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The optimal matrix method and optimal elemental method used to update finite element models may not provide accurate results. This situation occurs when the test modal model is incomplete, as is often the case in practice. An improved optimal elemental method is presented that defines a new objective function, and as a byproduct, circumvents the need for mass normalized modal shapes, which are also not readily available in practice. To solve the group of nonlinear equations created by the improved optimal method, the Lagrange multiplier method and Matlab function fmincon are employed. To deal with actual complex structures, the float-encoding genetic algorithm (FGA) is introduced to enhance the capability of the improved method. Two examples, a 7degree of freedom (DOF) mass-spring system and a 53-DOF planar frame, respectively, are updated using the improved method.The example results demonstrate the advantages of the improved method over existing optimal methods, and show that the genetic algorithm is an effective way to update the models used for actual complex structures. 相似文献
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探地雷达（GPR）时间域全波形反演计算量巨大,内存要求高,在微机上计算难度大.本文中作者基于GPU并行加速的维度提升反演策略,采用优化的共轭梯度法,避免了Hessian矩阵的计算,在普通微机上实现了时间域全波形二维GPR双参数（介电常数和电导率）快速反演.论文首先推导了二维TM波的时域有限差分法（FDTD）的交错网格离散差分格式及波场更新策略.然后,基于Lagrange乘数法,将约束问题转化为无约束最小问题,构建了共轭梯度法反演目标函数,采用Fletcher-Reeves公式与非精确线搜索Wolfe准则,确保了梯度方向修正因子及迭代步长选取的合理性.而GPU并行计算及维度提升反演策略的应用,数倍地提升了反演速度.最后,开展了3个模型的合成数据的反演实验,分别从观测方式、梯度优化及天线频率等方面,分析了这些因素对雷达全波形反演的影响,说明双参数的反演较单一的介电常数反演,能提供更丰富的信息约束,有效提高模型重建的精度. 相似文献
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在地球动力学和气候模拟等领域, 数值模拟产生的数据规模达到Tb至Pb量级。 实现这些海量数据的实时可视化和实时诊断分析面临很大的困难, 时空多尺度数据抽取可以解决这一瓶颈。 高精度数据的可视化结果展示需要高分辨率的显示设备, 并行的大屏幕显示技术是解决这一问题的有效手段。 地球科学数值模拟、 并行数据抽取和高分辨率显示都需要搭建高性能计算机集群。 本文在基于Lagrange插值的多维度、 多尺度、 多分辨率并行数据抽取算法的同时, 利用并行计算节点及LCD显示器, 基于Rocks cluster系统搭建起一个176核, 4×10×1024×1280分辨率的高性能计算模拟、 数据抽取和并行显示输出的集成平台, 并将该平台成功应用到气候模式模拟产生的海量数据的并行抽取和并行显示。 相似文献
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V. P. Trubitsyn A. N. Evseev M. N. Evseev E. V. Kharybin 《Izvestiya Physics of the Solid Earth》2011,47(12):1027-1033
The process of multiple self-nucleation and ascent of mantle plumes is studied in the numerical models of thermal convection.
The plumes are observed even in the simplest isoviscous models of thermal convection that leave aside the more complex rheology
of the material, thermochemical effects, phase transformations, etc., which, although controlling the features of plumes,
are not necessary for their formation. The origin of plumes is mainly due to the instability of the mantle flows at highly
intense (low-viscous) thermal convection. At high viscosity, convective flows form regular cells. As viscosity decreases,
the ascending and descending flows become narrower and unsteady. At a further decrease in viscosity, the ascending plumes
assume a mushroom-like shape and occasionally change their position in the mantle. The lifetime of each flow can attain 100
Ma. Using markers allows visualizing the evolution of the shape of the mantle plumes. 相似文献
6.
