综合小波分析与分形方法进行弱磁异常识别   总被引：1，自引：0，他引：1  

耿喜哲  张春华 《物探与化探》2002,26(2):126-130,125

利用小波分析塔式算法对单一分形模型数据进行处理,结合“随机共振”理论,对高精度弱磁异常中的噪声和误差进行有效的分析评价,依据趋势分析方法获得的剩余磁异常,提出“加窗移动”最小二乘方法对应用非整数阶微积分的布郎运动正态随机行走进行控制,为高精度弱磁异常的有效识别提供有益的指导。  相似文献   

水系形成与发展的元胞自动机模型研究          下载免费PDF全文

张俊勇  陈立  吴华林  张福然 《水科学进展》2007,18(5):695-700

河流水系的形成是在一定地质、地形、气候等条件下,水流自由发展的结果,具有自组织临界性。采用元胞自动机模型,对水系自组织形成的随机过程进行了模拟。通过改变地质、地形、气候等条件,模拟了与自然水系相吻合的多种河流水系。结合水槽实际,模拟了与水槽试验结果相似的水系形成。并通过概化形式,模拟了黄河源头东昆仑阿拉克湖地区第四纪水系演化过程,取得了良好的模拟效果。  相似文献   

Numerical analysis for random temperature fields of embankment in cold regions   总被引：1，自引：0，他引：1  

LIU ZhiQiang    LAI YuanMing  ZHANG MingYi & ZHANG XueFu State Key Laboratory of Frozen Soil Engineering  Cold  Arid Regions Environmental  Engineering Research Institute  Chi- nese Academy of Sciences  Lanzhou  China  School of Civil Engineering  Lanzhou Jiao Tong University  Lanzhou  China  Chongqing Jiao Tong University  Chongqing  China 《中国科学D辑(英文版)》2007,50(3):404-410

The stochastic finite element equations for random temperature are obtained using the first-order per-turbation technique taking into account the random thermal properties and boundary condition, based on heat transfer variational principle. The local average method for 2-D is used to discretize random fields. Then, the random temperature fields of embankment in cold regions are investigated on condi-tion that the thermal properties and boundary condition are taken as random fields, respectively, by using the program, which is written by the methods. The expected value of temperature field and the standard deviation of the temperature field of embankment in cold regions are obtained and analyzed.  相似文献   

Modelling dispersion in complex open channel flows: Fuzzy calibration (2)     

B. G. Hankin  K. J. Beven 《Stochastic Environmental Research and Risk Assessment (SERRA)》1998,12(6):397-412

Part 1 of this study assessed the effectiveness of dispersion models based around random particle tracking (RPT) applied an overbank flow in the Flood Channel Facility at HR Wallingford. Several of the RPT models that were used predicted the mixing behaviour of the tracer in the complex channel flow to within an acceptable accuracy. If there is no uniqueness in the model structure which can be used to represent the true system to within the limitations of the available observations, then this implies an inherent degree of ambiguity in our knowledge of the physically based model structure. This suggests that we should be less forthright in the optimisation of each individual model structure, and perhaps investigate more of the parameter combinations for each model which yield feasible simulations of the system. An alternative fuzzy calibration technique is introduced which avoids the optimisation process and takes account of uncertainties in the model structure, parameter sets and observed data in prediction.  相似文献   

The Need for a Common Framework for Collection and Interpretation of Data in Platinum-Group Element Geochemistry     

