The downstream gradation of particle sizes in the Squamish river,British Columbia     

Gary J. Brierley  Edward J Hickin 《地球表面变化过程与地形》1985,10(6):597-606

The exponential downstream decline in particle size predicted by Sternberg (1875) is examined within a highly active alpine fluvial environment, the gravel-bed Squamish River in southwestern British Columbia. Transect survey procedures for sampling within the coarse alluvial gravels are described in detail. Downstream trends for various particle size statistics, plotted with distance from a major sediment source, are considered according to two scenarios. Evaluation of overall trends indicates that the downstream expression derived by Sternberg (1875) is not the most appropriate; rather, curves are better described by power functions. This reflects a very rapid decline in particle size immediately downstream of the major sediment source. Secondly, evaluation of downstream trends in relation to channel planform determines that exponential functions with different coefficients describe adequately relations within individual planform reaches. There is insufficient evidence to suggest which of these two scenarios may be appropriate. Several lines of evidence suggest that the trends found are more the result of selective sediment transport phenomena than of abrasion, a condition attributed to channel competence within a system dominated by sediment-supply conditions.  相似文献   

硅酸钡铜的光吸收谱和EPR谱     

林传易  朱和宝  刘国彬 《矿物学报》1985,(4)

本文报道水热合成硅酸钡铜(BaCuSi_4O_(10))的光吸收谱和EPR谱。EPR测量表明,在硅酸钡铜中,Cu~(2 )离子位置有轴对称性。在这种对称性下,一般只能观察到三条Cu~(2 )离子的吸收谱带,但在BaCuSi_4O_(10)的吸收谱中却观察到了四条。这一矛盾用~2Eg激发态的动态Jahn-Teller效应来解释。本文提出的~2Eg和~2A_1g能级的相对次序与文献[2]的相反,文中对这一问题作了详细的分析。跃迁频率和g因子的计算值在实验误差范围内与观测值一致。  相似文献   

A study on the sensitivity of the radar scattering coefficient to oceanic winds     

Abhijit Sarkar  Raj Kumar 《Journal of Earth System Science》1985,94(3):249-259

Sensitivity of the radar scattering coefficient to the oceanic wind vector in the midangular range for frequencies from L- to Ku- band is studied. This is based on computations of scattering coefficient via the two-scale scattering theory employing a semi-empirical model for the ocean spectrum suggested by Fung and Lee and the slope distribution by Cox and Munk. Higher frequency and incident angles of over 45 degrees seem to yield better wind sensitivity.  相似文献   

Some observations on suspended sediment dynamics in Storbregrova,Jotunheimen     

Keith Richards 《地球表面变化过程与地形》1984,9(2):101-112

Observations are reported of the dynamics of suspended sediment transport in the meltstream of Storbreen in the Jotunheimen. Fine sediment is transferred from the subglacial to the proglacial environment during low flow (meltdominated) periods, and then removed from the catchment during high flow (rainfall-controlled) events. Both diurnal and storm period sediment load-discharge relationships involve clockwise hysteresis, but separate multivariate rating curves define variations of load with streamflow according to (1) the relative importance of meltwater and rainfall runoff, and (2) changes in the sediment source areas contributing to the stream at different times. Particle size variations in the suspended sediment also reflect varying source area influences.  相似文献   

Least squares parameter estimation in chaotic differential equations     

Josef Kallrath  Johannes P. Schlöder  Hans Georg Bock 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):353-371

A recent least squares algorithm, which is designed to adapt implicit models to given sets of data, especially models given by differential equations or dynamical systems, is reviewed and used to fit the Hénon-Heiles differential equations to chaotic data sets.This numerical approach for estimating parameters in differential equation models, called theboundary value problem approach, is based on discretizing the differential equations like a boundary value problem,e.g. by a multiple shooting or collocation method, and solving the resulting constrained least squares problem with a structure exploiting generalized Gauss-Newton-Method (Bock, 1981).Dynamical systems like the Hénon-Heiles system which can have initial values and parameters that lead to positive Lyapunov exponents or phase space filling Poincaré maps give rise to chaotic time series. Various scenarios representing ideal and noisy data generated from the Hénon-Heiles system in the chaotic region are analyzedw.r.t. initial conditions, parameters and Lyapunov exponents. The original initial conditions and parameters are recovered with a given accuracy. The Lyapunov spectrum is then computed directly from the identified differential equations and compared to the spectrum of the true dynamics.presently at IWR, Universität Heidelberg, Im Neuenheimer Feld 368, D-6900 Heidelberg, Germany  相似文献   

刺猬沟金矿石英包体成矿溶液电导度和红外光谱找矿标型     

武子玉  吴国学  刘斌  周永昶 《物探与化探》2004,28(6):546-548,552

石英是刺猬沟金矿重要的脉石矿物,也是金的主要载体.借助于成矿溶液电导度和红外光谱方法对刺猬沟金矿石英进行了分析,结果表明,成矿溶液电导度和红外光谱测定的DCO₂与石英中金含量呈正相关关系,成矿溶液电导度大于5.7 μS,DCO₂大于0.2矿化好.这对该找矿和矿床评价具有指导意义.  相似文献   

基于GPS技术的大桥自振频率测量研究   总被引：1，自引：2，他引：1  

张斌  黄声享  李晓华 《测绘信息与工程》2005,30(5):43-44

以GPS快速静态相对定位技术对武汉白沙洲长江大桥进行自振频率测试,采用GPS动态监测的方法,通过对悬索桥关键点的点位测量和三维位移进行动态实时监测以及对测量数据的分析,得出点位时程图,经频谱分析得出长江三桥的自振特征要素。  相似文献   

一种分离暴雨过程天气尺度和次天气尺度特征的方法   总被引：2，自引：0，他引：2       下载免费PDF全文

魏凤英  朱福康 《大气科学》2003,27(2):191-202

作者提出利用奇异谱主分量重建技术进行气象变量场尺度分离的新构想,并设计出尺度分离的具体实施方法.使用此方法对1998年7月下旬长江流域强暴雨过程的卫星观测亮温(TBB)场进行了试验性尺度分离.结果表明,该分离技术可以将这次暴雨过程天气尺度和次天气尺度系统的基本结构清晰地分离出来.在天气尺度场上,长江流域呈现出明显的切变线上连续性对流云系的特征.在次天气尺度场上,可以清楚地显现出偶极子系统的演变特征,其活动与暴雨过程有很好的对应.  相似文献   

土地利用动态遥感监测中变化信息的提取方法     

杨贵军  武文波  陈步尚  夏春林 《测绘与空间地理信息》2003,26(1):18-21

在参与2001年的全国土地利用动态遥感监测项目中,通过对遥感机理的深入研究,结合土地利用动态监测的遥感数据源、任务要求及满足生产实际的需要,在参考现有方法的基础上,对变化信息提取的整个过程进行了整理,并通过实践验证了变化信息提取方法的可靠性。  相似文献   

沙化土地野外光谱数据采集的技术方法探讨   总被引：5，自引：0，他引：5  

李海萍  庄大方  熊利亚 《武汉大学学报(信息科学版)》2003,28(4):484-487,491

根据对环北京地区沙化土地野外光谱数据采集工作，探讨了光谱数据采集的技术方法选择，并以ASD FieldSpec^FR全波段野外光谱仪所测数据为例进行分析，对影响光谱数据共享的辅助数据进行了讨论。  相似文献