L'archive ouverte pluridisciplinaire HAL , est destinée au dépôt et à la diffusion d'articles scientifiques de niveau recherche, publiés ou non, et de thèses, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Derniers Dépôts
Chimie
Économie et finance quantitative
Informatique
Mathématiques
Physique
Planète et Univers
Science non linéaire
Sciences cognitives
Sciences de l'environnement
Sciences de l'Homme et Société
Sciences de l'ingénieur
Sciences du Vivant
Statistiques
The intermolecular potential for the van der Waals complex of the carbon monoxide cation with helium is studied by means of the partially spin adapted coupled cluster RCCSD(T) method and the aug-cc-pVXZ family of basis sets. In the ground electronic state, correlated with the lowest electronic asymptote $X {^2\Sigma^+}$ of the monomer CO$^+$, the complex He($^1S$)-CO$^+$($^2\Sigma^+$) has a nonlinear equilibrium structure with a Jacobi angle of about 46 deg and a binding energy of about 275 cm$^{-1}$. For the complex He($^1S$)-CO$^+$($A {^2\Pi}$) we find equilibrium Jacobi angles of 78 deg and 90 deg and electronic binding energies of about 160 cm$^{-1}$ and 303 cm$^{-1}$ for the $A^{\prime\prime}$ and $A^{\prime}$ components, respectively, coalescing into the $\Pi$ state at linearity. Two-dimensional intermolecular potential energy surfaces are constructed for the ground electronic state and used to compute rotation-vibration states up to J=10 with the numerically exact discrete variable representation (DVR) technique. The He-CO$^+$ complex is found to have 19 bound even-parity J=0 states and 16 bound odd-parity J=1 states and to exhibit strong angular-radial coupling and quasilinear behaviour.
A RCCSD(T)/cc-pVQZ potential energy surface is constructed for the HOCO radical in the ground electronic state and used to compute rotation-vibration levels of HOCO and DOCO. Two numerical strategies are employed to study in detail the wave function properties. The importance of stretch−bend coupling, such as ν4/ν5 and ν3/ν4, for the internal dynamics is demonstrated. The rotational constants computed for the vibrational ground state of trans and cis conformers are in good agreement with experimental values.
An in situ experiment has been carried out inbioturbated Mediterranean coastal marine sediments (Gulfof Fos) in order to study the influence of hydrocarbons ondenitrification after 1, 4 and 6 months. In theabsence of hydrocarbons in the control sediments, the presenceof macrofauna stimulated denitrificationby 160%. This stimulation is induced by sediment reworkingthat favours both direct NO-3 supply fromthe water column and the penetration of O{2}, which in turnstimulated nitrification, the other source ofNO-3 in sediment. The presence of hydrocarbons in theexperimental sediments either stimulated orinhibited the denitrification. The denitrification response tothe presence of hydrocarbon is dependent onthe quantity of matter buried by the macrofauna activity. Insmall quantities, the organic matter relatedto hydrocarbons 120% enhanced the denitrification compared tothe controls. On the other hand, whenburied hydrocarbon concentrations were higher (>100 mgsaturated hydrocarbon fraction kg-1 drysediment), the denitrification was inhibited.On the basis of the results obtained, a descriptive model ofthe patterns of denitrification in relation to the presence ofmacrofauna and the distribution of hydrocarbons in sediments is proposed.
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.
FMRI time course processing is traditionally performed using linear regression followed by statistical hypothesis testing. While this analysis method is robust against noise, it relies strongly on the signal model. In this paper, we propose a non-parametric framework that is based on two main ideas. First, we introduce a problem-specific type of wavelet basis, for which we coin the term "activelets". The design of these wavelets is inspired by the form of the canonical hemodynamic response function. Second, we take advantage of sparsity-pursuing search techniques to find the most compact representation for the BOLD signal under investigation. The non-linear optimization allows to overcome the sensitivity-specificity trade-off that limits most standard techniques. Remarkably, the activelet framework does not require the knowledge of stimulus onset times; this property can be exploited to answer to new questions in neuroscience.
