56,793 research outputs found
Propellant slosh coupling with bending Interim report
Vibrational characteristics of large liquid propellant space vehicl
Nonlinear effects for island coarsening and stabilization during strained film heteroepitaxy
Nonlinear evolution of three-dimensional strained islands or quantum dots in
heteroepitaxial thin films is studied via a continuum elasticity model and the
development of a nonlinear dynamic equation governing the film morphological
profile. All three regimes of island array evolution are identified and
examined, including a film instability regime at early stage, a nonlinear
coarsening regime at intermediate times, and the crossover to a saturated
asymptotic state, with detailed behavior depending on film-substrate misfit
strains but not qualitatively on finite system sizes. The phenomenon of island
stabilization and saturation, which corresponds to the formation of steady but
non-ordered arrays of strained quantum dots, occurs at later time for smaller
misfit strain. It is found to be controlled by the strength of film-substrate
wetting interaction which would constrain the valley-to-peak mass transport and
hence the growth of island height, and also determined by the effect of elastic
interaction between surface islands and the high-order strain energy of
individual islands at late evolution stage. The results are compared to
previous experimental and theoretical studies on quantum dots coarsening and
saturation.Comment: 19 pages, 12 figures; submitted to Phys. Rev.
Can Cosmic Shear Shed Light on Low Cosmic Microwave Background Multipoles?
The lowest multipole moments of the cosmic microwave background (CMB) are
smaller than expected for a scale-invariant power spectrum. One possible
explanation is a cutoff in the primordial power spectrum below a comoving scale
of Mpc. This would affect not only the
CMB but also the cosmic-shear (CS) distortion of the CMB. Such a cutoff
increases significantly the cross-correlation between the large-angle CMB and
cosmic-shear patterns. The cross-correlation may be detectable at
which, when combined with the low CMB moments, may tilt the balance between a
result and a firm detection of a large-scale power-spectrum cutoff.
As an aside, we also note that the cutoff increases the large-angle
cross-correlation between the CMB and low-redshift tracers of the mass
distribution.Comment: 5 pages, 3 figures, revised statistical analysis, submitted to PR
Rational Trust Modeling
Trust models are widely used in various computer science disciplines. The
main purpose of a trust model is to continuously measure trustworthiness of a
set of entities based on their behaviors. In this article, the novel notion of
"rational trust modeling" is introduced by bridging trust management and game
theory. Note that trust models/reputation systems have been used in game theory
(e.g., repeated games) for a long time, however, game theory has not been
utilized in the process of trust model construction; this is where the novelty
of our approach comes from. In our proposed setting, the designer of a trust
model assumes that the players who intend to utilize the model are
rational/selfish, i.e., they decide to become trustworthy or untrustworthy
based on the utility that they can gain. In other words, the players are
incentivized (or penalized) by the model itself to act properly. The problem of
trust management can be then approached by game theoretical analyses and
solution concepts such as Nash equilibrium. Although rationality might be
built-in in some existing trust models, we intend to formalize the notion of
rational trust modeling from the designer's perspective. This approach will
result in two fascinating outcomes. First of all, the designer of a trust model
can incentivise trustworthiness in the first place by incorporating proper
parameters into the trust function, which can be later utilized among selfish
players in strategic trust-based interactions (e.g., e-commerce scenarios).
Furthermore, using a rational trust model, we can prevent many well-known
attacks on trust models. These two prominent properties also help us to predict
behavior of the players in subsequent steps by game theoretical analyses
Deterministically entangling distant nitrogen-vacancy centers by a nanomechanical cantilever
We present a practical scheme by global addressing to deterministically
entangle negatively charged nitrogen-vacancy (N-V) centers in distant diamonds
using a nano-mechanical cantilever with the magnetic tips strongly coupled to
the N-V electron spins. Symmetric Dicke states are generated as an example, and
the experimental feasibility and challenge of our scheme are discussed.Comment: 5 pages, 4 figure
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