102,197 research outputs found

### A New Viewpoint to the Discrete Approximation: Discrete Yang-Fourier Transforms of Discrete-time Fractal Signal

It is suggest that a new fractal model for the Yang-Fourier transforms of
discrete approximation based on local fractional calculus and the Discrete
Yang-Fourier transforms are investigated in detail.Comment: Key words: local fractional calculus, fractal, Yang Fourier
transforms, discrete approximation, discrete Yang-Fourier transforms
corrected sectio

### Applications of local fractional calculus to engineering in fractal time-space: Local fractional differential equations with local fractional derivative

This paper presents a better approach to model an engineering problem in
fractal-time space based on local fractional calculus. Some examples are given
to elucidate to establish governing equations with local fractional derivative.Comment: 10 page

### The role of the diffusive protons in the gamma-ray emission of supernova remnant RX J1713.7$-$3946 --- a two-zone model

RX~J1713.7$-$3946 is a prototype in the $\gamma$-ray-bright supernova
remnants (SNRs) and is in continuing debates on its hadronic versus leptonic
origin of the $\gamma$-ray emission. We explore the role played by the
diffusive relativistic protons that escape from the SNR shock wave in the
$\gamma$-ray emission, apart from the high-energy particles' emission from the
inside of the SNR. In the scenario that the SNR shock propagates in a clumpy
molecular cavity, we consider that the$\gamma$-ray emission from the inside of
the SNR may arise either from the inverse Compton scattering or from the
interaction between the trapped energetic protons and the shocked clumps. The
dominant origin between them depends on the electron-to-proton number ratio.
The diffusive protons that escaped from the shock wave during the expansion
history can provide an outer hadronic $\gamma$-ray component by bombarding the
surrounding dense matter. The broadband spectrum can be well explained by this
two-zone model, in which the $\gamma$-ray emission from the inside governs the
TeV band, while the outer emission component substantially contributes to the
GeV $\gamma$-rays. The two-zone model can also explain the TeV $\gamma$-ray
radial brightness profile that significantly stretches beyond the nonthermal
X-ray-emitting region. In the calculation, we present a simplified algorithm
for Li & Chen's (2010) "accumulative diffusion" model for escaping protons and
apply the Markov Chain Monte Carlo method to constrain the physical parameters.Comment: 18 pages (including 3 figures and 2 tables), accepted for publication
in Ap

### Nonreciprocal Directional Dichroism Induced by the Quantum Metric Dipole

We identify the quantum metric dipole as the geometric origin of the
nonreciprocal directional dichroism which describes the change in the
refractive index upon reversing the light propagation direction. Specifically,
we find that the static limit of the nonreciprocal directional dichroism
corresponds to a quadrupolar transport current from the quantum metric dipole,
in response to a quadrupolar electric field. Moreover, at finite frequency, we
demonstrate that the steepest slope of the averaged quantum metric dipole
determines a peak. Finally, we illustrate both features in a low-energy model

### m-Order Time Optimal Control Synthesis Function of Discrete System

In this paper, first of all, we introduce the basic concepts of generating
function in combinatorics and some combinatorial identities. In order to
facilitate the understanding of m-order time optimal control synthesis function
of discrete system (referred as m-order synthesis function), secondly, we
introduce the derivation process and control ideas of 2nd-order synthesis
function, and then deduce in detail the m-order synthesis function by means of
generating function. By use of the m-order tracking-form synthesis function
with filter factor, the methods of signal extraction and its predictive
compensation are presented in this paper, and their immunity and effectiveness
are verified by numerical simulation.Comment: 22 pages,13 figures. arXiv admin note: substantial text overlap with
arXiv:1806.0310

### Effects of Pressure on the Electronic Structures of LaOFeP

We studied the electronic structures of LaOFeP under applied pressure using
first-principles calculations. The electronic density of states at the Fermi
level decreases continuously with increasing pressure. The electron branches of
Fermi surfaces are rather robust to pressure, while the hole branches change
significantly. Two hole surfaces shrink into small ellipsoid-like surfaces and
disappear finally, at which the applied pressure is ~ 74.7 GPa. The pressure
response can be understood by the band structures around the Fermi level.
Comparative studies reveal that the disappearance of hole surfaces is mainly
due to the compression of the FeP layer along the c-axis of unit cell.Comment: 26 pages, 9 figure

