2,334 research outputs found
Influence of κ-carbide interface structure on the formability of lightweight steels
κ-carbide (κ) in high aluminium (Al) steels is grown from austenite (γ) via γ → γ + κ or γ → α + κ (α represents ferrite), and is a lamellar structure. This work demonstrates that the formability of high Al lightweight steels is affected by the lattice misfit and interface shape between κ and matrix. The cold workability can be improved by either to change the steel chemical constitution or to implement an electro-thermo-mechanical process. For ferrite-matrix-based high Al steel, electric-current promotes the spheroidization and refinement of κ structure and reduces volume fraction of κ phase. This retards the crack nucleation and propagation, and hence improves the materials formability. The observation is caused by a direct effect of electric-current rather than side effects
Stability of martensite with pulsed electric current in dual-phase steels
Softening frequently occurs in dual-phase steels under isothermal tempering of martensite. Recently, non-isothermal tempering is implemented to decrease the softening process in dual-phase steels. Here, we have discovered using high power electropulsing treatment can significantly enhance the strengthening effects via the formation of ultrafine-grained ferrite with nano-cementite particles in tempered martensitic-ferritic steels. To the best our knowledge, electropulsing treatment is a proper candidate to retard even to recovery the softening problems in the tempering of martensite in comparison with other isothermal and non-isothermal tempering methods
Cosmological constraints on the generalized holographic dark energy
We use the Markov ChainMonte Carlo method to investigate global constraints
on the generalized holographic (GH) dark energy with flat and non-flat universe
from the current observed data: the Union2 dataset of type supernovae Ia
(SNIa), high-redshift Gamma-Ray Bursts (GRBs), the observational Hubble data
(OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation
(BAO), and the cosmic microwave background (CMB) data. The most stringent
constraints on the GH model parameter are obtained. In addition, it is found
that the equation of state for this generalized holographic dark energy can
cross over the phantom boundary wde =-1.Comment: 14 pages, 5 figures. arXiv admin note: significant text overlap with
arXiv:1105.186
Group testing with Random Pools: Phase Transitions and Optimal Strategy
The problem of Group Testing is to identify defective items out of a set of
objects by means of pool queries of the form "Does the pool contain at least a
defective?". The aim is of course to perform detection with the fewest possible
queries, a problem which has relevant practical applications in different
fields including molecular biology and computer science. Here we study GT in
the probabilistic setting focusing on the regime of small defective probability
and large number of objects, and . We construct and
analyze one-stage algorithms for which we establish the occurrence of a
non-detection/detection phase transition resulting in a sharp threshold, , for the number of tests. By optimizing the pool design we construct
algorithms whose detection threshold follows the optimal scaling . Then we consider two-stages algorithms and analyze their
performance for different choices of the first stage pools. In particular, via
a proper random choice of the pools, we construct algorithms which attain the
optimal value (previously determined in Ref. [16]) for the mean number of tests
required for complete detection. We finally discuss the optimal pool design in
the case of finite
Surface structure and solidification morphology of aluminum nanoclusters
Classical molecular dynamics simulation with embedded atom method potential
had been performed to investigate the surface structure and solidification
morphology of aluminum nanoclusters Aln (n = 256, 604, 1220 and 2048). It is
found that Al cluster surfaces are comprised of (111) and (001) crystal planes.
(110) crystal plane is not found on Al cluster surfaces in our simulation. On
the surfaces of smaller Al clusters (n = 256 and 604), (111) crystal planes are
dominant. On larger Al clusters (n = 1220 and 2048), (111) planes are still
dominant but (001) planes can not be neglected. Atomic density on cluster
(111)/(001) surface is smaller/larger than the corresponding value on bulk
surface. Computational analysis on total surface area and surface energies
indicates that the total surface energy of an ideal Al nanocluster has the
minimum value when (001) planes occupy 25% of the total surface area. We
predict that a melted Al cluster will be a truncated octahedron after
equilibrium solidification.Comment: 22 pages, 6 figures, 34 reference
Diffractive Higgs Production at the LHC
We use diffractive parton distributions obtained from fits to the diffractive
structure function measured at HERA to predict cross sections for single
diffractive Higgs production at the LHC. The dominant background processes are
also considered. Although some 5% - 15% of Higgs events are predicted to be
diffractive in this model, the ratio of signal to background is not
significantly improved.Comment: 14 pages, LaTeX, incl. 6 postscript figures, uses epsf.st
Modelling solute transport in soil columns using advective-dispersive equations with fractional spatial derivatives
Solute transport in soils is commonly simulated with the advective–dispersive equation, or ADE. It has been reported that this model cannot take into account several important features of solute movement through soil. Recently, a new model has been suggested that results in a solute transport equation with fractional spatial derivatives, or FADE. We have assembled a database on published solute transport experiments in soil columns to test the new model. The FADE appears to be a useful generalization of the ADE. The order of the fractional differentiation reflects differences in physical conditions of the solute transport in soi
First Report of Alternaria Black Spot Disease Caused by Alternaria alternata on the Invasive Weed Solanum rostratum in Xinjiang, China
Solanum rostratum is a noxious weed, native to Mexico and the USA, which has invaded Liaoning, Jilin, Hebei, Inner
Mongolia, Shanxi, Xinjiang and Beijing, China (Eminniya et al., 2013). In August 2015, foliar symptoms of yellowish to black
spots were observed on plants of S. rostratum nearby an agricultural plantation in Changji, Xinjiang. The following year, about
17% of the 206 plants surveyed on about 0.2 ha of deserted farmland were infected from July-September (at 19-35°C under
29-97% RH)
Does accelerating universe indicates Brans-Dicke theory
The evolution of universe in Brans-Dicke (BD) theory is discussed in this
paper.
Considering a parameterized scenario for BD scalar field
which plays the role of gravitational "constant" ,
we apply the Markov Chain Monte Carlo method to investigate a global
constraints on BD theory with a self-interacting potential according to the
current observational data: Union2 dataset of type supernovae Ia (SNIa),
high-redshift Gamma-Ray Bursts (GRBs) data, observational Hubble data (OHD),
the cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and
the cosmic microwave background (CMB) data. It is shown that an expanded
universe from deceleration to acceleration is given in this theory, and the
constraint results of dimensionless matter density and parameter
are, and
which is consistent with the
result of current experiment exploration, . In
addition, we use the geometrical diagnostic method, jerk parameter , to
distinguish the BD theory and cosmological constant model in Einstein's theory
of general relativity.Comment: 16 pages, 3 figure
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