34,814 research outputs found
Molecular Dynamics Simulation of Collisions between Hydrogen and Graphite
Hydrogen adsorption by graphite is examined by classical molecular dynamics
simulation using a modified Brenner REBO potential. Such interactions are
typical in chemical sputtering experiments, and knowledge of the fundamental
behavior of hydrogen and graphene in collisional conditions is essential for
modeling the sputtering mechanism. The hydrogen adsorption rate is found to be
dependent on the incident hydrogen energy and not on graphene temperature.
Rather than destroying the graphene, hydrogen incidence at energies of less
than 100 eV can be classified into three regimes of adsorption, reflection and
penetration through one or more graphene layers. Incidence at the lowest
energies is shown to distort the graphene structure.Comment: 4 pages, 4 figures. Accepted for publication by j. Plasma Phys.
Proccedings for the joint conference of 19th International Conference on
Numerical Simulation of Plasmas and 7th Asia Pacific Plasma Theor
Dynamical breakdown of the Ising spin-glass order under a magnetic field
The dynamical magnetic properties of an Ising spin glass
FeMnTiO are studied under various magnetic fields. Having
determined the temperature and static field dependent relaxation time
from ac magnetization measurements under a dc bias field by a
general method, we first demonstrate that these data provide evidence for a
spin-glass (SG) phase transition only in zero field. We next argue that the
data of finite can be well interpreted by the droplet theory
which predicts the absence of a SG phase transition in finite fields.Comment: 4 pages, 5 figure
A unified framework for approximation in inverse problems for distributed parameter systems
A theoretical framework is presented that can be used to treat approximation techniques for very general classes of parameter estimation problems involving distributed systems that are either first or second order in time. Using the approach developed, one can obtain both convergence and stability (continuous dependence of parameter estimates with respect to the observations) under very weak regularity and compactness assumptions on the set of admissible parameters. This unified theory can be used for many problems found in the recent literature and in many cases offers significant improvements to existing results
Evolution of non-thermal emission from shell associated with AGN jets
We explore the evolution of the emissions by accelerated electrons in shocked
shells driven by jets in active galactic nuclei (AGNs). Focusing on powerful
sources which host luminous quasars, we evaluated the broadband emission
spectra by properly taking into account adiabatic and radiative cooling effects
on the electron distribution. The synchrotron radiation and inverse Compton
(IC) scattering of various photons that are mainly produced in the accretion
disc and dusty torus are considered as radiation processes. We show that the
resultant radiation is dominated by the IC emission for compact sources (<
10kpc), whereas the synchrotron radiation is more important for larger sources.
We also compare the shell emissions with those expected from the lobe under the
assumption that a fractions of the energy deposited in the shell and lobe
carried by the non-thermal electrons are and
, respectively. Then, we find that the shell
emissions are brighter than the lobe ones at infra-red and optical bands when
the source size is > 10kpc, and the IC emissions from the shell at > 10 GeV can
be observed with the absence of contamination from the lobe irrespective of the
source size. In particular, it is predicted that, for most powerful nearby
sources (), TeV gamma-rays produced via the IC
emissions can be detected by the modern Cherenkov telescopes such as MAGIC,
HESS and VERITAS.Comment: 13 pages, 5 figures, accepted for publication in Ap
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