Institute of Computational Mathematics and Scientific Engineering Computing

Beijing, China

Institute of Computational Mathematics and Scientific Engineering Computing

Beijing, China
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Liu S.,Tongji University | Wang H.,Tongji University | Fang S.,Tongji University | Huang G.,Institute of computational mathematics and scientific engineering computing | And 2 more authors.
SEG Technical Program Expanded Abstracts | Year: 2011

A 3D dynamic programming approach to first-arrival traveltime computation is extended to anisotropic velocity models with rugged topography, which is necessary for 3D kirchhoff integral migration or near-surface tomography in the piedmont area in southwestern China. The traveltime computation method based on Fermat's principle uses simple calculus techniques and a systematic mapping scheme to determine first-arrival times on a uniform grid, which has no limitation on large velocity contrast and space-varying anisotropic parameters. In order to get the minimum traveltime a set of nonlinear equations is solved on each grid point, where the wavefront velocity 1 / Sgroup ø is determined by group angle. This set of nonlinear equations can be expressed on the assumption that the wavefront velocity in VTI/TTI vertical symmetry transversely isotropic/tilted symmetry transversely isotropic media can be approximated by a truncated Fourier-type cosine series. The numerical example on VTI/TTI model demonstrates that the method is correct and effective. © 2011 Society of Exploration Geophysicists.


Huang X.,CAS Institute of Automation | Gong L.,Institute of Computational Mathematics and Scientific Engineering Computing
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Separating a foreground layer from stereo video in real-time is used in many applications such as live background substitution. Conventional separating models using stereo, contrast or color alone are usually not accurate enough to be satisfactory. Furthermore, the powerful tool of graph cut which is well suited for segmentation is known to be not efficient enough especially for high resolution images. In this paper, we conquer these difficulties by fusing stereo with color and contrast to model the segmentation problem as an minimum cut problem of a planar graph and solving it by a specialized algorithm, parametric shortest paths [8] with a dynamic tree structure, in O(nlogn) time. Experimental results demonstrate the high accuracy and efficiency of the algorithm. © 2011 Springer-Verlag Berlin Heidelberg.


Huang X.,CAS Institute of Automation | Gong L.,Institute of Computational Mathematics and Scientific Engineering Computing | Wang X.,Zhejiang University of Technology
2010 Chinese Conference on Pattern Recognition, CCPR 2010 - Proceedings | Year: 2010

Fast facial points fitting plays an important role in applications such as Human-Computer Interaction, entertainment, surveillance, and is highly relevant to the techniques of facial expression analysis, face recognition, 3D face model generation, etc. Active Appearance Models (AAMs) are generative models commonly used to fit face. They are sensitive to illumination and expression changes because they use only raw intensity to build observation models. In this paper, a real time facial points fitting approach using mixture observation models is presented. Furthermore, the 3D modes are used to constrain the AAM so that it can only generate model instances that can also be generated with the 3D modes. Finally, we give a derivative process for fast energy minimization using the inverse compositional algorithm. A coarse-to-fine fitting strategy is used for realtime and robust facial points fitting. We apply this algorithm to facial expression cloning of 3D Avatar system. Experimental results demonstrate that fitting the AAM with mixture observation models and 3D constraint outperforms other classical algorithms. ©2010 IEEE.


Kong L.,Jiangxi Normal University | Zhang J.,Institute of Computational Mathematics and Scientific Engineering Computing | Cao Y.,Jiangxi Normal University | Duan Y.,Anhui University of Science and Technology | Huang H.,Jiangxi Normal University
Computer Physics Communications | Year: 2010

In the manuscript, we propose an explicit symplectic partitioned Runge-Kutta Fourier pseudo-spectral (SPRK-FPS) scheme for the coupled Klein-Gordon-Schrödinger (KGS) equation. It is explicit in term of iteration since it is only required to solve two linear algebraic equations at each marching time step. Furthermore, it does not only symplectic geometric structure-preserving, but also charge-preserving and energy-preserving. The numerical results are in good agreement with the theoretical analysis. © 2010 Elsevier B.V. All rights reserved.


