32,899 research outputs found
Adaptive Neural Network Feedforward Control for Dynamically Substructured Systems
(c) 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works
The branch processes of vortex filaments and Hopf Invariant Constraint on Scroll Wave
In this paper, by making use of Duan's topological current theory, the
evolution of the vortex filaments in excitable media is discussed in detail.
The vortex filaments are found generating or annihilating at the limit points
and encountering, splitting, or merging at the bifurcation points of a complex
function . It is also shown that the Hopf invariant of knotted
scroll wave filaments is preserved in the branch processes (splitting, merging,
or encountering) during the evolution of these knotted scroll wave filaments.
Furthermore, it also revealed that the "exclusion principle" in some chemical
media is just the special case of the Hopf invariant constraint, and during the
branch processes the "exclusion principle" is also protected by topology.Comment: 9 pages, 5 figure
Hints of Standard Model Higgs Boson at the LHC and Light Dark Matter Searches
The most recent results of searches at the LHC for the Higgs boson h have
turned up possible hints of such a particle with mass m_h about 125 GeV
consistent with standard model (SM) expectations. This has many potential
implications for the SM and beyond. We consider some of them in the contexts of
a simple Higgs-portal dark matter (DM) model, the SM plus a real gauge-singlet
scalar field D as the DM candidate, and a couple of its variations. In the
simplest model with one Higgs doublet and three or four generations of
fermions, for D mass m_D DD tends to have a
substantial branching ratio. If future LHC data confirm the preliminary Higgs
indications, m_D will have to exceed m_h/2. To keep the DM lighter than m_h/2,
one will need to extend the model and also satisfy constraints from DM direct
searches. The latter can be accommodated if the model provides sizable isospin
violation in the DM-nucleon interactions. We explore this in a
two-Higgs-doublet model combined with the scalar field D. This model can offer
a 125-GeV SM-like Higgs and a light DM candidate having isospin-violating
interactions with nucleons at roughly the required level, albeit with some
degree of fine-tuning.Comment: 17 pages, 4 figures, slightly revised, main conclusions unchanged,
references added, matches published versio
Calculations on the Size Effects of Raman Intensities of Silicon Quantum Dots
Raman intensities of Si quantum dots (QDs) with up to 11,489 atoms (about 7.6
nm in diameter) for different scattering configurations are calculated. First,
phonon modes in these QDs, including all vibration frequencies and vibration
amplitudes, are calculated directly from the lattice dynamic matrix by using a
microscopic valence force field model combined with the group theory. Then the
Raman intensities of these quantum dots are calculated by using a
bond-polarizability approximation. The size effects of the Raman intensity in
these QDs are discussed in detail based on these calculations. The calculations
are compared with the available experimental observation. We are expecting that
our calculations can further stimulate more experimental measurements.Comment: 21 pages, 7 figure
- …