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2006-07-14
|
Lagrangian description of the radiation damping
|
We present a Lagrangian formalism to the dissipative system of a charge
interacting with its own radiation field, which gives rise to the radiation
damping \cite{Heitler}, by the indirect representation doubling the phase-space
dimensions.
|
0607370v1
|
1994-05-17
|
Damping Rate of a Hard Photon in a Relativistic Plasma
|
The damping rate of a hard photon in a hot relativistic QED and QCD plasma is
calculated using the resummation technique by Braaten and Pisarski.
|
9405309v1
|
1998-04-08
|
Evidence for xi- and t-dependent damping of the Pomeron Flux in the proton
|
We show that a triple-Regge parametrization of inclusive single diffraction
agrees with the data in the following two domains: (a) xi > 0.03 at all t, (b)
|t| > 1 GeV^2 at all xi. Since the triple-Regge parametrization fails when
applied to the full xi-t range of the total single-diffractive cross section,
we conclude that damping occurs only at low-xi and low-|t|. We give a (``toy'')
parametrization of the damping factor, D(xi), valid at low-|t|, which describes
the diffractive differential cross-section (dsig/dt) data at the ISR and
roughly accounts for the observed s-dependence of diffractive total
cross-section up to Tevatron energies. However, an effective damping factor
calculated for the CDF fitted function for dsig/dxidt at sqrt(s} = 1800 GeV and
|t| = 0.05 GeV^2, suggests that, at fixed-xi, damping increases as s increases.
We conjecture that, in the regions where the triple-Regge formalism describes
the data and there is no evidence of damping, factorization is valid and the
Pomeron-flux-factor may be universal. With the assumption that the observed
damping is due to multi-Pomeron exchange, our results imply that the recent UA8
demonstration that the effective Pomeron trajectory flattens for |t| > 1 GeV$^2
is evidence for the onset of the perturbative 2-gluon pomeron. Our damping
results may also shed some light on the self-consistency of recent measurements
of hard-diffractive jet production cross sections in the UA8, CDF and ZEUS
experiments.
|
9804257v1
|
2001-11-27
|
On the uniphase steady solutions of the nonlinear damped wave equation
|
We study the steady uniphase and multiphase solutions of the discretized
nonlinear damped wave equation.Conditions for the stability abd instability of
the steady solutions are given;in the instability case the linear stable and
unstable associated manifolds are described.
|
0111281v1
|
2006-09-05
|
Damping estimates for oscillatory integral operators with finite type singularities
|
We derive damping estimates and asymptotics of $L^p$ operator norms for
oscillatory integral operators with finite type singularities. The methods are
based on incorporating finite type conditions into $L^2$ almost orthogonality
technique of Cotlar-Stein.
|
0609145v1
|
2002-02-19
|
On "the authentic damping mechanism" of the phonon damping model. II
|
This article continues a discussion raised in previous publications (LANL
preprint server, nucl-th/0202006 and nucl-th/0202020). I try to convince my
opponents that general arguments are not "my case" and may be applied to their
model.
|
0202058v1
|
1996-12-27
|
Coherent and trajectory-coherent states of a damped harmonic oscillator
|
In this paper we construct the coherent and trajectory-coherent states of a
damped harmonic oscillator. We investigate the properties of this states.
|
9612051v2
|
2003-05-21
|
Probability representation of kinetic equation for open quantum system
|
The tomographic probability distribution is used to decribe the kinetic
equations for open quantum systems. Damped oscillator is studied. Purity
parameter evolution for different damping regime is considered.
|
0305119v1
|
2007-08-09
|
The resonant damping of fast magnetohydrodynamic oscillations in a system of two coronal slabs
|
Observations of transversal coronal loop oscillations very often show the
excitation and damping of oscillations in groups of coronal loops rather than
in individual and isolated structures. We present results on the oscillatory
properties (periods, damping rates, and spatial distribution of perturbations)
for resonantly damped oscillations in a system of two inhomogeneous coronal
slabs and compare them to the properties found in single slab loop models. A
system of two identical coronal loops is modeled, in Cartesian geometry, as
being composed by two density enhancements. The linear magnetohydrodynamic
(MHD) wave equations for oblique propagation of waves are solved and the
damping of the different solutions, due to the transversal inhomogeneity of the
density profile, is computed. The physics of the obtained results is analyzed
by an examination of the perturbed physical variables. We find that, due to the
interaction between the loops, the normal modes of oscillation present in a
single slab split into symmetric and antisymmetric oscillations when a system
of two identical slabs is considered. The frequencies of these solutions may
differ from the single slab results when the distance between the loops is of
the order of a few slab widths. Oblique propagation of waves weakens this
interaction, since solutions become more confined to the edges of the slabs.
The damping is strong for surface-like oscillations, while sausage body-like
solutions are unaffected. For some solutions, and small slab separations, the
damping in a system of two loops differs substantially from the damping of a
single loop.
|
0708.1251v1
|
2009-12-08
|
Exact Invariant Solutions for Generalized Invicid Burgers' Equation with Damping
|
In this work we study the Lie group analysis of a generalized invicid
Burgers' equations with damping. Seven inequivalent classes of this generalized
equation were classified and many exact and transformed solutions were obtained
for each class.
|
0912.1631v1
|
2011-07-28
|
Creating quantum discord through local generalized amplitude damping
|
We show that two qubits initially in completely classical state can create
quantum discord through a local generalized amplitude damping channel, but high
temperature will impede the creating of quantum discord.
|
1107.5670v1
|
2011-09-06
|
Damping of Alfven waves in solar partially ionized plasmas: effect of neutral helium in multi-fluid approach
|
Chromospheric and prominence plasmas contain neutral atoms, which may change
the plasma dynamics through collision with ions. Most of the atoms are neutral
hydrogen, but a significant amount of neutral helium may also be present in the
plasma with a particular temperature. Damping of MHD waves due to ion collision
with neutral hydrogen is well studied, but the effects of neutral helium are
largely unknown. We aim to study the effect of neutral helium in the damping of
Alfven waves in solar partially ionized plasmas. We consider three-fluid
magnetohydrodynamic (MHD) approximation, where one component is
electron-proton-singly ionized helium and other two components are the neutral
hydrogen and neutral helium atoms. We derive the dispersion relation of linear
Alfven waves in isothermal and homogeneous plasma. Then we solve the dispersion
relation and derive the damping rates of Alfven waves for different plasma
parameters. The presence of neutral helium significantly enhances the damping
of Alfven waves compared to the damping due to neutral hydrogen at certain
values of plasma temperature (10000-40000 K) and ionization. Damping rates have
a peak near the ion-neutral collision frequency, but decrease for the higher
part of wave spectrum. Collision of ions with neutral helium atoms can be of
importance for the damping of Alfven waves in chromospheric spicules and in
prominence-corona transition regions.
|
1109.1154v1
|
2012-03-08
|
Damping rates of solar-like oscillations across the HR diagram. Theoretical calculations confronted to CoRoT and Kepler observations
|
Space-borne missions CoRoT and {\it Kepler} are providing a rich harvest of
high-quality constraints on solar-like pulsators. Among the seismic parameters,
mode damping rates remains poorly understood and thus barely used to infer
physical properties of stars. Nevertheless, thanks to CoRoT and {\it Kepler}
space-crafts it is now possible to measure damping rates for hundreds of
main-sequence and thousands of red-giant stars with an unprecedented precision.
By using a non-adiabatic pulsation code including a time-dependent convection
treatment, we compute damping rates for stellar models representative for
solar-like pulsators from the main-sequence to the red-giant phase. This allows
us to reproduce the observations of both CoRoT and {\it Kepler}, which
validates our modeling of mode damping rates and thus the underlying physical
mechanisms included in the modeling. Actually, by considering the perturbations
of turbulent pressure and entropy (including perturbation of the dissipation
rate of turbulent energy into heat) by the oscillation in our computation, we
succeed in reproducing the observed relation between damping rates and
effective temperature.
Moreover, we discuss the physical reasons for mode damping rates to scale
with effective temperature, as observationally exhibited. Finally, this opens
the way for the use of mode damping rates to probe turbulent convection in
solar-like stars.
|
1203.1737v2
|
2012-09-14
|
Semi-linear structural damped waves
|
We study the global existence of small data solutions for Cauchy problem for
the semi-linear structural damped wave equation with source term.
|
1209.3204v2
|
2012-10-25
|
Decay rates for the damped wave equation on the torus
|
We address the decay rates of the energy for the damped wave equation when
the damping coefficient $b$ does not satisfy the Geometric Control Condition
(GCC). First, we give a link with the controllability of the associated
Schr\"odinger equation. We prove in an abstract setting that the observability
of the Schr\"odinger group implies that the semigroup associated to the damped
wave equation decays at rate $1/\sqrt{t}$ (which is a stronger rate than the
general logarithmic one predicted by the Lebeau Theorem).
Second, we focus on the 2-dimensional torus. We prove that the best decay one
can expect is $1/t$, as soon as the damping region does not satisfy GCC.
Conversely, for smooth damping coefficients $b$, we show that the semigroup
decays at rate $1/t^{1-\eps}$, for all $\eps >0$. The proof relies on a second
microlocalization around trapped directions, and resolvent estimates.
In the case where the damping coefficient is a characteristic function of a
strip (hence discontinuous), St\'{e}phane Nonnenmacher computes in an appendix
part of the spectrum of the associated damped wave operator, proving that the
semigroup cannot decay faster than $1/t^{2/3}$. In particular, our study shows
that the decay rate highly depends on the way $b$ vanishes.
|
1210.6879v1
|
2014-02-25
|
Asymptotic Profiles for wave equations with strong damping
|
We consider the Cauchy problem in ${\bf R}^{n}$ for strongly damped wave
equations. We derive asymptotic profiles of these solutions with weighted
$L^{1,1}({\bf R}^{n})$ data by using a method introduced in [10].
|
1402.6073v1
|
2014-04-17
|
Exponential stability of the wave equation with memory and time delay
|
We study the asymptotic behaviour of the wave equation with viscoelastic
damping in presence of a time-delayed damping. We prove exponential stability
if the amplitude of the time delay term is small enough.
|
1404.4456v1
|
2014-08-30
|
Marginalizing over the PageRank Damping Factor
|
In this note, we show how to marginalize over the damping parameter of the
PageRank equation so as to obtain a parameter-free version known as TotalRank.
