Numerical simulation of ductile shear localization: Plastic‐flow network and slip‐line field     

Sheng‐zu Wang  Jun‐xiu Sun  Jie‐yuan Ning 《国际地质力学数值与分析法杂志》2008,32(3):307-324

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Comparison of bootstrap confidence intervals for an ANN model of a karstic aquifer response     

Ioannis Trichakis  Ioannis Nikolos  George P. Karatzas 《水文研究》2011,25(18):2827-2836

Following many applications artificial neural networks (ANNs) have found in hydrology, a question has been rising for quantification of the output uncertainty. A pre‐optimized ANN simulated the hydraulic head change at two observation wells, having as input hydrological and meteorological parameters. In order to calculate confidence intervals (CI) for the ANN output two bootstrap methods were examined namely bootstrap percentile and BCa (Bias‐Corrected and accelerated). The actual coverage of the CI was compared to the theoretical coverage for different certainty levels as a means of examining the method's reliability. The results of this work support the idea that the bootstrap methods provide a simple tool for confidence interval computation of ANNs. Comparing the two methods, the percentile requires fewer calculations and yields narrower intervals with similar actual coverage to that of BCa. Overall, the actual coverage was proved lower than desired when not modeled points were present in the data subset. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

An ANN‐based model for spatiotemporal groundwater level forecasting     

Vahid Nourani  Asghar Asghari Mogaddam  Ata Ollah Nadiri 《水文研究》2008,22(26):5054-5066

This paper evaluates the feasibility of using an artificial neural network (ANN) methodology for estimating the groundwater levels in some piezometers placed in an aquifer in north‐western Iran. This aquifer is multilayer and has a high groundwater level in urban areas. Spatiotemporal groundwater level simulation in a multilayer aquifer is regarded as difficult in hydrogeology due to the complexity of the different aquifer materials. In the present research the performance of different neural networks for groundwater level forecasting is examined in order to identify an optimal ANN architecture that can simulate the piezometers water levels. Six different types of network architectures and training algorithms are investigated and compared in terms of model prediction efficiency and accuracy. The results of different experiments show that accurate predictions can be achieved with a standard feedforward neural network trained usung the Levenberg–Marquardt algorithm. The structure and spatial regressions of the ANN parameters (weights and biases) are then used for spatiotemporal model presentation. The efficiency of the spatio‐temporal ANN (STANN) model is compared with two hybrid neural‐geostatistics (NG) and multivariate time series‐geostatistics (TSG) models. It is found in this study that the ANNs provide the most accurate predictions in comparison with the other models. Based on the nonlinear intrinsic ANN approach, the developed STANN model gives acceptable results for the Tabriz multilayer aquifer. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Determination of the constriction size distribution of granular filters by filtration tests     

J. Sjah  E. Vincens 《国际地质力学数值与分析法杂志》2013,37(10):1231-1246

This paper presents the calibration of an experiment based on filtration tests, able to provide the cumulative constriction size distribution of granular materials. Here, simulations of these tests are performed using a discrete element method. Filters of same density but different thicknesses are created with a poly‐sized spherical material. Lateral periodic boundaries for the samples are used, and their size is calibrated so that a representative elementary volume is obtained. Fine particles are released on the created samples, and the particle size distribution of the collected material that successfully crossed the filters is computed. These particle size distributions are related to the underlying cumulative constriction size distribution (CSD) of the granular material involved in the samples. The CSD is derived using a probabilistic approach for the path length of individual particles through a granular material. We settle all the requisites related to the technique and to the fine particles that are released to allow reaching a correct CSD for the filter. The reference CSD used for the calibration of the experiment is obtained after a radical partition of the void space into Delaunay tetrahedra and a geometrical characterisation of constrictions on each tetrahedron face. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

The cityscapes of European capital cities     

Herman van der Wusten 《GeoJournal》2000,51(1-2):129-133

Capital cities are politico-administrative centers. They are command centers, they symbolize authority and also the unit that is governed. Primarily they are capitals of states, but other governance systems may also have capitals. In the European context there are now regional capital cities and at least the concept of a European capital. Particularly on account of their symbolic function but also for the uses made of its appearance in political life, the cityscape of capital cities is an interesting topic for research. There are different types of capital cities in Europe that give rise to different cityscapes. Existing urban networks and types of political regime are important in this respect. Although cityscapes are pretty stable, they are differently perceived over time and uses made of them also change. A research agenda for this intersection of historical, cultural and political geography should concentrate on the evolution of these cityscapes, their perception and the uses made of them in the acting out of politics.  相似文献   

GPS观测数据传输技术的研究     

纪小军  蔡惟鑫  谭适龄 《大地测量与地球动力学》1996,(3)

为改变目前ＧＰＳ观测数据邮递的数据传递方式，研究用公用电话网进行ＧＰＳ观测数据传递的传输技术。通过实验以及联调证明此项传输技术不仅传输速度高，而且传输准确，使用方便，系统功能强，还可服务于工程监测、自然灾害防御、地震前兆监测等需数据通信的领域  相似文献   

基于贝叶斯网络的Web访问模式挖掘模型系统     

刘军 《成都信息工程学院学报》2004,19(1):40-43

根据用户的访问记录,以及每次检索输入的关键词、用户的动作来动态更新用户的兴趣点.提出了一个能较好吻合这一思想的数据挖掘模型,以用户的停留时间、访问频率和用户输入的检索关键词为数据对象,进行用户兴趣分析,动态跟踪用户需求意向,简化检索过程,提高WEB资源的使用效率.  相似文献   

定点潮汐形变观测与GPS大地测量   总被引：7，自引：5，他引：2  

陈德福  李正媛  陈鹏 《大地测量与地球动力学》2003,23(1):107-113

论述了我国定点潮汐形变观测与GPS在观测周期，物理量，频域，实测精度，监测优势者方面的异同，认为定点潮汐形变观测是测震学与大地测量（含GPS）的必要补充，介绍了我国定点潮汐形变观测技术的发展与台网观测技术，以及它在我国10多次中强震测报中的应用。  相似文献   

省级气象业务宽带信息网络构建策略     

任晓炜 《成都信息工程学院学报》2005,20(4):447-450

根据目前省级气象部门业务发展需求,结合当地电信行业的发展状况,提出一种可持续发展的宽带网络构建方案.  相似文献   

神经网络专家系统外壳     

何险峰 《成都信息工程学院学报》1993,(4)

神经网络专家系统外壳软件,是用于帮助用户迅速开发直观图形解释的人工智能业务应用系统。它以直观的屏幕树图为媒介,实现了正、反向推理机、语义网络、神经元网络、框架结构、知识库管理和算术表达式树图等整体宏观统一;实现了专家系统与人工神经元网络、定性分析与定量计算的统一;无监督分类与监督分类的统一。因此,它的应用范围很广。  相似文献