A non‐linear coupled finite element–boundary element model for the prediction of vibrations due to vibratory and impact pile driving     

Hamid Reza Masoumi  Stijn François  Geert Degrande 《国际地质力学数值与分析法杂志》2009,33(2):245-274

This paper presents a non‐linear coupled finite element–boundary element approach for the prediction of free field vibrations due to vibratory and impact pile driving. Both the non‐linear constitutive behavior of the soil in the vicinity of the pile and the dynamic interaction between the pile and the soil are accounted for. A subdomain approach is used, defining a generalized structure consisting of the pile and a bounded region of soil around the pile, and an unbounded exterior linear soil domain. The soil around the pile may exhibit non‐linear constitutive behavior and is modelled with a time‐domain finite element method. The dynamic stiffness matrix of the exterior unbounded soil domain is calculated using a boundary element formulation in the frequency domain based on a limited number of modes defined on the interface between the generalized structure and the unbounded soil. The soil–structure interaction forces are evaluated as a convolution of the displacement history and the soil flexibility matrices, which are obtained by an inverse Fourier transformation from the frequency to the time domain. This results in a hybrid frequency–time domain formulation of the non‐linear dynamic soil–structure interaction problem, which is solved in the time domain using Newmark's time integration method; the interaction force time history is evaluated using the θ‐scheme in order to obtain stable solutions. The proposed hybrid formulation is validated for linear problems of vibratory and impact pile driving, showing very good agreement with the results obtained with a frequency‐domain solution. Linear predictions, however, overestimate the free field peak particle velocities as observed in reported field experiments during vibratory and impact pile driving at comparable levels of the transferred energy. This is mainly due to energy dissipation related to plastic deformations in the soil around the pile. Ground vibrations due to vibratory and impact pile driving are, therefore, also computed with a non‐linear model where the soil is modelled as an isotropic elastic, perfectly plastic solid, which yields according to the Drucker–Prager failure criterion. This results in lower predicted free field vibrations with respect to linear predictions, which are also in much better agreement with experimental results recorded during vibratory and impact pile driving. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

The shaft‐based methodological approach to the quantification of long limb bones and its relevance to understanding hominid subsistence in the Pleistocene: application to four Palaeolithic sites     

J. Yravedra  M. Domínguez‐Rodrigo 《第四纪科学杂志》2009,24(1):85-96

The present work contributes to the debate of skeletal part use in archaeology to reconstruct hominid economic behaviour during the Pleistocene. It doubles the sample of sites where comparison of long limb bone element quantification is made by using alternative identification techniques based on epiphyses and epiphyses plus shafts. A refined method of long limb element quantification using shafts is discussed and applied to four sites representing different time periods from the end of the Middle Pleistocene to the end of the Upper Pleistocene. It is shown that when long limb elements are properly quantified a hypothesis of early access to carcasses at these sites can be supported. The data thus drawn are also used to compare skeletal part evenness across the time periods represented by the four sites selected. The results indicate low‐cost transport decisions by hominids at these sites. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Evidence of hybridisation within the genus Chrysoblephus and conserved nuclear sequences of South African sparids (Teleostei: Sparidae)     

《African Journal of Marine Science》2013,35(4):505-510

Several hybridisation events have been recorded in marine fish, yet there is little information for southern African species. Here we present evidence for hybridisation within the genus Chrysoblephus (Sparidae), by analysing a fish caught off KwaZulu-Natal, off the east coast of South Africa. We utilise three mitochondrial (16S, COI and Cyt b) and four nuclear markers (1st intron of the S7 ribosomal protein gene, Tmo-4C4, Histone 3 and 18S rRNA) to resolve the hybrid parentage. MtDNA analyses support C. anglicus as the maternal lineage. Analyses of the Tmo-4C4 gene and the first intron of the S7 gene show six and four heterozygous positions for the hybrid fish respectively. The heterozygous positions are shared by C. anglicus and C. puniceus, which suggests C. puniceus to be the paternal lineage, with the hybrid being a first generation cross. Morphologically, the hybrid mostly resembles C. puniceus, with some meristic counts overlapping with other sparid species. Interestingly, only two of the four nuclear markers show variation within the sparids sampled in this study; 1 160 bp of 18S rRNA and Histone 3 were invariable even between the genera Chrysoblephus, Gymnocrotaphus, Petrus and Pachymetopon, suggesting conserved nuclear evolution or a rapid speciation within this group of endemic fishes.  相似文献   

龙门山甘溪组谢家湾段混积相和混积层序地层学特征   总被引：9，自引：2，他引：7  

郑荣才  周刚  董霞  胡忠贵 《沉积学报》2010,28(1):33-41

依据实测剖面资料和薄片鉴定结果,将龙门山下泥盆统甘溪组谢家湾段确定为以泥质为背景的Ⅰ型混积类型和Ⅱ型混积层序,其Ⅰ型混积类型的形成机理包括间断式和原地式两种混积形式,以风暴流所致的间断式混积为主。相关的混积相可划分为混积滨岸、碎屑混积陆棚和碳酸盐混积陆棚三种混积相类型,以及①滨岸潮缘残积物＋混积潮坪、②混积陆棚泥＋远源风暴流、③混积陆棚泥＋近源砂质风暴流、④混积陆棚泥＋近源混积风暴流和生物滩与点礁四种混积微相类型的沉积组合。其Ⅱ型混积层序可划分出SMST、TST、EHST和LHST四个沉积体系域,各体系域由不同的混积类型、混积序列和混积强度的准层序叠置而成,以SMST和LHST的原地式混积作用最强,TST的间断式混积作用最弱,而EHST具有交替的间断式与原地式叠加混积作用。  相似文献   

