复合褶皱数学模型的应用     

刘德良  杨晓勇  陈增兵 《安徽地质》1995,(4)

为便于对褶皱构造的几何形态进行描述、概括和实际应用，在划分出两个基本类型褶皱的基础上，用数学方程式对五种叠加褶皱进行了表述，这样，利用计算机可以快速准确地获得叠加褶皱的具体形态。  相似文献   

岩体损伤力学研究进展     

唐辉明  孙成伟 《地质科技情报》1995,14(4):85-92

论述了岩体损伤力学在岩体力学中的地位，并从细观和宏观两个方面系统介绍了其最新研究进展；对岩体损伤力学研究中的几个重要问题提出了见解，认为分形几何是研究损伤的有效手段。  相似文献   

An erosion criterion for gravel-bed rivers     

Pamela Naden 《地球表面变化过程与地形》1987,12(1):83-93

A theoretically-based erosion criterion is developed for gravel-bed rivers which incorporates the effect of both grain geometry and turbulent velocity fluctuations. It is derived from a balance of instantaneous drag, lift, and gravity forces operating on individual grains and is calculated for spherical grains arranged in three distinct geometries. To accommodate the temporal variation in bed shear stress, the model includes a stochastic element based on the characteristics of turbulence derived from the flume evidence of McQuivey (1973a, b). In terms of the Shields parameter, results show reasonable agreement with the range of observations quoted from the field and with the experimental data of Fenton and Abbott (1977). Finally, the argument is generalized to cover applications in the wider context of field conditions including a range of grain sizes and flow conditions.  相似文献   

A test of granulometric control of desert dune geometry   总被引：1，自引：0，他引：1  

R. J. Wasson  R. Hyde 《地球表面变化过程与地形》1983,8(4):301-312

I. G. Wilson's hypothesis of coarse-tail grain-size control of dune spacing was derived from three dunefields in the Sahara and, although it was supplemented by measurements of spacing from other parts of the world, the grain-size data come only from North Africa. In this paper the hypothesis is tested in the Australian dunefields. Australian dunes do not form separate categories on a P₂₀/s (twentieth percentile/spacing) plot and, when placed on Wilson's diagram, the Australian data form a continuum between dunes and draas. Ripples maintain their identity, suggesting that the average saltation length of sand controls ripple wavelength while dunes and Wilson's draas are formed by secondary flow of some kind. In Australia the spread of data on the P₂₀/s diagram indicates that grain-size is not the prime control on s. Data from Australia and the Sahara indicate that direct linear relationships between s and h (dune spacing and height means respectively for blocks of dunes) occur but they have different slopes in different areas. These differences possibly reflect variations in vegetation and substrate as well as differences in wind regime. The separation of dunes from draas in the Sahara reflects the greater role of grain-size in an area where coarse grains frequently occur in dune crests. The relative paucity of coarse grains in Australian dune crests may reflect the fine-grained alluvium from which the dunes are derived. These differences may be ascribed to differing topography in Australia and the Sahara.  相似文献   

Comparison of resection–intersection algorithms and projection geometries in radiostereometry     

Niclas Brlin 《ISPRS Journal of Photogrammetry and Remote Sensing》2002,56(5-6)

Three resection–intersection algorithms were applied to simulated projections and clinical data from radiostereometric patients. On simulated data, the more advanced bundle-adjustment-based algorithms outperformed the classical Selvik algorithm, even if the error reductions were small for some parameters. On clinical data, the results were inconclusive.The two different projection geometries had a much larger influence on the error size and distribution. For the biplanar configuration, the position and motion errors were small and almost isotropic. For the uniplanar configuration, the position errors were comparably high and anisotropic, but still resulted in a high accuracy for some motion parameters at the expense of others.The simplified resection–intersection algorithm by Selvik may still be considered a good and robust algorithm for radiostereometry. More studies will have to be performed to find out how the theoretical advantages of the bundle methods can be utilized in clinical radiostereometry.  相似文献   

EFFECTIVE DISCHARGE CALCULATION GUIDE     

D. S. BIEDENHARN  C. R. THORNE  P.J.SOAR.  R.D.HEY  and C. C. WATSONS Engineer  U.S. Army Corps of Engineers  Waterways Experiment Station  Vicksburg  MS  USA. Professor School of Geography  University of Nottingham  Nottingham NG RD  UK. Prof 《国际泥沙研究》2001,16(4)

1 mTRonvcnox: moareS Aun CoxcmSAJluvial rivers have the pOtenhal to adjust their shaPe and dimensions to all flows that tranSPOrtsediment, but Inglis (l94l) suggested that, for rivers that are in regime, a single steady flow could beidenhfied which would Produce the same bankfll dimensions as the natural sequence of events. Hereferrd to this now as the dondnan discharge.Wolman and Mller (l960) idenhfied that the flow doing most bed material transPort over a period ofyears may be taken tO…  相似文献   

土壤大孔隙流研究中分形几何的应用进展   总被引：7，自引：0，他引：7  

冯杰  郝振纯 《水文地质工程地质》2001,28(3):9-13

土壤中普遍存在的大孔隙使水及溶质快速穿过土壤，污染地下水，确定土壤大孔隙流性质需要大量的野外和室内实验。本文在对分形几何概念进行简要阐述的基础上，介绍了分形几何在土壤大孔隙流研究中所取得的成果，结果表明应用分形几何确定土壤大孔隙流性质是一种省时、省力和具有广泛代表性的方法，最后对分形几何在土壤在大孔隙流研究中应用前景作了展望。  相似文献   

适合于印刷品评价与控制的色度仪应满足的条件     

朱元泓 《武汉大学学报(信息科学版)》1992,(3)

本文从印刷工业颜色测量的需要出发,根据色度学理论、人的视觉特性和对印刷过程的分析提出印刷品评价对颜色测量仪的要求。包括对颜色测量理论的选择,对测量几何的要求;对测量光孔和测试色定位的要求;对照明光源和标准观察者类型的选择;对测量值的输出和测量速度等要求。这些内容对色度仪的设计和使用都具有重要意义。  相似文献   

宏观地震忽略吸收确定震源深度问题的通解及其精确度     

段星北 《地震研究》1992,15(3):271-282

分析G-R-闵公式后得出,它是从点源幅射场导出的,与地震宏观场不相应。因在近场震源不能视作点源。在分析过程中,导出相当于点源、线源或面源以及复杂源的幅射场的深度公式。对实际的地震,它的源类型一无所知,所以不预作假定,将源指标几何扩散率n作为待定参数,导出了一个物理意义明确而又普遍化的震源深度公式。此公式的诸解法中,以计算方法准确、精度高,作图法有直观的优点,但准确性差、精度低,图算法只作获取粗略值和考察数据均匀性用。计算了9个8级以上巨震、1个71/2大震,和两个M_L=3的有感地震的震源深度,经对比结果很好,利用计算得出震源类型,结合宏观场研究了这些地震的震源几何学。并且首次在国际上给出宏观地震震源深度值的标准误差。  相似文献   

2-D inversion of MT data with a variable model geometry     

A. Marcuello-Pascual  P. Kaikkonen  J. Pous 《Geophysical Journal International》1992,110(2):297-304

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