Showing papers by "Mines ParisTech published in 2003"

Image segmentation

Abstract: Firstly, the paper proposes an axiomatic definition for the notion of "segmentation" in image processing, which is based on the idea of a maximal partition. Then a key theorem links segmentation with connection, on the one hand, and with connective criteria on the other one. A series of lattice properties are then developed. In a last part, two examples of segmentations are proposed.

Image fusion—the ARSIS concept and some successful implementation schemes

Abstract: This article aims at explaining the ARSIS concept. By fusing two sets of images A and B, one with a high spatial resolution, the other with a low spatial resolution and different spectral bands, the ARSIS concept permits to synthesise the dataset B at the resolution of A that is as close as possible to reality. It is based on the assumption that the missing information is linked to the high frequencies in the sets A and B. It searches a relationship between the high frequencies in the multispectral set B and the set A and models this relationship. The general problem for the synthesis is presented first. The general properties of the fused product are given. Then, the ARSIS concept is discussed. The general scheme for the implementation of a method belonging to this concept is presented. Then, this article intends to help practitioners and researchers to better understand this concept through practical details about implementations. Two Multiscale Models are described as well as two Inter-Band Structure Models (IBSM). They are applied to an Ikonos image as an illustration case. The fused products are assessed by means of a known protocol comprising a series of qualitative and quantitative tests. The products are found of satisfactory quality. This case illustrates the differences existing between the various models, their advantages and limits. Tracks for future improvements are discussed.

Asymptotic stabilization via output feedback for lower triangular systems with output dependent incremental rate

Abstract: We study the global asymptotic stabilization by output feedback for systems whose dynamics are in a feedback form and where the nonlinear terms admit an incremental rate depending only on the measured output. The output feedback we consider is of the observer-controller type where the design of the controller follows from standard robust backstepping. The novelty is in the observer which is high-gain such as with a gain coming from a Riccati equation.

Sequential Data Assimilation Techniques in Oceanography

Abstract: Summary We review recent developments of sequential data assimilation techniques used in oceanography to integrate spatio-temporal observations into numerical models describing physical and ecological dynamics. Theoretical aspects from the simple case of linear dynamics to the general case of nonlinear dynamics are described from a geostatistical point-of-view. Current methods derived from the Kalman filter are presented from the least complex to the most general and perspectives for nonlinear estimation by sequential importance resampling filters are discussed. Furthermore an extension of the ensemble Kalman filter to transformed Gaussian variables is presented and illustrated using a simplified ecological model. The described methods are designed for predicting over geographical regions using a high spatial resolution under the practical constraint of keeping computing time sufficiently low to obtain the prediction before the fact. Therefore the paper focuses on widely used and computationally efficient methods.

Elastoviscoplastic constitutive frameworks for generalized continua

Abstract: A unifying thermomechanical constitutive framework for generalized continua including additional degrees of freedom or/and the second gradient of displacement is presented. Based on the analysis of the dissipation, state laws, flow rules and evolution equations are proposed for Cosserat, strain gradient and micromorphic continua. The case of the gradient of internal variable approach is also incorporated by regarding the nonlocal internal variable as an actual additional degree of freedom. The consistency of the continuum thermodynamical framework is ensured by the introduction of a viscoplastic pseudo–potential of dissipation, thus extending the classical class of so–called standard material models to generalized continua.

An intrinsic observer for a class of Lagrangian systems

Abstract: We propose a new design method of asymptotic observers for a class of nonlinear mechanical systems: Lagrangian systems with configuration (position) measurements. Our main contribution is to introduce a state (position and velocity) observer that is invariant under any changes of the configuration coordinates. The observer dynamics equations, as the Euler-Lagrange equations, are intrinsic. The design method uses the Riemannian structure defined by the kinetic energy on the configuration manifold. The local convergence is proved by showing that the Jacobian of the observer dynamics is negative definite (contraction) for a particular metric defined on the state-space, a metric derived from the kinetic energy and the observer gains. From a practical point of view, such intrinsic observers can be approximated, when the estimated configuration is close to the true one, by an explicit set of differential equations involving the Riemannian curvature tensor. These equations can be automatically generated via symbolic differentiations of the metric and potential up to order two. Numerical simulations for the ball and beam system, an example where the scalar curvature is always negative, show the effectiveness of such approximation when the measured positions are noisy or include high frequency neglected dynamics.

