240 research outputs found
Tri-critical behavior in rupture induced by disorder
We discover a qualitatively new behavior for systems where the load transfer
has limiting stress amplification as in real fiber composites. We find that the
disorder is a relevant field leading to tri--criticality, separating a
first-order regime where rupture occurs without significant precursors from a
second-order regime where the macroscopic elastic coefficient exhibit power law
behavior. Our results are based on analytical analysis of fiber bundle models
and numerical simulations of a two-dimensional tensorial spring-block system in
which stick-slip motion and fracture compete.Comment: Revtex, 10 pages, 4 figures available upon reques
Rupture Pressure Prediction for Composite High Pressure Tanks Using Acoustic Emission
The French Aerospace company AEROSPATIALE manufactures high pressure tanks for helium gas storage. Because these tanks are critical elements for rockets and satellites, a new approach has been developed to have a better knowledge of the structure reliability. Although numerical tools such as finite elements codes are used for the design of such structures and. quality rules are imposed to insure that the tanks manufactured are in accordance to the definition, it is conceivable that even a successful proof test could actually damage the composite and lead to a residual SF less than 2
Scale relativity and fractal space-time: theory and applications
In the first part of this contribution, we review the development of the
theory of scale relativity and its geometric framework constructed in terms of
a fractal and nondifferentiable continuous space-time. This theory leads (i) to
a generalization of possible physically relevant fractal laws, written as
partial differential equation acting in the space of scales, and (ii) to a new
geometric foundation of quantum mechanics and gauge field theories and their
possible generalisations. In the second part, we discuss some examples of
application of the theory to various sciences, in particular in cases when the
theoretical predictions have been validated by new or updated observational and
experimental data. This includes predictions in physics and cosmology (value of
the QCD coupling and of the cosmological constant), to astrophysics and
gravitational structure formation (distances of extrasolar planets to their
stars, of Kuiper belt objects, value of solar and solar-like star cycles), to
sciences of life (log-periodic law for species punctuated evolution, human
development and society evolution), to Earth sciences (log-periodic
deceleration of the rate of California earthquakes and of Sichuan earthquake
replicas, critical law for the arctic sea ice extent) and tentative
applications to system biology.Comment: 63 pages, 14 figures. In : First International Conference on the
Evolution and Development of the Universe,8th - 9th October 2008, Paris,
Franc
A Study of the Day - Night Effect for the Super - Kamiokande Detector: I. Time Averaged Solar Neutrino Survival Probability
This is the first of two articles aimed at providing comprehensive
predictions for the day-night (D-N) effect for the Super-Kamiokande detector in
the case of the MSW \nu_e \to \numt transition solution of the solar neutrino
problem. The one-year averaged probability of survival of the solar \nue
crossing the Earth mantle, the core, the inner 2/3 of the core, and the (core +
mantle) is calculated with high precision (better than 1%) using the elliptical
orbit approximation (EOA) to describe the Earth motion around the Sun. Results
for the survival probability in the indicated cases are obtained for a large
set of values of the MSW transition parameters and
from the ``conservative'' regions of the MSW solution,
derived by taking into account possible relatively large uncertainties in the
values of the B and Be neutrino fluxes. Our results show that the
one-year averaged D-N asymmetry in the survival probability for
neutrinos crossing the Earth core can be, in the case of , larger than the asymmetry in the probability for (only mantle
crossing + core crossing) neutrinos by a factor of up to six. The enhancement
is larger in the case of neutrinos crossing the inner 2/3 of the core. This
indicates that the Super-Kamiokande experiment might be able to test the
region of the MSW solution of the solar neutrino
problem by performing selective D-N asymmetry measurements.Comment: LaTeX2e - 18 Text Pages + 21 figures = 39 Pages. - Figures in PS +
text file sk1b14.tex requires two auxiliary files (included