We have developed a multiexposure image fusion method based on texture features, which exploits the edge preserving and intraregion smoothing property of nonlinear diffusion filters based on partial differential equations (PDE). With the captured multiexposure image series, we first decompose images into base layers and detail layers to extract sharp details and fine details, respectively. The magnitude of the gradient of the image intensity is utilized to encourage smoothness at homogeneous regions in preference to inhomogeneous regions. Then, we have considered texture features of the base layer to generate a mask (i.e., decision mask) that guides the fusion of base layers in multiresolution fashion. Finally, well-exposed fused image is obtained that combines fused base layer and the detail layers at each scale across all the input exposures. Proposed algorithm skipping complex High Dynamic Range Image (HDRI) generation and tone mapping steps to produce detail preserving image for display on standard dynamic range display devices. Moreover, our technique is effective for blending flash/no-flash image pair and multifocus images, that is, images focused on different targets.
Representing the image to be inpainted in an appropriate sparse representation dictionary, and combining elements from Bayesian statistics and modern harmonic analysis, we introduce an expectation maximization (EM) algorithm for image inpainting and interpolation. From a statistical point of view, the inpainting/interpolation can be viewed as an estimation problem with missing data. Toward this goal, we propose the idea of using the EM mechanism in a Bayesian framework, where a sparsity promoting prior penalty is imposed on the reconstructed coefficients. The EM framework gives a principled way to establish formally the idea that missing samples can be recovered/ interpolated based on sparse representations. We first introduce an easy and efficient sparserepresentation-based iterative algorithm for image inpainting. Additionally, we derive its theoretical convergence properties. Compared to its competitors, this algorithm allows a high degree of flexibility to recover different structural components in the image (piecewise smooth, curvilinear, texture, etc.). We also suggest some guidelines to automatically tune the regularization parameter.
We provide an example of a two-player zero-sum repeated game with public signals and perfect observation of the actions, where neither the value of the lambda-discounted game nor the value of the n-stage game converges, when respectively lambda goes to 0 and n goes to infinity. It is a counterexample to two long-standing conjectures, formulated by Mertens: first, in any zero-sum repeated game, the asymptotic value exists, and secondly, when Player 1 is more informed than Player 2, Player 1 is able to guarantee the limit value of the n-stage game in the long run. The aforementioned example involves seven states, two actions and two signals for each player. Remarkably, players observe the payoffs, and play in turn (at each step the action of one player only has an effect on the payoff and the transition). Moreover, it can be adapted to fit in the class of standard stochastic games where the state is not observed.
An averaging result is proved for stochastic evolution equations with highly oscillating coefficients. This result applies in particular to equations with almost periodic coefficients. The convergence to the solution of the averaged equation is obtained in distribution, as in previous works by Khasminskii and Vrkoč.
This paper deals with mathematical questions for Bose gases below the temperature T_BEC where Bose-Einstein condensation sets in. The model considered is of two-component type, consisting of a kinetic equation for the distribution function of a gas of (quasi-)particles interacting with a Bose condensate, which is described by a Gross-Pitaevskii equation. Existence results and moment estimates are proved in the space-homogeneous, isotropic case.
We address the existence of steady state Green-Keldysh correlation functions of interacting fermions
in mesoscopic systems for both the partitioning and partition-free scenarios. Under some spectral assumptions on the non-interacting model and for sufficiently small interaction strength, we show that the system evolves to a NESS which does not depend on the profile of the time-dependent coupling strength/bias. For the partitioned setting we also show that the steady state is independent of the initial state of the inner sample. Closed formulae for the NESS two-point correlation functions (Green-Keldysh functions), in the form of a convergent expansion, are derived. In the partitioning approach, we show that the 0th order term in the interaction strength of the charge current leads to the Landauer-Büttiker formula, while the 1st order correction contains the mean-field (Hartree-Fock) results.
We study a class of finite dimensional quantum dynamical semigroups exp(tL) whose generators L are sums of Lindbladians satisfying the detailed balance condition. Such semigroups arise in the weak coupling (van Hove) limit of Hamiltonian dynamical systems describing open quantum systems out of equilibrium. We prove a general entropic fluctuation theorem for this class of semigroups by relating the cumulant generating function of entropy transport to the spectrum of a family of deformations of the generator L. We show that, besides the celebrated Evans-Searles symmetry, this cumulant generating function also satisfies the translation symmetry recently discovered by Andrieux et al., and that in the linear regime near equilibrium these two symmetries yield Kubo's and Onsager's linear response relations.
