Velocity profile of a sand cloud blowing over a gravel surface   总被引：2，自引：0，他引：2  

Zhibao Dong  Hongtao Wang  Xiaoping Liu  Fang Li  Aiguo Zhao 《Geomorphology》2002,45(3-4)

Particle dynamic analyzer (PDA) measurement technology was used to study the turbulent characteristics and the variation with height of the mean horizontal (in the downwind direction) and vertical (in the upward direction) particle velocity of a sand cloud blowing over a gravel surface. The results show that the mean horizontal particle velocity of the cloud increases with height, while the mean vertical velocity decreases with height. The variation of the mean horizontal velocity with height is, to some extent, similar to the wind profile that increases logarithmically with height in the turbulent boundary layer. The variation of the mean vertical velocity with height is much more complex than that of the mean horizontal velocity. The increase of the resultant mean velocity with height can be expressed by a modified power function. Particle turbulence in the downwind direction decreases with height, while that in the vertical direction is complex. For fine sands (0.2–0.3 mm and 0.3–0.4 mm), there is a tendency for the particle turbulence to increase with height. In the very near-surface layer (<4 mm), the movement of blown sand particles is very complex due to the rebound of particles on the bed and the interparticle collisions in the air. Wind starts to accelerate particle movement about 4 mm from the surface. The initial rebound on the bed and the interparticle collisions in the air have a profound effect on particle movement below that height, where particle concentration is very high and wind velocity is very low.  相似文献   

不对称抽道集共反射面元叠加方法探讨     

邱苏胡旭芝  沈骥千 《中国煤田地质》2003,15(2):49-51,F004,58

总结不对称抽道集共反射面元叠加方法的工作经验，提出自由观测面自由反射界面不对称抽道集共反射面元叠加方法的处理思路和计算方法。在自由观测面的条件下，反射界面可分为简单倾斜平面、规则曲面和自由反射界面三种情况，针对不同情况讨论共反射面元的叠加方法。综合一般情况下的共反射面元叠加方法，提出了“鳞片法”的处理思路。  相似文献   

多元回归模型在坝基渗透稳定性预测中的应用   总被引：2，自引：0，他引：2  

王初生  唐辉明  杨裕云 《华东地质学院学报》2003,26(4):367-370

在坝的失事事故中，渗透破坏占了30～40％。坝基渗流长期观测资料是病险土石坝渗透稳定性预测的主要依据。多元回归模型是定量处理观测数据的有力工具。本文根据坝基水文地质特征的差异性以及渗流场的非平面性，将多元回归数学模型应用于坝基渗透稳定性预测中，给出了在计算机上实现的计算算例。通过对陆浑水库的研究分析，对坝基渗透稳定现状及变化趋势的有了进一步认识，成功地解决了影响水库正常运行的坝基渗流问题，为水库投入正常高水位运行提供了详实的依据。其研究成果与其它方法结论一致，从而证明多元回归模型具有较强的实用性。  相似文献   

The Role of Organic Matter During Metal Enrichment in Permian Kupferschiefer of the Rudna Mine,Southwest Poland     

孙玉壮  WILHELM PüTTMANN 《中国地球化学学报》2003,22(1):1-10

The bulk composition of organic matter and saturated and aromatic hydrocarbons extracted from 16 samples collected from two Kuperschiefer profiles in the Rudna mine,Southwest Poland has been analyzed to study the role of organic matter during base metal enrichment in the Kupferschiefer shale.The results indicated that the extract yields and saturated hydrocarbon yields decreased with increasing base metal contents.GC and GC/MS analyses indicated that n -alkanes and alkylated aromatic compounds were depleted and may have served as hydrogen donators for thermochemical sulfate reduction.The enrichment of base metal is closely connected with the destruction of hydrocarbons.  相似文献   

MATLAB及其在重力基点网平差中的应用     

冯治汉 《物探化探计算技术》2003,25(4):336-339

MATLAB作为最优秀的数学软件之一，在国内外工程技术界产生愈来愈大的影响，其强大的数据计算和图形显示功能尤为突出。复杂的物探重力基点网平差计算通过用MATLAB的矩阵计算功能，变得简单易懂。而编制的MATLAB的M文件程序，计算快速准确。相信MATLAB在物探数据处理工作中将发挥重要的作用。  相似文献   

