Showing papers by "École normale supérieure de Cachan published in 2003"
TL;DR: In this article, a closed loop parametrical identification procedure for continuous-time constant linear systems is introduced, which exhibits good robustness properties with respect to a large variety of additive perturbations is based on the following mathematical tools: (1) module theory; (2) differential algebra; (3) operational calculus.
Abstract: A closed loop parametrical identification procedure for continuous-time constant linear systems is introduced. This approach which exhibits good robustness properties with respect to a large variety of additive perturbations is based on the following mathematical tools: (1) module theory; (2) differential algebra; (3) operational calculus. Several concrete case-studies with computer simulations demonstrate the efficiency of our on-line identification scheme.
510 citations
TL;DR: In this article, the authors considered the Kolmogorov equation associated with the stochastic Navier-Stokes equations in 3D and proved existence of a solution in the strict or mild sense.
209 citations
TL;DR: This work develops a new detection algorithm that relies on the Helmoltz principle, which leads to a vanishing point detector with a low false alarms rate and a high precision level, which does not rely on any a priori information on the image or calibration parameters, and does not require any parameter tuning.
Abstract: Even though vanishing points in digital images result from parallel lines in the 3D scene, most of the proposed detection algorithms are forced to rely heavily either on additional properties (like orthogonality or coplanarity and equal distance) of the underlying 3D lines, or on knowledge of the camera calibration parameters, in order to avoid spurious responses. In this work, we develop a new detection algorithm that relies on the Helmoltz principle recently proposed for computer vision by Desolneux et al (2001; 2003), both at the line detection and line grouping stages. This leads to a vanishing point detector with a low false alarms rate and a high precision level, which does not rely on any a priori information on the image or calibration parameters, and does not require any parameter tuning.
173 citations
TL;DR: In this article, four series of dyes with dimethylamino electron donor groups and N-R-pyridinium (R = methyl Me, phenyl Ph, 2,4-dinitrophenyl 2, 4-DNPh, or 2-pyrimidyl 2-Pym) electron acceptors are studied as their hexafluorophosphate salts.
Abstract: Four series of dyes with dimethylamino electron donor groups and N-R-pyridinium (R = methyl Me, phenyl Ph, 2,4-dinitrophenyl 2,4-DNPh, or 2-pyrimidyl 2-Pym) electron acceptors are studied as their hexafluorophosphate salts. The intramolecular charge-transfer (ICT) energies (E-max) of these compounds decrease within each of the series in the order R = Me > Ph > 2,4-DNPh > 2-Pym, as the electron-accepting ability of the pyridinium ring increases. Hyper-Rayleigh scattering with femtosecond 1300 or 800 nm lasers yields fluorescence-free first hyperpolarizabilities ?, and static first hyperpolarizabilities ?(0)[H] are obtained via the two-state model. Dipole moment changes ??(12) for the ICT transitions obtained from Stark spectroscopy afford ?(0)[S] values by using ?(0) = 3??(12)(?(12))(2)/2 (E-max)(2) (?(12) = transition dipole moment). The ?(0)[S] data show that the combination of pyridyl N-arylation with conjugation extension affords large increases in ?(0). The ?(0)[H] data generally agree with this conclusion, but resonance effects may explain some apparent anomalies. X-ray structural studies on various salts reveal that the use of tosylate anions is not a generally applicable approach to engineering noncentrosymmetric structures of pyridinium salts. However, trans-N-phenyl-4-(4-dimethylaminophenyl-4-buta-1,3-dienyl)pyridinium hexafluorophosphate adopts the polar space group Cc, and shows a very large powder second harmonic generation efficiency from a 1907 nm laser; which is similar to that of the well-studied material trans-4'-(dimethylamino)-N-methyl-4-stilbazolium tosylate (DAST).
168 citations
TL;DR: In this paper, a procedure based on three point bend size effect tests on notched specimens is presented, where complete load deflection curves are used for the identification of the constitutive relations.
Abstract: The calibration of nonlocal models which contain an internal length has been among the major issues conditioning the implementation of this kind of failure models. Direct calibration from uniaxial testing, where the state of strain remains homogeneous throughout the specimen, is impossible. The softening law is not directly accessible because the strains cannot remain homogeneous during the entire test. In the absence of local information on the displacement field and on micro cracking in the fracture process zone, the calibration has to rely on inverse analysis. This paper presents such a procedure based on three point bend size effect tests on notched specimens. The complete load deflection curves are used for the identification of the constitutive relations. Manual calibration is discussed first. It is emphasised that calibration on the load deflexion curve from a single experiment is not objective. We show that Bazant's size effect law, which is related to peak loads only, may serve as a helpful guide to reach the closest fit. Then, automatic calibration is described. An optimal set of model parameters can be obtained within a reasonable number of iterations.
