41,026 research outputs found
Direct Transient Analysis of a Fuze Assembly by Axisymmetric Solid Elements
A fuze assembly, which consists of three major parts, nose, collar and sleeve, was designed to survive severe transverse impact giving a maximum base acceleration of 20.000 G. It is shown that hoop failure occurred in the collar after the impact. They also showed that by bonding the collar to the nose, the collar was able to survive the same impact. To find out the effectiveness of the bonding quantitatively, axisymmetric solid elements TRAPAX and TRIAAX were used in modelling the fuze and direct transient analysis was performed. The dynamic stresses in selected elements on the bonded and unbonded collars were compared. The peak hoop stresses in the unbonded collar were found to be up to three times higher than those in the bonded collar. The NASTRAN results explained the observed hoop failure in the unbonded collar. In addition, static and eigenvalue runs were performed as checks on the models prior to the transient runs. The use of the MPCAX cards and the existence and contributors of the calculated first several nearly identical natural frequencies are addressed
Interaction induced topological phase transition in Bernevig-Hughes-Zhang model
We study interaction induced topological phase transition in
Bernevig-Hughes-Zhang model. Topological nature of the phase transition is
revealed by directly calculating the Z2 index of the interacting system from
the single-particle Green's function. The interacting Z2 index is also
consistently checked through the edge spectra. Combined with ab initio methods,
present approach is a useful tool searching for correlated topological
insulating materials from the first-principle point of view.Comment: 4.5 pages, 4 figures, reference adde
Magnetism of Cold Fermionic Atoms on p-Band of an Optical Lattice
We carry out \textit{ab initio} study of ground state phase diagram of
spin-1/2 cold fermionic atoms within two-fold degenerate -band of an
anisotropic optical lattice. Using the Gutzwiller variational approach, we show
that a robust ferromagnetic phase exists for a vast range of band fillings and
interacting strengths. The ground state crosses over from spin density wave
state to spin-1 Neel state at half filling. Additional harmonic trap will
induce spatial separation of varies phases. We also discuss several relevant
observable consequences and detection methods. Experimental test of the results
reported here may shed some light on the long-standing issue of itinerant
ferromagnetism.Comment: 5 pages, 4 figure
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