A new macroscopic approach to modelise membrane wrinkling is presented. Most of the studies of the literature about membrane behaviour are macroscopic and phenomenological, the influence of wrinkles being accounted by non-linear constitutive laws without compressive stiffness. The present method is multi-scale and it permits to predict the wavelength and the spatial distribution of wrinkling amplitude. It belongs to the family of Landau-Ginzburg bifurcation equations and especially it relies on the technique of Fourier series with slowly varying coefficients. The result is a new family of macroscopic membrane models that are deduced from Föppl-Von Karman plate equations. Numerical solutions are presented giving the size of the wrinkles as a function of the applied compressive and tensile stresses.
The Korba aquifer on the east coast of Cape Bon has been overexploited since the 1960s with a resultant reversal of the hydraulic gradient and a degradation of the quality due to seawater intrusion. In 2008, the authorities introduced integrated water resources planning based on a managed aquifer recharge with treated wastewater. Water quality monitoring was implemented in order to determine the different system components and trace the effectiveness of the artificial recharge. Groundwater samples taken from recharge control piezometers and surrounding farm wells were analyzed for their chemical contents, for their boron isotopes, a proven tracer of groundwater salinization and domestic sewage, and their carbamazepine content, an anti-epileptic known to pass through wastewater treatment and so recognized as a pertinent tracer of wastewater contamination. The system equilibrium was permanently disturbed by the different temporal dynamics of continuous processes such as cation exchange, and by threshold processes linked to oxidation-reductive conditions. The boron isotopic compositions significantly shifted back-and-forth due to mixing with end-members of various origins. Under the variable contribution of meteoric recharge, the Plio-Quaternary groundwater (δ11B of 35-40.6‰, a mean B concentration of 30 µmol/L, no carbamazepine, n=7) was subject to seawater intrusion that induced a high δ11B level (δ11B of 41.5-48.0‰, a mean B concentration of 36 µmol/L, and n=8). Fresh groundwater (δ11B of 19.89‰, B concentration of 2.8 µmol/L, no carbamazepine) was detected close to the recharge site and may represent the deep Miocene pole which feeds the upper Plio-Quaternary aquifer. The managed recharge water (δ11B of 10.67-13.8‰, n=3) was brackish and of poor quality with a carbamazepine content showing a large short term variability with an average daily levels of 328 ± 61 ng/L. A few piezometers in the vicinity of the recharge site gradually acquired a B isotopic composition close to the wastewater signature and showed an increasing carbamazepine content (from 20 to 910 ng/L). The combination of boron isotopic signatures with boron and carbamazepine contents is a useful tool to assess sources and mixing of treated wastewaters in groundwaters. Effluent quality needs to be greatly improved before injection to prevent further degradation of groundwater quality.
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.
About 80% and more than 90% of the dissolved organic carbon (DOC) in the bottom water of Lake Pavin were isolated, respectively, on Amberlite XAD and Spherodex DEAE resins. Trace element concentrations in the fractions isolated were analyzed by using ICP-MS. Uranium, molybdenum, and antimony were found to be about 40% associated with fulvic and hydrophilic acids adsorbed on XAD resins at pH 2, the metal-organic association being not dissociated. Much higher percentages of the same elements, plus vanadium, were adsorbed on the DEAE resin at the pH of natural water, possibly because of the better preservation of acid labile organic complexes or of the supplementary adsorption of inorganic compounds. Ultrafiltration and dialysis made it possible to exclude colloidal fractions together with much U (78%), Mo (80%), V (55%), and DOC (65%). These elements and many others (including barium) were previously found to be quite reactive at the bottom of the lake, (apparently being scavenged by settling particles, which are mostly diatoms, then dissolved at the sediment-water interface). Conversely, trace elements with a conservative behavior in the bottom layer (such as lithium and cesium) were not found associated with dissolved organic mater (DOM). Barium was not strongly associated with the extractable DOM, which may argue for a direct interaction with inorganic particles or the existence of very labile complexes. Our work suggests the existence of relatively stable (nonacid labile) U and Mo-DOM colloidal associations in the anoxic bottom waters of the lake and their importance in the scavenging of those metals.
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.