Our discussion is meant as a reference and intended to provide a guided tour
towards an interesting result that has applications in information retrieval
and classification.
|
1409.0104v1
|
2014-10-29
|
Blowup for the nonlinear Schrödinger equation with an inhomogeneous damping term in the $L^2$ critical case
|
We consider the nonlinear Schr\"odinger equation with $L^2$-critical exponent
and an inhomogeneous damping term. By using the tools developed by Merle and
Raphael, we prove the existence of blowup phenomena in the energy space
$H^1(\mathbb{R})$.
|
1410.8011v1
|
2014-11-28
|
Landau damping
|
Landau damping is calculated using real variables, clarifying the physical
mechanism.
|
1411.7793v1
|
2014-12-16
|
Linear Collisionless Landau Damping in Hilbert Space
|
The equivalence between the Laplace transform [Landau L., J. Phys. USSR, 10
(1946), 25] and Hermite transform [Zocco and Schekochihin, Phys. Plasmas, 18,
102309 (2011)] solutions of the linear collisionless Landau damping problem is
proven.
|
1412.4913v1
|
2015-07-08
|
Calculation of continuum damping of Alfvén eigenmodes in 2D and 3D cases
|
In ideal MHD, shear Alfv\'{e}n eigenmodes may experience dissipationless
damping due to resonant interaction with the shear Alfv\'{e}n continuum. This
continuum damping can make a significant contribution to the overall
growth/decay rate of shear Alfv\'{e}n eigenmodes, with consequent implications
for fast ion transport. One method for calculating continuum damping is to
solve the MHD eigenvalue problem over a suitable contour in the complex plane,
thereby satisfying the causality condition. Such an approach can be implemented
in three-dimensional ideal MHD codes which use the Galerkin method. Analytic
functions can be fitted to numerical data for equilibrium quantities in order
to determine the value of these quantities along the complex contour. This
approach requires less resolution than the established technique of calculating
damping as resistivity vanishes and is thus more computationally efficient. The
complex contour method has been applied to the three-dimensional finite element
ideal MHD code CKA . In this paper we discuss the application of the complex
contour technique to calculate the continuum damping of global modes in tokamak
as well as torsatron, W7X and H1-NF stellarator cases. To the authors'
knowledge these stellarator calculations represent the first calculation of
continuum damping for eigenmodes in fully three-dimensional equilibria. The
continuum damping of global modes in W7X and H1-NF stellarator configurations
investigated is found to depend sensitively on coupling to numerous poloidal
and toroidal harmonics.
|
1507.02072v1
|
2015-08-16
|
Jeans instability and hydrodynamic roots of Landau damping
|
Landau damping of Langmuir waves is shown to have hydrodynamic roots, and, in
principle, might have been predicted (along with Langmuir waves) several
decades earlier, soon after Jeans (1902) paper appeared.
|
1508.03809v1
|
2015-12-07
|
Damped and zero-damped quasinormal modes of charged, nearly extremal black holes
|
Despite recent progress, the complete understanding of the perturbations of
charged, rotating black holes as described by the Kerr-Newman metric remains an
open and fundamental problem in relativity. In this study, we explore the
existence of families of quasinormal modes of Kerr-Newman black holes whose
decay rates limit to zero at extremality, called zero-damped modes in past
studies. We review the nearly extremal and WKB approximation methods for
spin-weighted scalar fields (governed by the Dudley-Finley equation) and give
an accounting of the regimes where scalar zero-damped and damped modes exist.
Using Leaver's continued fraction method, we verify that these approximations
give accurate predictions for the frequencies in their regimes of validity. In
the nonrotating limit, we argue that gravito-electromagnetic perturbations of
nearly extremal Reissner-Nordstr\"{o}m black holes have zero-damped modes in
addition to the well-known spectrum of damped modes. We provide an analytic
formula for the frequencies of these modes, verify their existence using a
numerical search, and demonstrate the accuracy of our formula. These results,
along with recent numerical studies, point to the existence of a simple
universal equation for the frequencies of zero-damped gravito-electromagnetic
modes of Kerr-Newman black holes, whose precise form remains an open question.
|
1512.02247v2
|
2016-09-24
|
Recovering the damping rates of cyclotron damped plasma waves from simulation data
|
Plasma waves with frequencies close to the particular gyrofrequencies of the
charged particles in the plasma lose energy due to cyclotron damping. We
briefly discuss the gyro-resonance of low frequency plasma waves and ions
particularly with regard to particle-in-cell (PiC) simulations. A setup is
outlined which uses artificially excited waves in the damped regime of the wave
mode's dispersion relation to track the damping of the wave's electromagnetic
fields. Extracting the damping rate directly from the field data in real or
Fourier space is an intricate and non-trivial task. We therefore present a
simple method of obtaining the damping rate {\Gamma} from the simulation data.
This method is described in detail, focusing on a step-by-step explanation of
the course of actions. In a first application to a test simulation we find that
the damping rates obtained from this simulation generally are in good agreement
with theoretical predictions. We then compare the results of one-, two- and
three-dimensional simulation setups and simulations with different physical
parameter sets.
|
1609.07646v2
|
2016-10-25
|
Quadratically damped oscillators with non-linear restoring force
|
In this paper we qualitatively analyse quadratically damped oscillators with
non-linear restoring force. In particular, we obtain Hamiltonian structure and
analytical form of the energy functions.
|
1610.07821v1
|
2016-11-24
|
Longitudinal Stability Study for the FACET-II e+ Damping Ring
|
This is an initial study of the longitudinal, single-bunch stability in the
proposed FACET-II e+ damping ring. It is preliminary because many vacuum
chamber objects of the ring have not yet been designed.
|
1611.08042v1
|
2017-08-25
|
On the entropy gain under the action of amplitude damping channel on qutrit
|
After realising qutrit in the form of bipartite system we estimate from below
the entropy gain under the action of the amplitude damping channel.
|
1708.07710v1
|
2017-10-24
|
Demonstration of a switchable damping system to allow low-noise operation of high-Q low-mass suspension systems
|
Low mass suspension systems with high-Q pendulum stages are used to enable
quantum radiation pressure noise limited experiments. Utilising multiple
pendulum stages with vertical blade springs and materials with high quality
factors provides attenuation of seismic and thermal noise, however damping of
these high-Q pendulum systems in multiple degrees of freedom is essential for
practical implementation. Viscous damping such as eddy-current damping can be
employed but introduces displacement noise from force noise due to thermal
fluctuations in the damping system. In this paper we demonstrate a passive
damping system with adjustable damping strength as a solution for this problem
that can be used for low mass suspension systems without adding additional
displacement noise in science mode. We show a reduction of the damping factor
by a factor of 8 on a test suspension and provide a general optimisation for
this system.
|
1710.08698v2
|
2017-11-30
|
Asymptotic for a second order evolution equation with vanishing damping term and Tikhonov regularization
|
We investigate the asymptotic behavior of solutions to a second order
differential equation with vanishing damping term, convex potential and
regularizing Tikhonov term.
|
1711.11241v1
|
2018-10-04
|
Damping of slow surface sausage modes in photospheric waveguides
|
There has been considerable interest in sausage modes in photospheric
waveguides like pores and sunspots, and slow surface sausage modes (SSSMs) have
been suggested to damp ufficiently rapidly to account for chromospheric
heating. Working in the framework of linear resistive magnetohydrodynamics, we
examine how efficient electric resistivity and resonant absorption in the cusp
continuum can be for damping SSSMs in a photospheric waveguide with equilibrium
parameters compatible with recent measurements of a photospheric pore. For
SSSMs with the measured wavelength, we find that the damping rate due to the
cusp resonance is substantially less strong than theoretically expected with
the thin-boundary approximation. The damping-time-to-period ratio ($\tau/P$) we
derive for standing modes, equivalent to the damping-length-to-wavelength ratio
for propagating modes given the extremely weak dispersion, can reach only $\sim
180$. However, the accepted values for electric resistivity ($\eta$) correspond
to a regime where both the cusp resonance and resistivity play a role. The
values for $\tau/P$ attained at the largest allowed $\eta$ may reach $\sim 30$.
We conclude that electric resistivity can be considerably more efficient than
the cusp resonance for damping SSSMs in the pore in question, and it needs to
be incorporated into future studies on the damping of SSSMs in photospheric
waveguides in general.
|
1810.02051v1
|
2018-10-20
|
Landau Damping in a weakly collisional regime
|
In this paper, we consider the nonlinear Vlasov-Poisson equations in a weakly
collisional regime and study the linear Boltzmann collision operator. We prove
that Landau damping still occurs in this case.
|
1810.10955v1
|
2018-10-26
|
Energy regenerative damping in variable impedance actuators for long-term robotic deployment
|
Energy efficiency is a crucial issue towards longterm deployment of compliant
robots in the real world. In the context of variable impedance actuators
(VIAs), one of the main focuses has been on improving energy efficiency through
reduction of energy consumption. However, the harvesting of dissipated energy
in such systems remains under-explored. This study proposes a novel variable
damping module design enabling energy regeneration in VIAs by exploiting the
regenerative braking effect of DC motors. The proposed damping module uses four
switches to combine regenerative and dynamic braking, in a hybrid approach that
enables energy regeneration without a reduction in the range of damping
achievable. A physical implementation on a simple VIA mechanism is presented in
which the regenerative properties of the proposed module are characterised and
compared against theoretical predictions. To investigate the role of variable
regenerative damping in terms of energy efficiency of longterm operation,
experiments are reported in which the VIA equipped with the proposed damping
module performs sequential reaching to a series of stochastic targets. The
results indicate that the combination of variable stiffness and variable
regenerative damping is preferable to achieve the optimal trade-off between
task performance and energy efficiency. Use of the latter results in a 25%
performance improvement on overall performance metrics (incorporating reaching
accuracy, settling time, energy consumption and regeneration), over comparable
schemes where either stiffness or damping are fixed.
