Starting from a two-variable system of reaction-diffusion equations, an algorithm is devised for efficient simulation of waves in excitable media. The spatio-temporal resolution of the simulation can be varied continu...
Starting from a two-variable system of reaction-diffusion equations, an algorithm is devised for efficient simulation of waves in excitable media. The spatio-temporal resolution of the simulation can be varied continuously. For fine resolutions the algorithm provides accurate solution of the underlying reaction-diffusion equations. For coarse resolutions, the algorithm provides qualitative simulations at small computational cost.
High frequency linearized inversion estimates a critical component of the earth's velocity field from measurements of scattered acoustic waves captured by various source and receiver pairs (acquisition geometry). ...
High frequency linearized inversion estimates a critical component of the earth's velocity field from measurements of scattered acoustic waves captured by various source and receiver pairs (acquisition geometry). The method partitions the velocity field into two components: an assumed long-scale velocity component and an unknown short-scale velocity component. A standard imaging operation (migration) locates those positions where the short-scale velocity is non-zero. In strongly refracting velocity fields, several scattering paths (pairs of incident and reflected bicharacteristics) with equal travel times may produce artifacts in the short-scale image. This paper explains why these artifacts arise and how they may be removed. For general acquisition geometry. we give an imaging condition: To product an artifact-free image, scattering paths gust. be reconstructible from two pieces of information;(a) The travel time for the pair of bicharacteristics and (b) The projection of the bicharacteristics at the source and receiver onto the cotangent bundle of the acquisition manifold.
Laminated multiphase composite plates reinforced with carbon nanotubes (CNTs) and carbon fibers in an epoxy matrix offer excellent mechanical performance for lightweight, high-strength applications. This study focuses...
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Electron collision with lithium atoms is calculated by using R-matrix method. The scattering parameters are applied in the determination of the electron impact broadening and shift of the lithium resonance line 2s2S-2...
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Electron collision with lithium atoms is calculated by using R-matrix method. The scattering parameters are applied in the determination of the electron impact broadening and shift of the lithium resonance line 2s2S-2p2P. The width and shift are obtained based on the impact approximation. A largest discrepancy of 30 percent for the broadening width is found from a semiclassical calculation.
Boundary conditions for molecular dynamics simulation of crystalline solids are considered with the objective of eliminating the reflection of phonons.A variational formalism is presented to construct boundary conditi...
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Boundary conditions for molecular dynamics simulation of crystalline solids are considered with the objective of eliminating the reflection of phonons.A variational formalism is presented to construct boundary conditions that minimize total phonon *** boundary conditions that involve a few neighbors of the boundary atoms and limited number of time steps are found using the variational *** effects are studied and compared with other boundary conditions such as truncated exact boundary conditions or by appending border atoms where artificial damping forces are *** general it is found that,with the same cost or complexity,the variational boundary conditions perform much better than the truncated exact boundary conditions or by appending border atoms with empirical damping *** issues of implementation are discussed for real *** to brittle fracture dynamics is illustrated.
This paper studies the nonsequential double ionization （NSDI） process of diatomic molecules aligned parallel and perpendicular to an intense linearly polarized laser field by using a three-dimensional semiclassical ...
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This paper studies the nonsequential double ionization （NSDI） process of diatomic molecules aligned parallel and perpendicular to an intense linearly polarized laser field by using a three-dimensional semiclassical model. With this model, it achieves insight into the ion momentum distribution under the combined influence of a two-centre Coulomb potential and an intense laser field, and this result shows the significant influence of molecular alignment on the ratio between double and single ionization rate. Careful investigations show that the NSDI process for different alignment molecules has a close relation to the laser intensity and the different bounding electron distribution has a significant influence on the final ion momentum distribution.
Image denoising is still a challenge of image processing. Buades et al. proposed a nonlocal means （NL-means） approach. This method had a remarkable denoising results at high expense of computational cost. In this pa...
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Image denoising is still a challenge of image processing. Buades et al. proposed a nonlocal means （NL-means） approach. This method had a remarkable denoising results at high expense of computational cost. In this paper, We compared several fast non-local means methods, and proposed a new fast algorithm. Numerical experiments showed that our algorithm considerably reduced the computational cost, and obtained visually pleasant images.
We calculated the vibrational free energies of the selected ordered compounds in the Ag-Cu system by using two kinds of methods: (1) calculating the phonon dispersion and density of states and the consequently vibrati...
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We calculated the vibrational free energies of the selected ordered compounds in the Ag-Cu system by using two kinds of methods: (1) calculating the phonon dispersion and density of states and the consequently vibrational free energies by using the method of ab initio inverted interatomic potentials and dynamic matrix;(2) the vibrational free energies determined by a Debye-Griineisen approximation. The Ag-Cu phase diagram is calculated by the cluster variation method. The results show that the solubility at Ag-rich end of the calculated phase diagram considering vibrational modes by using the first method is in better agreement with the experimental.
A fairly comprehensive analysis is presented for the gradient descent dynamics for training two-layer neural network models in the situation when the parameters in both layers are *** initialization schemes as well as...
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A fairly comprehensive analysis is presented for the gradient descent dynamics for training two-layer neural network models in the situation when the parameters in both layers are *** initialization schemes as well as general regimes for the network width and training data size are *** the overparametrized regime,it is shown that gradient descent dynamics can achieve zero training loss exponentially fast regardless of the quality of the *** addition,it is proved that throughout the training process the functions represented by the neural network model are uniformly close to those of a kernel *** general values of the network width and training data size,sharp estimates of the generalization error are established for target functions in the appropriate reproducing kernel Hilbert space.
The problem of propagation of turbulent premixed flame is analyzed using the field equation introduced recently by Kerstein, Ashurst and Williams (1987). The dynamic renormalization group method is applied to this equ...
The problem of propagation of turbulent premixed flame is analyzed using the field equation introduced recently by Kerstein, Ashurst and Williams (1987). The dynamic renormalization group method is applied to this equation and the formula for the turbulent flame velocity is derived in the lowest order in the ε-expansion. The formula, which does not include adjustable parameters, agrees well with experimental (Abdel-Gayed et al., 1984) and numerical (Ashurst & Barr 1983) results on flame propagation in high-Reynolds number turbulent media. Ways to design transport and large-eddy (sub-grid) models for simulation of combustion processes, based on the ideas developed in the present paper, are discussed.
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