Cyclicity in ℓp\ell^p spaces and zero sets of the Fourier transforms

We study the cyclicity of vectors $u$ in $\ell^p(\mathbb{Z})$. It is known that a vector $u$ is cyclic in $\ell^2(\mathbb{Z})$ if and only if the zero set, $\mathcal{Z}(\widehat{u})$, of its Fourier transform, $\widehat{u}$, has Lebesgue measure zero and $\log |\widehat{u}| \not \in L^1(\mathbb{T})$, where $\mathbb{T}$ is the unit circle. Here we show that, unlike $\ell^2(\mathbb{Z})$, there is no characterization of the cyclicity of $u$ in $\ell^p(\mathbb{Z})$, $1<p<2$, in terms of $\mathcal{Z}(\widehat{u})$ and the divergence of the integral $\int\_\mathbb{T} \log |\widehat{u}|$. Moreover we give both necessary conditions and sufficient conditions for $u$ to be cyclic in $\ell^p(\mathbb{Z})$, $1<p<2$.Comment: Australian Journal of Mathematical Analysis and Applications, Austral Internet Publishing, A Para{\^i}tr

Enaction-Based Artificial Intelligence: Toward Coevolution with Humans in the Loop

This article deals with the links between the enaction paradigm and artificial intelligence. Enaction is considered a metaphor for artificial intelligence, as a number of the notions which it deals with are deemed incompatible with the phenomenal field of the virtual. After explaining this stance, we shall review previous works regarding this issue in terms of artifical life and robotics. We shall focus on the lack of recognition of co-evolution at the heart of these approaches. We propose to explicitly integrate the evolution of the environment into our approach in order to refine the ontogenesis of the artificial system, and to compare it with the enaction paradigm. The growing complexity of the ontogenetic mechanisms to be activated can therefore be compensated by an interactive guidance system emanating from the environment. This proposition does not however resolve that of the relevance of the meaning created by the machine (sense-making). Such reflections lead us to integrate human interaction into this environment in order to construct relevant meaning in terms of participative artificial intelligence. This raises a number of questions with regards to setting up an enactive interaction. The article concludes by exploring a number of issues, thereby enabling us to associate current approaches with the principles of morphogenesis, guidance, the phenomenology of interactions and the use of minimal enactive interfaces in setting up experiments which will deal with the problem of artificial intelligence in a variety of enaction-based ways

A multi-step assembly process: drawing, flanging and hemming of metallic sheets

International audienceThis paper presents hemming tests on complex geometries, combining curved surfaces and radii of curvature in the plane. The samples are firstly prestrained in order to obtain a strain history prior to flanging and hemming. The choice of the sample geome-tries as well as prior plastic strains is based on a survey of current geometries hemmed in automotive doors. A device has been designed to hem these samples both by classical and roll-hemming processes and to allow a comparison between both technologies. Roll-in, which characterizes the change of geometry of the hemmed zone between flanging and hemming, and loads are obtained during this multistep process. Results show that roll-in observed in roll-hemming is lower than in classical hemming and that its evolution greatly differs between the two processes. The analysis of the results on different samples shows that it is difficult to establish rules on the variation of other parameters in such a complex multistep process and that it requires an intensive use of numerical simulation

Occurrence and numerical prediction of surface defects during flanging of metallic sheets

International audienceSurface defects can develop on automotive exterior panels after drawing and flanging steps, during springback and may alter significantly the vehicle quality. These defects are characterized by a small depth below 0.5 mm and are then difficult to detect numerically. This study focuses on the surface defects for two parts: an industrial upper corner of a front door and a L-shaped part designed on purpose to reproduce at a small scale surface defects that occur after flanging. Dimensions of these defects are measured from profiles obtained either with a non-contacting method or a tridimensional measuring machine. Numerical simulations of the processes are performed with the commercial codes PamStamp2G or Abaqus and deformed meshes are analyzed in the same way as the experimental data. There is a good correlation between experiments and simulations concerning the spatial position of the defect and their dimensions. Moreover, a buckling analysis during springback is performed for the L-shaped part, showing that the position of the defect corresponds to one of the buckling mode

