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The relationship between charge distribution, charge packet formation and electroluminescence in XLPE under DC
Different reports describing the internal distribution of space charge in cross-linked polyethylene (XLPE) under DC field have been published recently. The most striking fact observed is the organization of the space charge into charge packets that cross the insulation. All models for charge packet formation imply that carrier recombination will occur. As the recombination region is potentially a luminescence one it is of interest to record the electroluminescence in this regime. This topic is addressed in this paper
Error-correcting code on a cactus: a solvable model
An exact solution to a family of parity check error-correcting codes is
provided by mapping the problem onto a Husimi cactus. The solution obtained in
the thermodynamic limit recovers the replica symmetric theory results and
provides a very good approximation to finite systems of moderate size. The
probability propagation decoding algorithm emerges naturally from the analysis.
A phase transition between decoding success and failure phases is found to
coincide with an information-theoretic upper bound. The method is employed to
compare Gallager and MN codes.Comment: 7 pages, 3 figures, with minor correction
Lâ -estimates in optimal transport for non quadratic costs
For cost functions c(x, y) = h(x- y) , with hâ C2(Rn\ { 0 }) â© C1(Rn) homogeneous of degree p> 1 , we show Lâ-estimates of Tx- x on balls, where T is an h-monotone map. Estimates for the interpolating mappings Tt= t(T- I) + I are deduced from this
A microscopic description of the aging dynamics: fluctuation-dissipation relations, effective temperature and heterogeneities
We consider the dynamics of a diluted mean-field spin glass model in the
aging regime. The model presents a particularly rich heterogeneous behavior. In
order to catch this behavior, we perform a **spin-by-spin analysis** for a
**given disorder realization**. The results compare well with the outcome of a
static calculation which uses the ``survey propagation'' algorithm of Mezard,
Parisi, and Zecchina [Sciencexpress 10.1126/science.1073287 (2002)]. We thus
confirm the connection between statics and dynamics at the level of single
degrees of freedom. Moreover, working with single-site quantities, we can
introduce a new response-vs-correlation plot, which clearly shows how
heterogeneous degrees of freedom undergo coherent structural rearrangements.
Finally we discuss the general scenario which emerges from our work and
(possibly) applies to more realistic glassy models. Interestingly enough, some
features of this scenario can be understood recurring to thermometric
considerations.Comment: 4 pages, 5 figures (7 eps files
Analyses of shocked quartz at the global K-P boundary indicate an origin from a single, high-angle, oblique impact at Chicxulub
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Characterizing HV XLPE cables by electrical, chemical and microstructural measurements on cable peeling: Effects of surface roughness, thermal treatment and peeling location
Characterization of the electrical, chemical, and microstructural properties of high voltage cables was the first step of the European project âARTEMISâ, which has the aim of investigating degradation processes and constructing aging models for the diagnosis of cross-linked polyethylene (XLPE) cables. Cables produced by two different manufacturers were subjected to a large number of electrical, microstructural, and chemical characterizations, using cable peelings, instead of lengths of whole cables, as specimens for the measurements. Here the effect of surface deformation and roughness due to peeling and the relevance and significance of thermal pre-treatment prior to electrical and other measurements is discussed. Special emphasis is put on space charge, conduction current and luminescence measurements. We also consider the dependence of these properties on the spatial position of the specimen within the cable. It is shown that even though the two faces of the cable peel specimens have different roughness, the low-field electrical properties seem quite insensitive to surface roughness, while significant differences are detectable at high fields. Thermal pre-treatment is required to stabilize the insulating material to enable us to obtain reproducible results and reliable inter-comparisons throughout the whole project. The spatial position of the specimens along the cable radius can also have a non-negligible influence on the measured properties, due to differential microstructure and chemical composition
The GRB Variability/Peak Luminosity Correlation: new results
We report test results of the correlation between time variability and peak
luminosity of Gamma-Ray Bursts (GRBs), using a larger sample (32) of GRBs with
known redshift than that available to Reichart et al. (2001), and using as
variability measure that introduced by these authors. The results are puzzling.
Assuming an isotropic-equivalent peak luminosity, as done by Reichart et al.
(2001), a correlation is still found, but it is less relevant, and inconsistent
with a power law as previously reported. Assuming as peak luminosity that
corrected for GRB beaming for a subset of 16 GRBs with known beaming angle, the
correlation becomes little less significant.Comment: 11 pages, 10 figures, MNRAS, accepte
Probing the diffusive behaviour of beam-halo dynamics in circular accelerators
Circular particle accelerators at the energy frontier are based on superconducting magnets that are extremely sensitive to beam losses as these might induce quenches, i.e. transitions to the normal-conducting state. Furthermore, the energy stored in the circulating beam is so large that hardware integrity is put in serious danger, and machine protection becomes essential for reaching the nominal accelerator performance. In this challenging context, the beam halo becomes a potential source of performance limitations and its dynamics needs to be understood in detail to assess whether it could be an issue for the accelerator. In this paper, we discuss in detail a recent framework, based on a diffusive approach, to model beam-halo dynamics. The functional form of the optimal estimate of the perturbative series, as given by Nekhoroshevâs theorem, is used to provide the functional form of the action diffusion coefficient. The goal is to propose an effective model for the beam-halo dynamics and to devise an efficient experimental procedure to obtain an accurate measurement of the diffusion coefficient
Cavity method for quantum spin glasses on the Bethe lattice
We propose a generalization of the cavity method to quantum spin glasses on
fixed connectivity lattices. Our work is motivated by the recent refinements of
the classical technique and its potential application to quantum computational
problems. We numerically solve for the phase structure of a connectivity
transverse field Ising model on a Bethe lattice with couplings, and
investigate the distribution of various classical and quantum observables.Comment: 27 pages, 9 figure
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