适合复杂地形的高阶Boussinesq水波方程   总被引：17，自引：4，他引：17  

邹志利 《海洋学报》2001,23(1):109-119

针对海底坡度较大(量阶为O(1))或海底曲率较大的复杂地形,建立了一个新型高阶Boussinesq水波方程.该方程可用于研究海底存在若干相互平行沙坝引起的Bragg反射问题.方程的水平速度沿水深的分布为四次多项式,色散性和变浅作用性能的精度比经典Boussinesq方程高了一阶.方程在浅水水域可以是完全非线性的.  相似文献   

Beta Distribution of Surface Elevation of Random Waves   总被引：2，自引：0，他引：2  

ZHANG  Jun 《中国海洋工程》2001,(1):53-60

A probability density function (PDF) is derived of beta distribution with both λ3 (skewness) and λ4 (kurtosis) as parameters for weakly nonlinear wave surface elevation by use of a method recently proposed by Srokosz. This PDF not only has a simpler form than the well-known Gram-Charlier Series PDF derived by Longuet-Higgins. but also overcomes an obvious shortcoming of the latter that when the series is unsuitably truncated, the resulting PDF is locally negative. To test the derived beta PDF, laboratorial experiments of wind waves are conducted. The experimental data indicate that the theoretical requirements of the parameters in the beta PDF are fulfilled. The experimental results show that the present PDF is in better agreement with the measured data than the beta PDF only including parameter λ3, and also than the Gram-Charlier Series PDF truncated up to the term of H6.  相似文献   

电磁海流计传感器性能的比较     

林红军 《海洋技术学报》2005,24(2):13-17

电磁海流计在海洋调查和研究中起着非常重要的作用。当前被广泛应用的电磁海流计的传感器基本采用三种不同的结构形式：球形结构、盘形结构和环形结构。而三种结构形式的传感器具有各自不同的技术参数和性能。文章对不同结构形式电磁海流计传感器的特点进行简要的比较和分析。我们在研制和使用电磁海流计时，应根据不同的设计要求和特定的应用环境和条件，选择适当形式结构的传感器，力求得到良好的结果。  相似文献   

结构损伤线性及非线性特征谱模式识别及应用     

孟昭秦  何林  刘仕军 《地球科学与环境学报》1999,21(3)

利用时间序列动态数据处理与建模对结构有损状态进行线性和非线性过程处理，用这两种方法对结构的物理状态进行谱分析和模态频率的提取进行了比较，计算结果表明非线性 Ｓ Ｅ Ｔ Ａ Ｒ 模型在特征谱的识别与提取上比线性 Ａ Ｒ Ｍ Ａ Ｘ 模型更有效，对微小损伤更灵敏。说明了在参数识别中非线性 Ｓ Ｅ Ｔ Ａ Ｒ 模型对物体损伤情况下振动数据建模较为客观，更能反映振动体系的损伤信息，是损伤识别数学模型有效的方法。  相似文献   

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安卫平  秦长源  耿爱玲 《大地测量与地球动力学》2008,28(3):27-35

????????(Gunbel)????????????????????(??????????????),????????????????????Σ?????о???????????临??????????,???????????????,?????????????????о??е???á????,????????????????????о?:?????????Ч???ù??????;???????????????????????????????????÷??????????????????????????????о?,???????÷???????????,?????????????μ????顪???й?????????????????????????????????????????????о???????????????????????????????????С??  相似文献   

近53a中国气温异常分布的非线性特征     

郭品文  徐同  居丽丽 《南京气象学院学报》2009,32(1):11-16

运用一种基于神经网络的非线性主成分分析法（nonlinear principal component analysis,NLP-CA）对中国1951—2003年53 a四季气温距平场（surface air temperature anomaly,SATA）进行分析,NLPCA第一模态结果显示中国四季气温异常具有一定的非线性特征,并且具有显著的季节性差异,即春、夏两季的非线性较强,秋、冬两季较弱。一维NLPCA对原始气温距平场的近似比一维PCA（principal component analysis）更好地反映了气温场的实际分布情况。  相似文献   

大气运动非线性不稳定性研究的若干新进展   总被引：1，自引：1，他引：1       下载免费PDF全文

穆穆 《大气科学》1995,19(4):494-509

本文简要介绍了近年来运用Arnold方法（能量—Casimir方法）研究大气运动非线性不稳定性所取得的若干新进展，讨论了该理论深入发展的前景及其应用问题。  相似文献   

Environmental determinism in Holocene research: causality or coincidence?   总被引：2，自引：0，他引：2  

Paul Coombes  Keith Barber 《Area》2005,37(3):303-311

The past decade has seen a revival of environmental determinism in palaeoenvironmental research, with palaeoclimatic shifts implicated in the collapse of many past civilizations. Implicit in these studies is a belief that the observed cultural transitions can be causally related to the magnitude of climatic change. However, examination of the processes of these declines suggests that many exhibit patterns characteristic of complexity cascading within self-organized systems. If so, the nonlinear nature of these systems' responses to external forcing means that the assumption of causality in many of these cases should be considered questionable.  相似文献   

岩土工程中一类双重非线性问题的处理方法   总被引：1，自引：0，他引：1  

武亚军  栾茂田  杨敏 《岩土力学》2004,25(Z1):41-46

针对土体和土体与结构接触面上的双重非线性性质,提出了采用理想弹塑性模型来模拟土体和采用非线性弹性-理想塑性模型来模拟土体与结构接触面相结合的方法,详细叙述了该方法的原理和数值实现方法。编制了面向对象的有限元计算程序,通过对地基极限承载力的计算验证了理想塑性模型的正确性,通过对一个受弹性基础梁作用的弹塑性地基分析验证了本文方法的适用性。计算结果表明,该方法简单实用,有一定的推广应用价值。  相似文献   

Investigations of nonlinear performances of implicit pseudodynamic algorithms     

張順益  黃裕鈞  宋裕祺 《地震工程与工程振动(英文版)》2006,5(2):257-266

Although it has been shown that the implementation of the HHT-α method can result in improved error propagation properties in pseudodynamic testing if the equation of motion is used instead of the difference equation to evaluate the next step acceleration, this paper proves that this method might lead to instability when used to solve a nonlinear system. Its unconditional stability is verified only for linear elastic systems, while for nonlinear systems, instability occurs as the step degree of convergence is less than 1. It is worth noting that the step degree of convergence can frequently be less than 1 in pseudodynamic testing, since a convergent solution is achieved only when the step degree of convergence is close to 1 regardless of whether its value is greater or less than 1. Therefore, the application of this scheme to pseudodynamic testing should be prohibited, since the possibility of instability might incorrectly destroy a specimen. Consequently, the implementation of the HHT-α method by using the difference equation to determine the next step acceleration is recommended for use in pseudodynamic testing.  相似文献