145 citations
TL;DR: A new fluorescent molecular sensor based on a calix[4]arene bearing four dansyl groups exhibits very efficient binding in acetonitrile-water for lead and the changes of emission properties allows a detection limit of 4 microg L(-1).
137 citations
TL;DR: This paper deals with assessment and correction of tool path in 5-axis machining using two curves; each one corresponding to the trajectory of two particular points of the tool axis using a kinematics approach.
Abstract: This paper deals with assessment and correction of tool path in 5-axis machining. The tool trajectory is described using two curves; each one corresponding to the trajectory of two particular points of the tool axis. The assessment of the tool path is performed via the calculation of the envelope surface, which is calculated using a kinematics approach. The geometrical deviations between the envelope surface and the nominal surface are calculated. When necessary, the tool path is corrected, so that the envelope surface fits the ideal surface as much as possible. This correction is carried out by the deformation of both curves that are representative of the tool trajectory. We choose to illustrate our purpose through flank milling of sculptured surfaces.
131 citations
TL;DR: Under vacuum evaporation, thin films with high optical quality are obtained and exhibit spontaneous second-order nonlinear optical activity, likely due to subtle balance between strong dipole-dipole interactions and steric crowding causing self-assembly and noncentrosymmetric local ordering.
Abstract: A novel synthetic approach to a series of bulky triarylamines substituted by various electron-withdrawing groups and forming amorphous materials is presented. Under vacuum evaporation, thin films with high optical quality are obtained and exhibit spontaneous second-order nonlinear optical activity. This unprecedented result is likely due to subtle balance between strong dipole-dipole interactions and steric crowding causing self-assembly and noncentrosymmetric local ordering, stable up to one year.
129 citations
TL;DR: In this article, the authors address several issues pertaining to efficiency of the computational approach geared towards modeling of inelastic behavior of a heterogeneous structure, which is represented by a multi-scale model.
118 citations
TL;DR: In this article, the authors analyzed international experimental published data on leaching concerned with several parameters, like material parameters such as water-to-binder ratio and silica fume content, and environmental parameters, such as pH and temperature.
Abstract: The leaching of cement-based materials in aggressive water is studied according to several protocols of accelerated or non-accelerated tests. The paper analyses international experimental published data on leaching concerned with several parameters, like material parameters as water-to-binder ratio and silica fume content, and environmental parameters, like pH and temperature. Then, a simplified model based on this analysis is developed to predict the kinetics of leaching. This model assumes that the rate of leaching follows a square root of time. Each parameter is introduced as a weight function. Particularly, the paper introduces the coupling between the built database and the model.
98 citations
09 Jun 2003
TL;DR: A new extension of the Skolem class for first-order logic is considered, including the built-in equational theory of exclusive or, and the decidability of this class is proved by resolution techniques.
Abstract: We consider a new extension of the Skolem class for first-order logic and prove its decidability by resolution techniques. We then extend this class including the built-in equational theory of exclusive or. Again, we prove the decidability of the class by resolution techniques. Considering such fragments of first-order logic is motivated by the automatic verification of cryptographic protocols, for an arbitrary number of sessions; the first-order formalization is an approximation of the set of possible traces, for instance relaxing the nonce freshness assumption. As a consequence, we get some new decidability results for the verification of cryptographic protocols with exclusive or.
TL;DR: Polarization measurements of local S-SHG responses reveal the local field anisotropy in enhancement regions and prove the incoherent and strongly depolarized nature of the emission, which is attributed to ultrafast fluctuations of the enhancement location in the focal volume.
Abstract: The localization of surface second-harmonic generation (S-SHG) enhancements from granular gold structures that exhibit local plasmon resonance was investigated. A two-photon microscopy technique was used to perform high spatial resolution S-SHG imaging. The magnitude and the spatial density of S-SHG enhancement confined in submicroscopic regions are strongly dependent on the morphology of the gold's surface. Polarization measurements of local S-SHG responses reveal the local field anisotropy in enhancement regions and furthermore prove the incoherent and strongly depolarized nature of the emission, which is attributed to ultrafast fluctuations of the enhancement location in the focal volume.