《Physics of the Earth and Planetary Interiors》1982,28(3):261-268
The Runcorn stress equations and 2–30° harmonic coefficients of the geopotential have been applied to determine the mantle convection pattern beneath China. The pattern is compared with geophysical and geological observations and it is found that the directional change belts of mantle flows coincide with the major fault belts between tectonic units of China. The stress field generated by mantle flows, except in the Tian Shan region, also coincide with the stress field of recent tectonic movement in China. The Tarim and Junggar basins are formed by tensional stresses due to divergent mantle convection currents under northwest China. The formation of the Qinhai-Xizang (Tibet) plateau is due mainly to the compression of the Tarim block and Indian plate, caused by convergent mantle convection currents. The shear-fault belts in central China (100–105°E) are generated by the running change belt of mantle flows, a well-known N-S seismic zone. In eastern China, tensional faults, grabens, lake and sea depressions are related to the eastward displacement of continental lithosphere exerted by eastward dispersal mantle flows under this region.This paper provides new material for further study of the force source mechanism of recent tectonic movement from the viewpoint of mantle convection currents. 相似文献
7.
伴随方法在海洋数值模式中的应用 总被引：7，自引：0，他引：7
本文通过对变分资料同化方法在气象学和海洋学方面特别是在海洋数值模式中应用的简单回顾，评价了伴随方法在方法论上的优越性，首先引入包含海洋数值模式控制方程组的拉格朗日乘子，说明变分资料同化的数学原理；介绍伴随方法应用中目标函数的构造方法，简单说明了伴随方法中伴随方程的导出和伴随方法实际应用的步骤，最后就近几年国外研究进展做了简单概括。 相似文献
8.
According to an opinion widespread in the literature, high viscosity regions (HVRs) in the mantle always affect the structure of mantle flows, changing it in both the HVR itself and the entire mantle. Moreover, a simplified relation is often adopted according to which the flow velocity in the HVR decreases in inverse proportion to viscosity. Therefore, in order to treat a smoother value, some authors introduce a new variable equal to the product of the flow velocity and the viscosity value in a given place. On the basis of numerical modeling, this paper shows that HVRs of two types should be distinguished in the mantle. If an HVR is immobile, mantle flows actually do not penetrate it. If the viscosity increase is more than five orders, the HVR behaves as a solid and flow velocities within it almost vanish. However, if an HVR is free, it moves together with the mantle flow. Then, the general structure of flows changes weakly and flow velocities within the HVR become approximately equal to the average velocity of flows in the absence of the HVR. Horizontal layers and vertical columns differing in viscosity from the mantle behave as regions of the first type, whose flow velocities can differ by a few orders. However, even such large-scale regions as the continental lithosphere, whose viscosity is four to five orders higher than in the surrounding mantle, float together with continents at velocities comparable to mantle flows, i.e., behave as regions of the second type. 相似文献
9.
利用中国地震台网和ISC台站1980～2004年的地震数据，反演了南海东北部及其邻近地区的Pn波速度结构和各向异性.上地幔顶部的速度变化揭示出区域地质构造的深部特征：华南地区速度较高并且变化平缓，具有构造稳定地区的岩石层地幔特征；华南沿海尤其是滨海断裂带附近出现低速异常，表明该断裂可能穿过壳幔边界深达上地幔顶部.南海北部至台湾海峡较高的速度与华南地区类似，反映出大陆边缘和陆架地区的岩石层地幔性质；西沙海槽附近较高的速度不仅反映了华南大陆向南的延伸，而且与海槽裂谷拉张引起的地幔上拱有关，整个南海北部没有发现大规模地幔热流的活动痕迹.相比之下，南海东部次海盆的上地幔顶部存在明显的低速异常，对应于海底扩张中心的地幔上涌区，表明岩石层地幔强烈减薄甚至缺失；台湾东部－吕宋－菲律宾北部的低速异常与地震、火山活动以及岩浆作用紧密相关，揭示了西太平洋岛弧俯冲带的活动特征；南海东北部的洋－陆边界清晰，南海东部和菲律宾海西部较高的速度代表了海洋岩石层地幔的性质.Pn波各向异性反映出区域性构造应力状态及岩石层地幔的变形痕迹：华南地区的各向异性较小，说明这一构造稳定地区的岩石层地幔变形程度较弱；南海北部的快波方向与地壳浅表层构造的伸展方向一致，主要反映了中、新生代以来的大陆边缘张裂和剪切作用对岩石层地幔结构的影响；琉球－台湾－吕宋岛弧两侧各向异性十分强烈，平行于海沟的快波方向表明菲律宾海板块和欧亚大陆的相互作用导致俯冲板块前缘的岩石层地幔强烈变形；台湾东南海域快波方向的变化可能与欧亚大陆和菲律宾海板块俯冲机制的转换以及岩石层被撕裂有关. 相似文献
10.
