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We assess a variant of linear-response range-separated time-dependent density-functional theory (TDDFT), combining a long-range Hartree-Fock (HF) exchange kernel with a short-range adiabatic exchange-correlation kernel in the local-density approximation (LDA) for calculating isotropic C6 dispersion coefficients of homodimers of a number of closed-shell atoms and small molecules. This range-separated TDDFT tends to give underestimated C6 coefficients of small molecules with a mean absolute percentage error of about 5%, a slight improvement over standard TDDFT in the adiabatic LDA which tends to overestimate them with a mean absolute percentage error of 8%, but close to time-dependent Hartree-Fock which has a mean absolute percentage error of about 6%. These results thus show that introduction of long-range HF exchange in TDDFT has a small but beneficial impact on the values of C6 coefficients. It also confirms that the present variant of range-separated TDDFT is a reasonably accurate method even using only a LDA-type density functional and without adding an explicit treatment of long-range correlation.
A predictive model of the Falcon enhanced gravity separator has been derived from a physical analysis of its separation principle, and validated against experimental data. After summarizing the previous works that led to this model and the hypotheses on which they rely, the model is extended to cover a wide range of operating conditions and particle properties. The most significant development presented here is the extension of the analytical law to concentrated suspensions, which makes it applicable to actual plant operating conditions. Two examples of industrial use cases are described and studied by interrogation of the model: dredged sediment waste reduction and coal recovery from fine tailings. Comparisons with empirical studies available in the literature show a good agreement between model predictions and industrial data. The model is then used to identify separation efficiency limitations as well as possible solutions to overcome them. These two examples serve to show how this predictive model can be used to obtain valuable information to improve physical separation processes using a Falcon concentrator, or to evaluate Falcon separator's abilities for new applications.
A series of novel organically templated metal sulfates, [C(5)H(14)N(2)][M(II)(H(2)O)(6)](SO(4))(2) with (M(II) = Mn (1), Fe (2), Co (3) and Ni (4)), have been successfully synthesized by slow evaporation and characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, thermogravimetric analysis and magnetic measurements. All compounds were prepared using a racemic source of the 2-methylpiperazine and they crystallized in the monoclinic systems, P2(1)/n for (1, 3) and P2(1)/c for (2,4). Crystal data are as follows: [C(5)H(14)N(2)][Mn(H(2)O)(6)](SO(4))(2), a = 6.6385(10) Å, b = 11.0448(2) Å, c = 12.6418(2) Å, β = 101.903(10)°, V = 906.98(3) Å(3), Z = 2; [C(5)H(14)N(2)][Fe(H(2)O)(6)](SO(4))(2), a = 10.9273(2) Å, b = 7.8620(10) Å, c = 11.7845(3) Å, β = 116.733(10)°, V = 904.20(3) Å(3), Z = 2; [C(5)H(14)N(2)][Co(H(2)O)(6)](SO(4))(2), a = 6.5710(2) Å, b = 10.9078(3) Å, c = 12.5518(3) Å, β = 101.547(2)°, V = 881.44(4) Å(3), Z = 2; [C(5)H(14)N(2)][Ni(H(2)O)(6)](SO(4))(2), a = 10.8328(2) Å, b = 7.8443(10) Å, c = 11.6790(2) Å, β = 116.826(10)°, V = 885.63(2) Å(3), Z = 2. The three-dimensional structure networks for these compounds consist of isolated [M(II)(H(2)O)(6)](2+) and [C(5)H(14)N(2)](2+) cations and (SO(4))(2-) anions linked by hydrogen-bonds only. The use of racemic 2-methylpiperazine results in crystallographic disorder of the amines and creation of inversion centers. The magnetic measurements indicate that the Mn complex (1) is paramagnetic, while compounds 2, 3 and 4, (M(II) = Fe, Co, Ni respectively) exhibit single ion anisotropy.
