11,209 research outputs found
Exact Analysis of Scaling and Dominant Attractors Beyond the Exponential Potential
By considering the potential parameter as a function of another
potential parameter [47], We successfully extend the analysis of
two-dimensional autonomous dynamical system of quintessence scalar field model
to the analysis of three-dimension, which makes us be able to research the
critical points of a large number of potentials beyond the exponential
potential exactly. We find that there are ten critical points in all, three
points } are general points which are possessed by all
quintessence models regardless of the form of potentials and the rest points
are closely connected to the concrete potentials. It is quite surprising that,
apart from the exponential potential, there are a large number of potentials
which can give the scaling solution when the function
equals zero for one or some values of
and if the parameter also satisfies the condition
Eq.(16) or Eq.(17) at the same time. We give the differential equations to
derive these potentials from . We also find that, if some
conditions are satisfied, the de-Sitter-like dominant point and the
scaling solution point (or ) can be stable simultaneously but
and can not be stable simultaneity. Although we survey scaling
solutions beyond the exponential potential for ordinary quintessence models in
standard general relativity, this method can be applied to other extensively
scaling solution models studied in literature[46] including coupled
quintessence, (coupled-)phantom scalar field, k-essence and even beyond the
general relativity case . we also discuss the disadvantage
of our approach.Comment: 16 pages,no figure, this new revision has taken the suggestions from
CQG referees and has been accepted for publication in Classical and Quantum
Gravit
The Hybrid Dynamic Prototype Construction and Parameter Optimization with Genetic Algorithm for Support Vector Machine
The optimized hybrid artificial intelligence model is a potential tool to deal with construction engineering and management problems. Support vector machine (SVM) has achieved excellent performance in a wide variety of applications. Nevertheless, how to effectively reduce the training complexity for SVM is still a serious challenge. In this paper, a novel order-independent approach for instance selection, called the dynamic condensed nearest neighbor (DCNN) rule, is proposed to adaptively construct prototypes in the training dataset and to reduce the redundant or noisy instances in a classification process for the SVM. Furthermore, a hybrid model based on the genetic algorithm (GA) is proposed to simultaneously optimize the prototype construction and the SVM kernel parameters setting to enhance the classification accuracy. Several UCI benchmark datasets are considered to compare the proposed hybrid GA-DCNN-SVM approach with the previously published GA-based method. The experimental results illustrate that the proposed hybrid model outperforms the existing method and effectively improves the classification performance for the SVM
Coupled Quintessence and Phantom Based On a Dilaton
Based on dilatonic dark energy model, we consider two cases: dilaton field
with positive kinetic energy(coupled quintessence) and with negative kinetic
energy(phantom). In the two cases, we investigate the existence of attractor
solutions which correspond to an equation of state parameter and a
cosmic density parameter . We find that the coupled term
between matter and dilaton can't affect the existence of attractor solutions.
In the Mexican hat potential, the attractor behaviors, the evolution of state
parameter and cosmic density parameter , are shown
mathematically. Finally, we show the effect of coupling term on the evolution
of and with
respect to numerically.Comment: 9 pages, 11 figures, some references and Journal-ref adde
The flavor-changing bottom-strange quark production in the littlest Higgs model with T parity at the ILC
In the littlest Higgs model with T-parity (LHT) the mirror quarks induce the
special flavor structures and some new flavor-changing (FC) couplings which
could greatly enhance the production rates of the FC processes. We in this
paper study some bottom and anti-strange production processes in the LHT model
at the International Linear Collider (ILC), i.e.,
and . The results show that the production
rates of these processes are sizeable for the favorable values of the
parameters. Therefore, it is quite possible to test the LHT model or make some
constrains on the relevant parameters of the LHT through the detection of these
processes at the ILC.Comment: 12 pages, 8 figure
Modularization of multi-qubit controlled phase gate and its NMR implementation
Quantum circuit network is a set of circuits that implements a certain
computation task. Being at the center of the quantum circuit network, the
multi-qubit controlled phase shift is one of the most important quantum gates.