A Study of the Day - Night Effect for the Super-Kamiokande Detector: II. Electron Spectrum Deformations and Day - Night Asymmetries
Using the results of a high precision calculation of the solar neutrino
survival probability for Earth crossing neutrinos in the case of MSW transition solution of the solar neutrino problem, performed
in an earlier study, we derive predictions for the one-year averaged day-night
(D-N) asymmetry in the deformations of the - spectrum to be measured with
the Super - Kamiokande detector, and for the D-N asymmetry in the energy-
integrated one year signal in this detector. The asymmetries are calculated for
solar crossing the Earth mantle only, the core and the (mantle + core)
for a large representative set of values of the MSW transition parameters
and from the ``conservative'' MSW solution
region obtained by taking into account possible uncertainties in the values of
the B and Be neutrino fluxes. The effect of the uncertainties in the
value of the bulk matter density and in the chemical composition of the core,
on the D-N asymmetry predictions is discussed. It is shown, in particular, that
for the one year average D-N asymmetry for
neutrinos crossing the Earth core can be larger than the asymmetry for (only
mantle crossing + core crossing) neutrinos by a factor of up to six. Iso -
(D-N) asymmetry contours in the plane for the
Super - Kamiokande detector are derived in the region \sin^2 2\theta_v \gsim
10^{-4} for only mantle crossing, core crossing and (only mantle crossing +
core crossing) neutrinos. Our results indicate that the Super - Kamiokande
experiment might be able to test the region of the
MSW solution of the solar neutrino problem by performing selective D-N
asymmetry measurements.Comment: LaTeX, 18 pages, 3 Tables, 16 Figures in 7 postscript file
Rocky Planetesimals as the Origin of Metals in DZ Stars
{Abridged}. An analysis of the calcium and hydrogen abundances, Galactic
positions and kinematics of 146 DZ stars from the Sloan Digital Sky Survey
demonstrates that interaction with the interstellar medium cannot account for
their externally polluted atmospheres. The calcium-to-hydrogen ratios for the
37 DZA stars are dominated by super-solar values, as are the lower limits for
the remaining 109 DZ stars. All together their metal-contaminated convective
envelopes contain 10^{20+-2} g of calcium, commensurate with the masses of
calcium inferred for large asteroids. It is probable that these stars are
contaminated by circumstellar matter; the rocky remains of terrestrial
planetary systems. In this picture, two predictions emerge: 1) at least 3.5% of
all main sequence A- and F-type stars build terrestrial planets; and 2) the DZA
stars are externally polluted by both metals and hydrogen, and hence constrain
the frequency and mass of water-rich, extrasolar planetesimals.Comment: Accepted to MNRA
Dragon-kings: mechanisms, statistical methods and empirical evidence
This introductory article presents the special Discussion and Debate volume
"From black swans to dragon-kings, is there life beyond power laws?" published
in Eur. Phys. J. Special Topics in May 2012. We summarize and put in
perspective the contributions into three main themes: (i) mechanisms for
dragon-kings, (ii) detection of dragon-kings and statistical tests and (iii)
empirical evidence in a large variety of natural and social systems. Overall,
we are pleased to witness significant advances both in the introduction and
clarification of underlying mechanisms and in the development of novel
efficient tests that demonstrate clear evidence for the presence of
dragon-kings in many systems. However, this positive view should be balanced by
the fact that this remains a very delicate and difficult field, if only due to
the scarcity of data as well as the extraordinary important implications with
respect to hazard assessment, risk control and predictability.Comment: 20 page
Mantle Pb paradoxes : the sulfide solution
Author Posting. Š Springer, 2006. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Contributions to Mineralogy and Petrology 152 (2006): 295-308, doi:10.1007/s00410-006-0108-1.There is growing evidence that the budget of Pb in mantle peridotites is largely
contained in sulfide, and that Pb partitions strongly into sulfide relative to silicate melt. In
addition, there is evidence to suggest that diffusion rates of Pb in sulfide (solid or melt)
are very fast. Given the possibility that sulfide melt âwetsâ sub-solidus mantle silicates,
and has very low viscosity, the implications for Pb behavior during mantle melting are
profound. There is only sparse experimental data relating to Pb partitioning between