|
1810.11246v3
|
2018-12-26
|
A class large solution of the 2D MHD equations with velocity and magnetic damping
|
In this paper, we construct a class global large solution to the
two-dimensional MHD equations with damp terms in the nonhomogeneous Sobolev
framework.
|
1812.10310v2
|
2019-01-24
|
Generalization of Stokes-Einstein relation to coordinate dependent damping and diffusivity: An apparent conflict
|
Brownian motion with coordinate dependent damping and diffusivity is
ubiquitous. Understanding equilibrium of a Brownian particle with coordinate
dependent diffusion and damping is a contentious area. In this paper, we
present an alternative approach based on already established methods to this
problem. We solve for the equilibrium distribution of the over-damped dynamics
using Kramers-Moyal expansion. We compare this with the over-damped limit of
the generalized Maxwell-Boltzmann distribution. We show that the equipartition
of energy helps recover the Stokes-Einstein relation at constant diffusivity
and damping of the homogeneous space. However, we also show that, there exists
no homogeneous limit of coordinate dependent diffusivity and damping with
respect to the applicability of Stokes-Einstein relation when it does not hold
locally. In the other scenario where the Stokes-Einstein relation holds
locally, one needs to impose a restriction on the local maximum velocity of the
Brownian particle to make the modified Maxwell-Boltzmann distribution coincide
with the modified Boltzmann distribution in the over-damped limit.
|
1901.08358v4
|
2019-02-19
|
Linear inviscid damping near monotone shear flows
|
We give an elementary proof of sharp decay rates and the linear inviscid
damping near monotone shear flow in a periodic channel, first obtained in [14].
We shall also obtain the precise asymptotics of the solutions, measured in the
space $L^{\infty}$.
|
1902.06849v1
|
2019-04-18
|
Damping of Propagating Kink Waves in the Solar Corona
|
Alfv\'enic waves have gained renewed interest since the existence of
ubiquitous propagating kink waves were discovered in the corona. {It has long
been suggested that Alfv\'enic} waves play an important role in coronal heating
and the acceleration of the solar wind. To this effect, it is imperative to
understand the mechanisms that enable their energy to be transferred to the
plasma. Mode conversion via resonant absorption is believed to be one of the
main mechanisms for kink wave damping, and is considered to play a key role in
the process of energy transfer. This study examines the damping of propagating
kink waves in quiescent coronal loops using the Coronal Multi-channel
Polarimeter (CoMP). A coherence-based method is used to track the Doppler
velocity signal of the waves, enabling us to investigate the spatial evolution
of velocity perturbations. The power ratio of outward to inward propagating
waves is used to estimate the associated damping lengths and quality factors.
To enable accurate estimates of these quantities, {we provide the first
derivation of a likelihood function suitable for fitting models to the ratio of
two power spectra obtained from discrete Fourier transforms. Maximum likelihood
estimation is used to fit an exponential damping model to the observed
variation in power ratio as a function of frequency.} We confirm earlier
indications that propagating kink waves are undergoing frequency dependent
damping. Additionally, we find that the rate of damping decreases, or
equivalently the damping length increases, for longer coronal loops that reach
higher in the corona.
|
1904.08834v1
|
2019-05-19
|
Finite time blow up for wave equations with strong damping in an exterior domain
|
We consider the initial boundary value problem in exterior domain for
strongly damped wave equations with power type nonlinearity |u|^p. We will
establish blow-up results under some conditions on the initial data and the
exponent p.
|
1905.07782v1
|
2019-12-15
|
A result for nonexistence of global solutions to semi-linear structural damped wave model
|
Main goal of this note is to give a result for nonexistence of global
solutions and determine the critical exponent as well to a semi-linear
structurally damped wave equation.
|
1912.07066v1
|
2020-09-23
|
Remark on the exponential decay of the solutions of the damped wave equation
|
A condition which guaranties the exponential decay of the solutions of the
initial-boundary value problem for the damped wave equation is proved. A method
for the effective computability of the coefficient of exponential decay is also
presented.
|
2009.11244v1
|
2020-10-13
|
The Impact of Damping in Second-Order Dynamical Systems with Applications to Power Grid Stability
|
We consider a broad class of second-order dynamical systems and study the
impact of damping as a system parameter on the stability, hyperbolicity, and
bifurcation in such systems. We prove a monotonic effect of damping on the
hyperbolicity of the equilibrium points of the corresponding first-order
system. This provides a rigorous formulation and theoretical justification for
the intuitive notion that damping increases stability. To establish this
result, we prove a matrix perturbation result for complex symmetric matrices
with positive semidefinite perturbations to their imaginary parts, which may be
of independent interest. Furthermore, we establish necessary and sufficient
conditions for the breakdown of hyperbolicity of the first-order system under
damping variations in terms of observability of a pair of matrices relating
damping, inertia, and Jacobian matrices, and propose sufficient conditions for
Hopf bifurcation resulting from such hyperbolicity breakdown. The developed
theory has significant applications in the stability of electric power systems,
which are one of the most complex and important engineering systems. In
particular, we characterize the impact of damping on the hyperbolicity of the
swing equation model which is the fundamental dynamical model of power systems,
and demonstrate Hopf bifurcations resulting from damping variations.
|
2010.06662v2
|
2020-10-26
|
Linear Predictive Coding for Acute Stress Prediction from Computer Mouse Movements
|
Prior work demonstrated the potential of using the Linear Predictive Coding
(LPC) filter to approximate muscle stiffness and damping from computer mouse
movements to predict acute stress levels of users. Theoretically, muscle
stiffness and damping in the arm can be estimated using a mass-spring-damper
(MSD) biomechanical model. However, the damping frequency (i.e., stiffness) and
damping ratio values derived using LPC were not yet compared with those from a
theoretical MSD model. This work demonstrates that the damping frequency and
damping ratio from LPC are significantly correlated with those from an MSD
model, thus confirming the validity of using LPC to infer muscle stiffness and
damping. We also compare the stress level binary classification performance
using the values from LPC and MSD with each other and with neural network-based
baselines. We found comparable performance across all conditions demonstrating
LPC and MSD model-based stress prediction efficacy, especially for longer mouse
trajectories. Clinical relevance: This work demonstrates the validity of the
LPC filter to approximate muscle stiffness and damping and predict acute stress
from computer mouse movements.
|
2010.13836v3
|
2020-11-01
|
Sharp dimension estimates of the attractor of the damped 2D Euler-Bardina equations
|
We prove existence of the global attractor of the damped and driven 2D
Euler--Bardina equations on the torus and give an explicit two-sided estimate
of its dimension that is sharp as $\alpha\to0^+$.
|
2011.00607v1
|
2021-03-30
|
Strong solution of 3D-NSE with exponential damping
|
In this paper we prove the existence and uniqueness of strong solution of the
incompressible Navier-Stokes equations with damping $\alpha
(e^{\beta|u|^2}-1)u$.
|
2103.16707v1
|
2021-06-22
|
Choice of Damping Coefficient in Langevin Dynamics
|
This article considers the application of Langevin dynamics to sampling and
investigates how to choose the damping parameter in Langevin dynamics for the
purpose of maximizing thoroughness of sampling. Also, it considers the
computation of measures of sampling thoroughness.
|
2106.11597v1
|
2021-09-27
|
Damping transition in an open generalized Aubry-André-Harper model
|
We study the damping dynamics of the single-particle correlation for an open
system under periodic and aperiodic order, which is dominated by the Lindblad
master equation. In the absence of the aperiodic order, the Liouvillian
superoperator exhibits the non-Hermitian skin effect, which leads to
unidirectional damping dynamics, dubbed as "chiral damping". Due to the
non-Hermitian skin effect, the damping dynamics is boundary sensitive: The
long-time damping of such open systems is algebraic under periodic boundary
conditions but exponential under open boundary conditions. We reveal the phase
transition with the inclusion of the hopping amplitude modulation. By using the
spectral topology and a finite-size scaling analysis in the commensurate case,
we show there exists a phase transition of the skin effect with non-Bloch
anti-parity-time symmetry breaking. For the incommensurate case, we find richer
phases with the coexistence of the non-Hermitian skin effect and the Anderson
localization, which are separated by a generalized mobility edge. We reveal the
transition of the damping dynamics as a consequence of the phase transition.
