Winkler地基上材料非线性矩形薄板主参数共振-主共振研究     

杨志安  韩彦斌 《岩土力学》2006,27(Z2):733-738

研究Winkler地基上材料非线性矩形薄板的参数共振-主共振问题。建立Winkler地基上材料非线性矩形薄板的动力学方程。利用Galerkin方法将其转化为非线性振动方程。应用非线性振动的多尺度法求得系统满足主参数共振-主共振条件的近似解,并进行数值计算。分析激励、调谐值、阻尼系数、非线性参数、几何参数对共振响应曲线的影响。  相似文献   

Tracking the last sea-level cycle: seafloor morphology and shallow stratigraphy of the latest Quaternary New Jersey middle continental shelf     

Catherine Schuur Duncan  John A. Goff  James A. AustinJr.  Craig S. Fulthorpe 《Marine Geology》2000,170(3-4):395-421

Seafloor geomorphology and surficial stratigraphy of the New Jersey middle continental shelf provide a detailed record of sea-level change during the last advance and retreat of the Laurentide ice sheet (120 kyr B.P. to Present). A NW–SE-oriented corridor on the middle shelf between water depths of 40 m (the mid-shelf “paleo-shore”) and 100 m (the Franklin “paleo-shore”) encompasses 500 line-km of 2D Huntec boomer profiles (500–3500 Hz), an embedded 4.6 km² 3D volume, and a 490 km² swath bathymetry map. We use these data to develop a relative stratigraphy. Core samples from published studies also provide some chronological and sedimentological constraints on the upper <5 m of the stratigraphic succession.The following stratigraphic units and surfaces occur (from bottom to top): (1) “R”, a high-amplitude reflection that separates sediment >46.5 kyr old (by AMS ¹⁴C dating) from overlying sediment wedges; (2) the outer shelf wedge, a marine unit up to 50 m thick that onlaps “R”; (3) “Channels”, a reflection sub-parallel to the seafloor that incises “R”, and appears as a dendritic system of channels in map view; (4) “Channels” fill, the upper portion of which is sampled and known to represent deepening-upward marine sediments 12.3 kyr in age; (5) the “T” horizon, a seismically discontinuous surface that caps “Channels” fill; (6) oblique ridge deposits, coarse-grained shelly units comprised of km-scale, shallow shelf bedforms; and (7) ribbon-floored swales, bathymetric depressions parallel to modern shelf currents that truncate the oblique ridges and cut into surficial deposits.We interpret this succession of features in light of a global eustatic sea-level curve and the consequent migration of the coastline across the middle shelf during the last 120 kyr. The morphology of the New Jersey middle shelf shows a discrete sequence of stratigraphic elements, and reflects the pulsed episodicity of the last sea-level cycle. “R” is a complicated marine/non-marine erosional surface formed during the last regression, while the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum Wisconsin lowstand (i.e., marine oxygen isotope stage 3.1). “Channels” is a widespread fluvial subarial erosion surface formed at the late Wisconsin glacial maximum 22 kyr B.P. The shoreline migrated back across the mid-shelf corridor non-uniformly during the period represented by “Channels” fill. Oblique ridges are relict features on the New Jersey middle shelf, while the ribbon-floored swales represent modern shelf erosion. There is no systematic relationship between modern seafloor morphology and the very shallowly buried stratigraphic succession.  相似文献   

钢-混凝土组合连续梁桥动力响应试验研究   总被引：1，自引：0，他引：1  

郑则群  房贞政 《地震工程与工程振动》2006,26(4):175-181

钢-混凝土组合梁桥动力响应有其特点,本文结合福州光明港钢-混凝土组合连续梁桥实际工程,开展环境激励及汽车动载激励试验,并应用有限元进行分析和研究,表明理论计算与实测的频率和振型等动力特性较吻合,同时进行组合作用、横向支撑连接、体外预应力等参数研究,为该类型组合连续梁桥的动力性能研究与工程设计提供参考。  相似文献   

新型索承网壳结构非线性地震反应特性和参数分析   总被引：2，自引：0，他引：2  

李永梅  郑志英  张毅刚 《地震工程与工程振动》2006,26(6):93-100

本文根据新型大跨空间杂交结构———索承网壳结构的受力特点,选用梁元、杆元和索元的混合有限元模型,给出了一种有效的适用于该类结构的非线性动力响应的增量、迭代有限元计算方法。以K8型索承网壳结构为研究对象,进行了时域内的三向地震作用下的非线性反应分析。计算结果表明,该结构具有良好的抗震性能。文中针对地震响应的主要影响参数,对其地震响应规律作了系统的研究,得出矢跨比和撑杆长度是抗震设计的主要控制参数等有应用价值的结论。  相似文献   

多波束声呐图像条带中央和边缘残差处理方法     

朱正任  樊妙  邢喆  冯成凯  孙毅  阳凡林 《海洋技术学报》2019,38(5)

多波束声呐图像是进行海底底质分类的主要数据源之一,由于受海洋噪声、声波散射和混响、仪器设备等因素影响,其经各项常规改正后仍存在明显残差,突出表现在中央波束区和条带重叠区,难以形成高质量的声呐图像。文中分析了多波束声呐图像残差的成因及影响,提出了一种基于多条带最小二乘拟合的多波束声呐图像残差处理方法。首先,得到相邻声脉冲(ping)信号中央区域、重叠区域以及整体趋势的拟合函数;然后,通过拟合函数计算得到中央和重叠区域的残差改正系数;最后,通过改正系数进行残差改正。实验分析表明,该方法在保留原始细节的基础上,有效削弱了残差对声呐图像的影响,对多波束声呐图像处理具有参考和应用价值。  相似文献   

