3,997 research outputs found
Analyzing stability of a delay differential equation involving two delays
Analysis of the systems involving delay is a popular topic among applied
scientists. In the present work, we analyze the generalized equation
involving two delays
viz. and . We use the the stability conditions to
propose the critical values of delays. Using examples, we show that the chaotic
oscillations are observed in the unstable region only. We also propose a
numerical scheme to solve such equations.Comment: 10 pages, 7 figure
An alternating direction implicit spectral method for solving two dimensional multi-term time fractional mixed diffusion and diffusion-wave equations
In this paper, we consider the initial boundary value problem of the two
dimensional multi-term time fractional mixed diffusion and diffusion-wave
equations. An alternating direction implicit (ADI) spectral method is developed
based on Legendre spectral approximation in space and finite difference
discretization in time. Numerical stability and convergence of the schemes are
proved, the optimal error is , where are the
polynomial degree, time step size and the regularity of the exact solution,
respectively. We also consider the non-smooth solution case by adding some
correction terms. Numerical experiments are presented to confirm our
theoretical analysis. These techniques can be used to model diffusion and
transport of viscoelastic non-Newtonian fluids
A Low-Noise High-Density Alkali Metal Scalar Magnetometer
We present an experimental and theoretical study of a scalar atomic
magnetometer using an oscillating field-driven Zeeman resonance in a
high-density optically-pumped potassium vapor. We describe an experimental
implementation of an atomic gradiometer with a noise level below 10
fT/Hz^{1/2}, fractional field sensitivity below 10^{-9}/Hz^{1/2}, and an active
measurement volume of about 1.5 cm^3. We show that the fundamental field
sensitivity of a scalar magnetometer is determined by the rate of alkali-metal
spin-exchange collisions even though the resonance linewidth can be made much
smaller than the spin-exchange rate by pumping most atoms into a stretched spin
state.Comment: 10 pages, 7 figures. Version 2 is longer, with more complete
description of theoretical analysis and comparison between analytical and
experimental result
A survey on fuzzy fractional differential and optimal control nonlocal evolution equations
We survey some representative results on fuzzy fractional differential
equations, controllability, approximate controllability, optimal control, and
optimal feedback control for several different kinds of fractional evolution
equations. Optimality and relaxation of multiple control problems, described by
nonlinear fractional differential equations with nonlocal control conditions in
Banach spaces, are considered.Comment: This is a preprint of a paper whose final and definite form is with
'Journal of Computational and Applied Mathematics', ISSN: 0377-0427.
Submitted 17-July-2017; Revised 18-Sept-2017; Accepted for publication
20-Sept-2017. arXiv admin note: text overlap with arXiv:1504.0515
Radiating dipoles in photonic crystals
The radiation dynamics of a dipole antenna embedded in a Photonic Crystal are
modeled by an initially excited harmonic oscillator coupled to a non--Markovian
bath of harmonic oscillators representing the colored electromagnetic vacuum
within the crystal. Realistic coupling constants based on the natural modes of
the Photonic Crystal, i.e., Bloch waves and their associated dispersion
relation, are derived. For simple model systems, well-known results such as
decay times and emission spectra are reproduced. This approach enables direct
incorporation of realistic band structure computations into studies of
radiative emission from atoms and molecules within photonic crystals. We
therefore provide a predictive and interpretative tool for experiments in both
the microwave and optical regimes.Comment: Phys. Rev. E, accepte
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