Furthermore, we propose a possible scheme with ultracold atoms in a dissipative
momentum lattice to realize and detect the damping dynamics.
|
2109.12958v2
|
2022-01-20
|
Long Time Decay of Leray Solution of 3D-NSE With Exponential Damping
|
We study the uniqueness, the continuity in $L^2$ and the large time decay for
the Leray solutions of the $3D$ incompressible Navier-Stokes equations with
nonlinear exponential damping term $a (e^{b |u|^{\bf 4}}-1)u$, ($a,b>0$).
|
2201.08292v1
|
2023-03-20
|
Nonlinear Damping and Field-aligned Flows of Propagating Shear Alfvén Waves with Braginskii Viscosity
|
Braginskii MHD provides a more accurate description of many plasma
environments than classical MHD since it actively treats the stress tensor
using a closure derived from physical principles. Stress tensor effects
nonetheless remain relatively unexplored for solar MHD phenomena, especially in
nonlinear regimes. This paper analytically examines nonlinear damping and
longitudinal flows of propagating shear Alfv\'en waves. Most previous studies
of MHD waves in Braginskii MHD considered the strict linear limit of vanishing
wave perturbations. We show that those former linear results only apply to
Alfv\'en wave amplitudes in the corona that are so small as to be of little
interest, typically a wave energy less than $10^{-11}$ times the energy of the
background magnetic field. For observed wave amplitudes, the Braginskii viscous
dissipation of coronal Alfv\'en waves is nonlinear and a factor around $10^9$
stronger than predicted by the linear theory. Furthermore, the dominant damping
occurs through the parallel viscosity coefficient $\eta_0$, rather than the
perpendicular viscosity coefficient $\eta_2$ in the linearized solution. This
paper develops the nonlinear theory, showing that the wave energy density
decays with an envelope $(1+z/L_d)^{-1}$. The damping length $L_d$ exhibits an
optimal damping solution, beyond which greater viscosity leads to lower
dissipation as the viscous forces self-organise the longitudinal flow to
suppress damping. Although the nonlinear damping greatly exceeds the linear
damping, it remains negligible for many coronal applications.
|
2303.11128v1
|
2023-09-04
|
Joint Oscillation Damping and Inertia Provision Service for Converter-Interfaced Generation
|
As renewable generation becomes more prevalent, traditional power systems
dominated by synchronous generators are transitioning to systems dominated by
converter-interfaced generation. These devices, with their weaker damping
capabilities and lower inertia, compromise the system's ability to withstand
disturbances, pose a threat to system stability, and lead to oscillations and
poor frequency response performance. While some new converter-interfaced
generations are capable of providing superior damping and fast frequency
control, there is a lack of effective measures to incentivize manufacturers to
adopt them. To address this gap, this paper defines the joint oscillation
damping and inertia provision services at the system level, seeking to
encourage converter-interfaced generation to provide enhanced damping and fast
frequency response capabilities. Our approach is anchored in a novel convex
parametric formulation that combines oscillation mode and frequency stability
constraints. These constraints ensure a sufficient damping ratio for all
oscillation modes and maintain transient frequency trajectories within
acceptable limits. They are designed to integrate smoothly into various
operational and planning optimization frameworks. Using this formulation, we
introduce a joint service for oscillation damping and inertia provision based
on a cost-minimization problem. This facilitates the optimal allocation of
damping and virtual inertia to converters, achieving both small-signal
stability and frequency stability. Furthermore, we investigate the economic
effects of introducing this service into a new ancillary service market,
assessing its impact on system operations and cost-efficiency. Numerical tests
highlight the service's efficacy in ensuring both small-signal stability and
frequency stability, and offer insights into potential economic benefits.
|
2309.01321v1
|
2024-01-09
|
Damping Separation of Finite Open Systems in Gravity-Related Experiments in the Free Molecular Flow Regime
|
The residual gas damping of the test mass (TM) in the free molecular flow
regime is studied in the finite open systems for high-precision gravity-related
experiments. Through strict derivation, we separate the damping coefficients
for two finite open systems, i.e., the bi-plate system and the sensor core
system, into base damping and diffusion damping. This elucidates the
relationship between the free damping in the infinite gas volume and the
proximity damping in the constrained volume, unifies them into one microscopic
picture, and allows us to point out three pathways of energy dissipation in the
bi-plate gap. We also provide the conditions that need to be met to achieve
this separation. In applications, for space gravitational wave detection, our
results for the residual gas damping coefficient for the 4TM torsion balance
experiment is the closest one to the experimental and simulation data compared
to previous models. For the LISA mission, our estimation for residual gas
acceleration noise at the sensitive axis is consistent with the simulation
result, within about $5\%$ difference. In addition, in the test of the
gravitational inverse-square law, our results suggest that the constraint on
the distance between TM and the conducting membrane can be reduced by about
$28\%$.
|
2401.04808v1
|
2024-01-30
|
The Velocity-Space Signature of Transit-Time Damping
|
Transit-time damping (TTD) is a process in which the magnetic mirror force --
induced by the parallel gradient of magnetic field strength -- interacts with
resonant plasma particles, leading to the collisionless damping of
electromagnetic waves and the resulting energization of those particles through
the perpendicular component of the electric field, $E_\perp$. In this study, we
utilize the recently developed field-particle correlation technique to analyze
gyrokinetic simulation data. This method enables the identification of the
velocity-space structure of the TTD energy transfer rate between waves and
particles during the damping of plasma turbulence. Our analysis reveals a
unique bipolar pattern of energy transfer in velocity space characteristic of
TTD. By identifying this pattern, we provide clear evidence of TTD's
significant role in the damping of strong plasma turbulence. Additionally, we
compare the TTD signature with that of Landau damping (LD). Although they both
produce a bipolar pattern of phase-space energy density loss and gain about the
parallel resonant velocity of the \Alfvenic waves, they are mediated by
different forces and exhibit different behaviors as $v_\perp \to 0$. We also
explore how the dominant damping mechanism varies with ion plasma beta
$\beta_i$, showing that TTD dominates over LD for $\beta_i > 1$. This work
deepens our understanding of the role of TTD in the damping of weakly
collisional plasma turbulence and paves the way to seek the signature of TTD
using in situ spacecraft observations of turbulence in space plasmas.
|
2401.16697v1
|
2024-03-04
|
How long will the quasar UV/optical flickering be damped?
|
The UV/optical light curves of Active Galactic Nuclei (AGNs) are commonly
described by the Damped Random Walk (DRW) model. However, the physical
interpretation of the damping timescale, a key parameter in the DRW model,
remains unclear. Particularly, recent observations indicate a weak dependence
of the damping timescale upon both wavelength and accretion rate, clearly being
inconsistent with the accretion-disk theory. In this study, we investigate the
damping timescale in the framework of the Corona Heated Accretion disk
Reprocessing (CHAR) model, a physical model that describes AGN variability. We
find that while the CHAR model can reproduce the observed power spectral
densities of the 20-year light curves for 190 sources from \cite{Stone2022},
the observed damping timescale, as well as its weak dependence on wavelength,
can also be well recovered through fitting the mock light curves with DRW. We
further demonstrate that such weak dependence is artificial due to the effect
of inadequate durations of light curves, which leads to best-fitting damping
timescales lower than the intrinsic ones. After eliminating this effect, the
CHAR model indeed yields a strong dependence of the intrinsic damping timescale
on the bolometric luminosity and rest-frame wavelength. Our results highlight
the demand for sufficiently long light curves in AGN variability studies and
important applications of the CHAR model in such studies.
|
2403.01691v1
|
2005-04-18
|
Chemical Abundances in SFG and DLA
|
We investigate the chemical abundances of local star-forming galaxies which
cause Damped Lyman Alpha lines. A metallicity versus redshift diagram is
constructed, on which the chemical abundances of low-redshift star-forming
galaxy populations are compared with those of high-redshift Damped Lyman Alpha
systems. We disucss two types of experiments on individual star-forming
galaxies. In the first, the Damped Lyman Alpha line is created against an
internal ultraviolet light source generated by a star-forming cluster or a
supernova explosion. In the second, the Damped Lyman Alpha line is seen against
a background Quasar. The metallicities measured from ionized gas in the
star-forming regions, and neutral gas in the Damped Lyman Alpha systems, are
compared with one another on a case-by-case basis. We highlight the occurrence
of the star-forming galaxy/Quasar pair SBS 1543+593/HS 1543+5921, where the
emission- and absorption-line derived abundances give the same result. We argue
that we therefore can in principle, interpret Damped Lyman Alpha system
metallicities as an extension of star-forming galaxy metallicities to higher
redshifts, supporting that gas-rich galaxies had lower chemical abundances when
the were younger.
|
0504389v2
|
1995-09-06
|
Fermi Liquid Damping and NMR Relaxation in Superconductors
|
Electron collisions for a two dimensional Fermi liquid (FL) are shown to give
a quasiparticle damping with interesting frequency and temperature variations
in the BCS superconducting state. The spin susceptibility which determines the
structure of the damping is analyzed in the normal state for a Hubbard model
with a constant on--site Coulomb repulsion. This is then generalized to the
superconducting state by including coherence factors and self energy and vertex
corrections. Calculations of the NMR relaxation rate reveal that the FL damping
structure can reduce the Hebel--Slichter peak, in agreement with data on the
organic superconductor (MDT-TTF)$_2$AuI$_2$. However, the strongly suppressed
FL damping in the superconducting state does not eliminate the Hebel-Slichter
peak, and thus suggests that other mechanisms are needed to explain the NMR
data on (TMTSF)$_2$ClO$_4$, the BEDT organic compounds, and cuprate
superconductors. Predictions of the temperature variation of the damping and
the spin response are given over a wide frequency range as a guide to
experimental probes of the symmetry of the superconducting pairs.
|
9509028v1
|
1997-05-08
|
Topological asymmetry in the damping-pairing contribution of electron-boson scattering
|
We make a harmonic analysis of the pairing and damping contribution of a
finite $k$ range isotropic electron-phonon (or other boson) scattering in an
anisotropic two-dimensional electronic system. We show that the pairing
contribution of the anisotropic part of the electronic system can be much
larger than its damping contribution enhancing significantly T_c. The higher is
the order of the harmonic of the electronic anisotropy, smaller is its damping
contribution and higher can be the asymmetry in its damping-pairing
contribution. This could explain the puzzle of a much broader quasiparticle
peak in the n-doped than in the p-doped cuprates, their smaller T_c's being
also attributed to larger damping effects.
|
9705071v1
|
2000-03-29
|
Damping of condensate collective modes due to equilibration with the non-condensate
|
We consider the damping of condensate collective modes at finite temperatures
arising from lack of equilibrium between the condensate and the non-condensate
atoms, an effect that is ignored in the usual discussion of the collisionless
region. As a first approximation, we ignore the dynamics of the thermal cloud.