The dynamic solid-fluid-surface wave interaction problem can be solved with known Finite Element solutions. However, these solutions are complicated by the unsymmetric nature of the matrix equation to be solved. This paper shows how the numerical problem can be simplified by symmetrization, without loss of physical generality, using specialized Lagrange co-ordinates for the fluid free surface wave, and by introducing a Lagrange multiplier representing a generalized fluid pressure. With these improvements, solid-fluid-surface wave analysis capabilities can easily be added to most Finite Element structural analysis programs. Numerical examples of the performance of the improved formulation are given for earthquake analysis. 相似文献
11.
We compute the transfer of oceanic lithosphere material from the surface of the model to the inner convective mantle at successive
stages of the supercontinental cycle, in the time interval from the beginning of convergence of the continents to their complete
dispersal. The sequence of stages of a supercontinental cycle (Wilson cycle) is calculated with a two-dimensional numerical
model of assembling and dispersing continents driven by mantle flows; in turn, the flows themselves are forming under thermal
and mechanical influence of continents. We obtain that during the time of the order of 300 Myr the complete stirring of oceanic
lithosphere through whole mantle does not occur. This agrees with current ideas on the circulation of oceanic crust material.
Former oceanic crust material appears again at the Earth’s surface in the areas of mantle upstreams.
The numerical simulation demonstrates that the supercontinental cycle is a factor which intensifies stirring of the material,
especially in the region beneath the supercontinent. The reasons are a recurring formation of plumes in that region as well
as a global restructuring of mantle flow pattern due to the process of joining and separation of continents.
The computations of viscous shear stresses are also carried out in the mantle as a function of spatial coordinates and time.
With a simplified model of uniform mantle viscosity, the numerical experiment shows that the typical maximal shear stresses
in the major portion of the mantle measure about 5 MPa (50 bar). The typical maximal shear stresses located in the uppermost
part of mantle downgoing streams (in a zone that measures roughly 200 × 200 km) are approximately 8 times greater and equal
to 40 MPa (400 bar). 相似文献
12.
The upper mantle flow beneath the North China Platform 总被引：2，自引：0，他引：2
In this paper we establish an upper mantle convection model which is constrained by regional isostatic gravity anomalies. Comparing the computed convection patterns with the tectonic features of the North China Platform we find that there are two positive anomaly centers connected with upward flows. These anomalies belong to the tectonic units of the Shan-Xi geoanticline and the Lu-Xi geoanticline. The centers of downward flows are connected with the tectonic units of the Liao-Ji geosyncline. It is reasonable to suggest that the upward mantle flows push the lithosphere upward and generate the observed positive isostatic gravity anomaly. The downward mantle flows pull the lithosphere down and generate the negative anomaly. However, the use of simple analysis makes it difficult to explain the complex lithospheric dynamics of this region. In order to understand lithospheric structures and tectonic features we must investigate the mechanical properties of the lithosphere and the relationship between the lithosphere and the mantle. These problems are discussed in the last section of this paper. 相似文献
13.
In the kinematic theory of lithospheric plate tectonics, the position and parameters of the plates are predetermined in the initial and boundary conditions. However, in the self-consistent dynamical theory, the properties of the oceanic plates (just as the structure of the mantle convection) should automatically result from the solution of differential equations for energy, mass, and momentum transfer in viscous fluid. Here, the viscosity of the mantle material as a function of temperature, pressure, shear stress, and chemical composition should be taken from the data of laboratory experiments. The aim of this study is to reproduce the generation of the ensemble of the lithospheric plates and to trace their behavior inside the mantle by numerically solving the convection equations with minimum a priori data. The models demonstrate how the rigid lithosphere can break up into the separate plates that dive into the mantle, how the sizes and the number of the plates change during the evolution of the convection, and how the ridges and subduction zones may migrate in this case. The models also demonstrate how the plates may bend and break up when passing the depth boundary of 660 km and how the plates and plumes may affect the structure of the convection. In contrast to the models of convection without lithospheric plates or regional models, the structure of the mantle flows is for the first time calculated in the entire mantle with quite a few plates. This model shows that the mantle material is transported to the mid-oceanic ridges by asthenospheric flows induced by the subducting plates rather than by the main vertical ascending flows rising from the lower mantle. 相似文献
14.
