联合多代卫星测高数据建立中国近海垂线偏差模型          下载免费PDF全文

邓凯亮  暴景阳  章传银  刘雁春  许军  孙昊 《海洋测绘》2008,28(3):15-17

联合T/P数据、T/P新轨道数据、ERS2数据、GFO数据、Geosat GM数据和ERS-1/168数据,用测高卫星记录点的位置信息直接计算沿轨大地水准面的方向导数,在交叉点处联合方位角推求垂线偏差,然后利用Shepard插值法得到了中国近海2′×2′格网分辨率子午圈和卯酉圈垂线偏差模型。将其与2′×2′分辨率的CLS_SHOW 99垂线偏差模型比较,在子午圈分量上的RMS为0.87,″在卯酉圈分量上的RMS为1.45″。  相似文献   

加速遗传算法在预应力连续箱梁桥有限元模型修正中的应用     

林贤坤  覃柏英  张令弥  郭勤涛 《地震工程与工程振动》2013,33(4)

针对预应力混凝土连续箱梁桥的通扬运河大桥,建立其有限元模型.基于评价模型修正效果的频率指标与振型相关系数指标、柔度矩阵指标和挠度指标,定义三个目标函数,利用环境激励的试验模态参数,通过实数编码加速遗传算法对有限元模型进行了修正.相对于基于频率指标与振型相关系数指标定义的目标函数,基于柔度矩阵指标或挠度指标定义的目标函数修正的有限元模型,能同时较准确地反映其动态和静态特性,也能实现其试验模态振型较精确的质量归一化.  相似文献   

巴楚辉绿岩墙的岩石成因及其对塔里木大火成岩省岩浆演化的启示   总被引：1，自引：0，他引：1  

位荀  徐义刚 《岩石学报》2013,29(10):3323-3335

早二叠世塔里木大火成岩省主要有两期岩浆活动:以柯坪玄武岩为代表的喷出岩形成较早(~290Ma),以巴楚超基性-基性-长英质侵入体和岩墙为代表的侵入岩形成较晚(~280Ma)。本研究选取代表晚期岩浆活动的巴楚辉绿岩墙为研究对象,旨在为认识塔里木地幔柱活动及与岩石圈的相互作用提供更多信息。巴楚辉绿岩XHZ-10样品中的锆石均为继承性锆石,不能用来限定其侵位时代。然而,野外关系表明巴楚辉绿岩墙属于塔里木大火成岩省的第二期岩浆活动。巴楚辉绿岩墙经历了橄榄石、辉石和磁铁矿的分离结晶。Nd同位素比值与SiO₂和La/Nb比值的相关性以及继承性锆石年龄(2480~717Ma,主要集中在~800Ma)表明,新元古代基底的同化混染作用可以解释其ε_Nd具有较大的变化范围(-2.6~+5.1)。受混染程度最小的样品具有与洋岛玄武岩(OIB)极其相似的微量元素特征,并且具有亏损的Nd同位素组成(ε_Nd=~+5),暗示其来源于富集的对流地幔源区,与早期(~290Ma)具有岩石圈地幔源区特征的玄武岩形成鲜明对比。本文提出地幔柱侧向流动模型以解释两期岩浆的时空分布和地球化学差异:当地幔柱上升至塔里木岩石圈底部时,巨厚的岩石圈地幔(>140km)会阻碍其减压熔融;但不断积累在岩石圈底部的地幔柱物质提供足够的热,促使早期富集交代的岩石圈地幔发生部分熔融,形成~290Ma的玄武岩;地幔柱物质将向岩石圈厚度较薄的边缘地区侧向流动,发生减压熔融,形成的熔体侵位到地壳中形成超基性-基性-长英质侵入岩和辉绿岩墙,并诱发地壳的熔融形成长英质火山岩。  相似文献   

An analytical model of soil–structure interaction with swelling soils during droughts     

《Computers and Geotechnics》2013

Lightly loaded structures constructed on expansive soils may develop structural damage as a result of changes in the soil’s moisture content. This study investigated an analytical model of soil–structure interaction to assess the settlement of dwellings built on swelling soils when droughts occur. The building behavior was investigated with the Euler–Bernoulli beam theory, and the ground behavior was investigated with a Winkler-derived model based on the state surface approach. The analytical model results were compared to those of a finite element analysis using the Barcelona Expansive Model (BExM) performed with Code_Bright.The analytical model was then used to assess the settlement transmission ratio for a typology of clayey soils and different parameters of building. The results indicated that the final deflection of the building increased with the building length and soil suction. The building deflection due to the suction variations was inversely proportional to the load, the rigidity of the building and the embedding depth of the foundation. Increasing these parameters made the building less vulnerable to shrinkage and swelling action.  相似文献   