Chen J.,Chinese Academy of Sciences | Chen J.,University of California at Santa Barbara | Ming P.,Institute of Computational Mathematics and Scientific Engineering Computing | Yang J.Z.,Wuhan University
Communications in Computational Physics | Year: 2014

We introduce a newmultigrid method to study the lattice staticsmodel arising from nanoindentation. A constrained Cauchy-Born elasticity model is used as the coarse-grid operator. This method accelerates the relaxation process and considerably reduces the computational cost. In particular, it saves quite a bit when dislocations nucleate and move, as demonstrated by the simulation results. ©2014 Global-Science Press.


Ma Y.,Jiangxi Normal University | Kong L.,Jiangxi Normal University | Hong J.,Institute of Computational Mathematics and Scientific Engineering Computing | Cao Y.,Jiangxi Normal University
Computers and Mathematics with Applications | Year: 2011

In this paper, we develop a new kind of multisymplectic integrator for the coupled nonlinear Schrdinger (CNLS) equations. The CNLS equations are cast into multisymplectic formulation. Then it is split into a linear multisymplectic formulation and a nonlinear Hamiltonian system. The space of the linear subproblem is approximated by a high-order compact (HOC) method which is new in multisymplectic context. The nonlinear subproblem is integrated exactly. For splitting and approximation, we utilize an HOCSMS integrator. Its stability and conservation laws are investigated in theory. Numerical results are presented to demonstrate the accuracy, conservation laws, and to simulate various solitons as well, for the HOCSMS integrator. They are consistent with our theoretical analysis. © 2010 Elsevier Ltd. All rights reserved.


Kong L.,Jiangxi Normal University | Wang L.,Jiangxi Normal University | Yin X.,Institute of Computational Mathematics and Scientific Engineering Computing | Duan Y.,Anhui University of Science and Technology
AIP Conference Proceedings | Year: 2012

In the article, we discuss the conservation laws for the nonlinear Schrödinger equation with wave operator under multisymplectic integrator (MI). The discrete conservation laws of the numerical method are analyzed. It is verified that the proposed MI can stably simulate the multisymplectic Hamiltonian system excellent over long time. It is more accurate than some energy-preserving schemes though they are of the same accuracy. Moreover, the residual of mass is less than energy-preserving schemes under the same mesh partition over long-term. © 2012 American Institute of Physics.


Li X.,Pennsylvania State University | Ming P.,Institute of Computational Mathematics and Scientific Engineering Computing
Multiscale Modeling and Simulation | Year: 2014

We study three quasi-continuum approximations of a lattice model for crack propagation. The influence of the approximation on the bifurcation patterns is investigated. The estimate of the modeling error is applicable to near and beyond bifurcation points, which enables us to evaluate the approximation over a finite range of loading and multiple mechanical equilibria. © 2014 Society for Industrial and Applied Mathematics


Ren H.-R.,Zhejiang University | Huang G.-H.,Institute of Computational Mathematics and Scientific Engineering Computing | Wang H.-Z.,Tongji University | Chen S.-C.,Zhejiang University
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2013

In this paper, we summarize the influence of Hessian operator in seismic inversion methods and review the mathematical and physical meanings of the Hessian operator in the seismic inversion imaging. Hessian operator is the second derivation of the misfit function to the seismic model parameters. It can be seen by analyzing its Green's function formulation under the acoustic wave approximation that the Hessian reflects the effects of the seismic acquisition system and wavelet frequency band during the projection of information from the data spaces to the model spaces. We propose two pseudo-Hessian forms for the least-squares migration and the full waveform inversion separately. The application of plane-wave Hessian operator can lead to an amplitude-preserved migration result. The sub-offset Hessian can be used to the full waveform inversion to enhance the efficiency of inversion. At last, we discuss and evaluate the Hessian operator in seismic inversion imaging.

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