22,931 research outputs found
Pion condensation in a soft-wall AdS/QCD model
Finite isospin chemical potential and temperature have been
introduced in the framework of soft-wall AdS/QCD model. By self-consistently
solve the equation of motion, we obtain the phase boundary of pion condensation
phase, across which the system undergoes a phase transition between pion
condensation phase and normal phase. Comparing the free energy of solutions
with and without pion condensation, we find that the phase transition is of
first order type both at large and small . Qualitatively, the
behavior at large is in agreement with the lattice simulation in
Phys.Rev.D66(2002)034505, while the behavior at small is different from
lattice simulations and previous studies in hard wall AdS/QCD model. This
indicates that a full back-reaction model including the interaction of
gluo-dynamics and chiral dynamics might be necessary to describe the small
pion condensation phase. This study could provide certain clues to
build a more realistic holographic model.Comment: Regular article, 21 page
Empirical Modeling of Ducting Effects on a Mobile Microwave Link Over a Sea Surface
In this paper, signal enhancement due to the ducts over a sea surface is experimentally investigated and modeled. The investigation is carried out through the study of air-to-ground mobile microwave links over a tropical ocean with low airborne altitudes (0.37 - 1.83 km) at C band (5.7 GHz). The distance-dependence of the ducting induced enhancement (with reference to the free-space propagation) is linearly modeled, and the physical variations of the ducts are found to be Gaussian distributed. Empirical ducting coefficients and parameters for the Gaussian function are estimated and provided for the prediction of the distance-dependent signal enhancement due to the ducts in similar scenarios
Joint Video and Text Parsing for Understanding Events and Answering Queries
We propose a framework for parsing video and text jointly for understanding
events and answering user queries. Our framework produces a parse graph that
represents the compositional structures of spatial information (objects and
scenes), temporal information (actions and events) and causal information
(causalities between events and fluents) in the video and text. The knowledge
representation of our framework is based on a spatial-temporal-causal And-Or
graph (S/T/C-AOG), which jointly models possible hierarchical compositions of
objects, scenes and events as well as their interactions and mutual contexts,
and specifies the prior probabilistic distribution of the parse graphs. We
present a probabilistic generative model for joint parsing that captures the
relations between the input video/text, their corresponding parse graphs and
the joint parse graph. Based on the probabilistic model, we propose a joint
parsing system consisting of three modules: video parsing, text parsing and
joint inference. Video parsing and text parsing produce two parse graphs from
the input video and text respectively. The joint inference module produces a
joint parse graph by performing matching, deduction and revision on the video
and text parse graphs. The proposed framework has the following objectives:
Firstly, we aim at deep semantic parsing of video and text that goes beyond the
traditional bag-of-words approaches; Secondly, we perform parsing and reasoning
across the spatial, temporal and causal dimensions based on the joint S/T/C-AOG
representation; Thirdly, we show that deep joint parsing facilitates subsequent
applications such as generating narrative text descriptions and answering
queries in the forms of who, what, when, where and why. We empirically
evaluated our system based on comparison against ground-truth as well as
accuracy of query answering and obtained satisfactory results
A hybrid model approach for strange and multi-strange hadrons in 2.76 A TeV Pb+Pb collisions
Using the VISHNU hybrid model, we calculate the multiplicity, spectra, and
elliptic flow of , and in 2.76 A TeV Pb+Pb collisions.
Comparisons between our calculations and the ALICE measurements show that the
model generally describes the soft hadron data of these strange and
multi-strange hadrons at several centrality bins. Mass ordering of elliptic
flow among , K, p, , and has also been studied and
discussed. With a nice description of the particle yields, we explore chemical
and thermal freeze-out of various hadrons species at the LHC within the
framework of the VISHNU hybrid model.Comment: version 2: with several references added, published in PR
- …