Our calculations should be applicable to collective modes of the condensate
which are oscillating out-of-phase with the thermal cloud. We obtain a
generalized Stringari equation of motion for the condensate at finite
temperatures, which includes a damping term associated with the fact that the
condensate is not in diffusive equilibrium with the static thermal cloud. This
inter-component collisional damping of the condensate modes is comparable in
magnitude to the Landau damping considered in the recent literature.
|
0003481v5
|
2006-06-27
|
Theoretical limit of the minimal magnetization switching field and the optimal field pulse for Stoner particles
|
The theoretical limit of the minimal magnetization switching field and the
optimal field pulse design for uniaxial Stoner particles are investigated. Two
results are obtained. One is the existence of a theoretical limit of the
smallest magnetic field out of all possible designs. It is shown that the limit
is proportional to the damping constant in the weak damping regime and
approaches the Stoner-Wohlfarth (SW) limit at large damping. For a realistic
damping constant, this limit is more than ten times smaller than that of
so-called precessional magnetization reversal under a non-collinear static
field. The other is on the optimal field pulse design: If the magnitude of a
magnetic field does not change, but its direction can vary during a reversal
process, there is an optimal design that gives the shortest switching time. The
switching time depends on the field magnitude, damping constant, and magnetic
anisotropy. However, the optimal pulse shape depends only on the damping
constant.
|
0606681v1
|
2001-02-09
|
Magnetic effects on the viscous boundary layer damping of the r-modes in neutron stars
|
This paper explores the effects that magnetic fields have on the viscous
boundary layers (VBLs) that can form in neutron stars at the crust-core
interface, and it investigates the VBL damping of the gravitational-radiation
driven r-mode instability. Approximate solutions to the magnetohydrodynamic
equations valid in the VBL are found for ordinary-fluid neutron stars. It is
shown that magnetic fields above 10^9 Gauss significantly change the structure
of the VBL, and that magnetic fields decrease the VBL damping time.
Furthermore, VBL damping completely suppresses the r-mode instability for B >=
10^{12} Gauss. Thus, magnetic fields will profoundly affect the VBL damping of
the r-mode instability in hot young pulsars (that are cool enough to have
formed a solid crust). One can speculate that magnetic fields can affect the
VBL damping of this instability in LMXBs and other cold old pulsars (if they
have sufficiently large internal fields).
|
0102042v1
|
2002-07-26
|
Landau damping of partially incoherent Langmuir waves
|
It is shown that partial incoherence, in the form of stochastic phase noise,
of a Langmuir wave in an unmagnetized plasma gives rise to a Landau-type
damping. Starting from the Zakharov equations, which describe the nonlinear
interaction between Langmuir and ion-acoustic waves, a kinetic equation is
derived for the plasmons by introducing the Wigner-Moyal transform of the
complex Langmuir wave field. This equation is then used to analyze the
stability properties of small perturbations on a stationary solution consisting
of a constant amplitude wave with stochastic phase noise. The concomitant
dispersion relation exhibits the phenomenon of Landau-like damping. However,
this damping differs from the classical Landau damping in which a Langmuir
wave, interacting with the plasma electrons, loses energy. In the present
process, the damping is non-dissipative and is caused by the resonant
interaction between an instantaneously-produced disturbance, due to the
parametric interactions, and a partially incoherent Langmuir wave, which can be
considered as a quasi-particle composed of an ensemble of partially incoherent
plasmons.
|
0207050v1
|
2003-01-30
|
Dynamic effects of electromagnetic wave on a damped two-level atom
|
We studied the dynamic effects of an electromagnetic(EM) wave with circular
polarization on a two-level damped atom. The results demonstrate interesting ac
Stark split of energy levels of damped atom. The split levels have different
energies and lifetimes, both of which depend on the interaction and the damping
rate of atom. When the frequency of the EM wave is tuned to satisfy the
resonance condition in the strong coupling limit, the transition probability
exhibits Rabi oscillation. Momentum transfer between atom and EM wave shows
similar properties as the transition probability under resonance condition. For
a damped atom interacting with EM field, there exists no longer stable state.
More importantly, if the angular frequency of the EM wave is tuned the same as
the atomic transition frequency and its amplitude is adjusted appropriately
according to the damping coefficients, we can prepare a particular 'Dressed
State' of the coupled system between atom and EM field and can keep the system
coherently in this 'Dressed state' for a very long time. This opens another way
to prepare coherent atomic states.
|
0301166v1
|
2007-12-18
|
Spectroscopy of electronic defect states in Cu(In, Ga)(S, Se)$_2$-based heterojunctions and Schottky diodes under damp-heat exposure
|
The changes of defect characteristics induced by accelerated lifetime tests
on the heterostructure n-ZnO/i-ZnO/CdS/Cu(In, Ga)(S, Se)$_2$/Mo relevant for
photovoltaic energy conversion are investigated. We subject heterojunction and
Schottky devices to extended damp heat exposure at 85$^{\circ}$C ambient
temperature and 85% relative humidity for various time periods. In order to
understand the origin of the pronounced changes of the devices, we apply
current--voltage and capacitance--voltage measurements, admittance
spectroscopy, and deep-level transient spectroscopy. The fill factor and
open-circuit voltage of test devices are reduced after prolonged damp heat
treatment, leading to a reduced energy conversion efficiency. We observe the
presence of defect states in the vicinity of the CdS/chalcopyrite interface.
Their activation energy increases due to damp heat exposure, indicating a
reduced band bending at the Cu(In, Ga)(S, Se)$_2$ surface. The Fermi-level
pinning at the buffer/chalcopyrite interface, maintaining a high band bending
in as-grown cells, is lifted due to the damp-heat exposure. We also observe
changes in the bulk defect spectra due to the damp-heat treatment.
|
0712.2982v1
|
2008-05-07
|
Comparison Between Damping Coefficients of Measured Perforated Micromechanical Test Structures and Compact Models
|
Measured damping coefficients of six different perforated micromechanical
test structures are compared with damping coefficients given by published
compact models. The motion of the perforated plates is almost translational,
the surface shape is rectangular, and the perforation is uniform validating the
assumptions made for compact models. In the structures, the perforation ratio
varies from 24% - 59%. The study of the structure shows that the
compressibility and inertia do not contribute to the damping at the frequencies
used (130kHz - 220kHz). The damping coefficients given by all four compact
models underestimate the measured damping coefficient by approximately 20%. The
reasons for this underestimation are discussed by studying the various flow
components in the models.
|
0805.0893v1
|
2009-01-26
|
Dispersion of Waves in Relativistic Plasmas with Isotropic Particle Distributions
|
The dispersion laws of Langmuir and transverse waves are calculated in the
relativistic non-magnetized formalism for several isotropic particle
distributions: thermal, power-law, relativistic Lorentzian $\kappa,$ and hybrid
$\beta$. For Langmuir waves the parameters of superluminal undamped, subluminal
damped principal and higher modes are determined for a range of distribution
parameters. The undamped and principal damped modes are found to match
smoothly. Principal damped and second damped modes are found not to match
smoothly. The presence of maximum wavenumber is discovered above that no
longitudinal modes formally exist. The higher damped modes are discovered to be
qualitatively different for thermal and certain non-thermal distributions.
Consistently with the known results, the Landau damping is calculated to be
stronger for non-thermal power-law-like distributions. The dispersion law is
obtained for the single undamped transverse mode. The analytic results for the
simplest distributions are provided.
|
0901.4050v1
|
2009-03-28
|
Torsional waves propagation in an initially stressed dissipative cylinder
|
The present paper has been framed to show the effect of damping on the
propagation of torsional waves in an initially stressed, dissipative,
incompressible cylinder of infinite length. A governing equation has been
formulated on Biot's incremental deformation theory. The velocities of
torsional waves are obtained as complex ones, in which real part gives the
phase velocity of propagation and corresponding imaginary part gives the
damping. The study reveals that the damping of the medium has strong effect in
the propagation of torsional wave. Since every medium has damping so it is more
realistic to use the damped wave equation instead of the undamped wave
equation. The study also shows that the velocity of propagation of such waves
depend on the presence of initial stress. The influences of damping and initial
stresses are shown separately.
|
0903.4896v1
|
2009-04-29
|
Atomistic theory for the damping of vibrational modes in mono-atomic gold chains
|
We develop a computational method for evaluating the damping of vibrational
modes in mono-atomic metallic chains suspended between bulk crystals under
external strain. The damping is due to the coupling between the chain and
contact modes and the phonons in the bulk substrates. The geometry of the atoms
forming the contact is taken into account. The dynamical matrix is computed
with density functional theory in the atomic chain and the contacts using
finite atomic displacements, while an empirical method is employed for the bulk
substrate. As a specific example, we present results for the experimentally
realized case of gold chains in two different crystallographic directions. The
range of the computed damping rates confirm the estimates obtained by fits to
experimental data [Frederiksen et al., Phys. Rev. B, 75, 205413(R)(2007)]. Our
method indicates that an order-of-magnitude variation in the damping is
possible even for relatively small changes in the strain. Such detailed insight
is necessary for a quantitative analysis of damping in metallic atomic chains,
and in explaining the rich phenomenology seen in the experiments.
|
0904.4627v2
|
2009-12-20
|
A Kinetic Alfven wave cascade subject to collisionless damping cannot reach electron scales in the solar wind at 1 AU
|
(Abridged) Turbulence in the solar wind is believed to generate an energy
cascade that is supported primarily by Alfv\'en waves or Alfv\'enic
fluctuations at MHD scales and by kinetic Alfv\'en waves (KAWs) at kinetic
scales $k_\perp \rho_i\gtrsim 1$. Linear Landau damping of KAWs increases with
increasing wavenumber and at some point the damping becomes so strong that the
energy cascade is completely dissipated. A model of the energy cascade process
that includes the effects of linear collisionless damping of KAWs and the
associated compounding of this damping throughout the cascade process is used
to determine the wavenumber where the energy cascade terminates. It is found
that this wavenumber occurs approximately when $|\gamma/\omega|\simeq 0.25$,
where $\omega(k)$ and $\gamma(k)$ are, respectively, the real frequency and
damping rate of KAWs and the ratio $\gamma/\omega$ is evaluated in the limit as
the propagation angle approaches 90 degrees relative to the direction of the
mean magnetic field.
