条子泥一期工程对条子泥发育影响及工程防护措施   总被引：2，自引：0，他引：2  

陈才俊  徐向红 《海洋工程》2015,33(5):105-112

通过历史和现场观测资料并结合遥感卫片资料,对条子泥匡围一期工程两年多的建设过程中,由工程所引起对条子沙洲西大港、东大港、条鱼港等主要的潮沟,及相应的潮盆系统和二分水的剧烈变化进行了分析研究,总结了潮沟摆动治理经验。治理方法主要为丁坝群结合砼连锁块镇压排布防护技术等。  相似文献   

重庆“5.6”强风雹天气过程成因分析   总被引：8，自引：4，他引：8  

陈贵川  谌芸  乔林  刘德  李强  张亚萍  王文芳  张焱 《气象》2011,37(7):871-879

利用常规观测、NCEP分析场及雷达、自动站等资料对重庆＂5.6＂强风雹天气的成因进行了分析,结果表明：冷锋和副热带高空急流在风雹发生地近乎重叠的配置结构促进了次级环流的形成并有利于上升运动的强烈发展;风暴天气发生前,下垫面强烈加热、低层增温增湿、中高层干冷对大气对流不稳定性增强的作用显著;对流有效位能（CAPE）、K指数、SI指数高值区边缘的强指数梯度区、对流抑制（CIN）的小值区以及较强的垂直风切变对大风冰雹的预报有重要的指示意义;雷达回波显示多单体风暴具有三体散射、弱回波区等冰雹回波特征,中层径向辐合和反射率因子核心的反复上升下降也是形成地面大风和冰雹的重要特征;四川盆地东部东北西南向山脉对冷空气的移动有阻挡作用,山脉之间的槽状地形为多单体风暴的持续发展保留了较大的空间,明月山南麓的地形起到了强迫抬升和触发的作用,由于地形的阻挡形成狭管效应,加强了下击暴流形成的地面大风,是形成11级大风的重要因素。  相似文献   

带丁坝型半封闭矩形海湾中M_2分潮潮波和潮流特性分析     

钱学生  陈永平  张长宽 《海洋学报》2014,36(9):37-44

将黄渤海海域概化为矩形海湾,山东半岛概化为垂直于海岸的巨型丁坝,形成一个带丁坝型半封闭矩形海湾。利用DELFT3D-FLOW计算模块在上述海湾中进行了M2分潮数值模拟,对其无潮点和辐射状潮流场的特性进行了分析。研究发现:考虑科氏力影响和巨型丁坝反射作用,坝前形成了明显的无潮点,但在等水深条件下并未形成辐射状潮流场,而叠加上倾斜海底地形后其得以形成;无潮点和辐射状潮流场顶端位置受水深影响明显,随着平均水深的增大,无潮点将向湾口和湾中轴线方向偏移,而辐射状潮流场顶端则向湾口方向偏移。研究结果有助于加深对带丁坝型半封闭矩形海湾中驻潮波系统形成机制和动力特性的理解和认识。  相似文献   

Wave characteristics at the south part of the radial sand ridges of the Southern Yellow Sea     

杨斌  冯卫兵  张俞 《中国海洋工程》2014,28(3):317-330

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Tensile stiffness analysis on ocean dynamic power umbilical   总被引：1，自引：0，他引：1  

汤明刚  阎军  王野  岳前进 《中国海洋工程》2014,28(2):259-270

Tensile stiffness of ocean dynamic power umbilical is an important design parameter for functional implementation and structural safety. A column with radial stiffness which is wound by helical steel wires is constructed to predict the tensile stiffness value of umbilicals in the paper. The relationship between the tension and axial deformation is expressed analytically so the radial contraction of the column is achieved in the relationship by use of a simple finite element method. With an agreement between the theoretical prediction and the tension test results, the method is proved to be simple and efficient for the estimation of tensile stiffness of the ocean dynamic power umbilical.  相似文献   

A Velocity Dealiasing Scheme for C-band Weather Radar Systems简     

LI Gang  HE Guangxin  Xiaolei ZOU  Peter Sawin RAY 《大气科学进展》2014,31(1):17-26

A dealiasing algorithm for radar radial velocity observed by C-band Doppler radars is presented as an extension of an existing S-band dealiasing algorithm. This has operational significance in that many portable and many commercial broadcast radars, as well as approximately one half of the Chinese weather radar network （CINRAD）, are C-band radars. With a wavelength of about 5 cm, the Nyquist interval of C-band radars is just about one half that of S-band radars （wavelength of about 10 cm） and thus has more velocity folding. The proposed algorithm includes seven modules to remove noisy data, find the starting radials, dealias velocities, and apply least squares error checking in both the radial and azimuth directions. The proposed velocity dealiasing method was applied to one widespread rain case and three strong convective cases from radars operating in China. It was found that, on average, 92.95% of the aliased radial velocity data could be correctly de-aliased by the algorithm, resulting in 96.65% of the data being valid.  相似文献   