Force-feedback and physical modeling technologies now allow to achieve the same kind of relation with virtual instruments as with acoustic instruments, but the design of such elaborate models needs guidelines based on the study of the human sensory-motor system and behaviour. This article presents a qualitative study of a simulated instrumental interaction in the case of the virtual bowed string, using both waveguide and mass-interaction models. Subjects were invited to explore the possibilities of the simulations and to express themselves verbally at the same time, allowing us to identify key qualities of the proposed systems that determine the construction of an intimate and rich relationship with the users.
The charisma of the leader is conveyed through multiple aspects: his ideas and vision and his perceivable verbal and non verbal behaviors. Among these perceivable behaviors there are the acoustic characteristics of speech. We present here a study on the perception of charisma in political speech. We collected speech statements with different illocutionary value taken from two speeches given by Umberto Bossi, the leader of an Italian party, before and after a stroke which caused him a voice disorder. Stimuli from the two condition differed significantly in the acoustic-prosodic features. In the first part of the study 40 French listeners rated normal speech stimuli (20 pre- and 20 post-stroke) and in the second part 22 French (11 pre- and 11 post-stroke) and 31 Italians (15 pre- and 16 post-stroke) rated the de-lexicalized version of the same stimuli. Results for the first part of the study show that pitch contour in Bossi's pre-stroke speech positively influence the perception of his speech as charismatic, as opposed to those some years after the stroke. Results for the de-lexicalized speech confirm for French listeners our hypothesis of the influence of the pitch contour in Bossi's charisma perception but they are controversial for Italian participants that seem to perceive Bossi as more charismatic in the post-stroke condition.
Grâce aux technologies des interfaces à retour de force et de la modélisation physique, il semble aujourd'hui possible d'atteindre le même type de relation avec les objets virtuels qu'avec les instruments acoustiques. Mais la conception de systèmes artificiels si élaborés pose des questions profondes sur les conditions nécessaires à la mise en place d'une relation instrumentale. Cet article présente une étude qualitative d'une telle relation dans le cas du frottement sur une corde virtuelle, simulée à l'aide de modèles de type masses-interactions et guide d'onde. Des utilisateurs ont été invités à explorer les possibilités de différentes simulations tout en exprimant leurs impressions par rapport à cette situation, ce qui nous a permis d'identifier certaines des qualités clés des dispositifs testés qui conditionnent la construction d'une relation riche et intime avec l'utilisateur.
The Korba aquifer on the east coast of Cape Bon has been overexploited since the 1960s with a resultant reversal of the hydraulic gradient and a degradation of the quality due to seawater intrusion. In 2008, the authorities introduced integrated water resources planning based on a managed aquifer recharge with treated wastewater. Water quality monitoring was implemented in order to determine the different system components and trace the effectiveness of the artificial recharge. Groundwater samples taken from recharge control piezometers and surrounding farm wells were analyzed for their chemical contents, for their boron isotopes, a proven tracer of groundwater salinization and domestic sewage, and their carbamazepine content, an anti-epileptic known to pass through wastewater treatment and so recognized as a pertinent tracer of wastewater contamination. The system equilibrium was permanently disturbed by the different temporal dynamics of continuous processes such as cation exchange, and by threshold processes linked to oxidation-reductive conditions. The boron isotopic compositions significantly shifted back-and-forth due to mixing with end-members of various origins. Under the variable contribution of meteoric recharge, the Plio-Quaternary groundwater (δ11B of 35-40.6‰, a mean B concentration of 30 µmol/L, no carbamazepine, n=7) was subject to seawater intrusion that induced a high δ11B level (δ11B of 41.5-48.0‰, a mean B concentration of 36 µmol/L, and n=8). Fresh groundwater (δ11B of 19.89‰, B concentration of 2.8 µmol/L, no carbamazepine) was detected close to the recharge site and may represent the deep Miocene pole which feeds the upper Plio-Quaternary aquifer. The managed recharge water (δ11B of 10.67-13.8‰, n=3) was brackish and of poor quality with a carbamazepine content showing a large short term variability with an average daily levels of 328 ± 61 ng/L. A few piezometers in the vicinity of the recharge site gradually acquired a B isotopic composition close to the wastewater signature and showed an increasing carbamazepine content (from 20 to 910 ng/L). The combination of boron isotopic signatures with boron and carbamazepine contents is a useful tool to assess sources and mixing of treated wastewaters in groundwaters. Effluent quality needs to be greatly improved before injection to prevent further degradation of groundwater quality.
