École Nationale Supérieure de Création Industrielle

Because of the importance of the security issues in the management of medical information, we suggest the use of watermarking techniques to complete the existing measures for protecting medical images. We discuss the necessary requirements for such a system to be accepted by medical staff and its complementary role with respect with existing security systems. We present different scenarios, one devoted to the authentication and tracing of the images, the second to the integrity control of the patient's record.

Partitioning and transmutation (P&T) of minor actinides (MA) is currently studied to reduce the nuclear waste inventory. In this context, the fabrication of MA bearing materials is of great interest to achieve an effective recycling of these highly radioactive elements. To ensure the in-pile behavior, nuclear oxide fuels have to respect several criteria including preservation of the fluorite structure and defined oxygen to metal ratio (O/M). In the case of Am bearing materials, such as U(1-y)Am(y)O(2±x) (y = 0.10, 0.15, 0.20), the O/M determination is quite challenging using conventional methods (TGA, XRD) because of the particular thermodynamic properties of Am. Despite the lack of experimental data in the U-Am-O system, thermodynamical models are currently developed to effectively assess the O/M ratio. In this work, the O/M ratios were calculated for various oxygen potentials using the cation molar fraction determined by XAS measurements. These results are an important addition to the experimental data available for the U-Am-O system. Moreover, XRD and XAS indicated that the fabrication of fluorite U(1-y)Am(y)O(2±x) solid solution was achieved for all Am content and oxygen potentials investigated. On the basis of the molar fraction, a description of the solid solution was proposed depending on the considered sintering conditions. Finally, the occurrence of an unexpected charge compensation mechanism was pointed out.

With scientific evidence regarding the contribution of carbon emissions to global warming mounting, pressure is building for corrective policy actions. The potential for such policies poses a risk for invested capital. We describe how bond investors using traditional portfolio construction techniques can hedge portfolios against this climate risk without introducing unintended exposures that could sacrifice the portfolio’s benchmark-tracking properties. We hypothesize how a pickup in low-carbon investing may send out a pricing signal and preempt the connoted price correction. In that event, the transition toward a world economy with a sustainable level of carbon pollution would be accelerated, which would be beneficial for both the low-carbon investor and the environment.

This paper examines the role of iron in mullite nucleation and growth from kaolins. We chose two typical raw kaolins containing a reduced impurity level and characterized by very different degrees of crystallinity of the kaolinite phase. Both the structural iron in kaolinite and also some iron deposited onto phyllosilicate layers by a chemical route were considered. After firing in the 900–1100°C temperature range, the Fe environment was determined by Mössbauer spectroscopy. From X‐ray spectra of samples fired at 1250°C, mullite stoichiometries were obtained by Rietveld refinements. It was shown that iron contributes to the structural reorganization stage of the material, when mullite is nucleated. Fe atoms are essentially in octahedral sites, which favors an increase of the c parameter of the orthorhombic cell. The iron quantity attains a saturation level for an Fe‐to‐Al ratio between 0.3 and 0.4, depending on the raw kaolinite crystallinity. Besides mullite, the excess iron associates with titanium to form a pseudobrookite phase and hematite.

Ceramic suspensions composed of oppositely charged alumina and silica particles are studied experimentally and by means of Brownian dynamics simulations. Alumina and silica particles have quite similar sizes, the former having an average diameter larger by a factor 1.6. The suspension behavior is studied as a function of composition. The aggregation state, the aggregate composition, structural aspects at several length scales and the aggregate growth kinetics are analysed. A good agreement between numerical and experimental results is obtained. The simulations allow us to describe in detail the aggregation process and mechanisms. Simulations appear as an important tool to predict and control the particle assembly in such binary suspensions, whose behaviour depends on several parameters.