Influence of benthic sediment transport on cold‐water coral bank morphology and growth: the example of the Darwin Mounds,north‐east Atlantic     

ANDREW J. WHEELER  MAXIM KOZACHENKO  DOUG G. MASSON  VEERLE A. I. HUVENNE 《Sedimentology》2008,55(6):1875-1887

The Darwin Mounds are small (up to 70 m in diameter), discrete cold‐water coral banks found at c. 950 m water depth in the northern Rockall Trough, north‐east Atlantic. Formerly described in terms of their genesis, the Darwin Mounds are re‐evaluated here in terms of mound growth processes based on 100 and 410 kHz side‐scan sonar data. The side‐scan sonar coverage is divided into a series of acoustic facies representing increasing current speed and sediment transport/erosion from south to north: pockmark facies, ‘mounds within depressions’ facies, Darwin Mound facies, stippled seabed facies and sand wave facies. Mound morphometric changes are quantified and show a south‐to‐north divergence from an inherited morphology, reflecting the outline of coral‐colonized fluid escape structures, to developed, downstream elongated, elevated mound forms. It is postulated that increasing current speeds and bedload sand transport favour mound growth and development by a process of enhanced sand sedimentation within mounds due to current deceleration by frictional drag around coral colonies. Comparisons are made with similar growth processes attributed to comparably sized cold‐water coral mounds in the Porcupine Seabight, offshore Ireland.  相似文献   

一种针对侧扫声纳图像的数字镶嵌技术方法     

郭军  马桂云  马金凤  王爱学  易锋  冯强强 《测绘工程》2017,26(6)

以南海某海域实测侧扫声纳数据为例,研究侧扫声纳图像的数字镶嵌技术方法,对关键步骤进行详细的阐述。通过对原始侧扫声纳数据进行导航数据校正、海底线跟踪、斜距改正、TVG校正、船速校正、地理编码与重采样、拼接与镶嵌等处理,生成大区域、大范围、高分辨率、无缝拼接的侧扫声纳图像。实验结果证明声纳图像数字镶嵌技术的有效性,并取得理想的效果。  相似文献   

基于改进人工蜂群算法的概率积分法参数反演     

刘奇  朱建军  苏军明  何永红  孙明星 《测绘工程》2017,26(10)

针对传统算法在反演概率积分法参数时易发散且难以获得全局最优解的问题,提出利用自适应人工蜂群算法反演概率积分法参数。根据该算法在求解过程中收敛速度快,获得全局最优解的特点,将参数反演问题转化为组合优化问题,建立了自适应人工蜂群算法的概率积分法预计参数反演流程,并将计算结果与实际值进行对比分析。通过理论分析与实验证明,自适应人工蜂群算法反演概率积分法参数精度高,较最小二乘法和模矢法拟合效果好,可应用于矿山开采沉陷预计。  相似文献   

Flow processes and sediment deformation in the Canary Debris Flow on the NW African Continental Rise     

D. G. Masson  B. Van Niel  P. P. E. Weaver 《Sedimentary Geology》1997,110(3-4):163-179

The Canary Debris Flow formed an extensive deposit on the NW African Continental Margin west of the Canary Islands. Sidescan sonar images and 3.5-kHz profiles show that the middle part of the debris flow deposit consists of complex channel systems separated by banks and ridges of debris. Channels are typically up to 10 km wide and 10 to 20 m deep, and have little or no debris fill. They appear to feed a more laterally continuous debris flow sheet which is seen further downslope. Interchannel banks and ridges are composed of 5 to 20 m thick debris deposits. This morphology is remarkably similar to that seen in subaerial debris flows, and we therefore infer that the observed submarine debris flow morphology is a primary flow fabric, rather than the result of the debris flow interacting with or exploiting pre-existing channels. High-resolution Sidescan sonar images show that the debris flow surface is covered by sediment blocks up to 300 m in diameter. A single core collected from the flow shows that most of the 4.6-m flow thickness at the core site is composed of a single clast. The clast has been folded, with its upper part consisting of an inverted minor image of the lower part. The same sequence occurs again, in situ, beneath the debris flow, suggesting that the clast may have a local source, rather than having been derived from the debris flow source area, some 200 km upslope. This indicates that the debris flow was capable of substantial seabed erosion in the middle part of its course. In these middle reaches, erosion within the channelled areas probably occurred simultaneously with deposition in the interchannel areas. Interchannel deposits may contain both locally derived and original source area material.  相似文献   

深吃水半潜式平台参数共振研究     

毛欢  杨和振 《海洋工程》2016,34(1):18-24

深吃水半潜式平台(deep draft semi-submersible,DDS)作为一种新型海洋结构物,既继承了传统半潜式平台的优点,又改善了传统半潜式平台垂荡运动性能差的不足。但随着吃水的增加,DDS纵摇运动参数共振也成为一个不容忽视的问题。当DDS纵摇运动固有周期和垂荡运动周期满足一定关系时,纵摇运动将发生参数共振,纵摇角度将会显著增大。研究推导了DDS纵摇运动方程,并简化为标准的马修方程,运用希尔无穷行列式法求解马修方程,得到了含阻尼的马修稳定性图谱,并结合具体算例讨论了不同参数对DDS纵摇运动参数共振问题的影响。研究表明:深吃水半潜式平台的参数共振,是设计人员在设计之初必须考虑的问题;通过合理选取平台的系统参数,可以有效避免纵摇运动参数共振现象的发生。  相似文献