681 research outputs found
Classification in sparse, high dimensional environments applied to distributed systems failure prediction
Network failures are still one of the main causes of distributed systemsâ lack of reliability. To overcome this problem we present an improvement over a failure prediction system, based on Elastic Net Logistic Regression and the application of rare events prediction techniques, able to work with sparse, high dimensional datasets. Specifically, we prove its stability, fine tune its hyperparameter and improve its industrial utility by showing that, with a slight change in dataset creation, it can also predict the location of a failure, a key asset when trying to take a proactive approach to failure management
Failure Detection Lower Bounds on Registers and Consensus (Preliminary Version)
This paper addresses the problem of determining the weakest failure detector to implement consensus in a message passing system when t out of n processes can crash (including when n/2 =< t < n-1), by addressing the problem of determining the weakest failure detector to implement a register. We complement and, in a precise sense, generalise previous results on the implementability of consensus and registers in a message passing model (augmented with the failure detector abstraction)
Computing the Roughening Transition of Ising and Solid-On-Solid Models by BCSOS Model Matching
We study the roughening transition of the dual of the 2D XY model, of the
Discrete Gaussian model, of the Absolute Value Solid-On-Solid model and of the
interface in an Ising model on a 3D simple cubic lattice. The investigation
relies on a renormalization group finite size scaling method that was proposed
and successfully tested a few years ago. The basic idea is to match the
renormalization group flow of the interface observables with that of the
exactly solvable BCSOS model. Our estimates for the critical couplings are
, and for
the XY-model, the Discrete Gaussian model and the Absolute Value Solid-On-Solid
model, respectively. For the inverse roughening temperature of the Ising
interface we find . To the best of our knowledge,
these are the most precise estimates for these parameters published so far.Comment: 25 pages, LaTeX file, no figure
Results from the LHC Beam Dump Reliability Run
The LHC Beam Dumping System is one of the vital elements of the LHC Machine Protection System and has to operate reliably every time a beam dump request is made. Detailed dependability calculations have been made, resulting in expected rates for the different system failure modes. A 'reliability run' of the whole system, installed in its final configuration in the LHC, has been made to discover infant mortality problems and to compare the occurrence of the measured failure modes with their calculations
Charge distribution in two-dimensional electrostatics
We examine the stability of ringlike configurations of N charges on a plane
interacting through the potential . We interpret the equilibrium distributions in terms of a shell
model and compare predictions of the model with the results of numerical
simulations for systems with up to 100 particles.Comment: LaTe
Extended Universality of the Surface Curvature in Equilibrium Crystal Shapes
We investigate the universal property of curvatures in surface models which
display a flat phase and a rough phase whose criticality is described by the
Gaussian model. Earlier we derived a relation between the Hessian of the free
energy and the Gaussian coupling constant in the six-vertex model. Here we show
its validity in a general setting using renormalization group arguments. The
general validity of the relation is confirmed numerically in the RSOS model by
comparing the Hessian of the free energy and the Gaussian coupling constant in
a transfer matrix finite-size-scaling study. The Hessian relation gives clear
understanding of the universal curvature jump at roughening transitions and
facet edges and also provides an efficient way of locating the phase
boundaries.Comment: 19 pages, RevTex, 3 Postscript Figures, To appear in Phys. Rev.
Reduction of velocity fluctuations in a turbulent flow of gallium by an external magnetic field
The magnetic field of planets or stars is generated by the motion of a
conducting fluid through a dynamo instability. The saturation of the magnetic
field occurs through the reaction of the Lorentz force on the flow. In relation
to this phenomenon, we study the effect of a magnetic field on a turbulent flow
of liquid Gallium. The measurement of electric potential differences provides a
signal related to the local velocity fluctuations. We observe a reduction of
velocity fluctuations at all frequencies in the spectrum when the magnetic
field is increased.Comment: accepted for Physical Review
Finite-size scaling and the toroidal partition function of the critical asymmetric six-vertex model
Finite-size corrections to the energy levels of the asymmetric six-vertex
model transfer matrix are considered using the Bethe ansatz solution for the
critical region. The non-universal complex anisotropy factor is related to the
bulk susceptibilities. The universal Gaussian coupling constant is also
related to the bulk susceptibilities as , being the
Hessian of the bulk free energy surface viewed as a function of the two fields.
The modular covariant toroidal partition function is derived in the form of the
modified Coulombic partition function which embodies the effect of
incommensurability through two mismatch parameters. The effect of twisted
boundary conditions is also considered.Comment: 19 pages, 5 Postscript figure files in the form of uuencoded
compressed tar fil
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