Tropospheric inhomogeneities can form a major error source in differential synthetic aperture radar interferometry measurements, which are used in slow-deformation monitoring. Indeed, variations of atmospheric conditions between two radar acquisitions produce variations in the signal path of two images and, thus, additional fringes on differential interferograms. These effects have a strong influence on interferograms and must be compensated to obtain reliable deformation measurements. This paper presents a methodological approach to reduce at both global and local scales tropospheric contributions directly from differential interferograms. It first requires refined knowledge of the stable scatterers that can only be obtained from the analysis of a large population of multitemporal interferograms. The correction of global-scale atmospheric contribution exploits the correlation between phase and topography. The correction of local artifacts is based on the correlation between interferograms containing one common acquisition. This technique is validated on a database of 81 differential interferograms covering the Gulf of Corinth (Greece) and used to improve the measurements of ground deformation compared to global positioning system measurements

Fluorescent silica and alumina-like spherical particles with almost equal sizes are synthesized. Dilute aqueous suspensions are prepared with various ratios of those colloidal particles that exhibit opposite surface charges. These suspensions undergo heteroaggregation for a wide range of compositions. The structure of the formed aggregates is analyzed by means of confocal microscopy. The experimental results are compared to those of Brownian dynamics simulations in which the interactions between colloids are modeled by the DLVO potential. Good agreement between experiments and simulations is obtained.

Publication in the conference proceedings of EUSIPCO, Toulouse, France, 2002

In this work, we present an evolution of the Damped and Delayed Sinusoidal (DDS) model introduced within the framework of the general signal modeling. This model, named the Partial Damped and Delayed Sinusoidal (PDDS) model, takes into account a single time delay parameter for a set (sum) of damped sinusoids. The proposed modification is more consistent with the transient audio modeling problem. The validity of the approach is shown by its comparison with the well-known Exponentially Damped Sinusoids (EDS) approach. Finally, the performances of the three models based high-resolution parameter estimation algorithms are compared on synthetic fast time-varying signals, and on two typical audio transients.

Silicon oxycarbide glasses (Si/C/O) of various compositions have been obtained after pyrolysis of polysiloxane gels produced by the sol–gel method. Four gels were synthesized from various structures of silicon precursors: MTES issued from methyltriethoxysilane CH 3 Si(–OEt) 3 , VTES from vinyltriethoxysilane CH 2 =CH–Si(–OEt) 3 , PTES from phenyltriethoxysilane C 6 H 5 –Si(–OEt) 3 and D H T H 1/9 for that issued from the 1/9 molar ratio of methyldiethoxysilane D H (CH 3 )HSi–(OEt) 2 and T H triethoxysilane HSi(–OEt) 3 . The resulting materials at 1000°C can be described as an oxycarbide phase with the presence of either an excess of carbon or silicon depending on the starting structure of the precursor used to prepare the gels. By thermogravimetric analysis (TGA) coupled with mass spectrometry (MS), we followed the thermal behavior of each compound from 1000° to 1500°C. Based on these results and chemical analysis data, we have established the main reactions that occur during the decomposition of the oxycarbide glasses. At low temperature ( T <1400°C), the dominant mechanism for carbon‐rich materials first involves a solid‐state reaction of SiO 2 and C leading to SiC formation and removal of CO. That reaction proceeds at high temperature (above 1400°C), as long as the amount of carbon in the material is high enough (PTES). When the system is depleted of its free carbon (VTES, MTES), however, another reaction can also proceed parallel to the former one, where SiO 2 and SiC react leading to a loss of SiO and CO. The combination of an excess of silicon and a dense state of the material improves the thermo‐chemical stability of the silicon oxycarbide phase present in the D H T H 1/9 glass. By placing the chemical compositions in the ternary Si–C–O diagram, we could then determine the evolution at high temperature of any system of mixed Si/C x /O y phases.

The structures of cobalt clusters are investigated by simulations and experiments. The growth process of isolated clusters in gas phase is simulated by molecular dynamics, growing clusters atom by atom from a small seed up to the size of 600 atoms. Experimentally, clusters are generated by a laser ablation cluster generator using low energy clusters beam deposition. Then, the deposited aggregates are characterized with high resolution transmission electronic microscope. Simulation results are compared with the experiment, and with previous density functional theory and semiempirical calculations, obtaining a good agreement both for the geometric structures and for the behavior of lattice contraction. Finally, aggregation simulations are performed to determine the nucleation rate of cobalt monomers.

