367 research outputs found
Water tunnel flow visualization using a laser
Laser systems for flow visualization in water tunnels (similar to the vapor screen technique used in wind tunnels) can provide two-dimensional cross-sectional views of complex flow fields. This parametric study documents the practical application of the laser-enhanced visualization (LEV) technique to water tunnel testing. Aspects of the study include laser power levels, flow seeding (using flourescent dyes and embedded particulates), model preparation, and photographic techniques. The results of this study are discussed to provide potential users with basic information to aid in the design and setup of an LEV system
A negative mass theorem for surfaces of positive genus
We define the "sum of squares of the wavelengths" of a Riemannian surface
(M,g) to be the regularized trace of the inverse of the Laplacian. We normalize
by scaling and adding a constant, to obtain a "mass", which is scale invariant
and vanishes at the round sphere. This is an anlaog for closed surfaces of the
ADM mass from general relativity. We show that if M has positive genus then on
each conformal class, the mass attains a negative minimum. For the minimizing
metric, there is a sharp logarithmic Hardy-Littlewood-Sobolev inequality and a
Moser-Trudinger-Onofri type inequality.Comment: 8 page
On classes of non-Gaussian asymptotic minimizers in entropic uncertainty principles
In this paper we revisit the Bialynicki-Birula & Mycielski uncertainty
principle and its cases of equality. This Shannon entropic version of the
well-known Heisenberg uncertainty principle can be used when dealing with
variables that admit no variance. In this paper, we extend this uncertainty
principle to Renyi entropies. We recall that in both Shannon and Renyi cases,
and for a given dimension n, the only case of equality occurs for Gaussian
random vectors. We show that as n grows, however, the bound is also
asymptotically attained in the cases of n-dimensional Student-t and Student-r
distributions. A complete analytical study is performed in a special case of a
Student-t distribution. We also show numerically that this effect exists for
the particular case of a n-dimensional Cauchy variable, whatever the Renyi
entropy considered, extending the results of Abe and illustrating the
analytical asymptotic study of the student-t case. In the Student-r case, we
show numerically that the same behavior occurs for uniformly distributed
vectors. These particular cases and other ones investigated in this paper are
interesting since they show that this asymptotic behavior cannot be considered
as a "Gaussianization" of the vector when the dimension increases
Quantum information entropies of the eigenstates and the coherent state of the P\"oschl-Teller potential
The position and momentum space information entropies, of the ground state of
the P\"oschl-Teller potential, are exactly evaluated and are found to satisfy
the bound, obtained by Beckner, Bialynicki-Birula and Mycielski. These
entropies for the first excited state, for different strengths of the potential
well, are then numerically obtained. Interesting features of the entropy
densities, owing their origin to the excited nature of the wave functions, are
graphically demonstrated. We then compute the position space entropies of the
coherent state of the P\"oschl-Teller potential, which is known to show revival
and fractional revival. Time evolution of the coherent state reveals many
interesting patterns in the space-time flow of information entropy.Comment: Revtex4, 11 pages, 11 eps figures and a tabl
Closure properties of solutions to heat inequalities
We prove that if are
sufficiently well-behaved solutions to certain heat inequalities on then
the function given by
also satisfies a heat inequality of a
similar type provided . On
iterating, this result leads to an analogous statement concerning -fold
convolutions. As a corollary, we give a direct heat-flow proof of the sharp
-fold Young convolution inequality and its reverse form.Comment: 12 page
Differences in Performance Decline Between Sex Under Simulated Military Operational Stress Differences In Performance Decline Between Sex Under Simulated Military Operational Stress
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Differential Responses in the Growth Hormone-Insulin-Like Growth Factor-1 Axis Following Simulated Military Operational Stress
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Normalization Removes Differences in Contractile Properties and Corticospinal Excitability Between Single- and Multi-Joint Exercises
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Impact of Operational Stress on Motor Evoked Potentials in Military Personnel
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