3,444 research outputs found
Effect of sweep angle on the pressure distributions and effectiveness of the ogee tip in diffusing a line vortex
Low-speed wind tunnel tests were conducted to study the influence of sweep angle on the pressure distributions of an ogee-tip configuration with relation to the effectiveness of the ogee tip in diffusing a line vortex. In addition to the pressure data, performance and flow-visualization data were obtained in the wind tunnel tests to evaluate the application of the ogee tip to aircraft configurations. The effect of sweep angle on the performance characteristics of a conventional-tip model, having equivalent planform area, was also investigated for comparison with the ogee-tip configuration. Results of the investigation generally indicate that sweep angle has little effect on the characteristics of the ogee in diffusing a line vortex
Small violations of full correlation Bell inequalities for multipartite pure random states
We estimate the probability of random -qudit pure states violating
full-correlation Bell inequalities with two dichotomic observables per site.
These inequalities can show violations that grow exponentially with , but we
prove this is not the typical case. For many-qubit states the probability to
violate any of these inequalities by an amount that grows linearly with is
vanishingly small. If each system's Hilbert space dimension is larger than two,
on the other hand, the probability of seeing \emph{any} violation is already
small. For the qubits case we discuss furthermore the consequences of this
result for the probability of seeing arbitrary violations (\emph i.e., of any
order of magnitude) when experimental imperfections are considered.Comment: 16 pages, one colum
Coal desulfurization by low temperature chlorinolysis, phase 1
The reported activity covers laboratory scale experiments on twelve bituminous, sub-bituminous and lignite coals, and preliminary design and specifications for bench-scale and mini-pilot plant equipment
Transient Random Walks in Random Environment on a Galton-Watson Tree
We consider a transient random walk in random environment on a
Galton--Watson tree. Under fairly general assumptions, we give a sharp and
explicit criterion for the asymptotic speed to be positive. As a consequence,
situations with zero speed are revealed to occur. In such cases, we prove that
is of order of magnitude , with . We also
show that the linearly edge reinforced random walk on a regular tree always has
a positive asymptotic speed, which improves a recent result of Collevecchio
\cite{Col06}
Critical behavior in a cross-situational lexicon learning scenario
The associationist account for early word-learning is based on the
co-occurrence between objects and words. Here we examine the performance of a
simple associative learning algorithm for acquiring the referents of words in a
cross-situational scenario affected by noise produced by out-of-context words.
We find a critical value of the noise parameter above which learning
is impossible. We use finite-size scaling to show that the sharpness of the
transition persists across a region of order about ,
where is the number of learning trials, as well as to obtain the
learning error (scaling function) in the critical region. In addition, we show
that the distribution of durations of periods when the learning error is zero
is a power law with exponent -3/2 at the critical point
Fractal time random walk and subrecoil laser cooling considered as renewal processes with infinite mean waiting times
There exist important stochastic physical processes involving infinite mean
waiting times. The mean divergence has dramatic consequences on the process
dynamics. Fractal time random walks, a diffusion process, and subrecoil laser
cooling, a concentration process, are two such processes that look
qualitatively dissimilar. Yet, a unifying treatment of these two processes,
which is the topic of this pedagogic paper, can be developed by combining
renewal theory with the generalized central limit theorem. This approach
enables to derive without technical difficulties the key physical properties
and it emphasizes the role of the behaviour of sums with infinite means.Comment: 9 pages, 7 figures, to appear in the Proceedings of Cargese Summer
School on "Chaotic dynamics and transport in classical and quantum systems
Similarity transformations approach for a generalized Fokker-Planck equation
By using similarity transformations approach, the exact propagator for a
generalized one-dimensional Fokker-Planck equation, with linear drift force and
space-time dependent diffusion coefficient, is obtained. The method is simple
and enables us to recover and generalize special cases studied through the Lie
algebraic approach and the Green function technique.Comment: 8 pages, no figure
Non-Markovian dynamics for bipartite systems
We analyze the appearance of non-Markovian effects in the dynamics of a
bipartite system coupled to a reservoir, which can be described within a class
of non-Markovian equations given by a generalized Lindblad structure. A novel
master equation, which we term quantum Bloch-Boltzmann equation, is derived,
describing both motional and internal states of a test particle in a quantum
framework. When due to the preparation of the system or to decoherence effects
one of the two degrees of freedom is amenable to a classical treatment and not
resolved in the final measurement, though relevant for the interaction with the
reservoir, non-Markovian behaviors such as stretched exponential or power law
decay of coherences can be put into evidence.Comment: published version, 15 pages, revtex, no figure
Levy distribution in many-particle quantum systems
Levy distribution, previously used to describe complex behavior of classical
systems, is shown to characterize that of quantum many-body systems. Using two
complimentary approaches, the canonical and grand-canonical formalisms, we
discovered that the momentum profile of a Tonks-Girardeau gas, -- a
one-dimensional gas of impenetrable (hard-core) bosons, harmonically
confined on a lattice at finite temperatures, obeys Levy distribution. Finally,
we extend our analysis to different confinement setups and demonstrate that the
tunable Levy distribution properly reproduces momentum profiles in
experimentally accessible regions. Our finding allows for calibration of
complex many-body quantum states by using a unique scaling exponent.Comment: 7 pages, 6 figures, results are generalized, new examples are adde
Subordination model of anomalous diffusion leading to the two-power-law relaxation responses
We derive a general pattern of the nonexponential, two-power-law relaxation
from the compound subordination theory of random processes applied to anomalous
diffusion. The subordination approach is based on a coupling between the very
large jumps in physical and operational times. It allows one to govern a
scaling for small and large times independently. Here we obtain explicitly the
relaxation function, the kinetic equation and the susceptibility expression
applicable to the range of experimentally observed power-law exponents which
cannot be interpreted by means of the commonly known Havriliak-Negami fitting
function. We present a novel two-power relaxation law for this range in a
convenient frequency-domain form and show its relationship to the
Havriliak-Negami one.Comment: 5 pages; 3 figures; corrected versio
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