On the orthogonality of surface wave eigenfunctions in cylindrical coordinates     

M. G. Bostock 《Geophysical Journal International》1990,103(3):763-767

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The Agulhas Ridge, South Atlantic: The Peculiar Structure of a Fracture Zone     

Gabriele Uenzelmann-Neben  Karsten Gohl 《Marine Geophysical Researches》2004,25(3-4):305-319

The Agulhas Ridge is a prominent topographic feature that parallels the Agulhas-Falkland Fracture Zone (AFFZ). Seismic reflection and wide angle/refraction data have led to the classification of this feature as a transverse ridge. Changes in spreading rate and direction associated with ridge jumps, combined with asymmetric spreading within the Agulhas Basin, modified the stress field across the fracture zone. Moreover, passing the Agulhas Ridge’s location between 80 and 69 Ma, the Bouvet and Shona Hotspots may have supplied excess material to this part of the AFFZ thus altering the ridge’s structure. The low crustal velocities and overthickened crust of the northern Agulhas Ridge segment indicate a possible continental affinity that suggests it may be formed by a small continental sliver, which was severed off the Maurice Ewing Bank during the opening of the South Atlantic. In early Oligocene times the Agulhas Ridge was tectono-magmatically reactivated, as documented by the presence of basement highs disturbing and disrupting the sedimentary column in the Cape Basin. We consider the Discovery Hotspot, which distributes plume material southwards across the AAFZ, as a source for the magmatic material.  相似文献   

Impact Buckling and Post-Buckling of Elasto-Viscoplastic Cylindrical Shell Under Torsion     

Wang Deyu Chen Tieyun Associate Professor 《中国海洋工程》1997,(1)

The dynamic torsional buckling and post-buckling of elasto-plastic circular cylindrical shell isstudied.By the usage of the Bodner-Partom constitutive relation,the present visco-plastic problem is treat-ed as an orthotropic elastic problem.Based on the nonlinear large deflection shell therory,the governingdynamic buckling equation is solved by the Runge-Kutta method,and the critical buckling stress is deter-mined by the B-R criterion.The present paper is mainly focused on the imperfection sensitivity,the strainrate sensitivity,and the dynamic post-buckling characters for the shell loaded dynamically with a constantshear strain rate.Numerical results show that the critical shear stress and imperfection sensitivity will in-crease with the increase of strain rate.It is found that the elastic buckling stress is more sensitive toimperfection than the visco-plastic buckling.The present research also reveals some dynamic post-bucklingcharacters for the cylindrical shell,and it is shown that the shell will vibra  相似文献   

Transformation of Lambert Conic Conformal Coordinates from a Global Datum to a Local Datum     

E. Grafarend  F. Okeke 《Marine Geodesy》2007,30(4):297-313

This paper treats the problem of how to transform from global datum, for example, from the International Terrestrial Reference System (ITRS), to a local datum, for example, regional or national, for the practical case of the Lambert projection of the sphere or the ellipsoid-of-revolution to the cone. We design the two projection constants n(ϕ₁, ϕ₂) and m(ϕ₁) for the Universal Lambert Conic projection of the ellipsoid-of-revolution. The task to transform from a global datum with respect to the ellipsoid-of-revolution E_A,B² to local datum with respect to the alternative ellipsoid-of-revolution E_a,b², without local ellipsoidal height, is solved by an extended numerical example. Ideas in this paper could be of interest to those working with maps and coordinates transformation from global geodetic datum to local geodetic datum and vice versa, under the Universal Lambert Conic projection, and applicable to precise positioning and navigation, boundary demarcation and determination in the marine environment.  相似文献   

The Vema Transverse Ridge (Central Atlantic)     

Kastens  Kim  Bonatti  Enrico  Caress  David  Carrara  Gabriela  Dauteuil  Olivier  Frueh-Green  Gretchen  Ligi  Marco  Tartarotti  Paola 《Marine Geophysical Researches》1998,20(6):533-556

