排序方式： 共有84条查询结果，搜索用时 31 毫秒
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基于最大相关最小冗余度算法和随机森林回归算法,该文提出一种对欧洲中期天气预报中心（ECMWF）集合预报产品进行暴雨预报的释用方法。该方法采用最大相关最小冗余度算法,对ECMWF集合预报的51个成员进行筛选,选取若干个与预报对象相关性最大、相互间冗余度最小的成员作为随机森林回归算法的输入因子。利用ECMWF集合预报降水量平均值对建模样本进行分类,使预报模型的建模样本更具有针对性。通过2012年4月—2015年12月的交叉独立样本试验预报和2016年1—9月的业务预报试验的统计结果表明:该释用方法的暴雨预报TS和ETS评分,均比采用ECMWF集合预报产品51个成员降水量预报进行插值后取平均值的释用方法分别提高了0.07和0.05以上,显示了较好的数值预报产品释用效果。 相似文献
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Patricia Frontiera John Radke 《International journal of geographical information science》2013,27(3):337-360
This research compares the geographic information retrieval (GIR) performance of a set of logistic regression models with those of five non‐probabilistic methods that compute a spatial similarity score for a query–document pair. All methods are applied to a test collection of queries and documents indexed spatially by two convex conservative geometric approximations: the minimum bounding box (MBB) and the convex hull. In the comparison, the tested logistic regression models outperform, in terms of standard information retrieval recall and precision measures, all of the non‐probabilistic methods. The retrieval performance achieved by the logistic regression models on MBB approximations is similar to that achieved by the use of the non‐probabilistic methods on convex hulls. Although these results are valid only for the test collection used in this study, they suggest that a logistic regression approach to GIR provides an alternative to the use of higher‐quality geometric representations that are more difficult to obtain, implement, and process. Additionally, this research demonstrates the ability of a probabilistic approach to effectively incorporate information about geographic context in the spatial ranking process. 相似文献
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Accurate prediction of ground surface settlement is necessary for effectively controlling the settlement that develops during tunneling. Many models have been established for this purpose by extracting the relationship between the settlement and the factors that influence it. However, most of the models focused on the maximum ground surface settlement and do not involve dynamic and real-time predictions. This paper investigated how tunneling-induced ground surface settlement developed using a smooth relevance vector machine with a wavelet kernel (wsRVM). Various factors that affect this settlement, including geometrical, geological and shield operational parameters were considered. The model was applied to earth pressure balance (EPB) shield-driven tunnels. The results indicate that the prediction model performs well and that the distribution of the predictions can provide a measure of the prediction uncertainty. Unlike conventional methods that requireadditional efforts to determine relevant model parameters, the proposed method can optimize the parameters in the training process. The results of the parametric study conducted show that the model performance can be improved by the optimization and that the method can serve as a simple tool for practitioners to use in estimating ground surface settlement development during tunneling. 相似文献
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改革开放以来,内蒙古经济获得快速发展,取得可喜成就。但是．各地区的经济发展非常不平衡,地区经济差距显著。本文首先揭示了地区经济差距的现状,然后详细地分析各地区对外开放的差异及对地区经济的影响,并运用数学的回归分析法,进行了相关性分析,结果显示二者之间呈现密切的相关关系。 相似文献
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本文首次将效果测度分析方法应用在膨胀土胀缩等级判定分析的研究。选用某工程实例进行膨胀土胀缩等级的判定分析,取得了满意的结果。 相似文献
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为进一步提高堆石坝材料参数反演模型的计算精度与适用性,建立了基于量子遗传算法（QGA）与多输出混合核相关向量机（MMRVM）的自适应反演模型。通过引入混合核函数,使所构建的MMRVM能够高精度地模拟材料参数与大坝沉降间的复杂非线性关系,从而代替耗时较长的有限元（FEM）计算。通过利用参数较固化的QGA优化确定MMRVM核参数,使反演模型具有自适应性。以实测沉降数据为依据,充分发挥QGA的全局搜索能力反演筑坝材料本构模型参数。在分析模型所需测点个数与信噪比对计算结果影响的基础上,通过公伯峡堆石坝应用实例证明：QGA-MMRVM可快速、精确地反演堆石坝筑坝材料本构模型参数,模型凭借其自适应性在实际工程中具有良好的应用前景和推广价值。 相似文献
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为解决多输出边坡变形预测问题,提高预测模型的精度及计算效率,提出基于多输出相关向量机（MRVM）的边坡变形预测新模型。通过将标准RVM的单输出功能拓展到多维输出功能的方式建立MRVM,并利用PSO算法优化其参数。以某大型干坞边坡变形为例,基于MRVM建立边坡坡顶水平变形与沉降变形预测模型,并对其精度及计算效率进行分析。实验结果表明,MRVM的精度高于BP 神经网络、支持向量机（SVM）、RVM,证实拓展RVM所采用的方法可行,并具有较好的边坡预测精度;MRVM的计算时间远小于BP 神经网络、支持向量机（SVM）、RVM,具有较高的计算效率,并简化了建模程序,实现了对边坡的多个变形量进行同时预测。 相似文献
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This research is part of a larger effort to better understand and quantify the epistemic model uncertainty in dynamic response-history simulations. This paper focuses on how calibration methods influence model uncertainty. Structural models in earthquake engineering are typically built up from independently calibrated component models. During component calibration, engineers often use experimental component response under quasi-static loading to find parameters that minimize the error in structural response under dynamic loading. Since the calibration and the simulation environments are different, if a calibration method wants to provide optimal parameters for simulation, it has to focus on features of the component response that are important from the perspective of global structural behavior. Relevance describes how efficiently a calibration method can focus on such important features. A framework of virtual experiments and a methodology is proposed to evaluate the influence of calibration relevance on model error in simulations. The evaluation is demonstrated through a case study with buckling-restrained braced frames (BRBF). Two calibration methods are compared in the case study. The first, highly relevant calibration method is based on stiffness and hardening characteristics of braces; the second, less relevant calibration method is based on the axial force response of braces. The highly relevant calibration method consistently identified the preferable parameter sets. In contrast, the less relevant calibration method showed poor to mediocre performance. The framework and methodology presented here are not limited to BRBF. They have the potential to facilitate and systematize the improvement of component-model calibration methods for any structural system. 相似文献
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Quantitative trends in sponge ecology research 总被引：2，自引：1，他引：1
Mikel A. Becerro 《Marine Ecology》2008,29(2):167-177
Abstract It is almost dogmatic that sponges are one of the most relevant groups in benthic marine communities, a statement generally based upon their diversity and abundance in natural communities. But beyond their conspicuousness, do we really know the role that sponges play in nature? Using a series of productivity indicators, this review evaluates the relevance of sponge research to the general scientific community, particularly the contribution of sponge ecology to the broader science of ecology. The relevance of sponge research ranked second out of eight taxonomic groups. Ecology accounted for most of the sponge research output but it ranked poorly compared to the relative importance of the ecological literature in the remaining taxonomic groups. Sponge ecology focused primarily on the species level of organization even though the relevance of these studies fell well below expected. This review suggests that the ecological relevance of sponges is insufficiently supported by ecological data and would benefit from better scientific support. Sponge ecology has the opportunity to contribute to the broader science of ecology in numerous topics where sponge research may be particularly relevant. Broader ecological contributions will help verify the ecological relevance that the great diversity and abundance of sponges suggest. 相似文献