地形高度依赖水平局地化尺度方案在台风数值模拟中的应用试验          下载免费PDF全文

夏宇  张涵斌  陈静  陈良吕  刘昕 《大气科学学报》2022,45(2):257-267

为了探究GRAPES区域集合三维变分混合同化系统中"地形高度依赖水平局地化尺度方案"对台风预报性能的影响,以"苏迪罗"台风(2015)和"杜鹃"台风(2015)为例,开展了集合变分混合同化系统在台风中的应用试验,对比分析了"地形高度依赖水平局地化尺度方案"和非"地形高度依赖水平局地化尺度方案"集合变分混合同化后台风路径...  相似文献   

基于密度模型稀疏表征的重力反演方法     

于会臻  王金铎  王千军 《地球物理学报》2021,64(3):1061-1073

重力反演是恢复地下密度空间分布的有效工具,而选择合理的密度模型约束方法是提升重力反演分辨率和可靠性的关键.常规约束方法大多是从剖分网格空间中的密度模型出发,通过调整光滑或稀疏约束权重来匹配反演目标,但当地质体类型多样、异常分离不准确及网格剖分方案不合理时,模型约束的合理性与灵活性难以得到有效保证.为此,本文提出了一种基于密度模型稀疏表征的重力反演方法.首先假设待反演的密度模型表征为模型特征矩阵和稀疏分解系数的线性组合,之后重新推导了重力反演目标函数,并给出了分解系数的稀疏求解过程.相比现有重力反演方法,用于构建模型特征矩阵的特征模型可包含不同类型地质体的先验几何信息,分解系数的稀疏性保证了待反演目标来自于最典型的地质模式组合.最后,通过模型试验及实际资料验证了基于密度模型稀疏表征的重力反演方法的有效性.  相似文献   

基于P2P和KML的地理空间信息服务     

胡诚  边馥苓 《地理空间信息》2012,(2):1-3,179

针对传统C/S架构下服务器性能和网络传输限制等问题,分析了基于P2P技术和KML地理空间信息服务的特点及其协作方式,设计了两者相结合的地理空间信息服务架构,结合数字城市项目应用对模型加速数据传输的有效性进行了验证。  相似文献   

Combining passive integrated transponder tags with conventional T‐bar tags to improve tag reporting rates in a rock lobster trap fishery     

Stewart D. Frusher  David Hall  Paul Burch  Caleb Gardner 《新西兰海洋与淡水研究杂志》2013,47(1):347-353

Tag reporting rate is an important parameter required for estimating fishing and natural mortality in fished populations. It is an extremely difficult parameter to estimate and can vary both during the fishing season and between fishing years. Improving tag reporting rates has been identified as a cost‐effective way of improving precision in fishing and natural mortality estimates derived from tagging data. In this study we evaluated the use of passive integrated transponder (PIT) tags to improve tag reporting rates in a lobster (Jasus edwardsii) trap fishery. To minimise the risk of PIT tag ingestion by consumers, we tested insertion of the PIT tag into the base of the antennae, the base of the walking leg, and the base of the telson. The base of the antennae proved to be the best option for lobster health although impacts were observed at all tag insertion sites. We further developed and tested a hybrid tag that combined a conventional external T‐bar tag with a PIT tag embedded within the shaft. PIT tag scanners were positioned in bottlenecks in the capture process so that all lobsters retained on board the vessel were passed through a scanner. Thus, the tag reporting rate was expected to be 100% for the subsample of the fleet fitted with scanners when scanners were operational. Scanner malfunction was a major issue and further engineering solutions are required to ensure that scanners are reliable when working in harsh marine conditions such as on‐board fishing vessels. Advantages of the hybrid tag are: the ability to be detected by both automatic detectors and fishers; known tag‐induced mortality and tag loss rates from previous research; and PIT tagging without risk of human ingestion.  相似文献   

辽宁省黄海沿岸人工岸线潮间带大型海藻调查与分析研究   总被引：1，自引：1，他引：0  

冯天威  刘正一  付晚涛  秦松 《海洋科学》2013,37(12):17-27

为调查辽宁省黄海沿岸人工岸线上潮间带大型海藻多样性情况, 于2011 年10 月至2012 年6 月在大连湾、獐子岛、旅顺及丹东进行采样, 并与其附近天然岸线上海藻进行对比。调查结果显示, 在人工岸线上共发现17 种海藻, 以红藻与绿藻为主, 其中11 种可在相邻天然岸线发现。海藻多样性天然岸线＞混合岸线＞人工岸线, 但人工岸线上绿藻种类与天然岸线上的基本相同。在大连湾及獐子岛地区, 无机氮低的海域, 海藻多样性高; pH 高的海域, 海藻多样性高。调查中发现有人工岸线与天然岸线共存的混合岸线, 此岸线可看作是生境岸线(living shoreline)的一个变形, 为生物保护及生态恢复提供了新思路。  相似文献   

Seismic Hybrid Control and its Robustness in Girder Bridges     

《Marine Georesources & Geotechnology》2013,31(3-4):307-314

Two seismic hybrid control methods are studied in this article to mitigate the seismic hazard of girder bridges; one is applied for short-span simply supported, box section girders of concrete bridges using the hybrid mass damper (HMD), the other is applied for long-span girders of concrete bridges to hybridize viscoelastic dampers and actuators. The robustness of the control effect has been paid more attention here. The randomicity of the seismic excitation and the stability of the control algorithm are also taken into account.  相似文献