南黄海西部2007年4月的逆温跃层          下载免费PDF全文

苏劼  熊学军  刘浩  卢德杰 《海岸工程》2017,36(1)

利用南黄海西部2007-04的温盐实测资料,采用海洋层结谱表达法及自适应识别,得到逆温跃层的"五点三要素",形成强度要素平面分布图.分析表明,逆温跃层的存在与黄海暖流水有直接的关系:1)4月份,黄海暖流水受到的海面冷却仍是产生逆温跃层的普遍原因,在该海区黄海暖流向北延伸和向两侧拓展的区域都有该种类型的逆温跃层存在,位置相对较浅;2)但在偏南的黄海暖流主干区,海面冷却产生的效应被主流区的热量补充所抵消,逆温跃层很弱甚至消失,这是该月份逆温跃层分布区向北退缩并在南部中心附近呈现缺失区的主要原因;3)南下的鲁北沿岸流水的冷水叠加在黄海暖流水的暖水上方,使逆温跃层加强,使得冷暖水的作用区成为强逆温跃层区;4)黄海暖流左侧冷沿岸流水及右侧冷水的前端向黄海暖流楔入,其前端往往覆盖在底层高温高盐的黄海暖流水上方形成下逆温跃层,从而形成双逆温跃层.这些特点,较以前认知更加客观、全面、细致和准确.  相似文献   

Adaptive Observer Based Backstepping Controller Design for Dynamic Ship Positioning     

DENG Fang  WANG Long-jin  JIAO Dong-mei 《海洋工程》2017,31(5):639-645

Modified adaptive observer based backstepping control system for dynamic positioning of ship is proposed. As an improvement, the adaptive observer takes the first-order wave frequency model and the bias term which represent the slowly varying environmental disturbances and the unmodeled dynamics. Thus, the wave-frequency motions are filtered out, and only the reconstructed low-frequency motions are sent as inputs of the controller. Furthermore, as the ship dynamics parameters are unknown, the adaptive estimation law is designed for both the unknown ship dynamics and the unmeasured state variables. Based on the estimated states and parameters, backstepping controller considering the integral action is designed. Global exponential stability (GES) for the total system is proved using Lyapunov direct method. Simulation results show a good performance of the observer and control system.  相似文献   

Mass rig system for shaking table tests of slender columns          下载免费PDF全文

Pedro F. Silva  Arash Sangtarashha  Rigoberto Burgueño 《地震工程与结构动力学》2015,44(15):2717-2736

A new mass rig system is proposed to minimize the deficiencies in current shaking table testing setups. This is accomplished by placing the inertial mass on a convex path designed to impose P‐Delta demands on slender cantilever columns. The design and performance of the mass rig system, and the principles used in deriving the equations of motion and their analytical validation against results obtained from shaking table tests, are presented. Formulation of the governing equations of motion was based on Lagrangian mechanics and solved using an implicit linear acceleration method with an adaptive time step formulation. Friction developed in the sliding system was also incorporated in the equations of motion. Experimental results validated the accuracy in the derivation and solution of the equations of motion. Validated by analytical and experimental results, P‐Delta effects were found to increase the displacement demands on slender columns in the low‐frequency range of acceleration input, while in the high‐frequency range P‐Delta effects led to no increase and in some cases even a reduction in displacement demands. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Statistical models for shear strength of RC beam‐column joints using machine‐learning techniques          下载免费PDF全文

Jong‐Su Jeon  Abdollah Shafieezadeh  Reginald DesRoches 《地震工程与结构动力学》2014,43(14):2075-2095

This paper proposes a new set of probabilistic joint shear strength models using the conventional multiple linear regression method, and advanced machine‐learning methods of multivariate adaptive regression splines (MARS) and symbolic regression (SR). In order to achieve high‐fidelity regression models with reduced model errors and bias, this study constructs extensive experimental databases for reinforced and unreinforced concrete joints by collecting existing beam‐column joint subassemblage tests from multiple sources. Various influential parameters that affect joint shear strength such as material properties, design parameters, and joint configuration are investigated through tests of statistical significance. After performing a set of regression analyses, the comparison of simulation results indicates that MARS approach is the best estimation method. Moreover, the accuracy of analytical predictions of the derived MARS model is compared with that of existing joint shear strength relationships. The comparison results show that the proposed model is more accurate compared to existing relationships. This joint shear strength prediction model can be readily implemented into joint response models for evaluation of earthquake performance and inelastic responses of building frames. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Isolation of plane shear wave using water saturated trench barrier     