We present a mathematical study of the order book as a multidimensional continuous- time Markov chain where the order ow is modeled by independent Poisson processes. Our aim is to bridge the gap between the microscopic description of price formation (agent- based modeling), and the Stochastic Di erential Equations approach used classically to describe price evolution at macroscopic time scales. To do this, we rely on the theory of in nitesimal generators and Foster-Lyapunov stability criteria for Markov chains. We motivate our approach using an elementary example where the spread is kept constant (\perfect market making"). Then we compute the in nitesimal generator associated with the order book in a general setting, and link the price dynamics to the instantaneous state of the order book. In the last section, we prove that the order book is ergodic| in particular it has a stationary distribution|that it converges to its stationary state exponentially fast, and that the large-scale limit of the price process is a Brownian motion.
In this paper, we consider a discrete time economy where we assume that the short term interest rate follows a quadratic term structure of a regime switching asset process. The possible non-linear structure and the fact that the interest rate can have different economic or financial trends justify the interest of Regime Switching Quadratic Term Structure Model (RS-QTSM). Indeed, this regime switching process depends on the values of a Markov chain with a time dependent transition probability matrix which can well captures the different states (regimes) of the economy. We prove that under this modelling that the conditional zero coupon bond price admits also a quadratic term structure. Moreover, the stochastic coefficients which appear in this decomposition satisfy an explicit system of coupled stochastic backward recursions.
In this note, we cast a Hawkes process-based order book model into a markovian setting, and using techniques from the theory of Markov chains and stochastic stability [16], show that the order book is stable and leads to a di usive price limit at large time scales.
This work describes and evaluates a novel interactive visual clustering system. It combines a 2D projection with a clustering algorithm that operates on this projected data. Users can interact directly through the 2D representation, by providing examples according to their expert ground truth. Each interaction incrementally updates the 2D projection and the associated clustering. Experiments show the effectiveness of the method, with as few as one interaction leading to a tangible influence on the visualization.
Super-resolution (SR) aims at combining a number of aliased images of the same scene into a higher resolution image by using the difference in sampling caused by camera motion. As the problem of SR is generally ill-posed, techniques developed in the literature often rely on hypotheses on the regularity of the image. In this paper, we try to minimize these assumptions for the interpolation part of super-resolution. We describe situations where super-resolution interpolation is invertible and/or well conditioned. We first study the interpolation problem for large numbers of images when motions are pure translations. Then, we look at the more generic problem of super-resolution interpolation with translations and rotations. We give a simple condition on the number of images and zoom factor for perfect recovery of the high resolution image. We also study the conditioning in the critical case and propose regularization methods which adapts to local sampling variations. Thus, we avoid the generation of artifacts when the acquired data is noisy.
In this paper, we revisit the view based security framework for XML without imposing any of the previously considered restrictions on the class of queries, the class of DTDs, and the type of annotations used to define the view. First, we study {\em query rewriting} with views when the classes used to define queries and views are Regular XPath and MSO. Next, we investigate problems of {\em static analysis} of security access specifications (SAS): we introduce the novel class of \emph{interval-bounded} SAS and we define three different manners to compare views (i.e. queries), with a security point of view. We provide a systematic study of the complexity for deciding these three comparisons, when the depth of the XML documents is bounded, when the document may have an arbitrary depth but the queries defining the views are restricted to guarantee the interval-bounded property, and in the general setting without restriction on queries and document.
We present two extended forms of Fisher information that fit well in the context of nonextensive thermostatistics. We show that there exists an interplay between these generalized Fisher information, the generalized $q$-Gaussian distributions and the $q$-entropies. The minimum of the generalized Fisher information among distributions with a fixed moment, or with a fixed $q$-entropy is attained, in both cases, by a generalized $q$-Gaussian distribution. This complements the fact that the $q$-Gaussians maximize the $q$-entropies subject to a moment constraint, and yields new variational characterizations of the generalized $q$-Gaussians. We show that the generalized Fisher information naturally pop up in the expression of the time derivative of the $q$-entropies, for distributions satisfying a certain nonlinear heat equation. This result includes as a particular case the classical de Bruijn identity. Then we study further properties of the generalized Fisher information and of their minimization. We show that, though non additive, the generalized Fisher information of a combined system is upper bounded. In the case of mixing, we show that the generalized Fisher information is convex for $q\geq1.$ Finally, we show that the minimization of the generalized Fisher information subject to moment constraints satisfies a Legendre structure analog to the Legendre structure of thermodynamics.
