472 research outputs found
DEM simulation of the mechanical properties of SiC ceramic under pre-stressing
In this paper, the method of discrete element model (DEM) simulation was used to investigate the mechanical properties of SiC ceramic materials under the action of pre-stress. Using the bonded particle model (BPM), several different numerical tests (such as UCT, TPB, SENB tests) of SiC ceramic were established. Different pre-stress values were applied on the lateral surface of the ceramic specimen during the numerical simulation process, all tests were carried out at least 5 times with different random number, and the average mechanical properties results were calculated. It was showed that the existence of pre-stress has a significant effect on the mechanical properties of materials. It can enhance the strength of materials, while the force action on material in machining process force or action force the crack’s initiation and propagation was limited
Equations of State for Nonlinear Sigma-Models II: Relations between Resummation Schemes, and Crossover Phenomena
It is shown how a recent method to systematically extrapolate and resum the
loop expansion for nonlinear sigma-models is related to solutions of the
renormalization group equation. This relation is used to generalize the
explicit equations of state obtained previously to models which display
crossover phenomena. As an example we discuss Wegner's localization model and
consider the crossover from symplectic to unitary symmetry.Comment: 14pp., REVTeX, 1 figur
Generalized hole-particle transformations and spin reflection positivity in multi-orbital systems
We propose a scheme combining spin reflection positivity and generalized
hole-particle and orbital transformations to characterize the symmetry
properties of the ground state for some correlated electron models on bipartite
lattices. In particular, we rigorously determine at half-filling and for
different regions of the parameter space the spin, orbital and pairing
pseudospin of the ground state of generalized two-orbital Hubbard models which
include the Hund's rule coupling.Comment: 6 pages, 2 figure
Skyrmions in Higher Landau Levels
We calculate the energies of quasiparticles with large numbers of reversed
spins (``skyrmions'') for odd integer filling factors 2k+1, k is greater than
or equals 1. We find, in contrast with the known result for filling factor
equals 1 (k = 0), that these quasiparticles always have higher energy than the
fully polarized ones and hence are not the low energy charged excitations, even
at small Zeeman energies. It follows that skyrmions are the relevant
quasiparticles only at filling factors 1, 1/3 and 1/5.Comment: 10 pages, RevTe
Persistent Currents and Dissipation in Narrow Bilayer Quantum Hall Bars
Bilayer quantum Hall states support a flow of nearly dissipationless
staggered current which can only decay through collective channels. We study
the dominant finite-temperature dissipation mechanism which in narrow bars is
driven by thermal nucleation of pseudospin solitons. We find the
finite-temperature resistivity, predict the resulting staggered current-voltage
characteristics, and calculate the associated zero-temperature critical
staggered current and gate voltage.Comment: 4 pgs. REVTeX, 3 eps figure
Anisotropic Transport of Quantum Hall Meron-Pair Excitations
Double-layer quantum Hall systems at total filling factor can
exhibit a commensurate-incommensurate phase transition driven by a magnetic
field oriented parallel to the layers. Within the commensurate
phase, the lowest charge excitations are believed to be linearly-confined Meron
pairs, which are energetically favored to align with . In order
to investigate this interesting object, we propose a gated double-layer Hall
bar experiment in which can be rotated with respect to the
direction of a constriction. We demonstrate the strong angle-dependent
transport due to the anisotropic nature of linearly-confined Meron pairs and
discuss how it would be manifested in experiment.Comment: 4 pages, RevTex, 3 postscript figure
Effect of Subband Landau Level Coupling to the Linearly Dispersing Collective Mode in a Quantum Hall Ferromagnet
In a recent experiment (Phys. Rev. Lett. {\bf 87}, 036903 (2001)), Spielman
et al observed a linearly dispersing collective mode in quantum Hall
ferromagnet. While it qualitatively agrees with the Goldstone mode dispersion
at small wave vector, the experimental mode velocity is slower than that
calculated by previous theories by a factor about 0.55. A better agreement with
the experimental data may possibly be achieved by taking the subband Landau
level coupling into account due to the finiteness of the layer thickness. A
novel coupling of quantum fluctuation to the tunneling is briefly discussed.Comment: 4 pages; published versio
Hyperglycemia-induced inhibition of DJ-1 expression compromised the effectiveness of ischemic postconditioning cardioprotection in rats
published_or_final_versio
Solitons in polarized double layer quantum Hall systems
A new manifestation of interlayer coherence in strongly polarized double
layer quantum Hall systems with total filling factor
in the presence of a small or zero tunneling is theoretically
predicted. It is shown that moving (for small tunneling) and spatially
localized (for zero tunneling) stable pseudospin solitons develop which could
be interpreted as mobile or static charge-density excitations.
The possibility of their experimental observation is also discussed.Comment: Phys. Rev. B (accepted
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