Iain McDonald 《Geostandards and Geoanalytical Research》1998,22(1):85-91

Platinum-group element (PGE) concentrations and the distribution of the metals in rocks serve as important tracers of mantle processes, as well as extraterrestrial input into crustal environments, but common standards regarding the gathering and presentation of PGE data have never been formalized. Effective modelling assumes that concentration data are within acceptable levels of precision, yet the practices used in some studies to determine precision do not adequately assess precision and, as a result, the uncertainties on PGE concentrations and PGE ratios are sometimes consistently underestimated. This article argues that replicate analyses of unknowns must be adopted more widely in order to overcome this problem. Related to the issue of uncertainties on PGE concentrations, is the issue of uncertainty associated with normalisation. Arguments have recently been put forward as to the significance of small positive or negative anomalies on chondrite nor-malized plots. At least four CI chondrite PGE datasets (of varying age and quality) are currently used for normalisation and significantly different patterns can be derived simply by using one dataset rather than another. This article is intended to open a debate within the PGE research community by asking whether more consistency needs to be applied in PGE analysis and in the subsequent interpretation of data. A rigorous assessment of the real uncertainties on PGE concentrations and the adoption of a standard CI chondrite PGE dataset, in order to eliminate bias from normalisation, are suggested to be central to this.  相似文献   

Adaptive fuzzy controller design for dynamic positioning system of vessels     

《Applied Ocean Research》2015

This paper develops an adaptive fuzzy controller for the dynamic positioning (DP) system of vessels with unknown dynamic model parameters and unknown time-varying environmental disturbances. The controller is designed by combining the adaptive fuzzy system with the vectorial backstepping method. An adaptive fuzzy system is employed to approximate the uncertain term induced by unknown dynamic model parameters and unknown time-varying environmental disturbances. It is theoretically proved that the proposed adaptive fuzzy DP controller can make the vessel be maintained at the desired values of its position and heading with arbitrary accuracy, while guaranteeing the uniform ultimate boundedness of all signals in the closed-loop DP control system of vessels. Simulation studies with comparisons on a supply vessel are carried out, and the results illustrate the effectiveness of the proposed control scheme.  相似文献   

基于随机森林的中小跨径公路梁桥双柱墩地震易损性模型     

鲁冠亚  王克海  邱文华  张秉哲 《地震工程与工程振动》2022,42(1):94-103

为准确建立线路中小跨径梁桥桥墩的地震易损性模型,采用统计工具得到某山区高速公路桥梁双柱墩的结构、几何和材料特性的概率分布,由拉丁超立方体抽样生成桥墩属性数据集,建立了参数化的有限元模型.通过Pushover分析和基于非弹性需求谱的能力谱方法获取双柱墩的地震需求和抗震性能数据点,提出由随机森林(RF)模型建立桥墩地震易损...  相似文献   

随机介质模型的一种构造方法   总被引：1，自引：0，他引：1  

王金山  陈可洋  吴清岭  杨微 《物探与化探》2010,34(2)

为更好地描述真实的地下介质特点,提出了一种局部随机位置或固定位置任意形状截取法并结合多尺度建模技术来共同构造随机介质模型的新方法。从现有的随机建模理论出发,在有效的建模区域内产生或者给定局部扰动位置,以此作为局部扰动分布区的中心点,引入局部扰动半径R和局部随机或给定扰动角度θ两个模型特征量,采用局部位置任意形状截取法并充填各种随机介质,从而构造各种不同的随机介质模型。给出了局部位置任意形状截取法的基本步骤和应用实例。  相似文献   

消减地震勘探随机噪声:导数算子约束下的维纳滤波     

聂鹏飞  曾谦  马海涛  李月  林红波 《吉林大学学报(地球科学版)》2010,40(6):1471-1478

为使传统的维纳滤波方法在最小均方准则下的解更准确、稳定,采用正则化思想,提出导数算子约束下的最小均方准则;在这种准则下,推导了维纳滤波因子及其频率响应.通过在不同频段取不同的正则化函数值,控制滤波结果.理论及实际地震勘探资料的分析表明:正则化维纳滤波去噪效果比传统维纳滤波好,且对有效波的损失较小,表明了文中所取正则项的可行性及有效性.最后讨论了通过建立正则化函数关系式,方便地提供正则化函数值以及圆滑振幅谱对改进滤波效果的可能性.  相似文献   

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王志平  陶庭叶  高飞 《大地测量与地球动力学》2014,34(4):161-164

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