PHG (parallel hierarchical grid) is a scalable parallel adaptive finite element toolbox under active developmentat the State Key Laboratory of Scientific and engineeringcomputing, Chinese Academy of sciences. This pa...
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PHG (parallel hierarchical grid) is a scalable parallel adaptive finite element toolbox under active developmentat the State Key Laboratory of Scientific and engineeringcomputing, Chinese Academy of sciences. This paper demonstrates its application to adaptive finite element computations of electromagnetic problems. Two examples on solving the time harmonic Maxwell's equations are shown. Results of some large scale adaptive finite element simulations with up to 1 billion degrees of freedom and using up to 2048 CPUs are presented.
We have developed a new strategy and espouse a novel paradigm for large-scale computing and real-time interactive visualization. This philosophy calls for intense interactive sessions for a couple of hours at a time a...
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We show that edge stresses introduce intrinsic ripples in freestanding graphene sheets even in the absence of any thermal effects. Compressive edge stresses along zigzag and armchair edges of the sheet cause out-of-pl...
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We show that edge stresses introduce intrinsic ripples in freestanding graphene sheets even in the absence of any thermal effects. Compressive edge stresses along zigzag and armchair edges of the sheet cause out-of-plane warping to attain several degenerate mode shapes. Based on elastic plate theory, we identify scaling laws for the amplitude and penetration depth of edge ripples as a function of wavelength. We also demonstrate that edge stresses can lead to twisting and scrolling of nanoribbons as seen in experiments. Our results underscore the importance of accounting for edge stresses in thermal theories and electronic structure calculations for freestanding graphene sheets.
Polarization switching in ferroelectric polymers is studied using a multiscale framework. A continuum Landau-Ginzburg-Devonshire model for a first-order phase transition is parametrized for ideal all trans chains of P...
Polarization switching in ferroelectric polymers is studied using a multiscale framework. A continuum Landau-Ginzburg-Devonshire model for a first-order phase transition is parametrized for ideal all trans chains of P(VDF-TrFE) (70:30) copolymers using data obtained from molecular-dynamics (MD) simulations. Thermal fluctuations and kinetics are accounted for by using a time-dependent Ginzburg-Landau model where the length and time scales, as well as the thermal noise amplitude, are also set from MD simulations. This method is used to investigate the nature of polarization switching in ferroelectric polymers and to test recent claims that ultrathin ferroelectric polymer films undergo intrinsic switching. Our simulations show that for a defect-free system, domain nucleation due to thermal fluctuations prevents homogeneous switching of the polarization, even at very small thicknesses. However, this nucleation does not substantially decrease the coercive field compared to the intrinsic value.
In this paper, grammian solutions of Ishimori-(I) (Ish-(I)) equation are firstly obtained by Hirota's direct *** the source generation procedure is utilized to generate the Ishimori-(I) equation with self-cons...
In this paper, grammian solutions of Ishimori-(I) (Ish-(I)) equation are firstly obtained by Hirota's direct *** the source generation procedure is utilized to generate the Ishimori-(I) equation with self-consistent sources (Ish-(I) ESCS) and its grammian solutions are *** a simple example, the (1, 1) dromion solution is examined.
In this paper, a general expression of the 3D hybrid imaging method based on acoustic wavefield extrapolation is presented. Moreover, the planewave synthesization method is given. The numerical results of 3D shot-prof...
作者：
Wei-nan EPing-bing MingDepartment of Mathematics and PACM
Princeton University LSEC
Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China
We study continuum and atomistic models for the elastodynamics of crystalline solids at zero temperature. We establish sharp criterion for the regime of validity of the nonlinear elastic wave equations derived from th...
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We study continuum and atomistic models for the elastodynamics of crystalline solids at zero temperature. We establish sharp criterion for the regime of validity of the nonlinear elastic wave equations derived from the well-known Cauchy-Born rule.
In this paper, we investigate the quadratic approximation methods. After studying the basic idea of simplex methods, we construct several new search directions by combining the local information progressively obtained...
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In this paper, we investigate the quadratic approximation methods. After studying the basic idea of simplex methods, we construct several new search directions by combining the local information progressively obtained during the iterates of the algorithm to form new subspaces. And the quadratic model is solved in the new subspaces. The motivation is to use the information disclosed by the former steps to construct more promising directions. For most tested problems, the number of functions evaluations have been reduced obviously through our algorithms.
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