Generalized dual porosity: A numerical method for representing spatially variable sub-grid scale processes     

George A. Zyvoloski  Bruce A. Robinson  Hari S. Viswanathan 《Advances in water resources》2008

A generalized dual porosity method (GDPM) has been developed to incorporate sub-grid scale heterogeneity into large-scale flow and transport simulations. The method is spatially variable in the sense that the method can be applied with different levels of resolution for different spatial nodes in the simulation. The method utilizes the nodal connectivity structure and linear equation solvers of unstructured grids like those used in the finite element method, and can be applied to any problem without externally modifying the numerical grid. The algorithm scales linearly in CPU time and storage with the number of GDPM nodes. We demonstrate the utility and computational efficiency of the technique with two verification problems and an example problem of a field site.  相似文献   

Statistical features of foreshocks in comparison with other earthquake clusters   总被引：2，自引：0，他引：2  

Yosihiko Ogata  Tokuji Utsu  Koichi Katsura 《Geophysical Journal International》1995,121(1):233-254

  相似文献   

Generalized maximum-likelihood estimation of variance components with inverted gamma prior   总被引：2，自引：2，他引：0  

J. Grodecki 《Journal of Geodesy》1999,73(7):367-374

A new method for the estimation of variance components is presented. The proposed method combines the concept of maximum-likelihood estimation with the Bayesian approach and facilitates computationally efficient introduction of prior information into the estimation process. Received: 22 April 1998 / Accepted: 19 April 1999  相似文献   

基于GAM模型的南海鸢乌贼CPUE时空分布及其与环境因子的关系     

晏磊  李杰  张鹏  杨炳忠  王腾 《海洋通报》2021,40(2)

根据2013—2016年南海两艘灯光罩网渔船的生产统计资料,结合卫星遥感获取的环境因子数据,运用广义可加模型(GAM)分析了南海春季鸢乌贼渔场分布及其与时空和环境因子的关系。结果表明:2013—2014年鸢乌贼单位捕捞努力量渔获量(CPUE,Catch Per Unit Effort)呈增长趋势,而2015—2016年CPUE明显下降。2013—2015年鸢乌贼中心渔场主要分布在114°E—115°E,10°N—12°N区域,而2016年中心渔场向西偏移;GAM模型对CPUE的总偏差解释率为66.40%,其中经度、纬度、海表温度和叶绿素浓度4个因子与CPUE显著相关(P0.05),影响因子按重要性排列,从大到小依次为:经度、纬度、叶绿素浓度和海表温度。而年份、月份和海表盐度对CPUE影响不显著(P0.05)。鸢乌贼适宜海表温度为27℃～30℃,适宜叶绿素浓度为0.10～0.15 mg/m3。  相似文献   

弱形式时域完美匹配层——滞弹性近场波动数值模拟   总被引：1，自引：0，他引：1       下载免费PDF全文

谢志南  郑永路  章旭斌  唐丽华 《地球物理学报》2019,62(8):3140-3154

本文旨在构建适用于滞弹性近场时域波动有限元模拟的高精度人工边界条件：完美匹配层（Perfectly Matched Layer：PML）,其中阻尼介质时域本构基于广义标准线性体建立.与以往研究不同,本文采用复坐标延拓技术变换弱形式波动方程构建了可直接用有限元离散的弱形式时域PML,规避以往独立对无限域内波动方程及界面条件进行延拓可导致的PML场方程和界面条件匹配不合理引发数值失稳、计算精度低下等问题.其次,针对PML中多极点有理分式与频域函数乘积的傅里叶反变换难以计算的问题,利用PML精度对复坐标延拓函数中延拓参数微调不敏感这一特点,明确给出了参数微调准则以规避多重极点,进而利用有理分式分解给出了一种普适、简便的计算方法,极大地简化了PML计算.基于该方法可实现任意高阶PML.最后,将本文构建滞弹性PML与高阶勒让德谱元（高精度集中质量有限元）结合得到滞弹性近场波动谱元离散方案.基于算例验证了滞弹性PML的计算效率、精度及新离散方案的长持时稳定特性.新离散方案可应用于计入实际介质阻尼的地震波动正、反问题数值模拟,提高波形模拟的精度以及地下波速结构反演的精度和可靠性.  相似文献   

气候变化对水文季节性迁移的影响：以水库汛期分期和极值降水为例     

章梦杰  郭家力  林伟  郭靖  舒章康  李英海  张静文 《气候变化研究进展》2019,15(2):158-166

气候变化影响下水利工程的可靠设计和安全运行是广大决策者、研究者和公众共同关注的热点问题。以清江流域为研究对象,首先采用模糊集合分析法对不同温室气体排放情景(A2、A1B和B1)下的逐日降水资料进行汛期分期,再通过广义极值分布(GEV)函数对各分期的极值降水序列进行频率分析。结果表明,降水季节性迁移直接影响汛期分期;3种排放情景下未来各时段(2011—2030年、2046—2065年和2080—2099年)的主汛期较基准期均推迟且有缩短趋势。对于极值降水量级,未来情景下明显小于基准期,且这种差距随着重现期的增大而增大;主汛期明显大于前汛期和后汛期,且在时段之间的差异明显大于排放情景之间的差异。  相似文献   

