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641.
The present paper deals to the quintom model of dark energy. We introduce a first-order formalism, which shows how to relate
the potential that specifies the scalar field model to Hubble’s parameter. Reviewing briefly the quintom scenario of dark
energy, we present a general procedure to solve the equations of motion for quintom model driven by a couple scalar fields
with first-order differential equations. 相似文献
642.
We demonstrate a compact and slitless spectrometer with high resolution formed by cascading a Fabry-Perot etalon (FPE) and a cylindrical beam volume hologram (CBVH). The most significant advantage of this combined spectrometer is that we can independently encode spectral information of a diffuse beam in a 2D plane. Also, we show that in this slitless configuration we can simultaneously benefit from the advantages of both elements: the high resolution of the FPE and the large spectral range of the CBVH. Here, we report on the experimental demonstration of a spectrometer with better than 0.2 nm resolution. 相似文献
643.
Rabbani Yahya Hajinajaf Nima Tavakoli Omid 《Journal of Thermal Analysis and Calorimetry》2019,135(3):1687-1697
Journal of Thermal Analysis and Calorimetry - In this study, silicone oil as the base fluid and carbonyl iron powder with the average particle size of 2.7 µm as the disperse phase was... 相似文献
644.
645.
In disordered spin systems with antiferromagnetic Heisenberg exchange, transitions into and out of a magnetic-field-induced ordered phase pass through unique regimes. Using quantum Monte Carlo simulations to study the zero-temperature behavior, these intermediate regions are determined to be Bose-glass phases. The localization of field-induced triplons causes a finite compressibility and, hence, glassiness in the disordered phase. 相似文献
646.
An experimental study of variation of sensitivity with recording and sensitizing intensities in two-center recording is presented. The experimental results are in good agreement with the theoretical predictions. It is shown experimentally, for what is to our knowledge the first time, that the sensitivity is a function of the ratio of recording to sensitizing intensities and not the absolute intensities. Also, the ratio of recording to sensitizing intensities should be small to obtain high sensitivity values. We also report the highest sensitivity (S=0.15 cm/J) that has been achieved to date for a LiNbO3:Fe:Mn crystal. 相似文献
647.
[structure: see text] The widely used internal standard for NMR studies in aqueous solution DSS (sodium 4,4-dimethyl-4-silapentane-1-sulfonate) can interact with cationic peptides, diminishing its value for such studies. This paper introduces DSA (4,4-dimethyl-4-silapentane-1-ammonium trifluoroacetate) as a new internal standard that does not suffer from this problem. 相似文献
648.
J. Sadeghi M.R. Setare B. Pourhassan 《The European Physical Journal C - Particles and Fields》2008,53(1):95-97
In this paper we consider the two dimensional black hole and use Wald’s formula to find its entropy. Also we consider higher
derivative terms. We discuss the case of a massless black hole and find its free energy. 相似文献
649.
R. Ansari F. Sadeghi B. Motevalli 《Communications in Nonlinear Science & Numerical Simulation》2013,18(3):769-784
Amongst possible new nanomechanical devices created based on carbon nanostructures, high-frequency nanoscale oscillators, or the so-called gigahertz oscillators have attracted much attention. In this paper, the oscillatory behavior of spherical fullerenes inside carbon nanotubes is thoroughly investigated. To this end, the continuum approximation together with Lennard-Jones potential is used to evaluate the van der Waals potential energy and interaction force. The equation of motion is directly solved based on the actual force distribution between the two nanostructures, without any simplifying assumption. A semi-analytical expression is obtained for the oscillation frequency into which the effect of initial conditions is incorporated. Thereafter, this newly derived expression is utilized in order to present a comprehensive study on the effects of different system variables such as geometrical parameters and initial conditions on the oscillation frequency. Based upon these studies, some new features of such oscillations have been revealed. 相似文献
650.
In this paper we introduce the notion of Σ-colouring of a graph G: For given subsets Σ(v) of neighbours of v, for every v∈V (G), this is a proper colouring of the vertices of G such that, in addition, vertices that appear together in some Σ(v) receive different colours. This concept generalises the notion of colouring the square of graphs and of cyclic colouring of graphs embedded in a surface. We prove a general result for graphs embeddable in a fixed surface, which implies asymptotic versions of Wegner’s and Borodin’s Conjecture on the planar version of these two colourings. Using a recent approach of Havet et al., we reduce the problem to edge-colouring of multigraphs, and then use Kahn’s result that the list chromatic index is close to the fractional chromatic index. Our results are based on a strong structural lemma for graphs embeddable in a fixed surface, which also implies that the size of a clique in the square of a graph of maximum degree Δ embeddable in some fixed surface is at most $ \frac{3} {2}\Delta $ plus a constant. 相似文献