We study the asymptotic behavior of the maximum likelihood estimator corresponding to the observation of a trajectory of a Skew Brownian motion, through a uniform time discretization. We characterize the speed of convergence and the limiting distribution when the step size goes to zero, which in this case are non-classical, under the null hypothesis of the Skew Brownian motion being an usual Brownian motion. This allows to design a test on the skewness parameter. We show that numerical simulations that can be easily performed to estimate the skewness parameter, and provide an application in Biology.
Using an approach recently developed by Nourdin and Poly, we improve the rate in an inequality for the total variation distance between two double Wiener-Itô integrals originally due to Davydov and Martynova. An application to the rate of convergence of a functional of a correlated two-dimensional fractional Brownian motion towards the Rosenblatt random variable is then given, following a previous study by Maejima and Tudor.
The selective laser melting process (SLM), belonging to the family of additive manufacturing processes, can create complex geometry parts from a CAD file. Previously, only prototypes were created by SLM, but now this process is used to manufacture quickly and directly functional parts. For example, in the PEP (Centre Technique de la Plasturgie), this process is used to manufacture tooling parts or injection molds with cooling channels that can't be obtained by conventional routes. During the process, the laser beam generates violent heating and cooling cycles in the material inducing important thermal gradients in the consolidated part. The cyclic thermal expansions and contractions exceeding the maximum elastic strain of the material induce heterogeneous plastic strains and generate internal stresses the level of which can reaches the yield stress of the material and cracks may appear during the process. This paper deals with the measurement and analysis of residual stresses during the selective laser melting of a simple part in maraging steel. The objective of this study is the analysis of experimental results to validate the numerical model previously presented in [1]. A new method is proposed to evaluate the residual stresses induced during the SLM process, a rosette is fixed on the bottom face of the support. The residual stresses in the created part are calculated from strain and temperature variations when the fused layer is consolidating during the cooling between two layers. Process parameters like the powder thickness or the cooling time between successive layers are studied in this paper.
Selective laser melting (SLM) first developed for rapid prototyping (RP) is now used for rapid manufacturing of parts with inner complex shapes that cannot be made by more conventional routes. For example, production of injection moulds with cooling channels is of special interest. In this paper, a numerical model of SLM process was investigated to simulate the genesis of residual stresses. The proposed numerical modelling is based upon a double meshing with a multi-step birth and death technique of manufactured part. The influence of the mesh size is analysed with element as small as the powder layer thickness for 2D and 3D geometries of simple parts. Comparisons between plane stress, plane strain, and 3D analysis are presented in order to propose a simplified approach.
We derive an exact formula for the complex frequency in spatio-temporal stability analysis that is valid for arbitrary complex wave numbers. The usefulness of the formula lies in the fact that it depends only on purely temporal quantities, which are easily calculated. We apply the formula to two model dispersion relations: the linearized complex Ginzburg-Landau equation, and a model of wake instability. In the first case, a quadratic truncation of the exact formula applies; in the second, the same quadratic truncation yields an estimate of the parameter values at which the transition to absolute instability occurs; the error in the estimate decreases upon increasing the order of the truncation. We outline ways in which the formula can be used to characterize stability results obtained from purely numerical calculations, and point to a further application in global stability analyses.
Self-potential (SP) data are of interest to vadose zone hydrology because of their direct sensitivity to water flow and ionic transport. There is unfortunately little consensus in the literature about how to best model SP data under partially saturated conditions and different approaches (often supported by one laboratory data set alone) have been proposed. We argue herein that this lack of agreement can largely be traced to electrode effects that have not been properly taken into account. A series of drainage and imbibition experiments are considered, in which we find that previously proposed approaches to remove electrode effects are unlikely to provide adequate corrections. Instead, we explicitly model the electrode effects together with classical SP contributions using a flow and transport model. The simulated data agree overall with the observed SP signals and allow decomposing the different signal contributions to analyze them separately. By reviewing other published experimental data, we suggest that most of them include electrode effects that have not been properly taken into account. Our results suggest that previously presented SP theory works well when considering the modeling uncertainties presently associated with electrode effects. Additional work is warranted to not only develop suitable electrodes for laboratory experiments, but also to assure that associated electrode effects that appear inevitable in longer-term experiments are predictable, such that they can be incorporated in the modeling framework.
