Victimologie-Criminologie. Approches cliniques

Lebigot, François; Bessoles, Philippe

doi:10.3917/chaso.lebig.2005.01

Cited by 4 publications

(3 citation statements)

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“…Errors were computed analytically where possible and propagated using the 'uncertainties' Python package [46]. Alternatively, intervals of confidence were computed by bootstrap for the covariance estimation [14] and by BCa bootstrap otherwise using the 'scikit-bootstrap' Python package [22,47].…”

Section: Error Analysismentioning

confidence: 99%

Numerical test of the Edwards conjecture shows that all packings are equally probable at jamming

et al. 2017

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In the late 1980s, Sam Edwards proposed a possible statisticalmechanical framework to describe the properties of disordered granular materials 1 . A key assumption underlying the theory was that all jammed packings are equally likely. In the intervening years it has never been possible to test this bold hypothesis directly. Here we present simulations that provide direct evidence that at the unjamming point, all packings of soft repulsive particles are equally likely, even though generically, jammed packings are not. Typically, jammed granular systems are observed precisely at the unjamming point since grains are not very compressible. Our results therefore support Edwards' original conjecture. We also present evidence that at unjamming the configurational entropy of the system is maximal.In science, most breakthroughs cannot be derived from known physical laws: they are based on inspired conjectures 2 . Comparison with experiment of the predictions based on such a hypothesis allows us to eliminate conjectures that are clearly wrong. However, there is a distinction between testing the consequences of a conjecture and testing the conjecture itself. A case in point is Edwards' theory of granular media. In the late 1980s, Edwards and Oakeshott 1 proposed that many of the physical properties of granular materials ('powders') could be predicted using a theoretical framework that was based on the assumption that all distinct packings of such a material are equally likely to be observed. The logarithm of the number of such packings was postulated to play the same role as entropy does in Gibbs' statistical-mechanical description of the thermodynamic properties of equilibrium systems. However, statistical-mechanical entropy and granular entropy are very different objects. Until now, the validity of Edwards' hypothesis could not be tested directlymainly because the number of packings involved is so large that direct enumeration is utterly infeasible-and, as a consequence, the debate about the Edwards hypothesis has focused on its consequences, rather than on its assumptions. Here we present results that show that now, at last, it is possible to test Edwards' hypothesis directly by numerical simulation. To our own surprise, we find that the hypothesis appears to be correct precisely at the point where a powder is just at the (un)jamming threshold. However, at higher densities, the hypothesis fails. At the unjamming transition, the configurational entropy of jammed states appears to be at a maximum.The concept of 'ensembles' plays a key role in equilibrium statistical mechanics, as developed by J. Willard Gibbs, well over a century ago 3 . The crucial assumption that Gibbs made to arrive at a tractable theoretical framework to describe the equilibrium properties of gases, liquid and solids was that, at a fixed total energy, every state of the system is equally likely to be observed. The distinction between, say, a liquid at thermal equilibrium and a granular material is that in a liquid, atoms undergo thermal motion whereas...

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Section: Error Analysismentioning

confidence: 99%

Numerical test of the Edwards conjecture shows that all packings are equally probable at jamming

et al. 2017

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“…In the case of the SynT method with gravimetric (C 3 F 6 ) and volumetric (C 7 H 14 ) loadings, u ( n 2 ) is estimated from a function of f ( Q , ρ). The uncertainties were estimated utilizing the uncertainties package in Python 3.0 …”

Section: Experimental Uncertaintymentioning

confidence: 99%

Investigation of Synthetic and Analytic Methods for Measuring Phase Equilibria in the Hexafluoropropylene + Methylcyclohexane System

Nelson

2023

J. Chem. Eng. Data

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Isothermal vapor–liquid equilibrium data for the binary system 1,1,2,3,3,3-hexafluoro-1-propene + methylcyclohexane are presented over a temperature range of (273–313) K. Both static-synthetic and static-analytic techniques were employed. For the synthesis of binary mixtures using the synthetic technique, gravimetric, volumetric, and manometric methods were performed. Total composition data (T-P-z) were converted to phase equilibrium data (T-P-x-y) using the phase densities and the volume of the equilibrium cell. The uncertainties in the measured variables were estimated using methods outlined by the National Institute of Standards and Technology. The Peng-Robinson equation of state and the Wong-Sandler mixing rule were utilized to model the data, with the Gibbs excess energy for the mixing rule being determined using the Non-Random-Two-Liquid activity coefficient model.

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“…By implementing the transformation modules in Python, the instrument scientist has access to a large library of numerical processing facilities based on NumPy and SciPy (Oliphant, 2007) and, in particular, libraries which support propagation of uncertainties (Lebigot, 2013). The reductus library includes additional facilities for unit conversion, data rebinning, interpolation and weighted least-squares solving as well as its own simplified uncertainties package for handling large data sets.…”

Section: Operationsmentioning

confidence: 99%

reductus: a stateless Python data reduction service with a browser front end

Maranville

Ratcliff²,

Kienzle

2018

J Appl Crystallogr

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The online data reduction service reductus transforms measurements in experimental science from laboratory coordinates into physically meaningful quantities with accurate estimation of uncertainties from instrumental settings and properties. This reduction process is based on a few well known transformations, but flexibility in the application of the transforms and algorithms supports flexibility in experiment design, enabling a broader range of measurements than a rigid reduction scheme for data. The user interface allows easy construction of arbitrary pipelines from well known data transforms using a visual data flow diagram. Source data are drawn from a networked, open data repository. The Python back end uses intelligent caching to store intermediate results of calculations for a highly responsive user experience. The reference implementation allows immediate reduction of measurements as they are recorded for the three neutron reflectometry instruments at the NIST Center for Neutron Research, without the need for visiting scientists to install additional software on their own computers.

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Victimologie-Criminologie. Approches cliniques

Cited by 4 publications

References 0 publications

Numerical test of the Edwards conjecture shows that all packings are equally probable at jamming

Numerical test of the Edwards conjecture shows that all packings are equally probable at jamming

Investigation of Synthetic and Analytic Methods for Measuring Phase Equilibria in the Hexafluoropropylene + Methylcyclohexane System

reductus: a stateless Python data reduction service with a browser front end

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