Controlled Precipitation of Zinc Oxide Particles at Room Temperature

Abstract: Zinc nitrate precipitated with NaOH solution at room temperature under double-jet conditions produced micrometric zinc oxide particles with ellipsoid or starlike morphology separated by only a slight variation of pH (9.5 and 10.5, respectively). The formation kinetics of starlike particles was followed by SEM observations, suggesting that they result from a solid-state transformation of the hydroxide matrix. This mechanism involved the nucleation of 30-nm ZnO particles inside the matrix, followed by their aggregation into starlike particles. The introduction of sodium sulfate or sodium dodecyl sulfate in the bath before precipitation led to a drastic size reduction and to a diversity of particle shapes (from half-ellipsoids to full ellipsoids). The presence of these additives provided important hints on particle formation and confirmed that submicronic particles resulted from nanocrystals oriented aggregation.

Influence of chitosan characteristics on polymer properties. I: Crystallographic properties

Abstract: The properties of chitosan depend on several parameters including its origin (shrimp, squid, fungi etc), characteristics (mol fraction of N-acetylation; molecular weight) and treatments used to condition it (dissolving, precipitation, drying). These parameters can influence the material's sorption properties for metal ions. It has been suggested that the changes in sorption properties are related to the crystallinity of the material. The present work focuses on the study of the crystallographic properties of samples prepared from shrimp, squid and fungi sources, with different characteristics and conditioned by several physical treatments (dissolving, reprecipitation and drying, including oven-drying, freeze-drying), prior to subsequent studies of their sorption properties for platinum (discussed in Part II of this manuscript). © 2003 Society of Chemical Industry

Grain refinement in AZ91 magnesium alloy during thermomechanical processing

Abstract: Microstructural changes during high-temperature extrusion and torsion of an AZ91 alloy (Mg–9Al–1Zn, wt.%) were investigated. In the experimental domain studied, dynamic recrystallisation (DRX) occurs and the effect of temperature and strain rate on the resulting recrystallised grain size was investigated. Complete recrystallisation in torsion is associated with the development of a stress plateau after softening from the peak stress, which is systematically observed in the first steps of straining. The resulting grain size can be related to the value of the peak stress. It appears that the precipitation of the Mg 17 Al 12 phase does not affect significantly the torsion behaviour of the alloy in the experimental domain investigated here. This study supports the idea that very fine-scale microstructures (i.e. with a mean grain size smaller than 5 μm) can be easily produced by DRX during high-temperature extrusion of the AZ91 alloy.

Automatic analysis of DNA microarray images using mathematical morphology.

Abstract: Motivation: DNA microarrays are an experimental technology which consists in arrays of thousands of discrete DNA sequences that are printed on glass microscope slides. Image analysis is an important aspect of microarray experiments. The aim of this step is to reduce an image of spots into a table with a measure of the intensity for each spot. Efficient, accurate and automatic analysis of DNA spot images is essential in order to use this technology in laboratory routines. Results: We present an automatic non-supervised set of algorithms for a fast and accurate spot data extraction from DNA microarrays using morphological operators which are robust to both intensity variation and artefacts. The approach can be summarised as follows. Initially, ag ridding algorithm yields the automatic segmentation of the microarray image into spot quadrants which are later individually analysed. Then the analysis of the spot quadrant images is achieved in five steps. First, a prequantification, the spot size distribution law is calculated. Second, the background noise extraction is performed using a morphological filtering by area. Third, an orthogonal grid provides the first approach to the spot locus. Fourth, the spot segmentation or spot boundaries definition is carried out using the watershed transformation. And fifth, the outline of detected spots allows the signal quantification or spot intensities extraction; in this respect, a noise model has been investigated. The performance of the algorithm has been compared with two packages: ScanAlyze and Genepix, showing its robustness and precision. Availability: Ap rototype system integrated in PDI32 (an image processing software for Windows) may be obtained from the authors on request.

Flat systems, equivalence and trajectory generation

Abstract: Flat systems, an important subclass of nonlinear control systems introduced via differential-algebraic methods, are defined in a differential geometric framework. We utilize the infinite dimensional geometry developed by Vinogradov and coworkers: a control system is a diffiety, or more precisely, an ordinary diffiety, i.e. a smooth infinite-dimensional manifold equipped with a privileged vector field. After recalling the definition of a Lie-Backlund mapping, we say that two systems are equivalent if they are related by a Lie-Backlund isomorphism. Flat systems are those systems which are equivalent to a controllable linear one. The interest of such an abstract setting relies mainly on the fact that the above system equivalence is interpreted in terms of endogenous dynamic feedback. The presentation is as elementary as possible and illustrated by the VTOL aircraft.

