321,437 research outputs found
Exactly-once quantity transfer
Strongly consistent systems supporting distributed transactions can be prone to high latency and do not tolerate partitions. The present trend of using weaker forms of consistency, to achieve high availability, poses notable challenges in writing applications due to the lack of linearizability, e.g., to ensure global invariants, or perform mutator operations on a distributed datatype. This paper addresses a specific problem: the exactly-once transfer of a "quantity" from one node to another on an unreliable network (coping with message duplication, loss, or reordering) and without any form of global synchronization. This allows preserving a global property (the sum of quantities remains unchanged) without requiring global linearizability and only through using pairwise interactions between nodes, therefore allowing partitions in the system. We present the novel quantity-transfer algorithm while focusing on a specific use-case: a redistribution protocol to keep the quantities in a set of nodes balanced; in particular, averaging a shared real number across nodes. Since this is a work in progress, we briefly discuss the correctness of the protocol, and we leave potential extensions and empirical evaluations for future work.This work is financed by the FCT Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within project UID/EEA/50014/2013; and by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement 609551, SyncFree project.info:eu-repo/semantics/publishedVersio
Analytic calculation of energy transfer and heat flux in a one-dimensional system
In the context of the problem of heat conduction in one-dimensional systems,
we present an analytical calculation of the instantaneous energy transfer
across a tagged particle in a one-dimensional gas of equal-mass, hard-point
particles. From this, we obtain a formula for the steady-state energy flux, and
identify and separate the mechanical work and heat conduction contributions to
it. The nature of the Fourier law for the model, and the nonlinear dependence
of the rate of mechanical work on the stationary drift velocity of the tagged
particle, are analyzed and elucidated.Comment: 17 pages including title pag
Metastable states of the Ising chain with Kawasaki dynamics
We consider a ferromagnetic Ising chain evolving under Kawasaki dynamics at
zero temperature. We investigate the statistics of the metastable
configurations in which the system gets blocked (statistics of energy, spin
correlations, distribution of domain sizes). A systematic comparison is made
with analytical predictions for the ensemble of all blocked configurations
taken with equal a priori weights (Edwards approach).Comment: 22 pages, 3 Tables, 6 Figure
Transfer-matrix scaling from disorder-averaged correlation lengths for diluted Ising systems
A transfer matrix scaling technique is developed for randomly diluted
systems, and applied to the site-diluted Ising model on a square lattice in two
dimensions. For each allowed disorder configuration between two adjacent
columns, the contribution of the respective transfer matrix to the decay of
correlations is considered only as far as the ratio of its two largest
eigenvalues, allowing an economical calculation of a configuration-averaged
correlation length. Standard phenomenological-renormalisation procedures are
then used to analyse aspects of the phase boundary which are difficult to
assess accurately by alternative methods. For magnetic site concentration
close to , the extent of exponential behaviour of the curve
is clearly seen for over two decades of variation of . Close to the
pure-system limit, the exactly-known reduced slope is reproduced to a very good
approximation, though with non-monotonic convergence. The averaged correlation
lengths are inserted into the exponent-amplitude relationship predicted by
conformal invariance to hold at criticality. The resulting exponent
remains near the pure value (1/4) for all intermediate concentrations until it
crosses over to the percolation value at the threshold.Comment: RevTeX 3, 11 pages +5 figures, uuencoded, to appear in Phys. Rev. B
(1994), PUC/RJ preprin
Kernel-phases for high-contrast detection beyond the resolution limit
The detection of high contrast companions at small angular separation appears
feasible in conventional direct images using the self-calibration properties of
interferometric observable quantities. In the high-Strehl regime, available
from space borne observatories and using AO in the mid-infrared, quantities
comparable to the closure-phase that are used with great success in
non-redundant masking inteferometry, can be extracted from direct images, even
taken with a redundant aperture. These new phase-noise immune observable
quantities, called Kernel-phases, are determined a-priori from the knowledge of
the geometry of the pupil only. Re-analysis of HST/NICMOS archive and other
ground based AO images, using this new Kernel-phase algorithm, demonstrates the
power of the method, and its ability to detect companions at the resolution
limit and beyond.Comment: 7 pages, 4 figures, 2011 SPIE conference proceeding
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