Comparison of shortest sailing distance through random and regular sampling points     

Harbitz  Alf; Pennington  Michael 《ICES Journal of Marine Science》2004,61(1):140-147

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基于海浪谱的沉箱式防波堤动力分析方法   总被引：1，自引：0，他引：1  

王元战  洪宁宁  唐照评 《海洋工程》2007,25(3):1-6,39

利用海浪谱JONSWAP谱生成随机波浪,并结合改进的波浪力时程模型生成一个连续的、持续时间相对较长的随机波浪力作用过程。假设五十年设计基准期内防波堤每年遭受一次风暴,利用波浪谱随机生成五十次风暴波浪作用过程,对防波堤五十年设计基准期的响应过程进行一次随机模拟,以此作为一个样本。经过对大量随机模拟产生的样本进行统计分析,实现对防波堤整个设计基准期内的安全度进行概率评估。最后,通过算例对该方法的应用进行了演示。  相似文献   

Simplified procedure for laterally loaded drilled shafts in spatially random clays     

Zhe Luo  Zhongyang Wu  Longlong Fu 《Marine Georesources & Geotechnology》2020,38(5):539-552

Abstract

In this article, a simplified approach for the reliability-based design of laterally loaded drilled shafts considering the spatial variability of soil property is presented. This simplified approach utilizes a conventional reliability method implemented using the variance reduction technique. An algorithm for back-calculating the reduction factor and characteristic length for various shaft slenderness ratios is proposed. This simplified approach can yield responses for drilled shafts that are equivalent to those obtained using random field modeling (RFM), which is a far more complex process. The simplified approach does not require the knowledge of random field theory and can be an efficient design tool in geotechnical engineering practice.  相似文献   

Repetitive fishing, local depletion, and fishing efficiencies in the Kerguelen Islands fisheries     

Bez  N.; De Oliveira  E.; Duhamel  G. 《ICES Journal of Marine Science》2006,63(3):532-542

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Numerical Simulation of Breaking Wave Based on Higher-Order Mild Slope Equation   总被引：4，自引：0，他引：4  

TAO Jianhua 《中国海洋工程》2001,(2):269-280

The "surface roller" to simulate wave energy dissipation of wave breaking is introduced into the random wave model based on approximate parabolic mild slope equation in this paper to simulate the random wave transportation including diffraction, refraction and breaking in nearshore areas. The roller breaking random wave higher-order approximate parabolic equation model has been verified by the existing experimental data for a plane slope beach and a circular shoal, and the numerical results of random wave breaking model agree with the experimental data very well. This model can be applied to calculate random wave propagation from deep to shallow water in large areas near the shore over natu ral topography.  相似文献   

随机波浪作用下海床动力响应及液化的理论分析   总被引：2，自引：1，他引：1  

王忠涛  栾茂田  JENG Dong-Sheng  刘占阁 《岩土力学》2008,29(8):2051-2056

运用随机波浪理论,基于广义Biot动力固结理论,建立了能够考虑波浪荷载随机特性影响的计算海床动力响应及液化深度的解析数值模型,并从时域上进行求解分析.通过与传统线性规则波浪荷载作用下海床动力响应及液化深度的数值结果的对比分析,详细讨论了考虑波浪荷载的随机特性对于求解海床动力响应及液化深度的影响程度.结果表明,根据随机波浪理论计算得到的海床中的超孔隙水压力、水平有效应力、竖向有效应力、剪应力表现出较强的不规则性,其幅值沿着海床深度方向的变化趋势与根据线性规则波浪理论计算得到结果的变化趋势基本相同,但在同数量级上更大,同时计算得到的海床最大液化深度明显大于根据线性规则波浪理论计算得到的结果.因此,在海洋地基设计和自由场地安全评估时应该合理地考虑波浪荷载的随机特性.  相似文献   