Robust and reliable metamodels for mechanized tunnel simulations     

《Computers and Geotechnics》2014

The main objective of this paper is to construct a robust and reliable metamodel for the mechanized tunnel simulation in computationally expensive applications. To accomplish this, four metamodeling approaches have been implemented and their performance has been systematically evaluated through a comparative study utilizing pure mathematical test functions. These metamodels are quadratic polynomial regression, moving least squares, proper orthogonal decomposition with radial basis functions, and an extended version of the latest approach. This extended version has been proposed by the authors and named proper orthogonal decomposition with extended radial basis functions. After that, a system identification study for mechanized tunneling has been conducted through the back analysis of synthetic measurements. In this study, the best performing metamodel, that is the one suggested by the authors, has been employed to surrogate a complex and computationally expensive 3D finite element simulation of the mechanized tunnel. The obtained results demonstrate that the proposed metamodel can reliably replace the finite element simulation model and drastically reduce the expensive computation time of the back analysis subroutine.  相似文献   

全球超大城市空间扩张及分形特征研究     

侯亚丽  匡文慧  窦银银 《地理学报》2022,77(11):2687-2702

超大城市是全球经济、文化以及高科技产业发展的承载体和重要纽带,其形态结构特征和人口聚集效应是城市化影响的典型表现,然而当前对于全球超大城市形态特征及扩张模式的研究相对不足。基于2000—2020年全球城市土地利用/覆盖变化数据（GULUC-30）,利用城市扩张强度差异指数分析了超大城市用地的时空变化规律;而后运用面积—半径标度分析模型研究了超大城市的分形特征及扩张模式,最后基于城市用地面积和城市人口之间的线性关系评价城市用地效率。结果发现：① 2000—2020年东南亚和东亚的中国超大城市用地扩张最剧烈,城市用地面积分别扩张了3148.32 km²和5996.26 km²,城市扩张强度差异指数平均值大于3;② 2000—2020年超大城市的形态特征和扩张模式向着更加集约和紧凑的方向发展,径向维数平均值由1.54增加至1.56,分维差呈逐年减少趋势,城市内部结构一体化特征显著;③ 北美和欧洲的超大城市用地效率低,2020年城市用地面积与城市人口比值系数范围为0.89~4.11;南亚和非洲城市用地效率高,比值范围为0.23~0.87。超大城市空间扩张格局和形态变化的认识对于城市用地的集约利用和可持续发展具有重要参考价值。严格控制超大城市扩张规模,促进城市用地的均衡发展是建设韧性城市和实现城市地区可持续发展的必要条件。  相似文献   

An enhanced constitutive model for crushable granular materials     

Ali Daouadji  Pierre‐Yves Hicher 《国际地质力学数值与分析法杂志》2010,34(6):555-580

Studies in the past have tried to reproduce the mechanical behaviour of granular materials by proposing constitutive relations based on a common assumption that model parameters and parameters describing the properties, including gradation of individual grains are inevitably linked. However successful these models have proved to be, they cannot account for the changes in granular assembly behaviour if the grains start to break during mechanical loading. This paper proposes to analyse the relation between grading change and the mechanical behaviour of granular assembly. A way to model the influence of grain breakage is to use a critical state‐based model. The influence of the amount of grain breakage during loading, depending on the individual grain strength and size distribution, can be introduced into constitutive relations by means of a new parameter that controls the evolution of critical state with changes in grain size distribution. Experimental data from a calcareous sand, a quartz sand, and a rockfill material were compared with numerical results and good‐quality simulations were obtained. The main consequences of grain breakage are increased compressibility and a gradual dilatancy disappearance in the granular material. The critical state concept is also enriched by considering its overall relation to the evolution of the granular material. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Spectroscopic binaries near the north Galactic Pole     

R. F. Griffin  D. W. Beggs 《Journal of Astrophysics and Astronomy》1991,12(4):289-310

Orbits based principally on radial-velocity measurements made with the Haute-Provence Coravel spectrometer are presented for eight binary systems which include some of the faintest HD stars in the Galactic-Pole field. They are HD 103418 (which is double-lined), 105021, 108151, 113169, 113323, 113650, 113714, and 116514. Their periods range from 3.7 to 15.1 days. Very little else is known about any of them.  相似文献