Use of Noise to Augment Training Data: A Neural Network Method of Mineral–Potential Mapping in Regions of Limited Known Deposit Examples     

Warick M. Brown  Tamás D. Gedeon  David I. Groves 《Natural Resources Research》2003,12(2):141-152

One of the main factors that affects the performance of MLP neural networks trained using the backpropagation algorithm in mineral-potential mapping isthe paucity of deposit relative to barren training patterns. To overcome this problem, random noise is added to the original training patterns in order to create additional synthetic deposit training data. Experiments on the effect of the number of deposits available for training in the Kalgoorlie Terrane orogenic gold province show that both the classification performance of a trained network and the quality of the resultant prospectivity map increasesignificantly with increased numbers of deposit patterns. Experiments are conducted to determine the optimum amount of noise using both uniform and normally distributed random noise. Through the addition of noise to the original deposit training data, the number of deposit training patterns is increased from approximately 50 to 1000. The percentage of correct classifications significantly improves for the independent test set as well as for deposit patterns in the test set. For example, using ±40% uniform random noise, the test-set classification performance increases from 67.9% and 68.0% to 72.8% and 77.1% (for test-set overall and test-set deposit patterns, respectively). Indices for the quality of the resultant prospectivity map, (i.e. D/A, D × (D/A), where D is the percentage of deposits and A is the percentage of the total area for the highest prospectivity map-class, and area under an ROC curve) also increase from 8.2, 105, 0.79 to 17.9, 226, 0.87, respectively. Increasing the size of the training-stop data set results in a further increase in classification performance to 73.5%, 77.4%, 14.7, 296, 0.87 for test-set overall and test-set deposit patterns, D/A, D × (D/A), and area under the ROC curve, respectively.  相似文献   

Statistical properties of reflection traveltimes in 3-D randomly inhomogeneous and anisomeric media   总被引：1，自引：0，他引：1  

Yu. A. Kravtsov  T. M. Müller  S. A. Shapiro  S. Buske 《Geophysical Journal International》2003,154(3):841-851

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结构随机响应的一种改进的概率谱叠加方法     

孙凌  吴知丰  周成功  周生震 《世界地震工程》2003,19(2):156-162

目前有一些关于多自由度结构体系的地震响应中响应峰值按降序(即由大到小的顺序)排列时的峰值统计性质的研究。本文对这些研究中的概率方法提出一些改进。由于这些改进，概率谱叠加方法在实际应用中就变得更准确和实用。本文以五层的结构模型为例，计算其在埃尔森特罗(1940)地震激励下的响应，并与时程分析结果进行比较。结果表明，改进的概率谱叠加方法能够谁确的计算较高几阶重要响应峰值的幅值。  相似文献   

中国大陆及其邻区强震活动与活动地块关系研究   总被引：16，自引：0，他引：16  

马宏生  张国民  刘杰  李丽  陈化然 《地学前缘》2003,10(Z1):74-80

从活动地块假说出发 ,在活动地块研究的基础上 ,探讨了中国大陆及邻区活动地块与强震活动的关系。研究指出 ,主要构造变形和强烈地震大都发生在活动地块边界。在占总面积 17%的活动地块边界上 ,集中了全部的 8级以上巨大地震和 86 %的 7级以上大地震 ,其释放能量占全部总能量的 95 %以上 ,表明中国大陆及其邻区活动地块边界带控制了绝大部分的强地震。从活动地块的整体来看 ,强震活动不仅显示出显著的韵律性特征 ,而且其高、低起伏基本上与中国大陆地区一致 ,只是强震活跃时段有时稍长于中国大陆。各轮回强震活动都有各自活动的主体地区 ,反映了不同活跃期内地块的不同活动方式。文中还从现今地壳运动角度 ,讨论了活动地块运动速率与强地震活动水平之间的可能联系。  相似文献   

重庆秀山寒武纪海相碳酸盐的锶同位素组成及其地层学意义     

石和  黄思静  沈立成  张萌 《地层学杂志》2003,27(1):71-76

锶同位素地层学是化学地层学的组成部分 ,简要介绍重庆市秀山县溶溪乡罗家沟寒武系剖面海相碳酸盐的锶同位素分析结果 ,建立了该剖面的锶同位素演化曲线 ,并与 Gao及 Denison等的同期锶演化曲线作了对比 ,秀山寒武纪锶同位素演化曲线与其他两条同期曲线有较大相似性 ,据此提出了秀山寒武系剖面部分主要年代地层界线的参考意见 ,并简述了寒武纪全球海平面变化的概况。  相似文献   