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.
A high-resolution sedimentological and geochemical study of a high-altitude proglacial lake (Lake Blanc, Aiguilles Rouges, 2352m a.s.l.) revealed 195 turbidites, 190 of which are related to flood events over the last 1400 years. We used the coarsest sediment fraction of each turbidite as a proxy for the intensity of each flood event. Because most flood events at this locality are triggered by localized summer convective precipitation events, the reconstructed sedimentary record reveals changes in the frequency and intensity of such events over the last millennium. Comparisons with other temperature, palaeohydrological and glacier reconstructions in the region suggest that the most intense events occurred during the warmest periods, i.e. during the Medieval Climate Anomaly (AD 800-1300) and the current period of global warming. On a multi-decadal time scale, almost all the flood frequency peaks seem to correspond to warmer periods, whereas multi-centennial variations in flood frequency appear to follow the regional precipitation pattern. Consequently, this new Alpine flood record provides further evidence of a link between climate warming and an increase in the frequency and intensity of flooding on a multidecadal time scale, whereas the centennial variability in flood frequencies is related to regional precipitation patterns.
Force-feedback and physical modeling technologies now allow to achieve the same kind of relation with virtual instruments as with acoustic instruments, but the design of such elaborate models needs guidelines based on the study of the human sensory-motor system and behaviour. This article presents a qualitative study of a simulated instrumental interaction in the case of the virtual bowed string, using both waveguide and mass-interaction models. Subjects were invited to explore the possibilities of the simulations and to express themselves verbally at the same time, allowing us to identify key qualities of the proposed systems that determine the construction of an intimate and rich relationship with the users.
La recherche présentée vise à décrire l'influence des connaissances mathématiques des enseignants primaires sur leur gestion didactique de tâches mathématiques. Elle s'appuie sur une comparaison à ce sujet entre enseignants chinois et étatsuniens (Ma, 1999), sur les catégories de connaissances mathématiques pour l'enseignement (Ball, Thames & Phelps, 2008), sur la structuration du milieu et sa déclinaison en niveaux d'activité du professeur (Margolinas, 2002), et sur les critères de pertinence mathématique du professeur élaborés par Bloch (2009). Dans une première partie, des entretiens avec des enseignants vaudois ont permis de mettre en évidence certaines similitudes avec les enseignants interrogés par Ma. Dans une seconde partie, quatre enseignants ont été observés durant leur enseignement de l'algorithme de la multiplication par un nombre à plusieurs chiffres. Les résultats ont été considérés à plusieurs niveaux d'analyse allant jusqu'au grain très fin de la structuration du milieu. Ils font apparaître des liens entre connaissances mathématiques, pertinence et choix didactiques des enseignants.
Cet article examine les pratiques patrimoniales développées autour de la Mahdiyya soudanaise (1881-1898) durant le Condominium anglo-égyptien (1899-1956). Tout en tenant compte de l'évolution sémantique des concepts de patrimoine et de turâth, il vise à montrer que cette période controversée de l'histoire soudanaise fut l'enjeu de processus de patrimonialisation, de dé-patrimonialisation et de contre-patrimonialisation déclenchés par des acteurs aux intérêts politiques et idéologiques très divergents : les néo-Mahdistes, qui avaient pour objectif l'accession du Soudan à une indépendance totale ; les Unionistes, qui préconisaient l'union politique du Soudan avec l'Egypte ; et les administrateurs britanniques, pour qui l'établissement d'un système colonial effectif impliquait l'anéantissement matériel et symbolique du régime mahdiste. L'analyse est notamment consacrée à la Mahdiyya en tant qu'objet oscillant entre patrimoine national et héritage familial, ceci à travers la figure de proue du mouvement néo-mahdiste, Sayyid 'Abd al-Rahman al-Mahdî (1885-1959). Outre diverses modalités de patrimonialisation sociales et intellectuelles mises en œuvre du côté néo-mahdiste, l'article met en évidence les efforts britanniques de dé-patrimonisalisation de la Mahdiyya ainsi que l'élaboration d'un contre-modèle patrimonial fondé sur la sacralisation mémorielle du général Charles George Gordon (1833-1885). Enfin, les tentatives des Unionistes visant à contrecarrer la patrimonialisation nationale de la Mahdiyya mettent en relief le fossé politique, idéologique et religieux séparant les deux principales tendances du nationalisme soudanais à l'époque du Condominium, qui trouvent leur expression dans les célèbres slogans "Le Soudan aux Soudanais" et "L'unité de la vallée du Nil".
