4,596 research outputs found
Upstream open loop control of the recirculation area downstream of a backward-facing step
The flow downstream a backward-facing step is controlled using a pulsed jet
placed upstream of the step edge. Experimental velocity fields are computed and
used to the recirculation area quantify. The effects of jet amplitude,
frequency and duty cycle on this recirculation area are investigated for two
Reynolds numbers (Re=2070 and Re=2900). The results of this experimental study
demonstrate that upstream actuation can be as efficient as actuation at the
step edge when exciting the shear layer at its natural frequency. Moreover it
is shown that it is possible to minimize both jet amplitude and duty cycle and
still achieve optimal efficiency. With minimal amplitude and a duty-cycle as
low as 10\% the recirculation area is nearly canceled
Generic design of Chinese remaindering schemes
We propose a generic design for Chinese remainder algorithms. A Chinese
remainder computation consists in reconstructing an integer value from its
residues modulo non coprime integers. We also propose an efficient linear data
structure, a radix ladder, for the intermediate storage and computations. Our
design is structured into three main modules: a black box residue computation
in charge of computing each residue; a Chinese remaindering controller in
charge of launching the computation and of the termination decision; an integer
builder in charge of the reconstruction computation. We then show that this
design enables many different forms of Chinese remaindering (e.g.
deterministic, early terminated, distributed, etc.), easy comparisons between
these forms and e.g. user-transparent parallelism at different parallel grains
Política económica y poder político. Moneda y fisco en el reinado de Alfonso X el Sabio [Reseña]
Guillermo CASTÁN LANASPA, Política económica y poder
político. Moneda y fisco en el reinado de Alfonso X el Sabio,
Junta de Castilla y León, Consejería de
Educación y Cultura, 2000, 234 pp.
(ISBN : 84-746-95-765)
Sensitivity analysis of a branching process evolving on a network with application in epidemiology
We perform an analytical sensitivity analysis for a model of a
continuous-time branching process evolving on a fixed network. This allows us
to determine the relative importance of the model parameters to the growth of
the population on the network. We then apply our results to the early stages of
an influenza-like epidemic spreading among a set of cities connected by air
routes in the United States. We also consider vaccination and analyze the
sensitivity of the total size of the epidemic with respect to the fraction of
vaccinated people. Our analysis shows that the epidemic growth is more
sensitive with respect to transmission rates within cities than travel rates
between cities. More generally, we highlight the fact that branching processes
offer a powerful stochastic modeling tool with analytical formulas for
sensitivity which are easy to use in practice.Comment: 17 pages (30 with SI), Journal of Complex Networks, Feb 201
Reliable ABC model choice via random forests
Approximate Bayesian computation (ABC) methods provide an elaborate approach
to Bayesian inference on complex models, including model choice. Both
theoretical arguments and simulation experiments indicate, however, that model
posterior probabilities may be poorly evaluated by standard ABC techniques. We
propose a novel approach based on a machine learning tool named random forests
to conduct selection among the highly complex models covered by ABC algorithms.
We thus modify the way Bayesian model selection is both understood and
operated, in that we rephrase the inferential goal as a classification problem,
first predicting the model that best fits the data with random forests and
postponing the approximation of the posterior probability of the predicted MAP
for a second stage also relying on random forests. Compared with earlier
implementations of ABC model choice, the ABC random forest approach offers
several potential improvements: (i) it often has a larger discriminative power
among the competing models, (ii) it is more robust against the number and
choice of statistics summarizing the data, (iii) the computing effort is
drastically reduced (with a gain in computation efficiency of at least fifty),
and (iv) it includes an approximation of the posterior probability of the
selected model. The call to random forests will undoubtedly extend the range of
size of datasets and complexity of models that ABC can handle. We illustrate
the power of this novel methodology by analyzing controlled experiments as well
as genuine population genetics datasets. The proposed methodologies are
implemented in the R package abcrf available on the CRAN.Comment: 39 pages, 15 figures, 6 table
Psychologie du consommateur et comportement d'achat - mise en place et validation d'une échelle de personnalité
This paper presents the building and validation of a new personality inventory measuring 23 traits of personality and dedicated to market research applications. Validation has been realized with two consumer panels, managed by Mediametrie and BVA institute. The main objective of the research is to provide an operational and reliable instrument for marketing research studies exploring the link between consumer behavior and personality.psychology; marketing; personality inventory; consumer behavior
Les processus de décision dans un gouvernement urbain selon les Ordennances d'Ávila (1487)
Sin resume
Bibliothèques publiques : de la neutralité au pluralisme?
L\u27entretien-fleuve qui suit fera date, par la richesse et la limpidité des réflexions de l\u27inspecteur général Jean-Luc Gautier-Gentès qui, à travers la laïcité, interroge la bibliothèque publique d\u27aujourd\u27hui dans tous ses aspects identitaire, technique, humain. Ce texte a été adressé à la Commission de réflexion sur l\u27application du principe de laïcité dans la République, à la demande de son président, Bernard Stasi, médiateur de la République
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