### Singular perturbations with multiple poles of the simple polynomials

In this article, we study the dynamics of the following family of rational
maps with one parameter: \begin{equation*} f_\lambda(z)=
z^n+\frac{\lambda^2}{z^n-\lambda}, \end{equation*} where $n\geq 3$ and
$\lambda\in\mathbb{C}^*$. This family of rational maps can be viewed as a
singular perturbations of the simple polynomial $P_n(z)=z^n$. We give a
characterization of the topological properties of the Julia sets of the family
$f_\lambda$ according to the dynamical behaviors of the orbits of the free
critical points.Comment: 15 pages, 5 figures, to appear in Qualitative Theory of Dynamical
System

### Electromagnetically Induced Entanglement

We present a novel quantum phenomenon named electromagnetically induced
entanglement in the conventional Lambda-type three-level atomic system driven
by a strong pump field and a relatively weak probe field. Nearly perfect
entanglement between the pump and probe fields can be achieved with a low
coherence decay rate between the two lower levels, high pump-field intensity,
and large optical depth of the atomic ensemble. The physical origin is quantum
coherence between the lower doublet produced by the pump and probe fields,
similar to the well-known electromagnetically induced transparency. This method
would greatly facilitate the generation of nondegenerate narrow-band
continuous-variable entanglement between bright light beams by using only
coherent laser fields, and may find potential and broad applications in
realistic quantum information processing.Comment: 15pages, 4figure

### Performance Analysis of Millimeter-Wave Relaying: Impacts of Beamwidth and Self-Interference

We study the maximum achievable rate of a two-hop amplified-and-forward (AF)
relaying millimeter-wave (mm-wave) system, where two AF relaying schemes, i.e.,
half-duplex (HD) and full-duplex (FD) are discussed. By considering the two-ray
mm-wave channel and the Gaussian-type directional antenna, jointly, the impacts
of the beamwidth and the self-interference coefficient on maximum achievable
rates are investigated. Results show that, under a sum-power constraint, the
rate of FD-AF mm-wave relaying outperforms its HD counterpart only when
antennas with narrower beamwidth and smaller self-interference coefficient are
applied. However, when the sum-power budget is sufficiently high or the
beamwidth of directional antenna is sufficiently small, direct transmission
becomes the best strategy, rather than the AF relaying schemes. For both
relaying schemes, we show that the rates of both AF relaying schemes scale as $\mathcal{O}\left(\min\left\lbrace\theta_m^{-1},\theta_m^{-2}\right\rbrace\right)$ with respect to beamwidth $\theta_ m$, and the rate of FD-AF relaying
scales as $\mathcal{O}\left(\mu^{-\frac{1}{2}}\right)$ with respect to
self-interference coefficient $\mu$. Besides, we show that, ground
reflections may significantly affect the performance of mm-wave communications,
constructively or destructively. Thus, the impact of ground reflections
deserves careful considerations for analyzing or designing future mm-wave
wireless networks.Comment: Accepted by IEEE Transactions on Communication

### Note on the super inflation in loop quantum cosmology

Phenomenological effect of the super-inflation in loop quantum cosmology
(LQC) is discussed. We investigate the case that the Universe is filled with
the interacting field between massive scalar field and radiation. Considering
the damping coefficient $\Gamma$ as a constant, the changes of the scale factor
during super-inflation with four different initial conditions are discussed,
and we find that the changes of the scale factor depends on the initial values
of energy density of the scalar field and radiation at the bounce point. But no
matter which initial condition is chosen, the radiation always dominated at the
late time. Moreover, we investigate whether the super-inflation can provide
enough e-folding number. For the super-inflation starts from the quantum bounce
point, the initial value of Hubble parameter $H(t_i)\sim0$, then it is possible
to solve the flatness problem and horizon problem. As an example, following the
method of \cite{Amoros-prd} to calculate particle horizon on the condition that
the radiation dominated at bounce point, and we find that the Universe has had
enough time to be homogeneous and isotopic.Comment: 9 pages, 4 figures. Physics Letters B, online publication complete:
13-NOV-201

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