FMRI time course processing is traditionally performed using linear regression followed by statistical hypothesis testing. While this analysis method is robust against noise, it relies strongly on the signal model. In this paper, we propose a non-parametric framework that is based on two main ideas. First, we introduce a problem-specific type of wavelet basis, for which we coin the term "activelets". The design of these wavelets is inspired by the form of the canonical hemodynamic response function. Second, we take advantage of sparsity-pursuing search techniques to find the most compact representation for the BOLD signal under investigation. The non-linear optimization allows to overcome the sensitivity-specificity trade-off that limits most standard techniques. Remarkably, the activelet framework does not require the knowledge of stimulus onset times; this property can be exploited to answer to new questions in neuroscience.
We have developed a multiexposure image fusion method based on texture features, which exploits the edge preserving and intraregion smoothing property of nonlinear diffusion filters based on partial differential equations (PDE). With the captured multiexposure image series, we first decompose images into base layers and detail layers to extract sharp details and fine details, respectively. The magnitude of the gradient of the image intensity is utilized to encourage smoothness at homogeneous regions in preference to inhomogeneous regions. Then, we have considered texture features of the base layer to generate a mask (i.e., decision mask) that guides the fusion of base layers in multiresolution fashion. Finally, well-exposed fused image is obtained that combines fused base layer and the detail layers at each scale across all the input exposures. Proposed algorithm skipping complex High Dynamic Range Image (HDRI) generation and tone mapping steps to produce detail preserving image for display on standard dynamic range display devices. Moreover, our technique is effective for blending flash/no-flash image pair and multifocus images, that is, images focused on different targets.
The ability of measuring accurately airborne pollen concentration in the environment is an important goal for palynology. It has been unsatisfactory for agile usage to date. Huge volumes of airborne particles prevent palynologists from opportunely processing statistically suitable information. Additionally, measurements from stationary pollen monitors cannot be accurately associated to individuals. In the context of computer vision, this paper presents the outline for the structure of an image based pollen detection system, under the framework of the Personalized Pollen Profiling and Geospatial Mapping project based on individual information of allergic patient profile measured at multiple points from personal mobile wearable devices. With features from classical geometric and optical measures to specialised palynological information, it is feasible to characterise different pollen taxa images. Optimal selection of features allows a pattern detection system to split and recognise each taxon exactly. Gathering such accurate individual pollen concentration data in a geo-spatial context will benefit not only to patients through more precise medication but also to the improvement of pollen distribution models and forecasting.
Nonribosomal peptides (NRPs) are molecules produced by microorganisms that have a broad spectrum of biological activities and pharmaceutical applications (e.g., antibiotic, immunomodulating, and antitumor activities). One particularity of the NRPs is the biodiversity of their monomers, extending far beyond the 20 proteogenic amino acid residues. Norine, a comprehensive database of NRPs, allowed us to review for the first time the main characteristics of the NRPs and especially their monomer biodiversity. Our analysis highlighted a significant similarity relationship between NRPs synthesized by bacteria and those isolated from metazoa, especially from sponges, supporting the hypothesis that some NRPs isolated from sponges are actually synthesized by symbiotic bacteria rather than by the sponges themselves. A comparison of peptide monomeric compositions as a function of biological activity showed that some monomers are specific to a class of activities. An analysis of the monomer compositions of peptide products predicted from genomic information (metagenomics and high-throughput genome sequencing) or of new peptides detected by mass spectrometry analysis applied to a culture supernatant can provide indications of the origin of a peptide and/or its biological activity.
