51,665 research outputs found
Inference and Optimization of Real Edges on Sparse Graphs - A Statistical Physics Perspective
Inference and optimization of real-value edge variables in sparse graphs are
studied using the Bethe approximation and replica method of statistical
physics. Equilibrium states of general energy functions involving a large set
of real edge-variables that interact at the network nodes are obtained in
various cases. When applied to the representative problem of network resource
allocation, efficient distributed algorithms are also devised. Scaling
properties with respect to the network connectivity and the resource
availability are found, and links to probabilistic Bayesian approximation
methods are established. Different cost measures are considered and algorithmic
solutions in the various cases are devised and examined numerically. Simulation
results are in full agreement with the theory.Comment: 21 pages, 10 figures, major changes: Sections IV to VII updated,
Figs. 1 to 3 replace
Asymptotic properties of eigenmatrices of a large sample covariance matrix
Let where is a matrix
with i.i.d. complex standardized entries having finite fourth moments. Let
in which
and where
is the Mar\v{c}enko--Pastur law with parameter ; which
converges to a positive constant as , and and are unit vectors in ,
having indices and , ranging in a compact subset
of a finite-dimensional Euclidean space. In this paper, we prove that the
sequence converges weakly to a
-dimensional Gaussian process. This result provides further evidence in
support of the conjecture that the distribution of the eigenmatrix of is
asymptotically close to that of a Haar-distributed unitary matrix.Comment: Published in at http://dx.doi.org/10.1214/10-AAP748 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Myocardial fibrosis in stroke survivors
Stroke survivors are most likely to die of cardiac death, yet few undergo comprehensive cardiac assessment to look for reversible causes. Myocardial fibrosis (MF) is not only the hallmark of cardiomyopathy, but also a substrate for sudden cardiac death, ventricular tachyarrhythmia and heart failure. Procollagen carboxyl-terminal telopeptide (PICP) was found to be a marker of MF. The relationship between PICP and cardiac abnormalities in stroke survivors is unknown. We recently showed that MF in stroke survivors can be treated by spironolactone and amiloride in a randomised placebo-controlled cross-over study with reduction in PICP levels and QTc [1]
Diversity and Adaptation in Large Population Games
We consider a version of large population games whose players compete for
resources using strategies with adaptable preferences. The system efficiency is
measured by the variance of the decisions. In the regime where the system can
be plagued by the maladaptive behavior of the players, we find that diversity
among the players improves the system efficiency, though it slows the
convergence to the steady state. Diversity causes a mild spread of resources at
the transient state, but reduces the uneven distribution of resources in the
steady state.Comment: 8 pages, 3 figure
Ignition characterization of LOX/hydrocarbon propellants
The results of an evaluation of the ignition characteristics of the gaseous oxygen (Gox)/Ethanol propellant combination are presented. Ignition characterization was accomplished through the analysis, design, fabrication and testing of a spark initiated torch igniter and prototype 620 lbF thruster/igniter assembly. The igniter was tested over a chamber pressure range of 74 to 197 psia and mixture ratio range of 0.778 to 3.29. Cold (-92 to -165 F) and ambient (44 to 80 F) propellant temperatures were used. Spark igniter ignition limits and thruster steady state and pulse mode, performance, cooling and stability data are presented. Spark igniter ignition limits are presented in terms of cold flow pressure, ignition chamber diameter and mixture ratio. Thruster performance is presented in terms of vacuum specific impulse versus engine mixture ratio. Gox/Ethanol propellants were shown to be ignitable over a wide range of mixture ratios. Cold propellants were shown to have a minor effect on igniter ignition limits. Thruster pulse mode capability was demonstrated with multiple pulses of 0.08 sec duration and less
Models of Financial Markets with Extensive Participation Incentives
We consider models of financial markets in which all parties involved find
incentives to participate. Strategies are evaluated directly by their virtual
wealths. By tuning the price sensitivity and market impact, a phase diagram
with several attractor behaviors resembling those of real markets emerge,
reflecting the roles played by the arbitrageurs and trendsetters, and including
a phase with irregular price trends and positive sums. The positive-sumness of
the players' wealths provides participation incentives for them. Evolution and
the bid-ask spread provide mechanisms for the gain in wealth of both the
players and market-makers. New players survive in the market if the
evolutionary rate is sufficiently slow. We test the applicability of the model
on real Hang Seng Index data over 20 years. Comparisons with other models show
that our model has a superior average performance when applied to real
financial data.Comment: 17 pages, 16 figure
Melt-growth dynamics in CdTe crystals
We use a new, quantum-mechanics-based bond-order potential (BOP) to reveal
melt-growth dynamics and fine-scale defect formation mechanisms in CdTe
crystals. Previous molecular dynamics simulations of semiconductors have shown
qualitatively incorrect behavior due to the lack of an interatomic potential
capable of predicting both crystalline growth and property trends of many
transitional structures encountered during the melt crystal
transformation. Here we demonstrate successful molecular dynamics simulations
of melt-growth in CdTe using a BOP that significantly improves over other
potentials on property trends of different phases. Our simulations result in a
detailed understanding of defect formation during the melt-growth process.
Equally important, we show that the new BOP enables defect formation mechanisms
to be studied at a scale level comparable to empirical molecular dynamics
simulation methods with a fidelity level approaching quantum-mechanical method
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