60,120 research outputs found
Graphyne: Hexagonal network of carbon with versatile Dirac cones
We study alpha, beta, and gamma graphyne, a class of graphene allotropes with
carbon triple bonds, using a first-principles density-functional method and
tight-binding calculation. We find that graphyne has versatile Dirac cones and
it is due to remarkable roles of the carbon triple bonds in electronic and
atomic structures. The carbon triple bonds modulate effective hopping matrix
elements and reverse their signs, resulting in Dirac cones with reversed
chirality in alpha graphyne, momentum shift of the Dirac point in beta
graphyne, and switch of the energy gap in gamma graphyne. Furthermore, the
triple bonds provide chemisorption sites of adatoms which can break sublattice
symmetry while preserving planar sp2-bonding networks. These features of
graphyne open new possibilities for electronic applications of carbon-based
two-dimensional materials and derived nanostructures.Comment: 5 pages, 5 figures, 1 tabl
Analog-digital simulation of transient-induced logic errors and upset susceptibility of an advanced control system
A simulation study is described which predicts the susceptibility of an advanced control system to electrical transients resulting in logic errors, latched errors, error propagation, and digital upset. The system is based on a custom-designed microprocessor and it incorporates fault-tolerant techniques. The system under test and the method to perform the transient injection experiment are described. Results for 2100 transient injections are analyzed and classified according to charge level, type of error, and location of injection
Quantum Key Distribution Using Quantum Faraday Rotators
We propose a new quantum key distribution (QKD) protocol based on the fully
quantum mechanical states of the Faraday rotators. The protocol is
unconditionally secure against collective attacks for multi-photon source up to
two photons on a noisy environment. It is also robust against impersonation
attacks. The protocol may be implemented experimentally with the current
spintronics technology on semiconductors.Comment: 7 pages, 7 EPS figure
Time-dependent coupled oscillator model for charged particle motion in the presence of a time varyingmagnetic field
The dynamics of time-dependent coupled oscillator model for the charged
particle motion subjected to a time-dependent external magnetic field is
investigated. We used canonical transformation approach for the classical
treatment of the system, whereas unitary transformation approach is used when
managing the system in the framework of quantum mechanics. For both approaches,
the original system is transformed to a much more simple system that is the sum
of two independent harmonic oscillators which have time-dependent frequencies.
We therefore easily identified the wave functions in the transformed system
with the help of invariant operator of the system. The full wave functions in
the original system is derived from the inverse unitary transformation of the
wave functions associated to the transformed system.Comment: 16 page
Axial charges of octet and decuplet baryons
We present a study of axial charges of baryon ground and resonant states with
relativistic constituent quark models. In particular, the axial charges of
octet and decuplet , , , , , and
baryons are considered. The theoretical predictions are compared to existing
experimental data and results from other approaches, notably from lattice
quantum chromodynamics and chiral perturbation theory. The relevance of axial
charges with regard to -dressing and spontaneous chiral-symmetry breaking
is discussed
Mechanical behavior and failure phenomenon of an in situ-toughened silicon nitride
The Weibull modulus, fracture toughness and crack growth resistance of an in-situ toughened, silicon nitride material used to manufacture a turbine combustor were determined from room temperature to 1371 C. The material exhibited an elongated grain structure that resulted in improved fracture toughness, nonlinear crack growth resistance, and good elevated temperature strength. However, low temperature strength was limited by grains of excessive length (30 to 100 microns). These excessively long grains were surrounded by regions rich in sintering additives
Cosmological Luminosity Evolution of QSO/AGN Population
We apply the observed optical/X-ray spectral states of the Galactic black
hole candidates (GBHCs) to the cosmological QSO luminosity evolution under the
assumptions that QSOs and GBHCs are powered by similar accretion processes and
that their emission mechanisms are also similar. The QSO luminosity function
(LF) evolution in various energy bands is strongly affected by the spectral
evolution which is tightly correlated with the luminosity evolution. We
generate a random sample of QSOs born nearly synchronously by allowing the QSOs
to have redshifts in a narrow range around an initial high redshift, black hole
masses according to a power-law, and mass accretion rates near Eddington rates.
The QSOs evolve as a single long-lived population on the cosmological time
scale. The pure luminosity evolution results in distinct luminosity evolution
features due to the strong spectral evolution. Most notably, different energy
bands (optical/UV, soft X-ray, and hard X-ray) show different evolutionary
trends and the hard X-ray LF in particular shows an apparent reversal of the
luminosity evolution (from decreasing to increasing luminosity) at low
redshifts, which is not seen in the conventional pure luminosity evolution
scenario without spectral evolution. The resulting mass function of black holes
(BHs), which is qualitatively consistent with the observed QSO LF evolution,
shows that QSO remnants are likely to be found as BHs with masses in the range
10**8-5x10**10 solar masses. The long-lived single population of QSOs are
expected to leave their remnants as supermassive BHs residing in rare, giant
elliptical galaxies.Comment: 9 pages, 2 figures, ApJ
Calculating using HYP staggered fermions
We present preliminary results for calculated using HYP
staggered fermions in the quenched approximation. We compare different choices
of quenched penguin operators.Comment: 3 pages, 4 figures, Contribution to Lattice 2004 International
Symposiu
- …