Bioturbation is known to stimulate microbial communities, especially in macrofaunal burrows where the abundance and activities of bacteria are increased. Until now, these microbial communities have been poorly characterized and an important ecological question remains: do burrow walls harbor similar or specific communities compared with anoxic and surface sediments? The bacterial community structure of coastal sediments inhabited by the polychaete worm Hediste diversicolor was investigated. Surface, burrow wall and anoxic sediments were collected at the Carteau beach (Gulf of Fos, Mediterranean Sea). Bacterial diversity was determined by analyzing small subunit ribosomal RNA (16S rRNA) sequences from three clone libraries (168, 179 and 129 sequences for the surface, burrow wall and anoxic sediments, respectively). Libraries revealed 306 different operational taxonomic units (OTUs) belonging to at least 15 bacterial phyla. Bioinformatic analyses and comparisons between the three clone libraries showed that the burrow walls harbored a specific bacterial community structure which differed from the surface and anoxic environments. More similarities were nevertheless found with the surface assemblage. Inside the burrow walls, the bacterial community was characterized by high biodiversity, which probably results from the biogeochemical heterogeneity of the burrow system. (C) 2011 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.
The fate of ingested eukaryotic photoautotrophic fatty acids during gut transit in the lugwormArenicolamarina (L.) and the influence of A. marina's faeces on the evolution of fatty acid distribution and bacterial community structure in superficial sediments were studied under laboratory conditions. Dead phytoplanktonic cells (food portions) were fed to individual A. marina and subsequently incubated, or allowed to directly incubate in the presence of fresh egesta or non-ingested sediment. Changes in fatty acid composition and genetic structure of bacterial communities during gut transit and/or incubation were monitored using gas-chromatography/mass-spectrometry and a DNA fingerprint approach (RISA), respectively. Results, supported by principal component analyses, suggest that A. marina's feeding activity can directly and indirectly affect the lipid biomarker composition and the bacterial community structure of inhabited sediments. Faecal casts produced fromfood portions appeared qualitatively enriched in saturated fatty acids relative to (poly)unsaturated ones due, partly, to an increase of some bacterial fatty acids and to the preferential removal of some polyunsaturated fatty acids (PUFAs). The incubation of food portions in the presence of fresh A. marina's egesta (designed to study the indirect impact of feeding by A. marina) induced a significant increase in the concentrations of C20 and C22 polyunsaturated fatty acids (PUFAs), whereas these compounds almost disappeared following direct feeding and subsequent incubation, indicating that some dietary fatty acidsmay be more accessible to biodegradation following passage through the gut of A. marina. The aforementioned increase in PUFAs was attributed to a bacterial production during incubation, suggesting the presence of PUFA-producing bacteria in the fresh egesta of A. marina. Those bacteria were either enteric bacteria thatwere releasedwith the egesta or ingested bacteria that have survived gut passage, as suggested by the variations of the bacterial community structure (i.e. RISA profiles) during incubation. The results suggest that aged faeces from A. marina might be, in some circumstances, of relatively high nutritional value to trophic levels which are unable to synthesize essential PUFAs de novo. The presence of PUFA-producing bacteria in guts of marine lugworms deserves further attention.
An improved Lozi function with alternate coefficients has been proposed. The modifications in the model allow to remove the holes in the attractor which are not desirable, but appeared in the previous Lozi function; in this way, an everywhere dense attractor can be obtained. Moreover, the strong sensitivity to the type of binarisation (conversion of real values to 0 and 1) has been demonstrated; this conversion to binary numbers is instrumental to apply the NIST tests for randomness. The results have been validated and compared via NIST tests, for the different methods of quantization. Finally, is has been verfied that the multi-random properties of the output signal have been improved thanks to the following strategies : under-sampling of the output signal, and the system order increasing. Keywords. Nonlinear dynamical system, ring-coupled map, Lozi function, NIST tests, discrete-time map, dense chaotic attractor, pseudo random number generator 1 I
The extreme characteristics of long wave run-up are studied in this paper. First we give a brief overview of the existing theory which is mainly based on the hodograph transformation (Carrier & Greenspan, 1958). Then, using numerical simulations, we build on the work of Stefanakis et al. (2011) for an infinite sloping beach and we find that resonant run-up amplification of monochromatic waves is robust to spectral perturbations of the incoming wave and resonant regimes do exist for certain values of the frequency. In the setting of a finite beach attached to a constant depth region, resonance can only be observed when the incoming wavelength is larger than the distance from the undisturbed shoreline to the seaward boundary. Wavefront steepness is also found to play a role in wave run-up, with steeper waves reaching higher run-up values.
