901 research outputs found
Effects of non-universal large scales on conditional structure functions in turbulence
We report measurements of conditional Eulerian and Lagrangian structure
functions in order to assess the effects of non-universal properties of the
large scales on the small scales in turbulence. We study a 1m 1m
1.5m flow between oscillating grids which produces
while containing regions of nearly homogeneous and highly inhomogeneous
turbulence. Large data sets of three-dimensional tracer particle velocities
have been collected using stereoscopic high speed cameras with real-time image
compression technology. Eulerian and Lagrangian structure functions are
measured in both homogeneous and inhomogeneous regions of the flow. We
condition the structure functions on the instantaneous large scale velocity or
on the grid phase. At all scales, the structure functions depend strongly on
the large scale velocity, but are independent of the grid phase. We see clear
signatures of inhomogeneity near the oscillating grids, but even in the
homogeneous region in the center we see a surprisingly strong dependence on the
large scale velocity that remains at all scales. Previous work has shown that
similar correlations extend to very high Reynolds numbers. Comprehensive
measurements of these effects in a laboratory flow provide a powerful tool for
assessing the effects of shear, inhomogeneity and intermittency of the large
scales on the small scales in turbulence
The equation of state for two flavor QCD at N_t=6
We calculate the two flavor equation of state for QCD on lattices with
lattice spacing a=(6T)^{-1} and find that cutoff effects are substantially
reduced compared to an earlier study using a=(4T)^{-1}. However, it is likely
that significant cutoff effects remain. We fit the lattice data to expected
forms of the free energy density for a second order phase transition at
zero-quark-mass, which allows us to extrapolate the equation of state to m_q=0
and to extract the speed of sound. We find that the equation of state depends
weakly on the quark mass for small quark mass.Comment: 24 pages, latex, 11 postscipt figure
Whistles as potential indicators of stress in bottlenose dolphins (Tursiops truncatus
We examined the possibility that parameters of bottlenose dolphin signature whistles may serve as indicators of stress. Bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida, were recorded during brief capturerelease events, which are potentially a source of short-term stress to these dolphins, although no effects of chronic or long-term stress have been observed over the 37+-year duration of the research. Whistles recorded during both brief capture-release and undisturbed, free-ranging conditions were examined to determine whether whistle parameters differ during capture-release versus undisturbed conditions; at the beginning of a capturerelease session versus at the end of a session; during an individual's 1st capture-release session versus later capture-release sessions; and when a mother is caught and released with a dependent calf versus without a dependent calf (i.e., she has no dependent calf at the time of capture-release). We examined a variety of acoustic parameters, including whistle rate, number of loops (repetitive elements), maximum and minimum frequency, and loop, interloop, and whistle duration. We found that whistle rate and number of loops were greater during brief capture-release events than during undisturbed conditions; number of loops decreased and loop duration increased over the duration of a capture-release session; whistle rates decreased with number of capture-release sessions; and females caught and released with dependent calves produced whistles with higher maximum frequencies and shorter interloop intervals than when they did not have dependent calves. Thus, whistles appear to have potential as noninvasive indicators of stress in bottlenose dolphins. Further research is warranted in this area, for example by correlating physiological indices to whistle rates under varying levels of stress. Reliable, noninvasive correlates of stress could be used to monitor dolphins in a variety of circumstances, such as during exposure to anthropogenic noise
Proposed initiative would study Earth's weathering engine
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94818/1/eost14765.pd
Quenched hadron spectroscopy with improved staggered quark action
We investigate light hadron spectroscopy with an improved quenched staggered
quark action. We compare the results obtained with an improved gauge plus an
improved quark action, an improved gauge plus standard quark action, and the
standard gauge plus standard quark action. Most of the improvement in the
spectroscopy results is due to the improved gauge sector. However, the improved
quark action substantially reduces violations of Lorentz invariance, as
evidenced by the meson dispersion relations.Comment: New references adde
Hurst's Rescaled Range Statistical Analysis for Pseudorandom Number Generators used in Physical Simulations
The rescaled range statistical analysis (R/S) is proposed as a new method to
detect correlations in pseudorandom number generators used in Monte Carlo
simulations. In an extensive test it is demonstrated that the RS analysis
provides a very sensitive method to reveal hidden long run and short run
correlations. Several widely used and also some recently proposed pseudorandom
number generators are subjected to this test. In many generators correlations
are detected and quantified.Comment: 12 pages, 12 figures, 6 tables. Replaces previous version to correct
citation [19
Two-Flavor Staggered Fermion Thermodynamics at N_t = 12
We present results of an ongoing study of the nature of the high temperature
crossover in QCD with two light fermion flavors. These results are obtained
with the conventional staggered fermion action at the smallest lattice spacing
to date---approximately 0.1 fm. Of particular interest are a study of the
temperature of the crossover a determination of the induced baryon charge and
baryon susceptibility, the scalar susceptibility, and the chiral order
parameter, used to test models of critical behavior associated with chiral
symmetry restoration. From our new data and published results for N_t = 4, 6,
and 8, we determine the QCD magnetic equation of state from the chiral order
parameter using O(4) and mean field critical exponents and compare it with the
corresponding equation of state obtained from an O(4) spin model and mean field
theory. We also present a scaling analysis of the Polyakov loop, suggesting a
temperature dependent ``constituent quark free energy.''Comment: LaTeX 25 pages, 15 Postscript figure
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