4,350 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
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
Computing the entropy of user navigation in the web
Navigation through the web, colloquially known as "surfing", is one of the main activities of users during web interaction. When users follow a navigation trail they often tend to get disoriented in terms of the goals of their original query and thus the discovery of typical user trails could be useful in providing navigation assistance. Herein, we give a theoretical underpinning of user navigation in terms of the entropy of an underlying Markov chain modelling the web topology. We present a novel method for online incremental computation of the entropy and a large deviation result regarding the length of a trail to realize the said entropy. We provide an error analysis for our estimation of the entropy in terms of the divergence between the empirical and actual probabilities. We then indicate applications of our algorithm in the area of web data mining. Finally, we present an extension of our technique to higher-order Markov chains by a suitable reduction of a higher-order Markov chain model to a first-order one
Separation of trajectories and its Relation to Entropy for Intermittent Systems with a Zero Lyapunov exponent
One dimensional intermittent maps with stretched exponential separation of
nearby trajectories are considered. When time goes infinity the standard
Lyapunov exponent is zero. We investigate the distribution of
,
where is determined by the nonlinearity of the map in the vicinity of
marginally unstable fixed points. The mean of is determined
by the infinite invariant density. Using semi analytical arguments we calculate
the infinite invariant density for the Pomeau-Manneville map, and with it
obtain excellent agreement between numerical simulation and theory. We show
that \alpha \left is equal to Krengel's entropy and
to the complexity calculated by the Lempel-Ziv compression algorithm. This
generalized Pesin's identity shows that \left and
Krengel's entropy are the natural generalizations of usual Lyapunov exponent
and entropy for these systems.Comment: 12 pages, 10 figure
Ureide Metabolism in Non-nodulated Phaseolus vulgaris L
The distribution of ureide-N was studied throughout vegetative and reproductive growth of non-nodulated Phaseolus vulgaris L. (bushbean) grown in nitrate nutrient solution. Largest increases in ureide-N per plant were correlated with flowering and early pod formation and with seed filling. Highest amounts of ureides per organ were measured in stems and axillary trifoliates. Highest concentrations (μmol ureide-N g−1 fr. wt.) were measured in young developing organs and stems. Seeds did not accumulate ureides until the ureide content of pods had reached a maximum. Results obtained using the inhibitor of xanthine oxidase, allopurinol, are consistent with the origin of ureides via purine degradation but alternative pathways cannot be discounted. Leaves and stems were shown to have the ability to degrade allantoate via an enzymic proces
Thermodynamic phase transitions for Pomeau-Manneville maps
We study phase transitions in the thermodynamic description of
Pomeau-Manneville intermittent maps from the point of view of infinite ergodic
theory, which deals with diverging measure dynamical systems. For such systems,
we use a distributional limit theorem to provide both a powerful tool for
calculating thermodynamic potentials as also an understanding of the dynamic
characteristics at each instability phase. In particular, topological pressure
and Renyi entropy are calculated exactly for such systems. Finally, we show the
connection of the distributional limit theorem with non-Gaussian fluctuations
of the algorithmic complexity proposed by Gaspard and Wang [Proc. Natl. Acad.
Sci. USA 85, 4591 (1988)].Comment: 5 page
Statistical Properties of the Final State in One-dimensional Ballistic Aggregation
We investigate the long time behaviour of the one-dimensional ballistic
aggregation model that represents a sticky gas of N particles with random
initial positions and velocities, moving deterministically, and forming
aggregates when they collide. We obtain a closed formula for the stationary
measure of the system which allows us to analyze some remarkable features of
the final `fan' state. In particular, we identify universal properties which
are independent of the initial position and velocity distributions of the
particles. We study cluster distributions and derive exact results for extreme
value statistics (because of correlations these distributions do not belong to
the Gumbel-Frechet-Weibull universality classes). We also derive the energy
distribution in the final state. This model generates dynamically many
different scales and can be viewed as one of the simplest exactly solvable
model of N-body dissipative dynamics.Comment: 19 pages, 5 figures include
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
Entropy-driven cutoff phenomena
In this paper we present, in the context of Diaconis' paradigm, a general
method to detect the cutoff phenomenon. We use this method to prove cutoff in a
variety of models, some already known and others not yet appeared in
literature, including a chain which is non-reversible w.r.t. its stationary
measure. All the given examples clearly indicate that a drift towards the
opportune quantiles of the stationary measure could be held responsible for
this phenomenon. In the case of birth- and-death chains this mechanism is
fairly well understood; our work is an effort to generalize this picture to
more general systems, such as systems having stationary measure spread over the
whole state space or systems in which the study of the cutoff may not be
reduced to a one-dimensional problem. In those situations the drift may be
looked for by means of a suitable partitioning of the state space into classes;
using a statistical mechanics language it is then possible to set up a kind of
energy-entropy competition between the weight and the size of the classes.
Under the lens of this partitioning one can focus the mentioned drift and prove
cutoff with relative ease.Comment: 40 pages, 1 figur
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