Transverse ridges are elongate reliefs running parallel and adjacent to transform/fracture zones offsetting mid-ocean ridges. A major transverse ridge runs adjacent to the Vema transform (Central Atlantic), that offsets the Mid-Atlantic Ridge by 320 km. Multibeam morphobathymetric coverage of the entire Vema Transverse ridge shows it is an elongated (300 km), narrow (<30 km at the base) relief that constitutes a topographic anomaly rising up to 4 km above the predicted thermal contraction level. Morphology and lithology suggest that the Vema Transverse ridge is an uplifted sliver of oceanic lithosphere. Topographic and lithological asymmetry indicate that the transverse ridge was formed by flexure of a lithospheric sliver, uncoupled on its northern side by the transform fault. The transverse ridge can be subdivided in segments bound by topographic discontinuities that are probably fault-controlled, suggesting some differential uplift and/or tilting of the different segments. Two of the segments are capped by shallow water carbonate platforms, that formed about 3–4 m.y. ago, at which time the crust of the transverse ridge was close to sea level. Sampling by submersible and dredging indicates that a relatively undisturbed section of oceanic lithosphere is exposed on the northern slope of the transverse ridge. Preliminary studies of mantle-derived ultramafic rocks from this section suggest temporal variations in mantle composition. An inactive fracture zone scarp (Lema fracture zone) was mapped south of the Vema Transverse ridge. Based on morphology, a fossil RTI was identified about 80 km west of the presently active RTI, suggesting that a ridge jump might have occurred about 2.2 m.a. Most probable causes for the formation of the Vema Transverse ridge are vertical motions of lithospheric slivers due to small changes in the direction of spreading of the plates bordering the Vema Fracture Zone.  相似文献   

海岸带专题地图编绘相关问题     

顾燕  张鹰 《海洋技术学报》2004,23(2):103-106

海岸带是影响人类活动的重要地带，海岸带专题地图能够详细表示出海岸带的特性。随着海洋经济的发展，海岸图的需求日益增加。从地图的数学要素出发，提出目前海岸图绘制存在的问题，并从地图学、海洋学、遥感地学的角度，对地图投影的选择、坐标系转换、比例尺对海岸图编绘的影响及控制点的确定等问题进行了综合分析。  相似文献   

Instrumentation and Numerical Analysis of Cylindrical Diaphragm Wall Movement During Deep Excavation at Coastal Area     

Dong Soo Kim  Byoung Chul Lee 《Marine Georesources & Geotechnology》2005,23(1):117-136

The lateral deflection of a cylindrical diaphragm wall and the associated ground movement induced by deep excavation are analyzed by performing site instrumentations and numerical analyses in the coastal area of Korea. Wall lateral deflection, rebar stress, and pore water pressure were measured and analyzed in eight directions. Variations of soil properties with the decrease of confining pressure are compared by performing various in situ tests before ad after excavation. To calculate the wall lateral deflection accurately, the effects of small strain nonlinearity, confining pressure, and the hysteresis loading/unloading loop developed during excavation are considered in the proposed numerical analysis. By comparing numerical results with measured ones, the importances of considering small strain nonlinearity and confining pressure reduction in the nonlinear (FEM) are emphasized. Also, the effects of wall stiffness on the performance of cylindrical diaphragm walls are studied for future similar excavation in the coastal area.  相似文献   

高斯投影公式的机助推导     

殷海峰  白征东  程伯辉 《测绘科学》2008,33(2):7-9

随着GPS应用的普及,高斯投影在测量中出现的机会越来越多。许多文献上都给出了推导过程,这个推导过程的运算量是非常大的,而且计算精度难于提高。经过研究,一种易于编程的递推公式被发现,虽然这个公式在计算量上没有减少,但是可以较好地解决精度问题。  相似文献   

土地调查中有关城镇与农村土地面积问题的研究     

吕长广  李淑青 《山东地质》2008,(9):36-38

第二次全国土地调查工作中,城镇与农村地区的土地面积在计算方法上有所不同：农村地区的土地面积是以椭球面为基准的面积,即球面面积;城镇地区的土地面积是以平面为基准的面积,即平面面积。二者之间存在差异并按一定规律变化,当调查区处于投影带边缘附近时,同一图斑的球面面积与平面面积之间的差异达到最大。由于采用不同的计算方法而导致面积数量的差异,在进行农村与城镇有关土地数据整合时会出现矛盾。为了建立城乡统一的土地管理信息系统,保证土地面积的一致性,应当采取相应措施消除二者之间的差异。  相似文献   

跨带土地利用规划图的编制研究   总被引：1，自引：0，他引：1  

赵晶  周梅玫  王慧珍  张向军 《测绘与空间地理信息》2008,31(4)

在县级土地利用规划用图中,常涉及到跨投影带的地图拼接问题,一般使用邻带转换法实现跨带区域的地图显示,该方法在实际应用中存在面积和角度变形相对较大的不足.本文采用自定义中央经线的投影转带方法,经过高斯投影变换,较好地解决了县域范围的跨带拼接显示并有效控制了相关变形.  相似文献