2,769 research outputs found
Physical Simulation of Inarticulate Robots
In this note we study the structure and the behavior of inarticulate robots.
We introduce a robot that moves by successive revolvings. The robot's structure
is analyzed, simulated and discussed in detail
Robust classification via MOM minimization
We present an extension of Vapnik's classical empirical risk minimizer (ERM)
where the empirical risk is replaced by a median-of-means (MOM) estimator, the
new estimators are called MOM minimizers. While ERM is sensitive to corruption
of the dataset for many classical loss functions used in classification, we
show that MOM minimizers behave well in theory, in the sense that it achieves
Vapnik's (slow) rates of convergence under weak assumptions: data are only
required to have a finite second moment and some outliers may also have
corrupted the dataset.
We propose an algorithm inspired by MOM minimizers. These algorithms can be
analyzed using arguments quite similar to those used for Stochastic Block
Gradient descent. As a proof of concept, we show how to modify a proof of
consistency for a descent algorithm to prove consistency of its MOM version. As
MOM algorithms perform a smart subsampling, our procedure can also help to
reduce substantially time computations and memory ressources when applied to
non linear algorithms.
These empirical performances are illustrated on both simulated and real
datasets
Synthesis of Attributed Feature Models From Product Descriptions: Foundations
Feature modeling is a widely used formalism to characterize a set of products
(also called configurations). As a manual elaboration is a long and arduous
task, numerous techniques have been proposed to reverse engineer feature models
from various kinds of artefacts. But none of them synthesize feature attributes
(or constraints over attributes) despite the practical relevance of attributes
for documenting the different values across a range of products. In this
report, we develop an algorithm for synthesizing attributed feature models
given a set of product descriptions. We present sound, complete, and
parametrizable techniques for computing all possible hierarchies, feature
groups, placements of feature attributes, domain values, and constraints. We
perform a complexity analysis w.r.t. number of features, attributes,
configurations, and domain size. We also evaluate the scalability of our
synthesis procedure using randomized configuration matrices. This report is a
first step that aims to describe the foundations for synthesizing attributed
feature models
Directional Dynamics along Arbitrary Curves in Cellular Automata
This paper studies directional dynamics in cellular automata, a formalism
previously introduced by the third author. The central idea is to study the
dynamical behaviour of a cellular automaton through the conjoint action of its
global rule (temporal action) and the shift map (spacial action): qualitative
behaviours inherited from topological dynamics (equicontinuity, sensitivity,
expansivity) are thus considered along arbitrary curves in space-time. The main
contributions of the paper concern equicontinuous dynamics which can be
connected to the notion of consequences of a word. We show that there is a
cellular automaton with an equicontinuous dynamics along a parabola, but which
is sensitive along any linear direction. We also show that real numbers that
occur as the slope of a limit linear direction with equicontinuous dynamics in
some cellular automaton are exactly the computably enumerable numbers
Constraining short-range spin-dependent forces with polarized He
We have searched for a short-range spin-dependent interaction using the spin
relaxation of hyperpolarized He. Such a new interaction would be mediated
by a hypothetical light scalar boson with \CP-violating couplings to the
neutron. The walls of the He cell would generate a pseudomagnetic field and
induce an extra depolarization channel. We did not see any anomalous spin
relaxation and we report the limit for interaction ranges between
and : , where () are the (pseudo)scalar coupling
constant, improving the previous best limit by 1 order of magnitude
Search for a new short-range spin-dependent force with polarized Helium 3
Measuring the depolarization rate of a He hyperpolarized gas is a
sensitive method to probe hypothetical short-range spin-dependent forces. A
dedicated experiment is being set up at the Institute Laue Langevin in Grenoble
to improve the sensitivity. We presented the status of the experiment at the
10th PATRAS Workshop on Axions, WIMPs and WISPs.Comment: Presented at the 10th PATRAS Workshop on Axions, WIMPs and WISP
Évaluation de la croissance et de l'activité antagoniste de pseudozyma SPP. en conditions in situ
Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2008-2009Dans cette étude, nous avons comparé le potentiel de lutte biologique et le développement de quatre espèces du genre Pseudozyma {P. antárctica, P. flocculosa, P. fusiformata et P. rugulosa), reconnues pour leur production de glycolipides aux propriétés antifongiques in vitro. Pour ce faire, nous avons d'abord généré des transformants GFP et conçu des amorces spécifiques pour chacune des espèces testées. Par la suite, nous avons pu observer ces espèces en conditions naturelles et quantifier leurs populations en temps réel, sur des feuilles saines et infectées par le blanc. Bien que Pseudozyma spp. présentent plusieurs caractéristiques similaires, seulement P. flocculosa a été en mesure de contrôler efficacement le blanc et de croître en sa présence, comme en témoigne l'augmentation constante de sa population, tel qu'observée en qRT-PCR. De tels résultats suggèrent ainsi que la production de glycolipides n'est pas le seul facteur définissant l'activité antagoniste de Pseudozyma spp. en conditions naturelles. De plus, ces résultats soulignent également la nécessité d'avoir recours à des tests in situ pour une juste évaluation du potentiel de lutte biologique d'un champignon ainsi qu'une compréhension exhaustive de son écologie, et ce toujours dans le but d'optimiser l'efficacité d'un agent de lutte biologique potentie
Description of the unsteady flow pattern from peak efficiency to near surge in subsonic centrifugal compressor stage
This paper aims to describe the flow structure modifications when the operating point moves from peak efficiency to near stall condition in a moderate pressure ratio centrifugal compressor stage consisted of a splittered unshrouded impeller and a vaned diffuser. The investigations are based on three-dimensional U-RANS simulation results. The flow is described in the impeller and in the vaned diffuser through time-averaged flow quantities and unsteady fluctuations. Results show that at low mass flow rate, the effects of secondary flow in the impeller are more pronounced, inducing both, high time-averaged values and temporal fluctuations of the flow angle near the shroud at the diffuser inlet, leading to vane suction side boundary layer separation. Pressure waves due to impeller diffuser interaction spread through the vaned diffuser generating unsteadiness which intensifies at near surge condition
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