拱坝系统三维非线性地震波动分析   总被引：18，自引：1，他引：18  

杜修力  陈厚群 《地震工程与工程振动》1996,16(3):39-47

本文将显式有限元结合外推人工边界的方法发展应用于三维非线性近场波动问题的研究。首次提出了拱坝－库水－地基系统三维非线性地震反应波动分析方法，并与传统的无质量地基分析方法进行了比较。  相似文献   

Bias and uncertainty in regression-calibrated models of groundwater flow in heterogeneous media     

Richard L. Cooley  Steen Christensen 《Advances in water resources》2006

Groundwater models need to account for detailed but generally unknown spatial variability (heterogeneity) of the hydrogeologic model inputs. To address this problem we replace the large, m-dimensional stochastic vector β that reflects both small and large scales of heterogeneity in the inputs by a lumped or smoothed m-dimensional approximation γθ_∗, where γ is an interpolation matrix and θ_∗ is a stochastic vector of parameters. Vector θ_∗ has small enough dimension to allow its estimation with the available data. The consequence of the replacement is that model function f(γθ_∗) written in terms of the approximate inputs is in error with respect to the same model function written in terms of β, f(β), which is assumed to be nearly exact. The difference f(β) − f(γθ_∗), termed model error, is spatially correlated, generates prediction biases, and causes standard confidence and prediction intervals to be too small. Model error is accounted for in the weighted nonlinear regression methodology developed to estimate θ_∗ and assess model uncertainties by incorporating the second-moment matrix of the model errors into the weight matrix. Techniques developed by statisticians to analyze classical nonlinear regression methods are extended to analyze the revised method. The analysis develops analytical expressions for bias terms reflecting the interaction of model nonlinearity and model error, for correction factors needed to adjust the sizes of confidence and prediction intervals for this interaction, and for correction factors needed to adjust the sizes of confidence and prediction intervals for possible use of a diagonal weight matrix in place of the correct one. If terms expressing the degree of intrinsic nonlinearity for f(β) and f(γθ_∗) are small, then most of the biases are small and the correction factors are reduced in magnitude. Biases, correction factors, and confidence and prediction intervals were obtained for a test problem for which model error is large to test robustness of the methodology. Numerical results conform with the theoretical analysis.  相似文献   

非线性时间序列分析的最新进展及其在地球科学中的应用前景   总被引：14，自引：0，他引：14  

洪时中 《地球科学进展》1999,14(6):559-565

评述了非线性时间序列分析的最新进展,包括相空间重构、序列性质的鉴别、建模与预报,同时介绍了非线性时间序列分析在地球科学中的应用概况。  相似文献   

Generalized inverses of nonlinear mappings and the nonlinear geodetic datum problem     

A. Dermanis 《Journal of Geodesy》1998,72(2):71-100

Motivated by the existing theory of the geometric characteristics of linear generalized inverses of linear mappings, an attempt is made to establish a corresponding mathematical theory for nonlinear generalized inverses of nonlinear mappings in finite- dimensional spaces. The theory relies on the concept of fiberings consisting of disjoint manifolds (fibers) in which the domain and range spaces of the mappings are partitioned. Fiberings replace the quotient spaces generated by some characteristic subspaces in the linear case. In addition to the simple generalized inverse, the minimum-distance and the x ₀-nearest generalized inverse are introduced and characterized, in analogy with the least-squares and the minimum-norm generalized inverses of the linear case. The theory is specialized to the geodetic mapping from network coordinates to observables and the nonlinear transformations (Baarda's S-transformations) between different solutions are defined with the help of transformation parameters obtained from the solution of nonlinear equations. In particular, the transformations from any solution to an x ₀-nearest solution (corresponding to Meissl's inner solution) are given for two- and three-dimensional networks for both the similarity and the rigid transformation case. Finally the nonlinear theory is specialized to the linear case with the help of the singular-value decomposition and algebraic expressions with specific geometric meaning are given for all possible types of generalized inverses. Received: 11 April 1996 / Accepted: 19 April 1997  相似文献   

判断后续强震的指标     

陈荣华  罗灼礼 《地震》1999,19(1):49-53

从非线性观点出发,研究了15次后续强震前较大地震发生的特点。研究结果表明,后续强震前2次较大地震地方平太阴时夹角上△τ小于45°,以及2次较大地震震级呈上升趋势是判断后面是否发生强震的2个指标。  相似文献   

岩石破裂强度变化对孕震系统地震活动影响的动力学模型研究     

李丽  石耀霖 《内陆地震》1998,12(1):29-35

以构造块体成组孕震模型为基础,讨论了孕震系统在局部孕震体强度发生变化时整个系统中的地震活动性变化特征。分析了岩石介质强度在其正常背景下发生弱化和强化后,孕震系统中各地震带上地震活动的时、空、强分布特征。结果表明,在外界影响（即边界动力作用）不变的情况下,不论是系统局部发生弱化还是强化,强度变化不仅影响到发生变化的地区中的地震活动性,而且对与其相连的地区及系统内其它没有发生变化的地震带上的地震活动都有强烈的影响  相似文献   