sulfide and silicate, and no data on Pb diffusion rates in sulfides. A full understanding of
Pb behavior in sulfide may hold the key to several long-standing and important Pb
paradoxes and enigmas. The classical Pb isotope paradox arises from the fact that all
known mantle reservoirs lie to the right of the Geochron, with no consensus as to the
identity of the âbalancingâ reservoir. We propose that long-term segregation of sulfide
(containing Pb) to the core may resolve this paradox. Another Pb paradox arises from the fact that the Ce/Pb ratio of both OIB and MORB
is greater than bulk earth, and constant at a value of 25. The constancy of this âcanonical
ratioâ implies similar partition coefficients for Ce and Pb during magmatic processes
(Hofmann et al. 1986), whereas most experimental studies show that Pb is more
incompatible in silicates than Ce. Retention of Pb in residual mantle sulfide during
melting has the potential to bring the bulk partitioning of Ce into equality with Pb if the
sulfide melt/silicate melt partition coefficient for Pb has a value of ~ 14. Modeling shows
that the Ce/Pb (or Nd/Pb) of such melts will still accurately reflect that of the source, thus
enforcing the paradox that OIB and MORB mantles have markedly higher Ce/Pb (and
Nd/Pb) than the bulk silicate earth. This implies large deficiencies of Pb in the mantle
sources for these basalts. Sulfide may play other important roles during magmagenesis:
1). advective/diffusive sulfide networks may form potent metasomatic agents (in both
introducing and obliterating Pb isotopic heterogeneities in the mantle); 2). silicate melt
networks may easily exchange Pb with ambient mantle sulfides (by diffusion or
assimilation), thus âsamplingâ Pb in isotopically heterogeneous mantle domains
differently from the silicate-controlled isotope tracer systems (Sr, Nd, Hf), with an
apparent âde-couplingâ of these systems.Our intemperance
should not be blamed on the support we gratefully acknowledge from NSF: EAR-
0125917 to SRH and OCE-0118198 to GAG
A Study of the Day - Night Effect for the \SK Detector: III. The Case of Transitions into Sterile Neutrino
Using the results of a high precision calculation of the solar neutrino
survival probability for Earth crossing neutrinos in the case of MSW transition solution of the solar neutrino problem, we derive predictions
for the one-year averaged day-night (D-N) asymmetries in the deformed
recoil- spectrum and in the energy-integrated event rate due to the solar
neutrinos, to be measured with the Super - Kamiokande detector. The asymmetries
are calculated for three event samples, produced by solar crossing the
Earth mantle only, the core, and the mantle only + the core (the full night
sample). The effects of the uncertainties in the value of the bulk matter
density and in the chemical composition of the Earth core on the predictions
for the D-N asymmetries are investigated. The dependence of the D - N effect
related observables on the threshold recoil - e- kinetic energy, TeTh, is
studied. It is shown, in particular, that for the
one year average D-N - asymmetry in the sample of events due to the
core-crossing neutrinos is larger than the asymmetry in the full night sample
typically by a factor . We find, however, that at small mixing
angles \sin^2 2 \theta_V \ltap 0.014, the D-N asymmetry in the case of solar
transitions is considerably smaller than if the transitions
were into an active neutrino, . In particular, a
precision better than 1% in the measurement of any of the three one year
averaged D-N asymmetries considered by us would be required to test the small
mixing angle nonadiabatic solution at \sin^2 2\theta_V
~\ltap ~0.01.Comment: 61 pages (28 text, 7 tables, 40 figures (26 pages)), LaTeX, for any
Comment contact [email protected], [email protected]
Benchmark numerical simulations of rarefied non-reacting gas flows using an open-source DSMC code
Validation and verification represent an important element in the development of a computational code. The aim is establish both confidence in the algorithm and its suitability for the intended purpose. In this paper, a direct simulation Monte Carlo solver, called dsmcFoam, is carefully investigated for its ability to solve low and high speed non-reacting gas flows in simple and complex geometries. The test cases are: flow over sharp and truncated flat plates, the Mars Pathfinder probe, a micro-channel with heated internal steps, and a simple micro-channel. For all the cases investigated, dsmcFoam demonstrates very good agreement with experimental and numerical data available in the literature
- âŚ