14,323 research outputs found
On universal decoherence under gravity: a perspective through the Equivalence Principle
In Nature Phys. 11, 668 (2015) (Ref. [1]), a composite particle prepared in a
pure initial quantum state and propagated in a uniform gravitational field is
shown to undergo a decoherence process at a rate determined by the
gravitational acceleration. By assuming Einstein's Equivalence Principle to be
valid, we demonstrate, first in a Lorentz frame with accelerating detectors,
and then directly in the Lab frame with uniform gravity, that the dephasing
between the different internal states arise not from gravity but rather from
differences in their rest mass, and the mass dependence of the de Broglie
wave's dispersion relation. We provide an alternative view to the situation
considered by Ref. [1], where we propose that gravity plays a kinematic role in
the loss of fringe visibility by giving the detector a transverse velocity
relative to the particle beam; visibility can be easily recovered by giving the
screen an appropriate uniform velocity. We finally propose that dephasing due
to gravity may in fact take place for certain modifications to the
gravitational potential where the Equivalence Principle is violated.Comment: 5 pages, 3 figure
Towards Long-endurance Flight: Design and Implementation of a Variable-pitch Gasoline-engine Quadrotor
Majority of today's fixed-pitch, electric-power quadrotors have short flight
endurance ( 1 hour) which greatly limits their applications. This paper
presents a design methodology for the construction of a long-endurance
quadrotor using variable-pitch rotors and a gasoline-engine. The methodology
consists of three aspects. Firstly, the rotor blades and gasoline engine are
selected as a pair, so that sufficient lift can be comfortably provided by the
engine. Secondly, drivetrain and airframe are designed. Major challenges
include airframe vibration minimization and power transmission from one engine
to four rotors while keeping alternate rotors contra-rotating. Lastly, a PD
controller is tuned to facilitate preliminary flight tests. The methodology has
been verified by the construction and successful flight of our gasoline
quadrotor prototype, which is designed to have a flight time of 2 to 3 hours
and a maximum take-off weight of 10 kg.Comment: 6 page
Global current account adjustment: a decomposition
The rising current account deficit in the USA has attracted considerable attention in recent years. We use the "business cycle accounting" methodology to identify the principal distortions that have affected the external accounts of the US. In particular, we measure distortions in the optimality conditions of a simple two-country general equilibrium model using data from the US and the other G7 countries. We then feed these measured distortions into the model individually and use the simulated counterfactual paths of the current account to determine the contribution of each of these "wedges" to the overall external imbalance of the USA. We find that no single wedge in isolation can account closely for the observed current account. However, a combination of productivity differences and deviations from risk-sharing between the US and the rest of the G7 does the best job in accounting for most of the measured movement of the US current account.
Flow of emotional messages in artificial social networks
Models of message flows in an artificial group of users communicating via the
Internet are introduced and investigated using numerical simulations. We
assumed that messages possess an emotional character with a positive valence
and that the willingness to send the next affective message to a given person
increases with the number of messages received from this person. As a result,
the weights of links between group members evolve over time. Memory effects are
introduced, taking into account that the preferential selection of message
receivers depends on the communication intensity during the recent period only.
We also model the phenomenon of secondary social sharing when the reception of
an emotional e-mail triggers the distribution of several emotional e-mails to
other people.Comment: 10 pages, 7 figures, submitted to International Journal of Modern
Physics
An introduction to the interim digital SAR processor and the characteristics of the associated Seasat SAR imagery
Basic engineering data regarding the Interim Digital SAR Processor (IDP) and the digitally correlated Seasat synthetic aperature radar (SAR) imagery are presented. The correlation function and IDP hardware/software configuration are described, and a preliminary performance assessment presented. The geometric and radiometric characteristics, with special emphasis on those peculiar to the IDP produced imagery, are described
The NN phase shifts in the extended quark-delocalization, color-screening model
An alternative method is applied to the study of nucleon-nucleon(NN)
scattering phase shifts in the framework of extended quark delocalization,
color-screening model(QDCSM), where the one-pion-exchange(OPE) with short-range
cutoff is included.Comment: 5 pages, 3 figures, two-colum
Opinion Mining on Non-English Short Text
As the type and the number of such venues increase, automated analysis of
sentiment on textual resources has become an essential data mining task. In
this paper, we investigate the problem of mining opinions on the collection of
informal short texts. Both positive and negative sentiment strength of texts
are detected. We focus on a non-English language that has few resources for
text mining. This approach would help enhance the sentiment analysis in
languages where a list of opinionated words does not exist. We propose a new
method projects the text into dense and low dimensional feature vectors
according to the sentiment strength of the words. We detect the mixture of
positive and negative sentiments on a multi-variant scale. Empirical evaluation
of the proposed framework on Turkish tweets shows that our approach gets good
results for opinion mining
Uniform polynomial rates of convergence for a class of L\'evy-driven controlled SDEs arising in multiclass many-server queues
We study the ergodic properties of a class of controlled stochastic
differential equations (SDEs) driven by -stable processes which arise
as the limiting equations of multiclass queueing models in the Halfin-Whitt
regime that have heavy-tailed arrival processes. When the safety staffing
parameter is positive, we show that the SDEs are uniformly ergodic and enjoy a
polynomial rate of convergence to the invariant probability measure in total
variation, which is uniform over all stationary Markov controls resulting in a
locally Lipschitz continuous drift. We also derive a matching lower bound on
the rate of convergence (under no abandonment). On the other hand, when all
abandonment rates are positive, we show that the SDEs are exponentially ergodic
uniformly over the above-mentioned class of controls. Analogous results are
obtained for L\'evy-driven SDEs arising from multiclass many-server queues
under asymptotically negligible service interruptions. For these equations, we
show that the aforementioned ergodic properties are uniform over all stationary
Markov controls. We also extend a key functional central limit theorem
concerning diffusion approximations so as to make it applicable to the models
studied here
- …