Dilute aqueous suspensions of silicon nanoparticles and sodium carboxymethylcellulose salt (CMC) are studied experimentally and numerically by brownian dynamics simulations. The study focuses on the adsorption of CMC on silicon and on the aggregation state as a function of the suspension composition. To perform simulations, a coarse-grained model has first been developed for the CMC molecules. Then, this model has been applied to study numerically the behavior of suspensions of silicon and CMC. Simulation parameters have been fixed on the basis of experimental characterizations. Results of brownian dynamics simulations performed with our model are found in qualitative good agreement with experiments and allow a good description of the main features of the experimental behavior.

We derive the form of the best non-linear functions for performing independent component analysis (ICA) by maximum likelihood estimation. We show that both the form of nonlinearity and the relative gradient update equations for likelihood maximization naturally generalize to the complex case, and that they coincide with the real case. We discuss several special cases for the score function as well as adaptive scores.

Shape recognition systems usually order a fixed number of best matches to each query, but do not address or answer the two following questions: Is a query shape in a given database? How can we be sure that a match is correct? This communication deals with these two key points. A database being given, with each shape S and each distance /spl delta/, we associate its number of false alarms NFA(S, /spl delta/), namely the expectation of the number of shapes at distance /spl delta/ in the database. Assume that NFA(S, /spl delta/) is very small with respect to 1, and that a shape S' is found at distance /spl delta/ from S in the database. This match could not occur just by chance and is therefore a meaningful detection. Its explanation is usually the common origin of both shapes. Experimental evidence will show that NFA(S, /spl delta/) can be predicted accurately.

This paper present the results from a comprehensive study undertaken to investigate and develop alkali-activated binders (AABs) with laterite soil as the aluminosilicate precursor. In this study, the effect of the silica modulus (SiO2/Na2O) of the activator on the setting time, rheological properties and strength development were investigated. Iron-rich laterite sourced from West Africa was used as the aluminosilicate precursor alongside sodium silicate and sodium hydroxide for the production of the activator. The activators were prepared to have varying silica modulus of 1.3, 1.5, 1.7 and 2. The findings from this study showed that the silica modulus of the activator used in the synthesis of the laterite-based AABs has a significant influence on the resulting properties of the binders. It was found out the optimum silica modulus is 1.3 and increasing the silica modulus of the activator results in detrimental effects on the hardened properties of the AABs. In the same context, increasing the silica modulus of the activator from 1.3 to 2.0 extended the final setting of the binder time by 56.1% while the compressive strength at 56 days reduced by 57%. Microstructural investigation on the binders showed that the main products of alkali activation of the calcined laterite are quartz, ilmenite, hematite and maghemite. It was concluded that laterite-based AABs with good performance can be produced with a silica modulus of 1.3 and used as a possible alternative for Portland cement as a binder.

Numerical simulations constitute a precious tool for understanding the role of key parameters influencing the colloidal arrangement in suspensions, which is crucial for many applications. The present paper investigates numerically the role of hydrodynamic interactions on the aggregation processes in colloidal suspensions. Three simulation techniques are used: Brownian dynamics without hydrodynamic interactions, Brownian dynamics including some of the hydrodynamic interactions, using the Yamakawa-Rotne-Prager tensor, and stochastic rotation dynamics coupled with molecular dynamics. A system of monodisperse colloids strongly interacting through a generalized Lennard-Jones potential is studied for a colloid volume fraction ranging from 2.5 to 20%. Interestingly, effects of the hydrodynamic interactions are shown in the details of the aggregation processes. It is observed that the hydrodynamic interactions slow down the aggregation kinetics in the initial nucleation stage, while they speed up the next cluster coalescence stage. It is shown that the latter is due to an enhanced cluster diffusion in the simulations including hydrodynamic interactions. The higher the colloid volume fraction, the more pronounced the effects on the aggregation kinetics. It is also observed that hydrodynamic interactions slow down the reorganization kinetics. It turns out that the Brownian dynamics technique using the Yamakawa-Rotne-Prager tensor tends to overestimate the effects on cluster diffusion and cluster reorganization, even if it can be a method of choice for very dilute suspensions.