The water wave theory traditionally assumes the fluid to be perfect, thus neglecting all effects of the viscosity. However, the explanation of several experimental data sets requires the explicit inclusion of dissipative effects. In order to meet these practical problems, the theory of visco-potential flows has been developed (see P.-F. Liu & A. Orfila (2004) and D. Dutykh & F. Dias (2007)). Then, usually this formulation is further simplified by developing the potential in an entire series in the vertical coordinate and by introducing thus, the long wave approximation. In the present study we propose a derivation of dissipative Boussinesq equations which is based on asymptotic expansions of the Dirichlet-to-Neumann (D2N) operator. Both employed methods yield the same system by different ways.
Les tâches d'empan de mémoire de travail sont des tâches dans lesquelles des items doivent être maintenus en mémoire à court terme pendant qu'un traitement concurrent est effectué. Le but de la présente étude était de déterminer si, comme le soutient le modèle de partage temporel des ressources (Barrouillet, Bernardin, & Camos, 2004), les traitements gênent le maintien parce que les deux composantes entrent en compétition pour des processus communs ou plus simplement parce que les stratégies de maintien des items à rappeler sont perturbées par l'intrusion de l'information à traiter simultanément. Quatre-vingt sujets adultes étaient soumis à une tâche d'empan où ils devaient maintenir des lettres en même temps qu'ils devaient juger soit de la parité soit de la position spatiale de nombre présentés successivement à l'écran. Par ailleurs, ces nombres apparaissaient à un rythme régulier et donc prévisible ou bien aléatoire. Conformément à nos attentes, et contrairement à l'hypothèse d'une perturbation des stratégies de maintien, les jugements de parité qui nécessitent des récupérations en mémoire entraînaient de plus faibles empans que la tâche spatiale qui ne requiert qu'une sélection de réponse alors que le rythme de réalisation de la tâche secondaire n'avait pas d'effet sur les empans.
The functional organization of the PFC from anterior to posterior regions reflects a hierarchy of cognitive control whereby progressively anterior sub-regions are associated with higher-order control. The present study aimed at providing behavioral evidence for two predictions issuing from this cascade model. First, even the lower-most sub-part of the cognitive control hierarchy, i.e. motor programming, should interfere with higher controlled processes such as maintenance in working memory. Second, this effect should be commensurate with the time during which control is required. In a computer-paced complex span task, adults had to maintain letters while they performed a secondary task. The demand imposed by this task was manipulated either at the selection or at the motor programming stage of response preparation. Results revealed that both manipulations have a disruptive effect on verbal memory, and that this effect is commensurate with the extra-time during which response selection and motor programming require cognitive control.
Memorizing is crucial for human beings because it constitutes the fundamental step in acquiring knowledge. Among the different memory systems, the one called "working memory" works continuously to simultaneously memorize and process information. It is particularly important in children who are continually confronted to learning situations. It has long been considered that memorizing required verbalizing and repeating. The present paper offers an alternative conception: working memory relies on attentional mechanisms constrained by time and do not depend on verbal characteristics. The empirical analyses we present here do not only conduct to important theoretical conclusions, they also give a glimpse of practical applications for preventing school failure.