V. P. Trubitsyn 《Izvestiya Physics of the Solid Earth》2008,44(11):857-872
Based on data of seismic tomography, the structure of the mantle flows of the contemporary Earth and the continental drift are calculated. Results of calculation of the contemporary motion of continents and their future drift for 150 Myr are presented. The present-day positions of six continents and the nine largest islands are taken as an initial state. The contemporary temperature distribution in the mantle is calculated according to the data of seismic tomography. The 3-D distribution of seismic wave velocities is converted into the density distribution and then into the temperature distribution. The Stokes equation is numerically solved for flows in a viscous mantle with floating continents for the given initial temperature distribution. In this way, the velocities of convective flows are determined in the entire present-day mantle and the surface distribution for the Earth’s heat flux is obtained. The reliability of the calculated flows in the mantle is estimated by the comparison of the calculated velocities of the contemporary continents and oceanic lithosphere with data of satellite measurements. Further, evolutionary equations of convection with floating continents were numerically solved. The calculated structure of mantle flows, temperature distribution, and position of continents are presented for a time moment 150 Myr in the future. The resulting successive changes in the position of continents in time show how islands (in particular, Japan and Indonesia) will be attached to continents and how continents will converge, exhibiting a tendency toward the formation of a new supercontinent in the southern hemisphere of the Earth. 相似文献
15.
V. P. Trubitsyn A. N. Evseev A. A. Baranov A. P. Trubitsyn 《Izvestiya Physics of the Solid Earth》2007,43(12):981-991
An endothermic phase transition at a depth of 660 km in the mantle partially slows down mantle flows. Many models considering the possibility of temporary layering of flows with separation of convection in the upper and lower mantle have been constructed over the past two decades. The slowing-down effect of the endothermic phase transition is very sensitive to the slope of the phase-equilibrium curve. However, laboratory measurements contain considerable uncertainties admitting both a partial convection layering and only an insignificant slowing down of a part of downgoing mantle flows. In this work, we present results of calculations of mantle flows within a wide range of phase-transition parameter values, determine ranges of one-and two-layer convection, and derive dependences of the amplitude and period of oscillations on phase-transition parameters. 相似文献
16.
— We discuss and illustrate graphically with simple 2-D problems, four common pitfalls in geophysical nonlinear inversion. The first one establishes that the Lagrange multiplier, used to incorporate a priori information in the geophysical inverse problem, should be the largest value still compatible with a reasonable data fitting. This procedure should be used only when the interpreter is sure about the importance of the a priori information used to stabilize the inverse problem relative to the geophysical observations. Because this is rarely the case, the user should use the smallest Lagrange multiplier still producing stable solutions. The second pitfall is an attempt to automatically estimate the Lagrange multiplier by decreasing it along the iterative process used to solve the nonlinear optimization problem. Consequently, at the last iteration, the Lagrange multiplier may be so small that the problem may become ill-posed and any computed solution in this case is meaningless. The third pitfall is related to the incorporation of a priori information by a technique known as “Jumping.” This formulation, from the viewpoint of the class of Acceptable Gradient Methods, is incomplete and may lead to a premature halt in the iteration, and, consequently, to solutions far from the true one. Finally, the fourth pitfall is an inadequate convergence criterion which stops the iteration when the data misfit drops just below the noise level, irrespective of the fact that the functional to be minimized may not have attained its minimum. This means that the a priori information has not been completely incorporated, so that this stopping criterion partially neutralizes the effect of the stabilizing functional, and opens the possibility of obtaining unstable, meaningless estimates. 相似文献
17.