Suspensions of carbon blacks and spherical carbon particles are studied experimentally and numerically to understand the role of the particle shape on the tendency to percolation. Two commercial carbon blacks and one lab-synthesized spherical carbon are used. The percolation thresholds in suspensions are experimentally determined by two complementary methods: impedance spectroscopy and rheology. Brownian dynamics simulations are performed to explain the experimental results taking into account the fractal shape of the aggregates in the carbon blacks. The results of Brownian dynamics simulations are in good agreement with the experimental results and allow one to explain the experimental behavior of suspensions.

We are investigating actuators that are able to provide different types of haptic sensations and that can be wrapped around a wide range of surfaces and objects. Our first prototype, BubbleWrap, consists of a matrix of electromagnetic actuators, enclosed in fabric, with individually controllable cells that expand and contract. It provides both active haptic feedback, using vibration, as well passive haptic feedback, using shape and firmness. An initial experiment demonstrated that users could reliably discriminate among the three firmness levels displayed on our prototype.

Abstract The characteristics of vacancy and self-interstitial clustering behaviour have been studied in a Ag-9 at. ′% Zn alloy during irradiation in an electron microscope operated at 800 or 1000 keV in the temperature range between 250 and 410 K. The salient feature of the observations was that, for irradiation temperatures below 300 K, only stacking-fault tetrahedra were nucleated while, for irradiations above 360 K, all defect agglomerates were faulted dislocation loops of interstitial type. Deeper insight into the mobility of point defects was gained by the realization of two-step irradiations. These have shown that preformed interstitial loops shrank during subsequent re-irradiation below 300 K. This demonstrates, using conventional methods of analysis for the dynamics of the defect populations associated with a fast particle flux, that vacancies migrate faster than selfinterstitials at low temperatures. The present evidence for this unique behaviour of elementary defects in a metal lattice is in agreement with previous anelasticity results obtained in other concentrated AgZn alloys, in which the single vacancy has been identified to be the faster moving defect.

Environmental context. Despite the widespread occurrence of arsenobetaine in marine animals the origin of this arsenic compound remains unknown. A current hypothesis is that arsenobetaine is formed from more complex arsenic compounds found in marine algae. To test this hypothesis, we examined the arsenic compounds in a mangrove ecosystem where algae play a limited role in primary productivity. Abstract. Marine algae are known to bioaccumulate arsenic and transform it into arsenosugars, which are thought to be precursors of the major arsenic compound, arsenobetaine, found in marine animals. Marine ecosystems based on mangrove forests have high nutrient input from mangrove leaves, and thus provide a unique opportunity to study the cycling of arsenic in a marine system where algae are not the dominant food source. Two mangrove forests in Phuket, Thailand were selected as sampling sites for this study. For comparison, samples were also collected from two coral reef sites at and near Phuket. The samples collected included mangrove leaves, corals, algae, molluscs, fish and crustaceans. Arsenic contents in the samples and in aqueous extracts of the samples were determined by hydride generation atomic absorption spectrometry following a dry-ashing mineralisation procedure, and arsenic species were determined in the aqueous extracts by HPLC-MS (mainly ICPMS). Mangrove leaves contained only low concentrations of total arsenic (0.10–0.73 mg kg–1 dry mass) and the aqueous extracts thereof contained inorganic arsenic species, methylarsonate and dimethylarsinate, but arsenosugars were not detected. The total mean arsenic contents (3.2–86 mg kg–1 dry mass) of the animals from the mangrove ecosystem, however, were typical of those found in animal samples from other marine ecosystems. Similarly the arsenic compounds present were typical of those in animals from other marine ecosystems comprising mainly arsenobetaine with smaller quantities of other common arsenicals including arsenosugars, arsenocholine, tetramethylarsonium ion, trimethylarsine oxide and dimethylarsinate. A trimethylated arsenosugar, which is not commonly reported in marine organisms, was a significant arsenical (6–8% of total As) in some gastropod species from the mangrove ecosystem. The coral samples contained mainly arsenosugars and arsenobetaine, and the other animals collected from the coral ecosystem contained essentially the same pattern of arsenicals found for the mangrove animals. The data suggest that food chains based on algae are not necessary for animals to accumulate large concentrations of arsenobetaine.