1,678 research outputs found
Twinning and grain subdivision during dynamic deformation of a Mg AZ31 sheet alloy at room temperature
The microstructural evolution of an AZ31 rolled sheet during dynamic deformation at strain rates of âŒ103 sâ1 has been investigated by electron backscatter diffraction, X-ray and neutron diffraction. The influence of orientation on the predominant deformation mechanisms and on the recovery processes taking place during deformation has been systematically examined. The results have been compared with those corresponding to the same alloy tested quasi-statically under equivalent conditions. It has been found that strain rate enhances the activation of extension twinning dramatically, while contraction and secondary twinning are not significantly influenced. The polarity of extension twinning is even reversed in some grains under selected testing conditions. Significant grain subdivision by the formation of geometrically necessary boundaries (GNBs) takes place during both quasi-static and dynamic deformation of this AZ31 alloy. It is remarkable that GNBs of high misorientations form even at the highest strain rates. The phenomenon of recovery has been found to be orientation dependen
Structure of the neutron-rich N=7 isotones 10Li and 9He
The near threshold structure of the unbound N=7 isotones 10Li and 9He has
been investigated using proton removal and breakup from intermediate energy (35
MeV/nucleon) secondary beams of 11Be and 14,15B. The coincident detection of
the beam velocity 9Li and 8He fragments and neutrons permitted the relative
energy of the in-flight decay of 10Li and 9He to be reconstructed. Both systems
were found to exhibited virtual s-wave strength near threshold together with a
higher-lying resonance.Comment: 4 pages, 2 figures, Contribution to INPC2010 - "International Nuclear
Physics Conference", Vancouver, Canada, 4-9 July 2010, Proceedings to be
published in Journal of Physics: Conference Serie
Finding Your Literature Match -- A Recommender System
The universe of potentially interesting, searchable literature is expanding
continuously. Besides the normal expansion, there is an additional influx of
literature because of interdisciplinary boundaries becoming more and more
diffuse. Hence, the need for accurate, efficient and intelligent search tools
is bigger than ever. Even with a sophisticated search engine, looking for
information can still result in overwhelming results. An overload of
information has the intrinsic danger of scaring visitors away, and any
organization, for-profit or not-for-profit, in the business of providing
scholarly information wants to capture and keep the attention of its target
audience. Publishers and search engine engineers alike will benefit from a
service that is able to provide visitors with recommendations that closely meet
their interests. Providing visitors with special deals, new options and
highlights may be interesting to a certain degree, but what makes more sense
(especially from a commercial point of view) than to let visitors do most of
the work by the mere action of making choices? Hiring psychics is not an
option, so a technological solution is needed to recommend items that a visitor
is likely to be looking for. In this presentation we will introduce such a
solution and argue that it is practically feasible to incorporate this approach
into a useful addition to any information retrieval system with enough usage.Comment: Contribution to the proceedings of the colloquium Future Professional
Communication in Astronomy II, 13-14 April 2010, Cambridge, Massachusetts. 11
pages, 4 figures
Free and smooth boundaries in 2-D finite-difference schemes for transient elastic waves
A method is proposed for accurately describing arbitrary-shaped free
boundaries in single-grid finite-difference schemes for elastodynamics, in a
time-domain velocity-stress framework. The basic idea is as follows: fictitious
values of the solution are built in vacuum, and injected into the numerical
integration scheme near boundaries. The most original feature of this method is
the way in which these fictitious values are calculated. They are based on
boundary conditions and compatibility conditions satisfied by the successive
spatial derivatives of the solution, up to a given order that depends on the
spatial accuracy of the integration scheme adopted. Since the work is mostly
done during the preprocessing step, the extra computational cost is negligible.
Stress-free conditions can be designed at any arbitrary order without any
numerical instability, as numerically checked. Using 10 grid nodes per minimal
S-wavelength with a propagation distance of 50 wavelengths yields highly
accurate results. With 5 grid nodes per minimal S-wavelength, the solution is
less accurate but still acceptable. A subcell resolution of the boundary inside
the Cartesian meshing is obtained, and the spurious diffractions induced by
staircase descriptions of boundaries are avoided. Contrary to what occurs with
the vacuum method, the quality of the numerical solution obtained with this
method is almost independent of the angle between the free boundary and the
Cartesian meshing.Comment: accepted and to be published in Geophys. J. In
- âŠ