S. M. Molodensky 《Izvestiya Physics of the Solid Earth》2008,44(8):615-621
New, unique information on the inertial and dissipative coupling of the liquid core and the mantle has been retrieved from modern high-precision (radiointerferometer and GPS) data on tidal variations in the rotation velocity and nutation of the Earth. Comparison of theoretical and observed data provided new estimates for the dynamic flattening of the outer liquid and the inner solid cores, mantle quality factor, viscosity of the liquid core, and electromagnetic coupling of the liquid core and the mantle [Molodensky, 2004, 2006]. As was shown in the first part of the paper [Molodensky, 2008] (further referred to as [I]), generation of eddy flows in Proudman-Taylor columns, whose orientation is controlled by the topography of the liquid core-mantle boundary, should be taken into account for correct estimation of the inertial coupling (see formulas (8) and (34) in [I]). The range of periods within which this effect plays a significant role is determined by the decay time of these flows. This time is estimated in the paper for the case where dissipation is related to viscous friction at the core-mantle boundary or with the electromagnetic coupling of the liquid core and the mantle. Because of significant uncertainties in modern data on the viscosity of the liquid core, the magnetic field intensity at the core-mantle boundary, and the electrical conductivity of the lower mantle, the dissipative coupling of the liquid core and the mantle cannot be calculated as yet. However, as shown in the paper, the decay time of eddy flows is connected with the attenuation time of subdiurnal free nutation and with the liquid core viscosity. This enables the estimation of the frequency dependence of the dissipative coupling in a fairly wide range. It is shown that the range of periods for which relations (8) and (34) in [I] are valid encompasses the best-studied length-of-day variations and, therefore, these relations are applicable to analysis of the majority of modern data. 相似文献
18.
A. A. Kirdyashkin N. L. Dobretsov A. G. Kirdyashkin 《Izvestiya Physics of the Solid Earth》2009,45(8):684-700
Heat and mass transfer processes in the conduit of a thermochemical plume located beneath an oceanic plate far from a mid-ocean ridge (MOR) proceed under conditions of horizontal convective flows penetrating the plume conduit. In the region of a mantle flow approaching the plume conduit (in the frontal part of the conduit), the mantle material heats and melts. The melt moves through the plume conduit at the average velocity of flow v and is crystallized on the opposite side of the conduit (in the frontal part of the conduit). The heat and the chemical dope transferred by the conduit to the mantle flow are carried away by crystallized mantle material at the velocity v.The local coefficients of heat transfer at the boundary of the plume conduit are theoretically determined and the balance of heat fluxes through the side of the plume conduit per linear meter of the conduit height. The total heat generation rate, transmitted by the Hawaiian plume into the upper and lower mantle, is evaluated. With the use of regular patterns of heat transfer in the lower mantle, which is modeled on the horizontal layer, heated from below and cooled from above, the diameter of the plume source, the kinematic viscosity of the melt in the plume conduit, and the velocity of horizontal lower-mantle flows are evaluated and the dependences of the temperature drop, viscosity and Rayleigh number for the lower mantle on the diameter of the plume source are presented. 相似文献
19.
Santa Man Shrestha Hideji Kawakami Eric Augustus Tingatinga Hidenori Mogi 《地震工程与工程振动(英文版)》2010,9(4):481-491
A new method for wave propagation modeling is introduced in this paper. By using the constraint optimization (Lagrange multiplier) method, the sum of weighted squared Fourier amplitudes is minimized when subjected to a constraint. The sum of the maximum amplitudes obtained from all output models is normalized to unity and is taken as a constraint. In this method, all the actual time histories are considered as outputs and dealt with equally. Independently of the combinations of time histories (or the first ... 相似文献
20.
Hualalai is one of five volcanoes whose eruptions built the island of Hawaii. The historic 1800–1801 flows and the analyzed prehistoric flows exposed at the surface are alkalic basalts except for a trachyte cone and flow at Puu Waawaa and a trachyte maar deposit near Waha Pele. The 1800–1801 eruption produced two flows: the upper Kaupulehu flow and the lower Huehue flow. The analyzed lavas of the two 1800–1801 flows are geochemically identical with the exception of a few samples from the toe of the Huehue flow that appear to be derived from a separate magmatic batch. The analyzed prehistoric basalts are nearly identical to the 1800–1801 flows but include some lavas that have undergone considerable shallow crystal fractionation. The least fractionated alkalic basalts from Hualalai are in equilibrium with mantle olivine (Fo87) indicating that the Hawaiian mantle source region is not unusually iron-rich. The 1800–1801 and analyzed prehistoric basalts can be generated by about 5–10% partial fusion of a garnet-bearing source relatively enriched in the light-rare-earths. The mantle underlying the Hawaiian Islands is chemically and mineralogically heterogeneous before and after extraction of the magmas that make up the volcanoes. 相似文献