catchments.  相似文献   

Tensionless–frictionless interaction of flexible annular foundation with a transversely isotropic multi‐layered half‐space          下载免费PDF全文

Morteza Eskandari‐Ghadi  Ghasem Gorji‐Bandpey  Azizollah Ardeshir‐Behrestaghi  Seyed Masoud Nabizadeh 《国际地质力学数值与分析法杂志》2015,39(2):155-174

A transversely isotropic multi‐layered half‐space, with axis of material symmetry perpendicular to the free surface, supports a flexible either annular or solid circle foundation. The contact area of the foundation and the half‐space is considered to be both frictionless and tensionless. The foundation is assumed to be affected by a vertical static axisymmetric load. Detailed analysis of the interaction of these two systems with different thickness of layers is the target of this paper. With the use of ring load Green's functions for both the foundation and the continuum half‐space, an integral equation accompanied with some inequalities is introduced to model the complex BVP. With the incorporation of ring‐shape FEM, we are capable of capturing both regular and singular solution smoothly. The validity of the combination of the analytical and numerical method is proved with comparing the results of this paper with a number of benchmark cases of both linear and nonlinear interaction of circular and annular foundation with half‐space. Some new illustrations are presented to portray the aspect of the anisotropy and layering of the half‐space. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Developing millennial tree ring chronologies in the fire‐prone North American boreal forest     

DOMINIQUE ARSENEAULT  BENJAMIN DY  FABIO GENNARETTI  JULIA AUTIN  YVES BÉGIN 《第四纪科学杂志》2013,28(3):283-292

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