《Soil Dynamics and Earthquake Engineering》2014

The article presents a theoretical investigation of the propagation of normally and obliquely incident plane shear waves past a rectangular trench filled up with water saturated soil sandwiched between anisotropic elastic media. The motivation for this work is due to the effectiveness of the isolation of waves by the in-filled rectangular trench. Unlike the most of the previous researchers, this model considers the soil–structure interaction effects and directly determines the influence of barrier in the form of in-filled trench on the mode of wave propagation. It is of interest to determine the reflection and transmission coefficients, and the energy partition distribution of shear waves in the in-filled rectangular trench showing the influence of barrier on the propagation of waves. An extensive parametric study through numerical computation is carried out to investigate the influence of the material properties of the in-filled trench and the amplitude ratios on shear waves. The in-filled trench barrier directly declines the intensity of waves significantly in such a way that the waves do not create any hazards to the nearby structures, if exists at all.  相似文献   

微量元素在湖积物、土壤的垂向分布与稻谷中的分配   总被引：22，自引：7，他引：15       下载免费PDF全文

廖启林  黄顺生  范迪富  吴新民  朱伯万  翁志华  华明  陈宝  冯金顺 《第四纪研究》2005,25(3):331-339

报道了“江苏省国土生态地球化学调查”项目有关湖积物、土壤柱微量元素垂向分布及稻谷样元素分配研究的初步成果。通过对有关样品元素含量的分析对比,指出洪泽湖沉积柱元素垂向分布与其动荡的沉积环境关系密切、太湖局部沉积物在其目前20cm以上深度存在人为重金属污染,这二湖沉积物中其氮与总有机碳含量呈显著正相关;认为城市化可使当地土壤环境受重金属等污染的深度显著加大、城市土壤环境受人为活动的影响要显著高于农村;发现Mo易富集于稻米、重金属与营养元素易富集于稻皮、各元素在米-谷间的分配关系不确定。  相似文献   

成矿规律若干问题研究   总被引：17，自引：8，他引：9  

梅友松 《地质与勘探》2005,41(6):3-14

文章特为庆祝北京矿产地质研究院成立50周年而作.内容分3个部分:(1)有色金属矿床成矿分区.论述了重要有色金属(含贵金属)矿床共生组合特点及其产生的原因,包括大陆地壳基底岩层成分分区与后生金属矿床成矿分区的关系;在钾含量高低不同的岩石系列环境中金属矿床产出特点.(2)金属域边缘线性构造成矿相关问题概述.在成矿分区所形成的金属域内,重要有色金属矿床产出特点概括地说是,在空间上产于地质(构造)体的转化(过渡)部位,在时间上形成于成矿地质过程的转化时期,定位于有利的转化界面附近.在此基础上,论述了成矿(区)带产出特点和控制矿田、矿床和矿体产出的构造等.(3)同位成矿及其找矿意义.论述了幔源与壳源在地壳中形成的岩浆房作用下,特别是在上地壳下部产出的影响地域广、关系矿种多的岩浆房和含矿热卤水库的作用下,在陆壳基底成分的支配和影响下,保持相对稳定的成矿热活动中心,具有成矿与保存最佳条件的配置和协同作用,就可产生同位成矿作用,进而形成大型-超大型矿床.  相似文献   

土木工程结构鲁棒控制的发展   总被引：1，自引：0，他引：1  

韩兵康  张静怡 《地震工程与工程振动》2004,24(6):131-135

评述了结构控制的发展,指出发展结构鲁棒控制策略的重要性。重点评述了结构双重调谐质量阻尼器(DTMD)和多重双重调谐质量阻尼器(MDTMD)的控制策略,提出了需进一步发展主动双重调谐质量阻尼器(ADTMD)和主动多重双重调谐质量阻尼器(AMDTMD)控制策略、此外,评述了结构鲁棒控制的设计准则与高层建筑和大跨桥梁在风与地震作用下的统一自适应主动鲁棒控制策略。  相似文献   

Adaptive finite element modeling of marine controlled-source electromagnetic fields in two-dimensional general anisotropic media   总被引：4，自引：0，他引：4  

LI Yuguo  LUO Ming  PEI Jianxin 《中国海洋大学学报(英文版)》2013,12(1):1-5

In this paper, we extend the scope of numerical simulations of marine controlled-source electromagnetic (CSEM) fields in a particular case of anisotropy (dipping anisotropy) to the general case of anisotropy by using an adaptive finite element approach. In comparison to a dipping anisotropy case, the first order spatial derivatives of the strike-parallel components arise in the partial differential equations for generally anisotropic media, which cause a non-symmetric linear system of equations for finite element modeling. The adaptive finite element method is employed to obtain numerical solutions on a sequence of refined unstructured triangular meshes, which allows for arbitrary model geometries including bathymetry and dipping layers. Numerical results of a 2D anisotropic model show both anisotropy strike and dipping angles have great influence on the marine CSEM responses.  相似文献   

�в�����Ӧ�ع�TLS     

陈西江  花向红  鲁铁定  翟高鹏  杨燕景 《大地测量与地球动力学》2012,32(3):90-93

TLS??????????????У????????????в??????????????????????????????????????????в???????????????????????TLS??????????У??????????????????????????????в???з?????????????????TLS?????????????????????????в???????????????в?????????????á???????????????????÷???????????  相似文献