4,415 research outputs found
Scaling of the turbulence transition threshold in a pipe
We report the results of an experimental investigation of the transition to
turbulence in a pipe over approximately an order of magnitude range in . A
novel scaling law is uncovered using a systematic experimental procedure which
permits contact to be made with modern theoretical thinking. The principal
result we uncover is a scaling law which indicates that the amplitude of
perturbation required to cause transition scales as .Comment: 4 pages, RevTex (submitted to Phys. Rev. Lett.
What We Want in a Judge
This Article recognizes the current state of bankruptcy courts and the qualities that make Judge Barry Schermer a quintessential figure in adjudicating these types of cases. Mullin describes important qualities needed in a bankruptcy judge including morality and integrity, as well as versatility and predictability, among others. The Author confirms these qualities in Judge Schermer, as well the additional qualities of patience and the ability to reverse a decision he feels was incorrect
Existence of Long-Range Order for Trapped Interacting Bosons
We derive an inequality governing ``long range'' order for a localized
Bose-condensed state, relating the condensate fraction at a given temperature
with effective curvature radius of the condensate and total particle number.
For the specific example of a one-dimensional, harmonically trapped dilute Bose
condensate, it is shown that the inequality gives an explicit upper bound for
the Thomas-Fermi condensate size which may be tested in current experiments.Comment: 4 pages, 1 figure, RevTex4. Title changed at the request of editors;
to appear in Phys. Rev. Letter
Highly sensitive alkane odour sensors based on functionalised gold nanoparticles
We deposit dense, ordered, thin films of Au-dodecanethiol core/shell nanoparticles by the Langmuir-Schafer (LS) printing method, and find that their resistance at ambient temperature responds selectively and sensitively to alkane odours. Response is a rapid resistance increase due to swelling, and is strongest for alkane odours where the alkane chain is similar in length to the dodecane shell. For decane odours, we find a response to concentrations as low as 15 ppm, about 600 times below the lower explosive limit. Response is weaker, but still significant, to aromatic odours (e.g. Toluene, Xylene), while potential interferants such as polar and/or hydrogen-bonding odours (e.g. alcohols, ketones, water vapour) are somewhat rejected. Resistance is weakly dependent on temperature, and recovers rapidly and completely to its original value within the error margin of measurement. (C) 2011 Elsevier B.V. All rights reserved
Novel dynamical effects and glassy response in strongly correlated electronic system
We find an unconventional nucleation of low temperature paramagnetic metal
(PMM) phase with monoclinic structure from the matrix of high-temperature
antiferromagnetic insulator (AFI) phase with tetragonal structure in strongly
correlated electronic system . Such unconventional
nucleation leads to a decease in resistivity by several orders with relaxation
at a fixed temperature without external perturbation. The novel dynamical
process could arise from the competition of strain fields, Coulomb
interactions, magnetic correlations and disorders. Such competition may
frustrate the nucleation, giving rise to a slow, nonexponential relaxation and
"physical aging" behavior.Comment: 5 pages, 4 figure
Shear-flow transition: the basin boundary
The structure of the basin of attraction of a stable equilibrium point is
investigated for a dynamical system (W97) often used to model transition to
turbulence in shear flows. The basin boundary contains not only an equilibrium
point Xlb but also a periodic orbit P, and it is the latter that mediates the
transition. Orbits starting near Xlb relaminarize. We offer evidence that this
is due to the extreme narrowness of the region complementary to basin of
attraction in that part of phase space near Xlb. This leads to a proposal for
interpreting the 'edge of chaos' in terms of more familiar invariant sets.Comment: 11 pages; submitted for publication in Nonlinearit
Lifetime statistics in transitional pipe flow
Several experimental and numerical studies have shown that turbulent motions
in circular pipe flow near transitional Reynolds numbers may not persist
forever, but may decay. We study the properties of these decaying states within
direct numerical simulations for Reynolds numbers up to 2200 and in pipes with
lengths equal to 5, 9 and 15 times the diameter. We show that the choice of the
ensemble of initial conditions affects the short time parts of lifetime
distributions, but does not change the characteristic decay rate for long
times. Comparing lifetimes for pipes of different length we notice a linear
increase in the characteristic lifetime with length, which reproduces the
experimental results when extrapolated to 30 diameters, the length of an
equilibrium turbulent puff at these Reynolds numbers.Comment: 10 pages, 11 figure
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