In this paper, we apply the method of modular structuring in classical computer
architecture to quantum computer and give a recursive realization of the
multi-qubit phase gate. This realization of the controlled phase shift gate is
convenient in realizing certain quantum algorithms. We have experimentally
implemented this modularized multi-qubit controlled phase gate in a three qubit
nuclear magnetic resonance quantum system. The network is demonstrated
experimentally using line selective pulses in nuclear magnetic resonance
technique. The procedure has the advantage of being simple and easy to
implement.Comment: to appear in Journal of Optics B: Quantum and Semiclassical Optic
Quantifying Inactive Lithium in Lithium Metal Batteries
Inactive lithium (Li) formation is the immediate cause of capacity loss and
catastrophic failure of Li metal batteries. However, the chemical component and
the atomic level structure of inactive Li have rarely been studied due to the
lack of effective diagnosis tools to accurately differentiate and quantify Li+
in solid electrolyte interphase (SEI) components and the electrically isolated
unreacted metallic Li0, which together comprise the inactive Li. Here, by
introducing a new analytical method, Titration Gas Chromatography (TGC), we can
accurately quantify the contribution from metallic Li0 to the total amount of
inactive Li. We uncover that the Li0, rather than the electrochemically formed
SEI, dominates the inactive Li and capacity loss. Using cryogenic electron
microscopies to further study the microstructure and nanostructure of inactive
Li, we find that the Li0 is surrounded by insulating SEI, losing the electronic
conductive pathway to the bulk electrode. Coupling the measurements of the Li0
global content to observations of its local atomic structure, we reveal the
formation mechanism of inactive Li in different types of electrolytes, and
identify the true underlying cause of low Coulombic efficiency in Li metal
deposition and stripping. We ultimately propose strategies to enable the highly
efficient Li deposition and stripping to enable Li metal anode for next
generation high energy batteries
Weak Spin Fluctuation with Finite Wave Vector and Superconducting Gap Symmetry in KxFe2-ySe2: 77Se Nuclear Magnetic Resonance
We report Se-nuclear magnetic resonance (NMR) results down to
sufficiently low temperatures under magnetic fields parallel to both the
-plane and the c-axis in a paramagnetic/superconducting (PM/SC) phase of
KFeSe. The observation of anisotropy in the orbital part of the
Knight shift results in the anisotropy of its spin part increasing on
approaching the transition temperature. The anisotropy of the Korringa relation
suggests the presence of the weak spin fluctuations with a finite wave vector
, which induce the magnetic fluctuations along the ab-plane at the Se
site. Such fluctuations do not correspond to the stripe correlation
of the Fe moment observed in many Fe-based superconductors, and are not
contradictory to weak correlations. The nuclear spin-lattice
relaxation rate shows a field-independent behavior
at low temperatures for , which is attributed to the nonzero
density of states at the Fermi level and can be explained by the sign-changing
order parameter even for nodeless gaps. The temperature dependence of
is reproduced well by nodeless models with two isotropic gaps or a single
anisotropic gap. The obtained gap magnitude in the isotropic two-gap model is
comparable to those obtained in the angle-resolved photoemission spectroscopy
experiments.Comment: 6 pages, 6 figures, Accepted for the publication in J. Phys. Soc. Jp
PmoB subunit of particulate methane monooxygenase (pMMO) in Methylococcus capsulatus (Bath): The Cu^I sponge and its function
In this study, we describe efforts to clarify the role of the copper cofactors associated with subunit B (PmoB) of the particulate methane monooxygenase (pMMO) from Methylococcus capsulatus (Bath) (M. capsulatus). This subunit exhibits strong affinity toward Cu^I ions. To elucidate the high copper affinity of the subunit, the full-length PmoB, and the N-terminal truncated mutants PmoB_(33–414) and PmoB_(55–414), each fused to the maltose-binding protein (MBP), are cloned and over-expressed into Escherichia coli (E. coli) K12 TB1 cells. The Y374F, Y374S and M300L mutants of these protein constructs are also studied. When this E. coli is grown with the pmoB gene in 1.0 mM Cu^(II), it behaves like M. capsulatus (Bath) cultured under high copper stresswith abundant membrane accumulation and high CuI content. The recombinantPmoB proteins are verified by Western blotting of antibodies directed against the MBP sub-domain in each of the copper-enriched PmoB proteins. Cu K-edge X-rayabsorption near edge spectroscopy (XANES) of the copper ions confirms that all the PmoB recombinants are Cu^I proteins. All the PmoB proteins show evidence of a “dicopper site” according to analysis of the Cu extended X-ray absorption edge fine structure (EXAFS) of the membranes. No specific activities toward methane and propene oxidation are observed with the recombinant membrane-bound PmoB proteins. However, significant production of hydrogen peroxide is observed in the case of the PmoB_(33–414) mutant. Reaction of the dicopper site with dioxygenproduces hydrogen peroxide and leads to oxidation of the CuI ions residing in the C-terminal sub-domain of the PmoB subunit
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