1,158 research outputs found
Statefinder diagnostic for modified Chaplygin gas cosmology in f(R,T) gravity with particle creation
In this paper, we have studied flat
Friedmann--Lema\^{\i}tre--Robertson--Walker (FLRW) model with modified
Chaplygin gas (MCG) having equation of state p_{m}=A\rho -% \frac{B}{\rho
^{\gamma }}, where , and is any
positive constant in }{\footnotesize \ gravity with
particle creation. We have considered a simple parametrization of the Hubble
parameter in order to solve the field equations and discussed the time
evolution of different cosmological parameters for some obtained models showing
unique behavior of scale factor. We have also discussed the statefinder
diagnostic pair that characterizes the evolution of obtained models
and explore their stability. The physical consequences of the models and their
kinematic behaviors have also been scrutinized here in some detail.Comment: 21 pages, 23 figures. arXiv admin note: text overlap with
arXiv:1603.02573 by other author
Analysis with observational constraints in -cosmology in gravity
An exact cosmological solution of Einstein field equations (EFEs) is derived
for a dynamical vacuum energy in gravity for
Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time. A parametrization of the
Hubble parameter is used to find a deterministic solution of EFE. The
cosmological dynamics of our model is discussed in detail. We have analyzed the
time evolution of physical parameters and obtained their bounds analytically.
Moreover, the behavior of these parameters are shown graphically in terms of
redshift . Our model is consistent with the formation of structure in the
Universe. The role of the coupling constant is discussed in
the evolution of the equation of state parameter. The statefinder and Om
diagnostic analysis is used to distinguish our model with other dark energy
models. The maximum likelihood analysis has been reviewed to obtain the
constraints on the Hubble parameter and the model parameter by taking
into account the observational Hubble data set , the Union 2.1
compilation data set , the Baryon Acoustic Oscillation data , and
the joint data set + and + + . It is
demonstrated that the model is in good agreement with various observations.Comment: 21 PAGES, 20 FIGURE
Stabilization of high Tc phase in bismuth cuprate superconductor by lead doping
It has been widely ascertained that doping of lead in Bi-Sr-Ca-Cu-O systems promotes the growth of high T sub c (110 K) phase, improves critical current density, and lowers processing temperature. A systematic study was undertaken to determine optimum lead content and processing conditions to achieve these properties. A large number of samples with cationic compositions of Bi(2-x)Pb(x)Sr2Ca2Cu3 (x = 0.2 to 2.0) were prepared by conventional solid state reaction technique. Samples of all compositions were annealed together at a temperature and characterized through resistance temperature (R-T) measurements and x ray diffraction to determine the zero resistance temperature, T sub c(0) and to identify presence of phases, respectively. The annealing temperature was varied between 790 and 880 C to optimize processing parameters. Results are given. In brief, an optimum process is reported along with composition of leaded bismuth cuprate superconductor which yields nearly a high T sub c single phase with highly stable superconducting properties
Stabilization of high T(sub c) phase in bismuth cuprate superconductor by lead doping
It has widely been ascertained that doping of lead in Bi:Sr:Ca:Cu:O systems promotes the growth of high T(sub c) (110 K) phase, improves critical current density, and lowers processing temperature. A systematic investigation is undertaken to determine optimum lead content and processing conditions to achieve these. A large number of samples with cationic compositions of Bi(2-x)Pb(x)Sr2Ca2Cu3 (x = 0.2 to 2.0) were prepared by conventional solid state reaction technique. Samples of all compositions were annealed together at a temperature and characterized through resistance-temperature (R-T) measurements and x ray diffraction (XRD) to determine the zero resistance temperature, T(sub c)(0) and to identify presence of phases, respectively. The annealing temperature was varied between 790 C to optimize processing parameters. Results are given. In brief, an optimum process is reported along with composition of leaded bismuth cuprate superconductor which yields nearly a high T(sub c) single phase with highly stable superconducting properties
Probabilistic structural analysis methods for space transportation propulsion systems
Information on probabilistic structural analysis methods for space propulsion systems is given in viewgraph form. Information is given on deterministic certification methods, probability of failure, component response analysis, stress responses for 2nd stage turbine blades, Space Shuttle Main Engine (SSME) structural durability, and program plans.
Off-grid solar photovoltaic systems for rural electrification and emissions mitigation in India
Over one billion people lack access to electricity and many of them in rural areas far from existing infrastructure. Off-grid systems can provide an alternative to extending the grid network and using renewable energy, for example solar photovoltaics (PV) and battery storage, can mitigate greenhouse gas emissions from electricity that would otherwise come from fossil fuel sources. This paper presents a model capable of comparing several mature and emerging PV technologies for rural electrification with diesel generation and grid extension for locations in India in terms of both the levelised cost and lifecycle emissions intensity of electricity. The levelised cost of used electricity, ranging from $0.46–1.20/kWh, and greenhouse gas emissions are highly dependent on the PV technology chosen, with battery storage contributing significantly to both metrics. The conditions under which PV and storage becomes more favourable than grid extension are calculated and hybrid systems of PV, storage and diesel generation are evaluated. Analysis of expected price evolutions suggest that the most cost-effective hybrid systems will be dominated by PV generation around 2018
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