新疆渭干河黑孜水库年径流随机数学模型的建立     

李爱玲  周聿超 《干旱区地理》1994,17(3):66-73

黑孜水库是新疆最大的山区拦河水库，具有灌溉、防洪、发电等综合效益。为了使水库调节遇到各种丰、平枯水的组成情况，以便最佳调节运用以发挥其最大效益。本文应用黑孜水库水文站已有３６年年径流序列将其中折趋势、跳跃、周期、随机和纯随机５种成份分析出来，建立各自的数学模型，然后综合成总全数学模型，用以延长年径流序列。延长后的序列经过各种统计检验，保持了原有序列的统计特性，所以是可以实用的。  相似文献   

耀斑-激波的南-北非对称性传播          下载免费PDF全文

魏奉思  邓晓东 《地球物理学报》1987,30(5):443-449

本文根据宇宙线Forbush下降幅度随源耀斑纬度分布的新近结果,采用无量纲化的MHD平面斜激波跃变条件,推算得到子午面内一种可能的耀斑-激波模型。发现耀斑-激波在太阳子午面内的传播相对耀斑法线方向是非对称的,激波面后的动力学参数与磁场具有截然相反的非对称性分布;激波传播的最快方向倾向日球电流片方向。该模型可以解释太阳耀斑-地磁、宇宙线效应中的南-北非对称性现象,有助于了解高速等离子体和非均匀背景场之间的相互作用过程。  相似文献   

Optimum bunker size and location in underground coal mine conveyor systems     

Suresh C. Baral  Carlos Daganzo  Michael Hood 《Geotechnical and Geological Engineering》1987,5(4):391-404

Summary The transportation of coal out of a mine is usually done by a serially linked system of conveyors. It is apparent that in a serially dependent system of this type the failure of any one component (conveyor) causes the complete system to be shut down. The provision of bunkers at strategically located points in the conveyor system can result in the production of coal even in the event of failure of some outbye conveyors. Although the use of bunkers can increase mine system availability, the maximum possible system availability may not be attained if the bunker capacity is inadequate and/or the location of these bunkers in the system is inappropriate. This paper presents a stochastic model by which the optimum capacities and locations of bunkers can be determined for a system consisting of a single production section and a system of serially linked conveyors.  相似文献   

Digital simulation of multivariate two- and three-dimensional stochastic processes with a spectral turning bands method   总被引：3，自引：0，他引：3  

Aristotelis Mantoglou 《Mathematical Geology》1987,19(2):129-149

The space domain version of the turning bands method can simulate multidimensional stochastic processes (random fields) having particular forms of covariance functions. To alleviate this limitation a spectral representation of the turning bands method in the two-dimensional case has shown that the spectral approach allows simulation of isotropic two-dimensional processes having any covariance or spectral density function. The present paper extends the spectral turning bands method (STBM) even further for simulation of much more general classes of multidimensional stochastic processes. Particular extensions include: (i) simulation of three-dimensional processes using STBM, (ii) simulation of anisotropic two- or three-dimensional stochastic processes, (iii) simulation of multivariate stochastic processes, and (iv) simulation of spatial averaged (integrated) processes. The turning bands method transforms the multidimensional simulation problem into a sum of a series of one-dimensional simulations. Explicit and simple expressions relating the cross-spectral density functions of the one-dimensional processes to the cross-spectral density function of the multidimensional process are derived. Using such expressions the one-dimensional processes can be simulated using a simple one-dimensional spectral method. Examples illustrating that the spectral turning bands method preserves the theoretical statistics are presented. The spectral turning bands method is inexpensive in terms of computer time compared to other multidimensional simulation methods. In fact, the cost of the turning bands method grows as the square root or the cubic root of the number of points simulated in the discretized random field, in the two- or three-dimensional case, respectively, whereas the cost of other multidimensional methods grows linearly with the number of simulated points. The spectral turning bands method currently is being used in hydrologic applications. This method is also applicable to other fields where multidimensional simulations are needed, e.g., mining, oil reservoir modeling, geophysics, remote sensing, etc.  相似文献   