La sécurité sanitaire pour les fruits et légumes frais est depuis une vingtaine d’années une préoccupation majeure pour les consommateurs et les gouvernements, notamment ceux du Nord de l’Europe. Notre étude s’intéresse au contrôle de la sécurité sanitaire pour les filières de légumes frais. Elle précise notamment comment s’organisent ces filières pour se conformer aux standards privés de la grande distribution et ainsi pouvoir accéder aux marchés d’exportation et aux marchés nationaux dits modernes. La plupart des travaux traitant de l’adoption de référentiels certifiés de bonnes pratiques agricoles ou de techniques de protection intégrée ne prennent pas en compte l’organisation de la filière et les interactions entre les acteurs de cette filière. Pour pallier ce manque, l’article analyse l’influence des relations verticales en se basant sur la Théorie des Coûts de Transaction. Plus précisément, on considère les incitations et les procédures de gestion mises en ½oeuvre par les stations de conditionnement pour contrôler les producteurs et gérer le risque lié aux pesticides. Deux enquêtes ont été réalisées dans la région du Souss-Massa-Draâ au Maroc. La première considère trente stations spécialisées en tomate. Elle fournit des résultats contrastés quant à l’hypothèse selon laquelle, plus la filière est intégrée et plus le contrôle est réalisé à travers une supervision directe, et moins à travers la mise en ½uvre d’un système incitatif. La seconde enquête considère 86 producteurs. Elle confirme que les filières les plus intégrées sont les plus efficaces en termes de protection des investissements spécifiques dans la production raisonnée. L’adoption de la lutte biologique et des référentiels de bonnes pratiques agricoles est ainsi plus importante lorsque les serres sont détenues par des stations privées, plutôt que par des producteurs indépendants des stations. / Fresh produce pesticide safety risk has grown into a major concern of North European consumers and governments for the last twenty years. Our study expands on safety control issues and gives insights into how fresh vegetable chains organize to comply with retail private safety standards and thus get access to export and modern domestic markets. Most studies on the adoption of good agricultural practice certifications and integrated pest management overlook the influence of food chain organization. Building on Transaction Cost Economics, our paper aims to fill this gap by studying the influence of vertical linkages, more precisely the incentives and managerial procedures crafted by packing stations in order to control farmers' behavior and manage the pesticide safety risk. Two surveys have been conducted to that purpose in the Moroccan Souss-Massa-Draâ region. Our first survey of thirty tomato packers provides only mixed results about our first hypothesis: that the more the supply chain is integrated (from contracted growers to full ownership) the more the control of pesticide safety risk is achieved through direct supervision rather than outcome-based incentives. Our second survey of 86 producers confirms that integrated chains are more efficient in safeguarding specific investments in safety management, which results in greater diffusion of biocontrol and good agricultural practice certification within the greenhouses that are owned by private packers rather than independent farmers.
In Southern France, where most wildfires occur, the fire size has never exceeded 6744 ha since 1991, whereas mega-fires have burned huge areas in other Mediterranean countries such as Spain and Portugal. It was interesting to find out what main factors drove the ignition of the largest fires that had occurred in this region of France. The study was carried out using the forest fires database Prométhée that records all fires occurring in the 15 départements of Southern France since 1973. However, the records preceding 1997 are not reliable, only the 1997–2010 period was investigated. Less than 1% of the fires (N = 260) recorded during this period were equal or larger than 100 ha whereas 78% of the fires were smaller than 1 ha. However these large fires accounted for 78% of the burned area and 66% of these fires occurred during the summer (July–August). The number of large fires and the burned area per year and per département were calculated and the proportions of fires causes were determined. In each département, the impact of different explanatory variables (land-cover, topographic, climatic or socio-economic) on the number of large fires and on the size of the burned area was investigated using multivariate and regression analyses. Results showed that high shrubland and pasture covers, high population and minor road densities as well as dryness in fall to spring were positively linked to the number of large fires whereas high forest cover, ruggedness, wetness in fall to spring were negatively linked to this parameter. High wildland vegetation cover, especially shrubland, wetness in fall–winter, dryness in summer during a long period, high unemployment rate and tourism pressure were positively linked to the burned area whereas wetness in summer, high farmland and pasture covers and high population density were negatively linked to this parameter. However, only shrubland cover and ruggedness were significant descriptors of both fire occurrence and burned area. The départements the most affected by such fires were those situated in the eastern part of the region, on the Mediterranean coast and the main fire cause was arson
Dans un contexte de pression urbaine et de déprise agricole, les interfaces habitat-forêt se multiplient en France méditerranéenne et deviennent une véritable préoccupation pour la gestion des territoires et du risque d'incendie de forêt. Dans le département des Bouches-du-Rhône, les chercheurs d'Irstea ont utilisé la méthodologie de cartographie diachronique pour y mesurer le développement spatio-temporel de ces espaces afin d'aider les décideurs à cibler les priorités d'actions de prévention.