多源在线地理编码服务分类优化模型     

廖薇薇  柳林  周素红  宋广文  李秋萍  刘凯 《热带地理》2018,38(2):255-263

利用在线地理编码API解决海量中文地址快速编码问题,在此基础上,利用简单的规则对编码结果进行清洗、标记,最后通过基于系统聚类与随机森林的分类优化模型,将多平台编码结果分类处理、优化。利用广州市盗窃案件地址对模型进行训练与验证,结果表明：相比未处理的编码结果,经模型优化过的编码结果整体位置误差距离减小。高德的地理编码服务有着最好的编码质量,但训练样本的高德编码误差均值仍高达590.43 m,经模型优化后,样本的编码误差均值降至173.73 m,验证样本编码误差均值由554.88 m（高德）降至180.04 m,降低了67.49%,高德90.08%的异常编码结果被清洗优化。对于训练样本与验证样本,模型优化效果相似;对于地址类型不同的案件、位于市区与市郊的案件,模型优化效果相似,说明模型具有一定普适性。该模型能够方便快捷地将海量社会经济信息转化为空间数据,提高编码精度,为地理大数据的研究提供更好的数据支持。  相似文献   

基于随机森林模型的咸潮预报     

苏程佳  陈莎  陈晓宏 《热带地理》2018,38(3):432-439

在候选预报因子的基础上,通过Pearson相关系数和重要度指数分别确定了主要预报因子及其滞后期,进而利用确定滞后期的预报因子建立基于随机森林的咸潮预报模型,并应用于磨刀门水道大涌口站的枯水期咸潮预报。结果发现：通过相关系数确定的主要预报因子与含氯度之间存在1~3 d不等的滞后期;考虑预报因子滞后作用的随机森林模型,其预报结果不仅能很好地满足咸潮预报的精度要求,而且明显优于未考虑预报因子滞后作用的随机森林模型,即考虑预报因子的滞后作用能显著提高模型的拟合效果。此外,与传统的马尔科夫链相比,随机森林模型的预报结果不仅精度更高,而且在中长期预报上更有优势。  相似文献   

Markov random field-based method for super-resolution mapping of forest encroachment from remotely sensed ASTER image     

L.K. Tiwari  S.K. Sinha  S. Saran  V.A. Tolpekin  P.L.N. Raju 《国际地球制图》2016,31(4):428-445

Forest encroachment (FE) is a problem in Andaman and Nicobar Islands (ANI) in India for environment and planning. Small gaps created in the forest slowly expand its periphery disturbing the biodiversity. Therefore, intrusion of poachers, slash and burn and other factors causing FE must be carefully detected and monitored. Remote sensing offers a great opportunity to accomplish this task because of its synoptic view. Conventional classification methods with remotely sensed images are problematic because of small size of FE and mixed landcover composition. This study presents an application of super-resolution mapping (SRM) based on Markov random field for detection of FE using ASTER (15 m) images. The SRM results were validated using multispectral IRS LISS-IV (5.8 m) image. Non-contiguous FE patches of various sizes and shapes are characterized using the spatial contextual information. The novelty of this approach lies in the identification and separability of small FE pockets which could not be achieved with pixel-based maximum likelihood classifier (MLC). The SRM parameters were optimized and found comparable to previous studies. Classification accuracy obtained with SRM at scale factor 3 is κ = 0.62 that is superior to accuracy of MLC (κ = 0.51). SRM is a promising tool for detection and monitoring of FE at Rutland Island in ANI, India.  相似文献   

基于SVD的叠后地震资料随机噪声分离方法     

姜宇航  刘财  宋超  高月  鹿琪 《世界地质》2016,35(2):543-548

笔者提出基于SVD的叠后地震资料随机噪声分离方法,在地震剖面的同相轴水平或接近水平时可以有效地分离出地震剖面中的随机噪声,提高地震剖面的分辨率。为了说明SVD随机噪声分离方法的有效性和高效性,建立模型试验,在合成地震记录中加入随机噪声,之后进行实际地震资料处理,分别用SVD方法和基于小波变换的分层阈值方法对加入随机噪声的合成记录和加入随机噪声的实际资料进行随机噪声分离处理。对比发现,SVD随机噪声分离方法相比于基于小波变换的分层阈值方法更加有效且高效。  相似文献