龙门山构造带晚新生代剥蚀作用与均衡隆升的地表过程研究     

闫亮  李勇  邓涛  颜照坤  云锟  邵崇建  董顺利 《地球学报》2019,40(1):76-92

基于SRTM DEM数据,以青藏高原东缘龙门山地区为研究区域,本文通过条带状剖面分析、古地形面(残余面)恢复以及弹性挠曲模拟等研究手段,计算了青藏高原东缘龙门山地区晚新生代地壳均衡隆升与地表剥蚀之间的定量关系,探讨了龙门山地区表面剥蚀作用与均衡隆升作用之间的地表响应过程,从而为研究青藏高原东缘龙门山地区晚新生代以来的剥蚀—成山作用的隆升机制提供定量依据。研究表明:(1)晚新生代以来龙门山的地表剥蚀量为(0.74～1.14)×105km3;(2)大量的地表剥蚀作用驱动了青藏高原东缘龙门山的地壳均衡反弹,使龙门山隆升了近2 km;(3)龙门山地区地表剥蚀量和均衡隆升量具有空间匹配性,岷山断块及龙门山中、南段的均衡隆升量高于青藏高原东缘其它区域,反映了晚新生代以来龙门山地区在不同分段内差异化的构造地貌形态及与剥蚀—隆升相关的地表过程。(4)龙门山的隆升是多期、多种隆升机制叠加的产物,其隆升过程具有历史性和复合性。均衡隆升和剥蚀作用在相似的时间尺度上和空间尺度上控制着龙门山地貌的形成,约束了青藏高原东缘龙门山的隆升机制。  相似文献   

On the evaluation of deflections of the vertical using FFT technique     

Huang Motao  Zhai Guojun  Guan Zheng  Quyang Yongzhong 《地球空间信息科学学报》2013,16(1):5-13

There exist three types of convolution formulae for the efficient evaluation of gravity field convolution integrals, i.e., the planar 2D convolution, the spherical 2D convolution and the spherical 1D convolution. The largest drawback of both the planar and the spherical 2D FFT methods is that, due to the approximations in the kernel function, only inexact results can be achieved. Apparently, the reason is the meridian convergence at higher latitudes. As the meridians converge, the ??,?λ blocks do not form a rectangular grid, as is assumed in 2D FFT methods. It should be pointed out that the meridian convergence not only leads to an approximation error in the kernel function, but also causes an approximation error during the implementation of 2D FFT in computer. In order to meet the increasing need for precise determination of the vertica deflections, this paper derives a more precise planar 2D FFT formula for the computation of the vertical deflections. After having made a detailed comparison between the planar and the spherical 2D FFT formulae, we find out the main source of errors causing the loss in accuracy by applying the conventional spherical 2D FFT method. And then, a modified spherical 2D FFT formula for the computation of the vertical deflections is developed in this paper. A series of numerical tests have been carried out to illustrate the improvement made upon the old spherical 2D FFT. The second part of this paper is to discuss the influences of the spherical harmonic reference field, the limited capsize, and the singular integral on the computation of the vertical deflections. The results of the vertical deflections over China by applying the spherical 1D FFT formula with different integration radii have been compared to the astro-observed vertical deflections in the South China Sea to obtain a set of optimum deflection computation parameters.  相似文献   

现代大地测量学中的垂线偏差     

丁一帆  李月锋  丁行斌 《大地测量与地球动力学》2006,26(2):115-119

从大地测量学的角度论述了垂线偏差概念从传统到现代的发展和演变,比较全面地探讨了现代垂线偏差的含义和测定方法。通过对垂线偏差量级和误差大小的具体分析,得出结论一般长周期的、幅度较小的非潮汐变化要小于潮汐变化,但短周期的、幅度较大的非潮汐变化则可能与潮汐变化相当,个别地区甚至还会超过潮汐变化,这种情况完全可以用重复重力测量的方法检测到,这也说明重复测量的方法是可行的。  相似文献   

Large Deflection Dynamic Response Analysis of Flexible Hull Beams by the Multibody System Method     

ZHANG Xiaojun WU Guorong 《中国海洋大学学报(英文版)》2007,6(2):205-208

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中国西太平洋海域1′×1′垂线偏差模型及精度评估     

王虎彪  王勇  柴华  鲍李峰 《测绘学报》2017,46(9):1073-1079

联合多种测高数据和重力异常数据,设计了观测点距离和测高精度融合的定权方法,采用最小二乘方法和Vening-Meinesz公式,分别构建了西太平洋海域(0°N—40°N,105°E—145°E)1′×1′网格化垂线偏差数字模型。选取两个不同特征区域,将垂线偏差的两个数字模型和EGM2008模型三者进行相互比较分析。结果表明:卯酉分量η的均方根差大于子午分量ξ的均方根差,海底地形复杂的南海特征区域的垂线偏差均方根差大于西太平洋中部的均方根差,构建的两个垂线偏差模型总体均方根差优于1.6″。  相似文献   

Visa restrictions and economic globalisation     

《Applied geography (Sevenoaks, England)》2017

The cross-border mobility of people, goods and services, and capital has expanded enormously both in intensity and diversity over recent decades. States have a general interest in facilitating these flows in order to benefit from economic globalisation. Yet, mainly due to security concerns, most governments grant visa-free mobility only very selectively. Drawing on a new bilateral visa policy database covering up to 194 destination and 214 origin countries over the 1995 to 2013 period, our analysis finds that the introduction of a visa restriction by a destination country for citizens from a particular origin country deters tourism inflows by about 20 per cent. Visa restrictions also reduce bilateral trade and foreign investment, but to a smaller extent than previous studies have suggested. We further find that some of the deterred flows in tourists and goods and services are redirected to other (visa-free) destinations. This deterrence-cum-deflection effect of restrictive visa policies implies significant economic costs for both visa-issuing and visa-targeted countries, but it creates some positive externalities for countries with a more liberal visa policy. Liberalised visa policies would in particular help poorer countries to partake more in the benefits of economic globalisation.  相似文献