1,854 research outputs found
A dissipated energy comparison to evaluate fatigue resistance using 2PB
Flexural fatigue due to repeated traffic loading is a process of cumulative damage and one of the main failure modes of flexible pavement structures. Typically, micro-cracks originate at the bottom of an asphalt concrete layer due to horizontal tensile strains. Micro-cracking starts to propagate towards the upper layers under repeated loading which can lead to pavement failure.
Different approaches are usually used to characterise fatigue resistance in asphalt mixtures including the phenomenological approach, the fracture mechanics approach and the dissipated energy approach. This paper presents a comparison of fatigue resistance calculated for different dissipated energy models using 2 Point Bending (2PB) at IFSTTAR in Nantes. 2PB tests have been undertaken under different loading and environmental conditions in order to evaluate the properties of the mixtures (stiffness, dissipated energy, fatigue life and healing effect)
Axiomatic approach to radiation reaction of scalar point particles in curved spacetime
Several different methods have recently been proposed for calculating the
motion of a point particle coupled to a linearized gravitational field on a
curved background. These proposals are motivated by the hope that the point
particle system will accurately model certain astrophysical systems which are
promising candidates for observation by the new generation of gravitational
wave detectors. Because of its mathematical simplicity, the analogous system
consisting of a point particle coupled to a scalar field provides a useful
context in which to investigate these proposed methods. In this paper, we
generalize the axiomatic approach of Quinn and Wald in order to produce a
general expression for the self force on a point particle coupled to a scalar
field following an arbitrary trajectory on a curved background. Our equation
includes the leading order effects of the particle's own fields, commonly
referred to as ``self force'' or ``radiation reaction'' effects. We then
explore the equations of motion which follow from this expression in the
absence of non-scalar forces.Comment: 17 pages, 1 figur
Crystallization of two forms of a cyclodextrin inclusion complex containing a common organic guest
The isolation and structural elucidation by single crystal Xray diffraction of triclinic and monoclinic modifications of an inclusion complex of b-cyclodextrin with the same guest, methylparaben, are reported
The Transition from Inspiral to Plunge for a Compact Body in a Circular Equatorial Orbit Around a Massive, Spinning Black Hole
There are three regimes of gravitational-radiation-reaction-induced inspiral
for a compact body with mass mu, in a circular, equatorial orbit around a Kerr
black hole with mass M>>mu: (i) The "adiabatic inspiral regime", in which the
body gradually descends through a sequence of circular, geodesic orbits. (ii) A
"transition regime", near the innermost stable circular orbit (isco). (iii) The
"plunge regime", in which the body travels on a geodesic from slightly below
the isco into the hole's horizon. This paper gives an analytic treatment of the
transition regime and shows that, with some luck, gravitational waves from the
transition might be measurable by the space-based LISA mission.Comment: 8 Pages and 3 Figures; RevTeX; submitted to Physical Review
Perturbative evolution of particle orbits around Kerr black holes: time domain calculation
Treating the Teukolsky perturbation equation numerically as a 2+1 PDE and
smearing the singularities in the particle source term by the use of narrow
Gaussian distributions, we have been able to reproduce earlier results for
equatorial circular orbits that were computed using the frequency domain
formalism. A time domain prescription for a more general evolution of nearly
geodesic orbits under the effects of radiation reaction is presented. This
approach can be useful when tackling the more realistic problem of a
stellar-mass black hole moving on a generic orbit around a supermassive black
hole under the influence of radiation reaction forces.Comment: 8 pages, 5 figures, problems with references and double-printing
fixe
Pragmatic approach to gravitational radiation reaction in binary black holes
We study the relativistic orbit of binary black holes in systems with small
mass ratio. The trajectory of the smaller object (another black hole or a
neutron star), represented as a particle, is determined by the geodesic
equation on the perturbed massive black hole spacetime. The particle itself
generates the gravitational perturbations leading to a problem that needs
