Accuracy and precision of fish-count data from a "dual-frequency identification sonar" (DIDSON) imaging system     

Holmes  John A.; Cronkite  George M.W.; Enzenhofer  Hermann J.; Mulligan  Timothy J. 《ICES Journal of Marine Science》2006,63(3):543-555

  相似文献   

Reliability-based comparative study for mooring lines design criteria     

Alberto Omar Vazquez-Hernandez  Gilberto Bruno Ellwanger  Luís Volnei Sudati Sagrilo   《Applied Ocean Research》2006,28(6):398-406

The characteristic environmental load effect for the design of mooring systems of floating units can be defined by means of three procedures: (a) the one associated to an extreme sea state with a given return period, (b) the worst one from a set of sea states on a contour line associated to a return period or (c) the extreme one based on response statistics for a long-term period. This work presents the result of a reliability-based partial safety factor calibration study for a LRFD mooring line design criteria considering the three approaches mentioned above. The calibration exercise is applied to three FPSOs considering North Sea environmental conditions and different water depths: 200, 800 and 3000 m. The mooring systems investigated take into account mooring lines made up of chains and polyester ropes. It is shown that, among all cases investigated, the design procedure based on the long-term response is the one that presents less scattered reliability indices around the target level.  相似文献   

A methodology for assessing the reliability of taut and slack mooring systems against instability     

A.A. Shah  A. Umar  N.A. Siddiqui   《Ocean Engineering》2005,32(10):1216-1234

In the present study, a methodology for reliability assessment of slack and taut mooring systems against instability has been presented. For this purpose, first, stability analysis of slack and taut mooring systems has been carried out and instable regions are obtained using procedure available in the literature. Having known the instable region(s), methodology for reliability assessment has been proposed which is based on Monte Carlo Simulation technique. After using the proposed methodology, probabilities of failure and reliability indices has been obtained for the above systems. Some parametric studies, such as, effect of lower and upper limits of instability and effect of frequency range of generations are also included to obtain the results of practical interest.  相似文献   

Risk Assessment for Tuzla Naval Base Breakwater   总被引：5，自引：0，他引：5  

Can Elmar BALAS 《中国海洋工程》2003,17(3)

1 .IntroductionTurkeywasstruckbytwomajorearthquakeeventsonAugust 1 7thandNovember 1 2th ,1 999,namedIzmit (Mw=7.4 )andD櫣ｚｃｅ (Mw=7.2 )earthquakes,respectively .ThestationsoperatedbytheGeneralDirectorateofDisasterAffairs,theKandilliObservatoryandEarthquakeResearchInstituteofIstanbulTechnicalUniversitymeasuredatleast 2 7stronggroundmotionsfortheIzmitearthquakewithin 2 0 0kmofthefault.AsignificantsegmentofthefaultrupturedintheareabetweenthewestofGolcukandtheeastofLakeSapanca .Inthesou…  相似文献   

边坡整体稳定的可靠性分析方法   总被引：8，自引：0，他引：8  

韩玉芳  刘德辅  董胜 《海岸工程》2001,20(4):7-14

边坡整体滑动稳定性的可靠性分析是建立在土体具有的抗力大于荷载效应的概率基础上进行设计和校验的。在条分法的基础上推导出了进行边坡稳定可靠性分析的统一极限状态方程 ,将土的容重γ、内摩擦角φ、粘聚力 c作为随机变量 ,当其为非正态分布时 ,进行当量正态化 ,考虑变量相关的情况 ,用简化相关法对随机变量进行统计分析 ,并以 Bishop圆弧滑动法为例 ,用 JC法求解边坡的可靠性指标及失效概率 ,给出计算安全系数和可靠性指标的算法程序。并就影响可靠性指标的因素如抗剪强度指标、变量分布形式、土性参数的变异性等进行了讨论。  相似文献   

