169 research outputs found
Reconstruction of modified gravity with ghost dark energy models
In this work, we reconstruct the modified gravity for different ghost
and generalized ghost dark energy models in FRW flat universe, which describe
the accelerated expansion of the universe. The equation of state of
reconstructed - gravity has been calculated. We show that the
corresponding gravity of ghost dark energy model can behave like phantom
or quintessence. We also show that the equation of state of reconstructed
gravity for generalized ghost model can transit from quintessence regime
to the phantom regime as indicated by recent observations.Comment: 13 pages, some references and one author are added. Accepted for
publication by MPL
Interacting entropy-corrected holographic dark energy with apparent horizon as an infrared cutoff
In this work we consider the entropy-corrected version of interacting
holographic dark energy (HDE), in the non-flat universe enclosed by apparent
horizon. Two corrections of entropy so-called logarithmic 'LEC' and power-law
'PLEC' in HDE model with apparent horizon as an IR-cutoff are studied. The
ratio of dark matter to dark energy densities , equation of state parameter
and deceleration parameter are obtained. We show that the cosmic
coincidence is satisfied for both interacting models. By studying the effect of
interaction in EoS parameter, we see that the phantom divide may be crossed and
also find that the interacting models can drive an acceleration expansion at
the present and future, while in non-interacting case, this expansion can
happen only at the early time. The graphs of deceleration parameter for
interacting models, show that the present acceleration expansion is preceded by
a sufficiently long period deceleration at past. Moreover, the thermodynamical
interpretation of interaction between LECHDE and dark matter is described. We
obtain a relation between the interaction term of dark components and thermal
fluctuation in a non-flat universe, bounded by the apparent horizon. In
limiting case, for ordinary HDE, the relation of interaction term versus
thermal fluctuation is also calculated.Comment: 20 pages, 8 figures, figures changed, some Ref. is added, changed
some sentences, accepted by General relativity and gravitation (GERG
Power-law entropy corrected new holographic scalar field models of dark energy with modified IR-cutoff
In this work, the PLECHDE model with Granda-Oliveros (G-O) IR-cutoff is
studied. The evolution of dark energy density, deceleration and EoS parameters
are calculated. I demonstrate that under a condition, our universe can
accelerate near the phantom barrier at present time. We calculate these
parameters also in PLECHDE at Ricci scale, when when and ,
and at last a comparison between Ricci scale, G-O cutoff and non-corrected HDE
without matter field with G-O cutoff is done. The correspondence between this
model and some scalar field of dark energy models is established. By this
method, the evolutionary treatment of kinetic energy and potential for
quintessence, tachyon, K-essence and dilaton fields, are obtained. I show that
the results has a good compatibility with previous work in the limiting case of
flat, dark dominated and non corrected holographic dark energy.Comment: 15 pages, one table, some sentences and references are added,
accepted by modern Phys. L. A (MPLA
Quality evaluation of digital twins generated based on uav photogrammetry and tls: Bridge case study
In the current modern era of information and technology, emerging remote advancements have been widely established for detailed virtual inspections and assessments of infrastructure assets, especially bridges. These technologies are capable of creating an accurate digital representation of the existing assets, commonly known as the digital twins. Digital twins are suitable alternatives to in-person and on-site based assessments that can provide safer, cheaper, more reliable, and less distributive bridge inspections. In the case of bridge monitoring, Unmanned Aerial Vehicle (UAV) photogrammetry and Terrestrial Laser Scanning (TLS) are among the most common advanced technologies that hold the potential to provide qualitative digital models; however, the research is still lacking a reliable methodology to evaluate the generated point clouds in terms of quality and geometric accuracy for a bridge size case study. Therefore, this paper aims to provide a comprehensive methodology along with a thorough bridge case study to evaluate two digital point clouds developed from an existing Australian heritage bridge via both UAV-based photogrammetry and TLS. In this regard, a range of proposed approaches were employed to compare point clouds in terms of points’ distribution, level of outlier noise, data completeness, surface deviation, and geometric accuracy. The comparative results of this case study not only proved the capability and applicability of the proposed methodology and approaches in evaluating these two voluminous point clouds, but they also exhibited a higher level of point density and more acceptable agreements with as-is measurements in TLS-based point clouds subjected to the implementation of a precise data capture and a 3D reconstruction model
Molecular survey of aminoglycoside-resistant Acinetobacter baumannii isolated from tertiary hospitals in Qazvin, Iran
Aminoglycoside-modifying enzymes (AMEs) and 16S rRNA methylases (16S RMTase) are two main resistance mechanisms against
aminoglycosides. This study aimed to evaluate the frequency of AMEs and 16S rRNA methylase genes among aminoglycoside nonsusceptible Acinetobacter baumannii isolates and to assess their clonal relationship using repetitive extragenic palindromic-PCR (rep-PCR).