Influence of prestrain on the numerical simulation of the roller hemming process

International audienceThis study focuses on the numerical simulation of roller hemming of an aluminium alloy sample with a curved geometry; this non-planar geometry is obtained by a prestrain procedure similar to deep drawing process. Material characterization was performed through tensile and simple shear tests at different orientations on the sheet plane. The influence of considering the Bauschinger effect, anisotropy, and the strain history on the final geometry was studied. A specific laboratory device for roller hemming was designed to forward an experimental database. The numerical simulation of the roller hemming of these samples is presented here, as well as the correlation between the calculations and the experimental tests, notably the roll-in value and the prediction of wrinkling

Analyse multi-niveaux de l’activité en situation de formation : proposition méthodologique pour une étude synchronique et diachronique

Cette contribution propose de rendre compte d’une méthodologie de construction des données empiriques issue de l’articulation entre l’approche sociotechnique des environnements de formation (Albero, 2010a/b/c) et le cadre théorique et méthodologique du cours d’action (Theureau, 2006, 2015), dans le cadre d’une analyse de l’activité en situation de formation. Cette articulation a pour but de comprendre l’activité des formateurs et des apprenants dans une perspective diachronique et synchronique, en s’intéressant à l’influence de la dimension sociale, matérielle et symbolique de l’environnement de formation sur l’activité et ses transformations successives.This paper proposes to give a report of the methodology of construction of empirical data based on a structuring of the social-technical approach (Albero, 2010a/b/c) and the theoretical framework of the course of action (Theureau, 2006, 2015), as part of an analysis of activity in training situation. This structuring aims to understand the activity of trainers and learners in a diachronic and synchronic perspective, interesting in the effect of social, material and symbolic dimension of training environment on activity and successive transformations

Rethinking paradigms for studying mechanisms of action of plant bioactives

Many foods in our diets such as berries, tea, chocolate and wine contain flavonoids, which are natural components of plants. A substantial body of evidence supports the role of flavonoids in providing protection against cardio-metabolic diseases and disorders. Despite the nearly exponential growth in flavonoid research in the past 20 years, limited progress has been made in understanding how these dietary components work. Research initially focused on their antioxidant activity without taking into account their metabolism, which now appears extensive. This has provided a new research impetus to understand the biological activity of the flavonoid metabolites. Here, we outline recent research, which suggests a highly complex interplay between metabolism, intestinal microflora, the immune system and various tissues of our body

Crystal plasticity and phenomenological approaches for the simulation of deformation behavior in thin copper alloy sheets

In the expanding context of device miniaturization, forming processes of ultra thin sheet metals are gaining importance. Numerical simulation of these processes requires accurate material modeling. In this study, both the phenomenological modeling approach and the crystal plasticity finite element method (CPFEM) are considered. Theoretical definitions of both models, numerical implementation as well as their parameter identification procedures are outlined. Subsequently they are compared on a one to one basis, mainly with regards to their ability to predict mechanical responses for a variety of strain loading paths.Agence Nationale de la Recherche, ANR-12-RMNP-0009-0

Polyphenol levels in human urine after intake of six different polyphenol-rich beverages

Dietary polyphenols are suggested to participate in the prevention of CVD and cancer. It is essential for epidemiological studies to be able to compare intake of the main dietary polyphenols in populations. The present paper describes a fast method suitable for the analysis of polyphenols in urine, selected as potential biomarkers of intake. This method is applied to the estimation of polyphenol recovery after ingestion of six different polyphenol-rich beverages. Fifteen polyphenols including mammalian lignans (enterodiol and enterolactone), several phenolic acids (chlorogenic, caffeic, m-coumaric, gallic, and 4-Omethylgallic acids), phloretin and various flavonoids (catechin, epicatechin, quercetin, isorhamnetin, kaempferol, hesperetin, and naringenin) were simultaneously quantified in human urine by HPLC coupled with electrospray ionisation mass-MS (HPLC-electrospray-tandem mass spectrometry) with a run time of 6 min per sample. The method has been validated with regard to linearity, precision, and accuracy in intra- and inter-day assays. It was applied to urine samples collected from nine volunteers in the 24 h following consumption of either green tea, a grape-skin extract, cocoa beverage, coffee, grapefruit juice or orange juice. Levels of urinary excretion suggest that chlorogenic acid, gallic acid, epicatechin, naringenin or hesperetin could be used as specific biomarkers to evaluate the consumption of coffee, wine, tea or cocoa, and citrus juices respectively