测量控制网优化设计的可靠性准则法     

张正禄  邓勇  罗长林  杨奇儒 《测绘科学》2008,33(2):23-24,30

测量控制网优化设计与网的精度、可靠性、灵敏度以及费用等准则有关,但这些准则之间的关系又十分密切,本文提出了一种基于观测值内部可靠性指标的测量控制网模拟法优化设计新方法,介绍了其原理和特点,并用实例说明了用该方法的计算步骤和优化效益。  相似文献   

GPS网中已知点粗差探测时限差的研究     

伊晓东  杨耀宇  郭英起 《测绘与空间地理信息》2008,31(1):4-5

在利用附合导线法对GPS网中已知点的可靠性进行检核时,本文对如何合理地、客观地确定限差,以达到有效检核的目的进行了探讨,提出了检核限差标准。并结合实例进行计算和分析,成功地剔除了含有粗差的已知点。  相似文献   

基于蒙特卡罗法的多级黄土滑坡可靠性分析   总被引：2，自引：1，他引：1  

何淑军张春山  吴树仁 《地质通报》2008,27(11)

滑坡稳定性分析目前工程中一般采用极限平衡算法。为了确定滑坡的稳定性系数,在计算过程中要将岩土体、计算模型简化,忽略一些影响滑坡稳定的次要因素,把影响滑坡稳定的各种主要因素作为确定参数。由于滑坡岩土体本身的非均质性及其参数确定具有随机性和变异性,用唯一的稳定系数不能客观地反映整个滑坡的真实安全程度。以陕西省夏呀河滑坡为例,通过野外详细调查、工程勘探和室内土工试验,初步确定该滑坡存在四级滑动面,难以用简单的单一滑动面计算其稳定性。因此,先采用推力传递系数法对滑坡体上的四级滑坡分别进行滑坡稳定性计算,得到该滑坡体上的四级滑坡稳定系数。再采用蒙特卡罗法对该四级滑坡进行可靠性分析,得到其可靠度,定量地表达夏呀河四级滑坡的安全程度。同时对比分析夏呀河四级滑坡的稳定系数和失稳概率,综合评价该滑坡体上的四级滑坡的稳定性及其风险概率,为滑坡的工程治理及预测预警、灾害危险性评价提供依据。  相似文献   

Reliability Based Assessment of Shallow Foundations Using Mathcad     

Ahmad Shlash Alawneh  Osama K. Nusier  Ahmed Abdul-Ezel Al-Mufty 《Geotechnical and Geological Engineering》2006,24(3):637-660

A reliability based method was used to design and analyse shallow foundations using first-order Taylor series approximation. The computer program Mathcad was used to facilitate all mathematical and computional efforts. This method is an effective tool to assist the foundation designers and analyists to investigate how reliable their designs or analyses are in relation to the ultimate bearing capacity of the foundations. The approach presented in this paper provides a reliable alternative for design and analysis of shallow foundations, rather than the conventional design methods, which employs the assumptions of a specified saftey factor. Several examples were presented for design and analysis of strip footings embedded in sandy soil, and rectangular and square footings analysis embedded in clayey soils. The program input and output of each example are also presented and discussed.  相似文献   

泥石流汇流槽可靠度分析   总被引：2，自引：1，他引：2  

易朋莹  陈洪凯  唐红梅  吴四飞 《中国地质灾害与防治学报》2005,16(3):142-147

汇流槽是泥石流治理工程中常用的工程措施之一。文章基于汇流槽的倾倒破坏、滑移破坏及地基破坏模式，通过对汇流槽设计影响强烈的岩土参数、几何特征、荷载因素等敏感因子的求解方法及分布特征分析，从汇流槽的抗倾稳定、抗滑稳定和基底应力要求三方面建立极限状态方程。对于每个极限状态方程，在泰勒级数对非线性极限状态方程线性化后，运用一次二阶矩的理论，先假定失效点P^＊，求解出相应的均值和方差。然后根据可靠的定义，得到相应的可靠度指标，通过迭代法求解真正失效点的可靠度指标βi。最后根据3个状态方程相互独立的假定，得出整个结构的可靠度指标β。该方法在平川泥石流防治工程中得到了成功的运用。这对于可靠度设计方法在泥石流防治工程中的运用进行了有益的探讨。  相似文献