江苏高邮地震台地磁变化与地震关系的初探   总被引：1，自引：1，他引：1  

赵卫红  蒋延林  赵永红  王福才  赵峰  张骞  李凤如 《山西地震》2003,(4):36-39

分析了江苏高邮地磁台1980年至2002年地磁垂直分量日变幅逐日比值的高值异常与江苏及邻区ML5．0以上地震之间的关系，发现它们之间有良好的对应关系，通过分析地磁垂直分量谐波幅度的逐日比，提出了适用于高邮地磁台的地震分析预报参数，并对其内检预报效能进行了评价。  相似文献   

曲线拟合法在地电场资料处理中的应用          下载免费PDF全文

王兰炜  赵家骝  席继楼  王燕琼 《地震工程学报》2003,25(2):131-135

地电场和电阻率同场地观测时，电阻率观测会干扰地电场的观测数据发生大幅度变化。本主要探讨通过曲线拟合的方法消除这种干扰及其它随机干扰，并给出了对实际观测数据处理的结果。  相似文献   

Efficiency of base isolation systems in structural seismic protection and energetic assessment     

Giuseppe Carlo Marano  Rita Greco 《地震工程与结构动力学》2003,32(10):1505-1531

This paper concerns the seismic response of structures isolated at the base by means of High Damping Rubber Bearings (HDRB). The analysis is performed by using a stochastic approach, and a Gaussian zero mean filtered non‐stationary stochastic process is used in order to model the seismic acceleration acting at the base of the structure. More precisely, the generalized Kanai–Tajimi model is adopted to describe the non‐stationary amplitude and frequency characteristics of the seismic motion. The hysteretic differential Bouc–Wen model (BWM) is adopted in order to take into account the non‐linear constitutive behaviour both of the base isolation device and of the structure. Moreover, the stochastic linearization method in the time domain is adopted to estimate the statistical moments of the non‐linear system response in the state space. The non‐linear differential equation of the response covariance matrix is then solved by using an iterative procedure which updates the coefficients of the equivalent linear system at each step and searches for the solution of the response covariance matrix equation. After the system response variance is estimated, a sensitivity analysis is carried out. The final aim of the research is to assess the real capacity of base isolation devices in order to protect the structures from seismic actions, by avoiding a non‐linear response, with associated large plastic displacements and, therefore, by limiting related damage phenomena in structural and non‐structural elements. In order to attain this objective the stochastic response of a non‐linear n‐dof shear‐type base‐isolated building is analysed; the constitutive law both of the structure and of the base devices is described, as previously reported, by adopting the BWM and by using appropriate parameters for this model, able to suitably characterize an ordinary building and the base isolators considered in the study. The protection level offered to the structure by the base isolators is then assessed by evaluating the reduction both of the displacement response and the hysteretic dissipated energy. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Comparative study of the inelastic response of base isolated buildings   总被引：1，自引：0，他引：1  

Daniel Ordoez  Dora Foti  Luis Bozzo 《地震工程与结构动力学》2003,32(1):151-164

This article presents a numeric comparative study of the inelastic structural response of base isolated buildings. The comparative study includes the following isolation systems: laminated rubber bearings, New Zealand one, pure friction and the frictional pendulum ones. The study is based on obtaining non‐linear response spectra for various design parameters using six earthquake records. Usually the base isolation of a new building seeks to maintain the structure in the linear elastic range. The response of old weak buildings or the response of new ones subjected to extreme earthquakes may not be, necessarily, in the aforementioned ideal elastic range. Consequently, it is important to characterize the response of isolated buildings responding inelastically. A conclusion from this research is that the isolators affect significantly the structural response of weak systems. Rubber isolators seem slightly less sensitive to plastification that may occur in the structure compared to friction isolators. Ductility demands in the structure are affected significantly by friction and neoprene protected systems, in particular sliding ones where larger demands are obtained. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

基于信息块法的矢量符号库的建立和符号化实现   总被引：3，自引：1，他引：3  

吴丽春  胡鹏 《武汉大学学报(信息科学版)》2003,28(5):600-603

基于试验成果，详细介绍了基于信息块法的矢量地图符号库的建立和空间信息的符号化。  相似文献