A numerical model for induction heating processes coupling electromagnetism and thermomechanics

Abstract: This paper presents a mathematical and numerical model developed for coupling the various physical phenomena (electromagnetic, thermal and mechanical) taking place in axisymmetrical induction heating processes. All three electromagnetic, thermal and mechanical models are time dependent and take full account of the electromagnetic and thermal non-linear effect especially with magnetic materials. The electromagnetic problem is discretized and solved in the workpiece, air and inductors. The heat transfer equation and the mechanical equilibrium equations are solved in the workpiece only, both using a finite element method. The mechanical model can take into account thermoelastic-plastic behaviour for the part. The model has been successfully applied to several cases of induction heating. Comparisons between numerical and experimental results show an excellent agreement.

Incremental mining of sequential patterns in large databases

Abstract: In this paper, we consider the problem of the incremental mining of sequential patterns when new transactions or new customers are added to an original database. We present a new algorithm for mining frequent sequences that uses information collected during an earlier mining process to cut down the cost of finding new sequential patterns in the updated database. Our test shows that the algorithm performs significantly faster than the naive approach of mining the whole updated database from scratch. The difference is so pronounced that this algorithm could also be useful for mining sequential patterns, since in many cases it is faster to apply our algorithm than to mine sequential patterns using a standard algorithm, by breaking down the database into an original database plus an increment.

Chitosan-Supported Palladium Catalyst. 3. Influence of Experimental Parameters on Nitrophenol Degradation

Abstract: Glutaraldehyde cross-linked chitosan was loaded with palladium and then reduced by means of an in situ hydrogen generation procedure (Zn in sulfuric acid solution) to prepare a chitosan-supported palladium catalyst. This catalyst was successfully used to degrade nitrophenol in dilute solutions in the presence of sodium formate as the hydrogen donor. The optimum initial pH was below pH 4. The pH strongly increased during the reaction. The influence of the initial concentration of nitrophenol and sodium formate was studied in order to determine the minimum molar ratio between these compounds to achieve the complete conversion of the nitrogenous product. The pseudo-first-order equation was shown to fit degradation kinetics in most cases; however, in some cases it was necessary to use a variable-order equation in order to model the kinetics. Decreasing catalyst particle size increased degradation rate; the kinetic parameter varied linearly with the reciprocal of the diameter, indicating that film diffusion ma...

What if we Talked Politics a Little

Abstract: Political enunciation remains an enigma as long as it is considered from the standpoint of information transfer. It remains as unintelligible as religious talk. The paper explores the specificty of this regime and especially the strange link it has with the canonical definition of enunciation in linguistics and semiotics. The ‘political circle’ is reconstituted and thus also the reasons why a ‘transparent’ or ‘rational'political speech act destroys the very conditions of group formation.

Real-time color segmentation of road signs

Abstract: This subject is part of a more challenging research project aimed at developing a computer vision system, embedded in a car, and capable of identifying and locating road signs. Several constraints limit the possible solutions are first identified. For instance in such an application, we definitely need a real-time system; in addition, we wish to limit our choice to a single camera methodology to keep the hardware as simple as possible and finally our approach must work efficiently on low cost hardware. For this purpose we first rely on a color segmentation strategy to recognize the road signs. We have studied the behavior of the RGB components of several road signs from sunrise to sunset. From these results we have shown that the simple comparison of the RGB components taken two by two is sufficient to segment road signs in real-time. From this segmentation it should be much easier to identify the shape (and meaning) of a particular sign.

Comparison of the Sorption of Anionic Dyes on Activated Carbon and Chitosan Derivatives from Dilute Solutions

Abstract: Activated carbon and chitosan were investigated for the sorption of several dyes. While the sorption on activated carbon was largely independent of the pH, the sorption of dyes on chitosan was controlled by the acidity of the solution. Anionic dye sorption onto chitosan occurred through electrostatic attraction on protonated amine groups. Sorption experiments were focused on dilute solutions and sorption capacities ranged between 200 and 2000 μmol g−1 for chitosan and between 50 and 900 μmol g−1 for activated carbon. Since, in most cases, equilibrium was reached within the first 12 hours of contact, sorption kinetics are relatively fast. However, both sorption capacities (sorption isotherms) and kinetics depended on the type of dyes. The attempt to correlate sorption performance to the structure of the dye failed. Sorption kinetics are strongly influenced not only by intraparticle diffusion resistance but also by the affinity of the dye for the sorbent.