Cet article établit des courbes de référence pour la croissance en hauteur dominante des hêtraies régulières de plaine du Nord de la France. Il se fonde sur la campagne d'analyses de tiges menée par l'Office National des Forêts au cours des dernières années. Comme pouvaient le suggérer les faisceaux antérieurement utilisés (courbes Schober dans le Nord-Est, et Hamilton-Christie dans le Nord-Ouest), on confirme une différence d'allures de croissance entre les deux régions, avec des courbes plus tendues dans le Nord-Est. De même, à une échelle intra-régionale et dans une moindre mesure, une différence de forme de croissance distingue une zone atlantique côtière, et une zone intérieure où la croissance est plus soutenue. Le phénomène présente un caractère graduel sur l'ensemble de la zone de production, et traduit vraisemblablement une influence climatique. Ces hêtraies ont également fait l'objet d'une analyse plus spécifique de l'évolution de leur productivité à long-terme. On relate brièvement ces évolutions, que l'on intègre de façon simple aux courbes de référence.
Compressed sensing (CS) is a theory which guarantees the exact recovery of sparse signals from a few number of linear projections. The sampling schemes suggested by current CS theories are often of little relevance since they cannot be implemented on practical acquisition systems. In this paper, we study a new random sampling approach that consists in selecting a set of blocks that are predefined by the application of interest. A typical example is the case where the blocks consist in horizontal lines in the 2D Fourier plane. We provide theoretical results on the number of blocks that are required for exact sparse signal reconstruction in a noise free setting. We illustrate this theory for various sensing matrices appearing in applications such as time-frequency bases. A typical result states that it is sufficient to acquire no more than $O\left( s \ln^2(n) \right)$ lines in the 2D Fourier domain for the perfect reconstruction of an $s$-sparse image of size $\sqrt{n} \times \sqrt{n}$ . The proposed results have a large number of potential applications in systems such as magnetic resonance imaging, radio-interferometry or ultra-sound imaging.
Wavelet analysis has been found to be a powerful tool for the nonparametric estimation of spatially-variable objects. We discuss in detail wavelet methods in nonparametric regression, where the data are modelled as observations of a signal contaminated with additive Gaussian noise, and provide an extensive review of the vast literature of wavelet shrinkage and wavelet thresholding estimators developed to denoise such data. These estimators arise from a wide range of classical and empirical Bayes methods treating either individual or blocks of wavelet coefficients. We compare various estimators in an extensive simulation study on a variety of sample sizes, test functions, signal-to-noise ratios and wavelet filters. Because there is no single criterion that can adequately summarise the behaviour of an estimator, we use various criteria to measure performance in finite sample situations. Insight into the performance of these estimators is obtained from graphical outputs and numerical tables. In order to provide some hints of how these estimators should be used to analyse real data sets, a detailed practical step-by-step illustration of a wavelet denoising analysis on electrical consumption is provided. Matlab codes are provided so that all figures and tables in this paper can be reproduced.
This paper is concerned with the problem of the alignment of multiple sets of curves. We analyze two real examples arising from the biomedical area for which we need to test whether there are any statistically significant differences between two subsets of subjects. To synchronize a set of curves, we propose a new nonparametric landmark-based registration method based on the alignment of the structural intensity of the zero-crossings of a wavelet transform. The structural intensity is a multiscale technique recently proposed by Bigot (2003, 2005) which highlights the main features of a signal observed with noise. We conduct a simulation study to compare our landmark-based registration approach with some existing methods for curve alignment. For the two real examples, we compare the registered curves with FANOVA techniques, and a detailed analysis of the warping functions is provided.
À l'attention du déposant
Le dépôt doit être effectué en accord avec les co-auteurs et dans le respect de la politique des éditeurs
La mise en ligne est assujettie à une modération, la direction de HAL se réservant le droit de refuser les articles ne correspondant pas aux critères de l'archive (voir le guide du déposant )
Tout dépôt est définitif, aucun retrait ne sera effectué après la mise en ligne de l'article
Consulter le ManuHAL Les fichiers textes au format pdf ou les fichiers images composant votre dépôt sont maintenant envoyés au CINES dans un contexte d'archivage à long terme.
À l'attention des lecteurs
Dans un contexte de diffusion électronique, tout auteur conserve ses droits intellectuels, notamment le fait de devoir être correctement cité et reconnu comme l'auteur d'un document.
Déposer
La convention de partenariat en faveur des archives ouvertes et de la plateforme mutualisée HAL a été signée le 2 avril 2013 :
en savoir plus
Déposer
Documents avec texte intégral
Evolution des dépôts
Contact
Actualités
À voir