|
0912.4026v2
|
2010-07-27
|
Alfvèn wave phase-mixing and damping in the ion cyclotron range of frequencies
|
Aims. To determine the effect of the Hall term in the generalised Ohm's law
on the damping and phase mixing of Alfven waves in the ion cyclotron range of
frequencies in uniform and non-uniform equilibrium plasmas. Methods. Wave
damping in a uniform plasma is treated analytically, whilst a Lagrangian remap
code (Lare2d) is used to study Hall effects on damping and phase mixing in the
presence of an equilibrium density gradient. Results. The magnetic energy
associated with an initially Gaussian field perturbation in a uniform resistive
plasma is shown to decay algebraically at a rate that is unaffected by the Hall
term to leading order in k^2di^2 where k is wavenumber and di is ion skin
depth. A similar algebraic decay law applies to whistler perturbations in the
limit k^2di^2>>1. In a non-uniform plasma it is found that the
spatially-integrated damping rate due to phase mixing is lower in Hall MHD than
it is in MHD, but the reduction in the damping rate, which can be attributed to
the effects of wave dispersion, tends to zero in both the weak and strong phase
mixing limits.
|
1007.4752v2
|
2011-02-24
|
Environment-assisted quantum Minority games
|
The effect of entanglement and correlated noise in a four-player quantum
Minority game is investigated. Different time correlated quantum memory
channels are considered to analyze the Nash equilibrium payoff of the 1st
player. It is seen that the Nash equilibrium payoff is substantially enhanced
due to the presence of correlated noise. The behaviour of damping channels
(amplitude damping and phase damping) is approximately similar. However,
bit-phase flip channel heavily influences the minority game as compared to
other channels in the presence of correlated noise. On the other hand, phase
flip channel has a symmetrical behaviour around 50% noise threshold. The
significant reduction in payoffs due to decoherence is well compensated due to
the presence of correlated noise. However, the Nash equilibrium of the game
does not change in the presence of noise. It is seen that in case of
generalized amplitude damping channel, entanglement plays a significant role at
lower level of decoherence. The channel has less dominant effects on the payoff
at higher values of decoherence. Furthermore, amplitude damping and generalized
amplitude damping channels have almost comparable effects at lower level of
decoherence $(p<0.5)$. Therefore, the game deserves careful study during its
implementation due to prominent role of noise for different channels.
|
1102.5056v2
|
2011-03-17
|
Viscous damping of r-modes: Large amplitude saturation
|
We analyze the viscous damping of r-mode oscillations of compact stars,
taking into account non-linear viscous effects in the large-amplitude regime.
The qualitatively different cases of hadronic stars, strange quark stars, and
hybrid stars are studied. We calculate the viscous damping times of r-modes,
obtaining numerical results and also general approximate analytic expressions
that explicitly exhibit the dependence on the parameters that are relevant for
a future spindown evolution calculation. The strongly enhanced damping of large
amplitude oscillations leads to damping times that are considerably lower than
those obtained when the amplitude dependence of the viscosity is neglected.
Consequently, large-amplitude viscous damping competes with the gravitational
instability at all physical frequencies and could stop the r-mode growth in
case this is not done before by non-linear hydrodynamic mechanisms.
|
1103.3521v2
|
2011-05-01
|
Viscous damping of nanobeam resonators: humidity, thermal noise and the paddling effect
|
The nanobeam resonator is the key mechanical component in the
nano-electromechanical system. In addition to its high frequency originating
from its low dimension, the performance is significantly influenced by the
circumstances, especially at nanoscale where a large surface area of the
material is exposed. Molecular dynamics simulations and theoretical analysis
are used for a quantitative prediction on the damping behavior, such as the
critical damping condition and lifetime, of nanobeam resonators that directly
maps the fluid-structure properties and interaction information into dynamical
behaviors. We show here how the humidity defines the critical damping condition
through viscous forces, marking the transition from under-damping to
over-damping regime at elevated humidity. Novel phenomena such as the thermal
fluctuation and paddling effects are also discussed.
|
1105.0139v1
|
2011-06-07
|
Damping by branching: a bioinspiration from trees
|
Man-made slender structures are known to be sensitive to high levels of
vibration, due to their flexibility, which often cause irreversible damage. In
nature, trees repeatedly endure large amplitudes of motion, mostly caused by
strong climatic events, yet with minor or no damage in most cases. A new
damping mechanism inspired by the architecture of trees is here identified and
characterized in the simplest tree-like structure, a Y-shape branched
structure. Through analytical and numerical analyses of a simple
two-degree-of-freedom model, branching is shown to be the key ingredient in
this protective mechanism that we call damping-by-branching. It originates in
the geometrical nonlinearities so that it is specifically efficient to damp out
large amplitudes of motion. A more realistic model, using flexible beam
approximation, shows that the mechanism is robust. Finally, two bioinspired
architectures are analyzed, showing significant levels of damping achieved via
branching with typically 30% of the energy being dissipated in one oscillation.
This concept of damping-by-branching is of simple practical use in the design
of slender flexible structures.
|
1106.1283v1
|
2011-11-29
|
Dispersion and damping of potential surface waves in a degenerate plasma
|
Potential (electrostatic) surface waves in plasma half-space with degenerate
electrons are studied using the quasi-classical mean-field kinetic model. The
wave spectrum and the collisionless damping rate are obtained numerically for a
wide range of wavelengths. In the limit of long wavelengths, the wave frequency
$\omega$ approaches the cold-plasma limit $\omega=\omega_p/\sqrt{2}$ with
$\omega_p$ being the plasma frequency, while at short wavelengths, the wave
spectrum asymptotically approaches the spectrum of zero-sound mode propagating
along the boundary. It is shown that the surface waves in this system remain
weakly damped at all wavelengths (in contrast to strongly damped surface waves
in Maxwellian electron plasmas), and the damping rate nonmonotonically depends
on the wavelength, with the maximum (yet small) damping occuring for surface
waves with wavelength of $\approx5\pi\lambda_{F}$, where $\lambda_{F}$ is the
Thomas-Fermi length.
|
1111.6723v1
|
2012-01-29
|
Smooth attractors of finite dimension for von Karman evolutions with nonlinear frictional damping localized in a boundary layer
|
In this paper dynamic von Karman equations with localized interior damping
supported in a boundary collar are considered. Hadamard well-posedness for von
Karman plates with various types of nonlinear damping are well-known, and the
long-time behavior of nonlinear plates has been a topic of recent interest.
Since the von Karman plate system is of "hyperbolic type" with critical
nonlinearity (noncompact with respect to the phase space), this latter topic is
particularly challenging in the case of geometrically constrained and nonlinear
damping. In this paper we first show the existence of a compact global
attractor for finite-energy solutions, and we then prove that the attractor is
both smooth and finite dimensional. Thus, the hyperbolic-like flow is
stabilized asymptotically to a smooth and finite dimensional set.
Key terms: dynamical systems, long-time behavior, global attractors,
nonlinear plates, nonlinear damping, localized damping
|
1201.6072v1
|
2012-06-15
|
Landau Damping in a Turbulent Setting
|
To address the problem of Landau damping in kinetic turbulence, the forcing
of the linearized Vlasov equation by a stationary random source is considered.
It is found that the time-asymptotic density response is dominated by resonant
particle interactions that are synchronized with the source. The energy
consumption of this response is calculated, implying an effective damping rate,
which is the main result of this paper. Evaluating several cases, it is found
that the effective damping rate can differ from the Landau damping rate in
magnitude and also, remarkably, in sign. A limit is demonstrated in which the
density and current become phase-locked, which causes the effective damping to
be negligible; this potentially resolves an energy paradox that arises in the
application of critical balance to a kinetic turbulence cascade.
|
1206.3415v4
|
2012-07-17
|
Asymptotic Dynamics of a Class of Coupled Oscillators Driven by White Noises
|
This paper is devoted to the study of the asymptotic dynamics of a class of
coupled second order oscillators driven by white noises. It is shown that any
system of such coupled oscillators with positive damping and coupling
coefficients possesses a global random attractor. Moreover, when the damping
and the coupling coefficients are sufficiently large, the global random
attractor is a one-dimensional random horizontal curve regardless of the
strength of the noises, and the system has a rotation number, which implies
that the oscillators in the system tend to oscillate with the same frequency
eventually and therefore the so called frequency locking is successful. The
results obtained in this paper generalize many existing results on the
asymptotic dynamics for a single second order noisy oscillator to systems of
coupled second order noisy oscillators. They show that coupled damped second
order oscillators with large damping have similar asymptotic dynamics as the
limiting coupled first order oscillators as the damping goes to infinite and
also that coupled damped second order oscillators have similar asymptotic
dynamics as their proper space continuous counterparts, which are of great
practical importance.
|
1207.3864v1
|
2013-10-29
|
Influence of sample geometry on inductive damping measurement methods
|
We study the precession frequency and effective damping of patterned
permalloy thin films of different geometry using integrated inductive test
structures. The test structures consist of coplanar wave guides fabricated onto
patterned permalloy stripes of different geometry. The width, length and
position of the permalloy stripe with respect to the center conductor of the
wave guide are varied. The precession frequency and effective damping of the
different devices is derived by inductive measurements in time and frequency
domain in in-plane magnetic fields. While the precession frequencies do not
reveal a significant dependence on the sample geometry we find a decrease of
the measured damping with increasing width of the permalloy centered underneath
the center conductor of the coplanar wave guide. We attribute this effect to an
additional damping contribution due to inhomogeneous line broadening at the
edges of the permalloy stripes which does not contribute to the inductive
signal provided the permalloy stripe is wider than the center conductor.
