黄东海海区总悬浮物散射特性研究   总被引：2，自引：0，他引：2  

刘炜  李铜基  朱建华  陈清莲 《海洋技术学报》2007,26(2):42-46

我国黄东海水体散射特性非常复杂,这是造成该海域水色区划特点显著的原因之一。文中利用2003年4月黄东海试验数据(HD200304)对总悬浮物(TSM,Total Suspended Matter)的后向散射概率~bbs和单位散射系数bs*进行研究。基于对现场数据的统计分析,我们开发了总悬浮物后向散射概率模型,通过相对偏差分析表明,有近90%的样品反演相对偏差控制在±30%之内。对总悬浮物单位散射系数研究时,选择555 nm为参考波段,开发了不同波段间总悬浮物单位散射系数关系模型,通过相对偏差分析表明,有近94%的样品反演相对偏差在±10%之内,反演效果非常好。  相似文献   

波群作用于垂直桩柱的峰力统计性质     

徐立论  陈志军  焦海英 《中国海洋大学学报(自然科学版)》1994,(1)

研究具有窄谱和Ｗｅｉｂｕｌｌ波高分布的波群对非线性桩柱系统作用力的统计性质。求得了桩桩的波浪峰力的各种特征值及其比值。指出这些数值不仅是阻力一惯性力参数ｂＨ的函数，也随着波群因子而变化。本文模式更具广泛性。文中给出了一系列计算图表，可从理论计算波群作用于桩柱的波浪峰力。  相似文献   

防波堤风险分析研究框架   总被引：1，自引：0，他引：1  

李炎保  马青山  蒋学炼 《海洋通报》2006,25(1):16-23

介绍了防波堤风险分析研究的内容、方法和目前的研究进展。防波堤风险分析包涵四个主要方面:防波堤风险辨识、防波堤风险估计、防波堤风险评价和防波堤风险控制。具体内容包括:防波堤系统正常使用极限状态和承载力极限状态的界定,波浪不确定性的识别和描述,防波堤失效模式的探讨,单一模式失效概率和系统失效概率的计算,两种极限状态失效后果的量化,成本-获益分析,效用分析,可接受风险准则和降低风险的措施。防波堤风险分析的目的在于为决策者明确工程中存在的诸多不确定性因素,提供充足信息,实现项目的决策优化。  相似文献   

风浪周期分布与谱宽度的关系     

文凡  高志一 《海洋湖沼通报》2006,(3):1-5

本文通过分析实验室风浪周期分布,发现风浪周期累积概率分布曲线低于Longuet-Higgins理论结果,在小概率周期区域实验结果与理论结果的差异明显。对实验结果进一步分析发现,在谱不是很窄时,在小概率处风浪周期累积概率随谱宽度的增大而降低,这与窄谱假定下的理论结果相反,Longuet-Higgins理论结果在小概率处不便于描述周期分布随谱宽度的变化。根据实验结果提出风浪周期的Weibull分布经验公式,Weibull分布中的参数依赖于谱宽度。  相似文献   

一种用于海底类型聚类的新方法(英文)     

Jianhu Zhao  Hongmei Zhang  Feihu Ma  Juanjuan Li 《地球空间信息科学学报》2008,11(4):279-282

By using sonar imaging, this paper presents a new algorithm for the clustering of seabed types based on the self-organizing feature maps （SOFM） neural network. The theory as well as data processing is studied in detail. Some valuable conclusions and suggestions are given  相似文献   

Minimizing the effects of inaccurate sediment description in borehole data using rough sets and transition probability     

Gift Dumedah  Nadine Schuurman 《Journal of Geographical Systems》2008,10(3):291-315

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Comparison of numerical models of two debris flows in the Cortina d’ Ampezzo area,Dolomites, Italy   总被引：2，自引：0，他引：2  

Maria Concetta Armento  Rinaldo Genevois  Pia Rosella Tecca 《Landslides》2008,5(1):143-150