In this cross-sectional study, a total of 192 A. baumannii isolates were collected from the patients hospitalized in Qazvin, Iran (January
2016 to January 2018). Identification of isolates was performed by standard laboratory methods and API 20E strips. Antimicrobial
susceptibility was determined by Kirby–Bauer method followed by examination of the genes encoding the AMEs and 16S RMTase by
PCR and sequencing methods. The clonal relationship of isolates was carried out by rep-PCR. In total, 98.4% of isolates were nonsusceptible to aminoglycosides, 98.4%, 97.9% and 83.9% of isolates were found to be non-susceptible against gentamicin, tobramycin and
amikacin, respectively. The frequencies of aph(30
)-VI, aac(60
)-Ib, aac(3)-II, aph(30
)-Ia and armA genes were 59.3%, 39.2%, 39.2%, 31.7% and
69.8%, respectively, either alone or in combination. Rep-PCR results showed that the aminoglycoside non-susceptible isolates belonged to
three distinct clones: A (79.4%), B (17.5%) and C (3.2%). The findings of this study showed a high frequency for AMEs with the
emergence of armA genes among the aminoglycoside non-susceptible A. baumannii isolates. Rational administration of aminoglycosides as
well as using an appropriate infection control policy may reduce the presence of resistance to antibiotics in medical centres
Interacting New Agegraphic Dark Energy in a Cyclic Universe
The main goal of this work is investigation of NADE in the cyclic universe
scenario. Since, cyclic universe is explained by a phantom phase (),
it is shown when there is no interaction between matter and dark energy, ADE
and NADE do not produce a phantom phase, then can not describe cyclic universe.
Therefore, we study interacting models of ADE and NADE in the modified
Friedmann equation. We find out that, in the high energy regime, which it is a
necessary part of cyclic universe evolution, only NADE can describe this
phantom phase era for cyclic universe. Considering deceleration parameter tells
us that the universe has a deceleration phase after an acceleration phase, and
NADE is able to produce a cyclic universe. Also it is found valuable to study
generalized second law of thermodynamics. Since the loop quantum correction is
taken account in high energy regime, it may not be suitable to use standard
treatment of thermodynamics, so we turn our attention to the result of
\citep{29}, which the authors have studied thermodynamics in loop quantum
gravity, and we show that which condition can satisfy generalized second law of
thermodynamics.Comment: 8 pages, 3 figure
QCD ghost f(T)-gravity model
Within the framework of modified teleparallel gravity, we reconstruct a f(T)
model corresponding to the QCD ghost dark energy scenario. For a spatially flat
FRW universe containing only the pressureless matter, we obtain the time
evolution of the torsion scalar T (or the Hubble parameter). Then, we calculate
the effective torsion equation of state parameter of the QCD ghost f(T)-gravity
model as well as the deceleration parameter of the universe. Furthermore, we
fit the model parameters by using the latest observational data including
SNeIa, CMB and BAO data. We also check the viability of our model using a
cosmographic analysis approach. Moreover, we investigate the validity of the
generalized second law (GSL) of gravitational thermodynamics for our model.
Finally, we point out the growth rate of matter density perturbation. We
conclude that in QCD ghost f(T)-gravity model, the universe begins a matter
dominated phase and approaches a de Sitter regime at late times, as expected.
Also this model is consistent with current data, passes the cosmographic test,
satisfies the GSL and fits the data of the growth factor well as the LCDM
model.Comment: 19 pages, 9 figures, 2 tables. arXiv admin note: substantial text
overlap with arXiv:1111.726
Interacting Ricci Dark Energy with Logarithmic Correction
Motivated by the holographic principle, it has been suggested that the dark
energy density may be inversely proportional to the area of the event
horizon of the universe. However, such a model would have a causality problem.
In this work, we consider the entropy-corrected version of the holographic dark
energy model in the non-flat FRW universe and we propose to replace the future
event horizon area with the inverse of the Ricci scalar curvature. We obtain
the equation of state (EoS) parameter , the deceleration
parameter and in the presence of interaction between Dark
Energy (DE) and Dark Matter (DM). Moreover, we reconstruct the potential and
the dynamics of the tachyon, K-essence, dilaton and quintessence scalar field
models according to the evolutionary behavior of the interacting
entropy-corrected holographic dark energy model.Comment: 24 pages, accepted for publication in 'Astrophysics and Space
Science, DOI:10.1007/s10509-012-1031-8
Cosmological evolution and statefinder diagnostic for new holographic dark energy model in non flat universe
In this paper, the holographic dark energy model with new infrared cut-off
proposed by Granda and Oliveros has been investigated in spatially non flat
universe. The dependency of the evolution of equation of state, deceleration
parameter and cosmological evolution of Hubble parameter on the parameters of
new HDE model are calculated. Also, the statefinder parameters and in
this model are derived and the evolutionary trajectories in plane are
plotted. We show that the evolutionary trajectories are dependent on the model
parameters of new HDE model. Eventually, in the light of SNe+BAO+OHD+CMB
observational data, we plot the evolutionary trajectories in and
planes for best fit values of the parameters of new HDE model.Comment: 11 pages, 5 figures, Accepted by Astrophys. Space Sc
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