Stochastic analysis of lithologic sequences: Bed thickness distribution   总被引：1，自引：0，他引：1  

Tomasz Zydorowicz  Stanislaw J. Matysiak 《Mathematical Geology》1984,16(4):315-326

A stochastic model of bed thickness distribution is given. The following scheme of sedimentation and bed formation is assumed: (1)sedimentation consists of an unending sequence of alternating periods of deposition and erosion; (2)succession of sedimentary environments is described in terms of a transition probability matrix; (3)each depositional period accumulates a bed of sediments; (4)net accumulation exceeds erosion; (5)amounts of deposition and erosion are independent random variables. The equations for transformation of bed thickness distribution from sedimentary environment to geologic record are obtained. The sedimentological significance of these equations is discussed.  相似文献   

Testing linear models of sea-floor topography     

Alberto Malinverno 《Pure and Applied Geophysics》1989,131(1-2):139-155

Stochastic models can generate profiles that resemble topography by taking uncorrelated, zero-average noise as input, introducing some correlation in the time series of noise, and integrating the resulting correlated noise. The output profile will depict a nonstationary, randomly rough surface. Two models have been chosen for comparison: a fractal model, in which the noise is correlated even at large distances, and an autoregressive model of order 1, in which the correlation of the noise decays rapidly. Both models have as an end-member a random walk, which is the integration of uncorrelated noise. The models have been fitted to profiles of submarine topography, and the sample autocorrelation, power spectrum and variogram have been compared to the theoretical predictions. The results suggest that a linear system approach is a viable method to model and classify sea-floor topography. The comparison does not show substantial disagreement of the data with either the autoregressive or the fractal model, although a fractal model seems to give a better fit. However, the amplitudes predicted by a nonstationary fractal model for long wavelengths (of the order of 1000 km) are unreasonably large. When viewed through a large window, ocean floor topography is likely to have an expected value determined by isostasy, and to be stationary. Nonstationary models are best applied to wavelengths of the order of 100 km or less.  相似文献   

1986年2月特大电离层暴的动力学表现     

苏元智  黄信榆 《地球物理学报》1989,32(5):507-515

1986年2月的太阳耀斑爆发导致了强烈的磁暴和电离层暴。 对我国多个台站有关电离层观测记录的分析表明:这次电离层暴呈现出显著的纬度效应,井在武昌、广州等地区形成了明显的“暴中心”。在暴变期间,伴随有大尺度的TID。在某些时段内,F区电子密度剖面产生了特殊的畸变。 对暴变形态特征及其形成机制进行了一些初步讨论。  相似文献   

随机动力处理在天气形势预报中的应用及微机业务系统   总被引：1，自引：0，他引：1  

朱正心 《大气科学》1995,19(1):111-115

本文运用欧洲中期天气预报中心的数值预报产品，组成平均高度场，通过具有耗散强迫低阶动力学系统的控制方程，作随机动力处理，对有限区域500 hPa高度场作下一旬的平均高度场预报，经试验证明其结果能给中期预报提供依据。  相似文献   

随机序列轮长与轮次的统计规律   总被引：10，自引：1，他引：10       下载免费PDF全文

马秀峰 《水科学进展》1994,5(2):95-103

平稳随机序列的轮次,服从二阶线性齐次差分方程。其中,独立序列的差分方程以状态发生的平均概率为二重特征根,并能用先验条件确定差分方程通解中的常数。非独立序列的差分方程有二个相异的特征根,需根据样本资料来确定差分方程通解中的常数。经用干旱序列及实测水文序列检验,证实了方法的适用性。  相似文献   

河床冲刷粗化的随机模拟   总被引：3，自引：0，他引：3       下载免费PDF全文

冷魁  王明甫 《水科学进展》1994,5(2):111-118

对冲刷与粗化的相互作用机制进行了分析,并在非均匀沙床面暴露度的随机分布特性、流速分布及起动规律研究的基础上,提出了河床冲刷粗化的随机模型。该模型能同时对河床冲刷深度及粗化稳定级配进行计算。由实验及野外实测资料的验证表明,计算结果与实测值基本相符。  相似文献