Consequences for inductive determination of the effective damping using such
integrated reference samples are discussed.
|
1310.7817v1
|
2014-03-13
|
The best decay rate of the damped plate equation in a square
|
In this paper we study the best decay rate of the solutions of a damped plate
equation in a square and with a homogeneous Dirichlet boundary conditions. We
show that the fastest decay rate is given by the supremum of the real part of
the spectrum of the infinitesimal generator of the underlying semigroup, if the
damping coefficient is in $L^\infty(\Omega).$ Moreover, we give some numerical
illustrations by spectral computation of the spectrum associated to the damped
plate equation. The numerical results obtained for various cases of damping are
in a good agreement with theoretical ones. Computation of the spectrum and
energy of discrete solution of damped plate show that the best decay rate is
given by spectral abscissa of numerical solution.
|
1403.3199v1
|
2014-04-02
|
Determination of the cross-field density structuring in coronal waveguides using the damping of transverse waves
|
Time and spatial damping of transverse magnetohydrodynamic (MHD) kink
oscillations is a source of information on the cross-field variation of the
plasma density in coronal waveguides. We show that a probabilistic approach to
the problem of determining the density structuring from the observed damping of
transverse oscillations enables us to obtain information on the two parameters
that characterise the cross-field density profile. The inference is performed
by computing the marginal posterior distributions for density contrast and
transverse inhomo- geneity length-scale using Bayesian analysis and damping
ratios for transverse oscillations under the assumption that damping is
produced by resonant absorption. The obtained distributions show that, for
damping times of a few oscillatory periods, low density contrasts and short
inho- mogeneity length scales are more plausible in explaining observations.
This means that valuable information on the cross-field density profile can be
obtained even if the inversion problem, with two unknowns and one observable,
is a mathematically ill-posed problem.
|
1404.0584v1
|
2014-04-14
|
Distributed Approximate Message Passing for Compressed Sensing
|
In this paper, an efficient distributed approach for implementing the
approximate message passing (AMP) algorithm, named distributed AMP (DAMP), is
developed for compressed sensing (CS) recovery in sensor networks with the
sparsity K unknown. In the proposed DAMP, distributed sensors do not have to
use or know the entire global sensing matrix, and the burden of computation and
storage for each sensor is reduced. To reduce communications among the sensors,
a new data query algorithm, called global computation for AMP (GCAMP), is
proposed. The proposed GCAMP based DAMP approach has exactly the same recovery
solution as the centralized AMP algorithm, which is proved theoretically in the
paper. The performance of the DAMP approach is evaluated in terms of the
communication cost saved by using GCAMP. For comparison purpose, thresholding
algorithm (TA), a well known distributed Top-K algorithm, is modified so that
it also leads to the same recovery solution as the centralized AMP. Numerical
results demonstrate that the GCAMP based DAMP outperforms the Modified TA based
DAMP, and reduces the communication cost significantly.
|
1404.3766v2
|
2014-12-17
|
The most metal-rich damped Lyman alpha systems at z>1.5 I: The Data
|
We present HIRES observations for 30 damped Lyman alpha systems, selected on
the basis of their large metal column densities from previous, lower resolution
data. The measured metal column densities for Fe, Zn, S, Si, Cr, Mn, and Ni are
provided for these 30 systems. Combined with previously observed large metal
column density damped Lyman alpha systems, we present a sample of 44 damped
Lyman alpha systems observed with high resolution spectrographs (R~30000).
These damped Lyman alpha systems probe the most chemically evolved systems at
redshifts greater than 1.5. We discuss the context of our sample with the
general damped Lyman alpha population, demonstrating that we are probing the
top 10% of metal column densities with our sample. In a companion paper, we
will present an analysis of the sample's elemental abundances in the context of
galactic chemical enrichment.
|
1412.5491v1
|
2015-02-16
|
Role of nonlinear anisotropic damping in the magnetization dynamics of topological solitons
|
The consequences of nonlinear anisotropic damping, driven by the presence of
Rashba spin-orbit coupling in thin ferromagnetic metals, are examined for the
dynamics of topological magnetic solitons such as domain walls, vortices, and
skyrmions. The damping is found to affect Bloch and N\'eel walls differently in
the steady state regime below Walker breakdown and leads to a monotonic
increase in the wall velocity above this transition for large values of the
Rashba coefficient. For vortices and skyrmions, a generalization of the damping
tensor within the Thiele formalism is presented. It is found that chiral
components of the damping affect vortex- and hedgehog-like skyrmions in
different ways, but the dominant effect is an overall increase in the
viscous-like damping.
|
1502.04695v2
|
2015-03-26
|
Transient nutations decay in diluted paramagnetic solids: a radiation damping mechanism
|
Here, a theory of the intensity and concentration dependent damping of
nutation signals observed by Boscaino et al. (Phys. Rev B 48, 7077 (1993);
Phys. Rev. A 59, 4087 (1999)) and by others in various two-level spin systems
is proposed. It is shown that in diluted paramagnetic solids contribution of
dipole-dipole interaction to the nutation decay is negligibly small. We
elaborated a cavity loss (radiation damping) mechanism that explains the
intensity- and concentration dependence of the damping. It is shown that
instead of ordinary Bloch's transverse T2 and longitudinal T1 damping
parameters the decay of transverse and longitudinal spin components in nutation
process are described by one and the same intensity-, concentration-,
frequency- and time dependent damping parameter.
|
1503.07641v2
|
2015-08-17
|
Increased magnetic damping of a single domain wall and adjacent magnetic domains detected by spin torque diode in a nanostripe
|
We use spin-torque resonance to probe simultaneously and separately the
dynamics of a magnetic domain wall and of magnetic domains in a nanostripe
magnetic tunnel junction. Thanks to the large associated resistance variations
we are able to analyze quantitatively the resonant properties of these single
nanoscale magnetic objects. In particular, we find that the magnetic damping of
both domains and domain walls is doubled compared to the damping value of their
host magnetic layer. We estimate the contributions to damping arising from
dipolar couplings between the different layers in the junction and from the
intralayer spin pumping effect. We find that they cannot explain the large
damping enhancement that we observe. We conclude that the measured increased
damping is intrinsic to large amplitudes excitations of spatially localized
modes or solitons such as vibrating or propagating domain walls
|
1508.04043v1
|
2016-04-27
|
Influence of nonlocal damping on the field-driven domain wall motion
|
We derive the complete expression of nonlocal damping in noncollinear
magnetization due to the nonuniform spin current pumped by precessional
magnetization and incorporate it into a generalized Thiele equation to study
its effects on the dynamics of the transverse and vortex domain walls (DWs) in
ferromagnetic nanowires. We demonstrate that the transverse component of
nonlocal damping slows down the field-driven DW propagation and increases the
Walker breakdown field whereas it is neglected in many previous works in
literature. The experimentally measured DW mobility variation with the damping
tuned by doping with heavy rare-earth elements that had discrepancy from
micromagnetic simulation are now well understood with the nonlocal damping. Our
results suggest that the nonlocal damping should be properly included as a
prerequisite for quantitative studies of current-induced torques in
noncollinear magnetization.
|
1604.07971v2
|
2016-04-27
|
Damping of the Collective Amplitude Mode in Superconductors with Strong Electron-Phonon Coupling
|
We study the effect of strong electron-phonon interactions on the damping of
the Higgs amplitude mode in superconductors by means of non-equilibrium
dynamical mean-field simulations of the Holstein model. In contrast to the BCS
dynamics, we find that the damping of the Higgs mode strongly depends on the
temperature, becoming faster as the systen approaches the transition
temperature. The damping at low temperatures is well described by a power-law,
while near the transition temperature the damping shows exponential-like
behavior. We explain this crossover by a temperature-dependent quasiparticle
lifetime caused by the strong electron- phonon coupling, which smears the
superconducting gap edge and makes the relaxation of the Higgs mode into
quasiparticles more efficient at elevated temperatures. We also reveal that the
phonon dynamics can soften the Higgs mode, which results in a slower damping.
|
1604.08073v2
|
2016-05-29
|
Damped Infinite Energy Solutions of the 3D Euler and Boussinesq Equations
|
We revisit a family of infinite-energy solutions of the 3D incompressible
Euler equations proposed by Gibbon et al. [9] and shown to blowup in finite
time by Constantin [6]. By adding a damping term to the momentum equation we
examine how the damping coefficient can arrest this blowup. Further, we show
that similar infinite-energy solutions of the inviscid 3D Boussinesq system
with damping can develop a singularity in finite time as long as the damping
effects are insufficient to arrest the (undamped) 3D Euler blowup in the
associated damped 3D Euler system.
|
1605.08965v3
|
2016-06-14
|
Anomalous Damping of a Micro-electro-mechanical Oscillator in Superfluid $^3$He-B
|
The mechanical resonance properties of a micro-electro-mechanical oscillator
with a gap of 1.25 $\mu$m was studied in superfluid $^3$He-B at various
pressures. The oscillator was driven in the linear damping regime where the
damping coefficient is independent of the oscillator velocity. The quality
factor of the oscillator remains low ($Q\approx 80$) down to 0.1 $T_c$, 4
orders of magnitude less than the intrinsic quality factor measured in vacuum
at 4 K. In addition to the Boltzmann temperature dependent contribution to the
damping, a damping proportional to temperature was found to dominate at low
temperatures. We propose a multiple scattering mechanism of the surface Andreev
bound states to be a possible cause for the anomalous damping.
|
1606.04483v2
|
2016-12-16
|
Dynamics of cohering and decohering power under Markovian channels
|
In this paper, we investigate the cohering and decohering power for the
one-qubit Markovian channels with respect to coherence in terms of the
$l_{1}$-norm, the R$\acute{e}$nyi $\alpha$-relative entropy and the Tsallis
$\alpha$-relative entropy. In the case of $\alpha=2$, the cohering and
decohering power of the amplitude damping channel, the phase damping channel,
the depolarizing channel, and the flip channels under the three measures of
coherence are calculated analytically. The decohering power on the $x, y, z$
basis referring to the amplitude damping channel, the phase damping channel,
the flip channel for every measure we investigated is equal. This property also
happens in the cohering power of the phase damping channel, the depolarizing
channel, and the flip channels. However, the decohering power of the
depolarizing channel is independent to the reference basis, and the cohering
power of the amplitude damping channel on the $x, y$ basis is different to that
on the $z$ basis.
