3,958 research outputs found
Statefinder diagnostic for the modified polytropic Cardassian universe
We apply the Statefinder diagnostic to the Modified Polytropic Cardassian
Universe in this work. We find that the Statefinder diagnostic is quite
effective to distinguish Cardassian models from a series of other cosmological
models. The plane is used to classify the Modified Polytropic Cardassian
models into six cases. The evolutionary trajectories in the plane for the
cases with different and reveal different evolutionary properties
of the universe. In addition, we combine the observational data, the
Cosmic Microwave Background (CMB) data and the Baryonic Acoustic Oscillation
(BAO) data to make a joint analysis. We find that \textbf{Case 2} can be
excluded at the 68.3% confidence level and any case is consistent with the
observations at the 95.4% confidence level.Comment: Comments: Final version for publication in Physical Review D [minor
revision to match the appear version] Journal-ref: Physical Review D 75,
083515 (2007
Cosmological constraints from Radial Baryon Acoustic Oscillation measurements and Observational Hubble data
We use the Radial Baryon Acoustic Oscillation (RBAO) measurements, distant
type Ia supernovae (SNe Ia), the observational data (OHD) and the Cosmic
Microwave Background (CMB) shift parameter data to constrain cosmological
parameters of CDM and XCDM cosmologies and further examine the role of
OHD and SNe Ia data in cosmological constraints. We marginalize the likelihood
function over by integrating the probability density to obtain the best fitting results and the confidence regions
in the plane.With the combination analysis for
both of the {\rm }CDM and XCDM models, we find that the confidence
regions of 68.3%, 95.4% and 99.7% levels using OHD+RBAO+CMB data are in good
agreement with that of SNe Ia+RBAO+CMB data which is consistent with the result
of Lin et al's work. With more data of OHD, we can probably constrain the
cosmological parameters using OHD data instead of SNe Ia data in the future.Comment: 8 pages, 6 figures, 2 tables, accepted for publication in Physics
Letters
Thermodynamical properties of dark energy with the equation of state
The thermodynamical properties of dark energy are usually investigated with
the equation of state . Recent observations
show that our universe is accelerating, and the apparent horizon and the event
horizon vary with redshift . When definitions of the temperature and entropy
of a black hole are used to the two horizons of the universe, we examine the
thermodynamical properties of the universe which is enveloped by the apparent
horizon and the event horizon respectively. We show that the first and the
second laws of thermodynamics inside the apparent horizon in any redshift are
satisfied, while they are broken down inside the event horizon in some
redshift. Therefore, the apparent horizon for the universe may be the boundary
of thermodynamical equilibrium for the universe like the event horizon for a
black hole.Comment: 6 pages, 5 figures, Accepted for publication in Physical Review
Large-scale Land Cover Classification in GaoFen-2 Satellite Imagery
Many significant applications need land cover information of remote sensing
images that are acquired from different areas and times, such as change
detection and disaster monitoring. However, it is difficult to find a generic
land cover classification scheme for different remote sensing images due to the
spectral shift caused by diverse acquisition condition. In this paper, we
develop a novel land cover classification method that can deal with large-scale
data captured from widely distributed areas and different times. Additionally,
we establish a large-scale land cover classification dataset consisting of 150
Gaofen-2 imageries as data support for model training and performance
evaluation. Our experiments achieve outstanding classification accuracy
compared with traditional methods.Comment: IGARSS'18 conference pape
Optical Properties of Quantum-Confined Semiconductor Structures Driven by Strong Terahertz Fields
Detectable MeV neutrinos from black hole neutrino-dominated accretion flows
Neutrino-dominated accretion flows (NDAFs) around rotating stellar-mass black
holes (BHs) have been theorized as the central engine of relativistic jets
launched in massive star core collapse events or compact star mergers. In this
work, we calculate the electron neutrino/anti-neutrino spectra of NDAFs by
fully taking into account the general relativistic effects, and investigate the
effects of viewing angle, BH spin, and mass accretion rate on the results. We
show that even though a typical NDAF has a neutrino luminosity lower than that
of a typical supernova (SN), it can reach
peaking at MeV, making them potentially detectable with the upcoming
sensitive MeV neutrino detectors if they are close enough to Earth. Based on
the observed GRB event rate in the local universe and requiring that at least 3
neutrinos are detected to claim a detection, we estimate a detection rate up to
(0.10-0.25) per century for GRB-related NDAFs by the Hyper-Kamiokande
(Hyper-K) detector if one neglects neutrino oscillation. If one assumes that
all Type Ib/c SNe have an engine-driven NDAF, the Hyper-K detection rate would
be (1-3) per century. By considering neutrino oscillations, the
detection rate may decrease by a factor of 2-3. Detecting one such event would
establish the observational evidence of NDAFs in the universe.Comment: 7 pages, 2 figures, 2 tables, accepted for publication in PR
Simulation of human thermal responses in a confined space
Latest human thermal comfort models, such as the IESD-Fiala model, are active multi-nodal
thermal models that simulate physiological regulatory responses, e.g. changing metabolic rate
and skin blood flow, shivering and sweating. Commercial CFD packages, such as ANSYS
CFX, are widely used in studying transient thermal environment. The purpose of this study is
to develop and demonstrate the method for integrating human thermal comfort models with
the CFD environment for detailed transient simulations. Different integration strategies are
discussed in this paper, as well as the technical problems with using detailed (clothed) 3-D
model in the coupled simulation. It is highlighted that further research is required to exploit
the full potential of the integrated model in environmental design
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