07 Apr 2003
TL;DR: It is shown that it is always sufficient to consider a bounded number of agents b (b = 2 for secrecy properties for example): if there is an attack involving n agents, then there is a attack involving at most b agents.
Abstract: We consider arbitrary cryptographic protocols and security properties. We show that it is always sufficient to consider a bounded number of agents b (actually b = 2 in most of the cases): if there is an attack involving n agents, then there is an attack involving at most b agents.
TL;DR: The property language characterizing the power of reachability testing is used to provide a definition of characteristics properties with respect to a timed version of the ready simulation preorder, for nodes of τ-free, deterministic timed automata.
TL;DR: In this paper, the beam lattice network is used to model the cohesive and compressive forces between the neighboring cells, which can describe large rigid body motion and the most salient fracture mechanisms.
TL;DR: 3D numerical simulation of the Navier-Stokes equations shows that the flow partitioning can be highly sensitive to deviations from exact symmetry if inertial effects are present, indicating that physiological variability should be severely restricted in order to ensure adequate fluid distribution through a tree.
Abstract: Uniform flow distribution in a symmetric volume can be realized through a symmetric branched tree. It is shown here, however, by 3D numerical simulation of the Navier-Stokes equations, that the flow partitioning can be highly sensitive to deviations from exact symmetry if inertial effects are present. The flow asymmetry is quantified and found to depend on the Reynolds number. Moreover, for a given Reynolds number, we show that the flow distribution depends on the aspect ratio of the branching elements as well as their angular arrangement. Our results indicate that physiological variability should be severely restricted in order to ensure adequate fluid distribution through a tree.
01 Jan 2003
TL;DR: The mathematical study of travelling waves, in the context of two-dimensional potential flows in one or several layers of perfect fluid(s) and in the presence of free surface and interfaces, can be formulated as an ill-posed evolution problem, where the horizontal space variable plays the role of “time” as mentioned in this paper.
Abstract: The mathematical study of travelling waves, in the context of two-dimensional potential flows in one or several layers of perfect fluid(s) and in the presence of free surface and interfaces, can be formulated as an ill-posed evolution problem, where the horizontal space variable plays the role of “time”. In the finite depth case, the study of near equilibria waves reduces to a low-dimensional reversible ordinary differential equation. In most cases, it appears that the problem is a perturbation of an integrable system, where all types of solutions are known. We describe the method of study and review typical results. In addition, we study the infinite depth limit, which is indeed a case of physical interest. In such a case, the above reduction technique fails because the linearized operator possesses an essential spectrum filling the whole real axis, and new adapted tools are necessary. We also discuss the latest results on the existence of travelling waves in stratified fluids and on three-dimensional travelling waves, in the same spirit of reversible dynamical systems. Finally, we review the recent results on the classical two-dimensional standing wave problem.
TL;DR: It is shown that gestalt grouping laws can be translated into quantitative laws allowing the automatic computation of gestalts in digital images, and two preliminary sets of experiments are described, where the gestalt detection performance of several subjects with the predictable detection curve are compared.
Abstract: In 1923, Max Wertheimer proposed a research programme and method in visual perception. He conjectured the existence of a small set of geometric grouping laws governing the perceptual synthesis of phenomenal objects, or ‘‘gestalt’’ from the atomic retina input. In this paper, we review this set of geometric grouping laws, using the works of Metzger, Kanizsa and their schools. In continuation, we explain why the Gestalt theory research programme can be translated into a Computer Vision programme. This translation is not straightforward, since Gestalt theory never addressed two fundamental matters: image sampling and image information measurements. Using these advances, we shall show that gestalt grouping laws can be translated into quantitative laws allowing the automatic computation of gestalts in digital images. From the psychophysical viewpoint, a main issue is raised: the computer vision gestalt detection methods deliver predictable perception thresholds. Thus, we are set in a position where we can build artificial images and check whether some kind of agreement can be found between the computationally predicted thresholds and the psychophysical ones. We describe and discuss two preliminary sets of experiments, where we compared the gestalt detection performance of several subjects with the predictable detection curve. In our opinion, the results of this experimental comparison support the idea of a much more systematic interaction between computational predictions in Computer Vision and psychophysical experiments. � 2003 Elsevier Ltd. All rights reserved.
TL;DR: In this article, an original configuration of low-profile directive antennas is presented in V-band, where the focusing effect is performed by a plane-parallel Fabry-Perot resonator illuminated by a printed antenna.
