We present a first-principles study of the magnetic anisotropy of ultrathin Fe films on Cu3Au (0 0 1), to investigate the origin of the magnetic reorientation transition observed experimentally. Our results indicate a...
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A general technique for the generation of canonical channel models and demonstrate the application of the technique to time-frequency and time-scale integral kernel operators is developed. As an example, the derivatio...
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Suspensions of aerobic bacteria often develop flows from the interplay of chemotaxis and buoyancy. We find in sessile drops that flows related to those in the Boycott effect of sedimentation carry bioconvective plumes...
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Suspensions of aerobic bacteria often develop flows from the interplay of chemotaxis and buoyancy. We find in sessile drops that flows related to those in the Boycott effect of sedimentation carry bioconvective plumes down the slanted meniscus and concentrate cells at the drop edge, while in pendant drops such self-concentration occurs at the bottom. On scales much larger than a cell, concentrated regions in both geometries exhibit transient, reconstituting, high-speed jets straddled by vortex streets. A mechanism for large-scale coherence is proposed based on hydrodynamic interactions between swimming cells.
It is shown that sigma-delta (/spl Sigma//spl Delta/) algorithms can be used effectively to quantize finite frame expansions for R/sup d/. Error estimates for various quantized frame expansions are derived, and, in pa...
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It is shown that sigma-delta (/spl Sigma//spl Delta/) algorithms can be used effectively to quantize finite frame expansions for R/sup d/. Error estimates for various quantized frame expansions are derived, and, in particular, it is shown that /spl Sigma//spl Delta/ quantizers outperform the standard PCM schemes.
We provide methods of computing multivalued solutions to the Euler-Poisson system and test them in the context of a klystron amplifier. An Eulerian formulation capable of computing multivalued solutions is derived fro...
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We provide methods of computing multivalued solutions to the Euler-Poisson system and test them in the context of a klystron amplifier. An Eulerian formulation capable of computing multivalued solutions is derived from a kinetic description of the Euler-Poisson system and a moment closure. The system of the moment equations may be closed due to the special structure of the solution in phase space. The Eulerian moment equations are computed for a velocity modulated electron beam, which has been shown by prior Lagrangian theories to break in a finite time and form multivalued solutions. The results of the Eulerian moment equations are compared to direct computation of the kinetic equations and a Lagrangian method also developed in the paper. We use the Lagrangian formulation for the explicit computation of wave breaking time and location for typical velocity modulation boundary conditions.
An alternating direction finite element scheme for a class of moving boundary problems is studied. Using coordinate transformations of the spatial variants, a new domain independent of the time is obtained and an ADFE...
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This paper examines how pre-cracks existed on tubular cantilever beams alter their mechanical behaviour. From both quasi-static and impact tests with over 70 specimens, it has been revealed that pre-cracks make the do...
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This paper examines how pre-cracks existed on tubular cantilever beams alter their mechanical behaviour. From both quasi-static and impact tests with over 70 specimens, it has been revealed that pre-cracks make the dominant failure pattern of tubular beams switch from fully plastic collapse to crack propagation, thereby dramatically reduce their overall loading-carrying capacity. The inclination of the pre-crack is found not to affect the direction of crack opening.
In this Letter, we report on the densest-known packings of congruent ellipsoids. The family of new packings consists of crystal arrangements of spheroids with a wide range of aspect ratios, and with density φ always ...
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In this Letter, we report on the densest-known packings of congruent ellipsoids. The family of new packings consists of crystal arrangements of spheroids with a wide range of aspect ratios, and with density φ always surpassing that of the densest Bravais lattice packing φ≈0.7405. A remarkable maximum density of ϕ≈0.7707 is achieved for maximal aspect ratios larger than 3, when each ellipsoid has 14 touching neighbors. Our results are directly relevant to understanding the equilibrium behavior of systems of hard ellipsoids, and, in particular, the solid and glassy phases.
Calculated polar magneto-optic Kerr rotation and ellipticity angles are presented for the system Cu4Ni8CunNi9∕Cu(100), n=2,…,10. Contrary to the common belief, the Kerr signals are found to be not directly proportio...
Calculated polar magneto-optic Kerr rotation and ellipticity angles are presented for the system Cu4Ni8CunNi9∕Cu(100), n=2,…,10. Contrary to the common belief, the Kerr signals are found to be not directly proportional to the total magnetic moment. It will be shown that in order to assign at least indirectly the size (and sign) of the Kerr angles and therefore the type of coupling to a kind of total magnetic moment, one has to consider weighted layer-resolved moments, e.g., weighted by the damping factors of the reflected waves. As to be expected the occurring oscillations in the Kerr angles with respect to the spacer thickness resemble closely those for the interlayer exchange coupling energy.
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