8,539 research outputs found
Thermomechanical Behavior of the HL-LHC 11 Tesla Nb3Sn Magnet Coil Constituents during Reaction Heat Treatment
The knowledge of the temperature induced changes of the superconductor
volume, and of the thermo-mechanical behaviour of the different coil and
tooling materials is required for predicting the coil geometry and the stress
distribution in the coil after the Nb3Sn reaction heat treatment. In the
present study we have measured the Young's and shear moduli of the HL-LHC 11 T
Nb3Sn dipole magnet coil and reaction tool constituents during in situ heat
cycles with the dynamic resonance method. The thermal expansion behaviours of
the coil components and of a free standing Nb3Sn wire were compared based on
dilation experiments.Comment: 6 pages, 12 figures, presented at MT25 conferenc
Dissociation of CH4 by electron impact: Production of metastable hydrogen and carbon fragments
Metastable fragments produced by electron impact excitation of CH4 have been investigated for incident electron energies from threshold to 300 eV. Only metastable hydrogen and carbon atoms were observed. Onset energies for the production of metastable hydrogen atoms were observed at electron impact energies of 22.0 + or - .5 eV, 25.5 + or - .6 eV, 36.7 + or - .6 eV and 66 + or - 3 eV, and at 26.6 + or - .6 eV for the production of metastable carbon atoms. Most of the fragments appear to have been formed in high-lying Rydberg states. The total metastable hydrogen cross section reaches a maximum value of approximately 1 X 10 to the minus 18th power sq cm at 100 eV. At the same energy, the metastable carbon cross section is 2 x 10 to the minus 19th power sq cm
Gravitational Waves from coalescing binaries: Estimation of parameters
The paper presents a statistical model which reproduces the results of Monte
Carlo simulations to estimate the parameters of the gravitational wave signal
from a coalesing binary system. The model however is quite general and would be
useful in other parameter estimation problems.Comment: LaTeX with RevTeX macros, 4 figure
Modeling Maxwell's demon with a microcanonical Szilard engine
Following recent work by Marathe and Parrondo [PRL, 104, 245704 (2010)], we
construct a classical Hamiltonian system whose energy is reduced during the
adiabatic cycling of external parameters, when initial conditions are sampled
microcanonically. Combining our system with a device that measures its energy,
we propose a cyclic procedure during which energy is extracted from a heat bath
and converted to work, in apparent violation of the second law of
thermodynamics. This paradox is resolved by deriving an explicit relationship
between the average work delivered during one cycle of operation, and the
average information gained when measuring the system's energy
Topological Entropy of Braids on the Torus
A fast method is presented for computing the topological entropy of braids on
the torus. This work is motivated by the need to analyze large braids when
studying two-dimensional flows via the braiding of a large number of particle
trajectories. Our approach is a generalization of Moussafir's technique for
braids on the sphere. Previous methods for computing topological entropies
include the Bestvina--Handel train-track algorithm and matrix representations
of the braid group. However, the Bestvina--Handel algorithm quickly becomes
computationally intractable for large braid words, and matrix methods give only
lower bounds, which are often poor for large braids. Our method is
computationally fast and appears to give exponential convergence towards the
exact entropy. As an illustration we apply our approach to the braiding of both
periodic and aperiodic trajectories in the sine flow. The efficiency of the
method allows us to explore how much extra information about flow entropy is
encoded in the braid as the number of trajectories becomes large.Comment: 19 pages, 44 figures. SIAM journal styl
Binary inspiral, gravitational radiation, and cosmology
Observations of binary inspiral in a single interferometric gravitational
wave detector can be cataloged according to signal-to-noise ratio and
chirp mass . The distribution of events in a catalog composed of
observations with greater than a threshold depends on the
Hubble expansion, deceleration parameter, and cosmological constant, as well as
the distribution of component masses in binary systems and evolutionary
effects. In this paper I find general expressions, valid in any homogeneous and
isotropic cosmological model, for the distribution with and of
cataloged events; I also evaluate these distributions explicitly for relevant
matter-dominated Friedmann-Robertson-Walker models and simple models of the
neutron star mass distribution. In matter dominated Friedmann-Robertson-Walker
cosmological models advanced LIGO detectors will observe binary neutron star
inspiral events with from distances not exceeding approximately
, corresponding to redshifts of (0.26) for
(), at an estimated rate of 1 per week. As the binary system mass
increases so does the distance it can be seen, up to a limit: in a matter
dominated Einstein-deSitter cosmological model with () that limit
is approximately (1.7) for binaries consisting of two
black holes. Cosmological tests based on catalogs of the
kind discussed here depend on the distribution of cataloged events with
and . The distributions found here will play a pivotal role in testing
cosmological models against our own universe and in constructing templates for
the detection of cosmological inspiraling binary neutron stars and black holes.Comment: REVTeX, 38 pages, 9 (encapsulated) postscript figures, uses epsf.st
Filtering post-Newtonian gravitational waves from coalescing binaries
Gravitational waves from inspiralling binaries are expected to be detected
using a data analysis technique known as {\it matched filtering.} This
technique is applicable whenever the form of the signal is known accurately.
Though we know the form of the signal precisely, we will not know {\it a
priori} its parameters. Hence it is essential to filter the raw output through
a host of search templates each corresponding to different values of the
parameters. The number of search templates needed in detecting the Newtonian
waveform characterized by three independent parameters is itself several
thousands. With the inclusion of post-Newtonian corrections the inspiral
waveform will have four independent parameters and this, it was thought, would
lead to an increase in the number of filters by several orders of
magnitude---an unfavorable feature since it would drastically slow down data
analysis. In this paper I show that by a judicious choice of signal parameters
we can work, even when the first post-Newtonian corrections are included, with
as many number of parameters as in the Newtonian case. In other words I
demonstrate that the effective dimensionality of the signal parameter space
does not change when first post-Newtonian corrections are taken into account.Comment: 5 pages, revtex, 2 figures available upon reques
The Cosmological Constant and Advanced Gravitational Wave Detectors
Interferometric gravitational wave detectors could measure the frequency
sweep of a binary inspiral [characterized by its chirp mass] to high accuracy.
The observed chirp mass is the intrinsic chirp mass of the binary source
multiplied by , where is the redshift of the source. Assuming a
non-zero cosmological constant, we compute the expected redshift distribution
of observed events for an advanced LIGO detector. We find that the redshift
distribution has a robust and sizable dependence on the cosmological constant;
the data from advanced LIGO detectors could provide an independent measurement
of the cosmological constant.Comment: 13 pages plus 5 figure, LaTeX. Revised and final version, to appear
in Phys. Rev.
Observations of Unsteady Airfoil Flows
http://deepblue.lib.umich.edu/bitstream/2027.42/96610/1/39015087358597.pd
Crustal Oscillations of Slowly Rotating Relativistic Stars
We study low-amplitude crustal oscillations of slowly rotating relativistic
stars consisting of a central fluid core and an outer thin solid crust. We
estimate the effect of rotation on the torsional toroidal modes and on the
interfacial and shear spheroidal modes. The results compared against the
Newtonian ones for wide range of neutron star models and equations of state.Comment: 15 page
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