The accurate prediction of runout distances, velocities and the knowledge of flow rheology can reduce the casualties and property damage produced by debris flows, providing a means to delineate hazard areas, to estimate hazard intensities for input into risk studies and to provide parameters for the design of protective measures. The application of most of models that describe the propagation and deposition of debris flow requires detailed topography, rheological and hydrological data that are not always available for the debris-flow hazard delineation and estimation. In the Cortina d’Ampezzo area, Eastern Dolomites, Italy, most of the slope instabilities are represented by debris flows; 325 debris-flow prone watersheds have been mapped in the geomorphological hazard map of this area. We compared the results of simulations of two well-documented debris flows in the Cortina d’Ampezzo area, carried on with two different single-phase, non-Newtonian models, the one-dimensional DAN-W and the two-dimensional FLO-2D, to test the possibility to simulate the dynamic behaviour of a debris flow with a model using a limited range of input parameters. FLO-2D model creates a more accurate representation of the hazard area in terms of flooded area, but the results in terms of runout distances and deposits thickness are similar to DAN-W results. Using DAN-W, the most appropriate rheology to describe the debris-flow behaviour is the Voellmy model. When detailed topographical, rheological and hydrological data are not available, DAN-W, which requires less detailed data, is a valuable tool to predict debris-flow hazard. Parameters obtained through back-analysis with both models can be applied to predict hazard in other areas characterized by similar geology, morphology and climate.  相似文献   

Multi-Scale Texture Modeling     

Ralf Hielscher  Helmut Schaeben 《Mathematical Geosciences》2008,40(1):63-82

Patterns of crystallographic preferred orientation are referred to as texture. The specific subject of texture analysis is the experimental determination and interpretation of the statistical distribution of orientations of crystals within a specimen of polycrystalline material, which could be metals or rocks. The objective is to relate an observed pattern of preferred orientation to its generating processes and vice versa. In geosciences, texture of minerals in rocks is used to infer constraints on their tectono-metamorphic history. Since most physical properties of crystals, such as elastic moduli, the coefficients of thermal expansion, or chemical resistance to etching depends on crystal symmetry and orientation, the presence of texture imparts directional properties to the polycrystalline material. A major issue of mathematical texture analysis is the resolution of the inverse problem to determine a reasonable orientation density function on SO(3) from measured pole intensities on , which relates to the inverse of the totally geodesic Radon transform. This communication introduces a wavelet approach into mathematical texture analysis. Wavelets on the two-dimensional sphere and on the rotational group SO(3) are discussed, and an algorithms for a wavelet decomposition on both domains following the ideas of Ta-Hsin Li is given. The relationship of these wavelets on both domains with respect to the totally geodesic Radon transform is investigated. In particular, it is shown that the Radon transform of these wavelets on SO(3) are again wavelets on . A novel algorithm for the inversion of experimental pole intensities to an orientation density function based on this relationship is developed.  相似文献   

Bayesian estimation of seismic hazard for two sites in Switzerland     

Erik Rüttener  Juan José Egozcue  Dieter Mayer-Rosa  Stephan Mueller 《Natural Hazards》1996,14(2-3):165-178

Seismic hazard analysis is based on data and models, which both are imprecise and uncertain. Especially the interpretation of historical information into earthquake parameters, e.g. earthquake size and location, yields ambiguous and imprecise data. Models based on probability distributions have been developed in order to quantify and represent these uncertainties. Nevertheless, the majority of the procedures applied in seismic hazard assessment do not take into account these uncertainties, nor do they show the variance of the results. Therefore, a procedure based on Bayesian statistics was developed to estimate return periods for different ground motion intensities (MSK scale).Bayesian techniques provide a mathematical model to estimate the distribution of random variables in presence of uncertainties. The developed method estimates the probability distribution of the number of occurrences in a Poisson process described by the parameter . The input data are the historical occurrences of intensities for a particular site, represented by a discrete probability distribution for each earthquake. The calculation of these historical occurrences requires a careful preparation of all input parameters, i.e. a modelling of their uncertainties. The obtained results show that the variance of the recurrence rate is smaller in regions with higher seismic activity than in less active regions. It can also be demonstrated that long return periods cannot be estimated with confidence, because the time period of observation is too short. This indicates that the long return periods obtained by seismic source methods only reflects the delineated seismic sources and the chosen earthquake size distribution law.  相似文献   

A quantitative bifurcation analysis of Hénon-like 2D maps     

C. Polymilis  G. Servizi  Ch. Skokos 《Celestial Mechanics and Dynamical Astronomy》1996,66(4):365-385

We numerically study the bifurcations of two nonlinear maps, with the same linear part, which depend on a parameter namely the Hénon quadratic map and the so called beam-beam map. Many families of periodic orbits which bifurcate from the central family, are studied. Each family undergoes a sequence of period doubling bifurcations in the quadratic map, But the behavior of the beam-beam map is completely different. Inverse bifurcations occur in both maps. But some families of the same type which bifurcate inversely in the quadratic map do not bifurcate inversely in the beam-beam map, even though both maps have common linear part.  相似文献