regularization. Here we study perturbations around a Schwarzschild black hole
using Moncrief's gauge invariant formalism. We decompose the perturbations into
multipoles to show that all metric coefficients are at the
location of the particle. Summing over , to reconstruct the full metric,
gives a formally divergent result. We succeed in bringing this sum to a
generalized Riemann's function regularization scheme and show that this
is tantamount to subtract the piece to each multipole. We
explicitly carry out this regularization and numerically compute the first
order geodesics. Application of this method to general orbits around rotating
black holes would generate accurate templates for gravitational wave laser
interferometric detectors.Comment: 5 pages, 2 figures, improved text and figures. To appear in PR
Magnetic Domain Patterns Depending on the Sweeping Rate of Magnetic Fields
The domain patterns in a thin ferromagnetic film are investigated in both
experiments and numerical simulations. Magnetic domain patterns under a zero
field are usually observed after an external magnetic field is removed. It is
demonstrated that the characteristics of the domain patterns depend on the
decreasing rate of the external field, although it can also depend on other
factors. Our numerical simulations and experiments show the following
properties of domain patterns: a sea-island structure appears when the field
decreases rapidly from the saturating field to the zero field, while a
labyrinth structure is observed for a slowly decreasing field. The mechanism of
the dependence on the field sweeping rate is discussed in terms of the concepts
of crystallization.Comment: 4 pages, 3 figure
Gravitational radiation reaction and inspiral waveforms in the adiabatic limit
We describe progress evolving an important limit of binary orbits in general
relativity, that of a stellar mass compact object gradually spiraling into a
much larger, massive black hole. These systems are of great interest for
gravitational wave observations. We have developed tools to compute for the
first time the radiated fluxes of energy and angular momentum, as well as
instantaneous snapshot waveforms, for generic geodesic orbits. For special
classes of orbits, we compute the orbital evolution and waveforms for the
complete inspiral by imposing global conservation of energy and angular
momentum. For fully generic orbits, inspirals and waveforms can be obtained by
augmenting our approach with a prescription for the self force in the adiabatic
limit derived by Mino. The resulting waveforms should be sufficiently accurate
to be used in future gravitational-wave searches.Comment: Accepted for publication in Phys. Rev. Let
A Toy Model for Testing Finite Element Methods to Simulate Extreme-Mass-Ratio Binary Systems
Extreme mass ratio binary systems, binaries involving stellar mass objects
orbiting massive black holes, are considered to be a primary source of
gravitational radiation to be detected by the space-based interferometer LISA.
The numerical modelling of these binary systems is extremely challenging
because the scales involved expand over several orders of magnitude. One needs
to handle large wavelength scales comparable to the size of the massive black
hole and, at the same time, to resolve the scales in the vicinity of the small
companion where radiation reaction effects play a crucial role. Adaptive finite
element methods, in which quantitative control of errors is achieved
automatically by finite element mesh adaptivity based on posteriori error
estimation, are a natural choice that has great potential for achieving the
high level of adaptivity required in these simulations. To demonstrate this, we
present the results of simulations of a toy model, consisting of a point-like
source orbiting a black hole under the action of a scalar gravitational field.Comment: 29 pages, 37 figures. RevTeX 4.0. Minor changes to match the
published versio
Radiation reaction and the self-force for a point mass in general relativity
A point particle of mass m moving on a geodesic creates a perturbation h, of
the spacetime metric g, that diverges at the particle. Simple expressions are
given for the singular m/r part of h and its quadrupole distortion caused by
the spacetime. Subtracting these from h leaves a remainder h^R that is C^1. The
self-force on the particle from its own gravitational field corrects the
worldline at O(m) to be a geodesic of g+h^R. For the case that the particle is
a small non-rotating black hole, an approximate solution to the Einstein
equations is given with error of O(m^2) as m approaches 0.Comment: 4 pages, RevTe
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