A fast mesh deformation method using explicit interpolation

A novel mesh deformation algorithm for unstructured polyhedral meshes is developed utilizing a tree-code optimization of a simple direct interpolation method. The algorithm is shown to provide mesh quality that is competitive with radial basis function based methods, with markedly better performance in preserving boundary layer orthogonality in viscous meshes. The parallelization of the algorithm is described, and the algorithm cost is demonstrated to be O(n log n). The parallel implementation was used to deform meshes of 100 million nodes on nearly 200 processors demonstrating that the method scales to large mesh sizes. Results are provided for a simulation of a high Reynolds number fluid–structure interaction case using this technique.     

Femtosecond laser ablation of neurons in <Emphasis Type="Italic">C</Emphasis>. <Emphasis Type="Italic">elegans</Emphasis> for behavioral studies

In this paper, the interaction between the inhomogeneous and anisotropic cloak covered infinitely long PEC circular cylinder and the parallel electric-line-source is investigated in detail. First, the permittivity and permeability tensors of the cloak are defined according to Pendry’s model, then the wave equation in the metamaterial cloak is derived; second, the far/near properties of the model are investigated, and using the boundary conditions the electromagnetic fields of the whole region are calculated analytically; finally, based on the analytical expressions, the electric fields of the whole region are demonstrated through numerical results which show the effects of invisibility. Finally, the effects of loss on the performance of the invisible cloak are investigated.     

Technical Reports: Time-Resolved Activities at the Advanced Photon Source Requiring the Pulsed Structure of the X-ray Beam

Scientific research in the time domain using the pulsed structure of the X-ray beams from a third-generation synchrotron source, such as the Advanced Photon Source (APS), has become a major interest among synchrotron users. The traditional material science, chemistry, and biology communities are getting an early glimpse of the potential impact of fast time-resolved X-ray studies. The scientific disciplines that have benefited from these studies include atomic and molecular physics, biology, chemical science, condensed matter physics, engineering science, environmental science, material science, and nuclear science. Technically, the turn-key-type femtosecond (fs) optical lasers with high peak power, used as pumps in many X-ray pump-probe experiments, have only recently become available.     

Unusual nucleation and growth of γ′ iron nitride upon nitriding Fe–4.75 at.% Al alloy

The influence of substitutionally dissolved Al in ferritic Fe–4.75 at.% Al alloy on the nucleation and growth of γ′ iron nitride (Fe₄N_{1? x} ) was investigated upon nitriding in NH₃/H₂ gas mixtures. The nitrided specimens were characterised employing optical microscopy, scanning electron microscopy, transmission electron microscopy, electron probe microanalysis and X-ray diffraction. As compared to the nitriding of pure ferrite (α-Fe), where a layer of γ′ develops at the surface, upon nitriding ferritic Fe–4.75 at.% Al an unusual morphology of γ′ plates develops at the surface, which plates deeply penetrate the substrate. In the diffusion zone, nano-sized precipitates of γ′ and of metastable, cubic (NaCl-type) AlN occur, having, with the ferrite matrix, a Nishiyama–Wassermann orientation relationship and a Bain orientation relationship, respectively. The γ′ plates contain a high density of stacking faults and fine ε iron nitride (Fe₂N_{1? z} ) precipitates, although the formation of ε iron nitride is not expected for the employed nitriding parameters. On the basis of dedicated nitriding experiments it is shown that the unusual microstructural development is a consequence of the negligible solubility of Al in γ′ and the obstructed precipitation of the thermodynamically stable, hexagonal (wurtzite-type) AlN in ferrite.     

Equality of the Spectral and Dynamical Definitions of Reflection

For full-line Jacobi matrices, Schrödinger operators, and CMV matrices, we show that being reflectionless, in the sense of the well-known property of m-functions, is equivalent to a lack of reflection in the dynamics in the sense that any state that goes entirely to x = ?∞ as t → ?∞ goes entirely to x = ∞ as t → ∞. This allows us to settle a conjecture of Deift and Simon from 1983 regarding ergodic Jacobi matrices.