Abstract: An original configuration of low-profile directive antennas is presented in V-band. The focusing effect is performed by a plane-parallel Fabry-Perot (FP) resonator illuminated by a printed antenna. Both reflecting mirrors are made of metal strip gratings. The dimensions of the strips and slots of the nonperiodic output mirror are much smaller than the working wavelength; they are computed locally so that this mirror behaves as a spherical equiphase surface. Theoretical and experimental results show that the radiation patterns are symmetric and have low sidelobes. The antenna directivity is controlled by the value of the synthesized radius of curvature, that is to say by the nonperiodic distribution of the metal strips. It typically varies between 15 and 23.5 dB at 60 GHz. This new radiating structure is much more compact than substrate lenses and is compatible with low-cost multilayer technologies at millimeter wave frequencies. This is a possible candidate for user mobile-stations of indoor broadband communication systems.
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TL;DR: In this paper, a high-resolution two-photon excitation microscopy study was conducted to investigate the orientational distributions of molecular ensembles at room temperature. Butt et al. presented a more general approach to investigate molecular behavior in complex environments which affect their orientations and interactions.
Abstract: We present high resolution two-photon excitation microscopy studies combining two-photon fluorescence (TPF) and second harmonic generation (SHG) in order to probe orientational distributions of molecular ensembles at room temperature. A detailed polarization analysis of TPF and SHG signals is used in order to unravel the parameters of the molecular orientational statistical distribution, using a technique which can be extended and generalized to a broad variety of molecular arrangements. A polymer film containing molecules active for TPF and/or SHG emission is studied as a model system. Polarized TPF is shown to provide information on specific properties pertaining to incoherent emission in molecular media, such as excitation transfer. SHG, being highly sensitive to a slight departure from centrosymmetry such as induced by an external electric field in the medium, complements TPF. The response of each signal to a variable excitation polarization allows investigation of molecular behavior in complex environments which affect their orientations and interactions.
TL;DR: Characterised the substrate specificity of the Apn1 protein towards 5,6-dihydropyrimidine, 5-hydroxy-2'-deoxyuridine and 2, 6-diamino-4-Hydroxy-5-N-methylformamidopyrimidine deoxynucleotide and it is shown that NIR is one of the major pathways for repair of oxidative DNA base damage.
Abstract: Despite the progress in understanding the base excision repair (BER) pathway it is still unclear why known mutants deficient in DNA glycosylases that remove oxidised bases are not sensitive to oxidising agents. One of the back-up repair pathways for oxidative DNA damage is the nucleotide incision repair (NIR) pathway initiated by two homologous AP endonucleases: the Nfo protein from Escherichia coli and Apn1 protein from Saccharomyces cerevisiae. These endonucleases nick oxidatively damaged DNA in a DNA glycosylase-independent manner, providing the correct ends for DNA synthesis coupled to repair of the remaining 5'-dangling nucleotide. NIR provides an advantage compared to DNA glycosylase-mediated BER, because AP sites, very toxic DNA glycosylase products, do not form. Here, for the first time, we have characterised the substrate specificity of the Apn1 protein towards 5,6-dihydropyrimidine, 5-hydroxy-2'-deoxyuridine and 2,6-diamino-4-hydroxy-5-N-methylformamidopyrimidine deoxynucleotide. Detailed kinetic comparisons of Nfo, Apn1 and various DNA glycosylases using different DNA substrates were made. The apparent K(m) and kcat/K(m) values of the reactions suggest that in vitro DNA glycosylase/AP lyase is somewhat more efficient than the AP endonuclease. However, in vivo, using cell-free extracts from paraquat-induced E.coli and from S.cerevisiae, we show that NIR is one of the major pathways for repair of oxidative DNA base damage.
TL;DR: In this article, the diameters of the vortex cores depend sensitively on their orientation with respect to the chain axis and that vortex formation can be controlled by the presence of smaller particles in the chains.
Abstract: A detailed understanding of the formation of magnetic vortices in closely spaced ferromagnetic nanoparticles is important for the design of ultra-high-density magnetic devices. Here, we use electron holography and micromagnetic simulations to characterize three-dimensional magnetic vortices in chains of FeNi nanoparticles. We show that the diameters of the vortex cores depend sensitively on their orientation with respect to the chain axis and that vortex formation can be controlled by the presence of smaller particles in the chains.
TL;DR: The tyrT core promoter structure is optimised to combine high transcriptional activity with acute sensitivity to at least three major independent regulatory inputs: negative superhelicity, FIS and ppGpp.
