225,816 research outputs found
Gradient design of metal hollow sphere (MHS) foams with density gradients
This is the post-print version of the final paper published in Composites Part B: Engineering. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2011 Elsevier B.V.Metal hollow sphere (MHS) structures with a density gradient have attracted increasing attention in the effort to pursue improved energy absorption properties. In this paper, dynamic crushing of MHS structures of different gradients are discussed, with the gradients being received by stacks of hollow spheres of the same external diameter but different wall thicknesses in the crushing direction. Based on the dynamic performance of MHS structures with uniform density, a crude semi-empirical model is developed for the design of MHS structures in terms of gradient selections for energy absorption and protection against impact. Following this, dynamic responses of density graded MHS foams are comparatively analyzed using explicit finite element simulation and the proposed formula. Results show that the simple semi-empirical model can predict the response of density gradient MHS foams and is ready-to-use in the gradient design of MHS structures.The National Science Foundation of China and the State Key Laboratory of Explosion Science
and Technology (Beijing Institute of Technology
A Quasi-Spherical Gravitational Wave Solution in Kaluza-Klein Theory
An exact solution of the source-free Kaluza-Klein field equations is
presented. It is a 5D generalization of the Robinson-Trautman quasi-spherical
gravitational wave with a cosmological constant. The properties of the 5D
solution are briefly described.Comment: 10 pages Latex, Revtex, submitted to GR
Parity Nonconservation in the Photodisintegration of the Deuteron at Low Energy
The parity-nonconserving asymmetry in the deuteron photodisintegration,
, is considered with the photon energy ranged up to 10
MeV above the threshold. The aim is to improve upon a schematic estimate
assuming the absence of tensor as well as spin-orbit forces in the
nucleon-nucleon interaction. The major contributions are due to the
vector-meson exchanges, and the strong suppression of the pion-exchange
contribution is confirmed. A simple argument, going beyond the observation of
an algebraic cancellation, is presented. Contributions of meson-exchange
currents are also considered, but found to be less significant.Comment: 12 pages, 6 figures, typeset by REVTeX (two-column format) and BIBTe
Parity violation in scattering and vector-meson weak-coupling constants
We calculate the parity-nonconserving longitudinal asymmetry in the elastic
scattering at the energies where experimental data are available.
In addition to the standard one-meson exchange weak potential, the variation of
the strong-coupling constants and the non-standard effects such as form factors
and -exchange description of the -exchange potential are taken
into account. With the extra effects, we investigate the compatibility of the
experimental data and the presently-known range of the vector-meson
weak-coupling constants.Comment: Contribution to the proceedings of the 3rd Asia-Pacific conference on
few-body problems in physics, Suranaree Univ. of Technology, Nakhon
Ratchasima, Thailand, July 26 - 30, 200
Orbital elements of barium stars formed through a wind accretion scenario
Taking the total angular momentum conservation in place of the tangential
momentum conservation, and considering the square and higher power terms of
orbital eccentricity e, the changes of orbital elements of binaries are
calculated for wind accretion scenario. These new equations are used to
quantitatively explain the observed (e,logP) properties of normal G, K giants
and barium stars. Our results reflect the evolution from G, K giant binaries to
barium binaries, moreover, the barium stars with longer orbital periods P>1600
days may be formed by accreting part of the ejecta from the intrinsic AGB stars
through wind accretion scenario.Comment: 7 pages, LaTex, 4 PS figures and 1 table included, accepted for
publication in A &
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