声波全波形反演目标函数性态   总被引：7，自引：4，他引：3       下载免费PDF全文

董良国  迟本鑫  陶纪霞  刘玉柱 《地球物理学报》2013,56(10):3445-3460

地震波传播的复杂性所引起的地震反演中强烈的非线性问题是目前全波形反演在技术上遇到的最大难题,了解全波形反演中不同的目标函数随不同物性参数的不同摄动尺度的变化性态,对选择合理的反演方法和反演策略具有重要意义.本文参照Jannane等对波形反演目标函数性态的分析方法,通过变密度声波方程,分析了多种地震数据子集的不同目标函数随物性参数的摄动尺度的变化关系,重点分析了它们的非线性程度,为进行分步骤、分尺度全波形反演方法和反演策略的选择提供了理论指导.  相似文献   

Nonlinear aspects of sea surface temperature in Monterey Bay     

Laurence C. Breaker 《Progress in Oceanography》2006,69(1):61-89

Nonlinear aspects of sea surface temperature (SST) in Monterey Bay are examined, based on an 85-year record of daily observations from Pacific Grove, California. Oceanic processes that affect the waters of Monterey Bay are described, processes that could contribute to nonlinearity in the record. Exploratory data analysis reveals that the record at Pacific Grove is non-Gaussian and, most likely, nonstationary. A more recent test for stationarity based on a power law approximation to the slope of the power spectrum indicates that the record is stationary for frequencies up to ∼8 cycles per year (∼45 days), but nonstationary at higher frequencies. To examine the record at Pacific Grove for nonlinear behavior, third-order statistics, including the skewness, statistical measures of asymmetry, the bicorrelation, and the bispectrum, were employed. The bicorrelation revealed maxima located approximately 365 days apart, reflecting a nonlinear contribution to the annual cycle. Based on a 365-day moving window, the running skewness is positive almost 80% of the time, reflecting the overall impact of warming influences. The asymmetry is positive approximately 75% of the time, consistent with the asymmetric shape of the mean annual cycle. Based on the skewness and asymmetry, nonlinearities in the record, when they occur, appear to be event-driven with time scales possibly as short as several days, to several years. In many cases, these events are related to warm water intrusions into the bay, and El Niño warming episodes.The power spectrum indicates that the annual cycle is a dominant source of variability in the record and that there is a relatively strong semiannual component as well. To determine whether or not the annual and semiannual cycles are harmonically related, the bispectrum and bicoherence were calculated. The bispectrum is nonzero, providing a strong indication of nonlinearity in the record. The bicoherence indicates that the annual cycle is a major source of nonlinearity and further implies that the annual and semiannual cycles are harmonically related. Based on the wavelet power spectrum (WPS), the appearance of the semiannual cycle is transitory; however, pathways between the annual and semiannual cycles appear at certain times when nonlinear interaction between them could occur. Comparisons between the WPS and the running skewness suggest that there is a tendency for periods when pathways exist, to coincide with increased positive skewness, and, often, with El Niño warming episodes. The Hilbert-Huang transform, a relatively new tool for nonstationary and nonlinear spectral analysis, was used to further examine the origin of the semiannual cycle. The time-dependent Hilbert spectrum reveals large and erratic variations in frequency associated with semiannual cycle but far greater stability associated with the annual cycle. As a result, the time-integrated Hilbert spectrum does not indicate the presence of a semiannual cycle. The method of surrogates from the field of nonlinear dynamics was also employed to test the Hopkins record for nonlinearity. Differences between the data and the surrogates were found that were statistically significant, implying the existence of nonlinearity in the record. Using the method of surrogates together with a one-year moving window, El Niño warming episodes appear to be a likely source of nonlinearity, consistent with the other analyses that were performed. Finally, the influence of stochastic variability due to serial correlation in the data was examined by comparing standardized statistics for the observations and for simulations based on an autoregressive model whose properties were obtained from the observations. The magnitude of the variability for the simulations was found to be far less than that associated with the original data, and thus stochastic variability does not appear to be a factor that significantly affects the interpretation of our results.  相似文献   

Probability distribution of random wave–current forces     

Jin-Bao Song   《Ocean Engineering》2006,33(17-18):2435-2453

Based on the second-order solutions obtained for the three-dimensional weakly nonlinear random waves propagating over a steady uniform current in finite water depth, the joint statistical distribution of the velocity and acceleration of the fluid particle in the current direction is derived using the characteristic function expansion method. From the joint distribution and the Morison equation, the theoretical distributions of drag forces, inertia forces and total random forces caused by waves propagating over a steady uniform current are determined. The distribution of inertia forces is Gaussian as that derived using the linear wave model, whereas the distributions of drag forces and total random forces deviate slightly from those derived utilizing the linear wave model. The distributions presented can be determined by the wave number spectrum of ocean waves, current speed and the second order wave–wave and wave–current interactions. As an illustrative example, for fully developed deep ocean waves, the parameters appeared in the distributions near still water level are calculated for various wind speeds and current speeds by using Donelan–Pierson–Banner spectrum and the effects of the current and the nonlinearity of ocean waves on the distribution are studied.  相似文献   

二阶非线性随机海浪波面高度和波面垂直速度的联合分布     

管长龙 《海洋与湖沼》1997,28(5):503-508

基于Longuet－Higgins提出的非线性随机海浪模型，在二阶近似下通过直接计算联合分布的各阶矩，导出了非线性海浪波面高度和波面垂直速度的联合分布。该分布为非正态，其形式为截断的级数，而非由累积矩母函数方法可能得到的渐近无穷级数。由于非线性的影响，波面高度与波面垂直速度不再相互独立。  相似文献