Incluye reseña de Pedro de PADILLA. La verdadera historia y admirable suceso del Segundo Cerco de Diu. Estudios de Hélio J. S. ALVES, Marsha SWISLOCKI y Lara VILÀ; edición de José J. LABRADOR HERRAIZ y Ralph A. DIFRANCO. México, Frente de Afirmación Hispanista, A. C., 2011. 571 p.
une présentation réflexive et critique du dispositif Graines d'explorateurs (équipe ACCES, IFÉ-ENS de Lyon)
Les transitions démographiques du XXe siècle sont distinctes des transitions européennes antérieures. Nous analysons ici les différentes transitions démographiques en Amérique latine. Puis, dans une seconde partie, nous observons les tendances démographiques des pays arabes, notamment ceux d'Afrique du Nord, et nous montrons dans quelle mesure ils présentent des évolutions similaires ou différentes de celles des pays latino-américains. En Amérique latine, on observe dans les dernières décennies une augmentation très significative des unions libres se formant à des âges jeunes. En Afrique du Nord, c'est à la fois l'élévation de l'âge au mariage et la contraception qui expliquent la baisse de la fécondité. Une différence majeure avec l'Amérique latine est l'absence de conceptions hors mariage dans les pays du Maghreb et les autres pays arabes. Dans les deux régions, on observe le malthusianisme de pauvreté.
Super-resolution (SR) aims at combining a number of aliased images of the same scene into a higher resolution image by using the difference in sampling caused by camera motion. As the problem of SR is generally ill-posed, techniques developed in the literature often rely on hypotheses on the regularity of the image. In this paper, we try to minimize these assumptions for the interpolation part of super-resolution. We describe situations where super-resolution interpolation is invertible and/or well conditioned. We first study the interpolation problem for large numbers of images when motions are pure translations. Then, we look at the more generic problem of super-resolution interpolation with translations and rotations. We give a simple condition on the number of images and zoom factor for perfect recovery of the high resolution image. We also study the conditioning in the critical case and propose regularization methods which adapts to local sampling variations. Thus, we avoid the generation of artifacts when the acquired data is noisy.
The selective laser melting process (SLM), belonging to the family of additive manufacturing processes, can create complex geometry parts from a CAD file. Previously, only prototypes were created by SLM, but now this process is used to manufacture quickly and directly functional parts. For example, in the PEP (Centre Technique de la Plasturgie), this process is used to manufacture tooling parts or injection molds with cooling channels that can't be obtained by conventional routes. During the process, the laser beam generates violent heating and cooling cycles in the material inducing important thermal gradients in the consolidated part. The cyclic thermal expansions and contractions exceeding the maximum elastic strain of the material induce heterogeneous plastic strains and generate internal stresses the level of which can reaches the yield stress of the material and cracks may appear during the process. This paper deals with the measurement and analysis of residual stresses during the selective laser melting of a simple part in maraging steel. The objective of this study is the analysis of experimental results to validate the numerical model previously presented in [1]. A new method is proposed to evaluate the residual stresses induced during the SLM process, a rosette is fixed on the bottom face of the support. The residual stresses in the created part are calculated from strain and temperature variations when the fused layer is consolidating during the cooling between two layers. Process parameters like the powder thickness or the cooling time between successive layers are studied in this paper.
Selective laser melting (SLM) first developed for rapid prototyping (RP) is now used for rapid manufacturing of parts with inner complex shapes that cannot be made by more conventional routes. For example, production of injection moulds with cooling channels is of special interest. In this paper, a numerical model of SLM process was investigated to simulate the genesis of residual stresses. The proposed numerical modelling is based upon a double meshing with a multi-step birth and death technique of manufactured part. The influence of the mesh size is analysed with element as small as the powder layer thickness for 2D and 3D geometries of simple parts. Comparisons between plane stress, plane strain, and 3D analysis are presented in order to propose a simplified approach.
