1,009 research outputs found
A plausible method for fatigue life prediction of boats in a data scarce environment
Within the marine world many boats are constructed from composite materials, that useclassification society rules to predict their strength. As these vessels age, fatigue and remaining lifetime are of considerable interest to owners and operators. This paper seeks to identify an appropriate S-N curve and produce an example lifetime calculation
Dynamic study of adhesively bonded double lap composite joints
Composite structures may be subjected to high loading rates in naval applications.Hence, the composite assemblyâs dynamic behaviour needs investigation. This paperpresents an investigation on the structural rate dependent behaviour of adhesivelybounded double lap joints. High rate tests showed ringing in the force/displacementcurves. An attempt was made to determine the origins of this phenomenon
US Office of Naval Research, Solid Mechanics Program Review
The purpose of this extended abstract is to provide an overview of activities relating to performance assessments. The work described is wide ranging and not intended to provide a detailed account of any particular approach
Probing the QCD Equation of State
We propose a novel quasiparticle interpretation of the equation of state of
deconfined QCD at finite temperature. Using appropriate thermal masses, we
introduce a phenomenological parametrisation of the onset of confinement in the
vicinity of the phase transition. Lattice results of bulk thermodynamic
quantities are well reproduced, the extension to small quark chemical potential
is also successful. We then apply the model to dilepton production and charm
suppression in ultrarelativistic heavy-ion collisions.Comment: 6 pages, 8 figures. Invited talk presented by R. A. Schneider at the
XVI International Conference on Particles and Nuclei (PANIC02), Osaka, Japan,
September 30 - October 4, 200
The traveling salesman problem on cubic and subcubic graphs
We study the traveling salesman problem (TSP) on the metric completion of cubic and subcubic graphs, which is known to be NP-hard. The problem is of interest because of its relation to the famous 4/3-conjecture for metric TSP, which says that the integrality gap, i.e., the worst case ratio between the optimal value of a TSP instance and that of its linear programming relaxation (the subtour elimination relaxation), is 4/3. We present the first algorithm for cubic graphs with approximation ratio 4/3. The proof uses polyhedral techniques in a surprising way, which is of independent interest. In fact we prove constructively that for any cubic graph on TeX vertices a tour of length TeX exists, which also implies the 4/3-conjecture, as an upper bound, for this class of graph-TSP. Recently, Mömke and Svensson presented an algorithm that gives a 1.461-approximation for graph-TSP on general graphs and as a side result a 4/3-approximation algorithm for this problem on subcubic graphs, also settling the 4/3-conjecture for this class of graph-TSP. The algorithm by Mömke and Svensson is initially randomized but the authors remark that derandomization is trivial. We will present a different way to derandomize their algorithm which leads to a faster running time. All of the latter also works for multigraphs
From QCD lattice calculations to the equation of state of quark matter
We describe two-flavor QCD lattice data for the pressure at finite
temperature and zero chemical potential within a quasiparticle model. Relying
only on thermodynamic selfconsistency, the model is extended to nonzero
chemical potential. The results agree with lattice calculations in the region
of small chemical potential.Comment: 5 eps figure
Phases of QCD, Thermal Quasiparticles and Dilepton Radiation from a Fireball
We calculate dilepton production rates from a fireball adapted to the
kinematical conditions realized in ultrarelativistic heavy ion collisions over
a broad range of beam energies. The freeze-out state of the fireball is fixed
by hadronic observables. We use this information combined with the initial
geometry of the collision region to follow the space-time evolution of the
fireball. Assuming entropy conservation, its bulk thermodynamic properties can
then be uniquely obtained once the equation of state (EoS) is specified. The
high-temperature (QGP) phase is modelled by a non-perturbative quasiparticle
model that incorporates a phenomenological confinement description, adapted to
lattice QCD results. For the hadronic phase, we interpolate the EoS into the
region where a resonance gas approach seems applicable, keeping track of a
possible overpopulation of the pion phase space. In this way, the fireball
evolution is specified without reference to dilepton data, thus eliminating it
as an adjustable parameter in the rate calculations. Dilepton emission in the
QGP phase is then calculated within the quasiparticle model. In the hadronic
phase, both temperature and finite baryon density effects on the photon
spectral function are incorporated. Existing dilepton data from CERES at 158
and 40 AGeV Pb-Au collisions are well described, and a prediction for the
PHENIX setup at RHIC for sqrt(s) = 200 AGeV is given.Comment: 31 pages, 15 figures, final versio
Band structure and reflectance for a nonlinear one-dimensional photonic crystal
We consider a model for a one-dimensional photonic crystal formed by a
succession of Kerr-type equidistant spaceless interfaces immersed in a linear
medium. We calculate the band structure and reflectance of this structure as a
function of the incident wave intensity, and find two main behaviors: the
appearance of prohibited bands, and the separation and narrowing of these
bands. A system with these features is obtained by alternating very thin slabs
of a soft matter material with thicker solid films, which can be used to design
a device to control light propagation for specific wavelength intervals and
light intensities.Comment: 6 pages, 6 figure
Quasi-particle model for lattice QCD: quark-gluon plasma in heavy ion collisions
We propose a quasi-particle model to describe the lattice QCD equation of
state for pure SU(3) gauge theory in its deconfined state, for .
The method involves mapping the interaction part of the equation of state to an
effective fugacity of otherwise non-interacting quasi-gluons. We find that this
mapping is exact. Using the quasi-gluon distribution function, we determine the
energy density and the modified dispersion relation for the single particle
energy, in which the trace anomaly is manifest. As an application, we first
determine the Debye mass, and then the important transport parameters, {\it
viz}, the shear viscosity, and the shear viscosity to entropy density
ratio, . We find that both and
are sensitive to the interactions, and that the interactions significantly
lower both and .Comment: 10 pages, 8 figures, epj class file, version accepted for publication
in Euro. Phys.J
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