Characterizing parameter sensitivity and uncertainty for a snow model across hydroclimatic regimes     

Minxue He  Terri S. Hogue  Kristie J. FranzSteven A. Margulis  Jasper A. Vrugt 《Advances in water resources》2011,34(1):114-127

The National Weather Service (NWS) uses the SNOW17 model to forecast snow accumulation and ablation processes in snow-dominated watersheds nationwide. Successful application of the SNOW17 relies heavily on site-specific estimation of model parameters. The current study undertakes a comprehensive sensitivity and uncertainty analysis of SNOW17 model parameters using forcing and snow water equivalent (SWE) data from 12 sites with differing meteorological and geographic characteristics. The Generalized Sensitivity Analysis and the recently developed Differential Evolution Adaptive Metropolis (DREAM) algorithm are utilized to explore the parameter space and assess model parametric and predictive uncertainty. Results indicate that SNOW17 parameter sensitivity and uncertainty generally varies between sites. Of the six hydroclimatic characteristics studied, only air temperature shows strong correlation with the sensitivity and uncertainty ranges of two parameters, while precipitation is highly correlated with the uncertainty of one parameter. Posterior marginal distributions of two parameters are also shown to be site-dependent in terms of distribution type. The SNOW17 prediction ensembles generated by the DREAM-derived posterior parameter sets contain most of the observed SWE. The proposed uncertainty analysis provides posterior parameter information on parameter uncertainty and distribution types that can serve as a foundation for a data assimilation framework for hydrologic models.  相似文献   

云南地区中小地震静力学和动力学参数定标关系   总被引：1，自引：0，他引：1  

刘丽芳  杨晶琼  华卫  苏有锦  刘杰 《中国地震》2011,27(3):268-279

通过消除S波观测谱中的传播路径、场地响应、仪器响应等影响因素,得到中小地震的震源谱.根据Brune震源模型,运用遗传算法计算了地震矩、应力降、震源半径等震源参数;通过考虑由于有限的仪器带宽带来的地震辐射能量低估及补偿问题,测定了中小地震辐射能量;分析了云南地区ML2.0 ～5.3地震静力学和动力学参数定标关系.结果表明:地震矩为2.1×1012～1.2 ×1016N·m,地震矩M0和震级ML的线性关系式为lgM0=1.01ML+10.59;震源破裂半径在86.9～1220.4m之间,地震矩M0与震源半径a之间的关系式为lgM0 =0.003a+ 12.90;应力降结果介于0.03 ～57.55MPa之间,当M0＜4×1014N.m时,应力降随地震矩的增大而增大,当M0≥4 ×1014N·m时,应力降与地震矩之间无明显的依赖关系;地震矩M0与拐角频率∫c明显有依赖关系,二者之间的关系式为lgfc=- lgM0+5.32;地震辐射能量ER在3.01×106～2.06×1012J之间,地震辐射能量ER与震级ML之间的关系为lgER=1.18ML+5.69.当M0＜4×1014N·m时,折合能量有随地震矩增大而增大的趋势,当M0≥4×1014N·m时,折合能量不随地震矩的增大而变化;地震视应力范围为0.02～31.4MPa之间,视应力与震源深度之间没有明显的依赖性.  相似文献   

Prediction of probabilistic settlements via spectral stochastic meshless local Petrov–Galerkin method     

Guang-Yih Sheu 《Computers and Geotechnics》2011

This study introduces the prediction of probabilistic settlements with the uncertainty in the spatial variability of Young’s modulus to illustrate the preliminary development of a spectral stochastic meshless local Petrov–Galerkin (SSMLPG) method. Generalized polynomial chaos expansions of Young’s moduli and a two-dimensional meshfree weak–strong formulation in elasticity are combined to derive the SSMLPG formulation. Because of the local and truly meshless nature, the SSMLPG method is more computationally efficient than available stochastic numerical methods. Two examples further show that SSMLPG-based predictions remain sufficiently accurate even in case of scattered nodes. Therefore, the SSMLPG method can be a valuable alternative for solving stochastic boundary-value problems.  相似文献   

一种新的声速剖面结构参数化方法     

张旭  张永刚  张健雪  董楠 《海洋学报》2011,33(5):54-60

在Munk模型和GDEM模型的基础上,提出了一种新的声速剖面结构参数化模型,即分层声速剖面模型(LSSPM).模型用含9个参数的四层分段函数分别描述混合层、主跃层、深海声道层和深海等温层的声速结构,形式简明、直观.数值实验结果表明,LSSPM模型对声速剖面的拟合可达到较高的精度,且对于中国周边的深海和浅海区域有较好的适...  相似文献