|
1612.05355v1
|
2017-01-19
|
Decoherence effects on multiplayer cooperative quantum games
|
We study the behavior of cooperative multiplayer quantum games [35,36] in the
presence of decoherence using different quantum channels such as amplitude
damping, depolarizing and phase damping. It is seen that the outcomes of the
games for the two damping channels with maximum values of decoherence reduce to
same value. However, in comparison to phase damping channel, the payoffs of
cooperators are strongly damped under the influence\ amplitude damping channel
for\ the lower values of decoherence parameter. In the case of depolarizing
channel, the game is a no-payoff game irrespective of the degree of
entanglement in the initial state for the larger values of decoherence
parameter. The decoherence gets the cooperators worse off.
|
1701.05342v1
|
2017-07-30
|
Blow-up for semilinear damped wave equations with sub-Strauss exponent in the scattering case
|
It is well-known that the critical exponent for semilinear damped wave
equations is Fujita exponent when the damping is effective. Lai, Takamura and
Wakasa in 2017 have obtained a blow-up result not only for super-Fujita
exponent but also for the one closely related to Strauss exponent when the
damping is scaling invariant and its constant is relatively small,which has
been recently extended by Ikeda and Sobajima. Introducing a multiplier for the
time-derivative of the spatial integral of unknown functions, we succeed in
employing the technics on the analysis for semilinear wave equations and
proving a blow-up result for semilinear damped wave equations with sub-Strauss
exponent when the damping is in the scattering range.
|
1707.09583v3
|
2017-10-09
|
Resonant absorption of surface sausage and surface kink modes under photospheric conditions
|
We study the effect of resonant absorption of surface sausage and surface
kink modes under photospheric conditions where the slow surface sausage modes
undergo resonant damping in the slow continuum and the surface kink modes in
the slow and Alfv\'{e}n continua at the transitional layers. We use recently
derived analytical formulas to obtain the damping rate (time). By considering
linear density and linear pressure profiles for the transitional layers, we
show that resonant absorption in the slow continuum could be an efficient
mechanism for the wave damping of the slow surface sausage and slow surface
kink modes whilst the damping rate of the slow surface kink mode in the
Alfv\'{e}n continuum is weak. It is also found that the resonant damping of the
fast surface kink mode is much stronger than that of the slow surface kink
mode, showing a similar efficiency as under coronal conditions. It is worth to
notice that the slow body sausage and kink modes can also resonantly damp in
the slow continuum for those linear profiles.
|
1710.03350v2
|
2017-11-21
|
Nonexistence of global solutions of nonlinear wave equations with weak time-dependent damping related to Glassey conjecture
|
This work is devoted to the nonexistence of global-in-time energy solutions
of nonlinear wave equation of derivative type with weak time-dependent damping
in the scattering and scale invariant range. By introducing some multipliers to
absorb the damping term, we succeed in establishing the same upper bound of the
lifespan for the scattering damping as the non-damped case, which is a part of
so-called Glassey conjecture on nonlinear wave equations. We also study an
upper bound of the lifespan for the scale invariant damping with the same
method.
|
1711.07591v2
|
2018-01-03
|
Stabilisation of wave equations on the torus with rough dampings
|
For the damped wave equation on a compact manifold with {\em continuous}
dampings, the geometric control condition is necessary and sufficient for
{uniform} stabilisation. In this article, on the two dimensional torus, in the
special case where $a(x) = \sum\_{j=1}^N a\_j 1\_{x\in R\_j}$ ($R\_j$ are
polygons), we give a very simple necessary and sufficient geometric condition
for uniform stabilisation. We also propose a natural generalization of the
geometric control condition which makes sense for $L^\infty$ dampings. We show
that this condition is always necessary for uniform stabilisation (for any
compact (smooth) manifold and any $L^\infty$ damping), and we prove that it is
sufficient in our particular case on $\mathbb{T}^2$ (and for our particular
dampings).
|
1801.00983v2
|
2018-03-12
|
Optical Rotation of Levitated Spheres in High Vacuum
|
A circularly polarized laser beam is used to levitate and control the
rotation of microspheres in high vacuum. At low pressure, rotation frequencies
as high as 6 MHz are observed for birefringent vaterite spheres, limited by
centrifugal stresses. Due to the extremely low damping in high vacuum,
controlled optical rotation of amorphous SiO$_2$ spheres is also observed at
rates above several MHz. At $10^{-7}$ mbar, a damping time of $6\times10^4$ s
is measured for a $10\ \mu$m diameter SiO$_2$ sphere. No additional damping
mechanisms are observed above gas damping, indicating that even longer damping
times may be possible with operation at lower pressure. The controlled optical
rotation of microspheres at MHz frequencies with low damping, including for
materials that are not intrinsically birefringent, provides a new tool for
performing precision measurements using optically levitated systems.
|
1803.04297v1
|
2018-03-23
|
A conservation law with spatially localized sublinear damping
|
We consider a general conservation law on the circle, in the presence of a
sublinear damping. If the damping acts on the whole circle, then the solution
becomes identically zero in finite time, following the same mechanism as the
corresponding ordinary differential equation. When the damping acts only
locally in space, we show a dichotomy: if the flux function is not zero at the
origin, then the transport mechanism causes the extinction of the solution in
finite time, as in the first case. On the other hand, if zero is a
non-degenerate critical point of the flux function, then the solution becomes
extinct in finite time only inside the damping zone, decays algebraically
uniformly in space, and we exhibit a boundary layer, shrinking with time,
around the damping zone. Numerical illustrations show how similar phenomena may
be expected for other equations.
|
1803.08767v1
|
2019-03-06
|
Microwave magnon damping in YIG films at millikelvin temperatures
|
Magnon systems used in quantum devices require low damping if coherence is to
be maintained. The ferrimagnetic electrical insulator yttrium iron garnet (YIG)
has low magnon damping at room temperature and is a strong candidate to host
microwave magnon excitations in future quantum devices. Monocrystalline YIG
films are typically grown on gadolinium gallium garnet (GGG) substrates. In
this work, comparative experiments made on YIG waveguides with and without GGG
substrates indicate that the material plays a significant role in increasing
the damping at low temperatures. Measurements reveal that damping due to
temperature-peak processes is dominant above 1 K. Damping behaviour that we
show can be attributed to coupling to two-level fluctuators (TLFs) is observed
below 1 K. Upon saturating the TLFs in the substrate-free YIG at 20 mK,
linewidths of 1.4 MHz are achievable: lower than those measured at room
temperature.
|
1903.02527v3
|
2019-09-21
|
Stability for coupled waves with locally disturbed Kelvin-Voigt damping
|
We consider a coupled wave system with partial Kelvin-Voigt damping in the
interval (-1,1), where one wave is dissipative and the other does not. When the
damping is effective in the whole domain (-1,1) it was proven in H.Portillo
Oquendo and P.Sanez Pacheco, optimal decay for coupled waves with Kelvin-voigt
damping, Applied Mathematics Letters 67 (2017), 16-20. That the energy is
decreasing over the time with a rate equal to $t^{-\frac{1}{2}}$. In this
paper, using the frequency domain method we show the effect of the coupling and
the non smoothness of the damping coefficient on the energy decay. Actually, as
expected we show the lack of exponential stability, that the semigroup loses
speed and it decays polynomially with a slower rate then given in, H.Portillo
Oquendo and P.Sanez Pacheco, optimal decay for coupled waves with Kelvin-voigt
damping, Applied Mathematics Letters 67 (2017), 16-20, down to zero at least as
$t^{-\frac{1}{12}}$.
|
1909.09838v1
|
2020-05-15
|
Slow magnetosonic wave absorption by pressure induced ionization-recombination dissipation
|
A new mechanisms for damping of slow magnetosonic waves (SMW) by pressure
induced oscillations of the ionization degree is proposed. An explicit formula
for the damping rate is quantitatively derived. Physical conditions where the
new mechanism will dominate are briefly discussed. The ionization-recombination
damping is frequency independent and has no hydrodynamic interpretation.
Roughly speaking large area of partially ionized plasma are damper for basses
of SMW while usual MHD mechanisms operate as a low pass filter. The derived
damping rate is proportional to the square of the sine between the constant
magnetic field and the wave-vector. Angular distribution of the spectral
density of SMW and Alfv\'en waves (AW) created by turbulent regions and passing
through large regions of partially ionized plasma is qualitatively considered.
The calculated damping rate is expressed by the electron impact cross section
of the hydrogen atom and in short all details of the proposed damping
mechanisms are well studied.
|
2005.07730v1
|
2020-06-30
|
Polynomial stabilization of non-smooth direct/indirect elastic/viscoelastic damping problem involving Bresse system
|
We consider an elastic/viscoelastic transmission problem for the Bresse
system with fully Dirichlet or Dirichlet-Neumann-Neumann boundary conditions.
The physical model consists of three wave equations coupled in certain pattern.
The system is damped directly or indirectly by global or local Kelvin-Voigt
damping. Actually, the number of the dampings, their nature of distribution
(locally or globally) and the smoothness of the damping coefficient at the
interface play a crucial role in the type of the stabilization of the
corresponding semigroup. Indeed, using frequency domain approach combined with
multiplier techniques and the construction of a new multiplier function, we
establish different types of energy decay rate (see the table of stability
results below). Our results generalize and improve many earlier ones in the
literature and in particular some studies done on the Timoshenko system with
Kelvin-Voigt damping.
|
2006.16595v2
|
2020-07-02
|
Uniformly-Damped Binomial Filters: Five-percent Maximum Overshoot Optimal Response Design
|
In this paper, the five-percent maximum overshoot design of uniformly-damped
binomial filters (transfer-functions) is introduced. First, the butterworth
filter response is represented as a damped-binomial filter response. To extend
the maximum-overshoot response of the second-order butterworth to higher
orders, the binomial theorem is extended to the uniformly-damped binomial
theorem. It is shown that the five-percent uniformly-damped binomial filter is
a compromise between the butterworth filter and the standard binomial filter,
with respect to the filter-approximation problem in the time and frequency
domain. Finally, this paper concludes that in applications of interest, such as
step-tracking, where both strong filtering and a fast, smooth
transient-response, with negligible overshoot are desired, the response of the
normalized five-percent uniformly-damped binomial form is a candidate
replacement for both the butterworth and standard binomial filter forms.
|
2007.00890v3
|
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