TL;DR: In this article, a large-scale microelectrode array is presented, which allows a dielectrophoretic positioning of cells in a matrix form, under conditions of negative DEP.
TL;DR: In this article, the authors present the results of an identification procedure of the coefficients of a force model for a given tool workpiece couple for the prediction of the defects of the tool during the cutting.
Abstract: The flatness defects observed in flank milling with cutters of long series are mainly due to the tool deflections during the machining process. This article present the results of an identification procedure of the coefficients of a force model for a given tool workpiece couple for the prediction of the defects of the tool during the cutting. The calibration method proposed meets a double aim: to define an experimental protocol that takes the industrial constraints of time and cost into account and to work out a protocol which minimizes uncertainties likely to alter the interpretation of the results (environmental, software or mechanical uncertainties). For that, the procedure envisages the machining of a simple plane starting from a raw part formed by a tilted plane, allowing for the variation of the tool engagement conditions. The tool deviation during the cutting process is indirectly identified by measuring the machined surface. The observed straightness defect conditions can be explained by the evolution of the cutting pressures applied to the cutting edges in catch during the cutter rotation. The precision was considerably improved by the taking into account of the cutter slope defect in the calculation of the load applied to the tool. After identification of the tool-workpiece couple, the prediction model was applied to some examples and allowed to determine the variations of form and position of the surface points with a margin of 5%.
TL;DR: In this paper, the femtosecond Z-scan method for push-pull molecules was used to investigate the nonlinear refractive index and the two-photon absorption.
TL;DR: In this paper, a high-resolution two-photon excitation microscopy study was conducted to investigate the orientational distributions of molecular ensembles at room temperature. Butt et al. presented a more general approach that combines twophoton fluorescence (TPF) and second harmonic generation (SHG).
Abstract: We present high resolution two-photon excitation microscopy studies combining two-photon fluorescence (TPF) and second harmonic generation (SHG) in order to probe orientational distributions of molecular ensembles at room temperature. A detailed polarization analysis of TPF and SHG signals is used in order to unravel the parameters of the molecular orientational statistical distribution, using a technique which can be extended and generalized to a broad variety of molecular arrangements. A polymer film containing molecules active for TPF and/or SHG emission is studied as a model system. Polarized TPF is shown to provide information on specific properties pertaining to incoherent emission in molecular media, such as excitation transfer. SHG, being highly sensitive to a slight departure from centrosymmetry such as induced by an external electric field in the medium, complements TPF. The response of each signal to a variable excitation polarization allows investigation of molecular behavior in complex enviro...
TL;DR: The tree of shapes of an image as mentioned in this paper is a mix of the component trees of upper and lower level sets, and its existence under fairly weak assumptions and its completeness are proven.
Abstract: This chapter presents the tree of shapes of an image, a mix of the component trees of upper and lower level sets. Its existence under fairly weak assumptions and its completeness are proven. Ignoring the small details of the image, we show the essentially finite nature of the tree. Finally, we illustrate these theoretical results with a direct application to gray level quantization.
TL;DR: In this article, a bifunctional capping ligand is used to obtain pyrrol-functionalized monodispersed nano-crystalline TiO2 (anatase) particles in a single step.
Abstract: A bifunctional capping ligand is used to obtain pyrrol-functionalized monodispersed nano-crystalline TiO2 (anatase) particles in a single step. The pyrrole functionalities in the shell are then (electro)chemically polymerized to create a polypyrrole (PPy)/TiO2 hybrid nano-composite film (see Figure). Further electronic modification of the conducting polymer is possible, leading to a great variety of potential applications.
TL;DR: In this paper, a finite element model capable of describing both the deformation which accumulates during the hardening phase as the precursor to failure and the failure process leading to softening phenomena induced by shear slip lines is presented.
Abstract: In this work, we present a finite element model capable of describing both the plastic deformation which accumulates during the hardening phase as the precursor to failure and the failure process leading to softening phenomena induced by shear slip lines. This is achieved by activating subsequently hardening and softening mechanisms with the localization condition which separates them. The chosen model problem of von Mises plasticity is addressed in detail, along with particular combination of mixed and enhanced finite element approximations which are selected to control the locking phenomena and guarantee mesh-invariant computation of plastic dissipation. Several numerical simulations are presented in order to illustrate the ability of the presented model to predict the final orientation of the shear slip lines for the case of non-proportional loading.