在MapInfo中实现区域对象样点布设功能   总被引：1，自引：0，他引：1  

王唤良  朱建军  张贵 《测绘工程》2003,12(4):30-32

随着GIS在森林资源管理中应用的不断深入，在GIS系统中实现林业专业抽样设计功能是非常必要的。本文使用MapBasic鳊程语言实现三种样点布设功能。操作时，用鼠标点击欲布样点区域，在弹出对话框中作出回答，就能得到样点布设图和样点坐标表。  相似文献   

Crossover from Nonlinearity Controlled to Heterogeneity Controlled Mixing in Two-Phase Porous Media Flows     

Frederico Furtado  Felipe Pereira 《Computational Geosciences》2003,7(2):115-135

We use high resolution Monte Carlo simulations to study the dispersive mixing in two-phase, immiscible, porous media flow that results from the interaction of the nonlinearities in the flow equations with geologic heterogeneity. Our numerical experiments show that distinct dispersive regimes occur depending on the relative strength of nonlinearity and heterogeneity. In particular, for a given degree of multiscale heterogeneity, controlled by the Hurst exponent which characterizes the underlying stochastic model for the heterogeneity, linear and nonlinear flows are essentially identical in their degree of dispersion, if the heterogeneity is strong enough. As the heterogeneity weakens, the dispersion rates cross over from those of linear heterogeneous flows to those typical of nonlinear homogeneous flows.  相似文献   

控制网优化设计中的蒙特卡罗法     

朱江  包欢 《测绘学院学报》2003,20(3):174-176

介绍了蒙特卡罗法的基本步骤以及伪随机数的检验方法；结合工程控制网的设计给出了一个实际算例，算例的结果表明该方法切实有效。  相似文献   

Dynamic stochastic estimation of physical variables   总被引：1，自引：0，他引：1  

George Christakos  Vijayanivas R. Raghu 《Mathematical Geology》1996,28(3):341-365

A fundamental problem facing the physical sciences today is analysis of natural variations and mapping of spatiotemporal processes. Detailed maps describing the space/time distribution of groundwater contaminants, atmospheric pollutant deposition processes, rainfall intensity variables, external intermittency functions, etc. are tools whose importance in practical applications cannot be overestimated. Such maps are valuable inputs for numerous applications including, for example, solute transport, storm modeling, turbulent-nonturbulent flow characterization, weather prediction, and human exposure to hazardous substances. The approach considered here uses the spatiotemporal random field theory to study natural space/time variations and derive dynamic stochastic estimates of physical variables. The random field model is constructed in a space/time continuum that explicitly involves both spatial and temporal aspects and provides a rigorous representation of spatiotemporal variabilities and uncertainties. This has considerable advantages as regards analytical investigations of natural processes. The model is used to study natural space/time variations of springwater calcium ion data from the Dyle River catchment area, Belgium. This dataset is characterized by a spatially nonhomogeneous and temporally nonstationary variability that is quantified by random field parameters, such as orders of space/time continuity and random field increments. A rich class of covariance models is determined from the properties of the random field increments. The analysis leads to maps of continuity orders and covariances reflecting space/time calcium ion correlations and trends. Calcium ion estimates and the associated statistical errors are calculated at unmeasured locations/instants over the Dyle region using a space/time kriging algorithm. In practice, the interpretation of the results of the dynamic stochastic analysis should take into consideration the scale effects.  相似文献   

随机地震荷载作用下饱和粉土的液化特性   总被引：3，自引：0，他引：3  

王建华  王承春 《岩土力学》1997,18(3):1-6

为了考虑随机地震荷载作用下饱和粉土的液化特性，研究了如何通过合理的地震响应分析确定饱和粉土层受到的随机地震荷载，进一步探讨了随机地震荷载作用下的动三轴试验技术，以及利用此种试验分析饱和粉土液化特性的方法。研究结果为形成判别饱和粉土层地震液化可能性的新方法提供了依据。  相似文献