Within the frame of the French Grenelle for the environment, in the agricultural sector, the need to orient consumers toward environmental-friendly products was emphasised. In June 2011, a new certification was hence promulgated by decree: the agriculture of high environmental value (HEV). This certification aims at harmonising all agri-environmental initiatives and is based on a semi-quantitative system for the environmental impact assessment of agricultural practices. This certification consists of three levels of commitment, with only the highest level being recognised by a logo on products. At the same time, a national experimentation phase was launched (July 2011) on eco-labelling involving dozens of companies with their own labelling projects on consuming goods. Life-cycle analysis (LCA) is the recommended method within the national methodological framework for eco-labelling. It is a holistic method that quantifies environmental impacts along the product life-cycle. The certification HEV and LCA are based on very different approaches of impact assessment, which can be complementary. However, the two approaches are also likely to compete with one another in terms of visibility, implementation and potential economic added-value. LCA-based eco-labelling is becoming mandatory, whereas the HEV certification is voluntary. Development of LCA-based eco-labelling is thus more likely to develop. Both approaches remain under development and numerous methodological questions are still open. More generally, eco-labelling also raises questions on the difficulty to find a good compromise between scientific reliability and efficient communication.
Background
BACKGROUND: A key to understanding the evolution of the nervous system on a large phylogenetic scale is the identification of homologous neuronal types. Here, we focus this search on the sensory and motor neurons of bilaterians, exploiting their well-defined molecular signatures in vertebrates. Sensorimotor circuits in vertebrates are of two types: somatic (that sense the environment and respond by shaping bodily motions) and visceral (that sense the interior milieu and respond by regulating vital functions). These circuits differ by a small set of largely dedicated transcriptional determinants: Brn3 is expressed in many somatic sensory neurons, first and second order (among which mechanoreceptors are uniquely marked by the Brn3+/Islet+/Drgx+ signature), somatic motoneurons uniquely co-express Lhx3/4 and Mnx1, while the vast majority of neurons, sensory and motor, involved in respiration, blood circulation or digestion are molecularly defined by their expression and dependence on the pan-visceral determinant Phox2b. RESULTS: We explore the status of the sensorimotor transcriptional code of vertebrates in mollusks, a lophotrochozoan clade that provides a rich repertoire of physiologically identified neurons. In the gastropods Lymnaea stagnalis and Aplysia californica, we show that homologues of Brn3, Drgx, Islet, Mnx1, Lhx3/4 and Phox2 differentially mark neurons with mechanoreceptive, locomotory and cardiorespiratory functions. Moreover, in the cephalopod Sepia officinalis, we show that Phox2 marks the stellate ganglion (in line with the respiratory --- i.e. visceral--- ancestral role of the mantle, its target organ), while the anterior pedal ganglion, which controls the prehensile and locomotory arms, expresses Mnx. CONCLUSIONS: Despite considerable divergence in overall neural architecture, a molecular underpinning for the functional allocation of neurons to interactions with the environment or to homeostasis was inherited from the urbilaterian ancestor by contemporary protostomes and deuterostomes.
To take account of the uncertainties introduced on the soft magnetic materials properties (magnetic behavior law, iron losses) during the manufacturing process, the present work deals with the stochastic modeling of the magnetic behavior law B-H and iron losses of claw pole stator generator. Twenty eight (28) samples of slinky stator (SS) coming from the same production chain have been investigated. The used approaches are similar to those used in mechanics. The accuracy of existing anhysteretic models has been tested first using cross validation techniques. The well known iron loss separation model has been implemented to take into account the variability of the losses. Then, the Multivariate Gaussian distribution is chosen to model the variability and dependencies between identified parameters, for both behavior law and iron loss models. The developed stochastic models allow predicting a 98% confidence interval for the considered samples
Using an approach recently developed by Nourdin and Poly, we improve the rate in an inequality for the total variation distance between two double Wiener-Itô integrals originally due to Davydov and Martynova. An application to the rate of convergence of a functional of a correlated two-dimensional fractional Brownian motion towards the Rosenblatt random variable is then given, following a previous study by Maejima and Tudor.
We propose a family of multivariate heavy-tailed distributions that allow variable marginal amounts of tailweight. The originality comes from introducing multidimensional instead of univariate scale variables for the mixture of scaled Gaussian family of distributions. In contrast to most existing approaches, the derived distributions can account for a variety of shapes and have a simple tractable form with a closed-form probability density function whatever the dimension. We examine a number of properties of these distributions and illustrate them in the particular case of Pearson type VII and ttails. For these latter cases, we provide maximum likelihood estimation of the parameters and illustrate their modelling flexibility on simulated and real data clustering example.
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